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Foster H, Wilson C, Philippou H, Foster R. Progress toward a Glycoprotein VI Modulator for the Treatment of Thrombosis. J Med Chem 2020; 63:12213-12242. [PMID: 32463237 DOI: 10.1021/acs.jmedchem.0c00262] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Pathogenic thrombus formation accounts for the etiology of many serious conditions including myocardial infarction, stroke, deep vein thrombosis, and pulmonary embolism. Despite the development of numerous anticoagulants and antiplatelet agents, the mortality rate associated with these diseases remains high. In recent years, however, significant epidemiological evidence and clinical models have emerged to suggest that modulation of the glycoprotein VI (GPVI) platelet receptor could be harnessed as a novel antiplatelet strategy. As such, many peptidic agents have been described in the past decade, while more recent efforts have focused on the development of small molecule modulators. Herein the rationale for targeting GPVI is summarized and the published GPVI modulators are reviewed, with particular focus on small molecules. A qualitative pharmacophore hypothesis for small molecule ligands at GPVI is also presented.
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Affiliation(s)
- Holly Foster
- School of Chemistry and Leeds Institute of Cardiovascular and Metabolic Medicine (LICAMM), School of Medicine, University of Leeds, Leeds LS2 9JT, U.K
| | - Clare Wilson
- Leeds Institute of Cardiovascular and Metabolic Medicine (LICAMM), School of Medicine, University of Leeds, Leeds LS2 9JT, U.K
| | - Helen Philippou
- Leeds Institute of Cardiovascular and Metabolic Medicine (LICAMM), School of Medicine, University of Leeds, Leeds LS2 9JT, U.K
| | - Richard Foster
- School of Chemistry and Leeds Institute of Cardiovascular and Metabolic Medicine (LICAMM), School of Medicine, University of Leeds, Leeds LS2 9JT, U.K
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Montague SJ, Hicks SM, Lee CSM, Coupland LA, Parish CR, Lee WM, Andrews RK, Gardiner EE. Fibrin exposure triggers αIIbβ3-independent platelet aggregate formation, ADAM10 activity and glycoprotein VI shedding in a charge-dependent manner. J Thromb Haemost 2020; 18:1447-1458. [PMID: 32198957 DOI: 10.1111/jth.14797] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 03/11/2020] [Indexed: 12/20/2022]
Abstract
BACKGROUND Collagen and fibrin engagement and activation of glycoprotein (GP) VI induces proteolytic cleavage of the GPVI ectodomain generating shed soluble GPVI (sGPVI). Collagen-mediated GPVI shedding requires intracellular signalling to release the sGPVI, mediated by A Disintegrin And Metalloproteinase 10 (ADAM10); however, the precise mechanism by which fibrin induces GPVI shedding remains elusive. Plasma sGPVI levels are elevated in patients with coagulopathies, sepsis, or inflammation and can predict onset of sepsis and sepsis-related mortality; therefore, it is clinically important to understand the mechanisms of GPVI shedding under conditions of minimal collagen exposure. OBJECTIVES Our aim was to characterize mechanisms by which fibrin-GPVI interactions trigger GPVI shedding. METHODS Platelet aggregometry, sGPVI ELISA, and an ADAM10 fluorescence resonance energy transfer assay were used to measure fibrin-mediated platelet responses. RESULTS Fibrin induced αIIbβ3-independent washed platelet aggregate formation, GPVI shedding, and increased ADAM10 activity, all of which were insensitive to pre-treatment with inhibitors of Src family kinases but were divalent cation- and metalloproteinase-dependent. In contrast, treatment of washed platelets with other GPVI ligands, collagen, and collagen-related peptide caused αIIbβ3-dependent platelet aggregation and GPVI release but did not increase constitutive ADAM10 activity. CONCLUSIONS Fibrin engages GPVI in a manner that differs from other GPVI ligands. Inclusion of polyanionic molecules disrupted fibrin-induced platelet aggregate formation and sGPVI release, suggesting that electrostatic charge may play a role in fibrin/GPVI engagement. It may be feasible to exploit this property and specifically disrupt GPVI/fibrin interactions whilst sparing GPVI/collagen engagement.Fibrin engages GPVI in a manner that differs from other GPVI ligands. Inclusion of polyanionic molecules disrupted fibrin-induced platelet aggregate formation and sGPVI release, suggesting that electrostatic charge may play a role in fibrin/GPVI engagement. It may be feasible to exploit this property and specifically disrupt GPVI/fibrin interactions whilst sparing GPVI/collagen engagement.
