11 results on '"Xin Smith"'
Search Results
2. Adaptor SKAP-55 binds p21 activating exchange factor RasGRP1 and negatively regulates the p21-ERK pathway in T-cells.
- Author
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Helga Schneider, Hongyan Wang, Monika Raab, Elke Valk, Xin Smith, Matt Lovatt, Zhonglin Wu, Braudel Maqueira-Iglesias, Klaus Strebhardt, and Christopher E Rudd
- Subjects
Medicine ,Science - Abstract
While the adaptor SKAP-55 mediates LFA-1 adhesion on T-cells, it is not known whether the adaptor regulates other aspects of signaling. SKAP-55 could potentially act as a node to coordinate the modulation of adhesion with downstream signaling. In this regard, the GTPase p21(ras) and the extracellular signal-regulated kinase (ERK) pathway play central roles in T-cell function. In this study, we report that SKAP-55 has opposing effects on adhesion and the activation of the p21(ras) -ERK pathway in T-cells. SKAP-55 deficient primary T-cells showed a defect in LFA-1 adhesion concurrent with the hyper-activation of the ERK pathway relative to wild-type cells. RNAi knock down (KD) of SKAP-55 in T-cell lines also showed an increase in p21(ras) activation, while over-expression of SKAP-55 inhibited activation of ERK and its transcriptional target ELK. Three observations implicated the p21(ras) activating exchange factor RasGRP1 in the process. Firstly, SKAP-55 bound to RasGRP1 via its C-terminus, while secondly, the loss of binding abrogated SKAP-55 inhibition of ERK and ELK activation. Thirdly, SKAP-55-/- primary T-cells showed an increased presence of RasGRP1 in the trans-Golgi network (TGN) following TCR activation, the site where p21(ras) becomes activated. Our findings indicate that SKAP-55 has a dual role in regulating p21(ras)-ERK pathway via RasGRP1, as a possible mechanism to restrict activation during T-cell adhesion.
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- 2008
- Full Text
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3. T-cell immune adaptor SKAP1 regulates the induction of collagen-induced arthritis in mice
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Alison Taylor, Christopher E. Rudd, and Xin Smith
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0301 basic medicine ,musculoskeletal diseases ,SKAP1 ,T cell ,Immunology ,Arthritis ,Adaptor ,Lymphocyte Activation ,Article ,03 medical and health sciences ,Mice ,0302 clinical medicine ,Immune system ,Cell Movement ,SKAP-55 ,medicine ,Immunology and Allergy ,Animals ,Lymphocyte function-associated antigen 1 ,Receptor ,Collagen Type II ,Mice, Knockout ,business.industry ,T-cells ,Interleukin-17 ,medicine.disease ,Phosphoproteins ,Arthritis, Experimental ,Lymphocyte Function-Associated Antigen-1 ,3. Good health ,Murine autoimmune arthritis ,030104 developmental biology ,medicine.anatomical_structure ,Mice, Inbred DBA ,Th17 Cells ,Joints ,Interleukin 17 ,Disease Susceptibility ,Signal transduction ,business ,030215 immunology ,Signal Transduction - Abstract
Highlights • Skap1-deficient (skap1-/-) mice are resistant to the induction of collagen induced arthritis (CIA). • Skap1-/- mice show a reduction in presence of IL-17+ (Th17) T-cells in response to CII peptide. • No effect was seen on the production of other cytokines such as IL-10. • Our findings implicate SKAP1 as a novel upstream regulator murine autoimmune arthritis., SKAP1 is an immune cell adaptor that couples the T-cell receptor with the ‘inside-out’ signalling pathway for LFA-1 mediated adhesion in T-cells. A connection of SKAP1 to the regulation of an autoimmune disorder has not previously been reported. In this study, we show that Skap1-deficient (skap1-/-) mice are highly resistant to the induction of collagen-induced arthritis (CIA), both in terms of incidence or severity. Skap1-/- T-cells were characterised by a selective reduction in the presence IL-17+ (Th17) in response to CII peptide and a marked reduction of joint infiltrating T-cells in Skap1-/- mice. SKAP1 therefore represents a novel connection to Th17 producing T-cells and is new potential target in the therapeutic intervention in autoimmune and inflammatory diseases.
