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CSlo encodes calcium-activated potassium channels in the chick's cochlea.

ABSTRACT: Large conductance, calcium-activated (BK) potassium channels play a central role in the excitability of cochlear hair cells. In mammalian brains, one class of these channels, termed Slo, is encoded by homologues of the Drosophila 'slowpoke' gene. By homology screening with mouse Sla cDNA, we have isolated a full-length clone (cSlo1) from a chick's cochlear cDNA library, rSlol had greater than 90% identity with mouse Slo at the amino acid level, and was even better matched to a human brain Slo at the amino and carboxy termini. cSlol had none of the additional exons found in splice variants from mammalian brain. The reverse transcriptase polymerase chain reaction (RT-PCR) was used to show expression of cSlal in the microdissected hair cell epithelium basilar papilla. Transient transfection of HIEK 293 cells demonstrated that cSlol encoded a potassium channel whose conductance averaged 224 pS at +60 mV in symmetrical 140 mM K. Macroscopic currents through cSlol channels were blocked by scorpion toxin or tetraethyl ammonium, and were voltage and calcium dependent. cSlol is likely to encode BK-type calcium-activated potassium channels in cochlear hair cells.

SUBMITTER: Jiang GJ

PROVIDER: S-EPMC1688420 | biostudies-other | 1997 May

REPOSITORIES: biostudies-other

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CSlo encodes calcium-activated potassium channels in the chick's cochlea.

Jiang G J GJ Zidanic M M Michaels R L RL Michael T H TH Griguer C C Fuchs P A PA

Proceedings. Biological sciences 19970501 1382

Large conductance, calcium-activated (BK) potassium channels play a central role in the excitability of cochlear hair cells. In mammalian brains, one class of these channels, termed Slo, is encoded by homologues of the Drosophila 'slowpoke' gene. By homology screening with mouse Sla cDNA, we have isolated a full-length clone (cSlo1) from a chick's cochlear cDNA library, rSlol had greater than 90% identity with mouse Slo at the amino acid level, and was even better matched to a human brain Slo at ...[more]

PMID: 9178544

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Project description:Background and purposeControlling vascular tone involves K(+) efflux through endothelial cell small- and intermediate-conductance calcium-activated potassium channels (K(Ca)2.3 and K(Ca)3.1, respectively). We investigated the expression of these channels in astrocytes and the possibility that, by a similar mechanism, they might contribute to neurovascular coupling.Experimental approachTransgenic mice expressing enhanced green fluorescent protein (eGFP) in astrocytes were used to assess K(Ca)2.3 and K(Ca)3.1 expression by immunohistochemistry and RT-PCR. K(Ca) currents in eGFP-positive astrocytes were determined in situ using whole-cell patch clamp electrophysiology. The contribution of K(Ca)3.1 to neurovascular coupling was investigated in pharmacological experiments using electrical field stimulation (EFS) to evoke parenchymal arteriole dilatation in FVB/NJ mouse brain slices and whisker stimulation to evoke changes in cerebral blood flow in vivo, measured by laser Doppler flowmetry.Key resultsK(Ca)3.1 immunoreactivity was restricted to astrocyte processes and endfeet and RT-PCR confirmed astrocytic K(Ca)2.3 and K(Ca)3.1 mRNA expression. With 200 nM [Ca(2+)](i) , the K(Ca)2.1-2.3/K(Ca)3.1 opener NS309 increased whole-cell currents. CyPPA, a K(Ca)2.2/K(Ca)2.3 opener, was without effect. With 1 µM [Ca(2+)](i) , the K(Ca)3.1 inhibitor TRAM-34 reduced currents whereas apamin (K(Ca)2.1-2.3 blocker) had no effect. CyPPA also inhibited currents evoked by NS309 in HEK293 cells expressing K(Ca)3.1. EFS-evoked Fluo-4 fluorescence confirmed astrocyte endfoot recruitment into neurovascular coupling. TRAM-34 inhibited EFS-evoked arteriolar dilatation by 50% whereas charybdotoxin, a blocker of K(Ca)3.1 and the large-conductance K(Ca) channel, K(Ca)1.1, inhibited dilatation by 82%. TRAM-34 reduced the cortical hyperaemic response to whisker stimulation by 40%.Conclusion and implicationsAstrocytes express functional K(Ca)3.1 channels, and these contribute to neurovascular coupling.

Dataset Information

CSlo encodes calcium-activated potassium channels in the chick's cochlea.

Publications

CSlo encodes calcium-activated potassium channels in the chick's cochlea.

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