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Affiliation(s)
- Samantha J Montague
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Sarah M Hicks
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Christine S-M Lee
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Lucy A Coupland
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Christopher R Parish
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Woei M Lee
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT, Australia
| | - Robert K Andrews
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
| | - Elizabeth E Gardiner
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
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Asghar MA, Yousuf RI, Shoaib MH, Asghar MA. Antibacterial, anticoagulant and cytotoxic evaluation of biocompatible nanocomposite of chitosan loaded green synthesized bioinspired silver nanoparticles. Int J Biol Macromol 2020; 160:934-943. [PMID: 32470586 DOI: 10.1016/j.ijbiomac.2020.05.197] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 05/16/2020] [Accepted: 05/22/2020] [Indexed: 11/17/2022]
Abstract
Present work reports the green synthesis of chitosan functionalized silver nanoparticles (CS-AgNPs) using ethanolic buds extract of Sygyzium aromaticum. CS-AgNPs were characterized physically, evaluated for antibacterial, anticoagulant and antiplatelet activities, and toxicity profile. The physical characterization of CS-AgNPs was done by UV/vis, SEM, TEM, FTIR and EDX. The sphericity was found uniform. FTIR and EXD showed noninterfering few impurities. The antibacterial activity against VRSA (ZI, 23.2 ± 0.51 mm) and MRSA (ZI, 25.8 ± 0.32 mm) were determined. The rise in bleeding and thromboplastin was observed highly significant while increased in prothrombin and activated partial prothrombin time in significant manner at both the doses of CS-AgNPs (0.025 mg/kg and 0.05 mg/kg). Reduction in the levels of fibrinogen was also highly significant. Platelet aggregation decreased at high dose of CS-AgNPs i.e. 55.14 ± 8.25% (arachidonic acid) and 13.06 ± 2.17% (collagen). Thrombin antithrombin (TAT) complex activity was found highest for CS-AgNPs. Cytotoxicity was assessed using HeLa cell lines (LC50; 125 μg/ml) and brine shrimp lethality tests (LC50; 518 μg/ml). The work suggests that green synthesized chitosan functionalized silver nanoparticles may be utilized as an effective antibacterial agent and anticoagulant with low toxicity. The current findings will open a new window for nanomedicine development and future clinical application.
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Affiliation(s)
- Muhammad Arif Asghar
- Department of Pharmaceutics, Faculty of Pharmacy and Pharmaceutical Sciences, University of Karachi, Karachi 75270, Pakistan
| | - Rabia Ismail Yousuf
- Department of Pharmaceutics and Bioavailability and Bioequivalence Research Facility, Faculty of Pharmacy and Pharmaceutical Sciences, University of Karachi, Karachi 75270, Pakistan.
| | - Muhammad Harris Shoaib
- Department of Pharmaceutics and Bioavailability and Bioequivalence Research Facility, Faculty of Pharmacy and Pharmaceutical Sciences, University of Karachi, Karachi 75270, Pakistan.
| | - Muhammad Asif Asghar
- Food and Feed Safety Laboratory, Food and Marine Resources Research Centre, PCSIR Laboratories Complex, Shahrah-e-Salimuzzaman Siddiqui, Off University Road, 75280, Karachi, Sindh 74200, Pakistan
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Lordan R, Tsoupras A, Zabetakis I. Platelet activation and prothrombotic mediators at the nexus of inflammation and atherosclerosis: Potential role of antiplatelet agents. Blood Rev 2020; 45:100694. [PMID: 32340775 DOI: 10.1016/j.blre.2020.100694] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 03/22/2020] [Accepted: 04/07/2020] [Indexed: 12/20/2022]
Abstract
Platelets are central to inflammation-related manifestations of cardiovascular diseases (CVD) such as atherosclerosis. Platelet-activating factor (PAF), thrombin, thromboxane A2 (TxA2), and adenosine diphosphate (ADP) are some of the key agonists of platelet activation that are at the intersection between a plethora of inflammatory pathways that modulate pro-inflammatory and coagulation processes. The aim of this article is to review the role of platelets and the relationship between their structure, function, and the interactions of their constituents in systemic inflammation and atherosclerosis. Antiplatelet therapies are discussed with a view to primary prevention of CVD by the clinical reduction of platelet reactivity and inflammation. Current antiplatelet therapies are effective in reducing cardiovascular risk but increase bleeding risk. Novel therapeutic antiplatelet approaches beyond current pharmacological modalities that do not increase the risk of bleeding require further investigation. There is potential for specifically designed nutraceuticals that may become safer alternatives to pharmacological antiplatelet agents for the primary prevention of CVD but there is serious concern over their efficacy and regulation, which requires considerably more research.
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Affiliation(s)
- Ronan Lordan
- Department of Biological Sciences, University of Limerick, Limerick, Ireland; Health Research Institute (HRI), University of Limerick, Limerick, Ireland; Institute for Translational Medicine and Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-5158, USA.
| | - Alexandros Tsoupras
- Department of Biological Sciences, University of Limerick, Limerick, Ireland; Health Research Institute (HRI), University of Limerick, Limerick, Ireland
| | - Ioannis Zabetakis
- Department of Biological Sciences, University of Limerick, Limerick, Ireland; Health Research Institute (HRI), University of Limerick, Limerick, Ireland
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Nicolas J, Magli S, Rabbachin L, Sampaolesi S, Nicotra F, Russo L. 3D Extracellular Matrix Mimics: Fundamental Concepts and Role of Materials Chemistry to Influence Stem Cell Fate. Biomacromolecules 2020; 21:1968-1994. [PMID: 32227919 DOI: 10.1021/acs.biomac.0c00045] [Citation(s) in RCA: 270] [Impact Index Per Article: 67.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Synthetic 3D extracellular matrices (ECMs) find application in cell studies, regenerative medicine, and drug discovery. While cells cultured in a monolayer may exhibit unnatural behavior and develop very different phenotypes and genotypes than in vivo, great efforts in materials chemistry have been devoted to reproducing in vitro behavior in in vivo cell microenvironments. This requires fine-tuning the biochemical and structural actors in synthetic ECMs. This review will present the fundamentals of the ECM, cover the chemical and structural features of the scaffolds used to generate ECM mimics, discuss the nature of the signaling biomolecules required and exploited to generate bioresponsive cell microenvironments able to induce a specific cell fate, and highlight the synthetic strategies involved in creating functional 3D ECM mimics.
