151
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T-cell receptor-induced NF-kappaB activation is negatively regulated by E3 ubiquitin ligase Cbl-b. Mol Cell Biol 2008; 28:2470-80. [PMID: 18227156 DOI: 10.1128/mcb.01505-07] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
It has previously been shown that E3 ubiquitin ligase Casitas B-lineage lymphoma-b (Cbl-b) negatively regulates T-cell activation, but the molecular mechanism(s) underlying this inhibition is not completely defined. In this study, we report that the loss of Cbl-b selectively results in aberrant activation of NF-kappaB upon T-cell antigen receptor (TCR) ligation, which is mediated by phosphatidylinositol 3-kinase (PI3-K)/Akt and protein kinase C-theta (PKC-theta). TCR-induced hyperactivation of Akt in the absence of Cbl-b may potentiate the formation of caspase recruitment domain-containing membrane-associated guanylate kinase protein 1 (CARMA1)-B-cell lymphoma/leukemia 10 (Bcl10)-mucosa-associated lymphatic tissue 1(MALT1) (CBM) complex, which appears to be independent of PKC-theta. Cbl-b associates with PKC-theta upon TCR stimulation and regulates TCR-induced PKC-theta activation via Vav-1, which couples PKC-theta to PI3-K and allows it to be phosphorylated. PKC-theta then couples IkappaB kinases (IKKs) to the CBM complex, resulting in the activation of the IKK complex. Therefore, our data provide the first evidence to demonstrate that the down-regulation of TCR-induced NF-kappaB activation by Cbl-b is mediated coordinately by both Akt-dependent and PKC-theta-dependent signaling pathways in primary T cells.
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152
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Cronin SJF, Penninger JM. From T-cell activation signals to signaling control of anti-cancer immunity. Immunol Rev 2008; 220:151-68. [PMID: 17979845 DOI: 10.1111/j.1600-065x.2007.00570.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The activation of resting T cells is crucial to most immune processes. Recognition of foreign antigen by T-cell receptors has to be correctly translated into signal transduction events necessary for the induction of an effective immune response. In this review, we discuss the essential signals, molecules, and processes necessary to achieve full T-cell activation. In addition to describing these key biological events, we also discuss how T-cell receptor signaling may be harnessed to yield new therapeutic targets for a next generation of anti-cancer drugs.
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Affiliation(s)
- Shane J F Cronin
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
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153
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PIP3 pathway in regulatory T cells and autoimmunity. Immunol Res 2008; 39:194-224. [PMID: 17917066 DOI: 10.1007/s12026-007-0075-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 01/07/2023]
Abstract
Regulatory T cells (Tregs) play an important role in preventing both autoimmune and inflammatory diseases. Many recent studies have focused on defining the signal transduction pathways essential for the development and the function of Tregs. Increasing evidence suggest that T-cell receptor (TCR), interleukin-2 (IL-2) receptor (IL-2R), and co-stimulatory receptor signaling are important in the early development, peripheral homeostasis, and function of Tregs. The phosphoinositide-3 kinase (PI3K)-regulated pathway (PIP3 pathway) is one of the major signaling pathways activated upon TCR, IL-2R, and CD28 stimulation, leading to T-cell activation, proliferation, and cell survival. Activation of the PIP3 pathway is also negatively regulated by two phosphatidylinositol phosphatases SHIP and PTEN. Several mouse models deficient for the molecules involved in PIP3 pathway suggest that impairment of PIP3 signaling leads to dysregulation of immune responses and, in some cases, autoimmunity. This review will summarize the current understanding of the importance of the PIP3 pathway in T-cell signaling and the possible roles this pathway performs in the development and the function of Tregs.
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154
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Regulation of T Cell Differentiation and Allergic Responses by the E3 Ubiquitin Ligase Itch. THE UBIQUITIN SYSTEM IN HEALTH AND DISEASE 2008:137-52. [DOI: 10.1007/2789_2008_106] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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155
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Abstract
Activation of the phosphoinositide 3-kinase (PI3K) pathway promotes proliferation and survival in many different cell types of the immune system. PI3K acts downstream of receptors that mediate proliferation and survival in T cells, and required roles for individual class I PI3K catalytic isoforms have been established. Interestingly, mice with either augmented or diminished PI3K activity in T cells develop lymphoproliferation and signs of autoimmunity. Here, we summarize our current knowledge of mouse strains with hyperactive or reduced PI3K, different isoforms of class I PI3K in T cell-mediated immunity and autoimmunity, and the therapeutic implications for modulating this pathway for treatment of various autoimmune diseases.
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Affiliation(s)
- Jean S Oak
- Department of Molecular Biology and Biochemistry, Center for Immunology, University of California, Irvine, CA 92697, USA
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156
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Xu Y, Ikegami M, Wang Y, Matsuzaki Y, Whitsett JA. Gene expression and biological processes influenced by deletion of Stat3 in pulmonary type II epithelial cells. BMC Genomics 2007; 8:455. [PMID: 18070348 PMCID: PMC2234434 DOI: 10.1186/1471-2164-8-455] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Accepted: 12/10/2007] [Indexed: 11/10/2022] Open
Abstract
Background The signal transducer and activator of transcription 3 (STAT3) mediates gene expression in response to numerous growth factors and cytokines, playing an important role in many cellular processes. To better understand the molecular mechanisms by which Stat3 influences gene expression in the lung, the effect of pulmonary epithelial cell specific deletion of Stat3 on genome wide mRNA expression profiling was assessed. Differentially expressed genes were identified from Affymetrix Murine GeneChips analysis and subjected to gene ontology classification, promoter analysis, pathway mapping and literature mining. Results Total of 791 mRNAs were significantly increased and 314 mRNAs were decreased in response to the deletion of Stat3Δ/Δ in the lung. STAT is the most enriched cis-elements in the promoter regions of those differentially expressed genes. Deletion of Stat3 induced genes influencing protein metabolism, transport, chemotaxis and apoptosis and decreased the expression of genes mediating lipid synthesis and metabolism. Expression of Srebf1 and 2, genes encoding key regulators of fatty acid and steroid biosynthesis, was decreased in type II cells from the Stat3Δ/Δ mice, consistent with the observation that lung surfactant phospholipids content was decreased. Stat3 influenced both pro- and anti-apoptotic pathways that determine cell death or survival. Akt, a potential transcriptional target of Stat3, was identified as an important participant in Stat3 mediated pathways including Jak-Stat signaling, apoptosis, Mapk signaling, cholesterol and fatty acid biosynthesis. Conclusion Deletion of Stat3 from type II epithelial cells altered the expression of genes regulating diverse cellular processes, including cell growth, apoptosis and lipid metabolism. Pathway analysis indicates that STAT3 regulates cellular homeostasis through a complex regulatory network that likely enhances alveolar epithelial cell survival and surfactant/lipid synthesis, necessary for the protection of the lung during injury.
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Affiliation(s)
- Yan Xu
- Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Department of Pediatrics, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH, USA.
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157
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Lin AE, Mak TW. The role of E3 ligases in autoimmunity and the regulation of autoreactive T cells. Curr Opin Immunol 2007; 19:665-73. [PMID: 18036806 DOI: 10.1016/j.coi.2007.10.002] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Revised: 10/01/2007] [Accepted: 10/02/2007] [Indexed: 11/30/2022]
Abstract
The ubiquitination of proteins by E3 ligases has become an important regulatory mechanism for a variety of immune functions, including the maintenance of self tolerance and suppression of autoreactive T cell development. This review highlights recent advances in our knowledge of the functions in this context of known and potential E3 ligases, including autoimmune regulator (AIRE), TNF receptor-associated factor 6 (TRAF6), Casitas B cell lymphoma b (Cbl-b), gene related to anergy in lymphocytes (GRAIL), Itch, and Roquin. We discuss how disruptions to these molecules may contribute to the loss of T cell homeostasis and the pathogenesis of autoimmunity. We also report on the implications of the potential coordinated actions of these molecules for T cell anergy and regulatory T cell (Treg) functions. The great diversity of E3 ligases and the growing list of cellular processes in which ubiquitination plays a role make for an exciting field of research. Findings emerging from these investigations may suggest ways to exploit the therapeutic potential of manipulating ubiquitination, particularly for autoimmune disorders.
