title: Characterization of recombinant human cardiac KCNQ1/KCNE1 channels (I (Ks)) stably expressed in HEK 293 cells.
abstract: The present study was designed to characterize pharmacological, biophysical and electrophysiological properties of the recombinant human cardiac I (Ks) (KCNQ1/KCNE1) channels at physiological temperature. Human cardiac KCNQ1 and KCNE1 genes were cotransfected into HEK 293 cells, and a cell clone stably expressing both genes was selected. Membrane currents were recorded using a perforated patch-clamp technique. The typical I (Ks) was slowly activated upon depolarization voltages in HEK 293 cells stably expressing human cardiac KCNQ1 and KCNE1 genes, and the current was inhibited by I (Ks) blockers HMR 1556 and chromanol 293B, with 50% inhibitory concentrations (IC(50)s) of 83.8 nM: and 9.2 muM: , respectively. I (Ks) showed a significant temperature-dependent increase in its magnitude upon elevating bath temperature to 36 degrees C from room temperature (21 degrees C). The current was upregulated by the beta-adrenoceptor agonist isoproterenol, and the effect was reversed by H89. In addition, I (Ks) was inhibited by Ba(2+) in a concentration-dependent manner (IC(50) = 1.4 mM). Action potential clamp revealed a "bell-shaped" time course of I (Ks) during the action potential, and maximal peak current was seen at the plateau of the action potential. A significant use- and frequency-dependent increase of I (Ks) was observed during a train of action potential clamp. These results indicate that the recombinant human cardiac I (Ks) stably expressed in HEK 293 cells is similar to native I (Ks) in drug sensitivity and regulated by Ba(2+) and beta-adrenoceptor via the cyclic adenosine monophosphate/protein kinase A pathway. Importantly, the current exhibits significant temperature dependence, a bell-shaped time course during action potential and prominent use- or frequency-dependent accumulation during a train of action potentials.
authors.affiliation: Department of Medicine and Research Centre of Heart, Brain, Hormone, and Healthy Aging, Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, People's Republic of China.
authors.forename: Ming-Qing
authors.initials: MQ
authors.lastname: Dong
authors.forename: Chu-Pak
authors.initials: CP
authors.lastname: Lau
authors.forename: Zhan
authors.initials: Z
authors.lastname: Gao
authors.forename: Gea-Ny
authors.initials: GN
authors.lastname: Tseng
authors.forename: Gui-Rong
authors.initials: GR
authors.lastname: Li
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D001464:Barium / Q000494:pharmacology; D002478:Cells, Cultured; D002839:Chromans / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D051657:KCNQ1 Potassium Channel / Q000037:antagonists & inhibitors / Q000502:physiology*; D007668:Kidney / Q000196:embryology / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D014162:Transfection
chemical_list: D000318:Adrenergic beta-Agonists; D002839:Chromans; C420023:HMR 1556; D007546:Isoquinolines; C489622:KCNE1 protein, human; D051657:KCNQ1 Potassium Channel; D026902:Potassium Channel Blockers; D024642:Potassium Channels, Voltage-Gated; D047428:Protein Kinase Inhibitors; D011994:Recombinant Proteins; D013449:Sulfonamides; C103474:6-cyano-4-(N-ethylsulfonyl-N-methylamino)-3-hydroxy-2,2-dimethylchromane; D001464:Barium; D017868:Cyclic AMP-Dependent Protein Kinases; D007545:Isoproterenol; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide