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Bernhard Nieswandt - One of the best experts on this subject based on the ideXlab platform.
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the novel oral syk inhibitor bl1002494 protects mice from arterial thrombosis and thromboinflammatory brain infarction
Arteriosclerosis Thrombosis and Vascular Biology, 2016Co-Authors: Judith M M Van Eeuwijk, David Stegner, David J Lamb, Peter Kraft, Sarah E Beck, Ina Thielmann, Friedemann Kiefer, Barbara Walzog, Guido Stoll, Bernhard NieswandtAbstract:Objective—Ischemic stroke, which is mainly caused by thromboembolic occlusion of brain arteries, is the second leading cause of death and disability worldwide with limited treatment options. The platelet Collagen Receptor glycoprotein VI (GPVI) is a key player in arterial thrombosis and a critical determinant of stroke outcome, making its signaling pathway an attractive target for pharmacological intervention. The spleen tyrosine kinase (Syk) is an essential signaling mediator downstream of not only GPVI but also other platelet and immune cell Receptors. We sought to assess whether Syk might be an effective antithrombotic target. Approach and Results—We demonstrate that mice lacking Syk in platelets specifically are protected from arterial thrombus formation and ischemic stroke but display unaltered hemostasis. Furthermore, we show that mice treated with the novel, selective, and orally bioavailable Syk inhibitor BI1002494 were protected in a model of arterial thrombosis and had smaller infarct sizes and ...
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targeting glycoprotein vi and the immunoReceptor tyrosine based activation motif signaling pathway
Arteriosclerosis Thrombosis and Vascular Biology, 2014Co-Authors: David Stegner, Elizabeth J Haining, Bernhard NieswandtAbstract:Coronary artery thrombosis and ischemic stroke are often initiated by the disruption of an atherosclerotic plaque and consequent intravascular platelet activation. Thus, antiplatelet drugs are central in the treatment and prevention of the initial, and subsequent, vascular events. However, novel pharmacological targets for platelet inhibition remain an important goal of cardiovascular research because of the negative effect of existing antiplatelet drugs on primary hemostasis. One promising target is the platelet Collagen Receptor glycoprotein VI. Blockade or antibody-mediated depletion of this Receptor in circulating platelets is beneficial in experimental models of thrombosis and thrombo-inflammatory diseases, such as stroke, without impairing hemostasis. In this review, we summarize the importance of glycoprotein VI and (hem)immunoReceptor tyrosine-based activation motif signaling in hemostasis, thrombosis, and thrombo-inflammatory processes and discuss the targeting strategies currently under development for inhibiting glycoprotein VI and its signaling.
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the dimeric platelet Collagen Receptor gpvi fc reduces platelet adhesion to activated endothelium and preserves myocardial function after transient ischemia in mice
American Journal of Physiology-cell Physiology, 2012Co-Authors: Tanja Schonberger, Bernhard Nieswandt, Oliver Borst, Peter Seizer, Ildiko Konrad, Steffen Massberg, Melanie Ziegler, Carmen Ochmann, Tobias Jurgens, Harald F LangerAbstract:Platelets play a critical role in the pathophysiology of reperfusion, sepsis, and cardiovascular diseases. In a multiple step process, they adhere to activated endothelium and release proinflammatory cytokines thereby promoting the inflammatory process. Glycoprotein VI (GPVI) is the major Collagen Receptor on the platelet surface and triggers platelet activation and primary hemostasis. Activation of GPVI leads to stable platelet adhesion and degranulation of platelet granules. However, GPVI is critically involved in platelet adhesion to activated endothelium without exposure of subendothelial matrix. Earlier studies show that the soluble GPVI-Fc binds to Collagen and protects mice from atherosclerosis and decreases neointima proliferation after arterial injury. Here, we show for the first time that recombinant GPVI-Fc binds to activated endothelium mainly via vitronectin and prevents platelet/endothelial interaction. Administration of GPVI-Fc reduced infarct size and preserved cardiac function in a mouse model of myocardial infarction. This process was associated with reduced GPVI-induced platelet degranulation and release of proinflammatory cytokines in vitro and in vivo. Taken together, administration of GPVI-Fc offers a novel strategy to control platelet-mediated inflammation and to preserve myocardial function following myocardial infarction.
