1
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Matsuda K, Jung W, Sato Y, Kobayashi T, Yamagishi M, Kim T, Yajima J. Myosin-induced F-actin fragmentation facilitates contraction of actin networks. Cytoskeleton (Hoboken) 2024; 81:339-355. [PMID: 38456577 PMCID: PMC11333167 DOI: 10.1002/cm.21848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 01/19/2024] [Accepted: 02/21/2024] [Indexed: 03/09/2024]
Abstract
Mechanical forces play a crucial role in diverse physiological processes, such as cell migration, cytokinesis, and morphogenesis. The actin cytoskeleton generates a large fraction of the mechanical forces via molecular interactions between actin filaments (F-actins) and myosin motors. Recent studies have shown that the common tendency of actomyosin networks to contract into a smaller structure deeply involves F-actin buckling induced by motor activities, fragmentation of F-actins, and the force-dependent unbinding of cross-linkers that inter-connect F-actins. The fragmentation of F-actins was shown to originate from either buckling or tensile force from previous single-molecule experiments. While the role of buckling in network contraction has been studied extensively, to date, the role of tension-induced F-actin fragmentation in network contraction has not been investigated. In this study, we employed in vitro experiments and an agent-based computational model to illuminate when and how the tension-induced F-actin fragmentation facilitates network contraction. Our experiments demonstrated that F-actins can be fragmented due to tensile forces, immediately followed by catastrophic rupture and contraction of networks. Using the agent-based model, we showed that F-actin fragmentation by tension results in distinct rupture dynamics different from that observed in networks only with cross-linker unbinding. Moreover, we found that tension-induced F-actin fragmentation is particularly important for the contraction of networks with high connectivity. Results from our study shed light on an important regulator of the contraction of actomyosin networks which has been neglected. In addition, our results provide insights into the rupture mechanisms of polymeric network structures and bio-inspired materials.
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Affiliation(s)
- Kyohei Matsuda
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, 153-8902, Japan
| | - Wonyeong Jung
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, 47907, United States
| | - Yusei Sato
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, 153-8902, Japan
| | - Takuya Kobayashi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, 153-8902, Japan
| | - Masahiko Yamagishi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, 153-8902, Japan
- Komaba Institute for Science, The University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
| | - Taeyoon Kim
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, 47907, United States
- Faculty of Science and Technology, Keio University, Kohoku Ward, Yokohama 223-0061, Japan
| | - Junichiro Yajima
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, 153-8902, Japan
- Komaba Institute for Science, The University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
- Research Center for Complex Systems Biology, The University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
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2
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Serrano Nájera G, Plum AM, Steventon B, Weijer CJ, Serra M. Control of Modular Tissue Flows Shaping the Embryo in Avian Gastrulation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.04.601785. [PMID: 39026830 PMCID: PMC11257462 DOI: 10.1101/2024.07.04.601785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
Avian gastrulation requires coordinated flows of thousands of cells to form the body plan. We quantified these flows using their fundamental kinematic units: one attractor and two repellers constituting its Dynamic Morphoskeleton (DM). We have also elucidated the mechanistic origin of the attractor, marking the primitive streak (PS), and controlled its shape, inducing gastrulation flows in the chick embryo that are typical of other vertebrates. However, the origins of repellers and dynamic embryo shape remain unclear. Here, we address these questions using active matter physics and experiments. Repeller 1, separating the embryo proper (EP) from extraembryonic (EE) tissues, arises from the tug-of-war between EE epiboly and EP isotropic myosin-induced active stress. Repeller 2, bisecting the anterior and posterior PS and associated with embryo shape change, arises from anisotropic myosin-induced active intercalation in the mesendoderm. Combining mechanical confinement with inhibition of mesendoderm induction, we eliminated either one or both repellers, as predicted by our model. Our results reveal a remarkable modularity of avian gastrulation flows delineated by the DM, uncovering the mechanistic roles of EE epiboly, EP active constriction, mesendoderm intercalation and ingression. These findings offer a new perspective for deconstructing morphogenetic flows, uncovering their modular origin, and aiding synthetic morphogenesis.
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Affiliation(s)
| | - Alex M. Plum
- Department of Physics, University of California San Diego, CA 92093, USA
| | - Ben Steventon
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
| | - Cornelis J. Weijer
- Division of Molec. Cell and Dev. Biology, School of Life Sciences, Univ. of Dundee, UK
| | - Mattia Serra
- Department of Physics, University of California San Diego, CA 92093, USA
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3
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Chinthalapudi K, Heissler SM. Structure, regulation, and mechanisms of nonmuscle myosin-2. Cell Mol Life Sci 2024; 81:263. [PMID: 38878079 PMCID: PMC11335295 DOI: 10.1007/s00018-024-05264-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 04/24/2024] [Accepted: 04/30/2024] [Indexed: 06/23/2024]
Abstract
Members of the myosin superfamily of molecular motors are large mechanochemical ATPases that are implicated in an ever-expanding array of cellular functions. This review focuses on mammalian nonmuscle myosin-2 (NM2) paralogs, ubiquitous members of the myosin-2 family of filament-forming motors. Through the conversion of chemical energy into mechanical work, NM2 paralogs remodel and shape cells and tissues. This process is tightly controlled in time and space by numerous synergetic regulation mechanisms to meet cellular demands. We review how recent advances in structural biology together with elegant biophysical and cell biological approaches have contributed to our understanding of the shared and unique mechanisms of NM2 paralogs as they relate to their kinetics, regulation, assembly, and cellular function.
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Affiliation(s)
- Krishna Chinthalapudi
- Department of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University College of Medicine, Columbus, OH, 43210, USA
| | - Sarah M Heissler
- Department of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University College of Medicine, Columbus, OH, 43210, USA.
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4
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Maxian O, Mogilner A. Helical motors and formins synergize to compact chiral filopodial bundles: A theoretical perspective. Eur J Cell Biol 2024; 103:151383. [PMID: 38237507 DOI: 10.1016/j.ejcb.2023.151383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 12/19/2023] [Accepted: 12/30/2023] [Indexed: 01/28/2024] Open
Abstract
Chiral actin bundles have been shown to play an important role in cell dynamics, but our understanding of the molecular mechanisms which combine to generate chirality remains incomplete. To address this, we numerically simulate a crosslinked filopodial bundle under the actions of helical myosin motors and/or formins and examine the collective buckling and twisting of the actin bundle. We first show that a number of proposed mechanisms to buckle polymerizing actin bundles without motor activity fail under biologically-realistic parameters. We then demonstrate that a simplified model of myosin spinning action at the bundle base effectively "braids" the bundle, but cannot control compaction at the fiber tips. Finally, we show that formin-mediated polymerization and motor activity can act synergitically to compact filopodium bundles, as motor activity bends filaments into shapes that activate twist forces induced by formins. Stochastic fluctuations of actin polymerization rates and slower cross linking dynamics both increase buckling and decrease compaction. We discuss implications of our findings for mechanisms of cytoskeletal chirality.
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Affiliation(s)
- Ondrej Maxian
- Courant Institute, New York University, New York, NY 10012, USA; Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60615, USA; Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60615, USA
| | - Alex Mogilner
- Courant Institute, New York University, New York, NY 10012, USA; Department of Biology, New York University, New York, NY 10012, USA.
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5
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Mittal N, Michels EB, Massey AE, Qiu Y, Royer-Weeden SP, Smith BR, Cartagena-Rivera AX, Han SJ. Myosin-independent stiffness sensing by fibroblasts is regulated by the viscoelasticity of flowing actin. COMMUNICATIONS MATERIALS 2024; 5:6. [PMID: 38741699 PMCID: PMC11090405 DOI: 10.1038/s43246-024-00444-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 01/02/2024] [Indexed: 05/16/2024]
Abstract
The stiffness of the extracellular matrix induces differential tension within integrin-based adhesions, triggering differential mechanoresponses. However, it has been unclear if the stiffness-dependent differential tension is induced solely by myosin activity. Here, we report that in the absence of myosin contractility, 3T3 fibroblasts still transmit stiffness-dependent differential levels of traction. This myosin-independent differential traction is regulated by polymerizing actin assisted by actin nucleators Arp2/3 and formin where formin has a stronger contribution than Arp2/3 to both traction and actin flow. Intriguingly, despite only slight changes in F-actin flow speed observed in cells with the combined inhibition of Arp2/3 and myosin compared to cells with sole myosin inhibition, they show a 4-times reduction in traction than cells with myosin-only inhibition. Our analyses indicate that traditional models based on rigid F-actin are inadequate for capturing such dramatic force reduction with similar actin flow. Instead, incorporating the F-actin network's viscoelastic properties is crucial. Our new model including the F-actin viscoelasticity reveals that Arp2/3 and formin enhance stiffness sensitivity by mechanically reinforcing the F-actin network, thereby facilitating more effective transmission of flow-induced forces. This model is validated by cell stiffness measurement with atomic force microscopy and experimental observation of model-predicted stiffness-dependent actin flow fluctuation.
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Affiliation(s)
- Nikhil Mittal
- Department of Biomedical Engineering, Michigan Technological University, Houghton, MI, USA
- Health Research Institute, Michigan Technological University, Houghton, MI, USA
| | - Etienne B. Michels
- Department of Biomedical Engineering, Michigan Technological University, Houghton, MI, USA
| | - Andrew E. Massey
- Section on Mechanobiology, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA
| | - Yunxiu Qiu
- Department of Biomedical Engineering, Michigan State University, Lansing, MI, USA
| | - Shaina P. Royer-Weeden
- Department of Biomedical Engineering, Michigan Technological University, Houghton, MI, USA
| | - Bryan R. Smith
- Department of Biomedical Engineering, Michigan State University, Lansing, MI, USA
| | - Alexander X. Cartagena-Rivera
- Section on Mechanobiology, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA
| | - Sangyoon J. Han
- Department of Biomedical Engineering, Michigan Technological University, Houghton, MI, USA
- Health Research Institute, Michigan Technological University, Houghton, MI, USA
- Department of Mechanical Engineering and Engineering Mechanics, Michigan Technological University, Houghton, MI, USA
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6
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Artcibasova A, Wang L, Anchisi S, Yamauchi Y, Schmolke M, Matthias P, Stelling J. A quantitative model for virus uncoating predicts influenza A infectivity. Cell Rep 2023; 42:113558. [PMID: 38103200 DOI: 10.1016/j.celrep.2023.113558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 10/13/2023] [Accepted: 11/22/2023] [Indexed: 12/18/2023] Open
Abstract
For virus infection of new host cells, the disassembly of the protective outer protein shell (capsid) is a critical step, but the mechanisms and host-virus interactions underlying the dynamic, active, and regulated uncoating process are largely unknown. Here, we develop an experimentally supported, multiscale kinetics model that elucidates mechanisms of influenza A virus (IAV) uncoating in cells. Biophysical modeling demonstrates that interactions between capsid M1 proteins, host histone deacetylase 6 (HDAC6), and molecular motors can physically break the capsid in a tug-of-war mechanism. Biochemical analysis and biochemical-biophysical modeling identify unanchored ubiquitin chains as essential and allow robust prediction of uncoating efficiency in cells. Remarkably, the different infectivity of two clinical strains can be ascribed to a single amino acid variation in M1 that affects binding to HDAC6. By identifying crucial modules of viral infection kinetics, the mechanisms and models presented here could help formulate novel strategies for broad-range antiviral treatment.
