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Joannou K, Baldwin TA. Destined for the intestine: thymic selection of TCRαβ CD8αα intestinal intraepithelial lymphocytes. Clin Exp Immunol 2023; 213:67-75. [PMID: 37137518 PMCID: PMC10324546 DOI: 10.1093/cei/uxad049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 03/22/2023] [Accepted: 04/30/2023] [Indexed: 05/05/2023] Open
Abstract
The immune system is composed of a variety of different T-cell lineages distributed through both secondary lymphoid tissue and non-lymphoid tissue. The intestinal epithelium is a critical barrier surface that contains numerous intraepithelial lymphocytes that aid in maintaining homeostasis at that barrier. This review focuses on T-cell receptor αβ (TCRαβ) CD8αα intraepithelial lymphocytes, and how recent advances in the field clarify how this unique T-cell subset is selected, matures, and functions in the intestines. We consider how the available evidence reveals a story of ontogeny starting from agonist selection of T cells in the thymus and finishing through the specific signaling environment of the intestinal epithelium. We conclude with how this story raises further key questions about the development of different ontogenic waves of TCRαβ CD8αα IEL and their importance for intestinal epithelial homeostasis.
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Affiliation(s)
- Kevin Joannou
- Department of Medical Microbiology and Immunology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Troy A Baldwin
- Department of Medical Microbiology and Immunology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
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2
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Beckmann D, Langnaese K, Gottfried A, Hradsky J, Tedford K, Tiwari N, Thomas U, Fischer KD, Korthals M. Ca 2+ Homeostasis by Plasma Membrane Ca 2+ ATPase (PMCA) 1 Is Essential for the Development of DP Thymocytes. Int J Mol Sci 2023; 24:ijms24021442. [PMID: 36674959 PMCID: PMC9865543 DOI: 10.3390/ijms24021442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 12/22/2022] [Accepted: 12/30/2022] [Indexed: 01/13/2023] Open
Abstract
The strength of Ca2+ signaling is a hallmark of T cell activation, yet the role of Ca2+ homeostasis in developing T cells before expressing a mature T cell receptor is poorly understood. We aimed to unveil specific functions of the two plasma membrane Ca2+ ATPases expressed in T cells, PMCA1 and PMCA4. On a transcriptional and protein level we found that PMCA4 was expressed at low levels in CD4-CD8- double negative (DN) thymocytes and was even downregulated in subsequent stages while PMCA1 was present throughout development and upregulated in CD4+CD8+ double positive (DP) thymocytes. Mice with a targeted deletion of Pmca1 in DN3 thymocytes had an almost complete block of DP thymocyte development with an accumulation of DN4 thymocytes but severely reduced numbers of CD8+ immature single positive (ISP) thymocytes. The DN4 thymocytes of these mice showed strongly elevated basal cytosolic Ca2+ levels and a pre-mature CD5 expression, but in contrast to the DP thymocytes they were only mildly prone to apoptosis. Surprisingly, mice with a germline deletion of Pmca4 did not show any signs of altered progression through the developmental thymocyte stages, nor altered Ca2+ homeostasis throughout this process. PMCA1 is, therefore, non-redundant in keeping cellular Ca2+ levels low in the early thymocyte development required for the DN to DP transition.
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Affiliation(s)
- David Beckmann
- Institute for Biochemistry and Cell Biology, Medical Faculty, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany
| | - Kristina Langnaese
- Institute for Biochemistry and Cell Biology, Medical Faculty, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany
| | - Anna Gottfried
- Institute for Biochemistry and Cell Biology, Medical Faculty, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany
| | - Johannes Hradsky
- Institute for Biochemistry and Cell Biology, Medical Faculty, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany
| | - Kerry Tedford
- Institute for Biochemistry and Cell Biology, Medical Faculty, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany
| | - Nikhil Tiwari
- Department of Cellular Neuroscience, Leibniz Institute for Neurobiology, 39120 Magdeburg, Germany
| | - Ulrich Thomas
- Department of Cellular Neuroscience, Leibniz Institute for Neurobiology, 39120 Magdeburg, Germany
| | - Klaus-Dieter Fischer
- Institute for Biochemistry and Cell Biology, Medical Faculty, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany
- Correspondence:
| | - Mark Korthals
- Institute for Biochemistry and Cell Biology, Medical Faculty, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany
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Kästle M, Merten C, Hartig R, Plaza-Sirvent C, Schmitz I, Bommhardt U, Schraven B, Simeoni L. Type of PaperY192 within the SH2 Domain of Lck Regulates TCR Signaling Downstream of PLC-γ1 and Thymic Selection. Int J Mol Sci 2022; 23:ijms23137271. [PMID: 35806279 PMCID: PMC9267008 DOI: 10.3390/ijms23137271] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Revised: 06/24/2022] [Accepted: 06/27/2022] [Indexed: 02/04/2023] Open
Abstract
Signaling via the TCR, which is initiated by the Src-family tyrosine kinase Lck, is crucial for the determination of cell fates in the thymus. Because of its pivotal role, ablation of Lck results in a profound block of T-cell development. Here, we show that, in addition to its well-known function in the initiation of TCR signaling, Lck also acts at a more downstream level. This novel function of Lck is determined by the tyrosine residue (Y192) located in its SH2 domain. Thymocytes from knock-in mice expressing a phosphomimetic Y192E mutant of Lck initiate TCR signaling upon CD3 cross-linking up to the level of PLC-γ1 phosphorylation. However, the activation of downstream pathways including Ca2+ influx and phosphorylation of Erk1/2 are impaired. Accordingly, positive and negative selections are blocked in LckY192E knock-in mice. Collectively, our data indicate that Lck has a novel function downstream of PLCγ-1 in the regulation of thymocyte differentiation and selection.
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Affiliation(s)
- Matthias Kästle
- Institute of Molecular and Clinical Immunology, Medical Faculty, Otto-von-Guericke University, 39120 Magdeburg, Germany; (M.K.); (C.M.); (R.H.); (C.P.-S.); (I.S.); (U.B.)
| | - Camilla Merten
- Institute of Molecular and Clinical Immunology, Medical Faculty, Otto-von-Guericke University, 39120 Magdeburg, Germany; (M.K.); (C.M.); (R.H.); (C.P.-S.); (I.S.); (U.B.)
| | - Roland Hartig
- Institute of Molecular and Clinical Immunology, Medical Faculty, Otto-von-Guericke University, 39120 Magdeburg, Germany; (M.K.); (C.M.); (R.H.); (C.P.-S.); (I.S.); (U.B.)
| | - Carlos Plaza-Sirvent
- Institute of Molecular and Clinical Immunology, Medical Faculty, Otto-von-Guericke University, 39120 Magdeburg, Germany; (M.K.); (C.M.); (R.H.); (C.P.-S.); (I.S.); (U.B.)
- Department of Molecular Immunology, Ruhr-University Bochum, 44801 Bochum, Germany
| | - Ingo Schmitz
- Institute of Molecular and Clinical Immunology, Medical Faculty, Otto-von-Guericke University, 39120 Magdeburg, Germany; (M.K.); (C.M.); (R.H.); (C.P.-S.); (I.S.); (U.B.)
- Department of Molecular Immunology, Ruhr-University Bochum, 44801 Bochum, Germany
| | - Ursula Bommhardt
- Institute of Molecular and Clinical Immunology, Medical Faculty, Otto-von-Guericke University, 39120 Magdeburg, Germany; (M.K.); (C.M.); (R.H.); (C.P.-S.); (I.S.); (U.B.)
- Health Campus Immunology, Infectiology and Inflammation (GC-I3), Medical Faculty, Otto-von-Guericke University, 39120 Magdeburg, Germany
- Center for Health and Medical Prevention (CHaMP), Otto-von-Guericke University, 39120 Magdeburg, Germany
| | - Burkhart Schraven
- Institute of Molecular and Clinical Immunology, Medical Faculty, Otto-von-Guericke University, 39120 Magdeburg, Germany; (M.K.); (C.M.); (R.H.); (C.P.-S.); (I.S.); (U.B.)
- Health Campus Immunology, Infectiology and Inflammation (GC-I3), Medical Faculty, Otto-von-Guericke University, 39120 Magdeburg, Germany
- Center for Health and Medical Prevention (CHaMP), Otto-von-Guericke University, 39120 Magdeburg, Germany
- Correspondence: (B.S.); (L.S.)
| | - Luca Simeoni
- Institute of Molecular and Clinical Immunology, Medical Faculty, Otto-von-Guericke University, 39120 Magdeburg, Germany; (M.K.); (C.M.); (R.H.); (C.P.-S.); (I.S.); (U.B.)
- Health Campus Immunology, Infectiology and Inflammation (GC-I3), Medical Faculty, Otto-von-Guericke University, 39120 Magdeburg, Germany
- Center for Health and Medical Prevention (CHaMP), Otto-von-Guericke University, 39120 Magdeburg, Germany
- Correspondence: (B.S.); (L.S.)
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4
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NFAT Factors Are Dispensable for the Development but Are Critical for the Maintenance of Foxp3+ Regulatory T Cells. Cells 2022; 11:cells11091397. [PMID: 35563702 PMCID: PMC9104130 DOI: 10.3390/cells11091397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 04/11/2022] [Accepted: 04/13/2022] [Indexed: 11/16/2022] Open
Abstract
The transcription factors of the nuclear factor of activated T cell (NFAT) family play a crucial role in multiple aspects of T cell function. It has recently been reported that NFATs play an important role in the suppressive function of CD4+CD25+Foxp3+ regulatory T (Treg) cells. In this study, we have investigated the role of NFATs in the thymic development of Treg cells in mice. We show that NFAT factors are dispensable for the development of Foxp3+ Treg cells in the thymus but are critical for the maintenance of both the phenotype and survival of Treg cells in the thymus as well as in peripheral lymphoid organs. Specifically, the homeostasis of CD4+CD25+Foxp3+ but not the CD4+CD25−Foxp3+ fraction is severely perturbed when NFAT signaling is blocked, leading to a strongly reduced Treg population. We underscored this intriguing effect of NFAT on CD4+CD25+Foxp3+ Treg cells to the disruption of survival signals provided by interleukin 2 (IL-2). Accordingly, blocking Treg cell death by abolishing the activity of pro-apoptotic Bcl-2 family member Bim, compensated for the survival defects induced due to a lack of NFAT-IL-2-IL-2R signaling. Inhibition of NFAT activity led to a strong reduction in the number of Foxp3+ Treg cells; however, it did not influence the level of Foxp3 expression on an individual cell basis. In addition, we show a differential effect of IL-2 and IL-7 signaling on Foxp3+ Treg versus CD4+CD25− T cell development, again underlining the dispensability of NFAT signaling in the development, but not in the maintenance of Foxp3+ Treg cells.
