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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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Jiang S, Ren Z, Yang Y, Liu Q, Zhou S, Xiao Y. The GPIHBP1-LPL complex and its role in plasma triglyceride metabolism: Insights into chylomicronemia. Biomed Pharmacother 2023; 169:115874. [PMID: 37951027 DOI: 10.1016/j.biopha.2023.115874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 11/06/2023] [Accepted: 11/07/2023] [Indexed: 11/13/2023] Open
Abstract
GPIHBP1 is a protein found in the endothelial cells of capillaries that is anchored by glycosylphosphatidylinositol and binds to high-density lipoproteins. GPIHBP1 attaches to lipoprotein lipase (LPL), subsequently carrying the enzyme and anchoring it to the capillary lumen. Enabling lipid metabolism is essential for the marginalization of lipoproteins alongside capillaries. Studies underscore the significance of GPIHBP1 in transporting, stabilizing, and aiding in the marginalization of LPL. The intricate interplay between GPIHBP1 and LPL has provided novel insights into chylomicronemia in recent years. Mutations hindering the formation or reducing the efficiency of the GPIHBP1-LPL complex are central to the onset of chylomicronemia. This review delves into the structural nuances of the GPIHBP1-LPL interaction, the consequences of mutations in the complex leading to chylomicronemia, and cutting-edge advancements in chylomicronemia treatment.
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Affiliation(s)
- Shali Jiang
- Department of Cardiovascular Medicine, Second Xiangya Hospital of Central South University, Changsha, Hunan 410011, PR China; Xiangya School of Medicine, Central South University, Changsha, Hunan 410013, PR China
| | - Zhuoqun Ren
- Department of Cardiovascular Medicine, Second Xiangya Hospital of Central South University, Changsha, Hunan 410011, PR China; Xiangya School of Medicine, Central South University, Changsha, Hunan 410013, PR China
| | - Yutao Yang
- Department of Cardiovascular Medicine, Second Xiangya Hospital of Central South University, Changsha, Hunan 410011, PR China; Xiangya School of Medicine, Central South University, Changsha, Hunan 410013, PR China
| | - Qiming Liu
- Department of Cardiovascular Medicine, Second Xiangya Hospital of Central South University, Changsha, Hunan 410011, PR China
| | - Shenghua Zhou
- Department of Cardiovascular Medicine, Second Xiangya Hospital of Central South University, Changsha, Hunan 410011, PR China
| | - Yichao Xiao
- Department of Cardiovascular Medicine, Second Xiangya Hospital of Central South University, Changsha, Hunan 410011, PR China.
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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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Kurooka N, Eguchi J, Wada J. Role of glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1 in hypertriglyceridemia and diabetes. J Diabetes Investig 2023; 14:1148-1156. [PMID: 37448184 PMCID: PMC10512915 DOI: 10.1111/jdi.14056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 06/25/2023] [Accepted: 06/28/2023] [Indexed: 07/15/2023] Open
Abstract
In diabetes, the impairment of insulin secretion and insulin resistance contribute to hypertriglyceridemia, as the enzymatic activity of lipoprotein lipase (LPL) depends on insulin action. The transport of LPL to endothelial cells and its enzymatic activity are maintained by the formation of lipolytic complex depending on the multiple positive (glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1 [GPIHBP1], apolipoprotein C-II [APOC2], APOA5, heparan sulfate proteoglycan [HSPG], lipase maturation factor 1 [LFM1] and sel-1 suppressor of lin-12-like [SEL1L]) and negative regulators (APOC1, APOC3, angiopoietin-like proteins [ANGPTL]3, ANGPTL4 and ANGPTL8). Among the regulators, GPIHBP1 is a crucial molecule for the translocation of LPL from parenchymal cells to the luminal surface of capillary endothelial cells, and maintenance of lipolytic activity; that is, hydrolyzation of triglyceride into free fatty acids and monoglyceride, and conversion from chylomicron to chylomicron remnant in the exogenous pathway and from very low-density lipoprotein to low-density lipoprotein in the endogenous pathway. The null mutation of GPIHBP1 causes severe hypertriglyceridemia and pancreatitis, and GPIGBP1 autoantibody syndrome also causes severe hypertriglyceridemia and recurrent episodes of acute pancreatitis. In patients with type 2 diabetes, the elevated serum triglyceride levels negatively correlate with circulating LPL levels, and positively with circulating APOC1, APOC3, ANGPTL3, ANGPTL4 and ANGPTL8 levels. In contrast, circulating GPIHBP1 levels are not altered in type 2 diabetes patients with higher serum triglyceride levels, whereas they are elevated in type 2 diabetes patients with diabetic retinopathy and nephropathy. The circulating regulators of lipolytic complex might be new biomarkers for lipid and glucose metabolism, and diabetic vascular complications.
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Affiliation(s)
- Naoko Kurooka
- Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Faculty of Medicine, Dentistry and Pharmaceutical SciencesOkayama UniversityOkayamaJapan
| | - Jun Eguchi
- Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Faculty of Medicine, Dentistry and Pharmaceutical SciencesOkayama UniversityOkayamaJapan
| | - Jun Wada
- Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Faculty of Medicine, Dentistry and Pharmaceutical SciencesOkayama UniversityOkayamaJapan
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Kumari A, Grønnemose AL, Kristensen KK, Winther AML, Young SG, Jørgensen TJD, Ploug M. Inverse effects of APOC2 and ANGPTL4 on the conformational dynamics of lid-anchoring structures in lipoprotein lipase. Proc Natl Acad Sci U S A 2023; 120:e2221888120. [PMID: 37094117 PMCID: PMC10160976 DOI: 10.1073/pnas.2221888120] [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: 01/03/2023] [Accepted: 03/28/2023] [Indexed: 04/26/2023] Open
Abstract
The lipolytic processing of triglyceride-rich lipoproteins (TRLs) by lipoprotein lipase (LPL) is crucial for the delivery of dietary lipids to the heart, skeletal muscle, and adipose tissue. The processing of TRLs by LPL is regulated in a tissue-specific manner by a complex interplay between activators and inhibitors. Angiopoietin-like protein 4 (ANGPTL4) inhibits LPL by reducing its thermal stability and catalyzing the irreversible unfolding of LPL's α/β-hydrolase domain. We previously mapped the ANGPTL4 binding site on LPL and defined the downstream unfolding events resulting in LPL inactivation. The binding of LPL to glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 protects against LPL unfolding. The binding site on LPL for an activating cofactor, apolipoprotein C2 (APOC2), and the mechanisms by which APOC2 activates LPL have been unclear and controversial. Using hydrogen-deuterium exchange/mass spectrometry, we now show that APOC2's C-terminal α-helix binds to regions of LPL surrounding the catalytic pocket. Remarkably, APOC2's binding site on LPL overlaps with that for ANGPTL4, but their effects on LPL conformation are distinct. In contrast to ANGPTL4, APOC2 increases the thermal stability of LPL and protects it from unfolding. Also, the regions of LPL that anchor the lid are stabilized by APOC2 but destabilized by ANGPTL4, providing a plausible explanation for why APOC2 is an activator of LPL, while ANGPTL4 is an inhibitor. Our studies provide fresh insights into the molecular mechanisms by which APOC2 binds and stabilizes LPL-and properties that we suspect are relevant to the conformational gating of LPL's active site.
