Activation of Phospholipase C β by Gβγ and Gα q Involves C-Terminal Rearrangement to Release Autoinhibition

Structure. 2020 Jul 7;28(7):810-819.e5. doi: 10.1016/j.str.2020.04.012. Epub 2020 May 12.

Abstract

Phospholipase C (PLC) enzymes hydrolyze phosphoinositide lipids to inositol phosphates and diacylglycerol. Direct activation of PLCβ by Gαq and/or Gβγ subunits mediates signaling 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 (CTDs) separated by a flexible linker. The structure of PLCβ3 bound to Gαq is known, however, for both Gαq and 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). Gαq showed decreased deuterium incorporation at the Gαq binding site on PLCβ. In vitro Gβγ-dependent activation of PLC is inhibited by the distal CTD. The results suggest that disruption of autoinhibitory interactions with the CTD leads to increased PLCβ hydrolase activity.

Keywords: G protein; G-protein-coupled receptor; GPCR; Gαq; Gβγ; HDX-MS; hydrogen-deuterium exchange; lipids; membrane interactions; phospholipase C; protein dynamics; signal transduction.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural