1
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Sun ZG, Yadav V, Amiri S, Cao W, De La Cruz EM, Murrell M. Cofilin-mediated actin filament network flexibility facilitates 2D to 3D actomyosin shape change. Eur J Cell Biol 2024; 103:151379. [PMID: 38168598 DOI: 10.1016/j.ejcb.2023.151379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 12/06/2023] [Accepted: 12/16/2023] [Indexed: 01/05/2024] Open
Abstract
The organization of actin filaments (F-actin) into crosslinked networks determines the transmission of mechanical stresses within the cytoskeleton and subsequent changes in cell and tissue shape. Principally mediated by proteins such as α-actinin, F-actin crosslinking increases both network connectivity and rigidity, thereby facilitating stress transmission at low crosslinking yet attenuating transmission at high crosslinker concentration. Here, we engineer a two-dimensional model of the actomyosin cytoskeleton, in which myosin-induced mechanical stresses are controlled by light. We alter the extent of F-actin crosslinking by the introduction of oligomerized cofilin. At pH 6.5, F-actin severing by cofilin is weak, but cofilin bundles and crosslinks filaments. Given its effect of lowering the F-actin bending stiffness, cofilin- crosslinked networks are significantly more flexible and softer in bending than networks crosslinked by α-actinin. Thus, upon local activation of myosin-induced contractile stress, the network bends out-of-plane in contrast to the in-plane compression as observed with networks crosslinked by α-actinin. Here, we demonstrate that local effects on filament mechanics by cofilin introduces novel large-scale network material properties that enable the sculpting of complex shapes in the cell cytoskeleton.
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Affiliation(s)
- Zachary Gao Sun
- Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Physics, Yale University, 217 Prospect Street, New Haven, CT 06511, USA; Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, CT 06520, USA
| | - Vikrant Yadav
- Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Biomedical Engineering, Yale University, New Haven, CT 06511, USA
| | - Sorosh Amiri
- Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Mechanical Engineering and Material Science, Yale University, New Haven, CT 06511, USA
| | - Wenxiang Cao
- Department of Molecular Biology & Biophysics, Yale University, New Haven, CT 06511, USA
| | - Enrique M De La Cruz
- Department of Molecular Biology & Biophysics, Yale University, New Haven, CT 06511, USA
| | - Michael Murrell
- Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Biomedical Engineering, Yale University, New Haven, CT 06511, USA; Department of Physics, Yale University, 217 Prospect Street, New Haven, CT 06511, USA; Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, CT 06520, USA.
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2
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Sakamoto R, Banerjee DS, Yadav V, Chen S, Gardel M, Sykes C, Banerjee S, Murrell MP. Membrane tension induces F-actin reorganization and flow in a biomimetic model cortex. Commun Biol 2023; 6:325. [PMID: 36973388 PMCID: PMC10043271 DOI: 10.1038/s42003-023-04684-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Accepted: 03/07/2023] [Indexed: 03/28/2023] Open
Abstract
AbstractThe accumulation and transmission of mechanical stresses in the cell cortex and membrane determines the mechanics of cell shape and coordinates essential physical behaviors, from cell polarization to cell migration. However, the extent that the membrane and cytoskeleton each contribute to the transmission of mechanical stresses to coordinate diverse behaviors is unclear. Here, we reconstitute a minimal model of the actomyosin cortex within liposomes that adheres, spreads and ultimately ruptures on a surface. During spreading, accumulated adhesion-induced (passive) stresses within the membrane drive changes in the spatial assembly of actin. By contrast, during rupture, accumulated myosin-induced (active) stresses within the cortex determine the rate of pore opening. Thus, in the same system, devoid of biochemical regulation, the membrane and cortex can each play a passive or active role in the generation and transmission of mechanical stress, and their relative roles drive diverse biomimetic physical behaviors.
