101
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Kersseboom R, Ta VBT, Zijlstra AJE, Middendorp S, Jumaa H, van Loo PF, Hendriks RW. Bruton's tyrosine kinase and SLP-65 regulate pre-B cell differentiation and the induction of Ig light chain gene rearrangement. THE JOURNAL OF IMMUNOLOGY 2006; 176:4543-52. [PMID: 16585544 DOI: 10.4049/jimmunol.176.8.4543] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Bruton's tyrosine kinase (Btk) and the adapter protein SLP-65 (Src homology 2 domain-containing leukocyte-specific phosphoprotein of 65 kDa) transmit precursor BCR (pre-BCR) signals that are essential for efficient developmental progression of large cycling into small resting pre-B cells. We show that Btk- and SLP-65-deficient pre-B cells have a specific defect in Ig lambda L chain germline transcription. In Btk/SLP-65 double-deficient pre-B cells, both kappa and lambda germline transcripts are severely reduced. Although these observations point to an important role for Btk and SLP-65 in the initiation of L chain gene rearrangement, the possibility remained that these signaling molecules are only required for termination of pre-B cell proliferation or for pre-B cell survival, whereby differentiation and L chain rearrangement is subsequently initiated in a Btk/SLP-65-independent fashion. Because transgenic expression of the antiapoptotic protein Bcl-2 did not rescue the developmental arrest of Btk/SLP-65 double-deficient pre-B cells, we conclude that defective L chain opening in Btk/SLP-65-deficient small resting pre-B cells is not due to their reduced survival. Next, we analyzed transgenic mice expressing the constitutively active Btk mutant E41K. The expression of E41K-Btk in Ig H chain-negative pro-B cells induced 1) surface marker changes that signify cellular differentiation, including down-regulation of surrogate L chain and up-regulation of CD2, CD25, and MHC class II; and 2) premature rearrangement and expression of kappa and lambda light chains. These findings demonstrate that Btk and SLP-65 transmit signals that induce cellular maturation and Ig L chain rearrangement independently of their role in termination of pre-B cell expansion.
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Affiliation(s)
- Rogier Kersseboom
- Department of Immunology, Erasmus Medical Center, Rotterdam, The Netherlands
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102
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Olsson S, Sundler R. Different roles for non-receptor tyrosine kinases in arachidonate release induced by zymosan and Staphylococcus aureus in macrophages. JOURNAL OF INFLAMMATION-LONDON 2006; 3:8. [PMID: 16674821 PMCID: PMC1479341 DOI: 10.1186/1476-9255-3-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2005] [Accepted: 05/04/2006] [Indexed: 11/10/2022]
Abstract
Background Yeast and bacteria elicit arachidonate release in macrophages, leading to the formation of leukotrienes and prostaglandins, important mediators of inflammation. Receptors recognising various microbes have been identified, but the signalling pathways are not entirely understood. Cytosolic phospholipase A2 is a major down-stream target and this enzyme is regulated by both phosphorylation and an increase in intracellular Ca2+. Potential signal components are MAP kinases, phosphatidylinositol 3-kinase and phospholipase Cγ2. The latter can undergo tyrosine phosphorylation, and Src family kinases might carry out this phosphorylation. Btk, a Tec family kinase, could also be important. Our aim was to further elucidate the role of Src family kinases and Btk. Methods Arachidonate release from murine peritoneal macrophages was measured by prior radiolabeling. Furthermore, immunoprecipitation and Western blotting were used to monitor changes in activity/phosphorylation of intermediate signal components. To determine the role of Src family kinases two different inhibitors with broad specificity (PP2 and the Src kinase inhibitor 1, SKI-1) were used as well as the Btk inhibitor LFM-A13. Results Arachidonate release initiated by either Staphylococcus aureus or yeast-derived zymosan beads was shown to depend on members of the Src kinase family as well as Btk. Src kinases were found to act upstream of Btk, phosphatidylinositol 3-kinase, phospholipase Cγ2 and the MAP kinases ERK and p38, thereby affecting all branches of the signalling investigated. In contrast, Btk was not involved in the activation of the MAP-kinases. Since the cytosolic phospholipase A2 in macrophages is regulated by both phosphorylation (via ERK and p38) and an increase in intracellular Ca2+, we propose that members of the Src kinase family are involved in both types of regulation, while the role of Btk may be restricted to the latter type. Conclusion Arachidonate release induced by either Staphylococcus aureus or zymosan was found to depend on Src family kinases as well as Btk. While members of the Src kinase family were shown to act upstream of Btk and the MAP kinases, Btk plays another role independent of MAP kinases, but down-stream of the Src family kinases.
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Affiliation(s)
- Sandra Olsson
- Department of Experimental Medical Science Lund University, BMC, B12, SE-22184 Lund, Sweden
| | - Roger Sundler
- Department of Experimental Medical Science Lund University, BMC, B12, SE-22184 Lund, Sweden
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103
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Abstract
BOB.1/OBF.1 is a lymphocyte-restricted transcriptional coactivator. It binds together with the Oct1 and Oct2 transcription factors to DNA and enhances their transactivation potential. Mice deficient for the transcriptional coactivator BOB.1/OBF.1 show several defects in differentiation, function and signaling of B cells. In search of BOB.1/OBF.1 regulated genes we identified Btk—a cytoplasmic tyrosine kinase—as a direct target of BOB.1/OBF.1. Analyses of the human as well as murine Btk promoters revealed a non-consensus octamer site close to the start site of transcription. Here we show that Oct proteins together with BOB.1/OBF.1 are able to form ternary complexes on these sites in vitro and in vivo. This in turn leads to the induction of Btk promoter activity in synergism with the transcription factor PU.1. Btk, like BOB.1/OBF.1, plays a critical role in B cell development and B cell receptor signalling. Therefore the down-regulation of Btk expression in BOB.1/OBF.1-deficient B cells could be related to the functional and developmental defects observed in BOB.1/OBF.1-deficient mice.
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Affiliation(s)
| | - Thomas Wirth
- To whom correspondence should be addressed. Tel: 0049 731 502 3262; Fax: 0049 731 502 2892;
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104
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Hendriks RW, Kersseboom R. Involvement of SLP-65 and Btk in tumor suppression and malignant transformation of pre-B cells. Semin Immunol 2006; 18:67-76. [PMID: 16300960 DOI: 10.1016/j.smim.2005.10.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Signals from the precursor-B cell receptor (pre-BCR) are essential for selection and clonal expansion of pre-B cells that have performed productive immunoglobulin heavy chain V(D)J recombination. In the mouse, the downstream signaling molecules SLP-65 and Btk cooperate to limit proliferation and induce differentiation of pre-B cells, thereby acting as tumor suppressors to prevent pre-B cell leukemia. In contrast, recent observations in human BCR-ABL1(+) pre-B lymphoblastic leukemia cells demonstrate that Btk is constitutively phosphorylated and activated by the BCR-ABL1 fusion protein. As a result, activated Btk transmits survival signals that are essential for the transforming activity of oncogenic Abl tyrosine kinase.
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Affiliation(s)
- Rudi W Hendriks
- Department of Immunology, Erasmus MC Rotterdam, P.O. Box 1738, NL-3000 DR Rotterdam, The Netherlands.
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105
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Abstract
The activation threshold of cells in the immune system is often tuned by cell surface molecules. The Fc receptors expressed on various hematopoietic cells constitute critical elements for activating or downmodulating immune responses and combines humoral and cell-mediated immunity. Thus, Fc receptors are the intelligent sensors of the immune status in the individual. However, impaired regulation by Fc receptors will lead to unresponsiveness or hyperreactivity to foreign as well as self-antigens. Murine models for autoimmune disease indicate the indispensable roles of the inhibitory Fc receptor in the suppression of such disorders, whereas activating-type FcRs are crucial for the onset and exacerbation of the disease. The development of many autoimmune diseases in humans may be caused by impairment of the human Fc receptor regulatory system. This review is aimed at providing a current overview of the mechanism of Fc receptor-based immune regulation and the possible scenario of how autoimmune disease might result from their dysfunction.
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Affiliation(s)
- Toshiyuki Takai
- Department of Experimental Immunology and CREST Program of Japan Science and Technology Agency, Institute of Development, Aging and Cancer, Tohoku University, Sendai 980-8575, Japan.
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106
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Su Z, Guo X, Barker DS, Shoemaker RL, Marchase RB, Blalock JE. A store-operated nonselective cation channel in human lymphocytes. Cell Mol Neurobiol 2005; 25:625-47. [PMID: 16075382 DOI: 10.1007/s10571-005-4005-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2004] [Accepted: 04/14/2004] [Indexed: 12/27/2022]
Abstract
1. Agonist interaction with phospholipase C-linked receptors at the plasma membrane can elicit both Ca2+ and Na+ influxes in lymphocytes. While Ca2+ influx is mediated by Ca2+ release-activated Ca2+ (CRAC) channels, the pathway responsible for Na+ influx is largely unknown. 2. We show that thapsigargin, ionomycin, ADP-ribose and IP3 activated a nonselective cation channel in lymphocytes that had a slightly outwardly rectifying I-V relationship, and a single channel conductance of 23.1 pS. We termed this channel a Ca2+ release-activated nonselective cation (CRANC) channel. 3. On activation in cell-attached configuration, switching to an inside-out configuration abolished CRANC channel activity. 4. Transfection of Jurkat T cells with antisense oligonucleotides for LTRPC2 reduced capacitative Ca2+ entry. 5. These results suggest that CRANC channels are responsible for the Na+ influx as well as a portion of the Ca2+ influx in lymphocytes induced by store depletion, that sustained activation of CRANC channels requires some property of the environment of a cell depleted of its Ca2+ stores; and that LTRPC2 protein is a likely component of the CRANC channel.
