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Dai Y, Ignatyeva N, Xu H, Wali R, Toischer K, Brandenburg S, Lenz C, Pronto J, Fakuade FE, Sossalla S, Zeisberg EM, Janshoff A, Kutschka I, Voigt N, Urlaub H, Rasmussen TB, Mogensen J, Lehnart SE, Hasenfuss G, Ebert A. An Alternative Mechanism of Subcellular Iron Uptake Deficiency in Cardiomyocytes. Circ Res 2023; 133:e19-e46. [PMID: 37313752 DOI: 10.1161/circresaha.122.321157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 05/26/2023] [Indexed: 06/15/2023]
Abstract
BACKGROUND Systemic defects in intestinal iron absorption, circulation, and retention cause iron deficiency in 50% of patients with heart failure. Defective subcellular iron uptake mechanisms that are independent of systemic absorption are incompletely understood. The main intracellular route for iron uptake in cardiomyocytes is clathrin-mediated endocytosis. METHODS We investigated subcellular iron uptake mechanisms in patient-derived and CRISPR/Cas-edited induced pluripotent stem cell-derived cardiomyocytes as well as patient-derived heart tissue. We used an integrated platform of DIA-MA (mass spectrometry data-independent acquisition)-based proteomics and signaling pathway interrogation. We employed a genetic induced pluripotent stem cell model of 2 inherited mutations (TnT [troponin T]-R141W and TPM1 [tropomyosin 1]-L185F) that lead to dilated cardiomyopathy (DCM), a frequent cause of heart failure, to study the underlying molecular dysfunctions of DCM mutations. RESULTS We identified a druggable molecular pathomechanism of impaired subcellular iron deficiency that is independent of systemic iron metabolism. Clathrin-mediated endocytosis defects as well as impaired endosome distribution and cargo transfer were identified as a basis for subcellular iron deficiency in DCM-induced pluripotent stem cell-derived cardiomyocytes. The clathrin-mediated endocytosis defects were also confirmed in the hearts of patients with DCM with end-stage heart failure. Correction of the TPM1-L185F mutation in DCM patient-derived induced pluripotent stem cells, treatment with a peptide, Rho activator II, or iron supplementation rescued the molecular disease pathway and recovered contractility. Phenocopying the effects of the TPM1-L185F mutation into WT induced pluripotent stem cell-derived cardiomyocytes could be ameliorated by iron supplementation. CONCLUSIONS Our findings suggest that impaired endocytosis and cargo transport resulting in subcellular iron deficiency could be a relevant pathomechanism for patients with DCM carrying inherited mutations. Insight into this molecular mechanism may contribute to the development of treatment strategies and risk management in heart failure.
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Affiliation(s)
- Yuanyuan Dai
- Heart Research Center Goettingen, Clinic for Cardiology and Pneumology, University Medical Center Goettingen, Georg-August University of Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., S.S., E.M.Z., S.E.L., G.H., A.E.)
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
| | - Nadezda Ignatyeva
- Heart Research Center Goettingen, Clinic for Cardiology and Pneumology, University Medical Center Goettingen, Georg-August University of Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., S.S., E.M.Z., S.E.L., G.H., A.E.)
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
| | - Hang Xu
- Heart Research Center Goettingen, Clinic for Cardiology and Pneumology, University Medical Center Goettingen, Georg-August University of Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., S.S., E.M.Z., S.E.L., G.H., A.E.)
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
| | - Ruheen Wali
- Heart Research Center Goettingen, Clinic for Cardiology and Pneumology, University Medical Center Goettingen, Georg-August University of Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., S.S., E.M.Z., S.E.L., G.H., A.E.)
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
| | - Karl Toischer
- Heart Research Center Goettingen, Clinic for Cardiology and Pneumology, University Medical Center Goettingen, Georg-August University of Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., S.S., E.M.Z., S.E.L., G.H., A.E.)
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
- Heart Center, Clinic for Cardiology and Pneumology, University Medical Center Goettingen (K.T., S.B., S.S., G.H.), University of Goettingen, Germany
| | - Sören Brandenburg
- Heart Research Center Goettingen, Clinic for Cardiology and Pneumology, University Medical Center Goettingen, Georg-August University of Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., S.S., E.M.Z., S.E.L., G.H., A.E.)
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
- Heart Center, Clinic for Cardiology and Pneumology, University Medical Center Goettingen (K.T., S.B., S.S., G.H.), University of Goettingen, Germany
| | - Christof Lenz
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
- Department of Clinical Chemistry, University Medical Center Goettingen, (C.L., H.U.), University of Goettingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC; C.L., F.E.F., N.V., S.E.L.), University of Goettingen, Germany
- Bioanalytical Mass Spectrometry, Max Planck Institute for Multidisciplinary Sciences, Goettingen (C.L., H.U.)
| | - Julius Pronto
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
- Institute of Pharmacology and Toxicology, University Medical Center Goettingen, (J.P., F.E.F., N.V.), University of Goettingen, Germany
| | - Funsho E Fakuade
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
- Institute of Pharmacology and Toxicology, University Medical Center Goettingen, (J.P., F.E.F., N.V.), University of Goettingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC; C.L., F.E.F., N.V., S.E.L.), University of Goettingen, Germany
| | - Samuel Sossalla
- Heart Research Center Goettingen, Clinic for Cardiology and Pneumology, University Medical Center Goettingen, Georg-August University of Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., S.S., E.M.Z., S.E.L., G.H., A.E.)
- Heart Center, Clinic for Cardiology and Pneumology, University Medical Center Goettingen (K.T., S.B., S.S., G.H.), University of Goettingen, Germany
- Department for Internal Medicine II, University Medical Center Regensburg (S.S.)
| | - Elisabeth M Zeisberg
- Heart Research Center Goettingen, Clinic for Cardiology and Pneumology, University Medical Center Goettingen, Georg-August University of Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., S.S., E.M.Z., S.E.L., G.H., A.E.)
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
| | - Andreas Janshoff
- Institute for Physical Chemistry (A.J.), University of Goettingen, Germany
| | - Ingo Kutschka
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
- Department of Thoracic and Cardiovascular Surgery, University Medical Center Göttingen (I.K.)
| | - Niels Voigt
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
- Institute of Pharmacology and Toxicology, University Medical Center Goettingen, (J.P., F.E.F., N.V.), University of Goettingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC; C.L., F.E.F., N.V., S.E.L.), University of Goettingen, Germany
| | - Henning Urlaub
- Department of Clinical Chemistry, University Medical Center Goettingen, (C.L., H.U.), University of Goettingen, Germany
- Bioanalytical Mass Spectrometry, Max Planck Institute for Multidisciplinary Sciences, Goettingen (C.L., H.U.)
| | | | - Jens Mogensen
- Department of Cardiology, Aalborg University Hospital, Denmark (J.M.)
| | - Stephan E Lehnart
- Heart Research Center Goettingen, Clinic for Cardiology and Pneumology, University Medical Center Goettingen, Georg-August University of Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., S.S., E.M.Z., S.E.L., G.H., A.E.)
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC; C.L., F.E.F., N.V., S.E.L.), University of Goettingen, Germany
| | - Gerd Hasenfuss
- Heart Research Center Goettingen, Clinic for Cardiology and Pneumology, University Medical Center Goettingen, Georg-August University of Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., S.S., E.M.Z., S.E.L., G.H., A.E.)
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
- Heart Center, Clinic for Cardiology and Pneumology, University Medical Center Goettingen (K.T., S.B., S.S., G.H.), University of Goettingen, Germany
| | - Antje Ebert
- Heart Research Center Goettingen, Clinic for Cardiology and Pneumology, University Medical Center Goettingen, Georg-August University of Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., S.S., E.M.Z., S.E.L., G.H., A.E.)
- DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany (Y.D., N.I., H.X., R.W., K.T., S.B., C.L., J.P., F.E.F., E.M.Z., I.K., N.V., S.E.L., G.H., A.E.)
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Kopylova GV, Berg VY, Kochurova AM, Matyushenko AM, Bershitsky SY, Shchepkin DV. The effects of the tropomyosin cardiomyopathy mutations on the calcium regulation of actin-myosin interaction in the atrium and ventricle differ. Biochem Biophys Res Commun 2021; 588:29-33. [PMID: 34942531 DOI: 10.1016/j.bbrc.2021.12.051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 12/15/2021] [Indexed: 12/17/2022]
Abstract
The molecular mechanisms of pathogenesis of atrial myopathy associated with hypertrophic (HCM) and dilated (DCM) mutations of sarcomeric proteins are still poorly understood. For this, one needs to investigate the effects of the mutations on actin-myosin interaction in the atria separately from ventricles. We compared the impact of the HCM and DCM mutations of tropomyosin (Tpm) on the calcium regulation of the thin filament interaction with atrial and ventricular myosin using an in vitro motility assay. We found that the mutations differently affect the calcium regulation of actin-myosin interaction in the atria and ventricles. The DCM E40K Tpm mutation significantly reduced the maximum sliding velocity of thin filaments with ventricular myosin and its Ca2+-sensitivity. With atrial myosin, its effects were less pronounced. The HCM I172T mutation reduced the Ca2+-sensitivity of the sliding velocity of filaments with ventricular myosin but increased it with the atrial one. The HCM L185R mutation did not affect actin-myosin interaction in the atria. The results indicate that the difference in the effects of Tpm mutations on the actin-myosin interaction in the atria and ventricles may be responsible for the difference in pathological changes in the atrial and ventricular myocardium.
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Affiliation(s)
- Galina V Kopylova
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia
| | - Valentina Y Berg
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia
| | - Anastasia M Kochurova
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia
| | - Alexander M Matyushenko
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Sergey Y Bershitsky
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia
| | - Daniil V Shchepkin
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia.