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Affiliation(s)
- Julien Nicolas
- Université Paris-Saclay, CNRS, Institut Galien Paris-Saclay, , 92296 Châtenay-Malabry, France
| | - Sofia Magli
- University of Milano-Bicocca, Department of Biotechnology and Biosciences, Piazza della Scienza 2, 20126 Milan, Italy
| | - Linda Rabbachin
- University of Milano-Bicocca, Department of Biotechnology and Biosciences, Piazza della Scienza 2, 20126 Milan, Italy
| | - Susanna Sampaolesi
- University of Milano-Bicocca, Department of Biotechnology and Biosciences, Piazza della Scienza 2, 20126 Milan, Italy
| | - Francesco Nicotra
- University of Milano-Bicocca, Department of Biotechnology and Biosciences, Piazza della Scienza 2, 20126 Milan, Italy
| | - Laura Russo
- University of Milano-Bicocca, Department of Biotechnology and Biosciences, Piazza della Scienza 2, 20126 Milan, Italy
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Lakshmanan HHS, Melrose AR, Sepp ALI, Mitrugno A, Ngo ATP, Khader A, Thompson R, Sallee D, Pang J, Mangin PH, Jandrot-Perrus M, Aslan JE, McCarty OJT. The basement membrane protein nidogen-1 supports platelet adhesion and activation. Platelets 2020; 32:424-428. [PMID: 32233694 DOI: 10.1080/09537104.2020.1745170] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The core structure of the extracellular basement membrane is made up of self-assembling networks of collagen and laminin which associate with each other through the bridging adapter proteins including the sulfated monomeric glycoprotein nidogen. While collagen and laminin are known to support platelet adhesion and activation via β1 integrins and glycoprotein (GP) VI, respectively, whether nidogen contributes to platelet activation and hemostasis is unknown. In this study, we demonstrate that recombinant human nidogen-1 supports platelet adhesion and stimulates platelet activation in a phospholipase-C γ-2 (PLCγ2), Src and Syk kinase-dependent manner downstream. Platetet adhesion to nidogen-1 was inhibited by blocking the platelet receptors GPVI and β1 integrins. Platelet adhesion to nidogen-1 activated the IκB kinase (IKK) complex, while pharmacological inhibition of IKK blocked platelet spreading on nidogen. Taken together our results suggest that nidogen may play a redundant role in hemostasis by activating platelets downstream of GPVI.
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Affiliation(s)
| | - Alexander R Melrose
- Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR, USA
| | - Anna-Liisa I Sepp
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, USA.,Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, USA
| | - Annachiara Mitrugno
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, USA
| | - Anh T P Ngo
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, USA
| | - Ayesha Khader
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, USA
| | - Rachel Thompson
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, USA.,Biomedical Engineering Department, University of Connecticut, Storrs, CT, USA
| | - Daniel Sallee
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, USA
| | - Jiaqing Pang
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, USA
| | - Pierre H Mangin
- INSERM, EFS Grand-Est, BPPS UMR-S 1255, FMTS, Université De Strasbourg, Strasbourg, France
| | - Martine Jandrot-Perrus
- Laboratory of Vascular Translational Science, Sorbonne Paris Cité, Institut National de la Santé et de la Recherche Médicale (INSERM), Université Paris Diderot, Paris, France
| | - Joseph E Aslan
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, USA.,Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR, USA
| | - Owen J T McCarty
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, USA
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58
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Therapeutic strategies for thrombosis: new targets and approaches. Nat Rev Drug Discov 2020; 19:333-352. [PMID: 32132678 DOI: 10.1038/s41573-020-0061-0] [Citation(s) in RCA: 167] [Impact Index Per Article: 41.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/16/2020] [Indexed: 12/19/2022]
Abstract
Antiplatelet agents and anticoagulants are a mainstay for the prevention and treatment of thrombosis. However, despite advances in antithrombotic therapy, a fundamental challenge is the side effect of bleeding. Improved understanding of the mechanisms of haemostasis and thrombosis has revealed new targets for attenuating thrombosis with the potential for less bleeding, including glycoprotein VI on platelets and factor XIa of the coagulation system. The efficacy and safety of new agents are currently being evaluated in phase III trials. This Review provides an overview of haemostasis and thrombosis, details the current landscape of antithrombotic agents, addresses challenges with preventing thromboembolic events in patients at high risk and describes the emerging therapeutic strategies that may break the inexorable link between antithrombotic therapy and bleeding risk.
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Abstract
Rheumatoid arthritis (RA) is an autoimmune disease in which a variety of circulating pro-inflammatory cells and dysregulated molecules are involved in disease aetiology and progression. Platelets are an important cellular element in the circulation that can bind several dysregulated molecules (such as collagen, thrombin and fibrinogen) that are present both in the synovium and the circulation of patients with RA. Platelets not only respond to dysregulated molecules in their environment but also transport and express their own inflammatory mediators, and serve as regulators at the boundary between haemostasis and immunity. Activated platelets also produce microparticles, which further convey signalling molecules and receptors to the synovium and circulation, thereby positioning these platelet-derived particles as strategic regulators of inflammation. These diverse functions come together to make platelets facilitators of cellular crosstalk in RA. Thus, the receptor functions, ligand binding potential and dysregulated signalling pathways in platelets are becoming increasingly important for treatment in RA. This Review aims to highlight the role of platelets in RA and the need to closely examine platelets as health indicators when designing effective pharmaceutical targets in this disease.
