title: Rb+ efflux through functional activation of cardiac KCNQ1/minK channels by the benzodiazepine R-L3 (L-364,373).
abstract: The slow delayed rectifier K+ current, Iks, encoded by KCNQ1 (KvLQT1)/KCNE1 (mink) genes, contributes to cardiac action potential repolarization and determines the heartbeat rate. Mutations in either KCNQ1 or KCNE1 that reduce Iks cause long-QT syndrome (LQTS), a disorder of ventricular repolarization that results in cardiac arrhythmia and sudden death. A well-recognized potential treatment for LQTS caused by reduction of Iks is to enhance functional activation of cardiac KCNQ1/KCNE1 channels. In the present study, we generated a stable Chinese hamster ovary cell line that expresses KCNQ1/KCNE1 channels confirmed by electrophysiology. Using a pharmacological tool compound R-L3 (L-364,373 [(3-R)-1,3-dihydro-5-(2-fluorophenyl)-3-(1H-indol- 3-ylmethyl)-1-methyl-2H-1,4-benzodiazepin-2-one]), which activates KCNQ1/mink channels, we then developed and validated a non-radioactive rubidium (Rb+) efflux assay that directly measures the functional activity of KCNQ1/KCNE1 channels by atomic absorption spectroscopy. Our results show that the validated Rb+ efflux assay can be used for screening of KCNQ1/KCNE1 openers that potentially treat LQTS in both inherited and acquired forms. In addition, the assay also can be used for evaluation of possible long-QT liability during cardiac selectivity of new chemical entities.
authors.affiliation: Discovery Neuroscience, Wyeth Research, Princeton, NJ 08543, USA.
authors.forename: Flora
authors.initials: F
authors.lastname: Jow
authors.forename: Eugene
authors.initials: E
authors.lastname: Tseng
authors.forename: Taneya
authors.initials: T
authors.lastname: Maddox
authors.forename: Ru
authors.initials: R
authors.lastname: Shen
authors.forename: Dianne
authors.initials: D
authors.lastname: Kowal
authors.forename: John
authors.initials: J
authors.lastname: Dunlop
authors.forename: Belew
authors.initials: B
authors.lastname: Mekonnen
authors.forename: KeWei
authors.initials: K
authors.lastname: Wang
mesh_terms: D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D001569:Benzodiazepines / Q000494:pharmacology*; D016466:CHO Cells; D002839:Chromans / Q000494:pharmacology; D006224:Cricetinae; D054815:Cyclic Nucleotide-Gated Cation Channels; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical / Q000379:methods; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D051657:KCNQ1 Potassium Channel / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D008133:Long QT Syndrome / Q000235:genetics / Q000503:physiopathology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009206:Myocardium / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000737:chemistry / Q000494:pharmacology; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D015203:Reproducibility of Results; D012307:Risk Factors; D012413:Rubidium / Q000378:metabolism*; D013054:Spectrophotometry, Atomic / Q000379:methods; D019789:Tetraethylammonium / Q000494:pharmacology
chemical_list: C112297:10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone; D000873:Anthracenes; D002839:Chromans; D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D051657:KCNQ1 Potassium Channel; C484268:Kcne1 protein, rat; C113498:L 364373; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D001569:Benzodiazepines; D019789:Tetraethylammonium; D011189:Potassium Chloride; C029141:2,2,5,7,8-pentamethyl-1-hydroxychroman; D012413:Rubidium