Research Paper
Subject Category: Pharmacokinetics, drug metabolism, toxicology
British Journal of Pharmacology (2008) 155, 957–966; doi:10.1038/bjp.2008.325; published online 25 August 2008
Pharmacology of the short QT syndrome N588K-hERG K+ channel mutation: differential impact on selected class I and class III antiarrhythmic drugs
M J McPate1, R S Duncan1, J C Hancox1 and H J Witchel1,2
1Cardiovascular Research Laboratories, Department of Physiology and Pharmacology, School of Medical Sciences, University of Bristol, Bristol, UK
Correspondence: Professor JC Hancox, Cardiovascular Research Laboratories, Department of Physiology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK. E-mail: jules.hancox@bristol.ac.uk; Dr HJ Witchel, Cardiovascular Research Laboratories, Department of Physiology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK. E-mail: h.witchel@bsms.ac.uk
2Current address: Brighton and Sussex Medical School, University of Sussex, Falmer BN1 9PX, UK.
Received 25 February 2008; Revised 9 June 2008; Accepted 17 July 2008; Published online 25 August 2008.
Abstract
Background and purpose:
The short QT syndrome (SQTS) is associated with cardiac arrhythmias and sudden death. The SQT1 form of SQTS results from an inactivation-attenuated, gain-of-function mutation (N588K) to the human ether-à-go-go-related gene (hERG) potassium channel. Pharmacological blockade of this mutated hERG channel may have therapeutic value. However, hERG-blocking potencies of canonical inhibitors such as E-4031 and D-sotalol are significantly reduced for N588K-hERG. Here, five hERG-blocking drugs were compared to determine their relative potencies for inhibiting N588K channels, and two other inactivation-attenuated mutant channels were tested to investigate the association between impaired inactivation and altered drug potency.
Experimental approach:
Whole-cell patch clamp measurements of hERG current (IhERG) mediated by wild-type and mutant (N588K, S631A and N588K/S631A) channels were made at 37 °C CHO cells.
Key results:
The N588K mutation attenuated IhERG inhibition in the following order: E-4031>amiodarone>quinidine>propafenone>disopyramide. Comparing the three inactivation mutants, the two single mutations, although occurring in different modules of the channel, attenuated inactivation to a nearly identical degree, whereas the double mutant caused considerably greater attenuation, permitting the titration of inactivation. Attenuation of channel inhibition was similar between the single mutants for each drug, and was significantly greater with the double mutant.
Conclusions and implications:
The degree of drug inhibition of hERG channels may vary based on the level of channel inactivation. Drugs previously identified as useful for treating SQT1 have the least dependence on hERG inactivation. In addition, our findings indicate that amiodarone may warrant further investigation as a potential treatment for SQT1.
Keywords:
hERG, human ether-à-go-go-related gene, IKr, inactivation, KCNH2, KV11.1, N588K, QT interval, rapid delayed rectifier potassium current, short QT syndrome, SQTS
Abbreviations:
IKr, the 'rapid' delayed rectifier potassium current; SQT1, the form of short QT syndrome associated with the N588K mutation of hERG; SQTS, short QT syndrome; WT, wild type
