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Abstract
PURPOSE OF REVIEW This review summarizes our current understanding of the processes of apolipoprotein(a) secretion, assembly of the Lp(a) particle and removal of Lp(a) from the circulation. We also identify existing knowledge gaps that need to be addressed in future studies. RECENT FINDINGS The Lp(a) particle is assembled in two steps: a noncovalent, lysine-dependent interaction of apo(a) with apoB-100 inside hepatocytes, followed by extracellular covalent association between these two molecules to form circulating apo(a).The production rate of Lp(a) is primarily responsible for the observed inverse correlation between apo(a) isoform size and Lp(a) levels, with a contribution of catabolism restricted to larger Lp(a) isoforms.Factors that affect apoB-100 secretion from hepatocytes also affect apo(a) secretion.The identification of key hepatic receptors involved in Lp(a) clearance in vivo remains unclear, with a role for the LDL receptor seemingly restricted to conditions wherein LDL concentrations are low, Lp(a) is highly elevated and LDL receptor number is maximally upregulated. SUMMARY The key role for production rate of Lp(a) [including secretion and assembly of the Lp(a) particle] rather than its catabolic rate suggests that the most fruitful therapies for Lp(a) reduction should focus on approaches that inhibit production of the particle rather than its removal from circulation.
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Affiliation(s)
| | - Marlys L Koschinsky
- Robarts Research Institute
- Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada
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2
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Lipoprotein(a) beyond the kringle IV repeat polymorphism: The complexity of genetic variation in the LPA gene. Atherosclerosis 2022; 349:17-35. [PMID: 35606073 PMCID: PMC7613587 DOI: 10.1016/j.atherosclerosis.2022.04.003] [Citation(s) in RCA: 59] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 02/23/2022] [Accepted: 04/01/2022] [Indexed: 12/24/2022]
Abstract
High lipoprotein(a) [Lp(a)] concentrations are one of the most important genetically determined risk factors for cardiovascular disease. Lp(a) concentrations are an enigmatic trait largely controlled by one single gene (LPA) that contains a complex interplay of several genetic elements with many surprising effects discussed in this review. A hypervariable coding copy number variation (the kringle IV type-2 repeat, KIV-2) generates >40 apolipoprotein(a) protein isoforms and determines the median Lp(a) concentrations. Carriers of small isoforms with up to 22 kringle IV domains have median Lp(a) concentrations up to 5 times higher than those with large isoforms (>22 kringle IV domains). The effect of the apo(a) isoforms are, however, modified by many functional single nucleotide polymorphisms (SNPs) distributed over the complete range of allele frequencies (<0.1% to >20%) with very pronounced effects on Lp(a) concentrations. A complex interaction is present between the apo (a) isoforms and LPA SNPs, with isoforms partially masking the effect of functional SNPs and, vice versa, SNPs lowering the Lp(a) concentrations of affected isoforms. This picture is further complicated by SNP-SNP interactions, a poorly understood role of other polymorphisms such as short tandem repeats and linkage structures that are poorly captured by common R2 values. A further layer of complexity derives from recent findings that several functional SNPs are located in the KIV-2 repeat and are thus not accessible to conventional sequencing and genotyping technologies. A critical impact of the ancestry on correlation structures and baseline Lp(a) values becomes increasingly evident. This review provides a comprehensive overview on the complex genetic architecture of the Lp(a) concentrations in plasma, a field that has made tremendous progress with the introduction of new technologies. Understanding the genetics of Lp(a) might be a key to many mysteries of Lp(a) and booster new ideas on the metabolism of Lp(a) and possible interventional targets.
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Koutsogianni AD, Liberopoulos E, Tellis K, Tselepis AD. Oxidized phospholipids and lipoprotein(a): An update. Eur J Clin Invest 2022; 52:e13710. [PMID: 34837383 DOI: 10.1111/eci.13710] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Revised: 10/21/2021] [Accepted: 10/21/2021] [Indexed: 12/17/2022]
Abstract
Over the past few years, there has been an undiminished interest in lipoprotein(a) [Lp(a)] and oxidized phospholipids (OxPLs), mainly carried on this lipoprotein. Elevated Lp(a) has been established as an independent causal risk factor for cardiovascular disease. OxPLs play an important role in atherosclerosis. The main questions that remain to be answered, however, is to what extent OxPLs contribute to the atherogenicity of Lp(a), what effect hypolipidaemic medications may have on their levels and the potential clinical benefit of their reduction. This narrative review aimed to summarize currently available data on OxPLs and cardiovascular risk, as well as the effect of established and emerging hypolipidaemic medications on Lp(a)-OxPLs.
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Affiliation(s)
| | - Evangelos Liberopoulos
- Department of Internal Medicine, Faculty of Medicine, University of Ioannina, Ioannina, Greece
| | - Konstantinos Tellis
- Department of Chemistry, Atherothrombosis Research Centre/Laboratory of Biochemistry, University of Ioannina, Ioannina, Greece
| | - Alexandros D Tselepis
- Department of Chemistry, Atherothrombosis Research Centre/Laboratory of Biochemistry, University of Ioannina, Ioannina, Greece
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Reyes-Soffer G, Ginsberg HN, Berglund L, Duell PB, Heffron SP, Kamstrup PR, Lloyd-Jones DM, Marcovina SM, Yeang C, Koschinsky ML. Lipoprotein(a): A Genetically Determined, Causal, and Prevalent Risk Factor for Atherosclerotic Cardiovascular Disease: A Scientific Statement From the American Heart Association. Arterioscler Thromb Vasc Biol 2022; 42:e48-e60. [PMID: 34647487 PMCID: PMC9989949 DOI: 10.1161/atv.0000000000000147] [Citation(s) in RCA: 191] [Impact Index Per Article: 95.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
High levels of lipoprotein(a) [Lp(a)], an apoB100-containing lipoprotein, are an independent and causal risk factor for atherosclerotic cardiovascular diseases through mechanisms associated with increased atherogenesis, inflammation, and thrombosis. Lp(a) is predominantly a monogenic cardiovascular risk determinant, with ≈70% to ≥90% of interindividual heterogeneity in levels being genetically determined. The 2 major protein components of Lp(a) particles are apoB100 and apolipoprotein(a). Lp(a) remains a risk factor for cardiovascular disease development even in the setting of effective reduction of plasma low-density lipoprotein cholesterol and apoB100. Despite its demonstrated contribution to atherosclerotic cardiovascular disease burden, we presently lack standardization and harmonization of assays, universal guidelines for diagnosing and providing risk assessment, and targeted treatments to lower Lp(a). There is a clinical need to understand the genetic and biological basis for variation in Lp(a) levels and its relationship to disease in different ancestry groups. This scientific statement capitalizes on the expertise of a diverse basic science and clinical workgroup to highlight the history, biology, pathophysiology, and emerging clinical evidence in the Lp(a) field. Herein, we address key knowledge gaps and future directions required to mitigate the atherosclerotic cardiovascular disease risk attributable to elevated Lp(a) levels.
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Bourgeois R, Bourgault J, Despres AA, Perrot N, Guertin J, Girard A, Mitchell PL, Gotti C, Bourassa S, Scipione CA, Gaudreault N, Boffa MB, Koschinsky ML, Pibarot P, Droit A, Thériault S, Mathieu P, Bossé Y, Arsenault BJ. Lipoprotein Proteomics and Aortic Valve Transcriptomics Identify Biological Pathways Linking Lipoprotein(a) Levels to Aortic Stenosis. Metabolites 2021; 11:metabo11070459. [PMID: 34357353 PMCID: PMC8307014 DOI: 10.3390/metabo11070459] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/13/2021] [Accepted: 07/14/2021] [Indexed: 12/17/2022] Open
Abstract
Lipoprotein(a) (Lp(a)) is one of the most important risk factors for the development of calcific aortic valve stenosis (CAVS). However, the mechanisms through which Lp(a) causes CAVS are currently unknown. Our objectives were to characterize the Lp(a) proteome and to identify proteins that may be differentially associated with Lp(a) in patients with versus without CAVS. Our second objective was to identify genes that may be differentially regulated by exposure to high versus low Lp(a) levels in explanted aortic valves from patients with CAVS. We isolated Lp(a) from the blood of 21 patients with CAVS and 22 volunteers and performed untargeted label-free analysis of the Lp(a) proteome. We also investigated the transcriptomic signature of calcified aortic valves from patients who underwent aortic valve replacement with high versus low Lp(a) levels (n = 118). Proteins involved in the protein activation cascade, platelet degranulation, leukocyte migration, and response to wounding may be associated with Lp(a) depending on CAVS status. The transcriptomic analysis identified genes involved in cardiac aging, chondrocyte development, and inflammation as potentially influenced by Lp(a). Our multi-omic analyses identified biological pathways through which Lp(a) may cause CAVS, as well as key molecular events that could be triggered by Lp(a) in CAVS development.
