1
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Nowacka A, Getz AM, Bessa-Neto D, Choquet D. Activity-dependent diffusion trapping of AMPA receptors as a key step for expression of early LTP. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230220. [PMID: 38853553 DOI: 10.1098/rstb.2023.0220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2024] [Accepted: 04/11/2024] [Indexed: 06/11/2024] Open
Abstract
This review focuses on the activity-dependent diffusion trapping of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) as a crucial mechanism for the expression of early long-term potentiation (LTP), a process central to learning and memory. Despite decades of research, the precise mechanisms by which LTP induction leads to an increase in AMPAR responses at synapses have been elusive. We review the different hypotheses that have been put forward to explain the increased AMPAR responsiveness during LTP. We discuss the dynamic nature of AMPAR complexes, including their constant turnover and activity-dependent modifications that affect their synaptic accumulation. We highlight a hypothesis suggesting that AMPARs are diffusively trapped at synapses through activity-dependent interactions with protein-based binding slots in the post-synaptic density (PSD), offering a potential explanation for the increased synaptic strength during LTP. Furthermore, we outline the challenges still to be addressed before we fully understand the functional roles and molecular mechanisms of AMPAR dynamic nanoscale organization in LTP. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.
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Affiliation(s)
- Agata Nowacka
- University of Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297 , Bordeaux F-33000, France
| | - Angela M Getz
- University of Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297 , Bordeaux F-33000, France
- University of Bordeaux, CNRS, INSERM, Bordeaux Imaging Center, BIC, UMS 3420, US 4 , Bordeaux F-33000, France
| | - Diogo Bessa-Neto
- University of Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297 , Bordeaux F-33000, France
| | - Daniel Choquet
- University of Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297 , Bordeaux F-33000, France
- University of Bordeaux, CNRS, INSERM, Bordeaux Imaging Center, BIC, UMS 3420, US 4 , Bordeaux F-33000, France
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2
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Lin H, Li S, Shu HB. The Membrane-Associated MARCH E3 Ligase Family: Emerging Roles in Immune Regulation. Front Immunol 2019; 10:1751. [PMID: 31404274 PMCID: PMC6669941 DOI: 10.3389/fimmu.2019.01751] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 07/10/2019] [Indexed: 01/13/2023] Open
Abstract
The membrane-associated RING-CH-type finger (MARCH) proteins of E3 ubiquitin ligases have emerged as critical regulators of immune responses. MARCH proteins target immune receptors, viral proteins as well as components in innate immune response for polyubiquitination and degradations via distinct routes. This review summarizes the current progress about MARCH proteins and their regulation on immune responses.
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Affiliation(s)
- Heng Lin
- Department of Infectious Diseases, Frontier Science Center for Immunology and Metabolism, Medical Research Institute, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Shu Li
- Department of Infectious Diseases, Frontier Science Center for Immunology and Metabolism, Medical Research Institute, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Hong-Bing Shu
- Department of Infectious Diseases, Frontier Science Center for Immunology and Metabolism, Medical Research Institute, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, China
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3
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Fatehchand K, Ren L, Elavazhagan S, Fang H, Mo X, Vasilakos JP, Dietsch GN, Hershberg RM, Tridandapani S, Butchar JP. Toll-like Receptor 4 Ligands Down-regulate Fcγ Receptor IIb (FcγRIIb) via MARCH3 Protein-mediated Ubiquitination. J Biol Chem 2015; 291:3895-904. [PMID: 26694610 DOI: 10.1074/jbc.m115.701151] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Indexed: 11/06/2022] Open
Abstract
Monocytes and macrophages are critical for the effectiveness of monoclonal antibody therapy. Responses to antibody-coated tumor cells are largely mediated by Fcγ receptors (FcγRs), which become activated upon binding to immune complexes. FcγRIIb is an inhibitory FcγR that negatively regulates these responses, and it is expressed on monocytes and macrophages. Therefore, deletion or down-regulation of this receptor may substantially enhance therapeutic outcomes. Here we screened a panel of Toll-like receptor (TLR) agonists and found that those selective for TLR4 and TLR8 could significantly down-regulate the expression of FcγRIIb. Upon further examination, we found that treatment of monocytes with TLR4 agonists could lead to the ubiquitination of FcγRIIb protein. A search of our earlier microarray database of monocytes activated with the TLR7/8 agonist R-848 (in which FcγRIIb was down-regulated) revealed an up-regulation of membrane-associated ring finger (C3HC4) 3 (MARCH3), an E3 ubiquitin ligase. Therefore, we tested whether LPS treatment could up-regulate MARCH3 in monocytes and whether this E3 ligase was involved with LPS-mediated FcγRIIb down-regulation. The results showed that LPS activation of TLR4 significantly increased MARCH3 expression and that siRNA against MARCH3 prevented the decrease in FcγRIIb following LPS treatment. These data suggest that activation of TLR4 on monocytes can induce a rapid down-regulation of FcγRIIb protein and that this involves ubiquitination.
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Affiliation(s)
| | - Li Ren
- the Key Laboratory for Molecular Enzymology and Engineering, Ministry of Education, Jilin University, Changchun, 130000 Jilin, China
| | | | | | - Xiaokui Mo
- Center for Biostatistics, Ohio State University, Columbus, Ohio 43210
| | - John P Vasilakos
- the 3M Drug Delivery Systems Division, St. Paul, Minnesota 55144, and
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4
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Abstract
Most biological activities of antibodies depend on their ability to engage Receptors for the Fc portion of immunoglobulins (FcRs) on a variety of cell types. As FcRs can trigger positive and negative signals, as these signals control several biological activities in individual cells, as FcRs are expressed by many cells of hematopoietic origin, mostly of the myeloid lineage, as these cells express various combinations of FcRs, and as FcR-expressing cells have different functional repertoires, antibodies can exert a wide spectrum of biological activities. Like B and T Cell Receptors (BCRs and TCRs), FcRs are bona fide immunoreceptors. Unlike BCRs and TCRs, however, FcRs are immunoreceptors with an adaptive specificity for antigen, with an adaptive affinity for antibodies, with an adaptive structure and with an adaptive signaling. They induce adaptive biological responses that depend on their tissue distribution and on FcR-expressing cells that are selected locally by antibodies. They critically determine health and disease. They are thus exquisitely adaptive therapeutic tools.
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Affiliation(s)
| | - Falk Nimmerjahn
- Department of Biology, Institute of Genetics, University of Erlangen-Nürnberg, Erlangen, Germany
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5
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Storch B, Meixlsperger S, Jumaa H. The Ig-alpha ITAM is required for efficient differentiation but not proliferation of pre-B cells. Eur J Immunol 2007; 37:252-60. [PMID: 17163454 DOI: 10.1002/eji.200636667] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Signals from the pre-B cell receptor (pre-BCR) mediated by the cytoplasmic tails of Ig-alpha/Ig-beta are essential for developing B cells. To analyze the role of Ig-alpha ITAM and non-ITAM tyrosines in pre-BCR signaling, we reconstituted individual tyrosine mutants of Ig-alpha in src homology 2 domain-containing leukocyte protein of 65 kDa (SLP-65)/Ig-alpha double-deficient pre-B cells. We show that the Ig-alpha mutants led to comparable pre-BCR expression on the cell surface, while the pre-BCR-induced tyrosine phosphorylation was different. We further show that the reconstitution of Ig-alpha and the resulting pre-BCR expression led to enrichment of the pre-BCR-expressing cells in vitro irrespective of the introduced Ig-alpha mutation. We show that, even though the enrichment rate increased by lowering the IL-7 concentration, residual amounts of IL-7 were required for optimal enrichment. Our results indicate that surface IL-7 receptor expression is modulated by the pre-BCR, thereby increasing the IL-7 sensitivity of the respective cells. In contrast to the comparable pre-B cell proliferation, however, the Ig-alpha mutants differed in their capacity to induce calcium flux and activate efficient pre-B cell differentiation. Together, our data suggest that ITAM tyrosines and Y204 are required for efficient pre-B cell differentiation but not proliferation.
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MESH Headings
- Adaptor Proteins, Signal Transducing/biosynthesis
- Adaptor Proteins, Signal Transducing/genetics
- Amino Acid Motifs/genetics
- Animals
- B-Lymphocyte Subsets/cytology
- B-Lymphocyte Subsets/immunology
- B-Lymphocyte Subsets/metabolism
- CD79 Antigens/deficiency
- CD79 Antigens/genetics
- CD79 Antigens/physiology
- Cell Differentiation/genetics
- Cell Differentiation/immunology
- Cell Proliferation
- Cells, Cultured
- Membrane Glycoproteins/biosynthesis
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/physiology
- Mice
- Mice, Inbred BALB C
- Mutagenesis, Site-Directed
- Phosphorylation
- Pre-B Cell Receptors
- Receptors, Antigen, B-Cell/biosynthesis
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/physiology
- Signal Transduction/genetics
- Signal Transduction/immunology
- Stem Cells/cytology
- Stem Cells/immunology
- Stem Cells/metabolism
- Tyrosine/genetics
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Affiliation(s)
- Bettina Storch
- Institute for Biologie III, Albert Ludwigs-University of Freiburg, Freiburg, Germany
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6
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Kabak S, Clark MR. Membrane-targeted peptides derived from Igalpha attenuate B-cell antigen receptor function. Biochem Biophys Res Commun 2005; 324:1249-55. [PMID: 15504349 DOI: 10.1016/j.bbrc.2004.09.184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2004] [Indexed: 12/30/2022]
Abstract
Within the B-cell antigen receptor (BCR), heterodimers of Igalpha/Igbeta couple the receptor to intracellular signaling pathways. In the resting state, Igalpha associates with Src-family tyrosine kinases (SFTKs) which contain some basal activity. Upon engagement of the receptor, the SFTKs phosphorylate tyrosine residues in the BCR that recruit and activate the tyrosine kinase Syk, initiating signaling pathways. To test the hypothesis that disrupting the association between the resting receptor and the SFTKs would attenuate both basal and induced receptor activities, we expressed non-phosphorylatable membrane-targeted analogs of Igalpha (Igalpha/M) or Igbeta (Igbeta/M) in B lymphocytes. Both Igalpha/M and Igbeta/M inhibited BCR-induced calcium mobilization, but only Igalpha/M was able to diminish tyrosine phosphorylation. In an immature B-cell line, Igalpha/M attenuated both receptor-induced and basal apoptosis. Taken together, these data demonstrate the importance of the resting receptor complex and suggest therapeutic strategies for regulating receptor-mediated functions.
