1
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Kiyamudeen F, Rajapaksha M, Atapattu N, Kularatne SD, Schröder S, Hooper AJ, Burnett JR, Jasinge E. Homozygous LPL and GPIHBP1 variants causing familial chylomicronaemia syndrome in Sri Lankan children. Pathology 2024:S0031-3025(24)00125-9. [PMID: 38777740 DOI: 10.1016/j.pathol.2024.02.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Revised: 02/16/2024] [Accepted: 02/28/2024] [Indexed: 05/25/2024]
Affiliation(s)
| | | | - Navoda Atapattu
- Department of Paediatrics, Lady Ridgeway Hospital for Children, Colombo, Sri Lanka
| | | | | | - Amanda J Hooper
- Department of Clinical Biochemistry, PathWest Laboratory Medicine, Royal Perth Hospital and Fiona Stanley Hospital Network, Perth, WA, Australia; School of Medicine, University of Western Australia, Perth, WA, Australia
| | - John R Burnett
- Department of Clinical Biochemistry, PathWest Laboratory Medicine, Royal Perth Hospital and Fiona Stanley Hospital Network, Perth, WA, Australia; School of Medicine, University of Western Australia, Perth, WA, Australia
| | - Eresha Jasinge
- Department of Chemical Pathology, Lady Ridgeway Hospital for Children, Colombo, Sri Lanka
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2
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Yang Y, Beigneux AP, Song W, Nguyen LP, Jung H, Tu Y, Weston TA, Tran CM, Xie K, Yu RG, Tran AP, Miyashita K, Nakajima K, Murakami M, Chen YQ, Zhen EY, Kim JR, Kim PH, Birrane G, Tontonoz P, Ploug M, Konrad RJ, Fong LG, Young SG. Hypertriglyceridemia in Apoa5-/- mice results from reduced amounts of lipoprotein lipase in the capillary lumen. J Clin Invest 2023; 133:e172600. [PMID: 37824203 PMCID: PMC10688983 DOI: 10.1172/jci172600] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 10/05/2023] [Indexed: 10/14/2023] Open
Abstract
Why apolipoprotein AV (APOA5) deficiency causes hypertriglyceridemia has remained unclear, but we have suspected that the underlying cause is reduced amounts of lipoprotein lipase (LPL) in capillaries. By routine immunohistochemistry, we observed reduced LPL staining of heart and brown adipose tissue (BAT) capillaries in Apoa5-/- mice. Also, after an intravenous injection of LPL-, CD31-, and GPIHBP1-specific mAbs, the binding of LPL Abs to heart and BAT capillaries (relative to CD31 or GPIHBP1 Abs) was reduced in Apoa5-/- mice. LPL levels in the postheparin plasma were also lower in Apoa5-/- mice. We suspected that a recent biochemical observation - that APOA5 binds to the ANGPTL3/8 complex and suppresses its capacity to inhibit LPL catalytic activity - could be related to the low intracapillary LPL levels in Apoa5-/- mice. We showed that an ANGPTL3/8-specific mAb (IBA490) and APOA5 normalized plasma triglyceride (TG) levels and intracapillary LPL levels in Apoa5-/- mice. We also showed that ANGPTL3/8 detached LPL from heparan sulfate proteoglycans and GPIHBP1 on the surface of cells and that the LPL detachment was blocked by IBA490 and APOA5. Our studies explain the hypertriglyceridemia in Apoa5-/- mice and further illuminate the molecular mechanisms that regulate plasma TG metabolism.
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Affiliation(s)
- Ye Yang
- Department of Medicine and
- Human Genetics, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | | | | | | | | | | | | | | | | | | | | | - Kazuya Miyashita
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Yan Q. Chen
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Eugene Y. Zhen
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | | | | | - Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, UCLA, Los Angeles, California, USA
| | - Michael Ploug
- Finsen Laboratory, Copenhagen University Hospital–Rigshospitalet, Copenhagen, Denmark
- Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Robert J. Konrad
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | | | - Stephen G. Young
- Department of Medicine and
- Human Genetics, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
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3
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Song W, Beigneux AP, Weston TA, Chen K, Yang Y, Nguyen LP, Guagliardo P, Jung H, Tran AP, Tu Y, Tran C, Birrane G, Miyashita K, Nakajima K, Murakami M, Tontonoz P, Jiang H, Ploug M, Fong LG, Young SG. The lipoprotein lipase that is shuttled into capillaries by GPIHBP1 enters the glycocalyx where it mediates lipoprotein processing. Proc Natl Acad Sci U S A 2023; 120:e2313825120. [PMID: 37871217 PMCID: PMC10623010 DOI: 10.1073/pnas.2313825120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Accepted: 09/19/2023] [Indexed: 10/25/2023] Open
Abstract
Lipoprotein lipase (LPL), the enzyme that carries out the lipolytic processing of triglyceride-rich lipoproteins (TRLs), is synthesized by adipocytes and myocytes and secreted into the interstitial spaces. The LPL is then bound by GPIHBP1, a GPI-anchored protein of endothelial cells (ECs), and transported across ECs to the capillary lumen. The assumption has been that the LPL that is moved into capillaries remains attached to GPIHBP1 and that GPIHBP1 serves as a platform for TRL processing. In the current studies, we examined the validity of that assumption. We found that an LPL-specific monoclonal antibody (mAb), 88B8, which lacks the ability to detect GPIHBP1-bound LPL, binds avidly to LPL within capillaries. We further demonstrated, by confocal microscopy, immunogold electron microscopy, and nanoscale secondary ion mass spectrometry analyses, that the LPL detected by mAb 88B8 is located within the EC glycocalyx, distant from the GPIHBP1 on the EC plasma membrane. The LPL within the glycocalyx mediates the margination of TRLs along capillaries and is active in TRL processing, resulting in the delivery of lipoprotein-derived lipids to immediately adjacent parenchymal cells. Thus, the LPL that GPIHBP1 transports into capillaries can detach and move into the EC glycocalyx, where it functions in the intravascular processing of TRLs.
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Affiliation(s)
- Wenxin Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Anne P. Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Thomas A. Weston
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Kai Chen
- Department of Chemistry, The University of Hong Kong, Hong Kong, China
- School of Molecular Sciences, The University of Western Australia, Perth6009, Australia
| | - Ye Yang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Le Phuong Nguyen
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Paul Guagliardo
- Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Perth6009, Australia
| | - Hyesoo Jung
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Anh P. Tran
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Yiping Tu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Caitlyn Tran
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, MA02215
| | - Kazuya Miyashita
- Department of Clinical Laboratory Medicine, Gunma University School of Medicine, Maebashi371-8511, Japan
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University School of Medicine, Maebashi371-8511, Japan
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University School of Medicine, Maebashi371-8511, Japan
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, CA90095
| | - Haibo Jiang
- Department of Chemistry, The University of Hong Kong, Hong Kong, China
| | - Michael Ploug
- Finsen Laboratory, Copenhagen University Hospital-Rigshospitalet, Copenhagen NDK–2200, Denmark
- Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen NDK-2200, Denmark
| | - Loren G. Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Stephen G. Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA90095
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4
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Song W, Yang Y, Heizer P, Tu Y, Weston TA, Kim JR, Munguia P, Jung H, Fong JLC, Tran C, Ploug M, Beigneux AP, Young SG, Fong LG. Intracapillary LPL levels in brown adipose tissue, visualized with an antibody-based approach, are regulated by ANGPTL4 at thermoneutral temperatures. Proc Natl Acad Sci U S A 2023; 120:e2219833120. [PMID: 36787365 PMCID: PMC9974459 DOI: 10.1073/pnas.2219833120] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 01/18/2023] [Indexed: 02/15/2023] Open
Abstract
Lipoprotein lipase (LPL) is secreted into the interstitial spaces by parenchymal cells and then transported into capillaries by GPIHBP1. LPL carries out the lipolytic processing of triglyceride (TG)-rich lipoproteins (TRLs), but the tissue-specific regulation of LPL is incompletely understood. Plasma levels of TG hydrolase activity after heparin injection are often used to draw inferences about intravascular LPL levels, but the validity of these inferences is unclear. Moreover, plasma TG hydrolase activity levels are not helpful for understanding LPL regulation in specific tissues. Here, we sought to elucidate LPL regulation under thermoneutral conditions (30 °C). To pursue this objective, we developed an antibody-based method to quantify (in a direct fashion) LPL levels inside capillaries. At 30 °C, intracapillary LPL levels fell sharply in brown adipose tissue (BAT) but not heart. The reduced intracapillary LPL levels were accompanied by reduced margination of TRLs along capillaries. ANGPTL4 expression in BAT increased fourfold at 30 °C, suggesting a potential explanation for the lower intracapillary LPL levels. Consistent with that idea, Angptl4 deficiency normalized both LPL levels and TRL margination in BAT at 30 °C. In Gpihbp1-/- mice housed at 30 °C, we observed an ANGPTL4-dependent decrease in LPL levels within the interstitial spaces of BAT, providing in vivo proof that ANGPTL4 regulates LPL levels before LPL transport into capillaries. In conclusion, our studies have illuminated intracapillary LPL regulation under thermoneutral conditions. Our approaches will be useful for defining the impact of genetic variation and metabolic disease on intracapillary LPL levels and TRL processing.
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Affiliation(s)
- Wenxin Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Ye Yang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Patrick Heizer
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Yiping Tu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Thomas A. Weston
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Joonyoung R. Kim
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Priscilla Munguia
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Hyesoo Jung
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Jared L.-C. Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Caitlyn Tran
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Michael Ploug
- Finsen Laboratory, RigshospitaletDK-2200Copenhagen N, Denmark
- Biotech Research and Innovation Centre, University of CopenhagenDK-220Copenhagen N, Denmark
| | - Anne P. Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Stephen G. Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Loren G. Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
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5
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Young SG, Song W, Yang Y, Birrane G, Jiang H, Beigneux AP, Ploug M, Fong LG. A protein of capillary endothelial cells, GPIHBP1, is crucial for plasma triglyceride metabolism. Proc Natl Acad Sci U S A 2022; 119:e2211136119. [PMID: 36037340 PMCID: PMC9457329 DOI: 10.1073/pnas.2211136119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 07/18/2022] [Indexed: 11/18/2022] Open
Abstract
GPIHBP1, a protein of capillary endothelial cells (ECs), is a crucial partner for lipoprotein lipase (LPL) in the lipolytic processing of triglyceride-rich lipoproteins. GPIHBP1, which contains a three-fingered cysteine-rich LU (Ly6/uPAR) domain and an intrinsically disordered acidic domain (AD), captures LPL from within the interstitial spaces (where it is secreted by parenchymal cells) and shuttles it across ECs to the capillary lumen. Without GPIHBP1, LPL remains stranded within the interstitial spaces, causing severe hypertriglyceridemia (chylomicronemia). Biophysical studies revealed that GPIHBP1 stabilizes LPL structure and preserves LPL activity. That discovery was the key to crystallizing the GPIHBP1-LPL complex. The crystal structure revealed that GPIHBP1's LU domain binds, largely by hydrophobic contacts, to LPL's C-terminal lipid-binding domain and that the AD is positioned to project across and interact, by electrostatic forces, with a large basic patch spanning LPL's lipid-binding and catalytic domains. We uncovered three functions for GPIHBP1's AD. First, it accelerates the kinetics of LPL binding. Second, it preserves LPL activity by inhibiting unfolding of LPL's catalytic domain. Third, by sheathing LPL's basic patch, the AD makes it possible for LPL to move across ECs to the capillary lumen. Without the AD, GPIHBP1-bound LPL is trapped by persistent interactions between LPL and negatively charged heparan sulfate proteoglycans (HSPGs) on the abluminal surface of ECs. The AD interrupts the HSPG interactions, freeing LPL-GPIHBP1 complexes to move across ECs to the capillary lumen. GPIHBP1 is medically important; GPIHBP1 mutations cause lifelong chylomicronemia, and GPIHBP1 autoantibodies cause some acquired cases of chylomicronemia.