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Affiliation(s)
- Alina Artcibasova
- Department of Biosystems Science and Engineering and SIB Swiss Institute of Bioinformatics, ETH Zurich, 4058 Basel, Switzerland
| | - Longlong Wang
- Friedrich Miescher Institute for Biomedical Research (FMI), 4058 Basel, Switzerland; Faculty of Sciences, University of Basel, 4031 Basel, Switzerland
| | - Stephanie Anchisi
- Department of Microbiology and Molecular Medicine and Geneva Center of Inflammation Research, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland
| | - Yohei Yamauchi
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
| | - Mirco Schmolke
- Department of Microbiology and Molecular Medicine and Geneva Center of Inflammation Research, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland
| | - Patrick Matthias
- Friedrich Miescher Institute for Biomedical Research (FMI), 4058 Basel, Switzerland; Faculty of Sciences, University of Basel, 4031 Basel, Switzerland.
| | - Jörg Stelling
- Department of Biosystems Science and Engineering and SIB Swiss Institute of Bioinformatics, ETH Zurich, 4058 Basel, Switzerland.
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7
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Vitriol EA, Quintanilla MA, Tidei JJ, Troughton LD, Cody A, Cisterna BA, Jane ML, Oakes PW, Beach JR. Nonmuscle myosin 2 filaments are processive in cells. Biophys J 2023; 122:3678-3689. [PMID: 37218133 PMCID: PMC10541485 DOI: 10.1016/j.bpj.2023.05.014] [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: 02/24/2023] [Revised: 04/26/2023] [Accepted: 05/18/2023] [Indexed: 05/24/2023] Open
Abstract
Directed transport of cellular components is often dependent on the processive movements of cytoskeletal motors. Myosin 2 motors predominantly engage actin filaments of opposing orientation to drive contractile events and are therefore not traditionally viewed as processive. However, recent in vitro experiments with purified nonmuscle myosin 2 (NM2) demonstrated myosin 2 filaments could move processively. Here, we establish processivity as a cellular property of NM2. Processive runs in central nervous system-derived CAD cells are most apparent on bundled actin in protrusions that terminate at the leading edge. We find that processive velocities in vivo are consistent with in vitro measurements. NM2 makes these processive runs in its filamentous form against lamellipodia retrograde flow, though anterograde movement can still occur in the absence of actin dynamics. Comparing the processivity of NM2 isoforms, we find that NM2A moves slightly faster than NM2B. Finally, we demonstrate that this is not a cell-specific property, as we observe processive-like movements of NM2 in the lamella and subnuclear stress fibers of fibroblasts. Collectively, these observations further broaden NM2 functionality and the biological processes in which the already ubiquitous motor can contribute.
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Affiliation(s)
- Eric A Vitriol
- Department of Neuroscience and Regenerative Medicine, Augusta University, Augusta, Georgia.
| | - Melissa A Quintanilla
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois
| | - Joseph J Tidei
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois
| | - Lee D Troughton
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois
| | - Abigail Cody
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois
| | - Bruno A Cisterna
- Department of Neuroscience and Regenerative Medicine, Augusta University, Augusta, Georgia
| | - Makenzie L Jane
- Department of Neuroscience and Regenerative Medicine, Augusta University, Augusta, Georgia
| | - Patrick W Oakes
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois.
| | - Jordan R Beach
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois.
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8
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Balaban AE, Nguyen LTS, Parajón E, Robinson DN. Nonmuscle myosin IIB is a driver of cellular reprogramming. Mol Biol Cell 2023; 34:ar71. [PMID: 37074945 PMCID: PMC10295488 DOI: 10.1091/mbc.e21-08-0386] [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: 08/09/2021] [Revised: 03/27/2023] [Accepted: 04/10/2023] [Indexed: 04/20/2023] Open
Abstract
Nonmuscle myosin IIB (NMIIB) is considered a primary force generator during cell motility. Yet many cell types, including motile cells, do not necessarily express NMIIB. Given the potential of cell engineering for the next wave of technologies, adding back NMIIB could be a strategy for creating supercells with strategically altered cell morphology and motility. However, we wondered what unforeseen consequences could arise from such an approach. Here, we leveraged pancreatic cancer cells, which do not express NMIIB. We generated a series of cells where we added back NMIIB and strategic mutants that increase the ADP-bound time or alter the phosphorylation control of bipolar filament assembly. We characterized the cellular phenotypes and conducted RNA-seq analysis. The addition of NMIIB and the different mutants all have specific consequences for cell morphology, metabolism, cortical tension, mechanoresponsiveness, and gene expression. Major modes of ATP production are shifted, including alterations in spare respiratory capacity and the dependence on glycolysis or oxidative phosphorylation. Several metabolic and growth pathways undergo significant changes in gene expression. This work demonstrates that NMIIB is highly integrated with many cellular systems and simple cell engineering has a profound impact that extends beyond the primary contractile activity presumably being added to the cells.
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Affiliation(s)
- Amanda E. Balaban
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Ly T. S. Nguyen
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Eleana Parajón
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Douglas N. Robinson
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Departments of Pharmacology and Molecular Sciences, Medicine, and Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218
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9
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Vitriol EA, Quintanilla MA, Tidei JJ, Troughton LD, Cody A, Cisterna BA, Jane ML, Oakes PW, Beach JR. Non-muscle myosin 2 filaments are processive in cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.24.529920. [PMID: 36865321 PMCID: PMC9980172 DOI: 10.1101/2023.02.24.529920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2023]
Abstract
Directed transport of cellular components is often dependent on the processive movements of cytoskeletal motors. Myosin 2 motors predominantly engage actin filaments of opposing orientation to drive contractile events, and are therefore not traditionally viewed as processive. However, recent in vitro experiments with purified non-muscle myosin 2 (NM2) demonstrated myosin 2 filaments could move processively. Here, we establish processivity as a cellular property of NM2. Processive runs in central nervous system-derived CAD cells are most apparent as processive movements on bundled actin in protrusions that terminate at the leading edge. We find that processive velocities in vivo are consistent with in vitro measurements. NM2 makes these processive runs in its filamentous form against lamellipodia retrograde flow, though anterograde movement can still occur in the absence of actin dynamics. Comparing the processivity of NM2 isoforms, we find that NM2A moves slightly faster than NM2B. Finally, we demonstrate that this is not a cell-specific property, as we observe processive-like movements of NM2 in the lamella and subnuclear stress fibers of fibroblasts. Collectively, these observations further broaden NM2 functionality and the biological processes in which the already ubiquitous motor can contribute.
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Affiliation(s)
- Eric A Vitriol
- Department of Neuroscience and Regenerative Medicine, Augusta University, Augusta, GA
| | - Melissa A Quintanilla
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Joseph J Tidei
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Lee D Troughton
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Abigail Cody
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Bruno A Cisterna
- Department of Neuroscience and Regenerative Medicine, Augusta University, Augusta, GA
| | - Makenzie L Jane
- Department of Neuroscience and Regenerative Medicine, Augusta University, Augusta, GA
| | - Patrick W Oakes
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Jordan R Beach
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
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10
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Morris T, Sue E, Geniesse C, Brieher WM, Tang VW. Synaptopodin stress fiber and contractomere at the epithelial junction. J Cell Biol 2022; 221:e202011162. [PMID: 35416930 PMCID: PMC9011326 DOI: 10.1083/jcb.202011162] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 10/07/2021] [Accepted: 02/09/2022] [Indexed: 12/27/2022] Open
Abstract
The apical junction of epithelial cells can generate force to control cell geometry and perform contractile processes while maintaining barrier function and adhesion. Yet, the structural basis for force generation at the apical junction is not fully understood. Here, we describe two synaptopodin-dependent actomyosin structures that are spatially, temporally, and structurally distinct. The first structure is formed by the retrograde flow of synaptopodin initiated at the apical junction, creating a sarcomeric stress fiber that lies parallel to the apical junction. Contraction of the apical stress fiber is associated with either clustering of membrane components or shortening of junctional length. Upon junction maturation, apical stress fibers are disassembled. In mature epithelial monolayer, a motorized "contractomere" capable of "walking the junction" is formed at the junctional vertex. Actomyosin activities at the contractomere produce a compressive force evident by actin filament buckling and measurement with a new α-actinin-4 force sensor. The motility of contractomeres can adjust junctional length and change cell packing geometry during cell extrusion and intercellular movement. We propose a model of epithelial homeostasis that utilizes contractomere motility to support junction rearrangement while preserving the permeability barrier.
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Affiliation(s)
- Timothy Morris
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
| | - Eva Sue
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
| | - Caleb Geniesse
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
| | - William M Brieher
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
| | - Vivian W Tang
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
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11
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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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12
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Kučera O, Siahaan V, Janda D, Dijkstra SH, Pilátová E, Zatecka E, Diez S, Braun M, Lansky Z. Anillin propels myosin-independent constriction of actin rings. Nat Commun 2021; 12:4595. [PMID: 34321459 PMCID: PMC8319318 DOI: 10.1038/s41467-021-24474-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 06/21/2021] [Indexed: 02/07/2023] Open
Abstract
Constriction of the cytokinetic ring, a circular structure of actin filaments, is an essential step during cell division. Mechanical forces driving the constriction are attributed to myosin motor proteins, which slide actin filaments along each other. However, in multiple organisms, ring constriction has been reported to be myosin independent. How actin rings constrict in the absence of motor activity remains unclear. Here, we demonstrate that anillin, a non-motor actin crosslinker, indispensable during cytokinesis, autonomously propels the contractility of actin bundles. Anillin generates contractile forces of tens of pico-Newtons to maximise the lengths of overlaps between bundled actin filaments. The contractility is enhanced by actin disassembly. When multiple actin filaments are arranged into a ring, this contractility leads to ring constriction. Our results indicate that passive actin crosslinkers can substitute for the activity of molecular motors to generate contractile forces in a variety of actin networks, including the cytokinetic ring.
