1
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Ragusa R, Caselli C. Focus on cardiac troponin complex: From gene expression to cardiomyopathy. Genes Dis 2024; 11:101263. [PMID: 39211905 PMCID: PMC11357864 DOI: 10.1016/j.gendis.2024.101263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 01/26/2024] [Accepted: 02/21/2024] [Indexed: 09/04/2024] Open
Abstract
The cardiac troponin complex (cTn) is a regulatory component of sarcomere. cTn consists of three subunits: cardiac troponin C (cTnC), which confers Ca2+ sensitivity to muscle; cTnI, which inhibits the interaction of cross-bridge of myosin with thin filament during diastole; and cTnT, which has multiple roles in sarcomere, such as promoting the link between the cTnI-cTnC complex and tropomyosin within the thin filament and influencing Ca2+ sensitivity of cTn and force development during contraction. Conditions that interfere with interactions within cTn and/or other thin filament proteins can be key factors in the regulation of cardiac contraction. These conditions include alterations in myofilament Ca2+ sensitivity, direct changes in cTn function, and triggering downstream events that lead to adverse cardiac remodeling and impairment of heart function. This review describes gene expression and post-translational modifications of cTn as well as the conditions that can adversely affect the delicate balance among the components of cTn, thereby promoting contractile dysfunction.
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Affiliation(s)
- Rosetta Ragusa
- Institute of Clinical Physiology, CNR, via Moruzzi 1, Pisa 56124, Italy
| | - Chiara Caselli
- Institute of Clinical Physiology, CNR, via Moruzzi 1, Pisa 56124, Italy
- Fondazione Toscana Gabriele Monasterio, via Moruzzi 1, Pisa 56124, Italy
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2
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Landim-Vieira M, Pinto JR. Can evolution-based studies inform modern medicine? Science 2024; 385:1420-1421. [PMID: 39325918 DOI: 10.1126/science.ads2585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/28/2024]
Abstract
Comparative genomic analyses provide mechanistic clues to cardiac muscle regulation.
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Affiliation(s)
- Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL, USA
| | - Jose Renato Pinto
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL, USA
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3
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Chatterjee S, Leach-Mehrwald M, Huang CK, Xiao K, Fuchs M, Otto M, Lu D, Dang V, Winkler T, Dunbar CE, Thum T, Bär C. Telomerase is essential for cardiac differentiation and sustained metabolism of human cardiomyocytes. Cell Mol Life Sci 2024; 81:196. [PMID: 38658440 PMCID: PMC11043037 DOI: 10.1007/s00018-024-05239-7] [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: 10/24/2023] [Revised: 03/29/2024] [Accepted: 04/12/2024] [Indexed: 04/26/2024]
Abstract
Telomeres as the protective ends of linear chromosomes, are synthesized by the enzyme telomerase (TERT). Critically short telomeres essentially contribute to aging-related diseases and are associated with a broad spectrum of disorders known as telomeropathies. In cardiomyocytes, telomere length is strongly correlated with cardiomyopathies but it remains ambiguous whether short telomeres are the cause or the result of the disease. In this study, we employed an inducible CRISPRi human induced pluripotent stem cell (hiPSC) line to silence TERT expression enabling the generation of hiPSCs and hiPSC-derived cardiomyocytes with long and short telomeres. Reduced telomerase activity and shorter telomere lengths of hiPSCs induced global transcriptomic changes associated with cardiac developmental pathways. Consequently, the differentiation potential towards cardiomyocytes was strongly impaired and single cell RNA sequencing revealed a shift towards a more smooth muscle cell like identity in the cells with the shortest telomeres. Poor cardiomyocyte function and increased sensitivity to stress directly correlated with the extent of telomere shortening. Collectively our data demonstrates a TERT dependent cardiomyogenic differentiation defect, highlighting the CRISPRi TERT hiPSCs model as a powerful platform to study the mechanisms and consequences of short telomeres in the heart and also in the context of telomeropathies.
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Affiliation(s)
- Shambhabi Chatterjee
- Institute of Molecular and Translational Therapeutic Strategies (IMTTS), Hannover Medical School, Hannover, Germany
- Center of Translational Regenerative Medicine, Hannover Medical School, Hannover, Germany
- Fraunhofer Institute for Toxicology and Experimental Medicine, Hannover, Germany
| | - Megan Leach-Mehrwald
- Institute of Molecular and Translational Therapeutic Strategies (IMTTS), Hannover Medical School, Hannover, Germany
| | - Cheng-Kai Huang
- Institute of Molecular and Translational Therapeutic Strategies (IMTTS), Hannover Medical School, Hannover, Germany
| | - Ke Xiao
- Institute of Molecular and Translational Therapeutic Strategies (IMTTS), Hannover Medical School, Hannover, Germany
- Fraunhofer Institute for Toxicology and Experimental Medicine, Hannover, Germany
| | - Maximilian Fuchs
- Fraunhofer Institute for Toxicology and Experimental Medicine, Hannover, Germany
| | - Mandy Otto
- Fraunhofer Institute for Toxicology and Experimental Medicine, Hannover, Germany
| | - Dongchao Lu
- Institute of Molecular and Translational Therapeutic Strategies (IMTTS), Hannover Medical School, Hannover, Germany
- Center of Translational Regenerative Medicine, Hannover Medical School, Hannover, Germany
| | - Vinh Dang
- Translational Stem Cell Biology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Thomas Winkler
- Translational Stem Cell Biology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Cynthia E Dunbar
- Translational Stem Cell Biology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Thomas Thum
- Institute of Molecular and Translational Therapeutic Strategies (IMTTS), Hannover Medical School, Hannover, Germany
- Center of Translational Regenerative Medicine, Hannover Medical School, Hannover, Germany
| | - Christian Bär
- Institute of Molecular and Translational Therapeutic Strategies (IMTTS), Hannover Medical School, Hannover, Germany.
- Center of Translational Regenerative Medicine, Hannover Medical School, Hannover, Germany.
- Fraunhofer Institute for Toxicology and Experimental Medicine, Hannover, Germany.
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4
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Garg A, Lavine KJ, Greenberg MJ. Assessing Cardiac Contractility From Single Molecules to Whole Hearts. JACC Basic Transl Sci 2024; 9:414-439. [PMID: 38559627 PMCID: PMC10978360 DOI: 10.1016/j.jacbts.2023.07.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 07/14/2023] [Accepted: 07/14/2023] [Indexed: 04/04/2024]
Abstract
Fundamentally, the heart needs to generate sufficient force and power output to dynamically meet the needs of the body. Cardiomyocytes contain specialized structures referred to as sarcomeres that power and regulate contraction. Disruption of sarcomeric function or regulation impairs contractility and leads to cardiomyopathies and heart failure. Basic, translational, and clinical studies have adapted numerous methods to assess cardiac contraction in a variety of pathophysiological contexts. These tools measure aspects of cardiac contraction at different scales ranging from single molecules to whole organisms. Moreover, these studies have revealed new pathogenic mechanisms of heart disease leading to the development of novel therapies targeting contractility. In this review, the authors explore the breadth of tools available for studying cardiac contractile function across scales, discuss their strengths and limitations, highlight new insights into cardiac physiology and pathophysiology, and describe how these insights can be harnessed for therapeutic candidate development and translational.
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Affiliation(s)
- Ankit Garg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
- Center for Cardiovascular Research, Division of Cardiology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Kory J. Lavine
- Center for Cardiovascular Research, Division of Cardiology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael J. Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
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5
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Gokhan I, Dong W, Grubman D, Mezue K, Yang D, Wang Y, Gandhi PU, Kwan JM, Hu JR. Clinical Biochemistry of Serum Troponin. Diagnostics (Basel) 2024; 14:378. [PMID: 38396417 PMCID: PMC10887818 DOI: 10.3390/diagnostics14040378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Revised: 01/29/2024] [Accepted: 01/30/2024] [Indexed: 02/25/2024] Open
Abstract
Accurate measurement and interpretation of serum levels of troponin (Tn) is a central part of the clinical workup of a patient presenting with chest pain suspicious for acute coronary syndrome (ACS). Knowledge of the molecular characteristics of the troponin complex and test characteristics of troponin measurement assays allows for a deeper understanding of causes of false positive and false negative test results in myocardial injury. In this review, we discuss the molecular structure and functions of the constituent proteins of the troponin complex (TnT, TnC, and TnI); review the different isoforms of Tn and where they are from; survey the evolution of clinical Tn assays, ranging from first-generation to high-sensitivity (hs); provide a primer on statistical interpretation of assay results based on different clinical settings; and discuss potential causes of false results. We also summarize the advances in technologies that may lead to the development of future Tn assays, including the development of point of care assays and wearable Tn sensors for real-time continuous measurement.
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Affiliation(s)
- Ilhan Gokhan
- Yale School of Medicine, Yale University, New Haven, CT 06510, USA; (I.G.)
| | - Weilai Dong
- Yale School of Medicine, Yale University, New Haven, CT 06510, USA; (I.G.)
| | - Daniel Grubman
- Yale School of Medicine, Yale University, New Haven, CT 06510, USA; (I.G.)
| | - Kenechukwu Mezue
- Section of Cardiovascular Medicine, Yale School of Medicine, Yale University, New Haven, CT 06510, USA (J.M.K.)
| | - David Yang
- Department of Emergency Medicine, Yale School of Medicine, Yale University, New Haven, CT 06510, USA
| | - Yanting Wang
- Division of Cardiovascular Disease and Hypertension, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA
| | - Parul U. Gandhi
- Section of Cardiovascular Medicine, Yale School of Medicine, Yale University, New Haven, CT 06510, USA (J.M.K.)
| | - Jennifer M. Kwan
- Section of Cardiovascular Medicine, Yale School of Medicine, Yale University, New Haven, CT 06510, USA (J.M.K.)
| | - Jiun-Ruey Hu
- Section of Cardiovascular Medicine, Yale School of Medicine, Yale University, New Haven, CT 06510, USA (J.M.K.)
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6
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Liu S, Yue S, Guo Y, Han JY, Wang H. Sorafenib induces cardiotoxicity through RBM20-mediated alternative splicing of sarcomeric and mitochondrial genes. Pharmacol Res 2023; 198:107017. [PMID: 38006979 DOI: 10.1016/j.phrs.2023.107017] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 09/12/2023] [Accepted: 11/22/2023] [Indexed: 11/27/2023]
Abstract
Sorafenib, a multi-targeted tyrosine kinase inhibitor, is a first-line treatment for advanced solid tumors, but it induces many adverse cardiovascular events, including myocardial infarction and heart failure. These cardiac defects can be mediated by alternative splicing of genes critical for heart function. Whether alternative splicing plays a role in sorafenib-induced cardiotoxicity remains unclear. Transcriptome of rat hearts or human cardiomyocytes treated with sorafenib was analyzed and validated to define alternatively spliced genes and their impact on cardiotoxicity. In rats, sorafenib caused severe cardiotoxicity with decreased left ventricular systolic pressure, elongated sarcomere, enlarged mitochondria and decreased ATP. This was associated with alternative splicing of hundreds of genes in the hearts, many of which were targets of a cardiac specific splicing factor, RBM20. Sorafenib inhibited RBM20 expression in both rat hearts and human cardiomyocytes. The splicing of RBM20's targets, SLC25A3 and FHOD3, was altered into fetal isoforms with decreased function. Upregulation of RBM20 during sorafenib treatment reversed the pathogenic splicing of SLC25A3 and FHOD3, and enhanced the phosphate transport into mitochondria by SLC25A3, ATP synthesis and cell survival.We envision this regulation may happen in many drug-induced cardiotoxicity, and represent a potential druggable pathway for mitigating sorafenib-induced cardiotoxicity.
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Affiliation(s)
- Songming Liu
- Department of Biomedical Informatics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Shanshan Yue
- Department of Integration of Chinese and Western Medicine, School of Basic Medical Sciences, Peking University, Beijing 100191, China; Tasly Microcirculation Research Center, Peking University Health Science Center, Beijing 100191, China
| | - Yuxuan Guo
- Peking University Institute of Cardiovascular Sciences, Peking University Health Science Center, School of Basic Medical Sciences, Beijing 100191, China
| | - Jing-Yan Han
- Department of Integration of Chinese and Western Medicine, School of Basic Medical Sciences, Peking University, Beijing 100191, China; Tasly Microcirculation Research Center, Peking University Health Science Center, Beijing 100191, China.
| | - Huan Wang
- Department of Biomedical Informatics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China; Institute of Systems Biomedicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China.
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7
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Gotthardt M, Badillo-Lisakowski V, Parikh VN, Ashley E, Furtado M, Carmo-Fonseca M, Schudy S, Meder B, Grosch M, Steinmetz L, Crocini C, Leinwand L. Cardiac splicing as a diagnostic and therapeutic target. Nat Rev Cardiol 2023; 20:517-530. [PMID: 36653465 DOI: 10.1038/s41569-022-00828-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/09/2022] [Indexed: 01/19/2023]
Abstract
Despite advances in therapeutics for heart failure and arrhythmias, a substantial proportion of patients with cardiomyopathy do not respond to interventions, indicating a need to identify novel modifiable myocardial pathobiology. Human genetic variation associated with severe forms of cardiomyopathy and arrhythmias has highlighted the crucial role of alternative splicing in myocardial health and disease, given that it determines which mature RNA transcripts drive the mechanical, structural, signalling and metabolic properties of the heart. In this Review, we discuss how the analysis of cardiac isoform expression has been facilitated by technical advances in multiomics and long-read and single-cell sequencing technologies. The resulting insights into the regulation of alternative splicing - including the identification of cardiac splice regulators as therapeutic targets and the development of a translational pipeline to evaluate splice modulators in human engineered heart tissue, animal models and clinical trials - provide a basis for improved diagnosis and therapy. Finally, we consider how the medical and scientific communities can benefit from facilitated acquisition and interpretation of splicing data towards improved clinical decision-making and patient care.
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Affiliation(s)
- Michael Gotthardt
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany.
- DZHK (German Center for Cardiovascular Research Partner Site Berlin), Berlin, Germany.