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5
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TREML4 receptor regulates inflammation and innate immune cell death during polymicrobial sepsis. Nat Immunol 2020; 21:1585-1596. [DOI: 10.1038/s41590-020-0789-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 08/21/2020] [Indexed: 12/20/2022]
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6
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Li KP, Ladle BH, Kurtulus S, Sholl A, Shanmuganad S, Hildeman DA. T-cell receptor signal strength and epigenetic control of Bim predict memory CD8 + T-cell fate. Cell Death Differ 2020; 27:1214-1224. [PMID: 31558776 PMCID: PMC7206134 DOI: 10.1038/s41418-019-0410-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 05/31/2019] [Accepted: 08/21/2019] [Indexed: 12/24/2022] Open
Abstract
Most effector CD8+ T cells die, while some persist and become either "effector" (TEM) or "central" (TCM) memory T cells. Paradoxically, effector CD8+ T cells with greater memory potential have higher levels of the pro-apoptotic molecule Bim. Here, we report, using a novel Bim-mCherry knock-in mouse, that cells with high levels of Bim preferentially develop into TCM cells. Bim levels remained stable and were regulated by DNA methylation at the Bim promoter. Notably, high levels of Bcl-2 were required for Bimhi cells to survive. Using Nur77-GFP mice as an indicator of TCR signal strength, Nur77 levels correlated with Bim expression and Nur77hi cells also selectively developed into TCM cells. Altogether, these data show that Bim levels and TCR signal strength are predictive of TEM- vs. TCM-cell fate. Further, given the many other biologic functions of Bim, these mice will have broad utility beyond CD8+ T-cell fate.
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Affiliation(s)
- Kun-Po Li
- Immunology Graduate Program, Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, Cincinnati, OH, 45229, USA
| | - Brian H Ladle
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, Cincinnati, OH, 45229, USA
- Johns Hopkins Hospital, 1800 Orleans Street, The Charlotte R. Bloomberg Children's Center Building, 11th Floor, Baltimore, MD, 21287, USA
| | - Sema Kurtulus
- Immunology Graduate Program, Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, Cincinnati, OH, 45229, USA
| | - Allyson Sholl
- Division of Immunobiology, Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, Cincinnati, OH, 45229, USA
| | - Sharmila Shanmuganad
- Immunology Graduate Program, Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, Cincinnati, OH, 45229, USA
| | - David A Hildeman
- Immunology Graduate Program, Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, Cincinnati, OH, 45229, USA.
- Division of Immunobiology, Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, Cincinnati, OH, 45229, USA.
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Distelhorst CW, Bootman MD. Creating a New Cancer Therapeutic Agent by Targeting the Interaction between Bcl-2 and IP 3 Receptors. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a035196. [PMID: 31110129 DOI: 10.1101/cshperspect.a035196] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Bcl-2 is a member of a family of proteins that regulate cell survival. Expression of Bcl-2 is aberrantly elevated in many types of cancer. Within cells of the immune system, Bcl-2 has a physiological role in regulating immune responses. However, in cancers arising from cells of the immune system Bcl-2 promotes cell survival and proliferation. This review summarizes discoveries over the past 30 years that have elucidated Bcl-2's role in the normal immune system, including its actions in regulating calcium (Ca2+) signals necessary for the immune response, and for Ca2+-mediated apoptosis at the end of an immune response. How Bcl-2 modulates the release of Ca2+ from intracellular stores via inositol 1,4,5-trisphosphate receptors (IP3R) is discussed, and in particular, the role of Bcl-2/IP3R interactions in promoting the survival of cancer cells by preventing Ca2+-mediated cell death. The development and usage of a peptide, referred to as TAT-Pep8, or more recently, BIRD-2, that induces death of cancer cells by inhibiting Bcl-2's control over IP3R-mediated Ca2+ elevation is discussed. Studies aimed at discovering a small molecule that mimics BIRD-2's anticancer mechanism of action are summarized, along with the prospect of such a compound becoming a novel therapeutic option for cancer.
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Affiliation(s)
- Clark W Distelhorst
- Departments of Medicine and Pharmacology, Case Western Reserve University School of Medicine, University Hospitals Cleveland Medical Center, Cleveland, Ohio 44106, USA
| | - Martin D Bootman
- School of Life, Health, and Chemical Science, The Open University, Milton Keynes MK7 6AA, United Kingdom
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Distelhorst CW. Targeting Bcl-2-IP 3 receptor interaction to treat cancer: A novel approach inspired by nearly a century treating cancer with adrenal corticosteroid hormones. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1865:1795-1804. [PMID: 30053503 DOI: 10.1016/j.bbamcr.2018.07.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 07/18/2018] [Accepted: 07/19/2018] [Indexed: 12/12/2022]
Abstract
Bcl-2 inhibits cell death by at least two different mechanisms. On the one hand, its BH3 domain binds to pro-apoptotic proteins such as Bim and prevents apoptosis induction. On the other hand, the BH4 domain of Bcl-2 binds to the inositol 1,4,5-trisphosphate receptor (IP3R), preventing Ca2+ signals that mediate cell death. In normal T-cells, Bcl-2 levels increase during the immune response, protecting against cell death, and then decline as apoptosis ensues and the immune response dissipates. But in many cancers Bcl-2 is aberrantly expressed and exploited to prevent cell death by inhibiting IP3R-mediated Ca2+ elevation. This review summarizes what is known about the mechanism of Bcl-2's control over IP3R-mediated Ca2+ release and cell death induction. Early insights into the role of Ca2+ elevation in corticosteroid-mediated cell death serves as a model for how targeting IP3R-mediated Ca2+ elevation can be a highly effective therapeutic approach for different types of cancer. Moreover, the successful development of ABT-199 (Venetoclax), a small molecule targeting the BH3 domain of Bcl-2 but without effects on Ca2+, serves as proof of principle that targeting Bcl-2 can be an effective therapeutic approach. BIRD-2, a synthetic peptide that inhibits Bcl-2-IP3R interaction, induces cell death induction in ABT-199 (Venetoclax)-resistant cancer models, attesting to the value of developing therapeutic agents that selectively target Bcl-2-IP3R interaction, inducing Ca2+-mediated cell death.
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Affiliation(s)
- Clark W Distelhorst
- Case Western University School of Medicine, Case Comprehensive Cancer Center, University Hospitals Cleveland Medical Center, Cleveland, OH 44106, United States of America.
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Wang J, He N, Zhang N, Quan D, Zhang S, Zhang C, Yu RT, Atkins AR, Zhu R, Yang C, Cui Y, Liddle C, Downes M, Xiao H, Zheng Y, Auwerx J, Evans RM, Leng Q. NCoR1 restrains thymic negative selection by repressing Bim expression to spare thymocytes undergoing positive selection. Nat Commun 2017; 8:959. [PMID: 29038463 PMCID: PMC5643384 DOI: 10.1038/s41467-017-00931-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 08/07/2017] [Indexed: 11/09/2022] Open
Abstract
Thymocytes must pass both positive and negative selections to become mature T cells. Negative selection purges thymocytes whose T-cell receptors (TCR) exhibit high affinity to self-peptide MHC complexes (self pMHC) to avoid autoimmune diseases, while positive selection ensures the survival and maturation of thymocytes whose TCRs display intermediate affinity to self pMHCs for effective immunity, but whether transcriptional regulation helps conserve positively selected thymocytes from being purged by negative selection remains unclear. Here we show that the specific deletion of nuclear receptor co-repressor 1 (NCoR1) in T cells causes excessive negative selection to reduce mature thymocyte numbers. Mechanistically, NCoR1 protects positively selected thymocytes from negative selection by suppressing Bim expression. Our study demonstrates a critical function of NCoR1 in coordinated positive and negative selections in the thymus.Thymocytes are screened by two processes, termed positive and negative selections, which are permissive only for immature thymocytes with intermediate avidity to the selecting ligands. Here the authors show that the nuclear receptor NCoR1 suppresses Bim1 to inhibit negative selection and promote thymocyte survival.
