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Corneth OBJ, Neys SFH, Hendriks RW. Aberrant B Cell Signaling in Autoimmune Diseases. Cells 2022; 11:cells11213391. [PMID: 36359789 PMCID: PMC9654300 DOI: 10.3390/cells11213391] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 10/15/2022] [Accepted: 10/24/2022] [Indexed: 11/30/2022] Open
Abstract
Aberrant B cell signaling plays a critical in role in various systemic and organ-specific autoimmune diseases. This is supported by genetic evidence by many functional studies in B cells from patients or specific animal models and by the observed efficacy of small-molecule inhibitors. In this review, we first discuss key signal transduction pathways downstream of the B cell receptor (BCR) that ensure that autoreactive B cells are removed from the repertoire or functionally silenced. We provide an overview of aberrant BCR signaling that is associated with inappropriate B cell repertoire selection and activation or survival of peripheral B cell populations and plasma cells, finally leading to autoantibody formation. Next to BCR signaling, abnormalities in other signal transduction pathways have been implicated in autoimmune disease. These include reduced activity of several phosphates that are downstream of co-inhibitory receptors on B cells and increased levels of BAFF and APRIL, which support survival of B cells and plasma cells. Importantly, pathogenic synergy of the BCR and Toll-like receptors (TLR), which can be activated by endogenous ligands, such as self-nucleic acids, has been shown to enhance autoimmunity. Finally, we will briefly discuss therapeutic strategies for autoimmune disease based on interfering with signal transduction in B cells.
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2
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Getahun A. Role of inhibitory signaling in peripheral B cell tolerance*. Immunol Rev 2022; 307:27-42. [PMID: 35128676 PMCID: PMC8986582 DOI: 10.1111/imr.13070] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 01/17/2022] [Indexed: 12/16/2022]
Abstract
At least 20% of B cells in the periphery expresses an antigen receptor with a degree of self-reactivity. If activated, these autoreactive B cells pose a risk as they can contribute to the development of autoimmune diseases. To prevent their activation, both B cell-intrinsic and extrinsic tolerance mechanisms are in place in healthy individuals. In this review article, I will focus on B cell-intrinsic mechanisms that prevent the activation of autoreactive B cells in the periphery. I will discuss how inhibitory signaling circuits are established in autoreactive B cells, focusing on the Lyn-SHIP-1-SHP-1 axis, how they contribute to peripheral immune tolerance, and how disruptions of these circuits can contribute to the development of autoimmunity.
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Affiliation(s)
- Andrew Getahun
- Department of Immunology and Microbiology University of Colorado SOM Aurora Colorado USA
- Department of Immunology and Genomic Medicine National Jewish Health Denver Colorado USA
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3
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Séïté JF, Goutsmedt C, Youinou P, Pers JO, Hillion S. Intravenous immunoglobulin induces a functional silencing program similar to anergy in human B cells. J Allergy Clin Immunol 2014; 133:181-8.e1-9. [DOI: 10.1016/j.jaci.2013.08.042] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Revised: 08/26/2013] [Accepted: 08/28/2013] [Indexed: 12/29/2022]
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4
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Activation of the B cell receptor leads to increased membrane proximity of the Igα cytoplasmic domain. PLoS One 2013; 8:e79148. [PMID: 24244439 PMCID: PMC3823606 DOI: 10.1371/journal.pone.0079148] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 09/18/2013] [Indexed: 01/24/2023] Open
Abstract
Binding of antigen to the B cell receptor (BCR) induces conformational changes in BCR's cytoplasmic domains that are concomitant with phosphorylation of the immunoreceptor tyrosine-based activation motifs (ITAMs). Recently, reversible folding of the CD3ε and ξ chain ITAMs into the plasma membrane has been suggested to regulate T cell receptor signaling. Here we show that the Igα and Igβ cytoplasmic domains of the BCR do not associate with plasma membrane in resting B cells. However, antigen binding and ITAM phosphorylation specifically increased membrane proximity of Igα, but not Igβ. Thus, BCR activation is accompanied by asymmetric conformational changes, possibly promoting the binding of Igα and Igβ to differently localized signaling complexes.
