Pertussis-toxin-sensitive Galpha subunits selectively bind to C-terminal domain of neuronal GIRK channels: evidence for a heterotrimeric G-protein-channel complex

Mol Cell Neurosci. 2005 Feb;28(2):375-89. doi: 10.1016/j.mcn.2004.10.009.


Neuronal G-protein-gated inwardly rectifying potassium (Kir3; GIRK) channels are activated by G-protein-coupled receptors that selectively interact with PTX-sensitive (Galphai/o) G proteins. Although the Gbetagamma dimer is known to activate GIRK channels, the role of the Galphai/o subunit remains unclear. Here, we established that Galphao subunits co-immunoprecipitate with neuronal GIRK channels. In vitro binding studies led to the identification of six amino acids in the GIRK2 C-terminal domain essential for Galphao binding. Further studies suggested that the Galphai/obetagamma heterotrimer binds to the GIRK2 C-terminal domain via Galpha and not Gbetagamma. Galphai/o binding-impaired GIRK2 channels exhibited reduced receptor-activated currents, but retained normal ethanol- and Gbetagamma-activated currents. Finally, PTX-insensitive Galphaq or Galphas subunits did not bind to the GIRK2 C-terminus. Together, these results suggest that the interaction of PTX-sensitive Galphai/o subunit with the GIRK2 C-terminal domain regulates G-protein receptor coupling, and may be important for establishing specific Galphai/o signaling pathways.

Publication types

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

MeSH terms

  • Amino Acid Sequence / physiology
  • Animals
  • Binding Sites / physiology
  • Brain / physiology
  • Cell Line
  • Cell Membrane / metabolism*
  • Ethanol / pharmacology
  • Female
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • GTP-Binding Protein alpha Subunits / drug effects
  • GTP-Binding Protein alpha Subunits / metabolism*
  • GTP-Binding Protein beta Subunits / drug effects
  • GTP-Binding Protein beta Subunits / metabolism
  • Heterotrimeric GTP-Binding Proteins / chemistry
  • Heterotrimeric GTP-Binding Proteins / drug effects
  • Heterotrimeric GTP-Binding Proteins / metabolism*
  • Humans
  • Neurons / metabolism
  • Neurons / physiology*
  • Oocytes
  • Pertussis Toxin / pharmacology*
  • Potassium Channels, Inwardly Rectifying / chemistry
  • Potassium Channels, Inwardly Rectifying / drug effects
  • Potassium Channels, Inwardly Rectifying / metabolism*
  • Protein Binding / physiology
  • Protein Structure, Tertiary / physiology
  • Rats
  • Receptors, G-Protein-Coupled / chemistry
  • Receptors, G-Protein-Coupled / drug effects
  • Receptors, G-Protein-Coupled / metabolism
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Xenopus


  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • GTP-Binding Protein alpha Subunits
  • GTP-Binding Protein beta Subunits
  • Potassium Channels, Inwardly Rectifying
  • Receptors, G-Protein-Coupled
  • Ethanol
  • Pertussis Toxin
  • Heterotrimeric GTP-Binding Proteins