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Zhou L, Yang J, Zhang K, Wang T, Jiang S, Zhang X. Rising Star in Immunotherapy: Development and Therapeutic Potential of Small-Molecule Inhibitors Targeting Casitas B Cell Lymphoma-b (Cbl-b). J Med Chem 2024; 67:816-837. [PMID: 38181380 DOI: 10.1021/acs.jmedchem.3c01361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2024]
Abstract
Casitas B cell lymphoma-b (Cbl-b) is a vital negative regulator of TCR and BCR signaling pathways, playing a significant role in setting an appropriate threshold for the activation of T cells and controlling the tolerance of peripheral T cells via a variety of mechanisms. Overexpression of Cbl-b leads to immune hyporesponsiveness of T cells. Conversely, the deficiency of Cbl-b in T cells results in markedly increased production of IL-2, even in the lack of CD28 costimulation in vitro. And Cbl-b-/- mice spontaneously reject multifarious cancers. Therefore, Cbl-b may be associated with immune-mediated diseases, and blocking Cbl-b could be considered as a new antitumor immunotherapy strategy. In this review, the possible regulatory mechanisms and biological potential of Cbl-b for antitumor immunotherapy are summarized. Besides, the potential roles of Cbl-b in immune-mediated diseases are comprehensively discussed, with emphasis on Cbl-b immune-oncology agents in the preclinical stage and clinical trials.
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Affiliation(s)
- Lixin Zhou
- Department of Medicinal Chemistry, School of Pharmacy and School of Engineering, China Pharmaceutical University, Nanjing 210009, China
| | - Jiamei Yang
- Department of Medicinal Chemistry, School of Pharmacy and School of Engineering, China Pharmaceutical University, Nanjing 210009, China
| | - Kuojun Zhang
- Department of Medicinal Chemistry, School of Pharmacy and School of Engineering, China Pharmaceutical University, Nanjing 210009, China
| | - Tianyu Wang
- Department of Medicinal Chemistry, School of Pharmacy and School of Engineering, China Pharmaceutical University, Nanjing 210009, China
| | - Sheng Jiang
- Department of Medicinal Chemistry, School of Pharmacy and School of Engineering, China Pharmaceutical University, Nanjing 210009, China
| | - Xiangyu Zhang
- Department of Medicinal Chemistry, School of Pharmacy and School of Engineering, China Pharmaceutical University, Nanjing 210009, China
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2
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Liu X, Chipurupalli S, Jiang P, Tavasoli M, Yoo BH, McPhee M, Mazinani S, Francia G, Kerbel RS, Rosen KV. ErbB2/Her2-dependent downregulation of a cell death-promoting protein BLNK in breast cancer cells is required for 3D breast tumor growth. Cell Death Dis 2022; 13:687. [PMID: 35933456 PMCID: PMC9357009 DOI: 10.1038/s41419-022-05117-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 07/15/2022] [Accepted: 07/19/2022] [Indexed: 01/21/2023]
Abstract
A significant proportion of breast cancers are driven by ErbB2/Her2 oncoprotein that they overexpress. These malignancies are typically treated with various ErbB2-targeted drugs, but many such cancers develop resistance to these agents and become incurable. Conceivably, treatment of ErbB2-positive cancers could be facilitated by use of agents blocking oncogenic signaling mechanisms downstream of ErbB2. However, current understanding of these mechanisms is limited. The ability of solid tumor cells to resist anoikis, cell death triggered by cell detachment from the extracellular matrix (ECM), is thought to be critical for 3D tumor growth. In an effort to understand the mechanisms of ErbB2-driven breast cancer cell anoikis resistance we found that detachment of non-malignant breast epithelial cells from the ECM upregulates a cell death-promoting tumor suppressor adapter protein BLNK and that ErbB2 blocks this upregulation by reducing tumor cell levels of transcription factor IRF6. We further observed that trastuzumab, a therapeutic anti-ErbB2 antibody, upregulates BLNK in human trastuzumab-sensitive but not trastuzumab-resistant ErbB2-positive breast cancer cells. Moreover, we established that BLNK promotes anoikis by activating p38 MAP kinase and that ErbB2-dependent BLNK downregulation blocks breast cancer cell anoikis. In search for pharmacological approaches allowing to upregulate BLNK in tumor cells we found that clinically approved proteasome inhibitor bortezomib upregulates IRF6 and BLNK in human breast cancer cells and inhibits their 3D growth in a BLNK-dependent manner. In addition, we found that BLNK upregulation in human ErbB2-positive breast cancer cells blocks their ability to form tumors in mice. Furthermore, we used publicly available data on mRNA levels in multiple breast cancers to demonstrate that increased BLNK mRNA levels correlate with increased relapse-free survival in a cohort of approximately 400 patients with ErbB2-positive breast cancer. In summary, we discovered a novel mechanism of ErbB2-driven 3D breast tumor growth mediated by ErbB2-dependent BLNK downregulation.
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Affiliation(s)
- Xiaoyang Liu
- grid.55602.340000 0004 1936 8200Departments of Pediatrics & Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS Canada
| | - Sandhya Chipurupalli
- grid.55602.340000 0004 1936 8200Departments of Pediatrics & Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS Canada
| | - Peijia Jiang
- grid.55602.340000 0004 1936 8200Departments of Pediatrics & Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS Canada
| | - Mahtab Tavasoli
- grid.55602.340000 0004 1936 8200Department of Pharmacology, Department of Pediatrics, Dalhousie University, Halifax, NS Canada
| | - Byong Hoon Yoo
- grid.55602.340000 0004 1936 8200Departments of Pediatrics & Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS Canada
| | - Michael McPhee
- grid.55602.340000 0004 1936 8200Departments of Pediatrics & Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS Canada
| | - Sina Mazinani
- grid.55602.340000 0004 1936 8200Departments of Pediatrics & Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS Canada
| | - Giulio Francia
- grid.267324.60000 0001 0668 0420Border Biomedical Research Center, University of Texas at El Paso (UTEP), El Paso, TX USA
| | - Robert S. Kerbel
- grid.17063.330000 0001 2157 2938Biological Sciences Platform, Sunnybrook Research Institute, Toronto, ON Canada ,grid.17063.330000 0001 2157 2938University of Toronto Department of Medical Biophysics, Toronto, ON Canada
| | - Kirill V. Rosen
- grid.55602.340000 0004 1936 8200Departments of Pediatrics & Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS Canada
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3
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Shen Y, Ma Y, Xie J, Lin L, Shi Y, Li X, Shen P, Pan X, Ren H. A regulatory role for CD72 expression on B cells and increased soluble CD72 in primary Sjogren's syndrome. BMC Immunol 2020; 21:21. [PMID: 32306893 PMCID: PMC7168817 DOI: 10.1186/s12865-020-00351-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 04/06/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND CD72, a co-receptor of B cell receptor (BCR), has been reported to have both positive and negative effects on B cell functions in several immunological diseases. The B cell plays an important role in the pathogenesis of primary Sjogren's syndrome (pSS). However, whether CD72 is involved in the process remains unknown. This study aimed to observe the possible role of CD72 in the pathogenesis of pSS. RESULTS A total of 60 cases who fulfilled the American-European Consensus Group (AECG) criteria for the diagnosis of pSS and 61 gender and age-matched healthy controls were recruited in this study. The percentage of CD72+ B cells was 85.31 ± 8.37% in pSS patients and 76.91 ± 8.50% in healthy controls(p < 0.001). The percentage of CD72+ B cells was correlated to serum IgG levels in patients [β = 0.018(0.001-0.036), p = 0.034]. The level of serum soluble CD72 was significantly higher in pSS patients than the one in healthy controls (0.41 (0.29) vs 0.07 (0.08) ng/mL, p < 0.001). CONCLUSIONS The percentage of CD72+ B cells was upregulated in pSS patients and was correlated to the serum IgG level, which revealed the hyperactivity of B cells in this disease. The serum soluble CD72 level was also increased in pSS patients. These results indicated a potential role of CD72 in the pathogenesis of pSS.
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Affiliation(s)
- Yuqi Shen
- Department of Nephrology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Yuhua Ma
- Department of Nephrology, Traditional Chinese Medicine Hospital of KunShan, Suzhou, China
| | - Jingyuan Xie
- Department of Nephrology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Li Lin
- Department of Nephrology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Yifan Shi
- Department of Nephrology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Xiao Li
- Department of Nephrology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Pingyan Shen
- Department of Nephrology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Xiaoxia Pan
- Department of Nephrology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Hong Ren
- Department of Nephrology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China.
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4
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Hong R, Lai N, Xiong E, Ouchida R, Sun J, Zhou Y, Tang Y, Hikida M, Tsubata T, Tagawa M, Wang Y, Wang JY. Distinct roles of BCNP1 in B-cell development and activation. Int Immunol 2020; 32:17-26. [PMID: 31412363 DOI: 10.1093/intimm/dxz055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 08/11/2019] [Indexed: 11/13/2022] Open
Abstract
B-cell novel protein 1 (BCNP1) has recently been identified as a new B-cell receptor (BCR) signaling molecule but its physiological function remains unknown. Here, we demonstrate that mice deficient in BCNP1 exhibit impaired B-cell maturation and a reduction of B-1a cells. BCNP1-deficient spleen B cells show enhanced survival, proliferation and Ca2+ influx in response to BCR cross-linking as compared with wild-type spleen B cells. Consistently, mutant B cells show elevated phosphorylation of SYK, B-cell linker protein (BLNK) and PLCγ2 upon BCR cross-linking. In vivo, BCNP1-deficient mice exhibit enhanced humoral immune responses to T-independent and T-dependent antigens. Moreover, aged mutant mice contain elevated levels of serum IgM and IgG3 antibodies and exhibit polyclonal and monoclonal B-cell expansion in lymphoid organs. These results reveal distinct roles for BCNP1 in B-cell development, activation and homeostasis.
