Functional and pharmacological properties of canine ERG potassium channels.
We established HEK-293 cell lines that stably express functional canine ether-à-go-go-related gene (cERG) K(+) channels and examined their biophysical and pharmacological properties with whole cell patch clamp and (35)S-labeled MK-499 ([(35)S]MK-499) binding displacement. Functionally, cERG current had the hallmarks of cardiac delayed rectifier K(+) current (I(Kr)). Channel opening was time- and voltage dependent with threshold near -40 mV. The half-maximum activation voltage was -7.8 +/- 2.4 mV at 23 degrees C, shifting to -31.9 +/- 1.2 mV at 36 degrees C. Channels activated with a time constant of 13 +/- 1 ms at +20 mV, showed prominent inward rectification at depolarized potentials, were highly K(+) selective (Na(+)-to-K(+) permeability ratio = 0.007), and were potently inhibited by I(Kr) blockers. Astemizole, terfenadine, cisapride, and MK-499 inhibited cERG and human ERG (hERG) currents with IC(50) values of 1.3, 13, 19, and 15 nM and 1.2, 9, 14, and 21 nM, respectively, and competitively displaced [(35)S]MK-499 binding from cERG and hERG with IC(50) values of 0.4, 12, 35, and 0.6 nM and 0.8, 5, 47, and 0.7 nM, respectively. cERG channels had biophysical properties appropriate for canine action potential repolarization and were pharmacologically sensitive to agents known to prolong QT. A novel MK-499 binding assay provides a new tool to detect agents affecting ERG channels.
Wang
Jixin
J
Department of Molecular Pharmacology, Merck Research Laboratories, West Point, Pennsylvania 19486, USA.
Della Penna
Kimberly
K
Wang
Hao
H
Karczewski
Jerzy
J
Connolly
Thomas M
TM
Koblan
Kenneth S
KS
Bennett
Paul B
PB
Salata
Joseph J
JJ
D000818:Animals; D001578:Benzopyrans / Q000378:metabolism / Q000494:pharmacology; D001667:Binding, Competitive; D015153:Blotting, Western; D002460:Cell Line; D004285:Dogs / Q000502:physiology*; D000072237:ERG1 Potassium Channel; D004553:Electric Conductivity; D051638:Ether-A-Go-Go Potassium Channels; D006801:Humans; D007158:Immunologic Techniques; D015640:Ion Channel Gating; D007700:Kinetics; D018408:Patch-Clamp Techniques; D010880:Piperidines / Q000378:metabolism / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D013194:Staining and Labeling; D013696:Temperature
D001578:Benzopyrans; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D010880:Piperidines; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; C087257:L 706000; D011188:Potassium