1
|
Choi J, Ceribelli M, Phelan JD, Häupl B, Huang DW, Wright GW, Hsiao T, Morris V, Ciccarese F, Wang B, Corcoran S, Scheich S, Yu X, Xu W, Yang Y, Zhao H, Zhou J, Zhang G, Muppidi J, Inghirami GG, Oellerich T, Wilson WH, Thomas CJ, Staudt LM. Molecular targets of glucocorticoids that elucidate their therapeutic efficacy in aggressive lymphomas. Cancer Cell 2024; 42:833-849.e12. [PMID: 38701792 PMCID: PMC11168741 DOI: 10.1016/j.ccell.2024.04.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 03/29/2024] [Accepted: 04/09/2024] [Indexed: 05/05/2024]
Abstract
Glucocorticoids have been used for decades to treat lymphomas without an established mechanism of action. Using functional genomic, proteomic, and chemical screens, we discover that glucocorticoids inhibit oncogenic signaling by the B cell receptor (BCR), a recurrent feature of aggressive B cell malignancies, including diffuse large B cell lymphoma and Burkitt lymphoma. Glucocorticoids induce the glucocorticoid receptor (GR) to directly transactivate genes encoding negative regulators of BCR stability (LAPTM5; KLHL14) and the PI3 kinase pathway (INPP5D; DDIT4). GR directly represses transcription of CSK, a kinase that limits the activity of BCR-proximal Src-family kinases. CSK inhibition attenuates the constitutive BCR signaling of lymphomas by hyperactivating Src-family kinases, triggering their ubiquitination and degradation. With the knowledge that glucocorticoids disable oncogenic BCR signaling, they can now be deployed rationally to treat BCR-dependent aggressive lymphomas and used to construct mechanistically sound combination regimens with inhibitors of BTK, PI3 kinase, BCL2, and CSK.
Collapse
MESH Headings
- Humans
- Glucocorticoids/pharmacology
- Receptors, Antigen, B-Cell/metabolism
- Animals
- Signal Transduction/drug effects
- Receptors, Glucocorticoid/metabolism
- Mice
- Cell Line, Tumor
- Lymphoma, Large B-Cell, Diffuse/drug therapy
- Lymphoma, Large B-Cell, Diffuse/genetics
- Lymphoma, Large B-Cell, Diffuse/metabolism
- Burkitt Lymphoma/drug therapy
- Burkitt Lymphoma/genetics
- Burkitt Lymphoma/metabolism
- Burkitt Lymphoma/pathology
- Molecular Targeted Therapy/methods
- Phosphatidylinositol 3-Kinases/metabolism
- src-Family Kinases/metabolism
- Gene Expression Regulation, Neoplastic/drug effects
Collapse
Affiliation(s)
- Jaewoo Choi
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Michele Ceribelli
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD, USA
| | - James D Phelan
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Björn Häupl
- Department of Medicine II, Hematology/Oncology, Goethe University, Frankfurt, Germany; German Cancer Consortium (DKTK), Partner Site Frankfurt/Mainz, 60528 Frankfurt am Main, Germany
| | - Da Wei Huang
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - George W Wright
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Tony Hsiao
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Vivian Morris
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Francesco Ciccarese
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA; Immunology and Molecular Oncology Unit, Veneto Institute of Oncology IOV-IRCCS, via Gattamelata 64, 35128 Padova, Italy
| | - Boya Wang
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Sean Corcoran
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Sebastian Scheich
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA; Department of Medicine II, Hematology/Oncology, Goethe University, Frankfurt, Germany; German Cancer Consortium (DKTK), Partner Site Frankfurt/Mainz, 60528 Frankfurt am Main, Germany; University Cancer Center (UCT) Frankfurt, University Hospital, Goethe University, 60590 Frankfurt am Main, Germany; Frankfurt Cancer Institute, Goethe University, 60596 Frankfurt am Main, Germany
| | - Xin Yu
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Weihong Xu
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Yandan Yang
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Hong Zhao
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Joyce Zhou
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Grace Zhang
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Jagan Muppidi
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Giorgio G Inghirami
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA
| | - Thomas Oellerich
- Department of Medicine II, Hematology/Oncology, Goethe University, Frankfurt, Germany; German Cancer Consortium (DKTK), Partner Site Frankfurt/Mainz, 60528 Frankfurt am Main, Germany
| | - Wyndham H Wilson
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Craig J Thomas
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA; Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD, USA
| | - Louis M Staudt
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
| |
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
Xu Y, Zheng C, Ashaq MS, Zhou Q, Li Y, Lu C, Zhao B. Regulatory role of E3 ubiquitin ligases in normal B lymphopoiesis and B-cell malignancies. Life Sci 2023; 331:122043. [PMID: 37633415 DOI: 10.1016/j.lfs.2023.122043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 08/14/2023] [Accepted: 08/23/2023] [Indexed: 08/28/2023]
Abstract
E3 ubiquitin ligases play an essential role in protein ubiquitination, which is involved in the regulation of protein degradation, protein-protein interactions and signal transduction. Increasing evidences have shed light on the emerging roles of E3 ubiquitin ligases in B-cell development and related malignances. This comprehensive review summarizes the current understanding of E3 ubiquitin ligases in B-cell development and their contribution to B-cell malignances, which could help explore the molecular mechanism of normal B-cell development and provide potential therapeutic targets of the related diseases.
Collapse
Affiliation(s)
- Yan Xu
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; Department of Pharmacology, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Chengzu Zheng
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; Department of Pharmacology, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Muhammad Sameer Ashaq
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; Department of Pharmacology, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Qian Zhou
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; Department of Pharmacology, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Yuan Li
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; Department of Pharmacology, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Chunhua Lu
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Baobing Zhao
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; Department of Pharmacology, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China.
| |
Collapse
|
4
|
Jafari D, Mousavi MJ, Keshavarz Shahbaz S, Jafarzadeh L, Tahmasebi S, Spoor J, Esmaeilzadeh A. E3 ubiquitin ligase Casitas B lineage lymphoma-b and its potential therapeutic implications for immunotherapy. Clin Exp Immunol 2021; 204:14-31. [PMID: 33306199 DOI: 10.1111/cei.13560] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 11/17/2020] [Accepted: 12/02/2020] [Indexed: 12/25/2022] Open
Abstract
The distinction of self from non-self is crucial to prevent autoreactivity and ensure protection from infectious agents and tumors. Maintaining the balance between immunity and tolerance of immune cells is strongly controlled by several sophisticated regulatory mechanisms of the immune system. Among these, the E3 ligase ubiquitin Casitas B cell lymphoma-b (Cbl-b) is a newly identified component in the ubiquitin-dependent protein degradation system, which is thought to be an important negative regulator of immune cells. An update on the current knowledge and new concepts of the relevant immune homeostasis program co-ordinated by Cbl-b in different cell populations could pave the way for future immunomodulatory therapies of various diseases, such as autoimmune and allergic diseases, infections, cancers and other immunopathological conditions. In the present review, the latest findings are comprehensively summarized on the molecular structural basis of Cbl-b and the suppressive signaling mechanisms of Cbl-b in physiological and pathological immune responses, as well as its emerging potential therapeutic implications for immunotherapy in animal models and human diseases.
