1
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Barr VA, Piao J, Balagopalan L, McIntire KM, Schoenberg FP, Samelson LE. Heterogeneity of Signaling Complex Nanostructure in T Cells Activated Via the T Cell Antigen Receptor. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2023; 29:1503-1522. [PMID: 37488826 PMCID: PMC11230849 DOI: 10.1093/micmic/ozad072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Revised: 06/08/2023] [Accepted: 06/18/2023] [Indexed: 07/26/2023]
Abstract
Activation of the T cell antigen receptor (TCR) is a key step in initiating the adaptive immune response. Single-molecule localization techniques have been used to investigate the arrangement of proteins within the signaling complexes formed around activated TCRs, but a clear picture of nanoscale organization in stimulated T cells has not emerged. Here, we have improved the examination of T cell nanostructure by visualizing individual molecules of six different proteins in a single sample of activated Jurkat T cells using the multiplexed antibody-size limited direct stochastic optical reconstruction microscopy (madSTORM) technique. We formally define irregularly shaped regions of interest, compare areas where signaling complexes are concentrated with other areas, and improve the statistical analyses of the locations of molecules. We show that nanoscale organization of proteins is mainly confined to the areas with dense concentrations of TCR-based signaling complexes. However, randomly distributed molecules are also found in some areas containing concentrated signaling complexes. These results are consistent with the view that the proteins within signaling complexes are connected by numerous weak interactions, leading to flexible, dynamic, and mutable structures which produce large variations in the nanostructure found in activated T cells.
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Affiliation(s)
- Valarie A Barr
- Laboratory of Cellular & Molecular Biology, Building 37 Room 2066, 37 Convent Drive, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892-4256, USA
| | - Juan Piao
- Department of Statistics, University of California at Los Angeles, 8965 Math Sciences Building, Los Angeles, CA 90095-1554, USA
| | - Lakshmi Balagopalan
- Laboratory of Cellular & Molecular Biology, Building 37 Room 2066, 37 Convent Drive, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892-4256, USA
| | - Katherine M McIntire
- Laboratory of Cellular & Molecular Biology, Building 37 Room 2066, 37 Convent Drive, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892-4256, USA
| | - Frederic P Schoenberg
- Department of Statistics, University of California at Los Angeles, 8965 Math Sciences Building, Los Angeles, CA 90095-1554, USA
| | - Lawrence E Samelson
- Laboratory of Cellular & Molecular Biology, Building 37 Room 2066, 37 Convent Drive, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892-4256, USA
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2
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Koretzky GA. Building on the Past, Meeting the Moment. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2023; 210:849-854. [PMID: 36947823 DOI: 10.4049/jimmunol.2390003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/24/2023]
Affiliation(s)
- Gary A Koretzky
- Department of Internal Medicine, Weill Cornell Medicine, New York, NY
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca NY
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3
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Böning MAL, Parzmair GP, Jeron A, Düsedau HP, Kershaw O, Xu B, Relja B, Schlüter D, Dunay IR, Reinhold A, Schraven B, Bruder D. Enhanced Susceptibility of ADAP-Deficient Mice to Listeria monocytogenes Infection Is Associated With an Altered Phagocyte Phenotype and Function. Front Immunol 2021; 12:724855. [PMID: 34659211 PMCID: PMC8515145 DOI: 10.3389/fimmu.2021.724855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 09/03/2021] [Indexed: 12/04/2022] Open
Abstract
The adhesion and degranulation-promoting adaptor protein (ADAP) serves as a multifunctional scaffold and is involved in the formation of immune signaling complexes. To date, only limited data exist regarding the role of ADAP in pathogen-specific immunity during in vivo infection, and its contribution in phagocyte-mediated antibacterial immunity remains elusive. Here, we show that mice lacking ADAP (ADAPko) are highly susceptible to the infection with the intracellular pathogen Listeria monocytogenes (Lm) by showing enhanced immunopathology in infected tissues together with increased morbidity, mortality, and excessive infiltration of neutrophils and monocytes. Despite high phagocyte numbers in the spleen and liver, ADAPko mice only inefficiently controlled pathogen growth, hinting at a functional impairment of infection-primed phagocytes in the ADAP-deficient host. Flow cytometric analysis of hallmark pro-inflammatory mediators and unbiased whole genome transcriptional profiling of neutrophils and inflammatory monocytes uncovered broad molecular alterations in the inflammatory program in both phagocyte subsets following their activation in the ADAP-deficient host. Strikingly, ex vivo phagocytosis assay revealed impaired phagocytic capacity of neutrophils derived from Lm-infected ADAPko mice. Together, our data suggest that an alternative priming of phagocytes in ADAP-deficient mice during Lm infection induces marked alterations in the inflammatory profile of neutrophils and inflammatory monocytes that contribute to enhanced immunopathology while limiting their capacity to eliminate the pathogen and to prevent the fatal outcome of the infection.
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Affiliation(s)
- Martha A L Böning
- Infection Immunology, Institute of Medical Microbiology, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany.,Immune Regulation, Helmholtz Centre for Infection Research, Braunschweig, Germany.,Institute of Molecular and Clinical Immunology, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany
| | - Gerald P Parzmair
- Infection Immunology, Institute of Medical Microbiology, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany.,Immune Regulation, Helmholtz Centre for Infection Research, Braunschweig, Germany.,Institute of Molecular and Clinical Immunology, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany
| | - Andreas Jeron
- Infection Immunology, Institute of Medical Microbiology, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany.,Immune Regulation, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Henning P Düsedau
- Institute of Inflammation and Neurodegeneration, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany
| | - Olivia Kershaw
- Department of Veterinary Medicine, Institute of Veterinary Pathology, Freie Universität, Berlin, Germany
| | - Baolin Xu
- Experimental Radiology, Department of Radiology and Nuclear Medicine, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany
| | - Borna Relja
- Experimental Radiology, Department of Radiology and Nuclear Medicine, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany
| | - Dirk Schlüter
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Hannover, Germany.,Institute of Medical Microbiology and Hospital Hygiene, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany
| | - Ildiko Rita Dunay
- Institute of Inflammation and Neurodegeneration, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany.,Center for Behavioral Brain Sciences, Otto-von-Guericke University, Magdeburg, Germany
| | - Annegret Reinhold
- Institute of Molecular and Clinical Immunology, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany
| | - Burkhart Schraven
- Institute of Molecular and Clinical Immunology, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany
| | - Dunja Bruder
- Infection Immunology, Institute of Medical Microbiology, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke University, Magdeburg, Germany.,Immune Regulation, Helmholtz Centre for Infection Research, Braunschweig, Germany
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4
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Dinur-Schejter Y, Zaidman I, Mor-Shaked H, Stepensky P. The Clinical Aspect of Adaptor Molecules in T Cell Signaling: Lessons Learnt From Inborn Errors of Immunity. Front Immunol 2021; 12:701704. [PMID: 34456914 PMCID: PMC8397411 DOI: 10.3389/fimmu.2021.701704] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 07/26/2021] [Indexed: 12/22/2022] Open
Abstract
Adaptor molecules lack enzymatic and transcriptional activities. Instead, they exert their function by linking multiple proteins into intricate complexes, allowing for transmitting and fine-tuning of signals. Many adaptor molecules play a crucial role in T-cell signaling, following engagement of the T-cell receptor (TCR). In this review, we focus on Linker of Activation of T cells (LAT) and SH2 domain-containing leukocyte protein of 76 KDa (SLP-76). Monogenic defects in these adaptor proteins, with known roles in T-cell signaling, have been described as the cause of human inborn errors of immunity (IEI). We describe the current knowledge based on defects in cell lines, murine models and human patients. Germline mutations in Adhesion and degranulation adaptor protein (ADAP), have not resulted in a T-cell defect.
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Affiliation(s)
- Yael Dinur-Schejter
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel.,The Bone Marrow Transplantation and Cancer Immunotherapy Department, Hadassah Ein Kerem Medical Center, Jerusalem, Israel.,Allergy and Clinical Immunology Unit, Hadassah Ein-Kerem Medical Center, Jerusalem, Israel
| | - Irina Zaidman
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel.,The Bone Marrow Transplantation and Cancer Immunotherapy Department, Hadassah Ein Kerem Medical Center, Jerusalem, Israel
| | - Hagar Mor-Shaked
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel.,Monique and Jacques Roboh Department of Genetic Research, Hadassah Ein Kerem Medical Center, Jerusalem, Israel
| | - Polina Stepensky
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel.,The Bone Marrow Transplantation and Cancer Immunotherapy Department, Hadassah Ein Kerem Medical Center, Jerusalem, Israel
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5
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Yablonski D. Bridging the Gap: Modulatory Roles of the Grb2-Family Adaptor, Gads, in Cellular and Allergic Immune Responses. Front Immunol 2019; 10:1704. [PMID: 31402911 PMCID: PMC6669380 DOI: 10.3389/fimmu.2019.01704] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 07/08/2019] [Indexed: 01/07/2023] Open
Abstract
Antigen receptor signaling pathways are organized by adaptor proteins. Three adaptors, LAT, Gads, and SLP-76, form a heterotrimeric complex that mediates signaling by the T cell antigen receptor (TCR) and by the mast cell high affinity receptor for IgE (FcεRI). In both pathways, antigen recognition triggers tyrosine phosphorylation of LAT and SLP-76. The recruitment of SLP-76 to phospho-LAT is bridged by Gads, a Grb2 family adaptor composed of two SH3 domains flanking a central SH2 domain and an unstructured linker region. The LAT-Gads-SLP-76 complex is further incorporated into larger microclusters that mediate antigen receptor signaling. Gads is positively regulated by dimerization, which promotes its cooperative binding to LAT. Negative regulation occurs via phosphorylation or caspase-mediated cleavage of the linker region of Gads. FcεRI-mediated mast cell activation is profoundly impaired in LAT- Gads- or SLP-76-deficient mice. Unexpectedly, the thymic developmental phenotype of Gads-deficient mice is much milder than the phenotype of LAT- or SLP-76-deficient mice. This distinction suggests that Gads is not absolutely required for TCR signaling, but may modulate its sensitivity, or regulate a particular branch of the TCR signaling pathway; indeed, the phenotypic similarity of Gads- and Itk-deficient mice suggests a functional connection between Gads and Itk. Additional Gads binding partners include costimulatory proteins such as CD28 and CD6, adaptors such as Shc, ubiquitin regulatory proteins such as USP8 and AMSH, and kinases such as HPK1 and BCR-ABL, but the functional implications of these interactions are not yet fully understood. No interacting proteins or function have been ascribed to the evolutionarily conserved N-terminal SH3 of Gads. Here we explore the biochemical and functional properties of Gads, and its role in regulating allergy, T cell development and T-cell mediated immunity.
