1
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Irving M. Functional control of myosin motors in the cardiac cycle. Nat Rev Cardiol 2024:10.1038/s41569-024-01063-5. [PMID: 39030271 DOI: 10.1038/s41569-024-01063-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/02/2024] [Indexed: 07/21/2024]
Abstract
Contraction of the heart is driven by cyclical interactions between myosin and actin filaments powered by ATP hydrolysis. The modular structure of heart muscle and the organ-level synchrony of the heartbeat ensure tight reciprocal coupling between this myosin ATPase cycle and the macroscopic cardiac cycle. The myosin motors respond to the cyclical activation of the actin and myosin filaments to drive the pressure changes that control the inflow and outflow valves of the heart chambers. Opening and closing of the valves in turn switches the myosin motors between roughly isometric and roughly isotonic contraction modes. Peak filament stress in the heart is much smaller than in fully activated skeletal muscle, although the myosin filaments in the two muscle types have the same number of myosin motors. Calculations indicate that only ~5% of the myosin motors in the heart are needed to generate peak systolic pressure, although many more motors are needed to drive ejection. Tight regulation of the number of active motors is essential for the efficient functioning of the healthy heart - this control is commonly disrupted by gene variants associated with inherited heart disease, and its restoration might be a useful end point in the development of novel therapies.
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Affiliation(s)
- Malcolm Irving
- Randall Centre for Cell and Molecular Biophysics and BHF Centre for Research Excellence, King's College London, London, UK.
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2
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Auguin D, Robert-Paganin J, Réty S, Kikuti C, David A, Theumer G, Schmidt AW, Knölker HJ, Houdusse A. Omecamtiv mecarbil and Mavacamten target the same myosin pocket despite opposite effects in heart contraction. Nat Commun 2024; 15:4885. [PMID: 38849353 PMCID: PMC11161628 DOI: 10.1038/s41467-024-47587-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 04/03/2024] [Indexed: 06/09/2024] Open
Abstract
Inherited cardiomyopathies are common cardiac diseases worldwide, leading in the late stage to heart failure and death. The most promising treatments against these diseases are small molecules directly modulating the force produced by β-cardiac myosin, the molecular motor driving heart contraction. Omecamtiv mecarbil and Mavacamten are two such molecules that completed phase 3 clinical trials, and the inhibitor Mavacamten is now approved by the FDA. In contrast to Mavacamten, Omecamtiv mecarbil acts as an activator of cardiac contractility. Here, we reveal by X-ray crystallography that both drugs target the same pocket and stabilize a pre-stroke structural state, with only few local differences. All-atom molecular dynamics simulations reveal how these molecules produce distinct effects in motor allostery thus impacting force production in opposite way. Altogether, our results provide the framework for rational drug development for the purpose of personalized medicine.
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Affiliation(s)
- Daniel Auguin
- Structural Motility, Institut Curie, Université Paris Sciences et Lettres, Sorbonne Université, CNRS UMR144, Paris, 75248, France
- Laboratoire de Physiologie, Ecologie et Environnement (P2E), UPRES EA 1207/USC INRAE-1328, UFR Sciences et Techniques, Université d'Orléans, Orléans, France
| | - Julien Robert-Paganin
- Structural Motility, Institut Curie, Université Paris Sciences et Lettres, Sorbonne Université, CNRS UMR144, Paris, 75248, France
| | - Stéphane Réty
- Laboratoire de Biologie et Modélisation de la Cellule, ENS de Lyon, CNRS, UMR 5239, Inserm, U1293, Université Claude Bernard Lyon 1, Lyon, France
| | - Carlos Kikuti
- Structural Motility, Institut Curie, Université Paris Sciences et Lettres, Sorbonne Université, CNRS UMR144, Paris, 75248, France
| | - Amandine David
- Structural Motility, Institut Curie, Université Paris Sciences et Lettres, Sorbonne Université, CNRS UMR144, Paris, 75248, France
| | | | | | | | - Anne Houdusse
- Structural Motility, Institut Curie, Université Paris Sciences et Lettres, Sorbonne Université, CNRS UMR144, Paris, 75248, France.
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3
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Jani VP, Song T, Gao C, Gong H, Sadayappan S, Kass DA, Irving TC, Ma W. The structural OFF and ON states of myosin can be decoupled from the biochemical super- and disordered-relaxed states. PNAS NEXUS 2024; 3:pgae039. [PMID: 38328779 PMCID: PMC10849796 DOI: 10.1093/pnasnexus/pgae039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Accepted: 01/19/2024] [Indexed: 02/09/2024]
Abstract
There is a growing awareness that both thick-filament and classical thin-filament regulations play central roles in modulating muscle contraction. Myosin ATPase assays have demonstrated that under relaxed conditions, myosin may reside either in a high-energy-consuming disordered-relaxed (DRX) state available for binding actin to generate force or in an energy-sparing super-relaxed (SRX) state unavailable for actin binding. X-ray diffraction studies have shown that the majority of myosin heads are in a quasi-helically ordered OFF state in a resting muscle and that this helical ordering is lost when myosin heads are turned ON for contraction. It has been assumed that myosin heads in SRX and DRX states are equivalent to the OFF and ON states, respectively, and the terms have been used interchangeably. In this study, we use X-ray diffraction and ATP turnover assays to track the structural and biochemical transitions of myosin heads, respectively, induced with either omecamtiv mecarbil (OM) or piperine in relaxed porcine myocardium. We find that while OM and piperine induce dramatic shifts of myosin heads from the OFF to the ON state, there are no appreciable changes in the population of myosin heads in the SRX and DRX states in both unloaded and loaded preparations. Our results show that biochemically defined SRX and DRX can be decoupled from structurally defined OFF and ON states. In summary, while SRX/DRX and OFF/ON transitions can be correlated in some cases, these two phenomena are measured using different approaches, reflect different properties of the thick filament, and should be investigated and interpreted separately.
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Affiliation(s)
- Vivek P Jani
- Department of Biomedical Engineering, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Taejeong Song
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45229, USA
| | - Chengqian Gao
- College of Basic Medical Sciences, Dalian Medical University, Dalian, Liaoning 116044, China
| | - Henry Gong
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Sakthivel Sadayappan
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45229, USA
| | - David A Kass
- Department of Biomedical Engineering, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Thomas C Irving
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
- Center for Synchrotron Radiation Research and Instrumentation, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Weikang Ma
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
- Center for Synchrotron Radiation Research and Instrumentation, Illinois Institute of Technology, Chicago, IL 60616, USA
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4
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Parijat P, Attili S, Hoare Z, Shattock M, Kenyon V, Kampourakis T. Discovery of a novel cardiac-specific myosin modulator using artificial intelligence-based virtual screening. Nat Commun 2023; 14:7692. [PMID: 38001148 PMCID: PMC10673995 DOI: 10.1038/s41467-023-43538-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 11/13/2023] [Indexed: 11/26/2023] Open
Abstract
Direct modulation of cardiac myosin function has emerged as a therapeutic target for both heart disease and heart failure. However, the development of myosin-based therapeutics has been hampered by the lack of targeted in vitro screening assays. In this study we use Artificial Intelligence-based virtual high throughput screening (vHTS) to identify novel small molecule effectors of human β-cardiac myosin. We test the top scoring compounds from vHTS in biochemical counter-screens and identify a novel chemical scaffold called 'F10' as a cardiac-specific low-micromolar myosin inhibitor. Biochemical and biophysical characterization in both isolated proteins and muscle fibers show that F10 stabilizes both the biochemical (i.e. super-relaxed state) and structural (i.e. interacting heads motif) OFF state of cardiac myosin, and reduces force and left ventricular pressure development in isolated myofilaments and Langendorff-perfused hearts, respectively. F10 is a tunable scaffold for the further development of a novel class of myosin modulators.
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Affiliation(s)
- Priyanka Parijat
- Randall Centre for Cell and Molecular Biophysics; and British Heart Foundation Centre of Research Excellence, King's College London, London, SE1 1UL, United Kingdom
| | - Seetharamaiah Attili
- Randall Centre for Cell and Molecular Biophysics; and British Heart Foundation Centre of Research Excellence, King's College London, London, SE1 1UL, United Kingdom
| | - Zoe Hoare
- School of Cardiovascular and Metabolic Medicine and Sciences; Rayne Institute and British Heart Foundation Centre of Research Excellence, King's College London, London, SE5 9NU, United Kingdom
| | - Michael Shattock
- School of Cardiovascular and Metabolic Medicine and Sciences; Rayne Institute and British Heart Foundation Centre of Research Excellence, King's College London, London, SE5 9NU, United Kingdom
| | | | - Thomas Kampourakis
- Randall Centre for Cell and Molecular Biophysics; and British Heart Foundation Centre of Research Excellence, King's College London, London, SE1 1UL, United Kingdom.
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5
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Auguin D, Robert-Paganin J, Réty S, Kikuti C, David A, Theumer G, Schmidt AW, Knölker HJ, Houdusse A. Omecamtiv mecarbil and Mavacamten target the same myosin pocket despite antagonistic effects in heart contraction. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.15.567213. [PMID: 38014327 PMCID: PMC10680719 DOI: 10.1101/2023.11.15.567213] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Inherited cardiomyopathies are amongst the most common cardiac diseases worldwide, leading in the late-stage to heart failure and death. The most promising treatments against these diseases are small-molecules directly modulating the force produced by β-cardiac myosin, the molecular motor driving heart contraction. Two of these molecules that produce antagonistic effects on cardiac contractility have completed clinical phase 3 trials: the activator Omecamtiv mecarbil and the inhibitor Mavacamten. In this work, we reveal by X-ray crystallography that both drugs target the same pocket and stabilize a pre-stroke structural state, with only few local differences. All atoms molecular dynamics simulations reveal how these molecules can have antagonistic impact on the allostery of the motor by comparing β-cardiac myosin in the apo form or bound to Omecamtiv mecarbil or Mavacamten. Altogether, our results provide the framework for rational drug development for the purpose of personalized medicine.
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Affiliation(s)
- Daniel Auguin
- Structural Motility, UMR 144 CNRS/Curie Institute, PSL Research University, 26 rue d'Ulm, 75258 Paris cedex 05, France
- Laboratoire de Biologie des Ligneux et des Grandes Cultures, Université d'Orléans, UPRES EA 1207, INRAE- USC1328, F-45067 Orléans, France
| | - Julien Robert-Paganin
- Structural Motility, UMR 144 CNRS/Curie Institute, PSL Research University, 26 rue d'Ulm, 75258 Paris cedex 05, France
| | - Stéphane Réty
- Laboratoire de Biologie et Modélisation de la Cellule, ENS de Lyon, University Claude Bernard, CNRS UMR 5239, INSERM U1210, 46 Allée d'Italie Site Jacques Monod, F-69007 Lyon, France
| | - Carlos Kikuti
- Structural Motility, UMR 144 CNRS/Curie Institute, PSL Research University, 26 rue d'Ulm, 75258 Paris cedex 05, France
| | - Amandine David
- Structural Motility, UMR 144 CNRS/Curie Institute, PSL Research University, 26 rue d'Ulm, 75258 Paris cedex 05, France
| | - Gabriele Theumer
- Faculty of Chemistry, TU Dresden, Bergstraße 66, 01069 Dresden, Germany
| | - Arndt W Schmidt
- Faculty of Chemistry, TU Dresden, Bergstraße 66, 01069 Dresden, Germany
| | | | - Anne Houdusse
- Structural Motility, UMR 144 CNRS/Curie Institute, PSL Research University, 26 rue d'Ulm, 75258 Paris cedex 05, France
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6
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Landim-Vieira M, Knollmann BC. Danicamtiv Recruits Myosin Motors to Aid the Failing Heart. Circ Res 2023; 133:444-446. [PMID: 37590375 DOI: 10.1161/circresaha.123.323366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 08/19/2023]
Affiliation(s)
- Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University, College of Medicine, Tallahassee, FL (M.L-V.)
| | - Bjorn C Knollmann
- Division of Clinical Pharmacology, Vanderbilt Center for Arrhythmia Research and Therapeutics, Vanderbilt University Medical Center, Nashville, TN (B.C. Knollmann)
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7
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Ostrominski JW, Guo R, Elliott PM, Ho CY. Cardiac Myosin Inhibitors for Managing Obstructive Hypertrophic Cardiomyopathy: JACC: Heart Failure State-of-the-Art Review. JACC. HEART FAILURE 2023; 11:735-748. [PMID: 37407153 DOI: 10.1016/j.jchf.2023.04.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 04/17/2023] [Accepted: 04/26/2023] [Indexed: 07/07/2023]
Abstract
Hypertrophic cardiomyopathy (HCM) is frequently caused by pathogenic variants in genes encoding sarcomere proteins and is characterized by left ventricular (LV) hypertrophy, hypercontractility, and-in many cases-left ventricular outflow tract (LVOT) obstruction. Despite standard management, obstructive HCM (oHCM) can still cause substantial morbidity, highlighting the critical need for more effective disease-specific therapeutic approaches. Over the past decade, improved understanding of the molecular pathobiology of HCM has culminated in development of cardiac myosin inhibitors (CMIs), a novel drug class that in recent randomized clinical trials has been shown to decrease LVOT obstruction, improve exercise capacity, and ameliorate symptom burden in patients with oHCM. Although promising, areas of uncertainty remain, including the long-term safety and efficacy of CMIs and whether they have the potential to modify progression of disease. Herein, we review key milestones in the clinical development of CMIs, contextualize CMIs with established oHCM therapies, and discuss future challenges and opportunities for the use of CMIs across the HCM spectrum.
