Preventing Site-specific Calpain Proteolysis of Junctophilin-2 Protects Against Stress-induced E-C Uncoupling and Heart Failure

Junctophilin-2 (JP2) is an essential component of the excitation-contraction coupling apparatus in cardiomyocytes and becomes proteolytically cleaved in response to stress. We previously mapped the primary calpain cleavage site to JP2 residues 565-566 using in vitro assays. To determine whether this site is responsible for JP2 cleavage in vivo, we generated calpain resistant JP2 (JP2CR) knock-in mice lacking this site. We find JP2 is not cleaved in JP2CR mice during pressure overload stress resulting in better cardiac outcomes and an attenuated transcriptional response relative to wildtype mice.