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Affiliation(s)
- Amy Erica Lin
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
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158
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Schymeinsky J, Then C, Sindrilaru A, Gerstl R, Jakus Z, Tybulewicz VLJ, Scharffetter-Kochanek K, Walzog B. Syk-mediated translocation of PI3Kdelta to the leading edge controls lamellipodium formation and migration of leukocytes. PLoS One 2007; 2:e1132. [PMID: 17987119 PMCID: PMC2063580 DOI: 10.1371/journal.pone.0001132] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Accepted: 10/10/2007] [Indexed: 12/19/2022] Open
Abstract
The non-receptor tyrosine kinase Syk is mainly expressed in the hematopoietic system and plays an essential role in beta(2) integrin-mediated leukocyte activation. To elucidate the signaling pathway downstream of Syk during beta2 integrin (CD11/CD18)-mediated migration and extravasation of polymorphonuclear neutrophils (PMN), we generated neutrophil-like differentiated HL-60 (dHL-60) cells expressing a fluorescently tagged Syk mutant lacking the tyrosine residue at the position 323 (Syk-Tyr323) that is known to be required for the binding of the regulatory subunit p85 of the phosphatidylinositol 3-kinase (PI3K) class I(A). Syk-Tyr323 was found to be critical for the enrichment of the catalytic subunit p110delta of PI3K class I(A) as well as for the generation of PI3K products at the leading edge of the majority of polarized cells. In accordance, the translocation of PI3K p110delta to the leading edge was diminished in Syk deficient murine PMN. Moreover, the expression of EGFP-Syk Y323F interfered with proper cell polarization and it impaired efficient migration of dHL-60 cells. In agreement with a major role of beta2 integrins in the recruitment of phagocytic cells to sites of lesion, mice with a Syk-deficient hematopoietic system demonstrated impaired PMN infiltration into the wounded tissue that was associated with prolonged cutaneous wound healing. These data imply a novel role of Syk via PI3K p110delta signaling for beta2 integrin-mediated migration which is a prerequisite for efficient PMN recruitment in vivo.
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Affiliation(s)
- Jürgen Schymeinsky
- Department of Physiology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Cornelia Then
- Department of Physiology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Anca Sindrilaru
- Department of Dermatology and Allergic Diseases, University of Ulm, Ulm, Germany
| | - Ronald Gerstl
- Department of Physiology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Zoltán Jakus
- Department of Physiology, Semmelweis University School of Medicine, Budapest, Hungary
| | - Victor L. J. Tybulewicz
- Division of Immune Cell Biology, National Institute for Medical Research, London, United Kingdom
| | | | - Barbara Walzog
- Department of Physiology, Ludwig-Maximilians-University Munich, Munich, Germany
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159
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Abstract
The engagement of the T-cell receptor (TCR) causes the rapid recruitment of multiple signaling molecules into clusters with the TCR. Upon receptor activation, the adapters LAT and SLP-76, visualized as chimeric proteins tagged with yellow fluorescent protein, transiently associate with and then rapidly dissociate from the TCR. Previously, we demonstrated that after recruitment into signaling clusters, SLP-76 is endocytosed in vesicles via a lipid raft-dependent pathway that requires the interaction of the endocytic machinery with ubiquitylated proteins. In this study, we focus on LAT and demonstrate that signaling clusters containing this adapter are internalized into distinct intracellular compartments and dissipate rapidly upon TCR activation. The internalization of LAT was inhibited in cells expressing versions of the ubiquitin ligase c-Cbl mutated in the RING domain and in T cells from mice lacking c-Cbl. Moreover, c-Cbl RING mutant forms suppressed LAT ubiquitylation and caused an increase in cellular LAT levels, as well as basal and TCR-induced levels of phosphorylated LAT. Collectively, these data indicate that following the rapid formation of signaling complexes upon TCR stimulation, c-Cbl activity is involved in the internalization and possible downregulation of a subset of activated signaling molecules.
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160
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Abstract
Directing both innate and adaptive immune responses against foreign pathogens with correct timing, location and specificity is a fundamental objective for the immune system. Full activation of CD4+ T cells requires the binding of peptide-MHC complexes coupled with accessory signals provided by the antigen-presenting cell. However, aberrant activation of the T-cell receptor alone in mature T cells can produce a long-lived state of functional unresponsiveness, known as anergy. Recent studies probing both immune signalling pathways and the ubiquitin-proteasome system have helped to refine and elaborate current models for the molecular mechanisms underlying T-cell anergy. Controlling anergy induction and maintenance will be a key component in the future to mitigate unwanted T-cell activation that leads to autoimmune disease.
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Affiliation(s)
- C Garrison Fathman
- Stanford University School of Medicine, Department of Medicine, Division of Immunology and Rheumatology, CCSR Building, 269 Campus Drive, Room 2225, Stanford, California 94305-5166, USA.
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161
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Zhang L, Zhao Y. The regulation of Foxp3 expression in regulatory CD4(+)CD25(+)T cells: multiple pathways on the road. J Cell Physiol 2007; 211:590-7. [PMID: 17311282 DOI: 10.1002/jcp.21001] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Regulatory T cells (Treg cells) have been well documented to have a crucial physiological role in preventing the development of autoimmune diseases and keeping self-tolerance. Foxp3, a recently identified member of the forkhead transcription factors, serves as a master regulator for the development and function of CD4(+)CD25(+)Treg cells. Though it is well defined that Foxp3 expression is sufficient to program CD4(+)CD25(+)Treg cell development, the physiological factors initiating intracellular Foxp3 expression remain poorly understood so far. In the present manuscript, we try to summarize the recent advances regarding the regulatory roles of T-cell receptor (TCR), co-stimulatory molecules, interleukin-2 (IL-2), transforming growth factor-beta (TGF-beta) and beyond pathways on Foxp3 expression.
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Affiliation(s)
- Lianjun Zhang
- Transplantation Biology Research Division, State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
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162
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Abstract
Signaling through lymphocyte antigen receptors has the potential to initiate several distinct outcomes: proliferation, differentiation, apoptosis, or functional unresponsiveness. Expansion and differentiation of effector T cells is required for defense against foreign antigens, whereas functional unresponsiveness, termed anergy, is a cell-intrinsic mechanism that contributes to peripheral self-tolerance. Other mechanisms of peripheral tolerance include the 'dominant' tolerance imposed by regulatory T cells and immunosuppression mediated by interleukin-10 and transforming growth factor-beta. T- and B-cell antigen receptor ligation induces an increase in intracellular calcium levels as well as activating additional signaling pathways that are further potentiated by costimulatory receptors. In this review, we argue that cell-intrinsic programs of peripheral anergy and tolerance are imposed by sustained calcium signaling in lymphocytes. We address in particular the role of the calcium-dependent transcription factor nuclear factor for activation of T cells, which is activated by antigen receptor stimulation and, depending on the presence or absence of input from its transcriptional partner, activator protein-1, dictates two distinct transcriptional programs: activation or tolerance.
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Affiliation(s)
- Madhuri Borde
- The CBR Institute for Biomedical Research and the Department of Pathology, Harvard Medical School, Boston, MA 02115, USA
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163
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Schartner JM, Fathman CG, Seroogy CM. Preservation of self: An overview of E3 ubiquitin ligases and T cell tolerance. Semin Immunol 2007; 19:188-96. [PMID: 17403607 DOI: 10.1016/j.smim.2007.02.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Accepted: 02/16/2007] [Indexed: 02/01/2023]
Abstract
Until recently ubiquitination of a protein was thought to simply serve the mundane task of targeting a protein for proteasomal degradation. Accumulating evidence over the past decade has demonstrated the importance of ubiquitination in non-degradative functions including regulating cellular signaling, that highlight its role in human disease and thus potential development of novel therapeutics. Much has been written about ubiquitination in the immune system, in this review we will outline our current knowledge of ubiquitination with respect to T cell tolerance. Specifically, we will provide on overview of E3 ubiquitin ligases and their role in various states of CD4+ T cell tolerance: central and peripheral.
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Affiliation(s)
- J M Schartner
- University of Wisconsin, Department of Pediatrics, Division of Allergy/Immunology/Rheumatology, Madison, WI 53792, USA
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164
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Kitaura Y, Jang IK, Wang Y, Han YC, Inazu T, Cadera EJ, Schlissel M, Hardy RR, Gu H. Control of the B cell-intrinsic tolerance programs by ubiquitin ligases Cbl and Cbl-b. Immunity 2007; 26:567-78. [PMID: 17493844 PMCID: PMC1948079 DOI: 10.1016/j.immuni.2007.03.015] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 01/04/2007] [Accepted: 03/29/2007] [Indexed: 01/13/2023]
Abstract
B cell receptor (BCR) signaling plays a critical role in B cell tolerance and activation. Here, we show that mice with B cell-specific ablation of both Cbl and Cbl-b (Cbl-/-Cblb-/-) manifested systemic lupus erythematosus (SLE)-like autoimmune disease. The Cbl double deficiency resulted in a substantial increase in marginal zone (MZ) and B1 B cells. The mutant B cells were not hyperresponsive in terms of proliferation and antibody production upon BCR stimulation; however, B cell anergy to protein antigen appeared to be impaired. Concomitantly, BCR-proximal signaling, including tyrosine phosphorylation of Syk tyrosine kinase, Phospholipase C-gamma2 (PLC-gamma2), and Rho-family GTP-GDP exchange factor Vav, and Ca2+ mobilization were enhanced, whereas tyrosine phosphorylation of adaptor protein BLNK was substantially attenuated in the mutant B cells. These results suggested that the loss of coordination between these pathways was responsible for the impaired B cell tolerance induction. Thus, Cbl proteins control B cell-intrinsic checkpoint of immune tolerance, possibly through coordinating multiple BCR-proximal signaling pathways during anergy induction.
