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Hooley E, Papagrigoriou E, Navdaev A, Pandey AV, Clemetson JM, Clemetson KJ, Emsley J. The crystal structure of the platelet activator aggretin reveals a novel (alphabeta)2 dimeric structure. Biochemistry 2008; 47:7831-7. [PMID: 18597489 DOI: 10.1021/bi800528t] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Aggretin is a C-type lectin purified from Calloselasma rhodostoma snake venom. It is a potent activator of platelets, resulting in a collagen-like response by binding and clustering platelet receptor CLEC-2. We present here the crystal structure of aggretin at 1.7 A which reveals a unique tetrameric quaternary structure. The two alphabeta heterodimers are arranged through 2-fold rotational symmetry, resulting in an antiparallel side-by-side arrangement. Aggretin thus presents two ligand binding sites on one surface and can therefore cluster ligands in a manner reminiscent of convulxin and flavocetin. To examine the molecular basis of the interaction with CLEC-2, we used a molecular modeling approach of docking the aggretin alphabeta structure with the CLEC-2 N-terminal domain (CLEC-2N). This model positions the CLEC-2N structure face down in the "saddle"-shaped binding site which lies between the aggretin alpha and beta lectin-like domains. A 2-fold rotation of this complex to generate the aggretin tetramer reveals dimer contacts for CLEC-2N which bring the N- and C-termini into the proximity of each other, and a series of contacts involving two interlocking beta-strands close to the N-terminus are described. A comparison with homologous lectin-like domains from the immunoreceptor family reveals a similar but not identical dimerization mode, suggesting this structure may represent the clustered form of CLEC-2 capable of signaling across the platelet membrane.
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Affiliation(s)
- Elizabeth Hooley
- Centre for Biomolecular Sciences, School of Pharmacy, University of Nottingham, UK
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152
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Valera I, Fernández N, Trinidad AG, Alonso S, Brown GD, Alonso A, Crespo MS. Costimulation of dectin-1 and DC-SIGN triggers the arachidonic acid cascade in human monocyte-derived dendritic cells. THE JOURNAL OF IMMUNOLOGY 2008; 180:5727-36. [PMID: 18390758 DOI: 10.4049/jimmunol.180.8.5727] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Inflammatory mediators derived from arachidonic acid (AA) alter the function of dendritic cells (DC), but data regarding their biosynthesis resulting from stimulation of opsonic and nonopsonic receptors are scarce. To address this issue, the production of eicosanoids by human monocyte-derived DC stimulated via receptors involved in Ag recognition was assessed. Activation of FcgammaR induced AA release, short-term, low-grade PG biosynthesis, and IL-10 production, whereas zymosan, which contains ligands of both the mannose receptor and the human beta-glucan receptor dectin-1, induced a wider set of responses including cyclooxygenase 2 induction and biosynthesis of leukotriene C(4) and IL-12p70. The cytosolic phospholipase A(2) inhibitor pyrrolidine 1 completely inhibited AA release stimulated via all receptors, whereas the spleen tyrosine kinase (Syk) inhibitors piceatannol and R406 fully blocked AA release in response to immune complexes, but only partially blocked the effect of zymosan. Furthermore, anti-dectin-1 mAb partially inhibited the response to zymosan, and this inhibition was enhanced by mAb against DC-specific ICAM-3-grabbing nonintegrin (SIGN). Immunoprecipitation of DC lysates showed coimmunoprecipitation of DC-SIGN and dectin-1, which was confirmed using Myc-dectin-1 and DC-SIGN constructs in HEK293 cells. These data reveal a robust metabolism of AA in human DC stimulated through both opsonic and nonopsonic receptors. The FcgammaR route depends on the ITAM/Syk/cytosolic phospholipase A(2) axis, whereas the response to zymosan involves the interaction with the C-type lectin receptors dectin-1 and DC-SIGN. These findings help explain the distinct functional properties of DC matured by immune complexes vs those matured by beta-glucans.
