Poster abstracts

Poster number 69 submitted by Tyler Stevens

Classifying of arrhythmogenic cardiomyopathy-linked desmoplakin variants through molecular mechanism of pathogenicity

Tyler L. Stevens (Molecular, Cellular, and Developmental Biology ), Heather Manring (Physiology and Cell Biology, The Ohio State University), Taylor Albertelli (Chemistry and Biochemistry, James Madison University), Ronald Ng, Stuart Campbell (Biomedical Engineering, Yale University), Nathan T. Wright (Chemistry and Biochemistry, James Madison University), Maegen Ackermann (Physiology and Cell Biology, The Ohio State University)

Abstract:
Arrhythmogenic Cardiomyopathy (ACM) is a disease that affects 1 in 2000 Americans yearly and segregates with sudden cardiac death (SCD). Up to 60% of ACM cases are associated with variants in desmosomal genes, however the molecular mechanisms associated with ACM remain unclear. Of those 60% of cases, up to 20% are linked to the desmoplakin gene, DSP, encoding a desmosomal protein. Of the variants within DSP there are 140 missense mutations, and of those missense mutations only 23.6% of are categorized as pathogenic, the remaining 76.4% have unknown pathogenicity. DSP is a structural protein responsible for linking intermediate filaments to the intercalated disc membrane and contributes to the structural integrity between myocytes. Within its NH2-terminus DSP contains a hotspot region for ACM-linked variants. Of the 20 variants within the hotspot region, 9 are pathogenic but the remaining 11 are classified as unknown pathogenicity. Our team has previously examined the biomolecular properties of the pathogenic hotspot-variants and identified that select variants display increased susceptibility to calpain-dependent degradation. Herein, we sought to test the hypothesis that additional DSP hotspot-variants of unknown pathogenicity will demonstrate increased susceptibility to calpain-mediated degradation. By comparing hotspot-variants of known and unknown pathogenicity, we aim to categorize different variants according to unique ACM patho-mechanisms. We used molecular dynamics, assessing essential intramolecular interactions and surface area exposure of a calpain target site within DSP, to predict pathogenicity. We show that 7 of the 11 variants of unknown pathogenicity display alterations in either the intramolecular interactions or surface area exposure of the cleavage site. Using biochemical assays, we have identified 14 of the 20 hotspot-variants result in increased calpain-mediated degradation, including 9 of the 11 variants of unknown pathogenicity. Future studies focus on establishing a mechanism of protection for calpain sensitive mutants.

Keywords: Arrhythmogenic , Cardiomyopathy , Desmoplakin