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anti glycoprotein vi treatment severely compromises hemostasis in mice with reduced alpha2beta1 levels or concomitant aspirin therapy
Circulation, 2004Co-Authors: Sabine Gruner, Valerie Schulte, Miroslava Prostredna, Barsom Aktas, Alexandra Moers, Thomas Krieg, Stefan Offermanns, Beate Eckes, Bernhard NieswandtAbstract:Background— Platelet inhibition is a major strategy to prevent arterial thrombosis, but it is frequently associated with increased bleeding because of impaired primary hemostasis. The activating platelet Collagen Receptor, glycoprotein VI (GP VI), may serve as a powerful antithrombotic target because its inhibition or absence results in profound protection against arterial thrombosis but no major bleeding in mice. Methods and Results— Mice lacking (−/−) or expressing half-levels (+/−) of the other major platelet Collagen Receptor, integrin α2β1, were injected with the anti–GP VI antibody JAQ1 and analyzed on day 5. Anti–GP VI treatment resulted in a marked hemostatic defect in α2−/− or α2+/− mice, as shown by dramatically prolonged tail bleeding times. Platelet adhesion to Collagen was studied in an ex vivo whole-blood perfusion system under high shear conditions. Weak integrin activation by thromboxane A2 (TxA2) Receptor stimulation restored defective adhesion of anti–GP VI–treated wild-type but not α2−/...
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a novel viper venom metalloproteinase alborhagin is an agonist at the platelet Collagen Receptor gpvi
Journal of Biological Chemistry, 2001Co-Authors: Robert K Andrews, David Tulasne, Michael C Berndt, Bernhard Nieswandt, Elizabeth E Gardiner, Naoki Asazuma, Oscar Berlanga, Ian A Smith, Stephen P WatsonAbstract:Abstract The interaction of platelet membrane glycoprotein VI (GPVI) with Collagen can initiate (patho)physiological thrombus formation. The viper venom C-type lectin family proteins convulxin and alboaggregin-A activate platelets by interacting with GPVI. In this study, we isolated from white-lipped tree viper (Trimeresurus albolabris) venom, alborhagin, which is functionally related to convulxin because it activates platelets but is structurally different and related to venom metalloproteinases. Alborhagin-induced platelet aggregation (EC50, <7.5 μg/ml) was inhibitable by an anti-αIIbβ3 antibody, CRC64, and the Src family kinase inhibitor PP1, suggesting that alborhagin activates platelets, leading to αIIbβ3-dependent aggregation. Additional evidence suggested that, like convulxin, alborhagin activated platelets by a mechanism involving GPVI. First, alborhagin- and convulxin-treated platelets showed a similar tyrosine phosphorylation pattern, including a similar level of phospholipase Cγ2 phosphorylation. Second, alborhagin induced GPVI-dependent responses in GPVI-transfected K562 and Jurkat cells. Third, alborhagin-dependent aggregation of mouse platelets was inhibited by the anti-GPVI monoclonal antibody JAQ1. Alborhagin had minimal effect on convulxin binding to GPVI-expressing cells, indicating that these venom proteins may recognize distinct binding sites. Characterization of alborhagin as a GPVI agonist that is structurally distinct from convulxin demonstrates the versatility of snake venom toxins and provides a novel probe for GPVI-dependent platelet activation.
Stephen P Watson - One of the best experts on this subject based on the ideXlab platform.
