1
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Patsalis C, Kyriakou S, Georgiadou M, Ioannou L, Constantinou L, Soteriou V, Jossif A, Evangelidou P, Sismani C, Kypri E, Ioannides M, Koumbaris G. Investigating TNNC1 gene inheritance and clinical outcomes through a comprehensive familial study. Am J Med Genet A 2025; 197:e63838. [PMID: 39248034 DOI: 10.1002/ajmg.a.63838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 07/16/2024] [Accepted: 07/27/2024] [Indexed: 09/10/2024]
Abstract
Hypertrophic cardiomyopathy (HCM) and restrictive cardiomyopathy (RCM) have significant phenotypic overlap and a similar genetic background, both caused mainly by variants in sarcomeric genes. HCM is the most common cardiomyopathy, while RCM is a rare and often underdiagnosed heart condition, with a poor prognosis. This study focuses on a large family with four infants diagnosed with fatal RCM associated with biventricular hypertrophy. Affected infants were found to be homozygous for NM_003280.3(TNNC1):c.23C>T(p.Ala8Val) variant. Interestingly, this variant resulted in a low penetrance and mild form of hypertrophic cardiomyopathy (HCM) in relatives carrying a single copy of the variant. Overall, this study underscores the complex nature of genetic inheritance in cardiomyopathies and the wide range of clinical presentations they can exhibit. This emphasizes the vital role of genetic testing in providing essential insights crucial for diagnosis, prognosis, early intervention, and the development of potential treatment strategies.
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Affiliation(s)
| | | | | | | | | | | | - Antonis Jossif
- Paedi Center for Specialized Pediatrics, Nicosia, Cyprus
| | - Paola Evangelidou
- Department of Cytogenetics and Genomics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
| | - Carolina Sismani
- Department of Cytogenetics and Genomics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
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2
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Collibee SE, Romero A, Muci AR, Hwee DT, Chuang C, Hartman JJ, Motani AS, Ashcraft L, DeRosier A, Grillo M, Lu Q, Malik FI, Morgan BP. Cardiac Troponin Activator CK-963 Increases Cardiac Contractility in Rats. J Med Chem 2024; 67:7859-7869. [PMID: 38451215 PMCID: PMC11129196 DOI: 10.1021/acs.jmedchem.3c02412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 02/21/2024] [Accepted: 02/23/2024] [Indexed: 03/08/2024]
Abstract
Novel cardiac troponin activators were identified using a high throughput cardiac myofibril ATPase assay and confirmed using a series of biochemical and biophysical assays. HTS hit 2 increased rat cardiomyocyte fractional shortening without increasing intracellular calcium concentrations, and the biological target of 1 and 2 was determined to be the cardiac thin filament. Subsequent optimization to increase solubility and remove PDE-3 inhibition led to the discovery of CK-963 and enabled pharmacological evaluation of cardiac troponin activation without the competing effects of PDE-3 inhibition. Rat echocardiography studies using CK-963 demonstrated concentration-dependent increases in cardiac fractional shortening up to 95%. Isothermal calorimetry studies confirmed a direct interaction between CK-963 and a cardiac troponin chimera with a dissociation constant of 11.5 ± 3.2 μM. These results provide evidence that direct activation of cardiac troponin without the confounding effects of PDE-3 inhibition may provide benefit for patients with cardiovascular conditions where contractility is reduced.
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Affiliation(s)
- Scott E. Collibee
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
| | - Antonio Romero
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
| | - Alexander R. Muci
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
| | - Darren T. Hwee
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
| | - Chihyuan Chuang
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
| | - James J. Hartman
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
| | - Alykhan S. Motani
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
| | - Luke Ashcraft
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
| | - Andre DeRosier
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
| | - Mark Grillo
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
| | - Qing Lu
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
| | - Fady I. Malik
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
| | - Bradley P. Morgan
- Cytokinetics,
Inc., 350 Oyster Point Boulevard, South San Francisco, California 94080, United States
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3
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Hessel AL, Engels NM, Kuehn MN, Nissen D, Sadler RL, Ma W, Irving TC, Linke WA, Harris SP. Myosin-binding protein C regulates the sarcomere lattice and stabilizes the OFF states of myosin heads. Nat Commun 2024; 15:2628. [PMID: 38521794 PMCID: PMC10960836 DOI: 10.1038/s41467-024-46957-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 03/15/2024] [Indexed: 03/25/2024] Open
Abstract
Muscle contraction is produced via the interaction of myofilaments and is regulated so that muscle performance matches demand. Myosin-binding protein C (MyBP-C) is a long and flexible protein that is tightly bound to the thick filament at its C-terminal end (MyBP-CC8C10), but may be loosely bound at its middle- and N-terminal end (MyBP-CC1C7) to myosin heads and/or the thin filament. MyBP-C is thought to control muscle contraction via the regulation of myosin motors, as mutations lead to debilitating disease. We use a combination of mechanics and small-angle X-ray diffraction to study the immediate and selective removal of the MyBP-CC1C7 domains of fast MyBP-C in permeabilized skeletal muscle. We show that cleavage leads to alterations in crossbridge kinetics and passive structural signatures of myofilaments that are indicative of a shift of myosin heads towards the ON state, highlighting the importance of MyBP-CC1C7 to myofilament force production and regulation.
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Affiliation(s)
- Anthony L Hessel
- Institute of Physiology II, University of Muenster, Muenster, Germany.
- Accelerated Muscle Biotechnologies Consultants, Boston, MA, USA.
| | - Nichlas M Engels
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA
| | - Michel N Kuehn
- Institute of Physiology II, University of Muenster, Muenster, Germany
- Accelerated Muscle Biotechnologies Consultants, Boston, MA, USA
| | - Devin Nissen
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Rachel L Sadler
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | - Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Thomas C Irving
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Wolfgang A Linke
- Institute of Physiology II, University of Muenster, Muenster, Germany
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4
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Song T, McNamara JW, Baby A, Ma W, Landim-Vieira M, Natesan S, Pinto JR, Lorenz JN, Irving TC, Sadayappan S. Unlocking the Role of sMyBP-C: A Key Player in Skeletal Muscle Development and Growth. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.23.563591. [PMID: 38076858 PMCID: PMC10705270 DOI: 10.1101/2023.10.23.563591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
Skeletal muscle is the largest organ in the body, responsible for gross movement and metabolic regulation. Recently, variants in the MYBPC1 gene have been implicated in a variety of developmental muscle diseases, such as distal arthrogryposis. How MYBPC1 variants cause disease is not well understood. Here, through a collection of novel gene-edited mouse models, we define a critical role for slow myosin binding protein-C (sMyBP-C), encoded by MYBPC1, across muscle development, growth, and maintenance during prenatal, perinatal, postnatal and adult stages. Specifically, Mybpc1 knockout mice exhibited early postnatal lethality and impaired skeletal muscle formation and structure, skeletal deformity, and respiratory failure. Moreover, a conditional knockout of Mybpc1 in perinatal, postnatal and adult stages demonstrates impaired postnatal muscle growth and function secondary to disrupted actomyosin interaction and sarcomere structural integrity. These findings confirm the essential role of sMyBP-C in skeletal muscle and reveal specific functions in both prenatal embryonic musculoskeletal development and postnatal muscle growth and function.
