|
1
|
Brosolo G, Da Porto A, Marcante S, Picci A, Capilupi F, Capilupi P, Bulfone L, Vacca A, Bertin N, Vivarelli C, Comand J, Catena C, Sechi LA. Lipoprotein(a): Just an Innocent Bystander in Arterial Hypertension? Int J Mol Sci 2023; 24:13363. [PMID: 37686169 PMCID: PMC10487946 DOI: 10.3390/ijms241713363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 08/25/2023] [Accepted: 08/25/2023] [Indexed: 09/10/2023] Open
Abstract
Elevated plasma lipoprotein(a) [Lp(a)] is a relatively common and highly heritable trait conferring individuals time-dependent risk of developing atherosclerotic cardiovascular disease (CVD). Following its first description, Lp(a) triggered enormous scientific interest in the late 1980s, subsequently dampened in the mid-1990s by controversial findings of some prospective studies. It was only in the last decade that a large body of evidence has provided strong arguments for a causal and independent association between elevated Lp(a) levels and CVD, causing renewed interest in this lipoprotein as an emerging risk factor with a likely contribution to cardiovascular residual risk. Accordingly, the 2022 consensus statement of the European Atherosclerosis Society has suggested inclusion of Lp(a) measurement in global risk estimation. The development of highly effective Lp(a)-lowering drugs (e.g., antisense oligonucleotides and small interfering RNA, both blocking LPA gene expression) which are still under assessment in phase 3 trials, will provide a unique opportunity to reduce "residual cardiovascular risk" in high-risk populations, including patients with arterial hypertension. The current evidence in support of a specific role of Lp(a) in hypertension is somehow controversial and this narrative review aims to overview the general mechanisms relating Lp(a) to blood pressure regulation and hypertension-related cardiovascular and renal damage.
Collapse
Affiliation(s)
- Gabriele Brosolo
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Andrea Da Porto
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- Diabetes and Metabolism Unit, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Stefano Marcante
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Alessandro Picci
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Filippo Capilupi
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Patrizio Capilupi
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Luca Bulfone
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Antonio Vacca
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Nicole Bertin
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- Thrombosis and Hemostasis Unit, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Cinzia Vivarelli
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
| | - Jacopo Comand
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Cristiana Catena
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Leonardo A. Sechi
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
- Diabetes and Metabolism Unit, Clinica Medica, University of Udine, 33100 Udine, Italy
- Thrombosis and Hemostasis Unit, Clinica Medica, University of Udine, 33100 Udine, Italy
| |
Collapse
|
|
2
|
Koschinsky ML, Stroes ESG, Kronenberg F. Daring to dream: Targeting lipoprotein(a) as a causal and risk-enhancing factor. Pharmacol Res 2023; 194:106843. [PMID: 37406784 DOI: 10.1016/j.phrs.2023.106843] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 06/15/2023] [Accepted: 06/27/2023] [Indexed: 07/07/2023]
Abstract
Lipoprotein(a) [Lp(a)], a distinct lipoprotein class, has become a major focus for cardiovascular research. This review is written in light of the recent guideline and consensus statements on Lp(a) and focuses on 1) the causal association between Lp(a) and cardiovascular outcomes, 2) the potential mechanisms by which elevated Lp(a) contributes to cardiovascular diseases, 3) the metabolic insights on the production and clearance of Lp(a) and 4) the current and future therapeutic approaches to lower Lp(a) concentrations. The concentrations of Lp(a) are under strict genetic control. There exists a continuous relationship between the Lp(a) concentrations and risk for various endpoints of atherosclerotic cardiovascular disease (ASCVD). One in five people in the Caucasian population is considered to have increased Lp(a) concentrations; the prevalence of elevated Lp(a) is even higher in black populations. This makes Lp(a) a cardiovascular risk factor of major public health relevance. Besides the association between Lp(a) and myocardial infarction, the relationship with aortic valve stenosis has become a major focus of research during the last decade. Genetic studies provided strong support for a causal association between Lp(a) and cardiovascular outcomes: carriers of genetic variants associated with lifelong increased Lp(a) concentration are significantly more frequent in patients with ASCVD. This has triggered the development of drugs that can specifically lower Lp(a) concentrations: mRNA-targeting therapies such as anti-sense oligonucleotide (ASO) therapies and short interfering RNA (siRNA) therapies have opened new avenues to lower Lp(a) concentrations more than 95%. Ongoing Phase II and III clinical trials of these compounds are discussed in this review.
Collapse
Affiliation(s)
- Marlys L Koschinsky
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada; Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - Erik S G Stroes
- Department of Vascular Medicine, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, the Netherlands
| | - Florian Kronenberg
- Institute of Genetic Epidemiology, Medical University of Innsbruck, Innsbruck, Austria.
| |
Collapse
|
|
3
|
Chemello K, Chan DC, Lambert G, Watts GF. Recent advances in demystifying the metabolism of lipoprotein(a). Atherosclerosis 2022; 349:82-91. [DOI: 10.1016/j.atherosclerosis.2022.04.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 03/29/2022] [Accepted: 04/01/2022] [Indexed: 12/24/2022]
|
|
4
|
Clark JR, Gemin M, Youssef A, Marcovina SM, Prat A, Seidah NG, Hegele RA, Boffa MB, Koschinsky ML. Sortilin enhances secretion of apolipoprotein(a) through effects on apolipoprotein B secretion and promotes uptake of lipoprotein(a). J Lipid Res 2022; 63:100216. [PMID: 35469919 PMCID: PMC9131257 DOI: 10.1016/j.jlr.2022.100216] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 04/06/2022] [Accepted: 04/08/2022] [Indexed: 12/30/2022] Open
Abstract
Elevated plasma lipoprotein(a) (Lp(a)) is an independent, causal risk factor for atherosclerotic cardiovascular disease and calcific aortic valve stenosis. Lp(a) is formed in or on hepatocytes from successive noncovalent and covalent interactions between apo(a) and apoB, although the subcellular location of these interactions and the nature of the apoB-containing particle involved remain unclear. Sortilin, encoded by the SORT1 gene, modulates apoB secretion and LDL clearance. We used a HepG2 cell model to study the secretion kinetics of apo(a) and apoB. Overexpression of sortilin increased apo(a) secretion, while siRNA-mediated knockdown of sortilin expression correspondingly decreased apo(a) secretion. Sortilin binds LDL but not apo(a) or Lp(a), indicating that its effect on apo(a) secretion is likely indirect. Indeed, the effect was dependent on the ability of apo(a) to interact noncovalently with apoB. Overexpression of sortilin enhanced internalization of Lp(a), but not apo(a), by HepG2 cells, although neither sortilin knockdown in these cells or Sort1 deficiency in mice impacted Lp(a) uptake. We found several missense mutations in SORT1 in patients with extremely high Lp(a) levels; sortilin containing some of these mutations was more effective at promoting apo(a) secretion than WT sortilin, though no differences were found with respect to Lp(a) internalization. Our observations suggest that sortilin could play a role in determining plasma Lp(a) levels and corroborate in vivo human kinetic studies which imply that secretion of apo(a) and apoB are coupled, likely within the hepatocyte.
Collapse
Affiliation(s)
- Justin R Clark
- Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Matthew Gemin
- Department of Chemistry & Biochemistry, University of Windsor, Windsor, ON, Canada
| | - Amer Youssef
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | | | - Annik Prat
- Institut de Recherches Cliniques de Montreal, Montréal, QC, Canada
| | - Nabil G Seidah
- Institut de Recherches Cliniques de Montreal, Montréal, QC, Canada
| | - Robert A Hegele
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada; Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada; Department of Medicine, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Michael B Boffa
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada; Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Marlys L Koschinsky
- Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada; Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada.
| |
Collapse
|
|
5
|
Gonen A, Yang X, Yeang C, Alekseeva E, Koschinsky M, Witztum JL, Boffa M, Tsimikas S. Generation and characterization of LPA-KIV9, a murine monoclonal antibody binding a single site on apolipoprotein (a). J Lipid Res 2020; 61:1263-1270. [PMID: 32641432 PMCID: PMC7469883 DOI: 10.1194/jlr.ra120000830] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Lipoprotein (a) [Lp(a)] is a risk factor for CVD and a target of therapy, but Lp(a) measurements are not globally standardized. Commercially available assays generally use polyclonal antibodies that detect multiple sites within the kringle (K)IV2 repeat region of Lp(a) and may lead to inaccurate assessments of plasma levels. With increasing awareness of Lp(a) as a cardiovascular risk factor and the active clinical development of new potential therapeutic approaches, the broad availability of reagents capable of providing isoform independence of Lp(a) measurements is paramount. To address this issue, we generated a murine monoclonal antibody that binds to only one site on apo(a). A BALB/C mouse was immunized with a truncated version of apo(a) that contained eight total KIV repeats, including only one copy of KIV2 We generated hybridomas, screened them, and successfully produced a KIV2-independent monoclonal antibody, named LPA-KIV9. Using a variety of truncated apo(a) constructs to map its binding site, we found that LPA-KIV9 binds to KIV9 without binding to plasminogen. Fine peptide mapping revealed that LPA-KIV9 bound to the sequence 4076LETPTVV4082 on KIV9 In conclusion, the generation of monoclonal antibody LPA-KIV9 may be a useful reagent in basic research studies and in the clinical application of Lp(a) measurements.
Collapse
Affiliation(s)
- Ayelet Gonen
- Division of Endocrinology and Metabolism, Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Xiaohong Yang
- Vascular Medicine Program, Sulpizio Cardiovascular Center, Division of Cardiology, University of California San Diego, La Jolla, CA, USA
| | - Calvin Yeang
- Vascular Medicine Program, Sulpizio Cardiovascular Center, Division of Cardiology, University of California San Diego, La Jolla, CA, USA
| | - Elena Alekseeva
- Division of Endocrinology and Metabolism, Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Marlys Koschinsky
- Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada
| | - Joseph L Witztum
- Division of Endocrinology and Metabolism, Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Michael Boffa
- Department of Biochemistry, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Sotirios Tsimikas
- Vascular Medicine Program, Sulpizio Cardiovascular Center, Division of Cardiology, University of California San Diego, La Jolla, CA, USA
| |
Collapse
|
|
6
|
Sabbah N, Jaisson S, Garnotel R, Anglés-Cano E, Gillery P. Small size apolipoprotein(a) isoforms enhance inflammatory and proteolytic potential of collagen-primed monocytes. Lipids Health Dis 2019; 18:166. [PMID: 31470857 PMCID: PMC6717332 DOI: 10.1186/s12944-019-1106-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 08/14/2019] [Indexed: 01/03/2023] Open
Abstract
Background Atherosclerosis is an inflammatory process involving activation of monocytes recruited by various chemoattractant factors, among which lipoprotein(a) and its specific apolipoprotein apo(a). Lp(a) contains a specific apolipoprotein apo(a) which size is determined by a variable number of repeats of a specific structural domain, the kringle IV type 2 (IV-2). Lp(a) plasma concentration and apo(a) size is inversely correlated, and smaller apo(a) are major risk factors for coronary heart disease. Design and methods The aim of this study was to evaluate the effect of recombinant apo(a) isoforms (containing 10, 18 or 34 kringles) on monocytes interacting with type I collagen. Results Apo(a) isoforms stimulated reactive oxygen species (ROS) and matrix metalloproteinase-9 (MMP-9) production by monocytes, and not modified monocytes adhesion on type I collagen. This effect was specific of apo(a) since no effect was observed in the presence of plasminogen and was inversely related to apo(a) size. The lysine analogue 6-aminohexanoic acid which blocks the lysine binding sites (LBS), and carboxypeptidase B (CpB) which cleaves carboxy-terminal lysine residues, abolished apo(a)-induced ROS and MMP-9 production, highlighting an effect mediated by apo(a) lysing-binding sites. Conclusions These results indicate that activation of collagen-primed monocytes stimulated with apo(a) is a Kringle number-dependent effect and reinforce the hypothesis of a role for small size apo(a) isoforms in atherothrombosis.
