1
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Tanner BCW. Design Principles and Benefits of Spatially Explicit Models of Myofilament Function. Methods Mol Biol 2024; 2735:43-62. [PMID: 38038843 DOI: 10.1007/978-1-0716-3527-8_4] [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] [Indexed: 12/02/2023]
Abstract
Spatially explicit models of muscle contraction include fine-scale details about the spatial, kinetic, and/or mechanical properties of the biological processes being represented within the model network. Over the past 25 years, this has primarily consisted of a set of mathematical and computational algorithms representing myosin cross-bridge activity, Ca2+-activation of contraction, and ensemble force production within a half-sarcomere representation of the myofilament network. Herein we discuss basic design principles associated with creating spatially explicit models of myofilament function, as well as model assumptions underlying model development. A brief overview of computational approaches is introduced. Opportunities for new model directions that could investigate coupled regulatory pathways between the thick-filament and thin-filaments are also presented. Given the modular design and flexibility associated with spatially explicit models, we highlight some advantages of this approach compared to other model formulations.
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Affiliation(s)
- Bertrand C W Tanner
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, USA.
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2
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Pedersen RT, Snoberger A, Pyrpassopoulos S, Safer D, Drubin DG, Ostap EM. Endocytic myosin-1 is a force-insensitive, power-generating motor. J Cell Biol 2023; 222:e202303095. [PMID: 37549220 PMCID: PMC10406613 DOI: 10.1083/jcb.202303095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 05/17/2023] [Accepted: 07/24/2023] [Indexed: 08/09/2023] Open
Abstract
Myosins are required for clathrin-mediated endocytosis, but their precise molecular roles in this process are not known. This is, in part, because the biophysical properties of the relevant motors have not been investigated. Myosins have diverse mechanochemical activities, ranging from powerful contractility against mechanical loads to force-sensitive anchoring. To better understand the essential molecular contribution of myosin to endocytosis, we studied the in vitro force-dependent kinetics of the Saccharomyces cerevisiae endocytic type I myosin called Myo5, a motor whose role in clathrin-mediated endocytosis has been meticulously studied in vivo. We report that Myo5 is a low-duty-ratio motor that is activated ∼10-fold by phosphorylation and that its working stroke and actin-detachment kinetics are relatively force-insensitive. Strikingly, the in vitro mechanochemistry of Myo5 is more like that of cardiac myosin than that of slow anchoring myosin-1s found on endosomal membranes. We, therefore, propose that Myo5 generates power to augment actin assembly-based forces during endocytosis in cells.
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Affiliation(s)
- Ross T.A. Pedersen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Aaron Snoberger
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Serapion Pyrpassopoulos
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Daniel Safer
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - David G. Drubin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - E. Michael Ostap
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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3
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Pedersen RTA, Snoberger A, Pyrpassopoulos S, Safer D, Drubin DG, Ostap EM. Endocytic myosin-1 is a force-insensitive, power-generating motor. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.21.533689. [PMID: 36993306 PMCID: PMC10055380 DOI: 10.1101/2023.03.21.533689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Myosins are required for clathrin-mediated endocytosis, but their precise molecular roles in this process are not known. This is, in part, because the biophysical properties of the relevant motors have not been investigated. Myosins have diverse mechanochemical activities, ranging from powerful contractility against mechanical loads to force-sensitive anchoring. To better understand the essential molecular contribution of myosin to endocytosis, we studied the in vitro force-dependent kinetics of the Saccharomyces cerevisiae endocytic type I myosin called Myo5, a motor whose role in clathrin-mediated endocytosis has been meticulously studied in vivo. We report that Myo5 is a low-duty-ratio motor that is activated ∼10-fold by phosphorylation, and that its working stroke and actin-detachment kinetics are relatively force-insensitive. Strikingly, the in vitro mechanochemistry of Myo5 is more like that of cardiac myosin than like that of slow anchoring myosin-1s found on endosomal membranes. We therefore propose that Myo5 generates power to augment actin assembly-based forces during endocytosis in cells. Summary Pedersen, Snoberger et al. measure the force-sensitivity of the yeast endocytic the myosin-1 called Myo5 and find that it is more likely to generate power than to serve as a force-sensitive anchor in cells. Implications for Myo5's role in clathrin-mediated endocytosis are discussed.
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Affiliation(s)
- Ross TA Pedersen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
- Present address: Department of Embryology, Carnegie Institution for Science, Baltimore, MD 21218
- Equal Contribution
| | - Aaron Snoberger
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
- Equal Contribution
| | - Serapion Pyrpassopoulos
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Daniel Safer
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - David G Drubin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - E Michael Ostap
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
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4
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Clippinger Schulte SR, Scott B, Barrick SK, Stump WT, Blackwell T, Greenberg MJ. Single-molecule mechanics and kinetics of cardiac myosin interacting with regulated thin filaments. Biophys J 2023; 122:2544-2555. [PMID: 37165621 PMCID: PMC10323011 DOI: 10.1016/j.bpj.2023.05.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 04/18/2023] [Accepted: 05/05/2023] [Indexed: 05/12/2023] Open
Abstract
The cardiac cycle is a tightly regulated process wherein the heart generates force to pump blood to the body during systole and then relaxes during diastole. Disruption of this finely tuned cycle can lead to a range of diseases including cardiomyopathies and heart failure. Cardiac contraction is driven by the molecular motor myosin, which pulls regulated thin filaments in a calcium-dependent manner. In some muscle and nonmuscle myosins, regulatory proteins on actin tune the kinetics, mechanics, and load dependence of the myosin working stroke; however, it is not well understood whether or how thin-filament regulatory proteins tune the mechanics of the cardiac myosin motor. To address this critical gap in knowledge, we used single-molecule techniques to measure the kinetics and mechanics of the substeps of the cardiac myosin working stroke in the presence and absence of thin filament regulatory proteins. We found that regulatory proteins gate the calcium-dependent interactions between myosin and the thin filament. At physiologically relevant ATP concentrations, cardiac myosin's mechanics and unloaded kinetics are not affected by thin-filament regulatory proteins. We also measured the load-dependent kinetics of cardiac myosin at physiologically relevant ATP concentrations using an isometric optical clamp, and we found that thin-filament regulatory proteins do not affect either the identity or magnitude of myosin's primary load-dependent transition. Interestingly, at low ATP concentrations at both saturating and physiologically relevant subsaturating calcium concentrations, thin-filament regulatory proteins have a small effect on actomyosin dissociation kinetics, suggesting a mechanism beyond simple steric blocking. These results have important implications for the modeling of cardiac physiology and diseases.
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Affiliation(s)
- Sarah R Clippinger Schulte
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Brent Scott
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Samantha K Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - W Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Thomas Blackwell
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri.
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5
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Raffa V. Force: A messenger of axon outgrowth. Semin Cell Dev Biol 2023; 140:3-12. [PMID: 35817654 DOI: 10.1016/j.semcdb.2022.07.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 07/05/2022] [Accepted: 07/05/2022] [Indexed: 01/28/2023]
Abstract
The axon is a sophisticated macromolecular machine composed of interrelated parts that transmit signals like spur gears transfer motion between parallel shafts. The growth cone is a fine sensor that integrates mechanical and chemical cues and transduces these signals through the generation of a traction force that pushes the tip and pulls the axon shaft forward. The axon shaft, in turn, senses this pulling force and transduces this signal in an orchestrated response, coordinating cytoskeleton remodeling and intercalated mass addition to sustain and support the advancing of the tip. Extensive research suggests that the direct application of active force is per se a powerful inducer of axon growth, potentially bypassing the contribution of the growth cone. This review provides a critical perspective on current knowledge of how the force is a messenger of axon growth and its mode of action for controlling navigation, including aspects that remain unclear. It also focuses on novel approaches and tools designed to mechanically manipulate axons, and discusses their implications in terms of potential novel therapies for re-wiring the nervous system.
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Affiliation(s)
- Vittoria Raffa
- Department of Biology, University of Pisa, SS12 Abetone e Brennero, 4, 56127 Pisa, Italy.
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6
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Lee LA, Barrick SK, Buvoli AE, Walklate J, Stump WT, Geeves M, Greenberg MJ, Leinwand LA. Distinct effects of two hearing loss-associated mutations in the sarcomeric myosin MYH7b. J Biol Chem 2023; 299:104631. [PMID: 36963494 PMCID: PMC10141508 DOI: 10.1016/j.jbc.2023.104631] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 03/08/2023] [Accepted: 03/17/2023] [Indexed: 03/26/2023] Open
Abstract
For decades, sarcomeric myosin heavy chain proteins were assumed to be restricted to striated muscle where they function as molecular motors that contract muscle. However, MYH7b, an evolutionarily ancient member of this myosin family, has been detected in mammalian nonmuscle tissues, and mutations in MYH7b are linked to hereditary hearing loss in compound heterozygous patients. These mutations are the first associated with hearing loss rather than a muscle pathology, and because there are no homologous mutations in other myosin isoforms, their functional effects were unknown. We generated recombinant human MYH7b harboring the D515N or R1651Q hearing loss-associated mutation and studied their effects on motor activity and structural and assembly properties, respectively. The D515N mutation had no effect on steady-state actin-activated ATPase rate or load-dependent detachment kinetics but increased actin sliding velocity because of an increased displacement during the myosin working stroke. Furthermore, we found that the D515N mutation caused an increase in the proportion of myosin heads that occupy the disordered-relaxed state, meaning more myosin heads are available to interact with actin. Although we found no impact of the R1651Q mutation on myosin rod secondary structure or solubility, we observed a striking aggregation phenotype when this mutation was introduced into nonmuscle cells. Our results suggest that each mutation independently affects MYH7b function and structure. Together, these results provide the foundation for further study of a role for MYH7b outside the sarcomere.
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Affiliation(s)
- Lindsey A Lee
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA; BioFrontiers Institute, Boulder, Colorado, USA
| | - Samantha K Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Ada E Buvoli
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA; BioFrontiers Institute, Boulder, Colorado, USA
| | - Jonathan Walklate
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - W Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Michael Geeves
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Leslie A Leinwand
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA; BioFrontiers Institute, Boulder, Colorado, USA.
