1
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Caron NS, Aly AEE, Findlay Black H, Martin DDO, Schmidt ME, Ko S, Anderson C, Harvey EM, Casal LL, Anderson LM, Rahavi SMR, Reid GSD, Oda MN, Stanimirovic D, Abulrob A, McBride JL, Leavitt BR, Hayden MR. Systemic delivery of mutant huntingtin lowering antisense oligonucleotides to the brain using apolipoprotein A-I nanodisks for Huntington disease. J Control Release 2024; 367:27-44. [PMID: 38215984 DOI: 10.1016/j.jconrel.2024.01.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Revised: 12/09/2023] [Accepted: 01/09/2024] [Indexed: 01/14/2024]
Abstract
Efficient delivery of therapeutics to the central nervous system (CNS) remains a major challenge for the treatment of neurological diseases. Huntington disease (HD) is a dominantly inherited neurodegenerative disorder caused by a CAG trinucleotide expansion mutation in the HTT gene which codes for a toxic mutant huntingtin (mHTT) protein. Pharmacological reduction of mHTT in the CNS using antisense oligonucleotides (ASO) ameliorates HD-like phenotypes in rodent models of HD, with such therapies being investigated in clinical trials for HD. In this study, we report the optimization of apolipoprotein A-I nanodisks (apoA-I NDs) as vehicles for delivery of a HTT-targeted ASO (HTT ASO) to the brain and peripheral organs for HD. We demonstrate that apoA-I wild type (WT) and the apoA-I K133C mutant incubated with a synthetic lipid, 1,2-dimyristoyl-sn-glycero-3-phosphocholine, can self-assemble into monodisperse discoidal particles with diameters <20 nm that transmigrate across an in vitro blood-brain barrier model of HD. We demonstrate that apoA-I NDs are well tolerated in vivo, and that apoA-I K133C NDs show enhanced distribution to the CNS and peripheral organs compared to apoA-I WT NDs following systemic administration. ApoA-I K133C conjugated with HTT ASO forms NDs (HTT ASO NDs) that induce significant mHTT lowering in the liver, skeletal muscle and heart as well as in the brain when delivered intravenously in the BACHD mouse model of HD. Furthermore, HTT ASO NDs increase the magnitude of mHTT lowering in the striatum and cortex compared to HTT ASO alone following intracerebroventricular administration. These findings demonstrate the potential utility of apoA-I NDs as biocompatible vehicles for enhancing delivery of mutant HTT lowering ASOs to the CNS and peripheral organs for HD.
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Affiliation(s)
- Nicholas S Caron
- Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada; BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada; Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Amirah E-E Aly
- Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada; BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada; Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Hailey Findlay Black
- Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada; BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada; Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Dale D O Martin
- Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada; BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada; Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada; Department of Biology, University of Waterloo, Ontario, Canada
| | - Mandi E Schmidt
- Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada; BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada; Department of Neuroscience, University of British Columbia, Vancouver, British Columbia, Canada
| | - Seunghyun Ko
- Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada
| | - Christine Anderson
- Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada
| | - Emily M Harvey
- Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada
| | - Lorenzo L Casal
- Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada
| | - Lisa M Anderson
- Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada
| | - Seyed M R Rahavi
- BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada; Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Gregor S D Reid
- BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada; Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Danica Stanimirovic
- Human Health Therapeutics Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
| | - Abedelnasser Abulrob
- Human Health Therapeutics Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
| | - Jodi L McBride
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR, USA; Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR, USA
| | - Blair R Leavitt
- Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada; BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada; Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Michael R Hayden
- Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada; BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada; Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
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2
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Chroni A, Kardassis D. HDL Dysfunction Caused by Mutations in apoA-I and Other Genes that are Critical for HDL Biogenesis and Remodeling. Curr Med Chem 2019. [DOI: 10.2174/0929867325666180313114950] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The “HDL hypothesis” which suggested that an elevation in HDL cholesterol
(HDL-C) levels by drugs or by life style changes should be paralleled by a decrease in the
risk for Cardiovascular Disease (CVD) has been challenged by recent epidemiological and
clinical studies using HDL-raising drugs. HDL components such as proteins, lipids or small
RNA molecules, but not cholesterol itself, possess various atheroprotective functions in different
cell types and accumulating evidence supports the new hypothesis that HDL functionality
is more important than HDL-C levels for CVD risk prediction. Thus, the detailed characterization
of changes in HDL composition and functions in various pathogenic conditions
is critically important in order to identify new biomarkers for diagnosis, prognosis and therapy
monitoring of CVD. Here we provide an overview of how HDL composition, size and
functionality are affected in patients with monogenic disorders of HDL metabolism due to
mutations in genes that participate in the biogenesis and the remodeling of HDL. We also review
the findings from various mouse models with genetic disturbances in the HDL biogenesis
pathway that have been generated for the validation of the data obtained in human patients
and how these models could be utilized for the evaluation of novel therapeutic strategies such
as the use of adenovirus-mediated gene transfer technology that aim to correct HDL abnormalities.