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Affiliation(s)
- Isela Valera
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, Valladolid, Spain
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153
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Watson AA, Eble JA, O'Callaghan CA. Crystal structure of rhodocytin, a ligand for the platelet-activating receptor CLEC-2. Protein Sci 2008; 17:1611-6. [PMID: 18583525 DOI: 10.1110/ps.035568.108] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Binding of the snake venom protein rhodocytin to CLEC-2, a receptor on the surface of human platelets, initiates a signaling cascade leading to platelet activation and aggregation. We have previously solved the structure of CLEC-2. The 2.4 A resolution crystal structure of rhodocytin presented here demonstrates that it is the first snake venom or other C-type lectin-like protein to assemble as a non-disulfide linked (alphabeta)(2) tetramer. Rhodocytin is highly adapted for interaction with CLEC-2 and displays a concave binding surface, which is highly complementary to the experimentally determined binding interface on CLEC-2. Using computational dynamic methods, surface electrostatic charge and hydrophobicity analyses, and protein-protein docking predictions, we propose that the (alphabeta)(2) rhodocytin tetramer induces clustering of CLEC-2 receptors on the platelet surface, which will trigger major signaling events resulting in platelet activation and aggregation.
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Affiliation(s)
- Aleksandra A Watson
- Henry Wellcome Building for Molecular Physiology, University of Oxford, Oxford OX3 7BN, United Kingdom
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154
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Riba R, Hughes CE, Graham A, Watson SP, Naseem KM. Globular adiponectin induces platelet activation through the collagen receptor GPVI-Fc receptor gamma chain complex. J Thromb Haemost 2008; 6:1012-20. [PMID: 18419742 DOI: 10.1111/j.1538-7836.2008.02982.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND The adipocyte-derived cytokine, adiponectin (Ad), exerts potent vascular effects, although the direct effects of Ad on blood platelets are unclear. OBJECTIVE The influence of globular Ad (gAd) on blood platelet function was investigated. RESEARCH DESIGN AND METHODS We measured platelet aggregation and tyrosine phosphorylation signaling events in human and mouse platelets. The ability of gAd to activate Glycoprotein VI (GPVI) activity was determined with a NFAT luciferase reporter assay. RESULTS gAd, but not full length Ad, induced rapid aggregation and granule secretion of human and mouse platelets through a pathway that is ablated under conditions of Src kinase inhibition, indicating a tyrosine kinase-dependent mechanism. Consistent with this, gAd stimulates rapid tyrosine phosphorylation of several proteins in human and mouse platelets. The pattern of increase in tyrosine phosphorylation was similar to that induced by collagen, with the tyrosine kinase Syk and PLCgamma2 being identified among the list of tyrosine phosphorylated proteins. As collagen activates platelet through the GPVI-Fc receptor gamma-chain (FcRgamma) complex, we used FcRgamma null platelets (which also lack GPVI) to explore the mechanism by which gAd stimulates platelets. Stimulation of tyrosine phosphorylation and platelet aggregation by gAd was abolished in FcRgamma null platelets and markedly reduced in the absence of PLCgamma2. Further, GPVI was confirmed as a collagen receptor for gAd by increased luciferase activity in Jurkat T-cells transfected with GPVI. CONCLUSIONS We identify gAd as a novel ligand for GPVI that stimulates tyrosine kinase-dependent platelet aggregation. Our data raise the possibility that gAd may promote unwanted platelet activation at sites of vascular injury.
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Affiliation(s)
- R Riba
- Centre for Atherothrombosis Research, University of Bradford, Bradford, UK
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155
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Abram CL, Lowell CA. The diverse functions of Src family kinases in macrophages. FRONT BIOSCI-LANDMRK 2008; 13:4426-50. [PMID: 18508521 DOI: 10.2741/3015] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Macrophages are key components of the innate immune response. These cells possess a diverse repertoire of receptors that allow them to respond to a host of external stimuli including cytokines, chemokines, and pathogen-associated molecules. Signals resulting from these stimuli activate a number of macrophage functional responses such as adhesion, migration, phagocytosis, proliferation, survival, cytokine release and production of reactive oxygen and nitrogen species. The cytoplasmic tyrosine kinase Src and its family members (SFKs) have been implicated in many intracellular signaling pathways in macrophages, initiated by a diverse set of receptors ranging from integrins to Toll-like receptors. However, it has been difficult to implicate any given member of the family in any specific pathway. SFKs appear to have overlapping and complementary functions in many pathways. Perhaps the function of these enzymes is to modulate the overall intracellular signaling network in macrophages, rather than operating as exclusive signaling switches for defined pathways. In general, SFKs may function more like rheostats, influencing the amplitude of many pathways.