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Affiliation(s)
- Stephen G. Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
| | - Wenxin Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
| | - Ye Yang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
| | - Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215
| | - Haibo Jiang
- Department of Chemistry, The University of Hong Kong, Hong Kong, China
| | - Anne P. Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen 2200N, Denmark
- Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Loren G. Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
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6
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Song W, Beigneux AP, Winther AML, Kristensen KK, Grønnemose AL, Yang Y, Tu Y, Munguia P, Morales J, Jung H, de Jong PJ, Jung CJ, Miyashita K, Kimura T, Nakajima K, Murakami M, Birrane G, Jiang H, Tontonoz P, Ploug M, Fong LG, Young SG. Electrostatic sheathing of lipoprotein lipase is essential for its movement across capillary endothelial cells. J Clin Invest 2022; 132:157500. [PMID: 35229724 PMCID: PMC8884915 DOI: 10.1172/jci157500] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 01/19/2022] [Indexed: 12/18/2022] Open
Abstract
GPIHBP1, an endothelial cell (EC) protein, captures lipoprotein lipase (LPL) within the interstitial spaces (where it is secreted by myocytes and adipocytes) and transports it across ECs to its site of action in the capillary lumen. GPIHBP1’s 3-fingered LU domain is required for LPL binding, but the function of its acidic domain (AD) has remained unclear. We created mutant mice lacking the AD and found severe hypertriglyceridemia. As expected, the mutant GPIHBP1 retained the capacity to bind LPL. Unexpectedly, however, most of the GPIHBP1 and LPL in the mutant mice was located on the abluminal surface of ECs (explaining the hypertriglyceridemia). The GPIHBP1-bound LPL was trapped on the abluminal surface of ECs by electrostatic interactions between the large basic patch on the surface of LPL and negatively charged heparan sulfate proteoglycans (HSPGs) on the surface of ECs. GPIHBP1 trafficking across ECs in the mutant mice was normalized by disrupting LPL-HSPG electrostatic interactions with either heparin or an AD peptide. Thus, GPIHBP1’s AD plays a crucial function in plasma triglyceride metabolism; it sheathes LPL’s basic patch on the abluminal surface of ECs, thereby preventing LPL-HSPG interactions and freeing GPIHBP1-LPL complexes to move across ECs to the capillary lumen.
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Affiliation(s)
- Wenxin Song
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Anne-Marie L Winther
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Kristian K Kristensen
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Anne L Grønnemose
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Ye Yang
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Yiping Tu
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Priscilla Munguia
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Jazmin Morales
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Hyesoo Jung
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Pieter J de Jong
- Children's Hospital Oakland Research Institute, Oakland, California, USA
| | - Cris J Jung
- Children's Hospital Oakland Research Institute, Oakland, California, USA
| | - Kazuya Miyashita
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan.,Immuno-Biological Laboratories (IBL), Fujioka, Gunma, Japan
| | - Takao Kimura
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
| | - Haibo Jiang
- Department of Chemistry, The University of Hong Kong, Hong Kong
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, UCLA, Los Angeles, California, USA
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Loren G Fong
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Stephen G Young
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA.,Department of Human Genetics, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
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Liu S, Wang Z, Zheng X, Zhang Y, Wei S, OuYang H, Liang J, Chen N, Zeng W, Jiang J. Case Report: Successful Management of a 29-Day-Old Infant With Severe Hyperlipidemia From a Novel Homozygous Variant of GPIHBP1 Gene. Front Pediatr 2022; 10:792574. [PMID: 35359903 PMCID: PMC8960264 DOI: 10.3389/fped.2022.792574] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Accepted: 02/03/2022] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND Severe hyperlipidemia is characterized by markedly elevated blood triglyceride levels and severe early-onset cardiovascular diseases, pancreatitis, pancreatic necrosis or persistent multiple organ failure if left untreated. It is a rare autosomal recessive metabolic disorder originated from the variants of lipoprotein lipase gene, and previous studies have demonstrated that most cases with severe hyperlipidemia are closely related to the variants of some key genes for lipolysis, such as LPL, APOC2, APOA5, LMF1, and GPIHBP1. Meanwhile, other unidentified causes also exist and are equally worthy of attention. METHODS The 29-day-old infant was diagnosed with severe hyperlipidemia, registering a plasma triglyceride level as high as 25.46 mmol/L. Whole exome sequencing was conducted to explore the possible pathogenic gene variants for this patient. RESULTS The infant was put on a low-fat diet combined with pharmacological therapy, which was successful in restraining the level of serum triglyceride and total cholesterol to a low to medium range during the follow-ups. The patient was found to be a rare novel homozygous duplication variant-c.45_48dupGCGG (Pro17Alafs*22) in GPIHBP1 gene-leading to a frameshift which failed to form the canonical termination codon TGA. The mutant messenger RNA should presumably produce a peptide consisting of 16 amino acids at the N-terminus, with 21 novel amino acids on the heels of the wild-type protein. CONCLUSIONS Our study expands on the spectrum of GPIHBP1 variants and contributes to a more comprehensive understanding of the genetic diagnosis, genetic counseling, and multimodality therapy of families with severe hyperlipidemia. Our experience gained in this study is also contributory to a deeper insight into severe hyperlipidemia and highlights the importance of molecular genetic tests.
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Affiliation(s)
- Shu Liu
- Children Inherited Metabolism and Endocrine Department, Guangdong Women and Children Hospital, Guangzhou, China
| | - Zhiqing Wang
- Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Xianhua Zheng
- Department of Clinical Laboratory, Guangdong Women and Children Hospital, Guangzhou, China
| | - Ye Zhang
- Children Inherited Metabolism and Endocrine Department, Guangdong Women and Children Hospital, Guangzhou, China
| | - Sisi Wei
- Children Inherited Metabolism and Endocrine Department, Guangdong Women and Children Hospital, Guangzhou, China
| | - Haimei OuYang
- Children Inherited Metabolism and Endocrine Department, Guangdong Women and Children Hospital, Guangzhou, China
| | - Jinqun Liang
- Children Inherited Metabolism and Endocrine Department, Guangdong Women and Children Hospital, Guangzhou, China
| | - Nuan Chen
- Children Inherited Metabolism and Endocrine Department, Guangdong Women and Children Hospital, Guangzhou, China
| | - Weihong Zeng
- Children Inherited Metabolism and Endocrine Department, Guangdong Women and Children Hospital, Guangzhou, China
| | - Jianhui Jiang
- Children Inherited Metabolism and Endocrine Department, Guangdong Women and Children Hospital, Guangzhou, China
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8
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Kristensen KK, Leth-Espensen KZ, Kumari A, Grønnemose AL, Lund-Winther AM, Young SG, Ploug M. GPIHBP1 and ANGPTL4 Utilize Protein Disorder to Orchestrate Order in Plasma Triglyceride Metabolism and Regulate Compartmentalization of LPL Activity. Front Cell Dev Biol 2021; 9:702508. [PMID: 34336854 PMCID: PMC8319833 DOI: 10.3389/fcell.2021.702508] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 06/23/2021] [Indexed: 12/12/2022] Open
Abstract
Intravascular processing of triglyceride-rich lipoproteins (TRLs) is crucial for delivery of dietary lipids fueling energy metabolism in heart and skeletal muscle and for storage in white adipose tissue. During the last decade, mechanisms underlying focal lipolytic processing of TRLs along the luminal surface of capillaries have been clarified by fresh insights into the functions of lipoprotein lipase (LPL); LPL's dedicated transporter protein, glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1); and its endogenous inhibitors, angiopoietin-like (ANGPTL) proteins 3, 4, and 8. Key discoveries in LPL biology include solving the crystal structure of LPL, showing LPL is catalytically active as a monomer rather than as a homodimer, and that the borderline stability of LPL's hydrolase domain is crucial for the regulation of LPL activity. Another key discovery was understanding how ANGPTL4 regulates LPL activity. The binding of ANGPTL4 to LPL sequences adjacent to the catalytic cavity triggers cooperative and sequential unfolding of LPL's hydrolase domain resulting in irreversible collapse of the catalytic cavity and loss of LPL activity. Recent studies have highlighted the importance of the ANGPTL3-ANGPTL8 complex for endocrine regulation of LPL activity in oxidative organs (e.g., heart, skeletal muscle, brown adipose tissue), but the molecular mechanisms have not been fully defined. New insights have also been gained into LPL-GPIHBP1 interactions and how GPIHBP1 moves LPL to its site of action in the capillary lumen. GPIHBP1 is an atypical member of the LU (Ly6/uPAR) domain protein superfamily, containing an intrinsically disordered and highly acidic N-terminal extension and a disulfide bond-rich three-fingered LU domain. Both the disordered acidic domain and the folded LU domain are crucial for the stability and transport of LPL, and for modulating its susceptibility to ANGPTL4-mediated unfolding. This review focuses on recent advances in the biology and biochemistry of crucial proteins for intravascular lipolysis.
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Affiliation(s)
- Kristian Kølby Kristensen
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Katrine Zinck Leth-Espensen
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Anni Kumari
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Anne Louise Grønnemose
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Anne-Marie Lund-Winther
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Stephen G Young
- Departments of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States.,Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
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9
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Luz JG, Beigneux AP, Asamoto DK, He C, Song W, Allan CM, Morales J, Tu Y, Kwok A, Cottle T, Meiyappan M, Fong LG, Kim JE, Ploug M, Young SG, Birrane G. The structural basis for monoclonal antibody 5D2 binding to the tryptophan-rich loop of lipoprotein lipase. J Lipid Res 2020; 61:1347-1359. [PMID: 32690595 DOI: 10.1194/jlr.ra120000993] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
For three decades, the LPL-specific monoclonal antibody 5D2 has been used to investigate LPL structure/function and intravascular lipolysis. 5D2 has been used to measure LPL levels, block the triglyceride hydrolase activity of LPL, and prevent the propensity of concentrated LPL preparations to form homodimers. Two early studies on the location of the 5D2 epitope reached conflicting conclusions, but the more convincing report suggested that 5D2 binds to a tryptophan (Trp)-rich loop in the carboxyl terminus of LPL. The same loop had been implicated in lipoprotein binding. Using surface plasmon resonance, we showed that 5D2 binds with high affinity to a synthetic LPL peptide containing the Trp-rich loop of human (but not mouse) LPL. We also showed, by both fluorescence and UV resonance Raman spectroscopy, that the Trp-rich loop binds lipids. Finally, we used X-ray crystallography to solve the structure of the Trp-rich peptide bound to a 5D2 Fab fragment. The Trp-rich peptide contains a short α-helix, with two Trps projecting into the antigen recognition site. A proline substitution in the α-helix, found in mouse LPL, is expected to interfere with several hydrogen bonds, explaining why 5D2 cannot bind to mouse LPL.
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Affiliation(s)
- John G Luz
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - DeeAnn K Asamoto
- Department of Chemistry and Biochemistry, University of California San Diego, San Diego, CA, USA
| | - Cuiwen He
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Wenxin Song
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Christopher M Allan
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Jazmin Morales
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Yiping Tu
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Adam Kwok
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Thomas Cottle
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Muthuraman Meiyappan
- Analytical Development, Pharmaceutical Sciences, Takeda Pharmaceutical Company, Lexington, MA, USA
| | - Loren G Fong
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Judy E Kim
- Department of Chemistry and Biochemistry, University of California San Diego, San Diego, CA, USA
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA .,Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA
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10
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Young SG, Fong LG, Beigneux AP, Allan CM, He C, Jiang H, Nakajima K, Meiyappan M, Birrane G, Ploug M. GPIHBP1 and Lipoprotein Lipase, Partners in Plasma Triglyceride Metabolism. Cell Metab 2019; 30:51-65. [PMID: 31269429 PMCID: PMC6662658 DOI: 10.1016/j.cmet.2019.05.023] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Lipoprotein lipase (LPL), identified in the 1950s, has been studied intensively by biochemists, physiologists, and clinical investigators. These efforts uncovered a central role for LPL in plasma triglyceride metabolism and identified LPL mutations as a cause of hypertriglyceridemia. By the 1990s, with an outline for plasma triglyceride metabolism established, interest in triglyceride metabolism waned. In recent years, however, interest in plasma triglyceride metabolism has awakened, in part because of the discovery of new molecules governing triglyceride metabolism. One such protein-and the focus of this review-is GPIHBP1, a protein of capillary endothelial cells. GPIHBP1 is LPL's essential partner: it binds LPL and transports it to the capillary lumen; it is essential for lipoprotein margination along capillaries, allowing lipolysis to proceed; and it preserves LPL's structure and activity. Recently, GPIHBP1 was the key to solving the structure of LPL. These developments have transformed the models for intravascular triglyceride metabolism.
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Affiliation(s)
- Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| | - Loren G Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Christopher M Allan
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Cuiwen He
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Haibo Jiang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; School of Molecular Sciences, University of Western Australia, Crawley 6009, Australia
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Department of Medicine, Maebashi, Gunma 371-0805, Japan
| | - Muthuraman Meiyappan
- Discovery Therapeutics, Takeda Pharmaceutical Company Ltd., Cambridge, MA 02142, USA
| | - Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen DK-2200, Denmark; Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen DK-2200, Denmark.