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Affiliation(s)
- Angeliki Chroni
- Institute of Biosciences and Applications, National Center for Scientific Research , Greece
| | - Dimitris Kardassis
- Department of Basic Medical Sciences, University of Crete Medical School and Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology of Hellas, Heraklion 71003, Greece
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3
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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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4
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Abstract
Cardiovascular disease (CVD) is the leading cause of death globally. For close to four decades, we have known that high density lipoprotein (HDL) levels are inversely correlated with the risk of CVD. HDL is a complex particle that consists of proteins, phospholipids, and cholesterol and has the ability to carry micro-RNAs. HDL is constantly undergoing remodelling throughout its life-span and carries out many functions. This review summarizes many of the different aspects of HDL from its assembly, the receptors it interacts with, along with the functions it performs and how it can be altered in disease. While HDL is a key cholesterol efflux particle, this review highlights the many other important functions of HDL in the innate immune system and details the potential therapeutic uses of HDL outside of CVD.
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5
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Gursky O, Jones MK, Mei X, Segrest JP, Atkinson D. Structural basis for distinct functions of the naturally occurring Cys mutants of human apolipoprotein A-I. J Lipid Res 2013; 54:3244-57. [PMID: 24038317 DOI: 10.1194/jlr.r037911] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
HDL removes cell cholesterol and protects against atherosclerosis. ApoA-I provides a flexible structural scaffold and an important functional ligand on the HDL surface. We propose structural models for apoA-I(Milano) (R173C) and apoA-I(Paris) (R151C) mutants that show high cardioprotection despite low HDL levels. Previous studies established that two apoA-I molecules encircle HDL in an antiparallel, helical double-belt conformation. Recently, we solved the atomic structure of lipid-free Δ(185-243)apoA-I and proposed a conformational ensemble for apoA-I(WT) on HDL. Here we modify this ensemble to understand how intermolecular disulfides involving C173 or C151 influence protein conformation. The double-belt conformations are modified by belt rotation, main-chain unhinging around Gly, and Pro-induced helical bending, and they are verified by comparison with previous experimental studies and by molecular dynamics simulations of apoA-I(Milano) homodimer. In our models, the molecular termini repack on various-sized HDL, while packing around helix-5 in apoA-I(WT), helix-6 in apoA-I(Paris), or helix-7 in apoA-I(Milano) homodimer is largely conserved. We propose how the disulfide-induced constraints alter the protein conformation and facilitate dissociation of the C-terminal segment from HDL to recruit additional lipid. Our models unify previous studies of apoA-I(Milano) and demonstrate how the mutational effects propagate to the molecular termini, altering their conformations, dynamics, and function.
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Affiliation(s)
- Olga Gursky
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118
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6
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Oda MN, Budamagunta MS, Borja MS, Petrlova J, Voss JC, Lagerstedt JO. The secondary structure of apolipoprotein A-I on 9.6-nm reconstituted high-density lipoprotein determined by EPR spectroscopy. FEBS J 2013; 280:3416-24. [PMID: 23668303 PMCID: PMC3906832 DOI: 10.1111/febs.12334] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 05/09/2013] [Accepted: 05/09/2013] [Indexed: 01/09/2023]
Abstract
Apolipoprotein A-I (ApoA-I) is the major protein component of high-density lipoprotein (HDL), and is critical for maintenance of cholesterol homeostasis. During reverse cholesterol transport, HDL transitions between an array of subclasses, differing in size and composition. This process requires ApoA-I to adapt to changes in the shape of the HDL particle, transiting from an apolipoprotein to a myriad of HDL subclass-specific conformations. Changes in ApoA-I structure cause alterations in HDL-specific enzyme and receptor-binding properties, and thereby direct the HDL particle through the reverse cholesterol transport pathway. In this study, we used site-directed spin label spectroscopy to examine the conformational details of the ApoA-I central domain on HDL. The motional dynamics and accessibility to hydrophobic/hydrophilic relaxation agents of ApoA-I residues 99–163 on 9.6-nm reconstituted HDL was analyzed by EPR. In previous analyses, we examined residues 6–98 and 164–238 (of ApoA-I's 243 residues), and combining these findings with the current results, we have generated a full-length map of the backbone structure of reconstituted HDL-associated ApoA-I. Remarkably, given that the majority of ApoA-I's length is composed of amphipathic helices, we have identified nonhelical residues, specifically the presence of a β-strand (residues 149–157). The significance of these nonhelical residues is discussed, along with the other features, in the context of ApoA-I function in contrast to recent models derived by other methods.