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Affiliation(s)
- Shara Kabak
- Departments of Medicine and Pathology, Section of Rheumatology, Committee on Immunology, University of Chicago, Chicago, IL 60637, USA
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7
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Pike KA, Ratcliffe MJH. Dual Requirement for the Igα Immunoreceptor Tyrosine-Based Activation Motif (ITAM) and a Conserved Non-Igα ITAM Tyrosine in Supporting Igαβ-Mediated B Cell Development. THE JOURNAL OF IMMUNOLOGY 2005; 174:2012-20. [PMID: 15699130 DOI: 10.4049/jimmunol.174.4.2012] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Surface Ig (sIg) expression is a critical checkpoint during avian B cell development. Only cells that express sIg colonize bursal follicles, clonally expand, and undergo Ig diversification by gene conversion. Expression of a heterodimer, in which the extracellular and transmembrane domains of murine CD8alpha or CD8beta are fused to the cytoplasmic domains of chicken Igalpha (chIgalpha) or Igbeta, respectively (murine CD8alpha (mCD8alpha):chIgalpha + mCD8beta:chIgbeta), or an mCD8alpha:chIgalpha homodimer supported bursal B cell development as efficiently as endogenous sIg. In this study we demonstrate that B cell development, in the absence of chIgbeta, requires both the Igalpha ITAM and a conserved non-ITAM Igalpha tyrosine (Y3) that has been associated with binding to B cell linker protein (BLNK). When associated with the cytoplasmic domain of Igbeta, the Igalpha ITAM is not required for the induction of strong calcium mobilization or BLNK phosphorylation, but is still necessary to support B cell development. In contrast, mutation of the Igalpha Y3 severely compromised calcium mobilization when expressed as either a homodimer or a heterodimer with the cytoplasmic domain of Igbeta. However, coexpression of the cytoplasmic domain of Igbeta partially complemented the Igalpha Y3 mutation, rescuing higher levels of BLNK phosphorylation and, more strikingly, supporting B cell development.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Amino Acid Motifs
- Animals
- Antigens, CD/genetics
- Antigens, CD/physiology
- Avian Sarcoma Viruses/genetics
- Avian Sarcoma Viruses/immunology
- B-Lymphocytes/cytology
- B-Lymphocytes/immunology
- B-Lymphocytes/metabolism
- CD79 Antigens
- Calcium Signaling/genetics
- Calcium Signaling/immunology
- Carrier Proteins/metabolism
- Cell Differentiation/immunology
- Cell Line, Tumor
- Cells, Cultured
- Chick Embryo
- Chickens
- Conserved Sequence
- Cytoplasm/immunology
- Cytoplasm/metabolism
- Dimerization
- Mice
- Mutagenesis, Site-Directed
- Phosphoproteins/metabolism
- Phosphorylation
- Protein Structure, Tertiary/genetics
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/physiology
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/physiology
- Tyrosine/genetics
- Tyrosine/metabolism
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Affiliation(s)
- Kelly A Pike
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
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8
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Pike KA, Baig E, Ratcliffe MJH. The avian B-cell receptor complex: distinct roles of Igalpha and Igbeta in B-cell development. Immunol Rev 2004; 197:10-25. [PMID: 14962183 DOI: 10.1111/j.0105-2896.2004.0111.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The bursa of Fabricius has evolved in birds as a gut-associated site of B-cell lymphopoiesis that is segregated from the development of other hematopoietic lineages. Despite differences in the developmental progression of chicken as compared to murine B-cell lymphopoiesis, cell-surface immunoglobulin (sIg) expression has been conserved in birds as an essential checkpoint in B-cell development. B-cell precursors that express an sIg complex that includes the evolutionarily conserved Igalpha/beta heterodimer colonize lymphoid follicles in the bursa, whereas B-cell precursors that fail to express sIg due to non-productive V(D)J recombination are eliminated. Productive retroviral gene transfer has allowed us to introduce chimeric receptor constructs into developing B-cell precursors in vivo. Chimeric proteins comprising the extracellular and transmembrane regions of murine CD8alpha fused to the cytoplasmic domain of chicken Igalpha efficiently supported B-cell development in precursors that lacked endogenous sIg expression. By contrast, expression of an equivalent chimeric receptor containing the cytoplasmic domain of Igbeta actively inhibited B-cell development. Consequently, the cytoplasmic domains of Igalpha and Igbeta play functionally distinct roles in chicken B-cell development.
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Affiliation(s)
- Kelly A Pike
- Department of Immunology, University of Toronto,Toronto, Ontario, Canada
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9
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Grafton G, Stokes L, Toellner KM, Gordon J. A non-voltage-gated calcium channel with L-type characteristics activated by B cell receptor ligation. Biochem Pharmacol 2003; 66:2001-9. [PMID: 14599558 DOI: 10.1016/j.bcp.2003.07.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In mature B cells engagement of the antigen-receptor (BCR) results in a peak of Ca(2+) from mobilisation of internal stores followed by a lower but sustained elevation that is dependent upon extracellular Ca(2+). The Ca(2+) channel involved in the sustained elevation remains uncharacterised. Here we have presented evidence that although non-excitable, B cells expressed a BCR-activated Ca(2+) channel sharing some properties of conventional L-type voltage-gated channels. Human lymphoma B cells expressed a transcript having homology to a highly conserved region on the pore-forming alpha(1.2) subunit of L-type voltage-gated Ca(2+) channels. The alpha(1.2) protein was expressed together with the beta1 subunit, while an antibody raised against the extracellular portion of L-type Ca(2+) channels caused a Ca(2+) flux in these cells. Drugs that block classical L-type channels abolished the BCR-induced Ca(2+) flux while directly activating a plasma membrane Ca(2+) channel: activation of the channel, separate from Ca(2+) influx, inhibited BCR-induced Ca(2+) release from intracellular stores. BAYK8644-a drug that binds to open L-type channels-failed to release intracellular Ca(2+) in the absence of BCR cross-linking but instantly abolished the BCR-induced Ca(2+) peak and established the sustained phase of the response. The BCR-activated calcium channel appeared to terminate the initial peak of BCR-induced Ca(2+) release and initiate the sustained phase of the signal.
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Affiliation(s)
- Gillian Grafton
- MRC Centre for Immune Regulation, The Medical School, University of Birmingham, Birmingham B15 2TT, Edgbaston, UK.
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10
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Granboulan M, Lankar D, Raposo G, Bonnerot C, Hivroz C. Phosphoinositide 3-kinase activation by Igbeta controls de novo formation of an antigen-processing compartment. J Biol Chem 2003; 278:4331-8. [PMID: 12459553 DOI: 10.1074/jbc.m209885200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Antigens that bind B cell antigen receptor (BCR) are preferentially and rapidly processed for antigen presentation. The BCR is a multimeric complex containing a signaling module composed of Igalpha and Igbeta. Signaling pathways implicated in antigen presentation through the BCR are ill defined. Here we demonstrate that phosphoinositide 3-kinase (PI3K) inhibitors preclude antigen presentation induced by BCR or Igbeta but not Igalpha. Unraveling the mechanisms responsible for this inhibition, we show that PI3K inhibitors block neither antigen internalization nor degradation. Rather PI3K inhibitors block de novo formation of a multivesicular antigen processing compartment, which is induced by triggering of the BCR or Igbeta. Strikingly, we found using fluorescent probes binding specifically to PI3K products that BCR and Igbeta but not Igalpha induce PI3K activation in endocytic compartments wherein antigen is transported. Altogether, these results strongly suggest that Igbeta couples the BCR to PI3K activation that is instrumental for de novo formation of the antigen processing compartment and efficient antigen presentation.
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Affiliation(s)
- Marie Granboulan
- INSERM U520, UMR 144, Institut Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France
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11
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Sheu JJC, Cheng T, Chen HY, Lim C, Chang TW. Comparative effects of human Ig alpha and Ig beta in inducing autoreactive antibodies against B cells in mice. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2003; 170:1158-66. [PMID: 12538671 DOI: 10.4049/jimmunol.170.3.1158] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Human and mouse Ig alpha molecules share only 58% amino acid sequence identity in their extracellular regions. However, mice immunized with a recombinant Fc fusion protein containing the extracellular portion of human Ig alpha produced significant amounts of IgG capable of binding to Ig alpha on mouse B cells. The induced auto/cross-reactive Abs could down-regulate B cell levels and the consequent humoral immune responses against an irrelevant Ag in treated mice. Analogous immunization with an Fc fusion protein containing the extracellular portion of human Ig beta gave a much weaker response to mouse Ig beta, although human and mouse Ig beta, like their Ig alpha counterparts, share 56% sequence identity in their extracellular regions. Protein sequence analyses indicated that a potential immunogenic segment, located at the C-terminal loop of the extracellular domain, has an amino acid sequence that is identical between human and mouse Ig alpha. A mAb A01, which could bind to both human and mouse Ig alpha, was found to be specific to a peptide encompassing this immunogenic segment. These findings suggest that specific auto/cross-reactivity against self Ig alpha can be induced by a molecular mimicry presented by a foreign Ig alpha.
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MESH Headings
- Amino Acid Sequence
- Animals
- Antibodies, Bispecific/metabolism
- Antigen-Antibody Reactions
- Antigens, CD/administration & dosage
- Antigens, CD/genetics
- Antigens, CD/immunology
- Antigens, CD/metabolism
- Autoantibodies/biosynthesis
- Autoantibodies/metabolism
- B-Lymphocytes/immunology
- B-Lymphocytes/metabolism
- Binding Sites, Antibody
- CD79 Antigens
- Cell Death/immunology
- Cell Line
- Down-Regulation/immunology
- Humans
- Immune Sera/metabolism
- Immunization
- Immunoglobulin Fc Fragments/administration & dosage
- Immunoglobulin Fc Fragments/genetics
- Immunoglobulin Fc Fragments/immunology
- Injections, Intraperitoneal
- Lymphopenia/immunology
- Male
- Mice
- Mice, Inbred BALB C
- Molecular Sequence Data
- Ovalbumin/administration & dosage
- Ovalbumin/immunology
- Receptors, Antigen, B-Cell/administration & dosage
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/immunology
- Receptors, Antigen, B-Cell/metabolism
- Recombinant Fusion Proteins/administration & dosage
- Recombinant Fusion Proteins/immunology
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Affiliation(s)
- Jim J C Sheu
- Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan
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12
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Nakamura K, Malykhin A, Coggeshall KM. The Src homology 2 domain-containing inositol 5-phosphatase negatively regulates Fcgamma receptor-mediated phagocytosis through immunoreceptor tyrosine-based activation motif-bearing phagocytic receptors. Blood 2002; 100:3374-82. [PMID: 12384440 DOI: 10.1182/blood-2002-03-0787] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Molecular mechanisms by which the Src homology 2 domain-containing inositol 5-phosphatase (SHIP) negatively regulates phagocytosis in macrophages are unclear. We addressed the issue using bone marrow-derived macrophages from FcgammaR- or SHIP-deficient mice. Phagocytic activities of macrophages from FcgammaRII(b)(-/-) and SHIP(-/-) mice were enhanced to a similar extent, relative to those from wild type. However, calcium influx was only marginally affected in FcgammaRII(b)(-/-), but greatly enhanced in SHIP(-/-) macrophages. Furthermore, SHIP was phosphorylated on tyrosine residues upon FcgammaR aggregation even in macrophages from FcgammaRII(b)(-/-) mice or upon clustering of a chimeric receptor containing CD8 and the immunoreceptor tyrosine-based activation motif (ITAM)-bearing gamma-chain or human-restricted FcgammaRIIa. These findings indicate that, unlike B cells, SHIP is efficiently phosphorylated in the absence of an immunoreceptor tyrosine-based inhibition motif (ITIM)-bearing receptor. We further demonstrate that SHIP directly bound to phosphorylated peptides derived from FcgammaRIIa with a high affinity, comparable to that of FcgammaRII(b). Lastly, FcgammaRIIa-mediated phagocytosis was significantly enhanced in THP-1 cells overexpressing dominant-negative form of SHIP in the absence of FcgammaRII(b). These results indicate that SHIP negatively regulates FcgammaR-mediated phagocytosis through all ITAM-containing IgG receptors using a molecular mechanism distinct from that in B cells.
