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Kunapuli SP, Tsygankov AY. TULA-Family Regulators of Platelet Activation. Int J Mol Sci 2022; 23:ijms232314910. [PMID: 36499237 PMCID: PMC9736690 DOI: 10.3390/ijms232314910] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 11/17/2022] [Accepted: 11/21/2022] [Indexed: 11/30/2022] Open
Abstract
The two members of the UBASH3/TULA/STS-protein family have been shown to critically regulate cellular processes in multiple biological systems. The regulatory function of TULA-2 (also known as UBASH3B or STS-1) in platelets is one of the best examples of the involvement of UBASH3/TULA/STS proteins in cellular regulation. TULA-2 negatively regulates platelet signaling mediated by ITAM- and hemITAM-containing membrane receptors that are dependent on the protein tyrosine kinase Syk, which currently represents the best-known dephosphorylation target of TULA-2. The biological responses of platelets to collagen and other physiological agonists are significantly downregulated as a result. The protein structure, enzymatic activity and regulatory functions of UBASH3/TULA/STS proteins in the context of platelet responses and their regulation are discussed in this review.
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2
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Kostyak JC, Mauri BR, Dangelmaier C, Patel A, Zhou Y, Eble JA, Tsygankov AY, McKenzie SE, Kunapuli SP. TULA-2 Deficiency Enhances Platelet Functional Responses to CLEC-2 Agonists. TH OPEN 2018; 2:e411-e419. [PMID: 31249969 PMCID: PMC6524918 DOI: 10.1055/s-0038-1676358] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2018] [Accepted: 10/10/2018] [Indexed: 02/06/2023] Open
Abstract
Platelet activation is essential for hemostasis. Central to platelet activation are the signals transmitted through surface receptors such as glycoprotein VI, the protease-activated receptors, and C-type lectin-like receptor 2 (CLEC-2). CLEC-2 is a HemITAM (hem-immunoreceptor tyrosine activation motif)-bearing receptor that binds podoplanin and signals through spleen tyrosine kinase (Syk). T-cell ubiquitin ligand-2 (TULA-2) is a protein tyrosine phosphatase that is highly expressed in platelets and targets phosphorylated Y352 of Syk. We wanted to determine whether TULA-2 regulates Syk phosphorylation and activity downstream of CLEC-2. To that end, we used TULA-2 knockout mice and wild-type (WT) littermate controls. We found that TULA-2 deficiency enhances the aggregation and secretion response following stimulation with an excitatory CLEC-2 antibody or the CLEC-2 agonist rhodocytin. Consistently, Syk phosphorylation of Y346 is enhanced, as well as phosphorylation of the downstream signaling molecule PLCγ2, in TULA-2 knockout platelets treated with either CLEC-2 antibody or rhodocytin, compared with WT control platelets. Furthermore, the kinetics of Syk phosphorylation, as well as that of PLCγ2 and SLP-76, is enhanced in TULA-2 knockout platelets treated with 2.5-μg/mL CLEC-2 antibody compared with WT platelets. Similarly, thromboxane production was enhanced, in both amount and kinetics, in TULA-2
−/−
platelets treated with 2.5-μg/mL CLEC-2 antibody. TULA-2 acts as a negative regulator of CLEC-2 signaling by dephosphorylating Syk on Y346 and restraining subsequent Syk-mediated signaling.
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Affiliation(s)
- John C Kostyak
- Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, United States
| | - Benjamin R Mauri
- Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, United States
| | - Carol Dangelmaier
- Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, United States
| | - Akruti Patel
- Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, United States
| | - Yuhang Zhou
- Cardeza Foundation for Hematologic Research, Department of Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, United States
| | - Johannes A Eble
- Institute of Physiological Chemistry and Pathobiochemistry, University of Munster, Waldeyerstasse, Munster, Germany
| | - Alexander Y Tsygankov
- Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, United States.,Department of Immunology and Microbiology, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, United States
| | - Steven E McKenzie
- Cardeza Foundation for Hematologic Research, Department of Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, United States
| | - Satya P Kunapuli
- Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, United States
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3
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Tsygankov AY. TULA-family proteins: Jacks of many trades and then some. J Cell Physiol 2018; 234:274-288. [PMID: 30076707 DOI: 10.1002/jcp.26890] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 06/13/2018] [Indexed: 12/17/2022]
Abstract
UBASH3/STS/TULA is a novel two-member family, which exerts several key regulatory effects in multiple cell types. UBASH3B/STS-1/TULA-2 is a highly active protein tyrosine phosphatase; its major target appears to be a specific regulatory site of protein tyrosine kinases of the Syk family, dephosphorylation of which inhibits Syk and Zap-70 kinases and suppresses receptor signaling mediated by these kinases. UBASH3A/STS-2/TULA exhibits substantial homology to UBASH3B/STS-1/TULA-2, but possesses only a small fraction of phosphatase activity of UBASH3B/STS-1/TULA-2, and thus, its regulatory effect may be based also on the phosphatase-independent mechanisms. Critical physiologic effects of these proteins have been demonstrated in T lymphocytes, platelets, stem cells, and other important cell types. These proteins have also been shown to play a key role in such pathologic conditions as autoimmunity, cancer, and thrombosis. The review focuses on the recent studies of this important family of cellular regulators.
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Affiliation(s)
- Alexander Y Tsygankov
- Department of Microbiology and Immunology, Fels Institute for Cancer Research and Molecular Biology and Sol Sherry Thrombosis Center, Temple University School of Medicine, Philadelphia, Pennsylvania
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4
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Reppschläger K, Gosselin J, Dangelmaier CA, Thomas DH, Carpino N, McKenzie SE, Kunapuli SP, Tsygankov AY. TULA-2 Protein Phosphatase Suppresses Activation of Syk through the GPVI Platelet Receptor for Collagen by Dephosphorylating Tyr(P)346, a Regulatory Site of Syk. J Biol Chem 2016; 291:22427-22441. [PMID: 27609517 DOI: 10.1074/jbc.m116.743732] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 08/30/2016] [Indexed: 12/14/2022] Open
Abstract
Protein-tyrosine phosphatase TULA-2 has been shown to regulate receptor signaling in several cell types, including platelets. Platelets are critical for maintaining vascular integrity; this function is mediated by platelet aggregation in response to recognition of the exposed basement membrane collagen by the GPVI receptor, which is non-covalently associated with the signal-transducing FcRγ polypeptide chain. Our previous studies suggested that TULA-2 plays an important role in negatively regulating signaling through GPVI-FcRγ and indicated that the tyrosine-protein kinase Syk is a key target of the regulatory action of TULA-2 in platelets. However, the molecular basis of the down-regulatory effect of TULA-2 on Syk activation via FcRγ remained unclear. In this study, we demonstrate that suppression of Syk activation by TULA-2 is mediated, to a substantial degree, by dephosphorylation of Tyr(P)346, a regulatory site of Syk, which becomes phosphorylated soon after receptor ligation and plays a critical role in initiating the process that yields fully activated Syk. TULA-2 is capable of dephosphorylating Tyr(P)346 with high efficiency, thus controlling the overall activation of Syk, but is less efficient in dephosphorylating other regulatory sites of this kinase. Therefore, dephosphorylation of Tyr(P)346 may be considered an important "checkpoint" in the regulation of Syk activation process. Putative biological functions of TULA-2-mediated dephosphorylation of Tyr(P)346 may include deactivation of receptor-activated Syk or suppression of Syk activation by suboptimal stimulation.
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Affiliation(s)
- Kevin Reppschläger
- From the Departments of Microbiology and Immunology and.,Ernst-Moritz-Arndt-University Greifswald, 17489 Greifswald, Germany
| | - Jeanne Gosselin
- From the Departments of Microbiology and Immunology and.,Polytech Clermont-Ferrand, Ingenieur Genie Biologique, Clermont-Ferrand, Auvergne 63178, France, and
| | - Carol A Dangelmaier
- the Sol Sherry Thrombosis Research Center, Temple University Lewis Katz School of Medicine, Philadelphia, Pennsylvania 19140
| | - Dafydd H Thomas
- the Sol Sherry Thrombosis Research Center, Temple University Lewis Katz School of Medicine, Philadelphia, Pennsylvania 19140.,PMV Pharmaceuticals, Cranbury Township, New Jersey 08512
| | - Nick Carpino
- the Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York 11794
| | - Steven E McKenzie
- the Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Satya P Kunapuli
- the Sol Sherry Thrombosis Research Center, Temple University Lewis Katz School of Medicine, Philadelphia, Pennsylvania 19140.,Physiology and
| | - Alexander Y Tsygankov
- From the Departments of Microbiology and Immunology and .,the Sol Sherry Thrombosis Research Center, Temple University Lewis Katz School of Medicine, Philadelphia, Pennsylvania 19140
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Talab F, Allen JC, Thompson V, Lin K, Slupsky JR. LCK is an important mediator of B-cell receptor signaling in chronic lymphocytic leukemia cells. Mol Cancer Res 2013; 11:541-54. [PMID: 23505068 DOI: 10.1158/1541-7786.mcr-12-0415-t] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
B-cell receptor (BCR) signals promote survival of chronic lymphocytic leukemia (CLL) cells, and it is believed that overexpressed and constitutively active Lyn mediates this signaling. Here, we show that CLL cells express lymphocyte-specific protein tyrosine kinase (LCK) and that inhibition of this Src family tyrosine kinase with the specific inhibitor [4-amino-5-(4-phenoxyphenyl)-7H-pyrrolo[3,2-d]pyrimidin-7-yl-cyclopentane (Lck-i)], or reduction of its expression with siRNA, blocks the induction of CD79a, Syk, inhibitor of IκB kinase (IKK), Akt, and extracellular signal-regulated kinase (ERK) phosphorylation by BCR cross-linking in these cells. Furthermore, we show that CLL cells with high levels of LCK expression have higher levels of BCR-mediated IKK, Akt, and ERK phosphorylation as well as cell survival than CLL cells with low levels of LCK expression. We also show that treatment of CLL cells with Lck-i inhibits BCR cross-linking-induced cell survival. Taken together, these data show a major role for LCK in proximal and distal BCR-mediated signaling in CLL cells and suggest that LCK expression is important in the pathogenesis of this disease. On a clinical level, these studies advocate the use of specific LCK inhibitors in the treatment of progressive CLL.
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Affiliation(s)
- Fatima Talab
- Department of Molecular and Clinical Cancer Medicine, University of Liverpool, Liverpool, United Kingdom
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6
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Ghosh D, Kis-Toth K, Juang YT, Tsokos GC. CREMα suppresses spleen tyrosine kinase expression in normal but not systemic lupus erythematosus T cells. ACTA ACUST UNITED AC 2012; 64:799-807. [PMID: 21953500 DOI: 10.1002/art.33375] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE T cells from patients with systemic lupus erythematosus (SLE) display increased amounts of spleen tyrosine kinase (Syk), which is involved in the aberrant CD3/T cell receptor-mediated signaling process, and increased amounts of CREMα, which suppresses the production of interleukin-2. Syk expression can be suppressed by CREMα. This study was undertaken to investigate why CREMα fails to suppress Syk expression in SLE T cells. METHODS CREMα was overexpressed in healthy T cells by transfection with CREMα expression vector, and Syk expression and phosphorylation were measured. A newly identified cAMP response element (CRE) site on the SYK promoter was characterized by chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift assay. The CREMα-mediated repression of Syk expression was further evaluated by analyzing SYK promoter activity. T cells from SLE patients and healthy individuals were subjected to ChIP to evaluate CREMα binding and histone H3 acetylation. RESULTS Increased CREMα levels suppressed Syk expression by direct binding to a CRE site of the SYK promoter in T cells from healthy individuals but failed to do so in T cells from SLE patients. The failure of CREMα to suppress Syk expression in SLE T cells was due to weaker binding to the CRE site of the SYK promoter compared to healthy T cells because the promoter site is hypoacetylated in SLE T cells and therefore of limited access to transcription factors. CONCLUSION Our findings indicate that epigenetic alteration of the SYK promoter in SLE T cells results in the inability of the transcriptional repressor CREMα to bind and suppress the expression of Syk, resulting in aberrant T cell signaling.