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Affiliation(s)
- Anni Kumari
- Finsen Laboratory, Copenhagen University Hospital-Rigshospitalet, DK-2200Copenhagen N, Denmark
- Finsen Laboratory, Biotech Research and Innovation Centre, University of Copenhagen, DK-2200Copenhagen N, Denmark
| | - Anne Louise Grønnemose
- Finsen Laboratory, Copenhagen University Hospital-Rigshospitalet, DK-2200Copenhagen N, Denmark
- Finsen Laboratory, Biotech Research and Innovation Centre, University of Copenhagen, DK-2200Copenhagen N, Denmark
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK–5320Odense, Denmark
| | - Kristian K. Kristensen
- Finsen Laboratory, Copenhagen University Hospital-Rigshospitalet, DK-2200Copenhagen N, Denmark
- Finsen Laboratory, Biotech Research and Innovation Centre, University of Copenhagen, DK-2200Copenhagen N, Denmark
| | - Anne-Marie L. Winther
- Finsen Laboratory, Copenhagen University Hospital-Rigshospitalet, DK-2200Copenhagen N, Denmark
- Finsen Laboratory, Biotech Research and Innovation Centre, University of Copenhagen, DK-2200Copenhagen N, Denmark
| | - 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
| | - Thomas J. D. Jørgensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK–5320Odense, Denmark
| | - Michael Ploug
- Finsen Laboratory, Copenhagen University Hospital-Rigshospitalet, DK-2200Copenhagen N, Denmark
- Finsen Laboratory, Biotech Research and Innovation Centre, University of Copenhagen, DK-2200Copenhagen N, Denmark
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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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Sustar U, Groselj U, Khan SA, Shafi S, Khan I, Kovac J, Bizjan BJ, Battelino T, Sadiq F. A homozygous variant in the GPIHBP1 gene in a child with severe hypertriglyceridemia and a systematic literature review. Front Genet 2022; 13:983283. [PMID: 36051701 PMCID: PMC9424485 DOI: 10.3389/fgene.2022.983283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 07/18/2022] [Indexed: 11/13/2022] Open
Abstract
Background: Due to nonspecific symptoms, rare dyslipidaemias are frequently misdiagnosed, overlooked, and undertreated, leading to increased risk for severe cardiovascular disease, pancreatitis and/or multiple organ failures before diagnosis. Better guidelines for the recognition and early diagnosis of rare dyslipidaemias are urgently required. Methods: Genomic DNA was isolated from blood samples of a Pakistani paediatric patient with hypertriglyceridemia, and from his parents and siblings. Next-generation sequencing (NGS) was performed, and an expanded dyslipidaemia panel was employed for genetic analysis. Results: The NGS revealed the presence of a homozygous missense pathogenic variant c.230G>A (NM_178172.6) in exon 3 of the GPIHBP1 (glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1) gene resulting in amino acid change p.Cys77Tyr (NP_835466.2). The patient was 5.5 years old at the time of genetic diagnosis. The maximal total cholesterol and triglyceride levels were measured at the age of 10 months (850.7 mg/dl, 22.0 mmol/L and 5,137 mg/dl, 58.0 mmol/L, respectively). The patient had cholesterol deposits at the hard palate, eruptive xanthomas, lethargy, poor appetite, and mild splenomegaly. Both parents and sister were heterozygous for the familial variant in the GPIHBP1 gene. Moreover, in the systematic review, we present 62 patients with pathogenic variants in the GPIHBP1 gene and clinical findings, associated with hyperlipoproteinemia. Conclusion: In a child with severe hypertriglyceridemia, we identified a pathogenic variant in the GPIHBP1 gene causing hyperlipoproteinemia (type 1D). In cases of severe elevations of plasma cholesterol and/or triglycerides genetic testing for rare dyslipidaemias should be performed as soon as possible for optimal therapy and patient management.
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Affiliation(s)
- Ursa Sustar
- Department of Endocrinology, Diabetes and Metabolism, University Children’s Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Urh Groselj
- Department of Endocrinology, Diabetes and Metabolism, University Children’s Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
- Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, CA, United States
- *Correspondence: Urh Groselj, ; Fouzia Sadiq,
| | - Sabeen Abid Khan
- Department of Paediatrics, Shifa College of Medicine, Shifa Tameer-e-Millat University, Islamabad, Pakistan
| | - Saeed Shafi
- Department of Anatomy, Shifa Tameer-e-Millat University, Islamabad, Pakistan
| | - Iqbal Khan
- Department of Vascular Surgery, Shifa International Hospital, Islamabad, Pakistan
- Department of Vascular Surgery, Shifa Tameer-e-Millat University, Islamabad, Pakistan
| | - Jernej Kovac
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
- Clinical Institute for Special Laboratory Diagnostics, University Children’s Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia
| | - Barbara Jenko Bizjan
- Clinical Institute for Special Laboratory Diagnostics, University Children’s Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia
| | - Tadej Battelino
- Department of Endocrinology, Diabetes and Metabolism, University Children’s Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Fouzia Sadiq
- Directorate of Research, Shifa Tameer-e-Millat University, Islamabad, Pakistan
- *Correspondence: Urh Groselj, ; Fouzia Sadiq,
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Zhang G, Yang Q, Mao W, Hu Y, Pu N, Deng H, Yu X, Zhang J, Zhou J, Ye B, Li G, Li B, Ke L, Tong Z, Murakami M, Kimura T, Nakajima K, Cao W, Liu Y, Li W. GPIHBP1 autoantibody is an independent risk factor for the recurrence of hypertriglyceridemia-induced acute pancreatitis. J Clin Lipidol 2022; 16:626-634. [DOI: 10.1016/j.jacl.2022.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 08/01/2022] [Accepted: 08/02/2022] [Indexed: 10/15/2022]
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Kaewkrasaesin C, Chatchomchuan W, Muanpetch S, Khovidhunkit W. ANGPTL3 and ANGPTL8 in Thai subjects with hyperalphalipoproteinemia and severe hypertriglyceridemia. J Clin Lipidol 2021; 15:752-759. [PMID: 34535418 DOI: 10.1016/j.jacl.2021.08.059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Revised: 08/21/2021] [Accepted: 08/25/2021] [Indexed: 10/20/2022]
Abstract
BACKGROUND The role of ANGPTL3 and ANGPTL8 in lipid regulation in patients with very high levels of HDL-cholesterol and triglyceride is unknown. OBJECTIVE We examined plasma levels of ANGPTL3 and ANGPTL8 in subjects with hyperalphalipoproteinemia (HALP) and in those with severe hypertriglyceridemia (HTG). METHODS Plasma ANGPTL3 and ANGPTL8 levels were measured by ELISA in 320 subjects, consisting of HALP subjects with HDL-cholesterol ≥100 mg/dl (n=90) and healthy controls (n=90) and subjects with triglyceride ≥886 mg/dl (n=89) and control subjects (n=51). RESULTS The mean plasma ANGPTL3 level was significantly higher in the HALP group compared to that of the controls (297 ± 112 ng/mL vs. 230 ± 100 ng/mL, p<0.001). Similarly, the mean plasma ANGPTL8 level was also higher in the HALP group (30 ± 11 ng/mL vs. 20 ± 8 ng/mL, p<0.001). Both ANGPTL3 and ANGPTL8 levels positively correlated with HDL-cholesterol levels. In the severe HTG group, plasma ANGPTL3 level was significantly higher than those in the control group (223 ± 105 ng/mL vs. 151 ± 60 ng/mL, p<0.001), but not ANGPTL8 (23 ± 20 ng/mL vs. 31 ± 23 ng/mL in controls, p=0.028). Only ANGPTL3, but not ANGPTL8, levels positively correlated with triglyceride levels. CONCLUSION Plasma level of ANGPTL3 was increased in both HALP and severe HTG whereas an increase in plasma level of ANGPTL8 was found only in HALP, and not in severe HTG, suggesting that both ANGPTL3 and ANGPTL8 might play distinct roles in lipid regulation on these two extremes of dyslipidemia.
