Targeting microtubule dynamics improves cardiac sodium channel function in arrhythmogenic cardiomyopathy

Abstract

Abstract Background Pathophysiological conditions such as heart failure and cardiomyopathy are associated with alterations in microtubule (MT) dynamics (in particular increased MT detyrosination), which have detrimental effects on cardiac function. Since the MT network is also involved in trafficking of ion channels to the cell membrane, its remodeling may also affect sodium channel (Nav1.5) function. Indeed, sodium current (INa) is typically decreased in the setting of heart failure and (arrhythmogenic) cardiomyopathy. Purpose To investigate the impact of MT detyrosination on Nav1.5 and INa in a mouse model of arrhythmogenic cardiomyopathy (tamoxifen-activated cardiac-specific knockout of plakophilin-2 (PKP2cKO)). Methods and Results Freshly isolated cardiomyocytes (CMs) from PKP2cKO mice were incubated for 2-4 hours with either 10 µM parthenolide (PTL; a compound that decreases the fraction of detyrosinated MTs) or vehicle only (DMSO). Vehicle-treated CMs from PKP2cKO mice displayed significantly increased levels of detyrosinated tubulin as compared to wild type (WT), which was attenuated by PTL treatment. PTL significantly increased whole-cell INa without affecting gating properties in PKP2cKO CMs, while it did not affect INa in WT CMs. Macropatch measurements demonstrated that PTL increased INa at both the cell end (Intercalated disc, ID) and lateral membrane (LM) of PKP2cKO CMs. Accordingly, stochastic optical reconstruction microscopy (STORM), a super-resolution approach, revealed that PTL increased Nav1.5 cluster density at both ID and LM of PKP2cKO CMs. Conclusions Reducing MT detyrosination by PTL increases Nav1.5 cluster density and sodium current magnitude in a mouse model of arrhythmogenic cardiomyopathy. These findings identify restoration of MT dynamics as a potential novel anti-arrhythmic therapeutic in the setting of cardiac pathology.