title: Identification of IKr and its trafficking disruption induced by probucol in cultured neonatal rat cardiomyocytes.
abstract: The human ether-a-go-go-related gene (hERG) encodes a channel that conducts the rapidly activating delayed rectifier K(+) current (I(Kr)), which is important for cardiac repolarization. Mutations in hERG reduce I(Kr) and cause congenital long QT syndrome (LQTS). More frequently, common medications can reduce I(Kr) and cause LQTS as a side effect. Protein trafficking abnormalities are responsible for most hERG mutation-related LQTS and are recently recognized as a mechanism for drug-induced LQTS. Whereas hERG trafficking has been studied in recombinant expression systems, there has been no reported study on cardiac I(Kr) trafficking at the protein level. In the present study, we identified that I(Kr) is present in cultured neonatal rat ventricular myocytes and can be robustly recorded using Cs(+) as the charge carrier. We further discovered that 4,4'-(isopropylidenedithio)-bis-(2,6-di-t-butylphenol) (probucol), a cholesterol-lowering drug that induces LQTS, disrupted I(Kr) trafficking and prolonged the cardiac action potential duration. Probucol did not directly block I(Kr). Probucol also disrupted hERG trafficking and did not block hERG channels expressed in human embryonic kidney 293 cells. We conclude that probucol induces LQTS by disrupting ether-a-go-go-related gene trafficking, and that primary culture of neonatal rat cardiomyocytes represents a useful system for studying native I(Kr) trafficking.
authors: Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre and Department of Physiology, Faculty of Medicine, University of Manitoba, 351 Tache Avenue, Winnipeg, Manitoba, Canada.
authors: Jun
authors: J
authors: Guo
authors: Hamid
authors: H
authors: Massaeli
authors: Wentao
authors: W
authors: Li
authors: Jianmin
authors: J
authors: Xu
authors: Tao
authors: T
authors: Luo
authors: James
authors: J
authors: Shaw
authors: Lorrie A
authors: LA
authors: Kirshenbaum
authors: Shetuan
authors: S
authors: Zhang
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000831:Animals, Newborn; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002586:Cesium / Q000378:metabolism; D000072237:ERG1 Potassium Channel; D004594:Electrophysiology; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D008297:Male; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D010880:Piperidines / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011341:Probucol / Q000494:pharmacology*; D021381:Protein Transport / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D014162:Transfection
chemical_list: D000889:Anti-Arrhythmia Agents; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D010880:Piperidines; D011725:Pyridines; D034741:RNA, Small Interfering; C063968:E 4031; D002586:Cesium; D011341:Probucol; D011188:Potassium