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Affiliation(s)
- Taejeong Song
- Center for Cardiovascular Research, Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - James W. McNamara
- Center for Cardiovascular Research, Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Akhil Baby
- Center for Cardiovascular Research, Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH, USA
- Department of Genetic Engineering, School of Biotechnology, Madurai Kamaraj University, Madurai, India
| | - Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL, USA
| | - Sankar Natesan
- Department of Genetic Engineering, School of Biotechnology, Madurai Kamaraj University, Madurai, India
| | - Jose Renato Pinto
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL, USA
| | - John N. Lorenz
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Thomas C. Irving
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Sakthivel Sadayappan
- Center for Cardiovascular Research, Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH, USA
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5
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Rodriguez Garcia M, Schmeckpeper J, Landim-Vieira M, Coscarella IL, Fang X, Ma W, Spran PA, Yuan S, Qi L, Kahmini AR, Shoemaker MB, Atkinson JB, Kekenes-Huskey PM, Irving TC, Chase PB, Knollmann BC, Pinto JR. Disruption of Z-Disc Function Promotes Mechanical Dysfunction in Human Myocardium: Evidence for a Dual Myofilament Modulatory Role by Alpha-Actinin 2. Int J Mol Sci 2023; 24:14572. [PMID: 37834023 PMCID: PMC10572656 DOI: 10.3390/ijms241914572] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2023] [Revised: 09/19/2023] [Accepted: 09/20/2023] [Indexed: 10/15/2023] Open
Abstract
The ACTN2 gene encodes α-actinin 2, located in the Z-disc of the sarcomeres in striated muscle. In this study, we sought to investigate the effects of an ACTN2 missense variant of unknown significance (p.A868T) on cardiac muscle structure and function. Left ventricular free wall samples were obtained at the time of cardiac transplantation from a heart failure patient with the ACTN2 A868T heterozygous variant. This variant is in the EF 3-4 domain known to interact with titin and α-actinin. At the ultrastructural level, ACTN2 A868T cardiac samples presented small structural changes in cardiomyocytes when compared to healthy donor samples. However, contractile mechanics of permeabilized ACTN2 A868T variant cardiac tissue displayed higher myofilament Ca2+ sensitivity of isometric force, reduced sinusoidal stiffness, and faster rates of tension redevelopment at all Ca2+ levels. Small-angle X-ray diffraction indicated increased separation between thick and thin filaments, possibly contributing to changes in muscle kinetics. Molecular dynamics simulations indicated that while the mutation does not significantly impact the structure of α-actinin on its own, it likely alters the conformation associated with titin binding. Our results can be explained by two Z-disc mediated communication pathways: one pathway that involves α-actinin's interaction with actin, affecting thin filament regulation, and the other pathway that involves α-actinin's interaction with titin, affecting thick filament activation. This work establishes the role of α-actinin 2 in modulating cross-bridge kinetics and force development in the human myocardium as well as how it can be involved in the development of cardiac disease.
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Affiliation(s)
| | - Jeffrey Schmeckpeper
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | | | | | - Xuan Fang
- Department of Cell & Molecular Physiology, Loyola University, Chicago, IL 60660, USA
| | - Weikang Ma
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Payton A. Spran
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Shengyao Yuan
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Lin Qi
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Aida Rahimi Kahmini
- Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, FL 32306, USA;
| | - M. Benjamin Shoemaker
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - James B. Atkinson
- Department of Pathology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | | | - Thomas C. Irving
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Prescott Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Björn C. Knollmann
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jose Renato Pinto
- Biomedical Sciences, Florida State University, Tallahassee, FL 32306, USA
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6
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Hessel AL, Engels NM, Kuehn M, Nissen D, Sadler RL, Ma W, Irving TC, Linke WA, Harris SP. Myosin-binding protein C forms C-links and stabilizes OFF states of myosin. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.10.556972. [PMID: 37745361 PMCID: PMC10515747 DOI: 10.1101/2023.09.10.556972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
Contraction force in muscle is produced by the interaction of myosin motors in the thick filaments and actin in the thin filaments and is fine-tuned by other proteins such as myosin-binding protein C (MyBP-C). One form of control is through the regulation of myosin heads between an ON and OFF state in passive sarcomeres, which leads to their ability or inability to interact with the thin filaments during contraction, respectively. MyBP-C is a flexible and long protein that is tightly bound to the thick filament at its C-terminal end but may be loosely bound at its middle- and N-terminal end (MyBP-CC1C7). Under considerable debate is whether the MyBP-CC1C7 domains directly regulate myosin head ON/OFF states, and/or link thin filaments ("C-links"). Here, we used a combination of mechanics and small-angle X-ray diffraction to study the immediate and selective removal of the MyBP-CC1C7 domains of fast MyBP-C in permeabilized skeletal muscle. After cleavage, the thin filaments were significantly shorter, a result consistent with direct interactions of MyBP-C with thin filaments thus confirming C-links. Ca2+ sensitivity was reduced at shorter sarcomere lengths, and crossbridge kinetics were increased across sarcomere lengths at submaximal activation levels, demonstrating a role in crossbridge kinetics. Structural signatures of the thick filaments suggest that cleavage also shifted myosin heads towards the ON state - a marker that typically indicates increased Ca2+ sensitivity but that may account for increased crossbridge kinetics at submaximal Ca2+ and/or a change in the force transmission pathway. Taken together, we conclude that MyBP-CC1C7 domains play an important role in contractile performance which helps explain why mutations in these domains often lead to debilitating diseases.
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Affiliation(s)
- Anthony L Hessel
- Institute of Physiology II, University of Muenster; Muenster, Germany
| | - Nichlas M Engels
- Department of Cellular and Molecular Medicine, University of Arizona; Tucson, AZ, USA
| | - Michel Kuehn
- Institute of Physiology II, University of Muenster; Muenster, Germany
| | - Devin Nissen
- BioCAT, Department of Biology, Illinois Institute of Technology; Chicago, IL, USA
| | - Rachel L Sadler
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | - Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology; Chicago, IL, USA
| | - Thomas C Irving
- BioCAT, Department of Biology, Illinois Institute of Technology; Chicago, IL, USA
| | - Wolfgang A Linke
- Institute of Physiology II, University of Muenster; Muenster, Germany
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7
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Coscarella IL, Landim-Vieira M, Rastegarpouyani H, Chase PB, Irianto J, Pinto JR. Nucleus Mechanosensing in Cardiomyocytes. Int J Mol Sci 2023; 24:13341. [PMID: 37686151 PMCID: PMC10487505 DOI: 10.3390/ijms241713341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 08/20/2023] [Accepted: 08/22/2023] [Indexed: 09/10/2023] Open
Abstract
Cardiac muscle contraction is distinct from the contraction of other muscle types. The heart continuously undergoes contraction-relaxation cycles throughout an animal's lifespan. It must respond to constantly varying physical and energetic burdens over the short term on a beat-to-beat basis and relies on different mechanisms over the long term. Muscle contractility is based on actin and myosin interactions that are regulated by cytoplasmic calcium ions. Genetic variants of sarcomeric proteins can lead to the pathophysiological development of cardiac dysfunction. The sarcomere is physically connected to other cytoskeletal components. Actin filaments, microtubules and desmin proteins are responsible for these interactions. Therefore, mechanical as well as biochemical signals from sarcomeric contractions are transmitted to and sensed by other parts of the cardiomyocyte, particularly the nucleus which can respond to these stimuli. Proteins anchored to the nuclear envelope display a broad response which remodels the structure of the nucleus. In this review, we examine the central aspects of mechanotransduction in the cardiomyocyte where the transmission of mechanical signals to the nucleus can result in changes in gene expression and nucleus morphology. The correlation of nucleus sensing and dysfunction of sarcomeric proteins may assist the understanding of a wide range of functional responses in the progress of cardiomyopathic diseases.
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Affiliation(s)
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL 32306, USA
| | - Hosna Rastegarpouyani
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
- Institute for Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
| | - Prescott Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Jerome Irianto
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL 32306, USA
| | - Jose Renato Pinto
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL 32306, USA
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8
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Wiseman RW, Brown CM, Beck TW, Brault JJ, Reinoso TR, Shi Y, Chase PB. Creatine Kinase Equilibration and ΔG ATP over an Extended Range of Physiological Conditions: Implications for Cellular Energetics, Signaling, and Muscle Performance. Int J Mol Sci 2023; 24:13244. [PMID: 37686064 PMCID: PMC10487889 DOI: 10.3390/ijms241713244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 08/22/2023] [Accepted: 08/24/2023] [Indexed: 09/10/2023] Open
Abstract
In this report, we establish a straightforward method for estimating the equilibrium constant for the creatine kinase reaction (CK Keq″) over wide but physiologically and experimentally relevant ranges of pH, Mg2+ and temperature. Our empirical formula for CK Keq″ is based on experimental measurements. It can be used to estimate [ADP] when [ADP] is below the resolution of experimental measurements, a typical situation because [ADP] is on the order of micromolar concentrations in living cells and may be much lower in many in vitro experiments. Accurate prediction of [ADP] is essential for in vivo studies of cellular energetics and metabolism and for in vitro studies of ATP-dependent enzyme function under near-physiological conditions. With [ADP], we were able to obtain improved estimates of ΔGATP, necessitating the reinvestigation of previously reported ADP- and ΔGATP-dependent processes. Application to actomyosin force generation in muscle provides support for the hypothesis that, when [Pi] varies and pH is not altered, the maximum Ca2+-activated isometric force depends on ΔGATP in both living and permeabilized muscle preparations. Further analysis of the pH studies introduces a novel hypothesis around the role of submicromolar ADP in force generation.