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5
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Luger D, Yang YA, Raviv A, Weinberg D, Banerjee S, Lee MJ, Trepel J, Yang L, Wakefield LM. Expression of the B-cell receptor component CD79a on immature myeloid cells contributes to their tumor promoting effects. PLoS One 2013; 8:e76115. [PMID: 24146823 PMCID: PMC3797715 DOI: 10.1371/journal.pone.0076115] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 08/20/2013] [Indexed: 12/31/2022] Open
Abstract
The role of myeloid derived suppressor cells (MDSCs) in promoting tumorigenesis is well-established, and significant effort is being made to further characterize surface markers on MDSCs both for better diagnosis and as potential targets for therapy. Here we show that the B cell receptor adaptor molecule CD79a is unexpectedly expressed on immature bone marrow myeloid cells, and is upregulated on MDSCs generated in multiple different mouse models of metastatic but not non-metastatic cancer. CD79a on MDSCs is upregulated and activated in response to soluble factors secreted by tumor cells. Activation of CD79a on mouse MDSCs, by crosslinking with a specific antibody, maintained their immature phenotype (CD11b+Gr1+), enhanced their migration, increased their suppressive effect on T cell proliferation, and increased secretion of pro-tumorigenic cytokines such as IL-6 and CCL22. Furthermore, crosslinking CD79a on myeloid cells activated signaling through Syk, BLNK, ERK and STAT3 phosphorylation. In vivo, CD79+ myeloid cells showed enhanced ability to promote primary tumor growth and metastasis. Finally we demonstrate that CD79a is upregulated on circulating myeloid cells from lung cancer patients, and that CD79a+ myeloid cells infiltrate human breast tumors. We propose that CD79a plays a functional role in the tumor promoting effects of myeloid cells, and may represent a novel target for cancer therapy.
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Affiliation(s)
- Dror Luger
- Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Yu-an Yang
- Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Asaf Raviv
- Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Douglas Weinberg
- Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Subhadra Banerjee
- Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Min-Jung Lee
- Medical Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Jane Trepel
- Medical Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Li Yang
- Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Lalage M. Wakefield
- Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America
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6
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Crystal structures of mouse and human RP105/MD-1 complexes reveal unique dimer organization of the toll-like receptor family. J Mol Biol 2011; 413:815-25. [PMID: 21959264 DOI: 10.1016/j.jmb.2011.09.020] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 09/09/2011] [Accepted: 09/13/2011] [Indexed: 01/18/2023]
Abstract
The Toll-like receptor (TLR) 4/MD-2 heterodimer senses lipopolysaccharide (LPS). RP105 (radioprotective 105 kDa), a TLR-related molecule, is similar to TLR4 in that the extracellular leucine-rich repeats associate with MD-1, the MD-2-like molecule. MD-2 has a unique hydrophobic cavity that directly binds to lipid A, the active center of LPS. LPS-bound MD-2 opens the secondary interface with TLR4, leading to dimerization of TLR4/MD-2. MD-1 also has a hydrophobic cavity that accommodates lipid IVa, a precursor of lipid A, suggesting a role for the RP105/MD-1 heterodimer in sensing LPS or related microbial products. Little is known, however, about the structure of the RP105/MD-1 heterodimer or its oligomer. Here, we have determined the crystal structures of mouse and human RP105/MD-1 complexes at 1.9 and 2.8 Å resolutions, respectively. Both mouse and human RP105/MD-1 exhibit dimerization of the 1:1 RP105/MD-1 complex, demonstrating a novel organization. The "m"-shaped 2:2 RP105/MD-1 complex exhibits an inverse arrangement, with N-termini interacting in the middle. Thus, the dimerization interface of RP105/MD-1 is located on the opposite side of the complex, compared to the 2:2 TLR4/MD-2 complex. These results demonstrate that the 2:2 RP105/MD-1 complex is distinct from previously reported TLR dimers, including TLR4/MD-2, TLR1/TLR2, TLR2/TLR6, and TLR3, all of which facilitate homotypic or heterotypic interaction of the C-terminal cytoplasmic signaling domain.
