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Oswald J, Constantine M, Adegbuyi A, Omorogbe E, Dellomo AJ, Ehrlich ES. E3 Ubiquitin Ligases in Gammaherpesviruses and HIV: A Review of Virus Adaptation and Exploitation. Viruses 2023; 15:1935. [PMID: 37766341 PMCID: PMC10535929 DOI: 10.3390/v15091935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 09/10/2023] [Accepted: 09/12/2023] [Indexed: 09/29/2023] Open
Abstract
For productive infection and replication to occur, viruses must control cellular machinery and counteract restriction factors and antiviral proteins. Viruses can accomplish this, in part, via the regulation of cellular gene expression and post-transcriptional and post-translational control. Many viruses co-opt and counteract cellular processes via modulation of the host post-translational modification machinery and encoding or hijacking kinases, SUMO ligases, deubiquitinases, and ubiquitin ligases, in addition to other modifiers. In this review, we focus on three oncoviruses, Epstein-Barr virus (EBV), Kaposi's sarcoma herpesvirus (KSHV), and human immunodeficiency virus (HIV) and their interactions with the ubiquitin-proteasome system via viral-encoded or cellular E3 ubiquitin ligase activity.
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Affiliation(s)
| | | | | | | | | | - Elana S. Ehrlich
- Department of Biological Sciences, Towson University, Towson, MD 21252, USA
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2
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The Central Role of the Ubiquitin-Proteasome System in EBV-Mediated Oncogenesis. Cancers (Basel) 2022; 14:cancers14030611. [PMID: 35158879 PMCID: PMC8833352 DOI: 10.3390/cancers14030611] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 01/19/2022] [Accepted: 01/24/2022] [Indexed: 12/30/2022] Open
Abstract
Simple Summary Epstein–Barr virus (EBV) is the first discovered human tumor virus, which contributes to the oncogenesis of many human cancers. The ubiquitin–proteasome system is a key player during EBV-mediated oncogenesis and has been developed as a crucial therapeutic target for treatment. In this review, we briefly describe how EBV antigens can modulate the ubiquitin–proteasome system for targeted protein degradation and how they are regulated in the EBV life cycle to mediate oncogenesis. Additionally, the developed proteasome inhibitors are discussed for the treatment of EBV-associated cancers. Abstract Deregulation of the ubiquitin–proteasome system (UPS) plays a critical role in the development of numerous human cancers. Epstein–Barr virus (EBV), the first known human tumor virus, has evolved distinct molecular mechanisms to manipulate the ubiquitin–proteasome system, facilitate its successful infection, and drive opportunistic cancers. The interactions of EBV antigens with the ubiquitin–proteasome system can lead to oncogenesis through the targeting of cellular factors involved in proliferation. Recent studies highlight the central role of the ubiquitin–proteasome system in EBV infection. This review will summarize the versatile strategies in EBV-mediated oncogenesis that contribute to the development of specific therapeutic approaches to treat EBV-associated malignancies.
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Tsang CM, Lui VWY, Bruce JP, Pugh TJ, Lo KW. Translational genomics of nasopharyngeal cancer. Semin Cancer Biol 2019; 61:84-100. [PMID: 31521748 DOI: 10.1016/j.semcancer.2019.09.006] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 09/11/2019] [Accepted: 09/11/2019] [Indexed: 12/26/2022]
Abstract
Nasopharyngeal carcinoma (NPC), also named the Cantonese cancer, is a unique cancer with strong etiological association with infection of the Epstein-Barr virus (EBV). With particularly high prevalence in Southeast Asia, the involvement of EBV and genetic aberrations contributive to NPC tumorigenesis have remained unclear for decades. Recently, genomic analysis of NPC has defined it as a genetically homogeneous cancer, driven largely by NF-κB signaling caused by either somatic aberrations of NF-κB negative regulators or by overexpression of the latent membrane protein 1 (LMP1), an EBV viral oncoprotein. This represents a landmark finding of the NPC genome. Exome and RNA sequencing data from new EBV-positive NPC models also highlight the importance of PI3K pathway aberrations in NPC. We also realize for the first time that NPC mutational burden, mutational signatures, MAPK/PI3K aberrations, and MHC Class I gene aberrations, are prognostic for patient outcome. Together, these multiple genomic discoveries begin to shape the focus of NPC therapy development. Given the challenge of NF-κB targeting in human cancers, more innovative drug discovery approaches should be explored to target the unique atypical NF-κB activation feature of NPC. Our next decade of NPC research should focus on further identification of the -omic landscapes of recurrent and metastatic NPC, development of gene-based precision medicines, as well as large-scale drug screening with the newly developed and well-characterized EBV-positive NPC models. Focused preclinical and clinical investigations on these major directions may identify new and effective targeting strategies to further improve survival of NPC patients.