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Affiliation(s)
- Michael N Oda
- Children's Hospital Oakland Research Institute, CA, USA
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7
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Sequence-specific apolipoprotein A-I effects on lecithin:cholesterol acyltransferase activity. Mol Cell Biochem 2013; 378:283-90. [DOI: 10.1007/s11010-013-1619-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 03/02/2013] [Indexed: 01/08/2023]
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8
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Rocco AG, Sensi C, Gianazza E, Calabresi L, Franceschini G, Sirtori CR, Eberini I. Structural and dynamic features of apolipoprotein A-I cysteine mutants, Milano and Paris, in synthetic HDL. J Mol Graph Model 2010; 29:406-14. [DOI: 10.1016/j.jmgm.2010.08.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 07/29/2010] [Accepted: 08/05/2010] [Indexed: 12/16/2022]
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9
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Murphy AJ, Chin-Dusting J, Sviridov D. Reconstituted HDL: a therapy for atherosclerosis and beyond. ACTA ACUST UNITED AC 2009. [DOI: 10.2217/clp.09.68] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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10
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Sviridov D, Mukhamedova N, T. Remaley A, Chin-Dusting J, Nestel P. Antiatherogenic Functionality of High Density Lipoprotein: How Much versus How Gooden-subtitle=. J Atheroscler Thromb 2008; 15:52-62. [DOI: 10.5551/jat.e571] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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11
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Zannis VI, Koukos G, Drosatos K, Vezeridis A, Zanni EE, Kypreos KE, Chroni A. Discrete roles of apoA-I and apoE in the biogenesis of HDL species: lessons learned from gene transfer studies in different mouse models. Ann Med 2008; 40 Suppl 1:14-28. [PMID: 18246469 DOI: 10.1080/07853890701687219] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Using adenovirus-mediated gene transfer in apolipoprotein A-I (apoA-I)-deficient mice, we have established that apoA-I mutations inhibit discrete steps in a pathway that leads to the biogenesis and remodeling of high-density lipoprotein (HDL). To this point, five discrete categories of apoA-I mutants have been characterized that may affect the interactions of apoA-I with ATP-binding cassette superfamily A, member 1 (ABCA1) or lecithin:cholesterol acyl transferase (LCAT) or may influence the plasma phospholipid transfer protein activity or may cause various forms of dyslipidemia. Biogenesis of HDL is not a unique property of apoA-I. Using adenovirus-mediated gene transfer of apoE in apoA-I- or ABCA1-deficient mice, we have established that apolipoprotein E (apoE) also participates in a novel pathway of biogenesis of apoE-containing HDL particles. This process requires the functions of the ABCA1 lipid transporter and LCAT, and it is promoted by substitution of hydrophobic residues in the 261 to 269 region of apoE by Ala. The apoE-containing HDL particles formed in the circulation may have atheroprotective properties. ApoE-containing HDL may also have important biological functions in the brain that confer protection from Alzheimer's disease.
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Affiliation(s)
- Vassilis I Zannis
- Molecular Genetics, Whitaker Cardiovascular Institute, Departments of Medicine and Biochemistry, Boston University School of Medicine, Boston, MA 02118-2394, USA.
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12
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Koukos G, Chroni A, Duka A, Kardassis D, Zannis V. Naturally occurring and bioengineered apoA-I mutations that inhibit the conversion of discoidal to spherical HDL: the abnormal HDL phenotypes can be corrected by treatment with LCAT. Biochem J 2007; 406:167-74. [PMID: 17506726 PMCID: PMC1948983 DOI: 10.1042/bj20070296] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In the present study we have used adenovirus-mediated gene transfer of apoA-I (apolipoprotein A-I) mutants in apoA-I-/- mice to investigate how structural mutations in apoA-I affect the biogenesis and the plasma levels of HDL (high-density lipoprotein). The natural mutants apoA-I(R151C)Paris, apoA-I(R160L)Oslo and the bioengineered mutant apoA-I(R149A) were secreted efficiently from cells in culture. Their capacity to activate LCAT (lecithin:cholesterol acyltransferase) in vitro was greatly reduced, and their ability to promote ABCA1 (ATP-binding cassette transporter A1)-mediated cholesterol efflux was similar to that of WT (wild-type) apoA-I. Gene transfer of the three mutants in apoA-I-/- mice generated aberrant HDL phenotypes. The total plasma cholesterol of mice expressing the apoA-I(R160L)Oslo, apoA-I(R149A) and apoA-I(R151C)Paris mutants was reduced by 78, 59 and 61% and the apoA-I levels were reduced by 68, 64 and 55% respectively, as compared with mice expressing the WT apoA-I. The CE (cholesteryl ester)/TC (total cholesterol) ratio of HDL was decreased and the apoA-I was distributed in the HDL3 region. apoA-I(R160L)Oslo and apoA-I(R149A) promoted the formation of prebeta1 and alpha4-HDL subpopulations and gave a mixture of discoidal and spherical particles. apoA-I(R151C)Paris generated subpopulations of different sizes that migrate between prebeta and alpha-HDL and formed mostly spherical and a few discoidal particles. Simultaneous treatment of mice with adenovirus expressing any of the three mutants and human LCAT normalized plasma apoA-I, HDL cholesterol levels and the CE/TC ratio. It also led to the formation of spherical HDL particles consisting mostly of alpha-HDL subpopulations of larger size. The correction of the aberrant HDL phenotypes by treatment with LCAT suggests a potential therapeutic intervention for HDL abnormalities that result from specific mutations in apoA-I.