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Affiliation(s)
- Jianrong Wang
- CAS Key Laboratory of Molecular Virology & Immunology, Unit of Immune Regulation, Institut Pasteur of Shanghai, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, 200031 China
| | - Nanhai He
- Gene Expression Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037 USA
| | - Na Zhang
- CAS Key Laboratory of Molecular Virology & Immunology, Unit of Immune Regulation, Institut Pasteur of Shanghai, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, 200031 China
- Obstetrics and Gynecology Hospital, Shanghai Key Laboratory of Female Reproductive Endocrine-related Disease, the Academy of Integrative Medicine, Fudan University, Shanghai, 200011 China
| | - Dexian Quan
- CAS Key Laboratory of Molecular Virology & Immunology, Unit of Immune Regulation, Institut Pasteur of Shanghai, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, 200031 China
| | - Shuo Zhang
- CAS Key Laboratory of Molecular Virology & Immunology, Unit of Immune Regulation, Institut Pasteur of Shanghai, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, 200031 China
| | - Caroline Zhang
- Gene Expression Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037 USA
| | - Ruth T. Yu
- Gene Expression Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037 USA
| | - Annette R. Atkins
- Gene Expression Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037 USA
| | - Ruihong Zhu
- CAS Key Laboratory of Molecular Virology & Immunology, Unit of Immune Regulation, Institut Pasteur of Shanghai, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, 200031 China
| | - Chunhui Yang
- CAS Key Laboratory of Molecular Virology & Immunology, Unit of Immune Regulation, Institut Pasteur of Shanghai, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, 200031 China
| | - Ying Cui
- CAS Key Laboratory of Molecular Virology & Immunology, Unit of Immune Regulation, Institut Pasteur of Shanghai, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, 200031 China
| | - Christopher Liddle
- Storr Liver Centre, Westmead Millennium Institute, Sydney Medical School, University of Sydney, Sydney, NSW 2006 Australia
| | - Michael Downes
- Gene Expression Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037 USA
| | - Hui Xiao
- CAS Key Laboratory of Molecular Virology & Immunology, Unit of Immune Regulation, Institut Pasteur of Shanghai, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, 200031 China
| | - Ye Zheng
- Immunobiology and Microbial Pathogenesis Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037 USA
| | - Johan Auwerx
- Laboratory of Integrative and Systems Physiology, École Polytechnique Fédérale de Lausanne, Station 15, Lausanne, CH-1015 Switzerland
| | - Ronald M. Evans
- Gene Expression Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037 USA
| | - Qibin Leng
- CAS Key Laboratory of Molecular Virology & Immunology, Unit of Immune Regulation, Institut Pasteur of Shanghai, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, 200031 China
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10
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Hemon P, Renaudineau Y, Debant M, Le Goux N, Mukherjee S, Brooks W, Mignen O. Calcium Signaling: From Normal B Cell Development to Tolerance Breakdown and Autoimmunity. Clin Rev Allergy Immunol 2017; 53:141-165. [DOI: 10.1007/s12016-017-8607-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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11
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Increased Fetal Thymocytes Apoptosis Contributes to Prenatal Nicotine Exposure-induced Th1/Th2 Imbalance in Male Offspring Mice. Sci Rep 2016; 6:39013. [PMID: 27976742 PMCID: PMC5157046 DOI: 10.1038/srep39013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 11/16/2016] [Indexed: 12/22/2022] Open
Abstract
Nicotine, a definite risk factor during pregnancy, is an immunomodulator. This study was designed to investigate the effects of prenatal nicotine exposure (PNE) on the balance of Th1/Th2 in offspring, and further explore the developmental origin mechanisms from the perspective of fetal thymocytes apoptosis. Pregnant Balb/c mice were administered 1.5 mg/kg nicotine subcutaneously twice per day from gestational day (GD) 9 to GD18. Results showed that PNE could cause a Th2 shift in male offspring, manifested as increased ratio of IgG1/IgG2a, IL-4 production in serum, and IL-4/IFN-γ expression ratio in spleen. Increased apoptosis of total thymocytes and CD4SP and reduced cell proportion of CD4SP were found in PNE male offspring on postnatal day (PND) 14 and PND 49. In the fetuses, decreased body weight and organ index of fetal thymus, histological changes in fetal thymus, reduced CD4SP proportion and increased fetal thymocyte apoptosis were observed in nicotine group. The increased mRNA expression of genes involved in Fas-mediated apoptotic pathway and protein expression of Fas were also detected. In conclusion, PNE could cause a Th2 shift in male offspring mediated by reduced CD4+ T cells output, which may result from the increasing apoptosis of total thymocytes and CD4SP.
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12
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Lavik AR, Zhong F, Chang MJ, Greenberg E, Choudhary Y, Smith MR, McColl KS, Pink J, Reu FJ, Matsuyama S, Distelhorst CW. A synthetic peptide targeting the BH4 domain of Bcl-2 induces apoptosis in multiple myeloma and follicular lymphoma cells alone or in combination with agents targeting the BH3-binding pocket of Bcl-2. Oncotarget 2016; 6:27388-402. [PMID: 26317541 PMCID: PMC4694997 DOI: 10.18632/oncotarget.4489] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 07/01/2015] [Indexed: 12/21/2022] Open
Abstract
Bcl-2 inhibits apoptosis by two distinct mechanisms but only one is targeted to treat Bcl-2-positive malignancies. In this mechanism, the BH1-3 domains of Bcl-2 form a hydrophobic pocket, binding and inhibiting pro-apoptotic proteins, including Bim. In the other mechanism, the BH4 domain mediates interaction of Bcl-2 with inositol 1,4, 5-trisphosphate receptors (IP3Rs), inhibiting pro-apoptotic Ca2+ signals. The current anti-Bcl-2 agents, ABT-263 (Navitoclax) and ABT-199 (Venetoclax), induce apoptosis by displacing pro-apoptotic proteins from the hydrophobic pocket, but do not inhibit Bcl-2-IP3R interaction. Therefore, to target this interaction we developed BIRD-2 (Bcl-2 IP3 Receptor Disruptor-2), a decoy peptide that binds to the BH4 domain, blocking Bcl-2-IP3R interaction and thus inducing Ca2+-mediated apoptosis in chronic lymphocytic leukemia, multiple myeloma, and follicular lymphoma cells, including cells resistant to ABT-263, ABT-199, or the Bruton’s tyrosine kinase inhibitor Ibrutinib. Moreover, combining BIRD-2 with ABT-263 or ABT-199 enhances apoptosis induction compared to single agent treatment. Overall, these findings provide strong rationale for developing novel therapeutic agents that mimic the action of BIRD-2 in targeting the BH4 domain of Bcl-2 and disrupting Bcl-2-IP3R interaction.
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Affiliation(s)
- Andrew R Lavik
- Division of Hematology/Oncology, Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, Cleveland, Ohio, USA
| | - Fei Zhong
- Division of Hematology/Oncology, Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, Cleveland, Ohio, USA
| | - Ming-Jin Chang
- Division of Hematology/Oncology, Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, Cleveland, Ohio, USA
| | - Edward Greenberg
- Division of Hematology/Oncology, Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, Cleveland, Ohio, USA.,Department of Medicine, MetroHealth Medical Center and Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Yuvraj Choudhary
- Division of Hematology/Oncology, Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, Cleveland, Ohio, USA
| | - Mitchell R Smith
- Department of Translational Hematology and Oncology Research, Taussig Cancer Institute, The Cleveland Clinic Foundation, Cleveland, Ohio, USA.,Case Comprehensive Cancer Center, Cleveland, Ohio, USA
| | - Karen S McColl
- Division of Hematology/Oncology, Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, Cleveland, Ohio, USA
| | - John Pink
- Case Comprehensive Cancer Center, Cleveland, Ohio, USA
| | - Frederic J Reu
- Department of Translational Hematology and Oncology Research, Taussig Cancer Institute, The Cleveland Clinic Foundation, Cleveland, Ohio, USA.,Case Comprehensive Cancer Center, Cleveland, Ohio, USA
| | - Shigemi Matsuyama
- Division of Hematology/Oncology, Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, Cleveland, Ohio, USA.,Case Comprehensive Cancer Center, Cleveland, Ohio, USA
| | - Clark W Distelhorst
- Division of Hematology/Oncology, Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, Cleveland, Ohio, USA.,Case Comprehensive Cancer Center, Cleveland, Ohio, USA
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13
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Miller AT, Dahlberg C, Sandberg ML, Wen BG, Beisner DR, Hoerter JAH, Parker A, Schmedt C, Stinson M, Avis J, Cienfuegos C, McPate M, Tranter P, Gosling M, Groot-Kormelink PJ, Dawson J, Pan S, Tian SS, Seidel HM, Cooke MP. Inhibition of the Inositol Kinase Itpkb Augments Calcium Signaling in Lymphocytes and Reveals a Novel Strategy to Treat Autoimmune Disease. PLoS One 2015; 10:e0131071. [PMID: 26121493 PMCID: PMC4488288 DOI: 10.1371/journal.pone.0131071] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 05/28/2015] [Indexed: 02/02/2023] Open
Abstract
Emerging approaches to treat immune disorders target positive regulatory kinases downstream of antigen receptors with small molecule inhibitors. Here we provide evidence for an alternative approach in which inhibition of the negative regulatory inositol kinase Itpkb in mature T lymphocytes results in enhanced intracellular calcium levels following antigen receptor activation leading to T cell death. Using Itpkb conditional knockout mice and LMW Itpkb inhibitors these studies reveal that Itpkb through its product IP4 inhibits the Orai1/Stim1 calcium channel on lymphocytes. Pharmacological inhibition or genetic deletion of Itpkb results in elevated intracellular Ca2+ and induction of FasL and Bim resulting in T cell apoptosis. Deletion of Itpkb or treatment with Itpkb inhibitors blocks T-cell dependent antibody responses in vivo and prevents T cell driven arthritis in rats. These data identify Itpkb as an essential mediator of T cell activation and suggest Itpkb inhibition as a novel approach to treat autoimmune disease.
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Affiliation(s)
- Andrew T. Miller
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
- * E-mail:
| | - Carol Dahlberg
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Mark L. Sandberg
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Ben G. Wen
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Daniel R. Beisner
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - John A. H. Hoerter
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Albert Parker
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Christian Schmedt
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Monique Stinson
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Jacqueline Avis
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Cynthia Cienfuegos
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Mark McPate
- Novartis Pharmaceuticals UK Limited, Respiratory Disease Area, Horsham, West Sussex, United Kingdom
| | - Pamela Tranter
- Novartis Pharmaceuticals UK Limited, Respiratory Disease Area, Horsham, West Sussex, United Kingdom
| | - Martin Gosling
- Novartis Pharmaceuticals UK Limited, Respiratory Disease Area, Horsham, West Sussex, United Kingdom
| | - Paul J. Groot-Kormelink
- Novartis Institutes for Biomedical Research, Musculoskeletal Disease Area, Basel, Switzerland
| | - Janet Dawson
- Novartis Pharma AG, Novartis Institutes for Biomed. Research, Basel, Switzerland
| | - Shifeng Pan
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Shin-Shay Tian
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - H. Martin Seidel
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Michael P. Cooke
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
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14
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Greenberg EF, Lavik AR, Distelhorst CW. Bcl-2 regulation of the inositol 1,4,5-trisphosphate receptor and calcium signaling in normal and malignant lymphocytes: potential new target for cancer treatment. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1843:2205-10. [PMID: 24642270 PMCID: PMC4119508 DOI: 10.1016/j.bbamcr.2014.03.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 03/07/2014] [Accepted: 03/10/2014] [Indexed: 01/23/2023]
Abstract
The anti-apoptotic protein Bcl-2 is a versatile regulator of cell survival. Its interactions with its own pro-apoptotic family members are widely recognized for their role in promoting the survival of cancer cells. These interactions are thus being targeted for cancer treatment. Less widely recognized is the interaction of Bcl-2 with the inositol 1,4,5-trisphosphate receptor (InsP3R), an InsP3-gated Ca(2+) channel located on the endoplasmic reticulum. The nature of this interaction, the mechanism by which it controls Ca(2+) release from the ER, its role in T-cell development and survival, and the possibility of targeting it as a novel cancer treatment strategy are summarized in this review. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.