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Affiliation(s)
- Robert Woodbury Wiseman
- Departments of Physiology and Radiology, Michigan State University, East Lansing, MI 48824, USA;
| | - Caleb Micah Brown
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Thomas Wesley Beck
- Department of Radiology, University of Washington, Seattle, WA 98195, USA
| | - Jeffrey John Brault
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA;
| | - Tyler Robert Reinoso
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Yun Shi
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Prescott Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
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9
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Tikunova SB, Thuma J, Davis JP. Mouse Models of Cardiomyopathies Caused by Mutations in Troponin C. Int J Mol Sci 2023; 24:12349. [PMID: 37569724 PMCID: PMC10419064 DOI: 10.3390/ijms241512349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Revised: 07/27/2023] [Accepted: 08/01/2023] [Indexed: 08/13/2023] Open
Abstract
Cardiac muscle contraction is regulated via Ca2+ exchange with the hetero-trimeric troponin complex located on the thin filament. Binding of Ca2+ to cardiac troponin C, a Ca2+ sensing subunit within the troponin complex, results in a series of conformational re-arrangements among the thin filament components, leading to an increase in the formation of actomyosin cross-bridges and muscle contraction. Ultimately, a decline in intracellular Ca2+ leads to the dissociation of Ca2+ from troponin C, inhibiting cross-bridge cycling and initiating muscle relaxation. Therefore, troponin C plays a crucial role in the regulation of cardiac muscle contraction and relaxation. Naturally occurring and engineered mutations in troponin C can lead to altered interactions among components of the thin filament and to aberrant Ca2+ binding and exchange with the thin filament. Mutations in troponin C have been associated with various forms of cardiac disease, including hypertrophic, restrictive, dilated, and left ventricular noncompaction cardiomyopathies. Despite progress made to date, more information from human studies, biophysical characterizations, and animal models is required for a clearer understanding of disease drivers that lead to cardiomyopathies. The unique use of engineered cardiac troponin C with the L48Q mutation that had been thoroughly characterized and genetically introduced into mouse myocardium clearly demonstrates that Ca2+ sensitization in and of itself should not necessarily be considered a disease driver. This opens the door for small molecule and protein engineering strategies to help boost impaired systolic function. On the other hand, the engineered troponin C mutants (I61Q and D73N), genetically introduced into mouse myocardium, demonstrate that Ca2+ desensitization under basal conditions may be a driving factor for dilated cardiomyopathy. In addition to enhancing our knowledge of molecular mechanisms that trigger hypertrophy, dilation, morbidity, and mortality, these cardiomyopathy mouse models could be used to test novel treatment strategies for cardiovascular diseases. In this review, we will discuss (1) the various ways mutations in cardiac troponin C might lead to disease; (2) relevant data on mutations in cardiac troponin C linked to human disease, and (3) all currently existing mouse models containing cardiac troponin C mutations (disease-associated and engineered).
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Affiliation(s)
- Svetlana B. Tikunova
- Department of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH 43210, USA (J.P.D.)
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10
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Zhu L, Landim-Vieira M, Garcia MR, Pinto JR, Chalovich JM. Negative Charges Introduced Near the IT Helix of Cardiac Troponin T Stabilize the Active State of Actin Filaments. Biochemistry 2023; 62:2137-2146. [PMID: 37379571 PMCID: PMC10576618 DOI: 10.1021/acs.biochem.3c00279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/30/2023]
Abstract
The disordered and basic C-terminal 14 residues of human troponin T (TnT) are essential for full inhibition of actomyosin ATPase activity at low Ca2+ levels and for limiting activation at saturating Ca2+. In previous studies, stepwise truncation of the C-terminal region of TnT increased activity in proportion to the number of positive charges eliminated. To define key basic residues more closely, we generated phosphomimetic-like mutants of TnT. Phosphomimetic mutants were chosen because of reports that phosphorylation of TnT, including sites within the C terminal region, depressed activity, contrary to our expectations. Four constructs were made where one or more Ser and Thr residues were replaced with Asp residues. The S275D and T277D mutants, near the IT helix and adjacent to basic residues, produced the greatest activation of ATPase rates in solution; the effects of the S275D mutant were recapitulated in muscle fiber preparations with enhanced myofilament Ca2+ sensitivity. Actin filaments containing S275D TnT were also shown to be incapable of populating the inactive state at low Ca2+ levels. Actin filaments containing both S275D/T284D were not statistically different from those containing only S275D in both solution and cardiac muscle preparation studies. Finally, actin filaments containing T284D TnT, closer to the C-terminus and not adjacent to a basic residue, had the smallest effect on activity. Thus, the effects of negative charge placement in the C-terminal region of TnT were greatest near the IT helix and adjacent to a basic residue.
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Affiliation(s)
- Li Zhu
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27858, United States
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32304, United States
| | - Michelle Rodriguez Garcia
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32304, United States
| | - Jose R Pinto
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32304, United States
| | - Joseph M Chalovich
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27858, United States
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11
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Landim-Vieira M, Ma W, Song T, Rastegarpouyani H, Gong H, Coscarella IL, Bogaards SJP, Conijn SP, Ottenheijm CAC, Hwang HS, Papadaki M, Knollmann BC, Sadayappan S, Irving TC, Galkin VE, Chase PB, Pinto JR. Cardiac troponin T N-domain variant destabilizes the actin interface resulting in disturbed myofilament function. Proc Natl Acad Sci U S A 2023; 120:e2221244120. [PMID: 37252999 PMCID: PMC10265946 DOI: 10.1073/pnas.2221244120] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 05/04/2023] [Indexed: 06/01/2023] Open
Abstract
Missense variant Ile79Asn in human cardiac troponin T (cTnT-I79N) has been associated with hypertrophic cardiomyopathy and sudden cardiac arrest in juveniles. cTnT-I79N is located in the cTnT N-terminal (TnT1) loop region and is known for its pathological and prognostic relevance. A recent structural study revealed that I79 is part of a hydrophobic interface between the TnT1 loop and actin, which stabilizes the relaxed (OFF) state of the cardiac thin filament. Given the importance of understanding the role of TnT1 loop region in Ca2+ regulation of the cardiac thin filament along with the underlying mechanisms of cTnT-I79N-linked pathogenesis, we investigated the effects of cTnT-I79N on cardiac myofilament function. Transgenic I79N (Tg-I79N) muscle bundles displayed increased myofilament Ca2+ sensitivity, smaller myofilament lattice spacing, and slower crossbridge kinetics. These findings can be attributed to destabilization of the cardiac thin filament's relaxed state resulting in an increased number of crossbridges during Ca2+ activation. Additionally, in the low Ca2+-relaxed state (pCa8), we showed that more myosin heads are in the disordered-relaxed state (DRX) that are more likely to interact with actin in cTnT-I79N muscle bundles. Dysregulation of the myosin super-relaxed state (SRX) and the SRX/DRX equilibrium in cTnT-I79N muscle bundles likely result in increased mobility of myosin heads at pCa8, enhanced actomyosin interactions as evidenced by increased active force at low Ca2+, and increased sinusoidal stiffness. These findings point to a mechanism whereby cTnT-I79N weakens the interaction of the TnT1 loop with the actin filament, which in turn destabilizes the relaxed state of the cardiac thin filament.
