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Jalali F, Nazari MA, Bahrami A, Perrier P, Payan Y. FIM: A fatigued-injured muscle model based on the sliding filament theory. Comput Biol Med 2023; 164:107367. [PMID: 37595519 DOI: 10.1016/j.compbiomed.2023.107367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Revised: 07/24/2023] [Accepted: 08/12/2023] [Indexed: 08/20/2023]
Abstract
Skeletal muscle modeling has a vital role in movement studies and the development of therapeutic approaches. In the current study, a Huxley-based model for skeletal muscle is proposed, which demonstrates the impact of impairments in muscle characteristics. This model focuses on three identified ions: H+, inorganic phosphate Pi, and Ca2+. Modifications are made to actin-myosin attachment and detachment rates to study the effects of H+ and Pi. Additionally, an activation coefficient is included to represent the role of calcium ions interacting with troponin, highlighting the importance of Ca2+. It is found that maximum isometric muscle force decreases by 9.5% due to a reduction in pH from 7.4 to 6.5 and by 47.5% in case of the combination of a reduction in pH and an increase of Pi concentration up to 30 mM, respectively. Then the force decline caused by a fall in the active calcium ions is studied. When only 15% of the total calcium in the myofibrillar space is able to interact with troponin, up to 80% force drop is anticipated by the model. The proposed fatigued-injured muscle model is useful to study the effect of various shortening velocities and initial muscle-tendon lengths on muscle force; in addition, the benefits of the model go beyond predicting the force in different conditions as it can also predict muscle stiffness and power. The power and stiffness decrease by 40% and 6.5%, respectively, due to the pH reduction, and the simultaneous accumulation of H+ and Pi leads to a 50% and 18% drop in power and stiffness.
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Affiliation(s)
- Fatemeh Jalali
- School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
| | - Mohammad Ali Nazari
- School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran; Univ. Grenoble Alpes, CNRS, Grenoble INP, TIMC, 38000, Grenoble, France.
| | - Arash Bahrami
- School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
| | - Pascal Perrier
- Univ. Grenoble Alpes, CNRS, Grenoble INP, GIPSA-lab, 38000, Grenoble, France
| | - Yohan Payan
- Univ. Grenoble Alpes, CNRS, Grenoble INP, TIMC, 38000, Grenoble, France
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2
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Wiseman RW, Brown CM, Beck TW, Brault JJ, Reinoso TR, Shi Y, Chase PB. Creatine Kinase Equilibration and ΔG ATP over an Extended Range of Physiological Conditions: Implications for Cellular Energetics, Signaling, and Muscle Performance. Int J Mol Sci 2023; 24:13244. [PMID: 37686064 PMCID: PMC10487889 DOI: 10.3390/ijms241713244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 08/22/2023] [Accepted: 08/24/2023] [Indexed: 09/10/2023] Open
Abstract
In this report, we establish a straightforward method for estimating the equilibrium constant for the creatine kinase reaction (CK Keq″) over wide but physiologically and experimentally relevant ranges of pH, Mg2+ and temperature. Our empirical formula for CK Keq″ is based on experimental measurements. It can be used to estimate [ADP] when [ADP] is below the resolution of experimental measurements, a typical situation because [ADP] is on the order of micromolar concentrations in living cells and may be much lower in many in vitro experiments. Accurate prediction of [ADP] is essential for in vivo studies of cellular energetics and metabolism and for in vitro studies of ATP-dependent enzyme function under near-physiological conditions. With [ADP], we were able to obtain improved estimates of ΔGATP, necessitating the reinvestigation of previously reported ADP- and ΔGATP-dependent processes. Application to actomyosin force generation in muscle provides support for the hypothesis that, when [Pi] varies and pH is not altered, the maximum Ca2+-activated isometric force depends on ΔGATP in both living and permeabilized muscle preparations. Further analysis of the pH studies introduces a novel hypothesis around the role of submicromolar ADP in force generation.
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Affiliation(s)
- Robert Woodbury Wiseman
- Departments of Physiology and Radiology, Michigan State University, East Lansing, MI 48824, USA;
| | - Caleb Micah Brown
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Thomas Wesley Beck
- Department of Radiology, University of Washington, Seattle, WA 98195, USA
| | - Jeffrey John Brault
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA;
| | - Tyler Robert Reinoso
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Yun Shi
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Prescott Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
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3
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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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4
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Kawai M, Stehle R, Pfitzer G, Iorga B. Phosphate has dual roles in cross-bridge kinetics in rabbit psoas single myofibrils. J Gen Physiol 2021; 153:211791. [PMID: 33599680 PMCID: PMC7885270 DOI: 10.1085/jgp.202012755] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Revised: 12/04/2020] [Accepted: 01/15/2021] [Indexed: 11/27/2022] Open
Abstract
In this study, we aimed to study the role of inorganic phosphate (Pi) in the production of oscillatory work and cross-bridge (CB) kinetics of striated muscle. We applied small-amplitude sinusoidal length oscillations to rabbit psoas single myofibrils and muscle fibers, and the resulting force responses were analyzed during maximal Ca2+ activation (pCa 4.65) at 15°C. Three exponential processes, A, B, and C, were identified from the tension transients, which were studied as functions of Pi concentration ([Pi]). In myofibrils, we found that process C, corresponding to phase 2 of step analysis during isometric contraction, is almost a perfect single exponential function compared with skinned fibers, which exhibit distributed rate constants, as described previously. The [Pi] dependence of the apparent rate constants 2πb and 2πc, and that of isometric tension, was studied to characterize the force generation and Pi release steps in the CB cycle, as well as the inhibitory effect of Pi. In contrast to skinned fibers, Pi does not accumulate in the core of myofibrils, allowing sinusoidal analysis to be performed nearly at [Pi] = 0. Process B disappeared as [Pi] approached 0 mM in myofibrils, indicating the significance of the role of Pi rebinding to CBs in the production of oscillatory work (process B). Our results also suggest that Pi competitively inhibits ATP binding to CBs, with an inhibitory dissociation constant of ∼2.6 mM. Finally, we found that the sinusoidal waveform of tension is mostly distorted by second harmonics and that this distortion is closely correlated with production of oscillatory work, indicating that the mechanism of generating force is intrinsically nonlinear. A nonlinear force generation mechanism suggests that the length-dependent intrinsic rate constant is asymmetric upon stretch and release and that there may be a ratchet mechanism involved in the CB cycle.
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Affiliation(s)
- Masataka Kawai
- Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA
| | - Robert Stehle
- Institute of Vegetative Physiology, University of Köln, Köln, Germany
| | - Gabriele Pfitzer
- Institute of Vegetative Physiology, University of Köln, Köln, Germany.,Institute of Neurophysiology, University of Köln, Köln, Germany
| | - Bogdan Iorga
- Institute of Vegetative Physiology, University of Köln, Köln, Germany.,Department of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany.,Department of Physical Chemistry, Faculty of Chemistry, University of Bucharest, Bucharest, Romania
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5
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The effects of inorganic phosphate on contractile function of slow skeletal muscle fibres are length-dependent. Biochem Biophys Res Commun 2020; 533:818-823. [DOI: 10.1016/j.bbrc.2020.09.092] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 09/22/2020] [Indexed: 11/22/2022]
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6
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Offer G, Ranatunga K. The Location and Rate of the Phosphate Release Step in the Muscle Cross-Bridge Cycle. Biophys J 2020; 119:1501-1512. [DOI: 10.1016/j.bpj.2020.09.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 08/27/2020] [Accepted: 09/02/2020] [Indexed: 11/26/2022] Open
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7
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Regazzoni F, Dedè L, Quarteroni A. Active Force Generation in Cardiac Muscle Cells: Mathematical Modeling and Numerical Simulation of the Actin-Myosin Interaction. VIETNAM JOURNAL OF MATHEMATICS 2020; 49:87-118. [PMID: 34722731 PMCID: PMC8549950 DOI: 10.1007/s10013-020-00433-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 05/21/2020] [Indexed: 06/13/2023]
Abstract
Cardiac in silico numerical simulations are based on mathematical models describing the physical processes involved in the heart function. In this review paper, we critically survey biophysically-detailed mathematical models describing the subcellular mechanisms behind the generation of active force, that is the process by which the chemical energy of ATP (adenosine triphosphate) is transformed into mechanical work, thus making the muscle tissue contract. While presenting these models, that feature different levels of biophysical detail, we analyze the trade-off between the accuracy in the description of the subcellular mechanisms and the number of parameters that need to be estimated from experiments. Then, we focus on a generalized version of the classic Huxley model, built on the basis of models available in the literature, that is able to reproduce the main experimental characterizations associated to the time scales typical of a heartbeat-such as the force-velocity relationship and the tissue stiffness in response to small steps-featuring only four independent parameters. Finally, we show how those parameters can be calibrated starting from macroscopic measurements available from experiments.
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Affiliation(s)
- Francesco Regazzoni
- MOX - Dipartimento di Matematica, Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Luca Dedè
- MOX - Dipartimento di Matematica, Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Alfio Quarteroni
- MOX - Dipartimento di Matematica, Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133 Milano, Italy
- Mathematics Institute, École Polytechnique Fédérale de Lausanne (EPFL), Av. Piccard, CH-1015 Lausanne, Switzerland
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8
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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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9
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Degens H, Jones DA. Are Force Enhancement after Stretch and Muscle Fatigue Due to Effects of Elevated Inorganic Phosphate and Low Calcium on Cross Bridge Kinetics? ACTA ACUST UNITED AC 2020; 56:medicina56050249. [PMID: 32443826 PMCID: PMC7279286 DOI: 10.3390/medicina56050249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 05/18/2020] [Indexed: 11/20/2022]
Abstract
Background and Objectives: Muscle fatigue is characterised by (1) loss of force, (2) decreased maximal shortening velocity and (3) a greater resistance to stretch that could be due to reduced intracellular Ca2+ and increased Pi, which alter cross bridge kinetics. Materials and Methods: To investigate this, we used (1) 2,3-butanedione monoxime (BDM), believed to increase the proportion of attached but non-force-generating cross bridges; (2) Pi that increases the proportion of attached cross bridges, but with Pi still attached; and (3) reduced activating Ca2+. We used permeabilised rat soleus fibres, activated with pCa 4.5 at 15 °C. Results: The addition of 1 mM BDM or 15 mM Pi, or the lowering of the Ca2+ to pCa 5.5, all reduced the isometric force by around 50%. Stiffness decreased in proportion to isometric force when the fibres were activated at pCa 5.5, but was well maintained in the presence of Pi and BDM. Force enhancement after a stretch increased with the length of stretch and Pi, suggesting a role for titin. Maximum shortening velocity was reduced by about 50% in the presence of BDM and pCa 5.5, but was slightly increased by Pi. Neither decreasing Ca2+ nor increasing Pi alone mimicked the effects of fatigue on muscle contractile characteristics entirely. Only BDM elicited a decrease of force and slowing with maintained stiffness, similar to the situation in fatigued muscle. Conclusions: This suggests that in fatigue, there is an accumulation of attached but low-force cross bridges that cannot be the result of the combined action of reduced Ca2+ or increased Pi alone, but is probably due to a combination of factors that change during fatigue.