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3
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Muresan CG, Sun ZG, Yadav V, Tabatabai AP, Lanier L, Kim JH, Kim T, Murrell MP. F-actin architecture determines constraints on myosin thick filament motion. Nat Commun 2022; 13:7008. [PMID: 36385016 PMCID: PMC9669029 DOI: 10.1038/s41467-022-34715-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 11/03/2022] [Indexed: 11/17/2022] Open
Abstract
Active stresses are generated and transmitted throughout diverse F-actin architectures within the cell cytoskeleton, and drive essential behaviors of the cell, from cell division to migration. However, while the impact of F-actin architecture on the transmission of stress is well studied, the role of architecture on the ab initio generation of stresses remains less understood. Here, we assemble F-actin networks in vitro, whose architectures are varied from branched to bundled through F-actin nucleation via Arp2/3 and the formin mDia1. Within these architectures, we track the motions of embedded myosin thick filaments and connect them to the extent of F-actin network deformation. While mDia1-nucleated networks facilitate the accumulation of stress and drive contractility through enhanced actomyosin sliding, branched networks prevent stress accumulation through the inhibited processivity of thick filaments. The reduction in processivity is due to a decrease in translational and rotational motions constrained by the local density and geometry of F-actin.
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Affiliation(s)
- Camelia G Muresan
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT, 06511, USA
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT, 06516, USA
| | - Zachary Gao Sun
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT, 06516, USA
- Department of Physics, Yale University, 217 Prospect Street, New Haven, CT, 06511, USA
| | - Vikrant Yadav
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT, 06511, USA
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT, 06516, USA
| | - A Pasha Tabatabai
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT, 06511, USA
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT, 06516, USA
| | - Laura Lanier
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT, 06511, USA
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT, 06516, USA
| | - June Hyung Kim
- Weldon School of Biomedical Engineering, Purdue University, 206S. Martin Jischke Drive, West Lafayette, IN, 47907, USA
| | - Taeyoon Kim
- Weldon School of Biomedical Engineering, Purdue University, 206S. Martin Jischke Drive, West Lafayette, IN, 47907, USA
| | - Michael P Murrell
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT, 06511, USA.
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT, 06516, USA.
- Department of Physics, Yale University, 217 Prospect Street, New Haven, CT, 06511, USA.
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4
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Tabatabai AP, Seara DS, Tibbs J, Yadav V, Linsmeier I, Murrell MP. Detailed Balance Broken by Catch Bond Kinetics Enables Mechanical-Adaptation in Active Materials. ADVANCED FUNCTIONAL MATERIALS 2021; 31:2006745. [PMID: 34393691 PMCID: PMC8357268 DOI: 10.1002/adfm.202006745] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Indexed: 05/04/2023]
Abstract
Unlike nearly all engineered materials which contain bonds that weaken under load, biological materials contain "catch" bonds which are reinforced under load. Consequently, materials, such as the cell cytoskeleton, can adapt their mechanical properties in response to their state of internal, non-equilibrium (active) stress. However, how large-scale material properties vary with the distance from equilibrium is unknown, as are the relative roles of active stress and binding kinetics in establishing this distance. Through course-grained molecular dynamics simulations, the effect of breaking of detailed balance by catch bonds on the accumulation and dissipation of energy within a model of the actomyosin cytoskeleton is explored. It is found that the extent to which detailed balance is broken uniquely determines a large-scale fluid-solid transition with characteristic time-reversal symmetries. The transition depends critically on the strength of the catch bond, suggesting that active stress is necessary but insufficient to mount an adaptive mechanical response.