- Department of Cardiology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
| | - Victor Badillo-Lisakowski
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- DZHK (German Center for Cardiovascular Research Partner Site Berlin), Berlin, Germany
| | - Victoria Nicole Parikh
- Stanford Center for Inherited Cardiovascular Disease, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Euan Ashley
- Stanford Center for Inherited Cardiovascular Disease, Stanford University School of Medicine, Palo Alto, CA, USA
- Stanford Genome Technology Center, Stanford University, Palo Alto, CA, USA
- Department of Genetics, School of Medicine, Stanford University, Stanford, CA, USA
| | - Marta Furtado
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Maria Carmo-Fonseca
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Sarah Schudy
- Institute for Cardiomyopathies, Department of Medicine III, University of Heidelberg, Heidelberg, Germany
| | - Benjamin Meder
- Institute for Cardiomyopathies, Department of Medicine III, University of Heidelberg, Heidelberg, Germany
- DZHK (German Center for Cardiovascular Research Partner Site Heidelberg-Mannheim), Heidelberg, Germany
| | - Markus Grosch
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
| | - Lars Steinmetz
- Stanford Genome Technology Center, Stanford University, Palo Alto, CA, USA
- Department of Genetics, School of Medicine, Stanford University, Stanford, CA, USA
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
| | - Claudia Crocini
- Department of Molecular, Cellular, and Developmental Biology and BioFrontiers Institute, University of Colorado, Boulder, CO, USA
| | - Leslie Leinwand
- Department of Molecular, Cellular, and Developmental Biology and BioFrontiers Institute, University of Colorado, Boulder, CO, USA
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8
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Gerzen OP, Votinova VO, Potoskueva IK, Nabiev SR, Nikitina LV. Characteristics of Actin—Myosin Interaction in Different Regions of Rat Heart. J EVOL BIOCHEM PHYS+ 2022. [DOI: 10.1134/s0022093022070110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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9
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Cejas RB, Tamaño-Blanco M, Fontecha JE, Blanco JG. Impact of DYRK1A Expression on TNNT2 Splicing and Daunorubicin Toxicity in Human iPSC-Derived Cardiomyocytes. Cardiovasc Toxicol 2022; 22:701-712. [PMID: 35596909 PMCID: PMC9236996 DOI: 10.1007/s12012-022-09746-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 04/21/2022] [Indexed: 11/26/2022]
Abstract
Cardiac troponin T (encoded by TNNT2) is involved in the contraction of cardiomyocytes during beating. The alternative splicing of TNNT2 results in four transcript variants with differential Ca2+ sensitivity. The splicing of TNNT2 involves phosphorylation of the splicing factor SRSF6 by DYRK1A. Altered TNNT2 splicing patterns have been identified in failing human hearts. There is a paucity of studies describing DYRK1A-SRSF6-TNNT2 interplays in human cardiomyocytes. Also, it is not known whether the sensitivity of cardiomyocytes to cardiotoxic anthracyclines is modified in the context of variable DYRK1A-TNNT2 expression. In this study, we investigated the impact of DYRK1A on the endogenous expression of TNNT2 splicing variants in iPSC-derived cardiomyocytes. We also examined whether DYRK1A expression modifies the sensitivity of cardiomyocytes to the cardiotoxic drug daunorubicin (DAU). DYRK1A over-expression increased the abundance of TNNT2 fetal variants by ~ 58% whereas the abundance of the adult cTnT3 variant decreased by ~ 27%. High DYRK1A expression increased the phosphorylation of SRSF6 by ~ 25-65%. DAU cytotoxicity was similar between cardiomyocytes with variable levels of DYRK1A expression. DYRK1A over-expression ameliorated the impact of DAU on beating frequency. This study lays the foundation to further investigate the contribution of variable DYRK1A-TNNT2 expression to Ca2+ handling and beating in human cardiomyocytes.
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Affiliation(s)
- Romina Beatriz Cejas
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, The State University of New York at Buffalo, Buffalo, NY, 14214, USA
| | - Miriam Tamaño-Blanco
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, The State University of New York at Buffalo, Buffalo, NY, 14214, USA
| | - John Edgar Fontecha
- Group for Applied Mathematical Modeling and Analytics (GAMMA), Industrial and Systems Engineering, The State University of New York at Buffalo, Buffalo, NY, 14214, USA
| | - Javier Guillermo Blanco
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, The State University of New York at Buffalo, Buffalo, NY, 14214, USA.
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10
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Greenman AC, Diffee GM, Power AS, Wilkins GT, Gold OMS, Erickson JR, Baldi JC. Treadmill running increases the calcium sensitivity of myofilaments in diabetic rats. J Appl Physiol (1985) 2022; 132:1350-1360. [PMID: 35482324 DOI: 10.1152/japplphysiol.00785.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cardiovascular benefits of regular exercise are unequivocal, yet patients with type 2 diabetes respond poorly to exercise due to a reduced cardiac reserve. The contractile response of diabetic cardiomyocytes to beta-adrenergic stimulation is attenuated, which may result in altered myofilament calcium sensitivity and post-translational modifications of cardiac troponin I (cTnI). Treadmill running increases myofilament calcium sensitivity in non‑diabetic rats, and thus we hypothesized that endurance training would increase calcium sensitivity of diabetic cardiomyocytes and alter site-specific phosphorylation of cTnI. Calcium sensitivity, or pCa50, was measured in Zucker Diabetic Fatty (ZDF) non-diabetic (nDM) and diabetic (DM) rat hearts after 8 weeks of either a sedentary (SED) or progressive treadmill running (TR) intervention. Skinned cardiomyocytes were connected to a capacitance-gauge transducer and a torque motor to measure force as a function of pCa (‑log[Ca2+]). Specific phospho-sites on cTnI and O‑GlcNAcylation were quantified by immunoblot and total protein phosphorylation by fluorescent gel staining (ProQ Diamond). The novel finding in this study was that training increased pCa50 in both DM and nDM cardiomyocytes (p = 0.009). Phosphorylation of cTnI amino acid residues Ser23/24, a crucial protein kinase A site, and Threonine (Thr)144, was lower in DM hearts, but there was no effect of training on site-specific phosphorylation. Additionally, total phosphorylation and O-GlcNAcylation levels were not different between SED and TR groups. These findings suggest that regular exercise may benefit the diabetic heart by specifically targeting myofilament contractile function.
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Affiliation(s)
- Angela Claire Greenman
- Department of Medicine, Otago Medical School, University of Otago, Dunedin, New Zealand.,Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
| | - Gary M Diffee
- Department of Kinesiology, University of Wisconsin-Madison, Madison, WI
| | - Amelia S Power
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
| | - Gerard T Wilkins
- Department of Medicine, Otago Medical School, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
| | - Olivia M S Gold
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
| | - Jeffrey R Erickson
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
| | - James C Baldi
- Department of Medicine, Otago Medical School, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
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11
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Shafaattalab S, Li AY, Gunawan MG, Kim B, Jayousi F, Maaref Y, Song Z, Weiss JN, Solaro RJ, Qu Z, Tibbits GF. Mechanisms of Arrhythmogenicity of Hypertrophic Cardiomyopathy-Associated Troponin T ( TNNT2) Variant I79N. Front Cell Dev Biol 2022; 9:787581. [PMID: 34977031 PMCID: PMC8718794 DOI: 10.3389/fcell.2021.787581] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 11/16/2021] [Indexed: 12/24/2022] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is the most common heritable cardiovascular disease and often results in cardiac remodeling and an increased incidence of sudden cardiac arrest (SCA) and death, especially in youth and young adults. Among thousands of different variants found in HCM patients, variants of TNNT2 (cardiac troponin T—TNNT2) are linked to increased risk of ventricular arrhythmogenesis and sudden death despite causing little to no cardiac hypertrophy. Therefore, studying the effect of TNNT2 variants on cardiac propensity for arrhythmogenesis can pave the way for characterizing HCM in susceptible patients before sudden cardiac arrest occurs. In this study, a TNNT2 variant, I79N, was generated in human cardiac recombinant/reconstituted thin filaments (hcRTF) to investigate the effect of the mutation on myofilament Ca2+ sensitivity and Ca2+ dissociation rate using steady-state and stopped-flow fluorescence techniques. The results revealed that the I79N variant significantly increases myofilament Ca2+ sensitivity and decreases the Ca2+ off-rate constant (koff). To investigate further, a heterozygous I79N+/−TNNT2 variant was introduced into human-induced pluripotent stem cells using CRISPR/Cas9 and subsequently differentiated into ventricular cardiomyocytes (hiPSC-CMs). To study the arrhythmogenic properties, monolayers of I79N+/− hiPSC-CMs were studied in comparison to their isogenic controls. Arrhythmogenesis was investigated by measuring voltage (Vm) and cytosolic Ca2+ transients over a range of stimulation frequencies. An increasing stimulation frequency was applied to the cells, from 55 to 75 bpm. The results of this protocol showed that the TnT-I79N cells had reduced intracellular Ca2+ transients due to the enhanced cytosolic Ca2+ buffering. These changes in Ca2+ handling resulted in beat-to-beat instability and triangulation of the cardiac action potential, which are predictors of arrhythmia risk. While wild-type (WT) hiPSC-CMs were accurately entrained to frequencies of at least 150 bpm, the I79N hiPSC-CMs demonstrated clear patterns of alternans for both Vm and Ca2+ transients at frequencies >75 bpm. Lastly, a transcriptomic analysis was conducted on WT vs. I79N+/−TNNT2 hiPSC-CMs using a custom NanoString codeset. The results showed a significant upregulation of NPPA (atrial natriuretic peptide), NPPB (brain natriuretic peptide), Notch signaling pathway components, and other extracellular matrix (ECM) remodeling components in I79N+/− vs. the isogenic control. This significant shift demonstrates that this missense in the TNNT2 transcript likely causes a biophysical trigger, which initiates this significant alteration in the transcriptome. This TnT-I79N hiPSC-CM model not only reproduces key cellular features of HCM-linked mutations but also suggests that this variant causes uncharted pro-arrhythmic changes to the human action potential and gene expression.
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Affiliation(s)
- Sanam Shafaattalab
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.,Cellular and Regenerative Medicine Centre, BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - Alison Y Li
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.,Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, BC, Canada
| | - Marvin G Gunawan
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.,Cellular and Regenerative Medicine Centre, BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - BaRun Kim
- Cellular and Regenerative Medicine Centre, BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - Farah Jayousi
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.,Cellular and Regenerative Medicine Centre, BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - Yasaman Maaref
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.,Cellular and Regenerative Medicine Centre, BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - Zhen Song
- UCLA Cardiac Computation Lab, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - James N Weiss
- UCLA Cardiac Computation Lab, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - R John Solaro
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, United States
| | - Zhilin Qu
- UCLA Cardiac Computation Lab, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Glen F Tibbits
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.,Cellular and Regenerative Medicine Centre, BC Children's Hospital Research Institute, Vancouver, BC, Canada.,Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.,Department of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada
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12
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Hassoun R, Budde H, Mügge A, Hamdani N. Cardiomyocyte Dysfunction in Inherited Cardiomyopathies. Int J Mol Sci 2021; 22:11154. [PMID: 34681814 PMCID: PMC8541428 DOI: 10.3390/ijms222011154] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/08/2021] [Accepted: 10/13/2021] [Indexed: 01/10/2023] Open
Abstract
Inherited cardiomyopathies form a heterogenous group of disorders that affect the structure and function of the heart. Defects in the genes encoding sarcomeric proteins are associated with various perturbations that induce contractile dysfunction and promote disease development. In this review we aimed to outline the functional consequences of the major inherited cardiomyopathies in terms of myocardial contraction and kinetics, and to highlight the structural and functional alterations in some sarcomeric variants that have been demonstrated to be involved in the pathogenesis of the inherited cardiomyopathies. A particular focus was made on mutation-induced alterations in cardiomyocyte mechanics. Since no disease-specific treatments for familial cardiomyopathies exist, several novel agents have been developed to modulate sarcomere contractility. Understanding the molecular basis of the disease opens new avenues for the development of new therapies. Furthermore, the earlier the awareness of the genetic defect, the better the clinical prognostication would be for patients and the better the prevention of development of the disease.
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Affiliation(s)
- Roua Hassoun
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
| | - Heidi Budde
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
| | - Andreas Mügge
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
| | - Nazha Hamdani
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
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13
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Pellerin D, Aykanat A, Ellezam B, Troiano EC, Karamchandani J, Dicaire MJ, Petitclerc M, Robertson R, Allard-Chamard X, Brunet D, Konersman CG, Mathieu J, Warman Chardon J, Gupta VA, Beggs AH, Brais B, Chrestian N. Novel Recessive TNNT1 Congenital Core-Rod Myopathy in French Canadians. Ann Neurol 2020; 87:568-583. [PMID: 31970803 DOI: 10.1002/ana.25685] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2019] [Revised: 01/06/2020] [Accepted: 01/19/2020] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Recessive null variants of the slow skeletal muscle troponin T1 (TNNT1) gene are a rare cause of nemaline myopathy that is fatal in infancy due to respiratory insufficiency. Muscle biopsy shows rods and fiber type disproportion. We report on 4 French Canadians with a novel form of recessive congenital TNNT1 core-rod myopathy. METHODS Patients underwent full clinical characterization, lower limb magnetic resonance imaging (MRI), muscle biopsy, and genetic testing. A zebrafish loss-of-function model using morpholinos was created to assess the pathogenicity of the identified variant. Wild-type or mutated human TNNT1 mRNAs were coinjected with morpholinos to assess their abilities to rescue the morphant phenotype. RESULTS Three adults and 1 child shared a novel missense homozygous variant in the TNNT1 gene (NM_003283.6: c.287T > C; p.Leu96Pro). They developed from childhood very slowly progressive limb-girdle weakness with rigid spine and disabling contractures. They suffered from restrictive lung disease requiring noninvasive mechanical ventilation in 3 patients, as well as recurrent episodes of rhabdomyolysis triggered by infections, which were relieved by dantrolene in 1 patient. Older patients remained ambulatory into their 60s. MRI of the leg muscles showed fibrofatty infiltration predominating in the posterior thigh and the deep posterior leg compartments. Muscle biopsies showed multiminicores and lobulated fibers, rods in half the patients, and no fiber type disproportion. Wild-type TNNT1 mRNA rescued the zebrafish morphants, but mutant transcripts failed to do so. INTERPRETATION This study expands the phenotypic spectrum of TNNT1 myopathy and provides functional evidence for the pathogenicity of the newly identified missense mutation. ANN NEUROL 2020;87:568-583.
