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Nishimura Y, Shi S, Li Q, Bershadsky AD, Viasnoff V. Crosstalk between myosin II and formin functions in the regulation of force generation and actomyosin dynamics in stress fibers. Cells Dev 2021; 168:203736. [PMID: 34455135 DOI: 10.1016/j.cdev.2021.203736] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 07/23/2021] [Accepted: 08/16/2021] [Indexed: 10/20/2022]
Abstract
REF52 fibroblasts have a well-developed contractile machinery, the most prominent elements of which are actomyosin stress fibers with highly ordered organization of actin and myosin IIA filaments. The relationship between contractile activity and turnover dynamics of stress fibers is not sufficiently understood. Here, we simultaneously measured the forces exerted by stress fibers (using traction force microscopy or micropillar array sensors) and the dynamics of actin and myosin (using photoconversion-based monitoring of actin incorporation and high-resolution fluorescence microscopy of myosin II light chain). Our data revealed new features of the crosstalk between myosin II-driven contractility and stress fiber dynamics. During normal stress fiber turnover, actin incorporated all along the stress fibers and not only at focal adhesions. Incorporation of actin into stress fibers/focal adhesions, as well as actin and myosin II filaments flow along stress fibers, strongly depends on myosin II activity. Myosin II-dependent generation of traction forces does not depend on incorporation of actin into stress fibers per se, but still requires formin activity. This previously overlooked function of formins in maintenance of the actin cytoskeleton connectivity could be the main mechanism of formin involvement in traction force generation.
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Affiliation(s)
- Yukako Nishimura
- Mechanobiology Institute, National University of Singapore, T-Lab, 5A Engineering Drive 1, 117411, Singapore; Division of Developmental Physiology, Institute for Genetic Medicine, Hokkaido University, Kita-15, Nishi-7, Kita-ku, Sapporo 060-0815, Japan
| | - Shidong Shi
- Mechanobiology Institute, National University of Singapore, T-Lab, 5A Engineering Drive 1, 117411, Singapore
| | - Qingsen Li
- IFOM-FIRC Institute of Molecular Oncology, Via Adamello, 16, 20139 Milan, Italy
| | - Alexander D Bershadsky
- Mechanobiology Institute, National University of Singapore, T-Lab, 5A Engineering Drive 1, 117411, Singapore; Department of Molecular Cell Biology, Weizmann Institute of Science, 234 Herzl Street, POB 26, Rehovot 7610001, Israel.
| | - Virgile Viasnoff
- Mechanobiology Institute, National University of Singapore, T-Lab, 5A Engineering Drive 1, 117411, Singapore; CNRS UMI 3639, Singapore; Department of Biological Sciences, National university of Singapore, S3 #05-01, 16 Science Drive 4, 117558, Singapore.
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Abstract
Septins are an integral component of the cytoskeleton, assembling into higher-order oligomers and filamentous polymers that associate with actin filaments, microtubules and membranes. Here, we review septin interactions with actin and microtubules, and septin-mediated regulation of the organization and dynamics of these cytoskeletal networks, which is critical for cellular morphogenesis. We discuss how actomyosin-associated septins function in cytokinesis, cell migration and host defense against pathogens. We highlight newly emerged roles of septins at the interface of microtubules and membranes with molecular motors, which point to a 'septin code' for the regulation of membrane traffic. Additionally, we revisit the functions of microtubule-associated septins in mitosis and meiosis. In sum, septins comprise a unique module of cytoskeletal regulators that are spatially and functionally specialized and have properties of bona fide actin-binding and microtubule-associated proteins. With many questions still outstanding, the study of septins will continue to provide new insights into fundamental problems of cytoskeletal organization and function.
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Affiliation(s)
- Guillaume Charras
- London Centre for Nanotechnology, University College London, London, UK.
- Department of Cell and Developmental Biology, University College London, London, UK.
- Institute for the Physics of Living Systems, University College London, London, UK.
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54
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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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