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Teppert K, Wang X, Anders K, Evaristo C, Lock D, Künkele A. Joining Forces for Cancer Treatment: From "TCR versus CAR" to "TCR and CAR". Int J Mol Sci 2022; 23:14563. [PMID: 36498890 PMCID: PMC9739809 DOI: 10.3390/ijms232314563] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 11/14/2022] [Accepted: 11/19/2022] [Indexed: 11/24/2022] Open
Abstract
T cell-based immunotherapy has demonstrated great therapeutic potential in recent decades, on the one hand, by using tumor-infiltrating lymphocytes (TILs) and, on the other hand, by engineering T cells to obtain anti-tumor specificities through the introduction of either engineered T cell receptors (TCRs) or chimeric antigen receptors (CARs). Given the distinct design of both receptors and the type of antigen that is encountered, the requirements for proper antigen engagement and downstream signal transduction by TCRs and CARs differ. Synapse formation and signal transduction of CAR T cells, despite further refinement of CAR T cell designs, still do not fully recapitulate that of TCR T cells and might limit CAR T cell persistence and functionality. Thus, deep knowledge about the molecular differences in CAR and TCR T cell signaling would greatly advance the further optimization of CAR designs and elucidate under which circumstances a combination of both receptors would improve the functionality of T cells for cancer treatment. Herein, we provide a comprehensive review about similarities and differences by directly comparing the architecture, synapse formation and signaling of TCRs and CARs, highlighting the knowns and unknowns. In the second part of the review, we discuss the current status of combining CAR and TCR technologies, encouraging a change in perspective from "TCR versus CAR" to "TCR and CAR".
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Affiliation(s)
- Karin Teppert
- Miltenyi Biotec B.V. & Co. KG, 51429 Bergisch Gladbach, Germany
| | - Xueting Wang
- Miltenyi Biotec B.V. & Co. KG, 51429 Bergisch Gladbach, Germany
| | - Kathleen Anders
- German Cancer Consortium (DKTK), 10117 Berlin, Germany
- German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - César Evaristo
- Miltenyi Biotec B.V. & Co. KG, 51429 Bergisch Gladbach, Germany
| | - Dominik Lock
- Miltenyi Biotec B.V. & Co. KG, 51429 Bergisch Gladbach, Germany
| | - Annette Künkele
- German Cancer Consortium (DKTK), 10117 Berlin, Germany
- German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
- Department of Pediatric Oncology and Hematology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 13353 Berlin, Germany
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2
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Luff DH, Wojdyla K, Oxley D, Chessa T, Hudson K, Hawkins PT, Stephens LR, Barry ST, Okkenhaug K. PI3Kδ Forms Distinct Multiprotein Complexes at the TCR Signalosome in Naïve and Differentiated CD4 + T Cells. Front Immunol 2021; 12:631271. [PMID: 33763075 PMCID: PMC7982423 DOI: 10.3389/fimmu.2021.631271] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 02/02/2021] [Indexed: 11/14/2022] Open
Abstract
Phosphoinositide 3-kinases (PI3Ks) play a central role in adaptive immunity by transducing signals from the T cell antigen receptor (TCR) via production of PIP3. PI3Kδ is a heterodimer composed of a p110δ catalytic subunit associated with a p85α or p85β regulatory subunit and is preferentially engaged by the TCR upon T cell activation. The molecular mechanisms leading to PI3Kδ recruitment and activation at the TCR signalosome remain unclear. In this study, we have used quantitative mass spectrometry, biochemical approaches and CRISPR-Cas9 gene editing to uncover the p110δ interactome in primary CD4+ T cells. Moreover, we have determined how the PI3Kδ interactome changes upon the differentiation of small naïve T cells into T cell blasts expanded in the presence of IL-2. Our interactomic analyses identified multiple constitutive and inducible PI3Kδ-interacting proteins, some of which were common to naïve and previously-activated T cells. Our data reveals that PI3Kδ rapidly interacts with as many as seven adaptor proteins upon TCR engagement, including the Gab-family proteins, GAB2 and GAB3, a CD5-CBL signalosome and the transmembrane proteins ICOS and TRIM. Our results also suggest that PI3Kδ pre-forms complexes with the adaptors SH3KBP1 and CRKL in resting cells that could facilitate the localization and activation of p110δ at the plasma membrane by forming ternary complexes during early TCR signalling. Furthermore, we identify interactions that were not previously known to occur in CD4+ T cells, involving BCAP, GAB3, IQGAP3 and JAML. We used CRISPR-Cas9-mediated gene knockout in primary T cells to confirm that BCAP is a positive regulator of PI3K-AKT signalling in CD4+ T cell blasts. Overall, our results provide evidence for a large protein network that regulates the recruitment and activation of PI3Kδ in T cells. Finally, this work shows how the PI3Kδ interactome is remodeled as CD4+ T cells differentiate from naïve T cells to activated T cell blasts. These activated T cells upregulate additional PI3Kδ adaptor proteins, including BCAP, GAB2, IQGAP3 and ICOS. This rewiring of TCR-PI3K signalling that occurs upon T cell differentiation may serve to reduce the threshold of activation and diversify the inputs for the PI3K pathway in effector T cells.
