GIRK channel modulation by assembly with allosterically regulated RGS proteins

Proc Natl Acad Sci U S A. 2012 Dec 4;109(49):19977-82. doi: 10.1073/pnas.1214337109. Epub 2012 Nov 19.

Abstract

G-protein-activated inward-rectifying K(+) (GIRK) channels hyperpolarize neurons to inhibit synaptic transmission throughout the nervous system. By accelerating G-protein deactivation kinetics, the regulator of G-protein signaling (RGS) protein family modulates the timing of GIRK activity. Despite many investigations, whether RGS proteins modulate GIRK activity in neurons by mechanisms involving kinetic coupling, collision coupling, or macromolecular complex formation has remained unknown. Here we show that GIRK modulation occurs by channel assembly with R7-RGS/Gβ5 complexes under allosteric control of R7 RGS-binding protein (R7BP). Elimination of R7BP occludes the Gβ5 subunit that interacts with GIRK channels. R7BP-bound R7-RGS/Gβ5 complexes and Gβγ dimers interact noncompetitively with the intracellular domain of GIRK channels to facilitate rapid activation and deactivation of GIRK currents. By disrupting this allosterically regulated assembly mechanism, R7BP ablation augments GIRK activity. This enhanced GIRK activity increases the drug effects of agonists acting at G-protein-coupled receptors that signal via GIRK channels, as indicated by greater antinociceptive effects of GABA(B) or μ-opioid receptor agonists. These findings show that GIRK current modulation in vivo requires channel assembly with allosterically regulated RGS protein complexes, which provide a target for modulating GIRK activity in neurological disorders in which these channels have crucial roles, including pain, epilepsy, Parkinson's disease and Down syndrome.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Allosteric Regulation / physiology*
  • Analysis of Variance
  • Animals
  • Bioluminescence Resonance Energy Transfer Techniques
  • DNA Primers / genetics
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels / genetics
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels / metabolism*
  • GTP-Binding Protein beta Subunits / metabolism*
  • HEK293 Cells
  • Hippocampus / cytology
  • Hippocampus / physiology
  • Humans
  • Immunoblotting
  • Immunoprecipitation
  • Mice
  • Mice, Knockout
  • Microscopy, Fluorescence
  • Multiprotein Complexes / metabolism*
  • Mutagenesis
  • Nerve Tissue Proteins / metabolism*
  • Neurons / metabolism*
  • RGS Proteins / genetics
  • RGS Proteins / metabolism*

Substances

  • DNA Primers
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • GTP-Binding Protein beta Subunits
  • Gnb5 protein, mouse
  • Multiprotein Complexes
  • Nerve Tissue Proteins
  • R7BP protein, mouse
  • RGS Proteins