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Affiliation(s)
- Raphaëlle Bourgeois
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
- Department of Medicine, Faculty of Medicine, Université Laval, Québec, QC G1V 0A6, Canada
| | - Jérôme Bourgault
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
- Department of Medicine, Faculty of Medicine, Université Laval, Québec, QC G1V 0A6, Canada
| | - Audrey-Anne Despres
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
- Department of Medicine, Faculty of Medicine, Université Laval, Québec, QC G1V 0A6, Canada
| | - Nicolas Perrot
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
- Department of Medicine, Faculty of Medicine, Université Laval, Québec, QC G1V 0A6, Canada
| | - Jakie Guertin
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
- Department of Medicine, Faculty of Medicine, Université Laval, Québec, QC G1V 0A6, Canada
| | - Arnaud Girard
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
- Department of Medicine, Faculty of Medicine, Université Laval, Québec, QC G1V 0A6, Canada
| | - Patricia L. Mitchell
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
| | - Clarisse Gotti
- Proteomics Platform of the CHU de Québec, QC G1V 4G2, Canada; (C.G.); (S.B.); (A.D.)
| | - Sylvie Bourassa
- Proteomics Platform of the CHU de Québec, QC G1V 4G2, Canada; (C.G.); (S.B.); (A.D.)
| | - Corey A. Scipione
- Toronto General Research Institute, University Health Network, Toronto, ON M5G 2C4, Canada;
| | - Nathalie Gaudreault
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
| | - Michael B. Boffa
- Robarts Research Institute, London, ON N6A 5B7, Canada; (M.B.B.); (M.L.K.)
| | | | - Philippe Pibarot
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
- Department of Medicine, Faculty of Medicine, Université Laval, Québec, QC G1V 0A6, Canada
| | - Arnaud Droit
- Proteomics Platform of the CHU de Québec, QC G1V 4G2, Canada; (C.G.); (S.B.); (A.D.)
- Centre de Recherche du CHU de Québec, Québec, QC G1V 4G2, Canada
| | - Sébastien Thériault
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
- Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Université Laval, Québec, QC G1V 0A6, Canada
| | - Patrick Mathieu
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
- Department of Surgery, Faculty of Medicine, Université Laval, Québec, QC G1V 0A6, Canada
| | - Yohan Bossé
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
- Department of Molecular Medicine, Faculty of Medicine, Université Laval, Québec, QC G1V 0A6, Canada
| | - Benoit J. Arsenault
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada; (R.B.); (J.B.); (A.-A.D.); (N.P.); (J.G.); (A.G.); (P.L.M.); (N.G.); (P.P.); (S.T.); (P.M.); (Y.B.)
- Department of Medicine, Faculty of Medicine, Université Laval, Québec, QC G1V 0A6, Canada
- Correspondence: ; Tel.: +1-418-656-8711 (ext. 3498)
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Abstract
Lipoprotein(a) [Lp(a)] is an atherogenic lipoprotein with a strong genetic regulation. Up to 90% of the concentrations are explained by a single gene, the LPA gene. The concentrations show a several-hundred-fold interindividual variability ranging from less than 0.1 mg/dL to more than 300 mg/dL. Lp(a) plasma concentrations above 30 mg/dL and even more above 50 mg/dL are associated with an increased risk for cardiovascular disease including myocardial infarction, stroke, aortic valve stenosis, heart failure, peripheral arterial disease, and all-cause mortality. Since concentrations above 50 mg/dL are observed in roughly 20% of the Caucasian population and in an even higher frequency in African-American and Asian-Indian ethnicities, it can be assumed that Lp(a) is one of the most important genetically determined risk factors for cardiovascular disease.Carriers of genetic variants that are associated with high Lp(a) concentrations have a markedly increased risk for cardiovascular events. Studies that used these genetic variants as a genetic instrument to support a causal role for Lp(a) as a cardiovascular risk factor are called Mendelian randomization studies. The principle of this type of studies has been introduced and tested for the first time ever with Lp(a) and its genetic determinants.There are currently no approved pharmacologic therapies that specifically target Lp(a) concentrations. However, some therapies that target primarily LDL cholesterol have also an influence on Lp(a) concentrations. These are mainly PCSK9 inhibitors that lower LDL cholesterol by 60% and Lp(a) by 25-30%. Furthermore, lipoprotein apheresis lowers both, Lp(a) and LDL cholesterol, by about 60-70%. Some sophisticated study designs and statistical analyses provided support that lowering Lp(a) by these therapies also lowers cardiovascular events on top of the effect caused by lowering LDL cholesterol, although this was not the main target of the therapy. Currently, new therapies targeting RNA such as antisense oligonucleotides (ASO) or small interfering RNA (siRNA) against apolipoprotein(a), the main protein of the Lp(a) particle, are under examination and lower Lp(a) concentrations up to 90%. Since these therapies specifically lower Lp(a) concentrations without influencing other lipoproteins, they will serve the last piece of the puzzle whether a decrease of Lp(a) results also in a decrease of cardiovascular events.
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Hoekstra M, Chen HY, Rong J, Dufresne L, Yao J, Guo X, Tsai MY, Tsimikas S, Post WS, Vasan RS, Rotter JI, Larson MG, Thanassoulis G, Engert JC. Genome-Wide Association Study Highlights APOH as a Novel Locus for Lipoprotein(a) Levels-Brief Report. Arterioscler Thromb Vasc Biol 2021; 41:458-464. [PMID: 33115273 PMCID: PMC7769958 DOI: 10.1161/atvbaha.120.314965] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 10/12/2020] [Indexed: 02/07/2023]
Abstract
OBJECTIVE Lp(a) (lipoprotein[a]) is an independent risk factor for cardiovascular diseases and plasma levels are primarily determined by variation at the LPA locus. We performed a genome-wide association study in the UK Biobank to determine whether additional loci influence Lp(a) levels. Approach and Results: We included 293 274 White British individuals in the discovery analysis. Approximately 93 095 623 variants were tested for association with natural log-transformed Lp(a) levels using linear regression models adjusted for age, sex, genotype batch, and 20 principal components of genetic ancestry. After quality control, 131 independent variants were associated at genome-wide significance (P≤5×10-8). In addition to validating previous associations at LPA, APOE, and CETP, we identified a novel variant at the APOH locus, encoding β2GPI (beta2-glycoprotein I). The APOH variant rs8178824 was associated with increased Lp(a) levels (β [95% CI] [ln nmol/L], 0.064 [0.047-0.081]; P=2.8×10-13) and demonstrated a stronger effect after adjustment for variation at the LPA locus (β [95% CI] [ln nmol/L], 0.089 [0.076-0.10]; P=3.8×10-42). This association was replicated in a meta-analysis of 5465 European-ancestry individuals from the Framingham Offspring Study and Multi-Ethnic Study of Atherosclerosis (β [95% CI] [ln mg/dL], 0.16 [0.044-0.28]; P=0.0071). CONCLUSIONS In a large-scale genome-wide association study of Lp(a) levels, we identified APOH as a novel locus for Lp(a) in individuals of European ancestry. Additional studies are needed to determine the precise role of β2GPI in influencing Lp(a) levels as well as its potential as a therapeutic target.
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Affiliation(s)
- Mary Hoekstra
- Division of Experimental Medicine, McGill University, Montreal, Quebec
- Preventive and Genomic Cardiology, McGill University Health Centre and Research Institute, Montreal, Quebec
| | - Hao Yu Chen
- Division of Experimental Medicine, McGill University, Montreal, Quebec
- Preventive and Genomic Cardiology, McGill University Health Centre and Research Institute, Montreal, Quebec
| | - Jian Rong
- Boston University’s and NHLBI’s Framingham Heart Study, Boston, Massachusetts
| | - Line Dufresne
- Preventive and Genomic Cardiology, McGill University Health Centre and Research Institute, Montreal, Quebec
| | - Jie Yao
- The Institute for Translational Genomics and Population Sciences, Department of Pediatrics, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California
| | - Xiuqing Guo
- The Institute for Translational Genomics and Population Sciences, Department of Pediatrics, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California
| | - Michael Y. Tsai
- Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota
| | - Sotirios Tsimikas
- Division of Cardiovascular Medicine, Sulpizio Cardiovascular Center, University of California San Diego, La Jolla, California
| | - Wendy S. Post
- Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | | | - Jerome I. Rotter
- The Institute for Translational Genomics and Population Sciences, Department of Pediatrics, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California
| | - Martin G. Larson
- Boston University’s and NHLBI’s Framingham Heart Study, Boston, Massachusetts
| | - George Thanassoulis
- Division of Experimental Medicine, McGill University, Montreal, Quebec
- Preventive and Genomic Cardiology, McGill University Health Centre and Research Institute, Montreal, Quebec
| | - James C. Engert
- Division of Experimental Medicine, McGill University, Montreal, Quebec
- Preventive and Genomic Cardiology, McGill University Health Centre and Research Institute, Montreal, Quebec
- Department of Human Genetics, McGill University, Montreal, Quebec
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Santonastaso A, Maggi M, De Jonge H, Scotti C. High resolution structure of human apolipoprotein (a) kringle IV type 2: beyond the lysine binding site. J Lipid Res 2020; 61:1687-1696. [PMID: 32907988 DOI: 10.1194/jlr.ra120001023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipoprotein (a) [Lp(a)] is characterized by an LDL-like composition in terms of lipids and apoB100, and by one copy of a unique glycoprotein, apo(a). The apo(a) structure is mainly based on the repetition of tandem kringle domains with high homology to plasminogen kringles 4 and 5. Among them, kringle IV type 2 (KIV-2) is present in a highly variable number of genetically encoded repeats, whose length is inversely related to Lp(a) plasma concentration and cardiovascular risk. Despite it being the major component of apo(a), the actual function of KIV-2 is still unclear. Here, we describe the first high-resolution crystallographic structure of this domain. It shows a general fold very similar to other KIV domains with high and intermediate affinity for the lysine analog, ε-aminocaproic acid. Interestingly, KIV-2 presents a lysine binding site (LBS) with a unique shape and charge distribution. KIV-2 affinity for predicted small molecule binders was found to be negligible in surface plasmon resonance experiments; and with the LBS being nonfunctional, we propose to rename it "pseudo-LBS". Further investigation of the protein by computational small-molecule docking allowed us to identify a possible heparin-binding site away from the LBS, which was confirmed by specific reverse charge mutations abolishing heparin binding. This study opens new possibilities to define the pathogenesis of Lp(a)-related diseases and to facilitate the design of specific therapeutic drugs.