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7
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Clippinger Schulte SR, Scott B, Barrick SK, Stump WT, Blackwell T, Greenberg MJ. Single Molecule Mechanics and Kinetics of Cardiac Myosin Interacting with Regulated Thin Filaments. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.09.522880. [PMID: 36711892 PMCID: PMC9881944 DOI: 10.1101/2023.01.09.522880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The cardiac cycle is a tightly regulated process wherein the heart generates force to pump blood to the body during systole and then relaxes during diastole. Disruption of this finely tuned cycle can lead to a range of diseases including cardiomyopathies and heart failure. Cardiac contraction is driven by the molecular motor myosin, which pulls regulated thin filaments in a calcium-dependent manner. In some muscle and non-muscle myosins, regulatory proteins on actin tune the kinetics, mechanics, and load dependence of the myosin working stroke; however, it is not well understood whether or how thin filament regulatory proteins tune the mechanics of the cardiac myosin motor. To address this critical gap in knowledge, we used single-molecule techniques to measure the kinetics and mechanics of the substeps of the cardiac myosin working stroke in the presence and absence of thin filament regulatory proteins. We found that regulatory proteins gate the calcium-dependent interactions between myosin and the thin filament. At physiologically relevant ATP concentrations, cardiac myosin's mechanics and unloaded kinetics are not affected by thin filament regulatory proteins. We also measured the load-dependent kinetics of cardiac myosin at physiologically relevant ATP concentrations using an isometric optical clamp, and we found that thin filament regulatory proteins do not affect either the identity or magnitude of myosin's primary load-dependent transition. Interestingly, at low ATP concentrations, thin filament regulatory proteins have a small effect on actomyosin dissociation kinetics, suggesting a mechanism beyond simple steric blocking. These results have important implications for both disease modeling and computational models of muscle contraction. Significance Statement Human heart contraction is powered by the molecular motor β-cardiac myosin, which pulls on thin filaments consisting of actin and the regulatory proteins troponin and tropomyosin. In some muscle and non-muscle systems, these regulatory proteins tune the kinetics, mechanics, and load dependence of the myosin working stroke. Despite having a central role in health and disease, it is not well understood whether the mechanics or kinetics of β-cardiac myosin are affected by regulatory proteins. We show that regulatory proteins do not affect the mechanics or load-dependent kinetics of the working stroke at physiologically relevant ATP concentrations; however, they can affect the kinetics at low ATP concentrations, suggesting a mechanism beyond simple steric blocking. This has important implications for modeling of cardiac physiology and diseases.
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8
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Mizutani M, Miyata M. Direct Measurement of Kinetic Force Generated by Mycoplasma. Methods Mol Biol 2023; 2646:337-346. [PMID: 36842128 DOI: 10.1007/978-1-0716-3060-0_28] [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] [Indexed: 04/28/2023]
Abstract
Optical tweezers enable us to measure the force generated by bacterial motility and motor proteins. Here, we describe a method, using optical tweezers and related techniques, to measure the force generated during Mycoplasma gliding. An avidin-conjugated polystyrene bead trapped by a focused laser beam is bound to the surface-biotinylated Mycoplasma cell, which pulls the bead from the trap center of the laser. The force generated by Mycoplasma is calculated from a displacement measured and a spring constant of the laser trap.
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Affiliation(s)
- Masaki Mizutani
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan.
| | - Makoto Miyata
- Graduate School of Science, Osaka City University, Osaka, Japan
- Graduate School of Science, Osaka Metropolitan University, Osaka, Japan
- The OCU Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka City University, Osaka, Japan
- The OMU Advanced Research Center for Natural Science and Technology, Osaka Metropolitan University, Osaka, Japan
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9
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Yang Y, Fu Z, Zhu W, Hu H, Wang J. Application of optical tweezers in cardiovascular research: More than just a measuring tool. Front Bioeng Biotechnol 2022; 10:947918. [PMID: 36147537 PMCID: PMC9486066 DOI: 10.3389/fbioe.2022.947918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 08/12/2022] [Indexed: 12/04/2022] Open
Abstract
Recent advances in the field of optical tweezer technology have shown intriguing potential for applications in cardiovascular medicine, bringing this laboratory nanomechanical instrument into the spotlight of translational medicine. This article summarizes cardiovascular system findings generated using optical tweezers, including not only rigorous nanomechanical measurements but also multifunctional manipulation of biologically active molecules such as myosin and actin, of cells such as red blood cells and cardiomyocytes, of subcellular organelles, and of microvessels in vivo. The implications of these findings in the diagnosis and treatment of diseases, as well as potential perspectives that could also benefit from this tool, are also discussed.
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Affiliation(s)
- Yi Yang
- Department of Cardiology, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China
- Cardiovascular Key Laboratory of Zhejiang Province, Hangzhou, China
| | - Zhenhai Fu
- Quantum Sensing Center, Zhejiang Lab, Hangzhou, China
| | - Wei Zhu
- Department of Cardiology, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China
- Cardiovascular Key Laboratory of Zhejiang Province, Hangzhou, China
- *Correspondence: Wei Zhu, ; Huizhu Hu, ; Jian’an Wang,
| | - Huizhu Hu
- Quantum Sensing Center, Zhejiang Lab, Hangzhou, China
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou, China
- *Correspondence: Wei Zhu, ; Huizhu Hu, ; Jian’an Wang,
| | - Jian’an Wang
- Department of Cardiology, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China
- Cardiovascular Key Laboratory of Zhejiang Province, Hangzhou, China
- *Correspondence: Wei Zhu, ; Huizhu Hu, ; Jian’an Wang,
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10
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Optimization of Mechanosensitive Cross-Talk between Matrix Stiffness and Protein Density: Independent Matrix Properties Regulate Spreading Dynamics of Myocytes. Cells 2022; 11:cells11132122. [PMID: 35805206 PMCID: PMC9265304 DOI: 10.3390/cells11132122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 06/29/2022] [Accepted: 07/02/2022] [Indexed: 11/25/2022] Open
Abstract
Cells actively sense differences in topology, matrix elasticity and protein composition of the extracellular microenvironment and adapt their function and morphology. In this study, we focus on the cross-talk between matrix stiffness and protein coating density that regulates morphology and proliferation dynamics of single myocytes. For this, C2C12 myocytes were monitored on L-DOPA functionalized hydrogels of 22 different elasticity and fibronectin density compositions. Static images were recorded and statistically analyzed to determine morphological differences and to identify the optimized extracellular matrix (ECM). Using that information, selected ECMs were used to study the dynamics before and after cell proliferation by statistical comparison of distinct cell states. We observed a fibronectin-density-independent increase of the projected cell area until 12 kPa. Additionally, changes in fibronectin density led to an area that was optimum at about 2.6 μg/cm2, which was confirmed by independent F-actin analysis, revealing a maximum actin-filament-to-cell-area ratio of 7.5%. Proliferation evaluation showed an opposite correlation between cell spreading duration and speed to matrix elasticity and protein density, which did not affect cell-cycle duration. In summary, we identified an optimized ECM composition and found that independent matrix properties regulate distinct cell characteristics.
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11
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Sun S, Karki C, Gao BZ, Li L. Molecular mechanisms of cardiac actomyosin transforming from rigor state to post-rigor state. J Chem Phys 2022; 156:035101. [PMID: 35065578 PMCID: PMC9305598 DOI: 10.1063/5.0078166] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Sudden cardiac death contributed to half of all deaths from cardiovascular diseases. The mechanism of the kinetic cycle of cardiac myosin is crucial for heart protection and drug development. The state change in the myosin kinetic cycle from the rigor state to the post-rigor state is fundamental to explain binding and dissociation. Here, we used β-cardiac myosin in the rigor and post-rigor states to model the actomyosin complexes. Molecular dynamics simulations, electrostatic analysis, and energetic analysis of actomyosin complexes were performed in this work. The results showed that there are fewer interactions and lower electrostatic binding strength in the post-rigor state than in the rigor state. In the post-rigor state, there were higher free binding energy, fewer salt bridges, and fewer hydrogen bonds. The results showed a lower binding affinity in the post-rigor state than in the rigor state. The decrease in the binding affinity provided important conditions for dissociation of the myosin from the actin filament. Although previous studies focused mostly on the binding process, this study provides evidence of dissociation, which is even more important in the myosin kinetic cycle. This research on the mechanism of myosin kinetic cycles provides a novel direction for future genetic disease studies.
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Affiliation(s)
- Shengjie Sun
- Computational Science Program, The University of Texas at El Paso, 500 W University Ave., El Paso, Texas 79968, USA
| | - Chitra Karki
- Computational Science Program, The University of Texas at El Paso, 500 W University Ave., El Paso, Texas 79968, USA
| | - Bruce Z. Gao
- Department of Bioengineering, Clemson University, Clemson, South Carolina 29634, USA
| | - Lin Li
- Author to whom correspondence should be addressed:
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12
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Gardini L, Woody MS, Kashchuk AV, Goldman YE, Ostap EM, Capitanio M. High-Speed Optical Traps Address Dynamics of Processive and Non-Processive Molecular Motors. Methods Mol Biol 2022; 2478:513-557. [PMID: 36063333 PMCID: PMC9987584 DOI: 10.1007/978-1-0716-2229-2_19] [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] [Indexed: 11/26/2022]
Abstract
Interactions between biological molecules occur on very different time scales, from the minutes of strong protein-protein bonds, down to below the millisecond duration of rapid biomolecular interactions. Conformational changes occurring on sub-ms time scales and their mechanical force dependence underlie the functioning of enzymes (e.g., motor proteins) that are fundamental for life. However, such rapid interactions are beyond the temporal resolution of most single-molecule methods. We developed ultrafast force-clamp spectroscopy (UFFCS), a single-molecule technique based on laser tweezers that allows us to investigate early and very fast dynamics of a variety of enzymes and their regulation by mechanical load. The technique was developed to investigate the rapid interactions between skeletal muscle myosin and actin, and then applied to the study of different biological systems, from cardiac myosin to processive myosin V, microtubule-binding proteins, transcription factors, and mechanotransducer proteins. Here, we describe two different implementations of UFFCS instrumentation and protocols using either acousto- or electro-optic laser beam deflectors, and their application to the study of processive and non-processive motor proteins.
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Affiliation(s)
- Lucia Gardini
- LENS, European Laboratory for Non-Linear Spectroscopy, Florence, Italy
- National Institute of Optics, National Research Council (INO-CNR), Florence, Italy
| | - Michael S Woody
- Department of Physiology and Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Anatolii V Kashchuk
- LENS, European Laboratory for Non-Linear Spectroscopy, Florence, Italy
- Department of Physics and Astronomy, University of Florence, Florence, Italy
| | - Yale E Goldman
- Department of Physiology and Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
| | - E Michael Ostap
- Department of Physiology and Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
| | - Marco Capitanio
- LENS, European Laboratory for Non-Linear Spectroscopy, Florence, Italy.
- Department of Physics and Astronomy, University of Florence, Florence, Italy.