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Affiliation(s)
- Edward F Greenberg
- Division of Hematology/Oncology, Case Western Reserve University School of Medicine, Case Comprehensive Cancer Center, University Hospitals Case Medical Center, USA; MetroHealth Medical Center, USA.
| | - Andrew R Lavik
- Division of Hematology/Oncology, Case Western Reserve University School of Medicine, Case Comprehensive Cancer Center, University Hospitals Case Medical Center, USA.
| | - Clark W Distelhorst
- Division of Hematology/Oncology, Case Western Reserve University School of Medicine, Case Comprehensive Cancer Center, University Hospitals Case Medical Center, USA.
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15
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Loss of IP3R-dependent Ca2+ signalling in thymocytes leads to aberrant development and acute lymphoblastic leukemia. Nat Commun 2014; 5:4814. [PMID: 25215520 DOI: 10.1038/ncomms5814] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 07/25/2014] [Indexed: 01/28/2023] Open
Abstract
Calcium ions (Ca(2+)) function as universal second messengers in eukaryotic cells, including immune cells. Ca(2+) is crucial for peripheral T-lymphocyte activation and effector functions, and influences thymocyte selection and motility in the developing thymus. However, the role of Ca(2+) signalling in early T-lymphocyte development is not well understood. Here we show that the inositol triphosphate receptors (IP3Rs) Ca(2+) ion channels are required for proliferation, survival and developmental progression of T-lymphocyte precursors. Our studies indicate that signalling via IP3Rs represses Sox13, an antagonist of the developmentally important transcription factor Tcf-1. In the absence of IP3R-mediated Ca(2+) signalling, repression of key Notch transcriptional targets--including Hes1--fail to occur in post β-selection thymocytes, and mice develop aggressive T-cell malignancies that resemble human T-cell acute lymphoblastic leukemia (T-ALL). These data indicate that IP3R-mediated Ca(2+) signalling reinforces Tcf-1 activity to both ensure normal development and prevent thymocyte neoplasia.
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16
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Tanaka-Nakanishi A, Yasunaga JI, Takai K, Matsuoka M. HTLV-1 bZIP factor suppresses apoptosis by attenuating the function of FoxO3a and altering its localization. Cancer Res 2013; 74:188-200. [PMID: 24177179 DOI: 10.1158/0008-5472.can-13-0436] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
As the infectious agent causing human adult T-cell leukemia (ATL), the human T-cell leukemia virus type 1 (HTLV-1) virus spreads in vivo primarily by cell-to-cell transmission. However, the factors that determine its transmission efficiency are not fully understood. The viral genome encodes the HTLV-1 bZIP factor (HBZ), which is expressed in all ATL cases and is known to promote T-cell proliferation. In this study, we investigated the hypothesis that HBZ also influences the survival of T cells. Through analyzing the transcriptional profile of HBZ-expressing cells, we learned that HBZ suppressed transcription of the proapoptotic gene Bim (Bcl2l11) and that HBZ-expressing cells were resistant to activation-induced apoptosis. Mechanistic investigations into how HBZ suppresses Bim expression revealed that HBZ perturbs the localization and function of FoxO3a, a critical transcriptional activator of the genes encoding Bim and also Fas ligand (FasL). By interacting with FoxO3a, HBZ not only attenuated DNA binding by FoxO3a but also sequestered the inactive form of FoxO3a in the nucleus. In a similar manner, HBZ also inhibited FasL transcription induced by T-cell activation. Further study of ATL cells identified other Bim perturbations by HBZ, including at the level of epigenetic alteration, histone modification in the promoter region of the Bim gene. Collectively, our results indicated that HBZ impairs transcription of the Bim and FasL genes by disrupting FoxO3a function, broadening understanding of how HBZ acts to promote proliferation of HTLV-1-infected T cells by blocking their apoptosis.
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Affiliation(s)
- Azusa Tanaka-Nakanishi
- Authors' Affiliation: Laboratory of Virus Control, Institute for Virus Research, Kyoto University, Sakyo-ku, Kyoto, Japan
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17
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Dzhagalov IL, Chen KG, Herzmark P, Robey EA. Elimination of self-reactive T cells in the thymus: a timeline for negative selection. PLoS Biol 2013; 11:e1001566. [PMID: 23700386 PMCID: PMC3660248 DOI: 10.1371/journal.pbio.1001566] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 04/11/2013] [Indexed: 01/22/2023] Open
Abstract
Two-photon microscopy and flow cytometry reveal the timing of thymocyte death and the surprisingly close coupling between cell death and phagocytosis during negative selection in thymic slices. The elimination of autoreactive T cells occurs via thymocyte apoptosis and removal by thymic phagocytes, but the sequence of events in vivo, and the relationship between thymocyte death and phagocytic clearance, are unknown. Here we address these questions by following a synchronized cohort of thymocytes undergoing negative selection within a three-dimensional thymic tissue environment, from the initial encounter with a negative selecting ligand to thymocyte death and clearance. Encounter with cognate peptide–MHC complexes results in rapid calcium flux and migratory arrest in auto-reactive thymocytes over a broad range of peptide concentrations, followed by a lag period in which gene expression changes occurred, but there was little sign of thymocyte death. Caspase 3 activation and thymocyte loss were first detectable at 2 and 3 hours, respectively, and entry of individual thymocytes into the death program occurred asynchronously over the next 10 hours. Two-photon time-lapse imaging revealed that thymocyte death and phagocytosis occurred simultaneously, often with thymocytes engulfed prior to changes in chromatin and membrane permeability. Our data provide a timeline for negative selection and reveal close coupling between cell death and clearance in the thymus. As an important safeguard against autoimmunity, T cells bearing autoreactive T cell antigen receptors are eliminated during their development in the thymus, a process known as negative selection. Although much is known about the molecular events involved in negative selection, surprisingly little is known about the dynamic aspects of the process. Here we examine a synchronized population of developing T cells (thymocytes) undergoing negative selection within three-dimensional living thymic tissue. We show that the initial encounter with negative selecting ligands results in migratory arrest, but in spite of this synchronous early response, individual thymocytes then undergo delayed and asynchronous entry into the death program between 2 and 12 hours thereafter. Using time-lapse two-photon imaging, we reveal that thymocyte death and the clearance of the dead cells invariably occur together, with many thymocytes already engulfed by a macrophage before the cell death-related changes in chromatin and membrane permeability are evident. These data provide a timeline of the major events during negative selection, and suggest close coupling between thymocyte death and clearance by macrophages.
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Affiliation(s)
- Ivan Lilyanov Dzhagalov
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Katherine Grace Chen
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Paul Herzmark
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Ellen A. Robey
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
- * E-mail:
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18
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Oh-Hora M, Komatsu N, Pishyareh M, Feske S, Hori S, Taniguchi M, Rao A, Takayanagi H. Agonist-selected T cell development requires strong T cell receptor signaling and store-operated calcium entry. Immunity 2013; 38:881-95. [PMID: 23499491 DOI: 10.1016/j.immuni.2013.02.008] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 02/11/2013] [Indexed: 01/08/2023]
Abstract
T cell receptor (TCR) signaling driven by interaction of the TCR with specific complexes of self-peptide and the major histocompatibility complex determines T cell fate in thymic development. However, the signaling pathway through which TCR signal strength regulates distinct T cell lineages remains unknown. Here we have used mice lacking the endoplasmic reticulum Ca2+ sensors stromal interaction molecule 1 (STIM1) and STIM2 to show that STIM-induced store-operated Ca2+ entry is not essential for thymic development of conventional TCRαβ+ T cells but is specifically required for the development of agonist-selected T cells (regulatory T cells, invariant natural killer T cells, and TCRαβ+ CD8αα+ intestinal intraepithelial lymphocytes). The severe impairment of agonist-selected T cell development is mainly due to a defect in interleukin-2 (IL-2) or IL-15 signaling. Thus, STIM1 and STIM2-mediated store-operated Ca2+ influx, leading to efficient activation of NFAT (nuclear factor of activated T cells), is critical for the postselection maturation of agonist-selected T cells.
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Affiliation(s)
- Masatsugu Oh-Hora
- Department of Cell Signaling, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
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19
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Mittelstadt PR, Monteiro JP, Ashwell JD. Thymocyte responsiveness to endogenous glucocorticoids is required for immunological fitness. J Clin Invest 2012; 122:2384-94. [PMID: 22653054 DOI: 10.1172/jci63067] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Accepted: 04/18/2012] [Indexed: 12/21/2022] Open
Abstract
Generation of a self-tolerant but antigen-responsive T cell repertoire occurs in the thymus. Although glucocorticoids are usually considered immunosuppressive, there is also evidence that they play a positive role in thymocyte selection. To address the question of how endogenous glucocorticoids might influence the adaptive immune response, we generated GRlck-Cre mice, in which the glucocorticoid receptor gene (GR) is deleted in thymocytes prior to selection. These mice were immunocompromised, with reduced polyclonal T cell proliferative responses to alloantigen, defined peptide antigens, and viral infection. This was not due to an intrinsic proliferation defect, because GR-deficient T cells responded normally when the TCR was cross-linked with antibodies or when the T cell repertoire was "fixed" with αβ TCR transgenes. Varying the affinity of self ligands in αβ TCR transgenic mice showed that affinities that would normally lead to thymocyte-positive selection caused negative selection, and alterations in the TCR repertoire of polyclonal T cells were confirmed by analysis of TCR Vβ CDR3 regions. Thus, endogenous glucocorticoids are required for a robust adaptive immune response because of their promotion of the selection of T cells that have sufficient affinity for self, and the absence of thymocyte glucocorticoid signaling results in an immunocompromised state.
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Affiliation(s)
- Paul R Mittelstadt
- Laboratory of Immune Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, USA
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20
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Patrussi L, Giommoni N, Pellegrini M, Gamberucci A, Baldari CT. p66Shc-dependent apoptosis requires Lck and CamKII activity. Apoptosis 2011; 17:174-86. [DOI: 10.1007/s10495-011-0663-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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21
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Staton TL, Lazarevic V, Jones DC, Lanser AJ, Takagi T, Ishii S, Glimcher LH. Dampening of death pathways by schnurri-2 is essential for T-cell development. Nature 2011; 472:105-9. [PMID: 21475200 PMCID: PMC3077958 DOI: 10.1038/nature09848] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Accepted: 01/18/2011] [Indexed: 11/09/2022]
Abstract
Generation of a diverse and self-tolerant T cell repertoire requires appropriate interpretation of T cell receptor (TCR) signals by CD4+CD8+ double positive (DP) thymocytes. Thymocyte cell fate is dictated by the nature of TCR:MHC-peptide interactions, with signals of higher strength leading to death (negative selection) and signals of intermediate strength leading to differentiation (positive selection)1. Molecules that regulate T cell development by modulating TCR signal strength have been described but components that specifically define the boundaries between positive and negative selection remain unknown. Here we show that repression of TCR-induced death pathways is critical for proper interpretation of positive selecting signals in vivo, and identify Schnurri2 (Shn2) as a crucial death dampener. Our results indicate that Shn2−/− DP thymocytes inappropriately undergo negative selection in response to positive selecting signals, thus leading to disrupted T cell development. Shn2−/− DP thymocytes are more sensitive to TCR-induced death in vitro and die in response to positive selection interactions in vivo. However, Shn2-deficient thymocytes can be positively selected when TCR-induced death is genetically-ablated. Shn2 levels increase after TCR stimulation suggesting that integration of multiple TCR:MHC-peptide interactions may fine tune the death threshold. Mechanistically, Shn2 functions downstream of TCR proximal signaling compenents to dampen Bax activation and the mitochondrial death pathway. Our findings uncover a critical regulator of T cell development that controls the balance between death and differentiation.