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60
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Dunster JL, Unsworth AJ, Bye AP, Haining EJ, Sowa MA, Di Y, Sage T, Pallini C, Pike JA, Hardy AT, Nieswandt B, García Á, Watson SP, Poulter NS, Gibbins JM, Pollitt AY. Interspecies differences in protein expression do not impact the spatiotemporal regulation of glycoprotein VI mediated activation. J Thromb Haemost 2020; 18:485-496. [PMID: 31680418 PMCID: PMC7027541 DOI: 10.1111/jth.14673] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 10/29/2019] [Accepted: 10/30/2019] [Indexed: 12/13/2022]
Abstract
BACKGROUND Accurate protein quantification is a vital prerequisite for generating meaningful predictions when using systems biology approaches, a method that is increasingly being used to unravel the complexities of subcellular interactions and as part of the drug discovery process. Quantitative proteomics, flow cytometry, and western blotting have been extensively used to define human platelet protein copy numbers, yet for mouse platelets, a model widely used for platelet research, evidence is largely limited to a single proteomic dataset in which the total amount of proteins was generally comparatively higher than those found in human platelets. OBJECTIVES To investigate the functional implications of discrepancies between levels of mouse and human proteins in the glycoprotein VI (GPVI) signalling pathway using a systems pharmacology model of GPVI. METHODS The protein copy number of mouse platelet receptors was determined using flow cytometry. The Virtual Platelet, a mathematical model of GPVI signalling, was used to determine the consequences of protein copy number differences observed between human and mouse platelets. RESULTS AND CONCLUSION Despite the small size of mouse platelets compared to human platelets they possessed a greater density of surface receptors alongside a higher concentration of intracellular signalling proteins. Surprisingly the predicted temporal profile of Syk activity was similar in both species with predictions supported experimentally. Super resolution microscopy demonstrates that the spatial distribution of Syk is similar between species, suggesting that the spatial distribution of receptors and signalling molecules in activated platelets, rather than their copy number, is important for signalling pathway regulation.
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Affiliation(s)
- Joanne L. Dunster
- Institute for Cardiovascular and Metabolic Research (ICMR)School of Biological SciencesUniversity of ReadingReadingUK
| | - Amanda J. Unsworth
- Institute for Cardiovascular and Metabolic Research (ICMR)School of Biological SciencesUniversity of ReadingReadingUK
- Department of Life SciencesSchool of Science and EngineeringManchester Metropolitan UniversityManchesterUK
| | - Alexander P. Bye
- Institute for Cardiovascular and Metabolic Research (ICMR)School of Biological SciencesUniversity of ReadingReadingUK
| | - Elizabeth J. Haining
- Institute of Cardiovascular Sciences (ICVS)College of Medical and Dental SciencesUniversity of BirminghamBirminghamUK
| | - Marcin A. Sowa
- Institute for Cardiovascular and Metabolic Research (ICMR)School of Biological SciencesUniversity of ReadingReadingUK
- Platelet Proteomics GroupCenter for Research in Molecular Medicine and Chronic Diseases (CIMUS)Universidade de Santiago de CompostelaSantiago de CompostelaSpain
| | - Ying Di
- Institute of Cardiovascular Sciences (ICVS)College of Medical and Dental SciencesUniversity of BirminghamBirminghamUK
| | - Tanya Sage
- Institute for Cardiovascular and Metabolic Research (ICMR)School of Biological SciencesUniversity of ReadingReadingUK
| | - Chiara Pallini
- Institute of Cardiovascular Sciences (ICVS)College of Medical and Dental SciencesUniversity of BirminghamBirminghamUK
| | - Jeremy A. Pike
- Centre of Membrane Proteins and Receptors (COMPARE)Universities of Birmingham and NottinghamMidlandsBirminghamUK
| | - Alexander T. Hardy
- Institute of Cardiovascular Sciences (ICVS)College of Medical and Dental SciencesUniversity of BirminghamBirminghamUK
| | - Bernhard Nieswandt
- Department of Experimental BiomedicineUniversity HospitalUniversity of WürzburgWürzburgGermany
| | - Ángel García
- Platelet Proteomics GroupCenter for Research in Molecular Medicine and Chronic Diseases (CIMUS)Universidade de Santiago de CompostelaSantiago de CompostelaSpain
| | - Steve P. Watson
- Institute of Cardiovascular Sciences (ICVS)College of Medical and Dental SciencesUniversity of BirminghamBirminghamUK
- Centre of Membrane Proteins and Receptors (COMPARE)Universities of Birmingham and NottinghamMidlandsBirminghamUK
| | - Natalie S. Poulter
- Institute of Cardiovascular Sciences (ICVS)College of Medical and Dental SciencesUniversity of BirminghamBirminghamUK
- Centre of Membrane Proteins and Receptors (COMPARE)Universities of Birmingham and NottinghamMidlandsBirminghamUK
| | - Jonathan M. Gibbins
- Institute for Cardiovascular and Metabolic Research (ICMR)School of Biological SciencesUniversity of ReadingReadingUK
| | - Alice Y. Pollitt
- Institute for Cardiovascular and Metabolic Research (ICMR)School of Biological SciencesUniversity of ReadingReadingUK
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Nurden AT. Clinical significance of altered collagen-receptor functioning in platelets with emphasis on glycoprotein VI. Blood Rev 2019; 38:100592. [PMID: 31351674 DOI: 10.1016/j.blre.2019.100592] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 07/05/2019] [Accepted: 07/19/2019] [Indexed: 01/01/2023]
Abstract
Much interest surrounds the receptors α2β1 and glycoprotein VI (GPVI) whose synchronized action mediates the attachment and activation of platelets on collagen, essential for preventing blood loss but also the most thrombogenic component of the vessel wall. Subject to density variations on platelets through natural polymorphisms, the absence of α2β1 or GPVI uniquely leads to a substantial block of hemostasis without causing major bleeding. Specific to the megakaryocyte lineage, GPVI and its signaling pathways are most promising targets for anti-thrombotic therapy. This review looks at the clinical consequences of the loss of collagen receptor function with emphasis on both the inherited and acquired loss of GPVI with brief mention of mouse models when necessary. A detailed survey of rare case reports of patients with inherited disease-causing variants of the GP6 gene is followed by an assessment of the causes and clinical consequences of acquired GPVI deficiency, a more frequent finding most often due to antibody-induced platelet GPVI shedding. Release of soluble GPVI is brought about by platelet metalloproteinases; a process induced by ligand or antibody binding to GPVI or even high shear forces. Also included is an assessment of the clinical importance of GPVI-mediated platelet interactions with fibrin and of the promise shown by the pharmacological inhibition of GPVI in a cardiovascular context. The role for GPVI in platelet function in inflammation and in the evolution and treatment of major illnesses such as rheumatoid arthritis, cancer and sepsis is also discussed.
