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Kollimada S, Senger F, Vignaud T, Théry M, Blanchoin L, Kurzawa L. The biochemical composition of the actomyosin network sets the magnitude of cellular traction forces. Mol Biol Cell 2021; 32:1737-1748. [PMID: 34410837 PMCID: PMC8684728 DOI: 10.1091/mbc.e21-03-0109] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The regulation of cellular force production relies on the complex interplay between a well-conserved set of proteins of the cytoskeleton: actin, myosin, and α-actinin. Despite our deep knowledge of the role of these proteins in force production at the molecular scale, our understanding of the biochemical regulation of the magnitude of traction forces generated at the entire-cell level has been limited, notably by the technical challenge of measuring traction forces and the endogenous biochemical composition in the same cell. In this study, we developed an alternative Traction-Force Microscopy (TFM) assay, which used a combination of hydrogel micropatterning to define cell adhesion and shape and an intermediate fixation/immunolabeling step to characterize strain energies and the endogenous protein contents in single epithelial cells. Our results demonstrated that both the signal intensity and the area of the Focal Adhesion (FA)–associated protein vinculin showed a strong positive correlation with strain energy in mature FAs. Individual contents from actin filament and phospho-myosin displayed broader deviation in their linear relationship to strain energies. Instead, our quantitative analyzes demonstrated that their relative amount exhibited an optimum ratio of phospho-myosin to actin, allowing maximum force production by cells. By contrast, although no correlation was identified between individual α-actinin content and strain energy, the ratio of α-actinin to actin filaments was inversely related to strain energy. Hence, our results suggest that, in the cellular model studied, traction-force magnitude is dictated by the relative numbers of molecular motors and cross-linkers per actin filament, rather than the amounts of an individual component in the cytoskeletal network. This assay offers new perspectives to study in more detail the complex interplay between the endogenous biochemical composition of individual cells and the force they produce.
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Affiliation(s)
- Somanna Kollimada
- Interdisciplinary Research Institute of Grenoble, Laboratoire de Physiologie Cellulaire & Végétale, CytoMorpho Lab, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
| | - Fabrice Senger
- Interdisciplinary Research Institute of Grenoble, Laboratoire de Physiologie Cellulaire & Végétale, CytoMorpho Lab, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
| | - Timothée Vignaud
- Interdisciplinary Research Institute of Grenoble, Laboratoire de Physiologie Cellulaire & Végétale, CytoMorpho Lab, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France.,Clinique de chirurgie digestive et endocrinienne, Hôtel Dieu, Nantes, 44093, France
| | - Manuel Théry
- Interdisciplinary Research Institute of Grenoble, Laboratoire de Physiologie Cellulaire & Végétale, CytoMorpho Lab, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France.,Institut de Recherche Saint Louis, U976 Human Immunology Pathophysiology Immunotherapy (HIPI), CytoMorpho Lab, University of Paris, INSERM, CEA, Paris, France
| | - Laurent Blanchoin
- Interdisciplinary Research Institute of Grenoble, Laboratoire de Physiologie Cellulaire & Végétale, CytoMorpho Lab, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France.,Institut de Recherche Saint Louis, U976 Human Immunology Pathophysiology Immunotherapy (HIPI), CytoMorpho Lab, University of Paris, INSERM, CEA, Paris, France
| | - Laëtitia Kurzawa
- Interdisciplinary Research Institute of Grenoble, Laboratoire de Physiologie Cellulaire & Végétale, CytoMorpho Lab, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
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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: 173] [Impact Index Per Article: 34.6] [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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3
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Dasbiswas K, Hu S, Schnorrer F, Safran SA, Bershadsky AD. Ordering of myosin II filaments driven by mechanical forces: experiments and theory. Philos Trans R Soc Lond B Biol Sci 2019; 373:rstb.2017.0114. [PMID: 29632266 DOI: 10.1098/rstb.2017.0114] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/30/2017] [Indexed: 12/27/2022] Open
Abstract
Myosin II filaments form ordered superstructures in both cross-striated muscle and non-muscle cells. In cross-striated muscle, myosin II (thick) filaments, actin (thin) filaments and elastic titin filaments comprise the stereotypical contractile units of muscles called sarcomeres. Linear chains of sarcomeres, called myofibrils, are aligned laterally in registry to form cross-striated muscle cells. The experimentally observed dependence of the registered organization of myofibrils on extracellular matrix elasticity has been proposed to arise from the interactions of sarcomeric contractile elements (considered as force dipoles) through the matrix. Non-muscle cells form small bipolar filaments built of less than 30 myosin II molecules. These filaments are associated in registry forming superstructures ('stacks') orthogonal to actin filament bundles. Formation of myosin II filament stacks requires the myosin II ATPase activity and function of the actin filament crosslinking, polymerizing and depolymerizing proteins. We propose that the myosin II filaments embedded into elastic, intervening actin network (IVN) function as force dipoles that interact attractively through the IVN. This is in analogy with the theoretical picture developed for myofibrils where the elastic medium is now the actin cytoskeleton itself. Myosin stack formation in non-muscle cells provides a novel mechanism for the self-organization of the actin cytoskeleton at the level of the entire cell.This article is part of the theme issue 'Self-organization in cell biology'.
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Affiliation(s)
- Kinjal Dasbiswas
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
| | - Shiqiong Hu
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Republic of Singapore.,Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Frank Schnorrer
- Aix Marseille University, CNRS, IBDM, 13288 Marseille, France
| | - Samuel A Safran
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Alexander D Bershadsky
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Republic of Singapore .,Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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4
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McEvoy E, Deshpande VS, McGarry P. Transient active force generation and stress fibre remodelling in cells under cyclic loading. Biomech Model Mechanobiol 2019; 18:921-937. [PMID: 30783833 DOI: 10.1007/s10237-019-01121-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 01/21/2019] [Indexed: 12/27/2022]
Abstract
The active cytoskeleton is known to play an important mechanistic role in cellular structure, spreading, and contractility. Contractility is actively generated by stress fibres (SF), which continuously remodel in response to physiological dynamic loading conditions. The influence of actin-myosin cross-bridge cycling on SF remodelling under dynamic loading conditions has not previously been uncovered. In this study, a novel SF cross-bridge cycling model is developed to predict transient active force generation in cells subjected to dynamic loading. Rates of formation of cross-bridges within SFs are governed by the chemical potentials of attached and unattached myosin heads. This transient cross-bridge cycling model is coupled with a thermodynamically motivated framework for SF remodelling to analyse the influence of transient force generation on cytoskeletal evolution. A 1D implementation of the model is shown to correctly predict complex patterns of active cell force generation under a range of dynamic loading conditions, as reported in previous experimental studies.
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Affiliation(s)
- Eoin McEvoy
- Discipline of Biomedical Engineering, National University of Ireland Galway, Galway, Ireland
| | | | - Patrick McGarry
- Discipline of Biomedical Engineering, National University of Ireland Galway, Galway, Ireland.
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5
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The homeostatic ensemble for cells. Biomech Model Mechanobiol 2018; 17:1631-1662. [PMID: 29987699 DOI: 10.1007/s10237-018-1048-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Accepted: 06/26/2018] [Indexed: 12/12/2022]
Abstract
Cells are quintessential examples of out-of-equilibrium systems, but they maintain a homeostatic state over a timescale of hours to days. As a consequence, the statistics of all observables is remarkably consistent. Here, we develop a statistical mechanics framework for living cells by including the homeostatic constraint that exists over the interphase period of the cell cycle. The consequence is the introduction of the concept of a homeostatic ensemble and an associated homeostatic temperature, along with a formalism for the (dynamic) homeostatic equilibrium that intervenes to allow living cells to evade thermodynamic decay. As a first application, the framework is shown to accurately predict the observed effect of the mechanical environment on the in vitro response of smooth muscle cells. This includes predictions that both the mean values and diversity/variability in the measured values of observables such as cell area, shape and tractions decrease with decreasing stiffness of the environment. Thus, we argue that the observed variabilities are inherent to the entropic nature of the homeostatic equilibrium of cells and not a result of in vitro experimental errors.
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Abstract
The actin cytoskeleton-a collection of actin filaments with their accessory and regulatory proteins-is the primary force-generating machinery in the cell. It can produce pushing (protrusive) forces through coordinated polymerization of multiple actin filaments or pulling (contractile) forces through sliding actin filaments along bipolar filaments of myosin II. Both force types are particularly important for whole-cell migration, but they also define and change the cell shape and mechanical properties of the cell surface, drive the intracellular motility and morphogenesis of membrane organelles, and allow cells to form adhesions with each other and with the extracellular matrix.
