DETERMINING THE INTRAMOLECULAR MECHANISMS DRIVING ALTERED CONTRACTION IN THE MYOSIN MUTATIONS E525K AND V606M

Abstract

Force generation in the heart relies on the interaction of myosin and actin filaments, a tightly regulated process where subtle changes can lead to heart disease. Mutations in β-cardiac myosin impact the number of available myosin molecules, their binding to actin, and their ATP utilization rate. Understanding how this family of mutations alter heart contraction requires investigation of myosin at the single molecule, the sub-cellular, and the physiological level. This study investigates the mechanism of altered myosin function in two β-myosin mutations (E525K and V606M). The first project, presented in Chapter 2, uses molecular dynamics simulations of E525K and V606M myosin to highlight a regulatory role for the loop 2 structure in crossbridge binding. The second project, presented in chapter 3, involves a deep investigation of the E525K mutation using stem cell derived cardiomyocyte. Cells and tissues with the E525K mutation showed decreased force generation, consistent with dilated cardiomyopathy; however, single myofibril preparations demonstrated that myofibrils containing E525K myosin can generate more force than wild type under some conditions. These findings underscore the importance of multi-scale studies of myosin mutations. While single-molecule biochemical assays are informative, they may not always reflect the complete picture. As cardiac medicine moves towards personalized treatment, in-depth understanding of how specific myosin mutations alter chemomechanics is vital for designing tailored drugs for cardiomyopathy.