Collapse
Affiliation(s)
- Nadia Sabbah
- University of Reims- Champagne-Ardenne, CNRS, MEDyC UMR 7369, Reims, France. .,Endocrinology and Metabolic Diseases Department, Cayenne hospital, Cayenne, French Guiana. .,Clinical Investigation Center Antilles French Guiana (INSERM CIC 1424), Cayenne, French Guiana.
| | - Stéphane Jaisson
- University of Reims- Champagne-Ardenne, CNRS, MEDyC UMR 7369, Reims, France.,Laboratory of Biochemisry-Pharmacology-Toxicology, University Hospital of Reims, Maison Blanche Hospital, Reims, France
| | - Roselyne Garnotel
- Laboratory of Biochemisry-Pharmacology-Toxicology, University Hospital of Reims, Maison Blanche Hospital, Reims, France
| | - Eduardo Anglés-Cano
- Inserm UMR_S1140 "Innovative Therapies in Haemostasis"Faculté de Pharmacie de Paris, Paris, France
| | - Philippe Gillery
- University of Reims- Champagne-Ardenne, CNRS, MEDyC UMR 7369, Reims, France.,Laboratory of Biochemisry-Pharmacology-Toxicology, University Hospital of Reims, Maison Blanche Hospital, Reims, France
| |
Collapse
|
|
7
|
Boffa MB, Koschinsky ML. Oxidized phospholipids as a unifying theory for lipoprotein(a) and cardiovascular disease. Nat Rev Cardiol 2019; 16:305-318. [DOI: 10.1038/s41569-018-0153-2] [Citation(s) in RCA: 114] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
|
|
8
|
Scipione CA, Koschinsky ML, Boffa MB. Lipoprotein(a) in clinical practice: New perspectives from basic and translational science. Crit Rev Clin Lab Sci 2017; 55:33-54. [PMID: 29262744 DOI: 10.1080/10408363.2017.1415866] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Elevated plasma concentrations of lipoprotein(a) (Lp(a)) are a causal risk factor for coronary heart disease (CHD) and calcific aortic valve stenosis (CAVS). Genetic, epidemiological and in vitro data provide strong evidence for a pathogenic role for Lp(a) in the progression of atherothrombotic disease. Despite these advancements and a race to develop new Lp(a) lowering therapies, there are still many unanswered and emerging questions about the metabolism and pathophysiology of Lp(a). New studies have drawn attention to Lp(a) as a contributor to novel pathogenic processes, yet the mechanisms underlying the contribution of Lp(a) to CVD remain enigmatic. New therapeutics show promise in lowering plasma Lp(a) levels, although the complete mechanisms of Lp(a) lowering are not fully understood. Specific agents targeted to apolipoprotein(a) (apo(a)), namely antisense oligonucleotide therapy, demonstrate potential to decrease Lp(a) to levels below the 30-50 mg/dL (75-150 nmol/L) CVD risk threshold. This therapeutic approach should aid in assessing the benefit of lowering Lp(a) in a clinical setting.
Collapse
Affiliation(s)
- Corey A Scipione
- a Department of Advanced Diagnostics , Toronto General Hospital Research Institute, UHN , Toronto , Canada
| | - Marlys L Koschinsky
- b Robarts Research Institute , Western University , London , Canada.,c Department of Physiology & Pharmacology , Schulich School of Medicine & Dentistry, Western University , London , Canada
| | - Michael B Boffa
- d Department of Biochemistry , Western University , London , Canada
| |
Collapse
|
|
9
|
Kostner KM, Kostner GM. Lipoprotein (a): a historical appraisal. J Lipid Res 2016; 58:1-14. [PMID: 27821413 DOI: 10.1194/jlr.r071571] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 11/01/2016] [Indexed: 11/20/2022] Open
Abstract
Initially, lipoprotein (a) [Lp(a)] was believed to be a genetic variant of lipoprotein (Lp)-B. Because its lipid moiety is almost identical to LDL, Lp(a) has been deliberately considered to be highly atherogenic. Lp(a) was detected in 1963 by Kare Berg, and individuals who were positive for this factor were called Lpa+ Lpa+ individuals were found more frequently in patients with coronary heart disease than in controls. After the introduction of quantitative methods for monitoring of Lp(a), it became apparent that Lp(a), in fact, is present in all individuals, yet to a greatly variable extent. The genetics of Lp(a) had been a mystery for a long time until Gerd Utermann discovered that apo(a) is expressed by a variety of alleles, giving rise to a unique size heterogeneity. This size heterogeneity, as well as countless mutations, is responsible for the great variability in plasma Lp(a) concentrations. Initially, we proposed to evaluate the risk of myocardial infarction at a cut-off for Lp(a) of 30-50 mg/dl, a value that still is adopted in numerous epidemiological studies. Due to new therapies that lower Lp(a) levels, there is renewed interest and still rising research activity in Lp(a). Despite all these activities, numerous gaps exist in our knowledge, especially as far as the function and metabolism of this fascinating Lp are concerned.
Collapse
Affiliation(s)
- Karam M Kostner
- Department of Cardiology, Mater Hospital and University of Queensland, Brisbane, 4101 Queensland, Australia
| | - Gert M Kostner
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, A-8010 Graz, Austria
| |
Collapse
|
|
10
|
Boffa MB, Koschinsky ML. Lipoprotein (a): truly a direct prothrombotic factor in cardiovascular disease? J Lipid Res 2015; 57:745-57. [PMID: 26647358 DOI: 10.1194/jlr.r060582] [Citation(s) in RCA: 170] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Indexed: 01/13/2023] Open
Abstract
Elevated plasma concentrations of lipoprotein (a) [Lp(a)] have been determined to be a causal risk factor for coronary heart disease, and may similarly play a role in other atherothrombotic disorders. Lp(a) consists of a lipoprotein moiety indistinguishable from LDL, as well as the plasminogen-related glycoprotein, apo(a). Therefore, the pathogenic role for Lp(a) has traditionally been considered to reflect a dual function of its similarity to LDL, causing atherosclerosis, and its similarity to plasminogen, causing thrombosis through inhibition of fibrinolysis. This postulate remains highly speculative, however, because it has been difficult to separate the prothrombotic/antifibrinolytic functions of Lp(a) from its proatherosclerotic functions. This review surveys the current landscape surrounding these issues: the biochemical basis for procoagulant and antifibrinolytic effects of Lp(a) is summarized and the evidence addressing the role of Lp(a) in both arterial and venous thrombosis is discussed. While elevated Lp(a) appears to be primarily predisposing to thrombotic events in the arterial tree, the fact that most of these are precipitated by underlying atherosclerosis continues to confound our understanding of the true pathogenic roles of Lp(a) and, therefore, the most appropriate therapeutic target through which to mitigate the harmful effects of this lipoprotein.
Collapse
Affiliation(s)
- Michael B Boffa
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada
| | - Marlys L Koschinsky
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada Robarts Research Institute, Western University, London, ON, Canada
| |
Collapse
|
|
11
|
Scipione CA, Sayegh SE, Romagnuolo R, Tsimikas S, Marcovina SM, Boffa MB, Koschinsky ML. Mechanistic insights into Lp(a)-induced IL-8 expression: a role for oxidized phospholipid modification of apo(a). J Lipid Res 2015; 56:2273-85. [PMID: 26474593 DOI: 10.1194/jlr.m060210] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Indexed: 12/14/2022] Open
Abstract
Elevated lipoprotein (a) [Lp(a)] levels are a causal risk factor for coronary heart disease. Accumulating evidence suggests that Lp(a) can stimulate cellular inflammatory responses through the kringle-containing apolipoprotein (a) [apo(a)] component. Here, we report that recombinant apo(a) containing 17 kringle (17K) IV domains elicits a dose-dependent increase in interleukin (IL)-8 mRNA and protein expression in THP-1 and U937 macrophages. This effect was blunted by mutation of the lysine binding site in apo(a) kringle IV type 10, which resulted in the loss of oxidized phospholipid (oxPL) on apo(a). Trypsin-digested 17K had the same stimulatory effect on IL-8 expression as intact apo(a), while enzymatic removal of oxPL from apo(a) significantly blunted this effect. Using siRNA to assess candidate receptors, we found that CD36 and TLR2 may play roles in apo(a)-mediated IL-8 stimulation. Downstream of these receptors, inhibitors of MAPKs, Jun N-terminal kinase and ERK1/2, abolished the effect of apo(a) on IL-8 gene expression. To assess the roles of downstream transcription factors, luciferase reporter gene experiments were conducted using an IL-8 promoter fragment. The apo(a)-induced expression of this reporter construct was eliminated by mutation of IL-8 promoter binding sites for either NF-κB or AP-1. Our results provide a mechanistic link between oxPL modification of apo(a) and stimulation of proinflammatory intracellular signaling pathways.
