401
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Kononova O, Litvinov RI, Zhmurov A, Alekseenko A, Cheng CH, Agarwal S, Marx KA, Weisel JW, Barsegov V. Molecular mechanisms, thermodynamics, and dissociation kinetics of knob-hole interactions in fibrin. J Biol Chem 2013; 288:22681-92. [PMID: 23720752 DOI: 10.1074/jbc.m113.472365] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Polymerization of fibrin, the primary structural protein of blood clots and thrombi, occurs through binding of knobs 'A' and 'B' in the central nodule of fibrin monomer to complementary holes 'a' and 'b' in the γ- and β-nodules, respectively, of another monomer. We characterized the A:a and B:b knob-hole interactions under varying solution conditions using molecular dynamics simulations of the structural models of fibrin(ogen) fragment D complexed with synthetic peptides GPRP (knob 'A' mimetic) and GHRP (knob 'B' mimetic). The strength of A:a and B:b knob-hole complexes was roughly equal, decreasing with pulling force; however, the dissociation kinetics were sensitive to variations in acidity (pH 5-7) and temperature (T = 25-37 °C). There were similar structural changes in holes 'a' and 'b' during forced dissociation of the knob-hole complexes: elongation of loop I, stretching of the interior region, and translocation of the moveable flap. The disruption of the knob-hole interactions was not an "all-or-none" transition as it occurred through distinct two-step or single step pathways with or without intermediate states. The knob-hole bonds were stronger, tighter, and more brittle at pH 7 than at pH 5. The B:b knob-hole bonds were weaker, looser, and more compliant than the A:a knob-hole bonds at pH 7 but stronger, tighter, and less compliant at pH 5. Surprisingly, the knob-hole bonds were stronger, not weaker, at elevated temperature (T = 37 °C) compared with T = 25 °C due to the helix-to-coil transition in loop I that helps stabilize the bonds. These results provide detailed qualitative and quantitative characteristics underlying the most significant non-covalent interactions involved in fibrin polymerization.
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Affiliation(s)
- Olga Kononova
- Department of Chemistry, University of Massachusetts, Lowell, Massachusetts 01854, USA
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402
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Abstract
Focal adhesions mediate force transfer between ECM-integrin complexes and the cytoskeleton. Although vinculin has been implicated in force transmission, few direct measurements have been made, and there is little mechanistic insight. Using vinculin-null cells expressing vinculin mutants, we demonstrate that vinculin is not required for transmission of adhesive and traction forces but is necessary for myosin contractility-dependent adhesion strength and traction force and for the coupling of cell area and traction force. Adhesion strength and traction forces depend differentially on vinculin head (V(H)) and tail domains. V(H) enhances adhesion strength by increasing ECM-bound integrin-talin complexes, independently from interactions with vinculin tail ligands and contractility. A full-length, autoinhibition-deficient mutant (T12) increases adhesion strength compared with VH, implying roles for both vinculin activation and the actin-binding tail. In contrast to adhesion strength, vinculin-dependent traction forces absolutely require a full-length and activated molecule; V(H) has no effect. Physical linkage of the head and tail domains is required for maximal force responses. Residence times of vinculin in focal adhesions, but not T12 or V(H), correlate with applied force, supporting a mechanosensitive model for vinculin activation in which forces stabilize vinculin's active conformation to promote force transfer.
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403
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Schiller HB, Hermann MR, Polleux J, Vignaud T, Zanivan S, Friedel CC, Sun Z, Raducanu A, Gottschalk KE, Théry M, Mann M, Fässler R. β1- and αv-class integrins cooperate to regulate myosin II during rigidity sensing of fibronectin-based microenvironments. Nat Cell Biol 2013; 15:625-36. [PMID: 23708002 DOI: 10.1038/ncb2747] [Citation(s) in RCA: 331] [Impact Index Per Article: 30.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Accepted: 04/04/2013] [Indexed: 12/14/2022]
Abstract
How different integrins that bind to the same type of extracellular matrix protein mediate specific functions is unclear. We report the functional analysis of β1- and αv-class integrins expressed in pan-integrin-null fibroblasts seeded on fibronectin. Reconstitution with β1-class integrins promotes myosin-II-independent formation of small peripheral adhesions and cell protrusions, whereas expression of αv-class integrins induces the formation of large focal adhesions. Co-expression of both integrin classes leads to full myosin activation and traction-force development on stiff fibronectin-coated substrates, with αv-class integrins accumulating in adhesion areas exposed to high traction forces. Quantitative proteomics linked αv-class integrins to a GEF-H1-RhoA pathway coupled to the formin mDia1 but not myosin II, and α5β1 integrins to a RhoA-Rock-myosin II pathway. Our study assigns specific functions to distinct fibronectin-binding integrins, demonstrating that α5β1integrins accomplish force generation, whereas αv-class integrins mediate the structural adaptations to forces, which cooperatively enable cells to sense the rigidity of fibronectin-based microenvironments.
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Affiliation(s)
- Herbert B Schiller
- Department of Molecular Medicine, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
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404
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Schiller HB, Fässler R. Mechanosensitivity and compositional dynamics of cell-matrix adhesions. EMBO Rep 2013; 14:509-19. [PMID: 23681438 DOI: 10.1038/embor.2013.49] [Citation(s) in RCA: 202] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 03/21/2013] [Indexed: 12/27/2022] Open
Abstract
Cells perceive information about the biochemical and biophysical properties of their tissue microenvironment through integrin-mediated cell-matrix adhesions, which connect the cytoskeleton with the extracellular matrix and thereby allow cohesion and long-range mechanical connections within tissues. The formation of cell-matrix adhesions and integrin signalling involves the dynamic recruitment and assembly of an inventory of proteins, collectively termed the 'adhesome', at the adhesive site. The recruitment of some adhesome proteins, most notably the Lin11-, Isl1- and Mec3-domain-containing proteins, depends on mechanical tension generated by myosin II-mediated contractile forces exerted on cell-matrix adhesions. When exposed to force, mechanosensitive adhesome proteins can change their conformation or expose cryptic-binding sites leading to the recruitment of proteins, rearrangement of the cytoskeleton, reinforcement of the adhesive site and signal transduction. Biophysical methods and proteomics revealed force ranges within the adhesome and cytoskeleton, and also force-dependent changes in adhesome composition. In this review, we provide an overview of the compositional dynamics of cell-matrix adhesions, discuss the most prevalent functional domains in adhesome proteins and review literature and concepts about mechanosensing mechanisms that operate at the adhesion site.
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Affiliation(s)
- Herbert B Schiller
- Department of Molecular Medicine, Max Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany
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405
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Chu C, Celik E, Rico F, Moy VT. Elongated membrane tethers, individually anchored by high affinity α4β1/VCAM-1 complexes, are the quantal units of monocyte arrests. PLoS One 2013; 8:e64187. [PMID: 23691169 PMCID: PMC3656870 DOI: 10.1371/journal.pone.0064187] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 04/12/2013] [Indexed: 11/18/2022] Open
Abstract
The α4β1 integrin facilitates both monocyte rolling and adhesion to the vascular endothelium and is physiologically activated by monocyte chemoattractant protein (MCP-1). The current study investigated the initial events in the adhesion of THP-1 cells to immobilized Vascular Cell Adhesion Molecule 1 (VCAM-1). Using AFM force measurements, cell adhesion was shown to be mediated by two populations of α4β1/VCAM-1 complexes. A low affinity form of α4β1 was anchored to the elastic elements of the cytoskeleton, while a higher affinity conformer was coupled to the viscous elements of the cell membrane. Within 100 ms of contact, THP-1 cells, stimulated by co-immobilized MCP-1, exhibited a tremendous increase in adhesion to VCAM-1. Enhanced cell adhesion was accompanied by a local decoupling of the cell membrane from the cytoskeleton and the formation of long membrane tethers. The tethers were individually anchored by multiple α4β1/VCAM-1 complexes that prolonged the extension of the viscous tethers. In vivo, the formation of these membrane tethers may provide the quantal structural units for the arrest of rolling monocytes within the blood vessels.
