Studies into molecular mechanisms of skeletal muscle contraction: Applications to transgenic mice with inherited cardiomyopathies

Muscle contraction results from ATP-coupled interactions of myosin cross-bridges with actin filaments. Although much of the general mechanism of contraction has been known for over 50 years, emerging advanced techniques have identified some of the key intermediate steps and regulating parameters. My doctoral research involves utilizing one such high resolution technique – single molecule fluorescence spectroscopy to discern the motion and conformation of myosin cross-bridges in ex-vivo muscle. An important goal of muscle research is to measure the rate of the power stroke and its regulation. Therefore, part of my thesis is focused on characterizing the pre- and post- power stroke states of muscle contraction and how it is modulated by Regulatory Light Chain (RLC) phosphorylation. I also applied our fluorescence polarization technique with single molecule sensitivity to unravel the deranged contractile properties of muscle in people afflicted with Familial Hypertrophic Cardiomyopathy (FHC) disease.;Some of the significant conclusions drawn from my project include 1. Evidence for the existence of distinct pre- and post- power stroke states of myosin cross-bridges during contraction in Ex Vivo muscle 2. Regulatory Light Chain phosphorylation disturbs cross-bridge organization and enhances the power stroke state of contraction and 3. FHC induced by mutations in Troponin-T protein impairs myosin cross-bridge interaction with actin and alters cross-bridge kinetics. Clinically, site targeted small molecules (peptides) can now be screened to correct for hypo-contractile or hyper-contractile properties associated with FHC. Our technique may also serve as a diagnosis tool for early identification of FHC disease. Finally increasing the basal ATPase activity of resting muscle by RLC phosphorylation is of therapeutic importance in treating individuals with Obesity, Type II Diabetes and Metabolic syndrome.