Phospholipase A2: its role in ADP- and thrombin-induced platelet activation mechanisms.

ADP and thrombin are two of the most important agonists of platelet aggregation--a cellular response that is critical for maintaining normal hemostasis. However, aberrant platelet aggregation induced by these agonists plays a central role in the pathogenesis of cardiovascular and cerebrovascular diseases. Agonist-induced primary or secondary activation of phospholipases leads to generation of the second messengers that participate in biochemical reactions essential to a number of platelet responses elicited by ADP and thrombin. Phospholipase A2 (PLA2) has been linked to cardiovascular diseases. However, the mechanism(s) of activation of PLA2 in platelets stimulated by ADP and thrombin has remained less well defined and much less appreciated. The purpose of this review is to examine and compare the molecular mechanisms of activation of PLA2 in platelets stimulated by ADP and thrombin.