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J Mol Cell Cardiol. 2017 Sep;110:61-69. doi: 10.1016/j.yjmcc.2017.07.009. Epub 2017 Jul 22.

D242N, a KV7.1 LQTS mutation uncovers a key residue for IKs voltage dependence.

Author information

1
Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain.
2
Molecular Physiology Laboratory, Dpt. de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Spain.
3
Computational Physiopathology Unit, Dpt. of Electrical, Electronic and Information Engineering "Guglielmo Marconi", University of Bologna, Italy.
4
Dpt. of Cardiology, Hospital Universitario Virgen de la Arrixaca de Murcia, Spain.
5
Instituto de Química Médica CSIC, Madrid, Spain.
6
Dpt. of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Science, University College London, London, UK.
7
Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain. Electronic address: tgonzalez@iib.uam.es.
8
Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain. Electronic address: cvalenzuela@iib.uam.es.

Abstract

KV7.1 and KCNE1 co-assemble to give rise to the IKs current, one of the most important repolarizing currents of the cardiac action potential. Its relevance is underscored by the identification of >500 mutations in KV7.1 and, at least, 36 in KCNE1, that cause Long QT Syndrome (LQTS). The aim of this study was to characterize the biophysical and cellular consequences of the D242N KV7.1 mutation associated with the LQTS. The mutation is located in the S4 transmembrane segment, within the voltage sensor of the KV7.1 channel, disrupting the conserved charge balance of this region. Perforated patch-clamp experiments show that, unexpectedly, the mutation did not disrupt the voltage-dependent activation but it removed the inactivation and slowed the activation kinetics of D242N KV7.1 channels. Biotinylation of cell-surface protein and co-immunoprecipitation experiments revealed that neither plasma membrane targeting nor co-assembly between KV7.1 and KCNE1 was altered by the mutation. However, the association of D242N KV7.1 with KCNE1 strongly shifted the voltage dependence of activation to more depolarized potentials (+50mV), hindering IKs current at physiologically relevant membrane potentials. Both functional and computational analysis suggest that the clinical phenotype of the LQTS patients carrying the D242N mutation is due to impaired action potential adaptation to exercise and, in particular, to increase in heart rate. Moreover, our data identify D242 aminoacidic position as a potential residue involved in the KCNE1-mediated regulation of the voltage dependence of activation of the KV7.1 channel.

KEYWORDS:

Electrophysiology; K(V)7.1; KCNE1; Long QT syndrome

PMID:
28739325
DOI:
10.1016/j.yjmcc.2017.07.009
[Indexed for MEDLINE]

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