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Affiliation(s)
- Tatyana Svitkina
- Department of Biology, University of Pennsylvania, 221 Leidy Labs, Philadelphia, Pennsylvania 19104
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7
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Hu S, Dasbiswas K, Guo Z, Tee YH, Thiagarajan V, Hersen P, Chew TL, Safran SA, Zaidel-Bar R, Bershadsky AD. Long-range self-organization of cytoskeletal myosin II filament stacks. Nat Cell Biol 2017; 19:133-141. [PMID: 28114270 DOI: 10.1038/ncb3466] [Citation(s) in RCA: 124] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 12/15/2016] [Indexed: 12/12/2022]
Abstract
Although myosin II filaments are known to exist in non-muscle cells, their dynamics and organization are incompletely understood. Here, we combined structured illumination microscopy with pharmacological and genetic perturbations, to study the process of actomyosin cytoskeleton self-organization into arcs and stress fibres. A striking feature of the myosin II filament organization was their 'registered' alignment into stacks, spanning up to several micrometres in the direction orthogonal to the parallel actin bundles. While turnover of individual myosin II filaments was fast (characteristic half-life time 60 s) and independent of actin filament turnover, the process of stack formation lasted a longer time (in the range of several minutes) and required myosin II contractility, as well as actin filament assembly/disassembly and crosslinking (dependent on formin Fmnl3, cofilin1 and α-actinin-4). Furthermore, myosin filament stack formation involved long-range movements of individual myosin filaments towards each other suggesting the existence of attractive forces between myosin II filaments. These forces, possibly transmitted via mechanical deformations of the intervening actin filament network, may in turn remodel the actomyosin cytoskeleton and drive its self-organization.
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Affiliation(s)
- Shiqiong Hu
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore
| | - Kinjal Dasbiswas
- Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.,James Franck Institute, University of Chicago, Chicago, Illinois 60637, USA
| | - Zhenhuan Guo
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore
| | - Yee-Han Tee
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore
| | | | - Pascal Hersen
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.,Laboratoire Matire et Systèmes Complexes, UMR 7057 CNRS &Université Paris Diderot, Paris 75013, France
| | - Teng-Leong Chew
- Advanced Imaging Center, HHMI Janelia Research Campus, Ashburn, Virginia 20147, USA
| | - Samuel A Safran
- Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ronen Zaidel-Bar
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore
| | - Alexander D Bershadsky
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.,Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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Vernerey FJ, Akalp U. Role of catch bonds in actomyosin mechanics and cell mechanosensitivity. Phys Rev E 2016; 94:012403. [PMID: 27575160 PMCID: PMC5542069 DOI: 10.1103/physreve.94.012403] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Indexed: 01/10/2023]
Abstract
We propose a mechanism of adherent cell mechanosensing, based on the idea that the contractile actomyosin machinery behaves as a catch bond. For this, we construct a simplified model of the actomyosin structure that constitutes the building block of stress fibers and express the stability of cross bridges in terms of the force-dependent bonding energy of the actomyosin bond. Consistent with experimental measurements, we then consider that the energy barrier of the actomyosin bond increases for tension and show that this response is enough to explain the force-induced stabilization of a stress fiber. Further numerical simulations at the cellular level show that the catch-bond hypothesis can help in understanding and predict the sensitivity of adherent cells to substrate stiffness.
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Affiliation(s)
- Franck J. Vernerey
- Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309, USA
| | - Umut Akalp
- Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309, USA
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9
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Hiebl B, Cui J, Kratz K, Frank O, Schossig M, Richau K, Lee S, Jung F, Lendlein A. Viability, morphology and function of primary endothelial cells on poly(n-butyl acrylate) networks having elastic moduli comparable to arteries. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION 2016; 23:901-15. [PMID: 21457619 DOI: 10.1163/092050611x566144] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Soft hydrophobic poly(n-butyl acrylate) networks (cPnBA) were developed as entropy elastic substrates for passive mechanical stimulation of cells, where the elastic modulus of the cPnBAs could be systematically adjusted by variation of the cross-link density. The networks were synthesized by thermally-induced radical polymerization from n-butyl acrylate, with poly(propylene glycol) dimethacrylate (PPGDMA) acting as cross-linker, whereby the purity of the cPnBAs was confirmed by(1) H-NMR spectroscopy and gas chromatography. In this work two cPnBA polymer networks with an elastic modulus around 200 kPa and 1 MPa were investigated having an elastic modulus similar to that of arteries. Both cPnBAs exhibited an almost smooth surface with a surface roughness (R q) in the wet state ranging from 17 to 37 nm and a similar zetapotential, indicating an almost identical chemical composition within the topmost surface layer in terms of functional groups. In contrast, wettability of the samples was found to be different with an advancing angle ( advancing) of 123 ± 3.8° for cPnBA0250, while for cPnBA1100 significantly lower values for advancing (111 ± 3.8°) were obtained. First in vitro tests were performed with primary endothelial cells (HUVEC) to study its effects on vascular cell functions. Within the time period of cultivation (72 h), the cells on the cPnBA samples reached subconfluence and showed a viability rate of almost 100%. Although cell density differed after 72 h with more cells on cPnBA0250 than on cPnBA1100, both materials showed no significant effect on the cell morphology, the cellular LDH-release, which was used as marker for the integrity of the cell membrane, and the organisation of the VE-cadherin. However, lower cell density and less actin stress fibre formation on cPnBA1100 might indicate that cell-material interaction was weaker on cPnBA1100 than on cPnBA0250. The secretion of the vasoactive cytokines prostacyclin (PGI2) and thromboxane A2 (TXA2) was low compared to previously reported values. However, the anti-thrombogenic ratio of PGI2/TXA2 - which is balanced under physiological conditions - with much higher PGI2 compared to TXA2 (up to 17.6-fold after 72 h for cPnBA1100) suggests that this material might be effective to preventing thrombosis.
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Affiliation(s)
- B Hiebl
- a Center for Biomaterial Development, Institute of Polymer Research, Helmholtz-Zentrum Geesthacht, Teltow, Germany; Berlin-Brandenburg Center for Regenerative Therapies (BCRT), Berlin, Germany
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10
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Contractility of single cardiomyocytes differentiated from pluripotent stem cells depends on physiological shape and substrate stiffness. Proc Natl Acad Sci U S A 2015; 112:12705-10. [PMID: 26417073 DOI: 10.1073/pnas.1508073112] [Citation(s) in RCA: 317] [Impact Index Per Article: 35.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Single cardiomyocytes contain myofibrils that harbor the sarcomere-based contractile machinery of the myocardium. Cardiomyocytes differentiated from human pluripotent stem cells (hPSC-CMs) have potential as an in vitro model of heart activity. However, their fetal-like misalignment of myofibrils limits their usefulness for modeling contractile activity. We analyzed the effects of cell shape and substrate stiffness on the shortening and movement of labeled sarcomeres and the translation of sarcomere activity to mechanical output (contractility) in live engineered hPSC-CMs. Single hPSC-CMs were cultured on polyacrylamide substrates of physiological stiffness (10 kPa), and Matrigel micropatterns were used to generate physiological shapes (2,000-µm(2) rectangles with length:width aspect ratios of 5:1-7:1) and a mature alignment of myofibrils. Translation of sarcomere shortening to mechanical output was highest in 7:1 hPSC-CMs. Increased substrate stiffness and applied overstretch induced myofibril defects in 7:1 hPSC-CMs and decreased mechanical output. Inhibitors of nonmuscle myosin activity repressed the assembly of myofibrils, showing that subcellular tension drives the improved contractile activity in these engineered hPSC-CMs. Other factors associated with improved contractility were axially directed calcium flow, systematic mitochondrial distribution, more mature electrophysiology, and evidence of transverse-tubule formation. These findings support the potential of these engineered hPSC-CMs as powerful models for studying myocardial contractility at the cellular level.
