Figure 6.

Model depicting the relationship between cPLA₂α and αIIbβ3. MnCl₂-induced fibrinogen binding to platelets induces the activation of αIIbβ3-associated cPLA₂α, leading to the release of AA from membrane phospholipids and cyclooxygenase-mediated thromboxane A₂ production. Activation of the TxA₂/prostaglandin H₂ receptor by thromboxane A₂ leads to the production of inositol-1,4,5-triphosphate and IP3 receptor-mediated release of free calcium from the dense tubular system. The elevation in cytosolic Ca²⁺ concentration, in turn, promotes the activation of PKC-β and its subsequent recruitment to αIIbβ3 via RACK1. Another consequence of G-protein-mediated Ca²⁺ release downstream of TxA₂, thrombin, or ADP receptors is the activation of additional pools of cPLA₂α (dotted lines). COX indicates cyclooxygenase; TXA₂, thromboxane A₂, TP, thromboxane A₂/prostaglandin H₂ receptor, IP3, inositol-1,4,5-triphosphate.