The protein kinase C inhibitor, bisindolylmaleimide (I), inhibits voltage-dependent K+ channels in coronary arterial smooth muscle cells.
We examined the effects of the protein kinase C (PKC) inhibitor, bisindolylmaleimide (BIM) (I), on voltage-dependent K+ (K(V)) channels in rabbit coronary arterial smooth muscle cells using whole-cell patch clamp technique. BIM (I) reversibly and dose-dependently inhibited the K(V) currents with an apparent Kd value of 0.27 microM. The inhibition of the K(V) current by BIM (I) was highly voltage-dependent between -30 and +10 mV (voltage range of channel activation), and the additive inhibition of the K(V) current by BIM (I) was voltage-dependence in the full activation voltage range. The rate constants of association and dissociation for BIM (I) were 18.4 microM(-1) s(-1) and 4.7 s(-1), respectively. BIM (I) had no effect on the steady-state activation and inactivation of K(V) channels. BIM (I) caused use-dependent inhibition of K(V) current, which was consistent with the slow recovery from inactivation in the presence of BIM (I) (recovery time constants were 856.95 +/- 282.6 ms for control, and 1806.38 +/- 110.0 ms for 300 nM BIM (I)). ATP-sensitive K+ (K(ATP)), inward rectifier K+ (K(IR)), Ca2+-activated K+ (BK(Ca)) channels, which regulate the membrane potential and arterial tone, were not affected by BIM (I). The PKC inhibitor, chelerythrine, and protein kinase A (PKA) inhibitor, PKA-IP, had little effect on the K(V) current and did not significantly alter the inhibitory effects of BIM (I) on the K(V) current. These results suggest that BIM (I) inhibits K(V) channels in a phosphorylation-independent, and voltage-, time- and use-dependent manner.
Park
Won Sun
WS
Department of Physiology and National Research Laboratory for Cellular Signalling, Seoul National University College of Medicine, 28 Yonkeun-Dong, Seoul, 110-799, South Korea.
Son
Youn Kyoung
YK
Ko
Eun A
EA
Ko
Jae-Hong
JH
Lee
Hyang Ae
HA
Park
Kyoung Sun
KS
Earm
Yung E
YE
D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects* / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D007211:Indoles / Q000494:pharmacology*; D008297:Male; D008301:Maleimides / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D011817:Rabbits
D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D024642:Potassium Channels, Voltage-Gated; D011493:Protein Kinase C; C088060:bisindolylmaleimide