1
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Bhale AS, Venkataraman K. Leveraging knowledge of HDLs major protein ApoA1: Structure, function, mutations, and potential therapeutics. Biomed Pharmacother 2022; 154:113634. [PMID: 36063649 DOI: 10.1016/j.biopha.2022.113634] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 08/27/2022] [Accepted: 08/30/2022] [Indexed: 11/02/2022] Open
Abstract
Apolipoprotein A1 (ApoA1) is a member of the Apolipoprotein family of proteins. It's a vital protein that helps in the production of high-density lipoprotein (HDL) particles, which are crucial for reverse cholesterol transport (RCT). It also has anti-inflammatory, anti-atherogenic, anti-apoptotic, and anti-thrombotic properties. These functions interact to give HDL particles their cardioprotective characteristics. ApoA1 has recently been investigated for its potential role in atherosclerosis, diabetes, neurological diseases, cancer, and certain infectious diseases. Since ApoA1's discovery, numerous mutations have been reported that affect its structural integrity and alter its function. Hence these insights have led to the development of clinically relevant peptides and synthetic reconstituted HDL (rHDL) that mimics the function of ApoA1. As a result, this review has aimed to provide an organized explanation of our understanding of the ApoA1 protein structure and its role in various essential pathways. Furthermore, we have comprehensively reviewed the important ApoA1 mutations (24 mutations) that are reported to be involved in various diseases. Finally, we've focused on the therapeutic potentials of some of the beneficial mutations, small peptides, and synthetic rHDL that are currently being researched or developed, since these will aid in the development of novel therapeutics in the future.
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Affiliation(s)
- Aishwarya Sudam Bhale
- Centre for Bio-Separation Technology, Vellore Institute of Technology, Vellore 632014, Tamil Nadu, India
| | - Krishnan Venkataraman
- Centre for Bio-Separation Technology, Vellore Institute of Technology, Vellore 632014, Tamil Nadu, India.
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2
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Battle S, Gogonea V, Willard B, Wang Z, Fu X, Huang Y, Graham LM, Cameron SJ, DiDonato JA, Crabb JW, Hazen SL. The pattern of apolipoprotein A-I lysine carbamylation reflects its lipidation state and the chemical environment within human atherosclerotic aorta. J Biol Chem 2022; 298:101832. [PMID: 35304099 PMCID: PMC9010765 DOI: 10.1016/j.jbc.2022.101832] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 02/28/2022] [Accepted: 03/11/2022] [Indexed: 01/09/2023] Open
Abstract
Protein lysine carbamylation is an irreversible post-translational modification resulting in generation of homocitrulline (N-ε-carbamyllysine), which no longer possesses a charged ε-amino moiety. Two distinct pathways can promote protein carbamylation. One results from urea decomposition, forming an equilibrium mixture of cyanate (CNO−) and the reactive electrophile isocyanate. The second pathway involves myeloperoxidase (MPO)-catalyzed oxidation of thiocyanate (SCN−), yielding CNO− and isocyanate. Apolipoprotein A-I (apoA-I), the major protein constituent of high-density lipoprotein (HDL), is a known target for MPO-catalyzed modification in vivo, converting the cardioprotective lipoprotein into a proatherogenic and proapoptotic one. We hypothesized that monitoring site-specific carbamylation patterns of apoA-I recovered from human atherosclerotic aorta could provide insights into the chemical environment within the artery wall. To test this, we first mapped carbamyllysine obtained from in vitro carbamylation of apoA-I by both the urea-driven (nonenzymatic) and inflammatory-driven (enzymatic) pathways in lipid-poor and lipidated apoA-I (reconstituted HDL). Our results suggest that lysine residues within proximity of the known MPO-binding sites on HDL are preferentially targeted by the enzymatic (MPO) carbamylation pathway, whereas the nonenzymatic pathway leads to nearly uniform distribution of carbamylated lysine residues along the apoA-I polypeptide chain. Quantitative proteomic analyses of apoA-I from human aortic atheroma identified 16 of the 21 lysine residues as carbamylated and suggested that the majority of apoA-I carbamylation in vivo occurs on “lipid-poor” apoA-I forms via the nonenzymatic CNO− pathway. Monitoring patterns of apoA-I carbamylation recovered from arterial tissues can provide insights into both apoA-I structure and the chemical environment within human atheroma.
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Affiliation(s)
- Shawna Battle
- Department of Cardiovascular & Metabolic Sciences, Cleveland Clinic, Cleveland, OH; Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH
| | - Valentin Gogonea
- Department of Cardiovascular & Metabolic Sciences, Cleveland Clinic, Cleveland, OH; Department of Chemistry, Cleveland State University, Cleveland, OH
| | - Belinda Willard
- Proteomics Shared Laboratory Resource, Cleveland Clinic, Cleveland, OH
| | - Zeneng Wang
- Department of Cardiovascular & Metabolic Sciences, Cleveland Clinic, Cleveland, OH; Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH
| | - Xiaoming Fu
- Department of Cardiovascular & Metabolic Sciences, Cleveland Clinic, Cleveland, OH
| | - Ying Huang
- Department of Cardiovascular & Metabolic Sciences, Cleveland Clinic, Cleveland, OH
| | - Linda M Graham
- Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH; Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA; Heart Vascular and Thoracic Institute, Cleveland Clinic, Cleveland, OH
| | - Scott J Cameron
- Department of Cardiovascular & Metabolic Sciences, Cleveland Clinic, Cleveland, OH; Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH; Heart Vascular and Thoracic Institute, Cleveland Clinic, Cleveland, OH; Taussig Cancer Center, Cleveland Clinic, Cleveland, OH
| | - Joseph A DiDonato
- Department of Cardiovascular & Metabolic Sciences, Cleveland Clinic, Cleveland, OH; Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH
| | - John W Crabb
- Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH; Cole Eye Institute, Cleveland Clinic, Cleveland, OH
| | - Stanley L Hazen
- Department of Cardiovascular & Metabolic Sciences, Cleveland Clinic, Cleveland, OH; Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH; Department of Chemistry, Cleveland State University, Cleveland, OH; Heart Vascular and Thoracic Institute, Cleveland Clinic, Cleveland, OH.
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3
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Jin Y, Chifodya K, Han G, Jiang W, Chen Y, Shi Y, Xu Q, Xi Y, Wang J, Zhou J, Zhang H, Ding Y. High-density lipoprotein in Alzheimer's disease: From potential biomarkers to therapeutics. J Control Release 2021; 338:56-70. [PMID: 34391838 DOI: 10.1016/j.jconrel.2021.08.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 08/09/2021] [Accepted: 08/10/2021] [Indexed: 12/17/2022]
Abstract
The inverse correlation between high-density lipoprotein (HDL) levels in vivo and the risk of Alzheimer's disease (AD) has become an inspiration for HDL-inspired AD therapy, including plain HDL and various intelligent HDL-based drug delivery systems. In this review, we will focus on the two endogenous HDL subtypes in the central nervous system (CNS), apolipoprotein E-based HDL (apoE-HDL) and apolipoprotein A-I-based HDL (apoA-I-HDL), especially their influence on AD pathophysiology to reveal HDL's potential as biomarkers for risk prediction, and summarize the relevant therapeutic mechanisms to propose possible treatment strategies. We will emphasize the latest advances of HDL as therapeutics (plain HDL and HDL-based drug delivery systems) to discuss the potential for AD therapy and review innovative techniques in the preparation of HDL-based nanoplatforms to provide a basis for the rational design and future development of anti-AD drugs.
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Affiliation(s)
- Yi Jin
- Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Ministry of Education, Nanjing 210009, China; State Key Laboratory of Natural Medicines, Department of Pharmaceutics, China Pharmaceutical University, Nanjing 210009, China; NMPA Key Laboratory for Research and Evaluation of Pharmaceutical Preparations and Excipients, Nanjing 210009, China
| | - Kudzai Chifodya
- State Key Laboratory of Natural Medicines, Department of Pharmaceutics, China Pharmaceutical University, Nanjing 210009, China
| | - Guochen Han
- Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Ministry of Education, Nanjing 210009, China; State Key Laboratory of Natural Medicines, Department of Pharmaceutics, China Pharmaceutical University, Nanjing 210009, China; NMPA Key Laboratory for Research and Evaluation of Pharmaceutical Preparations and Excipients, Nanjing 210009, China
| | - Wenxin Jiang
- State Key Laboratory of Natural Medicines, Department of Pharmaceutics, China Pharmaceutical University, Nanjing 210009, China
| | - Yun Chen
- State Key Laboratory of Natural Medicines, Department of Pharmaceutics, China Pharmaceutical University, Nanjing 210009, China
| | - Yang Shi
- State Key Laboratory of Natural Medicines, Department of Pharmaceutics, China Pharmaceutical University, Nanjing 210009, China
| | - Qiao Xu
- State Key Laboratory of Natural Medicines, Department of Pharmaceutics, China Pharmaceutical University, Nanjing 210009, China
| | - Yilong Xi
- State Key Laboratory of Natural Medicines, Department of Pharmaceutics, China Pharmaceutical University, Nanjing 210009, China
| | - Jun Wang
- Department of Geriatrics, Affiliated Hospital of Nantong University, Nantong 226001, China
| | - Jianping Zhou
- Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Ministry of Education, Nanjing 210009, China; State Key Laboratory of Natural Medicines, Department of Pharmaceutics, China Pharmaceutical University, Nanjing 210009, China; NMPA Key Laboratory for Research and Evaluation of Pharmaceutical Preparations and Excipients, Nanjing 210009, China.
| | - Huaqing Zhang
- Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Ministry of Education, Nanjing 210009, China; State Key Laboratory of Natural Medicines, Department of Pharmaceutics, China Pharmaceutical University, Nanjing 210009, China; NMPA Key Laboratory for Research and Evaluation of Pharmaceutical Preparations and Excipients, Nanjing 210009, China.
| | - Yang Ding
- Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Ministry of Education, Nanjing 210009, China; State Key Laboratory of Natural Medicines, Department of Pharmaceutics, China Pharmaceutical University, Nanjing 210009, China; NMPA Key Laboratory for Research and Evaluation of Pharmaceutical Preparations and Excipients, Nanjing 210009, China.
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4
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Interaction of lipid-free apolipoprotein A-I with cholesterol revealed by molecular modeling. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2021; 1869:140614. [PMID: 33548491 DOI: 10.1016/j.bbapap.2021.140614] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 01/23/2021] [Accepted: 01/28/2021] [Indexed: 11/22/2022]
Abstract
We report the modeling of the interaction of differently self-associated lipid-free apoA-I with cholesterol monomer and tail-to-tail (TT) or face-to-face (FF) cholesterol dimer. Cholesterol dimerization is exploited to reconcile the existing experimental data on cholesterol binding to apoA-I with extremely low critical micelle concentration of cholesterol. Two crystal structures of 1-43 N-truncated apolipoprotein Δ(1-43)A-I tetramer (PDB ID: 1AV1, structure B), 185-243 C-truncated apolipoprotein Δ(185-243)A-I dimer (PDB ID: 3R2P, structure M) were analyzed. Cholesterol monomers bind to multiple binding sites in apoA-I monomer, dimer and tetramer with low, moderate and high energy (-10 to -28 kJ/mol with Schrödinger package), still insufficient to overcome the thermodynamic restriction by cholesterol micellization (-52.8 kJ/mol). The binding sites partially coincide with the putative cholesterol-binding motifs. However, apoA-I monomer and dimer existing in structure B, that contain nonoverlapping and non-interacting pairs of binding sites with high affinity for TT and FF cholesterol dimers, can bind in common 14 cholesterol molecules that correspond to existing values. ApoA-I monomer and dimer in structure M can bind in common 6 cholesterol molecules. The values of respective total energy of cholesterol binding up to 64.5 and 67.0 kJ/mol for both B and M structures exceed the free energy of cholesterol micellization. We hypothesize that cholesterol dimers may simultaneously interact with extracellular monomer and dimer of lipid-free apoA-I, that accumulate at acid pH in atheroma. The thermodynamically allowed apolipoprotein-cholesterol interaction outside the macrophage may represent a new mechanism of cholesterol transport by apoA-I from atheroma, in addition to ABCA1-mediated cholesterol efflux.
