1
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Flormann DAD, Kainka L, Montalvo G, Anton C, Rheinlaender J, Thalla D, Vesperini D, Pohland MO, Kaub KH, Schu M, Pezzano F, Ruprecht V, Terriac E, Hawkins RJ, Lautenschläger F. The structure and mechanics of the cell cortex depend on the location and adhesion state. Proc Natl Acad Sci U S A 2024; 121:e2320372121. [PMID: 39042691 PMCID: PMC11295003 DOI: 10.1073/pnas.2320372121] [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: 11/28/2023] [Accepted: 06/16/2024] [Indexed: 07/25/2024] Open
Abstract
Cells exist in different phenotypes and can transition between them. A phenotype may be characterized by many different aspects. Here, we focus on the example of whether the cell is adhered or suspended and choose particular parameters related to the structure and mechanics of the actin cortex. The cortex is essential to cell mechanics, morphology, and function, such as for adhesion, migration, and division of animal cells. To predict and control cellular functions and prevent malfunctioning, it is necessary to understand the actin cortex. The structure of the cortex governs cell mechanics; however, the relationship between the architecture and mechanics of the cortex is not yet well enough understood to be able to predict one from the other. Therefore, we quantitatively measured structural and mechanical cortex parameters, including cortical thickness, cortex mesh size, actin bundling, and cortex stiffness. These measurements required developing a combination of measurement techniques in scanning electron, expansion, confocal, and atomic force microscopy. We found that the structure and mechanics of the cortex of cells in interphase are different depending on whether the cell is suspended or adhered. We deduced general correlations between structural and mechanical properties and show how these findings can be explained within the framework of semiflexible polymer network theory. We tested the model predictions by perturbing the properties of the actin within the cortex using compounds. Our work provides an important step toward predictions of cell mechanics from cortical structures and suggests how cortex remodeling between different phenotypes impacts the mechanical properties of cells.
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Affiliation(s)
- D. A. D. Flormann
- Department of Physics, Saarland University, Saarbrücken 66123, Germany
| | - L. Kainka
- Department of Physics, Saarland University, Saarbrücken 66123, Germany
| | - G. Montalvo
- Department of Physics, Saarland University, Saarbrücken 66123, Germany
| | - C. Anton
- Department of Physics, Saarland University, Saarbrücken 66123, Germany
| | - J. Rheinlaender
- Faculty of Science, Institute of Applied Physics, University of Tübingen, Tübingen72076, Germany
| | - D. Thalla
- Department of Physics, Saarland University, Saarbrücken 66123, Germany
| | - D. Vesperini
- Department of Physics, Saarland University, Saarbrücken 66123, Germany
| | - M. O. Pohland
- Department of Physics, Saarland University, Saarbrücken 66123, Germany
| | - K. H. Kaub
- Department of Physics, Saarland University, Saarbrücken 66123, Germany
- Department of Biophysical Chemistry, Georg-August-University, Göttingen37077, Germany
| | - M. Schu
- Department of Physics, Saarland University, Saarbrücken 66123, Germany
| | - F. Pezzano
- Center for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona08003, Spain
| | - V. Ruprecht
- Center for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona08003, Spain
- Universitat Pompeu Fabra, Barcelona08002, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona08010, Spain
| | - E. Terriac
- Department of Physics, Saarland University, Saarbrücken 66123, Germany
| | - R. J. Hawkins
- Department of Physics and Astronomy, University of Sheffield, SheffieldS3 7RH, United Kingdom
- African Institute for Mathematical Sciences, Accra20046, Ghana
| | - F. Lautenschläger
- Department of Physics, Saarland University, Saarbrücken 66123, Germany
- Center for Biophysics, Saarland University, Saarbrücken66123, Germany
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2
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Yi H, Gong D, Daddysman MK, Renn M, Scherer NF. Distinct Sub- to Superdiffuse Insulin Granule Transport Behaviors in β-Cells Are Strongly Affected by Granule Age. J Phys Chem B 2024; 128:6246-6256. [PMID: 38861346 DOI: 10.1021/acs.jpcb.4c01403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2024]
Abstract
Intracellular transport is a complex process that is difficult to describe by a single general model for motion. Here, we study the transport of insulin containing vesicles, termed granules, in live MIN6 cells. We characterize how the observed heterogeneity is affected by different intracellular factors by constructing a MIN6 cell line by CRISPR-CAS9 that constitutively expresses mCherry fused to insulin and is thus packaged in granules. Confocal microscopy imaging and single particle tracking of the granule transport provide long trajectories of thousands of single granule trajectories for statistical analysis. Mean squared displacement (MSD), angle correlation distribution, and step size distribution analysis allowed identifying five distinct granule transport subpopulations, from nearly immobile and subdiffusive to run-pause and superdiffusive. The subdiffusive subpopulation recapitulates the subordinated random walk we reported earlier (Tabei, 2013; ref 18). We show that the transport characteristics of the five subpopulations have a strong dependence on the age of insulin granules. The five subpopulations also reflect the effect of local microtubule and actin networks on transport in different cellular regions. Our results provide robust metrics to clarify the heterogeneity of granule transport and demonstrate the roles of microtubule versus actin networks with granule age since initial packaging in the Golgi.
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Affiliation(s)
- Hannah Yi
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637, United States
| | - Daozheng Gong
- Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637, United States
- Graduate Program in Biophysical Science, University of Chicago, Chicago, Illinois 60637, United States
| | - Matthew K Daddysman
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637, United States
| | - Martha Renn
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637, United States
| | - Norbert F Scherer
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637, United States
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3
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Redford SA, Colen J, Shivers JL, Zemsky S, Molaei M, Floyd C, Ruijgrok PV, Vitelli V, Bryant Z, Dinner AR, Gardel ML. Motor crosslinking augments elasticity in active nematics. SOFT MATTER 2024; 20:2480-2490. [PMID: 38385209 PMCID: PMC10933839 DOI: 10.1039/d3sm01176c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 01/12/2024] [Indexed: 02/23/2024]
Abstract
In active materials, uncoordinated internal stresses lead to emergent long-range flows. An understanding of how the behavior of active materials depends on mesoscopic (hydrodynamic) parameters is developing, but there remains a gap in knowledge concerning how hydrodynamic parameters depend on the properties of microscopic elements. In this work, we combine experiments and multiscale modeling to relate the structure and dynamics of active nematics composed of biopolymer filaments and molecular motors to their microscopic properties, in particular motor processivity, speed, and valency. We show that crosslinking of filaments by both motors and passive crosslinkers not only augments the contributions to nematic elasticity from excluded volume effects but dominates them. By altering motor kinetics we show that a competition between motor speed and crosslinking results in a nonmonotonic dependence of nematic flow on motor speed. By modulating passive filament crosslinking we show that energy transfer into nematic flow is in large part dictated by crosslinking. Thus motor proteins both generate activity and contribute to nematic elasticity. Our results provide new insights for rationally engineering active materials.
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Affiliation(s)
- Steven A Redford
- The Graduate Program in Biophysical Sciences, University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA.
| | - Jonathan Colen
- Department of Physics, University of Chicago, Chicago, IL 60637, USA
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
| | - Jordan L Shivers
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
- Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | - Sasha Zemsky
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Program in Biophysics, Stanford University, Stanford, CA 94305, USA
| | - Mehdi Molaei
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA
| | - Carlos Floyd
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
- Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | - Paul V Ruijgrok
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Vincenzo Vitelli
- Department of Physics, University of Chicago, Chicago, IL 60637, USA
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
| | - Zev Bryant
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Aaron R Dinner
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA.
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
- Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | - Margaret L Gardel
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA.
- Department of Physics, University of Chicago, Chicago, IL 60637, USA
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA
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4
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Chou WH, Molaei M, Wu H, Oakes PW, Beach JR, Gardel ML. Limiting pool and actin architecture controls myosin cluster sizes in adherent cells. Biophys J 2024; 123:157-171. [PMID: 38062704 PMCID: PMC10808045 DOI: 10.1016/j.bpj.2023.12.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 09/11/2023] [Accepted: 12/04/2023] [Indexed: 12/19/2023] Open
Abstract
The actomyosin cytoskeleton generates mechanical forces that power important cellular processes, such as cell migration, cell division, and mechanosensing. Actomyosin self-assembles into contractile networks and bundles that underlie force generation and transmission in cells. A central step is the assembly of the myosin II filament from myosin monomers, regulation of which has been extensively studied. However, myosin filaments are almost always found as clusters within the cell cortex. While recent studies characterized cluster nucleation dynamics at the cell periphery, how myosin clusters grow on stress fibers remains poorly characterized. Here, we utilize a U2OS osteosarcoma cell line with endogenously tagged myosin II to measure the myosin cluster size distribution in the lamella of adherent cells. We find that myosin clusters can grow with Rho-kinase (ROCK) activity alone in the absence of myosin motor activity. Time-lapse imaging reveals that myosin clusters grow via increased myosin association to existing clusters, which is potentiated by ROCK-dependent myosin filament assembly. Enabling myosin motor activity allows further myosin cluster growth through myosin association that is dependent on F-actin architecture. Using a toy model, we show that myosin self-affinity is sufficient to recapitulate the experimentally observed myosin cluster size distribution, and that myosin cluster sizes are determined by the pool of myosin available for cluster growth. Together, our findings provide new insights into the regulation of myosin cluster sizes within the lamellar actomyosin cytoskeleton.
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Affiliation(s)
- Wen-Hung Chou
- Graduate Program in Biophysical Sciences, The University of Chicago, Chicago, Illinois; Institute of Biophysical Dynamics, The University of Chicago, Chicago, Illinois
| | - Mehdi Molaei
- Institute of Biophysical Dynamics, The University of Chicago, Chicago, Illinois; Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois
| | - Huini Wu
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Chicago, Illinois
| | - Patrick W Oakes
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Chicago, Illinois
| | - Jordan R Beach
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Chicago, Illinois
| | - Margaret L Gardel
- Institute of Biophysical Dynamics, The University of Chicago, Chicago, Illinois; Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois; James Franck Institute, The University of Chicago, Chicago, Illinois; Department of Physics, The University of Chicago, Chicago, Illinois.
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5
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Banerjee DS, Freedman SL, Murrell MP, Banerjee S. Growth-induced collective bending and kinetic trapping of cytoskeletal filaments. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.09.574885. [PMID: 38260433 PMCID: PMC10802417 DOI: 10.1101/2024.01.09.574885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Growth and turnover of actin filaments play a crucial role in the construction and maintenance of actin networks within cells. Actin filament growth occurs within limited space and finite subunit resources in the actin cortex. To understand how filament growth shapes the emergent architecture of actin networks, we developed a minimal agent-based model coupling filament mechanics and growth in a limiting subunit pool. We find that rapid filament growth induces kinetic trapping of highly bent actin filaments. Such collective bending patterns are long-lived, organized around nematic defects, and arises from competition between filament polymerization and bending elasticity. The stability of nematic defects and the extent of kinetic trapping are amplified by an increase in the abundance of the actin pool and by crosslinking the network. These findings suggest that kinetic trapping is a robust consequence of growth in crowded environments, providing a route to program shape memory in actin networks.