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3
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Dorsch LM, Kuster DWD, Jongbloed JDH, Boven LG, van Spaendonck-Zwarts KY, Suurmeijer AJH, Vink A, du Marchie Sarvaas GJ, van den Berg MP, van der Velden J, Brundel BJJM, van der Zwaag PA. The effect of tropomyosin variants on cardiomyocyte function and structure that underlie different clinical cardiomyopathy phenotypes. Int J Cardiol 2020; 323:251-258. [PMID: 32882290 DOI: 10.1016/j.ijcard.2020.08.101] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 08/20/2020] [Accepted: 08/28/2020] [Indexed: 12/27/2022]
Abstract
Background - Variants within the alpha-tropomyosin gene (TPM1) cause dominantly inherited cardiomyopathies, including dilated (DCM), hypertrophic (HCM) and restrictive (RCM) cardiomyopathy. Here we investigated whether TPM1 variants observed in DCM and HCM patients affect cardiomyocyte physiology differently. Methods - We identified a large family with DCM carrying a recently identified TPM1 gene variant (T201M) and a child with RCM with compound heterozygote TPM1 variants (E62Q and M281T) whose family members carrying single variants show diastolic dysfunction and HCM. The effects of TPM1 variants (T201M, E62Q or M281T) and of a plasmid containing both the E62Q and M281T variants on single-cell Ca2+ transients (CaT) in HL-1 cardiomyocytes were studied. To define toxic threshold levels, we performed dose-dependent transfection of TPM1 variants. In addition, cardiomyocyte structure was studied in human cardiac biopsies with TPM1 variants. Results - Overexpression of TPM1 variants led to time-dependent progressive deterioration of CaT, with the smallest effect seen for E62Q and larger and similar effects seen for the T201M and M281T variants. Overexpression of E62Q/M281T did not exacerbate the effects seen with overexpression of a single TPM1 variant. T201M (DCM) replaced endogenous tropomyosin dose-dependently, while M281T (HCM) did not. Human cardiac biopsies with TPM1 variants revealed loss of sarcomeric structures. Conclusion - All TPM1 variants result in reduced cardiomyocyte CaT amplitudes and loss of sarcomeric structures. These effects may underlie pathophysiology of different cardiomyopathy phenotypes.
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Affiliation(s)
- Larissa M Dorsch
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands.
| | - Diederik W D Kuster
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
| | - Jan D H Jongbloed
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Ludolf G Boven
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Karin Y van Spaendonck-Zwarts
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands; Department of Clinical Genetics, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
| | - Albert J H Suurmeijer
- Department of Pathology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Aryan Vink
- Department of Pathology, University Medical Center Utrecht, Utrecht, the Netherlands
| | | | - Maarten P van den Berg
- Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Jolanda van der Velden
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
| | - Bianca J J M Brundel
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
| | - Paul A van der Zwaag
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
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Matyushenko AM, Levitsky DI. Molecular Mechanisms of Pathologies of Skeletal and Cardiac Muscles Caused by Point Mutations in the Tropomyosin Genes. BIOCHEMISTRY (MOSCOW) 2020; 85:S20-S33. [PMID: 32087052 DOI: 10.1134/s0006297920140023] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The review is devoted to tropomyosin (Tpm) - actin-binding protein, which plays a crucial role in the regulation of contraction of skeletal and cardiac muscles. Special attention is paid to myopathies and cardiomyopathies - severe hereditary diseases of skeletal and cardiac muscles associated with point mutations in Tpm genes. The current views on the molecular mechanisms of these diseases and the effects of such mutations on the Tpm structure and functions are considered in detail. Besides, some part of the review is devoted to analysis of the properties of Tpm homodimers and heterodimers with myopathic substitutions of amino acid residues in only one of the two chains of the Tpm dimeric molecule.
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Affiliation(s)
- A M Matyushenko
- Bach Institute of Biochemistry, Federal Research Center on Fundamentals of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia.
| | - D I Levitsky
- Bach Institute of Biochemistry, Federal Research Center on Fundamentals of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia. .,Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia
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Aboelkassem Y, McCabe KJ, Huber GA, Regnier M, McCammon JA, McCulloch AD. A Stochastic Multiscale Model of Cardiac Thin Filament Activation Using Brownian-Langevin Dynamics. Biophys J 2019; 117:2255-2272. [PMID: 31547973 PMCID: PMC6990154 DOI: 10.1016/j.bpj.2019.08.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 07/31/2019] [Accepted: 08/02/2019] [Indexed: 11/16/2022] Open
Abstract
We use Brownian-Langevin dynamics principles to derive a coarse-graining multiscale myofilament model that can describe the thin-filament activation process during contraction. The model links atomistic molecular simulations of protein-protein interactions in the thin-filament regulatory unit to sarcomere-level activation dynamics. We first calculate the molecular interaction energy between tropomyosin and actin surface using Brownian dynamics simulations. This energy profile is then generalized to account for the observed tropomyosin transitions between its regulatory stable states. The generalized energy landscape then served as a basis for developing a filament-scale model using Langevin dynamics. This integrated analysis, spanning molecular to thin-filament scales, is capable of tracking the events of the tropomyosin conformational changes as it moves over the actin surface. The tropomyosin coil with flexible overlap regions between adjacent tropomyosins is represented in the model as a system of coupled stochastic ordinary differential equations. The proposed multiscale approach provides a more detailed molecular connection between tropomyosin dynamics, the trompomyosin-actin interaction-energy landscape, and the generated force by the sarcomere.
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Affiliation(s)
- Yasser Aboelkassem
- Department of Bioengineering, University of California San Diego, La Jolla, California.
| | - Kimberly J McCabe
- Department of Bioengineering, University of California San Diego, La Jolla, California
| | - Gary A Huber
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California
| | - Michael Regnier
- Department of Bioengineering, University of Washington, Seattle, Washington
| | - J Andrew McCammon
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California
| | - Andrew D McCulloch
- Department of Bioengineering, University of California San Diego, La Jolla, California
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Cardiomyopathy-associated mutations in tropomyosin differently affect actin–myosin interaction at single-molecule and ensemble levels. J Muscle Res Cell Motil 2019; 40:299-308. [DOI: 10.1007/s10974-019-09560-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 10/15/2019] [Indexed: 01/31/2023]
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Thin filament dysfunctions caused by mutations in tropomyosin Tpm3.12 and Tpm1.1. J Muscle Res Cell Motil 2019; 41:39-53. [PMID: 31270709 PMCID: PMC7109180 DOI: 10.1007/s10974-019-09532-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 06/26/2019] [Indexed: 12/14/2022]
Abstract
Tropomyosin is the major regulator of the thin filament. In striated muscle its function is to bind troponin complex and control the access of myosin heads to actin in a Ca2+-dependent manner. It also participates in the maintenance of thin filament length by regulation of tropomodulin and leiomodin, the pointed end-binding proteins. Because the size of the overlap between actin and myosin filaments affects the number of myosin heads which interact with actin, the filament length is one of the determinants of force development. Numerous point mutations in genes encoding tropomyosin lead to single amino acid substitutions along the entire length of the coiled coil that are associated with various types of cardiomyopathy and skeletal muscle disease. Specific regions of tropomyosin interact with different binding partners; therefore, the mutations affect diverse tropomyosin functions. In this review, results of studies on mutations in the genes TPM1 and TPM3, encoding Tpm1.1 and Tpm3.12, are described. The paper is particularly focused on mutation-dependent alterations in the mechanisms of actin-myosin interactions and dynamics of the thin filament at the pointed end.
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Lehman W, Moore JR, Campbell SG, Rynkiewicz MJ. The Effect of Tropomyosin Mutations on Actin-Tropomyosin Binding: In Search of Lost Time. Biophys J 2019; 116:2275-2284. [PMID: 31130236 PMCID: PMC6588729 DOI: 10.1016/j.bpj.2019.05.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 05/06/2019] [Accepted: 05/09/2019] [Indexed: 12/14/2022] Open
Abstract
The initial binding of tropomyosin onto actin filaments and then its polymerization into continuous cables on the filament surface must be precisely tuned to overall thin-filament structure, function, and performance. Low-affinity interaction of tropomyosin with actin has to be sufficiently strong to localize the tropomyosin on actin, yet not so tight that regulatory movement on filaments is curtailed. Likewise, head-to-tail association of tropomyosin molecules must be favorable enough to promote tropomyosin cable formation but not so tenacious that polymerization precedes filament binding. Arguably, little molecular detail on early tropomyosin binding steps has been revealed since Wegner's seminal studies on filament assembly almost 40 years ago. Thus, interpretation of mutation-based actin-tropomyosin binding anomalies leading to cardiomyopathies cannot be described fully. In vitro, tropomyosin binding is masked by explosive tropomyosin polymerization once cable formation is initiated on actin filaments. In contrast, in silico analysis, characterizing molecular dynamics simulations of single wild-type and mutant tropomyosin molecules on F-actin, is not complicated by tropomyosin polymerization at all. In fact, molecular dynamics performed here demonstrates that a midpiece tropomyosin domain is essential for normal actin-tropomyosin interaction and that this interaction is strictly conserved in a number of tropomyosin mutant species. Elsewhere along these mutant molecules, twisting and bending corrupts the tropomyosin superhelices as they "lose their grip" on F-actin. We propose that residual interactions displayed by these mutant tropomyosin structures with actin mimic ones that occur in early stages of thin-filament generation, as if the mutants are recapitulating the assembly process but in reverse. We conclude therefore that an initial binding step in tropomyosin assembly onto actin involves interaction of the essential centrally located domain.
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Affiliation(s)
- William Lehman
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts.
| | - Jeffrey R Moore
- Department of Biological Sciences, University of Massachusetts-Lowell, Lowell, Massachusetts
| | - Stuart G Campbell
- Departments of Biomedical Engineering and Cellular and Molecular Physiology, Yale University, New Haven, Connecticut
| | - Michael J Rynkiewicz
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts
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Ishii S, Suzuki M, Ishiwata S, Kawai M. Functional significance of HCM mutants of tropomyosin, V95A and D175N, studied with in vitro motility assays. Biophys Physicobiol 2019; 16:28-40. [PMID: 30923661 PMCID: PMC6435021 DOI: 10.2142/biophysico.16.0_28] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 12/18/2018] [Indexed: 12/21/2022] Open
Abstract
The majority of hypertrophic cardiomyopathy (HCM) is caused by mutations in sarcomere proteins. We examined tropomyosin (Tpm)’s HCM mutants in humans, V95A and D175N, with in vitro motility assay using optical tweezers to evaluate the effects of the Tpm mutations on the actomyosin interaction at the single molecular level. Thin filaments were reconstituted using these Tpm mutants, and their sliding velocity and force were measured at varying Ca2+ concentrations. Our results indicate that the sliding velocity at pCa ≥8.0 was significantly increased in mutants, which is expected to cause a diastolic problem. The velocity that can be activated by Ca2+ decreased significantly in mutants causing a systolic problem. With sliding force, Ca2+ activatable force decreased in V95A and increased in D175N, which may cause a systolic problem. Our results further demonstrate that the duty ratio determined at the steady state of force generation in saturating [Ca2+] decreased in V95A and increased in D175N. The Ca2+ sensitivity and cooperativity were not significantly affected by the mutations. These results suggest that the two mutants modulate molecular processes of the actomyosin interaction differently, but to result in the same pathology known as HCM.