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Affiliation(s)
- Deborah Yablonski
- The Immune Cell Signaling Lab, Department of Immunology, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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6
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Yablonski D. Bridging the Gap: Modulatory Roles of the Grb2-Family Adaptor, Gads, in Cellular and Allergic Immune Responses. Front Immunol 2019; 10:1704. [PMID: 31402911 DOI: 10.3389/fimmu.2019.01704/full] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 07/08/2019] [Indexed: 05/22/2023] Open
Abstract
Antigen receptor signaling pathways are organized by adaptor proteins. Three adaptors, LAT, Gads, and SLP-76, form a heterotrimeric complex that mediates signaling by the T cell antigen receptor (TCR) and by the mast cell high affinity receptor for IgE (FcεRI). In both pathways, antigen recognition triggers tyrosine phosphorylation of LAT and SLP-76. The recruitment of SLP-76 to phospho-LAT is bridged by Gads, a Grb2 family adaptor composed of two SH3 domains flanking a central SH2 domain and an unstructured linker region. The LAT-Gads-SLP-76 complex is further incorporated into larger microclusters that mediate antigen receptor signaling. Gads is positively regulated by dimerization, which promotes its cooperative binding to LAT. Negative regulation occurs via phosphorylation or caspase-mediated cleavage of the linker region of Gads. FcεRI-mediated mast cell activation is profoundly impaired in LAT- Gads- or SLP-76-deficient mice. Unexpectedly, the thymic developmental phenotype of Gads-deficient mice is much milder than the phenotype of LAT- or SLP-76-deficient mice. This distinction suggests that Gads is not absolutely required for TCR signaling, but may modulate its sensitivity, or regulate a particular branch of the TCR signaling pathway; indeed, the phenotypic similarity of Gads- and Itk-deficient mice suggests a functional connection between Gads and Itk. Additional Gads binding partners include costimulatory proteins such as CD28 and CD6, adaptors such as Shc, ubiquitin regulatory proteins such as USP8 and AMSH, and kinases such as HPK1 and BCR-ABL, but the functional implications of these interactions are not yet fully understood. No interacting proteins or function have been ascribed to the evolutionarily conserved N-terminal SH3 of Gads. Here we explore the biochemical and functional properties of Gads, and its role in regulating allergy, T cell development and T-cell mediated immunity.
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Affiliation(s)
- Deborah Yablonski
- The Immune Cell Signaling Lab, Department of Immunology, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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7
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Lewis JB, Scangarello FA, Murphy JM, Eidell KP, Sodipo MO, Ophir MJ, Sargeant R, Seminario MC, Bunnell SC. ADAP is an upstream regulator that precedes SLP-76 at sites of TCR engagement and stabilizes signaling microclusters. J Cell Sci 2018; 131:jcs215517. [PMID: 30305305 PMCID: PMC6240300 DOI: 10.1242/jcs.215517] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 09/17/2018] [Indexed: 12/31/2022] Open
Abstract
Antigen recognition by the T cell receptor (TCR) directs the assembly of essential signaling complexes known as SLP-76 (also known as LCP2) microclusters. Here, we show that the interaction of the adhesion and degranulation-promoting adaptor protein (ADAP; also known as FYB1) with SLP-76 enables the formation of persistent microclusters and the stabilization of T cell contacts, promotes integrin-independent adhesion and enables the upregulation of CD69. By analyzing point mutants and using a novel phospho-specific antibody, we show that Y595 is essential for normal ADAP function, that virtually all tyrosine phosphorylation of ADAP is restricted to a Y595-phosphorylated (pY595) pool, and that multivalent interactions between the SLP-76 SH2 domain and its binding sites in ADAP are required to sustain ADAP phosphorylation. Although pY595 ADAP enters SLP-76 microclusters, non-phosphorylated ADAP is enriched in protrusive actin-rich structures. The pre-positioning of ADAP at the contact sites generated by these structures favors the retention of nascent SLP-76 oligomers and their assembly into persistent microclusters. Although ADAP is frequently depicted as an effector of SLP-76, our findings reveal that ADAP acts upstream of SLP-76 to convert labile, Ca2+-competent microclusters into stable adhesive junctions with enhanced signaling potential.
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Affiliation(s)
- Juliana B Lewis
- Program in Immunology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Frank A Scangarello
- Program in Immunology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
- Medical Scientist Training Program, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Joanne M Murphy
- Department of Immunology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Keith P Eidell
- Program in Immunology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Michelle O Sodipo
- Department of Immunology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Michael J Ophir
- Program in Immunology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Ryan Sargeant
- Pacific Immunology Corporation, Ramona, CA 92065, USA
| | | | - Stephen C Bunnell
- Program in Immunology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
- Department of Immunology, Tufts University School of Medicine, Boston, MA 02111, USA
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8
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Nguyen GT, Green ER, Mecsas J. Neutrophils to the ROScue: Mechanisms of NADPH Oxidase Activation and Bacterial Resistance. Front Cell Infect Microbiol 2017; 7:373. [PMID: 28890882 PMCID: PMC5574878 DOI: 10.3389/fcimb.2017.00373] [Citation(s) in RCA: 430] [Impact Index Per Article: 61.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 08/02/2017] [Indexed: 12/16/2022] Open
Abstract
Reactive oxygen species (ROS) generated by NADPH oxidase play an important role in antimicrobial host defense and inflammation. Their deficiency in humans results in recurrent and severe bacterial infections, while their unregulated release leads to pathology from excessive inflammation. The release of high concentrations of ROS aids in clearance of invading bacteria. Localization of ROS release to phagosomes containing pathogens limits tissue damage. Host immune cells, like neutrophils, also known as PMNs, will release large amounts of ROS at the site of infection following the activation of surface receptors. The binding of ligands to G-protein-coupled receptors (GPCRs), toll-like receptors, and cytokine receptors can prime PMNs for a more robust response if additional signals are encountered. Meanwhile, activation of Fc and integrin directly induces high levels of ROS production. Additionally, GPCRs that bind to the bacterial-peptide analog fMLP, a neutrophil chemoattractant, can both prime cells and trigger low levels of ROS production. Engagement of these receptors initiates intracellular signaling pathways, resulting in activation of downstream effector proteins, assembly of the NADPH oxidase complex, and ultimately, the production of ROS by this complex. Within PMNs, ROS released by the NADPH oxidase complex can activate granular proteases and induce the formation of neutrophil extracellular traps (NETs). Additionally, ROS can cross the membranes of bacterial pathogens and damage their nucleic acids, proteins, and cell membranes. Consequently, in order to establish infections, bacterial pathogens employ various strategies to prevent restriction by PMN-derived ROS or downstream consequences of ROS production. Some pathogens are able to directly prevent the oxidative burst of phagocytes using secreted effector proteins or toxins that interfere with translocation of the NADPH oxidase complex or signaling pathways needed for its activation. Nonetheless, these pathogens often rely on repair and detoxifying proteins in addition to these secreted effectors and toxins in order to resist mammalian sources of ROS. This suggests that pathogens have both intrinsic and extrinsic mechanisms to avoid restriction by PMN-derived ROS. Here, we review mechanisms of oxidative burst in PMNs in response to bacterial infections, as well as the mechanisms by which bacterial pathogens thwart restriction by ROS to survive under conditions of oxidative stress.
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Affiliation(s)
- Giang T Nguyen
- Graduate Program in Immunology, Sackler School of Graduate Biomedical Sciences, Tufts UniversityBoston, MA, United States
| | - Erin R Green
- Department of Molecular Biology and Microbiology, Tufts University School of MedicineBoston, MA, United States
| | - Joan Mecsas
- Graduate Program in Immunology, Sackler School of Graduate Biomedical Sciences, Tufts UniversityBoston, MA, United States.,Department of Molecular Biology and Microbiology, Tufts University School of MedicineBoston, MA, United States
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9
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Barr VA, Sherman E, Yi J, Akpan I, Rouquette-Jazdanian AK, Samelson LE. Development of nanoscale structure in LAT-based signaling complexes. J Cell Sci 2016; 129:4548-4562. [PMID: 27875277 PMCID: PMC5201021 DOI: 10.1242/jcs.194886] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 11/04/2016] [Indexed: 12/30/2022] Open
Abstract
The adapter molecule linker for activation of T cells (LAT) plays a crucial role in forming signaling complexes induced by stimulation of the T cell receptor (TCR). These multi-molecular complexes are dynamic structures that activate highly regulated signaling pathways. Previously, we have demonstrated nanoscale structure in LAT-based complexes where the adapter SLP-76 (also known as LCP2) localizes to the periphery of LAT clusters. In this study, we show that initially LAT and SLP-76 are randomly dispersed throughout the clusters that form upon TCR engagement. The segregation of LAT and SLP-76 develops near the end of the spreading process. The local concentration of LAT also increases at the same time. Both changes require TCR activation and an intact actin cytoskeleton. These results demonstrate that the nanoscale organization of LAT-based signaling complexes is dynamic and indicates that different kinds of LAT-based complexes appear at different times during T cell activation.
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Affiliation(s)
- Valarie A Barr
- Laboratory of Cellular and Molecular Biology, CCR, NCI, NIH, Bethesda, MD 20892, USA
| | - Eilon Sherman
- Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel
| | - Jason Yi
- Laboratory of Cellular and Molecular Biology, CCR, NCI, NIH, Bethesda, MD 20892, USA
| | - Itoro Akpan
- Laboratory of Cellular and Molecular Biology, CCR, NCI, NIH, Bethesda, MD 20892, USA
| | | | - Lawrence E Samelson
- Laboratory of Cellular and Molecular Biology, CCR, NCI, NIH, Bethesda, MD 20892, USA
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10
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Hillen KM, Gather R, Enders A, Pircher H, Aichele P, Fisch P, Blumenthal B, Schamel WW, Straub T, Goodnow CC, Ehl S. T cell expansion is the limiting factor of virus control in mice with attenuated TCR signaling: implications for human immunodeficiency. THE JOURNAL OF IMMUNOLOGY 2015; 194:2725-34. [PMID: 25672755 DOI: 10.4049/jimmunol.1400328] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Defining the minimal thresholds for effective antiviral T cell immunity is important for clinical decisions in immunodeficient patients. TCR signaling is critical for T cell development, activation, and effector functions. In this article, we analyzed which of these TCR-mediated processes is limiting for antiviral immunity in a mouse strain with reduced expression of SLP-76 (twp mice). Despite severe T cell activation defects in vitro, twp mice generated a normal proportion of antiviral effector T cells postinfection with lymphocytic choriomeningitis virus (LCMV). Twp CD8(+) T cells showed impaired polyfunctional cytokine production, whereas cytotoxicity as the crucial antiviral effector function for LCMV control was normal. The main limiting factor in the antiviral response of twp mice was impaired T cell proliferation and survival, leading to a 5- to 10-fold reduction of antiviral T cells at the peak of the immune response. This was still sufficient to control infection with the LCMV Armstrong strain, but the more rapidly replicating LCMV-WE induced T cell exhaustion and viral persistence. Thus, under conditions of impaired TCR signaling, reduced T cell expansion was the limiting factor in antiviral immunity. These findings have implications for understanding antiviral immunity in patients with T cell deficiencies.
