title: The human Nav1.5 F1486 deletion associated with long QT syndrome leads to impaired sodium channel inactivation and reduced lidocaine sensitivity.
abstract: The deletion of phenylalanine 1486 (F1486del) in the human cardiac voltage-gated sodium channel (hNav1.5) is associated with fatal long QT (LQT) syndrome. In this study we determined how F1486del impairs the functional properties of hNav1.5 and alters action potential firing in heterologous expression systems (human embryonic kidney (HEK) 293 cells) and their native cardiomyocyte background. Cells expressing hNav1.5-F1486del exhibited a loss-of-function alteration, reflected by an 80% reduction of peak current density, and several gain-of-function alterations, including reduced channel inactivation, enlarged window current, substantial augmentation of persistent late sodium current and an increase in ramp current. We also observed substantial action potential duration (APD) prolongation and prominent early afterdepolarizations (EADs) in neonatal cardiomyocytes expressing the F1486del channels, as well as in computer simulations of myocyte activity. In addition, lidocaine sensitivity was dramatically reduced, which probably contributed to the poor therapeutic outcome observed in the patient carrying the hNav1.5-F1486del mutation. Therefore, despite the significant reduction in peak current density, the F1486del mutation also leads to substantial gain-of-function alterations that are sufficient to cause APD prolongation and EADs, the predominant characteristic of LQTs. These data demonstrate that hNav1.5 mutations can have complex functional consequences and highlight the importance of identifying the specific molecular defect when evaluating potential treatments for individuals with prolonged QT intervals.
authors: Riley Heart Research Center, Department of Pediatrics Herman B. Wells Center for Pediatric Research & Department of Pharmacology and Toxicology, Indiana University School of Medicine, 1044 W. Walnut Street, R4 W302D, Indianapolis, IN 46202, USA. wshou@iupui.edu
authors: Weihua
authors: W
authors: Song
authors: Yucheng
authors: Y
authors: Xiao
authors: Hanying
authors: H
authors: Chen
authors: Nicole M
authors: NM
authors: Ashpole
authors: Andrew D
authors: AD
authors: Piekarz
authors: Peilin
authors: P
authors: Ma
authors: Andy
authors: A
authors: Hudmon
authors: Theodore R
authors: TR
authors: Cummins
authors: Weinian
authors: W
authors: Shou
mesh_terms: D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D004361:Drug Tolerance / Q000235:genetics*; D057809:HEK293 Cells; D006801:Humans; D066298:In Vitro Techniques; D008012:Lidocaine / Q000494:pharmacology*; D008133:Long QT Syndrome / Q000235:genetics*; D009154:Mutation; D032383:Myocytes, Cardiac / Q000502:physiology; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D061567:Voltage-Gated Sodium Channel Blockers / Q000494:pharmacology
chemical_list: D000779:Anesthetics, Local; D000889:Anti-Arrhythmia Agents; D062554:NAV1.5 Voltage-Gated Sodium Channel; C568320:SCN5A protein, human; D061567:Voltage-Gated Sodium Channel Blockers; D008012:Lidocaine