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7
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Dragone LL, Shaw LA, Myers MD, Weiss A. SLAP, a regulator of immunoreceptor ubiquitination, signaling, and trafficking. Immunol Rev 2010; 232:218-28. [PMID: 19909366 DOI: 10.1111/j.1600-065x.2009.00827.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Src-like adapter proteins (SLAP and SLAP-2) constitute a family of proteins that are expressed in a variety of cell types but are studied most extensively in lymphocytes. They have been shown to associate with proximal components of the T-cell receptor (TCR) and B-cell receptor (BCR) signaling complexes. An interaction of SLAP with c-Cbl leads to the ubiquitination and degradation of phosphorylated components of the TCR- and BCR-signaling complexes. The absence of this process in immature SLAP-deficient T and B cells leads to increased immunoreceptor levels due to decreased intracellular retention and degradation. We propose a model in which SLAP-dependent regulation of immunoreceptor levels allows for finer control of immunoreceptor signaling. Thus, SLAP functions to dampen immunoreceptor signaling, thereby influencing lymphocyte development and repertoire selection.
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Ouchida R, Kurosaki T, Wang JY. A Role for Lysosomal-Associated Protein Transmembrane 5 in the Negative Regulation of Surface B Cell Receptor Levels and B Cell Activation. THE JOURNAL OF IMMUNOLOGY 2010; 185:294-301. [PMID: 20519653 DOI: 10.4049/jimmunol.1000371] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
MESH Headings
- Animals
- Antibody Affinity
- B-Lymphocyte Subsets/enzymology
- B-Lymphocyte Subsets/immunology
- B-Lymphocyte Subsets/metabolism
- Cell Line, Tumor
- Cells, Cultured
- Chickens
- Down-Regulation/immunology
- Epitopes, B-Lymphocyte/immunology
- Haptens/administration & dosage
- Haptens/immunology
- Haptens/metabolism
- Immediate-Early Proteins/deficiency
- Immediate-Early Proteins/genetics
- Immediate-Early Proteins/physiology
- Immunoglobulin M/biosynthesis
- Immunoglobulin M/metabolism
- Lymphocyte Activation/immunology
- Lysosomes/enzymology
- Membrane Proteins/deficiency
- Membrane Proteins/genetics
- Membrane Proteins/physiology
- Mice
- Mice, Knockout
- Nitrophenols/administration & dosage
- Nitrophenols/immunology
- Nitrophenols/metabolism
- Phenylacetates/administration & dosage
- Phenylacetates/immunology
- Phenylacetates/metabolism
- Receptors, Antigen, B-Cell/antagonists & inhibitors
- Receptors, Antigen, B-Cell/biosynthesis
- Receptors, Antigen, B-Cell/metabolism
- Up-Regulation/immunology
- gamma-Globulins/administration & dosage
- gamma-Globulins/immunology
- gamma-Globulins/metabolism
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Affiliation(s)
- Rika Ouchida
- Laboratory for Immune Diversity, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Yokohama, Japan
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9
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Abstract
Lymphocyte homeostasis poses a multi-faceted biological puzzle, because steady pre-immune populations must be maintained at an acceptable steady state to yield effective protection, despite stringent selective events during their generation. In addition, activated, memory and both short- and long-term effectors must be governed by independent homeostatic mechanisms. Finally, advancing age is accompanied by substantial changes that impact the dynamics and behavior of these pools, leading to cumulative homeostatic perturbations and compensation. Our laboratory has focused on the over-arching role of BLyS family ligands and receptors in these processes. These studies have led to a conceptual framework within which distinct homeostatic niches are specified by BLyS receptor signatures, which define the BLyS family ligands that can afford survival. The cues for establishing these receptor signatures, as well as the downstream survival mechanisms involved, are integrated with cell extrinsic inputs via cross talk among downstream mediators. A refined understanding of these relationships should yield insight into the selection and maintenance of B cell subsets, as well as an appreciation of how homeostatic mechanisms may contribute to immunosenescence.