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13
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Microtubule Dumbbells to Assess the Effect of Force Geometry on Single Kinesin Motors. Methods Mol Biol 2022; 2478:559-583. [PMID: 36063334 PMCID: PMC9987583 DOI: 10.1007/978-1-0716-2229-2_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The cytoskeletal motors myosin, kinesin, and dynein and their corresponding tracks, actin and microtubules, are force generating ATPases responsible for motility and morphological changes at the intracellular, cellular, and tissue levels. The pioneering application of optical tweezers to measure the force-producing properties of cytoskeletal motors has provided an unparalleled understanding of their mechanochemistry. The mechanosensitivity of processive, microtubule-based motors has largely been studied in the optical trap using the "single-bead" assay, where a bead-attached motor is held adjacent to a cytoskeletal filament as it processively steps along it. However, because of the geometrical constraints in the conventional single-bead assay, the motor-filament bond is not only loaded parallel to the long axis of the filament, but also perpendicular to the long axis of the filament. This perpendicular force, which is inherent in the conventional single-bead assay, accelerates the motor-filament detachment and has not been carefully considered in prior experiments. An alternative approach is the "three-bead" assay, which was developed for the study of non-processive myosin motors. The vertical force component is minimized in this assay, and the total opposing force is mainly parallel to the microtubule. Experiments with kinesin show that microtubule attachment durations can be highly variable and last for up to tenfold longer times in the three-bead assay, compared to the single-bead assay. Thus, the ability of kinesin to bear mechanical load and remain attached to microtubules depends on the forces in more than one dimension. In this chapter, we provide detailed methods for preparing the proteins, buffers, flow chambers, and bead-filament assemblies for performing the three-bead assay with microtubules and their motors.
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14
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Pospich S, Sweeney HL, Houdusse A, Raunser S. High-resolution structures of the actomyosin-V complex in three nucleotide states provide insights into the force generation mechanism. eLife 2021; 10:e73724. [PMID: 34812732 PMCID: PMC8735999 DOI: 10.7554/elife.73724] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 11/22/2021] [Indexed: 11/13/2022] Open
Abstract
The molecular motor myosin undergoes a series of major structural transitions during its force-producing motor cycle. The underlying mechanism and its coupling to ATP hydrolysis and actin binding are only partially understood, mostly due to sparse structural data on actin-bound states of myosin. Here, we report 26 high-resolution cryo-EM structures of the actomyosin-V complex in the strong-ADP, rigor, and a previously unseen post-rigor transition state that binds the ATP analog AppNHp. The structures reveal a high flexibility of myosin in each state and provide valuable insights into the structural transitions of myosin-V upon ADP release and binding of AppNHp, as well as the actomyosin interface. In addition, they show how myosin is able to specifically alter the structure of F-actin.
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Affiliation(s)
- Sabrina Pospich
- Department of Structural Biochemistry, Max Planck Institute of Molecular PhysiologyDortmundGermany
| | - H Lee Sweeney
- Department of Pharmacology and Therapeutics and the Myology Institute, University of FloridaGainesvilleUnited States
| | - Anne Houdusse
- Structural Motility, Institut Curie, Centre National de la Recherche ScientifiqueParisFrance
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular PhysiologyDortmundGermany
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15
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Barrick SK, Greenberg MJ. Cardiac myosin contraction and mechanotransduction in health and disease. J Biol Chem 2021; 297:101297. [PMID: 34634306 PMCID: PMC8559575 DOI: 10.1016/j.jbc.2021.101297] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 10/06/2021] [Accepted: 10/07/2021] [Indexed: 12/17/2022] Open
Abstract
Cardiac myosin is the molecular motor that powers heart contraction by converting chemical energy from ATP hydrolysis into mechanical force. The power output of the heart is tightly regulated to meet the physiological needs of the body. Recent multiscale studies spanning from molecules to tissues have revealed complex regulatory mechanisms that fine-tune cardiac contraction, in which myosin not only generates power output but also plays an active role in its regulation. Thus, myosin is both shaped by and actively involved in shaping its mechanical environment. Moreover, these studies have shown that cardiac myosin-generated tension affects physiological processes beyond muscle contraction. Here, we review these novel regulatory mechanisms, as well as the roles that myosin-based force generation and mechanotransduction play in development and disease. We describe how key intra- and intermolecular interactions contribute to the regulation of myosin-based contractility and the role of mechanical forces in tuning myosin function. We also discuss the emergence of cardiac myosin as a drug target for diseases including heart failure, leading to the discovery of therapeutics that directly tune myosin contractility. Finally, we highlight some of the outstanding questions that must be addressed to better understand myosin's functions and regulation, and we discuss prospects for translating these discoveries into precision medicine therapeutics targeting contractility and mechanotransduction.
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Affiliation(s)
- Samantha K Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA.
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16
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Mizutani M, Sasajima Y, Miyata M. Force and Stepwise Movements of Gliding Motility in Human Pathogenic Bacterium Mycoplasma pneumoniae. Front Microbiol 2021; 12:747905. [PMID: 34630372 PMCID: PMC8498583 DOI: 10.3389/fmicb.2021.747905] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 08/24/2021] [Indexed: 11/23/2022] Open
Abstract
Mycoplasma pneumoniae, a human pathogenic bacterium, binds to sialylated oligosaccharides and glides on host cell surfaces via a unique mechanism. Gliding motility is essential for initiating the infectious process. In the present study, we measured the stall force of an M. pneumoniae cell carrying a bead that was manipulated using optical tweezers on two strains. The stall forces of M129 and FH strains were averaged to be 23.7 and 19.7 pN, respectively, much weaker than those of other bacterial surface motilities. The binding activity and gliding speed of the M129 strain on sialylated oligosaccharides were eight and two times higher than those of the FH strain, respectively, showing that binding activity is not linked to gliding force. Gliding speed decreased when cell binding was reduced by addition of free sialylated oligosaccharides, indicating the existence of a drag force during gliding. We detected stepwise movements, likely caused by a single leg under 0.2-0.3 mM free sialylated oligosaccharides. A step size of 14-19 nm showed that 25-35 propulsion steps per second are required to achieve the usual gliding speed. The step size was reduced to less than half with the load applied using optical tweezers, showing that a 2.5 pN force from a cell is exerted on a leg. The work performed in this step was 16-30% of the free energy of the hydrolysis of ATP molecules, suggesting that this step is linked to the elementary process of M. pneumoniae gliding. We discuss a model to explain the gliding mechanism, based on the information currently available.
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Affiliation(s)
- Masaki Mizutani
- Graduate School of Science, Osaka City University, Osaka, Japan
| | - Yuya Sasajima
- Graduate School of Science, Osaka City University, Osaka, Japan
| | - Makoto Miyata
- Graduate School of Science, Osaka City University, Osaka, Japan.,The OCU Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka City University, Osaka, Japan
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17
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Scott B, Marang C, Woodward M, Debold EP. Myosin's powerstroke occurs prior to the release of phosphate from the active site. Cytoskeleton (Hoboken) 2021; 78:185-198. [PMID: 34331410 DOI: 10.1002/cm.21682] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 07/15/2021] [Accepted: 07/19/2021] [Indexed: 02/06/2023]
Abstract
Myosins are a family of motor proteins responsible for various forms of cellular motility, including muscle contraction and vesicular transport. The most fundamental aspect of myosin is its ability to transduce the chemical energy from the hydrolysis of ATP into mechanical work, in the form of force and/or motion. A key unanswered question of the transduction process is the timing of the force-generating powerstroke relative to the release of phosphate (Pi ) from the active site. We examined the ability of single-headed myosin Va to generate a powerstroke in a single molecule laser trap assay while maintaining Pi in its active site, by either elevating Pi in solution or by introducing a mutation in myosin's active site (S217A) to slow Pi -release from the active site. Upon binding to the actin filament, WT myosin generated a powerstoke rapidly (≥500 s-1 ) and without a detectable delay, both in the absence and presence of 30 mM Pi . The elevated levels of Pi did, however, affect event lifetime, eliminating the longest 25% of binding events, confirming that Pi rebound to myosin's active site and accelerated detachment. The S217A construct also generated a powerstroke similar in size and rate upon binding to actin despite the slower Pi release rate. These findings provide direct evidence that myosin Va generates a powerstroke with Pi still in its active site. Therefore, the findings are most consistent with a model in which the powerstroke occurs prior to the release of Pi from the active site.
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Affiliation(s)
- Brent Scott
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts, USA
| | - Christopher Marang
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts, USA
| | - Mike Woodward
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts, USA
| | - Edward P Debold
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts, USA
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18
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Al Azzam O, Trussell CL, Reinemann DN. Measuring force generation within reconstituted microtubule bundle assemblies using optical tweezers. Cytoskeleton (Hoboken) 2021; 78:111-125. [PMID: 34051127 DOI: 10.1002/cm.21678] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 05/20/2021] [Accepted: 05/25/2021] [Indexed: 11/07/2022]
Abstract
Kinesins and microtubule associated proteins (MAPs) are critical to sustain life, facilitating cargo transport, cell division, and motility. To interrogate the mechanistic underpinnings of their function, these microtubule-based motors and proteins have been studied extensively at the single molecule level. However, a long-standing issue in the single molecule biophysics field has been how to investigate motors and associated proteins within a physiologically relevant environment in vitro. While the one motor/one filament orientation of a traditional optical trapping assay has revolutionized our knowledge of motor protein mechanics, this reductionist geometry does not reflect the structural hierarchy in which many motors work within the cellular environment. Here, we review approaches that combine the precision of optical tweezers with reconstituted ensemble systems of microtubules, MAPs, and kinesins to understand how each of these unique elements work together to perform large scale cellular tasks, such as but not limited to building the mitotic spindle. Not only did these studies develop novel techniques for investigating motor proteins in vitro, but they also illuminate ensemble filament and motor synergy that helps bridge the mechanistic knowledge gap between previous single molecule and cell level studies.
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Affiliation(s)
- Omayma Al Azzam
- Department of Chemical Engineering, University of Mississippi, University, Mississippi, USA
| | - Cameron Lee Trussell
- Department of Chemical Engineering, University of Mississippi, University, Mississippi, USA
| | - Dana N Reinemann
- Department of Chemical Engineering, University of Mississippi, University, Mississippi, USA.,Department of Biomedical Engineering, University of Mississippi, University, Mississippi, USA
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19
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Lavrenyuk K, Conway D, Dahl KN. Imaging methods in mechanosensing: a historical perspective and visions for the future. Mol Biol Cell 2021; 32:842-854. [PMID: 33788578 PMCID: PMC8108522 DOI: 10.1091/mbc.e20-10-0671] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Over the past three decades, as mechanobiology has become a distinct area of study, researchers have developed novel imaging tools to discover the pathways of biomechanical signaling. Early work with substrate engineering and particle tracking demonstrated the importance of cell–extracellular matrix interactions on the cell cycle as well as the mechanical flux of the intracellular environment. Most recently, tension sensor approaches allowed directly measuring tension in cell–cell and cell–substrate interactions. We retrospectively analyze how these various optical techniques progressed the field and suggest our vision forward for a unified theory of cell mechanics, mapping cellular mechanosensing, and novel biomedical applications for mechanobiology.
