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Wang ZJ, Thomson M. Localization of signaling receptors maximizes cellular information acquisition in spatially structured natural environments. Cell Syst 2022; 13:530-546.e12. [PMID: 35679857 DOI: 10.1016/j.cels.2022.05.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 02/08/2022] [Accepted: 05/12/2022] [Indexed: 01/25/2023]
Abstract
Cells in natural environments, such as tissue or soil, sense and respond to extracellular ligands with intricately structured and non-monotonic spatial distributions, sculpted by processes such as fluid flow and substrate adhesion. In this work, we show that spatial sensing and navigation can be optimized by adapting the spatial organization of signaling pathways to the spatial structure of the environment. We develop an information-theoretic framework for computing the optimal spatial organization of a sensing system for a given signaling environment. We find that receptor localization previously observed in cells maximizes information acquisition in simulated natural contexts, including tissue and soil. Specifically, information acquisition is maximized when receptors form localized patches at regions of maximal ligand concentration. Receptor localization extends naturally to produce a dynamic protocol for continuously redistributing signaling receptors, which when implemented using simple feedback, boosts cell navigation efficiency by 30-fold.
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Affiliation(s)
- Zitong Jerry Wang
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
| | - Matt Thomson
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
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2
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Jensen RK, Bajic G, Sen M, Springer TA, Vorup-Jensen T, Andersen GR. Complement Receptor 3 Forms a Compact High-Affinity Complex with iC3b. THE JOURNAL OF IMMUNOLOGY 2021; 206:3032-3042. [PMID: 34117107 DOI: 10.4049/jimmunol.2001208] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 04/13/2021] [Indexed: 11/19/2022]
Abstract
Complement receptor 3 (CR3, also known as Mac-1, integrin αMβ2, or CD11b/CD18) is expressed on a subset of myeloid and certain activated lymphoid cells. CR3 is essential for the phagocytosis of complement-opsonized particles such as pathogens and apoptotic or necrotic cells opsonized with the complement fragment iC3b and, to a lesser extent, C3dg. Although the interaction between the iC3b thioester domain and the ligand binding CR3 αM I-domain is structurally and functionally well characterized, the nature of additional CR3-iC3b interactions required for phagocytosis of complement-opsonized objects remains obscure. In this study, we analyzed the interaction between iC3b and the 150-kDa headpiece fragment of the CR3 ectodomain. Surface plasmon resonance experiments demonstrated a 30 nM affinity of the CR3 headpiece for iC3b compared with 515 nM for the iC3b thioester domain, whereas experiments monitoring binding of iC3b to CR3-expressing cells suggested an affinity of 50 nM for the CR3-iC3b interaction. Small angle x-ray scattering analysis revealed that iC3b adopts an extended but preferred conformation in solution. Upon interaction with CR3, iC3b rearranges to form a compact receptor-ligand complex. Overall, the data suggest that the iC3b-CR3 interaction is of high affinity and relies on minor contacts formed between CR3 and regions outside the iC3b thioester domain. Our results rationalize the more efficient phagocytosis elicited by iC3b than by C3dg and pave the way for the development of specific therapeutics for the treatment of inflammatory and neurodegenerative diseases that do not interfere with the recognition of noncomplement CR3 ligands.
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Affiliation(s)
- Rasmus K Jensen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Goran Bajic
- Laboratory of Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA.,Department of Pediatrics, Harvard Medical School, Boston, MA.,Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Mehmet Sen
- Department of Biology and Biochemistry, University of Houston, Houston, TX
| | - Timothy A Springer
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA.,Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA; and
| | | | - Gregers R Andersen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark;
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3
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Bose N, Chan ASH, Guerrero F, Maristany CM, Qiu X, Walsh RM, Ertelt KE, Jonas AB, Gorden KB, Dudney CM, Wurst LR, Danielson ME, Elmasry N, Magee AS, Patchen ML, Vasilakos JP. Binding of Soluble Yeast β-Glucan to Human Neutrophils and Monocytes is Complement-Dependent. Front Immunol 2013; 4:230. [PMID: 23964276 PMCID: PMC3740326 DOI: 10.3389/fimmu.2013.00230] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 07/22/2013] [Indexed: 01/24/2023] Open
Abstract
The immunomodulatory properties of yeast β-1,3/1,6 glucans are mediated through their ability to be recognized by human innate immune cells. While several studies have investigated binding of opsonized and unopsonized particulate β-glucans to human immune cells mainly via complement receptor 3 (CR3) or Dectin-1, few have focused on understanding the binding characteristics of soluble β-glucans. Using a well-characterized, pharmaceutical-grade, soluble yeast β-glucan, this study evaluated and characterized the binding of soluble β-glucan to human neutrophils and monocytes. The results demonstrated that soluble β-glucan bound to both human neutrophils and monocytes in a concentration-dependent and receptor-specific manner. Antibodies blocking the CD11b and CD18 chains of CR3 significantly inhibited binding to both cell types, establishing CR3 as the key receptor recognizing the soluble β-glucan in these cells. Binding of soluble β-glucan to human neutrophils and monocytes required serum and was also dependent on incubation time and temperature, strongly suggesting that binding was complement-mediated. Indeed, binding was reduced in heat-inactivated serum, or in serum treated with methylamine or in serum reacted with the C3-specific inhibitor compstatin. Opsonization of soluble β-glucan was demonstrated by detection of iC3b, the complement opsonin on β-glucan-bound cells, as well as by the direct binding of iC3b to β-glucan in the absence of cells. Binding of β-glucan to cells was partially inhibited by blockade of the alternative pathway of complement, suggesting that the C3 activation amplification step mediated by this pathway also contributed to binding.
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4
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Leander R, Dai S, Schlesinger LS, Friedman A. A mathematical model of CR3/TLR2 crosstalk in the context of Francisella tularensis infection. PLoS Comput Biol 2012; 8:e1002757. [PMID: 23133361 PMCID: PMC3486853 DOI: 10.1371/journal.pcbi.1002757] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 09/05/2012] [Indexed: 02/04/2023] Open
Abstract
Complement Receptor 3 (CR3) and Toll-like Receptor 2 (TLR2) are pattern recognition receptors expressed on the surface of human macrophages. Although these receptors are essential components for recognition by the innate immune system, pathogen coordinated crosstalk between them can suppress the production of protective cytokines and promote infection. Recognition of the virulent Schu S4 strain of the intracellular pathogen Francisella tularensis by host macrophages involves CR3/TLR2 crosstalk. Although experimental data provide evidence that Lyn kinase and PI3K are essential components of the CR3 pathway that influences TLR2 activity, additional responsible upstream signaling components remain unknown. In this paper we construct a mathematical model of CR3 and TLR2 signaling in response to F. tularensis. After demonstrating that the model is consistent with experimental results we perform numerical simulations to evaluate the contributions that Akt and Ras-GAP make to ERK inhibition. The model confirms that phagocytosis-associated changes in the composition of the cell membrane can inhibit ERK activity and predicts that Akt and Ras-GAP synergize to inhibit ERK.