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Affiliation(s)
- John W Ostrominski
- Division of Cardiovascular Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Ruby Guo
- Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Perry M Elliott
- Centre for Heart Muscle Disease, Institute of Cardiological Sciences, University College London and St Bartholomew's Hospital, London, United Kingdom
| | - Carolyn Y Ho
- Division of Cardiovascular Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
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8
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Fujita H, Kaneshiro J, Takeda M, Sasaki K, Yamamoto R, Umetsu D, Kuranaga E, Higo S, Kondo T, Asano Y, Sakata Y, Miyagawa S, Watanabe TM. Estimation of crossbridge-state during cardiomyocyte beating using second harmonic generation. Life Sci Alliance 2023; 6:e202302070. [PMID: 37236659 PMCID: PMC10215972 DOI: 10.26508/lsa.202302070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Revised: 04/21/2023] [Accepted: 04/21/2023] [Indexed: 05/28/2023] Open
Abstract
Estimation of dynamic change of crossbridge formation in living cardiomyocytes is expected to provide crucial information for elucidating cardiomyopathy mechanisms, efficacy of an intervention, and others. Here, we established an assay system to dynamically measure second harmonic generation (SHG) anisotropy derived from myosin filaments depended on their crossbridge status in pulsating cardiomyocytes. Experiments utilizing an inheritable mutation that induces excessive myosin-actin interactions revealed that the correlation between sarcomere length and SHG anisotropy represents crossbridge formation ratio during pulsation. Furthermore, the present method found that ultraviolet irradiation induced an increased population of attached crossbridges that lost the force-generating ability upon myocardial differentiation. Taking an advantage of infrared two-photon excitation in SHG microscopy, myocardial dysfunction could be intravitally evaluated in a Drosophila disease model. Thus, we successfully demonstrated the applicability and effectiveness of the present method to evaluate the actomyosin activity of a drug or genetic defect on cardiomyocytes. Because genomic inspection alone may not catch the risk of cardiomyopathy in some cases, our study demonstrated herein would be of help in the risk assessment of future heart failure.
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Affiliation(s)
- Hideaki Fujita
- Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan
| | - Junichi Kaneshiro
- Laboratory for Comprehensive Bioimaging, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Maki Takeda
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Kensuke Sasaki
- Laboratory for Comprehensive Bioimaging, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Rikako Yamamoto
- Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan
| | - Daiki Umetsu
- Laboratory for Histogenetic Dynamics, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka, Japan
| | - Erina Kuranaga
- Laboratory for Histogenetic Dynamics, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Shuichiro Higo
- Department of Medical Therapeutics for Heart Failure, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Takumi Kondo
- Department of Medical Therapeutics for Heart Failure, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yoshihiro Asano
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yasushi Sakata
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Shigeru Miyagawa
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Tomonobu M Watanabe
- Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan
- Laboratory for Comprehensive Bioimaging, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
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9
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Grinzato A, Auguin D, Kikuti C, Nandwani N, Moussaoui D, Pathak D, Kandiah E, Ruppel KM, Spudich JA, Houdusse A, Robert-Paganin J. Cryo-EM structure of the folded-back state of human β-cardiac myosin. Nat Commun 2023; 14:3166. [PMID: 37258552 PMCID: PMC10232470 DOI: 10.1038/s41467-023-38698-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 05/11/2023] [Indexed: 06/02/2023] Open
Abstract
To save energy and precisely regulate cardiac contractility, cardiac muscle myosin heads are sequestered in an 'off' state that can be converted to an 'on' state when exertion is increased. The 'off' state is equated with a folded-back structure known as the interacting-heads motif (IHM), which is a regulatory feature of all class-2 muscle and non-muscle myosins. We report here the human β-cardiac myosin IHM structure determined by cryo-electron microscopy to 3.6 Å resolution, providing details of all the interfaces stabilizing the 'off' state. The structure shows that these interfaces are hot spots of hypertrophic cardiomyopathy mutations that are thought to cause hypercontractility by destabilizing the 'off' state. Importantly, the cardiac and smooth muscle myosin IHM structures dramatically differ, providing structural evidence for the divergent physiological regulation of these muscle types. The cardiac IHM structure will facilitate development of clinically useful new molecules that modulate IHM stability.
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Affiliation(s)
- Alessandro Grinzato
- CM01 beamline. European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - Daniel Auguin
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, CNRS UMR144, F-75005, Paris, France
- Laboratoire de Biologie des Ligneux et des Grandes Cultures, Université d'Orléans, UPRES EA 1207, INRA-USC1328, F-45067, Orléans, France
| | - Carlos Kikuti
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, CNRS UMR144, F-75005, Paris, France
| | - Neha Nandwani
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Dihia Moussaoui
- BM29 BIOSAXS beamline, European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - Divya Pathak
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Eaazhisai Kandiah
- CM01 beamline. European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - Kathleen M Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA.
- Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, 94305, USA.
| | - James A Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Anne Houdusse
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, CNRS UMR144, F-75005, Paris, France.
| | - Julien Robert-Paganin
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, CNRS UMR144, F-75005, Paris, France.
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10
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Grinzato A, Auguin D, Kikuti C, Nandwani N, Moussaoui D, Pathak D, Kandiah E, Ruppel KM, Spudich JA, Houdusse A, Robert-Paganin J. Cryo-EM structure of the folded-back state of human β-cardiac myosin. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.15.536999. [PMID: 37131793 PMCID: PMC10153137 DOI: 10.1101/2023.04.15.536999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
During normal levels of exertion, many cardiac muscle myosin heads are sequestered in an off-state even during systolic contraction to save energy and for precise regulation. They can be converted to an on-state when exertion is increased. Hypercontractility caused by hypertrophic cardiomyopathy (HCM) myosin mutations is often the result of shifting the equilibrium toward more heads in the on-state. The off-state is equated with a folded-back structure known as the interacting head motif (IHM), which is a regulatory feature of all muscle myosins and class-2 non-muscle myosins. We report here the human β-cardiac myosin IHM structure to 3.6 Å resolution. The structure shows that the interfaces are hot spots of HCM mutations and reveals details of the significant interactions. Importantly, the structures of cardiac and smooth muscle myosin IHMs are dramatically different. This challenges the concept that the IHM structure is conserved in all muscle types and opens new perspectives in the understanding of muscle physiology. The cardiac IHM structure has been the missing puzzle piece to fully understand the development of inherited cardiomyopathies. This work will pave the way for the development of new molecules able to stabilize or destabilize the IHM in a personalized medicine approach. *This manuscript was submitted to Nature Communications in August 2022 and dealt efficiently by the editors. All reviewers received this version of the manuscript before 9 208 August 2022. They also received coordinates and maps of our high resolution structure on the 18 208 August 2022. Due to slowness of at least one reviewer, this contribution was delayed for acceptance by Nature Communications and we are now depositing in bioRxiv the originally submitted version written in July 2022 for everyone to see. Indeed, two bioRxiv contributions at lower resolution but adding similar concepts on thick filament regulation were deposited this week in bioRxiv, one of the contributions having had access to our coordinates. We hope that our data at high resolution will be helpful for all readers that appreciate that high resolution information is required to build accurate atomic models and discuss implications for sarcomere regulation and the effects of cardiomyopathy mutations on heart muscle function.
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Affiliation(s)
- Alessandro Grinzato
- CM01 beamline. European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - Daniel Auguin
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, CNRS UMR144, F-75005 Paris, France
- Laboratoire de Biologie des Ligneux et des Grandes Cultures, Université d’Orléans, UPRES EA 1207, INRA-USC1328, F-45067 Orléans, France
| | - Carlos Kikuti
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, CNRS UMR144, F-75005 Paris, France
| | - Neha Nandwani
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, United States
| | - Dihia Moussaoui
- BM29 BIOSAXS beamline, European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - Divya Pathak
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, United States
| | - Eaazhisai Kandiah
- CM01 beamline. European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - Kathleen M. Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, United States
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California 94305, United States
| | - James A. Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, United States
| | - Anne Houdusse
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, CNRS UMR144, F-75005 Paris, France
| | - Julien Robert-Paganin
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, CNRS UMR144, F-75005 Paris, France
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11
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Fukuda N, Granzier H, Ishiwata S, Morimoto S. Editorial: Recent Advances on Myocardium Physiology, Volume II. Front Physiol 2023; 14:1170396. [PMID: 37008018 PMCID: PMC10053225 DOI: 10.3389/fphys.2023.1170396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 02/27/2023] [Indexed: 03/14/2023] Open
Affiliation(s)
- Norio Fukuda
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan
- *Correspondence: Norio Fukuda,
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, United States
| | - Shin’ichi Ishiwata
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo, Japan
| | - Sachio Morimoto
- School of Health Sciences at Fukuoka, International University of Health and Welfare, Fukuoka, Japan
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12
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Gaar-Humphreys KR, van den Brink A, Wekking M, Asselbergs FW, van Steenbeek FG, Harakalova M, Pei J. Targeting lipid metabolism as a new therapeutic strategy for inherited cardiomyopathies. Front Cardiovasc Med 2023; 10:1114459. [PMID: 36760574 PMCID: PMC9907444 DOI: 10.3389/fcvm.2023.1114459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 01/03/2023] [Indexed: 01/20/2023] Open
Abstract
Inherited cardiomyopathies caused by pathological genetic variants include multiple subtypes of heart disease. Advances in next-generation sequencing (NGS) techniques have allowed for the identification of numerous genetic variants as pathological variants. However, the disease penetrance varies among mutated genes. Some can be associated with more than one disease subtype, leading to a complex genotype-phenotype relationship in inherited cardiomyopathies. Previous studies have demonstrated disrupted metabolism in inherited cardiomyopathies and the importance of metabolic adaptations in disease onset and progression. In addition, genotype- and phenotype-specific metabolic alterations, especially in lipid metabolism, have been revealed. In this mini-review, we describe the metabolic changes that are associated with dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM), which account for the largest proportion of inherited cardiomyopathies. We also summarize the affected expression of genes involved in fatty acid oxidation (FAO) in DCM and HCM, highlighting the potential of PPARA-targeting drugs as FAO modulators in treating patients with inherited cardiomyopathies.
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Affiliation(s)
- Karen R. Gaar-Humphreys
- Division Heart and Lungs, Department of Cardiology, Circulatory Health Research Center, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands,Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, Netherlands
| | - Alyssa van den Brink
- Division Heart and Lungs, Department of Cardiology, Circulatory Health Research Center, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands,Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, Netherlands
| | - Mark Wekking
- Division Heart and Lungs, Department of Cardiology, Circulatory Health Research Center, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands,Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, Netherlands
| | - Folkert W. Asselbergs
- Department of Cardiology, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, Netherlands,Health Data Research United Kingdom and Institute of Health Informatics, University College London, London, United Kingdom
| | - Frank G. van Steenbeek
- Division Heart and Lungs, Department of Cardiology, Circulatory Health Research Center, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands,Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, Netherlands,Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, Netherlands
| | - Magdalena Harakalova
- Division Heart and Lungs, Department of Cardiology, Circulatory Health Research Center, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands,Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, Netherlands,Netherlands Heart Institute, Utrecht, Netherlands
| | - Jiayi Pei
- Division Heart and Lungs, Department of Cardiology, Circulatory Health Research Center, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands,Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, Netherlands,Netherlands Heart Institute, Utrecht, Netherlands,*Correspondence: Jiayi Pei,
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13
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Antonovic AK, Ochala J, Fornili A. Comparative study of binding pocket structure and dynamics in cardiac and skeletal myosin. Biophys J 2023; 122:54-62. [PMID: 36451546 PMCID: PMC9822794 DOI: 10.1016/j.bpj.2022.11.2942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 11/11/2022] [Accepted: 11/28/2022] [Indexed: 11/30/2022] Open
Abstract
The development of small molecule myosin modulators has seen an increased effort in recent years due to their possible use in the treatment of cardiac and skeletal myopathies. Omecamtiv mecarbil (OM) is the first-in-class cardiac myotrope and the first to enter clinical trials. Its selectivity toward slow/beta-cardiac myosin lies at the heart of its function; however, little is known about the underlying reasons for selectivity to this isoform as opposed to other closely related ones such as fast-type skeletal myosins. In this work, we compared the structure and dynamics of the OM binding site in cardiac and in fasttype IIa skeletal myosin to identify possible reasons for OM selectivity. We found that the different shape, size, and composition of the binding pocket in skeletal myosin directly affects the binding mode and related affinity of OM, which is potentially a result of weaker interactions and less optimal molecular recognition. Moreover, we identified a side pocket adjacent to the OM binding site that shows increased accessibility in skeletal myosin compared with the cardiac isoform. These findings could pave the way to the development of skeletal-selective compounds that can target this region of the protein and potentially be used to treat congenital myopathies where muscle weakness is related to myosin loss of function.