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Affiliation(s)
- Alan T Nurden
- Institut de Rhythmologie et de Modélisation Cardiaque, PTIB, Hôpital Xavier Arnozan, 33600 Pessac, France.
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62
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Developments in inhibiting platelet aggregation based on different design strategies. Future Med Chem 2019; 11:1757-1775. [PMID: 31288579 DOI: 10.4155/fmc-2018-0345] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Platelet aggregation is the central event in hemostasis and thrombosis. Up to now, many agents inhibiting platelet aggregation have been approved for the treatment of thrombotic disorders. In this review, we mainly summarized the progress in the research of platelet aggregation inhibitors based on different design strategies. The advantage and challenge of corresponding targets are also discussed in this article. We hope more platelet aggregation inhibitors with efficacy and safety will be discovered in the future.
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63
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Role of Platelet Glycoprotein VI and Tyrosine Kinase Syk in Thrombus Formation on Collagen-Like Surfaces. Int J Mol Sci 2019; 20:ijms20112788. [PMID: 31181592 PMCID: PMC6600290 DOI: 10.3390/ijms20112788] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 05/29/2019] [Accepted: 06/04/2019] [Indexed: 01/20/2023] Open
Abstract
Platelet interaction with collagens, via von Willebrand factor, is a potent trigger of shear-dependent thrombus formation mediated by subsequent engagement of the signaling collagen receptor glycoprotein (GP)VI, enforced by integrin α2β1. Protein tyrosine kinase Syk is central in the GPVI-induced signaling pathway, leading to elevated cytosolic Ca2+. We aimed to determine the Syk-mediated thrombogenic activity of several collagen peptides and (fibrillar) type I and III collagens. High-shear perfusion of blood over microspots of these substances resulted in thrombus formation, which was assessed by eight parameters and was indicative of platelet adhesion, activation, aggregation, and contraction, which were affected by the Syk inhibitor PRT-060318. In platelet suspensions, only collagen peptides containing the consensus GPVI-activating sequence (GPO)n and Horm-type collagen evoked Syk-dependent Ca2+ rises. In whole blood under flow, Syk inhibition suppressed platelet activation and aggregation parameters for the collagen peptides with or without a (GPO)n sequence and for all of the collagens. Prediction models based on a regression analysis indicated a mixed role of GPVI in thrombus formation on fibrillar collagens, which was abolished by Syk inhibition. Together, these findings indicate that GPVI-dependent signaling through Syk supports platelet activation in thrombus formation on collagen-like structures regardless of the presence of a (GPO)n sequence.
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GPVI surface expression and signalling pathway activation are increased in platelets from obese patients: Elucidating potential anti-atherothrombotic targets in obesity. Atherosclerosis 2019; 281:62-70. [PMID: 30658193 PMCID: PMC6403451 DOI: 10.1016/j.atherosclerosis.2018.12.023] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 11/23/2018] [Accepted: 12/21/2018] [Indexed: 02/02/2023]
Abstract
BACKGROUND AND AIMS Platelets play a fundamental role in the increased atherothrombotic risk related to central obesity since they show hyperactivation and lower sensitivity to antiplatelet therapy in obese patients. The main goal of this study was to identify platelet biomarkers related to the risk of atherothrombosis in obese patients, confirm platelet activation levels in these patients, and identify altered activation pathways. METHODS Platelets were obtained from cohorts of obese patients and age- and sex-matched lean controls. Biochemical and proteome analyses were done by two-dimensional differential in-gel electrophoresis (2D-DIGE), mass spectrometry, and immunoblotting. Functional and mechanistic studies were conducted with aggregation assays and flow cytometry. RESULTS We confirmed an up-regulation of αIIb and fibrinogen isoforms in platelets from obese patients. A complementary platelet aggregation approach showed platelets from obese patients are hyper-reactive in response to collagen and collagen-related peptide (CRP), revealing the collagen receptor Glycoprotein VI (GPVI) signalling as one of the altered pathways. We also found the active form of Src (pTyr418) is up-regulated in platelets from obese individuals, which links proteomics to aggregation data. Moreover, we showed that CRP-activated platelets present higher levels of tyrosine phosphorylated PLCγ2 in obese patients, confirming alterations in GPVI signalling. In line with the above, flow cytometry studies show higher surface expression levels of total GPVI and GPVI-dimer in obese platelets, both correlating with BMI. CONCLUSIONS Our results suggest a higher activation state of SFKs-mediated signalling pathways in platelets from obese patients, with a primary involvement of GPVI signalling.
