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Sacher S, Mukherjee A, Ray A. Deciphering structural aspects of reverse cholesterol transport: mapping the knowns and unknowns. Biol Rev Camb Philos Soc 2023; 98:1160-1183. [PMID: 36880422 DOI: 10.1111/brv.12948] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 02/03/2023] [Accepted: 02/24/2023] [Indexed: 03/08/2023]
Abstract
Atherosclerosis is a major contributor to the onset and progression of cardiovascular disease (CVD). Cholesterol-loaded foam cells play a pivotal role in forming atherosclerotic plaques. Induction of cholesterol efflux from these cells may be a promising approach in treating CVD. The reverse cholesterol transport (RCT) pathway delivers cholesteryl ester (CE) packaged in high-density lipoproteins (HDL) from non-hepatic cells to the liver, thereby minimising cholesterol load of peripheral cells. RCT takes place via a well-organised interplay amongst apolipoprotein A1 (ApoA1), lecithin cholesterol acyltransferase (LCAT), ATP binding cassette transporter A1 (ABCA1), scavenger receptor-B1 (SR-B1), and the amount of free cholesterol. Unfortunately, modulation of RCT for treating atherosclerosis has failed in clinical trials owing to our lack of understanding of the relationship between HDL function and RCT. The fate of non-hepatic CEs in HDL is dependent on their access to proteins involved in remodelling and can be regulated at the structural level. An inadequate understanding of this inhibits the design of rational strategies for therapeutic interventions. Herein we extensively review the structure-function relationships that are essential for RCT. We also focus on genetic mutations that disturb the structural stability of proteins involved in RCT, rendering them partially or completely non-functional. Further studies are necessary for understanding the structural aspects of RCT pathway completely, and this review highlights alternative theories and unanswered questions.
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Affiliation(s)
- Sukriti Sacher
- Department of Computational Biology, Indraprastha Institute of Information Technology, Okhla Phase III, New Delhi, 110019, India
| | - Abhishek Mukherjee
- Dhiti Life Sciences Pvt Ltd, B-107, Okhla Phase I, New Delhi, 110020, India
| | - Arjun Ray
- Department of Computational Biology, Indraprastha Institute of Information Technology, Okhla Phase III, New Delhi, 110019, India
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2
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Choi HY, Choi S, Iatan I, Ruel I, Genest J. Biomedical Advances in ABCA1 Transporter: From Bench to Bedside. Biomedicines 2023; 11:biomedicines11020561. [PMID: 36831097 PMCID: PMC9953649 DOI: 10.3390/biomedicines11020561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 02/07/2023] [Accepted: 02/13/2023] [Indexed: 02/17/2023] Open
Abstract
ATP-binding cassette transporter A1 (ABCA1) has been identified as the molecular defect in Tangier disease. It is biochemically characterized by absence of high-density lipoprotein cholesterol (HDL-C) in the circulation, resulting in the accumulation of cholesterol in lymphoid tissues. Accumulation of cholesterol in arteries is an underlying cause of atherosclerosis, and HDL-C levels are inversely associated with the presence of atherosclerotic cardiovascular disease (ASCVD). ABCA1 increases HDL-C levels by driving the generation of new HDL particles in cells, and cellular cholesterol is removed in the process of HDL generation. Therefore, pharmacological strategies that promote the HDL biogenic process by increasing ABCA1 expression and activity have been intensively studied to reduce ASCVD. Many ABCA1-upregulating agents have been developed, and some have shown promising effects in pre-clinical studies, but no clinical trials have met success yet. ABCA1 has long been an attractive drug target, but the failed clinical trials have indicated the difficulty of therapeutic upregulation of ABCA1, as well as driving us to: improve our understanding of the ABCA1 regulatory system; to develop more specific and sophisticated strategies to upregulate ABCA1 expression; and to search for novel druggable targets in the ABCA1-dependent HDL biogenic process. In this review, we discuss the beginning, recent advances, challenges and future directions in ABCA1 research aimed at developing ABCA1-directed therapies for ASCVD.
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Affiliation(s)
- Hong Y. Choi
- Research Institute of the McGill University Health Centre, Montréal, QC H4A 3J1, Canada
- Correspondence: ; Tel.: +1-514-934-1934 (ext. 35796)
| | - Senna Choi
- Research Institute of the McGill University Health Centre, Montréal, QC H4A 3J1, Canada
| | - Iulia Iatan
- Centre for Heart Lung Innovation, Department of Medicine, St. Paul’s Hospital, University of British Columbia, Vancouver, BC V6Z 1Y6, Canada
| | - Isabelle Ruel
- Research Institute of the McGill University Health Centre, Montréal, QC H4A 3J1, Canada
| | - Jacques Genest
- Research Institute of the McGill University Health Centre, Montréal, QC H4A 3J1, Canada
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3
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Xue H, Zhang M, Liu J, Wang J, Ren G. Cryo-electron tomography related radiation-damage parameters for individual-molecule 3D structure determination. Front Chem 2022; 10:889203. [PMID: 36110139 PMCID: PMC9468540 DOI: 10.3389/fchem.2022.889203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 07/13/2022] [Indexed: 11/28/2022] Open
Abstract
To understand the dynamic structure-function relationship of soft- and biomolecules, the determination of the three-dimensional (3D) structure of each individual molecule (nonaveraged structure) in its native state is sought-after. Cryo-electron tomography (cryo-ET) is a unique tool for imaging an individual object from a series of tilted views. However, due to radiation damage from the incident electron beam, the tolerable electron dose limits image contrast and the signal-to-noise ratio (SNR) of the data, preventing the 3D structure determination of individual molecules, especially at high-resolution. Although recently developed technologies and techniques, such as the direct electron detector, phase plate, and computational algorithms, can partially improve image contrast/SNR at the same electron dose, the high-resolution structure, such as tertiary structure of individual molecules, has not yet been resolved. Here, we review the cryo-electron microscopy (cryo-EM) and cryo-ET experimental parameters to discuss how these parameters affect the extent of radiation damage. This discussion can guide us in optimizing the experimental strategy to increase the imaging dose or improve image SNR without increasing the radiation damage. With a higher dose, a higher image contrast/SNR can be achieved, which is crucial for individual-molecule 3D structure. With 3D structures determined from an ensemble of individual molecules in different conformations, the molecular mechanism through their biochemical reactions, such as self-folding or synthesis, can be elucidated in a straightforward manner.
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Affiliation(s)
- Han Xue
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
- Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Meng Zhang
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
| | - Jianfang Liu
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
| | - Jianjun Wang
- Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Gang Ren
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
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Picataggi A, Rodrigues A, Cromley DA, Wang H, Wiener JP, Garliyev V, Billheimer JT, Grabiner BC, Hurt JA, Chen AC, Han X, Rader DJ, Praticò D, Lyssenko NN. Specificity of ABCA7-mediated cell lipid efflux. Biochim Biophys Acta Mol Cell Biol Lipids 2022; 1867:159157. [PMID: 35381375 PMCID: PMC9058236 DOI: 10.1016/j.bbalip.2022.159157] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 03/04/2022] [Accepted: 03/29/2022] [Indexed: 12/31/2022]
Abstract
Adenosine triphosphate-binding cassette transporter subfamily A member 7 (ABCA7) performs incompletely understood biochemical functions that affect pathogenesis of Alzheimer's disease. ABCA7 is most similar in primary structure to ABCA1, the protein that mediates cell lipid efflux and formation of high-density lipoprotein (HDL). Lipid metabolic labeling/tracer efflux assays were employed to investigate lipid efflux in BHK-ABCA7(low expression), BHK-ABCA7(high expression) and BHK-ABCA1 cells. Shotgun lipid mass spectrometry was used to determine lipid composition of HDL synthesized by BHK-ABCA7 and BHK-ABCA1 cells. BHK-ABCA7(low) cells exhibited significant efflux only of choline-phospholipid and phosphatidylinositol. BHK-ABCA7(high) cells had significant cholesterol and choline-phospholipid efflux to apolipoprotein (apo) A-I, apo E, the 18A peptide, HDL, plasma and cerebrospinal fluid and significant efflux of sphingosine-lipid, serine-lipid (which is composed of phosphatidylserine and phosphatidylethanolamine in BHK cells) and phosphatidylinositol to apo A-I. In efflux assays to apo A-I, after adjustment to choline-phospholipid, ABCA7-mediated efflux removed ~4 times more serine-lipid and phosphatidylinositol than ABCA1-mediated efflux, while ABCA1-mediated efflux removed ~3 times more cholesterol than ABCA7-mediated efflux. Shotgun lipidomic analysis revealed that ABCA7-HDL had ~20 mol% less phosphatidylcholine and 3-5 times more serine-lipid and phosphatidylinositol than ABCA1-HDL, while ABCA1-HDL contained only ~6 mol% (or ~1.1 times) more cholesterol than ABCA7-HDL. The discrepancy between the tracer efflux assays and shotgun lipidomics with respect to cholesterol may be explained by an underestimate of ABCA7-mediated cholesterol efflux in the former approach. Overall, these results suggest that ABCA7 lacks specificity for phosphatidylcholine and releases significantly but not dramatically less cholesterol in comparison with ABCA1.