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Affiliation(s)
- Anna Katarina Antonovic
- School of Physical and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Julien Ochala
- Department of Biomedical Sciences, University of Copenhagen, København N 2200, Denmark; Centre of Human and Applied Physiological Sciences, King's College London, London SE1 9RT, United Kingdom
| | - Arianna Fornili
- School of Physical and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom.
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14
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Sevrieva IR, Ponnam S, Yan Z, Irving M, Kampourakis T, Sun YB. Phosphorylation-dependent interactions of myosin-binding protein C and troponin coordinate the myofilament response to protein kinase A. J Biol Chem 2023; 299:102767. [PMID: 36470422 PMCID: PMC9826837 DOI: 10.1016/j.jbc.2022.102767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 11/23/2022] [Accepted: 11/24/2022] [Indexed: 12/12/2022] Open
Abstract
PKA-mediated phosphorylation of sarcomeric proteins enhances heart muscle performance in response to β-adrenergic stimulation and is associated with accelerated relaxation and increased cardiac output for a given preload. At the cellular level, the latter translates to a greater dependence of Ca2+ sensitivity and maximum force on sarcomere length (SL), that is, enhanced length-dependent activation. However, the mechanisms by which PKA phosphorylation of the most notable sarcomeric PKA targets, troponin I (cTnI) and myosin-binding protein C (cMyBP-C), lead to these effects remain elusive. Here, we specifically altered the phosphorylation level of cTnI in heart muscle cells and characterized the structural and functional effects at different levels of background phosphorylation of cMyBP-C and with two different SLs. We found Ser22/23 bisphosphorylation of cTnI was indispensable for the enhancement of length-dependent activation by PKA, as was cMyBP-C phosphorylation. This high level of coordination between cTnI and cMyBP-C may suggest coupling between their regulatory mechanisms. Further evidence for this was provided by our finding that cardiac troponin (cTn) can directly interact with cMyBP-C in vitro, in a phosphorylation- and Ca2+-dependent manner. In addition, bisphosphorylation at Ser22/Ser23 increased Ca2+ sensitivity at long SL in the presence of endogenously phosphorylated cMyBP-C. When cMyBP-C was dephosphorylated, bisphosphorylation of cTnI increased Ca2+ sensitivity and decreased cooperativity at both SLs, which may translate to deleterious effects in physiological settings. Our results could have clinical relevance for disease pathways, where PKA phosphorylation of cTnI may be functionally uncoupled from cMyBP-C phosphorylation due to mutations or haploinsufficiency.
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Affiliation(s)
- Ivanka R Sevrieva
- Randall Centre for Cell and Molecular Biophysics, and British Heart Foundation Centre of Research Excellence, King's College London, London, United Kingdom.
| | - Saraswathi Ponnam
- Randall Centre for Cell and Molecular Biophysics, and British Heart Foundation Centre of Research Excellence, King's College London, London, United Kingdom
| | - Ziqian Yan
- Randall Centre for Cell and Molecular Biophysics, and British Heart Foundation Centre of Research Excellence, King's College London, London, United Kingdom
| | - Malcolm Irving
- Randall Centre for Cell and Molecular Biophysics, and British Heart Foundation Centre of Research Excellence, King's College London, London, United Kingdom
| | - Thomas Kampourakis
- Randall Centre for Cell and Molecular Biophysics, and British Heart Foundation Centre of Research Excellence, King's College London, London, United Kingdom
| | - Yin-Biao Sun
- Randall Centre for Cell and Molecular Biophysics, and British Heart Foundation Centre of Research Excellence, King's College London, London, United Kingdom
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15
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Caremani M, Marcello M, Morotti I, Pertici I, Squarci C, Reconditi M, Bianco P, Piazzesi G, Lombardi V, Linari M. The force of the myosin motor sets cooperativity in thin filament activation of skeletal muscles. Commun Biol 2022; 5:1266. [DOI: 10.1038/s42003-022-04184-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 10/28/2022] [Indexed: 11/19/2022] Open
Abstract
AbstractContraction of striated muscle is regulated by a dual mechanism involving both thin, actin-containing filament and thick, myosin-containing filament. Thin filament is activated by Ca2+ binding to troponin, leading to tropomyosin displacement that exposes actin sites for interaction with myosin motors, extending from the neighbouring stress-activated thick filaments. Motor attachment to actin contributes to spreading activation along the thin filament, through a cooperative mechanism, still unclear, that determines the slope of the sigmoidal relation between isometric force and pCa (−log[Ca2+]), estimated by Hill coefficient nH. We use sarcomere-level mechanics in demembranated fibres of rabbit skeletal muscle activated by Ca2+ at different temperatures (12–35 °C) to show that nH depends on the motor force at constant number of attached motors. The definition of the role of motor force provides fundamental constraints for modelling the dynamics of thin filament activation and defining the action of small molecules as possible therapeutic tools.
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16
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Forouzandehmehr M, Paci M, Koivumäki JT, Hyttinen J. Altered contractility in mutation-specific hypertrophic cardiomyopathy: A mechano-energetic in silico study with pharmacological insights. Front Physiol 2022; 13:1010786. [PMID: 36388127 PMCID: PMC9659818 DOI: 10.3389/fphys.2022.1010786] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 10/14/2022] [Indexed: 07/25/2023] Open
Abstract
Introduction: Mavacamten (MAVA), Blebbistatin (BLEB), and Omecamtiv mecarbil (OM) are promising drugs directly targeting sarcomere dynamics, with demonstrated efficacy against hypertrophic cardiomyopathy (HCM) in (pre)clinical trials. However, the molecular mechanism affecting cardiac contractility regulation, and the diseased cell mechano-energetics are not fully understood yet. Methods: We present a new metabolite-sensitive computational model of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) electromechanics to investigate the pathology of R403Q HCM mutation and the effect of MAVA, BLEB, and OM on the cell mechano-energetics. Results: We offer a mechano-energetic HCM calibration of the model, capturing the prolonged contractile relaxation due to R403Q mutation (∼33%), without assuming any further modifications such as an additional Ca2+ flux to the thin filaments. The HCM model variant correctly predicts the negligible alteration in ATPase activity in R403Q HCM condition compared to normal hiPSC-CMs. The simulated inotropic effects of MAVA, OM, and BLEB, along with the ATPase activities in the control and HCM model variant agree with in vitro results from different labs. The proposed model recapitulates the tension-Ca2+ relationship and action potential duration change due to 1 µM OM and 5 µM BLEB, consistently with in vitro data. Finally, our model replicates the experimental dose-dependent effect of OM and BLEB on the normalized isometric tension. Conclusion: This work is a step toward deep-phenotyping the mutation-specific HCM pathophysiology, manifesting as altered interfilament kinetics. Accordingly, the modeling efforts lend original insights into the MAVA, BLEB, and OM contributions to a new interfilament balance resulting in a cardioprotective effect.
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17
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Månsson A, Rassier DE. Insights into Muscle Contraction Derived from the Effects of Small-Molecular Actomyosin-Modulating Compounds. Int J Mol Sci 2022; 23:ijms232012084. [PMID: 36292937 PMCID: PMC9603234 DOI: 10.3390/ijms232012084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Revised: 09/25/2022] [Accepted: 10/03/2022] [Indexed: 01/10/2023] Open
Abstract
Bottom-up mechanokinetic models predict ensemble function of actin and myosin based on parameter values derived from studies using isolated proteins. To be generally useful, e.g., to analyze disease effects, such models must also be able to predict ensemble function when actomyosin interaction kinetics are modified differently from normal. Here, we test this capability for a model recently shown to predict several physiological phenomena along with the effects of the small molecular compound blebbistatin. We demonstrate that this model also qualitatively predicts effects of other well-characterized drugs as well as varied concentrations of MgATP. However, the effects of one compound, amrinone, are not well accounted for quantitatively. We therefore systematically varied key model parameters to address this issue, leading to the increased amplitude of the second sub-stroke of the power stroke from 1 nm to 2.2 nm, an unchanged first sub-stroke (5.3−5.5 nm), and an effective cross-bridge attachment rate that more than doubled. In addition to better accounting for the effects of amrinone, the modified model also accounts well for normal physiological ensemble function. Moreover, a Monte Carlo simulation-based version of the model was used to evaluate force−velocity data from small myosin ensembles. We discuss our findings in relation to key aspects of actin−myosin operation mechanisms causing a non-hyperbolic shape of the force−velocity relationship at high loads. We also discuss remaining limitations of the model, including uncertainty of whether the cross-bridge elasticity is linear or not, the capability to account for contractile properties of very small actomyosin ensembles (<20 myosin heads), and the mechanism for requirements of a higher cross-bridge attachment rate during shortening compared to during isometric contraction.
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Affiliation(s)
- Alf Månsson
- Department of Chemistry and Biomedical Sciences, Linnaeus University, 391 82 Kalmar, Sweden
- Correspondence: ; Tel.: +46-708-866243
| | - Dilson E. Rassier
- Department of Kinesiology and Physical Education, McGill University, Montreal, QC H2W 1S4, Canada
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18
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Kawana M, Spudich JA, Ruppel KM. Hypertrophic cardiomyopathy: Mutations to mechanisms to therapies. Front Physiol 2022; 13:975076. [PMID: 36225299 PMCID: PMC9548533 DOI: 10.3389/fphys.2022.975076] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Accepted: 08/22/2022] [Indexed: 01/10/2023] Open
Abstract
Hypertrophic cardiomyopathy (HCM) affects more than 1 in 500 people in the general population with an extensive burden of morbidity in the form of arrhythmia, heart failure, and sudden death. More than 25 years since the discovery of the genetic underpinnings of HCM, the field has unveiled significant insights into the primary effects of these genetic mutations, especially for the myosin heavy chain gene, which is one of the most commonly mutated genes. Our group has studied the molecular effects of HCM mutations on human β-cardiac myosin heavy chain using state-of-the-art biochemical and biophysical tools for the past 10 years, combining insights from clinical genetics and structural analyses of cardiac myosin. The overarching hypothesis is that HCM-causing mutations in sarcomere proteins cause hypercontractility at the sarcomere level, and we have shown that an increase in the number of myosin molecules available for interaction with actin is a primary driver. Recently, two pharmaceutical companies have developed small molecule inhibitors of human cardiac myosin to counteract the molecular consequences of HCM pathogenesis. One of these inhibitors (mavacamten) has recently been approved by the FDA after completing a successful phase III trial in HCM patients, and the other (aficamten) is currently being evaluated in a phase III trial. Myosin inhibitors will be the first class of medication used to treat HCM that has both robust clinical trial evidence of efficacy and that targets the fundamental mechanism of HCM pathogenesis. The success of myosin inhibitors in HCM opens the door to finding other new drugs that target the sarcomere directly, as we learn more about the genetics and fundamental mechanisms of this disease.
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Affiliation(s)
- Masataka Kawana
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, United States,Department of Medicine, Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA, United States
| | - James A. Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, United States
| | - Kathleen M. Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, United States,*Correspondence: Kathleen M. Ruppel,
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19
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Singh RR, Slater RE, Wang J, Wang C, Guo Q, Motani AS, Hartman JJ, Sadayappan S, Ason BL. Distinct Mechanisms for Increased Cardiac Contraction Through Selective Alteration of Either Myosin or Troponin Activity. JACC Basic Transl Sci 2022; 7:1021-1037. [DOI: 10.1016/j.jacbts.2022.04.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 04/15/2022] [Accepted: 04/18/2022] [Indexed: 10/14/2022]
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20
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Nakanishi T, Oyama K, Tanaka H, Kobirumaki-Shimozawa F, Ishii S, Terui T, Ishiwata S, Fukuda N. Effects of omecamtiv mecarbil on the contractile properties of skinned porcine left atrial and ventricular muscles. Front Physiol 2022; 13:947206. [PMID: 36082222 PMCID: PMC9445838 DOI: 10.3389/fphys.2022.947206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 07/04/2022] [Indexed: 11/13/2022] Open
Abstract
Omecamtiv mecarbil (OM) is a novel inotropic agent for heart failure with systolic dysfunction. OM prolongs the actomyosin attachment duration, which enhances thin filament cooperative activation and accordingly promotes the binding of neighboring myosin to actin. In the present study, we investigated the effects of OM on the steady-state contractile properties in skinned porcine left ventricular (PLV) and atrial (PLA) muscles. OM increased Ca2+ sensitivity in a concentration-dependent manner in PLV, by left shifting the mid-point (pCa50) of the force-pCa curve (ΔpCa50) by ∼0.16 and ∼0.33 pCa units at 0.5 and 1.0 μM, respectively. The Ca2+-sensitizing effect was likewise observed in PLA, but less pronounced with ΔpCa50 values of ∼0.08 and ∼0.22 pCa units at 0.5 and 1.0 μM, respectively. The Ca2+-sensitizing effect of OM (1.0 μM) was attenuated under enhanced thin filament cooperative activation in both PLV and PLA; this attenuation occurred directly via treatment with fast skeletal troponin (ΔpCa50: ∼0.16 and ∼0.10 pCa units in PLV and PLA, respectively) and indirectly by increasing the number of strongly bound cross-bridges in the presence of 3 mM MgADP (ΔpCa50: ∼0.21 and ∼0.08 pCa units in PLV and PLA, respectively). It is likely that this attenuation of the Ca2+-sensitizing effect of OM is due to a decrease in the number of “recruitable” cross-bridges that can potentially produce active force. When cross-bridge detachment was accelerated in the presence of 20 mM inorganic phosphate, the Ca2+-sensitizing effect of OM (1.0 μM) was markedly decreased in both types of preparations (ΔpCa50: ∼0.09 and ∼0.03 pCa units in PLV and PLA, respectively). The present findings suggest that the positive inotropy of OM is more markedly exerted in the ventricle than in the atrium, which results from the strongly bound cross-bridge-dependent allosteric activation of thin filaments.
