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Chi X, Shetty SK, Shows HW, Hjelmaas AJ, Malcolm EK, Davies BSJ. Angiopoietin-like 4 Modifies the Interactions between Lipoprotein Lipase and Its Endothelial Cell Transporter GPIHBP1. J Biol Chem 2015; 290:11865-77. [PMID: 25809481 DOI: 10.1074/jbc.m114.623769] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Indexed: 12/26/2022] Open
Abstract
The release of fatty acids from plasma triglycerides for tissue uptake is critically dependent on the enzyme lipoprotein lipase (LPL). Hydrolysis of plasma triglycerides by LPL can be disrupted by the protein angiopoietin-like 4 (ANGPTL4), and ANGPTL4 has been shown to inactivate LPL in vitro. However, in vivo LPL is often complexed to glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) on the surface of capillary endothelial cells. GPIHBP1 is responsible for trafficking LPL across capillary endothelial cells and anchors LPL to the capillary wall during lipolysis. How ANGPTL4 interacts with LPL in this context is not known. In this study, we investigated the interactions of ANGPTL4 with LPL-GPIHBP1 complexes on the surface of endothelial cells. We show that ANGPTL4 was capable of binding and inactivating LPL complexed to GPIHBP1 on the surface of endothelial cells. Once inactivated, LPL dissociated from GPIHBP1. We also show that ANGPTL4-inactivated LPL was incapable of binding GPIHBP1. ANGPTL4 was capable of binding, but not inactivating, LPL at 4 °C, suggesting that binding alone was not sufficient for ANGPTL4's inhibitory activity. We observed that although the N-terminal coiled-coil domain of ANGPTL4 by itself and full-length ANGPTL4 both bound with similar affinities to LPL, the N-terminal fragment was more potent in inactivating both free and GPIHBP1-bound LPL. These results led us to conclude that ANGPTL4 can both bind and inactivate LPL complexed to GPIHBP1 and that inactivation of LPL by ANGPTL4 greatly reduces the affinity of LPL for GPIHBP1.
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Affiliation(s)
- Xun Chi
- From the Department of Biochemistry, Fraternal Order of Eagles Diabetes Research Center and Obesity Research and Education Initiative, University of Iowa, Iowa City, Iowa 52242
| | - Shwetha K Shetty
- From the Department of Biochemistry, Fraternal Order of Eagles Diabetes Research Center and Obesity Research and Education Initiative, University of Iowa, Iowa City, Iowa 52242
| | - Hannah W Shows
- From the Department of Biochemistry, Fraternal Order of Eagles Diabetes Research Center and Obesity Research and Education Initiative, University of Iowa, Iowa City, Iowa 52242
| | - Alexander J Hjelmaas
- From the Department of Biochemistry, Fraternal Order of Eagles Diabetes Research Center and Obesity Research and Education Initiative, University of Iowa, Iowa City, Iowa 52242
| | - Emily K Malcolm
- From the Department of Biochemistry, Fraternal Order of Eagles Diabetes Research Center and Obesity Research and Education Initiative, University of Iowa, Iowa City, Iowa 52242
| | - Brandon S J Davies
- From the Department of Biochemistry, Fraternal Order of Eagles Diabetes Research Center and Obesity Research and Education Initiative, University of Iowa, Iowa City, Iowa 52242
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Harrington JM, Nishanova T, Pena SR, Hess M, Scelsi CL, Widener J, Hajduk SL. A retained secretory signal peptide mediates high density lipoprotein (HDL) assembly and function of haptoglobin-related protein. J Biol Chem 2014; 289:24811-20. [PMID: 25037218 DOI: 10.1074/jbc.m114.567578] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Haptoglobin-related protein (Hpr) is a component of a minor subspecies of high density lipoproteins (HDL) that function in innate immunity. Here we show that assembly of Hpr into HDL is mediated by its retained N-terminal signal peptide, an unusual feature for a secreted protein and the major difference between Hpr and the soluble acute phase protein haptoglobin (Hp). The 18-amino acid signal peptide is necessary for binding to HDL and interacts directly with the hydrocarbon region of lipids. Utilizing model liposomes, we show that the rate of assembly and steady-state distribution of Hpr in lipid particles is mediated by the physical property of lipid fluidity. Dye release assays reveal that Hpr interacts more rapidly with fluid liposomes. Conversely, steady-state binding assays indicate that more rigid lipid compositions stabilize Hpr association. Lipid association also plays a role in facilitating hemoglobin binding by Hpr. Our data may offer an explanation for the distinct distribution of Hpr among HDL subspecies. Rather than protein-protein interactions mediating localization, direct interaction with phospholipids and sensitivity to lipid fluidity may be sufficient for localization of Hpr and may represent a mechanism of HDL subspeciation.