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Affiliation(s)
- Alan Pasha Tabatabai
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT 06511, USA; Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT 06516, USA
| | - Daniel S Seara
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT 06516, USA; Department of Physics, Yale University, 217 Prospect Street, New Haven, CT 06511, USA
| | - Joseph Tibbs
- Department of Physics, University of Northern Iowa, Cedar Falls, IA 50614, USA
| | - Vikrant Yadav
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT 06511, USA; Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT 06516, USA
| | - Ian Linsmeier
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT 06511, USA; Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT 06516, USA
| | - Michael P Murrell
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT 06511, USA; Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, CT 06516, USA; Department of Physics, Yale University, 217 Prospect Street, New Haven, CT 06511, USA
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5
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Bleicher P, Nast-Kolb T, Sciortino A, de la Trobe YA, Pokrant T, Faix J, Bausch AR. Intra-bundle contractions enable extensile properties of active actin networks. Sci Rep 2021; 11:2677. [PMID: 33514794 PMCID: PMC7846802 DOI: 10.1038/s41598-021-81601-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 01/05/2021] [Indexed: 12/27/2022] Open
Abstract
The cellular cortex is a dynamic and contractile actomyosin network modulated by actin-binding proteins. We reconstituted a minimal cortex adhered to a model cell membrane mimicking two processes mediated by the motor protein myosin: contractility and high turnover of actin monomers. Myosin reorganized these networks by extensile intra‑bundle contractions leading to an altered growth mechanism. Hereby, stress within tethered bundles induced nicking of filaments followed by repair via incorporation of free monomers. This mechanism was able to break the symmetry of the previously disordered network resulting in the generation of extensile clusters, reminiscent of structures found within cells.
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Affiliation(s)
- P Bleicher
- Physik-Department, Lehrstuhl für Biophysik E27, Technische Universität München, Garching, Germany. .,Center for Protein Assemblies (CPA), Ernst-Otto-Fischer Str. 8, 85747, Garching, Germany.
| | - T Nast-Kolb
- Physik-Department, Lehrstuhl für Biophysik E27, Technische Universität München, Garching, Germany.,Center for Protein Assemblies (CPA), Ernst-Otto-Fischer Str. 8, 85747, Garching, Germany
| | - A Sciortino
- Physik-Department, Lehrstuhl für Biophysik E27, Technische Universität München, Garching, Germany.,Center for Protein Assemblies (CPA), Ernst-Otto-Fischer Str. 8, 85747, Garching, Germany
| | - Y A de la Trobe
- Physik-Department, Lehrstuhl für Biophysik E27, Technische Universität München, Garching, Germany.,Center for Protein Assemblies (CPA), Ernst-Otto-Fischer Str. 8, 85747, Garching, Germany
| | - T Pokrant
- Institut für Biophysikalische Chemie, Medizinische Hochschule Hannover, Hannover, Germany
| | - J Faix
- Institut für Biophysikalische Chemie, Medizinische Hochschule Hannover, Hannover, Germany
| | - A R Bausch
- Physik-Department, Lehrstuhl für Biophysik E27, Technische Universität München, Garching, Germany. .,Center for Protein Assemblies (CPA), Ernst-Otto-Fischer Str. 8, 85747, Garching, Germany.
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6
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Winkelman JD, Anderson CA, Suarez C, Kovar DR, Gardel ML. Evolutionarily diverse LIM domain-containing proteins bind stressed actin filaments through a conserved mechanism. Proc Natl Acad Sci U S A 2020; 117:25532-25542. [PMID: 32989126 PMCID: PMC7568268 DOI: 10.1073/pnas.2004656117] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The actin cytoskeleton assembles into diverse load-bearing networks, including stress fibers (SFs), muscle sarcomeres, and the cytokinetic ring to both generate and sense mechanical forces. The LIM (Lin11, Isl- 1, and Mec-3) domain family is functionally diverse, but most members can associate with the actin cytoskeleton with apparent force sensitivity. Zyxin rapidly localizes via its LIM domains to failing SFs in cells, known as strain sites, to initiate SF repair and maintain mechanical homeostasis. The mechanism by which these LIM domains associate with stress fiber strain sites (SFSS) is not known. Additionally, it is unknown how widespread strain sensing is within the LIM protein family. We identify that the LIM domain-containing region of 18 proteins from the Zyxin, Paxillin, Tes, and Enigma proteins accumulate to SFSS. Moreover, the LIM domain region from the fission yeast protein paxillin like 1 (Pxl1) also localizes to SFSS in mammalian cells, suggesting that the strain sensing mechanism is ancient and highly conserved. We then used sequence and domain analysis to demonstrate that tandem LIM domains contribute additively, for SFSS localization. Employing in vitro reconstitution, we show that the LIM domain-containing region from mammalian zyxin and fission yeast Pxl1 binds to mechanically stressed F-actin networks but does not associate with relaxed actin filaments. We propose that tandem LIM domains recognize an F-actin conformation that is rare in the relaxed state but is enriched in the presence of mechanical stress.
