The cardiac troponin complex (CTn) is made up of cardiac troponin T (CTnT), that attaches the complex to the thin filament;cardiac troponin I (CTnI), involved in the inhibition of muscle contraction and cardiac/slow skeletal troponin C (CTnC), that binds Ca2+ and triggers contraction. Altogether, the CTn, regulates muscle contraction, i.e., Ca2+ sensitivity of force development, maximal force development and basal force. Cardiac/Slow Skeletal Troponin C (C/SSTnC) is the only component of CTn that is expressed and present in both cardiac and slow skeletal muscles. It is considered the primary Ca2+ sensor of striated muscle and has been a target of Hypertrophic (HCM) and Dilated (DCM) Cardiomyopathies. HCM or DCM are genetic disorders caused by the mutations in the TnC gene that are characterized by morphological changes in the ventricular walls and altered Ca2+ handling of the diseased heart. HCM mutations in troponin cause the cardiac myofilament to become sensitized to Ca2+ which is implicated as causing arrhythmias and sudden cardiac death. In contrast, troponin mutations related to DCM desensitize myofilaments to Ca2+ which often leads to congestive heart failure. CTn mutations related to cardiomyopathy have been extensively studied in the cardiac system. However, the functional consequences of cardiomyopathic C/SSTnC mutants also present in slow skeletal muscle are unknown. The question to be addressed in this grant is: What are the functional consequences of C/SSTnC mutations linked to HCM and DCM in the regulation of slow skeletal muscle contraction? How do they compare to those found in cardiac muscle? To accomplish this, in vitro systems will be utilized as well as skinned fibers which will be used to measure the force/pCa relationship. These measurements will be performed in both skeletal and cardiac muscles. An HCM CTnC knock-in mouse generated in the laboratory will be characterized to determine the in vivo consequences of the mutation in intact and skinned fibers.
The aims of this proposal address the functional differences that underlie the phenotypes of C/SSTnC mutations in cardiac and skeletal muscles. These studies will investigate whether slow skeletal muscle containing C/SSTnC mutations develops skeletal abnormalities similar to those seen in the heart and whether the function of skeletal muscle is altered in the mutation-knock in mouse model. The questions that are being addressed are: Is the change that occurs in the skeletal system comparable to changes that occur in cardiac muscle? If the functional changes in slow skeletal muscle appear minimal what additional components absent in the regulation of cardiac muscle assist in rescuing the effects of the mutation? Successful execution of these aims will lead to a better understanding of cardiac versus slow skeletal muscle disorders associated with mutations in the TnC gene.
Cardiac/Slow Skeletal Troponin C (C/SSTnC) is the only component of CTn that is expressed and present in both cardiac and slow skeletal muscles. This proposal will elucidate the physiological consequences of troponin C mutants related to Hypertrophic (HCM) and dilated (DCM) cardiomyopathy in slow skeletal muscle. These studies will investigate whether slow skeletal muscle containing C/SSTnC mutations develops skeletal abnormalities similar to those seen in the heart and whether the function of skeletal muscle is altered. We will use innovative and novel approaches including knock-in mice to provide critical insights into this disease in skeletal muscle.
|Kawai, Masataka; Johnston, Jamie R; Karam, Tarek et al. (2017) Myosin Rod Hypophosphorylation and CB Kinetics in Papillary Muscles from a TnC-A8V KI Mouse Model. Biophys J 112:1726-1736|
|Dossat, Amanda M; Sanchez-Gonzalez, Marcos A; Koutnik, Andrew P et al. (2017) Pathogenesis of depression- and anxiety-like behavior in an animal model of hypertrophic cardiomyopathy. FASEB J 31:2492-2506|
|Zot, Henry G; Hasbun, Javier E; Michell, Clara A et al. (2016) Enhanced troponin I binding explains the functional changes produced by the hypertrophic cardiomyopathy mutation A8V of cardiac troponin C. Arch Biochem Biophys 601:97-104|
|Figueiredo-Freitas, Cícero; Dulce, Raul A; Foster, Matthew W et al. (2015) S-Nitrosylation of Sarcomeric Proteins Depresses Myofilament Ca2+)Sensitivity in Intact Cardiomyocytes. Antioxid Redox Signal 23:1017-34|
|Chang, Audrey N; Battiprolu, Pavan K; Cowley, Patrick M et al. (2015) Constitutive phosphorylation of cardiac myosin regulatory light chain in vivo. J Biol Chem 290:10703-16|
|Parvatiyar, Michelle S; Pinto, Jose Renato (2015) Pathogenesis associated with a restrictive cardiomyopathy mutant in cardiac troponin T is due to reduced protein stability and greatly increased myofilament Ca2+ sensitivity. Biochim Biophys Acta 1850:365-72|
|Martins, Adriano S; Parvatiyar, Michelle S; Feng, Han-Zhong et al. (2015) In Vivo Analysis of Troponin C Knock-In (A8V) Mice: Evidence that TNNC1 Is a Hypertrophic Cardiomyopathy Susceptibility Gene. Circ Cardiovasc Genet 8:653-664|
|Dweck, David; Sanchez-Gonzalez, Marcos A; Chang, Audrey N et al. (2014) Long term ablation of protein kinase A (PKA)-mediated cardiac troponin I phosphorylation leads to excitation-contraction uncoupling and diastolic dysfunction in a knock-in mouse model of hypertrophic cardiomyopathy. J Biol Chem 289:23097-111|
|Venkataraman, Raghav; Baldo, Marcelo Perim; Hwang, Hyun Seok et al. (2013) Myofilament calcium de-sensitization and contractile uncoupling prevent pause-triggered ventricular tachycardia in mouse hearts with chronic myocardial infarction. J Mol Cell Cardiol 60:8-15|
|Wang, Yingcai; Pinto, Jose Renato; Solis, Raquel Sancho et al. (2012) Generation and functional characterization of knock-in mice harboring the cardiac troponin I-R21C mutation associated with hypertrophic cardiomyopathy. J Biol Chem 287:2156-67|
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