1551
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Sun T, Han D, Riehemann K, Rhemann K, Chi L, Fuchs H. Stereospecific Interaction between Immune Cells and Chiral Surfaces. J Am Chem Soc 2007; 129:1496-7. [PMID: 17283984 DOI: 10.1021/ja0686155] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Taolei Sun
- Physicalisches Institut, Muenster University, D-48149 Muenster, Germany.
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1552
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Sawada Y, Tamada M, Dubin-Thaler BJ, Cherniavskaya O, Sakai R, Tanaka S, Sheetz MP. Force sensing by mechanical extension of the Src family kinase substrate p130Cas. Cell 2007; 127:1015-26. [PMID: 17129785 PMCID: PMC2746973 DOI: 10.1016/j.cell.2006.09.044] [Citation(s) in RCA: 701] [Impact Index Per Article: 41.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Revised: 08/20/2006] [Accepted: 09/25/2006] [Indexed: 11/23/2022]
Abstract
How physical force is sensed by cells and transduced into cellular signaling pathways is poorly understood. Previously, we showed that tyrosine phosphorylation of p130Cas (Cas) in a cytoskeletal complex is involved in force-dependent activation of the small GTPase Rap1. Here, we mechanically extended bacterially expressed Cas substrate domain protein (CasSD) in vitro and found a remarkable enhancement of phosphorylation by Src family kinases with no apparent change in kinase activity. Using an antibody that recognized extended CasSD in vitro, we observed Cas extension in intact cells in the peripheral regions of spreading cells, where higher traction forces are expected and where phosphorylated Cas was detected, suggesting that the in vitro extension and phosphorylation of CasSD are relevant to physiological force transduction. Thus, we propose that Cas acts as a primary force sensor, transducing force into mechanical extension and thereby priming phosphorylation and activation of downstream signaling.
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Affiliation(s)
- Yasuhiro Sawada
- Department of Biological Sciences, Columbia University, Sherman Fairchild Center Room 715, MC-2416, 1212 Amsterdam Avenue, New York, NY 10027, USA.
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1553
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Kinashi T. Integrin Regulation of Lymphocyte Trafficking: Lessons from Structural and Signaling Studies. Adv Immunol 2007; 93:185-227. [PMID: 17383542 DOI: 10.1016/s0065-2776(06)93005-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
High trafficking capability of lymphocytes is crucial in immune surveillance and antigen responses. Central to this regulatory process is a dynamic control of lymphocyte adhesion behavior regulated by chemokines and adhesion receptors such as integrins. Modulation of lymphocyte adhesive responses occurs in a wide range of time window from less than a second to hours, enabling rolling lymphocyte to attach to and migrate through endothelium and interact with antigen-presenting cells. While there has been a rapid progress in the understanding of integrin structure, elucidation of signaling events to relay extracellular signaling to integrins in physiological contexts has recently emerged from studies using gene-targeting and gene-silencing technique. Regulatory molecules critical for integrin activity control distribution of integrins, polarized cell morphology and motility, suggesting a signaling network that coordinates integrin function with lymphocyte migration. Here, I review recent studies of integrin structural changes and intracellular signal molecules that trigger integrin activation (inside-out signals), and discuss molecular mechanisms that control lymphocyte integrins and how inside-out signals coordinately modulate adhesive reactions and cell shape and migration.
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Affiliation(s)
- Tatsuo Kinashi
- Department of Molecular Genetics, Institute of Biomedical Science, Kansai Medical University, Kyoto 606, Japan
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1554
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Abstract
We discuss herein the theory as well as some design considerations of magnetic tweezers. This method of generating force on magnetic particles bound to biological entities is shown to have a number of advantages over other techniques: forces are exerted in noncontact mode, they can be large in magnitude (order of 10 nanonewtons), and adjustable in direction, static or oscillatory. One apparatus built in our laboratory is described in detail, along with examples of experimental applications and results.