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Affiliation(s)
- Kristina M Hillen
- Center for Chronic Immunodeficiency, University Medical Center Freiburg and University of Freiburg, 79106 Freiburg, Germany; Institute of Medical Microbiology and Hygiene, Department of Immunology, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Ruth Gather
- Center for Chronic Immunodeficiency, University Medical Center Freiburg and University of Freiburg, 79106 Freiburg, Germany; Institute of Medical Microbiology and Hygiene, Department of Immunology, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Anselm Enders
- Ramaciotti Immunization Genomics Laboratory, Department of Immunology, John Curtin School of Medical Research, Australian National University, Canberra, Acton 2601, Australian Capital Territory, Australia
| | - Hanspeter Pircher
- Institute of Medical Microbiology and Hygiene, Department of Immunology, University of Freiburg, 79104 Freiburg, Germany
| | - Peter Aichele
- Institute of Medical Microbiology and Hygiene, Department of Immunology, University of Freiburg, 79104 Freiburg, Germany
| | - Paul Fisch
- Institute of Pathology, University Medical Center Freiburg, 79106 Freiburg, Germany; and
| | - Britta Blumenthal
- Institute of Pathology, University Medical Center Freiburg, 79106 Freiburg, Germany; and
| | - Wolfgang W Schamel
- Institute of Pathology, University Medical Center Freiburg, 79106 Freiburg, Germany; and
| | - Tobias Straub
- Institute of Medical Microbiology and Hygiene, Department of Immunology, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Christopher C Goodnow
- Department of Immunology, John Curtin School of Medical Research, The Australian National University, Canberra, Acton 2601, Australian Capital Territory, Australia
| | - Stephan Ehl
- Center for Chronic Immunodeficiency, University Medical Center Freiburg and University of Freiburg, 79106 Freiburg, Germany;
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11
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Modulation of TCR responsiveness by the Grb2-family adaptor, Gads. Cell Signal 2014; 27:125-34. [PMID: 25452106 DOI: 10.1016/j.cellsig.2014.10.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 10/16/2014] [Indexed: 12/11/2022]
Abstract
T cell antigen receptor (TCR) signaling depends on three interacting adaptor proteins: SLP-76, Gads, and LAT. Their mechanisms of signaling have been extensively explored, with the aid of fortuitously isolated LAT- and SLP-76-deficient T cell lines, but no such tools were available for Gads, a Grb2-family adaptor that bridges the TCR-inducible interaction between SLP-76 and LAT. TALEN-directed genome editing was applied to disrupt the first coding exon of human Gads in the Jurkat T cell line. Gads was dispensable for TCR-induced phosphorylation of SLP-76, but was a dose-dependent amplifier of TCR-induced CD69 expression. Gads conferred responsiveness to weak TCR stimuli, leading to PLC-γ1 phosphorylation and calcium flux. TALEN-derived, Gads-deficient T cell lines provide a uniquely tractable genetic platform for exploring its regulatory features, such as Gads phosphorylation at T262, which we observed by mass spectrometry. Upon mutation of this site, TCR responsiveness and sensitivity to weak TCR stimuli were increased. This study demonstrates the feasibility of TALEN-based reverse genetics in Jurkat T cells, while enriching our understanding of Gads as a regulated modulator of TCR sensitivity.
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12
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Joseph N, Reicher B, Barda-Saad M. The calcium feedback loop and T cell activation: how cytoskeleton networks control intracellular calcium flux. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:557-68. [PMID: 23860253 DOI: 10.1016/j.bbamem.2013.07.009] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 06/30/2013] [Accepted: 07/08/2013] [Indexed: 12/31/2022]
Abstract
During T cell activation, the engagement of a T cell with an antigen-presenting cell (APC) results in rapid cytoskeletal rearrangements and a dramatic increase of intracellular calcium (Ca(2+)) concentration, downstream to T cell antigen receptor (TCR) ligation. These events facilitate the organization of an immunological synapse (IS), which supports the redistribution of receptors, signaling molecules and organelles towards the T cell-APC interface to induce downstream signaling events, ultimately supporting T cell effector functions. Thus, Ca(2+) signaling and cytoskeleton rearrangements are essential for T cell activation and T cell-dependent immune response. Rapid release of Ca(2+) from intracellular stores, e.g. the endoplasmic reticulum (ER), triggers the opening of Ca(2+) release-activated Ca(2+) (CRAC) channels, residing in the plasma membrane. These channels facilitate a sustained influx of extracellular Ca(2+) across the plasma membrane in a process termed store-operated Ca(2+) entry (SOCE). Because CRAC channels are themselves inhibited by Ca(2+) ions, additional factors are suggested to enable the sustained Ca(2+) influx required for T cell function. Among these factors, we focus here on the contribution of the actin and microtubule cytoskeleton. The TCR-mediated increase in intracellular Ca(2+) evokes a rapid cytoskeleton-dependent polarization, which involves actin cytoskeleton rearrangements and microtubule-organizing center (MTOC) reorientation. Here, we review the molecular mechanisms of Ca(2+) flux and cytoskeletal rearrangements, and further describe the way by which the cytoskeletal networks feedback to Ca(2+) signaling by controlling the spatial and temporal distribution of Ca(2+) sources and sinks, modulating TCR-dependent Ca(2+) signals, which are required for an appropriate T cell response. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.
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Affiliation(s)
- Noah Joseph
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Barak Reicher
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Mira Barda-Saad
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel.
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13
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Murine natural killer immunoreceptors use distinct proximal signaling complexes to direct cell function. Blood 2013; 121:3135-46. [PMID: 23407547 DOI: 10.1182/blood-2012-12-474361] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Signaling pathways leading to natural killer (NK)-cell effector function are complex and incompletely understood. Here, we investigated the proximal signaling pathways downstream of the immunotyrosine-based activation motif (ITAM) bearing activating receptors. We found that the adaptor molecule SH2 domain-containing leukocyte protein of 76 kD (SLP-76) is recruited to microclusters at the plasma membrane in activated NK cells and that this is required for initiation of downstream signaling and multiple NK-cell effector functions in vitro and in vivo. Surprisingly, we found that 2 types of proximal signaling complexes involving SLP-76 were formed. In addition to the canonical membrane complex formed between SLP-76 and linker for activation of T cells (LAT) family members, a novel LAT family-independent SLP-76-dependent signaling pathway was identified. The LAT family-independent pathway involved the SH2 domain of SLP-76 and adhesion and degranulation-promoting adaptor protein (ADAP). Both the LAT family-dependent and ADAP-dependent pathway contributed to interferon-gamma production and cytotoxicity; however, they were not essential for other SLP-76-dependent events, including phosphorylation of AKT and extracellular signal-related kinase and cellular proliferation. These results demonstrate that NK cells possess an unexpected bifurcation of proximal ITAM-mediated signaling, each involving SLP-76 and contributing to optimal NK-cell function.
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14
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Block H, Herter JM, Rossaint J, Stadtmann A, Kliche S, Lowell CA, Zarbock A. Crucial role of SLP-76 and ADAP for neutrophil recruitment in mouse kidney ischemia-reperfusion injury. ACTA ACUST UNITED AC 2012; 209:407-21. [PMID: 22291096 PMCID: PMC3280874 DOI: 10.1084/jem.20111493] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Leukocyte recruitment to the kidney during acute injury is mediated by E-selectin–mediated rolling and requires SLP-76 and the adaptor protein ADAP. Neutrophils trigger inflammation-induced acute kidney injury (AKI), a frequent and potentially lethal occurrence in humans. Molecular mechanisms underlying neutrophil recruitment to sites of inflammation have proved elusive. In this study, we demonstrate that SLP-76 (SH2 domain–containing leukocyte phosphoprotein of 76 kD) and ADAP (adhesion and degranulation promoting adaptor protein) are involved in E-selectin–mediated integrin activation and slow leukocyte rolling, which promotes ischemia-reperfusion–induced AKI in mice. By using genetically engineered mice and transduced Slp76−/− primary leukocytes, we demonstrate that ADAP as well as two N-terminal–located tyrosines and the SH2 domain of SLP-76 are required for downstream signaling and slow leukocyte rolling. The Tec family kinase Bruton tyrosine kinase is downstream of SLP-76 and, together with ADAP, regulates PI3Kγ (phosphoinositide 3-kinase–γ)- and PLCγ2 (phospholipase Cγ2)-dependent pathways. Blocking both pathways completely abolishes integrin affinity and avidity regulation. Thus, SLP-76 and ADAP are involved in E-selectin–mediated integrin activation and neutrophil recruitment to inflamed kidneys, which may underlie the development of life-threatening ischemia-reperfusion–induced AKI in humans.
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Affiliation(s)
- Helena Block
- Department of Anesthesiology and Critical Care Medicine, University of Münster, 48149 Münster, Germany
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15
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Burns JC, Corbo E, Degen J, Gohil M, Anterasian C, Schraven B, Koretzky GA, Kliche S, Jordan MS. The SLP-76 Src homology 2 domain is required for T cell development and activation. THE JOURNAL OF IMMUNOLOGY 2011; 187:4459-66. [PMID: 21949020 DOI: 10.4049/jimmunol.0903379] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The adapter protein Src homology 2 (SH2) domain-containing leukocyte protein of 76 kDa (SLP-76) is critical for multiple aspects of T cell development and function. Through its protein-binding domains, SLP-76 serves as a platform for the assembly of multiple enzymes and adapter proteins that function together to activate second messengers required for TCR signal propagation. The N terminus of SLP-76, which contains three tyrosines that serve as docking sites for SH2 domain-containing proteins, and the central proline-rich region of SLP-76 have been well studied and are known to be important for both thymocyte selection and activation of peripheral T cells. Less is known about the function of the C-terminal SH2 domain of SLP-76. This region inducibly associates with ADAP and HPK1. Combining regulated deletion of endogenous SLP-76 with transgenic expression of a SLP-76 SH2 domain mutant, we demonstrate that the SLP-76 SH2 domain is required for peripheral T cell activation and positive selection of thymocytes, a function not previously attributed to this region. This domain is also important for T cell proliferation, IL-2 production, and phosphorylation of protein kinase D and IκB. ADAP-deficient T cells display similar, but in some cases less severe, defects despite phosphorylation of a negative regulatory site on SLP-76 by HPK1, a function that is lost in SLP-76 SH2 domain mutant T cells.
