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MacKeigan DT, Yu SY, Chazot N, Zhang D, Khoury CJ, Lei X, Bhoria P, Shen C, Chen P, Zhu G, Rand ML, Heximer S, Ni H. Apolipoprotein A-IV polymorphisms Q360H and T347S attenuate its endogenous inhibition of thrombosis. Biochem Biophys Res Commun 2024; 712-713:149946. [PMID: 38643717 DOI: 10.1016/j.bbrc.2024.149946] [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: 03/25/2024] [Accepted: 04/15/2024] [Indexed: 04/23/2024]
Abstract
Platelets are small anucleate cells that play a key role in thrombosis and hemostasis. Our group previously identified apolipoprotein A-IV (apoA-IV) as an endogenous inhibitor of thrombosis by competitive blockade of the αIIbβ3 integrin on platelets. ApoA-IV inhibition of platelets was dependent on the N-terminal D5/D13 residues, and enhanced with absence of the C-terminus, suggesting it sterically hinders its N-terminal platelet binding site. The C-terminus is also the site of common apoA-IV polymorphisms apoA-IV-1a (T347S) and apoA-IV-2 (Q360H). Interestingly, both are linked with an increased risk of cardiovascular disease, however, the underlying mechanism remains unclear. Here, we generated recombinant apoA-IV and found that the Q360H or T347S polymorphisms dampened its inhibition of platelet aggregation in human platelet-rich plasma and gel-filtered platelets, reduced its inhibition of platelet spreading, and its inhibition of P-selectin on activated platelets. Using an ex vivo thrombosis assay, we found that Q360H and T347S attenuated its inhibition of thrombosis at both high (1800s-1) and low (300s-1) shear rates. We then demonstrate a conserved monomer-dimer distribution among apoA-IV WT, Q360H, and T347S and use protein structure modelling software to show Q360H and T347S enhance C-terminal steric hindrance over the N-terminal platelet-binding site. These data provide critical insight into increased cardiovascular risk for individuals with Q360H or T347S polymorphisms.
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Affiliation(s)
- Daniel T MacKeigan
- Department of Physiology, University of Toronto, ON, Canada; Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Toronto Platelet Immunobiology Group, Toronto, ON, Canada
| | - Si-Yang Yu
- Department of Cardiology, The First Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, China; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Noa Chazot
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Dachuan Zhang
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Christopher J Khoury
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Xi Lei
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Toronto Platelet Immunobiology Group, Toronto, ON, Canada; CCOA Therapeutics Inc., Toronto, ON, Canada
| | - Preeti Bhoria
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada; CCOA Therapeutics Inc., Toronto, ON, Canada
| | - Chuanbin Shen
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Pingguo Chen
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Canadian Blood Services Centre for Innovation, Toronto, ON, Canada
| | - Guangheng Zhu
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Toronto Platelet Immunobiology Group, Toronto, ON, Canada; CCOA Therapeutics Inc., Toronto, ON, Canada
| | - Margaret L Rand
- Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada; Division of Haematology/Oncology, Translational Medicine, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
| | - Scott Heximer
- Department of Physiology, University of Toronto, ON, Canada; Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, University of Toronto, Toronto, ON, Canada
| | - Heyu Ni
- Department of Physiology, University of Toronto, ON, Canada; Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada; CCOA Therapeutics Inc., Toronto, ON, Canada; Canadian Blood Services Centre for Innovation, Toronto, ON, Canada; Department of Medicine, University of Toronto, ON, Canada.
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Bhale AS, Meilhac O, d'Hellencourt CL, Vijayalakshmi MA, Venkataraman K. Cholesterol transport and beyond: Illuminating the versatile functions of HDL apolipoproteins through structural insights and functional implications. Biofactors 2024. [PMID: 38661230 DOI: 10.1002/biof.2057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Accepted: 04/02/2024] [Indexed: 04/26/2024]
Abstract
High-density lipoproteins (HDLs) play a vital role in lipid metabolism and cardiovascular health, as they are intricately involved in cholesterol transport and inflammation modulation. The proteome of HDL particles is indeed complex and distinct from other components in the bloodstream. Proteomics studies have identified nearly 285 different proteins associated with HDL; however, this review focuses more on the 15 or so traditionally named "apo" lipoproteins. Important lipid metabolizing enzymes closely working with the apolipoproteins are also discussed. Apolipoproteins stand out for their integral role in HDL stability, structure, function, and metabolism. The unique structure and functions of each apolipoprotein influence important processes such as inflammation regulation and lipid metabolism. These interactions also shape the stability and performance of HDL particles. HDLs apolipoproteins have multifaceted roles beyond cardiovascular diseases (CVDs) and are involved in various physiological processes and disease states. Therefore, a detailed exploration of these apolipoproteins can offer valuable insights into potential diagnostic markers and therapeutic targets. This comprehensive review article aims to provide an in-depth understanding of HDL apolipoproteins, highlighting their distinct structures, functions, and contributions to various physiological processes. Exploiting this knowledge holds great potential for improving HDL function, enhancing cholesterol efflux, and modulating inflammatory processes, ultimately benefiting individuals by limiting the risks associated with CVDs and other inflammation-based pathologies. Understanding the nature of all 15 apolipoproteins expands our knowledge of HDL metabolism, sheds light on their pathological implications, and paves the way for advancements in the diagnosis, prevention, and treatment of lipid and inflammatory-related disorders.