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Affiliation(s)
- Ondřej Kučera
- grid.418095.10000 0001 1015 3316Institute of Biotechnology, Czech Academy of Sciences, BIOCEV, Vestec, Prague West, Czechia ,grid.5583.b0000 0001 2299 8025Present Address: CytoMorpho Lab, Laboratoire Physiologie Cellulaire & Végétale, Institut de recherche interdisciplinaire de Grenoble, Commissariat à l’énergie atomique et aux énergies alternatives (CEA), Grenoble, France
| | - Valerie Siahaan
- grid.418095.10000 0001 1015 3316Institute of Biotechnology, Czech Academy of Sciences, BIOCEV, Vestec, Prague West, Czechia
| | - Daniel Janda
- grid.418095.10000 0001 1015 3316Institute of Biotechnology, Czech Academy of Sciences, BIOCEV, Vestec, Prague West, Czechia
| | - Sietske H. Dijkstra
- grid.418095.10000 0001 1015 3316Institute of Biotechnology, Czech Academy of Sciences, BIOCEV, Vestec, Prague West, Czechia
| | - Eliška Pilátová
- grid.418095.10000 0001 1015 3316Institute of Biotechnology, Czech Academy of Sciences, BIOCEV, Vestec, Prague West, Czechia
| | - Eva Zatecka
- grid.418095.10000 0001 1015 3316Institute of Biotechnology, Czech Academy of Sciences, BIOCEV, Vestec, Prague West, Czechia
| | - Stefan Diez
- grid.4488.00000 0001 2111 7257B CUBE – Center for Molecular Bioengineering, TU Dresden, Dresden, Germany ,grid.419537.d0000 0001 2113 4567Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany ,grid.4488.00000 0001 2111 7257Cluster of Excellence Physics of Life, Technische Universität Dresden, Dresden, Germany
| | - Marcus Braun
- grid.418095.10000 0001 1015 3316Institute of Biotechnology, Czech Academy of Sciences, BIOCEV, Vestec, Prague West, Czechia
| | - Zdenek Lansky
- grid.418095.10000 0001 1015 3316Institute of Biotechnology, Czech Academy of Sciences, BIOCEV, Vestec, Prague West, Czechia
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13
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Huang W, Matsui TS, Saito T, Kuragano M, Takahashi M, Kawahara T, Sato M, Deguchi S. Mechanosensitive myosin II but not cofilin primarily contributes to cyclic cell stretch-induced selective disassembly of actin stress fibers. Am J Physiol Cell Physiol 2021; 320:C1153-C1163. [PMID: 33881935 DOI: 10.1152/ajpcell.00225.2020] [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] [Indexed: 11/22/2022]
Abstract
Cells adapt to applied cyclic stretch (CS) to circumvent chronic activation of proinflammatory signaling. Currently, the molecular mechanism of the selective disassembly of actin stress fibers (SFs) in the stretch direction, which occurs at the early stage of the cellular response to CS, remains controversial. Here, we suggest that the mechanosensitive behavior of myosin II, a major cross-linker of SFs, primarily contributes to the directional disassembly of the actomyosin complex SFs in bovine vascular smooth muscle cells and human U2OS osteosarcoma cells. First, we identified that CS with a shortening phase that exceeds in speed the inherent contractile rate of individual SFs leads to the disassembly. To understand the biological basis, we investigated the effect of expressing myosin regulatory light-chain mutants and found that SFs with less actomyosin activities disassemble more promptly upon CS. We consequently created a minimal mathematical model that recapitulates the salient features of the direction-selective and threshold-triggered disassembly of SFs to show that disassembly or, more specifically, unbundling of the actomyosin bundle SFs is enhanced with sufficiently fast cell shortening. We further demonstrated that similar disassembly of SFs is inducible in the presence of an active LIM-kinase-1 mutant that deactivates cofilin, suggesting that cofilin is dispensable as opposed to a previously proposed mechanism.
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Affiliation(s)
- Wenjing Huang
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Tsubasa S Matsui
- Division of Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Japan
| | - Takumi Saito
- Division of Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Japan
| | - Masahiro Kuragano
- Graduate School of Chemical Science and Engineering, Hokkaido University, Sapporo, Japan
| | - Masayuki Takahashi
- Graduate School of Chemical Science and Engineering, Hokkaido University, Sapporo, Japan
| | - Tomohiro Kawahara
- Department of Biological Functions Engineering, Kyushu Institute of Technology, Kitakyushu, Japan
| | - Masaaki Sato
- Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai, Japan
| | - Shinji Deguchi
- Division of Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Japan
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14
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Brizendine RK, Anuganti M, Cremo CR. Evidence for S2 flexibility by direct visualization of quantum dot-labeled myosin heads and rods within smooth muscle myosin filaments moving on actin in vitro. J Gen Physiol 2021; 153:e202012751. [PMID: 33439241 PMCID: PMC7809879 DOI: 10.1085/jgp.202012751] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 11/18/2020] [Accepted: 12/10/2020] [Indexed: 12/21/2022] Open
Abstract
Myosins in muscle assemble into filaments by interactions between the C-terminal light meromyosin (LMM) subdomains of the coiled-coil rod domain. The two head domains are connected to LMM by the subfragment-2 (S2) subdomain of the rod. Our mixed kinetic model predicts that the flexibility and length of S2 that can be pulled away from the filament affects the maximum distance working heads can move a filament unimpeded by actin-attached heads. It also suggests that it should be possible to observe a head remain stationary relative to the filament backbone while bound to actin (dwell), followed immediately by a measurable jump upon detachment to regain the backbone trajectory. We tested these predictions by observing filaments moving along actin at varying ATP using TIRF microscopy. We simultaneously tracked two different color quantum dots (QDs), one attached to a regulatory light chain on the lever arm and the other attached to an LMM in the filament backbone. We identified events (dwells followed by jumps) by comparing the trajectories of the QDs. The average dwell times were consistent with known kinetics of the actomyosin system, and the distribution of the waiting time between observed events was consistent with a Poisson process and the expected ATPase rate. Geometric constraints suggest a maximum of ∼26 nm of S2 can be unzipped from the filament, presumably involving disruption in the coiled-coil S2, a result consistent with observations by others of S2 protruding from the filament in muscle. We propose that sufficient force is available from the working heads in the filament to overcome the stiffness imposed by filament-S2 interactions.
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Affiliation(s)
| | | | - Christine R. Cremo
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Reno, NV
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15
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Rens EG, Merks RM. Cell Shape and Durotaxis Explained from Cell-Extracellular Matrix Forces and Focal Adhesion Dynamics. iScience 2020; 23:101488. [PMID: 32896767 PMCID: PMC7482025 DOI: 10.1016/j.isci.2020.101488] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 07/13/2020] [Accepted: 08/18/2020] [Indexed: 12/26/2022] Open
Abstract
Many cells are small and rounded on soft extracellular matrices (ECM), elongated on stiffer ECMs, and flattened on hard ECMs. Cells also migrate up stiffness gradients (durotaxis). Using a hybrid cellular Potts and finite-element model extended with ODE-based models of focal adhesion (FA) turnover, we show that the full range of cell shape and durotaxis can be explained in unison from dynamics of FAs, in contrast to previous mathematical models. In our 2D cell-shape model, FAs grow due to cell traction forces. Forces develop faster on stiff ECMs, causing FAs to stabilize and, consequently, cells to spread on stiff ECMs. If ECM stress further stabilizes FAs, cells elongate on substrates of intermediate stiffness. We show that durotaxis follows from the same set of assumptions. Our model contributes to the understanding of the basic responses of cells to ECM stiffness, paving the way for future modeling of more complex cell-ECM interactions.
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Affiliation(s)
- Elisabeth G. Rens
- Scientific Computing, CWI, Science Park 123, 1098 XG Amsterdam, the Netherlands
- Mathematics Department, University of British Columbia, Mathematics Road 1984, Vancouver, BC V6T 1Z2, Canada
| | - Roeland M.H. Merks
- Scientific Computing, CWI, Science Park 123, 1098 XG Amsterdam, the Netherlands
- Mathematical Institute, Leiden University, Niels Bohrweg 1, 2333 CA Leiden, the Netherlands
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16
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4-Hydroxyacetophenone modulates the actomyosin cytoskeleton to reduce metastasis. Proc Natl Acad Sci U S A 2020; 117:22423-22429. [PMID: 32848073 DOI: 10.1073/pnas.2014639117] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Metastases are the cause of the vast majority of cancer deaths. In the metastatic process, cells migrate to the vasculature, intravasate, extravasate, and establish metastatic colonies. This pattern of spread requires the cancer cells to change shape and to navigate tissue barriers. Approaches that block this mechanical program represent new therapeutic avenues. We show that 4-hydroxyacetophenone (4-HAP) inhibits colon cancer cell adhesion, invasion, and migration in vitro and reduces the metastatic burden in an in vivo model of colon cancer metastasis to the liver. Treatment with 4-HAP activates nonmuscle myosin-2C (NM2C) (MYH14) to alter actin organization, inhibiting the mechanical program of metastasis. We identify NM2C as a specific therapeutic target. Pharmacological control of myosin isoforms is a promising approach to address metastatic disease, one that may be readily combined with other therapeutic strategies.
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17
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Saito T, Huang W, Matsui TS, Kuragano M, Takahashi M, Deguchi S. What factors determine the number of nonmuscle myosin II in the sarcomeric unit of stress fibers? Biomech Model Mechanobiol 2020; 20:155-166. [PMID: 32776260 DOI: 10.1007/s10237-020-01375-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 08/01/2020] [Indexed: 01/05/2023]
Abstract
Actin stress fibers (SFs), a contractile apparatus in nonmuscle cells, possess a contractile unit that is apparently similar to the sarcomere of myofibrils in muscles. The function of SFs has thus often been addressed based on well-characterized properties of muscles. However, unlike the fixed number of myosin molecules in myofibrils, the number of nonmuscle myosin II (NMII) within the contractile sarcomeric unit in SFs is quite low and variable for some reason. Here we address what factors may determine the specific number of NMII in SFs. We suggest with a theoretical model that the number lies just in between the function of SFs for bearing cellular tension under static conditions and for promptly disintegrating upon forced cell shortening. We monitored shortening-induced disintegration of SFs in human osteosarcoma U2OS cells expressing mutants of myosin regulatory light chain that virtually regulates the interaction of NMII with actin filaments, and the behaviors observed were indeed consistent with the theoretical consequences. This situation-specific nature of SFs may allow nonmuscle cells to respond adaptively to mechanical stress to circumvent activation of pro-inflammatory signals as previously indicated, i.e., a behavior distinct from that of muscles that are basically specialized for exhibiting contractile activity.