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Affiliation(s)
- Chatchon Kaewkrasaesin
- Division of Endocrinology and Metabolism, Department of Medicine, and Hormonal and Metabolic Disorders Research Unit, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand; Department of Medicine, and Excellence Center for Diabetes, Hormone, and Metabolism, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
| | - Waralee Chatchomchuan
- Division of Endocrinology and Metabolism, Department of Medicine, and Hormonal and Metabolic Disorders Research Unit, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand; Department of Medicine, and Excellence Center for Diabetes, Hormone, and Metabolism, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
| | - Suwanna Muanpetch
- Department of Medicine, and Excellence Center for Diabetes, Hormone, and Metabolism, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
| | - Weerapan Khovidhunkit
- Division of Endocrinology and Metabolism, Department of Medicine, and Hormonal and Metabolic Disorders Research Unit, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand; Department of Medicine, and Excellence Center for Diabetes, Hormone, and Metabolism, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand.
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10
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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: 19] [Impact Index Per Article: 6.3] [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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11
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The Importance of Lipoprotein Lipase Regulation in Atherosclerosis. Biomedicines 2021; 9:biomedicines9070782. [PMID: 34356847 PMCID: PMC8301479 DOI: 10.3390/biomedicines9070782] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/02/2021] [Accepted: 07/04/2021] [Indexed: 02/07/2023] Open
Abstract
Lipoprotein lipase (LPL) plays a major role in the lipid homeostasis mainly by mediating the intravascular lipolysis of triglyceride rich lipoproteins. Impaired LPL activity leads to the accumulation of chylomicrons and very low-density lipoproteins (VLDL) in plasma, resulting in hypertriglyceridemia. While low-density lipoprotein cholesterol (LDL-C) is recognized as a primary risk factor for atherosclerosis, hypertriglyceridemia has been shown to be an independent risk factor for cardiovascular disease (CVD) and a residual risk factor in atherosclerosis development. In this review, we focus on the lipolysis machinery and discuss the potential role of triglycerides, remnant particles, and lipolysis mediators in the onset and progression of atherosclerotic cardiovascular disease (ASCVD). This review details a number of important factors involved in the maturation and transportation of LPL to the capillaries, where the triglycerides are hydrolyzed, generating remnant lipoproteins. Moreover, LPL and other factors involved in intravascular lipolysis are also reported to impact the clearance of remnant lipoproteins from plasma and promote lipoprotein retention in capillaries. Apolipoproteins (Apo) and angiopoietin-like proteins (ANGPTLs) play a crucial role in regulating LPL activity and recent insights into LPL regulation may elucidate new pharmacological means to address the challenge of hypertriglyceridemia in atherosclerosis development.
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12
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The intrinsic instability of the hydrolase domain of lipoprotein lipase facilitates its inactivation by ANGPTL4-catalyzed unfolding. Proc Natl Acad Sci U S A 2021; 118:2026650118. [PMID: 33723082 DOI: 10.1073/pnas.2026650118] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The complex between lipoprotein lipase (LPL) and its endothelial receptor (GPIHBP1) is responsible for the lipolytic processing of triglyceride-rich lipoproteins (TRLs) along the capillary lumen, a physiologic process that releases lipid nutrients for vital organs such as heart and skeletal muscle. LPL activity is regulated in a tissue-specific manner by endogenous inhibitors (angiopoietin-like [ANGPTL] proteins 3, 4, and 8), but the molecular mechanisms are incompletely understood. ANGPTL4 catalyzes the inactivation of LPL monomers by triggering the irreversible unfolding of LPL's α/β-hydrolase domain. Here, we show that this unfolding is initiated by the binding of ANGPTL4 to sequences near LPL's catalytic site, including β2, β3-α3, and the lid. Using pulse-labeling hydrogen‒deuterium exchange mass spectrometry, we found that ANGPTL4 binding initiates conformational changes that are nucleated on β3-α3 and progress to β5 and β4-α4, ultimately leading to the irreversible unfolding of regions that form LPL's catalytic pocket. LPL unfolding is context dependent and varies with the thermal stability of LPL's α/β-hydrolase domain (T m of 34.8 °C). GPIHBP1 binding dramatically increases LPL stability (T m of 57.6 °C), while ANGPTL4 lowers the onset of LPL unfolding by ∼20 °C, both for LPL and LPL•GPIHBP1 complexes. These observations explain why the binding of GPIHBP1 to LPL retards the kinetics of ANGPTL4-mediated LPL inactivation at 37 °C but does not fully suppress inactivation. The allosteric mechanism by which ANGPTL4 catalyzes the irreversible unfolding and inactivation of LPL is an unprecedented pathway for regulating intravascular lipid metabolism.
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13
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A novel GPIHBP1 mutation related to familial chylomicronemia syndrome: A series of cases. Atherosclerosis 2021; 322:31-38. [PMID: 33706081 DOI: 10.1016/j.atherosclerosis.2021.02.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 02/10/2021] [Accepted: 02/18/2021] [Indexed: 01/13/2023]
Abstract
BACKGROUND AND AIMS GPIHBP1 is an accessory protein of lipoprotein lipase (LPL) essential for its functioning. Mutations in the GPIHBP1 gene cause a deficit in the action of LPL, leading to severe hypertriglyceridemia and increased risk for acute pancreatitis. METHODS We describe twelve patients (nine women) with a novel homozygous mutation in intron 2 of the GPIHBP1 gene. RESULTS All patients were from the Northeastern region of Brazil and presented the same homozygous variant located in a highly conserved 3' splicing acceptor site of the GPIHBP1 gene. This new variant was named c.182-1G > T, according to HGVS recommendations. We verified this new GPIHBP1 variant's effect by using the Human Splicing Finder (HSF) tool. This mutation changes the GPIHBP1 pre-mRNA processing and possibly causes the skipping of the exon 3 of the GPIHBP1 gene, affecting almost 50% of the cysteine-rich Lys6 GPIHBP1 domain. Patients presented with severe hypertriglyceridemia (2351 mg/dl [885-20600]) and low HDL (18 mg/dl [5-41). Four patients (33%) had a previous history of acute pancreatitis. CONCLUSIONS We describe a novel GPIHBP1 pathogenic intronic mutation of patients from the Northeast region of Brazil, suggesting the occurrence of a founder effect.
