Co-activation of P2Y1 and P2Y12 is necessary for complete platelet activation. P2Y1 is coupled to Gq and helps trigger the release of calcium from internal stores, leading to weak and reversible platelet aggregation. P2Y12 is Gi coupled, inhibiting adenylate cyclase, leading to decreased cAMP, a consequent decrease in cAMP-dependent protein kinase activity which increases cytoplasmic [Ca2+], necessary for activation (Woulfe et al. 2001).
In activated platelets, P2Y12 signaling is required for the amplification of aggregation induced by all platelet agonists including collagen, thrombin, thromboxane, adrenaline and serotonin. P2Y12 activation causes potentiation of thromboxane generation, secretion leading to irreversible platelet aggregation and thrombus stabilization.