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Affiliation(s)
- Tracy L Staton
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts 02115, USA
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22
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Thompson J, Burger ML, Whang H, Winoto A. Protein kinase C regulates mitochondrial targeting of Nur77 and its family member Nor-1 in thymocytes undergoing apoptosis. Eur J Immunol 2010; 40:2041-9. [PMID: 20411565 DOI: 10.1002/eji.200940231] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Nur77 orphan steroid receptor and its family member Nor-1 are required for apoptosis of developing T cells. In thymocytes, signals from the TCR complex induce Nur77 and Nor-1 expression followed by translocation from the nucleus to mitochondria. Nur77 and Nor-1 associate with Bcl-2 in the mitochondria, resulting in a conformation change that exposes the Bcl-2 BH3 domain, a presumed pro-apoptotic molecule of Bcl-2. As Nur77 and Nor-1 are heavily phosphorylated, we examined the requirement of Nur77 and Nor-1 phosphorylation in mitochondria translocation and Bcl-2 BH3 exposure. We found that HK434, a PKC agonist, in combination with calcium ionophore, can induce Nur77 and Nor-1 phosphorylation, translocation, Bcl-2 BH3 exposure and thymocyte apoptosis. Inhibitors of both classical and novel forms of PKC were able to block this process. In contrast, only the general but not classical PKC-specific inhibitors were able to block the same process initiated by PMA, a commonly used PKC agonist. These data demonstrate a differential activation of PKC isoforms by PMA and HK434 in thymocytes, and show the importance of PKC in mitochondria translocation of Nur77/Nor-1 and Bcl-2 conformation change during TCR-induced thymocyte apoptosis.
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Affiliation(s)
- Jennifer Thompson
- Cancer Research Laboratory and Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California, Berkeley, CA, USA
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23
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24
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Harr MW, Distelhorst CW. Apoptosis and autophagy: decoding calcium signals that mediate life or death. Cold Spring Harb Perspect Biol 2010; 2:a005579. [PMID: 20826549 DOI: 10.1101/cshperspect.a005579] [Citation(s) in RCA: 147] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Calcium is a versatile and dynamic 2nd messenger that is essential for the survival of all higher organisms. In cells that undergo activation or excitation, calcium is released from the endoplasmic/sarcoplasmic reticulum to activate calcium-dependent kinases and phosphatases, thereby regulating numerous cellular processes; for example, apoptosis and autophagy. In the case of apoptosis, endogenous ligands or pharmacological agents induce prolonged cytosolic calcium elevation, which in turn leads to cell death. In contrast, there is now evidence that calcium regulates autophagy by several mechanisms, and these may be important for maintaining cell survival. Here we summarize what is known about how calcium regulates these life and death decisions. We pay particular attention to pathways that have been described in lymphocytes and cardiomyocytes, as these systems provide optimal models for understanding calcium signaling in the context of normal cell physiology.
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Affiliation(s)
- Michael W Harr
- Division of Hematology and Oncology, Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
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25
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Edgar CE, Lindquist LD, McKean DL, Strasser A, Bram RJ. CAML regulates Bim-dependent thymocyte death. Cell Death Differ 2010; 17:1566-76. [PMID: 20300112 PMCID: PMC2890044 DOI: 10.1038/cdd.2010.30] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Appropriate control of apoptosis during T lymphocyte differentiation is critical for destruction of T cells bearing potentially autoreactive or useless immuno-receptors and for survival of those T cells bearing antigen receptors that may recognize foreign proteins. Despite the well-established importance of thymocyte survival, the exact signals regulating thymocyte apoptosis have not been fully elucidated. Here, we show that thymocytes lacking the endoplasmic reticulum protein calcium-modulating cyclophilin ligand (CAML) failed to undergo normal T-cell development and exhibited dramatically increased rates of apoptosis. In vitro, CAML-deficient thymocytes accumulated high levels of reactive oxygen species (ROS) and underwent abnormally accelerated death in response to several cytotoxic stimuli, including treatment with etoposide, cytokine deprivation, or Fas ligation. Although neither p53 deletion nor loss of Fas rescued the survival and continued development of CAML-deficient thymocytes, removal of the pro-apoptotic BH3-only Bcl-2 family member Bim significantly restored their survival. This work reveals CAML to be a critically important regulator of ROS- and Bim-dependent thymocyte death.
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Affiliation(s)
- C E Edgar
- Department of Immunology, Mayo Clinic College of Medicine, Rochester, MN, USA
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26
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Endoplasmic reticulum stress and BCL-2 family members. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 687:65-77. [PMID: 20919638 DOI: 10.1007/978-1-4419-6706-0_4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In the eukaryotic cell, the endoplasmic reticulum (ER) plays an important role as the site of lipid synthesis, protein folding and protein maturation. Stringent regulation of redox and calcium homeostasis is paramount, failure of which leads accumulation of unfolded and aggregating proteins resulting in a condition known as ER stress. Eukaryotic cells deal with ER stress by eliciting the unfolded protein response (UPR). This pathway splits into two streams depending on the severity and longevity of the ER stress, where the cell must make a choice for the good of the organism between survival and programmed cell death. The BCL-2 family of proteins is central to the cell death arm of the UPR pathway. This chapter discusses the recent findings on the involvement of BCL-2 family members in the apoptotic process initiated by ER stress and a related process called autophagy. Understanding the molecular mechanisms involved in ER stress and autophagy could have a profound implications developing new therapies for many ER stress associated diseases and cancer.
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27
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Sauer K, Huang YH, Lin H, Sandberg M, Mayr GW. Phosphoinositide and inositol phosphate analysis in lymphocyte activation. CURRENT PROTOCOLS IN IMMUNOLOGY 2009; Chapter 11:11.1.1-11.1.46. [PMID: 19918943 PMCID: PMC4500525 DOI: 10.1002/0471142735.im1101s87] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Lymphocyte antigen receptor engagement profoundly changes the cellular content of phosphoinositide lipids and soluble inositol phosphates. Among these, the phosphoinositides phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 3,4,5-trisphosphate (PIP3) play key signaling roles by acting as pleckstrin homology (PH) domain ligands that recruit signaling proteins to the plasma membrane. Moreover, PIP2 acts as a precursor for the second messenger molecules diacylglycerol and soluble inositol 1,4,5-trisphosphate (IP3), essential mediators of PKC, Ras/Erk, and Ca2+ signaling in lymphocytes. IP3 phosphorylation by IP3 3-kinases generates inositol 1,3,4,5-tetrakisphosphate (IP4), an essential soluble regulator of PH domain binding to PIP3 in developing T cells. Besides PIP2, PIP3, IP3, and IP4, lymphocytes produce multiple other phosphoinositides and soluble inositol phosphates that could have important physiological functions. To aid their analysis, detailed protocols that allow one to simultaneously measure the levels of multiple different phosphoinositide or inositol phosphate isomers in lymphocytes are provided here. They are based on thin layer, conventional and high-performance liquid chromatographic separation methods followed by radiolabeling or non-radioactive metal-dye detection. Finally, less broadly applicable non-chromatographic methods for detection of specific phosphoinositide or inositol phosphate isomers are discussed. Support protocols describe how to obtain pure unstimulated CD4+CD8+ thymocyte populations for analyses of inositol phosphate turnover during positive and negative selection, key steps in T cell development.
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Affiliation(s)
- Karsten Sauer
- The Scripps Research Institute, La Jolla, California
| | | | - Hongying Lin
- University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Mark Sandberg
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California
| | - Georg W Mayr
- University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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28
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Ren D, Kim H, Tu HC, Westergard TD, Fisher JK, Rubens JA, Korsmeyer SJ, Hsieh JJD, Cheng EHY. The VDAC2-BAK rheostat controls thymocyte survival. Sci Signal 2009; 2:ra48. [PMID: 19706873 DOI: 10.1126/scisignal.2000274] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The proapoptotic proteins BAX and BAK constitute the mitochondrial apoptotic gateway that executes cellular demise after integrating death signals. The lethal BAK is kept in check by voltage-dependent anion channel 2 (VDAC2), a mammalian-restricted VDAC isoform. Here, we provide evidence showing a critical role for the VADC2-BAK complex in determining thymocyte survival in vivo. Genetic depletion of Vdac2 in the thymus resulted in excessive cell death and hypersensitivity to diverse death stimuli including engagement of the T cell receptor. These phenotypes were completely rescued by the concurrent deletion of Bak but not that of Bax. Thus, the VDAC2-BAK axis provides a mechanism that governs the homeostasis of thymocytes. Our study reveals a sophisticated built-in rheostat that likely fine-tunes immune competence to balance autoimmunity and immunodeficiency.