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Affiliation(s)
- Hans Degens
- Department of Life Sciences, Manchester Metropolitan University, Research Centre for Musculoskeletal Sciences & Sport Medicine, Manchester M1 5GD, UK;
- Institute of Sport Science and Innovations, Lithuanian Sports University, LT-44221 Kaunas, Lithuania
- Correspondence: ; Tel.: +44-161-247-5686
| | - David A. Jones
- Department of Life Sciences, Manchester Metropolitan University, Research Centre for Musculoskeletal Sciences & Sport Medicine, Manchester M1 5GD, UK;
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10
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Robert-Paganin J, Pylypenko O, Kikuti C, Sweeney HL, Houdusse A. Force Generation by Myosin Motors: A Structural Perspective. Chem Rev 2019; 120:5-35. [PMID: 31689091 DOI: 10.1021/acs.chemrev.9b00264] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Generating force and movement is essential for the functions of cells and organisms. A variety of molecular motors that can move on tracks within cells have evolved to serve this role. How these motors interact with their tracks and how that, in turn, leads to the generation of force and movement is key to understanding the cellular roles that these motor-track systems serve. This review is focused on the best understood of these systems, which is the molecular motor myosin that moves on tracks of filamentous (F-) actin. The review highlights both the progress and the limits of our current understanding of how force generation can be controlled by F-actin-myosin interactions. What has emerged are insights they may serve as a framework for understanding the design principles of a number of types of molecular motors and their interactions with their tracks.
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Affiliation(s)
- Julien Robert-Paganin
- Structural Motility , UMR 144 CNRS/Curie Institute , 26 rue d'ulm , 75258 Paris cedex 05 , France
| | - Olena Pylypenko
- Structural Motility , UMR 144 CNRS/Curie Institute , 26 rue d'ulm , 75258 Paris cedex 05 , France
| | - Carlos Kikuti
- Structural Motility , UMR 144 CNRS/Curie Institute , 26 rue d'ulm , 75258 Paris cedex 05 , France
| | - H Lee Sweeney
- Department of Pharmacology & Therapeutics and the Myology Institute , University of Florida College of Medicine , PO Box 100267, Gainesville , Florida 32610-0267 , United States
| | - Anne Houdusse
- Structural Motility , UMR 144 CNRS/Curie Institute , 26 rue d'ulm , 75258 Paris cedex 05 , France
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11
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Månsson A. The effects of inorganic phosphate on muscle force development and energetics: challenges in modelling related to experimental uncertainties. J Muscle Res Cell Motil 2019; 42:33-46. [PMID: 31620962 PMCID: PMC7932973 DOI: 10.1007/s10974-019-09558-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 10/09/2019] [Indexed: 02/03/2023]
Abstract
Muscle force and power are developed by myosin cross-bridges, which cyclically attach to actin, undergo a force-generating transition and detach under turnover of ATP. The force-generating transition is intimately associated with release of inorganic phosphate (Pi) but the exact sequence of events in relation to the actual Pi release step is controversial. Details of this process are reflected in the relationships between [Pi] and the developed force and shortening velocity. In order to account for these relationships, models have proposed branched kinetic pathways or loose coupling between biochemical and force-generating transitions. A key hypothesis underlying the present study is that such complexities are not required to explain changes in the force–velocity relationship and ATP turnover rate with altered [Pi]. We therefore set out to test if models without branched kinetic paths and Pi-release occurring before the main force-generating transition can account for effects of varied [Pi] (0.1–25 mM). The models tested, one assuming either linear or non-linear cross-bridge elasticity, account well for critical aspects of muscle contraction at 0.5 mM Pi but their capacity to account for the maximum power output vary. We find that the models, within experimental uncertainties, account for the relationship between [Pi] and isometric force as well as between [Pi] and the velocity of shortening at low loads. However, in apparent contradiction with available experimental findings, the tested models produce an anomalous force–velocity relationship at elevated [Pi] and high loads with more than one possible velocity for a given load. Nevertheless, considering experimental uncertainties and effects of sarcomere non-uniformities, these discrepancies are insufficient to refute the tested models in favour of more complex alternatives.
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Affiliation(s)
- Alf Månsson
- Department of Chemistry and Biomedical Sciences, Faculty of Health and Life Sciences, Linnaeus University, Universitetskajen, 391 82, Kalmar, Sweden.
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12
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Recessive MYH7-related myopathy in two families. Neuromuscul Disord 2019; 29:456-467. [PMID: 31130376 DOI: 10.1016/j.nmd.2019.04.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 04/02/2019] [Accepted: 04/05/2019] [Indexed: 02/08/2023]
Abstract
Myopathies due to recessive MYH7 mutations are exceedingly rare, reported in only two families to date. We describe three patients from two families (from Australia and the UK) with a myopathy caused by recessive mutations in MYH7. The Australian family was homozygous for a c.5134C > T, p.Arg1712Trp mutation, whilst the UK patient was compound heterozygous for a truncating (c.4699C > T; p.Gln1567*) and a missense variant (c.4664A > G; p.Glu1555Gly). All three patients shared key clinical features, including infancy/childhood onset, pronounced axial/proximal weakness, spinal rigidity, severe scoliosis, and normal cardiac function. There was progressive respiratory impairment necessitating non-invasive ventilation despite preserved ambulation, a combination of features often seen in SEPN1- or NEB-related myopathies. On biopsy, the Australian proband showed classical myosin storage myopathy features, while the UK patient showed multi-minicore like areas. To establish pathogenicity of the Arg1712Trp mutation, we expressed mutant MYH7 protein in COS-7 cells, observing abnormal mutant myosin aggregation compared to wild-type. We describe skinned myofiber studies of patient muscle and hypertrophy of type II myofibers, which may be a compensatory mechanism. In summary, we have expanded the phenotype of ultra-rare recessive MYH7 disease, and provide novel insights into associated changes in muscle physiology.
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13
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Robinett JC, Hanft LM, Geist J, Kontrogianni-Konstantopoulos A, McDonald KS. Regulation of myofilament force and loaded shortening by skeletal myosin binding protein C. J Gen Physiol 2019; 151:645-659. [PMID: 30705121 PMCID: PMC6504288 DOI: 10.1085/jgp.201812200] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 01/11/2019] [Indexed: 12/28/2022] Open
Abstract
Myosin binding protein C (MyBP-C) is thought to regulate the contraction of skeletal muscle. Robinett et al. show that phosphorylation of slow skeletal MyBP-C modulates contraction by recruiting cross-bridges, modifying cross-bridge kinetics, and altering internal drag forces in the C-zone. Myosin binding protein C (MyBP-C) is a 125–140-kD protein located in the C-zone of each half-thick filament. It is thought to be an important regulator of contraction, but its precise role is unclear. Here we investigate mechanisms by which skeletal MyBP-C regulates myofilament function using rat permeabilized skeletal muscle fibers. We mount either slow-twitch or fast-twitch skeletal muscle fibers between a force transducer and motor, use Ca2+ to activate a range of forces, and measure contractile properties including transient force overshoot, rate of force development, and loaded sarcomere shortening. The transient force overshoot is greater in slow-twitch than fast-twitch fibers at all Ca2+ activation levels. In slow-twitch fibers, protein kinase A (PKA) treatment (a) augments phosphorylation of slow skeletal MyBP-C (sMyBP-C), (b) doubles the magnitude of the relative transient force overshoot at low Ca2+ activation levels, and (c) increases force development rates at all Ca2+ activation levels. We also investigate the role that phosphorylated and dephosphorylated sMyBP-C plays in loaded sarcomere shortening. We test the hypothesis that MyBP-C acts as a brake to filament sliding within the myofilament lattice by measuring sarcomere shortening as thin filaments traverse into the C-zone during lightly loaded slow-twitch fiber contractions. Before PKA treatment, shortening velocity decelerates as sarcomeres traverse from ∼3.10 to ∼3.00 µm. After PKA treatment, sarcomeres shorten a greater distance and exhibit less deceleration during similar force clamps. After sMyBP-C dephosphorylation, sarcomere length traces display a brief recoil (i.e., “bump”) that initiates at ∼3.06 µm during loaded shortening. Interestingly, the timing of the bump shifts with changes in load but manifests at the same sarcomere length. Our results suggest that sMyBP-C and its phosphorylation state regulate sarcomere contraction by a combination of cross-bridge recruitment, modification of cross-bridge cycling kinetics, and alteration of drag forces that originate in the C-zone.
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Affiliation(s)
- Joel C Robinett
- Department of Medical Pharmacology and Physiology, School of Medicine, University of Missouri, Columbia, MO
| | - Laurin M Hanft
- Department of Medical Pharmacology and Physiology, School of Medicine, University of Missouri, Columbia, MO
| | - Janelle Geist
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD
| | | | - Kerry S McDonald
- Department of Medical Pharmacology and Physiology, School of Medicine, University of Missouri, Columbia, MO
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14
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Woodward M, Debold EP. Acidosis and Phosphate Directly Reduce Myosin's Force-Generating Capacity Through Distinct Molecular Mechanisms. Front Physiol 2018; 9:862. [PMID: 30042692 PMCID: PMC6048269 DOI: 10.3389/fphys.2018.00862] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 06/18/2018] [Indexed: 12/04/2022] Open
Abstract
Elevated levels of the metabolic by-products, including acidosis (i.e., high [H+]) and phosphate (Pi) are putative agents of muscle fatigue; however, the mechanism through which they affect myosin’s function remain unclear. To elucidate these mechanisms, we directly examined the effect of acidosis (pH 6.5 vs. 7.4), alone and in combination with elevated levels of Pi on the force-generating capacity of a mini-ensemble of myosin using a laser trap assay. Acidosis decreased myosin’s average force-generating capacity by 20% (p < 0.05). The reduction was due to both a decrease in the force generated during each actomyosin interaction, as well as an increase in the number of binding events generating negative forces. Adding Pi to the acidic condition resulted in a quantitatively similar decrease in force but was solely due to an elimination of all high force-generating events (>2 pN), resulting from an acceleration of the myosin’s rate of detachment from actin. Acidosis and Pi also had distinct effects on myosin’s steady state ATPase rate with acidosis slowing it by ∼90% (p > 0.05), while the addition of Pi under acidic conditions caused a significant recovery in the ATPase rate. These data suggest that these two fatigue agents have distinct effects on myosin’s cross-bridge cycle that may underlie the synergistic effect that they have muscle force. Thus these data provide novel molecular insight into the mechanisms underlying the depressive effects of Pi and H+ on muscle contraction during fatigue.
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Affiliation(s)
- Mike Woodward
- Muscle Biophysics Lab, Department of Kinesiology, University of Massachusetts, Amherst, MA, United States
| | - Edward P Debold
- Muscle Biophysics Lab, Department of Kinesiology, University of Massachusetts, Amherst, MA, United States
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15
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Wang L, Geist J, Grogan A, Hu LYR, Kontrogianni-Konstantopoulos A. Thick Filament Protein Network, Functions, and Disease Association. Compr Physiol 2018; 8:631-709. [PMID: 29687901 PMCID: PMC6404781 DOI: 10.1002/cphy.c170023] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Sarcomeres consist of highly ordered arrays of thick myosin and thin actin filaments along with accessory proteins. Thick filaments occupy the center of sarcomeres where they partially overlap with thin filaments. The sliding of thick filaments past thin filaments is a highly regulated process that occurs in an ATP-dependent manner driving muscle contraction. In addition to myosin that makes up the backbone of the thick filament, four other proteins which are intimately bound to the thick filament, myosin binding protein-C, titin, myomesin, and obscurin play important structural and regulatory roles. Consistent with this, mutations in the respective genes have been associated with idiopathic and congenital forms of skeletal and cardiac myopathies. In this review, we aim to summarize our current knowledge on the molecular structure, subcellular localization, interacting partners, function, modulation via posttranslational modifications, and disease involvement of these five major proteins that comprise the thick filament of striated muscle cells. © 2018 American Physiological Society. Compr Physiol 8:631-709, 2018.