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Affiliation(s)
- Deb Sankar Banerjee
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
| | | | - Michael P Murrell
- Department of Biomedical Engineering, Yale University, 10 Hillhouse Avenue, New Haven, CT, USA
- Systems Biology Institute, 850 West Campus Drive, West Haven, CT, USA
- Department of Physics, Yale University, 217 Prospect Street, New Haven, CT, USA
| | - Shiladitya Banerjee
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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6
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Najma B, Wei WS, Baskaran A, Foster PJ, Duclos G. Microscopic interactions control a structural transition in active mixtures of microtubules and molecular motors. Proc Natl Acad Sci U S A 2024; 121:e2300174121. [PMID: 38175870 PMCID: PMC10786313 DOI: 10.1073/pnas.2300174121] [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: 01/04/2023] [Accepted: 10/07/2023] [Indexed: 01/06/2024] Open
Abstract
Microtubules and molecular motors are essential components of the cellular cytoskeleton, driving fundamental processes in vivo, including chromosome segregation and cargo transport. When reconstituted in vitro, these cytoskeletal proteins serve as energy-consuming building blocks to study the self-organization of active matter. Cytoskeletal active gels display rich emergent dynamics, including extensile flows, locally contractile asters, and bulk contraction. However, it is unclear how the protein-protein interaction kinetics set their contractile or extensile nature. Here, we explore the origin of the transition from extensile bundles to contractile asters in a minimal reconstituted system composed of stabilized microtubules, depletant, adenosine 5'-triphosphate (ATP), and clusters of kinesin-1 motors. We show that the microtubule-binding and unbinding kinetics of highly processive motor clusters set their ability to end-accumulate, which can drive polarity sorting of the microtubules and aster formation. We further demonstrate that the microscopic time scale of end-accumulation sets the emergent time scale of aster formation. Finally, we show that biochemical regulation is insufficient to fully explain the transition as generic aligning interactions through depletion, cross-linking, or excluded volume interactions can drive bundle formation despite end-accumulating motors. The extensile-to-contractile transition is well captured by a simple self-assembly model where nematic and polar aligning interactions compete to form either bundles or asters. Starting from a five-dimensional organization phase space, we identify a single control parameter given by the ratio of the different component concentrations that dictates the material-scale organization. Overall, this work shows that the interplay of biochemical and mechanical tuning at the microscopic level controls the robust self-organization of active cytoskeletal materials.
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Affiliation(s)
- Bibi Najma
- Department of Physics, Brandeis University, Waltham, MA02453
| | - Wei-Shao Wei
- Department of Physics, Brandeis University, Waltham, MA02453
| | - Aparna Baskaran
- Department of Physics, Brandeis University, Waltham, MA02453
| | - Peter J. Foster
- Department of Physics, Brandeis University, Waltham, MA02453
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7
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Molaei M, Redford SA, Chou WH, Scheff D, de Pablo JJ, Oakes PW, Gardel ML. Measuring response functions of active materials from data. Proc Natl Acad Sci U S A 2023; 120:e2305283120. [PMID: 37819979 PMCID: PMC10589671 DOI: 10.1073/pnas.2305283120] [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: 03/31/2023] [Accepted: 08/08/2023] [Indexed: 10/13/2023] Open
Abstract
From flocks of birds to biomolecular assemblies, systems in which many individual components independently consume energy to perform mechanical work exhibit a wide array of striking behaviors. Methods to quantify the dynamics of these so-called active systems generally aim to extract important length or time scales from experimental fields. Because such methods focus on extracting scalar values, they do not wring maximal information from experimental data. We introduce a method to overcome these limitations. We extend the framework of correlation functions by taking into account the internal headings of displacement fields. The functions we construct represent the material response to specific types of active perturbation within the system. Utilizing these response functions we query the material response of disparate active systems composed of actin filaments and myosin motors, from model fluids to living cells. We show we can extract critical length scales from the turbulent flows of an active nematic, anticipate contractility in an active gel, distinguish viscous from viscoelastic dissipation, and even differentiate modes of contractility in living cells. These examples underscore the vast utility of this method which measures response functions from experimental observations of complex active systems.
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Affiliation(s)
- Mehdi Molaei
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL60637
- James Franck Institute, University of Chicago, Chicago, IL60637
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL60637
| | - Steven A. Redford
- James Franck Institute, University of Chicago, Chicago, IL60637
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL60637
- Graduate Program in Biophysical Sciences, University of Chicago, Chicago, IL60637
| | - Wen-Hung Chou
- James Franck Institute, University of Chicago, Chicago, IL60637
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL60637
- Graduate Program in Biophysical Sciences, University of Chicago, Chicago, IL60637
| | - Danielle Scheff
- James Franck Institute, University of Chicago, Chicago, IL60637
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL60637
- Department of Physics, University of Chicago, Chicago, IL60637
| | - Juan J. de Pablo
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL60637
| | - Patrick W. Oakes
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL60153
| | - Margaret L. Gardel
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL60637
- James Franck Institute, University of Chicago, Chicago, IL60637
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL60637
- Department of Physics, University of Chicago, Chicago, IL60637
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8
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McGorty RJ, Currie CJ, Michel J, Sasanpour M, Gunter C, Lindsay KA, Rust MJ, Katira P, Das M, Ross JL, Robertson-Anderson RM. Kinesin and myosin motors compete to drive rich multiphase dynamics in programmable cytoskeletal composites. PNAS NEXUS 2023; 2:pgad245. [PMID: 37575673 PMCID: PMC10416814 DOI: 10.1093/pnasnexus/pgad245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 07/07/2023] [Accepted: 07/17/2023] [Indexed: 08/15/2023]
Abstract
The cellular cytoskeleton relies on diverse populations of motors, filaments, and binding proteins acting in concert to enable nonequilibrium processes ranging from mitosis to chemotaxis. The cytoskeleton's versatile reconfigurability, programmed by interactions between its constituents, makes it a foundational active matter platform. However, current active matter endeavors are limited largely to single force-generating components acting on a single substrate-far from the composite cytoskeleton in cells. Here, we engineer actin-microtubule (MT) composites, driven by kinesin and myosin motors and tuned by crosslinkers, to ballistically restructure and flow with speeds that span three orders of magnitude depending on the composite formulation and time relative to the onset of motor activity. Differential dynamic microscopy analyses reveal that kinesin and myosin compete to delay the onset of acceleration and suppress discrete restructuring events, while passive crosslinking of either actin or MTs has an opposite effect. Our minimal advection-diffusion model and spatial correlation analyses correlate these dynamics to structure, with motor antagonism suppressing reconfiguration and demixing, while crosslinking enhances clustering. Despite the rich formulation space and emergent formulation-dependent structures, the nonequilibrium dynamics across all composites and timescales can be organized into three classes-slow isotropic reorientation, fast directional flow, and multimode restructuring. Moreover, our mathematical model demonstrates that diverse structural motifs can arise simply from the interplay between motor-driven advection and frictional drag. These general features of our platform facilitate applicability to other active matter systems and shed light on diverse ways that cytoskeletal components can cooperate or compete to enable wide-ranging cellular processes.
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Affiliation(s)
- Ryan J McGorty
- Department of Physics and Biophysics, University of San Diego, San Diego, CA 92110, USA
| | - Christopher J Currie
- Department of Physics and Biophysics, University of San Diego, San Diego, CA 92110, USA
| | - Jonathan Michel
- School of Physics and Astronomy, Rochester Institute of Technology, Rochester, NY 14623, USA
| | - Mehrzad Sasanpour
- Department of Physics and Biophysics, University of San Diego, San Diego, CA 92110, USA
| | - Christopher Gunter
- Department of Mechanical Engineering, San Diego State University, San Diego, CA 92182, USA
| | - K Alice Lindsay
- Department of Physics, Syracuse University, Syracuse, NY 13244, USA
| | - Michael J Rust
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Parag Katira
- Department of Mechanical Engineering, San Diego State University, San Diego, CA 92182, USA
| | - Moumita Das
- School of Physics and Astronomy, Rochester Institute of Technology, Rochester, NY 14623, USA
| | - Jennifer L Ross
- Department of Physics, Syracuse University, Syracuse, NY 13244, USA
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9
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Chou WH, Molaei M, Wu H, Oakes PW, Beach JR, Gardel ML. Limiting Pool and Actin Architecture Controls Myosin Cluster Sizes in Adherent Cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.07.544121. [PMID: 37333106 PMCID: PMC10274763 DOI: 10.1101/2023.06.07.544121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
The actomyosin cytoskeleton generates mechanical forces that power important cellular processes, such as cell migration, cell division, and mechanosensing. Actomyosin self-assembles into contractile networks and bundles that underlie force generation and transmission in cells. A central step is the assembly of the myosin II filament from myosin monomers, regulation of which has been extensively studied. However, myosin filaments are almost always found as clusters within the cell cortex. While recent studies characterized cluster nucleation dynamics at the cell periphery, how myosin clusters grow on stress fibers remains poorly characterized. Here, we utilize a U2OS osteosarcoma cell line with endogenously tagged myosin II to measure the myosin cluster size distribution in the lamella of adherent cells. We find that myosin clusters can grow with Rho-kinase (ROCK) activity alone in the absence of myosin motor activity. Time-lapse imaging reveals that myosin clusters grow via increased myosin association to existing clusters, which is potentiated by ROCK-dependent myosin filament assembly. Enabling myosin motor activity allows further myosin cluster growth through myosin association that is dependent on F-actin architecture. Using a toy model, we show that myosin self-affinity is sufficient to recapitulate the experimentally observed myosin cluster size distribution, and that myosin cluster sizes are determined by the pool of myosin available for cluster growth. Together, our findings provide new insights into the regulation of myosin cluster sizes within the lamellar actomyosin cytoskeleton.
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10
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Ni H, Ni Q, Papoian GA, Trache A, Jiang Y. Myosin and [Formula: see text]-actinin regulation of stress fiber contractility under tensile stress. Sci Rep 2023; 13:8662. [PMID: 37248294 PMCID: PMC10227020 DOI: 10.1038/s41598-023-35675-7] [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: 01/12/2023] [Accepted: 05/19/2023] [Indexed: 05/31/2023] Open
Abstract
Stress fibers are actomyosin bundles that regulate cellular mechanosensation and force transduction. Interacting with the extracellular matrix through focal adhesion complexes, stress fibers are highly dynamic structures regulated by myosin motors and crosslinking proteins. Under external mechanical stimuli such as tensile forces, the stress fiber remodels its architecture to adapt to external cues, displaying properties of viscoelastic materials. How the structural remodeling of stress fibers is related to the generation of contractile force is not well understood. In this work, we simulate mechanochemical dynamics and force generation of stress fibers using the molecular simulation platform MEDYAN. We model stress fiber as two connecting bipolar bundles attached at the ends to focal adhesion complexes. The simulated stress fibers generate contractile force that is regulated by myosin motors and [Formula: see text]-actinin crosslinkers. We find that stress fibers enhance contractility by reducing the distance between actin filaments to increase crosslinker binding, and this structural remodeling ability depends on the crosslinker turnover rate. Under tensile pulling force, the stress fiber shows an instantaneous increase of the contractile forces followed by a slow relaxation into a new steady state. While the new steady state contractility after pulling depends only on the overlap between actin bundles, the short-term contractility enhancement is sensitive to the tensile pulling distance. We further show that this mechanical response is also sensitive to the crosslinker turnover rate. Our results provide new insights into the stress fiber mechanics that have significant implications for understanding cellular adaptation to mechanical signaling.