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10
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Dylke J, Lopes J, Dang-Lawson M, Machtaler S, Matsuuchi L. Role of the extracellular and transmembrane domain of Ig-alpha/beta in assembly of the B cell antigen receptor (BCR). Immunol Lett 2007; 112:47-57. [PMID: 17675166 DOI: 10.1016/j.imlet.2007.06.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Revised: 06/26/2007] [Accepted: 06/27/2007] [Indexed: 01/27/2023]
Abstract
The B cell antigen receptor (BCR) is expressed on the surface of B-lymphocytes where it binds antigen and transmits signals that regulate B cell activation, growth and differentiation. The BCR is composed of membrane IgM (mIgM) and two signaling proteins, Ig-alpha and Ig-beta. If either of the signaling proteins is not expressed, the incomplete mIgM-containing BCR will not traffic to the cell surface. Our hypothesis is that specific protein:protein interactions between both the extracellular and transmembrane (TM) regions of Ig-alpha and Ig-beta are necessary for receptor assembly, cell surface expression and effective signaling to support the proper development of B cells. While previous work has shown the importance of the TM region in BCR assembly, this study indicates that a heterodimer of the extracellular domains of Ig-alpha and Ig-beta are also required for proper association with mIgM. Cell lines expressing mutated Ig-alpha proteins that did not heterodimerize with Ig-beta in the extracellular and TM domains were unable to properly assemble the BCR. Conversely, an Ig-alpha mutant with an Ig-beta cytoplasmic tail (Cbeta (alpha/alpha/beta)) was able to assemble with the rest of the BCR, in particular with Ig-beta, and traffic to the cell surface. Thus, both the extracellular and TM regions of the Ig-alpha/Ig-beta must be properly associated in order for the BCR to assemble.
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Affiliation(s)
- Janis Dylke
- Cell Biology Group, Department of Zoology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
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11
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Fuentes-Pananá EM, Bannish G, Karnell FG, Treml JF, Monroe JG. Analysis of the Individual Contributions of Igα (CD79a)- and Igβ (CD79b)-Mediated Tonic Signaling for Bone Marrow B Cell Development and Peripheral B Cell Maturation. THE JOURNAL OF IMMUNOLOGY 2006; 177:7913-22. [PMID: 17114463 DOI: 10.4049/jimmunol.177.11.7913] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The individual contribution of Igalpha and Igbeta for BCR-triggered fates is unclear. Prior evidence supports conflicting ideas concerning unique as well as redundant functions for these proteins in the context of BCR/pre-BCR signaling. Part of this ambiguity may reflect the recent appreciation that Igalpha and Igbeta participate in both Ag-independent (tonic) and Ag-dependent signaling. The present study undertook defining the individual requirement for Igalpha and Igbeta under conditions where only ligand-independent tonic signaling was operative. In this regard, we have constructed chimeric proteins containing one or two copies of the cytoplasmic domains of either Igalpha or Igbeta and Igalpha/Igbeta heterodimers with targeted Tyr-->Phe modifications. The ability of these proteins to act as surrogate receptors and trigger early bone marrow and peripheral B cell maturation was tested in RAG2(-/-) primary pro-B cell lines and in gene transfer experiments in the muMT mouse model. We considered that the threshold for a functional activity mediated by the pre-BCR/BCR might only be reached when two functional copies of the Igalpha/Igbeta ITAM domain are expressed together, and therefore the specificity conferred by these proteins can only be observed in these conditions. We found that the ligand-independent tonic signal is sufficient to drive development into mature follicular B cells and both Igalpha and Igbeta chains supported formation of this population. In contrast, neither marginal zone nor B1 mature B cell subsets develop from bone marrow precursors under conditions where only tonic signals are generated.
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Affiliation(s)
- Ezequiel M Fuentes-Pananá
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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12
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Dragone LL, Myers MD, White C, Gadwal S, Sosinowski T, Gu H, Weiss A. Src-like adaptor protein (SLAP) regulates B cell receptor levels in a c-Cbl-dependent manner. Proc Natl Acad Sci U S A 2006; 103:18202-7. [PMID: 17110436 PMCID: PMC1838730 DOI: 10.1073/pnas.0608965103] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Src-like adaptor protein (SLAP) and c-Cbl recently have been shown to cooperate in regulating T cell receptor (TCR) levels in developing T cells. SLAP also is expressed in developing B cells, and its deficiency leads to alterations in B cell receptor (BCR) levels and B cell development. Hence, we hypothesized that SLAP and c-Cbl may cooperate during B cell development to regulate BCR levels. In mice deficient in both SLAP and c-Cbl, we found that B cell development is altered, suggesting that they function through intersecting pathways. To study the mechanism by which SLAP and c-Cbl alter BCR levels, we coexpressed them in a mature mouse B cell line (Bal-17). First we determined that SLAP associates with proximal components of the BCR complex after stimulation and internalization. Coexpression of SLAP and c-Cbl in Bal-17 led to decreased surface and total BCR levels. This decrease in BCR levels depended on intact Src homology 2 (SH2) and C-terminal domains of SLAP. In addition, a mutation in the SH2 domain of SLAP blocked its colocalization with c-Cbl and the BCR complex, whereas deletion of the C terminus did not affect its localization. Last, coexpression of SLAP and c-Cbl altered BCR complex recycling. This alteration in BCR complex recycling depended on enzymatically active c-Cbl and Src family kinases, as well as the intact SH2 and C-terminal domains of SLAP. These data suggest that SLAP has a conserved function in B and T cells by adapting c-Cbl to the antigen-receptor complex and targeting it for degradation.