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Affiliation(s)
- Georgios Koukos
- *Molecular Genetics, Departmental of Medicine and Biochemistry, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118, U.S.A
- †Department of Basic Sciences, University of Crete Medical School, Heraklion, GR-71110, Greece
| | - Angeliki Chroni
- ‡Institute of Biology, National Center for Scientific Research ‘Demokritos’, 15310 Agia Paraskevi, Athens, Greece
| | - Adelina Duka
- *Molecular Genetics, Departmental of Medicine and Biochemistry, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118, U.S.A
| | - Dimitris Kardassis
- ‡Institute of Biology, National Center for Scientific Research ‘Demokritos’, 15310 Agia Paraskevi, Athens, Greece
- §Institute of Molecular Biology and Biotechnology, FORTH (Foundation for Research and Technology-Hellas), Heraklion, Crete, Greece
| | - Vassilis I. Zannis
- *Molecular Genetics, Departmental of Medicine and Biochemistry, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118, U.S.A
- ‡Institute of Biology, National Center for Scientific Research ‘Demokritos’, 15310 Agia Paraskevi, Athens, Greece
- To whom correspondence should be addressed (email )
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13
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Robinson JG, Davidson MH. Investigational drugs targeting HDL-C metabolism and reverse cholesterol transport. ACTA ACUST UNITED AC 2007. [DOI: 10.2217/17460875.2.3.285] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Haidar B, Kiss RS, Sarov-Blat L, Brunet R, Harder C, McPherson R, Marcel YL. Cathepsin D, a Lysosomal Protease, Regulates ABCA1-mediated Lipid Efflux. J Biol Chem 2006; 281:39971-81. [PMID: 17032648 DOI: 10.1074/jbc.m605095200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
To identify genes involved in the regulation of plasma high density lipoprotein (HDL) cholesterol (HDL-C) levels, patients with low HDL-C and age- and sex-matched controls (normal HDL-C) were extensively characterized. Comparative transcriptome analysis was carried out in cholesterol-loaded monocyte-derived macrophages from low HDL subjects segregated into groups with or without cholesterol efflux defects or ABCA1 mutations. Clusters of differentially regulated genes were evident in the low HDL groups as compared with controls. Of particular note, expression of cathepsin D (CTSD), a lysosomal proteinase, was reduced by approximately 50% in monocyte-derived macrophages of low HDL-C subjects, most significantly those with cholesterol efflux defects but without mutations in ABCA1 (p < 0.01). These results were verified by reverse transcription-PCR and replicated in a second cohort. We show here that blocking the activity or expression of CTSD, by pepstatin or CTSD small interfering RNA, respectively, reduced ABCA1 expression and protein abundance in both macrophages and CHO cells and apolipoprotein A-I-mediated lipid efflux by more than 70%. Conversely, expression of CTSD increased both ABCA1 mRNA expression and cellular ABCA1 protein. Consistent with its role in the proteolytic processing of prosaposin, inactivation of CTSD function resulted in the accumulation of glycosphingo-lipid and free cholesterol in late endosomes/lysosomes, a phenotype similar to NPC1 deficiency. Inhibition of CTSD also caused retention of ABCA1 in lysosomal compartments, reducing its trafficking to the plasma membrane. These studies demonstrate a novel and potentially important role for CTSD in intracellular cholesterol trafficking and ABCA1-mediated efflux. Therefore, decreased CTSD expression may contribute to low plasma HDL-C levels.