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Affiliation(s)
- Decheng Ren
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
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Gatzka M, Newton RH, Walsh CM. Altered thymic selection and increased autoimmunity caused by ectopic expression of DRAK2 during T cell development. THE JOURNAL OF IMMUNOLOGY 2009; 183:285-97. [PMID: 19542440 DOI: 10.4049/jimmunol.0803530] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Negative regulation of TCR signaling is an important mechanism enforcing immunological self-tolerance to prevent inappropriate activation of T cells and thus the development of autoimmune diseases. The lymphoid-restricted serine/threonine kinase death-associated protein-related apoptotic kinase-2 (DRAK2) raises the TCR activation threshold by targeting TCR-induced calcium mobilization in thymocytes and peripheral T cells and regulates positive thymic selection and peripheral T cell activation. Despite a hypersensitivity of peripheral drak2-deficient T cells, drak2-deficient mice are enigmatically resistant to induced autoimmunity in the model experimental autoimmune encephalomyelitis. To further evaluate the differential role of DRAK2 in central vs peripheral tolerance and to assess its impact on the development of autoimmune diseases, we have generated a transgenic (Tg) mouse strain ectopically expressing DRAK2 via the lck proximal promoter (1017-DRAK2 Tg mice). This transgene led to highest expression levels in double-positive thymocytes that are normally devoid of DRAK2. 1017-DRAK2 Tg mice displayed a reduction of single-positive CD4(+) and CD8(+) thymocytes in context with diminished negative selection in male HY TCR x 1017-DRAK2 Tg mice as well as peripheral T cell hypersensitivity, enhanced susceptibility to experimental autoimmune encephalomyelitis, and spontaneous autoimmunity. These findings suggest that alteration in thymocyte signaling thresholds impacts the sensitivity of peripheral T cell pools.
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Affiliation(s)
- Martina Gatzka
- Department of Molecular Biology and Biochemistry/Institute for Immunology, University of California, Irvine, 92697, USA
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The BH4 domain of Bcl-2 inhibits ER calcium release and apoptosis by binding the regulatory and coupling domain of the IP3 receptor. Proc Natl Acad Sci U S A 2009; 106:14397-402. [PMID: 19706527 DOI: 10.1073/pnas.0907555106] [Citation(s) in RCA: 232] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Although the presence of a BH4 domain distinguishes the antiapoptotic protein Bcl-2 from its proapoptotic relatives, little is known about its function. BH4 deletion converts Bcl-2 into a proapoptotic protein, whereas a TAT-BH4 fusion peptide inhibits apoptosis and improves survival in models of disease due to accelerated apoptosis. Thus, the BH4 domain has antiapoptotic activity independent of full-length Bcl-2. Here we report that the BH4 domain mediates interaction of Bcl-2 with the inositol 1,4,5-trisphosphate (IP3) receptor, an IP3-gated Ca(2+) channel on the endoplasmic reticulum (ER). BH4 peptide binds to the regulatory and coupling domain of the IP3 receptor and inhibits IP3-dependent channel opening, Ca(2+) release from the ER, and Ca(2+)-mediated apoptosis. A peptide inhibitor of Bcl-2-IP3 receptor interaction prevents these BH4-mediated effects. By inhibiting proapoptotic Ca(2+) signals at their point of origin, the Bcl-2 BH4 domain has the facility to block diverse pathways through which Ca(2+) induces apoptosis.
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31
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Abstract
The healthy immune system makes use of a variety of surveillance mechanisms at different stages of lymphoid development to prevent the occurrence and expansion of potentially harmful autoreactive T cell clones. Disruption of these mechanisms may lead to inappropriate activation of T cells and the development of autoimmune and lymphoproliferative diseases [such as multiple sclerosis, rheumatoid arthritis, lupus erythematosus, diabetes and autoimmune lymphoproliferative syndrome (ALPS)]. Clonal deletion of T cells with high affinities for self-peptide-MHC via programmed cell death (apoptosis) is an essential mechanism leading to self-tolerance. Referred to as negative selection, central tolerance in the thymus serves as the first checkpoint for the developing T cell repertoire and involves the apoptotic elimination of potentially autoreactive T cells clones bearing high affinity T cell receptors (TCR) that recognize autoantigens presented by thymic epithelial cells. Autoreactive T cells that escape negative selection are held in check in the periphery by either functional inactivation ("anergy") or extrathymic clonal deletion, both of which are dependent on the strength and frequency of the TCR signal and the costimulatory context, or by regulatory T cells. This review provides an overview of the different molecular executioners of cell death programs that are vital to intrathymic or extrathymic clonal deletion of T cells. Further, the potential involvement of various apoptotic signaling paradigms are discussed with respect to the genesis and pathophysiology of autoimmune disease.
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Affiliation(s)
- Martina Gatzka
- Department of Molecular Biology and Biochemistry, Center for Immunology, University of California, Irvine, CA, USA.
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Beyersdorf N, Braun A, Vögtle T, Varga-Szabo D, Galdos RR, Kissler S, Kerkau T, Nieswandt B. STIM1-independent T cell development and effector function in vivo. THE JOURNAL OF IMMUNOLOGY 2009; 182:3390-7. [PMID: 19265116 DOI: 10.4049/jimmunol.0802888] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Store-operated Ca(2+) entry (SOCE) is believed to be of pivotal importance in T cell physiology. To test this hypothesis, we generated mice constitutively lacking the SOCE-regulating Ca(2+) sensor stromal interaction molecule 1 (STIM1). In vitro analyses showed that SOCE and Ag receptor complex-triggered Ca(2+) flux into STIM1-deficient T cells is virtually abolished. In vivo, STIM1-deficient mice developed a lymphoproliferative disease despite normal thymic T cell maturation and normal frequencies of CD4(+)Foxp3(+) regulatory T cells. Unexpectedly, STIM1-deficient bone marrow chimeric mice mounted humoral immune responses after vaccination and STIM1-deficient T cells were capable of inducing acute graft-versus-host disease following adoptive transfer into allogeneic hosts. These results demonstrate that STIM1-dependent SOCE is crucial for homeostatic T cell proliferation, but of much lesser importance for thymic T cell differentiation or T cell effector functions.
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Affiliation(s)
- Niklas Beyersdorf
- Institute for Virology and Immunobiology, Deutsche Forschungsgemeinschaft Research Center for Experimental Biomedicine, University of Würzburg, Germany
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Stang SL, Lopez-Campistrous A, Song X, Dower NA, Blumberg PM, Wender PA, Stone JC. A proapoptotic signaling pathway involving RasGRP, Erk, and Bim in B cells. Exp Hematol 2009; 37:122-134. [PMID: 19100522 DOI: 10.1016/j.exphem.2008.09.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Revised: 09/16/2008] [Accepted: 09/17/2008] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Bryostatin-1 and related diacylglycerol (DAG) analogues activate RasGRPs in lymphocytes, thereby activating Ras and mimicking some aspects of immune receptor signaling. To define the role of RasGRPs in lymphocyte apoptosis and to identify potential therapeutic uses for DAG analogues in lymphocyte disorders, we characterized the response of lymphoma-derived cell lines to DAG analogues. MATERIALS AND METHODS Human lymphoma-derived B cell lines and mouse primary B cells were treated with bryostatin-1 or its synthetic analogue "pico." Ras signaling partners and Bcl-2 family members were studied with biochemical assays. Cellular responses were monitored using growth and apoptosis assays. RESULTS Stimulation of B cells with DAG analogues results in activation of protein kinase C/RasGRP-Ras-Raf-Mek-Erk signaling and phosphorylation of the proapoptotic BH3-only protein Bim. In vitro, Bim is phosphorylated by Erk on sites previously associated with increased apoptotic activity. In Toledo B cells derived from a non-Hodgkin's lymphoma (B-NHL), DAG analogue stimulation leads to extensive apoptosis. Apoptosis can be suppressed by either downregulation of Bim or overexpression of Bcl-2. It is associated with the formation of Bak-Bax complexes and increased mitochondrial membrane permeability. Toledo B-NHL cell apoptosis shows a striking dependence on sustained signaling. CONCLUSION In B cells, Erk activation leads directly to phosphorylation of Bim on sites associated with activation of Bim. In Toledo B-NHL cells, the dependence of apoptosis on sustained signaling suggests that Bcl-2 family members could interpret signal duration, an important determinant of B cell receptor-mediated negative selection. Certain cases of B-NHL might respond to DAG analogue treatment by the mechanism outlined here.
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Affiliation(s)
- Stacey L Stang
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
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Koelsch U, Schraven B, Simeoni L. SIT and TRIM determine T cell fate in the thymus. THE JOURNAL OF IMMUNOLOGY 2009; 181:5930-9. [PMID: 18941181 DOI: 10.4049/jimmunol.181.9.5930] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Thymic selection is a tightly regulated developmental process essential for establishing central tolerance. The intensity of TCR-mediated signaling is a key factor for determining cell fate in the thymus. It is widely accepted that low-intensity signals result in positive selection, whereas high-intensity signals induce negative selection. Transmembrane adaptor proteins have been demonstrated to be important regulators of T cell activation. However, little is known about their role during T cell development. Herein, we show that SIT (SHP2 Src homology domain containing tyrosine phosphatase 2-interacting transmembrane adaptor protein) and TRIM (TCR-interacting molecule), two structurally related transmembrane adaptors, cooperatively regulate TCR signaling potential, thereby influencing the outcome of thymic selection. Indeed, loss of both SIT and TRIM resulted in the up-regulation of CD5, CD69, and TCRbeta, strong MAPK activation, and, consequently, enhanced positive selection. Moreover, by crossing SIT/TRIM double-deficient mice onto transgenic mice bearing TCRs with different avidity/affinity, we found profound alterations in T cell development. Indeed, in female HY TCR transgenic mice, positive selection was completely converted into negative selection resulting in small thymi devoided of double-positive thymocytes. More strikingly, in a nonselecting background, SIT/TRIM double-deficient single-positive T cells developed, were functional, and populated the periphery. In summary, we demonstrated that SIT and TRIM regulate cell fate of developing thymocytes, thus identifying them as essential regulators of central tolerance.
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Affiliation(s)
- Uwe Koelsch
- Institute of Molecular and Clinical Immunology, Otto-von-Guericke University, Magdeburg, Germany
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35
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Abstract
The elimination of unwanted cells by programmed cell death is a common feature of animal development. Genetic studies in the nematode Caenorhabditis elegans, the fruit fly Drosophila melanogaster, and the mouse have not only revealed the molecular machineries that cause the programmed demise of specific cells, but have also allowed us to get a glimpse of the types of pathways that regulate these machineries during development. Rather than serving as a broad overview of programmed cell death during development, this review focuses on recent advances in our understanding of the regulation of specific programmed cell death events during nematode, fly, and mouse development. Recent studies have revealed that many of the regulatory pathways involved play additional important roles in development, which confirms that the programmed cell death fate is an integral aspect of animal development.