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Affiliation(s)
- Chi Man Tsang
- Department of Anatomical and cellular Pathology and State Key Laboratory of Translational Oncology, The Chinese University of Hong Kong, Hong Kong Special Administrative Region
| | - Vivian Wai Yan Lui
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong Special Administrative Region
| | - Jeffrey P Bruce
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, M5G 1L7, Canada
| | - Trevor J Pugh
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, M5G 1L7, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, M5G 1L7, Canada; Ontario Institute for Cancer Research, Toronto, ON, M5G 1L7, Canada
| | - Kwok Wai Lo
- Department of Anatomical and cellular Pathology and State Key Laboratory of Translational Oncology, The Chinese University of Hong Kong, Hong Kong Special Administrative Region.
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4
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Yu G, Hsu WL, Coghill AE, Yu KJ, Wang CP, Lou PJ, Liu Z, Jones K, Vogt A, Wang M, Mbulaiteye SM, Chen HH, Boland J, Yeager M, Diehl SR, Chen CJ, Hildesheim A, Goldstein AM. Whole-Exome Sequencing of Nasopharyngeal Carcinoma Families Reveals Novel Variants Potentially Involved in Nasopharyngeal Carcinoma. Sci Rep 2019; 9:9916. [PMID: 31289279 PMCID: PMC6617453 DOI: 10.1038/s41598-019-46137-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 06/17/2019] [Indexed: 02/06/2023] Open
Abstract
Genetic susceptibility is likely involved in nasopharyngeal carcinoma (NPC), a cancer caused by Epstein-Barr virus (EBV) infection. Understanding of genetic factors involved in NPC and how they contribute to EBV-induced carcinogenesis is limited. We conducted whole-exome capture/sequencing among 251 individuals from 97 multiplex families from Taiwan (205 affected, 21 obligate carriers, and 25 unaffected) using SeqCap EZ Human Exome Library v3.0 and Illumina HiSeq. Aligned sequences were filtered to identify likely-to-be-functional deleterious variants that co-segregated with disease. Ingenuity Pathway analysis was performed. Circulating magnesium levels were measured in 13 individuals in 2 families with NIPAL1 mutations and in 197 sporadic NPC cases and 237 controls. We identified variants in 12 genes likely involved in cancer pathogenesis, viral infection or immune responses to infection. These included genes postulated to be involved in magnesium transport (NIPAL1), EBV cell entry (ITGB6), modulation of EBV infection (BCL2L12, NEDD4L), telomere biology (CLPTM1L, BRD2, HNRNPU), modulation of cAMP signaling (RAPGEF3), DNA repair (PRKDC, MLH1), and Notch signaling (NOTCH1, DLL3). Pathway based analysis demonstrated enrichment for Notch signaling genes (p-value = 0.0006). Evaluation of individuals within NIPAL1 families suggested lower serum magnesium in NPC compared to unaffected members. A significant reduction in serum magnesium levels was observed among sporadic NPC cases compared to controls (7.1% NPC/1.7% controls below normal range; OR = 4.5; 95% CI = 1.4,14) and is consistent with findings demonstrating a role for magnesium channeling in T-cell responses to EBV. We identified novel genes associated with NPC that point to new areas of inquiry to better understand genetic factors that determine the fate of viral infections and/or otherwise predisposes to NPC.