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Affiliation(s)
- Daisy H Luff
- Laboratory of Lymphocyte Signalling and Development, The Babraham Institute, Cambridge, United Kingdom
| | - Katarzyna Wojdyla
- Mass Spectrometry Facility, The Babraham Institute, Cambridge, United Kingdom.,Signalling Programme, The Babraham Institute, Cambridge, United Kingdom
| | - David Oxley
- Mass Spectrometry Facility, The Babraham Institute, Cambridge, United Kingdom
| | - Tamara Chessa
- Signalling Programme, The Babraham Institute, Cambridge, United Kingdom
| | - Kevin Hudson
- Bioscience, Oncology R&D, AstraZeneca, Cambridge, United Kingdom
| | - Phillip T Hawkins
- Signalling Programme, The Babraham Institute, Cambridge, United Kingdom
| | - Len R Stephens
- Signalling Programme, The Babraham Institute, Cambridge, United Kingdom
| | - Simon T Barry
- Bioscience, Oncology R&D, AstraZeneca, Cambridge, United Kingdom
| | - Klaus Okkenhaug
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
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Kabanova A, Zurli V, Baldari CT. Signals Controlling Lytic Granule Polarization at the Cytotoxic Immune Synapse. Front Immunol 2018. [PMID: 29515593 PMCID: PMC5826174 DOI: 10.3389/fimmu.2018.00307] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Cytotoxic immunity relies on specialized effector T cells, the cytotoxic T cells, which are endowed with specialized cytolytic machinery that permits them to induce death of their targets. Upon recognition of a target cell, cytotoxic T cells form a lytic immune synapse and by docking the microtubule-organizing center at the synaptic membrane get prepared to deliver a lethal hit of enzymes contained in lytic granules. New insights suggest that the directionality of lytic granule trafficking along the microtubules represents a fine means to tune the functional outcome of the encounter between a T cell and its target. Thus, mechanisms regulating the directionality of granule transport may have a major impact in settings characterized by evasion from the cytotoxic response, such as chronic infection and cancer. Here, we review our current knowledge on the signaling pathways implicated in the polarized trafficking at the immune synapse of cytotoxic T cells, complementing it with information on the regulation of this process in natural killer cells. Furthermore, we highlight some of the parameters which we consider critical in studying the polarized trafficking of lytic granules, including the use of freshly isolated cytotoxic T cells, and discuss some of the major open questions.
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Affiliation(s)
- Anna Kabanova
- Department of Life Sciences, University of Siena, Siena, Italy
| | - Vanessa Zurli
- Department of Life Sciences, University of Siena, Siena, Italy
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Zhang MS, Sandouk A, Houtman JCD. Glycerol Monolaurate (GML) inhibits human T cell signaling and function by disrupting lipid dynamics. Sci Rep 2016; 6:30225. [PMID: 27456316 PMCID: PMC4960522 DOI: 10.1038/srep30225] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 07/01/2016] [Indexed: 12/16/2022] Open
Abstract
Glycerol Monolaurate (GML) is a naturally occurring fatty acid widely utilized in food, cosmetics, and homeopathic supplements. GML is a potent antimicrobial agent that targets a range of bacteria, fungi, and enveloped viruses but select findings suggest that GML also has immunomodulatory functions. In this study, we have mechanistically examined if GML affects the signaling and functional output of human primary T cells. We found that GML potently altered order and disorder dynamics in the plasma membrane that resulted in reduced formation of LAT, PLC-γ, and AKT microclusters. Altered membrane events induced selective inhibition of TCR-induced phosphorylation of regulatory P85 subunit of PI3K and AKT as well as abrogated calcium influx. Ultimately, GML treatment potently reduced TCR-induced production of IL-2, IFN-γ, TNF-α, and IL-10. Our data reveal that the widely used anti-microbial agent GML also alters the lipid dynamics of human T cells, leading to their defective signaling and function.
