KCNQ4 channels expressed in mammalian cells: functional characteristics and pharmacology.
Human cloned KCNQ4 channels were stably expressed in HEK-293 cells and characterized with respect to function and pharmacology. Patch-clamp measurements showed that the KCNQ4 channels conducted slowly activating currents at potentials more positive than -60 mV. From the Boltzmann function fitted to the activation curve, a half-activation potential of -32 mV and an equivalent gating charge of 1.4 elementary charges was determined. The instantaneous current-voltage relationship revealed strong inward rectification. The KCNQ4 channels were blocked in a voltage-independent manner by the memory-enhancing M current blockers XE-991 and linopirdine with IC(50) values of 5.5 and 14 microM, respectively. The antiarrhythmic KCNQ1 channel blocker bepridil inhibited KCNQ4 with an IC(50) value of 9.4 microM, whereas clofilium was without significant effect at 100 microM. The KCNQ4-expressing cells exhibited average resting membrane potentials of -56 mV in contrast to -12 mV recorded in the nontransfected cells. In conclusion, the activation and pharmacology of KCNQ4 channels resemble those of M currents, and it is likely that the function of the KCNQ4 channel is to regulate the subthreshold electrical activity of excitable cells.
Division of Cellular and Molecular Physiology, Department of Medical Physiology, University of Copenhagen, DK-2200 Copenhagen N, Denmark.
R
R
Søgaard
T
T
Ljungstrøm
K A
KA
Pedersen
S P
SP
Olesen
B S
BS
Jensen
D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D015764:Bepridil / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002478:Cells, Cultured; D004594:Electrophysiology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D051656:KCNQ Potassium Channels; D007668:Kidney / Q000166:cytology; D008322:Mammals; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009865:Oocytes / Q000502:physiology; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011725:Pyridines / Q000494:pharmacology; D014162:Transfection; D014981:Xenopus
C112297:10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone; D000873:Anthracenes; D002121:Calcium Channel Blockers; D007211:Indoles; D051656:KCNQ Potassium Channels; C117367:KCNQ4 protein, human; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011725:Pyridines; D015764:Bepridil; C061017:linopirdine