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Affiliation(s)
- Tomohiro Nakanishi
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan
- Department of Anesthesiology, The Jikei University School of Medicine, Tokyo, Japan
| | - Kotaro Oyama
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan
- Quantum Beam Science Research Directorate, National Institutes for Quantum Science and Technology, Gunma, Japan
| | - Hiroyuki Tanaka
- Laboratory of Marine Biotechnology and Microbiology, Hokkaido University, Hakodate, Japan
| | | | - Shuya Ishii
- Quantum Beam Science Research Directorate, National Institutes for Quantum Science and Technology, Gunma, Japan
| | - Takako Terui
- Department of Anesthesiology, The Jikei University School of Medicine, Tokyo, Japan
| | - Shin’ichi Ishiwata
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo, Japan
| | - Norio Fukuda
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan
- *Correspondence: Norio Fukuda,
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21
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Longobardi S, Sher A, Niederer SA. Quantitative mapping of force-pCa curves to whole heart contraction and relaxation. J Physiol 2022; 600:3497-3516. [PMID: 35737959 PMCID: PMC9540007 DOI: 10.1113/jp283352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Accepted: 06/21/2022] [Indexed: 11/17/2022] Open
Abstract
Abstract The force–pCa (F–pCa) curve is used to characterize steady‐state contractile properties of cardiac muscle cells in different physiological, pathological and pharmacological conditions. This provides a reduced preparation in which to isolate sarcomere mechanisms. However, it is unclear how changes in the F–pCa curve impact emergent whole‐heart mechanics quantitatively. We study the link between sarcomere and whole‐heart function using a multiscale mathematical model of rat biventricular mechanics that describes sarcomere, tissue, anatomy, preload and afterload properties quantitatively. We first map individual cell‐level changes in sarcomere‐regulating parameters to organ‐level changes in the left ventricular function described by pressure–volume loop characteristics (e.g. end‐diastolic and end‐systolic volumes, ejection fraction and isovolumetric relaxation time). We next map changes in the sarcomere‐regulating parameters to changes in the F–pCa curve. We demonstrate that a change in the F–pCa curve can be caused by multiple different changes in sarcomere properties. We demonstrate that changes in sarcomere properties cause non‐linear and, importantly, non‐monotonic changes in left ventricular function. As a result, a change in sarcomere properties yielding changes in the F–pCa curve that improve contractility does not guarantee an improvement in whole‐heart function. Likewise, a desired change in whole‐heart function (i.e. ejection fraction or relaxation time) is not caused by a unique shift in the F–pCa curve. Changes in the F–pCa curve alone cannot be used to predict the impact of a compound on whole‐heart function.
![]() Key points The force–pCa (F–pCa) curve is used to assess myofilament calcium sensitivity after pharmacological modulation and to infer pharmacological effects on whole‐heart function. We demonstrate that there is a non‐unique mapping from changes in F–pCa curves to changes in left ventricular (LV) function. The effect of changes in F–pCa on LV function depend on the state of the heart and could be different for different pathological conditions. Screening of compounds to impact whole‐heart function by F–pCa should be combined with active tension and calcium transient measurements to predict better how changes in muscle function will impact whole‐heart physiology.
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Affiliation(s)
- Stefano Longobardi
- Cardiac Electromechanics Research Group, School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
| | - Anna Sher
- Pfizer Worldwide Research, Development and Medical, Cambridge, MA, USA
| | - Steven A Niederer
- Cardiac Electromechanics Research Group, School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
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22
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Khomtchouk BB, Lee YS, Khan ML, Sun P, Mero D, Davidson MH. Targeting the cytoskeleton and extracellular matrix in cardiovascular disease drug discovery. Expert Opin Drug Discov 2022; 17:443-460. [PMID: 35258387 PMCID: PMC9050939 DOI: 10.1080/17460441.2022.2047645] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
INTRODUCTION Currently, cardiovascular disease (CVD) drug discovery has focused primarily on addressing the inflammation and immunopathology aspects inherent to various CVD phenotypes such as cardiac fibrosis and coronary artery disease. However, recent findings suggest new biological pathways for cytoskeletal and extracellular matrix (ECM) regulation across diverse CVDs, such as the roles of matricellular proteins (e.g. tenascin-C) in regulating the cellular microenvironment. The success of anti-inflammatory drugs like colchicine, which targets microtubule polymerization, further suggests that the cardiac cytoskeleton and ECM provide prospective therapeutic opportunities. AREAS COVERED Potential therapeutic targets include proteins such as gelsolin and calponin 2, which play pivotal roles in plaque development. This review focuses on the dynamic role that the cytoskeleton and ECM play in CVD pathophysiology, highlighting how novel target discovery in cytoskeletal and ECM-related genes may enable therapeutics development to alter the regulation of cellular architecture in plaque formation and rupture, cardiac contractility, and other molecular mechanisms. EXPERT OPINION Further research into the cardiac cytoskeleton and its associated ECM proteins is an area ripe for novel target discovery. Furthermore, the structural connection between the cytoskeleton and the ECM provides an opportunity to evaluate both entities as sources of potential therapeutic targets for CVDs.
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Affiliation(s)
- Bohdan B Khomtchouk
- Department of Medicine, Section of Computational Biomedicine and Biomedical Data Science, Institute for Genomics and Systems Biology, University of Chicago, Chicago, IL, USA
| | - Yoon Seo Lee
- The College of the University of Chicago, Chicago, IL, USA
| | - Maha L Khan
- The College of the University of Chicago, Chicago, IL, USA
| | - Patrick Sun
- The College of the University of Chicago, Chicago, IL, USA
| | | | - Michael H Davidson
- Department of Medicine, Section of Cardiology, University of Chicago, Chicago, IL, USA
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23
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Halas M, Langa P, Warren CM, Goldspink PH, Wolska BM, Solaro RJ. Effects of Sarcomere Activators and Inhibitors Targeting Myosin Cross-Bridges on Ca2+-Activation of Mature and Immature Mouse Cardiac Myofilaments. Mol Pharmacol 2022; 101:286-299. [PMID: 35236770 PMCID: PMC9092471 DOI: 10.1124/molpharm.121.000420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 02/16/2022] [Indexed: 11/22/2022] Open
Abstract
We tested the hypothesis that isoform shifts in sarcomeres of the immature heart modify the effect of cardiac myosin-directed sarcomere inhibitors and activators. Omecamtiv mecarbil (OM) activates tension and is in clinical trials for the treatment of adult acute and chronic heart failure. Mavacamten (Mava) inhibits tension and is in clinical trials to relieve hyper-contractility and outflow obstruction in advanced genetic hypertrophic cardiomyopathy (HCM) linked commonly to mutations in sarcomeric proteins. To address the effect of these agents in developing sarcomeres we isolated heart fiber bundles, extracted membranes with Triton X-100, and measured tension developed over a range of Ca2+ concentrations with and without OM or Mava treatment. We made measurements in fiber bundles from hearts of adult non-transgenic controls (NTG) expressing cardiac troponin I (cTnI), and from hearts of transgenic mice (TG-ssTnI) expressing the fetal/neonatal form, slow skeletal troponin I (ssTnI). We also compared fibers from 7+14-day-old NTG mice expressing ssTnI and cTnI. These studies were repeated with 7+14-day old transgenic mice (TG-cTnT-R92Q) expressing a mutant form of cardiac TnT (cTnT) linked to HCM. OM increased Ca2+-sensitivity and decreased cooperative activation in both ssTnI- and cTnI- regulated myofilaments with a similar effect reducing sub-maximal tension in immature and mature myofilaments. Although Mava decreased tension similarly in cTnI- and ssTnI-regulated myofilaments controlled either by cTnT or cTnT-R92Q, its effect involved a depressed Ca2+-sensitivity in the mature cTnT-R92-myofilaments. Our data demonstrate an influence of myosin and thin filament-associated proteins on the actions of myosin-directed agents such as OM and Mava. Significance Statement The effects of myosin-targeted activators and inhibitors on Ca2+-activated tension in developing cardiac sarcomeres presented here provide novel, ex-vivo evidence as to their actions in early-stage cardiac disorders. These studies advance understanding of the molecular mechanisms of these agents that is important in pre-clinical studies employing sarcomere Ca2+-response as a screening approach. The data also inform the use of commonly immature cardiac myocytes generated from human inducible pluripotent stem cells in screening for sarcomere activators and inhibitors.
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Affiliation(s)
- Monika Halas
- Physiology and Biophysics, University of Illinois at Chicago, United States
| | - Paulina Langa
- Physiology and Biophysics, University of Illinois at Chicago, United States
| | - Chad M Warren
- Physiology and Biophysics, University of Illinois at Chicago, United States
| | - Paul H Goldspink
- Physiology and Biophysics, University of Illinois at Chicago, United States
| | - Beata M Wolska
- Department of Medicine, University of Illinois at Chicago, United States
| | - R John Solaro
- Physiology and Biophysics, University of Illinois at Chicago, United States
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24
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Day SM, Tardiff JC, Ostap EM. Myosin modulators: emerging approaches for the treatment of cardiomyopathies and heart failure. J Clin Invest 2022; 132:148557. [PMID: 35229734 PMCID: PMC8884898 DOI: 10.1172/jci148557] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Myosin modulators are a novel class of pharmaceutical agents that are being developed to treat patients with a range of cardiomyopathies. The therapeutic goal of these drugs is to target cardiac myosins directly to modulate contractility and cardiac power output to alleviate symptoms that lead to heart failure and arrhythmias, without altering calcium signaling. In this Review, we discuss two classes of drugs that have been developed to either activate (omecamtiv mecarbil) or inhibit (mavacamten) cardiac contractility by binding to β-cardiac myosin (MYH7). We discuss progress in understanding the mechanisms by which the drugs alter myosin mechanochemistry, and we provide an appraisal of the results from clinical trials of these drugs, with consideration for the importance of disease heterogeneity and genetic etiology for predicting treatment benefit.
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Affiliation(s)
- Sharlene M Day
- Division of Cardiovascular Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jil C Tardiff
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona, USA
| | - E Michael Ostap
- Pennsylvania Muscle Institute and Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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25
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Two Classes of Myosin Inhibitors, Para-nitroblebbistatin and Mavacamten, Stabilize β-Cardiac Myosin in Different Structural and Functional States. J Mol Biol 2021; 433:167295. [PMID: 34627791 DOI: 10.1016/j.jmb.2021.167295] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 09/28/2021] [Accepted: 10/01/2021] [Indexed: 11/20/2022]
Abstract
In addition to a conventional relaxed state, a fraction of myosins in the cardiac muscle exists in a low-energy consuming super-relaxed (SRX) state, which is kept as a reserve pool that may be engaged under sustained increased cardiac demand. The conventional relaxed and the super-relaxed states are widely assumed to correspond to a structure where myosin heads are in an open configuration, free to interact with actin, and a closed configuration, inhibiting binding to actin, respectively. Disruption of the myosin SRX population is an emerging model in different heart diseases, such as hypertrophic cardiomyopathy, which results in excessive muscle contraction, and stabilizing them using myosin inhibitors is budding as an attractive therapeutic strategy. Here we examined the structure-function relationships of two myosin ATPase inhibitors, mavacamten and para-nitroblebbistatin, and found that binding of mavacamten at a site different than para-nitroblebbistatin populates myosin into the SRX state. Para-nitroblebbistatin, binding to a distal pocket to the myosin lever arm near the nucleotide-binding site, does not affect the usual myosin SRX state but instead appears to render myosin into a new, perhaps much more inhibited, 'ultra-relaxed' state. X-ray scattering-based rigid body modeling shows that both mavacamten and para-nitroblebbistatin induce novel conformations in human β-cardiac heavy meromyosin that diverge significantly from the hypothetical open and closed states, and furthermore, mavacamten treatment causes greater compaction than para-nitroblebbistatin. Taken together, we conclude that mavacamten and para-nitroblebbistatin stabilize myosin in different structural states, and such states may give rise to different functional energy-sparing states.