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Affiliation(s)
- Michael S Zhang
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, United States
| | - Aline Sandouk
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, United States
| | - Jon C D Houtman
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, United States
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5
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Jung SH, Yoo EH, Yu MJ, Song HM, Kang HY, Cho JY, Lee JR. ARAP, a Novel Adaptor Protein, Is Required for TCR Signaling and Integrin-Mediated Adhesion. THE JOURNAL OF IMMUNOLOGY 2016; 197:942-52. [PMID: 27335501 DOI: 10.4049/jimmunol.1501913] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 05/19/2016] [Indexed: 11/19/2022]
Abstract
A novel adaptor protein was identified by analyzing phosphotyrosine proteomes from membrane rafts of activated T cells. This protein showed sequence similarity to a well-known T cell adaptor protein, adhesion and degranulation-promoting adaptor protein (ADAP); therefore, the novel protein was designated activation-dependent, raft-recruited ADAP-like phosphoprotein (ARAP). Suppression of ARAP impaired the major signaling pathways downstream of the TCR. ARAP associated with the Src homology 2 domain of Src homology 2-containing leukocyte protein of 76 kDa via the phosphorylation of two YDDV motifs in response to TCR stimulation. ARAP also mediated integrin activation but was not involved in actin polymerization. The results of this study indicate that a novel T cell adaptor protein, ARAP, plays a unique role in T cells as a part of both the proximal activation signaling and inside-out signaling pathways that result in integrin activation and T cell adhesion.
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Affiliation(s)
- Seung Hee Jung
- Department of Life Science, College of Natural Sciences, Ewha Womans University, Seoul 03760, Korea
| | - Eun Hye Yoo
- Department of Life Science, College of Natural Sciences, Ewha Womans University, Seoul 03760, Korea; Research Center for Cellular Homeostasis, Ewha Womans University, Seoul 03760, Korea; and
| | - Mi Jin Yu
- Department of Life Science, College of Natural Sciences, Ewha Womans University, Seoul 03760, Korea; Research Center for Cellular Homeostasis, Ewha Womans University, Seoul 03760, Korea; and
| | - Hyeon Myeong Song
- Department of Life Science, College of Natural Sciences, Ewha Womans University, Seoul 03760, Korea
| | - Hee Yoon Kang
- Department of Life Science, College of Natural Sciences, Ewha Womans University, Seoul 03760, Korea
| | - Je-Yoel Cho
- Department of Veterinary Biochemistry, College of Veterinary Medicine, Seoul National University, Seoul 08826, Korea
| | - Jong Ran Lee
- Department of Life Science, College of Natural Sciences, Ewha Womans University, Seoul 03760, Korea; Research Center for Cellular Homeostasis, Ewha Womans University, Seoul 03760, Korea; and
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6
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Lee MJ, Yoshimoto E, Saijo S, Iwakura Y, Lin X, Katz HR, Kanaoka Y, Barrett NA. Phosphoinositide 3-Kinase δ Regulates Dectin-2 Signaling and the Generation of Th2 and Th17 Immunity. THE JOURNAL OF IMMUNOLOGY 2016; 197:278-87. [PMID: 27194783 DOI: 10.4049/jimmunol.1502485] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 04/27/2016] [Indexed: 11/19/2022]
Abstract
The C-type lectin receptor Dectin-2 can trigger the leukotriene C4 synthase-dependent generation of cysteinyl leukotrienes and the caspase-associated recruitment domain 9- and NF-κB-dependent generation of cytokines, such as IL-23, IL-6, and TNF-α, to promote Th2 and Th17 immunity, respectively. Dectin-2 activation also elicits the type 2 cytokine IL-33, but the mechanism by which Dectin-2 induces these diverse innate mediators is poorly understood. In this study, we identify a common upstream requirement for PI3Kδ activity for the generation of each Dectin-2-dependent mediator elicited by the house dust mite species, Dermatophagoides farinae, using both pharmacologic inhibition and small interfering RNA knockdown of PI3Kδ in bone marrow-derived dendritic cells. PI3Kδ activity depends on spleen tyrosine kinase (Syk) and regulates the activity of protein kinase Cδ, indicating that PI3Kδ is a proximal Syk-dependent signaling intermediate. Inhibition of PI3Kδ also reduces cysteinyl leukotrienes and cytokines elicited by Dectin-2 cross-linking, confirming the importance of this molecule in Dectin-2 signaling. Using an adoptive transfer model, we demonstrate that inhibition of PI3Kδ profoundly reduces the capacity of bone marrow-derived dendritic cells to sensitize recipient mice for Th2 and Th17 pulmonary inflammation in response to D. farinae Furthermore, administration of a PI3Kδ inhibitor during the sensitization of wild-type mice prevents the generation of D. farinae-induced pulmonary inflammation. These results demonstrate that PI3Kδ regulates Dectin-2 signaling and its dendritic cell function.
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Affiliation(s)
- Min Jung Lee
- Department of Medicine, Harvard Medical School, Boston, MA 02115; Jeff and Penny Vinik Center for Allergic Disease Research, Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA 02115
| | - Eri Yoshimoto
- Department of Medicine, Harvard Medical School, Boston, MA 02115; Jeff and Penny Vinik Center for Allergic Disease Research, Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA 02115
| | - Shinobu Saijo
- Division of Molecular Immunology, Medical Mycology Research Center, Chiba University, Chiba 260-8673, Japan
| | - Yoichiro Iwakura
- Research Institute for Biomedical Sciences, Tokyo University of Science, Chiba 278-0022, Japan; and
| | - Xin Lin
- Department of Molecular and Cellular Oncology, University of Texas, MD Anderson Cancer Center, Houston, TX 77030
| | - Howard R Katz
- Department of Medicine, Harvard Medical School, Boston, MA 02115; Jeff and Penny Vinik Center for Allergic Disease Research, Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA 02115
| | - Yoshihide Kanaoka
- Department of Medicine, Harvard Medical School, Boston, MA 02115; Jeff and Penny Vinik Center for Allergic Disease Research, Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA 02115
| | - Nora A Barrett
- Department of Medicine, Harvard Medical School, Boston, MA 02115; Jeff and Penny Vinik Center for Allergic Disease Research, Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA 02115;
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7
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Chapman NM, Yoder AN, Barbón KM, Bilal MY, Connolly SF, Houtman JCD. Proline-rich tyrosine kinase 2 controls PI3-kinase activation downstream of the T cell antigen receptor in human T cells. J Leukoc Biol 2014; 97:285-96. [PMID: 25387834 DOI: 10.1189/jlb.2a1013-568rrr] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
TCR-induced signaling controls T cell activation that drives adaptive immunity against infections, but it can also induce dysfunctional T cell responses that promote pathologic disease. The PI3K pathway regulates many downstream effector responses after TCR stimulation. However, the molecular mechanisms that induce PI3K function downstream of the TCR are not fully understood. We have previously shown that Pyk2 is activated downstream of the TCR in a PI3K-independent manner. Although Pyk2 controls adhesion, proliferation, and cytokine production in T cells, the mechanisms by which it controls these processes are not known. In this study, we generated Pyk2-deficient human T cells to elucidate further the role that this kinase plays in TCR-induced effector functions and signaling. We observed that Pyk2 localized with the p85 regulatory subunit of PI3K at the LAT complex and that PI3K-dependent signaling was impaired in Pyk2-deficient T cells. Likewise, functions downstream of PI3K, including IFN-γ production and proliferation, were also suppressed in human T cells deficient in Pyk2. Collectively, these data demonstrate that Pyk2 is a critical regulator of PI3K function downstream of the TCR.
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Affiliation(s)
- Nicole M Chapman
- *Interdisciplinary Graduate Program in Immunology and Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Ashley N Yoder
- *Interdisciplinary Graduate Program in Immunology and Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Kathryn M Barbón
- *Interdisciplinary Graduate Program in Immunology and Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Mahmood Y Bilal
- *Interdisciplinary Graduate Program in Immunology and Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Sean F Connolly
- *Interdisciplinary Graduate Program in Immunology and Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Jon C D Houtman
- *Interdisciplinary Graduate Program in Immunology and Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
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8
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Molecular mechanisms and functional implications of polarized actin remodeling at the T cell immunological synapse. Cell Mol Life Sci 2014; 72:537-556. [PMID: 25355055 DOI: 10.1007/s00018-014-1760-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 09/22/2014] [Accepted: 10/13/2014] [Indexed: 02/05/2023]
Abstract
Transient,specialized cell-cell interactions play a central role in leukocyte function by enabling specific intercellular communication in the context of a highly dynamic systems level response. The dramatic structural changes required for the formation of these contacts are driven by rapid and precise cytoskeletal remodeling events. In recent years, the immunological synapse that forms between a T lymphocyte and its antigen-presenting target cell has emerged as an important model system for understanding immune cell interactions. In this review, we discuss how regulators of the cortical actin cytoskeleton control synaptic architecture and in this way specify T cell function.
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9
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Ji Q, Ding Y, Salomon AR. SRC homology 2 domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76) N-terminal tyrosine residues regulate a dynamic signaling equilibrium involving feedback of proximal T-cell receptor (TCR) signaling. Mol Cell Proteomics 2014; 14:30-40. [PMID: 25316710 DOI: 10.1074/mcp.m114.037861] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
SRC homology 2 domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76) is a cytosolic adaptor protein that plays an important role in the T-cell receptor-mediated T-cell signaling pathway. SLP-76 links proximal receptor stimulation to downstream effectors through interaction with many signaling proteins. Previous studies showed that mutation of three tyrosine residues, Tyr(112), Tyr(128), and Tyr(145), in the N terminus of SLP-76 results in severely impaired phosphorylation and activation of Itk and PLCγ1, which leads to defective calcium mobilization, Erk activation, and NFAT activation. To expand our knowledge of the role of N-terminal phosphorylation of SLP-76 from these three tyrosine sites, we characterized nearly 1000 tyrosine phosphorylation sites via mass spectrometry in SLP-76 reconstituted wild-type cells and SLP-76 mutant cells in which three tyrosine residues were replaced with phenylalanines (Y3F mutant). Mutation of the three N-terminal tyrosine residues of SLP-76 phenocopied SLP-76-deficient cells for the majority of tyrosine phosphorylation sites observed, including feedback on proximal T-cell receptor signaling proteins. Meanwhile, reversed phosphorylation changes were observed on Tyr(192) of Lck when we compared mutants to the complete removal of SLP-76. In addition, N-terminal tyrosine sites of SLP-76 also perturbed phosphorylation of Tyr(440) of Fyn, Tyr(702) of PLCγ1, Tyr(204), Tyr(397), and Tyr(69) of ZAP-70, revealing new modes of regulation on these sites. All these findings confirmed the central role of N-terminal tyrosine sites of SLP-76 in the pathway and also shed light on novel signaling events that are uniquely regulated by SLP-76 N-terminal tyrosine residues.
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Affiliation(s)
- Qinqin Ji
- From the ‡Department of Chemistry, Brown University Providence, RI 02903
| | - Yiyuan Ding
- From the ‡Department of Chemistry, Brown University Providence, RI 02903
| | - Arthur R Salomon
- From the ‡Department of Chemistry, Brown University Providence, RI 02903; §Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University Providence, RI 02903
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10
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Higo K, Oda M, Morii H, Takahashi J, Harada Y, Ogawa S, Abe R. Quantitative analysis by surface plasmon resonance of CD28 interaction with cytoplasmic adaptor molecules Grb2, Gads and p85 PI3K. Immunol Invest 2014; 43:278-91. [DOI: 10.3109/08820139.2013.875039] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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11
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Le Floc'h A, Tanaka Y, Bantilan NS, Voisinne G, Altan-Bonnet G, Fukui Y, Huse M. Annular PIP3 accumulation controls actin architecture and modulates cytotoxicity at the immunological synapse. ACTA ACUST UNITED AC 2013; 210:2721-37. [PMID: 24190432 PMCID: PMC3832928 DOI: 10.1084/jem.20131324] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
In T cells, PI3K activation in the periphery of the immune synapse leads to PIP3 accumulation that promotes actin polymerization in a pathway important for cytotoxic function. The immunological synapse formed by a T lymphocyte on the surface of a target cell contains a peripheral ring of filamentous actin (F-actin) that promotes adhesion and facilitates the directional secretion of cytokines and cytolytic factors. We show that growth and maintenance of this F-actin ring is dictated by the annular accumulation of phosphatidylinositol trisphosphate (PIP3) in the synaptic membrane. PIP3 functions in this context by recruiting the exchange factor Dock2 to the periphery of the synapse, where it drives actin polymerization through the Rho-family GTPase Rac. We also show that synaptic PIP3 is generated by class IA phosphoinositide 3-kinases that associate with T cell receptor microclusters and are activated by the GTPase Ras. Perturbations that inhibit or promote PIP3-dependent F-actin remodeling dramatically affect T cell cytotoxicity, demonstrating the functional importance of this pathway. These results reveal how T cells use lipid-based signaling to control synaptic architecture and modulate effector responses.
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Affiliation(s)
- Audrey Le Floc'h
- Immunology Program, 2 Computational Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065
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12
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Ladygina N, Gottipati S, Ngo K, Castro G, Ma JY, Banie H, Rao TS, Fung-Leung WP. PI3Kγ kinase activity is required for optimal T-cell activation and differentiation. Eur J Immunol 2013; 43:3183-96. [PMID: 24030559 PMCID: PMC4209804 DOI: 10.1002/eji.201343812] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2013] [Revised: 07/21/2013] [Accepted: 09/09/2013] [Indexed: 01/23/2023]
Abstract
Phosphatidylinositol-3-kinase gamma (PI3Kγ) is a leukocyte-specific lipid kinase with
signaling function downstream of G protein-coupled receptors to regulate cell trafficking, but its
role in T cells remains unclear. To investigate the requirement of PI3Kγ kinase
activity in T-cell function, we studied T cells from PI3Kγ kinase-dead knock-in
(PI3KγKD/KD) mice expressing the kinase-inactive PI3Kγ protein. We show
that CD4+ and CD8+ T cells from
PI3KγKD/KD mice exhibit impaired TCR/CD28-mediated activation that could not be
rescued by exogenous IL-2. The defects in proliferation and cytokine production were also evident in
naïve and memory T cells. Analysis of signaling events in activated
PI3KγKD/KD T cells revealed a reduction in phosphorylation of protein
kinase B (AKT) and ERK1/2, a decrease in lipid raft formation, and a delay in cell cycle
progression. Furthermore, PI3KγKD/KD CD4+ T cells
displayed compromised differentiation toward Th1, Th2, Th17, and induced Treg cells.
PI3KγKD/KD mice also exhibited an impaired response to immunization and a reduced
delayed-type hypersensitivity to Ag challenge. These findings indicate that PI3Kγ kinase
activity is required for optimal T-cell activation and differentiation, as well as for mounting an
efficient T cell-mediated immune response. The results suggest that PI3Kγ kinase
inhibitors could be beneficial in reducing the undesirable immune response in autoimmune
diseases.
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13
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Cao L, Ding Y, Hung N, Yu K, Ritz A, Raphael BJ, Salomon AR. Quantitative phosphoproteomics reveals SLP-76 dependent regulation of PAG and Src family kinases in T cells. PLoS One 2012; 7:e46725. [PMID: 23071622 PMCID: PMC3469622 DOI: 10.1371/journal.pone.0046725] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 09/07/2012] [Indexed: 12/14/2022] Open
Abstract
The SH2-domain-containing leukocyte protein of 76 kDa (SLP-76) plays a critical scaffolding role in T cell receptor (TCR) signaling. As an adaptor protein that contains multiple protein-binding domains, SLP-76 interacts with many signaling molecules and links proximal receptor stimulation to downstream effectors. The function of SLP-76 in TCR signaling has been widely studied using the Jurkat human leukaemic T cell line through protein disruption or site-directed mutagenesis. However, a wide-scale characterization of SLP-76-dependant phosphorylation events is still lacking. Quantitative profiling of over a hundred tyrosine phosphorylation sites revealed new modes of regulation of phosphorylation of PAG, PI3K, and WASP while reconfirming previously established regulation of Itk, PLCγ, and Erk phosphorylation by SLP-76. The absence of SLP-76 also perturbed the phosphorylation of Src family kinases (SFKs) Lck and Fyn, and subsequently a large number of SFK-regulated signaling molecules. Altogether our data suggests unique modes of regulation of positive and negative feedback pathways in T cells by SLP-76, reconfirming its central role in the pathway.
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Affiliation(s)
- Lulu Cao
- Department of Chemistry, Brown University, Providence, Rhode Island, United States of America
| | - Yiyuan Ding
- Department of Chemistry, Brown University, Providence, Rhode Island, United States of America
| | - Norris Hung
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, United States of America
| | - Kebing Yu
- Department of Chemistry, Brown University, Providence, Rhode Island, United States of America
| | - Anna Ritz
- Department of Computer Science, Brown University, Providence, Rhode Island, United States of America
| | - Benjamin J. Raphael
- Department of Computer Science, Brown University, Providence, Rhode Island, United States of America
| | - Arthur R. Salomon
- Department of Chemistry, Brown University, Providence, Rhode Island, United States of America
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, United States of America
- * E-mail:
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Draber P, Halova I, Levi-Schaffer F, Draberova L. Transmembrane adaptor proteins in the high-affinity IgE receptor signaling. Front Immunol 2012; 2:95. [PMID: 22566884 PMCID: PMC3342071 DOI: 10.3389/fimmu.2011.00095] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Accepted: 12/28/2011] [Indexed: 11/24/2022] Open
Abstract
Aggregation of the high-affinity IgE receptor (FcεRI) initiates a cascade of signaling events leading to release of preformed inflammatory and allergy mediators and de novo synthesis and secretion of cytokines and other compounds. The first biochemically well defined step of this signaling cascade is tyrosine phosphorylation of the FcεRI subunits by Src family kinase Lyn, followed by recruitment and activation of spleen tyrosine kinase (Syk). Activity of Syk is decisive for the formation of multicomponent signaling assemblies, the signalosomes, in the vicinity of the receptors. Formation of the signalosomes is dependent on the presence of transmembrane adaptor proteins (TRAPs). These proteins are characterized by a short extracellular domain, a single transmembrane domain, and a cytoplasmic tail with various motifs serving as anchors for cytoplasmic signaling molecules. In mast cells five TRAPs have been identified [linker for activation of T cells (LAT), non-T cell activation linker (NTAL), linker for activation of X cells (LAX), phosphoprotein associated with glycosphingolipid-enriched membrane microdomains (PAG), and growth factor receptor-bound protein 2 (Grb2)-binding adaptor protein, transmembrane (GAPT)]; engagement of four of them (LAT, NTAL, LAX, and PAG) in FcεRI signaling has been documented. Here we discuss recent progress in the understanding of how TRAPs affect FcεRI-mediated mast cell signaling. The combined data indicate that individual TRAPs have irreplaceable roles in important signaling events such as calcium response, degranulation, cytokines production, and chemotaxis.