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Affiliation(s)
- Yasuyuki Kitaura
- Department of Microbiology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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165
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Liu YC. The E3 ubiquitin ligase Itch in T cell activation, differentiation, and tolerance. Semin Immunol 2007; 19:197-205. [PMID: 17433711 PMCID: PMC2680672 DOI: 10.1016/j.smim.2007.02.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Accepted: 02/16/2007] [Indexed: 12/11/2022]
Abstract
Tagging a small molecule ubiquitin to a protein substrate, or protein ubiquitination, plays an important role in the immune responses. This process is catalyzed by a cascade of enzymatic reactions, with the E3 ubiquitin ligases being the critical enzymes that determine the specificity of substrate recognition. The E3 ligase Itch was identified from a mutant mouse which displays skin scratching and abnormal immune disorders. In the past few years, much progress has been made in our understanding of Itch-promoted protein ubiquitination, modulation of its ligase activity by upstream kinases, and the kinase-ligase interaction in T cell differentiation and tolerance induction.
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Affiliation(s)
- Yun-Cai Liu
- Division of Cell Biololgy, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA.
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166
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Li W, Gao B, Lee SM, Bennett K, Fang D. RLE-1, an E3 ubiquitin ligase, regulates C. elegans aging by catalyzing DAF-16 polyubiquitination. Dev Cell 2007; 12:235-46. [PMID: 17276341 DOI: 10.1016/j.devcel.2006.12.002] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2006] [Revised: 08/27/2006] [Accepted: 12/05/2006] [Indexed: 11/27/2022]
Abstract
The forkhead transcription factor, DAF-16, a downstream target of the insulin/IGF-I signaling pathway in C. elegans, is indispensable both for lifespan regulation and stress resistance. The molecular mechanisms involved in regulating DAF-16 transcriptional activation remain undefined. Here, we have identified an E3 ubiquitin ligase, RLE-1 (regulation of longevity by E3), which regulates aging in C. elegans. Disruption of RLE-1 expression in C. elegans increases lifespan; this extension of lifespan is due to elevated DAF-16 protein but not to changes of daf-16 mRNA levels. We have also found that RLE-1 catalyzes DAF-16 ubiquitination, leading to degradation by the proteasome. Elimination of RLE-1 expression in C. elegans causes increased transcriptional activation and sustained nuclear localization of DAF-16. Overexpression of DAF-16 in rle-1 mutants increases worm lifespan, while disruption of DAF-16 expression in rle-1 mutants reverses their longevity. Thus, RLE-1 is an E3 ubiquitin ligase of DAF-16 that regulates C. elegans aging.
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Affiliation(s)
- Wensheng Li
- Department of Otolaryngology-Head & Neck Surgery, University of Missouri School of Medicine, One Hospital Dr., Columbia, MO 65212, USA
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167
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Wohlfert EA, Clark RB. 'Vive la Résistance!'--the PI3K-Akt pathway can determine target sensitivity to regulatory T cell suppression. Trends Immunol 2007; 28:154-60. [PMID: 17329168 DOI: 10.1016/j.it.2007.02.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2006] [Revised: 01/24/2007] [Accepted: 02/14/2007] [Indexed: 12/22/2022]
Abstract
CD4+CD25+ regulatory T (Treg) cells have emerged as important regulators of immune responses but the mechanisms through which Treg cells mediate suppression are still unclear. Recently, several studies have identified murine models of spontaneous autoimmunity or genetically engineered mice in which the Treg cells function normally but the CD4+CD25- T effector (Teff) cells are resistant to Treg-mediated suppression. Here, we postulate that the activation status of the phosphatidylinositol 3-kinase (PI3K)-Akt pathway in Teff cells is a primary determinant of Teff cell sensitivity to Treg cell-mediated suppression, and that when the PI3K-Akt pathway is hyperactivated in Teff cells, these cells are resistant to Treg cell-mediated suppression. We further postulate that this paradigm can mechanistically link abnormalities in the PI3K-Akt pathway to the development of autoimmunity.
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Affiliation(s)
- Elizabeth A Wohlfert
- Department of Immunology, University of Connecticut Health Center, Farmington, CT 06032, USA
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168
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Tarner IH, Fathman CG. Does our current understanding of the molecular basis of immune tolerance predict new therapies for autoimmune disease? ACTA ACUST UNITED AC 2006; 2:491-9. [PMID: 16951704 DOI: 10.1038/ncprheum0272] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2005] [Accepted: 07/13/2006] [Indexed: 12/29/2022]
Abstract
The creation of specific immune tolerance has often been referred to as the ultimate goal of immunotherapy, because it would allow autoimmune disease to be reversed without the need for nonspecific and potentially harmful immunosuppressive therapy. Studies performed during the past decade have been immensely fruitful in terms of advances in our understanding of the cellular and molecular mechanisms of immune tolerance, and have paved the way for successful exploitation of these mechanisms for therapeutic purposes. Important developments include an increased understanding of central and peripheral tolerance, and treatment strategies that mimic the mechanisms behind deletion of self-reactive cells, the identification of crucial gene products that are involved in the induction of anergy, and the characterization of regulatory T cells and protocols for their induction and expansion for therapeutic applications. These landmarks of immune-tolerance research are summarized and their potential use in the immunotherapy of autoimmune disease discussed.
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Affiliation(s)
- Ingo H Tarner
- Department of Internal Medicine and Rheumatology, Justus-Liebig-University of Giessen, Kerckhoff-Klinik Bad Nauheim, Division of Rheumatology and Clinical Immunology, Bad Nauheim, Germany
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169
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Su L, Lineberry N, Huh Y, Soares L, Fathman CG. A Novel E3 Ubiquitin Ligase Substrate Screen Identifies Rho Guanine Dissociation Inhibitor as a Substrate of Gene Related to Anergy in Lymphocytes. THE JOURNAL OF IMMUNOLOGY 2006; 177:7559-66. [PMID: 17114425 DOI: 10.4049/jimmunol.177.11.7559] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ubiquitination of eukaryotic proteins regulates a broad range of cellular processes, including regulation of T cell activation and tolerance. We have previously demonstrated that gene related to anergy in lymphocytes (GRAIL), a ring finger ubiquitin E3 ligase, is required for the induction of T cell anergy; however, the substrate(s) for GRAIL E3 ligase activity is/are unknown. In this study, we report a novel prokaryotic system developed to screen for substrates of E3 ligases. Using this screen, Rho guanine dissociation inhibitor (RhoGDI) was identified as a potential substrate of GRAIL. GRAIL was subsequently demonstrated to bind and ubiquitinate RhoGDI, although GRAIL-mediated ubiquitination of RhoGDI did not result in proteosomal degradation. Expression of GRAIL in T cells resulted in specific inhibition of RhoA GTPase activation; activation of Rac1, cdc42, and Ras GTPases were not affected. Interestingly, stable T cell lines expressing dominant-negative RhoA mimicked the GRAIL-mediated IL-2 inhibition phenotype, and T cells expressing constitutively active RhoA were able to overcome GRAIL-mediated inhibition of IL-2 expression. These findings validate our prokaryotic screen as a method of identifying substrates for ubiquitin E3 ligases and suggest a role for Rho effector molecules in T cell anergy.
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Affiliation(s)
- Leon Su
- Department of Medicine, Division of Immunology and Rheumatology, Stanford University, Stanford, CA 94305, USA
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170
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Fearns C, Pan Q, Mathison JC, Chuang TH. Triad3A Regulates Ubiquitination and Proteasomal Degradation of RIP1 following Disruption of Hsp90 Binding. J Biol Chem 2006; 281:34592-600. [PMID: 16968706 DOI: 10.1074/jbc.m604019200] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Toll-like receptors (TLRs) play a crucial role in innate immunity by recognizing microbial pathogens. Triad3A is an E3 ubiquitin-protein ligase that interacts with the Toll/interleukin-1 receptor domain of TLRs and promotes their proteolytic degradation. In the present study, we further investigated its activity on signaling molecules downstream of TLRs and tumor necrosis factor (TNF) receptor 1. Triad3A promoted down-regulation of two TIR domain-containing adapter proteins, TIRAP and TRIF, as well as a RIP1 but had no effect on other adapter molecules in either the TLRs or TNF-alpha signaling pathways. Multiple sequence alignment analysis suggested that RIP1 contains a TIR homologous domain, and mutation of amino acid residues in this domain identified three residues critical for its interaction with Triad3A. Moreover, Triad3A acted as a negative regulator in TNF-alpha signaling. Reduction of Triad3A expression by small interference RNAs rendered cells hyperresponsive to TNF-alpha stimulation. Conversely, overexpression of Triad3A in cells blocked TNF-alpha-induced cell activation. This negative regulation was effected independently of changes in the cellular protein level of RIP1. Further studies indicated that RIP1 formed a complex with Triad3A and heat shock protein 90 (Hsp90), which is a chaperone protein capable of maintaining the stability of its client proteins. Treatment of cells with geldanamycin to disrupt the Hsp90 complex led to proteasomal degradation of RIP1. Depletion of Triad3A by small interference RNA treatment inhibited geldanamycin-activated ubiquitination and proteolytic degradation of RIP1. These results suggest that Triad3A is an E3 ubiquitin-protein ligase to RIP1 and that Hsp90 and Triad3A cooperatively maintain the homeostasis of RIP1.