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11
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A thermodynamically motivated model for stress-fiber reorganization. Biomech Model Mechanobiol 2015; 15:761-89. [DOI: 10.1007/s10237-015-0722-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2015] [Accepted: 08/24/2015] [Indexed: 10/23/2022]
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12
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Crevenna AH, Arciniega M, Dupont A, Mizuno N, Kowalska K, Lange OF, Wedlich-Söldner R, Lamb DC. Side-binding proteins modulate actin filament dynamics. eLife 2015; 4. [PMID: 25706231 PMCID: PMC4375888 DOI: 10.7554/elife.04599] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 02/20/2015] [Indexed: 01/10/2023] Open
Abstract
Actin filament dynamics govern many key physiological processes from cell motility to tissue morphogenesis. A central feature of actin dynamics is the capacity of filaments to polymerize and depolymerize at their ends in response to cellular conditions. It is currently thought that filament kinetics can be described by a single rate constant for each end. In this study, using direct visualization of single actin filament elongation, we show that actin polymerization kinetics at both filament ends are strongly influenced by the binding of proteins to the lateral filament surface. We also show that the pointed-end has a non-elongating state that dominates the observed filament kinetic asymmetry. Estimates of flexibility as well as effects on fragmentation and growth suggest that the observed kinetic diversity arises from structural alteration. Tuning elongation kinetics by exploiting the malleability of the filament structure may be a ubiquitous mechanism to generate a rich variety of cellular actin dynamics. DOI:http://dx.doi.org/10.7554/eLife.04599.001 Actin is one of the most abundant proteins in cells. It forms networks of filaments that provide structural support and generate the forces needed for cell movement, division, and many other processes in cells. Filaments of actin continuously change in length as actin molecules are added or removed at the ends. One end of an actin filament—called the barbed-end—grows much faster than the other, known as the pointed-end. Many other proteins also help the actin filaments to form. Some of these proteins bind to the ends of the filaments, where they directly control the growth of the filaments. Other proteins bind along the length of the filaments, but how these ‘side-binding’ proteins influence the growth of filaments is not clear. In this study, Crevenna et al. used a technique called ‘total internal reflection fluorescence (TIRF) microscopy’ to study how several side-binding proteins affect the growth of actin filaments in an artificial system. The growth of the barbed-ends was strongly influenced by which side-binding protein was interacting with the filament. For example, the barbed-end grew rapidly when a protein called VASP was present but grew more slowly in the presence of the protein α-actinin. Although the growth at the pointed-end was generally slow and sporadic, the side-binding proteins also had noticeable effects. Crevenna et al. found that when the side-binding proteins were present at low levels, filament growth was similar for all proteins studied. It was only when the proteins were present at higher levels that the growth of the actin filaments was altered depending on the specific side-binding protein present. One side-binding protein called α-actinin also altered the shape of the actin filament so that when it was present at high levels, the filaments curved in a particular direction. Together, these results suggest that the growth, structure, and flexibility of actin filaments can be strongly influenced by the various proteins that bind along the length of the filaments. The next challenges are to understand the precise details of how these side-binding proteins are able to alter the growth and shape of actin and investigate how they influence other processes that control the structure of actin networks in cells. DOI:http://dx.doi.org/10.7554/eLife.04599.002
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Affiliation(s)
- Alvaro H Crevenna
- Physical Chemistry, Department of Chemistry and Center for Nanoscience, Ludwig-Maximilians-Universität München, Munich, Germany.,Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Marcelino Arciniega
- Max Planck Institute of Biochemistry, Martinsried, Germany.,Department of Chemistry, Technische Universität München, Garching, Germany
| | - Aurélie Dupont
- Physical Chemistry, Department of Chemistry and Center for Nanoscience, Ludwig-Maximilians-Universität München, Munich, Germany.,NanoSystems Initiative Munich, Ludwig-Maximilians-Universität München, Munich, Germany.,Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Naoko Mizuno
- Cellular and Membrane Trafficking, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Kaja Kowalska
- Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Oliver F Lange
- Department of Chemistry, Technische Universität München, Garching, Germany.,Biomolecular NMR and Munich Center for Integrated Protein Science, Technische Universität München, Garching, Germany.,Institute of Structural Biology, Helmholtz Zentrum München, Neuherberg, Germany
| | - Roland Wedlich-Söldner
- Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, Martinsried, Germany.,Institute of Cell Dynamics and Imaging, Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), University of Münster, Münster, Germany
| | - Don C Lamb
- Physical Chemistry, Department of Chemistry and Center for Nanoscience, Ludwig-Maximilians-Universität München, Munich, Germany.,NanoSystems Initiative Munich, Ludwig-Maximilians-Universität München, Munich, Germany.,Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
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13
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Nie W, Wei MT, Ou-Yang HD, Jedlicka SS, Vavylonis D. Formation of contractile networks and fibers in the medial cell cortex through myosin-II turnover, contraction, and stress-stabilization. Cytoskeleton (Hoboken) 2015; 72:29-46. [PMID: 25641802 DOI: 10.1002/cm.21207] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 12/31/2014] [Indexed: 12/24/2022]
Abstract
The morphology of adhered cells depends crucially on the formation of a contractile meshwork of parallel and cross-linked fibers along the contacting surface. The motor activity and minifilament assembly of non-muscle myosin-II is an important component of cortical cytoskeletal remodeling during mechanosensing. We used experiments and computational modeling to study cortical myosin-II dynamics in adhered cells. Confocal microscopy was used to image the medial cell cortex of HeLa cells stably expressing myosin regulatory light chain tagged with GFP (MRLC-GFP). The distribution of MRLC-GFP fibers and focal adhesions was classified into three types of network morphologies. Time-lapse movies show: myosin foci appearance and disappearance; aligning and contraction; stabilization upon alignment. Addition of blebbistatin, which perturbs myosin motor activity, leads to a reorganization of the cortical networks and to a reduction of contractile motions. We quantified the kinetics of contraction, disassembly and reassembly of myosin networks using spatio-temporal image correlation spectroscopy (STICS). Coarse-grained numerical simulations include bipolar minifilaments that contract and align through specified interactions as basic elements. After assuming that minifilament turnover decreases with increasing contractile stress, the simulations reproduce stress-dependent fiber formation in between focal adhesions above a threshold myosin concentration. The STICS correlation function in simulations matches the function measured in experiments. This study provides a framework to help interpret how different cortical myosin remodeling kinetics may contribute to different cell shape and rigidity depending on substrate stiffness.
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Affiliation(s)
- Wei Nie
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania
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14
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Ribeiro SA, D'Ambrosio MV, Vale RD. Induction of focal adhesions and motility in Drosophila S2 cells. Mol Biol Cell 2014; 25:3861-9. [PMID: 25273555 PMCID: PMC4244196 DOI: 10.1091/mbc.e14-04-0863] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In this study, normally immotile S2 cells are engineered to induce the formation of focal adhesions and cell motility by the transfection of a single gene encoding an integrin subunit. It is demonstrated that the focal adhesions recruit expected components and exhibit mechanosensitive behavior on integrin-ligand substrates of different stiffnesses. Focal adhesions are dynamic structures that interact with the extracellular matrix on the cell exterior and actin filaments on the cell interior, enabling cells to adhere and crawl along surfaces. We describe a system for inducing the formation of focal adhesions in normally non–ECM-adherent, nonmotile Drosophila S2 cells. These focal adhesions contain the expected molecular markers such as talin, vinculin, and p130Cas, and they require talin for their formation. The S2 cells with induced focal adhesions also display a nonpolarized form of motility on vitronectin-coated substrates. Consistent with findings in mammalian cells, the degree of motility can be tuned by changing the stiffness of the substrate and was increased after the depletion of PAK3, a p21-activated kinase. A subset of nonmotile, nonpolarized cells also exhibited focal adhesions that rapidly assembled and disassembled around the cell perimeter. Such cooperative and dynamic fluctuations of focal adhesions were decreased by RNA interference (RNAi) depletion of myosin II and focal adhesion kinase, suggesting that this behavior requires force and focal adhesion maturation. These results demonstrate that S2 cells, a cell line that is well studied for cytoskeletal dynamics and readily amenable to protein manipulation by RNAi, can be used to study the assembly and dynamics of focal adhesions and mechanosensitive cell motility.
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Affiliation(s)
- Susana A Ribeiro
- Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158
| | - Michael V D'Ambrosio
- Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158
| | - Ronald D Vale
- Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158
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15
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Structure and biomechanics of the endothelial transcellular circumferential invasion array in tumor invasion. PLoS One 2014; 9:e89758. [PMID: 24587014 PMCID: PMC3933692 DOI: 10.1371/journal.pone.0089758] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 01/24/2014] [Indexed: 11/19/2022] Open
Abstract
Cancer cells breach the endothelium not only through cell-cell junctions but also via individual endothelial cells (ECs), or transcellular invasion. The underlying EC forms a circular structure around the transcellular invasion pore that is dependent on myosin light chain kinase (MLCK) and myosin II regulatory light chain (RLC) phosphorylation. Here we offer mechanistic insights into transcellular invasive array formation amid persistent tensile force from activated EC myosin. Fluorescence recovery after photobleaching (FRAP) experiments, sarcomeric distance measurements using super-resolution microscopy and electron microscopy provide details about the nature of the myosin II invasion array. To probe the relationship between biomechanical forces and the tension required to maintain the curvature of contractile filaments, we targeted individual actin-myosin fibers at the invasion site for photoablation. We showed that adjacent filaments rapidly replace the ablat11ed structures. We propose that the transcellular circumferential invasion array (TCIA) provides the necessary constraint within the EC to blunt the radial compression from the invading cancer cell.