Collapse
Affiliation(s)
- Corey A Scipione
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada
| | - Sera E Sayegh
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada
| | - Rocco Romagnuolo
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada
| | - Sotirios Tsimikas
- Vascular Medicine Program, University of California San Diego, La Jolla, CA
| | - Santica M Marcovina
- Department of Medicine, Northwest Lipid Research Laboratories, University of Washington, Seattle, WA
| | - Michael B Boffa
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada
| | - Marlys L Koschinsky
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada
| |
Collapse
|
|
12
|
Ahn JH, Lee HJ, Lee EK, Yu HK, Lee TH, Yoon Y, Kim SJ, Kim JS. Antiangiogenic kringles derived from human plasminogen and apolipoprotein(a) inhibit fibrinolysis through a mechanism that requires a functional lysine-binding site. Biol Chem 2011; 392:347-56. [PMID: 21194375 DOI: 10.1515/bc.2011.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Many proteins in the fibrinolysis pathway contain antiangiogenic kringle domains. Owing to the high degree of homology between kringle domains, there has been a safety concern that antiangiogenic kringles could interact with common kringle proteins during fibrinolysis leading to adverse effects in vivo. To address this issue, we investigated the effects of several antiangiogenic kringle proteins including angiostatin, apolipoprotein(a) kringles IV(9)-IV(10)-V (LK68), apolipoprotein(a) kringle V (rhLK8) and a derivative of rhLK8 mutated to produce a functional lysine-binding site (Lys-rhLK8) on the entire fibrinolytic process in vitro and analyzed the role of lysine binding. Angiostatin, LK68 and Lys-rhLK8 increased clot lysis time in a dose-dependent manner, inhibited tissue-type plasminogen activator-mediated plasminogen activation on a thrombin-modified fibrinogen (TMF) surface, showed binding to TMF and significantly decreased the amount of plasminogen bound to TMF. The inhibition of fibrinolysis by these proteins appears to be dependent on their functional lysine-binding sites. However, rhLK8 had no effect on these processes owing to an inability to bind lysine. Collectively, these results indicate that antiangiogenic kringles without lysine binding sites might be safer with respect to physiological fibrinolysis than lysine-binding antiangiogenic kringles. However, the clinical significance of these findings will require further validation in vivo.
Collapse
Affiliation(s)
- Jin-Hyung Ahn
- Cancer Biology Team, Mogam Biotechnology Research Institute, Yongin, Kyonggi-do, South Korea
| | | | | | | | | | | | | | | |
Collapse
|
|
13
|
The apo(a) gene (TTTTA)n promoter polymorphism and its association with variability in exons of the kringle IV types 8 to 10. Clin Chim Acta 2009; 405:39-42. [DOI: 10.1016/j.cca.2009.03.054] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 03/30/2009] [Accepted: 03/30/2009] [Indexed: 11/22/2022]
|
|
14
|
Apolipoprotein(a) stimulates vascular endothelial cell growth and migration and signals through integrin alphaVbeta3. Biochem J 2009; 418:325-36. [PMID: 18821851 DOI: 10.1042/bj20080744] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Elevated plasma concentrations of Lp(a) [lipoprotein(a)] are an emerging risk factor for atherothrombotic disease. Apo(a) [apolipoprotein(a)], the unique glycoprotein component of Lp(a), contains tandem repeats of a plasminogen kringle (K) IV-like domain. In the light of recent studies suggesting that apo(a)/Lp(a) affects endothelial function, we evaluated the effects of apo(a)/Lp(a) on growth and migration of cultured HUVECs (human umbilical-vein endothelial cells). Two full-length r-apo(a) [recombinant apo(a)] variants (12K and 17K), as well as Lp(a), were able to stimulate HUVEC growth and migration to a comparable extent; 17K r-apo(a) also decreased the levels of total and active transforming growth factor-beta secreted by these cells. Using additional r-apo(a) variants corresponding to deletions and/or site-directed mutants of various kringle domains in the molecule, we were able to determine that the observed effects of full-length r-apo(a) on HUVECs were dependent on the presence of a functional lysine-binding site(s) in the apo(a) molecule. With respect to signalling events elicited by apo(a) in HUVECs, we found that 17K treatment of the cells increased the phosphorylation level of FAK (focal adhesion kinase) and MAPKs (mitogen-activated protein kinases), including ERK (extracellular-signal-regulated kinase), p38 and JNK (c-Jun N-terminal kinase). In addition, we showed that LM609, the function-blocking antibody to integrin alphaVbeta3, abrogated the effects of 17K r-apo(a) and Lp(a) on HUVECs. Taken together, the results of the present study suggest that the apo(a) component of Lp(a) signals through integrin alphaVbeta3 to activate endothelial cells.
Collapse
|
|
15
|
Feric NT, Boffa MB, Johnston SM, Koschinsky ML. Apolipoprotein(a) inhibits the conversion of Glu-plasminogen to Lys-plasminogen: a novel mechanism for lipoprotein(a)-mediated inhibition of plasminogen activation. J Thromb Haemost 2008; 6:2113-20. [PMID: 18983515 DOI: 10.1111/j.1538-7836.2008.03183.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Elevated plasma concentrations of lipoprotein(a) [Lp(a)] are associated with an increased risk for thrombotic disorders. Lp(a) is a unique lipoprotein consisting of a low-density lipoprotein-like moiety covalently linked to apolipoprotein(a) [apo(a)], a homologue of the fibrinolytic proenzyme plasminogen. Several in vitro and in vivo studies have shown that Lp(a)/apo(a) can inhibit tissue-type plasminogen activator-mediated plasminogen activation on fibrin surfaces, although the mechanism of inhibition by apo(a) remains controversial. Essential to fibrin clot lysis are a number of plasmin-dependent positive feedback reactions that enhance the efficiency of plasminogen activation, including the plasmin-mediated conversion of Glu-plasminogen to Lys-plasminogen. OBJECTIVE Using acid-urea gel electrophoresis to resolve the two forms of radiolabeled plasminogen, we determined whether apo(a) is able to inhibit Glu-plasminogen to Lys-plasminogen conversion. METHODS The assays were performed in the absence or presence of different recombinant apo(a) species, including point mutants, deletion mutants and variants that represent greater than 90% of the known apo(a) isoform sizes. RESULTS Apo(a) substantially suppressed Glu-plasminogen conversion. Critical roles were identified for the kringle IV types 5-9 and kringle V; contributory roles for sequences within the amino-terminal half of the molecule were also observed. Additionally, with the exception of the smallest naturally-occurring isoform of apo(a), isoform size was found not to contribute to the inhibitory capacity of apo(a). CONCLUSION These findings underscore a novel contribution to the understanding of Lp(a)/apo(a)-mediated inhibition of plasminogen activation: the ability of the apo(a) component of Lp(a) to inhibit the key positive feedback step of plasmin-mediated Glu-plasminogen to Lys-plasminogen conversion.
Collapse
Affiliation(s)
- N T Feric
- Department of Biochemistry, Queen's University, Kingston, ON, Canada
| | | | | | | |
Collapse
|
|
16
|
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.
Collapse
Affiliation(s)
- Angela D'Angelo
- Molecular Medicine Laboratory, University of Pavia, IRCCS Policlinico San Matteo, Piazzale Golgi 2, Pavia, Italy
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
|
17
|
Jenner JL, Seman LJ, Millar JS, Lamon-Fava S, Welty FK, Dolnikowski GG, Marcovina SM, Lichtenstein AH, Barrett PHR, deLuca C, Schaefer EJ. The metabolism of apolipoproteins (a) and B-100 within plasma lipoprotein (a) in human beings. Metabolism 2005; 54:361-9. [PMID: 15736114 DOI: 10.1016/j.metabol.2004.10.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The metabolism of apolipoproteins (apo) (a) and B-100 within plasma lipoprotein (a) [Lp(a)] was examined in the fed state in 23 subjects aged 41 to 79 years who received a primed-constant infusion of [5,5,5-2H3] leucine over 15 hours. Lipoprotein (a) was isolated from the whole plasma using a lectin affinity-based method. Apolipoprotein (a) and apoB-100 were separated by gel electrophoresis, and tracer enrichment of each apolipoprotein was measured using gas chromatography/mass spectrometry. Data were fit to a multicompartmental model to determine fractional catabolic rates (FCRs) and secretion rates (SRs). The FCRs of apo(a) and apoB-100 (mean +/- SEM) within plasma Lp(a) were significantly different (0.220 +/- 0.030 pool/d and 0.416 +/- 0.040 pool/d, respectively; P < .001). Apolipoprotein (a) SR (0.50 +/- 0.08 mg/[kg per d]) was significantly lower than that of apoB-100 SR (1.53 +/- 0.22 mg/[kg per d]; P < .001) of Lp(a). Plasma concentrations of Lp(a) were correlated significantly with both apo(a) SR and apoB-100 SR (r = 0.837 and r = 0.789, respectively; P < .001) and negatively with apo(a) FCR and Lp(a) apoB-100 FCR (r = -0.547 and r = -0.717, respectively; P < .01). These data implicate different metabolic fates for apo(a) and apoB-100 within Lp(a) in the fed state. We therefore hypothesize that apo(a) does not remain covalently linked to a single apoB-100 lipoprotein but that it rather reassociates at least once with another apoB-100 particle, probably newly synthesized, during its plasma metabolism.
Collapse
Affiliation(s)
- Jennifer L Jenner
- Lipid Metabolism Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
|
18
|
Boffa MB, Marcovina SM, Koschinsky ML. Lipoprotein(a) as a risk factor for atherosclerosis and thrombosis: mechanistic insights from animal models. Clin Biochem 2004; 37:333-43. [PMID: 15087247 DOI: 10.1016/j.clinbiochem.2003.12.007] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2003] [Revised: 12/10/2003] [Accepted: 12/10/2003] [Indexed: 02/05/2023]
Abstract
Evidence continues to accumulate from epidemiological studies that elevated plasma concentrations of lipoprotein(a) [Lp(a)] are a risk factor for a variety of atherosclerotic and thrombotic disorders. Lp(a) is a unique lipoprotein particle consisting of a moiety identical to low-density lipoprotein to which the glycoprotein apolipoprotein(a) [apo(a)] that is homologous to plasminogen is covalently attached. These features have suggested that Lp(a) may contribute to both proatherogenic and prothrombotic/antifibrinolytic processes and in vitro studies have identified many such candidate mechanisms. Despite intensive research, however, definition of the molecular mechanisms underlying the epidemiological data has proven elusive. Moreover, an effective and well-tolerated regimen to lower Lp(a) levels has yet to be developed. The use of animal models holds great promise for resolving these questions. Establishment of animal models for Lp(a) has been hampered by the absence of this lipoprotein from common small laboratory animals. Transgenic mice and rabbits expressing human apo(a) have been developed and these have been used to: (i) examine regulation of apo(a) gene expression; (ii) study the mechanism and molecular determinants of Lp(a) assembly from LDL and apo(a); (iii) demonstrate that apo(a)/Lp(a) are indeed proatherogenic and antifibrinolytic; and (iv) identify structural domains in apo(a) that mediate its pathogenic effects. The recent construction of transgenic apo(a) rabbits is a particularly promising development in view of the excellent utility of the rabbit as a model of advanced atherosclerosis.