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Affiliation(s)
- Colleen Fearns
- Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA
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171
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Buckler JL, Walsh PT, Porrett PM, Choi Y, Turka LA. Cutting edge: T cell requirement for CD28 costimulation is due to negative regulation of TCR signals by PTEN. THE JOURNAL OF IMMUNOLOGY 2006; 177:4262-6. [PMID: 16982858 DOI: 10.4049/jimmunol.177.7.4262] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Recent studies suggest that the phosphatase and tensin homolog deleted on chromosome 10 (PTEN) plays a critical role in the maintenance of self-tolerance. Using T cell-specific PTEN knockout mice (PTENDeltaT), we have identified a novel mechanism by which PTEN regulates T cell tolerance. We found that TCR stimulation alone, without CD28 costimulation, is sufficient to induce hyperactivation of the PI3K pathway, which leads to enhanced IL-2 production by naive PTENDeltaT T cells. Importantly, as a result of this increased response to TCR stimulation, PTENDeltaT CD4(+) T cells no longer require CD28 costimulation for in vitro or in vivo expansion. In fact, unlike wild-type T cells, PTENDeltaT CD4(+) T cells are not anergized by delivery of TCR stimulation alone. These data suggest that by negatively regulating TCR signals, PTEN imposes a requirement for CD28 costimulation, thus defining a novel mechanism for its role in self-tolerance.
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Affiliation(s)
- Jodi L Buckler
- Department of Medicine, University of Pennsylvania, 415 Curie Boulevard, Philadelphia, PA 19104-6144, USA
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172
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Swaminathan G, Tsygankov AY. The Cbl family proteins: ring leaders in regulation of cell signaling. J Cell Physiol 2006; 209:21-43. [PMID: 16741904 DOI: 10.1002/jcp.20694] [Citation(s) in RCA: 228] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The proto-oncogenic protein c-Cbl was discovered as the cellular form of v-Cbl, a retroviral transforming protein. This was followed over the years by important discoveries, which identified c-Cbl and other Cbl-family proteins as key players in several signaling pathways. c-Cbl has donned the role of a multivalent adaptor protein, capable of interacting with a plethora of proteins, and has been shown to positively influence certain biological processes. The identity of c-Cbl as an E3 ubiquitin ligase unveiled the existence of an important negative regulatory pathway involved in maintaining homeostasis in protein tyrosine kinase (PTK) signaling. Recent years have also seen the emergence of novel regulators of Cbl, which have provided further insights into the complexity of Cbl-influenced pathways. This review will endeavor to provide a summary of current studies focused on the effects of Cbl proteins on various biological processes and the mechanism of these effects. The major sections of the review are as follows: Structure and genomic organization of Cbl proteins; Phosphorylation of Cbl; Interactions of Cbl; Localization of Cbl; Mechanism of effects of Cbl: (a) Ubiquitylation-dependent events: This section elucidates the mechanism of Cbl-mediated downregulation of EGFR and details the PTK and non-PTKs targeted by Cbl. In addition, it addresses the functional requirements for E3 Ubiquitin ligase activity of Cbl and negative regulation of Cbl-mediated downregulation of PTKs, (b) Adaptor functions: This section discusses the mechanisms of adaptor functions of Cbl in mitogen-activated protein kinase (MAPK) activation, insulin signaling, regulation of Ras-related protein 1 (Rap1), PI-3' kinase signaling, and regulation of Rho-family GTPases and cytoskeleton; Biological functions: This section gives an account of the diverse biological functions of Cbl and includes the role of Cbl in transformation, T-cell signaling and thymus development, B-cell signaling, mast-cell degranulation, macrophage functions, bone development, neurite growth, platelet activation, muscle degeneration, and bacterial invasion; Conclusions and perspectives.
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Affiliation(s)
- Gayathri Swaminathan
- Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
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173
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Choi H, Cho SY, Schwartz RH, Choi K. Dual effects of Sprouty1 on TCR signaling depending on the differentiation state of the T cell. THE JOURNAL OF IMMUNOLOGY 2006; 176:6034-45. [PMID: 16670312 DOI: 10.4049/jimmunol.176.10.6034] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Sprouty (Spry) is known to be a negative feedback inhibitor of growth factor receptor signaling through inhibition of the Ras/MAPK pathway. Several groups, however, have reported a positive role for Spry involving sequestration of the inhibitory protein c-Cbl. Thus, Spry may have various functions in the regulation of receptor-mediated signaling depending on the context. In the immune system, the function of Spry is unknown. In this study, we investigated the role of Spry1 in T cell activation. Spry1, among the four mammalian homologs, was specifically induced by TCR signaling of CD4(+) murine T cells. In fully differentiated Th1 clones, overexpressed Spry1 inhibited TCR signaling and decreased IL-2 production while reducing expression with specific siRNA transfection had the opposite effect, increasing IL-2 production. In contrast, in naive T cells, Spry1 overexpression enhanced TCR signaling, and increased proliferation and IL-2 production, while siRNA transfection again had the opposite effect, reducing IL-2 production following activation. The enhancing effect in naive cells was abrogated by preactivation of the T cells with Ag and APC, indicating that the history of exposure to Ag is correlated with a hierarchy of T cell responsiveness to Spry1. Furthermore, both the NF-AT and MAPK pathways were influenced by Spry1, implying a different molecular mechanism from that for growth factor receptor signaling. Thus, Spry1 uses a novel mechanism to bring about differential effects on TCR signaling through the same receptor, depending on the differentiation state of the T cell.
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Affiliation(s)
- Heonsik Choi
- Laboratory of Cellular and Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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174
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Fortier JM, Kornbluth J. NK Lytic-Associated Molecule, Involved in NK Cytotoxic Function, Is an E3 Ligase. THE JOURNAL OF IMMUNOLOGY 2006; 176:6454-63. [PMID: 16709802 DOI: 10.4049/jimmunol.176.11.6454] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
NK lytic-associated molecule (NKLAM) is a protein involved in the cytolytic function of NK cells and CTLs. It has been localized to the cytolytic granules in NK cells and is up-regulated when cells are exposed to cytokines IL-2 or IFN-beta. We report in this study that NKLAM contains a cysteine-rich really interesting new gene (RING) in between RING-RING domain, and that this domain possesses strong homology to the RING domain of the known E3 ubiquitin ligase, Dorfin. To determine whether NKLAM functions as an E3 ligase, we performed coimmunoprecipitation binding assays with ubiquitin conjugates (Ubcs) UbcH7, UbcH8, and UbcH10. We demonstrated that both UbcH7 and UbcH8 bind to full-length NKLAM. We then performed a similar binding assay using endogenous NKLAM and UbcH8 expressed by human NK clone NK3.3 to show that the protein interaction occurs in vivo. Using the yeast two-hybrid system, we identified uridine kinase like-1 (URKL-1) protein as a substrate for NKLAM. We confirmed that NKLAM and URKL-1 interact in mammalian cells by using both immunoprecipitation and confocal microscopy. We demonstrated decreased protein expression and enhanced ubiquitination of URKL-1 in the presence of NKLAM. These data indicate that NKLAM is a RING finger protein that binds Ubcs and has as one of its substrates, URKL-1, thus defining this cytolytic protein as an E3 ubiquitin ligase.
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Affiliation(s)
- Julie M Fortier
- Department of Pathology, St. Louis University School of Medicine, St. Louis, MO 63104, USA
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175
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Reiley WW, Zhang M, Jin W, Losiewicz M, Donohue KB, Norbury CC, Sun SC. Regulation of T cell development by the deubiquitinating enzyme CYLD. Nat Immunol 2006; 7:411-7. [PMID: 16501569 DOI: 10.1038/ni1315] [Citation(s) in RCA: 181] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Accepted: 01/27/2006] [Indexed: 11/09/2022]
Abstract
T cell receptor signaling is essential for the generation and maturation of T lymphocyte precursors. Here we identify the deubiquitinating enzyme CYLD as a positive regulator of proximal T cell receptor signaling in thymocytes. CYLD physically interacted with active Lck and promoted recruitment of active Lck to its substrate, Zap70. CYLD also removed both Lys 48- and Lys 63-linked polyubiquitin chains from Lck. Because of a cell-autonomous defect in T cell development, CYLD-deficient mice had substantially fewer mature CD4(+) and CD8(+) single-positive thymocytes and peripheral T cells.