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Affiliation(s)
- Kirill Lavrenyuk
- Carnegie Mellon University, College of Engineering, Pittsburgh, PA 15213
| | - Daniel Conway
- Virginia Commonwealth University, College of Engineering, Richmond, VA 23284
| | - Kris Noel Dahl
- Carnegie Mellon University, College of Engineering, Pittsburgh, PA 15213
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20
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Greenberg MJ, Tardiff JC. Complexity in genetic cardiomyopathies and new approaches for mechanism-based precision medicine. J Gen Physiol 2021; 153:211741. [PMID: 33512404 PMCID: PMC7852459 DOI: 10.1085/jgp.202012662] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Accepted: 01/07/2021] [Indexed: 12/11/2022] Open
Abstract
Genetic cardiomyopathies have been studied for decades, and it has become increasingly clear that these progressive diseases are more complex than originally thought. These complexities can be seen both in the molecular etiologies of these disorders and in the clinical phenotypes observed in patients. While these disorders can be caused by mutations in cardiac genes, including ones encoding sarcomeric proteins, the disease presentation varies depending on the patient mutation, where mutations even within the same gene can cause divergent phenotypes. Moreover, it is challenging to connect the mutation-induced molecular insult that drives the disease pathogenesis with the various compensatory and maladaptive pathways that are activated during the course of the subsequent progressive, pathogenic cardiac remodeling. These inherent complexities have frustrated our ability to understand and develop broadly effective treatments for these disorders. It has been proposed that it might be possible to improve patient outcomes by adopting a precision medicine approach. Here, we lay out a practical framework for such an approach, where patient subpopulations are binned based on common underlying biophysical mechanisms that drive the molecular disease pathogenesis, and we propose that this function-based approach will enable the development of targeted therapeutics that ameliorate these effects. We highlight several mutations to illustrate the need for mechanistic molecular experiments that span organizational and temporal scales, and we describe recent advances in the development of novel therapeutics based on functional targets. Finally, we describe many of the outstanding questions for the field and how fundamental mechanistic studies, informed by our more nuanced understanding of the clinical disorders, will play a central role in realizing the potential of precision medicine for genetic cardiomyopathies.
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Affiliation(s)
- Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
| | - Jil C Tardiff
- Department of Biomedical Engineering, University of Arizona, Tucson, AZ.,Department of Medicine, University of Arizona, Tucson, AZ
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21
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Wang T, Brenner B, Nayak A, Amrute-Nayak M. Acto-Myosin Cross-Bridge Stiffness Depends on the Nucleotide State of Myosin II. NANO LETTERS 2020; 20:7506-7512. [PMID: 32897722 DOI: 10.1021/acs.nanolett.0c02960] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
How various myosin isoforms fulfill the diverse physiological requirements of distinct muscle types remain unclear. Myosin II isoforms expressed in skeletal muscles determine the mechanical performance of the specific muscles. Here, we employed a single-molecule optical trapping method and compared the chemomechanical properties of slow and fast muscle myosin II isoforms. Stiffness of the myosin motor is key to its force-generating ability during muscle contraction. We found that acto-myosin (AM) cross-bridge stiffness depends on its nucleotide state as the myosin progresses through the ATPase cycle. The strong actin bound "AM.ADP" state exhibited >2 fold lower stiffness than "AM rigor" state. The two myosin isoforms displayed similar "rigor" stiffness. We conclude that the time-averaged stiffness of the slow myosin is lower due to prolonged duration of the AM.ADP state, which determines the force-generating potential and contraction speed of the muscle, elucidating the basis for functional diversity among myosins.
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Affiliation(s)
- Tianbang Wang
- Institute of Molecular and Cell Physiology, Hannover Medical School, 30625 Hannover, Germany
| | - Bernhard Brenner
- Institute of Molecular and Cell Physiology, Hannover Medical School, 30625 Hannover, Germany
| | - Arnab Nayak
- Institute of Molecular and Cell Physiology, Hannover Medical School, 30625 Hannover, Germany
| | - Mamta Amrute-Nayak
- Institute of Molecular and Cell Physiology, Hannover Medical School, 30625 Hannover, Germany
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22
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Ewert W, Franz P, Tsiavaliaris G, Preller M. Structural and Computational Insights into a Blebbistatin-Bound Myosin•ADP Complex with Characteristics of an ADP-Release Conformation along the Two-Step Myosin Power Stoke. Int J Mol Sci 2020; 21:ijms21197417. [PMID: 33049993 PMCID: PMC7582316 DOI: 10.3390/ijms21197417] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 10/06/2020] [Indexed: 01/13/2023] Open
Abstract
The motor protein myosin drives a wide range of cellular and muscular functions by generating directed movement and force, fueled through adenosine triphosphate (ATP) hydrolysis. Release of the hydrolysis product adenosine diphosphate (ADP) is a fundamental and regulatory process during force production. However, details about the molecular mechanism accompanying ADP release are scarce due to the lack of representative structures. Here we solved a novel blebbistatin-bound myosin conformation with critical structural elements in positions between the myosin pre-power stroke and rigor states. ADP in this structure is repositioned towards the surface by the phosphate-sensing P-loop, and stabilized in a partially unbound conformation via a salt-bridge between Arg131 and Glu187. A 5 Å rotation separates the mechanical converter in this conformation from the rigor position. The crystallized myosin structure thus resembles a conformation towards the end of the two-step power stroke, associated with ADP release. Computationally reconstructing ADP release from myosin by means of molecular dynamics simulations further supported the existence of an equivalent conformation along the power stroke that shows the same major characteristics in the myosin motor domain as the resolved blebbistatin-bound myosin-II·ADP crystal structure, and identified a communication hub centered on Arg232 that mediates chemomechanical energy transduction.
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Affiliation(s)
- Wiebke Ewert
- Institute for Biophysical Chemistry, Structural Bioinformatics and Chemical Biology, Hannover Medical School, 30625 Hannover, Germany;
| | - Peter Franz
- Institute for Biophysical Chemistry, Cellular Biophysics, Hannover Medical School, 30625 Hannover, Germany; (P.F.); (G.T.)
| | - Georgios Tsiavaliaris
- Institute for Biophysical Chemistry, Cellular Biophysics, Hannover Medical School, 30625 Hannover, Germany; (P.F.); (G.T.)
| | - Matthias Preller
- Institute for Biophysical Chemistry, Structural Bioinformatics and Chemical Biology, Hannover Medical School, 30625 Hannover, Germany;
- Department of Natural Sciences, University of Applied Sciences Bonn-Rhein-Sieg, 53359 Rheinbach, Germany
- Correspondence: ; Tel.: +49-511-532-2804
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23
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Single-Molecule Biophysical Techniques to Study Actomyosin Force Transduction. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020. [PMID: 32451857 DOI: 10.1007/978-3-030-38062-5_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Inside the cellular environment, molecular motors can work in concert to conduct a variety of important physiological functions and processes that are vital for the survival of a cell. However, in order to decipher the mechanism of how these molecular motors work, single-molecule microscopy techniques have been popular methods to understand the molecular basis of the emerging ensemble behavior of these motor proteins.In this chapter, we discuss various single-molecule biophysical imaging techniques that have been used to expose the mechanics and kinetics of myosins. The chapter should be taken as a general overview and introductory guide to the many existing techniques; however, since other chapters will discuss some of these techniques more thoroughly, the readership should refer to those chapters for further details and discussions. In particular, we will focus on scattering-based single-molecule microscopy methods, some of which have become more popular in the recent years and around which the work in our laboratories has been centered.
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24
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Dai EN, Heo S, Mauck RL. "Looping In" Mechanics: Mechanobiologic Regulation of the Nucleus and the Epigenome. Adv Healthc Mater 2020; 9:e2000030. [PMID: 32285630 DOI: 10.1002/adhm.202000030] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 02/17/2020] [Accepted: 02/18/2020] [Indexed: 12/11/2022]
Abstract
Cells respond to physical cues in their microenvironment. These cues result in changes in cell behavior, some of which are transient, and others of which are permanent. Understanding and leveraging permanent alteration of cell behavior induced by mechanical cues, or "mechanical memories," is an important aim in cell and tissue engineering. Herein, this paper reviews the existing literature outlining how cells may store memories of biophysical cues with a specific focus on the nucleus, the storehouse of information in eukaryotic cells. In particular, this review details mechanically driven adaptations in nuclear structure and genome organization and outlines potential mechanisms by which mechanical memories may be encoded within the structure and organization of the nucleus and chromatin.
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Affiliation(s)
- Eric N. Dai
- Departments of Orthopaedic Surgery and Bioengineering University of Pennsylvania Philadelphia PA 19104 USA
- Translational Musculoskeletal Research Center Corporal Michael J. Crescenz VA Medical Center Philadelphia PA 19104 USA
| | - Su‐Jin Heo
- Departments of Orthopaedic Surgery and Bioengineering University of Pennsylvania Philadelphia PA 19104 USA
- Translational Musculoskeletal Research Center Corporal Michael J. Crescenz VA Medical Center Philadelphia PA 19104 USA
| | - Robert L. Mauck
- Departments of Orthopaedic Surgery and Bioengineering University of Pennsylvania Philadelphia PA 19104 USA
- Translational Musculoskeletal Research Center Corporal Michael J. Crescenz VA Medical Center Philadelphia PA 19104 USA
- McKay Orthopaedic Research Laboratory University of Pennsylvania Philadelphia PA 19104‐6081 USA
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25
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Linari M, Piazzesi G, Pertici I, Dantzig JA, Goldman YE, Lombardi V. Straightening Out the Elasticity of Myosin Cross-Bridges. Biophys J 2020; 118:994-1002. [PMID: 31968230 PMCID: PMC7063436 DOI: 10.1016/j.bpj.2020.01.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 12/21/2019] [Accepted: 01/06/2020] [Indexed: 11/30/2022] Open
Abstract
In a contracting muscle, myosin cross-bridges extending from thick filaments pull the interdigitating thin (actin-containing) filaments during cyclical ATP-driven interactions toward the center of the sarcomere, the structural unit of striated muscle. Cross-bridge attachments in the sarcomere have been reported to exhibit a similar stiffness under both positive and negative forces. However, in vitro measurements on filaments with a sparse complement of heads detected a decrease of the cross-bridge stiffness at negative forces attributed to the buckling of the subfragment 2 tail portion. Here, we review some old and new data that confirm that cross-bridge stiffness is nearly linear in the muscle filament lattice. The implications of high myosin stiffness at positive and negative strains are considered in muscle fibers and in nonmuscle intracellular cargo transport.
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Affiliation(s)
- Marco Linari
- PhysioLab, Department of Biology, University of Florence, Sesto Fiorentino, Italy
| | - Gabriella Piazzesi
- PhysioLab, Department of Biology, University of Florence, Sesto Fiorentino, Italy
| | - Irene Pertici
- PhysioLab, Department of Biology, University of Florence, Sesto Fiorentino, Italy
| | - Jody A Dantzig
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Yale E Goldman
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
| | - Vincenzo Lombardi
- PhysioLab, Department of Biology, University of Florence, Sesto Fiorentino, Italy.