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Affiliation(s)
- Aishwarya Sudam Bhale
- Centre for Bio-Separation Technology, Vellore Institute of Technology, Vellore, Tamil Nadu, India
| | - Olivier Meilhac
- Inserm, UMR 1188 Diabète Athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, Saint-Pierre, France
| | - Christian Lefebvre d'Hellencourt
- Inserm, UMR 1188 Diabète Athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, Saint-Pierre, France
| | | | - Krishnan Venkataraman
- Centre for Bio-Separation Technology, Vellore Institute of Technology, Vellore, Tamil Nadu, India
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Kmochová T, Kidd KO, Orr A, Hnízda A, Hartmannová H, Hodaňová K, Vyleťal P, Naušová K, Brinsa V, Trešlová H, Sovová J, Barešová V, Svojšová K, Vrbacká A, Stránecký V, Robins VC, Taylor A, Martin L, Rivas-Chavez A, Payne R, Bleyer HA, Williams A, Rennke HG, Weins A, Short PJ, Agrawal V, Storsley LJ, Waikar SS, McPhail ED, Dasari S, Leung N, Hewlett T, Yorke J, Gaston D, Geldenhuys L, Samuels M, Levine AP, West M, Hůlková H, Pompach P, Novák P, Weinberg RB, Bedard K, Živná M, Sikora J, Bleyer AJ, Kmoch S. Autosomal dominant ApoA4 mutations present as tubulointerstitial kidney disease with medullary amyloidosis. Kidney Int 2024; 105:799-811. [PMID: 38096951 DOI: 10.1016/j.kint.2023.11.021] [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: 04/13/2023] [Revised: 11/03/2023] [Accepted: 11/10/2023] [Indexed: 01/21/2024]
Abstract
Sporadic cases of apolipoprotein A-IV medullary amyloidosis have been reported. Here we describe five families found to have autosomal dominant medullary amyloidosis due to two different pathogenic APOA4 variants. A large family with autosomal dominant chronic kidney disease (CKD) and bland urinary sediment underwent whole genome sequencing with identification of a chr11:116692578 G>C (hg19) variant encoding the missense mutation p.L66V of the ApoA4 protein. We identified two other distantly related families from our registry with the same variant and two other distantly related families with a chr11:116693454 C>T (hg19) variant encoding the missense mutation p.D33N. Both mutations are unique to affected families, evolutionarily conserved and predicted to expand the amyloidogenic hotspot in the ApoA4 structure. Clinically affected individuals suffered from CKD with a bland urinary sediment and a mean age for kidney failure of 64.5 years. Genotyping identified 48 genetically affected individuals; 44 individuals had an estimated glomerular filtration rate (eGFR) under 60 ml/min/1.73 m2, including all 25 individuals with kidney failure. Significantly, 11 of 14 genetically unaffected individuals had an eGFR over 60 ml/min/1.73 m2. Fifteen genetically affected individuals presented with higher plasma ApoA4 concentrations. Kidney pathologic specimens from four individuals revealed amyloid deposits limited to the medulla, with the mutated ApoA4 identified by mass-spectrometry as the predominant amyloid constituent in all three available biopsies. Thus, ApoA4 mutations can cause autosomal dominant medullary amyloidosis, with marked amyloid deposition limited to the kidney medulla and presenting with autosomal dominant CKD with a bland urinary sediment. Diagnosis relies on a careful family history, APOA4 sequencing and pathologic studies.
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Affiliation(s)
- Tereza Kmochová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Kendrah O Kidd
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic; Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Andrew Orr
- Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada; Department of Pathology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Aleš Hnízda
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Hana Hartmannová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Kateřina Hodaňová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Petr Vyleťal
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Karolína Naušová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Vítězslav Brinsa
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Helena Trešlová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Jana Sovová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Veronika Barešová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Klára Svojšová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Alena Vrbacká
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Viktor Stránecký
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Victoria C Robins
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Abbigail Taylor
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Lauren Martin
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Ana Rivas-Chavez
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Riley Payne
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Heidi A Bleyer
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Adrienne Williams
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Helmut G Rennke
- Pathology Department, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Astrid Weins
- Pathology Department, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | | | - Varun Agrawal
- Division of Nephrology and Hypertension, Larner College of Medicine, University of Vermont, Burlington, Vermont, USA
| | - Leroy J Storsley
- Department of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Sushrut S Waikar
- Section of Nephrology, Boston University Chobanian and Avedisian School of Medicine, Boston, Massachusetts, USA
| | - Ellen D McPhail
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA
| | - Surendra Dasari
- Department of Quantitative Health Sciences, Mayo Clinic, Rochester, Minnesota, USA
| | - Nelson Leung
- Division of Nephrology and Hypertension, Division of Hematology, Mayo Clinic, Rochester, Minnesota, USA
| | - Tom Hewlett
- Division of Nephrology, Department of Medicine, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Jake Yorke
- Department of Pathology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Daniel Gaston
- Department of Pathology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Laurette Geldenhuys
- Department of Pathology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Mark Samuels
- Department of Medicine Université de Montréal, Montreal, Quebec, Canada; Department of Biochemistry, Université de Montréal, Montreal, Quebec, Canada; Centre de Recherche du CHU Ste-Justine, Montreal, Quebec, Canada
| | - Adam P Levine
- Research Department of Pathology, University College London, London, UK
| | - Michael West
- Division of Nephrology, Department of Medicine, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Helena Hůlková
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic; Institute of Pathology, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Petr Pompach
- Institute of Microbiology of the Czech Academy of Sciences, Vestec, Czech Republic
| | - Petr Novák
- Institute of Microbiology of the Czech Academy of Sciences, Vestec, Czech Republic
| | - Richard B Weinberg
- Section on Gastroenterology, Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA; Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Karen Bedard
- Department of Pathology and Laboratory Medicine, Izaak Walton Killam Hospital, Halifax Nova Scotia, Canada
| | - Martina Živná
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic; Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Jakub Sikora
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic; Institute of Pathology, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Anthony J Bleyer
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic; Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
| | - Stanislav Kmoch
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic; Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
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Zhang W, Liu XH, Zhou JT, Cheng C, Xu J, Yu J, Li X. Apolipoprotein A-IV restrains fat accumulation in skeletal and myocardial muscles by inhibiting lipogenesis and activating PI3K-AKT signalling. Arch Physiol Biochem 2023:1-11. [PMID: 36594510 DOI: 10.1080/13813455.2022.2163261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 12/10/2022] [Indexed: 01/04/2023]
Abstract
BACKGROUND One of the pathological characteristics of obesity is fat accumulation of skeletal muscles (SKM) and the myocardium, involving mechanisms of insulin resistance and abnormal lipid metabolism. Apolipoprotein A-IV (ApoA-IV) is an essential gene in both glucose and lipid metabolisms. MATERIALS AND METHODS Using high-fat diet (HFD) induced obese apoA-IV-knockout mice and subsequent introduction of exogenous recombinant-ApoA-IV protein and adeno-associated virus (AAV)-transformed apoA-IV, we examined lipid metabolism indicators of SKM and the myocardium, which include triglyceride (TG) content, RT-PCR for lipogenic indicators and western blotting for AKT phosphorylation. Similarly, we used high-glucose-fed or palmitate (Pal)-induced C2C12 cells co-cultured with ApoA-IV protein to evaluate glucose uptake, the phosphoinositide 3-kinase (PI3K)-AKT pathway, and lipid metabolisms. RESULTS In stable obese animal models, we find ApoA-IV-knockout mice show elevated TG content, enhanced expression of lipogenic enzymes and diminished phosphorylated AKT in SKM and the myocardium, but both stable hepatic expression of AAV-apoA-IV and brief ApoA-IV protein administration suppress lipogenesis and promote AKT phosphorylation. In a myoblast cell line C2C12, ApoA-IV protein suppresses Pal-induced lipid accumulation and lipogenesis but enhances AKT activation and glucose uptake, and the effect is abolished by a PI3K inhibitor. CONCLUSION We find that ApoA-IV reduces fat accumulation by suppressing lipogenesis and improves glucose uptake in SKM and the myocardium by regulating the PI3K-AKT pathway.