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Affiliation(s)
- William W Reiley
- Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA
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176
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Taniguchi CM, Emanuelli B, Kahn CR. Critical nodes in signalling pathways: insights into insulin action. Nat Rev Mol Cell Biol 2006; 7:85-96. [PMID: 16493415 DOI: 10.1038/nrm1837] [Citation(s) in RCA: 1954] [Impact Index Per Article: 108.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Physiologically important cell-signalling networks are complex, and contain several points of regulation, signal divergence and crosstalk with other signalling cascades. Here, we use the concept of 'critical nodes' to define the important junctions in these pathways and illustrate their unique role using insulin signalling as a model system.
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Affiliation(s)
- Cullen M Taniguchi
- Joslin Diabetes Center, One Joslin Place, Boston, Massachusetts 02215, USA
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177
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Thien C, Langdon W. c-Cbl and Cbl-b ubiquitin ligases: substrate diversity and the negative regulation of signalling responses. Biochem J 2006; 391:153-66. [PMID: 16212556 PMCID: PMC1276912 DOI: 10.1042/bj20050892] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The activation of signalling pathways by ligand engagement with transmembrane receptors is responsible for determining many aspects of cellular function and fate. While these outcomes are initially determined by the nature of the ligand and its receptor, it is also essential that intracellular enzymes, adaptor proteins and transcription factors are correctly assembled to convey the intended response. In recent years, it has become evident that proteins that regulate the amplitude and duration of these signalling responses are also critical in determining the function and fate of cells. Of these, the Cbl family of E3 ubiquitin ligases and adaptor proteins has emerged as key negative regulators of signals from many types of cell-surface receptors. The array of receptors and downstream signalling proteins that are regulated by Cbl proteins is diverse; however, in most cases, the receptors have a common link in that they either possess a tyrosine kinase domain or they form associations with cytoplasmic PTKs (protein tyrosine kinases). Thus Cbl proteins become involved in signalling responses at a time when PTKs are first activated and therefore provide an initial line of defence to ensure that signalling responses proceed at the desired intensity and duration.
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Affiliation(s)
- Christine B. F. Thien
- School of Surgery and Pathology, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
- Correspondence may be addressed to either author (email or )
| | - Wallace Y. Langdon
- School of Surgery and Pathology, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
- Correspondence may be addressed to either author (email or )
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178
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Wohlfert EA, Gorelik L, Mittler R, Flavell RA, Clark RB. Cutting Edge: Deficiency in the E3 Ubiquitin Ligase Cbl-b Results in a Multifunctional Defect in T Cell TGF-β Sensitivity In Vitro and In Vivo. THE JOURNAL OF IMMUNOLOGY 2006; 176:1316-20. [PMID: 16424156 DOI: 10.4049/jimmunol.176.3.1316] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Mice deficient in the E3 ubiquitin ligase Cbl-b have CD28-independent T cells and develop autoimmunity. We previously reported that Cbl-b-/- CD4+CD25- T effector cells are resistant in vitro to the antiproliferative effects of CD4+CD25+ regulatory T cells and TGF-beta. We have now asked whether the resistance noted in Cbl-b-/- T cells is restricted solely to TGF-beta's antiproliferative effects, whether the TGF-beta resistance has in vivo relevance, and whether a defect can be identified in the TGF-beta signaling pathway. We now demonstrate the following: 1) in vitro, Cbl-b deficiency prevents the TGF-beta-mediated induction of Foxp3+ functional regulatory T cells; 2) in vivo, Cbl-b-/- mice show a significantly enhanced response to a tumor that is strictly TGF-beta regulated; and 3) Cbl-b-/- T effector cells have defective TGF-beta-mediated Smad2 phosphorylation. These studies are the first to document that the E3 ubiquitin ligase Cbl-b plays an integral role in T cell TGF-beta signaling, and that its absence results in multifunctional TGF-beta-related defects that have important disease-related implications.
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Affiliation(s)
- Elizabeth A Wohlfert
- Department of Immunology, Center for Immunotherapy of Cancer and Infectious Diseases, University of Connecticut Health Center, Farmington, CT 06032, USA
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179
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Schmitz ML, Krappmann D. Controlling NF-κB activation in T cells by costimulatory receptors. Cell Death Differ 2006; 13:834-42. [PMID: 16410801 DOI: 10.1038/sj.cdd.4401845] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Full and productive activation of T lymphocytes relies on the simultaneous delivery of T cell receptor (TCR)- and coreceptor-derived signals. In naïve T cells engagement of the TCR alone causes anergy, while TCR triggering of preactivated T cells results in activation-induced cell death. Costimulatory signals are prominently mirrored by the activation of NF-kappaB, which needs input from the TCR as well as from coreceptors in order to be fully activated and to fulfil its crucial function in the immune response. Coreceptor-generated signals tightly control the duration and amplitude of the NF-kappaB response. The activation of IkappaB kinase (IKK) complex at the contact zone between a T cell and an antigen-presenting cell offers the unique opportunity to study the spatial organization of IKK activation. Recent studies indicate that coreceptor pathways influence the threshold activities of many signalling mediators and thus act on multiple layers of the NF-kappaB pathway.
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Affiliation(s)
- M L Schmitz
- Institute for Biochemistry, Justus-Liebig-University, Medical Faculty, Friedrichstrasse 24, Giessen 35392, Germany.
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180
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Liu YC, Penninger J, Karin M. Immunity by ubiquitylation: a reversible process of modification. Nat Rev Immunol 2006; 5:941-52. [PMID: 16322747 PMCID: PMC7096784 DOI: 10.1038/nri1731] [Citation(s) in RCA: 195] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Conjugation of ubiquitin to a protein substrate provides a tag that either marks the labelled protein for degradation or modulates its function. The process of ubiquitylation, which is catalysed by coordinated enzymatic reactions that require enzymes known as E1, E2 and E3, has an important role in the modulation of immune responses. Immune tolerance is induced in the thymus and the periphery through diverse mechanisms, and E3 ligases are involved in thymic antigen presentation, T-cell anergy and follicular B helper T-cell development. The immunological defect in mice with a disrupted itchy (Itch) locus results from a defect in degradation of the transcription factor JUNB. This process is tightly regulated by upstream protein kinases that modulate the activity of the E3 ligase ITCH rather than directly affect JUNB, as commonly thought. Nuclear factor-κB (NF-κB) signalling is crucial for both innate and adaptive immunity and is regulated by K48 (Lys48)-linked polyubiquitylation (which targets inhibitor of NF-κB (IκB) for proteasomal-dependent degradation), K63-linked polyubiquitylation (which activates IκB kinase, IKK) and A20-mediated de-ubiquitylation. E3 ligases also regulate other cytokine-induced cellular responses, such as transforming-growth-factor-β-mediated signalling and interferon (IFN)-triggered gene expression. The ubiquitin-like molecule ISG15 (IFN-stimulated protein of 15 kDa) participates in IFN-mediated signalling, and defects in de-ISGylation result in resistance to viral infection.
The conjugation of ubiquitin, a 76-amino-acid peptide, to a protein substrate provides a tag that either marks the labelled protein for degradation or modulates its function. The process of protein ubiquitylation — which is catalysed by coordinated enzymatic reactions that are mediated by enzymes known as E1, E2 and E3 — has an important role in the modulation of immune responses. Importantly, protein ubiquitylation is a reversible process, and removal of ubiquitin molecules is mediated by de-ubiquitylating enzymes: for example, A20, which has been implicated in the regulation of immune responses. In addition, the conjugation of ubiquitin-like molecules, such as ISG15 (interferon-stimulated protein of 15 kDa), to proteins is also involved in immune regulation. This Review covers recent progress in our understanding of protein ubiquitylation in the immune system.
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Affiliation(s)
- Yun-Cai Liu
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA.
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181
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Myers MD, Sosinowski T, Dragone LL, White C, Band H, Gu H, Weiss A. Src-like adaptor protein regulates TCR expression on thymocytes by linking the ubiquitin ligase c-Cbl to the TCR complex. Nat Immunol 2005; 7:57-66. [PMID: 16327786 DOI: 10.1038/ni1291] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Accepted: 10/05/2005] [Indexed: 11/09/2022]
Abstract
The adaptor molecule SLAP and E3 ubiquitin ligase c-Cbl each regulate expression of T cell receptor (TCR)-CD3 on thymocytes. Here we provide genetic and biochemical evidence that both molecules function in the same pathway. TCR-CD3 expression was similar in the absence of SLAP and/or c-Cbl. SLAP and c-Cbl were found to interact, and their expression together downregulated CD3epsilon. This required multiple domains in SLAP and the ring finger of c-Cbl. Furthermore, expression of SLAP and c-Cbl together induced TCRzeta ubiquitination and degradation, preventing the accumulation of fully assembled recycling TCR complexes. These studies indicate that SLAP links the E3 ligase activity of c-Cbl to the TCR, allowing for stage-specific regulation of TCR expression.