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Affiliation(s)
- Li Wang
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland, USA
| | - Janelle Geist
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland, USA
| | - Alyssa Grogan
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland, USA
| | - Li-Yen R. Hu
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland, USA
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16
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Percario V, Boncompagni S, Protasi F, Pertici I, Pinzauti F, Caremani M. Mechanical parameters of the molecular motor myosin II determined in permeabilised fibres from slow and fast skeletal muscles of the rabbit. J Physiol 2018; 596:1243-1257. [PMID: 29148051 DOI: 10.1113/jp275404] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 11/10/2017] [Indexed: 12/31/2022] Open
Abstract
KEY POINTS The different performance of slow and fast muscles is mainly attributed to diversity of the myosin heavy chain (MHC) isoform expressed within them. In this study fast sarcomere-level mechanics has been applied to Ca2+ -activated single permeabilised fibres isolated from soleus (containing the slow myosin isoform) and psoas (containing the fast myosin isoform) muscles of rabbit for a comparative definition of the mechano-kinetics of force generation by slow and fast myosin isoforms in situ. The stiffness and the force of the slow myosin isoform are three times smaller than those of the fast isoform, suggesting that the stiffness of the myosin motor is a determinant of the isoform-dependent functional diversity between skeletal muscles. These results open the question of the mechanism that can reconcile the reduced performance of the slow MHC with the higher efficiency of the slow muscle. ABSTRACT The skeletal muscle exhibits large functional differences depending on the myosin heavy chain (MHC) isoform expressed in its molecular motor, myosin II. The differences in the mechanical features of force generation by myosin isoforms were investigated in situ by using fast sarcomere-level mechanical methods in permeabilised fibres (sarcomere length 2.4 μm, temperature 12°C, 4% dextran T-500) from slow (soleus, containing the MHC-1 isoform) and fast (psoas, containing the MHC-2X isoform) skeletal muscle of the rabbit. The stiffness of the half-sarcomere was determined at the plateau of Ca2+ -activated isometric contractions and in rigor and analysed with a model that accounted for the filament compliance to estimate the stiffness of the myosin motor (ε). ε was 0.56 ± 0.04 and 1.70 ± 0.37 pN nm-1 for the slow and fast isoform, respectively, while the average strain per attached motor (s0 ) was similar (∼3.3 nm) in both isoforms. Consequently the force per motor (F0 = εs0 ) was three times smaller in the slow isoform than in the fast isoform (1.89 ± 0.43 versus 5.35 ± 1.51 pN). The fraction of actin-attached motors responsible for maximum isometric force at saturating Ca2+ (T0,4.5 ) was 0.47 ± 0.09 in soleus fibres, 70% larger than that in psoas fibres (0.29 ± 0.08), so that F0 in slow fibres was decreased by only 53%. The lower stiffness and force of the slow myosin isoform open the question of the molecular basis of the higher efficiency of slow muscle with respect to fast muscle.
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Affiliation(s)
- Valentina Percario
- PhysioLab, Department of Biology, University of Florence, Florence, Italy
| | - Simona Boncompagni
- CeSI-Met - Centre for Research on Ageing and Translational Medicine, University G. d'Annunzio, I-66100, Chieti, Italy.,DNICS - Department of Neuroscience, Imaging and Clinical Sciences, University G. d'Annunzio, I-66100, Chieti, Italy
| | - Feliciano Protasi
- CeSI-Met - Centre for Research on Ageing and Translational Medicine, University G. d'Annunzio, I-66100, Chieti, Italy.,DMSI - Department of Medicine and Aging Science, University G. d'Annunzio, I-66100, Chieti, Italy
| | - Irene Pertici
- PhysioLab, Department of Biology, University of Florence, Florence, Italy
| | - Francesca Pinzauti
- PhysioLab, Department of Biology, University of Florence, Florence, Italy
| | - Marco Caremani
- PhysioLab, Department of Biology, University of Florence, Florence, Italy
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17
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Kinetic coupling of phosphate release, force generation and rate-limiting steps in the cross-bridge cycle. J Muscle Res Cell Motil 2017; 38:275-289. [PMID: 28918606 DOI: 10.1007/s10974-017-9482-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 09/12/2017] [Indexed: 10/18/2022]
Abstract
A basic goal in muscle research is to understand how the cyclic ATPase activity of cross-bridges is converted into mechanical force. A direct approach to study the chemo-mechanical coupling between Pi release and the force-generating step is provided by the kinetics of force response induced by a rapid change in [Pi]. Classical studies on fibres using caged-Pi discovered that rapid increases in [Pi] induce fast force decays dependent on final [Pi] whose kinetics were interpreted to probe a fast force-generating step prior to Pi release. However, this hypothesis was called into question by studies on skeletal and cardiac myofibrils subjected to Pi jumps in both directions (increases and decreases in [Pi]) which revealed that rapid decreases in [Pi] trigger force rises with slow kinetics, similar to those of calcium-induced force development and mechanically-induced force redevelopment at the same [Pi]. A possible explanation for this discrepancy came from imaging of individual sarcomeres in cardiac myofibrils, showing that the fast force decay upon increase in [Pi] results from so-called sarcomere 'give'. The slow force rise upon decrease in [Pi] was found to better reflect overall sarcomeres cross-bridge kinetics and its [Pi] dependence, suggesting that the force generation coupled to Pi release cannot be separated from the rate-limiting transition. The reasons for the different conclusions achieved in fibre and myofibril studies are re-examined as the recent findings on cardiac myofibrils have fundamental consequences for the coupling between Pi release, rate-limiting steps and force generation. The implications from Pi-induced force kinetics of myofibrils are discussed in combination with historical and recent models of the cross-bridge cycle.
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18
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Nocella M, Cecchi G, Colombini B. Phosphate increase during fatigue affects crossbridge kinetics in intact mouse muscle at physiological temperature. J Physiol 2017; 595:4317-4328. [PMID: 28332714 DOI: 10.1113/jp273672] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 03/03/2017] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS Actomyosin ATP hydrolysis occurring during muscle contraction releases inorganic phosphate [Pi ] in the myoplasm. High [Pi ] reduces force and affects force kinetics in skinned muscle fibres at low temperature. These effects decrease at high temperature, raising the question of their importance under physiological conditions. This study provides the first analysis of the effects of Pi on muscle performance in intact mammalian fibres at physiological temperature. Myoplasmic [Pi ] was raised by fatiguing the fibres with a series of tetanic contractions. [Pi ] increase reduces muscular force mainly by decreasing the force of the single molecular motor, the crossbridge, and alters the crossbridge response to fast length perturbation indicating faster kinetics. These results are in agreement with schemes of actomyosin ATPase and the crossbridge cycle including a low- or no-force state and show that fibre length changes perturb the Pi -sensitive force generation of the crossbridge cycle. ABSTRACT Actomyosin ATP hydrolysis during muscle contraction releases inorganic phosphate, increasing [Pi ] in the myoplasm. Experiments in skinned fibres at low temperature (10-12°C) have shown that [Pi ] increase depresses isometric force and alters the kinetics of actomyosin interaction. However, the effects of Pi decrease with temperature and this raises the question of the role of Pi under physiological conditions. The present experiments were performed to investigate this point. Intact fibre bundles isolated from the flexor digitorum brevis of C57BL/6 mice were stimulated with a series of tetanic contractions at 1.5 s intervals at 33°C. As show previously the most significant change induced by a bout of contractile activity similar to the initial 10 tetani of the series was an increase of [Pi ] without significant Ca2+ or pH changes. Measurements of force, stiffness and responses to fast stretches and releases were therefore made on the 10th tetanus of the series and compared with control. We found that (i) tetanic force at the 10th tetanus was ∼20% smaller than control without a significant decrease of crossbridge stiffness; and (ii) the force recovery following quick stretches and releases was faster than in control. These results indicate that at physiological temperature the increase of [Pi ] occurring during early fatigue reduces tetanic force mainly by depressing the individual crossbridge force and accelerating crossbridge kinetics.
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Affiliation(s)
- M Nocella
- Department of Experimental and Clinical Medicine, University of Florence, Viale G. B. Morgagni, 63, 50134, Florence, Italy
| | - G Cecchi
- Department of Experimental and Clinical Medicine, University of Florence, Viale G. B. Morgagni, 63, 50134, Florence, Italy
| | - B Colombini
- Department of Experimental and Clinical Medicine, University of Florence, Viale G. B. Morgagni, 63, 50134, Florence, Italy
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19
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Bershitsky SY, Koubassova NA, Ferenczi MA, Kopylova GV, Narayanan T, Tsaturyan AK. The Closed State of the Thin Filament Is Not Occupied in Fully Activated Skeletal Muscle. Biophys J 2017; 112:1455-1461. [PMID: 28402887 DOI: 10.1016/j.bpj.2017.02.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 01/25/2017] [Accepted: 02/16/2017] [Indexed: 11/29/2022] Open
Abstract
Muscle contraction is powered by actin-myosin interaction controlled by Ca2+ via the regulatory proteins troponin (Tn) and tropomyosin (Tpm), which are associated with actin filaments. Tpm forms coiled-coil dimers, which assemble into a helical strand that runs along the whole ∼1 μm length of a thin filament. In the absence of Ca2+, Tn that is tightly bound to Tpm binds actin and holds the Tpm strand in the blocked, or B, state, where Tpm shields actin from the binding of myosin heads. Ca2+ binding to Tn releases the Tpm from actin so that it moves azimuthally around the filament axis to a closed, or C, state, where actin is partially available for weak binding of myosin heads. Upon transition of the weak actin-myosin bond into a strong, stereo-specific complex, the myosin heads push Tpm strand to the open, or O, state allowing myosin binding sites on several neighboring actin monomers to become open for myosin binding. We used low-angle x-ray diffraction at the European Synchrotron Radiation Facility to check whether the O- to C-state transition in fully activated fibers of fast skeletal muscle of the rabbit occurs during transition from isometric contraction to shortening under low load. No decrease in the intensity of the second actin layer line at reciprocal radii in the range of 0.15-0.275 nm-1 was observed during shortening suggesting that an azimuthal Tpm movement from the O- to C-state does not occur, although during shortening muscle stiffness is reduced compared to the isometric state, and the intensities of other actin layer lines demonstrate a ∼2-fold decrease in the fraction of myosin heads strongly bound to actin. The data show that a small fraction of actin-bound myosin heads is sufficient for supporting the O-state and, therefore the C-state is not occupied in fully activated skeletal muscle that produces mechanical work at low load.
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Affiliation(s)
- Sergey Y Bershitsky
- Institute of Immunology and Physiology, Russian Academy of Sciences, Laboratory of Biological Motility, Yekaterinburg, Russia.
| | | | - Michael A Ferenczi
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Galina V Kopylova
- Institute of Immunology and Physiology, Russian Academy of Sciences, Laboratory of Biological Motility, Yekaterinburg, Russia
| | | | - Andrey K Tsaturyan
- Institute of Mechanics, M.V. Lomonosov Moscow University, Moscow, Russia
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20
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Comparison of elementary steps of the cross-bridge cycle in rat papillary muscle fibers expressing α- and β-myosin heavy chain with sinusoidal analysis. J Muscle Res Cell Motil 2016; 37:203-214. [PMID: 27942960 DOI: 10.1007/s10974-016-9456-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Accepted: 09/27/2016] [Indexed: 10/20/2022]
Abstract
In mammalian ventricles, two myosin heavy chain (MHC) isoforms have been identified. Small animals express α-MHC, whereas large animals express β-MHC, which contribute to a large difference in the heart rate. Sprague-Dawley rats possessing ~99% α-MHC were treated with propylthiouracil to result in 100% β-MHC. Papillary muscles were skinned, dissected into small fibers, and used for experiments. To understand the functional difference between α-MHC and β-MHC, skinned-fibers were activated under the intracellular ionic conditions: 5 mM MgATP, 1 mM Mg2+, 8 mM Pi, 200 mM ionic strength, pH 7.00 at 25 °C. Small amplitude sinusoidal length oscillations were applied in the frequency range 0.13-100 Hz (corresponding time domain: 1.6-1200 ms), and effects of Ca2+, Pi, and ATP were studied. The results show that Ca2+ sensitivity was slightly less (10-15%) in β-MHC than α-MHC containing fibers. Sinusoidal analysis at pCa 4.66 (full Ca2+ activation) demonstrated that, the apparent rate constants were 2-4× faster in α-MHC containing fibers. The ATP study demonstrated that, in β-MHC containing fibers, K 1 (ATP association constant) was greater (1.7×), k 2 and k -2 (cross-bridge detachment and its reversal rate constants) were smaller (×0.6). The Pi study demonstrated that, in β-MHC containing fibers, k 4 (rate constant of the force-generation step) and k -4 were smaller (0.75× and 0.25×, respectively), resulting in greater K 4 (3×). There were no differences in active tension, rigor stiffness, or K 2 (equilibrium constant of the cross-bridge detachment step). Our study further demonstrated that there were no differences in parameters between fibers obtained from left and right ventricles, but with an exception in K 5 (Pi association constant).