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MESH Headings
- Amino Acid Motifs
- Animals
- Antigens, CD/chemistry
- Antigens, CD/metabolism
- Bone Marrow Cells/cytology
- CD8 Antigens/genetics
- CD8 Antigens/physiology
- Calcium Signaling
- GPI-Linked Proteins
- Humans
- Macrophages/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Phagocytosis/physiology
- Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases
- Phosphoric Monoester Hydrolases/chemistry
- Phosphoric Monoester Hydrolases/deficiency
- Phosphoric Monoester Hydrolases/genetics
- Phosphoric Monoester Hydrolases/physiology
- Phosphorylation
- Phosphotyrosine/physiology
- Protein Processing, Post-Translational
- Receptors, IgG/chemistry
- Receptors, IgG/deficiency
- Receptors, IgG/metabolism
- Recombinant Fusion Proteins/metabolism
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Affiliation(s)
- Koji Nakamura
- Program in Immunobiology and Cancer, The Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK 73104, USA
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13
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Wienands J, Engels N. Multitasking of Ig-alpha and Ig-beta to regulate B cell antigen receptor function. Int Rev Immunol 2002; 20:679-96. [PMID: 11913945 DOI: 10.3109/08830180109045585] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Since their discovery as signaling subunits of the B cell antigen receptor (BCR), Ig-alpha and Ig-beta are discussed to serve either a redundant or distinct function for B cell development, maintenance, and activation. Dependent upon the experimental system that has been used to address this issue, evidence could be provided to support both possibilities. Only recently has it become clear that Ig-alpha and Ig-beta possess a unique signaling identity but that both together are required to orchestrate proper B cell function in vivo. Here we discuss some of the underlying mechanisms that may involve direct coupling to discrete subsets of BCR effector proteins, such as protein tyrosine kinases or the intracellular adaptor SLP-65/BLNK.
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Affiliation(s)
- J Wienands
- Department of Biochemistry and Molecular Immunology, University of Bielefeld, Germany.
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14
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Kabak S, Skaggs BJ, Gold MR, Affolter M, West KL, Foster MS, Siemasko K, Chan AC, Aebersold R, Clark MR. The direct recruitment of BLNK to immunoglobulin alpha couples the B-cell antigen receptor to distal signaling pathways. Mol Cell Biol 2002; 22:2524-35. [PMID: 11909947 PMCID: PMC133735 DOI: 10.1128/mcb.22.8.2524-2535.2002] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2001] [Revised: 12/18/2001] [Accepted: 12/24/2001] [Indexed: 01/30/2023] Open
Abstract
Following B-cell antigen receptor (BCR) ligation, the cytoplasmic domains of immunoglobulin alpha (Ig alpha) and Ig beta recruit Syk to initiate signaling cascades. The coupling of Syk to several distal substrates requires linker protein BLNK. However, the mechanism by which BLNK is recruited to the BCR is unknown. Using chimeric receptors with wild-type and mutant Ig alpha cytoplasmic tails we show that the non-immunoreceptor tyrosine-based activation motif (ITAM) tyrosines, Y176 and Y204, are required to activate BLNK-dependent pathways. Subsequent analysis demonstrated that BLNK bound directly to phospho-Y204 and that fusing BLNK to mutated Ig alpha reconstituted downstream signaling events. Moreover, ligation of the endogenous BCR induced Y204 phosphorylation and BLNK recruitment. These data demonstrate that the non-ITAM tyrosines of Ig alpha couple Syk activation to BLNK-dependent pathways.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Animals
- Antigens, CD/genetics
- Antigens, CD/metabolism
- CD79 Antigens
- Carrier Proteins/chemistry
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Clone Cells
- Enzyme Precursors/metabolism
- Intracellular Signaling Peptides and Proteins
- Isoenzymes/metabolism
- Mice
- Models, Molecular
- Mutation
- Phospholipase C gamma
- Phosphoproteins/chemistry
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- Protein-Tyrosine Kinases/metabolism
- Receptor, Platelet-Derived Growth Factor beta/genetics
- Receptor, Platelet-Derived Growth Factor beta/metabolism
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/metabolism
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Signal Transduction
- Syk Kinase
- Type C Phospholipases/metabolism
- src Homology Domains
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Affiliation(s)
- Shara Kabak
- Committee on Immunology, Section of Rheumatology, University of Chicago, Chicago, Illinois 60637, USA
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15
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Siemasko K, Skaggs BJ, Kabak S, Williamson E, Brown BK, Song W, Clark MR. Receptor-facilitated antigen presentation requires the recruitment of B cell linker protein to Igalpha. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 168:2127-38. [PMID: 11859098 DOI: 10.4049/jimmunol.168.5.2127] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Ags that cross-link the B cell Ag receptor are preferentially and rapidly delivered to the MHC class II-enriched compartment for processing into peptides and subsequent loading onto MHC class II. Proper sorting of Ag/receptor complexes requires the recruitment of Syk to the phosphorylated immunoreceptor tyrosine-based activation motif tyrosines of the B cell Ag receptor constituent Igalpha. We postulated that the Igalpha nonimmunoreceptor tyrosine-based activation motif tyrosines, Y(176) and Y(204), contributed to receptor trafficking. Igalpha(YDeltaF(176,204))/Igbeta receptors were targeted to late endosomes, but were excluded from the vesicle lumen and could not facilitate the presentation of Ag to T cells. Subsequent analysis demonstrated that phosphorylation of Y(176)/Y(204) recruited the B cell linker protein, Vav, and Grb2. Reconstitution of Igalpha(YDeltaF(176,204))/Igbeta with the B cell linker protein rescued both receptor-facilitated Ag presentation and entry into the MHC class II-enriched compartment. Thus, aggregation accelerates receptor trafficking by recruiting two separate signaling modules required for transit through sequential checkpoints.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Amino Acid Motifs
- Animals
- Antigen Presentation
- Antigens, CD/chemistry
- Antigens, CD/genetics
- Antigens, CD/metabolism
- B-Lymphocytes/immunology
- B-Lymphocytes/ultrastructure
- CD79 Antigens
- Carrier Proteins/physiology
- Cell Cycle Proteins
- Endocytosis
- Endosomes/metabolism
- GRB2 Adaptor Protein
- Mice
- Microscopy, Immunoelectron
- Models, Immunological
- Models, Molecular
- Phosphoproteins/physiology
- Phosphorylation
- Phosphotyrosine/physiology
- Proteins/metabolism
- Proto-Oncogene Proteins/metabolism
- Proto-Oncogene Proteins c-vav
- Receptors, Antigen, B-Cell/chemistry
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/metabolism
- Receptors, Antigen, B-Cell/physiology
- Recombinant Fusion Proteins/metabolism
- Tumor Cells, Cultured
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Affiliation(s)
- Karyn Siemasko
- Department of Medicine, Section of Rheumatology, University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, USA
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16
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Tridandapani S, Siefker K, Teillaud JL, Carter JE, Wewers MD, Anderson CL. Regulated expression and inhibitory function of Fcgamma RIIb in human monocytic cells. J Biol Chem 2002; 277:5082-9. [PMID: 11741917 DOI: 10.1074/jbc.m110277200] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human monocytes/macrophages express three classes of receptors for IgG: FcgammaRI, FcgammaRII, and FcgammaRIII. The expression and function of these receptors has been extensively studied with the exception of one, FcgammaRIIb. While the mRNA for FcgammaRIIb has been detected in human monocytes, the protein has remained elusive. Studies in mouse models indicated that the macrophage FcgammaRIIb serves to down-regulate FcgammaR-mediated phagocytosis and immune complex-induced inflammation. FcgammaRIIb has also been shown to modulate the action of cytotoxic antibodies against tumors in mouse models. Hence, an understanding of how FcgammaRIIb expression is regulated is of great importance. Here we demonstrate for the first time FcgammaRIIb protein expression and function in human monocytes. We also report that the expression of FcgammaRIIb is highly up-regulated by interleukin-4, a Th2 cytokine, and that the up-regulation of FcgammaRIIb results in a decrease in the phagocytic efficiency of interleukin-4-treated THP-1 cells. Furthermore co-clustering FcgammaRIIb with FcgammaRIIa resulted in enhanced phosphorylation of the inositol phosphatase SHIP, association of SHIP with Shc, and phosphorylation of additional proteins around 120 and 60-65 kDa, with a concomitant attenuation of Akt activation. We, therefore, propose that FcgammaRIIb serves to inhibit FcgammaRI/IIa-mediated macrophage activation using SHIP as its effector.