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Affiliation(s)
- Zhengchang Su
- Department of Physiology and Biophysics, Schools of Medicine and Dentistry, University of Alabama at Birmingham, 1918 University Boulevard, Birmingham, Alabama 35294, USA
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107
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Iwaki S, Tkaczyk C, Satterthwaite AB, Halcomb K, Beaven MA, Metcalfe DD, Gilfillan AM. Btk plays a crucial role in the amplification of Fc epsilonRI-mediated mast cell activation by kit. J Biol Chem 2005; 280:40261-70. [PMID: 16176929 DOI: 10.1074/jbc.m506063200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Stem cell factor (SCF) acts in synergy with antigen to enhance the calcium signal, degranulation, activation of transcription factors, and cytokine production in human mast cells. However, the underlying mechanisms for this synergy remain unclear. Here we show, utilizing bone marrow-derived mast cells (BMMCs) from Btk and Lyn knock-out mice, that activation of Btk via Lyn plays a key role in promoting synergy. As in human mast cells, SCF enhanced degranulation and cytokine production in BMMCs. In Btk-/- BMMCs, in which there was a partial reduction in the capacity to degranulate in response to antigen, SCF was unable to enhance the residual antigen-mediated degranulation. Furthermore, as with antigen, the ability of SCF to promote cytokine production was abrogated in the Btk-/- BMMCs. The impairment of responses in Btk-/- cells correlated with an inability of SCF to augment phospholipase Cgamma1 activation and calcium mobilization, and to phosphorylate NFkappaB and NFAT for cytokine gene transcription in these cells. Similar studies with Lyn-/- and Btk-/-/Lyn-/- BMMCs indicated that Lyn was a regulator of Btk for these responses. These data demonstrate, for the first time, that Btk is a key regulator of a Kit-mediated amplification pathway that augments Fc epsilonRI-mediated mast cell activation.
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Affiliation(s)
- Shoko Iwaki
- Laboratory of Allergic Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892-1881, USA
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108
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Chiu D, Ma K, Scott A, Duronio V. Acute activation of Erk1/Erk2 and protein kinase B/akt proceed by independent pathways in multiple cell types. FEBS J 2005; 272:4372-84. [PMID: 16128807 DOI: 10.1111/j.1742-4658.2005.04850.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We used two inhibitors of the signaling enzyme phosphatidylinositol 3-kinase (PtdIns3K), wortmannin and LY294002, to evaluate the potential involvement of PtdIns3K in the activation of the MAP kinases (MAPK), Erk1 and Erk2. In dose-response studies carried out on six different cell lines and a primary cell culture, we analyzed the ability of the inhibitors to block phosphorylation of protein kinase B/akt (PKB/akt) at Ser473 as a measure of PtdIns3K activity, or the phosphorylation of Erk1/2 at activating Thr/Tyr sites as a measure of the extent of activation of MAPK/Erk kinase (MEK/Erk). In three different hemopoietic cell lines stimulated with cytokines, and in HEK293 cells, stimulated with serum, either wortmannin or LY294002, but never both, could partially block phosphorylation of Erks. The same observations were made in a B-cell line and in primary fibroblasts. In only one cell type, the A20 B cells, was there a closer correlation between the PtdIns3K inhibition by both inhibitors, and their corresponding effects on Erk phosphorylation. However, this stands out as an exception that gives clues to the mechanism by which cross-talk might occur. In all other cells, acute activation of the pathway leading to Erk phosphorylation could proceed independently of PtdIns3K activation. In a biological assay comparing these two pathways, the ability of LY294002 and the MEK inhibitor, U0126, to induce apoptosis were tested. Whereas LY294002 caused death of cytokine-dependent hemopoietic cells, U0126 had little effect, but both inhibitors together had a synergistic effect. The data show that these two pathways are regulating very different downstream events involved in cell survival.
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Affiliation(s)
- Doris Chiu
- Department of Medicine, University of British Columbia and Vancouver Coastal Health Research Institute, Jack Bell Research Centre, Vancouver, Canada
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109
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Feldhahn N, Klein F, Mooster JL, Hadweh P, Sprangers M, Wartenberg M, Bekhite MM, Hofmann WK, Herzog S, Jumaa H, Rowley JD, Müschen M. Mimicry of a constitutively active pre-B cell receptor in acute lymphoblastic leukemia cells. ACTA ACUST UNITED AC 2005; 201:1837-52. [PMID: 15939795 PMCID: PMC2213268 DOI: 10.1084/jem.20042101] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Pre-B cells undergo apoptosis unless they are rescued by pre-B cell receptor-dependent survival signals. We previously showed that the BCR-ABL1 kinase that is expressed in pre-B lymphoblastic leukemia bypasses selection for pre-B cell receptor-dependent survival signals. Investigating possible interference of BCR-ABL1 with pre-B cell receptor signaling, we found that neither SYK nor SLP65 can be phosphorylated in response to pre-B cell receptor engagement. Instead, Bruton's tyrosine kinase (BTK) is constitutively phosphorylated by BCR-ABL1. Activated BTK is essential for survival signals that otherwise would arise from the pre-B cell receptor, including activation of PLCgamma1, autonomous Ca2+ signaling, STAT5-phosphorylation, and up-regulation of BCLX(L). Inhibition of BTK activity specifically induces apoptosis in BCR-ABL1+ leukemia cells to a similar extent as inhibition of BCR-ABL1 kinase activity itself. However, BCR-ABL1 cannot directly bind to full-length BTK. Instead, BCR-ABL1 induces the expression of a truncated splice variant of BTK that acts as a linker between the two kinases. As opposed to full-length BTK, truncated BTK lacks kinase activity yet can bind to BCR-ABL1 through its SRC-homology domain 3. Acting as a linker, truncated BTK enables BCR-ABL1-dependent activation of full-length BTK, which initiates downstream survival signals and mimics a constitutively active pre-B cell receptor.
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Affiliation(s)
- Niklas Feldhahn
- Laboratory for Molecular Stem Cell Biology, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
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110
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Nishimoto H, Lee SW, Hong H, Potter KG, Maeda-Yamamoto M, Kinoshita T, Kawakami Y, Mittler RS, Kwon BS, Ware CF, Croft M, Kawakami T. Costimulation of mast cells by 4-1BB, a member of the tumor necrosis factor receptor superfamily, with the high-affinity IgE receptor. Blood 2005; 106:4241-8. [PMID: 16123219 PMCID: PMC1416206 DOI: 10.1182/blood-2005-04-1358] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Mast cells are the major effector-cell type for immediate hypersensitivity and other forms of allergic reactions. Expression of 4-1BB, a member of the tumor necrosis factor receptor superfamily, is induced at mRNA and protein levels on stimulation through the high-affinity receptor for immunoglobulin E (IgE; FcepsilonRI). In this study, we present evidence that agonistic anti-4-1BB antibodies can enhance FcepsilonRI-induced cytokine production and secretion. Consistent with this, 4-1BB-deficient mast cells exhibit reduced degranulation and cytokine production on FcepsilonRI stimulation. Analysis of 4-1BB ligand (4-1BBL)-deficient cells supported this notion. As a potential mechanism for these defects, we identified a defect in Ca2+ flux induced by FcepsilonRI stimulation. The defective Ca2+ flux could be accounted for by the reduced activity of Lyn/Btk/phospholipase C-gamma2 pathway and constitutive interactions between 4-1BB and Lyn. Therefore, FcepsilonRI-inducible 4-1BB plays a costimulatory function together with FcepsilonRI stimulation.
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MESH Headings
- Agammaglobulinaemia Tyrosine Kinase
- Animals
- Antibodies, Monoclonal/immunology
- Antigens, CD/genetics
- Antigens, CD/immunology
- Antigens, CD/metabolism
- Calcium/pharmacology
- Cell Proliferation
- Cells, Cultured
- Cytokines/biosynthesis
- Cytokines/metabolism
- Gene Expression Regulation
- Mast Cells/cytology
- Mast Cells/immunology
- Mast Cells/metabolism
- Mice
- Mice, Knockout
- Phospholipase C gamma/metabolism
- Protein-Tyrosine Kinases/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, IgE/immunology
- Receptors, IgE/metabolism
- Receptors, Nerve Growth Factor/deficiency
- Receptors, Nerve Growth Factor/genetics
- Receptors, Nerve Growth Factor/immunology
- Receptors, Nerve Growth Factor/metabolism
- Receptors, Tumor Necrosis Factor/deficiency
- Receptors, Tumor Necrosis Factor/genetics
- Receptors, Tumor Necrosis Factor/immunology
- Receptors, Tumor Necrosis Factor/metabolism
- Signal Transduction
- Tumor Necrosis Factor Receptor Superfamily, Member 9
- src-Family Kinases/metabolism
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Affiliation(s)
- Hajime Nishimoto
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, 10355 Science Center Dr, San Diego, CA 92121, USA
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111
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Redondo PC, Ben-Amor N, Salido GM, Bartegi A, Pariente JA, Rosado JA. Ca2+-independent activation of Bruton's tyrosine kinase is required for store-mediated Ca2+ entry in human platelets. Cell Signal 2005; 17:1011-21. [PMID: 15894173 DOI: 10.1016/j.cellsig.2004.11.019] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2004] [Revised: 11/24/2004] [Accepted: 11/25/2004] [Indexed: 11/29/2022]
Abstract
Store-mediated Ca(2+) entry (SMCE), which is rapidly activated by depletion of the intracellular Ca(2+) stores, is a major mechanism for Ca(2+) influx. Several studies have involved tyrosine kinases in the activation of SMCE, such as pp60(src), although at present those involved in the early activation steps are unknown. Here we report the involvement of Bruton's tyrosine kinase (Btk) in the early stages of SMCE in human platelets. Cell treatment with thrombin or thapsigargin (TG) plus ionomycin (Iono) results in rapid activation of Btk, which was independent of rise in intracellular Ca(2+) concentration ([Ca(2+)](i)) but dependent on H(2)O(2) generation. Platelet treatment with Btk inhibitors, LFM-A13 or terreic acid, significantly reduced TG+Iono- and thrombin-evoked SMCE. Btk was rapidly activated by addition of low concentrations of H(2)O(2), whose effect on Ca(2+) entry was prevented by Btk inhibitors. Our results indicate that pp60(src) and Btk co-immunoprecipitate after platelet stimulation with TG+Iono, thrombin or H(2)O(2). In addition, we have found that LFM-A13 impaired actin filament reorganization after store depletion and agonist-induced activation of pp60(src), while the inhibitor of pp60(src), a protein that requires actin reorganization for its activation, did not modify Btk activation, suggesting that Btk is upstream of pp60(src). We propose a role for Btk in the early steps of activation of SMCE in human platelets.