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Affiliation(s)
- Takumi Saito
- Division of Bioengineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.,Japan Society for the Promotion of Science, Tokyo, Japan
| | - Wenjing Huang
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Tsubasa S Matsui
- Division of Bioengineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan
| | - Masahiro Kuragano
- Graduate School of Engineering, Muroran Institute of Technology, Muroran, Japan
| | - Masayuki Takahashi
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan
| | - Shinji Deguchi
- Division of Bioengineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
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18
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Horváth ÁI, Gyimesi M, Várkuti BH, Képiró M, Szegvári G, Lőrincz I, Hegyi G, Kovács M, Málnási-Csizmadia A. Effect of allosteric inhibition of non-muscle myosin 2 on its intracellular diffusion. Sci Rep 2020; 10:13341. [PMID: 32769996 PMCID: PMC7415145 DOI: 10.1038/s41598-020-69853-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 07/03/2020] [Indexed: 12/12/2022] Open
Abstract
Subcellular dynamics of non-muscle myosin 2 (NM2) is crucial for a broad-array of cellular functions. To unveil mechanisms of NM2 pharmacological control, we determined how the dynamics of NM2 diffusion is affected by NM2′s allosteric inhibitors, i.e. blebbistatin derivatives, as compared to Y-27632 inhibiting ROCK, NM2′s upstream regulator. We found that NM2 diffusion is markedly faster in central fibers than in peripheral stress fibers. Y-27632 accelerated NM2 diffusion in both peripheral and central fibers, whereas in peripheral fibers blebbistatin derivatives slightly accelerated NM2 diffusion at low, but markedly slowed it at high inhibitor concentrations. In contrast, rapid NM2 diffusion in central fibers was unaffected by direct NM2 inhibition. Using our optopharmacological tool, Molecular Tattoo, sub-effective concentrations of a photo-crosslinkable blebbistatin derivative were increased to effective levels in a small, irradiated area of peripheral fibers. These findings suggest that direct allosteric inhibition affects the diffusion profile of NM2 in a markedly different manner compared to the disruption of the upstream control of NM2. The pharmacological action of myosin inhibitors is channeled through autonomous molecular processes and might be affected by the load acting on the NM2 proteins.
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Affiliation(s)
- Ádám I Horváth
- MTA-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, 1117, Budapest, Hungary
| | - Máté Gyimesi
- MTA-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, 1117, Budapest, Hungary
| | - Boglárka H Várkuti
- MTA-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, 1117, Budapest, Hungary
| | - Miklós Képiró
- MTA-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, 1117, Budapest, Hungary
| | - Gábor Szegvári
- MTA-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, 1117, Budapest, Hungary
| | - István Lőrincz
- MTA-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, 1117, Budapest, Hungary
| | - György Hegyi
- MTA-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, 1117, Budapest, Hungary
| | - Mihály Kovács
- MTA-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, 1117, Budapest, Hungary.
| | - András Málnási-Csizmadia
- MTA-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, 1117, Budapest, Hungary.
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19
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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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20
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Alimohamadi H, Smith AS, Nowak RB, Fowler VM, Rangamani P. Non-uniform distribution of myosin-mediated forces governs red blood cell membrane curvature through tension modulation. PLoS Comput Biol 2020; 16:e1007890. [PMID: 32453720 PMCID: PMC7274484 DOI: 10.1371/journal.pcbi.1007890] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 06/05/2020] [Accepted: 04/21/2020] [Indexed: 12/11/2022] Open
Abstract
The biconcave disk shape of the mammalian red blood cell (RBC) is unique to the RBC and is vital for its circulatory function. Due to the absence of a transcellular cytoskeleton, RBC shape is determined by the membrane skeleton, a network of actin filaments cross-linked by spectrin and attached to membrane proteins. While the physical properties of a uniformly distributed actin network interacting with the lipid bilayer membrane have been assumed to control RBC shape, recent experiments reveal that RBC biconcave shape also depends on the contractile activity of nonmuscle myosin IIA (NMIIA) motor proteins. Here, we use the classical Helfrich-Canham model for the RBC membrane to test the role of heterogeneous force distributions along the membrane and mimic the contractile activity of sparsely distributed NMIIA filaments. By incorporating this additional contribution to the Helfrich-Canham energy, we find that the RBC biconcave shape depends on the ratio of forces per unit volume in the dimple and rim regions of the RBC. Experimental measurements of NMIIA densities at the dimple and rim validate our prediction that (a) membrane forces must be non-uniform along the RBC membrane and (b) the force density must be larger in the dimple than the rim to produce the observed membrane curvatures. Furthermore, we predict that RBC membrane tension and the orientation of the applied forces play important roles in regulating this force-shape landscape. Our findings of heterogeneous force distributions on the plasma membrane for RBC shape maintenance may also have implications for shape maintenance in different cell types. The spectrin-actin network of the membrane skeleton plays an important role in controlling specialized cell membrane morphology. In the paradigmatic red blood cell (RBC), where actin filaments are present exclusively in the membrane skeleton, recent experiments reveal that nonmuscle myosin IIA (NMIIA) motor contractility maintains the RBC biconcave disk shape. In this study, we have identified criteria for micron-scale distributions of NMIIA forces at the membrane required to maintain the biconcave disk shape of an RBC in the resting condition. Supported by experimental measurements of RBC NMIIA distribution, we showed that a heterogeneous force distribution with a larger force density at the dimple is able to capture the experimentally observed biconcave morphology of an RBC with better accuracy compared to previous models that did not consider the heterogeneity in the force distribution. Furthermore, we showed that the biconcave geometry of the RBC is closely regulated by the effective membrane tension and the direction of applied forces on the membrane. These findings can be generalized to any force-mediated membrane shape, providing insight into the role of actomyosin forces in prescribing and maintaining the morphology of different cell types.
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Affiliation(s)
- Haleh Alimohamadi
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, United States of America
| | - Alyson S. Smith
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, United States of America
| | - Roberta B. Nowak
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, United States of America
| | - Velia M. Fowler
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, United States of America
- Department of Biological Sciences, University of Delaware, Newark, Delaware, United States of America
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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21
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How Actin Tracks Affect Myosin Motors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1239:183-197. [DOI: 10.1007/978-3-030-38062-5_9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
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22
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Berger F, Klumpp S, Lipowsky R. Force-Dependent Unbinding Rate of Molecular Motors from Stationary Optical Trap Data. NANO LETTERS 2019; 19:2598-2602. [PMID: 30835477 DOI: 10.1021/acs.nanolett.9b00417] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Molecular motors walk along filaments until they detach stochastically with a force-dependent unbinding rate. Here, we show how this unbinding rate can be obtained from the analysis of experimental data of molecular motors moving in stationary optical traps. Two complementary methods are presented, based on the analysis of the distribution for the unbinding forces and of the motor's force traces. In the first method, analytically derived force distributions for slip bonds, slip-ideal bonds, and catch bonds are used to fit the cumulative distributions of the unbinding forces. The second method is based on the statistical analysis of the observed force traces. We validate both methods with stochastic simulations and apply them to experimental data for kinesin-1.
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Affiliation(s)
- Florian Berger
- Laboratory of Sensory Neuroscience , The Rockefeller University , New York , New York 10065 , United States
| | - Stefan Klumpp
- Institute for the Dynamics of Complex Systems , Georg-August University Göttingen , 37077 Göttingen , Germany
| | - Reinhard Lipowsky
- Theory and Bio-Systems , Max Planck Institute of Colloids and Interfaces , 14424 Potsdam , Germany
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23
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Giantin Is Required for Post-Alcohol Recovery of Golgi in Liver Cells. Biomolecules 2018; 8:biom8040150. [PMID: 30453527 PMCID: PMC6316505 DOI: 10.3390/biom8040150] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 11/09/2018] [Accepted: 11/12/2018] [Indexed: 12/17/2022] Open
Abstract
In hepatocytes and alcohol-metabolizing cultured cells, Golgi undergoes ethanol (EtOH)-induced disorganization. Perinuclear and organized Golgi is important in liver homeostasis, but how the Golgi remains intact is unknown. Work from our laboratories showed that EtOH-altered cellular function could be reversed after alcohol removal; we wanted to determine whether this recovery would apply to Golgi. We used alcohol-metabolizing HepG2 (VA-13) cells (cultured with or without EtOH for 72 h) and rat hepatocytes (control and EtOH-fed (Lieber–DeCarli diet)). For recovery, EtOH was removed and replenished with control medium (48 h for VA-13 cells) or control diet (10 days for rats). Results: EtOH-induced Golgi disassembly was associated with de-dimerization of the largest Golgi matrix protein giantin, along with impaired transport of selected hepatic proteins. After recovery from EtOH, Golgi regained their compact structure, and alterations in giantin and protein transport were restored. In VA-13 cells, when we knocked down giantin, Rab6a GTPase or non-muscle myosin IIB, minimal changes were observed in control conditions, but post-EtOH recovery was impaired. Conclusions: These data provide a link between Golgi organization and plasma membrane protein expression and identify several proteins whose expression is important to maintain Golgi structure during the recovery phase after EtOH administration.