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Affiliation(s)
- Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL32306
| | - Weikang Ma
- Department of Biology, Illinois Institute of Technology, Chicago, IL60616
| | - Taejeong Song
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH45267
| | - Hosna Rastegarpouyani
- Department of Biological Science, Florida State University, Tallahassee, FL32306
- Institude of Molecular Biophysics, Florida State University, Tallahassee, FL32306
| | - Henry Gong
- Department of Biology, Illinois Institute of Technology, Chicago, IL60616
| | - Isabella Leite Coscarella
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL32306
| | - Sylvia J. P. Bogaards
- Department of Physiology, Amsterdam University Medical Center, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
| | - Stefan P. Conijn
- Department of Physiology, Amsterdam University Medical Center, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
| | - Coen A. C. Ottenheijm
- Department of Physiology, Amsterdam University Medical Center, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
| | - Hyun S. Hwang
- Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, FL32306
| | - Maria Papadaki
- Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Chicago, IL60153
| | - Bjorn C. Knollmann
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN37232
| | - Sakthivel Sadayappan
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH45267
| | - Thomas C. Irving
- Department of Biology, Illinois Institute of Technology, Chicago, IL60616
| | - Vitold E. Galkin
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA23507
| | - P. Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL32306
| | - Jose Renato Pinto
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL32306
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12
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Rayani K, Hantz ER, Haji-Ghassemi O, Li AY, Spuches AM, Van Petegem F, Solaro RJ, Lindert S, Tibbits GF. The effect of Mg 2+ on Ca 2+ binding to cardiac troponin C in hypertrophic cardiomyopathy associated TNNC1 variants. FEBS J 2022; 289:7446-7465. [PMID: 35838319 PMCID: PMC9836626 DOI: 10.1111/febs.16578] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 05/14/2022] [Accepted: 07/13/2022] [Indexed: 01/14/2023]
Abstract
Cardiac troponin C (cTnC) is the critical Ca2+ -sensing component of the troponin complex. Binding of Ca2+ to cTnC triggers a cascade of conformational changes within the myofilament that culminate in force production. Hypertrophic cardiomyopathy (HCM)-associated TNNC1 variants generally induce a greater degree and duration of Ca2+ binding, which may underly the hypertrophic phenotype. Regulation of contraction has long been thought to occur exclusively through Ca2+ binding to site II of cTnC. However, work by several groups including ours suggest that Mg2+ , which is several orders of magnitude more abundant in the cell than Ca2+ , may compete for binding to the same cTnC regulatory site. We previously used isothermal titration calorimetry (ITC) to demonstrate that physiological concentrations of Mg2+ may decrease site II Ca2+ -binding in both N-terminal and full-length cTnC. Here, we explore the binding of Ca2+ and Mg2+ to cTnC harbouring a series of TNNC1 variants thought to be causal in HCM. ITC and thermodynamic integration (TI) simulations show that A8V, L29Q and A31S elevate the affinity for both Ca2+ and Mg2+ . Further, L48Q, Q50R and C84Y that are adjacent to the EF hand binding motif of site II have a more significant effect on affinity and the thermodynamics of the binding interaction. To the best of our knowledge, this work is the first to explore the role of Mg2+ in modifying the Ca2+ affinity of cTnC mutations linked to HCM. Our results indicate a physiologically significant role for cellular Mg2+ both at baseline and when elevated on modifying the Ca2+ binding properties of cTnC and the subsequent conformational changes which precede cardiac contraction.
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Affiliation(s)
- Kaveh Rayani
- Molecular Cardiac Physiology Group, Simon Fraser University, Burnaby, Canada
| | - Eric R Hantz
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH, USA
| | - Omid Haji-Ghassemi
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, Canada
| | - Alison Y Li
- Molecular Cardiac Physiology Group, Simon Fraser University, Burnaby, Canada
| | - Anne M Spuches
- Department of Chemistry, 300 Science and Technology, East Carolina University, Greenville, NC, USA
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, Canada
| | - R John Solaro
- Department of Physiology and Biophysics and the Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, USA
| | - Steffen Lindert
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH, USA
| | - Glen F Tibbits
- Molecular Cardiac Physiology Group, Simon Fraser University, Burnaby, Canada
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, Canada
- BC Children's Hospital Research Institute, Vancouver, Canada
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13
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Ma W, Irving TC. Small Angle X-ray Diffraction as a Tool for Structural Characterization of Muscle Disease. Int J Mol Sci 2022; 23:3052. [PMID: 35328477 PMCID: PMC8949570 DOI: 10.3390/ijms23063052] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 03/01/2022] [Accepted: 03/02/2022] [Indexed: 02/01/2023] Open
Abstract
Small angle X-ray fiber diffraction is the method of choice for obtaining molecular level structural information from striated muscle fibers under hydrated physiological conditions. For many decades this technique had been used primarily for investigating basic biophysical questions regarding muscle contraction and regulation and its use confined to a relatively small group of expert practitioners. Over the last 20 years, however, X-ray diffraction has emerged as an important tool for investigating the structural consequences of cardiac and skeletal myopathies. In this review we show how simple and straightforward measurements, accessible to non-experts, can be used to extract biophysical parameters that can help explain and characterize the physiology and pathology of a given experimental system. We provide a comprehensive guide to the range of the kinds of measurements that can be made and illustrate how they have been used to provide insights into the structural basis of pathology in a comprehensive review of the literature. We also show how these kinds of measurements can inform current controversies and indicate some future directions.
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Affiliation(s)
- Weikang Ma
- The Biophysics Collaborative Access Team (BioCAT), Center for Synchrotron Radiation Research and Instrumentation (CSSRI), Illinois Institute of Technology, Chicago, IL 60616, USA;
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Thomas C. Irving
- The Biophysics Collaborative Access Team (BioCAT), Center for Synchrotron Radiation Research and Instrumentation (CSSRI), Illinois Institute of Technology, Chicago, IL 60616, USA;
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
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14
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Molecular basis of force-pCa relation in MYL2 cardiomyopathy mice: Role of the super-relaxed state of myosin. Proc Natl Acad Sci U S A 2022; 119:2110328119. [PMID: 35177471 PMCID: PMC8872785 DOI: 10.1073/pnas.2110328119] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2022] [Indexed: 01/22/2023] Open
Abstract
Many forms of cardiomyopathy manifest with changes in sarcomeric structure, function, and energetics. We used small-angle X-ray diffraction and myosin super-relaxed (SRX) state approaches to investigate the mechanisms underlying the clinical phenotypes associated with HCM-related D166V (aspartate-to-valine) and DCM-linked D94A (aspartate-to-alanine) mutations in the cardiac myosin RLC (MYL2 gene). Modulation of myosin function through dysregulation of the SRX state was closely coupled with structural rearrangements and the Ca2+ dependence of force development in HCM–D166V mice. The DCM–D94A model favored the SRX state without altering structure/force–pCa relationships. Understanding the regulation of SRX ↔ DRX equilibrium in the normal heart and how it is changed in heart disease may advance future therapeutics of patients suffering from the mutated MYL2 gene. In this study, we investigated the role of the super-relaxed (SRX) state of myosin in the structure–function relationship of sarcomeres in the hearts of mouse models of cardiomyopathy-bearing mutations in the human ventricular regulatory light chain (RLC, MYL2 gene). Skinned papillary muscles from hypertrophic (HCM–D166V) and dilated (DCM–D94A) cardiomyopathy models were subjected to small-angle X-ray diffraction simultaneously with isometric force measurements to obtain the interfilament lattice spacing and equatorial intensity ratios (I11/I10) together with the force-pCa relationship over a full range of [Ca2+] and at a sarcomere length of 2.1 μm. In parallel, we studied the effect of mutations on the ATP-dependent myosin energetic states. Compared with wild-type (WT) and DCM–D94A mice, HCM–D166V significantly increased the Ca2+ sensitivity of force and left shifted the I11/I10-pCa relationship, indicating an apparent movement of HCM–D166V cross-bridges closer to actin-containing thin filaments, thereby allowing for their premature Ca2+ activation. The HCM–D166V model also disrupted the SRX state and promoted an SRX-to-DRX (super-relaxed to disordered relaxed) transition that correlated with an HCM-linked phenotype of hypercontractility. While this dysregulation of SRX ↔ DRX equilibrium was consistent with repositioning of myosin motors closer to the thin filaments and with increased force-pCa dependence for HCM–D166V, the DCM–D94A model favored the energy-conserving SRX state, but the structure/function–pCa data were similar to WT. Our results suggest that the mutation-induced redistribution of myosin energetic states is one of the key mechanisms contributing to the development of complex clinical phenotypes associated with human HCM–D166V and DCM–D94A mutations.
