RGS protein specificity towards Gq- and Gi/o-mediated ERK 1/2 and Akt activation, in vitro

J Biochem Mol Biol. 2007 Nov 30;40(6):899-910. doi: 10.5483/bmbrep.2007.40.6.899.

Abstract

Extracellular Regulated Kinases (ERK) and Protein Kinase B (Akt) are intermediaries in relaying extracellular growth signals to intracellular targets. Each pathway can become activated upon stimulation of G protein-coupled receptors mediated by G(q) and G(i/o) proteins subjected to regulation by RGS proteins. The goal of the study was to delineate the specificity in which cardiac RGS proteins modulate G(q)and G(i/o)-induced ERK and Akt phosphorylation. To isolate G(q)- and G(i/o)-mediated effects, we exclusively expressed muscarinic M(2) or M(3) receptors in COS-7 cells. Western blot analyses demonstrated increase of phosphorylation of ERK 1.7-/3.3-fold and Akt 2.4-/6-fold in M(2)-/M(3)- expressing cells through carbachol stimulation. In co-expressions, M(3)/G(q)-induced activation of Akt was exclusively blunted through RGS3s/RGS3, whereas activation of ERK was inhibited additionally through RGS2/RGS5. M(2)/G(i/o) induced Akt activation was inhibited by all RGS proteins tested. RGS2 had no effect on M(2)/G(i/o)-induced ERK activation. The high degree of specificity in RGS proteins-depending modulation of G(q)- and G(i/o)-mediated ERK and Akt activation in the muscarinic network cannot merely be attributed exclusively to RGS protein selectivity towards G(q) or G(i/o) proteins. Counter-regulatory mechanisms and inter-signaling cross-talk may alter the sensitivity of GPCR-induced ERK and Akt activation to RGS protein regulation.

MeSH terms

  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • Enzyme Activation
  • Extracellular Signal-Regulated MAP Kinases / metabolism*
  • GTP-Binding Protein alpha Subunits, Gi-Go / metabolism*
  • GTP-Binding Protein alpha Subunits, Gq-G11 / metabolism*
  • Humans
  • In Vitro Techniques
  • Myocytes, Cardiac / metabolism
  • Phospholipase C beta / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism*
  • RGS Proteins / genetics
  • RGS Proteins / metabolism*
  • Rats
  • Receptor Cross-Talk
  • Receptor, Muscarinic M2 / genetics
  • Receptor, Muscarinic M2 / metabolism
  • Receptor, Muscarinic M3 / genetics
  • Receptor, Muscarinic M3 / metabolism
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Signal Transduction
  • Transfection

Substances

  • RGS Proteins
  • Receptor, Muscarinic M2
  • Receptor, Muscarinic M3
  • Recombinant Proteins
  • Proto-Oncogene Proteins c-akt
  • Extracellular Signal-Regulated MAP Kinases
  • Phospholipase C beta
  • GTP-Binding Protein alpha Subunits, Gi-Go
  • GTP-Binding Protein alpha Subunits, Gq-G11