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11
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Abstract
Lipoprotein lipase (LPL), the enzyme that hydrolyzes triglycerides in plasma lipoproteins, is assumed to be active only as a homodimer. In support of this idea, several groups have reported that the size of LPL, as measured by density gradient ultracentrifugation, is ∼110 kDa, twice the size of LPL monomers (∼55 kDa). Of note, however, in those studies the LPL had been incubated with heparin, a polyanionic substance that binds and stabilizes LPL. Here we revisited the assumption that LPL is active only as a homodimer. When freshly secreted human LPL (or purified preparations of LPL) was subjected to density gradient ultracentrifugation (in the absence of heparin), LPL mass and activity peaks exhibited the size expected of monomers (near the 66-kDa albumin standard). GPIHBP1-bound LPL also exhibited the size expected for a monomer. In the presence of heparin, LPL size increased, overlapping with a 97.2-kDa standard. We also used density gradient ultracentrifugation to characterize the LPL within the high-salt and low-salt peaks from a heparin-Sepharose column. The catalytically active LPL within the high-salt peak exhibited the size of monomers, whereas most of the inactive LPL in the low-salt peak was at the bottom of the tube (in aggregates). Consistent with those findings, the LPL in the low-salt peak, but not that in the high-salt peak, was easily detectable with single mAb sandwich ELISAs, in which LPL is captured and detected with the same antibody. We conclude that catalytically active LPL can exist in a monomeric state.
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12
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Dong W, Yang J, Zhang Q, Jiang L. Role of GPIHBP1 in regulating milk protein traits in dairy cattle. Anim Biotechnol 2018; 31:81-85. [PMID: 30570382 DOI: 10.1080/10495398.2018.1536064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) is among the many candidate genes for regulating milk production traits in dairy cattle that have been identified via quantitative trait locus (QTL) mapping and genome-wide association studies (GWAS). Our previous studies confirmed that a G-to-A mutation at chr14:2553998 is the main cause of GPIHBP1-related effects on milk fat content. In this study, we discovered that GPIHBP1 may be a strong candidate gene for the regulation of milk protein traits. We performed overexpression and RNAi experiments to assess GPIHBP1 in bovine primary mammary epithelial cells (BMECs) and identified mRNA expression patterns of several important milk protein-related genes using real-time quantitative PCR. After the transient transfection of BMECs with GPIHBP1, the transcription levels of casein genes (CSN1S1, CSN1S2, CSN2, and CSN3) and lactoferrin (LTF) decreased, whereas beta-lactoglobulin (LGB) expression increased. The GPIHBP1 RNAi experiment produced changes in gene expression that were completely opposite to those observed in the GPIHBP1 overexpression experiment. Furthermore, among the assessed genes, CSN3, LTF, and LGB exhibited significant changes in mRNA expression (p < 0.05). The findings of this study show that bovine GPIHBP1 is involved in the process of milk protein biosynthesis and may be considered as a functional gene for the milk protein yield trait.
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Affiliation(s)
- Wanting Dong
- Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture & National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, P.R. China
| | - Jie Yang
- Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture & National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, P.R. China
| | - Qin Zhang
- Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture & National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, P.R. China
| | - Li Jiang
- Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture & National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, P.R. China
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13
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Structure of the lipoprotein lipase-GPIHBP1 complex that mediates plasma triglyceride hydrolysis. Proc Natl Acad Sci U S A 2018; 116:1723-1732. [PMID: 30559189 PMCID: PMC6358717 DOI: 10.1073/pnas.1817984116] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Lipoprotein lipase (LPL) is responsible for the intravascular processing of triglyceride-rich lipoproteins. The LPL within capillaries is bound to GPIHBP1, an endothelial cell protein with a three-fingered LU domain and an N-terminal intrinsically disordered acidic domain. Loss-of-function mutations in LPL or GPIHBP1 cause severe hypertriglyceridemia (chylomicronemia), but structures for LPL and GPIHBP1 have remained elusive. Inspired by our recent discovery that GPIHBP1's acidic domain preserves LPL structure and activity, we crystallized an LPL-GPIHBP1 complex and solved its structure. GPIHBP1's LU domain binds to LPL's C-terminal domain, largely by hydrophobic interactions. Analysis of electrostatic surfaces revealed that LPL contains a large basic patch spanning its N- and C-terminal domains. GPIHBP1's acidic domain was not defined in the electron density map but was positioned to interact with LPL's large basic patch, providing a likely explanation for how GPIHBP1 stabilizes LPL. The LPL-GPIHBP1 structure provides insights into mutations causing chylomicronemia.
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14
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Ariza MJ, Rioja J, Ibarretxe D, Camacho A, Díaz-Díaz JL, Mangas A, Carbayo-Herencia JA, Ruiz-Ocaña P, Lamíquiz-Moneo I, Mosquera D, Sáenz P, Masana L, Muñiz-Grijalvo O, Pérez-Calahorra S, Valdivielso P, Suárez Tembra M, Iglesias GP, Carbayo Herencia J, Guerrero Buitrago C, Vila L, Morales Coca C, Llargués Rocabruna E, Perea Castillo V, Pedro-Botet J, Climent E, Mauri Pont M, Pinto X, Ortega Martínez de la Victoria E, Amor J, Zambón Rados D, Blanco Vaca F, Ramiro Lozano J, Fuentes Jiménez F, Soler I, Ferrer C, Zamora Cervantes A, Vila Belmonte A, Novoa Mogollón F, Sanchez-Hernández R, Expósito Montesdeoca A, Romero Jiménez M, González García M, Bueno Díez M, Brea Hernando A, Lahoz C, Mostaza Prieto J, Millán Núñez-Cortés J, Reinares García L, Blanco Echevarría A, Ariza Corbo MJ, Rioja Villodres J, Sánchez-Chaparro M, Jansen Chaparro S, Sáenz Aranzubía P, Martorell Mateu E, Almagro Múgica F, Muñiz Grijalvo O, Masana Martín L, Plana Gil N, Ibarretxe Gerediaga D, Rodríguez Borjabad C, Zabala López S, Hernández Mijares A, Ascaso Gimilio J, Pérez García L, Civeira Murillo F, Pérez-Calahorra S, Lamiquiz-Moneo I, Mateo Gallego R, Marco Benedí V, Ferrando Vela J. Molecular basis of the familial chylomicronemia syndrome in patients from the National Dyslipidemia Registry of the Spanish Atherosclerosis Society. J Clin Lipidol 2018; 12:1482-1492.e3. [DOI: 10.1016/j.jacl.2018.07.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 07/09/2018] [Accepted: 07/24/2018] [Indexed: 01/16/2023]
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15
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Liu C, Li L, Guo D, Lv Y, Zheng X, Mo Z, Xie W. Lipoprotein lipase transporter GPIHBP1 and triglyceride-rich lipoprotein metabolism. Clin Chim Acta 2018; 487:33-40. [PMID: 30218660 DOI: 10.1016/j.cca.2018.09.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 09/11/2018] [Accepted: 09/11/2018] [Indexed: 02/05/2023]
Abstract
Increased plasma triglyceride serves as an independent risk factor for cardiovascular disease (CVD). Lipoprotein lipase (LPL), which hydrolyzes circulating triglyceride, plays a crucial role in normal lipid metabolism and energy balance. Hypertriglyceridemia is possibly caused by gene mutations resulting in LPL dysfunction. There are many factors that both positively and negatively interact with LPL thereby impacting TG lipolysis. Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1), a newly identified factor, appears essential for transporting LPL to the luminal side of the blood vessel and offering a platform for TG hydrolysis. Numerous lines of evidence indicate that GPIHBP1 exerts distinct functions and plays diverse roles in human triglyceride-rich lipoprotein (TRL) metabolism. In this review, we discuss the GPIHBP1 gene, protein, its expression and function and subsequently focus on its regulation and provide critical evidence supporting its role in TRL metabolism. Underlying mechanisms of action are highlighted, additional studies discussed and potential therapeutic targets reviewed.
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Affiliation(s)
- Chuhao Liu
- Clinical Anatomy & Reproductive Medicine Application Institute, University of South China, Hengyang 421001, Hunan, China; 2016 Class of Excellent Doctor, University of South China, Hengyang 421001, Hunan, China
| | - Liang Li
- Department of Pathophysiology, University of South China, Hengyang 421001, Hunan, China
| | - Dongming Guo
- Clinical Anatomy & Reproductive Medicine Application Institute, University of South China, Hengyang 421001, Hunan, China
| | - Yuncheng Lv
- Clinical Anatomy & Reproductive Medicine Application Institute, University of South China, Hengyang 421001, Hunan, China
| | - XiLong Zheng
- Department of Biochemistry and Molecular Biology, The Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, The University of Calgary, Health Sciences Center, 3330 Hospital Dr NW, Calgary T2N 4N1, Alberta, Canada; Key Laboratory of Molecular Targets & Clinical Pharmacology, School of Pharmaceutical Sciences, Guangzhou Medical University, Guangzhou 511436, Guangdong, China
| | - Zhongcheng Mo
- Clinical Anatomy & Reproductive Medicine Application Institute, University of South China, Hengyang 421001, Hunan, China.
| | - Wei Xie
- Clinical Anatomy & Reproductive Medicine Application Institute, University of South China, Hengyang 421001, Hunan, China.
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16
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A disordered acidic domain in GPIHBP1 harboring a sulfated tyrosine regulates lipoprotein lipase. Proc Natl Acad Sci U S A 2018; 115:E6020-E6029. [PMID: 29899144 DOI: 10.1073/pnas.1806774115] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The intravascular processing of triglyceride-rich lipoproteins depends on lipoprotein lipase (LPL) and GPIHBP1, a membrane protein of endothelial cells that binds LPL within the subendothelial spaces and shuttles it to the capillary lumen. In the absence of GPIHBP1, LPL remains mislocalized within the subendothelial spaces, causing severe hypertriglyceridemia (chylomicronemia). The N-terminal domain of GPIHBP1, an intrinsically disordered region (IDR) rich in acidic residues, is important for stabilizing LPL's catalytic domain against spontaneous and ANGPTL4-catalyzed unfolding. Here, we define several important properties of GPIHBP1's IDR. First, a conserved tyrosine in the middle of the IDR is posttranslationally modified by O-sulfation; this modification increases both the affinity of GPIHBP1-LPL interactions and the ability of GPIHBP1 to protect LPL against ANGPTL4-catalyzed unfolding. Second, the acidic IDR of GPIHBP1 increases the probability of a GPIHBP1-LPL encounter via electrostatic steering, increasing the association rate constant (kon) for LPL binding by >250-fold. Third, we show that LPL accumulates near capillary endothelial cells even in the absence of GPIHBP1. In wild-type mice, we expect that the accumulation of LPL in close proximity to capillaries would increase interactions with GPIHBP1. Fourth, we found that GPIHBP1's IDR is not a key factor in the pathogenicity of chylomicronemia in patients with the GPIHBP1 autoimmune syndrome. Finally, based on biophysical studies, we propose that the negatively charged IDR of GPIHBP1 traverses a vast space, facilitating capture of LPL by capillary endothelial cells and simultaneously contributing to GPIHBP1's ability to preserve LPL structure and activity.