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15
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Ma W, Gong H, Jani V, Lee KH, Landim-Vieira M, Papadaki M, Pinto JR, Aslam MI, Cammarato A, Irving T. Myofibril orientation as a metric for characterizing heart disease. Biophys J 2022; 121:565-574. [PMID: 35032456 PMCID: PMC8874025 DOI: 10.1016/j.bpj.2022.01.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 12/28/2021] [Accepted: 01/11/2022] [Indexed: 11/17/2022] Open
Abstract
Myocyte disarray is a hallmark of many cardiac disorders. However, the relationship between alterations in the orientation of individual myofibrils and myofilaments to disease progression has been largely underexplored. This oversight has predominantly been because of a paucity of methods for objective and quantitative analysis. Here, we introduce a novel, less-biased approach to quantify myofibrillar and myofilament orientation in cardiac muscle under near-physiological conditions and demonstrate its superiority as compared with conventional histological assessments. Using small-angle x-ray diffraction, we first investigated changes in myofibrillar orientation at increasing sarcomere lengths in permeabilized, relaxed, wild-type mouse myocardium from the left ventricle by assessing the angular spread of the 1,0 equatorial reflection (angle σ). At a sarcomere length of 1.9 μm, the angle σ was 0.23 ± 0.01 rad, decreased to 0.19 ± 0.01 rad at a sarcomere length of 2.1 μm, and further decreased to 0.15 ± 0.01 rad at a sarcomere length of 2.3 μm (p < 0.0001). Angle σ was significantly larger in R403Q, a MYH7 hypertrophic cardiomyopathy model, porcine myocardium (0.24 ± 0.01 rad) compared with wild-type myocardium (0.14 ± 0.005 rad; p < 0.0001), as well as in human heart failure tissue (0.19 ± 0.006 rad) when compared with nonfailing samples (0.17 ± 0.007 rad; p = 0.01). These data indicate that diseased myocardium suffers from greater myofibrillar disorientation compared with healthy controls. Finally, we showed that conventional, histology-based analysis of disarray can be subject to user bias and/or sampling error and lead to false positives. Our method for directly assessing myofibrillar orientation avoids the artifacts introduced by conventional histological approaches that assess myocyte orientation and only indirectly evaluate myofibrillar orientation, and provides a precise and objective metric for phenotypically characterizing myocardium. The ability to obtain excellent x-ray diffraction patterns from frozen human myocardium provides a new tool for investigating structural anomalies associated with cardiac diseases.
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Affiliation(s)
- Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, Illinois.
| | - Henry Gong
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, Illinois
| | - Vivek Jani
- Department of Biomedical Engineering, The Johns Hopkins School of Medicine, The Johns Hopkins University, Baltimore, Maryland; Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Kyoung Hwan Lee
- Division of Cell Biology and Imaging, Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University, Tallahassee, Florida
| | - Maria Papadaki
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois
| | - Jose R Pinto
- Department of Biomedical Sciences, Florida State University, Tallahassee, Florida
| | - M Imran Aslam
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Anthony Cammarato
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland; Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Thomas Irving
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, Illinois
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16
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Zhang Y, Pang X, Yang Y, Yan S. Effect of calcium ion on the morphology structure and compression elasticity of muscle fibers from honeybee abdomen. J Biomech 2021; 127:110652. [PMID: 34358879 DOI: 10.1016/j.jbiomech.2021.110652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 07/21/2021] [Accepted: 07/25/2021] [Indexed: 10/20/2022]
Abstract
Muscle contraction activated by calcium ion is the key to reveal that honeybee abdomen can achieve various physiological activities through flexible exercises and contributes to a powerful mechanical function of muscle fibers. To investigate the stimulating effect of calcium ion on muscle fibers of honeybee abdomen, atomic force microscopy was used to measure the morphology structure and mechanical properties of muscle fibers from honeybee abdomen in different calcium ion solutions. The periodic morphology structure of muscle fibers stimulated by different calcium ion concentration changed greatly, and the sarcomere length contracted from 6.53 μm to 4.29 μm as the calcium ion concentration increased from 0.11 mM to 10 mM. The mechanical measurement showed that the elastic modulus of Z-line reached the maximum, followed by M-line, overlap zone and I-band in sequence at the same calcium ion concentration, and was approximately 3.636, 2.450, 2.284, 2.748 times that of I-band from 0.11 mM to 10 mM calcium ion concentration. Combining the experimental analysis, the calcium ion threshold range was obtained based on the response surface method. This work adequately elucidates biological structure and biomechanics of muscle fibers from honeybee abdomen and could provide reference for other similar muscle system.
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Affiliation(s)
- Yuling Zhang
- Division of Intelligent and Biomechanical Systems, State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, PR China
| | - Xu Pang
- School of Engineering and Technology, China University of Geosciences (Beijing), 100083 Beijing, PR China
| | - Yunqiang Yang
- School of Engineering and Technology, China University of Geosciences (Beijing), 100083 Beijing, PR China
| | - Shaoze Yan
- Division of Intelligent and Biomechanical Systems, State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, PR China.
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17
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Shi Y, Bethea JP, Hetzel-Ebben HL, Landim-Vieira M, Mayper RJ, Williams RL, Kessler LE, Ruiz AM, Gargiulo K, Rose JSM, Platt G, Pinto JR, Washburn BK, Chase PB. Mandibular muscle troponin of the Florida carpenter ant Camponotus floridanus: extending our insights into invertebrate Ca 2+ regulation. J Muscle Res Cell Motil 2021; 42:399-417. [PMID: 34255253 DOI: 10.1007/s10974-021-09606-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 07/07/2021] [Indexed: 12/18/2022]
Abstract
Ants use their mandibles for a variety of functions and behaviors. We investigated mandibular muscle structure and function from major workers of the Florida carpenter ant Camponotus floridanus: force-pCa relation and velocity of unloaded shortening of single, permeabilized fibres, primary sequences of troponin subunits (TnC, TnI and TnT) from a mandibular muscle cDNA library, and muscle fibre ultrastructure. From the mechanical measurements, we found Ca2+-sensitivity of isometric force was markedly shifted rightward compared with vertebrate striated muscle. From the troponin sequence results, we identified features that could explain the rightward shift of Ca2+-activation: the N-helix of TnC is effectively absent and three of the four EF-hands of TnC (sites I, II and III) do not adhere to canonical sequence rules for divalent cation binding; two alternatively spliced isoforms of TnI were identified with the alternatively spliced exon occurring in the region of the IT-arm α-helical coiled-coil, and the N-terminal extension of TnI may be involved in modulation of regulation, as in mammalian cardiac muscle; and TnT has a Glu-rich C-terminus. In addition, a structural homology model was built of C. floridanus troponin on the thin filament. From analysis of electron micrographs, we found thick filaments are almost as long as the 6.8 μm sarcomeres, have diameter of ~ 16 nm, and typical center-to-center spacing of ~ 46 nm. These results have implications for the mechanisms by which mandibular muscle fibres perform such a variety of functions, and how the structure of the troponin complex aids in these tasks.
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Affiliation(s)
- Yun Shi
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Julia P Bethea
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Hannah L Hetzel-Ebben
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL, 32306, USA
| | - Ross J Mayper
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Regan L Williams
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Lauren E Kessler
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Amanda M Ruiz
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Kathryn Gargiulo
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Jennifer S M Rose
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Grayson Platt
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Jose R Pinto
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL, 32306, USA
| | - Brian K Washburn
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - P Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA. .,Department of Biological Science, Florida State University, Biology Unit One, Box 3064370, Tallahassee, FL, 32306-4370, USA.