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26
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Pyrpassopoulos S, Shuman H, Ostap EM. Modulation of Kinesin's Load-Bearing Capacity by Force Geometry and the Microtubule Track. Biophys J 2019; 118:243-253. [PMID: 31883614 PMCID: PMC6952184 DOI: 10.1016/j.bpj.2019.10.045] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 10/03/2019] [Accepted: 10/15/2019] [Indexed: 11/27/2022] Open
Abstract
Kinesin motors and their associated microtubule tracks are essential for long-distance transport of cellular cargos. Intracellular activity and proper recruitment of kinesins is regulated by biochemical signaling, cargo adaptors, microtubule-associated proteins, and mechanical forces. In this study, we found that the effect of opposing forces on the kinesin-microtubule attachment duration depends strongly on experimental assay geometry. Using optical tweezers and the conventional single-bead assay, we show that detachment of kinesin from the microtubule is likely accelerated by forces vertical to the long axis of the microtubule due to contact of the single bead with the underlying microtubule. We used the three-bead assay to minimize the vertical force component and found that when the opposing forces are mainly parallel to the microtubule, the median value of attachment durations between kinesin and microtubules can be up to 10-fold longer than observed using the single-bead assay. Using the three-bead assay, we also found that not all microtubule protofilaments are equivalent interacting substrates for kinesin and that the median value of attachment durations of kinesin varies by more than 10-fold, depending on the relative angular position of the forces along the circumference of the microtubule. Thus, depending on the geometry of forces across the microtubule, kinesin can switch from a fast detaching motor (median attachment duration <0.2 s) to a persistent motor that sustains attachment (median attachment duration >3 s) at high forces (5 pN). Our data show that the load-bearing capacity of the kinesin motor is highly variable and can be dramatically affected by off-axis forces and forces across the microtubule lattice, which has implications for a range of cellular activities, including cell division and organelle transport.
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Affiliation(s)
- Serapion Pyrpassopoulos
- Pennsylvania Muscle Institute, Department of Physiology, and the Center for Engineering Mechanobiology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania.
| | - Henry Shuman
- Pennsylvania Muscle Institute, Department of Physiology, and the Center for Engineering Mechanobiology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania
| | - E Michael Ostap
- Pennsylvania Muscle Institute, Department of Physiology, and the Center for Engineering Mechanobiology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania.
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27
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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: 70] [Impact Index Per Article: 14.0] [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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28
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Woody MS, Winkelmann DA, Capitanio M, Ostap EM, Goldman YE. Single molecule mechanics resolves the earliest events in force generation by cardiac myosin. eLife 2019; 8:49266. [PMID: 31526481 PMCID: PMC6748826 DOI: 10.7554/elife.49266] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 09/03/2019] [Indexed: 12/31/2022] Open
Abstract
Key steps of cardiac mechanochemistry, including the force-generating working stroke and the release of phosphate (Pi), occur rapidly after myosin-actin attachment. An ultra-high-speed optical trap enabled direct observation of the timing and amplitude of the working stroke, which can occur within <200 μs of actin binding by β-cardiac myosin. The initial actomyosin state can sustain loads of at least 4.5 pN and proceeds directly to the stroke or detaches before releasing ATP hydrolysis products. The rates of these processes depend on the force. The time between binding and stroke is unaffected by 10 mM Pi which, along with other findings, indicates the stroke precedes phosphate release. After Pi release, Pi can rebind enabling reversal of the working stroke. Detecting these rapid events under physiological loads provides definitive indication of the dynamics by which actomyosin converts biochemical energy into mechanical work.
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Affiliation(s)
- Michael S Woody
- Graduate Group in Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Donald A Winkelmann
- Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Rutgers University, Piscataway, United States
| | - Marco Capitanio
- LENS - European Laboratory for Non-linear Spectroscopy, Sesto Fiorentino, Italy.,Department of Physics and Astronomy, University of Florence, Sesto Fiorentino, Italy
| | - E Michael Ostap
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Yale E Goldman
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
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29
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Behaviors and Energy Source of Mycoplasma gallisepticum Gliding. J Bacteriol 2019; 201:JB.00397-19. [PMID: 31308069 DOI: 10.1128/jb.00397-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 07/04/2019] [Indexed: 01/06/2023] Open
Abstract
Mycoplasma gallisepticum, an avian-pathogenic bacterium, glides on host tissue surfaces by using a common motility system with Mycoplasma pneumoniae In the present study, we observed and analyzed the gliding behaviors of M. gallisepticum in detail by using optical microscopes. M. gallisepticum glided at a speed of 0.27 ± 0.09 μm/s with directional changes relative to the cell axis of 0.6 degree ± 44.6 degrees/5 s without the rolling of the cell body. To examine the effects of viscosity on gliding, we analyzed the gliding behaviors under viscous environments. The gliding speed was constant in various concentrations of methylcellulose but was affected by Ficoll. To investigate the relationship between binding and gliding, we analyzed the inhibitory effects of sialyllactose on binding and gliding. The binding and gliding speed sigmoidally decreased with sialyllactose concentration, indicating the cooperative binding of the cell. To determine the direct energy source of gliding, we used a membrane-permeabilized ghost model. We permeabilized M. gallisepticum cells with Triton X-100 or Triton X-100 containing ATP and analyzed the gliding of permeabilized cells. The cells permeabilized with Triton X-100 did not show gliding; in contrast, the cells permeabilized with Triton X-100 containing ATP showed gliding at a speed of 0.014 ± 0.007 μm/s. These results indicate that the direct energy source for the gliding motility of M. gallisepticum is ATP.IMPORTANCE Mycoplasmas, the smallest bacteria, are parasitic and occasionally commensal. Mycoplasma gallisepticum is related to human-pathogenic mycoplasmas-Mycoplasma pneumoniae and Mycoplasma genitalium-which cause so-called "walking pneumonia" and nongonococcal urethritis, respectively. These mycoplasmas trap sialylated oligosaccharides, which are common targets among influenza viruses, on host trachea or urinary tract surfaces and glide to enlarge the infected areas. Interestingly, this gliding motility is not related to other bacterial motilities or eukaryotic motilities. Here, we quantitatively analyze cell behaviors in gliding and clarify the direct energy source. The results provide clues for elucidating this unique motility mechanism.
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Månsson A. Comparing models with one versus multiple myosin-binding sites per actin target zone: The power of simplicity. J Gen Physiol 2019; 151:578-592. [PMID: 30872560 PMCID: PMC6445577 DOI: 10.1085/jgp.201812301] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 02/16/2019] [Indexed: 01/21/2023] Open
Abstract
Models of muscle contraction often assume that a myosin motor interacts with areas of one to three distinct binding sites along an actin filament. Månsson shows that computational models employing different numbers of sites return similar predictions, suggesting one-site models are often sufficient. Mechanokinetic statistical models describe the mechanisms of muscle contraction on the basis of the average behavior of a large ensemble of actin–myosin motors. Such models often assume that myosin II motor domains bind to regularly spaced, discrete target zones along the actin-based thin filaments and develop force in a series of strain-dependent transitions under the turnover of ATP. The simplest models assume that there is just one myosin-binding site per target zone and a uniform spatial distribution of the myosin motor domains in relation to each site. However, most of the recently developed models assume three myosin-binding sites per target zone, and some models include a spatially explicit 3-D treatment of the myofilament lattice and thereby of the geometry of the actin–myosin contact points. Here, I show that the predictions for steady-state contractile behavior of muscle are very similar whether one or three myosin-binding sites per target zone is assumed, provided that the model responses are appropriately scaled to the number of sites. Comparison of the model predictions for isometrically contracting mammalian muscle cells suggests that each target zone contains three or more myosin-binding sites. Finally, I discuss the strengths and weaknesses of one-site spatially inexplicit models in relation to three-site models, including those that take into account the detailed 3-D geometry of the myofilament lattice. The results of this study suggest that single-site models, with reduced computational cost compared with multisite models, are useful for several purposes, e.g., facilitated molecular mechanistic insights.
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Affiliation(s)
- Alf Månsson
- Department of Chemistry and Biomedical Sciences, Faculty of Health and Life Sciences, Linnaeus University, Kalmar, Sweden
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Woody MS, Greenberg MJ, Barua B, Winkelmann DA, Goldman YE, Ostap EM. Positive cardiac inotrope omecamtiv mecarbil activates muscle despite suppressing the myosin working stroke. Nat Commun 2018; 9:3838. [PMID: 30242219 PMCID: PMC6155018 DOI: 10.1038/s41467-018-06193-2] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 08/21/2018] [Indexed: 02/05/2023] Open
Abstract
Omecamtiv mecarbil (OM) is a positive cardiac inotrope in phase-3 clinical trials for treatment of heart failure. Although initially described as a direct myosin activator, subsequent studies are at odds with this description and do not explain OM-mediated increases in cardiac performance. Here we show, via single-molecule, biophysical experiments on cardiac myosin, that OM suppresses myosin's working stroke and prolongs actomyosin attachment 5-fold, which explains inhibitory actions of the drug observed in vitro. OM also causes the actin-detachment rate to become independent of both applied load and ATP concentration. Surprisingly, increased myocardial force output in the presence of OM can be explained by cooperative thin-filament activation by OM-inhibited myosin molecules. Selective suppression of myosin is an unanticipated route to muscle activation that may guide future development of therapeutic drugs.
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Affiliation(s)
- Michael S Woody
- Graduate Group in Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania, 700A Clinical Research Building, Philadelphia, PA, 19104-6085, USA
| | - Michael J Greenberg
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, 700A Clinical Research Building, Philadelphia, PA, 19104-6085, USA.,Department of Biochemistry and Molecular Biophysics, Washington University in Saint Louis, St. Louis, 63110, MO, USA
| | - Bipasha Barua
- Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Rutgers University, 675 Hoes Lane, Piscataway, NJ, 08854, USA
| | - Donald A Winkelmann
- Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Rutgers University, 675 Hoes Lane, Piscataway, NJ, 08854, USA
| | - Yale E Goldman
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, 700A Clinical Research Building, Philadelphia, PA, 19104-6085, USA.
| | - E Michael Ostap
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, 700A Clinical Research Building, Philadelphia, PA, 19104-6085, USA.