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a novel viper venom metalloproteinase alborhagin is an agonist at the platelet Collagen Receptor gpvi
Journal of Biological Chemistry, 2001Co-Authors: Robert K Andrews, David Tulasne, Michael C Berndt, Bernhard Nieswandt, Elizabeth E Gardiner, Naoki Asazuma, Oscar Berlanga, Ian A Smith, Stephen P WatsonAbstract:Abstract The interaction of platelet membrane glycoprotein VI (GPVI) with Collagen can initiate (patho)physiological thrombus formation. The viper venom C-type lectin family proteins convulxin and alboaggregin-A activate platelets by interacting with GPVI. In this study, we isolated from white-lipped tree viper (Trimeresurus albolabris) venom, alborhagin, which is functionally related to convulxin because it activates platelets but is structurally different and related to venom metalloproteinases. Alborhagin-induced platelet aggregation (EC50, <7.5 μg/ml) was inhibitable by an anti-αIIbβ3 antibody, CRC64, and the Src family kinase inhibitor PP1, suggesting that alborhagin activates platelets, leading to αIIbβ3-dependent aggregation. Additional evidence suggested that, like convulxin, alborhagin activated platelets by a mechanism involving GPVI. First, alborhagin- and convulxin-treated platelets showed a similar tyrosine phosphorylation pattern, including a similar level of phospholipase Cγ2 phosphorylation. Second, alborhagin induced GPVI-dependent responses in GPVI-transfected K562 and Jurkat cells. Third, alborhagin-dependent aggregation of mouse platelets was inhibited by the anti-GPVI monoclonal antibody JAQ1. Alborhagin had minimal effect on convulxin binding to GPVI-expressing cells, indicating that these venom proteins may recognize distinct binding sites. Characterization of alborhagin as a GPVI agonist that is structurally distinct from convulxin demonstrates the versatility of snake venom toxins and provides a novel probe for GPVI-dependent platelet activation.
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a novel viper venom metalloproteinase alborhagin is an agonist at the platelet Collagen Receptor gpvi
Journal of Biological Chemistry, 2001Co-Authors: Robert K Andrews, David Tulasne, Michael C Berndt, Bernhard Nieswandt, Elizabeth E Gardiner, Naoki Asazuma, Oscar Berlanga, Ian A Smith, Stephen P WatsonAbstract:The interaction of platelet membrane glycoprotein VI (GPVI) with Collagen can initiate (patho)physiological thrombus formation. The viper venom C-type lectin family proteins convulxin and alboaggregin-A activate platelets by interacting with GPVI. In this study, we isolated from white-lipped tree viper (Trimeresurus albolabris) venom, alborhagin, which is functionally related to convulxin because it activates platelets but is structurally different and related to venom metalloproteinases. Alborhagin-induced platelet aggregation (EC50,
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evidence that phospholipase c gamma2 interacts with slp 76 syk lyn lat and the fc Receptor gamma chain after stimulation of the Collagen Receptor glycoprotein vi in human platelets
FEBS Journal, 1999Co-Authors: Barbara S Gross, Steven K Melford, Stephen P WatsonAbstract:Platelet activation by Collagen is mediated by the sequential tyrosine phosphorylation of the Fc Receptor γ-chain (FcR γ-chain), which is part of the Collagen Receptor glycoprotein VI, the tyrosine kinase Syk and phospholipase C-γ2 (PLC-γ2). In this study tyrosine-phosphorylated proteins that associate with PLC-γ2 after stimulation by a Collagen-related peptide (CRP) were characterized using glutathione S-transferase fusion proteins of PLC-γ2 Src homology (SH) domains and by immunoprecipitation of endogenous PLC-γ2. The majority of the tyrosine-phosphorylated proteins that associate with PLC-γ2 bind to its C-terminal SH2 domain. These were found to include PLC-γ2, Syk, SH2-domain-containing leucocyte protein of 76 kDa (SLP-76), Lyn, linker for activation of T cells (LAT) and the FcR γ-chain. Direct association was detected between PLC-γ2 and SLP-76, and between PLC-γ2 and LAT upon CRP stimulation of platelets by far-Western blotting. FcR γ-chain and Lyn were found to co-immunoprecipitate with PLC-γ2 as well as with unidentified 110-kDa and 75-kDa phosphoproteins. The absence of an in vivo association between Syk and PLC-γ2 in platelets is in contrast with that for PLC-γ1 and Syk in B cells. The in vivo function of PLC-γ2 SH2 domains was examined through measurement of Ca2+ increases in mouse megakaryocytes that had been microinjected with recombinant proteins. This revealed that the C-terminal SH2 domain is involved in the regulation of PLC-γ2. These data indicate that the C-terminal SH2 domain of PLC-γ2 is important for PLC-γ2 regulation through possible interactions with SLP-76, Syk, Lyn, LAT and the FcR γ-chain.
