The long-term goal of this work is to identify components inside the cardiac cell that are involved with the development of cardiomyopathic diseases. This proposal focuses on cardiac troponin C (cTnC), the on-off switch of the contractile apparatus and a major cardiomyocyte intracellular Ca2+ buffer.
Aim ed at understanding the regulatory properties of the troponin complex in vivo and its link to abnormal intracellular Ca2+ handling governing heart disease, this proposal is of considerable health relevance. Mutations in the regulatory complex of the thin filament (tropomyosin, troponin T and troponin I) associated with phenotypic outcomes of hypertrophic (HCM) and dilated (DCM) cardiomyopathies are suggested to indirectly disrupt cardiac muscle contraction by altering the Ca2+-binding properties of cTnC. However, effects of cTnC mutants that influence Ca2+-sensitive contractile responses have yet to be tested for their pathogenic capacity in living organisms. The central hypothesis guiding this proposal is that changes in cTnC N-terminus Ca2+-binding affinity, alone, can evoke cardiac remodeling in vivo. We further posit that ablation of a dedicated high-fidelity kinase has the potential to reverse the hypercontractile state imposed by Ca2+-sensitizing HCM-linked cTnC mutants.
Aim 1 will evaluate direct changes in cTnC Ca2+-binding affinity in the thin filament as a critical determinant underlying cardiomyopathic development.
This Aim tests the hypothesis that cTnC mutants increasing Ca2+-binding affinity in the N-domain (regulatory) can instigate diastolic dysfunction, leading to HCM; while a designed mutant decreasing cTnC Ca2+- binding affinity will recapitulate a DCM-reminiscent phenotype. Cardiac patho-physiological, biophysical and biochemical approaches will be used to dissect the role of cTnC mutations in our newly developed knock-in (KI) mice. The antithetical effects that these cTnC mutants exert on Ca2+-binding dynamics will be investigated early, prior to development of distinctive cardiac remodeling. In addition, this projet will further define TNNC1 (cTnC- encoding gene) as a cardiomyopathy-susceptibility gene.
Aim 2 will establish mechanistic and potential therapeutic links regarding normalization of myofilament Ca2+-sensitivity.
This Aim examines whether conditional removal of a dedicated sarcomeric kinase will correct the myofilament Ca2+ response, diminish the hypercontractile phenotype and improve cardiac relaxation, thus reversing post-symptomatic HCM disease. The consequences of conditional removal of this kinase in KI cTnC-HCM hearts will be monitored as a function of time. The last aim can serve as a proof-of-concept for the development of targeted therapies aimed at modulating the activity of dedicated sarcomeric kinases. The novel concepts generated here will define the role of cTnC in initiating and modulating one class of cardiomyopathies, thus opening avenues for development of new tailored therapeutic approaches.
Cardiomyopathies are common and devastating cardiac disorders in which the heart changes in size and structure to compensate for its inability to meet the body's demand for oxygenated blood. This proposal will: (i) define a new cardiomyopathy-susceptibility gene, (ii) identify central elements in the cardiac myofilament that regulate contraction and relaxation of the heart and are directly implicated in the development of distinct cardiomyopathies; and (iii) test a new genetic strategy to reverse hypertrophic growth in hearts. Understanding the underlying mechanisms at different levels, from finite molecular details up through integrated biological systems, may ultimately generate the necessary insight required to develop tailored therapeutic strategies which will be able to counter disease processes in the heart.
|Serra, Andrey Jorge; Proki?, Marko D; Vasconsuelo, Andrea et al. (2018) Oxidative Stress in Muscle Diseases: Current and Future Therapy. Oxid Med Cell Longev 2018:6439138|
|Wang, Lili; Kim, Kyungsoo; Parikh, Shan et al. (2018) Hypertrophic cardiomyopathy-linked mutation in troponin T causes myofibrillar disarray and pro-arrhythmic action potential changes in human iPSC cardiomyocytes. J Mol Cell Cardiol 114:320-327|
|Gonzalez-Martinez, David; Johnston, Jamie R; Landim-Vieira, Maicon et al. (2018) Structural and functional impact of troponin C-mediated Ca2+ sensitization on myofilament lattice spacing and cross-bridge mechanics in mouse cardiac muscle. J Mol Cell Cardiol 123:26-37|
|Bollen, Ilse A E; Schuldt, Maike; Harakalova, Magdalena et al. (2017) Genotype-specific pathogenic effects in human dilated cardiomyopathy. J Physiol 595:4677-4693|
|Marques, Mayra de A; Pinto, Jose Renato; Moraes, Adolfo H et al. (2017) Allosteric Transmission along a Loosely Structured Backbone Allows a Cardiac Troponin C Mutant to Function with Only One Ca2+ Ion. J Biol Chem 292:2379-2394|
|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|
|Veltri, Tiago; Landim-Vieira, Maicon; Parvatiyar, Michelle S et al. (2017) Hypertrophic Cardiomyopathy Cardiac Troponin C Mutations Differentially Affect Slow Skeletal and Cardiac Muscle Regulation. Front Physiol 8:221|
|Wang, Lili; Kryshtal, Dmytro O; Kim, Kyungsoo et al. (2017) Myofilament Calcium-Buffering Dependent Action Potential Triangulation in Human-Induced Pluripotent Stem Cell Model of Hypertrophic Cardiomyopathy. J Am Coll Cardiol 70:2600-2602|
|Veltri, Tiago; de Oliveira, Guilherme A P; Bienkiewicz, Ewa A et al. (2017) Amide hydrogens reveal a temperature-dependent structural transition that enhances site-II Ca2+-binding affinity in a C-domain mutant of cardiac troponin C. Sci Rep 7:691|
|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|
Showing the most recent 10 out of 12 publications