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- 2016
4. SKAP1 Protein PH Domain Determines RapL Membrane Localization and Rap1 Protein Complex Formation for T Cell Receptor (TCR) Activation of LFA-1
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Klaus Strebhardt, Yves Matthess, Christopher E. Rudd, Monika Raab, and Xin Smith
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SKAP1 ,T-Lymphocytes ,T cell ,Telomere-Binding Proteins ,Immunology ,Receptors, Antigen, T-Cell ,Integrin ,chemical and pharmacologic phenomena ,Biology ,PI3K ,Biochemistry ,Jurkat cells ,Shelterin Complex ,Inside-out Signaling ,Cell membrane ,Jurkat Cells ,Phosphatidylinositol 3-Kinases ,Cell Adhesion ,medicine ,Humans ,Lymphocyte function-associated antigen 1 ,Molecular Biology ,Adaptor Proteins, Signal Transducing ,Monomeric GTP-Binding Proteins ,Protein Translocation ,T Cells ,Cell Membrane ,T-cell receptor ,hemic and immune systems ,Cell Biology ,Intercellular Adhesion Molecule-1 ,Phosphoproteins ,Lymphocyte Function-Associated Antigen-1 ,Protein Structure, Tertiary ,Up-Regulation ,Transport protein ,Cell biology ,Protein Transport ,medicine.anatomical_structure ,Multiprotein Complexes ,Mutation ,Lymphocyte ,Rap1 ,Apoptosis Regulatory Proteins ,LFA-1 - Abstract
Although essential for T cell function, the identity of the T cell receptor (TCR) “inside-out” pathway for the activation of lymphocyte function-associated antigen 1 (LFA-1) is unclear. SKAP1 (SKAP-55) is the upstream regulator needed for TCR-induced RapL-Rap1 complex formation and LFA-1 activation. In this paper, we show that SKAP1 is needed for RapL binding to membranes in a manner dependent on the PH domain of SKAP1 and the PI3K pathway. A SKAP1 PH domain-inactivating mutation (i.e. R131M) markedly impaired RapL translocation to membranes for Rap1 and LFA-1 binding and the up-regulation of LFA-1-intercellular adhesion molecule 1 (ICAM-1) binding. Further, N-terminal myr-tagged SKAP1 for membrane binding facilitated constitutive RapL membrane and Rap1 binding and effectively substituted for PI3K and TCR ligation in the activation of LFA-1 in T cells.
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- 2011
5. CTLA-4 disrupts ZAP70 microcluster formation with reduced T cell/APC dwell times and calcium mobilization
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Hebin Liu, Christopher E. Rudd, Georges Bismuth, Helga Schneider, and Xin Smith
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Cell signaling ,T-Lymphocytes ,T cell ,Immunology ,Antigen-Presenting Cells ,chemical and pharmacologic phenomena ,Cell Communication ,Biology ,Lymphocyte Activation ,Article ,Calcium in biology ,Immunological synapse ,Mice ,Antigens, CD ,Cell Movement ,Cell Adhesion ,medicine ,Animals ,Humans ,Immunology and Allergy ,CTLA-4 Antigen ,Antigen-presenting cell ,Cell adhesion ,ZAP-70 Protein-Tyrosine Kinase ,ZAP70 ,hemic and immune systems ,Antigens, Differentiation ,Cell biology ,medicine.anatomical_structure ,CTLA-4 ,Calcium - Abstract
CTLA-4 is a co-receptor that modulates the threshold of T cell activation and autoimmunity. We previously showed that CTLA-4 reverses the TCR-mediated stop signal needed for T cell/APC interactions [Schneider et al., Science 2006, 313: 1972]. In this study, using a different T cell system, we show that CTLA-4 expression changed the behavior of T8.1 T cells by reducing the contact time between T cell and APC, preventing re-inforced contacts, and reducing the contact area at the immunological synapse. This led to a major reduction in Ca(2+) influx/mobilization and interleukin-2 production. Further, anti-CD3/CTLA-4 increased T cell motility on antibody-coated glass slides, concurrent with an abrogation of ZAP70 microcluster formation. Our findings further support a role for CTLA-4 in limiting the interaction between T cell and APC that is needed for optimal activation.