Collapse
Affiliation(s)
- Michael B Boffa
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada
| | | | | |
Collapse
|
|
19
|
O'Neil CH, Boffa MB, Hancock MA, Pickering JG, Koschinsky ML. Stimulation of Vascular Smooth Muscle Cell Proliferation and Migration by Apolipoprotein(a) Is Dependent on Inhibition of Transforming Growth Factor-β Activation and on the Presence of Kringle IV Type 9. J Biol Chem 2004; 279:55187-95. [PMID: 15498766 DOI: 10.1074/jbc.m409860200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Elevated plasma concentrations of lipoprotein(a) are a risk factor for the development of a variety of atherosclerotic disorders. Despite intensive study, the mechanisms by which lipoprotein(a) promotes these disorders remain to be unequivocally defined. It has been demonstrated that lipoprotein(a), through its unique constituent apolipoprotein(a) (apo(a)), stimulates vascular smooth muscle cell (SMC) migration and proliferation. These effects arise from the ability of apo(a) to inhibit the formation of active transforming growth factor beta (TGF-beta) from its latent precursor, which in turn is caused by the ability of apo(a) to decrease the formation of plasmin from its precursor plasminogen. We utilized a battery of recombinant apo(a) variants that represent systematic deletions of the various domains in the molecule to further probe the mechanism underlying the effect of apo(a) on SMC responses. All recombinant apo(a) variants that contained kringle IV type 9 were able to stimulate SMC proliferation and migration and to decrease the formation of active TGF-beta; conversely all recombinant apo(a) variants lacking kringle IV type 9 had no effect on these parameters. The kringle IV type 9-dependent effects of apo(a) on SMC proliferation required the presence of plasminogen, suggesting for the first time that this kringle mediates the ability of apo(a) to inhibit pericellular plasmin formation.
Collapse
Affiliation(s)
- Caroline H O'Neil
- Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | | | | | | | | |
Collapse
|
|
20
|
Tholstrup T, Samman S. Postprandial lipoprotein(a) is affected differently by specific individual dietary fatty acids in healthy young men. J Nutr 2004; 134:2550-5. [PMID: 15465746 DOI: 10.1093/jn/134.10.2550] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Lipoprotein(a) [Lp(a)] is considered a risk factor for coronary heart disease. Our aim was to investigate the effect of individual fatty acids on postprandial plasma Lp(a) and its association with lipemia and tissue plasminogen activator (t-PA). Five test fats dominated by (approximately 43% g/kg) stearic (S), palmitic (P), oleic, C18:1 trans (T), or linoleic acid were produced by interesterification. Sixteen young healthy men were served the individual test fats incorporated into meals (1g fat/kg body wt) after a 12-h fast in random order on different days, separated by 3-wk washout periods. Blood samples were drawn before and 2, 4, 6, and 8 h after eating. There was a pronounced increase in Lp(a) concentrations after intake of the test meals, and the test fats resulted in a difference in Lp(a) response (P < 0.001; diet x time interaction). However, T fat did not change Lp(a) during the time course studied. T fat resulted in less area under the plasma Lp(a) concentration curve compared to S and P fat (P </= 0.003). Test fat with saturated fatty acids resulted in the highest Lp(a) and lowest plasma triacylglycerol (TAG) response, with the reversed situation for T fat. There was no association between Lp(a) and t-PA. In conclusion, intake of meals high in individual dietary fatty acids increased postprandial plasma Lp(a) differently. There seems to be a complex regulatory role of plasma TAG on nonfasting plasma Lp(a) concentrations.
Collapse
Affiliation(s)
- Tine Tholstrup
- Research Department of Human Nutrition and Center for Advanced Food Studies, The Royal Veterinary and Agricultural University, Frederiksberg, Denmark.
| | | |
Collapse
|
|
21
|
Sharp RJ, Perugini MA, Marcovina SM, McCormick SPA. Structural features of apolipoprotein B synthetic peptides that inhibit lipoprotein(a) assembly. J Lipid Res 2004; 45:2227-34. [PMID: 15375179 DOI: 10.1194/jlr.m400163-jlr200] [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] [Indexed: 11/20/2022] Open
Abstract
Lipoprotein(a) [Lp(a)] is assembled via an initial noncovalent interaction between apolipoprotein B100 (apoB) and apolipoprotein(a) [apo(a)] that facilitates the formation of a disulfide bond between the two proteins. We previously reported that a lysine-rich, alpha-helical peptide spanning human apoB amino acids 4372-4392 was an effective inhibitor of Lp(a) assembly in vitro. To identify the important structural features required for inhibitory action, new variants of the apoB4372-4392 peptide were investigated. Introduction of a central leucine to proline substitution abolished the alpha-helical structure of the peptide and disrupted apo(a) binding and inhibition of Lp(a) formation. Substitution of hydrophobic residues in the apoB4372-4392 peptide disrupted apo(a) binding and inhibition of Lp(a) assembly without disrupting the alpha-helical structure. Substitution of all four lysine residues in the peptide with arginine decreased the IC50 from 40 microM to 5 microM . Complexing of the arginine-substituted peptide to dimyristoylphosphatidylcholine improved its activity further, yielding an IC50 of 1 microM. We conclude that the alpha-helical structure of apoB4372-4392, in combination with hydrophobic residues at the lipid/water interface, is crucial for its interaction with apo(a). Furthermore, the interaction of apoB4372-4392 with apo(a) is not lysine specific, because substitutions with arginine result in a more effective inhibitor.
Collapse
Affiliation(s)
- Rebecca J Sharp
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | | | | | | |
Collapse
|
|
22
|
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.
Collapse
|
|
23
|
Liu CYY, Broadhurst R, Marcovina SM, McCormick SPA. Mutation of lysine residues in apolipoprotein B-100 causes defective lipoprotein[a] formation. J Lipid Res 2004; 45:63-70. [PMID: 13130121 DOI: 10.1194/jlr.m300071-jlr200] [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] [Indexed: 11/20/2022] Open
Abstract
Lipoprotein[a] (Lp[a]) is assembled by a two-step process involving an initial lysine-dependent binding between apolipoprotein B-100 (apoB-100) and apolipoprotein[a] (apo[a]) that facilitates the formation of a disulphide bond between apoB-100Cys4,326 and apo[a]Cys4,057. Previous studies of transgenic mice expressing apoB-95 (4,330 amino acids) and apoB-97 (4,397 amino acids) have shown that apoB-100 amino acids 4,330-4,397 are important for the initial binding to apo[a]. Furthermore, a lysine-rich peptide spanning apoB-100 amino acids 4,372-4,392 has recently been shown to bind apo[a] and inhibit Lp[a] assembly in vitro. This suggests that a putative apo[a] binding site exists in the apoB-4,372-4,392 region. The aim of our study was to establish whether the apoB-4,372-4,392 sequence was important for Lp[a] assembly in the context of the full-length apoB-100. Transgenic mice were created that expressed a mutant human apoB-100, apoB-100K4-->S4, in which all four lysine residues in the 4,372-4,392 sequence were mutated to serines. The apoB-100K4-->S4 mutant showed a reduced capacity to form Lp[a] in vitro compared with wild-type human apoB-100. Double transgenic mice expressing both apoB-100K4-->S4 and apo[a] contained significant amounts of free apo[a] in the plasma, indicating a less-efficient assembly of Lp[a] in vivo. Taken together, these results clearly show that the apoB-4,372-4,392 sequence plays a role in Lp[a] assembly.
Collapse
Affiliation(s)
- Catherine Y Y Liu
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | | | | | | |
Collapse
|
|
24
|
Becker L, Cook PM, Wright TG, Koschinsky ML. Quantitative Evaluation of the Contribution of Weak Lysine-binding Sites Present within Apolipoprotein(a) Kringle IV Types 6–8 to Lipoprotein(a) Assembly. J Biol Chem 2004; 279:2679-88. [PMID: 14581473 DOI: 10.1074/jbc.m309414200] [Citation(s) in RCA: 27] [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
During lipoprotein(a) (Lp(a)) assembly, non-covalent interactions between apolipoprotein(a) (apo(a)) and low density lipoprotein precede specific disulfide bond formation. Studies have shown that the non-covalent step involves an interaction between the weak lysine-binding sites (WLBS) present within each of apo(a) kringle IV types 6, 7, and 8 (KIV(6-8)), and two lysine residues (Lys(680) and Lys(690)) within the NH(2) terminus of the apolipoprotein B-100 (apoB) component of low density lipoprotein. In the present study, we introduced single point mutations (E56G) into each of the WLBS present in apo(a) KIV(6-8) and expressed these mutations in the context of a 17-kringle (17K) recombinant apo(a) variant. Single mutations that disrupt the WLBS in KIV(6), KIV(7), and KIV(8), as well as mutants that disrupt the WLBS in both KIV(6) and KIV(7), or both KIV(7) and KIV(8), were assessed for their ability to form non-covalent and covalent Lp(a) complexes. Our results demonstrate that both apo(a) KIV(7) and KIV(8), but not KIV(6), are required for maximally efficient non-covalent and covalent Lp(a) assembly. Single mutations in the WLBS of KIV(7) or KIV(8) resulted in a 3-fold decrease in the affinity of 17K recombinant apo(a) for apoB, and a 20% reduction in the rate of covalent Lp(a) formation. Tandem mutations in the WLBS in both KIV(7) and KIV(8) resulted in a 13-fold reduction in the binding affinity between apo(a) and apoB, and a 75% reduction in the rate of the covalent step of Lp(a) formation. We also showed that KIV(7) and KIV(8) specifically bind with high affinity to apoB-derived peptides containing Lys(690) or Lys(680), respectively. Taken together, our data demonstrate that specific interactions between apo(a) KIV(7) and KIV(8) and Lys(680) and Lys(690) in apoB mediate a high affinity non-covalent interaction between apo(a) and low density lipoprotein, which dictates the efficiency of covalent Lp(a) formation.
Collapse
Affiliation(s)
- Lev Becker
- Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | | | | | | |
Collapse
|
|
25
|
Marcovina SM, Koschinsky ML, Albers JJ, Skarlatos S. Report of the National Heart, Lung, and Blood Institute Workshop on Lipoprotein(a) and Cardiovascular Disease: Recent Advances and Future Directions. Clin Chem 2003; 49:1785-96. [PMID: 14578310 DOI: 10.1373/clinchem.2003.023689] [Citation(s) in RCA: 195] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractIt has been estimated that ∼37% of the US population judged to be at high risk for developing coronary artery disease (CAD), based on the National Cholesterol Education Program guidelines, have increased plasma lipoprotein(a) [Lp(a)], whereas Lp(a) is increased in only 14% of those judged to be at low risk. Therefore, the importance of establishing a better understanding of the relative contribution of Lp(a) to the risk burden for CAD and other forms of vascular disease, as well as the underlying mechanisms, is clearly evident. However, the structural complexity and size heterogeneity of Lp(a) have hindered the development of immunoassays to accurately measure Lp(a) concentrations in plasma. The large intermethod variation in Lp(a) values has made it difficult to compare data from different clinical studies and to achieve a uniform interpretation of clinical data. A workshop was recently convened by the National Heart, Lung, and Blood Institute (NHLBI) to evaluate our current understanding of Lp(a) as a risk factor for atherosclerotic disorders; to determine how future studies could be designed to more clearly define the extent to which, and mechanisms by which, Lp(a) participates in these processes; and to present the results of the NHLBI-supported program for the evaluation and standardization of Lp(a) immunoassays. This report includes the most recent data presented by the workshop participants and the resulting practical and research recommendations.