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14
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Miyashita K, Lutz J, Hudgins LC, Toib D, Ashraf AP, Song W, Murakami M, Nakajima K, Ploug M, Fong LG, Young SG, Beigneux AP. Chylomicronemia from GPIHBP1 autoantibodies. J Lipid Res 2020; 61:1365-1376. [PMID: 32948662 PMCID: PMC7604722 DOI: 10.1194/jlr.r120001116] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Some cases of chylomicronemia are caused by autoantibodies against glycosylphosphatidylinositol-anchored HDL binding protein 1 (GPIHBP1), an endothelial cell protein that shuttles LPL to the capillary lumen. GPIHBP1 autoantibodies prevent binding and transport of LPL by GPIHBP1, thereby disrupting the lipolytic processing of triglyceride-rich lipoproteins. Here, we review the "GPIHBP1 autoantibody syndrome" and summarize clinical and laboratory findings in 22 patients. All patients had GPIHBP1 autoantibodies and chylomicronemia, but we did not find a correlation between triglyceride levels and autoantibody levels. Many of the patients had a history of pancreatitis, and most had clinical and/or serological evidence of autoimmune disease. IgA autoantibodies were present in all patients, and IgG4 autoantibodies were present in 19 of 22 patients. Patients with GPIHBP1 autoantibodies had low plasma LPL levels, consistent with impaired delivery of LPL into capillaries. Plasma levels of GPIHBP1, measured with a monoclonal antibody-based ELISA, were very low in 17 patients, reflecting the inability of the ELISA to detect GPIHBP1 in the presence of autoantibodies (immunoassay interference). However, GPIHBP1 levels were very high in five patients, indicating little capacity of their autoantibodies to interfere with the ELISA. Recently, several GPIHBP1 autoantibody syndrome patients were treated successfully with rituximab, resulting in the disappearance of GPIHBP1 autoantibodies and normalization of both plasma triglyceride and LPL levels. The GPIHBP1 autoantibody syndrome should be considered in any patient with newly acquired and unexplained chylomicronemia.
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Affiliation(s)
- Kazuya Miyashita
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Japan
- Immuno-Biological Laboratories (IBL), Fujioka, Gunma, Japan
| | - Jens Lutz
- Medical Clinic, Nephrology-Infectious Diseases, Central Rhine Hospital Group, Koblenz, Germany
| | - Lisa C Hudgins
- Rogosin Institute, Weill Cornell Medical College, New York, NY, USA
| | - Dana Toib
- Department of Pediatrics, Drexel University, Philadelphia, PA, USA
- Section of Pediatric Rheumatology, St. Christopher's Hospital for Children, Philadelphia, PA, USA
| | - Ambika P Ashraf
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Wenxin Song
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Japan
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Japan
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark
- Biotechnology Research Innovation Center, Copenhagen University, Copenhagen, Denmark
| | - Loren G Fong
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - 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
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
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15
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Unfolding of monomeric lipoprotein lipase by ANGPTL4: Insight into the regulation of plasma triglyceride metabolism. Proc Natl Acad Sci U S A 2020; 117:4337-4346. [PMID: 32034094 DOI: 10.1073/pnas.1920202117] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The binding of lipoprotein lipase (LPL) to GPIHBP1 focuses the intravascular hydrolysis of triglyceride-rich lipoproteins on the surface of capillary endothelial cells. This process provides essential lipid nutrients for vital tissues (e.g., heart, skeletal muscle, and adipose tissue). Deficiencies in either LPL or GPIHBP1 impair triglyceride hydrolysis, resulting in severe hypertriglyceridemia. The activity of LPL in tissues is regulated by angiopoietin-like proteins 3, 4, and 8 (ANGPTL). Dogma has held that these ANGPTLs inactivate LPL by converting LPL homodimers into monomers, rendering them highly susceptible to spontaneous unfolding and loss of enzymatic activity. Here, we show that binding of an LPL-specific monoclonal antibody (5D2) to the tryptophan-rich lipid-binding loop in the carboxyl terminus of LPL prevents homodimer formation and forces LPL into a monomeric state. Of note, 5D2-bound LPL monomers are as stable as LPL homodimers (i.e., they are not more prone to unfolding), but they remain highly susceptible to ANGPTL4-catalyzed unfolding and inactivation. Binding of GPIHBP1 to LPL alone or to 5D2-bound LPL counteracts ANGPTL4-mediated unfolding of LPL. In conclusion, ANGPTL4-mediated inactivation of LPL, accomplished by catalyzing the unfolding of LPL, does not require the conversion of LPL homodimers into monomers. Thus, our findings necessitate changes to long-standing dogma on mechanisms for LPL inactivation by ANGPTL proteins. At the same time, our findings align well with insights into LPL function from the recent crystal structure of the LPL•GPIHBP1 complex.
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16
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Yu J, Murthy V, Liu SL. Relating GPI-Anchored Ly6 Proteins uPAR and CD59 to Viral Infection. Viruses 2019; 11:E1060. [PMID: 31739586 PMCID: PMC6893729 DOI: 10.3390/v11111060] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 11/10/2019] [Accepted: 11/12/2019] [Indexed: 12/30/2022] Open
Abstract
The Ly6 (lymphocyte antigen-6)/uPAR (urokinase-type plasminogen activator receptor) superfamily protein is a group of molecules that share limited sequence homology but conserved three-fingered structures. Despite diverse cellular functions, such as in regulating host immunity, cell adhesion, and migration, the physiological roles of these factors in vivo remain poorly characterized. Notably, increasing research has focused on the interplays between Ly6/uPAR proteins and viral pathogens, the results of which have provided new insight into viral entry and virus-host interactions. While LY6E (lymphocyte antigen 6 family member E), one key member of the Ly6E/uPAR-family proteins, has been extensively studied, other members have not been well characterized. Here, we summarize current knowledge of Ly6/uPAR proteins related to viral infection, with a focus on uPAR and CD59. Our goal is to provide an up-to-date view of the Ly6/uPAR-family proteins and associated virus-host interaction and viral pathogenesis.
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Affiliation(s)
- Jingyou Yu
- Center for Retrovirus Research, The Ohio State University, Columbus, OH 43210, USA; (J.Y.); (V.M.)
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA
| | - Vaibhav Murthy
- Center for Retrovirus Research, The Ohio State University, Columbus, OH 43210, USA; (J.Y.); (V.M.)
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA
| | - Shan-Lu Liu
- Center for Retrovirus Research, The Ohio State University, Columbus, OH 43210, USA; (J.Y.); (V.M.)
