The glycoprotein VI phospholipase Cγ2 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 adhesion, completely relied on each of the following signaling modules: glycoprotein VI (GPVI), FcR gamma-chain, Src kinases, adaptor protein LAT, and phospholipase C gamma 2 (PLC gamma 2). On flow in the presence of tissue factor, these signaling components were essential for platelet aggregation and greatly enhanced fibrin clot formation. Collagen-stimulated thrombin generation relied on the presence and activity of GPVI, FcR gamma-chain, Src kinase, LAT, and PLC gamma 2. The physiological importance of this GPVI pathway was shown in a FeCl3-induced in vivo murine thrombosis model. In both venules and arterioles, signaling through GPVI, FcR gamma-chain, and Src kinases enhanced the formation of phosphatidylserine-exposing and fibrin-rich thrombi. Conclusions - The GPVI-PLC gamma 2 activation pathway regulates collagen-dependent coagulation in venous and arterial thrombus formation.