Differential effects of RGS proteins on G alpha(q) and G alpha(11) activity

Cell Signal. 2007 Jan;19(1):103-13. doi: 10.1016/j.cellsig.2006.05.027. Epub 2006 Jun 7.

Abstract

Heterotrimeric G proteins play a pivotal role in GPCR signalling; they link receptors to intracellular effectors and their inactivation by RGS proteins is a key factor in resetting the pathway following stimulation. The precise GPCR:G protein:RGS combination determines the nature and duration of the response. Investigating the activity of particular combinations is difficult in cells which contain multiples of each component. We have therefore utilised a previously characterised yeast system to express mammalian proteins in isolation. Human G alpha(q) and G alpha(11) spontaneously activated the yeast pheromone-response pathway by a mechanism which required the formation of G alpha-GTP. This provided an assay for the specific activity of human RGS proteins. RGS1, RGS2, RGS3 and RGS4 inhibited the spontaneous activity of both G alpha(q) and G alpha(11) but, in contrast, RGS5 and RGS16 were much less effective against G alpha(11) than G alpha(q). Interestingly, RGS2 and RGS3 were able to inhibit signalling from the constitutively active G alpha(q)QL/G alpha(11)QL mutants, confirming the GAP-independent activity of these RGS proteins. To determine if the RGS-G alpha specificity was maintained under conditions of GPCR stimulation, minor modifications to the C-terminus of G alpha(q)/G alpha(11) enabled coupling to an endogenous receptor. RGS2 and RGS3 were effective inhibitors of both G alpha subunits even at high levels of receptor stimulation, emphasising their GAP-independent activity. At low levels of stimulation RGS5 and RGS16 retained their differential G alpha activity, further highlighting that RGS proteins can discriminate between two very closely related G alpha subunits.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • GTP-Binding Protein alpha Subunits, Gq-G11 / genetics
  • GTP-Binding Protein alpha Subunits, Gq-G11 / metabolism*
  • Humans
  • Mutation
  • Pheromones / metabolism
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • RGS Proteins / genetics
  • RGS Proteins / physiology*
  • Schizosaccharomyces / cytology
  • Schizosaccharomyces / metabolism
  • Signal Transduction*

Substances

  • Pheromones
  • Protein Subunits
  • RGS Proteins
  • GTP-Binding Protein alpha Subunits, Gq-G11