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- 2008
6. Selective Blockade of IL-15 by Soluble IL-15 Receptor α-Chain Enhances Cardiac Allograft Survival
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Xin Smith, Eleanor M. Bolton, Xiao-Qing Wei, Holger Ruchatz, Foo Y. Liew, and J. Andrew Bradley
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Cytotoxicity, Immunologic ,Male ,Immunology ,Spleen ,Pharmacology ,Lymphocyte Activation ,Mice ,Mice, Inbred AKR ,Graft Enhancement, Immunologic ,Isoantibodies ,In vivo ,Animals ,Transplantation, Homologous ,Immunology and Allergy ,Medicine ,Receptor ,Interleukin-15 ,Mice, Inbred BALB C ,Receptors, Interleukin-15 ,business.industry ,Graft Survival ,Receptors, Interleukin-2 ,Histocompatibility ,Mice, Inbred C57BL ,Transplantation ,CTL ,Mononuclear cell infiltration ,medicine.anatomical_structure ,Solubility ,Interleukin 15 ,Mice, Inbred CBA ,Cytokines ,Heart Transplantation ,business ,Injections, Intraperitoneal ,T-Lymphocytes, Cytotoxic - Abstract
IL-15 is a T cell growth factor that shares many functional similarities with IL-2 and has recently been shown to be present in tissue and organ allografts, leading to speculation that IL-15 may contribute to graft rejection. Here, we report on the in vivo use of an IL-15 antagonist, a soluble fragment of the murine IL-15R α-chain, to investigate the contribution of IL-15 to the rejection of fully vascularized cardiac allografts in a mouse experimental model. Administration of soluble fragment of the murine IL-15R α-chain (sIL-15Rα) to CBA/Ca (H-2k) recipients for 10 days completely prevented rejection of minor histocompatibility complex-mismatched B10.BR (H-2k) heart grafts (median survival time (MST) of >100 days vs MST of 10 days for control recipients) and led to a state of donor-specific immunologic tolerance. Treatment of CBA/Ca recipients with sIL-15Rα alone had only a modest effect on the survival of fully MHC-mismatched BALB/c (H-2d) heart grafts. However, administration of sIL-15Rα together with a single dose of a nondepleting anti-CD4 mAb (YTS 177.9) delayed mononuclear cell infiltration of the grafts and markedly prolonged graft survival (MST of 60 days vs MST of 20 days for treatment with anti-CD4 alone). Prolonged graft survival was accompanied in vitro by reduced proliferation and IFN-γ production by spleen cells, whereas CTL and alloantibody levels were similar to those in animals given anti-CD4 mAb alone. These findings demonstrate that IL-15 plays an important role in the rejection of a vascularized organ allograft and that antagonists to IL-15 may be of therapeutic value in preventing allograft rejection.
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- 2000
7. The chemokine CXCL12 generates costimulatory signals in T cells to enhance phosphorylation and clustering of the adaptor protein SLP-76
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Xin Smith, Hebin Liu, Christopher E. Rudd, Yuning Lu, Karsten Köhler, and Helga Schneider
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Receptors, CXCR4 ,genetic structures ,CD3 Complex ,CD3 ,T cell ,T-Lymphocytes ,Gene Expression ,Enzyme-Linked Immunosorbent Assay ,Biochemistry ,Jurkat cells ,Jurkat Cells ,Mice ,medicine ,Cytotoxic T cell ,Animals ,Cluster Analysis ,Humans ,Phosphorylation ,Molecular Biology ,CXCL16 ,Adaptor Proteins, Signal Transducing ,Cell Proliferation ,ZAP-70 Protein-Tyrosine Kinase ,biology ,T-cell receptor ,Signal transducing adaptor protein ,Cell Biology ,equipment and supplies ,Phosphoproteins ,eye diseases ,Actins ,Chemokine CXCL12 ,Cell biology ,medicine.anatomical_structure ,Microscopy, Fluorescence ,Mutation ,biology.protein ,XCL2 ,Tyrosine ,sense organs ,Spleen ,Signal Transduction - Abstract