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glycoprotein vi is the Collagen Receptor in platelets which underlies tyrosine phosphorylation of the fc Receptor γ chain
FEBS Letters, 1997Co-Authors: Jonathan M Gibbins, Minoru Okuma, Richard W Farndale, Mike Barnes, Stephen P WatsonAbstract:We have recently shown that Collagen activates platelets through a pathway dependent on the Fc Receptor gamma-chain and the tyrosine kinase Syk. We report here that the Fc Receptor gamma-chain and the candidate Collagen Receptor glycoprotein VI (GPVI) co-associate. Furthermore, cross-linking GPVI stimulates a similar pattern of tyrosine phosphorylation to that stimulated by Collagen, including tyrosine phosphorylation of Fc Receptor gamma-chain. These results support a model where GPVI couples Collagen-stimulation of platelets to phosphorylation of the Fc Receptor gamma-chain leading to activation of Syk and phospholipase Cgamma2.
Stephanie M Jung - One of the best experts on this subject based on the ideXlab platform.
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dimers of the platelet Collagen Receptor glycoprotein vi bind specifically to fibrin fibers during clot formation but not to intact fibrinogen
Journal of Thrombosis and Haemostasis, 2021Co-Authors: Masaaki Moroi, Richard W Farndale, Isuru Induruwa, Stephanie M JungAbstract:OBJECTIVE The platelet Collagen Receptor glycoprotein VI (GPVI) has an independent role as a Receptor for fibrin produced via the coagulation cascade. However, various reports of GPVI binding to immobilized fibrin(ogen) are not consistent. As a Collagen Receptor, GPVI-dimer is the functional form, but whether GPVI dimers or monomers bind to fibrin remains controversial. To resolve this, we analyzed GPVI binding to nascent fibrin clots, which more closely approximate physiological conditions. METHODS AND RESULTS ELISA using biotinyl-fibrinogen immobilized on streptavidin-coated wells indicated that GPVI dimers do not bind intact fibrinogen. Clots were formed by adding thrombin to a mixture of near-plasma level of fibrinogen and recombinant GPVI ectodomain: GPVI dimer (GPVI-Fc2 or Revacept) or monomer (GPVI-His: single chain of Revacept GPVI domain, with His tag). Clot-bound proteins were analyzed by SDS-PAGE/immunoblotting. GPVI-dimer bound to noncrosslinked fibrin clots with classical one-site binding kinetics, with µM-level KD , and to crosslinked clots with higher affinity. Anti-GPVI-dimer (mFab-F) inhibited the binding. However, GPVI-His binding to either type of clot was nonsaturable and nearly linear, indicating very low affinity or nonspecific binding. In clots formed in the presence of platelets, clot-bound platelet-derived proteins were integrin αIIbβ3, present at high levels, and GPVI. CONCLUSIONS We conclude that dimeric GPVI is the Receptor for fibrin, exhibiting a similar KD to those obtained for its binding to fibrinogen D-fragment and D-dimer, suggesting that fibrin(ogen)'s GPVI-binding site becomes exposed after fibrin formation or cleavage to fragment D. Analysis of platelets bound to fibrin clots indicates that platelet GPVI binds to fibrin fibers comprising the clot.
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platelet Collagen Receptor glycoprotein vi dimer recognizes fibrinogen and fibrin through their d domains contributing to platelet adhesion and activation during thrombus formation
Journal of Thrombosis and Haemostasis, 2018Co-Authors: Isuru Induruwa, Arkadiusz Bonna, Richard W Farndale, Masaaki Moroi, J D Malcor, Joannamarie Howes, E A Warburton, Stephanie M JungAbstract: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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differential inhibition of human atherosclerotic plaque induced platelet activation by dimeric gpvi fc and anti gpvi antibodies functional and imaging studies
Journal of the American College of Cardiology, 2015Co-Authors: Janina Jamasbi, Gotz Munch, Remco T A Megens, Mariaelvy Bianchini, Martin Ungerer, Alexander Faussner, Shachar Sherman, Adam Walker, Pankaj Goyal, Stephanie M JungAbstract:Background Glycoprotein VI (GPVI) is the essential platelet Collagen Receptor in atherothrombosis, but its inhibition causes only a mild bleeding tendency. Thus, targeting this Receptor has selective antithrombotic potential.