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Affiliation(s)
- Shuya Ishii
- Department of Physics, Faculty of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Madoka Suzuki
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan.,PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
| | - Shin'ichi Ishiwata
- Department of Physics, Faculty of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Masataka Kawai
- Department of Anatomy and Cell Biology, College of Medicine, University of Iowa, Iowa City, IA 52242, USA
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10
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Schmidt W, Cammarato A. The actin 'A-triad's' role in contractile regulation in health and disease. J Physiol 2019; 598:2897-2908. [PMID: 30770548 DOI: 10.1113/jp276741] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 01/30/2019] [Indexed: 12/15/2022] Open
Abstract
Striated muscle contraction is regulated by Ca2+ -dependent modulation of myosin cross-bridge binding to F-actin by the thin filament troponin (Tn)-tropomyosin (Tm) complex. In the absence of Ca2+ , Tn binds to actin and constrains Tm to an azimuthal location where it sterically occludes myosin binding sites along the thin filament surface. This limits force production and promotes muscle relaxation. In addition to Tn-actin interactions, inhibitory Tm positioning requires associations between other thin filament constituents. For example, the actin 'A-triad', composed of residues K326, K328 and R147, forms numerous, highly favourable electrostatic contacts with Tm that are critical for establishing its inhibitory azimuthal binding position. Here, we review recent findings, including the identification and interrogation of modifications within and proximal to the A-triad that are associated with disease and/or altered muscle behaviour, which highlight the surface feature's role in F-actin-Tm interactions and contractile regulation.
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Affiliation(s)
- William Schmidt
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, 733 N Broadway, 21205, Baltimore, MD, USA
| | - Anthony Cammarato
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, 733 N Broadway, 21205, Baltimore, MD, USA.,Department of Physiology, Johns Hopkins University School of Medicine, 733 N Broadway, 21205, Baltimore, MD, USA
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11
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van der Velden J, Stienen GJM. Cardiac Disorders and Pathophysiology of Sarcomeric Proteins. Physiol Rev 2019; 99:381-426. [PMID: 30379622 DOI: 10.1152/physrev.00040.2017] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The sarcomeric proteins represent the structural building blocks of heart muscle, which are essential for contraction and relaxation. During recent years, it has become evident that posttranslational modifications of sarcomeric proteins, in particular phosphorylation, tune cardiac pump function at rest and during exercise. This delicate, orchestrated interaction is also influenced by mutations, predominantly in sarcomeric proteins, which cause hypertrophic or dilated cardiomyopathy. In this review, we follow a bottom-up approach starting from a description of the basic components of cardiac muscle at the molecular level up to the various forms of cardiac disorders at the organ level. An overview is given of sarcomere changes in acquired and inherited forms of cardiac disease and the underlying disease mechanisms with particular reference to human tissue. A distinction will be made between the primary defect and maladaptive/adaptive secondary changes. Techniques used to unravel functional consequences of disease-induced protein changes are described, and an overview of current and future treatments targeted at sarcomeric proteins is given. The current evidence presented suggests that sarcomeres not only form the basis of cardiac muscle function but also represent a therapeutic target to combat cardiac disease.
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Affiliation(s)
- Jolanda van der Velden
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, Amsterdam , The Netherlands ; and Department of Physiology, Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Ger J M Stienen
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, Amsterdam , The Netherlands ; and Department of Physiology, Kilimanjaro Christian Medical University College, Moshi, Tanzania
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12
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Matyushenko AM, Shchepkin DV, Kopylova GV, Popruga KE, Artemova NV, Pivovarova AV, Bershitsky SY, Levitsky DI. Structural and Functional Effects of Cardiomyopathy-Causing Mutations in the Troponin T-Binding Region of Cardiac Tropomyosin. Biochemistry 2016; 56:250-259. [PMID: 27983818 DOI: 10.1021/acs.biochem.6b00994] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is a severe heart disease caused by missense mutations in genes encoding sarcomeric proteins of cardiac muscle. Many of these mutations are identified in the gene encoding the cardiac isoform of tropomyosin (Tpm), an α-helical coiled-coil actin-binding protein that plays a key role in Ca2+-regulated contraction of cardiac muscle. We employed various methods to characterize structural and functional features of recombinant human Tpm species carrying HCM mutations that lie either within the troponin T-binding region in the C-terminal part of Tpm (E180G, E180V, and L185R) or near this region (I172T). The results of our structural studies show that all these mutations affect, although differently, the thermal stability of the C-terminal part of the Tpm molecule: mutations E180G and I172T destabilize this part of the molecule, whereas mutation E180V strongly stabilizes it. Moreover, various HCM-causing mutations have different and even opposite effects on the stability of the Tpm-actin complexes. Studies of reconstituted thin filaments in the in vitro motility assay have shown that those HCM-associated mutations that lie within the troponin T-binding region of Tpm similarly increase the Ca2+ sensitivity of the sliding velocity of the filaments and impair their relaxation properties, causing a marked increase in the sliding velocity in the absence of Ca2+, while mutation I172T decreases the Ca2+ sensitivity and has no influence on the sliding velocity under relaxing conditions. Finally, our data demonstrate that various HCM mutations can differently affect the structural and functional properties of Tpm and cause HCM by different molecular mechanisms.
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Affiliation(s)
- Alexander M Matyushenko
- A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences , Leninsky Prospect 33, Moscow 119071, Russian Federation.,Department of Biochemistry, School of Biology, Moscow State University , Lenin Hills 1, bld 12, Moscow 119234, Russian Federation
| | - Daniil V Shchepkin
- Institute of Immunology and Physiology, Russian Academy of Sciences , Pervomayskaya Street 106, Yekaterinburg 620049, Russian Federation
| | - Galina V Kopylova
- Institute of Immunology and Physiology, Russian Academy of Sciences , Pervomayskaya Street 106, Yekaterinburg 620049, Russian Federation
| | - Katerina E Popruga
- A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences , Leninsky Prospect 33, Moscow 119071, Russian Federation.,Department of Biochemistry, School of Biology, Moscow State University , Lenin Hills 1, bld 12, Moscow 119234, Russian Federation
| | - Natalya V Artemova
- A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences , Leninsky Prospect 33, Moscow 119071, Russian Federation
| | - Anastasia V Pivovarova
- A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences , Leninsky Prospect 33, Moscow 119071, Russian Federation
| | - Sergey Y Bershitsky
- Institute of Immunology and Physiology, Russian Academy of Sciences , Pervomayskaya Street 106, Yekaterinburg 620049, Russian Federation
| | - Dmitrii I Levitsky
- A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences , Leninsky Prospect 33, Moscow 119071, Russian Federation.,A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University , Lenin Hills 1, bld 40, Moscow 119234, Russian Federation
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13
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Marston SB. Why Is there a Limit to the Changes in Myofilament Ca 2+-Sensitivity Associated with Myopathy Causing Mutations? Front Physiol 2016; 7:415. [PMID: 27725803 PMCID: PMC5035734 DOI: 10.3389/fphys.2016.00415] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 09/05/2016] [Indexed: 12/15/2022] Open
Abstract
Mutations in striated muscle contractile proteins have been found to be the cause of a number of inherited muscle diseases; in most cases the mechanism proposed for causing the disease is derangement of the thin filament-based Ca2+-regulatory system of the muscle. When considering the results of experiments reported over the last 15 years, one feature has been frequently noted, but rarely discussed: the magnitude of changes in myofilament Ca2+-sensitivity due to myopathy-causing mutations in skeletal or heart muscle seems to be always in the range 1.5-3x EC50. Such consistency suggests it may be related to a fundamental property of muscle regulation; in this article we will investigate whether this observation is true and consider why this should be so. A literature search found 71 independent measurements of HCM mutation-induced change of EC50 ranging from 1.15 to 3.8-fold with a mean of 1.87 ± 0.07 (sem). We also found 11 independent measurements of increased Ca2+-sensitivity due to mutations in skeletal muscle proteins ranging from 1.19 to 2.7-fold with a mean of 2.00 ± 0.16. Investigation of dilated cardiomyopathy-related mutations found 42 independent determinations with a range of EC50 wt/mutant from 0.3 to 2.3. In addition we found 14 measurements of Ca2+-sensitivity changes due skeletal muscle myopathy mutations ranging from 0.39 to 0.63. Thus, our extensive literature search, although not necessarily complete, found that, indeed, the changes in myofilament Ca2+-sensitivity due to disease-causing mutations have a bimodal distribution and that the overall changes in Ca2+-sensitivity are quite small and do not extend beyond a three-fold increase or decrease in Ca2+-sensitivity. We discuss two mechanism that are not necessarily mutually exclusive. Firstly, it could be that the limit is set by the capabilities of the excitation-contraction machinery that supplies activating Ca2+ and that striated muscle cannot work in a way compatible with life outside these limits; or it may be due to a fundamental property of the troponin system and the permitted conformational transitions compatible with efficient regulation.
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Affiliation(s)
- Steven B Marston
- National Heart & Lung Institute, Imperial College London London, UK
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14
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Omecamtiv Mecarbil, a Cardiac Myosin Activator, Increases Ca2+ Sensitivity in Myofilaments With a Dilated Cardiomyopathy Mutant Tropomyosin E54K. J Cardiovasc Pharmacol 2016; 66:347-53. [PMID: 26065842 DOI: 10.1097/fjc.0000000000000286] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Apart from transplant, there are no satisfactory therapies for the severe depression in contractility in familial dilated cardiomyopathy (DCM). Current heart failure treatments that act by increasing contractility involve signaling cascades that alter calcium homeostasis and induce arrhythmias. Omecamtiv mecarbil is a promising new inotropic agent developed for heart failure that may circumvent such limitations. Omecamtiv is a direct cardiac myosin activator that promotes and prolongs the strong myosin-actin binding conformation to increase the duration of systolic elastance. We tested the effect of omecamtiv on Ca(2+) sensitivity of myofilaments of a DCM mouse model containing a tropomyosin E54K mutation. We compared tension and ATPase activity of detergent-extracted myofilaments with and without treatment with 316 nM omecamtiv at varying pCa values. When transgenic myofilaments were treated with omecamtiv, the pCa50 for activation of tension increased from 5.70 ± 0.02 to 5.82 ± 0.02 and ATPase activity increased from 5.73 ± 0.06 to 6.07 ± 0.04. This significant leftward shift restored Ca(2+) sensitivity to levels no longer significantly different from controls. Proteomic studies lacked changes in sarcomeric protein phosphorylation. Our data demonstrate that omecamtiv can potentially augment cardiac contractility in DCM by increasing Ca(2+) sensitivity. The use of direct myosin activators addresses functional defects without incurring the adverse side effects of Ca(2+)-dependent treatments.