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Affiliation(s)
- Debjani Ghosh
- Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA
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7
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Gilbert C, Barat C, Cantin R, Tremblay MJ. Involvement of Src and Syk Tyrosine Kinases in HIV-1 Transfer from Dendritic Cells to CD4+T Lymphocytes. THE JOURNAL OF IMMUNOLOGY 2007; 178:2862-71. [PMID: 17312130 DOI: 10.4049/jimmunol.178.5.2862] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Dendritic cells (DCs) are considered as key mediators of the early events in HIV-1 infection at mucosal sites. Although several aspects of the complex interactions between DCs and HIV-1 have been elucidated, there are still basic questions that remain to be answered about DCs/HIV-1 interplay. In this study, we examined the contribution of nonreceptor TKs in the known ability of DCs to efficiently transfer HIV-1 to CD4(+) T cells in trans. Experiments performed with specific inhibitors of Src and Syk family members indicate that these tyrosine kinases (TKs) are participating to HIV-1 transfer from immature monocyte-derived DCs (IM-MDDCs) to autologous CD4(+) T cells. Experiments with IM-MDDCs transfected with small interfering RNAs targeting Lyn and Syk confirmed the importance of these nonreceptor TKs in HIV-1 transmission. The Src- and Syk-mediated effect on virus transfer was linked with infection of IM-MDDCs in cis-as monitored by quantifying integrated viral DNA and de novo virus production. The process of HIV-1 transmission from IM-MDDCs to CD4(+) T cells was unaffected following treatment with protein kinase C and protein kinase A inhibitors. These data suggest that Src and Syk TKs play a functional role in productive HIV-1 infection of IM-MDDCs. Additional work is needed to facilitate our comprehension of the various mechanisms underlying the exact contribution of Src and Syk TKs to this phenomenon.
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Affiliation(s)
- Caroline Gilbert
- Centre de Recherche en Infectiologie, Centre Hospitalier de l'Université Laval, and Faculté de Médecine, Université Laval, 2705 Boulevard Laurier, Quebec, Canada
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9
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Steinberg M, Adjali O, Swainson L, Merida P, Di Bartolo V, Pelletier L, Taylor N, Noraz N. T-cell receptor–induced phosphorylation of the ζ chain is efficiently promoted by ZAP-70 but not Syk. Blood 2004; 104:760-7. [PMID: 15059847 DOI: 10.1182/blood-2003-12-4314] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractEngagement of the T-cell receptor (TCR) results in the activation of Lck/Fyn and ZAP-70/Syk tyrosine kinases. Lck-mediated tyrosine phosphorylation of signaling motifs (ITAMs) in the CD3-ζ subunits of the TCR is an initial step in the transduction of signaling cascades. However, ζ phosphorylation is also promoted by ZAP-70, as TCR-induced ζ phosphorylation is defective in ZAP-70–deficient T cells. We show that this defect is corrected by stable expression of ZAP-70, but not Syk, in primary and transformed T cells. Indeed, these proteins are differentially coupled to the TCR with a 5- to 10-fold higher association of ZAP-70 with ζ as compared to Syk. Low-level Syk-ζ binding is associated with significantly less Lck coupled to the TCR. Moreover, diminished coupling of Lck to ζ correlates with a poor phosphorylation of the positive regulatory tyr352 residue of Syk. Thus, recruitment of Lck into the TCR complex with subsequent ζ chain phosphorylation is promoted by ZAP-70 but not Syk. Importantly, the presence of ZAP-70 positively regulates the TCR-induced tyrosine phosphorylation of Syk. The interplay between Syk and ZAP-70 in thymocytes, certain T cells, and B-chronic lymphocytic leukemia cells, in which they are coexpressed, will therefore modulate the amplitude of antigen-mediated receptor signaling.
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Affiliation(s)
- Marcos Steinberg
- Institut de Génétique Moléculaire de Montpellier, Centre National de la Recherche Scientifique Unité de Recherches 5535/Institut Fédératife de Recherche, F-34293 Montpellier 5, France
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10
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Yang Y, Villain P, Mustelin T, Couture C. Critical role of Ser-520 phosphorylation for membrane recruitment and activation of the ZAP-70 tyrosine kinase in T cells. Mol Cell Biol 2003; 23:7667-77. [PMID: 14560012 PMCID: PMC207614 DOI: 10.1128/mcb.23.21.7667-7677.2003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Regulation of protein tyrosine kinases (PTKs) by tyrosine phosphorylation is well recognized; in fact, nearly all PTKs require phosphorylation of tyrosine residues in their "activation loop" for catalytic activity. In contrast, the phosphorylation of PTKs on serine and threonine residues has not been studied nearly as much. We report that the ZAP-70 PTK contains predominately phosphoserine in normal T lymphocytes as well as in Jurkat T leukemia cells. We have identified one site of phosphorylation as Ser-520 and find this site to be important for the recruitment and activation of ZAP-70 in T cells. Mutant ZAP-70-S520A had reduced ability to autophosphorylate and to mediate antigen receptor-induced interleukin 2 gene activation and was not enriched at the plasma membrane. These defects were rescued by addition of a myristylation signal to the N terminus of ZAP-70-S520A to force its plasma membrane and lipid raft localization. We conclude that phosphorylation of ZAP-70 at Ser-520 plays an important role in the correct localization of ZAP-70 and in priming ZAP-70 for its acute recruitment and activation upon antigen receptor ligation.
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Affiliation(s)
- Yaoming Yang
- Program of Signal Transduction, Burnham Institute, La Jolla, California, USA
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11
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Maeno K, Sada K, Kyo S, Miah SMS, Kawauchi-Kamata K, Qu X, Shi Y, Yamamura H. Adaptor protein 3BP2 is a potential ligand of Src homology 2 and 3 domains of Lyn protein-tyrosine kinase. J Biol Chem 2003; 278:24912-20. [PMID: 12709437 DOI: 10.1074/jbc.m301201200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Adaptor protein 3BP2, a c-Abl-Src homology 3 (SH3) domain-binding protein, is known to play a regulatory role in T-cell receptor-mediated transcriptional activation of nuclear factor of activated T cell and activator protein 1 by interacting with Syk/ZAP-70 protein-tyrosine kinase. We have previously demonstrated that aggregation of high affinity IgE receptor (FcepsilonRI) induces tyrosine phosphorylation of 3BP2, and overexpression of the 3BP2-SH2 domain suppresses antigen-induced degranulation in rat basophilic leukemia RBL-2H3 mast cell line. In this report, we attempt to analyze the biological relevance of 3BP2 tyrosine phosphorylation. By using the transient expression system in COS-7 cells, we have demonstrated that 3BP2 was predominantly phosphorylated on Tyr174, Tyr183, and Tyr446 when it was coexpressed with Syk. An in vitro binding study revealed that phosphorylation of Tyr446 by Syk was likely to create a binding site for the Lyn-SH2 domain in RBL-2H3 cells. In addition, proline-rich region of 3BP2 bound to the Lyn-SH3 domain. Conformational microscopic analysis showed that Lyn and 3BP2 are constitutively colocalized in RBL-2H3 cells. Overexpression of 3BP2 in RBL-2H3 cells resulted in an enhancement of Lyn autophosphorylation. These results suggest that the adaptor protein 3BP2 is a potential regulator of Lyn protein-tyrosine kinase as a ligand of its SH3/SH2 domains in FcepsilonRI-mediated signaling in mast cells.
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Affiliation(s)
- Koichiro Maeno
- Division of Proteomics, Department of Genome Sciences, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Japan
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12
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Wang X, Huynh H, Gjörloff-Wingren A, Monosov E, Stridsberg M, Fukuda M, Mustelin T. Enlargement of secretory vesicles by protein tyrosine phosphatase PTP-MEG2 in rat basophilic leukemia mast cells and Jurkat T cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 168:4612-9. [PMID: 11971009 DOI: 10.4049/jimmunol.168.9.4612] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Stimulus-induced secretion of bioactive polypeptides is a fundamental aspect of the immune system. Secretory proteins are synthesized in the endoplasmic reticulum and are transported through the Golgi apparatus to the trans-Golgi network, where they are sorted into transport vesicles that bud off and fuse into condensing vacuoles, which subsequently undergo an editing and concentration process to become mature secretory vesicles. In this study, we report that the PTP-MEG2 protein tyrosine phosphatase is located on these vesicles in mast cells. Expression of PTP-MEG2 caused a striking enlargement of these vesicles in both rat basophilic leukemia mast cells and Jurkat T leukemia cells into giant vesicles with diameters of up to several micrometers. The fused vesicles did not acquire markers for other compartments and were adjacent to the trans-Golgi network, contained carboxypeptidase E, chromogranin C, and IL-2, and had an electron-dense core typical of secretory vesicles. Expression of PTP-MEG2 also caused a reduction in the secretion of IL-2 from stimulated Jurkat cells. The effects of PTP-MEG2 on secretory vesicles required the catalytic activity of PTP-MEG2 and was rapidly reversed by pervanadate. We propose that PTP-MEG2 represents a novel connection between tyrosine dephosphorylation and the regulation of secretory vesicles in hematopoietic cells.
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Affiliation(s)
- Xiaodong Wang
- Program of Signal Transduction, Cancer Research Center, The Burnham Institute, La Jolla, CA 92037, USA
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13
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Torgersen KM, Vang T, Abrahamsen H, Yaqub S, Horejsí V, Schraven B, Rolstad B, Mustelin T, Taskén K. Release from tonic inhibition of T cell activation through transient displacement of C-terminal Src kinase (Csk) from lipid rafts. J Biol Chem 2001; 276:29313-8. [PMID: 11390365 DOI: 10.1074/jbc.c100014200] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In resting peripheral T cells, Csk is constitutively present in lipid rafts through an interaction with the Csk SH2-binding protein, PAG, also known as Cbp. Upon triggering of the T cell antigen receptor (TCR), PAG/Cbp is rapidly dephosphorylated leading to dissociation of Csk from lipid rafts. However, tyrosine phosphorylation of PAG/Cbp resumes after 3--5 min, at which time Csk reassociates with the rafts. Cells overexpressing a mutant Csk that lacks the catalytic domain, but displaces endogenous Csk from lipid rafts, have elevated basal levels of TCR-zeta-chain phosphorylation and spontaneous activation of an NFAT-AP1 reporter from the proximal interleukin-2 promoter as well as stronger and more sustained responses to TCR triggering than controls. We suggest that a transient release from Csk-mediated inhibition by displacement of Csk from lipid rafts is important for normal T cell activation.
