Abstract P3130: Preventing Site-specific Calpain Cleavage Of Junctophilin-2 Protects Against Stress-induced E-c Coupling Dysfunction And Heart Failure Development In Mice

Abstract

In heart failure (HF), excitation-contraction (E-C) coupling processes become disrupted, resulting in abnormal Ca 2+ homeostasis that triggers cardiac dysfunction. Junctophilin-2 (JP2) is an essential E-C coupling constituent for maintaining cardiomyocyte integrity and cardiac function both at baseline and in response to stress. We previously showed that calpain-mediated proteolytic cleavage of JP2 at arginine 565 / threonine 566 (R 565 /T 566 ) is key to its downregulation in the diseased heart. However, it remains unclear whether preventing site-specific proteolysis of JP2 can prevent cardiac remodeling and HF progression following stress. To investigate this, calpain-resistant mutant JP2 knockin mice (JP2 CR ) were generated by deleting residues 563-568 spanning the primary calpain cleavage site. Studies in cultured cardiomyocytes treated with isoproterenol (ISO) showed that JP2 CR is resistant to stress-induced loss of JP2 integrity and T-tubule disorganization compared to wild-type (WT) cardiomyocytes. Further, in vivo studies demonstrate JP2 CR mice are more resistant to pressure overload stress having significantly less abnormal Ca 2+ homeostasis, cardiac dysfunction, hypertrophy, lung edema and fibrosis relative to WT mice. Western blot analysis revealed JP2 CR hearts have preserved expression levels of several key E-C coupling proteins, including RyR2, SERCA2a and Ca V 1.2. RNA-Sequencing analysis further revealed attenuated pressure overload induced hypertrophic and heart failure-related transcriptional reprogramming in JP2 CR hearts. These findings indicate that preserving JP2-dependent E-C coupling by prohibiting the site-specific calpain-cleavage of JP2 offers cardiac protection against stress-induced hypertrophy and heart failure. Our data indicate that preventing JP2 cleavage by gene therapy approaches may hold great therapeutic potential for treating heart failure.