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Affiliation(s)
- Rongjian Hong
- Department of Immunology, School of Basic Medical Sciences.,Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science, Collaborative Innovation Center for Brain Science, Fudan University, Shanghai 200032, China
| | - Nannan Lai
- Department of Immunology, School of Basic Medical Sciences
| | - Ermeng Xiong
- Department of Immunology, School of Basic Medical Sciences
| | - Rika Ouchida
- Division of Mucosal Immunology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Jiping Sun
- Department of Immunology, School of Basic Medical Sciences
| | - Yang Zhou
- Department of Immunology, School of Basic Medical Sciences.,Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science, Collaborative Innovation Center for Brain Science, Fudan University, Shanghai 200032, China
| | - Yue Tang
- Department of Immunology, School of Basic Medical Sciences
| | - Masaki Hikida
- Faculty of Engineering Science, Graduate School of Engineering Science, Akita University, Akita, Japan
| | - Takeshi Tsubata
- Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Masatoshi Tagawa
- Division of Pathology and Cell Therapy, Chiba Cancer Center Research Institute, Chiba, Japan
| | - Yanqing Wang
- Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science, Collaborative Innovation Center for Brain Science, Fudan University, Shanghai 200032, China
| | - Ji-Yang Wang
- Department of Immunology, School of Basic Medical Sciences.,Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science, Collaborative Innovation Center for Brain Science, Fudan University, Shanghai 200032, China.,Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
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5
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Schraven AL, Stannard HJ, Ong OTW, Old JM. Immunogenetics of marsupial B-cells. Mol Immunol 2019; 117:1-11. [PMID: 31726269 DOI: 10.1016/j.molimm.2019.10.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 10/17/2019] [Accepted: 10/30/2019] [Indexed: 11/19/2022]
Abstract
Marsupials and eutherians are mammals that differ in their physiological traits, predominately their reproductive and developmental strategies; eutherians give birth to well-developed young, while marsupials are born highly altricial after a much shorter gestation. These developmental traits also result in differences in the development of the immune system of eutherian and marsupial species. In eutherians, B-cells are the key to humoral immunity as they are found in multiple lymphoid organs and have the unique ability to mediate the production of antigen-specific antibodies in the presence of extracellular pathogens. The development of B-cells in marsupials has been reported and hypothesised to be similar to that of eutherians, except that haematopoiesis occurs in the liver, postpartum, until the bone marrow fully matures. In eutherians, specific genes are linked to specific stages in B-cell development, maturation, and differentiation processes, and have been identified including immunoglobulins (heavy and light chains), cluster of differentiation markers (CD10, 19, 34 and CD79α/β), signal transduction molecules (BTK, Lyn and Syk) and transcriptional regulators (EBF1, E2A, and Pax5). This review aims to discuss the known similarities and differences between marsupial and eutherian B-cells, in regards to their genetic presence, homology, and developmental stages, as well as to highlight the areas requiring further investigation. By enhancing our understanding of the genes that are involved with B-cells in the marsupial lineage, it will, in turn, aid our understanding of the marsupial immune system and support the development of specific immunological reagents for research and wildlife conservation purposes.
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Affiliation(s)
- Andrea L Schraven
- School of Science and Health, Hawkesbury Campus, Western Sydney University, Locked bag 1797, Penrith, NSW 2751, Australia
| | - Hayley J Stannard
- Charles Sturt University, School of Animal and Veterinary Sciences, Wagga Wagga, NSW 2678, Australia
| | - Oselyne T W Ong
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Julie M Old
- School of Science and Health, Hawkesbury Campus, Western Sydney University, Locked bag 1797, Penrith, NSW 2751, Australia.
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6
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Łyszkiewicz M, Kotlarz D, Ziȩtara N, Brandes G, Diestelhorst J, Glage S, Hobeika E, Reth M, Huber LA, Krueger A, Klein C. LAMTOR2 (p14) Controls B Cell Differentiation by Orchestrating Endosomal BCR Trafficking. Front Immunol 2019; 10:497. [PMID: 30936881 PMCID: PMC6431647 DOI: 10.3389/fimmu.2019.00497] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 02/25/2019] [Indexed: 01/06/2023] Open
Abstract
B-cell development and function depend on stage-specific signaling through the B-cell antigen receptor (BCR). Signaling and intracellular trafficking of the BCR are connected, but the molecular mechanisms of this link are incompletely understood. Here, we investigated the role of the endosomal adaptor protein and member of the LAMTOR/Ragulator complex LAMTOR2 (p14) in B-cell development. Efficient conditional deletion of LAMTOR2 at the pre-B1 stage using mb1-Cre mice resulted in complete developmental arrest. Deletion of LAMTOR2 using Cd19-Cre mice permitted analysis of residual B cells at later developmental stages, revealing that LAMTOR2 was critical for the generation and activation of mature B lymphocytes. Loss of LAMTOR2 resulted in aberrant BCR signaling due to delayed receptor internalization and endosomal trafficking. In conclusion, we identify LAMTOR2 as critical regulator of BCR trafficking and signaling that is essential for early B-cell development in mice.
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Affiliation(s)
- Marcin Łyszkiewicz
- Institute of Immunology, Hannover Medical School, Hannover, Germany.,Department of Pediatrics, Dr. von Hauner Children's Hospital, University Hospital, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Daniel Kotlarz
- Department of Pediatrics, Dr. von Hauner Children's Hospital, University Hospital, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Natalia Ziȩtara
- Institute of Immunology, Hannover Medical School, Hannover, Germany.,Department of Pediatrics, Dr. von Hauner Children's Hospital, University Hospital, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Gudrun Brandes
- Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany
| | - Jana Diestelhorst
- Department of Pediatrics, Dr. von Hauner Children's Hospital, University Hospital, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Silke Glage
- Institute of Laboratory Animal Science, Hannover Medical School, Hannover, Germany
| | - Elias Hobeika
- Institute of Immunology, Ulm University, Ulm, Germany
| | - Michael Reth
- Max Planck Institute of Immunobiology and Epigenetics, Freiburg, Germany
| | - Lukas A Huber
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Andreas Krueger
- Institute of Immunology, Hannover Medical School, Hannover, Germany.,Institute for Molecular Medicine, Goethe-University Frankfurt, Frankfurt am Main, Germany
| | - Christoph Klein
- Department of Pediatrics, Dr. von Hauner Children's Hospital, University Hospital, Ludwig-Maximilians-University Munich, Munich, Germany
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7
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Incrocci R, McAloon J, Montesano M, Bardahl J, Vagvala S, Stone A, Swanson-Mungerson M. Epstein-Barr virus LMP2A utilizes Syk and PI3K to activate NF-κB in B-cell lymphomas to increase MIP-1α production. J Med Virol 2019; 91:845-855. [PMID: 30609049 DOI: 10.1002/jmv.25381] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 11/02/2018] [Accepted: 12/04/2018] [Indexed: 12/26/2022]
Abstract
The incidence of Hodgkin's lymphoma (HL) is growing due to an increase in Epstein-Barr virus (EBV)-associated HL in AIDS patients. The HL tumor microenvironment is vital for the survival of the malignant Hodgkin-Reed Sternberg (HRS) cells of HL, which express the EBV protein latent membrane protein 2A (LMP2A). While previous work shows that LMP2A mimics B-cell receptor (BCR) signaling to promote the survival of HRS cells, the ability of LMP2A to establish and maintain the tumor microenvironment through the production of chemokines remains unknown. Since BCR signaling induces the production of the chemokine macrophage inflammatory protein-1α (MIP-1α), and since LMP2A is a BCR mimic, we hypothesized that LMP2A increases MIP-1α levels. A comparison of multiple LMP2A-negative and -positive cell lines demonstrates that LMP2A increases MIP-1α. Additionally, LMP2A-mutant cell lines and pharmacologic inhibitors indicate that LMP2A activates a Syk/PI3K/NF-κB pathway to enhance MIP-1α. Finally, based on the finding that an NF-κB inhibitor decreased MIP-1α RNA/protein in LMP2A-positive cells, we are the first to demonstrate that LMP2A increases the nuclear localization of the NF-κB p65 subunit using DNA-binding assays and confocal microscopy in human B cells. These findings not only have implications for the treatment of HL, but also other LMP2A-expressing B-cell tumors that overexpress NF-κB.
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Affiliation(s)
- Ryan Incrocci
- Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Downers Grove, Illinois
| | - Jason McAloon
- Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, Illinois
| | - Michael Montesano
- Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, Illinois.,Department of Biomedical Sciences, College of Graduate Studies, Midwestern University, Downers Grove, Illinois
| | - Jonathan Bardahl
- Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, Illinois.,Department of Biomedical Sciences, College of Graduate Studies, Midwestern University, Downers Grove, Illinois
| | - Saivenkat Vagvala
- Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, Illinois
| | - Amanda Stone
- Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, Illinois
| | - Michelle Swanson-Mungerson
- Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Downers Grove, Illinois.,Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, Illinois
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8
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Zhang Q, Lee WB, Kang JS, Kim LK, Kim YJ. Integrin CD11b negatively regulates Mincle-induced signaling via the Lyn-SIRPα-SHP1 complex. Exp Mol Med 2018; 50:e439. [PMID: 29400702 PMCID: PMC5992981 DOI: 10.1038/emm.2017.256] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 07/31/2017] [Indexed: 12/22/2022] Open
Abstract
During mycobacteria infection, anti-inflammatory responses allow the host to avoid tissue damage caused by overactivation of the immune system; however, little is known about the negative modulators that specifically control mycobacteria-induced immune responses. Here we demonstrate that integrin CD11b is a critical negative regulator of mycobacteria cord factor-induced macrophage-inducible C-type lectin (Mincle) signaling. CD11b deficiency resulted in hyperinflammation following mycobacterial infection. Activation of Mincle by mycobacterial components turns on not only the Syk signaling pathway but also CD11b signaling and induces formation of a Mincle–CD11b signaling complex. The activated CD11b recruits Lyn, SIRPα and SHP1, which dephosphorylate Syk to inhibit Mincle-mediated inflammation. Furthermore, the Lyn activator MLR1023 effectively suppressed Mincle signaling, indicating the possibility of Lyn-mediated control of inflammatory responses. These results describe a new role for CD11b in fine-tuning the immune response against mycobacterium infection.
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Affiliation(s)
- Quanri Zhang
- Department of Integrated Omics for Biomedical Science, Graduate School, Yonsei University, Seoul, Republic of Korea
| | - Wook-Bin Lee
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea
| | - Ji-Seon Kang
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea
| | - Lark Kyun Kim
- Severance Biomedical Science Institute and BK21 PLUS Project to Medical Sciences, Seoul, Republic of Korea.,Severance Institute for Vascular and Metabolic Research, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Young-Joon Kim
- Department of Integrated Omics for Biomedical Science, Graduate School, Yonsei University, Seoul, Republic of Korea.,Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea
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9
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Mishra AR, Chaturvedi A. B Cell Receptor Signaling and Compartmentalization by Confocal Microscopy. Methods Mol Biol 2018; 1707:121-129. [PMID: 29388104 DOI: 10.1007/978-1-4939-7474-0_9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Binding of antigen to the B cell receptor (BCR) triggers both BCR signaling and endocytosis simultaneously. BCR signaling pathways and their regulation have been studied extensively by both biochemical methods and flow cytometry, resulting in a comprehensive understanding of the temporal dynamics of the signaling enzymes and effector proteins. However, spatial regulation of these signaling pathways in subcellular pathways is relatively poorly understood. Here, we describe a method to study the spatio-temporal distribution of phosphorylated-kinases in antigen-activated B cells by confocal microscopy. This method can also be applied to other cell types where it is of interest to understand the spatial distribution of signaling enzymes and their effector proteins.
