Calmodulin interacts with the platelet ADP receptor P2Y1.

P2Y1 [P2 (purinergic type-2)-receptor 1] is a G-protein-coupled ADP receptor that regulates platelet activation and ADP-induced Ca2+ signalling. Studies using P2Y1-knockout mice, G(q)-deficient mice or P2Y1-selective inhibitors have previously identified a key role for P2Y1 in pathophysiological thrombus formation at high shear stress. We provide evidence that a positively charged juxtamembrane sequence within the cytoplasmic C-terminal tail of P2Y1 can bind directly to the cytosolic regulatory protein calmodulin. Deletion by mutagenesis of the calmodulin-binding domain of P2Y1 inhibits intracellular Ca2+ flux in transfected cells. These results suggest that the interaction of calmodulin with the P2Y1 C-terminal tail may regulate P2Y1-dependent platelet aggregation.