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26
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Barrick SK, Greenberg MJ. Cardiac myosin contraction and mechanotransduction in health and disease. J Biol Chem 2021; 297:101297. [PMID: 34634306 PMCID: PMC8559575 DOI: 10.1016/j.jbc.2021.101297] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 10/06/2021] [Accepted: 10/07/2021] [Indexed: 12/17/2022] Open
Abstract
Cardiac myosin is the molecular motor that powers heart contraction by converting chemical energy from ATP hydrolysis into mechanical force. The power output of the heart is tightly regulated to meet the physiological needs of the body. Recent multiscale studies spanning from molecules to tissues have revealed complex regulatory mechanisms that fine-tune cardiac contraction, in which myosin not only generates power output but also plays an active role in its regulation. Thus, myosin is both shaped by and actively involved in shaping its mechanical environment. Moreover, these studies have shown that cardiac myosin-generated tension affects physiological processes beyond muscle contraction. Here, we review these novel regulatory mechanisms, as well as the roles that myosin-based force generation and mechanotransduction play in development and disease. We describe how key intra- and intermolecular interactions contribute to the regulation of myosin-based contractility and the role of mechanical forces in tuning myosin function. We also discuss the emergence of cardiac myosin as a drug target for diseases including heart failure, leading to the discovery of therapeutics that directly tune myosin contractility. Finally, we highlight some of the outstanding questions that must be addressed to better understand myosin's functions and regulation, and we discuss prospects for translating these discoveries into precision medicine therapeutics targeting contractility and mechanotransduction.
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Affiliation(s)
- Samantha K Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA.
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27
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Parikh J, Rumbell T, Butova X, Myachina T, Acero JC, Khamzin S, Solovyova O, Kozloski J, Khokhlova A, Gurev V. Generative adversarial networks for construction of virtual populations of mechanistic models: simulations to study Omecamtiv Mecarbil action. J Pharmacokinet Pharmacodyn 2021; 49:51-64. [PMID: 34716531 PMCID: PMC8837558 DOI: 10.1007/s10928-021-09787-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 09/23/2021] [Indexed: 11/30/2022]
Abstract
Biophysical models are increasingly used to gain mechanistic insights by fitting and reproducing experimental and clinical data. The inherent variability in the recorded datasets, however, presents a key challenge. In this study, we present a novel approach, which integrates mechanistic modeling and machine learning to analyze in vitro cardiac mechanics data and solve the inverse problem of model parameter inference. We designed a novel generative adversarial network (GAN) and employed it to construct virtual populations of cardiac ventricular myocyte models in order to study the action of Omecamtiv Mecarbil (OM), a positive cardiac inotrope. Populations of models were calibrated from mechanically unloaded myocyte shortening recordings obtained in experiments on rat myocytes in the presence and absence of OM. The GAN was able to infer model parameters while incorporating prior information about which model parameters OM targets. The generated populations of models reproduced variations in myocyte contraction recorded during in vitro experiments and provided improved understanding of OM’s mechanism of action. Inverse mapping of the experimental data using our approach suggests a novel action of OM, whereby it modifies interactions between myosin and tropomyosin proteins. To validate our approach, the inferred model parameters were used to replicate other in vitro experimental protocols, such as skinned preparations demonstrating an increase in calcium sensitivity and a decrease in the Hill coefficient of the force–calcium (F–Ca) curve under OM action. Our approach thereby facilitated the identification of the mechanistic underpinnings of experimental observations and the exploration of different hypotheses regarding variability in this complex biological system.
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Affiliation(s)
| | | | - Xenia Butova
- Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences (UB RAS), Yekaterinburg, Russia
| | - Tatiana Myachina
- Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences (UB RAS), Yekaterinburg, Russia
| | - Jorge Corral Acero
- Department of Engineering Science, Institute of Biomedical Engineering, University of Oxford, Oxford, UK
| | - Svyatoslav Khamzin
- Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences (UB RAS), Yekaterinburg, Russia
| | - Olga Solovyova
- Ural Federal University, Yekaterinburg, Russia.,Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences (UB RAS), Yekaterinburg, Russia
| | | | - Anastasia Khokhlova
- Ural Federal University, Yekaterinburg, Russia.,Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences (UB RAS), Yekaterinburg, Russia
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28
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Cheng Z, Fang T, Huang J, Guo Y, Alam M, Qian H. Hypertrophic Cardiomyopathy: From Phenotype and Pathogenesis to Treatment. Front Cardiovasc Med 2021; 8:722340. [PMID: 34760939 PMCID: PMC8572854 DOI: 10.3389/fcvm.2021.722340] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 09/17/2021] [Indexed: 02/05/2023] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is a very common inherited cardiovascular disease (CAD) and the incidence is about 1/500 of the common population. It is caused by more than 1,400 mutations in 11 or more genes encoding the proteins of the cardiac sarcomere. HCM presents a heterogeneous clinical profile and complex pathophysiology and HCM is the most important cause of sudden cardiac death (SCD) in young people. HCM also contributes to functional disability from heart failure and stroke (caused by atrial fibrillation). Current treatments for HCM (medication, myectomy, and alcohol septal ablation) are geared toward slowing down the disease progression and symptom relief and implanted cardiac defibrillator (ICD) to prevent SCD. HCM is, however, entering a period of tight translational research that holds promise for the major advances in disease-specific therapy. Main insights into the genetic landscape of HCM have improved our understanding of molecular pathogenesis and pointed the potential targets for the development of therapeutic agents. We reviewed the critical discoveries about the treatments, mechanism of HCM, and their implications for future research.
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Affiliation(s)
- Zeyi Cheng
- Department of Cardiovascular Surgery, West China Hospital, Sichuan University, Chengdu, China
| | - Tingting Fang
- Department of Cardiology, West China Hospital, Sichuan University, Chengdu, China
| | - Jinglei Huang
- School of Medicine, Lanzhou University, Lanzhou, China
| | - Yingqiang Guo
- Department of Cardiovascular Surgery, West China Hospital, Sichuan University, Chengdu, China
| | - Mahboob Alam
- Division of Cardiovascular Medicine, Department of Medicine, Baylor College of Medicine, Houston, TX, United States
| | - Hong Qian
- Department of Cardiovascular Surgery, West China Hospital, Sichuan University, Chengdu, China
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29
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Hassoun R, Budde H, Mügge A, Hamdani N. Cardiomyocyte Dysfunction in Inherited Cardiomyopathies. Int J Mol Sci 2021; 22:11154. [PMID: 34681814 PMCID: PMC8541428 DOI: 10.3390/ijms222011154] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/08/2021] [Accepted: 10/13/2021] [Indexed: 01/10/2023] Open
Abstract
Inherited cardiomyopathies form a heterogenous group of disorders that affect the structure and function of the heart. Defects in the genes encoding sarcomeric proteins are associated with various perturbations that induce contractile dysfunction and promote disease development. In this review we aimed to outline the functional consequences of the major inherited cardiomyopathies in terms of myocardial contraction and kinetics, and to highlight the structural and functional alterations in some sarcomeric variants that have been demonstrated to be involved in the pathogenesis of the inherited cardiomyopathies. A particular focus was made on mutation-induced alterations in cardiomyocyte mechanics. Since no disease-specific treatments for familial cardiomyopathies exist, several novel agents have been developed to modulate sarcomere contractility. Understanding the molecular basis of the disease opens new avenues for the development of new therapies. Furthermore, the earlier the awareness of the genetic defect, the better the clinical prognostication would be for patients and the better the prevention of development of the disease.
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Affiliation(s)
- Roua Hassoun
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
| | - Heidi Budde
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
| | - Andreas Mügge
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
| | - Nazha Hamdani
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
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30
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Crocini C, Gotthardt M. Cardiac sarcomere mechanics in health and disease. Biophys Rev 2021; 13:637-652. [PMID: 34745372 PMCID: PMC8553709 DOI: 10.1007/s12551-021-00840-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 08/27/2021] [Indexed: 12/23/2022] Open
Abstract
The sarcomere is the fundamental structural and functional unit of striated muscle and is directly responsible for most of its mechanical properties. The sarcomere generates active or contractile forces and determines the passive or elastic properties of striated muscle. In the heart, mutations in sarcomeric proteins are responsible for the majority of genetically inherited cardiomyopathies. Here, we review the major determinants of cardiac sarcomere mechanics including the key structural components that contribute to active and passive tension. We dissect the molecular and structural basis of active force generation, including sarcomere composition, structure, activation, and relaxation. We then explore the giant sarcomere-resident protein titin, the major contributor to cardiac passive tension. We discuss sarcomere dynamics exemplified by the regulation of titin-based stiffness and the titin life cycle. Finally, we provide an overview of therapeutic strategies that target the sarcomere to improve cardiac contraction and filling.
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Affiliation(s)
- Claudia Crocini
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Neuromuscular and Cardiovascular Cell Biology, Berlin, Germany
- German Center for Cardiovascular Research (DZHK) Partner Site Berlin, Berlin, Germany
- BioFrontiers Institute & Department of Molecular and Cellular Development, University of Colorado Boulder, Boulder, USA
| | - Michael Gotthardt
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Neuromuscular and Cardiovascular Cell Biology, Berlin, Germany
- German Center for Cardiovascular Research (DZHK) Partner Site Berlin, Berlin, Germany
- Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany
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31
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Kampourakis T, Irving M. The regulatory light chain mediates inactivation of myosin motors during active shortening of cardiac muscle. Nat Commun 2021; 12:5272. [PMID: 34489440 PMCID: PMC8421338 DOI: 10.1038/s41467-021-25601-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 08/13/2021] [Indexed: 11/29/2022] Open
Abstract
The normal function of heart muscle depends on its ability to contract more strongly at longer length. Increased venous filling stretches relaxed heart muscle cells, triggering a stronger contraction in the next beat- the Frank-Starling relation. Conversely, heart muscle cells are inactivated when they shorten during ejection, accelerating relaxation to facilitate refilling before the next beat. Although both effects are essential for the efficient function of the heart, the underlying mechanisms were unknown. Using bifunctional fluorescent probes on the regulatory light chain of the myosin motor we show that its N-terminal domain may be captured in the folded OFF state of the myosin dimer at the end of the working-stroke of the actin-attached motor, whilst its C-terminal domain joins the OFF state only after motor detachment from actin. We propose that sequential folding of myosin motors onto the filament backbone may be responsible for shortening-induced de-activation in the heart.
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Affiliation(s)
- Thomas Kampourakis
- Randall Centre for Cell and Molecular Biophysics, King's College London, London, UK.
- British Heart Foundation Centre of Research Excellence, King's College London, London, UK.
| | - Malcolm Irving
- Randall Centre for Cell and Molecular Biophysics, King's College London, London, UK
- British Heart Foundation Centre of Research Excellence, King's College London, London, UK
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32
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Lookin O, Kuznetsov D, Protsenko Y. Omecamtiv mecarbil attenuates length-tension relationship in healthy rat myocardium and preserves it in monocrotaline-induced pulmonary heart failure. Clin Exp Pharmacol Physiol 2021; 49:84-93. [PMID: 34459025 DOI: 10.1111/1440-1681.13584] [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: 05/04/2021] [Revised: 08/24/2021] [Accepted: 08/26/2021] [Indexed: 01/10/2023]
Abstract
The cardiac-specific myosin activator, omecamtiv mecarbil (OM), is an effective inotrope for treating heart failure but its effects on active force and Ca2+ kinetics in healthy and diseased myocardium remain poorly studied. We tested the effect of two concentrations of OM (0.2 and 1 µmol/L in saline) on isometric contraction and Ca-transient (CaT) in right ventricular trabeculae of healthy rats (CONT, n = 8) and rats with monocrotaline-induced pulmonary heart failure (MCT, n = 8). The contractions were obtained under preload of 75%-100% of optimal length (tension-length relationship). The 0.2 µmol/L OM did not affect the diastolic level, amplitude, or kinetics of isometric contraction and CaT, irrespective of the group of rats or preload. The 1 µmol/L OM significantly suppressed active tension-length relationships in CONT but not in MCT, while leading in both groups to a significantly prolonged relaxation. CaT time-to-peak was unaffected in CONT and MCT, but CaT decay was slightly accelerated in its early phase and considerably prolonged in its late phase to a similar extent in both groups. We conclude that the substantial prolongation of CaT decay is due to enhanced Ca2+ utilisation by troponin C mediated by the direct effect of OM on the cooperative activation of myofilaments. The lack of beneficial effect of OM in the healthy rat myocardium may be due to a relatively high level of activating Ca2+ in cells with normal Ca2+ handling, whereas the preservation of the tension-length relationship in the failing heart may relate to the diminished Ca2+ levels of sarcoplasmic reticulum.