Collapse
Affiliation(s)
- D Jafari
- Department of Immunology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran.,Immunotherapy Research and Technology Group, Zanjan University of Medical Sciences, Zanjan, Iran
| | - M J Mousavi
- Department of Hematology, Faculty of Allied medicine, Bushehr University of Medical Sciences, Bushehr, Iran.,Department of Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - S Keshavarz Shahbaz
- Department of Immunology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - L Jafarzadeh
- Department of Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - S Tahmasebi
- Department of Immunology, School of public health, Tehran University of Medical Sciences, Tehran, Iran
| | - J Spoor
- Erasmus University Medical Centre, Erasmus University Rotterdam, Rotterdam, the Netherlands
| | - A Esmaeilzadeh
- Department of Immunology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran.,Immunotherapy Research and Technology Group, Zanjan University of Medical Sciences, Zanjan, Iran.,Cancer Gene Therapy Research Center, Zanjan University of Medical Sciences, Zanjan, Iran
| |
Collapse
|
5
|
Beauchamp E, Yap MC, Iyer A, Perinpanayagam MA, Gamma JM, Vincent KM, Lakshmanan M, Raju A, Tergaonkar V, Tan SY, Lim ST, Dong WF, Postovit LM, Read KD, Gray DW, Wyatt PG, Mackey JR, Berthiaume LG. Targeting N-myristoylation for therapy of B-cell lymphomas. Nat Commun 2020; 11:5348. [PMID: 33093447 PMCID: PMC7582192 DOI: 10.1038/s41467-020-18998-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 09/18/2020] [Indexed: 01/05/2023] Open
Abstract
Myristoylation, the N-terminal modification of proteins with the fatty acid myristate, is critical for membrane targeting and cell signaling. Because cancer cells often have increased N-myristoyltransferase (NMT) expression, NMTs were proposed as anti-cancer targets. To systematically investigate this, we performed robotic cancer cell line screens and discovered a marked sensitivity of hematological cancer cell lines, including B-cell lymphomas, to the potent pan-NMT inhibitor PCLX-001. PCLX-001 treatment impacts the global myristoylation of lymphoma cell proteins and inhibits early B-cell receptor (BCR) signaling events critical for survival. In addition to abrogating myristoylation of Src family kinases, PCLX-001 also promotes their degradation and, unexpectedly, that of numerous non-myristoylated BCR effectors including c-Myc, NFκB and P-ERK, leading to cancer cell death in vitro and in xenograft models. Because some treated lymphoma patients experience relapse and die, targeting B-cell lymphomas with a NMT inhibitor potentially provides an additional much needed treatment option for lymphoma.
Collapse
Affiliation(s)
- Erwan Beauchamp
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, T6G 2H7, AB, Canada.,Pacylex Pharmaceuticals Inc., Edmonton, AB, Canada
| | - Megan C Yap
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, T6G 2H7, AB, Canada.,Pacylex Pharmaceuticals Inc., Edmonton, AB, Canada
| | - Aishwarya Iyer
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, T6G 2H7, AB, Canada
| | - Maneka A Perinpanayagam
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, T6G 2H7, AB, Canada.,Pacylex Pharmaceuticals Inc., Edmonton, AB, Canada
| | - Jay M Gamma
- Departments of Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, T6G 2H7, AB, Canada
| | - Krista M Vincent
- Departments of Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, T6G 2H7, AB, Canada
| | - Manikandan Lakshmanan
- Mouse Models of Human Cancer Unit, Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, 138673, Singapore
| | - Anandhkumar Raju
- Advanced Molecular Pathology Lab, Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore, 138673.,Department of Pathology, National University of Singapore, Singapore, Singapore
| | - Vinay Tergaonkar
- Advanced Molecular Pathology Lab, Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore, 138673.,Department of Pathology, National University of Singapore, Singapore, Singapore
| | - Soo Yong Tan
- Advanced Molecular Pathology Lab, Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore, 138673.,Department of Pathology, National University of Singapore, Singapore, Singapore
| | - Soon Thye Lim
- Department of Medical Oncology, National Cancer Centre Singapore, 11 Hospital Drive, Outram Road, Singapore, 169610, Singapore
| | - Wei-Feng Dong
- Departments of Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, T6G 2H7, AB, Canada
| | - Lynne M Postovit
- Departments of Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, T6G 2H7, AB, Canada
| | - Kevin D Read
- Drug Discovery Unit, School of Life Sciences, University of Dundee, James Black Centre, Dow Street, Dundee, DD1 5EH, UK
| | - David W Gray
- Drug Discovery Unit, School of Life Sciences, University of Dundee, James Black Centre, Dow Street, Dundee, DD1 5EH, UK
| | - Paul G Wyatt
- Drug Discovery Unit, School of Life Sciences, University of Dundee, James Black Centre, Dow Street, Dundee, DD1 5EH, UK
| | - John R Mackey
- Pacylex Pharmaceuticals Inc., Edmonton, AB, Canada.,Departments of Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, T6G 2H7, AB, Canada
| | - Luc G Berthiaume
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, T6G 2H7, AB, Canada. .,Pacylex Pharmaceuticals Inc., Edmonton, AB, Canada.
| |
Collapse
|
6
|
Zhang T, Sun J, Cheng J, Yin W, Li J, Miller H, Herrada AA, Gu H, Song H, Chen Y, Gong Q, Liu C. The role of ubiquitinase in B cell development and function. J Leukoc Biol 2020; 109:395-405. [PMID: 32816356 DOI: 10.1002/jlb.1mr0720-185rr] [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: 08/01/2019] [Revised: 07/16/2020] [Accepted: 07/18/2020] [Indexed: 11/10/2022] Open
Abstract
Ubiquitinases are a select group of enzymes that modify target proteins through ubiquitination, which plays a crucial role in the regulation of protein degradation, location, and function. B lymphocytes that originated from bone marrow hematopoietic stem cells (HSC), exert humoral immune functions by differentiating into plasma cells and producing antibodies. Previous studies have shown that ubiquitination is involved in the regulation of the cell cycle and signal transduction important for B lymphocyte development and function. In this review, how ubiquitinases regulate B cell development, activation, apoptosis, and proliferation is discussed, which could help in understanding the physiological processes and diseases related to B cells and also provides potential new targets for further studies.