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Pertici I, Bongini L, Melli L, Bianchi G, Salvi L, Falorsi G, Squarci C, Bozó T, Cojoc D, Kellermayer MSZ, Lombardi V, Bianco P. A myosin II nanomachine mimicking the striated muscle. Nat Commun 2018; 9:3532. [PMID: 30166542 PMCID: PMC6117265 DOI: 10.1038/s41467-018-06073-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 08/02/2018] [Indexed: 11/08/2022] Open
Abstract
The contraction of striated muscle (skeletal and cardiac muscle) is generated by ATP-dependent interactions between the molecular motor myosin II and the actin filament. The myosin motors are mechanically coupled along the thick filament in a geometry not achievable by single-molecule experiments. Here we show that a synthetic one-dimensional nanomachine, comprising fewer than ten myosin II dimers purified from rabbit psoas, performs isometric and isotonic contractions at 2 mM ATP, delivering a maximum power of 5 aW. The results are explained with a kinetic model fitted to the performance of mammalian skeletal muscle, showing that the condition for the motor coordination that maximises the efficiency in striated muscle is a minimum of 32 myosin heads sharing a common mechanical ground. The nanomachine offers a powerful tool for investigating muscle contractile-protein physiology, pathology and pharmacology without the potentially disturbing effects of the cytoskeletal-and regulatory-protein environment.
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Affiliation(s)
- Irene Pertici
- PhysioLab, University of Florence, Florence, 50019, Italy
| | | | - Luca Melli
- PhysioLab, University of Florence, Florence, 50019, Italy
- F. Hoffmann-La Roche Ltd, Basel, 4053, Switzerland
| | - Giulio Bianchi
- PhysioLab, University of Florence, Florence, 50019, Italy
| | - Luca Salvi
- PhysioLab, University of Florence, Florence, 50019, Italy
- Department of Biochemistry, University of Munich, Munich, 81377, Germany
| | - Giulia Falorsi
- PhysioLab, University of Florence, Florence, 50019, Italy
| | | | - Tamás Bozó
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, H-1094, Hungary
| | | | - Miklós S Z Kellermayer
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, H-1094, Hungary
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Do Actomyosin Single-Molecule Mechanics Data Predict Mechanics of Contracting Muscle? Int J Mol Sci 2018; 19:ijms19071863. [PMID: 29941816 PMCID: PMC6073448 DOI: 10.3390/ijms19071863] [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: 05/23/2018] [Revised: 06/19/2018] [Accepted: 06/20/2018] [Indexed: 12/15/2022] Open
Abstract
In muscle, but not in single-molecule mechanics studies, actin, myosin and accessory proteins are incorporated into a highly ordered myofilament lattice. In view of this difference we compare results from single-molecule studies and muscle mechanics and analyze to what degree data from the two types of studies agree with each other. There is reasonable correspondence in estimates of the cross-bridge power-stroke distance (7–13 nm), cross-bridge stiffness (~2 pN/nm) and average isometric force per cross-bridge (6–9 pN). Furthermore, models defined on the basis of single-molecule mechanics and solution biochemistry give good fits to experimental data from muscle. This suggests that the ordered myofilament lattice, accessory proteins and emergent effects of the sarcomere organization have only minor modulatory roles. However, such factors may be of greater importance under e.g., disease conditions. We also identify areas where single-molecule and muscle data are conflicting: (1) whether force generation is an Eyring or Kramers process with just one major power-stroke or several sub-strokes; (2) whether the myofilaments and the cross-bridges have Hookean or non-linear elasticity; (3) if individual myosin heads slip between actin sites under certain conditions, e.g., in lengthening; or (4) if the two heads of myosin cooperate.
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Liu C, Kawana M, Song D, Ruppel KM, Spudich JA. Controlling load-dependent kinetics of β-cardiac myosin at the single-molecule level. Nat Struct Mol Biol 2018; 25:505-514. [PMID: 29867217 PMCID: PMC6092189 DOI: 10.1038/s41594-018-0069-x] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 04/26/2018] [Indexed: 01/29/2023]
Abstract
Concepts in molecular tension sensing in biology are growing and have their origins in studies of muscle contraction. In the heart muscle, a key parameter of contractility is the detachment rate of myosin from actin, which determines the time that myosin is bound to actin in a force-producing state and, importantly, depends on the load (force) against which myosin works. Here we measure the detachment rate of single molecules of human β-cardiac myosin and its load dependence. We find that both can be modulated by both small-molecule compounds and cardiomyopathy-causing mutations. Furthermore, effects of mutations can be reversed by introducing appropriate compounds. Our results suggest that activating versus inhibitory perturbations of cardiac myosin are discriminated by the aggregate result on duty ratio, average force, and ultimately average power output and suggest that cardiac contractility can be controlled by tuning the load-dependent kinetics of single myosin molecules.
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Affiliation(s)
- Chao Liu
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, USA.
| | - Masataka Kawana
- Department of Medicine, Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA, USA
| | - Dan Song
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, USA
| | - Kathleen M Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, USA
- Department of Pediatrics (Cardiology), Stanford University School of Medicine, Stanford, CA, USA
| | - James A Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, USA.
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Woody MS, Capitanio M, Ostap EM, Goldman YE. Electro-optic deflectors deliver advantages over acousto-optical deflectors in a high resolution, ultra-fast force-clamp optical trap. OPTICS EXPRESS 2018; 26:11181-11193. [PMID: 29716042 PMCID: PMC6005679 DOI: 10.1364/oe.26.011181] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 03/30/2018] [Accepted: 03/30/2018] [Indexed: 06/02/2023]
Abstract
We characterized experimental artifacts arising from the non-linear response of acousto-optical deflectors (AODs) in an ultra-fast force-clamp optical trap and have shown that using electro-optical deflectors (EODs) instead eliminates these artifacts. We give an example of the effects of these artifacts in our ultra-fast force clamp studies of the interaction of myosin with actin filaments. The experimental setup, based on the concept of Capitanio et al. [Nat. Methods 9, 1013-1019 (2012)] utilizes a bead-actin-bead dumbbell held in two force-clamped optical traps which apply a load to the dumbbell to move it at a constant velocity. When myosin binds to actin, the filament motion stops quickly as the total force from the optical traps is transferred to the actomyosin attachment. We found that in our setup, AODs were unsuitable for beam steering due to non-linear variations in beam intensity and deflection angle as a function of driving frequency, likely caused by low-amplitude standing acoustic waves in the deflectors. These aberrations caused instability in the force feedback loops leading to artifactual jumps in the trap position. We demonstrate that beam steering with EODs improves the performance of our instrument. Combining the superior beam-steering capability of the EODs, force acquisition via back-focal-plane interferometry, and dual high-speed FPGA-based feedback loops, we apply precise and constant loads to study the dynamics of interactions between actin and myosin. The same concept applies to studies of other biomolecular interactions.
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Affiliation(s)
- Michael S. Woody
- University of Pennsylvania, Pennsylvania Muscle Institute and Department of Physiology, 415 Curie Blvd, Philadelphia, Pennsylvania, USA 19104
| | - Marco Capitanio
- LENS - European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy
- Department of Physics and Astronomy, University of Florence, Via Sansone 1, 50019 Sesto Fiorentino, Italy
| | - E. Michael Ostap
- University of Pennsylvania, Pennsylvania Muscle Institute and Department of Physiology, 415 Curie Blvd, Philadelphia, Pennsylvania, USA 19104
| | - Yale E. Goldman
- University of Pennsylvania, Pennsylvania Muscle Institute and Department of Physiology, 415 Curie Blvd, Philadelphia, Pennsylvania, USA 19104
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36
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Mizutani M, Tulum I, Kinosita Y, Nishizaka T, Miyata M. Detailed Analyses of Stall Force Generation in Mycoplasma mobile Gliding. Biophys J 2018; 114:1411-1419. [PMID: 29590598 PMCID: PMC5883615 DOI: 10.1016/j.bpj.2018.01.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 01/24/2018] [Accepted: 01/29/2018] [Indexed: 02/01/2023] Open
Abstract
Mycoplasma mobile is a bacterium that uses a unique mechanism to glide on solid surfaces at a velocity of up to 4.5 μm/s. Its gliding machinery comprises hundreds of units that generate the force for gliding based on the energy derived from ATP; the units catch and pull sialylated oligosaccharides fixed to solid surfaces. In this study, we measured the stall force of wild-type and mutant strains of M. mobile carrying a bead manipulated using optical tweezers. The strains that had been enhanced for binding exhibited weaker stall forces than the wild-type strain, indicating that stall force is related to force generation rather than to binding. The stall force of the wild-type strain decreased linearly from 113 to 19 picoNewtons after the addition of 0-0.5 mM free sialyllactose (a sialylated oligosaccharide), with a decrease in the number of working units. After the addition of 0.5 mM sialyllactose, the cells carrying a bead loaded using optical tweezers exhibited stepwise movements with force increments. The force increments ranged from 1 to 2 picoNewtons. Considering the 70-nm step size, this small-unit force may be explained by the large gear ratio involved in the M. mobile gliding machinery.
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Affiliation(s)
- Masaki Mizutani
- Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Japan
| | - Isil Tulum
- Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Japan; The OCU Advanced Research Institute for Natural Science and Technology, Osaka City University, Sumiyoshi-ku, Osaka, Japan
| | - Yoshiaki Kinosita
- Department of Physics, Faculty of Science, Gakushuin University, Toshima-ku, Tokyo, Japan
| | - Takayuki Nishizaka
- Department of Physics, Faculty of Science, Gakushuin University, Toshima-ku, Tokyo, Japan
| | - Makoto Miyata
- Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Japan; The OCU Advanced Research Institute for Natural Science and Technology, Osaka City University, Sumiyoshi-ku, Osaka, Japan.
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Ishii S, Kawai M, Ishiwata S, Suzuki M. Estimation of actomyosin active force maintained by tropomyosin and troponin complex under vertical forces in the in vitro motility assay system. PLoS One 2018; 13:e0192558. [PMID: 29420610 PMCID: PMC5805308 DOI: 10.1371/journal.pone.0192558] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 01/25/2018] [Indexed: 12/02/2022] Open
Abstract
The interaction between actin filaments and myosin molecular motors is a power source of a variety of cellular functions including cell division, cell motility, and muscular contraction. In vitro motility assay examines actin filaments interacting with myosin molecules that are adhered to a substrate (e.g., glass surface). This assay has been the standard method of studying the molecular mechanisms of contraction under an optical microscope. While the force generation has been measured through an optically trapped bead to which an actin filament is attached, a force vector vertical to the glass surface has been largely ignored with the in vitro motility assay. The vertical vector is created by the gap (distance) between the trapped bead and the glass surface. In this report, we propose a method to estimate the angle between the actin filament and the glass surface by optically determining the gap size. This determination requires a motorized stage in a standard epi-fluorescence microscope equipped with optical tweezers. This facile method is applied to force measurements using both pure actin filaments, and thin filaments reconstituted from actin, tropomyosin and troponin. We find that the angle-corrected force per unit filament length in the active condition (pCa = 5.0) decreases as the angle between the filament and the glass surface increases; i.e. as the force in the vertical direction increases. At the same time, we demonstrate that the force on reconstituted thin filaments is approximately 1.5 times larger than that on pure actin filaments. The range of angles we tested was between 11° and 36° with the estimated measurement error less than 6°. These results suggest the ability of cytoplasmic tropomyosin isoforms maintaining actomyosin active force to stabilize cytoskeletal architecture.