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Affiliation(s)
- Oleg Lookin
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russian Federation
| | - Daniil Kuznetsov
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russian Federation
| | - Yuri Protsenko
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russian Federation
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33
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Mamidi R, Holmes JB, Doh CY, Dominic KL, Madugula N, Stelzer JE. cMyBPC phosphorylation modulates the effect of omecamtiv mecarbil on myocardial force generation. J Gen Physiol 2021; 153:211867. [PMID: 33688929 PMCID: PMC7953254 DOI: 10.1085/jgp.202012816] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 01/27/2021] [Indexed: 01/15/2023] Open
Abstract
Omecamtiv mecarbil (OM), a direct myosin motor activator, is currently being tested as a therapeutic replacement for conventional inotropes in heart failure (HF) patients. It is known that HF patients exhibit dysregulated β-adrenergic signaling and decreased cardiac myosin-binding protein C (cMyBPC) phosphorylation, a critical modulator of myocardial force generation. However, the functional effects of OM in conditions of altered cMyBPC phosphorylation have not been established. Here, we tested the effects of OM on force generation and cross-bridge (XB) kinetics using murine myocardial preparations isolated from wild-type (WT) hearts and from hearts expressing S273A, S282A, and S302A substitutions (SA) in the M domain, between the C1 and C2 domains of cMyBPC, which cannot be phosphorylated. At submaximal Ca2+ activations, OM-mediated force enhancements were less pronounced in SA than in WT myocardial preparations. Additionally, SA myocardial preparations lacked the dose-dependent increases in force that were observed in WT myocardial preparations. Following OM incubation, the basal differences in the rate of XB detachment (krel) between WT and SA myocardial preparations were abolished, suggesting that OM differentially affects the XB behavior when cMyBPC phosphorylation is reduced. Similarly, in myocardial preparations pretreated with protein kinase A to phosphorylate cMyBPC, incubation with OM significantly slowed krel in both the WT and SA myocardial preparations. Collectively, our data suggest there is a strong interplay between the effects of OM and XB behavior, such that it effectively uncouples the sarcomere from cMyBPC phosphorylation levels. Our findings imply that OM may significantly alter the in vivo cardiac response to β-adrenergic stimulation.
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Affiliation(s)
- Ranganath Mamidi
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH
| | - Joshua B Holmes
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH
| | - Chang Yoon Doh
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH
| | - Katherine L Dominic
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH
| | - Nikhil Madugula
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH
| | - Julian E Stelzer
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH
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34
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Akinaga K, Azumi Y, Mogi K, Toyoizumi R. Stage-dependent sequential organization of nascent smooth muscle cells and its implications for the gut coiling morphogenesis in Xenopus larva. ZOOLOGY 2021; 146:125905. [PMID: 33631602 DOI: 10.1016/j.zool.2021.125905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 01/25/2021] [Accepted: 02/07/2021] [Indexed: 10/22/2022]
Abstract
In vertebrates, gut coiling proceeds left-right asymmetrically during expansion of the gastrointestinal tract with highly organized muscular structures facilitating peristalsis. In this report, we explored the mechanisms of larval gut coiling morphogenesis relevant to its nascent smooth muscle cells using highly transparent Xenopus early larvae. First, to visualize the dynamics of intestinal smooth muscle cells, whole-mount specimens were immunostained with anti-smooth muscle-specific actin (SM-actin) antibody. We found that the nascent gut of Xenopus early larvae gradually expands the SM-actin-positive region in a stage-dependent manner. Transverse orientation of smooth muscle cells was first established, and next, the cellular longitudinal orientation along the gut axis was followed to make a meshwork of the contractile cells. Finally, anisotropic torsion by the smooth muscle cells was generated in the center of gut coiling, suggesting that twisting force might be involved in the late phase of coiling morphogenesis of the gut. Administration of S-(-)-Blebbistatin to attenuate the actomyosin contraction in vivo resulted in cancellation of coiling of the gut. Development of decapitation embryos, trunk 'torso' explants, and gut-only explants revealed that initial coiling of the gut proceeds without interactions with the other parts of the body including the central nervous system. We newly developed an in vitro model to assess the gut coiling morphogenesis, indicating that coiling pattern of the nascent Xenopus gut is partially gut-autonomous. Using this gut explant culture technique, inhibition of actomyosin contraction was performed by administrating either actin polymerization inhibitor, myosin light chain kinase inhibitor, or calmodulin antagonist. All of these reagents decreased the extent of gut coiling morphogenesis in vitro. Taken together, these results suggest that the contraction force generated by actomyosin-rich intestinal smooth muscle cells during larval stages is essential for the normal coiling morphogenesis of this muscular tubular organ.
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Affiliation(s)
- Kaoru Akinaga
- Department of Biological Sciences, Faculty of Science, Kanagawa University, Tsuchiya 2946, Hiratsuka City, Kanagawa, 259-1293, Japan
| | - Yoshitaka Azumi
- Department of Biological Sciences, Faculty of Science, Kanagawa University, Tsuchiya 2946, Hiratsuka City, Kanagawa, 259-1293, Japan; Research Institute for Integrated Science, Kanagawa University, Japan
| | - Kazue Mogi
- Research Institute for Integrated Science, Kanagawa University, Japan
| | - Ryuji Toyoizumi
- Department of Biological Sciences, Faculty of Science, Kanagawa University, Tsuchiya 2946, Hiratsuka City, Kanagawa, 259-1293, Japan; Research Institute for Integrated Science, Kanagawa University, Japan.
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35
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Schmid M, Toepfer CN. Cardiac myosin super relaxation (SRX): a perspective on fundamental biology, human disease and therapeutics. Biol Open 2021; 10:bio057646. [PMID: 33589442 PMCID: PMC7904003 DOI: 10.1242/bio.057646] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The fundamental basis of muscle contraction 'the sliding filament model' (Huxley and Niedergerke, 1954; Huxley and Hanson, 1954) and the 'swinging, tilting crossbridge-sliding filament mechanism' (Huxley, 1969; Huxley and Brown, 1967) nucleated a field of research that has unearthed the complex and fascinating role of myosin structure in the regulation of contraction. A recently discovered energy conserving state of myosin termed the super relaxed state (SRX) has been observed in filamentous myosins and is central to modulating force production and energy use within the sarcomere. Modulation of myosin function through SRX is a rapidly developing theme in therapeutic development for both cardiovascular disease and infectious disease. Some 70 years after the first discoveries concerning muscular function, modulation of myosin SRX may bring the first myosin targeted small molecule to the clinic, for treating hypertrophic cardiomyopathy (Olivotto et al., 2020). An often monogenic disease HCM afflicts 1 in 500 individuals, and can cause heart failure and sudden cardiac death. Even as we near therapeutic translation, there remain many questions about the governance of muscle function in human health and disease. With this review, we provide a broad overview of contemporary understanding of myosin SRX, and explore the complexities of targeting this myosin state in human disease.This article has an associated Future Leaders to Watch interview with the authors of the paper.
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Affiliation(s)
- Manuel Schmid
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, UK
| | - Christopher N Toepfer
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, UK
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
- Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
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36
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Abstract
Since the discovery of muscle in the 19th century, myosins as molecular motors have been extensively studied. However, in the last decade, a new functional super-relaxed (SRX) state of myosin has been discovered, which has a 10-fold slower ATP turnover rate than the already-known non-actin-bound, disordered relaxed (DRX) state. These two states are in dynamic equilibrium under resting muscle conditions and are thought to be significant contributors to adaptive thermogenesis in skeletal muscle and can act as a reserve pool that may be recruited when there is a sustained demand for increased cardiac muscle power. This report provides an evolutionary perspective of how striated muscle contraction is regulated by modulating this myosin DRX↔SRX state equilibrium. We further discuss this equilibrium with respect to different physiological and pathophysiological perturbations, including insults causing hypertrophic cardiomyopathy, and small-molecule effectors that modulate muscle contractility in diseased pathology.
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Affiliation(s)
- Suman Nag
- Department of Biology, MyoKardia IncBrisbaneUnited States
| | - Darshan V Trivedi
- Department of Biochemistry, Stanford University School of MedicineStanfordUnited States
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37
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Greenberg MJ, Tardiff JC. Complexity in genetic cardiomyopathies and new approaches for mechanism-based precision medicine. J Gen Physiol 2021; 153:211741. [PMID: 33512404 PMCID: PMC7852459 DOI: 10.1085/jgp.202012662] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Accepted: 01/07/2021] [Indexed: 12/11/2022] Open
Abstract
Genetic cardiomyopathies have been studied for decades, and it has become increasingly clear that these progressive diseases are more complex than originally thought. These complexities can be seen both in the molecular etiologies of these disorders and in the clinical phenotypes observed in patients. While these disorders can be caused by mutations in cardiac genes, including ones encoding sarcomeric proteins, the disease presentation varies depending on the patient mutation, where mutations even within the same gene can cause divergent phenotypes. Moreover, it is challenging to connect the mutation-induced molecular insult that drives the disease pathogenesis with the various compensatory and maladaptive pathways that are activated during the course of the subsequent progressive, pathogenic cardiac remodeling. These inherent complexities have frustrated our ability to understand and develop broadly effective treatments for these disorders. It has been proposed that it might be possible to improve patient outcomes by adopting a precision medicine approach. Here, we lay out a practical framework for such an approach, where patient subpopulations are binned based on common underlying biophysical mechanisms that drive the molecular disease pathogenesis, and we propose that this function-based approach will enable the development of targeted therapeutics that ameliorate these effects. We highlight several mutations to illustrate the need for mechanistic molecular experiments that span organizational and temporal scales, and we describe recent advances in the development of novel therapeutics based on functional targets. Finally, we describe many of the outstanding questions for the field and how fundamental mechanistic studies, informed by our more nuanced understanding of the clinical disorders, will play a central role in realizing the potential of precision medicine for genetic cardiomyopathies.
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Affiliation(s)
- Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
| | - Jil C Tardiff
- Department of Biomedical Engineering, University of Arizona, Tucson, AZ.,Department of Medicine, University of Arizona, Tucson, AZ
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38
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Parijat P, Kondacs L, Alexandrovich A, Gautel M, Cobb AJA, Kampourakis T. High Throughput Screen Identifies Small Molecule Effectors That Modulate Thin Filament Activation in Cardiac Muscle. ACS Chem Biol 2021; 16:225-235. [PMID: 33315370 DOI: 10.1021/acschembio.0c00908] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Current therapeutic interventions for both heart disease and heart failure are largely insufficient and associated with undesired side effects. Biomedical research has emphasized the role of sarcomeric protein function for the normal performance and energy efficiency of the heart, suggesting that directly targeting the contractile myofilaments themselves using small molecule effectors has therapeutic potential and will likely result in greater drug efficacy and selectivity. In this study, we developed a robust and highly reproducible fluorescence polarization-based high throughput screening (HTS) assay that directly targets the calcium-dependent interaction between cardiac troponin C (cTnC) and the switch region of cardiac troponin I (cTnISP), with the aim of identifying small molecule effectors of the cardiac thin filament activation pathway. We screened a commercially available small molecule library and identified several hit compounds with both inhibitory and activating effects. We used a range of biophysical and biochemical methods to characterize hit compounds and identified fingolimod, a sphingosin-1-phosphate receptor modulator, as a new troponin-based small molecule effector. Fingolimod decreased the ATPase activity and calcium sensitivity of demembranated cardiac muscle fibers in a dose-dependent manner, suggesting that the compound acts as a calcium desensitizer. We investigated fingolimod's mechanism of action using a combination of computational studies, biophysical methods, and synthetic chemistry, showing that fingolimod bound to cTnC repels cTnISP via mainly electrostatic repulsion of its positively charged tail. These results suggest that fingolimod is a potential new lead compound/scaffold for the development of troponin-directed heart failure therapeutics.
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Affiliation(s)
- Priyanka Parijat
- Randall Centre for Cell and Molecular Biophysics, King’s College London, and British Heart Foundation Centre of Research Excellence, London SE1 1UL, United Kingdom
| | - Laszlo Kondacs
- Department of Chemistry, King’s College London, 7 Trinity Street, London, SE1 1DB, United Kingdom
| | - Alexander Alexandrovich
- Randall Centre for Cell and Molecular Biophysics, King’s College London, and British Heart Foundation Centre of Research Excellence, London SE1 1UL, United Kingdom
| | - Mathias Gautel
- Randall Centre for Cell and Molecular Biophysics, King’s College London, and British Heart Foundation Centre of Research Excellence, London SE1 1UL, United Kingdom
| | - Alexander J. A. Cobb
- Department of Chemistry, King’s College London, 7 Trinity Street, London, SE1 1DB, United Kingdom
| | - Thomas Kampourakis
- Randall Centre for Cell and Molecular Biophysics, King’s College London, and British Heart Foundation Centre of Research Excellence, London SE1 1UL, United Kingdom
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39
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Hashem S, Davies WG, Fornili A. Heart Failure Drug Modifies the Intrinsic Dynamics of the Pre-Power Stroke State of Cardiac Myosin. J Chem Inf Model 2020; 60:6438-6446. [PMID: 33283509 DOI: 10.1021/acs.jcim.0c00953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Omecamtiv mecarbil (OM), currently investigated for the treatment of heart failure, is the first example of a new class of drugs (cardiac myotropes) that can modify muscle contractility by directly targeting sarcomeric proteins. Using atomistic molecular dynamics simulations, we show that the binding of OM to the pre-power stroke state of cardiac myosin inhibits the functional motions of the protein and potentially affects Pi release from the nucleotide binding site. We also show that the changes in myosin ATPase activity induced by a set of OM analogues can be predicted from their relative affinity to the pre-power stroke state compared to the near rigor one, indicating that conformational selectivity plays an important role in determining the activity of these compounds.
