OBJECTIVE: In the blood coagulation process, the rate of thrombin formation is critically dependent on phosphatidylserine (PtdSer) at the surface of activated platelets. Thrombin synergistically enhances the collagen-induced platelet procoagulant response. The objective of this study is to elucidate the mechanism of this synergistic action with a focus on the intracellular Ca2+ concentration ([Ca2+]i) and the various platelet receptors for thrombin. METHODS AND RESULTS: We demonstrate that procoagulant activity is related to a sustained increased [Ca2+]i, which in turn depends on extracellular Ca2+ influx. Increased PtdSer exposure coincides with increased [Ca2+]i and was observed in a subpopulation (approximately 14%) of the platelets after stimulation with thrombin plus collagen. 2D2-Fab fragments against the thrombin binding site on GPIbalpha made clear that this receptor did not signal for platelet procoagulant activity. Inhibition of protease-activated receptor 1 (PAR-1) and PAR-4 by selective intracellular inhibitors and selective desensitization of these receptors revealed that PAR-1, but not PAR-4, activation is a prerequisite for both sustained elevations in [Ca2+]i and procoagulant activity induced by collagen plus thrombin. CONCLUSIONS: The interaction of thrombin with PAR-1 mediates a synergistic effect on collagen-induced procoagulant activity by inducing a sustained elevation in [Ca2+]i in a subpopulation of platelets.
OBJECTIVE: In the blood coagulation process, the rate of thrombin formation is critically dependent on phosphatidylserine (PtdSer) at the surface of activated platelets. Thrombin synergistically enhances the collagen-induced platelet procoagulant response. The objective of this study is to elucidate the mechanism of this synergistic action with a focus on the intracellular Ca2+ concentration ([Ca2+]i) and the various platelet receptors for thrombin. METHODS AND RESULTS: We demonstrate that procoagulant activity is related to a sustained increased [Ca2+]i, which in turn depends on extracellular Ca2+ influx. Increased PtdSer exposure coincides with increased [Ca2+]i and was observed in a subpopulation (approximately 14%) of the platelets after stimulation with thrombin plus collagen. 2D2-Fab fragments against the thrombin binding site on GPIbalpha made clear that this receptor did not signal for platelet procoagulant activity. Inhibition of protease-activated receptor 1 (PAR-1) and PAR-4 by selective intracellular inhibitors and selective desensitization of these receptors revealed that PAR-1, but not PAR-4, activation is a prerequisite for both sustained elevations in [Ca2+]i and procoagulant activity induced by collagen plus thrombin. CONCLUSIONS: The interaction of thrombin with PAR-1 mediates a synergistic effect on collagen-induced procoagulant activity by inducing a sustained elevation in [Ca2+]i in a subpopulation of platelets.
Authors: Judith M E M Cosemans; Saskia E M Schols; Lucia Stefanini; Susanne de Witt; Marion A H Feijge; Karly Hamulyák; Hans Deckmyn; Wolfgang Bergmeier; Johan W M Heemskerk Journal: Blood Date: 2010-10-29 Impact factor: 22.113
Authors: Isaac Jardin; Nidhal Ben Amor; Ahgleb Bartegi; José A Pariente; Ginés M Salido; Juan A Rosado Journal: Biochem J Date: 2007-01-01 Impact factor: 3.857
Authors: Karl Kunzelmann; Bernd Nilius; Grzegorz Owsianik; Rainer Schreiber; Jiraporn Ousingsawat; Lalida Sirianant; Podchanart Wanitchakool; Edouard M Bevers; Johan W M Heemskerk Journal: Pflugers Arch Date: 2013-06-08 Impact factor: 3.657
Authors: N M Dashkevich; M V Ovanesov; A N Balandina; S S Karamzin; P I Shestakov; N P Soshitova; A A Tokarev; M A Panteleev; F I Ataullakhanov Journal: Biophys J Date: 2012-11-20 Impact factor: 4.033