Inhibition of an inward rectifier potassium channel (Kir2.3) by G-protein betagamma subunits.
The molecular basis of G-protein inhibition of inward rectifier K+ currents was examined by co-expression of G-proteins and cloned Kir2 channel subunits in Xenopus oocytes. Channels encoded by Kir2.3 (HRK1/HIR/BIRK2/BIR11) were completely suppressed by co-expression with G-protein betagamma subunits, whereas channels encoded by Kir2. 1 (IRK1), which shares 60% amino acid identity with Kir2.3, were unaffected. Co-expression of Galphai1 and Galphaq subunits also partially suppressed Kir2.3 currents, but Galphat, Galphas, and a constitutively active mutant of Galphail (Q204L) were ineffective. Gbetagamma and Kir2.3 subunits were co-immunoprecipitated using an anti-Kir2.3 antibody. Direct binding of G-protein betagamma subunits to fusion proteins containing Kir2.3 N terminus, but not to fusion proteins containing Kir2.1 N terminus, was also demonstrated. The results are consistent with suppression of Kir2.3 currents resulting from a direct protein-protein interaction between the channel and G-protein betagamma subunits. When Kir2.1 and Kir2.3 subunits were coexpressed, the G-protein inhibitory phenotype of Kir2.3 was dominant, suggesting that co-expression of Kir2.3 with other Kir subunits might give rise to novel G-protein-inhibitable inward rectifier currents.
Cohen
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Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA. cnichols@cellbio.wustl.edu
Sha
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Makhina
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Lopatin
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Linder
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Snyder
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Nichols
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D000818:Animals; D015153:Blotting, Western; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D010641:Phenotype; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000378:metabolism; D014981:Xenopus
C099489:KCNJ4 protein, human; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011994:Recombinant Proteins; D019204:GTP-Binding Proteins