Effects of the PKC inhibitors chelerythrine and bisindolylmaleimide I (GF 109203X) on delayed rectifier K+ currents.
Protein kinase C (PKC) inhibitors are useful tools for studying PKC-dependent regulation of ion channels. For this purpose, high PKC specificity is a basic requirement excluding any direct interaction between the PKC inhibitor and the ion channel. In the present study, the effects of two frequently applied PKC inhibitors, chelerythine and bisindolylmaleimide I, were studied on the rapid and slow components of the delayed rectifier K(+) current (I(Kr) and I(Ks)) in canine ventricular cardiomyocytes and on the human ether-à-go-go-related gene (hERG) channels expressed in human embryonic kidney (HEK) cells. The whole cell version of the patch clamp technique was used in all experiments. Chelerythrine and bisindolylmaleimide I (both 1 μM) suppressed I(Kr) in canine ventricular cells. This inhibition developed rapidly, suggesting a direct drug-channel interaction. In HEK cells heterologously expressing hERG channels, chelerythrine and bisindolylmaleimide I blocked hERG current in a concentration-dependent manner, having EC(50) values of 0.11 ± 0.01 and 0.76 ± 0.04 μM, respectively. Both chelerythrine and bisindolylmaleimide I strongly modified gating kinetics of hERG--voltage dependence of activation was shifted towards more negative voltages and activation was accelerated. Deactivation was slowed by bisindolylmaleimide I but not by chelerythrine. I(Ks) was not significantly altered by bisindolylmaleimide I and chelerythrine. No significant effect of 0.1 μM bisindolylmaleimide I or 0.1 μM PMA (PKC activator) was observed on I(Kr) arguing against significant contribution of PKC to regulation of I(Kr). It is concluded that neither chelerythrine nor bisindolylmaleimide I is suitable for selective PKC blockade due to their direct blocking actions on the hERG channel.
Department of Physiology, University of Debrecen, 4012, Debrecen, P.O. Box 22, Hungary.
Gábor
G
Harmati
Ferenc
F
Papp
Norbert
N
Szentandrássy
László
L
Bárándi
Ferenc
F
Ruzsnavszky
Balázs
B
Horváth
Tamás
T
Bányász
János
J
Magyar
György
G
Panyi
Zoltán
Z
Krasznai
Péter P
PP
Nánási
D000818:Animals; D053119:Benzophenanthridines / Q000494:pharmacology*; D002478:Cells, Cultured; D051668:Delayed Rectifier Potassium Channels / Q000037:antagonists & inhibitors*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000037:antagonists & inhibitors; D057809:HEK293 Cells; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D008301:Maleimides / Q000494:pharmacology*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D013997:Time Factors; D014162:Transfection
D053119:Benzophenanthridines; D051668:Delayed Rectifier Potassium Channels; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D007211:Indoles; C000606913:KCNH2 protein, human; D008301:Maleimides; D047428:Protein Kinase Inhibitors; C016299:chelerythrine; D011493:Protein Kinase C; C070515:bisindolylmaleimide I