Rescue of loss-of-function long QT syndrome-associated mutations in KV7.1/KCNE1 by the endocannabinoid N-arachidonoyl-L-serine (ARA-S)

Abstract

Background and Purpose

Congenital long QT syndrome (LQTS) involves genetic mutations affecting ion channels, leading to a prolonged QT interval and increased risk of potentially lethal ventricular arrhythmias. Mutations in the genes encoding K_V7.1/KCNE1 are the most frequent, with channel loss-of-function contributing to LQTS. The endocannabinoid N-arachidonoyl-L-serine (ARA-S) has been shown to facilitate activation of wild type K_V7.1/KCNE1 channels and to counteract a prolonged QT interval in isolated guinea pig hearts. In this study, we examine the ability of ARA-S to facilitate activation of LQTS-associated mutations, in various regions of the channel, and hence to counteract loss-of-function.

Experimental Approach

The two-electrode voltage clamp technique on Xenopus oocytes expressing human K_V7.1/KCNE1 channels was used to investigate the effects of ARA-S in 20 LQTS type 1-associated mutations distributed across the channel. Thereafter, different electrophysiology was used to assess ARA-S effects in mammalian cells.

Key Results

ARA-S enhanced the function of all mutated channels by shifting V₅₀ and increasing current amplitude. However, the magnitude of effect varied, related to whether mutations were in one of the two putative ARA-S binding sites on the channel as suggested by molecular dynamics simulations. ARA-S displayed translational potential by facilitating channel opening in mammalian cells and shortening the action potential duration in cardiomyocytes.

Conclusions and Implications

This study demonstrates the rescuing capability of ARA-S on a diverse set of LQTS mutants. These insights may aid in developing drug compounds using ARA-S sites and mechanisms and guide interpretation of which LQTS mutants respond well to such compounds.