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Affiliation(s)
- David Pellerin
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada
| | - Asli Aykanat
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Benjamin Ellezam
- Department of Pathology, Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada
| | - Emily C Troiano
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Jason Karamchandani
- Department of Pathology, Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada
| | - Marie-Josée Dicaire
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada
| | - Marc Petitclerc
- Department of Neurology, Hôpital Hôtel-Dieu de Lévis, Lévis, Quebec, Canada
| | - Rebecca Robertson
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada
| | - Xavier Allard-Chamard
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada
| | - Denis Brunet
- Department of Neurology, Hôpital de l'Enfant Jésus, Université Laval, Quebec City, Quebec, Canada
| | | | - Jean Mathieu
- Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada.,Neuromuscular Disease Clinic, Centre Intégré Universitaire de Santé et de Services Sociaux du Saguenay-Lac-Saint-Jean, Jonquière, Quebec, Canada
| | - Jodi Warman Chardon
- Department of Neurosciences, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
| | - Vandana A Gupta
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Alan H Beggs
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Bernard Brais
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada.,Neuromuscular Disease Clinic, Centre Intégré Universitaire de Santé et de Services Sociaux du Saguenay-Lac-Saint-Jean, Jonquière, Quebec, Canada.,Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - Nicolas Chrestian
- Department of Child Neurology, Centre Hospitalier de l'Université Laval et Centre Mère-Enfant Soleil, Université Laval, Quebec City, Quebec, Canada
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14
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Quiñones-Lombraña A, Blanco JG. Comparative analysis of the DYRK1A-SRSF6-TNNT2 pathway in myocardial tissue from individuals with and without Down syndrome. Exp Mol Pathol 2019; 110:104268. [PMID: 31201803 PMCID: PMC6754281 DOI: 10.1016/j.yexmp.2019.104268] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 05/22/2019] [Accepted: 06/11/2019] [Indexed: 10/26/2022]
Abstract
Down syndrome (trisomy 21) is characterized by genome-wide imbalances that result in a range of phenotypic manifestations. Altered expression of DYRK1A in the trisomic context has been linked to some Down syndrome phenotypes. DYRK1A regulates the splicing of cardiac troponin (TNNT2) through a pathway mediated by the master splicing factor SRSF6. Here, we documented the expression of the DYRK1A-SRSF6-TNNT2 pathway in a collection of myocardial samples from persons with and without Down syndrome. Results suggest that "gene dosage effect" may drive the expression of DYRK1A mRNA but has no effect on DYRK1A protein levels in trisomic myocardium. The levels of phosphorylated DYRK1A-Tyr321 tended to be higher (~35%) in myocardial samples from donors with Down syndrome. The levels of phosphorylated SRSF6 were 2.6-fold higher in trisomic myocardium. In line, the expression of fetal TNNT2 variants was higher in myocardial tissue with trisomy 21. These data provide a representative picture on the extent of inter-individual variation in myocardial DYRK1A-SRSF6-TNNT2 expression in the context of Down syndrome.
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Affiliation(s)
- Adolfo Quiñones-Lombraña
- Department of Pharmaceutical Sciences, University at Buffalo, The State University of New York (SUNY), Buffalo, New York, United States of America
| | - Javier G Blanco
- Department of Pharmaceutical Sciences, University at Buffalo, The State University of New York (SUNY), Buffalo, New York, United States of America.
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15
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Clippinger SR, Cloonan PE, Greenberg L, Ernst M, Stump WT, Greenberg MJ. Disrupted mechanobiology links the molecular and cellular phenotypes in familial dilated cardiomyopathy. Proc Natl Acad Sci U S A 2019; 116:17831-17840. [PMID: 31427533 PMCID: PMC6731759 DOI: 10.1073/pnas.1910962116] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Familial dilated cardiomyopathy (DCM) is a leading cause of sudden cardiac death and a major indicator for heart transplant. The disease is frequently caused by mutations of sarcomeric proteins; however, it is not well understood how these molecular mutations lead to alterations in cellular organization and contractility. To address this critical gap in our knowledge, we studied the molecular and cellular consequences of a DCM mutation in troponin-T, ΔK210. We determined the molecular mechanism of ΔK210 and used computational modeling to predict that the mutation should reduce the force per sarcomere. In mutant cardiomyocytes, we found that ΔK210 not only reduces contractility but also causes cellular hypertrophy and impairs cardiomyocytes' ability to adapt to changes in substrate stiffness (e.g., heart tissue fibrosis that occurs with aging and disease). These results help link the molecular and cellular phenotypes and implicate alterations in mechanosensing as an important factor in the development of DCM.
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Affiliation(s)
- Sarah R Clippinger
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - Paige E Cloonan
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - Lina Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - Melanie Ernst
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - W Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
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16
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Oki K, Wei B, Feng HZ, Jin JP. The loss of slow skeletal muscle isoform of troponin T in spindle intrafusal fibres explains the pathophysiology of Amish nemaline myopathy. J Physiol 2019; 597:3999-4012. [PMID: 31148174 PMCID: PMC6675633 DOI: 10.1113/jp278119] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 05/29/2019] [Indexed: 01/17/2023] Open
Abstract
KEY POINTS The pathogenic mechanism and the neuromuscular reflex-related phenotype (e.g. tremors accompanied by clonus) of Amish nemaline myopathy, as well as of other recessively inherited TNNT1 myopathies, remain to be clarified. The truncated slow skeletal muscle isoform of troponin T (ssTnT) encoded by the mutant TNNT1 gene is unable to incorporate into myofilaments and is degraded in muscle cells. By contrast to extrafusal muscle fibres, spindle intrafusal fibres of normal mice contain a significant level of cardiac TnT and a low molecular weight splice form of ssTnT. Intrafusal fibres of ssTnT-knockout mice have significantly increased cardiac TnT. Rotarod and balance beam tests have revealed abnormal neuromuscular co-ordination in ssTnT-knockout mice and a blunted response to a spindle sensitizer, succinylcholine. The loss of ssTnT and a compensatory increase of cardiac TnT in intrafusal nuclear bag fibres may increase myofilament Ca2+ -sensitivity and tension, impairing spindle function, thus identifying a novel mechanism for the development of targeted treatment. ABSTRACT A nonsense mutation at codon Glu180 of TNNT1 gene causes Amish nemaline myopathy (ANM), a recessively inherited disease with infantile lethality. TNNT1 encodes the slow skeletal muscle isoform of troponin T (ssTnT). The truncated ssTnT is unable to incorporate into myofilament and is degraded in muscle cells. The symptoms of ANM include muscle weakness, atrophy, contracture and tremors accompanied by clonus. An ssTnT-knockout (KO) mouse model recapitulates key features of ANM such as atrophy of extrafusal slow muscle fibres and increased fatigability. However, the neuromuscular reflex-related symptoms of ANM have not been explained. By isolating muscle spindles from ssTnT-KO and control mice aiming to examine the composition of myofilament proteins, we found that, in contrast to extrafusal fibres, intrafusal fibres contain a significant level of cardiac TnT and the low molecular weight splice form of ssTnT. Intrafusal fibres from ssTnT-KO mice have significantly increased cardiac TnT. Rotarod and balance beam tests revealed impaired neuromuscular co-ordination in ssTnT-KO mice, indicating abnormality in spindle functions. Unlike the wild-type control, the beam running ability of ssTnT-KO mice had a blunted response to a spindle sensitizer, succinylcholine. Immunohistochemistry detected ssTnT and cardiac TnT in nuclear bag fibres, whereas fast skeletal muscle TnT was detected in nuclear chain fibres, and cardiac α-myosin was present in one of the two nuclear bag fibres. The loss of ssTnT and a compensatory increase of cardiac TnT in nuclear bag fibres would increase myofilament Ca2+ -sensitivity and tension, thus affecting spindle activities. This mechanism provides an explanation for the pathophysiology of ANM, as well as a novel target for treatment.
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Affiliation(s)
| | | | - Han-Zhong Feng
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - J.-P. Jin
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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17
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Kagemoto T, Oyama K, Yamane M, Tsukamoto S, Kobirumaki-Shimozawa F, Li A, Dos Remedios C, Fukuda N, Ishiwata S. Sarcomeric Auto-Oscillations in Single Myofibrils From the Heart of Patients With Dilated Cardiomyopathy. Circ Heart Fail 2019; 11:e004333. [PMID: 29980594 DOI: 10.1161/circheartfailure.117.004333] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 05/31/2018] [Indexed: 01/30/2023]
Abstract
BACKGROUND Left ventricular wall motion is depressed in patients with dilated cardiomyopathy (DCM). However, whether or not the depressed left ventricular wall motion is caused by impairment of sarcomere dynamics remains to be fully clarified. METHODS AND RESULTS We analyzed the mechanical properties of single sarcomere dynamics during sarcomeric auto-oscillations (calcium spontaneous oscillatory contractions [Ca-SPOC]) that occurred at partial activation under the isometric condition in myofibrils from donor hearts and from patients with severe DCM (New York Heart Association classification III-IV). Ca-SPOC reproducibly occurred in the presence of 1 μmol/L free Ca2+ in both nonfailing and DCM myofibrils, and sarcomeres exhibited a saw-tooth waveform along single myofibrils composed of quick lengthening and slow shortening. The period of Ca-SPOC was longer in DCM myofibrils than in nonfailing myofibrils, in association with prolonged shortening time. Lengthening time was similar in both groups. Then, we performed Tn (troponin) exchange in myofibrils with a DCM-causing homozygous mutation (K36Q) in cTnI (cardiac TnI). On exchange with the Tn complex from healthy porcine ventricles, period, shortening time, and shortening velocity in cTnI-K36Q myofibrils became similar to those in Tn-reconstituted nonfailing myofibrils. Protein kinase A abbreviated period in both Tn-reconstituted nonfailing and cTnI-K36Q myofibrils, demonstrating acceleration of cross-bridge kinetics. CONCLUSIONS Sarcomere dynamics was found to be depressed under loaded conditions in DCM myofibrils because of impairment of thick-thin filament sliding. Thus, microscopic analysis of Ca-SPOC in human cardiac myofibrils is beneficial to systematically unveil the kinetic properties of single sarcomeres in various types of heart disease.
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Affiliation(s)
- Tatsuya Kagemoto
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo, Japan (T.K., M.Y., S.I.)
| | - Kotaro Oyama
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan (K.O., S.T., F.K.-S., N.F.)
| | - Mitsunori Yamane
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo, Japan (T.K., M.Y., S.I.)
| | - Seiichi Tsukamoto
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan (K.O., S.T., F.K.-S., N.F.)
| | - Fuyu Kobirumaki-Shimozawa
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan (K.O., S.T., F.K.-S., N.F.)
| | - Amy Li
- School of Medical Sciences, Bosch Institute, The University of Sydney, Australia (A.L., C.D.R.)
| | - Cristobal Dos Remedios
- School of Medical Sciences, Bosch Institute, The University of Sydney, Australia (A.L., C.D.R.)
| | - Norio Fukuda
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan (K.O., S.T., F.K.-S., N.F.).
| | - Shin'ichi Ishiwata
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo, Japan (T.K., M.Y., S.I.).
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18
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Matsuo T, Kono F, Fujiwara S. Effects of the cardiomyopathy-causing E244D mutation of troponin T on the structures of cardiac thin filaments studied by small-angle X-ray scattering. J Struct Biol 2018; 205:196-205. [PMID: 30599212 DOI: 10.1016/j.jsb.2018.12.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 12/07/2018] [Accepted: 12/10/2018] [Indexed: 02/04/2023]
Abstract
Small-angle X-ray scattering experiments were carried out to investigate the structural changes of cardiac thin filaments induced by the cardiomyopathy-causing E244D mutation in troponin T (TnT). We examined native thin filaments (NTF) from a bovine heart, reconstituted thin filaments containing human cardiac wild-type Tn (WTF), and filaments containing the E244D mutant of Tn (DTF), in the absence and presence of Ca2+. Analysis by model calculation showed that upon Ca2+-activation, tropomyosin (Tm) and Tn in the WTF and NTF moved together in a direction to expose myosin-binding sites on actin. On the other hand, Tm and Tn of the DTF moved in the opposite directions to each other upon Ca2+-activation. These movements caused Tm to expose more myosin-binding sites on actin than the WTF, suggesting that the affinity of myosin for actin is higher for the DTF. Thus, the mutation-induced structural changes in thin filaments would increase the number of myosin molecules bound to actin compared with the WTF, resulting in the force enhancement observed for the E244D mutation.
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Affiliation(s)
- Tatsuhito Matsuo
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 2-4 Shirakata, Tokai, Naka-Gun, Ibaraki 319-1106, Japan
| | - Fumiaki Kono
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 2-4 Shirakata, Tokai, Naka-Gun, Ibaraki 319-1106, Japan
| | - Satoru Fujiwara
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 2-4 Shirakata, Tokai, Naka-Gun, Ibaraki 319-1106, Japan.
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19
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Wang Q, Zhu C, Sun M, Maimaiti R, Ford SP, Nathanielsz PW, Ren J, Guo W. Maternal obesity impairs fetal cardiomyocyte contractile function in sheep. FASEB J 2018; 33:2587-2598. [PMID: 30289749 DOI: 10.1096/fj.201800988r] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Obesity is a major public health problem worldwide. In the United States, one-third of women of reproductive age are obese. Human studies show that maternal obesity (MO) predisposes offspring to cardiovascular disease. However, the underlying mechanisms remain unclear. Given the similarities between pregnancy in sheep and humans, we studied sheep to examine the impact of MO on fetal cardiomyocyte contractility at term. We observed that MO impaired cardiomyocyte contractility by reducing peak shortening and shortening/relengthening velocity, prolonging time to relengthening. MO disrupted Ca2+ homeostasis in fetal cardiomyocytes, increasing intracellular Ca2+ and inducing cellular Ca2+ insensitivity. The Ca2+-release channel was impaired, but Ca2+ uptake was unaffected by MO. The upstream kinases that phosphorylate the Ca2+-release channel-ryanodine receptor-2, PKA, and calmodulin-dependent protein kinase II-were activated in MO fetuses. Contractile dysfunction was associated with an increased ratio of myosin heavy chain (MHC)-β to MHC-α and upregulated cardiac troponin (cTn)-T and tropomyosin, as well as cTn-I phosphorylation. In summary, this is the first characterization of the effects of MO on fetal cardiomyocyte contractility. Our findings indicate that MO impairs fetal cardiomyocyte contractility through altered intracellular Ca2+ handling, overloading fetal cardiomyocyte intracellular Ca2+ and aberrant myofilament protein composition. These mechanisms may contribute to developmental programming by MO of offspring cardiac function and predisposition to later life cardiovascular disease in the offspring.-Wang, Q., Zhu, C., Sun, M., Maimaiti, R., Ford, S. P., Nathanielsz, P. W., Ren, J., Guo, W. Maternal obesity impairs fetal cardiomyocyte contractile function in sheep.