Collapse
Affiliation(s)
- Tong Zhang
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jianxuan Sun
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jiali Cheng
- Department of hematology, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Wuhan, China
| | - Wei Yin
- Wuhan Children's Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jingwen Li
- Department of hematology, Wuhan Union Hospital, Tongji Medical college, Huazhong University of Science and Technology, Wuhan, China
| | - Heather Miller
- Department of Intracellular Pathogens, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, USA
| | - Andrés A Herrada
- Lymphatic and Inflammation Research Laboratory, Facultad de Ciencias de la Salud, Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, Talca, Chile
| | - Heng Gu
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hongmei Song
- Department of Pediatrics, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, No 1, Shuaifuyuan, Dongcheng District, Beijing, China
| | - Yan Chen
- The Second Department of Pediatrics, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China
| | - Quan Gong
- Department of Immunology, School of Medicine, Yangtze University, Jingzhou, China.,Clinical Molecular Immunology Center, School of Medicine, Yangtze University, Jingzhou, China
| | - Chaohong Liu
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| |
Collapse
|
7
|
Castellanos-Martínez R, Jiménez-Camacho KE, Schnoor M. Cortactin Expression in Hematopoietic Cells. THE AMERICAN JOURNAL OF PATHOLOGY 2020; 190:958-967. [DOI: 10.1016/j.ajpath.2019.12.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 11/28/2019] [Accepted: 12/30/2019] [Indexed: 02/07/2023]
|
8
|
Brian BF, Jolicoeur AS, Guerrero CR, Nunez MG, Sychev ZE, Hegre SA, Sætrom P, Habib N, Drake JM, Schwertfeger KL, Freedman TS. Unique-region phosphorylation targets LynA for rapid degradation, tuning its expression and signaling in myeloid cells. eLife 2019; 8:e46043. [PMID: 31282857 PMCID: PMC6660195 DOI: 10.7554/elife.46043] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 07/06/2019] [Indexed: 12/23/2022] Open
Abstract
The activity of Src-family kinases (SFKs), which phosphorylate immunoreceptor tyrosine-based activation motifs (ITAMs), is a critical factor regulating myeloid-cell activation. We reported previously that the SFK LynA is uniquely susceptible to rapid ubiquitin-mediated degradation in macrophages, functioning as a rheostat regulating signaling (Freedman et al., 2015). We now report the mechanism by which LynA is preferentially targeted for degradation and how cell specificity is built into the LynA rheostat. Using genetic, biochemical, and quantitative phosphopeptide analyses, we found that the E3 ubiquitin ligase c-Cbl preferentially targets LynA via a phosphorylated tyrosine (Y32) in its unique region. This distinct mode of c-Cbl recognition depresses steady-state expression of LynA in macrophages derived from mice. Mast cells, however, express little c-Cbl and have correspondingly high LynA. Upon activation, mast-cell LynA is not rapidly degraded, and SFK-mediated signaling is amplified relative to macrophages. Cell-specific c-Cbl expression thus builds cell specificity into the LynA checkpoint.
Collapse
Affiliation(s)
- Ben F Brian
- Department of PharmacologyUniversity of MinnesotaMinneapolisUnited States
| | | | - Candace R Guerrero
- College of Biological Sciences Center for Mass Spectrometry and ProteomicsUniversity of MinnesotaMinneapolisUnited States
| | - Myra G Nunez
- Department of PharmacologyUniversity of MinnesotaMinneapolisUnited States
| | - Zoi E Sychev
- Department of PharmacologyUniversity of MinnesotaMinneapolisUnited States
| | - Siv A Hegre
- Department of Clinical and Molecular MedicineNorwegian University of Science and TechnologyTrondheimNorway
| | - Pål Sætrom
- Department of Clinical and Molecular MedicineNorwegian University of Science and TechnologyTrondheimNorway
- Department of Computer ScienceNorwegian University of Science and TechnologyTrondheimNorway
| | - Nagy Habib
- Department of Surgery and CancerHammersmith Hospital, Imperial College LondonLondonUnited Kingdom
| | - Justin M Drake
- Department of PharmacologyUniversity of MinnesotaMinneapolisUnited States
- Masonic Cancer CenterUniversity of MinnesotaMinneapolisUnited States
- Department of UrologyUniversity of MinnesotaMinneapolisUnited States
| | - Kathryn L Schwertfeger
- Department of PharmacologyUniversity of MinnesotaMinneapolisUnited States
- Masonic Cancer CenterUniversity of MinnesotaMinneapolisUnited States
- Center for ImmunologyUniversity of MinnesotaMinneapolisUnited States
- Department of Laboratory Medicine and PathologyUniversity of MinnesotaMinneapolisUnited States
| | - Tanya S Freedman
- Department of PharmacologyUniversity of MinnesotaMinneapolisUnited States
- Masonic Cancer CenterUniversity of MinnesotaMinneapolisUnited States
- Center for ImmunologyUniversity of MinnesotaMinneapolisUnited States
- Center for Autoimmune Diseases ResearchUniversity of MinnesotaMinneapolisUnited States
| |
Collapse
|
9
|
Martini V, Frezzato F, Severin F, Raggi F, Trimarco V, Martinello L, Molfetta R, Visentin A, Facco M, Semenzato G, Paolini R, Trentin L. Abnormal regulation of BCR signalling by c-Cbl in chronic lymphocytic leukaemia. Oncotarget 2018; 9:32219-32231. [PMID: 30181811 PMCID: PMC6114956 DOI: 10.18632/oncotarget.25951] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 07/21/2018] [Indexed: 11/25/2022] Open
Abstract
Abnormalities of molecules involved in signal transduction pathways are connected to Chronic Lymphocytic Leukemia (CLL) pathogenesis and a critical role has been already ascribed to B-Cell Receptor (BCR)-Lyn axis. E3 ubiquitin ligase c-Cbl, working together with adapter protein CIN85, controls the degradation of protein kinases involved in BCR signaling. To investigate cell homeostasis in CLL, we studied c-Cbl since in normal B cells it is involved in the ubiquitin-dependent Lyn degradation and in the down-regulation of BCR signaling. We found that c-Cbl is overexpressed and not ubiquitinated after BCR engagement. We observed that c-Cbl did not associate to CIN85 in CLL with respect to normal B cells at steady state, nor following BCR engagement. c-Cbl association to Lyn was not detectable in CLL after BCR stimulation, as it happens in normal B cells. In some CLL patients, c-Cbl is constitutively phosphorylated at Y731 and in the same subjects, it associated to regulatory subunit p85 of PI3K. Moreover, c-Cbl is constitutive associated to Cortactin in those CLL patients presenting Cortactin overexpression and bad prognosis. These results support the hypothesis that c-Cbl, rather than E3 ligase activity, could have an adaptor function in turn influencing cell homeostasis in CLL.
Collapse
Affiliation(s)
- Veronica Martini
- Department of Medicine, Hematology and Clinical Immunology Branch, University School of Medicine, Padua, Italy.,Venetian Institute of Molecular Medicine, VIMM, Padua, Italy
| | - Federica Frezzato
- Department of Medicine, Hematology and Clinical Immunology Branch, University School of Medicine, Padua, Italy.,Venetian Institute of Molecular Medicine, VIMM, Padua, Italy
| | - Filippo Severin
- Department of Medicine, Hematology and Clinical Immunology Branch, University School of Medicine, Padua, Italy.,Venetian Institute of Molecular Medicine, VIMM, Padua, Italy
| | - Flavia Raggi
- Department of Medicine, Hematology and Clinical Immunology Branch, University School of Medicine, Padua, Italy.,Venetian Institute of Molecular Medicine, VIMM, Padua, Italy
| | - Valentina Trimarco
- Department of Medicine, Hematology and Clinical Immunology Branch, University School of Medicine, Padua, Italy.,Venetian Institute of Molecular Medicine, VIMM, Padua, Italy
| | - Leonardo Martinello
- Department of Medicine, Hematology and Clinical Immunology Branch, University School of Medicine, Padua, Italy.,Venetian Institute of Molecular Medicine, VIMM, Padua, Italy
| | - Rosa Molfetta
- Department of Molecular Medicine, University of La Sapienza, Rome, Italy
| | - Andrea Visentin
- Department of Medicine, Hematology and Clinical Immunology Branch, University School of Medicine, Padua, Italy.,Venetian Institute of Molecular Medicine, VIMM, Padua, Italy
| | - Monica Facco
- Department of Medicine, Hematology and Clinical Immunology Branch, University School of Medicine, Padua, Italy.,Venetian Institute of Molecular Medicine, VIMM, Padua, Italy
| | - Gianpietro Semenzato
- Department of Medicine, Hematology and Clinical Immunology Branch, University School of Medicine, Padua, Italy.,Venetian Institute of Molecular Medicine, VIMM, Padua, Italy
| | - Rossella Paolini
- Department of Molecular Medicine, University of La Sapienza, Rome, Italy
| | - Livio Trentin
- Department of Medicine, Hematology and Clinical Immunology Branch, University School of Medicine, Padua, Italy.,Venetian Institute of Molecular Medicine, VIMM, Padua, Italy
| |
Collapse
|
10
|
Allen JC, Talab F, Slupsky JR. Targeting B-cell receptor signaling in leukemia and lymphoma: how and why? Int J Hematol Oncol 2016; 5:37-53. [PMID: 30302202 DOI: 10.2217/ijh-2016-0003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 05/13/2016] [Indexed: 01/04/2023] Open
Abstract
B-lymphocytes are dependent on B-cell receptor (BCR) signaling for the constant maintenance of their physiological function, and in many B-cell malignancies this signaling pathway is prone to aberrant activation. This understanding has led to an ever-increasing interest in the signaling networks activated following ligation of the BCR in both normal and malignant cells, and has been critical in establishing an array of small molecule inhibitors targeting BCR-induced signaling. By dissecting how different malignancies signal through BCR, researchers are contributing to the design of more customized therapeutics which have greater efficacy and lower toxicity than previous therapies. This allows clinicians access to an array of approaches to best treat patients whose malignancies have BCR signaling as a driver of pathogenesis.