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21
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Smith IC, Bellissimo C, Herzog W, Tupling AR. Can inorganic phosphate explain sag during unfused tetanic contractions of skeletal muscle? Physiol Rep 2016; 4:4/22/e13043. [PMID: 27884960 PMCID: PMC5358005 DOI: 10.14814/phy2.13043] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 10/31/2016] [Indexed: 12/31/2022] Open
Abstract
We test the hypothesis that cytosolic inorganic phosphate (Pi) can account for the contraction‐induced reductions in twitch duration which impair summation and cause force to decline (sag) during unfused tetanic contractions of fast‐twitch muscle. A five‐state model of crossbridge cycling was used to simulate twitch and unfused tetanic contractions. As Pi concentration ([Pi]) was increased from 0 to 30 mmol·L−1, twitch duration decreased, with progressive reductions in sensitivity to Pi as [Pi] was increased. When unfused tetani were simulated with rising [Pi], sag was most pronounced when initial [Pi] was low, and when the magnitude of [Pi] increase was large. Fast‐twitch extensor digitorum longus (EDL) muscles (sag‐prone, typically low basal [Pi]) and slow‐twitch soleus muscles (sag‐resistant, typically high basal [Pi]) were isolated from 14 female C57BL/6 mice. Muscles were sequentially incubated in solutions containing either glucose or pyruvate to create typical and low Pi environments, respectively. Twitch duration was greater (P < 0.05) in pyruvate than glucose in both muscles. Stimuli applied at intervals approximately three times the time to peak twitch tension resulted in sag of 35.0 ± 3.7% in glucose and 50.5 ± 1.4% in pyruvate in the EDL (pyruvate > glucose; P < 0.05), and 3.9 ± 0.3% in glucose and 37.8 ± 2.7% in pyruvate in the soleus (pyruvate > glucose; P < 0.05). The influence of Pi on crossbridge cycling provides a tenable mechanism for sag. Moreover, the low basal [Pi] in fast‐twitch relative to slow‐twitch muscle has promise as an explanation for the fiber‐type dependency of sag.
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Affiliation(s)
- Ian C Smith
- Human Performance Lab, University of Calgary, Calgary, Alberta, Canada
| | | | - Walter Herzog
- Human Performance Lab, University of Calgary, Calgary, Alberta, Canada
| | - A Russell Tupling
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada
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22
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Houdusse A, Sweeney HL. How Myosin Generates Force on Actin Filaments. Trends Biochem Sci 2016; 41:989-997. [PMID: 27717739 DOI: 10.1016/j.tibs.2016.09.006] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 09/14/2016] [Accepted: 09/14/2016] [Indexed: 12/18/2022]
Abstract
How myosin interacts with actin to generate force is a subject of considerable controversy. The major debate centers on understanding at what point in force generation the inorganic phosphate is released with respect to the lever arm swing, or powerstroke. Resolving the controversy is essential for understanding how force is produced as well as the mechanisms underlying disease-causing mutations in myosin. Recent structural insights into the powerstroke have come from a high-resolution structure of myosin in a previously unseen state and from an electron cryomicroscopy (cryo-EM) 3D reconstruction of the actin-myosin-MgADP complex. Here, we argue that seemingly contradictory data from time-resolved fluorescence resonance energy transfer (FRET) studies can be reconciled, and we put forward a model for myosin force generation on actin.
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Affiliation(s)
- Anne Houdusse
- Structural Motility, Institut Curie, PSL Research University, CNRS, UMR 144, F-75005, Paris, France; Sorbonne Universités, UPMC Univ Paris06, Sorbonne Universités, IFD, 4 Place Jussieu, 75252 Paris cedex 05, France.
| | - H Lee Sweeney
- Department of Pharmacology & Therapeutics and the Myology Institute, University of Florida College of Medicine, PO Box 100267, Gainesville, FL 32610-0267, USA.
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23
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Greenberg MJ, Arpağ G, Tüzel E, Ostap EM. A Perspective on the Role of Myosins as Mechanosensors. Biophys J 2016; 110:2568-2576. [PMID: 27332116 PMCID: PMC4919425 DOI: 10.1016/j.bpj.2016.05.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 04/13/2016] [Accepted: 05/16/2016] [Indexed: 11/26/2022] Open
Abstract
Cells are dynamic systems that generate and respond to forces over a range of spatial and temporal scales, spanning from single molecules to tissues. Substantial progress has been made in recent years in identifying the molecules and pathways responsible for sensing and transducing mechanical signals to short-term cellular responses and longer-term changes in gene expression, cell identity, and tissue development. In this perspective article, we focus on myosin motors, as they not only function as the primary force generators in well-studied mechanobiological processes, but also act as key mechanosensors in diverse functions including intracellular transport, signaling, cell migration, muscle contraction, and sensory perception. We discuss how the biochemical and mechanical properties of different myosin isoforms are tuned to fulfill these roles in an array of cellular processes, and we highlight the underappreciated diversity of mechanosensing properties within the myosin superfamily. In particular, we use modeling and simulations to make predictions regarding how diversity in force sensing affects the lifetime of the actomyosin bond, the myosin power output, and the ability of myosin to respond to a perturbation in force for several nonprocessive myosin isoforms.
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Affiliation(s)
- Michael J Greenberg
- Biochemistry and Molecular Biophysics, Washington University, St. Louis, Missouri
| | - Göker Arpağ
- Worcester Polytechnic Institute, Worcester, Massachusetts
| | - Erkan Tüzel
- Worcester Polytechnic Institute, Worcester, Massachusetts
| | - E Michael Ostap
- Pennsylvania Muscle Institute and Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
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24
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Germinario E, Bondì M, Cencetti F, Donati C, Nocella M, Colombini B, Betto R, Bruni P, Bagni MA, Danieli-Betto D. S1P3 receptor influences key physiological properties of fast-twitch extensor digitorum longus muscle. J Appl Physiol (1985) 2016; 120:1288-300. [DOI: 10.1152/japplphysiol.00345.2015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 12/23/2015] [Indexed: 12/15/2022] Open
Abstract
To examine the role of sphingosine 1-phosphate (S1P) receptor 3 (S1P3) in modulating muscle properties, we utilized transgenic mice depleted of the receptor. Morphological analyses of extensor digitorum longus (EDL) muscle did not show evident differences between wild-type and S1P3-null mice. The body weight of 3-mo-old S1P3-null mice and the mean cross-sectional area of transgenic EDL muscle fibers were similar to those of wild-type. S1P3 deficiency enhanced the expression level of S1P1 and S1P2 receptors mRNA in S1P3-null EDL muscle. The contractile properties of S1P3-null EDL diverge from those of wild-type, largely more fatigable and less able to recover. The absence of S1P3 appears responsible for a lower availability of calcium during fatigue. S1P supplementation, expected to stimulate residual S1P receptors and signaling, reduced fatigue development of S1P3-null muscle. Moreover, in the absence of S1P3, denervated EDL atrophies less than wild-type. The analysis of atrophy-related proteins in S1P3-null EDL evidences high levels of the endogenous regulator of mitochondria biogenesis peroxisome proliferative-activated receptor-γ coactivator 1α (PGC-1α); preserving mitochondria could protect the muscle from disuse atrophy. In conclusion, the absence of S1P3 makes the muscle more sensitive to fatigue and slows down atrophy development after denervation, indicating that S1P3 is involved in the modulation of key physiological properties of the fast-twitch EDL muscle.
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Affiliation(s)
- Elena Germinario
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- IIM, Interuniversity Institute of Myology, Italy
| | - Michela Bondì
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Francesca Cencetti
- IIM, Interuniversity Institute of Myology, Italy
- Department of Biomedical, Experimental and Clinical Sciences, Mario Serio, University of Firenze, Florence, Italy
| | - Chiara Donati
- IIM, Interuniversity Institute of Myology, Italy
- Department of Biomedical, Experimental and Clinical Sciences, Mario Serio, University of Firenze, Florence, Italy
| | - Marta Nocella
- IIM, Interuniversity Institute of Myology, Italy
- Department of Experimental and Clinical Medicine, University of Firenze, Florence, Italy
| | - Barbara Colombini
- IIM, Interuniversity Institute of Myology, Italy
- Department of Experimental and Clinical Medicine, University of Firenze, Florence, Italy
| | - Romeo Betto
- IIM, Interuniversity Institute of Myology, Italy
- CNR-Institute for Neuroscience, CNR, Padova, Italy
| | - Paola Bruni
- IIM, Interuniversity Institute of Myology, Italy
- Department of Biomedical, Experimental and Clinical Sciences, Mario Serio, University of Firenze, Florence, Italy
| | - Maria Angela Bagni
- IIM, Interuniversity Institute of Myology, Italy
- Department of Experimental and Clinical Medicine, University of Firenze, Florence, Italy
| | - Daniela Danieli-Betto
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- IIM, Interuniversity Institute of Myology, Italy
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25
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Manders E, Bonta PI, Kloek JJ, Symersky P, Bogaard HJ, Hooijman PE, Jasper JR, Malik FI, Stienen GJM, Vonk-Noordegraaf A, de Man FS, Ottenheijm CAC. Reduced force of diaphragm muscle fibers in patients with chronic thromboembolic pulmonary hypertension. Am J Physiol Lung Cell Mol Physiol 2016; 311:L20-8. [PMID: 27190061 DOI: 10.1152/ajplung.00113.2016] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 05/17/2016] [Indexed: 11/22/2022] Open
Abstract
Patients with pulmonary hypertension (PH) suffer from inspiratory muscle weakness. However, the pathophysiology of inspiratory muscle dysfunction in PH is unknown. We hypothesized that weakness of the diaphragm, the main inspiratory muscle, is an important contributor to inspiratory muscle dysfunction in PH patients. Our objective was to combine ex vivo diaphragm muscle fiber contractility measurements with measures of in vivo inspiratory muscle function in chronic thromboembolic pulmonary hypertension (CTEPH) patients. To assess diaphragm muscle contractility, function was studied in vivo by maximum inspiratory pressure (MIP) and ex vivo in diaphragm biopsies of the same CTEPH patients (N = 13) obtained during pulmonary endarterectomy. Patients undergoing elective lung surgery served as controls (N = 15). Muscle fiber cross-sectional area (CSA) was determined in cryosections and contractility in permeabilized muscle fibers. Diaphragm muscle fiber CSA was not significantly different between control and CTEPH patients in both slow-twitch and fast-twitch fibers. Maximal force-generating capacity was significantly lower in slow-twitch muscle fibers of CTEPH patients, whereas no difference was observed in fast-twitch muscle fibers. The maximal force of diaphragm muscle fibers correlated significantly with MIP. The calcium sensitivity of force generation was significantly reduced in fast-twitch muscle fibers of CTEPH patients, resulting in a ∼40% reduction of submaximal force generation. The fast skeletal troponin activator CK-2066260 (5 μM) restored submaximal force generation to levels exceeding those observed in control subjects. In conclusion, diaphragm muscle fiber contractility is hampered in CTEPH patients and contributes to the reduced function of the inspiratory muscles in CTEPH patients.