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16
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Koestler SA, Steffen A, Nemethova M, Winterhoff M, Luo N, Holleboom JM, Krupp J, Jacob S, Vinzenz M, Schur F, Schlüter K, Gunning PW, Winkler C, Schmeiser C, Faix J, Stradal TEB, Small JV, Rottner K. Arp2/3 complex is essential for actin network treadmilling as well as for targeting of capping protein and cofilin. Mol Biol Cell 2013; 24:2861-75. [PMID: 23885122 PMCID: PMC3771948 DOI: 10.1091/mbc.e12-12-0857] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Acute suppression of Arp2/3 complex activity in lamellipodia demonstrates its essential role in actin network treadmilling and filament organization and geometry. Arp2/3 complex activity also defines the recruitment of crucial independent factors, including capping protein and cofilin, and is essential for lamellipodia-based keratocyte migration. Lamellipodia are sheet-like protrusions formed during migration or phagocytosis and comprise a network of actin filaments. Filament formation in this network is initiated by nucleation/branching through the actin-related protein 2/3 (Arp2/3) complex downstream of its activator, suppressor of cAMP receptor/WASP-family verprolin homologous (Scar/WAVE), but the relative relevance of Arp2/3-mediated branching versus actin filament elongation is unknown. Here we use instantaneous interference with Arp2/3 complex function in live fibroblasts with established lamellipodia. This allows direct examination of both the fate of elongating filaments upon instantaneous suppression of Arp2/3 complex activity and the consequences of this treatment on the dynamics of other lamellipodial regulators. We show that Arp2/3 complex is an essential organizer of treadmilling actin filament arrays but has little effect on the net rate of actin filament turnover at the cell periphery. In addition, Arp2/3 complex serves as key upstream factor for the recruitment of modulators of lamellipodia formation such as capping protein or cofilin. Arp2/3 complex is thus decisive for filament organization and geometry within the network not only by generating branches and novel filament ends, but also by directing capping or severing activities to the lamellipodium. Arp2/3 complex is also crucial to lamellipodia-based migration of keratocytes.
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Affiliation(s)
- Stefan A Koestler
- Institute of Genetics, University of Bonn, D-53115 Bonn, Germany Institute of Molecular Biotechnology, Austrian Academy of Sciences, A-1030 Vienna, Austria Johann Radon Institute for Computational and Applied Mathematics, Austrian Academy of Sciences, A-1030 Vienna, Austria Institute for Biophysical Chemistry, Hannover Medical School, D-30625 Hannover, Germany Helmholtz Centre for Infection Research, D-38124 Braunschweig, Germany Institute for Molecular Cell Biology, University of Münster, D-48149 Münster, Germany Oncology Research Unit, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia Faculty of Mathematics, University of Vienna, A-1090 Vienna, Austria
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17
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Oelz D. A viscous two-phase model for contractile actomyosin bundles. J Math Biol 2013; 68:1653-76. [DOI: 10.1007/s00285-013-0682-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Revised: 04/24/2013] [Indexed: 12/11/2022]
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18
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Abstract
Cross-linked actomyosin bundles retract when severed in vivo by laser ablation, or when isolated from the cell and micromanipulated in vitro in the presence of ATP. We identify the timescale for contraction as a viscoelastic time τ, where the viscosity is due to (internal) protein friction. We obtain an estimate of the order of magnitude of the contraction time τ ≈ 10-100 s, consistent with available experimental data for circumferential microfilament bundles and stress fibers. Our results are supported by an exactly solvable, hydrodynamic model of a retracting bundle as a cylinder of isotropic, active matter, from which the order of magnitude of the active stress is estimated.
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Affiliation(s)
- Natsuhiko Yoshinaga
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
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19
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Tojkander S, Gateva G, Lappalainen P. Actin stress fibers--assembly, dynamics and biological roles. J Cell Sci 2012; 125:1855-64. [PMID: 22544950 DOI: 10.1242/jcs.098087] [Citation(s) in RCA: 515] [Impact Index Per Article: 42.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Actin filaments assemble into diverse protrusive and contractile structures to provide force for a number of vital cellular processes. Stress fibers are contractile actomyosin bundles found in many cultured non-muscle cells, where they have a central role in cell adhesion and morphogenesis. Focal-adhesion-anchored stress fibers also have an important role in mechanotransduction. In animal tissues, stress fibers are especially abundant in endothelial cells, myofibroblasts and epithelial cells. Importantly, recent live-cell imaging studies have provided new information regarding the mechanisms of stress fiber assembly and how their contractility is regulated in cells. In addition, these studies might elucidate the general mechanisms by which contractile actomyosin arrays, including muscle cell myofibrils and cytokinetic contractile ring, can be generated in cells. In this Commentary, we discuss recent findings concerning the physiological roles of stress fibers and the mechanism by which these structures are generated in cells.
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Affiliation(s)
- Sari Tojkander
- Institute of Biotechnology, University of Helsinki, Finland
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20
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Wu J, Dickinson RB, Lele TP. Investigation of in vivo microtubule and stress fiber mechanics with laser ablation. Integr Biol (Camb) 2012; 4:471-9. [PMID: 22495508 DOI: 10.1039/c2ib20015e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Laser ablation has emerged as a useful technique to study the mechanical properties of the cytoskeleton in living cells. Laser ablation perturbs the force balance in the cytoskeleton, resulting in a dynamic response which can be imaged. Quantitative measurement of the dynamic response allows the testing of mechanical theories of the cytoskeleton in living cells. This review discusses recent work in applying laser ablation to study stress fiber and microtubule mechanics in living endothelial cells. These studies reveal that molecular motors are major determinants of the mechanical properties of the cytoskeleton in cells.
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Affiliation(s)
- Jun Wu
- Department of Chemical Engineering, University of Florida, Gainesville, FL 32611, USA.
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21
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Actin dynamics associated with focal adhesions. Int J Cell Biol 2012; 2012:941292. [PMID: 22505938 PMCID: PMC3312244 DOI: 10.1155/2012/941292] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 11/16/2011] [Indexed: 01/09/2023] Open
Abstract
Cell-matrix adhesion plays a major role during cell migration. Proteins from adhesion structures connect the extracellular matrix to the actin cytoskeleton, allowing the growing actin network to push the plasma membrane and the contractile cables (stress fibers) to pull the cell body. Force transmission to the extracellular matrix depends on several parameters including the regulation of actin dynamics in adhesion structures, the contractility of stress fibers, and the mechanosensitive response of adhesion structures. Here we highlight recent findings on the molecular mechanisms by which actin assembly is regulated in adhesion structures and the molecular basis of the mechanosensitivity of focal adhesions.
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22
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Xu D, Kishi H, Kawamichi H, Kajiya K, Takada Y, Kobayashi S. Sphingosylphosphorylcholine induces stress fiber formation via activation of Fyn-RhoA-ROCK signaling pathway in fibroblasts. Cell Signal 2011; 24:282-9. [PMID: 21951603 DOI: 10.1016/j.cellsig.2011.09.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Revised: 08/19/2011] [Accepted: 09/08/2011] [Indexed: 01/03/2023]
Abstract
Sphingosylphosphorylcholine (SPC), a bioactive sphingolipid, has recently been reported to modulate actin cytoskeleton rearrangement. We have previously demonstrated Fyn tyrosine kinase is involved in SPC-induced actin stress fiber formation in fibroblasts. However, Fyn-dependent signaling pathway remains to be elucidated. The present study demonstrates that RhoA-ROCK signaling downstream of Fyn controls stress fiber formation in SPC-treated fibroblasts. Here, we found that SPC-induced stress fiber formation was inhibited by C3 transferase, dominant negative RhoA or ROCK. SPC activated RhoA, which was blocked by pharmacological inhibition of Fyn activity or dominant negative Fyn. Constitutively active Fyn (ca-Fyn) stimulated stress fiber formation and localized with F-actin at the both ends of stress fibers, both of which were prevented by Fyn translocation inhibitor eicosapentaenoic acid (EPA). In contrast, inhibition of ROCK abolished only the formation of stress fibers, without affecting the localization of ca-Fyn. These results allow the identification of the molecular events downstream SPC in stress fiber formation for a better understanding of stress fiber formation involving Fyn.
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Affiliation(s)
- Dan Xu
- Department of Molecular Physiology and Medical Bioregulation, Yamaguchi University Graduate School of Medicine, Minami-Kogushi, Ube, Japan
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23
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Kaunas R, Deguchi S. Multiple Roles for Myosin II in Tensional Homeostasis Under Mechanical Loading. Cell Mol Bioeng 2011. [DOI: 10.1007/s12195-011-0175-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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24
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Modeling myosin-dependent rearrangement and force generation in an actomyosin network. J Theor Biol 2011; 281:65-73. [PMID: 21514305 DOI: 10.1016/j.jtbi.2011.04.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Revised: 03/21/2011] [Accepted: 04/07/2011] [Indexed: 11/21/2022]
Abstract
Actomyosin contractility is a major force-generating mechanism that drives rearrangement of actomyosin networks; it is fundamental to cellular functions such as cellular reshaping and movement. Thus, to clarify the mechanochemical foundation of the emergence of cellular functions, understanding the relationship between actomyosin contractility and rearrangement of actomyosin networks is crucial. For this purpose, in this study, we present a new particulate-based model for simulating the motions of actin, non-muscle myosin II, and α-actinin. To confirm the model's validity, we successfully simulated sliding and bending motions of actomyosin filaments, which are observed as fundamental behaviors in dynamic rearrangement of actomyosin networks in migrating keratocytes. Next, we simulated the dynamic rearrangement of actomyosin networks. Our simulation results indicate that an increase in the density fraction of myosin induces a higher-order structural transition of actomyosin filaments from networks to bundles, in addition to increasing the force generated by actomyosin filaments in the network. We compare our simulation results with experimental results and confirm that actomyosin bundles bridging focal adhesions and the characteristics of myosin-dependent rearrangement of actomyosin networks agree qualitatively with those observed experimentally.