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Affiliation(s)
- Qiurong Wang
- Center for the Study of Fetal Programming, University of Wyoming, Laramie, Wyoming, USA.,Animal Science Department, University of Wyoming, Laramie, Wyoming, USA; and
| | - Chaoqun Zhu
- Animal Science Department, University of Wyoming, Laramie, Wyoming, USA; and
| | - Mingming Sun
- Animal Science Department, University of Wyoming, Laramie, Wyoming, USA; and
| | - Rexiati Maimaiti
- Animal Science Department, University of Wyoming, Laramie, Wyoming, USA; and
| | - Stephen P Ford
- Center for the Study of Fetal Programming, University of Wyoming, Laramie, Wyoming, USA.,Animal Science Department, University of Wyoming, Laramie, Wyoming, USA; and
| | - Peter W Nathanielsz
- Center for the Study of Fetal Programming, University of Wyoming, Laramie, Wyoming, USA.,Animal Science Department, University of Wyoming, Laramie, Wyoming, USA; and
| | - Jun Ren
- Center for Cardiovascular Research and Alternative Medicine, University of Wyoming, Laramie, Wyoming, USA
| | - Wei Guo
- Center for the Study of Fetal Programming, University of Wyoming, Laramie, Wyoming, USA.,Animal Science Department, University of Wyoming, Laramie, Wyoming, USA; and.,Center for Cardiovascular Research and Alternative Medicine, University of Wyoming, Laramie, Wyoming, USA
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20
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Johnson D, Angus CW, Chalovich JM. Stepwise C-Terminal Truncation of Cardiac Troponin T Alters Function at Low and Saturating Ca 2. Biophys J 2018; 115:702-712. [PMID: 30057009 DOI: 10.1016/j.bpj.2018.06.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 06/19/2018] [Accepted: 06/29/2018] [Indexed: 11/16/2022] Open
Abstract
Activation of striated muscle contraction occurs in response to Ca2+ binding to troponin C. The resulting reorganization of troponin repositions tropomyosin on actin and permits activation of myosin-catalyzed ATP hydrolysis. It now appears that the C-terminal 14 amino acids of cardiac troponin T (TnT) control the level of activity at both low and high Ca2+. We made a series of C-terminal truncation mutants of human cardiac troponin T, isoform 2, to determine if the same residues of TnT are involved in the low and high Ca2+ effects. We measured the effect of these mutations on the normalized ATPase activity at saturating Ca2+. Changes in acrylodan tropomyosin fluorescence and the degree of Ca2+ stimulation of the rate of binding of rigor myosin subfragment 1 to pyrene-labeled actin-tropomyosin-troponin were measured at low Ca2+. These measurements define the distribution of actin-tropomyosin-troponin among the three regulatory states. Residues SKTR and GRWK of TnT were required for the functioning of TnT at both low and high Ca2+. Thus, the effects on forming the inactive B-state and in retarding formation of the active M-state require the same regions of TnT. We also observed that the rate of binding of rigor subfragment 1 to pyrene-labeled regulated actin at saturating Ca2+ was higher for the truncation mutants than for wild-type TnT. This violated an assumption necessary for determining the B-state population by this kinetic method.
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Affiliation(s)
- Dylan Johnson
- Department of Biochemistry, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - C William Angus
- Department of Biochemistry, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Joseph M Chalovich
- Department of Biochemistry, Brody School of Medicine, East Carolina University, Greenville, North Carolina.
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21
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Iorga B, Schwanke K, Weber N, Wendland M, Greten S, Piep B, Dos Remedios CG, Martin U, Zweigerdt R, Kraft T, Brenner B. Differences in Contractile Function of Myofibrils within Human Embryonic Stem Cell-Derived Cardiomyocytes vs. Adult Ventricular Myofibrils Are Related to Distinct Sarcomeric Protein Isoforms. Front Physiol 2018; 8:1111. [PMID: 29403388 PMCID: PMC5780405 DOI: 10.3389/fphys.2017.01111] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Accepted: 12/15/2017] [Indexed: 01/10/2023] Open
Abstract
Characterizing the contractile function of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) is key for advancing their utility for cellular disease models, promoting cell based heart repair, or developing novel pharmacological interventions targeting cardiac diseases. The aim of the present study was to understand whether steady-state and kinetic force parameters of β-myosin heavy chain (βMyHC) isoform-expressing myofibrils within human embryonic stem cell-derived cardiomyocytes (hESC-CMs) differentiated in vitro resemble those of human ventricular myofibrils (hvMFs) isolated from adult donor hearts. Contractile parameters were determined using the same micromechanical method and experimental conditions for both types of myofibrils. We identified isoforms and phosphorylation of main sarcomeric proteins involved in the modulation of force generation of both, chemically demembranated hESC-CMs (d-hESC-CMs) and hvMFs. Our results indicate that at saturating Ca2+ concentration, both human-derived contractile systems developed forces with similar rate constants (0.66 and 0.68 s−1), reaching maximum isometric force that was significantly smaller for d-hESC-CMs (42 kPa) than for hvMFs (94 kPa). At submaximal Ca2+-activation, where intact cardiomyocytes normally operate, contractile parameters of d-hESC-CMs and hvMFs exhibited differences. Ca2+ sensitivity of force was higher for d-hESC-CMs (pCa50 = 6.04) than for hvMFs (pCa50 = 5.80). At half-maximum activation, the rate constant for force redevelopment was significantly faster for d-hESC-CMs (0.51 s−1) than for hvMFs (0.28 s−1). During myofibril relaxation, kinetics of the slow force decay phase were significantly faster for d-hESC-CMs (0.26 s−1) than for hvMFs (0.21 s−1), while kinetics of the fast force decay were similar and ~20x faster. Protein analysis revealed that hESC-CMs had essentially no cardiac troponin-I, and partially non-ventricular isoforms of some other sarcomeric proteins, explaining the functional discrepancies. The sarcomeric protein isoform pattern of hESC-CMs had features of human cardiomyocytes at an early developmental stage. The study indicates that morphological and ultrastructural maturation of βMyHC isoform-expressing hESC-CMs is not necessarily accompanied by ventricular-like expression of all sarcomeric proteins. Our data suggest that hPSC-CMs could provide useful tools for investigating inherited cardiac diseases affecting contractile function during early developmental stages.
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Affiliation(s)
- Bogdan Iorga
- Department of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany.,Department of Physical Chemistry, Faculty of Chemistry, University of Bucharest, Bucharest, Romania
| | - Kristin Schwanke
- Department of Cardiac, Thoracic, Transplantation and Vascular Surgery, Leibniz Research Laboratories for Biotechnology and Artificial Organs, REBIRTH-Center for Regenerative Medicine, Hannover Medical School, Hannover, Germany
| | - Natalie Weber
- Department of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Meike Wendland
- Department of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Stephan Greten
- Department of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Birgit Piep
- Department of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | | | - Ulrich Martin
- Department of Cardiac, Thoracic, Transplantation and Vascular Surgery, Leibniz Research Laboratories for Biotechnology and Artificial Organs, REBIRTH-Center for Regenerative Medicine, Hannover Medical School, Hannover, Germany
| | - Robert Zweigerdt
- Department of Cardiac, Thoracic, Transplantation and Vascular Surgery, Leibniz Research Laboratories for Biotechnology and Artificial Organs, REBIRTH-Center for Regenerative Medicine, Hannover Medical School, Hannover, Germany
| | - Theresia Kraft
- Department of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Bernhard Brenner
- Department of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
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22
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Wang L, Kim K, Parikh S, Cadar AG, Bersell KR, He H, Pinto JR, Kryshtal DO, Knollmann BC. Hypertrophic cardiomyopathy-linked mutation in troponin T causes myofibrillar disarray and pro-arrhythmic action potential changes in human iPSC cardiomyocytes. J Mol Cell Cardiol 2018; 114:320-327. [PMID: 29217433 PMCID: PMC5800960 DOI: 10.1016/j.yjmcc.2017.12.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 12/01/2017] [Accepted: 12/03/2017] [Indexed: 12/25/2022]
Abstract
BACKGROUND Mutations in cardiac troponin T (TnT) are linked to increased risk of ventricular arrhythmia and sudden death despite causing little to no cardiac hypertrophy. Studies in mice suggest that the hypertrophic cardiomyopathy (HCM)-associated TnT-I79N mutation increases myofilament Ca sensitivity and is arrhythmogenic, but whether findings from mice translate to human cardiomyocyte electrophysiology is not known. OBJECTIVES To study the effects of the TnT-I79N mutation in human cardiomyocytes. METHODS Using CRISPR/Cas9, the TnT-I79N mutation was introduced into human induced pluripotent stem cells (hiPSCs). We then used the matrigel mattress method to generate single rod-shaped cardiomyocytes (CMs) and studied contractility, Ca handling and electrophysiology. RESULTS Compared to isogenic control hiPSC-CMs, TnT-I79N hiPSC-CMs exhibited sarcomere disorganization, increased systolic function and impaired relaxation. The Ca-dependence of contractility was leftward shifted in mutation containing cardiomyocytes, demonstrating increased myofilament Ca sensitivity. In voltage-clamped hiPSC-CMs, TnT-I79N reduced intracellular Ca transients by enhancing cytosolic Ca buffering. These changes in Ca handling resulted in beat-to-beat instability and triangulation of the cardiac action potential, which are predictors of arrhythmia risk. The myofilament Ca sensitizer EMD57033 produced similar action potential triangulation in control hiPSC-CMs. CONCLUSIONS The TnT-I79N hiPSC-CM model not only reproduces key cellular features of TnT-linked HCM such as myofilament disarray, hypercontractility and diastolic dysfunction, but also suggests that this TnT mutation causes pro-arrhythmic changes of the human ventricular action potential.
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Affiliation(s)
- Lili Wang
- Division of Clinical Pharmacology, Vanderbilt Univ Medical Ctr, Nashville, TN, Medical Research Building IV, Rm.1275, 2215B Garland Ave, Nashville, TN 37232, USA
| | - Kyungsoo Kim
- Division of Clinical Pharmacology, Vanderbilt Univ Medical Ctr, Nashville, TN, Medical Research Building IV, Rm.1275, 2215B Garland Ave, Nashville, TN 37232, USA
| | - Shan Parikh
- Division of Clinical Pharmacology, Vanderbilt Univ Medical Ctr, Nashville, TN, Medical Research Building IV, Rm.1275, 2215B Garland Ave, Nashville, TN 37232, USA
| | - Adrian Gabriel Cadar
- Division of Cardiovascular Medicine, Vanderbilt Univ Medical Ctr, Nashville, TN, Light Hall 1155A, 2215B Garland Ave, Nashville, TN 37232, USA
| | - Kevin R Bersell
- Division of Clinical Pharmacology, Vanderbilt Univ Medical Ctr, Nashville, TN, Medical Research Building IV, Rm.1275, 2215B Garland Ave, Nashville, TN 37232, USA
| | - Huan He
- Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL 32306, USA; Translational Science Laboratory, Florida State University College of Medicine, 1115 W. Call Street, Tallahassee, FL 32306, USA
| | - Jose R Pinto
- Department of Biomedical Sciences, Florida State University College of Medicine, 1115 W. Call Street, Tallahassee, FL 32306, USA
| | - Dmytro O Kryshtal
- Division of Clinical Pharmacology, Vanderbilt Univ Medical Ctr, Nashville, TN, Medical Research Building IV, Rm.1275, 2215B Garland Ave, Nashville, TN 37232, USA.
| | - Bjorn C Knollmann
- Division of Clinical Pharmacology, Vanderbilt Univ Medical Ctr, Nashville, TN, Medical Research Building IV, Rm.1275, 2215B Garland Ave, Nashville, TN 37232, USA.
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Veltri T, Landim-Vieira M, Parvatiyar MS, Gonzalez-Martinez D, Dieseldorff Jones KM, Michell CA, Dweck D, Landstrom AP, Chase PB, Pinto JR. Hypertrophic Cardiomyopathy Cardiac Troponin C Mutations Differentially Affect Slow Skeletal and Cardiac Muscle Regulation. Front Physiol 2017; 8:221. [PMID: 28473771 PMCID: PMC5397416 DOI: 10.3389/fphys.2017.00221] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 03/27/2017] [Indexed: 12/22/2022] Open
Abstract
Mutations in TNNC1-the gene encoding cardiac troponin C (cTnC)-that have been associated with hypertrophic cardiomyopathy (HCM) and cardiac dysfunction may also affect Ca2+-regulation and function of slow skeletal muscle since the same gene is expressed in both cardiac and slow skeletal muscle. Therefore, we reconstituted rabbit soleus fibers and bovine masseter myofibrils with mutant cTnCs (A8V, C84Y, E134D, and D145E) associated with HCM to investigate their effects on contractile force and ATPase rates, respectively. Previously, we showed that these HCM cTnC mutants, except for E134D, increased the Ca2+ sensitivity of force development in cardiac preparations. In the current study, an increase in Ca2+ sensitivity of isometric force was only observed for the C84Y mutant when reconstituted in soleus fibers. Incorporation of cTnC C84Y in bovine masseter myofibrils reduced the ATPase activity at saturating [Ca2+], whereas, incorporation of cTnC D145E increased the ATPase activity at inhibiting and saturating [Ca2+]. We also tested whether reconstitution of cardiac fibers with troponin complexes containing the cTnC mutants and slow skeletal troponin I (ssTnI) could emulate the slow skeletal functional phenotype. Reconstitution of cardiac fibers with troponin complexes containing ssTnI attenuated the Ca2+ sensitization of isometric force when cTnC A8V and D145E were present; however, it was enhanced for C84Y. In summary, although the A8V and D145E mutants are present in both muscle types, their functional phenotype is more prominent in cardiac muscle than in slow skeletal muscle, which has implications for the protein-protein interactions within the troponin complex. The C84Y mutant warrants further investigation since it drastically alters the properties of both muscle types and may account for the earlier clinical onset in the proband.