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Affiliation(s)
- Rachel Leander
- Mathematical Biosciences Institute, The Ohio State University, Columbus, Ohio, United States of America
| | - Shipan Dai
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, United States of America
| | - Larry S. Schlesinger
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, United States of America
| | - Avner Friedman
- Mathematical Biosciences Institute, The Ohio State University, Columbus, Ohio, United States of America
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5
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Goh JWK, Tan YS, Dodds AW, Reid KBM, Lu J. The class A macrophage scavenger receptor type I (SR-AI) recognizes complement iC3b and mediates NF-κB activation. Protein Cell 2010; 1:174-87. [PMID: 21203986 DOI: 10.1007/s13238-010-0020-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2009] [Accepted: 12/15/2009] [Indexed: 12/01/2022] Open
Abstract
The macrophage scavenger receptor SR-AI binds to host tissue debris to perform clearance and it binds to bacteria for phagocytosis. In addition, SR-AI modulates macrophage activation through cell signaling. However, investigation of SR-AI signaling on macrophages is complicated due to its promiscuous ligand specificity that overlaps with other macrophage receptors. Therefore, we expressed SR-AI on HEK 293T cells to investigate its ligand binding and signaling. On 293Tcells, SR-AI could respond to E. coli DH5α, leading to NF-κB activation and IL-8 production. However, this requires E. coli DH5α to be sensitized by fresh serum that is treated with heat-inactivation or complement C3 depletion. Anti-C3 antibody inhibits the binding of SR-AI to serum-sensitized DH5α and blocks DH5α stimulation of SR-AI signaling. Further analysis showed that SR-AI can directly bind to purified iC3b but not C3 or C3b. By mutagenesis, The SRCR domain of SR-AI was found to be essential in SR-AI binding to serum-sensitized DH5α. These results revealed a novel property of SR-AI as a complement receptor for iC3b-opsonized bacteria that can elicit cell signaling.
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Affiliation(s)
- Jason W K Goh
- Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Singapore
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6
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Robert P, Benoliel AM, Pierres A, Bongrand P. What is the biological relevance of the specific bond properties revealed by single-molecule studies? J Mol Recognit 2008; 20:432-47. [PMID: 17724759 DOI: 10.1002/jmr.827] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
During the last decade, many authors took advantage of new methodologies based on atomic force microscopy (AFM), biomembrane force probes (BFPs), laminar flow chambers or optical traps to study at the single-molecule level the formation and dissociation of bonds between receptors and ligands attached to surfaces. Experiments provided a wealth of data revealing the complexity of bond response to mechanical forces and the dependence of bond rupture on bond history. These results supported the existence of multiple binding states and/or reaction pathways. Also, single bond studies allowed us to monitor attachments mediated by a few bonds. The aim of this review is to discuss the impact of this new information on our understanding of biological molecules and phenomena. The following points are discussed: (i) which parameters do we need to know in order to predict the behaviour of an encounter between receptors and ligands, (ii) which information is actually yielded by single-molecule studies and (iii) is it possible to relate this information to molecular structure?
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7
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Li YF, Tang RH, Puan KJ, Law SKA, Tan SM. The cytosolic protein talin induces an intermediate affinity integrin alphaLbeta2. J Biol Chem 2007; 282:24310-9. [PMID: 17591777 DOI: 10.1074/jbc.m701860200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The integrin alphaLbeta2 mediates leukocyte adhesion and migration that are required for a functional immune system. It is known that inside-out signaling triggers alphaLbeta2 conformational changes, which affect its ligand-binding affinity. At least three alphaLbeta2 affinity states (low, intermediate, and high) were described. The cytosolic protein talin connects alphaLbeta2 to the actin filament. The talin head domain is also known to activate alphaLbeta2 ligand binding. However, it remains to be determined whether talin promotes an intermediate or high affinity alphaLbeta2. In this study using transfectants and T cells, we showed that talin induced an intermediate affinity alphaLbeta2 that adhered constitutively to its ligand intercellular adhesion molecule (ICAM)-1 but not ICAM-3. Adhesion to ICAM-3 was induced when an additional exogenous activating agent was included. Similar profiles were observed with soluble ICAMs. In addition, the intermediate affinity alphaLbeta2 induced by talin allowed adhesion and migration of T cells on immobilized ICAMs.
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Affiliation(s)
- Yan-Feng Li
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551
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8
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Tang ML, Kong LS, Law SKA, Tan SM. Down-regulation of integrin alpha M beta 2 ligand-binding function by the urokinase-type plasminogen activator receptor. Biochem Biophys Res Commun 2006; 348:1184-93. [PMID: 16905120 DOI: 10.1016/j.bbrc.2006.07.179] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2006] [Accepted: 07/28/2006] [Indexed: 10/24/2022]
Abstract
The cell adhesion molecule integrin alphaMbeta2 associates with the urokinase-type plasminogen activator receptor (uPAR) on monocytes and neutrophils. uPAR also associates with members of the beta1 and beta3 integrins, and it modulates the ligand-binding function of these integrins. In this study, we showed that co-expressing uPAR with alphaMbeta2 in 293 transfectants down-regulated the ligand-binding capacity of alphaMbeta2 to denatured protein, fibrinogen, and intercellular adhesion molecule 1 (ICAM-1). Migration of transfectants on fibrinogen mediated by alphaMbeta2 was reduced in the presence of uPAR. In addition, the constitutive ligand-binding property of an alphaMbeta2 mutant was attenuated by its association with uPAR. Co-immunoprecipitation analyses using a panel of alphaMbeta2-specific mAbs suggest shielding of the ligand-recognition site of alphaMbeta2 by uPAR.
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Affiliation(s)
- Man-Li Tang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
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9
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Tang RH, Law SKA, Tan SM. Selective recruitment of src family kinase Hck by leukocyte integrin αMβ2but not αLβ2or αXβ2. FEBS Lett 2006; 580:4435-42. [PMID: 16854414 DOI: 10.1016/j.febslet.2006.06.099] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Revised: 06/12/2006] [Accepted: 06/23/2006] [Indexed: 02/04/2023]
Abstract
Integrins are type I heterodimeric (alpha/beta) cell adhesion molecules. They trigger cell-signaling by recruiting cytosolic molecules to their cytoplasmic tails. Integrin alpha cytoplasmic tail contributes towards integrin function specificity, an important feature of integrins having different alpha subunits but sharing the same beta subunit. Herein, we show that the src family kinase Hck co-capped selectively with leukocyte integrin alpha(M)beta(2) but not alpha(L)beta(2) or alpha(X)beta(2). This was disrupted when the alpha(M) cytoplasmic tail was substituted with that of alpha(L) or alpha(X). Co-capping was recovered by alpha(L) or alpha(X) cytoplasmic tail truncation or forced separation of the alpha and beta cytoplasmic tails via salt-bridge disruption.