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112
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Abstract
The proliferation and differentiation of lymphocytes are regulated by receptors localized on the cell surface. Engagement of these receptors induces the activation of intracellular signaling proteins that transmit the receptor signals to distinct targets and control the cellular responses. The first signaling proteins to be discovered in higher organisms were the products of oncogenes. For example, the kinases Src and Abelson (Abl) were originally identified as oncogenes and were later characterized as important proteins for signal transduction in various cell types, including lymphocytes. Now, as many cellular signaling molecules have been discovered and ordered into certain pathways, we can better understand why particular signaling proteins are associated with tumorigenesis. In this review, we discuss recent progress in unraveling the molecular mechanisms of signaling pathways that control the proliferation and differentiation of early B cells. We point out the concepts of auto-inhibition and subcellular localization as crucial aspects in the regulation of B cell signaling.
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Affiliation(s)
- Hassan Jumaa
- Institute for Biology III, Albert-Ludwigs University of Freiburg and Max Planck Institute for Immunobiology, 79108 Freiburg, Germany.
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113
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Kitaura J, Eto K, Kinoshita T, Kawakami Y, Leitges M, Lowell CA, Kawakami T. Regulation of highly cytokinergic IgE-induced mast cell adhesion by Src, Syk, Tec, and protein kinase C family kinases. THE JOURNAL OF IMMUNOLOGY 2005; 174:4495-504. [PMID: 15814670 DOI: 10.4049/jimmunol.174.8.4495] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Mast cells play a critical role in IgE-dependent immediate hypersensitivity. Recent studies have shown that, contrary to the traditional view, binding of monomeric IgE to Fc epsilon RI results in a number of biological outcomes in mast cells, including survival. However, IgE molecules display heterogeneity in inducing cytokine production; highly cytokinergic (HC) IgEs cause extensive Fc epsilon RI aggregation, which leads to potent enhancement of survival and other activation events, whereas poorly cytokinergic (PC) IgEs can do so inefficiently. The present study demonstrates that HC, but not PC, IgEs can efficiently induce adhesion and spreading of mouse mast cells on fibronectin-coated plates in slow and sustained kinetics. HC IgE-induced adhesion through beta1 and beta7 integrins promotes survival, IL-6 production, and DNA synthesis. Importantly, we have identified Lyn and Syk as requisite tyrosine kinases and Hck, Btk, and protein kinase C theta as contributory kinases in HC IgE-induced adhesion and spreading, whereas protein kinase C epsilon plays a negative role. Consistent with these results, Lyn, Syk, and Btk are activated in HC IgE-stimulated cells in a slower but more sustained manner, compared with cells stimulated with IgE and Ag. Thus, binding of HC IgEs to Fc epsilon RI induces adhesion of mast cells to fibronectin by modulating cellular activation signals in a unique fashion.
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Affiliation(s)
- Jiro Kitaura
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121, USA
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114
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Schwartzberg PL, Finkelstein LD, Readinger JA. TEC-family kinases: regulators of T-helper-cell differentiation. Nat Rev Immunol 2005; 5:284-95. [PMID: 15803148 DOI: 10.1038/nri1591] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The TEC-family protein tyrosine kinases ITK, RLK and TEC have been identified as key components of T-cell-receptor signalling that contribute to the regulation of phospholipase C-gamma, the mobilization of Ca(2+) and the activation of mitogen-activated protein kinases. Recent data also show that TEC kinases contribute to T-cell-receptor-driven actin reorganization and cell polarization, which are required for productive T-cell activation. Functional studies have implicated TEC kinases as important mediators of pathways that control the differentiation of CD4(+) T helper cells. Here, we review studies of signalling pathways that involve TEC kinases and how these pathways might contribute to the regulation of T-helper-cell differentiation and function.
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Affiliation(s)
- Pamela L Schwartzberg
- National Human Genome Research Institute, National Institutes of Health, 4A38/49 Convent Drive, Bethesda, Maryland 20892, USA.
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115
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Nakamura A, Akiyama K, Takai T. Fc receptor targeting in the treatment of allergy, autoimmune diseases and cancer. Expert Opin Ther Targets 2005; 9:169-90. [PMID: 15757489 DOI: 10.1517/14728222.9.1.169] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Immune activation and inhibitory receptors play an important role in the maintenance of an adequate activation threshold of various cells in our immune system. Analyses of murine models show that the inhibitory Fcreceptor, FcgammaRIIB plays an indispensable role in the suppression of anti-body-mediated allergy and autoimmunity. In contrast, the activating-type Fcreceptors (FcRs) are essential for the development of these diseases, suggesting that regulation of inhibitory or activating FcR is an ideal target as a therapeutic agent. In addition, recent crystal structural analyses of FcR-Ig-Fc fragment complexes provide an effective approach for developing FcR-targeting drugs. This review summarises recent advances of FcR, which were mainly obtained by murine studies, and highlights novel antibodies as possible FcR-targeting therapies for allergy, autoimmune diseases and cancer.
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Affiliation(s)
- Akira Nakamura
- Tohoku University, Department of Experimental Immunology and CREST programme of Japan Science and Technology Agency, Institute of Development, ageing and Cancer, Seiryo 4-1, Sendai 980-8575, Japan.
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116
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Moreno-García ME, López-Bojórques LN, Zentella A, Humphries LA, Rawlings DJ, Santos-Argumedo L. CD38 signaling regulates B lymphocyte activation via a phospholipase C (PLC)-gamma 2-independent, protein kinase C, phosphatidylcholine-PLC, and phospholipase D-dependent signaling cascade. THE JOURNAL OF IMMUNOLOGY 2005; 174:2687-95. [PMID: 15728476 DOI: 10.4049/jimmunol.174.5.2687] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The CD38 cell surface receptor is a potent activator for splenic, B lymphocytes. The molecular mechanisms regulating this response, however, remain incompletely characterized. Activation of the nonreceptor tyrosine kinase, Btk, is essential for CD38 downstream signaling function. The major Btk-dependent substrate in B cells, phospholipase C-gamma2 (PLC-gamma2), functions to generate the key secondary messengers, inositol-1,4,5 trisphosphate and diacylglycerol. Surprisingly, CD38 ligation results in no detectable increase in phosphoinositide metabolism and only a minimal increase in cytosolic calcium. We hypothesized that Btk functioned independently of PLC-gamma2 in the CD38 signaling pathway. Accordingly, we demonstrate that CD38 cross-linking does not result in the functional phosphorylation of PLC-gamma2 nor an increase in inositol-1,4,5 trisphosphate production. Furthermore, splenic B cells exhibit a normal CD38-mediated, proliferative response in the presence of the phosphoinositide-PLC inhibitor, U73122. Conversely, protein kinase C (PKC) beta-deficient mice, or PKC inhibitors, indicated the requirement for diacylglycerol-dependent PKC isoforms in this pathway. Loss of PKC activity blocked CD38-dependent, B cell proliferation, NF-kappaB activation, and subsequent expression of cyclin-D2. These results suggested that an alternate diacylglycerol-producing phospholipase must participate in CD38 signaling. Consistent with this idea, CD38 increased the enzymatic activity of the phosphatidylcholine (PC)-metabolizing enzymes, PC-PLC and phospholipase D. The PC-PLC inhibitor, D609, completely blocked CD38-dependent B cell proliferation, IkappaB-alpha degradation, and cyclin-D2 expression. Analysis of Btk mutant B cells demonstrated a partial requirement for Btk in the activation of both enzymes. Taken together, these data demonstrate that CD38 initiates a novel signaling cascade leading to Btk-, PC-PLC-, and phospholipase D-dependent, PLC-gamma2-independent, B lymphocyte activation.
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Affiliation(s)
- Miguel E Moreno-García
- Departments of Cell Biology, Centro de Investigación y Estudios Avanzados, Mexico D.F. Mexico
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117
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Abstract
The Tec family tyrosine kinases are now recognized as important mediators of antigen receptor signaling in lymphocytes. Three members of this family, Itk, Rlk, and Tec, are expressed in T cells and activated in response to T cell receptor (TCR) engagement. Although initial studies demonstrated a role for these proteins in TCR-mediated activation of phospholipase C-gamma, recent data indicate that Tec family kinases also regulate actin cytoskeletal reorganization and cellular adhesion following TCR stimulation. In addition, Tec family kinases are activated downstream of G protein-coupled chemokine receptors, where they play parallel roles in the regulation of Rho GTPases, cell polarization, adhesion, and migration. In all these systems, however, Tec family kinases are not essential signaling components, but instead function to modulate or amplify signaling pathways. Although they quantitatively reduce proximal signaling, mutations that eliminate Tec family kinases in T cells nonetheless qualitatively alter T cell development and differentiation.
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Affiliation(s)
- Leslie J Berg
- Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
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118
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Rajaiya J, Hatfield M, Nixon JC, Rawlings DJ, Webb CF. Bruton's tyrosine kinase regulates immunoglobulin promoter activation in association with the transcription factor Bright. Mol Cell Biol 2005; 25:2073-84. [PMID: 15743806 PMCID: PMC1061591 DOI: 10.1128/mcb.25.6.2073-2084.2005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Revised: 07/06/2004] [Accepted: 12/13/2004] [Indexed: 01/19/2023] Open
Abstract
Bright (B-cell regulator of immunoglobulin heavy chain transcription) binding to immunoglobulin heavy chain loci after B-cell activation is associated with increased heavy chain transcription. Our earlier reports demonstrated that Bright coimmunoprecipitates with Bruton's tyrosine kinase (Btk) and that these proteins associate in a DNA-binding complex in primary B cells. B cells from immunodeficient mice with a mutation in Btk failed to produce stable Bright DNA-binding complexes. In order to determine if Btk is important for Bright function, a transcription activation assay was established and analyzed using real-time PCR technology. Cells lacking both Bright and Btk were transfected with Bright and/or Btk along with an immunoglobulin heavy chain reporter construct. Immunoglobulin gene transcription was enhanced when Bright and Btk were coexpressed. In contrast, neither Bright nor Btk alone led to activation of heavy chain transcription. Furthermore, Bright function required both Btk kinase activity and sequences within the pleckstrin homology domain of Btk. Bright was not appreciably phosphorylated by Btk; however, a third tyrosine-phosphorylated protein coprecipitated with Bright. Thus, the ability of Bright to enhance immunoglobulin transcription critically requires functional Btk.