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Affiliation(s)
- Jeremy C Burns
- Department of Cancer Biology, Signal Transduction Program, Abramson Family Cancer Research Center, University of Pennsylvania, Philadelphia, PA 19104, USA
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16
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Sequential phosphorylation of SLP-76 at tyrosine 173 is required for activation of T and mast cells. EMBO J 2011; 30:3160-72. [PMID: 21725281 DOI: 10.1038/emboj.2011.213] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Accepted: 06/03/2011] [Indexed: 02/03/2023] Open
Abstract
Cooperatively assembled signalling complexes, nucleated by adaptor proteins, integrate information from surface receptors to determine cellular outcomes. In T and mast cells, antigen receptor signalling is nucleated by three adaptors: SLP-76, Gads and LAT. Three well-characterized SLP-76 tyrosine phosphorylation sites recruit key components, including a Tec-family tyrosine kinase, Itk. We identified a fourth, evolutionarily conserved SLP-76 phosphorylation site, Y173, which was phosphorylated upon T-cell receptor stimulation in primary murine and Jurkat T cells. Y173 was required for antigen receptor-induced phosphorylation of phospholipase C-γ1 (PLC-γ1) in both T and mast cells, and for consequent downstream events, including activation of the IL-2 promoter in T cells, and degranulation and IL-6 production in mast cells. In intact cells, Y173 phosphorylation depended on three, ZAP-70-targeted tyrosines at the N-terminus of SLP-76 that recruit and activate Itk, a kinase that selectively phosphorylated Y173 in vitro. These data suggest a sequential mechanism whereby ZAP-70-dependent priming of SLP-76 at three N-terminal sites triggers reciprocal regulatory interactions between Itk and SLP-76, which are ultimately required to couple active Itk to its substrate, PLC-γ1.
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17
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Wu GF, Corbo E, Schmidt M, Smith-Garvin JE, Riese MJ, Jordan MS, Laufer TM, Brown EJ, Maltzman JS. Conditional deletion of SLP-76 in mature T cells abrogates peripheral immune responses. Eur J Immunol 2011; 41:2064-73. [PMID: 21469089 DOI: 10.1002/eji.201040809] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Revised: 03/08/2011] [Accepted: 03/25/2011] [Indexed: 01/23/2023]
Abstract
The adaptor protein Src homology 2 domain-containing leukocyte-specific protein of 76 kDa (SLP-76) is central to the organization of intracellular signaling downstream of the T-cell receptor (TCR). Evaluation of its role in mature, primary T cells has been hampered by developmental defects that occur in the absence of WT SLP-76 protein in thymocytes. Here, we show that following tamoxifen-regulated conditional deletion of SLP-76, mature, antigen-inexperienced T cells maintain normal TCR surface expression but fail to transduce TCR-generated signals. Conditionally deficient T cells fail to proliferate in response to antigenic stimulation or a lymphopenic environment. Mice with induced deletion of SLP-76 are resistant to induction of the CD4+ T-cell-mediated autoimmune disease experimental autoimmune encephalomyelitis. Altogether, our findings demonstrate the critical role of SLP-76-mediated signaling in initiating T-cell-directed immune responses both in vitro and in vivo and highlight the ability to analyze signaling processes in mature T cells in the absence of developmental defects.
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Affiliation(s)
- Gregory F Wu
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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18
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Chiang J, Hodes RJ. Cbl enforces Vav1 dependence and a restricted pathway of T cell development. PLoS One 2011; 6:e18542. [PMID: 21490975 PMCID: PMC3072394 DOI: 10.1371/journal.pone.0018542] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Accepted: 03/03/2011] [Indexed: 11/29/2022] Open
Abstract
Extensive studies of pre-TCR- and TCR-dependent signaling have led to characterization of a pathway deemed essential for efficient T cell development, and comprised of a cascade of sequential events involving phosphorylation of Lck and ZAP-70, followed by phosphorylation of LAT and SLP-76, and subsequent additional downstream events. Of interest, however, reports from our lab as well as others have indicated that the requirements for ZAP-70, LAT, and SLP-76 are partially reversed by inactivation of c-Cbl (Cbl), an E3 ubiquitin ligase that targets multiple molecules for ubiquitination and degradation. Analysis of signaling events in these Cbl knockout models, including the recently reported analysis of SLP-76 transgenes defective in interaction with Vav1, suggested that activation of Vav1 might be a critical event in alternative pathways of T cell development. To extend the analysis of signaling requirements for thymic development, we have therefore assessed the effect of Cbl inactivation on the T cell developmental defects that occur in Vav1-deficient mice. The defects in Vav1-deficient thymic development, including a marked defect in DN3-DN4 transition, were completely reversed by Cbl inactivation, accompanied by enhanced phosphorylation of PLC-γ1 and ERKs in response to pre-TCR/TCR cross-linking of Vav1-/-Cbl-/- DP thymocytes. Taken together, these results suggest a substantially modified paradigm for pre-TCR/TCR signaling and T cell development. The observed consensus pathways of T cell development, including requirements for ZAP-70, LAT, SLP-76, and Vav1, appear to reflect the restriction by Cbl of an otherwise much broader set of molecular pathways capable of mediating T cell development.
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Affiliation(s)
- Jeffrey Chiang
- Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America.
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19
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Sylvain NR, Nguyen K, Bunnell SC. Vav1-mediated scaffolding interactions stabilize SLP-76 microclusters and contribute to antigen-dependent T cell responses. Sci Signal 2011; 4:ra14. [PMID: 21386095 DOI: 10.1126/scisignal.2001178] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The guanine nucleotide exchange factor (GEF) Vav1 synergizes with the adaptor protein SLP-76 (Src homology 2 domain--containing leukocyte phosphoprotein of 76 kD) to support T cell development and activation. In response to ligation of the T cell receptor (TCR), SLP-76 is assembled into microclusters that provide an essential platform for the signaling events that drive T cell activation. We found that Vav1 selectively entered SLP-76 microclusters, rather than TCR microclusters, influencing their stability and function. The carboxyl terminus of Vav1, which consists of Src homology domains, was both necessary and sufficient for the entry of Vav1 into SLP-76 microclusters; however, this fragment of Vav1 was insufficient to stabilize the microclusters, and it potently suppressed T cell activation. This indicated that the amino terminus of Vav1, which has the GEF domain, also contributed to the integrity of SLP-76 microclusters and thereby to T cell activation. These microcluster-stabilizing functions were independent of the GEF activity in the amino terminus of Vav1 and were unaffected if the GEF function of Vav1 was either inactivated or constitutively activated by mutation. In contrast, Vav1 deletion mutants lacking either the calponin homology domain or the catalytic core of the GEF exhibited mild scaffolding defects, but they differentially affected TCR-dependent calcium ion (Ca²+) responses. We conclude that multiple GEF-independent scaffolding functions distributed throughout the amino terminus of Vav1 contribute to the activation of T cells by acting synergistically to increase the stability and function of SLP-76 microclusters.
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Affiliation(s)
- Nicholas R Sylvain
- Program in Immunology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
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20
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Shim EK, Jung SH, Lee JR. Role of two adaptor molecules SLP-76 and LAT in the PI3K signaling pathway in activated T cells. THE JOURNAL OF IMMUNOLOGY 2011; 186:2926-35. [PMID: 21282515 DOI: 10.4049/jimmunol.1001785] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Previously, we identified p85, a subunit of PI3K, as one of the molecules that interacts with the N-terminal region of Src homology 2 domain-containing leukocyte protein of 76 kDa (SLP-76). We also demonstrated that tyrosine phosphorylation either at the 113 and/or 128 position is sufficient for the association of SLP-76 with the Src homology 2 domain near the N terminus of p85. The present study further examines the role of the association of these two molecules on the activation of PI3K signaling cascade. Experiments were done to determine the role of SLP-76, either wild-type, tyrosine mutants, or membrane-targeted forms of various SLP-76 constructs, on the membrane localization and phosphorylation of Akt, which is an event downstream of PI3K activation. Reconstitution studies with these various SLP-76 constructs in a Jurkat variant cell line that lacks SLP-76 or linker for activation of T cells (LAT) show that the activation of PI3K pathway following TCR ligation requires both SLP-76 and LAT adaptor proteins. The results suggest that SLP-76 associates with p85 after T cell activation and that LAT recruits this complex to the membrane, leading to Akt activation.
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Affiliation(s)
- Eun Kyung Shim
- Division of Life and Pharmaceutical Sciences, Ewha Womans University, Seoul 120-750, Korea
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21
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Understanding signal integration through targeted mutations of an adapter protein. FEBS Lett 2010; 584:4901-9. [PMID: 20965179 DOI: 10.1016/j.febslet.2010.10.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 10/13/2010] [Indexed: 11/23/2022]
Abstract
Immunoreceptor engagement leads to the activation of multiple second messenger cascades, and integration of these pathways requires proper function of a number of adapter proteins. Although adapters possess no intrinsic enzymatic function, they nucleate the formation of multi-molecular protein complexes to support downstream signaling. Since adapters contain functionally distinct domains, intense investigation has been devoted to understanding how these regions act to integrate signals. This review describes the evolution of studies investigating one of these adapters, the SH2 domain-containing leukocyte protein of 76 kDa. Through utilizing biochemical, genetic and imaging techniques, a model has emerged describing how this adapter regulates signals resulting in complex immune responses.
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22
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Independent and cooperative roles of adaptor molecules in proximal signaling during FcepsilonRI-mediated mast cell activation. Mol Cell Biol 2010; 30:4188-96. [PMID: 20606011 DOI: 10.1128/mcb.00305-10] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Activation through FcepsilonRI, a high-affinity IgE-binding receptor, is critical for mast cell function during allergy. The formation of a multimolecular proximal signaling complex nucleated by the adaptor molecules SLP-76 and LAT1 is required for activation through this receptor. Based on previous T-cell studies, current dogma dictates that LAT1 is required for plasma membrane recruitment and function of SLP-76. Unexpectedly, we found that the recruitment and phosphorylation of SLP-76 were preserved in LAT1(-/-) mast cells and that SLP-76(-/-) and LAT1(-/-) mast cells harbored distinct functional and biochemical defects. The LAT1-like molecule LAT2 was responsible for the preserved membrane localization and phosphorylation of SLP-76 in LAT1(-/-) mast cells. Although LAT2 supported SLP-76 phosphorylation and recruitment to the plasma membrane, LAT2 only partially compensated for LAT1-mediated cell signaling due to its decreased ability to stabilize interactions with phospholipase Cgamma (PLCgamma). Comparison of SLP-76(-/-) LAT1(-/-) and SLP-76(-/-) mast cells revealed that some functions of LAT1 could occur independently of SLP-76. We propose that while SLP-76 and LAT1 depend on each other for many of their functions, LAT2/SLP-76 interactions and SLP-76-independent LAT1 functions also mediate a positive signaling pathway downstream of FcepsilonRI in mast cells.
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23
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Jordan MS, Koretzky GA. Coordination of receptor signaling in multiple hematopoietic cell lineages by the adaptor protein SLP-76. Cold Spring Harb Perspect Biol 2010; 2:a002501. [PMID: 20452948 DOI: 10.1101/cshperspect.a002501] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The adaptor protein SLP-76 is expressed in multiple hematopoietic lineages including T cells, platelets, and neutrophils. SLP-76 mediated signaling is dependent on its multiple protein interaction domains, as it creates a scaffold on which key signaling complexes are built. SLP-76 is critical for supporting signaling downstream of both immunoreceptors and integrins. The signaling molecules used both upstream and downstream of SLP-76 are similar among these receptors and across cell types; however, important differences exist. Appreciating how SLP-76 coordinates signal transduction across different cell and receptor types provides insights into the complex interplay of pathways critical for activation of cells of the immune system that are essential for host defense.