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Affiliation(s)
- Shaima Hashem
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - William George Davies
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Arianna Fornili
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom.,The Thomas Young Centre for Theory and Simulation of Materials, London WC1E 6BN, United Kingdom
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40
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Lopez Davila AJ, Zhu L, Fritz L, Kraft T, Chalovich JM. The Positively Charged C-Terminal Region of Human Skeletal Troponin T Retards Activation and Decreases Calcium Sensitivity. Biochemistry 2020; 59:4189-4201. [PMID: 33074652 DOI: 10.1021/acs.biochem.0c00499] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Calcium binding to troponin C (TnC) activates striated muscle contraction by removing TnI (troponin I) from its inhibitory site on actin. Troponin T (TnT) links TnI with tropomyosin, causing tropomyosin to move from an inhibitory position on actin to an activating position. Positive charges within the C-terminal region of human cardiac TnT limit Ca2+ activation. We now show that the positively charged region of TnT has an even larger impact on skeletal muscle regulation. We prepared one variant of human skeletal TnT that had the C-terminal 16 residues truncated (Δ16) and another with an added C-terminal Cys residue and Ala substituted for the last 6 basic residues (251C-HAHA). Both mutants reduced (based on S1 binding kinetics) or eliminated (based on acrylodan-tropomyosin fluorescence) the first inactive state of actin at <10 nM free Ca2+. 251C-HAHA-TnT and Δ16-TnT mutants greatly increased ATPase activation at 0.2 mM Ca2+, even without high-affinity cross-bridge binding. They also shifted the force-pCa curve of muscle fibers to lower Ca2+ by 0.8-1.2 pCa units (the larger shift for 251C-HAHA-TnT). Shifts in force-pCa were maintained in the presence of para-aminoblebbistatin. The effects of modification of the C-terminal region of TnT on the kinetics of S1 binding to actin were somewhat different from those observed earlier with the cardiac analogue. In general, the C-terminal region of human skeletal TnT is critical to regulation, just as it is in the cardiac system, and is a potential target for modulating activity.
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Affiliation(s)
- Alfredo Jesus Lopez Davila
- Institute of Molecular and Cell Physiology, Hannover Medical School, Carl-Neuberg-Street 1, 103-Block 1-Ebene 03-1010, Hannover 30625, Germany
| | - Li Zhu
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27834, United States
| | - Leon Fritz
- Institute of Molecular and Cell Physiology, Hannover Medical School, Carl-Neuberg-Street 1, 103-Block 1-Ebene 03-1010, Hannover 30625, Germany
| | - Theresia Kraft
- Institute of Molecular and Cell Physiology, Hannover Medical School, Carl-Neuberg-Street 1, 103-Block 1-Ebene 03-1010, Hannover 30625, Germany
| | - Joseph M Chalovich
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27834, United States
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41
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Ma W, Childers M, Murray J, Moussavi-Harami F, Gong H, Weiss R, Daggett V, Irving T, Regnier M. Myosin dynamics during relaxation in mouse soleus muscle and modulation by 2'-deoxy-ATP. J Physiol 2020; 598:5165-5182. [PMID: 32818298 PMCID: PMC7719615 DOI: 10.1113/jp280402] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 08/13/2020] [Indexed: 01/29/2023] Open
Abstract
KEY POINTS Skeletal muscle relaxation has been primarily studied by assessing the kinetics of force decay. Little is known about the resultant dynamics of structural changes in myosin heads during relaxation. The naturally occurring nucleotide 2-deoxy-ATP (dATP) is a myosin activator that enhances cross-bridge binding and kinetics. X-ray diffraction data indicate that with elevated dATP, myosin heads were extended closer to actin in relaxed muscle and myosin heads return to an ordered, resting state after contraction more quickly. Molecular dynamics simulations of post-powerstroke myosin suggest that dATP induces structural changes in myosin heads that increase the surface area of the actin-binding regions promoting myosin interaction with actin, which could explain the observed delays in the onset of relaxation. This study of the dATP-induced changes in myosin may be instructive for determining the structural changes desired for other potential myosin-targeted molecular compounds to treat muscle diseases. ABSTRACT Here we used time-resolved small-angle X-ray diffraction coupled with force measurements to study the structural changes in FVB mouse skeletal muscle sarcomeres during relaxation after tetanus contraction. To estimate the rate of myosin deactivation, we followed the rate of the intensity recovery of the first-order myosin layer line (MLL1) and restoration of the resting spacing of the third and sixth order of meridional reflection (SM3 and SM6 ) following tetanic contraction. A transgenic mouse model with elevated skeletal muscle 2-deoxy-ATP (dATP) was used to study how myosin activators may affect soleus muscle relaxation. X-ray diffraction evidence indicates that with elevated dATP, myosin heads were extended closer to actin in resting muscle. Following contraction, there is a slight but significant delay in the decay of force relative to WT muscle while the return of myosin heads to an ordered resting state was initially slower, then became more rapid than in WT muscle. Molecular dynamics simulations of post-powerstroke myosin suggest that dATP induces structural changes in myosin that increase the surface area of the actin-binding regions, promoting myosin interaction with actin. With dATP, myosin heads may remain in an activated state near the thin filaments following relaxation, accounting for the delay in force decay and the initial delay in recovery of resting head configuration, and this could facilitate subsequent contractions.
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Affiliation(s)
- Weikang Ma
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago IL
| | - Matthew Childers
- Department of Bioengineering, University of Washington, Seattle WA
| | - Jason Murray
- Department of Bioengineering, University of Washington, Seattle WA
| | | | - Henry Gong
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago IL
| | - Robert Weiss
- Department of Biomedical Sciences, Cornell University, Ithaca NY
| | - Valerie Daggett
- Department of Bioengineering, University of Washington, Seattle WA
| | - Thomas Irving
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago IL
| | - Michael Regnier
- Department of Bioengineering, University of Washington, Seattle WA
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42
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Hasenfuss G. Is myosin activation a new treatment for heart failure? Eur J Heart Fail 2020; 22:1659-1661. [DOI: 10.1002/ejhf.1983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/11/2020] [Accepted: 08/14/2020] [Indexed: 11/05/2022] Open
Affiliation(s)
- Gerd Hasenfuss
- Clinic for Cardiology and Pneumology University Medical Center Göttingen Göttingen Germany
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43
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Muretta JM. The Myosin SRX Comes into Focus. Biophys J 2020; 119:1041-1042. [PMID: 32853563 DOI: 10.1016/j.bpj.2020.08.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/05/2020] [Accepted: 08/10/2020] [Indexed: 11/29/2022] Open
Affiliation(s)
- Joseph M Muretta
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota.
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44
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Voors AA, Tamby JF, Cleland JG, Koren M, Forgosh LB, Gupta D, Lund LH, Camacho A, Karra R, Swart HP, Pellicori P, Wagner F, Hershberger RE, Prasad N, Anderson R, Anto A, Bell K, Edelberg JM, Fang L, Henze M, Kelly C, Kurio G, Li W, Wells K, Yang C, Teichman SL, Del Rio CL, Solomon SD. Effects of danicamtiv, a novel cardiac myosin activator, in heart failure with reduced ejection fraction: experimental data and clinical results from a phase 2a trial. Eur J Heart Fail 2020; 22:1649-1658. [PMID: 32558989 PMCID: PMC7689751 DOI: 10.1002/ejhf.1933] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 06/04/2020] [Accepted: 06/10/2020] [Indexed: 12/28/2022] Open
Abstract
AIMS Both left ventricular (LV) and left atrial (LA) dysfunction and remodelling contribute to adverse outcomes in heart failure with reduced ejection fraction (HFrEF). Danicamtiv is a novel, cardiac myosin activator that enhances cardiomyocyte contraction. METHODS AND RESULTS We studied the effects of danicamtiv on LV and LA function in non-clinical studies (ex vivo: skinned muscle fibres and myofibrils; in vivo: dogs with heart failure) and in a randomized, double-blind, single- and multiple-dose phase 2a trial in patients with stable HFrEF (placebo, n = 10; danicamtiv, n = 30; 50-100 mg twice daily for 7 days). Danicamtiv increased ATPase activity and calcium sensitivity in LV and LA myofibrils/muscle fibres. In dogs with heart failure, danicamtiv improved LV stroke volume (+10.6 mL, P < 0.05) and LA emptying fraction (+10.7%, P < 0.05). In patients with HFrEF (mean age 60 years, 25% women, ischaemic heart disease 48%, mean LV ejection fraction 32%), treatment-emergent adverse events, mostly mild, were reported in 17 patients (57%) receiving danicamtiv and 4 patients (40%) receiving placebo. Danicamtiv (at plasma concentrations ≥2000 ng/mL) increased stroke volume (up to +7.8 mL, P < 0.01), improved global longitudinal (up to -1.0%, P < 0.05) and circumferential strain (up to -3.3%, P < 0.01), decreased LA minimal volume index (up to -2.4 mL/m2 , P < 0.01) and increased LA function index (up to 6.1, P < 0.01), when compared with placebo. CONCLUSIONS Danicamtiv was well tolerated and improved LV systolic function in patients with HFrEF. A marked improvement in LA volume and function was also observed in patients with HFrEF, consistent with pre-clinical findings of direct activation of LA contractility.
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Affiliation(s)
| | | | - John G Cleland
- Robertson Centre for Biostatistics and Clinical Trials Unit, University of Glasgow, Glasgow, UK
| | - Michael Koren
- Jacksonville Center for Clinical Research, Jacksonville, FL, USA
| | | | | | - Lars H Lund
- Department of Medicine, Karolinska Institutet, Stockholm, Sweden.,Karolinska University Hospital, Heart and Vascular Theme, Stockholm, Sweden
| | | | - Ravi Karra
- Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - Henk P Swart
- Antonius Ziekenhuis Sneek, Sneek, The Netherlands
| | - Pierpaolo Pellicori
- Robertson Centre for Biostatistics and Clinical Trials Unit, University of Glasgow, Glasgow, UK
| | | | - Ray E Hershberger
- Divisions of Human Genetics and Cardiovascular Medicine, The Ohio State University, Columbus, OH, USA
| | - Narayana Prasad
- Cardiovascular Imaging Core Laboratory, Brigham and Women's Hospital, Boston, MA, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | - Scott D Solomon
- Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
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45
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Governali S, Caremani M, Gallart C, Pertici I, Stienen G, Piazzesi G, Ottenheijm C, Lombardi V, Linari M. Orthophosphate increases the efficiency of slow muscle-myosin isoform in the presence of omecamtiv mecarbil. Nat Commun 2020; 11:3405. [PMID: 32636378 PMCID: PMC7341760 DOI: 10.1038/s41467-020-17143-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 05/26/2020] [Indexed: 02/08/2023] Open
Abstract
Omecamtiv mecarbil (OM) is a putative positive inotropic tool for treatment of systolic heart dysfunction, based on the finding that in vivo it increases the ejection fraction and in vitro it prolongs the actin-bond life time of the cardiac and slow-skeletal muscle isoforms of myosin. OM action in situ, however, is still poorly understood as the enhanced Ca2+-sensitivity of the myofilaments is at odds with the reduction of force and rate of force development observed at saturating Ca2+. Here we show, by combining fast sarcomere-level mechanics and ATPase measurements in single slow demembranated fibres from rabbit soleus, that the depressant effect of OM on the force per attached motor is reversed, without effect on the ATPase rate, by physiological concentrations of inorganic phosphate (Pi) (1-10 mM). This mechanism could underpin an energetically efficient reduction of systolic tension cost in OM-treated patients, whenever [Pi] increases with heart-beat frequency. Omecamtiv mecarbil is a small molecule effector under clinical trial for the treatment of systolic heart failure. Here the authors define the molecular mechanisms of its inotropic action and find it can increase the efficiency of contraction in muscle fibres when the orthophosphate concentration rises with the beat frequency.