Richard W Farndale - One of the best experts on this subject based on the ideXlab platform.
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dimers of the platelet Collagen Receptor glycoprotein vi bind specifically to fibrin fibers during clot formation but not to intact fibrinogen
Journal of Thrombosis and Haemostasis, 2021Co-Authors: Masaaki Moroi, Richard W Farndale, Isuru Induruwa, Stephanie M JungAbstract:OBJECTIVE The platelet Collagen Receptor glycoprotein VI (GPVI) has an independent role as a Receptor for fibrin produced via the coagulation cascade. However, various reports of GPVI binding to immobilized fibrin(ogen) are not consistent. As a Collagen Receptor, GPVI-dimer is the functional form, but whether GPVI dimers or monomers bind to fibrin remains controversial. To resolve this, we analyzed GPVI binding to nascent fibrin clots, which more closely approximate physiological conditions. METHODS AND RESULTS ELISA using biotinyl-fibrinogen immobilized on streptavidin-coated wells indicated that GPVI dimers do not bind intact fibrinogen. Clots were formed by adding thrombin to a mixture of near-plasma level of fibrinogen and recombinant GPVI ectodomain: GPVI dimer (GPVI-Fc2 or Revacept) or monomer (GPVI-His: single chain of Revacept GPVI domain, with His tag). Clot-bound proteins were analyzed by SDS-PAGE/immunoblotting. GPVI-dimer bound to noncrosslinked fibrin clots with classical one-site binding kinetics, with µM-level KD , and to crosslinked clots with higher affinity. Anti-GPVI-dimer (mFab-F) inhibited the binding. However, GPVI-His binding to either type of clot was nonsaturable and nearly linear, indicating very low affinity or nonspecific binding. In clots formed in the presence of platelets, clot-bound platelet-derived proteins were integrin αIIbβ3, present at high levels, and GPVI. CONCLUSIONS We conclude that dimeric GPVI is the Receptor for fibrin, exhibiting a similar KD to those obtained for its binding to fibrinogen D-fragment and D-dimer, suggesting that fibrin(ogen)'s GPVI-binding site becomes exposed after fibrin formation or cleavage to fragment D. Analysis of platelets bound to fibrin clots indicates that platelet GPVI binds to fibrin fibers comprising the clot.
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platelet Collagen Receptor glycoprotein vi dimer recognizes fibrinogen and fibrin through their d domains contributing to platelet adhesion and activation during thrombus formation
Journal of Thrombosis and Haemostasis, 2018Co-Authors: Isuru Induruwa, Arkadiusz Bonna, Richard W Farndale, Masaaki Moroi, J D Malcor, Joannamarie Howes, E A Warburton, Stephanie M JungAbstract: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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cell Collagen interactions the use of peptide toolkits to investigate Collagen Receptor interactions
Biochemical Society Transactions, 2008Co-Authors: Richard W Farndale, Birgit Leitinger, Ton Lisman, Dominique Bihan, Samir W Hamaia, Christiane S Smerling, Nicholas Pugh, Antonios D Konitsiotis, Philip G De GrootAbstract:Fibrillar Collagens provide the most fundamental platform in the vertebrate organism for the attachment of cells and matrix molecules. We have identified specific sites in Collagens to which cells can attach, either directly or through protein intermediaries. Using Toolkits of triple-helical peptides, each peptide comprising 27 residues of Collagen primary sequence and overlapping with its neighbours by nine amino acids, we have mapped the binding of Receptors and other proteins on to Collagens II or III. Integrin α2β1 binds to several GXX′GER motifs within the Collagens, the affinities of which differ sufficiently to control cell adhesion and migration independently of the cellular regulation of the integrin. The platelet Receptor, Gp (glycoprotein) VI binds well to GPO (where O is hydroxyproline)-containing model peptides, but to very few Toolkit peptides, suggesting that sequence in addition to GPO triplets is important in defining GpVI binding. The Toolkits have been applied to the plasma protein vWF (von Willebrand factor), which binds to only a single sequence, identified by truncation and amino acid substitution within Toolkit peptides, as GXRGQOGVMGFO in Collagens II and III. Intriguingly, the Receptor tyrosine kinase, DDR2 (discoidin domain Receptor 2) recognizes three sites in Collagen II, including its vWF-binding site, although the amino acids that support the interaction differ slightly within this motif. Furthermore, the secreted protein BM-40 (basement membrane protein 40) also binds well to this same region. Thus the availability of extracellular Collagen-binding proteins may be important in regulating and facilitating direct Collagen–Receptor interaction.