Collapse
Affiliation(s)
- John C Allen
- Department of Molecular & Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, L69 3GE, UK.,Department of Molecular & Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, L69 3GE, UK
| | - Fatima Talab
- Redx Oncology Plc, Duncan Building, Royal Liverpool University Hospital, Daulby Street, Liverpool, L69 3GA, UK.,Redx Oncology Plc, Duncan Building, Royal Liverpool University Hospital, Daulby Street, Liverpool, L69 3GA, UK
| | - Joseph R Slupsky
- Department of Molecular & Clinical Cancer Medicine, Institute of Translational Medicine, University of Liverpool, Ashton Street, Liverpool, L69 3GE, UK.,Department of Molecular & Clinical Cancer Medicine, Institute of Translational Medicine, University of Liverpool, Ashton Street, Liverpool, L69 3GE, UK
| |
Collapse
|
11
|
Carson WF, Guernsey LA, Singh A, Secor ER, Wohlfert EA, Clark RB, Schramm CM, Kunkel SL, Thrall RS. Cbl-b Deficiency in Mice Results in Exacerbation of Acute and Chronic Stages of Allergic Asthma. Front Immunol 2015; 6:592. [PMID: 26635806 PMCID: PMC4653292 DOI: 10.3389/fimmu.2015.00592] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 11/04/2015] [Indexed: 01/21/2023] Open
Abstract
Mice sensitized to ovalbumin (OVA) develop allergic airway disease (AAD) with short-term daily OVA aerosol challenge; inflammation resolves with long-term OVA aerosol exposure, resulting in local inhalational tolerance (LIT). Cbl-b is an E3 ubiquitin ligase involved with CD28 signaling; Cbl-b−/− effector T cells are resistant to regulatory T cell-mediated suppression in vitro and in vivo. The present study utilized Cbl-b−/− mice to investigate the role of Cbl-b in the development of AAD and LIT. Cbl-b−/− mice exhibited increased airway inflammation during AAD, which failed to resolve with long-term OVA aerosol exposure. Exacerbation of inflammation in Cbl-b−/− mice correlated with increased proinflammatory cytokine levels and expansion of effector T cells in the BAL during AAD, but did not result in either a modulation of lymphocyte subsets in systemic tissues or in OVA-specific IgE in serum. These results implicate a role for Cbl-b in the resolution of allergic airway inflammation.
Collapse
Affiliation(s)
- William F Carson
- Department of Pathology, University of Michigan , Ann Arbor, MI , USA
| | - Linda A Guernsey
- Department of Immunology, University of Connecticut Health Center , Farmington, CT , USA
| | - Anurag Singh
- Department of Immunology, University of Connecticut Health Center , Farmington, CT , USA
| | - Eric R Secor
- Department of Immunology, University of Connecticut Health Center , Farmington, CT , USA
| | - Elizabeth A Wohlfert
- Department of Pediatrics, University of Connecticut Health Center , Farmington, CT , USA
| | - Robert B Clark
- Department of Immunology, University of Connecticut Health Center , Farmington, CT , USA
| | - Craig M Schramm
- Department of Microbiology and Immunology, University at Buffalo , Buffalo, NY , USA
| | - Steven L Kunkel
- Department of Pathology, University of Michigan , Ann Arbor, MI , USA
| | - Roger S Thrall
- Department of Immunology, University of Connecticut Health Center , Farmington, CT , USA
| |
Collapse
|
12
|
Shintani T, Ohara-Waki F, Kitanaka A, Tanaka T, Kubota Y. Cbl negatively regulates erythropoietin-induced growth and survival signaling through the proteasomal degradation of Src kinase. Blood Cells Mol Dis 2014; 53:211-8. [PMID: 25084697 DOI: 10.1016/j.bcmd.2014.06.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 06/30/2014] [Indexed: 12/12/2022]
Abstract
We examined the biological functions of the gene Cbl in erythropoietin (EPO) signaling using Cbl-deficient F-36P human erythroleukemia cells by the introduction of the Cbl siRNA expression vector. Knockdown of Cbl promoted EPO-dependent proliferation and survival of F-36P cells, especially at a low concentration of EPO (0.01U/mL), similar to serum concentrations of EPO in healthy volunteers (0.005-0.04U/mL). We found that Src was degraded mainly by the proteasomal pathway because the proteasome inhibitor MG-132 but not the lysosome inhibitor NH4Cl suppressed the EPO-induced degradation of Src in F-36P cells and that knockdown of Cbl inhibited EPO-induced ubiquitination and degradation of Src in F-36P cells. The experiments using the Src inhibitor PP1 and co-expression experiments further confirmed that Cbl and the kinase activity of Src are required for the EPO-induced ubiquitination of Src. In addition, the co-expression experiments and in vitro kinase assay demonstrated that the EPO-induced tyrosine phosphorylation and ubiquitination of Cbl were dependent on the kinase activity of Src but not Jak2. Thus, Cbl negatively regulates EPO signaling mainly through the proteasome-dependent degradation of Src, and the E3 ligase activity of Cbl and its tyrosine phosphorylation are regulated by Src but not Jak2.
Collapse
Affiliation(s)
- Takamichi Shintani
- Department of Community Medicine, Faculty of Medicine, Kagawa University, Kagawa 761-0793, Japan
| | - Fusako Ohara-Waki
- Department of Internal Medicine, Takamatsu Red Cross Hospital, Kagawa 760-0017, Japan
| | - Akira Kitanaka
- Department of Gastroenterology and Hematology, Faculty of Medicine, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Terukazu Tanaka
- Faculty of Medicine, Kagawa University, Kagawa 761-0793, Japan
| | - Yoshitsugu Kubota
- Department of Community Medicine, Faculty of Medicine, Kagawa University, Kagawa 761-0793, Japan.
| |
Collapse
|
13
|
Slupsky JR. Does B cell receptor signaling in chronic lymphocytic leukaemia cells differ from that in other B cell types? SCIENTIFICA 2014; 2014:208928. [PMID: 25101192 PMCID: PMC4102070 DOI: 10.1155/2014/208928] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 06/02/2014] [Indexed: 06/03/2023]
Abstract
Chronic lymphocytic leukaemia (CLL) is an incurable malignancy of mature B cells. CLL is important clinically in Western countries because of its commonality and because of the significant morbidity and mortality associated with the progressive form of this incurable disease. The B cell receptor (BCR) expressed on the malignant cells in CLL contributes to disease pathogenesis by providing signals for survival and proliferation, and the signal transduction pathway initiated by engagement of this receptor is now the target of several therapeutic strategies. The purpose of this review is to outline current understanding of the BCR signal cascade in normal B cells and then question whether this understanding applies to CLL cells. In particular, this review studies the phenomenon of anergy in CLL cells, and whether certain adaptations allow the cells to overcome anergy and allow full BCR signaling to take place. Finally, this review analyzes how BCR signals can be therapeutically targeted for the treatment of CLL.
