Biological basis of cardiac thick filament regulation

Project Summary Cardiac muscle contraction fundamentally relies on the activity of myosin to generate force. For a basic understanding of cardiac muscle contraction and to address the unmet needs in treating heart diseases, it is essential to elucidate the molecular mechanisms by which cardiac myosin and its regulatory partner, cardiac myosin-binding protein-C (cMyBP-C) modulate force generation. A disruption in the equilibrium between the structural states of cardiac myosin is known to cause altered energy consumption and impaired muscle contraction. Thus, manipulation of myosin structural states is a promising approach to treat cardiomyopathies. However, our understanding of the basic mechanisms underlying the regulation of myosin structural states is poor. In particular, the lack of detailed structural information on myosin and cMyBP-C interactions presents a significant barrier to developing more effective approaches to manipulate myosin structural states to benefit patients. Therefore, the central goal of this proposal is to fill this knowledge gap by establishing previously unrecognized structural and functional mechanisms in basic thick filament function. To achieve this goal, we have devised a unique experimental plan and a multidisciplinary team to systematically address thick filament function from the atom to whole organ levels. In Aim 1, we will determine the structures of distinct myosin states in a double-headed configuration. In Aim 2, we will determine how myosin conformations govern cMyBP-C binding and regulate cardiac thick filament. In Aim 3, we will determine the in vivo functional consequences of manipulation of thick filament structure using cMyBP-C phosphorylation and myosin binding small molecules. Collectively, these studies will enhance our understanding of basic biological processes mediated by myosin and cMyBP-C in the heart and have the potential to advance the development of more precise cardiac thick filament targeted treatments.