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Affiliation(s)
- K M Torgersen
- Department of Medical Biochemistry, Institute of Basic Medical Sciences, University of Oslo, Box 1112, Blindern, N-0317 Oslo, Norway
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14
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Vang T, Torgersen KM, Sundvold V, Saxena M, Levy FO, Skålhegg BS, Hansson V, Mustelin T, Taskén K. Activation of the COOH-terminal Src kinase (Csk) by cAMP-dependent protein kinase inhibits signaling through the T cell receptor. J Exp Med 2001; 193:497-507. [PMID: 11181701 PMCID: PMC2195911 DOI: 10.1084/jem.193.4.497] [Citation(s) in RCA: 255] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
In T cells, cAMP-dependent protein kinase (PKA) type I colocalizes with the T cell receptor-CD3 complex (TCR/CD3) and inhibits T cell function via a previously unknown proximal target. Here we examine the mechanism for this PKA-mediated immunomodulation. cAMP treatment of Jurkat and normal T cells reduces Lck-mediated tyrosine phosphorylation of the TCR/CD3 zeta chain after T cell activation, and decreases Lck activity. Phosphorylation of residue Y505 in Lck by COOH-terminal Src kinase (Csk), which negatively regulates Lck, is essential for the inhibitory effect of cAMP on zeta chain phosphorylation. PKA phosphorylates Csk at S364 in vitro and in vivo leading to a two- to fourfold increase in Csk activity that is necessary for cAMP-mediated inhibition of TCR-induced interleukin 2 secretion. Both PKA type I and Csk are targeted to lipid rafts where proximal T cell activation occurs, and phosphorylation of raft-associated Lck by Csk is increased in cells treated with forskolin. We propose a mechanism whereby PKA through activation of Csk intersects signaling by Src kinases and inhibits T cell activation.
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Affiliation(s)
- Torkel Vang
- Department of Medical Biochemistry, Institute of Basic Medical Sciences, University of Oslo, N-0317 Oslo, Norway
| | - Knut Martin Torgersen
- Department of Medical Biochemistry, Institute of Basic Medical Sciences, University of Oslo, N-0317 Oslo, Norway
| | - Vibeke Sundvold
- Institute of Immunology, University of Oslo, The National Hospital, N-0027 Oslo, Norway
| | - Manju Saxena
- La Jolla Institute for Allergy and Immunology, San Diego, California 92121
| | - Finn Olav Levy
- Department of Medical Biochemistry, Institute of Basic Medical Sciences, University of Oslo, N-0317 Oslo, Norway
| | - Bjørn S. Skålhegg
- Department of Medical Biochemistry, Institute of Basic Medical Sciences, University of Oslo, N-0317 Oslo, Norway
| | - Vidar Hansson
- Department of Medical Biochemistry, Institute of Basic Medical Sciences, University of Oslo, N-0317 Oslo, Norway
| | - Tomas Mustelin
- La Jolla Institute for Allergy and Immunology, San Diego, California 92121
- La Jolla Cancer Research Center, The Burnham Institute, La Jolla, California 92037
| | - Kjetil Taskén
- Department of Medical Biochemistry, Institute of Basic Medical Sciences, University of Oslo, N-0317 Oslo, Norway
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15
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Tabata H, Matsuoka T, Endo F, Nishimura Y, Matsushita S. Ligation of HLA-DR molecules on B cells induces enhanced expression of IgM heavy chain genes in association with Syk activation. J Biol Chem 2000; 275:34998-5005. [PMID: 10948188 DOI: 10.1074/jbc.m002089200] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Signals transmitted by class II major histocompatibility complex are important regarding cell function related to antigen presentation. We examined effects of DR-mediated signaling on Ig production from B cells. Cross-linking HLA-DR molecules on B cells by solid-phase anti-HLA-DR monoclonal antibodies, led to an increased production of IgM, without proliferation or apoptosis. This event was accompanied by an enhanced expression of both membrane- and secretory-type IgM heavy chain mRNA. When peptide-pulsed B cells were co-incubated with an HLA-DR-restricted T cell clone treated by the protein synthesis inhibitor emetine, peptide-induced de novo expression of lymphokines and cell-surface molecules on T cells can be neglected. CD40-CD154 interaction was not involved in IgM enhancement, in such a system. The protein-tyrosine kinase inhibitors and the Syk inhibitor piceatannol, but not the Src inhibitor PP2 had a marked inhibitory effect on IgM secretion. Furthermore, ligation of HLA-DR on B cells using the F(ab')2 fragment of anti-DR monoclonal antibody, enhanced Syk activity. Our data suggest that HLA-DR on B cells not only present antigenic peptides to T cells, but also up-regulate IgM production, in association with Syk activation and without the involvement of Src kinases, hence the possible physiological relevance of Src-independent Syk activation.
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Affiliation(s)
- H Tabata
- Division of Immunogenetics, Department of Neuroscience and Immunology, Kumamoto University Graduate School of Medical Sciences and the Department of Pediatrics, Kumamoto University School of Medicine, Kumamoto 860-0811, Japan
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16
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Noraz N, Schwarz K, Steinberg M, Dardalhon V, Rebouissou C, Hipskind R, Friedrich W, Yssel H, Bacon K, Taylor N. Alternative antigen receptor (TCR) signaling in T cells derived from ZAP-70-deficient patients expressing high levels of Syk. J Biol Chem 2000; 275:15832-8. [PMID: 10748099 DOI: 10.1074/jbc.m908568199] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ZAP-70-deficient patients present with nonfunctional CD4+ T cells in the periphery. We find that a subset of primary ZAP-70-deficient T cells, expressing high levels of the related protein-tyrosine kinase Syk, can proliferate in vitro. These cells (denoted herein as Syk(hi)/ZAP-70(-) T cells) provide a unique model in which the contribution of Syk to TCR-mediated responses can be explored in a nontransformed background. Importantly, CD3-induced responses, such as tyrosine phosphorylation of cellular substrates (LAT, SLP76, and PLC-gamma1), as well as calcium mobilization, which are defective in T cells expressing neither ZAP-70 nor Syk, are observed in Syk(hi)/ZAP-70(-) T cells. However, Syk(hi)/ZAP-70(-) T cells differ from control T cells with respect to the T cell antigen receptor (TCR)-mediated activation of the MAPK cascades: extracellular signal-regulated kinase activity and recruitment of the JNK and p38 stress-related MAPK pathways are diminished. This distinct phenotype of Syk(hi)/ZAP-70(-) T cells is associated with a profound decrease in CD3-mediated interleukin 2 secretion and proliferation relative to control T cells. Thus, ZAP-70 and Syk appear to play distinct roles in transducing a TCR-mediated signal.
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Affiliation(s)
- N Noraz
- Institut de Génétique Moléculaire de Montpellier, CNRS UMR 5535, 1919 Route de Mende, 34293 Montpellier, Cedex 5, France.
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17
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Bouhdoud L, Villain P, Merzouki A, Arella M, Couture C. T-cell receptor-mediated anergy of a human immunodeficiency virus (HIV) gp120-specific CD4(+) cytotoxic T-cell clone, induced by a natural HIV type 1 variant peptide. J Virol 2000; 74:2121-30. [PMID: 10666241 PMCID: PMC111692 DOI: 10.1128/jvi.74.5.2121-2130.2000] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) infection triggers a cytotoxic T-lymphocyte (CTL) response mediated by CD8(+) and perhaps CD4(+) CTLs. The mechanisms by which HIV-1 escapes from this CTL response are only beginning to be understood. However, it is already clear that the extreme genetic variability of the virus is a major contributing factor. Because of the well-known ability of altered peptide ligands (APL) to induce a T-cell receptor (TCR)-mediated anergic state in CD4(+) helper T cells, we investigated the effects of HIV-1 sequence variations on the proliferation and cytotoxic activation of a human CD4(+) CTL clone (Een217) specific for an epitope composed of amino acids 410 to 429 of HIV-1 gp120. We report that a natural variant of this epitope induced a functional anergic state rendering the T cells unable to respond to their antigenic ligand and preventing the proliferation and cytotoxic activation normally induced by the original antigenic peptide. Furthermore, the stimulation of Een217 cells with this APL generated altered TCR-proximal signaling events that have been associated with the induction of T-cell anergy in CD4(+) T cells. Importantly, the APL-induced anergic state of the Een217 T cells could be prevented by the addition of interleukin 2, which restored their ability to respond to their nominal antigen. Our data therefore suggest that HIV-1 variants can induce a state of anergy in HIV-specific CD4(+) CTLs. Such a mechanism may allow a viral variant to not only escape the CTL response but also facilitate the persistence of other viral strains that may otherwise be recognized and eliminated by HIV-specific CTLs.
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Affiliation(s)
- L Bouhdoud
- Molecular Oncology Group, Lady Davis Institute for Medical Research, Montréal, Québec, Canada
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18
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Miscia S, Di Baldassarre A, Sabatino G, Bonvini E, Rana RA, Vitale M, Di Valerio V, Manzoli FA. Inefficient Phospholipase C Activation and Reduced Lck Expression Characterize the Signaling Defect of Umbilical Cord T Lymphocytes. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.163.5.2416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
Adult and neonatal immunocompetent cells exhibit important functional distinctions, including differences in cytokine production and susceptibility to tolerance induction. We have investigated the molecular features that characterize the immune response of cord blood-derived T lymphocytes compared with that of adult T lymphocytes. Our findings demonstrate that phospholipase C (PLC) isozymes, which play a pivotal role in the control of protein kinase C activation and Ca2+ mobilization, are differently expressed in cord and adult T lymphocytes. PLCβ1 and δ1 are expressed at higher levels in cord T cells, while PLCβ2 and γ1 expression is higher in adult T lymphocytes. PLCδ2 and γ2 appear to be equally expressed in both cell types. In addition, a functional defect in PLC activation via CD3 ligation or pervanadate treatment, stimuli that activate tyrosine kinases, was observed in cord blood T cells, whereas treatment with aluminum tetrafluoride (AlF4−), a G protein activator, demonstrated a similar degree of PLC activation in cord and adult T cells. The impaired PLC activation of cord blood-derived T cells was associated with a a very low expression of the Src kinase, Lck, along with a reduced level of ZAP70. No mitogenic response to CD3 ligation was observed in cord T cells. However, no signaling defect was apparent downstream of PLC activation, as demonstrated by the mitogenic response of cord T cells to the pharmacologic activation of protein kinase C and Ca2+ by treatment with PMA and ionomycin. Thus, neonatal cord blood-derived T cells show a signaling immaturity associated with inadequate PLCγ activation and decreased Lck expression.