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17
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He C, Hu X, Jung RS, Larsson M, Tu Y, Duarte-Vogel S, Kim P, Sandoval NP, Price TR, Allan CM, Raney B, Jiang H, Bensadoun A, Walzem RL, Kuo RI, Beigneux AP, Fong LG, Young SG. Lipoprotein lipase reaches the capillary lumen in chickens despite an apparent absence of GPIHBP1. JCI Insight 2017; 2:96783. [PMID: 29046479 DOI: 10.1172/jci.insight.96783] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 09/11/2017] [Indexed: 12/17/2022] Open
Abstract
In mammals, GPIHBP1 is absolutely essential for transporting lipoprotein lipase (LPL) to the lumen of capillaries, where it hydrolyzes the triglycerides in triglyceride-rich lipoproteins. In all lower vertebrate species (e.g., birds, amphibians, reptiles, fish), a gene for LPL can be found easily, but a gene for GPIHBP1 has never been found. The obvious question is whether the LPL in lower vertebrates is able to reach the capillary lumen. Using purified antibodies against chicken LPL, we showed that LPL is present on capillary endothelial cells of chicken heart and adipose tissue, colocalizing with von Willebrand factor. When the antibodies against chicken LPL were injected intravenously into chickens, they bound to LPL on the luminal surface of capillaries in heart and adipose tissue. LPL was released rapidly from chicken hearts with an infusion of heparin, consistent with LPL being located inside blood vessels. Remarkably, chicken LPL bound in a specific fashion to mammalian GPIHBP1. However, we could not identify a gene for GPIHBP1 in the chicken genome, nor could we identify a transcript for GPIHBP1 in a large chicken RNA-seq data set. We conclude that LPL reaches the capillary lumen in chickens - as it does in mammals - despite an apparent absence of GPIHBP1.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Tara R Price
- Department of Poultry Science and Faculty of Nutrition, Texas A&M University, College Station, Texas, USA
| | | | - Brian Raney
- University of California, Santa Cruz Genomics Institute and
| | - Haibo Jiang
- Department of Medicine and.,Centre for Microscopy, Characterisation, and Analysis, The University of Western Australia, Western Australia, Perth, Australia
| | - André Bensadoun
- Division of Nutritional Science, Cornell University, Ithaca, New York, USA
| | - Rosemary L Walzem
- Department of Poultry Science and Faculty of Nutrition, Texas A&M University, College Station, Texas, USA
| | - Richard I Kuo
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | | | | | - Stephen G Young
- Department of Medicine and.,Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
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18
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Functional validation of GPIHBP1 and identification of a functional mutation in GPIHBP1 for milk fat traits in dairy cattle. Sci Rep 2017; 7:8546. [PMID: 28819221 PMCID: PMC5561204 DOI: 10.1038/s41598-017-08668-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 07/12/2017] [Indexed: 11/08/2022] Open
Abstract
In a previous genome-wide association study (GWAS) on milk production traits in a Chinese Holstein population, we revealed that GPIHBP1 is a novel promising candidate gene for milk fat content traits. In this study, we performed over-expression and RNAi experiments on GPIHBP1 in bovine primary mammary epithelial cells. The results showed that the expression of several important milk fat-related genes (LPL, CD36, VLDLR, ACACA and FASN) increased or decreased when the expression of GPIHBP1 was up- or down-regulated. To identify the potential functional SNP involved, we explored the genetic variants of GPIHBP1 and found that a G/A mutation (chr14:2553998) in the promoter region of GPIHBP1 significantly reduced promoter activity and had an effect on transcription factor binding sites. This finding was consistent with the lower expression of GPIHBP1 observed in the mammary gland tissue of cows harboring the homozygous AA mutation compared with wild-type homozygous GG or heterozygous AG. Furthermore, association analysis showed that cows with the AA genotype outperformed those with the GG and AG genotypes in terms of the milk fat percentage. Our study demonstrates that GPIHBP1 could be a strong candidate gene for milk fat content traits and, in particular, the G to A mutation at chr14:2553998 within GPIHBP1 could be a functional mutation related to its effects.
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19
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GPIHBP1 autoantibodies in a patient with unexplained chylomicronemia. J Clin Lipidol 2017; 11:964-971. [PMID: 28666713 DOI: 10.1016/j.jacl.2017.05.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 05/23/2017] [Indexed: 12/28/2022]
Abstract
BACKGROUND GPIHBP1, a glycolipid-anchored protein of capillary endothelial cells, binds lipoprotein lipase (LPL) in the interstitial spaces and transports it to the capillary lumen. GPIHBP1 deficiency prevents LPL from reaching the capillary lumen, resulting in low intravascular LPL levels, impaired intravascular triglyceride processing, and severe hypertriglyceridemia (chylomicronemia). A recent study showed that some cases of hypertriglyceridemia are caused by autoantibodies against GPIHBP1 ("GPIHBP1 autoantibody syndrome"). OBJECTIVE Our objective was to gain additional insights into the frequency of the GPIHBP1 autoantibody syndrome in patients with unexplained chylomicronemia. METHODS We used enzyme-linked immunosorbent assays to screen for GPIHBP1 autoantibodies in 33 patients with unexplained chylomicronemia and then used Western blots and immunocytochemistry studies to characterize the GPIHBP1 autoantibodies. RESULTS The plasma of 1 patient, a 36-year-old man with severe hypertriglyceridemia, contained GPIHBP1 autoantibodies. The autoantibodies, which were easily detectable by Western blot, blocked the ability of GPIHBP1 to bind LPL. The plasma levels of LPL mass and activity were low. The patient had no history of autoimmune disease, but his plasma was positive for antinuclear antibodies. CONCLUSIONS One of 33 patients with unexplained chylomicronemia had the GPIHBP1 autoantibody syndrome. Additional studies in large lipid clinics will be helpful for better defining the frequency of this syndrome and for exploring the best strategies for treatment.
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20
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Allan CM, Jung CJ, Larsson M, Heizer PJ, Tu Y, Sandoval NP, Dang TLP, Jung RS, Beigneux AP, de Jong PJ, Fong LG, Young SG. Mutating a conserved cysteine in GPIHBP1 reduces amounts of GPIHBP1 in capillaries and abolishes LPL binding. J Lipid Res 2017; 58:1453-1461. [PMID: 28476858 DOI: 10.1194/jlr.m076943] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 05/04/2017] [Indexed: 12/22/2022] Open
Abstract
Mutation of conserved cysteines in proteins of the Ly6 family cause human disease-chylomicronemia in the case of glycosylphosphatidylinositol-anchored HDL binding protein 1 (GPIHBP1) and paroxysmal nocturnal hemoglobinuria in the case of CD59. A mutation in a conserved cysteine in CD59 prevented the protein from reaching the surface of blood cells. In contrast, mutation of conserved cysteines in human GPIHBP1 had little effect on GPIHBP1 trafficking to the surface of cultured CHO cells. The latter findings were somewhat surprising and raised questions about whether CHO cell studies accurately model the fate of mutant GPIHBP1 proteins in vivo. To explore this concern, we created mice harboring a GPIHBP1 cysteine mutation (p.C63Y). The p.C63Y mutation abolished the ability of mouse GPIHBP1 to bind LPL, resulting in severe chylomicronemia. The mutant GPIHBP1 was detectable by immunohistochemistry on the surface of endothelial cells, but the level of expression was ∼70% lower than in WT mice. The mutant GPIHBP1 protein in mouse tissues was predominantly monomeric. We conclude that mutation of a conserved cysteine in GPIHBP1 abolishes the ability of GPIHBP1 to bind LPL, resulting in mislocalization of LPL and severe chylomicronemia. The mutation reduced but did not eliminate GPIHBP1 on the surface of endothelial cells in vivo.
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Affiliation(s)
- Christopher M Allan
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Cris J Jung
- Children's Hospital Oakland Research Institute, Oakland, CA 94609
| | - Mikael Larsson
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Patrick J Heizer
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Yiping Tu
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Norma P Sandoval
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Tiffany Ly P Dang
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Rachel S Jung
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Anne P Beigneux
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095.
| | - Pieter J de Jong
- Children's Hospital Oakland Research Institute, Oakland, CA 94609
| | - Loren G Fong
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095.
| | - Stephen G Young
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095; Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095.
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Beigneux AP, Miyashita K, Ploug M, Blom DJ, Ai M, Linton MF, Khovidhunkit W, Dufour R, Garg A, McMahon MA, Pullinger CR, Sandoval NP, Hu X, Allan CM, Larsson M, Machida T, Murakami M, Reue K, Tontonoz P, Goldberg IJ, Moulin P, Charrière S, Fong LG, Nakajima K, Young SG. Autoantibodies against GPIHBP1 as a Cause of Hypertriglyceridemia. N Engl J Med 2017; 376:1647-1658. [PMID: 28402248 PMCID: PMC5555413 DOI: 10.1056/nejmoa1611930] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
BACKGROUND A protein that is expressed on capillary endothelial cells, called GPIHBP1 (glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1), binds lipoprotein lipase and shuttles it to its site of action in the capillary lumen. A deficiency in GPIHBP1 prevents lipoprotein lipase from reaching the capillary lumen. Patients with GPIHBP1 deficiency have low plasma levels of lipoprotein lipase, impaired intravascular hydrolysis of triglycerides, and severe hypertriglyceridemia (chylomicronemia). During the characterization of a monoclonal antibody-based immunoassay for GPIHBP1, we encountered two plasma samples (both from patients with chylomicronemia) that contained an interfering substance that made it impossible to measure GPIHBP1. That finding raised the possibility that those samples might contain GPIHBP1 autoantibodies. METHODS Using a combination of immunoassays, Western blot analyses, and immunocytochemical studies, we tested the two plasma samples (as well as samples from other patients with chylomicronemia) for the presence of GPIHBP1 autoantibodies. We also tested the ability of GPIHBP1 autoantibodies to block the binding of lipoprotein lipase to GPIHBP1. RESULTS We identified GPIHBP1 autoantibodies in six patients with chylomicronemia and found that these autoantibodies blocked the binding of lipoprotein lipase to GPIHBP1. As in patients with GPIHBP1 deficiency, those with GPIHBP1 autoantibodies had low plasma levels of lipoprotein lipase. Three of the six patients had systemic lupus erythematosus. One of these patients who had GPIHBP1 autoantibodies delivered a baby with plasma containing maternal GPIHBP1 autoantibodies; the infant had severe but transient chylomicronemia. Two of the patients with chylomicronemia and GPIHBP1 autoantibodies had a response to treatment with immunosuppressive agents. CONCLUSIONS In six patients with chylomicronemia, GPIHBP1 autoantibodies blocked the ability of GPIHBP1 to bind and transport lipoprotein lipase, thereby interfering with lipoprotein lipase-mediated processing of triglyceride-rich lipoproteins and causing severe hypertriglyceridemia. (Funded by the National Heart, Lung, and Blood Institute and the Leducq Foundation.).
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Affiliation(s)
- Anne P Beigneux
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Kazuya Miyashita
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Michael Ploug
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Dirk J Blom
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Masumi Ai
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - MacRae F Linton
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Weerapan Khovidhunkit
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Robert Dufour
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Abhimanyu Garg
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Maureen A McMahon
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Clive R Pullinger
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Norma P Sandoval
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Xuchen Hu
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Christopher M Allan
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Mikael Larsson
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Tetsuo Machida
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Masami Murakami
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Karen Reue
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Peter Tontonoz
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Ira J Goldberg
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Philippe Moulin
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Sybil Charrière
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Loren G Fong
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Katsuyuki Nakajima
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Stephen G Young
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
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Stroes E, Moulin P, Parhofer KG, Rebours V, Löhr JM, Averna M. Diagnostic algorithm for familial chylomicronemia syndrome. ATHEROSCLEROSIS SUPP 2017; 23:1-7. [PMID: 27998715 DOI: 10.1016/j.atherosclerosissup.2016.10.002] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Hu X, Sleeman MW, Miyashita K, Linton MF, Allan CM, He C, Larsson M, Tu Y, Sandoval NP, Jung RS, Mapar A, Machida T, Murakami M, Nakajima K, Ploug M, Fong LG, Young SG, Beigneux AP. Monoclonal antibodies that bind to the Ly6 domain of GPIHBP1 abolish the binding of LPL. J Lipid Res 2016; 58:208-215. [PMID: 27875259 DOI: 10.1194/jlr.m072462] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 10/31/2016] [Indexed: 01/18/2023] Open
Abstract
GPIHBP1, an endothelial cell protein, binds LPL in the interstitial spaces and shuttles it to its site of action inside blood vessels. For years, studies of human GPIHBP1 have been hampered by an absence of useful antibodies. We reasoned that monoclonal antibodies (mAbs) against human GPIHBP1 would be useful for 1) defining the functional relevance of GPIHBP1's Ly6 and acidic domains to the binding of LPL; 2) ascertaining whether human GPIHBP1 is expressed exclusively in capillary endothelial cells; and 3) testing whether GPIHBP1 is detectable in human plasma. Here, we report the development of a panel of human GPIHBP1-specific mAbs. Two mAbs against GPIHBP1's Ly6 domain, RE3 and RG3, abolished LPL binding, whereas an antibody against the acidic domain, RF4, did not. Also, mAbs RE3 and RG3 bound with reduced affinity to a mutant GPIHBP1 containing an Ly6 domain mutation (W109S) that abolishes LPL binding. Immunohistochemistry studies with the GPIHBP1 mAbs revealed that human GPIHBP1 is expressed only in capillary endothelial cells. Finally, we created an ELISA that detects GPIHBP1 in human plasma. That ELISA should make it possible for clinical lipidologists to determine whether plasma GPIHBP1 levels are a useful biomarker of metabolic or vascular disease.