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Affiliation(s)
- Clare L Abram
- Department of Laboratory Medicine, University of California, San Francisco, CA 94143, USA
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156
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Cooper JA, Qian H. A mechanism for SRC kinase-dependent signaling by noncatalytic receptors. Biochemistry 2008; 47:5681-5688. [PMID: 18444664 DOI: 10.1021/bi8003044] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A fundamental issue in cell biology is how signals are transmitted across membranes. A variety of transmembrane receptors, including multichain immune recognition receptors, lack catalytic activity and require Src family kinases (SFKs) for signal transduction. However, many receptors only bind and activate SFKs after ligand-induced receptor dimerization. This presents a conundrum: How do SFKs sense the dimerization of receptors to which they are not already bound? Most proposals for resolving this enigma invoke additional players, such as lipid rafts or receptor conformational changes. Here we used simple thermodynamics to show that SFK activation is a natural outcome of clustering of receptors with SFK phosphorylation sites, provided that there is phosphorylation-dependent receptor-SFK association and an SFK bound to one receptor can phosphorylate the second receptor or its associated SFK in a dimer. A simple system of receptor, SFK, and an unregulated protein tyrosine phosphatase (PTP) can account for ligand-induced changes in phosphorylation observed in cells. We suggest that a core signaling system comprising a receptor with SFK phosphorylation sites, an SFK, and an unregulated PTP provides a robust mechanism for transmembrane signal transduction. Other events that regulate signaling in specific cases may have evolved for fine-tuning of this basic mechanism.
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Affiliation(s)
- Jonathan A Cooper
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109
| | - Hong Qian
- Department of Applied Mathematics, University of Washington, Seattle, Washington 98195
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157
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Huysamen C, Willment JA, Dennehy KM, Brown GD. CLEC9A is a novel activation C-type lectin-like receptor expressed on BDCA3+ dendritic cells and a subset of monocytes. J Biol Chem 2008; 283:16693-701. [PMID: 18408006 PMCID: PMC2562446 DOI: 10.1074/jbc.m709923200] [Citation(s) in RCA: 240] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
We describe here the first characterization of CLEC9A, a group V C-type lectin-like receptor located in the “Dectin-1 cluster” of related receptors, which are encoded within the natural killer (NK)-gene complex. Expression of human CLEC9A is highly restricted in peripheral blood, being detected only on BDCA3+ dendritic cells and on a small subset of CD14+CD16- monocytes. CLEC9A is expressed at the cell surface as a glycosylated dimer and can mediate endocytosis, but not phagocytosis. CLEC9A possesses a cytoplasmic immunoreceptor tyrosine-based activation-like motif that can recruit Syk kinase, and we demonstrate, using receptor chimeras, that this receptor can induce proinflammatory cytokine production. These data indicate that CLEC9A functions as an activation receptor.
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Affiliation(s)
- Cristal Huysamen
- Division of Immunology, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, 7925, South Africa
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158
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Christou CM, Pearce AC, Watson AA, Mistry AR, Pollitt AY, Fenton-May AE, Johnson LA, Jackson DG, Watson SP, O'Callaghan CA. Renal cells activate the platelet receptor CLEC-2 through podoplanin. Biochem J 2008; 411:133-40. [PMID: 18215137 PMCID: PMC2749330 DOI: 10.1042/bj20071216] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have recently shown that the C-type lectin-like receptor, CLEC-2, is expressed on platelets and that it mediates powerful platelet aggregation by the snake venom toxin rhodocytin. In addition, we have provided indirect evidence for an endogenous ligand for CLEC-2 in renal cells expressing HIV-1. This putative ligand facilitates transmission of HIV through its incorporation into the viral envelope and binding to CLEC-2 on platelets. The aim of the present study was to identify the ligand on these cells which binds to CLEC-2 on platelets. Recombinant CLEC-2 exhibits specific binding to HEK-293T (human embryonic kidney) cells in which the HIV can be grown. Furthermore, HEK-293T cells activate both platelets and CLEC-2-transfected DT-40 B-cells. The transmembrane protein podoplanin was identified on HEK-293T cells and was demonstrated to mediate both binding of HEK-293T cells to CLEC-2 and HEK-293T cell activation of CLEC-2-transfected DT-40 B-cells. Podoplanin is expressed on renal cells (podocytes). Furthermore, a direct interaction between CLEC-2 and podoplanin was confirmed using surface plasmon resonance and was shown to be independent of glycosylation of CLEC-2. The interaction has an affinity of 24.5+/-3.7 microM. The present study identifies podoplanin as a ligand for CLEC-2 on renal cells.