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Affiliation(s)
- Guoqin Yu
- Integrative Tumor Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA, 20892
| | - Wan-Lun Hsu
- Genomics Research Center, Academia Sinica, and Graduate Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan
| | - Anna E Coghill
- Infections and Immunoepidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA, 20892
| | - Kelly J Yu
- Infections and Immunoepidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA, 20892
| | - Cheng-Ping Wang
- Department of Otolaryngology, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan
| | - Pei-Jen Lou
- Department of Otolaryngology, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan
| | - Zhiwei Liu
- Infections and Immunoepidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA, 20892
| | - Kristie Jones
- Cancer Genomics Research Laboratory, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20892 and LEIDOS, Frederick, MD, USA
| | - Aurelie Vogt
- Cancer Genomics Research Laboratory, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20892 and LEIDOS, Frederick, MD, USA
| | - Mingyi Wang
- Cancer Genomics Research Laboratory, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20892 and LEIDOS, Frederick, MD, USA
| | - Sam M Mbulaiteye
- Infections and Immunoepidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA, 20892
| | - Hao-Hui Chen
- Department of Otolaryngology, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan
| | - Joseph Boland
- Cancer Genomics Research Laboratory, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20892 and LEIDOS, Frederick, MD, USA
| | - Meredith Yeager
- Cancer Genomics Research Laboratory, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20892 and LEIDOS, Frederick, MD, USA
| | | | - Chien-Jen Chen
- Genomics Research Center, Academia Sinica, and Graduate Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan
| | - Allan Hildesheim
- Infections and Immunoepidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA, 20892.
| | - Alisa M Goldstein
- Clinical Genetics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA, 20892.
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Regulation of autoimmune disease by the E3 ubiquitin ligase Itch. Cell Immunol 2019; 340:103916. [PMID: 31126634 DOI: 10.1016/j.cellimm.2019.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 04/03/2019] [Indexed: 12/14/2022]
Abstract
Itch is a HECT type E3 ubiquitin ligase that is required to prevent the development of autoimmune disease in both mice and humans. Itch is expressed in most mammalian cell types, and, based on published data, it regulates many cellular pathways ranging from T cell differentiation to liver tumorigenesis. Since 1998, when Itch was first discovered, hundreds of publications have described mechanisms through which Itch controls various biologic activities in both immune and non-immune cells. Other studies have provided insight into how Itch catalytic activity is regulated. However, while autoimmunity is the primary clinical feature that occurs in both mice and humans lacking Itch, and Itch control of immune cell function has been well-studied, it remains unclear how Itch prevents the emergence of autoimmune disease. In this review, we explore recent discoveries that advance our understanding of how Itch regulates immune cell biology, and the extent to which these clarify how Itch prevents autoimmune disease. Additionally, we discuss how molecular regulators of Itch impact its ability to control these processes, as this may provide clues on how to therapeutically target Itch to treat patients with autoimmune disease.
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Spleen Tyrosine Kinase Inhibitor TAK-659 Prevents Splenomegaly and Tumor Development in a Murine Model of Epstein-Barr Virus-Associated Lymphoma. mSphere 2018; 3:3/4/e00378-18. [PMID: 30135222 PMCID: PMC6106053 DOI: 10.1128/mspheredirect.00378-18] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The novel SYK and FLT3 inhibitor TAK-659 prevents the enlargement of spleen and tumor development in a mouse model of EBV-associated lymphoma by counteracting the activation of cellular kinase SYK through the viral LMP2A gene by inducing cell death in tumor cells but not in nontumor cells. These findings indicate that TAK-659 may be a very effective nontoxic therapeutic molecule especially for EBV-positive hematologic malignancies. Epstein-Barr virus (EBV) is associated with several B and epithelial cell cancers. EBV-encoded latent membrane protein 2A (LMP2A) contributes to cellular transformation by mimicking B cell receptor signaling. LMP2A/MYC double transgenic mice develop splenomegaly and B cell lymphoma much faster than MYC transgenic mice do. In this study, we explored the potential therapeutic efficacy of a novel spleen tyrosine kinase (SYK) and FLT3 inhibitor TAK-659 for development of a treatment option for EBV-associated malignancies. In our transgenic model, TAK-659 treatment totally abrogated splenomegaly and tumor development in LMP2A/MYC mice in both pretumor and tumor cell transfer experiments. TAK-659 treatment killed tumor cells, but not host cells within the spleen and tumors. Furthermore, TAK-659 treatment abrogated metastasis of tumor cells into bone marrow. Our data also show that TAK-659 inhibits SYK phosphorylation and induces apoptosis in LMP2A/MYC tumor cells at low nanomolar concentrations. Therefore, TAK-659 may provide an effective therapeutic option for treatment of LMP2A-positive EBV-associated malignancies and should be explored further in clinical trials. IMPORTANCE The novel SYK and FLT3 inhibitor TAK-659 prevents the enlargement of spleen and tumor development in a mouse model of EBV-associated lymphoma by counteracting the activation of cellular kinase SYK through the viral LMP2A gene by inducing cell death in tumor cells but not in nontumor cells. These findings indicate that TAK-659 may be a very effective nontoxic therapeutic molecule especially for EBV-positive hematologic malignancies.