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Affiliation(s)
- Wenqian Zhang
- National & Local Joint Engineering Research Center of Biodiagnosis and Biotherapy, Precision Medical Institute, The Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
- Department of Cardiology, The Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an, PR China
- Department of Computer Science, City University of Hong Kong, Kowloon Tong, Hong Kong, China
| | - Xiao-Huan Liu
- National & Local Joint Engineering Research Center of Biodiagnosis and Biotherapy, Precision Medical Institute, The Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
- Department of Cardiology, The Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an, PR China
| | - Jin-Ting Zhou
- Bio-evidence Sciences Academy (BSA), Xi'an Jiaotong University, Western China Science & Technology Innovation Harbour, Xi'an, China
| | - Cheng Cheng
- Bio-evidence Sciences Academy (BSA), Xi'an Jiaotong University, Western China Science & Technology Innovation Harbour, Xi'an, China
| | - Jing Xu
- Division of Endocrinology, The Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Jun Yu
- OneHealth Technology Company, Xi'an, China
| | - Xiaoming Li
- National & Local Joint Engineering Research Center of Biodiagnosis and Biotherapy, Precision Medical Institute, The Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
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Qu J, Ko CW, Tso P, Bhargava A. Apolipoprotein A-IV: A Multifunctional Protein Involved in Protection against Atherosclerosis and Diabetes. Cells 2019; 8:E319. [PMID: 30959835 PMCID: PMC6523623 DOI: 10.3390/cells8040319] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Revised: 03/31/2019] [Accepted: 04/02/2019] [Indexed: 12/19/2022] Open
Abstract
Apolipoprotein A-IV (apoA-IV) is a lipid-binding protein, which is primarily synthesized in the small intestine, packaged into chylomicrons, and secreted into intestinal lymph during fat absorption. In the circulation, apoA-IV is present on chylomicron remnants, high-density lipoproteins, and also in lipid-free form. ApoA-IV is involved in a myriad of physiological processes such as lipid absorption and metabolism, anti-atherosclerosis, platelet aggregation and thrombosis, glucose homeostasis, and food intake. ApoA-IV deficiency is associated with atherosclerosis and diabetes, which renders it as a potential therapeutic target for treatment of these diseases. While much has been learned about the physiological functions of apoA-IV using rodent models, the action of apoA-IV at the cellular and molecular levels is less understood, let alone apoA-IV-interacting partners. In this review, we will summarize the findings on the molecular function of apoA-IV and apoA-IV-interacting proteins. The information will shed light on the discovery of apoA-IV receptors and the understanding of the molecular mechanism underlying its mode of action.
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Affiliation(s)
- Jie Qu
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E Galbraith Road, Cincinnati, OH 45237-0507, USA.
| | - Chih-Wei Ko
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E Galbraith Road, Cincinnati, OH 45237-0507, USA.
| | - Patrick Tso
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E Galbraith Road, Cincinnati, OH 45237-0507, USA.
| | - Aditi Bhargava
- Department of Obstetrics, Gynecology & Reproductive Sciences, University of California, 513 Parnassus Avenue, San Francisco, CA 94143-0556, USA.
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6
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Xu XR, Wang Y, Adili R, Ju L, Spring CM, Jin JW, Yang H, Neves MAD, Chen P, Yang Y, Lei X, Chen Y, Gallant RC, Xu M, Zhang H, Song J, Ke P, Zhang D, Carrim N, Yu SY, Zhu G, She YM, Cyr T, Fu W, Liu G, Connelly PW, Rand ML, Adeli K, Freedman J, Lee JE, Tso P, Marchese P, Davidson WS, Jackson SP, Zhu C, Ruggeri ZM, Ni H. Apolipoprotein A-IV binds αIIbβ3 integrin and inhibits thrombosis. Nat Commun 2018; 9:3608. [PMID: 30190457 PMCID: PMC6127106 DOI: 10.1038/s41467-018-05806-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Accepted: 07/19/2018] [Indexed: 12/29/2022] Open
Abstract
Platelet αIIbβ3 integrin and its ligands are essential for thrombosis and hemostasis, and play key roles in myocardial infarction and stroke. Here we show that apolipoprotein A-IV (apoA-IV) can be isolated from human blood plasma using platelet β3 integrin-coated beads. Binding of apoA-IV to platelets requires activation of αIIbβ3 integrin, and the direct apoA-IV-αIIbβ3 interaction can be detected using a single-molecule Biomembrane Force Probe. We identify that aspartic acids 5 and 13 at the N-terminus of apoA-IV are required for binding to αIIbβ3 integrin, which is additionally modulated by apoA-IV C-terminus via intra-molecular interactions. ApoA-IV inhibits platelet aggregation and postprandial platelet hyperactivity. Human apoA-IV plasma levels show a circadian rhythm that negatively correlates with platelet aggregation and cardiovascular events. Thus, we identify apoA-IV as a novel ligand of αIIbβ3 integrin and an endogenous inhibitor of thrombosis, establishing a link between lipoprotein metabolism and cardiovascular diseases. Activation of integrin αIIbβ3 at the surface of platelets is required for their aggregation and for thrombus formation. Here Xu et al. identify apolipoprotein A-IV as a novel ligand for platelet αIIbβ3 integrin, and find it inhibits platelet aggregation and thrombosis.