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5
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First eight residues of apolipoprotein A-I mediate the C-terminus control of helical bundle unfolding and its lipidation. PLoS One 2020; 15:e0221915. [PMID: 31945064 PMCID: PMC6964839 DOI: 10.1371/journal.pone.0221915] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 12/30/2019] [Indexed: 11/23/2022] Open
Abstract
The crystal structure of a C-terminal deletion of apolipoprotein A-I (apoA1) shows a large helical bundle structure in the amino half of the protein, from residues 8 to 115. Using site directed mutagenesis, guanidine or thermal denaturation, cell free liposome clearance, and cellular ABCA1-mediated cholesterol efflux assays, we demonstrate that apoA1 lipidation can occur when the thermodynamic barrier to this bundle unfolding is lowered. The absence of the C-terminus renders the bundle harder to unfold resulting in loss of apoA1 lipidation that can be reversed by point mutations, such as Trp8Ala, and by truncations as short as 8 residues in the amino terminus, both of which facilitate helical bundle unfolding. Locking the bundle via a disulfide bond leads to loss of apoA1 lipidation. We propose a model in which the C-terminus acts on the N-terminus to destabilize this helical bundle. Upon lipid binding to the C-terminus, Trp8 is displaced from its interaction with Phe57, Arg61, Leu64, Val67, Phe71, and Trp72 to destabilize the bundle. However, when the C-terminus is deleted, Trp8 cannot be displaced, the bundle cannot unfold, and apoA1 cannot be lipidated.
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6
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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: 184] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [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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7
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Ray A, Ghosh A, Chakraborty R, Upadhyay SK, Maiti S, Sengupta S, Thukral L. Specific Cholesterol Binding Drives Drastic Structural Alterations in Apolipoprotein A1. J Phys Chem Lett 2018; 9:6060-6065. [PMID: 30256643 DOI: 10.1021/acs.jpclett.8b02042] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Proteins typically adopt a multitude of flexible and rapidly interconverting conformers, many of which are governed by specific protein interaction domains. Whereas disc-shaped oligomeric HDL and its major protein component ApoA1 have been the focus of several investigations, the structural properties of monomeric ApoA1 remain poorly understood. Using tens of independent molecular simulations (>50 μs), we reveal that ApoA1 adopts a compact conformation. Upon the addition of a physiological concentration of cholesterol to ApoA1, the monomeric protein spontaneously formed a circular conformation. Remarkably, these drastic structural perturbations are driven by a specific cholesterol binding site at the C-terminal and a novel cholesterol binding site at the N-terminal. We propose a mechanism whereby ApoA1 opens in a stagewise manner and mutating the N-terminal binding site destroys the open "belt-shaped" topology. Complementary experiments confirm that the structural changes are induced by specific association of cholesterol with ApoA1, not by the nonspecific hydrophobic effect.
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Affiliation(s)
- Arjun Ray
- CSIR-Institute of Genomics and Integrative Biology , South Campus, Mathura Road , New Delhi 110 025 , India
- Academy of Scientific and Innovative Research (AcSIR) , CSIR- Institute of Genomics and Integrative Biology , Mathura Road Campus , New Delhi 110025 , India
| | - Asmita Ghosh
- CSIR-Institute of Genomics and Integrative Biology , South Campus, Mathura Road , New Delhi 110 025 , India
- Academy of Scientific and Innovative Research (AcSIR) , CSIR- Institute of Genomics and Integrative Biology , Mathura Road Campus , New Delhi 110025 , India
| | - Rahul Chakraborty
- CSIR-Institute of Genomics and Integrative Biology , South Campus, Mathura Road , New Delhi 110 025 , India
- Academy of Scientific and Innovative Research (AcSIR) , CSIR- Institute of Genomics and Integrative Biology , Mathura Road Campus , New Delhi 110025 , India
| | - Santosh Kumar Upadhyay
- CSIR-Institute of Genomics and Integrative Biology , South Campus, Mathura Road , New Delhi 110 025 , India
| | - Souvik Maiti
- CSIR-Institute of Genomics and Integrative Biology , South Campus, Mathura Road , New Delhi 110 025 , India
- Academy of Scientific and Innovative Research (AcSIR) , CSIR- Institute of Genomics and Integrative Biology , Mathura Road Campus , New Delhi 110025 , India
| | - Shantanu Sengupta
- CSIR-Institute of Genomics and Integrative Biology , South Campus, Mathura Road , New Delhi 110 025 , India
- Academy of Scientific and Innovative Research (AcSIR) , CSIR- Institute of Genomics and Integrative Biology , Mathura Road Campus , New Delhi 110025 , India
| | - Lipi Thukral
- CSIR-Institute of Genomics and Integrative Biology , South Campus, Mathura Road , New Delhi 110 025 , India
- Academy of Scientific and Innovative Research (AcSIR) , CSIR- Institute of Genomics and Integrative Biology , Mathura Road Campus , New Delhi 110025 , India
- Interdisciplinary Center for Scientific Computing , University of Heidelberg , Im Neuenheimer Feld 205 , 69120 Heidelberg , Germany
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8
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Witkowski A, Chan GKL, Boatz JC, Li NJ, Inoue AP, Wong JC, van der Wel PCA, Cavigiolio G. Methionine oxidized apolipoprotein A-I at the crossroads of HDL biogenesis and amyloid formation. FASEB J 2018; 32:3149-3165. [PMID: 29401604 DOI: 10.1096/fj.201701127r] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Apolipoprotein A-I (apoA-I) shares with other exchangeable apolipoproteins a high level of structural plasticity. In the lipid-free state, the apolipoprotein amphipathic α-helices interact intra- and intermolecularly, providing structural stabilization by self-association. We have reported that lipid-free apoA-I becomes amyloidogenic upon physiologically relevant (myeloperoxidase-mediated) Met oxidation. In this study, we established that Met oxidation promotes amyloidogenesis by reducing the stability of apoA-I monomers and irreversibly disrupting self-association. The oxidized apoA-I monomers also exhibited increased cellular cholesterol release capacity and stronger association with macrophages, compared to nonoxidized apoA-I. Of physiologic relevance, preformed oxidized apoA-I amyloid fibrils induced amyloid formation in nonoxidized apoA-I. This process was enhanced when self-association of nonoxidized apoA-I was disrupted by thermal treatment. Solid state NMR analysis revealed that aggregates formed by seeded nonoxidized apoA-I were structurally similar to those formed by the oxidized protein, featuring a β-structure-rich amyloid fold alongside α-helices retained from the native state. In atherosclerotic lesions, the conditions that promote apoA-I amyloid formation are readily available: myeloperoxidase, active oxygen species, low pH, and high concentration of lipid-free apoA-I. Our results suggest that even partial Met oxidation of apoA-I can nucleate amyloidogenesis, thus sequestering and inactivating otherwise antiatherogenic and HDL-forming apoA-I.-Witkowski, A., Chan, G. K. L., Boatz, J. C., Li, N. J., Inoue, A. P., Wong, J. C., van der Wel, P. C. A., Cavigiolio, G. Methionine oxidized apolipoprotein A-I at the crossroads of HDL biogenesis and amyloid formation.
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Affiliation(s)
- Andrzej Witkowski
- Children's Hospital Oakland Research Institute (CHORI), Oakland, California, USA
| | - Gary K L Chan
- Children's Hospital Oakland Research Institute (CHORI), Oakland, California, USA
| | - Jennifer C Boatz
- Department of Structural Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Nancy J Li
- Children's Hospital Oakland Research Institute (CHORI), Oakland, California, USA
| | - Ayuka P Inoue
- Children's Hospital Oakland Research Institute (CHORI), Oakland, California, USA
| | - Jaclyn C Wong
- Children's Hospital Oakland Research Institute (CHORI), Oakland, California, USA
| | | | - Giorgio Cavigiolio
- Children's Hospital Oakland Research Institute (CHORI), Oakland, California, USA
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9
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Melchior JT, Walker RG, Cooke AL, Morris J, Castleberry M, Thompson TB, Jones MK, Song HD, Rye KA, Oda MN, Sorci-Thomas MG, Thomas MJ, Heinecke JW, Mei X, Atkinson D, Segrest JP, Lund-Katz S, Phillips MC, Davidson WS. A consensus model of human apolipoprotein A-I in its monomeric and lipid-free state. Nat Struct Mol Biol 2017; 24:1093-1099. [PMID: 29131142 PMCID: PMC5749415 DOI: 10.1038/nsmb.3501] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 10/06/2017] [Indexed: 11/09/2022]
Abstract
Apolipoprotein (apo)A-I is an organizing scaffold protein that is critical to high-density lipoprotein (HDL) structure and metabolism, probably mediating many of its cardioprotective properties. However, HDL biogenesis is poorly understood, as lipid-free apoA-I has been notoriously resistant to high-resolution structural study. Published models from low-resolution techniques share certain features but vary considerably in shape and secondary structure. To tackle this central issue in lipoprotein biology, we assembled a team of structural biologists specializing in apolipoproteins and set out to build a consensus model of monomeric lipid-free human apoA-I. Combining novel and published cross-link constraints, small-angle X-ray scattering (SAXS), hydrogen-deuterium exchange (HDX) and crystallography data, we propose a time-averaged model consistent with much of the experimental data published over the last 40 years. The model provides a long-sought platform for understanding and testing details of HDL biogenesis, structure and function.