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Affiliation(s)
- Haoran Ni
- Institute for Physical Science and Technology, University of Maryland, College Park, MD, USA
| | - Qin Ni
- Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, MD, USA
| | - Garegin A. Papoian
- Institute for Physical Science and Technology, University of Maryland, College Park, MD, USA
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA
| | - Andreea Trache
- Department of Medical Physiology, Texas A &M University Health Science Center, Bryan, TX, USA
- Department of Biomedical Engineering, Texas A &M University, College Station, TX, USA
| | - Yi Jiang
- Department of Mathematics and Statistics, Georgia State University, Atlanta, GA, USA
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11
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Stam S, Gardel ML, Weirich KL. Direct detection of deformation modes on varying length scales in active biopolymer networks. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.15.540780. [PMID: 37292666 PMCID: PMC10245561 DOI: 10.1101/2023.05.15.540780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Correlated flows and forces that emerge from active matter orchestrate complex processes such as shape regulation and deformations in biological cells and tissues. The active materials central to cellular mechanics are cytoskeletal networks, where molecular motor activity drives deformations and remodeling. Here, we investigate deformation modes in actin networks driven by the molecular motor myosin II through quantitative fluorescence microscopy. We examine the deformation anisotropy at different length scales in networks of entangled, cross-linked, and bundled actin. In sparsely cross-linked networks, we find myosin-dependent biaxial buckling modes across length scales. In cross-linked bundled networks, uniaxial contraction is predominate on long length scales, while the uniaxial or biaxial nature of the deformation depends on bundle microstructure at shorter length scales. The anisotropy of deformations may provide insight to regulation of collective behavior in a variety of active materials.
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Affiliation(s)
- Samantha Stam
- Biophysical Sciences Graduate Program, University of Chicago, Chicago, IL 60637
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637
- Department of Oncological Sciences, University of Utah, Salt Lake City, UT 84112
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112
| | - Margaret L Gardel
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637
- James Franck Institute, University of Chicago, Chicago, IL 60637
- Department of Physics, University of Chicago, Chicago, IL 60637
| | - Kimberly L Weirich
- James Franck Institute, University of Chicago, Chicago, IL 60637
- Department of Materials Science & Engineering, Clemson University, Clemson, SC 29634
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12
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Andersen T, Wörthmüller D, Probst D, Wang I, Moreau P, Fitzpatrick V, Boudou T, Schwarz US, Balland M. Cell size and actin architecture determine force generation in optogenetically activated cells. Biophys J 2023; 122:684-696. [PMID: 36635962 PMCID: PMC9989885 DOI: 10.1016/j.bpj.2023.01.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 12/16/2022] [Accepted: 01/09/2023] [Indexed: 01/13/2023] Open
Abstract
Adherent cells use actomyosin contractility to generate mechanical force and to sense the physical properties of their environment, with dramatic consequences for migration, division, differentiation, and fate. However, the organization of the actomyosin system within cells is highly variable, with its assembly and function being controlled by small GTPases from the Rho family. To understand better how activation of these regulators translates into cell-scale force generation in the context of different physical environments, here we combine recent advances in non-neuronal optogenetics with micropatterning and traction force microscopy on soft elastic substrates. We find that, after whole-cell RhoA activation by the CRY2/CIBN optogenetic system with a short pulse of 100 ms, single cells contract on a minute timescale in proportion to their original traction force, before returning to their original tension setpoint with near perfect precision, on a longer timescale of several minutes. To decouple the biochemical and mechanical elements of this response, we introduce a mathematical model that is parametrized by fits to the dynamics of the substrate deformation energy. We find that the RhoA response builds up quickly on a timescale of 20 s, but decays slowly on a timescale of 50 s. The larger the cells and the more polarized their actin cytoskeleton, the more substrate deformation energy is generated. RhoA activation starts to saturate if optogenetic pulse length exceeds 50 ms, revealing the intrinsic limits of biochemical activation. Together our results suggest that adherent cells establish tensional homeostasis by the RhoA system, but that the setpoint and the dynamics around it are strongly determined by cell size and the architecture of the actin cytoskeleton, which both are controlled by the extracellular environment.
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Affiliation(s)
- T Andersen
- Université Grenoble Alpes, CNRS, LIPhy, F-38000 Grenoble, France
| | - D Wörthmüller
- Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany; BioQuant-Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany
| | - D Probst
- Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany; BioQuant-Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany
| | - I Wang
- Université Grenoble Alpes, CNRS, LIPhy, F-38000 Grenoble, France
| | - P Moreau
- Université Grenoble Alpes, CNRS, LIPhy, F-38000 Grenoble, France
| | - V Fitzpatrick
- Université Grenoble Alpes, CNRS, LIPhy, F-38000 Grenoble, France
| | - T Boudou
- Université Grenoble Alpes, CNRS, LIPhy, F-38000 Grenoble, France
| | - U S Schwarz
- Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany; BioQuant-Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany.
| | - M Balland
- Université Grenoble Alpes, CNRS, LIPhy, F-38000 Grenoble, France.
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13
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Besse M, Chaté H, Solon A. Metastability of Constant-Density Flocks. PHYSICAL REVIEW LETTERS 2022; 129:268003. [PMID: 36608197 DOI: 10.1103/physrevlett.129.268003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 12/06/2022] [Indexed: 06/17/2023]
Abstract
We study numerically the Toner-Tu field theory where the density field is maintained constant, a limit case of "Malthusian" flocks for which the asymptotic scaling of correlation functions in the ordered phase is known exactly. While we confirm these scaling laws, we also show that such constant-density flocks are metastable to the nucleation of a specific defect configuration, and are replaced by a globally disordered phase consisting of asters surrounded by shock lines that constantly evolves and remodels itself. We demonstrate that the main source of disorder lies along shock lines, rendering this active foam fundamentally different from the corresponding equilibrium system. We thus show that in the context of active matter also, a result obtained at all orders of perturbation theory can be superseded by nonperturbative effects, calling for a different approach.
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Affiliation(s)
- Marc Besse
- Sorbonne Université, CNRS, Laboratoire de Physique Théorique de la Matière Condensée, 75005 Paris, France
| | - Hugues Chaté
- Sorbonne Université, CNRS, Laboratoire de Physique Théorique de la Matière Condensée, 75005 Paris, France
- Service de Physique de l'Etat Condensé, CEA, CNRS Université Paris-Saclay, CEA-Saclay, 91191 Gif-sur-Yvette, France
- Computational Science Research Center, Beijing 100094, China
| | - Alexandre Solon
- Sorbonne Université, CNRS, Laboratoire de Physique Théorique de la Matière Condensée, 75005 Paris, France
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14
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Lamtyugina A, Qiu Y, Fodor É, Dinner AR, Vaikuntanathan S. Thermodynamic Control of Activity Patterns in Cytoskeletal Networks. PHYSICAL REVIEW LETTERS 2022; 129:128002. [PMID: 36179154 PMCID: PMC10014041 DOI: 10.1103/physrevlett.129.128002] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 07/26/2022] [Indexed: 06/16/2023]
Abstract
Biological materials, such as the actin cytoskeleton, exhibit remarkable structural adaptability to various external stimuli by consuming different amounts of energy. In this Letter, we use methods from large deviation theory to identify a thermodynamic control principle for structural transitions in a model cytoskeletal network. Specifically, we demonstrate that biasing the dynamics with respect to the work done by nonequilibrium components effectively renormalizes the interaction strength between such components, which can eventually result in a morphological transition. Our work demonstrates how a thermodynamic quantity can be used to renormalize effective interactions, which in turn can tune structure in a predictable manner, suggesting a thermodynamic principle for the control of cytoskeletal structure and dynamics.
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Affiliation(s)
| | - Yuqing Qiu
- Department of Chemistry, University of Chicago, Chicago, IL 60637
- James Franck Institute, University of Chicago, Chicago, IL 60637
| | - Étienne Fodor
- Department of Physics and Materials Science, University of Luxembourg, L-1511 Luxembourg
| | - Aaron R. Dinner
- Department of Chemistry, University of Chicago, Chicago, IL 60637
- James Franck Institute, University of Chicago, Chicago, IL 60637
| | - Suriyanarayanan Vaikuntanathan
- Department of Chemistry, University of Chicago, Chicago, IL 60637
- James Franck Institute, University of Chicago, Chicago, IL 60637
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15
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Sasanpour M, Achiriloaie DH, Lee G, Leech G, Hendija M, Lindsay KA, Ross JL, McGorty RJ, Robertson-Anderson RM. Reconstituting and Characterizing Actin-Microtubule Composites with Tunable Motor-Driven Dynamics and Mechanics. J Vis Exp 2022:10.3791/64228. [PMID: 36094259 PMCID: PMC10290881 DOI: 10.3791/64228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2023] Open
Abstract
The composite cytoskeleton, comprising interacting networks of semiflexible actin filaments and rigid microtubules, restructures and generates forces using motor proteins such as myosin II and kinesin to drive key processes such as migration, cytokinesis, adhesion, and mechanosensing. While actin-microtubule interactions are key to the cytoskeleton's versatility and adaptability, an understanding of their interplay with myosin and kinesin activity is still nascent. This work describes how to engineer tunable three-dimensional composite networks of co-entangled actin filaments and microtubules that undergo active restructuring and ballistic motion, driven by myosin II and kinesin motors, and are tuned by the relative concentrations of actin, microtubules, motor proteins, and passive crosslinkers. Protocols for fluorescence labeling of the microtubules and actin filaments to most effectively visualize composite restructuring and motion using multi-spectral confocal imaging are also detailed. Finally, the results of data analysis methods that can be used to quantitatively characterize non-equilibrium structure, dynamics, and mechanics are presented. Recreating and investigating this tunable biomimetic platform provides valuable insight into how coupled motor activity, composite mechanics, and filament dynamics can lead to myriad cellular processes from mitosis to polarization to mechano-sensation.
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Affiliation(s)
| | - Daisy H Achiriloaie
- Department of Physics and Biophysics, University of San Diego; W. M. Keck Science Department, Scripps College, Pitzer College, and Claremont McKenna College
| | - Gloria Lee
- Department of Physics and Biophysics, University of San Diego
| | - Gregor Leech
- Department of Physics and Biophysics, University of San Diego
| | - Maya Hendija
- Department of Physics and Biophysics, University of San Diego
| | | | | | - Ryan J McGorty
- Department of Physics and Biophysics, University of San Diego
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16
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Lemma B, Mitchell NP, Subramanian R, Needleman DJ, Dogic Z. Active Microphase Separation in Mixtures of Microtubules and Tip-Accumulating Molecular Motors. PHYSICAL REVIEW. X 2022; 12:031006. [PMID: 36643940 PMCID: PMC9835929 DOI: 10.1103/physrevx.12.031006] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Mixtures of filaments and molecular motors form active materials with diverse dynamical behaviors that vary based on their constituents' molecular properties. To develop a multiscale of these materials, we map the nonequilibrium phase diagram of microtubules and tip-accumulating kinesin-4 molecular motors. We find that kinesin-4 can drive either global contractions or turbulentlike extensile dynamics, depending on the concentrations of both microtubules and a bundling agent. We also observe a range of spatially heterogeneous nonequilibrium phases, including finite-sized radial asters, 1D wormlike chains, extended 2D bilayers, and system-spanning 3D active foams. Finally, we describe intricate kinetic pathways that yield microphase separated structures and arise from the inherent frustration between the orientational order of filamentous microtubules and the positional order of tip-accumulating molecular motors. Our work reveals a range of novel active states. It also shows that the form of active stresses is not solely dictated by the properties of individual motors and filaments, but is also contingent on the constituent concentrations and spatial arrangement of motors on the filaments.