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15
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Zheng W, Hitchcock-DeGregori SE, Barua B. Investigating the effects of tropomyosin mutations on its flexibility and interactions with filamentous actin using molecular dynamics simulation. J Muscle Res Cell Motil 2016; 37:131-147. [DOI: 10.1007/s10974-016-9447-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Accepted: 06/24/2016] [Indexed: 12/15/2022]
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16
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Song W, Wang X. The role of TGFβ1 and LRG1 in cardiac remodelling and heart failure. Biophys Rev 2015; 7:91-104. [PMID: 28509980 PMCID: PMC4322186 DOI: 10.1007/s12551-014-0158-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 11/26/2014] [Indexed: 12/12/2022] Open
Abstract
Heart failure is a life-threatening condition that carries a considerable emotional and socio-economic burden. As a result of the global increase in the ageing population, sedentary life-style, increased prevalence of risk factors, and improved survival from cardiovascular events, the incidence of heart failure will continue to rise. Despite the advances in current cardiovascular therapies, many patients are not suitable for or may not benefit from conventional treatments. Thus, more effective therapies are required. Transforming growth factor (TGF) β family of cytokines is involved in heart development and dys-regulated TGFβ signalling is commonly associated with fibrosis, aberrant angiogenesis and accelerated progression into heart failure. Therefore, a potential therapeutic pathway is to modulate TGFβ signalling; however, broad blockage of TGFβ signalling may cause unwanted side effects due to its pivotal role in tissue homeostasis. We found that leucine-rich α-2 glycoprotein 1 (LRG1) promotes blood vessel formation via regulating the context-dependent endothelial TGFβ signalling. This review will focus on the interaction between LRG1 and TGFβ signalling, their involvement in the pathogenesis of heart failure, and the potential for LRG1 to function as a novel therapeutic target.
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Affiliation(s)
- Weihua Song
- Division of Metabolic Medicine, Lee Kong Chian School of Medicine, Nanyang Technological University, Research Techno Plaza, X-Frontiers Block, Level 4, 50 Nan yang Drive, Singapore, 637553, Singapore
| | - Xiaomeng Wang
- Division of Metabolic Medicine, Lee Kong Chian School of Medicine, Nanyang Technological University, Research Techno Plaza, X-Frontiers Block, Level 4, 50 Nan yang Drive, Singapore, 637553, Singapore. .,Division of Cell Biology in Health and Disease, Institute of Molecular and Cell Biology, Singapore Agency for Science, Technology and Research, 61 Biopolis Drive, Proteos, Singapore, 138673, Singapore. .,Department of Cell Biology, Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V 9EL, UK.
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17
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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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18
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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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19
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Energy landscapes reveal the myopathic effects of tropomyosin mutations. Arch Biochem Biophys 2014; 564:89-99. [PMID: 25241052 DOI: 10.1016/j.abb.2014.09.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 09/03/2014] [Accepted: 09/09/2014] [Indexed: 11/24/2022]
Abstract
Striated muscle contraction is regulated by an interaction network connecting the effects of troponin, Ca(2+), and myosin-heads to the azimuthal positioning of tropomyosin along thin filaments. Many missense mutations, located at the actin-tropomyosin interface, however, reset the regulatory switching mechanism either by weakening or strengthening residue-specific interactions, leading to hyper- or hypo-contractile pathologies. Here, we compute energy landscapes for the actin-tropomyosin interface and quantify contributions of single amino acid residues to actin-tropomyosin binding. The method is a useful tool to assess effects of actin and tropomyosin mutations, potentially relating initial stages of myopathy to alterations in thin filament stability and regulation. Landscapes for mutant filaments linked to hyper-contractility provide a simple picture that describes a decrease in actin-tropomyosin interaction energy. Destabilizing the blocked (relaxed)-state parallels previously noted enhanced Ca(2+)-sensitivity conferred by these mutants. Energy landscapes also identify post-translational modifications that can rescue regulatory imbalances. For example, cardiomyopathy-associated E62Q tropomyosin mutation weakens actin-tropomyosin interaction, but phosphorylation of neighboring S61 rescues the binding-deficit, results confirmed experimentally by in vitro motility assays. Unlike results on hyper-contractility-related mutants, landscapes for tropomyosin mutants tied to hypo-contractility do not present a straightforward picture. These mutations may affect other components of the regulatory network, e.g., troponin-tropomyosin signaling.
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20
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Bai F, Caster HM, Rubenstein PA, Dawson JF, Kawai M. Using baculovirus/insect cell expressed recombinant actin to study the molecular pathogenesis of HCM caused by actin mutation A331P. J Mol Cell Cardiol 2014; 74:64-75. [PMID: 24793351 DOI: 10.1016/j.yjmcc.2014.04.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 04/21/2014] [Accepted: 04/22/2014] [Indexed: 01/07/2023]
Abstract
Recombinant WT human cardiac actin (WT actin) was expressed using the baculovirus/insect cell expression system, purified, and used to reconstitute the thin-filament of bovine cardiac muscle fibers, together with bovine cardiac tropomyosin (Tm) and troponin (Tn). Effects of [Ca(2+)], [ATP], [phosphate] and [ADP] on tension and tension transients were studied at 25°C by using sinusoidal analysis, and the results were compared with those of native fibers and fibers reconstituted with purified bovine cardiac actin (BVC actin). In actin filament reconstituted fibers (without Tm/Tn), those reconstituted with WT actin showed exactly the same active tension as those reconstituted with purified BVC actin (WT: 0.75±0.06 T0, N=11; BVC: 0.73±0.07 T0, N=12, where T0 is the tension of original fibers before extraction). After Tm/Tn reconstitution, fibers reconstituted with WT actin generated 0.85±0.06 T0 (N=11) compared to 0.98±0.04 T0 (N=12) recovered by those reconstituted with BVC actin. In the presence of Tm/Tn, WT actin reconstituted fibers showed exactly the same Ca(2+) sensitivity as those of the native fibers and BVC actin reconstituted fibers (pCa50: native fibers: 5.69±0.01, N=10; WT: 5.69±0.02, N=11; BVC: 5.68±0.02, N=12). Sinusoidal analysis showed that the cross-bridge kinetics were the same among native fibers, BVC actin reconstituted fibers and WT actin reconstituted fibers, followed by reconstitution of Tm/Tn. These results demonstrate that baculovirus/insect cell expressed actin has no significant differences from tissue purified actin and can be used for thin-filament reconstitution assays. One hypertrophic cardiomyopathy (HCM) causing actin mutant A331P actin was also expressed and studied similarly, and the results were compared to those of the WT actin. In the reconstituted fibers, A331P significantly decreased the tension both in the absence of Tm/Tn (0.55±0.03 T0, N=13) and in their presence (0.65±0.02 T0, N=13) compared to those of the WT (0.75±0.06 T0 and 0.85±0.06 T0, respectively, N=11). A331P also showed decreased pCa50 (5.57±0.03, N=13) compared to that of WT (5.69±0.02, N=11). The cross-bridge kinetics and its distribution were similar between WT and A331P actin reconstituted fibers, indicating that force/cross-bridge was decreased by A331P. In conclusion, A331P causes a weakened cross-bridge force, which leads to a decreased active tension, reduces left-ventricular ejection fraction, and eventually results in the HCM phenotype.
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Affiliation(s)
- Fan Bai
- Department of Anatomy and Cell Biology, The University of Iowa, Iowa City, IA 52242-1109, USA.
| | - Hannah M Caster
- Department of Anatomy and Cell Biology, The University of Iowa, Iowa City, IA 52242-1109, USA.
| | - Peter A Rubenstein
- Department of Biochemistry, The University of Iowa, Iowa City, IA 52242-1109, USA.
| | - John F Dawson
- Department of Molecular & Cellular Biology, University of Guelph, College of Biological Science, Guelph, Ontario N1G 2 W1, Canada.
| | - Masataka Kawai
- Department of Anatomy and Cell Biology, The University of Iowa, Iowa City, IA 52242-1109, USA; Department of Internal Medicine, The University of Iowa, Iowa City, IA 52242-1109, USA.
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21
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Kalyva A, Parthenakis FI, Marketou ME, Kontaraki JE, Vardas PE. Biochemical characterisation of Troponin C mutations causing hypertrophic and dilated cardiomyopathies. J Muscle Res Cell Motil 2014; 35:161-78. [PMID: 24744096 DOI: 10.1007/s10974-014-9382-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 04/02/2014] [Indexed: 01/27/2023]
Abstract
Cardiac muscle contraction occurs through an interaction of the myosin head with the actin filaments, a process which is regulated by the troponin complex together with tropomyosin and is Ca(2+) dependent. Mutations in genes encoding sarcomeric proteins are a common cause of familial hypertrophic and dilated cardiomyopathies. The scope of this review is to gather information from studies regarding the in vitro characterisation of six HCM and six DCM mutations on the cardiac TnC gene and to suggest, if possible, how they may lead to dysfunction. Since TnC is the subunit responsible for Ca(2+) binding, mutations in the TnC could possibly have a strong impact on Ca(2+) binding affinities. Furthermore, the interactions of mutant TnCs with their binding partners could be altered. From the characterisation studies available to date, we can conclude that the HCM mutations on TnC increase significantly the Ca(2+) sensitivity of force development or of ATPase activity, producing large pCa shifts in comparison to WT TnC. In contrast, the DCM mutations on TnC have a tendency to decrease the Ca(2+) sensitivity of force development or of ATPase activity in comparison to WT TnC. Furthermore, the DCM mutants of TnC are not responsive to the TnI phosphorylation signal resulting in filaments that preserve their Ca(2+) sensitivity in contrast to WT filaments that experience a decrease in Ca(2+) sensitivity upon TnI phosphorylation.
