Identification of peptides that inhibit regulator of G protein signaling 4 function

Pharmacology. 2008;82(2):97-104. doi: 10.1159/000138387. Epub 2008 Jun 12.


Regulators of G protein signaling (RGS) are a family of GTPase-activating proteins (GAP) that interact with heterotrimeric G proteins in the negative regulation of G-protein-coupled receptor (GPCR) signaling. RGS4, the first identified mammalian member of the RGS family, has been implicated in many GPCR signaling pathways involved in disease states. We report herein the identification of a 16-amino-acid peptide (P17) as an inhibitor of RGS4. The peptide was found by screening a random peptide library using RGS4 as 'bait' in a yeast two-hybrid system. This peptide inhibited RGS4 GAP activity on Galpha(i1)in a GTPase assay, and blocked the interaction between RGS4 and Galpha(i1)in a pull-down assay. The peptide displayed dose-dependent inhibition of RGS4 and Galpha-interacting protein (GAIP) GAP activities, yet showed no substantial effect on RGS7. Electrophysiological studies in Xenopus oocytes demonstrated that P17 attenuates RGS4 modulation of M(2) muscarinic receptor stimulation of GIRK (G-protein-mediated inwardly rectifying potassium) channels. Deletion of an arginine at the N terminus of P17 abolished its ability to inhibit RGS4 GAP activity, as did deletions of C-terminal residues. The P17 peptide showed no similarity to any known peptide sequence. Further investigation and optimization of the peptide may provide unique information for the development of RGS4 inhibitors for future therapeutic application.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Dose-Response Relationship, Drug
  • Drug Design
  • Electrophysiology
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels / metabolism
  • GTP Phosphohydrolases / metabolism
  • GTP-Binding Protein alpha Subunits, Gi-Go / drug effects
  • GTP-Binding Protein alpha Subunits, Gi-Go / metabolism
  • Humans
  • Oocytes
  • Peptide Library
  • Peptides / administration & dosage
  • Peptides / chemistry
  • Peptides / pharmacology*
  • RGS Proteins / antagonists & inhibitors*
  • Receptor, Muscarinic M2 / metabolism
  • Signal Transduction / drug effects*
  • Two-Hybrid System Techniques
  • Xenopus laevis


  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • Peptide Library
  • Peptides
  • RGS Proteins
  • Receptor, Muscarinic M2
  • RGS4 protein
  • GTP Phosphohydrolases
  • GTP-Binding Protein alpha Subunits, Gi-Go