Identification of ether à go-go and calcium-activated potassium channels in human melanoma cells.
Ion channels and intracellular Ca2+ are thought to be involved in cell proliferation and may play a role in tumor development. We therefore characterized Ca(2+)-regulated potassium channels in the human melanoma cell lines IGR1, IPC298, and IGR39 using electrophysiological and molecular biological methods. All cell lines expressed outwardly rectifying K+ channels. Rapidly activating delayed rectifier channels were detected in IGR39 cells. The activation kinetics of voltage-gated K+ channels in IRG1 and IPC298 cells displayed characteristics of ether à go-go (eag) channels as they were much slower and depended both on the holding potential and on extracellular Mg2+. In addition, they could be blocked by physiological concentrations of intracellular Ca2+. In accordance with these electrophysiological results, analysis of mRNA revealed the expression of a gene coding for h-eag1 channels in IGR1 and IPC298 cells, but not in IGR39 cells. At elevated Ca2+ concentrations various types of Ca(2+)-activated K+ channels with single-channel characteristics similar to IK and SK channels were detected in IGR1 cells. The whole-cell Ca(2+)-activated K+ currents were not voltage dependent, insensitive for 100 nm apamin and 200 microm d-tubocurarine, but were blocked by charybdotoxin (100 nm) and clotrimazole (50 nm). Analysis of mRNA revealed the expression of hSK1, hSK2, and hIK channels in IGR1 cells.
Meyer
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Arbeitsgruppe Molekulare und zelluläre Biophysik am Klinikum der Friedrich-Schiller-Universität Jena, Drackendorfer Strasse 1, D-07747 Jena, Germany.
Schönherr
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Gavrilova-Ruch
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Wohlrab
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Heinemann
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SH
D002118:Calcium / Q000378:metabolism*; D006801:Humans; D015640:Ion Channel Gating; D008545:Melanoma / Q000503:physiopathology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000032:analysis / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D014407:Tumor Cells, Cultured
D015221:Potassium Channels; D012333:RNA, Messenger; D002118:Calcium