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65
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Rayes J, Watson SP, Nieswandt B. Functional significance of the platelet immune receptors GPVI and CLEC-2. J Clin Invest 2019; 129:12-23. [PMID: 30601137 DOI: 10.1172/jci122955] [Citation(s) in RCA: 195] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Although platelets are best known for their role in hemostasis, they are also crucial in development, host defense, inflammation, and tissue repair. Many of these roles are regulated by the immune-like receptors glycoprotein VI (GPVI) and C-type lectin receptor 2 (CLEC-2), which signal through an immunoreceptor tyrosine-based activation motif (ITAM). GPVI is activated by collagen in the subendothelial matrix, by fibrin and fibrinogen in the thrombus, and by a remarkable number of other ligands. CLEC-2 is activated by the transmembrane protein podoplanin, which is found outside of the vasculature and is upregulated in development, inflammation, and cancer, but there is also evidence for additional ligands. In this Review, we discuss the physiological and pathological roles of CLEC-2 and GPVI and their potential as targets in thrombosis and thrombo-inflammatory disorders (i.e., disorders in which inflammation plays a critical role in the ensuing thrombosis) relative to current antiplatelet drugs.
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Affiliation(s)
- Julie Rayes
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Steve P Watson
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom.,Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, United Kingdom
| | - Bernhard Nieswandt
- Institute of Experimental Biomedicine, University Hospital and Rudolf Virchow Center, University of Würzburg, Würzburg, Germany
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68
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Mechanisms of receptor shedding in platelets. Blood 2018; 132:2535-2545. [DOI: 10.1182/blood-2018-03-742668] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 10/12/2018] [Indexed: 02/07/2023] Open
Abstract
Abstract
The ability to upregulate and downregulate surface-exposed proteins and receptors is a powerful process that allows a cell to instantly respond to its microenvironment. In particular, mobile cells in the bloodstream must rapidly react to conditions where infection or inflammation are detected, and become proadhesive, phagocytic, and/or procoagulant. Platelets are one such blood cell that must rapidly acquire and manage proadhesive and procoagulant properties in order to execute their primary function in hemostasis. The regulation of platelet membrane properties is achieved via several mechanisms, one of which involves the controlled metalloproteolytic release of adhesion receptors and other proteins from the platelet surface. Proteolysis effectively lowers receptor density and reduces the reactivity of platelets, and is a mechanism to control robust platelet activation. Recent research has also established clear links between levels of platelet receptors and platelet lifespan. In this review, we will discuss the current knowledge of metalloproteolytic receptor regulation in the vasculature with emphasis on the platelet receptor system to highlight how receptor density can influence both platelet function and platelet survival.
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69
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Yang CH, Hsia CW, Jayakumar T, Sheu JR, Hsia CH, Khamrang T, Chen YJ, Manubolu M, Chang Y. Structure⁻Activity Relationship Study of Newly Synthesized Iridium-III Complexes as Potential Series for Treating Thrombotic Diseases. Int J Mol Sci 2018; 19:ijms19113641. [PMID: 30463221 PMCID: PMC6274890 DOI: 10.3390/ijms19113641] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 11/05/2018] [Accepted: 11/15/2018] [Indexed: 01/07/2023] Open
Abstract
Platelets play a major role in hemostatic events and are associated with various pathological events, such as arterial thrombosis and atherosclerosis. Iridium (Ir) compounds are potential alternatives to platinum compounds, since they exert promising anticancer effects without cellular toxicity. Our recent studies found that Ir compounds show potent antiplatelet properties. In this study, we evaluated the in vitro antiplatelet, in vivo antithrombotic and structure⁻activity relationship (SAR) of newly synthesized Ir complexes, Ir-1, Ir-2 and Ir-4, in agonists-induced human platelets. Among the tested compounds, Ir-1 was active in inhibiting platelet aggregation induced by collagen; however, Ir-2 and Ir-4 had no effects even at their maximum concentrations of 50 μM against collagen and 500 μM against U46619-induced aggregation. Similarly, Ir-1 was potently inhibiting of adenosine triphosphate (ATP) release, calcium mobilization ([Ca2+]i) and P-selectin expression induced by collagen-induced without cytotoxicity. Likewise, Ir-1 expressively suppressed collagen-induced Akt, PKC, p38MAPKs and JNK phosphorylation. Interestingly, Ir-2 and Ir-4 had no effect on platelet function analyzer (PFA-100) collagen-adenosine diphosphate (C-ADP) and collagen-epinephrine (C-EPI) induced closure times in mice, but Ir-1 caused a significant increase when using C-ADP stimulation. Other in vivo studies revealed that Ir-1 significantly prolonged the platelet plug formation, increased tail bleeding times and reduced the mortality of adenosine diphosphate (ADP)-induced acute pulmonary thromboembolism in mice. Ir-1 has no substitution on its phenyl group, a water molecule (like cisplatin) can replace its chloride ion and, hence, the rate of hydrolysis might be tuned by the substituent on the ligand system. These features might have played a role for the observed effects of Ir-1. These results indicate that Ir-1 may be a lead compound to design new antiplatelet drugs for the treatment of thromboembolic diseases.