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Affiliation(s)
- Alice Santonastaso
- Department of Molecular Medicine, Unit of Immunology and General Pathology, University of Pavia, Pavia, Italy
| | - Maristella Maggi
- Department of Molecular Medicine, Unit of Immunology and General Pathology, University of Pavia, Pavia, Italy
| | - Hugo De Jonge
- Department of Molecular Medicine, Unit of Immunology and General Pathology, University of Pavia, Pavia, Italy
| | - Claudia Scotti
- Department of Molecular Medicine, Unit of Immunology and General Pathology, University of Pavia, Pavia, Italy.
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El-Assaad F, Krilis SA, Giannakopoulos B. Posttranslational forms of beta 2-glycoprotein I in the pathogenesis of the antiphospholipid syndrome. Thromb J 2016; 14:20. [PMID: 27766046 PMCID: PMC5056467 DOI: 10.1186/s12959-016-0115-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The antiphospholipid syndrome (APS) is an autoimmune disease characterised by a procoagulant state that predisposes to recurrent thrombosis and miscarriages. Two major discoveries have advanced our understanding of the underlying complex pathogenesis of the APS. The first was the discovery that beta-2 glycoprotein-1 (β2GPI) is the major auto antigen in APS. The second was the discovery in more recent years that β2GPI contains allosteric disulphide bonds susceptible to posttranslational modification that may be involved in the development of autoantibodies in APS. The main allosteric disulphide bond in the fifth domain of β2GPI can exist in two redox states: free thiol or oxidised. It is the conformational transformation of β2GPI from its free thiol form to its more immunogenic oxidised form that exposes neo-epitopes on the first and fifth domains. The purpose of this review is to highlight the recent findings on the posttranslational forms of β2GPI in the pathogenesis of APS. We suggest that novel assays quantitating the different redox forms of β2GPI in plasma or serum may be used to supplement existing clinical and laboratory assays to more accurately stratify risk of thrombosis or miscarriage in APS patients.
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Affiliation(s)
- Fatima El-Assaad
- Department of Infectious Diseases, Immunology, and Sexual Health, St. George Hospital, Level 1, 2 South Street, Kogarah, NSW 2217 Australia ; St. George and Sutherland Clinical School, Faculty of Medicine, University of New South Wales Australia, Research and Education Centre, Level 3, 4 - 10 South St, Kogarah, NSW 2217 Australia
| | - Steven A Krilis
- Department of Infectious Diseases, Immunology, and Sexual Health, St. George Hospital, Level 1, 2 South Street, Kogarah, NSW 2217 Australia ; St. George and Sutherland Clinical School, Faculty of Medicine, University of New South Wales Australia, Research and Education Centre, Level 3, 4 - 10 South St, Kogarah, NSW 2217 Australia
| | - Bill Giannakopoulos
- Department of Infectious Diseases, Immunology, and Sexual Health, St. George Hospital, Level 1, 2 South Street, Kogarah, NSW 2217 Australia ; St. George and Sutherland Clinical School, Faculty of Medicine, University of New South Wales Australia, Research and Education Centre, Level 3, 4 - 10 South St, Kogarah, NSW 2217 Australia
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10
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Schmidt K, Noureen A, Kronenberg F, Utermann G. Structure, function, and genetics of lipoprotein (a). J Lipid Res 2016; 57:1339-59. [PMID: 27074913 DOI: 10.1194/jlr.r067314] [Citation(s) in RCA: 305] [Impact Index Per Article: 38.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Indexed: 12/29/2022] Open
Abstract
Lipoprotein (a) [Lp(a)] has attracted the interest of researchers and physicians due to its intriguing properties, including an intragenic multiallelic copy number variation in the LPA gene and the strong association with coronary heart disease (CHD). This review summarizes present knowledge of the structure, function, and genetics of Lp(a) with emphasis on the molecular and population genetics of the Lp(a)/LPA trait, as well as aspects of genetic epidemiology. It highlights the role of genetics in establishing Lp(a) as a risk factor for CHD, but also discusses uncertainties, controversies, and lack of knowledge on several aspects of the genetic Lp(a) trait, not least its function.
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Affiliation(s)
- Konrad Schmidt
- Divisions of Human Genetics Medical University of Innsbruck, Innsbruck, Austria Genetic Epidemiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Asma Noureen
- Genetic Epidemiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Florian Kronenberg
- Genetic Epidemiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Gerd Utermann
- Divisions of Human Genetics Medical University of Innsbruck, Innsbruck, Austria
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11
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Clerc F, Reiding KR, Jansen BC, Kammeijer GSM, Bondt A, Wuhrer M. Human plasma protein N-glycosylation. Glycoconj J 2015; 33:309-43. [PMID: 26555091 PMCID: PMC4891372 DOI: 10.1007/s10719-015-9626-2] [Citation(s) in RCA: 293] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 09/30/2015] [Accepted: 10/05/2015] [Indexed: 01/09/2023]
Abstract
Glycosylation is the most abundant and complex protein modification, and can have a profound structural and functional effect on the conjugate. The oligosaccharide fraction is recognized to be involved in multiple biological processes, and to affect proteins physical properties, and has consequentially been labeled a critical quality attribute of biopharmaceuticals. Additionally, due to recent advances in analytical methods and analysis software, glycosylation is targeted in the search for disease biomarkers for early diagnosis and patient stratification. Biofluids such as saliva, serum or plasma are of great use in this regard, as they are easily accessible and can provide relevant glycosylation information. Thus, as the assessment of protein glycosylation is becoming a major element in clinical and biopharmaceutical research, this review aims to convey the current state of knowledge on the N-glycosylation of the major plasma glycoproteins alpha-1-acid glycoprotein, alpha-1-antitrypsin, alpha-1B-glycoprotein, alpha-2-HS-glycoprotein, alpha-2-macroglobulin, antithrombin-III, apolipoprotein B-100, apolipoprotein D, apolipoprotein F, beta-2-glycoprotein 1, ceruloplasmin, fibrinogen, immunoglobulin (Ig) A, IgG, IgM, haptoglobin, hemopexin, histidine-rich glycoprotein, kininogen-1, serotransferrin, vitronectin, and zinc-alpha-2-glycoprotein. In addition, the less abundant immunoglobulins D and E are included because of their major relevance in immunology and biopharmaceutical research. Where available, the glycosylation is described in a site-specific manner. In the discussion, we put the glycosylation of individual proteins into perspective and speculate how the individual proteins may contribute to a total plasma N-glycosylation profile determined at the released glycan level.
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Affiliation(s)
- Florent Clerc
- Center for Proteomics and Metabolomics, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Karli R Reiding
- Center for Proteomics and Metabolomics, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Bas C Jansen
- Center for Proteomics and Metabolomics, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Guinevere S M Kammeijer
- Center for Proteomics and Metabolomics, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Albert Bondt
- Center for Proteomics and Metabolomics, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.,Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Manfred Wuhrer
- Center for Proteomics and Metabolomics, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands. .,Division of BioAnalytical Chemistry, VU University Amsterdam, Amsterdam, The Netherlands.
