AAV9-mediated βIII-tubulin Ser172 phospho-mimic expression improves arrhythmic and inflammatory remodeling in dystrophic cardiomyopathy

Abstract

BackgroundDuchenne muscular dystrophy (DMD) cardiomyopathy is characterized by progressive microtubule remodeling, connexin-43 (Cx43) dysregulation, and ventricular arrhythmias. We previously demonstrated phospho-mimic knock-in of {beta}III-tubulin S172E preserves microtubule organization and attenuates cardiac pathology in mdx mice. However, whether these protective effects can be reproduced using a clinically relevant gene-delivery strategy remains unknown. Methods and ResultsWe generated a cardiomyocyte-specific adeno-associated virus serotype 9 (AAV9) vector expressing phospho-mimic {beta}III-tubulin (Tubb3-S172E) under the cardiac troponin T promoter and delivered it to 4-5-month-old wild-type and mdx mice. Cardiac Tubb3-S172E expression was confirmed by quantitative qPCR and immunoblotting. In mdx mice, AAV9-mediated Tubb3-S172E expression significantly reduced mononuclear inflammatory infiltration, restored Cx43 localization at intercalated discs, and attenuated isoproterenol-induced arrhythmia susceptibility. In contrast, cardiac fibrosis, Nav1.5 protein expression, and peak sodium current density were not significantly improved. Overexpression of wild-type {beta}III-tubulin in healthy hearts increased Cx43 lateralization and arrhythmia susceptibility, indicating that {beta}III-tubulin phosphorylation state rather than protein abundance determines its protective function. ConclusionsCardiomyocyte-targeted delivery of phospho-mimic {beta}III-tubulin partially recapitulates the protective effects observed in the genetic S172E knock-in model. These findings identify {beta}III-tubulin Ser172 phosphorylation as a critical regulator of microtubule-dependent electrical remodeling and support therapeutic modulation of this pathway in Duchenne muscular dystrophy cardiomyopathy. Research PerspectiveO_LICardiomyocyte-targeted AAV9 delivery of phospho-mimic aIII-tubulin improves Cx43 organization, inflammatory remodeling, and arrhythmia susceptibility in dystrophic hearts, demonstrating that therapeutic modulation of {beta}III-tubulin Ser172 phosphorylation partially recapitulates the protective effects observed in the genetic S172E model. C_LIO_LIThe dissociation between improved electrical remodeling and persistent Nav1.5 and fibrotic abnormalities suggests that {beta}III-tubulin Ser172 phosphorylation selectively regulates specific microtubule-dependent pathological pathways in dystrophic cardiomyopathy. C_LIO_LIFuture studies should define the molecular mechanisms linking {beta}III-tubulin Ser172 phosphorylation to cardiomyocyte-immune cell communication and determine how this pathway coordinates electrical and inflammatory remodeling in dystrophic hearts. C_LI