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Affiliation(s)
- John T Melchior
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio, USA
| | - Ryan G Walker
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio, USA
| | - Allison L Cooke
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio, USA
| | - Jamie Morris
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio, USA
| | - Mark Castleberry
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio, USA
| | - Thomas B Thompson
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio, USA
| | - Martin K Jones
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Hyun D Song
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Kerry-Anne Rye
- School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
| | - Michael N Oda
- Children's Hospital Oakland Research Institute, Oakland, California, USA
| | - Mary G Sorci-Thomas
- Department of Medicine, Section on Endocrinology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Michael J Thomas
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Jay W Heinecke
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Xiaohu Mei
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts, USA
| | - David Atkinson
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Jere P Segrest
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Sissel Lund-Katz
- Division of Translational Medicine and Human Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Michael C Phillips
- Division of Translational Medicine and Human Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - W Sean Davidson
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio, USA
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10
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Lai CT, Sun W, Palekar RU, Thaxton CS, Schatz GC. Molecular Dynamics Simulation and Experimental Studies of Gold Nanoparticle Templated HDL-like Nanoparticles for Cholesterol Metabolism Therapeutics. ACS APPLIED MATERIALS & INTERFACES 2017; 9:1247-1254. [PMID: 28001031 DOI: 10.1021/acsami.6b12249] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
High-density lipoprotein (HDL) plays an important role in the transport and metabolism of cholesterol. Mimics of HDL are being explored as potentially powerful therapeutic agents for removing excess cholesterol from arterial plaques. Gold nanoparticles (AuNPs) functionalized with apolipoprotein A-I and with the lipids 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[3-(2-pyridyldithio)propionate] have been demonstrated to be robust acceptors of cellular cholesterol. However, detailed structural information about this functionalized HDL AuNP is still lacking. In this study, we have used X-ray photoelectron spectroscopy and lecithin/cholesterol acyltransferase activation experiments together with coarse-grained and all-atom molecular dynamics simulations to model the structure and cholesterol uptake properties of the HDL AuNP construct. By simulating different apolipoprotein-loaded AuNPs, we find that lipids are oriented differently in regions with and without apoA-I. We also show that in this functionalized HDL AuNP, the distribution of cholesteryl ester maintains a reverse concentration gradient that is similar to the gradient found in native HDL.
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Affiliation(s)
- Cheng-Tsung Lai
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Wangqiang Sun
- Department of Urology, Northwestern University , Chicago, Illinois 60611, United States
- Simpson Querrey Institute for Bionanotechnology , 303 East Superior, Chicago, Illinois 60611, United States
- International Institute for Nanotechnology, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Rohun U Palekar
- Department of Urology, Northwestern University , Chicago, Illinois 60611, United States
- Simpson Querrey Institute for Bionanotechnology , 303 East Superior, Chicago, Illinois 60611, United States
- International Institute for Nanotechnology, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - C Shad Thaxton
- Department of Urology, Northwestern University , Chicago, Illinois 60611, United States
- Simpson Querrey Institute for Bionanotechnology , 303 East Superior, Chicago, Illinois 60611, United States
- International Institute for Nanotechnology, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - George C Schatz
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
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11
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Oda MN. Lipid-free apoA-I structure - Origins of model diversity. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:221-233. [PMID: 27890580 DOI: 10.1016/j.bbalip.2016.11.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 10/20/2016] [Accepted: 11/20/2016] [Indexed: 01/22/2023]
Abstract
Apolipoprotein A-I (apoA-I) is a prominent member of the exchangeable apolipoprotein class of proteins, capable of transitioning between lipid-bound and lipid-free states. It is the primary structural and functional protein of high density lipoprotein (HDL). Lipid-free apoA-I is critical to de novo HDL formation as it is the preferred substrate of the lipid transporter, ATP Binding Cassette Transporter A1 (ABCA1) Remaley et al. (2001) [1]. Lipid-free apoA-I is an important element in reverse cholesterol transport and comprehension of its structure is a core issue in our understanding of cholesterol metabolism. However, lipid-free apoA-I is highly conformationally dynamic making it a challenging subject for structural analysis. Over the past 20years there have been significant advances in overcoming the dynamic nature of lipid-free apoA-I, which have resulted in a multitude of proposed conformational models.
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Affiliation(s)
- Michael N Oda
- Children's Hospital Oakland Research Institute, Oakland, CA 94609, United States.
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12
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Pollard RD, Fulp B, Sorci-Thomas MG, Thomas MJ. High-Density Lipoprotein Biogenesis: Defining the Domains Involved in Human Apolipoprotein A-I Lipidation. Biochemistry 2016; 55:4971-81. [PMID: 27501467 DOI: 10.1021/acs.biochem.6b00347] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The first step in removing cholesterol from a cell is the ATP-binding cassette transporter 1 (ABCA1)-driven transfer of cholesterol to lipid-free or lipid-poor apolipoprotein A-I (apoA-I), which yields cholesterol-rich nascent high-density lipoprotein (nHDL) that then matures in plasma to spherical, cholesteryl ester-rich HDL. However, lipid-free apoA-I has a three-dimensional (3D) conformation that is significantly different from that of lipidated apoA-I on nHDL. By comparing the lipid-free apoA-I 3D conformation of apoA-I to that of 9-14 nm diameter nHDL, we formulated the hypothetical helical domain transitions that might drive particle formation. To test the hypothesis, ten apoA-I mutants were prepared that contained two strategically placed cysteines several of which could form intramolecular disulfide bonds and others that could not form these bonds. Mass spectrometry was used to identify amino acid sequence and intramolecular disulfide bond formation. Recombinant HDL (rHDL) formation was assessed with this group of apoA-I mutants. ABCA1-driven nHDL formation was measured in four mutants and wild-type apoA-I. The mutants contained cysteine substitutions in one of three regions: the N-terminus, amino acids 34 and 55 (E34C to S55C), central domain amino acids 104 and 162 (F104C to H162C), and the C-terminus, amino acids 200 and 233 (L200C to L233C). Mutants were studied in the locked form, with an intramolecular disulfide bond present, or unlocked form, with the cysteine thiol blocked by alkylation. Only small amounts of rHDL or nHDL were formed upon locking the central domain. We conclude that both the N- and C-terminal ends assist in the initial steps in lipid acquisition, but that opening of the central domain was essential for particle formation.
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Affiliation(s)
- Ricquita D Pollard
- Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine , Winston-Salem, North Carolina 27101, United States
| | - Brian Fulp
- Department of Biochemistry, Wake Forest School of Medicine , Winston-Salem, North Carolina 27101, United States
| | - Mary G Sorci-Thomas
- Departments of Medicine, Division of Endocrinology, Pharmacology and Toxicology, and Blood Research Institute, BloodCenter of Wisconsin, Medical College of Wisconsin , Milwaukee, Wisconsin 53226, United States
| | - Michael J Thomas
- Department of Pharmacology and Toxicology, Medical College of Wisconsin , 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, United States
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13
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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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14
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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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15
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Gogonea V. Structural Insights into High Density Lipoprotein: Old Models and New Facts. Front Pharmacol 2016; 6:318. [PMID: 26793109 PMCID: PMC4709926 DOI: 10.3389/fphar.2015.00318] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 12/22/2015] [Indexed: 11/13/2022] Open
Abstract
The physiological link between circulating high density lipoprotein (HDL) levels and cardiovascular disease is well-documented, albeit its intricacies are not well-understood. An improved appreciation of HDL function and overall role in vascular health and disease requires at its foundation a better understanding of the lipoprotein's molecular structure, its formation, and its process of maturation through interactions with various plasma enzymes and cell receptors that intervene along the pathway of reverse cholesterol transport. This review focuses on summarizing recent developments in the field of lipid free apoA-I and HDL structure, with emphasis on new insights revealed by newly published nascent and spherical HDL models constructed by combining low resolution structures obtained from small angle neutron scattering (SANS) with contrast variation and geometrical constraints derived from hydrogen-deuterium exchange (HDX), crosslinking mass spectrometry, electron microscopy, Förster resonance energy transfer, and electron spin resonance. Recently published low resolution structures of nascent and spherical HDL obtained from SANS with contrast variation and isotopic labeling of apolipoprotein A-I (apoA-I) will be critically reviewed and discussed in terms of how they accommodate existing biophysical structural data from alternative approaches. The new low resolution structures revealed and also provided some answers to long standing questions concerning lipid organization and particle maturation of lipoproteins. The review will discuss the merits of newly proposed SANS based all atom models for nascent and spherical HDL, and compare them with accepted models. Finally, naturally occurring and bioengineered mutations in apoA-I, and their impact on HDL phenotype, are reviewed and discuss together with new therapeutics employed for restoring HDL function.
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Affiliation(s)
- Valentin Gogonea
- Department of Chemistry, Cleveland State UniversityCleveland, OH, USA; Departments of Cellular and Molecular Medicine and the Center for Cardiovascular Diagnostics and Prevention, Cleveland ClinicCleveland, OH, USA
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16
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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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17
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Dalla-Riva J, Lagerstedt JO, Petrlova J. Structural and Functional Analysis of the ApolipoproteinA-I A164S Variant. PLoS One 2015; 10:e0143915. [PMID: 26605794 PMCID: PMC4659549 DOI: 10.1371/journal.pone.0143915] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 11/11/2015] [Indexed: 01/15/2023] Open
Abstract
Apolipoprotein A-I (apoA-I) is the main protein involved in the formation of high-density lipoprotein (HDL), it is the principal mediator of the reverse cholesterol transfer (RCT) pathway and provides cardio-protection. In addition to functional wild-type apoA-I, several variants have been shown to associate with hereditary amyloidosis. In this study we have performed biophysical and biochemical analyses of the structure and functional properties of the A164S variant of apoA-I (1:500 in the Danish general population), which is the first known mutation of apoA-I that leads to an increased risk of ischaemic heart disease (IHD), myocardial infarction and mortality without associated low HDL cholesterol levels. Despite the fact that epidemiologically IHD is associated with low plasma levels of HDL, the A164S mutation is linked to normal plasma levels of lipids, HDL and apoA-I, suggesting impaired functionality of this variant. Using biophysical techniques (e.g., circular dichroism spectroscopy and electron microscopy) to determine secondary structure, stability and pro-amyloidogenic property of the lipid free A164S apoA-I variant, our observations suggest similarity in structural properties between apoA-I WT and apoA-I A164S. However, the A164S apoA-I variant exhibits lower binding affinity to lipids but forms similar sized HDL particles to those produced by WT.
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Affiliation(s)
| | - Jens O. Lagerstedt
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- * E-mail:
| | - Jitka Petrlova
- Department of Experimental Medical Science, Lund University, Lund, Sweden
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18
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Zhang X, Lei D, Zhang L, Rames M, Zhang S. A model of lipid-free apolipoprotein A-I revealed by iterative molecular dynamics simulation. PLoS One 2015; 10:e0120233. [PMID: 25793886 PMCID: PMC4368682 DOI: 10.1371/journal.pone.0120233] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 01/29/2015] [Indexed: 01/06/2023] Open
Abstract
Apolipoprotein A-I (apo A-I), the major protein component of high-density lipoprotein, has been proven inversely correlated to cardiovascular risk in past decades. The lipid-free state of apo A-I is the initial stage which binds to lipids forming high-density lipoprotein. Molecular models of lipid-free apo A-I have been reported by methods like X-ray crystallography and chemical cross-linking/mass spectrometry (CCL/MS). Through structural analysis we found that those current models had limited consistency with other experimental results, such as those from hydrogen exchange with mass spectrometry. Through molecular dynamics simulations, we also found those models could not reach a stable equilibrium state. Therefore, by integrating various experimental results, we proposed a new structural model for lipid-free apo A-I, which contains a bundled four-helix N-terminal domain (1–192) that forms a variable hydrophobic groove and a mobile short hairpin C-terminal domain (193–243). This model exhibits an equilibrium state through molecular dynamics simulation and is consistent with most of the experimental results known from CCL/MS on lysine pairs, fluorescence resonance energy transfer and hydrogen exchange. This solution-state lipid-free apo A-I model may elucidate the possible conformational transitions of apo A-I binding with lipids in high-density lipoprotein formation.