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Affiliation(s)
- Bassam Haidar
- Lipoprotein and Atherosclerosis Research Group, University of Ottawa Heart Institute, Ottawa, Ontario, K1Y 4W7, Canada
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15
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Chroni A, Duka A, Kan HY, Liu T, Zannis VI. Point mutations in apolipoprotein A-I mimic the phenotype observed in patients with classical lecithin:cholesterol acyltransferase deficiency. Biochemistry 2006; 44:14353-66. [PMID: 16245952 DOI: 10.1021/bi050962o] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have analyzed the effect of charged to neutral amino acid substitutions around the kinks flanking helices 4 and 6 of apoA-I and of the deletion of helix 6 on the in vivo activity of LCAT and the biogenesis of HDL. The LCAT activation capacity of apoA-I in vitro was nearly abolished by the helix 6 point (helix 6P-apoA-I[R160V/H162A]) and deletion {helix 6Delta-apoA-I[Delta(144-165)]} mutants, but was reduced to 50% in the helix 4 point mutant (helix 4P-apoA-I[D102A/D103A]). Following adenovirus-mediated gene transfer in apoA-I deficient mice, the level of plasma HDL cholesterol was greatly reduced in helix 6P and helix 6Delta mutants. Electron microscopy and two-dimensional gel electrophoresis showed that the helix 6P mutant formed predominantly high levels of apoA-I containing discoidal particles and had an increased prebeta1-HDL/alpha-HDL ratio. The helix 6Delta mutant formed few spherical particles and had an increased prebeta1-HDL/alpha-HDL ratio. Mice infected with adenovirus expressing the helix 4P mutant or wild-type apoA-I had normal HDL cholesterol and formed spherical alpha-HDL particles. Coinfection of mice with adenoviruses expressing human LCAT and the helix 6P mutant dramatically increased plasma HDL and apoA-I levels and converted the discoidal into spherical HDL, indicating that the LCAT activity was rate-limiting for the biogenesis of HDL. The LCAT treatment caused only a small increase in HDL cholesterol and apoA-I levels and in alpha-HDL particle numbers in the helix 6Delta mutant. The findings indicate a critical contribution of residue 160 of apoA-I to the in vivo activity of LCAT and the subsequent maturation of HDL and explain the low HDL levels in heterozygous subjects carrying this mutation.
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Affiliation(s)
- Angeliki Chroni
- Molecular Genetics, Whitaker Cardiovascular Institute, Department of Medicine, Center for Advanced Biomedical Research, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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16
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Zhu X, Wu G, Zeng W, Xue H, Chen B. Cysteine mutants of human apolipoprotein A-I: a study of secondary structural and functional properties. J Lipid Res 2005; 46:1303-11. [PMID: 15805548 DOI: 10.1194/jlr.m400401-jlr200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Apolipoprotein A-I(Milano) (A-I(M)) (R173C), a natural mutant of human apolipoprotein A-I (apoA-I), and five other cysteine variants of apoA-I at residues 52 (S52C), 74 (N74C), 107 (K107C), 129 (G129C), and 195 (K195C) were generated. Cysteine residues were incorporated in each of the various helices at the same helical wheel position as for the substitution in A-I(M). The secondary structural properties of the monomeric mutants, their abilities to bind lipid and to promote cholesterol efflux from THP-1 macrophages, and the possibility of antiperoxidation were investigated. Results showed that the alpha helical contents of all of the cysteine mutants were similar to that of wild-type apoA-I (wtapoA-I). The cysteine variant of A-I(M) at residue 173 [A-I(M)(R173C)] exhibited weakened structural stability, whereas A-I(G129C) a more stable structure than wtapoA-I. A-I(G129C) and A-I(K195C) exhibited significantly impaired capabilities to bind lipid compared with wtapoA-I. A-I(K107C) possessed a higher capacity to promote cholesterol efflux from macrophages than wtapoA-I, and A-I(M)(R173C) and A-I(K195C) exhibited an impaired efflux capability. Neither A-I(M)(R173C) nor any other cysteine mutant could resist oxidation against lipoxygenase. In summary, in spite of the similar mutant position on the helix, these variants exhibited different structural features or biological activities, suggesting the potential influence of the local environment of mutations on the whole polypeptide chain.
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Affiliation(s)
- Xuewei Zhu
- Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China 100005
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17
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Abstract
PURPOSE OF REVIEW High-density lipoprotein cholesterol (HDL-C) has been well established as an inverse predictor of coronary heart disease (CHD), and in recent years, investigations have focused on the genetic regulation of high-density lipoprotein. Although numerous candidate genes contribute to the low HDL-C phenotype, their impact on CHD is heterogeneous, reflecting diverse gene-gene interactions and gene-environmental relationships. This review summarizes recent data involving HDL regulatory genes and their role in atherothrombosis. RECENT FINDINGS The primary genetic determinants associated with relative HDL-C deficiency states are the ATP binding cassette protein, ABCA1; apolipoprotein (APO) A1; and lecithin cholesteryl acyl transferase. Other potentially important candidates invoked in low HDL-C syndromes in humans include APOC3, lipoprotein lipase, sphingomyelin phosphodiesterase 1, and glucocerebrosidase. Molecular variation in ABCAI and APOAI and, in selected cases, lecithin cholesteryl acyl transferase deficiency have been associated with increased CHD, whereas two notable variants, APOAIMilano and APOAIParis, are associated with reduced risk. SUMMARY Low HDL-C syndromes have generally been correlated with an increased risk of CHD. However, single-gene abnormalities responsible for HDL-C deficiency states may have variable effects on atherothrombotic risk.