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Affiliation(s)
- Charita M. Christou
- Henry Wellcome Building for Molecular Physiology, University of Oxford, Roosevelt Drive, Oxford. OX3 7BN, UK
| | - Andrew C. Pearce
- Centre for Cardiovascular Sciences, Institute of Biomedical Research, The Medical School, University of Birmingham, Birmingham, B15 2TT, UK
| | - Aleksandra A. Watson
- Henry Wellcome Building for Molecular Physiology, University of Oxford, Roosevelt Drive, Oxford. OX3 7BN, UK
| | - Anita R. Mistry
- Henry Wellcome Building for Molecular Physiology, University of Oxford, Roosevelt Drive, Oxford. OX3 7BN, UK
| | - Alice Y. Pollitt
- Centre for Cardiovascular Sciences, Institute of Biomedical Research, The Medical School, University of Birmingham, Birmingham, B15 2TT, UK
| | - Angharad E. Fenton-May
- Henry Wellcome Building for Molecular Physiology, University of Oxford, Roosevelt Drive, Oxford. OX3 7BN, UK
| | - Louise A. Johnson
- The Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - David G. Jackson
- The Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Steve P. Watson
- Centre for Cardiovascular Sciences, Institute of Biomedical Research, The Medical School, University of Birmingham, Birmingham, B15 2TT, UK
| | - Chris A. O'Callaghan
- Henry Wellcome Building for Molecular Physiology, University of Oxford, Roosevelt Drive, Oxford. OX3 7BN, UK
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159
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Abstract
Macrophages are cells that function as a first line of defence against invading microorganisms. One of the hallmarks of macrophages is their ability to become activated in response to exogenous 'danger signals'. Most microbes have molecular patterns (PAMPS) that are recognized by macrophages and trigger this activation response. There are many aspects of the activation response to PAMPS that are recapitulated when macrophages encounter endogenous danger signals. In response to damaged or stressed self, macrophages undergo physiological changes that include the initiation of signal transduction cascades from germline-encoded receptors, resulting in the elaboration of chemokines, cytokines and toxic mediators. This response to endogenous mediators can enhance inflammation, and thereby contribute to autoimmune pathologies. Often the overall inflammatory response is the result of cooperative activation signals from both exogenous and endogenous signals. Macrophage activation plays a critical role, not only in the initiation of the inflammatory response but also in the resolution of this response. The clearance of granulocytes and the elaboration of anti-inflammatory mediators by macrophages contribute to the dissolution of the inflammatory response. Thus, macrophages are a key player in the initiation, propagation and resolution of inflammation. This review summarizes our understanding of the role of macrophages in inflammation. We pay particular attention to the endogenous danger signals that macrophages may encounter and the responses that these signals induce. The molecular mechanisms responsible for these responses and the diseases that result from inappropriately controlled macrophage activation are also examined.
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Affiliation(s)
- X Zhang
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
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160
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Abstract
The identification of antigen-recognizing receptors in the innate immune system significantly helped us to understand the initiation and regulation of the innate immune response. Dectin-1 was recently identified as the most important receptor for beta-glucan. Recognition of beta-glucan by dectin-1 triggers effective immune response, including phagocytosis and proinflammatory factor production, to eliminate infecting fungi, which especially benefits immunocompromised patients against opportunistic fungal infection. In addition, dectin-1 is involved in the adaptive immune response as well as autoimmune diseases and immune tolerance. In this paper, we will mainly focus on the characteristics of dectin-1 and its biological role in immune response.