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Affiliation(s)
- Susheela Tridandapani
- Department of Internal Medicine, The Ohio State University, Columbus, Ohio 43210, USA
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17
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Kraus M, Pao LI, Reichlin A, Hu Y, Canono B, Cambier JC, Nussenzweig MC, Rajewsky K. Interference with immunoglobulin (Ig)alpha immunoreceptor tyrosine-based activation motif (ITAM) phosphorylation modulates or blocks B cell development, depending on the availability of an Igbeta cytoplasmic tail. J Exp Med 2001; 194:455-69. [PMID: 11514602 PMCID: PMC2193498 DOI: 10.1084/jem.194.4.455] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
To determine the function of immunoglobulin (Ig)alpha immunoreceptor tyrosine-based activation motif (ITAM) phosphorylation, we generated mice in which Igalpha ITAM tyrosines were replaced by phenylalanines (Igalpha(FF/FF)). Igalpha(FF/FF) mice had a specific reduction of B1 and marginal zone B cells, whereas B2 cell development appeared to be normal, except that lambda1 light chain usage was increased. The mutants responded less efficiently to T cell-dependent antigens, whereas T cell-independent responses were unaffected. Upon B cell receptor ligation, the cells exhibited heightened calcium flux, weaker Lyn and Syk tyrosine phosphorylation, and phosphorylation of Igalpha non-ITAM tyrosines. Strikingly, when the Igalpha ITAM mutation was combined with a truncation of Igbeta, B cell development was completely blocked at the pro-B cell stage, indicating a crucial role of ITAM phosphorylation in B cell development.
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Affiliation(s)
- M Kraus
- Institute for Genetics, University of Cologne, D-50931 Cologne, Germany.
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18
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Abstract
Antigen receptors on lymphocytes utilize different signaling modes to control the positive and negative selection of lymphocytes. In addition, these receptors have to detect the amount and affinity of the antigen and set delicate threshold values for the activation of lymphocytes. It is suggested that the antigen receptors on B and T-cells form oligomeric complexes, inside of which, signals can be processed and amplified in a manner that might explain the different signaling outputs of these receptors.
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Affiliation(s)
- M Reth
- Dept of Molecular Immunology, Biology III, University of Freiburg and Max-Planck-Institute for Immunobiology, Stübeweg 51, 79108 Freiburg, Germany.
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19
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Engels N, Wollscheid B, Wienands J. Association of SLP-65/BLNK with the B cell antigen receptor through a non-ITAM tyrosine of Ig-alpha. Eur J Immunol 2001; 31:2126-34. [PMID: 11449366 DOI: 10.1002/1521-4141(200107)31:7<2126::aid-immu2126>3.0.co;2-o] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The cytoplasmic adaptor protein SLP-65 (BLNK or BASH) is a critical downstream effector of the B cell antigen receptor (BCR). Tyrosine-phosphorylated SLP-65 assembles intracellular signaling complexes such as the Ca(2 +) initiation complex encompassing phospholipase C-gamma2 and Bruton's tyrosine kinase. It is, however, unclear how the SLP-65 signaling module can be recruited to the plasma membrane. Here we show that following B cell stimulation, SLP-65 associates directly with the BCR signaling subunit, the Ig-alpha / Ig-beta heterodimer. The interaction is mediated by the Src homology 2 domain of SLP-65 and the phosphorylated Ig-alpha tyrosine 204, which is located outside of the immunoreceptor tyrosine-based activation motif. Our data identify an unexpected BCR phosphorylation pattern and indicate that Ig-alpha has the capability to serve as transmembrane adaptor in BCR signaling.
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Affiliation(s)
- N Engels
- Institute of Biology III, University of Freiburg and Max Planck Institute of Immunobiology, Freiburg, Germany
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20
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Abstract
The development of B cells requires the expression of an antigen receptor at distinct points during maturation. The Ig-alpha/beta heterodimer signals for these receptors, and mice harboring a truncation of the Ig-alpha intracellular domain (mb-1(delta(c)/delta(c)) have severely reduced peripheral B cell numbers. Here we report that immature mb-1(delta(c)/delta(c) B cells are activated despite lacking a critical Ig-alpha-positive signaling motif. As a consequence of abnormal activation, transitional immature IgMhighIgDlow B cells are largely absent in mb-1delta(c)/delta(c) mutants, accounting for the paucity of mature B cells. Thus, Ig-alpha cytoplasmic tail truncation yields an antigen receptor complex on immature B cells that signals constitutively. These data illustrate a role for Ig-alpha in negatively regulating antigen receptor signaling during B cell development.
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MESH Headings
- Animals
- Antigens, CD/biosynthesis
- Antigens, CD/chemistry
- Antigens, CD/genetics
- Antigens, CD/physiology
- B-Lymphocytes/cytology
- B7-2 Antigen
- CD79 Antigens
- Dimerization
- Immunoglobulin M/biosynthesis
- Immunophenotyping
- Liver/cytology
- Liver/embryology
- Lymphocyte Count
- Lymphoid Tissue/pathology
- Membrane Glycoproteins/biosynthesis
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Phosphorylation
- Protein Processing, Post-Translational
- Protein-Tyrosine Kinases/metabolism
- Receptors, Antigen, B-Cell/chemistry
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/physiology
- Sequence Deletion
- Signal Transduction
- Specific Pathogen-Free Organisms
- Terminator Regions, Genetic
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Affiliation(s)
- R M Torres
- Basel Institute for Immunology, Switzerland.
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21
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Kraus M, Saijo K, Torres RM, Rajewsky K. Ig-alpha cytoplasmic truncation renders immature B cells more sensitive to antigen contact. Immunity 1999; 11:537-45. [PMID: 10591179 DOI: 10.1016/s1074-7613(00)80129-6] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
To study the function of Ig-alpha in the selection of autoreactive B cells, we have analyzed mb-1 cytoplasmic truncation mutant mice (mb-1delta(c)/delta(c)), which coexpress transgenes encoding hen egg lysozyme (HEL) and HEL-specific immunoglobulin. We demonstrate that in the presence of soluble HEL (sHEL) and dependent on the mb-1delta(c) mutation, most immature B cells bearing the HEL-specific Ig transgene undergo rearrangements of endogenous kappa light chains, resulting in loss of HEL specificity. Moreover, immature B cells from Ig-alpha mutant mice respond to BCR cross-linking with an exaggerated and prolonged calcium response and induction of protein tyrosine phosphorylation. Our data imply a negative signaling role for Ig-alpha in immature B cells.
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MESH Headings
- Animals
- Antibody Specificity
- Antigens, CD/chemistry
- Antigens, CD/genetics
- Antigens, CD/immunology
- Apoptosis
- Autoantigens/genetics
- Autoantigens/immunology
- CD79 Antigens
- Calcium Signaling/immunology
- Clonal Deletion
- Crosses, Genetic
- Gene Rearrangement, B-Lymphocyte, Light Chain
- Immunoglobulin kappa-Chains/immunology
- Immunologic Capping
- Lymphocyte Activation/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Muramidase/genetics
- Muramidase/immunology
- Mutagenesis, Site-Directed
- Phosphorylation
- Protein Processing, Post-Translational/immunology
- Protein Structure, Tertiary
- Protein-Tyrosine Kinases/physiology
- Receptors, Antigen, B-Cell/chemistry
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/immunology
- Sequence Deletion
- Terminator Regions, Genetic
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Affiliation(s)
- M Kraus
- Department of Immunology, Institute for Genetics, University of Cologne, Germany.
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22
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Freedman BD, Liu QH, Somersan S, Kotlikoff MI, Punt JA. Receptor avidity and costimulation specify the intracellular Ca2+ signaling pattern in CD4(+)CD8(+) thymocytes. J Exp Med 1999; 190:943-52. [PMID: 10510084 PMCID: PMC2195644 DOI: 10.1084/jem.190.7.943] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/1999] [Accepted: 08/03/1999] [Indexed: 11/07/2022] Open
Abstract
Thymocyte maturation is governed by antigen-T cell receptor (TCR) affinity and the extent of TCR aggregation. Signals provided by coactivating molecules such as CD4 and CD28 also influence the fate of immature thymocytes. The mechanism by which differences in antigen-TCR avidity encode unique maturational responses of lymphocytes and the influence of coactivating molecules on these signaling processes is not fully understood. To better understand the role of a key second messenger, calcium, in governing thymocyte maturation, we measured the intracellular free calcium concentration ([Ca2+]i) response to changes in TCR avidity and costimulation. We found that TCR stimulation initiates either amplitude- or frequency-encoded [Ca2+]i changes depending on (a) the maturation state of stimulated thymocytes, (b) the avidity of TCR interactions, and (c) the participation of specific coactivating molecules. Calcium signaling within immature but not mature thymocytes could be modulated by the avidity of CD3/CD4 engagement. Low avidity interactions induced biphasic calcium responses, whereas high avidity engagement initiated oscillatory calcium changes. Notably, CD28 participation converted the calcium response to low avidity receptor engagement from a biphasic to oscillatory pattern. These data suggest that calcium plays a central role in encoding the nature of the TCR signal received by thymocytes and, consequently, a role in thymic selection.
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Affiliation(s)
- B D Freedman
- Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania 19104, USA.
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23
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Brachet V, Péhau-Arnaudet G, Desaymard C, Raposo G, Amigorena S. Early endosomes are required for major histocompatiblity complex class II transport to peptide-loading compartments. Mol Biol Cell 1999; 10:2891-904. [PMID: 10473634 PMCID: PMC25528 DOI: 10.1091/mbc.10.9.2891] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Antigen presentation to CD4(+) T lymphocytes requires transport of newly synthesized major histocompatibility complex (MHC) class II molecules to the endocytic pathway, where peptide loading occurs. This step is mediated by a signal located in the cytoplasmic tail of the MHC class II-associated Ii chain, which directs the MHC class II-Ii complexes from the trans-Golgi network (TGN) to endosomes. The subcellular machinery responsible for the specific targeting of MHC class II molecules to the endocytic pathway, as well as the first compartments these molecules enter after exit from the TGN, remain unclear. We have designed an original experimental approach to selectively analyze this step of MHC class II transport. Newly synthesized MHC class II molecules were caused to accumulate in the Golgi apparatus and TGN by incubating the cells at 19 degrees C, and early endosomes were functionally inactivated by in vivo cross-linking of transferrin (Tf) receptor-containing endosomes using Tf-HRP complexes and the HRP-insoluble substrate diaminobenzidine. Inactivation of Tf-containing endosomes caused a marked delay in Ii chain degradation, peptide loading, and MHC class II transport to the cell surface. Thus, early endosomes appear to be required for delivery of MHC class II molecules to the endocytic pathway. Under cross-linking conditions, most alphabetaIi complexes accumulated in tubules and vesicles devoid of gamma-adaptin and/or mannose-6-phosphate receptor, suggesting an AP1-independent pathway for the delivery of newly synthesized MHC class II molecules from the TGN to endosomes.