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Affiliation(s)
- Emmy Manders
- Department of Pulmonology, VU University Medical Center/Institute for Cardiovascular Research, Amsterdam, The Netherlands; Department of Physiology, VU University Medical Center/Institute for Cardiovascular Research, The Netherlands
| | - Peter I Bonta
- Department of Respiratory Medicine, Amsterdam Medical Center, University of Amsterdam, The Netherlands
| | - Jaap J Kloek
- Department of Cardiothoracic Surgery, VU University Medical Center, Amsterdam, The Netherlands
| | - Petr Symersky
- Department of Cardiothoracic Surgery, VU University Medical Center, Amsterdam, The Netherlands
| | - Harm-Jan Bogaard
- Department of Pulmonology, VU University Medical Center/Institute for Cardiovascular Research, Amsterdam, The Netherlands
| | - Pleuni E Hooijman
- Department of Physiology, VU University Medical Center/Institute for Cardiovascular Research, The Netherlands
| | - Jeff R Jasper
- Research & Early Development, Cytokinetics Inc., South San Francisco, California
| | - Fady I Malik
- Research & Early Development, Cytokinetics Inc., South San Francisco, California
| | - Ger J M Stienen
- Department of Physiology, VU University Medical Center/Institute for Cardiovascular Research, The Netherlands; Faculty of Science, Department of Physics and Astronomy, VU University, Amsterdam, The Netherlands; and
| | - Anton Vonk-Noordegraaf
- Department of Pulmonology, VU University Medical Center/Institute for Cardiovascular Research, Amsterdam, The Netherlands
| | - Frances S de Man
- Department of Pulmonology, VU University Medical Center/Institute for Cardiovascular Research, Amsterdam, The Netherlands
| | - Coen A C Ottenheijm
- Department of Physiology, VU University Medical Center/Institute for Cardiovascular Research, The Netherlands; Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona
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26
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Temperature effect on the chemomechanical regulation of substeps within the power stroke of a single Myosin II. Sci Rep 2016; 6:19506. [PMID: 26786569 PMCID: PMC4726395 DOI: 10.1038/srep19506] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 12/14/2015] [Indexed: 11/08/2022] Open
Abstract
Myosin IIs in the skeletal muscle are highly efficient nanoscale machines evolved in nature. Understanding how they function can not only bring insights into various biological processes but also provide guidelines to engineer synthetic nanoscale motors working in the vicinity of thermal noise. Though it was clearly demonstrated that the behavior of a skeletal muscle fiber, or that of a single myosin was strongly affected by the temperature, how exactly the temperature affects the kinetics of a single myosin is not fully understood. By adapting the newly developed transitional state model, which successfully explained the intriguing motor force regulation during skeletal muscle contraction, here we systematically explain how exactly the power stroke of a single myosin proceeds, with the consideration of the chemomechanical regulation of sub-steps within the stroke. The adapted theory is then utilized to investigate the temperature effect on various aspects of the power stroke. Our analysis suggests that, though swing rates, the isometric force, and the maximal stroke size all strongly vary with the temperature, the temperature can have a very small effect on the releasable elastic energy within the power stroke.
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Donkervoort S, Papadaki M, de Winter JM, Neu MB, Kirschner J, Bolduc V, Yang ML, Gibbons MA, Hu Y, Dastgir J, Leach ME, Rutkowski A, Foley AR, Krüger M, Wartchow EP, McNamara E, Ong R, Nowak KJ, Laing NG, Clarke NF, Ottenheijm C, Marston SB, Bönnemann CG. TPM3 deletions cause a hypercontractile congenital muscle stiffness phenotype. Ann Neurol 2015; 78:982-994. [PMID: 26418456 DOI: 10.1002/ana.24535] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 09/02/2015] [Accepted: 09/05/2015] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Mutations in TPM3, encoding Tpm3.12, cause a clinically and histopathologically diverse group of myopathies characterized by muscle weakness. We report two patients with novel de novo Tpm3.12 single glutamic acid deletions at positions ΔE218 and ΔE224, resulting in a significant hypercontractile phenotype with congenital muscle stiffness, rather than weakness, and respiratory failure in one patient. METHODS The effect of the Tpm3.12 deletions on the contractile properties in dissected patient myofibers was measured. We used quantitative in vitro motility assay to measure Ca(2+) sensitivity of thin filaments reconstituted with recombinant Tpm3.12 ΔE218 and ΔE224. RESULTS Contractility studies on permeabilized myofibers demonstrated reduced maximal active tension from both patients with increased Ca(2+) sensitivity and altered cross-bridge cycling kinetics in ΔE224 fibers. In vitro motility studies showed a two-fold increase in Ca(2+) sensitivity of the fraction of filaments motile and the filament sliding velocity concentrations for both mutations. INTERPRETATION These data indicate that Tpm3.12 deletions ΔE218 and ΔE224 result in increased Ca(2+) sensitivity of the troponin-tropomyosin complex, resulting in abnormally active interaction of the actin and myosin complex. Both mutations are located in the charged motifs of the actin-binding residues of tropomyosin 3, thus disrupting the electrostatic interactions that facilitate accurate tropomyosin binding with actin necessary to prevent the on-state. The mutations destabilize the off-state and result in excessively sensitized excitation-contraction coupling of the contractile apparatus. This work expands the phenotypic spectrum of TPM3-related disease and provides insights into the pathophysiological mechanisms of the actin-tropomyosin complex.
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Affiliation(s)
- S Donkervoort
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - M Papadaki
- National Heart and Lung Institute, Imperial College London, London, UK
| | - J M de Winter
- Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands
| | - M B Neu
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - J Kirschner
- Department of Neuropediatrics and Muscle Disorders, University Medical Center Freiburg, Freiburg, Germany
| | - V Bolduc
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - M L Yang
- University of Colorado School of Medicine, Department of Pediatrics and Neurology, Section of Child Neurology, Aurora, CO, USA
| | - M A Gibbons
- University of Colorado Denver School of Medicine, Aurora, CO, USA
| | - Y Hu
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - J Dastgir
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - M E Leach
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA.,Children's National Health System, Washington DC, USA
| | - A Rutkowski
- Kaiser SCPMG, Cure CMD, P.O. Box 701, Olathe, KS 66051, USA
| | - A R Foley
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - M Krüger
- Department of General Pediatrics, Adolescent Medicine and Neonatology, University Medical Center Freiburg, Freiburg, Germany
| | - E P Wartchow
- Department of Pathology, Children's Hospital Colorado, Aurora, Colorado, USA
| | - E McNamara
- Neuromuscular Diseases Laboratory, Centre for Medical Research, Faculty of Medicine, Dentistry and Health Sciences, The University of Western Australia Crawley, WA, Australia
| | - R Ong
- Neuromuscular Diseases Laboratory, Centre for Medical Research, Faculty of Medicine, Dentistry and Health Sciences, The University of Western Australia Crawley, WA, Australia
| | - K J Nowak
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - N G Laing
- Centre for Medical Research, University of Western Australia, Harry Perkins Institute of Medical Research, QEII Medical Centre, Perth, Western Australia, Australia
| | - N F Clarke
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, University of Sydney, Sydney, Australia
| | - Cac Ottenheijm
- Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands
| | - S B Marston
- National Heart and Lung Institute, Imperial College London, London, UK
| | - C G Bönnemann
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
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Zimmermann D, Santos A, Kovar DR, Rock RS. Actin age orchestrates myosin-5 and myosin-6 run lengths. Curr Biol 2015; 25:2057-62. [PMID: 26190073 DOI: 10.1016/j.cub.2015.06.033] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 05/21/2015] [Accepted: 06/16/2015] [Indexed: 12/14/2022]
Abstract
Unlike a static and immobile skeleton, the actin cytoskeleton is a highly dynamic network of filamentous actin (F-actin) polymers that continuously turn over. In addition to generating mechanical forces and sensing mechanical deformation, dynamic F-actin networks serve as cellular tracks for myosin motor traffic. However, much of our mechanistic understanding of processive myosins comes from in vitro studies in which motility was studied on pre-assembled and artificially stabilized, static F-actin tracks. In this work, we examine the role of actin dynamics in single-molecule myosin motility using assembling F-actin and two highly processive motors, myosin-5 and myosin-6. These two myosins have distinct functions in the cell and travel in opposite directions along actin filaments [1-3]. Myosin-5 walks toward the barbed ends of F-actin, traveling to sites of actin polymerization at the cell periphery [4]. Myosin-6 walks toward the pointed end of F-actin [5], traveling toward the cell center along older segments of the actin filament. We find that myosin-5 takes 1.3- to 1.5-fold longer runs on ADP•Pi (young) F-actin, whereas myosin-6 takes 1.7- to 3.6-fold longer runs along ADP (old) F-actin. These results suggest that conformational differences between ADP•Pi and ADP F-actin tailor these myosins to walk farther toward their preferred actin filament end. Taken together, these experiments define a new mechanism by which myosin traffic may sort to different F-actin networks depending on filament age.
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Affiliation(s)
- Dennis Zimmermann
- Department of Molecular Genetics and Cell Biology, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA
| | - Alicja Santos
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; Department of Biochemistry and Molecular Biology, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA.
| | - Ronald S Rock
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA.
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Caremani M, Melli L, Dolfi M, Lombardi V, Linari M. Force and number of myosin motors during muscle shortening and the coupling with the release of the ATP hydrolysis products. J Physiol 2015; 593:3313-32. [PMID: 26041599 DOI: 10.1113/jp270265] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 05/31/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Muscle contraction is due to cyclical ATP-driven working strokes in the myosin motors while attached to the actin filament. Each working stroke is accompanied by the release of the hydrolysis products, orthophosphate and ADP. The rate of myosin-actin interactions increases with the increase in shortening velocity. We used fast half-sarcomere mechanics on skinned muscle fibres to determine the relation between shortening velocity and the number and strain of myosin motors and the effect of orthophosphate concentration. A model simulation of the myosin-actin reaction explains the results assuming that orthophosphate and then ADP are released with rates that increase as the motor progresses through the working stroke. The ADP release rate further increases by one order of magnitude with the rise of negative strain in the final motor conformation. These results provide the molecular explanation of the relation between the rate of energy liberation and shortening velocity during muscle contraction. The chemo-mechanical cycle of the myosin II--actin reaction in situ has been investigated in Ca(2+)-activated skinned fibres from rabbit psoas, by determining the number and strain (s) of myosin motors interacting during steady shortening at different velocities (V) and the effect of raising inorganic phosphate (Pi) concentration. It was found that in control conditions (no added Pi ), shortening at V ≤ 350 nm s(-1) per half-sarcomere, corresponding to force (T) greater than half the isometric force (T0 ), decreases the number of myosin motors in proportion to the reduction of T, so that s remains practically constant and similar to the T0 value independent of V. At higher V the number of motors decreases less than in proportion to T, so that s progressively decreases. Raising Pi concentration by 10 mM, which reduces T0 and the number of motors by 40-50%, does not influence the dependence on V of number and strain. A model simulation of the myosin-actin reaction in which the structural transitions responsible for the myosin working stroke and the release of the hydrolysis products are orthogonal explains the results assuming that Pi and then ADP are released with rates that increase as the motor progresses through the working stroke. The rate of ADP release from the conformation at the end of the working stroke is also strain-sensitive, further increasing by one order of magnitude within a few nanometres of negative strain. These results provide the molecular explanation of the relation between the rate of energy liberation and the load during muscle contraction.