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25
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Multiple-labelling immunoEM using different sizes of colloidal gold: alternative approaches to test for differential distribution and colocalization in subcellular structures. Histochem Cell Biol 2011; 135:317-26. [PMID: 21327857 DOI: 10.1007/s00418-011-0788-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/01/2011] [Indexed: 10/18/2022]
Abstract
Various methods for quantifying cellular immunogold labelling on transmission electron microscope thin sections are currently available. All rely on sound random sampling principles and are applicable to single immunolabelling across compartments within a given cell type or between different experimental groups of cells. Although methods are also available to test for colocalization in double/triple immunogold labelling studies, so far, these have relied on making multiple measurements of gold particle densities in defined areas or of inter-particle nearest neighbour distances. Here, we present alternative two-step approaches to codistribution and colocalization assessment that merely require raw counts of gold particles in distinct cellular compartments. For assessing codistribution over aggregate compartments, initial statistical evaluation involves combining contingency table and chi-squared analyses to provide predicted gold particle distributions. The observed and predicted distributions allow testing of the appropriate null hypothesis, namely, that there is no difference in the distribution patterns of proteins labelled by different sizes of gold particle. In short, the null hypothesis is that of colocalization. The approach for assessing colabelling recognises that, on thin sections, a compartment is made up of a set of sectional images (profiles) of cognate structures. The approach involves identifying two groups of compartmental profiles that are unlabelled and labelled for one gold marker size. The proportions in each group that are also labelled for the second gold marker size are then compared. Statistical analysis now uses a 2 × 2 contingency table combined with the Fisher exact probability test. Having identified double labelling, the profiles can be analysed further in order to identify characteristic features that might account for the double labelling. In each case, the approach is illustrated using synthetic and/or experimental datasets and can be refined to correct observed labelling patterns to specific labelling patterns. These simple and efficient approaches should be of more immediate utility to those interested in codistribution and colocalization in multiple immunogold labelling investigations.
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26
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Russell RJ, Grubbs AY, Mangroo SP, Nakasone SE, Dickinson RB, Lele TP. Sarcomere length fluctuations and flow in capillary endothelial cells. Cytoskeleton (Hoboken) 2011; 68:150-6. [DOI: 10.1002/cm.20501] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Accepted: 12/23/2010] [Indexed: 11/09/2022]
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27
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Abnormal actomyosin assembly in proliferating and differentiating myoblasts upon expression of a cytosolic DMPK isoform. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:867-77. [PMID: 21295081 DOI: 10.1016/j.bbamcr.2011.01.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Revised: 01/05/2011] [Accepted: 01/24/2011] [Indexed: 01/17/2023]
Abstract
DMPK, the product of the mutated gene in myotonic dystrophy type 1, belongs to the subfamily of Rho-associated serine-threonine protein kinases, whose members play a role in actin-based cell morphodynamics. Not much is known about the physiological role of differentially localized individual DMPK splice isoforms. We report here that prominent stellar-shaped stress fibers are formed during early and late steps of differentiation in DMPK-deficient myoblast-myotubes upon complementation with the short cytosolic DMPK E isoform. Expression of DMPK E led to an increased phosphorylation status of MLC2. We found no such effects with vectors that encode a mutant DMPK E which was rendered enzymatically inactive or any of the long C-terminally anchored DMPK isoforms. Presence of stellar structures appears associated with changes in cell shape and motility and a delay in myogenesis. Our data strongly suggest that cytosolic DMPK participates in remodeling of the actomyosin cytoskeleton in developing skeletal muscle cells. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.
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28
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Rivera Rosado LA, Horn TA, McGrath SC, Cotter RJ, Yang JT. Association between α4 integrin cytoplasmic tail and non-muscle myosin IIA regulates cell migration. J Cell Sci 2011; 124:483-92. [PMID: 21224395 DOI: 10.1242/jcs.074211] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
α4β1 integrin regulates cell migration via cytoplasmic interactions. Here, we report an association between the cytoplasmic tail of α4 integrin (α4 tail) and non-muscle myosin IIA (MIIA), demonstrated by co-immunoprecipitation of the MIIA heavy chain (HC) with anti-α4-integrin antibodies and pull-down of MIIA-HC with recombinant α4 tail from cell lysates. The association between the α4 tail and MIIA does not require paxillin binding or phosphorylation at Ser988 in the α4 tail. We found that substituting Glu982 in the α4 tail with alanine (E982A) disrupts the α4-MIIA association without interfering with the paxillin binding or Ser988 phosphorylation. By comparing stably transfected CHO cells, we show that the E982A mutation reduces the ability of α4β1 integrin to mediate cell spreading and to promote front-back polarization. In addition, we show that E982A impairs shear-flow-induced migration of the α4-integrin-expressing CHO cells by reducing their migration speed and directional persistence. The E982A mutation also leads to defects in the organization of MIIA filament bundles. Furthermore, when cells are plated on fibronectin and simulated with shear flow, α4β1 integrin forms filament-like patterns that co-align with MIIA filament bundles. These results provide a new mechanism for linking integrins to the actomyosin cytoskeleton and for regulating cell migration by integrins and non-muscle myosin II.
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Affiliation(s)
- Leslie A Rivera Rosado
- Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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29
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D’Aguanno S, D’Alessandro A, Pieroni L, Roveri A, Zaccarin M, Marzano V, Canio MD, Bernardini S, Federici G, Urbani A. New Insights into Neuroblastoma Cisplatin Resistance: A Comparative Proteomic and Meta-Mining Investigation. J Proteome Res 2010; 10:416-28. [DOI: 10.1021/pr100457n] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Simona D’Aguanno
- Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy, S. Lucia Foundation - IRCCS, Rome, Italy, and Departement of Biological Chemistry, University of Padova, Padova, Italy
| | - Annamaria D’Alessandro
- Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy, S. Lucia Foundation - IRCCS, Rome, Italy, and Departement of Biological Chemistry, University of Padova, Padova, Italy
| | - Luisa Pieroni
- Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy, S. Lucia Foundation - IRCCS, Rome, Italy, and Departement of Biological Chemistry, University of Padova, Padova, Italy
| | - Antonella Roveri
- Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy, S. Lucia Foundation - IRCCS, Rome, Italy, and Departement of Biological Chemistry, University of Padova, Padova, Italy
| | - Mattia Zaccarin
- Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy, S. Lucia Foundation - IRCCS, Rome, Italy, and Departement of Biological Chemistry, University of Padova, Padova, Italy
| | - Valeria Marzano
- Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy, S. Lucia Foundation - IRCCS, Rome, Italy, and Departement of Biological Chemistry, University of Padova, Padova, Italy
| | - Michele De Canio
- Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy, S. Lucia Foundation - IRCCS, Rome, Italy, and Departement of Biological Chemistry, University of Padova, Padova, Italy
| | - Sergio Bernardini
- Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy, S. Lucia Foundation - IRCCS, Rome, Italy, and Departement of Biological Chemistry, University of Padova, Padova, Italy
| | - Giorgio Federici
- Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy, S. Lucia Foundation - IRCCS, Rome, Italy, and Departement of Biological Chemistry, University of Padova, Padova, Italy
| | - Andrea Urbani
- Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy, S. Lucia Foundation - IRCCS, Rome, Italy, and Departement of Biological Chemistry, University of Padova, Padova, Italy
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30
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Smith MA, Blankman E, Gardel ML, Luettjohann L, Waterman CM, Beckerle MC. A zyxin-mediated mechanism for actin stress fiber maintenance and repair. Dev Cell 2010; 19:365-76. [PMID: 20833360 DOI: 10.1016/j.devcel.2010.08.008] [Citation(s) in RCA: 163] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Revised: 06/24/2010] [Accepted: 07/09/2010] [Indexed: 10/24/2022]
Abstract
To maintain mechanical homeostasis, cells must recognize and respond to changes in cytoskeletal integrity. By imaging live cells expressing fluorescently tagged cytoskeletal proteins, we observed that actin stress fibers undergo local, acute, force-induced elongation and thinning events that compromise their stress transmission function, followed by stress fiber repair that restores this capability. The LIM protein zyxin rapidly accumulates at sites of strain-induced stress fiber damage and is essential for stress fiber repair and generation of traction force. Zyxin promotes recruitment of the actin regulatory proteins α-actinin and VASP to compromised stress fiber zones. α-Actinin plays a critical role in restoration of actin integrity at sites of local stress fiber damage, whereas both α-actinin and VASP independently contribute to limiting stress fiber elongation at strain sites, thus promoting stabilization of the stress fiber. Our findings demonstrate a mechanism for rapid repair and maintenance of the structural integrity of the actin cytoskeleton.
