Molecular Insights into the Rescue Mechanism of an hERG Activator Against Severe LQT2 Mutations

Abstract

Mutations in the hERG potassium channel are a major cause of long QT syndrome type 2 (LQT2), which can lead to sudden cardiac death. The hERG channel plays a critical role in the repolarization of the myocardial action potential, and loss-of-function mutations prolong cardiac repolarization. In this study, we investigated the efficacy and mechanism of ICA-105574, an hERG activator, in shortening the duration of cardiac repolarization in severe LQT2 variants. We characterized the in vivo efficacy of ICA-105574 in shortening the QT duration in an animal model and the in vitroIKrcurrent in cellular models mimicking severe hERG channel mutations (A561V, G628S, and L779P). We then used molecular dynamics simulations to investigate the molecular mechanisms of ICA-105574 action. In vivo, ICA-105574 significantly shortened the QT interval. LQT2 mutations drastically reducedIKramplitude and suppressed tail currents in cellular models. ICA-105574 restoredIKrin A561V and G628S. Finally, in silico data showed that ICA-105574 stabilizes a pattern of interactions similar to gain-of-function SQT1 mutations and can reverse the G628S modifications, through an allosteric network linking the binding site to the selectivity filter and the S5P turret helix, thereby restoring its K+ion permeability. Our results support the development of hERG activators as pharmacological molecules against some severe LQT2 mutations and suggest that molecular dynamics simulations can be used to test the ability of molecules to modulate hERG function in silico, paving the way for the rational design of new hERG activators.Significance StatementLong QT syndrome 2 (LQT2) results fromKCNH2gene mutations that affect the hERG channel, which is critical for cardiac repolarization. To investigate the therapeutic potential of ICA-105574, we used in vivo, in vitro and in silico models. In vivo, ICA-105574 significantly shortened the QT interval. In vitro, ICA-105574 selectively increased hERG current amplitude in severe LQT2 mutations (A561V, G628S) but not in L779P. Ourin-silicoanalysis suggests a potential mechanism, similar to SQT1 mutations, modulating an allosteric network linking the ICA-105574 binding site to the selectivity filter and the S5P turret helix. These findings deepen the understanding of hERG activation and suggest a potential therapeutic approach for LQT2.