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Affiliation(s)
- Anurag R Mishra
- Department of Biosciences and Bioengineering, Indian Institute of Technology, Indore, India
| | - Akanksha Chaturvedi
- Department of Biology, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune, Maharashtra, India.
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10
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Biajoux V, Natt J, Freitas C, Alouche N, Sacquin A, Hemon P, Gaudin F, Fazilleau N, Espéli M, Balabanian K. Efficient Plasma Cell Differentiation and Trafficking Require Cxcr4 Desensitization. Cell Rep 2016; 17:193-205. [DOI: 10.1016/j.celrep.2016.08.068] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 07/07/2016] [Accepted: 08/19/2016] [Indexed: 01/08/2023] Open
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11
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Dengue Virus Directly Stimulates Polyclonal B Cell Activation. PLoS One 2015; 10:e0143391. [PMID: 26656738 PMCID: PMC4675537 DOI: 10.1371/journal.pone.0143391] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 11/04/2015] [Indexed: 02/03/2023] Open
Abstract
Dengue infection is associated to vigorous inflammatory response, to a high frequency of activated B cells, and to increased levels of circulating cross-reactive antibodies. We investigated whether direct infection of B cells would promote activation by culturing primary human B lymphocytes from healthy donors with DENV in vitro. B cells were susceptible, but poorly permissive to infection. Even though, primary B cells cultured with DENV induced substantial IgM secretion, which is a hallmark of polyclonal B cell activation. Notably, DENV induced the activation of B cells obtained from either DENV immune or DENV naïve donors, suggesting that it was not dependent on DENV-specific secondary/memory response. B cell stimulation was dependent on activation of MAPK and CD81. B cells cultured with DENV also secreted IL-6 and presented increased expression of CD86 and HLA-DR, which might contribute to B lymphocyte co-stimulatory function. Indeed, PBMCs, but not isolated B cells, secreted high amounts of IgG upon DENV culture, suggesting that interaction with other cell types in vivo might promote Ig isotype switching and IgG secretion from different B cell clones. These findings suggest that activation signaling pathways triggered by DENV interaction with non-specific receptors on B cells might contribute to the exacerbated response observed in dengue patients.
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12
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Kang MM, Shan SL, Wen XY, Shan HS, Wang ZJ. Tumor-Suppression Mechanisms of Protein Tyrosine Phosphatase O and Clinical Applications. Asian Pac J Cancer Prev 2015; 16:6215-23. [PMID: 26434819 DOI: 10.7314/apjcp.2015.16.15.6215] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Tyrosine phosphorylation plays an important role in regulating human physiological and pathological processes. Functional stabilization of tyrosine phosphorylation largely contributes to the balanced, coordinated regulation of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Research has revealed PTPs play an important suppressive role in carcinogenesis and progression by reversing oncoprotein functions. Receptor-type protein tyrosine phosphatase O (PTPRO) as one member of the PTPs family has also been identified to have some roles in tumor development. Some reports have shown PTPRO over-expression in tumors can not only inhibit the frequency of tumor cell division and induce tumor cell death, but also suppress migration. However, the tumor-suppression mechanisms are very complex and understanding is incomplete, which in some degree blocks the further development of PTPRO. Hence, in order to resolve this problem, we here have summarized research findings to draw meaningful conclusions. We found tumor-suppression mechanisms of PTPRO to be diverse, such as controlling G0/G1 of the tumor cell proliferation cycle, inhibiting substrate phosphorylation, down-regulating transcription activators and other activities. In clinical anticancer efforts, expression level of PTPRO in tumors can not only serve as a biomarker to monitor the prognosis of patients, but act as an epigenetic biomarker for noninvasive diagnosis. In addition, the re-activation of PTPRO in tumor tissues, not only can induce tumor volume reduction, but also enhance the susceptibility to chemotherapy drugs. So, we can propose that these research findings of PTPRO will not only support new study ideas and directions for other tumor- suppressors, importantly, but also supply a theoretical basis for researching new molecular targeting agents in the future.
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Affiliation(s)
- Man-Man Kang
- The Center of Radiation Oncology, the 82th Hospital of People's Liberation Army of China, Huaian, Jiangsu, China E-mail : ,
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13
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Uhde M, Kuehl S, Richardt U, Fleischer B, Osterloh A. Differential regulation of marginal zone and follicular B cell responses by CD83. Int Immunol 2013; 25:507-20. [PMID: 23728778 DOI: 10.1093/intimm/dxt021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023] Open
Abstract
Transgenic over-expression of CD83 on B cells leads to a reduced response to BCR engagement but to an enhanced secretion of IL-10 upon LPS stimulation. In this study, we analyzed the differential influence of CD83 on the stimulation of different B cell subsets via the BCR or TLR4. Neither wild type nor CD83 transgenic (CD83tg) B cells produced any IL-10 in response to BCR stimulation. BCR engagement led to reduced activation of LYN, SYK and ERK1/2 resulting in reduced numbers of proliferating cells in all CD83tg B cell subsets. Moreover, CD83tg follicular (FO) but not marginal zone (MZ) or transitional (TN) B cells showed significantly enhanced cell death. In contrast, LPS stimulation led to normal frequencies of proliferating CD83tg FO, MZ and TN B cells although TLR4 engagement did not rescue FO B cells from apoptosis. Furthermore, LPS stimulation led to high IL-10 production derived from CD83tg MZ B cells that reacted to LPS stimulation with enhanced ERK1/2 activation. Finally, we show that CD83 co-localizes with the BCR complex as well as with the LPS receptor complex suggesting that CD83 interacts with components of both signaling complexes. Taken together, the results of this study show that CD83 already inhibits the initiation of BCR signaling leading to insufficient activation signals in all B cells and reduced survival especially of FO B cells. On the other hand, CD83 supports TLR4-mediated IL-10 release exclusively in MZ B cells. Thus, CD83 differentially modulates FO and MZ B cell responses.
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Affiliation(s)
- Melanie Uhde
- Department of Immunology, Bernhard Nocht Institute for Tropical Medicine, Hamburg 20359, Germany
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Li R, Wang T, Bird S, Zou J, Dooley H, Secombes CJ. B cell receptor accessory molecule CD79α: characterisation and expression analysis in a cartilaginous fish, the spiny dogfish (Squalus acanthias). FISH & SHELLFISH IMMUNOLOGY 2013; 34:1404-15. [PMID: 23454429 PMCID: PMC4034164 DOI: 10.1016/j.fsi.2013.02.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 02/08/2013] [Accepted: 02/18/2013] [Indexed: 05/16/2023]
Abstract
CD79α (also known as Igα) is a component of the B cell antigen receptor complex and plays an important role in B cell signalling. The CD79α protein is present on the surface of B cells throughout their life cycle, and is absent on all other healthy cells, making it a highly reliable marker for B cells in mammals. In this study the spiny dogfish (Squalus acanthias) CD79α (SaCD79α) is described and its expression studied under constitutive and stimulated conditions. The spiny dogfish CD79α cDNA contains an open reading frame of 618 bp, encoding a protein of 205 amino acids. Comparison of the SaCD79α gene with that of other species shows that the gross structure (number of exons, exon/intron boundaries, etc.) is highly conserved across phylogeny. Additionally, analysis of the 5' flanking region shows SaCD79α lacks a TATA box and possesses binding sites for multiple transcription factors implicated in its B cell-specific gene transcription in other species. Spiny dogfish CD79α is most highly expressed in immune tissues, such as spleen, epigonal and Leydig organ, and its transcript level significantly correlates with those of spiny dogfish immunoglobulin heavy chains. Additionally, CD79α transcription is up-regulated, to a small but significant degree, in peripheral blood cells following stimulation with pokeweed mitogen. These results strongly indicate that, as in mammals, spiny dogfish CD79α is expressed by shark B cells where it associates with surface-bound immunoglobulin to form a fully functional BCR, and thus may serve as a pan-B cell marker in future shark immunological studies.
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Affiliation(s)
- Ronggai Li
- Scottish Fish Immunology Research Centre, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen AB24 2TZ, UK
| | - Tiehui Wang
- Scottish Fish Immunology Research Centre, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen AB24 2TZ, UK
| | - Steve Bird
- Department of Biological Sciences, School of Science and Engineering, University of Waikato, New Zealand
| | - Jun Zou
- Scottish Fish Immunology Research Centre, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen AB24 2TZ, UK
| | - Helen Dooley
- Scottish Fish Immunology Research Centre, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen AB24 2TZ, UK
| | - Christopher J. Secombes
- Scottish Fish Immunology Research Centre, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen AB24 2TZ, UK
- Corresponding author. Tel.: +44 1224 278272; fax: +44 (0)1224 272396.
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15
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Lucas CR, Cordero-Nieves HM, Erbe RS, McAlees JW, Bhatia S, Hodes RJ, Campbell KS, Sanders VM. Prohibitins and the cytoplasmic domain of CD86 cooperate to mediate CD86 signaling in B lymphocytes. THE JOURNAL OF IMMUNOLOGY 2012; 190:723-36. [PMID: 23241883 DOI: 10.4049/jimmunol.1201646] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
CD86 engagement on a CD40L/IL-4-primed murine B cell activates signaling intermediates that promote NF-κB activation to increase Oct-2 and mature IgG1 mRNA and protein expression, as well as the rate of IgG1 transcription, without affecting class switch recombination. One of the most proximal signaling intermediates identified is phospholipase Cγ2, a protein reported to bind tyrosine residues, which are absent in the cytoplasmic domain of CD86. Using a proteomics-based identification approach, we show that the tyrosine-containing transmembrane adaptor proteins prohibitin (Phb)1 and Phb2 bind to CD86. The basal expression of Phb1/2 and association with CD86 was low in resting B cells, whereas the level of expression and association increased primarily after priming with CD40. The CD86-induced increase in Oct-2 and IgG1 was less when either Phb1/2 expression was reduced by short hairpin RNA or the cytoplasmic domain of CD86 was truncated or mutated at serine/threonine protein kinase C phosphorylation sites, which did not affect Phb1/2 binding to CD86. Using this approach, we also show that Phb1/2 and the CD86 cytoplasmic domain are required for the CD86-induced phosphorylation of IκBα, which we previously reported leads to NF-κB p50/p65 activation, whereas only Phb1/2 was required for the CD86-induced phosphorylation of phospholipase Cγ2 and protein kinase Cα/β(II), which we have previously reported leads to NF-κB (p65) phosphorylation and subsequent nuclear translocation. Taken together, these findings suggest that Phb1/2 and the CD86 cytoplasmic domain cooperate to mediate CD86 signaling in a B cell through differential phosphorylation of distal signaling intermediates required to increase IgG1.