Collapse
Affiliation(s)
- Joseph R. Slupsky
- Department of Molecular and Clinical Cancer Medicine, University of Liverpool, 6th Floor, Duncan Building, Daulby Street, Liverpool L69 3GA, UK
| |
Collapse
|
14
|
Hatton O, Lambert SL, Krams SM, Martinez OM. Src kinase and Syk activation initiate PI3K signaling by a chimeric latent membrane protein 1 in Epstein-Barr virus (EBV)+ B cell lymphomas. PLoS One 2012; 7:e42610. [PMID: 22880054 PMCID: PMC3411813 DOI: 10.1371/journal.pone.0042610] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 07/09/2012] [Indexed: 02/06/2023] Open
Abstract
The B lymphotrophic γ-herpesvirus EBV is associated with a variety of lymphoid- and epithelial-derived malignancies, including B cell lymphomas in immunocompromised and immunosuppressed individuals. The primary oncogene of EBV, latent membrane protein 1 (LMP1), activates the PI3K/Akt pathway to induce the autocrine growth factor, IL-10, in EBV-infected B cells, but the mechanisms underlying PI3K activation remain incompletely understood. Using small molecule inhibition and siRNA strategies in human B cell lines expressing a chimeric, signaling-inducible LMP1 protein, nerve growth factor receptor (NGFR)-LMP1, we show that NGFR-LMP1 utilizes Syk to activate PI3K/Akt signaling and induce IL-10 production. NGFR-LMP1 signaling induces phosphorylation of BLNK, a marker of Syk activation. Whereas Src kinases are often required for Syk activation, we show here that PI3K/Akt activation and autocrine IL-10 production by NGFR-LMP1 involves the Src family kinase Fyn. Finally, we demonstrate that NGFR-LMP1 induces phosphorylation of c-Cbl in a Syk- and Fyn-dependent fashion. Our results indicate that the EBV protein LMP1, which lacks the canonical ITAM required for Syk activation, can nevertheless activate Syk, and the Src kinase Fyn, resulting in downstream c-Cbl and PI3K/Akt activation. Fyn, Syk, and PI3K/Akt antagonists thus may present potential new therapeutic strategies that target the oncogene LMP1 for treatment of EBV+ B cell lymphomas.
Collapse
Affiliation(s)
- Olivia Hatton
- Program in Immunology, Stanford University School of Medicine, Stanford, California, United States of America
- Department of Surgery/Division of Abdominal Transplantation, Stanford University School of Medicine, Stanford, California, United States of America
| | - Stacie L. Lambert
- Program in Immunology, Stanford University School of Medicine, Stanford, California, United States of America
- Department of Surgery/Division of Abdominal Transplantation, Stanford University School of Medicine, Stanford, California, United States of America
| | - Sheri M. Krams
- Program in Immunology, Stanford University School of Medicine, Stanford, California, United States of America
- Department of Surgery/Division of Abdominal Transplantation, Stanford University School of Medicine, Stanford, California, United States of America
| | - Olivia M. Martinez
- Program in Immunology, Stanford University School of Medicine, Stanford, California, United States of America
- Department of Surgery/Division of Abdominal Transplantation, Stanford University School of Medicine, Stanford, California, United States of America
| |
Collapse
|
15
|
|
16
|
Abstract
Protein kinases are important regulators of intracellular signal transduction pathways and play critical roles in diverse cellular functions. Once a protein kinase is activated, its activity is subsequently downregulated through a variety of mechanisms. Accumulating evidence indicates that the activation of protein kinases commonly initiates their downregulation via the ubiquitin/proteasome pathway. Failure to regulate protein kinase activity or expression levels can cause human diseases.
Collapse
Affiliation(s)
- Zhimin Lu
- Department of Neuro-Oncology and Molecular and Cellular Oncology, University of Texas M. D. Anderson Cancer, Houston, TX 77030, USA.
| | | |
Collapse
|
17
|
Dale BM, Traum D, Erdjument-Bromage H, Tempst P, Greenberg S. Phagocytosis in macrophages lacking Cbl reveals an unsuspected role for Fc gamma receptor signaling and actin assembly in target binding. THE JOURNAL OF IMMUNOLOGY 2009; 182:5654-62. [PMID: 19380812 DOI: 10.4049/jimmunol.0803942] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Fc gamma receptor (Fc gammaR)-mediated phagocytosis is known to require tyrosine kinases (TKs). We identified c-Cbl and Cbl-b as proteins that undergo tyrosine phosphorylation during phagocytosis. Cbl-deficient macrophages displayed enhanced Fc gammaR-mediated signaling and phagocytosis. Surprisingly, binding of IgG-coated targets (EIgG) was also enhanced. c-Cbl-deficient macrophages expressed less Fc gammaRIIb, the inhibitory Fc gamma receptor; however, this did not account for enhanced target binding. We isolated the function of one Fc receptor isoform, Fc gammaRI, using IgG2a-coated targets (EIgG2a). Cbl-deficient macrophages demonstrated a disproportionate increase in binding EIgG2a, suggesting that signal strength regulates binding efficiency toward opsonized targets. In resting cells, Fc gammaRI colocalized with the Src family TK Hck in F-actin-rich structures, which was enhanced in Cbl-deficient macrophages. Target binding was sensitive to TK inhibitors, profoundly inhibited following depletion of cholesterol, and ablated at 4 degrees C or in the presence of inhibitors of actin polymerization. Sensitivity of EIgG binding to cytoskeletal disruption was inversely proportional to opsonin density. These findings challenge the view that Fc gammaR-mediated binding is a passive event. They suggest that dynamic engagement of TKs and the cytoskeleton enables macrophages to serve as cellular "Venus fly traps", with the capacity to capture phagocytic targets under conditions of limiting opsonin density.
Collapse
Affiliation(s)
- Benjamin M Dale
- Department of Pharmacology, Columbia University College of Physicians & Surgeons, New York, NY 10032, USA
| | | | | | | | | |
Collapse
|
18
|
|
19
|
Jacob M, Todd L, Sampson MF, Puré E. Dual role of Cbl links critical events in BCR endocytosis. Int Immunol 2008; 20:485-97. [PMID: 18283045 DOI: 10.1093/intimm/dxn010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Receptor endocytosis down-regulates ligand-induced signaling in a timely manner and depends on cytoskeletal remodeling. In B lymphocytes, internalization of B cell receptors (BCRs) is also critical to antigen presentation. However, the mechanisms underlying BCR endocytosis are not fully understood. Similarly, the molecular mechanisms linking endocytosis to cytoskeletal remodeling remain poorly defined. We used flow cytometry, pull-down assays, immunochemistry and fluorescence microscopy to investigate BCR internalization in the DT40 B cell line. We demonstrate that ablation of Cbl impacts BCR endocytosis and the underlying cytoskeletal dynamics. Specifically, we demonstrate that ligand-induced endocytosis is impaired in Cbl-/- cells and that the ubiquitin ligase activity is required for Cbl to promote endocytosis. We also show that phosphorylation of CrkII, activation of Rac downstream of CrkII and BCR capping require Cbl. Furthermore, we show that the association of Cbl and CrkII requires phosphorylation of Cbl, but not its ubiquitin ligase activity. Our data indicate that Cbl promotes BCR endocytosis and attenuates ligand-induced signaling by virtue of its ability to orchestrate receptor ubiquitylation and cytoskeletal dynamics.