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Affiliation(s)
| | | | - Giuseppe Sabatino
- †Cattedra di Neonatologia, Università degli Studi “G. D’Annunzio,” Chieti, Italy
| | - Ezio Bonvini
- ¶Laboratory of Immunobiology, Division of Monoclonal Antibodies, Center for Biologics Evaluation and Research, Bethesda, MD 20852
| | | | - Marco Vitale
- §Dipartimento di Scienze Biomediche e Biotecnologie, Sezione di Anatomia Umana, Università di Brescia, Brescia, Italy; and
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19
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Abstract
Studies with motheaten mice, which lack the SHP1 protein tyrosine phosphatase, indicate that this enzyme plays an important negative role in T cell antigen receptor (TCR) signaling. The physiological substrates for SHP1 in T lymphocytes, however, have remained unclear or controversial. To define these targets for SHP1 we have compared the effects of constitutively active and inactive mutants of SHP1 on TCR signaling. Expression of wild-type SHP1 had a very small effect on the TCR-induced tyrosine phosphorylation of ZAP-70 and Syk, even when SHP1 was overexpressed 20 - 100-fold over endogenous SHP1. Inactive SHP1-D421A and wild-type SHP2 were without effects. Constitutively active SHP1-DeltaSH2 had a more pronounced effect on ZAP-70 and Syk, even when expressed at near physiological levels. SHP1-DeltaSH2 also inhibited events downstream of ZAP-70 and Syk, such as activation of the mitogen-activated protein kinase Erk2 and the transcriptional activation of the interleukin-2 gene. In contrast, a constitutively active SHP2-DeltaSH2 had no statistically significant effect (although it caused a slight augmentation in some individual experiments). None of the constructs influenced the anti-CD3-induced tyrosine phosphorylation of the TCR zeta-chain or phospholipase Cgamma1, indicating that Src family kinase function was intact. Taken together, our findings support the notion that ZAP-70 and Syk can be direct substrates for SHP1 in intact cells. However, the two SH2 domains of SHP1 did not facilitate its recognition of ZAP-70 and Syk as substrates in intact cells. Therefore, we suggest that SHP1 is not actively recruited to inhibit TCR signaling induced by ligation of this receptor alone. Instead, we propose that ligation of a distinct inhibitory receptor leads to the recruitment of SHP1 via its SH2 domains, activation of SHP1 and subsequently inhibition of TCR signals if the inhibitory receptor is juxtaposed to the TCR.
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Affiliation(s)
- J Brockdorff
- La Jolla Institute for Allergy and Immunology, San Diego, California, USA
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20
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Germain RN, Stefanová I. The dynamics of T cell receptor signaling: complex orchestration and the key roles of tempo and cooperation. Annu Rev Immunol 1999; 17:467-522. [PMID: 10358766 DOI: 10.1146/annurev.immunol.17.1.467] [Citation(s) in RCA: 317] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
T cells constantly sample their environment using receptors (TCR) that possess both a germline-encoded low affinity for major histocompatibility complex (MHC) molecules and a highly diverse set of CDR3 regions contributing to a range of affinities for specific peptides bound to these MHC molecules. The decision of a T cell "to sense and to respond" with proliferation and effector activity rather than "to sense, live on, but not respond" is dependent on TCR interaction with a low number of specific foreign peptide:MHC molecule complexes recognized simultaneously with abundant self peptide-containing complexes. Interaction with self-complexes alone, on the other hand, generates a signal for survival without a full activation response. Current models for how this distinction is achieved are largely based on translating differences in receptor affinity for foreign versus self ligands into intracellular signals that differ in quality, intensity, and/or duration. A variety of rate-dependent mechanisms involving assembly of molecular oligomers and enzymatic modification of proteins underlie this differential signaling. Recent advances have been made in measuring TCR:ligand interactions, in understanding the biochemical origin of distinct proximal and distal signaling events resulting from TCR binding to various ligands, and in appreciating the role of feedback pathways. This new information can be synthesized into a model of how self and foreign ligand recognition each evoke the proper responses from T cells, how these two classes of signaling events interact, and how pathologic responses may arise as a result of the underlying properties of the system. The principles of signal spreading and stochastic resonance incorporated into this model reveal a striking similarity in mechanisms of decision-making among T cells, neurons, and bacteria.
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Affiliation(s)
- R N Germain
- Lymphocyte Biology Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA. ,
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21
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A Common Signaling Pathway Via Syk and Lyn Tyrosine Kinases Generated From Capping of the Sialomucins CD34 and CD43 in Immature Hematopoietic Cells. Blood 1999. [DOI: 10.1182/blood.v93.11.3723.411k02_3723_3735] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The sialomucin CD34 is a useful marker for hematopoietic stem/progenitor cells. However, the role of CD34 remains poorly understood. Here we investigate the functions of CD34 and another sialomucin CD43 coexpressed on hematopoietic stem/progenitor cells. Stimulation of undifferentiated hematopoietic KG1a cells with anti-CD34 or anti-CD43 induced homotypic cytoadhesion, accompanied by formation of a long-lived cap of CD34 and CD43 respectively, which colocalized with F-actin. Stimulation with either antibody specifically increased tyrosine phosphorylation of the identical set of proteins of Lyn, Syk, pp60, pp69, and pp77 at the capping site. These events were similar to those observed in monocytic U937 cells ectopically expressing CD34. After stimulation of KG1a cells, coimmunoprecipitation of Lyn with pp69 and pp77 and of Syk with pp37 was detected in the membrane fraction. Blockade of antibody-induced cap formation by treatment with cytochalasin D leads to inhibition of tyrosine phosphorylation of Syk and pp77 and homotypic cytoadhesion. Moreover, normal human CD34+ bone marrow cells showed cap formation of CD34 or CD43 after stimulation. These results suggest that crosslinking of either CD34 or CD43 activates the same signaling pathway for cytoadhesion through Lyn, Syk, and the novel tyrosine-phosphorylated proteins within hematopoiesis.
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22
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A Common Signaling Pathway Via Syk and Lyn Tyrosine Kinases Generated From Capping of the Sialomucins CD34 and CD43 in Immature Hematopoietic Cells. Blood 1999. [DOI: 10.1182/blood.v93.11.3723] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe sialomucin CD34 is a useful marker for hematopoietic stem/progenitor cells. However, the role of CD34 remains poorly understood. Here we investigate the functions of CD34 and another sialomucin CD43 coexpressed on hematopoietic stem/progenitor cells. Stimulation of undifferentiated hematopoietic KG1a cells with anti-CD34 or anti-CD43 induced homotypic cytoadhesion, accompanied by formation of a long-lived cap of CD34 and CD43 respectively, which colocalized with F-actin. Stimulation with either antibody specifically increased tyrosine phosphorylation of the identical set of proteins of Lyn, Syk, pp60, pp69, and pp77 at the capping site. These events were similar to those observed in monocytic U937 cells ectopically expressing CD34. After stimulation of KG1a cells, coimmunoprecipitation of Lyn with pp69 and pp77 and of Syk with pp37 was detected in the membrane fraction. Blockade of antibody-induced cap formation by treatment with cytochalasin D leads to inhibition of tyrosine phosphorylation of Syk and pp77 and homotypic cytoadhesion. Moreover, normal human CD34+ bone marrow cells showed cap formation of CD34 or CD43 after stimulation. These results suggest that crosslinking of either CD34 or CD43 activates the same signaling pathway for cytoadhesion through Lyn, Syk, and the novel tyrosine-phosphorylated proteins within hematopoiesis.
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23
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Weil R, Levraud JP, Dodon MD, Bessia C, Hazan U, Kourilsky P, Israël A. Altered expression of tyrosine kinases of the Src and Syk families in human T-cell leukemia virus type 1-infected T-cell lines. J Virol 1999; 73:3709-17. [PMID: 10196263 PMCID: PMC104146 DOI: 10.1128/jvi.73.5.3709-3717.1999] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During the late phase of adult T-cell leukemia/lymphoma, a severe lymphoproliferative disorder caused by human T-cell leukemia virus type 1 (HTLV-1), leukemic cells no longer produce interleukin-2. Several studies have reported the lack of the Src-like protein tyrosine kinase Lck and overexpression of Lyn and Fyn in these cells. In this report we demonstrate that, in addition to the downregulation of TCR, CD45, and Lck (which are key components of T-cell activation), HTLV-1-infected cell lines demonstrate a large increase of FynB, a Fyn isoform usually poorly expressed in T cells. Furthermore, similar to anergic T cells, Fyn is hyperactive in one of these HTLV-1-infected T-cell lines, probably as a consequence of Csk downregulation. A second family of two proteins, Zap-70 and Syk, relay the signal of T-cell activation. We demonstrate that in contrast to uninfected T cells, Zap-70 is absent in HTLV-1-infected T cells, whereas Syk is overexpressed. In searching for the mechanism responsible for FynB overexpression and Zap-70 downregulation, we have investigated the ability of the Tax and Rex proteins to modulate Zap-70 expression and the alternative splicing mechanism which gives rise to either FynB or FynT. By using Jurkat T cells stably transfected with the tax and rex genes or inducibly expressing the tax gene, we found that the expression of Rex was necessary to increase fynB expression, suggesting that Rex controls fyn gene splicing. Conversely, with the same Jurkat clones, we found that the expression of Tax but not Rex could downregulate Zap-70 expression. These results suggest that the effect of Tax and Rex must cooperate to deregulate the pathway of T-cell activation in HTLV-1-infected T cells.
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Affiliation(s)
- R Weil
- Unité de Biologie Moléculaire de l'Expression Génique, URA 1773 Centre National de la Recherche Scientifique, 75724 Paris Cedex 15, France.
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24
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Duprez V, Blank U, Chrétien S, Gisselbrecht S, Mayeux P. Physical and functional interaction between p72(syk) and erythropoietin receptor. J Biol Chem 1998; 273:33985-90. [PMID: 9852052 DOI: 10.1074/jbc.273.51.33985] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Erythropoietin (Epo) regulates the proliferation and differentiation of erythroid cells through interaction with a cell surface receptor (EpoR) that belongs to the cytokine receptor family. The Jak2 tyrosine kinase was previously shown to bind to the EpoR, to be activated upon Epo stimulation, and to play a critical role in Epo-induced proliferation. However, little is known about the role of other tyrosine kinases in Epo signaling. In this paper, we examined whether Syk was involved in EpoR activation. Coimmunoprecipitation experiments showed that the phosphorylated EpoR was associated with the Syk kinase in activated UT7 cells. The interaction of Epo with its receptor led to an increased kinase activity. The use of recombinant Syk Src homology 2 (SH2) domains expressed in tandem or individually revealed that both N- and C-SH2 domains of Syk participated in EpoR binding with a major contribution of the C-terminal SH2 domain. Far Western blotting further indicated that Syk directly binds to the EpoR and that the interaction of Syk with EpoR only occurred after Epo activation. These data suggest that phosphorylation of EpoR on tyrosine residues may mediate Syk binding to the receptor through interaction between the two SH2 domains of Syk and tyrosines of the receptor. We propose that in addition to Jak2, Syk protein kinase may be a component of EpoR signaling.
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Affiliation(s)
- V Duprez
- Institut National de la Santé et de la Recherche Médicale, Unité 363, ICGM, Hopital Cochin, 27 rue du Faubourg Saint Jacques, Paris, France.
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25
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Keshvara LM, Isaacson CC, Yankee TM, Sarac R, Harrison ML, Geahlen RL. Syk- and Lyn-Dependent Phosphorylation of Syk on Multiple Tyrosines Following B Cell Activation Includes a Site That Negatively Regulates Signaling. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.161.10.5276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
The Syk protein tyrosine kinase is an essential component of the B cell Ag receptor signaling pathway. Syk is phosphorylated on tyrosine following B cell activation. However, the sites that are modified and the kinases responsible for these modifications have yet to be determined. To approach this problem, we used a mapping strategy based on the electrophoretic separation of peptides on alkaline polyacrylamide gels to identify the tryptic phosphopeptides derived from metabolically labeled Syk. In this work, we report that Syk from activated B cells is phosphorylated principally on six tyrosines: one located between the tandem SH2 domains (Tyr130); three in the linker region (Tyr317, Tyr342, and Tyr346); and two in the catalytic domain (Tyr519 and Tyr520). The linker region sites are the primary targets of the Src family protein tyrosine kinase, Lyn, and include a site that negatively (Tyr317) regulates receptor signaling. Efficient phosphorylation of the catalytic domain and inter-SH2 domain tyrosines is catalyzed primarily by Syk itself, but only occurs to an appreciable extent in cells that express Lyn. We propose that these sites are phosphorylated following the binding of Syk to immunoreceptor tyrosine-based activation motif.