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Affiliation(s)
- Marco Caremani
- Laboratory of Physiology, Department of Biology, University of Florence, Sesto Fiorentino, 50019, Italy
| | - Luca Melli
- Laboratory of Physiology, Department of Biology, University of Florence, Sesto Fiorentino, 50019, Italy
| | - Mario Dolfi
- Laboratory of Physiology, Department of Biology, University of Florence, Sesto Fiorentino, 50019, Italy
| | - Vincenzo Lombardi
- Laboratory of Physiology, Department of Biology, University of Florence, Sesto Fiorentino, 50019, Italy
| | - Marco Linari
- Laboratory of Physiology, Department of Biology, University of Florence, Sesto Fiorentino, 50019, Italy
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Dong C, Chen B. Catch-slip bonds can be dispensable for motor force regulation during skeletal muscle contraction. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:012723. [PMID: 26274218 DOI: 10.1103/physreve.92.012723] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Indexed: 06/04/2023]
Abstract
It is intriguing how multiple molecular motors can perform coordinated and synchronous functions, which is essential in various cellular processes. Recent studies on skeletal muscle might have shed light on this issue, where rather precise motor force regulation was partly attributed to the specific stochastic features of a single attached myosin motor. Though attached motors can randomly detach from actin filaments either through an adenosine triphosphate (ATP) hydrolysis cycle or through "catch-slip bond" breaking, their respective contribution in motor force regulation has not been clarified. Here, through simulating a mechanical model of sarcomere with a coupled Monte Carlo method and finite element method, we find that the stochastic features of an ATP hydrolysis cycle can be sufficient while those of catch-slip bonds can be dispensable for motor force regulation.
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Affiliation(s)
- Chenling Dong
- Department of Engineering Mechanics, Zhejiang University, Hangzhou, People's Republic of China
| | - Bin Chen
- Department of Engineering Mechanics, Zhejiang University, Hangzhou, People's Republic of China
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31
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How actin initiates the motor activity of Myosin. Dev Cell 2015; 33:401-12. [PMID: 25936506 DOI: 10.1016/j.devcel.2015.03.025] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Revised: 02/23/2015] [Accepted: 03/30/2015] [Indexed: 11/22/2022]
Abstract
Fundamental to cellular processes are directional movements driven by molecular motors. A common theme for these and other molecular machines driven by ATP is that controlled release of hydrolysis products is essential for using the chemical energy efficiently. Mechanochemical transduction by myosin motors on actin is coupled to unknown structural changes that result in the sequential release of inorganic phosphate (Pi) and MgADP. We present here a myosin structure possessing an actin-binding interface and a tunnel (back door) that creates an escape route for Pi with a minimal rotation of the myosin lever arm that drives movements. We propose that this state represents the beginning of the powerstroke on actin and that Pi translocation from the nucleotide pocket triggered by actin binding initiates myosin force generation. This elucidates how actin initiates force generation and movement and may represent a strategy common to many molecular machines.
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32
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Poorly understood aspects of striated muscle contraction. BIOMED RESEARCH INTERNATIONAL 2015; 2015:245154. [PMID: 25961006 PMCID: PMC4415482 DOI: 10.1155/2015/245154] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 10/28/2014] [Indexed: 11/23/2022]
Abstract
Muscle contraction results from cyclic interactions between the contractile proteins myosin and actin, driven by the turnover of adenosine triphosphate (ATP). Despite intense studies, several molecular events in the contraction process are poorly understood, including the relationship between force-generation and phosphate-release in the ATP-turnover. Different aspects of the force-generating transition are reflected in the changes in tension development by muscle cells, myofibrils and single molecules upon changes in temperature, altered phosphate concentration, or length perturbations. It has been notoriously difficult to explain all these events within a given theoretical framework and to unequivocally correlate observed events with the atomic structures of the myosin motor. Other incompletely understood issues include the role of the two heads of myosin II and structural changes in the actin filaments as well as the importance of the three-dimensional order. We here review these issues in relation to controversies regarding basic physiological properties of striated muscle. We also briefly consider actomyosin mutation effects in cardiac and skeletal muscle function and the possibility to treat these defects by drugs.
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Offer G, Ranatunga KW. The endothermic ATP hydrolysis and crossbridge attachment steps drive the increase of force with temperature in isometric and shortening muscle. J Physiol 2015; 593:1997-2016. [PMID: 25564737 DOI: 10.1113/jphysiol.2014.284992] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 01/03/2015] [Indexed: 11/08/2022] Open
Abstract
The isometric tetanic tension of skeletal muscle increases with temperature because attached crossbridge states bearing a relatively low force convert to those bearing a higher force. It was previously proposed that the tension-generating step(s) in the crossbridge cycle was highly endothermic and was therefore itself directly targeted by changes in temperature. However, this did not explain why a rapid rise in temperature (a temperature jump) caused a much slower rate of rise of tension than a rapid length step. This led to suggestions that the step targeted by a temperature rise is not the tension-generating step but is an extra step in the attached pathway of the crossbridge cycle, perhaps located on a parallel pathway. This enigma has been a major obstacle to a full understanding of the operation of the crossbridge cycle. We have now used a previously developed mechano-kinetic model of the crossbridge cycle in frog muscle to simulate the temperature dependence of isometric tension and shortening velocity. We allowed all five steps in the cycle to be temperature-sensitive. Models with different starting combinations of enthalpy changes and activation enthalpies for the five steps were refined by downhill simplex runs and scored by their ability to fit experimental data on the temperature dependence of isometric tension and the relationship between force and shortening velocity in frog muscle. We conclude that the first tension-generating step may be weakly endothermic and that the rise of tension with temperature is largely driven by the preceding two strongly endothermic steps of ATP hydrolysis and attachment of M.ADP.Pi to actin. The refined model gave a reasonable fit to the available experimental data and after a temperature jump the overall rate of tension rise was much slower than after a length step as observed experimentally. The findings aid our understanding of the crossbridge cycle by showing that it may not be necessary to include an additional temperature-sensitive step.
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Affiliation(s)
- Gerald Offer
- Muscle Contraction Group, School of Physiology and Pharmacology, Medical Sciences Building, University of Bristol, UK
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34
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A new mechanokinetic model for muscle contraction, where force and movement are triggered by phosphate release. J Muscle Res Cell Motil 2014; 35:295-306. [PMID: 25319769 DOI: 10.1007/s10974-014-9391-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 09/26/2014] [Indexed: 10/24/2022]
Abstract
The atomic structure of myosin-S1 suggests that its working stroke, which generates tension and shortening in muscle, is triggered by the release of inorganic phosphate from the active site. This mechanism is the basis of a new mechanokinetic model for contractility, using the biochemical actomyosin ATPase cycle, strain-dependent kinetics and dimeric myosins on buckling rods. In this model, phosphate-dependent aspects of contractility arise from a rapid reversible release of phosphate from the initial bound state (A.M.ADP.Pi), which triggers the stroke. Added phosphate drives bound myosin towards this initial state, and the transient tension response to a phosphate jump reflects the rate at which it detaches from actin. Predictions for the tensile and energetic properties of striated muscle as a function of phosphate level, including the tension responses to length steps and Pi-jumps, are compared with experimental data from rabbit psoas fibres at 10 °C. The phosphate sensitivity of isometric tension is maximal when the actin affinity of M.ADP.Pi is near unity. Hence variations in actin affinity modulate the phosphate dependence of isometric tension, and may explain why phosphate sensitivity is temperature-dependent or absent in different muscles.
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35
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Guellich A, Negroni E, Decostre V, Demoule A, Coirault C. Altered cross-bridge properties in skeletal muscle dystrophies. Front Physiol 2014; 5:393. [PMID: 25352808 PMCID: PMC4196474 DOI: 10.3389/fphys.2014.00393] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 09/23/2014] [Indexed: 12/20/2022] Open
Abstract
Force and motion generated by skeletal muscle ultimately depends on the cyclical interaction of actin with myosin. This mechanical process is regulated by intracellular Ca2+ through the thin filament-associated regulatory proteins i.e.; troponins and tropomyosin. Muscular dystrophies are a group of heterogeneous genetic affections characterized by progressive degeneration and weakness of the skeletal muscle as a consequence of loss of muscle tissue which directly reduces the number of potential myosin cross-bridges involved in force production. Mutations in genes responsible for skeletal muscle dystrophies (MDs) have been shown to modify the function of contractile proteins and cross-bridge interactions. Altered gene expression or RNA splicing or post-translational modifications of contractile proteins such as those related to oxidative stress, may affect cross-bridge function by modifying key proteins of the excitation-contraction coupling. Micro-architectural change in myofilament is another mechanism of altered cross-bridge performance. In this review, we provide an overview about changes in cross-bridge performance in skeletal MDs and discuss their ultimate impacts on striated muscle function.
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Affiliation(s)
- Aziz Guellich
- Service de Cardiologie, Hôpital Henri Mondor, University Paris-Est Créteil Créteil, France ; Equipe 8, Institut National de la Santé et de la Recherche Médicale Créteil, France
| | - Elisa Negroni
- UMRS 974, Institut National de la Santé et de la Recherche Médicale Paris, France ; UM 76, Université Pierre et Marie Curie, Sorbonne Universités Paris, France ; UMR 7215, Centre National de la Recherche Scientifique Paris, France ; Institut de Myologie Paris, France
| | | | - Alexandre Demoule
- UMRS 974, Institut National de la Santé et de la Recherche Médicale Paris, France ; UM 76, Université Pierre et Marie Curie, Sorbonne Universités Paris, France ; UMR 7215, Centre National de la Recherche Scientifique Paris, France ; Institut de Myologie Paris, France ; Assistance Publique-Hopitaux de Paris, Service de Pneumologie et Reanimation Medicale Paris, France
| | - Catherine Coirault
- UMRS 974, Institut National de la Santé et de la Recherche Médicale Paris, France ; UM 76, Université Pierre et Marie Curie, Sorbonne Universités Paris, France ; UMR 7215, Centre National de la Recherche Scientifique Paris, France ; Institut de Myologie Paris, France
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Nelson CR, Debold EP, Fitts RH. Phosphate and acidosis act synergistically to depress peak power in rat muscle fibers. Am J Physiol Cell Physiol 2014; 307:C939-50. [PMID: 25186012 DOI: 10.1152/ajpcell.00206.2014] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Skeletal muscle fatigue is characterized by the buildup of H(+) and inorganic phosphate (Pi), metabolites that are thought to cause fatigue by inhibiting muscle force, velocity, and power. While the individual effects of elevated H(+) or Pi have been well characterized, the effects of simultaneously elevating the ions, as occurs during fatigue in vivo, are still poorly understood. To address this, we exposed slow and fast rat skinned muscle fibers to fatiguing levels of H(+) (pH 6.2) and Pi (30 mM) and determined the effects on contractile properties. At 30°C, elevated Pi and low pH depressed maximal shortening velocity (Vmax) by 15% (4.23 to 3.58 fl/s) in slow and 31% (6.24 vs. 4.55 fl/s) in fast fibers, values similar to depressions from low pH alone. Maximal isometric force dropped by 36% in slow (148 to 94 kN/m(2)) and 46% in fast fibers (148 to 80 kN/m(2)), declines substantially larger than what either ion exerted individually. The strong effect on force combined with the significant effect on velocity caused peak power to decline by over 60% in both fiber types. Force-stiffness ratios significantly decreased with pH 6.2 + 30 mM Pi in both fiber types, suggesting these ions reduced force by decreasing the force per bridge and/or increasing the number of low-force bridges. The data indicate the collective effects of elevating H(+) and Pi on maximal isometric force and peak power are stronger than what either ion exerts individually and suggest the ions act synergistically to reduce muscle function during fatigue.