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Affiliation(s)
- Calvin Chu
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida, United States of America
| | - Emrah Celik
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida, United States of America
| | - Felix Rico
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida, United States of America
| | - Vincent T. Moy
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida, United States of America
- * E-mail:
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406
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Kong F, Li Z, Parks WM, Dumbauld DW, García AJ, Mould AP, Humphries MJ, Zhu C. Cyclic mechanical reinforcement of integrin-ligand interactions. Mol Cell 2013; 49:1060-8. [PMID: 23416109 PMCID: PMC3615084 DOI: 10.1016/j.molcel.2013.01.015] [Citation(s) in RCA: 111] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 11/12/2012] [Accepted: 01/11/2013] [Indexed: 12/11/2022]
Abstract
Cells regulate adhesion in response to internally generated and externally applied forces. Integrins connect the extracellular matrix to the cytoskeleton and provide cells with mechanical anchorages and signaling platforms. Here we show that cyclic forces applied to a fibronectin-integrin α5β1 bond switch the bond from a short-lived state with 1 s lifetime to a long-lived state with 100 s lifetime. We term this phenomenon "cyclic mechanical reinforcement," as the bond strength remembers the history of force application and accumulates over repeated cycles, but does not require force to be sustained. Cyclic mechanical reinforcement strengthens the fibronectin-integrin α5β1 bond through the RGD binding site of the ligand with the synergy binding site greatly facilitating the process. A flexible integrin hybrid domain is also important for cyclic mechanical reinforcement. Our results reveal a mechanical regulation of receptor-ligand interactions and identify a molecular mechanism for cell adhesion strengthening by cyclic forces.
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Affiliation(s)
- Fang Kong
- Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Zhenhai Li
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - William M. Parks
- Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - David W. Dumbauld
- Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Andrés J. García
- Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - A. Paul Mould
- Welcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, M13 9PT, England, UK
| | - Martin J. Humphries
- Welcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, M13 9PT, England, UK
| | - Cheng Zhu
- Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
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407
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Li N, Mao D, Lü S, Tong C, Zhang Y, Long M. Distinct binding affinities of Mac-1 and LFA-1 in neutrophil activation. THE JOURNAL OF IMMUNOLOGY 2013; 190:4371-81. [PMID: 23514737 DOI: 10.4049/jimmunol.1201374] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Macrophage-1 Ag (Mac-1) and lymphocyte function-associated Ag-1 (LFA-1), two β2 integrins expressed on neutrophils (PMNs), mediate PMN recruitment cascade by binding to intercellular adhesive molecule 1. Distinct functions of LFA-1-initiating PMN slow rolling and firm adhesion but Mac-1-mediating cell crawling are assumed to be governed by the differences in their binding affinities and kinetic rates. In this study, we applied an adhesion frequency approach to compare their kinetics in the quiescent and activated states using three molecular systems, constitutively expressed receptors on PMNs, wild-type and high-affinity (HA) full-length constructs transfected on 293T cells, and wild-type and HA recombinant extracellular constructs. Data indicate that the difference in binding affinity between Mac-1 and LFA-1 is on-rate dominated with slightly or moderately varied off-rate. This finding was further confirmed when both β2 integrins were activated by chemokines (fMLF or IL-8), divalent cations (Mg(2+) or Mn(2+)), or disulfide bond lockage on an HA state. Structural analyses reveal that such the kinetics difference is likely attributed to the distinct conformations at the interface of Mac-1 or LFA-1 and intercellular adhesive molecule 1. This work furthers the understandings in the kinetic differences between Mac-1 and LFA-1 and in their biological correlations with molecular activation and structural bases.
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Affiliation(s)
- Ning Li
- Key Laboratory of Microgravity (National Microgravity Laboratory) and Center of Biomechanics and Bioengineering, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
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408
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Actin depolymerization under force is governed by lysine 113:glutamic acid 195-mediated catch-slip bonds. Proc Natl Acad Sci U S A 2013; 110:5022-7. [PMID: 23460697 DOI: 10.1073/pnas.1218407110] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
As a key element in the cytoskeleton, actin filaments are highly dynamic structures that constantly sustain forces. However, the fundamental question of how force regulates actin dynamics is unclear. Using atomic force microscopy force-clamp experiments, we show that tensile force regulates G-actin/G-actin and G-actin/F-actin dissociation kinetics by prolonging bond lifetimes (catch bonds) at a low force range and by shortening bond lifetimes (slip bonds) beyond a threshold. Steered molecular dynamics simulations reveal force-induced formation of new interactions that include a lysine 113(K113):glutamic acid 195 (E195) salt bridge between actin subunits, thus suggesting a molecular basis for actin catch-slip bonds. This structural mechanism is supported by the suppression of the catch bonds by the single-residue replacements K113 to serine (K113S) and E195 to serine (E195S) on yeast actin. These results demonstrate and provide a structural explanation for actin catch-slip bonds, which may provide a mechanoregulatory mechanism to control cell functions by regulating the depolymerization kinetics of force-bearing actin filaments throughout the cytoskeleton.
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409
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Hoffmann M, Schwarz US. A kinetic model for RNA-interference of focal adhesions. BMC SYSTEMS BIOLOGY 2013; 7:2. [PMID: 23311633 PMCID: PMC3616989 DOI: 10.1186/1752-0509-7-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Accepted: 12/21/2012] [Indexed: 01/09/2023]
Abstract
BACKGROUND Focal adhesions are integrin-based cell-matrix contacts that transduce and integrate mechanical and biochemical cues from the environment. They develop from smaller and more numerous focal complexes under the influence of mechanical force and are key elements for many physiological and disease-related processes, including wound healing and metastasis. More than 150 different proteins localize to focal adhesions and have been systematically classified in the adhesome project (http://www.adhesome.org). First RNAi-screens have been performed for focal adhesions and the effect of knockdown of many of these components on the number, size, shape and location of focal adhesions has been reported. RESULTS We have developed a kinetic model for RNA interference of focal adhesions which represents some of its main elements: a spatially layered structure, signaling through the small GTPases Rac and Rho, and maturation from focal complexes to focal adhesions under force. The response to force is described by two complementary scenarios corresponding to slip and catch bond behavior, respectively. Using estimated and literature values for the model parameters, three time scales of the dynamics of RNAi-influenced focal adhesions are identified: a sub-minute time scale for the assembly of focal complexes, a sub-hour time scale for the maturation to focal adhesions, and a time scale of days that controls the siRNA-mediated knockdown. Our model shows bistability between states dominated by focal complexes and focal adhesions, respectively. Catch bonding strongly extends the range of stability of the state dominated by focal adhesions. A sensitivity analysis predicts that knockdown of focal adhesion components is more efficient for focal adhesions with slip bonds or if the system is in a state dominated by focal complexes. Knockdown of Rho leads to an increase of focal complexes. CONCLUSIONS The suggested model provides a kinetic description of the effect of RNA-interference of focal adhesions. Its predictions are in good agreement with known experimental results and can now guide the design of RNAi-experiments. In the future, it can be extended to include more components of the adhesome. It also could be extended by spatial aspects, for example by the differential activation of the Rac- and Rho-pathways in different parts of the cell.
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Affiliation(s)
- Max Hoffmann
- BioQuant, Heidelberg University, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany
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410
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Chen W, Lou J, Evans EA, Zhu C. Observing force-regulated conformational changes and ligand dissociation from a single integrin on cells. ACTA ACUST UNITED AC 2013; 199:497-512. [PMID: 23109670 PMCID: PMC3483124 DOI: 10.1083/jcb.201201091] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A biomembrane force probe visualizes force-regulated reversible switches between bent and extended conformations of αLβ2 integrin on the surface of a living cell. As adhesion molecules, integrins connect a cell to its environment and transduce signals across the membrane. Their different functional states correspond to distinct conformations. Using a biomembrane force probe, we observed real-time reversible switches between bent and extended conformations of a single integrin, αLβ2, on the surface of a living cell by measuring its nanometer-scale headpiece displacements, bending and unbending frequencies, and molecular stiffness changes. We determined the stabilities of these conformations, their dynamic equilibrium, speeds and rates of conformational changes, and the impact of divalent cations and tensile forces. We quantified how initial and subsequent conformations of αLβ2 regulate the force-dependent kinetics of dissociation from intercellular adhesion molecule 1. Our findings provide new insights into how integrins function as nanomachines to precisely control cell adhesion and signaling.
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Affiliation(s)
- Wei Chen
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
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411
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Abstract
The development of biophysical approaches to analyze integrin–ligand binding allows us to visualize in real time the conformational changes that shift the bond affinity between low- and high-affinity states. In this issue, Chen et al. (2012. J. Cell Biol.http://dx.doi.org/jcb.201201091) use these approaches to validate some aspects of the classical integrin regulation model; however, their data suggest that much of the regulation occurs after ligand binding rather than in preparation for ligand binding to occur.
