Figure 6.

Thrombin-induced platelet activation. Two pathways exist on the platelet for activation by thrombin. The pathway described in this article involves the initial cleavage of GP V from the GP Ib–IX–V complex at low thrombin concentrations, resulting in a hyperresponsive platelet. Occupancy of the binding site on GP Ibα by thrombin results in a signaling response that leads to αΙΙbβ3 activation. Additionally, thrombin can cleave the PARs on platelets, and this cleavage will then also stimulate platelet aggregation.