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24
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Cardiomyocytes Sense Matrix Rigidity through a Combination of Muscle and Non-muscle Myosin Contractions. Dev Cell 2018; 44:326-336.e3. [PMID: 29396114 PMCID: PMC5807060 DOI: 10.1016/j.devcel.2017.12.024] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 11/09/2017] [Accepted: 12/22/2017] [Indexed: 12/31/2022]
Abstract
Mechanical properties are cues for many biological processes in health or disease. In the heart, changes to the extracellular matrix composition and cross-linking result in stiffening of the cellular microenvironment during development. Moreover, myocardial infarction and cardiomyopathies lead to fibrosis and a stiffer environment, affecting cardiomyocyte behavior. Here, we identify that single cardiomyocyte adhesions sense simultaneous (fast oscillating) cardiac and (slow) non-muscle myosin contractions. Together, these lead to oscillating tension on the mechanosensitive adaptor protein talin on substrates with a stiffness of healthy adult heart tissue, compared with no tension on embryonic heart stiffness and continuous stretching on fibrotic stiffness. Moreover, we show that activation of PKC leads to the induction of cardiomyocyte hypertrophy in a stiffness-dependent way, through activation of non-muscle myosin. Finally, PKC and non-muscle myosin are upregulated at the costameres in heart disease, indicating aberrant mechanosensing as a contributing factor to long-term remodeling and heart failure. Talin in cardiomyocytes is unstretched, cyclically stretched, or continuously stretched Talin stretching depends on stiffness, myofibrillar tension, and non-myofibrillar tension Non-myofibrillar contractility requires PKC, Src, FHOD1, and non-muscle myosin PKC and non-muscle myosin activity are enhanced in cardiac disease
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25
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Noll N, Mani M, Heemskerk I, Streichan SJ, Shraiman BI. Active Tension Network model suggests an exotic mechanical state realized in epithelial tissues. NATURE PHYSICS 2017; 13:1221-1226. [PMID: 30687408 PMCID: PMC6344062 DOI: 10.1038/nphys4219] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 06/28/2017] [Indexed: 05/22/2023]
Abstract
Mechanical interactions play a crucial role in epithelial morphogenesis, yet understanding the complex mechanisms through which stress and deformation affect cell behavior remains an open problem. Here we formulate and analyze the Active Tension Network (ATN) model, which assumes that the mechanical balance of cells within a tissue is dominated by cortical tension and introduces tension-dependent active remodeling of the cortex. We find that ATNs exhibit unusual mechanical properties. Specifically, an ATN behaves as a fluid at short times, but at long times supports external tension like a solid. Furthermore, an ATN has an extensively degenerate equilibrium mechanical state associated with a discrete conformal - "isogonal" - deformation of cells. The ATN model predicts a constraint on equilibrium cell geometries, which we demonstrate to approximately hold in certain epithelial tissues. We further show that isogonal modes are observed in the fruit y embryo, accounting for the striking variability of apical areas of ventral cells and helping understand the early phase of gastrulation. Living matter realizes new and exotic mechanical states, the study of which helps to understand biological phenomena.
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Affiliation(s)
- Nicholas Noll
- Department of Physics, University of California Santa Barbara
| | - Madhav Mani
- Department of Applied Mathematics, Northwestern University
| | | | - Sebastian J Streichan
- Department of Physics, University of California Santa Barbara
- Kavli Institute for Theoretical Physics
| | - Boris I Shraiman
- Department of Physics, University of California Santa Barbara
- Kavli Institute for Theoretical Physics
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26
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Pathan-Chhatbar S, Taft MH, Reindl T, Hundt N, Latham SL, Manstein DJ. Three mammalian tropomyosin isoforms have different regulatory effects on nonmuscle myosin-2B and filamentous β-actin in vitro. J Biol Chem 2017; 293:863-875. [PMID: 29191834 PMCID: PMC5777259 DOI: 10.1074/jbc.m117.806521] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 11/16/2017] [Indexed: 12/19/2022] Open
Abstract
The metazoan actin cytoskeleton supports a wide range of contractile and transport processes. Recent studies have shown how the dynamic association with specific tropomyosin isoforms generates actin filament populations with distinct functional properties. However, critical details of the associated molecular interactions remain unclear. Here, we report the properties of actomyosin–tropomyosin complexes containing filamentous β-actin, nonmuscle myosin-2B (NM-2B) constructs, and either tropomyosin isoform Tpm1.8cy (b.–.b.d), Tpm1.12br (b.–.b.c), or Tpm3.1cy (b.–.a.d). Our results show the extent to which the association of filamentous β-actin with these different tropomyosin cofilaments affects the actin-mediated activation of NM-2B and the release of the ATP hydrolysis products ADP and phosphate from the active site. Phosphate release gates a transition from weak to strong F-actin–binding states. The release of ADP has the opposite effect. These changes in dominant rate-limiting steps have a direct effect on the duty ratio, the fraction of time that NM-2B spends in strongly F-actin–bound states during ATP turnover. The duty ratio is increased ∼3-fold in the presence of Tpm1.12 and 5-fold for both Tpm1.8 and Tpm3.1. The presence of Tpm1.12 extends the time required per ATP hydrolysis cycle 3.7-fold, whereas it is shortened by 27 and 63% in the presence of Tpm1.8 and Tpm3.1, respectively. The resulting Tpm isoform–specific changes in the frequency, duration, and efficiency of actomyosin interactions establish a molecular basis for the ability of these complexes to support cellular processes with widely divergent demands in regard to force production, capacity to move processively, and speed of movement.
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Affiliation(s)
| | | | | | | | | | - Dietmar J Manstein
- From the Institute for Biophysical Chemistry and .,the Division for Structural Biochemistry, Hannover Medical School, 30625 Hannover, Germany
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27
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Gramlich MW, Klyachko VA. Actin/Myosin-V- and Activity-Dependent Inter-synaptic Vesicle Exchange in Central Neurons. Cell Rep 2017; 18:2096-2104. [PMID: 28249156 DOI: 10.1016/j.celrep.2017.02.010] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 12/13/2016] [Accepted: 01/31/2017] [Indexed: 11/18/2022] Open
Abstract
Vesicle sharing between synaptic boutons is an important component of the recycling process that synapses employ to maintain vesicle pools. However, the mechanisms supporting and regulating vesicle transport during the inter-synaptic exchange remain poorly understood. Using nanometer-resolution tracking of individual synaptic vesicles and advanced computational algorithms, we find that long-distance axonal transport of synaptic vesicles between hippocampal boutons is partially mediated by the actin network, with myosin V as the primary actin-dependent motor that drives this vesicle transport. Furthermore, we find that vesicle exit from the synapse to the axon and long-distance vesicle transport are both rapidly and dynamically regulated by activity. We corroborated these findings with two complementary modeling approaches of vesicle exit, which closely reproduced experimental observations. These findings uncover the roles of actin and myosin V in supporting the inter-synaptic vesicle exchange and reveal that this process is dynamically modulated in an activity-dependent manner.
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Affiliation(s)
- Michael W Gramlich
- Departments of Cell Biology and Physiology, Biomedical Engineering, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Vitaly A Klyachko
- Departments of Cell Biology and Physiology, Biomedical Engineering, Washington University School of Medicine, St. Louis, MO 63110, USA.
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28
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Ridge LA, Mitchell K, Al-Anbaki A, Shaikh Qureshi WM, Stephen LA, Tenin G, Lu Y, Lupu IE, Clowes C, Robertson A, Barnes E, Wright JA, Keavney B, Ehler E, Lovell SC, Kadler KE, Hentges KE. Non-muscle myosin IIB (Myh10) is required for epicardial function and coronary vessel formation during mammalian development. PLoS Genet 2017; 13:e1007068. [PMID: 29084269 PMCID: PMC5697871 DOI: 10.1371/journal.pgen.1007068] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 11/21/2017] [Accepted: 10/11/2017] [Indexed: 01/01/2023] Open
Abstract
The coronary vasculature is an essential vessel network providing the blood supply to the heart. Disruptions in coronary blood flow contribute to cardiac disease, a major cause of premature death worldwide. The generation of treatments for cardiovascular disease will be aided by a deeper understanding of the developmental processes that underpin coronary vessel formation. From an ENU mutagenesis screen, we have isolated a mouse mutant displaying embryonic hydrocephalus and cardiac defects (EHC). Positional cloning and candidate gene analysis revealed that the EHC phenotype results from a point mutation in a splice donor site of the Myh10 gene, which encodes NMHC IIB. Complementation testing confirmed that the Myh10 mutation causes the EHC phenotype. Characterisation of the EHC cardiac defects revealed abnormalities in myocardial development, consistent with observations from previously generated NMHC IIB null mouse lines. Analysis of the EHC mutant hearts also identified defects in the formation of the coronary vasculature. We attribute the coronary vessel abnormalities to defective epicardial cell function, as the EHC epicardium displays an abnormal cell morphology, reduced capacity to undergo epithelial-mesenchymal transition (EMT), and impaired migration of epicardial-derived cells (EPDCs) into the myocardium. Our studies on the EHC mutant demonstrate a requirement for NMHC IIB in epicardial function and coronary vessel formation, highlighting the importance of this protein in cardiac development and ultimately, embryonic survival.
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Affiliation(s)
- Liam A. Ridge
- Division of Evolution and Genome Sciences, School of Biological Sciences, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Karen Mitchell
- Division of Evolution and Genome Sciences, School of Biological Sciences, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Ali Al-Anbaki
- Division of Evolution and Genome Sciences, School of Biological Sciences, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Wasay Mohiuddin Shaikh Qureshi
- Division of Evolution and Genome Sciences, School of Biological Sciences, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Louise A. Stephen
- Division of Evolution and Genome Sciences, School of Biological Sciences, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Gennadiy Tenin
- Division of Evolution and Genome Sciences, School of Biological Sciences, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Yinhui Lu
- Wellcome Trust Centre for Cell-Matrix Research, Division of Cell-Matrix Biology and Regenerative Medicine, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Irina-Elena Lupu
- Division of Evolution and Genome Sciences, School of Biological Sciences, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Christopher Clowes
- Division of Evolution and Genome Sciences, School of Biological Sciences, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Abigail Robertson
- Division of Evolution and Genome Sciences, School of Biological Sciences, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Emma Barnes
- Syngenta Ltd, Jealott’s Hill International Research Centre, Bracknell, United Kingdom
| | - Jayne A. Wright
- Syngenta Ltd, Jealott’s Hill International Research Centre, Bracknell, United Kingdom
| | - Bernard Keavney
- Division of Cardiovascular Sciences, School of Medical Sciences, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
- Manchester Heart Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester, United Kingdom
| | - Elisabeth Ehler
- The Randall Division of Cell and Molecular Biophysics and the Cardiovascular Division, Kings College London, London, United Kingdom
| | - Simon C. Lovell
- Division of Evolution and Genome Sciences, School of Biological Sciences, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Karl E. Kadler
- Wellcome Trust Centre for Cell-Matrix Research, Division of Cell-Matrix Biology and Regenerative Medicine, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Kathryn E. Hentges
- Division of Evolution and Genome Sciences, School of Biological Sciences, Faculty of Biology, Medicine, and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
- * E-mail:
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29
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Activity-Dependence of Synaptic Vesicle Dynamics. J Neurosci 2017; 37:10597-10610. [PMID: 28954868 DOI: 10.1523/jneurosci.0383-17.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 08/08/2017] [Accepted: 08/15/2017] [Indexed: 11/21/2022] Open
Abstract
The proper function of synapses relies on efficient recycling of synaptic vesicles. The small size of synaptic boutons has hampered efforts to define the dynamical states of vesicles during recycling. Moreover, whether vesicle motion during recycling is regulated by neural activity remains largely unknown. We combined nanoscale-resolution tracking of individual synaptic vesicles in cultured hippocampal neurons from rats of both sexes with advanced motion analyses to demonstrate that the majority of recently endocytosed vesicles undergo sequences of transient dynamical states including epochs of directed, diffusional, and stalled motion. We observed that vesicle motion is modulated in an activity-dependent manner, with dynamical changes apparent in ∼20% of observed boutons. Within this subpopulation of boutons, 35% of observed vesicles exhibited acceleration and 65% exhibited deceleration, accompanied by corresponding changes in directed motion. Individual vesicles observed in the remaining ∼80% of boutons did not exhibit apparent dynamical changes in response to stimulation. More quantitative transient motion analyses revealed that the overall reduction of vesicle mobility, and specifically of the directed motion component, is the predominant activity-evoked change across the entire bouton population. Activity-dependent modulation of vesicle mobility may represent an important mechanism controlling vesicle availability and neurotransmitter release.SIGNIFICANCE STATEMENT Mechanisms governing synaptic vesicle dynamics during recycling remain poorly understood. Using nanoscale resolution tracking of individual synaptic vesicles in hippocampal synapses and advanced motion analysis tools we demonstrate that synaptic vesicles undergo complex sets of dynamical states that include epochs of directed, diffusive, and stalled motion. Most importantly, our analyses revealed that vesicle motion is modulated in an activity-dependent manner apparent as the reduction in overall vesicle mobility in response to stimulation. These results define the vesicle dynamical states during recycling and reveal their activity-dependent modulation. Our study thus provides fundamental new insights into the principles governing synaptic function.