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Affiliation(s)
- Lakhu M. Keshvara
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907
| | - Christina C. Isaacson
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907
| | - Thomas M. Yankee
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907
| | - Radmila Sarac
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907
| | - Marietta L. Harrison
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907
| | - Robert L. Geahlen
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907
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26
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Deckert M, Tartare-Deckert S, Hernandez J, Rottapel R, Altman A. Adaptor function for the Syk kinases-interacting protein 3BP2 in IL-2 gene activation. Immunity 1998; 9:595-605. [PMID: 9846481 DOI: 10.1016/s1074-7613(00)80657-3] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Syk-family tyrosine kinases are essential for lymphocyte development and activation. Using a yeast two-hybrid screen to identify Syk kinases-interacting proteins (SKIPs), we isolated 3BP2, an Abl SH3-interacting protein of unknown function. 3BP2 was selectively expressed in hematopoietic/lymphoid tissues and bound via its SH2 domain activated Syk-family kinases in mammalian cells, including in antigen receptor-stimulated T cells. In addition to Zap-70, the 3BP2 SH2 domain associated in vitro with LAT, Grb2, PLCgamma1, and Cbl from activated T cell lysates. Transient 3BP2 overexpression induced transcriptional activation of the IL-2 promoter and its NFAT or AP-1 elements. This activity was dependent on the SH2 and pleckstrin-homology domains of 3BP2, and required functional Syk kinases, Ras, and calcineurin. Thus, 3BP2 is an important adaptor that may couple activated Zap-70/Syk to a LAT-containing signaling complex involved in TCR-mediated gene transcription.
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Affiliation(s)
- M Deckert
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA
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27
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Zhang J, Kimura T, Siraganian RP. Mutations in the Activation Loop Tyrosines of Protein Tyrosine Kinase Syk Abrogate Intracellular Signaling But Not Kinase Activity. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.161.8.4366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
The protein tyrosine kinase Syk plays a pivotal role in mediating the high-affinity IgE receptor (FcεRI)-induced degranulation of mast cells. To examine the mechanism of Syk regulation, the two tyrosine residues at 519 and 520 in the putative activation loop of rat Syk were mutated to phenylalanine either singly or in combination. The various mutants were expressed in a Syk-negative variant of the RBL-2H3 (rat basophilic leukemia 2H3) mast cell line. In these transfected cell lines, mutant Syk did show increased tyrosine phosphorylation in vivo and increased enzymatic activity in vitro after FcεRI aggregation. There were conformational changes detected by an Ab when the wild-type and mutant Syk were either tyrosine phosphorylated or bound to tyrosine-phosphorylated immunoreceptor tyrosine-based activation motif peptides. However, these mutant Syk were incapable of transducing FcεRI signaling. In cells in which the expression level of mutant Syk was similar to that of the wild-type Syk, FcεRI cross-linking induced no increase in cellular protein tyrosine phosphorylation, no increase in tyrosine phosphorylation of phospholipase C-γ2 and mitogen-activated protein kinase, and no histamine release. Overexpression of Y519F or Y520F Syk mutants partially reconstituted the signaling pathways. These results indicate that these tyrosines in the putative activation loop are not essential for the enzymatic activity of Syk or for the conformational changes induced by binding of tyrosine-phosphorylated immunoreceptor tyrosine-based activation motif peptides. However, these tyrosines are necessary for Syk-mediated propagation of FcεRI signaling.
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Affiliation(s)
- Juan Zhang
- Receptors and Signal Transduction Section, Oral Infection and Immunity Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892
| | - Teruaki Kimura
- Receptors and Signal Transduction Section, Oral Infection and Immunity Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892
| | - Reuben P. Siraganian
- Receptors and Signal Transduction Section, Oral Infection and Immunity Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892
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28
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Saxena M, Williams S, Gilman J, Mustelin T. Negative regulation of T cell antigen receptor signal transduction by hematopoietic tyrosine phosphatase (HePTP). J Biol Chem 1998; 273:15340-4. [PMID: 9624114 DOI: 10.1074/jbc.273.25.15340] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The hematopoietic tyrosine phosphatase (HePTP) is predominantly expressed in thymocytes and T lymphocytes and at lower levels in other hematopoietic cells. Expression of the gene is enhanced by the T cell growth factor interleukin-2, suggesting a role for HePTP in T cell proliferation or differentiation. We report that HePTP blocks T cell antigen receptor (TCR)-induced transcriptional activation of a reporter gene driven by a nuclear factor of activated T cells(NFAT)/AP-1 element taken from the interleukin-2 gene promoter. This effect was specific to HePTP and was abolished by a mutation (C270S) that impaired its phosphatase activity. Co-expression of HePTP also reduced TCR-induced activation of the mitogen-activated protein kinase Erk2 and the TCR-induced appearance of phosphorylated Erk. In contrast, HePTP did not affect the activation of the N-terminal c-Jun kinase, Jnk. Together these findings suggest that HePTP plays an active negative role in TCR signaling by dephosphorylating one or several signaling molecules between the receptor and the mitogen-activated protein kinase pathway.
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Affiliation(s)
- M Saxena
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA
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29
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von Willebrand M, Williams S, Tailor P, Mustelin T. Phosphorylation of the Grb2- and phosphatidylinositol 3-kinase p85-binding p36/38 by Syk in Lck-negative T cells. Cell Signal 1998; 10:407-13. [PMID: 9720763 DOI: 10.1016/s0898-6568(97)00139-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Activation of the mitogen-activated protein kinase (MAPK) pathway by the T-cell antigen receptor (TCR) in T cells involves a positive role for phosphatidylinositol 3-kinase (PI3K) activity. We recently reported that over-expression of the Syk protein tyrosine kinase in the Lck-negative JCaM1 cells enabled the TCR to induce a normal activation of the Erk2 MAPK and enhanced transcription of a reporter gene driven by the nuclear factor of activated T cells and AP-1. Because this system allows us to analyse the targets for Syk in receptor-mediated signalling, we examined the role of PI3K in signalling events between the TCR-regulated Syk and the downstream activation of Erk2. We report that inhibition of PI3K by wortmannin or an inhibitory p85 construct, p85deltaiSH2, reduced the TCR-induced Syk-dependent activation of Erk2, as well as the appearance of phospho-Erk and phospho-Mek. At the same time, expression of Syk resulted in the activation-dependent phosphorylation of three proteins that bound to the src homology 2 (SH2) domains of PI3K p85. The strongest of these bands had an apparent molecular mass of 36-38 kDa on SDS gels, and it was quantitatively removed from the lysates by adsorption to a fusion protein containing the SH2 domain of Grb2. The appearance of this band was Syk dependent, and it was seen only upon triggering of the TCR complex. Thus, p36/38 was phosphorylated by Syk or a Syk-regulated kinase, and this protein may provide a link to the recruitment and activation of PI3K, as well as to the Ras-MAPK pathway, in TCR-triggered T cells.
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Affiliation(s)
- M von Willebrand
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121, USA
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30
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Kennedy AP, Sekulić A, Irvin BJ, Nilson AE, Dilworth SM, Abraham RT. Polyomavirus middle T antigen as a probe for T cell antigen receptor-coupled signaling pathways. J Biol Chem 1998; 273:11505-13. [PMID: 9565564 DOI: 10.1074/jbc.273.19.11505] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Stimulation of the T cell antigen receptor (TCR) triggers a complex series of signaling events that culminate in T cell activation and proliferation. The complex structure of the TCR has hindered efforts to link specific signaling events induced by TCR cross-linkage to downstream activation responses, such as interleukin-2 (IL-2) gene transcription. Previous studies have shown that the polyomavirus-derived oncoprotein, middle T antigen (mT), transforms rodent fibroblasts by interacting with and activating several cytoplasmic signaling proteins (Src kinases, phospholipase C (PLC)-gamma1, Shc, and phosphoinositide 3-kinase (PI3-K) implicated in cell growth control. In this study, we demonstrate that expression of mT activates Jurkat T cells, as measured by increases in IL-2 promoter- and NFAT (nuclear factor of activated T cells)-dependent reporter gene transcription. The transcriptional response provoked by mT was blocked by the immunosuppressive drug FK506, a potent inhibitor of TCR-mediated IL-2 gene expression. Mutations that disrupted the binding of mT to Src kinases or PLC-gamma1 abrogated the ability of mT to deliver the signals needed for IL-2 promoter activation. In contrast, a mT mutant that failed to bind PI3-K induced a markedly elevated transcriptional response in Jurkat cells, whereas mutation of the Shc binding site in mT had little effect on the transactivating potential of this viral oncoprotein. Additional studies demonstrated that the association of mT with PLC-gamma1 was necessary and sufficient to activate both Ca2+- and Ras-dependent signaling cascades in Jurkat cells. These results indicate that PLC-gamma1 activation plays pivotal and pleiotropic roles in the stimulation of IL-2 gene expression, whereas activation of PI3-K negatively modulates this response in Jurkat T cells.
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Affiliation(s)
- A P Kennedy
- Division of Oncology Research and Department of Immunology, Mayo Clinic, Rochester, Minnesota 55905, USA
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31
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Wong J, Straus D, Chan AC. Genetic evidence of a role for Lck in T-cell receptor function independent or downstream of ZAP-70/Syk protein tyrosine kinases. Mol Cell Biol 1998; 18:2855-66. [PMID: 9566904 PMCID: PMC110664 DOI: 10.1128/mcb.18.5.2855] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/1997] [Accepted: 02/13/1998] [Indexed: 02/07/2023] Open
Abstract
T-cell antigen receptor (TCR) engagement results in sequential activation of the Src protein tyrosine kinases (PTKs) Lck and Fyn and the Syk PTKs, ZAP-70 and Syk. While the Src PTKs mediate the phosphorylation of TCR-associated signaling subunits and the phosphorylation and activation of the Syk PTKs, the lack of a constitutively active Syk PTK has prohibited the analysis of Lck function downstream of these initiating signaling events. We describe here the generation of an activated Syk family PTK by substituting the kinase domain of Syk for the homologous region in ZAP-70 (designated as KS for kinase swap). Expression of the KS chimera resulted in its autophosphorylation, the phosphorylation of cellular proteins, the upregulation of T-cell activation markers, and the induction of interleukin-2 gene synthesis in a TCR-independent fashion. The KS chimera and downstream ZAP-70 or Syk substrates, such as SLP-76, were still phosphorylated when expressed in Lck-deficient JCaM1.6 T cells. However, expression of the KS chimera in JCaM1.6 cells failed to rescue downstream signaling events, demonstrating a functional role for Lck beyond the activation of the ZAP-70 and Syk PTKs. These results indicate that downstream TCR signaling pathways may be differentially regulated by ZAP-70 and Lck PTKs and provide a mechanism by which effector functions may be selectively activated in response to TCR stimulation.