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH 43210, USA
- Viruses and Emerging Pathogens Program, Infectious Diseases Institute, The Ohio State University, Columbus, OH 43210, USA
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17
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Abstract
Our understanding of the role of the vascular endothelium has evolved over the past 2 decades, with the recognition that it is a dynamically regulated organ and that it plays a nodal role in a variety of physiological and pathological processes. Endothelial cells (ECs) are not only a barrier between the circulation and peripheral tissues, but also actively regulate vascular tone, blood flow, and platelet function. Dysregulation of ECs contributes to pathological conditions such as vascular inflammation, atherosclerosis, hypertension, cardiomyopathy, retinopathy, neuropathy, and cancer. The close anatomic relationship between vascular endothelium and highly vascularized metabolic organs/tissues suggests that the crosstalk between ECs and these organs is vital for both vascular and metabolic homeostasis. Numerous reports support that hyperlipidemia, hyperglycemia, and other metabolic stresses result in endothelial dysfunction and vascular complications. However, how ECs may regulate metabolic homeostasis remains poorly understood. Emerging data suggest that the vascular endothelium plays an unexpected role in the regulation of metabolic homeostasis and that endothelial dysregulation directly contributes to the development of metabolic disorders. Here, we review recent studies about the pivotal role of ECs in glucose and lipid homeostasis. In particular, we introduce the concept that the endothelium adjusts its barrier function to control the transendothelial transport of fatty acids, lipoproteins, LPLs (lipoprotein lipases), glucose, and insulin. In addition, we summarize reports that ECs communicate with metabolic cells through EC-secreted factors and we discuss how endothelial dysregulation contributes directly to the development of obesity, insulin resistance, dyslipidemia, diabetes mellitus, cognitive defects, and fatty liver disease.
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Affiliation(s)
- Xinchun Pi
- From the Section of Athero & Lipo, Department of Medicine, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX (X.P., L.X.)
| | - Liang Xie
- From the Section of Athero & Lipo, Department of Medicine, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX (X.P., L.X.)
| | - Cam Patterson
- University of Arkansas for Medical Sciences, Little Rock (C.P.)
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18
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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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19
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Leth JM, Leth-Espensen KZ, Kristensen KK, Kumari A, Lund Winther AM, Young SG, Ploug M. Evolution and Medical Significance of LU Domain-Containing Proteins. Int J Mol Sci 2019; 20:ijms20112760. [PMID: 31195646 PMCID: PMC6600238 DOI: 10.3390/ijms20112760] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 05/31/2019] [Accepted: 06/04/2019] [Indexed: 12/13/2022] Open
Abstract
Proteins containing Ly6/uPAR (LU) domains exhibit very diverse biological functions and have broad taxonomic distributions in eukaryotes. In general, they adopt a characteristic three-fingered folding topology with three long loops projecting from a disulfide-rich globular core. The majority of the members of this protein domain family contain only a single LU domain, which can be secreted, glycolipid anchored, or constitute the extracellular ligand binding domain of type-I membrane proteins. Nonetheless, a few proteins contain multiple LU domains, for example, the urokinase receptor uPAR, C4.4A, and Haldisin. In the current review, we will discuss evolutionary aspects of this protein domain family with special emphasis on variations in their consensus disulfide bond patterns. Furthermore, we will present selected cases where missense mutations in LU domain-containing proteins leads to dysfunctional proteins that are causally linked to genesis of human disease.
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Affiliation(s)
- Julie Maja Leth
- Finsen Laboratory, Ole Maaloes Vej 5, Righospitalet, DK-2200 Copenhagen, Denmark.
- Biotechnology Research Innovation Centre (BRIC), Ole Maaloes Vej 5, University of Copenhagen, DK-2200 Copenhagen, Denmark.
| | - Katrine Zinck Leth-Espensen
- Finsen Laboratory, Ole Maaloes Vej 5, Righospitalet, DK-2200 Copenhagen, Denmark.
- Biotechnology Research Innovation Centre (BRIC), Ole Maaloes Vej 5, University of Copenhagen, DK-2200 Copenhagen, Denmark.
| | - Kristian Kølby Kristensen
- Finsen Laboratory, Ole Maaloes Vej 5, Righospitalet, DK-2200 Copenhagen, Denmark.
- Biotechnology Research Innovation Centre (BRIC), Ole Maaloes Vej 5, University of Copenhagen, DK-2200 Copenhagen, Denmark.
| | - Anni Kumari
- Finsen Laboratory, Ole Maaloes Vej 5, Righospitalet, DK-2200 Copenhagen, Denmark.
- Biotechnology Research Innovation Centre (BRIC), Ole Maaloes Vej 5, University of Copenhagen, DK-2200 Copenhagen, Denmark.
| | - Anne-Marie Lund Winther
- Finsen Laboratory, Ole Maaloes Vej 5, Righospitalet, DK-2200 Copenhagen, Denmark.
- Biotechnology Research Innovation Centre (BRIC), Ole Maaloes Vej 5, University of Copenhagen, DK-2200 Copenhagen, Denmark.
| | - Stephen G Young
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
- Department of Human Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| | - Michael Ploug
- Finsen Laboratory, Ole Maaloes Vej 5, Righospitalet, DK-2200 Copenhagen, Denmark.
- Biotechnology Research Innovation Centre (BRIC), Ole Maaloes Vej 5, University of Copenhagen, DK-2200 Copenhagen, Denmark.
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20
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Allan CM, Heizer PJ, Tu Y, Sandoval NP, Jung RS, Morales JE, Sajti E, Troutman TD, Saunders TL, Cusanovich DA, Beigneux AP, Romanoski CE, Fong LG, Young SG. An upstream enhancer regulates Gpihbp1 expression in a tissue-specific manner. J Lipid Res 2019; 60:869-879. [PMID: 30598475 PMCID: PMC6446700 DOI: 10.1194/jlr.m091322] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 12/02/2018] [Indexed: 01/22/2023] Open
Abstract
Glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1), the protein that shuttles LPL to the capillary lumen, is essential for plasma triglyceride metabolism. When GPIHBP1 is absent, LPL remains stranded within the interstitial spaces and plasma triglyceride hydrolysis is impaired, resulting in severe hypertriglyceridemia. While the functions of GPIHBP1 in intravascular lipolysis are reasonably well understood, no one has yet identified DNA sequences regulating GPIHBP1 expression. In the current studies, we identified an enhancer element located ∼3.6 kb upstream from exon 1 of mouse Gpihbp1. To examine the importance of the enhancer, we used CRISPR/Cas9 genome editing to create mice lacking the enhancer (Gpihbp1Enh/Enh). Removing the enhancer reduced Gpihbp1 expression by >90% in the liver and by ∼50% in heart and brown adipose tissue. The reduced expression of GPIHBP1 was insufficient to prevent LPL from reaching the capillary lumen, and it did not lead to hypertriglyceridemia-even when mice were fed a high-fat diet. Compound heterozygotes (Gpihbp1Enh/- mice) displayed further reductions in Gpihbp1 expression and exhibited partial mislocalization of LPL (increased amounts of LPL within the interstitial spaces of the heart), but the plasma triglyceride levels were not perturbed. The enhancer element that we identified represents the first insight into DNA sequences controlling Gpihbp1 expression.