Collapse
Affiliation(s)
- Santica M Marcovina
- Department of Medicine, University of Washington, Northwest Lipid Research Laboratories, 2121 N. 35th St., Seattle, WA 98103, USA.
| | | | | | | |
Collapse
|
|
26
|
Abstract
PURPOSE OF REVIEW Since the homology between apolipoprotein(a) (apo(a)) and plasminogen was discovered in 1987, the role of lipoprotein(a) (Lp(a)) as an inhibitor of the normal fibrinolytic role of plasmin(ogen) has been a major research focus. In this review we summarize recent basic research aimed at identifying mechanisms by which Lp(a) can either inhibit fibrinolysis or promote coagulation, as well as recent clinical studies of Lp(a) as a risk factor for thrombosis either in the presence or absence of atherosclerosis. RECENT FINDINGS It has recently been reported that the inhibition of plasminogen activation by apo(a) results from the interaction of apo(a) with the ternary complex of tissue-type plasminogen activator, plasminogen and fibrin, rather than competition of apo(a) and plasminogen for binding sites on fibrin. Lp(a) species containing smaller apo(a) isoforms bind more avidly to fibrin and are better inhibitors of plasminogen activation. Recent clinical studies have provided strong evidence that Lp(a), either alone or in synergy with other thrombotic risk factors, significantly increases the risk of venous thromboembolism and ischemic stroke. SUMMARY Lp(a) both attenuates fibrinolysis, through inhibition of plasminogen activation, and promotes coagulation, through alleviation of extrinsic pathway inhibition. Further basic and clinical studies are required to more clearly define the role of Lp(a) in thrombotic disorders, and to determine the extent to which thrombotic risk is dependent on apo(a) isoform size.
Collapse
Affiliation(s)
- Santica M Marcovina
- Department of Medicine, University of Washington, Seattle, Washington 98103, USA.
| | | |
Collapse
|
|
27
|
Hancock MA, Boffa MB, Marcovina SM, Nesheim ME, Koschinsky ML. Inhibition of plasminogen activation by lipoprotein(a): critical domains in apolipoprotein(a) and mechanism of inhibition on fibrin and degraded fibrin surfaces. J Biol Chem 2003; 278:23260-9. [PMID: 12697748 DOI: 10.1074/jbc.m302780200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Similarity between the apolipoprotein(a) (apo(a)) moiety of lipoprotein(a) (Lp(a)) and plasminogen suggests a potentially important link between atherosclerosis and thrombosis. Lp(a) may interfere with tissue plasminogen activator (tPA)-mediated plasminogen activation in fibrinolysis, thereby generating a hypercoagulable state in vivo. A fluorescence-based system was employed to study the effect of apo(a) on plasminogen activation in the presence of native fibrin and degraded fibrin cofactors and in the absence of positive feedback reactions catalyzed by plasmin. Human Lp(a) and a physiologically relevant, 17-kringle recombinant apo(a) species exhibited strong inhibition with both cofactors. A variant lacking the protease domain also exhibited strong inhibition, indicating that the apo(a)-plasminogen binding interaction mediated by the apo(a) protease domain does not ultimately inhibit plasminogen activation. A variant in which the strong lysine-binding site in kringle IV type 10 had been abolished exhibited substantially reduced inhibition whereas another lacking the kringle V domain showed no inhibition. Amino-terminal truncation mutants of apo(a) also revealed that additional sequences within kringle IV types 1-4 are required for maximal inhibition. To investigate the inhibition mechanism, the concentrations of plasminogen, cofactor, and a 12-kringle recombinant apo(a) species were systematically varied. Kinetics for both cofactors conformed to a single, equilibrium template model in which apo(a) can interact with all three fibrinolytic components and predicts the formation of ternary (cofactor, tPA, and plasminogen) and quaternary (cofactor, tPA, plasminogen, and apo(a)) catalytic complexes. The latter complex exhibits a reduced turnover number, thereby accounting for inhibition of plasminogen activation in the presence of apo(a)/Lp(a).
Collapse
Affiliation(s)
- Mark A Hancock
- Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada.
| | | | | | | | | |
Collapse
|
|
28
|
Becker L, Webb BA, Chitayat S, Nesheim ME, Koschinsky ML. A ligand-induced conformational change in apolipoprotein(a) enhances covalent Lp(a) formation. J Biol Chem 2003; 278:14074-81. [PMID: 12566443 DOI: 10.1074/jbc.m212855200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lipoprotein(a) (Lp(a)) assembly proceeds via a two-step mechanism in which initial non-covalent interactions between apolipoprotein(a) (apo(a)) and low density lipoprotein precede disulfide bond formation. In this study, we used analytical ultracentrifugation, differential scanning calorimetry, and intrinsic fluorescence to demonstrate that in the presence of the lysine analog epsilon-aminocaproic acid, apo(a) undergoes a substantial conformational change from a "closed" to an "open" structure that is characterized by an increase in the hydrodynamic radius (approximately 10%), an alteration in domain stability, as well as a decrease in tryptophan fluorescence. Although epsilon-aminocaproic acid is a well characterized inhibitor of the non-covalent interaction between apo(a) and low density lipoprotein, we report the novel observation that this ligand at low concentrations (100 microm-1 mm) significantly enhances covalent Lp(a) assembly by altering the conformation of apo(a). We developed a model for the kinetics of Lp(a) assembly that incorporates the conformational change as a determinant of the efficiency of the process; this model quantitatively explains our experimental observations. Interestingly, an analogous conformational change has been previously described for plasminogen resulting in an increase in the hydrodynamic radius, an increase in tryptophan fluorescence, and an acceleration of the rate of plasminogen activation. Although the functions of apo(a) and plasminogen have diverged considerably, elements of structural and conformational homology have been retained leading to similar regulation of two unrelated biological processes.
Collapse
Affiliation(s)
- Lev Becker
- Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | | | | | | | | |
Collapse
|
|
29
|
Hill BC, Becker L, Anand V, Kusmierczyk A, Marcovina SM, Rahman MN, Gabel BR, Jia Z, Boffa MB, Koschinsky ML. A role for apolipoprotein(a) in protection of the low-density lipoprotein component of lipoprotein(a) from copper-mediated oxidation. Arch Biochem Biophys 2003; 412:186-95. [PMID: 12667482 DOI: 10.1016/s0003-9861(03)00032-8] [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] [Indexed: 10/27/2022]
Abstract
Low-density lipoprotein (LDL) oxidation is stimulated by copper. Addition of a recombinant form of apolipoprotein(a) (apo(a); the distinguishing protein component of lipoprotein(a)) containing 17 plasminogen kringle IV-like domains (17K r-apo(a)) protects LDL against oxidation by copper. Protection is specific to apo(a) and is not achieved by plasminogen or serum albumin. When Cu(2+) is added to 17K r-apo(a), its intrinsic fluorescence is quenched in a concentration-dependent and saturable manner. Quenching is unchanged whether performed aerobically or anaerobically and is reversible by ethylenediaminetetraacetate, suggesting that it is due to equilibrium binding of Cu(2+) and not to oxidative destruction of tryptophan residues. The fluorescence change exhibits a sigmoid dependence on copper concentration, and time courses of quenching are complex. At copper concentrations below 10 microM there is little quenching, whereas above 10 microM quenching proceeds immediately as a double-exponential decay. The affinity and kinetics of copper binding to 17K r-apo(a) are diminished in the presence of the lysine analogue epsilon -aminocaproic acid. We propose that copper binding to the kringle domains of 17K is mediated by a His-X-His sequence that is located about 5A from the closest tryptophan residue of the lysine binding pocket. Copper binding may account for the natural resistance to copper-mediated oxidation of lipoprotein(a) relative to LDL that has been previously reported and for the protection afforded by apo(a) from copper-mediated oxidation of LDL that we describe in the present study.
Collapse
Affiliation(s)
- Bruce C Hill
- Department of Biochemistry, Queen's University, Kingston, Ont, Canada K7L 3N6
| | | | | | | | | | | | | | | | | | | |
Collapse
|
|
30
|
Caterer NR, Graversen JH, Jacobsen C, Moestrup SK, Sigurskjold BW, Etzerodt M, Thøgersen HC. Specificity determinants in the interaction of apolipoprotein(a) kringles with tetranectin and LDL. Biol Chem 2002; 383:1743-50. [PMID: 12530539 DOI: 10.1515/bc.2002.195] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Lipoprotein(a) is composed of low density lipoprotein and apolipoprotein(a). Apolipoprotein(a) has evolved from plasminogen and contains 10 different plasminogen kringle 4 homologous domains [KIV(1-110)]. Previous studies indicated that lipoprotein(a) non-covalently binds the N-terminal region of lipoprotein B100 and the plasminogen kringle 4 binding plasma protein tetranectin. In this study recombinant KIV(2), KIV(7) and KIV(10) derived from apolipoprotein(a) were produced in E. coli and the binding to tetranectin and low density lipoprotein was examined. Only KIV(10) bound to tetranectin and binding was similar to that of plasminogen kringle 4 to tetranectin. Only KIV(7) bound to LDL. In order to identify the residues responsible for the difference in specificity between KIV(7) and KIV(10), a number of surface-exposed residues located around the lysine binding clefts were exchanged. Ligand binding analysis of these derivatives showed that Y62, and to a minor extent W32 and E56, of KIV(7) are important for LDL binding to KIV(7), whereas R32 and D56 of KIV(10) are required for tetranectin binding of KIV(10).