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7
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Global Proteomic Changes Induced by the Epstein-Barr Virus Oncoproteins Latent Membrane Protein 1 and 2A. mBio 2018; 9:mBio.00959-18. [PMID: 29921667 PMCID: PMC6016245 DOI: 10.1128/mbio.00959-18] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The Epstein-Barr virus (EBV) oncoproteins latent membrane protein 1 (LMP1) and LMP2A constitutively activate multiple signaling pathways, and both have been shown to interact with cellular ubiquitin ligases and affect cellular ubiquitination. To detect the LMP1- and LMP2A-mediated effects on the global cellular proteome, epithelial cell lines expressing LMP1 or LMP2A were analyzed using label-free quantitative proteomics. To identify proteins whose ubiquitination is affected by the viral proteins, the cells were cultured in the presence and absence of deubiquitinase (DUB) and proteasome inhibitors. More than 7,700 proteins were identified with high confidence and considerably more proteins showed significant differences in expression in the presence of inhibitors. Few of the differentially expressed proteins with or without inhibitors were common between LMP1 and LMP2A, confirming that the viral proteins induce unique changes in cell expression and function. However, ingenuity pathway analysis (IPA) of the data indicated that LMP1 and LMP2A modulate many of the same cellular regulatory pathways, including cell death and survival, cell movement, and actin filament dynamics. In addition, various proteasome subunits, ubiquitin-specific peptidases and conjugating enzymes, vesicle trafficking proteins, and NF-κB and mitogen-activated protein kinase signaling proteins were affected by LMP1 or LMP2A. These findings suggest that LMP1 and LMP2A may commonly target critical cell pathways through effects on distinct genes, with many cellular proteins modified by ubiquitination and/or degradation. The Epstein-Barr virus proteins latent membrane protein 1 and 2 have potent effects on cell growth and signaling. Both proteins bind to specific ubiquitin ligases and likely modulate the cellular proteome through ubiquitin-mediated effects on stability and intracellular location. In this study, a comprehensive proteomic analysis of the effects of LMP1 and LMP2A revealed that both proteins affected proteasome subunits, ubiquitin-specific conjugases and peptidases, and vesical trafficking proteins. The data suggest that the effects of these proteins on the abundance and ubiquitination of cellular proteins are in part responsible for their effects on cell growth regulation.
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8
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Gan J, Qiao N, Strahan R, Zhu C, Liu L, Verma SC, Wei F, Cai Q. Manipulation of ubiquitin/SUMO pathways in human herpesviruses infection. Rev Med Virol 2016; 26:435-445. [DOI: 10.1002/rmv.1900] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 07/03/2016] [Accepted: 07/25/2016] [Indexed: 12/17/2022]
Affiliation(s)
- Jin Gan
- MOE & MOH Key Laboratory of Medical Molecular Virology, School of Basic Medicine, Shanghai Medical College; Fudan University; Shanghai China
| | - Niu Qiao
- Department of Medical Systems Biology, School of Basic Medical Sciences; Department of Translational Medicine, Shanghai Public Health Clinical Center; Institutes of Biomedical Sciences, Fudan University; Shanghai China
| | - Roxanne Strahan
- Department of Microbiology & Immunology; University of Nevada, Reno School of Medicine; Reno NV USA
| | - Caixia Zhu
- MOE & MOH Key Laboratory of Medical Molecular Virology, School of Basic Medicine, Shanghai Medical College; Fudan University; Shanghai China
| | - Lei Liu
- Department of Medical Systems Biology, School of Basic Medical Sciences; Department of Translational Medicine, Shanghai Public Health Clinical Center; Institutes of Biomedical Sciences, Fudan University; Shanghai China
| | - Subhash C. Verma
- Department of Microbiology & Immunology; University of Nevada, Reno School of Medicine; Reno NV USA
| | - Fang Wei
- ShengYushou Center of Cell Biology and Immunology, School of Life Sciences and Biotechnology; Shanghai Jiao Tong University; Shanghai China
| | - Qiliang Cai
- MOE & MOH Key Laboratory of Medical Molecular Virology, School of Basic Medicine, Shanghai Medical College; Fudan University; Shanghai China
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9
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Abstract