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Affiliation(s)
- Barbara Conradt
- Department of Genetics, Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
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36
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Richards S, Watanabe C, Santos L, Craxton A, Clark EA. Regulation of B-cell entry into the cell cycle. Immunol Rev 2008; 224:183-200. [PMID: 18759927 DOI: 10.1111/j.1600-065x.2008.00652.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
B cells are induced to enter the cell cycle by stimuli including ligation of the B-cell receptor (BCR) complex and Toll-like receptor (TLR) agonists. This review discusses the contribution of several molecules, which act at distinct steps in B-cell activation. The adapter molecule Bam32 (B-lymphocyte adapter of 32 kDa) helps promote BCR-induced cell cycle entry, while the secondary messenger superoxide has the opposite effect. Bam32 and superoxide may fine tune BCR-induced activation by competing for the same limited resources, namely Rac1 and the plasma membrane phospholipid PI(3,4)P(2). The co-receptor CD22 can inhibit BCR-induced proliferation by binding to novel CD22 ligands. Finally, regulators of B-cell survival and death also play roles in B-cell transit through the cell cycle. Caspase 6 negatively regulates CD40- and TLR-dependent G(1) entry, while acting later in the cell cycle to promote S-phase entry. Caspase 6 deficiency predisposes B cells to differentiate rather than proliferate after stimulation. Bim, a pro-apoptotic Bcl-2 family member, exerts a positive regulatory effect on cell cycle entry, which is opposed by Bcl-2. New insights into what regulates B-cell transit through the cell cycle may lead to thoughtful design of highly selective drugs that target pathogenic B cells.
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Affiliation(s)
- Sabrina Richards
- Department of Immunology and Microbiology, University of Washington, Seattle, WA 98195, USA
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37
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McCaughtry TM, Hogquist KA. Central tolerance: what have we learned from mice? Semin Immunopathol 2008; 30:399-409. [PMID: 19015857 DOI: 10.1007/s00281-008-0137-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Accepted: 10/01/2008] [Indexed: 10/21/2022]
Abstract
Producing a healthy immune system capable of defending against pathogens, while avoiding autoimmunity, is dependent on thymic selection. Positive selection yields functional T cells that have the potential to recognize both self and foreign antigens. Therefore, negative selection exists to manage potentially self-reactive cells. Negative selection results from the induction of anergy, receptor editing, clonal diversion (agonist selection), and/or clonal deletion (apoptosis) in self-reactive clones. Clonal deletion has been inherently difficult to study because the cells of interest are undergoing apoptosis and being eliminated quickly. Furthermore, analysis of clonal deletion in humans has proved even more difficult due to availability of samples and lack of reagents. Mouse models have thus been instrumental in achieving our current understanding of central tolerance, and the evolution of elegant model systems has led to an explosion of new data to be assimilated. This review will focus on recent advances in the field of clonal deletion with respect to three aspects: the development of physiological model systems, signaling pathways that lead to apoptosis, and antigen presenting cell types involved in the induction of clonal deletion.
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Affiliation(s)
- Tom M McCaughtry
- Center for Immunology, Laboratory Medicine & Pathology, University of Minnesota, Mayo Mail Code 334, 420 Delaware Street SE, Minneapolis, MN, 55454, USA
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38
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Rong Y, Distelhorst CW. Bcl-2 protein family members: versatile regulators of calcium signaling in cell survival and apoptosis. Annu Rev Physiol 2008; 70:73-91. [PMID: 17680735 DOI: 10.1146/annurev.physiol.70.021507.105852] [Citation(s) in RCA: 276] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Bcl-2 family members are important regulators of cell survival and cell death. Researchers have focused mainly on mitochondria, where both proapoptotic and antiapoptotic family members function to regulate the release of cytochrome c and other mediators of apoptosis. However, as reviewed here, Bcl-2 family members also operate on another front, the endoplasmic reticulum (ER), to both positively and negatively regulate the release of Ca2+. There is abundant evidence that Ca2+ signals trigger apoptosis in response to a wide variety of agents and conditions. Conversely, Ca2+ signals can also mediate cell survival. Recent findings indicate that Bcl-2 interacts with inositol 1,4,5-trisphosphate (IP3) receptor Ca2+ channels on the ER, regulating their opening in response to IP3- and thus inhibiting IP3-mediated Ca2+ signals that induce apoptosis while enhancing Ca2+ signals that support cell survival.
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Affiliation(s)
- Yiping Rong
- Department of Medicine and Pharmacology, Comprehensive Cancer Center and University Hospitals of Cleveland, Case Western Reserve University, Cleveland, OH 44106, USA.
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39
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Jordan MS, Smith JE, Burns JC, Austin JET, Nichols KE, Aschenbrenner AC, Koretzky GA. Complementation in trans of altered thymocyte development in mice expressing mutant forms of the adaptor molecule SLP76. Immunity 2008; 28:359-69. [PMID: 18342008 DOI: 10.1016/j.immuni.2008.01.010] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2007] [Revised: 12/28/2007] [Accepted: 01/25/2008] [Indexed: 11/16/2022]
Abstract
The adaptor protein SLP76 directs signaling downstream of the T cell receptor (TCR) and is essential for thymocyte development. SLP76 contains three N-terminal tyrosines that are critical for its function. To define the role of these residues in thymocyte development, we generated two lines of "knock-in" mice, one expressing a mutation in tyrosine 145 (Y145F) and a second harboring two point mutations at tyrosines 112 and 128 (Y112-128F). We show here that although thymocyte development requires both Y145- and Y112-128-generated signals, selection was more dependent upon Y145. Although several proximal TCR signaling events were defective in both mutant mice, phosphorylation of the guanine nucleotide exchange factor, Vav1, and activation of Itk-dependent pathways were differentially affected by mutations at Y112-128 and Y145, respectively. Analysis of mice expressing one Y145F and one Y112-128F allele revealed that these mutants could complement one another in trans, demonstrating cooperativity between two or more SLP76 molecules. Thus, the N-terminal tyrosines of SLP76 are required for thymocyte selection but can function on separate molecules to support TCR signaling.
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Affiliation(s)
- Martha S Jordan
- Cancer Biology, Abramson Family Cancer Research Institute, 427 BRBII/III, University of Pennsylvania School of Medicine, Philadelphia, PA, 19104, USA
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40
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Lee EF, Czabotar PE, van Delft MF, Michalak EM, Boyle MJ, Willis SN, Puthalakath H, Bouillet P, Colman PM, Huang DCS, Fairlie WD. A novel BH3 ligand that selectively targets Mcl-1 reveals that apoptosis can proceed without Mcl-1 degradation. ACTA ACUST UNITED AC 2008; 180:341-55. [PMID: 18209102 PMCID: PMC2213596 DOI: 10.1083/jcb.200708096] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Like Bcl-2, Mcl-1 is an important survival factor for many cancers, its expression contributing to chemoresistance and disease relapse. However, unlike other prosurvival Bcl-2–like proteins, Mcl-1 stability is acutely regulated. For example, the Bcl-2 homology 3 (BH3)–only protein Noxa, which preferentially binds to Mcl-1, also targets it for proteasomal degradation. In this paper, we describe the discovery and characterization of a novel BH3-like ligand derived from Bim, BimS2A, which is highly selective for Mcl-1. Unlike Noxa, BimS2A is unable to trigger Mcl-1 degradation, yet, like Noxa, BimS2A promotes cell killing only when Bcl-xL is absent or neutralized. Furthermore, killing by endogenous Bim is not associated with Mcl-1 degradation. Thus, functional inactivation of Mcl-1 does not always require its elimination. Rather, it can be efficiently antagonized by a BH3-like ligand tightly engaging its binding groove, which is confirmed here with a structural study. Our data have important implications for the discovery of compounds that might kill cells whose survival depends on Mcl-1.
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Affiliation(s)
- Erinna F Lee
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia
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41
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Abstract
CD8(+) cytotoxic and CD4(+) helper/inducer T cells develop from common thymocyte precursors that express both CD4 and CD8 molecules. Upon T cell receptor signaling, these cells initiate a differentiation program that includes complex changes in CD4 and CD8 expression, allowing identification of transitional intermediates in this developmental pathway. Little is known about regulation of these early transitions or their specific importance to CD4 and CD8 T cell development. Here, we show a severe block at the CD4(lo)CD8(lo) transitional stage of positive selection caused by loss of the nuclear HMG box protein TOX. As a result, CD4 lineage T cells, including regulatory T and CD1d-dependent natural killer T cells, fail to develop. In contrast, functional CD8(+) T cells develop in TOX-deficient mice. Our data suggest that TOX-dependent transition to the CD4(+)CD8(lo) stage is required for continued development of class II major histocompatibility complex-specific T cells, regardless of ultimate lineage fate.
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Affiliation(s)
- Parinaz Aliahmad
- Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA
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42
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Gallo EM, Winslow MM, Canté-Barrett K, Radermacher AN, Ho L, McGinnis L, Iritani B, Neilson JR, Crabtree GR. Calcineurin sets the bandwidth for discrimination of signals during thymocyte development. Nature 2008; 450:731-5. [PMID: 18046413 DOI: 10.1038/nature06305] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Accepted: 09/26/2007] [Indexed: 01/15/2023]
Abstract
At critical times in development, cells are able to convert graded signals into discrete developmental outcomes; however, the mechanisms involved are poorly understood. During thymocyte development, cell fate is determined by signals originating from the alphabeta T-cell receptor. Low-affinity/avidity interactions between the T-cell receptor and peptide-MHC complexes direct differentiation to the single-positive stage (positive selection), whereas high-affinity/avidity interactions induce death by apoptosis (negative selection). Here we show that mice deficient in both calcineurin and nuclear factor of activated T cells (NFAT)c2/c3 lack a population of preselection thymocytes with enhanced ability to activate the mitogen-activated protein kinase (Raf-MEK-ERK) pathway, and fail to undergo positive selection. This defect can be partially rescued with constitutively active Raf, indicating that calcineurin controls MAPK signalling. Analysis of mice deficient in both Bim (which is required for negative selection) and calcineurin revealed that calcineurin-induced ERK (extracellular signal-regulated kinase) sensitization is required for differentiation in response to 'weak' positive selecting signals but not in response to 'strong' negative selecting signals (which normally induce apoptosis). These results indicate that early calcineurin/NFAT signalling produces a developmental period of ERK hypersensitivity, allowing very weak signals to induce positive selection. This mechanism might be generally useful in the discrimination of graded signals that induce different cell fates.
