Referenced in: none

Automatically associated channels: Kv1.5

Title: Kv1.5 channelopathy due to KCNA5 loss-of-function mutation causes human atrial fibrillation.

Authors: Timothy M Olson, Alexey E Alekseev, Xiaoke K Liu, Sungjo Park, Leonid V Zingman, Martin Bienengraeber, Srinivasan Sattiraju, Jeffrey D Ballew, Arshad Jahangir, Andre Terzic

Journal, date & volume: Hum. Mol. Genet., 2006 Jul 15 , 15, 2185-91

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/16772329

Abstract
Atrial fibrillation is a rhythm disorder characterized by chaotic electrical activity of cardiac atria. Predisposing to stroke and heart failure, this common condition is increasingly recognized as a heritable disorder. To identify genetic defects conferring disease susceptibility, patients with idiopathic atrial fibrillation, lacking traditional risk factors, were evaluated. Genomic DNA scanning revealed a nonsense mutation in KCNA5 that encodes Kv1.5, a voltage-gated potassium channel expressed in human atria. The heterozygous E375X mutation, present in a familial case of atrial fibrillation and absent in 540 unrelated control individuals, introduced a premature stop codon disrupting the Kv1.5 channel protein. The truncation eliminated the S4-S6 voltage sensor, pore region and C-terminus, preserving the N-terminus and S1-S3 transmembrane domains that secure tetrameric subunit assembly. Heterologously expressed recombinant E375X mutant failed to generate the ultrarapid delayed rectifier current I(Kur) vital for atrial repolarization and exerted a dominant-negative effect on wild-type current. Loss of channel function translated into action potential prolongation and early after-depolarization in human atrial myocytes, increasing vulnerability to stress-provoked triggered activity. The pathogenic link between compromised Kv1.5 function and susceptibility to atrial fibrillation was verified, at the organism level, in a murine model. Rescue of the genetic defect was achieved by aminoglycoside-induced translational read-through of the E375X premature stop codon, restoring channel function. This first report of Kv1.5 loss-of-function channelopathy establishes KCNA5 mutation as a novel risk factor for repolarization deficiency and atrial fibrillation.