Itch or itchy E3 ubiquitin ligase was initially discovered by genetic studies on the mouse coat color changes, and its deletion results in an itchy phenotype with constant skin scratching and multi-organ inflammation. It is a member of the homologous to E6-associated protein C-terminus (HECT)-type family of E3 ligases, with the protein-interacting WW-domains for the recruitment of substrate and the HECT domain for the transfer of ubiquitin to the substrate. Since its discovery, numerous studies have demonstrated that Itch is involved in the control of many aspects of immune responses including T-cell activation and tolerance and T-helper cell differentiation. Itch is also implicated in other biological contexts such as tumorigenesis, development, and stress responses. Many signaling pathways are regulated by Itch-promoted ubiquitylation of diverse target proteins. Itch is also involved in human diseases. Here, we discuss the major progress in understanding the biological significance of Itch-promoted protein ubiquitylation in the immune and other systems and in Itch-mediated regulation of signal transduction.
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Affiliation(s)
- Daisuke Aki
- Institute for Immunology, Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, China.,Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA, USA
| | - Wen Zhang
- Institute for Immunology, Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, China
| | - Yun-Cai Liu
- Institute for Immunology, Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, China.,Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA, USA
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10
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Koshizuka T, Tanaka K, Suzutani T. Degradation of host ubiquitin E3 ligase Itch by human cytomegalovirus UL42. J Gen Virol 2016; 97:196-208. [DOI: 10.1099/jgv.0.000336] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Affiliation(s)
- Tetsuo Koshizuka
- Department of Microbiology, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima 960-1295, Japan
| | - Keiichiro Tanaka
- Department of Microbiology, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima 960-1295, Japan
| | - Tatsuo Suzutani
- Department of Microbiology, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima 960-1295, Japan
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11
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Cai LM, Lyu XM, Luo WR, Cui XF, Ye YF, Yuan CC, Peng QX, Wu DH, Liu TF, Wang E, Marincola FM, Yao KT, Fang WY, Cai HB, Li X. EBV-miR-BART7-3p promotes the EMT and metastasis of nasopharyngeal carcinoma cells by suppressing the tumor suppressor PTEN. Oncogene 2015; 34:2156-66. [PMID: 25347742 DOI: 10.1038/onc.2014.341] [Citation(s) in RCA: 159] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 07/01/2014] [Accepted: 09/12/2014] [Indexed: 02/07/2023]
Abstract
The epithelial-mesenchymal transition (EMT) is crucial to cancer progression and metastasis. Although multiple cellular miRNAs have been identified to regulate the EMT and metastasis in cancers, the role of viral miRNAs in cancer progression remains largely unknown. Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated malignancy typically characterized by its early metastasis. In the present study, we have discovered the involvement of a viral miRNA, EBV-miR-BART7-3p, in the EMT and metastasis of NPC cells. Initially, we observed that EBV-miR-BART7-3p was highly expressed in NPC and positively correlated with lymph node metastasis and clinical stage of NPC. Subsequently, we demonstrated that EBV-miR-BART7-3p enhanced cell migration/invasion in vitro, cancer metastasis in vivo, and particularly the EMT characterized by loss of epithelial markers and gain of mesenchymal features in NPC cells. Furthermore, mechanistic studies disclosed that EBV-miR-BART7-3p targeted a major human tumor suppressor PTEN, modulating PI3K/Akt/GSK-3β signaling and eventually leading to the high expression and nuclear accumulation of Snail and β-catenin, which favor EMT. Knockdown of PTEN could phenocopy the effect of EBV-miR-BART7-3p, whereas re-expression of PTEN resulted in a phenotypic reversion. Moreover, these findings were supported by an observation of an EBV-positive cell model in which silencing of endogenous EBV-miR-BART7-3p partially attenuated cell migration/invasion and altered EMT protein expression pattern via reverting PI3K/Akt, Snail and β-catenin expression. Thus, this study suggests a novel mechanism by which EBV-miR-BART7-3p modulates the EMT and metastasis of NPC cells, and a clinical implication of EBV-miR-BART7-3p as a potential biomarker or therapeutic target.