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Affiliation(s)
- Monica Tanase
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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1555
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Lee W, Ko YJ, Lee KB. Immobilization of fibronectin onto a large area nanoimprinted polystyrene patterns. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2007; 2007:5858-5860. [PMID: 18003346 DOI: 10.1109/iembs.2007.4353680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A well known fibrous protein, fibronectin was successfully immobilized onto well-fabricated nanopatterns of polystyrene (PS) substrates. The nanopatterns with finely-defined physical dimensions were obtained by nanoimprinting lithography (NIL) using anodized aluminum oxide (AAO) molds of which the pore sizes were controlled in nanometer scale; 45 nm, 250 nm and 410 nm for the widths and 110 nm and 500 nm for the pitches. Discrete changes of the surface images before and after the protein-adsorption on the patterns were demonstrated by scanning electron microscope (SEM), and the effect of the patterned features on the immobilization has been investigated and discussed.
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Affiliation(s)
- Wonbae Lee
- Department of Biomedical Engineering, College of Medicine, Korea University, Seoul 136-705, Korea.
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1556
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Abstract
Mechanical stress and stiffness are increasingly recognized to play important roles in numerous cell biological processes, notably cell differentiation and tissue morphogenesis. Little definite is known, however, about how stress propagates through different cell structures or how it is converted to biochemical signals via mechanotransduction, due in large part to the difficulty of interpreting many cell mechanics experiments. A newly developed technique, two-point microrheology (TPM), can provide highly interpretable, quantitative measurements of cells' frequency-dependent shear moduli and spectra of their fluctuating intracellular stresses. TPM is a noninvasive method based on measuring the Brownian motion of large numbers of intracellular particles using multiple-particle tracking. While requiring only hardware available in many cell biology laboratories, a phase microscope and digital video camera, as a statistical technique, it also requires the automated analysis of many thousands of micrographs. Here we describe in detail the algorithms and software tools used for such large-scale multiple-particle tracking as well as common sources of error and the microscopy methods needed to minimize them. Moreover, we describe the physical principles behind TPM and other passive microrheological methods, their limitations, and typical results for cultured epithelial cells.
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Affiliation(s)
- John C Crocker
- Department of Chemical and Biomolecular Engineering, Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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1557
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Pickard BG. Delivering Force and Amplifying Signals in Plant Mechanosensing. MECHANOSENSITIVE ION CHANNELS, PART A 2007. [DOI: 10.1016/s1063-5823(06)58014-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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1558
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Dang JM, Leong KW. Myogenic Induction of Aligned Mesenchymal Stem Cell Sheets by Culture on Thermally Responsive Electrospun Nanofibers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2007; 19:2775-2779. [PMID: 18584057 PMCID: PMC2440686 DOI: 10.1002/adma.200602159] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Affiliation(s)
- Jiyoung M. Dang
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205 (USA)
| | - Kam W. Leong
- Department of Biomedical, Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708 (USA) E-mail:
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1559
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Colombelli J, Reynaud EG, Stelzer EHK. Investigating Relaxation Processes in Cells and Developing Organisms: From Cell Ablation to Cytoskeleton Nanosurgery. Methods Cell Biol 2007; 82:267-91. [PMID: 17586260 DOI: 10.1016/s0091-679x(06)82008-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Dynamic microscopy of living cells and organisms alone does not reveal the high level of complexity of cellular and subcellular organization. All observable processes rely on the activity of biochemical and biophysical processes and many occur at a physiological equilibrium. Experimentally, it is not trivial to apply a perturbation that targets a specific process without perturbing the overall equilibrium of a cell. Drugs and more recently RNAi certainly have general and undesired effects on cell physiology and metabolism. In particular, they affect the entire cell. Pulsed lasers allow to severe biological tissues with a precision in the range of hundreds of nanometers and to achieve ablation on the level of a single cell or a subcellular compartment. In this chapter, we present an efficient implementation of a picosecond UV-A pulsed laser-based nanosurgery system and review the different mechanisms of ablation that can be achieved at different levels of cellular organization. We discuss the performance of the ablation process in terms of the energy deposited onto the sample and compare our implementation to others recently employed for cellular and subcellular surgery. Above the energy threshold of ionization, we demonstrate how to achieve single-cell ablation through the induction of mechanical perturbation and cavitation in living organisms. Below this threshold, we induce cytoskeleton severing inside live cells. By combining nanosurgery with fast live-imaging fluorescence microscopy, we show how the apparent equilibrium of the cytoskeleton can be perturbed regionally inside a cell.