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18
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Marques MA, Landim-Vieira M, Moraes AH, Sun B, Johnston JR, Dieseldorff Jones KM, Cino EA, Parvatiyar MS, Valera IC, Silva JL, Galkin VE, Chase PB, Kekenes-Huskey PM, de Oliveira GAP, Pinto JR. Anomalous structural dynamics of minimally frustrated residues in cardiac troponin C triggers hypertrophic cardiomyopathy. Chem Sci 2021; 12:7308-7323. [PMID: 34163821 PMCID: PMC8171346 DOI: 10.1039/d1sc01886h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 04/11/2021] [Indexed: 12/13/2022] Open
Abstract
Cardiac TnC (cTnC) is highly conserved among mammals, and genetic variants can result in disease by perturbing Ca2+-regulation of myocardial contraction. Here, we report the molecular basis of a human mutation in cTnC's αD-helix (TNNC1-p.C84Y) that impacts conformational dynamics of the D/E central-linker and sampling of discrete states in the N-domain, favoring the "primed" state associated with Ca2+ binding. We demonstrate cTnC's αD-helix normally functions as a central hub that controls minimally frustrated interactions, maintaining evolutionarily conserved rigidity of the N-domain. αD-helix perturbation remotely alters conformational dynamics of the N-domain, compromising its structural rigidity. Transgenic mice carrying this cTnC mutation exhibit altered dynamics of sarcomere function and hypertrophic cardiomyopathy. Together, our data suggest that disruption of evolutionary conserved molecular frustration networks by a myofilament protein mutation may ultimately compromise contractile performance and trigger hypertrophic cardiomyopathy.
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Affiliation(s)
- Mayra A Marques
- Institute of Medical Biochemistry Leopoldo de Meis, National Institute of Structural Biology and Bioimaging, National Center of Nuclear Magnetic Resonance Jiri Jonas, Federal University of Rio de Janeiro 373 Carlos Chagas Filho Av, Room: E-10 Rio de Janeiro RJ 21941-902 Brazil +55-21-3938-6756
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University, College of Medicine 1115 West Call Street, Room: 1370 (lab) - 1350-H (office) Tallahassee FL 32306 USA +1-850-645-0016
| | - Adolfo H Moraes
- Department of Chemistry, Federal University of Minas Gerais Belo Horizonte MG Brazil
| | - Bin Sun
- Department of Cell and Molecular Physiology, Loyola University Chicago Maywood IL USA
| | - Jamie R Johnston
- Department of Biomedical Sciences, Florida State University, College of Medicine 1115 West Call Street, Room: 1370 (lab) - 1350-H (office) Tallahassee FL 32306 USA +1-850-645-0016
| | - Karissa M Dieseldorff Jones
- Department of Biomedical Sciences, Florida State University, College of Medicine 1115 West Call Street, Room: 1370 (lab) - 1350-H (office) Tallahassee FL 32306 USA +1-850-645-0016
| | - Elio A Cino
- Department of Biochemistry and Immunology, Federal University of Minas Gerais Belo Horizonte MG Brazil
| | - Michelle S Parvatiyar
- Department of Nutrition, Food and Exercise Sciences, Florida State University Tallahassee FL USA
| | - Isela C Valera
- Department of Nutrition, Food and Exercise Sciences, Florida State University Tallahassee FL USA
| | - Jerson L Silva
- Institute of Medical Biochemistry Leopoldo de Meis, National Institute of Structural Biology and Bioimaging, National Center of Nuclear Magnetic Resonance Jiri Jonas, Federal University of Rio de Janeiro 373 Carlos Chagas Filho Av, Room: E-10 Rio de Janeiro RJ 21941-902 Brazil +55-21-3938-6756
| | - Vitold E Galkin
- Department of Physiological Sciences, Eastern Virginia Medical School Norfolk VA USA
| | - P Bryant Chase
- Department of Biological Science, Florida State University Tallahassee FL USA
| | | | - Guilherme A P de Oliveira
- Institute of Medical Biochemistry Leopoldo de Meis, National Institute of Structural Biology and Bioimaging, National Center of Nuclear Magnetic Resonance Jiri Jonas, Federal University of Rio de Janeiro 373 Carlos Chagas Filho Av, Room: E-10 Rio de Janeiro RJ 21941-902 Brazil +55-21-3938-6756
| | - Jose Renato Pinto
- Department of Biomedical Sciences, Florida State University, College of Medicine 1115 West Call Street, Room: 1370 (lab) - 1350-H (office) Tallahassee FL 32306 USA +1-850-645-0016
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19
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Zot HG, Chase PB, Hasbun JE, Pinto JR. Mechanical contribution to muscle thin filament activation. J Biol Chem 2020; 295:15913-15922. [PMID: 32900850 DOI: 10.1074/jbc.ra120.014438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 09/04/2020] [Indexed: 11/06/2022] Open
Abstract
Vertebrate striated muscle thin filaments are thought to be thermodynamically activated in response to an increase in Ca2+ concentration. We tested this hypothesis by measuring time intervals for gliding runs and pauses of individual skeletal muscle thin filaments in cycling myosin motility assays. A classic thermodynamic mechanism predicts that if chemical potential is constant, transitions between runs and pauses of gliding thin filaments will occur at constant rate as given by a Poisson distribution. In this scenario, rate is given by the odds of a pause, and hence, run times between pauses fit an exponential distribution that slopes negatively for all observable run times. However, we determined that relative density of observed run times fits an exponential only at low Ca2+ levels that activate filament gliding. Further titration with Ca2+, or adding excess regulatory proteins tropomyosin and troponin, shifted the relative density of short run times to fit the positive slope of a gamma distribution, which derives from waiting times between Poisson events. Events that arise during a run and prevent the chance of ending a run for a random interval of time account for the observed run time distributions, suggesting that the events originate with cycling myosin. We propose that regulatory proteins of the thin filament require the mechanical force of cycling myosin to achieve the transition state for activation. During activation, combinations of cycling myosin that contribute insufficient activation energy delay deactivation.
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Affiliation(s)
- Henry G Zot
- Department of Biology, University of West Georgia, Carrollton, Georgia, USA; Department of Biomedical Sciences, Florida State University, Tallahassee, Florida, USA.
| | - P Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, Florida, USA
| | - Javier E Hasbun
- Department of Physics, University of West Georgia, Carrollton, Georgia, USA
| | - Jose R Pinto
- Department of Biomedical Sciences, Florida State University, Tallahassee, Florida, USA
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20
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A comprehensive guide to genetic variants and post-translational modifications of cardiac troponin C. J Muscle Res Cell Motil 2020; 42:323-342. [PMID: 33179204 DOI: 10.1007/s10974-020-09592-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 10/24/2020] [Indexed: 02/07/2023]
Abstract
Familial cardiomyopathy is an inherited disease that affects the structure and function of heart muscle and has an extreme range of phenotypes. Among the millions of affected individuals, patients with hypertrophic (HCM), dilated (DCM), or left ventricular non-compaction (LVNC) cardiomyopathy can experience morphologic changes of the heart which lead to sudden death in the most detrimental cases. TNNC1, the gene that codes for cardiac troponin C (cTnC), is a sarcomere gene associated with cardiomyopathies in which probands exhibit young age of presentation and high death, transplant or ventricular fibrillation events relative to TNNT2 and TNNI3 probands. Using GnomAD, ClinVar, UniProt and PhosphoSitePlus databases and published literature, an extensive list to date of identified genetic variants in TNNC1 and post-translational modifications (PTMs) in cTnC was compiled. Additionally, a recent cryo-EM structure of the cardiac thin filament regulatory unit was used to localize each functionally studied amino acid variant and each PTM (acetylation, glycation, s-nitrosylation, phosphorylation) in the structure of cTnC. TNNC1 has a large number of variants (> 100) relative to other genes of the same transcript size. Surprisingly, the mapped variant amino acids and PTMs are distributed throughout the cTnC structure. While many cardiomyopathy-associated variants are localized in α-helical regions of cTnC, this was not statistically significant χ2 (p = 0.72). Exploring the variants in TNNC1 and PTMs of cTnC in the contexts of cardiomyopathy association, physiological modulation and potential non-canonical roles provides insights into the normal function of cTnC along with the many facets of TNNC1 as a cardiomyopathic gene.