The CXC chemokine CXCL12 mediates the chemoattraction of T cells and enhances the stimulation of T cells through the T cell receptor (TCR). The adaptor SLP-76 [Src homology 2 (SH2) domain-containing leukocyte protein of 76 kD] has two key tyrosine residues, Tyr(113) and Tyr(128), that mediate signaling downstream of the TCR. We investigated the effect of CXCL12 on SLP-76 phosphorylation and the TCR-dependent formation of SLP-76 microclusters. Although CXCL12 alone failed to induce SLP-76 cluster formation, it enhanced the number, stability, and phosphorylation of SLP-76 microclusters formed in response to stimulation of the TCR by an activating antibody against CD3, a component of the TCR complex. Addition of CXCL12 to anti-CD3-stimulated cells resulted in F-actin polymerization that stabilized SLP-76 microclusters in the cells' periphery at the interface with antibody-coated coverslips and increased the interaction between SLP-76 clusters and those containing ZAP-70, the TCR-associated kinase that phosphorylates SLP-76, as well as increased TCR-dependent gene expression. Costimulation with CXCL12 and anti-CD3 increased the extent of phosphorylation of SLP-76 at Tyr(113) and Tyr(128), but not that of other TCR-proximal components, and mutation of either one of these residues impaired the CXCL12-dependent effect on SLP-76 microcluster formation, F-actin polymerization, and TCR-dependent gene expression. The effects of CXCL12 on SLP-76 microcluster formation were dependent on the coupling of its receptor CXCR4 to G(i)-family G proteins (heterotrimeric guanine nucleotide-binding proteins). Thus, we identified a costimulatory mechanism by which CXCL12 and antigen converge at SLP-76 microcluster formation to enhance T cell responses.
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- 2013
8. OX40 (CD134) blockade inhibits the co-stimulatory cascade and promotes heart allograft survival
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Herbert Schwarz, Xin Smith, Eleanor M. Bolton, J. Andrew Bradley, Ming Cai, Allison J. Curry, and Jo Chikwe
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medicine.medical_treatment ,Recombinant Fusion Proteins ,T-Lymphocytes ,Immunoglobulins ,CHO Cells ,Major histocompatibility complex ,Lymphocyte Activation ,Receptors, Tumor Necrosis Factor ,Mice ,Mice, Inbred AKR ,Antigen ,Cricetinae ,Medicine ,Animals ,Humans ,Transplantation, Homologous ,CD134 ,IL-2 receptor ,Heart transplantation ,Inflammation ,Transplantation ,Mice, Inbred BALB C ,biology ,business.industry ,Graft Survival ,Skin Transplantation ,Receptors, OX40 ,Blockade ,Mononuclear cell infiltration ,Immunology ,Models, Animal ,biology.protein ,Mice, Inbred CBA ,Heart Transplantation ,business - Abstract
Background CD134 (OX40) is a member of the tumor necrosis factor receptor superfamily that is expressed as a late event in T-cell activation and contributes to the generation of immunologic memory. CD134 blockade effectively ameliorates inflammation in models of autoimmune disease, but its role in transplantation has been less well studied. Methods The authors used an OX40-immunoglobulin (Ig) fusion protein to examine the contribution of this co-stimulatory molecule to the in vitro alloimmune response and studied the ability of CD134 blockade to prevent cardiac allograft rejection in mouse models of heart transplantation using strains representing both major histocompatibility complex (MHC) (BALB/c to CBA/Ca) and minor histocompatibility complex (mHC) (B10.BR to CBA/Ca) antigen mismatches. Results CD134 upregulation on in vitro alloactivated T cells was delayed compared with CD69 and CD25, and inhibition of T-cell proliferation was critically dependent on the timing of OX40-Ig administration. Heart allograft survival in a fully allogeneic, MHC-mismatched strain combination was not influenced by CD134 blockade alone, but OX40-Ig treatment in the mHC-mismatched model resulted in long-term graft survival (median survival time extended from 14 days to >100 days). Early mononuclear cell infiltration of the graft was similar in both rejecting and long-surviving heart grafts, but OX40-Ig treatment appeared to delay cellular infiltration. Conclusions These results show that CD134-CD134L interaction plays an important role in the co-stimulatory cascade and that blockade of this molecular interaction may be of therapeutic value in helping to prevent allograft rejection.