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Affiliation(s)
- Martha S Jordan
- Abramson Family Cancer Institute, University of Pennsylvania, Philadelphia, 19104, USA
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24
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The adapter protein SLP-76 mediates "outside-in" integrin signaling and function in T cells. Mol Cell Biol 2009; 29:5578-89. [PMID: 19667077 DOI: 10.1128/mcb.00283-09] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The adapter protein SH2 domain-containing leukocyte protein of 76 kDa (SLP-76) is an essential mediator of signaling from the T-cell antigen receptor (TCR). We report here that SLP-76 also mediates signaling downstream of integrins in T cells and that SLP-76-deficient T cells fail to support adhesion to integrin ligands. In response to both TCR and integrin stimulation, SLP-76 relocalizes to surface microclusters that colocalize with phosphorylated signaling proteins. Disruption of SLP-76 recruitment to the protein named LAT (linker for activation of T cells) inhibits SLP-76 clustering downstream of the TCR but not downstream of integrins. Conversely, an SLP-76 mutant unable to bind ADAP (adhesion and degranulation-promoting adapter protein) forms clusters following TCR but not integrin engagement and fails to support T-cell adhesion to integrin ligands. These findings demonstrate that SLP-76 relocalizes to integrin-initiated signaling complexes by a mechanism different from that employed during TCR signaling and that SLP-76 relocalization corresponds to SLP-76-dependent integrin function in T cells.
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SLP-76-ADAP adaptor module regulates LFA-1 mediated costimulation and T cell motility. Proc Natl Acad Sci U S A 2009; 106:12436-41. [PMID: 19617540 DOI: 10.1073/pnas.0900510106] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Although adaptor ADAP (FYB) and its binding to SLP-76 has been implicated in TcR-induced "inside-out" signaling for LFA-1 activation in T cells, little is known regarding its role in LFA-1-mediated "outside-in" signaling. In this study, we demonstrate that ADAP and SLP-76-ADAP binding are coupled to LFA-1 costimulation of IL-2 production, F-actin clustering, cell polarization, and T cell motility. LFA-1 enhancement of anti-CD3-induced IL-2 production was completely dependent on SLP-76-ADAP binding. Further, anti-CD3 was found to require CD11a ligation by antibody or ICAM1 to cause T cell polarization. ADAP augmented this polarization induced by anti-CD3/CD11a, but not by anti-CD3 alone. ADAP expression with LFA-1 ligation alone was sufficient to polarize T cells directly and to increase T cell motility whereas the loss of ADAP in ADAP-/- primary T cells reduced motility. A mutant lacking SLP-76-binding sites (M12) blocked LFA-1 costimulation of IL-2 production, polarization, and motility. LFA-1-ADAP polarization was also dependent on src kinases, Rho GTPases, phospholipase C, and phosphoinositol 3-kinase. Our findings provide evidence of an obligatory role for the SLP-76-ADAP module in LFA-1-mediated costimulation in T cells.
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26
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Koretzky GA. The Role of SH2 Domain-containing Leukocyte Phosphoprotein of 76 kDa in the Regulation of Immune Cell Development and Function. Immune Netw 2009; 9:75-83. [PMID: 20107536 PMCID: PMC2803302 DOI: 10.4110/in.2009.9.3.75] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Accepted: 05/14/2009] [Indexed: 01/14/2023] Open
Abstract
Recent years have seen an explosion of new knowledge defining the molecular events that are critical for development and activation of immune cells. Much of this new information has come from a careful molecular dissection of key signal transduction pathways that are initiated when immune cell receptors are engaged. In addition to the receptors themselves and critical effector molecules, these signaling pathways depend on adapters, proteins that have no intrinsic effector function but serve instead as scaffolds to nucleate multimolecular complexes. This review summarizes some of what has been learned about one such adapter protein, SH2 domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76), and how it regulates and integrates signals after engagement of immunoreceptors and integrins on various immune cell lineages.
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Affiliation(s)
- Gary A Koretzky
- Department of Pathology and Laboratory Medicine and Department of Medicine, Abramson Family Cancer Research Institute, University of Pennsylvania School of Medicine, Philadelphia, PA, 19104, USA
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27
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Bezman NA, Baker RG, Lenox LE, Jordan MS, Koretzky GA. Cutting edge: rescue of pre-TCR but not mature TCR signaling in mice expressing membrane-targeted SLP-76. THE JOURNAL OF IMMUNOLOGY 2009; 182:5183-7. [PMID: 19380761 DOI: 10.4049/jimmunol.0802176] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
SLP-76 (Src homology 2 domain-containing leukocyte phosphoprotein of 76 kDa) organizes signaling from immunoreceptors, including the platelet collagen receptor, the pre-TCR, and the TCR, and is required for T cell development. In this study we examine a mouse in which wild-type SLP-76 is replaced with a mutant constitutively targeted to the cell membrane. Membrane-targeted SLP-76 (MTS) supports ITAM signaling in platelets and from the pre-TCR. Signaling from the mature TCR, however, is defective in MTS thymocytes, resulting in failed T cell differentiation. Defective thymic selection by MTS is not rescued by a SLP-76 mutant whose localization is restricted to the cytosol. Thus, fixed localization of SLP-76 reveals differential requirements for the subcellular localization of signaling complexes downstream of the pre-TCR vs mature TCR.
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Affiliation(s)
- Natalie A Bezman
- Abramson Family Cancer Research Institute, Philadelphia, PA 19104, USA
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28
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The importance of Src homology 2 domain-containing leukocyte phosphoprotein of 76 kilodaltons sterile-alpha motif domain in thymic selection and T-cell activation. Blood 2009; 114:74-84. [PMID: 19401562 DOI: 10.1182/blood-2008-09-177832] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The Src homology 2 domain-containing leukocyte phosphoprotein of 76 kilodaltons (SLP-76) is a cytosolic adaptor protein essential for thymocyte development and T-cell activation. It contains a sterile-alpha motif (SAM) domain, 3 phosphotyrosine motifs, a proline-rich region, and a Src homology 2 domain. Whereas the other domains have been extensively studied, the role of the SAM domain in SLP-76 function is not known. To understand the function of this domain, we generated SLP-76 knockin mice with the SAM domain deleted. Analysis of these mice showed that thymocyte development was partially blocked at the double-positive to single-positive transition. Positive and negative thymic selection was also impaired. In addition, we analyzed T-cell receptor (TCR)-mediated signaling in T cells from these mutant mice. TCR-mediated inositol 1,4,5-triphosphate production, calcium flux, and extracellular signal-regulated kinase activation were decreased, leading to defective interleukin-2 production and proliferation. Moreover, despite normal association between Gads and SLP-76, TCR-mediated formation of SLP-76 microclusters was impaired by the deletion of the SAM domain. Altogether, our data demonstrated that the SAM domain is indispensable for optimal SLP-76 signaling.
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29
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Abstract
The analysis of lymphocyte signaling was greatly enhanced by the advent of gene targeting, which allows the selective inactivation of a single gene. Although this gene 'knockout' approach is often informative, in many cases, the phenotype resulting from gene ablation might not provide a complete picture of the function of the corresponding protein. If a protein has multiple functions within a single or several signaling pathways, or stabilizes other proteins in a complex, the phenotypic consequences of a gene knockout may manifest as a combination of several different perturbations. In these cases, gene targeting to 'knock in' subtle point mutations might provide more accurate insight into protein function. However, to be informative, such mutations must be carefully based on structural and biophysical data.
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Affiliation(s)
- Alexander Saveliev
- Medical Research Council National Institute for Medical Research, London, UK
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30
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Abstract
Integrins are cell surface heterodimers that bind adhesion molecules expressed on other cells or in the extracellular matrix. Integrin-mediated interactions are critical for T cell development in the thymus, migration of T cells in the periphery, and induction of T cell effector functions. In resting T cells, integrins are maintained in a low affinity state. Engagement of the T cell receptor or chemokine receptors increases integrin affinity, enabling integrins to bind their ligands and initiate a signaling cascade resulting in altered cell morphology and motility. Our laboratory is interested how adapter proteins, mediators of intracellular signal transduction, regulate both signals from the T cell receptor to integrins (inside-out signaling) and (outside-in) signals from integrins into the cell.
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31
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Raberger J, Boucheron N, Sakaguchi S, Penninger JM, Ellmeier W. Impaired T-cell development in the absence of Vav1 and Itk. Eur J Immunol 2009; 38:3530-42. [PMID: 19009524 DOI: 10.1002/eji.200838388] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Vav1 and the Tec family kinase Itk act in similar T-cell activation pathways. Both molecules interact with members of the Cbl family of E3 ubiquitin ligases, and signaling defects in Vav1(-/-) T cells are rescued upon deletion of Cbl-b. In this study we investigate the relation between Itk and Cbl-b or Vav1 by generating Itk/Cbl-b and Itk/Vav1 double-deficient mice. Deletion of Cbl-b in Itk(-/-) CD4(+) T cells restored proliferation and partially IL-2 production, and also led to a variable rescue of IL-4 production. Thus, Itk and Vav1 act mechanistically similarly in peripheral T cells, since the defects in Itk(-/-) T cells, as in Vav1(-/-) T cells, are rescued if cells are released from the negative regulation mediated by Cbl-b. In addition, only few peripheral CD4(+) and CD8(+) T cells were present in Vav1(-/-)Itk(-/-) mice due to severely impaired thymocyte differentiation. Vav1(-/-)Itk(-/-) thymocyte numbers were strongly reduced compared with WT, Itk(-/-) or Vav1(-/-) mice, and double-positive thymocytes displayed increased cell death and impaired positive selection. Therefore, our data also reveal that the combined activity of Vav1 and Itk is required for proper T-cell development and the generation of the peripheral T-cell pool.