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Affiliation(s)
- Cassandra R Nelson
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin; and
| | - Edward P Debold
- Department of Kinesiology, University of Massachusetts-Amherst, Amherst, Massachusetts
| | - Robert H Fitts
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin; and
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37
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Brunello E, Caremani M, Melli L, Linari M, Fernandez-Martinez M, Narayanan T, Irving M, Piazzesi G, Lombardi V, Reconditi M. The contributions of filaments and cross-bridges to sarcomere compliance in skeletal muscle. J Physiol 2014; 592:3881-99. [PMID: 25015916 DOI: 10.1113/jphysiol.2014.276196] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Force generation in the muscle sarcomere is driven by the head domain of the myosin molecule extending from the thick filament to form cross-bridges with the actin-containing thin filament. Following attachment, a structural working stroke in the head pulls the thin filament towards the centre of the sarcomere, producing, under unloaded conditions, a filament sliding of ∼ 11 nm. The mechanism of force generation by the myosin head depends on the relationship between cross-bridge force and movement, which is determined by compliances of the cross-bridge (C(cb)) and filaments. By measuring the force dependence of the spacing of the high-order myosin- and actin-based X-ray reflections from sartorius muscles of Rana esculenta we find a combined filament compliance (Cf) of 13.1 ± 1.2 nm MPa(-1), close to recent estimates from single fibre mechanics (12.8 ± 0.5 nm MPa(-1)). C(cb) calculated using these estimates is 0.37 ± 0.12 nm pN(-1), a value fully accounted for by the compliance of the myosin head domain, 0.38 ± 0.06 nm pN(-1), obtained from the intensity changes of the 14.5 nm myosin-based X-ray reflection in response to 3 kHz oscillations imposed on single muscle fibres in rigor. Thus, a significant contribution to C(cb) from the myosin tail that joins the head to the thick filament is excluded. The low C(cb) value indicates that the myosin head generates isometric force by a small sub-step of the 11 nm stroke that drives filament sliding at low load. The implications of these results for the mechanism of force generation by myosins have general relevance for cardiac and non-muscle myosins as well as for skeletal muscle.
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Affiliation(s)
- Elisabetta Brunello
- Laboratorio di Fisiologia, Dipartimento di Biologia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Italy
| | - Marco Caremani
- Laboratorio di Fisiologia, Dipartimento di Biologia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Italy
| | - Luca Melli
- Laboratorio di Fisiologia, Dipartimento di Biologia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Italy
| | - Marco Linari
- Laboratorio di Fisiologia, Dipartimento di Biologia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Italy
| | | | | | - Malcolm Irving
- Randall Division, King's College London, London, SE1 1UL, UK
| | - Gabriella Piazzesi
- Laboratorio di Fisiologia, Dipartimento di Biologia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Italy
| | - Vincenzo Lombardi
- Laboratorio di Fisiologia, Dipartimento di Biologia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Italy
| | - Massimo Reconditi
- Laboratorio di Fisiologia, Dipartimento di Biologia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Italy Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, UdR Firenze, Italy
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38
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Debold EP, Walcott S, Woodward M, Turner MA. Direct observation of phosphate inhibiting the force-generating capacity of a miniensemble of Myosin molecules. Biophys J 2014; 105:2374-84. [PMID: 24268149 DOI: 10.1016/j.bpj.2013.09.046] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 09/03/2013] [Accepted: 09/26/2013] [Indexed: 10/26/2022] Open
Abstract
Elevated levels of phosphate (Pi) reduce isometric force, providing support for the notion that the release of Pi from myosin is closely associated with the generation of muscular force. Pi is thought to rebind to actomyosin in an ADP-bound state and reverse the force-generating steps, including the rotation of the lever arm (i.e., the powerstroke). Despite extensive study, this mechanism remains controversial, in part because it fails to explain the effects of Pi on isometric ATPase and unloaded shortening velocity. To gain new insight into this process, we determined the effect of Pi on the force-generating capacity of a small ensemble of myosin (∼12 myosin heads) using a three-bead laser trap assay. In the absence of Pi, myosin pulled the actin filament out of the laser trap an average distance of 54 ± 4 nm, translating into an average peak force of 1.2 pN. By contrast, in the presence of 30 mM Pi, myosin generated only enough force to displace the actin filament by 13 ± 1 nm, generating just 0.2 pN of force. The elevated Pi also caused a >65% reduction in binding-event lifetime, suggesting that Pi induces premature detachment from a strongly bound state. Definitive evidence of a Pi-induced powerstroke reversal was not observed, therefore we determined if a branched kinetic model in which Pi induces detachment from a strongly bound, postpowerstroke state could explain these observations. The model was able to accurately reproduce not only the data presented here, but also the effects of Pi on both isometric ATPase in muscle fibers and actin filament velocity in a motility assay. The ability of the model to capture the findings presented here as well as previous findings suggests that Pi-induced inhibition of force may proceed along a kinetic pathway different from that of force generation.
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Affiliation(s)
- Edward P Debold
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts.
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39
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The myofilament elasticity and its effect on kinetics of force generation by the myosin motor. Arch Biochem Biophys 2014; 552-553:108-16. [DOI: 10.1016/j.abb.2014.02.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 02/05/2014] [Accepted: 02/28/2014] [Indexed: 10/25/2022]
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Malfatti E, Lehtokari VL, Böhm J, De Winter JM, Schäffer U, Estournet B, Quijano-Roy S, Monges S, Lubieniecki F, Bellance R, Viou MT, Madelaine A, Wu B, Taratuto AL, Eymard B, Pelin K, Fardeau M, Ottenheijm CAC, Wallgren-Pettersson C, Laporte J, Romero NB. Muscle histopathology in nebulin-related nemaline myopathy: ultrastrastructural findings correlated to disease severity and genotype. Acta Neuropathol Commun 2014; 2:44. [PMID: 24725366 PMCID: PMC4234932 DOI: 10.1186/2051-5960-2-44] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 03/20/2014] [Indexed: 01/09/2023] Open
Abstract
Nemaline myopathy (NM) is a rare congenital myopathy characterised by hypotonia, muscle weakness, and often skeletal muscle deformities with the presence of nemaline bodies (rods) in the muscle biopsy. The nebulin (NEB) gene is the most commonly mutated and is thought to account for approximately 50% of genetically diagnosed cases of NM. We undertook a detailed muscle morphological analysis of 14 NEB-mutated NM patients with different clinical forms to define muscle pathological patterns and correlate them with clinical course and genotype. Three groups were identified according to clinical severity. Group 1 (n = 5) comprises severe/lethal NM and biopsy in the first days of life. Group 2 (n = 4) includes intermediate NM and biopsy in infancy. Group 3 (n = 5) comprises typical/mild NM and biopsy in childhood or early adult life. Biopsies underwent histoenzymological, immunohistochemical and ultrastructural analysis. Fibre type distribution patterns, rod characteristics, distribution and localization were investigated. Contractile performance was studied in muscle fibre preparations isolated from seven muscle biopsies from each of the three groups. G1 showed significant myofibrillar dissociation and smallness with scattered globular rods in one third of fibres; there was no type 1 predominance. G2 presented milder sarcomeric dissociation, dispersed or clustered nemaline bodies, and type 1 predominance/uniformity. In contrast, G3 had well-delimited clusters of subsarcolemmal elongated rods and type 1 uniformity without sarcomeric alterations. In accordance with the clinical and morphological data, functional studies revealed markedly low forces in muscle bundles from G1 and a better contractile performance in muscle bundles from biopsies of patients from G2, and G3. In conclusion NEB-mutated NM patients present a wide spectrum of morphological features. It is difficult to establish firm genotype phenotype correlation. Interestingly, there was a correlation between clinical severity on the one hand and the degree of sarcomeric dissociation and contractility efficiency on the other. By contrast the percentage of fibres occupied by rods, as well as the quantity and the sub sarcolemmal position of rods, appears to inversely correlate with severity. Based on our observations, we propose myofibrillar dissociation and changes in contractility as an important cause of muscle weakness in NEB-mutated NM patients.
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Brandt PW, Poggesi C. Clusters of bound Ca(2+) initiate contraction in fast skeletal muscle. Arch Biochem Biophys 2013; 552-553:60-7. [PMID: 24374032 DOI: 10.1016/j.abb.2013.12.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Revised: 12/04/2013] [Accepted: 12/17/2013] [Indexed: 11/30/2022]
Abstract
Ca(2+)-binding to troponin C ultimately controls force in muscle leading to the expectation that the two curves, pCa/force and pCa/Ca(2+) binding, will coincide. Using an improved fluorescence apparatus to measure Ca(2+)-binding, we confirm a displacement between the position and shape of the pCa/Ca(2+)-binding and pCa/force curves. This displacement may be part of a mechanism that reduces the noise inherent in the control process. There must always be some Ca(2+)-binding events even at 10 or 100nM, well below threshold for muscle contraction. To minimize the response to such random binding events we suggest that clusters of adjacent Ca(2+)-binding sites must be filled before contraction is initiated. Clusters promote the reconfiguration of the thin filament to the "On" state; this simultaneously increases thin filaments' affinity for myosin heads and of troponin C for Ca(2+) producing the highly cooperative pCa/force curve. The cluster requirement displaces the Ca(2+)-binding from the force curve as observed. The thin filament conformational changes and the accompanying affinity increases introduce a discontinuity in the pCa/Ca(2+)-binding curve. The curve, therefore, is most appropriately fit by two separate Hill equations, a simple non-cooperative one (midpoint, pK1, n1∼1) for the foot and a second cooperative one (pK2, n2∼2.5) for the upper part. With this fit pK2 is larger than pK1 as our argument requires, in contrast to fitting to the sum of two Hill equations. It also expresses the idea that there may be three states of the thin filament.
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Affiliation(s)
- Philip W Brandt
- Department of Pathology, Columbia University, NY, NY 10032, USA
| | - Corrado Poggesi
- Dipartimento di Medicina Sperimentale e Clinica, Università degli Studi di Firenze, Firenze 50134, Italy.
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Abstract
Skeletal muscle fatigue is defined as the fall of force or power in response to contractile activity. Both the mechanisms of fatigue and the modes used to elicit it vary tremendously. Conceptual and technological advances allow the examination of fatigue from the level of the single molecule to the intact organism. Evaluation of muscle fatigue in a wide range of disease states builds on our understanding of basic function by revealing the sources of dysfunction in response to disease.
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Affiliation(s)
- Jane A Kent-Braun
- Department of Kinesiology, University of Massachusetts-Amherst, Amherst, Massachusetts, USA.
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Persson M, Bengtsson E, ten Siethoff L, Månsson A. Nonlinear cross-bridge elasticity and post-power-stroke events in fast skeletal muscle actomyosin. Biophys J 2013; 105:1871-81. [PMID: 24138863 PMCID: PMC3797597 DOI: 10.1016/j.bpj.2013.08.044] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 08/21/2013] [Accepted: 08/28/2013] [Indexed: 11/21/2022] Open
Abstract
Generation of force and movement by actomyosin cross-bridges is the molecular basis of muscle contraction, but generally accepted ideas about cross-bridge properties have recently been questioned. Of the utmost significance, evidence for nonlinear cross-bridge elasticity has been presented. We here investigate how this and other newly discovered or postulated phenomena would modify cross-bridge operation, with focus on post-power-stroke events. First, as an experimental basis, we present evidence for a hyperbolic [MgATP]-velocity relationship of heavy-meromyosin-propelled actin filaments in the in vitro motility assay using fast rabbit skeletal muscle myosin (28-29°C). As the hyperbolic [MgATP]-velocity relationship was not consistent with interhead cooperativity, we developed a cross-bridge model with independent myosin heads and strain-dependent interstate transition rates. The model, implemented with inclusion of MgATP-independent detachment from the rigor state, as suggested by previous single-molecule mechanics experiments, accounts well for the [MgATP]-velocity relationship if nonlinear cross-bridge elasticity is assumed, but not if linear cross-bridge elasticity is assumed. In addition, a better fit is obtained with load-independent than with load-dependent MgATP-induced detachment rate. We discuss our results in relation to previous data showing a nonhyperbolic [MgATP]-velocity relationship when actin filaments are propelled by myosin subfragment 1 or full-length myosin. We also consider the implications of our results for characterization of the cross-bridge elasticity in the filament lattice of muscle.