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Affiliation(s)
- Ren-Hong Tang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
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10
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Shi Y, Tohyama Y, Kadono T, He J, Miah SMS, Hazama R, Tanaka C, Tohyama K, Yamamura H. Protein-tyrosine kinase Syk is required for pathogen engulfment in complement-mediated phagocytosis. Blood 2006; 107:4554-62. [PMID: 16449524 DOI: 10.1182/blood-2005-09-3616] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The protein tyrosine kinase Syk plays a central role in Fcgamma receptor-mediated phagocytosis in the adaptive immune system. We show here that Syk also plays an essential role in complement-mediated phagocytosis in innate immunity. Macrophage-like differentiated HL60 cells and C3bi-opsonized zymosan comprised the pathogen-phagocyte system. C3bi-opsonized zymosan particles promptly attached to the cells and were subsequently engulfed via complement receptor 3. During this process, Syk became tyrosine phosphorylated and accumulated around the nascent phagosomes. The transfer of Syk-siRNA or dominant-negative Syk (DN-Syk) into HL60 cells resulted in impaired phagocytosis. Quenching assays using fluorescent zymosan revealed that most of the attached zymosan particles were located inside parental HL60 cells, whereas few were ingested by the mutant cells. These data indicated that Syk is required for the engulfment of C3bi-opsonized zymosan. During C3bi-zymosan-induced phagocytosis, actin accumulation occurred around phagosomes and was followed by depolymerization, and further RhoA was activated together with tyrosine phosphorylation of Vav. These responses including the actin remodeling were suppressed in Syk-siRNA- or DN-Syk-expressing cells. Our results demonstrated that Syk plays an indispensable role in complement-mediated phagocytosis by regulating both actin dynamics and the RhoA activation pathway and that these functions of Syk lead to phagosome formation and pathogen engulfment.
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Affiliation(s)
- Yuhong Shi
- Department of Genome Sciences, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
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11
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Vitte J, Benoliel AM, Eymeric P, Bongrand P, Pierres A. Beta-1 integrin-mediated adhesion may be initiated by multiple incomplete bonds, thus accounting for the functional importance of receptor clustering. Biophys J 2005; 86:4059-74. [PMID: 15189901 PMCID: PMC1304306 DOI: 10.1529/biophysj.103.038778] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The regulation of cell integrin receptors involves modulation of membrane expression, shift between different affinity states, and topographical redistribution on the cell membrane. Here we attempted to assess quantitatively the functional importance of receptor clustering. We studied beta-1 integrin-mediated attachment of THP-1 cells to fibronectin-coated surfaces under low shear flow. Cells displayed multiple binding events with a half-life of the order of 1 s. The duration of binding events after the first second after arrest was quantitatively accounted for by a model assuming the existence of a short-time intermediate binding state with 3.6 s(-1) dissociation rate and 1.3 s(-1) transition frequency toward a more stable state. Cell binding to surfaces coated with lower fibronectin densities was concluded to be mediated by single molecular interactions, whereas multiple bonds were formed <1 s after contact with higher fibronectin surface densities. Cell treatment with microfilament inhibitors or a neutral antiintegrin antibody decreased bond number without changing aforementioned kinetic parameters whereas a function enhancing antibody increased the rate of bond formation and/or the lifetime of intermediate state. Receptor aggregation was induced by treating cells with neutral antiintegrin antibody and antiimmunoglobulin antibodies. A semiquantitative confocal microscopy study suggested that this treatment increased between 40% and 100% the average number of integrin receptors located in a volume of approximately 0.045 microm(3) surrounding each integrin. This aggregation induced up to 2.7-fold increase of the average number of bonds. Flow cytometric analysis of fluorescent ligand binding showed that THP-1 cells displayed low-affinity beta-1 integrins with a dissociation constant in the micromolar range. It is concluded that the initial step of cell adhesion was mediated by multiple incomplete bonds rather than a single equilibrium-state ligand receptor association. This interpretation accounts for the functional importance of integrin clustering.
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Affiliation(s)
- Joana Vitte
- Laboratoire d'Immunologie, Institut National de la Sante et de la Recherche Medicale U600, Centre National de la Recherche Scientifique FRE2059, Hopital de Ste-Marguerite, Marseille, France
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12
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Vitte J, Pierres A, Benoliel AM, Bongrand P. Direct quantification of the modulation of interaction between cell- or surface-bound LFA-1 and ICAM-1. J Leukoc Biol 2004; 76:594-602. [PMID: 15240749 DOI: 10.1189/jlb.0204077] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The functional activity of leukocyte integrins is highly regulated by several mechanisms related to intrinsic molecular properties and receptor interaction with the cell membrane. Here, we present a microkinetic study of the lymphocyte function-associated antigen-1-mediated interaction between flowing Jurkat cells and surface- or cell-bound intercellular adhesion molecule-1 (ICAM-1). We conclude that adhesion is initiated by the formation of a single bond with approximately 0.3 s(-1) dissociation rate, and attachment is subsequently strengthened by the formation of additional bonds during the next 10 s; exposing cells to Mg2+ or Mn2+ resulted in up to a 16-fold increase of the binding frequency, in line with reported measurements performed on isolated molecules with surface plasmon resonance methodology; cell-bound ICAM-1 molecules were more efficient in mediating adhesion than Fc-ICAM-1, properly oriented and bound by surface-adsorbed protein A; and quantitative analysis of binding frequency suggested that adhesion efficiency was ten- to 100-fold lower than the maximum value allowed by previously determined association rates of soluble molecules. It is concluded that the presented methodology provides a simple and unique way of dissecting the initial step of cell adhesion and discriminating between affinity and avidity modulation of adhesion receptors.
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Affiliation(s)
- Joana Vitte
- Laboratory of Immunology, INSERM U600, CNRS FRE 2059, Univ. Mediterranée, Hôpital de Ste-Marguerite, 270 Bd de Ste-Marguerite, 13009 France
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13
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Bristow CL, Mercatante DR, Kole R. HIV-1 preferentially binds receptors copatched with cell-surface elastase. Blood 2003; 102:4479-86. [PMID: 12933574 DOI: 10.1182/blood-2003-05-1635] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human leukocyte elastase (HLE) interacts with HIV-1 glycoprotein (gp)41, suggesting a nonenzymatic receptor function for HLE in the context of HIV-1. HLE is found localized to the cell surface, but not granules in HIV permissive clones, and to granules, but not the cell surface of HIV nonpermissive clones. Inducing cell-surface HLE expression on HLE null, HIV nonpermissive clones permits HIV infectivity. HIV binding and infectivity diminish in proportion to HLE RNA subtraction. HIV binding and infectivity show dose dependence for the natural HLE ligand alpha1 proteinase inhibitor (alpha1antitrypsin, alpha1PI). Chemokines prevent, whereas alpha1PI promotes, copatching of HLE with the canonical HIV receptors. Recent demonstration that decreased viral RNA is significantly correlated with decreased circulating alpha1PI in HIV seropositive individuals is consistent with a model in which HLE and alpha1PI can serve as HIV coreceptor and cofactor, respectively, and potentially participate in the pathophysiology of HIV disease progression.
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Affiliation(s)
- Cynthia L Bristow
- Laboratory of Cellular Physiology and Immunology, The Rockefeller University and Population Council, New York, NY 10021, USA.
