Fig. 8. Model for the effects of platelet DAB2 on platelet aggregation. DAB2 is secreted from platelets upon agonist-induced platelet aggregation. Secreted DAB2 binds to the extracellular region of IIb integrin and interferes with the IIbß3-integrin–fibrinogen interaction that results in the inhibition of platelet aggregation. Whether or not Ser24 phosphorylation of platelet DAB2 plays a role during platelet activation and aggregation still needs to be established.