hKCNE4 inhibits the hKCNQ1 potassium current without affecting the activation kinetics.
All five members of the KCNE beta-subunit family are capable of modulating the KCNQ1 potassium current. We have previously published that the murine variant of KCNE4 inhibits the human KCNQ1 current [J. Physiol. 542 (2002) 119]. Recently, this finding has been challenged by Teng et al., stating that the human variant of KCNE4 does not attenuate the KCNQ1 current but does slightly modulate the activation kinetics of the channel after expression in Xenopus laevis oocytes [Biochem. Biophys. Res. Commun. 303 (2003) 808]. In the present study, a detailed investigation on the ability of human and murine KCNE4 to affect either human or murine KCNQ1 currents has been performed. We find that the hKCNE4 subunit drastically inhibits the hKCNQ1 current after expression in X. laevis oocytes. This inhibitory effect is also observed for both hKCNE4 and mKCNE4 when either of these subunits is co-expressed with mKCNQ1. Analyses of the current properties of hKCNQ1 revealed that activation kinetics are independent of the presence of hKCNE4. hKCNE4 has, however, the ability to prevent the inactivation observed for the KCNQ1 current. Based upon previous studies and the present results, it is concluded that both hKCNE4 and mKCNE4 have a drastic inhibitory impact on both hKCNQ1 and mKCNQ1 currents.
Grunnet
Morten
M
Department of Medical Physiology, The Panum Institute, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark. mgrunnet@mfi.ku.dk
Olesen
Søren-Peter
SP
Klaerke
Dan A
DA
Jespersen
Thomas
T
D000818:Animals; D002478:Cells, Cultured; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology*; D051379:Mice; D009865:Oocytes / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014982:Xenopus laevis
C470587:KCNE4 protein, mouse; C502068:KCNE5 protein, human; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; C496910:Kcnq1 protein, mouse; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins; D011188:Potassium