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12
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13
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Ma L, Wu J, Niu D, Yu R, Song J, Zhang C, Wang J. Serum lipoprotein(a) complexes with beta2-glycoprotein I levels in patients with ischemic stroke. Clin Chim Acta 2014; 429:163-7. [DOI: 10.1016/j.cca.2013.11.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 11/19/2013] [Accepted: 11/25/2013] [Indexed: 11/30/2022]
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14
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Wang C, Niu DM, Hu J, Guan XC, Yang W, Wang JJ, Zhang CY, Zhang CN. Elevated serum β2-glycoprotein-I-lipoprotein(a) complexes levels are associated with the presence and complications in type 2 diabetes mellitus. Diabetes Res Clin Pract 2013; 100:250-6. [PMID: 23549246 DOI: 10.1016/j.diabres.2013.03.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 02/16/2013] [Accepted: 03/01/2013] [Indexed: 01/30/2023]
Abstract
AIMS To examine the serum levels of β2-glycoprotein I-lipoprotein(a) complexes [β2-GPI-Lp(a)] in type 2 diabetes mellitus (T2DM) patients and evaluate the association of the complexes with complications in T2DM. METHODS Fifty two T2DM patients (22 with complications and 30 free of complications) and 52 age/gender-matched healthy controls were studied. Serum concentrations of β2-GPI-Lp(a) and ox-Lp(a) were measured by "sandwich" ELISAs and their associations with complications were examined using multiple linear regression. RESULTS Mean serum β2-GPI-Lp(a) (1.19 ± 0.30 U/mL vs. 0.89 ± 0.20 U/mL, p<0.001) and ox-Lp(a) concentrations (13.34 ± 11.73 mg/L vs. 5.26 ± 3.34 mg/L, p<0.001) were both significantly higher in T2DM than in controls. The area under the ROC curve (AUC) for β2-GPI-Lp(a) and ox-Lp(a) was 0.725 and 0.738, respectively. β2-GPI-Lp(a) levels were markedly higher in patients with complications than those without complication (1.39 ± 0.28 U/mL vs. 1.04 ± 0.31 U/mL, p<0.01), whereas no marked difference was found in ox-Lp(a). In multivariate regression analysis, the association between β2-GPI-Lp(a) and complications remained significant (β=0.249, p<0.05, respectively) after adjustments were made for other traits. CONCLUSIONS Elevated β2-GPI-Lp(a) may reflect chronic underlying pathophysiological processes involved in development of complications of T2DM.
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Affiliation(s)
- Cheng Wang
- Department of Clinical Laboratory, Jinling Hospital, Clinical School of Medicine, Nanjing University, Nanjing, People's Republic of China
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15
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Abstract
Plasma lipoprotein(a) [Lp(a)] is a quantitative genetic trait with a very broad and skewed distribution, which is largely controlled by genetic variants at the LPA locus on chromosome 6q27. Based on genetic evidence provided by studies conducted over the last two decades, Lp(a) is currently considered to be the strongest genetic risk factor for coronary heart disease (CHD). The copy number variation of kringle IV in the LPA gene has been strongly associated with both Lp(a) levels in plasma and risk of CHD, thereby fulfilling the main criterion for causality in a Mendelian randomization approach. Alleles with a low kringle IV copy number that together have a population frequency of 25-35% are associated with a doubling of the relative risk for outcomes, which is exceptional in the field of complex genetic phenotypes. The recently identified binding of oxidized phospholipids to Lp(a) is considered as one of the possible mechanisms that may explain the pathogenicity of Lp(a). Drugs that have been shown to lower Lp(a) have pleiotropic effects on other CHD risk factors, and an improvement of cardiovascular endpoints is up to now lacking. However, it has been established in a proof of principle study that lowering of very high Lp(a) by apheresis in high-risk patients with already maximally reduced low-density lipoprotein cholesterol levels can dramatically reduce major coronary events.
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Affiliation(s)
- F Kronenberg
- Division of Genetic Epidemiology, Innsbruck Medical University, Innsbruck, Austria
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16
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Zhang C, Li X, Niu D, Zi R, Wang C, Han A, Wang X, Li K, Wang J. Increased serum levels of β₂-GPI-Lp(a) complexes and their association with premature atherosclerosis in patients with rheumatoid arthritis. Clin Chim Acta 2011; 412:1332-6. [PMID: 21473861 DOI: 10.1016/j.cca.2011.03.029] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2010] [Revised: 03/26/2011] [Accepted: 03/28/2011] [Indexed: 11/17/2022]
Abstract
BACKGROUND Our recent study found the existence of complexes of β₂-glycoprotein I (β₂-GPI) with lipoprotein(a)[Lp(a)] in circulation and the complex concentrations were increased in sera of systemic lupus erythematosus patients. The concentration of β₂-GPI-Lp(a) and its relationship with premature atherosclerosis were evaluated in rheumatoid arthritis (RA) patients. METHODS Serum concentrations of β₂-GPI-Lp(a) were measured in 53 active RA patients and 40 healthy controls by a "sandwich" ELISA. β₂-GPI-ox-LDL, ox-Lp(a), ox-LDL and anti-β₂-GPI were also measured by ELISAs. In addition, inflammatory markers were examined. RESULTS Serum β₂-GPI-Lp(a) (1.12±0.25 U/ml vs. 0.87±0.19 U/ml, P<0.0001) and β₂-GPI-ox-LDL (1.01±0.20 U/ml vs. 0.80±0.08 U/ml, P<0.0001) concentrations in RA were both significantly higher than those of controls. Ox-Lp(a) (8.38±6.69 mg/l vs. 5.49±4.31 mg/l, P<0.05) and ox-LDL (0.68±0.65 mg/l vs. 0.37±0.13 mg/l, P=0.001) were also higher in RA than in controls. The area under the ROC curve (AUC) for β₂-GPI-Lp(a) (0.787) was larger than for ox-Lp(a) (0.731). AUC of β₂-GPI-ox-LDL (0.858) was also larger than for ox-LDL (0.785). β₂-GPI-Lp(a) and β₂-GPI-ox-LDL were positively correlated with ox-Lp(a), ox-LDL and CRP, respectively. CONCLUSIONS β₂-GPI-Lp(a) complex concentrations increased in active RA. Inflammation and oxidative stress in RA contribute to the increase of ox-Lp(a) and subsequently the formation of β₂-GPI-Lp(a).
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Affiliation(s)
- Chunni Zhang
- Department of Biochemistry, Jinling Hospital, Clinical School of Medical College, Nanjing University, 210002 Nanjing, PR China
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17
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Zhang C, Li K, Shi B, Wang X, Liu X, Qin W, Han A, Wang J. Detection of serum β2-GPI–Lp(a) complexes in patients with systemic lupus erythematosus. Clin Chim Acta 2010; 411:395-9. [DOI: 10.1016/j.cca.2009.12.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Revised: 12/03/2009] [Accepted: 12/09/2009] [Indexed: 11/29/2022]
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18
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Della Donna L, Ronci M, Sacchetta P, Di Ilio C, Biolatti B, Federici G, Nebbia C, Urbani A. A food safety control low mass-range proteomics platform for the detection of illicit treatments in veal calves by MALDI-TOF-MS serum profiling. Biotechnol J 2009; 4:1596-609. [DOI: 10.1002/biot.200900085] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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19
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Bu C, Gao L, Xie W, Zhang J, He Y, Cai G, McCrae KR. beta2-glycoprotein i is a cofactor for tissue plasminogen activator-mediated plasminogen activation. ACTA ACUST UNITED AC 2009; 60:559-68. [PMID: 19180513 DOI: 10.1002/art.24262] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
OBJECTIVE Regulation of the conversion of plasminogen to plasmin by tissue plasminogen activator (tPA) is critical in the control of fibrin deposition. While several plasminogen activators have been described, soluble plasma cofactors that stimulate fibrinolysis have not been characterized. The purpose of this study was to investigate the effects of beta(2)-glycoprotein I (beta(2)GPI), an abundant plasma glycoprotein, on tPA-mediated plasminogen activation. METHODS The effect of beta(2)GPI on tPA-mediated activation of plasminogen was assessed using amidolytic assays, a fibrin gel, and plasma clots. Binding of beta(2)GPI to tPA and plasminogen was determined in parallel. The effects of IgG fractions and anti-beta(2)GPI antibodies from patients with antiphospholipid syndrome (APS) on tPA-mediated plasminogen activation were also measured. RESULTS Beta(2)-glycoprotein I stimulated tPA-dependent plasminogen activation in the fluid phase and within a fibrin gel. The beta(2)GPI region responsible for stimulating tPA activity was shown to be at least partly contained within beta(2)GPI domain V. In addition, beta(2)GPI bound tPA with high affinity (K(d) approximately 20 nM), stimulated tPA amidolytic activity, and caused an overall 20-fold increase in the catalytic efficiency (K(cat)/K(m)) of tPA-mediated conversion of Glu-plasminogen to plasmin. Moreover, depletion of beta(2)GPI from plasma led to diminished rates of clot lysis, with restoration of normal lysis rates following beta(2)GPI repletion. Stimulation of tPA-mediated plasminogen activity by beta(2)GPI was inhibited by monoclonal anti-beta(2)GPI antibodies as well as by anti-beta(2)GPI antibodies from patients with APS. CONCLUSION These findings suggest that beta(2)GPI may be an endogenous regulator of fibrinolysis. Impairment of beta(2)GPI-stimulated fibrinolysis by anti-beta(2)GPI antibodies may contribute to the development of thrombosis in patients with APS.