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Affiliation(s)
- John M Harrington
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
| | - Tuiumkan Nishanova
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
| | - Savannah Rose Pena
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
| | - Matthew Hess
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
| | - Chris L Scelsi
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
| | - Justin Widener
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
| | - Stephen L Hajduk
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
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Larsson M, Vorrsjö E, Talmud P, Lookene A, Olivecrona G. Apolipoproteins C-I and C-III inhibit lipoprotein lipase activity by displacement of the enzyme from lipid droplets. J Biol Chem 2013; 288:33997-34008. [PMID: 24121499 DOI: 10.1074/jbc.m113.495366] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Apolipoproteins (apo) C-I and C-III are known to inhibit lipoprotein lipase (LPL) activity, but the molecular mechanisms for this remain obscure. We present evidence that either apoC-I or apoC-III, when bound to triglyceride-rich lipoproteins, prevent binding of LPL to the lipid/water interface. This results in decreased lipolytic activity of the enzyme. Site-directed mutagenesis revealed that hydrophobic amino acid residues centrally located in the apoC-III molecule are critical for attachment to lipid emulsion particles and consequently inhibition of LPL activity. Triglyceride-rich lipoproteins stabilize LPL and protect the enzyme from inactivating factors such as angiopoietin-like protein 4 (angptl4). The addition of either apoC-I or apoC-III to triglyceride-rich particles severely diminished their protective effect on LPL and rendered the enzyme more susceptible to inactivation by angptl4. These observations were seen using chylomicrons as well as the synthetic lipid emulsion Intralipid. In the presence of the LPL activator protein apoC-II, more of apoC-I or apoC-III was needed for displacement of LPL from the lipid/water interface. In conclusion, we show that apoC-I and apoC-III inhibit lipolysis by displacing LPL from lipid emulsion particles. We also propose a role for these apolipoproteins in the irreversible inactivation of LPL by factors such as angptl4.
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Affiliation(s)
- Mikael Larsson
- Department of Medical Biosciences/Physiological Chemistry, Umeå University, SE-901 87 Umeå, Sweden
| | - Evelina Vorrsjö
- Department of Medical Biosciences/Physiological Chemistry, Umeå University, SE-901 87 Umeå, Sweden
| | - Philippa Talmud
- Centre for Cardiovascular Genetics, Institute of Cardiovascular Science, University College London, 5 University Street, London WC1E 6JF, United Kingdom
| | - Aivar Lookene
- Department of Chemistry, Tallinn University of Technology, Tallinn 12618, Estonia
| | - Gunilla Olivecrona
- Department of Medical Biosciences/Physiological Chemistry, Umeå University, SE-901 87 Umeå, Sweden.
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Josekutty J, Iqbal J, Iwawaki T, Kohno K, Hussain MM. Microsomal triglyceride transfer protein inhibition induces endoplasmic reticulum stress and increases gene transcription via Ire1α/cJun to enhance plasma ALT/AST. J Biol Chem 2013; 288:14372-14383. [PMID: 23532846 DOI: 10.1074/jbc.m113.459602] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Microsomal triglyceride transfer protein (MTP) is a target to reduce plasma lipids because of its indispensable role in triglyceride-rich lipoprotein biosynthesis. MTP inhibition in Western diet fed mice decreased plasma triglycerides/cholesterol, whereas increasing plasma alanine/aspartate aminotransferases (ALT/AST) and hepatic triglycerides/free cholesterol. Free cholesterol accumulated in the endoplasmic reticulum (ER) and mitochondria resulting in ER and oxidative stresses. Mechanistic studies revealed that MTP inhibition increased transcription of the GPT/GOT1 genes through up-regulation of the IRE1α/cJun pathway leading to increased synthesis and release of ALT1/AST1. Thus, transcriptional up-regulation of GPT/GOT1 genes is a major mechanism, in response to ER stress, elevating plasma transaminases. Increases in plasma and tissue transaminases might represent a normal response to stress for survival.
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Affiliation(s)
- Joby Josekutty
- School of Graduate Studies, Molecular and Cell Biology Program, State University of New York Downstate Medical Center, Brooklyn, New York 11203; Departments of Cell Biology and Pediatrics, State University of New York Downstate Medical Center, Brooklyn, New York 11203
| | - Jahangir Iqbal
- Departments of Cell Biology and Pediatrics, State University of New York Downstate Medical Center, Brooklyn, New York 11203
| | - Takao Iwawaki
- Advanced Scientific Research Leaders Development Unit, Gunma University, Gunma, Japan
| | - Kenji Kohno
- Nara Institute of Science and Technology, Nara, Japan
| | - M Mahmood Hussain
- Departments of Cell Biology and Pediatrics, State University of New York Downstate Medical Center, Brooklyn, New York 11203.
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Rao AM, Bitla AR, Reddy EP, Sivakumar V, Srinivasa Rao PVLN. Lipid abnormalities, lipoprotein (a) and apoprotein pattern in non-dialyzed patients with chronic kidney disease. Indian J Clin Biochem 2010; 25:47-50. [PMID: 23105883 DOI: 10.1007/s12291-010-0010-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The present study was carried out to explore the altered lipid, lipoprotein and apoprotein abnormalities along with lipoprotein (a) in chronic kidney disease patients with stage I to V which were further divided into group 1 (stage I and II), group 2 (stage III and IV) and group 3 (stage V). 50 chronic kidney disease patients with stage I to V and 20 healthy normal subjects as controls were recruited for this study. Among the various parameters tested triglyceride levels were high in group 1 and 2, whereas VLDL cholesterol, Lp (a) and apo B levels were significantly high in all the groups when compared to controls (P<0.05). However, LDL cholesterol level was significantly low in group 3 only as compared to control group (P<0.05). Apoprotein AI values also showed significant decrease in all groups as compared to controls (P<0.05). Though total cholesterol levels in group 1 and LDL levels in group 1 and 2 were higher than controls, but the values attained not statistically significant (P>0.05). In conclusion high levels of VLDL cholesterol, Lp (a), apo B and low levels of apoprotein AI as reported in this study are the major lipid disorders in the development of cardiovascular complications at all the stages in these patients.
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Affiliation(s)
- A Madhusudhana Rao
- Department of Biochemistry, Sri Venkaterswara Institute of Medical Sciences, Tirupati, 517507 Chittor, AP India ; Department of Biochemistry, PSG Institute of Medical Sciences & Research, Peelamedu, Coimbatore, 641004 Tamilnadu India
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