Cell Physiol Biochem 2016 Jan 01;393:1031-9. doi: 10.1159/000447810.

Up-Regulation of the Large-Conductance Ca2+-Activated K+ Channel by Glycogen Synthase Kinase GSK3β.

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BACKGROUND/AIMS: The pleotropic functions of the large conductance Ca2+-activated K+ channels (maxi K+ channel or BK channels) include regulation of neuronal excitation and cell volume. Kinases participating in those functions include the glycogen synthase kinase GSK3 ß which is under negative control of protein kinase B (PKB/Akt). GSK3ß is inhibited by the antidepressant Lithium. The present study thus explored whether GSK3ß modifies the activity of BK channels. METHODS: cRNA encoding the Ca2+ insensitive BK channel mutant BKM513I+Δ899-903 was injected into Xenopus laevis oocytes without or with additional injection of cRNA encoding wild-type GSK3ß, inactive K85RGSK3ß, or wild-type GSK3ß with wild-type PKB. K+ channel activity was measured utilizing dual electrode voltage clamp. RESULTS: BK channel activity in BKM513I+Δ899-903 expressing oocytes was significantly increased by co-expression of GSK3ß, but not by co-expression of K85RGSK3ß. The effect of wild type GSK3ß was abrogated by additional co-expression of wild-type PKB and by 24 hours incubation with Lithium (1 mM). Disruption of channel insertion into the cell membrane by brefeldin A (5 µM) was followed by a decline of the current to a similar extent in oocytes expressing BK and GSK3ß and in oocytes expressing BK alone. CONCLUSION: GSK3ß may up-regulate BK channels, an effect disrupted by Lithium or additional expression of PKB and possibly participating in the regulation of cell volume and excitability.

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Species referenced: Xenopus laevis
Genes referenced: akt1 gsk3b