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Affiliation(s)
- Xuchen Hu
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Mark W Sleeman
- Monash Biomedicine Discovery Institute and Antibody Technologies Facility, Monash University, Victoria, Australia
| | - Kazuya Miyashita
- Department of Clinical Laboratory Medicine, Graduate School of Medicine, Gunma University, Maebashi, Japan
| | - MacRae F Linton
- Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville, TN
| | - Christopher M Allan
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Cuiwen He
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Mikael Larsson
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Yiping Tu
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Norma P Sandoval
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Rachel S Jung
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Alaleh Mapar
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Tetsuo Machida
- Department of Clinical Laboratory Medicine, Graduate School of Medicine, Gunma University, Maebashi, Japan
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Graduate School of Medicine, Gunma University, Maebashi, Japan
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Graduate School of Medicine, Gunma University, Maebashi, Japan
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Loren G Fong
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Stephen G Young
- Departments of Medicine University of California Los Angeles, Los Angeles, CA .,Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Anne P Beigneux
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
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Allan CM, Larsson M, Hu X, He C, Jung RS, Mapar A, Voss C, Miyashita K, Machida T, Murakami M, Nakajima K, Bensadoun A, Ploug M, Fong LG, Young SG, Beigneux AP. An LPL-specific monoclonal antibody, 88B8, that abolishes the binding of LPL to GPIHBP1. J Lipid Res 2016; 57:1889-1898. [PMID: 27494936 DOI: 10.1194/jlr.m070813] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Indexed: 12/26/2022] Open
Abstract
LPL contains two principal domains: an amino-terminal catalytic domain (residues 1-297) and a carboxyl-terminal domain (residues 298-448) that is important for binding lipids and binding glycosylphosphatidylinositol-anchored high density lipoprotein binding protein 1 (GPIHBP1) (an endothelial cell protein that shuttles LPL to the capillary lumen). The LPL sequences required for GPIHBP1 binding have not been examined in detail, but one study suggested that sequences near LPL's carboxyl terminus (residues ∼403-438) were crucial. Here, we tested the ability of LPL-specific monoclonal antibodies (mAbs) to block the binding of LPL to GPIHBP1. One antibody, 88B8, abolished LPL binding to GPIHBP1. Consistent with those results, antibody 88B8 could not bind to GPIHBP1-bound LPL on cultured cells. Antibody 88B8 bound poorly to LPL proteins with amino acid substitutions that interfered with GPIHBP1 binding (e.g., C418Y, E421K). However, the sequences near LPL's carboxyl terminus (residues ∼403-438) were not sufficient for 88B8 binding; upstream sequences (residues 298-400) were also required. Additional studies showed that these same sequences are required for LPL binding to GPIHBP1. In conclusion, we identified an LPL mAb that binds to LPL's GPIHBP1-binding domain. The binding of both antibody 88B8 and GPIHBP1 to LPL depends on large segments of LPL's carboxyl-terminal domain.
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Affiliation(s)
- Christopher M Allan
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Mikael Larsson
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Xuchen Hu
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Cuiwen He
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Rachel S Jung
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Alaleh Mapar
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Constance Voss
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | | | - Tetsuo Machida
- Gunma University, Graduate School of Medicine, Maebashi, Japan
| | - Masami Murakami
- Gunma University, Graduate School of Medicine, Maebashi, Japan
| | | | - André Bensadoun
- Division of Nutritional Science, Cornell University, Ithaca, NY
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen N, Denmark; Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen N, Denmark
| | - Loren G Fong
- Departments of Medicine University of California Los Angeles, Los Angeles, CA.
| | - Stephen G Young
- Departments of Medicine University of California Los Angeles, Los Angeles, CA; Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA.
| | - Anne P Beigneux
- Departments of Medicine University of California Los Angeles, Los Angeles, CA.
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Fong LG, Young SG, Beigneux AP, Bensadoun A, Oberer M, Jiang H, Ploug M. GPIHBP1 and Plasma Triglyceride Metabolism. Trends Endocrinol Metab 2016; 27:455-469. [PMID: 27185325 PMCID: PMC4927088 DOI: 10.1016/j.tem.2016.04.013] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 04/26/2016] [Accepted: 04/27/2016] [Indexed: 10/21/2022]
Abstract
GPIHBP1, a GPI-anchored protein in capillary endothelial cells, is crucial for the lipolytic processing of triglyceride-rich lipoproteins (TRLs). GPIHBP1 shuttles lipoprotein lipase (LPL) to its site of action in the capillary lumen and is essential for the margination of TRLs along capillaries - such that lipolytic processing can proceed. GPIHBP1 also reduces the unfolding of the LPL catalytic domain, thereby stabilizing LPL catalytic activity. Many different GPIHBP1 mutations have been identified in patients with severe hypertriglyceridemia (chylomicronemia), the majority of which interfere with folding of the protein and abolish its capacity to bind and transport LPL. The discovery of GPIHBP1 has substantially revised our understanding of intravascular triglyceride metabolism but has also raised many new questions for future research.
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Affiliation(s)
- Loren G Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
| | - Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA; Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - André Bensadoun
- Division of Nutritional Science, Cornell University, Ithaca, NY 14853, USA
| | - Monika Oberer
- Institute of Molecular Biosciences, University of Graz and BioTechMed, Graz, Austria
| | - Haibo Jiang
- Centre for Microscopy, Characterisation, and Analysis, The University of Western Australia
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, 2200 Copenhagen N, Denmark; Biotech Research and Innovation Centre (BRIC), University of Copenhagen, 220 Copenhagen N, Denmark.
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Abstract
PURPOSE OF REVIEW A major step in energy metabolism is hydrolysis of triacylglycerol-rich lipoproteins (TRLs) to release fatty acids that can be used or stored. This is accomplished by lipoprotein lipase (LPL) at 'binding lipolysis sites' at the vascular endothelium. A multitude of interactions are involved in this seemingly simple reaction. Recent advances in the understanding of some of these factors will be discussed in an attempt to build a comprehensive picture. RECENT FINDINGS The first event in catabolism of TRLs is that they dock at the vascular endothelium. This requires LPL and GPIHBP1, the endothelial transporter of LPL.Kinetic studies in rats with labeled chylomicrons showed that once a chylomicron has docked in the heart it stays for minutes and a large number of triacylglycerol molecules are split. The distribution of binding between tissues reflects the amount of LPL, as evident from studies with mutant mice.Clearance of TRLs is often slowed down in metabolic disease, as was demonstrated both in mice and men. In mice, this was directly connected to decreased amounts of endothelial LPL. SUMMARY The LPL system is central in energy metabolism and results from interplay between several factors. Rapid and exciting progress is being made.
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Affiliation(s)
- Gunilla Olivecrona
- Department of Medical Biosciences/Physiological Chemistry, Umeå University, Umeå, Sweden
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Dijk W, Beigneux AP, Larsson M, Bensadoun A, Young SG, Kersten S. Angiopoietin-like 4 promotes intracellular degradation of lipoprotein lipase in adipocytes. J Lipid Res 2016; 57:1670-83. [PMID: 27034464 DOI: 10.1194/jlr.m067363] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Indexed: 01/17/2023] Open
Abstract
LPL hydrolyzes triglycerides in triglyceride-rich lipoproteins along the capillaries of heart, skeletal muscle, and adipose tissue. The activity of LPL is repressed by angiopoietin-like 4 (ANGPTL4) but the underlying mechanisms have not been fully elucidated. Our objective was to study the cellular location and mechanism for LPL inhibition by ANGPTL4. We performed studies in transfected cells, ex vivo studies, and in vivo studies with Angptl4(-/-) mice. Cotransfection of CHO pgsA-745 cells with ANGPTL4 and LPL reduced intracellular LPL protein levels, suggesting that ANGPTL4 promotes LPL degradation. This conclusion was supported by studies of primary adipocytes and adipose tissue explants from wild-type and Angptl4(-/-) mice. Absence of ANGPTL4 resulted in accumulation of the mature-glycosylated form of LPL and increased secretion of LPL. Blocking endoplasmic reticulum (ER)-Golgi transport abolished differences in LPL abundance between wild-type and Angptl4(-/-) adipocytes, suggesting that ANGPTL4 acts upon LPL after LPL processing in the ER. Finally, physiological changes in adipose tissue ANGPTL4 expression during fasting and cold resulted in inverse changes in the amount of mature-glycosylated LPL in wild-type mice, but not Angptl4(-/-) mice. We conclude that ANGPTL4 promotes loss of intracellular LPL by stimulating LPL degradation after LPL processing in the ER.
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Affiliation(s)
- Wieneke Dijk
- Nutrition, Metabolism, and Genomics Group, Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands
| | - Anne P Beigneux
- Departments of Medicine David Geffen School of Medicine, University of California, Los Angeles, CA
| | - Mikael Larsson
- Departments of Medicine David Geffen School of Medicine, University of California, Los Angeles, CA
| | - André Bensadoun
- Division of Nutritional Sciences, Cornell University, Ithaca, NY
| | - Stephen G Young
- Departments of Medicine David Geffen School of Medicine, University of California, Los Angeles, CA Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA
| | - Sander Kersten
- Nutrition, Metabolism, and Genomics Group, Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands Division of Nutritional Sciences, Cornell University, Ithaca, NY
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Clinical and genetic features of 3 patients with familial chylomicronemia due to mutations in GPIHBP1 gene. J Clin Lipidol 2016; 10:915-921.e4. [PMID: 27578123 DOI: 10.1016/j.jacl.2016.03.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 03/11/2016] [Accepted: 03/12/2016] [Indexed: 12/30/2022]
Abstract
BACKGROUND Familial chylomicronemia is a recessive disorder that may be due to mutations in lipoprotein lipase (LPL) and in other proteins such as apolipoprotein C-II and apolipoprotein A-V (activators of LPL), GPIHBP1 (the molecular platform required for LPL activity on endothelial surface), and LMF1 (a factor required for intracellular formation of active LPL). METHODS We sequenced the familial chylomicronemia candidate genes in 2 adult females presenting long-standing hypertriglyceridemia and a history of acute pancreatitis. RESULTS Both probands had plasma triglyceride >10 mmol/L but no mutations in the LPL gene. The sequence of the other candidate genes showed that one patient was homozygous for a novel missense mutation p.(Cys83Arg), and the other was homozygous for a previously reported nonsense mutation p.(Cys 89*), respectively, in GPIHBP1. Family screening showed that the hypertriglyceridemic brother of the p.(Cys83Arg) homozygote was also homozygous for this mutation. He had no history of pancreatitis. The p.(Cys83Arg) heterozygous carriers had normal triglyceride levels. The substitution of a cysteine residue in the Ly6 domain of GPIHBP1 is predicted to abolish one of the disulfide bridges required to maintain the structure of GPIHBP1. The p.(Cys89*) mutation results in a truncated protein devoid of function. CONCLUSIONS Both mutant GPIHBP1 proteins are expected to be incapable of transferring LPL from the subendothelial space to the endothelial surface.