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Affiliation(s)
- David Boettiger
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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412
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Javadi Y, Fernandez JM, Perez-Jimenez R. Protein Folding Under Mechanical Forces: A Physiological View. Physiology (Bethesda) 2013; 28:9-17. [DOI: 10.1152/physiol.00017.2012] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mechanical forces regulate the function of numerous proteins relevant to physiology. The functions and folding of proteins have been under scrutiny for decades, but it was not until recently that mechanical forces have been considered. Here, we review different techniques for studying protein folding, highlighting their physiological significance.
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Affiliation(s)
- Yalda Javadi
- Department of Biological Sciences, Columbia University, New York, New York; and
- University of Cambridge, Department of Chemistry, Cambridge, United Kingdom
| | - Julio M. Fernandez
- Department of Biological Sciences, Columbia University, New York, New York; and
| | - Raul Perez-Jimenez
- Department of Biological Sciences, Columbia University, New York, New York; and
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413
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Huelsz-Prince G, Belkin AM, vanBavel E, Bakker EN. Activation of Extracellular Transglutaminase 2 by Mechanical Force in the Arterial Wall. J Vasc Res 2013; 50:383-95. [DOI: 10.1159/000354222] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 07/05/2013] [Indexed: 11/19/2022] Open
Abstract
Inward remodeling of small arteries occurs after prolonged vasoconstriction, low blood flow, and in several models of hypertension. The cross-linking enzyme, transglutaminases 2 (TG2), is able to induce inward remodeling and stiffening of arteries. The activity of TG2 is dependent on its conformation, which can be open or closed, and on its redox state. Several factors have been shown to be involved in modulating TG2 activity, including Ca<sup>2+</sup> and GTP/GDP concentrations, as well as the redox state of the environment. This review introduces the hypothesis that mechanical force could be involved in regulating the activity of TG2 during inward remodeling by promoting its open and reduced active state. Several aspects of TG2, such as its structure and localization, are assessed in order to provide arguments that support the hypothesis. We conclude that a direct activation of TG2 by mechanical force exerted by smooth muscle cells may explain the link between smooth muscle activation and inward remodeling, as observed in several physiological and pathological conditions.
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414
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Abstract
The recognition of peptide/MHC antigens by T-cells has continued to challenge the imagination of immunologists, biochemists, and cell biologists alike. This is at least in part because T-cell recognition connects a diversity of issues and transcends many scientific disciplines. A fundamental unsolved issue is how T-cells manage to detect even a single molecule of an agonist pMHC complex, which is vastly outnumbered by endogenous pMHCs, many of which involve the same MHC molecule. They do so although TCRs are cross-reactive and typically low in affinity when measured in isolation. Importantly, T-cell antigen recognition takes place within the contact zone between a T-cell and the antigen-presenting cell, termed the immunological synapse. This bimembrane structure sets the stage for the antigen-binding events and all subsequent molecular recognition events. There is increasing evidence that the molecular dynamics of receptor-ligand interactions are not only dependent on the intrinsic properties of the binding partners but also become transformed by cell biological parameters such as the geometrical constraints within the immune synapse, mechanical forces, and local molecular crowding. To appreciate the complete picture, we think a multidisciplinary approach is imperative, which includes genetics, biochemistry, and structure determination and also biophysical analyses and the latest molecular imaging techniques. Here, we review earlier pioneering work and also recent developments in the fascinating and interdisciplinary science of T-cell antigen recognition. In many ways, this work may present a useful "roadmap" for work in other systems of cell-cell recognition, which underlie many fundamental biological phenomenons of interest.
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415
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Chen B, Kemkemer R, Deibler M, Spatz J, Gao H. Cyclic stretch induces cell reorientation on substrates by destabilizing catch bonds in focal adhesions. PLoS One 2012; 7:e48346. [PMID: 23152769 PMCID: PMC3495948 DOI: 10.1371/journal.pone.0048346] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2012] [Accepted: 09/24/2012] [Indexed: 01/13/2023] Open
Abstract
A minimal model of cellular mechanosensing system that consists of a single stress fiber adhering on a substrate via two focal adhesions made of catch bonds is adopted to investigate the phenomena of cell reorientation on substrates induced by an applied uniaxial cyclic stretch. The model indicates that the catch bonds in the focal adhesions experience a periodically oscillating internal force with amplitude and frequency controlled by two intrinsic clocks of the stress fiber, one associated with localized activation and the other with homogeneous activation of sarcomere units along the stress fiber. It is shown that this oscillating force due to cyclic stretch tends to destabilize focal adhesions by reducing the lifetime of catch bonds. The resulting slide or relocation of focal adhesions then causes the associated stress fiber to shorten and rotate to configurations nearly perpendicular to the stretching direction. These predicted behaviors from our model are consistent with a wide range of experimental observations.
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Affiliation(s)
- Bin Chen
- Department of Engineering Mechanics, Zhejiang University, Hangzhou, People's Republic of China
- Engineering Mechanics, Institute of High Performance Computing, A*STAR, Singapore, Singapore
| | - Ralf Kemkemer
- Max-Planck-Institute for Intelligent Systems, Department of New Materials and Biosystems, Stuttgart, Germany
| | - Martin Deibler
- Max-Planck-Institute for Intelligent Systems, Department of New Materials and Biosystems, Stuttgart, Germany
- Department of Biophysical Chemistry, University of Heidelberg, Heidelberg, Germany
| | - Joachim Spatz
- Max-Planck-Institute for Intelligent Systems, Department of New Materials and Biosystems, Stuttgart, Germany
- Department of Biophysical Chemistry, University of Heidelberg, Heidelberg, Germany
| | - Huajian Gao
- School of Engineering, Brown University, Providence, Rhode Island, United States of America
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416
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Ladoux B, Nicolas A. Physically based principles of cell adhesion mechanosensitivity in tissues. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2012; 75:116601. [PMID: 23085962 DOI: 10.1088/0034-4885/75/11/116601] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The minimal structural unit that defines living organisms is a single cell. By proliferating and mechanically interacting with each other, cells can build complex organization such as tissues that ultimately organize into even more complex multicellular living organisms, such as mammals, composed of billions of single cells interacting with each other. As opposed to passive materials, living cells actively respond to the mechanical perturbations occurring in their environment. Tissue cell adhesion to its surrounding extracellular matrix or to neighbors is an example of a biological process that adapts to physical cues. The adhesion of tissue cells to their surrounding medium induces the generation of intracellular contraction forces whose amplitude adapts to the mechanical properties of the environment. In turn, solicitation of adhering cells with physical forces, such as blood flow shearing the layer of endothelial cells in the lumen of arteries, reinforces cell adhesion and impacts cell contractility. In biological terms, the sensing of physical signals is transduced into biochemical signaling events that guide cellular responses such as cell differentiation, cell growth and cell death. Regarding the biological and developmental consequences of cell adaptation to mechanical perturbations, understanding mechanotransduction in tissue cell adhesion appears as an important step in numerous fields of biology, such as cancer, regenerative medicine or tissue bioengineering for instance. Physicists were first tempted to view cell adhesion as the wetting transition of a soft bag having a complex, adhesive interaction with the surface. But surprising responses of tissue cell adhesion to mechanical cues challenged this view. This, however, did not exclude that cell adhesion could be understood in physical terms. It meant that new models and descriptions had to be created specifically for these biological issues, and could not straightforwardly be adapted from dead matter. In this review, we present physical concepts of tissue cell adhesion and the unexpected cellular responses to mechanical cues such as external forces and stiffness sensing. We show how biophysical approaches, both experimentally and theoretically, have contributed to our understanding of the regulation of cellular functions through physical force sensing mechanisms. Finally, we discuss the different physical models that could explain how tissue cell adhesion and force sensing can be coupled to internal mechanosensitive processes within the cell body.
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Affiliation(s)
- Benoit Ladoux
- Laboratoire Matière et Systèmes Complexes (MSC), CNRS UMR 7057 & Université Paris Diderot, Paris, France.