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Affiliation(s)
- L-M Cai
- Cancer Research Institute, Southern Medical University, Guangzhou, China
| | - X-M Lyu
- 1] Cancer Research Institute, Southern Medical University, Guangzhou, China [2] Department of Laboratory Medicine, the Third Affiliated Hospital, Southern Medical University, Guangzhou, China
| | - W-R Luo
- Cancer Research Institute, Southern Medical University, Guangzhou, China
| | - X-F Cui
- Department of ENT, 463 Hospital of the Chinese PLA, Shenyang, China
| | - Y-F Ye
- Cancer Research Institute, Southern Medical University, Guangzhou, China
| | - C-C Yuan
- Cancer Research Institute, Southern Medical University, Guangzhou, China
| | - Q-X Peng
- School of Chinese Traditional Medicine, Southern Medical University, Guangzhou, China
| | - D-H Wu
- Department of Radiation Oncology, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - T-F Liu
- Department of Pathology, Southern Medical University, Guangzhou, China
| | - E Wang
- Infectious Diseases and Immunogenetics Section, DTM, Clinical Center, the National Institutes of Health, Bethesda, MD, USA
| | - F-M Marincola
- Infectious Diseases and Immunogenetics Section, DTM, Clinical Center, the National Institutes of Health, Bethesda, MD, USA
| | - K-T Yao
- Cancer Research Institute, Southern Medical University, Guangzhou, China
| | - W-Y Fang
- Cancer Research Institute, Southern Medical University, Guangzhou, China
| | - H-B Cai
- School of Chinese Traditional Medicine, Southern Medical University, Guangzhou, China
| | - X Li
- Cancer Research Institute, Southern Medical University, Guangzhou, China
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12
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Tsang CM, Tsao SW. The role of Epstein-Barr virus infection in the pathogenesis of nasopharyngeal carcinoma. Virol Sin 2015; 30:107-21. [PMID: 25910483 DOI: 10.1007/s12250-015-3592-5] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 04/16/2015] [Indexed: 12/21/2022] Open
Abstract
Nasopharyngeal carcinoma (NPC) is closely associated with Epstein-Barr virus (EBV) infection. EBV episomes are detected in almost all NPC cells. The role of EBV in NPC pathogenesis has long been postulated but remains enigmatic. In contrast to infection of B lymphocytes, EBV infection does not directly transform nasopharyngeal epithelial cells into proliferative clones with malignant potential. EBV infection of normal pharyngeal epithelial cells is predominantly lytic in nature. Genetic alterations in premalignant nasopharyngeal epithelium, in combination with inflammatory stimulation in the nasopharyngeal mucosa, presumably play essential roles in the establishment of a latent EBV infection in infected nasopharyngeal epithelial cells during the early development of NPC. Establishment of latent EBV infection in premalignant nasopharyngeal epithelial cells and expression of latent viral genes, including the BART transcripts and BART-encoded microRNAs, are crucial features of NPC. Expression of EBV genes may drive further malignant transformation of premalignant nasopharyngeal epithelial cells into cancer cells. The difficulties involved in the establishment of NPC cell lines and the progressive loss of EBV epsiomes in NPC cells propagated in culture strongly implicate the contribution of host stromal components to the growth of NPC cells in vivo and maintenance of EBV in infected NPC cells. Defining the growth advantages of EBV-infected NPC cells in vivo will lead to a better understanding of the contribution of EBV infection in NPC pathogenesis, and may lead to the identification of novel therapeutic targets for NPC treatment.