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Affiliation(s)
- Athanasia Kalyva
- Molecular Cardiology Laboratory, Department of Cardiology, School of Medicine, University of Crete, Crete, Greece,
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22
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Lehrer SS, Geeves MA. The myosin-activated thin filament regulatory state, M − -open: a link to hypertrophic cardiomyopathy (HCM). J Muscle Res Cell Motil 2014; 35:153-60. [DOI: 10.1007/s10974-014-9383-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 04/03/2014] [Indexed: 01/31/2023]
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Karpicheva OE, Redwood CS, Borovikov YS. The E117K mutation in β-tropomyosin disturbs concerted conformational changes of actomyosin in muscle fibers. Arch Biochem Biophys 2014; 549:12-6. [PMID: 24657080 DOI: 10.1016/j.abb.2014.03.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 02/10/2014] [Accepted: 03/10/2014] [Indexed: 10/25/2022]
Abstract
The effect of the skeletal myopathy-causing E117K mutation in human β-tropomyosin on actomyosin structure during the ATPase cycle was studied using fluorescent probes bound to actin subdomain 1 and the myosin head. Multistep changes in flexural rigidity of actin filament and in spatial arrangement of actin subdomain 1 and myosin SH1 helix in troponin-free ghost muscle fibers were revealed. During the ATPase cycle E117K tropomyosin inhibited the rotation of subdomain 1 by 46% and the tilt of the SH1 helix by 49% compared with wild-type. At strong-binding stages the proportion of strong binding sub-states in the actomyosin population is decreased by the mutation. At weak-binding stages abnormally high numbers of switched-on actin monomers were observed, thus indicating a disturbance in concerted conformational changes of actomyosin. These structural alterations are likely to underlie the contractile deficit observed with this mutation.
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Affiliation(s)
- Olga E Karpicheva
- Laboratory of Mechanisms of Cell Motility, Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia
| | - Charles S Redwood
- Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Yurii S Borovikov
- Laboratory of Mechanisms of Cell Motility, Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia.
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24
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Wilson K, Lucchesi PA. Myofilament dysfunction as an emerging mechanism of volume overload heart failure. Pflugers Arch 2014; 466:1065-77. [PMID: 24488008 DOI: 10.1007/s00424-014-1455-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 01/17/2014] [Accepted: 01/19/2014] [Indexed: 11/28/2022]
Abstract
Two main hemodynamic overload mechanisms [i.e., volume and pressure overload (VO and PO, respectively] result in heart failure (HF), and these two mechanisms have divergent pathologic alterations and different pathophysiological mechanisms. Extensive evidence from animal models and human studies of PO demonstrate a clear association with alterations in Ca(2+) homeostasis. By contrast, emerging evidence from animal models and patients with regurgitant valve disease and dilated cardiomyopathy point toward a more prominent role of myofilament dysfunction. With respect to VO HF, key features of excitation-contraction coupling defects, myofilament dysfunction, and extracellular matrix composition will be discussed.
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Affiliation(s)
- Kristin Wilson
- Center for Cardiovascular and Pulmonary Research and The Heart Center, Nationwide Children's Hospital, Columbus, OH, USA
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25
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Bai F, Caster HM, Pinto JR, Kawai M. Analysis of the molecular pathogenesis of cardiomyopathy-causing cTnT mutants I79N, ΔE96, and ΔK210. Biophys J 2013; 104:1979-88. [PMID: 23663841 DOI: 10.1016/j.bpj.2013.04.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 03/27/2013] [Accepted: 04/02/2013] [Indexed: 11/19/2022] Open
Abstract
Three troponin T (TnT) mutants that cause hypertrophic, restrictive, and dilated cardiomyopathy (I79N, ΔE96, and ΔK210, respectively), were examined using the thin-filament extraction/reconstitution technique. Effects of Ca(2+), ATP, phosphate, and ADP concentrations on force and its transients were studied at 25°C. Maximal Ca(2+) tension (THC) and Ca(2+)-activatable tension (Tact), respectively, were similar among I79N, ΔE96, and WT, whereas ΔK210 led to a significantly lower THC (∼20% less) and Tact (∼25% less) than did WT. In pCa solution containing 8 mM Pi and ionic strength adjusted to 200 mM, the Ca(2+) sensitivity (pCa50) of I79N (5.63 ± 0.02) and ΔE96 (5.60 ± 0.03) was significantly greater than that of WT (5.45 ± 0.04), but the pCa50 of ΔK210 (5.54 ± 0.04) remained similar to that of WT. Five equilibrium constants were deduced using sinusoidal analysis. All three mutants showed significantly lower K0 (ADP association constant) and larger K4 (equilibrium constant of force generation step) relative to the corresponding values for WT. I79N and ΔK210 were associated with a K2 (equilibrium constant of cross-bridge detachment step) significantly lower than that of ΔE96 and WT. These results demonstrated that at pCa 4.66, the force/cross-bridge is ∼18% less in I79N and ∼41% less in ΔK210 than that in WT. These results indicate that the molecular pathogenesis of the cardiac TnT mutation-related cardiomyopathies is different for each mutation.
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Affiliation(s)
- Fan Bai
- Department of Anatomy and Cell Biology, The University of Iowa, Iowa City, Iowa, USA
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26
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Redwood C, Robinson P. Alpha-tropomyosin mutations in inherited cardiomyopathies. J Muscle Res Cell Motil 2013; 34:285-94. [DOI: 10.1007/s10974-013-9358-5] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 08/23/2013] [Indexed: 10/26/2022]
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Nuclear tropomyosin and troponin in striated muscle: new roles in a new locale? J Muscle Res Cell Motil 2013; 34:275-84. [DOI: 10.1007/s10974-013-9356-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 07/23/2013] [Indexed: 01/03/2023]
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28
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Sequeira V, Nijenkamp LLAM, Regan JA, van der Velden J. The physiological role of cardiac cytoskeleton and its alterations in heart failure. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:700-22. [PMID: 23860255 DOI: 10.1016/j.bbamem.2013.07.011] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 07/01/2013] [Accepted: 07/08/2013] [Indexed: 12/11/2022]
Abstract
Cardiac muscle cells are equipped with specialized biochemical machineries for the rapid generation of force and movement central to the work generated by the heart. During each heart beat cardiac muscle cells perceive and experience changes in length and load, which reflect one of the fundamental principles of physiology known as the Frank-Starling law of the heart. Cardiac muscle cells are unique mechanical stretch sensors that allow the heart to increase cardiac output, and adjust it to new physiological and pathological situations. In the present review we discuss the mechano-sensory role of the cytoskeletal proteins with respect to their tight interaction with the sarcolemma and extracellular matrix. The role of contractile thick and thin filament proteins, the elastic protein titin, and their anchorage at the Z-disc and M-band, with associated proteins are reviewed in physiologic and pathologic conditions leading to heart failure. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé
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Affiliation(s)
- Vasco Sequeira
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - Louise L A M Nijenkamp
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - Jessica A Regan
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands; Department of Physiology, Molecular Cardiovascular Research Program, Sarver Heart Center, University of Arizona, Tucson, AZ 85724, USA
| | - Jolanda van der Velden
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands; ICIN-Netherlands Heart Institute, The Netherlands.
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A study of tropomyosin's role in cardiac function and disease using thin-filament reconstituted myocardium. J Muscle Res Cell Motil 2013; 34:295-310. [PMID: 23700264 DOI: 10.1007/s10974-013-9343-z] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 05/07/2013] [Indexed: 10/26/2022]
Abstract
Tropomyosin (Tm) is the key regulatory component of the thin-filament and plays a central role in the cardiac muscle's cooperative activation mechanism. Many mutations of cardiac Tm are related to hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and left ventricular noncompaction (LVNC). Using the thin-filament extraction/reconstitution technique, we are able to incorporate various Tm mutants and protein isoforms into a muscle fiber environment to study their roles in Ca(2+) regulation, cross-bridge kinetics, and force generation. The thin-filament reconstitution technique poses several advantages compared to other in vitro and in vivo methods: (1) Tm mutants and isoforms are placed into the real muscle fiber environment to exhibit their effect on a level much higher than simple protein complexes; (2) only the primary and immediate effects of Tm mutants are studied in the thin-filament reconstituted myocardium; (3) lethal mutants of Tm can be studied without causing a problem; and (4) inexpensive. In transgenic models, various secondary effects (myocyte disarray, ECM fibrosis, altered protein phosphorylation levels, etc.) also affect the performance of the myocardium, making it very difficult to isolate the primary effect of the mutation. Our studies on Tm have demonstrated that: (1) Tm positively enhances the hydrophobic interaction between actin and myosin in the "closed state", which in turn enhances the isometric tension; (2) Tm's seven periodical repeats carry distinct functions, with the 3rd period being essential for the tension enhancement; (3) Tm mutants lead to HCM by impairing the relaxation on one hand, and lead to DCM by over inhibition of the AM interaction on the other hand. Ca(2+) sensitivity is affected by inorganic phosphate, ionic strength, and phosphorylation of constituent proteins; hence it may not be the primary cause of the pathogenesis. Here, we review our current knowledge regarding Tm's effect on the actomyosin interaction and the early molecular pathogenesis of Tm mutation related to HCM, DCM, and LVNC.
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Janco M, Kalyva A, Scellini B, Piroddi N, Tesi C, Poggesi C, Geeves MA. α-Tropomyosin with a D175N or E180G mutation in only one chain differs from tropomyosin with mutations in both chains. Biochemistry 2012; 51:9880-90. [PMID: 23170982 PMCID: PMC3711130 DOI: 10.1021/bi301323n] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
α-Tropomyosin (Tm) carrying hypertrophic cardiomyopathy mutation D175N or E180G was expressed in Escherichia coli. We have assembled dimers of two polypeptide chains in vitro that carry one (αα*) or two (α*α*) copies of the mutation. We found that the presence of the mutation has little effect on dimer assembly, thereby predicting that individuals heterozygous for the Tm mutations are likely to express both αα* and α*α* Tm. Depending on the expression level, the heterodimer may be the predominant form in individuals carrying the mutation. Thus, it is important to define differences in the properties of Tm molecules carrying one or two copies of the mutation. We examined the Tm homo- and heterodimer properties: actin affinity, thermal stability, calcium regulation of myosin subfragment 1 binding, and calcium regulation of myofibril force. We report that the properties of the heterodimer may be similar to those of the wild-type homodimer (actin affinity, thermal stability, D175N αα*), similar to those of the mutant homodimer (calcium sensitivity, D175N αα*), intermediate between the two (actin affinity, E180G αα*), or different from both (thermal stability, E180G αα*). Thus, the properties of the homodimer are not a completely reliable guide to the properties of the heterodimer.