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Affiliation(s)
- Bezia Lemma
- Physics Department, Harvard University, Cambridge, Massachusetts 02138, USA
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
- Physics Department, University of California, Santa Barbara, California 93106, USA
| | - Noah P. Mitchell
- Physics Department, University of California, Santa Barbara, California 93106, USA
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA
| | - Radhika Subramanian
- Molecular Biology Department, Massachusetts General Hospital Boston, Massachusetts 02114, USA
- Genetics Department, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Daniel J. Needleman
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Molecular and Cellular Biology Department, Harvard University, Cambridge, Massachusetts 02138, USA
- Center for Computational Biology, Flatiron Institute, New York, New York 10010, USA
| | - Zvonimir Dogic
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
- Physics Department, University of California, Santa Barbara, California 93106, USA
- Biomolecular Science and Engineering Department, University of California, Santa Barbara, California 93106, USA
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17
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Verwei HN, Lee G, Leech G, Petitjean II, Koenderink GH, Robertson-Anderson RM, McGorty RJ. Quantifying Cytoskeleton Dynamics Using Differential Dynamic Microscopy. J Vis Exp 2022:10.3791/63931. [PMID: 35781524 PMCID: PMC10398790 DOI: 10.3791/63931] [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] [Indexed: 08/05/2023] Open
Abstract
Cells can crawl, self-heal, and tune their stiffness due to their remarkably dynamic cytoskeleton. As such, reconstituting networks of cytoskeletal biopolymers may lead to a host of active and adaptable materials. However, engineering such materials with precisely tuned properties requires measuring how the dynamics depend on the network composition and synthesis methods. Quantifying such dynamics is challenged by variations across the time, space, and formulation space of composite networks. The protocol here describes how the Fourier analysis technique, differential dynamic microscopy (DDM), can quantify the dynamics of biopolymer networks and is particularly well suited for studies of cytoskeleton networks. DDM works on time sequences of images acquired using a range of microscopy modalities, including laser-scanning confocal, widefield fluorescence, and brightfield imaging. From such image sequences, one can extract characteristic decorrelation times of density fluctuations across a span of wave vectors. A user-friendly, open-source Python package to perform DDM analysis is also developed. With this package, one can measure the dynamics of labeled cytoskeleton components or of embedded tracer particles, as demonstrated here with data of intermediate filament (vimentin) networks and active actin-microtubule networks. Users with no prior programming or image processing experience will be able to perform DDM using this software package and associated documentation.
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Affiliation(s)
- Hannah N Verwei
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University
| | - Gloria Lee
- Department of Physics and Biophysics, University of San Diego
| | - Gregor Leech
- Department of Physics and Biophysics, University of San Diego
| | - Irene Istúriz Petitjean
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology
| | - Gijsje H Koenderink
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology
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18
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Ciocanel MV, Chandrasekaran A, Mager C, Ni Q, Papoian GA, Dawes A. Simulated actin reorganization mediated by motor proteins. PLoS Comput Biol 2022; 18:e1010026. [PMID: 35389987 PMCID: PMC9017880 DOI: 10.1371/journal.pcbi.1010026] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 04/19/2022] [Accepted: 03/15/2022] [Indexed: 11/24/2022] Open
Abstract
Cortical actin networks are highly dynamic and play critical roles in shaping the mechanical properties of cells. The actin cytoskeleton undergoes significant reorganization in many different contexts, including during directed cell migration and over the course of the cell cycle, when cortical actin can transition between different configurations such as open patched meshworks, homogeneous distributions, and aligned bundles. Several types of myosin motor proteins, characterized by different kinetic parameters, have been involved in this reorganization of actin filaments. Given the limitations in studying the interactions of actin with myosin in vivo, we propose stochastic agent-based models and develop a set of data analysis measures to assess how myosin motor proteins mediate various actin organizations. In particular, we identify individual motor parameters, such as motor binding rate and step size, that generate actin networks with different levels of contractility and different patterns of myosin motor localization, which have previously been observed experimentally. In simulations where two motor populations with distinct kinetic parameters interact with the same actin network, we find that motors may act in a complementary way, by tuning the actin network organization, or in an antagonistic way, where one motor emerges as dominant. This modeling and data analysis framework also uncovers parameter regimes where spatial segregation between motor populations is achieved. By allowing for changes in kinetic rates during the actin-myosin dynamic simulations, our work suggests that certain actin-myosin organizations may require additional regulation beyond mediation by motor proteins in order to reconfigure the cytoskeleton network on experimentally-observed timescales. Cell shape is dictated by a scaffolding network called the cytoskeleton. Actin filaments, a main component of the cytoskeleton, are found predominantly at the periphery of the cell, where they organize into different patterns in response to various stimuli, such as progression through the cell cycle. The actin filament reorganizations are mediated by motor proteins from the myosin superfamily. Using a realistic stochastic model that simulates actin filament and motor protein dynamics and interactions, we systematically vary motor protein kinetics and investigate their effect on actin filament organization. Using novel measures of spatial organization, we quantify conditions under which motor proteins, either alone or in combination, can produce the different actin filament organizations observed in vitro and in vivo. These results yield new insights into the role of motor proteins, as well as into how multiple types of motors can work collectively to produce specific actomyosin network patterns.
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Affiliation(s)
- Maria-Veronica Ciocanel
- Department of Mathematics and Biology, Duke University, Durham, North Carolina, United States of America
- * E-mail:
| | - Aravind Chandrasekaran
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, United States of America
| | - Carli Mager
- Department of Biochemistry, The Ohio State University, Columbus, Ohio, United States of America
| | - Qin Ni
- Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland, United States of America
| | - Garegin A. Papoian
- Department of Chemistry and Biochemistry and Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, United States of America
| | - Adriana Dawes
- Department of Mathematics and Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
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19
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Balasubramaniam L, Mège RM, Ladoux B. Active nematics across scales from cytoskeleton organization to tissue morphogenesis. Curr Opin Genet Dev 2022; 73:101897. [DOI: 10.1016/j.gde.2021.101897] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 12/07/2021] [Accepted: 12/21/2021] [Indexed: 11/28/2022]
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20
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Extensile to contractile transition in active microtubule-actin composites generates layered asters with programmable lifetimes. Proc Natl Acad Sci U S A 2022; 119:2115895119. [PMID: 35086931 PMCID: PMC8812548 DOI: 10.1073/pnas.2115895119] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/21/2021] [Indexed: 12/15/2022] Open
Abstract
We study a reconstituted composite system consisting of an active microtubule network interdigitated with a passive network of entangled F-actin filaments. Increasing the concentration of filamentous actin controls the emergent dynamics, inducing a transition from turbulent-like flows to bulk contractions. At intermediate concentrations, where the active stresses change their symmetry from anisotropic extensile to isotropic contracting, the composite separates into layered asters that coexist with the background turbulent fluid. Contracted onion-like asters have a radially extending microtubule-rich cortex that envelops alternating layers of microtubules and F-actin. These self-regulating structures undergo internal reorganization, which appears to minimize the surface area and maintain the ordered layering, even when undergoing aster merging events. Finally, the layered asters are metastable structures. Their lifetime, which ranges from minutes to hours, is encoded in the material properties of the composite. These results challenge the current models of active matter. They demonstrate self-organized dynamical states and patterns evocative of those observed in the cytoskeleton do not require precise biochemical regulation, but can arise from purely mechanical interactions of actively driven filamentous materials.
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21
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Sherer LA, Courtemanche N. Cooperative bundling by fascin generates actin structures with architectures that depend on filament length. Front Cell Dev Biol 2022; 10:974047. [PMID: 36120572 PMCID: PMC9479110 DOI: 10.3389/fcell.2022.974047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 08/12/2022] [Indexed: 11/30/2022] Open
Abstract
The assembly of actin-based structures with precisely defined architectures supports essential cellular functions, including motility, intracellular transport, and division. The geometric arrangements of the filaments within actin structures are stabilized via the association of crosslinking proteins, which bind two filaments simultaneously. Because actin polymerization and crosslinking occur concurrently within the dynamic environment of the cell, these processes likely play interdependent roles in shaping the architectures of actin-based structures. To dissect the contribution of polymerization to the construction of higher-order actin structures, we investigated how filament elongation affects the formation of simple, polarized actin bundles by the crosslinking protein fascin. Using populations of actin filaments to represent distinct stages of elongation, we found that the rate of bundle assembly increases with filament length. Fascin assembles short filaments into discrete bundles, whereas bundles of long filaments merge with one another to form interconnected networks. Although filament elongation promotes bundle coalescence, many connections formed between elongating bundles are short-lived and are followed by filament breakage. Our data suggest that initiation of crosslinking early in elongation aligns growing filaments, creating a template for continued bundle assembly as elongation proceeds. This initial alignment promotes the assembly of bundles that are resistant to large changes in curvature that are required for coalescence into interconnected networks. As a result, bundles of short filaments remain straighter and more topologically discrete as elongation proceeds than bundles assembled from long filaments. Thus, uncoordinated filament elongation and crosslinking can alter the architecture of bundled actin networks, highlighting the importance of maintaining precise control over filament length during the assembly of specialized actin structures.
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22
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Sobral AF, Chan FY, Norman MJ, Osório DS, Dias AB, Ferreira V, Barbosa DJ, Cheerambathur D, Gassmann R, Belmonte JM, Carvalho AX. Plastin and spectrin cooperate to stabilize the actomyosin cortex during cytokinesis. Curr Biol 2021; 31:5415-5428.e10. [PMID: 34666005 PMCID: PMC8699742 DOI: 10.1016/j.cub.2021.09.055] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 06/22/2021] [Accepted: 09/21/2021] [Indexed: 11/16/2022]
Abstract
Cytokinesis, the process that partitions the mother cell into two daughter cells, requires the assembly and constriction of an equatorial actomyosin network. Different types of non-motor F-actin crosslinkers localize to the network, but their functional contribution remains poorly understood. Here, we describe a synergy between the small rigid crosslinker plastin and the large flexible crosslinker spectrin in the C. elegans one-cell embryo. In contrast to single inhibitions, co-inhibition of plastin and the βH-spectrin (SMA-1) results in cytokinesis failure due to progressive disorganization and eventual collapse of the equatorial actomyosin network. Cortical localization dynamics of non-muscle myosin II in co-inhibited embryos mimic those observed after drug-induced F-actin depolymerization, suggesting that the combined action of plastin and spectrin stabilizes F-actin in the contractile ring. An in silico model predicts that spectrin is more efficient than plastin at stabilizing the ring and that ring formation is relatively insensitive to βH-spectrin length, which is confirmed in vivo with a sma-1 mutant that lacks 11 of its 29 spectrin repeats. Our findings provide the first evidence that spectrin contributes to cytokinesis and highlight the importance of crosslinker interplay for actomyosin network integrity.
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Affiliation(s)
- Ana Filipa Sobral
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal; ICBAS - Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, 4050-313 Porto, Portugal
| | - Fung-Yi Chan
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal
| | - Michael J Norman
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA; Quantitative and Computational Developmental Biology Cluster, North Carolina State University, Raleigh, NC 27695, USA
| | - Daniel S Osório
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal
| | - Ana Beatriz Dias
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal
| | - Vanessa Ferreira
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal
| | - Daniel J Barbosa
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal
| | - Dhanya Cheerambathur
- Wellcome Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Reto Gassmann
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal
| | - Julio Monti Belmonte
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA; Quantitative and Computational Developmental Biology Cluster, North Carolina State University, Raleigh, NC 27695, USA
| | - Ana Xavier Carvalho
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal.