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14
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Xiong JP, Stehle T, Goodman SL, Arnaout MA. New insights into the structural basis of integrin activation. Blood 2003; 102:1155-9. [PMID: 12714499 DOI: 10.1182/blood-2003-01-0334] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Integrins are cell adhesion receptors that communicate biochemical and mechanical signals in a bidirectional manner across the plasma membrane and thus influence most cellular functions. Intracellular signals switch integrins into a ligand-competent state as a result of elicited conformational changes in the integrin ectodomain. Binding of extracellular ligands induces, in turn, structural changes that convey distinct signals to the cell interior. The structural basis of this bidirectional signaling has been the focus of intensive study for the past 3 decades. In this perspective, we develop a new hypothesis for integrin activation based on recent crystallographic, electron microscopic, and biochemical studies.
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Affiliation(s)
- Jian-Ping Xiong
- Renal Unit, Leukocyte Biology and Inflammation Program, Structural Biology Program, Massachusetts General Hospital, and Harvard Medical School, Charlestown, MA 02129, USA
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15
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Bansal VS, Vaidya S, Somers EP, Kanuga M, Shevell D, Weikel R, Detmers PA. Small molecule antagonists of complement receptor type 3 block adhesion and adhesion-dependent oxidative burst in human polymorphonuclear leukocytes. J Pharmacol Exp Ther 2003; 304:1016-24. [PMID: 12604677 DOI: 10.1124/jpet.102.045286] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The leukocyte integrin complement receptor type 3 (CR3, Mac-1, CD11b/CD18) is the predominant beta(2) integrin receptor of polymorphonuclear leukocytes (PMNs). This cell surface receptor plays a central role in innate immunity against pathogens as well as being a major cellular effector of inflammation and tissue injury. Two small molecules, compounds 1 and 2, have been identified, that interact with CR3 and prevent CR3 from binding to its natural ligand, C3bi. Compounds 1 and 2 have IC(50) values of 0.14 and 0.33 microM, respectively, for the inhibition of binding of monomeric C3bi-alkaline phosphatase to immobilized CR3. Both compounds also inhibit binding of CR3 to biotinylated sheep red blood cells opsonized with C3bi, with IC(50) values in the micromolar range. Inhibition of ligand binding by the compounds is not easily reversed and requires light, suggesting the formation of a covalent adduct through photoactivation. Compounds 1 and 2 also inhibit adhesion of human PMNs to fibrinogen in response to tumor necrosis factor (TNF) or PMA, with IC(50) values of 2.5 to >10 microM. They block the adhesion-dependent production of H(2)O(2) stimulated by TNF or phorbol 12-myristate 13-acetate (PMA) with IC(50) values of 0.2 to 0.8 microM and 1 to 3 microM, respectively. Limited structure-activity relationship studies based on compound 2 indicate the importance of the two benzothiazole rings, an ethyl side chain, and the length of the carbon chain linking the rings. Further modification of these groups may help in making compounds appropriate for in vivo studies.
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Affiliation(s)
- Vinay S Bansal
- Department of Pharmacology, Merck & Co., Rahway, New Jersey 07065, USA.
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16
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Shaw JM, Al-Shamkhani A, Boxer LA, Buckley CD, Dodds AW, Klein N, Nolan SM, Roberts I, Roos D, Scarth SL, Simmons DL, Tan SM, Law SK. Characterization of four CD18 mutants in leucocyte adhesion deficient (LAD) patients with differential capacities to support expression and function of the CD11/CD18 integrins LFA-1, Mac-1 and p150,95. Clin Exp Immunol 2001; 126:311-8. [PMID: 11703376 PMCID: PMC1906209 DOI: 10.1046/j.1365-2249.2001.01661.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Leucocyte adhesion deficiency (LAD) is a hereditary disorder caused by mutations in the CD18 (beta2 integrin) gene. Four missense mutations have been identified in three patients. CD18(A270V) supports, at a diminished level, CD11b/CD18 (Mac-1, alphaMbeta2 integrin) and CD11c/CD18 (p150,95, alphaXbeta2 integrin) expression and function but not CD11a/CD18 (LFA-1, alphaLbeta2 integrin) expression. Conversely, CD18(A341P) supports a limited level of expression and function of CD11a/CD18, but not of the other two CD11/CD18 antigens. CD18(C590R) and CD18(R593C) show a decreasing capacity to associate with the CD11a, CD11c and CD11b subunits. Transfectants expressing the CD11a/CD18 with the C590R and R593C mutations are more adhesive than transfectants expressing wild-type LFA-1, and express the reporter epitope of the monoclonal antibody 24 constitutively. Thus, the four mutations affect CD18 differently in its capacities to support CD11/CD18 expression and adhesion. These results not only provide a biochemical account for the clinical diversity of patients with leucocyte adhesion deficiency, but also offer novel insights into the structural basis of interaction between the alpha and beta subunits, which is an integral component in our understanding of integrin-mediated adhesion and its regulation.
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Affiliation(s)
- J M Shaw
- MRC Immunochemistry Unit, Department of Biochemistry, University of Oxford, UK
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17
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Sabri S, Soler M, Foa C, Pierres A, Benoliel A, Bongrand P. Glycocalyx modulation is a physiological means of regulating cell adhesion. J Cell Sci 2000; 113 ( Pt 9):1589-600. [PMID: 10751150 DOI: 10.1242/jcs.113.9.1589] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Here we present experimental evidence that phagocytic cells use modulation of specific components of their glycocalyx to regulate their binding capacity. Particles coated with antibodies specific for the CD32 medium affinity IgG receptor were driven along human monocytic THP-1 cells (expressing CD32) in a flow chamber operated at low shear rate. Surprisingly, only minimal adhesion was observed. However, when cells were activated by exposure to fibronectin-coated surfaces and/or soluble γ interferon, adhesion efficiency was dramatically increased, whereas the apparent glycocalyx thickness displayed 20% decrease, and the surface density of CD43/leukosialin carbohydrate epitopes displayed 30–40% decrease on activated cells. The existence of a causal link between adhesion increase and glycocalyx alteration was strongly supported by the finding that (i) both phenomena displayed similar kinetics, (ii) an inverse relationship between THP-1 cell binding capacity and glycocalyx density was demonstrated at the individual cell level, and (iii) adhesion enhancement could not be ascribed to an increased binding site density or improved functional capacity of activated cells. Additional experiments revealed that cell-to-particle adhesion resulted in delayed (i.e. more than a few minutes) egress of CD43/leukosialin from contact areas. Since the time scale of particle attachment was less than a second, surface mobility should not affect the potential of CD43 to impair the initial step of adhesion. Finally, studies performed with fluorescent lectins suggested that THP-1 cell activation and increased adhesive potential were related to a decrease of O-glysosylation rather than N-glycosylation of surface glycoproteins.