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Affiliation(s)
- Antonino Picataggi
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Amrith Rodrigues
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Debra A Cromley
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Hu Wang
- Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Joel P Wiener
- Alzheimer's Center at Temple, Department of Neural Sciences, Lewis Katz School of Medicine at Temple University, Philadelphia, PA 19140, USA
| | - Viktor Garliyev
- Alzheimer's Center at Temple, Department of Neural Sciences, Lewis Katz School of Medicine at Temple University, Philadelphia, PA 19140, USA
| | - Jeffrey T Billheimer
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | | | | | - Xianlin Han
- Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Daniel J Rader
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Domenico Praticò
- Alzheimer's Center at Temple, Department of Neural Sciences, Lewis Katz School of Medicine at Temple University, Philadelphia, PA 19140, USA
| | - Nicholas N Lyssenko
- Alzheimer's Center at Temple, Department of Neural Sciences, Lewis Katz School of Medicine at Temple University, Philadelphia, PA 19140, USA.
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5
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Hafiane A, Gianopoulos I, Sorci-Thomas MG, Daskalopoulou SS. Current models of apolipoprotein A-I lipidation by adenosine triphosphate binding cassette transporter A1. Curr Opin Lipidol 2022; 33:139-145. [PMID: 34581311 DOI: 10.1097/mol.0000000000000786] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW The primary cardioprotective function of high-density lipoprotein (HDL) is to remove excess cellular free cholesterol (FC) from peripheral tissues and deliver it to the liver. Here, we summarize recent research that examines apolipoprotein A-I (apoA-I) lipidation models by adenosine triphosphate binding cassette transporter A1 (ABCA1) and discuss its relevance in atherosclerotic cardiovascular disease (ASCVD). RECENT FINDINGS The first step in HDL formation involves the interaction between apoA-I and ABCA1, where ABCA1 mediates the removal of FC and phospholipids from lipid-laden macrophages to form discoidal nascent HDL (nHDL). However, there are currently no clear-cut systematic models that characterize HDL formation. A number of recent studies have investigated the importance of apoA-I C- and N-terminal domains required for optimal cholesterol efflux and nHDL production. Furthermore, functional ABCA1 is required for direct or indirect binding to apoA-I where ABCA1 dimer-monomer interconversion facilitates apoA-I lipidation from plasma membrane microdomains. Microparticles are also another lipid source for apoA-I solubilization into nHDL. SUMMARY ApoA-I and ABCA1 are key factors in macrophage-mediated cholesterol efflux and nHDL production. Understanding of the key steps in HDL formation may unlock the therapeutic potential of HDL and improve clinical management of ASCVD.
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Affiliation(s)
- Anouar Hafiane
- Division of Experimental Medicine, Department of Medicine, Faculty of Medicine, Research Institute of the McGill University Health Centre, McGill University, Montreal, Canada
| | - Ioanna Gianopoulos
- Division of Experimental Medicine, Department of Medicine, Faculty of Medicine, Research Institute of the McGill University Health Centre, McGill University, Montreal, Canada
| | - Mary G Sorci-Thomas
- Division of Endocrinology, Metabolism and Clinical Nutrition, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Stella S Daskalopoulou
- Division of Experimental Medicine, Department of Medicine, Faculty of Medicine, Research Institute of the McGill University Health Centre, McGill University, Montreal, Canada
- Division of Internal Medicine, Department of Medicine, Faculty of Medicine, McGill University Health Centre, McGill University Montreal, Montreal, Canada
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6
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Juhl AD, Wüstner D. Pathways and Mechanisms of Cellular Cholesterol Efflux-Insight From Imaging. Front Cell Dev Biol 2022; 10:834408. [PMID: 35300409 PMCID: PMC8920967 DOI: 10.3389/fcell.2022.834408] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 02/04/2022] [Indexed: 12/24/2022] Open
Abstract
Cholesterol is an essential molecule in cellular membranes, but too much cholesterol can be toxic. Therefore, mammalian cells have developed complex mechanisms to remove excess cholesterol. In this review article, we discuss what is known about such efflux pathways including a discussion of reverse cholesterol transport and formation of high-density lipoprotein, the function of ABC transporters and other sterol efflux proteins, and we highlight their role in human diseases. Attention is paid to the biophysical principles governing efflux of sterols from cells. We also discuss recent evidence for cholesterol efflux by the release of exosomes, microvesicles, and migrasomes. The role of the endo-lysosomal network, lipophagy, and selected lysosomal transporters, such as Niemann Pick type C proteins in cholesterol export from cells is elucidated. Since oxysterols are important regulators of cellular cholesterol efflux, their formation, trafficking, and secretion are described briefly. In addition to discussing results obtained with traditional biochemical methods, focus is on studies that use established and novel bioimaging approaches to obtain insight into cholesterol efflux pathways, including fluorescence and electron microscopy, atomic force microscopy, X-ray tomography as well as mass spectrometry imaging.
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Affiliation(s)
- Alice Dupont Juhl
- Department of Biochemistry and Molecular Biology, PhyLife, Physical Life Sciences, University of Southern Denmark, Odense, Denmark
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, PhyLife, Physical Life Sciences, University of Southern Denmark, Odense, Denmark
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7
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Bedi S, Morris J, Shah A, Hart RC, Jerome WG, Aller SG, Tang C, Vaisar T, Bornfeldt KE, Segrest JP, Heinecke JW, Davidson WS. Conformational flexibility of apolipoprotein A-I amino- and carboxy-termini is necessary for lipid binding but not cholesterol efflux. J Lipid Res 2022; 63:100168. [PMID: 35051413 PMCID: PMC8953623 DOI: 10.1016/j.jlr.2022.100168] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 01/03/2022] [Accepted: 01/11/2022] [Indexed: 11/25/2022] Open
Abstract
Because of its critical role in HDL formation, significant efforts have been devoted to studying apolipoprotein A-I (APOA1) structural transitions in response to lipid binding. To assess the requirements for the conformational freedom of its termini during HDL particle formation, we generated three dimeric APOA1 molecules with their termini covalently joined in different combinations. The dimeric (d)-APOA1C-N mutant coupled the C-terminus of one APOA1 molecule to the N-terminus of a second with a short alanine linker, whereas the d-APOA1C-C and d-APOA1N-N mutants coupled the C-termini and the N-termini of two APOA1 molecules, respectively, using introduced cysteine residues to form disulfide linkages. We then tested the ability of these constructs to generate reconstituted HDL by detergent-assisted and spontaneous phospholipid microsolubilization methods. Using cholate dialysis, we demonstrate WT and all APOA1 mutants generated reconstituted HDL particles of similar sizes, morphologies, compositions, and abilities to activate lecithin:cholesterol acyltransferase. Unlike WT, however, the mutants were incapable of spontaneously solubilizing short chain phospholipids into discoidal particles. We found lipid-free d-APOA1C-N and d-APOA1N-N retained most of WT APOA1's ability to promote cholesterol efflux via the ATP binding cassette transporter A1, whereas d-APOA1C-C exhibited impaired cholesterol efflux. Our data support the double belt model for a lipid-bound APOA1 structure in nascent HDL particles and refute other postulated arrangements like the "double super helix." Furthermore, we conclude the conformational freedom of both the N- and C-termini of APOA1 is important in spontaneous microsolubilization of bulk phospholipid but is not critical for ABCA1-mediated cholesterol efflux.