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Affiliation(s)
- V Brachet
- Institut National de la Santé et de la Recherche Médicale U520, Institut Curie, Section Recherche, 75005 Paris, France
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24
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Benlagha K, Guglielmi P, Cooper MD, Lassoued K. Modifications of Igalpha and Igbeta expression as a function of B lineage differentiation. J Biol Chem 1999; 274:19389-96. [PMID: 10383452 DOI: 10.1074/jbc.274.27.19389] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transcription of the mb1 and B29 genes is initiated when lymphoid progenitors enter the B cell differentiation pathway, and their transmembrane Igalpha and Igbeta products constitute essential signaling components of pre-B and B cell antigen receptors. We analyzed Igalpha/Igbeta biosynthesis, heterogeneity, and molecular interactions as a function of human B lineage differentiation in cell lines representative of the pro-B, pre-B, and B cell stages. All B lineage representatives produced a 36-kDa Igbeta form and three principal Igalpha forms, transient 33/40-kDa species and a mature 44-kDa glycoprotein. Deglycosylation revealed a major Igalpha core protein of 25 kDa and a minor 21-kDa Igalpha protein, apparently the product of an alternatively spliced mRNA. In pro-B cells, the Igalpha and Igbeta molecules existed primarily in separate unassembled pools, exhibited an immature glycosylation pattern, did not associate with surrogate light chain proteins, and were retained intracellularly. Their unanticipated association with the Lyn protein-tyrosine kinase nevertheless suggests functional potential for the Igalpha/Igbeta molecules in pro-B cells. Greater heterogeneity of the Igalpha and Igbeta molecules in pre-B and B cell lines was attributable to increased glycosylation complexity. Finally, the Igalpha/Igbeta heterodimers associated with fully assembled IgM molecules as a terminal event in B cell receptor assembly.
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Affiliation(s)
- K Benlagha
- Laboratoire d'Immunopathologie, Institut d'Hématologie, Hôpital Saint-Louis, 75475 Paris Cédex 10, France
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25
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Lankar D, Briken V, Adler K, Weiser P, Cassard S, Blank U, Viguier M, Bonnerot C. Syk tyrosine kinase and B cell antigen receptor (BCR) immunoglobulin-alpha subunit determine BCR-mediated major histocompatibility complex class II-restricted antigen presentation. J Exp Med 1998; 188:819-31. [PMID: 9730884 PMCID: PMC2213387 DOI: 10.1084/jem.188.5.819] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/1998] [Revised: 04/28/1998] [Indexed: 11/04/2022] Open
Abstract
Stimulation of CD4(+) helper T lymphocytes by antigen-presenting cells requires the degradation of exogenous antigens into antigenic peptides which associate with major histocompatibility complex (MHC) class II molecules in endosomal or lysosomal compartments. B lymphocytes mediate efficient antigen presentation first by capturing soluble antigens through clonally distributed antigen receptors (BCRs), composed of membrane immunoglobulin (Ig) associated with Ig-alpha/Ig-beta heterodimers which, second, target antigens to MHC class II-containing compartments. We report that antigen internalization and antigen targeting through the BCR or its Ig-alpha-associated subunit to newly synthesized class II lead to the presentation of a large spectrum of T cell epitopes, including some cryptic T cell epitopes. To further characterize the intracellular mechanisms of BCR-mediated antigen presentation, we used two complementary experimental approaches: mutational analysis of the Ig-alpha cytoplasmic tail, and overexpression in B cells of dominant negative syk mutants. Thus, we found that the syk tyrosine kinase, an effector of the BCR signal transduction pathway, is involved in the presentation of peptide- MHC class II complexes through antigen targeting by BCR subunits.
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MESH Headings
- Animals
- Antigen Presentation
- Antigens, CD/chemistry
- Antigens, CD/physiology
- Antigens, Viral/metabolism
- B-Lymphocytes/enzymology
- B-Lymphocytes/immunology
- B-Lymphocytes/metabolism
- Bacteriophage lambda/immunology
- CD79 Antigens
- Cytoplasm/immunology
- DNA-Binding Proteins
- Enzyme Precursors/metabolism
- Enzyme Precursors/physiology
- Epitopes, T-Lymphocyte/metabolism
- Histocompatibility Antigens Class II/immunology
- Histocompatibility Antigens Class II/metabolism
- Intracellular Signaling Peptides and Proteins
- Lymphocyte Activation
- Lymphoma, B-Cell
- Mice
- Protein-Tyrosine Kinases/metabolism
- Protein-Tyrosine Kinases/physiology
- Rats
- Receptors, Antigen, B-Cell/chemistry
- Receptors, Antigen, B-Cell/physiology
- Repressor Proteins/immunology
- Syk Kinase
- Tumor Cells, Cultured
- Tyrosine/physiology
- Viral Proteins
- Viral Regulatory and Accessory Proteins
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Affiliation(s)
- D Lankar
- INSERM CJF 95-01, Institut Curie, Section Recherche, Paris, France
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26
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Pao LI, Famiglietti SJ, Cambier JC. Asymmetrical Phosphorylation and Function of Immunoreceptor Tyrosine-Based Activation Motif Tyrosines in B Cell Antigen Receptor Signal Transduction. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.160.7.3305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
CD79a and CD79b function as transducers of B cell antigen receptor signals via a cytoplasmic sequence, termed the immunoreceptor tyrosine-based activation motif (ITAM). ITAMs contain two conserved tyrosines that may become phosphorylated upon receptor aggregation and bind distinct effectors by virtue of the distinct preference of phosphotyrosyl-containing sequences for SH2 domains. To explore the function of CD79a and CD79b ITAM tyrosines, we created membrane molecules composed of MHC class II I-Ak extracellular and transmembrane domains, and CD79a or CD79b cytoplasmic domains in which one or both of the ITAM tyrosines were mutated to phenylalanine. Functional analysis revealed that both ITAM tyrosines are required for ligand-induced Syk phosphorylation. However CD79a-ITAM and CD79b-ITAM tyrosine phosphorylations were asymmetrical, with >80% of phosphorylation occurring on the N-terminal tyrosine (Y-E-G-L). Thus, these findings suggest that following receptor ligation, only a minor proportion of phosphorylated ITAMs are doubly phosphorylated and thus can engage Syk. Only the N-terminal ITAM tyrosine of CD79a was required for ligand-mediated phosphorylation of the receptor and a subset of downstream substrates, including p62, p110, and Shc, and for Ca2+ mobilization. However, responses mediated through CD79b exhibited a greater dependence on the presence of both tyrosines. Neither tyrosine in CD79a or CD79b appeared absolutely essential for Src family kinase phosphorylation. These results indicate that phosphorylations of the tyrosines in CD79a and CD79b occur with very different stoichiometry, and the respective tyrosyl residues have distinct functions.
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Affiliation(s)
- Lily I. Pao
- Division of Basic Sciences, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO 80206
| | - Sara J. Famiglietti
- Division of Basic Sciences, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO 80206
| | - John C. Cambier
- Division of Basic Sciences, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO 80206
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27
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Cassard S, Salamero J, Hanau D, Spehner D, Davoust J, Fridman WH, Bonnerot C. A Tyrosine-Based Signal Present in Ig α Mediates B Cell Receptor Constitutive Internalization. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.160.4.1767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Abstract
B lymphocytes express Ag receptors (BCR) that are composed of ligand binding subunits, the membrane Igs, associated with Ig α/Ig β heterodimers. One main BCR function is to bind and to internalize Ags. Peptides generated from these internalized Ags may be presented to T lymphocytes. Here, we have analyzed the involvement of BCR Ig α/Ig β components in BCR constitutive endocytosis. The role of Ig α subunit in BCR constitutive endocytosis was first determined in the context of an IgM-based BCR. In contrast with BCR that contain wild-type Ig α, surface BCR lacking Ig α cytoplasmic domain were not constitutively internalized. The respective roles of Ig α and Ig β subunits were then analyzed by expressing chimeric molecules containing the cytoplasmic domains of either subunits in a B cell line. Only the Ig α cytoplasmic domain contained an internalization signal that allowed constitutive endocytosis of Ig α chimeras via coated pits and accumulation in sorting-recycling endosomes. This internalization signal is contained in its immunoreceptor tyrosine-based activation motif. These results indicate that Ig α, through its immunoreceptor tyrosine-based activation motif, may account for the ability of IgM/IgD BCR to constitutively internalize monovalent Ags.
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Affiliation(s)
| | - Jean Salamero
- ‡UMR 144 CNRS, Molecular Mechanisms of Intracellular Trafficking Laboratory, Institut Curie, Paris
| | - Daniel Hanau
- §Laboratoire d’Histocompatibilité, Centre Régional de Transfusion Sanguine and
| | - Daniele Spehner
- ¶INSERM Unité 74, Institut de Virologie, Faculté de Médecine, Strasbourg; and
| | - Jean Davoust
- ∥Centre d’Immunologie INSERM-CNRS de Marseille-Luminy, Marseille, France
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28
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Role of Immunoreceptor Tyrosine-Based Activation Motif in Signal Transduction from Antigen and Fc Receptors**Received for publication October 7, 1997. Adv Immunol 1998. [DOI: 10.1016/s0065-2776(08)60608-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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29
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Grafton G, Goodall M, Gregory CD, Gordon J. Mechanisms of antigen receptor-dependent apoptosis of human B lymphoma cells probed with a panel of 27 monoclonal antibodies. Cell Immunol 1997; 182:45-56. [PMID: 9427809 DOI: 10.1006/cimm.1997.1205] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The present study has used a panel of 23 monoclonal antibodies to IgM and 4 to IgD in order to probe parameters influencing sIg-dependent apoptosis in an IgM/IgD-expressing Burkitt lymphoma line. No direct correlation was observed between the capacity of the different anti-mu to drive cells into apoptosis and either their domain specificity or their affinity for sIgM. There was, however, a direct correlation between the functional outcome and the ability of the monoclonal antibodies to elicit a rise in intracellular Ca2+. For apoptosis to occur, the Ca2+ response had to attain a threshold value of approximately 100 nM. A direct role for Ca2+ in the delivery of the apoptotic signal was demonstrated using thapsigargin to raise intracellular Ca2+ levels. Antigen receptor ligation was linked to Ca2+ increases by tyrosine kinases as revealed by direct analysis of protein tyrosine phosphorylation and the effects of selective protein tyrosine kinase-inhibiting tyrphostins. These findings reveal a central role for the antigen receptor-generated Ca2+ signal in driving apoptosis in human B lymphoma cells and stresses the need to use a panel of reagents when probing function with presumed ligand-mimetic monoclonal antibodies.