Collapse
Affiliation(s)
- Nigel R Caterer
- Laboratory of Gene Expression, Department of Molecular and Structural Biology, Aarhus, DK-8000 Aarhus C, Denmark
| | | | | | | | | | | | | |
Collapse
|
|
31
|
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
|
|
32
|
Ye Q, Rahman MN, Koschinsky ML, Jia Z. High-resolution crystal structure of apolipoprotein(a) kringle IV type 7: insights into ligand binding. Protein Sci 2001; 10:1124-9. [PMID: 11369850 PMCID: PMC2374005 DOI: 10.1110/ps.01701] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Apolipoprotein(a) [apo(a)] consists of a series of tandemly repeated modules known as kringles that are commonly found in many proteins involved in the fibrinolytic and coagulation cascades, such as plasminogen and thrombin, respectively. Specifically, apo(a) contains multiple tandem repeats of domains similar to plasminogen kringle IV (designated as KIV(1) to KIV(10)) followed by sequences similar to the kringle V and protease domains of plasminogen. The KIV domains of apo(a) differ with respect to their ability to bind lysine or lysine analogs. KIV(10) represents the high-affinity lysine-binding site (LBS) of apo(a); a weak LBS is predicted in each of KIV(5)-KIV(8) and has been directly demonstrated in KIV(7). The present study describes the first crystal structure of apo(a) KIV(7), refined to a resolution of 1.45 A, representing the highest resolution for a kringle structure determined to date. A critical substitution of Tyr-62 in KIV(7) for the corresponding Phe-62 residue in KIV(10), in conjunction with the presence of Arg-35 in KIV(7), results in the formation of a unique network of hydrogen bonds and electrostatic interactions between key LBS residues (Arg-35, Tyr-62, Asp-54) and a peripheral tyrosine residue (Tyr-40). These interactions restrain the flexibility of key LBS residues (Arg-35, Asp-54) and, in turn, reduce their adaptability in accommodating lysine and its analogs. Steric hindrance involving Tyr-62, as well as the elimination of critical ligand-stabilizing interactions within the LBS are also consequences of this interaction network. Thus, these subtle yet critical structural features are responsible for the weak lysine-binding affinity exhibited by KIV(7) relative to that of KIV(10).
Collapse
Affiliation(s)
- Q Ye
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada, K7L 3N6
| | | | | | | |
Collapse
|
|
33
|
Becker L, McLeod RS, Marcovina SM, Yao Z, Koschinsky ML. Identification of a critical lysine residue in apolipoprotein B-100 that mediates noncovalent interaction with apolipoprotein(a). J Biol Chem 2001; 276:36155-62. [PMID: 11473115 DOI: 10.1074/jbc.m104789200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have previously shown that lipoprotein(a) (Lp(a)) assembly involves an initial noncovalent interaction between sequences within apolipoprotein(a) (apo(a)) kringle IV types 5-8 and the amino terminus of apolipoprotein B-100 (sequences between amino acids 680 and 781 in apoB-100), followed by formation of a disulfide bond. In the present study, citraconylation of lysine residues in apoB-100 abolished the ability of the modified low density lipoprotein to associate with apo(a), thereby demonstrating a direct role for lysine residues in apoB in the first step of Lp(a) assembly. To identify specific lysine residues in the amino terminus of apoB that are required for the noncovalent interaction, we initially used an affinity chromatography method in which recombinant forms of apo(a) (r-apo(a)) were immobilized on Sepharose beads. Assessment of the ability of carboxyl-terminal truncations of apoB-18 to bind to r-apo(a)-Sepharose revealed that a 25-amino acid sequence in apoB (amino acids 680-704) bound specifically to apo(a) in a lysine-dependent manner; citraconylation of the lysine residues in the apoB derivative encoding this sequence abolished the binding interaction. Using fluorescence spectrometry, we found that a synthetic peptide corresponding to this sequence bound directly to apo(a); the peptide also reduced covalent Lp(a) formation. Lysine residues present in this sequence (Lys(680) and Lys(690)) were mutated to alanine in the context of apoB-18. We found that the apoB-18 species containing the Lys(680) mutation was incapable of binding to r-apo(a)-Sepharose columns, whereas the apoB-18 species containing the Lys(690) mutation exhibited slightly reduced binding to these columns. Taken together, our data indicate that Lys(680) is critical for the noncovalent interaction of apo(a) and apoB-100 that precedes covalent Lp(a) formation.
Collapse
Affiliation(s)
- L Becker
- Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | | | | | | | | |
Collapse
|
|
34
|
Roberts GA, Corcoran BT, Pfouts LL, Phillips JP, Farrell MA, Bouchier-Hayes DJ, Collins PB. Genetic Evaluation of Lipoprotein(a) in Intracranial Aneurysm Disease. Neurosurgery 2001. [DOI: 10.1227/00006123-200107000-00020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
|
|
35
|
Roberts GA, Corcoran BT, Pfouts LL, Phillips JP, Farrell MA, Bouchier-Hayes DJ, Collins PB. Genetic evaluation of lipoprotein(a) in intracranial aneurysm disease. Neurosurgery 2001; 49:133-40; discussion 141-2. [PMID: 11440434 DOI: 10.1097/00006123-200107000-00020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
OBJECTIVE Elevations in serum lipoprotein(a) [Lp(a)] levels have been reported in intracranial aneurysm (IA) disease. Our aim was to investigate a genetic basis for this observation. METHODS We performed a comparative analysis of size polymorphisms at two loci (kringle 4 [K4] and TTTTA pentanucleotide [PN] repeats) within the apolipoprotein(a) gene on Chromosome 6q26-27 among patients with sporadic IAs (n = 50), members of three IA families (n = 50), and control subjects (n = 50). RESULTS There was no significant difference in mean Lp(a) levels between patients with sporadic IAs and control subjects, but IA family members exhibited a more than twofold elevation in mean Lp(a) levels, compared with control subjects (29.2 versus 12.9 mg %). Inverse relationships between K4/PN numbers and serum Lp(a) levels were demonstrated; genotype frequencies did not differ significantly from a Hardy-Weinberg equilibrium or from published frequencies for other Caucasian populations. We detected no difference in mean K4 and PN genotypic indices between patients with IAs and control subjects (9.3 and 16.92 versus 9.0 and 16.92, respectively), but IA families did exhibit a lower mean K4 genotypic index (7.7), compared with control subjects. Superficial analysis of family pedigrees revealed no suggestion of linkage between K4/PN genotypes and IA disease. CONCLUSION The previously described elevation in Lp(a) levels among patients with sporadic IAs might be explained by an acute-phase response. Crude Lp(a) measurements might provide a useful predictive test for familial IA disease, but with the disadvantage of low specificity. The possibility of linkage of familial IA disease to a particular apolipoprotein(a) isoform size range has not been eliminated.
Collapse
Affiliation(s)
- G A Roberts
- Department of Neurosurgery, Beaumont Hospital, Dublin, Ireland.
| | | | | | | | | | | | | |
Collapse
|
|
36
|
Rahman MN, Petrounevitch V, Jia Z, Koschinsky ML. Antifibrinolytic effect of single apo(a) kringle domains: relationship to fibrinogen binding. PROTEIN ENGINEERING 2001; 14:427-38. [PMID: 11477223 DOI: 10.1093/protein/14.6.427] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Elevated plasma concentrations of lipoprotein(a) [Lp(a)] are associated with an increased risk for the development of atherosclerotic disease which may be attributable to the ability of Lp(a) to attenuate fibrinolysis. A generally accepted mechanism for this effect involves direct competition of Lp(a) with plasminogen for fibrin(ogen) binding sites thus reducing the efficiency of plasminogen activation. Efforts to determine the domains of apolipoprotein(a) [apo(a)] which mediate fibrin(ogen) interactions have yielded conflicting results. Thus, the purpose of the present study was to determine the ability of single KIV domains of apo(a) to bind plasmin-treated fibrinogen surfaces as well to determine their effect on fibrinolysis using an in vitro clot lysis assay. A bacterial expression system was utilized to express and purify apo(a) KIV (2), KIV (7), KIV (9) DeltaCys (which lacks the seventh unpaired cysteine) and KIV (10) which contains a strong lysine binding site. We also expressed and examined three mutant derivatives of KIV (10) to determine the effect of changing critical residues in the lysine binding site of this kringle on both fibrin(ogen) binding and fibrin clot lysis. Our results demonstrate that the strong lysine binding site in apo(a) KIV (10) is capable of mediating interactions with plasmin-modified fibrinogen in a lysine-dependent manner, and that this kringle can increase in vitro fibrin clot lysis time by approximately 43% at a concentration of 10 microM KIV (10). The ability of the KIV (10) mutant derivatives to bind plasmin-modified fibrinogen correlated with their lysine binding capacity. Mutation of Trp (70) to Arg abolished binding to both lysine-Sepharose and plasmin-modified fibrinogen, while the Trp (70) -->Phe and Arg (35) -->Lys substitutions each resulted in decreased binding to these substrates. None of the KIV (10) mutant derivatives appeared to affect fibrinolysis. Apo(a) KIV (7) contains a lysine- and proline-sensitive site capable of mediating binding to plasmin-modified fibrinogen, albeit with a lower apparent affinity than apo(a) KIV (10). However, apo(a) KIV (7) had no effect on fibrinolysis in vitro. Apo(a) KIV (2) and KIV (9) DeltaCys did not bind measurably to plasmin-modified fibrinogen surfaces and did not affect fibrinolysis in vitro.
Collapse
Affiliation(s)
- M N Rahman
- Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | | | | | | |
Collapse
|
|
37
|
Haque NS, Fallon JT, Taubman MB, Harpel PC. The chemokine receptor CCR8 mediates human endothelial cell chemotaxis induced by I-309 and Kaposi sarcoma herpesvirus-encoded vMIP-I and by lipoprotein(a)-stimulated endothelial cell conditioned medium. Blood 2001; 97:39-45. [PMID: 11133740 DOI: 10.1182/blood.v97.1.39] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The CC chemokine receptor 8 (CCR8) is expressed on monocytes and type 2 T lymphocytes. CCR8 is the sole receptor for the human CC chemokine I-309, as well as for viral monocyte inflammatory protein-I (vMIP-I), a human chemokine homologue induced in human cells by the Kaposi sarcoma-related human herpesvirus-8. Recently it was found that I-309 messenger RNA and protein are expressed by human umbilical vein endothelial cells (HUVECs) and that the secretion of endothelial I-309 is stimulated by apolipoprotein(a). I-309, vMIP-I, and the conditioned medium from apolipoprotein(a)-stimulated HUVECs induce endothelial chemotaxis. A polyclonal anti-CCR8 antibody and a newly developed murine monoclonal antibody against CCR8 inhibited this activity. The G-protein inhibitor pertussis toxin also inhibited endothelial chemotaxis, providing further evidence for a chemokine receptor-mediated effect. Endothelial cells contain CCR8 mRNA as shown by RNA blot analysis as well by direct sequence analysis. Immunohistochemical studies identified CCR8 and I-309 on the endothelium of human atherosclerotic plaques and in endothelial-derived spindle cells of Kaposi sarcoma. These results indicate that CCR8 is an endothelial receptor that may modulate endothelial function.