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23
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Lee G, Leech G, Lwin P, Michel J, Currie C, Rust MJ, Ross JL, McGorty RJ, Das M, Robertson-Anderson RM. Active cytoskeletal composites display emergent tunable contractility and restructuring. SOFT MATTER 2021; 17:10765-10776. [PMID: 34792082 PMCID: PMC9239752 DOI: 10.1039/d1sm01083b] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The cytoskeleton is a model active matter system that controls processes as diverse as cell motility and mechanosensing. While both active actomyosin dynamics and actin-microtubule interactions are key to the cytoskeleton's versatility and adaptability, an understanding of their interplay is lacking. Here, we couple microscale experiments with mechanistic modeling to elucidate how connectivity, rigidity, and force-generation affect emergent material properties in composite networks of actin, tubulin, and myosin. We use multi-spectral imaging, time-resolved differential dynamic microscopy and spatial image autocorrelation to show that ballistic contraction occurs in composites with sufficient flexibility and motor density, but that a critical fraction of microtubules is necessary to sustain controlled dynamics. The active double-network models we develop, which recapitulate our experimental findings, reveal that while percolated actomyosin networks are essential for contraction, only composites with comparable actin and microtubule densities can simultaneously resist mechanical stresses while supporting substantial restructuring. The comprehensive phase map we present not only provides important insight into the different routes the cytoskeleton can use to alter its dynamics and structure, but also serves as a much-needed blueprint for designing cytoskeleton-inspired materials that couple tunability with resilience and adaptability for diverse applications ranging from wound healing to soft robotics.
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Affiliation(s)
- Gloria Lee
- Department of Physics and Biophysics, University of San Diego, USA.
| | - Gregor Leech
- Department of Physics and Biophysics, University of San Diego, USA.
| | - Pancy Lwin
- School of Physics and Astronomy, Rochester Institute of Technology, USA
| | - Jonathan Michel
- School of Physics and Astronomy, Rochester Institute of Technology, USA
| | | | - Michael J Rust
- Department of Molecular Genetics and Cell Biology, University of Chicago, USA
| | | | - Ryan J McGorty
- Department of Physics and Biophysics, University of San Diego, USA.
| | - Moumita Das
- School of Physics and Astronomy, Rochester Institute of Technology, USA
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24
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Bashirzadeh Y, Redford SA, Lorpaiboon C, Groaz A, Moghimianavval H, Litschel T, Schwille P, Hocky GM, Dinner AR, Liu AP. Actin crosslinker competition and sorting drive emergent GUV size-dependent actin network architecture. Commun Biol 2021. [PMID: 34584211 DOI: 10.1101/2020.10.03.322354v1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/22/2023] Open
Abstract
The proteins that make up the actin cytoskeleton can self-assemble into a variety of structures. In vitro experiments and coarse-grained simulations have shown that the actin crosslinking proteins α-actinin and fascin segregate into distinct domains in single actin bundles with a molecular size-dependent competition-based mechanism. Here, by encapsulating actin, α-actinin, and fascin in giant unilamellar vesicles (GUVs), we show that physical confinement can cause these proteins to form much more complex structures, including rings and asters at GUV peripheries and centers; the prevalence of different structures depends on GUV size. Strikingly, we found that α-actinin and fascin self-sort into separate domains in the aster structures with actin bundles whose apparent stiffness depends on the ratio of the relative concentrations of α-actinin and fascin. The observed boundary-imposed effect on protein sorting may be a general mechanism for creating emergent structures in biopolymer networks with multiple crosslinkers.
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Affiliation(s)
- Yashar Bashirzadeh
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Steven A Redford
- James Franck Institute, University of Chicago, Chicago, IL, 60637, USA
- The graduate program in Biophysical Sciences, University of Chicago, Chicago, IL, 60637, USA
| | | | - Alessandro Groaz
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA
| | | | - Thomas Litschel
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, 82152, Martinsried, Germany
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
| | - Petra Schwille
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, 82152, Martinsried, Germany
| | - Glen M Hocky
- Department of Chemistry, New York University, New York, NY, 10003, USA
| | - Aaron R Dinner
- James Franck Institute, University of Chicago, Chicago, IL, 60637, USA.
- Department of Chemistry, University of Chicago, Chicago, IL, 60637, USA.
| | - Allen P Liu
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA.
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA.
- Department of Biophysics, University of Michigan, Ann Arbor, MI, 48109, USA.
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI, 48109, USA.
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25
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Bashirzadeh Y, Redford SA, Lorpaiboon C, Groaz A, Moghimianavval H, Litschel T, Schwille P, Hocky GM, Dinner AR, Liu AP. Actin crosslinker competition and sorting drive emergent GUV size-dependent actin network architecture. Commun Biol 2021; 4:1136. [PMID: 34584211 PMCID: PMC8478941 DOI: 10.1038/s42003-021-02653-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 09/08/2021] [Indexed: 02/07/2023] Open
Abstract
The proteins that make up the actin cytoskeleton can self-assemble into a variety of structures. In vitro experiments and coarse-grained simulations have shown that the actin crosslinking proteins α-actinin and fascin segregate into distinct domains in single actin bundles with a molecular size-dependent competition-based mechanism. Here, by encapsulating actin, α-actinin, and fascin in giant unilamellar vesicles (GUVs), we show that physical confinement can cause these proteins to form much more complex structures, including rings and asters at GUV peripheries and centers; the prevalence of different structures depends on GUV size. Strikingly, we found that α-actinin and fascin self-sort into separate domains in the aster structures with actin bundles whose apparent stiffness depends on the ratio of the relative concentrations of α-actinin and fascin. The observed boundary-imposed effect on protein sorting may be a general mechanism for creating emergent structures in biopolymer networks with multiple crosslinkers. By encapsulating proteins in giant unilamellar vesicles, Bashirzadeh et al find that actin crosslinkers, α-actinin and fascin, can self-assemble with actin into complex structures that depend on the degree of confinement. Further analysis and modeling show that α-actinin and fascin sort to separate domains of these structures. These insights may be generalizable to other biopolymer networks containing crosslinkers.
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Affiliation(s)
- Yashar Bashirzadeh
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Steven A Redford
- James Franck Institute, University of Chicago, Chicago, IL, 60637, USA.,The graduate program in Biophysical Sciences, University of Chicago, Chicago, IL, 60637, USA
| | | | - Alessandro Groaz
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA.,Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA
| | | | - Thomas Litschel
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, 82152, Martinsried, Germany.,John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
| | - Petra Schwille
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, 82152, Martinsried, Germany
| | - Glen M Hocky
- Department of Chemistry, New York University, New York, NY, 10003, USA
| | - Aaron R Dinner
- James Franck Institute, University of Chicago, Chicago, IL, 60637, USA. .,Department of Chemistry, University of Chicago, Chicago, IL, 60637, USA.
| | - Allen P Liu
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA. .,Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA. .,Department of Biophysics, University of Michigan, Ann Arbor, MI, 48109, USA. .,Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI, 48109, USA.
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26
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Pocaterra A, Scattolin G, Romani P, Ament C, Ribback S, Chen X, Evert M, Calvisi DF, Dupont S. Fascin1 empowers YAP mechanotransduction and promotes cholangiocarcinoma development. Commun Biol 2021; 4:763. [PMID: 34155338 PMCID: PMC8217270 DOI: 10.1038/s42003-021-02286-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 06/01/2021] [Indexed: 12/14/2022] Open
Abstract
Mechanical forces control cell behavior, including cancer progression. Cells sense forces through actomyosin to activate YAP. However, the regulators of F-actin dynamics playing relevant roles during mechanostransduction in vitro and in vivo remain poorly characterized. Here we identify the Fascin1 F-actin bundling protein as a factor that sustains YAP activation in response to ECM mechanical cues. This is conserved in the mouse liver, where Fascin1 regulates YAP-dependent phenotypes, and in human cholangiocarcinoma cell lines. Moreover, this is relevant for liver tumorigenesis, because Fascin1 is required in the AKT/NICD cholangiocarcinogenesis model and it is sufficient, together with AKT, to induce cholangiocellular lesions in mice, recapitulating genetic YAP requirements. In support of these findings, Fascin1 expression in human intrahepatic cholangiocarcinomas strongly correlates with poor patient prognosis. We propose that Fascin1 represents a pro-oncogenic mechanism that can be exploited during intrahepatic cholangiocarcinoma development to overcome a mechanical tumor-suppressive environment.
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Affiliation(s)
- Arianna Pocaterra
- Department of Molecular Medicine, University of Padua Medical School, Padua, Italy
| | - Gloria Scattolin
- Department of Molecular Medicine, University of Padua Medical School, Padua, Italy
| | - Patrizia Romani
- Department of Molecular Medicine, University of Padua Medical School, Padua, Italy
| | - Cindy Ament
- Institute of Pathology, University of Regensburg, Regensburg, Germany
| | - Silvia Ribback
- Institute of Pathology, University of Greifswald, Greifswald, Germany
| | - Xin Chen
- Department of Bioengineering and Therapeutic Sciences and Liver Center, University of California, San Francisco, California, USA
| | - Matthias Evert
- Institute of Pathology, University of Greifswald, Greifswald, Germany
| | - Diego F Calvisi
- Institute of Pathology, University of Greifswald, Greifswald, Germany
| | - Sirio Dupont
- Department of Molecular Medicine, University of Padua Medical School, Padua, Italy.
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27
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Weirich KL, Stam S, Munro E, Gardel ML. Actin bundle architecture and mechanics regulate myosin II force generation. Biophys J 2021; 120:1957-1970. [PMID: 33798565 DOI: 10.1016/j.bpj.2021.03.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 03/01/2021] [Accepted: 03/12/2021] [Indexed: 10/21/2022] Open
Abstract
The actin cytoskeleton is a soft, structural material that underlies biological processes such as cell division, motility, and cargo transport. The cross-linked actin filaments self-organize into a myriad of architectures, from disordered meshworks to ordered bundles, which are hypothesized to control the actomyosin force generation that regulates cell migration, shape, and adhesion. Here, we use fluorescence microscopy and simulations to investigate how actin bundle architectures with varying polarity, spacing, and rigidity impact myosin II dynamics and force generation. Microscopy reveals that mixed-polarity bundles formed by rigid cross-linkers support slow, bidirectional myosin II filament motion, punctuated by periods of stalled motion. Simulations reveal that these locations of stalled myosin motion correspond to sustained, high forces in regions of balanced actin filament polarity. By contrast, mixed-polarity bundles formed by compliant, large cross-linkers support fast, bidirectional motion with no traps. Simulations indicate that trap duration is directly related to force magnitude and that the observed increased velocity corresponds to lower forces resulting from both the increased bundle compliance and filament spacing. Our results indicate that the microstructures of actin assemblies regulate the dynamics and magnitude of myosin II forces, highlighting the importance of architecture and mechanics in regulating forces in biological materials.
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Affiliation(s)
- Kimberly L Weirich
- James Franck Institute, University of Chicago, Chicago, Illinois; Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois; Department of Materials Science and Engineering, Clemson University, Clemson, South Carolina
| | - Samantha Stam
- Biophysical Sciences Graduate Program, University of Chicago, Chicago, Illinois; Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois; Department of Molecular and Cellular Biology, University of California, Davis, Davis, California
| | - Edwin Munro
- Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois; Department of Molecular Genetics and Cellular Biology, University of Chicago, Chicago, Illinois
| | - Margaret L Gardel
- James Franck Institute, University of Chicago, Chicago, Illinois; Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois; Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois; Department of Physics, University of Chicago, Chicago, Illinois.
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28
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Locatelli E, Bianco V, Malgaretti P. Activity-Induced Collapse and Arrest of Active Polymer Rings. PHYSICAL REVIEW LETTERS 2021; 126:097801. [PMID: 33750170 DOI: 10.1103/physrevlett.126.097801] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 01/24/2021] [Accepted: 02/01/2021] [Indexed: 06/12/2023]
Abstract
We investigate, using numerical simulations, the conformations of isolated active ring polymers. We find that their behavior depends crucially on their size: Short rings (N≲100) swell, whereas longer rings (N≳200) collapse, at sufficiently high activity. By investigating the nonequilibrium process leading to the steady state, we find a universal route driving both outcomes; we highlight the central role of steric interactions, at variance with linear chains, and of topology conservation. We further show that the collapsed rings are arrested by looking at different observables, all underlining the presence of an extremely long timescales at the steady state, associated with the internal dynamics of the collapsed section. Finally, we found that in some circumstances the collapsed state spins about its axis.