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Affiliation(s)
- G Grafton
- Department of Immunology, Medical School, University of Birmingham, Edgbaston, UK
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30
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Mounho BJ, Davila DR, Burchiel SW. Characterization of intracellular calcium responses produced by polycyclic aromatic hydrocarbons in surface marker-defined human peripheral blood mononuclear cells. Toxicol Appl Pharmacol 1997; 145:323-30. [PMID: 9266805 DOI: 10.1006/taap.1997.8182] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Previous studies have demonstrated that polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (BaP) and 7,12-dimethybenz[a]anthracene (DMBA), and possibly 2,3,7,8-tetrachlorodibenzo(p)dioxin (TCDD), may exert their immunosuppressive effects by altering intracellular Ca2+ homeostasis in lymphocytes. In these studies, we examined the effects of two immunosuppressive PAHs (BaP and DMBA), two nonimmunosuppressive PAHs (benzo[e]pyrene (BeP) and anthracene (ANTH)), and TCDD on intracellular Ca2+ levels in surface marker-defined human peripheral blood mononuclear cells (HPBMC). BaP and DMBA, but not BeP and ANTH, were found to produce a time-dependent increase in intracellular Ca2+ with maximal effects achieved following 42- to 66-hr exposures. In a series of studies with HPBMC obtained from 10 donors exposed in vitro for 42 hr, BaP and DMBA were found to produce a significant increase in Ca2+ in CD3+ T cells, CD19+ B cells, and CD14+ monocytes. BeP and ANTH did not produce a statistically significant increase in Ca2+ in the group of donors, but occasionally produced an apparent nonspecific elevation of Ca2+ in HPBMC from individual donors. Interestingly, TCDD produced a small and statistically significant increase in Ca2+ only in B cells analyzed for the pooled 10 donors. Certain BaP metabolites, such as the 7,8-dihydrodiol and the 7,8-diol-9,10-epoxide, were more effective in elevating Ca2+ in HPBMC lymphocytes at 20 hr than was BaP. These results demonstrate in normal HPBMC that immunosuppressive PAHs alter intracellular Ca2+ homeostasis in B cells, T cells, and monocytes, and suggest that P450 metabolism may play an important role in the immunotoxicity of certain PAHs.
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Affiliation(s)
- B J Mounho
- The University of New Mexico College of Pharmacy, Toxicology Program, Albuquerque 87131-1066, USA
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31
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Abstract
AbstractThe majority of BALB/c mice immunized with the BCL1 lymphoma-derived idiotype (Id+) IgM and subsequently challenged with BCL1 tumor cells develop a state of tumor dormancy. The vast majority of dormant lymphoma cells are in cell cycle arrest, but there are also residual replicating cells. In the present studies, we attempted to define features of both the dormant lymphoma cells and the host that lead to escape from dormancy. Escape from dormancy occurs at a steady rate over a 2-year period, suggesting that it is a stochastic process. We found that, in the majority of mice, escape was due to the emergence of genetic variants that were no longer susceptible to the anti-Id–mediated induction of dormancy. Ten percent of these variants were Id−; the remainder were Id+ but could grow in the presence of anti-Id antibodies, suggesting that there were mutations in molecules involved in one or more mIg-mediated negative-signaling pathways. In two of five such escapees, alterations in either Syk, HS1, and/or Lyn were observed. In a small percentage of mice, a low titer of circulating anti-Id antibody before tumor challenge correlated with a subsequent, more rapid loss of dormancy.
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32
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Bonnerot C, Briken V, Amigorena S. Intracellular signaling and endosomal trafficking of immunoreceptors. Shared effectors underlying MHC class II-restricted antigen presentation. Immunol Lett 1997; 57:1-4. [PMID: 9232416 DOI: 10.1016/s0165-2478(97)00054-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The cells of the immune system express a wide variety of receptors, defined as immunoreceptors because they are involved in antigen recognition. B and T lymphocytes express clonally distributed receptors which recognize either soluble antigens, through B-cell receptors (BcR), or peptides associated to major histocompatibility complex (MHC) molecules, through T-cell receptors (TcR). Many lymphoid or myeloid cells, such as B lymphocytes, macrophages or dendritic cells, express receptors for antigen-antibody complexes, which recognize the Fc portion of immunoglobulins (FcR). Although their ligands are different, immunoreceptors share both structural and functional homologies. The BcRs, TcRs and most FcRs, are multichain complexes composed of a ligand binding module, including one or two chains which determine the specificity of antigen recognition and a transducing module, which includes two to six chains containing a conserved motif in their cytoplasmic tail (A.D. Keegan and W.E. Paul, Immunol. Today 13 (1992) 63-68). This motif, called ITAM for immunoreceptor tyrosine-based activation motif (M.G. Reth, Nature 338 (1989) 383-384 and J.C. Cambier, Immunol. Today 16 (1995) 110-114) consists of five conserved amino acid residues precisely spaced over an amino acid sequence (D2xY2xL7x2xL). ITAMs couple receptors to intracellular effectors which induce a cascade of events leading to both cell activation and to down regulation of the receptors. This review focuses on recent data supporting the involvement of cytosolic effectors of cell activation in the endosomal transport of immunoreceptors. The possible role of these cytosolic factors in lysosomal transport and MHC class II restricted antigen presentation is discussed.
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Affiliation(s)
- C Bonnerot
- CJF 95-01 INSERM, Cellular Biology of Antigen Presentation, Institut Curie, Paris, France.
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33
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Teh YM, Neuberger MS. The immunoglobulin (Ig)alpha and Igbeta cytoplasmic domains are independently sufficient to signal B cell maturation and activation in transgenic mice. J Exp Med 1997; 185:1753-8. [PMID: 9151700 PMCID: PMC2196318 DOI: 10.1084/jem.185.10.1753] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/1997] [Revised: 03/13/1997] [Indexed: 02/04/2023] Open
Abstract
The B cell antigen receptor, composed of membrane immunoglobulin (Ig) sheathed by the Igalpha/Igbeta heterodimer plays a critical role in mediating B cell development and responses to antigen. The cytoplasmic tails of Igalpha and Igbeta differ substantially but have been well conserved in evolution. Transfection experiments have revealed that, while these tails share an esssential tyrosine-based activation motif (ITAM), they perform differently in some but not all assays and have been proposed to recruit distinct downstream effectors. We have created transgenic mouse lines expressing chimeric receptors comprising an IgM fused to the cytoplasmic domain of each of the sheath polypeptides. IgM/alpha and IgM/beta chimeras (but not an IgM/beta with mutant ITAM) are each independently sufficient to mediate allelic exclusion, rescue B cell development in gene-targeted Igmu- mice that lack endogenous antigen receptors, as well as signal for B7 upregulation. While the (IgM/alpha) x (IgM/beta) double-transgenic mouse revealed somewhat more efficient allelic exclusion, our data indicate that each of the sheath polypeptides is sufficient to mediate many of the essential functions of the B cell antigen receptor, even if the combination gives optimal activity.
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MESH Headings
- Abatacept
- Animals
- Antigens, CD
- Antigens, Differentiation/metabolism
- B-Lymphocytes/immunology
- CTLA-4 Antigen
- Dimerization
- Flow Cytometry
- Immunoconjugates
- Immunoglobulin M/biosynthesis
- Interleukin-2/biosynthesis
- Lymphocyte Activation
- Lymphoma, B-Cell
- Mice
- Mice, Inbred C57BL
- Mice, Inbred CBA
- Mice, Transgenic
- Receptors, Antigen, B-Cell/biosynthesis
- Receptors, Antigen, B-Cell/chemistry
- Receptors, Antigen, B-Cell/physiology
- Recombinant Fusion Proteins/biosynthesis
- Signal Transduction
- Transfection
- Tumor Cells, Cultured
- Tyrosine
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Affiliation(s)
- Y M Teh
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 2QH, United Kingdom
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34
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Jensen WA, Pleiman CM, Beaufils P, Wegener AM, Malissen B, Cambier JC. Qualitatively distinct signaling through T cell antigen receptor subunits. Eur J Immunol 1997; 27:707-16. [PMID: 9079813 DOI: 10.1002/eji.1830270320] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
T cell antigen receptors (TCR) contain several subunits including CD3gamma, delta, and epsilon, and TCRzeta and eta which are capable of mediating signal transduction. It is unclear whether the signaling function of these subunits is completely redundant. To assess the relative signaling capabilities of TCR subunits, we compared proximal events in signal transduction by wild-type TCR complexes and TCR devoid of functional zeta subunits, as well as chimeric receptors containing the cytoplasmic domains of TCRzeta or CD3epsilon. Results demonstrate that in BW5147 wild-type TCR, tail-less zeta TCR, CD3epsilon, and TCRzeta transduce signals leading to tyrosine phosphorylation of similar sets of cellular substrates, including the receptor subunits, Fyn, ZAP-70, and phospholipase Cgamma1 (PLCgamma1). Surprisingly, unlike wild-type TCR, tail-less zeta TCR, and CD3epsilon, TCRzeta was incapable of transducing signals resulting in inositol triphosphate (IP3) generation or intracellular free calcium ([Ca2+]i) mobilization. These data indicate that tyrosine phosphorylation of PLCgamma1 is not sufficient to drive IP3 production and [Ca2+]i mobilization. Most importantly, data presented indicate that TCRzeta and CD3epsilon engage partially distinct signaling pathways.
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Affiliation(s)
- W A Jensen
- Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206, USA
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35
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Abstract
In the past year, significant progress in the area of Fc receptor biology has been made in three areas: identification of the protective FcR for serum IgG half-life (Brambell receptor), characterization of the mechanism(s) of inhibitory receptor Fc gamma RIIB signaling, and dissection of the in vivo roles of FcRs in inflammation.
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Affiliation(s)
- J V Ravetch
- Laboratory of Molecular Genetics and Immunology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
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36
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Isakov N. ITIMs and ITAMs. The Yin and Yang of antigen and Fc receptor-linked signaling machinery. Immunol Res 1997; 16:85-100. [PMID: 9048210 DOI: 10.1007/bf02786325] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The initial stages of an immune response are regulated at the level of the cell-surface antigen and Fc receptors. The extracellular portions of these receptors provide immune specificity and determine the nature of the responding effector cells, whereas the intracellular portion transduces signals into the cell and determines the intensity and duration of the immune response. Recent studies led to the identification of two types of modules within the cytoplasmic region of receptor subunits that are critical for the activation and termination of signal transduction pathways. Phosphorylation of the conserved tyrosine residues within the two modules, the immunoreceptor tyrosine-based activation motif (ITAM) and the immunoreceptor tyrosine-based inhibition motif (ITIM), is followed by the recruitment of different sets of SH2-containing molecules to the receptor site. These proteins regulate the receptor-linked signal transduction pathways in a positive or a negative fashion, which is a reminiscent of the ancestral Yin-Yang principle.