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Affiliation(s)
- Christopher R Lucas
- Integrated Biomedical Science Graduate Program, The Ohio State University, Columbus, OH 43210, USA
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16
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Wang YH, Fan L, Wang L, Zhang R, Zou ZJ, Fang C, Zhang LN, Li JY, Xu W. Expression levels of Lyn, Syk, PLCγ2 and ERK in patients with chronic lymphocytic leukemia, and higher levels of Lyn are associated with a shorter treatment-free survival. Leuk Lymphoma 2012; 54:1165-70. [DOI: 10.3109/10428194.2012.736983] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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17
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Zhang Z, Zhou L, Yang X, Wang Y, Zhang P, Hou L, Hu X, Xing Y, Liu Y, Li W, Han H. Notch-RBP-J-independent marginal zone B cell development in IgH transgenic mice with VH derived from a natural polyreactive antibody. PLoS One 2012; 7:e38894. [PMID: 22719978 PMCID: PMC3374804 DOI: 10.1371/journal.pone.0038894] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Accepted: 05/14/2012] [Indexed: 11/18/2022] Open
Abstract
Both the B cell antigen receptor (BCR) signaling and Notch signaling pathway play important roles in marginal zone (MZ) B cell development; however, if and how these two signaling pathways engage in crosstalk with each other remain unclear. In the present study, IgH transgenic mice (TgV(H)3B4) were crossed with mice with Notch downstream transcription factor RBP-J floxed alleles (RBP-J(f/f)) and Mx-Cre transgene. Subsequently, MZ B cell development was analyzed in 3B4/Cre/RBP-J(f/f) mice that expressed the transgenic 3B4 IgH and exhibited a deficiency in Notch signaling in B cells upon poly (I:C) injection. We observed that MZ B cell numbers were severely reduced, but still detectable in 3B4/Cre/RBP-J(f/f) mice, in contrast to increased numbers of MZ B cells in TgV(H)3B4 mice and almost no MZ B cells in Cre/RBP-J(f/f) mice. The majority of the MZ B cells in the 3B4/Cre/RBP-J(f/f) mice had the same antigen specificity with that of 3B4 antibody, indicating that a particular BCR specificity might direct MZ B cell development in the absence of Notch signaling. The number of MZ B precursor (MZP) cells was reduced sharply in 3B4/Cre/RBP-J(f/f) mice, and the number of transitional stage 1 and transitional stage 2 cells did not change that much, indicating that the interaction between BCR and Notch signaling likely occurred during the T2-MZP stage. Based on the transgenic mouse model, our data indicate that MZ B cells with certain BCR specificity can develop in a Notch-RBP-J independent manner.
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Affiliation(s)
- Zhuo Zhang
- Department of Dermatology, Xijing Hospital, Fourth Military Medical University, Xi'an, China
- Department of Neurology, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Lanhua Zhou
- Department of Dermatology, Xijing Hospital, Fourth Military Medical University, Xi'an, China
- Department of Dermatology, Affiliated Hospital of Institute of Aviation Medicine, Air Force, Beijing, China
| | - Xinwei Yang
- State Key Laboratory of Cancer Biology, Department of Medical Genetics and Developmental Biology, Fourth Military Medical University, Xi'an, China
| | - Yaochun Wang
- State Key Laboratory of Cancer Biology, Department of Medical Genetics and Developmental Biology, Fourth Military Medical University, Xi'an, China
| | - Ping Zhang
- State Key Laboratory of Cancer Biology, Department of Medical Genetics and Developmental Biology, Fourth Military Medical University, Xi'an, China
| | - Lihong Hou
- State Key Laboratory of Cancer Biology, Department of Medical Genetics and Developmental Biology, Fourth Military Medical University, Xi'an, China
| | - Xinbin Hu
- State Key Laboratory of Cancer Biology, Department of Medical Genetics and Developmental Biology, Fourth Military Medical University, Xi'an, China
| | - Ying Xing
- Department of Dermatology, Xijing Hospital, Fourth Military Medical University, Xi'an, China
- State Key Laboratory of Cancer Biology, Department of Medical Genetics and Developmental Biology, Fourth Military Medical University, Xi'an, China
| | - Yufeng Liu
- Department of Dermatology, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Wei Li
- Department of Dermatology, Xijing Hospital, Fourth Military Medical University, Xi'an, China
- State Key Laboratory of Cancer Biology, Department of Medical Genetics and Developmental Biology, Fourth Military Medical University, Xi'an, China
- * E-mail: (WL); (HH)
| | - Hua Han
- Department of Dermatology, Xijing Hospital, Fourth Military Medical University, Xi'an, China
- State Key Laboratory of Cancer Biology, Department of Medical Genetics and Developmental Biology, Fourth Military Medical University, Xi'an, China
- * E-mail: (WL); (HH)
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Davey AM, Pierce SK. Intrinsic differences in the initiation of B cell receptor signaling favor responses of human IgG(+) memory B cells over IgM(+) naive B cells. THE JOURNAL OF IMMUNOLOGY 2012; 188:3332-41. [PMID: 22379037 DOI: 10.4049/jimmunol.1102322] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The acquisition of long-lived memory B cells (MBCs) is critical for the defense against many infectious diseases. Despite their importance, little is known about how Ags trigger human MBCs, even though our understanding of the molecular basis of Ag activation of B cells in model systems has advanced considerably. In this study, we use quantitative, high-resolution, live-cell imaging at the single-cell and single-molecule levels to describe the earliest Ag-driven events in human isotype-switched, IgG-expressing MBCs and compare them with those in IgM-expressing naive B cells. We show that human MBCs are more robust than naive B cells at each step in the initiation of BCR signaling, including interrogation of Ag-containing membranes, formation of submicroscopic BCR oligomers, and recruitment and activation of signaling-associated kinases. Despite their robust response to Ag, MBCs remain highly sensitive to FcγRIIB-mediated inhibition. We also demonstrate that in the absence of Ag, a portion of MBC receptors spontaneously oligomerized, and phosphorylated kinases accumulated at the membrane and speculate that heightened constitutive signaling may play a role in maintaining MBC longevity. Using high-resolution imaging, we have provided a description of the earliest events in the Ag activation of MBCs and evidence for acquired cell-intrinsic differences in the initiation of BCR signaling in human naive and MBCs.
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Affiliation(s)
- Angel M Davey
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
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Chatterjee P, Tiwari RK, Rath S, Bal V, George A. Modulation of Antigen Presentation and B Cell Receptor Signaling in B Cells of Beige Mice. THE JOURNAL OF IMMUNOLOGY 2012; 188:2695-702. [DOI: 10.4049/jimmunol.1101527] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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20
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Chaturvedi A, Martz R, Dorward D, Waisberg M, Pierce SK. Endocytosed BCRs sequentially regulate MAPK and Akt signaling pathways from intracellular compartments. Nat Immunol 2011; 12:1119-26. [PMID: 21964606 DOI: 10.1038/ni.2116] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Accepted: 08/23/2011] [Indexed: 01/15/2023]
Abstract
Binding of antigen to the B cell antigen receptor (BCR) triggers both BCR signaling and endocytosis. How endocytosis regulates BCR signaling remains unknown. Here we report that BCR signaling was not extinguished by endocytosis of BCRs; instead, BCR signaling initiated at the plasma membrane continued as the BCR trafficked intracellularly with the sequential phosphorylation of kinases. Blocking the endocytosis of BCRs resulted in the recruitment of both proximal and downstream kinases to the plasma membrane, where mitogen-activated protein kinases (MAPKs) were hyperphosphorylated and the kinase Akt and its downstream target Foxo were hypophosphorylated, which led to the dysregulation of gene transcription controlled by these pathways. Thus, the cellular location of the BCR serves to compartmentalize kinase activation to regulate the outcome of signaling.
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Affiliation(s)
- Akanksha Chaturvedi
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA.
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21
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Simone O, Bejarano MT, Pierce SK, Antonaci S, Wahlgren M, Troye-Blomberg M, Donati D. TLRs innate immunereceptors and Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) CIDR1α-driven human polyclonal B-cell activation. Acta Trop 2011; 119:144-50. [PMID: 21620790 PMCID: PMC3406598 DOI: 10.1016/j.actatropica.2011.05.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Revised: 05/10/2011] [Accepted: 05/11/2011] [Indexed: 02/07/2023]
Abstract
Chronic malaria severely affects the immune system and causes polyclonal B-cell activation, as evidenced by the presence of hypergammaglobulinemia, elevated levels of autoantibodies, loss of B-cell memory and the frequent occurrence of Burkitt's lymphomas (BL) in children living in malaria endemic areas. Previous studies have shown that the cysteine-rich interdomain region 1α (CIDR1α) of the Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) of the FCR3S1.2 strain, subsequently named CIDR1α, interacts with B cells partially through the binding to the B-cell receptor (BCR). This interaction leads to an activated phenotype, increased survival, and a low degree of proliferation. CIDR1α preferentially activates the memory B-cell compartment, therefore PfEMP1 is considered to act as a polyclonal B-cell activator and its role in memory maintenance has been suggested. In this report, we extend the analysis of the PfEMP1-CIDR1α B-cell interaction and demonstrate that PfEMP1-CIDR1α increases the expression of TLR7 and TLR10 mRNA transcripts and sensitizes B cells to TLR9 signalling via the MyD88 adaptor molecule. Furthermore, despite its ability to bind to surface Igs, PfEMP1-CIDR1α-induced B-cell activation does not seem to proceed through the BCR, since it does not induce Lyn and/or phospho-tyrosine mediated signalling pathways. Rather PfEMP1-CIDR1α induces the phosphorylation of downstream kinases, such as ERK1/2, p38 and IKBα, in human B cells. These findings indicate that PfEMP1-CIDR1α induces a persistent activation of B cells, which in turn can contribute to the exhaustion and impairment of B-cell functions during chronic malaria infection.
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Affiliation(s)
- Olivia Simone
- Department of Internal Medicine, Immunology and Infectious Diseases, University of Bari Medical School, Policlinico of Bari, Italy.