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Affiliation(s)
- Chih-Hao Yang
- Department of Pharmacology, Schools of Medicine, College of Medicine, Taipei Medical University, No. 250, Wu Hsing St., Taipei 110, Taiwan.
| | - Chih-Wei Hsia
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, No. 250, Wu Hsing St., Taipei 110, Taiwan.
| | - Thanasekaran Jayakumar
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, No. 250, Wu Hsing St., Taipei 110, Taiwan.
| | - Joen-Rong Sheu
- Department of Pharmacology, Schools of Medicine, College of Medicine, Taipei Medical University, No. 250, Wu Hsing St., Taipei 110, Taiwan.
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, No. 250, Wu Hsing St., Taipei 110, Taiwan.
| | - Chih-Hsuan Hsia
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, No. 250, Wu Hsing St., Taipei 110, Taiwan.
| | - Themmila Khamrang
- Department of Chemistry, North Eastern Hill University, Shillong 793022, India.
| | - Yen-Jen Chen
- Department of Pharmacology, Schools of Medicine, College of Medicine, Taipei Medical University, No. 250, Wu Hsing St., Taipei 110, Taiwan.
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, No. 250, Wu Hsing St., Taipei 110, Taiwan.
| | - Manjunath Manubolu
- Department of Evolution, Ecology and Organismal Biology, Ohio State University, Columbus, OH 43212, USA.
| | - Yi Chang
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, No. 250, Wu Hsing St., Taipei 110, Taiwan.
- Department of Anesthesiology, Shin Kong Wu Ho-Su Memorial Hospital, No. 95, Wen Chang Rd., Taipei 111, Taiwan.
- School of Medicine, Fu-Jen Catholic University, No. 510, Zhong Zheng Rd, Xin Zhuang Dist., New Taipei City 242, Taiwan.
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Slater A, Perrella G, Onselaer MB, Martin EM, Gauer JS, Xu RG, Heemskerk JWM, Ariëns RAS, Watson SP. Does fibrin(ogen) bind to monomeric or dimeric GPVI, or not at all? Platelets 2018; 30:281-289. [DOI: 10.1080/09537104.2018.1508649] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Alexandre Slater
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Gina Perrella
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
- Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, Maastricht, The Netherlands
| | - Marie-Blanche Onselaer
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Eleyna M Martin
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Julia S Gauer
- Thrombosis and Tissue Repair Group, Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK
| | - Rui-Gang Xu
- Thrombosis and Tissue Repair Group, Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK
| | - Johan WM Heemskerk
- Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, Maastricht, The Netherlands
| | - Robert A S Ariëns
- Thrombosis and Tissue Repair Group, Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK
| | - Steve P Watson
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
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Lehmann M, Schoeman RM, Krohl PJ, Wallbank AM, Samaniuk JR, Jandrot-Perrus M, Neeves KB. Platelets Drive Thrombus Propagation in a Hematocrit and Glycoprotein VI-Dependent Manner in an In Vitro Venous Thrombosis Model. Arterioscler Thromb Vasc Biol 2018; 38:1052-1062. [PMID: 29472230 PMCID: PMC5920765 DOI: 10.1161/atvbaha.118.310731] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 02/06/2018] [Indexed: 12/17/2022]
Abstract
OBJECTIVE The objective of this study was to measure the role of platelets and red blood cells on thrombus propagation in an in vitro model of venous valvular stasis. APPROACH AND RESULTS A microfluidic model with dimensional similarity to human venous valves consists of a sinus distal to a sudden expansion, where for sufficiently high Reynolds numbers, 2 countercurrent vortices arise because of flow separation. The primary vortex is defined by the points of flow separation and reattachment. A secondary vortex forms in the deepest recess of the valve pocket characterized by low shear rates. An initial fibrin gel formed within the secondary vortex of a tissue factor-coated valve sinus. Platelets accumulated at the interface of the fibrin gel and the primary vortex. Red blood cells at physiological hematocrits were necessary to provide an adequate flux of platelets to support thrombus growth out of the valve sinus. A subpopulation of platelets that adhered to fibrin expose phosphatidylserine. Platelet-dependent thrombus growth was attenuated by inhibition of glycoprotein VI with a blocking Fab fragment or D-dimer. CONCLUSIONS A 3-step process regulated by hemodynamics was necessary for robust thrombus propagation: First, immobilized tissue factor initiates coagulation and fibrin deposition within a low flow niche defined by a secondary vortex in the pocket of a model venous valve. Second, a primary vortex delivers platelets to the fibrin interface in a red blood cell-dependent manner. Third, platelets adhere to fibrin, activate through glycoprotein VI, express phosphatidylserine, and subsequently promote thrombus growth beyond the valve sinus and into the bulk flow.
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Affiliation(s)
- Marcus Lehmann
- From the Chemical and Biological Engineering Department, Colorado School of Mines, Golden (M.L., R.M.S., P.J.K., A.M.W., J.R.S., K.B.N.)
| | - Rogier M Schoeman
- From the Chemical and Biological Engineering Department, Colorado School of Mines, Golden (M.L., R.M.S., P.J.K., A.M.W., J.R.S., K.B.N.)
| | - Patrick J Krohl
- From the Chemical and Biological Engineering Department, Colorado School of Mines, Golden (M.L., R.M.S., P.J.K., A.M.W., J.R.S., K.B.N.)
| | - Alison M Wallbank
- From the Chemical and Biological Engineering Department, Colorado School of Mines, Golden (M.L., R.M.S., P.J.K., A.M.W., J.R.S., K.B.N.)
| | - Joseph R Samaniuk
- From the Chemical and Biological Engineering Department, Colorado School of Mines, Golden (M.L., R.M.S., P.J.K., A.M.W., J.R.S., K.B.N.)
| | - Martine Jandrot-Perrus
- Laboratory of Vascular Translational Science, UMR_S1148, INSERM, University Paris Diderot, France (M.J.-P.)
| | - Keith B Neeves
- From the Chemical and Biological Engineering Department, Colorado School of Mines, Golden (M.L., R.M.S., P.J.K., A.M.W., J.R.S., K.B.N.)
