Desmoplakin Loss Leads to PKC- and Src-Mediated Contractile Dysfunction in Cardiomyocytes.

BACKGROUND: Mutations in DSP, which encodes the protein desmoplakin, lead to cardiomyopathy with unusually high penetrance that presents with arrhythmias, fibro-fatty infiltration, and eventually heart failure. However, the precise mechanism of contractile dysfunction and dilation is incompletely understood. Here, we investigate the pathogenesis of DSP-R451G, a missense mutation that results in complete degradation of desmoplakin protein. METHODS: We use 3 complementary models to characterize desmoplakin-linked cardiomyopathy: induced pluripotent stem cell-derived engineered heart tissue expressing R451G desmoplakin, a heterozygous DspWT/R451G knock-in mouse, and left-ventricular biopsy specimens. Tissue-engineered constructs are used to characterize contractility, calcium handling, sarcomere length, and cell signaling. These results are corroborated in the R451G mouse. To expand the generalizability of the findings, we compare them to those from human heart biopsies bearing 3 different desmoplakin mutations. RESULTS: Using induced pluripotent stem cell-derived engineered heart tissue and isolated mouse ventricular cardiomyocytes, we recapitulate a disease phenotype consistent with desmoplakin cardiomyopathy and identify shortened resting sarcomere length as a pathogenic mechanism for contractile dysfunction. Phosphorylation of Src and protein kinase C underlies sarcomere shortening in mutant tissues, and pharmacological inhibition of these kinases rescues sarcomere length. Notably, these sarcomeric and biochemical hallmarks are also present in human hearts bearing 3 different desmoplakin mutations. We next identify redistribution of mechanical force at cardiomyocyte junctions as a proximal factor that may promote mechanoactivation of proto-oncogene tyrosine-protein kinase Src. Finally, we rescue sarcomere length and contractile function in DSP-mutant engineered heart tissue with dasatinib, a Food and Drug Administration-approved receptor tyrosine kinase inhibitor. CONCLUSIONS: Our study reveals a mechanism by which a desmosomal mutation affects cardiomyocyte function at the sarcomere level through activation of key signaling pathways that have not previously been implicated in desmoplakin cardiomyopathy.