Gpibα Engagement Induces Activation of Human Platelet TF and Association with Constitutively Platelet Surface-Bound FVIIa

The membranes of activated platelets assemble clotting protein complexes and enzymatic reactions needed for hemostasis and causing pathological thrombosis. Several reports have shown that human platelets contain TF, but controversies remain on the functional contributions of platelet TF to coagulation initiation. Here, we delineate the mechanism that converts platelet-associated TF to a procoagulant molecule. By combining specific inhibitors with human platelets from normal probands or patients with Glanzmann thrombasthenia or homozygous GPVI deficiency, we analyzed the procoagulant activation of platelet TF by biochemical methods, confocal microscopy, platelet adhesion under flow on VWF an…