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30
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Alvarado J, Sheinman M, Sharma A, MacKintosh FC, Koenderink GH. Force percolation of contractile active gels. SOFT MATTER 2017; 13:5624-5644. [PMID: 28812094 DOI: 10.1039/c7sm00834a] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Living systems provide a paradigmatic example of active soft matter. Cells and tissues comprise viscoelastic materials that exert forces and can actively change shape. This strikingly autonomous behavior is powered by the cytoskeleton, an active gel of semiflexible filaments, crosslinks, and molecular motors inside cells. Although individual motors are only a few nm in size and exert minute forces of a few pN, cells spatially integrate the activity of an ensemble of motors to produce larger contractile forces (∼nN and greater) on cellular, tissue, and organismal length scales. Here we review experimental and theoretical studies on contractile active gels composed of actin filaments and myosin motors. Unlike other active soft matter systems, which tend to form ordered patterns, actin-myosin systems exhibit a generic tendency to contract. Experimental studies of reconstituted actin-myosin model systems have long suggested that a mechanical interplay between motor activity and the network's connectivity governs this contractile behavior. Recent theoretical models indicate that this interplay can be understood in terms of percolation models, extended to include effects of motor activity on the network connectivity. Based on concepts from percolation theory, we propose a state diagram that unites a large body of experimental observations. This framework provides valuable insights into the mechanisms that drive cellular shape changes and also provides design principles for synthetic active materials.
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Affiliation(s)
- José Alvarado
- Systems Biophysics Department, AMOLF, 1098 XG Amsterdam, The Netherlands.
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31
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Marchenko OO, Das S, Yu J, Novak IL, Rodionov VI, Efimova N, Svitkina T, Wolgemuth CW, Loew LM. A minimal actomyosin-based model predicts the dynamics of filopodia on neuronal dendrites. Mol Biol Cell 2017; 28:1021-1033. [PMID: 28228546 PMCID: PMC5391179 DOI: 10.1091/mbc.e16-06-0461] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 12/15/2016] [Accepted: 02/13/2017] [Indexed: 11/22/2022] Open
Abstract
A combination of computational and experimental approaches is used to show that the complex dynamics of dendritic filopodia, which is essential for synaptogenesis, is explained by a conceptually simple interplay among actin retrograde flow, myosin contractility, and substrate adhesion. Dendritic filopodia are actin-filled dynamic subcellular structures that sprout on neuronal dendrites during neurogenesis. The exploratory motion of the filopodia is crucial for synaptogenesis, but the underlying mechanisms are poorly understood. To study filopodial motility, we collected and analyzed image data on filopodia in cultured rat hippocampal neurons. We hypothesized that mechanical feedback among the actin retrograde flow, myosin activity, and substrate adhesion gives rise to various filopodial behaviors. We formulated a minimal one-dimensional partial differential equation model that reproduced the range of observed motility. To validate our model, we systematically manipulated experimental correlates of parameters in the model: substrate adhesion strength, actin polymerization rate, myosin contractility, and the integrity of the putative microtubule-based barrier at the filopodium base. The model predicts the response of the system to each of these experimental perturbations, supporting the hypothesis that our actomyosin-driven mechanism controls dendritic filopodia dynamics.
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Affiliation(s)
- Olena O Marchenko
- R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, CT 06030
| | - Sulagna Das
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, New York, NY 10461
| | - Ji Yu
- R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, CT 06030
| | - Igor L Novak
- R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, CT 06030
| | - Vladimir I Rodionov
- R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, CT 06030
| | - Nadia Efimova
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104
| | - Tatyana Svitkina
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104
| | - Charles W Wolgemuth
- Departments of Physics and Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721
| | - Leslie M Loew
- R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, CT 06030
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32
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Kobb AB, Zulueta-Coarasa T, Fernandez-Gonzalez R. Tension regulates myosin dynamics during Drosophila embryonic wound repair. J Cell Sci 2017; 130:689-696. [DOI: 10.1242/jcs.196139] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 01/03/2017] [Indexed: 12/14/2022] Open
Abstract
ABSTRACT
Embryos repair epithelial wounds rapidly in a process driven by collective cell movements. Upon wounding, actin and the molecular motor non-muscle myosin II are redistributed in the cells adjacent to the wound, forming a supracellular purse string around the lesion. Purse string contraction coordinates cell movements and drives rapid wound closure. By using fluorescence recovery after photobleaching in Drosophila embryos, we found that myosin turns over as the purse string contracts. Myosin turnover at the purse string was slower than in other actomyosin networks that had a lower level of contractility. Mathematical modelling suggested that myosin assembly and disassembly rates were both reduced by tension at the wound edge. We used laser ablation to show that tension at the purse string increased as wound closure progressed, and that the increase in tension was associated with reduced myosin turnover. Reducing purse string tension by laser-mediated severing resulted in increased turnover and loss of myosin. Finally, myosin motor activity was necessary for its stabilization around the wound and for rapid wound closure. Our results indicate that mechanical forces regulate myosin dynamics during embryonic wound repair.
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Affiliation(s)
- Anna B. Kobb
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G9
- Ted Rogers Centre for Heart Research, University of Toronto, Toronto, Ontario, Canada M5G 1M1
| | - Teresa Zulueta-Coarasa
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G9
- Ted Rogers Centre for Heart Research, University of Toronto, Toronto, Ontario, Canada M5G 1M1
| | - Rodrigo Fernandez-Gonzalez
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G9
- Ted Rogers Centre for Heart Research, University of Toronto, Toronto, Ontario, Canada M5G 1M1
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada M5S 3G5
- Developmental and Stem Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
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33
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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: 18] [Impact Index Per Article: 2.6] [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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34
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Livne A, Geiger B. The inner workings of stress fibers - from contractile machinery to focal adhesions and back. J Cell Sci 2016; 129:1293-304. [PMID: 27037413 DOI: 10.1242/jcs.180927] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Ventral stress fibers and focal adhesions are physically coupled structures that play key roles in cellular mechanics and force sensing. The tight functional interdependence between the two is manifested not only by their apparent proximity but also by the fact that ventral stress fibers and focal adhesions are simultaneously diminished upon actomyosin relaxation, and grow when subjected to external stretching. However, whereas the apparent co-regulation of the two structures is well-documented, the underlying mechanisms remains poorly understood. In this Commentary, we discuss some of the fundamental, yet still open questions regarding ventral stress fiber structure, its force-dependent assembly, as well as its capacity to generate force. We also challenge the common approach - i.e. ventral stress fibers are variants of the well-studied striated or smooth muscle machinery - by presenting and critically discussing alternative venues. By highlighting some of the less-explored aspects of the interplay between stress fibers and focal adhesions, we hope that this Commentary will encourage further investigation in this field.
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Affiliation(s)
- Ariel Livne
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Benjamin Geiger
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
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35
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Alcala DB, Haldeman BD, Brizendine RK, Krenc AK, Baker JE, Rock RS, Cremo CR. Myosin light chain kinase steady-state kinetics: comparison of smooth muscle myosin II and nonmuscle myosin IIB as substrates. Cell Biochem Funct 2016; 34:469-474. [PMID: 27528075 DOI: 10.1002/cbf.3209] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Revised: 07/07/2016] [Accepted: 07/11/2016] [Indexed: 01/31/2023]
Abstract
Myosin light chain kinase (MLCK) phosphorylates S19 of the myosin regulatory light chain (RLC), which is required to activate myosin's ATPase activity and contraction. Smooth muscles are known to display plasticity in response to factors such as inflammation, developmental stage, or stress, which lead to differential expression of nonmuscle and smooth muscle isoforms. Here, we compare steady-state kinetics parameters for phosphorylation of different MLCK substrates: (1) nonmuscle RLC, (2) smooth muscle RLC, and heavy meromyosin subfragments of (3) nonmuscle myosin IIB, and (4) smooth muscle myosin II. We show that MLCK has a ~2-fold higher kcat for both smooth muscle myosin II substrates compared with nonmuscle myosin IIB substrates, whereas Km values were very similar. Myosin light chain kinase has a 1.6-fold and 1.5-fold higher specificity (kcat /Km ) for smooth versus nonmuscle-free RLC and heavy meromyosin, respectively, suggesting that differences in specificity are dictated by RLC sequences. Of the 10 non-identical RLC residues, we ruled out 7 as possible underlying causes of different MLCK kinetics. The remaining 3 residues were found to be surface exposed in the N-terminal half of the RLC, consistent with their importance in substrate recognition. These data are consistent with prior deletion/chimera studies and significantly add to understanding of MLCK myosin interactions. SIGNIFICANCE OF THE STUDY Phosphorylation of nonmuscle and smooth muscle myosin by myosin light chain kinase (MLCK) is required for activation of myosin's ATPase activity. In smooth muscles, nonmuscle myosin coexists with smooth muscle myosin, but the two myosins have very different chemo-mechanical properties relating to their ability to maintain force. Differences in specificity of MLCK for different myosin isoforms had not been previously investigated. We show that the MLCK prefers smooth muscle myosin by a significant factor. These data suggest that nonmuscle myosin is phosphorylated more slowly than smooth muscle myosin during a contraction cycle.