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417
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Abstract
Classical cadherin cell-cell adhesion proteins play key morphogenetic roles during development and are essential for maintaining tissue integrity in multicellular organisms. Classical cadherins bind in two distinct conformations, X-dimer and strand-swap dimer; during cellular rearrangements, these adhesive states are exposed to mechanical stress. However, the molecular mechanisms by which cadherins resist tensile force and the pathway by which they convert between different conformations are unclear. Here, we use single molecule force measurements with an atomic force microscope (AFM) to show that E-cadherin, a prototypical classical cadherin, forms three types of adhesive bonds: catch bonds, which become longer lived in the presence of tensile force; slip bonds, which become shorter lived when pulled; and ideal bonds that are insensitive to mechanical stress. We show that X-dimers form catch bonds, whereas strand-swap dimers form slip bonds. Our data suggests that ideal bonds are formed as X-dimers convert to strand-swap binding. Catch, slip, and ideal bonds allow cadherins to withstand tensile force and tune the mechanical properties of adhesive junctions.
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418
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419
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420
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Assembly and disassembly of cell matrix adhesions. Curr Opin Cell Biol 2012; 24:569-81. [DOI: 10.1016/j.ceb.2012.06.010] [Citation(s) in RCA: 160] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Revised: 06/12/2012] [Accepted: 06/28/2012] [Indexed: 11/22/2022]
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421
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Rossier O, Octeau V, Sibarita JB, Leduc C, Tessier B, Nair D, Gatterdam V, Destaing O, Albigès-Rizo C, Tampé R, Cognet L, Choquet D, Lounis B, Giannone G. Integrins β1 and β3 exhibit distinct dynamic nanoscale organizations inside focal adhesions. Nat Cell Biol 2012; 14:1057-67. [PMID: 23023225 DOI: 10.1038/ncb2588] [Citation(s) in RCA: 283] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 08/23/2012] [Indexed: 12/12/2022]
Abstract
Integrins in focal adhesions (FAs) mediate adhesion and force transmission to extracellular matrices essential for cell motility, proliferation and differentiation. Different fibronectin-binding integrins, simultaneously present in FAs, perform distinct functions. Yet, how integrin dynamics control biochemical and biomechanical processes in FAs is still elusive. Using single-protein tracking and super-resolution imaging we revealed the dynamic nano-organizations of integrins and talin inside FAs. Integrins reside in FAs through free-diffusion and immobilization cycles. Integrin activation promotes immobilization, stabilized in FAs by simultaneous connection to fibronectin and actin-binding proteins. Talin is recruited in FAs directly from the cytosol without membrane free-diffusion, restricting integrin immobilization to FAs. Immobilized β3-integrins are enriched and stationary within FAs, whereas immobilized β1-integrins are less enriched and exhibit rearward movements. Talin is enriched and mainly stationary, but also exhibited rearward movements in FAs, consistent with stable connections with both β-integrins. Thus, differential transmission of actin motion to fibronectin occurs through specific integrins within FAs.
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Affiliation(s)
- Olivier Rossier
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, UMR 5297, F-33000 Bordeaux, France
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422
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Valdembri D, Serini G. Regulation of adhesion site dynamics by integrin traffic. Curr Opin Cell Biol 2012; 24:582-91. [PMID: 22981739 DOI: 10.1016/j.ceb.2012.08.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 06/19/2012] [Accepted: 08/20/2012] [Indexed: 01/14/2023]
Abstract
The dynamic control of integrin-mediated cell adhesion to extracellular matrix proteins is crucial for several physiological and pathological phenomena as diverse as embryonic morphogenesis, muscle contraction, tissue repair, and cancer cell dissemination. On one hand, the intrinsic conformational plasticity of integrins, which can be bidirectionally modulated by their ligands and cytosolic adaptors in combination with physical forces, is a key regulatory parameter. On the other hand, endo-exocytic integrin traffic logistics represent an additional important mode of control. Herein, we highlight how these two apparently parallel and independent strategies for tuning integrin function appear instead to be indissolubly intermingled, as eukaryotic cells have evolved distinct molecular strategies and endosomal pathways to traffic ligand-bound and ligand-free integrins.
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Affiliation(s)
- Donatella Valdembri
- Laboratory of Cell Adhesion Dynamics - IRCC and Department of Oncological Sciences, University of Torino School of Medicine, 10060, Candiolo, Italy
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423
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Torun H, Finkler O, Degertekin FL. Atomic force microscope based biomolecular force-clamp measurements using a micromachined electrostatic actuator. Ultramicroscopy 2012; 122:26-31. [PMID: 22960003 DOI: 10.1016/j.ultramic.2012.07.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 05/18/2012] [Accepted: 07/17/2012] [Indexed: 10/28/2022]
Abstract
The authors describe a method for biomolecular force clamp measurements using atomic force microscope (AFM) cantilevers and micromachined membrane-based electrostatic actuators. The actuators comprise of Parylene membranes with embedded side actuation electrodes and are fabricated on a silicon substrate. The devices have a displacement range of 1.8 μm with 200 V actuation voltage, and displacement uncertainty is 0.8 nm, including the noise and drift. The settling time, limited by the particular amplifier is 5 ms, with an inherent range down to 20 μs. A force clamp measurement setup using these actuators in a feedback loop has been used to measure bond life-times between human IgG and anti-human IgG molecules to demonstrate the feasibility of this method for biological experiments. The experimental findings are compared with a molecular pulling experiment and the results are found to be in good agreement.
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Affiliation(s)
- Hamdi Torun
- Department of Electrical and Electronics Engineering, Bogazici University, Bebek, TR-34342 Istanbul, Turkey.
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424
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Zarnitsyna V, Zhu C. T cell triggering: insights from 2D kinetics analysis of molecular interactions. Phys Biol 2012; 9:045005. [PMID: 22871794 DOI: 10.1088/1478-3975/9/4/045005] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Interaction of the T cell receptor (TCR) with pathogen-derived peptide presented by the major histocompatibility complex (pMHC) molecule is central to adaptive immunity as it initiates intracellular signaling to trigger T cell response to infection. Kinetic parameters of this interaction have been under intensive investigation for more than two decades using soluble pMHCs and/or TCRs with at least one of them in the solution (three-dimensional (3D) methods). Recently, several techniques have been developed to enable kinetic analysis on live T cells with pMHCs presented by surrogate antigen presenting cells (APCs) or supported planar lipid bilayers (two-dimensional (2D) methods). Comparison of 2D versus 3D parameters reveals drastic differences with broader ranges of 2D affinities and on-rates and orders of magnitude faster 2D off-rates for functionally distinct pMHCs. Here we review new 2D data and discuss how it may impact previously developed models of T cell discrimination between pMHCs of different potencies.
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Affiliation(s)
- Veronika Zarnitsyna
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30332, USA.
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425
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Chigaev A, Sklar LA. Aspects of VLA-4 and LFA-1 regulation that may contribute to rolling and firm adhesion. Front Immunol 2012; 3:242. [PMID: 22876249 PMCID: PMC3410440 DOI: 10.3389/fimmu.2012.00242] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 07/18/2012] [Indexed: 01/21/2023] Open
Abstract
Very Late Antigen-4 (CD49d/CD29, alpha4 beta1) and Lymphocyte Function-associated Antigen-1 (CD11a/CD18, alphaL beta2) integrins are representatives of a large family of adhesion receptors widely expressed on immune cells. They participate in cell recruitment to sites of inflammation, as well as multiple immune cell interactions. A unique feature of integrins is that integrin-dependent cell adhesion can be rapidly and reversibly modulated in response to cell signaling, because of a series of conformational changes within the molecule, which include changes in the affinity of the ligand binding pocket, molecular extension (unbending) and others. Here, we provide a concise comparative analysis of the conformational regulation of the two integrins with specific attention to the physiological differences between these molecules. We focus on recent data obtained using a novel technology, based on small fluorescent ligand-mimicking probes for the detection of integrin conformation in real-time on live cells at natural receptor abundance.
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Affiliation(s)
- Alexandre Chigaev
- Department of Pathology and Cancer Center, University of New Mexico Health Sciences Center, Albuquerque NM, USA
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426
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Moore SW, Sheetz MP. Biophysics of substrate interaction: influence on neural motility, differentiation, and repair. Dev Neurobiol 2012; 71:1090-101. [PMID: 21739614 DOI: 10.1002/dneu.20947] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The identity and behavior of a cell is shaped by the molecular and mechanical composition of its surroundings. Molecular cues have firmly established roles in guiding both neuronal fate decisions and the migration of cells and axons. However, there is growing evidence that topographical and rigidity cues in the extracellular environment act synergistically with these molecular cues. Like chemical cues, physical factors do not elicit a fixed response, but rather one that depends on the sensory makeup of the cell. Moreover, from developmental studies and the plasticity of neural tissue, it is evident that there is dynamic feedback between physical and chemical factors to produce the final morphology. Here, we focus on our current understanding of how these physical cues shape cellular differentiation and migration, and discuss their relevance to repairing the injured nervous system.
