The Role of GSK3B Mislocalization in Arrythmogenic Cardiomyopathy

Abstract

Arrythmogenic cardiomyopathy (ACM) is a genetic cardiomyopathy commonly inherited through dominant mutations in desmosomal genes (JUP, DSP, PKP2, DSG2, and DSC2). Characteristic phenotypes of ACM include ventricular arrhythmias, fibrofatty replacement of the myocardium, and desmosomal instability. While mechanistic linkages remain unknown, recent work has identified glucose synthase kinase (GSK3β) mislocalization as another common ACM phenotype. While inhibition of GSK3β has been shown to mitigate disease progression, it is unclear what role GSK3β plays in destabilization of the desmosome. We hypothesize that a mutation in a desmosomal protein causes initial desmosomal instability, and that GSK3β mislocalization to the intercalated disk happens secondary to this insult. To test this hypothesis, we constructed engineered heart tissues (EHTs) from iPSC-derived cardiomyocytes with an ACM-linked point mutation (R451G) in desmoplakin. Our previous work identified the primary effect of the R451G mutation as causing increased susceptibility to calpain mediated degradation. This mutation provides, in effect, a means of inducing targeted desmosomal instability by either allowing or inhibiting calpain activity. After verifying that expression of R451G desmoplakin resulted in unstable desmosomes, GSK3β mislocalization was assessed via immunofluorescent microscopy. EHTs were then treated either a calpain inhibitor or a GSK3β inhibitor, and the effects on desmosonal stability, gap junction remodeling, and GSK3β mislocalization were studied. This work will allow for further insights into pathomechanisms underlying ACM.