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Affiliation(s)
- Miro Janco
- School of Biosciences, University of Kent, Canterbury, Kent, United Kingdom
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31
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DCM-related tropomyosin mutants E40K/E54K over-inhibit the actomyosin interaction and lead to a decrease in the number of cycling cross-bridges. PLoS One 2012; 7:e47471. [PMID: 23077624 PMCID: PMC3471818 DOI: 10.1371/journal.pone.0047471] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 09/11/2012] [Indexed: 11/19/2022] Open
Abstract
Two DCM mutants (E40K and E54K) of tropomyosin (Tm) were examined using the thin-filament extraction/reconstitution technique. The effects of the Ca2+, ATP, phosphate (Pi), and ADP concentrations on isometric tension and its transients were studied at 25°C, and the results were compared to those for the WT protein. Our results indicate that both E40K and E54K have a significantly lower THC (high Ca2+ tension at pCa 4.66) (E40K: 1.21±0.06 Ta, ±SEM, N = 34; E54K: 1.24±0.07 Ta, N = 28), a significantly lower TLC (low- Ca2+ tension at pCa 7.0) (E40K: 0.07±0.02 Ta, N = 34; E54K: 0.06±0.02 Ta, N = 28), and a significantly lower Tact (Ca2+ activatable tension) (Tact = THC–TLC, E40K: 1.15±0.08 Ta, N = 34; E54K: 1.18±0.06 Ta, N = 28) than WT (THC = 1.53±0.07 Ta, TLC = 0.12±0.01 Ta, Tact = 1.40±0.07 Ta, N = 25). All tensions were normalized to Ta ( = 13.9±0.8 kPa, N = 57), the tension of actin-filament reconstituted cardiac fibers (myocardium) under the standard activating conditions. The Ca2+ sensitivity (pCa50) of E40K (5.23±0.02, N = 34) and E54K (5.24±0.03, N = 28) was similar to that of the WT protein (5.26±0.03, N = 25). The cooperativity increased significantly in E54K (3.73±0.25, N = 28) compared to WT (2.80±0.17, N = 25). Seven kinetic constants were deduced using sinusoidal analysis at pCa 4.66. These results enabled us to calculate the cross-bridge distribution in the strongly attached states, and thereby deduce the force/cross-bridge. The results indicate that the force/cross-bridge is ∼15% less in E54K than WT, but remains similar to that of the WT protein in the case of E40K. We conclude that over-inhibition of the actomyosin interaction by E40K and E54K Tm mutants leads to a decreased force-generating ability at systole, which is the main mechanism underlying the early pathogenesis of DCM.
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Margaret Sunitha S, Mercer JA, Spudich JA, Sowdhamini R. Integrative structural modelling of the cardiac thin filament: energetics at the interface and conservation patterns reveal a spotlight on period 2 of tropomyosin. Bioinform Biol Insights 2012; 6:203-23. [PMID: 23071391 PMCID: PMC3468436 DOI: 10.4137/bbi.s9798] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cardiomyopathies are a major health problem, with inherited cardiomyopathies, many of which are caused by mutations in genes encoding sarcomeric proteins, constituting an ever-increasing fraction of cases. To begin to study the mechanisms by which these mutations cause disease, we have employed an integrative modelling approach to study the interactions between tropomyosin and actin. Starting from the existing blocked state model, we identified a specific zone on the actin surface which is highly favourable to support tropomyosin sliding from the blocked/closed states to the open state. We then analysed the predicted actin-tropomyosin interface regions for the three states. Each quasi-repeat of tropomyosin was studied for its interaction strength and evolutionary conservation to focus on smaller surface zones. Finally, we show that the distribution of the known cardiomyopathy mutations of α-tropomyosin is consistent with our model. This analysis provides structural insights into the possible mode of interactions between tropomyosin and actin in the open state for the first time.
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Affiliation(s)
- S Margaret Sunitha
- National Centre for Biological Sciences (TIFR), GKVK Campus, Bellary Road, Bangalore, India
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33
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Ly S, Lehrer SS. Long-range effects of familial hypertrophic cardiomyopathy mutations E180G and D175N on the properties of tropomyosin. Biochemistry 2012; 51:6413-20. [PMID: 22794249 PMCID: PMC3447992 DOI: 10.1021/bi3006835] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Cardiac α-tropomyosin (Tm) single-site mutations D175N and E180G cause familial hypertrophic cardiomyopathy (FHC). Previous studies have shown that these mutations increase both Ca(2+) sensitivity and residual contractile activity at low Ca(2+) concentrations, which causes incomplete relaxation during diastole resulting in hypertrophy and sarcomeric disarray. However, the molecular basis for the cause and the difference in the severity of the manifested phenotypes of disease are not known. In this work we have (1) used ATPase studies using reconstituted thin filaments in solution to show that these FHC mutants result in an increase in Ca(2+) sensitivity and an increased residual level of ATPase, (2) shown that both FHC mutants increase the rate of cleavage at R133, ~45 residues N-terminal to the mutations, when free and bound to actin, (3) shown that for Tm-E180G, the increase in the rate of cleavage is greater than that for D175N, and (4) shown that for E180G, cleavage also occurs at a new site 53 residues C-terminal to E180G, in parallel with cleavage at R133. The long-range decreases in dynamic stability due to these two single-site mutations suggest increases in flexibility that may weaken the ability of Tm to inhibit activity at low Ca(2+) concentrations for D175N and to a greater degree for E180G, which may contribute to differences in the severity of FHC.
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Affiliation(s)
- Socheata Ly
- Cardiovascular Program, Boston Biomedical Research Institute, 64 Grove Street, Watertown, MA 02472
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34
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Loong CKP, Zhou HX, Chase PB. Familial hypertrophic cardiomyopathy related E180G mutation increases flexibility of human cardiac α-tropomyosin. FEBS Lett 2012; 586:3503-7. [PMID: 22958892 DOI: 10.1016/j.febslet.2012.08.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 08/02/2012] [Accepted: 08/03/2012] [Indexed: 01/10/2023]
Abstract
α-Tropomyosin (αTm) is central to Ca(2+)-regulation of cardiac muscle contraction. The familial hypertrophic cardiomyopathy mutation αTm E180G enhances Ca(2+)-sensitivity in functional assays. To investigate the molecular basis, we imaged single molecules of human cardiac αTm E180G by direct probe atomic force microscopy. Analyses of tangent angles along molecular contours yielded persistence length corresponding to ~35% increase in flexibility compared to wild-type. Increased flexibility of the mutant was confirmed by fitting end-to-end length distributions to the worm-like chain model. This marked increase in flexibility can significantly impact systolic and possibly diastolic phases of cardiac contraction, ultimately leading to hypertrophy.
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Affiliation(s)
- Campion K P Loong
- Department of Biological Science, The Florida State University, Tallahassee, FL 32306-4370, USA
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35
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The mutations associated with dilated cardiomyopathy. Biochem Res Int 2012; 2012:639250. [PMID: 22830024 PMCID: PMC3399391 DOI: 10.1155/2012/639250] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Revised: 04/25/2012] [Accepted: 05/17/2012] [Indexed: 01/18/2023] Open
Abstract
Cardiomyopathy is an important cause of heart failure and a major indication for heart transplantation in children and adults. This paper describes the state of the genetic knowledge of dilated cardiomyopathy (DCM). The identification of the causing mutation is important since presymptomatic interventions of DCM have proven value in preventing morbidity and mortality. Additionally, as in general in genetic studies, the identification of the mutated genes has a direct clinical impact for the families and population involved. Identifying causative mutations immediately amplifies the possibilities for disease prevention through carrier screening and prenatal testing. This often lifts a burden of social isolation from affected families, since healthy family members can be assured of having healthy children. Identification of the mutated genes holds the potential to lead to the understanding of disease etiology, pathophysiology, and therefore potential therapy. This paper presents the genetic variations, or disease-causing mutations, contributing to the pathogenesis of hereditary DCM, and tries to relate these to the functions of the mutated genes.
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36
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Loong CKP, Badr MA, Chase PB. Tropomyosin flexural rigidity and single ca(2+) regulatory unit dynamics: implications for cooperative regulation of cardiac muscle contraction and cardiomyocyte hypertrophy. Front Physiol 2012; 3:80. [PMID: 22493584 PMCID: PMC3318232 DOI: 10.3389/fphys.2012.00080] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Accepted: 03/18/2012] [Indexed: 01/04/2023] Open
Abstract
Striated muscle contraction is regulated by dynamic and cooperative interactions among Ca2+, troponin, and tropomyosin on the thin filament. While Ca2+ regulation has been extensively studied, little is known about the dynamics of individual regulatory units and structural changes of individual tropomyosin molecules in relation to their mechanical properties, and how these factors are altered by cardiomyopathy mutations in the Ca2+ regulatory proteins. In this hypothesis paper, we explore how various experimental and analytical approaches could broaden our understanding of the cooperative regulation of cardiac contraction in health and disease.
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Affiliation(s)
- Campion K P Loong
- Department of Biological Science, The Florida State University Tallahassee, FL, USA
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37
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Jiang Q, Lust RM, Strynar MJ, Dagnino S, DeWitt JC. Perflurooctanoic acid induces developmental cardiotoxicity in chicken embryos and hatchlings. Toxicology 2012; 293:97-106. [PMID: 22273728 DOI: 10.1016/j.tox.2012.01.005] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/04/2012] [Accepted: 01/10/2012] [Indexed: 01/09/2023]
Abstract
Perfluorooctanoic acid (PFOA) is a widespread environmental contaminant that is detectable in serum of the general U.S. population. PFOA is a known developmental toxicant that induces mortality in mammalian embryos and is thought to induce toxicity via interaction with the peroxisome proliferator activated receptor alpha (PPARα). As the cardiovascular system is crucial for embryonic survival, PFOA-induced effects on the heart may partially explain embryonic mortality. To assess impacts of PFOA exposure on the developing heart in an avian model, we used histopathology and immunohistochemical staining for myosin to assess morphological alterations in 19-day-old chicken embryo hearts after PFOA exposure. Additionally, echocardiography and cardiac myofibril ATPase activity assays were used to assess functional alterations in 1-day-old hatchling chickens following developmental PFOA exposure. Overall thinning and thinning of a dense layer of myosin in the right ventricular wall were observed in PFOA-exposed chicken embryo hearts. Alteration of multiple cardiac structural and functional parameters, including left ventricular wall thickness, left ventricular volume, heart rate, stroke volume, and ejection fraction were detected with echocardiography in the exposed hatchling chickens. Assessment of ATPase activity indicated that the ratio of cardiac myofibril calcium-independent ATPase activity to calcium-dependent ATPase activity was not affected, which suggests that developmental PFOA exposure may not affect cardiac energetics. In summary, structural and functional characteristics of the heart appear to be developmental targets of PFOA, possibly at the level of cardiomyocytes. Additional studies will investigate mechanisms of PFOA-induced developmental cardiotoxicity.