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Affiliation(s)
- Shimpi Bedi
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Jamie Morris
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Amy Shah
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Rachel C Hart
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - W Gray Jerome
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Stephen G Aller
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Chongren Tang
- Department of Medicine, University of Washington School of Medicine, Seattle, WA, USA
| | - Tomas Vaisar
- Department of Medicine, University of Washington School of Medicine, Seattle, WA, USA
| | - Karin E Bornfeldt
- Department of Medicine, University of Washington School of Medicine, Seattle, WA, USA
| | - Jere P Segrest
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Jay W Heinecke
- Department of Medicine, University of Washington School of Medicine, Seattle, WA, USA
| | - W Sean Davidson
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH, USA.
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8
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Choi HY, Ruel I, Choi S, Genest J. New Strategies to Promote Macrophage Cholesterol Efflux. Front Cardiovasc Med 2022; 8:795868. [PMID: 35004908 PMCID: PMC8733154 DOI: 10.3389/fcvm.2021.795868] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 12/03/2021] [Indexed: 12/11/2022] Open
Abstract
The capacity of macrophages to dispose of cholesterol deposited in the atherosclerotic plaque depends on their ability to activate cholesterol efflux pathways. To develop athero-protective therapies aimed at promoting macrophage cholesterol efflux, cholesterol metabolism in THP-1 monocyte-derived macrophages has been extensively studied, but the intrinsic sensitivity of monocytes and the lack of a standardized procedure to differentiate THP-1 monocytes into macrophages have made it difficult to utilize THP-1 macrophages in the same or similar degree of differentiation across studies. The variability has resulted in lack of understanding of how the differentiation affects cholesterol metabolism, and here we review and investigate the effects of THP-1 differentiation on cholesterol efflux. The degree of THP-1 differentiation was inversely associated with ATP binding cassette A1 (ABCA1) transporter-mediated cholesterol efflux. The differentiation-associated decrease in ABCA1-mediated cholesterol efflux occurred despite an increase in ABCA1 expression. In contrast, DSC1 expression decreased during the differentiation. DSC1 is a negative regulator of the ABCA1-mediated efflux pathway and a DSC1-targeting agent, docetaxel showed high potency and efficacy in promoting ABCA1-mediated cholesterol efflux in THP-1 macrophages. These data suggest that pharmacological targeting of DSC1 may be more effective than increasing ABCA1 expression in promoting macrophage cholesterol efflux. In summary, the comparison of THP-1 macrophage subtypes in varying degrees of differentiation provided new insights into cholesterol metabolism in macrophages and allowed us to identify a viable target DSC1 for the promotion of cholesterol efflux in differentiated macrophages. Docetaxel and other pharmacological strategies targeting DSC1 may hold significant potential for reducing atherogenic cholesterol deposition.
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Affiliation(s)
- Hong Y Choi
- Cardiovascular Research Laboratories, Research Institute of the McGill University Health Center, Montreal, QC, Canada
| | - Isabelle Ruel
- Cardiovascular Research Laboratories, Research Institute of the McGill University Health Center, Montreal, QC, Canada
| | - Shiwon Choi
- Cardiovascular Research Laboratories, Research Institute of the McGill University Health Center, Montreal, QC, Canada
| | - Jacques Genest
- Cardiovascular Research Laboratories, Research Institute of the McGill University Health Center, Montreal, QC, Canada
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9
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Lange Y, Steck TL. Active cholesterol 20 years on. Traffic 2020; 21:662-674. [PMID: 32930466 DOI: 10.1111/tra.12762] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 09/08/2020] [Accepted: 09/10/2020] [Indexed: 12/13/2022]
Abstract
This review considers the following hypotheses, some well-supported and some speculative. Almost all of the sterol molecules in plasma membranes are associated with bilayer phospholipids in complexes of varied strength and stoichiometry. These complexes underlie many of the material properties of the bilayer. The small fraction of cholesterol molecules exceeding the binding capacity of the phospholipids is thermodynamically active and serves diverse functions. It circulates briskly among the cell membranes, particularly through contact sites linking the organelles. Active cholesterol provides the upstream feedback signal to multiple mechanisms governing plasma membrane homeostasis, pegging the sterol level to a threshold set by its phospholipids. Active cholesterol could also be the cargo for various inter-organelle transporters and the form excreted from cells by reverse transport. Furthermore, it is integral to the function of caveolae; a mediator of Hedgehog regulation; and a ligand for the binding of cytolytic toxins to membranes. Active cholesterol modulates a variety of plasma membrane proteins-receptors, channels and transporters-at least in vitro.
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Affiliation(s)
- Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, Illinois, USA
| | - Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
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10
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Yelamanchili D, Liu J, Gotto AM, Hurley AE, Lagor WR, Gillard BK, Davidson WS, Pownall HJ, Rosales C. Highly conserved amino acid residues in apolipoprotein A1 discordantly induce high density lipoprotein assembly in vitro and in vivo. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1865:158794. [PMID: 32810603 DOI: 10.1016/j.bbalip.2020.158794] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 08/10/2020] [Accepted: 08/13/2020] [Indexed: 12/17/2022]
Abstract
OBJECTIVE Apolipoprotein A1 (APOA1) is essential to reverse cholesterol transport, a physiologically important process that protects against atherosclerotic cardiovascular disease. APOA1 is a 28 kDa protein comprising multiple lipid-binding amphiphatic helices initialized by proline residues, which are conserved across multiple species. We tested the hypothesis that the evolutionarily conserved residues are essential to high density lipoprotein (HDL) function. APPROACH We used biophysical and physiological assays of the function of APOA1P➔A variants, i.e., rHDL formation via dimyristoylphosphatidylcholine (DMPC) microsolubilization, activation of lecithin: cholesterol acyltransferase, cholesterol efflux from human monocyte-derived macrophages (THP-1) to each variant, and comparison of the size and composition of HDL from APOA1-/- mice receiving adeno-associated virus delivery of each human variant. RESULTS Differences in microsolubilization were profound and showed that conserved prolines, especially those in the C-terminus of APOA1, are essential to efficient rHDL formation. In contrast, P➔A substitutions produced small changes (-25 to +25%) in rates of cholesterol efflux and no differences in the rates of LCAT activation. The HDL particles formed following ectopic expression of each variant in APOA1-/- mice were smaller and more heterogeneous than those from control animals. CONCLUSION Studies of DMPC microsolubilization show that proline residues are essential to the optimal interaction of APOA1 with membranes, the initial step in cholesterol efflux and HDL production. In contrast, P➔A substitutions modestly reduce the cholesterol efflux capacity of APOA1, have no effect on LCAT activation, but according to the profound reduction in the size of HDL formed in vivo, P➔A substitutions alter HDL biogenesis, thereby implicating other cellular and in vivo processes as determinants of HDL metabolism and function.
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Affiliation(s)
- Dedipya Yelamanchili
- Center for Bioenergetics, Houston Methodist Research Institute, 6670 Bertner Avenue, Houston, TX 77030, USA.
| | - Jing Liu
- Center for Bioenergetics, Houston Methodist Research Institute, 6670 Bertner Avenue, Houston, TX 77030, USA; Department of Cardiovascular Surgery, Xiangya Hospital, Central South University, Changsha 410008, China.
| | - Antonio M Gotto
- Center for Bioenergetics, Houston Methodist Research Institute, 6670 Bertner Avenue, Houston, TX 77030, USA; Weill Cornell Medicine, 1305 York Avenue, New York, NY 10065, USA.
| | - Ayrea E Hurley
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
| | - Willam R Lagor
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
| | - Baiba K Gillard
- Center for Bioenergetics, Houston Methodist Research Institute, 6670 Bertner Avenue, Houston, TX 77030, USA; Weill Cornell Medicine, 1305 York Avenue, New York, NY 10065, USA.
| | - W Sean Davidson
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH 45237, USA.
| | - Henry J Pownall
- Center for Bioenergetics, Houston Methodist Research Institute, 6670 Bertner Avenue, Houston, TX 77030, USA; Weill Cornell Medicine, 1305 York Avenue, New York, NY 10065, USA.
| | - Corina Rosales
- Center for Bioenergetics, Houston Methodist Research Institute, 6670 Bertner Avenue, Houston, TX 77030, USA; Weill Cornell Medicine, 1305 York Avenue, New York, NY 10065, USA.