Collapse
Affiliation(s)
- Michele Jacob
- Wistar Institute and Ludwig Institute for Cancer Research, 3601 Spruce Street, Philadelphia, PA 19104-4268, USA.
| | | | | | | |
Collapse
|
20
|
Control of virus-specific CD8+ T-cell exhaustion and immune-mediated pathology by E3 ubiquitin ligase Cbl-b during chronic viral infection. J Virol 2008; 82:3353-68. [PMID: 18199651 DOI: 10.1128/jvi.01350-07] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
A characteristic feature in the immune response to many persistent viral infections is the dysfunction or deletion of antigen-specific T cells (exhaustion). This down-regulation of virus-specific T-cell response represents a critical control mechanism that exists within T-cell activation pathways to prevent lethal disease by inappropriate responses against disseminating virus infections. However, the molecular mechanisms by which the immune system determines whether to mount a full response to such infections remain largely unexplored. Here, we have established that in the murine lymphocytic choriomeningitis virus (LCMV) model, induction of the T-cell receptor signaling inhibitor molecule E3 ligase Cbl-b is critically involved in this decision. In particular, our data revealed that Cbl-b controls the program responsible for T-cell tolerance (exhaustion) induction during a chronic viral infection. Thus, Cbl-b(-/-) mice infected with a low dose of LCMV Docile mount a strong CD8(+) T-cell response that rapidly clears the infection, and the animals remain healthy; in contrast, down-regulation of the epitope-specific CD8(+) T-cell population in persistently infected Cbl-b(-/-) mice, compared to that in chronically infected B6 mice, was significantly delayed, and this was associated with increased morbidity and eventual death in nearly 20% of the animals. Interestingly, infection of Cbl-b(-/-) mice with a moderate virus dose resulted in rapid death with 100% mortality by 7 to 8 days after infection, caused by a dysregulated antiviral T-cell response, whereas the infected B6 mice survived and remained healthy. In conclusion, our results suggest that Cbl-b is critically involved in T-cell exhaustion and prevention of lethal disease.
Collapse
|
21
|
Song H, Zhang J, Chiang YJ, Siraganian RP, Hodes RJ. Redundancy in B Cell Developmental Pathways: c-Cbl Inactivation Rescues Early B Cell Development through a B Cell Linker Protein-Independent Pathway. THE JOURNAL OF IMMUNOLOGY 2007; 178:926-35. [PMID: 17202354 DOI: 10.4049/jimmunol.178.2.926] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Deficiency in the adaptor protein B cell linker protein (BLNK) results in a substantial but incomplete block in B cell development, suggesting that alternative pathways exist for B lineage differentiation. Another adaptor protein, c-Cbl, plays a negative regulatory role in several BCR-signaling pathways. We therefore investigated the role of c-Cbl during B cell development and addressed the possibility that redundancies in pathways for B cell differentiation could be further revealed by eliminating negative effects mediated by c-Cbl. Strikingly, c-Cbl inactivation reversed a number of the critical defects in early B cell differentiation that are seen in BLNK-deficient mice. c-Cbl(-/-)BLNK(-/-) mice exhibited normalized down-regulation of pre-BCR and CD43, up-regulation of MHC class II, and augmented L chain rearrangement, resulting in a successful transition from pre-B cells to immature B cells. c-Cbl inactivation also reversed the potentially tumor-predisposing hyperproliferative response of BLNK(-/-) pre-B cells to IL-7. Pre-BCR cross-linking induced enhanced and prolonged tyrosine phosphorylation in c-Cbl(-/-)BLNK(-/-) pre-BCR(+) pre-B cells compared with c-Cbl(+/-)BLNK(-/-) cells, including elevated phosphorylation of Lyn, Syk, Btk, and phospholipase C-gamma2. Our studies suggest that some, but not all, pre-BCR-triggered developmental events can be mediated by BLNK-independent pathways that are negatively regulated by c-Cbl, and further suggest that different events during early B cell development require different strength or duration of pre-BCR signaling.
Collapse
Affiliation(s)
- Haifeng Song
- Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | | | | | | | | |
Collapse
|
22
|
Gustin SE, Thien CBF, Langdon WY. Cbl-b is a negative regulator of inflammatory cytokines produced by IgE-activated mast cells. THE JOURNAL OF IMMUNOLOGY 2006; 177:5980-9. [PMID: 17056522 DOI: 10.4049/jimmunol.177.9.5980] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
c-Cbl and Cbl-b E3 ubiquitin ligases are abundantly expressed in hemopoietic cells where they negatively regulate the activity and levels of many cell surface receptors and associated signaling molecules. By comparing bone marrow-derived mast cells from c-Cbl and Cbl-b-deficient mice it has recently been shown that Cbl-b is the dominant family member for negatively regulating signaling responses from high-affinity IgE receptors. In this study, we suggest that a possible reason for the greater enhancement of IgE receptor signaling in Cbl-b-deficient mice is the relatively higher levels of Cbl-b protein over c-Cbl in mast cells compared with other hemopoietic cells. We also directly compare mast cells from c-Cbl and Cbl-b-deficient mice and find that loss of Cbl-b, but not c-Cbl, increases cell growth, retards receptor internalization, and causes the sustained tyrosine phosphorylation of Syk and its substrates. However, loss of Cbl-b does not enhance the activation of ERK or Akt, nor does it promote a greater calcium response. Furthermore, loss of Cbl-b or c-Cbl does not increase levels of the Syk or Lyn protein tyrosine kinases. Most notable, however, is the extremely large increase in the production of proinflammatory cytokines TNF-alpha, IL-6, and MCP-1 by Cbl-b(-/-) mast cells compared with levels produced by c-Cbl(-/-) or wild-type cells. This marked induction, which appears to be restricted to these three cytokines, is dependent on IgE receptor activation and correlates with enhanced IkappaB kinase phosphorylation. Thus, Cbl-b functions as a potent negative regulator of cytokines that promote allergic and inflammatory reactions.
Collapse
Affiliation(s)
- Sonja E Gustin
- School of Surgery and Pathology, University of Western Australia, Crawley, Western Australia 6009, Australia
| | | | | |
Collapse
|
23
|
Vascotto F, Le Roux D, Lankar D, Faure-André G, Vargas P, Guermonprez P, Lennon-Duménil AM. Antigen presentation by B lymphocytes: how receptor signaling directs membrane trafficking. Curr Opin Immunol 2006; 19:93-8. [PMID: 17140785 DOI: 10.1016/j.coi.2006.11.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2006] [Accepted: 11/21/2006] [Indexed: 12/16/2022]
Abstract
Antigen capture and presentation onto MHC class II molecules by B lymphocytes is mediated by their surface antigen receptor - the B-cell receptor (BCR). The BCR must therefore coordinate the transport of MHC class II- and antigen-containing vesicles for them to converge and ensure efficient processing. Recently, progress has been made in understanding which and how these vesicular transport events are molecularly linked to BCR signaling. In particular, recent studies have emphasized the key roles of membrane microdomains and the actin cytoskeleton in regulation of membrane trafficking upon BCR engagement.
