Activation of phospholipase C β by Gβγ and Gαqinvolves C-terminal rearrangement to release auto-inhibition

Abstract

AbstractPhospholipase C (PLC) enzymes hydrolyse phosphoinositide lipids to inositol phosphates and diacylglycerol. Direct activation of PLCβ by Gαqand/or Gβγ subunits mediates signalling by Gq and some Gi coupled G protein-coupled receptors (GPCRs), respectively. PLCβ isoforms contain a unique C-terminal extension, consisting of proximal and distal C-terminal domains (CTD) separated by a flexible linker. The structure of PLCβ3 bound to Gαqis known, however, for both Gαqand Gβγ, the mechanism for PLCβ activation on membranes is unknown. We examined PLCβ2 dynamics on membranes using hydrogen deuterium exchange mass spectrometry (HDX-MS). Gβγ caused a robust increase in dynamics of the distal C-terminal domain (CTD). Gαqshowed decreased deuterium incorporation at the Gαqbinding site on PLCβ.In vitroGβγ-dependent activation of PLC is inhibited by the distal CTD. The results suggest that disruption of auto-inhibitory interactions with the CTD, respectively, leads to increased PLCβ hydrolase activity.