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Affiliation(s)
- Chi Man Tsang
- Department of Anatomy, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China
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13
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Multifaceted role of the ubiquitin ligase Itch in immune regulation. Immunol Cell Biol 2015; 93:452-60. [DOI: 10.1038/icb.2014.118] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 12/10/2014] [Accepted: 12/10/2014] [Indexed: 12/17/2022]
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Raab-Traub N. Nasopharyngeal Carcinoma: An Evolving Role for the Epstein-Barr Virus. Curr Top Microbiol Immunol 2015; 390:339-63. [PMID: 26424653 DOI: 10.1007/978-3-319-22822-8_14] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The Epstein-Barr herpesvirus (EBV) is an important human pathogen that is closely linked to several major malignancies including the major epithelial tumor, undifferentiated nasopharyngeal carcinoma (NPC). This important tumor occurs with elevated incidence in specific areas, particularly in southern China but also in Mediterranean Africa and some regions of the Middle East. Regardless of tumor prevalence, undifferentiated NPC is consistently associated with EBV. The consistent detection of EBV in all cases of NPC, the maintenance of the viral genome in every cell, and the continued expression of viral gene products suggest that EBV is a necessary factor for the malignant growth in vivo. However, the molecular characterization of the infection and identification of critical events have been hampered by the difficulty in developing in vitro models of NPC. Epithelial cell infection is difficult in vitro and in contrast to B-cell infection does not result in immortalization and transformation. Cell lines established from NPC usually do not retain the genome, and the successful establishment of tumor xenografts is difficult. However, critical genetic changes that contribute to the onset and progression of NPC and key molecular properties of the viral genes expressed in NPC have been identified. In some cases, viral expression becomes increasingly restricted during tumor progression and tumor cells may express only the viral nuclear antigen EBNA1 and viral noncoding RNAs. As NPC develops in the immunocompetent, the continued progression of deregulated growth likely reflects the combination of expression of viral oncogenes in some cells and viral noncoding RNAs that likely function synergistically with changes in cellular RNA and miRNA expression.
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Affiliation(s)
- Nancy Raab-Traub
- Department of Microbiology, Lineberger Comprehensive Cancer Center, CB#7295, University of North Carolina, Chapel Hill, NC, 27599-7295, USA.
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15
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Abstract
LMP2A is an EBV-encoded protein with three domains: (a) an N-terminal cytoplasmic domain, which has PY motifs that bind to WW domain-containing E3 ubiquitin ligases and an ITAM that binds to SH2 domain-containing proteins, (b) a transmembrane domain with 12 transmembrane segments that localizes LMP2A in cellular membranes, and (c) a 27-amino acid C-terminal domain which mediates homodimerization and heterodimerization of LMP2 protein isoforms. The most prominent two isoforms of the protein are LMP2A and LMP2B. The LMP2B isoform lacks the 19-amino acid N-terminal domain found in LMP2A, which modulates cellular signaling resulting in a baseline activation of B cells and degradation of cellular kinases leading to the downregulation of normal B cell signaling pathways. These two seemingly contradictory processes allow EBV to establish and maintain latency. LMP2 is expressed in many EBV-associated malignancies. While its antigenic properties may be useful in developing LMP2-specific immunity, the LMP2A N-terminal motifs also provide a basis to target LMP2A-modulated cellular kinases for the development of treatment strategies.
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Scheffner M, Kumar S. Mammalian HECT ubiquitin-protein ligases: biological and pathophysiological aspects. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:61-74. [PMID: 23545411 DOI: 10.1016/j.bbamcr.2013.03.024] [Citation(s) in RCA: 214] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 02/18/2013] [Accepted: 03/22/2013] [Indexed: 10/27/2022]
Abstract
Members of the HECT family of E3 ubiquitin-protein ligases are characterized by a C-terminal HECT domain that catalyzes the covalent attachment of ubiquitin to substrate proteins and by N-terminal extensions of variable length and domain architecture that determine the substrate spectrum of a respective HECT E3. Since their discovery in 1995, it has become clear that deregulation of distinct HECT E3s plays an eminent role in human disease or disease-related processes including cancer, cardiovascular and neurological disorders, viral infections, and immune response. Thus, a detailed understanding of the structure-function aspects of HECT E3s as well as the identification and characterization of the substrates and regulators of HECT E3s is critical in developing new approaches in the treatment of respective diseases. In this review, we summarize what is currently known about mammalian HECT E3s, with a focus on their biological functions and roles in pathophysiology.This article is part of a Special Issue entitled: Ubiquitin-Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf.
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Affiliation(s)
- Martin Scheffner
- Department of Biology, Konstanz Research School Chemical Biology, University of Konstanz, Konstanz, Germany.
