REGULATION OF PHOSPHOLIPASE C-BETA ISOZYMES BY G-PROTEINS

Phospholipase C (PLC) isozymes ave known to be regulated in part, by heterotrimeric GTP-binding protein (G-protein) subunits, including G alpha subunits of the G(q) family and G beta gamma subunits. New data show that PLC can also be regulated by a high molecular weight G-protein that doubles as a cellular transglutaminase. Furthermore, a soluble phosphatidylinositol transfer protein (PITP) has been implicated in sustaining the activity of PLC by delivering substrate to the plasma membrane. Such diverse regulatory mechanisms imply that the PLC isozymes are precisely controlled and have specific roles in generating second messengers in response to various external stimuli.