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Affiliation(s)
- Xing Zhang
- Department of Applied Physics, Xi'an Jiaotong University, Xi'an, Shaanxi, People's Republic of China
- Molecular Foundry, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Dongsheng Lei
- Department of Applied Physics, Xi'an Jiaotong University, Xi'an, Shaanxi, People's Republic of China
- Molecular Foundry, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Lei Zhang
- Molecular Foundry, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Matthew Rames
- Molecular Foundry, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Shengli Zhang
- Department of Applied Physics, Xi'an Jiaotong University, Xi'an, Shaanxi, People's Republic of China
- * E-mail:
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19
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Segrest JP, Jones MK, Shao B, Heinecke JW. An experimentally robust model of monomeric apolipoprotein A-I created from a chimera of two X-ray structures and molecular dynamics simulations. Biochemistry 2014; 53:7625-40. [PMID: 25423138 PMCID: PMC4263436 DOI: 10.1021/bi501111j] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
High-density lipoprotein (HDL) retards atherosclerosis by accepting cholesterol from the artery wall. However, the structure of the proposed acceptor, monomeric apolipoprotein A-I (apoA-I), the major protein of HDL, is poorly understood. Two published models for monomeric apoA-I used cross-linking distance constraints to derive best fit conformations. This approach has limitations. (i) Cross-linked peptides provide no information about secondary structure. (ii) A protein chain can be folded in multiple ways to create a best fit. (iii) Ad hoc folding of a secondary structure is unlikely to produce a stable orientation of hydrophobic and hydrophilic residues. To address these limitations, we used a different approach. We first noted that the dimeric apoA-I crystal structure, (Δ185-243)apoA-I, is topologically identical to a monomer in which helix 5 forms a helical hairpin, a monomer with a hydrophobic cleft running the length of the molecule. We then realized that a second crystal structure, (Δ1-43)apoA-I, contains a C-terminal structure that fits snuggly via aromatic and hydrophobic interactions into the hydrophobic cleft. Consequently, we combined these crystal structures into an initial model that was subjected to molecular dynamics simulations. We tested the initial and simulated models and the two previously published models in three ways: against two published data sets (domains predicted to be helical by H/D exchange and six spin-coupled residues) and against our own experimentally determined cross-linking distance constraints. We note that the best fit simulation model, superior by all tests to previously published models, has dynamic features of a molten globule with interesting implications for the functions of apoA-I.
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Affiliation(s)
- Jere P Segrest
- Department of Medicine, Atherosclerosis Research Unit, and Center for Computational and Structural Dynamics, University of Alabama at Birmingham , Birmingham, Alabama 35294, United States
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20
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Petrlova J, Bhattacherjee A, Boomsma W, Wallin S, Lagerstedt JO, Irbäck A. Conformational and aggregation properties of the 1-93 fragment of apolipoprotein A-I. Protein Sci 2014; 23:1559-71. [PMID: 25131953 DOI: 10.1002/pro.2534] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 07/11/2014] [Accepted: 08/04/2014] [Indexed: 11/12/2022]
Abstract
Several disease-linked mutations of apolipoprotein A-I, the major protein in high-density lipoprotein (HDL), are known to be amyloidogenic, and the fibrils often contain N-terminal fragments of the protein. Here, we present a combined computational and experimental study of the fibril-associated disordered 1-93 fragment of this protein, in wild-type and mutated (G26R, S36A, K40L, W50R) forms. In atomic-level Monte Carlo simulations of the free monomer, validated by circular dichroism spectroscopy, we observe changes in the position-dependent β-strand probability induced by mutations. We find that these conformational shifts match well with the effects of these mutations in thioflavin T fluorescence and transmission electron microscopy experiments. Together, our results point to molecular mechanisms that may have a key role in disease-linked aggregation of apolipoprotein A-I.
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Affiliation(s)
- Jitka Petrlova
- Department of Experimental Medical Science, Lund University, BMC Floor C12, SE-221 84, Lund, Sweden
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21
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Gorshkova IN, Mei X, Atkinson D. Binding of human apoA-I[K107del] variant to TG-rich particles: implications for mechanisms underlying hypertriglyceridemia. J Lipid Res 2014; 55:1876-85. [PMID: 24919401 DOI: 10.1194/jlr.m047241] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We found earlier that apoA-I variants that induced hypertriglyceridemia (HTG) in mice had increased affinity to TG-rich lipoproteins and thereby impaired their catabolism. Here, we tested whether a naturally occurring human apoA-I mutation, Lys107del, associated with HTG also promotes apoA-I binding to TG-rich particles. We expressed apoA-I[Lys107del] variant in Escherichia coli, studied its binding to TG-rich emulsion particles, and performed a physicochemical characterization of the protein. Compared with WT apoA-I, apoA-I[Lys107del] showed enhanced binding to TG-rich particles, lower stability, and greater exposure of hydrophobic surfaces. The crystal structure of truncated, Δ(185-243), apoA-I suggests that deletion of Lys107 disrupts helix registration and disturbs a stabilizing salt bridge network in the N-terminal helical bundle. To elucidate the structural changes responsible for the altered function of apoA-I[Lys107del], we studied another mutant, apoA-I [Lys107Ala]. Our findings suggest that the registry shift and ensuing disruption of the inter-helical salt bridges in apoA-I[Lys107del] result in destabilization of the helical bundle structure and greater exposure of hydrophobic surfaces. We conclude that the structural changes in the apoA-I[Lys107del] variant facilitate its binding to TG-rich lipoproteins and thus, may reduce their lipolysis and contribute to the development of HTG in carriers of the mutation.
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Affiliation(s)
- Irina N Gorshkova
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118 Department of Medicine, Boston University School of Medicine, Boston, MA 02118
| | - Xiaohu Mei
- 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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22
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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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23
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Pollard RD, Fulp B, Samuel MP, Sorci-Thomas MG, Thomas MJ. The conformation of lipid-free human apolipoprotein A-I in solution. Biochemistry 2013; 52:9470-81. [PMID: 24308268 DOI: 10.1021/bi401080k] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Apolipoprotein AI (apoA-I) is the principal acceptor of lipids from ATP-binding cassette transporter A1, a process that yields nascent high density lipoproteins. Analysis of lipidated apoA-I conformation yields a belt or twisted belt in which two strands of apoA-I lie antiparallel to one another. In contrast, biophysical studies have suggested that a part of lipid-free apoA-I was arranged in a four-helix bundle. To understand how lipid-free apoA-I opens from a bundle to a belt while accepting lipid it was necessary to have a more refined model for the conformation of lipid-free apoA-I. This study reports the conformation of lipid-free human apoA-I using lysine-to-lysine chemical cross-linking in conjunction with disulfide cross-linking achieved using selective cysteine mutations. After proteolysis, cross-linked peptides were verified by sequencing using tandem mass spectrometry. The resulting structure is compact with roughly four helical regions, amino acids 44-186, bundled together. C- and N-terminal ends, amino acids 1-43 and 187-243, respectively, are folded such that they lie close to one another. An unusual feature of the molecule is the high degree of connectivity of lysine40 with six other lysines, lysines that are close, for example, lysine59, to distant lysines, for example, lysine239, that are at the opposite end of the primary sequence. These results are compared and contrasted with other reported conformations for lipid-free human apoA-I and an NMR study of mouse apoA-I.
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Affiliation(s)
- Ricquita D Pollard
- Department of Biochemistry and ‡Department of Pathology, Section on Lipid Sciences, Wake Forest School of Medicine , Medical Center Blvd, Winston-Salem, North Carolina 27157-1016, United States
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24
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Wang S, Gulshan K, Brubaker G, Hazen SL, Smith JD. ABCA1 mediates unfolding of apolipoprotein AI N terminus on the cell surface before lipidation and release of nascent high-density lipoprotein. Arterioscler Thromb Vasc Biol 2013; 33:1197-205. [PMID: 23559627 DOI: 10.1161/atvbaha.112.301195] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To gain insight into the mechanism by which ABCA1 generates nascent high-density lipoprotein. APPROACH AND RESULTS HEK293 cells were stably transfected with ABCA1 vectors, encoding wild type, and the W590S and C1477R Tangier disease mutation isoforms, along with the K939M ATP-binding domain mutant. Apolipoprotein AI (ApoAI) binding, plasma membrane remodeling, cholesterol efflux, apoAI cell surface unfolding, and apoAI cell surface lipidation were determined, the latter 2 measured using novel fluorescent apoAI indicators. The W590S isoform had decreased plasma membrane remodeling and lipid efflux activities, and the C1477R isoform had decreased apoAI binding, and lipid efflux activities, whereas the K939M isoform did not bind apoAI, remodel the membrane, or efflux cholesterol. However, all ABCA1 isoforms led to apoAI unfolding at the cell surface, which was higher for the isoforms that increased apoAI binding. ApoAI lipidation was not detected on ABCA1-expressing cells, only in the conditioned medium, consistent with rapid release of nascent high-density lipoprotein from ABCA1-expressing cells. CONCLUSIONS We identified a third activity of ABCA1, the ability to unfold the N terminus of apoAI on the cell surface. Our results support a model in which unfolded apoAI on the cell surface is an intermediate in its lipidation and that, once apoAI is lipidated, it forms an unstable structure that is rapidly released from the cells to generate high-density lipoprotein.
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Affiliation(s)
- Shuhui Wang
- Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, OH 44195, USA
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25
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Mitsche MA, Small DM. Surface pressure-dependent conformation change of apolipoprotein-derived amphipathic α-helices. J Lipid Res 2013; 54:1578-1588. [PMID: 23528259 DOI: 10.1194/jlr.m034462] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Amphipathic α-helices (AαH) are the primary structural motif of exchangeable apolipoproteins. AαHs in exchangeable apolipoproteins adsorb, remodel, and desorb at the surface of plasma lipoproteins in response to changes in their size or composition. A triolein/water (TO/W) interface was used as a model surface to study adsorption and desorption of AαHs at a lipoprotein-like interface. We previously reported that AαH peptides spontaneously adsorb to a TO/W interface, but they only partially desorb from the surface when the excess peptide was removed from the system. This finding suggests that "exchangeable" apolipoproteins are in fact partially exchangeable and only desorb from a surface in response to compression or change in composition. Here, we develop a thermodynamic and kinetic model to describe this phenomenon based on the change in the interfacial pressure (Π) of the C-terminal 46 amino acids of apolipoprotein A-I (C46) at a TO/W interface. This model suggests that apolipoproteins have at least two interfacial conformations that are in a surface concentration and Π-dependent equilibrium. This two-state surface equilibrium model, which is based on experimental data and is consistent with dynamic changes in Π(t), provides insights into the selective metabolism and clearance of plasma lipoproteins and the process of lipoprotein remodeling.
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Affiliation(s)
- Matthew A Mitsche
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA.
| | - Donald M Small
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA
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26
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Zheng C, Weisbrod CR, Chavez JD, Eng JK, Sharma V, Wu X, Bruce JE. XLink-DB: database and software tools for storing and visualizing protein interaction topology data. J Proteome Res 2013; 12:1989-95. [PMID: 23413830 DOI: 10.1021/pr301162j] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
As large-scale cross-linking data becomes available, new software tools for data processing and visualization are required to replace manual data analysis. XLink-DB serves as a data storage site and visualization tool for cross-linking results. XLink-DB accepts data generated with any cross-linker and stores them in a relational database. Cross-linked sites are automatically mapped onto PDB structures if available, and results are compared to existing protein interaction databases. A protein interaction network is also automatically generated for the entire data set. The XLink-DB server, including examples, and a help page are available for noncommercial use at http://brucelab.gs.washington.edu/crosslinkdbv1/ . The source code can be viewed and downloaded at https://sourceforge.net/projects/crosslinkdb/?source=directory .