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Affiliation(s)
- Leonard L. Dragone
- Division of Pediatric Immunology/Rheumatology, Department of Pediatrics, and
| | - Margaret D. Myers
- Howard Hughes Medical Institute
- Division of Rheumatology, Department of Medicine, and
- Rosalind Russell Medical Research Center for Arthritis, University of California, San Francisco, CA 94143
| | - Carmen White
- Division of Pediatric Immunology/Rheumatology, Department of Pediatrics, and
| | - Shyam Gadwal
- University of Maryland Baltimore County, Baltimore, MD 21250
| | | | - Hua Gu
- Microbiology Department, Columbia University, College of Physician and Surgeons, New York, NY 10032
| | - Arthur Weiss
- Howard Hughes Medical Institute
- Division of Rheumatology, Department of Medicine, and
- Rosalind Russell Medical Research Center for Arthritis, University of California, San Francisco, CA 94143
- To whom correspondence should be addressed at:
Howard Hughes Medical Institute, University of California, 513 Parnassus Avenue, Box 0795, San Francisco, CA 94143. E-mail:
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13
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Acevedo-Suárez CA, Kilkenny DM, Reich MB, Thomas JW. Impaired intracellular calcium mobilization and NFATc1 availability in tolerant anti-insulin B cells. THE JOURNAL OF IMMUNOLOGY 2006; 177:2234-41. [PMID: 16887983 DOI: 10.4049/jimmunol.177.4.2234] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
B lymphocytes that recognize soluble self-Ags are routinely found in normal individuals in a functionally inactive or anergic state. Current models indicate that this tolerant state is maintained by interactions with self-Ags that uncouple the BCR from downstream signaling pathways and increase levels of free calcium. Contrary to this expectation, B cells that harbor anti-insulin Ig transgenes (125Tg) are maintained in a tolerant state even though free calcium levels remain normal and tyrosine kinase substrate phosphorylation is preserved following BCR stimulation. Under basal conditions, intracellular levels of inositol 1,4,5-trisphosphate are increased and NFATc1 levels are reduced in 125Tg B cells. The 125Tg B cells are markedly impaired in their ability to mobilize calcium upon stimulation with ionomycin, and BCR-induced calcium mobilization from internal stores is decreased. In contrast, poisoning intracellular calcium pumps with thapsigargin increases calcium mobilization in 125Tg B cells. Changes in calcium signaling are accompanied by a failure of 125Tg B cells to translocate NFATc1 into the nucleus following stimulation with either anti-IgM or ionomycin. Thus, disassociation of BCR from multiple signaling pathways is not essential for maintaining tolerance in anti-insulin 125Tg B cells. Rather, BCRs that are occupied by autologous insulin deliver signals that induce changes in intracellular calcium mobilization and maintain tolerance by preventing activation of key transcription factors such as NFAT.
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14
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Gazumyan A, Reichlin A, Nussenzweig MC. Ig beta tyrosine residues contribute to the control of B cell receptor signaling by regulating receptor internalization. J Exp Med 2006; 203:1785-94. [PMID: 16818674 PMCID: PMC2118343 DOI: 10.1084/jem.20060221] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Accepted: 06/02/2006] [Indexed: 12/14/2022] Open
Abstract
Immunoglobulin (Ig)alpha and Igbeta initiate B cell receptor (BCR) signaling through immune receptor tyrosine activation motifs (ITAMs) that are targets of SH2 domain-containing kinases. To examine the function of Igbeta ITAM tyrosine resides in mature B cells in vivo, we exchanged these residues for alanine by gene targeting (Igbeta(AA)). Mutant mice showed normal development of all B cell subtypes with the exception of B1 cells that were reduced by fivefold. However, primary B cells purified from Igbeta(AA) mice showed significantly decreased steady-state and ligand-mediated BCR internalization and higher levels of cell surface IgM and IgD. BCR cross-linking resulted in decreased Src and Syk activation but paradoxically enhanced and prolonged BCR signaling, as measured by cellular tyrosine phosphorylation, Ca(++) flux, AKT, and ERK activation. In addition, B cells with the ITAM mutant receptor showed an enhanced response to a T-independent antigen. Thus, Igbeta ITAM tyrosines help set BCR signaling threshold by regulating receptor internalization.