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Affiliation(s)
- Christopher M Allan
- 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
| | - Rachel S Jung
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA 90095
| | - Jazmin E Morales
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA 90095
| | - Eniko Sajti
- Department of Pediatrics, Division of Neurology, Rady Children's Hospital, University of California, San Diego, San Diego, CA 92123
| | - Ty D Troutman
- Department of Cellular and Molecular Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Thomas L Saunders
- University of Michigan Transgenic Animal Model Core, Department of Medicine, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Darren A Cusanovich
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721
| | - Anne P Beigneux
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA 90095
| | - Casey E Romanoski
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721.
| | - 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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Leth JM, Mertens HDT, Leth-Espensen KZ, Jørgensen TJD, Ploug M. Did evolution create a flexible ligand-binding cavity in the urokinase receptor through deletion of a plesiotypic disulfide bond? J Biol Chem 2019; 294:7403-7418. [PMID: 30894413 DOI: 10.1074/jbc.ra119.007847] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/10/2019] [Indexed: 11/06/2022] Open
Abstract
The urokinase receptor (uPAR) is a founding member of a small protein family with multiple Ly6/uPAR (LU) domains. The motif defining these LU domains contains five plesiotypic disulfide bonds stabilizing its prototypical three-fingered fold having three protruding loops. Notwithstanding the detailed knowledge on structure-function relationships in uPAR, one puzzling enigma remains unexplored. Why does the first LU domain in uPAR (DI) lack one of its consensus disulfide bonds, when the absence of this particular disulfide bond impairs the correct folding of other single LU domain-containing proteins? Here, using a variety of contemporary biophysical methods, we found that reintroducing the two missing half-cystines in uPAR DI caused the spontaneous formation of the corresponding consensus 7-8 LU domain disulfide bond. Importantly, constraints due to this cross-link impaired (i) the binding of uPAR to its primary ligand urokinase and (ii) the flexible interdomain assembly of the three LU domains in uPAR. We conclude that the evolutionary deletion of this particular disulfide bond in uPAR DI may have enabled the assembly of a high-affinity urokinase-binding cavity involving all three LU domains in uPAR. Of note, an analogous neofunctionalization occurred in snake venom α-neurotoxins upon loss of another pair of the plesiotypic LU domain half-cystines. In summary, elimination of the 7-8 consensus disulfide bond in the first LU domain of uPAR did have significant functional and structural consequences.
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Affiliation(s)
- Julie M Leth
- From the Finsen Laboratory, Rigshospitalet, DK-2200 Copenhagen N, Denmark.,the Biotech Research and Innovation Centre (BRIC), University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Haydyn D T Mertens
- the European Molecular Biology Laboratory Hamburg, Notkestrasse 85, D-22607 Hamburg, Germany, and
| | - Katrine Zinck Leth-Espensen
- From the Finsen Laboratory, Rigshospitalet, DK-2200 Copenhagen N, Denmark.,the Biotech Research and Innovation Centre (BRIC), University of Copenhagen, DK-2200 Copenhagen N, Denmark.,the Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5320 Odense M, Denmark
| | - Thomas J D Jørgensen
- the Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5320 Odense M, Denmark
| | - Michael Ploug
- From the Finsen Laboratory, Rigshospitalet, DK-2200 Copenhagen N, Denmark, .,the Biotech Research and Innovation Centre (BRIC), University of Copenhagen, DK-2200 Copenhagen N, Denmark
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22
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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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23
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GPIHBP1 autoantibody syndrome during interferon β1a treatment. J Clin Lipidol 2018; 13:62-69. [PMID: 30514621 DOI: 10.1016/j.jacl.2018.10.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 09/21/2018] [Accepted: 10/12/2018] [Indexed: 01/15/2023]
Abstract
BACKGROUND Autoantibodies against glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) cause chylomicronemia by blocking the ability of GPIHBP1 to bind lipoprotein lipase (LPL) and transport the enzyme to its site of action in the capillary lumen. OBJECTIVE A patient with multiple sclerosis developed chylomicronemia during interferon (IFN) β1a therapy. The chylomicronemia resolved when the IFN β1a therapy was discontinued. Here, we sought to determine whether the drug-induced chylomicronemia was caused by GPIHBP1 autoantibodies. METHODS We tested plasma samples collected during and after IFN β1a therapy for GPIHBP1 autoantibodies (by western blotting and with enzyme-linked immunosorbent assays). We also tested whether the patient's plasma blocked the binding of LPL to GPIHBP1 on GPIHBP1-expressing cells. RESULTS During IFN β1a therapy, the plasma contained GPIHBP1 autoantibodies, and those autoantibodies blocked GPIHBP1's ability to bind LPL. Thus, the chylomicronemia was because of the GPIHBP1 autoantibody syndrome. Consistent with that diagnosis, the plasma levels of GPIHBP1 and LPL were very low. After IFN β1a therapy was stopped, the plasma triglyceride levels returned to normal, and GPIHBP1 autoantibodies were undetectable. CONCLUSION The appearance of GPIHBP1 autoantibodies during IFN β1a therapy caused chylomicronemia. The GPIHBP1 autoantibodies disappeared when the IFN β1a therapy was stopped, and the plasma triglyceride levels fell within the normal range.
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Miyashita K, Fukamachi I, Machida T, Nakajima K, Young SG, Murakami M, Beigneux AP, Nakajima K. An ELISA for quantifying GPIHBP1 autoantibodies and making a diagnosis of the GPIHBP1 autoantibody syndrome. Clin Chim Acta 2018; 487:174-178. [PMID: 30287259 DOI: 10.1016/j.cca.2018.09.039] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 09/27/2018] [Accepted: 09/28/2018] [Indexed: 01/04/2023]
Abstract
BACKGROUND Autoantibodies against GPIHBP1, the endothelial cell transporter for lipoprotein lipase (LPL), cause severe hypertriglyceridemia ("GPIHBP1 autoantibody syndrome"). Affected patients have low serum GPIHBP1 and LPL levels. We report the development of a sensitive and specific ELISA, suitable for routine clinical use, to detect GPIHBP1 autoantibodies in serum and plasma. METHODS Serum and plasma samples were added to wells of an ELISA plate that had been coated with recombinant human GPIHBP1. GPIHBP1 autoantibodies bound to GPIHBP1 were detected with an HRP-labeled antibody against human immunoglobulin. Sensitivity, specificity, and reproducibility of the ELISA was evaluated with plasma or serum samples from patients with the GPIHBP1 autoantibody syndrome. RESULTS A solid-phase ELISA to detect and quantify GPIHBP1 autoantibodies in human plasma and serum was developed. Spiking recombinant human GPIHBP1 into the samples reduced the ability of the ELISA to detect GPIHBP1 autoantibodies. The ELISA is reproducible and sensitive; it can detect GPIHBP1 autoantibodies in samples diluted by >1000-fold. CONCLUSION We have developed a sensitive and specific ELISA for detecting GPIHBP1 autoantibodies in human serum and plasma; this assay will make it possible to rapidly diagnose the GPIHBP1 autoantibody syndrome.
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Affiliation(s)
| | | | - Tetsuo Machida
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Kiyomi Nakajima
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Stephen G Young
- Department of Medicine and David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90025, United States; Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90025, United States
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Anne P Beigneux
- Department of Medicine and David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90025, United States.