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22
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Jang IK, Zhang J, Gu H. Grb2, a simple adapter with complex roles in lymphocyte development, function, and signaling. Immunol Rev 2010; 232:150-9. [PMID: 19909362 DOI: 10.1111/j.1600-065x.2009.00842.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lymphocyte development, activation, and tolerance depend on antigen receptor signaling transduced via multiple intracellular signalosomes. These signalosomes are assembled by different adapters. Given that signaling molecules can be either positive or negative regulators for a biochemical target, the complex of a target with different regulator may dictate the final signaling outcome. Grb2 is a simple adapter known to be involved in a variety of growth factor receptor signaling. However, its role in antigen receptor signaling as well as lymphocyte development and function has emerged only recently. Despite its simple molecular structure, recent experiments show that Grb2 may play a complex role in T and B-cell antigen receptor signaling. In this article, we review recent findings about the physiological role of Grb2 in T and B-cell development and activation and summarize the current mechanistic understanding of how Grb2 exerts its function following T and B-cell antigen receptor stimulation.
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Affiliation(s)
- Ihn Kyung Jang
- Department of Microbiology and Immunology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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Tolar P, Pierce SK. A conformation-induced oligomerization model for B cell receptor microclustering and signaling. Curr Top Microbiol Immunol 2010; 340:155-69. [PMID: 19960313 PMCID: PMC3400257 DOI: 10.1007/978-3-642-03858-7_8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The B cell receptor (BCR) generates both antigen-independent and dependent intracellular signals that are essential for B cell development and antibody responses against pathogens. However, the molecular mechanisms underlying the initiation of BCR signaling are not understood completely yet. The advent of new imaging technologies is allowing the earliest events in B cell signaling to be viewed both in vivo in lymphoid tissues and in vitro in living cells, in real-time, down to the single molecule level. Here we review recent progress in the use of these technologies to decipher the earliest events that follow B cell antigen recognition. Based on recent data using these techniques, we propose a model for the initiation of BCR signaling in which the binding of antigen induces a conformational change in the BCR's extracellular domains leading to BCR oligomerization and signaling. We conclude that testing this model will require an in-depth understanding of the unique structural and organizational features of the BCR in the plasma membrane of living B cells in the presence and absence of antigen.
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Affiliation(s)
- Pavel Tolar
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20852
| | - Susan K. Pierce
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20852
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Abstract
Rho family GTPases are intracellular signaling proteins regulating multiple pathways involved in cell actomyosin organization, adhesion, and proliferation. Our knowledge of their cellular functions comes mostly from previous biochemical studies that used mutant overexpression approaches in various clonal cell lines. Recent progress in understanding Rho GTPase functions in blood cell development and regulation by gene targeting of individual Rho GTPases in mice has allowed a genetic understanding of their physiologic roles in hematopoietic progenitors and mature lineages. In particular, mouse gene-targeting studies have provided convincing evidence that individual members of the Rho GTPase family are essential regulators of cell type-specific functions and stimuli-specific pathways in regulating hematopoietic stem cell interaction with bone marrow niche, erythropoiesis, and red blood cell actin dynamics, phagocyte migration and killing, and T- and B-cell maturation. In addition, deregulation of Rho GTPase family members has been associated with multiple human hematologic diseases such as neutrophil dysfunction, leukemia, and Fanconi anemia, raising the possibility that Rho GTPases and downstream signaling pathways are of therapeutic value. In this review we discuss recent genetic studies of Rho GTPases in hematopoiesis and several blood lineages and the implications of Rho GTPase signaling in hematologic malignancies, immune pathology. and anemia.
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Abstract
Rituximab (RTX), a monoclonal antibody directed against the CD20 protein, is a drug commonly used in the treatment of B-cell-derived lymphoid neoplasias and of antibody-mediated autoimmune diseases. In addition to cell- and complement-mediated B-cell depletion, RTX is thought to inhibit B-cell survival and proliferation through negative regulation of canonical signaling pathways involving Akt, ERK, and mammalian target of rapamycin. However, surprisingly, although B-cell receptor (BCR) signaling has been considered critical for normal and more recently, for neoplastic B cells, the hypothesis that RTX could target BCR has never been investigated. Using follicular lymphoma cell lines as models, as well as normal B cells, we show here, for the first time, that pretreatment with RTX results in a time-dependent inhibition of the BCR-signaling cascade involving Lyn, Syk, PLC gamma 2, Akt, and ERK, and calcium mobilization. The inhibitory effect of RTX correlates with decrease of raft-associated cholesterol, complete inhibition of BCR relocalization into lipid raft microdomains, and down-regulation of BCR immunoglobulin expression. Thus, RTX-mediated alteration of BCR expression, dynamics, and signaling might contribute to the immunosuppressive activity of the drug.
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Sanyal M, Fernandez R, Levy S. Enhanced B cell activation in the absence of CD81. Int Immunol 2009; 21:1225-37. [PMID: 19737782 DOI: 10.1093/intimm/dxp090] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
CD81 is a component of the CD19/CD21 co-receptor complex in B cells. However, the role of CD81 in B cell activation has not been clearly elucidated. Here, we demonstrate that Cd81(-/-) B cells stimulated via their B cell receptor fluxed higher intracellular-free calcium ion along with increased phosphorylation of spleen tyrosine kinase and phospholipase gamma 2. Additionally, Cd81(-/-) B cells responded to toll like receptor 4 stimulation with increased nuclear factor-kappa B activation, cell proliferation and antibody secretion compared with wild-type B cells. Cd81(-/-) mice also mounted a significantly higher immune response to T-independent antigens than their wild-type counterparts. Finally, analysis of Cd81(-/-) B cells that were generated by bone marrow transplantation into Rag1(-/-) mice confirmed that the hyperactive phenotype is not dependent on the CD81-deficient environment. Taken together, these results indicate that CD81 plays a negative role in B cell activation in vitro and in vivo.
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Affiliation(s)
- Mrinmoy Sanyal
- Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
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27
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Stimulus duration and response time independently influence the kinetics of lytic cycle reactivation of Epstein-Barr virus. J Virol 2009; 83:10694-709. [PMID: 19656890 DOI: 10.1128/jvi.01172-09] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Epstein-Barr virus (EBV) can be reactivated from latency into the lytic cycle by many stimuli believed to operate by different mechanisms. Cell lines containing EBV differ in their responses to inducing stimuli, yet all stimuli require de novo protein synthesis (44). A crucial step preliminary to identifying these proteins and determining when they are required is to measure the duration of stimulus and response time needed for activation of expression of EBV BRLF1 and BZLF1, the earliest viral indicators of reactivation. Here we show, with four EBV-containing cell lines that respond to different inducing agents, that stimuli that are effective at reactivating EBV can be divided into two main groups. The histone deacetylase inhibitors sodium butyrate and trichostatin A require a relatively long period of exposure, from 2 to 4 h or longer. Phorbol esters, anti-immunoglobulin G (anti-IgG), and, surprisingly, 5-aza-2'-deoxycytidine require short exposures of 15 min or less. The cell/virus background influences the response time. Expression of the EBV BZLF1 and BRLF1 genes can be detected before 2 h in Akata cells treated with anti-IgG, but both long- and short-duration stimuli required 4 or more hr to activate BZLF1 and BRLF1 expression in HH514-16, Raji, or B95-8 cells. Thus, stimulus duration and response time are independent variables. Neither stimulus duration nor response time can be predicted by the number of cells activated into the lytic cycle. These experiments shed new light on the earliest events leading to lytic cycle reactivation of EBV.
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28
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Thomas S, Thirumalapura N, Crossley EC, Ismail N, Walker DH. Antigenic protein modifications in Ehrlichia. Parasite Immunol 2009; 31:296-303. [PMID: 19493209 PMCID: PMC2731653 DOI: 10.1111/j.1365-3024.2009.01099.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
To develop effective vaccination strategies againstEhrlichia, we have previously reported developing an animal model of cross-protection in which C57BL/6 mice primed withE. muris were resistant to lethal infection withIxodes ovatus ehrlichia (IOE). Polyclonal antibody produced in mice after priming withE. muris and later injected with IOE-detected antigenic proteins inE. muris and IOE cell lysates. Cross-reaction of antigenic proteins was observed when we probed both theE. muris and IOE cell lysates with IOE andE. muris-specific polyclonal antibody. Analysis of the total proteins ofE. muris and IOE by two dimensional electrophoresis showed that bothE. muris and IOE have the same antigenic proteins. Finally, studies on post-translational protein modifications using a novel technique, Eastern blotting, showed thatE. muris proteins are more lipoylated and glycosylated than those of IOE.
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Affiliation(s)
- S Thomas
- Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, USA
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Gowda T, Vrudhula S, Kim S. Prediction of pairwise gene interaction using threshold logic. Ann N Y Acad Sci 2009; 1158:276-86. [PMID: 19348649 DOI: 10.1111/j.1749-6632.2008.03763.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The two important problems of computational biology are the modeling of gene regulatory networks and the study of the network structure of complex biological systems. There is an increased use of mathematical and computational theory techniques to solve both these problems. The Boolean circuit model is one of the most popular modeling paradigms used to model gene regulatory networks. In this paper we try to make use of the properties of threshold logic (an alternative to Boolean logic to design digital circuits) to determine the network structure of gene systems. This approach uses the gene-expression data from microarray experiments as input. The proposed method was first used to build the gene network for a set of genes, proteins, and other molecular components based on in silico data. Then, the method was applied to a biological dataset to build the gene regulatory network for a core set of genes associated with melanoma. Some of the interactions found could be verified by earlier biological experiments reported in published literature. Other interactions that could not be validated by existing biological knowledge can provide insights into the investigation of bio-chemical pathways associated with melanoma development.
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Affiliation(s)
- Tejaswi Gowda
- School of Computing and Informatics, Arizona State University, Tempe, Arizona, USA.
