Unexpected down-regulation of the hIK1 Ca2+-activated K+ channel by its opener 1-ethyl-2-benzimidazolinone in HaCaT keratinocytes. Inverse effects on cell growth and proliferation.
We used a combination of electrophysiological and cell and molecular biological techniques to study the regulation and functional role of the intermediate conductance Ca(2+)-activated K(+) channel, hIK1, in HaCaT keratinocytes. When we incubated cells with the hIK1 opener, 1-ethyl-2-benzimidazolinone (1-EBIO), to investigate the cellular consequences of prolonged channel activity, an unexpected down-regulation of channels occurred within a few hours. The same effect was produced by the hIK1 openers chlorzoxazone and zoxazolamine and was also observed in a different cell line (C6 glioma cells). After 3 days of treatment with 1-EBIO, mRNA levels of hIK1 were substantially diminished and no channel activity was detected. Down-regulation of hIK1 was accompanied by a loss of mitogenic activity and a strong increase in cell size. After withdrawal of 1-EBIO, hIK1 mRNA and channel activity fully recovered and the cells resumed mitogenic activity. Our data present evidence for a novel feedback mechanism of hIK1 expression that appears to result from the paradoxical action of its pharmacological activator during prolonged application. Because the down-regulation of hIK1 bears immediate significance on the biological fate of keratinocytes, 1-EBIO and related compounds might emerge as potent tools to influence the proliferation of various non-excitable cells endowed with IK channels.
Koegel
Heidi
H
Institute of Physiology, University of Munich, Pettenkoferstrasse 12, D-80336 Munich, Germany. h.koegel@lrz.uni-muenchen.de
Kaesler
Susanne
S
Burgstahler
Ralf
R
Werner
Sabine
S
Alzheimer
Christian
C
D001562:Benzimidazoles / Q000494:pharmacology*; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D002455:Cell Division; D002460:Cell Line; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D005910:Glioma; D006801:Humans; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger / Q000235:genetics; D014407:Tumor Cells, Cultured
D001562:Benzimidazoles; D002120:Calcium Channel Agonists; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496923:KCNN4 protein, human; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger; C102635:1-ethyl-2-benzimidazolinone