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Affiliation(s)
- Margaret D Myers
- Department of Medicine, Rosalind Russell Medical Research Center for Arthritis, Howard Hughes Medical Institute, University of California San Francisco, 94143, USA
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182
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Bonnevier JL, Zhang R, Mueller DL. E3 ubiquitin ligases and their control of T cell autoreactivity. Arthritis Res Ther 2005; 7:233-42. [PMID: 16277698 PMCID: PMC1297590 DOI: 10.1186/ar1842] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
A loss of T cell tolerance underlies the development of most autoimmune diseases. The design of therapeutic strategies to reinstitute immune tolerance, however, is hampered by uncertainty regarding the molecular mechanisms involved in the inactivation of potentially autoreactive T cells. Recently, E3 ubiquitin ligases have been shown to mediate the development of a durable state of unresponsiveness in T cells called clonal anergy. In this review, we will discuss the mechanisms used by E3 ligases to control the activation of T cells and prevent the development of autoimmunity.
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Affiliation(s)
- Jody L Bonnevier
- Rheumatic and Autoimmune Diseases Division, and Center for Immunology, University of Minnesota Medical School, Minneapolis, MN, USA
| | - Ruan Zhang
- Rheumatic and Autoimmune Diseases Division, and Center for Immunology, University of Minnesota Medical School, Minneapolis, MN, USA
| | - Daniel L Mueller
- Rheumatic and Autoimmune Diseases Division, and Center for Immunology, University of Minnesota Medical School, Minneapolis, MN, USA
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183
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Affiliation(s)
- Clayton E Mathews
- Department of Pediatrics, The University of Pittsburgh, Pittsburgh, PA 15213, USA.
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184
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Herndon TM, Pirone DM, Tsokos GC, Chen CS. T cell-to-T cell clustering enhances NF-κB activity by a PI3K signal mediated by Cbl-b and Rho. Biochem Biophys Res Commun 2005; 332:1133-9. [PMID: 15922296 DOI: 10.1016/j.bbrc.2005.05.064] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Accepted: 05/10/2005] [Indexed: 11/25/2022]
Abstract
Full activation of T cells requires the binding of antigen to the T cell receptor and stimulation of the CD28 molecule, a process which typically occurs when T cells bind to an antigen presenting cell. The transcription factor, NF-kappaB, is an integration point for these two signals and its activation is critical for T cell function. Using antibodies to the TCR and CD28 molecules to activate Jurkat T cells, we show that cells that were permitted to aggregate into multi-cellular clusters increased NF-kappaB activity compared to unclustered cells. Inhibition of PI3K signaling with wortmannin decreased the clustering-mediated NF-kappaB signal. Over-expression of a dominant negative form of Cbl-b, an endogenous inhibitor of PI3K, in unclustered cells rescued NF-kappaB activation to the same levels caused by cell clustering. Inhibiting signaling through Rho with dominant negative RhoA abrogated both clustering-mediated and dominant negative Cbl-b-mediated NF-kappaB inactivation, but not TCR/CD28 mediated NF-kappaB activation. Taken together, these results suggest that in addition to pathways stimulated by classical T cell-APC interactions, another signal arising from T cell clustering can enhance activation.
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Affiliation(s)
- Thomas M Herndon
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
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185
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Krawczyk CM, Jones RG, Atfield A, Bachmaier K, Arya S, Odermatt B, Ohashi PS, Penninger JM. Differential control of CD28-regulated in vivo immunity by the E3 ligase Cbl-b. THE JOURNAL OF IMMUNOLOGY 2005; 174:1472-8. [PMID: 15661906 DOI: 10.4049/jimmunol.174.3.1472] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The E3 ubiquitin ligase Casitas B cell lymphoma-b (Cbl-b) plays a critical role in the development of autoimmunity and sets the threshold for T cell activation. In the absence of Cbl-b, T cells stimulated via the TCR respond similarly to those that have received a CD28-mediated costimulatory signal, suggesting that the absence of Cbl-b substitutes for CD28-mediated costimulation. In this study, we show that loss of Cbl-b restores Ig class switching and germinal center formation in Vav1 mutant mice in response to an in vivo viral challenge. Genetic inactivation of Cbl-b also rescues impaired antiviral IgG production in CD28-mutant mice. Moreover, loss of CD28 results in disorganization of follicular dendritic cell clusters, which is also rescued by the Cbl-b mutation. Intriguingly, despite restored antiviral in vivo immunity and follicular dendritic cell clusters, loss of Cbl-b did not rescue germinal center formation in CD28-deficient mice. Mechanistically, in vivo vesicular stomatitis virus-induced IL-4 and IFN-gamma production and up-regulation of the inducible costimulatory molecule ICOS were dependent on CD28, and could not be rescued by the loss of Cbl-b. These data provide genetic evidence that CD28-dependent in vivo immune responses and Ig class switching can be genetically uncoupled from germinal center formation and ICOS induction by Cbl-b-Vav1-regulated signaling pathways.
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Affiliation(s)
- Connie M Krawczyk
- MBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
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186
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Dangelmaier CA, Quinter PG, Jin J, Tsygankov AY, Kunapuli SP, Daniel JL. Rapid ubiquitination of Syk following GPVI activation in platelets. Blood 2005; 105:3918-24. [PMID: 15701717 PMCID: PMC1895068 DOI: 10.1182/blood-2004-09-3689] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Spleen tyrosine kinase (Syk) activation is a key intermediate step in the activation of platelets by the physiologic agonist collagen. We have found that Syk is rapidly ubiquitinated upon activation of platelets by collagen, collagen-related peptide (CRP), and convulxin. The Src family kinase inhibitors prevented Syk phosphorylation and its ubiquitination, indicating that the process is downstream of Src kinases. The ubiquitination of Syk did not cause degradation of the protein as evidenced by the lack of effect of proteasomal and lysosomal inhibitors. We separated ubiquitinated Syk from its nonubiquitinated counterpart and used an in vitro kinase assay to compare their activities. We found that the ubiquitinated Syk appeared to be about 5-fold more active. Using a phosphospecific antibody to Syk (Tyr525/Tyr526) that measures activated Syk, we found that most (60%-75%) of the active Syk is in the ubiquitinated fraction. This result explains the apparent high specific activity of ubiquitinated Syk. In c-Cbl-deficient mice, Syk is not ubiquitinated, implicating c-Cbl as the E3 ligase involved in Syk ubiquitination. Furthermore, Syk is not dephosphorylated in these mice. We propose that c-Cbl plays a regulatory role in glycoprotein VI (GPVI)/Fc receptor gamma (FcRgamma)-chain-dependent platelet activation through its interaction with Syk.
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Affiliation(s)
- Carol A Dangelmaier
- Department of Pharmacology, Temple University School of Medicine, 3420 N Broad St, Philadelphia, PA 19140, USA
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187
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Li D, Gál I, Vermes C, Alegre ML, Chong ASF, Chen L, Shao Q, Adarichev V, Xu X, Koreny T, Mikecz K, Finnegan A, Glant TT, Zhang J. Cutting Edge: Cbl-b: One of the Key Molecules Tuning CD28- and CTLA-4-Mediated T Cell Costimulation. THE JOURNAL OF IMMUNOLOGY 2004; 173:7135-9. [PMID: 15585834 DOI: 10.4049/jimmunol.173.12.7135] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Cbl-b negatively regulates CD28-dependent T cell activation. In this report, we tested the hypothesis that CD28 and CTLA-4 have opposite roles in tuning T cell activation threshold by controlling the levels of Cbl-b protein expression. We demonstrate that CD28 costimulation potentiates TCR-induced Cbl-b degradation, whereas CTLA-4-B7 interaction is required for Cbl-b re-expression. In support of this finding, Cbl-b expression in CTLA-4 knockout (KO) T cells is significantly reduced, and treating CTLA-4KO mice with human CTLA-4Ig to block CD28-B7 interaction restores Cbl-b expression on T cells. Furthermore, CD28 and CTLA-4 costimulatory effects are compromised in Cbl-bKO T cells. These observations indicate that CD28 and CTLA-4 tightly regulate Cbl-b expression which is critical for establishing the threshold for T cell activation.
