Electrophysiological characterization of three non-synonymous single nucleotide polymorphisms (R87Q, A251T, and P307S) found in hKv1.5

Abstract

Non-synonymous single nucleotide polymorphisms (SNPs) in the KCNA5/hKv1.5 gene, which encodes for a voltage-gated K+ channel responsible for the I (Kur) current in the human atria, have been recently reported. To gain further knowledge on potential influence of hKv1.5 SNPs, we searched for their presence in a specific population of 96 French-Canadians and characterized electrophysiological properties of the variants in two cell lines. The presumed promoter (-83 bp) and coding regions were sequenced. We found three heterozygous SNPs: R87Q, A251T, and P307S. Functional analysis of SNPs transfected in Chinese hamster ovary (CHO) cells showed that both R87Q and P307S diminished the inactivation amplitude (e.g., at +60 mV, amplitudes were 89+/-26, 23+/-4, and 22+/-7 pA/pF for the wild type, R87Q and P307S, respectively; n=8, 6, and 8, respectively). Inactivation was slowed with these variants (e.g., tau (fast) at +50 mV were 270+/-48, 490+/-66, and 340+/-45 ms for the wild type, R87Q, and P307S, respectively) while R87Q additionally accelerated the rate of hKv1.5 channel opening. A dominant-negative effect was observed for R87Q but not for P307S. SNPs properties were not reproduced when expressed in the HEK293 cell line, suggesting that the regulatory beta-subunit present in CHO cells (and the human heart) is essential for the SNPs effects that we have observed.

A pilot study to estimate the feasibility of assessing the relationships between polymorphisms in hKv1.5 and atrial fibrillation in patients following coronary artery bypass graft surgery

“…The effects of R87Q and P307S on hKv1.5 channel properties suggest that these SNPs may be involved in the familial and the postoperative forms of AF. The A251T variant is not likely to be responsible for AF because it does not modify the electrophysiological properties of hKv1.5 (13). R87Q and P307S SNPs may not promote AF by themselves, but they may be implicated in the development of this disease, in combination with other factors, such as the oxidative stress related to surgery.…”

“…We have previously characterized, in a FrenchCanadian population, the R87Q, A251T and P307S SNPs in this gene (13). These variants were found among post-CABG patients with AF, with respective allelic frequencies of 0.52%, 1.04% and 1.56%.…”

“…Even though the sample size was not sufficient to establish statistical significance for each individual mutation, the results suggest that these mutations may influence the development of postoperative AF. Indeed, these SNPs slow the inactivation process of the hKv1.5 current and, in addition, R87Q increases the rate of channel opening (13). Thus, these mutations accelerate atrial repolarization, which contributes to action potential shortening during AF.…”

“…Recently, we found the heterozygous single nucleotide polymorphisms (SNPs) R87Q, A251T and P307S in this channel in a population of 96 French Canadians (13). An electrophysiological analysis showed that the R87Q and P307S variants diminished the expression level of the channel and slowed its inactivation process in Chinese hamster ovary cells.…”

Ischemic, genetic and pharmacological origins of cardiac arrhythmias: The contribution of the Quebec Heart Institute

“…We also searched for mutations in hK v 1.5, a major repolarizing current of the human atria. In a population of 185 French-Canadians undergoing coronary bypass, we found three heterozygous single nucleotide polymorphisms (SNPs): R87Q, A251T and P307S (93,94). Functional analysis of the variants obtained after direct mutagenesis and expression in the CHO cell line showed that two variants (R87Q and P307S) affected the expression level of the channel in a dominant-negative manner.…”