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Affiliation(s)
| | - Caitlin A Anderson
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Cristian Suarez
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637;
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637
| | - Margaret L Gardel
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637;
- James Franck Institute, University of Chicago, Chicago, IL 60637
- Physics Department, University of Chicago, Chicago, IL 60637
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637
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7
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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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8
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Yadav V, Banerjee DS, Tabatabai AP, Kovar DR, Kim T, Banerjee S, Murrell MP. Filament Nucleation Tunes Mechanical Memory in Active Polymer Networks. ADVANCED FUNCTIONAL MATERIALS 2019; 29:1905243. [PMID: 32523502 PMCID: PMC7286550 DOI: 10.1002/adfm.201905243] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Indexed: 05/20/2023]
Abstract
Incorporating growth into contemporary material functionality presents a grand challenge in materials design. The F-actin cytoskeleton is an active polymer network which serves as the mechanical scaffolding for eukaryotic cells, growing and remodeling in order to determine changes in cell shape. Nucleated from the membrane, filaments polymerize and grow into a dense network whose dynamics of assembly and disassembly, or 'turnover', coordinates both fluidity and rigidity. Here, we vary the extent of F-actin nucleation from a membrane surface in a biomimetic model of the cytoskeleton constructed from purified protein. We find that nucleation of F-actin mediates the accumulation and dissipation of polymerization-induced F-actin bending energy. At high and low nucleation, bending energies are low and easily relaxed yielding an isotropic material. However, at an intermediate critical nucleation, stresses are not relaxed by turnover and the internal energy accumulates 100-fold. In this case, high filament curvatures template further assembly of F-actin, driving the formation and stabilization of vortex-like topological defects. Thus, nucleation coordinates mechanical and chemical timescales to encode shape memory into active materials.
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Affiliation(s)
- Vikrant Yadav
- Department of Biomedical Engineering, Yale University, 10 Hillhouse Avenue, New Haven, CT, USA
| | - Deb S Banerjee
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
| | - A Pasha Tabatabai
- Department of Biomedical Engineering, Yale University, 10 Hillhouse Avenue, New Haven, CT, USA
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 E. 58th St., CSLC 212, Chicago, IL, 60637, USA
| | - Taeyoon Kim
- 206 S Martin Jischke Drive, MJIS 3031, Weldon School of Biomedical Engineering, Purdue University ,West Lafayette, IN, USA
| | - Shiladitya Banerjee
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
| | - Michael P Murrell
- Systems Biology Institute, 850 West Campus Drive, West Haven, CT, USA
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9
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The Cytoskeleton-A Complex Interacting Meshwork. Cells 2019; 8:cells8040362. [PMID: 31003495 PMCID: PMC6523135 DOI: 10.3390/cells8040362] [Citation(s) in RCA: 179] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 04/15/2019] [Accepted: 04/15/2019] [Indexed: 12/22/2022] Open
Abstract
The cytoskeleton of animal cells is one of the most complicated and functionally versatile structures, involved in processes such as endocytosis, cell division, intra-cellular transport, motility, force transmission, reaction to external forces, adhesion and preservation, and adaptation of cell shape. These functions are mediated by three classical cytoskeletal filament types, as follows: Actin, microtubules, and intermediate filaments. The named filaments form a network that is highly structured and dynamic, responding to external and internal cues with a quick reorganization that is orchestrated on the time scale of minutes and has to be tightly regulated. Especially in brain tumors, the cytoskeleton plays an important role in spreading and migration of tumor cells. As the cytoskeletal organization and regulation is complex and many-faceted, this review aims to summarize the findings about cytoskeletal filament types, including substructures formed by them, such as lamellipodia, stress fibers, and interactions between intermediate filaments, microtubules and actin. Additionally, crucial regulatory aspects of the cytoskeletal filaments and the formed substructures are discussed and integrated into the concepts of cell motility. Even though little is known about the impact of cytoskeletal alterations on the progress of glioma, a final point discussed will be the impact of established cytoskeletal alterations in the cellular behavior and invasion of glioma.