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Affiliation(s)
- Michael Miller
- Department of Medicine, University of Maryland Hospital and Veterans Affairs Medical Center, Baltimore, Maryland, USA.
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18
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Ng DS. Treating low HDL—From bench to bedside. Clin Biochem 2004; 37:649-59. [PMID: 15302606 DOI: 10.1016/j.clinbiochem.2004.04.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Revised: 04/05/2004] [Accepted: 04/05/2004] [Indexed: 01/21/2023]
Abstract
The inverse relationship between the plasma high-density lipoprotein cholesterol (HDL-C) and the risk of coronary heart disease (CHD) is well recognized in the general population. However, the development of effective therapeutics targeting HDL continues to be challenging, which is due in part to the heterogeneity of its structure and composition and the complexity of its metabolism. In this paper, we review a number of recent advances in our understanding of HDL metabolism and its role in atherogenesis. We discuss the HDL-C raising effect of a selected number of currently available lipid-modifying drugs and on a selected number of novel HDL-targeted therapeutic strategies under development.
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Affiliation(s)
- Dominic S Ng
- Department of Medicine, St. Michael's Hospital, Toronto, Ontario, Canada.
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19
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Tian S, Jonas A. Structural and functional properties of apolipoprotein A-I mutants containing disulfide-linked cysteines at positions 124 or 232. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1599:56-64. [PMID: 12479405 DOI: 10.1016/s1570-9639(02)00377-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recombinant Cys mutants of apolipoprotein A-I (apoA-I) (A124C and A232C) have been prepared in disulfide-linked forms in order to assess the effects of unnatural covalent constraints on the folding of apoA-I in solution, its ability to bind lipids, form HDL-like particles, activate LCAT, and undergo structural adaptations to changing lipid contents. Both mutants, in dimer form, were shown to fold similarly to plasma apoA-I in solution, but had a slightly decreased alpha-helix content and no evidence of intermonomer interactions. All forms of the mutants bound to and disrupted dimyristoylphosphatidylcholine (DMPC) liposomes with similar kinetics and efficiency to plasma apoA-I, and formed reconstituted HDL (rHDL) particles with palmitoyloleoylphosphatidylcholine (POPC) in high yields at three different ratios of lipid/protein. While the monomeric mutants produced identical rHDL to plasma apoA-I, the disulfide-linked dimers had distinct particle distributions from each other and from native apoA-I. The A124C-dimer formed rHDL with diameters of 86 and 78 A, while the A232C-dimer predominantly formed 96 A rHDL. These particles, and particles containing plasma apoA-I (96 and 78 A), were purified prior to structural and functional analyses. The structural properties of particles with similar diameters were comparable, as were their reactivities with LCAT; however, their ability to undergo structural rearrangements differed. The larger rHDL particles (96 and 86 A) containing native apoA-I or A124C-dimer, rearranged into smaller 78 A particles, while the 96 A particles containing A232C-dimer were resistant to rearrangement and did not form 78 A particles. From the results, it is concluded that synthetic, random disulfide-linked dimers of apoA-I have many properties analogous to those of the naturally occurring Cys mutants, apoA-I-Milano and apoA-I-Paris, which are thought to have antiatherogenic effects in vivo. Also, the results have implications for current models of rHDL structure.
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Affiliation(s)
- Shaomin Tian
- Department of Biochemistry, College of Medicine, University of Illinois at Urbana-Champaign, 506 South Mathews Avenue, Urbana, IL 61801, USA
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20
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Klon AE, Segrest JP, Harvey SC. Comparative models for human apolipoprotein A-I bound to lipid in discoidal high-density lipoprotein particles. Biochemistry 2002; 41:10895-905. [PMID: 12206659 DOI: 10.1021/bi020315m] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have constructed a series of models for apolipoprotein A-I (apo A-I) bound to discoidal high-density lipoprotein (HDL) particles, based upon the molecular belt model [Segrest, J. P., et al. (1999) J. Biol. Chem. 274, 31755-31758] and helical hairpin models [Rogers, D. P., et al. (1998) Biochemistry 37, 11714-11725], and compared these with picket fence models [Phillips, J. C., et al. (1997) Biophys. J. 73, 2337-2346]. Molecular belt models for discoidal HDL particles with differing diameters are presented, illustrating that the belt model can explain the discrete changes in HDL particle size observed experimentally. Hairpin models are discussed for the binding of apo A-I to discoidal HDL particles with diameters identical to those for the molecular belt model. Two models are presented for the binding of three monomers of apo A-I to a 150 A diameter discoidal HDL particle. In one model, two monomers of apo A-I bind to the exterior of the HDL particle in an antiparallel belt, with a third monomer of apo A-I bound to the disk in a hairpin conformation. In the second model, all three monomers of apo A-I are bound to the discoidal HDL particle in a hairpin conformation. Previously published experimental data for each model are reviewed, with FRET favoring either the belt or hairpin models over the picket fence models for HDL particles with diameters of 105 A. Naturally occurring mutations appear to favor the belt model for the 105 A particles, while the 150 A HDL particles favor the presence of at least one hairpin.