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Affiliation(s)
- Lina Sun
- Transplantation Biology Research Division, State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Datui Road Yi 5, Beijing 100101, China
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161
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Huysamen C, Brown GD. The fungal pattern recognition receptor, Dectin-1, and the associated cluster of C-type lectin-like receptors. FEMS Microbiol Lett 2008; 290:121-8. [PMID: 19025564 PMCID: PMC2704933 DOI: 10.1111/j.1574-6968.2008.01418.x] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The mammalian natural killer gene complex (NKC) contains several families of type II transmembrane C-type lectin-like receptors (CLRs) that are best known for their involvement in the detection of virally infected or transformed cells, through the recognition of endogenous (or self) proteinacious ligands. However, certain CLR families within the NKC, particularly those expressed by myeloid cells, recognize structurally diverse ligands and perform a variety of other immune and homoeostatic functions. One such family is the 'Dectin-1 cluster' of CLRs, which includes MICL, CLEC-2, CLEC12B, CLEC9A, CLEC-1, Dectin-1 and LOX-1. Here, we review each of these CLRs, exploring our current understanding of their ligands and functions and highlighting where they have provided new insights into the underlying mechanisms of immunity and homeostasis.
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Affiliation(s)
- Cristal Huysamen
- Clinical Laboratory Sciences, Division of Immunology, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
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162
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Kato Y, Kaneko MK, Kunita A, Ito H, Kameyama A, Ogasawara S, Matsuura N, Hasegawa Y, Suzuki-Inoue K, Inoue O, Ozaki Y, Narimatsu H. Molecular analysis of the pathophysiological binding of the platelet aggregation-inducing factor podoplanin to the C-type lectin-like receptor CLEC-2. Cancer Sci 2008; 99:54-61. [PMID: 17944973 PMCID: PMC11159596 DOI: 10.1111/j.1349-7006.2007.00634.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The mucin-type sialoglycoprotein podoplanin (aggrus) is involved in tumor cell-induced platelet aggregation and tumor metastasis. C-type lectin-like receptor-2 (CLEC-2) was recently identified as an endogenous receptor of podoplanin on platelets. However, the pathophysiological importance and function of CLEC-2 have not been elucidated. Here we clarified the pathophysiological interaction between podoplanin and CLEC-2 in vitro and in vivo. Using several deletion mutants of CLEC-2 expressed as Fc chimeras, we first identified an important podoplanin-recognition domain in CLEC-2. Furthermore, the podoplanin-CLEC-2 interaction was confirmed using several deletion mutants of podoplanin expressed as Fc chimeras. Not only the disialyl-core1-attached glycopeptide but also the stereostructure of the podoplanin protein was found to be critical for the CLEC-2-binding activity of podoplanin. We next synthesized various glycopeptides of podoplanin that included both the platelet aggregation-stimulating domain and O-glycan on Thr52. Interestingly, a disialyl-core1-attached glycopeptide was recognized specifically by CLEC-2. Moreover, the anti-podoplanin monoclonal antibody NZ-1 suppressed both the podoplanin-CLEC-2 interaction and podoplanin-induced pulmonary metastasis, suggesting that CLEC-2 is the first pathophysiological receptor of podoplanin to be identified. In summary, we clarified the molecular interaction in vitro and in vivo between a platelet aggregation-inducing factor, podoplanin, and its specific pathophysiological receptor on platelets, CLEC-2. Podoplanin and CLEC-2 might represent promising therapeutic targets in cancer metastasis.