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
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25
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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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26
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Miyashita K, Fukamachi I, Nagao M, Ishida T, Kobayashi J, Machida T, Nakajima K, Murakami M, Ploug M, Beigneux AP, Young SG, Nakajima K. An enzyme-linked immunosorbent assay for measuring GPIHBP1 levels in human plasma or serum. J Clin Lipidol 2017; 12:203-210.e1. [PMID: 29246728 DOI: 10.1016/j.jacl.2017.10.022] [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: 07/12/2017] [Revised: 10/23/2017] [Accepted: 10/24/2017] [Indexed: 12/17/2022]
Abstract
BACKGROUND Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1), a glycosylphosphatidylinositol (GPI)-anchored protein of capillary endothelial cells, transports lipoprotein lipase to the capillary lumen and is essential for the lipolytic processing of triglyceride-rich lipoproteins. OBJECTIVE Because some GPI-anchored proteins have been detected in plasma, we tested whether GPIHBP1 is present in human blood and whether GPIHBP1 deficiency or a history of cardiovascular disease affected GPIHBP1 circulating levels. METHODS We developed 2 monoclonal antibodies against GPIHBP1 and used the antibodies to establish a sandwich enzyme-linked immunosorbent assay (ELISA) to measure GPIHBP1 levels in human blood. RESULTS The GPIHBP1 ELISA was linear in the 8 to 500 pg/mL range and allowed the quantification of GPIHBP1 in serum and in pre- and post-heparin plasma (including lipemic samples). GPIHBP1 was undetectable in the plasma of subjects with null mutations in GPIHBP1. Serum GPIHBP1 median levels were 849 pg/mL (range: 740-1014) in healthy volunteers (n = 28) and 1087 pg/mL (range: 877-1371) in patients with a history of cardiovascular or metabolic disease (n = 415). There was an extremely small inverse correlation between GPIHBP1 and triglyceride levels (r = 0.109; P < .0275). GPIHBP1 levels tended to be slightly higher in patients who had a major cardiovascular event after revascularization. CONCLUSION We developed an ELISA for quantifying GPIHBP1 in human blood. This assay will be useful to identify patients with GPIHBP1 deficiency and patients with GPIHBP1 autoantibodies. The potential of plasma GPIHBP1 as a biomarker for metabolic or cardiovascular disease is yet questionable but needs additional testing.
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Affiliation(s)
| | | | - Manabu Nagao
- Division of Cardiovascular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Tatsuro Ishida
- Division of Cardiovascular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Junji Kobayashi
- Department of General Internal Medicine, Kanazawa Medical University, Kanazawa, Ishikawa, Japan
| | - Tetsuo Machida
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Kiyomi 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
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark; Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - 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
| | - Katsuyuki Nakajima
- Department of General Internal Medicine, Kanazawa Medical University, Kanazawa, Ishikawa, Japan; Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
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27
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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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28
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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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29
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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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30
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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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Mysling S, Kristensen KK, Larsson M, Kovrov O, Bensadouen A, Jørgensen TJ, Olivecrona G, Young SG, Ploug M. The angiopoietin-like protein ANGPTL4 catalyzes unfolding of the hydrolase domain in lipoprotein lipase and the endothelial membrane protein GPIHBP1 counteracts this unfolding. eLife 2016; 5. [PMID: 27929370 PMCID: PMC5148603 DOI: 10.7554/elife.20958] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 11/14/2016] [Indexed: 01/08/2023] Open
Abstract
Lipoprotein lipase (LPL) undergoes spontaneous inactivation via global unfolding and this unfolding is prevented by GPIHBP1 (Mysling et al., 2016). We now show: (1) that ANGPTL4 inactivates LPL by catalyzing the unfolding of its hydrolase domain; (2) that binding to GPIHBP1 renders LPL largely refractory to this inhibition; and (3) that both the LU domain and the intrinsically disordered acidic domain of GPIHBP1 are required for this protective effect. Genetic studies have found that a common polymorphic variant in ANGPTL4 results in lower plasma triglyceride levels. We now report: (1) that this ANGPTL4 variant is less efficient in catalyzing the unfolding of LPL; and (2) that its Glu-to-Lys substitution destabilizes its N-terminal α-helix. Our work elucidates the molecular basis for regulation of LPL activity by ANGPTL4, highlights the physiological relevance of the inherent instability of LPL, and sheds light on the molecular defects in a clinically relevant variant of ANGPTL4. DOI:http://dx.doi.org/10.7554/eLife.20958.001
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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
| | - Oleg Kovrov
- Department of Medical Biosciences, Umeå University, Umeå, Sweden
| | - 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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Allan CM, Larsson M, Jung RS, Ploug M, Bensadoun A, Beigneux AP, Fong LG, Young SG. Mobility of "HSPG-bound" LPL explains how LPL is able to reach GPIHBP1 on capillaries. J Lipid Res 2016; 58:216-225. [PMID: 27811232 DOI: 10.1194/jlr.m072520] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 10/31/2016] [Indexed: 12/22/2022] Open
Abstract
In mice lacking glycosylphosphatidylinositol-anchored high density lipoprotein binding protein 1 (GPIHBP1), the LPL secreted by adipocytes and myocytes remains bound to heparan sulfate proteoglycans (HSPGs) on all cells within tissues. That observation raises a perplexing issue: Why isn't the freshly secreted LPL in wild-type mice captured by the same HSPGs, thereby preventing LPL from reaching GPIHBP1 on capillaries? We hypothesized that LPL-HSPG interactions are transient, allowing the LPL to detach and move to GPIHBP1 on capillaries. Indeed, we found that LPL detaches from HSPGs on cultured cells and moves to: 1) soluble GPIHBP1 in the cell culture medium; 2) GPIHBP1-coated agarose beads; and 3) nearby GPIHBP1-expressing cells. Movement of HSPG-bound LPL to GPIHBP1 did not occur when GPIHBP1 contained a Ly6 domain missense mutation (W109S), but was almost normal when GPIHBP1's acidic domain was mutated. To test the mobility of HSPG-bound LPL in vivo, we injected GPIHBP1-coated agarose beads into the brown adipose tissue of GPIHBP1-deficient mice. LPL moved quickly from HSPGs on adipocytes to GPIHBP1-coated beads, thereby depleting LPL stores on the surface of adipocytes. We conclude that HSPG-bound LPL in the interstitial spaces of tissues is mobile, allowing the LPL to move to GPIHBP1 on endothelial cells.
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Affiliation(s)
- Christopher M Allan
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Mikael Larsson
- 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
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, DK-2200 Copenhagen N, Denmark and Biotech Research and Innovation Centre (BRIC), University of Copenhagen, DK-220 Copenhagen N, Denmark
| | - André Bensadoun
- Division of Nutritional Science, Cornell University, Ithaca, NY 14853
| | - Anne P Beigneux
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - 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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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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Patni N, Brothers J, Xing C, Garg A. Type 1 hyperlipoproteinemia in a child with large homozygous deletion encompassing GPIHBP1. J Clin Lipidol 2016; 10:1035-1039.e2. [DOI: 10.1016/j.jacl.2016.04.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 03/30/2016] [Accepted: 04/03/2016] [Indexed: 01/12/2023]
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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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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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Wu M, Liu CZ, Joiner WJ. Structural Analysis and Deletion Mutagenesis Define Regions of QUIVER/SLEEPLESS that Are Responsible for Interactions with Shaker-Type Potassium Channels and Nicotinic Acetylcholine Receptors. PLoS One 2016; 11:e0148215. [PMID: 26828958 PMCID: PMC4735452 DOI: 10.1371/journal.pone.0148215] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 01/13/2016] [Indexed: 12/16/2022] Open
Abstract
Ly6 proteins are endogenous prototoxins found in most animals. They show striking structural and functional parallels to snake α-neurotoxins, including regulation of ion channels and cholinergic signaling. However, the structural contributions of Ly6 proteins to regulation of effector molecules is poorly understood. This question is particularly relevant to the Ly6 protein QUIVER/SLEEPLESS (QVR/SSS), which has previously been shown to suppress excitability and synaptic transmission by upregulating potassium (K) channels and downregulating nicotinic acetylcholine receptors (nAChRs) in wake-promoting neurons to facilitate sleep in Drosophila. Using deletion mutagenesis, co-immunoprecipitations, ion flux assays, surface labeling and confocal microscopy, we demonstrate that only loop 2 is required for many of the previously described properties of SSS in transfected cells, including interactions with K channels and nAChRs. Collectively our data suggest that QVR/SSS, and by extension perhaps other Ly6 proteins, target effector molecules using limited protein motifs. Mapping these motifs may be useful in rational design of drugs that mimic or suppress Ly6-effector interactions to modulate nervous system function.
