Characterisation of the Rat SK4/IK1 K+ Channel
| Autor: | Garcia-Alzamora M, K. Hamm, Zingaro L, I. Thiele, Markus Bleich, Michael Köttgen, von Hahn T, Richard Warth |
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| Rok vydání: | 2001 |
| Předmět: | |
| Zdroj: | Cellular Physiology and Biochemistry. 11:219-230 |
| ISSN: | 1421-9778 1015-8987 |
| DOI: | 10.1159/000051936 |
| Popis: | Background and Aims: The Ca2+-activated K+ channel rSK4 is the rat homologue of the human SK4/IK1 (KCNN4) channel. In colonic mucosa rSK4 plays a key role during acetylcholin-induced secretion. This study was aimed to characterize the properties of the rat SK4 channel.Methods: Electrophysiological measurements were performed on rSK4 expressing Xenopus laevis oocytes and rat colonic crypts. Intracellular Ca2+ activity was assessed by Oregon Green fluorescence measurements.Results: The 10 pS rSK4 expressed in oocytes was Ca2+-sensitive and inhibited by calmodulin antagonists. 1-ethyl-2-benzimidazolinone (1-EBIO), a known activator of SK4/IK1 channels, also activated rSK4. 1-EBIO affected the current neither at saturating Ca2+ activities nor under Ca2+-free conditions, but increased the Ca2+ sensitivity of rSK4. rSK4 was strongly activated by cytosolic ATP. However, PKA itself, PKA inhibitors and mutation of the PKA phosphorylation site (S332A) did not affect channel activity. The PKC activator 1,2-dioctanoyl-sn-glycerol and the PKC inhibitor bisindolylmaleimide also failed to influence rSK4.Conclusion: The Ca2+-sensitive rSK4 is activated by 1-EBIO probably via facilitation of the Ca2+-calmodulin-rSK4 interaction. The strong ATP-activation of rSK4 is likely to be caused by phosphorylation via a yet unknown kinase and might involve additional subunits. |
| Databáze: | OpenAIRE |
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