BPS2026 – Characterizing the desmoplakin-drug interaction using NMR saturation transfer difference experiments

Desmoplakin (DSP) is a desmosomal protein that plays an integral role in connecting the intermediate filaments from one cardiomyocyte to another. Mutations in DSP underlie about 5% of arrhythmogenic cardiomyopathy (ACM) cases. Recent data from our lab show that some disease-linked DSP mutations result in hypersensitive cleavage in the presence of calpain, an endogenous calcium-dependent protease. The resulting loss of DSP destabilizes the desmosome and leads to weakened cell-cell adhesion, which is correlated with fibrofatty infiltration in ACM. Our lab has shown that DSP mutant hypersensitivity to calpain is dependent upon the exposure of a usually occluded cleavage site on the DSP surface. Previous work found that small molecules stabilize DSP levels in the presence of calpain. Several dozen small molecules specifically inhibit DSP and DSP mutant degradation. However, parameters of how these drugs interact with DSP, including binding affinity, the binding orientation, and bioavailability in our system, are unknown. Here, using NMR saturation transfer difference (STD) experiments, we begin to quantify these characteristics of each DSP degradation-inhibiting small molecule in the presence of wild-type (WT) and mutant DSP strands. Future work will continue identifying these characteristics for each small molecule and calpain-sensitive mutation strain.