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30
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Xing Y, Li W, Lin Y, Fu M, Li CX, Zhang P, Liang L, Wang G, Gao TW, Han H, Liu YF. The influence of BCR density on the differentiation of natural poly-reactive B cells begins at an early stage of B cell development. Mol Immunol 2009; 46:1120-8. [DOI: 10.1016/j.molimm.2008.10.031] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2008] [Revised: 10/21/2008] [Accepted: 10/22/2008] [Indexed: 12/16/2022]
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31
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Barouch-Bentov R, Che J, Lee CC, Yang Y, Herman A, Jia Y, Velentza A, Watson J, Sternberg L, Kim S, Ziaee N, Miller A, Jackson C, Fujimoto M, Young M, Batalov S, Liu Y, Warmuth M, Wiltshire T, Cooke MP, Sauer K. A conserved salt bridge in the G loop of multiple protein kinases is important for catalysis and for in vivo Lyn function. Mol Cell 2009; 33:43-52. [PMID: 19150426 DOI: 10.1016/j.molcel.2008.12.024] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Revised: 06/30/2008] [Accepted: 12/23/2008] [Indexed: 12/12/2022]
Abstract
The glycine-rich G loop controls ATP binding and phosphate transfer in protein kinases. Here we show that the functions of Src family and Abl protein tyrosine kinases require an electrostatic interaction between oppositely charged amino acids within their G loops that is conserved in multiple other phylogenetically distinct protein kinases, from plants to humans. By limiting G loop flexibility, it controls ATP binding, catalysis, and inhibition by ATP-competitive compounds such as Imatinib. In WeeB mice, mutational disruption of the interaction results in expression of a Lyn protein with reduced catalytic activity, and in perturbed B cell receptor signaling. Like Lyn(-/-) mice, WeeB mice show profound defects in B cell development and function and succumb to autoimmune glomerulonephritis. This demonstrates the physiological importance of the conserved G loop salt bridge and at the same time distinguishes the in vivo requirement for the Lyn kinase activity from other potential functions of the protein.
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Affiliation(s)
- Rina Barouch-Bentov
- Genomics Institute of the Novartis Research Foundation, 10675 John J. Hopkins Drive, San Diego, CA 92121, USA
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32
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Wu HJ, Bondada S. CD72, a coreceptor with both positive and negative effects on B lymphocyte development and function. J Clin Immunol 2008; 29:12-21. [PMID: 19067131 DOI: 10.1007/s10875-008-9264-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Accepted: 11/10/2008] [Indexed: 10/21/2022]
Abstract
INTRODUCTION B lymphocytes remain in a resting state until activated by antigenic stimuli through interaction with the B cell receptor (BCR). Coreceptors on B cells can modulate the thresholds for signaling through the BCR for growth and differentiation. CD72 is a B cell coreceptor that has been shown to interact with CD100, a semaphorin, and to enhance BCR signaling. DISCUSSION CD72 ligation induces a variety of early signaling events such as activation of the Src kinases Blk and Lyn and the non-src kinase Btk leading to activation of the mitogen-activated protein (MAP) kinases, events usually associated with positive signaling. CD72 signals can enable Btk-deficient B cells to overcome their unresponsiveness to BCR signaling. On the other hand, BCR-mediated signals are enhanced in CD72-deficient cells but are reduced in CD100 null cells. The dual effects of CD72 on B cells can be explained by its association with positive and negative signaling molecules. Thus, CD72 interacts with SHP-1, an SH2-domain containing protein tyrosine phosphatase, a negative regulator of signaling, and Grb2, an adaptor protein associated with the Ras/MAPK pathway. Ligation of CD72 also triggered its association with CD19, a positive modulator of B cell receptor signaling. We propose a dual signaling hypothesis to explain the growth and differentiation promoting properties of CD72. Deficiency in either CD72 or CD100 leads to autoimmunity in mouse models. CD72 expression and polymorphisms exhibit some association with autoimmune diseases such as lupus, Sjogren's syndrome, and type 1 diabetes.
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Affiliation(s)
- Hsin-Jung Wu
- Section on Immunology and Immunogenetics, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02115, USA
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33
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Abstract
B lymphocytes are an integral part of the adaptive immune system. On antigen binding to the B-cell receptor (BCR), B cells rapidly proliferate and differentiate into antibody-secreting plasma cells. The p38 mitogen-activated protein kinase (MAPK) pathway functions downstream of the BCR to control cell proliferation, but the transcriptional effectors of this pathway in B cells have remained elusive. In the present study, we inactivated Mef2c exclusively in B cells by conditional gene targeting in mice. Loss of MEF2C function resulted in a reduced immune response to antigen, defective germinal center formation, and a severe defect in B-cell proliferation, and we show that MEF2C regulates proliferation in response to BCR stimulation via the p38 MAPK pathway. p38 directly phosphorylates MEF2C via three residues in the C-terminal transactivation domain, establishing MEF2C as a direct transcriptional effector of BCR signaling via p38 MAPK.
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34
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Chen Y, Wang X, Di L, Fu G, Chen Y, Bai L, Liu J, Feng X, McDonald JM, Michalek S, He Y, Yu M, Fu YX, Wen R, Wu H, Wang D. Phospholipase Cgamma2 mediates RANKL-stimulated lymph node organogenesis and osteoclastogenesis. J Biol Chem 2008; 283:29593-601. [PMID: 18728019 PMCID: PMC2570883 DOI: 10.1074/jbc.m802493200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 08/25/2008] [Indexed: 12/24/2022] Open
Abstract
Phospholipase Cgamma2 (PLCgamma2) is an important signaling effector of multiple receptors in the immune system. Here we show that PLCgamma2-deficient mice displayed impaired lymph node organogenesis but normal splenic structure and Peyer's patches. Receptor activator of NF-kappaB ligand (RANKL) is a tumor necrosis factor family cytokine and is essential for lymph node organogenesis. Importantly, PLCgamma2 deficiency severely impaired RANKL signaling, resulting in marked reduction of RANKL-induced activation of MAPKs, p38 and JNK, but not ERK. The lack of PLCgamma2 markedly diminished RANKL-induced activation of NF-kappaB, AP-1, and NFATc1. Moreover, PLCgamma2 deficiency impaired RANKL-mediated biological function, leading to failure of the PLCgamma2-deficient bone marrow macrophage precursors to differentiate into osteoclasts after RANKL stimulation. Re-introduction of PLCgamma2 but not PLCgamma1 restores RANKL-mediated osteoclast differentiation of PLCgamma2-deficient bone marrow-derived monocyte/macrophage. Taken together, PLCgamma2 is essential for RANK signaling, and its deficiency leads to defective lymph node organogenesis and osteoclast differentiation.
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Affiliation(s)
- Yabing Chen
- Department of Pathology, University of Alabama at Birmingham and Veterans Affairs Medical Center, Birmingham, Alabama 35294, USA
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35
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Verjan N, Ooi EL, Nochi T, Kondo H, Hirono I, Aoki T, Kiyono H, Yuki Y. A soluble nonglycosylated recombinant infectious hematopoietic necrosis virus (IHNV) G-protein induces IFNs in rainbow trout (Oncorhynchus mykiss). FISH & SHELLFISH IMMUNOLOGY 2008; 25:170-180. [PMID: 18499475 DOI: 10.1016/j.fsi.2008.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Revised: 03/31/2008] [Accepted: 04/09/2008] [Indexed: 05/26/2023]
Abstract
Viral glycoproteins interact with cell-surface receptors to mediate virus entry and innate immune system activation. We found that a soluble recombinant infectious hematopoietic necrosis virus G-protein (rIHNV-G) stimulated an early innate immune response mediated by proinflammatory cytokines, IFN1 and IFN-gamma in rainbow trout (Oncorhynchus mykiss) fry. Expression of both IFN1 and IFN-gamma mRNA transcripts was an early event and was rIHNV-G dose-dependent. In addition, preliminary evidence revealed that the innate immune response induced by rIHNV-G protein could protect rainbow trout fry from a subsequent IHNV virus challenge. Finally, the binding and distribution of FITC-rIHNV-G protein on rainbow trout spleen and head kidney leukocytes resemble morphological changes which occur on the cell membrane during antigen-receptor interaction including membrane reorganization, patching, polarization and capping. Thus a soluble nonglycosylated rIHNV-G protein could mediate the activation of rainbow trout leukocytes, with concomitant production of proinflammatory cytokines and IFNs.
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Affiliation(s)
- Noel Verjan
- Division of Mucosal Immunology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
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36
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Sahoo M, Edholm ES, Stafford JL, Bengtén E, Miller NW, Wilson M. B cell receptor accessory molecules in the channel catfish, Ictalurus punctatus. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2008; 32:1385-97. [PMID: 18572245 PMCID: PMC2561914 DOI: 10.1016/j.dci.2008.05.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Revised: 05/13/2008] [Accepted: 05/14/2008] [Indexed: 05/19/2023]
Abstract
B cell receptor (BCR) accessory molecules CD79a and CD79b homologs were identified in the channel catfish, Ictalurus punctatus. Both are found as single copy genes that encode proteins containing a signal peptide, an extracellular immunoglobulin domain, a transmembrane region and a cytoplasmic tail containing an immune-receptor tyrosine-dased activation motif (ITAM). IpCD79a and IpCD79b transcripts correlate well with IgM message expression. They are highly expressed in peripheral blood leukocytes (PBL) enriched in membrane (m) IgM+ cells and catfish clonal B cell lines, but not in catfish clonal T cells, indicating that IpCD79a and IpCD79b expression is B cell restricted. Studies using catfish clonal B cells (3B11) transfected with constructs encoding epitope-tagged IpCD79a and IpCD79b revealed that IpCD79a was expressed as a 45 kDa protein and IpCD79b was expressed as a 32 kDa protein. Furthermore, co-immunoprecipitations of epitope-tagged CD79 proteins demonstrate that these molecules are non-covalently associated with mIgM. These data correlate with some of the previous immunoprecipitation data demonstrating that catfish mIgM associates with proteins of 45 and 32 kDa.
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Affiliation(s)
- Manoranjan Sahoo
- Department of Microbiology, University of Mississippi Medical Center, 2500 North State Street, Jackson MS, 39216, USA
| | - Eva-Stina Edholm
- Department of Microbiology, University of Mississippi Medical Center, 2500 North State Street, Jackson MS, 39216, USA
| | - James L. Stafford
- Department of Biological Sciences Z508, University of Alberta, Edmonton, Alberta Canada T6G 2E9
| | - Eva Bengtén
- Department of Microbiology, University of Mississippi Medical Center, 2500 North State Street, Jackson MS, 39216, USA
| | - Norman W. Miller
- Department of Microbiology, University of Mississippi Medical Center, 2500 North State Street, Jackson MS, 39216, USA
| | - Melanie Wilson
- Department of Microbiology, University of Mississippi Medical Center, 2500 North State Street, Jackson MS, 39216, USA
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37
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Chaturvedi A, Dorward D, Pierce SK. The B cell receptor governs the subcellular location of Toll-like receptor 9 leading to hyperresponses to DNA-containing antigens. Immunity 2008; 28:799-809. [PMID: 18513998 PMCID: PMC2601674 DOI: 10.1016/j.immuni.2008.03.019] [Citation(s) in RCA: 223] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2007] [Revised: 02/27/2008] [Accepted: 03/25/2008] [Indexed: 11/29/2022]
Abstract
Synergistic engagement of the B cell receptor (BCR) and Toll-like receptor 9 (TLR9) in response to DNA-containing antigens underlies the production of many autoantibodies in systemic autoimmune diseases. However, the molecular basis of this synergistic engagement is not known. Given that these receptors are spatially segregated, with the BCR on the cell surface and TLR9 in endocytic vesicles, achieving synergy must involve unique mechanisms. We show that upon antigen binding, the BCR initiates signaling at the plasma membrane and continues to signal to activate MAP kinases as it traffics to autophagosome-like compartments. The internalized BCR signals through a phospholipase-D-dependent pathway to recruit TLR9-containing endosomes to the autophagosome via the microtubular network. The recruitment of TLR9 to the autophagosomes was necessary for hyperactivation of MAP kinases. This unique mechanism for BCR-induced TLR9 recruitment resulting in B cells hyperresponses may provide new targets for therapeutics for autoimmune diseases.