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Affiliation(s)
- Jaya Rajaiya
- Oklahoma Medical Research Foundation, Immunobiology and Cancer Research Program, 825 N.E. 13th St., Oklahoma City, OK 73104, USA
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119
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Lindvall JM, Blomberg KEM, Väliaho J, Vargas L, Heinonen JE, Berglöf A, Mohamed AJ, Nore BF, Vihinen M, Smith CIE. Bruton's tyrosine kinase: cell biology, sequence conservation, mutation spectrum, siRNA modifications, and expression profiling. Immunol Rev 2005; 203:200-15. [PMID: 15661031 DOI: 10.1111/j.0105-2896.2005.00225.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Bruton's tyrosine kinase (Btk) is encoded by the gene that when mutated causes the primary immunodeficiency disease X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (Xid) in mice. Btk is a member of the Tec family of protein tyrosine kinases (PTKs) and plays a vital, but diverse, modulatory role in many cellular processes. Mutations affecting Btk block B-lymphocyte development. Btk is conserved among species, and in this review, we present the sequence of the full-length rat Btk and find it to be analogous to the mouse Btk sequence. We have also analyzed the wealth of information compiled in the mutation database for XLA (BTKbase), representing 554 unique molecular events in 823 families and demonstrate that only selected amino acids are sensitive to replacement (P < 0.001). Although genotype-phenotype correlations have not been established in XLA, based on these findings, we hypothesize that this relationship indeed exists. Using short interfering-RNA technology, we have previously generated active constructs downregulating Btk expression. However, application of recently established guidelines to enhance or decrease the activity was not successful, demonstrating the importance of the primary sequence. We also review the outcome of expression profiling, comparing B lymphocytes from XLA-, Xid-, and Btk-knockout (KO) donors to healthy controls. Finally, in spite of a few genes differing in expression between Xid- and Btk-KO mice, in vivo competition between cells expressing either mutation shows that there is no selective survival advantage of cells carrying one genetic defect over the other. We conclusively demonstrate that for the R28C-missense mutant (Xid), there is no biologically relevant residual activity or any dominant negative effect versus other proteins.
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120
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Finkelstein LD, Schwartzberg PL. Tec kinases: shaping T-cell activation through actin. Trends Cell Biol 2005; 14:443-51. [PMID: 15308211 DOI: 10.1016/j.tcb.2003.07.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Following stimulation, T cells undergo marked actin-dependent changes in shape that are required for productive cellular interactions and movement during immune responses. Reorganization of the actin cytoskeletal is also necessary for the formation of an immunological synapse - the convergence of several signaling molecules at the plasma membrane that occurs after effective T-cell receptor (TCR) signaling. Much emerging evidence indicates that the Tec family of tyrosine kinases has a role in actin cytoskeleton reorganization. Specifically, T cells that lack or express mutant versions of the Tec kinase Itk show impaired TCR-induced actin polymerization, cell polarization and regulation of the signaling events involved in cytoskeletal reorganization. These data, as well as other findings, support roles for Tec kinases in actin cytoskeleton regulation.
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Affiliation(s)
- Lisa D Finkelstein
- National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
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121
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van den Akker E, van Dijk TB, Schmidt U, Felida L, Beug H, Löwenberg B, von Lindern M. The Btk inhibitor LFM-A13 is a potent inhibitor of Jak2 kinase activity. Biol Chem 2005; 385:409-13. [PMID: 15196000 DOI: 10.1515/bc.2004.045] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
LFM-A13, or alpha-cyano-beta-hydroxy-beta-methyl-N-(2,5-dibromophenyl)propenamide, was shown to inhibit Bruton's tyrosine kinase (Btk). Here we show that LFM-A13 efficiently inhibits erythropoietin (Epo)-induced phosphorylation of the erythropoietin receptor, Janus kinase 2 (Jak2) and downstream signalling molecules. However, the tyrosine kinase activity of immunoprecipitated or in vitro translated Btk and Jak2 was equally inhibited by LFM-A13 in in vitro kinase assays. Finally, Epo-induced signal transduction was also inhibited in cells lacking Btk. Taken together, we conclude that LFM-A13 is a potent inhibitor of Jak2 and cannot be used as a specific tyrosine kinase inhibitor to study the role of Btk in Jak2-dependent cytokine signalling.
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Affiliation(s)
- Emile van den Akker
- Department of Hematology, Erasmus MC, PO Box 1738, NL-3000 DR Rotterdam, The Netherlands
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122
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Abstract
Phosphoinositide 3-kinase (PI3K) activation is essential for lymphocyte proliferation driven by receptors for antigen, costimulatory ligands and cytokines. The lipid products of PI3K contribute to the assembly of membrane-associated signaling complexes by promoting recruitment of selected proteins from the cytoplasm. Many proteins possess domains that are able to bind selectively to PI3K products. Different 'PI3K effector' proteins are coupled to distinct biological responses, depending on cell type and on the receptor that is engaged. In B cells and T cells, Tec-family tyrosine kinases and Akt serine/threonine kinases are emerging as crucial mediators of proliferation and survival signals downstream of PI3K. Of particular interest is recent evidence that PI3K signaling controls increases in lymphocyte size and metabolic activity that accompany cell cycle progression.
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Affiliation(s)
- David A Fruman
- University of California, Irvine, Department of Molecular Biology and Biochemistry, 3242 McGaugh Hall, Irvine, California 92697-3900, USA.
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123
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Abstract
The modulation of inositol-1,4,5-trisphosphate (IP3), a product of phospholipase C (PLC) activity, is one of a common signaling mechanism used in many biological systems. B lymphocytes also rely on IP3 and subsequent calcium signaling to ensure appropriate developmental outcomes, as well as antigen-specific responses. In establishing the optimal intensity and duration of the PLC-gamma activity, an important role has emerged for adaptor molecules, which direct the appropriate subcellular localization of PLC-gamma and induce its conformational changes. Generated IP3 binds to IP3 receptors located on the endoplasmic reticulum (ER), which in turn is essential for triggering calcium release from the ER and subsequent entry of extracellular calcium by so-called Ca2+ entry channels. Recent data has begun to shed new light on the connection between the calcium release and the influx of extracellular calcium, and the molecular identity of the Ca2+ entry channels.
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MESH Headings
- Allosteric Regulation
- Animals
- B-Lymphocytes/immunology
- B-Lymphocytes/metabolism
- Calcium/immunology
- Calcium/metabolism
- Calcium Channels/immunology
- Calcium Channels/metabolism
- Endoplasmic Reticulum/immunology
- Endoplasmic Reticulum/metabolism
- Humans
- Inositol 1,4,5-Trisphosphate/immunology
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate Receptors/genetics
- Inositol 1,4,5-Trisphosphate Receptors/immunology
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- NFATC Transcription Factors/genetics
- NFATC Transcription Factors/immunology
- NFATC Transcription Factors/metabolism
- Phospholipase C gamma/genetics
- Phospholipase C gamma/immunology
- Phospholipase C gamma/metabolism
- Protein Transport/immunology
- Receptors, Antigen, B-Cell/immunology
- Receptors, Antigen, B-Cell/metabolism
- Signal Transduction/immunology
- Transcriptional Activation/immunology
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Affiliation(s)
- Masaki Hikida
- Laboratory for Lymphocyte Differentiation, RIKEN Research Center for Allergy and Immunology, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
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124
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Gimborn K, Lessmann E, Kuppig S, Krystal G, Huber M. SHIP Down-Regulates FcεR1-Induced Degranulation at Supraoptimal IgE or Antigen Levels. THE JOURNAL OF IMMUNOLOGY 2004; 174:507-16. [PMID: 15611277 DOI: 10.4049/jimmunol.174.1.507] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Cross-linking of the IgE-loaded high-affinity IgE receptor (FcepsilonR1) by multivalent Ags results in mast cell activation and subsequent release of multiple proinflammatory mediators. The dose-response curve for FcepsilonR1-mediated degranulation is bell-shaped, regardless of whether the IgE or the Ag concentration is varied. Although overall calcium influx follows this bell-shaped curve, intracellular calcium release continues to increase at supraoptimal IgE or Ag concentrations. As well, overall calcium mobilization adopts more transient kinetics when stimulations are conducted with supraoptimal instead of optimal Ag concentrations. Moreover, certain early signaling events continue to increase whereas degranulation drops under supraoptimal conditions. We identified SHIP, possibly in association with the FcepsilonR1 beta-chain, as a critical negative regulator acting within the inhibitory (supraoptimal) region of the dose-response curve that shifts the kinetics of calcium mobilization from a sustained to a transient response. Consistent with this, we found that degranulation of SHIP-deficient murine bone marrow-derived mast cells was not significantly reduced at supraoptimal Ag levels. A potential mediator of SHIP action, Bruton's tyrosine kinase, did not seem to play a role within the supraoptimal suppression of degranulation. Interestingly, SHIP was found to colocalize with the actin cytoskeleton (which has been shown previously to mediate the inhibition of degranulation at supraoptimal Ag doses). These results suggest that SHIP, together with other negative regulators, restrains bone marrow-derived mast cell activation at supraoptimal IgE or Ag concentrations in concert with the actin cytoskeleton.