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Affiliation(s)
- Diego B Alcala
- Department of Pharmacology, University of Nevada Reno School of Medicine, Reno, Nevada, USA
| | - Brian D Haldeman
- Department of Pharmacology, University of Nevada Reno School of Medicine, Reno, Nevada, USA
| | - Richard K Brizendine
- Department of Pharmacology, University of Nevada Reno School of Medicine, Reno, Nevada, USA
| | - Agata K Krenc
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - Josh E Baker
- Department of Pharmacology, University of Nevada Reno School of Medicine, Reno, Nevada, USA
| | - Ronald S Rock
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - Christine R Cremo
- Department of Pharmacology, University of Nevada Reno School of Medicine, Reno, Nevada, USA.
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36
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Greenberg MJ, Arpağ G, Tüzel E, Ostap EM. A Perspective on the Role of Myosins as Mechanosensors. Biophys J 2016; 110:2568-2576. [PMID: 27332116 PMCID: PMC4919425 DOI: 10.1016/j.bpj.2016.05.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 04/13/2016] [Accepted: 05/16/2016] [Indexed: 11/26/2022] Open
Abstract
Cells are dynamic systems that generate and respond to forces over a range of spatial and temporal scales, spanning from single molecules to tissues. Substantial progress has been made in recent years in identifying the molecules and pathways responsible for sensing and transducing mechanical signals to short-term cellular responses and longer-term changes in gene expression, cell identity, and tissue development. In this perspective article, we focus on myosin motors, as they not only function as the primary force generators in well-studied mechanobiological processes, but also act as key mechanosensors in diverse functions including intracellular transport, signaling, cell migration, muscle contraction, and sensory perception. We discuss how the biochemical and mechanical properties of different myosin isoforms are tuned to fulfill these roles in an array of cellular processes, and we highlight the underappreciated diversity of mechanosensing properties within the myosin superfamily. In particular, we use modeling and simulations to make predictions regarding how diversity in force sensing affects the lifetime of the actomyosin bond, the myosin power output, and the ability of myosin to respond to a perturbation in force for several nonprocessive myosin isoforms.
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Affiliation(s)
- Michael J Greenberg
- Biochemistry and Molecular Biophysics, Washington University, St. Louis, Missouri
| | - Göker Arpağ
- Worcester Polytechnic Institute, Worcester, Massachusetts
| | - Erkan Tüzel
- Worcester Polytechnic Institute, Worcester, Massachusetts
| | - E Michael Ostap
- Pennsylvania Muscle Institute and Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
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37
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Fenix AM, Taneja N, Buttler CA, Lewis J, Van Engelenburg SB, Ohi R, Burnette DT. Expansion and concatenation of non-muscle myosin IIA filaments drive cellular contractile system formation during interphase and mitosis. Mol Biol Cell 2016; 27:mbc.E15-10-0725. [PMID: 26960797 PMCID: PMC4850034 DOI: 10.1091/mbc.e15-10-0725] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 02/25/2016] [Accepted: 03/01/2016] [Indexed: 11/19/2022] Open
Abstract
Cell movement and cytokinesis are facilitated by contractile forces generated by the molecular motor, non-muscle myosin II (NMII). NMII molecules form a filament (NMII-F) through interactions of their C-terminal rod domains, positioning groups of N-terminal motor domains on opposite sides. The NMII motors then bind and pull actin filaments toward the NMII-F, thus driving contraction. Inside of crawling cells, NMIIA-Fs form large macromolecular ensembles (i.e., NMIIA-F stacks) but how this occurs is unknown. Here we show NMIIA-F stacks are formed through two non-mutually exclusive mechanisms: expansion and concatenation. During expansion, NMIIA molecules within the NMIIA-F spread out concurrent with addition of new NMIIA molecules. Concatenation occurs when multiple NMIIA-F/NMIIA-F stacks move together and align. We found NMIIA-F stack formation was regulated by both motor-activity and the availability of surrounding actin filaments. Furthermore, our data showed expansion and concatenation also formed the contractile ring in dividing cells. Thus, interphase and mitotic cells share similar mechanisms for creating large contractile units, and these are likely to underlie how other myosin II-based contractile systems are assembled.
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Affiliation(s)
- Aidan M Fenix
- Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Nilay Taneja
- Vanderbilt University School of Medicine, Nashville, TN 37232
| | | | - John Lewis
- Vanderbilt University School of Medicine, Nashville, TN 37232 Kalamazoo College, Kalamazoo, MI 49008
| | | | - Ryoma Ohi
- Vanderbilt University School of Medicine, Nashville, TN 37232
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38
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Surfing along Filopodia: A Particle Transport Revealed by Molecular-Scale Fluctuation Analyses. Biophys J 2016; 108:2114-25. [PMID: 25954870 DOI: 10.1016/j.bpj.2015.02.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 02/13/2015] [Accepted: 02/23/2015] [Indexed: 01/08/2023] Open
Abstract
Filopodia perform cellular functions such as environmental sensing or cell motility, but they also grab for particles and withdraw them leading to an increased efficiency of phagocytic uptake. Remarkably, withdrawal of micron-sized particles is also possible without noticeable movements of the filopodia. Here, we demonstrate that polystyrene beads connected by optical tweezers to the ends of adherent filopodia of J774 macrophages, are transported discontinuously toward the cell body. After a typical resting time of 1-2 min, the cargo is moved with alternating velocities, force constants, and friction constants along the surface of the filopodia. This surfing-like behavior along the filopodium is recorded by feedback-controlled interferometric three-dimensional tracking of the bead motions at 10-100 kHz. We measured transport velocities of up to 120 nm/s and transport forces of ∼ 70 pN. Small changes in position, fluctuation width, and temporal correlation, which are invisible in conventional microscopy, indicate molecular reorganization of transport-relevant proteins in different phases of the entire transport process. A detailed analysis implicates a controlled particle transport with fingerprints of a nanoscale unbinding/binding behavior. The manipulation and analysis methods presented in our study may also be helpful in other fields of cellular biophysics.
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Hundt N, Steffen W, Pathan-Chhatbar S, Taft MH, Manstein DJ. Load-dependent modulation of non-muscle myosin-2A function by tropomyosin 4.2. Sci Rep 2016; 6:20554. [PMID: 26847712 PMCID: PMC4742800 DOI: 10.1038/srep20554] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 01/06/2016] [Indexed: 01/14/2023] Open
Abstract
Tropomyosin isoforms play an important role in the organisation of cytoplasmic actomyosin complexes in regard to function and cellular localisation. In particular, Tpm4.2 is upregulated in rapidly migrating cells and responsible for the specific recruitment of the cytoplasmic class-2 myosin NM-2A to actin filaments during the formation of stress fibres. Here, we investigate how the decoration of F-actin with Tpm4.2 affects the motor properties of NM-2A under conditions of low and high load. In the absence of external forces, decoration of actin filaments with Tpm4.2 does not affect the gated release of ADP from NM-2A and the transition from strong to weak actin-binding states. In the presence of resisting loads, our results reveal a marked increase in the mechanosensitive gating between the leading and trailing myosin head. Thereby, the processive behaviour of NM-2A is enhanced in the presence of resisting loads. The load- and Tpm4.2-induced changes in the functional behaviour of NM-2A are in good agreement with the role of this myosin in the context of stress fibres and the maintenance of cellular tension.
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Affiliation(s)
- Nikolas Hundt
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Walter Steffen
- Molecular and Cell Physiology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Salma Pathan-Chhatbar
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Manuel H Taft
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Dietmar J Manstein
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.,Division for Structural Analysis, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
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40
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E-cadherin junctions as active mechanical integrators in tissue dynamics. Nat Cell Biol 2015; 17:533-9. [PMID: 25925582 DOI: 10.1038/ncb3136] [Citation(s) in RCA: 369] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
During epithelial morphogenesis, E-cadherin adhesive junctions play an important part in mechanically coupling the contractile cortices of cells together, thereby distributing the stresses that drive cell rearrangements at both local and tissue levels. Here we discuss the concept that cellular contractility and E-cadherin-based adhesion are functionally integrated by biomechanical feedback pathways that operate on molecular, cellular and tissue scales.
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41
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Poorly understood aspects of striated muscle contraction. BIOMED RESEARCH INTERNATIONAL 2015; 2015:245154. [PMID: 25961006 PMCID: PMC4415482 DOI: 10.1155/2015/245154] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 10/28/2014] [Indexed: 11/23/2022]
Abstract
Muscle contraction results from cyclic interactions between the contractile proteins myosin and actin, driven by the turnover of adenosine triphosphate (ATP). Despite intense studies, several molecular events in the contraction process are poorly understood, including the relationship between force-generation and phosphate-release in the ATP-turnover. Different aspects of the force-generating transition are reflected in the changes in tension development by muscle cells, myofibrils and single molecules upon changes in temperature, altered phosphate concentration, or length perturbations. It has been notoriously difficult to explain all these events within a given theoretical framework and to unequivocally correlate observed events with the atomic structures of the myosin motor. Other incompletely understood issues include the role of the two heads of myosin II and structural changes in the actin filaments as well as the importance of the three-dimensional order. We here review these issues in relation to controversies regarding basic physiological properties of striated muscle. We also briefly consider actomyosin mutation effects in cardiac and skeletal muscle function and the possibility to treat these defects by drugs.
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42
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Abstract
The human genome contains 39 myosin genes, divided up into 12 different classes. The structure, cellular function and biochemical properties of many of these isoforms remain poorly characterized and there is still some controversy as to whether some myosin isoforms are monomers or dimers. Myosin isoforms 6 and 10 contain a stable single α-helical (SAH) domain, situated just after the canonical lever. The SAH domain is stiff enough to be able to lengthen the lever allowing the myosin to take a larger step. In addition, atomic force microscopy and atomistic simulations show that SAH domains unfold at relatively low forces and have a high propensity to refold. These properties are likely to be important for protein function, enabling motors to carry cargo in dense actin networks, and other proteins to remain attached to binding partners in the crowded cell.
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43
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Abstract
Biological mechano-transduction and force-dependent changes scale from protein conformation (â„« to nm) to cell organization and multi-cell function (mm to cm) to affect cell organization, fate, and homeostasis. External forces play complex roles in cell organization, fate, and homeostasis. Changes in these forces, or how cells respond to them, can result in abnormal embryonic development and diseases in adults. How cells sense and respond to these mechanical stimuli requires an understanding of the biophysical principles that underlie changes in protein conformation and result in alterations in the organization and function of cells and tissues. Here, we discuss mechano-transduction as it applies to protein conformation, cellular organization, and multi-cell (tissue) function.