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Affiliation(s)
- Qixiao Jiang
- Department of Pharmacology and Toxicology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, United States
| | - Robert M Lust
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, United States
| | - Mark J Strynar
- Human Exposure and Atmospheric Sciences Division, Methods Development and Application Branch, National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27709, United States
| | - Sonia Dagnino
- Human Exposure and Atmospheric Sciences Division, Methods Development and Application Branch, National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27709, United States
| | - Jamie C DeWitt
- Department of Pharmacology and Toxicology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, United States.
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38
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Dwyer J, Iskratsch T, Ehler E. Actin in striated muscle: recent insights into assembly and maintenance. Biophys Rev 2011; 4:17-25. [PMID: 28510000 DOI: 10.1007/s12551-011-0062-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 11/17/2011] [Indexed: 01/28/2023] Open
Abstract
Striated muscle cells are characterised by a para-crystalline arrangement of their contractile proteins actin and myosin in sarcomeres, the basic unit of the myofibrils. A multitude of proteins is required to build and maintain the structure of this regular arrangement as well as to ensure regulation of contraction and to respond to alterations in demand. This review focuses on the actin filaments (also called thin filaments) of the sarcomere and will discuss how they are assembled during myofibrillogenesis and in hypertrophy and how their integrity is maintained in the working myocardium.
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Affiliation(s)
- Joseph Dwyer
- The Randall Division of Cell and Molecular Biophysics and The Cardiovascular Division, King's College London, British Heart Foundation Centre of Research Excellence, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Thomas Iskratsch
- The Randall Division of Cell and Molecular Biophysics and The Cardiovascular Division, King's College London, British Heart Foundation Centre of Research Excellence, New Hunt's House, Guy's Campus, London, SE1 1UL, UK.,Biological Sciences, Columbia University, 713 Fairchild Center, New York, NY, 10027, USA
| | - Elisabeth Ehler
- The Randall Division of Cell and Molecular Biophysics and The Cardiovascular Division, King's College London, British Heart Foundation Centre of Research Excellence, New Hunt's House, Guy's Campus, London, SE1 1UL, UK.
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Avner BS, Shioura KM, Scruggs SB, Grachoff M, Geenen DL, Helseth DL, Farjah M, Goldspink PH, Solaro RJ. Myocardial infarction in mice alters sarcomeric function via post-translational protein modification. Mol Cell Biochem 2011; 363:203-15. [PMID: 22160857 DOI: 10.1007/s11010-011-1172-z] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Accepted: 11/23/2011] [Indexed: 01/17/2023]
Abstract
Myocardial physiology in the aftermath of myocardial infarction (MI) before remodeling is an under-explored area of investigation. Here, we describe the effects of MI on the cardiac sarcomere with focus on the possible contributions of reactive oxygen species. We surgically induced MI in 6-7-month-old female CD1 mice by ligation of the left anterior descending coronary artery. Data were collected 3-4 days after MI or sham (SH) surgery. MI hearts demonstrated ventricular dilatation and systolic dysfunction upon echo cardiographic analysis. Sub-maximum Ca-activated tension in detergent-extracted fiber bundles from papillary muscles increased significantly in the preparations from MI hearts. Ca(2+) sensitivity increased after MI, whereas cooperativity of activation decreased. To assess myosin enzymatic integrity we measured splitting of Ca-ATP in myofibrillar preparations, which demonstrated a decline in Ca-ATPase activity of myofilament myosin. Biochemical analysis demonstrated post-translational modification of sarcomeric proteins. Phosphorylation of cardiac troponin I and myosin light chain 2 was reduced after MI in papillary samples, as measured using a phospho-specific stain. Tropomyosin was oxidized after MI, forming disulfide products detectable by diagonal non-reducing-reducing SDS-PAGE. Our analysis of myocardial protein oxidation post-MI also demonstrated increased S-glutathionylation. We functionally linked protein oxidation with sarcomere function by treating skinned fibers with the sulfhydryl reducing agent dithiothreitol, which reduced Ca(2+) sensitivity in MI, but not SH, samples. Our data indicate important structural and functional alterations to the cardiac sarcomere after MI, and the contribution of protein oxidation to this process.
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Affiliation(s)
- Benjamin S Avner
- Department of Physiology and Biophysics, (M/C 901), College of Medicine, University of Illinois at Chicago, 835 S. Wolcott Ave., Chicago, IL 60612-7342, USA
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Rysev NA, Karpicheva OE, Redwood CS, Borovikov YS. The effect of the Asp175Asn and Glu180Gly TPM1 mutations on actin-myosin interaction during the ATPase cycle. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1824:366-73. [PMID: 22155441 DOI: 10.1016/j.bbapap.2011.11.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Revised: 10/31/2011] [Accepted: 11/23/2011] [Indexed: 01/29/2023]
Abstract
Hypertrophic cardiomyopathy (HCM), characterized by cardiac hypertrophy and contractile dysfunction, is a major cause of heart failure. HCM can result from mutations in the gene encoding cardiac α-tropomyosin (TM). To understand how the HCM-causing Asp175Asn and Glu180Gly mutations in α-tropomyosin affect on actin-myosin interaction during the ATPase cycle, we labeled the SH1 helix of myosin subfragment-1 and the actin subdomain-1 with the fluorescent probe N-iodoacetyl-N'-(5-sulfo-1-naphtylo)ethylenediamine. These proteins were incorporated into ghost muscle fibers and their conformational states were monitored during the ATPase cycle by measuring polarized fluorescence. For the first time, the effect of these α-tropomyosins on the mobility and rotation of subdomain-1 of actin and the SH1 helix of myosin subfragment-1 during the ATP hydrolysis cycle have been demonstrated directly by polarized fluorimetry. Wild-type α-tropomyosin increases the amplitude of the SH1 helix and subdomain-1 movements during the ATPase cycle, indicating the enhancement of the efficiency of the work of cross-bridges. Both mutant TMs increase the proportion of the strong-binding sub-states, with the effect of the Glu180Gly mutation being greater than that of Asp175Asn. It is suggested that the alteration in the concerted conformational changes of actomyosin is likely to provide the structural basis for the altered cardiac muscle contraction.
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Affiliation(s)
- Nikita A Rysev
- Laboratory of Mechanisms of Cell Motility, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
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41
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The 3-state model of muscle regulation revisited: is a fourth state involved? J Muscle Res Cell Motil 2011; 32:203-8. [DOI: 10.1007/s10974-011-9263-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 09/13/2011] [Indexed: 10/17/2022]
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Borovikov YS, Avrova SV, Karpicheva OE, Robinson P, Redwood CS. The effect of the dilated cardiomyopathy-causing Glu40Lys TPM1 mutation on actin-myosin interactions during the ATPase cycle. Biochem Biophys Res Commun 2011; 411:496-500. [PMID: 21741356 DOI: 10.1016/j.bbrc.2011.06.138] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 06/20/2011] [Indexed: 10/18/2022]
Abstract
Dilated cardiomyopathy (DCM), characterized by cardiac dilatation and contractile dysfunction, is a major cause of heart failure. DCM can result from mutations in the gene encoding cardiac α-tropomyosin (TM). In order to understand how the dilated cardiomyopathy-causing Glu40Lys mutation in TM affects actomyosin interactions, thin filaments have been reconstituted in muscle ghost fibers by incorporation of labeled Cys707 of myosin subfragment-1 and Cys374 of actin with fluorescent probe 1.5-IAEDANS and α-tropomyosin (wild-type or Glu40Lys mutant). For the first time, the effect of these α-tropomyosins on the mobility and rotation of subdomain-1 of actin and the SH1 helix of myosin subfragment-1 during the ATP hydrolysis cycle have been demonstrated directly by polarized fluorimetry. The Glu40Lys mutant TM inhibited these movements at the transition from AM(∗∗)·ADP·Pi to AM state, indicating a decrease of the proportion of the strong-binding sub-states in the actomyosin population. These structural changes are likely to underlie the contractile deficit observed in human dilated cardiomyopathy.
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Affiliation(s)
- Yurii S Borovikov
- Laboratory of Mechanisms of Cell Motility, Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia.
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Kimura A. Contribution of genetic factors to the pathogenesis of dilated cardiomyopathy: the cause of dilated cardiomyopathy: genetic or acquired? (genetic-side). Circ J 2011; 75:1756-65; discussion 1765. [PMID: 21617319 DOI: 10.1253/circj.cj-11-0368] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dilated cardiomyopathy (DCM) is characterized by dilated ventricles and systolic dysfunction. Its etiology is not fully unraveled, but both extrinsic and intrinsic factors are considered to be involved. The intrinsic factors include genetic variations in the genes (ie, disease-causing mutations and disease-associated polymorphisms), which play key roles in controlling the susceptibility to the disease by affecting the performance, regulation, and/or maintenance of cardiac function. DCM can be classified into 2 types: hereditary and non-hereditary. The genetic variations, or disease-causing mutations, contributing to the pathogenesis of hereditary DCM can be found in various genes, especially those for sarcolemma elements, contractile elements, Z-disc elements, sarcoplasmic elements, and nuclear lamina elements of cardiomyocytes. On the other hand, disease-associated polymorphisms, which control the susceptibility to non-hereditary DCM, may be found in genes expressing not only in cardiomyocytes but also other non-cardiac cells involved in the immune system. Because functional alterations caused by these genetic variations can be classified into several categories, it is necessary to understand the pathogenesis and hence to develop diagnostic and therapeutic strategies for both hereditary and non-hereditary DCM from the viewpoint of genetic factors.