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11
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Castaño D, Rattanasopa C, Monteiro-Cardoso VF, Corlianò M, Liu Y, Zhong S, Rusu M, Liehn EA, Singaraja RR. Lipid efflux mechanisms, relation to disease and potential therapeutic aspects. Adv Drug Deliv Rev 2020; 159:54-93. [PMID: 32423566 DOI: 10.1016/j.addr.2020.04.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 04/29/2020] [Accepted: 04/30/2020] [Indexed: 02/06/2023]
Abstract
Lipids are hydrophobic and amphiphilic molecules involved in diverse functions such as membrane structure, energy metabolism, immunity, and signaling. However, altered intra-cellular lipid levels or composition can lead to metabolic and inflammatory dysfunction, as well as lipotoxicity. Thus, intra-cellular lipid homeostasis is tightly regulated by multiple mechanisms. Since most peripheral cells do not catabolize cholesterol, efflux (extra-cellular transport) of cholesterol is vital for lipid homeostasis. Defective efflux contributes to atherosclerotic plaque development, impaired β-cell insulin secretion, and neuropathology. Of these, defective lipid efflux in macrophages in the arterial walls leading to foam cell and atherosclerotic plaque formation has been the most well studied, likely because a leading global cause of death is cardiovascular disease. Circulating high density lipoprotein particles play critical roles as acceptors of effluxed cellular lipids, suggesting their importance in disease etiology. We review here mechanisms and pathways that modulate lipid efflux, the role of lipid efflux in disease etiology, and therapeutic options aimed at modulating this critical process.
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12
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Lei D, Liu J, Liu H, Cleveland TE, Marino JP, Lei M, Ren G. Single-Molecule 3D Images of "Hole-Hole" IgG1 Homodimers by Individual-Particle Electron Tomography. Sci Rep 2019; 9:8864. [PMID: 31221961 PMCID: PMC6586654 DOI: 10.1038/s41598-019-44978-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 05/30/2019] [Indexed: 12/20/2022] Open
Abstract
The engineering of immunoglobulin-G molecules (IgGs) is of wide interest for improving therapeutics, for example by modulating the activity or multiplexing the specificity of IgGs to recognize more than one antigen. Optimization of engineered IgG requires knowledge of three-dimensional (3D) structure of synthetic IgG. However, due to flexible nature of the molecules, their structural characterization is challenging. Here, we use our reported individual-particle electron tomography (IPET) method with optimized negative-staining (OpNS) for direct 3D reconstruction of individual IgG hole-hole homodimer molecules. The hole-hole homodimer is an undesired variant generated during the production of a bispecific antibody using the knob-into-hole heterodimer technology. A total of 64 IPET 3D density maps at ~15 Å resolutions were reconstructed from 64 individual molecules, revealing 64 unique conformations. In addition to the known Y-shaped conformation, we also observed an unusual X-shaped conformation. The 3D structure of the X-shaped conformation contributes to our understanding of the structural details of the interaction between two heavy chains in the Fc domain. The IPET approach, as an orthogonal technique to characterize the 3D structure of therapeutic antibodies, provides insight into the 3D structural variety and dynamics of heterogeneous IgG molecules.
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Affiliation(s)
- Dongsheng Lei
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Jianfang Liu
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Hongbin Liu
- Protein Analytical Chemistry, Genentech Inc., South San Francisco, CA, 94080, USA
| | - Thomas E Cleveland
- Institute for Bioscience and Biotechnology Research, National Institute of Standards and Technology and the University of Maryland, Rockville, MD, 20850, USA
| | - John P Marino
- Institute for Bioscience and Biotechnology Research, National Institute of Standards and Technology and the University of Maryland, Rockville, MD, 20850, USA
| | - Ming Lei
- Protein Analytical Chemistry, Genentech Inc., South San Francisco, CA, 94080, USA.
| | - Gang Ren
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
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13
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Chorlay A, Monticelli L, Veríssimo Ferreira J, Ben M'barek K, Ajjaji D, Wang S, Johnson E, Beck R, Omrane M, Beller M, Carvalho P, Rachid Thiam A. Membrane Asymmetry Imposes Directionality on Lipid Droplet Emergence from the ER. Dev Cell 2019; 50:25-42.e7. [PMID: 31155466 DOI: 10.1016/j.devcel.2019.05.003] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 01/11/2019] [Accepted: 05/02/2019] [Indexed: 01/18/2023]
Abstract
During energy bursts, neutral lipids fabricated within the ER bilayer demix to form lipid droplets (LDs). LDs bud off mainly in the cytosol where they regulate metabolism and multiple biological processes. They indeed become accessible to most enzymes and can interact with other organelles. How such directional emergence is achieved remains elusive. Here, we found that this directionality is controlled by an asymmetry in monolayer surface coverage. Model LDs emerge on the membrane leaflet of higher coverage, which is improved by the insertion of proteins and phospholipids. In cells, continuous LD emergence on the cytosol would require a constant refill of phospholipids to the ER cytosolic leaflet. Consistent with this model, cells deficient in phospholipids present an increased number of LDs exposed to the ER lumen and compensate by remodeling ER shape. Our results reveal an active cooperation between phospholipids and proteins to extract LDs from ER.
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Affiliation(s)
- Aymeric Chorlay
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRSSorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
| | - Luca Monticelli
- Laboratory of Molecular Microbiology and Structural Biochemistry, UMR5086 CNRS and University of Lyon, Lyon 69367, France
| | | | - Kalthoum Ben M'barek
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRSSorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
| | - Dalila Ajjaji
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRSSorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
| | - Sihui Wang
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Errin Johnson
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Rainer Beck
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Mohyeddine Omrane
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRSSorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
| | - Mathias Beller
- Institute for Mathematical Modeling of Biological Systems, Systems Biology of Lipid Metabolism, Heinrich Heine University, Düsseldorf, Germany
| | - Pedro Carvalho
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Abdou Rachid Thiam
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRSSorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France.
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14
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Enkavi G, Javanainen M, Kulig W, Róg T, Vattulainen I. Multiscale Simulations of Biological Membranes: The Challenge To Understand Biological Phenomena in a Living Substance. Chem Rev 2019; 119:5607-5774. [PMID: 30859819 PMCID: PMC6727218 DOI: 10.1021/acs.chemrev.8b00538] [Citation(s) in RCA: 173] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
![]()
Biological
membranes are tricky to investigate. They are complex
in terms of molecular composition and structure, functional
over a wide range of time scales, and characterized
by nonequilibrium conditions. Because of all of these
features, simulations are a great technique to study biomembrane
behavior. A significant part of the functional processes
in biological membranes takes place at the molecular
level; thus computer simulations are the method of
choice to explore how their properties emerge from specific
molecular features and how the interplay among the numerous
molecules gives rise to function over spatial and
time scales larger than the molecular ones. In this
review, we focus on this broad theme. We discuss the current
state-of-the-art of biomembrane simulations that, until
now, have largely focused on a rather narrow picture
of the complexity of the membranes. Given this, we
also discuss the challenges that we should unravel in the
foreseeable future. Numerous features such as the actin-cytoskeleton
network, the glycocalyx network, and nonequilibrium
transport under ATP-driven conditions have so far
received very little attention; however, the potential
of simulations to solve them would be exceptionally high. A
major milestone for this research would be that one day
we could say that computer simulations genuinely research
biological membranes, not just lipid bilayers.