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Affiliation(s)
- Shuya Ishii
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo, Japan
| | - Masataka Kawai
- Department of Anatomy and Cell Biology, College of Medicine, University of Iowa, Iowa City, IA, United States of America
| | - Shin'ichi Ishiwata
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo, Japan
| | - Madoka Suzuki
- PRESTO, Japan Science and Technology Agency (JST), Saitama, Kawaguchi, Japan
- Research Institute for Science and Engineering, Waseda University, Tokyo, Japan
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Kopylova G, Nabiev S, Shchepkin D, Bershitsky S. Carbonylation of atrial myosin prolongs its interaction with actin. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2018; 47:11-18. [PMID: 28409219 DOI: 10.1007/s00249-017-1209-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 03/22/2017] [Accepted: 04/07/2017] [Indexed: 11/26/2022]
Abstract
Carbonylation induced by hyperthyroidism suppresses force generation of skeletal myosin and sliding velocity of actin filaments in an in vitro motility assay. However, its effects on cardiac myosin at the molecular level have not been studied. Hyperthyroidism induces a change in expression of myosin heavy chains in ventricles, which may mask the effect of oxidation. In contrast to ventricular myosin, expression of myosin heavy chains in the atrium does not change upon hyperthyroidism and enables investigation of the effect of oxidation on cardiac myosin. We studied the influence of carbonylation, a type of protein oxidation, on the motor function of atrial myosin and Ca2+ regulation of actin-myosin interaction at the level of isolated proteins and single molecules using an in vitro motility assay and an optical trap. Carbonylation of atrial myosin prolonged its attached state on actin and decreased maximal sliding velocity of thin filaments over this myosin but did not affect the calcium sensitivity of the velocity. The results indicate that carbonylation of atrial myosin induced by hyperthyroidism can be a rate-limiting factor of atrium contractility and so participates in the genesis of heart failure in hyperthyroidism.
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Affiliation(s)
- G Kopylova
- Institute of Immunology and Physiology, Russian Academy of Sciences, Pervomayskaya ul. 106, Yekaterinburg, 620049, Russia.
| | - S Nabiev
- Institute of Immunology and Physiology, Russian Academy of Sciences, Pervomayskaya ul. 106, Yekaterinburg, 620049, Russia
| | - D Shchepkin
- Institute of Immunology and Physiology, Russian Academy of Sciences, Pervomayskaya ul. 106, Yekaterinburg, 620049, Russia
| | - S Bershitsky
- Institute of Immunology and Physiology, Russian Academy of Sciences, Pervomayskaya ul. 106, Yekaterinburg, 620049, Russia
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Fenwick AJ, Wood AM, Tanner BCW. Effects of cross-bridge compliance on the force-velocity relationship and muscle power output. PLoS One 2017; 12:e0190335. [PMID: 29284062 PMCID: PMC5746261 DOI: 10.1371/journal.pone.0190335] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 12/12/2017] [Indexed: 11/19/2022] Open
Abstract
Muscles produce force and power by utilizing chemical energy through ATP hydrolysis. During concentric contractions (shortening), muscles generate less force compared to isometric contractions, but consume greater amounts of energy as shortening velocity increases. Conversely, more force is generated and less energy is consumed during eccentric muscle contractions (lengthening). This relationship between force, energy use, and the velocity of contraction has important implications for understanding muscle efficiency, but the molecular mechanisms underlying this behavior remain poorly understood. Here we used spatially-explicit, multi-filament models of Ca2+-regulated force production within a half-sarcomere to simulate how force production, energy utilization, and the number of bound cross-bridges are affected by dynamic changes in sarcomere length. These computational simulations show that cross-bridge binding increased during slow-velocity concentric and eccentric contractions, compared to isometric contractions. Over the full ranges of velocities that we simulated, cross-bridge cycling and energy utilization (i.e. ATPase rates) increased during shortening, and decreased during lengthening. These findings are consistent with the Fenn effect, but arise from a complicated relationship between velocity-dependent cross-bridge recruitment and cross-bridge cycling kinetics. We also investigated how force production, power output, and energy utilization varied with cross-bridge and myofilament compliance, which is impossible to address under typical experimental conditions. These important simulations show that increasing cross-bridge compliance resulted in greater cross-bridge binding and ATPase activity, but less force was generated per cross-bridge and throughout the sarcomere. These data indicate that the efficiency of force production decreases in a velocity-dependent manner, and that this behavior is sensitive to cross-bridge compliance. In contrast, significant effects of myofilament compliance on force production were only observed during isometric contractions, suggesting that changes in myofilament compliance may not influence power output during non-isometric contractions as greatly as changes in cross-bridge compliance. These findings advance our understanding of how cross-bridge and myofilament properties underlie velocity-dependent changes in contractile efficiency during muscle movement.
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Affiliation(s)
- Axel J. Fenwick
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, Washington, United States of America
| | - Alexander M. Wood
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, Washington, United States of America
| | - Bertrand C. W. Tanner
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, Washington, United States of America
- * E-mail:
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Pyrpassopoulos S, Shuman H, Ostap EM. Adhesion force and attachment lifetime of the KIF16B-PX domain interaction with lipid membranes. Mol Biol Cell 2017; 28:3315-3322. [PMID: 28931594 PMCID: PMC5687032 DOI: 10.1091/mbc.e17-05-0324] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 08/28/2017] [Accepted: 09/13/2017] [Indexed: 11/21/2022] Open
Abstract
KIF16B is a motor that binds early endosomes and controls the recycling of receptors. It has a PX domain that binds PI(3)P, which has been proposed to mechanically link motor to cargo. We determined the strength of this bond and its lifetime under load, and found it to be a suitable mechanical linkage for the KIF16B motor under working conditions. KIF16B is a highly processive kinesin-3 family member that participates in the trafficking and tubulation of early endosomes along microtubules. KIF16B attaches to lipid cargoes via a PX motif at its C-terminus, which has nanomolar affinity for bilayers containing phosphatidylinositol-3-phosphate (PI[3]P). As the PX domain has been proposed to be a primary mechanical anchor for the KIF16B-cargo attachment, we measured the adhesion forces and detachment kinetics of the PX domain as it interacts with membranes containing 2% PI(3)P and 98% phosphatidylcholine. Using optical tweezers, we found that the adhesion strength of a single PX domain ranged between 19 and 54 pN at loading rates between 80 and 1500 pN/s. These forces are substantially larger than the interaction of the adhesion of a pleckstrin homology domain with phosphatidylinositol 4,5-bisphosphate. This increased adhesion is the result of the membrane insertion of hydrophobic residues adjacent to the PI(3)P binding site, in addition to electrostatic interactions with PI(3)P. Attachment lifetimes under load decrease monotonically with force, indicating slip-bond behavior. However, the lifetime of membrane attachment under load appears to be well matched to the duration of processive motility of the KIF16B motor, indicating the PX domain is a suitable mechanical anchor for intracellular transport.
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Affiliation(s)
- Serapion Pyrpassopoulos
- Pennsylvania Muscle Institute, Department of Physiology, and Center for Engineering Mechanobiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104
| | - Henry Shuman
- Pennsylvania Muscle Institute, Department of Physiology, and Center for Engineering Mechanobiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104
| | - E Michael Ostap
- Pennsylvania Muscle Institute, Department of Physiology, and Center for Engineering Mechanobiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104
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41
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Bibó A, Károlyi G, Kovács M. Unrevealed part of myosin's powerstroke accounts for high efficiency of muscle contraction. Biochim Biophys Acta Gen Subj 2017; 1861:2325-2333. [DOI: 10.1016/j.bbagen.2017.05.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 05/02/2017] [Accepted: 05/24/2017] [Indexed: 11/30/2022]
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Huang DL, Bax NA, Buckley CD, Weis WI, Dunn AR. Vinculin forms a directionally asymmetric catch bond with F-actin. Science 2017; 357:703-706. [PMID: 28818948 PMCID: PMC5821505 DOI: 10.1126/science.aan2556] [Citation(s) in RCA: 168] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 07/11/2017] [Indexed: 11/02/2022]
Abstract
Vinculin is an actin-binding protein thought to reinforce cell-cell and cell-matrix adhesions. However, how mechanical load affects the vinculin-F-actin bond is unclear. Using a single-molecule optical trap assay, we found that vinculin forms a force-dependent catch bond with F-actin through its tail domain, but with lifetimes that depend strongly on the direction of the applied force. Force toward the pointed (-) end of the actin filament resulted in a bond that was maximally stable at 8 piconewtons, with a mean lifetime (12 seconds) 10 times as long as the mean lifetime when force was applied toward the barbed (+) end. A computational model of lamellipodial actin dynamics suggests that the directionality of the vinculin-F-actin bond could establish long-range order in the actin cytoskeleton. The directional and force-stabilized binding of vinculin to F-actin may be a mechanism by which adhesion complexes maintain front-rear asymmetry in migrating cells.
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Affiliation(s)
- Derek L Huang
- Biophysics Program, Stanford University, Stanford, CA 94305, USA
| | - Nicolas A Bax
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Craig D Buckley
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
| | - William I Weis
- Biophysics Program, Stanford University, Stanford, CA 94305, USA.
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA
| | - Alexander R Dunn
- Biophysics Program, Stanford University, Stanford, CA 94305, USA.
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
- Stanford Cardiovascular Institute, Stanford University, Stanford, CA 94305, USA
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43
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Shchepkin DV, Nabiev SR, Kopylova GV, Matyushenko AM, Levitsky DI, Bershitsky SY, Tsaturyan AK. Cooperativity of myosin interaction with thin filaments is enhanced by stabilizing substitutions in tropomyosin. J Muscle Res Cell Motil 2017; 38:183-191. [PMID: 28540577 DOI: 10.1007/s10974-017-9472-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 05/22/2017] [Indexed: 11/24/2022]
Abstract
Muscle contraction is powered by myosin interaction with actin-based thin filaments containing Ca2+-regulatory proteins, tropomyosin and troponin. Coiled-coil tropomyosin molecules form a long helical strand that winds around actin filament and either shields actin from myosin binding or opens it. Non-canonical residues G126 and D137 in the central part of tropomyosin destabilize its coiled-coil structure. Their substitutions for canonical ones, G126R and D137L, increase structural stability and the velocity of sliding of reconstructed thin filaments along myosin coated surface. The effect of these stabilizing mutations on force of the actin-myosin interaction is unknown. It also remains unclear whether the stabilization affects single actin-myosin interactions or it modifies the cooperativity of the binding of myosin molecules to actin. We used an optical trap to measure the effects of the stabilization on step size, unitary force and duration of the interactions at low and high load and compared the results with those obtained in an in vitro motility assay. We found that significant prolongation of lifetime of the actin-myosin complex under high load observed at high extent of tropomyosin stabilization, i.e. with double mutant, G126R/D137L, correlates with higher force in the motility assay. Also, the higher the extent of stabilization of tropomyosin, the fewer myosin molecules are needed to propel the thin filaments. The data suggest that the effects of the stabilizing mutations in tropomyosin on the myosin interaction with regulated thin filaments are mainly realized via cooperative mechanisms by increasing the size of cooperative unit.