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Affiliation(s)
- Elena M Gallo
- Howard Hughes Medical Institute and the Department of Pathology, Stanford University, Stanford, California 94305, USA
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43
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Craxton A, Draves KE, Clark EA. Bim regulates BCR-induced entry of B cells into the cell cycle. Eur J Immunol 2007; 37:2715-22. [PMID: 17705137 DOI: 10.1002/eji.200737327] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
BH3-only Bcl-2 homologs are key regulators of the intrinsic apoptotic pathway. In particular, Bim, is critical for mediating apoptosis of hematopoietic cells including B cells. While studies using Bcl-2 Tg mice have defined an important role for Bcl-2 in cell cycle control, the role of BH3-only proteins is less clear. Using Bim KO mice, we show that Bim is required for B cells to enter the cell cycle normally. Bim KO B cells had reduced cell division compared to WT B cells in response to BCR, TLR3 or TLR4 signaling, whereas Bim deficiency did not affect TLR9-induced B cell division. Cell cycle progression in BCR- and LPS-stimulated Bim KO B cells was blocked at the G0-G1 stage. BCR-induced p130 degradation and pRb hyperphosphorylation on Ser807/811, which are critical for G1 entry, were reduced in Bim KO compared to WT B cells. Likewise, BCR-induced p27(Kip1) degradation was decreased in Bim KO compared to WT B cells. These defects in BCR-induced cell cycle entry correlated with a proximal defect in BCR-mediated intracellular calcium release in Bim KO B cells. Our results suggest that the balance of pro- and anti-apoptotic Bcl-2 family proteins is critical for controlling both cell cycle progression and apoptosis in B cells.
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Affiliation(s)
- Andrew Craxton
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
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44
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What do we know about the mechanisms of elimination of autoreactive T and B cells and what challenges remain. Immunol Cell Biol 2007; 86:57-66. [PMID: 18026176 DOI: 10.1038/sj.icb.7100141] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Tolerance to self-antigens within the adaptive immune system is safeguarded, at least in part, through deletion of autoreactive T and B lymphocytes. This deletion can occur during the development of these cells in primary lymphoid organs, the thymus or bone marrow, respectively, or at the mature stage in peripheral lymphoid tissues. Deletion of autoreactive lymphocytes is achieved to a large extent through apoptotic cell death. This review describes current understanding of the mechanisms that mediate apoptosis of autoreactive lymphocytes during their development in primary lymphoid organs and during their activation in the periphery. In particular, we discuss the roles of the proapoptotic Bcl-2 family member Bim and the small family of Nur77-related transcriptional regulators in lymphocyte negative selection. Finally, we speculate on the processes that may lead to the activation of Bim when antigen receptors are activated on autoreactive T or B cells.
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45
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Baldwin TA, Hogquist KA. Transcriptional analysis of clonal deletion in vivo. THE JOURNAL OF IMMUNOLOGY 2007; 179:837-44. [PMID: 17617574 DOI: 10.4049/jimmunol.179.2.837] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Engagement of the TCR on CD4(+)CD8(+) thymocytes initiates either a program of survival and differentiation (positive selection) or death (clonal deletion), which is dictated in large part by the affinity of the TCR for self-peptide-MHC complexes. Although much is known about the factors involved in positive selection, little is understood about the molecular mechanism leading to clonal deletion. To gain further insight into this process, we used a highly physiological TCR transgenic mouse model to compare gene expression changes under conditions of nonselection, positive selection, and negative selection. We identified 388 genes that were differentially regulated in negative selection compared with either nonselection or positive selection. These regulated genes fall into many functional categories including cell surface and intracellular signal transduction, survival and apoptosis, transcription and translation, and adhesion and migration. Additionally, we have compared our transcriptional profile to profiles of negative selection in other model systems in an effort to identify those genes with a higher probability of being functionally relevant. These included three up-regulated genes, bim, nur77, and ian1, and one down-regulated gene, lip1. Collectively, these data provide a framework for understanding the molecular basis of clonal deletion.
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Affiliation(s)
- Troy A Baldwin
- Center for Immunology, Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, USA
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46
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Brenner D, Golks A, Becker M, Müller W, Frey CR, Novak R, Melamed D, Kiefer F, Krammer PH, Arnold R. Caspase-cleaved HPK1 induces CD95L-independent activation-induced cell death in T and B lymphocytes. Blood 2007; 110:3968-77. [PMID: 17712048 DOI: 10.1182/blood-2007-01-071167] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Life and death of peripheral lymphocytes is strictly controlled to maintain physiologic levels of T and B cells. Activation-induced cell death (AICD) is one mechanism to delete superfluous lymphocytes by restimulation of their immunoreceptors and it depends partially on the CD95/CD95L system. Recently, we have shown that hematopoietic progenitor kinase 1 (HPK1) determines T-cell fate. While full-length HPK1 is essential for NF-kappaB activation in T cells, the C-terminal fragment of HPK1, HPK1-C, suppresses NF-kappaB and sensitizes toward AICD by a yet undefined cell death pathway. Here we show that upon IL-2-driven expansion of primary T cells, HPK1 is converted to HPK1-C by a caspase-3 activity below the threshold of apoptosis induction. HPK1-C selectively blocks induction of NF-kappaB-dependent antiapoptotic Bcl-2 family members but not of the proapoptotic Bcl-2 family member Bim. Interestingly, T and B lymphocytes from HPK1-C transgenic mice undergo AICD independently of the CD95/CD95L system but involving caspase-9. Knock down of HPK1/HPK1-C or Bim by small interfering RNA shows that CD95L-dependent and HPK1/HPK1-C-dependent cell death pathways complement each other in AICD of primary T cells. Our results define HPK1-C as a suppressor of antiapoptotic Bcl-2 proteins and provide a molecular basis for our understanding of CD95L-independent AICD of lymphocytes.
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Affiliation(s)
- Dirk Brenner
- Tumor Immunology Program, German Cancer Research Center (DKFZ), Heidelberg, Germany
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47
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Abstract
During the course of an immune response, antigen-reactive T cells clonally expand and then are removed by apoptosis to maintain immune homeostasis. Life and death of T cells is determined by multiple factors, such as T-cell receptor triggering, co-stimulation or cytokine signalling, and by molecules, such as caspase-8 (FLICE)-like inhibitory protein (FLIP) and haematopoietic progenitor kinase 1 (HPK1), which regulate the nuclear factor-kappaB (NF-kappaB) pathway. Here, we discuss the concepts of activation-induced cell death (AICD) and activated cell-autonomous death (ACAD) in the regulation of life and death in T cells.
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Affiliation(s)
- Peter H Krammer
- Tumour Immunology Program, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
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48
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Bauer A, Kirschnek S, Häcker G. Inhibition of apoptosis can be accompanied by increased Bim levels in T lymphocytes and neutrophil granulocytes. Cell Death Differ 2007; 14:1714-6. [PMID: 17585338 DOI: 10.1038/sj.cdd.4402185] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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49
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Canté-Barrett K, Winslow MM, Crabtree GR. Selective Role of NFATc3 in Positive Selection of Thymocytes. THE JOURNAL OF IMMUNOLOGY 2007; 179:103-10. [PMID: 17579027 DOI: 10.4049/jimmunol.179.1.103] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The four Ca(2+)-dependent NFATc proteins are both signal transducers and transcription factors that reside in the cytoplasm until dephosphorylation by calcineurin. Dephosphorylation exposes nuclear import sequences and sends NFATc proteins into the nucleus where they assemble with nuclear partners into NFAT transcription complexes. Recent genetic studies have indicated that calcineurin-NFAT signaling is a major determinant of vertebrate morphogenesis and development. Mice lacking calcineurin activity show a complete block in positive selection of CD4 and CD8 double-positive thymocytes, yet the role of the NFATc proteins in T cell development has been controversial. In this study, we address the requirement for NFATc3 in T cell development by generating NFATc3 conditional knockout mice. We show that specific deletion of NFATc3 in thymocytes causes a partial block at the double-negative stage 3 and also a partial block in positive selection. Furthermore, the defect does not become more pronounced when NFATc2 is also absent, consistent with the fact that NFATc2-null mice do not have a T cell developmental defect. Expression of a nuclear (and constitutively active) NFATc1 even at subphysiological levels can rescue the transition of double-negative to double-positive thymocytes in RAG-null mice, but is unable to rescue development of CD4 and CD8 single-positive cells. In addition to NFATc3, this suggests a role for NFATc1 in T cell development. Our studies indicate that the signals that direct positive selection likely use both NFATc1 and NFATc3 downstream of calcineurin.
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Affiliation(s)
- Kirsten Canté-Barrett
- Departments of Developmental Biology and Pathology, Howard Hughes Medical Institute, Stanford University, 279 Campus Drive, Stanford, CA 94305, USA
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Jost PJ, Weiss S, Ferch U, Gross O, Mak TW, Peschel C, Ruland J. Bcl10/Malt1 signaling is essential for TCR-induced NF-kappaB activation in thymocytes but dispensable for positive or negative selection. THE JOURNAL OF IMMUNOLOGY 2007; 178:953-60. [PMID: 17202357 DOI: 10.4049/jimmunol.178.2.953] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
During T cell development in the thymus, high-affinity/avidity TCR engagement induces negative selection by apoptosis, while lower affinity/avidity TCR interactions lead to positive selection and survival of thymocytes. Yet, the mechanisms that discriminate between positive and negative selection are not fully understood. One major regulator of survival and apoptosis in lymphoid cells is the transcription factor NF-kappaB. Several reports have indicated key roles for NF-kappaB in positive and negative selection. In peripheral T cells, TCR ligation activates NF-kappaB through a selective pathway that involves protein kinase Ctheta, Bcl10, and Malt1. While protein kinase Ctheta is dispensable for thymic TCR signaling, the molecular roles of Bcl10 and Malt1 in thymocytes have not been investigated. In the present study, we show that both Bcl10 and Malt1 are essential for TCR signaling in thymocytes as a genetic disruption of either molecule blocks TCR-induced NF-kappaB activation in these cells. To investigate the function of this pathway in thymic selection, we introduced the Bcl10 or Malt1 mutations into three well-established TCR transgenic mouse models. Surprisingly, using several in vivo or in vitro assays, we were unable to demonstrate a role for TCR-induced NF-kappaB activation in either positive or negative selection. Thus, while TCR signaling to NF-kappaB controls the activation of mature T cells, we suggest that this pathway is not involved in the positive or negative selection of thymocytes.
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Affiliation(s)
- Philipp J Jost
- Third Medical Department, Technical University of Munich, Klinikum rechts der Isar, Ismaninger Strasse 22, 81675 Munich, Germany
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