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Affiliation(s)
- Chunya Bu
- Tsinghua University, Shenzhen, China
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20
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Tsimikas S, Tsironis LD, Tselepis AD. New Insights Into the Role of Lipoprotein(a)-Associated Lipoprotein-Associated Phospholipase A
2
in Atherosclerosis and Cardiovascular Disease. Arterioscler Thromb Vasc Biol 2007; 27:2094-9. [PMID: 17626905 DOI: 10.1161/01.atv.0000280571.28102.d4] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Lipoprotein(a) [Lp(a)] plays an important role in atherosclerosis. The biological effects of Lp(a) have been attributed either to apolipoprotein(a) or to its low-density lipoprotein-like particle. Lp(a) contains platelet-activating factor acetylhydrolase, an enzyme that exhibits a Ca
2+
-independent phospholipase A
2
activity and is complexed to lipoproteins in plasma; thus, it is also referred to as lipoprotein-associated phospholipase A
2
. Substrates for lipoprotein-associated phospholipase A
2
include phospholipids containing oxidatively fragmented residues at the
sn-2
position (oxidized phospholipids; OxPLs). OxPLs may play important roles in vascular inflammation and atherosclerosis. Plasma levels of OxPLs present on apolipoprotein B-100 particles (OxPL/apolipoprotein B) are correlated with coronary artery, carotid, and peripheral arterial disease. Furthermore, OxPL/apolipoprotein B levels in plasma are strongly correlated with Lp(a) levels, are preferentially sequestered on Lp(a), and thus are potentially subjected to degradation by the Lp(a)-associated lipoprotein-associated phospholipase A
2
. The present review article focuses specifically on the characteristics of the lipoprotein-associated phospholipase A
2
associated with Lp(a) and discusses the possible role of this enzyme in view of emerging data showing that OxPLs in plasma are preferentially sequestered on Lp(a) and may significantly contribute to the increased atherogenicity of this lipoprotein.
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Affiliation(s)
- Sotirios Tsimikas
- Department of Medicine, University of California San Diego, La Jolla, Calif, USA
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21
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López-Lira F, Rosales-León L, Martínez VM, Ruiz Ordaz BH. The role of β2-glycoprotein I (β2GPI) in the activation of plasminogen. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2006; 1764:815-23. [PMID: 16480936 DOI: 10.1016/j.bbapap.2005.12.020] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2005] [Revised: 12/21/2005] [Accepted: 12/22/2005] [Indexed: 10/25/2022]
Abstract
Beta2-glycoprotein I (beta2GPI) is a glycoprotein of unknown physiological function. It is the main target antigen for antiphospholipid antibodies in patients with antiphospholipid syndrome (APS). beta2GPI binds with high affinity to the atherogenic lipoprotein Lp(a) which shares structural homology with plasminogen, a key molecule in the fibrinolytic system. Impaired fibrinolysis has been described in APS. The present work reports the interaction between beta2GPI and Glu-Plasminogen which may explain the recently described proteolytic effect of plasmin on beta2GPI. In the process of Glu-Plasminogen activation, we found an increase in plasmin generation both at fibrin and cellular surface level as a function of the concentration of beta2GPI added, suggesting an important role as a cofactor in the trimolecular complex beta2GPI-Plasminogen-tPA. This phenomenon represents a novel regulatory step both in the positive feedback mechanism for extrinsic fibrinolysis and in antithrombotic regulation. IgG anti-beta2GPI antibodies recognized the beta2GPI at the endothelial surface inducing its activation with an increase of ICAM-I and a decrease in the expression of thrombomodulin favoring a pro-thrombotic state in the vascular endothelium. The interference in the plasmin conversion by anti-beta2GPI antibodies could generate thrombosis as observed in APS.
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Affiliation(s)
- Francisco López-Lira
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, UNAM, Ciudad Universitaria 04510, México, D.F., Mexico
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22
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D'Angelo A, Geroldi D, Hancock MA, Valtulina V, Cornaglia AI, Spencer CA, Emanuele E, Calligaro A, Koschinsky ML, Speziale P, Visai L. The apolipoprotein(a) component of lipoprotein(a) mediates binding to laminin: contribution to selective retention of lipoprotein(a) in atherosclerotic lesions. Biochim Biophys Acta Mol Cell Biol Lipids 2005; 1687:1-10. [PMID: 15708348 DOI: 10.1016/j.bbalip.2004.10.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2004] [Revised: 10/08/2004] [Accepted: 10/14/2004] [Indexed: 11/16/2022]
Abstract
Lipoprotein(a) [Lp(a)] entrapment by vascular extracellular matrix may be important in atherogenesis. We sought to determine whether laminin, a major component of the basal membrane, may contribute to Lp(a) retention in the arterial wall. First, immunohistochemistry experiments were performed to examine the relative distribution of Lp(a) and laminin in human carotid artery specimens. There was a high degree of co-localization of Lp(a) and laminin in atherosclerotic specimens, but not in non-atherosclerotic sections. We then studied the binding interaction between Lp(a) and laminin in vitro. ELISA experiments showed that native Lp(a) particles and 17K and 12K recombinant apolipoprotein(a) [r-apo(a)] variants interacted strongly with laminin whereas LDL, apoB-100, and the truncated KIV(6-P), KIV(8-P), and KIV(9-P) r-apo(a) variants did not. Overall, the ELISA data demonstrated that Lp(a) binding to laminin is mediated by apo(a) and a combination of the lysine analogue epsilon-aminocaproic acid and salt effectively decreases apo(a) binding to laminin. Secondary binding analyses with 125I-labeled r-apo(a) revealed equilibrium dissociation constants (K(d)) of 180 and 360 nM for the 17K and 12K variants binding to laminin, respectively. Such similar K(d) values between these two r-apo(a) variants suggest that isoform size does not appear to influence apo(a) binding to laminin. In summary, our data suggest that laminin may bind to apo(a) in the atherosclerotic intima, thus contributing to the selective retention of Lp(a) in this milieu.
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Affiliation(s)
- Angela D'Angelo
- Molecular Medicine Laboratory, University of Pavia, IRCCS Policlinico San Matteo, Piazzale Golgi 2, Pavia, Italy
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23
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Tsironis LD, Katsouras CS, Lourida ES, Mitsios JV, Goudevenos J, Elisaf M, Tselepis AD. Reduced PAF-acetylhydrolase activity associated with Lp(a) in patients with coronary artery disease. Atherosclerosis 2004; 177:193-201. [PMID: 15488884 DOI: 10.1016/j.atherosclerosis.2004.07.030] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2003] [Revised: 06/18/2004] [Accepted: 07/16/2004] [Indexed: 11/18/2022]
Abstract
Lipoprotein(a) [Lp(a)] may be an independent risk factor for coronary artery disease (CAD). Lp(a) is enriched in platelet activating factor acetylhydrolase (PAF-AH), an enzyme which hydrolyzes and inactivates platelet activating factor (PAF) and oxidized phospholipids that are implicated in atherogenesis. We determined the mass and catalytic properties of the Lp(a)-associated PAF-AH in 28 CAD patients in relation to the LDL-associated enzyme ones. Results were then compared to those of 30 control subjects and 16 unrelated patients with primary hypercholesterolemia (Type IIA dyslipidemia) before and after atorvastatin therapy. The mass, the specific activity and kinetic constants of the Lp(a)-associated PAF-AH were significantly lower in CAD patients compared to those of either controls or hypercholesterolemic patients, a phenomenon not observed for LDL-associated PAF-AH. The enzyme specific activity and kinetic constants were significantly increased after removal of apo(a) from Lp(a) by reductive cleavage, which was not found in the control population, suggesting that the apo(a) moiety of Lp(a) from CAD patients may play an important role in the observed lower catalytic efficiency of PAF-AH. The reduced PAF-AH mass and specific activity on Lp(a) is a feature characteristic of this lipoprotein in CAD patients and may lead to a diminished capability of Lp(a) to degrade proinflammatory phospholipids. The consequences of this phenomenon as regards the pathophysiological role of Lp(a) in atherosclerosis remain to be established.
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Affiliation(s)
- Loukas D Tsironis
- Laboratory of Biochemistry, Department of Chemistry, Medical School, University of Ioannina, 45110 Ioannina, Greece
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Miyakis S, Robertson SA, Krilis SA. Beta-2 glycoprotein I and its role in antiphospholipid syndrome—lessons from knockout mice. Clin Immunol 2004; 112:136-43. [PMID: 15240156 DOI: 10.1016/j.clim.2004.02.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2004] [Accepted: 02/27/2004] [Indexed: 10/26/2022]
Abstract
The antiphospholipid syndrome is characterized by the presence in serum of autoantibodies against beta2GPI. Although the role of beta2GPI in the pathogenesis of antiphospholipid antibody syndrome (APS) is well recognized, its exact physiological functions still remain undisclosed. Several interactions of beta2GPI with components of the coagulation cascade have been proposed, resulting in both procoagulant and anticoagulant effects. Additionally, beta2GPI has been implicated in the mechanism of recurrent fetal loss entailed in APS. Recently, using a homologous recombination approach, reproduction of mice homozygous for deletion of the beta2GPI gene has been feasible. beta2GPI knockout mice offer a valuable tool for revealing the physiological role of the protein. These mice show decreased in vitro ability for thrombin generation. Furthermore, although mice lacking beta2GPI are fertile, the success of early pregnancy is moderately compromised and functional beta2GPI is believed necessary for optimal implantation and placental morphogenesis.