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Affiliation(s)
- Simon W Moore
- Department of Biological Sciences, Columbia University, Sherman Fairchild Center, Amsterdam Ave., New York, NY 10027, USA.
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427
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Boettiger D. Mechanical control of integrin-mediated adhesion and signaling. Curr Opin Cell Biol 2012; 24:592-9. [PMID: 22857903 DOI: 10.1016/j.ceb.2012.07.002] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 06/14/2012] [Accepted: 07/11/2012] [Indexed: 01/13/2023]
Abstract
Integrin-mediated adhesion is controlled by the number of bonds between cell surface integrins and substrate-bound ligands. Integrin-ligand affinity is modulated by chemical allostery, mechanical allostery and integrin clustering. This review analyzes how each of these factors changes through the phases of cell attachment, adhesion strengthening, and clustering. The analysis predicts a dominant role of mechanical factors in both adhesive regulation and integrin signaling for adherent cells. New approaches and experimental analyses will be required to substantiate this hypothesis.
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Affiliation(s)
- David Boettiger
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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428
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The leucocyte β2 (CD18) integrins: the structure, functional regulation and signalling properties. Biosci Rep 2012; 32:241-69. [PMID: 22458844 DOI: 10.1042/bsr20110101] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Leucocytes are highly motile cells. Their ability to migrate into tissues and organs is dependent on cell adhesion molecules. The integrins are a family of heterodimeric transmembrane cell adhesion molecules that are also signalling receptors. They are involved in many biological processes, including the development of metazoans, immunity, haemostasis, wound healing and cell survival, proliferation and differentiation. The leucocyte-restricted β2 integrins comprise four members, namely αLβ2, αMβ2, αXβ2 and αDβ2, which are required for a functional immune system. In this paper, the structure, functional regulation and signalling properties of these integrins are reviewed.
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429
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Roca-Cusachs P, Iskratsch T, Sheetz MP. Finding the weakest link: exploring integrin-mediated mechanical molecular pathways. J Cell Sci 2012; 125:3025-38. [PMID: 22797926 DOI: 10.1242/jcs.095794] [Citation(s) in RCA: 176] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
From the extracellular matrix to the cytoskeleton, a network of molecular links connects cells to their environment. Molecules in this network transmit and detect mechanical forces, which subsequently determine cell behavior and fate. Here, we reconstruct the mechanical pathway followed by these forces. From matrix proteins to actin through integrins and adaptor proteins, we review how forces affect the lifetime of bonds and stretch or alter the conformation of proteins, and how these mechanical changes are converted into biochemical signals in mechanotransduction events. We evaluate which of the proteins in the network can participate in mechanotransduction and which are simply responsible for transmitting forces in a dynamic network. Besides their individual properties, we also analyze how the mechanical responses of a protein are determined by their serial connections from the matrix to actin, their parallel connections in integrin clusters and by the rate at which force is applied to them. All these define mechanical molecular pathways in cells, which are emerging as key regulators of cell function alongside better studied biochemical pathways.
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Affiliation(s)
- Pere Roca-Cusachs
- University of Barcelona and Institute for Bioengineering of Catalonia, Barcelona, Spain.
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430
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Alon R, Feigelson SW. Chemokine-triggered leukocyte arrest: force-regulated bi-directional integrin activation in quantal adhesive contacts. Curr Opin Cell Biol 2012; 24:670-6. [PMID: 22770729 DOI: 10.1016/j.ceb.2012.06.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 05/24/2012] [Accepted: 06/11/2012] [Indexed: 10/28/2022]
Abstract
The arrest of rolling leukocytes on target vascular beds is mediated by specialized leukocyte integrins and their endothelial ligands. In the circulation, these integrins are generally maintained as inactive 'clasped' heterodimers. Encounter by leukocytes of specialized endothelial-presented chemoattractants termed arrest chemokines drive these integrins to undergo force-regulated biochemical conformational changes in response to signals from chemokine-stimulated Gi-protein coupled receptors (GPCRs) and actin remodeling Rho GTPases. To arrest rolling leukocytes, integrin:ligand bonds must undergo stabilization by several orders of magnitude within quantal submicron contacts that consist of discrete integrin:ligand bonds. We present a unifying three step model for rapid integrin activation by chemokines in the quantal arrest unit, the smallest firm adhesive contact formed by a rolling or a captured leukocyte: integrin extension triggered by talin, integrin headpiece opening driven by surface-immobilized ligand and stabilized by low force, and full heterodimer unclasping requiring integrin tail associations with actin-connected talin and Kindlin-3. Specialized GPCRs and their Gi-protein signaling assemblies drive these and other adaptors to specifically bind integrin cytoplasmic tails possibly in conjunction with de novo actin remodeling, thereby optimizing bi-directional activation of ligand-occupied integrins.
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Affiliation(s)
- Ronen Alon
- Department of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel.
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431
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Chang MW, Lo JM, Juan HF, Chang HY, Chuang CY. Combination of RGD compound and low-dose paclitaxel induces apoptosis in human glioblastoma cells. PLoS One 2012; 7:e37935. [PMID: 22655084 PMCID: PMC3360022 DOI: 10.1371/journal.pone.0037935] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Accepted: 04/26/2012] [Indexed: 12/01/2022] Open
Abstract
Background Integrins are a family of transmembrane adhesion proteins that mediate cell adhesion and intracellular signaling. Integrin-αvβ3 is expressed on the surface of human glioblastoma cells, and can be further induced by chemical stress. The Arg-Gly-Asp (RGD) motif-containing peptides are specifically bound to integrin-αvβ3, and to inhibit neovasculature underlying competition to normal extracellular matrix proteins. This study employed two types of RGD peptides, cyclic RGD (c(RGDyK)) and bi-cyclic RGD (E[c(RGDyK)]2) peptide, to human glioblastoma U87MG cells with combination of low dose Paclitaxel (PTX) pre-treatment to augment therapeutic activity for RGD peptide-induced apoptosis. Principal Findings Human glioblastoma U87MG cells were treated with RGD peptides in the absence or presence of initial exposure to low-dose 10 nM PTX. Results showed that integrin-αvβ3 expressing on the surface of U87MG cells was induced by 10 nM PTX pre-treatment for 12 hrs. Additionally, the U87MG cells pre-treated with PTX and followed by RGD peptides exhibited greater expression of caspases-3, -8 and -9 than those merely treated with single agent of PTX or RGD peptide. Furthermore, the caspase-3, -8 and -9 inhibitor presented significant protection against E[c(RGDyK)]2 peptide induced U87MG programmed cell death. The increased expression of PTX-induced integrin-αvβ3 was correlated with the enhanced apoptosis in U87MG cells. Conclusions This study provides a novel concept of targeting integrin-αvβ3 with RGD peptides in combination with low-dose PTX pre-treatment to improve efficiency in human glioblastoma treatment.