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Affiliation(s)
- Kerstin Gimborn
- Department of Molecular Immunology, Biology III, University of Freiburg and Max-Planck-Institute for Immunobiology, Stübeweg 51, 79104 Freiburg, Germany
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125
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Kim YJ, Sekiya F, Poulin B, Bae YS, Rhee SG. Mechanism of B-cell receptor-induced phosphorylation and activation of phospholipase C-gamma2. Mol Cell Biol 2004; 24:9986-99. [PMID: 15509800 PMCID: PMC525462 DOI: 10.1128/mcb.24.22.9986-9999.2004] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Phospholipase C-gamma2 (PLC-gamma2) plays an important role in B-cell signaling. Phosphorylation of various tyrosine residues of PLC-gamma2 has been implicated in regulation of its lipase activity. With the use of antibodies specific for each of the putative phosphorylation sites, we have now shown that PLC-gamma2 is phosphorylated on Y753, Y759, and Y1217 in response to engagement of the B-cell receptor in Ramos cells, as well as in murine splenic B cells. In cells stimulated maximally via this receptor, the extent of phosphorylation of Y1217 was three times that of Y753 or of Y759. Stimulation of Jurkat T cells or platelets via their immunoreceptors also elicited phosphorylation of Y753 and Y759 but not that of Y1217. A basal level of phosphorylation of Y753 was apparent in unstimulated lymphocytes. The extent of phosphorylation of Y753 and Y759, but not that of Y1217, correlated with the lipase activity of PLC-gamma2. Examination of the effects of various pharmacological inhibitors and of RNA interference in Ramos cells suggested that Btk is largely, but not completely, responsible for phosphorylation of Y753 and Y759, whereas phosphorylation of Y1217 is independent of Btk. Finally, phosphorylation of Y1217 and that of Y753 and Y759 occurred on different PLC-gamma2 molecules.
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Affiliation(s)
- Yeun Ju Kim
- Laboratory of Cell Signaling, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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126
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Tomlinson MG, Heath VL, Turck CW, Watson SP, Weiss A. SHIP Family Inositol Phosphatases Interact with and Negatively Regulate the Tec Tyrosine Kinase. J Biol Chem 2004; 279:55089-96. [PMID: 15492005 DOI: 10.1074/jbc.m408141200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Tec family of protein-tyrosine kinases (PTKs), that includes Tec, Itk, Btk, Bmx, and Txk, plays an essential role in phospholipase Cgamma (PLCgamma) activation following antigen receptor stimulation. This function requires activation of phosphatidylinositol 3-kinase (PI 3-kinase), which promotes Tec membrane localization through phosphatidylinositol 3,4,5-trisphosphate (PtdIns 3,4,5-P(3)) generation. The mechanism of negative regulation of Tec family PTKs is poorly understood. In this study, we show that the inositol 5' phosphatases SHIP1 and SHIP2 interact preferentially with Tec, compared with other Tec family members. Four lines of evidence suggest that SHIP phosphatases are negative regulators of Tec. First, SHIP1 and SHIP2 are potent inhibitors of Tec activity. Second, inactivation of the Tec SH3 domain, which is necessary and sufficient for SHIP binding, generates a hyperactive form of Tec. Third, SHIP1 inhibits Tec membrane localization. Finally, constitutively targeting Tec to the membrane relieves SHIP1-mediated inhibition. These data suggest that SHIP phosphatases can interact with and functionally inactivate Tec by de-phosphorylation of local PtdIns 3,4,5-P(3) and inhibition of Tec membrane localization.
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Affiliation(s)
- Michael G Tomlinson
- Department of Medicine and Howard Hughes Medical Institute, University of California-San Francisco, San Francisco, CA 94143, USA
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127
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128
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Nakamura A, Takai T. A role of FcgammaRIIB in the development of collagen-induced arthritis. Biomed Pharmacother 2004; 58:292-8. [PMID: 15194165 DOI: 10.1016/j.biopha.2004.04.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2004] [Indexed: 11/30/2022] Open
Abstract
Immune inhibitory receptors play an important role in the maintenance of adequate activation threshold of various cells in our immune system. The inhibitory Fc receptor, type IIB Fc receptor for IgG (FcgammaRIIB), is one of the critical molecules for the regulation of immune responses through antibodies. Analysis of murine models indicates that FcgammaRIIB plays an essential role in the suppression of various autoimmune disorders. Recent studies reveal the novel regulatory role of FcgammaR in the development of collagen-induced arthritis (CIA), an animal model relevant to human rheumatoid arthritis (RA). This review provides an overview of FcgammaRIIB-mediated immune regulation, highlighting the implication of FcgammaRIIB in the selection of peripheral B cell development during the CIA course.
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Affiliation(s)
- Akira Nakamura
- Department of Experimental Immunology and CREST program of Japan Science and Technology Agency, Institute of Development, Aging and Cancer, Tohoku University, Seiryo 4-1, Sendai 980-8575, Japan
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129
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Guo S, Ferl GZ, Deora R, Riedinger M, Yin S, Kerwin JL, Loo JA, Witte ON. A phosphorylation site in Bruton's tyrosine kinase selectively regulates B cell calcium signaling efficiency by altering phospholipase C-gamma activation. Proc Natl Acad Sci U S A 2004; 101:14180-5. [PMID: 15375214 PMCID: PMC521099 DOI: 10.1073/pnas.0405878101] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Loss of function of Bruton's tyrosine kinase (Btk) causes X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency in mice (xid). By using MS analysis and phosphopeptide-specific antibodies, we identified a tyrosine phosphorylation site (Y617) near the carboxyl terminus of the Btk domain from Btk expressed in 293T as well as DT-40 cells. Y617 is conserved in all Tec family kinases except murine Tec. Replacement of Y617 with a negatively charged glutamic acid (E) suppressed Btk-mediated phospholipase Cgamma2 activation and calcium response in DT-40 cells, whereas Akt activation was not affected. The Btk Y617E mutant could partially restore conventional B cell development and proliferation in Btk(-)/Tec(-) mice but failed to rescue CD5(+) B-1 cell development and the TI-II immune response to 2,4,6,-trinitrophenyl-Ficoll. These data suggest that Y617 phosphorylation or a negative charge at this site may down-regulate the function of Btk by selectively suppressing the B cell calcium signaling pathway.
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Affiliation(s)
- Shuling Guo
- Department of Microbiology, Immunology, and Molecular Genetics and Howard Hughes Medical Institute, University of California, Los Angeles, CA 90095, USA
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130
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Humphries LA, Dangelmaier C, Sommer K, Kipp K, Kato RM, Griffith N, Bakman I, Turk CW, Daniel JL, Rawlings DJ. Tec Kinases Mediate Sustained Calcium Influx via Site-specific Tyrosine Phosphorylation of the Phospholipase Cγ Src Homology 2-Src Homology 3 Linker. J Biol Chem 2004; 279:37651-61. [PMID: 15184383 DOI: 10.1074/jbc.m311985200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tyrosine phosphorylation of phospholipase Cgamma2 (PLCgamma2) is a crucial activation switch that initiates and maintains intracellular calcium mobilization in response to B cell antigen receptor (BCR) engagement. Although members from three distinct families of non-receptor tyrosine kinases can phosphorylate PLCgamma in vitro, the specific kinase(s) controlling BCR-dependent PLCgamma activation in vivo remains unknown. Bruton's tyrosine kinase (Btk)-deficient human B cells exhibit diminished inositol 1,4,5-trisphosphate production and calcium signaling despite a normal inducible level of total PLCgamma2 tyrosine phosphorylation. This suggested that Btk might modify a critical subset of residues essential for PLCgamma2 activity. To evaluate this hypothesis, we generated site-specific phosphotyrosine antibodies recognizing four putative regulatory residues within PLCgamma2. Whereas all four sites were rapidly modified in response to BCR engagement in normal B cells, Btk-deficient B cells exhibited a marked reduction in phosphorylation of the Src homology 2 (SH2)-SH3 linker region sites, Tyr(753) and Tyr(759). Phosphorylation of both sites was restored by expression of Tec, but not Syk, family kinases. In contrast, phosphorylation of the PLCgamma2 carboxyl-terminal sites, Tyr(1197) and Tyr(1217), was unaffected by the absence of functional Btk. Together, these data support a model whereby Btk/Tec kinases control sustained calcium signaling via site-specific phosphorylation of key residues within the PLCgamma2 SH2-SH3 linker.
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Affiliation(s)
- Lisa A Humphries
- Molecular Biology Institute and Department of Microbiology and Immunology, UCLA, Los Angeles, California 90095, USA
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131
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Yu PW, Tabuchi RS, Kato RM, Astrakhan A, Humblet-Baron S, Kipp K, Chae K, Ellmeier W, Witte ON, Rawlings DJ. Sustained correction of B-cell development and function in a murine model of X-linked agammaglobulinemia (XLA) using retroviral-mediated gene transfer. Blood 2004; 104:1281-90. [PMID: 15142874 DOI: 10.1182/blood-2003-09-3044] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Abstract
X-linked agammaglobulinemia (XLA) is a human immunodeficiency caused by mutations in Bruton tyrosine kinase (Btk) and characterized by an arrest in early B-cell development, near absence of serum immunoglobulin, and recurrent bacterial infections. Using Btk- and Tec-deficient mice (BtkTec–/–) as a model for XLA, we determined if Btk gene therapy could correct this disorder. Bone marrow (BM) from 5-fluorouracil (5FU)–treated BtkTec–/– mice was transduced with a retroviral vector expressing human Btk and transplanted into BtkTec–/– recipients. Mice engrafted with transduced hematopoietic cells exhibited rescue of both primary and peripheral B-lineage development, recovery of peritoneal B1 B cells, and correction of serum immunoglobulin M (IgM) and IgG3 levels. Gene transfer also restored T-independent type II immune responses, and B-cell antigen receptor (BCR) proliferative responses. B-cell progenitors derived from Btk-transduced stem cells exhibited higher levels of Btk expression than non-B cells; and marking studies demonstrated a selective advantage for Btk-transduced B-lineage cells. BM derived from primary recipients also rescued Btk-dependent function in secondary hosts that had received a transplant. Together, these data demonstrate that gene transfer into hematopoietic stem cells can reconstitute Btk-dependent B-cell development and function in vivo, and strongly support the feasibility of pursuing Btk gene transfer for XLA.