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Affiliation(s)
- J Wong
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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32
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Borowski P, Heiland M, Kornetzky L, Medem S, Laufs R. Purification of catalytic domain of rat spleen p72syk kinase and its phosphorylation and activation by protein kinase C. Biochem J 1998; 331 ( Pt 2):649-57. [PMID: 9531509 PMCID: PMC1219400 DOI: 10.1042/bj3310649] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The catalytic domain of p72(syk) kinase (CDp72(syk)) was purified from a 30000 g particulate fraction of rat spleen. The purification procedure employed sequential chromatography on columns of DEAE-Sephacel and Superdex-200, and elution from HA-Ultrogel by chloride. The analysis of the final CDp72(syk) preparation by SDS/PAGE revealed a major silver-stained 40 kDa protein. The kinase was identified by covalent modification of its ATP-binding site with [14C]5'-fluorosulphonylbenzoyladenosine and by immunoblotting with a polyclonal antibody against the 'linker' region of p72(syk). By using poly(Glu4, Tyr1) as a substrate, the specific activity of the enzyme was determined as 18.5 nmol Pi/min per mg. Casein, histones H1 and H2B and myelin basic protein were efficiently phosphorylated by CDp72(syk). The kinase exhibited a limited ability to phosphorylate random polymers containing tyrosine residues. CDp72(syk) autophosphorylation activity was associated with an activation of the kinase towards exogenous substrates. The extent of activation was dependent on the substrates added. CDp72(syk) was phosphorylated by protein kinase C (PKC) on serine and threonine residues. With a newly developed assay method, we demonstrated that the PKC-mediated phosphorylation had a strong activating effect on the tyrosine kinase activity of CDp72(syk). Studies extended to conventional PKC isoforms revealed an isoform-dependent manner (alpha > betaI = betaII > gamma) of CDp72(syk) phosphorylation. The different phosphorylation efficiencies of the PKC isoforms closely correlated with the ability to enhance the tyrosine kinase activity.
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Affiliation(s)
- P Borowski
- Institut für Medizinishe Mikrobiologie und Immunologie, Universitätskrankenhaus Eppendorf, Martinistrasse 52, 20246 Hamburg, Federal Republic of Germany
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33
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Eshhar Z, Fitzer-Attas CJ. Tyrosine kinase chimeras for antigen-selective T-body therapy. Adv Drug Deliv Rev 1998; 31:171-182. [PMID: 10837624 DOI: 10.1016/s0169-409x(97)00100-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Protein tyrosine kinases (PTKs) transmit activation signals in almost every cell type, including immune effector cells. The aberrant or constitutive activation of PTKs can often cause neoplastic transformation. The use of chimeric receptors based on PTKs may enable us to elucidate the signaling pathways of normal immune cells and other cell types, and the abnormal events that can lead to malignant transformation. In this review, we focus on antigen specific chimeric PTKs in which antibody-derived scFv are joined to the Syk family of PTKs. These chimeric receptors yielded reagents that can selectively redirect immune effector cells and specifically activate them to produce cytokines or lyse their target. The advantages of using such PTK-based chimeras to redirect lymphocytes to tumor targets and their potential as an immunotherapeutic approach to malignant disease is discussed.
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Affiliation(s)
- Z Eshhar
- Department of Immunology, The Weizmann Institute of Science, Rehovot 76100, Israel
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34
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Williams BL, Schreiber KL, Zhang W, Wange RL, Samelson LE, Leibson PJ, Abraham RT. Genetic evidence for differential coupling of Syk family kinases to the T-cell receptor: reconstitution studies in a ZAP-70-deficient Jurkat T-cell line. Mol Cell Biol 1998; 18:1388-99. [PMID: 9488454 PMCID: PMC108852 DOI: 10.1128/mcb.18.3.1388] [Citation(s) in RCA: 225] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/1997] [Accepted: 12/08/1997] [Indexed: 02/06/2023] Open
Abstract
T-cell antigen receptor (TCR) engagement activates multiple protein tyrosine kinases (PTKs), including the Src family member, Lck, and the Syk-related PTK, ZAP-70. Studies in ZAP-70-deficient humans have demonstrated that ZAP-70 plays crucial roles in T-cell activation and development. However, progress toward a detailed understanding of the regulation and function of ZAP-70 during TCR signaling has been hampered by the lack of a suitable T-cell model for biochemical and genetic analyses. In this report, we describe the isolation and phenotypic characterization of a Syk- and ZAP-70-negative somatic mutant derived from the Jurkat T-cell line. The P116 cell line displays severe defects in TCR-induced signaling functions, including protein tyrosine phosphorylation, intracellular Ca2+ mobilization, and interleukin-2 promoter-driven transcription. These signaling defects were fully reversed by reintroduction of catalytically active versions of either Syk or ZAP-70 into the P116 cells. However, in contrast to ZAP-70 expression, Syk expression triggered a significant degree of cellular activation in the absence of TCR ligation. Transfection experiments with ZAP-70-Syk chimeric proteins indicated that both the amino-terminal regulatory regions and the carboxy-terminal catalytic domains of Syk and ZAP-70 contribute to the distinctive functional properties of these PTKs. These studies underscore the crucial role of ZAP-70 in TCR signaling and offer a powerful genetic model for further analyses of ZAP-70 regulation and function in T cells.
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Affiliation(s)
- B L Williams
- Department of Immunology, Mayo Clinic, Rochester, Minnesota 55905, USA
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35
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von Willebrand M, Williams S, Saxena M, Gilman J, Tailor P, Jascur T, Amarante-Mendes GP, Green DR, Mustelin T. Modification of phosphatidylinositol 3-kinase SH2 domain binding properties by Abl- or Lck-mediated tyrosine phosphorylation at Tyr-688. J Biol Chem 1998; 273:3994-4000. [PMID: 9461588 DOI: 10.1074/jbc.273.7.3994] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In cells expressing the oncogenic Bcr-Abl tyrosine kinase, the regulatory p85 subunit of phosphatidylinositol 3-kinase is phosphorylated on tyrosine residues. We report that this phosphorylation event is readily catalyzed by the Abl and Lck protein-tyrosine kinases in vitro, by Bcr-Abl or a catalytically activated Lck-Y505F in co-transfected COS cells, and by endogenous kinases in transfected Jurkat T cells upon triggering of their T cell antigen receptor. Using these systems, we have mapped a major phosphorylation site to Tyr-688 in the C-terminal SH2 domain of p85. Tyrosine phosphorylation of p85 in vitro or in vivo was not associated with detectable change in the enzymatic activity of the phosphatidylinositol 3-kinase heterodimer, but correlated with a strong reduction in the binding of some, but not all, phosphoproteins to the SH2 domains of p85. This provides an additional candidate to the list of SH2 domains regulated by tyrosine phosphorylation and may explain why association of phosphatidylinositol 3-kinase with some cellular ligands is transient or of lower stoichiometry than anticipated.
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Affiliation(s)
- M von Willebrand
- Divisions of Cell Biology and Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA
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36
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Ståhls A, Hong SC, Liwszyc GE, Janeway C, Andersson LC, Wolff H. Signalling initiated with CD4-TCR or TCR-TCR interactions: comparison of tyrosine phosphorylation patterns and CD45 effects. Immunol Lett 1998; 60:103-9. [PMID: 9557951 DOI: 10.1016/s0165-2478(97)00136-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Antigen-triggered response in T cells is mediated by the T cell receptor (TCR)/CD3-complex. This signalling, however, is modulated by a number of other surface molecules. Among the most important of these is the CD4/CD8 molecule which associates with the TCR/CD3-complex and binds to the MHC complex. The molecular mechanisms involved in interactions between TCR-TCR and TCR-CD4 are not fully understood. We have earlier described an experimental model that allows us to dissect signals involving CD4-TCR interactions and those involving TCR-TCR interactions using a mouse CD4-CD8- T cell hybridoma cell-line transfected either with the TCR from a mouse T-helper 2 cell-line (D10) alone or with both the TCR and the CD4 molecule. To further characterize these two different modes of signalling in T lymphocytes we have studied the tyrosine phosphorylation patterns resulting from these interactions. In addition, we have studied the modulatory effect of the CD45 molecule on these interactions. In contrast to some earlier reports, we found that both the patterns of induced tyrosine phosphorylation and the effects of CD45 modulation were essentially similar in the CD4-TCR and the TCR-TCR signal transduction cascades. The results are consistent with a purely synergistically amplifying function for CD4 on the TCR-mediated signalling.
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Affiliation(s)
- A Ståhls
- Department of Pathology, University of Helsinki, Finland
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37
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Kühn U, Brand P, Willemsen J, Jonuleit H, Enk AH, van Brandwijk-Petershans R, Saloga J, Knop J, Becker D. Induction of Tyrosine Phosphorylation in Human MHC Class II-Positive Antigen-Presenting Cells by Stimulation with Contact Sensitizers. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.160.2.667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
To investigate the intracellular signaling mechanisms involved in the activation of APC by contact sensitizers, we studied the induction of tyrosine phosphorylation by these agents. Selective analysis of phosphotyrosine (p-tyr) in human Langerhans cells and different mononuclear cell types was achieved using a multicolor flow-cytometric technique. Stimulation with contact sensitizers revealed a distinct increase in p-tyr exclusively for MHC class II-positive cells. For different haptens, irritants, as well as activators of distinct signal transduction pathways, it was demonstrated that only strong sensitizers or the protein tyrosine phosphatase inhibitor sodium orthovanadate or cross-linking of MHC class II molecules were able to induce formation of p-tyr in human blood-derived dendritic cells serving as model for the dendritic cell family. This event required physiologic cell culture conditions and was blocked by specific inhibitors of protein tyrosine kinases. No evidence for the inhibition of protein tyrosine phosphatases by haptens was found. Western blot analysis of monocyte-enriched populations revealed an augmented phosphorylation of distinct proteins after hapten stimulation partly resembling the pattern noticed after cross-linking of HLA-DR molecules. In dendritic cells generated from mononuclear progenitors, the protein tyrosine kinase inhibitor genistein was able to block tyrosine phosphorylation as well as production of IL-1β mRNA transcripts. Our data underline the unique capacity of haptens to activate APC and the important role of tyrosine phosphorylation for this process.
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Affiliation(s)
- Ulrich Kühn
- Department of Dermatology, University of Mainz, Mainz, Germany
| | - Pia Brand
- Department of Dermatology, University of Mainz, Mainz, Germany
| | | | - Helmut Jonuleit
- Department of Dermatology, University of Mainz, Mainz, Germany
| | | | | | - Joachim Saloga
- Department of Dermatology, University of Mainz, Mainz, Germany
| | - Jürgen Knop
- Department of Dermatology, University of Mainz, Mainz, Germany
| | - Detlef Becker
- Department of Dermatology, University of Mainz, Mainz, Germany
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38
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Fitzer-Attas CJ, Schindler DG, Waks T, Eshhar Z. Harnessing Syk Family Tyrosine Kinases as Signaling Domains for Chimeric Single Chain of the Variable Domain Receptors: Optimal Design for T Cell Activation. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.160.1.145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Abstract
T cells of tumor bearers often show defective TCR-mediated signaling events and, therefore, exhibit impaired immune responses. As such, patients with heavy tumor burden are often not amenable to adoptive T cell therapy. To overcome this limitation, we have developed a chimeric receptor that joins an extracellular single chain Fv (scFv) of a specific Ab for Ag recognition to an intracellular protein tyrosine kinase (PTK) for signal propagation. Stimulation through the scFv-PTK receptor should bypass defective TCR-proximal events and directly access the T cell’s effector mechanisms. In this study we describe the optimization of a scFv-PTK configuration, leading to complete T cell activation. The cytosolic PTK Syk is superior to its family member, Zap-70, for intracellular signaling. As a transmembrane (TM) domain, CD4 performs better than CD8 when plastic-immobilized Ag serves as a stimulator. However, when APC are used to trigger chimeric receptors, the need for a flexible spacer between the scFv and TM domains becomes apparent. The CD8α-derived hinge successfully performs this task in chimeric scFv-Syk receptors regardless of its cysteine content. A cytotoxic T cell hybridoma expressing chimeric receptor genes composed of scFv-CD8hinge-CD8TM-Syk or scFv-CD8hinge-CD4TM-Syk is efficiently stimulated to produce IL-2 upon interaction with APC and specifically lyses appropriate target cells in a non-MHC-restricted manner.