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Affiliation(s)
- Yukinari Kato
- Research Center for Medical Glycoscience, National Institute of Advanced Industrial Science and Technology, Open Space Laboratory C-2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
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163
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164
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Li H, Chehade M, Liu W, Xiong H, Mayer L, Berin MC. Allergen-IgE complexes trigger CD23-dependent CCL20 release from human intestinal epithelial cells. Gastroenterology 2007; 133:1905-15. [PMID: 18054562 PMCID: PMC2174915 DOI: 10.1053/j.gastro.2007.09.024] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2007] [Accepted: 09/06/2007] [Indexed: 01/29/2023]
Abstract
BACKGROUND & AIMS In food allergic individuals, exposure to food allergens by the oral route can trigger immediate (within minutes) local hypersensitivity reactions in the intestine followed by a late-phase inflammatory response. Previous work has shown that CD23 is constitutively expressed by human intestinal epithelial cells and mediates the uptake of allergen-IgE complexes. We hypothesized that allergen-IgE complexes could also signal via CD23 to trigger an inflammatory cascade in the local environment. METHODS Caco-2 monolayers were stimulated with human IgE-antigen (Ag) complexes. IL-8 and CCL20 mRNA and protein were determined by RT-PCR and ELISA, respectively. Signaling pathways were assessed by immunoblotting. Endogenous CD23 expression was knocked down by stable transfection with CD23 shRNA retroviral plasmid. Migration assays were performed using human monocyte-derived dendritic cells. RESULTS Stimulation of Caco-2 cells with IgE-Ag complexes triggered upregulation of IL-8 and CCL20 at the mRNA and protein level. Allergen complexes induced phosphorylation of ERK and JNK, but not p38 MAP kinase or NK-kappaB, and resulted in AP-1 activation. Cross-linking of CD23 replicated the findings with IgE-Ag complexes, and silencing of CD23 expression abrogated the response to allergen-IgE complexes. Supernatant from IgE-Ag-stimulated epithelial cells induced migration of dendritic cells in a CCL20-dependent manner. Finally, immunostaining of duodenal biopsies demonstrated that CCL20 was constitutively expressed by epithelial cells in vivo. CONCLUSIONS Signaling via epithelial CD23 may participate in the late-phase inflammatory response by the release of chemokines capable of recruiting antigen presenting cells and effector cells of allergic inflammation.
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Affiliation(s)
- Hongxing Li
- Immunology Institute, Mount Sinai School of Medicine, New York, NY
| | - Mirna Chehade
- Department of Pediatrics, Mount Sinai School of Medicine, New York, NY
| | - Weicheng Liu
- Immunology Institute, Mount Sinai School of Medicine, New York, NY
| | - Huabao Xiong
- Immunology Institute, Mount Sinai School of Medicine, New York, NY
| | - Lloyd Mayer
- Immunology Institute, Mount Sinai School of Medicine, New York, NY
| | - M. Cecilia Berin
- Department of Pediatrics, Mount Sinai School of Medicine, New York, NY
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165
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Suzuki-Inoue K, Kato Y, Inoue O, Kaneko MK, Mishima K, Yatomi Y, Yamazaki Y, Narimatsu H, Ozaki Y. Involvement of the snake toxin receptor CLEC-2, in podoplanin-mediated platelet activation, by cancer cells. J Biol Chem 2007; 282:25993-6001. [PMID: 17616532 DOI: 10.1074/jbc.m702327200] [Citation(s) in RCA: 375] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Podoplanin (aggrus), a transmembrane sialoglycoprotein, is involved in tumor cell-induced platelet aggregation, tumor metastasis, and lymphatic vessel formation. However, the mechanism by which podoplanin induces these cellular processes including its receptor has not been elucidated to date. Podoplanin induced platelet aggregation with a long lag phase, which is dependent upon Src and phospholipase Cgamma2 activation. However, it does not bind to glycoprotein VI. This mode of platelet activation was reminiscent of the snake toxin rhodocytin, the receptor of which has been identified by us as a novel platelet activation receptor, C-type lectin-like receptor 2 (CLEC-2) (Suzuki-Inoue, K., Fuller, G. L., Garcia, A., Eble, J. A., Pohlmann, S., Inoue, O., Gartner, T. K., Hughan, S. C., Pearce, A. C., Laing, G. D., Theakston, R. D., Schweighoffer, E., Zitzmann, N., Morita, T., Tybulewicz, V. L., Ozaki, Y., and Watson, S. P. (2006) Blood 107, 542-549). Therefore, we sought to evaluate whether CLEC-2 serves as a physiological counterpart for podoplanin. Association between CLEC-2 and podoplanin was confirmed by flow cytometry. Furthermore, their association was dependent on sialic acid on O-glycans of podoplanin. Recombinant CLEC-2 inhibited platelet aggregation induced by podoplanin-expressing tumor cells or lymphatic endothelial cells, suggesting that CLEC-2 is responsible for platelet aggregation induced by endogenously expressed podoplanin on the cell surfaces. These findings suggest that CLEC-2 is a physiological target protein of podoplanin and imply that it is involved in podoplanin-induced platelet aggregation, tumor metastasis, and other cellular responses related to podoplanin.
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Affiliation(s)
- Katsue Suzuki-Inoue
- Department of Clinical and Laboratory Medicine, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan.
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