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Affiliation(s)
- Spiros Miyakis
- Department of Immunology, Allergy and Infectious Disease, St. George Hospital, University of New South Wales, Kogarah, NSW 2217, Australia
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25
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Koschinsky ML, Marcovina SM. Structure-function relationships in apolipoprotein(a): insights into lipoprotein(a) assembly and pathogenicity. Curr Opin Lipidol 2004; 15:167-74. [PMID: 15017359 DOI: 10.1097/00041433-200404000-00009] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
PURPOSE OF REVIEW Lipoprotein(a) is a structurally and functionally unique lipoprotein consisting of the glycoprotein apolipoprotein(a) covalently linked to LDL. Lipoprotein(a) is assembled extracellularly by a two-step mechanism, still incompletely understood, in which initial non-covalent interactions between apolipoprotein(a) and apolipoprotein B precede specific disulfide bond formation. Elevated concentrations of plasma lipoprotein(a) are a risk factor for a variety of vascular diseases, including coronary heart disease, ischaemic stroke and venous thrombosis. Whereas many pathogenic mechanisms have been proposed for lipoprotein(a), it remains to be conclusively demonstrated which mechanisms are relevant to human disease. RECENT FINDINGS Structural and functional studies have verified that apolipoprotein(a) kringle 4 types 6-8 contain lysine binding sites of a weaker affinity for lysine analogues than kringle 4 type 10. Recent evidence has conclusively shown a role for kringle 4 types 7 and 8 in lipoprotein(a) assembly. Moreover, apolipoprotein(a) has been shown to undergo a conformational change, from a closed to an open form, which accelerates the rate of covalent lipoprotein(a) assembly. Functional studies in vitro have identified the domains in apolipoprotein(a) that mediate its inhibitory effects on fibrin clot lysis, binding to fibrin and other biological substrates, and pro-inflammatory and anti-angiogenic properties. SUMMARY Extensive structure-function studies of apolipoprotein(a) have begun to yield important insights into the domains in apolipoprotein(a) that mediate lipoprotein(a) assembly and the pathogenic effects of this lipoprotein. Continued investigations of these relationships will contribute critically to unravelling the many outstanding questions about lipoprotein(a) metabolism and pathophysiology.
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26
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Miyakis S, Giannakopoulos B, Krilis SA. Beta 2 glycoprotein I-function in health and disease. Thromb Res 2004; 114:335-46. [PMID: 15507263 DOI: 10.1016/j.thromres.2004.07.017] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2004] [Revised: 07/18/2004] [Accepted: 07/23/2004] [Indexed: 10/26/2022]
Abstract
Beta-2 glycoprotein I (beta2GPI) is the principal target of autoantibodies in the antiphospholipid syndrome (APS). It is abundant in human plasma and shares high homology between different mammalian species. Although the exact physiological function of beta2GPI has not been fully elucidated, several interactions have been described with other proteins and with negatively charged surfaces, such as anionic phospholipids, dextran and heparin. beta2GPI is involved in the coagulation pathway, exerting both procoagulant and anticoagulant activities. Plasma from beta2GPI-deficient mice exhibits impaired thrombin generation in vitro. Recently, it has been demonstrated that beta2GPI binds factor (F) XI in vitro at concentrations lower than those of the protein in human plasma, and this binding inhibits FXI activation to FXIa by thrombin and FXIIa. Proteolytic cleavage of the fifth domain of beta2GPI abolishes its inhibition of FXI activation and results in reduced ability of the cleaved beta2GPI to bind phospholipids. It retains its ability to bind FXI. In vivo activation of FXI by thrombin is thought to be an important mechanism by which coagulation is accelerated via components of the contact activation pathway. Thus beta2GPI may attenuate the contact activation pathway by inhibiting activation of FXI by thrombin. Moreover, because beta2GPI is the dominant autoantigen in patients with APS, dysregulation of this pathway by autoantibodies may be an important mechanism for thrombosis in patients with APS.
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Affiliation(s)
- Spiros Miyakis
- Department of Immunology, Allergy and Infectious Diseases, University of New South Wales, St. George Hospital, 2 South Street, Kogarah, NSW 2217, Australia
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Gao PJ, Piao YF, Liu XD, Qu LK, Shi Y, Wang XC, Yang HY. Studies on specific interaction of beta-2-glycoprotein I with HBsAg. World J Gastroenterol 2003; 9:2114-6. [PMID: 12970918 PMCID: PMC4656686 DOI: 10.3748/wjg.v9.i9.2114] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To observe the binding activity of beta-2-glycoprotein I (β2GPI) to hepatitis B surface antigen (HBsAg) and the possible roles of β2GPI in hepatitis B virus (HBV) infection.
METHODS: The rationale of ELISA methods and ELISA-based research method and ligand-blotting technique were used to detect the specific interaction of β2GPI with HBsAg.
RESULTS: With the increase of rHBsAg, the binding of β2GPI to rHBsAg elevated, and these changes had statistic significance. When we added non-biotinlyated β2GPI, the OD value significantly decreased though they still were positively relevant to rHBsAg, suggesting non-biotinlyated β2GPI competed with biotinlyated β2GPI to saturate the binding sites on rHBsAg. Meanwhile BSA was used as negative control to substitute for rHBsAg coating the plates. The results indicated no interaction between β2GPI and BSA, suggesting the affinity of β2GPI to rHBsAg was specific. The ligand blotling indicated that β2GPI might bind to rHBsAg no matter whether it was under reduced condition or not.
CONCLUSION: The binding of β2GPI to HBsAg suggests that β2GPI may be a carrier of HBV and that β2GPI may play important roles in HBV infection.
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Affiliation(s)
- Pu-Jun Gao
- Department of Digestion, 1st Hospital affiliated to Jilin University, Changchun 130021, Jilin Province, China.
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28
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Abstract
Lipoprotein(a) is a cholesterol-enriched lipoprotein, consisting of a covalent linkage joining the unique and highly polymorphic apolipoprotein(a) to apolipoprotein B100, the main protein moiety of low-density lipoproteins. Although the concentration of lipoprotein(a) in humans is mostly genetically determined, acquired disorders might influence synthesis and catabolism of the particle. Raised concentration of lipoprotein(a) has been acknowledged as a leading inherited risk factor for both premature and advanced atherosclerosis at different vascular sites. The strong structural homologies with plasminogen and low-density lipoproteins suggest that lipoprotein(a) might represent the ideal bridge between the fields of atherosclerosis and thrombosis in the pathogenesis of vascular occlusive disorders. Unfortunately, the exact mechanisms by which lipoprotein(a) promotes, accelerates, and complicates atherosclerosis are only partially understood. In some clinical settings, such as in patients at exceptionally low risk for cardiovascular disease, the potential regenerative and antineoplastic properties of lipoprotein(a) might paradoxically counterbalance its athero-thrombogenicity, as attested by the compatibility between raised plasma lipoprotein(a) levels and longevity.
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Affiliation(s)
- Giuseppe Lippi
- Istituto di Chimica e Microscopia Clinica, Dipartimento di Scienze Morfologiche e Biomediche, Università degli Studi di Verona, Verona, Italy
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29
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Font J, Espinosa G, Tàssies D, Pino M, Khamashta MA, Gallart T, Cervera R, Escolar G, Hughes GRV, Ingelmo M, Ordinas A, Reverter JC. Effects of beta2-glycoprotein I and monoclonal anticardiolipin antibodies in platelet interaction with subendothelium under flow conditions. ARTHRITIS AND RHEUMATISM 2002; 46:3283-9. [PMID: 12483733 DOI: 10.1002/art.10634] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE To evaluate whether the effect of human monoclonal anticardiolipin antibodies (aCL) on platelet interaction with the subendothelium under flow conditions is dependent on beta(2)-glycoprotein I (beta(2)GPI). METHODS Three monoclonal IgM aCL with anti-beta(2)GPI activity (TM1B3, GR1D5, and EY2C9) obtained from patients with antiphospholipid syndrome, a monoclonal aCL with lupus anticoagulant activity but without anti-beta(2)GPI activity (FRO) obtained from a patient with a splenic lymphoma, and a control monoclonal IgM without aCL activity were used. TM1B3, GR1D5, EY2C9, FRO, and control IgM (30 microg/ml) were added to reconstituted blood containing gel-filtered platelets (200 x 10(9)/liter), factor VIII (100 units/dl), and fibrinogen (1.5 gm/liter). Samples were perfused (wall-shear rate 800 seconds(-1)), with and without the addition of purified beta(2)GPI (20 microg/ml), through annular chambers containing collagen-rich denuded vascular segments, and the percentages of surface covered by platelets and by thrombi were evaluated. RESULTS No differences in the percentages of surface covered by platelets and by thrombi were observed among samples with TM1B3, GR1D5, EY2C9, FRO, and control IgM added when reconstituted blood samples without beta(2)GPI were used. However, a significant increase in the percentage of surface covered by platelets was observed in the presence of TM1B3, GR1D5, and EY2C9 but not in the presence of FRO when samples containing beta(2)GPI were used. Increased thrombi formation was induced by TM1B3 and GR1D5 but not by EY2C9 or FRO in samples with added beta(2)GPI. CONCLUSION Monoclonal aCL require anti-beta(2)GPI activity to promote platelet interaction with the subendothelium under flow conditions.