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Affiliation(s)
- Giray Enkavi
- Department of Physics , University of Helsinki , P.O. Box 64, FI-00014 Helsinki , Finland
| | - Matti Javanainen
- Department of Physics , University of Helsinki , P.O. Box 64, FI-00014 Helsinki , Finland.,Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences , Flemingovo naḿesti 542/2 , 16610 Prague , Czech Republic.,Computational Physics Laboratory , Tampere University , P.O. Box 692, FI-33014 Tampere , Finland
| | - Waldemar Kulig
- Department of Physics , University of Helsinki , P.O. Box 64, FI-00014 Helsinki , Finland
| | - Tomasz Róg
- Department of Physics , University of Helsinki , P.O. Box 64, FI-00014 Helsinki , Finland.,Computational Physics Laboratory , Tampere University , P.O. Box 692, FI-33014 Tampere , Finland
| | - Ilpo Vattulainen
- Department of Physics , University of Helsinki , P.O. Box 64, FI-00014 Helsinki , Finland.,Computational Physics Laboratory , Tampere University , P.O. Box 692, FI-33014 Tampere , Finland.,MEMPHYS-Center for Biomembrane Physics
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15
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Liu J, Wu H, Huang C, Lei D, Zhang M, Xie W, Li J, Ren G. Optimized Negative-Staining Protocol for Lipid-Protein Interactions Investigated by Electron Microscopy. Methods Mol Biol 2019; 2003:163-173. [PMID: 31218618 PMCID: PMC6817366 DOI: 10.1007/978-1-4939-9512-7_8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A large number of proteins are capable of inserting themselves into lipids, and interacting with membranes, such as transmembrane proteins and apolipoproteins. Insights into the lipid-protein interactions are important in understanding biological processes, and the structure of proteins at the lipid binding stage can help identify their roles and critical functions. Previously, such structural determination was challenging to obtain because the traditional methods, such as X-ray crystallography, are unable to capture the conformational and compositional heterogeneity of protein-lipid complexes. Electron microscopy (EM) is an alternative approach to determining protein structures and visualizing lipid-protein interactions directly, and negative-staining (OpNS), a subset of EM techniques, is a rapid, frequently used qualitative approach. The concern, however, is that current NS protocols often generate artifacts with lipid-related proteins, such as rouleaux formation from lipoproteins. To overcome this artifact formation, Ren and his colleagues have refined early NS protocols, and developed an optimized NS protocol that validated by comparing images of lipoproteins from cryo-electron microscopy (cryo-EM). This optimized NS protocol produces "near native-state" particle images and high contrast images of the protein in its native lipid-binding state, which can be used to create higher-quality three-dimensional (3D) reconstruction by single-particle analysis and electron tomography (e.g. IPET). This optimized protocol is thus a promising hands-on approach for examining the structure of proteins at their lipid-binding status.
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Affiliation(s)
- Jianfang Liu
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Hao Wu
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Computer Science, College of Information Science and Technology, Beijing Normal University, Beijing, China
| | - Changyu Huang
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Dongsheng Lei
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Meng Zhang
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Wei Xie
- State Key Laboratory for Biocontrol, School of Life Sciences, The Sun Yat-Sen University, Guangzhou, Guangdong, China
- Center for Cellular and Structural Biology, The Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Jinping Li
- Department of Biomedical Sciences, Mercer University School of Medicine, Savannah, GA, USA
| | - Gang Ren
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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16
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Molecular dynamics simulations of lipid nanodiscs. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2094-2107. [PMID: 29729280 DOI: 10.1016/j.bbamem.2018.04.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 04/27/2018] [Accepted: 04/28/2018] [Indexed: 01/02/2023]
Abstract
A lipid nanodisc is a discoidal lipid bilayer stabilized by proteins, peptides, or polymers on its edge. Nanodiscs have two important connections to structural biology. The first is associated with high-density lipoprotein (HDL), a particle with a variety of functionalities including lipid transport. Nascent HDL (nHDL) is a nanodisc stabilized by Apolipoprotein A-I (APOA1). Determining the structure of APOA1 and its mimetic peptides in nanodiscs is crucial to understanding pathologies related to HDL maturation and designing effective therapies. Secondly, nanodiscs offer non-detergent membrane-mimicking environments and greatly facilitate structural studies of membrane proteins. Although seemingly similar, natural and synthetic nanodiscs are different in that nHDL is heterogeneous in size, due to APOA1 elasticity, and gradually matures to become spherical. Synthetic nanodiscs, in contrast, should be homogenous, stable, and size-tunable. This report reviews previous molecular dynamics (MD) simulation studies of nanodiscs and illustrates convergence and accuracy issues using results from new multi-microsecond atomistic MD simulations. These new simulations reveal that APOA1 helices take 10-20 μs to rearrange on the nanodisc, while peptides take 2 μs to migrate from the disc surfaces to the edge. These systems can also become kinetically trapped depending on the initial conditions. For example, APOA1 was trapped in a biologically irrelevant conformation for the duration of a 10 μs trajectory; the peptides were similarly trapped for 5 μs. It therefore remains essential to validate MD simulations of these systems with experiments due to convergence and accuracy issues. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo.
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17
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IgG Antibody 3D Structures and Dynamics. Antibodies (Basel) 2018; 7:antib7020018. [PMID: 31544870 PMCID: PMC6698877 DOI: 10.3390/antib7020018] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 04/13/2018] [Accepted: 04/16/2018] [Indexed: 12/19/2022] Open
Abstract
Antibodies are vital for human health because of their ability to function as nature's drugs by protecting the body from infection. In recent decades, antibodies have been used as pharmaceutics for targeted therapy in patients with cancer, autoimmune diseases, and cardiovascular diseases. Capturing the dynamic structure of antibodies and characterizing antibody fluctuation is critical for gaining a deeper understanding of their structural characteristics and for improving drug development. Current techniques for studying three-dimensional (3D) structural heterogeneity and variability of proteins have limitations in ascertaining the dynamic structural behavior of antibodies and antibody-antigen complexes. Here, we review current techniques used to study antibody structures with a focus on the recently developed individual-particle electron tomography (IPET) technique. IPET, as a particle-by-particle methodology for 3D structural characterization, has shown advantages in studying structural variety and conformational changes of antibodies, providing direct imaging data for biomolecular engineering to improve development and clinical application of synthetic antibodies.
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18
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Catte A, Wilson MR, Walker M, Oganesyan VS. Antimicrobial action of the cationic peptide, chrysophsin-3: a coarse-grained molecular dynamics study. SOFT MATTER 2018; 14:2796-2807. [PMID: 29595197 DOI: 10.1039/c7sm02152f] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Antimicrobial peptides (AMPs) are small cationic proteins that are able to destabilize a lipid bilayer structure through one or more modes of action. In this study, we investigate the processes of peptide aggregation and pore formation in lipid bilayers and vesicles by the highly cationic AMP, Chrysophsin-3 (chrys-3), using coarse-grained molecular dynamics (CG-MD) simulations and potential of mean force calculations. We study long 50 μs simulations of chrys-3 at different concentrations, both at the surface of dipalmitoylphosphatidylcholine (DPPC) and palmitoyloleoylphosphatidylcholine (POPC) bilayers, and also interacting within the interior of the lipid membrane. We show that aggregation of peptides at the surface, leads to pronounced deformation of lipid bilayers, leading in turn to lipid protrusions for peptide : ligand ratios > 1 : 12. In addition, aggregation of chrys-3 peptides within the centre of a lipid bilayer leads to spontaneous formation of pores and aggregates. Both mechanisms of interaction are consistent with previously reported experimental data for chrys-3. Similar results are observed also in POPC vesicles and mixed lipid bilayers composed of the zwitterionic lipid palmitoyloleoylphosphatidylethanolamine (POPE) and the negatively charged lipid palmitoyloleoylphosphatidylglycerol (POPG). The latter are employed as models of the bacterial membrane of Escherichia coli.
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Affiliation(s)
- Andrea Catte
- School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK.
