Effect of the I(to) activator NS5806 on cloned K(V)4 channels depends on the accessory protein KChIP2.
OBJECTIVE
The compound NS5806 increases the transient outward current (I(to)) in canine ventricular cardiomyocytes and slows current decay. In human and canine ventricle, I(to) is thought to be mediated by K(V)4.3 and various ancillary proteins, yet, the exact subunit composition of I(to) channels is still debated. Here we characterize the effect of NS5806 on heterologously expressed putative I(to) channel subunits and other potassium channels.


METHODS
Cloned K(V)4 channels were co-expressed with KChIP2, DPP6, DPP10, KCNE2, KCNE3 and K(V)1.4 in Xenopus laevis oocytes or CHO-K1 cells.


RESULTS
NS5806 increased K(V)4.3/KChIP2 peak current amplitudes with an EC(50) of 5.3 +/- 1.5microM and significantly slowed current decay. KCNE2, KCNE3, DPP6 and DPP10 modulated K(V)4.3 currents and the response to NS5806, but current decay was slowed only in complexes containing KChIP2. The effect of NS5806 on K(V)4.2 was similar to that on K(V)4.3, and current decay was only slowed in presence of KChIP2. However, for K(V)4.1, the slowing of current decay by NS5806 was independent of KChIP2. K(V)1.4 was strongly inhibited by 10 microM NS5806 and K(V)1.5 was inhibited to a smaller extent. Effects of NS5806 on kinetics of currents generated by K(V)4.3/KChIP2/DPP6 with K(V)1.4 in oocytes could reproduce those on cardiac I(to) in canine ventricular myocytes. K(V)7.1, K(V)11.1 and K(ir)2 currents were unaffected by NS5806.


CONCLUSIONS
NS5806 modulated K(V)4 channel gating depending on the presence of KChIP2, suggesting that NS5806 can potentially be used to address the molecular composition as well as the physiological role of cardiac I(to).
Lundby
A
A
The Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark.
Jespersen
T
T
Schmitt
N
N
Grunnet
M
M
Olesen
S-P
SP
Cordeiro
J M
JM
Calloe
K
K
D000818:Animals; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D003412:Cricetulus; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D007700:Kinetics; D051605:Kv Channel-Interacting Proteins / Q000235:genetics / Q000378:metabolism*; D051665:Kv1.4 Potassium Channel / Q000378:metabolism; D008564:Membrane Potentials; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010671:Phenylurea Compounds / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000378:metabolism; D051672:Shal Potassium Channels / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D013777:Tetrazoles / Q000494:pharmacology*; D014162:Transfection; D014982:Xenopus laevis
C541204:1-(3,5-bis-trifluoromethylphenyl)-3-(2,4-dibromo-6-(1H-tetrazol-5-yl)phenyl)urea; C497015:KCND1 protein, human; C497018:KCND2 protein, human; C497021:KCND3 protein, human; C489619:KCNE2 protein, human; C418492:KCNE3 protein, human; C496752:KCNIP2 protein, human; D051605:Kv Channel-Interacting Proteins; D051665:Kv1.4 Potassium Channel; D009419:Nerve Tissue Proteins; D010671:Phenylurea Compounds; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051672:Shal Potassium Channels; D013777:Tetrazoles; C503535:DPP6 protein, human; C476879:DPP10 protein, human; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D011188:Potassium