HEMOSTASIS, THROMBOSIS, AND VASCULAR BIOLOGY Role of the adapter protein SLP-76 in GPVI-dependent platelet procoagulant responses to collagen
نویسندگان
چکیده
The adapter protein SLP-76 is a critical mediator of signal transduction via the platelet collagen receptor glycoprotein VI (GPVI) and its coreceptor FcR . We tested the hypothesis that SLP-76 is required for collagen-induced procoagulant responses in murine platelets. Platelets from SLP-76 null (SLP-76 / ) or heterozygous (SLP-76 / ) mice were activated with the GPVI agonist convulxin, and surface expression of P-selectin (a marker of granule release) and annexin V binding (a marker of procoagulant phospholipid) were determined by flow cytometry. Convulxin induced surface expression of Pselectin in SLP-76 / platelets, but not SLP-76 / platelets (P < .01), and failed to stimulate annexin V binding to either SLP76 / or SLP-76 / platelets. Platelet procoagulant activity was measured in a prothrombinase assay. Convulxin did not stimulate procoagulant activity in either SLP-76 / or SLP-76 / platelets, but fibrillar collagen produced a 1.9-fold increase in procoagulant activity in both SLP-76 / and SLP-76 / platelets (P < .001 versus unstimulated platelets). Similar results were obtained with platelets from FcR null mice, for which collagen, but not convulxin, induced procoagulant activity (P < .01). Costimulation with thrombin and collagen produced a further (2.3-fold) increase in procoagulant activity in SLP76 / platelets (P < .05), but not in SLP76 / platelets. SLP-76 / platelets also exhibited less annexin V binding than SLP-76 / platelets after costimulation with thrombin and convulxin (P < .05). These findings demonstrate that an intact GPVI/FcR /SLP-76 signal transduction pathway is not essential for platelet procoagulant activity induced by collagen but is necessary for maximal procoagulant response to costimulation with thrombin plus collagen. Thus, both GPVI-dependent and GPVI-independent pathways contribute to collagen-induced platelet procoagulant activity. (Blood. 2002;100: 2839-2844)
منابع مشابه
The glycoprotein VI-phospholipase Cgamma2 signaling pathway controls thrombus formation induced by collagen and tissue factor in vitro and in vivo.
OBJECTIVE Both collagen and tissue factor can be initiating factors in thrombus formation. We investigated the signaling pathway of collagen-induced platelet activation in interaction with tissue factor-triggered coagulation during the thrombus-forming process. METHODS AND RESULTS In murine blood flowing over collagen, platelet exposure of phosphatidylserine and procoagulant activity, but not...
متن کاملVariation in human platelet glycoprotein VI content modulates glycoprotein VI-specific prothrombinase activity.
- Glycoprotein VI (GPVI) is a platelet-specific receptor for collagen that figures prominently in signal transduction. An addition to binding to type I and III collagens, GPVI is also bound specifically by collagen-related peptide and convulxin (CVX), a snake venom protein. We developed a quantitative assay of platelet GPVI in which biotin-conjugated CVX binds selectively to GPVI in separated t...
متن کاملPlatelet-collagen interaction: is GPVI the central receptor?
At sites of vascular injury, platelets come into contact with subendothelial collagen, which triggers their activation and the formation of a hemostatic plug. Besides glycoprotein Ib (GPIb) and alphaIIbbeta3 integrin, which indirectly interact with collagen via von Willebrand factor (VWF), several collagen receptors have been identified on platelets, most notably alpha2beta1 integrin and the im...
متن کاملHEMOSTASIS, THROMBOSIS, AND VASCULAR BIOLOGY Tec regulates platelet activation by GPVI in the absence of Btk
The Tec family kinase Btk plays an important role in the regulation of phospholipase C 2 (PLC 2) downstream of the collagen receptor glycoprotein VI (GPVI) in human platelets. Platelets also express a second member of this family, Tec; however, its function has not been analyzed. To address the role of Tec, we analyzed Btk / , Tec / , and Btk/Tec double-deficient (Btk / /Tec / ) platelets. Tec ...
متن کاملHEMOSTASIS, THROMBOSIS, AND VASCULAR BIOLOGY Glycoprotein VI–mediated platelet fibrinogen receptor activation occurs through calcium-sensitive and PKC-sensitive pathways without a requirement for secreted ADP
Collagen activates platelets by transducing signals through glycoprotein VI (GPVI). It is not clear whether collagen can directly activate fibrinogen receptors on the adherent platelets without a role for positive feedback agonists. We investigated the contribution of secondary G protein signaling to the mechanism of GPVI-stimulated platelet aggregation using the GPVI-selective agonists, convul...
متن کامل