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MESH Headings
- Abatacept
- Adaptor Proteins, Signal Transducing/biosynthesis
- Adaptor Proteins, Signal Transducing/deficiency
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/physiology
- Adjuvants, Immunologic/pharmacology
- Animals
- Antigens, CD
- Antigens, Differentiation/genetics
- Antigens, Differentiation/physiology
- B7-1 Antigen/metabolism
- B7-1 Antigen/pharmacology
- CD28 Antigens/genetics
- CD28 Antigens/physiology
- CTLA-4 Antigen
- Cell Proliferation
- Cells, Cultured
- Drug Synergism
- Female
- Growth Inhibitors/pharmacology
- Humans
- Immunoconjugates/pharmacology
- Lymphocyte Activation/genetics
- Lymphocyte Activation/immunology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Mice, Knockout
- Proto-Oncogene Proteins c-cbl
- T-Lymphocyte Subsets/cytology
- T-Lymphocyte Subsets/immunology
- T-Lymphocyte Subsets/metabolism
- Ubiquitin-Protein Ligases/biosynthesis
- Ubiquitin-Protein Ligases/deficiency
- Ubiquitin-Protein Ligases/genetics
- Ubiquitin-Protein Ligases/physiology
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Affiliation(s)
- Dongdong Li
- Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL 60612, USA
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188
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Abstract
The negative regulation of lymphocyte activation and function is mediated by inhibition of signaling through antigen-receptor, co-stimulation receptor or cytokine receptor. The suppression of downstream signaling through antigen-receptor is mediated by negative regulators including adaptors and effectors such as phosphatases. "Inhibitory adaptors" exhibit their inhibitory function directly or indirectly by the localization to the vicinity of the antigen-receptor on the membrane. The strategy of inhibition by inhibitory adaptors includes the recruitment of inhibitory effector molecules, sequestration of positive regulators, internalization/degradation of receptor complexes, and the blockade of the dynamic movement of positive regulators.
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Affiliation(s)
- Sho Yamasaki
- Laboratory for Cell Signaling, RIKEN Research Center for Allergy and Immunology, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
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189
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Wiedemann A, Müller S, Favier B, Penna D, Guiraud M, Delmas C, Champagne E, Valitutti S. T-cell activation is accompanied by an ubiquitination process occurring at the immunological synapse. Immunol Lett 2004; 98:57-61. [PMID: 15790509 DOI: 10.1016/j.imlet.2004.10.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 10/05/2004] [Accepted: 10/18/2004] [Indexed: 11/19/2022]
Abstract
The immunological synapse (IS) is a specialized signaling area formed at the contact site between T-cells and antigen-presenting cells (APC), where sustained engagement and signaling of TCR and accessory molecules occur. A key feature of T-cell antigen recognition is that the process of TCR/peptide-MHC interaction is self-limited by the internalization and degradation of triggered TCR and recruited signaling components. The mechanism of signaling component degradation involves their ubiquitination and targeting for degradation. Yet, the relationship between the ubiquitination process and TCR signaling as well as the cellular localization of TCR-induced ubiquitination are still elusive. In the present work, we visualize for the first time ubiquitination at the TCR signaling area. We show an enrichment of ubiquitin staining in TCR/CD3 caps in T-lymphocytes stimulated by anti-CD3 antibodies. Remarkably, we also show the recruitment of the ubiquitin ligase Cbl-b and a significant ubiquitination at the immunological synapse in antigen-stimulated T-cells. Our results identify the immunological synapse as the cellular area where TCR-induced protein ubiquitination occurs. They imply that the synapse is a specialized site where the activation process is not only triggered, but also controlled via ubiquitination of signaling actors.
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Affiliation(s)
- Aurelie Wiedemann
- INSERM U563, Institut Claude de Preval, CHU Purpan, 31059 Toulouse Cedex 3, France
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190
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Zhang J, Chiang YJ, Hodes RJ, Siraganian RP. Inactivation of c-Cbl or Cbl-b differentially affects signaling from the high affinity IgE receptor. THE JOURNAL OF IMMUNOLOGY 2004; 173:1811-8. [PMID: 15265912 DOI: 10.4049/jimmunol.173.3.1811] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The Cbl family of proteins negatively regulate signaling from tyrosine kinase-coupled receptors. Among the three members of this family, only c-Cbl and Cbl-b are expressed in hemopoietic cells. To examine the role of c-Cbl and Cbl-b in Fc epsilon RI signaling, mast cell cultures from wild-type, c-Cbl(-/-), and Cbl-b(-/-) mice were generated. Cell growth rates and cell surface expression of Fc epsilon RI were similar in the different cell populations. Compared with control cells, Cbl-b inactivation resulted in increases in Fc epsilon RI-induced Ca(2+) response and histamine release. Fc epsilon RI-induced tyrosine phosphorylation of total cellular proteins, Syk, and phospholipase C-gamma was also enhanced by Cbl-b deficiency, whereas receptor-initiated phosphorylation of Vav, JNK, and p38 kinases was not changed in these cells. In contrast to Cbl-b, c-Cbl deficiency had no detectable effect on Fc epsilon RI-induced histamine release or on the phosphorylation of total cellular proteins or Syk. The absence of c-Cbl increased the phosphorylation of ERK after receptor stimulation, but resulted in slightly reduced p38 phosphorylation and Ca(2+) response. These results suggest that Cbl-b and c-Cbl have divergent effects on Fc epsilon RI signal transduction and that Cbl-b, but not c-Cbl, functions as a negative regulator of Fc epsilon RI-induced degranulation.
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Affiliation(s)
- Juan Zhang
- Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA
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191
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Bai Y, Yang C, Hu K, Elly C, Liu YC. Itch E3 ligase-mediated regulation of TGF-beta signaling by modulating smad2 phosphorylation. Mol Cell 2004; 15:825-31. [PMID: 15350225 DOI: 10.1016/j.molcel.2004.07.021] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2003] [Revised: 06/16/2004] [Accepted: 06/21/2004] [Indexed: 12/22/2022]
Abstract
Protein ubiquitination has been implicated in the intracellular biochemical events transduced by TGF-beta receptor via different mechanisms including the degradation of Smads or their binding proteins. Here we show that loss of Itch E3 ligase in mouse embryonic fibroblasts (MEFs) results in reduced susceptibility of TGF-beta-induced cell growth arrest and decreased phosphorylation of Smad2, without apparent alteration in protein levels for Smad2, Smad4, and Smad7 in Itch-/- MEFs. Itch promotes ubiquitination of Smad2 and augments Smad2 phosphorylation that requires an intact ligase activity of Itch. Moreover, Itch facilitates complex formation between TGF-beta receptor and Smad2 and enhances TGF-beta-induced transcription. This study reveals a previously unrecognized positive TGF-beta signaling pathway via proteolysis-independent ubiquitination.
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Affiliation(s)
- Yongli Bai
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121, USA
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192
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Avota E, Müller N, Klett M, Schneider-Schaulies S. Measles virus interacts with and alters signal transduction in T-cell lipid rafts. J Virol 2004; 78:9552-9. [PMID: 15308747 PMCID: PMC506914 DOI: 10.1128/jvi.78.17.9552-9559.2004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
By a contact-dependent surface interaction, the measles virus (MV) glycoprotein complex induces a pronounced inhibition of T-cell proliferation. We now show that MV directly interacts with glycosphingolipid-enriched membrane microdomains on human primary T cells and alters recruitment and segregation of membrane proximal signaling components. Contact-dependent interference with T-cell receptor-stimulated tyrosine phosphorylation and Ca mobilization is a late event seen 24 h after MV treatment. In contrast, stimulated recruitment of pleckstrin homology domain-containing proteins such as Akt and Vav is inhibited early after MV contact, as is segregation of the activated Akt kinase from rafts. Tyrosine phosphorylation of the regulatory subunit of the phosphatidylinositol 3-kinase (PI3K), p85, is apparently normal then, yet this protein fails to partition to the lipid raft fraction, and this is associated with stable expression of its negative regulator Cbl-b. Thus, by interaction with lipid rafts, MV contact initially targets recruitment of PI3K by preventing stimulated Cbl-b degradation and activation of PI3K-dependent signaling components.
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Affiliation(s)
- Elita Avota
- Institute for Virology and Immunobiology, University of Würzburg, Würzburg, Germany
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193
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da Costa N, McGillivray C, Bai Q, Wood JD, Evans G, Chang KC. Restriction of dietary energy and protein induces molecular changes in young porcine skeletal muscles. J Nutr 2004; 134:2191-9. [PMID: 15333703 DOI: 10.1093/jn/134.9.2191] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Little is known about the molecular changes in response to dietary restriction (energy and/or protein) in young growing skeletal muscles. To profile such changes and to gain insights into the signaling molecules that could mediate the diet effects, a dedicated porcine skeletal muscle cDNA-microarray approach was used to characterize differential muscle gene expression between conventionally fed and diet-restricted (20% less protein and 7% less energy) growing pigs, reared from 9 to 21 wk of age. In both red and white muscles, diet restriction resulted in the accumulation of significantly more intramuscular fat, and in the increased expression of genes involved in substrate (protein, glycogen, and lipid) turnover, in translation and mitochondrial function, and in raising glycolytic and oxidative phosphorylation potentials. The unexpected increase in intramuscular lipids in diet-restricted growing pigs could have important health implications for restricted diets in childhood. Despite reduced circulating insulin, more genes, including several novel growth modulatory genes, had higher expression levels, indicating that the cellular response to dietary restriction is an active process. One such responsive gene, P311, was most highly expressed in striated muscles and had a differentiation-dependent increase of expression in murine C2C12 cells, suggesting a role in differentiation/postdifferentiation phenotype determination.