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Affiliation(s)
- Julien Colombelli
- Light Microscopy Group, Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), D-69117 Heidelberg, Germany
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1560
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Spatz JP, Geiger B. Molecular Engineering of Cellular Environments: Cell Adhesion to Nano‐Digital Surfaces. Methods Cell Biol 2007; 83:89-111. [PMID: 17613306 DOI: 10.1016/s0091-679x(07)83005-6] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Engineering of the cellular microenvironment has become a valuable means to guide cellular activities such as spreading, motility, differentiation, proliferation, or apoptosis. This chapter summarizes recent approaches to surface patterning such as topography and chemical patterning from the micrometer to the nanometer scale, and illustrates their application to cellular studies. Particular attention is devoted to nanolithography with self-assembled diblock copolymer micelles that are biofunctionalized with peptide ligands-a method that offers unsurpassed spatial resolution for the positioning of signaling molecules over extended surface areas. Such interfaces are defined here as "nano-digital surfaces," since they enable the counting of individual signaling complexes separated by a biologically inert background. The approach enables the testing of cellular responses to individual signaling molecules as well as their spatial ordering. Detailed consideration is also given to the fact that protein clusters such as those found at focal adhesion sites represent, to a large extent, hierarchically organized cooperativity among various proteins.
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Affiliation(s)
- Joachim P Spatz
- Department of New Materials and Biosystems, Max Planck Institute for Metals Research, Stuttgart, Germany
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1561
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Sengupta A, McCulloch CA. Functional Interactions of the Extracellular Matrix with Mechanosensitive Channels. CURRENT TOPICS IN MEMBRANES 2007. [DOI: 10.1016/s1063-5823(06)58007-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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1562
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Matthews BD, Thodeti CK, Ingber DE. Activation of Mechanosensitive Ion Channels by Forces Transmitted Through Integrins and the Cytoskeleton. MECHANOSENSITIVE ION CHANNELS, PART A 2007. [DOI: 10.1016/s1063-5823(06)58003-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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1563
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Abstract
A key challenge in stem cell research is to learn how to direct the differentiation of stem cells toward specific fates. In this issue of Cell, Engler et al. (2006) identify a new factor regulating stem cell fate: the elasticity of the matrix microenvironment. By changing the stiffness of the substrate, human mesenchymal stem cells could be directed along neuronal, muscle, or bone lineages.
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Affiliation(s)
- Sharona Even-Ram
- Craniofacial Developmental Biology and Regeneration Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA
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1564
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Puklin-Faucher E, Gao M, Schulten K, Vogel V. How the headpiece hinge angle is opened: New insights into the dynamics of integrin activation. J Cell Biol 2006; 175:349-60. [PMID: 17060501 PMCID: PMC2064575 DOI: 10.1083/jcb.200602071] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2006] [Accepted: 09/21/2006] [Indexed: 01/09/2023] Open
Abstract
How the integrin head transitions to the high-affinity conformation is debated. Although experiments link activation with the opening of the hinge angle between the betaA and hybrid domains in the ligand-binding headpiece, this hinge is closed in the liganded alpha(v)beta3 integrin crystal structure. We replaced the RGD peptide ligand of this structure with the 10th type III fibronectin module (FnIII10) and discovered through molecular dynamics (MD) equilibrations that when the conformational constraints of the leg domains are lifted, the betaA/hybrid hinge opens spontaneously. Together with additional equilibrations on the same nanosecond timescale in which small structural variations impeded hinge-angle opening, these simulations allowed us to identify the allosteric pathway along which ligand-induced strain propagates via elastic distortions of the alpha1 helix to the betaA/hybrid domain hinge. Finally, we show with steered MD how force accelerates hinge-angle opening along the same allosteric pathway. Together with available experimental data, these predictions provide a novel framework for understanding integrin activation.
