Interaction between the RGS domain of RGS4 with G protein alpha subunits mediates the voltage-dependent relaxation of the G protein-gated potassium channel

J Physiol. 2001 Aug 15;535(Pt 1):133-43. doi: 10.1111/j.1469-7793.2001.t01-1-00133.x.


1. In native cardiac myocytes, there is a time dependence to the G protein-gated inwardly rectifying K(+) (K(G)) channel current during voltage steps that accelerates as the concentration of acetylcholine is increased. This phenomenon has been called 'relaxation' and is not reproduced in the reconstituted Kir3.1/Kir3.4 channel in Xenopus oocytes. We have shown that RGS4, a regulator of G protein signalling, restores relaxation to the reconstituted Kir3.1/Kir3.4 channel. In this study, we examined the mechanism of this phenomenon by expressing various combinations of membrane receptors, G proteins, Kir3.0 subunits and mutants of RGS4 in Xenopus oocytes. 2. RGS4 restored relaxation to K(G) channels activated by the pertussis toxin (PTX)-sensitive G protein-coupled m(2)-muscarinic receptor but not to those activated by the G(s) protein-coupled beta(2)-adrenergic receptor. 3. RGS4 induced relaxation not only in heteromeric K(G) channels composed of Kir3.1 and Kir3.4 but also in homomeric assemblies of either an active mutant of Kir3.1 (Kir3.1/F137S) or an isoform of Kir3.2 (Kir3.2d). 4. Truncation mutants of RGS4 showed that the RGS domain itself was essential to reproduce the effect of wild-type RGS4 on the K(G) channel. 5. The mutation of residues in the RGS domain which interact with the alpha subunit of the G protein (G(alpha)) impaired the effect of RGS4. 6. This study therefore shows that interaction between the RGS domain and PTX-sensitive G(alpha) subunits mediates the effect of RGS4 on the agonist concentration-dependent relaxation of K(G) channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Electrophysiology
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • GTP-Binding Proteins / physiology*
  • Ion Channel Gating / drug effects
  • Ion Channel Gating / physiology*
  • Mice
  • Point Mutation / physiology
  • Potassium Channels / drug effects
  • Potassium Channels / physiology*
  • Protein Structure, Tertiary
  • RGS Proteins / chemistry
  • RGS Proteins / genetics
  • RGS Proteins / pharmacology
  • RGS Proteins / physiology*
  • Rats
  • Receptors, Adrenergic, beta / metabolism
  • Receptors, Muscarinic / metabolism
  • Swine
  • Xenopus laevis


  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • Kcnj3 protein, mouse
  • Potassium Channels
  • RGS Proteins
  • Receptors, Adrenergic, beta
  • Receptors, Muscarinic
  • RGS4 protein
  • GTP-Binding Proteins