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Affiliation(s)
- Tiago Veltri
- Department of Biomedical Sciences, Florida State University College of MedicineTallahassee, FL, USA
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University College of MedicineTallahassee, FL, USA
| | - Michelle S. Parvatiyar
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of MedicineMiami, FL, USA
| | - David Gonzalez-Martinez
- Department of Biomedical Sciences, Florida State University College of MedicineTallahassee, FL, USA
| | | | - Clara A. Michell
- Department of Biomedical Sciences, Florida State University College of MedicineTallahassee, FL, USA
| | - David Dweck
- Department of Biomedical Sciences, Florida State University College of MedicineTallahassee, FL, USA
| | - Andrew P. Landstrom
- Section of Pediatric Cardiology, Department of Pediatrics, Baylor College of MedicineHouston, TX, USA
| | - P. Bryant Chase
- Department of Biological Science, Florida State UniversityTallahassee, FL, USA
| | - Jose R. Pinto
- Department of Biomedical Sciences, Florida State University College of MedicineTallahassee, FL, USA
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Nguyen S, Siu R, Dewey S, Cui Z, Gomes AV. Amino Acid Changes at Arginine 204 of Troponin I Result in Increased Calcium Sensitivity of Force Development. Front Physiol 2016; 7:520. [PMID: 27895589 PMCID: PMC5108889 DOI: 10.3389/fphys.2016.00520] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 10/20/2016] [Indexed: 11/26/2022] Open
Abstract
Mutations in human cardiac troponin I (cTnI) have been associated with restrictive, dilated, and hypertrophic cardiomyopathies. The most commonly occurring residue on cTnI associated with familial hypertrophic cardiomyopathy (FHC) is arginine (R), which is also the most common residue at which multiple mutations occur. Two FHC mutations are known to occur at cTnI arginine 204, R204C and R204H, and both are associated with poor clinical prognosis. The R204H mutation has also been associated with restrictive cardiomyopathy (RCM). To characterize the effects of different mutations at the same residue (R204) on the physiological function of cTnI, six mutations at R204 (C, G, H, P, Q, W) were investigated in skinned fiber studies. Skinned fiber studies showed that all tested mutations at R204 caused significant increases in Ca2+ sensitivity of force development (ΔpCa50 = 0.22–0.35) when compared to wild-type (WT) cTnI. Investigation of the interactions between the cTnI mutants and WT cardiac troponin C (cTnC) or WT cardiac troponin T (cTnT) showed that all the mutations investigated, except R204G, affected either or both cTnI:cTnT and cTnI:cTnC interactions. The R204H mutation affected both cTnI:cTnT and cTnI:cTnC interactions while the R204C mutation affected only the cTnI:cTnC interaction. These results suggest that different mutations at the same site on cTnI could have varying effects on thin filament interactions. A mutation in fast skeletal TnI (R174Q, homologous to cTnI R204Q) also significantly increased Ca2+ sensitivity of force development (ΔpCa50 = 0.16). Our studies indicate that known cTnI mutations associated with poor prognosis (R204C and R204H) exhibit large increases in Ca2+ sensitivity of force development. Therefore, other R204 mutations that cause similar increases in Ca2+ sensitivity are also likely to have poor prognoses.
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Affiliation(s)
- Susan Nguyen
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis Davis, CA, USA
| | - Rylie Siu
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis Davis, CA, USA
| | - Shannamar Dewey
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis Davis, CA, USA
| | - Ziyou Cui
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis Davis, CA, USA
| | - Aldrin V Gomes
- Department of Neurobiology, Physiology, and Behavior, University of California, DavisDavis, CA, USA; Department of Physiology and Membrane Biology, University of California, DavisDavis, CA, USA
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25
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Zhu C, Chen Z, Guo W. Pre-mRNA mis-splicing of sarcomeric genes in heart failure. Biochim Biophys Acta Mol Basis Dis 2016; 1863:2056-2063. [PMID: 27825848 DOI: 10.1016/j.bbadis.2016.11.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Revised: 10/11/2016] [Accepted: 11/01/2016] [Indexed: 12/01/2022]
Abstract
Pre-mRNA splicing is an important biological process that allows production of multiple proteins from a single gene in the genome, and mainly contributes to protein diversity in eukaryotic organisms. Alternative splicing is commonly governed by RNA binding proteins to meet the ever-changing demands of the cell. However, the mis-splicing may lead to human diseases. In the heart of human, mis-regulation of alternative splicing has been associated with heart failure. In this short review, we focus on alternative splicing of sarcomeric genes and review mis-splicing related heart failure with relatively well studied Sarcomeric genes and splicing mechanisms with identified regulatory factors. The perspective of alternative splicing based therapeutic strategies in heart failure has also been discussed.
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Affiliation(s)
- Chaoqun Zhu
- Animal Science, College of Agriculture and Natural Resources, University of Wyoming, Laramie, WY 82071, USA
| | - Zhilong Chen
- Animal Science, College of Agriculture and Natural Resources, University of Wyoming, Laramie, WY 82071, USA; College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Wei Guo
- Animal Science, College of Agriculture and Natural Resources, University of Wyoming, Laramie, WY 82071, USA
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26
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Marques MDA, de Oliveira GAP. Cardiac Troponin and Tropomyosin: Structural and Cellular Perspectives to Unveil the Hypertrophic Cardiomyopathy Phenotype. Front Physiol 2016; 7:429. [PMID: 27721798 PMCID: PMC5033975 DOI: 10.3389/fphys.2016.00429] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 09/09/2016] [Indexed: 12/12/2022] Open
Abstract
Inherited myopathies affect both skeletal and cardiac muscle and are commonly associated with genetic dysfunctions, leading to the production of anomalous proteins. In cardiomyopathies, mutations frequently occur in sarcomeric genes, but the cause-effect scenario between genetic alterations and pathological processes remains elusive. Hypertrophic cardiomyopathy (HCM) was the first cardiac disease associated with a genetic background. Since the discovery of the first mutation in the β-myosin heavy chain, more than 1400 new mutations in 11 sarcomeric genes have been reported, awarding HCM the title of the “disease of the sarcomere.” The most common macroscopic phenotypes are left ventricle and interventricular septal thickening, but because the clinical profile of this disease is quite heterogeneous, these phenotypes are not suitable for an accurate diagnosis. The development of genomic approaches for clinical investigation allows for diagnostic progress and understanding at the molecular level. Meanwhile, the lack of accurate in vivo models to better comprehend the cellular events triggered by this pathology has become a challenge. Notwithstanding, the imbalance of Ca2+ concentrations, altered signaling pathways, induction of apoptotic factors, and heart remodeling leading to abnormal anatomy have already been reported. Of note, a misbalance of signaling biomolecules, such as kinases and tumor suppressors (e.g., Akt and p53), seems to participate in apoptotic and fibrotic events. In HCM, structural and cellular information about defective sarcomeric proteins and their altered interactome is emerging but still represents a bottleneck for developing new concepts in basic research and for future therapeutic interventions. This review focuses on the structural and cellular alterations triggered by HCM-causing mutations in troponin and tropomyosin proteins and how structural biology can aid in the discovery of new platforms for therapeutics. We highlight the importance of a better understanding of allosteric communications within these thin-filament proteins to decipher the HCM pathological state.
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Affiliation(s)
- Mayra de A Marques
- Programa de Biologia Estrutural, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica Leopoldo de Meis, Instituto Nacional de Biologia Estrutural e Bioimagem, Universidade Federal do Rio de Janeiro Rio de Janeiro, Brazil
| | - Guilherme A P de Oliveira
- Programa de Biologia Estrutural, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica Leopoldo de Meis, Instituto Nacional de Biologia Estrutural e Bioimagem, Universidade Federal do Rio de Janeiro Rio de Janeiro, Brazil
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27
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Gilda JE, Xu Q, Martinez ME, Nguyen ST, Chase PB, Gomes AV. The functional significance of the last 5 residues of the C-terminus of cardiac troponin I. Arch Biochem Biophys 2016; 601:88-96. [PMID: 26919894 PMCID: PMC4899223 DOI: 10.1016/j.abb.2016.02.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 02/06/2016] [Accepted: 02/22/2016] [Indexed: 11/15/2022]
Abstract
The C-terminal region of cardiac troponin I (cTnI) is known to be important in cardiac function, as removal of the last 17 C-terminal residues of human cTnI has been associated with myocardial stunning. To investigate the C-terminal region of cTnI, three C-terminal deletion mutations in human cTnI were generated: Δ1 (deletion of residue 210), Δ3 (deletion of residues 208-210), and Δ5 (deletion of residues 206-210). Mammalian two-hybrid studies showed that the interactions between cTnI mutants and cardiac troponin C (cTnC) or cardiac troponin T (cTnT) were impaired in Δ3 and Δ5 mutants when compared to wild-type cTnI. Troponin complexes containing 2-[4'-(iodoacetamido) anilino] naphthalene-6-sulfonic acid (IAANS) labeled cTnC showed that the troponin complex containing cTnI Δ5 had a small increase in Ca(2+) affinity (P < 0.05); while the cTnI Δ1- and Δ3 troponin complexes showed no difference in Ca(2+) affinity when compared to wild-type troponin. In vitro motility assays showed that all truncation mutants had increased Ca(2+) dependent motility relative to wild-type cTnI. These results suggest that the last 5 C-terminal residues of cTnI influence the binding of cTnI with cTnC and cTnT and affect the Ca(2+) dependence of filament sliding, and demonstrate the importance of this region of cTnI.
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Affiliation(s)
- Jennifer E Gilda
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, 95616, USA
| | - Qian Xu
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, 95616, USA
| | - Margaret E Martinez
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Susan T Nguyen
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, 95616, USA
| | - P Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Aldrin V Gomes
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, 95616, USA.
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28
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Lu S, Yin X. Overexpression of Dyrk1A regulates cardiac troponin T splicing in cells and mice. Biochem Biophys Res Commun 2016; 473:993-998. [PMID: 27049307 DOI: 10.1016/j.bbrc.2016.04.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 04/01/2016] [Indexed: 11/15/2022]
Abstract
The human heart expresses four isoforms of cardiac troponin T (cTnT) through alternative splicing of exons 4 and 5 of the cTnT gene. Alternative splicing of cTnT exon 5 is developmentally regulated. cTnT isoforms containing exon 5 are expressed in the fetal and neonatal heart but not in the mature heart. SRp55 is an essential splicing factor involved in cTnT exon 5 splicing and it is phosphorylated by Dyrk1A (dual specificity tyrosine phosphorylation regulated kinase 1A). In the present study, we found Dyrk1A interacted with SRp55 and enhanced its promotion of cTnT exon 5 inclusion. The shift from cTnT exon 5 inclusion to exclusion during development was delayed in the heart of Ts65Dn mice due to Dyrk1A overexpression. These results provide new insight into the role of Dyrk1A in the neonatal cardiac development.
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Affiliation(s)
- Shu Lu
- Department of Intensive Care Unit, Affiliated Hospital of Nantong University, Nantong, Jiangsu, 226001, PR China
| | - Xiaomin Yin
- Department of Biochemistry, Medical School, Nantong University, Nantong, Jiangsu, 226001, PR China; Department of Pharmacology, Xuanwu Hospital of Capital Medical University, Beijing 100053, PR China.
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Ladd AN. New Insights Into the Role of RNA-Binding Proteins in the Regulation of Heart Development. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 324:125-85. [PMID: 27017008 DOI: 10.1016/bs.ircmb.2015.12.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The regulation of gene expression during development takes place both at the transcriptional and posttranscriptional levels. RNA-binding proteins (RBPs) regulate pre-mRNA processing, mRNA localization, stability, and translation. Many RBPs are expressed in the heart and have been implicated in heart development, function, or disease. This chapter will review the current knowledge about RBPs in the developing heart, focusing on those that regulate posttranscriptional gene expression. The involvement of RBPs at each stage of heart development will be considered in turn, including the establishment of specific cardiac cell types and formation of the primitive heart tube, cardiac morphogenesis, and postnatal maturation and aging. The contributions of RBPs to cardiac birth defects and heart disease will also be considered in these contexts. Finally, the interplay between RBPs and other regulatory factors in the developing heart, such as transcription factors and miRNAs, will be discussed.
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Affiliation(s)
- A N Ladd
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States of America.
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30
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Jin JP. Evolution, Regulation, and Function of N-terminal Variable Region of Troponin T: Modulation of Muscle Contractility and Beyond. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 321:1-28. [DOI: 10.1016/bs.ircmb.2015.09.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Zhang T, Taylor J, Jiang Y, Pereyra AS, Messi ML, Wang ZM, Hereñú C, Delbono O. Troponin T3 regulates nuclear localization of the calcium channel Cavβ1a subunit in skeletal muscle. Exp Cell Res 2015; 336:276-86. [PMID: 25981458 DOI: 10.1016/j.yexcr.2015.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 05/06/2015] [Indexed: 11/24/2022]
Abstract
The voltage-gated calcium channel (Cav) β1a subunit (Cavβ1a) plays an important role in excitation-contraction coupling (ECC), a process in the myoplasm that leads to muscle-force generation. Recently, we discovered that the Cavβ1a subunit travels to the nucleus of skeletal muscle cells where it helps to regulate gene transcription. To determine how it travels to the nucleus, we performed a yeast two-hybrid screening of the mouse fast skeletal muscle cDNA library and identified an interaction with troponin T3 (TnT3), which we subsequently confirmed by co-immunoprecipitation and co-localization assays in mouse skeletal muscle in vivo and in cultured C2C12 muscle cells. Interacting domains were mapped to the leucine zipper domain in TnT3 COOH-terminus (160-244 aa) and Cavβ1a NH2-terminus (1-99 aa), respectively. The double fluorescence assay in C2C12 cells co-expressing TnT3/DsRed and Cavβ1a/YFP shows that TnT3 facilitates Cavβ1a nuclear recruitment, suggesting that the two proteins play a heretofore unknown role during early muscle differentiation in addition to their classical role in ECC regulation.
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Affiliation(s)
- Tan Zhang
- Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
| | - Jackson Taylor
- Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
| | - Yang Jiang
- Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
| | - Andrea S Pereyra
- Department of Histology, National University of La Plata, 1900 La Plata, Argentina
| | - Maria Laura Messi
- Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
| | - Zhong-Min Wang
- Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
| | - Claudia Hereñú
- Department of Histology, National University of La Plata, 1900 La Plata, Argentina
| | - Osvaldo Delbono
- Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA; Neuroscience Program, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA.