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Affiliation(s)
- Mark A Smith
- Department of Biology, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, USA
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31
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Kirmizis D, Logothetidis S. Atomic force microscopy probing in the measurement of cell mechanics. Int J Nanomedicine 2010; 5:137-45. [PMID: 20463929 PMCID: PMC2865008 DOI: 10.2147/ijn.s5787] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2010] [Indexed: 11/23/2022] Open
Abstract
Atomic force microscope (AFM) has been used incrementally over the last decade in cell biology. Beyond its usefulness in high resolution imaging, AFM also has unique capabilities for probing the viscoelastic properties of living cells in culture and, even more, mapping the spatial distribution of cell mechanical properties, providing thus an indirect indicator of the structure and function of the underlying cytoskeleton and cell organelles. AFM measurements have boosted our understanding of cell mechanics in normal and diseased states and provide future potential in the study of disease pathophysiology and in the establishment of novel diagnostic and treatment options.
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Affiliation(s)
- Dimitrios Kirmizis
- Department of Physics, Laboratory for Thin Films-Nanosystems and Nanometrology, Aristotle University, Thessaloniki, Greece.
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32
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Pulsation and stabilization: contractile forces that underlie morphogenesis. Dev Biol 2009; 341:114-25. [PMID: 19874815 DOI: 10.1016/j.ydbio.2009.10.031] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 10/18/2009] [Accepted: 10/20/2009] [Indexed: 11/20/2022]
Abstract
Embryonic development involves global changes in tissue shape and architecture that are driven by cell shape changes and rearrangements within cohesive cell sheets. Morphogenetic changes at the cell and tissue level require that cells generate forces and that these forces are transmitted between the cells of a coherent tissue. Contractile forces generated by the actin-myosin cytoskeleton are critical for morphogenesis, but the cellular and molecular mechanisms of contraction have been elusive for many cell shape changes and movements. Recent studies that have combined live imaging with computational and biophysical approaches have provided new insights into how contractile forces are generated and coordinated between cells and tissues. In this review, we discuss our current understanding of the mechanical forces that shape cells, tissues, and embryos, emphasizing the different modes of actomyosin contraction that generate various temporal and spatial patterns of force generation.
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33
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Sparrow JC, Schöck F. The initial steps of myofibril assembly: integrins pave the way. Nat Rev Mol Cell Biol 2009; 10:293-8. [PMID: 19190670 DOI: 10.1038/nrm2634] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Myofibril assembly results in a regular array of identical sarcomeres in striated muscle. Sarcomere structure is conserved across the animal kingdom, which implies that the mechanisms of myofibril assembly are also likely to be conserved. Recent advances from model genetic systems and insights from stress fibre cell biology have shed light on the mechanisms that set sarcomere spacing and the initial assembly of sarcomere arrays. We propose a model of integrin-dependent cell-matrix adhesion as the starting point for myofibrillogenesis.
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Affiliation(s)
- John C Sparrow
- Department of Biology, University of York, York, YO10 5YW, UK.
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34
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Yumura S, Ueda M, Sako Y, Kitanishi-Yumura T, Yanagida T. Multiple Mechanisms for Accumulation of Myosin II Filaments at the Equator During Cytokinesis. Traffic 2008; 9:2089-99. [DOI: 10.1111/j.1600-0854.2008.00837.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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35
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Abstract
Stress fibres are contractile acto-myosin structures found from many types of non-muscle cells, where they are involved in adhesion, motility and morphogenesis. Stress fibres typically display a periodic alpha-actinin-myosin II pattern and are thus suggested to resemble the sarcomeric actin filament structures of muscle cells. Mammalian cells contain three categories of stress fibres: ventral stress fibres that are attached to focal adhesions at both ends, dorsal stress fibres that are attached to focal adhesions typically at one end and transverse arcs that are curved acto-myosin bundles, which do not directly attach to focal adhesions. In this review, we discuss the definition of stress fibres, organization of actin filaments and other components within these contractile structures, and the mechanisms of stress fibre assembly.
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Affiliation(s)
- P Naumanen
- Institute of Biotechnology, PO Box 56, 00014 University of Helsinki, Finland
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36
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A multi-modular tensegrity model of an actin stress fiber. J Biomech 2008; 41:2379-87. [PMID: 18632107 DOI: 10.1016/j.jbiomech.2008.05.026] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 05/05/2008] [Accepted: 05/26/2008] [Indexed: 11/22/2022]
Abstract
Stress fibers are contractile bundles in the cytoskeleton that stabilize cell structure by exerting traction forces on the extracellular matrix. Individual stress fibers are molecular bundles composed of parallel actin and myosin filaments linked by various actin-binding proteins, which are organized end-on-end in a sarcomere-like pattern within an elongated three-dimensional network. While measurements of single stress fibers in living cells show that they behave like tensed viscoelastic fibers, precisely how this mechanical behavior arises from this complex supramolecular arrangement of protein components remains unclear. Here we show that computationally modeling a stress fiber as a multi-modular tensegrity network can predict several key behaviors of stress fibers measured in living cells, including viscoelastic retraction, fiber splaying after severing, non-uniform contraction, and elliptical strain of a puncture wound within the fiber. The tensegrity model can also explain how they simultaneously experience passive tension and generate active contraction forces; in contrast, a tensed cable net model predicts some, but not all, of these properties. Thus, tensegrity models may provide a useful link between molecular and cellular scale mechanical behaviors and represent a new handle on multi-scale modeling of living materials.
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SiRNA-mediated reduction of alpha-actinin-1 inhibits pressure-induced murine tumor cell wound implantation and enhances tumor-free survival. Neoplasia 2008; 10:217-22. [PMID: 18320066 DOI: 10.1593/neo.07945] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Revised: 12/10/2007] [Accepted: 12/11/2007] [Indexed: 12/21/2022] Open
Abstract
Viable cancer cells can commonly be recovered from surgical sites and venous blood during tumor resection. The adhesion of these cells to surrounding tissues may impact patient outcomes. Iatrogenic exposure to increased extracellular pressure modulates integrin binding affinity and stimulates colon cancer cell adhesion in vitro through an alpha-actinin-1-dependent signaling pathway. We hypothesized that preoperative small interfering RNA-mediated silencing of alpha-actinin-1 in tumor tissue could disrupt pressure-stimulated cancer cell adhesion to murine surgical wounds and thereby enhance subsequent tumor-free survival. Reducing alpha-actinin-1 in CT26 murine adenocarcinoma cells blocked cell adhesion to collagen in vitro and similarly inhibited pressure-induced CT26 implantation in murine surgical wounds in vivo. Surgical wound contamination with pressure-activated CT26 cells significantly reduced tumor-free survival compared to contamination with tumor cells maintained under ambient pressure. However, mice treated with pressure-activated CT26 cells preoperatively transfected with alpha-actinin-1-specific small interfering RNA displayed reduced surgical site implantation and increased tumor-free survival compared to mice exposed to pressure-activated cells expressing normal levels of alpha-actinin-1 protein. These results suggest that pressure activation of malignant cells promotes tumor development and impairs tumor-free survival. alpha-Actinin-1 may be an effective therapeutic target to inhibit perioperative pressure-stimulated tumor cell implantation.
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38
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Rosenberg M, Straussman R, Ben-Ya'acov A, Ronen D, Ravid S. MHC-IIB filament assembly and cellular localization are governed by the rod net charge. PLoS One 2008; 3:e1496. [PMID: 18231583 PMCID: PMC2204051 DOI: 10.1371/journal.pone.0001496] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Accepted: 12/26/2007] [Indexed: 12/23/2022] Open
Abstract
Background Actin-dependent myosin II molecular motors form an integral part of the cell cytoskeleton. Myosin II molecules contain a long coiled-coil rod that mediates filament assembly required for myosin II to exert its full activity. The exact mechanisms orchestrating filament assembly are not fully understood. Methodology/Principal Findings Here we examine mechanisms controlling filament assembly of non-muscle myosin IIB heavy chain (MHC-IIB). We show that in vitro the entire C-terminus region of net positive charge, found in myosin II rods, is important for self-assembly of MHC-IIB fragments. In contrast, no particular sequences in the rod region with net negative charge were identified as important for self-assembly, yet a minimal area from this region is necessary. Proper paracrystal formation by MHC-IIB fragments requires the 196aa charge periodicity along the entire coiled-coil region. In vivo, in contrast to self-assembly in vitro, negatively-charged regions of the coiled-coil were found to play an important role by controlling the intracellular localization of native MHC-IIB. The entire positively-charged region is also important for intracellular localization of native MHC-IIB. Conclusions/Significance A correct distribution of positive and negative charges along myosin II rod is a necessary component in proper filament assembly and intracellular localization of MHC-IIB.
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Affiliation(s)
- Michael Rosenberg
- Department of Biochemistry, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Ravid Straussman
- Department of Biochemistry, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Ami Ben-Ya'acov
- Department of Biochemistry, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Daniel Ronen
- Department of Biochemistry, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Shoshana Ravid
- Department of Biochemistry, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
- * To whom correspondence should be addressed. E-mail:
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Abstract
Animal cell movement is effected through a combination of protrusive and contractile events. Non-muscle cells contain stress fibres - bundles of actomyosin that are the major mediators of cell contraction and that can be compared to the highly organised actomyosin arrays of muscle cells. Recent studies have defined regulatory mechanisms that control stress fibre formation, placing the ROCK protein kinase at the centre of a complex signalling network controlling actomyosin contractility and stress fibre assembly. As we uncover the details of stress fibre construction, it is becoming clear that different categories of stress fibres exist. Some of these structures are less suited for cell motility and more suited to static contraction. In keeping with this, many specialised contractile cell types use stress fibres to remodel tissues and extracellular matrix.