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19
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Islam RM, Pourmousa M, Sviridov D, Gordon SM, Neufeld EB, Freeman LA, Perrin BS, Pastor RW, Remaley AT. Structural properties of apolipoprotein A-I mimetic peptides that promote ABCA1-dependent cholesterol efflux. Sci Rep 2018; 8:2956. [PMID: 29440748 PMCID: PMC5811490 DOI: 10.1038/s41598-018-20965-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 01/29/2018] [Indexed: 01/05/2023] Open
Abstract
Peptides mimicking the major protein of highdensity lipoprotein (HDL), apolipoprotein A-I (apoA-I), are promising therapeutics for cardiovascular diseases. Similar to apoA-I, their atheroprotective property is attributed to their ability to form discoidal HDL-like particles by extracting cellular cholesterol and phospholipids from lipid microdomains created by the ABCA1 transporter in a process called cholesterol efflux. The structural features of peptides that enable cholesterol efflux are not well understood. Herein, four synthetic amphipathic peptides denoted ELK, which only contain Glu, Leu, Lys, and sometimes Ala, and which have a wide range of net charges and hydrophobicities, were examined for cholesterol efflux. Experiments show that ELKs with a net neutral charge and a hydrophobic face that subtends an angle of at least 140° are optimal for cholesterol efflux. All-atom molecular dynamics simulations show that peptides that are effective in promoting cholesterol efflux stabilize HDL nanodiscs formed by these peptides by the orderly covering of the hydrophobic acyl chains on the edge of the disc. In contrast to apoA-I, which forms an anti-parallel double belt around the HDL, active peptides assemble in a mostly anti-parallel “picket fence” arrangement. These results shed light on the efflux ability of apoA-I mimetics and inform the future design of such therapeutics.
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Affiliation(s)
- Rafique M Islam
- School of Systems Biology, George Mason University, Fairfax, VA, 22030, USA.,Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Mohsen Pourmousa
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Denis Sviridov
- Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Scott M Gordon
- Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Edward B Neufeld
- Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Lita A Freeman
- Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - B Scott Perrin
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Richard W Pastor
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
| | - Alan T Remaley
- Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
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20
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Abstract
PURPOSE OF REVIEW The major cardio-protective function of HDL is to remove excess cellular cholesterol in the process of HDL particle formation and maturation. The HDL biogenic procedure requiring protein-lipid interactions has been incompletely understood, and here we discuss recent progress and insights into the mechanism of HDL biogenesis. RECENT FINDINGS The initial and rate-limiting step of HDL biogenesis is the interaction between apoA-I and plasma membrane microdomains created by ATP-binding cassette transporter A1 (ABCA1) transporter. Computer simulation of molecular dynamics suggests that ABCA1 translocates phospholipids from the inner to the outer leaflet of the plasma membrane to create a transbilayer density gradient leading to the formation of an exovesiculated plasma membrane microdomain. The cryo-electron microscopy structure of ABCA1 suggests that an elongated hydrophobic tunnel formed by the extracellular domain of ABCA1 may function as a passageway to deliver lipids to apoA-I. In contrast to ABCA1-created plasma membrane microdomains, desmocollin 1 (DSC1) contained in a cholesterol-rich plasma membrane microdomain binds apoA-I to prevent HDL biogenesis. The identification of DSC1-containing plasma membrane microdomains as a negative regulator of HDL biogenesis may offer potential therapeutic avenues. SUMMARY Isolation and characterization of plasma membrane microdomains involved in HDL biogenesis may lead to a better understanding of the molecular mechanism of HDL biogenesis.
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Affiliation(s)
- Jacques Genest
- Division of Cardiology, Research Institute of the McGill University Health Center, Montréal, Québec, Canada
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21
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Phillips MC. Is ABCA1 a lipid transfer protein? J Lipid Res 2018; 59:749-763. [PMID: 29305383 DOI: 10.1194/jlr.r082313] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 01/02/2018] [Indexed: 12/16/2022] Open
Abstract
ABCA1 functions as a lipid transporter because it mediates the transfer of cellular phospholipid (PL) and free (unesterified) cholesterol (FC) to apoA-I and related proteins present in the extracellular medium. ABCA1 is a membrane PL translocase and its enzymatic activity leads to transfer of PL molecules from the cytoplasmic leaflet to the exofacial leaflet of a cell plasma membrane (PM). The presence of active ABCA1 in the PM promotes binding of apoA-I to the cell surface. About 10% of this bound apoA-I interacts directly with ABCA1 and stabilizes the transporter. Most of the pool of cell surface-associated apoA-I is bound to lipid domains in the PM that are created by the activity of ABCA1. The amphipathic α-helices in apoA-I confer detergent-like properties on the protein enabling it to solubilize PL and FC in these membrane domains to create a heterogeneous population of discoidal nascent HDL particles. This review focuses on current understanding of the structure-function relationships of human ABCA1 and the molecular mechanisms underlying HDL particle production.
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Affiliation(s)
- Michael C Phillips
- Division of Translational Medicine and Human Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-5158
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22
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Abstract
PURPOSE OF REVIEW High-density lipoproteins (HDL) are thought to exert a protective role against atherosclerosis. The measurement of the cholesterol mass within HDL (HDL-C) represents a good biomarker of cardiovascular health, but HDL-C appears to be a poor therapeutic target. Here, we discuss new targets for the development of HDL-directed therapies. RECENT FINDINGS Among cardio-protective functions of HDL particles, the ability of HDL to remove cholesterol from cells involved in the early stages of atherosclerosis is considered one of the most important functions. This process, termed "HDL biogenesis," is initiated by the formation of highly specialized plasma membrane micro-domains by the ATP-binding cassette transporter A1 (ABCA1) and the binding of apolipoproteins (apo) such as apoA-I, the major protein moiety of HDL, to the micro-domains. Although early strategies aimed at increasing HDL biogenesis by upregulating ABCA1 or apoA-I gene expression have not met with clinical success, recent advances in understanding transcriptional, post-transcriptional, and post-translational regulatory pathways propose new targets for the promotion of HDL biogenesis. We have recently reported that a novel apoA-I-binding protein desmocollin 1 (DSC1) prevents HDL biogenesis and that inhibition of apoA-I-DSC1 interactions promotes HDL biogenesis by stabilizing ABCA1. This new HDL regulation pathway nominates DSC1 as an attractive pharmacological target. In the absence of clinically useful therapy to increase HDL biogenesis, finding novel targets to unlock the therapeutic potential of HDL is highly desired. Modulation of apoA-I-DSC1 interactions may be a viable strategy.
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Affiliation(s)
- Jacques Genest
- The Research Institute of the McGill University Health Center, 1001 boul. Decarie Bloc E, Office EM12212, Montreal, Québec, H4A 3J1, Canada
| | - Hong Y Choi
- The Research Institute of the McGill University Health Center, 1001 boul. Decarie Bloc E, Office EM12212, Montreal, Québec, H4A 3J1, Canada.