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Affiliation(s)
- Phyllis W Yu
- Children's Hospital and Regional Medical Center, 307 Westlake Ave North, Suite 300, Seattle, WA 98109, USA
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132
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Middendorp S, Zijlstra AJE, Kersseboom R, Dingjan GM, Jumaa H, Hendriks RW. Tumor suppressor function of Bruton tyrosine kinase is independent of its catalytic activity. Blood 2004; 105:259-65. [PMID: 15331445 DOI: 10.1182/blood-2004-07-2708] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During B-cell development in the mouse, Bruton tyrosine kinase (Btk) and the adaptor protein SLP-65 (Src homology 2 [SH2] domain-containing leukocyte protein of 65 kDa) limit the expansion and promote the differentiation of pre-B cells. Btk is thought to mainly function by phosphorylating phospholipase Cgamma2, which is brought into close proximity of Btk by SLP-65. However, this model was recently challenged by the identification of a role for Btk as a tumor suppressor in the absence of SLP-65 and by the finding that Btk function is partially independent of its kinase activity. To investigate if enzymatic activity is critical for the tumor suppressor function of Btk, we crossed transgenic mice expressing the kinase-inactive K430R-Btk mutant onto a Btk/SLP-65 double-deficient background. We found that K430R-Btk expression rescued the severe developmental arrest at the pre-B-cell stage in Btk/SLP-65 double-deficient mice. Moreover, K430R-Btk could functionally replace wild-type Btk as a tumor suppressor in SLP-65- mice: at 6 months of age, the observed pre-B-cell lymphoma frequencies were approximately 15% for SLP-65- mice, 44% for Btk/SLP-65-deficient mice, and 14% for K430R-Btk transgenic mice on the Btk/SLP-65-deficient background. Therefore, we conclude that Btk exerts its tumor suppressor function in pre-B cells as an adaptor protein, independent of its catalytic activity.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Agammaglobulinaemia Tyrosine Kinase
- Animals
- B-Lymphocytes/immunology
- B-Lymphocytes/metabolism
- B-Lymphocytes/pathology
- Calcium/metabolism
- Calcium Signaling
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Catalysis
- Cell Differentiation
- Cells, Cultured
- Immunoglobulin G/blood
- Immunoglobulin G/immunology
- Lymphoma, B-Cell/enzymology
- Lymphoma, B-Cell/genetics
- Lymphoma, B-Cell/metabolism
- Lymphoma, B-Cell/pathology
- Lysine/genetics
- Lysine/metabolism
- Mice
- Mice, Knockout
- Mice, Transgenic
- Phosphoproteins/deficiency
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- Phosphotyrosine/metabolism
- Protein-Tyrosine Kinases/deficiency
- Protein-Tyrosine Kinases/genetics
- Protein-Tyrosine Kinases/metabolism
- Receptors, Antigen, B-Cell/metabolism
- Survival Rate
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Affiliation(s)
- Sabine Middendorp
- Department of Immunology, Erasmus MC Rotterdam, Rotterdam, The Netherlands
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133
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Kraft S, Rana S, Jouvin MH, Kinet JP. The role of the FcepsilonRI beta-chain in allergic diseases. Int Arch Allergy Immunol 2004; 135:62-72. [PMID: 15316148 DOI: 10.1159/000080231] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The high affinity receptor for IgE, FcepsilonRI, is a multimeric surface receptor that is expressed exclusively as a tetramer on rodent cells, but exists as a tetramer or trimer on human cells. The tetrameric form is expressed on effector cells of allergic responses such as mast cells and basophils and is composed of an IgE-binding alpha-subunit, a beta-subunit and a gamma-subunit dimer. Complexes lacking the beta-subunit are found on human antigen-presenting cells. On mast cells and basophils, FcepsilonRI is essential for IgE-mediated acute allergic reactions. Crosslinking of FcepsilonRI by IgE and multivalent antigen induces a signaling cascade that culminates in the release of preformed mediators and the synthesis of lipid mediators and cytokines. The beta-subunit functions as an amplifier of FcepsilonRI expression and signaling. As a consequence, strongly enhanced mast cell effector functions and in vivo allergic reactions can be observed in the presence of FcepsilonRIbeta. In contrast, a truncated beta-isoform (betaT) that is produced by alternative splicing acts as an inhibitor of FcepsilonRI surface expression. Thus, by producing two proteins with antagonistic functions, the FcepsilonRIbeta gene could serve as a potent regulator of allergic responses. In addition, the genomic region encompassing the beta-chain has been linked to atopy and a number of polymorphisms within the FcepsilonRIbeta gene are associated with various atopic diseases. It remains to be elucidated how these polymorphisms might affect the allergic phenotype. These functions of the beta-chain together with the described genetic linkages to atopy make it a candidate for a role in the pathophysiology of allergic diseases.
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Affiliation(s)
- Stefan Kraft
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA
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134
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Allam A, Niiro H, Clark EA, Marshall AJ. The adaptor protein Bam32 regulates Rac1 activation and actin remodeling through a phosphorylation-dependent mechanism. J Biol Chem 2004; 279:39775-82. [PMID: 15247305 DOI: 10.1074/jbc.m403367200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The B cell adaptor molecule of 32 kDa (Bam32) is an adaptor that links the B cell antigen receptor (BCR) to ERK and JNK activation and ultimately to mitogenesis. After BCR cross-linking, Bam32 is recruited to the plasma membrane and accumulates within F-actin-rich membrane ruffles. Bam32 contains one Src homology 2 and one pleckstrin homology domain and is phosphorylated at a single site, tyrosine 139. To define the function of Bam32 in membrane-proximal signaling events, we established human B cell lines overexpressing wild-type or mutant Bam32 proteins. The basal level of F-actin increased in cells expressing wild-type or myristoylated Bam32 but decreased in cells expressing either an Src homology-2 or Tyr-139 Bam32 mutant. Overexpression of wild-type Bam32 also affected BCR-induced actin remodeling, which was visualized as increases in F-actin-rich membrane ruffles. In contrast, Bam32 mutants largely blocked the BCR-induced increase in cellular F-actin. The positive and negative effects of Bam32 variants on F-actin levels were closely mirrored by their effects on the activation of the GTPase Rac1, which is known to regulate actin remodeling in lymphocytes. Bam32-deficient DT40 B cells showed decreased Rac1 activation and a failure of Rac1 to co-localize with the BCR, whereas cells overexpressing Bam32 had increased constitutive Rac1 activation. These results suggest that Bam32 regulates the cytoskeleton through Rac1. Bam32 variants also affected downstream signaling to JNK in a manner similar to that of Rac1, suggesting that the effect of Bam32 on JNK activation may be at least partially mediated through Rac1. Our results demonstrate a novel phosphorylation-dependent function of Bam32 in regulating Rac1 activation and actin remodeling.
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Affiliation(s)
- Atef Allam
- Department of Immunology, University of Manitoba, Winnipeg, Manitoba R3E 0W3, Canada
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135
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Garçon F, Bismuth G, Isnardon D, Olive D, Nunès JA. Tec Kinase Migrates to the T Cell-APC Interface Independently of Its Pleckstrin Homology Domain. THE JOURNAL OF IMMUNOLOGY 2004; 173:770-5. [PMID: 15240663 DOI: 10.4049/jimmunol.173.2.770] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Tec is the prototypical member of the Tec tyrosine kinases family, which plays an important role in T cell signaling. We show in this study that Tec translocates to the immunological synapse when a T cell contacts a dendritic cell. Surprisingly, the presence of the pleckstrin homology (PH) domain of Tec is not required for this accumulation, and despite a strong activation of 3'-phosphorylated phosphoinositide lipids synthesis during the synapse formation, the Tec PH domain is not redistributed to the T cell plasma membrane. In contrast, we demonstrate that an active Src homology 3 domain is absolutely required, underlining the essential role played by this part of the molecule in the recruitment and/or stabilization of Tec at the immunological synapse. Our results nevertheless suggest that the PH domain controls the kinase activity of the molecule in vivo. We finally demonstrate that the two domains are necessary to trigger transcriptional events following Ag presentation. These data support a model in which the plasma membrane recruitment of the PH-containing protein Tec is not dependent on the production of 3'-phosphorylated phosphoinositide lipids by the PI3K, but rather on an intact Src homology 3 domain.
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Affiliation(s)
- Fabien Garçon
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 599, Université de la Méditerranée, Marseille, France
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136
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Bednarski JJ, Lyssiotis CA, Roush R, Boitano AE, Glick GD, Opipari AW. A Novel Benzodiazepine Increases the Sensitivity of B Cells to Receptor Stimulation with Synergistic Effects on Calcium Signaling and Apoptosis. J Biol Chem 2004; 279:29615-21. [PMID: 15123639 DOI: 10.1074/jbc.m403507200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bz-423 is a 1,4-benzodiazepine with selective lymphotoxic properties and potent therapeutic activity against lupus-like disease in autoimmune mice. In NZB/W lupus-prone mice, Bz-423 specifically kills germinal center B cells, which are the cells that drive disease both in this model and in human systemic lupus erythematosus. In this report, the mechanistic basis for the selective action of Bz-423 is investigated. We show that Bz-423-induces superoxide as an immediate early response and that this reactive oxygen species is more effective as a second messenger death signal in B cells activated by B cell receptor stimulation compared with resting cells. As a result, low [Bz-423] that are not cytotoxic to non-stimulated cells kill stimulated cells in synergy with anti-immunoglobulin M antibodies. Subsequent experiments demonstrated that Bz-423 extends the rise in intracellular calcium that accompanies anti-immunoglobulin M stimulation, and this effect mediates the synergistic death response. Because B cell hyperactivation and altered calcium signaling is a distinguishing feature of autoreactive lymphocytes in lupus, the mechanism by which Bz-423 induces apoptosis preferentially targets disease-causing cells on the basis of their activation state. Thus, molecules like Bz-423 could form the basis for new and selective anti-lupus agents.