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Affiliation(s)
- Petr Draber
- Department of Signal Transduction, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic Prague, Czech Republic
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15
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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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16
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Balagopalan L, Coussens NP, Sherman E, Samelson LE, Sommers CL. The LAT story: a tale of cooperativity, coordination, and choreography. Cold Spring Harb Perspect Biol 2010; 2:a005512. [PMID: 20610546 DOI: 10.1101/cshperspect.a005512] [Citation(s) in RCA: 133] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The adapter molecule LAT is a nucleating site for multiprotein signaling complexes that are vital for the function and differentiation of T cells. Extensive investigation of LAT in multiple experimental systems has led to an integrated understanding of the formation, composition, regulation, dynamic movement, and function of LAT-nucleated signaling complexes. This review discusses interactions of signaling molecules that bind directly or indirectly to LAT and the role of cooperativity in stabilizing LAT-nucleated signaling complexes. In addition, it focuses on how imaging studies visualize signaling assemblies as signaling clusters and demonstrate their dynamic nature and cellular fate. Finally, this review explores the function of LAT based on the interpretation of mouse models using various LAT mutants.
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17
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Jung SH, Jeong JH, Seul HJ, Lee JR. Competition between SLP76 and LAT for PLCγ1 binding in resting T cells. Eur J Immunol 2010; 40:2330-9. [DOI: 10.1002/eji.200939411] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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18
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Geahlen RL. Syk and pTyr'd: Signaling through the B cell antigen receptor. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1793:1115-27. [PMID: 19306898 DOI: 10.1016/j.bbamcr.2009.03.004] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Accepted: 03/06/2009] [Indexed: 11/18/2022]
Abstract
The B cell receptor (BCR) transduces antigen binding into alterations in the activity of intracellular signaling pathways through its ability to recruit and activate the cytoplasmic protein-tyrosine kinase Syk. The recruitment of Syk to the receptor, its activation and its subsequent interactions with downstream effectors are all regulated by its phosphorylation on tyrosine. This review discusses our current understanding of how this phosphorylation regulates the activity of Syk and its participation in signaling through the BCR.
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Affiliation(s)
- Robert L Geahlen
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA.
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19
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Abstract
The phosphoinositide 3-kinase (PI3K) signaling pathway plays a critical role in the development, activation, and homeostasis of T cells by modulating the expression of survival and mitogenic factors in response to a variety of stimuli. Ligation of the antigen receptor, costimulatory molecules, and cytokine receptors activate PI3K, resulting in the production of the lipid second messenger phosphatidylinositol-3,4,5-triphosphate (PIP(3)). A number of molecules help to regulate the activity of this pathway, including the lipid phosphatase PTEN (phosphatase and tensin homolog deleted on chromosome 10). By limiting the amount of PIP(3) available within the cell, PTEN directly opposes PI3K activity and influences the selection of developing thymocytes as well as the activation requirements of mature T cells. T cells with unchecked PI3K activity, as a result of PTEN deficiency, contribute to the development of both autoimmune disease and lymphoma. This review dissects our current understanding of PI3K and PTEN and discusses why appropriate balance of these molecules is necessary to maintain normal T-cell responses.
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Affiliation(s)
- Jodi L Buckler
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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20
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CD28 provides T-cell costimulation and enhances PI3K activity at the immune synapse independently of its capacity to interact with the p85/p110 heterodimer. Blood 2008; 111:1464-71. [PMID: 18006698 DOI: 10.1182/blood-2007-08-108050] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Abstract
Activation of PI3K is among the earliest signaling events observed in T cells after conjugate formation with antigen-presenting cells (APCs). The relevant PI3K catalytic isoform and relative contribution of the TcR and CD28 to PI3K activity at the immune synapse have not been determined unequivocally. Using a quantitative imaging-based assay, we show that the PI3K activity at the T cell–APC contact area is dependent on the p110δ, but not the p110γ, isoform of PI3K. CD28 enhanced PIP3 production at the T-cell synapse independently of its YMNM PI3K-recruitment motif that instead was required for efficient PKCθ recruitment. CD28 could partially compensate for the lack of p110δ activity during T-cell activation, which indicates that CD28 and p110δ act in parallel and complementary pathways to activate T cells. Consistent with this, CD28 and p110δ double-deficient mice were severely immune compromised. We therefore suggest that combined pharmaceutic targeting of p110δ activity and CD28 costimulation has potent therapeutic potential.