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Affiliation(s)
- N Isakov
- Department of Microbiology and Immunology, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva, Israel
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37
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Abstract
Current models of signal transduction from the antigen receptors on B and T cells still resemble equations with several unknown elements. Data from recent knockout experiments in cell lines and mice contradict the assumption that Src-family kinase and tyrosine kinases of the Syk/Zap-70 family are the transducer elements that set signaling from these receptors in motion. Using a functional definition of signaling elements, we discuss the current knowledge of signaling events from the BCR and suggest the existence of an as-yet-unknown BCR transducer complex.
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Affiliation(s)
- M Reth
- Department of Molecular Immunology, Biology III, University Freiburg, Germany.
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38
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Cassard S, Choquet D, Fridman WH, Bonnerot C. Regulation of ITAM signaling by specific sequences in Ig-beta B cell antigen receptor subunit. J Biol Chem 1996; 271:23786-91. [PMID: 8798606 DOI: 10.1074/jbc.271.39.23786] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
B cell antigen receptors (BCR) are composed of an antigen binding subunit, the membrane Ig, and Ig-alpha/Ig-beta heterodimers, that contain a transducing motif named ITAM for "immuno-receptor tyrosine-based activation motif." Ig-alpha and Ig-beta ITAMs only differ by four amino acids located before the second conserved tyrosine (DCSM in Ig-alpha and QTAT in Ig-beta), which determine the in vitro association of Ig-alpha with the src kinase fyn. We have previously shown that Ig-alpha and Ig-beta BCR subunits activate different signaling pathways by expressing, in B cells, FcgammaRII chimeras containing the cytoplasmic tails of Ig-alpha or Ig-beta. We report here that the signaling capacity of Ig-beta ITAM is regulated by peptide sequences located inside (QTAT region) or outside the ITAM (flanking sequences). Furthermore, when isolated, Ig-alpha and Ig-beta ITAM have similar abilities as the entire Ig-alpha tail and the whole BCR in triggering tyrosine kinase activation, an increase of intracellular calcium concentration as well as late events of cell activation as assessed by cytokine secretion. These data show that alterations that modify the ability of Ig-alpha and Ig-beta to interact in vitro with the src kinase fyn (switch between QTAT and DCSM) also determine signal transduction capabilities of these molecules expressed in B cells.
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Affiliation(s)
- S Cassard
- CJF 95-01, INSERM, Institut Curie, 75231 Paris cedex 05, France
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39
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Hou X, Dietrich J, Geisler NO. The cytoplasmic tail of FcgammaRIIIAalpha is involved in signaling by the low affinity receptor for immunoglobulin G. J Biol Chem 1996; 271:22815-22. [PMID: 8798459 DOI: 10.1074/jbc.271.37.22815] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The low affinity receptor for IgG, FcgammaRIIIA, is a multimeric receptor composed of the ligand binding subunit FcgammaRIIIAalpha (CD16) in association with the signal-transducing subunits zeta or gamma. Previous studies suggested that the cytoplasmic tail of FcgammaRIIIAalpha was not required for FcgammaRIIIAalpha-zeta association or signaling by FcgammaRIIIA. However, in these studies, the truncated FcgammaRIIIAalpha chains still expressed the four most membrane-proximal amino acids of the cytoplasmic tail (amino acids 230-233). By successive truncations from the C terminus of FcgammaRIIIAalpha, we have studied the role played by the membrane-proximal amino acids of the cytoplasmic tail of FcgammaRIIIAalpha in (i) FcgammaRIIIA expression, (ii) FcgammaRIIIAalpha-zeta association, and (iii) signal transduction. We provide evidence that this region is not required for FcgammaRIIIA expression or FcgammaRIIIAalpha-zeta association. However, signaling by FcgammaRIIIA is strictly dependent on the membrane-proximal amino acids in the cytoplasmic tail of FcgammaRIIIAalpha. Thus, total deletion of the cytoplasmic tail of FcgammaRIIIAalpha results in a severely impaired tyrosine phosphorylation of phospholipase C-gamma1, zap, and syk and rise in intracellular free Ca2+ following receptor ligation with specific anti-CD16 monoclonal antibody or Ig-anti-Ig complexes, suggesting that FcgammaRIIIAalpha-zeta association per se is not sufficient to establish the signal function of FcgammaRIIIA. In conclusion, the present findings demonstrate that the most membrane-proximal amino acids of the FcgammaRIIIAalpha cytoplasmic tail play a critical role in ligand-induced signal transduction by the FcgammaRIIIAalpha-zeta complex.
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Affiliation(s)
- X Hou
- Institute of Medical Microbiology and Immunology, University of Copenhagen, DK-2200 Copenhagen, Denmark
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40
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D'Ambrosio D, Hippen KL, Cambier JC. Distinct mechanisms mediate SHC association with the activated and resting B cell antigen receptor. Eur J Immunol 1996; 26:1960-5. [PMID: 8765045 DOI: 10.1002/eji.1830260842] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Ligation of the B cell antigen receptor (BCR) complex initiates tyrosine phosphorylation of the receptor's transducer components, Ig-alpha and Ig-beta and tyrosine kinase-dependent accumulation of GTP-bound, activated p21ras. The mechanism of receptor coupling to p21ras activation and the roles of Ig-alpha and Ig-beta are unknown. The results reported here indicate that the resting, nonphosphorylated BCR associates with the Grb-2/Sos-linker SHC via the Ig-alpha immunoreceptor-based tyrosine activation motif (ITAM). Ig-alpha specificity of this interaction is determined by the sequence DCSM found in Ig-alpha, but not Ig-beta. Tyrosine phosphorylation of Ig-alpha and Ig-beta ITAM allows recruitment of SHC, which now binds directly to both Ig-alpha and Ig-beta via a phosphotyrosine/SH2 interaction. In confirmation of recent studies by Saxton et al. (J. Immunol. 1994. 153: 623) receptor ligation leads to tyrosine phosphorylation of SHC and to the formation of a phospho-SHC/Grb2/Sos complex. In view of previous studies which demonstrated p21ras co-capping with ligated BCR, the data presented here suggest that Ig-alpha/beta- and SHC tyrosine phosphorylation-dependent recruitment of the Grb2/Sos complex to the receptor can occur and may provide a mechanism by which the nucleotide exchange activity of Sos could mediate activation of BCR-localized p21ras.
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Affiliation(s)
- D D'Ambrosio
- Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206, USA
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41
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Abstract
Receptor tyrosine kinases (RTK), like the PDGF-receptor, translate information from the extracellular environment into cytoplasmic signals that regulate a spectrum of cellular functions. RTK molecules consist of ligand binding extracellular domains, cytoplasmic kinase domains and tyrosine phosphorylation sites [Ullrich and Schlessinger, 1990 (Cell 61, 203-212); Heldin, 1992 (EMBO J. 11, 4251-4259)]. Upon ligand-induced RTK oligomerization, the kinase domains will become activated and induce auto(trans)phosphorylation of a number of cytoplasmic tyrosine residues. These phosphorylated tyrosine residues are incorporated in distinct sequence motifs and act as specific docking sites for SH2 domain-containing proteins [Songyang et al., 1993 (Cell 72, 767-778)]. In contrast to single- or oligo-chain RTK, immunological receptors such as antigen receptors, FcR and cytokine receptors are multi-chain complexes in which distinct receptor functions appear to be compartmentalized in distinct polypeptides. Here, we summarize current knowledge on the structural and functional characteristics of the B-cell antigen receptor complex (BCR) and address the specific ability of accessory molecules to recruit intracellular signaling intermediates towards the activated receptor complex.
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Affiliation(s)
- A C Lankester
- Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, Amsterdam
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42
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Luisiri P, Lee YJ, Eisfelder BJ, Clark MR. Cooperativity and segregation of function within the Ig-alpha/beta heterodimer of the B cell antigen receptor complex. J Biol Chem 1996; 271:5158-63. [PMID: 8617796 DOI: 10.1074/jbc.271.9.5158] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The B cell antigen receptor complex contains heterodimers of Ig-alpha and Ig-beta. The cytoplasmic tails of each of these chains contain two conserved tyrosines, phosphorylation of which initiates the signal transduction cascades activated by the receptor complex. Although the cytoplasmic domains of Ig-alpha and Ig-beta have been expressed individually and demonstrated to be competent signal transduction units, we postulated that within the context of a heterodimer, Ig-alpha and Ig-beta could have new, complementary or even synergistic functions. Therefore we developed a system to compare the signal transducing capacities of dimers of Ig-alpha/Ig-alpha, Ig-beta/Ig-beta, or Ig-alpha/Ig-beta. This was done by fusing the extracellular and transmembrane domains of either human platelet-derived growth factor receptor (PDGFR) alpha or beta to the cytoplasmic tail of either Ig-alpha or Ig-beta. Three cell lines expressing PDGFRbeta/Ig-alpha, PDGFRbeta/Ig-beta, or PDGFRalpha/Ig-beta together with PDGFRbeta/Ig-alpha were established in the murine B cell line A20 IIA1.6. While aggregation of each dimer by itself could induce the tyrosine phosphorylation of cellular substrates, only aggregation of the heterodimer induced the phosphorylation of substrates similar in range and intensity to that induced by the endogenous B cell antigen receptor complex. Interestingly, Ig-beta remarkably enhanced the rapidity (Tmax decreased from 5 to 1 min) and intensity (greater than 10-fold enhancement) of Ig-alpha phosphorylation. Conversely, the phosphorylation of Ig-beta was reduced to undetectable levels when co-aggregated with Ig-alpha. The enhancement of Ig-alpha phosphorylation by Ig-beta correlated with a lowering of the stimulation threshold for tyrosine kinase activation.