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monomeric glycine proline hydroxyproline 10 repeat sequence is a partial agonist of the platelet Collagen Receptor glycoprotein vi
Biochemical Journal, 1999Co-Authors: J Asselin, Richard W Farndale, C G Knight, M J Barnes, Steve P. WatsonAbstract:We have previously reported that a triple-helical, Collagen-related peptide (CRP; also known as CRP-XL) containing a glycine-proline-hydroxyproline (GPP*) repeat motif and cross-linked through cysteine residues at its N-terminus and C-terminus is a powerful stimulus of platelet aggregation and secretion through the surface Receptor glycoprotein VI (GPVI). The activation of platelets is associated with tyrosine phosphorylation of the tyrosine kinase Syk and phospholipase C gamma2 (PLCgamma2). We now report that the non-cross-linked backbone of CRP, monomeric CRP (mCRP), stimulates the tyrosine phosphorylation of Syk and PLCgamma2 in platelets and induces the weak secretion of [3H]5-hydroxytryptamine ([3H]5-HT) and aggregation. The action of mCRP does not seem to be due to spontaneous cross-linking, because alkylation of the cysteine residues leads to an increase in activity. The tripeptide backbone of CRP, GPP*10 (in which P* represents hydroxyproline) also stimulates platelet shape change and the weak tyrosine phosphorylation of Syk and PLCgamma2, but is unable to induce aggregation or secretion. The monomeric peptides partly inhibit the release of [3H]5-HT by CRP, suggesting that they are partial agonists of the Collagen Receptor GPVI. These results demonstrate that GPP* present as a repeat motif is sufficient to activate the platelet Collagen Receptor GPVI but that the cross-linking of monomers brings about an increase in activity.
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glycoprotein vi is the Collagen Receptor in platelets which underlies tyrosine phosphorylation of the fc Receptor γ chain
FEBS Letters, 1997Co-Authors: Jonathan M Gibbins, Minoru Okuma, Richard W Farndale, Mike Barnes, Stephen P WatsonAbstract:We have recently shown that Collagen activates platelets through a pathway dependent on the Fc Receptor gamma-chain and the tyrosine kinase Syk. We report here that the Fc Receptor gamma-chain and the candidate Collagen Receptor glycoprotein VI (GPVI) co-associate. Furthermore, cross-linking GPVI stimulates a similar pattern of tyrosine phosphorylation to that stimulated by Collagen, including tyrosine phosphorylation of Fc Receptor gamma-chain. These results support a model where GPVI couples Collagen-stimulation of platelets to phosphorylation of the Fc Receptor gamma-chain leading to activation of Syk and phospholipase Cgamma2.
Peter Seizer - One of the best experts on this subject based on the ideXlab platform.