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Affiliation(s)
- Julia Raberger
- Division of Immunobiology, Institute of Immunology, Center for Physiology, Pathophysiology and Immunology, Medical University of Vienna, Vienna, Austria
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32
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Chiang YJ, Jordan MS, Horai R, Schwartzberg PL, Koretzky GA, Hodes RJ. Cbl enforces an SLP76-dependent signaling pathway for T cell differentiation. J Biol Chem 2008; 284:4429-38. [PMID: 19074136 PMCID: PMC2640981 DOI: 10.1074/jbc.m808679200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
A signaling pathway involving ZAP-70, LAT, and SLP76 has been regarded as
essential for receptor-driven T cell development and activation. Consistent
with this model, mice deficient in SLP76 have a complete block at the double
negative 3 stage of T cell development. Recently, however, it has been
reported that inactivation of Cbl, a ubiquitin-protein isopeptide ligase,
partially rescues T cell development in SLP76-deficient mice. To probe the
influence of Cbl on domain-specific SLP76 functions, we reconstituted
SLP76-/- Cbl-/- mice with Slp76 transgenes
bearing mutations in each of three functional domains of SLP76 as follows:
Y3F, in which the amino-terminal tyrosine residues of SLP76 were mutated,
eliminating sites of SLP76 interaction with Vav, Nck, and Itk; Δ20, in
which 20 amino acids in the proline-rich region of SLP76 were deleted,
removing a binding site for Gads; and RK, in which arginine 448 of SLP76 was
replaced by lysine, abolishing function of the Src homology 2 domain. Although
each of these transgenes has been shown to partially rescue T cell development
in SLP76-/- mice, we report here that Cbl inactivation completely
reverses the severe double negative 3 developmental block that occurs in
SLP76-deficient mice expressing the Y3F transgene (Y3F mice) and
partially rescues the defect in positive selection in T cell receptor
transgenic Y3F mice, but in contrast fails to rescue thymic development of
SLP76-deficient mice expressing the Δ20 or RK transgene. Rescue in
SLP76-/-Cbl-/-Y3F double-positive thymocytes is
associated with enhanced tyrosine phosphorylation of signaling molecules,
including Lck, Vav, PLC-γ1, and ERKs, but not Itk, in response to T cell
receptor stimulation. Thus, our data demonstrate that Cbl suppresses
activation of a bypass signaling pathway and thereby enforces SLP76 dependence
of early T cell development.
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Affiliation(s)
- Y Jeffrey Chiang
- Experimental Immunology Branch, NCI, and NIA, National Institutes of Health, Bethesda, Maryland 20892, USA.
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33
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Takeda K, Harada Y, Watanabe R, Inutake Y, Ogawa S, Onuki K, Kagaya S, Tanabe K, Kishimoto H, Abe R. CD28 stimulation triggers NF-kappaB activation through the CARMA1-PKCtheta-Grb2/Gads axis. Int Immunol 2008; 20:1507-15. [PMID: 18829987 DOI: 10.1093/intimm/dxn108] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
CD28 stimulation contributes to activation of the IL-2 promoter by up-regulating the activity of several transcription factors, including nuclear factor kappaB (NF-kappaB)/Rel family members. However, the signal-transducing cascades linking the CD28 molecule and activation of NF-kappaB remain unclear. Protein kinase C (PKC) , CARMA1 and Bcl10 have recently been reported to integrate TCR-mediated NF-kappaB activation. However, since the data in these studies were drawn from experiments in which T cells were usually stimulated with both TCR and CD28, the relative contributions of TCR- and CD28-mediated signals to initiation of the NF-kappaB pathway remain elusive. To examine the role of these molecules in NF-kappaB activation through CD28-mediated stimulation, Bcl10 was over-expressed in Jurkat cells and their NF-kappaB activation by CD28- or TCR-cross-linking was evaluated. We found that CD28 stimulation alone can induce NF-kappaB activation in Bcl10-over-expressing Jurkat cells, whereas TCR stimulation alone has only little effect. In addition, we found that Bcl10-induced NF-kappaB activation through CD28-mediated stimulation could be blocked by the dominant-negative form of PKC or CARMA1. Furthermore, genetic studies revealed that Grb2/Gads binding, but not phosphatidylinositol 3-kinase binding, is important in CD28-mediated NF-kappaB activation. These findings indicate that the PKC-CARMA1-Bcl10 signaling pathway participates in the CD28 co-stimulatory signal independently of the TCR-signaling pathway, which leads us to propose that the activation of the NF-kappaB-signaling pathway via PKC-CARMA1-Bcl10 may be markedly dependent on CD28 stimulation rather than TCR stimulation.
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Affiliation(s)
- Kei Takeda
- Research Institute for Biological Sciences, Tokyo University of Science, 2669 Yamazaki, Noda, Chiba 278-0022, Japan
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34
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Bezman NA, Lian L, Abrams CS, Brass LF, Kahn ML, Jordan MS, Koretzky GA. Requirements of SLP76 tyrosines in ITAM and integrin receptor signaling and in platelet function in vivo. ACTA ACUST UNITED AC 2008; 205:1775-88. [PMID: 18663126 PMCID: PMC2525600 DOI: 10.1084/jem.20080240] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Src homology 2 domain–containing leukocyte phosphoprotein of 76 kD (SLP76), an adaptor that plays a critical role in platelet activation in vitro, contains three N-terminal tyrosine residues that are essential for its function. We demonstrate that mice containing complementary tyrosine to phenylalanine mutations in Y145 (Y145F) and Y112 and Y128 (Y112/128F) differentially regulate integrin and collagen receptor signaling. We show that mutation of Y145 leads to severe impairment of glycoprotein VI (GPVI)–mediated responses while preserving outside-in integrin signaling. Platelets from Y112/128F mice, although having mild defects in GPVI signaling, exhibit defective actin reorganization after GPVI or αIIbβ3 engagement. The in vivo consequences of these signaling defects correlate with the mild protection from thrombosis seen in Y112/128F mice and the near complete protection observed in Y145F mice. Using genetic complementation, we further demonstrate that all three phosphorylatable tyrosines are required within the same SLP76 molecule to support platelet activation by GPVI.
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Affiliation(s)
- Natalie A Bezman
- Leonard and Madlyn Abramson Family Cancer Research Institute, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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35
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Jordan MS, Smith JE, Burns JC, Austin JET, Nichols KE, Aschenbrenner AC, Koretzky GA. Complementation in trans of altered thymocyte development in mice expressing mutant forms of the adaptor molecule SLP76. Immunity 2008; 28:359-69. [PMID: 18342008 DOI: 10.1016/j.immuni.2008.01.010] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2007] [Revised: 12/28/2007] [Accepted: 01/25/2008] [Indexed: 11/16/2022]
Abstract
The adaptor protein SLP76 directs signaling downstream of the T cell receptor (TCR) and is essential for thymocyte development. SLP76 contains three N-terminal tyrosines that are critical for its function. To define the role of these residues in thymocyte development, we generated two lines of "knock-in" mice, one expressing a mutation in tyrosine 145 (Y145F) and a second harboring two point mutations at tyrosines 112 and 128 (Y112-128F). We show here that although thymocyte development requires both Y145- and Y112-128-generated signals, selection was more dependent upon Y145. Although several proximal TCR signaling events were defective in both mutant mice, phosphorylation of the guanine nucleotide exchange factor, Vav1, and activation of Itk-dependent pathways were differentially affected by mutations at Y112-128 and Y145, respectively. Analysis of mice expressing one Y145F and one Y112-128F allele revealed that these mutants could complement one another in trans, demonstrating cooperativity between two or more SLP76 molecules. Thus, the N-terminal tyrosines of SLP76 are required for thymocyte selection but can function on separate molecules to support TCR signaling.
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Affiliation(s)
- Martha S Jordan
- Cancer Biology, Abramson Family Cancer Research Institute, 427 BRBII/III, University of Pennsylvania School of Medicine, Philadelphia, PA, 19104, USA
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36
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Dluzniewska J, Zou L, Harmon IR, Ellingson MT, Peterson EJ. Immature hematopoietic cells display selective requirements for adhesion- and degranulation-promoting adaptor protein in development and homeostatsis. Eur J Immunol 2007; 37:3208-19. [PMID: 17948263 DOI: 10.1002/eji.200737094] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Adhesion- and degranulation-promoting adaptor protein (ADAP) modulates T cell development and function and promotes TCR signaling. Regulation of ADAP protein expression during thymopoiesis and in development of other hematopoietic lineages has not been explored. Using intracellular staining, we detected ADAP protein in bone marrow lymphocyte precursors. Like its binding partner SH2-containing leukocyte phosphoprotein of 76 kDa, ADAP is dynamically regulated during thymocyte positive selection. ADAP is also found in unconventional thymocytes, including NKT, CD8alphaalpha, and TCRgammadelta T cells. In peripheral T cells, ADAP is up-regulated after TCR stimulation and with acquisition of memory status. Although absent in splenic B cells, ADAP is present in pro-B cells, as well as in BM erythrocyte and myeloid progenitors. Studies with radiation chimeras show that ADAP is dispensable for NKT, CD8alphaalpha and TCRgammadelta T cell development, while confirming that ADAP is required for optimal development of conventional TCRalphabeta T cells in the thymus. Interestingly, ADAP is necessary for CD8alphaalpha homeostasis in the small intestinal epithelium, yet is dispensable for optimal reconstitution of splenic B cell populations. Our observations highlight the dynamic regulation of ADAP during T cell maturation and document expression patterns that suggest a possible role for ADAP in development of non-T hematopoietic lineages.
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Affiliation(s)
- Joanna Dluzniewska
- Department of Internal Medicine and Center for Immunology, University of Minnesota, Minneapolis, MN 55455, USA
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37
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Ramsey K, Luckashenak N, Koretzky GA, Clements JL. Impaired thymic selection in mice expressing altered levels of the SLP-76 adaptor protein. J Leukoc Biol 2007; 83:419-29. [PMID: 17965338 DOI: 10.1189/jlb.0507297] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Intracellular signaling initiated by ligation of the TCR influences cell fate at multiple points during the lifespan of a T cell. This is especially evident during thymic selection, where the nature of TCR-dependent signaling helps to establish a MHC-restricted, self-tolerant T cell repertoire. The Src homology 2 domain-containing leukocyte-specific phosphoprotein of 76 kDa (SLP-76) adaptor protein is a required intermediate in multiple signaling pathways triggered by TCR engagement, several of which have been implicated in dictating the outcome of thymic selection (e.g., intracellular calcium flux and activation of ERK family MAPKs). To determine if thymocyte maturation and selection at later stages of development are sensitive to perturbations in SLP-76 levels, we analyzed these crucial events using several transgenic (Tg) lines of mice expressing altered levels of SLP-76 in the thymus. In Tg mice expressing low levels of SLP-76 in preselection thymocytes, the CD4:CD8 ratio in the thymus and spleen was skewed in a manner consistent with impaired selection and/or maturation of CD4+ thymocytes. Low SLP-76 expression also correlated with reduced CD5 expression on immature thymocytes, consistent with reduced TCR signaling potential. In contrast, reconstitution of SLP-76 at higher levels resulted in normal thymic CD5 expression and CD4:CD8 ratios in the thymus and periphery. It is curious that thymic deletion of TCR-Tg (HY) thymocytes was markedly impaired in both lines of Tg-reconstituted SLP-76-/- mice. Studies using chimeric mice indicate that the defect in deletion of HY+ thymocytes is intrinsic to the developing thymocyte, suggesting that maintenance of sufficient SLP-76 expression from the endogenous locus is a key element in the selection process.