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MESH Headings
- Amino Acid Sequence
- Animals
- Antibodies
- Becaplermin
- Cell Line
- Conserved Sequence
- Gene Expression
- Humans
- Kinetics
- Macromolecular Substances
- Models, Structural
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Phosphoproteins/isolation & purification
- Phosphoproteins/metabolism
- Phosphorylation
- Platelet-Derived Growth Factor/pharmacology
- Protein Multimerization
- Proto-Oncogene Proteins c-sis
- Rabbits/immunology
- Receptors, Antigen, B-Cell/biosynthesis
- Receptors, Antigen, B-Cell/chemistry
- Receptors, Antigen, B-Cell/metabolism
- Receptors, Platelet-Derived Growth Factor/biosynthesis
- Receptors, Platelet-Derived Growth Factor/drug effects
- Receptors, Platelet-Derived Growth Factor/metabolism
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/metabolism
- Recombinant Proteins/pharmacology
- Signal Transduction
- Transfection
- Tyrosine
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Affiliation(s)
- P Luisiri
- Department of Medicine, University of Chicago, Illinois 60637, USA
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43
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Saouaf SJ, Kut SA, Fargnoli J, Rowley RB, Bolen JB, Mahajan S. Reconstitution of the B cell antigen receptor signaling components in COS cells. J Biol Chem 1995; 270:27072-8. [PMID: 7592958 DOI: 10.1074/jbc.270.45.27072] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
To elucidate interactions occurring between B cell protein tyrosine kinases and the signaling components of the B cell antigen receptor, we have co-transfected into COS cells individual tyrosine kinases together with chimeric cell surface receptors containing the cytoplasmic domains of Ig alpha or Ig beta. Of the tyrosine kinases transfected (Lyn, Blk, Hck, Syk, Fyn), only Blk was able to phosphorylate and subsequently associate with cotransfected Ig alpha and Ig beta chimeras in vivo. Association between Blk and the Ig alpha and Ig beta cytoplasmic domains was shown by mutational analyses to be the result of an SH2-phosphotyrosine interaction. We identified the tyrosine residues of the Ig alpha and Ig beta cytoplasmic domains was shown by mutational analyses to be the result of an SH2-phosphotyrosine interaction. We identified the tyrosine residues of the Ig alpha and Ig beta cytoplasmic domains phosphorylated by Blk. The enzymatic activity and membrane association of Blk were required for the observed phosphorylation of the Ig alpha and Ig beta chimeras. Sequences within the amino-terminal unique domain of Blk are responsible for recognition and subsequent phosphorylation of the Ig alpha chimera since transfer of the unique region of Blk to Fyn results in the chimeric kinase's ability to phosphorylate the cytoplasmic domain of Ig alpha. These findings indicate that the unique domain of Src family kinases may direct recognition of certain substrates leading to their phosphorylation.
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Affiliation(s)
- S J Saouaf
- Department of Oncology, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey 08543, USA
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44
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Daëron M, Latour S, Malbec O, Espinosa E, Pina P, Pasmans S, Fridman WH. The same tyrosine-based inhibition motif, in the intracytoplasmic domain of Fc gamma RIIB, regulates negatively BCR-, TCR-, and FcR-dependent cell activation. Immunity 1995; 3:635-46. [PMID: 7584153 DOI: 10.1016/1074-7613(95)90134-5] [Citation(s) in RCA: 370] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The cell-triggering properties of BCR, TCR and FcR depend on structurally related immunoreceptor tyrosine-based activation motifs (ITAMs). Fc gamma RIIB have no ITAM and do not trigger cell activation. When coaggregated to BCR, they inhibit B cell activation. We show here that, when coaggregated to these receptors, Fc gamma RIIB inhibit Fc epsilon RI-, Fc gamma RIIA-, and TCR-dependent cell activation. Inhibition also affected cell activation by single ITAMs, in isolated FcR or TCR subunits. The same tyrosine-based inhibitory motif (ITIM), which is highly conserved in murine and human Fc gamma RIIB and that was previously shown to inhibit BCR-dependent B cell activation, was required to regulate TCR- and FcR-dependent cell activation. Our findings endow Fc gamma RIIB, and thus IgG antibodies, with general immunoregulatory properties susceptible to act on all ITAM-containing receptors.
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MESH Headings
- Amino Acid Sequence
- Animals
- Basophils
- Down-Regulation/genetics
- Histamine Release/physiology
- Humans
- Lymphocyte Activation/immunology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred DBA
- Molecular Sequence Data
- Rats
- Receptors, Antigen, B-Cell/metabolism
- Receptors, Antigen, T-Cell/metabolism
- Receptors, Fc/metabolism
- Receptors, IgE/metabolism
- Receptors, IgG/chemistry
- Receptors, IgG/physiology
- Serotonin/metabolism
- Tumor Cells, Cultured
- Tyrosine/chemistry
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Affiliation(s)
- M Daëron
- Laboratoire d'Immunologie Cellulaire et Clinique, Institut National de la Santé et de la Recherche Médicale U255, Institut Curie, Paris, France
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45
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Malissen B, Ku G, Hermans M, Vivier E, Malissen M. Genetic dissection of the transducing subunits of the T-cell antigen receptor. Ann N Y Acad Sci 1995; 766:173-81. [PMID: 7486653 DOI: 10.1111/j.1749-6632.1995.tb26660.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
MESH Headings
- Amino Acid Sequence
- Animals
- Antigens, Differentiation, T-Lymphocyte/physiology
- Humans
- Macromolecular Substances
- Models, Structural
- Molecular Sequence Data
- Receptor-CD3 Complex, Antigen, T-Cell/chemistry
- Receptor-CD3 Complex, Antigen, T-Cell/metabolism
- Receptors, Antigen, T-Cell/biosynthesis
- Receptors, Antigen, T-Cell/chemistry
- Receptors, Antigen, T-Cell/genetics
- Signal Transduction
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Affiliation(s)
- B Malissen
- Centre d'Immunologie INSERM-CNRS de Marseille-Luminy, France
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46
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Affiliation(s)
- M J Berridge
- Babraham Institute, Department of Zoology, Cambridge, United Kingdom
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47
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Leitenberg D, Constant S, Lu DD, Smith BR, Bottomly K. CD4 and CD45 regulate qualitatively distinct patterns of calcium mobilization in individual CD4+ T cells. Eur J Immunol 1995; 25:2445-51. [PMID: 7589109 DOI: 10.1002/eji.1830250906] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
An early consequence of T cell activation is an increase in intracellular calcium concentration. Recent advances in video laser microscopic techniques enable the examination of individual cells over time following stimulation. Such studies have revealed that cells can undergo qualitatively distinct patterns of calcium mobilization, suggesting that different patterns of calcium flux may be associated with different signaling pathways and may differentially affect late events in cell activation. In this report, we identify distinct patterns of calcium mobilization in CD4+ T cells following the antibody-mediated cross-linking of either CD3 or CD4, or following the cross-linking of both CD3 and CD4 simultaneously. These effects can be further modified by the cross-linking of CD45. We find that antibody cross-linking of CD3 alone induces a single spike in the vast majority of cells shortly after the addition of the cross-linking antibody. In contrast, cross-linking CD4 alone induces a delayed pattern of repetitive calcium spikes which are decreased in amplitude compared to CD3 cross-linking. Simultaneous cross-linking of CD3 and CD4 induces a sustained increase in intracellular calcium mobilization which is dependent on the presence of extracellular calcium. This sustained increase in intracellular calcium concentration is also seen following physiologic cross-linking of CD3 and CD4 after T cell interaction with specific antigen and antigen-presenting cells. Finally, the simultaneous cross-linking of CD45, CD3 and CD4 abrogates the sustained increase in calcium seen following CD3 and CD4 cross-linking. These results suggest that the qualitative nature of T cell receptor signaling can be modulated by the molecular association of other signaling molecules, which may be part of the T cell receptor complex or not.
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Affiliation(s)
- D Leitenberg
- Howard Hughes Medical Institute, Section of Immunobiology, Yale University School of Medicine, New Haven, CT 06520-8011, USA
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48
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Bonnerot C, Lankar D, Hanau D, Spehner D, Davoust J, Salamero J, Fridman WH. Role of B cell receptor Ig alpha and Ig beta subunits in MHC class II-restricted antigen presentation. Immunity 1995; 3:335-47. [PMID: 7552998 DOI: 10.1016/1074-7613(95)90118-3] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The ability of the B cell antigen receptors (BCRs) to enhance MHC class II-restricted antigen presentation was ascribed to mig-associated Ig alpha/Ig beta heterodimers. The relative role of Ig alpha and Ig beta subunits in antigen presentation was investigated by fusing their cytoplasmic tails to the extracellular and transmembrane domains of Fc receptors. Ig alpha and Ig beta chimera mediate antigen internalization and increase the efficiency of antigen presentation, but they drive antigens to different endosomal compartments. Furthermore, antigens internalized by either chimera are degraded and presented with different kinetics. The cytoplasmic tail of Ig alpha targets antigen towards a major population of newly synthesized MHC class II located in class II-rich compartments. In contrast, Ig beta targets antigen towards a minor population of recycling MHC class II molecules, located in transferrin receptor-containing endosomes. Altogether, our data indicate that the composition of BCR could be therefore an important way to modulate the immune response.
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Affiliation(s)
- C Bonnerot
- Institut National de la Santé et de la Recherche Médicale Unit 255 Institut Curie, Paris, France
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49
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Fitts MG, Metzger DW, Hendershot LM, Mage RG. The rabbit B cell antigen receptor is non-covalently associated with unique heteromeric protein complexes: possible insights into the membrane IgM/IgD coexpression paradox. Mol Immunol 1995; 32:753-9. [PMID: 7659100 DOI: 10.1016/0161-5890(95)00028-d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We describe several proteins that are components of the rabbit B cell receptor complex. Two proteins (37 kDa and 42 kDa) were found in non-covalent association with IgM expressed on B cells from peripheral blood. These proteins were also immunoprecipitated by anti-B29 (Ig-beta) and anti-mb1 (Ig-alpha) monoclonal antibodies. As in the mouse and human, the IgM associated molecules were found as heteromeric structures with non-reduced apparent molecular weights of approximately 70-75 kDa. On rabbit B cells we also found these proteins in a 100-135 kDa complex which may represent trimeric or tetrameric structures. By Western blot, the 37 kDa protein was identified as rabbit Ig-beta (B29), suggesting that the 42 kDa protein is rabbit Ig-alpha. These data suggest that rabbit IgM is associated with both Ig-alpha/beta and Ig-(alpha beta)2 or alpha beta gamma complexes. When similar immunoprecipitation studies were performed on lysates made from B cells isolated from appendix follicles, we found two additional IgM associated protein complexes containing 34 kDa and 36 kDa proteins.
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Affiliation(s)
- M G Fitts
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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50
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Abstract
The specificity of immune responses depends upon the activation of only those lymphocytes that recognize the introduced antigen. In recent years, a great deal has been learned about the structure of lymphocyte receptors for antigens and about their signal transduction mechanism. These receptors activate intracellular protein tyrosine kinases of at least two families, the Src family and the Syk/ZAP-70 family. Recent studies have given us considerable insight into the interactions of these two types of kinases and how they mediate antigen receptor signaling.
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Affiliation(s)
- A L DeFranco
- Department of Microbiology and Immunology, University of California, San Francisco 94143-0552, USA
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