Abstract Mo066: A Bifunctional Actuator Reverses NaV1.5 Dysfunction Linked To Cardiac Arrhythmias

Cardiac voltage-gated sodium channels (NaV1.5) are critical for the initiation of action potentials within the heart. Alterations in NaV1.5 function significantly contribute to diverse inherited and acquired arrhythmias, such as Long QT syndrome (LQT), Brugada syndrome (BrS), mixed-syndrome, and heart failure. These pathologies are closely associated with two distinct modifications in NaV1.5 function: (1) a gain-of-function phenotype, characterized by incomplete inactivation of NaV1.5 leading to a sustained Na+ current (I NaL), and (2) a loss-of-function phenotype resulting in diminished peak Na+ current (I NaP). Despite the broad understanding of NaV1.5 implication in cardiac pathophysiology, the development of effective therapeutic strategies to reverse these dysfunctions remains challenging. Here, we introduce a novel bifunctional actuator that inhibits I NaL and upregulates I NaP, as a common molecular strategy to reverse pathophysiological changes in Nav-linked cardiac arrhythmias. To do so, we use a genetically encoded approach by engineering a selective nanobody (nb82) targeting NaV1.5, linked to (1) a peptide inhibitor targeting I NaL (FixR), and (2) the catalytic domain of a deubiquitinase (DUB) to enhance NaV1.5 membrane expression. Changes in I NaP and I NaL were assessed using whole-cell and multichannel electrophysiology techniques in both wild-type and channelopathic mutant channels. Our results demonstrate that NbFixR-DUB effectively reduces I NaL while concurrently increasing I NaP for multiple channelopathic mutations. Overall, this approach holds considerable promise for rectifying both loss-of-function and gain-of-function phenotypes in Nav channelopathies.