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Affiliation(s)
- Chunxiang Zheng
- Department of Chemistry, University of Washington , Seattle, Washington, United States
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27
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Abstract
Engineered nanoparticles (NPs) have found widespread application in technology and medicine. Whenever they come in contact with a living organism, interactions take place between the surfaces of the NPs and biomatter, in particular proteins, which are currently not well understood. We have introduced fluorescence correlation spectroscopy (FCS) and dual-focus FCS (2fFCS) to measure protein adsorption onto small NPs (~10-30 nm diameter). FCS allows us to measure, with subnanometer precision and as a function of protein concentration, the increase in hydrodynamic radius of the NPs due to protein adsorption. Investigations of the adsorption of a number of important serum proteins onto negatively charged, carboxyl-functionalized NPs revealed a stepwise increase of the NP size due to protein binding, clearly indicating that a protein monolayer enshrouds the NP. Structure-based calculations of the protein surface potentials reveal positively charged patches through which the proteins interact electrostatically with the negatively charged NP surfaces; the observed protein layer thickness is correlated with the molecular dimensions of the proteins binding in suitable orientations.
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Affiliation(s)
- G Ulrich Nienhaus
- Institute of Applied Physics and Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany.
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28
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Phillips MC. New insights into the determination of HDL structure by apolipoproteins: Thematic review series: high density lipoprotein structure, function, and metabolism. J Lipid Res 2012; 54:2034-2048. [PMID: 23230082 DOI: 10.1194/jlr.r034025] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Apolipoprotein (apo)A-I is the principal protein component of HDL, and because of its conformational adaptability, it can stabilize all HDL subclasses. The amphipathic α-helix is the structural motif that enables apoA-I to achieve this functionality. In the lipid-free state, the helical segments unfold and refold in seconds and are located in the N-terminal two thirds of the molecule where they are loosely packed as a dynamic, four-helix bundle. The C-terminal third of the protein forms an intrinsically disordered domain that mediates initial binding to phospholipid surfaces, which occurs with coupled α-helix formation. The lipid affinity of apoA-I confers detergent-like properties; it can solubilize vesicular phospholipids to create discoidal HDL particles with diameters of approximately 10 nm. Such particles contain a segment of phospholipid bilayer and are stabilized by two apoA-I molecules that are arranged in an anti-parallel, double-belt conformation around the edge of the disc, shielding the hydrophobic phospholipid acyl chains from exposure to water. The apoA-I molecules are in a highly dynamic state, and they stabilize discoidal particles of different sizes by certain segments forming loops that detach reversibly from the particle surface. The flexible apoA-I molecule adapts to the surface of spherical HDL particles by bending and forming a stabilizing trefoil scaffold structure. The above characteristics of apoA-I enable it to partner with ABCA1 in mediating efflux of cellular phospholipid and cholesterol and formation of a heterogeneous population of nascent HDL particles. Novel insights into the structure-function relationships of apoA-I should help reveal mechanisms by which HDL subclass distribution can be manipulated.
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Affiliation(s)
- Michael C Phillips
- Lipid Research Group, Division of Gastroenterology, Hepatology and Nutrition, The Children's Hospital of Philadelphia, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA.
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29
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Identification of sites in apolipoprotein A-I susceptible to chymase and carboxypeptidase A digestion. Biosci Rep 2012; 33:49-56. [PMID: 23072735 PMCID: PMC3522476 DOI: 10.1042/bsr20120094] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
MCs (mast cells) adversely affect atherosclerosis by promoting the progression of lesions and plaque destabilization. MC chymase cleaves apoA-I (apolipoprotein A-I), the main protein component of HDL (high-density lipoprotein). We previously showed that C-terminally truncated apoA-I (cleaved at the carboxyl side of Phe225) is present in normal human serum using a newly developed specific mAb (monoclonal antibody). In the present study, we aimed to identify chymase-induced cleavage sites in both lipid-free and lipid-bound (HDL3) forms of apoA-I. Lipid-free apoA-I was preferentially digested by chymase, at the C-terminus rather than the N-terminus. Phe229 and Tyr192 residues were the main cleavage sites. Interestingly, the Phe225 residue was a minor cleavage site. In contrast, the same concentration of chymase failed to digest apoA-I in HDL3; however, a 100-fold higher concentration of chymase modestly digested apoA-I in HDL3 at only the N-terminus, especially at Phe33. CPA (carboxypeptidase A) is another MC protease, co-localized with chymase in severe atherosclerotic lesions. CPA, in vitro, further cleaved C-terminal Phe225 and Phe229 residues newly exposed by chymase, but did not cleave Tyr192. These results indicate that several forms of C-terminally and N-terminally truncated apoA-I could exist in the circulation. They may be useful as new biomarkers to assess the risk of CVD (cardiovascular disease).
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30
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Chetty PS, Ohshiro M, Saito H, Dhanasekaran P, Lund-Katz S, Mayne L, Englander W, Phillips MC. Effects of the Iowa and Milano mutations on apolipoprotein A-I structure and dynamics determined by hydrogen exchange and mass spectrometry. Biochemistry 2012; 51:8993-9001. [PMID: 23066790 DOI: 10.1021/bi300926j] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The Iowa point mutation in apolipoprotein A-I (G26R) leads to a systemic amyloidosis condition, and the Milano mutation (R173C) is associated with hypoalphalipoproteinemia, a reduced plasma level of high-density lipoprotein. To probe the structural effects that lead to these outcomes, we used amide hydrogen-deuterium exchange coupled with a fragment separation/mass spectrometry analysis (HX MS). The Iowa mutation inserts an arginine residue into the nonpolar face of an α-helix that spans residues 7-44 and causes changes in structure and structural dynamics. This helix unfolds, and other helices in the N-terminal helix bundle domain are destabilized. The segment encompassing residues 116-158, largely unstructured in wild-type apolipoprotein A-I, becomes helical. The helix spanning residues 81-115 is destabilized by 2 kcal/mol, increasing the small fraction of time it is transiently unfolded to ≥1%, which allows proteolysis at residue 83 in vivo over time, releasing an amyloid-forming peptide. The Milano mutation situated on the polar face of the helix spanning residues 147-178 destabilizes the helix bundle domain only moderately, but enough to allow cysteine-mediated dimerization that leads to the altered functionality of this variant. These results show how the HX MS approach can provide a powerful means of monitoring, in a nonperturbing way and at close to amino acid resolution, the structural, dynamic, and energetic consequences of biologically interesting point mutations.
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Affiliation(s)
- Palaniappan Sevugan Chetty
- Lipid Research Group, Gastroenterology, Hepatology and Nutrition Division, Children's Hospital of Philadelphia, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104-4318, United States
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31
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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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32
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Sorci-Thomas MG, Owen JS, Fulp B, Bhat S, Zhu X, Parks JS, Shah D, Jerome WG, Gerelus M, Zabalawi M, Thomas MJ. Nascent high density lipoproteins formed by ABCA1 resemble lipid rafts and are structurally organized by three apoA-I monomers. J Lipid Res 2012; 53:1890-909. [PMID: 22750655 PMCID: PMC3413229 DOI: 10.1194/jlr.m026674] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 06/29/2012] [Indexed: 12/29/2022] Open
Abstract
This report details the lipid composition of nascent HDL (nHDL) particles formed by the action of the ATP binding cassette transporter A1 (ABCA1) on apolipoprotein A-I (apoA-I). nHDL particles of different size (average diameters of ∼ 12, 10, 7.5, and <6 nm) and composition were purified by size-exclusion chromatography. Electron microscopy suggested that the nHDL were mostly spheroidal. The proportions of the principal nHDL lipids, free cholesterol, glycerophosphocholine, and sphingomyelin were similar to that of lipid rafts, suggesting that the lipid originated from a raft-like region of the cell. Smaller amounts of glucosylceramides, cholesteryl esters, and other glycerophospholipid classes were also present. The largest particles, ∼ 12 nm and 10 nm diameter, contained ∼ 43% free cholesterol, 2-3% cholesteryl ester, and three apoA-I molecules. Using chemical cross-linking chemistry combined with mass spectrometry, we found that three molecules of apoA-I in the ∼ 9-14 nm nHDL adopted a belt-like conformation. The smaller (7.5 nm diameter) spheroidal nHDL particles carried 30% free cholesterol and two molecules of apoA-I in a twisted, antiparallel, double-belt conformation. Overall, these new data offer fresh insights into the biogenesis and structural constraints involved in forming nascent HDL from ABCA1.
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Affiliation(s)
- Mary G Sorci-Thomas
- Department of Pathology, Section on Lipid Sciences, Wake Forest Baptist Medical Center, Winston-Salem, NC 27157, USA.
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33
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Monti DM, Di Gaetano S, Del Giudice R, Giangrande C, Amoresano A, Monti M, Arciello A, Piccoli R. Apolipoprotein A-I amyloidogenic variant L174S, expressed and isolated from stably transfected mammalian cells, is associated with fatty acids. Amyloid 2012; 19:21-7. [PMID: 22295944 DOI: 10.3109/13506129.2011.651544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Sixteen variants of apolipoprotein A-I (ApoA-I) are associated with hereditary systemic amyloidoses, characterized by amyloid deposition in peripheral organs of patients. As these are heterozygous for the amyloidogenic variants, their isolation from plasma is impracticable and recombinant expression systems are needed. Here we report the expression of recombinant ApoA-I amyloidogenic variant Leu174 with Ser (L174S) in stably transfected Chinese hamster ovary-K1 cells. ApoA-I variant L174S was found to be efficiently secreted in the culture medium, from which it was isolated following a one-step purification procedure. Mass spectrometry analyses allowed the qualitative and quantitative definition of the amyloidogenic variant lipid content, which was found to consist of two saturated and two monounsaturated fatty acids. Interestingly, the same lipid species were found to be associated with the wild-type ApoA-I, expressed and isolated using the same cell system, with lower values of the lipid to protein molar ratios with respect to the amyloidogenic variant. A possible role of fatty acids in trafficking and secretion of apolipoproteins may be hypothesized.