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Affiliation(s)
- Jeffrey J Bednarski
- Departments of Chemistry and Obstetrics and Gynecology, University of Michigan, Ann Arbor, Michigan 48109, USA
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137
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Blois JT, Mataraza JM, Mecklenbraüker I, Tarakhovsky A, Chiles TC. B cell receptor-induced cAMP-response element-binding protein activation in B lymphocytes requires novel protein kinase Cdelta. J Biol Chem 2004; 279:30123-32. [PMID: 15138267 DOI: 10.1074/jbc.m402793200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cAMP-response element-binding protein (CREB) is activated by phosphorylation on Ser-133 and plays a key role in the proliferative and survival responses of mature B cells to B cell receptor (BCR) signaling. The signal link between the BCR and CREB activation depends on a phorbol ester (phorbol 12-myristate 13-acetate)-sensitive protein kinase C (PKC) activity and not protein kinase A or calmodulin kinase; however, the identity and role of the PKC(s) activity has not been elucidated. We found the novel PKCdelta (nPKCdelta) activator bistratene A is sufficient to induce CREB phosphorylation in murine splenic B cells. The pharmacological inhibitor Gö6976, which targets conventional PKCs and PKCmu, has no effect on CREB phosphorylation, whereas the nPKCdelta inhibitor rottlerin blocks CREB phosphorylation following BCR cross-linking. Bryostatin 1 selectively prevents nPKCdelta depletion by phorbol 12-myristate 13-acetate when coapplied, coincident with protection of BCR-induced CREB phosphorylation. Ectopic expression of a kinase-inactive nPKCdelta blocks BCR-induced CREB phosphorylation in A20 B cells. In addition, BCR-induced CREB phosphorylation is significantly diminished in nPKCdelta-deficient splenic B cells in comparison with wild type mice. Consistent with the essential role for Bruton's tyrosine kinase and phospholipase Cgamma2 in mediating PKC activation, Bruton's tyrosine kinase- and phospholipase Cgamma2-deficient B cells display defective CREB phosphorylation by the BCR. We also found that p90 RSK directly phosphorylates CREB on Ser-133 following BCR cross-linking and is positioned downstream of nPKCdelta. Taken together, these results suggest a model in which BCR engagement leads to the phosphorylation of CREB via a signaling pathway that requires nPKCdelta and p90 RSK in mature B cells.
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Affiliation(s)
- Joseph T Blois
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467, USA
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138
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Schmidt U, Boucheron N, Unger B, Ellmeier W. The role of Tec family kinases in myeloid cells. Int Arch Allergy Immunol 2004; 134:65-78. [PMID: 15133303 DOI: 10.1159/000078339] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Members of the Tec kinase family (Bmx, Btk, Itk, Rlk and Tec) are primarily expressed in the hematopoietic system and form, after the Src kinase family, the second largest class of non-receptor protein tyrosine kinases. During lymphocyte development and activation Tec kinases have important functions in signaling pathways downstream of the antigen receptors. Tec family kinases are also expressed in cells of the myeloid lineage. However, with the exception of mast cells and platelets, their biological role in the myeloid system is only poorly understood. This review summarizes the current knowledge about the function of Tec family kinases in hematopoietic cells of the myeloid lineage.
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Affiliation(s)
- Uwe Schmidt
- Medical University of Vienna, Institute of Immunology, Vienna, Austria
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139
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Tomlinson MG, Kane LP, Su J, Kadlecek TA, Mollenauer MN, Weiss A. Expression and function of Tec, Itk, and Btk in lymphocytes: evidence for a unique role for Tec. Mol Cell Biol 2004; 24:2455-66. [PMID: 14993283 PMCID: PMC355844 DOI: 10.1128/mcb.24.6.2455-2466.2004] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Tec protein tyrosine kinase is the founding member of a family that includes Btk, Itk, Bmx, and Txk. Btk is essential for B-cell receptor signaling, because mutations in Btk are responsible for X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (xid) in mice, whereas Itk is involved in T-cell receptor signaling. Tec is expressed in both T and B cells, but its role in antigen receptor signaling is not clear. In this study, we show that Tec protein is expressed at substantially lower levels in primary T and B cells relative to Itk and Btk, respectively. However, Tec is up-regulated upon T-cell activation and in Th1 and Th2 cells. In functional experiments that mimic Tec up-regulation, we find that Tec overexpression in lymphocyte cell lines is sufficient to induce phospholipase Cgamma (PLC-gamma) phosphorylation and NFAT (nuclear factor of activated T cells) activation. In contrast, overexpression of Btk, Itk, or Bmx does not induce NFAT activation. Tec-induced NFAT activation requires PLC-gamma, but not the adapters LAT, SLP-76, and BLNK, which are required for Btk and Itk to couple to PLC-gamma. Finally, we show that the unique effector function for Tec correlates with a unique subcellular localization. We hypothesize that Tec functions in activated and effector T lymphocytes to induce the expression of genes regulated by NFAT transcription factors.
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Affiliation(s)
- Michael G Tomlinson
- Department of Medicine and Howard Hughes Medical Institute, University of California, San Francisco, California 94143, USA
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140
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Krahn AK, Ma K, Hou S, Duronio V, Marshall AJ. Two distinct waves of membrane-proximal B cell antigen receptor signaling differentially regulated by Src homology 2-containing inositol polyphosphate 5-phosphatase. THE JOURNAL OF IMMUNOLOGY 2004; 172:331-9. [PMID: 14688341 DOI: 10.4049/jimmunol.172.1.331] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The phosphatidylinositol 3-kinase (PI3K) pathway plays a critical role in B cell activation and differentiation. Recruitment of pleckstrin homology (PH) domain-containing signal transduction proteins to the plasma membrane through binding to 3-phosphoinositide second messengers represents a major effector mechanism for PI3Ks. We have found that the PH domains of Bam32 and tandem PH domain-containing protein 2 (TAPP2) specify a temporally distinct wave of membrane recruitment compared with that of Bruton's tyrosine kinase (Btk), with recruitment of these two adaptors representing a later stage of the response. In this study we provide direct evidence that PH domain-dependent recruitment of Btk to the membrane is blocked by coligation of the inhibitory receptor FcgammaRII in human B lymphoma cells. In contrast, recruitment specified by the Bam32 or TAPP2 PH domains is completely insensitive to FcgammaRII inhibition. This differential regulation can be accounted for by Src homology 2-containing inositol polyphosphate 5-phosphatase (SHIP) activity alone, as expression of membrane-targeted SHIP completely abrogated Btk recruitment, but had no inhibitory effect on Bam32 or TAPP2 recruitment. Strikingly, kinetic analysis revealed that membrane recruitment of Bam32 and TAPP2 is actually more rapid under "inhibitory" signaling conditions. Analysis of 3-phosphoinositide generation under activating and inhibitory signaling conditions indicated that recruitment of Bam32 and TAPP2 is inversely correlated with the SHIP substrate/product ratio (phosphatidylinositol 3,4,5-trisphosphate/phosphatidylinositol 3,4-bisphosphate). Overexpression of TAPP2 in B cells led to an increase in the sustained phase of the calcium response and increased NF-AT-dependent transcriptional activation after B cell Ag receptor ligation. Together, these results suggest that Bam32 and TAPP2 adaptors define a novel group of SHIP-activated targets of PI3K that regulate B cell Ag receptor signaling.
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Affiliation(s)
- Allyson K Krahn
- Department of Immunology, University of Manitoba, 730 William Avenue, Winnipeg, Manitoba, Canada R3E 0W3
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141
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Maeda-Yamamoto M, Inagaki N, Kitaura J, Chikumoto T, Kawahara H, Kawakami Y, Sano M, Miyase T, Tachibana H, Nagai H, Kawakami T. O-Methylated Catechins from Tea Leaves Inhibit Multiple Protein Kinases in Mast Cells. THE JOURNAL OF IMMUNOLOGY 2004; 172:4486-92. [PMID: 15034065 DOI: 10.4049/jimmunol.172.7.4486] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Tea contains a variety of bioactive compounds. In this study, we show that two O-methylated catechins, (-)-epigallocatechin-3-O-(3-O-methyl) gallate and (-)-epigallocatechin-3-O-(4-O-methyl) gallate, inhibit in vivo mast cell-dependent allergic reactions more potently than their nonmethylated form, (-)-epigallocatechin-3-O-gallate. Consistent with this, these O-methylated catechins inhibit IgE/Ag-induced activation of mouse mast cells: histamine release, leukotriene release, and cytokine production and secretion were all inhibited. As a molecular basis for the catechin-mediated inhibition of mast cell activation, Lyn, Syk, and Bruton's tyrosine kinase, the protein tyrosine kinases, known to be critical for early activation events, are shown to be inhibited by the O-methylated catechins. In vitro kinase assays using purified proteins show that the O-methylated catechins can directly inhibit the above protein tyrosine kinases. These catechins inhibit IgE/Ag-induced calcium response as well as the activation of downstream serine/threonine kinases such as Akt and c-Jun N-terminal kinase. These observations for the first time have revealed the molecular mechanisms of antiallergic effects of tea-derived catechins.
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Affiliation(s)
- Mari Maeda-Yamamoto
- National Institute of Vegetable and Tea Science, National Agriculture Research Organization, and School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
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142
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Nixon JC, Rajaiya JB, Ayers N, Evetts S, Webb CF. The transcription factor, Bright, is not expressed in all human B lymphocyte subpopulations. Cell Immunol 2004; 228:42-53. [PMID: 15203319 DOI: 10.1016/j.cellimm.2004.03.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2003] [Accepted: 03/21/2004] [Indexed: 01/23/2023]
Abstract
Bright is an ARID family transcription factor that increases immunoglobulin heavy chain transcription. In the mouse, Bright expression is tightly regulated and B cell-restricted and the Bright protein associates with Bruton's tyrosine kinase (Btk), the defective enzyme in X-linked immunodeficiency. Human X-linked agammaglobulinemia results from defects in Btk and leads to early blocks in B lymphocyte development. Because so little is known about human Bright, we sought to determine where human Bright is expressed in normal B cell differentiation and whether it also forms complexes with Btk. Although human and mouse Bright exhibited similar expression patterns in normal B cells, many human transformed B cell lines did not express Bright protein. However, the human protein bound prototypic Bright DNA-binding motifs and, like mouse Bright, was capable of associating with Btk. These data suggest potentially important similarities exist in Bright expression and activity in human and mouse B lymphocytes.
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Affiliation(s)
- Jamee C Nixon
- Department of Microbiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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143
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Bonvini E, DeBell KE, Verí MC, Graham L, Stoica B, Laborda J, Aman MJ, DiBaldassarre A, Miscia S, Rellahan BL. On the mechanism coupling phospholipase Cgamma1 to the B- and T-cell antigen receptors. ADVANCES IN ENZYME REGULATION 2004; 43:245-69. [PMID: 12791395 DOI: 10.1016/s0065-2571(02)00033-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Ezio Bonvini
- Division of Monoclonal Antibodies, Center for Biologics Evaluation & Research, US-FDA, HFM-564, NIH Campus, Bldg.29B/Rm.3NN10, 8800 Rockville Pike, Bethesda, MD 20892, USA.