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the dimeric platelet Collagen Receptor gpvi fc reduces platelet adhesion to activated endothelium and preserves myocardial function after transient ischemia in mice
American Journal of Physiology-cell Physiology, 2012Co-Authors: Tanja Schonberger, Bernhard Nieswandt, Oliver Borst, Peter Seizer, Ildiko Konrad, Steffen Massberg, Melanie Ziegler, Carmen Ochmann, Tobias Jurgens, Harald F LangerAbstract:Platelets play a critical role in the pathophysiology of reperfusion, sepsis, and cardiovascular diseases. In a multiple step process, they adhere to activated endothelium and release proinflammatory cytokines thereby promoting the inflammatory process. Glycoprotein VI (GPVI) is the major Collagen Receptor on the platelet surface and triggers platelet activation and primary hemostasis. Activation of GPVI leads to stable platelet adhesion and degranulation of platelet granules. However, GPVI is critically involved in platelet adhesion to activated endothelium without exposure of subendothelial matrix. Earlier studies show that the soluble GPVI-Fc binds to Collagen and protects mice from atherosclerosis and decreases neointima proliferation after arterial injury. Here, we show for the first time that recombinant GPVI-Fc binds to activated endothelium mainly via vitronectin and prevents platelet/endothelial interaction. Administration of GPVI-Fc reduced infarct size and preserved cardiac function in a mouse model of myocardial infarction. This process was associated with reduced GPVI-induced platelet degranulation and release of proinflammatory cytokines in vitro and in vivo. Taken together, administration of GPVI-Fc offers a novel strategy to control platelet-mediated inflammation and to preserve myocardial function following myocardial infarction.
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influence of platelet count on the expression of platelet Collagen Receptor glycoprotein vi gpvi in patients with acute coronary syndrome
Thrombosis and Haemostasis, 2009Co-Authors: Boris Bigalke, Konstantinos Stellos, Tobias Geisler, Elisabeth Kremmer, Oliver Potz, Thomas O Joos, Dimitrios Stakos, Christian Bischofs, Bjorn F Kramer, Peter SeizerAbstract:Platelets play a key role in the development of an acute coronary syndrome (ACS) and contribute to cardiovascular events. Platelet Collagen Receptor glycoprotein VI (GPVI) contributes significantly to platelet adhesion and thrombus formation in ACS. We consecutively investigated both the platelet count and the platelet surface expression of GPVI in 843 patients with a symptomatic coronary artery disease verified by coronary angiography. Four hundred fourteen patients presented with stable angina pectoris and 429 patients with ACS. Platelet surface expression of GPVI and CD62P was determined by flow cytometry and platelet count with a coulter counter, plasmatic soluble GPVI was measured by ELISA. Platelet GPVI expression in patients with ACS was compared to platelet count. Patients with ACS showed significantly elevated GPVI expression levels in the first and second quartiles of platelet count compared to patients with higher platelet count [mean fluorescence intensity (MFI) ± standard deviation): 1st vs. 4th: 20.44 ± 6.1 vs. 18.62 ± 3.7; p=0.012; 2ndvs.3rd:21.2±8.5vs.18.76±3.7;P=0.03; 2ndvs.4th: 21.2±8.5vs.18.62±3.7;P=0.004], which was paralleled in trend for the CD62P expression [MFI: 1st vs. 4th: 11.2 ± 6.8 vs. 12.3 ± 9; p=0.057; 2nd vs. 3rd: 16.3 ± 16 vs.12.7 ± 5.3; p=0.138; 2nd vs. 4th: 16.3 ± 16 vs.11 ± 4.4; p=0.043]. In a subgroup of 48 patients with ACS, determination of soluble GPVI showed similar results [plasma GPVI (ng/ml): 1stvs.4th: 1.6 ± 0.6 vs. 1.2 ± 0.4; p=0.046; 1st vs. 3rd: 1.6 ± 0.6 vs. 1.1 ± 0.5; p=0.038; 2nd vs. 3rd: 1.9 ± 0.8 vs. 1.1 ± 0.5; p=0.04; 2nd vs. 4th: 1.9 ± 0.8 vs. 1.2 ± 0.4; p=0.056]. Thus, a lower platelet count comes along with a higher GPVI surface expression and plasma concentration in patients with ACS, which potentially reflects increased activation and enhanced recruitment of platelets to the site of vascular injury.
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regulation of platelet glycoprotein vi gpvi surface expression and of soluble gpvi in patients with atrial fibrillation af and acute coronary syndrome acs
Basic Research in Cardiology, 2009Co-Authors: Boris Bigalke, Konstantinos Stellos, H J Weig, Tobias Geisler, Peter Seizer, Elisabeth Kremmer, Oliver Potz, Thomas O Joos, Andreas E May, Stephan LindemannAbstract:Background The platelet Collagen Receptor glycoprotein VI (GPVI) mediates platelet adhesion to subendothelial matrix and thrombus formation in acute coronary syndrome (ACS). This study examined patients with both ACS and stable coronary artery disease (CAD), which presented with atrial fibrillation (AF) and sinus rhythm (SR).