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Affiliation(s)
- Akinori Kimura
- Department of Molecular Pathogenesis, Medical Research Institute, and Laboratory of Genome Diversity, Graduate School of Biomedical Science, Tokyo Medical and Dental University
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Bai F, Weis A, Takeda AK, Chase PB, Kawai M. Enhanced active cross-bridges during diastole: molecular pathogenesis of tropomyosin's HCM mutations. Biophys J 2011; 100:1014-23. [PMID: 21320446 DOI: 10.1016/j.bpj.2011.01.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Revised: 12/22/2010] [Accepted: 01/03/2011] [Indexed: 11/28/2022] Open
Abstract
Three HCM-causing tropomyosin (Tm) mutants (V95A, D175N, and E180G) were examined using the thin-filament extraction and reconstitution technique. The effects of Ca(2+), ATP, phosphate, and ADP concentrations on cross-bridge kinetics in myocardium reconstituted with each of these mutants were studied at 25°C, and compared to wild-type (WT) Tm at physiological ionic strength (200 mM). All three mutants showed significantly higher (2-3.5 fold) low Ca(2+) tension (T(LC)) and stiffness than WT at pCa 8.0. High Ca(2+) tension (T(HC)) was significantly higher for E180G than that for WT, whereas T(HC) of V95A and D175N was similar to WT; high Ca(2+) stiffness (Y(HC)) had the same trend. The Ca(2+) sensitivity of isometric force was significantly greater for V95A and E180G than for WT, whereas that of D175N remained the same as for WT; for all mutants, cooperativity was lower than for WT. Nine kinetic constants and the cross-bridge distribution were deduced using sinusoidal analysis. The number of force-generating cross bridges was similar among the D175N, E180G, and WT Tm forms, but it was significantly larger in the case of V95A than WT. We conclude that the increased number of actively cycling cross bridges at pCa 8 is the major cause of Tm mutation-related HCM pathogenesis, which may result in diastolic dysfunction. Decreased contractility (T(act)) in V95A and D175N may further contribute to the severity of myocyte hypertrophy and related prognosis of the disease.
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Affiliation(s)
- Fan Bai
- Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa, USA
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Chang B, Nishizawa T, Furutani M, Fujiki A, Tani M, Kawaguchi M, Ibuki K, Hirono K, Taneichi H, Uese K, Onuma Y, Bowles NE, Ichida F, Inoue H, Matsuoka R, Miyawaki T. Identification of a novel TPM1 mutation in a family with left ventricular noncompaction and sudden death. Mol Genet Metab 2011; 102:200-6. [PMID: 20965760 DOI: 10.1016/j.ymgme.2010.09.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Accepted: 09/23/2010] [Indexed: 01/12/2023]
Abstract
Left ventricular noncompaction (LVNC) is a cardiomyopathy morphologically characterized by 2-layered myocardium, numerous prominent trabeculations, and deep intertrabecular recesses communicating with the left ventricular cavity. The purpose of this study was to investigate patients with LVNC for possible disease causing mutations. We screened 4 genes (TAZ, LDB3, DTNA and TPM1) in 51 patients with LVNC for mutations by polymerase chain reaction and direct DNA sequencing. A novel missense substitution in exon 1 of TPM1 (c.109A>G: p.Lys37Glu) was identified in three affected members of a family with isolated LVNC. The substitution brings about a change in amino acid charge at a highly conserved residue and could result in aberrant mRNA splicing. This variant was not identified in 200 normal control samples. Pathologic analysis of a right ventricular myocardial specimen from the proband's maternal aunt revealed endocardial and subendocardial fibrosis with prominent elastin deposition, as well as the presence of adipose tissue between muscle layers, pathologic changes that are distinct from those seen in patients with HCM or DCM. Screening of the proband and her mother for variants in other sarcomeric protein-encoding candidate genes, MYH7, MYBPC3, TNNT2, TNNI3, ACTC, MYL2, and MYL3, did not identify any other non-synonymous variants or variants in splice donor-acceptor sequences that were potentially disease causing. We conclude TPM1 is a potential candidate disease-causing gene for isolated LVNC, especially in patients experiencing sudden death.
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Affiliation(s)
- Bo Chang
- Department of Pediatrics, University of Toyama, 2630 Sugitani, Toyama, Japan
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Song W, Dyer E, Stuckey D, Leung MC, Memo M, Mansfield C, Ferenczi M, Liu K, Redwood C, Nowak K, Harding S, Clarke K, Wells D, Marston S. Investigation of a transgenic mouse model of familial dilated cardiomyopathy. J Mol Cell Cardiol 2010; 49:380-9. [DOI: 10.1016/j.yjmcc.2010.05.009] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 05/17/2010] [Accepted: 05/18/2010] [Indexed: 11/25/2022]
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Parvatiyar MS, Pinto JR, Liang J, Potter JD. Predicting cardiomyopathic phenotypes by altering Ca2+ affinity of cardiac troponin C. J Biol Chem 2010; 285:27785-97. [PMID: 20566645 DOI: 10.1074/jbc.m110.112326] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Cardiac diseases associated with mutations in troponin subunits include hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and restrictive cardiomyopathy (RCM). Altered calcium handling in these diseases is evidenced by changes in the Ca(2+) sensitivity of contraction. Mutations in the Ca(2+) sensor, troponin C (TnC), were generated to increase/decrease the Ca(2+) sensitivity of cardiac skinned fibers to create the characteristic effects of DCM, HCM, and RCM. We also used a reconstituted assay to determine the mutation effects on ATPase activation and inhibition. One mutant (A23Q) was found with HCM-like properties (increased Ca(2+) sensitivity of force and normal levels of ATPase inhibition). Three mutants (S37G, V44Q, and L48Q) were identified with RCM-like properties (a large increase in Ca(2+) sensitivity, partial loss of ATPase inhibition, and increased basal force). Two mutations were identified (E40A and I61Q) with DCM properties (decreased Ca(2+) sensitivity, maximal force recovery, and activation of the ATPase at high [Ca(2+)]). Steady-state fluorescence was utilized to assess Ca(2+) affinity in isolated cardiac (c)TnCs containing F27W and did not necessarily mirror the fiber Ca(2+) sensitivity. Circular dichroism of mutant cTnCs revealed a trend where increased alpha-helical content correlated with increased Ca(2+) sensitivity in skinned fibers and vice versa. The main findings from this study were as follows: 1) cTnC mutants demonstrated distinct functional phenotypes reminiscent of bona fide HCM, RCM, and DCM mutations; 2) a region in cTnC associated with increased Ca(2+) sensitivity in skinned fibers was identified; and 3) the F27W reporter mutation affected Ca(2+) sensitivity, maximal force, and ATPase activation of some mutants.
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Affiliation(s)
- Michelle S Parvatiyar
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136, USA
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Callis TE, Jensen BC, Weck KE, Willis MS. Evolving molecular diagnostics for familial cardiomyopathies: at the heart of it all. Expert Rev Mol Diagn 2010; 10:329-51. [PMID: 20370590 PMCID: PMC5022563 DOI: 10.1586/erm.10.13] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cardiomyopathies are an important and heterogeneous group of common cardiac diseases. An increasing number of cardiomyopathies are now recognized to have familial forms, which result from single-gene mutations that render a Mendelian inheritance pattern, including hypertrophic cardiomyopathy, dilated cardiomyopathy, restrictive cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy and left ventricular noncompaction cardiomyopathy. Recently, clinical genetic tests for familial cardiomyopathies have become available for clinicians evaluating and treating patients with these diseases, making it necessary to understand the current progress and challenges in cardiomyopathy genetics and diagnostics. In this review, we summarize the genetic basis of selected cardiomyopathies, describe the clinical utility of genetic testing for cardiomyopathies and outline the current challenges and emerging developments.
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Affiliation(s)
- Thomas E Callis
- PGxHealth Division, Clinical Data, Inc., 5 Science Park, New Haven, CT 06511, USA
| | - Brian C Jensen
- McAllister Heart Institute, University of North Carolina, Chapel Hill, NC, 27599-7126, USA and Department of Internal Medicine, Section of Cardiology, University of North Carolina, Chapel Hill, NC 27599-7075, USA
| | - Karen E Weck
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599-7525, USA
| | - Monte S Willis
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599-7525, USA and McAllister Heart Institute, University of North Carolina at Chapel Hill, 2340B Medical Biomolecular Research Building, 103 Mason Farm Road, Chapel Hill, NC 27599-7525, USA Tel.: +1 919 843 1938 Fax: +1 919 843 4585
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Tardiff JC. Tropomyosin and dilated cardiomyopathy: revenge of the actinomyosin "gatekeeper". J Am Coll Cardiol 2010; 55:330-2. [PMID: 20117438 DOI: 10.1016/j.jacc.2009.11.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Accepted: 11/19/2009] [Indexed: 10/19/2022]
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50
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Rescue of familial cardiomyopathies by modifications at the level of sarcomere and Ca2+ fluxes. J Mol Cell Cardiol 2010; 48:834-42. [PMID: 20079744 DOI: 10.1016/j.yjmcc.2010.01.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 12/30/2009] [Accepted: 01/06/2010] [Indexed: 12/21/2022]
Abstract
Cardiomyopathies are a heterogeneous group of diseases of the myocardium associated with mechanical and/or electrical dysfunction that frequently show inappropriate ventricular hypertrophy or dilation. Current data suggest that numerous mutations in several genes can cause cardiomyopathies, and the severity of their phenotypes is also influenced by modifier genes. Two major types of inherited cardiomyopathies include familial hypertrophic cardiomyopathy (FHC) and dilated cardiomyopathy (DCM). FHC typically involves increased myofilament Ca(2+) sensitivity associated with diastolic dysfunction, whereas DCM often results in decreased myofilament Ca(2+) sensitivity and systolic dysfunction. Besides alterations in myofilament Ca(2+) sensitivity, alterations in the levels of Ca(2+)-handling proteins have also been described in both diseases. Recent work in animal models has attempted to rescue FHC and DCM via modifications at the myofilament level, altering Ca(2+) homeostasis by targeting Ca(2+)-handling proteins, such as the sarcoplasmic reticulum ATPase and phospholamban, or by interfering with the products of different modifiers genes. Although attempts to rescue cardiomyopathies in animal models have shown great promise, further studies are needed to validate these strategies in order to provide more effective and specific treatments.
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