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Affiliation(s)
- Beth L. Pruitt
- Department of Mechanical Engineering, Stanford University, Stanford, California, United States of America
- Cardiovascular Institute, Stanford University, Stanford, California, United States of America
- * E-mail: (BLP); (ARD); (WIW); (WJN)
| | - Alexander R. Dunn
- Department of Chemical Engineering, Stanford University, Stanford, California, United States of America
- Cardiovascular Institute, Stanford University, Stanford, California, United States of America
- * E-mail: (BLP); (ARD); (WIW); (WJN)
| | - William I. Weis
- Department of Structural Biology, Stanford University, Stanford, California, United States of America
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, California, United States of America
- * E-mail: (BLP); (ARD); (WIW); (WJN)
| | - W. James Nelson
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, California, United States of America
- Department of Biology, Stanford University, Stanford, California, United States of America
- * E-mail: (BLP); (ARD); (WIW); (WJN)
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44
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Jensen CS, Watanabe S, Rasmussen HB, Schmitt N, Olesen SP, Frost NA, Blanpied TA, Misonou H. Specific sorting and post-Golgi trafficking of dendritic potassium channels in living neurons. J Biol Chem 2014; 289:10566-10581. [PMID: 24569993 DOI: 10.1074/jbc.m113.534495] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Proper membrane localization of ion channels is essential for the function of neuronal cells. Particularly, the computational ability of dendrites depends on the localization of different ion channels in specific subcompartments. However, the molecular mechanisms that control ion channel localization in distinct dendritic subcompartments are largely unknown. Here, we developed a quantitative live cell imaging method to analyze protein sorting and post-Golgi vesicular trafficking. We focused on two dendritic voltage-gated potassium channels that exhibit distinct localizations: Kv2.1 in proximal dendrites and Kv4.2 in distal dendrites. Our results show that Kv2.1 and Kv4.2 channels are sorted into two distinct populations of vesicles at the Golgi apparatus. The targeting of Kv2.1 and Kv4.2 vesicles occurred by distinct mechanisms as evidenced by their requirement for specific peptide motifs, cytoskeletal elements, and motor proteins. By live cell and super-resolution imaging, we identified a novel trafficking machinery important for the localization of Kv2.1 channels. Particularly, we identified non-muscle myosin II as an important factor in Kv2.1 trafficking. These findings reveal that the sorting of ion channels at the Golgi apparatus and their subsequent trafficking by unique molecular mechanisms are crucial for their specific localizations within dendrites.
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Affiliation(s)
- Camilla Stampe Jensen
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark; Department of Neural and Pain Sciences, University of Maryland, Baltimore, Maryland 21201
| | - Shoji Watanabe
- Unit for Brain Pathology, Graduate School of Brain Science, Doshisha University, Kyoto 619-02225, Japan
| | - Hanne Borger Rasmussen
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Nicole Schmitt
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Søren-Peter Olesen
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Nicholas A Frost
- Department of Physiology, University of Maryland, Baltimore, Maryland 21201
| | - Thomas A Blanpied
- Department of Physiology, University of Maryland, Baltimore, Maryland 21201
| | - Hiroaki Misonou
- Department of Neural and Pain Sciences, University of Maryland, Baltimore, Maryland 21201; Unit for Brain Pathology, Graduate School of Brain Science, Doshisha University, Kyoto 619-02225, Japan.
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45
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Parameswaran H, Lutchen KR, Suki B. A computational model of the response of adherent cells to stretch and changes in substrate stiffness. J Appl Physiol (1985) 2014; 116:825-34. [PMID: 24408996 DOI: 10.1152/japplphysiol.00962.2013] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cells in the body exist in a dynamic mechanical environment where they are subject to mechanical stretch as well as changes in composition and stiffness of the underlying extracellular matrix (ECM). However, the underlying mechanisms by which cells sense and adapt to their dynamic mechanical environment, in particular to stretch, are not well understood. In this study, we hypothesized that emergent phenomena at the level of the actin network arising from active structural rearrangements driven by nonmuscle myosin II molecular motors play a major role in the cellular response to both stretch and changes in ECM stiffness. To test this hypothesis, we introduce a simple network model of actin-myosin interactions that links active self-organization of the actin network to the stiffness of the network and the traction forces generated by the network. We demonstrate that such a network replicates not only the effect of changes in substrate stiffness on cellular traction and stiffness and the dependence of rate of force development by a cell on the stiffness of its substrate, but also explains the physical response of adherent cells to transient and cyclic stretch. Our results provide strong indication that network phenomena governed by the active reorganization of the actin-myosin structure plays an important role in cellular mechanosensing and response to both changes in ECM stiffness and externally applied mechanical stretch.
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Qi Z, Pugh RA, Spies M, Chemla YR. Sequence-dependent base pair stepping dynamics in XPD helicase unwinding. eLife 2013; 2:e00334. [PMID: 23741615 PMCID: PMC3668415 DOI: 10.7554/elife.00334] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 04/26/2013] [Indexed: 11/13/2022] Open
Abstract
Helicases couple the chemical energy of ATP hydrolysis to directional translocation along nucleic acids and transient duplex separation. Understanding helicase mechanism requires that the basic physicochemical process of base pair separation be understood. This necessitates monitoring helicase activity directly, at high spatio-temporal resolution. Using optical tweezers with single base pair (bp) resolution, we analyzed DNA unwinding by XPD helicase, a Superfamily 2 (SF2) DNA helicase involved in DNA repair and transcription initiation. We show that monomeric XPD unwinds duplex DNA in 1-bp steps, yet exhibits frequent backsteps and undergoes conformational transitions manifested in 5-bp backward and forward steps. Quantifying the sequence dependence of XPD stepping dynamics with near base pair resolution, we provide the strongest and most direct evidence thus far that forward, single-base pair stepping of a helicase utilizes the spontaneous opening of the duplex. The proposed unwinding mechanism may be a universal feature of DNA helicases that move along DNA phosphodiester backbones. DOI:http://dx.doi.org/10.7554/eLife.00334.001.
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Affiliation(s)
- Zhi Qi
- Center for Biophysics and Computational Biology , University of Illinois at Urbana-Champaign , Urbana , United States
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47
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Matsui TS, Sato M, Deguchi S. High extensibility of stress fibers revealed by in vitro micromanipulation with fluorescence imaging. Biochem Biophys Res Commun 2013; 434:444-8. [PMID: 23583399 DOI: 10.1016/j.bbrc.2013.03.093] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 03/19/2013] [Indexed: 10/26/2022]
Abstract
Stress fibers (SFs), subcellular bundles of actin and myosin filaments, are physically connected at their ends to cell adhesions. The intracellular force transmitted via SFs plays an essential role in cell adhesion regulation and downstream signaling. However, biophysical properties intrinsic to individual SFs remain poorly understood partly because SFs are surrounded by other cytoplasmic components that restrict the deformation of the embedded materials. To characterize their inherent properties independent of other structural components, we isolated SFs from vascular smooth muscle cells and mechanically stretched them by in vitro manipulation while visualizing strain with fluorescent quantum dots attached along their length. SFs were elongated along their entire length, with the length being approximately 4-fold of the stress-free length. This surprisingly high extensibility was beyond that explained by the tandem connection of actin filaments and myosin II bipolar filaments present in SFs, thus suggesting the involvement of other structural components in their passive biophysical properties.
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48
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Abstract
Cytoskeletal trafficking systems are becoming more complex at every turn. A new study reports that a yeast myosin V walks on only a select few actin filaments - those that are decorated with tropomyosin.
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49
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Nagy A, Takagi Y, Billington N, Sun SA, Hong DKT, Homsher E, Wang A, Sellers JR. Kinetic characterization of nonmuscle myosin IIb at the single molecule level. J Biol Chem 2012; 288:709-22. [PMID: 23148220 DOI: 10.1074/jbc.m112.424671] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nonmuscle myosin IIB (NMIIB) is a cytoplasmic myosin, which plays an important role in cell motility by maintaining cortical tension. It forms bipolar thick filaments with ~14 myosin molecule dimers on each side of the bare zone. Our previous studies showed that the NMIIB is a moderately high duty ratio (~20-25%) motor. The ADP release step (~0.35 s(-1)) of NMIIB is only ~3 times faster than the rate-limiting phosphate release (0.13 ± 0.01 s(-1)). The aim of this study was to relate the known in vitro kinetic parameters to the results of single molecule experiments and to compare the kinetic and mechanical properties of single- and double-headed myosin fragments and nonmuscle IIB thick filaments. Examination of the kinetics of NMIIB interaction with actin at the single molecule level was accomplished using total internal reflection fluorescence (TIRF) with fluorescence imaging with 1-nm accuracy (FIONA) and dual-beam optical trapping. At a physiological ATP concentration (1 mm), the rate of detachment of the single-headed and double-headed molecules was similar (~0.4 s(-1)). Using optical tweezers we found that the power stroke sizes of single- and double-headed heavy meromyosin (HMM) were each ~6 nm. No signs of processive stepping at the single molecule level were observed in the case of NMIIB-HMM in optical tweezers or TIRF/in vitro motility experiments. In contrast, robust motility of individual fluorescently labeled thick filaments of full-length NMIIB was observed on actin filaments. Our results are in good agreement with the previous steady-state and transient kinetic studies and show that the individual nonprocessive nonmuscle myosin IIB molecules form a highly processive unit when polymerized into filaments.
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Affiliation(s)
- Attila Nagy
- Laboratory of Molecular Physiology, HLBI, National Institutes of Health, Bethesda, Maryland 20892, USA
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50
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Heissler SM, Manstein DJ. Nonmuscle myosin-2: mix and match. Cell Mol Life Sci 2012; 70:1-21. [PMID: 22565821 PMCID: PMC3535348 DOI: 10.1007/s00018-012-1002-9] [Citation(s) in RCA: 165] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2012] [Revised: 04/16/2012] [Accepted: 04/17/2012] [Indexed: 12/31/2022]
Abstract
Members of the nonmuscle myosin-2 (NM-2) family of actin-based molecular motors catalyze the conversion of chemical energy into directed movement and force thereby acting as central regulatory components of the eukaryotic cytoskeleton. By cyclically interacting with adenosine triphosphate and F-actin, NM-2 isoforms promote cytoskeletal force generation in established cellular processes like cell migration, shape changes, adhesion dynamics, endo- and exo-cytosis, and cytokinesis. Novel functions of the NM-2 family members in autophagy and viral infection are emerging, making NM-2 isoforms regulators of nearly all cellular processes that require the spatiotemporal organization of cytoskeletal scaffolding. Here, we assess current views about the role of NM-2 isoforms in these activities including the tight regulation of NM-2 assembly and activation through phosphorylation and how NM-2-mediated changes in cytoskeletal dynamics and mechanics affect cell physiological functions in health and disease.
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Affiliation(s)
- Sarah M. Heissler
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Dietmar J. Manstein
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
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