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Affiliation(s)
- Ming-Wei Chang
- Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan
| | - Jem-Mau Lo
- Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan
| | - Hsueh-Fen Juan
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
- Department of Life Science, National Taiwan University, Taipei, Taiwan
| | - Hsin-Yi Chang
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Chun-Yu Chuang
- Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan
- * E-mail:
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432
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Lim SM, Trzeciakowski JP, Sreenivasappa H, Dangott LJ, Trache A. RhoA-induced cytoskeletal tension controls adaptive cellular remodeling to mechanical signaling. Integr Biol (Camb) 2012; 4:615-27. [PMID: 22546924 DOI: 10.1039/c2ib20008b] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The ability to measure real-time mechanosensitive events at the subcellular level in response to discrete mechanical stimulation is a critical component in understanding mechanically-induced cellular remodeling. Vascular smooth muscle cells (VSMC) were transfected with RhoA constructs (wild type, dominant negative or constitutively active) or treated with ML-7 to induce specific cytoskeletal tension characteristics prior to mechanical stimulation. Tensile stress was applied to live VSMC using an atomic force microscope probe functionalized with extracellular matrix (ECM) proteins. The ECM induces selective integrin activation and focal adhesion formation, enabling direct manipulation of cortical actin through an active ECM-integrin-actin linkage. Therefore, locally induced mechanosensitive events triggered downstream activation of intracellular signaling pathways responsible for actin and focal adhesion remodeling throughout the cell. Integration of mechanical stimulation with simultaneous fluorescence imaging by spinning-disk confocal and total internal reflection fluorescence microscopy enabled visualization and quantification of molecular dynamic events at the sub-cellular level in real-time. Results provide evidence that the pre-existing cytoskeletal tension affects the actomyosin apparatus which in turn coordinates the ability of the cell to adapt to the externally applied stress. RhoA activation induced high cytoskeletal tension that correlated with increased stress fiber formation, cell stiffness, integrin activation and myosin phosphorylation. In contrast, blocking Rho-kinase or myosin function was characterized by low cytoskeletal tension with a decreased level of stress fiber formation, lower cell stiffness and integrin activation. Our findings show that VSMC sense and adapt to physical microenvironmental changes by a coordinated response of the actomyosin apparatus necessary to establish a new homeostatic state.
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Affiliation(s)
- Soon-Mi Lim
- Department of Systems Biology & Translational Medicine, Cardiovascular Research Institute, College of Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114, USA
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433
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Fennewald SM, Kantara C, Sastry SK, Resto VA. Laminin interactions with head and neck cancer cells under low fluid shear conditions lead to integrin activation and binding. J Biol Chem 2012; 287:21058-66. [PMID: 22547070 DOI: 10.1074/jbc.m112.360313] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Lymphatic metastasis of cancer cells involves movement from the primary tumor site to the lymph node, where the cells must be able to productively lodge and grow. It is there that tumor cells encounter cellular and non-cellular constituent elements that make up the lymph node parenchyma. Our work shows that head and neck squamous cell carcinoma (HNSCC) cell lines are able to bind to laminin, fibronectin, vitronectin, and hyaluronic acid, which are extracellular matrix elements within the lymph node parenchyma. HNSCC cell lines bound to laminin under lymphodynamic low shear stress (0.07 dynes/cm(2)), consistent with lymph flow via β1 integrins, including α2β1, α3β1, and α6β1. Binding occurred in the presence of shear stress and not in the absence of flow. Additionally, tumor cell binding to laminin under flow did result in calcium signaling. Our data indicate a novel role for β1 integrin-mediated binding of HNSCC cells to laminin under conditions of lymphodynamic flow that results in intracellular calcium signaling within the cancer cell.
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Affiliation(s)
- Susan M Fennewald
- Department of Otolaryngology, UTMB Health, University of Texas Medical Branch, Galveston, Texas 77555-0521, USA
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434
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Abstract
Integrins not only mediate cell-cell and cell-extracellular matrix adhesion, but also affect the multitude of signal transduction cascades in control of cell survival, proliferation, differentiation and organ development. Mutations in integrins or the major effectors of integrin signalling pathways cause defective organ development, immunodeficiency, cancer or autoimmune disease. Understanding of the signalling events that drive integrin activation and signalling is therefore crucial to uncover the molecular mechanisms of these diseases. This review discusses the key signalling complexes regulating integrin activation and function in both 'inside-out' and 'outside-in' pathways in T lymphocytes, including kinases, SLP-76, VAV1, ADAP, SKAP-55, RapL, RIAM, Rap1, Talin and Kindlin.
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Affiliation(s)
- Yanbo Zhang
- The State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
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435
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Shao B, Yago T, Coghill PA, Klopocki AG, Mehta-D'souza P, Schmidtke DW, Rodgers W, McEver RP. Signal-dependent slow leukocyte rolling does not require cytoskeletal anchorage of P-selectin glycoprotein ligand-1 (PSGL-1) or integrin αLβ2. J Biol Chem 2012; 287:19585-98. [PMID: 22511754 DOI: 10.1074/jbc.m112.361519] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In inflamed venules, neutrophils roll on P- or E-selectin, engage P-selectin glycoprotein ligand-1 (PSGL-1), and signal extension of integrin α(L)β(2) in a low affinity state to slow rolling on intercellular adhesion molecule-1 (ICAM-1). Cytoskeleton-dependent receptor clustering often triggers signaling, and it has been hypothesized that the cytoplasmic domain links PSGL-1 to the cytoskeleton. Chemokines cause rolling neutrophils to fully activate α(L)β(2), leading to arrest on ICAM-1. Cytoskeletal anchorage of α(L)β(2) has been linked to chemokine-triggered extension and force-regulated conversion to the high affinity state. We asked whether PSGL-1 must interact with the cytoskeleton to initiate signaling and whether α(L)β(2) must interact with the cytoskeleton to extend. Fluorescence recovery after photobleaching of transfected cells documented cytoskeletal restraint of PSGL-1. The lateral mobility of PSGL-1 similarly increased by depolymerizing actin filaments with latrunculin B or by mutating the cytoplasmic tail to impair binding to the cytoskeleton. Converting dimeric PSGL-1 to a monomer by replacing its transmembrane domain did not alter its mobility. By transducing retroviruses expressing WT or mutant PSGL-1 into bone marrow-derived macrophages from PSGL-1-deficient mice, we show that PSGL-1 required neither dimerization nor cytoskeletal anchorage to signal β(2) integrin-dependent slow rolling on P-selectin and ICAM-1. Depolymerizing actin filaments or decreasing actomyosin tension in neutrophils did not impair PSGL-1- or chemokine-mediated integrin extension. Unlike chemokines, PSGL-1 did not signal cytoskeleton-dependent swing out of the β(2)-hybrid domain associated with the high affinity state. The cytoskeletal independence of PSGL-1-initiated, α(L)β(2)-mediated slow rolling differs markedly from the cytoskeletal dependence of chemokine-initiated, α(L)β(2)-mediated arrest.
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Affiliation(s)
- Bojing Shao
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA
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436
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Hirata H, Lim CT, Miyata H. 3D Coupling of Fibronectin Fibril Arrangement with Topology of Ventral Plasma Membrane. ACTA ACUST UNITED AC 2012; 19:17-23. [DOI: 10.3109/15419061.2012.665968] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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437
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Pereverzev YV, Prezhdo E, Sokurenko EV. The two-pathway model of the biological catch-bond as a limit of the allosteric model. Biophys J 2012; 101:2026-36. [PMID: 22004757 DOI: 10.1016/j.bpj.2011.09.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 08/11/2011] [Indexed: 01/25/2023] Open
Abstract
Catch-binding is a counterintuitive phenomenon in which the lifetime of a receptor/ligand bond increases when a force is applied to break the bond. Several mechanisms have been proposed to rationalize catch-binding. In the two-pathway model, the force drives the system away from its native dissociation pathway into an alternative pathway involving a higher energy barrier. Here, we analyze an allosteric model suggesting that a force applied to the complex alters the distribution of receptor conformations, and as a result, induces changes in the ligand-binding site. The model assumes explicitly that the allosteric transitions govern the properties of the ligand site. We demonstrate that the dynamics of the ligand is described by two relaxation times, one of which arises from the allosteric site. Therefore, we argue that one can characterize the allosteric transitions by studying the receptor/ligand binding. We show that the allosteric description reduces to the two-pathway model in the limit when the allosteric transitions are faster than the bond dissociation. The formal results are illustrated with two systems, P-selectin/PSGL-1 and FimH/mannose, subjected to both constant and time-dependent forces. The report advances our understanding of catch-binding by combining alternative physical models into a unified description and makes the problem more tractable for the bond mechanics community.