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Affiliation(s)
- Anna Gazumyan
- Laboratory of Molecular Immunology and 2Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10021, USA.
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15
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Bléry M, Tze L, Miosge LA, Jun JE, Goodnow CC. Essential role of membrane cholesterol in accelerated BCR internalization and uncoupling from NF-kappa B in B cell clonal anergy. ACTA ACUST UNITED AC 2006; 203:1773-83. [PMID: 16801401 PMCID: PMC2118358 DOI: 10.1084/jem.20060552] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Divergent hypotheses exist to explain how signaling by the B cell receptor (BCR) is initiated after antigen binding and how it is qualitatively altered in anergic B cells to selectively uncouple from nuclear factor kappaB and c-Jun N-terminal kinase pathways while continuing to activate extracellular signal-regulated kinase and calcium-nuclear factor of activated T cell pathways. Here we find that BCRs on anergic cells are endocytosed at a very enhanced rate upon binding antigen, resulting in a large steady-state pool of intracellularly sequestered receptors that appear to be continuously cycling between surface and intracellular compartments. This endocytic mechanism is exquisitely sensitive to the lowering of plasma membrane cholesterol by methyl-beta-cyclodextrin, and, when blocked in this way, the sequestered BCRs return to the cell surface and RelA nuclear accumulation is stimulated. In contrast, when plasma membrane cholesterol is lowered and GM1 sphingolipid markers of membrane rafts are depleted in naive B cells, this does not diminish BCR signaling to calcium or RelA. These results provide a possible explanation for the signaling changes in clonal anergy and indicate that a chief function of membrane cholesterol in B cells is not to initiate BCR signaling, but instead to terminate a subset of signals by rapid receptor internalization.
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Affiliation(s)
- Mathieu Bléry
- John Curtin School of Medical Research, The Australian National University, Canberra ACT 2601, Australia
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16
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Abstract
Cells of the immune system possess many multisubunit receptors that are composed of a ligand-binding subunit associated with distinct signaling adaptors containing one or more immunoreceptor tyrosine-based activation motifs (ITAMs). These receptors include the T cell receptor, the B cell receptor, and many Fc receptors, as well as families of activating receptors on myeloid and natural killer cells. Receptors that associate with ITAM-containing adaptors classically have been viewed as transducing activating signals involving phosphorylation of the tyrosines within the ITAM and recruitment of Syk family tyrosine kinases. Receptors associated with ITAM-containing adaptors in myeloid cells have also been implicated in inhibition of cellular activation. Here, we discuss these new negative roles for signaling by receptors that associate with ITAM-bearing adaptors in myeloid and other cell types within the immune system.