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Affiliation(s)
- Stéphanie Pellegrin
- Department of Biochemistry, School of Medical Sciences, University of Bristol, BS8 1TD, UK.
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40
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Katoh K, Kano Y, Ookawara S. Role of stress fibers and focal adhesions as a mediator for mechano-signal transduction in endothelial cells in situ. Vasc Health Risk Manag 2008; 4:1273-82. [PMID: 19337541 PMCID: PMC2663434 DOI: 10.2147/vhrm.s3933] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Fluid shear stress is the mechanical force generated by the blood flow which is applied over the apical surface of endothelial cells in situ. The findings of a recent study suggest that stress fibers and its associated focal adhesions play roles in mechano-signal transduction mechanism. Stress fibers are present along the apical and the basal portion of the endothelial cells. Endothelial cells respond to fluid shear stress and change their morphological characteristics in both their cell shape and cytoskeletal organization. Atherosclerosis is a common disease of the arteries and it occurs in areas around the branching site of blood vessels where the cells are exposed to low fluid shear stress. The organization of stress fibers and focal adhesions are strongly influenced by shear stress, and therefore the generation of atherosclerotic lesions seem to be associated with the cytoskeletal components of endothelial cells. This review describes the possible role of the cytoskeleton as a mechano-transducer in endothelial cells in situ.
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Affiliation(s)
- Kazuo Katoh
- Department of Anatomy, School, of Medicine, Jichi Medical University, Yakushiji, Shimotsuke-city, Tochigi, Japan.
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41
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Craig DH, Haimovich B, Basson MD. Alpha-actinin-1 phosphorylation modulates pressure-induced colon cancer cell adhesion through regulation of focal adhesion kinase-Src interaction. Am J Physiol Cell Physiol 2007; 293:C1862-74. [PMID: 17898132 DOI: 10.1152/ajpcell.00118.2007] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Physical forces including pressure, strain, and shear can be converted into intracellular signals that regulate diverse aspects of cell biology. Exposure to increased extracellular pressure stimulates colon cancer cell adhesion by a beta(1)-integrin-dependent mechanism that requires an intact cytoskeleton and activation of focal adhesion kinase (FAK) and Src. alpha-Actinin facilitates focal adhesion formation and physically links integrin-associated focal adhesion complexes with the cytoskeleton. We therefore hypothesized that alpha-actinin may be necessary for the mechanical response pathway that mediates pressure-stimulated cell adhesion. We reduced alpha-actinin-1 and alpha-actinin-4 expression with isoform-specific small interfering (si)RNA. Silencing of alpha-actinin-1, but not alpha-actinin-4, blocked pressure-stimulated cell adhesion in human SW620, HT-29, and Caco-2 colon cancer cell lines. Cell exposure to increased extracellular pressure stimulated alpha-actinin-1 tyrosine phosphorylation and alpha-actinin-1 interaction with FAK and/or Src, and enhanced FAK phosphorylation at residues Y397 and Y576. The requirement for alpha-actinin-1 phosphorylation in the pressure response was investigated by expressing the alpha-actinin-1 tyrosine phosphorylation mutant Y12F in the colon cancer cells. Expression of Y12F blocked pressure-mediated adhesion and inhibited the pressure-induced association of alpha-actinin-1 with FAK and Src, as well as FAK activation. Furthermore, siRNA-mediated reduction of alpha-actinin-1 eliminated the pressure-induced association of alpha-actinin-1 and Src with beta(1)-integrin receptor, as well as FAK-Src complex formation. These results suggest that alpha-actinin-1 phosphorylation at Y12 plays a crucial role in pressure-activated cell adhesion and mechanotransduction by facilitating Src recruitment to beta(1)-integrin, and consequently the association of FAK with Src, to enhance FAK phosphorylation.
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Affiliation(s)
- David H Craig
- Department of Surgery, John D Dingell Veterans Affairs Medical Center, Wayne State University, and Karmanos Cancer Institute, Detroit, MI, USA
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42
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Hirata H, Tatsumi H, Sokabe M. Dynamics of actin filaments during tension-dependent formation of actin bundles. Biochim Biophys Acta Gen Subj 2007; 1770:1115-27. [PMID: 17498881 DOI: 10.1016/j.bbagen.2007.03.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2006] [Revised: 03/07/2007] [Accepted: 03/22/2007] [Indexed: 01/09/2023]
Abstract
The actin cytoskeleton stress fiber is an actomyosin-based contractile structure seen as a bundle of actin filaments. Although tension development in a cell is believed to regulate stress fiber formation, little is known for the underlying biophysical mechanisms. To address this question, we examined the effects of tension on the behaviors of individual actin filaments during stress fiber (actin bundle) formation using cytosol-free semi-intact fibroblast cells that were pre-treated with the Rho kinase inhibitor Y-27632 to disassemble stress fibers into a meshwork of actin filaments. These filaments were sparsely labeled with quantum dots for live tracking of their motions. When ATP and Ca(2+) were applied to the semi-intact cells to generate actomyosin-based forces, actin meshwork in the protruded lamellae was dragged toward the cell body, while the periphery of the meshwork remained in the original region, indicating that centripetally directed tension developed in the meshwork. Then the individual actin filaments in the meshwork moved towards the cell body accompanied with sudden changes in the direction of their movements, finally forming actin bundles along the direction of tension. Dragging the meshwork by externally applied mechanical forces also exerted essentially the same effects. These results suggest the existence of tension-dependent remodeling of cross-links within the meshwork during the rearrangement of actin filaments, thus demonstrating that tension is a key player to regulate the dynamics of individual actin filaments that leads to actin bundle formation.
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Affiliation(s)
- Hiroaki Hirata
- ICORP/SORST, Cell Mechanosensing Project, Japan Science and Technology Agency, 65 Tsurumai, Showa-ku, Nagoya, Aichi 466-8550, Japan
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43
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Sanger JW, Kang S, Siebrands CC, Freeman N, Du A, Wang J, Stout AL, Sanger JM. How to build a myofibril. J Muscle Res Cell Motil 2007; 26:343-54. [PMID: 16465476 DOI: 10.1007/s10974-005-9016-7] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Building a myofibril from its component proteins requires the interactions of many different proteins in a process whose details are not understood. Several models have been proposed to provide a framework for understanding the increasing data on new myofibrillar proteins and their localizations during muscle development. In this article we discuss four current models that seek to explain how the assembly occurs in vertebrate cross-striated muscles. The models hypothesize: (a) stress fiber-like structures as templates for the assembly of myofibrils, (b) assembly in which the actin filaments and Z-bands form subunits independently from A-band subunits, with the two subsequently joined together to form a myofibril, (c) premyofibrils as precursors of myofibrils, or (d) assembly occurring without any intermediary structures. The premyofibril model, proposed by the authors, is discussed in more detail as it could explain myofibrillogenesis under a variety of different conditions: in ovo, in explants, and in tissue culture studies on cardiac and skeletal muscles.
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Affiliation(s)
- Joseph W Sanger
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058, USA.
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44
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Cavnar PJ, Olenych SG, Keller TCS. Molecular identification and localization of cellular titin, a novel titin isoform in the fibroblast stress fiber. ACTA ACUST UNITED AC 2007; 64:418-33. [PMID: 17366640 DOI: 10.1002/cm.20193] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We previously discovered a large titin-like protein-c-titin-in chicken epithelial brush border and human blood platelet extracts that binds alpha-actinin and organizes arrays of myosin II bipolar filaments in vitro. RT-PCR analysis of total RNA from human megakaryoblastic (CHRF-288-11) and mouse fibroblast (3T3) nonmuscle cells reveal sequences identical to known titin gene exon sequences that encode parts of the Z-line, I-band, PEVK domain, A-band, and M-line regions of striated muscle titins. In the nonmuscle cells, these sequences are differentially spliced in patterns not reported for any striated muscle titin isoform. Rabbit polyclonal antibodies raised against expressed protein fragments encoded by the Z-repeat and kinase domain regions react with the c-titin band in Western blot analysis of platelet extracts and immunoprecipitate c-titin in whole platelet extracts. Immunofluorescent localization demonstrates that the majority of the c-titin colocalizes with alpha-actinin and actin in 3T3 and Indian Muntjac deer skin fibroblast stress fibers. Our results suggest that differential expression of titin gene exons in nonmuscle cells yields multiple novel isoforms of the protein c-titin that are associated with the actin stress fiber structures.