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Affiliation(s)
- Yuriy V Pereverzev
- Department of Chemistry, University of Rochester, Rochester, New York, USA
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438
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Legate KR, Takahashi S, Bonakdar N, Fabry B, Boettiger D, Zent R, Fässler R. Integrin adhesion and force coupling are independently regulated by localized PtdIns(4,5)2 synthesis. EMBO J 2012; 30:4539-53. [PMID: 21926969 DOI: 10.1038/emboj.2011.332] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2011] [Accepted: 08/19/2011] [Indexed: 01/23/2023] Open
Abstract
The 90-kDa isoform of the lipid kinase PIP kinase Type I γ (PIPKIγ) localizes to focal adhesions (FAs), where it provides a local source of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)). Although PtdIns(4,5)P(2) regulates the function of several FA-associated molecules, the role of the FA-specific pool of PtdIns(4,5)P(2) is not known. We report that the genetic ablation of PIPKIγ specifically from FAs results in defective integrin-mediated adhesion and force coupling. Adhesion defects in cells deficient in FAPtdIns(4,5)P(2) synthesis are corrected within minutes while integrin-actin force coupling remains defective over a longer period. Talin and vinculin, but not kindlin, are less efficiently recruited to new adhesions in these cells. These data demonstrate that the specific depletion of PtdIns(4,5)P(2) from FAs temporally separates integrin-ligand binding from integrin-actin force coupling by regulating talin and vinculin recruitment. Furthermore, it suggests that force coupling relies heavily on locally generated PtdIns(4,5)P(2) rather than bulk membrane PtdIns(4,5)P(2).
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Affiliation(s)
- Kyle R Legate
- Department of Molecular Medicine, Max Planck Institute of Biochemistry, Martinsried, Germany
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439
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Ozdemir T, Zhang P, Fu C, Dong C. Fibrin serves as a divalent ligand that regulates neutrophil-mediated melanoma cells adhesion to endothelium under shear conditions. Am J Physiol Cell Physiol 2012; 302:C1189-201. [PMID: 22262064 DOI: 10.1152/ajpcell.00346.2011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Elevated soluble fibrin (sFn) levels are characteristic of melanoma hematogeneous dissemination, where tumor cells interact intimately with host cells. Melanoma adhesion to the blood vessel wall is promoted by immune cell arrests and tumor-derived thrombin, a serine protease that converts soluble fibrinogen (sFg) into sFn. However, the molecular requirement for sFn-mediated melanoma-polymorphonuclear neutrophils (PMNs) and melanoma-endothelial interactions under physiological flow conditions remain elusive. To understand this process, we studied the relative binding capacities of sFg and sFn receptors e.g., α(v)β(3) integrin and intercellular adhesion molecule-1 (ICAM-1) expressed on melanoma cells, ICAM-1 on endothelial cells (EC), and CD11b/CD18 (Mac-1) on PMNs. Using a parallel-plate flow chamber, highly metastatic melanoma cells (1205Lu and A375M) and human PMNs were perfused over an EC monolayer expressing ICAM-1 in the presence of sFg or sFn. It was found that both the frequency and lifetime of direct melanoma adhesion or PMN-facilitated melanoma adhesion to the EC in a shear flow were increased by the presence of sFn in a concentration-dependent manner. In addition, sFn fragment D and plasmin-treated sFn failed to increase melanoma adhesion, implying that sFn-bridged cell adhesion requires dimer-mediated receptor-receptor cross-linking. Finally, analysis of the respective kinetics of sFn binding to Mac-1, ICAM-1, and α(v)β(3) by single bond cell tethering assays suggested that ICAM-1 and α(v)β(3) are responsible for initial capture and firm adhesion of melanoma cells. These results provide evidence that sFn enhances melanoma adhesion directly to ICAM-1 on the EC, while prolonged shear-resistant melanoma adhesion requires interactions with PMNs.
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Affiliation(s)
- Tugba Ozdemir
- Department of Bioengineering, Pennsylvania State University, University Park, 16802, USA
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440
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Abstract
Interaction of the integrin receptors with ligands determines the molecular basis of integrin-dependent cell adhesion. Integrin ligands are typically large proteins with relatively low binding affinities. This makes direct ligand-binding kinetic measurements somewhat difficult. Here we examine several real-time methods, aimed to overcome these experimental limitations and to distinguish the regulation of integrin conformation and affinity. This chapter includes: the use of a small ligand-mimetic probe for studies of inside-out regulation of integrin affinity and unbending, real-time cell aggregation and disaggregation kinetics to probe integrin conformational states and the number of integrin-ligand bonds, as well as the real-time monitoring of ligand-induced epitopes under signaling through G-protein-coupled receptors, and others. Experimental data obtained using these novel methods are summarized in terms of the current model of integrin activation.
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Affiliation(s)
- Alexandre Chigaev
- Department of Pathology and Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM, USA.
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441
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Feghhi S, Sniadecki NJ. Mechanobiology of platelets: techniques to study the role of fluid flow and platelet retraction forces at the micro- and nano-scale. Int J Mol Sci 2011; 12:9009-30. [PMID: 22272117 PMCID: PMC3257114 DOI: 10.3390/ijms12129009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 11/24/2011] [Accepted: 11/28/2011] [Indexed: 12/29/2022] Open
Abstract
Coagulation involves a complex set of events that are important in maintaining hemostasis. Biochemical interactions are classically known to regulate the hemostatic process, but recent evidence has revealed that mechanical interactions between platelets and their surroundings can also play a substantial role. Investigations into platelet mechanobiology have been challenging however, due to the small dimensions of platelets and their glycoprotein receptors. Platelet researchers have recently turned to microfabricated devices to control these physical, nanometer-scale interactions with a higher degree of precision. These approaches have enabled exciting, new insights into the molecular and biomechanical factors that affect platelets in clot formation. In this review, we highlight the new tools used to understand platelet mechanobiology and the roles of adhesion, shear flow, and retraction forces in clot formation.
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Affiliation(s)
- Shirin Feghhi
- Department of Mechanical Engineering, University of Washington, Stevens Way, Box 352600, Seattle, WA 98195, USA; E-Mail:
| | - Nathan J. Sniadecki
- Department of Mechanical Engineering, University of Washington, Stevens Way, Box 352600, Seattle, WA 98195, USA; E-Mail:
- Department of Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA 98105, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-206-685-6591; Fax: +1-206-685-8047
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442
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Wehrle-Haller B. Structure and function of focal adhesions. Curr Opin Cell Biol 2011; 24:116-24. [PMID: 22138388 DOI: 10.1016/j.ceb.2011.11.001] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Revised: 11/01/2011] [Accepted: 11/02/2011] [Indexed: 01/17/2023]
Abstract
Integrin-dependent cell adhesions come in different shapes and serve in different cell types for tasks ranging from cell-adhesion, migration, and the remodeling of the extracellular matrix to the formation and stabilization of immunological and chemical synapses. A major challenge consists in the identification of adhesion-specific as well as common regulatory mechanisms, motivating the need for a deeper analysis of protein-protein interactions in the context of intact focal adhesions. Specifically, it is critical to understand how small differences in binding of integrins to extracellular ligands and/or cytoplasmic adapter proteins affect the assembly and function of an entire focal adhesion. By using the talin-integrin pair as a starting point, I would like to discuss how specific protein-protein and protein-lipid interactions can control the behavior and function of focal adhesions. By responding to chemical and mechanical cues several allosterically regulated proteins create a dynamic multifunctional protein network that provides both adhesion to the extracellular matrix as well as intracellular signaling in response to mechanical changes in the cellular environment.
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Affiliation(s)
- Bernhard Wehrle-Haller
- University of Geneva, Department of Cell Physiology and Metabolism, Centre Médical Universitaire, 1. Rue Michel-Servet, 1211 Geneva 4, Switzerland.
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443
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Liu J, Agrawal NJ, Calderon A, Ayyaswamy PS, Eckmann DM, Radhakrishnan R. Multivalent binding of nanocarrier to endothelial cells under shear flow. Biophys J 2011; 101:319-26. [PMID: 21767483 DOI: 10.1016/j.bpj.2011.05.063] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2011] [Revised: 05/02/2011] [Accepted: 05/23/2011] [Indexed: 12/11/2022] Open
Abstract
We investigate the effects of particle size, shear flow, and resistance due to the glycocalyx on the multivalent binding of functionalized nanocarriers (NC) to endothelial cells (ECs). We address the much- debated issue of shear-enhanced binding by computing the binding free-energy landscapes of NC binding to the EC surface when the system is subjected to shear, using a model and simulation methodology based on the Metropolis Monte Carlo approach. The binding affinities calculated based on the free-energy profiles are found to be in excellent agreement with experimental measurements for different-sized NCs. The model suggests that increasing the size of NCs significantly increases the multivalency but only moderately enhances the binding affinities due to the entropy loss associated with bound receptors on the EC surface. A significant prediction of our model is that under flow conditions, the binding free energies of NCs are a nonmonotonic function of the shear force. They show a well-defined minimum at a critical shear value, and thus quantitatively mimic the shear-enhanced binding behavior observed in various experiments. More significantly, our results indicate that the interplay between multivalent binding and shear force can reproduce the shear-enhanced binding phenomenon, which suggests that under certain conditions, this phenomenon can also occur in systems that do not show a catch-bond behavior. In addition, the model also suggests that the impact of the glycocalyx thickness on NC binding affinity is exponential, implying a highly nonlinear effect of the glycocalyx on binding.
