Graded contribution of the Gβγ binding domains to GIRK channel activation
| Autor: | Eitan Reuveny, Noga Alagem, Rona Sadja |
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| Rok vydání: | 2002 |
| Předmět: |
Binding Sites
Potassium Channels Multidisciplinary Chemistry Xenopus Protein subunit GTP-Binding Protein beta Subunits GTP-Binding Protein gamma Subunits Gating Biological Sciences Heterotrimeric GTP-Binding Proteins Potassium channel Regulator of G protein signaling G Protein-Coupled Inwardly-Rectifying Potassium Channels Biochemistry Biophysics Animals G protein-coupled inwardly-rectifying potassium channel Potassium Channels Inwardly Rectifying Ion Channel Gating Binding domain |
| Zdroj: | Proceedings of the National Academy of Sciences. 99:10783-10788 |
| ISSN: | 1091-6490 0027-8424 |
| Popis: | G protein coupled inwardly rectifying K + channels (GIRK/Kir3.x) are mainly activated by a direct interaction with Gβγ subunits, released upon the activation of inhibitory neurotransmitter receptors. Although Gβγ binding domains on all four subunits have been found, the relative contribution of each of these binding sites to channel gating has not yet been defined. It is also not known whether GIRK channels open once all Gβγ sites are occupied, or whether gating is a graded process. We used a tandem tetrameric approach to enable the selective elimination of specific Gβγ binding domains in the tetrameric context. Here, we show that tandem tetramers are fully operational. Tetramers with only one wild-type channel subunit showed receptor-independent high constitutive activity. The presence of two or three wild-type subunits reconstituted receptor activation gradually. Furthermore, a tetramer with no GIRK1 Gβγ binding domain displayed slower kinetics of activation. The slowdown in activation was found to be independent of regulator of G protein signaling or receptor coupling, but this slowdown could be reversed once only one Gβγ binding domain of GIRK1 was added. These results suggest that partial activation can occur under low Gβγ occupancy and that full activation can be accomplished by the interaction with three Gβγ binding subunits. |
| Databáze: | OpenAIRE |
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