Abstract
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
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence / physiology
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Animals
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Binding Sites / physiology
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Brain / physiology
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Cell Line
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Cell Membrane / metabolism*
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Ethanol / pharmacology
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Female
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G Protein-Coupled Inwardly-Rectifying Potassium Channels
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GTP-Binding Protein alpha Subunits / drug effects
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GTP-Binding Protein alpha Subunits / metabolism*
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GTP-Binding Protein beta Subunits / drug effects
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GTP-Binding Protein beta Subunits / metabolism
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Heterotrimeric GTP-Binding Proteins / chemistry
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Heterotrimeric GTP-Binding Proteins / drug effects
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Heterotrimeric GTP-Binding Proteins / metabolism*
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Humans
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Neurons / metabolism
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Neurons / physiology*
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Oocytes
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Pertussis Toxin / pharmacology*
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Potassium Channels, Inwardly Rectifying / chemistry
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Potassium Channels, Inwardly Rectifying / drug effects
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Potassium Channels, Inwardly Rectifying / metabolism*
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Protein Binding / physiology
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Protein Structure, Tertiary / physiology
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Rats
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Receptors, G-Protein-Coupled / chemistry
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Receptors, G-Protein-Coupled / drug effects
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Receptors, G-Protein-Coupled / metabolism
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Signal Transduction / drug effects
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Signal Transduction / physiology
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Xenopus
Substances
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G Protein-Coupled Inwardly-Rectifying Potassium Channels
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GTP-Binding Protein alpha Subunits
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GTP-Binding Protein beta Subunits
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Potassium Channels, Inwardly Rectifying
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Receptors, G-Protein-Coupled
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Ethanol
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Pertussis Toxin
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Heterotrimeric GTP-Binding Proteins