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Affiliation(s)
- S Sabri
- Laboratoire d'Immunologie, INSERM U 387, Hôpital de Sainte-Marguerite, BP 29, France
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18
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Vanek NN, Simon SI, Jacques-Palaz K, Mariscalco MM, Dunny GM, Rakita RM. Enterococcus faecalis aggregation substance promotes opsonin-independent binding to human neutrophils via a complement receptor type 3-mediated mechanism. FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY 1999; 26:49-60. [PMID: 10518042 DOI: 10.1111/j.1574-695x.1999.tb01371.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Enterococcus faecalis aggregation substance (AS) mediates efficient adhesion between bacteria, thereby facilitating plasmid exchange as an integral part of a bacterial sex pheromone system. We examined the interaction of AS-bearing E. faecalis with human neutrophils (PMNs), an important component of the host defense system. AS promoted a markedly increased opsonin-independent bacterial binding to PMNs. Adhesion was dependent on the expression of the enterococcal Asc10 protein, which contains two Arg-Gly-Asp (RGD) sequences, and addition of exogenous RGD-containing peptides inhibited AS-mediated binding by 66%. AS-mediated adhesion was inhibited by 85% by anti-human complement receptor type 3 (CR3) monoclonal antibodies or by use of PMNs from a patient with leukocyte adhesion deficiency. However, AS-bearing E. faecalis cells were unable to bind to CHO-Mac-1 cells, expressing functionally active CR3, suggesting the potential need for additional PMN surface receptors for bacterial adhesion. Monoclonal antibodies against integrin-associated protein (CD47) and L-selectin, both of which may interact with CR3 and bind to ligands on E. faecalis, also inhibited AS-dependent binding. The non-opsonic binding of E. faecalis to PMNs may play an important role in this organism's pathogenesis.
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Affiliation(s)
- N N Vanek
- Division of Infectious Diseases, Department of Internal Medicine and Center for the Study of Emerging and Reemerging Pathogens, University of Texas Medical School, Houston, TX 77030, USA
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19
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Masson-Gadais B, Pierres A, Benoliel AM, Bongrand P, Lissitzky JC. Integrin (alpha) and beta subunit contribution to the kinetic properties of (alpha)2beta1 collagen receptors on human keratinocytes analyzed under hydrodynamic conditions. J Cell Sci 1999; 112 ( Pt 14):2335-45. [PMID: 10381389 DOI: 10.1242/jcs.112.14.2335] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The adhesion of keratinocytes to type I collagen or laminin 5 was studied in a laminar flow chamber. These experiments provided an insight into the binding kinetics of integrins in their natural environment and the effects of monoclonal antibodies specific for (alpha) and beta chains. Cells driven by a force too low to alter the natural lifetime of a single bond displayed multiple arrests. Studying the frequency and duration of these arrests yielded fairly direct information on the rate of bond formation (on-rate) and dissociation (off-rate). Off-rate values obtained on collagen or laminin 5 (0.06 seconds-1) were tenfold lower than values determined on selectins. Bond stability was strongly regulated by anti-beta1 chain antibodies since the off-rate was decreased sixfold by activating antibody TS2/16 and increased fivefold by inhibitory antibodies Lia1/2 or P4C10, whereas neutral antibody K20 had no effect on this parameter. Binding frequencies were not significantly changed by all these antibodies. In contrast, both binding frequency and off-rate were altered by antibodies specific for the (alpha)2 chain, suggesting that these antibodies interfered with ligand recognition and also with the ligand-beta1 chain interactions responsible for bond stabilization. The latter hypothesis was supported by the finding that the partial alteration of (alpha)2 chain function by inhibiting antibodies was corrected by anti-beta1 chain antibody TS2/16. These results could not be ascribed to allosteric changes of the functional region of beta1 integrin subunits regulated by TS2/16 since there was no competition between the binding of TS2/16 and anti-(alpha)2 chain antibodies. Interpreted within the framework of current concepts of integrin-ligand binding topology, these data suggest that ligand-alpha chain interactions may be qualitatively important in ligand recognition and also influence the formation of the ligand-beta1 subunit bonding involved in stabilization of the ligand-integrin complex by regulating its dissociation rate.
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Affiliation(s)
- B Masson-Gadais
- Laboratoire d'Immunologie, INSERM U 387, Hôpital de Sainte-Marguerite, BP 29, France
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20
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Wakshull E, Brunke-Reese D, Lindermuth J, Fisette L, Nathans RS, Crowley JJ, Tufts JC, Zimmerman J, Mackin W, Adams DS. PGG-glucan, a soluble beta-(1,3)-glucan, enhances the oxidative burst response, microbicidal activity, and activates an NF-kappa B-like factor in human PMN: evidence for a glycosphingolipid beta-(1,3)-glucan receptor. IMMUNOPHARMACOLOGY 1999; 41:89-107. [PMID: 10102791 DOI: 10.1016/s0162-3109(98)00059-9] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
PGG-Glucan, a soluble beta-(1,6)-branched beta-(1,3)-linked glucose homopolymer derived from the cell wall of the yeast Saccharomyces cerevisiae, is an immunomodulator which enhances leukocyte anti-infective activity and enhances myeloid and megakaryocyte progenitor proliferation. Incubation of human whole blood with PGG-Glucan significantly enhanced the oxidative burst response of subsequently isolated blood leukocytes to both soluble and particulate activators in a dose-dependent manner, and increased leukocyte microbicidal activity. No evidence for inflammatory cytokine production was obtained under these conditions. Electrophoretic mobility shift assays demonstrated that PGG-Glucan induced the activation of an NF-kappaB-like nuclear transcription factor in purified human neutrophils. The binding of 3H-PGG-Glucan to human leukocyte membranes was specific, concentration-dependent, saturable, and high affinity (Kd approximately 6 nM). A monoclonal antibody specific to the glycosphingolipid lactosylceramide was able to inhibit activation of the NF-kappaB-like factor by PGG-Glucan, and ligand binding data, including polysaccharide specificity, suggested that the PGG-Glucan binding moiety was lactosylceramide. These results indicate that PGG-Glucan enhances neutrophil anti-microbial functions and that interaction between this beta-glucan and human neutrophils is mediated by the glycosphingolipid lactosylceramide present at the cell surface.
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Affiliation(s)
- E Wakshull
- Department of Biology, Alpha-Beta Technology, Worcester, MA 01605, USA.
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21
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Li R, Rieu P, Griffith DL, Scott D, Arnaout MA. Two functional states of the CD11b A-domain: correlations with key features of two Mn2+-complexed crystal structures. J Biophys Biochem Cytol 1998; 143:1523-34. [PMID: 9852148 PMCID: PMC2132978 DOI: 10.1083/jcb.143.6.1523] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In the presence of bound Mn2+, the three- dimensional structure of the ligand-binding A-domain from the integrin CR3 (CD11b/CD18) is shown to exist in the "open" conformation previously described only for a crystalline Mg2+ complex. The open conformation is distinguished from the "closed" form by the solvent exposure of F302, a direct T209-Mn2+ bond, and the presence of a glutamate side chain in the MIDAS site. Approximately 10% of wild-type CD11b A-domain is present in an "active" state (binds to activation-dependent ligands, e.g., iC3b and the mAb 7E3). In the isolated domain and in the holoreceptor, the percentage of the active form can be quantitatively increased or abolished in F302W and T209A mutants, respectively. The iC3b-binding site is located on the MIDAS face and includes conformationally sensitive residues that undergo significant shifts in the open versus closed structures. We suggest that stabilization of the open structure is independent of the nature of the metal ligand and that the open conformation may represent the physiologically active form.