Collapse
Affiliation(s)
- Fulvia Vascotto
- Unité Inserm 653, Institut Curie, 12 rue Lhomond, 75005, Paris, France
| | | | | | | | | | | | | |
Collapse
|
24
|
Dragone LL, Myers MD, White C, Gadwal S, Sosinowski T, Gu H, Weiss A. Src-like adaptor protein (SLAP) regulates B cell receptor levels in a c-Cbl-dependent manner. Proc Natl Acad Sci U S A 2006; 103:18202-7. [PMID: 17110436 PMCID: PMC1838730 DOI: 10.1073/pnas.0608965103] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Src-like adaptor protein (SLAP) and c-Cbl recently have been shown to cooperate in regulating T cell receptor (TCR) levels in developing T cells. SLAP also is expressed in developing B cells, and its deficiency leads to alterations in B cell receptor (BCR) levels and B cell development. Hence, we hypothesized that SLAP and c-Cbl may cooperate during B cell development to regulate BCR levels. In mice deficient in both SLAP and c-Cbl, we found that B cell development is altered, suggesting that they function through intersecting pathways. To study the mechanism by which SLAP and c-Cbl alter BCR levels, we coexpressed them in a mature mouse B cell line (Bal-17). First we determined that SLAP associates with proximal components of the BCR complex after stimulation and internalization. Coexpression of SLAP and c-Cbl in Bal-17 led to decreased surface and total BCR levels. This decrease in BCR levels depended on intact Src homology 2 (SH2) and C-terminal domains of SLAP. In addition, a mutation in the SH2 domain of SLAP blocked its colocalization with c-Cbl and the BCR complex, whereas deletion of the C terminus did not affect its localization. Last, coexpression of SLAP and c-Cbl altered BCR complex recycling. This alteration in BCR complex recycling depended on enzymatically active c-Cbl and Src family kinases, as well as the intact SH2 and C-terminal domains of SLAP. These data suggest that SLAP has a conserved function in B and T cells by adapting c-Cbl to the antigen-receptor complex and targeting it for degradation.
Collapse
Affiliation(s)
- Leonard L. Dragone
- Division of Pediatric Immunology/Rheumatology, Department of Pediatrics, and
| | - Margaret D. Myers
- Howard Hughes Medical Institute
- Division of Rheumatology, Department of Medicine, and
- Rosalind Russell Medical Research Center for Arthritis, University of California, San Francisco, CA 94143
| | - Carmen White
- Division of Pediatric Immunology/Rheumatology, Department of Pediatrics, and
| | - Shyam Gadwal
- University of Maryland Baltimore County, Baltimore, MD 21250
| | | | - Hua Gu
- Microbiology Department, Columbia University, College of Physician and Surgeons, New York, NY 10032
| | - Arthur Weiss
- Howard Hughes Medical Institute
- Division of Rheumatology, Department of Medicine, and
- Rosalind Russell Medical Research Center for Arthritis, University of California, San Francisco, CA 94143
- To whom correspondence should be addressed at:
Howard Hughes Medical Institute, University of California, 513 Parnassus Avenue, Box 0795, San Francisco, CA 94143. E-mail:
| |
Collapse
|
25
|
Swaminathan G, Tsygankov AY. The Cbl family proteins: ring leaders in regulation of cell signaling. J Cell Physiol 2006; 209:21-43. [PMID: 16741904 DOI: 10.1002/jcp.20694] [Citation(s) in RCA: 228] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The proto-oncogenic protein c-Cbl was discovered as the cellular form of v-Cbl, a retroviral transforming protein. This was followed over the years by important discoveries, which identified c-Cbl and other Cbl-family proteins as key players in several signaling pathways. c-Cbl has donned the role of a multivalent adaptor protein, capable of interacting with a plethora of proteins, and has been shown to positively influence certain biological processes. The identity of c-Cbl as an E3 ubiquitin ligase unveiled the existence of an important negative regulatory pathway involved in maintaining homeostasis in protein tyrosine kinase (PTK) signaling. Recent years have also seen the emergence of novel regulators of Cbl, which have provided further insights into the complexity of Cbl-influenced pathways. This review will endeavor to provide a summary of current studies focused on the effects of Cbl proteins on various biological processes and the mechanism of these effects. The major sections of the review are as follows: Structure and genomic organization of Cbl proteins; Phosphorylation of Cbl; Interactions of Cbl; Localization of Cbl; Mechanism of effects of Cbl: (a) Ubiquitylation-dependent events: This section elucidates the mechanism of Cbl-mediated downregulation of EGFR and details the PTK and non-PTKs targeted by Cbl. In addition, it addresses the functional requirements for E3 Ubiquitin ligase activity of Cbl and negative regulation of Cbl-mediated downregulation of PTKs, (b) Adaptor functions: This section discusses the mechanisms of adaptor functions of Cbl in mitogen-activated protein kinase (MAPK) activation, insulin signaling, regulation of Ras-related protein 1 (Rap1), PI-3' kinase signaling, and regulation of Rho-family GTPases and cytoskeleton; Biological functions: This section gives an account of the diverse biological functions of Cbl and includes the role of Cbl in transformation, T-cell signaling and thymus development, B-cell signaling, mast-cell degranulation, macrophage functions, bone development, neurite growth, platelet activation, muscle degeneration, and bacterial invasion; Conclusions and perspectives.
Collapse
Affiliation(s)
- Gayathri Swaminathan
- Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
| | | |
Collapse
|
26
|
Drake L, McGovern-Brindisi EM, Drake JR. BCR ubiquitination controls BCR-mediated antigen processing and presentation. Blood 2006; 108:4086-93. [PMID: 16931624 PMCID: PMC1895444 DOI: 10.1182/blood-2006-05-025338] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
BCR-mediated antigen processing occurs at immunologically relevant antigen concentrations and hinges on the trafficking of antigen-BCR (Ag-BCR) complexes to class II-containing multivesicular bodies (MVBs) termed MIICs. However, the molecular mechanism underlying the trafficking of Ag-BCR complexes to and within MIICs is not well understood. In contrast, the trafficking of the epidermal growth factor receptor (EGFR) to and within MVBs occurs via a well-characterized ubiquitin-dependent mechanism, which is blocked by acute inhibition of proteasome activity. Using a highly characterized antigen-specific model system, it was determined that the immunoglobulin heavy chain subunit of the IgM BCR of normal (ie, nontransformed) B cells is ubiquitinated. Moreover, acute inhibition of proteasome activity delays the formation of ubiquitinated ligand-BCR complexes, alters the intracellular trafficking of internalized Ag-BCR complexes, and selectively blocks the BCR-mediated processing and presentation of cognate antigen, without inhibiting the endocytosis, processing, and presentation of non-cognate antigen internalized by fluidphase endocytosis. These results demonstrate that the trafficking of Ag-BCR complexes to and within MVB-like antigen processing compartments occurs via a molecular mechanism with similarities to that used by the EGFR, and establishes the EGFR as a paradigm for the further analysis of Ag-BCR trafficking to and within MIICs.
