The Tell–Tale Cardiac Thin Filament Model: An Investigation into the Dynamics of Contraction and Relaxation

Abstract

The correct function of cardiac sarcomeric proteins allow for people to maintain quality of life. However, mutations of the cardiac sarcomeric proteins can result in remodeling of the heart which typically results in death. I present a full atomistic cardiac thin filament model that I have developed and three studies that I conducted while at the University of Arizona, while pursuing my doctoral degree in chemistry The goal was to develop the model to be able to study the effects of the mutations on the thin filament proteins. First, I present the long process of developing the model that is still evolving as new information is available. Second, I present the study of two mutants, the troponin T R92L mutant and the tropomyosin D230N mutant. Molecular dynamics was used to simulate the wild–type and mutant versions of the model which resulted in a visualization of the change of interaction between the tropomyosin and troponin, specifically at the overlap region. Third, I present the study of calcium release which is the "gatekeeper" to cardiac contraction. Steered molecular dynamics was utilized to find a previously unseen molecular mechanism that alters the rate of calcium release depending on the mutant. Fourth, I present the study of the mechanism of the tropomyosin transition across the actin filament, in which a longitudinal transition is favored. The studies helped to provide an atomistic level understanding of the cardiac thin filament as well as the methodology to which the mutations disrupt the natural functions of the sarcomeric proteins. The new results of the research can provide new insight into how the effects of the disease causing mutations can be mitigated, potentially extending the life of people with the conditions.