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Affiliation(s)
- R Li
- Leukocyte Biology and Inflammation Program, Renal Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA
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22
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Simon SI, Neelamegham S, Taylor A, Smith CW. The multistep process of homotypic neutrophil aggregation: a review of the molecules and effects of hydrodynamics. CELL ADHESION AND COMMUNICATION 1998; 6:263-76. [PMID: 9823477 DOI: 10.3109/15419069809004482] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Homotypic adhesion of neutrophils stimulated with chemoattractant is analogous to capture on vascular endothelium in that both processes are supported by L-selectin and beta 2-integrin adhesion receptors. Under hydrodynamic shear, cell adhesion requires that receptors bind sufficient ligand over the duration of intercellular contact to withstand the hydrodynamic stresses. Using cone and plate viscometry to apply a uniform linear shear field to suspensions of neutrophils and flow cytometry to quantitate the size distribution of aggregates formed over the time course of formyl peptide stimulation, we conducted a detailed examination of the affect of shear rate and shear stress on the kinetics of cell aggregation. The efficiency of aggregate formation was fit from a mathematical model based on Smoluchowski's two-body collision theory. Over a range of venular shear rates (400-800 s-1), approximately 90% of the single cells are recruited into aggregates ranging from doublets to grouping larger than sextuplets. Adhesion efficiency fit to the kinetics of aggregation increased with shear rate from approximately 20% at 100 s-1 to a maximum level of approximately 80% at 400 s-1. This increase to peak adhesion efficiency was dependent on L-selectin and beta 2-integrin, and was resistant to shear stress up to approximately 7 dyn/cm2. When L-selectin was blocked with antibody, beta 2-integrin (CD11a,b) supported adhesion at low shear rates (< 400 s-1). Aggregates formed over the rapid phase of aggregation remain intact and resistant to shear up to 120 s. At the end of this plateau phase of stability, aggregates spontaneously dissociate back to singlets. The rate of cell disaggregation is linearly proportional to the applied shear rate. The binding kinetics of selectin and integrin appear to be optimized to function within discrete ranges of shear rate and stress, providing an intrinsic mechanism for the transition from neutrophil tethering to firm but reversible adhesion.
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Affiliation(s)
- S I Simon
- Department of Pediatrics, Speros P. Martel Section of Leukocyte Biology, Houston, TX 77030, USA.
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23
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Vines RR, Ramakrishnan G, Rogers JB, Lockhart LA, Mann BJ, Petri WA. Regulation of adherence and virulence by the Entamoeba histolytica lectin cytoplasmic domain, which contains a beta2 integrin motif. Mol Biol Cell 1998; 9:2069-79. [PMID: 9693367 PMCID: PMC25460 DOI: 10.1091/mbc.9.8.2069] [Citation(s) in RCA: 121] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/1998] [Accepted: 05/13/1998] [Indexed: 11/11/2022] Open
Abstract
Killing of human cells by the parasite Entamoeba histolytica requires adherence via an amebic cell surface lectin. Lectin activity in the parasite is regulated by inside-out signaling. The lectin cytoplasmic domain has sequence identity with a region of the beta2 integrin cytoplasmic tail implicated in regulation of integrin-mediated adhesion. Intracellular expression of a fusion protein containing the cytoplasmic domain of the lectin has a dominant negative effect on extracellular lectin-mediated cell adherence. Mutation of the integrin-like sequence abrogates the dominant negative effect. Amebae expressing the dominant negative mutant are less virulent in an animal model of amebiasis. These results suggest that inside-out signaling via the lectin cytoplasmic domain may control the extracellular adhesive activity of the amebic lectin and provide in vivo demonstration of the lectin's role in virulence.
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Affiliation(s)
- R R Vines
- Department of Microbiology, University of Virginia, Charlottesville, Virginia 22908, USA
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24
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Labadia ME, Jeanfavre DD, Caviness GO, Morelock MM. Molecular Regulation of the Interaction Between Leukocyte Function-Associated Antigen-1 and Soluble ICAM-1 by Divalent Metal Cations. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.161.2.836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
Surface plasmon resonance (SPR) was used to investigate and characterize the interaction between LFA-1 and sICAM-1 (a soluble form of ICAM-1). Full-length LFA-1 was immobilized on a hydrophobic surface, and sICAM-1 binding was monitored in a flow cell format. The binding of sICAM-1 to LFA-1 was specific and dependent upon Mg2+; Abs to both sICAM-1 and LFA-1 blocked the interaction, and EDTA abolished all binding. Association and dissociation rate constants (ka and kd, respectively) for sICAM-1 were 2.24 × 105 M−1 s−1 and 2.98 × 10−2 s−1, respectively, giving a calculated KICAM of 133 nM. Since the LFA-1/ICAM-1 interaction is highly sensitive to the presence of metal cations, SPR was also used to probe the affinity of the metal binding sites. The KMg values were 160 and 12 μM in the absence (EGTA) and the presence of Ca2+ (100 μM), respectively; in addition, KMn was 2 μM in the presence of Ca2+ (100 μM). Increasing Ca2+ into the millimolar concentration range, however, resulted in a competitive displacement of Mg2+/Mn2+ and decreased sICAM-1 binding. Based on these data, a synergistic model for the molecular regulation of LFA-1 by divalent metal cations is proposed, and implications to cellular adhesion are discussed.
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Affiliation(s)
- Mark E. Labadia
- Department of Biology, Boehringer Ingelheim Pharmaceuticals, Research and Development Center, Ridgefield, CT 06877
| | - Deborah Durham Jeanfavre
- Department of Biology, Boehringer Ingelheim Pharmaceuticals, Research and Development Center, Ridgefield, CT 06877
| | - Gary O. Caviness
- Department of Biology, Boehringer Ingelheim Pharmaceuticals, Research and Development Center, Ridgefield, CT 06877
| | - Maurice M. Morelock
- Department of Biology, Boehringer Ingelheim Pharmaceuticals, Research and Development Center, Ridgefield, CT 06877
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25
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Waltz DA, Natkin LR, Fujita RM, Wei Y, Chapman HA. Plasmin and plasminogen activator inhibitor type 1 promote cellular motility by regulating the interaction between the urokinase receptor and vitronectin. J Clin Invest 1997; 100:58-67. [PMID: 9202057 PMCID: PMC508165 DOI: 10.1172/jci119521] [Citation(s) in RCA: 214] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The urokinase receptor (uPAR) coordinates plasmin-mediated cell-surface proteolysis and promotes cellular adhesion via a binding site for vitronectin on uPAR. Because vitronectin also binds plasminogen activator inhibitor type 1 (PAI-1), and plasmin cleavage of vitronectin reduces PAI-1 binding, we explored the effects of plasmin and PAI-1 on the interaction between uPAR and vitronectin. PAI-1 blocked cellular binding of and adhesion to vitronectin by over 80% (IC50 approximately 5 nM), promoted detachment of uPAR-bearing cells from vitronectin, and increased cellular migration on vitronectin. Limited cleavage of vitronectin by plasmin also abolished cellular binding and adhesion and induced cellular detachment. A series of peptides surrounding a plasmin cleavage site (arginine 361) near the carboxy-terminal end of vitronectin were synthesized. Two peptides spanning res 364-380 blocked binding of uPAR to vitronectin (IC50 approximately 8-25 microM) identifying this region as an important site of uPAR-vitronectin interaction. These data illuminate a complex regulatory scheme for uPAR-dependent cellular adhesion to vitronectin: Active urokinase promotes adhesion and also subsequent detachment through activation of plasmin or complex formation with PAI-1. Excess PAI-1 may also promote migration by blocking cellular adhesion and/or promoting detachment, possibly accounting in part for the strong correlation between PAI-1 expression and tumor cell metastasis.