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Affiliation(s)
- Akanksha Chaturvedi
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20852
| | - David Dorward
- Microscopy Unit, Rocky Mountain Laboratories, Research Technologies Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, 59840
| | - Susan K. Pierce
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20852
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38
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Transcription factor Mef2c is required for B cell proliferation and survival after antigen receptor stimulation. Nat Immunol 2008; 9:603-12. [PMID: 18438409 PMCID: PMC2518613 DOI: 10.1038/ni.1609] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Accepted: 03/17/2008] [Indexed: 01/01/2023]
Abstract
Calcineurin is required for B cell receptor (BCR)-induced proliferation of mature B cells. Paradoxically, loss of NFAT transcription factors, themselves calcineurin targets, induces hyperactivity, which suggests that calcineurin targets other than NFAT are required for BCR-induced proliferation. Here we demonstrate a function for the calcineurin-regulated transcription factor Mef2c in B cells. BCR-induced calcium mobilization was intact after Mef2c deletion, but loss of Mef2c caused defects in B cell proliferation and survival after BCR stimulation in vitro and lower T cell-dependent antibody responses and germinal center formation in vivo. Mef2c activity was specific to BCR stimulation, as Toll-like receptor and CD40 signaling induced normal responses in Mef2c-deficient B cells. Mef2c-dependent targets included the genes encoding cyclin D2 and the prosurvival factor Bcl-x(L). Our results emphasize an unrecognized but critical function for Mef2c in BCR signaling.
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39
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Wang J, Bao N, Paris LL, Wang HY, Geahlen RL, Lu C. Detection of kinase translocation using microfluidic electroporative flow cytometry. Anal Chem 2007; 80:1087-93. [PMID: 18154306 DOI: 10.1021/ac702065e] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Directed localization of kinases within cells is important for their activation and involvement in signal transduction. Detection of these events has been largely carried out based on imaging of a low number of cells and subcellular fractionation/Western blotting. These conventional techniques either lack the high throughput desired for probing an entire cell population or provide only the average behaviors of cell populations without information from single cells. Here we demonstrate a new tool, referred to as microfluidic electroporative flow cytometry, to detect the translocation of an EGFP-tagged tyrosine kinase, Syk, to the plasma membrane in B cells at the level of the cell population. We combine electroporation with flow cytometry and observe the release of intracellular kinase out of the cells during electroporation. We found that the release of the kinase was strongly influenced by its subcellular localization. Cells stimulated through the antigen receptor have a fraction of the kinase at the plasma membrane and retain more kinase after electroporation than do cells without stimulation and translocation. We are able to differentiate a cell population with translocation from one without it with the information collected from individual cells of the entire population. This technique potentially allows detection of protein translocation at the single-cell level. Due to the frequent involvement of kinase translocations in disease processes such as oncogenesis, our approach will have utility for kinase-related drug discovery and tumor diagnosis and staging.
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Affiliation(s)
- Jun Wang
- Departments of Agricultural and Biological Engineering, School of Chemical Engineering, Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA
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40
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Abudula A, Grabbe A, Brechmann M, Polaschegg C, Herrmann N, Goldbeck I, Dittmann K, Wienands J. SLP-65 signal transduction requires Src homology 2 domain-mediated membrane anchoring and a kinase-independent adaptor function of Syk. J Biol Chem 2007; 282:29059-29066. [PMID: 17681949 DOI: 10.1074/jbc.m704043200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The family of SLPs (Src homology 2 domain-containing leukocyte adaptor proteins) are cytoplasmic signal effectors of lymphocyte antigen receptors. A main function of SLP is to orchestrate the assembly of Ca(2+)-mobilizing enzymes at the inner leaflet of the plasma membrane. For this purpose, SLP-76 in T cells utilizes the transmembrane adaptor LAT, but the mechanism of SLP-65 membrane anchoring in B cells remains an enigma. We now employed two genetic reconstitution systems to unravel structural requirements of SLP-65 for the initiation of Ca(2+) mobilization and subsequent activation of gene transcription. First, mutational analysis of SLP-65 in DT40 B cells revealed that its C-terminal Src homology 2 domain controls efficient tyrosine phosphorylation by the kinase Syk, plasma membrane recruitment, as well as downstream signaling to NFAT activation. Second, we dissected these processes by expressing SLP-65 in SLP-76-deficient T cells and found that a kinase-independent adaptor function of Syk is required to link phosphorylated SLP-65 to Ca(2+) mobilization. These approaches unmask a mechanistic complexity of SLP-65 activation and coupling to signaling cascades in that Syk is upstream as well as downstream of SLP-65. Moreover, membrane anchoring of the SLP-65-assembled Ca(2+) initiation complex, which appears to be fundamentally different from that of closely related SLP-76, does not necessarily involve a B cell-specific component.
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Affiliation(s)
- Abulizi Abudula
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Annika Grabbe
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Markus Brechmann
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Christian Polaschegg
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Nadine Herrmann
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Ingo Goldbeck
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Kai Dittmann
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany
| | - Jürgen Wienands
- Georg August University of Göttingen, Institute of Cellular & Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany.
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Kitaura Y, Jang IK, Wang Y, Han YC, Inazu T, Cadera EJ, Schlissel M, Hardy RR, Gu H. Control of the B cell-intrinsic tolerance programs by ubiquitin ligases Cbl and Cbl-b. Immunity 2007; 26:567-78. [PMID: 17493844 PMCID: PMC1948079 DOI: 10.1016/j.immuni.2007.03.015] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 01/04/2007] [Accepted: 03/29/2007] [Indexed: 01/13/2023]
Abstract
B cell receptor (BCR) signaling plays a critical role in B cell tolerance and activation. Here, we show that mice with B cell-specific ablation of both Cbl and Cbl-b (Cbl-/-Cblb-/-) manifested systemic lupus erythematosus (SLE)-like autoimmune disease. The Cbl double deficiency resulted in a substantial increase in marginal zone (MZ) and B1 B cells. The mutant B cells were not hyperresponsive in terms of proliferation and antibody production upon BCR stimulation; however, B cell anergy to protein antigen appeared to be impaired. Concomitantly, BCR-proximal signaling, including tyrosine phosphorylation of Syk tyrosine kinase, Phospholipase C-gamma2 (PLC-gamma2), and Rho-family GTP-GDP exchange factor Vav, and Ca2+ mobilization were enhanced, whereas tyrosine phosphorylation of adaptor protein BLNK was substantially attenuated in the mutant B cells. These results suggested that the loss of coordination between these pathways was responsible for the impaired B cell tolerance induction. Thus, Cbl proteins control B cell-intrinsic checkpoint of immune tolerance, possibly through coordinating multiple BCR-proximal signaling pathways during anergy induction.
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Affiliation(s)
- Yasuyuki Kitaura
- Department of Microbiology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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42
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Rogers JV, Choi YW, Giannunzio LF, Sabourin PJ, Bornman DM, Blosser EG, Sabourin CLK. Transcriptional responses in spleens from mice exposed to Yersinia pestis CO92. Microb Pathog 2007; 43:67-77. [PMID: 17531433 DOI: 10.1016/j.micpath.2007.04.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/12/2007] [Indexed: 12/11/2022]
Abstract
Yersinia pestis is one of the most threatening biological agents due to the associated high mortality and history of plague pandemics. Identifying molecular players in the host response to infection may enable the development of medical countermeasures against Y. pestis. In this study, microarrays were used to identify the host splenic response mechanisms to Y. pestis infection. Groups of Balb/c mice were injected intraperitoneally with 2-257CFU of Y. pestis strain CO92 or vehicle. One group was assessed for mortality rates and another group for transcriptional analysis. The time to death at the 8 and 257CFU challenge doses were 5.0+/-2.3 and 3.8+/-0.4 days, respectively. Gene profiling using Affymetrix Mouse Genome 430 2.0 Arrays revealed no probe sets were significantly altered for all five mice in the low-dose group when compared to the vehicle controls. However, 534 probe sets were significantly altered in the high dose versus vehicle controls; 384 probe sets were down-regulated and 150 probe sets were up-regulated. The predominant biological processes identified were immune function, cytoskeletal, apoptosis, cell cycle, and protein degradation. This study provides new information on the underlying transcriptional mechanisms in mice to Y. pestis infection.
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Affiliation(s)
- James V Rogers
- Battelle Memorial Institute, 505 King Avenue, JM-7, Columbus, OH 43201, USA.
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43
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Abstract
p62(dok) and Dok-3 are members of the Dok family of adaptors found in B cells, with the former cloned as a substrate of the p210(bcr/abl) oncoprotein in Ph + chronic myelogenous leukemia. A role for p62(dok) in FcgammaRIIB-mediated negative regulation of B-cell proliferation had been established previously. Here, we generated Dok-3(-/-) mice to assess the function of Dok-3 in B cells. Mice lacking Dok-3 have normal B-cell development but possess higher level of IgM antibodies in their sera. In comparison to wild-type mice, Dok-3(-/-) mice mounted significantly enhanced humoral immune responses to T cell-independent type I and II antigens. Dok-3-deficient B cells hyperproliferated, exhibited elevated level of calcium signaling as well as enhanced activation of NF-kappaB, JNK, and p38MAPK in response to B-cell receptor (BCR) engagement. In the absence of Dok-3, the localization of the inhibitory phosphatase SHIP-1 to the plasma membrane is intact while its phosphorylation is compromised, suggesting that Dok-3 could function to facilitate or sustain the activation of SHIP-1. The phenotype and responses of Dok-3(-/-) mice and B cells could be differentiated from those of the Dok-1(-/-) counterparts. Hence, we propose that Dok-3 plays a distinct and nonredundant role in the negative regulation of BCR signaling.