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Affiliation(s)
- Daniil V Shchepkin
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, 620049, Russia
| | - Salavat R Nabiev
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, 620049, Russia
| | - Galina V Kopylova
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, 620049, Russia
| | - Alexander M Matyushenko
- A.N. Bach Institute of Biochemistry, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia.,Department of Biochemistry, School of Biology, Moscow State University, Moscow, 119234, Russia
| | - Dmitrii I Levitsky
- A.N. Bach Institute of Biochemistry, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia.,A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, 119234, Russia
| | - Sergey Y Bershitsky
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, 620049, Russia
| | - Andrey K Tsaturyan
- Institute of Mechanics, Moscow State University, 1 Mitchurinsky prosp., Moscow, 119192, Russia.
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44
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Bameta T, Das D, Das D, Padinhateeri R, Inamdar MM. Sufficient conditions for the additivity of stall forces generated by multiple filaments or motors. Phys Rev E 2017; 95:022406. [PMID: 28297971 DOI: 10.1103/physreve.95.022406] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Indexed: 06/06/2023]
Abstract
Molecular motors and cytoskeletal filaments work collectively most of the time under opposing forces. This opposing force may be due to cargo carried by motors or resistance coming from the cell membrane pressing against the cytoskeletal filaments. Some recent studies have shown that the collective maximum force (stall force) generated by multiple cytoskeletal filaments or molecular motors may not always be just a simple sum of the stall forces of the individual filaments or motors. To understand this excess or deficit in the collective force, we study a broad class of models of both cytoskeletal filaments and molecular motors. We argue that the stall force generated by a group of filaments or motors is additive, that is, the stall force of N number of filaments (motors) is N times the stall force of one filament (motor), when the system is reversible at stall. Conversely, we show that this additive property typically does not hold true when the system is irreversible at stall. We thus present a novel and unified understanding of the existing models exhibiting such non-addivity, and generalise our arguments by developing new models that demonstrate this phenomena. We also propose a quantity similar to thermodynamic efficiency to easily predict this deviation from stall-force additivity for filament and motor collectives.
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Affiliation(s)
- Tripti Bameta
- UM-DAE Center for Excellence in Basic Sciences, University of Mumbai, Vidhyanagari Campus, Mumbai-400098, India
| | - Dipjyoti Das
- Department of Physics, Indian Institute of Technology, Bombay, Powai, Mumbai-400 076, India
| | - Dibyendu Das
- Department of Physics, Indian Institute of Technology, Bombay, Powai, Mumbai-400 076, India
| | - Ranjith Padinhateeri
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai-400 076, India
| | - Mandar M Inamdar
- Department of Civil Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai-400 076, India
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45
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Kawana M, Sarkar SS, Sutton S, Ruppel KM, Spudich JA. Biophysical properties of human β-cardiac myosin with converter mutations that cause hypertrophic cardiomyopathy. SCIENCE ADVANCES 2017; 3:e1601959. [PMID: 28246639 PMCID: PMC5302870 DOI: 10.1126/sciadv.1601959] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 01/09/2017] [Indexed: 05/20/2023]
Abstract
Hypertrophic cardiomyopathy (HCM) affects 1 in 500 individuals and is an important cause of arrhythmias and heart failure. Clinically, HCM is characterized as causing hypercontractility, and therapies are aimed toward controlling the hyperactive physiology. Mutations in the β-cardiac myosin comprise ~40% of genetic mutations associated with HCM, and the converter domain of myosin is a hotspot for HCM-causing mutations; however, the underlying primary effects of these mutations on myosin's biomechanical function remain elusive. We hypothesize that these mutations affect the biomechanical properties of myosin, such as increasing its intrinsic force and/or its duty ratio and therefore the ensemble force of the sarcomere. Using recombinant human β-cardiac myosin, we characterize the molecular effects of three severe HCM-causing converter domain mutations: R719W, R723G, and G741R. Contrary to our hypothesis, the intrinsic forces of R719W and R723G mutant myosins are decreased compared to wild type and unchanged for G741R. Actin and regulated thin filament gliding velocities are ~15% faster for R719W and R723G myosins, whereas there is no change in velocity for G741R. Adenosine triphosphatase activities and the load-dependent velocity change profiles of all three mutant proteins are very similar to those of wild type. These results indicate that the net biomechanical properties of human β-cardiac myosin carrying these converter domain mutations are very similar to those of wild type or are even slightly hypocontractile, leading us to consider an alternative mechanism for the clinically observed hypercontractility. Future work includes how these mutations affect protein interactions within the sarcomere that increase the availability of myosin heads participating in force production.
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Affiliation(s)
- Masataka Kawana
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
- Department of Medicine, Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Saswata S. Sarkar
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Shirley Sutton
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Kathleen M. Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
- Department of Pediatrics (Cardiology), Stanford University School of Medicine, Stanford, CA 94305, USA
- Corresponding author. (J.A.S.); (K.M.R.)
| | - James A. Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
- Corresponding author. (J.A.S.); (K.M.R.)
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46
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Bugiel M, Jannasch A, Schäffer E. Implementation and Tuning of an Optical Tweezers Force-Clamp Feedback System. Methods Mol Biol 2017; 1486:109-136. [PMID: 27844427 DOI: 10.1007/978-1-4939-6421-5_5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Feedback systems can be used to control the value of a system variable. In optical tweezers, active feedback is often implemented to either keep the position or tension applied to a single biomolecule constant. Here, we describe the implementation of the latter: an optical force-clamp setup that can be used to study the motion of processive molecular motors under a constant load. We describe the basics of a software-implemented proportional-integral-derivative (PID) controller, how to tune it, and how to determine its optimal feedback rate. Limitations, possible feed-forward applications, and extensions into two- and three-dimensional optical force clamps are discussed. The feedback is ultimately limited by thermal fluctuations and the compliance of the involved molecules. To investigate a particular mechanical process, understanding the basics and limitations of the feedback system will be helpful for choosing the proper feedback hardware, for optimizing the system parameters, and for the design of the experiment.
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Affiliation(s)
- Michael Bugiel
- Center for Plant Molecular Biology, Universität Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany
| | - Anita Jannasch
- Center for Plant Molecular Biology, Universität Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany
| | - Erik Schäffer
- Center for Plant Molecular Biology, Universität Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany.
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47
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Greenberg MJ, Shuman H, Ostap EM. Measuring the Kinetic and Mechanical Properties of Non-processive Myosins Using Optical Tweezers. Methods Mol Biol 2017; 1486:483-509. [PMID: 27844441 DOI: 10.1007/978-1-4939-6421-5_19] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The myosin superfamily of molecular motors utilizes energy from ATP hydrolysis to generate force and motility along actin filaments in a diverse array of cellular processes. These motors are structurally, kinetically, and mechanically tuned to their specific molecular roles in the cell. Optical trapping techniques have played a central role in elucidating the mechanisms by which myosins generate force and in exposing the remarkable diversity of myosin functions. Here, we present thorough methods for measuring and analyzing interactions between actin and non-processive myosins using optical trapping techniques.
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Affiliation(s)
- Michael J Greenberg
- Department of Physiology, The Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA. .,Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., Campus Box 8231, St. Louis, MO, 63110, USA.
| | - Henry Shuman
- Department of Physiology, The Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - E Michael Ostap
- Department of Physiology, The Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
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48
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Nikitina LV, Kopylova GV, Shchepkin DV, Nabiev SR, Bershitsky SY. Investigations of Molecular Mechanisms of Actin-Myosin Interactions in Cardiac Muscle. BIOCHEMISTRY (MOSCOW) 2016; 80:1748-63. [PMID: 26878579 DOI: 10.1134/s0006297915130106] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The functional characteristics of cardiac muscle depend on the composition of protein isoforms in the cardiomyocyte contractile machinery. In the ventricular myocardium of mammals, several isoforms of contractile and regulatory proteins are expressed - two isoforms of myosin (V1 and V3) and three isoforms of tropomyosin chains (α, β, and κ). Expression of protein isoforms depends on the animal species, its age and hormonal status, and this can change with pathologies of the myocardium. Mutations in these proteins can lead to cardiomyopathies. The functional significance of the protein isoform composition has been studied mainly on intact hearts or on isolated preparations of myocardium, which could not provide a clear comprehension of the role of each particular isoform. Present-day experimental techniques such as an optical trap and in vitro motility assay make it possible to investigate the phenomena of interactions of contractile and regulatory proteins on the molecular level, thus avoiding effects associated with properties of a whole muscle or muscle tissue. These methods enable free combining of the isoforms to test the molecular mechanisms of their participation in the actin-myosin interaction. Using the optical trap and the in vitro motility assay, we have studied functional characteristics of the cardiac myosin isoforms, molecular mechanisms of the calcium-dependent regulation of actin-myosin interaction, and the role of myosin and tropomyosin isoforms in the cooperativity mechanisms in myocardium. The knowledge of molecular mechanisms underlying myocardial contractility and its regulation is necessary for comprehension of cardiac muscle functioning, its disorders in pathologies, and for development of approaches for their correction.
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Affiliation(s)
- L V Nikitina
- Institute of Immunology and Physiology, Ural Division of the Russian Academy of Sciences, Ekaterinburg, 620041, Russia.
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49
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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: 111] [Impact Index Per Article: 13.9] [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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50
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Two-boundary first exit time of Gauss-Markov processes for stochastic modeling of acto-myosin dynamics. J Math Biol 2016; 74:1511-1531. [PMID: 27671484 DOI: 10.1007/s00285-016-1061-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 09/14/2016] [Indexed: 10/20/2022]
Abstract
We consider a stochastic differential equation in a strip, with coefficients suitably chosen to describe the acto-myosin interaction subject to time-varying forces. By simulating trajectories of the stochastic dynamics via an Euler discretization-based algorithm, we fit experimental data and determine the values of involved parameters. The steps of the myosin are represented by the exit events from the strip. Motivated by these results, we propose a specific stochastic model based on the corresponding time-inhomogeneous Gauss-Markov and diffusion process evolving between two absorbing boundaries. We specify the mean and covariance functions of the stochastic modeling process taking into account time-dependent forces including the effect of an external load. We accurately determine the probability density function (pdf) of the first exit time (FET) from the strip by solving a system of two non singular second-type Volterra integral equations via a numerical quadrature. We provide numerical estimations of the mean of FET as approximations of the dwell-time of the proteins dynamics. The percentage of backward steps is given in agreement to experimental data. Numerical and simulation results are compared and discussed.
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