Inhibitory effects of oxidants on n-type K+ channels in T lymphocytes and Xenopus oocytes.
Reactive oxygen species (ROS) appear to be involved in Fas-induced programmed cell death. We have previously demonstrated a tyrosine-kinase-dependent inhibition of the n-type K+ channels (Kn) by Fas stimulation. Thus, the effect of hydrogen peroxide (H2O2) on the function of Kn was examined using the patch-clamp technique. Incubation of Jurkat human T lymphocytes with 100 microM H2O2 resulted in a 46 +/- 5% inhibition of the macroscopic whole-cell current. Experiments performed at the single-channel level using the cell-attached configuration revealed that the probability of the channel being open diminished upon incubation in H2O2. The effect was not dependent on src-like kinases, since H2O2 did not trigger tyrosine phosphorylation of the Kn channel protein and herbimycin A did not prevent channel inhibition. Kv1.3 channels underly the Kn of T lymphocytes and were expressed in Xenopus oocytes and subjected to electrophysiological analysis by the two-electrode voltage-clamp technique. Application of 1 mM H2O2 and 500 microM t-BOOH (tert, butylhydroperoxide) resulted in a marked inhibition of the K+ current within 20 min. Both the membrane-permeable thiol-group oxidizing agent DTNP [2,2'-dithiobis-(5-nitropyridine)] and the membrane-impermeable DTNB [5,5'-Dithiobis-(2-nitrobenzoic acid)] (50 microM) inhibited Kv1.3 channels, suggesting that extracellular domains of Kv1.3 are affected. These results point to a direct modulation of Kn by various oxidative agents.
Szabó
I
I
Physiologisches Institut der Universität Tübingen, Gmelinstrasse 5, D-72076 Tübingen, Germany.
Nilius
B
B
Zhang
X
X
Busch
A E
AE
Gulbins
E
E
Suessbrich
H
H
Lang
F
F
D000818:Animals; D017209:Apoptosis; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D019169:Jurkat Cells; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects*; D014981:Xenopus
D016877:Oxidants; D015221:Potassium Channels; D006861:Hydrogen Peroxide