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Affiliation(s)
| | - Valentino Bianco
- Faculty of Chemistry, Chemical Physics Department, Complutense University of Madrid, Plaza de las Ciencias, Ciudad Universitaria, Madrid 28040, Spain
| | - Paolo Malgaretti
- Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany
- IV Institute for Theoretical Physics, University of Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
- Helmholtz Institut Erlangen-Nürnberg for Renewable Energy (IEK-11), Forschungszentrum Jülich, Fürther Strasse 248, 90429 Nürnberg, Germany
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29
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Su Z, Yu W, Liu T, Li X, Graham NJD, Lu Y, Wiesner MR. Discovery of Welcome Biopolymers in Surface Water: Improvements in Drinking Water Production. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:2076-2086. [PMID: 33435682 DOI: 10.1021/acs.est.0c05758] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The presence of biopolymers in surface waters and their significance for potable water supply have received little attention previously owing to their low concentrations. In this paper, we present the results of an extensive study that has investigated the role and benefits of biopolymers during the purification of surface water with reference to their specific biological and physico-chemical properties. Using samples collected from two representative surface waters in China and the United Kingdom, macromolecular biopolymers were separated and concentrated for subsequent investigation of their role in coagulation, metal ion adsorption, and membrane separation. Our results show that biopolymers significantly improve the antifouling capability of membrane nanofiltration, in combination with the enhanced conventional coagulation performance and additional security against several unhealthy metal pollutants (e.g., Fe, Al, and Cr). We believe this is the first study that reveals the versatile benefits and the fate of natural biopolymers in surface water purification processes.
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Affiliation(s)
- Zhaoyang Su
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
- Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina 27708, United States
| | - Wenzheng Yu
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Ting Liu
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Xing Li
- College of Architecture and Civil Engineering, Beijing University of Technology, Beijing 100024, China
| | - Nigel J D Graham
- Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Yonglong Lu
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Mark R Wiesner
- Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina 27708, United States
- Center for the Environmental Implications of Nanotechnology (CEINT), Duke University, Durham, North Carolina 27708, United States
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30
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Lee G, Leech G, Rust MJ, Das M, McGorty RJ, Ross JL, Robertson-Anderson RM. Myosin-driven actin-microtubule networks exhibit self-organized contractile dynamics. SCIENCE ADVANCES 2021; 7:7/6/eabe4334. [PMID: 33547082 PMCID: PMC7864579 DOI: 10.1126/sciadv.abe4334] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 12/21/2020] [Indexed: 06/02/2023]
Abstract
The cytoskeleton is a dynamic network of proteins, including actin, microtubules, and their associated motor proteins, that enables essential cellular processes such as motility, division, and growth. While actomyosin networks are extensively studied, how interactions between actin and microtubules, ubiquitous in the cytoskeleton, influence actomyosin activity remains an open question. Here, we create a network of co-entangled actin and microtubules driven by myosin II. We combine dynamic differential microscopy, particle image velocimetry, and particle tracking to show that both actin and microtubules undergo ballistic contraction with unexpectedly indistinguishable characteristics. This contractility is distinct from faster disordered motion and rupturing that active actin networks exhibit. Our results suggest that microtubules enable self-organized myosin-driven contraction by providing flexural rigidity and enhanced connectivity to actin networks. Beyond the immediate relevance to cytoskeletal dynamics, our results shed light on the design of active materials that can be precisely tuned by the network composition.
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Affiliation(s)
- Gloria Lee
- Department of Physics and Biophysics, University of San Diego, San Diego, CA 92110, USA
| | - Gregor Leech
- Department of Physics and Biophysics, University of San Diego, San Diego, CA 92110, USA
| | - Michael J Rust
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Moumita Das
- School of Physics and Astronomy, Rochester Institute of Technology, Rochester, NY 14623, USA
| | - Ryan J McGorty
- Department of Physics and Biophysics, University of San Diego, San Diego, CA 92110, USA
| | - Jennifer L Ross
- Department of Physics, Syracuse University, Syracuse, NY 13244, USA
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31
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Zhou Z, Joshi C, Liu R, Norton MM, Lemma L, Dogic Z, Hagan MF, Fraden S, Hong P. Machine learning forecasting of active nematics. SOFT MATTER 2021; 17:738-747. [PMID: 33220675 DOI: 10.1039/d0sm01316a] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Active nematics are a class of far-from-equilibrium materials characterized by local orientational order of force-generating, anisotropic constitutes. Traditional methods for predicting the dynamics of active nematics rely on hydrodynamic models, which accurately describe idealized flows and many of the steady-state properties, but do not capture certain detailed dynamics of experimental active nematics. We have developed a deep learning approach that uses a Convolutional Long-Short-Term-Memory (ConvLSTM) algorithm to automatically learn and forecast the dynamics of active nematics. We demonstrate our purely data-driven approach on experiments of 2D unconfined active nematics of extensile microtubule bundles, as well as on data from numerical simulations of active nematics.
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32
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Eliaz Y, Nedelec F, Morrison G, Levine H, Cheung MS. Insights from graph theory on the morphologies of actomyosin networks with multilinkers. Phys Rev E 2020; 102:062420. [PMID: 33466104 DOI: 10.1103/physreve.102.062420] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 12/02/2020] [Indexed: 11/07/2022]
Abstract
Quantifying the influence of microscopic details on the dynamics of development of the overall structure of a filamentous network is important in a number of biologically relevant contexts, but it is not obvious what order parameters can be used to adequately describe this complex process. In this paper we investigated the role of multivalent actin-binding proteins (ABPs) in reorganizing actin filaments into higher-order complex networks via a computer model of semiflexible filaments. We characterize the importance of local connectivity among actin filaments, as well as the global features of actomyosin networks. We first map the networks into local graph representations and then, using principles from network-theory order parameters, combine properties from these representations to gain insight into the heterogeneous morphologies of actomyosin networks at a global level. We find that ABPs with a valency greater than 2 promote filament bundles and large filament clusters to a much greater extent than bivalent multilinkers. We also show that active myosinlike motor proteins promote the formation of dendritic branches from a stalk of actin bundles. Our work motivates future studies to embrace network theory as a tool to characterize complex morphologies of actomyosin detected by experiments, leading to a quantitative understanding of the role of ABPs in manipulating the self-assembly of actin filaments into unique architectures that underlie the structural scaffold of a cell relating to its mobility and shape.
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Affiliation(s)
- Yossi Eliaz
- Department of Physics, University of Houston, Houston, Texas 77204, USA
- Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, USA
| | - Francois Nedelec
- Sainsbury Laboratory, Cambridge University, Bateman Street, CB2 1LR Cambridge, England, UK
| | - Greg Morrison
- Department of Physics, University of Houston, Houston, Texas 77204, USA
- Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, USA
| | - Herbert Levine
- Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, USA
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA
| | - Margaret S Cheung
- Department of Physics, University of Houston, Houston, Texas 77204, USA
- Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, USA
- Department of Bioengineering, Rice University, Houston, Texas 77005, USA
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33
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Abstract
Moumita Das, Michael Murrell and Christoph Schmidt introduce the Soft Matter collection on active matter.
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Affiliation(s)
- Moumita Das
- School of Physics and Astronomy, Rochester Institute of Technology, Rochester, NY 14623, USA.
| | - Christoph F Schmidt
- Department of Physics and Soft Matter Center, Duke University, Durham, NC 27708, USA.
| | - Michael Murrell
- Physics & Biomedical Engineering Departments, Systems Biology Institute, Yale University, New Haven, CT 06520, USA.
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34
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Dehapiot B, Clément R, Alégot H, Gazsó-Gerhát G, Philippe JM, Lecuit T. Assembly of a persistent apical actin network by the formin Frl/Fmnl tunes epithelial cell deformability. Nat Cell Biol 2020; 22:791-802. [PMID: 32483386 DOI: 10.1038/s41556-020-0524-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 04/17/2020] [Indexed: 01/01/2023]
Abstract
Tissue remodelling during Drosophila embryogenesis is notably driven by epithelial cell contractility. This behaviour arises from the Rho1-Rok-induced pulsatile accumulation of non-muscle myosin II pulling on actin filaments of the medioapical cortex. While recent studies have highlighted the mechanisms governing the emergence of Rho1-Rok-myosin II pulsatility, little is known about how F-actin organization influences this process. Here, we show that the medioapical cortex consists of two entangled F-actin subpopulations. One exhibits pulsatile dynamics of actin polymerization in a Rho1-dependent manner. The other forms a persistent and homogeneous network independent of Rho1. We identify the formin Frl (also known as Fmnl) as a critical nucleator of the persistent network, since modulating its level in mutants or by overexpression decreases or increases the network density. Absence of this network yields sparse connectivity affecting the homogeneous force transmission to the cell boundaries. This reduces the propagation range of contractile forces and results in tissue-scale morphogenetic defects.
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Affiliation(s)
- Benoit Dehapiot
- Aix Marseille Université, CNRS, IBDM-UMR7288, Turing Center for Living Systems, Marseille, France
| | - Raphaël Clément
- Aix Marseille Université, CNRS, IBDM-UMR7288, Turing Center for Living Systems, Marseille, France
| | - Hervé Alégot
- Aix Marseille Université, CNRS, IBDM-UMR7288, Turing Center for Living Systems, Marseille, France
| | - Gabriella Gazsó-Gerhát
- Institute of Genetics, Biological Research Centre, HAS, Szeged, Hungary.,Doctoral School of Biology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Jean-Marc Philippe
- Aix Marseille Université, CNRS, IBDM-UMR7288, Turing Center for Living Systems, Marseille, France
| | - Thomas Lecuit
- Aix Marseille Université, CNRS, IBDM-UMR7288, Turing Center for Living Systems, Marseille, France. .,Collège de France, Paris, France.
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35
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Lenz M. Reversal of contractility as a signature of self-organization in cytoskeletal bundles. eLife 2020; 9:51751. [PMID: 32149609 PMCID: PMC7082124 DOI: 10.7554/elife.51751] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 03/05/2020] [Indexed: 12/13/2022] Open
Abstract
Bundles of cytoskeletal filaments and molecular motors generate motion in living cells, and have internal structures ranging from very organized to apparently disordered. The mechanisms powering the disordered structures are debated, and existing models predominantly predict that they are contractile. We reexamine this prediction through a theoretical treatment of the interplay between three well-characterized internal dynamical processes in cytoskeletal bundles: filament assembly and disassembly, the attachement-detachment dynamics of motors and that of crosslinking proteins. The resulting self-organization is easily understood in terms of motor and crosslink localization, and allows for an extensive control of the active bundle mechanics, including reversals of the filaments’ apparent velocities and the possibility of generating extension instead of contraction. This reversal mirrors some recent experimental observations, and provides a robust criterion to experimentally elucidate the underpinnings of both actomyosin activity and the dynamics of microtubule/motor assemblies in vitro as well as in diverse intracellular structures ranging from contractile bundles to the mitotic spindle.