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Affiliation(s)
- Peter J Cavnar
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370, USA
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45
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Prokop A, Rosenberg MZ. Bioreactor for mammalian cell culture. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2006; 39:29-71. [PMID: 2510474 DOI: 10.1007/bfb0051951] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Purpose of this article is to review the current status of bioreactor design for mammalian cell culture. Morphological and biochemical features of two major mammalian cell groups, anchorage-dependent and independent cells are proposed as a basis for different behavior at their cultivation. Different bioreactor configurations are systematically discussed through enumerating elementary physical phenomena and through stressing their physiological significance. Special considerations are given to those areas which are inherent to mammalian cell bioreactor.
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46
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Rosenberg M, Ravid S. Protein kinase Cgamma regulates myosin IIB phosphorylation, cellular localization, and filament assembly. Mol Biol Cell 2006; 17:1364-74. [PMID: 16394101 PMCID: PMC1382324 DOI: 10.1091/mbc.e05-07-0597] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Nonmuscle myosin II is an important component of the cytoskeleton, playing a major role in cell motility and chemotaxis. We have previously demonstrated that, on stimulation with epidermal growth factor (EGF), nonmuscle myosin heavy chain II-B (NMHC-IIB) undergoes a transient phosphorylation correlating with its cellular localization. We also showed that members of the PKC family are involved in this phosphorylation. Here we demonstrate that of the two conventional PKC isoforms expressed by prostate cancer cells, PKCbetaII and PKCgamma, PKCgamma directly phosphorylates NMHC-IIB. Overexpression of wild-type and kinase dead dominant negative PKCgamma result in both altered NMHC-IIB phosphorylation and subcellular localization. We have also mapped the phosphorylation sites of PKCgamma on NMHC-IIB. Conversion of the PKCgamma phosphorylation sites to alanine residues, reduces the EGF-dependent NMHC-IIB phosphorylation. Aspartate substitution of these sites reduces NMHC-IIB localization into cytoskeleton. These results indicate that PKCgamma regulates NMHC-IIB phosphorylation and cellular localization in response to EGF stimulation.
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Affiliation(s)
- Michael Rosenberg
- Department of Biochemistry, Institute of Medical Sciences, Faculty of Medicine, The Hebrew University, Jerusalem 91120, Israel
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47
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Tran TC, Singleton C, Fraley TS, Greenwood JA. Cysteine-rich protein 1 (CRP1) regulates actin filament bundling. BMC Cell Biol 2005; 6:45. [PMID: 16336664 PMCID: PMC1318456 DOI: 10.1186/1471-2121-6-45] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2005] [Accepted: 12/08/2005] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cysteine-rich protein 1 (CRP1) is a LIM domain containing protein localized to the nucleus and the actin cytoskeleton. CRP1 has been demonstrated to bind the actin-bundling protein alpha-actinin and proposed to modulate the actin cytoskeleton; however, specific regulatory mechanisms have not been identified. RESULTS CRP1 expression increased actin bundling in rat embryonic fibroblasts. Although CRP1 did not affect the bundling activity of alpha-actinin, CRP1 was found to stabilize the interaction of alpha-actinin with actin bundles and to directly bundle actin microfilaments. Using confocal and photobleaching fluorescence resonance energy transfer (FRET) microscopy, we demonstrate that there are two populations of CRP1 localized along actin stress fibers, one associated through interaction with alpha-actinin and one that appears to bind the actin filaments directly. Consistent with a role in regulating actin filament cross-linking, CRP1 also localized to the membrane ruffles of spreading and PDGF treated fibroblasts. CONCLUSION CRP1 regulates actin filament bundling by directly cross-linking actin filaments and stabilizing the interaction of alpha-actinin with actin filament bundles.
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Affiliation(s)
- Thuan C Tran
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, USA
| | - CoreyAyne Singleton
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Tamara S Fraley
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Jeffrey A Greenwood
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, USA
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48
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Costa KD, Sim AJ, Yin FCP. Non-Hertzian Approach to Analyzing Mechanical Properties of Endothelial Cells Probed by Atomic Force Microscopy. J Biomech Eng 2005; 128:176-84. [PMID: 16524328 DOI: 10.1115/1.2165690] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Detailed measurements of cell material properties are required for understanding how cells respond to their mechanical environment. Atomic force microscopy (AFM) is an increasingly popular measurement technique that uniquely combines subcellular mechanical testing with high-resolution imaging. However, the standard method of analyzing AFM indentation data is based on a simplified “Hertz” theory that requires unrealistic assumptions about cell indentation experiments. The objective of this study was to utilize an alternative “pointwise modulus” approach, that relaxes several of these assumptions, to examine subcellular mechanics of cultured human aortic endothelial cells (HAECs). Data from indentations in 2‐to5‐μm square regions of cytoplasm reveal at least two mechanically distinct populations of cellular material. Indentations colocalized with prominent linear structures in AFM images exhibited depth-dependent variation of the apparent pointwise elastic modulus that was not observed at adjacent locations devoid of such structures. The average pointwise modulus at an arbitrary indentation depth of 200nm was 5.6±3.5kPa and 1.5±0.76kPa (mean±SD, n=7) for these two material populations, respectively. The linear structures in AFM images were identified by fluorescence microscopy as bundles of f-actin, or stress fibers. After treatment with 4μM cytochalasin B, HAECs behaved like a homogeneous linear elastic material with an apparent modulus of 0.89±0.46kPa. These findings reveal complex mechanical behavior specifically associated with actin stress fibers that is not accurately described using the standard Hertz analysis, and may impact how HAECs interact with their mechanical environment.
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Affiliation(s)
- Kevin D Costa
- Department of Biomedical Engineering, Columbia University, New York, NY, USA.
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49
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Kaunas R, Nguyen P, Usami S, Chien S. Cooperative effects of Rho and mechanical stretch on stress fiber organization. Proc Natl Acad Sci U S A 2005; 102:15895-900. [PMID: 16247009 PMCID: PMC1276069 DOI: 10.1073/pnas.0506041102] [Citation(s) in RCA: 298] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The small GTPase Rho regulates the formation of actin stress fibers in adherent cells through activation of its effector proteins Rho-kinase and mDia. We found in bovine aortic endothelial cells that inhibitions of Rho, Rho-kinase, and mDia (with C3, Y27632, and F1F2Delta1, respectively) suppressed stress fiber formation, but fibers appeared after 10% cyclic uniaxial stretch (1-Hz frequency). In contrast to the predominately perpendicular alignment of stress fibers to the stretch direction in normal cells, the stress fibers in cells with Rho pathway inhibition became oriented parallel to the stretch direction. In cells with normal Rho activity, the extent of perpendicular orientation of stress fibers depended on the magnitude of stretch. Expressing active RhoV14 plasmid in these cells enhanced the stretch-induced stress fiber orientation by an extent equivalent to an additional approximately 3% stretch. This augmentation of the stretch-induced perpendicular orientation by RhoV14 was blocked by Y27632 and by F1F2Delta1. Thus, the activity of the Rho pathway plays a critical role in determining both the direction and extent of stretch-induced stress fiber orientation in bovine aortic endothelial cells. Our results demonstrate that the stretch-induced stress fiber orientation is a function of the interplay between Rho pathway activity and the magnitude of stretching.
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Affiliation(s)
- Roland Kaunas
- Department of Bioengineering, The Whitaker Institute of Biomedical Engineering, University of California at San Diego, La Jolla, CA 92093, USA
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50
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Sato K, Adachi T, Matsuo M, Tomita Y. Quantitative evaluation of threshold fiber strain that induces reorganization of cytoskeletal actin fiber structure in osteoblastic cells. J Biomech 2005; 38:1895-901. [PMID: 16023478 DOI: 10.1016/j.jbiomech.2004.08.012] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/06/2004] [Indexed: 10/26/2022]
Abstract
The cytoskeletal stress fiber structure plays essential roles in various kinds of cellular functions such as shape maintenance, active motility and mechanosensing, and its structure is dynamically reorganized under each functional process. In known reorganization mechanisms of the stress fibers, a change in its mechanical condition has been suggested as one of the key mediators that affect the reorganization process. Some experimental studies have clarified that tension release in the stress fibers induces fiber depolymerization that is considered to be the initial phase of the reorganization process. However, quantitative mechanical values such as strain or stress that induce depolymerization have still not been evaluated. This study is aimed at the quantitative evaluation of the mechanical value that induces stress fiber depolymerization, to gain a basic understanding of the reorganization phenomenon from a mechanical viewpoint. Osteoblastic cells (MC3T3-E1) were cultured on prestretched silicone rubber substrate. Compressive deformation was applied to the cells by uniaxially releasing the prestretched substrate strain and change in the stress fiber structure was observed. The results indicated that the compressive strain magnitude, not in the whole cell body but in the stress fiber itself, is important to induce disassembly of the stress fiber structure. The existence of a threshold strain magnitude for initiating fiber disassembly was also suggested; the threshold strain magnitude was evaluated as approximately -0.20.
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Affiliation(s)
- Katsuya Sato
- Department of Mechanical and System Engineering, Division of Mechanics and Physics of Material Systems, Graduate School of Science and Technology, Kobe University, 1-1 Rokko-dai, Nada, Kobe 657-8501, Japan.
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