Cardiac muscle contraction is regulated by Ca2+ binding to the troponin complex, which consists of 3 subunits: troponin C, troponin I and troponin T. This proposal investigates the role of abnormally spliced cardiac troponin T (cTnT) in the pathogenesis of dilated cardiomyopathy (DCM) and the compensation for this abnormal cTnT by a cardiac troponin I (cTnl) polymorphism. We previously discovered the presence of cTnT variants with abnormally spliced N-terminal regions in turkey and mammalian models of DCM. Since abnormal cTnT splicing also occurs in myopathic and failing human hearts, these cTnT variants may play a role in the pathogenesis and pathophysiology of DCM and heart failure. We hypothesize that the cTnT heterogeneity resulting from the presence of 2 or more functionally distinct cTnT variants in the normally uniform adult cardiac muscle desynchronizes contraction and decreases myocardial efficiency. We have developed transgenic mice expressing the DCM-related cTnT variants in their cardiac muscle for functional characterization. We will examine the effects of the abnormal cTnTs on the activity of actomyosin ATPase, the contractility of single myocytes and skinned muscle strips, the function of isolated working hearts, and the in vivo cardiac function of the mice. Increased binding affinity to cTnl is a primary abnormality of the DCM-related cTnTs. We recently found a novel polymorphism of cTnl (Arg111Cys) in wild turkey hearts. Arg-m is conserved as Arg or Lys in all cardiac and skeletal muscle Tnls, and sits in a coiled-coil interface between Tnl and TnT. The Arg111Cys substitution in cTnl lowers its binding affinity for cTnT, which is potentially compensatory for DCM-related cTnT abnormalities. Therefore, the presence of the cTnl-Cysm allele in wild turkeys may prevent the onset of DCM and thus have a significant selection value. To investigate this hypothesis, we will biochemically and physiologically characterize the turkey cTnl-Cysm polymorphism in transgenic mice. We will then coexpress this cTnl polymorphism with the DCM cTnT in double-transgenic mice to examine its compensatory effects. Using these integrated physiological systems, this study will significantly contribute to our understanding of the structure-function relationships among the troponin subunits and lay a foundation for the prevention and treatment of cTnT cardiomyopathies.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL078773-01A1
Application #
6968595
Study Section
Cardiac Contractility, Hypertrophy, and Failure Study Section (CCHF)
Program Officer
Varghese, Jamie
Project Start
2005-07-01
Project End
2009-06-30
Budget Start
2005-07-01
Budget End
2006-06-30
Support Year
1
Fiscal Year
2005
Total Cost
$342,000
Indirect Cost
Name
Northshore University Healthsystem
Department
Type
DUNS #
154538107
City
Evanston
State
IL
Country
United States
Zip Code
60201
Mondal, Anupom; Jin, J-P (2016) Protein Structure-Function Relationship at Work: Learning from Myopathy Mutations of the Slow Skeletal Muscle Isoform of Troponin T. Front Physiol 7:449
Wei, Bin; Jin, J-P (2016) TNNT1, TNNT2, and TNNT3: Isoform genes, regulation, and structure-function relationships. Gene 582:1-13
Yu, Zhi-Bin; Wei, Hongguang; Jin, J-P (2012) Chronic coexistence of two troponin T isoforms in adult transgenic mouse cardiomyocytes decreased contractile kinetics and caused dilatative remodeling. Am J Physiol Cell Physiol 303:C24-32
Zhang, Zhiling; Feng, Han-Zhong; Jin, J-P (2011) Structure of the NH2-terminal variable region of cardiac troponin T determines its sensitivity to restrictive cleavage in pathophysiological adaptation. Arch Biochem Biophys 515:37-45
Wei, Bin; Jin, J-P (2011) Troponin T isoforms and posttranscriptional modifications: Evolution, regulation and function. Arch Biochem Biophys 505:144-54
Biesiadecki, Brandon J; Jin, J-P (2011) A high-throughput solid-phase microplate protein-binding assay to investigate interactions between myofilament proteins. J Biomed Biotechnol 2011:421701
Wei, Bin; Gao, Jimin; Huang, Xu-Pei et al. (2010) Mutual rescues between two dominant negative mutations in cardiac troponin I and cardiac troponin T. J Biol Chem 285:27806-16
Wang, Qinchuan; Lin, Jenny Li-Chun; Reinking, Benjamin E et al. (2010) Essential roles of an intercalated disc protein, mXinbeta, in postnatal heart growth and survival. Circ Res 106:1468-78
Li, Yuejin; Charles, Pierre-Yves Jean; Nan, Changlong et al. (2010) Correcting diastolic dysfunction by Ca2+ desensitizing troponin in a transgenic mouse model of restrictive cardiomyopathy. J Mol Cell Cardiol 49:402-11
Biesiadecki, Brandon J; Tachampa, Kittipong; Yuan, Chao et al. (2010) Removal of the cardiac troponin I N-terminal extension improves cardiac function in aged mice. J Biol Chem 285:19688-98

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