Collapse
MESH Headings
- Antibodies/pharmacology
- Chemokine CCL1
- Chemokine CXCL12
- Chemokines, CC/metabolism
- Chemokines, CC/pharmacology
- Chemokines, CXC/pharmacology
- Chemotactic Factors/pharmacology
- Chemotaxis/drug effects
- Coronary Artery Disease/metabolism
- Culture Media, Conditioned/pharmacology
- Endothelium, Vascular/cytology
- Herpesvirus 8, Human/chemistry
- Humans
- Immunohistochemistry
- Lipoprotein(a)/pharmacology
- Macrophage Inflammatory Proteins/pharmacology
- Pertussis Toxin
- RNA, Messenger/biosynthesis
- Receptors, CCR8
- Receptors, Chemokine/genetics
- Receptors, Chemokine/immunology
- Receptors, Chemokine/physiology
- Sarcoma, Kaposi/chemistry
- Umbilical Veins/cytology
- Viral Proteins
- Virulence Factors, Bordetella/pharmacology
Collapse
Affiliation(s)
- N S Haque
- Department of Medicine, Divisions of Hematology and Cardiology, and the Department of Pathology, The Mount Sinai School of Medicine, New York, NY 10029, USA
| | | | | | | |
Collapse
|
|
38
|
Xia J, May LF, Koschinsky ML. Characterization of the basis of lipoprotein [a] lysine-binding heterogeneity. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)31990-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
|
|
39
|
Cheesman EJ, Sharp RJ, Zlot CH, Liu CY, Taylor S, Marcovina SM, Young SG, McCormick SP. An analysis of the interaction between mouse apolipoprotein B100 and apolipoprotein(a). J Biol Chem 2000; 275:28195-200. [PMID: 10837476 DOI: 10.1074/jbc.m002772200] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The assembly of lipoprotein(a) (Lp(a)) involves an initial noncovalent interaction between apolipoprotein (apo) B100 and apo(a), followed by the formation of a disulfide bond between apoB100 cysteine 4326 and apo(a) cysteine 4057. The structural features of apoB100 that are required for its noncovalent interaction with apo(a) have not been fully defined. To analyze that initial interaction, we tested whether apo(a) could bind noncovalently to two apoB proteins that lack cysteine 4326: mouse apoB100 and human apoB100-C4326G. Our experiments demonstrated that both mouse apoB and the human apoB100-C4326G bind noncovalently to apo(a). We next sought to gain insights into the apoB amino acid sequences required for the interaction between apoB100 and apo(a). Previous studies of truncated human apoB proteins indicated that the carboxyl terminus of human apoB100 (amino acids 4330-4397) is important for Lp(a) assembly. To determine whether the carboxyl terminus of mouse apoB100 can interact with apo(a), transgenic mice were produced with a mutant human apoB gene construct in which human apoB100 amino acids 4279-4536 were replaced with the corresponding mouse apoB100 sequences and tyrosine 4326 was changed to a cysteine. The mutant apoB100 bound to apo(a) and formed bona fide disulfide-linked Lp(a), but Lp(a) assembly was less efficient than with wild-type human apoB100. The fact that Lp(a) assembly was less efficient with the mouse apoB sequences provides additional support for the notion that sequences in the carboxyl terminus of apoB100 are important for Lp(a) assembly.
Collapse
Affiliation(s)
- E J Cheesman
- Biochemistry Department, University of Otago, Dunedin 9001, New Zealand
| | | | | | | | | | | | | | | |
Collapse
|
|
40
|
Sangrar W, Koschinsky ML. Characterization of the interaction of recombinant apolipoprotein(a) with modified fibrinogen surfaces and fibrin clots. Biochem Cell Biol 2000. [DOI: 10.1139/o00-065] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Elevated levels of lipoprotein(a) [Lp(a)] in plasma are a significant risk factor for the development of atherosclerotic disease, a property which may arise from the ability of this lipoprotein to inhibit fibrinolysis. In the present study we have quantitated the binding of recombinant forms of apolipoprotein(a) [17K and 12K r-apo(a); containing 8 and 3 copies, respectively, of the major repeat kringle sequence (kringle IV type 2)] to modified fibrinogen surfaces. Iodinated 17K and 12K r-apo(a) bound to immobilized thrombin-modified fibrinogen (i.e., fibrin) surfaces with similar affinities (Kd~ 1.2 - 1.6 µM). The total concentration of binding sites (Bmax) present on the fibrin surface was ~4-fold greater for the 12K than for the 17K (Bmaxvalues of 0.81 ± 0.09 nM, and 0.20 ± 0.01 nM respectively), suggesting that the total binding capacity on fibrin surfaces is reduced for larger apolipoprotein(a) (apo(a)) species. Interestingly, binding of apo(a) to intact fibrin was not detected as assessed by measurement of intrinsic fluorescence of free apo(a) present in the supernatants of sedimented fibrin clots. In other experiments, the total concentration apo(a) binding sites available on plasmin-modified fibrinogen surfaces was shown to be 13.5-fold higher than the number of sites available on unmodified fibrin surfaces (Bmaxvalues of 2.7 ± 0.3 nM and 0.20 ± 0.01 nM respectively) while the affinity of apo(a) for these surfaces was similar. The increase in Bmaxwas correlated with plasmin-mediated exposure of C-terminal lysines since treatment of plasmin-modified fibrinogen surfaces with carboxypeptidase B produced a significant decrease in total binding signal as detected by ELISA (enzyme linked immunosorbent assay). Taken together, these data suggest that apo(a) binds to fibrin with poor affinity (low µM) and that the total concentration of apo(a) binding sites available on modified-fibrinogen surfaces is affected by both apo(a) isoform size and by the increased availability of C-terminal lysines on plasmin-degraded fibrinogen surfaces. However, the low affinity of apo(a) for fibrin indicates that Lp(a) may inhibit fibrinolysis through a mechanism distinct from binding to fibrin, such as binding to plasminogen.Key words: fibrinolysis, lipoprotein(a), plasminogen activation.
Collapse
|
|
41
|
Ramharack R, Bocan TM, Imperiale MJ, Spahr MA. Recombinant adenovirus vector mediated expression of lipoprotein (a) [Lp(a)] in rabbit plasma. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1438:322-8. [PMID: 10366775 DOI: 10.1016/s1388-1981(99)00065-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Lipoprotein (a) [Lp(a)] is a heterodimer of apolipoprotein (a) [apo(a)] and apolipoprotein B-100 (apoB-100) of low density lipoprotein linked by a disulfide bond. Apo(a) and apoB-100 are synthesized by the liver and covalently associate or couple to form Lp(a) extracellularly. Elevated plasma Lp(a) is an independent risk factor for vascular injury disorders such as restenosis after balloon angioplasty and accelerated graft atherosclerosis following heart transplantation. Lp(a) is not expressed in laboratory animals making studies of its pathophysiology difficult. To overcome this problem, we explored the possibility of generating Lp(a) in rabbit plasma using replication-deficient adenovirus vector mediated gene delivery. Rabbits were chosen because of their large vessels and unlike mouse or rat, rabbit apoB-100 could interact with apo(a) to generate Lp(a). The recombinant (r) adenovirus vector construct used encoded a 200 kDa apo(a) [Ad-apo(a)]. Ad-apo(a) injection into the rabbit marginal vein caused the appearance of plasma rLp(a). Injection of a r adenovirus vector expressing the bacterial LacZ gene (Ad-LacZ) or PBS (vehicle) did not result in detectable plasma rLp(a). These are the first results to demonstrate plasma expression of rLp(a) in rabbits using adenovirus vector mediated gene transfer. Therefore, this system may be suitable for investigating Lp(a)'s role in the development of vascular injury diseases in a rabbit model.
Collapse
Affiliation(s)
- R Ramharack
- Department of Cardiovascular Therapeutics, Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company, 2800 Plymouth Road, Ann Arbor, MI 48105, USA.
| | | | | | | |
Collapse
|
|
42
|
Noto D, Barbagallo CM, Cascio AL, Cefalù AB, Cavera G, Caldarella R, Marino G, Travali S, Cutaia I, Maringhini S, Notarbartolo A, Averna M. Lipoprotein(a) levels in relation to albumin concentration in childhood nephrotic syndrome. Kidney Int 1999; 55:2433-9. [PMID: 10354292 DOI: 10.1046/j.1523-1755.1999.00489.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Lipoprotein(a) [Lp(a)] is a lipoprotein consisting of a low-density lipoprotein (LDL) particle linked to a polymorphic glycoprotein, apoprotein(a) [apo(a)]. Prior studies have reported high Lp(a) levels in the nephrotic syndrome, but it is still controversial whether this is due to the degree of hypoalbuminemia or proteinuria. METHODS To investigate a model of nephrotic syndrome in the absence of renal failure, we studied a group of 84 children in different clinical stages of the disease for a period of five years. We evaluated the direct relationships between lipoproteins, including Lp(a), and/or plasma albumin and proteinuria. RESULTS Lp(a) levels were significantly higher in the subjects with the active disease compared with patients in remission, and were also significantly different when subjects were ranked by albumin quartiles. Multiple regression analysis revealed that Lp(a) levels were inversely correlated with apo(a) isoform size and plasma albumin levels but not with the proteinuria/creatinine clearance ratio. Among subjects in complete remission, Lp(a) levels were different in patients with albumin levels below or above the fifth percentile. After the improvement of the clinical stage of the disease, the Delta% variation of albumin levels was related to the Delta% of apoB and LDL cholesterol (LDL-C), but not with the Delta% variation of Lp(a), whereas the Delta% variation of LDL-C was, in turn, related to the Delta% of Lp(a) levels. CONCLUSIONS These results suggest that in the childhood nephrotic syndrome, the increased Lp(a) levels are mainly related to hypoalbuminemia, probably through a mechanism involving apoB overproduction, which leads to an increased number of LDL particles to be converted into Lp(a).
Collapse
Affiliation(s)
- D Noto
- Department of Internal Medicine, University of Palermo, Palermo, Italy
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
|
43
|
Abstract
Our understanding of the genetics, metabolism and pathophysiology of the atherogenic plasma lipoprotein Lp(a) has considerably increased over past years. Nevertheless, the precise mechanisms regulating the biosynthesis and assembly of Lp(a) are poorly understood and controversially discussed. Lp(a) plasma concentrations are determined by synthesis and not by degradation. Transcriptional and post-translational mechanisms have been identified as regulating Lp(a) production in primary hepatocytes and transfected cell lines. Assembly of Lp(a) occurs extracellularly from newly synthesized apolipoprotein(a) and circulating LDL. This view has recently been challenged by in-vivo kinetic studies in humans which are compatible with an intracellular assembly event. Lp(a) assembly is a complex two-step process of multiple non-covalent interactions between apolipoprotein(a) and apolipoprotein B-100 of LDL followed by covalent disulfide linkage of two free cysteine residues on both proteins.