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Affiliation(s)
- Josep Font
- Hospital Clinic and Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
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30
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Gaubatz JW, Hoogeveen RC, Hoffman AS, Ghazzaly KG, Pownall HJ, Guevara J, Koschinsky ML, Morrisett JD. Isolation, quantitation, and characterization of a stable complex formed by Lp[a] binding to triglyceride-rich lipoproteins. J Lipid Res 2001. [DOI: 10.1016/s0022-2275(20)31535-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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31
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Koutroubakis IE, Malliaraki N, Vardas E, Ganotakis E, Margioris AN, Manousos ON, Kouroumalis EA. Increased levels of lipoprotein (a) in Crohn's disease: a relation to thrombosis? Eur J Gastroenterol Hepatol 2001; 13:1415-9. [PMID: 11742189 DOI: 10.1097/00042737-200112000-00004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
OBJECTIVE Lipoprotein (a) is recognized as a risk factor for arterial and venous thrombosis, a property that might be related to its structural similarity to plasminogen. Since patients with inflammatory bowel disease frequently suffer from thromboembolic events, we studied the role of lipoprotein (a) in conjunction with lipids and apolipoproteins in Greek patients with ulcerative colitis and Crohn's disease. METHODS Lipoprotein (a), total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, apolipoprotein A-1 and apolipoprotein B-100 were determined in sera from 129 consecutive fasting Greek patients with inflammatory bowel disease (66 with ulcerative colitis and 63 with Crohn's disease) and from 66 matched healthy controls. RESULTS In Crohn's disease patients, the mean serum lipoprotein (a) level was significantly higher than in control patients (41.2 mg/dl vs 22.9 mg/dl; P = 0.005). Mean apolipoprotein A-1 and apolipoprotein B-100 levels were significantly lower in Crohn's disease patients than in the controls. In ulcerative colitis patients the mean levels of lipoprotein (a) and apolipoprotein A-1 were not significantly different to the controls, but the levels of apolipoprotein B-100 were significantly lower. Raised levels of lipoprotein (a) of > 30 mg/dl were found in 29 Crohn's disease patients (46%), 15 ulcerative colitis patients (23%) and 11 control patients (17%). Patients with active Crohn's disease had significantly higher mean lipoprotein (a) and lower apolipoprotein A-1 than patients with non-active disease. CONCLUSIONS Our results suggest that Crohn's disease patients have different lipoprotein (a) and apolipoprotein patterns compared to ulcerative colitis patients and healthy controls. These changes in Crohn's disease patients may possibly expose them to a higher risk of thrombosis.
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Affiliation(s)
- I E Koutroubakis
- Department of Gastroenterology, University Hospital Heraklion, Crete, Greece.
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32
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Abstract
Novel risk factors for the progression of atherosclerosis such as C-reactive protein (CRP) and adhesion molecules have stimulated much recent interest in the role of inflammation in atherosclerotic disease. There is also evidence emerging that autoimmunity may have a role in the pathogenesis of atherosclerosis. In this article we explore the evidence for the role of autoimmunity in human atherosclerosis, both in the general population and in the context of the antiphospholipid syndrome. In particular we will focus on several autoantigens, review the evidence for their role in the process of atherosclerosis and the nature of the immune responses.
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Affiliation(s)
- P A Gordon
- Lupus Research Unit, Rayne Institute, St Thomas' Hospital, London, UK.
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33
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Kobayashi K, Matsuura E, Liu Q, Furukawa JI, Kaihara K, Inagaki J, Atsumi T, Sakairi N, Yasuda T, Voelker DR, Koike T. A specific ligand for β2-glycoprotein I mediates autoantibody-dependent uptake of oxidized low density lipoprotein by macrophages. J Lipid Res 2001. [DOI: 10.1016/s0022-2275(20)31631-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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34
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Sheng Y, Reddel SW, Herzog H, Wang YX, Brighton T, France MP, Robertson SA, Krilis SA. Impaired thrombin generation in beta 2-glycoprotein I null mice. J Biol Chem 2001; 276:13817-21. [PMID: 11145969 DOI: 10.1074/jbc.m010990200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Autoimmune antibodies to beta(2)-glycoprotein I (beta2GPI) have been proposed to be clinically relevant because of their strong association with thrombosis, miscarriage, and thrombocytopenia. By using a homologous recombination approach, beta2GPI-null mice were generated to begin to understand the physiologic and pathologic role of this prominent plasma protein in mammals. When beta2GPI heterozygotes on a 129/Sv/C57BL/6 mixed genetic background were intercrossed, only 8.9% of the resulting 336 offspring possessed both disrupted alleles. These data suggest that beta2GPI plays a beneficial role in implantation and/or fetal development in at least some mouse strains. Although those beta2GPI-null mice that were born appeared to be relatively normal anatomically and histologically, subsequent analysis revealed that they possessed an impaired in vitro ability to generate thrombin relative to wild type mice. Thus, beta2GPI also appears to play an important role in thrombin-mediated coagulation.
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Affiliation(s)
- Y Sheng
- Department of Medicine and the Department of Immunology, Allergy, and Infectious Disease, University of New South Wales, The St. George Hospital, Sydney, New South Wales 2217, Australia
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35
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Klose R, Fresser F, Kochl S, Parson W, Kapetanopoulos A, Fruchart-Najib J, Baier G, Utermann G. Mapping of a minimal apolipoprotein(a) interaction motif conserved in fibrin(ogen) beta - and gamma -chains. J Biol Chem 2000; 275:38206-12. [PMID: 10980194 DOI: 10.1074/jbc.m003640200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lipoprotein(a) (Lp(a)) is a major independent risk factor for atherothrombotic disease in humans. The physiological function(s) of Lp(a) as well as the precise mechanism(s) by which high plasma levels of Lp(a) increase risk are unknown. Binding of apolipoprotein(a) (apo(a)) to fibrin(ogen) and other components of the blood clotting cascade has been demonstrated in vitro, but the domains in fibrin(ogen) critical for interaction are undefined. We used apo(a) kringle IV subtypes to screen a human liver cDNA library by the yeast GAL4 two-hybrid interaction trap system. Among positive clones that emerged from the screen, clones were identified as fibrinogen beta- and gamma-chains. Peptide-based pull-down experiments confirmed that the emerging peptide motif, conserved in the carboxyl-terminal globular domains of the fibrinogen beta and gamma modules specifically interacts with apo(a)/Lp(a) in human plasma as well as in cell culture supernatants of HepG2 and Chinese hamster ovary cells, ectopically expressing apo(a)/Lp(a). The influence of lysine in the fibrinogen peptides and of lysine binding sites in apo(a) for the interaction was evaluated by binding experiments with apo(a) mutants and a mutated fibrin(ogen) peptid. This confirmed the lysine binding sites in kringle IV type 10 of apo(a) as the major fibrin(ogen) binding site but also demonstrated lysine-independent interactions.
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Affiliation(s)
- R Klose
- Institute for Medical Biology and Human Genetics, Universität Innsbruck, 6020 Innsbruck, Austria
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36
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Yasuda S, Tsutsumi A, Chiba H, Yanai H, Miyoshi Y, Takeuchi R, Horita T, Atsumi T, Ichikawa K, Matsuura E, Koike T. beta(2)-glycoprotein I deficiency: prevalence, genetic background and effects on plasma lipoprotein metabolism and hemostasis. Atherosclerosis 2000; 152:337-46. [PMID: 10998461 DOI: 10.1016/s0021-9150(99)00496-7] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
beta(2)-glycoprotein I (beta(2)-GPI=apolipoprotein H) is an important autoantigen in patients with the antiphospholipid syndrome. It also plays a role in lipoprotein metabolism, such as anti-atherogenic property, triglyceride removal, and enhancement of lipoprotein lipase. Serum beta(2)-GPI concentration of 812 apparently healthy Japanese individuals was measured by sandwich EIA. Two families with complete beta(2)-GPI deficiency were identified. In one family, all affected had increased serum LDL-cholesterol levels or smaller particle sizes of LDL, while the other had no apparent abnormality in lipid metabolism. Individuals investigated had no history of thrombosis or overt abnormalities in hemostatic tests. A thymine corresponding to position 379 of the beta(2)-GPI cDNA was deleted in every beta(2)-GPI deficient individual. The incidence of this heterozygous deficiency determined by RFLP was 6. 3% in Japanese and none in Caucasians. Heterozygotes had significantly lower concentrations of serum beta(2)-GPI than did those without the mutation, yet no significantly different lipid profiles, such as total cholesterol, triglyceride, HDL-cholesterol, LDL-cholesterol, apoA-I, apoB and Lp(a), were observed. A low concentration of beta(2)-GPI seemed not to be associated with apparent abnormality in lipoprotein metabolism.