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21
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Johnson D, Landim-Vieira M, Solı S C, Zhu L, Robinson JM, Pinto JR, Chalovich JM. Eliminating the First Inactive State and Stabilizing the Active State of the Cardiac Regulatory System Alters Behavior in Solution and in Ordered Systems. Biochemistry 2020; 59:3487-3497. [PMID: 32840354 DOI: 10.1021/acs.biochem.0c00430] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Calcium binding to troponin C (TnC) is insufficient for full activation of myosin ATPase activity by actin-tropomyosin-troponin. Previous attempts to investigate full activation utilized ATP-free myosin or chemically modified myosin to stabilize the active state of regulated actin. We utilized the Δ14-TnT and the A8V-TnC mutants to stabilize the activated state at saturating Ca2+ and to eliminate one of the inactive states at low Ca2+. The observed effects differed in solution studies and in the more ordered in vitro motility assay and in skinned cardiac muscle preparations. At saturating Ca2+, full activation with Δ14-TnT·A8V-TnC decreased the apparent KM for actin-activated ATPase activity compared to bare actin filaments. Rates of in vitro motility increased at both high and low Ca2+ with Δ14-TnT; the maximum shortening speed at high Ca2+ increased 1.8-fold. Cardiac muscle preparations exhibited increased Ca2+ sensitivity and large increases in resting force with either Δ14-TnT or Δ14-TnT·A8V-TnC. We also observed a significant increase in the maximal rate of tension redevelopment. The results of full activation with Ca2+ and Δ14-TnT·A8V-TnC confirmed and extended several earlier observations using other means of reaching full activation. Furthermore, at low Ca2+, elimination of the first inactive state led to partial activation. This work also confirms, in three distinct experimental systems, that troponin is able to stabilize the active state of actin-tropomyosin-troponin without the need for high-affinity myosin binding. The results are relevant to the reason for two inactive states and for the role of force producing myosin in regulation.
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Affiliation(s)
- Dylan Johnson
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina, United States
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida, United States
| | - Christopher Solı S
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota 57007, United States
| | - Li Zhu
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina, United States
| | - John M Robinson
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota 57007, United States
| | - Jose R Pinto
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida, United States
| | - Joseph M Chalovich
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina, United States
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22
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Dieseldorff Jones KM, Vied C, Valera IC, Chase PB, Parvatiyar MS, Pinto JR. Sexual dimorphism in cardiac transcriptome associated with a troponin C murine model of hypertrophic cardiomyopathy. Physiol Rep 2020; 8:e14396. [PMID: 32189431 PMCID: PMC7081104 DOI: 10.14814/phy2.14396] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 02/13/2020] [Accepted: 02/16/2020] [Indexed: 12/12/2022] Open
Abstract
Heart disease remains the number one killer of women in the US. Nonetheless, studies in women and female animal models continue to be underrepresented in cardiac research. Hypertrophic cardiomyopathy (HCM), the most commonly inherited cardiac disorder, has been tied to sarcomeric protein variants in both sexes. Among the susceptible genes, TNNC1-encoding cardiac troponin C (cTnC)-causes a substantial HCM phenotype in mice. Mice bearing an HCM-associated cTnC-A8V point mutation exhibited a significant decrease in stroke volume and left ventricular diameter and volume. Importantly, isovolumetric contraction time was significantly higher for female HCM mice. We utilized a transcriptomic approach to investigate the basis underlying the sexual dimorphism observed in the cardiac physiology of adult male and female HCM mice. RNA sequencing revealed several altered canonical pathways within the HCM mice versus WT groups including an increase in eukaryotic initiation factor 2 signaling, integrin-linked kinase signaling, actin nucleation by actin-related protein-Wiskott-Aldrich syndrome family protein complex, regulation of actin-based motility by Rho kinase, vitamin D receptor/retinoid X receptor activation, and glutathione redox reaction pathways. In contrast, valine degradation, tricarboxylic acid cycle II, methionine degradation, and inositol phosphate compound pathways were notably down-regulated in HCM mice. These down-regulated pathways may be reduced in response to altered energetics in the hypertrophied hearts and may represent conservation of energy as the heart is compensating to meet increased contractile demands. HCM male versus female mice followed similar trends of the canonical pathways altered between HCM and WT. In addition, seven of the differentially expressed genes in both WT and HCM male versus female comparisons swapped directions in fold-change between the sexes. These findings suggest a sexually-dimorphic HCM phenotype due to a sarcomeric mutation and pinpoint several key targetable pathways and genes that may provide the means to alleviate the more severe decline in female cardiac function.
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Affiliation(s)
| | - Cynthia Vied
- Translational Science LaboratoryCollege of MedicineFlorida State UniversityTallahasseeFLUSA
| | - Isela C. Valera
- Department of Nutrition, Food and Exercise SciencesFlorida State UniversityTallahasseeFLUSA
| | - P. Bryant Chase
- Department of Biological ScienceFlorida State UniversityTallahasseeFLUSA
| | - Michelle S. Parvatiyar
- Department of Nutrition, Food and Exercise SciencesFlorida State UniversityTallahasseeFLUSA
| | - Jose R. Pinto
- Department of Biomedical SciencesCollege of MedicineFlorida State UniversityTallahasseeFLUSA
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23
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Landim-Vieira M, Johnston JR, Ji W, Mis EK, Tijerino J, Spencer-Manzon M, Jeffries L, Hall EK, Panisello-Manterola D, Khokha MK, Deniz E, Chase PB, Lakhani SA, Pinto JR. Familial Dilated Cardiomyopathy Associated With a Novel Combination of Compound Heterozygous TNNC1 Variants. Front Physiol 2020; 10:1612. [PMID: 32038292 PMCID: PMC6990120 DOI: 10.3389/fphys.2019.01612] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 12/23/2019] [Indexed: 12/11/2022] Open
Abstract
Familial dilated cardiomyopathy (DCM), clinically characterized by enlargement and dysfunction of one or both ventricles of the heart, can be caused by variants in sarcomeric genes including TNNC1 (encoding cardiac troponin C, cTnC). Here, we report the case of two siblings with severe, early onset DCM who were found to have compound heterozygous variants in TNNC1: p.Asp145Glu (D145E) and p.Asp132Asn (D132N), which were inherited from the parents. We began our investigation with CRISPR/Cas9 knockout of TNNC1 in Xenopus tropicalis, which resulted in a cardiac phenotype in tadpoles consistent with DCM. Despite multiple maneuvers, we were unable to rescue the tadpole hearts with either human cTnC wild-type or patient variants to investigate the cardiomyopathy phenotype in vivo. We therefore utilized porcine permeabilized cardiac muscle preparations (CMPs) reconstituted with either wild-type or patient variant forms of cTnC to examine effects of the patient variants on contractile function. Incorporation of 50% WT/50% D145E into CMPs increased Ca2+ sensitivity of isometric force, consistent with prior studies. In contrast, incorporation of 50% WT/50% D132N, which had not been previously reported, decreased Ca2+ sensitivity of isometric force. CMPs reconstituted 50–50% with both variants mirrored WT in regard to myofilament Ca2+ responsiveness. Sinusoidal stiffness (SS) (0.2% peak-to-peak) and the kinetics of tension redevelopment (kTR) at saturating Ca2+ were similar to WT for all preparations. Modeling of Ca2+-dependence of kTR support the observation from Ca2+ responsiveness of steady-state isometric force, that the effects on each mutant (50% WT/50% mutant) were greater than the combination of the two mutants (50% D132N/50% D145E). Further studies are needed to ascertain the mechanism(s) of these variants.