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- 2004
9. CO-STIMULATORY INHIBITION THROUGH CD134 (OX40) BLOCKADE PROMOTES MURINE HEART ALLOGRAFT SURVIVAL
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M Cai, Eleanor M. Bolton, J Chickwe, Xin Smith, J A. Bradley, Allison J. Curry, and H Schwarz
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Transplantation ,business.industry ,Medicine ,CD134 ,Pharmacology ,business ,Heart allograft ,Blockade - Published
- 2004
10. SKAP1 Protein PH Domain Determines RapL Membrane Localization and Rap 1 Protein Complex Formation for T Cell Receptor (TCR) Activation of LFA-1.
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Raab, Monika, Xin Smith, Matthess, Yves, Strebhardt, Klaus, and Rudd, Christopher E.
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T cell receptors , *CELL membranes , *LYMPHOCYTES , *ANTIGENS , *GENETIC mutation , *CELL adhesion molecules - Abstract
Although essential for T cell function, the identity of the T cell receptor (TCR) "inside-out" pathway for the activation of lymphocyte function-associated antigen 1 (LFA-1) is unclear. SKAP1 (SKAP-55) is the upstream regulator needed for TCR-induced RapL-Rap1 complex formation and LFA-1 activation. In this paper, we show that SKAP1 is needed for RapL binding to membranes in a manner dependent on the PH domain of SKAP1 and the PI3K pathway. A SKAP1 PH domain-inactivating mutation (i.e. R131M) markedly impaired RapL translocation to membranes for Rap1 and LFA-1 binding and the up-regulation of LFA-1-intercellular adhesion molecule 1 (ICAM-1) binding. Further, N-terminal myr-tagged SKAP1 for membrane binding facilitated constitutive RapL membrane and Rap1 binding and effectively substituted for PI3K and TCR ligation in the activation of LFA-1 in T cells. [ABSTRACT FROM AUTHOR]
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- 2011
- Full Text
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11. T Cell Receptor 'Inside-Out' Pathway via Signaling Module SKAP1-RapL Regulates T Cell Motility and Interactions in Lymph Nodes
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Klaus Strebhardt, Zhonglin Wu, Yuning Lu, John E. Ladbury, Hongyan Wang, Christopher E. Rudd, Monika Raab, and Xin Smith
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MST1 ,T-Lymphocytes ,T cell ,Immunology ,Cell ,Receptors, Antigen, T-Cell ,Motility ,Biology ,Article ,Mice ,03 medical and health sciences ,0302 clinical medicine ,Cell Movement ,Cell Adhesion ,medicine ,Animals ,Immunology and Allergy ,Receptor ,MOLIMMUNO ,Cells, Cultured ,Adaptor Proteins, Signal Transducing ,Monomeric GTP-Binding Proteins ,030304 developmental biology ,Mice, Knockout ,0303 health sciences ,T-cell receptor ,rap1 GTP-Binding Proteins ,Colocalization ,hemic and immune systems ,Dendritic Cells ,Phosphoproteins ,Lymphocyte Function-Associated Antigen-1 ,Cell biology ,Protein Transport ,Infectious Diseases ,medicine.anatomical_structure ,Mutation ,Lymph Nodes ,SKAP1 ,Apoptosis Regulatory Proteins ,Protein Binding ,Signal Transduction ,030215 immunology - Abstract
Summary Although essential for T cell function, the identity of the T cell receptor "inside-out" pathway for lymphocyte function-associated antigen 1 (LFA-1) adhesion has proved elusive. Here, we define the "inside-out" pathway mediated by N-terminal SKAP1 (SKAP-55) domain binding to the C-terminal SARAH domain of RapL. TcR induced Rap1-RapL complex formation and LFA-1 binding failed to occur in Skap1 −/− primary T cells. SKAP1 generated a SKAP1-RapL-Rap1 complex that bound to LFA-1, whereas a RapL mutation (L224A) that abrogated SKAP1 binding without affecting MST1 disrupted component colocalization in vesicles as well as T cell-dendritic cell (DC) conjugation. RapL expression also "slowed" T cell motility in D011.10 transgenic T cells in lymph nodes (LNs), an effect reversed by the L224A mutation with reduced dwell times between T cells and DCs. Overall, our findings define a TCR "inside-out" pathway via N-SKAP1-C-RapL that regulates T cell adhesion, motility, and arrest times with DCs in LNs.
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