W-7 modulates Kv4.3: pore block and Ca2+-calmodulin inhibition.
Ca(+)-calmodulin (Ca(2+)-CaM)-dependent protein kinase II (Ca(2+)/CaMKII) is an important regulator of cardiac ion channels, and its inhibition may be an approach for treatment of ventricular arrhythmias. Using the two-electrode voltage-clamp technique, we investigated the role of W-7, an inhibitor of Ca(2+)-occupied CaM, and KN-93, an inhibitor of Ca(2+)/CaMKII, on the K(v)4.3 channel in Xenopus laevis oocytes. W-7 caused a voltage- and concentration-dependent decrease in peak current, with IC(50) of 92.4 muM. The block was voltage dependent, with an effective electrical distance of 0.18 +/- 0.05, and use dependence was observed, suggesting that a component of W-7 inhibition of K(v)4.3 current was due to open-channel block. W-7 made recovery from open-state inactivation a biexponential process, also suggesting open-channel block. We compared the effects of W-7 with those of KN-93 after washout of 500 muM BAPTA-AM. KN-93 reduced peak current without evidence of voltage or use dependence. Both W-7 and KN-93 accelerated all components of inactivation. We used wild-type and mutated K(v)4.3 channels with mutant CaMKII consensus phosphorylation sites to examine the effects of W-7 and KN-93. In contrast to W-7, KN-93 at 35 muM selectively accelerated open-state inactivation in the wild-type vs. the mutant channel. W-7 had a significantly greater effect on recovery from inactivation in wild-type than in mutant channels. We conclude that, at certain concentrations, KN-93 selectively inhibits Ca(2+)/CaMKII activity in Xenopus oocytes and that the effects of W-7 are mediated by direct interaction with the channel pore and inhibition of Ca(2+)-CaM, as well as a change in activity of Ca(2+)-CaM-dependent enzymes, including Ca(2+)/CaMKII.
Qu
Yu-Jie
YJ
Department of Physiology and Biophysics, School of Medicine and Biomedical Sciences, University at Buffalo-State University of New York, 3435 Main Street, Buffalo, NY 14214, USA.
Bondarenko
Vladimir E
VE
Xie
Chang
C
Wang
Shimin
S
Awayda
Mouhamed S
MS
Strauss
Harold C
HC
Morales
Michael J
MJ
D000818:Animals; D001596:Benzylamines / Q000008:administration & dosage*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors*; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D016062:Porosity / Q000187:drug effects; D011188:Potassium / Q000378:metabolism*; D051672:Shal Potassium Channels / Q000187:drug effects / Q000502:physiology*; D013449:Sulfonamides / Q000008:administration & dosage*; D014982:Xenopus laevis; D000096926:Benzenesulfonamides
D001596:Benzylamines; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D011188:Potassium; D051672:Shal Potassium Channels; D013449:Sulfonamides; C072105:KN 93; D000096926:Benzenesulfonamides; C017967:W 7