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Mysling S, Kristensen KK, Larsson M, Beigneux AP, Gårdsvoll H, Fong LG, Bensadouen A, Jørgensen TJ, Young SG, Ploug M. The acidic domain of the endothelial membrane protein GPIHBP1 stabilizes lipoprotein lipase activity by preventing unfolding of its catalytic domain. eLife 2016; 5:e12095. [PMID: 26725083 PMCID: PMC4755760 DOI: 10.7554/elife.12095] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 01/02/2016] [Indexed: 12/19/2022] Open
Abstract
GPIHBP1 is a glycolipid-anchored membrane protein of capillary endothelial cells that binds lipoprotein lipase (LPL) within the interstitial space and shuttles it to the capillary lumen. The LPL•GPIHBP1 complex is responsible for margination of triglyceride-rich lipoproteins along capillaries and their lipolytic processing. The current work conceptualizes a model for the GPIHBP1•LPL interaction based on biophysical measurements with hydrogen-deuterium exchange/mass spectrometry, surface plasmon resonance, and zero-length cross-linking. According to this model, GPIHBP1 comprises two functionally distinct domains: (1) an intrinsically disordered acidic N-terminal domain; and (2) a folded C-terminal domain that tethers GPIHBP1 to the cell membrane by glycosylphosphatidylinositol. We demonstrate that these domains serve different roles in regulating the kinetics of LPL binding. Importantly, the acidic domain stabilizes LPL catalytic activity by mitigating the global unfolding of LPL's catalytic domain. This study provides a conceptual framework for understanding intravascular lipolysis and GPIHBP1 and LPL mutations causing familial chylomicronemia. DOI:http://dx.doi.org/10.7554/eLife.12095.001 Fat is an important part of our diet. The intestines absorb fats and package them into particles called lipoproteins. After reaching the bloodstream, the fat molecules (lipids) in the lipoproteins are broken down by an enzyme called lipoprotein lipase (LPL), which is located along the surface of small blood vessels. This releases nutrients that can be used by vital tissues – mainly the heart, skeletal muscle, and adipose tissues. LPL is produced by muscle and adipose tissue, but it is quickly swept up by a protein called GPIHBP1 and shuttled to its site of action inside the blood vessels. Mutations that alter the structure of LPL or GPIHBP1 can prevent the breakdown of lipids, resulting in high levels of lipids in the blood. This can lead to inflammation in the pancreas and also increases the risk of heart attacks and strokes. Many earlier studies have examined the properties of LPL, but our understanding of GPIHBP1 has been limited, mainly because it has been difficult to purify GPIHBP1 for analysis. Using genetically altered insect cells, Mysling et al. were able to purify two different forms of GPIHBP1 – a full-length version and a shorter version that lacked a small section at the end of the molecule known as the acidic domain. This revealed that the opposite end of the molecule – called the carboxyl-terminal domain – is primarily responsible for binding LPL and anchoring it inside blood vessels. Once LPL is bound to GPIHBP1, the acidic domain of GPIHBP1 helps to stabilize LPL. If GPIHBP1’s acidic domain is missing then LPL is more susceptible to losing its structure, rendering it incapable of breaking down the lipids in the blood. Mysling et al. describe a new model for how LPL and GPIHBP1 interact that explains how specific mutations in the genes that encode these proteins interfere with the delivery of LPL to small blood vessels. In the future, this could help researchers to develop new strategies to treat people with high levels of lipids in their blood. DOI:http://dx.doi.org/10.7554/eLife.12095.002
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Affiliation(s)
- Simon Mysling
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.,Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Kristian Kølby Kristensen
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Mikael Larsson
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Anne P Beigneux
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Henrik Gårdsvoll
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Loren G Fong
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - André Bensadouen
- Division of Nutritional Science, Cornell University, Ithaca, United States
| | - Thomas Jd Jørgensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Stephen G Young
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States.,Department of Human Genetics, University of California, Los Angeles, Los Angeles, United States
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
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Ariza MJ, Martínez-Hernández PL, Ibarretxe D, Rabacchi C, Rioja J, Grande-Aragón C, Plana N, Tarugi P, Olivecrona G, Calandra S, Valdivielso P. Novel mutations in the GPIHBP1 gene identified in 2 patients with recurrent acute pancreatitis. J Clin Lipidol 2015; 10:92-100.e1. [PMID: 26892125 DOI: 10.1016/j.jacl.2015.09.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 09/09/2015] [Accepted: 09/16/2015] [Indexed: 11/16/2022]
Abstract
BACKGROUND Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) has been demonstrated to be essential for the in vivo function of lipoprotein lipase (LPL), the major triglyceride (TG)-hydrolyzing enzyme involved in the intravascular lipolysis of TG-rich lipoproteins. Recently, loss-of-function mutations of GPIHBP1 have been reported as the cause of type I hyperlipoproteinemia in several patients. METHODS Two unrelated patients were referred to our Lipid Units because of a severe hypertriglyceridemia and recurrent pancreatitis. We measured LPL activity in postheparin plasma and serum ApoCII and sequenced LPL, APOC2, and GPIHBP1. RESULTS The 2 patients exhibited very low LPL activity not associated with mutations in LPL gene or with ApoCII deficiency. The sequence of GPIHBP1 revealed 2 novel point mutations. One patient (proband 1) was found to be homozygous for a C>A transversion in exon 3 resulting in the conversion of threonine to lysine at position 80 (p.Thr80Lys). The other patient (proband 2) was found to be homozygous for a G>T transversion in the third base of the ATG translation initiation codon in exon 1, resulting in the conversion of methionine to isoleucine (p.Met1Ile). CONCLUSION In conclusion, we have identified 2 novel GPIHBP1 missense mutations in 2 unrelated patients as the cause of their severe hypertriglyceridemia.
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Affiliation(s)
- María José Ariza
- Department of Medicine and Dermatology, Lipids and Atherosclerosis Laboratory, CIMES, University of Málaga, Málaga, Spain.
| | | | - Daiana Ibarretxe
- Vascular Medicine and Metabolism Unit, Research Unit on Lipids and Atherosclerosis, Sant Joan University Hospital, Universitat Rovira i Virgili, IISPV, Spanish Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM), Reus, Spain
| | - Claudio Rabacchi
- Department of Life Sciences, University of Modena & Reggio Emilia, Modena, Italy
| | - José Rioja
- Department of Medicine and Dermatology, Lipids and Atherosclerosis Laboratory, CIMES, University of Málaga, Málaga, Spain
| | | | - Nuria Plana
- Vascular Medicine and Metabolism Unit, Research Unit on Lipids and Atherosclerosis, Sant Joan University Hospital, Universitat Rovira i Virgili, IISPV, Spanish Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM), Reus, Spain
| | - Patrizia Tarugi
- Department of Life Sciences, University of Modena & Reggio Emilia, Modena, Italy
| | - Gunilla Olivecrona
- Department of Medical Biosciences, Physiological Chemistry, Umeå University, Umeå, Sweden
| | - Sebastiano Calandra
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena & Reggio Emilia Modena, Italy
| | - Pedro Valdivielso
- Department of Medicine and Dermatology, Lipids and Atherosclerosis Laboratory, CIMES, University of Málaga, Málaga, Spain; Internal Medicine Unit, Virgen de la Victoria University Hospital, Málaga, Spain
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31
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Adeyo O, Oberer M, Ploug M, Fong LG, Young SG, Beigneux AP. Heterogeneity in the properties of mutant secreted lymphocyte antigen 6/urokinase receptor-related protein 1 (SLURP1) in Mal de Meleda. Br J Dermatol 2015; 173:1066-9. [PMID: 25919322 DOI: 10.1111/bjd.13868] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- O Adeyo
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, 90095, CA, U.S.A
| | - M Oberer
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/3, A-8010, Graz, Austria
| | - M Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark
| | - L G Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, 90095, CA, U.S.A
| | - S G Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, 90095, CA, U.S.A.,Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, 90095, CA, U.S.A
| | - A P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, 90095, CA, U.S.A
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32
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Reimund M, Larsson M, Kovrov O, Kasvandik S, Olivecrona G, Lookene A. Evidence for Two Distinct Binding Sites for Lipoprotein Lipase on Glycosylphosphatidylinositol-anchored High Density Lipoprotein-binding Protein 1 (GPIHBP1). J Biol Chem 2015; 290:13919-34. [PMID: 25873395 DOI: 10.1074/jbc.m114.634626] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Indexed: 01/20/2023] Open
Abstract
GPIHBP1 is an endothelial membrane protein that transports lipoprotein lipase (LPL) from the subendothelial space to the luminal side of the capillary endothelium. Here, we provide evidence that two regions of GPIHBP1, the acidic N-terminal domain and the central Ly6 domain, interact with LPL as two distinct binding sites. This conclusion is based on comparative binding studies performed with a peptide corresponding to the N-terminal domain of GPIHBP1, the Ly6 domain of GPIHBP1, wild type GPIHBP1, and the Ly6 domain mutant GPIHBP1 Q114P. Although LPL and the N-terminal domain formed a tight but short lived complex, characterized by fast on- and off-rates, the complex between LPL and the Ly6 domain formed more slowly and persisted for a longer time. Unlike the interaction of LPL with the Ly6 domain, the interaction of LPL with the N-terminal domain was significantly weakened by salt. The Q114P mutant bound LPL similarly to the N-terminal domain of GPIHBP1. Heparin dissociated LPL from the N-terminal domain, and partially from wild type GPIHBP1, but was unable to elute the enzyme from the Ly6 domain. When LPL was in complex with the acidic peptide corresponding to the N-terminal domain of GPIHBP1, the enzyme retained its affinity for the Ly6 domain. Furthermore, LPL that was bound to the N-terminal domain interacted with lipoproteins, whereas LPL bound to the Ly6 domain did not. In summary, our data suggest that the two domains of GPIHBP1 interact independently with LPL and that the functionality of LPL depends on its localization on GPIHBP1.
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Affiliation(s)
- Mart Reimund
- From the Department of Chemistry, Tallinn University of Technology, Tallinn 12618, Estonia
| | - Mikael Larsson
- the Department of Medical Biosciences, Umeå University, SE-901 87 Umeå, Sweden, and
| | - Oleg Kovrov
- the Department of Medical Biosciences, Umeå University, SE-901 87 Umeå, Sweden, and
| | - Sergo Kasvandik
- the Institute of Technology, University of Tartu, Tartu 50411, Estonia
| | - Gunilla Olivecrona
- the Department of Medical Biosciences, Umeå University, SE-901 87 Umeå, Sweden, and
| | - Aivar Lookene
- From the Department of Chemistry, Tallinn University of Technology, Tallinn 12618, Estonia,
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33
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Intrinsic and extrinsic regulation of cardiac lipoprotein lipase following diabetes. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1851:163-71. [PMID: 25463481 DOI: 10.1016/j.bbalip.2014.11.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Revised: 11/10/2014] [Accepted: 11/12/2014] [Indexed: 02/07/2023]
Abstract
Cardiac lipoprotein lipase (LPL) is a pivotal enzyme controlling heart metabolism by providing the majority of fatty acids required by this organ. From activation in cardiomyocytes to secretion to the vascular lumen, cardiac LPL is regulated by multiple pathways, which are altered during diabetes. Hence, dimerization/activation of LPL is modified following diabetes, a process controlled by lipase maturation factor 1. The role of AMP-activated protein kinase, protein kinase D, and heparan sulfate proteoglycans, intrinsic factors that regulate the intracellular transport of LPL is also shifted, and is discussed. More recent studies have identified several exogenous factors released from endothelial cells (EC) and adipose tissue that are required for proper functioning of LPL. In response to hyperglycemia, both active and latent heparanase are released from EC to facilitate LPL secretion. Diabetes also increased the expression of glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) in EC, which mediates the transport of LPL across EC. Angiopoietin-like protein 4 secreted from the adipose tissue has the potential to reduce coronary LPL activity. Knowledge of these intrinsic and extrinsic factors could be used develop therapeutic targets to normalize LPL function, and maintain cardiac energy homeostasis after diabetes.
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Beigneux AP, Fong LG, Bensadoun A, Davies BSJ, Oberer M, Gårdsvoll H, Ploug M, Young SG. GPIHBP1 missense mutations often cause multimerization of GPIHBP1 and thereby prevent lipoprotein lipase binding. Circ Res 2014; 116:624-32. [PMID: 25387803 DOI: 10.1161/circresaha.116.305085] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
RATIONALE GPIHBP1, a GPI-anchored protein of capillary endothelial cells, binds lipoprotein lipase (LPL) in the subendothelial spaces and shuttles it to the capillary lumen. GPIHBP1 missense mutations that interfere with LPL binding cause familial chylomicronemia. OBJECTIVE We sought to understand mechanisms by which GPIHBP1 mutations prevent LPL binding and lead to chylomicronemia. METHODS AND RESULTS We expressed mutant forms of GPIHBP1 in Chinese hamster ovary cells, rat and human endothelial cells, and Drosophila S2 cells. In each expression system, mutation of cysteines in GPIHBP1's Ly6 domain (including mutants identified in patients with chylomicronemia) led to the formation of disulfide-linked dimers and multimers. GPIHBP1 dimerization/multimerization was not unique to cysteine mutations; mutations in other amino acid residues, including several associated with chylomicronemia, also led to protein dimerization/multimerization. The loss of GPIHBP1 monomers is relevant to the pathogenesis of chylomicronemia because only GPIHBP1 monomers-and not dimers or multimers-are capable of binding LPL. One GPIHBP1 mutant, GPIHBP1-W109S, had distinctive properties. GPIHBP1-W109S lacked the ability to bind LPL but had a reduced propensity for forming dimers or multimers, suggesting that W109 might play a more direct role in binding LPL. In support of that idea, replacing W109 with any of 8 other amino acids abolished LPL binding-and often did so without promoting the formation of dimers and multimers. CONCLUSIONS Many amino acid substitutions in GPIHBP1's Ly6 domain that abolish LPL binding lead to protein dimerization/multimerization. Dimerization/multimerization is relevant to disease pathogenesis, given that only GPIHBP1 monomers are capable of binding LPL.
