P2Y2 purinergic and M3 muscarinic acetylcholine receptors activate different phospholipase C-β isoforms that are uniquely susceptible to protein kinase C-dependent phosphorylation and inactivation

Abstract

Activation of phospholipase C-β (PLC-β) by G protein-coupled receptors typically results in rapid but transient second messenger generation. Although PLC-β deactivation may contribute to the transient nature of this response, the mechanisms governing PLC-β deactivation are poorly characterized. We investigated the involvement of protein kinase C (PKC) in the termination of PLC-β activation induced by endogenous P2Y2 purinergic receptors and transfected M3 muscarinic acetylcholine receptors (mAChR) in Chinese hamster ovary cells. Activation of P2Y2 receptors causes Gαq/11 to associate with PLC-β3, whereas M3 mAChR activation causes Gαq/11 to associate with both PLC-β1 and PLC-β3 in these cells. Phosphorylation of PLC-β3, but not PLC-β1, is induced by activating either P2Y2 receptors or M3 mAChR. We demonstrate that PKC rather than protein kinase A mediates the G protein-coupled receptor-induced phosphorylation of PLC-β3. The PKC-mediated phosphorylation of PLC-β3 diminishes the interaction of Gαq/11 with PLC-β3, thereby contributing to the termination PLC-β3 activity. These findings indicate that the distinct temporal profiles of PLC activation by P2Y2 receptors and mAChR may arise from the differential activation of PLC-β1 and PLC-β3 by the receptors, coupled with a selective PKC-mediated negative feedback mechanism that targets PLC-β3 but not PLC-β1.