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Affiliation(s)
- Xiaohong Ruby Xu
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada, M5S 1A1.,Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8.,Department of Acupuncture and Moxibustion, Guangdong Provincial Hospital of Chinese Medicine, Guangzhou, Guangdong, P.R. China, 510120.,Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, P.R. China, 510000
| | - Yiming Wang
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada, M5S 1A1.,Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8.,Canadian Blood Services Centre for Innovation, Toronto, ON, Canada, M5G 2M1
| | - Reheman Adili
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8
| | - Lining Ju
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA, 30332.,Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA, 30332.,Heart Research Institute, and Charles Perkins Centre, The University of Sydney, Camperdown, Australia, 2006
| | - Christopher M Spring
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8
| | - Joseph Wuxun Jin
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8.,Canadian Blood Services Centre for Innovation, Toronto, ON, Canada, M5G 2M1
| | - Hong Yang
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8.,Canadian Blood Services Centre for Innovation, Toronto, ON, Canada, M5G 2M1
| | - Miguel A D Neves
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8
| | - Pingguo Chen
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8.,Canadian Blood Services Centre for Innovation, Toronto, ON, Canada, M5G 2M1
| | - Yan Yang
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8.,Canadian Blood Services Centre for Innovation, Toronto, ON, Canada, M5G 2M1
| | - Xi Lei
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8
| | - Yunfeng Chen
- Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA, 30332.,Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA, 30332
| | - Reid C Gallant
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada, M5S 1A1.,Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8
| | - Miao Xu
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada, M5S 1A1.,Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8
| | - Hailong Zhang
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8
| | - Jina Song
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8.,Canadian Blood Services Centre for Innovation, Toronto, ON, Canada, M5G 2M1
| | - Peifeng Ke
- Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, P.R. China, 510000.,Department of Laboratory Medicine, Guangdong Provincial Hospital of Chinese Medicine, Guangzhou, Guangdong, P.R. China, 510120
| | - Dan Zhang
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8.,Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, P.R. China, 510000
| | - Naadiya Carrim
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8.,Canadian Blood Services Centre for Innovation, Toronto, ON, Canada, M5G 2M1
| | - Si-Yang Yu
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8.,Department of Cardiovascular Medicine, The Second Xiangya Hospital of Central South University, Changsha, Hunan, P.R. China, 410011
| | - Guangheng Zhu
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8
| | - Yi-Min She
- Centre for Biologics Research, Biologics and Genetic Therapies Directorate, HPFB, Health Canada, Ottawa, ON, Canada, K1A 0M2
| | - Terry Cyr
- Centre for Biologics Research, Biologics and Genetic Therapies Directorate, HPFB, Health Canada, Ottawa, ON, Canada, K1A 0M2
| | - Wenbin Fu
- Department of Acupuncture and Moxibustion, Guangdong Provincial Hospital of Chinese Medicine, Guangzhou, Guangdong, P.R. China, 510120.,Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, P.R. China, 510000
| | - Guoqing Liu
- Institute of Cardiovascular Science, Peking University Health Science Center, Beijing, P.R. China, 100083
| | - Philip W Connelly
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada, M5S 1A1.,Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8
| | - Margaret L Rand
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada, M5S 1A1.,Division of Haematology/Oncology, The Hospital for Sick Children, Toronto, ON, Canada, M5G 1X8
| | - Khosrow Adeli
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada, M5S 1A1.,Program in Molecular Structure & Function, The Hospital for Sick Children, Toronto, ON, Canada, M5G 1X8
| | - John Freedman
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada, M5S 1A1.,Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8.,Department of Medicine, University of Toronto, Toronto, ON, Canada, M5S 1A1
| | - Jeffrey E Lee
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada, M5S 1A1
| | - Patrick Tso
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH, USA, 45219
| | - Patrizia Marchese
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA, 92037
| | - W Sean Davidson
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH, USA, 45219
| | - Shaun P Jackson
- Heart Research Institute, and Charles Perkins Centre, The University of Sydney, Camperdown, Australia, 2006.,Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA, 92037
| | - Cheng Zhu
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA, 30332.,Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA, 30332.,Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA, 30332
| | - Zaverio M Ruggeri
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA, 92037
| | - Heyu Ni
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada, M5S 1A1. .,Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Toronto, ON, Canada, M5B 1W8. .,Canadian Blood Services Centre for Innovation, Toronto, ON, Canada, M5G 2M1. .,Department of Medicine, University of Toronto, Toronto, ON, Canada, M5S 1A1. .,Department of Physiology, University of Toronto, Toronto, ON, Canada, M5S 1A1.
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7
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Li X, Wang F, Xu M, Howles P, Tso P. ApoA-IV improves insulin sensitivity and glucose uptake in mouse adipocytes via PI3K-Akt Signaling. Sci Rep 2017; 7:41289. [PMID: 28117404 PMCID: PMC5259790 DOI: 10.1038/srep41289] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 12/19/2016] [Indexed: 01/12/2023] Open
Abstract
Insulin resistance is a risk factor for type 2 diabetes mellitus. We investigated the effect of ApoA-IV on glucose uptake in the adipose and muscle tissues of mice and cultured 3T3-L1 adipocytes. We found that treatment with ApoA-IV lowered fasting blood glucose in both WT and diabetic KKAy mice by increasing glucose uptake in cardiac muscle, white adipose tissue, and brown adipose tissue through a mechanism that was partially insulin independent. Cell culture experiments showed that ApoA-IV improved glucose uptake in adipocytes in the absence of insulin by upregulating GLUT4 translocation by PI3K mediated activation of Akt signaling pathways. Considering our previous finding that ApoA-IV treatment enhanced pancreatic insulin secretion, these results suggests that ApoA-IV acts directly upon adipose tissue to improve glucose uptake and indirectly via insulin signaling. Our findings warrant future studies to identify the receptor for ApoA-IV and the downstream targets of PI3K-Akt signaling that regulate glucose uptake in adipocytes as potential therapeutic targets for treating insulin resistance.
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Affiliation(s)
- Xiaoming Li
- National Local Joint Engineering Research Centre of Biodiagnostics and Biotherapy, The Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, 157 W 5th Rd, Xincheng, Xi'an 710004, China.,Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E. Galbraith Road, Cincinnati 45237-0507, USA
| | - Fei Wang
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E. Galbraith Road, Cincinnati 45237-0507, USA
| | - Min Xu
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E. Galbraith Road, Cincinnati 45237-0507, USA
| | - Philip Howles
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E. Galbraith Road, Cincinnati 45237-0507, USA
| | - Patrick Tso
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E. Galbraith Road, Cincinnati 45237-0507, USA
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8
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Li X, Xu M, Wang F, Ji Y, DavidsoN WS, Li Z, Tso P. Interaction of ApoA-IV with NR4A1 and NR1D1 Represses G6Pase and PEPCK Transcription: Nuclear Receptor-Mediated Downregulation of Hepatic Gluconeogenesis in Mice and a Human Hepatocyte Cell Line. PLoS One 2015; 10:e0142098. [PMID: 26556724 PMCID: PMC4640595 DOI: 10.1371/journal.pone.0142098] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 10/16/2015] [Indexed: 11/18/2022] Open
Abstract
We have previously shown that the nuclear receptor, NR1D1, is a cofactor in ApoA-IV-mediated downregulation of gluconeogenesis. Nuclear receptor, NR4A1, is involved in the transcriptional regulation of various genes involved in inflammation, apoptosis, and glucose metabolism. We investigated whether NR4A1 influences the effect of ApoA-IV on hepatic glucose metabolism. Our in situ proximity ligation assays and coimmunoprecipitation experiments indicated that ApoA-IV colocalized with NR4A1 in human liver (HepG2) and kidney (HEK-293) cell lines. The chromatin immunoprecipitation experiments and luciferase reporter assays indicated that the ApoA-IV and NR4A1 colocalized at the RORα response element of the human G6Pase promoter, reducing its transcriptional activity. Our RNA interference experiments showed that knocking down the expression of NR4A1 in primary mouse hepatocytes treated with ApoA-IV increased the expression of NR1D1, G6Pase, and PEPCK, and that knocking down NR1D1 expression increased the level of NR4A1. We also found that ApoA-IV induced the expression of endogenous NR4A1 in both cultured primary mouse hepatocytes and in the mouse liver, and decreased glucose production in primary mouse hepatocytes. Our findings showed that ApoA-IV colocalizes with NR4A1, which suppresses G6Pase and PEPCK gene expression at the transcriptional level, reducing hepatic glucose output and lowering blood glucose. The ApoA-IV-induced increase in NR4A1 expression in hepatocytes mediates further repression of gluconeogenesis. Our findings suggest that NR1D1 and NR4A1 serve similar or complementary functions in the ApoA-IV-mediated regulation of gluconeogenesis.