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Affiliation(s)
| | | | | | - Alf Månsson
- Department of Chemistry and Biomedical Sciences, Linnaeus University, Kalmar, Sweden
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Caremani M, Melli L, Dolfi M, Lombardi V, Linari M. The working stroke of the myosin II motor in muscle is not tightly coupled to release of orthophosphate from its active site. J Physiol 2013; 591:5187-205. [PMID: 23878374 PMCID: PMC3810818 DOI: 10.1113/jphysiol.2013.257410] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 07/19/2013] [Indexed: 11/08/2022] Open
Abstract
Skeletal muscle shortens faster against a lower load. This force-velocity relationship is the fundamental determinant of muscle performance in vivo and is due to ATP-driven working strokes of myosin II motors, during their cyclic interactions with the actin filament in each half-sarcomere. Crystallographic studies suggest that the working stroke is associated with the release of phosphate (Pi) and consists of 70 deg tilting of a light-chain domain that connects the catalytic domain of the myosin motor to the myosin tail and filament. However, the coupling of the working stroke with Pi release is still an unsolved question. Using nanometre-microsecond mechanics on skinned muscle fibres, we impose stepwise drops in force on an otherwise isometric contraction and record the isotonic velocity transient, to measure the mechanical manifestation of the working stroke of myosin motors and the rate of its regeneration in relation to the half-sarcomere load and [Pi]. We show that the rate constant of the working stroke is unaffected by [Pi], while the subsequent transition to steady velocity shortening is accelerated. We propose a new chemo-mechanical model that reproduces the transient and steady state responses by assuming that: (i) the release of Pi from the catalytic site of a myosin motor can occur at any stage of the working stroke, and (ii) a myosin motor, in an intermediate state of the working stroke, can slip to the next actin monomer during filament sliding. This model explains the efficient action of muscle molecular motors working as an ensemble in the half-sarcomere.
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Affiliation(s)
- Marco Caremani
- V. Lombardi: Department of Biology, University of Florence, Via G. Sansone, 1; 50019, Sesto Fiorentino, Italy.
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45
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Van Noten P, Van Leemputte M. Force depression and relaxation kinetics after active shortening and deactivation in mouse soleus muscle. J Biomech 2013; 46:1021-6. [DOI: 10.1016/j.jbiomech.2012.07.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 07/05/2012] [Accepted: 07/05/2012] [Indexed: 11/24/2022]
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46
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Wijnker PJM, Foster DB, Tsao AL, Frazier AH, dos Remedios CG, Murphy AM, Stienen GJM, van der Velden J. Impact of site-specific phosphorylation of protein kinase A sites Ser23 and Ser24 of cardiac troponin I in human cardiomyocytes. Am J Physiol Heart Circ Physiol 2012; 304:H260-8. [PMID: 23144315 DOI: 10.1152/ajpheart.00498.2012] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
PKA-mediated phosphorylation of contractile proteins upon β-adrenergic stimulation plays an important role in the regulation of cardiac performance. Phosphorylation of the PKA sites (Ser(23)/Ser(24)) of cardiac troponin (cTn)I results in a decrease in myofilament Ca(2+) sensitivity and an increase in the rate of relaxation. However, the relation between the level of phosphorylation of the sites and the functional effects in the human myocardium is unknown. Therefore, site-directed mutagenesis was used to study the effects of phosphorylation at Ser(23) and Ser(24) of cTnI on myofilament function in human cardiac tissue. Serines were replaced by aspartic acid (D) or alanine (A) to mimic phosphorylation and dephosphorylation, respectively. cTnI-DD mimics both sites phosphorylated, cTnI-AD mimics Ser(23) unphosphorylated and Ser(24) phosphorylated, cTnI-DA mimics Ser(23) phosphorylated and Ser(24) unphosphorylated, and cTnI-AA mimics both sites unphosphorylated. Force development was measured at various Ca(2+) concentrations in permeabilized cardiomyocytes in which the endogenous troponin complex was exchanged with these recombinant human troponin complexes. In donor cardiomyocytes, myofilament Ca(2+) sensitivity (pCa(50)) was significantly lower in cTnI-DD (pCa(50): 5.39 ± 0.01) compared with cTnI-AA (pCa(50): 5.50 ± 0.01), cTnI-AD (pCa(50): 5.48 ± 0.01), and cTnI-DA (pCa(50): 5.51 ± 0.01) at ~70% cTn exchange. No effects were observed on the rate of tension redevelopment. In cardiomyocytes from idiopathic dilated cardiomyopathic tissue, a linear decline in pCa(50) with cTnI-DD content was observed, saturating at ~55% bisphosphorylation. Our data suggest that in the human myocardium, phosphorylation of both PKA sites on cTnI is required to reduce myofilament Ca(2+) sensitivity, which is maximal at ~55% bisphosphorylated cTnI. The implications for in vivo cardiac function in health and disease are detailed in the DISCUSSION in this article.
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Affiliation(s)
- Paul J M Wijnker
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands.
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Two independent switches regulate cytoplasmic dynein's processivity and directionality. Proc Natl Acad Sci U S A 2012; 109:5289-93. [PMID: 22411823 DOI: 10.1073/pnas.1116315109] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Cytoplasmic dynein is a microtubule-based molecular motor that participates in a multitude of cell activities, from cell division to organelle transport. Unlike kinesin and myosin, where different tasks are performed by highly specialized members of these superfamilies, a single form of the dynein heavy chain is utilized for different functions. This versatility demands an extensive regulation of motor function. Using an improved application of an optical trap, we were now able to demonstrate that cytoplasmic dynein can generate a discrete power stroke as well as a processive walk in either direction; i.e., towards the plus- or towards the minus-end of a microtubule. Thus, dynein's motor functions can be described by four basic modes of motion: processive and nonprocessive movement, and movement in the forward and reverse directions. Importantly, these four modes of movement can be controlled by two switches. One switch, based on phosphate, determines the directionality of movement. The second switch, depending on magnesium, converts cytoplasmic dynein from a nonprocessive to a processive motor. The two switches can be triggered separately or jointly by changing concentrations of phosphate and magnesium in the local environment. The control of four modes of movement by two switches has major implications for our understanding of the cellular functions and regulation of cytoplasmic dynein. Based on recent studies of dynein's structure we are able to draw new conclusions on cytoplasmic dynein's stepping mechanism.
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48
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Caremani M, Lehman S, Lombardi V, Linari M. Orthovanadate and orthophosphate inhibit muscle force via two different pathways of the myosin ATPase cycle. Biophys J 2011; 100:665-674. [PMID: 21281581 DOI: 10.1016/j.bpj.2010.12.3723] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 12/09/2010] [Accepted: 12/15/2010] [Indexed: 11/28/2022] Open
Abstract
Measurements of the half-sarcomere stiffness during activation of skinned fibers from rabbit psoas (sarcomere length 2.5 μm, temperature 12°C) indicate that addition of 0.1 mM orthovanadate (Vi) to the solution produces a drop to ∼1/2 in number of force-generating myosin motors, proportional to the drop in steady isometric force (T(0)), an effect similar to that produced by the addition of 10 mM phosphate (Pi). However, in contrast to Pi, Vi does not change the rate of isometric force development. The depression of T(0) in a series of activations in presence of Vi is consistent with an apparent second-order rate constant of ∼1 × 10(3) M(-1) s(-1). The rate constant of T(0) recovery in a series of activations after removal of Vi is 3.5 × 10(-2) s(-1). These results, together with the finding in the literature that the ATPase rate is reduced by Vi in proportion to isometric force, are reproduced with a kinetic model of the acto-myosin cross-bridge cycle where binding of Vi to the force-generating actomyosin-ADP state induces detachment from actin to form a stable myosin-ADP-Vi complex that is not able to complete the hydrolysis cycle and reenters the cycle only via reattachment to actin upon activation in Vi-free solution.
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Affiliation(s)
- Marco Caremani
- Laboratory of Physiology, Department of Evolutionary Biology, Università di Firenze, Florence, Italy
| | - Steve Lehman
- Department of Integrative Biology, University of California, Berkeley, California
| | - Vincenzo Lombardi
- Laboratory of Physiology, Department of Evolutionary Biology, Università di Firenze, Florence, Italy
| | - Marco Linari
- Laboratory of Physiology, Department of Evolutionary Biology, Università di Firenze, Florence, Italy.
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Nocella M, Colombini B, Benelli G, Cecchi G, Bagni MA, Bruton J. Force decline during fatigue is due to both a decrease in the force per individual cross-bridge and the number of cross-bridges. J Physiol 2011; 589:3371-81. [PMID: 21540343 DOI: 10.1113/jphysiol.2011.209874] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Fatigue occurring during exercise can be defined as the inability to maintain the initial force or power output. As fatigue becomes pronounced, force and maximum velocity of shortening are greatly reduced and force relaxation is prolonged. In principle, force loss during fatigue can result from a decrease in the number of cross-bridges generating force or a decrease of the individual cross-bridge force or to both mechanisms. The present experiments were made to investigate this point in single fibres or small fibre bundles isolated from flexor digitorum brevis (FDB) of C57BL/6 mice at 22-24◦C. During a series of 105 tetanic contractions, we measured force and fibre stiffness by applying small sinusoidal length oscillations at 2.5 or 4 kHz frequency to the activated preparation and measuring the resulting force changes. Stiffness data were corrected for the influence of compliance in series with the cross-bridge ensemble. The results show that the force decline during the first 20 tetani is due to the reduction of force developed by the individual cross-bridges and thereafter as fatigue becomes more severe, the number of cross-bridges decreases. In spite of the force reduction in the early phase of fatigue, there was an increased rate of tetanic force development and relaxation. In the latter stages of fatigue, the rate of force development and relaxation became slower. Thus, the start of fatigue is characterised by decreased cross-bridge force development and as fatigue becomes more marked, the number of cross-bridges decreases. These findings are discussed in the context of the current hypotheses about fatigue mechanisms.
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Affiliation(s)
- Marta Nocella
- Department of Physiological Sciences, Universit`a degli Studi di Firenze, Viale G.B. Morgagni 63, 50134 Florence, Italy
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50
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Málnási-Csizmadia A, Kovács M. Emerging complex pathways of the actomyosin powerstroke. Trends Biochem Sci 2010; 35:684-90. [PMID: 20801044 DOI: 10.1016/j.tibs.2010.07.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Revised: 07/28/2010] [Accepted: 07/29/2010] [Indexed: 10/19/2022]
Abstract
Actomyosin powers muscle contraction and various cellular activities, including cell division, differentiation, intracellular transport and sensory functions. Despite their crucial roles, key aspects of force generation have remained elusive. To perform efficient force generation, the powerstroke must occur while myosin is bound to actin. Paradoxically, this process must be initiated when myosin is in a very low actin-affinity state. Recent results shed light on a kinetic pathway selection mechanism whereby the actin-induced activation of the swing of myosin's lever enables efficient mechanical functioning. Structural elements and biochemical principles involved in this mechanism are conserved among various NTPase-effector (e.g. kinesin-microtubule, G protein exchange factor and kinase-scaffold protein) systems that perform chemomechanical or signal transduction.
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