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Affiliation(s)
- D A Waltz
- Division of Respiratory Diseases, Children's Hospital, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts 02115, USA.
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26
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Mandeville JT, Maxfield FR. Effects of buffering intracellular free calcium on neutrophil migration through three-dimensional matrices. J Cell Physiol 1997; 171:168-78. [PMID: 9130464 DOI: 10.1002/(sici)1097-4652(199705)171:2<168::aid-jcp7>3.0.co;2-m] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Repeated transient increases in intracellular free calcium levels ([Ca2-]i) are required for polymorphonuclear neutrophil migration on two-dimensional surfaces coated with fibronectin or vitronectin. Cells in which [Ca2+]i is buffered with quin2 become stuck on these substrates. Neutrophils migrating through the extracellular matrix in vivo encounter these and other substrates in a three-dimensional architecture that may alter the spatial distribution of adhesion receptors in contact with the matrix. In this study, we used fluorescence confocal microscopy to obtain moving three-dimensional images of neutrophils migrating through a biological tissue (human amnion) in the presence and absence of [Ca2+]i-buffering with quin2. In the absence of buffering, [Ca2+]i transients similar to those seen in cells migrating in two-dimensions were observed. [Ca2+]i-buffered neutrophils were able to migrate into the matrix, but they became attached firmly to the substrate at the rear of the cell, resulting in a drastically elongated morphology. Immunofluorescence revealed that neutrophils adhered to regions of the matrix that contained fibronectin. RGD-containing peptides and antibodies that block integrin adhesion receptors for fibronectin and vitronectin were able to rescue the migration of quin2-treated cells through three-dimensional gels containing fibronectin and vitronectin. These data show that neutrophils migrating through physiologically relevant, three-dimensional matrices undergo repetitive increases in [Ca2+]i that are required for integrin-mediated detachment from the matrix.
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Affiliation(s)
- J T Mandeville
- Department of Pathology, Columbia University College of Physicians and Surgeons, New York, New York 10021, USA
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27
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Taylor AD, Neelamegham S, Hellums JD, Smith CW, Simon SI. Molecular dynamics of the transition from L-selectin- to beta 2-integrin-dependent neutrophil adhesion under defined hydrodynamic shear. Biophys J 1996; 71:3488-500. [PMID: 8968618 PMCID: PMC1233836 DOI: 10.1016/s0006-3495(96)79544-9] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Homotypic adhesion o2 neutrophils stimulated with chemoattractant is analogous to capture on vascular endothelium in that both processes depend on L-selectin and beta 2-integrin adhesion receptors. Under hydrodynamic shear, cell adhesion requires that receptors bind sufficient ligand over the duration of intercellular contact to withstand hydrodynamic stresses. Using cone-plate viscometry to apply a uniform linear shear field to suspensions of neutrophils, we conducted a detailed examination of the effect of shear rate and shear stress on the kinetics of cell aggregation. A collisional analysis based on Smoluchowski's flocculation theory was employed to fit the kinetics of aggregation with an adhesion efficiency. Adhesion efficiency increased with shear rate from approximately 20% at 100 s-1 to approximately 80% at 400 s-1. The increase in adhesion efficiency. Adhesion efficiency increased with shear rate from approximately 20% at 100 s-1 to approximately 80% at 400 s-1. The increase in adhesion efficiency with shear was dependent on L-selectin, and peak efficiency was maintained over a relatively narrow range of shear rates (400-800 s-1) and shear stresses (4-7 dyn/cm2). When L-selectin was blocked with antibody, beta 2-integrin (CD11a, b) supported adhesion at low shear rates (< 400 s-1). The binding kinetics of selectin and integrin appear to be optimized to function within discrete ranges of shear rate and stress, providing an intrinsic mechanism for the transition from neutrophil tethering to stable adhesion.
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Affiliation(s)
- A D Taylor
- Cox Laboratories for Biomedical Engineering, Rice University, Houston, Texas, USA
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28
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Cai TQ, Wright SD. Human leukocyte elastase is an endogenous ligand for the integrin CR3 (CD11b/CD18, Mac-1, alpha M beta 2) and modulates polymorphonuclear leukocyte adhesion. J Exp Med 1996; 184:1213-23. [PMID: 8879192 PMCID: PMC2192826 DOI: 10.1084/jem.184.4.1213] [Citation(s) in RCA: 140] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Integrin CR3 (CD11b/CD18, Mac-1, alpha M beta 2) mediates the transient adhesion of polymorphonuclear leukocytes (PMN) to surfaces coated with fibrinogen, C3bi, ICAM-1, and other ligands. Recent studies (Cai, T.-Q., and S.D. Wright 1995. J. Biol. Chem. 270:14358) suggest that adhesion may be favored by stimulus-dependent changes in the kinetics of ligand binding by CR3. Cell detachment, on the other hand, must occur by a different mechanism because binding kinetics cannot affect cell adhesion after binding of ligand has occurred. We have sought a mechanism that would reverse binding of ligand to CR3 and report here that lysates of PMN contain an endogenous ligand that binds CR3 and competes the binding of C3bi. Purification and sequence analysis identified the structurally homologous azurophilic granule proteins, elastase, protease 3, and azurocidin as candidates. Studies with purified elastase and azurocidin showed that each bound specifically to purified, immobilized CR3. Elastase may play a role in modulating integrin-mediated cell adhesion because it is expressed at the cell surface, and the expression level is inversely proportional to cell adhesivity. Furthermore, a monoclonal antibody against elastase prevented detachment of PMN from fibrinogen-coated surfaces and blocked chemotaxis, confirming a role for this protein in regulating integrin-mediated adhesion. These studies suggest a model for release of integrin-mediated cell adhesion in which endogenous ligands such as elastase may release adhesion by "'eluting" substrate-bound ligand. A role for the proteolytic activity of elastase appears likely but is not demonstrated in this study.
