OSR1 and SPAK Sensitivity of Large-Conductance Ca2+ Activated K+ Channel.
OBJECTIVE
The oxidative stress-responsive kinase 1 (OSR1) and the serine/threonine kinases SPAK (SPS1-related proline/alanine-rich kinase) are under the control of WNK (with-no-K [Lys]) kinases. OSR1 and SPAK participate in diverse functions including cell volume regulation and neuronal excitability. Cell volume and neuronal excitation are further modified by the large conductance Ca2+-activated K+ channels (maxi K+ channel or BK channels). An influence of OSR1 and/or SPAK on BK channel activity has, however, never been shown. The present study thus explored whether OSR1 and/or SPAK modify the activity of BK channels.


METHODS
cRNA encoding the Ca2+ insensitive BK channel mutant BKM513I+x0394;899-903 was injected into Xenopus laevis oocytes without or with additional injection of cRNA encoding wild-type OSR1 or wild-type SPAK, constitutively active T185EOSR1, catalytically inactive D164AOSR1, constitutively active T233ESPAK or catalytically inactive D212ASPAK. K+ channel activity was measured utilizing dual electrode voltage clamp.


RESULTS
BK channel activity in BKM513I+x0394;899-903 expressing oocytes was significantly decreased by co-expression of OSR1 or SPAK. The effect of wild-type OSR1/SPAK was mimicked by T185EOSR1 and T233ESPAK, but not by D164AOSR1 or D212ASPAK.


CONCLUSIONS
OSR1 and SPAK suppress BK channels, an effect possibly contributing to cell volume regulation and neuroexcitability.
Bernat
B
Elvira
Yogesh
Y
Singh
Jamshed
J
Warsi
Carlos
C
Munoz
Florian
F
Lang
D000818:Animals; D005434:Flow Cytometry; D006801:Humans; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000235:genetics / Q000378:metabolism*; D008214:Lymphocytes / Q000166:cytology / Q000378:metabolism; D008297:Male; D051379:Mice; D016296:Mutagenesis; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000254:growth & development / Q000378:metabolism
D051036:Large-Conductance Calcium-Activated Potassium Channels; C118135:OXSR1 protein, human; D017346:Protein Serine-Threonine Kinases; C486409:STK39 protein, human