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MESH Headings
- Adaptor Proteins, Signal Transducing/deficiency
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/physiology
- Amino Acid Motifs
- Animals
- Antigens, CD/physiology
- Calcium Signaling
- Cell Differentiation
- Cytokines/metabolism
- Enzyme Precursors/physiology
- Humans
- Intracellular Signaling Peptides and Proteins
- Lymphocytes/immunology
- Macrophage Activation
- Mice
- Mice, Knockout
- Mice, Transgenic
- Models, Biological
- Myeloid Cells/immunology
- Phosphorylation
- Phosphotyrosine/physiology
- Protein Processing, Post-Translational/physiology
- Protein Tyrosine Phosphatases/physiology
- Protein-Tyrosine Kinases/physiology
- Receptors, Antigen, B-Cell/chemistry
- Receptors, Antigen, B-Cell/immunology
- Receptors, Antigen, T-Cell/chemistry
- Receptors, Antigen, T-Cell/immunology
- Receptors, Fc/chemistry
- Receptors, Fc/immunology
- Receptors, Fc/physiology
- Receptors, IgG/physiology
- Receptors, Immunologic/chemistry
- Receptors, Immunologic/physiology
- Signal Transduction/physiology
- Syk Kinase
- T-Lymphocytes/cytology
- T-Lymphocytes/immunology
- ZAP-70 Protein-Tyrosine Kinase/physiology
- src Homology Domains
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Affiliation(s)
- Jessica A Hamerman
- Department of Microbiology and Immunology, Cancer Research Institute, University of California, Box 0414, HSE1001, San Francisco, CA 94143-0414, USA
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17
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Dragone LL, Myers MD, White C, Sosinowski T, Weiss A. Src-Like Adaptor Protein Regulates B Cell Development and Function. THE JOURNAL OF IMMUNOLOGY 2005; 176:335-45. [PMID: 16365426 DOI: 10.4049/jimmunol.176.1.335] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The avidity of BCRs and TCRs influences signal strength during processes of lymphocyte development. Avidity is determined by both the intrinsic affinity for Ag and surface levels of the Ag receptor. The Src-like adaptor protein (SLAP) is a regulator of TCR levels on thymocytes, and its deficiency alters thymocyte development. We hypothesized that SLAP, which is expressed in B cells, also is important in regulating BCR levels, signal strength, and B cell development. To test this hypothesis, we analyzed the B cell compartment in SLAP-deficient mice. We found increased splenic B cell numbers and decreased surface IgM levels on mature, splenic B cells deficient in SLAP. Immature bone marrow and splenic B cells from BCR-transgenic, SLAP-deficient mice were found to express higher surface levels of IgM. In contrast, mature splenic B cells from BCR-transgenic mice expressed decreased levels of surface BCR associated with decreased calcium flux and activation-induced markers, compared with controls. These data suggest that SLAP regulates BCR levels and signal strength during lymphocyte development.
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Affiliation(s)
- Leonard L Dragone
- Division of Pediatric Immunology/Rheumatology, Department of Pediatrics, University of California, San Francisco, CA 94143, USA
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Thomas MD, Kremer CS, Ravichandran KS, Rajewsky K, Bender TP. c-Myb Is Critical for B Cell Development and Maintenance of Follicular B Cells. Immunity 2005; 23:275-86. [PMID: 16169500 DOI: 10.1016/j.immuni.2005.08.005] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2004] [Revised: 07/28/2005] [Accepted: 08/03/2005] [Indexed: 01/01/2023]
Abstract
The c-Myb transcription factor is crucial during definitive hematopoiesis. However, the embryonic lethality of Myb traditional null mutations has precluded analysis of c-Myb function in lymphocytes. Using tissue-specific inactivation at the Myb locus, we demonstrate that loss of Myb causes a partial block during B cell development at the pro-B to pre-B cell transition, resulting in greatly decreased output of new B cells from the bone marrow. Furthermore, we demonstrate that Myb is not essential for the proliferation of splenic B cells, but that loss of c-Myb function prevents normal B cell homeostasis due to decreased splenic B cell survival. Decreased survival is accompanied by hyporesponsiveness to the B cell survival factor BLyS (also termed BAFF), decreased expression of the BLyS receptor 3 (BR3), and altered regulation of PKCdelta nuclear accumulation. Thus, c-Myb is important during multiple stages of B-lymphopoiesis.
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Affiliation(s)
- Matthew D Thomas
- Department of Microbiology, P.O. Box 800734, University of Virginia Health System, Charlottesville, VA 22908, USA
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Crowley JE, Treml LS, Stadanlick JE, Carpenter E, Cancro MP. Homeostatic niche specification among naïve and activated B cells: A growing role for the BLyS family of receptors and ligands. Semin Immunol 2005; 17:193-9. [PMID: 15826824 DOI: 10.1016/j.smim.2005.02.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
B lymphocyte homeostasis encompasses the establishment and maintenance of independently regulated niches, within which cells compete for viability promoting resources. The BLyS/BLyS receptor family controls the size and composition of these niches, by governing the selection and survival of most peripheral B cells. Moreover, different receptor-ligand sets from this family dominate the regulation of various B cell subsets. These observations suggest a model whereby the regulation of BLyS receptors by differentiative and stimulatory cues yield characteristic BLyS receptor signatures, thus specifying homeostatic niche and competitive advantage.
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Affiliation(s)
- Jenni E Crowley
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, 284 John Morgan Building, 36th And Hamilton Walk, Philadelphia, PA 19104-8062, USA
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