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Affiliation(s)
- Daria Maria Monti
- Department of Structural and Functional Biology, University of Naples Federico II, School of Biotechnological Sciences, Naples, Italy
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34
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Zehender F, Ziegler A, Schönfeld HJ, Seelig J. Thermodynamics of Protein Self-Association and Unfolding. The Case of Apolipoprotein A-I. Biochemistry 2012; 51:1269-80. [DOI: 10.1021/bi2013799] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- F. Zehender
- Division of Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056
Basel, Switzerland
| | - A. Ziegler
- Division of Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056
Basel, Switzerland
| | - H.-J. Schönfeld
- Pharmaceutical
Research, F. Hoffman-La Roche Ltd., CH-4070
Basel, Switzerland
| | - J. Seelig
- Division of Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056
Basel, Switzerland
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35
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Lagerstedt JO, Budamagunta MS, Liu GS, DeValle NC, Voss JC, Oda MN. The "beta-clasp" model of apolipoprotein A-I--a lipid-free solution structure determined by electron paramagnetic resonance spectroscopy. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:448-55. [PMID: 22245143 DOI: 10.1016/j.bbalip.2011.12.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2011] [Revised: 12/06/2011] [Accepted: 12/20/2011] [Indexed: 02/02/2023]
Abstract
Apolipoprotein A-I (apoA-I) is the major protein component of high density lipoproteins (HDL) and plays a central role in cholesterol metabolism. The lipid-free/lipid-poor form of apoA-I is the preferred substrate for the ATP-binding cassette transporter A1 (ABCA1). The interaction of apoA-I with ABCA1 leads to the formation of cholesterol laden high density lipoprotein (HDL) particles, a key step in reverse cholesterol transport and the maintenance of cholesterol homeostasis. Knowledge of the structure of lipid-free apoA-I is essential to understanding its critical interaction with ABCA1 and the molecular mechanisms underlying HDL biogenesis. We therefore examined the structure of lipid-free apoA-I by electron paramagnetic resonance spectroscopy (EPR). Through site directed spin label EPR, we mapped the secondary structure of apoA-I and identified sites of spin coupling as residues 26, 44, 64, 167, 217 and 226. We capitalize on the fact that lipid-free apoA-I self-associates in an anti-parallel manner in solution. We employed these sites of spin coupling to define the central plane in the dimeric apoA-I complex. Applying both the constraints of dipolar coupling with the EPR-derived pattern of solvent accessibility, we assembled the secondary structure into a tertiary context, providing a solution structure for lipid-free apoA-I. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).
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Affiliation(s)
- Jens O Lagerstedt
- Department of Experimental Medical Science, Lund University, S-221 84 Lund, Sweden
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36
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Petrlova J, Duong T, Cochran MC, Axelsson A, Mörgelin M, Roberts LM, Lagerstedt JO. The fibrillogenic L178H variant of apolipoprotein A-I forms helical fibrils. J Lipid Res 2011; 53:390-398. [PMID: 22184756 PMCID: PMC3276462 DOI: 10.1194/jlr.m020883] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
A number of amyloidogenic variants of apoA-I have been discovered but most have not
been analyzed. Previously, we showed that the G26R mutation of apoA-I leads to
increased β-strand structure, increased N-terminal protease susceptibility, and
increased fibril formation after several days of incubation. In vivo, this and other
variants mutated in the N-terminal domain (residues 26 to ∼90) lead to renal and
hepatic accumulation. In contrast, several mutations identified within residues 170
to 178 lead to cardiac, laryngeal, and cutaneous protein deposition. Here, we
describe the structural changes in the fibrillogenic variant L178H. Like G26R, the
initial structure of the protein exhibits altered tertiary conformation relative to
wild-type protein along with decreased stability and an altered lipid binding
profile. However, in contrast to G26R, L178H undergoes an increase in helical
structure upon incubation at 37°C with a half time (t1/2) of about 12
days. Upon prolonged incubation, the L178H mutant forms fibrils of a diameter of 10
nm that ranges in length from 30 to 120 nm. These results show that apoA-I, known for
its dynamic properties, has the ability to form multiple fibrillar conformations,
which may play a role in the tissue-specific deposition of the individual
variants.
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Affiliation(s)
- Jitka Petrlova
- Department of Experimental Medical Sciences, Lund University, S-221 84 Lund, Sweden; and
| | - Trang Duong
- Department of Chemistry, California State University Sacramento, Sacramento, CA 95819
| | - Megan C Cochran
- Department of Chemistry, California State University Sacramento, Sacramento, CA 95819
| | - Annika Axelsson
- Department of Experimental Medical Sciences, Lund University, S-221 84 Lund, Sweden; and
| | - Matthias Mörgelin
- Department of Experimental Medical Sciences, and Department of Infection Medicine, Lund University, S-221 84 Lund, Sweden; and
| | - Linda M Roberts
- Department of Chemistry, California State University Sacramento, Sacramento, CA 95819.
| | - Jens O Lagerstedt
- Department of Experimental Medical Sciences, Lund University, S-221 84 Lund, Sweden; and.
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37
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C-terminus of apolipoprotein A-I removes phospholipids from a triolein/phospholipids/water interface, but the N-terminus does not: a possible mechanism for nascent HDL assembly. Biophys J 2011; 101:353-61. [PMID: 21767487 DOI: 10.1016/j.bpj.2011.03.055] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 02/10/2011] [Accepted: 03/15/2011] [Indexed: 01/12/2023] Open
Abstract
Apolipoprotein A-I (ApoA-I) is the principle protein component of HDL, also known as "good cholesterol," which is an inverse marker for cardiovascular disease. The N-terminal 44 amino acids of ApoA-I (N44) are predicted to be responsible for stabilization of soluble ApoA-I, whereas the C-terminal 46 amino acids (C46) are predicted to initiate lipid binding and oligomerization. In this work, we apply what we believe to be a novel application of drop tensiometry to study the adsorption and desorption of N44 and C46 at a triolein/POPC/water (TO/POPC/W) interface. The amount of peptide that adsorbed to the surface was dependent on the surface concentration of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and pressure (Π) before adsorption. At a TO/POPC/W interface, the exclusion pressure (Π(EX)) of C46 was 25.8 mN/m, and was 19.3 mN/m for N44. Once adsorbed, both peptides formed a homogeneous surface with POPC but were progressively ejected from the surface by compression. During a compression, C46 removed POPC from the surface whereas N44 did not. Repeated compressions caused C46 to deplete entirely the surface of phospholipid. If full-length ApoA-I could also remove phospholipid, this could provide a mechanism for the transfer of surface components of chylomicrons and very low density lipoprotein to high density lipoprotein with the assistance of phospholipid transfer protein.
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38
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Jayaraman S, Abe-Dohmae S, Yokoyama S, Cavigiolio G. Impact of self-association on function of apolipoprotein A-I. J Biol Chem 2011; 286:35610-35623. [PMID: 21835924 DOI: 10.1074/jbc.m111.262485] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Self-association is an inherent property of the lipid-free forms of several exchangeable apolipoproteins, including apolipoprotein A-I (apoA-I), the main protein component of high density lipoproteins (HDL) and an established antiatherogenic factor. Monomeric lipid-free apoA-I is believed to be the biologically active species, but abnormal conditions, such as specific natural mutations or oxidation, produce an altered state of self-association that may contribute to apoA-I dysfunction. Replacement of the tryptophans of apoA-I with phenylalanines (ΔW-apoA-I) leads to unusually large and stable self-associated species. We took advantage of this unique solution property of ΔW-apoA-I to analyze the role of self-association in determining the structure and lipid-binding properties of apoA-I as well as ATP-binding cassette A1 (ABCA1)-mediated cellular lipid release, a relevant pathway in atherosclerosis. Monomeric ΔW-apoA-I and wild-type apoA-I activated ABCA1-mediated cellular lipid release with similar efficiencies, whereas the efficiency of high order self-associated species was reduced to less than 50%. Analysis of specific self-associated subclasses revealed that different factors influence the rate of HDL formation in vitro and ABCA1-mediated lipid release efficiency. The α-helix-forming ability of apoA-I is the main determinant of in vitro lipid solubilization rates, whereas loss of cellular lipid release efficiency is mainly caused by reduced structural flexibility by formation of stable quaternary interactions. Thus, stabilization of self-associated species impairs apoA-I biological activity through an ABCA1-mediated mechanism. These results afford mechanistic insights into the ABCA1 reaction and suggest self-association as a functional feature of apoA-I. Physiologic mechanisms may alter the native self-association state and contribute to apoA-I dysfunction.
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Affiliation(s)
- Shobini Jayaraman
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Sumiko Abe-Dohmae
- Department of Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
| | - Shinji Yokoyama
- Department of Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
| | - Giorgio Cavigiolio
- Children's Hospital Oakland Research Institute, Oakland, California 94609.
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39
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Ohnsorg PM, Rohrer L, Perisa D, Kateifides A, Chroni A, Kardassis D, Zannis VI, von Eckardstein A. Carboxyl terminus of apolipoprotein A-I (ApoA-I) is necessary for the transport of lipid-free ApoA-I but not prelipidated ApoA-I particles through aortic endothelial cells. J Biol Chem 2011; 286:7744-7754. [PMID: 21209084 DOI: 10.1074/jbc.m110.193524] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
High density lipoproteins (HDL) and apolipoprotein A-I (apoA-I) must leave the circulation and pass the endothelium to exert their atheroprotective actions in the arterial wall. We previously demonstrated that the transendothelial transport of apoA-I involves ATP-binding cassette transporter (ABC) A1 and re-secretion of lipidated particles. Transendothelial transport of HDL is modulated by ABCG1 and the scavenger receptor BI (SR-BI). We hypothesize that apoA-I transport is started by the ABCA1-mediated generation of a lipidated particle which is then transported by ABCA1-independent pathways. To test this hypothesis we analyzed the endothelial binding and transport properties of initially lipid-free as well as prelipidated apoA-I mutants. Lipid-free apoA-I mutants with a defective carboxyl-terminal domain showed an 80% decreased specific binding and 90% decreased specific transport by aortic endothelial cells. After prior cell-free lipidation of the mutants, the resulting HDL-like particles were transported through endothelial cells by an ABCG1- and SR-BI-dependent process. ApoA-I mutants with deletions of either the amino terminus or both the amino and carboxyl termini showed dramatic increases in nonspecific binding but no specific binding or transport. Prior cell-free lipidation did not rescue these anomalies. Our findings of stringent structure-function relationships underline the specificity of transendothelial apoA-I transport and suggest that lipidation of initially lipid-free apoA-I is necessary but not sufficient for specific transendothelial transport. Our data also support the model of a two-step process for the transendothelial transport of apoA-I in which apoA-I is initially lipidated by ABCA1 and then further processed by ABCA1-independent mechanisms.
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Affiliation(s)
- Pascale M Ohnsorg
- From the Institute of Clinical Chemistry, University Hospital of Zurich, 8091 Zurich, Switzerland,; the Competence Center for Systems Physiology and Metabolic Diseases, ETH and University of Zurich, 8091 Zurich, Switzerland
| | - Lucia Rohrer
- From the Institute of Clinical Chemistry, University Hospital of Zurich, 8091 Zurich, Switzerland,; the Center for Integrative Human Physiology, University of Zurich, 8091 Zurich, Switzerland
| | - Damir Perisa
- From the Institute of Clinical Chemistry, University Hospital of Zurich, 8091 Zurich, Switzerland,; the Center for Integrative Human Physiology, University of Zurich, 8091 Zurich, Switzerland
| | - Andreas Kateifides
- Molecular Genetics, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts 02118,; the Department of Biochemistry, Division of Basic Sciences, Institute of Molecular Biology and Biotechnology, University of Crete Medical School, 71201 Crete, Greece
| | - Angeliki Chroni
- the National Centre of Scientific Research "Demokritos," Institute of Biology, 15310 Athens, Greece, and
| | - Dimitris Kardassis
- the Department of Biochemistry, Division of Basic Sciences, Institute of Molecular Biology and Biotechnology, University of Crete Medical School, 71201 Crete, Greece
| | - Vassilis I Zannis
- Molecular Genetics, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts 02118,; the Department of Biochemistry, Division of Basic Sciences, Institute of Molecular Biology and Biotechnology, University of Crete Medical School, 71201 Crete, Greece
| | - Arnold von Eckardstein
- From the Institute of Clinical Chemistry, University Hospital of Zurich, 8091 Zurich, Switzerland,; the Competence Center for Systems Physiology and Metabolic Diseases, ETH and University of Zurich, 8091 Zurich, Switzerland,; the Center for Integrative Human Physiology, University of Zurich, 8091 Zurich, Switzerland,.