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Affiliation(s)
- T Q Cai
- Laboratory of Cellular Physiology and Immunology, Rockefeller University, New York 10021, USA
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29
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Qu A, Leahy DJ. The role of the divalent cation in the structure of the I domain from the CD11a/CD18 integrin. Structure 1996; 4:931-42. [PMID: 8805579 DOI: 10.1016/s0969-2126(96)00100-1] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND The integrin family of cell-surface receptors mediates a wide variety of cell-cell and cell-extracellular matrix interactions. Integrin-ligand interactions are invariably dependent on the presence of divalent cations, and a subset of integrins contain a approximately 200 amino acid inserted (I) domain that is important for ligand binding activity and contains a single divalent cation binding site. Many integrins are believed to respond to stimuli by undergoing a conformational change that increases their affinity for ligand, and there is a clear difference between two crystal structures of the CD11b I domain with different divalent cations (magnesium and manganese) bound. In addition to the different bound cation, a 'ligand mimetic' crystal lattice interaction in the CD11b I domain structure with bound magnesium has led to the interpretation that the different CD11b I domain structures represent different affinity states of I domains. The influence of the bound cation on I domain structure and function remains incompletely understood, however. The crystal structure of the CD11a I domain bound to manganese is known. We therefore set out to determine whether this structure changes when the metal ion is altered or removed. RESULTS We report here the crystal structures of the CD11a I domain determined in the absence of bound metal ion and with bound magnesium ion. No major structural rearrangements are observed in the metal-binding site of the CD11a I domain in the absence or presence of bound manganese ion. The structures of the CD11a I domain with magnesium or manganese bound are extremely similar. CONCLUSIONS The conformation of the CD11a I domain is not altered by changes in metal ion binding. The cation-dependence of ligand binding thus indicates that the metal ion is either involved in direct interaction with ligand or required to promote a favorable quaternary arrangement of the integrin.
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Affiliation(s)
- A Qu
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA
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30
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Abstract
Leukocytes circulate freely in the bloodstream until receiving signals which activate adhesive mechanisms essential for immune responsiveness. Key mediators of these adhesion events are heterodimeric cell surface receptors called integrins. It is now apparent that several components may contribute to successful integrin-mediated adhesion: alterations in individual receptors lead to enhanced affinity for ligand; integrin clustering causes an increase in avidity; by spreading, the adhering cell is less susceptible to shear force. Model systems have allowed us to examine the contribution of each of these factors in generating adhesion. In more physiologically relevant situations, it can now be questioned whether integrin-mediated adhesion is regulated via alterations in receptor affinity or avidity, or whether both these mechanisms are involved.
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Affiliation(s)
- M Stewart
- Leukocyte Adhesion Laboratory, Imperial Cancer Research Fund, London, United Kingdom
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31
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Abstract
The destructive potential of leucocytes needs to be fully held in check in the circulation, while being released at the site of tissue destruction and infection. Leucocyte adhesion molecules are the key to this regulation, the recognition by the leucocytes of areas of tissue damage, and to transendothelial migration of leucocytes into these areas. The three classes of leucocyte adhesion molecules-the integrins, selectins and immunoglobulin superfamily members-are reviewed with their ligands and presented in the context of leucocyte migration, activation and host defence.
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Affiliation(s)
- E J Brown
- Department of Infectious Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA
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32
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Pelletier AJ, Kunicki T, Quaranta V. Activation of the integrin alpha v beta 3 involves a discrete cation-binding site that regulates conformation. J Biol Chem 1996; 271:1364-70. [PMID: 8576125 DOI: 10.1074/jbc.271.3.1364] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
"Activation" of integrins is involved in the dramatic transition of leukocytes and platelets from suspension to adhesion. The integrin alpha v beta 3 is not known to take part in this sort of transition, even though it shares its beta subunit with alpha IIb beta 3, the activable integrin on platelets. In the context of a constitutively adhered cell, changes in activation state may be more subtle in their effects, but nonetheless important in regulating cell behavior. We hypothesized that alpha v beta 3 can undergo conformational changes analogous to those associated with alpha IIb beta 3 activation. Accordingly, we examined alpha v beta 3 on the surface of M21 cells (a human melanoma cell line) and found that, like alpha IIb beta 3, it can undergo conformational changes upon binding of a ligand analog and can be activated for ligand binding and migration by a monoclonal antibody directed against beta 3. Modulation of the binding of this activating antibody, AP5, ligand binding, and antibody-mediated activation all are associated with a discrete cation-binding site shared in both alpha IIb beta 3 and alpha v beta 3. Based on a measured Ki, this site has an apparent Kd for calcium of approximately 20 microM. At physiological levels of calcium, about 40% of the total alpha v beta 3 on a cell's surface is in a conformation detected by AP5. The data suggest a model for both alpha v beta 3 and alpha IIb beta 3 function in which the molecule can exist in either of (at least) two conformational states, one stabilized either by AP5 or ligand binding, refractory to calcium binding, and enhanced for ligand recognition, the other stabilized by calcium binding and refractory to AP5 and ligand binding. Functional analysis suggests that AP5 activates alpha v beta 3 by preventing occupation of this calcium site, and that the activated form of alpha v beta 3 differs functionally from the basal form. The active form is more conducive to migration and the basal to tight adhesion.
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Affiliation(s)
- A J Pelletier
- Department of Cell Biology, Scripps Research Institute, La Jolla, California 92037, USA
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Cai TQ, Law SK, Zhao HR, Wright SD. Reversible inactivation of purified leukocyte integrin CR3 (CD11b/CD18, alpha m beta 2) by removal of divalent cations from a cryptic site. CELL ADHESION AND COMMUNICATION 1995; 3:399-406. [PMID: 8640377 DOI: 10.3109/15419069509081294] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Integrins exhibit reversible changes in their ability to bind ligands and these changes enable transient cell adhesion. We recently showed that leukocyte integrin CR3 (complement receptor type three, CD11b/CD18, alpha m beta 2) may be purified in a form that is either capable or incapable of binding soluble, monomeric ligand and that "inactive" CR3 may be rendered capable of binding ligand by addition of an anti-CR3 mAb known as KIM-127 (Cai and Wright, JBC. 270: 14358, 1995). Here, we demonstrate that active CR3 may be rendered inactive by treatment of immobilized receptor with EDTA. EDTA-treated CR3 failed to bind ligand even in the presence of mM Ca2+ and Mg2+, suggesting that EDTA-treatment caused a change in the receptor that is not readily reversed. EDTA-treated receptor did, however, bind ligand upon addition of KIM-127 plus Mg2+ with an affinity (17.8 +/- 4.5 nM) similar to untreated, active receptor (12.5 +/- 4.7 nM). EDTA-treated CR3 thus exhibits the properties of inactive CR3, in which the ligand binding site is cryptic but subject to exposure by KIM-127. A candidate for the cryptic ligand binding site is the I-domain, a Mg2+-binding region in the alpha chain of CR3. We found that monomeric C3bi binds directly to recombinant I-domain in a Mg(2+)-dependent fashion with an affinity of 300 +/- 113 nM. These results thus suggest that CR3 may be inactivated by removing tightly bound divalent cation from a cryptic site in CR3.
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Affiliation(s)
- T Q Cai
- Laboratory of Cellular Physiology and Immunology, Rockefeller University, New York, NY 10021, USA
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