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10
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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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11
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Burden DL, Kim D, Cheng W, Chandler Lawler E, Dreyer DR, Keranen Burden LM. Mechanically Enhancing Planar Lipid Bilayers with a Minimal Actin Cortex. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:10847-10855. [PMID: 30149716 DOI: 10.1021/acs.langmuir.8b01847] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
All cells in all domains of life possess a cytoskeleton that provides mechanical resistance to deformation and general stability to the plasma membrane. Here, we utilize a two-dimensional scaffolding created by actin filaments to convey mechanical support upon relatively fragile planar bilayer membranes (black lipid membranes, BLMs). Robust biomembranes play a critical role in the development of protein nanopore sensor applications and might also prove helpful in ion-channel research. Our investigation utilizes a minimal actin cortex (MAC) that is formed by anchoring actin filaments to lipid membranes via a biotin-streptavidin-biotin bridge. We characterize the joined structure using various modes of optical microscopy, electrophysiology, and applied mechanical stress (including measurements of elastic modulus). Our findings show the resulting structure includes a thin supporting layer of actin. Electrical studies indicate that the integrity of the MAC-bilayer composite remains unchanged over the limits of our tests (i.e., hours to days). The actin filament structure can remain intact for months. Minimalistic layering of the actin support network produces an increase in the apparent elastic modulus of the MAC-derivatized bilayer by >100×, compared to unmodified BLMs. Furthermore, the resistance to applied stress improves with the number of actin layers, which can be cross-linked to arbitrary thicknesses, in principle. The weblike support structure retains the lateral fluidity of the BLM, maintains the high electrical resistance typical of traditional BLMs, enables relatively uninhibited molecular access to the lipid surface from bulk solution, and permits nanopore self-assembly and insertion in the bilayer. These interfacial features are highly desirable for ion-channel and nanopore sensing applications.
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Affiliation(s)
- Daniel L Burden
- Chemistry Department , Wheaton College , Wheaton , Illinois 60187 , United States
| | - Daniel Kim
- Chemistry Department , Wheaton College , Wheaton , Illinois 60187 , United States
| | - Wayland Cheng
- Chemistry Department , Wheaton College , Wheaton , Illinois 60187 , United States
| | | | - Daniel R Dreyer
- Chemistry Department , Wheaton College , Wheaton , Illinois 60187 , United States
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12
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Khan S, Guo TW, Misra S. A coevolution-guided model for the rotor of the bacterial flagellar motor. Sci Rep 2018; 8:11754. [PMID: 30082903 PMCID: PMC6079021 DOI: 10.1038/s41598-018-30293-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 07/19/2018] [Indexed: 01/17/2023] Open
Abstract
The Salmonella typhimurium trans-membrane FliF MS ring templates assembly of the rotary bacterial flagellar motor, which also contains a cytoplasmic C-ring. A full-frame fusion of FliF with the rotor protein FliG assembles rings in non-motile expression hosts. 3D electron microscopy reconstructions of these FliFFliG rings show three high electron-density sub-volumes. 3D-classification revealed heterogeneity of the assigned cytoplasmic volume consistent with FliG lability. We used residue coevolution to construct homodimer building blocks for ring assembly, with X-ray crystal structures from other species and injectisome analogs. The coevolution signal validates folds and, importantly, indicates strong homodimer contacts for three ring building motifs (RBMs), initially identified in injectisome structures. It also indicates that the cofolded domains of the FliG N-terminal domain (FliG_N) with embedded α-helical FliF carboxy-terminal tail homo-oligomerize. The FliG middle and C-terminal domains (FliG_MC) have a weak signal for homo-dimerization but have coevolved to conserve their stacking contact. The homodimers and their ring models fit well into the 3D reconstruction. We hypothesize that a stable FliF periplasmic hub provides a platform for FliG ring self-assembly, but the FliG_MC ring has only limited stability without the C-ring. We also present a mechanical model for torque transmission in the FliFFliG ring.