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Dubois-Deruy E, Belliard A, Mulder P, Bouvet M, Smet-Nocca C, Janel S, Lafont F, Beseme O, Amouyel P, Richard V, Pinet F. Interplay between troponin T phosphorylation and O-N-acetylglucosaminylation in ischaemic heart failure. Cardiovasc Res 2015; 107:56-65. [PMID: 25916824 DOI: 10.1093/cvr/cvv136] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 04/15/2015] [Indexed: 11/13/2022] Open
Abstract
AIMS Previous studies have reported that decreased serine 208 phosphorylation of troponin T (TnTpSer208) is associated with ischaemic heart failure (HF), but the molecular mechanisms and functional consequences of these changes are unknown. The aim of this study was to characterize the balance between serine phosphorylation and O-N-acetylglucosaminylation (O-GlcNAcylation) of TnT in HF, its mechanisms, and the consequences of modulating these post-translational modifications. METHODS AND RESULTS Decreased TnTpSer208 levels in the left ventricles of HF male Wistar rats were associated with reduced expression of PKCε but not of other cardiac PKC isoforms. In both isolated perfused rat hearts and cultured neonatal cardiomyocytes, the PKCε inhibitor εV1-2 decreased TnTpSer208 and simultaneously decreased cardiac contraction in isolated hearts and beating amplitude in neonatal cardiomyocytes (measured by atomic force microscopy). Down-regulating PKCε by silencing RNA (siRNA) also reduced TnTpSer208 in these cardiomyocytes, and PKCε-/- mice had lower TnTpSer208 levels than the wild-type. In parallel, HF increased TnT O-GlcNAcylation via both increased O-GlcNAc transferase and decreased O-GlcNAcase activity. Increasing O-GlcNAcylation (via O-GlcNAcase inhibition with Thiamet G) decreased TnTpSer208 in isolated hearts, while reducing O-GlcNAcylation (O-GlcNAc transferase siRNA) increased TnTpSer208 in neonatal cardiomyocytes. Mass spectrometry and NMR analysis identified O-GlcNAcylation of TnT on Ser190. CONCLUSION These data demonstrate interplay between Ser208 phosphorylation and Ser190 O-GlcNAcylation of TnT in ischaemic HF, linked to decreased activity of both PKCε and O-GlcNAcase and increased O-GlcNAc transferase activity. Modulation of these post-translational modifications of TnT may be a new therapeutic strategy in HF.
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Affiliation(s)
- Emilie Dubois-Deruy
- INSERM, U1167, 1 rue du Professeur Calmette, Lille, France Institut Pasteur de Lille, Lille, France University of Lille Nord de France, Lille, France
| | - Aude Belliard
- INSERM, U1167, 1 rue du Professeur Calmette, Lille, France Institut Pasteur de Lille, Lille, France University of Lille Nord de France, Lille, France
| | - Paul Mulder
- Inserm U1096, Rouen, France Institute for Research and Innovation in Biomedicine, University of Rouen, Rouen, France
| | - Marion Bouvet
- INSERM, U1167, 1 rue du Professeur Calmette, Lille, France Institut Pasteur de Lille, Lille, France University of Lille Nord de France, Lille, France
| | - Caroline Smet-Nocca
- University of Lille Nord de France, Lille, France CNRS UMR 8576, Villeneuve D'Ascq, France
| | | | - Frank Lafont
- Institut Pasteur de Lille, Lille, France University of Lille Nord de France, Lille, France Bioimaging Center Lille Nord de France, Lille, France CNRS UMR 8204, INSERM U1019, Lille, France
| | - Olivia Beseme
- INSERM, U1167, 1 rue du Professeur Calmette, Lille, France Institut Pasteur de Lille, Lille, France University of Lille Nord de France, Lille, France
| | - Philippe Amouyel
- INSERM, U1167, 1 rue du Professeur Calmette, Lille, France Institut Pasteur de Lille, Lille, France University of Lille Nord de France, Lille, France Centre Hospitalier Régional et Universitaire de Lille, Lille, France
| | - Vincent Richard
- Inserm U1096, Rouen, France Institute for Research and Innovation in Biomedicine, University of Rouen, Rouen, France
| | - Florence Pinet
- INSERM, U1167, 1 rue du Professeur Calmette, Lille, France Institut Pasteur de Lille, Lille, France University of Lille Nord de France, Lille, France
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Weeland CJ, van den Hoogenhof MM, Beqqali A, Creemers EE. Insights into alternative splicing of sarcomeric genes in the heart. J Mol Cell Cardiol 2015; 81:107-13. [PMID: 25683494 DOI: 10.1016/j.yjmcc.2015.02.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 01/15/2015] [Accepted: 02/05/2015] [Indexed: 12/14/2022]
Abstract
Driven by rapidly evolving technologies in next-generation sequencing, alternative splicing has emerged as a crucial layer in gene expression, greatly expanding protein diversity and governing complex biological processes in the cardiomyocyte. At the core of cardiac contraction, the physical properties of the sarcomere are carefully orchestrated through alternative splicing to fit the varying demands on the heart. By the recent discovery of RBM20 and RBM24, two major heart and skeletal muscle-restricted splicing factors, it became evident that alternative splicing events in the heart occur in regulated networks rather than in isolated events. Analysis of knockout mice of these splice factors has shed light on the importance of these fundamental processes in the heart. In this review, we discuss recent advances in our understanding of the role and regulation of alternative splicing in the developing and diseased heart, specifically within the sarcomere. Through various examples (titin, myomesin, troponin T, tropomyosin and LDB3) we illustrate how alternative splicing regulates the functional properties of the sarcomere. Finally, we evaluate opportunities and obstacles to modulate alternative splicing in therapeutic approaches for cardiac disease.
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Affiliation(s)
- Cornelis J Weeland
- Experimental Cardiology, Academic Medical Center, Meibergdreef 15, 1105AZ Amsterdam, The Netherlands
| | | | - Abdelaziz Beqqali
- Experimental Cardiology, Academic Medical Center, Meibergdreef 15, 1105AZ Amsterdam, The Netherlands
| | - Esther E Creemers
- Experimental Cardiology, Academic Medical Center, Meibergdreef 15, 1105AZ Amsterdam, The Netherlands.
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34
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Gupte TM, Haque F, Gangadharan B, Sunitha MS, Mukherjee S, Anandhan S, Rani DS, Mukundan N, Jambekar A, Thangaraj K, Sowdhamini R, Sommese RF, Nag S, Spudich JA, Mercer JA. Mechanistic heterogeneity in contractile properties of α-tropomyosin (TPM1) mutants associated with inherited cardiomyopathies. J Biol Chem 2014; 290:7003-15. [PMID: 25548289 DOI: 10.1074/jbc.m114.596676] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The most frequent known causes of primary cardiomyopathies are mutations in the genes encoding sarcomeric proteins. Among those are 30 single-residue mutations in TPM1, the gene encoding α-tropomyosin. We examined seven mutant tropomyosins, E62Q, D84N, I172T, L185R, S215L, D230N, and M281T, that were chosen based on their clinical severity and locations along the molecule. The goal of our study was to determine how the biochemical characteristics of each of these mutant proteins are altered, which in turn could provide a structural rationale for treatment of the cardiomyopathies they produce. Measurements of Ca(2+) sensitivity of human β-cardiac myosin ATPase activity are consistent with the hypothesis that hypertrophic cardiomyopathies are hypersensitive to Ca(2+) activation, and dilated cardiomyopathies are hyposensitive. We also report correlations between ATPase activity at maximum Ca(2+) concentrations and conformational changes in TnC measured using a fluorescent probe, which provide evidence that different substitutions perturb the structure of the regulatory complex in different ways. Moreover, we observed changes in protein stability and protein-protein interactions in these mutants. Our results suggest multiple mechanistic pathways to hypertrophic and dilated cardiomyopathies. Finally, we examined a computationally designed mutant, E181K, that is hypersensitive, confirming predictions derived from in silico structural analysis.
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Affiliation(s)
- Tejas M Gupte
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Farah Haque
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Binnu Gangadharan
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the Manipal University, Madhav Nagar, Manipal 576104, India
| | - Margaret S Sunitha
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Souhrid Mukherjee
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Swetha Anandhan
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Deepa Selvi Rani
- the Council for Scientific and Industrial Research-Centre for Cellular and Molecular Biology, Hyderabad 500007, India
| | - Namita Mukundan
- the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Amruta Jambekar
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Kumarasamy Thangaraj
- the Council for Scientific and Industrial Research-Centre for Cellular and Molecular Biology, Hyderabad 500007, India
| | - Ramanathan Sowdhamini
- the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Ruth F Sommese
- the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and
| | - Suman Nag
- the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and
| | - James A Spudich
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and
| | - John A Mercer
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the McLaughlin Research Institute, Great Falls, Montana 59405
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35
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Chang AN, Greenfield NJ, Singh A, Potter JD, Pinto JR. Structural and protein interaction effects of hypertrophic and dilated cardiomyopathic mutations in alpha-tropomyosin. Front Physiol 2014; 5:460. [PMID: 25520664 PMCID: PMC4251307 DOI: 10.3389/fphys.2014.00460] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Accepted: 11/10/2014] [Indexed: 12/16/2022] Open
Abstract
The potential alterations to structure and associations with thin filament proteins caused by the dilated cardiomyopathy (DCM) associated tropomyosin (Tm) mutants E40K and E54K, and the hypertrophic cardiomyopathy (HCM) associated Tm mutants E62Q and L185R, were investigated. In order to ascertain what the cause of the known functional effects may be, structural and protein-protein interaction studies were conducted utilizing actomyosin ATPase activity measurements and spectroscopy. In actomyosin ATPase measurements, both HCM mutants and the DCM mutant E54K caused increases in Ca2+-induced maximal ATPase activities, while E40K caused a decrease. Investigation of Tm's ability to inhibit actomyosin ATPase in the absence of troponin showed that HCM-associated mutant Tms did not inhibit as well as wildtype, whereas the DCM associated mutant E40K inhibited better. E54K did not inhibit the actomyosin ATPase activity at any concentration of Tm tested. Thermal denaturation studies by circular dichroism and molecular modeling of the mutations in Tm showed that in general, the DCM mutants caused localized destabilization of the Tm dimers, while the HCM mutants resulted in increased stability. These findings demonstrate that the structural alterations in Tm observed here may affect the regulatory function of Tm on actin, thereby directly altering the ATPase rates of myosin.
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Affiliation(s)
- Audrey N Chang
- Department of Molecular and Cellular Pharmacology, Leonard Miller School of Medicine, University of Miami Miami, FL, USA
| | - Norma J Greenfield
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University New Jersey, NJ, USA
| | - Abhishek Singh
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University New Jersey, NJ, USA ; Department of Cardiology, UCSF Medical Center, University of California, San Francisco San Francisco, CA, USA
| | - James D Potter
- Department of Molecular and Cellular Pharmacology, Leonard Miller School of Medicine, University of Miami Miami, FL, USA
| | - Jose R Pinto
- Department of Biomedical Sciences, Florida State University College of Medicine Tallahassee, FL, USA
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36
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Zhang T, Choi SJ, Wang ZM, Birbrair A, Messi ML, Jin JP, Marsh AP, Nicklas B, Delbono O. Human slow troponin T (TNNT1) pre-mRNA alternative splicing is an indicator of skeletal muscle response to resistance exercise in older adults. J Gerontol A Biol Sci Med Sci 2014; 69:1437-47. [PMID: 24368775 PMCID: PMC4296115 DOI: 10.1093/gerona/glt204] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 11/14/2013] [Indexed: 12/25/2022] Open
Abstract
Slow skeletal muscle troponin T (TNNT1) pre-messenger RNA alternative splicing (AS) provides transcript diversity and increases the variety of proteins the gene encodes. Here, we identified three major TNNT1 splicing patterns (AS1-3), quantified their expression in the vastus lateralis muscle of older adults, and demonstrated that resistance training modifies their relative abundance; specifically, upregulating AS1 and downregulating AS2 and AS3. In addition, abundance of TNNT1 AS2 correlated negatively with single muscle fiber-specific force after resistance training, while abundance of AS1 correlated negatively with V max. We propose that TNNT1 AS1, AS2 and the AS1/AS2 ratio are potential quantitative biomarkers of skeletal muscle adaptation to resistance training in older adults, and that their profile reflects enhanced single fiber muscle force in the absence of significant increases in fiber cross-sectional area.
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Affiliation(s)
- Tan Zhang
- Section on Gerontology and Geriatric Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Seung Jun Choi
- Section on Gerontology and Geriatric Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina. Present address: Division of Sports and Health, KyungSung University, Busan, South Korea
| | - Zhong-Min Wang
- Section on Gerontology and Geriatric Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Alexander Birbrair
- Section on Gerontology and Geriatric Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - María L Messi
- Section on Gerontology and Geriatric Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Jian-Ping Jin
- Department of Physiology, Wayne State University School of Medicine
| | - Anthony P Marsh
- Department of Health and Exercise Science, Wake Forest University, Winston-Salem, North Carolina
| | - Barbara Nicklas
- Section on Gerontology and Geriatric Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina. J Paul Sticht Center on Aging, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Osvaldo Delbono
- Section on Gerontology and Geriatric Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina. J Paul Sticht Center on Aging, Wake Forest School of Medicine, Winston-Salem, North Carolina.
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37
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Parvatiyar MS, Pinto JR. Pathogenesis associated with a restrictive cardiomyopathy mutant in cardiac troponin T is due to reduced protein stability and greatly increased myofilament Ca2+ sensitivity. Biochim Biophys Acta Gen Subj 2014; 1850:365-72. [PMID: 25450489 DOI: 10.1016/j.bbagen.2014.09.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 09/12/2014] [Accepted: 09/15/2014] [Indexed: 01/21/2023]
Abstract
BACKGROUND Dilated and hypertrophic cardiomyopathy mutations in troponin can blunt effects of protein kinase A (PKA) phosphorylation of cardiac troponin I (cTnI), decreasing myofilament Ca2+-sensitivity; however this effect has never been tested for restrictive cardiomyopathy (RCM) mutants. This study explores whether an RCM cardiac troponin T mutant (cTnT-ΔE96) interferes with convergent PKA regulation and if TnT instability contributes to greatly enhanced Ca2+-sensitivity in skinned fibers. METHODS Force of contraction in skinned cardiac porcine fiber and spectroscopic studies were performed. RESULTS A decrease of -0.26 and -0.25 pCa units in Ca2+-sensitivity of contraction after PKA incubation was observed for skinned fibers incorporated with WT or cTnT-ΔE96, respectively. To further assess whether cTnT-ΔE96 interferes solely with transmission of cTnI phosphorylation effects, skinned fibers were reconstituted with PKA pseudo-phosphorylated cTnI (cTnI-SS/DD.cTnC). Fibers displaced with cTnT-WT, reconstituted with cTnI-SS/DD.cTnC decreased Ca2+-sensitivity of force (pCa50=5.61) compared to control cTnI-WT.cTnC (pCa50=5.75), similarly affecting cTnT-ΔE96 (pCa50=6.03) compared to control \cTnI-WT.cTnC (pCa50=6.14). Fluorescence studies measuring cTnC(IAANS) Ca2+-affinity changes due to cTnT-ΔE96 indicated that higher complexity (thin filament) better recapitulates skinned fiber Ca2+ sensitive changes. Circular dichroism revealed reduced α-helicity and earlier thermal unfolding for cTnT-ΔE96 compared to WT. CONCLUSIONS Although ineffective in decreasing myofilament Ca2+-sensitivity to normal levels, cTnT-ΔE96 does not interfere with PKA cTnI phosphorylation mediated effects; 2) cTnT-ΔE96 requires actin to increase cTnC Ca2+-affinity; and 3) deletion of E96 reduces cTnT stability, likely disrupting crucial thin filament interactions. GENERAL SIGNIFICANCE The pathological effect of cTnT-ΔE96 is largely manifested by dramatic myofilament Ca2+-sensitization which still persists even after PKA phosphorylation mediated Ca2+-desensitization.
