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

Background Drug-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). Objective We aimed to investigate the dynamics of hERG channels in response to sotalol and to identify regulators of the susceptibility to developing diLQT. Methods We 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. Results While 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. Conclusions Our 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. What is new? What are the clinical implications? ### Competing Interest Statement JSH reports research grants from Bioserenity, Sanofi, Servier and Novo Nordisk; speaker, advisory board or consultancy fees from Amgen, Astra Zeneca, Bayer, Bioserenity, Bristol-Myers Squibb, Novartis, Novo-Nordisk, Vifor Pharma all unrelated to the present work. Other authors declare no competing financial interests. ### Clinical Trial This is sub-study of protocol [NCT01338441][1] ### Clinical Protocols ### Funding Statement This work was supported by grants from the Foundation Leducq (CVD18-05) and from the Fondation pour la Recherche Médicale (EQU201903007852). Outside the submitted work, JSH is supported by AP-HP, INSERM, ANR and is coordinating a French PIA Project (2018-PSPC-07, PACIFIC-preserved, BPIFrance) and a University Research Federation against heart failure (FHU2019, PREVENT_Heart Failure). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Not Applicable The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This is sub-study of protocol [NCT01338441][1] (IRB approved) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Not Applicable I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Not Applicable I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Not Applicable The data and material that support the findings of this study are available from the corresponding author upon reasonable request. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01338441&atom=%2Fmedrxiv%2Fearly%2F2023%2F02%2F23%2F2023.02.21.23286271.atom