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Affiliation(s)
- Shahid Khan
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, 20892, USA.
- Molecular Biology Consortium, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Tai Wei Guo
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, 20892, USA
| | - Saurav Misra
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, 20892, USA
- Department of Biochemistry & Molecular Biophysics, Kansas State University, Manhattan, KS, 66506, USA
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13
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Freedman SL, Banerjee S, Hocky GM, Dinner AR. A Versatile Framework for Simulating the Dynamic Mechanical Structure of Cytoskeletal Networks. Biophys J 2017; 113:448-460. [PMID: 28746855 DOI: 10.1016/j.bpj.2017.06.003] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 05/26/2017] [Accepted: 06/02/2017] [Indexed: 01/07/2023] Open
Abstract
Computer simulations can aid in understanding how collective materials properties emerge from interactions between simple constituents. Here, we introduce a coarse-grained model that enables simulation of networks of actin filaments, myosin motors, and cross-linking proteins at biologically relevant time and length scales. We demonstrate that the model qualitatively and quantitatively captures a suite of trends observed experimentally, including the statistics of filament fluctuations, and mechanical responses to shear, motor motilities, and network rearrangements. We use the simulation to predict the viscoelastic scaling behavior of cross-linked actin networks, characterize the trajectories of actin in a myosin motility assay, and develop order parameters to measure contractility of a simulated actin network. The model can thus serve as a platform for interpretation and design of cytoskeletal materials experiments, as well as for further development of simulations incorporating active elements.
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Affiliation(s)
- Simon L Freedman
- Department of Physics, University of Chicago, Chicago, Illinois; James Franck Institute, University of Chicago, Chicago, Illinois
| | - Shiladitya Banerjee
- Department of Physics and Astronomy, University College London, London, United Kingdom; Institute for Physics of Living Systems, University College London, London, United Kingdom
| | - Glen M Hocky
- James Franck Institute, University of Chicago, Chicago, Illinois; Department of Chemistry, University of Chicago, Chicago, Illinois
| | - Aaron R Dinner
- James Franck Institute, University of Chicago, Chicago, Illinois; Department of Chemistry, University of Chicago, Chicago, Illinois; Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois.
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14
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Linsmeier I, Banerjee S, Oakes PW, Jung W, Kim T, Murrell MP. Disordered actomyosin networks are sufficient to produce cooperative and telescopic contractility. Nat Commun 2016; 7:12615. [PMID: 27558758 PMCID: PMC5007339 DOI: 10.1038/ncomms12615] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 07/13/2016] [Indexed: 11/09/2022] Open
Abstract
While the molecular interactions between individual myosin motors and F-actin are well established, the relationship between F-actin organization and actomyosin forces remains poorly understood. Here we explore the accumulation of myosin-induced stresses within a two-dimensional biomimetic model of the disordered actomyosin cytoskeleton, where myosin activity is controlled spatiotemporally using light. By controlling the geometry and the duration of myosin activation, we show that contraction of disordered actin networks is highly cooperative, telescopic with the activation size, and capable of generating non-uniform patterns of mechanical stress. We quantitatively reproduce these collective biomimetic properties using an isotropic active gel model of the actomyosin cytoskeleton, and explore the physical origins of telescopic contractility in disordered networks using agent-based simulations.