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Affiliation(s)
- Xiaoming Li
- National Local Joint Engineering Research Center of Biodiagnostics and Biotherapy, The Second Affiliated Hospital of Medical College, Xi’an Jiaotong University, 157 W 5th Rd, Xincheng, Xi'an, Shaanxi, 710004, China
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E. Galbraith Road, Cincinnati, 45237–0507, United States of America
| | - Min Xu
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E. Galbraith Road, Cincinnati, 45237–0507, United States of America
| | - Fei Wang
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E. Galbraith Road, Cincinnati, 45237–0507, United States of America
| | - Yong Ji
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E. Galbraith Road, Cincinnati, 45237–0507, United States of America
| | - W. Sean DavidsoN
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E. Galbraith Road, Cincinnati, 45237–0507, United States of America
| | - Zongfang Li
- National Local Joint Engineering Research Center of Biodiagnostics and Biotherapy, The Second Affiliated Hospital of Medical College, Xi’an Jiaotong University, 157 W 5th Rd, Xincheng, Xi'an, Shaanxi, 710004, China
- * E-mail: (PT); (ZL)
| | - Patrick Tso
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, 2180 E. Galbraith Road, Cincinnati, 45237–0507, United States of America
- * E-mail: (PT); (ZL)
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9
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Deng X, Walker RG, Morris J, Davidson WS, Thompson TB. Role of Conserved Proline Residues in Human Apolipoprotein A-IV Structure and Function. J Biol Chem 2015; 290:10689-702. [PMID: 25733664 PMCID: PMC4409236 DOI: 10.1074/jbc.m115.637058] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Revised: 02/23/2015] [Indexed: 11/06/2022] Open
Abstract
Apolipoprotein (apo)A-IV is a lipid emulsifying protein linked to a range of protective roles in obesity, diabetes, and cardiovascular disease. It exists in several states in plasma including lipid-bound in HDL and chylomicrons and as monomeric and dimeric lipid-free/poor forms. Our recent x-ray crystal structure of the central domain of apoA-IV shows that it adopts an elongated helical structure that dimerizes via two long reciprocating helices. A striking feature is the alignment of conserved proline residues across the dimer interface. We speculated that this plays important roles in the structure of the lipid-free protein and its ability to bind lipid. Here we show that the systematic conversion of these prolines to alanine increased the thermodynamic stability of apoA-IV and its propensity to oligomerize. Despite the structural stabilization, we noted an increase in the ability to bind and reorganize lipids and to promote cholesterol efflux from cells. The novel properties of these mutants allowed us to isolate the first trimeric form of an exchangeable apolipoprotein and characterize it by small-angle x-ray scattering and chemical cross-linking. The results suggest that the reciprocating helix interaction is a common feature of all apoA-IV oligomers. We propose a model of how self-association of apoA-IV can result in spherical lipoprotein particles, a model that may have broader applications to other exchangeable apolipoprotein family members.
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Affiliation(s)
- Xiaodi Deng
- From the Departments of Molecular Genetics, Biochemistry and Microbiology and
| | - Ryan G Walker
- From the Departments of Molecular Genetics, Biochemistry and Microbiology and
| | - Jamie Morris
- Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237
| | - W Sean Davidson
- Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237
| | - Thomas B Thompson
- From the Departments of Molecular Genetics, Biochemistry and Microbiology and
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10
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Amyloid-Forming Properties of Human Apolipoproteins: Sequence Analyses and Structural Insights. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 855:175-211. [PMID: 26149931 DOI: 10.1007/978-3-319-17344-3_8] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Apolipoproteins are protein constituents of lipoproteins that transport cholesterol and fat in circulation and are central to cardiovascular health and disease. Soluble apolipoproteins can transiently dissociate from the lipoprotein surface in a labile free form that can misfold, potentially leading to amyloid disease. Misfolding of apoA-I, apoA-II, and serum amyloid A (SAA) causes systemic amyloidoses, apoE4 is a critical risk factor in Alzheimer's disease, and apolipoprotein misfolding is also implicated in cardiovascular disease. To explain why apolipoproteins are over-represented in amyloidoses, it was proposed that the amphipathic α-helices, which form the lipid surface-binding motif in this protein family, have high amyloid-forming propensity. Here, we use 12 sequence-based bioinformatics approaches to assess amyloid-forming potential of human apolipoproteins and to identify segments that are likely to initiate β-aggregation. Mapping such segments on the available atomic structures of apolipoproteins helps explain why some of them readily form amyloid while others do not. Our analysis shows that nearly all amyloidogenic segments: (i) are largely hydrophobic, (ii) are located in the lipid-binding amphipathic α-helices in the native structures of soluble apolipoproteins, (iii) are predicted in both native α-helices and β-sheets in the insoluble apoB, and (iv) are predicted to form parallel in-register β-sheet in amyloid. Most of these predictions have been verified experimentally for apoC-II, apoA-I, apoA-II and SAA. Surprisingly, the rank order of the amino acid sequence propensity to form amyloid (apoB>apoA-II>apoC-II≥apoA-I, apoC-III, SAA, apoC-I>apoA-IV, apoA-V, apoE) does not correlate with the proteins' involvement in amyloidosis. Rather, it correlates directly with the strength of the protein-lipid association, which increases with increasing protein hydrophobicity. Therefore, the lipid surface-binding function and the amyloid-forming propensity are both rooted in apolipoproteins' hydrophobicity, suggesting that functional constraints make it difficult to completely eliminate pathogenic apolipoprotein misfolding. We propose that apolipoproteins have evolved protective mechanisms against misfolding, such as the sequestration of the amyloidogenic segments via the native protein-lipid and protein-protein interactions involving amphipathic α-helices and, in case of apoB, β-sheets.
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11
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Walker RG, Deng X, Melchior JT, Morris J, Tso P, Jones MK, Segrest JP, Thompson TB, Davidson WS. The structure of human apolipoprotein A-IV as revealed by stable isotope-assisted cross-linking, molecular dynamics, and small angle x-ray scattering. J Biol Chem 2014; 289:5596-608. [PMID: 24425874 DOI: 10.1074/jbc.m113.541037] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Apolipoprotein (apo)A-IV plays important roles in dietary lipid and glucose metabolism, and knowledge of its structure is required to fully understand the molecular basis of these functions. However, typical of the entire class of exchangeable apolipoproteins, its dynamic nature and affinity for lipid has posed challenges to traditional high resolution structural approaches. We previously reported an x-ray crystal structure of a dimeric truncation mutant of apoA-IV, which showed a unique helix-swapping molecular interface. Unfortunately, the structures of the N and C termini that are important for lipid binding were not visualized. To build a more complete model, we used chemical cross-linking to derive distance constraints across the full-length protein. The approach was enhanced with stable isotope labeling to overcome ambiguities in determining molecular span of the cross-links given the remarkable similarities in the monomeric and dimeric apoA-IV structures. Using 51 distance constraints, we created a starting model for full-length monomeric apoA-IV and then subjected it to two modeling approaches: (i) molecular dynamics simulations and (ii) fitting to small angle x-ray scattering data. This resulted in the most detailed models yet for lipid-free monomeric or dimeric apoA-IV. Importantly, these models were of sufficient detail to direct the experimental identification of new functional residues that participate in a "clasp" mechanism to modulate apoA-IV lipid affinity. The isotope-assisted cross-linking approach should prove useful for further study of this family of apolipoproteins in both the lipid-free and -bound states.