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Affiliation(s)
- Anthony E Klon
- Department of Biochemistry and Molecular Genetics and Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294-0005, USA
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21
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Abstract
Approximately 46 human apolipoprotein A-I (apoA-I) coding sequence mutations have been reported to date. Roughly half of these mutations are associated with lower than average plasma concentrations of high-density lipoprotein (HDL) apoA-I. Mutations associated with low HDL apoA-I concentrations fall into two main categories: those which poorly activate the enzyme lecithin:cholesterol acyltransferase (LCAT) and those associated with amyloidosis. These phenotypically distinct groups of mutations are uniquely localized in different regions of the apoprotein sequence. Mutations associated with abnormal LCAT activation are located within repeats 5, 6, and 7, corresponding to amino acids 121 to 186, while many of the mutations found in amyloid deposits are clustered at the amino terminus of the protein, namely residues 1 to 90. These observations strongly support the idea that the tertiary structure of apoA-I determines its intravascular fate and ultimately the steady state concentration of plasma HDL.
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Affiliation(s)
- Mary G Sorci-Thomas
- Department of Pathology, Wake Forest University Baptist Medical Center, Winston-Salem, North Carolina, USA.
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22
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Bielicki JK, Oda MN. Apolipoprotein A-I(Milano) and apolipoprotein A-I(Paris) exhibit an antioxidant activity distinct from that of wild-type apolipoprotein A-I. Biochemistry 2002; 41:2089-96. [PMID: 11827556 DOI: 10.1021/bi011716p] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Apolipoprotein A-I(Milano) (apoA-I(Milano)) and apoA-I(Paris) are rare cysteine variants of apoA-I that produce a HDL deficiency in the absence of cardiovascular disease in humans. This paradox provides the basis for the hypothesis that the cysteine variants possess a beneficial activity not associated with wild-type apoA-I (apoA-I(WT)). In this study, a unique antioxidant activity of apoA-I(Milano) and apoA-I(Paris) is described. ApoA-I(Milano) was twice as effective as apoA-I(Paris) in preventing lipoxygenase-mediated oxidation of phospholipids, whereas apoA-I(WT) was poorly active. Antioxidant activity was observed using the monomeric form of the variants and was equally effective before and after initiation of oxidative events. ApoA-I(Milano) protected phospholipid from reactive oxygen species (ROS) generated via xanthine/xanthine oxidase (X/Xo) but failed to inhibit X/Xo-induced reduction of cytochrome c. These results indicate that apoA-I(Milano) was unable to directly quench ROS in the aqueous phase. There were no differences between lipid-free apoA-I(Milano,) apoA-I(Paris), and apoA-I(WT) in mediating the efflux of cholesterol from macrophages, indicating that the cysteine variants interacted normally with the ABCA1 efflux pathway. The results indicate that incorporation of a free thiol within an amphipathic alpha helix of apoA-I confers an antioxidant activity distinct from that of apoA-I(WT). These studies are the first to relate gain of function to rare cysteine mutations in the apoA-I primary sequence.
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Affiliation(s)
- John K Bielicki
- Genome Sciences Department, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
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23
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McManus DC, Scott BR, Franklin V, Sparks DL, Marcel YL. Proteolytic degradation and impaired secretion of an apolipoprotein A-I mutant associated with dominantly inherited hypoalphalipoproteinemia. J Biol Chem 2001; 276:21292-302. [PMID: 11292828 DOI: 10.1074/jbc.m100463200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have devised a combined in vivo, ex vivo, and in vitro approach to elucidate the mechanism(s) responsible for the hypoalphalipoproteinemia in heterozygous carriers of a naturally occurring apolipoprotein A-I (apoA-I) variant (Leu(159) to Arg) known as apoA-I Finland (apoA-I(FIN)). Adenovirus-mediated expression of apoA-I(FIN) decreased apoA-I and high density lipoprotein cholesterol concentrations in both wild-type C57BL/6J mice and in apoA-I-deficient mice expressing native human apoA-I (hapoA-I). Interestingly, apoA-I(FIN) was degraded in the plasma, and the extent of proteolysis correlated with the most significant reductions in murine apoA-I concentrations. ApoA-I(FIN) had impaired activation of lecithin:cholesterol acyltransferase in vitro compared with hapoA-I, but in a mixed lipoprotein preparation consisting of both hapoA-I and apoA-I(FIN) there was only a moderate reduction in the activation of this enzyme. Importantly, secretion of apoA-I was also decreased from primary apoA-I-deficient hepatocytes when hapoA-I was co-expressed with apoA-I(FIN) following infection with recombinant adenoviruses, a condition that mimics secretion in heterozygotes. Thus, this is the first demonstration of an apoA-I point mutation that decreases LCAT activation, impairs hepatocyte secretion of apoA-I, and makes apoA-I susceptible to proteolysis leading to dominantly inherited hypoalphalipoproteinemia.