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Affiliation(s)
- Serena Governali
- PhysioLab, Department of Biology, University of Florence, Sesto Fiorentino, 50019, Italy.,Department of Physiology, Amsterdam UMC (location VUmc), 1081 HZ, Amsterdam, The Netherlands
| | - Marco Caremani
- PhysioLab, Department of Biology, University of Florence, Sesto Fiorentino, 50019, Italy
| | - Cristina Gallart
- PhysioLab, Department of Biology, University of Florence, Sesto Fiorentino, 50019, Italy
| | - Irene Pertici
- PhysioLab, Department of Biology, University of Florence, Sesto Fiorentino, 50019, Italy
| | - Ger Stienen
- Department of Physiology, Amsterdam UMC (location VUmc), 1081 HZ, Amsterdam, The Netherlands.,Department of Physiology, Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Gabriella Piazzesi
- PhysioLab, Department of Biology, University of Florence, Sesto Fiorentino, 50019, Italy
| | - Coen Ottenheijm
- Department of Physiology, Amsterdam UMC (location VUmc), 1081 HZ, Amsterdam, The Netherlands
| | - Vincenzo Lombardi
- PhysioLab, Department of Biology, University of Florence, Sesto Fiorentino, 50019, Italy.
| | - Marco Linari
- PhysioLab, Department of Biology, University of Florence, Sesto Fiorentino, 50019, Italy
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46
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Bhagwan JR, Mosqueira D, Chairez-Cantu K, Mannhardt I, Bodbin SE, Bakar M, Smith JGW, Denning C. Isogenic models of hypertrophic cardiomyopathy unveil differential phenotypes and mechanism-driven therapeutics. J Mol Cell Cardiol 2020; 145:43-53. [PMID: 32531470 PMCID: PMC7487780 DOI: 10.1016/j.yjmcc.2020.06.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 05/18/2020] [Accepted: 06/05/2020] [Indexed: 12/14/2022]
Abstract
BACKGROUND Hypertrophic cardiomyopathy (HCM) is a prevalent and complex cardiovascular condition. Despite being strongly associated with genetic alterations, wide variation of disease penetrance, expressivity and hallmarks of progression complicate treatment. We aimed to characterize different human isogenic cellular models of HCM bearing patient-relevant mutations to clarify genetic causation and disease mechanisms, hence facilitating the development of effective therapeutics. METHODS We directly compared the p.β-MHC-R453C and p.ACTC1-E99K HCM-associated mutations in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and their healthy isogenic counterparts, generated using CRISPR/Cas9 genome editing technology. By harnessing several state-of-the-art HCM phenotyping techniques, these mutations were investigated to identify similarities and differences in disease progression and hypertrophic signaling pathways, towards establishing potential targets for pharmacological treatment. CRISPR/Cas9 knock-in of the genetically-encoded calcium indicator R-GECO1.0 to the AAVS1 locus into these disease models resulted in calcium reporter lines. RESULTS Confocal line scan analysis identified calcium transient arrhythmias and intracellular calcium overload in both models. The use of optogenetics and 2D/3D contractility assays revealed opposing phenotypes in the two mutations. Gene expression analysis highlighted upregulation of CALM1, CASQ2 and CAMK2D, and downregulation of IRF8 in p.β-MHC-R453C mutants, whereas the opposite changes were detected in p.ACTC1-E99K mutants. Contrasting profiles of nuclear translocation of NFATc1 and MEF2 between the two HCM models suggest differential hypertrophic signaling pathway activation. Calcium transient abnormalities were rescued with combination of dantrolene and ranolazine, whilst mavacamten reduced the hyper-contractile phenotype of p.ACTC1-E99K hiPSC-CMs. CONCLUSIONS Our data show that hypercontractility and molecular signaling within HCM are not uniform between different gene mutations, suggesting that a 'one-size fits all' treatment underestimates the complexity of the disease. Understanding where the similarities (arrhythmogenesis, bioenergetics) and differences (contractility, molecular profile) lie will allow development of therapeutics that are directed towards common mechanisms or tailored to each disease variant, hence providing effective patient-specific therapy.
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Affiliation(s)
- Jamie R Bhagwan
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK.
| | - Diogo Mosqueira
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK.
| | - Karolina Chairez-Cantu
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK
| | - Ingra Mannhardt
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, and DZHK (German Center for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Hamburg, Germany
| | - Sara E Bodbin
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK
| | - Mine Bakar
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK
| | - James G W Smith
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK; Faculty of Medicine and Health Sciences, Norwich Medical School, University of East Anglia,NR4 7UQ, UK
| | - Chris Denning
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK.
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47
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Cacciani N, Salah H, Li M, Akkad H, Backeus A, Hedstrom Y, Jena BP, Bergquist J, Larsson L. Chaperone co-inducer BGP-15 mitigates early contractile dysfunction of the soleus muscle in a rat ICU model. Acta Physiol (Oxf) 2020; 229:e13425. [PMID: 31799784 PMCID: PMC7187345 DOI: 10.1111/apha.13425] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 11/25/2019] [Accepted: 11/25/2019] [Indexed: 12/13/2022]
Abstract
Aim Critical illness myopathy (CIM) represents a common consequence of modern intensive care, negatively impacting patient health and significantly increasing health care costs; however, there is no treatment available apart from symptomatic and supportive interventions. The chaperone co‐inducer BGP‐15 has previously been shown to have a positive effect on the diaphragm in rats exposed to the intensive care unit (ICU) condition. In this study, we aim to explore the effects of BGP‐15 on a limb muscle (soleus muscle) in response to the ICU condition. Methods Sprague‐Dawley rats were subjected to the ICU condition for 5, 8 and 10 days and compared with untreated sham‐operated controls. Results BGP‐15 significantly improved soleus muscle fibre force after 5 days exposure to the ICU condition. This improvement was associated with the protection of myosin from post‐translational myosin modifications, improved mitochondrial structure/biogenesis and reduced the expression of MuRF1 and Fbxo31 E3 ligases. At longer durations (8 and 10 days), BGP‐15 had no protective effect when the hallmark of CIM had become manifest, that is, preferential loss of myosin. Unrelated to the effects on skeletal muscle, BGP‐15 had a strong positive effect on survival compared with untreated animals. Conclusions BGP‐15 treatment improved soleus muscle fibre and motor protein function after 5 days exposure to the ICU condition, but not at longer durations (8 and 10 days) when the preferential loss of myosin was manifest. Thus, long‐term CIM interventions targeting limb muscle fibre/myosin force generation capacity need to consider both the post‐translational modifications and the loss of myosin.
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Affiliation(s)
- Nicola Cacciani
- Department of Physiology and Pharmacology Karolinska Institutet Stockholm Sweden
| | - Heba Salah
- Department of Physiology and Pharmacology Karolinska Institutet Stockholm Sweden
| | - Meishan Li
- Department of Physiology and Pharmacology Karolinska Institutet Stockholm Sweden
| | - Hazem Akkad
- Department of Physiology and Pharmacology Karolinska Institutet Stockholm Sweden
| | - Anders Backeus
- Department of Physiology and Pharmacology Karolinska Institutet Stockholm Sweden
| | - Yvette Hedstrom
- Department of Physiology and Pharmacology Karolinska Institutet Stockholm Sweden
| | - Bhanu P. Jena
- Department of Physiology Wayne State University School of Medicine Detroit MI USA
| | - Jonas Bergquist
- Analytical Chemistry Department of Chemistry–Biomedical Centre Uppsala University Uppsala Sweden
| | - Lars Larsson
- Department of Physiology and Pharmacology Karolinska Institutet Stockholm Sweden
- Department of Clinical Neuroscience Clinical Neurophysiology Karolinska Institutet Stockholm Sweden
- Department of Biobehavioral Health The Pennsylvania State University University Park PA USA
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48
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López-Dávila AJ, Chalovich JM, Zittrich S, Piep B, Matinmehr F, Málnási-Csizmadia A, Rauscher AÁ, Kraft T, Brenner B, Stehle R. Cycling Cross-Bridges Contribute to Thin Filament Activation in Human Slow-Twitch Fibers. Front Physiol 2020; 11:144. [PMID: 32265723 PMCID: PMC7105683 DOI: 10.3389/fphys.2020.00144] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 02/11/2020] [Indexed: 11/13/2022] Open
Abstract
It has been shown that not only calcium but also strong binding myosin heads contribute to thin filament activation in isometrically contracting animal fast-twitch and cardiac muscle preparations. This behavior has not been studied in human muscle fibers or animal slow-twitch fibers. Human slow-twitch fibers are interesting since they contain the same myosin heavy chain isoform as the human heart. To explore myosin-induced activation of the thin filament in isometrically contracting human slow-twitch fibers, the endogenous troponin complex was exchanged for a well-characterized fast-twitch skeletal troponin complex labeled with the fluorescent dye N-((2-(Iodoacetoxy)ethyl)-N-methyl)amino-7-nitrobenz-2-oxa-1,3-diazole (fsTn-IANBD). The exchange was ≈70% complete (n = 8). The relative contributions of calcium and strong binding cross-bridges to thin filament activation were dissected by increasing the concentration of calcium from relaxing (pCa 7.5) to saturating levels (pCa 4.5) before and after incubating the exchanged fibers in the myosin inhibitor para-aminoblebbistatin (AmBleb). At pCa 4.5, the relative contributions of calcium and strong binding cross-bridges to thin filament activation were ≈69 and ≈31%, respectively. Additionally, switching from isometric to isotonic contraction at pCa 4.5 revealed that strong binding cross-bridges contributed ≈29% to thin filament activation (i.e., virtually the same magnitude obtained with AmBleb). Thus, we showed through two different approaches that lowering the number of strong binding cross-bridges, at saturating calcium, significantly reduced the activation of the thin filament in human slow-twitch fibers. The contribution of myosin to activation resembled that which was previously reported in rat cardiac and rabbit fast-twitch muscle preparations. This method could be applied to slow-twitch human fibers obtained from the soleus muscle of cardiomyopathy patients. Such studies could lead to a better understanding of the effect of point mutations of the cardiac myosin head on the regulation of muscle contraction and could lead to better management by pharmacological approaches.
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Affiliation(s)
| | - Joseph M Chalovich
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, NC, United States
| | - Stefan Zittrich
- Institute of Vegetative Physiology, University of Cologne, Cologne, Germany
| | - Birgit Piep
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hanover, Germany
| | - Faramarz Matinmehr
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hanover, Germany
| | - Andras Málnási-Csizmadia
- MTA-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary
| | | | - Theresia Kraft
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hanover, Germany
| | - Bernhard Brenner
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hanover, Germany
| | - Robert Stehle
- Institute of Vegetative Physiology, University of Cologne, Cologne, Germany
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Sarkar SS, Trivedi DV, Morck MM, Adhikari AS, Pasha SN, Ruppel KM, Spudich JA. The hypertrophic cardiomyopathy mutations R403Q and R663H increase the number of myosin heads available to interact with actin. SCIENCE ADVANCES 2020; 6:eaax0069. [PMID: 32284968 PMCID: PMC7124958 DOI: 10.1126/sciadv.aax0069] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Accepted: 01/09/2020] [Indexed: 05/20/2023]
Abstract
Hypertrophic cardiomyopathy (HCM) mutations in β-cardiac myosin and myosin binding protein-C (MyBP-C) lead to hypercontractility of the heart, an early hallmark of HCM. We show that hypercontractility caused by the HCM-causing mutation R663H cannot be explained by changes in fundamental myosin contractile parameters, much like the HCM-causing mutation R403Q. Using enzymatic assays with purified human β-cardiac myosin, we provide evidence that both mutations cause hypercontractility by increasing the number of functionally accessible myosin heads. We also demonstrate that the myosin mutation R403Q, but not R663H, ablates the binding of myosin with the C0-C7 fragment of MyBP-C. Furthermore, addition of C0-C7 decreases the wild-type myosin basal ATPase single turnover rate, while the mutants do not show a similar reduction. These data suggest that a primary mechanism of action for these mutations is to increase the number of myosin heads functionally available for interaction with actin, which could contribute to hypercontractility.
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Affiliation(s)
- Saswata S. Sarkar
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Darshan V. Trivedi
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Makenna M. Morck
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Arjun S. Adhikari
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Shaik N. Pasha
- National Centre for Biological Sciences (TIFR), GKVK Campus, Bellary Road, Bangalore, India
| | - Kathleen M. Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
- Department of Pediatrics (Cardiology), Stanford University School of Medicine, Stanford, CA 94305, USA
| | - James A. Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
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50
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Muir WW, Hamlin RL. Myocardial Contractility: Historical and Contemporary Considerations. Front Physiol 2020; 11:222. [PMID: 32296340 PMCID: PMC7137917 DOI: 10.3389/fphys.2020.00222] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 02/26/2020] [Indexed: 12/17/2022] Open
Abstract
The term myocardial contractility is thought to have originated more than 125 years ago and has remained and enigma ever since. Although the term is frequently used in textbooks, editorials and contemporary manuscripts its definition remains illusive often being conflated with cardiac performance or inotropy. The absence of a universally accepted definition has led to confusion, disagreement and misconceptions among physiologists, cardiologists and safety pharmacologists regarding its definition particularly in light of new discoveries regarding the load dependent kinetics of cardiac contraction and their translation to cardiac force-velocity and ventricular pressure-volume measurements. Importantly, the Starling interpretation of force development is length-dependent while contractility is length independent. Most historical definitions employ an operational approach and define cardiac contractility in terms of the hearts mechanical properties independent of loading conditions. Literally defined the term contract infers that something has become smaller, shrunk or shortened. The addition of the suffix “ility” implies the quality of this process. The discovery and clinical investigation of small molecules that bind to sarcomeric proteins independently altering force or velocity requires that a modern definition of the term myocardial contractility be developed if the term is to persist. This review reconsiders the historical and contemporary interpretations of the terms cardiac performance and inotropy and recommends a modern definition of myocardial contractility as the preload, afterload and length-independent intrinsic kinetically controlled, chemo-mechanical processes responsible for the development of force and velocity.
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Affiliation(s)
- William W Muir
- College of Veterinary Medicine, Lincoln Memorial University, Harrogate, TN, United States
| | - Robert L Hamlin
- College of Veterinary Medicine, The Ohio State University, Columbus, OH, United States
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