Heart failure can be a result of impaired cardiac contraction or relaxation or both, which are regulated by Ca2+induced thin filament activation and deactivation. Therefore, understanding the mechanism of thin filament regulation is of great importance in prevention and treatment of heart failure. The molecular basis of the thin filament regulation involves Ca2+induced alterations in the structure and structural kinetics and dynamics associated with the protein-protein interactions at the interface between troponin and actin. The objective of this proposal is to define the detailed kinetic mechanism that underlies Ca2+induced thin filament activation/deactivation and how it is affected by troponin phosphorylation and cardiomyopathy mutations found in cTnI. To achieve the goal, this proposal will address the following questions: 1) What is the kinetic role of different functional regions of cTnI in regulating crossbridge kinetics? 2) How do the structural dynamics of the cTnI C-domain play roles in thin filament regulation? and 3) How are the structural changes and structural kinetics of the thin filament modified in the skinned muscle fibers and myofibrils? The underlying hypothesis of this proposal is that the Ca2+induced structural transitions involving the different regions of troponin I at the interface between troponin and actin play different roles in regulating kinetics of the interaction between actin and mysoin, and the structural transitions can be affected by strong crossbridges, cardiomyopathy mutations, and phosphorylation of troponin proteins, as well as cellular lattice environment found in intact muscle cells. This project capitalizes on our FRET and fluorescence anisotropy expertise in determining protein structural kinetics and dynamics to exploit a new approach by implementing FRET methodologies into muscle fibers and myofibril measurements. This will enable us to acquire the urgently needed kinetic and dynamic information associated with the Ca2+induced thin filament regulation on muscle function. The results from this study will have a positive impact by advancing our understanding of the regulatory role of cardiac thin filament in cardiac muscle contraction and relaxation in health and disease.

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The objective of this proposal is to define the detailed kinetic mechanism that underlies Ca2+induced thin filament activation/deactivation and how it is affected by troponin phosphorylation and cardiomyopathy mutations found in cTnI. This application is related to research to improve depressed cardiac contractility under pathological conditions.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Special Emphasis Panel (ZRG1-CVRS-F (03))
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Evans, Frank
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Washington State University
Engineering (All Types)
Schools of Engineering
United States
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Schlecht, William; Li, King-Lun; Hu, Dehong et al. (2016) Fluorescence Based Characterization of Calcium Sensitizer Action on the Troponin Complex. Chem Biol Drug Des 87:171-81
Pulcastro, Hannah C; Awinda, Peter O; Methawasin, Mei et al. (2016) Increased Titin Compliance Reduced Length-Dependent Contraction and Slowed Cross-Bridge Kinetics in Skinned Myocardial Strips from Rbm (20ΔRRM) Mice. Front Physiol 7:322
Li, King-Lun; Ghashghaee, Nazanin Bohlooli; Solaro, R John et al. (2016) Sarcomere length dependent effects on the interaction between cTnC and cTnI in skinned papillary muscle strips. Arch Biochem Biophys 601:69-79
Li, King-Lun; Rieck, Daniel; Solaro, R John et al. (2014) In situ time-resolved FRET reveals effects of sarcomere length on cardiac thin-filament activation. Biophys J 107:682-93
Jayasundar, Jayant James; Xing, Jun; Robinson, John M et al. (2014) Molecular dynamics simulations of the cardiac troponin complex performed with FRET distances as restraints. PLoS One 9:e87135
Jacroux, Thomas; Bottenus, Danny; Rieck, Bennett et al. (2014) Cationic isotachophoresis separation of the biomarker cardiac troponin I from a high-abundance contaminant, serum albumin. Electrophoresis 35:2029-38
Schlecht, William; Zhou, Zhiqun; Li, King-Lun et al. (2014) FRET study of the structural and kinetic effects of PKC phosphomimetic cardiac troponin T mutants on thin filament regulation. Arch Biochem Biophys 550-551:1-11
Jacroux, Thomas; Rieck, Daniel C; Cui, Rong et al. (2013) Enzymatic amplification of DNA/RNA hybrid molecular beacon signaling in nucleic acid detection. Anal Biochem 432:106-14
Rieck, Daniel C; Li, King-Lun; Ouyang, Yexin et al. (2013) Structural basis for the in situ Ca(2+) sensitization of cardiac troponin C by positive feedback from force-generating myosin cross-bridges. Arch Biochem Biophys 537:198-209
Zhou, Zhiqun; Rieck, Daniel; Li, King-Lun et al. (2013) Structural and kinetic effects of hypertrophic cardiomyopathy related mutations R146G/Q and R163W on the regulatory switching activity of rat cardiac troponin I. Arch Biochem Biophys 535:56-67

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