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Affiliation(s)
- Ryan G Walker
- From the Departments of Molecular Genetics, Biochemistry and Microbiology and
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12
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Wang F, Pearson KJ, Davidson WS, Tso P. Specific sequences in N termini of apolipoprotein A-IV modulate its anorectic effect. Physiol Behav 2013; 120:136-42. [PMID: 23911688 DOI: 10.1016/j.physbeh.2013.07.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Revised: 06/19/2013] [Accepted: 07/22/2013] [Indexed: 10/26/2022]
Abstract
Rodent apoA-IV is expressed predominantly in small intestine and also expressed to a small extent in liver and hypothalamus. ApoA-IV has been shown to inhibit food intake in rats when injected centrally. In the current study, we hypothesize that a specific sequence within rat apoA-IV is responsible for mediating the anorectic effect. We use a bacterial expression system to generate truncation mutants (Δ249-371, Δ117-371 and Δ1-61) of rat apoA-IV and assess the ability of various regions of the molecule to inhibit food intake. The results indicate that a responsible sequence exists within the N-terminal 61 amino acids of rat apoA-IV. Synthetic peptides (1-30 EVTSDQVANVMWDYFTQLSNNAKEAVEQLQ, 1-15 EVTSDQVANVMWDYF and 17-30 QLSNNAKEAVEQLQ) were used to specify the region in between residues 1 and 30. A 14-mer peptide (17-30) encompassing this sequence was capable of reducing food intake in a dose-dependent manner whereas a peptide designed on a more C-terminal region (211-232) of apoA-IV (QEKLNHQMEGLAFQMKKNAEEL) failed to exhibit the dose-dependent anorectic effect. The isolation of this sequence provides a valuable tool for future work directed at identifying apoA-IV binding proteins and is a key step for exploring the potential of therapeutic manipulation of food intake via this pathway.
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Affiliation(s)
- Fei Wang
- Departments of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH, USA
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13
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Brown BE, Nobecourt E, Zeng J, Jenkins AJ, Rye KA, Davies MJ. Apolipoprotein A-I glycation by glucose and reactive aldehydes alters phospholipid affinity but not cholesterol export from lipid-laden macrophages. PLoS One 2013; 8:e65430. [PMID: 23741493 PMCID: PMC3669297 DOI: 10.1371/journal.pone.0065430] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Accepted: 04/29/2013] [Indexed: 11/18/2022] Open
Abstract
Increased protein glycation in people with diabetes may promote atherosclerosis. This study examined the effects of non-enzymatic glycation on the association of lipid-free apolipoproteinA-I (apoA-I) with phospholipid, and cholesterol efflux from lipid-loaded macrophages to lipid-free and lipid-associated apoA-I. Glycation of lipid-free apoA-I by methylglyoxal and glycolaldehyde resulted in Arg, Lys and Trp loss, advanced glycation end-product formation and protein cross-linking. The association of apoA-I glycated by glucose, methylglyoxal or glycolaldehyde with phospholipid multilamellar vesicles was impaired in a glycating agent dose-dependent manner, with exposure of apoA-I to both 30 mM glucose (42% decrease in kslow) and 3 mM glycolaldehyde (50% decrease in kfast, 60% decrease in kslow) resulting is significantly reduced affinity. Cholesterol efflux to control or glycated lipid-free apoA-I, or discoidal reconstituted HDL containing glycated apoA-I (drHDL), was examined using cholesterol-loaded murine (J774A.1) macrophages treated to increase expression of ATP binding cassette transporters A1 (ABCA1) or G1 (ABCG1). Cholesterol efflux from J774A.1 macrophages to glycated lipid-free apoA-I via ABCA1 or glycated drHDL via an ABCG1-dependent mechanism was unaltered, as was efflux to minimally modified apoA-I from people with Type 1 diabetes, or controls. Changes to protein structure and function were prevented by the reactive carbonyl scavenger aminoguanidine. Overall these studies demonstrate that glycation of lipid-free apoA-I, particularly late glycation, modifies its structure, its capacity to bind phospholipids and but not ABCA1- or ABCG1-dependent cholesterol efflux from macrophages.
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Affiliation(s)
- Bronwyn E. Brown
- The Heart Research Institute, Sydney, New South Wales, Australia
- Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia
| | | | - Jingmin Zeng
- The Heart Research Institute, Sydney, New South Wales, Australia
| | - Alicia J. Jenkins
- Department of Medicine (St Vincent's), The University of Melbourne, Melbourne, Victoria, Australia
| | - Kerry-Anne Rye
- The Heart Research Institute, Sydney, New South Wales, Australia
- Department of Medicine (St Vincent's), The University of Melbourne, Melbourne, Victoria, Australia
- Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia
| | - Michael J. Davies
- The Heart Research Institute, Sydney, New South Wales, Australia
- Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia
- * E-mail:
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14
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Deng X, Morris J, Chaton C, Schröder GF, Davidson WS, Thompson TB. Small-angle X-ray scattering of apolipoprotein A-IV reveals the importance of its termini for structural stability. J Biol Chem 2013; 288:4854-66. [PMID: 23288849 PMCID: PMC3576090 DOI: 10.1074/jbc.m112.436709] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 01/02/2013] [Indexed: 12/25/2022] Open
Abstract
ApoA-IV is an amphipathic protein that can emulsify lipids and has been linked to protective roles against cardiovascular disease and obesity. We previously reported an x-ray crystal structure of apoA-IV that was truncated at its N and C termini. Here, we have extended this work by demonstrating that self-associated states of apoA-IV are stable and can be structurally studied using small-angle x-ray scattering. Both the full-length monomeric and dimeric forms of apoA-IV were examined, with the dimer showing an elongated rod core with two nodes at opposing ends. The monomer is roughly half the length of the dimer with a single node. Small-angle x-ray scattering visualization of several deletion mutants revealed that removal of both termini can have substantial conformational effects throughout the molecule. Additionally, the F334A point mutation, which we previously showed increases apoA-IV lipid binding, also exhibited large conformational effects on the entire dimer. Merging this study's low-resolution structural information with the crystal structure provides insight on the conformation of apoA-IV as a monomer and as a dimer and further defines that a clasp mechanism may control lipid binding and, ultimately, protein function.