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Affiliation(s)
- Michelle S Parvatiyar
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Jose Renato Pinto
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL 32306, USA.
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38
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Sheng JJ, Jin JP. Gene regulation, alternative splicing, and posttranslational modification of troponin subunits in cardiac development and adaptation: a focused review. Front Physiol 2014; 5:165. [PMID: 24817852 PMCID: PMC4012202 DOI: 10.3389/fphys.2014.00165] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 04/10/2014] [Indexed: 12/19/2022] Open
Abstract
Troponin plays a central role in regulating the contraction and relaxation of vertebrate striated muscles. This review focuses on the isoform gene regulation, alternative RNA splicing, and posttranslational modifications of troponin subunits in cardiac development and adaptation. Transcriptional and posttranscriptional regulations such as phosphorylation and proteolysis modifications, and structure-function relationships of troponin subunit proteins are summarized. The physiological and pathophysiological significances are discussed for impacts on cardiac muscle contractility, heart function, and adaptations in health and diseases.
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Affiliation(s)
- Juan-Juan Sheng
- Department of Physiology, Wayne State University School of Medicine Detroit, MI, USA
| | - Jian-Ping Jin
- Department of Physiology, Wayne State University School of Medicine Detroit, MI, USA
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39
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Complex tropomyosin and troponin T isoform expression patterns in orbital and global fibers of adult dog and rat extraocular muscles. J Muscle Res Cell Motil 2013; 34:211-31. [PMID: 23700265 DOI: 10.1007/s10974-013-9346-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 05/02/2013] [Indexed: 12/12/2022]
Abstract
We reported marked differences in the myosin heavy and light chain (MHC and MLC) isoform composition of fast and slow fibers between the global and orbital layers of dog extraocular muscles. Many dog extraocular fibers, especially orbital fibers, have MHC and MLC isoform patterns that are distinct from those in limb skeletal muscles. Additional observations suggested possible differences in the tropomyosin (Tm) and troponin T (TnT) isoform composition of global and orbital fibers. Therefore, we tested, using SDS-PAGE and immunoblotting, whether differences in Tm and TnT isoform expression do, in fact, exist between global and orbital layers of dog and rat EOMs and to compare expression patterns among identified fast and slow single fibers from both muscle layers. The Tm isoforms expressed in global fast and slow fibers are the same as in limb fast (α-Tm and β-Tm) and slow (γ-Tm and β-Tm) fibers, respectively. Orbital slow orbital fibers, on the other hand, each co-express all three sarcomeric Tm isoforms (α, β and γ). The results indicate that fast global and orbital fibers express only fast isoforms of TnT, but the relative amounts of the individual isoforms are different from those in limb fast muscle fibers and an abundant fast TnT isoform in the orbital layer was not detected in fast limb muscles. Slow fibers in both layers express slow TnT isoforms and the relative amounts also differ from those in limb slow fibers. Unexpectedly, significant amounts of cardiac TnT isoforms were also detected in slow fibers, especially in the orbital layer in both species. TnI and TnC isoform patterns are the same as in fast and slow fibers in limb muscles. These results expand the understanding of the elaborate diversity in contractile protein isoform expression in mammalian extraocular muscle fibers and suggest that major differences in calcium-activation properties exist among these fibers, based upon Tm and TnT isoform expression patterns.
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40
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Lu QW, Wu XY, Morimoto S. Inherited cardiomyopathies caused by troponin mutations. JOURNAL OF GERIATRIC CARDIOLOGY : JGC 2013; 10:91-101. [PMID: 23610579 PMCID: PMC3627712 DOI: 10.3969/j.issn.1671-5411.2013.01.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 11/13/2012] [Accepted: 01/30/2013] [Indexed: 01/25/2023]
Abstract
Genetic investigations of cardiomyopathy in the recent two decades have revealed a large number of mutations in the genes encoding sarcomeric proteins as a cause of inherited hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), or restrictive cardiomyopathy (RCM). Most functional analyses of the effects of mutations on cardiac muscle contraction have revealed significant changes in the Ca(2+)-regulatory mechanism, in which cardiac troponin (cTn) plays important structural and functional roles as a key regulatory protein. Over a hundred mutations have been identified in all three subunits of cTn, i.e., cardiac troponins T, I, and C. Recent studies on cTn mutations have provided plenty of evidence that HCM- and RCM-linked mutations increase cardiac myofilament Ca(2+) sensitivity, while DCM-linked mutations decrease it. This review focuses on the functional consequences of mutations found in cTn in terms of cardiac myofilament Ca(2+) sensitivity, ATPase activity, force generation, and cardiac troponin I phosphorylation, to understand potential molecular and cellular pathogenic mechanisms of the three types of inherited cardiomyopathy.
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Affiliation(s)
- Qun-Wei Lu
- Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan 430074, China
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Zhang T, Birbrair A, Wang ZM, Taylor J, Messi ML, Delbono O. Troponin T nuclear localization and its role in aging skeletal muscle. AGE (DORDRECHT, NETHERLANDS) 2013; 35:353-370. [PMID: 22189912 PMCID: PMC3592954 DOI: 10.1007/s11357-011-9368-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 12/08/2011] [Indexed: 05/31/2023]
Abstract
Troponin T (TnT) is known to mediate the interaction between Tn complex and tropomyosin (Tm), which is essential for calcium-activated striated muscle contraction. This regulatory function takes place in the myoplasm, where TnT binds Tm. However, recent findings of troponin I and Tm nuclear translocation in Drosophila and mammalian cells imply other roles for the Tn-Tm complex. We hypothesized that TnT plays a nonclassical role through nuclear translocation. Immunoblotting with different antibodies targeting the NH2- or COOH-terminal region uncovered a pool of fast skeletal muscle TnT3 localized in the nuclear fraction of mouse skeletal muscle as either an intact or fragmented protein. Construction of TnT3-DsRed fusion proteins led to the further observation that TnT3 fragments are closely related to nucleolus and RNA polymerase activity, suggesting a role for TnT3 in regulating transcription. Functionally, overexpression of TnT3 fragments produced significant defects in nuclear shape and caused high levels of apoptosis. Interestingly, nuclear TnT3 and its fragments were highly regulated by aging, thus creating a possible link between the deleterious effects of TnT3 and sarcopenia. We propose that changes in nuclear TnT3 and its fragments cause the number of myonuclei to decrease with age, contributing to muscle damage and wasting.
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Affiliation(s)
- Tan Zhang
- />Department of Internal Medicine-Gerontology and Geriatric Medicine, Wake Forest School of Medicine, 1 Medical Center Blvd., Winston-Salem, NC 27157 USA
| | - Alexander Birbrair
- />Department of Internal Medicine-Gerontology and Geriatric Medicine, Wake Forest School of Medicine, 1 Medical Center Blvd., Winston-Salem, NC 27157 USA
- />Neuroscience Program, Wake Forest School of Medicine, 1 Medical Center Blvd., Winston-Salem, NC 27157 USA
| | - Zhong-Min Wang
- />Department of Internal Medicine-Gerontology and Geriatric Medicine, Wake Forest School of Medicine, 1 Medical Center Blvd., Winston-Salem, NC 27157 USA
| | - Jackson Taylor
- />Department of Internal Medicine-Gerontology and Geriatric Medicine, Wake Forest School of Medicine, 1 Medical Center Blvd., Winston-Salem, NC 27157 USA
- />Neuroscience Program, Wake Forest School of Medicine, 1 Medical Center Blvd., Winston-Salem, NC 27157 USA
| | - María Laura Messi
- />Department of Internal Medicine-Gerontology and Geriatric Medicine, Wake Forest School of Medicine, 1 Medical Center Blvd., Winston-Salem, NC 27157 USA
| | - Osvaldo Delbono
- />Department of Internal Medicine-Gerontology and Geriatric Medicine, Wake Forest School of Medicine, 1 Medical Center Blvd., Winston-Salem, NC 27157 USA
- />Neuroscience Program, Wake Forest School of Medicine, 1 Medical Center Blvd., Winston-Salem, NC 27157 USA
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Pinto JR, Gomes AV, Jones MA, Liang J, Nguyen S, Miller T, Parvatiyar MS, Potter JD. The functional properties of human slow skeletal troponin T isoforms in cardiac muscle regulation. J Biol Chem 2012; 287:37362-70. [PMID: 22977240 PMCID: PMC3481333 DOI: 10.1074/jbc.m112.364927] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Revised: 08/17/2012] [Indexed: 11/06/2022] Open
Abstract
Human slow skeletal troponin T (HSSTnT) shares a high degree of homology with cardiac TnT (CTnT). Although the presence of HSSTnT has not been confirmed in the heart at the protein level, detectable levels of HSSTnT mRNA have been found. Whether HSSTnT isoforms are expressed transiently remains unknown. Because transient re-expression of HSSTnT may be a potential mechanism of regulating function, we explored the effect of HSSTnT on the regulation of cardiac muscle. At least three HSSTnT isoforms have been found to exist in slow skeletal muscle: HSSTnT1 (+exons 5 and 12), HSSTnT2 (+exon 5, -exon 12), and HSSTnT3 (-exons 5 and 12). Another isoform, HSSTnT hypothetical (Hyp) (-exon 5, +exon 12), has only been found at the mRNA level. Compared with HCTnT3 (adult isoform), Tn complexes containing HSSTnT1, -2, and -3 did not alter the actomyosin ATPase activation and inhibition in the presence and absence of Ca(2+), respectively. HSSTnTHyp was not evaluated as it did not form a Tn complex under a variety of conditions. Porcine papillary skinned fibers displaced with HSSTnT1, -2, or -3 and reconstituted with human cardiac troponin I and troponin C (HCTnI·TnC) complex showed a decrease in the Ca(2+) sensitivity of force development and an increase in maximal recovered force (HSSTnT1 and -3) compared with HCTnT3. In contrast, HSSTnTHyp showed an increase in the Ca(2+) sensitivity of force development. This suggests that re- or overexpression of specific SSTnT isoforms might have therapeutic potential in the failing heart because they increase the maximal force of contraction. In addition, circular dichroism and proteolytic digestion experiments revealed structural differences between HSSTnT isoforms and HCTnT3 and that HSSTnT1 is more susceptible to calpain and trypsin proteolysis than the other HSSTnTs. Overall, HSSTnT isoforms despite being homologues of CTnT may display distinct functional properties in muscle regulation.
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Affiliation(s)
- Jose Renato Pinto
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136, USA.
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43
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Gollapudi S, Mamidi R, Mallampalli S, Chandra M. The N-terminal extension of cardiac troponin T stabilizes the blocked state of cardiac thin filament. Biophys J 2012; 103:940-8. [PMID: 23009843 PMCID: PMC3433604 DOI: 10.1016/j.bpj.2012.07.035] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 06/25/2012] [Accepted: 07/09/2012] [Indexed: 11/21/2022] Open
Abstract
Cardiac troponin T (cTnT) is a key component of contractile regulatory proteins. cTnT is characterized by a ∼32 amino acid N-terminal extension (NTE), the function of which remains unknown. To understand its function, we generated a transgenic (TG) mouse line that expressed a recombinant chimeric cTnT in which the NTE of mouse cTnT was removed by replacing its 1-73 residues with the corresponding 1-41 residues of mouse fast skeletal TnT. Detergent-skinned papillary muscle fibers from non-TG (NTG) and TG mouse hearts were used to measure tension, ATPase activity, Ca(2+) sensitivity (pCa(50)) of tension, rate of tension redevelopment, dynamic muscle fiber stiffness, and maximal fiber shortening velocity at sarcomere lengths (SLs) of 1.9 and 2.3 μm. Ca(2+) sensitivity increased significantly in TG fibers at both short SL (pCa(50) of 5.96 vs. 5.62 in NTG fibers) and long SL (pCa(50) of 6.10 vs. 5.76 in NTG fibers). Maximal cross-bridge turnover and detachment kinetics were unaltered in TG fibers. Our data suggest that the NTE constrains cardiac thin filament activation such that the transition of the thin filament from the blocked to the closed state becomes less responsive to Ca(2+). Our finding has implications regarding the effect of tissue- and disease-related changes in cTnT isoforms on cardiac muscle function.
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Affiliation(s)
| | | | | | - Murali Chandra
- Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology, Washington State University, Pullman, Washington
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Parvatiyar MS, Landstrom AP, Figueiredo-Freitas C, Potter JD, Ackerman MJ, Pinto JR. A mutation in TNNC1-encoded cardiac troponin C, TNNC1-A31S, predisposes to hypertrophic cardiomyopathy and ventricular fibrillation. J Biol Chem 2012; 287:31845-55. [PMID: 22815480 DOI: 10.1074/jbc.m112.377713] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Defined as clinically unexplained hypertrophy of the left ventricle, hypertrophic cardiomyopathy (HCM) is traditionally understood as a disease of the cardiac sarcomere. Mutations in TNNC1-encoded cardiac troponin C (cTnC) are a relatively rare cause of HCM. Here, we report clinical and functional characterization of a novel TNNC1 mutation, A31S, identified in a pediatric HCM proband with multiple episodes of ventricular fibrillation and aborted sudden cardiac death. Diagnosed at age 5, the proband is family history-negative for HCM or sudden cardiac death, suggesting a de novo mutation. TnC-extracted cardiac skinned fibers were reconstituted with the cTnC-A31S mutant, which increased Ca(2+) sensitivity with no effect on the maximal contractile force generation. Reconstituted actomyosin ATPase assays with 50% cTnC-A31S:50% cTnC-WT demonstrated Ca(2+) sensitivity that was intermediate between 100% cTnC-A31S and 100% cTnC-WT, whereas the mutant increased the activation of the actomyosin ATPase without affecting the inhibitory qualities of the ATPase. The secondary structure of the cTnC mutant was evaluated by circular dichroism, which did not indicate global changes in structure. Fluorescence studies demonstrated increased Ca(2+) affinity in isolated cTnC, the troponin complex, thin filament, and to a lesser degree, thin filament with myosin subfragment 1. These results suggest that this mutation has a direct effect on the Ca(2+) sensitivity of the myofilament, which may alter Ca(2+) handling and contribute to the arrhythmogenesis observed in the proband. In summary, we report a novel mutation in the TNNC1 gene that is associated with HCM pathogenesis and may predispose to the pathogenesis of a fatal arrhythmogenic subtype of HCM.
