Contraction of the heart occurs through regulated interactions of the myofilament proteins in response to increasing intracellular calcium concentrations. In heart failure both calcium dynamics and the response of the myofilaments to calcium are altered. These alterations impair systolic and diastolic function and are potentially reversible. This proposal seeks to define specific mechanisms for the effects of variants of the key regulatory protein troponin I which contribute to heart failure and hypertrophy. The hypothesis of this proposal is that post translational or genetic variants cardiac troponin I modify its function and play a central role in heart failure and the response to increased heart rate and afterload. The long-range goal of this work is to understand the underlying molecular mechanism by which these variants alter cardiac function in order to design strategies to prevent or treat cardiac dysfunction. The dissection of the molecular pathophysiology of troponin I variants will be approached in a series of highly collaborative integrative studies focused on modeling of myofilament disease-related post translational or genetic variants changes in vivo in murine models and in human cardiomyocytes. To address these goals the following aims are proposed: 1. To determine the degree and impact of altered site-specific phosphorylation of troponin I in human heart failure by quantitative phosphoproteomics in human cardiomyocytes and expression of recombinant phosphorylation site mutants of troponin I in human cardiomyocytes 2. To determine whether phosphorylation of PKA sites of troponin I or phospholamban are the dominant contributor to the in vivo frequency dependent acceleration of relaxation (FDAR) and the relaxation response to afterload by use of interbred mouse models and 3. To address the hypothesis that an exon 5 sequence variant of troponin I, which occurs with a 3 % frequency in African-Americans, influences the response to acute and chronic afterload through the use of an in vivo murine model. This work should provide insight into the in vivo effects of specific myofilament troponin I variants which contribute to pathophysiology of heart failure and hypertrophy. In the long-term this will assist in the development of novel therapies which address the correction of myofilament defects.

Public Health Relevance

Heart failure is a significant medical problem in the United States. This proposal will study troponin I, a protein which regulates contraction of the heart. The specific goals are to study the effect of genetic and protein modifications of this protein on heart function. In the long term this should assist in developing better treatments for heart failure.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Study Section
Cardiac Contractility, Hypertrophy, and Failure Study Section (CCHF)
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Przywara, Dennis
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Johns Hopkins University
Schools of Medicine
United States
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Li, Yuejin; Zhu, Guangshuo; Paolocci, Nazareno et al. (2017) Heart Failure-Related Hyperphosphorylation in the Cardiac Troponin I C Terminus Has Divergent Effects on Cardiac Function In Vivo. Circ Heart Fail 10:
Bales, Nathan D; Johnson, Nicole M; Judge, Daniel P et al. (2016) Comprehensive Versus Targeted Genetic Testing in Children with Hypertrophic Cardiomyopathy. Pediatr Cardiol 37:845-51
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Ramirez-Correa, Genaro A; Frazier, Aisha H; Zhu, Guangshuo et al. (2015) Cardiac troponin I Pro82Ser variant induces diastolic dysfunction, blunts ?-adrenergic response, and impairs myofilament cooperativity. J Appl Physiol (1985) 118:212-23
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Wijnker, Paul J M; Sequeira, Vasco; Foster, D Brian et al. (2014) Length-dependent activation is modulated by cardiac troponin I bisphosphorylation at Ser23 and Ser24 but not by Thr143 phosphorylation. Am J Physiol Heart Circ Physiol 306:H1171-81
Wijnker, Paul J M; Sequeira, Vasco; Witjas-Paalberends, E Rosalie et al. (2014) Phosphorylation of protein kinase C sites Ser42/44 decreases Ca(2+)-sensitivity and blunts enhanced length-dependent activation in response to protein kinase A in human cardiomyocytes. Arch Biochem Biophys 554:11-21
Ramirez-Correa, Genaro A; Martinez-Ferrando, Maria Isabel; Zhang, Pingbo et al. (2014) Targeted proteomics of myofilament phosphorylation and other protein posttranslational modifications. Proteomics Clin Appl 8:543-53

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