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

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 KV7.1/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 KV7.1/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 KV7.1/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.