Heart failure is a pressing problem in today?s society. Positive inotropic agents are needed in the treatment of heart failure due to left ventricular systolic dysfunction. Many of the currently used drugs (such as ?-adrenergic agonists and phosphodiesterase III inhibitors) are ineffective in the long-term since they are plagued with severe side effects. Calcium sensitizing agents are interesting alternative drug candidates if they can cause a positive inotropic effect without associated side effects. One possible target for calcium sensitizing drugs is cardiac troponin (cTn), a Ca2+-dependent switch, activating and deactivating the myofilament leading to contraction and relaxation. Cardiac cTn consists of three subunits: cTnC, cTnI and cTnT. Increasingly routine computational methods are used to study cTn. However, there remains a critical need for development of novel and more precise tools that expand understanding of molecular processes governing heart contraction in order to guide targeted drug discovery studies. The main objective of this proposal is to develop novel computational methods to predict and modulate calcium sensitization within cTnC. Results from computational method advances will be verified experimentally and the experimental results will drive additional method refinement. The proposed research is structured into three main stages. We will use computer-aided drug design studies to find and experimentally verify novel calcium sensitizing agents (Aim I) and then develop computational models to understand the molecular processes in cTn that underlie the observed sensitizing effect with direct feedback to experiments (Aims II and III). Method development work will focus on overcoming two main hurdles faced by current computational models of cardiomyocyte contraction. Firstly, we will develop new methodology to accurately predict calcium binding affinities to cTnC (Aim II). Based on strong preliminary data, we hypothesize that this requires polarizable force fields, without which Ca2+ binding is not adequately modeled and oversimplified in molecular dynamics (MD) simulations. Secondly, we will predict the degree to which drugs open up the cTnC-cTnI interface (Aim III). Based on preliminary data, our hypothesis is that microsecond MD simulations and new methodology are needed to determine the opening degree of the hydrophobic patch in drug-bound conformations. Results from computational method advances will be verified experimentally and the experimental results will drive additional method refinement and improve our initial drug discovery hits.
The proposed research is relevant to public health because it will result in the discovery of new calcium sensitizing agents that could promote treatment of heart failure. We are developing new computational models to understand the molecular contraction processes in troponin which will ultimately serve as the framework upon which improved therapies for heart failure patients are based. Therefore, the proposed research is relevant to the part of NIH?s mission that pertains to developing fundamental knowledge that will ultimately help reduce the burdens of human disease.
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