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platelet Collagen Receptor glycoprotein vi as a possible novel indicator for the acute coronary syndrome
American Heart Journal, 2008Co-Authors: Boris Bigalke, Konstantinos Stellos, Tobias Geisler, Peter Seizer, Elisabeth Kremmer, Andreas E May, Stephan Lindemann, Karin Daub, Harald F Langer, Meinrad GawazAbstract:Background Platelet Collagen Receptor glycoprotein VI (GPVI) plays a critical role in acute coronary thrombosis. This prospective study examined the predictive value of GPVI for acute coronary syndromes (ACS) in a large consecutive group of patients with symptomatic coronary artery disease to identify the high-risk cohort with imminent coronary events. Methods We evaluated 1,003 patients with symptomatic coronary artery disease, verified by coronary angiography, and determined the surface expression of GPVI using flow cytometry. In a subgroup of 471 patients, who were treated with aspirin plus clopidogrel for coronary stenting, adenosine disphosphate (20 μmol/L)–induced platelet aggregation was evaluated. Results Patients with ACS (n = 485) showed a significantly enhanced GPVI expression compared to patients with stable angina pectoris (SAP; n = 518) (mean fluorescence intensity for ACS 19.8 ± 5.9; SAP 18.7 ± 8.5, P = .01). Patients with elevated GPVI levels on admission (GPVI cutoff value ≥18.6 mean fluorescence intensity) had a 1.4-fold relative risk for ACS. Logistic regression analysis showed that an elevated platelet GPVI level may indicate ACS independent of biomarkers of myocardial necrosis including troponin, creatine kinase, and creatine kinase-MB. Patients with increased platelet activation (GPVI expression level ≥18.6) showed significant enhanced residual platelet aggregation despite dual antiplatelet therapy compared to patients with low GPVI levels ( P = .028). Conclusions Surface expression of GPVI is enhanced in patients with ACS and indicates an imminent acute coronary event before irreversible myocardial necrosis is evident. High GPVI levels are associated with increased residual platelet aggregation despite antiplatelet therapy. Therefore, GPVI is useful to identify the subgroup of patients with a high risk for coronary stent thrombosis and thromboischemic events.
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expression of platelet Collagen Receptor glycoprotein vi is associated with acute coronary syndrome
European Heart Journal, 2006Co-Authors: Boris Bigalke, Peter Seizer, Elisabeth Kremmer, Stephan Lindemann, Raila Ehlers, Karin Daub, Harald F Langer, Tanja Schonberger, Dorothea Siegelaxel, Andreas E MayAbstract:Aims Platelet Collagen Receptor glycoprotein VI (GPVI) is critical for the formation of arterial thrombosis. In this observational study, we examined the platelet surface expression of GPVI in patients with symptomatic coronary artery disease (CAD). Methods and results We evaluated a consecutive cohort of 367 patients with symptomatic CAD, who underwent coronary angiography. The surface expression of platelet activation markers (GPVI, CD62P, and CD42b) was determined by flow cytometry. Patients with acute coronary syndrome (ACS) showed a significantly enhanced GPVI expression on admission when compared with patients with stable angina pectoris (SAP) (ACS: 21.4 ± 9.7; SAP: 18.6 ± 7.1 mean fluorescence intensity ± SD; P = 0.004). The expression of GPVI correlated with CD62P ( r = 0.702; P = 0.001). Logistic regression analysis demonstrated that on admission, elevated platelet GPVI expression was associated with ACS, independent of markers of myocardial necrosis such as troponin and creatine kinase. Conclusion Platelet GPVI surface expression is elevated in patients with ACS and is associated with imminent acute coronary events. The determination of the platelet-specific thrombotic marker GPVI may help to identify patients at risk before myocardial ischaemia is evident.