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Affiliation(s)
- Eileen Puklin-Faucher
- Department of Materials, Swiss Federal Institute of Technology in Zurich (ETH Zurich), CH-8093 Zurich, Switzerland
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1565
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Janmey PA, Kinnunen PKJ. Biophysical properties of lipids and dynamic membranes. Trends Cell Biol 2006; 16:538-46. [PMID: 16962778 DOI: 10.1016/j.tcb.2006.08.009] [Citation(s) in RCA: 281] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Revised: 08/14/2006] [Accepted: 08/24/2006] [Indexed: 10/24/2022]
Abstract
The lipid bilayer is a 3D assembly with a rich variety of physical features that modulate cell signaling and protein function. Lateral and transverse forces within the membrane are significant and change rapidly as the membrane is bent or stretched and as new constituents are added, removed or chemically modified. Recent studies have revealed how differences in structure between the two leaflets of the bilayer and between different areas of the bilayer can interact together with membrane deformation to alter the activities of transmembrane channels and peripheral membrane binding proteins. Here, we highlight some recent reports that the physical properties of the membrane can help control the function of transmembrane proteins and the motor-dependent elongation of internal organelles, such as the endoplasmic reticulum.
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Affiliation(s)
- P A Janmey
- Institute for Medicine and Engineering, Department of Physiology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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1566
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Hamill OP. Twenty odd years of stretch-sensitive channels. Pflugers Arch 2006; 453:333-51. [PMID: 17021800 DOI: 10.1007/s00424-006-0131-0] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Accepted: 06/27/2006] [Indexed: 01/15/2023]
Abstract
After formation of the giga-seal, the membrane patch can be stimulated by hydrostatic or osmotic pressure gradients applied across the patch. This feature led to the discovery of stretch-sensitive or mechanosensitive (MS) channels, which are now known to be ubiquitously expressed in cells representative of all the living kingdoms. In addition to mechanosensation, MS channels have been implicated in many basic cell functions, including regulation of cell volume, shape, and motility. The successful cloning, overexpression, and crystallization of bacterial MS channel proteins combined with patch clamp and modeling studies have provided atomic insight into the working of these nanomachines. In particular, studies of MS channels have revealed new understanding of how the lipid bilayer modulates membrane protein function. Three major membrane protein families, transient receptor potential, 2 pore domain K(+), and the epithelial Na(+) channels, have been shown to form MS channels in animal cells, and their polymodal activation embrace fields far beyond mechanosensitivity. The discovery of new drugs highly selective for MS channels ("mechanopharmaceutics") and the demonstration of MS channel involvement in several major human diseases ("mechanochannelopathies") provide added motivation for devising new techniques and approaches for studying MS channels.
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Affiliation(s)
- O P Hamill
- Neurosciences and Cell Biology, UTMB, Galveston, TX, 77555, USA.
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1567
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Lu S, Bansal A, Soussou W, Berger TW, Madhukar A. Receptor-ligand-based specific cell adhesion on solid surfaces: hippocampal neuronal cells on bilinker functionalized glass. NANO LETTERS 2006; 6:1977-81. [PMID: 16968011 DOI: 10.1021/nl061139w] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Cell adhesion through binding between specific cell membrane receptors and corresponding cell-adhesion-molecule (CAM)-coated solid surfaces is examined. The morphology of surfaces at various modification steps leading to functionalization with cell-binding CAMs is characterized. In one week neuron cultures, enhanced growth on surfaces modified with neuron-binding versus astrocyte-binding CAMs is observed. However, nonspecific adhesion on a poly-D-lysine-coated positive control surface is found to be even higher. Potential reasons and further studies needed are discussed.