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Affiliation(s)
- Meilin Wu
- Department of Pharmacology, University of California San Diego, La Jolla, California, United States of America
| | - Clifford Z Liu
- UCSD undergraduate program, Marshall College, University of California San Diego, La Jolla, California, United States of America
| | - William J Joiner
- Department of Pharmacology, University of California San Diego, La Jolla, California, United States of America.,Center for Circadian Biology, University of California San Diego, La Jolla, California, United States of America
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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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Khovidhunkit W, Charoen S, Kiateprungvej A, Chartyingcharoen P, Muanpetch S, Plengpanich W. Rare and common variants in LPL and APOA5 in Thai subjects with severe hypertriglyceridemia: A resequencing approach. J Clin Lipidol 2015; 10:505-511.e1. [PMID: 27206937 DOI: 10.1016/j.jacl.2015.11.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 10/29/2015] [Accepted: 11/01/2015] [Indexed: 12/01/2022]
Abstract
BACKGROUND Severe hypertriglyceridemia usually results from a combination of genetic and environmental factors. Few data exist on the genetics of severe hypertriglyceridemia in Asian populations. OBJECTIVE To examine the genetic variants of 3 candidate genes known to influence triglyceride metabolism, LPL, APOC2, and APOA5, which encode lipoprotein lipase, apolipoprotein C-II, and apolipoprotein A-V, respectively, in a large group of Thai subjects with severe hypertriglyceridemia. METHODS We identified sequence variants of LPL, APOC2, and APOA5 by sequencing exons and exon-intron junctions in 101 subjects with triglyceride levels ≥ 10 mmol/L (886 mg/dL) and compared with those of 111 normotriglyceridemic subjects. RESULTS Six different rare variants in LPL were found in 13 patients, 2 of which were novel (1 heterozygous missense variant: p.Arg270Gly and 1 frameshift variant: p.Asp308Glyfs*3). Four previously identified heterozygous missense variants in LPL were p.Ala98Thr, p.Leu279Val, p.Leu279Arg, and p.Arg432Thr. Collectively, these rare variants were found only in the hypertriglyceridemic group but not in the control group (13% vs 0%, P < .0001). One common variant in APOA5 (p.Gly185Cys, rs2075291) was found at a higher frequency in the hypertriglyceridemic group compared with the control group (25% vs 6%, respectively, P < .0005). Altogether, rare variants in LPL or APOA5 and/or the common APOA5 p.Gly185Cys variant were found in 37% of the hypertriglyceridemic group vs 6% in the controls (P = 3.1 × 10(-8)). No rare variant in APOC2 was identified. CONCLUSIONS Rare variants in LPL and a common variant in APOA5 were more commonly found in Thai subjects with severe hypertriglyceridemia. A common p.Gly185Cys APOA5 variant, in particular, was quite prevalent and potentially contributed to hypertriglyceridemia in this group of patients.
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Affiliation(s)
- Weerapan Khovidhunkit
- Hormonal and Metabolic Disorders Research Unit, Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand; Department of Medicine, Excellence Center for Diabetes, Hormone, and Metabolism, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand.
| | - Supannika Charoen
- Hormonal and Metabolic Disorders Research Unit, Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Arunrat Kiateprungvej
- Hormonal and Metabolic Disorders Research Unit, Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Palm Chartyingcharoen
- Hormonal and Metabolic Disorders Research Unit, Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand; Department of Medicine, Excellence Center for Diabetes, Hormone, and Metabolism, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
| | - Suwanna Muanpetch
- Hormonal and Metabolic Disorders Research Unit, Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand; Department of Medicine, Excellence Center for Diabetes, Hormone, and Metabolism, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
| | - Wanee Plengpanich
- Hormonal and Metabolic Disorders Research Unit, Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand; Department of Medicine, Excellence Center for Diabetes, Hormone, and Metabolism, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
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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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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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Abstract
This Review discusses new developments in understanding the basis of chylomicronaemia--a challenging metabolic disorder for which there is an unmet clinical need. Chylomicronaemia presents in two distinct primary forms. The first form is very rare monogenic early-onset chylomicronaemia, which presents in childhood or adolescence and is often caused by homozygous mutations in the gene encoding lipoprotein lipase (LPL), its cofactors apolipoprotein C-II or apolipoprotein A-V, the LPL chaperone lipase maturation factor 1 or glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1. The second form, polygenic late-onset chylomicronaemia, which is caused by an accumulation of several genetic variants, can be exacerbated by secondary factors, such as poor diet, obesity, alcohol intake and uncontrolled type 1 or type 2 diabetes mellitus, and is more common than early-onset chylomicronaemia. Both forms of chylomicronaemia are associated with an increased risk of life-threatening pancreatitis; the polygenic form might also be associated with an increased risk of cardiovascular disease. Treatment of chylomicronaemia focuses on restriction of dietary fat and control of secondary factors, as available pharmacological therapies are only minimally effective. Emerging therapies that might prove more effective than existing agents include LPL gene therapy, inhibition of microsomal triglyceride transfer protein and diacylglycerol O-acyltransferase 1, and interference with the production and secretion of apoC-III and angiopoietin-like protein 3.
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Affiliation(s)
- Amanda J Brahm
- Department of Medicine, Schulich School of Medicine and Dentistry, Western University, 4288A-1151 Richmond Street North, London, ON N6A 5B7, Canada
| | - Robert A Hegele
- Department of Medicine, Schulich School of Medicine and Dentistry, Western University, 4288A-1151 Richmond Street North, London, ON N6A 5B7, Canada
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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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Affiliation(s)
- Sara N Vallerie
- From the Department of Medicine, Division of Metabolism, Endocrinology and Nutrition (S.N.V., K.E.B.), and Department of Pathology (K.E.B.), Diabetes and Obesity Center of Excellence, University of Washington School of Medicine, Seattle, WA
| | - Karin E Bornfeldt
- From the Department of Medicine, Division of Metabolism, Endocrinology and Nutrition (S.N.V., K.E.B.), and Department of Pathology (K.E.B.), Diabetes and Obesity Center of Excellence, University of Washington School of Medicine, Seattle, WA.
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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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