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Affiliation(s)
- Kimberley Ramsey
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA
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38
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Jordan MS, Maltzman JS, Kliche S, Shabason J, Smith JE, Obstfeld A, Schraven B, Koretzky GA. In vivo disruption of T cell development by expression of a dominant-negative polypeptide designed to abolish the SLP-76/Gads interaction. Eur J Immunol 2007; 37:2961-72. [PMID: 17823979 DOI: 10.1002/eji.200636855] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Multi-molecular complexes nucleated by adaptor proteins play a central role in signal transduction. In T cells, one central axis consists of the assembly of several signaling proteins linked together by the adaptors linker of activated T cells (LAT), Src homology 2 domain-containing leukocyte-specific phosphoprotein of 76 kDa (SLP-76), and Grb2-related adaptor downstream of Shc (Gads). Each of these adaptors has been shown to be important for normal T cell development, and their proper sub-cellular localization is critical for optimal function in cell lines. We previously demonstrated in Jurkat T cells and a rat basophilic leukemic cell line that expression of a 50-amino acid polypeptide identical to the site on SLP-76 that binds to Gads blocks proper localization of SLP-76 and SLP-76-dependent signaling events. Here we extend these studies to investigate the ability of this polypeptide to inhibit TCR-induced integrin activity in Jurkat cells and to inhibit in vivo thymocyte development and primary T cell function. These data provide evidence for the in vivo function of a dominant-negative peptide based upon the biology of SLP-76 action and suggest the possibility of therapeutic potential of targeting the SLP-76/Gads interaction.
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Affiliation(s)
- Martha S Jordan
- Department of Cancer Biology, Abramson Family Cancer Research Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
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39
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Abstract
Adapters are multidomain molecules that recruit effector proteins during signal transduction by immunoreceptors and integrins. The absence of these scaffolding molecules profoundly affects development and function of various hematopoietic lineages, underscoring their importance as regulators of signaling cascades. An emerging aspect of the mechanism by which engaged immunoreceptors and integrins transmit signals within the cell is by differential usage of various adapters that function to nucleate formation of distinct signaling complexes in a specific location within the cell. In this review, we discuss the mechanisms by which adapter proteins coordinate signal transduction with an emphasis on the role of subcellular compartmentalization in adapter function.
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Affiliation(s)
- Natalie Bezman
- Abramson Family Cancer Research Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
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40
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Abstract
Integrin adhesion receptors are critical for antigen recognition by T cells and for regulated recirculation and trafficking into and through various tissues in the body. T-cell receptor (TCR) signaling induces rapid increases in integrin function that facilitate T-cell activation by promoting stable contact with antigen-presenting cells and extracellular proteins in the environment. In this review, we outline the molecular mechanisms by which the TCR signals to integrins and present a model that highlights four key events: (i) initiation of proximal TCR signals nucleated by the linker for activated T cells (LAT) adapter protein and involving Itk, phospholipase C-gamma1, Vav1, and Src homology 2 domain-containing leukocyte-specific phosphoprotein of 76 kDa; (ii) transmission of integrin activation signals from the LAT signalosome to integrins by protein kinase (PK) C and the adapter protein, adhesion and degranulation-promoting adapter protein; (iii) assembly of integrin-associated signaling complexes that include PKD, the guanosine triphosphatase Rap1 and its effectors, and talin; and (iv) reorganization of the actin cytoskeleton by WAVE2 and other actin-remodeling proteins. These events coordinate changes in integrin conformation and clustering that result in enhanced integrin functional activity following TCR stimulation.
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Affiliation(s)
- Brandon J Burbach
- Department of Laboratory Medicine and Pathology, Center for Immunology, University of Minnesota Medical School, Minneapolis, MN 55455, USA
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41
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Abudula A, Grabbe A, Brechmann M, Polaschegg C, Herrmann N, Goldbeck I, Dittmann K, Wienands J. SLP-65 signal transduction requires Src homology 2 domain-mediated membrane anchoring and a kinase-independent adaptor function of Syk. J Biol Chem 2007; 282:29059-29066. [PMID: 17681949 DOI: 10.1074/jbc.m704043200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The family of SLPs (Src homology 2 domain-containing leukocyte adaptor proteins) are cytoplasmic signal effectors of lymphocyte antigen receptors. A main function of SLP is to orchestrate the assembly of Ca(2+)-mobilizing enzymes at the inner leaflet of the plasma membrane. For this purpose, SLP-76 in T cells utilizes the transmembrane adaptor LAT, but the mechanism of SLP-65 membrane anchoring in B cells remains an enigma. We now employed two genetic reconstitution systems to unravel structural requirements of SLP-65 for the initiation of Ca(2+) mobilization and subsequent activation of gene transcription. First, mutational analysis of SLP-65 in DT40 B cells revealed that its C-terminal Src homology 2 domain controls efficient tyrosine phosphorylation by the kinase Syk, plasma membrane recruitment, as well as downstream signaling to NFAT activation. Second, we dissected these processes by expressing SLP-65 in SLP-76-deficient T cells and found that a kinase-independent adaptor function of Syk is required to link phosphorylated SLP-65 to Ca(2+) mobilization. These approaches unmask a mechanistic complexity of SLP-65 activation and coupling to signaling cascades in that Syk is upstream as well as downstream of SLP-65. Moreover, membrane anchoring of the SLP-65-assembled Ca(2+) initiation complex, which appears to be fundamentally different from that of closely related SLP-76, does not necessarily involve a B cell-specific component.
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Affiliation(s)
- Abulizi Abudula
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Annika Grabbe
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Markus Brechmann
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Christian Polaschegg
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Nadine Herrmann
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Ingo Goldbeck
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Kai Dittmann
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Jürgen Wienands
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany.
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42
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Ménasché G, Kliche S, Bezman N, Schraven B. Regulation of T-cell antigen receptor-mediated inside-out signaling by cytosolic adapter proteins and Rap1 effector molecules. Immunol Rev 2007; 218:82-91. [PMID: 17624945 DOI: 10.1111/j.1600-065x.2007.00543.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Integrins are critical for the migration of T cells to lymphoid organs and to sites of inflammation and are also necessary for productive interactions between T cells and antigen-presenting cells. Integrin activation is enhanced following T-cell receptor (TCR) engagement, as signals initiated by the TCR increase affinity and avidity of integrins for their ligands. This process, known as inside-out signaling, has been shown to require several molecular components including the cytosolic adapter proteins adhesion and degranulation-promoting adapter protein and Src homology 2 domain-containing adapter protein of 55 kDa, the low molecular weight guanosine triphosphatase Rap1, and the Rap1 effector proteins Rap1 guanosine triphosphate-interacting adapter molecule, regulator of adhesion and cell polarization enriched in lymphoid tissues, and protein kinase D1. Herein, we review recent findings about how the TCR is linked to integrin activation through inside-out signaling.
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Affiliation(s)
- Gaël Ménasché
- Abramson Family Cancer Research Institute, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
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43
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Bogin Y, Ainey C, Beach D, Yablonski D. SLP-76 mediates and maintains activation of the Tec family kinase ITK via the T cell antigen receptor-induced association between SLP-76 and ITK. Proc Natl Acad Sci U S A 2007; 104:6638-43. [PMID: 17420479 PMCID: PMC1871838 DOI: 10.1073/pnas.0609771104] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
ITK (IL-2-inducible T cell kinase), a Tec family protein tyrosine kinase (PTK), is one of three PTKs required for T cell antigen receptor (TCR)-induced activation of phospholipase C-gamma1 (PLC-gamma1). Like Src and Abl family PTKs, ITK adopts an inactive, "closed" conformation, and its conversion to the active conformation is not well understood, nor have its direct substrates been identified. In a side-by-side comparison of ITK and ZAP-70 (zeta chain-associated protein kinase of 70 kDa), ITK efficiently phosphorylated Y(783) and Y(775) of PLC-gamma1, two phosphorylation sites that are critical for its activation, whereas ZAP-70 did not. SLP-76 (SH2-domain-containing leukocyte protein of 76 kDa), an adaptor required for TCR-induced activation of PLC-gamma1, was required for the phosphorylation of both PLC-gamma1 sites in intact cells. Furthermore, this event depended on the N-terminal tyrosines of SLP-76. Likewise, SLP-76, particularly its N-terminal tyrosines, was required for TCR-induced tyrosine phosphorylation and activation of ITK but was not required for the phosphorylation or activation of ZAP-70. Both ZAP-70 and ITK phosphorylated SLP-76 in vitro; thus, both PTKs are potential regulators of SLP-76, but only ITK is regulated by SLP-76. Upon TCR stimulation, a small fraction of ITK bound to SLP-76. This fraction, however, encompassed most of the catalytically active ITK. Catalytic activity was lost upon mild elution of ITK from the SLP-76-nucleated complex but was restored upon reconstitution of the complex. We propose that SLP-76 is required for ITK activation; furthermore, an ongoing physical interaction between SLP-76 and ITK is required to maintain ITK in an active conformation.
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Affiliation(s)
- Yaron Bogin
- The Rappaport Family Institute for Research in the Medical Sciences, The Bruce Rappaport Faculty of Medicine, Technion–Israel Institute of Technology, P.O. Box 9649, Bat Galim, Haifa 31096, Israel
| | - Carmit Ainey
- The Rappaport Family Institute for Research in the Medical Sciences, The Bruce Rappaport Faculty of Medicine, Technion–Israel Institute of Technology, P.O. Box 9649, Bat Galim, Haifa 31096, Israel
| | - Dvora Beach
- The Rappaport Family Institute for Research in the Medical Sciences, The Bruce Rappaport Faculty of Medicine, Technion–Israel Institute of Technology, P.O. Box 9649, Bat Galim, Haifa 31096, Israel
| | - Deborah Yablonski
- The Rappaport Family Institute for Research in the Medical Sciences, The Bruce Rappaport Faculty of Medicine, Technion–Israel Institute of Technology, P.O. Box 9649, Bat Galim, Haifa 31096, Israel
- *To whom correspondence should be addressed. E-mail:
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44
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Dennehy KM, Elias F, Na SY, Fischer KD, Hünig T, Lühder F. Mitogenic CD28 Signals Require the Exchange Factor Vav1 to Enhance TCR Signaling at the SLP-76-Vav-Itk Signalosome. THE JOURNAL OF IMMUNOLOGY 2007; 178:1363-71. [PMID: 17237383 DOI: 10.4049/jimmunol.178.3.1363] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Almost all physiological T cell responses require costimulation-engagement of the clonotypic TCR with MHC/Ag and CD28 by its ligands CD80/86. Whether CD28 provides signals that are qualitatively unique or quantitatively amplify TCR signaling is poorly understood. In this study, we use superagonistic CD28 Abs, which induce T cell proliferation without TCR coligation, to determine how CD28 contributes to mitogenic responses. We show that mitogenic CD28 signals require but do not activate the proximal TCR components TCRzeta and Zap-70 kinase. In cell lines lacking proximal TCR signaling, an early defect in the CD28 pathway is in phosphorylation of the adaptor molecule SLP-76, which we show is essential for recruitment of the exchange factor Vav leading to Ca(2+) flux and IL-2 production. Point mutations in CD28 that result in diminished Vav phosphorylation also result in defective Ca(2+) flux, IL-2 production, and Tec-kinase phosphorylation. Using Vav1-deficient mice, we further demonstrate the importance of Vav1 for efficient proliferation, IL-2 production, and Ca(2+) flux. Our results indicate that CD28 signals feed into the TCR signaling pathway at the level of the SLP-76 signalosome.