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Affiliation(s)
- Siyuan Lu
- Department of Physics, University of Southern California, Los Angeles, California 90089-0241, USA
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1568
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Bershadsky A, Kozlov M, Geiger B. Adhesion-mediated mechanosensitivity: a time to experiment, and a time to theorize. Curr Opin Cell Biol 2006; 18:472-81. [PMID: 16930976 DOI: 10.1016/j.ceb.2006.08.012] [Citation(s) in RCA: 310] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Accepted: 08/07/2006] [Indexed: 01/27/2023]
Abstract
Adhesion-mediated signaling provides cells with information about multiple parameters of their microenvironment, including mechanical characteristics. Often, such signaling is based on a unique feature of adhesion structures: their ability to grow and strengthen when force is applied to them, either from within the cell or from the outside. Such adhesion reinforcement is characteristic of integrin-mediated cell-matrix adhesions, but may also operate in other types of adhesion structures. Though the amount of knowledge about adhesion-mediated signaling is growing rapidly, the mechanisms underlying force-dependent regulation of junction assembly are largely unknown. Experiments have been carried out that have started to uncover the major signaling pathways involved in the response of adhesion sites to force. Theoretical models have also been used to address the physical mechanisms underlying adhesion-mediated mechanosensing.
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Affiliation(s)
- Alexander Bershadsky
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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1569
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Abstract
Cells can sense and transduce a broad range of mechanical forces into distinct sets of biochemical signals that ultimately regulate cellular processes, including adhesion, proliferation, differentiation, and apoptosis. Deciphering at the nanoscale the design principles by which sensory elements are integrated into structural protein motifs whose conformations can be switched mechanically is crucial to understand the process of transduction of force into biochemical signals that are then integrated to regulate mechanoresponsive pathways. While the major focus in the search for mechanosensory units has been on membrane proteins such as ion channels, integrins, and associated cytoplasmic complexes, a multimodular design of tandem repeats of various structural motifs is ubiquitously found among extracellular matrix proteins, as well as cell adhesion molecules, and among many intracellular players that physically link transmembrane proteins to the contractile cytoskeleton. Single-molecule studies have revealed an unexpected richness of mechanosensory motifs, including force-regulated conformational changes of loop-exposed molecular recognition sites, intermediate states in the unraveling pathway that might either expose cryptic binding or phosphorylation sites, or regions that display enzymatic activity only when unmasked by force. Insights into mechanochemical signal conversion principles will also affect various technological fields, from biotechnology to tissue engineering and drug development.
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Affiliation(s)
- Viola Vogel
- Laboratory for Biologically Oriented Materials, Department of Materials, Swiss Federal Institute of Technology, ETH Zurich, CH-8093 Switzerland.
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1570
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Hoffman BD, Massiera G, Van Citters KM, Crocker JC. The consensus mechanics of cultured mammalian cells. Proc Natl Acad Sci U S A 2006; 103:10259-10264. [PMID: 16793927 PMCID: PMC1502445 DOI: 10.1073/pnas.0510348103] [Citation(s) in RCA: 245] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Although understanding cells' responses to mechanical stimuli is seen as increasingly important for understanding cell biology, how to best measure, interpret, and model cells' mechanical properties remains unclear. We determine the frequency-dependent shear modulus of cultured mammalian cells by using four different methods, both unique and well established. This approach clarifies the effects of cytoskeletal heterogeneity, ATP-dependent processes, and cell regional variations on the interpretation of such measurements. Our results clearly indicate two qualitatively similar, but distinct, mechanical responses, corresponding to the cortical and intracellular networks, each having an unusual, weak power-law form at low frequency. The two frequency-dependent responses we observe are remarkably similar to those reported for a variety of cultured mammalian cells measured with different techniques, suggesting it is a useful consensus description. Finally, we discuss possible physical explanations for the observed mechanical response.
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Affiliation(s)
- Brenton D Hoffman
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, 220 South 33rd Street, Philadelphia, PA 19104; and
| | - Gladys Massiera
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, 220 South 33rd Street, Philadelphia, PA 19104; and
| | - Kathleen M Van Citters
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, 220 South 33rd Street, Philadelphia, PA 19104; and
| | - John C Crocker
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, 220 South 33rd Street, Philadelphia, PA 19104; and
- Institute for Medicine and Engineering, University of Pennsylvania, 3340 Smith Walk, Philadelphia, PA 19104
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1571
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1572
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Lee J, Shanbhag S, Kotov NA. Inverted colloidal crystals as three-dimensional microenvironments for cellular co-cultures. ACTA ACUST UNITED AC 2006. [DOI: 10.1039/b605797g] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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