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Affiliation(s)
- Anne P Beigneux
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles.
| | - Loren G Fong
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
| | - André Bensadoun
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
| | - Brandon S J Davies
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
| | - Monika Oberer
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
| | - Henrik Gårdsvoll
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
| | - Michael Ploug
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
| | - Stephen G Young
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
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Buonuomo PS, Bartuli A, Rabacchi C, Bertolini S, Calandra S. A 3-day-old neonate with severe hypertriglyceridemia from novel mutations of the GPIHBP1 gene. J Clin Lipidol 2014; 9:265-70. [PMID: 25911085 DOI: 10.1016/j.jacl.2014.10.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 10/01/2014] [Accepted: 10/06/2014] [Indexed: 12/16/2022]
Abstract
BACKGROUND Familial chylomicronemia is a genetic defect of the intravascular lipolysis of triglyceride (TG)-rich lipoproteins. Intravascular lipolysis involves the TG-hydrolase lipoprotein lipase (LPL) as well as other factors such as apolipoprotein CII and apolipoprotein AV (activators of LPL), GPIHBP1 (the molecular platform required for LPL activity on endothelial surface), and LMF1 (a factor required for intracellular formation of active LPL). METHODS We sequenced the familial chylomicronemia candidate genes in a neonate with chylomicronemia. RESULTS A 3-day-old newborn was found to have chylomicronemia (plasma TG 18.8 mmol/L, 1.667 mg/dL). The discontinuation of breastfeeding for 24 hours reduced plasma TG to 2.3 mmol/L (201 mg/dL), whereas its resumption induced a sharp TG increase (7.9 mmol/L, 690 mg/dL). The child was switched to a low-fat diet, which was effective in maintaining TG level below 3.5 mmol/L (294 mg/dL) during the first months of life. The child was found to be a compound heterozygous for 2 novel mutations in GPIHBP1 gene. The first mutation was a 9-bp deletion and 4-bp insertion in exon 2, causing a frameshift that abolished the canonical termination codon TGA. The predicted translation product of the mutant messenger RNA is a peptide that contains 51 amino acids of the N-terminal end of the wild-type protein followed by 252 novel amino acids. The second mutation was a nucleotide change (c.319T>C), causing an amino acid substitution p.(Ser107Pro) predicted in silico to be damaging. CONCLUSIONS GPIHBP1 mutations should be considered in neonates with chylomicronemia negative for mutations in LPL gene.
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Affiliation(s)
| | - Andrea Bartuli
- Rare Diseases and Medical Genetics, Bambino Gesù Children Hospital, Rome, Italy
| | - Claudio Rabacchi
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Stefano Bertolini
- Department of Internal Medicine, University of Genova, Genova, Italy
| | - Sebastiano Calandra
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy.
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Jiang H, Goulbourne CN, Tatar A, Turlo K, Wu D, Beigneux AP, Grovenor CRM, Fong LG, Young SG. High-resolution imaging of dietary lipids in cells and tissues by NanoSIMS analysis. J Lipid Res 2014; 55:2156-66. [PMID: 25143463 DOI: 10.1194/jlr.m053363] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nanoscale secondary ion MS (NanoSIMS) imaging makes it possible to visualize stable isotope-labeled lipids in cells and tissues at 50 nm lateral resolution. Here we report the use of NanoSIMS imaging to visualize lipids in mouse cells and tissues. After administering stable isotope-labeled fatty acids to mice by gavage, NanoSIMS imaging allowed us to visualize neutral lipids in cytosolic lipid droplets in intestinal enterocytes, chylomicrons at the basolateral surface of enterocytes, and lipid droplets in cardiomyocytes and adipocytes. After an injection of stable isotope-enriched triglyceride-rich lipoproteins (TRLs), NanoSIMS imaging documented delivery of lipids to cytosolic lipid droplets in parenchymal cells. Using a combination of backscattered electron (BSE) and NanoSIMS imaging, it was possible to correlate the chemical data provided by NanoSIMS with high-resolution BSE images of cell morphology. This combined imaging approach allowed us to visualize stable isotope-enriched TRLs along the luminal face of heart capillaries and the lipids within heart capillary endothelial cells. We also observed examples of TRLs within the subendothelial spaces of heart capillaries. NanoSIMS imaging provided evidence of defective transport of lipids from the plasma LPs to adipocytes and cardiomyocytes in mice deficient in glycosylphosphatidylinositol-anchored HDL binding protein 1.
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Affiliation(s)
- Haibo Jiang
- Materials Department, Oxford University, Oxford, United Kingdom
| | - Chris N Goulbourne
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA
| | - Angelica Tatar
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA
| | - Kirsten Turlo
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA
| | - Daniel Wu
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA
| | - Anne P Beigneux
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA
| | | | - Loren G Fong
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA
| | - Stephen G Young
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
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Plengpanich W, Young SG, Khovidhunkit W, Bensadoun A, Karnman H, Ploug M, Gårdsvoll H, Leung CS, Adeyo O, Larsson M, Muanpetch S, Charoen S, Fong LG, Niramitmahapanya S, Beigneux AP. Multimerization of glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) and familial chylomicronemia from a serine-to-cysteine substitution in GPIHBP1 Ly6 domain. J Biol Chem 2014; 289:19491-9. [PMID: 24847059 DOI: 10.1074/jbc.m114.558528] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
GPIHBP1, a glycosylphosphatidylinositol-anchored glycoprotein of microvascular endothelial cells, binds lipoprotein lipase (LPL) within the interstitial spaces and transports it across endothelial cells to the capillary lumen. The ability of GPIHBP1 to bind LPL depends on the Ly6 domain, a three-fingered structure containing 10 cysteines and a conserved pattern of disulfide bond formation. Here, we report a patient with severe hypertriglyceridemia who was homozygous for a GPIHBP1 point mutation that converted a serine in the GPIHBP1 Ly6 domain (Ser-107) to a cysteine. Two hypertriglyceridemic siblings were homozygous for the same mutation. All three homozygotes had very low levels of LPL in the preheparin plasma. We suspected that the extra cysteine in GPIHBP1-S107C might prevent the trafficking of the protein to the cell surface, but this was not the case. However, nearly all of the GPIHBP1-S107C on the cell surface was in the form of disulfide-linked dimers and multimers, whereas wild-type GPIHBP1 was predominantly monomeric. An insect cell GPIHBP1 expression system confirmed the propensity of GPIHBP1-S107C to form disulfide-linked dimers and to form multimers. Functional studies showed that only GPIHBP1 monomers bind LPL. In keeping with that finding, there was no binding of LPL to GPIHBP1-S107C in either cell-based or cell-free binding assays. We conclude that an extra cysteine in the GPIHBP1 Ly6 motif results in multimerization of GPIHBP1, defective LPL binding, and severe hypertriglyceridemia.
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Affiliation(s)
- Wanee Plengpanich
- From the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok 10330, Thailand
| | - Stephen G Young
- the Departments of Medicine and Human Genetics, UCLA, Los Angeles, California 90095
| | - Weerapan Khovidhunkit
- From the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok 10330, Thailand,
| | - André Bensadoun
- the Division of Nutritional Science, Cornell University, Ithaca, New York 14853
| | - Hirankorn Karnman
- From the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok 10330, Thailand
| | - Michael Ploug
- the Finsen Laboratory and Biotech Research and Innovation Center, Rigshospitalet, DK-2200 Copenhagen, Denmark
| | - Henrik Gårdsvoll
- the Finsen Laboratory and Biotech Research and Innovation Center, Rigshospitalet, DK-2200 Copenhagen, Denmark
| | | | | | - Mikael Larsson
- the Department of Medical Biosciences and Physiological Chemistry, Umeå University, SE-901 87 Umeå, Sweden, and
| | - Suwanna Muanpetch
- From the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok 10330, Thailand
| | - Supannika Charoen
- From the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok 10330, Thailand
| | | | - Sathit Niramitmahapanya
- the Department of Medicine, Rajavithi Hospital, College of Medicine, Rangsit University, Bangkok 10400, Thailand
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38
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Type 1 hyperlipoproteinemia due to a novel deletion of exons 3 and 4 in the GPIHBP1 gene. Atherosclerosis 2014; 234:30-3. [DOI: 10.1016/j.atherosclerosis.2014.02.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 01/23/2014] [Accepted: 02/06/2014] [Indexed: 11/22/2022]
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39
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Palmoplantar keratoderma along with neuromuscular and metabolic phenotypes in Slurp1-deficient mice. J Invest Dermatol 2014; 134:1589-1598. [PMID: 24499735 PMCID: PMC4214150 DOI: 10.1038/jid.2014.19] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 12/03/2013] [Accepted: 12/07/2013] [Indexed: 01/11/2023]
Abstract
Mutations in SLURP1 cause mal de Meleda, a rare palmoplantar keratoderma (PPK). SLURP1 is a secreted protein that is expressed highly in keratinocytes but has also been identified elsewhere (e.g., spinal cord neurons). Here, we examined Slurp1-deficient mice (Slurp1−/−) created by replacing exon 2 with β-gal and neo cassettes. Slurp1−/− mice developed severe PPK characterized by increased keratinocyte proliferation, an accumulation of lipid droplets in the stratum corneum, and a water barrier defect. In addition, Slurp1−/− mice exhibited reduced adiposity, protection from obesity on a high-fat diet, low plasma lipid levels, and a neuromuscular abnormality (hind limb clasping). Initially, it was unclear whether the metabolic and neuromuscular phenotypes were due to Slurp1 deficiency because we found that the targeted Slurp1 mutation reduced the expression of several neighboring genes (e.g., Slurp2, Lypd2). We therefore created a new line of knockout mice (Slurp1X−/− mice) with a simple nonsense mutation in exon 2. The Slurp1X mutation did not reduce the expression of adjacent genes, but Slurp1X−/− mice exhibited all of the phenotypes observed in the original line of knockout mice. Thus, Slurp1 deficiency in mice elicits metabolic and neuromuscular abnormalities in addition to PPK.
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40
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Yang J, Liu X, Zhang Q, Jiang L. Identification and quantitative mRNA analysis of a novel splice variant of GPIHBP1 in dairy cattle. J Anim Sci Biotechnol 2014; 5:50. [PMID: 25810903 PMCID: PMC4373091 DOI: 10.1186/2049-1891-5-50] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 10/20/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Identification of functional genes affecting milk production traits is very crucial for improving breeding efficiency in dairy cattle. Many potential candidate genes have been identified through our previous genome wide association study (GWAS). Of these, GPIHBP1 is an important novel candidate gene for milk production traits. However, the mRNA structure of the bovine GPIHBP1 gene is not fully determined up to now. RESULTS In this study, we identified a novel alternatively splice transcript variant (X5) which leads to a 31 bp insertion in exon 3 and also confirmed the other four existed transcripts (X1, X2, X3 and X4) of the bovine GPIHBP1 gene. We showed that transcript X5 with a 31 bp insertion and transcript X1 with an 8 bp deletion might have tremendous effect on the protein function and structure of GPIHBP1, respectively. With semi-quantitative PCR and quantitative real-time RT-PCR, we found that the mRNA expression of GPIHBP1, GPIHBP1-X1 and GPIHBP1-X5 in mammary gland of lactating cows were much higher than that in other tissues. CONCLUSIONS Our study reports a novel alternative splicing of GPIHBP1 in bovine for the first time and provide useful information for the further functional analyses of GPIHBP1 in dairy cattle.
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Affiliation(s)
- Jie Yang
- National Engineering Laboratory for Animal Breeding; Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture of China; College of Animal Science and Technology, China Agricultural University, Beijing, 100193 China
| | - Xuan Liu
- National Engineering Laboratory for Animal Breeding; Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture of China; College of Animal Science and Technology, China Agricultural University, Beijing, 100193 China
| | - Qin Zhang
- National Engineering Laboratory for Animal Breeding; Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture of China; College of Animal Science and Technology, China Agricultural University, Beijing, 100193 China
| | - Li Jiang
- National Engineering Laboratory for Animal Breeding; Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture of China; College of Animal Science and Technology, China Agricultural University, Beijing, 100193 China
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Abstract
PURPOSE OF REVIEW Apolipoprotein (apo) A-V functions to modulate intracellular and extracellular triacylglycerol metabolism. The present review addresses molecular mechanisms underlying these effects. The relevance of apoA-V to human disease conditions is illustrated by the strong correlation between single nucleotide polymorphisms in APOA5, elevated plasma triacylglycerol and dyslipidemic disease. RECENT FINDINGS Despite undergoing processing for secretion from hepatocytes, a portion of apoA-V escapes this destiny and accumulates as a component of cytosolic lipid droplets. Expression of recombinant apoA-V in hepatocarcinoma cells results in increased lipid droplet size and number at the expense of triacylglycerol secretion.ApoA-V modulates atherosclerosis in hypercholesterolemic apoE null mice. ApoE null/human apoA-V transgenic mice had reduced levels of triacylglycerol and cholesterol in plasma along with decreased aortic lesion size. SUMMARY ApoA-V modulates triacylglycerol metabolic fate. Following its synthesis, apoA-V enters the endoplasmic reticulum and associates with membrane defects created by triacylglycerol accumulation. Association of apoA-V with endoplasmic reticulum membrane defects promotes nascent lipid droplets budding toward the cytosol. Despite its low concentration in plasma (∼150 ng/ml), apoA-V modulates lipoprotein metabolism by binding to glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1. This interaction effectively localizes triacylglycerol-rich lipoproteins in the vicinity of glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein1's other ligand, lipoprotein lipase.