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Affiliation(s)
- Xiaodi Deng
- From the Department of Molecular Genetics, Biochemistry, and Microbiology, College of Medicine, University of Cincinnati, Cincinnati, Ohio 45267
| | - Jamie Morris
- the Department of Pathology and Laboratory Medicine, College of Medicine, Metabolic Diseases Institute, University of Cincinnati, Cincinnati, Ohio 45215, and
| | - Catherine Chaton
- From the Department of Molecular Genetics, Biochemistry, and Microbiology, College of Medicine, University of Cincinnati, Cincinnati, Ohio 45267
| | - Gunnar F. Schröder
- the Institute of Complex Systems (ICS-6), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - W. Sean Davidson
- the Department of Pathology and Laboratory Medicine, College of Medicine, Metabolic Diseases Institute, University of Cincinnati, Cincinnati, Ohio 45215, and
| | - Thomas B. Thompson
- From the Department of Molecular Genetics, Biochemistry, and Microbiology, College of Medicine, University of Cincinnati, Cincinnati, Ohio 45267
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15
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Duka A, Fotakis P, Georgiadou D, Kateifides A, Tzavlaki K, von Eckardstein L, Stratikos E, Kardassis D, Zannis VI. ApoA-IV promotes the biogenesis of apoA-IV-containing HDL particles with the participation of ABCA1 and LCAT. J Lipid Res 2012; 54:107-15. [PMID: 23132909 DOI: 10.1194/jlr.m030114] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The objective of this study was to establish the role of apoA-IV, ABCA1, and LCAT in the biogenesis of apoA-IV-containing HDL (HDL-A-IV) using different mouse models. Adenovirus-mediated gene transfer of apoA-IV in apoA-I(-/-) mice did not change plasma lipid levels. ApoA-IV floated in the HDL2/HDL3 region, promoted the formation of spherical HDL particles as determined by electron microscopy, and generated mostly α- and a few pre-β-like HDL subpopulations. Gene transfer of apoA-IV in apoA-I(-/-) × apoE(-/-) mice increased plasma cholesterol and triglyceride levels, and 80% of the protein was distributed in the VLDL/IDL/LDL region. This treatment likewise generated α- and pre-β-like HDL subpopulations. Spherical and α-migrating HDL particles were not detectable following gene transfer of apoA-IV in ABCA1(-/-) or LCAT(-/-) mice. Coexpression of apoA-IV and LCAT in apoA-I(-/-) mice restored the formation of HDL-A-IV. Lipid-free apoA-IV and reconstituted HDL-A-IV promoted ABCA1 and scavenger receptor BI (SR-BI)-mediated cholesterol efflux, respectively, as efficiently as apoA-I and apoE. Our findings are consistent with a novel function of apoA-IV in the biogenesis of discrete HDL-A-IV particles with the participation of ABCA1 and LCAT, and may explain previously reported anti-inflammatory and atheroprotective properties of apoA-IV.
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Affiliation(s)
- Adelina Duka
- Molecular Genetics, Boston University School of Medicine, Boston, MA, USA
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The structure of dimeric apolipoprotein A-IV and its mechanism of self-association. Structure 2012; 20:767-79. [PMID: 22579246 DOI: 10.1016/j.str.2012.02.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2011] [Revised: 02/02/2012] [Accepted: 02/24/2012] [Indexed: 12/27/2022]
Abstract
Apolipoproteins are key structural elements of lipoproteins and critical mediators of lipid metabolism. Their detergent-like properties allow them to emulsify lipid or exist in a soluble lipid-free form in various states of self-association. Unfortunately, these traits have hampered high-resolution structural studies needed to understand the biogenesis of cardioprotective high-density lipoproteins (HDLs). We derived a crystal structure of the core domain of human apolipoprotein (apo)A-IV, an HDL component and important mediator of lipid absorption. The structure at 2.4 Å depicts two linearly connected 4-helix bundles participating in a helix swapping arrangement that offers a clear explanation for how the protein self-associates as well as clues to the structure of its monomeric form. This also provides a logical basis for antiparallel arrangements recently described for lipid-containing particles. Furthermore, we propose a "swinging door" model for apoA-IV lipid association.
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Park JY, Park JH, Jang W, Hwang IK, Kim IJ, Kim HJ, Cho KH, Lee ST. Apolipoprotein A-IV is a novel substrate for matrix metalloproteinases. J Biochem 2011; 151:291-8. [PMID: 22170214 DOI: 10.1093/jb/mvr137] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Screening of matrix metalloproteinase (MMP)-14 substrates in human plasma using a proteomics approach previously identified apolipoprotein A-IV (apoA-IV) as a novel substrate for MMP-14. Here, we show that among the tested MMPs, purified apoA-IV is most susceptible to cleavage by MMP-7, and that apoA-IV in plasma can be cleaved more efficiently by MMP-7 than MMP-14. Purified recombinant apoA-IV (44-kDa) was cleaved by MMP-7 into several fragments of 41, 32, 29, 27, 24, 22 and 19 kDa. N-terminal sequencing of the fragments identified two internal cleavage sites for MMP-7 in the apoA-IV sequence, between Glu(185) and Leu(186), and between Glu(262) and Leu(263). The cleavage of lipid-bound apoA-IV by MMP-7 was less efficient than that of lipid-free apoA-IV. Further, MMP-7-mediated cleavage of apoA-IV resulted in a rapid loss of its intrinsic anti-oxidant activity. Based on the fact that apoA-IV plays important roles in lipid metabolism and possesses anti-oxidant activity, we suggest that cleavage of lipid-free apoA-IV by MMP-7 has pathological implications in the development of hyperlipidemia and atherosclerosis.
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Affiliation(s)
- Ji Yoon Park
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Republic of Korea
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Kim M, Kang TW, Lee HC, Han YM, Kim H, Shin HD, Cheong HS, Lee D, Kim SY, Kim YS. Identification of DNA methylation markers for lineage commitment of in vitro hepatogenesis. Hum Mol Genet 2011; 20:2722-33. [DOI: 10.1093/hmg/ddr171] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Weinberg RB, Cook VR. Distinctive structure and interfacial activity of the human apolipoprotein A-IV 347S isoprotein. J Lipid Res 2010; 51:2664-71. [PMID: 20554794 PMCID: PMC2918448 DOI: 10.1194/jlr.m007021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 06/16/2010] [Indexed: 11/20/2022] Open
Abstract
The T347S polymorphism in the human apolipoprotein (apo) A-IV gene is present at high frequencies among all the world's populations. Carriers of a 347S allele exhibit faster clearance of triglyceride-rich lipoproteins, greater adiposity, and increased risk for developing atherosclerosis, which suggests that this conservative amino acid substitution alters the structure of apo A-IV. Herein we have used spectroscopic and surface chemistry techniques to examine the structure, stability, and interfacial properties of the apo A-IV 347S isoprotein. Circular dichroism spectroscopy revealed that the 347S isoprotein has similar alpha-helical structure but lower thermodynamic stability than the 347T isoprotein. Fluorescence spectroscopy found that the 347S isoprotein exhibits an enhanced tyrosine emission and reduced tyrosine-->tryptophan energy transfer, and second derivative UV absorption spectra noted increased tyrosine exposure, suggesting that the 347S isoprotein adopts a looser tertiary conformation. Surface chemistry studies found that although the 347S isoprotein bound rapidly to the lipid interface, it has a lower interfacial exclusion pressure and lower elastic modulus than the 347T isoprotein. Together, these observations establish that the T347S substitution alters the conformation of apo A-IV and lowers its interfacial activity-changes that could account for the effect of this polymorphism on postprandial lipid metabolism.
