Kinetic analysis of phospholipase D: Allosteric modulation by monomeric GTPases, protein kinase C, and polyphosphoinositides

Abstract

In mammalian cells, phospholipase D activity is tightly regulated by diverse cellular signals including hormones, neurotransmitters, and growth factors. Multiple signaling pathways converge upon phospholipase D to modulate cellular actions such as cell growth, shape and secretion. The kinetic properties of protein kinase C and G-protein regulation of mammalian phospholipase D1 (PLD1) were examined in order to better understand interactions between PLD1 and its regulators. Activation by Arf-1, RhoA, Rac1, Cdc42, protein kinase Ca, and phosphatidylinositol 4,5-bisphosphate displayed surface dilution kinetics, but these effectors modulated different kinetic parameters. A kinetic description of PLD1 activation by multiple modulators reveals a mechanism for apparent synergy between activators. These findings suggest a role for PLD1 as a signaling node, in which integration of convergent signals occurs within discrete locales of the cellular membrane.