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Affiliation(s)
- Vineeta Sharma
- Children's Hospital Oakland Research Institute, Oakland, CA 94609, USA
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42
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Abstract
All organisms use fatty acids (FAs) for energy substrates and as precursors for membrane and signaling lipids. The most efficient way to transport and store FAs is in the form of triglycerides (TGs); however, TGs are not capable of traversing biological membranes and therefore need to be cleaved by TG hydrolases ("lipases") before moving in or out of cells. This biochemical process is generally called "lipolysis." Intravascular lipolysis degrades lipoprotein-associated TGs to FAs for their subsequent uptake by parenchymal cells, whereas intracellular lipolysis generates FAs and glycerol for their release (in the case of white adipose tissue) or use by cells (in the case of other tissues). Although the importance of lipolysis has been recognized for decades, many of the key proteins involved in lipolysis have been uncovered only recently. Important new developments include the discovery of glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1), the molecule that moves lipoprotein lipase from the interstitial spaces to the capillary lumen, and the discovery of adipose triglyceride lipase (ATGL) and comparative gene identification-58 (CGI-58) as crucial molecules in the hydrolysis of TGs within cells. This review summarizes current views of lipolysis and highlights the relevance of this process to human disease.
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Affiliation(s)
- Stephen G. Young
- Department of Medicine
- Department of Human Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
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43
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Adeyo O, Goulbourne CN, Bensadoun A, Beigneux AP, Fong LG, Young SG. Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 and the intravascular processing of triglyceride-rich lipoproteins. J Intern Med 2012; 272:528-40. [PMID: 23020258 PMCID: PMC3940157 DOI: 10.1111/joim.12003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Lipoprotein lipase (LPL) is produced by parenchymal cells, mainly adipocytes and myocytes, but is involved in hydrolysing triglycerides in plasma lipoproteins at the capillary lumen. For decades, the mechanism by which LPL reaches its site of action in capillaries was unclear, but this mystery was recently solved. Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1), a glycosylphosphatidylinositol-anchored protein of capillary endothelial cells, 'picks up' LPL from the interstitial spaces and shuttles it across endothelial cells to the capillary lumen. When GPIHBP1 is absent, LPL is mislocalized to the interstitial spaces, leading to severe hypertriglyceridaemia. Some cases of hypertriglyceridaemia in humans are caused by GPIHBP1 mutations that interfere with the ability of GPIHBP1 to bind to LPL, and some are caused by LPL mutations that impair the ability of LPL to bind to GPIHBP1. Here, we review recent progress in understanding the role of GPIHBP1 in health and disease and discuss some of the remaining unresolved issues regarding the processing of triglyceride-rich lipoproteins.
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Affiliation(s)
- O Adeyo
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
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44
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Kok BPC, Brindley DN. Myocardial fatty acid metabolism and lipotoxicity in the setting of insulin resistance. Heart Fail Clin 2012; 8:643-61. [PMID: 22999246 DOI: 10.1016/j.hfc.2012.06.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Management of diabetes and insulin resistance in the setting of cardiovascular disease has become an important issue in an increasingly obese society. Besides the development of hypertension and buildup of atherosclerotic plaques, the derangement of fatty acid and lipid metabolism in the heart plays an important role in promoting cardiac dysfunction and oxidative stress. This review discusses the mechanisms by which metabolic inflexibility in the use of fatty acids as the preferred cardiac substrate in diabetes produces detrimental effects on mechanical efficiency, mitochondrial function, and recovery from ischemia. Lipid accumulation and the consequences of toxic lipid metabolites are also discussed.
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Affiliation(s)
- Bernard P C Kok
- Signal Transduction Research Group, Department of Biochemistry, School of Translational Medicine, University of Alberta, 11207 87th Avenue, Edmonton, Alberta, Canada
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45
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Gin P, Goulbourne CN, Adeyo O, Beigneux AP, Davies BSJ, Tat S, Voss CV, Bensadoun A, Fong LG, Young SG. Chylomicronemia mutations yield new insights into interactions between lipoprotein lipase and GPIHBP1. Hum Mol Genet 2012; 21:2961-72. [PMID: 22493000 DOI: 10.1093/hmg/dds127] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Lipoprotein lipase (LPL) is a 448-amino-acid head-to-tail dimeric enzyme that hydrolyzes triglycerides within capillaries. LPL is secreted by parenchymal cells into the interstitial spaces; it then binds to GPIHBP1 (glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1) on the basolateral face of endothelial cells and is transported to the capillary lumen. A pair of amino acid substitutions, C418Y and E421K, abolish LPL binding to GPIHBP1, suggesting that the C-terminal portion of LPL is important for GPIHBP1 binding. However, a role for LPL's N terminus has not been excluded, and published evidence has suggested that only full-length homodimers are capable of binding GPIHBP1. Here, we show that LPL's C-terminal domain is sufficient for GPIHBP1 binding. We found, serendipitously, that two LPL missense mutations, G409R and E410V, render LPL susceptible to cleavage at residue 297 (a known furin cleavage site). The C terminus of these mutants (residues 298-448), bound to GPIHBP1 avidly, independent of the N-terminal fragment. We also generated an LPL construct with an in-frame deletion of the N-terminal catalytic domain (residues 50-289); this mutant was secreted but also was cleaved at residue 297. Once again, the C-terminal domain (residues 298-448) bound GPIHBP1 avidly. The binding of the C-terminal fragment to GPIHBP1 was eliminated by C418Y or E421K mutations. After exposure to denaturing conditions, the C-terminal fragment of LPL refolds and binds GPIHBP1 avidly. Thus, the binding of LPL to GPIHBP1 requires only the C-terminal portion of LPL and does not depend on full-length LPL homodimers.
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Affiliation(s)
- Peter Gin
- Department of Medicine, David Geffen School of Medicine, University of California-Los Angeles, CA 90095, USA
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Abstract
PURPOSE OF REVIEW We summarize recent progress on GPIHBP1, a molecule that transports lipoprotein lipase (LPL) to the capillary lumen, and discuss several newly studied molecules that appear important for the regulation of LPL activity. RECENT FINDINGS LPL, the enzyme responsible for the lipolytic processing of triglyceride-rich lipoproteins, interacts with multiple proteins and is regulated at multiple levels. Several regulators of LPL activity have been known for years and have been investigated thoroughly, but several have been identified only recently, including an endothelial cell protein that transports LPL to the capillary lumen, a microRNA that reduces LPL transcript levels, a sorting protein that targets LPL for uptake and degradation, and a transcription factor that increases the expression of apolipoproteins that regulate LPL activity. SUMMARY Proper regulation of LPL is important for controlling the delivery of lipid nutrients to tissues. Recent studies have identified GPIHBP1 as the molecule that transports LPL to the capillary lumen, and have also identified other molecules that are potentially important for regulating LPL activity. These new discoveries open new doors for understanding basic mechanisms of lipolysis and hyperlipidemia.
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Affiliation(s)
- Brandon S J Davies
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA.
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Johansen CT, Hegele RA. Allelic and phenotypic spectrum of plasma triglycerides. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:833-42. [PMID: 22033228 DOI: 10.1016/j.bbalip.2011.10.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Accepted: 10/04/2011] [Indexed: 01/10/2023]
Abstract
The genetic underpinnings of both normal and pathological variation in plasma triglyceride (TG) concentration are relatively well understood compared to many other complex metabolic traits. For instance, genome-wide association studies (GWAS) have revealed 32 common variants that are associated with plasma TG concentrations in healthy epidemiologic populations. Furthermore, GWAS in clinically ascertained hypertriglyceridemia (HTG) patients have shown that almost all of the same TG-raising alleles from epidemiologic samples are also associated with HTG disease status, and that greater accumulation of these alleles reflects the severity of the HTG phenotype. Finally, comprehensive resequencing studies show a burden of rare variants in some of these same genes - namely in LPL, GCKR, APOB and APOA5 - in HTG patients compared to normolipidemic controls. A more complete understanding of the genes and genetic variants associated with plasma TG concentration will enrich our understanding of the molecular pathways that modulate plasma TG metabolism, which may translate into clinical benefit. This article is part of a Special Issue entitled Triglyceride Metabolism and Disease.
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Charrière S, Peretti N, Bernard S, Di Filippo M, Sassolas A, Merlin M, Delay M, Debard C, Lefai E, Lachaux A, Moulin P, Marçais C. GPIHBP1 C89F neomutation and hydrophobic C-terminal domain G175R mutation in two pedigrees with severe hyperchylomicronemia. J Clin Endocrinol Metab 2011; 96:E1675-9. [PMID: 21816778 DOI: 10.1210/jc.2011-1444] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT GPIHBP1 is a new endothelial binding site for lipoprotein lipase (LPL), the key enzyme for intravascular lipolysis of triglyceride-rich lipoproteins (TGRL). We have identified two new missense mutations of the GPIHBP1 gene, C89F and G175R, by systematic sequencing in a cohort of 376 hyperchylomicronemic patients without mutations on the LPL, APOC2, or APOA5 gene. OBJECTIVE Phenotypic expression and functional consequences of these two mutations were studied. DESIGN We performed clinical and genotypic studies of probands and their families. GPIHBP1 functional alterations were studied in CHO pgsA-745 transfected cells. RESULTS Probands are an adult with a homozygous G175R mutation and a child with a hemizygous C89F neomutation and a deletion of the second allele. C89F mutation was associated with a C14F signal peptide polymorphism on the same haplotype. Both patients had resistant hyperchylomicronemia, low LPL activity, and history of acute pancreatitis. In CHO pgsA-745 cells, both G175R and C14F variants reduce the expression of GPIHBP1 at the cell surface. C89F mutation is responsible for a drastic LPL-binding defect to GPIHBP1. C14F may further potentiate C89F effect. CONCLUSIONS The emergence of hyperchylomicronemia in the generation after a neomutation further establishes a critical role for GPIHBP1 in TGRL physiopathology in humans. Our results highlight the crucial role of C65-C89 disulfide bond in LPL binding by GPIHBP1 Ly6 domain. Furthermore, we first report a mutation of the hydrophobic C-terminal domain that impairs GPIHBP1 membrane targeting.
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Affiliation(s)
- Sybil Charrière
- Hôpital Louis Pradel, Fédération d'Endocrinologie, Bron Cedex, France.
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49
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Young SG, Davies BSJ, Voss CV, Gin P, Weinstein MM, Tontonoz P, Reue K, Bensadoun A, Fong LG, Beigneux AP. GPIHBP1, an endothelial cell transporter for lipoprotein lipase. J Lipid Res 2011; 52:1869-84. [PMID: 21844202 DOI: 10.1194/jlr.r018689] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Interest in lipolysis and the metabolism of triglyceride-rich lipoproteins was recently reignited by the discovery of severe hypertriglyceridemia (chylomicronemia) in glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1)-deficient mice. GPIHBP1 is expressed exclusively in capillary endothelial cells and binds lipoprotein lipase (LPL) avidly. These findings prompted speculation that GPIHBP1 serves as a binding site for LPL in the capillary lumen, creating "a platform for lipolysis." More recent studies have identified a second and more intriguing role for GPIHBP1-picking up LPL in the subendothelial spaces and transporting it across endothelial cells to the capillary lumen. Here, we review the studies that revealed that GPIHBP1 is the LPL transporter and discuss which amino acid sequences are required for GPIHBP1-LPL interactions. We also discuss the human genetics of LPL transport, focusing on cases of chylomicronemia caused by GPIHBP1 mutations that abolish GPIHBP1's ability to bind LPL, and LPL mutations that prevent LPL binding to GPIHBP1.
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Affiliation(s)
- Stephen G Young
- Department of Medicine, University of California, Los Angeles, CA 90095, USA.
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