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Affiliation(s)
- Chee-Hoe Ng
- Laboratory of Molecular and Cellular Immunology, Biomedical Sciences Institutes, Agency for Science, Technology and Research, Proteos, Singapore
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44
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Chen Y, Pappu BP, Zeng H, Xue L, Morris SW, Lin X, Wen R, Wang D. B cell lymphoma 10 is essential for FcepsilonR-mediated degranulation and IL-6 production in mast cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2007; 178:49-57. [PMID: 17182539 DOI: 10.4049/jimmunol.178.1.49] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The adaptor protein B cell lymphoma 10 (Bcl10) plays an essential role in the functions of the AgRs in T and B cells. In this study, we report that Bcl10 also plays an important role in mast cells. Bcl10 is expressed in mast cells. Although Bcl10-deficient mast cells undergo normal development, we demonstrate that Bcl10 is essential for specific functions of FcepsilonR. Although Bcl10-deficient mast cells have normal de novo synthesis and release of the lipid mediator arachidonic acid, the mutant cells possess impaired FcepsilonR-mediated degranulation, indicated by decreased serotonin release, and impaired cytokine production, measured by release of IL-6. In addition, Bcl10-deficient mice display impaired IgE-mediated passive cutaneous anaphylaxis. Moreover, although Bcl10-deficient mast cells have normal FcepsilonR-mediated Ca(2+) flux, activation of PI3K, and activation of the three types of MAPKs (ERKs, JNK, and p38), the mutant cells have markedly diminished FcepsilonR-mediated activation of NF-kappaB and decreased activation of AP-1. Thus, Bcl10 is essential for FcepsilonR-induced activation of AP-1, NF-kappaB, degranulation, and cytokine production in mast cells.
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Affiliation(s)
- Yuhong Chen
- Blood Research Institute, Blood Center of Wisconsin, Milwaukee, WI 53226, USA
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45
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Schuster S, von Kamp A, Pachkov M. Understanding the roadmap of metabolism by pathway analysis. Methods Mol Biol 2007; 358:199-226. [PMID: 17035688 DOI: 10.1007/978-1-59745-244-1_12] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The theoretical investigation of the structure of metabolic systems has recently attracted increasing interest. In this chapter, the basic concepts of metabolic pathway analysis are described and various applications are outlined. In particular, the concepts of nullspace and elementary flux modes are explained. The presentation is illustrated by a simple example from tyrosine metabolism and a system describing lysine production in Corynebacterium glutamicum. The latter system gives rise to 37 elementary modes, 36 of which produce lysine with different molar yields. The examples illustrate that metabolic pathway analysis is a useful tool for better understanding the complex architecture of intracellular metabolism, for determining the pathways on which the molar conversion yield of a substrate-product pair under study is maximal, and for assigning functions to orphan genes (functional genomics). Moreover, problems emerging in the modeling of large networks are discussed. An outlook on current trends in the field concludes the chapter.
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Affiliation(s)
- Stefan Schuster
- Department of Bioinformatics, Friedrich-Schiller University of Jena, Germany
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46
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Xu S, Lee KG, Huo J, Kurosaki T, Lam KP. Combined deficiencies in Bruton tyrosine kinase and phospholipase Cgamma2 arrest B-cell development at a pre-BCR+ stage. Blood 2006; 109:3377-84. [PMID: 17164342 DOI: 10.1182/blood-2006-07-036418] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Bruton tyrosine kinase (Btk) and phospholipase Cgamma2 (PLCgamma2) are 2 key molecules involved in B-cell receptor (BCR) signaling. Biochemical studies have placed them in a linear signaling pathway, with Btk acting upstream of PLCgamma2. Consistent with this, mice lacking either molecule display a leaky but similar block in B-cell development. Here, we generated Btk(-/-) PLCgamma2(-/-) mice and showed that combined deficiencies in Btk and PLCgamma2 severely arrested B lymphopoiesis at the large pre-B-cell stage. In contrast to either single mutant, Btk(-/-) PLCgamma2(-/-) pre-B cells expressed high levels of pre-BCR on their cell surfaces and exhibited reduced immunoglobulin light chain gene rearrangements. Pre-BCR-induced calcium signaling was also drastically compromised in Btk(-/-) PLCgamma2(-/-) pre-B cells compared with wild-type and single-mutant cells. Interestingly, immunoglobulin heavy chain allelic exclusion remained intact in the absence of Btk and PLCgamma2. Overall, our results suggest that Btk and PLCgamma2 have combinatorial roles in regulating pre-B cell differentiation.
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Affiliation(s)
- Shengli Xu
- Laboratory of Molecular and Cellular Immunology, Biomedical Sciences Institute, Agency for Science, Technology and Research, 61 Biopolis Drive, Singapore 138673.
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47
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Abstract
Long-term infection with parasitic worms is generally associated with an immunological phenotype that is Th2-like and anti-inflammatory. This phenotype is probably an unintentional consequence of molecular characteristics of worms (as free-living worms also express polarising molecules) in combination with deliberate attempts by the parasites, via molecular secretions, to modulate the phenotype. This review is concerned with the identity of immunomodulatory worm products, the receptors that they interact with and the signal transduction pathways that they activate. It hopes to indicate how knowledge of these factors can explain the changes in gene expression that result in the characteristic worm-induced immunological phenotype.
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Affiliation(s)
- W Harnett
- Department of Immunology, University of Strathclyde, Glasgow G4 0NR, UK.
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Chen L, Juszczynski P, Takeyama K, Aguiar RCT, Shipp MA. Protein tyrosine phosphatase receptor-type O truncated (PTPROt) regulates SYK phosphorylation, proximal B-cell-receptor signaling, and cellular proliferation. Blood 2006; 108:3428-33. [PMID: 16888096 DOI: 10.1182/blood-2006-03-013821] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The strength and duration of B-cell-receptor (BCR) signaling depends upon the balance between protein tyrosine kinase (PTK) activation and protein tyrosine phosphatase (PTP) inhibition. BCR-dependent activation of the SYK PTK initiates downstream signaling events and amplifies the original BCR signal. Although BCR-associated SYK phosphorylation is clearly regulated by PTPs, SYK has not been identified as a direct PTP substrate. Herein, we demonstrate that SYK is a major substrate of a tissue-specific and developmentally regulated PTP, PTP receptor-type O truncated (PTPROt). PTPROt is a member of the PTPRO family (also designated GLEPP, PTP-Ø, PTP-oc, and PTPu2), a group of highly conserved receptor-type PTPs that are thought to function as tumor suppressor genes. The overexpression of PTPROt inhibited BCR-triggered SYK tyrosyl phosphorylation, activation of the associated adaptor proteins SHC and BLNK, and downstream signaling events, including calcium mobilization and mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) activation. PTPROt overexpression also inhibited lymphoma cell proliferation and induced apoptosis in the absence of BCR cross-linking, suggesting that the phosphatase modulates tonic BCR signaling.
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Affiliation(s)
- Linfeng Chen
- Dana-Farber Cancer Institute, 44 Binney St, Boston, MA 02115, USA
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49
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Zhou F, Hu J, Ma H, Harrison ML, Geahlen RL. Nucleocytoplasmic trafficking of the Syk protein tyrosine kinase. Mol Cell Biol 2006; 26:3478-91. [PMID: 16611990 PMCID: PMC1447433 DOI: 10.1128/mcb.26.9.3478-3491.2006] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The protein tyrosine kinase Syk couples the B-cell receptor (BCR) for antigen to multiple intracellular signaling pathways and also modulates cellular responses to inducers of oxidative stress in a receptor-independent fashion. In B cells, Syk is found in both the nuclear and cytoplasmic compartments but contains no recognizable nuclear localization or export signals. Through the analysis of a series of deletion mutants, we identified the presence of an unconventional shuttling sequence near the junction of the catalytic domain and the linker B region that accounts for Syk's subcellular localization. This localization is altered following prolonged engagement of the BCR, which causes Syk to be excluded from the nucleus. Nuclear exclusion requires the receptor-mediated activation of protein kinase C and new protein synthesis. Both of these processes also potentiate the activation of caspase 3 in cells in response to oxidative stress in a manner that is dependent on the localization of Syk outside of the nucleus. In contrast, restriction of Syk to the nucleus greatly diminishes the stress-induced activation of caspase 3.
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Affiliation(s)
- Fei Zhou
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, 201 S. University St., West Lafayette, IN 47907-2064, USA
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Xu S, Huo J, Chew WK, Hikida M, Kurosaki T, Lam KP. Phospholipase Cγ2 Dosage Is Critical for B Cell Development in the Absence of Adaptor Protein BLNK. THE JOURNAL OF IMMUNOLOGY 2006; 176:4690-8. [PMID: 16585562 DOI: 10.4049/jimmunol.176.8.4690] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
B cell linker (BLNK) protein and phospholipase Cgamma2 (PLCgamma2) are components of the BCR signalosome that activate calcium signaling in B cells. Mice lacking either molecule have a severe but incomplete block in B lymphopoiesis. In this study, we generated BLNK-/- PLCgamma2-/- mice to examine the effect of simultaneous disruption of both molecules on B cell development. We showed that BLNK-/- PLCgamma2-/- mice had compounded defects in B cell maturation compared with either single mutant, suggesting that these two molecules cooperatively or synergistically signaled B lymphopoiesis. However, Ig H chain allelic exclusion was maintained in single and double mutants, indicating that signals propagated by BLNK and PLCgamma2 were not involved in this process. Interestingly, in the absence of BLNK, B cell development was dependent on plcgamma2 gene dosage. This was evidenced by the proportionate decrease in splenic B cell population and increase in bone marrow surface pre-BCR+ cells in PLCgamma2-diploid, -haploid, and -null animals. Intracellular calcium signaling and ERK activation in response to BCR engagement were also proportionately decreased and delayed, respectively, with stepwise reduction of plcgamma2 dosage in a BLNK(null) background. Thus, these data indicate the importance of BLNK not only as a conduit to specifically channel BCR-signaling pathways and as a scaffold for the assembling of macromolecular complex, but also as an efficient aggregator or concentrator of PLCgamma2 molecules to effect optimal signaling for B cell generation and activation.
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Affiliation(s)
- Shengli Xu
- Laboratory of Immunology, Center for Molecular Medicine and Institute of Molecular and Cell Biology, Singapore
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