Structural and Phenotypic Correction of K210del Genetic Cardiomyopathy by an FDA Approved Drug

Abstract Dilated cardiomyopathy (DCM), which results from genetic disorders resulting in decreased myocardial contractility, is a leading cause of morbidity and mortality worldwide. There are several therapeutic challenges in treating DCM, which include poor understanding of the underlying mechanism of impaired myocardial contractility, and the difficulty of developing targeted therapies to reverse mutation-specific pathologies. The long, treacherous, and expensive path to new drug development, coupled with the rarity of individual mutations underscore the difficulties of drug development for DCMs. In the current report we focused on K210del, a DCM-causing mutation, which was identified over 20 years ago. This mutation is a three-nucleotide deletion of sarcomeric troponin T (TnnT), resulting in loss of lysine 210. Here we present the crystal structure of the troponin complex carrying the K210del mutation. We found that K210del leads to an allosteric shift in the troponin complex resulting in distortion of activation Ca 2+ binding domain of TnnC at S69, thereby resulting in calcium discoordination. Next, we adopted an in-silico approach to identify FDA approved drugs that may correct the structure of the mutant troponin complex, which led us to identify the bisphosphonate risedronate as a potential structural corrector. Co-crystallization of risedronate with the mutant troponin complex restored of the normal configuration of S69 and calcium coordination. At a phenotypic level, risedronate normalized force generation in iPSC-derived cardiomyocytes from a patient carrying the mutation, and restored calcium sensitivity in skinned papillary muscles isolated from K210del mutant mice. Importantly, systemic administration of risedronate to K210del mutant mice normalized left ventricular ejection fraction (LVEF) as determined by echocardiography and MRI. Collectively, these results identify the structural basis for decreased calcium sensitivity in K210del and highlight a path to structural and phenotypic correction as a potential therapeutic strategy in genetic cardiomyopathies.