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Affiliation(s)
- Ian Linsmeier
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, Connecticut 06520, USA
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, Connecticut 06516, USA
| | | | - Patrick W. Oakes
- James Franck Institute, University of Chicago, Chicago, Illinois 60637, USA
| | - Wonyeong Jung
- School of Mechanical Engineering, 585 Purdue Mall, Purdue University, West Lafayette, Indiana 47907, USA
| | - Taeyoon Kim
- Weldon School of Biomedical Engineering, 206 S Martin Jischke Drive, Purdue University, West Lafayette, Indiana 47907, USA
| | - Michael P. Murrell
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, Connecticut 06520, USA
- Systems Biology Institute, Yale University, 850 West Campus Drive, West Haven, Connecticut 06516, USA
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15
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Kassianidou E, Kumar S. A biomechanical perspective on stress fiber structure and function. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:3065-74. [PMID: 25896524 DOI: 10.1016/j.bbamcr.2015.04.006] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 04/05/2015] [Accepted: 04/08/2015] [Indexed: 01/11/2023]
Abstract
Stress fibers are actomyosin-based bundles whose structural and contractile properties underlie numerous cellular processes including adhesion, motility and mechanosensing. Recent advances in high-resolution live-cell imaging and single-cell force measurement have dramatically sharpened our understanding of the assembly, connectivity, and evolution of various specialized stress fiber subpopulations. This in turn has motivated interest in understanding how individual stress fibers generate tension and support cellular structure and force generation. In this review, we discuss approaches for measuring the mechanical properties of single stress fibers. We begin by discussing studies conducted in cell-free settings, including strategies based on isolation of intact stress fibers and reconstitution of stress fiber-like structures from purified components. We then discuss measurements obtained in living cells based both on inference of stress fiber properties from whole-cell mechanical measurements (e.g., atomic force microscopy) and on direct interrogation of single stress fibers (e.g., subcellular laser nanosurgery). We conclude by reviewing various mathematical models of stress fiber function that have been developed based on these experimental measurements. An important future challenge in this area will be the integration of these sophisticated biophysical measurements with the field's increasingly detailed molecular understanding of stress fiber assembly, dynamics, and signal transduction. This article is part of a Special Issue entitled: Mechanobiology.
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Affiliation(s)
- Elena Kassianidou
- Department of Bioengineering, University of California, Berkeley, United States
| | - Sanjay Kumar
- Department of Bioengineering, University of California, Berkeley, United States.
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16
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Ciobanasu C, Faivre B, Le Clainche C. Reconstituting actomyosin-dependent mechanosensitive protein complexes in vitro. Nat Protoc 2014; 10:75-89. [DOI: 10.1038/nprot.2014.200] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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17
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Abstract
A model actin cortex is constituted in vitro and used to monitor the relative movements of actin and myosin under conditions that promote or abrogate network contraction. Myosin II molecular motors efficiently drive contraction of a disordered, cortical F-actin network with attenuated relative actomyosin sliding. Myosin II motors embedded within the actin cortex generate contractile forces to modulate cell shape in essential behaviors, including polarization, migration, and division. In sarcomeres, myosin II–mediated sliding of antiparallel F-actin is tightly coupled to myofibril contraction. By contrast, cortical F-actin is highly disordered in polarity, orientation, and length. How the disordered nature of the actin cortex affects actin and myosin movements and resultant contraction is unknown. Here we reconstitute a model cortex in vitro to monitor the relative movements of actin and myosin under conditions that promote or abrogate network contraction. In weakly contractile networks, myosin can translocate large distances across stationary F-actin. By contrast, the extent of relative actomyosin sliding is attenuated during contraction. Thus actomyosin sliding efficiently drives contraction in actomyosin networks despite the high degree of disorder. These results are consistent with the nominal degree of relative actomyosin movement observed in actomyosin assemblies in nonmuscle cells.
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Affiliation(s)
- Michael Murrell
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637
| | - Margaret L Gardel
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637Department of Physics and James Franck Institute, University of Chicago, Chicago, IL 60637
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