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144
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Saito K, Tolias KF, Saci A, Koon HB, Humphries LA, Scharenberg A, Rawlings DJ, Kinet JP, Carpenter CL. BTK regulates PtdIns-4,5-P2 synthesis: importance for calcium signaling and PI3K activity. Immunity 2003; 19:669-78. [PMID: 14614854 DOI: 10.1016/s1074-7613(03)00297-8] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Intracellular signaling by most cell surface receptors requires the generation of two major second messengers, phosphatidylinositol-3,4,5-trisphosphate (PtdIns-3,4,5-P3) and inositol-1,4,5-trisphosphate (IP3). The enzymes that produce these second messengers, phosphoinositide 3-kinase (PI3K) and phospholipase C (PLC), utilize a common substrate, phosphatidylinositol-4,5-bisphosphate (PtdIns-4,5-P2). Until now, it has not been clear whether de novo PtdIns-4,5-P2 synthesis is necessary for PtdIns-3,4,5-P3 and IP3 production. Here we show that BTK, a member of the Tec family of cytoplasmic protein tyrosine kinases, associates with phosphatidylinositol-4-phosphate 5-kinases (PIP5Ks), the enzymes that synthesize PtdIns-4,5-P2. Upon B cell receptor activation, BTK brings PIP5K to the plasma membrane as a means of generating local PtdIns-4,5-P2 synthesis. This enzyme-enzyme interaction provides a shuttling mechanism that allows BTK to stimulate the production of the substrate required by both its upstream activator, PI3K, and its downstream target, PLC-gamma2.
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Affiliation(s)
- Kan Saito
- Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA
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145
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Abstract
The Tec family kinase Btk plays an important role in the regulation of phospholipase C gamma 2 (PLC gamma 2) downstream of the collagen receptor glycoprotein VI (GPVI) in human platelets. Platelets also express a second member of this family, Tec; however, its function has not been analyzed. To address the role of Tec, we analyzed Btk-/-, Tec-/-, and Btk/Tec double-deficient (Btk-/-/Tec-/-) platelets. Tec-/- platelets exhibit a minor reduction in aggregation to threshold concentrations of collagen or the GPVI-specific agonist collagen-related peptide (CRP), whereas responses to higher concentrations are normal. Tyrosine phosphorylation of PLC gamma 2 by collagen and CRP is not altered in Tec-/- platelets. However, Btk-/-/Tec-/- platelets exhibit a greater reduction in PLC gamma 2 phosphorylation than is seen in the absence of Btk, thus revealing an important role for Tec in this situation. Furthermore, Btk-/-/Tec-/- platelets fail to undergo an increase in Ca2+, aggregation, secretion, and spreading in response to collagen or CRP, whereas they aggregate normally to adenosine diphosphate (ADP) and spread on fibrinogen. A residual GPVI signal exists in the Btk-/-/Tec-/- platelets as CRP synergizes with ADP to mediate aggregation. These results demonstrate an essential requirement for Tec and Btk in platelet activation by GPVI and reveal a functional role for Tec in the regulation of PLC gamma 2 in the absence of Btk.
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Affiliation(s)
- Ben T Atkinson
- Department of Pharmacology, University of Oxford, Mansfield Rd, Oxford, OX1 3QT, United Kingdom.
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146
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Spaargaren M, Beuling EA, Rurup ML, Meijer HP, Klok MD, Middendorp S, Hendriks RW, Pals ST. The B cell antigen receptor controls integrin activity through Btk and PLCgamma2. ACTA ACUST UNITED AC 2003; 198:1539-50. [PMID: 14610042 PMCID: PMC2194118 DOI: 10.1084/jem.20011866] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Integrin-mediated adhesion and B cell antigen receptor (BCR) signaling play a critical role in B cell development and function, including antigen-specific B cell differentiation. Here we show that the BCR controls integrin α4β1 (VLA-4)-mediated adhesion of B cells to vascular cell adhesion molecule-1 and fibronectin. Molecular dissection of the underlying signaling mechanism by a combined biochemical, pharmacological, and genetic approach demonstrates that this BCR-controlled integrin-mediated adhesion requires the (consecutive) activation of Lyn, Syk, phosphatidylinositol 3-kinase, Bruton's tyrosine kinase (Btk), phospholipase C (PLC)γ2, IP3R-mediated Ca2+ release, and PKC. In contrast, activation of mitogen-activated protein kinase kinase (MEK) or extracellular signal–regulated kinase (ERK) is not required, and simultaneous activation of MEK, ERK, and PKB is not sufficient either. Furthermore, Btk is also involved in the control of integrin-mediated adhesion of preB cells. The control of integrin α4β1-mediated B cell adhesion by the BCR involves cytoskeletal reorganization and integrin clustering. These results reveal a novel function for the BCR and Btk, i.e., regulation of integrin α4β1 activity, thereby providing new insights into the control of B cell development and differentiation, as well as into the pathogenesis of the immunodeficiency disease X-linked agammaglobulineamia (XLA).
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Affiliation(s)
- Marcel Spaargaren
- Dept. of Pathology, Academic Medical Center, Meibergdreef 9 1105 AZ Amsterdam, Netherlands.
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147
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Abstract
The Tec kinase Btk is an important regulator of antigen receptor activation of phospholipase C-gamma (PLC-gamma). Data from Carpenter and colleagues (Saito et al., this issue of Immunity) now suggest that Btk also activates phosphatidylinositol-4-phosphate 5-kinase (PIP5K), thereby stimulating a positive feedback loop that generates PI(4,5)P2, the substrate for both phosphoinositide 3-kinase (PI3K) and PLC-gamma.
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Affiliation(s)
- Pamela L Schwartzberg
- National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
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148
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Antony P, Petro JB, Carlesso G, Shinners NP, Lowe J, Khan WN. B Cell receptor directs the activation of NFAT and NF-κB via distinct molecular mechanisms. Exp Cell Res 2003; 291:11-24. [PMID: 14597404 DOI: 10.1016/s0014-4827(03)00338-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BCR engagement initiates intracellular calcium ([Ca2+]i) mobilization which is critical for the activation of multiple transcription factors including NF-kappaB and NFAT. Previously, we showed that Bruton's tyrosine kinase (BTK)-deficient (btk-/-) B cells, which display a modestly reduced calcium response to BCR crosslinking, do not activate NF-kappaB. Here we show that BTK is also essential for the activation of NFAT following BCR engagement. Pharmacological mobilization of [Ca2+]i in BTK-deficient DT40 B cells (DT40.BTK) does not rescue BCR directed activation of NF-kappaB and only partially that of NFAT, suggesting existence of additional BTK-signaling pathways in this process. Therefore, we investigated a requirement for BTK in the production of diacylglycerol (DAG). We found that DT40.BTK B cells do not produce DAG in response to BCR engagement. Pharmacological inhibition of PKC isozymes and Ras revealed that the BCR-induced activation of NF-kappaB requires conventional PKCbeta, whereas that of NFAT may involve non-conventional PKCdelta and Ras pathways. Consistent with an essential role for BTK in the regulation of NFAT, B cells from btk-/- mice display defective expression of CD5, a gene under the control of NFAT. Together, these results suggest that BCR employs distinct BTK-dependent molecular mechanisms to regulate the activation of NF-kappaB versus NFAT.
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Affiliation(s)
- Pierre Antony
- Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA
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149
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Pribila JT, Shimizu Y. Signal transduction events regulating integrin function and T cell migration: new functions and complexity. Immunol Res 2003; 27:107-28. [PMID: 12637771 DOI: 10.1385/ir:27:1:107] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Integrin receptors facilitate T cell function by mediating adhesive events critical for T cell trafficking and recognition of foreign antigen, including interactions with vascular endothelium, extracellular matrix components, and antigen-presenting cells. Consequently, the functional activity of integrin receptors is acutely regulated by various intracellular signals delivered by other cell surface receptors, resulting in rapid changes in T cell adhesion and migration. This review highlights recent insights into our understanding of the signaling events by which the CD3/T cell receptor complex and chemokine receptors regulate integrin function and T cell migration. These studies highlight novel functions for several signaling molecules, including the tyrosine kinases Itk and ZAP-70, and the adapter protein SLAP-130/Fyb. In addition, analysis of the regulation of integrin function and chemokine-mediated migration has highlighted the critical role that spatial localization of signaling molecules plays in signal transduction, and the importance of the actin cytoskeleton in T cell function.
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Affiliation(s)
- Jonathan T Pribila
- Department of Laboratory Medicine and Pathology, Center for Immunology, Cancer Center, University of Minnesota Medical School, Minneapolis, MN 55455, USA
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Wilcox HM, Berg LJ. Itk phosphorylation sites are required for functional activity in primary T cells. J Biol Chem 2003; 278:37112-21. [PMID: 12842872 DOI: 10.1074/jbc.m304811200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Tec family kinase Itk plays a critical role in signal transduction downstream of the T cell antigen receptor and has been implicated in the activation of phospholipase C-gamma1, a key regulator of calcium mobilization and extracellular signal-regulated kinase (ERK) activation. We have shown previously that Itk is regulated by an activating transphosphorylation event in which Tyr-511 in the kinase domain is phosphorylated by Lck (Heyeck, S. D., Wilcox, H. M., Bunnell, S. C., and Berg, L. J. (1997) J. Biol. Chem. 272, 25401-25408). In this study, we present evidence for another mode of regulation for Itk, the autophosphorylation of Tyr-180 in the Src homology 3 (SH3) domain. To investigate the role of Itk trans- and autophosphorylation in T cell signaling, a retroviral transduction system was used to introduce different versions of Itk into Itk-deficient primary T cells. We report that Itk mutated at either the trans- or the autophosphorylation site is unable to fully restore cytokine production and ERK activation in the Itk-deficient cells; Itk-Y511F is severely defective, whereas Itk-Y180F has partial activity. Because phosphorylation at Tyr-180 is predicted to interfere with ligand binding by the SH3 domain, an SH3 point mutant that cannot bind ligand was also examined and found to be unable to restore function to the Itk-/- cells. These data provide new insights into the complex regulation of Itk in primary T cells.
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Affiliation(s)
- Heather M Wilcox
- Division of Medical Sciences, Harvard University, Cambridge, Massachusetts, USA
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