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23
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Zhu L, Petrlova J, Gysbers P, Hebert H, Wallin S, Jegerschöld C, Lagerstedt JO. Structures of apolipoprotein A-I in high density lipoprotein generated by electron microscopy and biased simulations. Biochim Biophys Acta Gen Subj 2017; 1861:2726-2738. [DOI: 10.1016/j.bbagen.2017.07.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 07/18/2017] [Accepted: 07/24/2017] [Indexed: 10/19/2022]
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24
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Yang Z, Cao Y, Hao D, Yuan X, Zhang L, Zhang S. Binding profiles of cholesterol ester transfer protein with current inhibitors: a look at mechanism and drawback. J Biomol Struct Dyn 2017; 36:2567-2580. [PMID: 28777919 DOI: 10.1080/07391102.2017.1363661] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Zhiwei Yang
- Department of Applied Physics, School of Science, Xi’an Jiaotong University, No. 28 Xianning West Road, Xi’an 710049, China
- Department of Applied Chemistry, School of Science, Xi’an Jiaotong University, Xi’an 710049, China
| | - Yang Cao
- Department of Applied Physics, School of Science, Xi’an Jiaotong University, No. 28 Xianning West Road, Xi’an 710049, China
| | - Dongxiao Hao
- Department of Applied Physics, School of Science, Xi’an Jiaotong University, No. 28 Xianning West Road, Xi’an 710049, China
| | - Xiaohui Yuan
- Institute of Biomedicine, Jinan University, Guangzhou 510632, China
- Guangdong Provincial Key Laboratory of Bioengineering Medicine, Jinan University, Guangzhou 510632, China
| | - Lei Zhang
- Department of Applied Physics, School of Science, Xi’an Jiaotong University, No. 28 Xianning West Road, Xi’an 710049, China
| | - Shengli Zhang
- Department of Applied Physics, School of Science, Xi’an Jiaotong University, No. 28 Xianning West Road, Xi’an 710049, China
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25
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Quach D, Vitali C, La FM, Xiao AX, Millar JS, Tang C, Rader DJ, Phillips MC, Lyssenko NN. Cell lipid metabolism modulators 2-bromopalmitate, D609, monensin, U18666A and probucol shift discoidal HDL formation to the smaller-sized particles: implications for the mechanism of HDL assembly. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1968-1979. [PMID: 27671775 DOI: 10.1016/j.bbalip.2016.09.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 08/27/2016] [Accepted: 09/23/2016] [Indexed: 12/17/2022]
Abstract
ATP-binding cassette transporter A1 (ABCA1) mediates formation of disc-shaped high-density lipoprotein (HDL) from cell lipid and lipid-free apolipoprotein A-I (apo A-I). Discoidal HDL particles are heterogeneous in physicochemical characteristics for reasons that are understood incompletely. Discoidal lipoprotein particles similar in characteristics and heterogeneity to cell-formed discoidal HDL can be reconstituted from purified lipids and apo A-I by cell-free, physicochemical methods. The heterogeneity of reconstituted HDL (rHDL) is sensitive to the lipid composition of the starting lipid/apo A-I mixture. To determine whether the heterogeneity of cell-formed HDL is similarly sensitive to changes in cell lipids, we investigated four compounds that have well-established effects on cell lipid metabolism and ABCA1-mediated cell cholesterol efflux. 2-Bromopalmitate, D609, monensin and U18666A decreased formation of the larger-sized, but dramatically increased formation of the smaller-sized HDL. 2-Bromopalmitate did not appear to affect ABCA1 activity, subcellular localization or oligomerization, but induced dissolution of the cholesterol-phospholipid complexes in the plasma membrane. Arachidonic and linoleic acids shifted HDL formation to the smaller-sized species. Tangier disease mutations and inhibitors of ABCA1 activity wheat germ agglutinin and AG 490 reduced formation of both larger-sized and smaller-sized HDL. The effect of probucol was similar to the effect of 2-bromopalmitate. Taking rHDL formation as a paradigm, we propose that ABCA1 mutations and activity inhibitors reduce the amount of cell lipid available for HDL formation, and the compounds in the 2-bromopalmitate group and the polyunsaturated fatty acids change cell lipid composition from one that favors formation of the larger-sized HDL particles to one that favors formation of the smaller-sized species.
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Affiliation(s)
- Duyen Quach
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Cecilia Vitali
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Fiona M La
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Angel X Xiao
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - John S Millar
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Chongren Tang
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, University of Washington, Seattle, WA, USA
| | - Daniel J Rader
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA; Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Michael C Phillips
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Nicholas N Lyssenko
- Division of Translational Medicine and Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
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26
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Abstract
Elevated levels of cholesteryl ester (CE)-enriched apoB containing plasma lipoproteins lead to increased foam cell formation, the first step in the development of atherosclerosis. Unregulated uptake of low-density lipoprotein cholesterol by circulating monocytes and other peripheral blood cells takes place through scavenger receptors and over time causes disruption in cellular cholesterol homeostasis. As lipoproteins are taken up, their CE core is hydrolyzed by liposomal lipases to generate free cholesterol (FC). FC can be either re-esterified and stored as CE droplets or shuttled to the plasma membrane for ATP-binding cassette transporter A1-mediated efflux. Because cholesterol is an essential component of all cellular membranes, some FC may be incorporated into microdomains or lipid rafts. These platforms are essential for receptor signaling and transduction, requiring rapid assembly and disassembly. ATP-binding cassette transporter A1 plays a major role in regulating microdomain cholesterol and is most efficient when lipid-poor apolipoprotein AI (apoAI) packages raft cholesterol into soluble particles that are eventually catabolized by the liver. If FC is not effluxed from the cell, it becomes esterified, CE droplets accumulate and microdomain cholesterol content becomes poorly regulated. This dysregulation leads to prolonged activation of immune cell signaling pathways, resulting in receptor oversensitization. The availability of apoAI or other amphipathic α-helix-rich apoproteins relieves the burden of excess microdomain cholesterol in immune cells allowing a reduction in immune cell proliferation and infiltration, thereby stimulating regression of foam cells in the artery. Therefore, cellular balance between FC and CE is essential for proper immune cell function and prevents chronic immune cell overstimulation and proliferation.
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Affiliation(s)
- Mary G Sorci-Thomas
- From the Division of Endocrinology, Metabolism and Clinical Nutrition, Department of Medicine and Senior Investigator, Blood Research Institute, BloodCenter of Wisconsin (M.G.S.-T.) and Department of Pharmacology and Toxicology (M.J.T.), Medical College of Wisconsin, Milwaukee, WI.
| | - Michael J Thomas
- From the Division of Endocrinology, Metabolism and Clinical Nutrition, Department of Medicine and Senior Investigator, Blood Research Institute, BloodCenter of Wisconsin (M.G.S.-T.) and Department of Pharmacology and Toxicology (M.J.T.), Medical College of Wisconsin, Milwaukee, WI
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27
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Mei X, Liu M, Herscovitz H, Atkinson D. Probing the C-terminal domain of lipid-free apoA-I demonstrates the vital role of the H10B sequence repeat in HDL formation. J Lipid Res 2016; 57:1507-17. [PMID: 27317763 DOI: 10.1194/jlr.m068874] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Indexed: 12/23/2022] Open
Abstract
apoA-I plays important structural and functional roles in reverse cholesterol transport. We have described the molecular structure of the N-terminal domain, Δ(185-243) by X-ray crystallography. To understand the role of the C-terminal domain, constructs with sequential elongation of Δ(185-243), by increments of 11-residue sequence repeats were studied and compared with Δ(185-243) and WT apoA-I. Constructs up to residue 230 showed progressively decreased percent α-helix with similar numbers of helical residues, similar detergent and lipid binding affinity, and exposed hydrophobic surface. These observations suggest that the C-terminal domain is unstructured with the exception of the last 11-residue repeat (H10B). Similar monomer-dimer equilibrium suggests that the H10B region is responsible for nonspecific aggregation. Cholesterol efflux progressively increased with elongation up to ∼60% of full-length apoA-I in the absence of the H10B. In summary, the sequential repeats in the C-terminal domain are probably unstructured with the exception of H10B. This segment appears to be responsible for initiation of lipid binding and aggregation, as well as cholesterol efflux, and thus plays a vital role during HDL formation. Based on these observations and the Δ(185-243) crystal structure, we propose a lipid-free apoA-I structural model in solution and update the mechanism of HDL biogenesis.
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Affiliation(s)
- Xiaohu Mei
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118
| | - Minjing Liu
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118
| | - Haya Herscovitz
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118
| | - David Atkinson
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118
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28
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Thiam AR, Forêt L. The physics of lipid droplet nucleation, growth and budding. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:715-22. [PMID: 27131867 DOI: 10.1016/j.bbalip.2016.04.018] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 04/05/2016] [Accepted: 04/22/2016] [Indexed: 11/25/2022]
Abstract
Lipid droplets (LDs) are intracellular oil-in-water emulsion droplets, covered by a phospholipid monolayer and mainly present in the cytosol. Despite their important role in cellular metabolism and growing number of newly identified functions, LD formation mechanism from the endoplasmic reticulum remains poorly understood. To form a LD, the oil molecules synthesized in the ER accumulate between the monolayer leaflets and induce deformation of the membrane. This formation process works through three steps: nucleation, growth and budding, exactly as in phase separation and dewetting phenomena. These steps involve sequential biophysical membrane remodeling mechanisms for which we present basic tools of statistical physics, membrane biophysics, and soft matter science underlying them. We aim to highlight relevant factors that could control LD formation size, site and number through this physics description. An emphasis will be given to a currently underestimated contribution of the molecular interactions between lipids to favor an energetically costless mechanism of LD formation.