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Affiliation(s)
- Michelle S Parvatiyar
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, Florida 33136, USA
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45
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Yu ZB, Wei H, Jin JP. Chronic coexistence of two troponin T isoforms in adult transgenic mouse cardiomyocytes decreased contractile kinetics and caused dilatative remodeling. Am J Physiol Cell Physiol 2012; 303:C24-32. [PMID: 22538236 DOI: 10.1152/ajpcell.00026.2012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Our previous in vivo and ex vivo studies suggested that coexistence of two or more troponin T (TnT) isoforms in adult cardiac muscle decreased cardiac function and efficiency (Huang QQ, Feng HZ, Liu J, Du J, Stull LB, Moravec CS, Huang X, Jin JP, Am J Physiol Cell Physiol 294: C213-C22, 2008; Feng HZ, Jin JP, Am J Physiol Heart Circ Physiol 299: H97-H105, 2010). Here we characterized Ca(2+)-regulated contractility of isolated adult cardiomyocytes from transgenic mice coexpressing a fast skeletal muscle TnT together with the endogenous cardiac TnT. Without the influence of extracellular matrix, coexistence of the two TnT isoforms resulted in lower shortening amplitude, slower shortening and relengthening velocities, and longer relengthening time. The level of resting cytosolic Ca(2+) was unchanged, but the peak Ca(2+) transient was lowered and the durations of Ca(2+) rising and decaying were longer in the transgenic mouse cardiomyocytes vs. the wild-type controls. Isoproterenol treatment diminished the differences in shortening amplitude and shortening and relengthening velocities, whereas the prolonged durations of relengthening and Ca(2+) transient in the transgenic cardiomyocytes remained. At rigor state, a result from depletion of Ca(2+), resting sarcomere length of the transgenic cardiomyocytes became shorter than that in wild-type cells. Inhibition of myosin motor diminished this effect of TnT function on cross bridges. The length but not width of transgenic cardiomyocytes was significantly increased compared with the wild-type controls, corresponding to longitudinal addition of sarcomeres and dilatative remodeling at the cellular level. These dominantly negative effects of normal fast TnT demonstrated that chronic coexistence of functionally distinct variants of TnT in adult cardiomyocytes reduces contractile performance with pathological consequences.
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Affiliation(s)
- Zhi-Bin Yu
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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Rani DS, Nallari P, Dhandapany PS, Tamilarasi S, Shah A, Archana V, AshokKumar M, Narasimhan C, Singh L, Thangaraj K. Cardiac Troponin T (TNNT2) mutations are less prevalent in Indian hypertrophic cardiomyopathy patients. DNA Cell Biol 2011; 31:616-24. [PMID: 22017532 DOI: 10.1089/dna.2011.1366] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We sought to determine the frequency of the genetic variations in the Troponin T (TNNT2) gene and its association in Indian cardiomyopathy patients. Sequencing of the entire TNNT2 gene in 162 hypertrophic cardiomyopathy (HCM) patients, along with 179 healthy controls, revealed a total of 15 variants. These included an A28V missense mutation, a novel single-nucleotide polymorphism (SNP) (g.7239;G→A) predicted to disturb the splicing significantly, three SNPs, rs3729547 (C→T), rs3729843 (G→A), rs3729842 (C→T), which were in high linkage disequilibrium, and a 5 bp polymorphism that skipped exon 4 during splicing, which was found to be significantly higher in HCM patients (del/del genotype, p=0.00011; deletion allele, p=0.00008). Further studies on the 5 bp polymorphism in 2092 randomly selected individuals belonging to 39 ethnic and endogamous populations from 19 states of India, and representing the major linguistic Indian families, revealed that the South and the Northwest Indians have a high frequency of 5 bp deletions. The missense mutations in TNNT2 are responsible for 15%-20% of familial HCM by impairing the function of the heart muscle. However, other than the 5 bp polymorphism, our comprehensive study on the Indian HCM patients have lowered the occurrence and overall prevalence of supposedly more aggressive and worst disease causing percentage of missense mutations in TNNT2 dramatically.
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Affiliation(s)
- Deepa Selvi Rani
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India
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47
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Pinto JR, Siegfried JD, Parvatiyar MS, Li D, Norton N, Jones MA, Liang J, Potter JD, Hershberger RE. Functional characterization of TNNC1 rare variants identified in dilated cardiomyopathy. J Biol Chem 2011; 286:34404-12. [PMID: 21832052 PMCID: PMC3190822 DOI: 10.1074/jbc.m111.267211] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Revised: 07/12/2011] [Indexed: 11/06/2022] Open
Abstract
TNNC1, which encodes cardiac troponin C (cTnC), remains elusive as a dilated cardiomyopathy (DCM) gene. Here, we report the clinical, genetic, and functional characterization of four TNNC1 rare variants (Y5H, M103I, D145E, and I148V), all previously reported by us in association with DCM (Hershberger, R. E., Norton, N., Morales, A., Li, D., Siegfried, J. D., and Gonzalez-Quintana, J. (2010) Circ. Cardiovasc. Genet. 3, 155-161); in the previous study, two variants (Y5H and D145E) were identified in subjects who also carried MYH7 and MYBPC3 rare variants, respectively. Functional studies using the recombinant human mutant cTnC proteins reconstituted into porcine papillary skinned fibers showed decreased Ca(2+) sensitivity of force development (Y5H and M103I). Furthermore, the cTnC mutants diminished (Y5H and I148V) or abolished (M103I) the effects of PKA phosphorylation on Ca(2+) sensitivity. Only M103I decreased the troponin activation properties of the actomyosin ATPase when Ca(2+) was present. CD spectroscopic studies of apo (absence of divalent cations)-, Mg(2+)-, and Ca(2+)/Mg(2+)-bound states indicated that all of the cTnC mutants (except I148V in the Ca(2+)/Mg(2+) condition) decreased the α-helical content. These results suggest that each mutation alters the function/ability of the myofilament to bind Ca(2+) as a result of modifications in cTnC structure. One variant (D145E) that was previously reported in association with hypertrophic cardiomyopathy and that produced results in vivo in this study consistent with prior hypertrophic cardiomyopathy functional studies was found associated with the MYBPC3 P910T rare variant, likely contributing to the observed DCM phenotype. We conclude that these rare variants alter the regulation of contraction in some way, and the combined clinical, molecular, genetic, and functional data reinforce the importance of TNNC1 rare variants in the pathogenesis of DCM.
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Affiliation(s)
| | - Jill D. Siegfried
- Cardiovascular Division, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida 33136
| | | | - Duanxiang Li
- Cardiovascular Division, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Nadine Norton
- Cardiovascular Division, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida 33136
| | | | - Jingsheng Liang
- From the Department of Molecular and Cellular Pharmacology and
| | - James D. Potter
- From the Department of Molecular and Cellular Pharmacology and
| | - Ray E. Hershberger
- Cardiovascular Division, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida 33136
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48
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Zhang Z, Feng HZ, Jin JP. Structure of the NH2-terminal variable region of cardiac troponin T determines its sensitivity to restrictive cleavage in pathophysiological adaptation. Arch Biochem Biophys 2011; 515:37-45. [PMID: 21924234 DOI: 10.1016/j.abb.2011.08.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 08/27/2011] [Accepted: 08/30/2011] [Indexed: 12/19/2022]
Abstract
We previously reported that the NH(2)-terminal variable region of cardiac troponin T (cTnT) is removed by restrictive μ-calpain cleavage in myocardial ischemia-reperfusion [24]. Selective removal of the NH(2)-terminal variable region of cTnT had a compensatory effect on myocardial contractility [25]. Here we further studied this posttranslational modification under pathophysiological conditions. Thrombin perfusion of isolated mouse hearts and cardiomyocytes induced the production of NH(2)-terminal truncated cTnT (cTnT-ND), suggesting a role of calcium overloading. Ouabain treatment of primary cultures of mouse cardiomyocytes in hypokalemic media, another calcium overloading condition, also produced cTnT-ND. Exploring the molecular mechanisms, we found that cTnT phosphorylation was primarily in the NH(2)-terminal region and the level of cTnT phosphorylation did not change under the calcium overloading conditions. However, alternatively spliced cTnT variants differing in the NH(2)-terminal primary structure produced significantly different levels of cTnT-ND in vivo in transgenic mouse hearts. The results suggest that stress conditions involving calcium overloading may convey an increased sensitivity of cTnT to the restrictive μ-calpain proteolysis, in which structure of the NH(2)-terminal variable region may play a determining role.
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Affiliation(s)
- Zhiling Zhang
- Section of Molecular Cardiology, Evanston Northwestern Healthcare, Northwestern University Feinberg School of Medicine, Evanston, IL 60201, USA
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Sarin V, Muthuchamy M, Heaps CL. Ca²⁺ sensitization of cardiac myofilament proteins contributes to exercise training-enhanced myocardial function in a porcine model of chronic occlusion. Am J Physiol Heart Circ Physiol 2011; 301:H1579-87. [PMID: 21856915 DOI: 10.1152/ajpheart.00294.2011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Exercise training has been shown to improve cardiac dysfunction in both patients and animal models of coronary artery disease; however, the underlying cellular and molecular mechanisms have not been completely understood. We hypothesized that exercise training would improve force generation in the myocardium distal to chronic coronary artery occlusion via altered intracellular Ca(2+) concentration ([Ca(2+)](i)) cycling and/or Ca(2+) sensitization of myofilaments. Ameroid occluders were surgically placed around the proximal left circumflex coronary artery of adult female Yucatan pigs. Twenty-two weeks postoperatively, the myocardium was isolated from nonoccluded (left anterior descending artery dependent) and collateral-dependent (formerly left circumflex coronary artery dependent) regions of sedentary (pen confined) and exercise-trained (treadmill run, 5 days/wk for 14 wk) pigs. Force measurements in myocardial strips showed that the percent change in force at stimulation frequencies of 3 and 4 Hz relative to 1 Hz was significantly higher in exercise-trained pigs compared with sedentary pigs. β-Adrenergic stimulation with dobutamine significantly improved force kinetics in myocardial strips of sedentary but not exercise-trained pigs at 1 Hz. Additionally, time to peak and half-decay of intracellular Ca(2+) (340-to-380-nm fluoresence ratio) responses at 1 Hz were significantly decreased in the collateral-dependent region of exercise-trained pigs with no difference in peak [Ca(2+)](i) between groups. Furthermore, the skinned myocardium from exercise-trained pigs showed an increase in Ca(2+) sensitivity compared with sedentary pigs. Immunoblot analysis revealed that the relative levels of cardiac troponin T and β(1)-adrenergic receptors were decreased in hearts from exercise-trained pigs independent of occlusion. Also, the ratio of phosphorylated to total myosin light chain-2, basal phosphorylation levels of cardiac troponin I (Ser(23) and Ser(24)), and cardiac myosin binding protein-C (Ser(282)) were unaltered by occlusion or exercise training. Thus, our data demonstrate that exercise training-enhanced force generation in the nonoccluded and collateral-dependent myocardium was associated with improved Ca(2+) transients, increased Ca(2+) sensitization of myofilament proteins, and decreased expression levels of β(1)-adrenergic receptors and cardiac troponin T.
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Affiliation(s)
- Vandana Sarin
- Michael E. DeBakey Institute for Comparative Cardiovascular Science and Biomedical Devices, Texas A&M University, College Station, Texas 77843, USA
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Pinto JR, Yang SW, Hitz MP, Parvatiyar MS, Jones MA, Liang J, Kokta V, Talajic M, Tremblay N, Jaeggi M, Andelfinger G, Potter JD. Fetal cardiac troponin isoforms rescue the increased Ca2+ sensitivity produced by a novel double deletion in cardiac troponin T linked to restrictive cardiomyopathy: a clinical, genetic, and functional approach. J Biol Chem 2011; 286:20901-12. [PMID: 21502316 DOI: 10.1074/jbc.m111.234336] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A novel double deletion in cardiac troponin T (cTnT) of two highly conserved amino acids (Asn-100 and Glu-101) was found in a restrictive cardiomyopathic (RCM) pediatric patient. Clinical evaluation revealed the presence of left atrial enlargement and marked left ventricle diastolic dysfunction. The explanted heart examined by electron microscopy revealed myofibrillar disarray and mild fibrosis. Pedigree analysis established that this mutation arose de novo. The patient tested negative for six other sarcomeric genes. The single and double recombinant cTnT mutants were generated, and their functional consequences were analyzed in porcine skinned cardiac muscle. In the adult Tn environment (cTnT3 + cardiac troponin I), the single cTnT3-ΔN100 and cTnT3-ΔE101 mutations had opposing effects on the Ca(2+) sensitivity of force development compared with WT, whereas the double deletion cTnT3-ΔN100/ΔE101 increased the Ca(2+) sensitivity + 0.19 pCa units. In addition, cTnT3-ΔN100/ΔE101 decreased the cooperativity of force development, suggesting alterations in intrafilament protein-protein interactions. In the fetal Tn environment, (cTnT1 + slow skeletal troponin I), the single (cTnT1-ΔN110) and double (cTnT1-ΔN110/ΔE111) deletions did not change the Ca(2+) sensitivity compared with control. To recreate the patient's heterozygous genotype, we performed a reconstituted ATPase activity assay. Thin filaments containing 50:50 cTnT3-ΔN100/ΔE101:cTnT3-WT also increased the myofilament Ca(2+) sensitivity compared with WT. Co-sedimentation of thin filament proteins indicated that no significant changes occurred in the binding of Tn containing the RCM cTnT mutation to actin-Tm. This report reveals the protective role of Tn fetal isoforms as they rescue the increased Ca(2+) sensitivity produced by a cTnT-RCM mutation and may account for the lack of lethality during gestation.
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Affiliation(s)
- Jose Renato Pinto
- University of Miami Miller School of Medicine, Miami, Florida 33136, USA
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