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Affiliation(s)
- Maicon Landim-Vieira
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, United States
| | - Jamie R Johnston
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, United States
| | - Weizhen Ji
- Pediatric Genomics Discovery Program, Department of Pediatrics, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Emily K Mis
- Pediatric Genomics Discovery Program, Department of Pediatrics, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Joshua Tijerino
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, United States
| | - Michele Spencer-Manzon
- Pediatric Genomics Discovery Program, Department of Pediatrics, Yale School of Medicine, Yale University, New Haven, CT, United States.,Department of Genetics, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Lauren Jeffries
- Pediatric Genomics Discovery Program, Department of Pediatrics, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - E Kevin Hall
- Department of Pediatrics, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - David Panisello-Manterola
- Pediatric Genomics Discovery Program, Department of Pediatrics, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Mustafa K Khokha
- Pediatric Genomics Discovery Program, Department of Pediatrics, Yale School of Medicine, Yale University, New Haven, CT, United States.,Department of Genetics, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Engin Deniz
- Pediatric Genomics Discovery Program, Department of Pediatrics, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - P Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL, United States
| | - Saquib A Lakhani
- Pediatric Genomics Discovery Program, Department of Pediatrics, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Jose Renato Pinto
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, United States
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24
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Johnston JR, Landim-Vieira M, Marques MA, de Oliveira GAP, Gonzalez-Martinez D, Moraes AH, He H, Iqbal A, Wilnai Y, Birk E, Zucker N, Silva JL, Chase PB, Pinto JR. The intrinsically disordered C terminus of troponin T binds to troponin C to modulate myocardial force generation. J Biol Chem 2019; 294:20054-20069. [PMID: 31748410 PMCID: PMC6937556 DOI: 10.1074/jbc.ra119.011177] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 11/13/2019] [Indexed: 12/15/2022] Open
Abstract
Aberrant regulation of myocardial force production represents an early biomechanical defect associated with sarcomeric cardiomyopathies, but the molecular mechanisms remain poorly defined. Here, we evaluated the pathogenicity of a previously unreported sarcomeric gene variant identified in a pediatric patient with sporadic dilated cardiomyopathy, and we determined a molecular mechanism. Trio whole-exome sequencing revealed a de novo missense variant in TNNC1 that encodes a p.I4M substitution in the N-terminal helix of cardiac troponin C (cTnC). Reconstitution of this human cTnC variant into permeabilized porcine cardiac muscle preparations significantly decreases the magnitude and rate of isometric force generation at physiological Ca2+-activation levels. Computational modeling suggests that this inhibitory effect can be explained by a decrease in the rates of cross-bridge attachment and detachment. For the first time, we show that cardiac troponin T (cTnT), in part through its intrinsically disordered C terminus, directly binds to WT cTnC, and we find that this cardiomyopathic variant displays tighter binding to cTnT. Steady-state fluorescence and NMR spectroscopy studies suggest that this variant propagates perturbations in cTnC structural dynamics to distal regions of the molecule. We propose that the intrinsically disordered C terminus of cTnT directly interacts with the regulatory N-domain of cTnC to allosterically modulate Ca2+ activation of force, perhaps by controlling the troponin I switching mechanism of striated muscle contraction. Alterations in cTnC-cTnT binding may compromise contractile performance and trigger pathological remodeling of the myocardium.
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Affiliation(s)
- Jamie R Johnston
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306
| | - Mayra A Marques
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica, Instituto Nacional de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - Guilherme A P de Oliveira
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica, Instituto Nacional de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - David Gonzalez-Martinez
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306
| | - Adolfo H Moraes
- Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil
| | - Huan He
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306
| | - Anwar Iqbal
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica, Instituto Nacional de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - Yael Wilnai
- Department of Pediatrics, Dana-Dwek ChildrenγÇÖs Hospital, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel 6423906
| | - Einat Birk
- Department of Cardiology, Schneider ChildrenγÇÖs Medical Center, Tel Aviv University, Petah Tikva, Israel 4920235
| | - Nili Zucker
- Department of Cardiology, Schneider ChildrenγÇÖs Medical Center, Tel Aviv University, Petah Tikva, Israel 4920235
| | - Jerson L Silva
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica, Instituto Nacional de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - P Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306
| | - Jose Renato Pinto
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306
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25
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Johnson D, Zhu L, Landim-Vieira M, Pinto JR, Chalovich JM. Basic residues within the cardiac troponin T C terminus are required for full inhibition of muscle contraction and limit activation by calcium. J Biol Chem 2019; 294:19535-19545. [PMID: 31712308 DOI: 10.1074/jbc.ra119.010966] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 11/08/2019] [Indexed: 11/06/2022] Open
Abstract
Striated muscle is activated by myosin- and actin-linked processes, with the latter being regulated through changes in the position of tropomyosin relative to the actin surface. The C-terminal region of cardiac troponin T (TnT), a tropomyosin-associated protein, is required for full TnT inactivation at low Ca2+ and for limiting its activation at saturating Ca2+ Here, we investigated whether basic residues in this TnT region are involved in these activities, whether the TnT C terminus undergoes Ca2+-dependent conformational changes, and whether these residues affect cardiac muscle contraction. We generated a human cardiac TnT variant in which we replaced seven C-terminal Lys and Arg residues with Ala and added a Cys residue at either position 289 or 275 to affix a fluorescent probe. At pCa 3.7, actin filaments containing high-alanine TnT had an elevated ATPase rate like that obtained when the last TnT 14 residues were deleted. Acrylodan-tropomyosin fluorescence changes and S1-actin binding kinetics revealed that at pCa 8, the high-alanine TnT-containing filaments did not enter the first inactive state. FRET analyses indicated that the C-terminal TnT region approached Cys-190 of tropomyosin as actin filaments transitioned to the inactive B state; that transition was abolished with high-alanine TnT. High-alanine TnT-containing cardiac muscle preparations had increased Ca2+ sensitivity of both steady-state isometric force and sinusoidal stiffness as well as increased maximum steady-state isometric force and sinusoidal stiffness. We conclude that C-terminal basic residues in cardiac TnT are critical for the regulation of cardiac muscle contraction.
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Affiliation(s)
- Dylan Johnson
- Department of Biochemistry and Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27834
| | - Li Zhu
- Department of Biochemistry and Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27834
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306
| | - Jose Renato Pinto
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306
| | - Joseph M Chalovich
- Department of Biochemistry and Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27834
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26
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Landim-Vieira M, Schipper JM, Pinto JR, Chase PB. Cardiomyocyte nuclearity and ploidy: when is double trouble? J Muscle Res Cell Motil 2019; 41:329-340. [PMID: 31317457 DOI: 10.1007/s10974-019-09545-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 07/12/2019] [Indexed: 01/23/2023]
Abstract
Considerable effort has gone into investigating mechanisms that underlie the developmental transition in which mammalian cardiomyocytes (CMs) switch from being able to proliferate during development, to essentially having lost that ability at maturity. This problem is interesting not only for scientific curiosity, but also for its clinical relevance because controlling the ability of mature CMs to replicate would provide a much-needed approach for restoring cardiac function in damaged hearts. In this review, we focus on the propensity of mature mammalian CMs to be multinucleated and polyploid, and the extent to which this may be necessary for normal physiology yet possibly disadvantageous in some circumstances. In this context, we explore whether the concept of the myonuclear domain (MND) in multinucleated skeletal muscle fibers might apply to cardiomyocytes, and whether cardio-MND size might be related to the transition of CMs to become multinuclear. Nuclei in CMs are almost certainly integrators of not only biochemical, but also-because of their central location within the myofibrils-mechanical information, and this multimodal, integrative function in adult CMs-involving molecules that have been extensively studied along with newly identified possibilities-could influence both gene expression as well as replication of the genome and the nuclei themselves.
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Affiliation(s)
- Maicon Landim-Vieira
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA
| | - Joslyn M Schipper
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA.,Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - J Renato Pinto
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA
| | - P Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL, USA. .,Department of Biological Science, Florida State University, Biology Unit One Room 206, 81 Chieftain Way, Tallahassee, FL, 32306-4370, USA.
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