Collapse
Affiliation(s)
- H Dieplinger
- Institute of Medical Biology and Human Genetics, University of Innsbruck, Austria
| | | |
Collapse
|
|
44
|
Frank S, Hrzenjak A, Kostner K, Sattler W, Kostner GM. Effect of tranexamic acid and delta-aminovaleric acid on lipoprotein(a) metabolism in transgenic mice. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1438:99-110. [PMID: 10216284 DOI: 10.1016/s1388-1981(99)00044-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The assembly of lipoprotein(a) (Lp(a)) is a two-step process which involves the interaction of kringle-4 (K-IV) domains in apolipoprotein(a) (apo(a)) with Lys groups in apoB-100. Lys analogues such as tranexamic acid (TXA) or delta-aminovaleric acid (delta-AVA) proved to prevent the Lp(a) assembly in vitro. In order to study the in vivo effect of Lys analogues, transgenic apo(a) or Lp(a) mice were treated with TXA or delta-AVA and plasma levels of free and low density lipoprotein bound apo(a) were measured. In parallel experiments, McA-RH 7777 cells, stably transfected with apo(a), were also treated with these substances and apo(a) secretion was followed. Treatment of transgenic mice with Lys analogues caused a doubling of plasma Lp(a) levels, while the ratio of free:apoB-100 bound apo(a) remained unchanged. In transgenic apo(a) mice a 1. 5-fold increase in plasma apo(a) levels was noticed. TXA significantly increased Lp(a) half-life from 6 h to 8 h. Incubation of McA-RH 7777 cells with Lys analogues resulted in an up to 1. 4-fold increase in apo(a) in the medium. The amount of intracellular low molecular weight apo(a) precursor remained unchanged. We hypothesize that Lys analogues increase plasma Lp(a) levels by increasing the dissociation of cell bound apo(a) in combination with reducing Lp(a) catabolism.
Collapse
Affiliation(s)
- S Frank
- Institute of Medical Biochemistry, University of Graz, Harrachgasse 21, 8010, Graz, Austria
| | | | | | | | | |
Collapse
|
|
45
|
Abstract
Since its identification by Kåre Berg in 1963, lipoprotein(a) [Lp(a)] has become a focus of research interest owing to the results of case-control and prospective studies linking elevated plasma levels of this lipoprotein with the development of coronary artery disease. Lp(a) contains a low-density lipoprotein (LDL)-like moiety, in which the apolipoprotein B-100 component is covalently linked to the unique glycoprotein apolipoprotein(a) [apo(a)]. Apo(a) is composed of repeated loop-shaped units called kringles, the sequences of which are highly similar to a kringle motif present in the fibrinolytic proenzyme plasminogen. Variability in the number of repeated kringle units in the apo(a) molecule gives rise to different-sized Lp(a) isoforms in the population. Based on the similarity of Lp(a) to both LDL and plasminogen, it has been hypothesized that the function of this unique lipoprotein may represent a link between the fields of atherosclerosis and thrombosis. However, determination of the function of Lp(a) in vivo remains elusive. Although Lp(a) has been shown to accumulate in atherosclerotic lesions, its contribution to the development of atheromas is unclear. This uncertainty is related in part to the structural complexity of the apo(a) component of Lp(a) (particularly apo(a) isoform size heterogeneity), which also poses a challenge for standardization of the measurement of Lp(a) in plasma. The fact that plasma Lp(a) levels are largely genetically determined and vary widely among different ethnic groups adds scientific interest to the ongoing study of this enigmatic particle. Most recently, the identification of proteolytic fragments of apo(a) in both plasma and urine has fueled speculation about the origin of these fragments and their possible function in the atherosclerotic process.
Collapse
Affiliation(s)
- S M Marcovina
- Department of Medicine, University of Washington, Seattle 98103-9103, USA
| | | |
Collapse
|
|
46
|
Chung FZ, Wu LH, Lee HT, Mueller WT, Spahr MA, Eaton SR, Tian Y, Settimi PD, Oxender DL, Ramharack R. Bacterial expression and characterization of human recombinant apolipoprotein(a) kringle IV type 9. Protein Expr Purif 1998; 13:222-8. [PMID: 9675066 DOI: 10.1006/prep.1998.0898] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Elevated plasma lipoprotein(a) [Lp(a)] is an independent risk factor for several vascular diseases. Lp(a) particles are generated through the formation of a disulfide bond between Cys4057 of kringle IV type 9, (KIVt9), of the multikringle apolipoprotein(a) [apo(a)] and a cysteine in apoB-100 low-density lipoprotein (LDL). To better understand this interaction, we have expressed and purified KIVt9 from Escherichia coli as a His-Tag fusionprotein. Dithiothreitol (DTT)-treated purified KIVt9 migrated as a single approximately 17. 3-kDa band on SDS-PAGE gels. Without DTT, an additional band twice the molecular weight of KIVt9 was observed. The double-size band presumably resulted from dimerization of individual kringles, through their unpaired cysteine residues, since a mutation Cys4057 --> Ser ([Ser4057]KIVt9) abolished dimer formation. Using a gel-shift assay, we showed that KIVt9 could couple to 14-amino-acid apoB-100 synthetic peptides (apoB3732-3745 and apoB4319-4332) containing Cys3734 or Cys4326. Both of these apoB-100 cysteines have been reported to associate with apo(a) to generate Lp(a). In the presence of either apoB-100 peptide, KIVt9 was shifted to a higher molecular weight that was consistent with the covalent addition of a 1.2-kDa apoB-100 peptide. Identical apoB-100 peptides in which the cysteine residues were replaced by alanine ([Ala3734]apoB3732-3745 and [Ala4326]apoB4319-4332) had no effect in the gel-shift assay. Furthermore, [Ser4057]KIVt9 did not covalently interact with apoB3732-3745 or apoB4319-4332. These results indicated that KIVt9 couples to the Cys-apoB-100 peptides through a disulfide linkage. This system may be suitable for further investigating the apo(a)/apoB-100 coupling reaction and the structure of KIVt9 through X-ray crystallographic studies.
Collapse
Affiliation(s)
- F Z Chung
- Department of Molecular Biology, Department of Medicinal Chemistry, Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Co., 2800 Plymouth Road, Ann Arbor, Michigan 48105, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
|
47
|
Hoover-Plow J, Skocir P. Enzymatic and chemical modifications of lipoprotein(a) selectively alter its lysine-binding functions. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1392:73-84. [PMID: 9593830 DOI: 10.1016/s0005-2760(98)00022-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The pathogenicity of lipoprotein(a) [Lp(a)] as a risk factor for cardiovascular disease may depend upon its lysine binding sites (LBS) which impart unique functions to Lp(a) not shared with low density lipoprotein. Biologically relevant modifications of Lp(a) were tested for alterations of LBS activity using two previously described functional assays, a LBS-Lp(a) immunoassay and a lysine-Sepharose bead assay. In the LBS-Lp(a) immunoassay, minimal changes in the LBS activity of Lp(a) were observed after modification with lipoprotein lipase, sphingomyelinase, or phospholipase C. In contrast, a significant (p<0.003) increase in the LBS activity of Lp(a) occurred after phospholipase A2 (PLA2) treatment, and this increase was confirmed using the lysine-Sepharose bead assay. The increase depended upon the release of fatty acids from Lp(a) by PLA2. A decrease in the LBS activity of Lp(a) occurred after oxidation of Lp(a) with 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) (44% decrease), but CuSO4 oxidation increased LBS activity (210%). N-acetylcysteine (NAC) treatment of Lp(a) decreased (48%) LBS activity while homocysteine treatment had no (89%) effect. Thus, modification of phospholipids and protein moieties can alter the LBS-activity of Lp(a). Such enzymatic and chemical modifications may contribute to the variability in LBS function of Lp(a) seen within the population.
Collapse
Affiliation(s)
- J Hoover-Plow
- Joseph J. Jacobs Center for Thrombosis and Vascular Biology, Department of Molecular Cardiology, FF20, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, USA.
| | | |
Collapse
|
|
48
|
McCormick SP, Nielsen LB. Expression of large genomic clones in transgenic mice: new insights into apolipoprotein B structure, function and regulation. Curr Opin Lipidol 1998; 9:103-11. [PMID: 9559266 DOI: 10.1097/00041433-199804000-00005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Extensive manipulation of the apolipoprotein B gene in yeast and bacterial artificial chromosome clones and subsequent expression of these clones in transgenic mice have provided fresh insights into several aspects of apolipoprotein B biology, including the identification of sequences important for lipoprotein (a) assembly, the demonstration that intestinal expression of apolipoprotein B is controlled by DNA sequences > 50 kb from the gene, and the extraordinary finding that apolipoprotein B is expressed in the heart.
Collapse
Affiliation(s)
- S P McCormick
- Biochemistry Department, University of Otago, Dunedin, New Zealand.
| | | |
Collapse
|
|
49
|
|
|
50
|
Rouy D, Duverger N, Lin SD, Emmanuel F, Houdebine LM, Denefle P, Viglietta C, Gong E, Rubin EM, Hughes SD. Apolipoprotein(a) yeast artificial chromosome transgenic rabbits. Lipoprotein(a) assembly with human and rabbit apolipoprotein B. J Biol Chem 1998; 273:1247-51. [PMID: 9422793 DOI: 10.1074/jbc.273.2.1247] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The in vivo analysis of lipoprotein(a) (Lp(a)), an independent atherosclerosis risk factor in humans, has been limited in part by its restricted distribution among mammals. Although transgenic mice have been created containing Lp(a), the relatively small size of the mouse has precluded some studies. To examine the properties of this molecule in a significantly larger mammal, we have used a 270-kilobase yeast artificial chromosome clone containing the human apolipoprotein(a) (apo(a)) gene and a 90-kilobase P1 phagemid clone containing the human apolipoprotein B (apoB) gene to create transgenic rabbits that express either or both transgenes. Expression of both transgenes was tissue specific and localized predominantly to the liver. Average apolipoprotein plasma levels in the rabbits were 2.5 mg/dl for apo(a) and 17.6 mg/dl for human apoB. In contrast to observations in apo(a) transgenic mice, we found that apo(a) plasma levels in the rabbits were stable throughout sexual maturity. Also, apo(a) formed a covalent association with the endogenous rabbit apoB albeit with a lower efficiency than its association with human apoB. The analysis of Lp(a) transgenic rabbits has provided new insights into apo(a) expression and Lp(a) assembly. In addition, these transgenic rabbits potentially will provide an improved experimental model for the in vivo analysis of Lp(a) and its role in promoting atherosclerosis and restenosis.
Collapse
Affiliation(s)
- D Rouy
- Rhône-Poulenc Rorer-Gencell, Atherosclerosis Department, Centre de Recherche de Vitry-Alfortville, 94403 Vitry sur Seine Cedex, France
| | | | | | | | | | | | | | | | | | | |
Collapse
|