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21
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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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22
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Okkenhaug K, Ali K, Vanhaesebroeck B. Antigen receptor signalling: a distinctive role for the p110delta isoform of PI3K. Trends Immunol 2007; 28:80-7. [PMID: 17208518 PMCID: PMC2358943 DOI: 10.1016/j.it.2006.12.007] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2006] [Revised: 11/24/2006] [Accepted: 12/18/2006] [Indexed: 11/24/2022]
Abstract
The activation of antigen receptors triggers two important signalling pathways originating from phosphatidylinositol(4,5)-bisphosphate [PtdIns(4,5)P2]. The first is phospholipase Cγ (PLCγ)-mediated hydrolysis of PtdIns(4,5)P2, resulting in the activation of Ras, protein kinase C and Ca2+ flux. This culminates in profound alterations in gene expression and effector-cell responses, including secretory granule exocytosis and cytokine production. By contrast, phosphoinositide 3-kinases (PI3Ks) phosphorylate PtdIns(4,5)P2 to yield phosphatidylinositol(3,4,5)-trisphosphate, activating signalling pathways that overlap with PLCγ or are PI3K-specific. Pathways that are PI3K-specific include Akt-mediated inactivation of Foxo transcription factors and transcription-independent regulation of glucose uptake and metabolism. The p110δ isoform of PI3K is the main source of PI3K activity following antigen recognition by B cells, T cells and mast cells. Here, we review the roles of p110δ in regulating antigen-dependent responses in these cell types.
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Affiliation(s)
- Klaus Okkenhaug
- Laboratory of Lymphocyte Signalling and Development, Babraham Institute, Cambridge, UK, CB2 4AT
| | - Khaled Ali
- Ludwig Institute for Cancer Research, London, UK, W1W 7BS
- Department of Biochemistry and Molecular Biology, University College London, London, UK, WC1E 6BT
| | - Bart Vanhaesebroeck
- Ludwig Institute for Cancer Research, London, UK, W1W 7BS
- Department of Biochemistry and Molecular Biology, University College London, London, UK, WC1E 6BT
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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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24
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Koretzky GA, Abtahian F, Silverman MA. SLP76 and SLP65: complex regulation of signalling in lymphocytes and beyond. Nat Rev Immunol 2006; 6:67-78. [PMID: 16493428 DOI: 10.1038/nri1750] [Citation(s) in RCA: 205] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
SLP76 and SLP65 are adaptor proteins that lack intrinsic enzymatic activity but contain multiple protein-binding domains. These proteins are essential for signalling downstream of integrins and receptors that contain immunoreceptor tyrosine-based activation motifs. The absence of these adaptor proteins profoundly affects various lineages in the haematopoietic compartment and severely compromises vascular development, highlighting their importance as regulators of signalling cascades. In this Review, we discuss the role of SLP76 and SLP65 in several signalling pathways in haematopoietic cells, with an emphasis on recent studies that provide insight into their mechanisms of action.
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Affiliation(s)
- Gary A Koretzky
- Department of Pathology and Laboratory Medicine, Abramson Family Cancer Research Institute, University of Pennsylvania, 415 BRBII/III, 421 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA.
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25
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Lü L, Zhou SY, Chen C, Weng SP, Chan SM, He JG. Complete genome sequence analysis of an iridovirus isolated from the orange-spotted grouper, Epinephelus coioides. Virology 2005; 339:81-100. [PMID: 15964605 DOI: 10.1016/j.virol.2005.05.021] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2005] [Revised: 03/09/2005] [Accepted: 05/11/2005] [Indexed: 10/25/2022]
Abstract
Orange-spotted grouper iridovirus (OSGIV) was the causative agent of serious systemic diseases with high mortality in the cultured orange-spotted grouper, Epinephelus coioides. Here we report the complete genome sequence of OSGIV. The OSGIV genome consists of 112,636 bp with a G+C content of 54%. 121 putative open reading frames (ORF) were identified with coding capacities for polypeptides varying from 40 to 1168 amino acids. The majority of OSGIV shared homologies to other iridovirus genes. Phylogenetic analysis of the major capsid protein, ATPase, cytosine DNA methyl transferase and DNA polymerase indicated that OSGIV was closely related to infectious spleen and kidney necrosis virus (ISKNV) and rock bream iridovirus (RBIV), but differed from lymphocytisvirus and ranavirus. The determination of the genome of OSGIV will facilitate a better understanding of the molecular mechanism underlying the pathogenesis of the OSGIV and may provide useful information to develop diagnosis method and strategies to control outbreak of OSGIV.
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Affiliation(s)
- Ling Lü
- State Key Laboratory for Biocontrol, School of Life Sciences, Zhongshan University, Guangzhou 510275, P. R. China
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