Mechanism of action and structural requirements of constrained peptide inhibitors of RGS proteins

Chem Biol Drug Des. 2006 Apr;67(4):266-74. doi: 10.1111/j.1747-0285.2006.00373.x.


Regulators of G-protein signaling (RGS) accelerate guanine triphosphate hydrolysis by Galpha-subunits and profoundly inhibit signaling by G protein-coupled receptors. The distinct expression patterns and pathophysiologic regulation of RGS proteins suggest that inhibitors may have therapeutic potential. We previously reported the design of a constrained peptide inhibitor of RGS4 (1: Ac-Val-Lys-[Cys-Thr-Gly-Ile-Cys]-Glu-NH2, S-S) based on the structure of the Galphai switch 1 region but its mechanism of action was not established. In the present study, we show that 1 inhibits RGS4 by mimicking and competing for binding with the switch 1 region of Galphai and that peptide 1 shows selectivity for RGS4 and RGS8 versus RGS7. Structure-activity relationships of analogs related to 1 are described that illustrate key features for RGS inhibition. Finally, we demonstrate activity of the methylene dithioether-bridged peptide inhibitor, 2, to modulate muscarinic receptor-regulated potassium currents in atrial myocytes. These data support the proposed mechanism of action of peptide RGS inhibitors, demonstrate their action in native cells, and provide a starting point for the design of RGS inhibitor drugs.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acetylcholine / metabolism
  • Acetylcholine / pharmacology
  • Animals
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels / metabolism
  • GTP Phosphohydrolases / metabolism
  • GTP-Binding Protein alpha Subunits / genetics
  • GTP-Binding Protein alpha Subunits / metabolism
  • GTPase-Activating Proteins / metabolism
  • Glycine / genetics
  • Glycine / metabolism
  • Humans
  • Kinetics
  • Male
  • Myocytes, Cardiac / drug effects
  • Myocytes, Cardiac / physiology
  • Patch-Clamp Techniques
  • Peptides, Cyclic / chemistry*
  • Peptides, Cyclic / metabolism
  • Peptides, Cyclic / pharmacology
  • Peptides, Cyclic / physiology*
  • RGS Proteins / antagonists & inhibitors*
  • RGS Proteins / metabolism
  • Rats
  • Rats, Inbred WKY
  • Serine / genetics
  • Serine / metabolism
  • Structure-Activity Relationship
  • Time Factors


  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • GTP-Binding Protein alpha Subunits
  • GTPase-Activating Proteins
  • Peptides, Cyclic
  • RGS Proteins
  • acetyl-valyl-lysyl-cyclo(cysteinyl-threonyl-glycyl-isoleucyl-cysteinyl)-glutamamide
  • RGS4 protein
  • Serine
  • GTP Phosphohydrolases
  • Acetylcholine
  • Glycine