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Affiliation(s)
| | - Daniel G. Schindler
- Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel
| | - Tova Waks
- Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel
| | - Zelig Eshhar
- Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel
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39
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Brumbaugh KM, Binstadt BA, Billadeau DD, Schoon RA, Dick CJ, Ten RM, Leibson PJ. Functional role for Syk tyrosine kinase in natural killer cell-mediated natural cytotoxicity. J Exp Med 1997; 186:1965-74. [PMID: 9396765 PMCID: PMC2199178 DOI: 10.1084/jem.186.12.1965] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/1997] [Revised: 10/09/1997] [Indexed: 02/05/2023] Open
Abstract
Natural killer (NK) cells are named based on their natural cytotoxic activity against a variety of target cells. However, the mechanisms by which sensitive targets activate killing have been difficult to study due to the lack of a prototypic NK cell triggering receptor. Pharmacologic evidence has implicated protein tyrosine kinases (PTKs) in natural killing; however, Lck-deficient, Fyn-deficient, and ZAP-70-deficient mice do not exhibit defects in natural killing despite demonstrable defects in T cell function. This discrepancy implies the involvement of other tyrosine kinases. Here, using combined biochemical, pharmacologic, and genetic approaches, we demonstrate a central role for the PTK Syk in natural cytotoxicity. Biochemical analyses indicate that Syk is tyrosine phosphorylated after stimulation with a panel of NK-sensitive target cells. Pharmacologic exposure to piceatannol, a known Syk family kinase inhibitor, inhibits natural cytotoxicity. In addition, gene transfer of dominant-negative forms of Syk to NK cells inhibits natural cytotoxicity. Furthermore, sensitive targets that are rendered NK-resistant by major histocompatibility complex (MHC) class I transfection no longer activate Syk. These data suggest that Syk activation is an early and requisite signaling event in the development of natural cytotoxicity directed against a variety of cellular targets.
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Affiliation(s)
- K M Brumbaugh
- Department of Immunology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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40
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Gong Q, White L, Johnson R, White M, Negishi I, Thomas M, Chan AC. Restoration of thymocyte development and function in zap-70-/- mice by the Syk protein tyrosine kinase. Immunity 1997; 7:369-77. [PMID: 9324357 DOI: 10.1016/s1074-7613(00)80358-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The Syk family of protein tyrosine kinases, consisting of ZAP-70 and Syk, associate with the pre- and alphabeta T cell antigen receptors (TCRs) and undergo tyrosine phosphorylation and activation following receptor engagement. Thymocyte development in zap-70-/- mice is blocked at the CD4+CD8+ TCR(lo) stage. The presence of Syk in the thymus has raised the possibility that Syk may be able to mediate TCR function. To determine if Syk can play a role in thymocyte development, we generated zap-70-/- mice expressing a human syk cDNA. Syk expression restored both thymocyte development and function. In addition, Syk function required the CD45 transmembrane protein tyrosine phosphatase. Hence, ZAP-70 and Syk can play overlapping functions and exhibit similar regulatory mechanisms in mediating alphabeta T cell development.
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Affiliation(s)
- Q Gong
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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41
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Farber DL, Acuto O, Bottomly K. Differential T cell receptor-mediated signaling in naive and memory CD4 T cells. Eur J Immunol 1997; 27:2094-101. [PMID: 9295050 DOI: 10.1002/eji.1830270838] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Naive and memory CD4 T cells differ in cell surface phenotype, function, activation requirements, and modes of regulation. To investigate the molecular bases for the dichotomies between naive and memory CD4 T cells and to understand how the T cell receptor (TCR) directs diverse functional outcomes, we investigated proximal signaling events triggered through the TCR/CD3 complex in naive and memory CD4 T cell subsets isolated on the basis of CD45 isoform expression. Naive CD4 T cells signal through TCR/CD3 similar to unseparated CD4 T cells, producing multiple tyrosine-phosphorylated protein species overall and phosphorylating the T cell-specific ZAP-70 tyrosine kinase which is recruited to the CD3zeta subunit of the TCR. Memory CD4 T cells, however, exhibit a unique pattern of signaling through TCR/CD3. Following stimulation through TCR/CD3, memory CD4 T cells produce fewer species of tyrosine-phosphorylated substrates and fail to phosphorylate ZAP-70, yet unphosphorylated ZAP-70 can associate with the TCR/CD3 complex. Moreover, a 26/28-kDa phosphorylated doublet is associated with CD3zeta in resting and activated memory but not in naive CD4 T cells. Despite these differences in the phosphorylation of ZAP-70 and CD3-associated proteins, the ZAP-70-related kinase, p72syk, exhibits similar phosphorylation in naive and memory T cell subsets, suggesting that this kinase could function in place of ZAP-70 in memory CD4 T cells. These results indicate that proximal signals are differentially coupled to the TCR in naive versus memory CD4 T cells, potentially leading to distinct downstream signaling events and ultimately to the diverse functions elicited by these two CD4 T cell subsets.
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Affiliation(s)
- D L Farber
- Section of Immunobiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, USA.
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42
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Vilen BJ, Famiglietti SJ, Carbone AM, Kay BK, Cambier JC. B cell antigen receptor desensitization: disruption of receptor coupling to tyrosine kinase activation. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 1997; 159:231-43. [PMID: 9200459 PMCID: PMC3931421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Antigen binding to the B cell receptor (BCR) induces receptor desensitization, a condition characterized by cellular unresponsiveness to subsequent Ag stimulation despite the continued ability to bind Ag. To better understand the molecular mechanism of this unresponsiveness, we have used complementary lymphoma (K46 mu) and Ig transgenic (3-83 mu delta) mouse models to study regulation of BCR signaling. Our findings in the lymphoma model show that an initial Ag encounter renders receptors unresponsive to subsequent Ag challenge, as measured by their inability to mobilize Ca2+ and to mediate phosphorylation of receptor-proximal kinases, including Lyn, Blk, and Syk. Most importantly, the Ig alpha and Ig beta components of desensitized receptors are not phosphorylated, and receptor-associated kinases are not activated upon Ag challenge. The molecular defect does not appear to result from Lyn inactivation, sequestration, or repression, since Lyn from desensitized cell lysates is activated in vitro by synthetic doubly phosphorylated immunoreceptor tyrosine-based activation motif peptides. A similar deficit in Ag-induced receptor phosphorylation was observed in desensitized B cells from 3-83 mu delta transgenic mice. These studies indicate that Ag receptor desensitization reflects an inability to initiate activation of receptor-associated kinases that normally phosphorylate receptor Ig alphabeta subunits, leading to signal propagation.
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Affiliation(s)
- B J Vilen
- Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206, USA
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43
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Uddin S, Sher DA, Alsayed Y, Pons S, Colamonici OR, Fish EN, White MF, Platanias LC. Interaction of p59fyn with interferon-activated Jak kinases. Biochem Biophys Res Commun 1997; 235:83-8. [PMID: 9196040 DOI: 10.1006/bbrc.1997.6741] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
During IFN alpha stimulation, p59(fyn) associates with the Type I IFNR-associated Tyk-2 kinase in several human hematopoietic cell lines in vivo. This interaction is direct, and is mediated by the SH2 domain in p59(fyn), as shown by binding studies using glutathione-S-transferase fusion proteins and far western blots. Furthermore, in response to IFN alpha-treatment of cells, the SH2 domain of Fyn interacts with the Tyk-2-associated c-cbl proto-oncogene product. In a similar manner, during IFN gamma stimulation, p59(fyn) associates via its SH2 domain with the activated form of the IFN gamma-dependent Jak-2 kinase. These data suggest that p59(fyn) is a common element in IFN alpha and IFN gamma signaling, and is selectively engaged by the Type I or II IFN receptors via specific interactions with distinct Jak kinases.
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Affiliation(s)
- S Uddin
- Department of Medicine, University of Illinois at Chicago and West Side Veterans Affairs Hospital, 60607, USA
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44
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Yamasaki S, Tachibana M, Shinohara N, Iwashima M. Lck-independent triggering of T-cell antigen receptor signal transduction by staphylococcal enterotoxins. J Biol Chem 1997; 272:14787-91. [PMID: 9169445 DOI: 10.1074/jbc.272.23.14787] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Superantigens (SAgs) activate T-cells in a manner specific to the Vbeta region of the T-cell antigen receptor. Stimulations by SAgs provoke drastic T-cell activation that leads to programmed cell death or the anergic state of responding cells. To characterize the signal transduction pathway initiated by SAgs, mutant lines derived from the human leukemic T-cell line Jurkat were tested for their reactivities against prototypic SAgs, staphylococcal enterotoxins. The J.CaM1.6 cell line, which lacks Lck expression and lost reactivity against T-cell antigen receptor-mediated stimulation, was activated by staphylococcal enterotoxins in a manner indistinguishable from the Jurkat cell line. In contrast, the J.45. 01 cell line, which lacks expression of functional CD45, showed severely impaired reactivity. The role of Lck appears to be replaced by another Src family protein-tyrosine kinase, Fyn. In J.CaM1.6 cells, Fyn was rapidly phosphorylated and activated after staphylococcal enterotoxin treatment. The kinase-inactive mutant of Fyn significantly suppressed the reactivity against staphylococcal enterotoxin E in J.CaM1.6 cells, and the expression of the active form of Fyn reconstituted reactivity against staphylococcal enterotoxin E in J.45.01 cells. These results demonstrate that SAgs activate T-cells in an Lck-independent pathway and that Fyn plays a critical role in the process.
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MESH Headings
- Antigens, CD/biosynthesis
- Antigens, Differentiation, T-Lymphocyte/biosynthesis
- Calcium/pharmacology
- Clone Cells
- Enterotoxins/pharmacology
- Genes, Reporter
- Humans
- Jurkat Cells
- Lectins, C-Type
- Luciferases/biosynthesis
- Lymphocyte Activation/drug effects
- Lymphocyte Specific Protein Tyrosine Kinase p56(lck)
- Mutagenesis
- Proto-Oncogene Proteins/metabolism
- Proto-Oncogene Proteins c-fyn
- Receptors, Antigen, T-Cell, alpha-beta/drug effects
- Receptors, Antigen, T-Cell, alpha-beta/physiology
- Signal Transduction/drug effects
- Staphylococcus
- Staphylococcus aureus
- Superantigens/pharmacology
- T-Lymphocytes/immunology
- Transfection
- src-Family Kinases/genetics
- src-Family Kinases/metabolism
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Affiliation(s)
- S Yamasaki
- Division of Cell and Information, Precursor Research for Embryonic Science and Technology, Japan Science and Technology Corporation, Tokyo 194, Japan
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45
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Couture C, Williams S, Gauthier N, Tailor P, Mustelin T. Role of Tyr518 and Tyr519 in the regulation of catalytic activity and substrate phosphorylation by Syk protein-tyrosine kinase. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 246:447-51. [PMID: 9208937 DOI: 10.1111/j.1432-1033.1997.00447.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The Syk protein-tyrosine kinase is expressed in many hematopoietic cells and is involved in signaling from various receptors for antigen and Fc portions of IgG and IgE. After cross-linking of these receptors, Syk is rapidly phosphorylated on tyrosine residues. We have previously reported that Syk expressed in COS cells is predominantly phosphorylated at both Tyr518 and Tyr519 at its putative autophosphorylation site. In this study, we have examined the role of each of these two residues for the catalytic activity of Syk in vitro and for the Syk-induced phosphorylation of cellular proteins in intact cells. Mutation of either residue had minor effects on the catalytic activity of Syk, and even the double mutant [F518, F519]Syk was about 60% as active as the wild-type enzyme. In intact cells, however, all three mutants consistently failed to induce the extensive tyrosine phosphorylation of cellular proteins typically observed with wild-type Syk. We have recently shown that the doubly phosphorylated Y518/Y519 site is also the site for association of Syk with the SH2 domain of the Lck kinase, which suggests that although phosphates at Y518/Y519 may enhance the catalytic activity of Syk, its interaction with Src family protein-tyrosine kinases is at least equally important for the induction of downstream substrate phosphorylation.