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Affiliation(s)
- Martin Lenz
- Université Paris-Saclay, CNRS, LPTMS, Orsay, France.,PMMH, CNRS, ESPCI Paris, PSL University, Sorbonne Université, Université de Paris, Paris, France
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36
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Banerjee S, Gardel ML, Schwarz US. The Actin Cytoskeleton as an Active Adaptive Material. ANNUAL REVIEW OF CONDENSED MATTER PHYSICS 2020; 11:421-439. [PMID: 33343823 PMCID: PMC7748259 DOI: 10.1146/annurev-conmatphys-031218-013231] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Actin is the main protein used by biological cells to adapt their structure and mechanics to their needs. Cellular adaptation is made possible by molecular processes that strongly depend on mechanics. The actin cytoskeleton is also an active material that continuously consumes energy. This allows for dynamical processes that are possible only out of equilibrium and opens up the possibility for multiple layers of control that have evolved around this single protein.Here we discuss the actin cytoskeleton from the viewpoint of physics as an active adaptive material that can build structures superior to man-made soft matter systems. Not only can actin be used to build different network architectures on demand and in an adaptive manner, but it also exhibits the dynamical properties of feedback systems, like excitability, bistability, or oscillations. Therefore, it is a prime example of how biology couples physical structure and information flow and a role model for biology-inspired metamaterials.
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Affiliation(s)
- Shiladitya Banerjee
- Department of Physics and Astronomy and Institute for the Physics of Living Systems, University College London, London WC1E 6BT, United Kingdom
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Margaret L Gardel
- Department of Physics, James Franck Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637, USA
| | - Ulrich S Schwarz
- Institute for Theoretical Physics and BioQuant, Heidelberg University, 69120 Heidelberg, Germany
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37
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Ludwig NB, Weirch KL, Alster E, Witten TA, Gardel ML, Dasbiswas K, Vaikuntanathan S. Nucleation and shape dynamics of model nematic tactoids around adhesive colloids. J Chem Phys 2020; 152:084901. [PMID: 32113348 DOI: 10.1063/1.5141997] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Recent experiments have shown how nematically ordered tactoid shaped actin droplets can be reorganized and divided by the action of myosin molecular motors. In this paper, we consider how similar morphological changes can potentially be achieved under equilibrium conditions. Using simulations, both atomistic and continuum, and a simple macroscopic model, we explore how the nucleation dynamics, shape changes, and the final steady state of a nematic tactoid droplet can be modified by interactions with model adhesive colloids that mimic a myosin motor cluster. We show how tactoid reorganization may occur in an equilibrium colloidal-nematic setting. We then suggest based on the simple macroscopic model how the simulation models may be extended to potentially stabilize divided tactoids.
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Affiliation(s)
- Nicholas B Ludwig
- Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
| | - Kimberly L Weirch
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA
| | - Eli Alster
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Thomas A Witten
- Department of Physics and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
| | - Margaret L Gardel
- Department of Physics and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
| | - Kinjal Dasbiswas
- Department of Physics, University of California, Merced, Merced, California 95343, USA
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38
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Scholz M, Weirich KL, Gardel ML, Dinner AR. Tuning molecular motor transport through cytoskeletal filament network organization. SOFT MATTER 2020; 16:2135-2140. [PMID: 32016200 DOI: 10.1039/c9sm01904a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Within cells, crosslinking proteins organize cytoskeletal filaments both temporally and spatially to create dynamic and structurally diverse networks. Molecular motors move on these networks for both force generation and transport processes. How the transport statistics depend on the network architecture remains poorly characterized. Using cross-linking proteins (α-actinin, fimbrin, fascin, or filamin) and purified actin, we create cytoskeletal networks with diverse microscopic architectures. We track the motion of myosin II motor proteins moving on these networks and calculate transport statistics. We observe that motor dynamics change predictably based on the bundling of filaments within the underlying networks and discuss implications for network function.
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Affiliation(s)
- Monika Scholz
- James Franck Institute, The University of Chicago, Chicago, IL 60637, USA. and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Kimberly L Weirich
- James Franck Institute, The University of Chicago, Chicago, IL 60637, USA. and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Margaret L Gardel
- James Franck Institute, The University of Chicago, Chicago, IL 60637, USA. and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA and Department of Physics, The University of Chicago, Chicago, IL 60637, USA
| | - Aaron R Dinner
- James Franck Institute, The University of Chicago, Chicago, IL 60637, USA. and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA and Department of Chemistry, The University of Chicago, Chicago, IL 60637, USA
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39
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Alvarado J, Cipelletti L, Koenderink GH. Uncovering the dynamic precursors to motor-driven contraction of active gels. SOFT MATTER 2019; 15:8552-8565. [PMID: 31637398 DOI: 10.1039/c9sm01172b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Cells and tissues have the remarkable ability to actively generate the forces required to change their shape. This active mechanical behavior is largely mediated by the actin cytoskeleton, a crosslinked network of actin filaments that is contracted by myosin motors. Experiments and active gel theories have established that the length scale over which gel contraction occurs is governed by a balance between molecular motor activity and crosslink density. By contrast, the dynamics that govern the contractile activity of the cytoskeleton remain poorly understood. Here we investigate the microscopic dynamics of reconstituted actin-myosin networks using simultaneous real-space video microscopy and Fourier-space dynamic light scattering. Light scattering reveals different regimes of microscopic dynamics as a function of sample age. We uncover two dynamical precursors that precede macroscopic gel contraction. One is characterized by a progressive acceleration of stress-induced rearrangements, while the other consists of sudden, heterogeneous rearrangements. Intriguingly, our findings suggest a qualitative analogy between self-driven rupture and collapse of active gels and the delayed rupture of passive gels observed in earlier studies of colloidal gels under external loads.
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Affiliation(s)
- José Alvarado
- AMOLF, Living Matter Department, 1098 XG Amsterdam, The Netherlands.
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40
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Andorfer R, Alper JD. From isolated structures to continuous networks: A categorization of cytoskeleton-based motile engineered biological microstructures. WILEY INTERDISCIPLINARY REVIEWS. NANOMEDICINE AND NANOBIOTECHNOLOGY 2019; 11:e1553. [PMID: 30740918 PMCID: PMC6881777 DOI: 10.1002/wnan.1553] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 12/27/2018] [Accepted: 12/28/2018] [Indexed: 11/06/2022]
Abstract
As technology at the small scale is advancing, motile engineered microstructures are becoming useful in drug delivery, biomedicine, and lab-on-a-chip devices. However, traditional engineering methods and materials can be inefficient or functionally inadequate for small-scale applications. Increasingly, researchers are turning to the biology of the cytoskeleton, including microtubules, actin filaments, kinesins, dyneins, myosins, and associated proteins, for both inspiration and solutions. They are engineering structures with components that range from being entirely biological to being entirely synthetic mimics of biology and on scales that range from isotropic continuous networks to single isolated structures. Motile biological microstructures trace their origins from the development of assays used to study the cytoskeleton to the array of structures currently available today. We define 12 types of motile biological microstructures, based on four categories: entirely biological, modular, hybrid, and synthetic, and three scales: networks, clusters, and isolated structures. We highlight some key examples, the unique functionalities, and the potential applications of each microstructure type, and we summarize the quantitative models that enable engineering them. By categorizing the diversity of motile biological microstructures in this way, we aim to establish a framework to classify these structures, define the gaps in current research, and spur ideas to fill those gaps. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Nanotechnology Approaches to Biology > Cells at the Nanoscale Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Therapeutic Approaches and Drug Discovery > Emerging Technologies.
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Affiliation(s)
- Rachel Andorfer
- Department of Bioengineering, Clemson University, Clemson, South Carolina
- Department of Physics and Astronomy, Clemson University, Clemson, South Carolina
| | - Joshua D. Alper
- Department of Physics and Astronomy, Clemson University, Clemson, South Carolina
- Department of Biological Sciences, Clemson University, Clemson, South Carolina
- Eukaryotic Pathogen Innovations Center, Clemson University, Clemson, South Carolina
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41
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Hafner AE, Krausser J, Šarić A. Minimal coarse-grained models for molecular self-organisation in biology. Curr Opin Struct Biol 2019; 58:43-52. [PMID: 31226513 DOI: 10.1016/j.sbi.2019.05.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 05/13/2019] [Accepted: 05/19/2019] [Indexed: 01/19/2023]
Abstract
The molecular machinery of life is largely created via self-organisation of individual molecules into functional assemblies. Minimal coarse-grained models, in which a whole macromolecule is represented by a small number of particles, can be of great value in identifying the main driving forces behind self-organisation in cell biology. Such models can incorporate data from both molecular and continuum scales, and their results can be directly compared to experiments. Here we review the state of the art of models for studying the formation and biological function of macromolecular assemblies in living organisms. We outline the key ingredients of each model and their main findings. We illustrate the contribution of this class of simulations to identifying the physical mechanisms behind life and diseases, and discuss their future developments.
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Affiliation(s)
- Anne E Hafner
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London WC1E 6BT, UK
| | - Johannes Krausser
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London WC1E 6BT, UK
| | - Anđela Šarić
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London WC1E 6BT, UK.
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42
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Abstract
The cytoskeleton is a collection of protein assemblies that dynamically impose spatial structure in cells and coordinate processes such as cell division and mechanical regulation. Biopolymer filaments, cross-linking proteins, and enzymatically active motor proteins collectively self-organize into various precise cytoskeletal assemblies critical for specific biological functions. An outstanding question is how the precise spatial organization arises from the component macromolecules. We develop a system to investigate simple physical mechanisms of self-organization in biological assemblies. Using a minimal set of purified proteins, we create droplets of cross-linked biopolymer filaments. Through the addition of enzymatically active motor proteins, we construct composite assemblies, evocative of cellular structures such as spindles, where the inherent anisotropy drives motor self-organization, droplet deformation, and division into two droplets. These results suggest that simple physical principles underlie self-organization in complex biological assemblies and inform bioinspired materials design.
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43
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Merkel M, Baumgarten K, Tighe BP, Manning ML. A minimal-length approach unifies rigidity in underconstrained materials. Proc Natl Acad Sci U S A 2019; 116:6560-6568. [PMID: 30894489 PMCID: PMC6452732 DOI: 10.1073/pnas.1815436116] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We present an approach to understand geometric-incompatibility-induced rigidity in underconstrained materials, including subisostatic 2D spring networks and 2D and 3D vertex models for dense biological tissues. We show that in all these models a geometric criterion, represented by a minimal length [Formula: see text], determines the onset of prestresses and rigidity. This allows us to predict not only the correct scalings for the elastic material properties, but also the precise magnitudes for bulk modulus and shear modulus discontinuities at the rigidity transition as well as the magnitude of the Poynting effect. We also predict from first principles that the ratio of the excess shear modulus to the shear stress should be inversely proportional to the critical strain with a prefactor of 3. We propose that this factor of 3 is a general hallmark of geometrically induced rigidity in underconstrained materials and could be used to distinguish this effect from nonlinear mechanics of single components in experiments. Finally, our results may lay important foundations for ways to estimate [Formula: see text] from measurements of local geometric structure and thus help develop methods to characterize large-scale mechanical properties from imaging data.