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Affiliation(s)
- Richard B Weinberg
- Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
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20
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Structure and function of the apoA-IV T347S and Q360H common variants. Biochem Biophys Res Commun 2010; 393:126-30. [PMID: 20117098 DOI: 10.1016/j.bbrc.2010.01.099] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Accepted: 01/23/2010] [Indexed: 11/21/2022]
Abstract
Human apolipoprotein A-IV (apoA-IV) is involved in chylomicron assembly and secretion, and in reverse cholesterol transport. Several apoA-IV isoforms exist, the most common in Caucasian populations being apoA-IV-1a (T347S) and apoA-IV-2 (Q360H). The objective of the present study was to investigate the impact of these common aminoacid substitutions on the ability of apoA-IV to bind lipids, to promote cell cholesterol efflux via ABCA1, and to maintain endothelial homeostasis. Recombinant forms of wild-type apoA-IV, apoA-IV Q360H, and apoA-IV T347S were produced in Escherichia coli. ApoA-IV Q360H and apoA-IV T347S showed a slightly higher alpha-helical content compared to wild-type apoA-IV, and associated with phospholipids faster than wild-type apoA-IV. The capacity to promote ABCA1-mediated cholesterol efflux was significantly greater for the apoA-IV T347S than the other apoA-IV isoforms. No differences were observed in the ability of apoA-IV isoforms to inhibit the production of VCAM-1 and IL-6 in TNFalpha-stimulated endothelial cells. In conclusion, the apoA-IV T347S common variant has increased lipid binding properties and cholesterol efflux capacity, while the apoA-IV Q360H variant has only slightly increased lipid binding properties. The two common aminoacid substitutions have no effect on the ability of apoA-IV to maintain endothelial homeostasis.
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21
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Tubb MR, Smith LE, Davidson WS. Purification of recombinant apolipoproteins A-I and A-IV and efficient affinity tag cleavage by tobacco etch virus protease. J Lipid Res 2009; 50:1497-504. [PMID: 19318686 DOI: 10.1194/jlr.d900003-jlr200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The expression of recombinant apolipoproteins provides experimental avenues that are not possible with plasma purified protein. The ability to specifically mutate residues or delete entire regions has proven to be a valuable tool for understanding the structure and function of apolipoproteins. A common feature of many recombinant systems is an affinity tag that allows for straightforward and high-yield purification of the target protein. A specific protease can then cleave the tag and yield the native recombinant protein. However, the application of this strategy to apolipoproteins has proven somewhat problematic because of the tendency for these highly flexible proteins to be nonspecifically cleaved at undesired sites within the native protein. Although systems have been developed using a variety of proteases, many suffer from low yield and, especially, the high cost of the enzyme.We developed a method that utilizes the tobacco etch virus protease to cleave a histidine-tag from apolipoproteins A-I and A-IV expressed in Escherichia coli. This protease can be easily and inexpensively expressed within most laboratories. We found that the protease efficiently cleaved the affinity tags from both apolipoproteins without nonspecific cleavage. All structural and functional measurements showed that the proteins were equivalent to native or previously characterized protein preparations. In addition to cost-effectiveness, advantages of the tobacco etch virus protease include a short cleavage time, low reaction temperature, and easy removal using the protease's own histidine-tag.
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Affiliation(s)
- Matthew R Tubb
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH 45237-0507, USA
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Massey JB, Pownall HJ, Macha S, Morris J, Tubb MR, Silva RAGD. Mass spectrometric determination of apolipoprotein molecular stoichiometry in reconstituted high density lipoprotein particles. J Lipid Res 2009; 50:1229-36. [PMID: 19179308 DOI: 10.1194/jlr.d800044-jlr200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Plasma HDL-cholesterol and apolipoprotein A-I (apoA-I) levels are strongly inversely associated with cardiovascular disease. However, the structure and protein composition of HDL particles is complex, as native and synthetic discoidal and spherical HDL particles can have from two to five apoA-I molecules per particle. To fully understand structure-function relationships of HDL, a method is required that is capable of directly determining the number of apolipoprotein molecules in heterogeneous HDL particles. Chemical cross-linking followed by SDS polyacrylamide gradient gel electrophoresis has been previously used to determine apolipoprotein stoichiometry in HDL particles. However, this method yields ambiguous results due to effects of cross-linking on protein conformation and, subsequently, its migration pattern on the gel. Here, we describe a new method based on cross-linking chemistry followed by MALDI mass spectrometry that determines the absolute mass of the cross-linked complex, thereby correctly determining the number of apolipoprotein molecules in a given HDL particle. Using well-defined, homogeneous, reconstituted apoA-I-containing HDL, apoA-IV-containing HDL, as well as apoA-I/apoA-II-containing HDL, we have validated this method. The method has the capability to determine the molecular ratio and molecular composition of apolipoprotein molecules in complex reconstituted HDL particles.
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Affiliation(s)
- John B Massey
- Section of Atherosclerosis and Vascular Medicine, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
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Tubb MR, Silva RAGD, Fang J, Tso P, Davidson WS. A three-dimensional homology model of lipid-free apolipoprotein A-IV using cross-linking and mass spectrometry. J Biol Chem 2008; 283:17314-23. [PMID: 18430727 PMCID: PMC2427326 DOI: 10.1074/jbc.m800036200] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2008] [Revised: 04/10/2008] [Indexed: 11/06/2022] Open
Abstract
Human apolipoprotein A-IV (apoA-IV) is a 46-kDa exchangeable plasma protein with many proposed functions. It is involved in chylomicron assembly and secretion, protection from atherosclerosis through a variety of mechanisms, and inhibition of food intake. There is little structural basis for these proposed functions due to the lack of a solved three-dimensional structure of the protein by x-ray crystallography or NMR. Based on previous studies, we hypothesized that lipid-free apoA-IV exists in a helical bundle, like other apolipoprotein family members and that regions near the N and C termini may interact. Utilizing a homobifunctional lysine cross-linking agent, we identified 21 intramolecular cross-links by mass spectrometry. These cross-links were used to constrain the building of a sequence threaded homology model using the I-TASSER server. Our results indicate that lipid-free apoA-IV does indeed exist as a complex helical bundle with the N and C termini in close proximity. This first structural model of lipid-free apoA-IV should prove useful for designing studies aimed at understanding how apoA-IV interacts with lipids and possibly with unknown protein partners.
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Affiliation(s)
- Matthew R Tubb
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237, USA
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Bibliography. Current world literature. Lipid metabolism. Curr Opin Lipidol 2008; 19:314-21. [PMID: 18460925 DOI: 10.1097/mol.0b013e328303e27e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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