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Affiliation(s)
- C Couture
- Department of Medicine, McGill University, Montreal, Canada
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46
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Ruzzene M, Brunati AM, Donella-Deana A, Marin O, Pinna LA. Specific stimulation of c-Fgr kinase by tyrosine-phosphorylated (poly)peptides--possible implication in the sequential mode of protein phosphorylation. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 245:701-7. [PMID: 9183008 DOI: 10.1111/j.1432-1033.1997.t01-1-00701.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Hematopoietic lineage cell-specific HS1 protein is converted into a substrate for c-Fgr by previous Syk-mediated phosphorylation, at site(s) that bind to the SH2 domain of c-Fgr [Ruzzene, M., Brunati, A. M., Marin, O., Donella-Deana, A. & Pinna, L. A. (1996) Biochemistry 35, 5327-5332]. Here we show that a phosphopeptide derived from one such site, HS1-(320-329)-phosphopeptide (PEGDYpEEVLE), enhances up to tenfold, in a dose-dependent manner, the catalytic activity of c-Fgr either assayed with peptide substrates or evaluated as intermolecular autophosphorylation of c-Fgr itself. The dephosphorylated HS1-(320-329)-peptide is totally ineffective, while the stimulatory efficacy of other phosphopeptides derived from the polyoma virus middle T antigen-(393-402) sequence, c-Src, and c-Fgr autophosphorylation sites, and the C-terminal c-Src site (Tyr527) is variable and correlates reasonably well with the predicted affinity for the c-Fgr SH2 domain. Stimulation of c-Fgr catalytic activity is also promoted by the full-length HS1 protein, previously tyrosine phosphorylated by Syk, and is accounted for by an increased Vmax while the Km values are unchanged. If the normal activator of c-Fgr kinase, Mg2+, is replaced by Mn2+, stimulation by HS1-(320-329)-phosphopeptide is still observable with peptide substrates, while autophosphorylation is, in contrast, inhibited by the phosphopeptide. These findings, in conjunction with the ability of previously autophosphorylated c-Fgr to be stimulated by HS1-(320-329)-phosphopeptide, support the view that stimulation of c-Fgr by phosphopeptide is not or is not entirely a consequence of increased autophosphorylation. Interestingly, neither Syk and C-terminal Src kinase nor three other members of the Src family (Lyn, Lck, and Fyn) are susceptible to stimulation by phosphopeptide, as observed with c-Fgr. These data support the notion that c-Fgr undergoes a unique mechanism of activation promoted by tyrosine-phosphorylated polypeptide that binds to its SH2 domain. This suggests that such a mode of regulation is peculiar of protein-tyrosine kinases committed to the secondary phosphorylation of sequentially phosphorylated proteins.
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Affiliation(s)
- M Ruzzene
- Dipartimento di Chimica Biologica and Centro per lo Studio delle Biomembrane del Consiglio Nazionale delle Ricerche, Padova, Italy
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Williams S, Couture C, Gilman J, Jascur T, Deckert M, Altman A, Mustelin T. Reconstitution of T cell antigen receptor-induced Erk2 kinase activation in Lck-negative JCaM1 cells by Syk. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 245:84-90. [PMID: 9128727 DOI: 10.1111/j.1432-1033.1997.00084.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The two related protein-tyrosine kinases Syk and Zap are rapidly phosphorylated on tyrosine residues and enzymatically activated upon crosslinking of the T cell antigen receptor. We have previously reported that the activation of Syk is less dependent on the Src family kinase Lck than the activation of Zap. Here we report that overexpression of Syk in the Lck-negative JCaM1 cells enabled the T cell antigen receptor/CD3 complex to induce a normal activation of the mitogen-activated protein kinase (MAPK) pathway and expression of a nuclear factor of activated T cells reporter construct. In contrast, Zap and other protein-tyrosine kinases were unable to reconstitute these signaling pathways when expressed at the same levels. In parallel, Syk was phosphorylated on tyrosine, while Zap was not. The Syk-mediated T cell antigen receptor-induced MAPK activation was detectable within 1 min of receptor stimulation and peaked at 3-5 min. The capacity of Syk to reconstitute the MAPK response required the catalytic activity of Syk, an intact autophosphorylation site (Y518 and Y519), both Src homology 2 domains and it was blocked by the inhibitory N17-mutated dominant-negative Ras construct. A Y341-->F mutant of Syk, which is deficient in its interaction with phospholipase Cy1 and Vav, was less efficient than wild-type Syk. Our results suggest that Syk, in contrast to Zap, can transduce signals from the T cell antigen receptor independently of Lck.
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Affiliation(s)
- S Williams
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego CA, USA
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48
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Fitzer-Attas CJ, Schindler DG, Waks T, Eshhar Z. Direct T cell activation by chimeric single chain Fv-Syk promotes Syk-Cbl association and Cbl phosphorylation. J Biol Chem 1997; 272:8551-7. [PMID: 9079685 DOI: 10.1074/jbc.272.13.8551] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The protein tyrosine kinase Syk is activated upon engagement of immune recognition receptors. We have focused on the identification of signaling elements immediately downstream to Syk in the pathway leading to T cell activation. To circumvent T cell receptor (TCR). CD3 activation of Src family kinases, we constructed a signaling molecule with an extracellular single chain Fv of an anti-TNP antibody, attached via a transmembrane region to Syk (scFv-Syk). In a murine T cell hybridoma, direct aggregation of chimeric Syk with antigen culminates in interleukin-2 production and target cell lysis. Initially, it causes an increase in the association between scFv-Syk and the cytosolic protein Cbl and subsequently promotes tyrosine phosphorylation of Cbl. Interestingly, although both Cbl and phospholipase C-gamma (PLC-gamma) are phosphorylated in this hybridoma upon TCR.CD3 cross-linking, these two events are uncoupled in scFv-Syk-transfected cells, in which we were unable to detect antigen-driven PLC-gamma phosphorylation. These results support a model in which Syk can initiate and directly activate the T cell's signaling machinery and position Cbl as a primary tyrosine kinase substrate in this pathway. Furthermore, for efficient PLC-gamma phosphorylation to occur in these cells, the combined actions of different tyrosine kinase families may be required.
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Affiliation(s)
- C J Fitzer-Attas
- Department of Immunology, The Weizmann Institute of Science, Rehovot 76100, Israel
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Junger WG, Hoyt DB, Hamreus M, Liu FC, Herdon-Remelius C, Junger W, Altman A. Hypertonic saline activates protein tyrosine kinases and mitogen-activated protein kinase p38 in T-cells. THE JOURNAL OF TRAUMA 1997; 42:437-43; discussion 443-5. [PMID: 9095111 DOI: 10.1097/00005373-199703000-00011] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVES In previous in vitro studies, we have found that hypertonic saline (HTS) can augment T-cell proliferation and restore the function of suppressed T-cells. Our animal models have shown that HTS resuscitation reverses immunosuppression after hemorrhage and reduces mortality from sepsis. In the present study, we investigated if and how HTS may influence T-cell signaling and function on a subcellular level. DESIGN Human peripheral blood mononuclear cells (PBMC) were used to determine the effect of HTS on T-cell interleukin 2 (IL-2) production and proliferation. Human Jurkat T-cells were used to study the effects of HTS on T-cell signal transduction, IL-2 mRNA transcription, and IL-2 expression. MATERIAL AND METHODS The effect of HTS on T-cell proliferation and IL-2 production was measured with PBMC and Jurkat T-cells. IL-2 mRNA transcription in HTS-treated Jurkat cells was measured by reverse transcriptase polymerase chain reaction. HTS-induced protein tyrosine phosphorylation in Jurkat T-cells was determined by immunoblotting with anti-phosphotyrosine antibodies. Expression in Jurkat cells of the mitogen-activated protein kinase p38 (MAPK p38), a signal transduction protein that is activated by osmotic stress, was determined by immunoblotting with anti-MAPK p38 antibodies. HTS-induced MAPK p38 activation in Jurkat cells was measured with an immune-complex kinase assay using ATF-2 as a substrate. MEASUREMENTS AND MAIN RESULTS Proliferation of activated human PBMC increased significantly upon addition of HTS to the culture medium. This effect of HTS was paralleled by enhanced IL-2 production of activated PBMC and Jurkat cells and IL-2 mRNA transcription of Jurkat cells. HTS exposure of Jurkat cells caused tyrosine phosphorylation of a number of cellular proteins. We found that Jurkat T-cells expressed MAPK p38 and that it was activated in the presence of HTS. All these effects of HTS on T-cell signaling and function were observed at NaCl concentrations that were within physiologically relevant levels (20-100 mmol/L hypertonicity). CONCLUSIONS In T-cells, HTS triggers a signaling pathway that includes increased tyrosine phosphorylation of several cellular proteins and activation of MAPK p38. HTS alone does not result in IL-2 mRNA transcription, IL-2 expression, or T-cell proliferation. However, in combination with other stimuli, HTS augments T-cell IL-2 expression and proliferation. We speculate that HTS could "resuscitate" suppressed T-cells in trauma patients by circumvention of, or substituting for, blocked signaling pathways.
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Affiliation(s)
- W G Junger
- Department of Surgery, University of California San Diego, USA
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Abstract
AbstractEngagement of the high-affinity IgG Fc receptor (FcγRI) activates a signal transduction pathway involving tyrosine phosphorylation of associated kinases. We compared the activation of the related protein tyrosine kinases (PTKs), Syk and ZAP-70, in FcγRI-mediated signaling. Cross-linking of the FcγRI multimeric receptor in monocytic cells results in tyrosine phosphorylation of the FcεRIγ subunit and association of Syk with this complex. We stably introduced ZAP-70 via a retroviral vector into two monocytic cell lines, U937 and THP-1, which normally do not express ZAP-70. Neither Syk nor MAP kinase activation was affected by the presence of ZAP-70. Although transduced ZAP-70 had in vitro kinase activity and associated with FcεRIγ after receptor aggregation, it was not tyrosine phosphorylated. In contrast, both ZAP-70 and Syk were phosphorylated in a T-cell line in which their respective levels of expression were similar to those detected in U937/ZAP-70 cells. Therefore, these results suggest that requirements for Syk and ZAP-70 phosphorylation are distinct in a monocytic cell context.
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