Isoform-dependent activation of adenylyl cyclase by proteolysis

Recent findings have suggested that the cellular proteolytic system plays a major role in the regulation of various intra- and extra-cellular signaling. It was previously shown that proteolytic treatment of adenylyl cyclase leads to the activation of this enzyme. We demonstrate that this activation occurs in an adenylyl cyclase isoform-dependent manner. The type II isoform was strongly activated (approximately 500%), the type III isoform was modestly activated (approximately 30%),and the type V isoform was inhibited by trypsin. Activation of type II adenylyl cyclase occurred in trypsin dose- and time-dependent manners and was blocked by a trypsin inhibitor in a dose-dependent manner. Other proteases, such as thrombin and plasminogen, similarly activated the type II isoform, but not the others. Our data suggest that proteolytic activation is an isoform- and thus cell type-dependent mechanism of altering adenylyl cyclase catalytic activity.