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Affiliation(s)
- Matthias Merkel
- Department of Physics, Syracuse University, Syracuse, NY 13244;
- Centre de Physique Théorique (CPT), Turing Center for Living Systems, Aix Marseille Univ, Université de Toulon, CNRS, 13009 Marseille, France
| | - Karsten Baumgarten
- Process & Energy Laboratory, Delft University of Technology, 2628 CB Delft, The Netherlands
| | - Brian P Tighe
- Process & Energy Laboratory, Delft University of Technology, 2628 CB Delft, The Netherlands
| | - M Lisa Manning
- Department of Physics, Syracuse University, Syracuse, NY 13244
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44
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Sonal, Ganzinger KA, Vogel SK, Mücksch J, Blumhardt P, Schwille P. Myosin-II activity generates a dynamic steady state with continuous actin turnover in a minimal actin cortex. J Cell Sci 2018; 132:jcs.219899. [PMID: 30538127 DOI: 10.1242/jcs.219899] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 10/16/2018] [Indexed: 01/24/2023] Open
Abstract
Dynamic reorganization of the actomyosin cytoskeleton allows fast modulation of the cell surface, which is vital for many cellular functions. Myosin-II motors generate the forces required for this remodeling by imparting contractility to actin networks. However, myosin-II activity might also have a more indirect contribution to cytoskeletal dynamics; it has been proposed that myosin activity increases actin turnover in various cellular contexts, presumably by enhancing disassembly. In vitro reconstitution of actomyosin networks has confirmed the role of myosin in actin network disassembly, but the reassembly of actin in these assays was limited by factors such as diffusional constraints and the use of stabilized actin filaments. Here, we present the reconstitution of a minimal dynamic actin cortex, where actin polymerization is catalyzed on the membrane in the presence of myosin-II activity. We demonstrate that myosin activity leads to disassembly and redistribution in this simplified cortex. Consequently, a new dynamic steady state emerges in which the actin network undergoes constant turnover. Our findings suggest a multifaceted role of myosin-II in the dynamics of the eukaryotic actin cortex. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Sonal
- Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | | | - Sven K Vogel
- Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Jonas Mücksch
- Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | | | - Petra Schwille
- Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
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45
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Seara DS, Yadav V, Linsmeier I, Tabatabai AP, Oakes PW, Tabei SMA, Banerjee S, Murrell MP. Entropy production rate is maximized in non-contractile actomyosin. Nat Commun 2018; 9:4948. [PMID: 30470750 PMCID: PMC6251913 DOI: 10.1038/s41467-018-07413-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Accepted: 10/31/2018] [Indexed: 11/09/2022] Open
Abstract
The actin cytoskeleton is an active semi-flexible polymer network whose non-equilibrium properties coordinate both stable and contractile behaviors to maintain or change cell shape. While myosin motors drive the actin cytoskeleton out-of-equilibrium, the role of myosin-driven active stresses in the accumulation and dissipation of mechanical energy is unclear. To investigate this, we synthesize an actomyosin material in vitro whose active stress content can tune the network from stable to contractile. Each increment in activity determines a characteristic spectrum of actin filament fluctuations which is used to calculate the total mechanical work and the production of entropy in the material. We find that the balance of work and entropy does not increase monotonically and the entropy production rate is maximized in the non-contractile, stable state of actomyosin. Our study provides evidence that the origins of entropy production and activity-dependent dissipation relate to disorder in the molecular interactions between actin and myosin.
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Affiliation(s)
- Daniel S Seara
- Department of Physics, Yale University, 217 Prospect Street, New Haven, CT, 06511, USA
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT, 06516, USA
| | - Vikrant Yadav
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT, 06516, USA
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT, 06511, USA
| | - Ian Linsmeier
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT, 06516, USA
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT, 06511, USA
| | - A Pasha Tabatabai
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT, 06516, USA
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT, 06511, USA
| | - Patrick W Oakes
- Department of Physics & Astronomy, and Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - S M Ali Tabei
- Physics Department, University of Northern Iowa, Cedar Falls, IA, 50614, USA
| | - Shiladitya Banerjee
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, Gower Street, London, WC1E 6BT, UK.
| | - Michael P Murrell
- Department of Physics, Yale University, 217 Prospect Street, New Haven, CT, 06511, USA.
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT, 06516, USA.
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT, 06511, USA.
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46
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Woodhouse FG, Ronellenfitsch H, Dunkel J. Autonomous Actuation of Zero Modes in Mechanical Networks Far from Equilibrium. PHYSICAL REVIEW LETTERS 2018; 121:178001. [PMID: 30411906 DOI: 10.1103/physrevlett.121.178001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 09/04/2018] [Indexed: 06/08/2023]
Abstract
A zero mode, or floppy mode, is a nontrivial coupling of mechanical components yielding a degree of freedom with no resistance to deformation. Engineered zero modes have the potential to act as microscopic motors or memory devices, but this requires an internal actuation mechanism that can overcome unwanted fluctuations in other modes and the dissipation inherent in real systems. In this Letter, we show theoretically and experimentally that complex zero modes in mechanical networks can be selectively mobilized by nonequilibrium activity. We find that a correlated active bath actuates an infinitesimal zero mode while simultaneously suppressing fluctuations in higher modes compared to thermal fluctuations, which we experimentally mimic by high frequency shaking of a physical network. Furthermore, self-propulsive dynamics spontaneously mobilize finite mechanisms as exemplified by a self-propelled topological soliton. Nonequilibrium activity thus enables autonomous actuation of coordinated mechanisms engineered through network topology.
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Affiliation(s)
- Francis G Woodhouse
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom
| | - Henrik Ronellenfitsch
- Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
| | - Jörn Dunkel
- Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
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47
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Roostalu J, Rickman J, Thomas C, Nédélec F, Surrey T. Determinants of Polar versus Nematic Organization in Networks of Dynamic Microtubules and Mitotic Motors. Cell 2018; 175:796-808.e14. [PMID: 30340043 PMCID: PMC6198040 DOI: 10.1016/j.cell.2018.09.029] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 06/25/2018] [Accepted: 09/13/2018] [Indexed: 11/03/2022]
Abstract
During cell division, mitotic motors organize microtubules in the bipolar spindle into either polar arrays at the spindle poles or a "nematic" network of aligned microtubules at the spindle center. The reasons for the distinct self-organizing capacities of dynamic microtubules and different motors are not understood. Using in vitro reconstitution experiments and computer simulations, we show that the human mitotic motors kinesin-5 KIF11 and kinesin-14 HSET, despite opposite directionalities, can both organize dynamic microtubules into either polar or nematic networks. We show that in addition to the motor properties the natural asymmetry between microtubule plus- and minus-end growth critically contributes to the organizational potential of the motors. We identify two control parameters that capture system composition and kinetic properties and predict the outcome of microtubule network organization. These results elucidate a fundamental design principle of spindle bipolarity and establish general rules for active filament network organization.
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Affiliation(s)
| | - Jamie Rickman
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Claire Thomas
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - François Nédélec
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
| | - Thomas Surrey
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
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48
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Kumar N, Zhang R, de Pablo JJ, Gardel ML. Tunable structure and dynamics of active liquid crystals. SCIENCE ADVANCES 2018; 4:eaat7779. [PMID: 30333990 PMCID: PMC6184751 DOI: 10.1126/sciadv.aat7779] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 08/31/2018] [Indexed: 05/21/2023]
Abstract
Active materials are capable of converting free energy into directional motion, giving rise to notable dynamical phenomena. Developing a general understanding of their structure in relation to the underlying nonequilibrium physics would provide a route toward control of their dynamic behavior and pave the way for potential applications. The active system considered here consists of a quasi-two-dimensional sheet of short (≈1 μm) actin filaments driven by myosin II motors. By adopting a concerted theoretical and experimental strategy, new insights are gained into the nonequilibrium properties of active nematics over a wide range of internal activity levels. In particular, it is shown that topological defect interactions can be led to transition from attractive to repulsive as a function of initial defect separation and relative orientation. Furthermore, by examining the +1/2 defect morphology as a function of activity, we found that the apparent elastic properties of the system (the ratio of bend-to-splay elastic moduli) are altered considerably by increased activity, leading to an effectively lower bend elasticity. At high levels of activity, the topological defects that decorate the material exhibit a liquid-like structure and adopt preferred orientations depending on their topological charge. Together, these results suggest that it should be possible to tune internal stresses in active nematic systems with the goal of designing out-of-equilibrium structures with engineered dynamic responses.
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Affiliation(s)
- Nitin Kumar
- James Franck Institute, The University of Chicago, Chicago, IL 60637, USA
- Department of Physics, The University of Chicago, Chicago, IL 60637, USA
| | - Rui Zhang
- Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA
| | - Juan J. de Pablo
- Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA
- Institute for Molecular Engineering, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Margaret L. Gardel
- James Franck Institute, The University of Chicago, Chicago, IL 60637, USA
- Department of Physics, The University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
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49
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Freedman SL, Hocky GM, Banerjee S, Dinner AR. Nonequilibrium phase diagrams for actomyosin networks. SOFT MATTER 2018; 14:7740-7747. [PMID: 30204203 PMCID: PMC6192427 DOI: 10.1039/c8sm00741a] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Living cells dynamically modulate the local morphologies of their actin networks to perform biological functions, including force transduction, intracellular transport, and cell division. A major challenge is to understand how diverse structures of the actin cytoskeleton are assembled from a limited set of molecular building blocks. Here we study the spontaneous self-assembly of a minimal model of cytoskeletal materials, consisting of semiflexible actin filaments, crosslinkers, and molecular motors. Using coarse-grained simulations, we demonstrate that by changing concentrations and kinetics of crosslinkers and motors, as well as filament lengths, we can generate three distinct structural phases of actomyosin assemblies: bundled, polarity-sorted, and contracted. We introduce new metrics to distinguish these structural phases and demonstrate their functional roles. We find that the binding kinetics of motors and crosslinkers can be tuned to optimize contractile force generation, motor transport, and mechanical response. By quantitatively characterizing the relationships between the modes of cytoskeletal self-assembly, the resulting structures, and their functional consequences, our work suggests new principles for the design of active materials.
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Affiliation(s)
- Simon L. Freedman
- Department of Physics, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Glen M. Hocky
- James Franck Institute & Department of Chemistry, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA, Chicago, IL, USA;
| | - Shiladitya Banerjee
- Department of Physics and Astronomy, University College London, Gower Street, London, WC1E-6BT
| | - Aaron R. Dinner
- James Franck Institute & Department of Chemistry, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA, Chicago, IL, USA;
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50
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Kemp JP, Brieher WM. The actin filament bundling protein α-actinin-4 actually suppresses actin stress fibers by permitting actin turnover. J Biol Chem 2018; 293:14520-14533. [PMID: 30049798 DOI: 10.1074/jbc.ra118.004345] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 07/21/2018] [Indexed: 01/07/2023] Open
Abstract
Cells organize actin filaments into contractile bundles known as stress fibers that resist mechanical stress, increase cell adhesion, remodel the extracellular matrix, and maintain tissue integrity. α-actinin is an actin filament bundling protein that is thought to be essential for stress fiber formation and stability. However, previous studies have also suggested that α-actinin might disrupt fibers, making the true function of this biomolecule unclear. Here we use fluorescence imaging to show that kidney epithelial cells depleted of α-actinin-4 via shRNA or CRISPR/Cas9, or expressing a disruptive mutant make more massive stress fibers that are less dynamic than those in WT cells, leading to defects in cell motility and wound healing. The increase in stress fiber mass and stability can be explained, in part, by increased loading of the filament component tropomyosin onto stress fibers in the absence of α-actinin, as monitored via immunofluorescence. We show using imaging and cosedimentation that α-actinin and tropomyosin compete for binding to F-actin and that tropomyosin shields actin filaments from cofilin-mediated disassembly in vitro and in cells. Perturbing tropomyosin in cells lacking α-actinin-4 results in a complete loss of stress fibers. Our results with α-actinin-4 on stress fiber organization are the opposite of what might have been predicted from previous in vitro biochemistry and further highlight how the complex interactions of multiple proteins competing for filament binding lead to unexpected functions for actin-binding proteins in cells.
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Affiliation(s)
| | - William M Brieher
- From the Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, Urbana, Illinois 61801
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