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Affiliation(s)
- Nuno da Costa
- Molecular Medicine Laboratory, Institute of Comparative Medicine, University of Glasgow Veterinary School, Glasgow G61 1QH, Scotland, UK.
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194
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Xu Z, George C, Jolly CA. CD28 activation does not down-regulate Cbl-b expression in aged rat T-lymphocytes. Mech Ageing Dev 2004; 125:595-602. [PMID: 15491677 DOI: 10.1016/j.mad.2004.06.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2003] [Revised: 05/18/2004] [Accepted: 06/16/2004] [Indexed: 01/11/2023]
Abstract
It is well known that T-lymphocyte proliferation declines ex vivo with age, and is associated with decreased expression and/or activity of stimulatory intracellular signaling proteins. However, the role of inhibitory intracellular signaling molecules like the ubiquitin ligase Cbl-b in regulating T-lymphocyte function in aging is largely unknown. Therefore, we tested the hypothesis that T-lymphocyte proliferation declines with age, in part, due to increased expression of Cbl-b. We show that young splenic T-lymphocytes reduced Cbl-b expression when stimulated with anti-CD3 and anti-CD28 antibodies, while in aged T-lymphocytes the CD28-dependent Cbl-b down-regulation did not occur. This effect did not appear to be due to reduced CD28 receptor expression on aged T-lymphocytes. The mechanism for lack of Cbl-b down-regulation may involve the proteasome since blocking proteasomal activity in young T-lymphocytes prevented Cbl-b down regulation while there was no effect in aged T-lymphocytes on Cbl-b expression. These data provide evidence for a novel mechanism by which aging reduces T-lymphocyte function.
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Affiliation(s)
- Zhun Xu
- Division of Nutritional Sciences, The University of Texas at Austin, 78712, USA
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195
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Abstract
E3 ubiquitin ligases have emerged as key molecular regulators of immune cell function. Three families of proteins with ubiquitin ligase activity have been described (the HECT, RING and U-box proteins), and each may be involved in the regulation of immune responses during infection by targeting specific inhibitory molecules for proteolytic destruction. Several HECT and RING E3 proteins have now also been linked to the induction and maintenance of immune self-tolerance: c-Cbl, Cbl-b, GRAIL, Itch and Nedd4 each negatively regulate T cell growth factor production and proliferation. This review will discuss the relationship between the ubiquitination of select components of the antigen-sensing signaling apparatus in T cells and the development and maintenance of the clonal anergy state.
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Affiliation(s)
- Daniel L Mueller
- Department of Medicine, Division of Rheumatic and Autoimmune Diseases, Center for Immunology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA.
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196
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Zhang J. Ubiquitin ligases in T cell activation and autoimmunity. Clin Immunol 2004; 111:234-40. [PMID: 15183144 DOI: 10.1016/j.clim.2004.02.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Accepted: 02/05/2004] [Indexed: 01/22/2023]
Abstract
Ubiquitination-mediated protein modifications are increasingly recognized as key regulatory events in many basic cell biology processes. A key class of enzymes called ubiquitin ligases, which has been shown to play a crucial role in the ubiquitination process, can positively or negatively regulate T cell responses. This review summarizes the recent advances defining the roles of several ubiquitin ligases in T cell activation and autoimmunity.
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Affiliation(s)
- Jian Zhang
- Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL 60612, USA.
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197
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Abstract
Cells of the immune system carry out diverse functions that are controlled by surface receptors for antigen, costimulatory molecules, cytokines, chemokines, and other ligands. A shared feature of signal transduction downstream of most receptors on immune cells, as in nonhematopoietic cell types, is the activation of phosphoinositide 3-kinase (PI3K). The mechanism by which this common signaling event is elicited by distinct receptors and contributes to unique functional outcomes is an intriguing puzzle. Understanding how specificity is achieved in PI3K signaling is of particular significance because altered regulation of this pathway is observed in many disease states, including leukemia and lymphoma. Here we review recent advances in the understanding of PI3K signaling mechanisms in different immune cells and receptor systems. We emphasize the concept that PI3K and its products are components of complex networks of interacting proteins and second messengers, rather than simple links in linear signaling cascades.
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Affiliation(s)
- Jonathan A Deane
- Department of Molecular Biology and Biochemistry, University of California, Irvine, 92697, USA.
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198
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Abstract
Ubiquitin (Ub)-protein conjugation represents a novel means of posttranscriptional modification in a proteolysis-dependent or -independent manner. E3 Ub ligases play a key role in governing the cascade of Ub transfer reactions by recognizing and catalyzing Ub conjugation to specific protein substrates. The E3s, which can be generally classified into HECT-type and RING-type families, are involved in the regulation of many aspects of the immune system, including the development, activation, and differentiation of lymphocytes, T cell-tolerance induction, antigen presentation, immune evasion, and virus budding. E3-promoted ubiquitination affects a wide array of biological processes, such as receptor downmodulation, signal transduction, protein processing or translocation, protein-protein interaction, and gene transcription, in addition to proteasome-mediated degradation. Deficiency or mutation of some of the E3s like Cbl, Cbl-b, or Itch, causes abnormal immune responses such as autoimmunity, malignancy, and inflammation. This review discusses our current understanding of E3 Ub ligases in both innate and adaptive immunity. Such knowledge may facilitate the development of novel therapeutic approaches for immunological diseases.
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Affiliation(s)
- Yun-Cai Liu
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA.
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199
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Jeon MS, Atfield A, Venuprasad K, Krawczyk C, Sarao R, Elly C, Yang C, Arya S, Bachmaier K, Su L, Bouchard D, Jones R, Gronski M, Ohashi P, Wada T, Bloom D, Fathman CG, Liu YC, Penninger JM. Essential Role of the E3 Ubiquitin Ligase Cbl-b in T Cell Anergy Induction. Immunity 2004; 21:167-77. [PMID: 15308098 DOI: 10.1016/j.immuni.2004.07.013] [Citation(s) in RCA: 269] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2003] [Revised: 06/01/2004] [Accepted: 06/07/2004] [Indexed: 11/25/2022]
Abstract
Antigen-specific immunotolerance limits the expansion of self-reactive T cells involved in autoimmune diseases. Here, we show that the E3 ubiquitin ligase Cbl-b is upregulated in T cells after tolerizing signals. Loss of Cbl-b in mice results in impaired induction of T cell tolerance both in vitro and in vivo. Importantly, rechallenge of Cbl-b mutant mice with the tolerizing antigen results in massive lethality. Moreover, ablation of Cbl-b resulted in exacerbated autoimmunity. Mechanistically, loss of Cbl-b rescues reduced calcium mobilization of anergic T cells, which was attributed to Cbl-b-mediated regulation of PLCgamma-1 phosphorylation. Our results show a critical role for Cbl-b in the regulation of peripheral tolerance and anergy of T cells.
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Affiliation(s)
- Myung-Shin Jeon
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA
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200
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Abstract
Regulation of tyrosine kinase-mediated cellular activation through antigen receptors is of great biological and practical significance. The evolutionarily conserved Cbl family ubiquitin ligases have emerged as key negative regulators of activated tyrosine kinase-coupled receptors, and their impaired function switches a normal immune response into autoimmunity. Cbl proteins facilitate the ubiquitinylation of activated tyrosine kinases and other signaling proteins and of the signaling chains of receptors themselves; monoubiquitin tag promotes sorting of activated receptors and associated proteins into internal vesicles of the multivesicular body, facilitating their lysosomal degradation, whereas polyubiquitin tag promotes proteasomal degradation. Notably, increased expression of Cbl proteins and other ubiquitin ligases is a component of anergic signaling program in T cells. Thus, controlled destruction of the signaling apparatus has emerged as a key to fine-tuning antigen receptor signaling. Further studies of this pathway are likely to elucidate the pathogenesis of autoimmune diseases and offer new therapeutic targets.
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Affiliation(s)
- Lei Duan
- Division of Molecular Oncology, Department of Medicine, Evanston Northwestern Healthcare Research Institute, Feinberg School of Medicine, Northwestern University, IL 60201, USA
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