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Affiliation(s)
- Jin Liu
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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444
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Influence of substrate rigidity on primary nucleation of cell adhesion: a thermal fluctuation model. J Colloid Interface Sci 2011; 366:200-208. [PMID: 21999957 DOI: 10.1016/j.jcis.2011.09.046] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 09/15/2011] [Accepted: 09/16/2011] [Indexed: 01/09/2023]
Abstract
Experimental investigations have demonstrated that cells can actively sense and respond to physical aspects of their environments, such as substrate stiffness of biomaterials, via integrin receptors with the help of stochastic thermal undulations of cell membranes. This paper develops a physical model for the mechanism of integrin-dependent cell-substrate adhesion nucleation in order to investigate the influence of substrate stiffness on primary adhesion formation. In this model, a series of so-called energy potential wells are established to quantitatively describe force-driven conformational changes of integrins on elastic substrates with different rigidities. A concept of nucleation domain is proposed to characterize the necessary condition of integrin-mediated cell-substrate primary adhesion formation. In the framework of classical statistical mechanics, the competitive relationship is investigated between the local thermal undulations of plasma membranes and the conformational conversions of substrate-binding integrins. The quantitative dependence of integrin-mediated adhesion nucleation on substrate rigidities is systematically explored, which shows a reasonable agreement with existing experimental results.
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445
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Sun L, Cheng QH, Gao HJ, Zhang YW. Effect of loading conditions on the dissociation behaviour of catch bond clusters. J R Soc Interface 2011; 9:928-37. [PMID: 21937488 DOI: 10.1098/rsif.2011.0553] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Under increasing tensile load, the lifetime of a single catch bond counterintuitively increases up to a maximum and then decreases exponentially like a slip bond. So far, the characteristics of single catch bond dissociation have been extensively studied. However, it remains unclear how a cluster of catch bonds behaves under tensile load. We perform computational analysis on the following models to examine the characteristics of clustered catch bonds: (i) clusters of catch bonds with equal load sharing, (ii) clusters of catch bonds with linear load sharing, and (iii) clusters of catch bonds in micropipette-manipulated cell detachment. We focus on the differences between the slip and catch bond clusters, identifying the critical factors for exhibiting the characteristics of catch bond mechanism for the multiple-bond system. Our computation reveals that for a multiple-bond cluster, the catch bond behaviour could only manifest itself under relatively uniform loading conditions and at certain stages of decohesion, explaining the difficulties in observing the catch bond mechanism under real biological conditions.
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Affiliation(s)
- L Sun
- Department of Materials Science and Engineering, National University of Singapore, Singapore
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446
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Margadant C, Monsuur HN, Norman JC, Sonnenberg A. Mechanisms of integrin activation and trafficking. Curr Opin Cell Biol 2011; 23:607-14. [PMID: 21924601 DOI: 10.1016/j.ceb.2011.08.005] [Citation(s) in RCA: 230] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 08/18/2011] [Indexed: 01/01/2023]
Abstract
Integrin adhesion receptors are essential for the normal function of most multicellular organisms, and defective integrin activation or integrin signaling is associated with an array of pathological conditions. Integrins are regulated by conformational changes, clustering, and trafficking, and regulatory mechanisms differ strongly between individual integrins and between cell types. Whereas integrins in circulating blood cells are activated by an inside-out-induced conformational change that favors high-affinity ligand binding, β1-integrins in adherent cells can be activated by force or clustering. In addition, endocytosis and recycling play an important role in the regulation of integrin turnover and integrin redistribution in adherent cells, especially during dynamic processes such as cell migration and invasion. Integrin trafficking is strongly regulated by their cytoplasmic tails, and the mechanisms are now being identified.
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Affiliation(s)
- Coert Margadant
- Division of Cell Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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447
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Frequency-Dependent Focal Adhesion Instability and Cell Reorientation Under Cyclic Substrate Stretching. Cell Mol Bioeng 2011. [DOI: 10.1007/s12195-011-0187-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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448
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Sarangapani KK, Qian J, Chen W, Zarnitsyna VI, Mehta P, Yago T, McEver RP, Zhu C. Regulation of catch bonds by rate of force application. J Biol Chem 2011; 286:32749-61. [PMID: 21775439 DOI: 10.1074/jbc.m111.240044] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The current paradigm for receptor-ligand dissociation kinetics assumes off-rates as functions of instantaneous force without impact from its prior history. This a priori assumption is the foundation for predicting dissociation from a given initial state using kinetic equations. Here we have invalidated this assumption by demonstrating the impact of force history with single-bond kinetic experiments involving selectins and their ligands that mediate leukocyte tethering and rolling on vascular surfaces during inflammation. Dissociation of bonds between L-selectin and P-selectin glycoprotein ligand-1 (PSGL-1) loaded at a constant ramp rate to a constant hold force behaved as catch-slip bonds at low ramp rates that transformed to slip-only bonds at high ramp rates. Strikingly, bonds between L-selectin and 6-sulfo-sialyl Lewis X were impervious to ramp rate changes. This ligand-specific force history effect resembled the effect of a point mutation at the L-selectin surface (L-selectinA108H) predicted to contact the former but not the latter ligand, suggesting that the high ramp rate induced similar structural changes as the mutation. Although the A108H substitution in L-selectin eliminated the ramp rate responsiveness of its dissociation from PSGL-1, the inverse mutation H108A in P-selectin acquired the ramp rate responsiveness. Our data are well explained by the sliding-rebinding model for catch-slip bonds extended to incorporate the additional force history dependence, with Ala-108 playing a pivotal role in this structural mechanism. These results call for a paradigm shift in modeling the mechanical regulation of receptor-ligand bond dissociation, which includes conformational coupling between binding pocket and remote regions of the interacting molecules.
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Affiliation(s)
- Krishna K Sarangapani
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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449
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Abstract
Cellular responses to mechanical forces are crucial in embryonic development and adult physiology, and are involved in numerous diseases, including atherosclerosis, hypertension, osteoporosis, muscular dystrophy, myopathies and cancer. These responses are mediated by load-bearing subcellular structures, such as the plasma membrane, cell-adhesion complexes and the cytoskeleton. Recent work has demonstrated that these structures are dynamic, undergoing assembly, disassembly and movement, even when ostensibly stable. An emerging insight is that transduction of forces into biochemical signals occurs within the context of these processes. This framework helps to explain how forces of varying strengths or dynamic characteristics regulate distinct signalling pathways.
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450
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Chen B, Gao H. Motor force homeostasis in skeletal muscle contraction. Biophys J 2011; 101:396-403. [PMID: 21767492 PMCID: PMC3136795 DOI: 10.1016/j.bpj.2011.05.061] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 05/09/2011] [Accepted: 05/31/2011] [Indexed: 01/13/2023] Open
Abstract
In active biological contractile processes such as skeletal muscle contraction, cellular mitosis, and neuronal growth, an interesting common observation is that multiple motors can perform coordinated and synchronous actions, whereas individual myosin motors appear to randomly attach to and detach from actin filaments. Recent experiment has demonstrated that, during skeletal muscle shortening at a wide range of velocities, individual myosin motors maintain a force of ~6 pN during a working stroke. To understand how such force-homeostasis can be so precisely regulated in an apparently chaotic system, here we develop a molecular model within a coupled stochastic-elastic theoretical framework. The model reveals that the unique force-stretch relation of myosin motor and the stochastic behavior of actin-myosin binding cause the average number of working motors to increase in linear proportion to the filament load, so that the force on each working motor is regulated at ~6 pN, in excellent agreement with experiment. This study suggests that it might be a general principle to use catch bonds together with a force-stretch relation similar to that of myosin motors to regulate force homeostasis in many biological processes.
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Affiliation(s)
- Bin Chen
- Engineering Mechanics, Institute of High Performance Computing, A∗STAR, Singapore
| | - Huajian Gao
- School of Engineering, Brown University, Providence, Rhode Island
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