- Department of Pediatrics, University of Colorado, Aurora (K.B.N.)
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72
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Gardiner EE. Proteolytic processing of platelet receptors. Res Pract Thromb Haemost 2018; 2:240-250. [PMID: 30046726 PMCID: PMC6055504 DOI: 10.1002/rth2.12096] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Accepted: 03/01/2018] [Indexed: 12/17/2022] Open
Abstract
Platelets have a major role in hemostasis and an emerging role in biological processes including inflammation and immunity. Many of these processes require platelet adhesion and localization at sites of tissue damage or infection and regulated platelet activation, mediated by platelet adheso-signalling receptors, glycoprotein (GP) Ib-IX-V and GPVI. Work from a number of laboratories has demonstrated that levels of these receptors are closely regulated by metalloproteinases of the A Disintegrin And Metalloproteinase (ADAM) family, primarily ADAM17 and ADAM10. It is becoming increasingly evident that platelets have important roles in innate immunity, inflammation, and in combating infection that extends beyond processes of hemostasis. This overview will examine the molecular events that regulate levels of platelet receptors and then assess ramifications for these events in settings where hemostasis, inflammation, and infection processes are triggered.
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Affiliation(s)
- Elizabeth E. Gardiner
- ACRF Department of Cancer Biology and TherapeuticsJohn Curtin School of Medical ResearchThe Australian National UniversityCanberraACTAustralia
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Induruwa I, Moroi M, Bonna A, Malcor J, Howes J, Warburton EA, Farndale RW, Jung SM. Platelet collagen receptor Glycoprotein VI-dimer recognizes fibrinogen and fibrin through their D-domains, contributing to platelet adhesion and activation during thrombus formation. J Thromb Haemost 2018; 16:389-404. [PMID: 29210180 PMCID: PMC5838801 DOI: 10.1111/jth.13919] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Indexed: 01/01/2023]
Abstract
Essentials Glycoprotein VI (GPVI) binds collagen, starting thrombogenesis, and fibrin, stabilizing thrombi. GPVI-dimers, not monomers, recognize immobilized fibrinogen and fibrin through their D-domains. Collagen, D-fragment and D-dimer may share a common or proximate binding site(s) on GPVI-dimer. GPVI-dimer-fibrin interaction supports spreading, activation and adhesion involving αIIbβ3. SUMMARY Background Platelet collagen receptor Glycoprotein VI (GPVI) binds collagen, initiating thrombogenesis, and stabilizes thrombi by binding fibrin. Objectives To determine if GPVI-dimer, GPVI-monomer, or both bind to fibrinogen substrates, and which region common to these substrates contains the interaction site. Methods Recombinant GPVI monomeric extracellular domain (GPVIex ) or dimeric Fc-fusion protein (GPVI-Fc2 ) binding to immobilized fibrinogen derivatives was measured by ELISA, including competition assays involving collagenous substrates and fibrinogen derivatives. Flow adhesion was performed with normal or Glanzmann thrombasthenic (GT) platelets over immobilized fibrinogen, with or without anti-GPVI-dimer or anti-αIIbβ3. Results Under static conditions, GPVIex did not bind to any fibrinogen substrate. GPVI-Fc2 exhibited specific, saturable binding to both D-fragment and D-dimer, which was inhibited by mFab-F (anti-GPVI-dimer), but showed low binding to fibrinogen and fibrin under our conditions. GPVI-Fc2 binding to D-fragment or D-dimer was abrogated by collagen type III, Horm collagen or CRP-XL (crosslinked collagen-related peptide), suggesting proximity between the D-domain and collagen binding sites on GPVI-dimer. Under low shear, adhesion of normal platelets to D-fragment, D-dimer, fibrinogen and fibrin was inhibited by mFab-F (inhibitor of GPVI-dimer) and abolished by Eptifibatide (inhibitor of αIIbβ3), suggesting that both receptors contribute to thrombus formation on these substrates, but αIIbβ3 makes a greater contribution. Notably, thrombasthenic platelets showed limited adhesion to fibrinogen substrates under flow, which was further reduced by mFab-F, supporting some independent GPVI-dimer involvement in this interaction. Conclusion Only dimeric GPVI interacts with fibrinogen D-domain, at a site proximate to its collagen binding site, to support platelet adhesion/activation/aggregate formation on immobilized fibrinogen and polymerized fibrin.
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Affiliation(s)
- I. Induruwa
- Department of Clinical NeurosciencesUniversity of CambridgeCambridgeUK
| | - M. Moroi
- Department of BiochemistryUniversity of CambridgeCambridgeUK
| | - A. Bonna
- Department of BiochemistryUniversity of CambridgeCambridgeUK
| | - J.‐D. Malcor
- Department of BiochemistryUniversity of CambridgeCambridgeUK
| | - J.‐M. Howes
- Department of BiochemistryUniversity of CambridgeCambridgeUK
| | - E. A. Warburton
- Department of Clinical NeurosciencesUniversity of CambridgeCambridgeUK
| | - R. W. Farndale
- Department of BiochemistryUniversity of CambridgeCambridgeUK
| | - S. M. Jung
- Department of BiochemistryUniversity of CambridgeCambridgeUK
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