Collapse
Affiliation(s)
- Lisa Drake
- Albany Medical College, Center for Immunology and Microbial Disease, 47 New Scotland Ave, MC-151, Albany, NY 12208, USA.
| | | | | |
Collapse
|
27
|
Gazumyan A, Reichlin A, Nussenzweig MC. Ig beta tyrosine residues contribute to the control of B cell receptor signaling by regulating receptor internalization. J Exp Med 2006; 203:1785-94. [PMID: 16818674 PMCID: PMC2118343 DOI: 10.1084/jem.20060221] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Accepted: 06/02/2006] [Indexed: 12/14/2022] Open
Abstract
Immunoglobulin (Ig)alpha and Igbeta initiate B cell receptor (BCR) signaling through immune receptor tyrosine activation motifs (ITAMs) that are targets of SH2 domain-containing kinases. To examine the function of Igbeta ITAM tyrosine resides in mature B cells in vivo, we exchanged these residues for alanine by gene targeting (Igbeta(AA)). Mutant mice showed normal development of all B cell subtypes with the exception of B1 cells that were reduced by fivefold. However, primary B cells purified from Igbeta(AA) mice showed significantly decreased steady-state and ligand-mediated BCR internalization and higher levels of cell surface IgM and IgD. BCR cross-linking resulted in decreased Src and Syk activation but paradoxically enhanced and prolonged BCR signaling, as measured by cellular tyrosine phosphorylation, Ca(++) flux, AKT, and ERK activation. In addition, B cells with the ITAM mutant receptor showed an enhanced response to a T-independent antigen. Thus, Igbeta ITAM tyrosines help set BCR signaling threshold by regulating receptor internalization.
Collapse
Affiliation(s)
- Anna Gazumyan
- Laboratory of Molecular Immunology and 2Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10021, USA.
| | | | | |
Collapse
|
28
|
Ross FP, Teitelbaum SL. alphavbeta3 and macrophage colony-stimulating factor: partners in osteoclast biology. Immunol Rev 2005; 208:88-105. [PMID: 16313343 DOI: 10.1111/j.0105-2896.2005.00331.x] [Citation(s) in RCA: 240] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Osteoclasts, the sole bone-resorbing cells, arise by fusion and differentiation of monocyte/macrophage precursors. Matrix degradation requires adhesion of the osteoclast to bone, an integrin alphavbeta3-mediated event that also stimulates signals which polarize the cell and secrete resorptive molecules such as hydrochloric acid and acidic proteases. Two cytokines are necessary and sufficient for osteoclastogenesis, receptor activator of nuclear factor kappaB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF), both produced by mesenchymal cells in the bone marrow environment. M-CSF promotes survival and proliferation of osteoclast precursors. It also contributes to their differentiation and regulates the cytoskeletal changes that accompany bone resorption. Binding of M-CSF to c-Fms, its receptor, recruits adapter proteins and cytosolic kinases, thereby activating a variety of intracellular signals. We herein review how alphavbeta3 and M-CSF, alone and in concert, impact production, survival, and function of the osteoclast, thereby controlling skeletal mass. Signals from alphavbeta3 and/or c-Fms activate Syk and Vav3, originally defined by their function in lymphoid cells. Genetic depletion of either protein generates a strong bone phenotype, underscoring the promise of osteoimmunobiology.
Collapse
Affiliation(s)
- F Patrick Ross
- Washington University School of Medicine, St. Louis, MO 63110, USA.
| | | |
Collapse
|
29
|
Kepley CL. Antigen-Induced Reduction in Mast Cell and Basophil Functional Responses due to Reduced Syk Protein Levels. Int Arch Allergy Immunol 2005; 138:29-39. [PMID: 16088210 DOI: 10.1159/000087355] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Accepted: 04/07/2005] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The high-affinity IgE receptor, FcepsilonRI, is unresponsive on mast cells and basophils from people in several populations through an unknown mechanism. Similarly, FcepsilonRI-positive basophils from 'nonreleasers' are IgE-unresponsive and are deficient in the tyrosine kinase Syk. OBJECTIVE To test the hypothesis that cross-linking FcepsilonRI on mast cells and basophils leads to FcepsilonRI nonresponsiveness through reduction in Syk protein levels. METHODS Human mast cells and basophils were used to determine if FcepsilonRI hyporesponsiveness correlated with reduced Syk levels. RESULTS It is shown that suboptimal antigen challenge, that did not lead to significant mediator release, induced nonresponsiveness and correlated with reduced Syk. Other IgE-associated signaling molecules were unaffected by the same treatment. The ability of IgE-unresponsive mast cells to regain FcepsilonRI responsiveness is paralleled by increased cellular Syk levels in vitro. The reduction of Syk levels with suboptimal antigen concentrations was calcium independent and mediated through a proteasome-dependent mechanism. CONCLUSION These findings confirm and extend our knowledge about a novel regulatory mechanism for maintaining FcepsilonRI in a quiescent state. This mechanism may also explain why low concentrations of allergen given to patients during allergen immunotherapy induce FcepsilonRI nonresponsiveness and therapeutic benefit without inducing systemic anaphylaxis.
Collapse
Affiliation(s)
- Christopher L Kepley
- Division of Rheumatology, Allergy and Immunology, Department of Internal Medicine, Virginia Commonwealth University Health Systems, Richmond, VA 23298, USA.
| |
Collapse
|
30
|
Flores-Borja F, Kabouridis PS, Jury EC, Isenberg DA, Mageed RA. Decreased Lyn expression and translocation to lipid raft signaling domains in B lymphocytes from patients with systemic lupus erythematosus. ACTA ACUST UNITED AC 2005; 52:3955-65. [PMID: 16320343 DOI: 10.1002/art.21416] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE B lymphocytes from patients with systemic lupus erythematosus (SLE) are hyperactive and produce anti-double-stranded DNA (anti-dsDNA) autoantibodies. The cause or causes of B cell defects in SLE are unknown. In this study, we determined the level and subcellular distribution of Lyn protein, a key negative regulator of B cell receptor signaling, and assessed whether altered Lyn expression is characteristic of B cells in the setting of SLE. METHODS Negative selection was used to isolate B lymphocytes from blood. Lipid raft signaling domains were purified from B cells obtained from 62 patients with SLE, 15 patients with rheumatoid arthritis, and 31 healthy controls, by gradient ultracentrifugation. The total Lyn protein level was determined by Western blotting, confocal microscopy, and fluorescein-activated cell sorting (FACS). The distribution of Lyn into lipid raft and nonlipid raft domains was determined by Western blotting and confocal microscopy. Lyn content in B cell subpopulations was determined by FACS. In order to assess B lymphocyte activity, we used (3)H-thymidine incorporation and enzyme-linked immunosorbent assay to measure spontaneous proliferation and IgG and cytokine production by B cells. RESULTS This study revealed that B lymphocytes from a majority of patients with SLE have a reduced level of Lyn and manifest altered translocation to lipid rafts. An investigation into the mechanisms of Lyn reduction suggested that increased ubiquitination is involved. This was evident from increased ubiquitination of Lyn and translocation of c-Cbl into lipid rafts. Studies of B cell responses showed that altered Lyn expression was associated with heightened spontaneous proliferation, anti-dsDNA autoantibodies, and increased interleukin-10 production. CONCLUSION This study provides evidence for altered Lyn expression in B cells from a majority of patients with SLE. Altered Lyn expression in SLE may influence the B cell receptor signaling and B cell hyperactivity that are characteristic of the disease.
Collapse
Affiliation(s)
- Fabian Flores-Borja
- William Harvey Institute, Queen Mary School of Medicine and Dentistry, London, UK
| | | | | | | | | |
Collapse
|