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Affiliation(s)
- S Yasuda
- Department of Medicine II, Hokkaido University School of Medicine, Kita15, Nishi 7, Kita-ku, 060-8635, Sapporo, Japan
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37
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Ma K, Simantov R, Zhang JC, Silverstein R, Hajjar KA, McCrae KR. High affinity binding of beta 2-glycoprotein I to human endothelial cells is mediated by annexin II. J Biol Chem 2000; 275:15541-8. [PMID: 10809787 DOI: 10.1074/jbc.275.20.15541] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Beta(2)-glycoprotein I (beta(2)GPI) is an abundant plasma phospholipid-binding protein and an autoantigen in the antiphospholipid antibody syndrome. Binding of beta(2)GPI to endothelial cells targets them for activation by anti-beta(2)GPI antibodies, which circulate and are associated with thrombosis in patients with the antiphospholipid antibody syndrome. However, the binding of beta(2)GPI to endothelial cells has not been characterized and is assumed to result from association of beta(2)GPI with membrane phospholipid. Here, we characterize the binding of beta(2)GPI to endothelial cells and identify the beta(2)GPI binding site. (125)I-beta(2)GPI bound with high affinity (K(d) approximately 18 nm) to human umbilical vein endothelial cells (HUVECs). Using affinity purification, we isolated beta(2)GPI-binding proteins of approximately 78 and approximately 36 kDa from HUVECs and EAHY.926 cells. Amino acid sequences of tryptic peptides from each of these were identical to sequences within annexin II. A role for annexin II in binding of beta(2)GPI to cells was confirmed by the observations that annexin II-transfected HEK 293 cells bound approximately 10-fold more (125)I-beta(2)GPI than control cells and that anti-annexin II antibodies inhibited the binding of (125)I-beta(2)GPI to HUVECs by approximately 90%. Finally, surface plasmon resonance studies revealed high affinity binding between annexin II and beta(2)GPI. These results demonstrate that annexin II mediates the binding of beta(2)GPI to endothelial cells.
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Affiliation(s)
- K Ma
- Hematology-Oncology Division, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4937, USA
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38
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Abstract
Lipoprotein(a) is an atherogenic, cholesterol ester-rich lipoprotein of unknown physiological function. The unusual species distribution of lipoprotein(a) and the extreme polymorphic nature of its distinguishing apolipoprotein component, apolipoprotein(a), have provided unique challenges for the investigation of its biochemistry, genetics, metabolism and atherogenicity. Some fundamental questions regarding this enigmatic lipoprotein have escaped elucidation, as will be highlighted in this review.
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Affiliation(s)
- H H Hobbs
- Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas 75235, USA.
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39
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George J, Gilburd B, Langevitz P, Levy Y, Nezlin R, Harats D, Shoenfeld Y. Beta2 glycoprotein I containing immune-complexes in lupus patients: association with thrombocytopenia and lipoprotein (a) levels. Lupus 1999; 8:116-20. [PMID: 10192505 DOI: 10.1191/096120399678847470] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
In this study we determined the prevalence and clinical associations of immune-complexes-containing beta-2-glycoprotein I (beta2GPI) in randomly selected SLE patients. We studied 38 consecutive SLE patients attending the Rheumatology Unit. Previous arterial or venous-thrombosis were documented by the appropriate diagnostic test. Lipid profile including total cholesterol, LDL, VLDL, HDL and Lp(a) levels were determined from the sera of the fasting patients. Antibodies to cardiolipin, oxidized LDL and beta2GPI were detected employing ELISA. Beta2GPI containing IgG immune-complexes were assayed by using a dot-blot assay. Fourteen SLE patients (36.8%) were found to be positive for the presence of IgG anti-beta2GPI antibodies. Ten of the SLE patients (26.3%) were found to have high levels of beta2GPI containing immune-complexes. There was a positive correlation between beta2GPI-IC levels and the occurrence of thrombocytopenia in the patients (P < 0.05). Furthermore, patients with SLE and venous thrombosis had higher levels of beta2GPI-IC when compared with thrombosis-free patients or with healthy controls (P < 0.05). Patients with higher Lp(a) levels (> 50 mg/dl) possessed higher levels of beta2GPI-IC as compared with patients with lower Lp(a) concentration (< 20 mg/dl) (P < 0.05). These results suggest that IC-containing beta2GPI can help in defining a subpopulation of SLE patients with increased risk of thrombocytopenia and further aid in resolving mechanisms of immune-mediated tissue damage.
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Affiliation(s)
- J George
- Department of Medicine B, Tel Aviv University, Israel
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40
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Roubey RAS. The Antiphospholipid Syndrome. Lupus 1999. [DOI: 10.1007/978-1-59259-703-1_29] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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41
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Kandiah DA, Sali A, Sheng Y, Victoria EJ, Marquis DM, Coutts SM, Krilis SA. Current insights into the "antiphospholipid" syndrome: clinical, immunological, and molecular aspects. Adv Immunol 1998; 70:507-63. [PMID: 9755344 DOI: 10.1016/s0065-2776(08)60393-4] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Advances in defining the target antigen(s) for the autoantibodies in the APS highlight the inadequacies of the current classification of these autoantibodies into anticardiolipin and LA antibodies. The discovery that beta 2GPI is the target antigen for the autoantibodies detected in solid-phase immunoassays has opened a number of areas of research linking these autoantibodies to atherogenesis and thrombus formation. Although the role of beta 2GPI in the regulation of blood coagulation in unclear, current evidence suggests that anti-beta 2GPI antibodies interfere with its "normal" role and appear to promote a procoagulant tendency. The expansion of research in this area and the diversity of the clinical manifestations of patients with APS have resulted in the inclusion of molecular biologists and pharmaceutical companies joining immunologists, hematologists, rheumatologists, obstetricians, neurologists, vascular surgeons, and protein and lipid biochemists in attempting to understand the pathophysiology of this condition. Although the published literature may result in conflicting results and introduce new controversies, developing standardized laboratory methods and extrapolation of in vitro experimental results to the vivo situation will advance our understanding of the regulation of the immune system and its interaction with normal hemostatic mechanisms. Since the authors' last review in 1991, the study and understanding of the pathophysiology of APS have evolved from lipid biochemistry to molecular techniques that may eventually provide specific therapies for the clinical manifestations of this condition. Although current treatment has improved the morbidity associated with this condition, especially in improving pregnancy outcomes, future therapies, as outlined in this review, may specifically address the biological abnormalities and have fewer side effects. Better diagnostic tools, such as magnetic resonance imaging with perfusion studies, will allow the study of the true incidence and prevalence of vascular flow changes/tissue ischemia and infarction associated with aPL antibodies and help determine treatment and prophylaxis for APS patients. APS is still the only hypercoagulable condition where both arterial and venous beds can be affected independently or in the same individual.
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Affiliation(s)
- D A Kandiah
- Department of Immunology, Allergy, and Infectious Disease, University of New South Wales School of Medicine, St. George Hospital, Kogarah, Australia
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42
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Abstract
Abstractβ2-Glycoprotein I (β2GPI) is a highly glycosylated plasma protein with the ability to bind negatively charged substances such as DNA, heparin, dextran sulfate, and negatively charged phospholipids. The most relevant physiological role of β2GPI is supposed to be the regulation of the function of anionic phospholipids like cardiolipin (CL). β2GPI consists of a single polypeptide chain (326 amino acid residues) with a molecular mass of about 50 kD and with five tandem repeated domains (I, II, III, IV, and V). In the previous study, we found that factor Xa can produce the nicked form by cleaving Lys 317-Thr 318, using recombinant human domain V (r-Domain V). However, the reaction was extremely slow. In the present paper, we found that plasmin can produce the nicked form of domain V, using recombinant domain V (r-Domain V) and β2GPI from human plasma. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, r-Domain V was rapidly cleaved into a nicked form by plasmin, very slowly by factor Xa, but not by thrombin, tissue-type plasminogen activator, urokinase, and tissue factor/factor VIIa. The cleavage site of r-Domain V and β2GPI by plasmin was proved to be Lys 317-Thr 318 by amino acid sequence analysis of the digest and of the C-terminal peptide isolated by high-performance liquid chromatography. The cleavage was completely inhibited by plasmin inhibitor (α2PI). The nicked form was demonstrated to show reduced affinity for CL with a dissociation constant of one order of magnitude larger than that of the intact β2GPI. To determine whether the specific cleavage of β2GPI by plasmin can occur also in plasma, human plasma was first acid-treated to inactivate α2PI and then incubated with urokinase. About 12% of β2GPI in plasma was nicked when α2PI activity decreased to 80%. The nicked form was not generated in plasminogen-depleted plasma. These results suggest that plasmin can produce the nicked form of β2GPI with the reduced ability to bind phospholipids in vivo.
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43
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Abstract
The availability of the sequenced genome of Saccharomyces cerevisiae (yeast) has culminated in the use of this model eukaryote to study human diseases at a basic level. This article describes the advantages of studying lipid metabolism in this genetically facile organism, including examples of conserved functions and genetic approaches to identifying new components of cholesterol homeostasis.
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Affiliation(s)
- S L Sturley
- Institute of Human Nutrition, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
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