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Affiliation(s)
- Abdou Rachid Thiam
- Laboratoire de Physique Statistique, École Normale Supérieure, PSL Research University, Université Paris Diderot Sorbonne Paris-Cité, Sorbonne Universités UPMC Univ Paris 06, CNRS, 24 rue Lhomond, 75005 Paris, France.
| | - Lionel Forêt
- Laboratoire de Physique Statistique, École Normale Supérieure, PSL Research University, Université Paris Diderot Sorbonne Paris-Cité, Sorbonne Universités UPMC Univ Paris 06, CNRS, 24 rue Lhomond, 75005 Paris, France
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29
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Abstract
In this issue of Structure, Segrest et al. (2015) present a novel picture for the ABCA1-mediated lipid loading of lipid-poor apoA-I.
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Affiliation(s)
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology, FI-33101 Tampere, Finland; MEMPHYS - Centre for Biomembrane Physics, University of Southern Denmark, 5230 Odense, Denmark.
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30
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Pan L, Segrest JP. Computational studies of plasma lipoprotein lipids. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2401-2420. [PMID: 26969087 DOI: 10.1016/j.bbamem.2016.03.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 03/03/2016] [Accepted: 03/04/2016] [Indexed: 12/27/2022]
Abstract
Plasma lipoproteins are macromolecular assemblies of proteins and lipids found in the blood. The lipid components of lipoproteins are amphipathic lipids such as phospholipids (PLs), and unesterified cholesterols (UCs) and hydrophobic lipids such as cholesteryl esters (CEs) and triglycerides (TGs). Since lipoproteins are soft matter supramolecular assemblies easily deformable by thermal fluctuations and they also exist in varying densities and protein/lipid components, a detailed understanding of their structure/function is experimentally difficult. Molecular dynamics (MD) simulation has emerged as a particularly promising way to explore the structure and dynamics of lipoproteins. The purpose of this review is to survey the current status of computational studies of the lipid components of the lipoproteins. Computational studies aim to explore three levels of complexity for the 3-dimensional structural dynamics of lipoproteins at various metabolic stages: (i) lipoprotein particles consist of protein with minimal lipid; (ii) lipoprotein particles consist of PL-rich discoidal bilayer-like lipid particles; (iii) mature circulating lipoprotein particles consist of CE-rich or TG-rich spheroidal lipid-droplet-like particles. Due to energy barriers involved in conversion between these species, other biomolecules also participate in lipoprotein biological assembly. For example: (i) lipid-poor apolipoprotein A-I (apoA-I) interacts with ATP-binding cassette transporter A1 (ABCA1) to produce nascent discoidal high density lipoprotein (dHDL) particles; (ii) lecithin-cholesterol acyltransferase (LCAT) mediates the conversion of UC to CE in dHDL, driving spheroidal HDL (sHDL) formation; (iii) transfer proteins, cholesterol ester transfer protein (CETP) and phospholipid transfer protein (PLTP), transfer both CE and TG and PL, respectively, between lipoprotein particles. Computational studies have the potential to explore different lipoprotein particles at each metabolic stage in atomistic detail. This review discusses the current status of computational methods including all-atom MD (AAMD), coarse-grain MD (CGMD), and MD-simulated annealing (MDSA) and their applications in lipoprotein structural dynamics and biological assemblies. Results from MD simulations are discussed and compared across studies in order to identify key findings, controversies, issues and future directions. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.
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Affiliation(s)
- Lurong Pan
- Division of Gerontology, Geriatrics, & Palliative Care, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, United States
| | - Jere P Segrest
- Division of Gerontology, Geriatrics, & Palliative Care, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, United States.
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31
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Melchior JT, Walker RG, Morris J, Jones MK, Segrest JP, Lima DB, Carvalho PC, Gozzo FC, Castleberry M, Thompson TB, Davidson WS. An Evaluation of the Crystal Structure of C-terminal Truncated Apolipoprotein A-I in Solution Reveals Structural Dynamics Related to Lipid Binding. J Biol Chem 2016; 291:5439-51. [PMID: 26755744 DOI: 10.1074/jbc.m115.706093] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2015] [Indexed: 11/06/2022] Open
Abstract
Apolipoprotein (apo) A-I mediates many of the anti-atherogenic functions attributed to high density lipoprotein. Unfortunately, efforts toward a high resolution structure of full-length apoA-I have not been fruitful, although there have been successes with deletion mutants. Recently, a C-terminal truncation (apoA-I(Δ185-243)) was crystallized as a dimer. The structure showed two helical bundles connected by a long, curved pair of swapped helical domains. To compare this structure to that existing under solution conditions, we applied small angle x-ray scattering and isotope-assisted chemical cross-linking to apoA-I(Δ185-243) in its dimeric and monomeric forms. For the dimer, we found evidence for the shared domains and aspects of the N-terminal bundles, but not the molecular curvature seen in the crystal. We also found that the N-terminal bundles equilibrate between open and closed states. Interestingly, this movement is one of the transitions proposed during lipid binding. The monomer was consistent with a model in which the long shared helix doubles back onto the helical bundle. Combined with the crystal structure, these data offer an important starting point to understand the molecular details of high density lipoprotein biogenesis.
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Affiliation(s)
- John T Melchior
- From the Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237
| | - Ryan G Walker
- the Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio 45237
| | - Jamie Morris
- From the Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237
| | - Martin K Jones
- the Department of Medicine and Atherosclerosis Research Unit, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Jere P Segrest
- the Department of Medicine and Atherosclerosis Research Unit, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Diogo B Lima
- the Laboratory for Proteomics and Protein Engineering, Carlos Chagas Institute, Fiocruz, Paraná, Brazil 81350-010, and
| | - Paulo C Carvalho
- the Laboratory for Proteomics and Protein Engineering, Carlos Chagas Institute, Fiocruz, Paraná, Brazil 81350-010, and
| | - Fábio C Gozzo
- the Dalton Mass Spectrometry Laboratory, University of Campinas, São Paulo 13083-970, Brazil
| | - Mark Castleberry
- the Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio 45237
| | - Thomas B Thompson
- the Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio 45237,
| | - W Sean Davidson
- From the Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237,
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32
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Yamauchi Y, Yokoyama S, Chang TY. ABCA1-dependent sterol release: sterol molecule specificity and potential membrane domain for HDL biogenesis. J Lipid Res 2015; 57:77-88. [PMID: 26497474 DOI: 10.1194/jlr.m063784] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Indexed: 01/28/2023] Open
Abstract
Mammalian cells synthesize various sterol molecules, including the C30 sterol, lanosterol, as cholesterol precursors in the endoplasmic reticulum. The build-up of precursor sterols, including lanosterol, displays cellular toxicity. Precursor sterols are found in plasma HDL. How these structurally different sterols are released from cells is poorly understood. Here, we show that newly synthesized precursor sterols arriving at the plasma membrane (PM) are removed by extracellular apoA-I in a manner dependent on ABCA1, a key macromolecule for HDL biogenesis. Analysis of sterol molecules by GC-MS and tracing the fate of radiolabeled acetate-derived sterols in normal and mutant Niemann-Pick type C cells reveal that ABCA1 prefers newly synthesized sterols, especially lanosterol, as the substrates before they are internalized from the PM. We also show that ABCA1 resides in a cholesterol-rich membrane domain resistant to the mild detergent, Brij 98. Blocking ACAT activity increases the cholesterol contents of this domain. Newly synthesized C29/C30 sterols are transiently enriched within this domain, but rapidly disappear from this domain with a half-life of less than 1 h. Our work shows that substantial amounts of precursor sterols are transported to a certain PM domain and are removed by the ABCA1-dependent pathway.
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Affiliation(s)
- Yoshio Yamauchi
- Department of Biochemistry II, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Shinji Yokoyama
- Nutritional Health Science Research Center and Department of Food and Nutritional Sciences, Chubu University, Kasugai 487-8501, Japan
| | - Ta-Yuan Chang
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
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