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40
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Maffre P, Nienhaus K, Amin F, Parak WJ, Nienhaus GU. Characterization of protein adsorption onto FePt nanoparticles using dual-focus fluorescence correlation spectroscopy. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2011; 2:374-83. [PMID: 22003445 PMCID: PMC3190609 DOI: 10.3762/bjnano.2.43] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Accepted: 06/06/2011] [Indexed: 05/18/2023]
Abstract
Using dual-focus fluorescence correlation spectroscopy, we have analyzed the adsorption of three human blood serum proteins, namely serum albumin, apolipoprotein A-I and apolipoprotein E4, onto polymer-coated, fluorescently labeled FePt nanoparticles (~12 nm diameter) carrying negatively charged carboxyl groups on their surface. For all three proteins, a step-wise increase in hydrodynamic radius with protein concentration was observed, strongly suggesting the formation of protein monolayers that enclose the nanoparticles. Consistent with this interpretation, the absolute increase in hydrodynamic radius can be correlated with the molecular shapes of the proteins known from X-ray crystallography and solution experiments, indicating that the proteins bind on the nanoparticles in specific orientations. The equilibrium dissociation coefficients, measuring the affinity of the proteins to the nanoparticles, were observed to differ by almost four orders of magnitude. These variations can be understood in terms of the electrostatic properties of the proteins. From structure-based calculations of the surface potentials, positively charged patches of different extents can be revealed, through which the proteins interact electrostatically with the negatively charged nanoparticle surfaces.
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Affiliation(s)
- Pauline Maffre
- Institute of Applied Physics and Center for Functional Nanostructures, Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Straße 1, 76131 Karlsruhe, Germany
| | - Karin Nienhaus
- Institute of Applied Physics and Center for Functional Nanostructures, Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Straße 1, 76131 Karlsruhe, Germany
| | - Faheem Amin
- Department of Physics, Philipps University Marburg, Renthof 7, 35037 Marburg, Germany
| | - Wolfgang J Parak
- Department of Physics, Philipps University Marburg, Renthof 7, 35037 Marburg, Germany
| | - G Ulrich Nienhaus
- Institute of Applied Physics and Center for Functional Nanostructures, Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Straße 1, 76131 Karlsruhe, Germany
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, IL 61801, USA
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41
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Prieto ED, Garda HA. Membrane insertion topology of the central apolipoprotein A-I region. Fluorescence studies using single tryptophan mutants. Biochemistry 2010; 50:466-79. [PMID: 21141907 DOI: 10.1021/bi1009634] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Apolipoprotein A-I (apoAI) contains several amphipathic α-helices. To carry out its function, it exchanges between lipid-free and different lipidated states as bound to membranes or to lipoprotein complexes of different morphology, size, and composition. When bound to membranes or to spherical lipoprotein surfaces, it is thought that most α-helices arrange with their long axis parallel to the membrane surface. However, we previously found that a central region spanning residues 87-112 is exclusively labeled by photoactivable reagents deeply located into the membrane (Córsico et al. (2001) J. Biol. Chem. 276, 16978-16985). A pair of amphipathic α-helical repeats with a particular charge distribution is predicted in this region. In order to study their insertion topology, three single tryptophan mutants, each one containing the tryptophan residue at a selected position in the hydrophobic face of the central Y-helices (W@93, W@104, and W@108), were used. From the accessibility to quenchers located at different membrane depths, distances from the bilayer center of 13.4, 10.5, and 15.7 Å were estimated for positions 93, 104, and 108, respectively. Reported data also indicate that distances between homologous positions (in particular for W@93 and W@104) are very short in dimers in aqueous solution, but they are larger in membrane-bound dimers. Data indicate that an intermolecular central Y-helix bundle would penetrate the membrane perpendicularly to the membrane surface. Intermolecular helix-helix interactions would occur through the hydrophilic helix faces in the membrane-bound bundle but through the hydrophobic faces in the case of dimers in solution.
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Affiliation(s)
- Eduardo D Prieto
- Instituto de Investigaciones Bioquímicas de La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de La Plata, Facultad de Ciencias Médicas, Calles 60 y 120, La Plata, Argentina
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42
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Alexander ET, Vedhachalam C, Sankaranarayanan S, de la Llera-Moya M, Rothblat GH, Rader DJ, Phillips MC. Influence of apolipoprotein A-I domain structure on macrophage reverse cholesterol transport in mice. Arterioscler Thromb Vasc Biol 2010; 31:320-7. [PMID: 21071688 DOI: 10.1161/atvbaha.110.216226] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE The goal of this study was to determine the influence of apolipoprotein A-I (apoA-I) tertiary structure domain properties on the antiatherogenic properties of the protein. Two chimeric hybrids with the N-terminal domains swapped (human-mouse apoA-I and mouse-human apoA-I) were expressed in apoA-I-null mice with adeno-associated virus (AAV) and used to study macrophage reverse cholesterol transport (RCT) in vivo. METHODS AND RESULTS The different apoA-I variants were expressed in apoA-I-null mice that were injected with [H(3)]cholesterol-labeled J774 mouse macrophages to measure RCT. Significantly more cholesterol was removed from the macrophages and deposited in the feces via the RCT pathway in mice expressing mouse-H apoA-I compared with all other groups. Analysis of the individual components of the RCT pathway demonstrated that mouse-H apoA-I promoted ATP-binding cassette transporter A1-mediated cholesterol efflux more efficiently than all other variants, as well as increasing the rate of cholesterol uptake into liver cells. CONCLUSIONS The structural domain properties of apoA-I affect the ability of the protein to mediate macrophage RCT. Replacement of the N-terminal helix bundle domain in the human apoA-I with the mouse apoA-I counterpart causes a gain of function with respect to macrophage RCT, suggesting that engineering some destabilization into the N-terminal helix bundle domain or increasing the hydrophobicity of the C-terminal domain of human apoA-I would enhance the antiatherogenic properties of the protein.
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Affiliation(s)
- Eric T Alexander
- Children's Hospital of Philadelphia, 3615 Civic Center Blvd., Philadelphia, PA 19104, USA
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43
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Tanaka M, Dhanasekaran P, Nguyen D, Nickel M, Takechi Y, Lund-Katz S, Phillips MC, Saito H. Influence of N-terminal helix bundle stability on the lipid-binding properties of human apolipoprotein A-I. Biochim Biophys Acta Mol Cell Biol Lipids 2010; 1811:25-30. [PMID: 21040803 DOI: 10.1016/j.bbalip.2010.10.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 10/19/2010] [Accepted: 10/24/2010] [Indexed: 11/26/2022]
Abstract
As the principal component of high-density lipoprotein (HDL), apolipoprotein (apo) A-I plays essential roles in lipid transport and metabolism. Because of its intrinsic conformational plasticity and flexibility, the molecular details of the tertiary structure of lipid-free apoA-I have not been fully elucidated. Previously, we demonstrated that the stability of the N-terminal helix bundle structure is modulated by proline substitution at the most hydrophobic region (residues around Y18) in the N-terminal domain. Here we examine the effect of proline substitution at S55 located in another relatively hydrophobic region compared to most of the helix bundle domain to elucidate the influences on the helix bundle structure and lipid interaction. Fluorescence measurements revealed that the S55P mutation had a modest effect on the stability of the bundle structure, indicating that residues around S55 are not pivotally involved in the helix bundle formation, in contrast to the insertion of proline at position 18. Although truncation of the C-terminal domain (Δ190-243) diminishes the lipid binding of apoA-I molecule, the mutation S55P in addition to the C-terminal truncation (S55P/Δ190-243) restored the lipid binding, suggesting that the S55P mutation causes a partial unfolding of the helix bundle to facilitate lipid binding. Furthermore, additional proline substitution at Y18 (Y18P/S55P/Δ190-243), which leads to a drastic unfolding of the helix bundle structure, yielded a greater lipid binding ability. Thus, proline substitutions in the N-terminal domain of apoA-I that destabilized the helix bundle promoted lipid solubilization. These results suggest that not only the hydrophobic C-terminal helical domain but also the stability of the N-terminal helix bundle in apoA-I are important modulators of the spontaneous solubilization of membrane lipids by apoA-I, a process that leads to the generation of nascent HDL particles.
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Affiliation(s)
- Masafumi Tanaka
- Department of Biophysical Chemistry, Kobe Pharmaceutical University, Kobe 658-8558, Japan.
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44
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Vuorela T, Catte A, Niemelä PS, Hall A, Hyvönen MT, Marrink SJ, Karttunen M, Vattulainen I. Role of lipids in spheroidal high density lipoproteins. PLoS Comput Biol 2010; 6:e1000964. [PMID: 21060857 PMCID: PMC2965744 DOI: 10.1371/journal.pcbi.1000964] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Accepted: 09/17/2010] [Indexed: 01/25/2023] Open
Abstract
We study the structure and dynamics of spherical high density lipoprotein (HDL) particles through coarse-grained multi-microsecond molecular dynamics simulations. We simulate both a lipid droplet without the apolipoprotein A-I (apoA-I) and the full HDL particle including two apoA-I molecules surrounding the lipid compartment. The present models are the first ones among computational studies where the size and lipid composition of HDL are realistic, corresponding to human serum HDL. We focus on the role of lipids in HDL structure and dynamics. Particular attention is paid to the assembly of lipids and the influence of lipid-protein interactions on HDL properties. We find that the properties of lipids depend significantly on their location in the particle (core, intermediate region, surface). Unlike the hydrophobic core, the intermediate and surface regions are characterized by prominent conformational lipid order. Yet, not only the conformations but also the dynamics of lipids are found to be distinctly different in the different regions of HDL, highlighting the importance of dynamics in considering the functionalization of HDL. The structure of the lipid droplet close to the HDL-water interface is altered by the presence of apoA-Is, with most prominent changes being observed for cholesterol and polar lipids. For cholesterol, slow trafficking between the surface layer and the regimes underneath is observed. The lipid-protein interactions are strongest for cholesterol, in particular its interaction with hydrophobic residues of apoA-I. Our results reveal that not only hydrophobicity but also conformational entropy of the molecules are the driving forces in the formation of HDL structure. The results provide the first detailed structural model for HDL and its dynamics with and without apoA-I, and indicate how the interplay and competition between entropy and detailed interactions may be used in nanoparticle and drug design through self-assembly.
