A large conductance [Ca(2+)](i)-independent K(+) channel expressed in HaCaT keratinocytes.
Patch-clamp recordings were carried out in the inside-out configuration in human keratinocytes of the cell line HaCaT. Patch pipettes were filled with 150 mM KCl, 1 mM CaCl(2) and 10 mM HEPES. In symmetrical KCl solutions, single channel currents from a large conductance channel (about 170 pS) were measured. Replacement of 120 mM KCl by K-aspartate had only a minor influence on the single channel conductance and on the reversal potential. In intracellular solution in which K(+) has been replaced by Na(+) or NMDG(+), the reversal potential shifted to > + 40 mV indicating K(+) as the main charge carrier. The channels were neither dependent on intracellular Ca(2+) (between 0.8 nM and 10 micro M), ATP (at 0 and 1 mM) nor Mg(2+) (at 0 and 0.5 mM). The mean current showed an outward rectification that can be mainly attributed to the voltage dependence of the open probability. The channels displayed bursting kinetics with a mean open time of about 2 ms and closed times of about 0.2, 2 and 20 ms. The mean open probability was usually low (0.05) but increased occasionally (0.6) mainly due to a lower probability of long closings. We conclude that these K(+) channels contribute to the resting potential of human keratinocytes which may control the Ca(2+) influx and thereby their proliferation and differentiation.
Julius-Bernstein-Institut for Physiology, Martin-Luther-University Halle-Wittenberg, Halle/Saale, Germany.
V H
VH
Nguyen
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F
Markwardt
D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*
D015221:Potassium Channels; D002118:Calcium