CAVIN1-Mediated Endocytosis: A Novel Mechanism Underlying The Interindividual Variability In Drug-Induced Long QT

BackgroundDrug-induced QT prolongation (diLQT) is a feared side-effect as exposing susceptible individuals to fatal arrhythmias. The occurrence of diLQT is primarily attributed to unintended drug interactions with cardiac ion channels, notably the hERG channels that generate the repolarizing current (IKr) and thereby regulate the late repolarization phase. There is an important inter-individual susceptibility to develop diLQT which is of unknown origin but can be reproduced in patient-specific iPSC-derived cardiomyocytes (iPS-CMs). ObjectiveWe aimed to investigate the dynamics of hERG channels in response to sotalol and to identify regulators of the susceptibility to developing diLQT. MethodsWe measured electrophysiological activity and cellular distribution of hERG channels after hERG blocker treatment in iPS-CMs derived from patients with highest or lowest sensitivity (HS or LS) to sotalol administration in vivo (i.e., based on the measure of the maximal change in QT interval 3 hours after administration). Specific small-interfering RNAs (siRNA) and CAVIN1-T2A-GFP adenovirus were used to manipulate CAVIN1 expression. ResultsWhile HS and LS iPS-CMs showed similar electrophysiological characteristics at the baseline, the late repolarization phase was prolonged, and IKr significantly decreased after exposure of HS iPS-CMs to low sotalol concentrations. IKr reduction was caused by a rapid translocation of hERG channel from the plasma membrane to the cytoskeleton upon sotalol application. This phenomenon was suppressed by blocking active endocytosis using dynasore. CAVIN1, essential for caveolae biogenesis, was two-times more expressed in HS iPS-CMs and its knockdown using siRNA decreased their sensitivity to sotalol. CAVIN1 overexpression in LS iPS-CMs using adenovirus showed reciprocal effects. Mechanistically, we found that treatment with sotalol promoted trafficking of the hERG channel from the plasma membrane to the cytoskeleton through caveolae and in a manner dependent on CAVIN1 expression. CAVIN1 silencing reduced the number of caveolae at the membrane and abrogated the internalization of hERG channel in sotalol-treated HS iPS-CMs. CAVIN1 also controlled cardiomyocyte responses to other hERG blockers such as E4031, vandetanib, and clarithromycin. ConclusionsOur study identifies unbridled turnover of the potassium channel hERG as a mechanism supporting the inter-individual susceptibility underlying diLQT development and demonstrates how this phenomenon is finely tuned by CAVIN1. CLINICAL PERSPECTIVEO_ST_ABSWhat is new?C_ST_ABS- The inter-individual susceptibility underlying diLQT development involves unbridled turnover of cardiac ion channels from the plasma membrane. - This phenomenon is finely tuned by CAVIN1, a protein that is essential for essential for caveolae biogenesis. - Treatment with hERG blocker promoted trafficking of the hERG channel from the plasma membrane to the cytoskeleton through caveolae and in a manner dependent on CAVIN1 expression. What are the clinical implications?- While congenital long QT is primarily from a genetic origin, the development of drug-induced long QT involves differences in the trafficking machinery of cardiac ion channels. - The prediction of CAVIN1 expression levels could help preventing drug-induced cardiotoxicity.