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Affiliation(s)
- Kevin M Dennehy
- Institute of Virology and Immunobiology, University of Würzburg, Würzburg, Germany
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45
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Beach D, Gonen R, Bogin Y, Reischl IG, Yablonski D. Dual role of SLP-76 in mediating T cell receptor-induced activation of phospholipase C-gamma1. J Biol Chem 2006; 282:2937-46. [PMID: 17148460 DOI: 10.1074/jbc.m606697200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Phospholipase C-gamma1 (PLC-gamma1) activation depends on a heterotrimeric complex of adaptor proteins composed of LAT, Gads, and SLP-76. Upon T cell receptor stimulation, a portion of PLC-gamma1 is recruited to a detergent-resistant membrane fraction known as the glycosphingolipid-enriched membrane microdomains (GEMs), or lipid rafts, to which LAT is constitutively localized. In addition to LAT, PLC-gamma1 GEM recruitment depended on SLP-76, and, in particular, required the Gads-binding domain of SLP-76. The N-terminal tyrosine phosphorylation sites and P-I region of SLP-76 were not required for PLC-gamma1 GEM recruitment, but were required for PLC-gamma1 phosphorylation at Tyr(783). Thus, GEM recruitment can be insufficient for full activation of PLC-gamma1 in the absence of a second SLP-76-mediated event. Indeed, a GEM-targeted derivative of PLC-gamma1 depended on SLP-76 for T cell receptor-induced phosphorylation at Tyr783 and subsequent NFAT activation. On a biochemical level, SLP-76 inducibly associated with both Vav and catalytically active ITK, which efficiently phosphorylated a PLC-gamma1 fragment at Tyr783 in vitro. Both associations were disrupted upon mutation of the N-terminal tyrosine phosphorylation sites of SLP-76. The P-I region deletion disrupted Vav association and reduced SLP-76-associated kinase activity. A smaller deletion within the P-I region, which does not impair PLC-gamma1 activation, did not impair the association with Vav, but reduced SLP-76-associated kinase activity. These results provide new insight into the multiple roles of SLP-76 and the functional importance of its interactions with other signaling proteins.
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Affiliation(s)
- Dvora Beach
- Rappaport Family Institute for Research in the Medical Sciences, Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 31096, Israel
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46
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Bunnell SC, Singer AL, Hong DI, Jacque BH, Jordan MS, Seminario MC, Barr VA, Koretzky GA, Samelson LE. Persistence of cooperatively stabilized signaling clusters drives T-cell activation. Mol Cell Biol 2006; 26:7155-66. [PMID: 16980618 PMCID: PMC1592897 DOI: 10.1128/mcb.00507-06] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antigen recognition triggers the recruitment of the critical adaptor protein SLP-76 to small macromolecular clusters nucleated by the T-cell receptor (TCR). These structures develop rapidly, in parallel with TCR-induced increases in tyrosine phosphorylation and cytosolic calcium, and are likely to contribute to TCR-proximal signaling. Previously, we demonstrated that these SLP-76-containing clusters segregate from the TCR and move towards the center of the contact interface. Neither the function of these clusters nor the structural requirements governing their persistence have been examined extensively. Here we demonstrate that defects in cluster assembly and persistence are associated with defects in T-cell activation in the absence of Lck, ZAP-70, or LAT. Clusters persist normally in the absence of phospholipase C-gamma1, indicating that in the absence of a critical effector, these structures are insufficient to drive T-cell activation. Furthermore, we show that the critical adaptors LAT and Gads localize with SLP-76 in persistent clusters. Mutational analyses of LAT, Gads, and SLP-76 indicated that multiple domains within each of these proteins contribute to cluster persistence. These data indicate that multivalent cooperative interactions stabilize these persistent signaling clusters, which may correspond to the functional complexes predicted by kinetic proofreading models of T-cell activation.
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Affiliation(s)
- Stephen C Bunnell
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland, USA.
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47
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Abtahian F, Bezman N, Clemens R, Sebzda E, Cheng L, Shattil SJ, Kahn ML, Koretzky GA. Evidence for the requirement of ITAM domains but not SLP-76/Gads interaction for integrin signaling in hematopoietic cells. Mol Cell Biol 2006; 26:6936-49. [PMID: 16943434 PMCID: PMC1592869 DOI: 10.1128/mcb.01040-06] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Syk tyrosine kinase and Src homology 2 (SH2) domain-containing leukocyte-specific phosphoprotein of 76 kDa (SLP-76) are signaling mediators activated downstream of immunoreceptor tyrosine-based activation motif (ITAM)-containing immunoreceptors and integrins. While the signaling cascades descending from integrins are similar to immunoreceptors, the mechanism of Syk activation and SLP-76 recruitment remains unclear. We used an in vivo structure-function approach to study the requirements for the domains of Syk and SLP-76 in immunoreceptor and integrin signaling. We found that both SH2 domains and the kinase domain of Syk are required for immunoreceptor-dependent signaling and cellular response via integrins. While the Gads-binding domain of SLP-76 is needed for immunoreceptor signaling, it appears dispensable for integrin signaling. Syk and SLP-76 also are required for initiating and/or maintaining separation between the blood and lymphatic vasculature. Therefore, we correlated the signaling requirement of the various domains of Syk and SLP-76 to their requirement in regulating vascular separation. Our data suggest ITAMs are required in Syk-dependent integrin signaling, demonstrate the separation of the structural features of SLP-76 to selectively support immunoreceptor versus integrin signaling, and provide evidence that the essential domains of SLP-76 for ITAM signals are those which most efficiently support separation between lymphatic and blood vessels.
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Affiliation(s)
- Farhad Abtahian
- Signal Transduction Program, Abramson Family Cancer Research Institute, University of Pennsylvania, 421 Curie Blvd., Philadelphia, PA 19104, USA
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48
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Trampont P, Zhang L, Ravichandran KS. ShcA mediates the dominant pathway to extracellular signal-regulated kinase activation during early thymic development. Mol Cell Biol 2006; 26:9035-44. [PMID: 16982683 PMCID: PMC1636838 DOI: 10.1128/mcb.00988-06] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
During thymic development, the beta selection checkpoint is regulated by pre-T-cell receptor-initiated signals. Progression through this checkpoint is influenced by phosphorylation and activation of the serine/threonine kinases extracellular signal-regulated kinase 1 (ERK1) and ERK2, but the in vivo relevance of specific upstream players leading to ERK activation is not known. Here, using mice with a conditional loss of the shc1 gene or expressing mutants of ShcA, we demonstrate that the adapter protein ShcA is responsible for up to 70% of ERK activation in double-negative (DN) thymocytes in vivo and ex vivo. We also identify two specific tyrosines on ShcA that promote ERK phosphorylation in vivo, and mice expressing ShcA with mutations of these tyrosines show impaired DN thymocyte development. This work provides the first in vivo demonstration of the relative requirement of upstream adapters in controlling ERK activation during beta selection and suggests a dominant role for ShcA.
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Affiliation(s)
- Paul Trampont
- Carter Immunology Center, MR4-4072D, Box 801386, University of Virginia, Charlottesville, VA 22908, USA
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49
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Barr VA, Balagopalan L, Barda-Saad M, Polishchuk R, Boukari H, Bunnell SC, Bernot KM, Toda Y, Nossal R, Samelson LE. T-Cell Antigen Receptor-Induced Signaling Complexes: Internalization Via a Cholesterol-Dependent Endocytic Pathway. Traffic 2006; 7:1143-62. [PMID: 16919152 DOI: 10.1111/j.1600-0854.2006.00464.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
T-cell antigen receptor engagement causes the rapid assembly of signaling complexes. The adapter protein SLP-76, detected as SLP-yellow fluorescent protein, initially clustered with the TCR and other proteins, then translocated medially on microtubules. As shown by total internal reflection fluorescence microscopy and the inhibition of SLP-76 movement at 16 degrees C, this movement required endocytosis. Immunoelectron microscopy showed SLP-76 staining of smooth pits and tubules. Cholesterol depletion decreased the movement of SLP-76 clusters, as did coexpression of the ubiquitin-interacting motif domain from eps15. These data are consistent with the internalization of SLP-76 via a lipid raft-dependent pathway that requires interaction of the endocytic machinery with ubiquitinylated proteins. The endocytosed SLP-76 clusters contained phosphorylated SLP-76 and phosphorylated LAT. The raft-associated, transmembrane protein LAT likely targets SLP-76 to endocytic vesicles. The endocytosis of active SLP-76 and LAT complexes suggests a possible mechanism for downregulation of signaling complexes induced by TCR activation.
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Affiliation(s)
- Valarie A Barr
- Laboratory of Cellular and Molecular Biology, Department of Health and Human Services, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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50
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Silverman MA, Shoag J, Wu J, Koretzky GA. Disruption of SLP-76 interaction with Gads inhibits dynamic clustering of SLP-76 and FcepsilonRI signaling in mast cells. Mol Cell Biol 2006; 26:1826-38. [PMID: 16479002 PMCID: PMC1430252 DOI: 10.1128/mcb.26.5.1826-1838.2006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We developed a confocal real-time imaging approach that allows direct observation of the subcellular localization pattern of proteins involved in proximal FcepsilonRI signaling in RBL cells and primary bone marrow-derived mast cells. The adaptor protein Src homology 2 (SH2) domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76) is critical for FcepsilonRI-induced calcium flux, degranulation, and cytokine secretion. In this study, we imaged SLP-76 and found it in the cytosol of unstimulated cells. Upon FcepsilonRI cross-linking, SLP-76 translocates to the cell membrane, forming clusters that colocalize with the FcepsilonRI, the tyrosine kinase Syk, the adaptor LAT, and phosphotyrosine. The disruption of the SLP-76 interaction with its constitutive binding partner, Gads, through the mutation of SLP-76 or the expression of the Gads-binding region of SLP-76, inhibits the translocation and clustering of SLP-76, suggesting that the interaction of SLP-76 with Gads is critical for appropriate subcellular localization of SLP-76. We further demonstrated that the expression of the Gads-binding region of SLP-76 in bone marrow-derived mast cells inhibits FcepsilonRI-induced calcium flux, degranulation, and cytokine secretion. These studies revealed, for the first time, that SLP-76 forms signaling clusters following FcepsilonRI stimulation and demonstrated that the Gads-binding region of SLP-76 regulates clustering of SLP-76 and FcepsilonRI-induced mast cell responses.
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Affiliation(s)
- Michael A Silverman
- Abramson Family Cancer Research Institute, Department of Pathology and Laboratory Medicine, Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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