Coupling Gbetagamma-dependent activation to channel opening via pore elements in inwardly rectifying potassium channels.
G protein-coupled inwardly rectifying potassium channels, GIRK/Kir3.x, are gated by the Gbetagamma subunits of the G protein. The molecular mechanism of gating was investigated by employing a novel yeast-based random mutagenesis approach that selected for channel mutants that are active in the absence of Gbetagamma. Mutations in TM2 were found that mimicked the Gbetagamma-activated state. The activity of these channel mutants was independent of receptor stimulation and of the availability of heterologously expressed Gbetagamma subunits but depended on PtdIns(4,5)P(2). The results suggest that the TM2 region plays a key role in channel gating following Gbetagamma binding in a phospholipid-dependent manner. This mechanism of gating in inwardly rectifying K+ channels may be similar to the involvement of the homologous region in prokaryotic KcsA potassium channel and, thus, suggests evolutionary conservation of the gating structure.
Sadja
R
R
Department of Biological Chemistry, Weizmann Institute of Science, 76100, Rehovot, Israel.
Smadja
K
K
Alagem
N
N
Reuveny
E
E
D000595:Amino Acid Sequence; D000818:Animals; D004553:Electric Conductivity; D005260:Female; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D015870:Gene Expression; D015723:Gene Library; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics / Q000494:pharmacology*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000235:genetics; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000494:pharmacology; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D012441:Saccharomyces cerevisiae / Q000235:genetics; D014162:Transfection; D014982:Xenopus laevis
D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D046911:Macromolecular Substances; D019269:Phosphatidylinositol 4,5-Diphosphate; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D020962:Heterotrimeric GTP-Binding Proteins