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Affiliation(s)
- Timo Vuorela
- Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Andrea Catte
- Department of Physics, Tampere University of Technology, Tampere, Finland
- Department of Medicine and Center for Computational and Structural Biology, University of Alabama, Birmingham, Alabama, United States of America
| | | | - Anette Hall
- Department of Physics, Tampere University of Technology, Tampere, Finland
| | | | - Siewert-Jan Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands
| | - Mikko Karttunen
- Department of Applied Mathematics, The University of Western Ontario, London, Ontario, Canada
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology, Tampere, Finland
- Department of Applied Physics, Aalto University School of Science and Technology, Espoo, Finland
- MEMPHYS–Center of Biomembrane Physics, Physics Department, University of Southern Denmark, Odense M, Denmark
- * E-mail:
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45
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Gomes AF, Gozzo FC. Chemical cross-linking with a diazirine photoactivatable cross-linker investigated by MALDI- and ESI-MS/MS. JOURNAL OF MASS SPECTROMETRY : JMS 2010; 45:892-9. [PMID: 20635431 DOI: 10.1002/jms.1776] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Crystallography and nuclear magnetic resonance are well-established methods to study protein tertiary structure and interactions. Despite their usefulness, such methods are not applicable to many protein systems. Chemical cross-linking of proteins coupled with mass spectrometry allows low-resolution characterization of proteins and protein complexes based on measuring distance constraints from cross-links. In this work, we have investigated cross-linking by means of a heterobifunctional cross-linker containing a traditional N-hydroxysuccinimide (NHS) ester and a UV photoactivatable diazirine group. Activation of the diazirine group yields a highly reactive carbene species, with potential to increase the number of cross-links compared with homobifunctional, NHS-based cross-linkers. Cross-linking reactions were performed on model systems such as synthetic peptides and equine myoglobin. After reduction of the disulfide bond, the formation of intra- and intermolecular cross-links was identified and the peptides modified with both NHS and diazirine moieties characterized. Fragmentation of these modified peptides reveals the presence of a marker ion for intramolecular cross-links, which facilitates identification.
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Affiliation(s)
- Alexandre F Gomes
- Institute of Chemistry, University of Campinas-UNICAMP and Instituto Nacional de Ciencia e Tecnologia de Bioanalitica, CP 6154, 13083-970, Campinas, Sao Paulo, Brazil
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46
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Fabris D, Yu ET. Elucidating the higher-order structure of biopolymers by structural probing and mass spectrometry: MS3D. JOURNAL OF MASS SPECTROMETRY : JMS 2010; 45:841-60. [PMID: 20648672 PMCID: PMC3432860 DOI: 10.1002/jms.1762] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Chemical probing represents a very versatile alternative for studying the structure and dynamics of substrates that are intractable by established high-resolution techniques. The implementation of MS-based strategies for the characterization of probing products has not only extended the range of applicability to virtually all types of biopolymers but has also paved the way for the introduction of new reagents that would not have been viable with traditional analytical platforms. As the availability of probing data is steadily increasing on the wings of the development of dedicated interpretation aids, powerful computational approaches have been explored to enable the effective utilization of such information to generate valid molecular models. This combination of factors has contributed to making the possibility of obtaining actual 3D structures by MS-based technologies (MS3D) a reality. Although approaches for achieving structure determination of unknown targets or assessing the dynamics of known structures may share similar reagents and development trajectories, they clearly involve distinctive experimental strategies, analytical concerns and interpretation paradigms. This Perspective offers a commentary on methods aimed at obtaining distance constraints for the modeling of full-fledged structures while highlighting common elements, salient distinctions and complementary capabilities exhibited by methods used in dynamics studies. We discuss critical factors to be addressed for completing effective structural determinations and expose possible pitfalls of chemical methods. We survey programs developed for facilitating the interpretation of experimental data and discuss possible computational strategies for translating sparse spatial constraints into all-atom models. Examples are provided to illustrate how the concerted application of very diverse probing techniques can lead to the solution of actual biological systems.
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Affiliation(s)
- Daniele Fabris
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County, Baltimore, MD, USA.
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47
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Bhat S, Sorci-Thomas MG, Calabresi L, Samuel MP, Thomas MJ. Conformation of dimeric apolipoprotein A-I milano on recombinant lipoprotein particles. Biochemistry 2010; 49:5213-24. [PMID: 20524691 DOI: 10.1021/bi1003734] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Apolipoprotein A-I Milano (apoA-I(Milano)) is a naturally occurring human mutation of wild-type apolipoprotein A-I (apoA-I(WT)) having cystine substituted for arginine(173). Two molecules of apo-I(WT) form disks with phospholipid having a defined relationship between the apoA-I(WT) molecules. ApoA-I(Milano) forms cystine homodimers that would not allow the protein to adopt the conformation reported for apoA-I(WT). The conformational constraints for dimeric apoA-I(Milano) recombinant high-density lipoprotein (rHDL) disks made with phospholipid were deduced from a combination of chemical cross-linking and mass spectrometry. Lysine-selective homobifunctional cross-linkers were reacted with homogeneous rHDL having diameters of 78 and 125 A. After reduction, cross-linked apoA-I(Milano) was separated from monomeric apoprotein by gel electrophoresis and then subjected to in-gel trypsin digest. Cross-linked peptides were confirmed by MS/MS sequencing. The cross-links provided distance constraints that were used to refine models of lipid-bound dimeric apoA-I(Milano). These studies suggest that a single dimeric apoA-I(Milano) on 78 A diameter rHDL girdles the edge of a phospholipid disk assuming a "belt" conformation similar to the "belt" region of apoA-I(WT) on rHDL. However, the C-terminal end of dimeric apoA-I(Milano) wraps around the periphery of the particle to shield the fatty acid chains from water rather than folding back onto the "belt" as does apoA-I(WT). The two apoA-I(Milano) dimers on a 125 A diameter rHDL do not encircle the periphery of a phospholipid disk but appear to reside on the surface of a laminar micelle.
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Affiliation(s)
- Shaila Bhat
- Department of Pathology, Center for Lipid Science, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, North Carolina 27157, USA
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48
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Shao B, Oda MN, Oram JF, Heinecke JW. Myeloperoxidase: an oxidative pathway for generating dysfunctional high-density lipoprotein. Chem Res Toxicol 2010; 23:447-54. [PMID: 20043647 DOI: 10.1021/tx9003775] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Accumulation of low-density lipoprotein (LDL)-derived cholesterol by artery wall macrophages triggers atherosclerosis, the leading cause of cardiovascular disease. Conversely, high-density lipoprotein (HDL) retards atherosclerosis by promoting cholesterol efflux from macrophages by the membrane-associated ATP-binding cassette transporter A1 (ABCA1) pathway. HDL has been proposed to lose its cardioprotective effects in subjects with atherosclerosis, but the underlying mechanisms are poorly understood. One potential pathway involves oxidative damage by myeloperoxidase (MPO), a heme enzyme secreted by human artery wall macrophages. We used mass spectrometry to demonstrate that HDL isolated from patients with established cardiovascular disease contains elevated levels of 3-chlorotyrosine and 3-nitrotyrosine, two characteristic products of MPO. When apolipoprotein A-I (apoA-I), the major HDL protein, was oxidized by MPO, its ability to promote cellular cholesterol efflux by ABCA1 was impaired. Moreover, oxidized apoA-I was unable to activate lecithin:cholesterol acyltransferase (LCAT), which rapidly converts free cholesterol to cholesteryl ester, a critical step in HDL maturation. Biochemical studies implicated tyrosine chlorination and methionine oxygenation in the loss of ABCA1 and LCAT activity by oxidized apoA-I. Oxidation of specific residues in apoA-I inhibited two key steps in cholesterol efflux from macrophages, raising the possibility that MPO initiates a pathway for generating dysfunctional HDL in humans.
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Affiliation(s)
- Baohai Shao
- Department of Medicine, University of Washington, 815 Mercer Street, Seattle, Washington 98109, USA.
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49
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Cavigiolio G, Geier EG, Shao B, Heinecke JW, Oda MN. Exchange of apolipoprotein A-I between lipid-associated and lipid-free states: a potential target for oxidative generation of dysfunctional high density lipoproteins. J Biol Chem 2010; 285:18847-57. [PMID: 20385548 DOI: 10.1074/jbc.m109.098434] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
An important event in cholesterol metabolism is the efflux of cellular cholesterol by apolipoprotein A-I (apoA-I), the major protein of high density lipoproteins (HDL). Lipid-free apoA-I is the preferred substrate for ATP-binding cassette A1, which promotes cholesterol efflux from macrophage foam cells in the arterial wall. However, the vast majority of apoA-I in plasma is associated with HDL, and the mechanisms for the generation of lipid-free apoA-I remain poorly understood. In the current study, we used fluorescently labeled apoA-I that exhibits a distinct fluorescence emission spectrum when in different states of lipid association to establish the kinetics of apoA-I transition between the lipid-associated and lipid-free states. This approach characterized the spontaneous and rapid exchange of apoA-I between the lipid-associated and lipid-free states. In contrast, the kinetics of apoA-I exchange were significantly reduced when apoA-I on HDL was cross-linked with a bi-functional reagent or oxidized by myeloperoxidase. Our observations support the hypothesis that oxidative damage to apoA-I by myeloperoxidase limits the ability of apoA-I to be liberated in a lipid-free form from HDL. This impairment of apoA-I exchange reaction may be a trait of dysfunctional HDL contributing to reduced ATP-binding cassette A1-mediated cholesterol efflux and atherosclerosis.
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Affiliation(s)
- Giorgio Cavigiolio
- Children's Hospital Oakland Research Institute, Oakland, California 94609, USA
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50
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Koyama M, Tanaka M, Dhanasekaran P, Lund-Katz S, Phillips MC, Saito H. Interaction between the N- and C-terminal domains modulates the stability and lipid binding of apolipoprotein A-I. Biochemistry 2010; 48:2529-37. [PMID: 19239199 DOI: 10.1021/bi802317v] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The tertiary structures of human and mouse apolipoprotein A-I (apoA-I) are comprised of an N-terminal helix bundle and a separate C-terminal domain. To define the possible intramolecular interaction between the N- and the C-terminal domains, we examined the effects on protein stability and lipid-binding properties of exchanging either the C-terminal domain or helix between human and mouse apoA-I. Chemical denaturation experiments demonstrated that replacement of the C-terminal domain or helical segment in human apoA-I with the mouse counterparts largely destabilizes the N-terminal helix bundle. Removal of the C-terminal domain or alpha-helix in human apoA-I had a similar effect on the destabilization of the helix bundle against urea denaturation, indicating that the C-terminal helical segment mainly contributes to stabilizing the N-terminal helix bundle structure in the apoA-I molecule. Consistent with this, KI quenching experiments indicated that removal or replacement of the C-terminal domain or helix in human apoA-I causes Trp residues in the N-terminal domain to become exposed to solvent. Measurements of the heats of binding to egg phosphatidylcholine (PC) vesicles and the kinetics of solubilization of dimyristoyl PC vesicles demonstrated that the destabilized human N-terminal helix bundle can strongly interact with lipids without the hydrophobic C-terminal helix. In addition, site-specific labeling of the N- and C-terminal helices by acrylodan to probe the conformational stability and the spatial proximity of the two domains indicated that the C-terminal helix is located near the N-terminal helix bundle, leading to a relatively less solvent-exposed, more organized conformation of the C-terminal domain. Taken together, these results suggest that interaction between the N- and C-terminal tertiary structure domains in apoA-I modulates the stability and lipid-binding properties of the N-terminal helix bundle.
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Affiliation(s)
- Mao Koyama
- Department of Biophysical Chemistry, Kobe Pharmaceutical University, 4-19-1 Motoyamakitamachi, Higashinada-ku, Kobe 658-8558, Japan
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