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Affiliation(s)
- D C McManus
- Lipoprotein and Atherosclerosis Research Group, Department of Pathology, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
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24
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Brouillette CG, Anantharamaiah GM, Engler JA, Borhani DW. Structural models of human apolipoprotein A-I: a critical analysis and review. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1531:4-46. [PMID: 11278170 DOI: 10.1016/s1388-1981(01)00081-6] [Citation(s) in RCA: 191] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human apolipoprotein (apo) A-I has been the subject of intense investigation because of its well-documented anti-atherogenic properties. About 70% of the protein found in high density lipoprotein complexes is apo A-I, a molecule that contains a series of highly homologous amphipathic alpha-helices. A number of significant experimental observations have allowed increasing sophisticated structural models for both the lipid-bound and the lipid-free forms of the apo A-I molecule to be tested critically. It seems clear, for example, that interactions between amphipathic domains in apo A-I may be crucial to understanding the dynamic nature of the molecule and the pathways by which the lipid-free molecule binds to lipid, both in a discoidal and a spherical particle. The state of the art of these structural studies is discussed and placed in context with current models and concepts of the physiological role of apo A-I and high-density lipoprotein in atherosclerosis and lipid metabolism.
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Affiliation(s)
- C G Brouillette
- Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham, AL 35294-0005, USA.
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25
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Liu H, Labeur C, Xu CF, Ferrell R, Lins L, Brasseur R, Rosseneu M, Weiss KM, Humphries SE, Talmud PJ. Characterization of the lipid-binding properties and lipoprotein lipase inhibition of a novel apolipoprotein C-III variant Ala23Thr. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)31969-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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26
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Klon AE, Jones MK, Segrest JP, Harvey SC. Molecular belt models for the apolipoprotein A-I Paris and Milano mutations. Biophys J 2000; 79:1679-85. [PMID: 10969027 PMCID: PMC1301059 DOI: 10.1016/s0006-3495(00)76417-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Models for the binding of the 200-residue carboxy-terminal domain of two mutants of apolipoprotein A-I (apo A-I), apo A-I(R173C)(Milano) and apo A-I(R151C)(Paris), to lipid in discoidal high-density lipoprotein (HDL) particles are presented. In both models, two monomers of the mutant apo A-I molecule bind to lipid in an antiparallel manner, with the long axes of their helical repeats running perpendicular to the normal of the lipid bilayer to form a single disulfide-linked homodimer. The overall structures of the models of these two mutants are very similar, differing only in helix-helix registration. Thus these models are consistent with experimental observations that reconstituted HDL particles containing apo A-I(Milano) and apo A-I(Paris) are very similar in diameter to reconstituted HDL particles containing wild-type apo A-I, and they support the belief that apo A-I binds to lipid in discoidal HDL particles via the belt conformation.
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Affiliation(s)
- A E Klon
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama 35294 USA
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27
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Hayden MR, Clee SM, Brooks-Wilson A, Genest J, Attie A, Kastelein JJ. Cholesterol efflux regulatory protein, Tangier disease and familial high-density lipoprotein deficiency. Curr Opin Lipidol 2000; 11:117-22. [PMID: 10787172 DOI: 10.1097/00041433-200004000-00003] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cellular cholesterol efflux, by which cholesterol is transported from peripheral cells to HDL acceptor molecules for transport to the liver, is the first step of reverse cholesterol transport. Two genetic disorders, Tangier disease and some cases of familial HDL deficiency, have defects of cellular cholesterol efflux. The recent discovery of mutations in the ABC1 gene, which encodes the cholesterol efflux regulatory protein, in both these disorders establishes cholesterol efflux regulatory protein as a rate-limiting factor in reverse cholesterol transport.
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Affiliation(s)
- M R Hayden
- Centre for Molecular Medicine & Therapeutics, Department of Medical Genetics, University of British Columbia, Vancouver, Canada.
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