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Dergai O, Dergai M, Skrypkina I, Matskova L, Tsyba L, Gudkova D, Rynditch A. The LMP2A protein of Epstein-Barr virus regulates phosphorylation of ITSN1 and Shb adaptors by tyrosine kinases. Cell Signal 2012; 25:33-40. [PMID: 22975684 DOI: 10.1016/j.cellsig.2012.09.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 09/04/2012] [Indexed: 01/20/2023]
Abstract
Latent Membrane Protein 2A (LMP2A) is an Epstein-Barr virus-encoded protein that is important for the maintenance of latent infection. Its activity affects cellular differentiation, migration, proliferation and B cell survival. LMP2A resembles a constitutively activated B cell antigen receptor and exploits host kinases to activate a set of downstream signaling pathways. In the current study we demonstrate the interaction of LMP2A with intersectin 1 (ITSN1), a key endocytic adaptor protein. This interaction occurs via both the N- and C-tails of LMP2A and is mediated by the SH3 domains of ITSN1. Additionally, we identified the Shb adaptor and the Syk kinase as novel binding ligands of ITSN1. The Shb adaptor interacts simultaneously with the phosphorylated tyrosines of LMP2A and the SH3 domains of ITSN1 and mediates indirect interaction of ITSN1 to LMP2A. Syk kinase promotes phosphorylation of both ITSN1 and Shb adaptors in LMP2A-expressing cells. In contrast to ITSN1, Shb phosphorylation depends additionally on Lyn kinase activity. Considering that Shb and ITSN1 are implicated in various receptor tyrosine kinase signaling, our results indicate that LMP2A can affect a number of signaling pathways by regulating the phosphorylation of the ITSN1 and Shb adaptors.
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Affiliation(s)
- Oleksandr Dergai
- State Key Laboratory of Molecular and Cellular Biology, Institute of Molecular Biology and Genetics, 150 Zabolotnogo Street, Kyiv 03680, Ukraine
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18
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Han J, Chen JN, Zhang ZG, Li HG, Ding YG, Du H, Shao CK. Sequence variations of latent membrane protein 2A in Epstein-Barr virus-associated gastric carcinomas from Guangzhou, southern China. PLoS One 2012; 7:e34276. [PMID: 22470549 PMCID: PMC3314615 DOI: 10.1371/journal.pone.0034276] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Accepted: 02/25/2012] [Indexed: 12/29/2022] Open
Abstract
Latent membrane protein 2A (LMP2A), expressed in most Epstein-Barr virus (EBV)-associated malignancies, has been demonstrated to be responsible for the maintenance of latent infection and epithelial cell transformation. Besides, it could also act as the target for a CTL-based therapy for EBV-associated malignancies. In the present study, sequence variations of LMP2A in EBV-associated gastric carcinoma (EBVaGC) and healthy EBV carriers from Guangzhou, southern China, where nasopharyngeal carcinoma (NPC) is endemic, were investigated. Widespread sequence variations in the LMP2A gene were found, with no sequence identical to the B95.8 prototype. No consistent mutation was detected in all isolates. The immunoreceptor tyrosine-based activation motif (ITAM) and PY motifs in the amino terminus of LMP2A were strictly conserved, suggesting their important roles in virus infection; while 8 of the 17 identified CTL epitopes in the transmembrane region of LMP2A were affected by at least one point mutation, which may implicate that the effect of LMP2A polymorphisms should be considered when LMP2A-targeted immunotherapy is conducted. The polymorphisms of LMP2A in EBVaGC in gastric remnant carcinoma (GRC) were for the first time investigated in the world. The LMP2A sequence variations in EBVaGC in GRC were somewhat different from those in EBVaGC in conventional gastric carcinoma. The sequence variations of LMP2A in EBVaGC were similar to those in throat washing of healthy EBV carriers, indicating that these variations are due to geographic-associated polymorphisms rather than EBVaGC-associated mutations. This, to our best knowledge, is the first detailed investigation of LMP2A polymorphisms in EBVaGC in Guangzhou, southern China, where NPC is endemic.
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Affiliation(s)
- Jing Han
- Department of Pathology, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Jian-ning Chen
- Department of Pathology, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Zhi-gang Zhang
- Department of Pathology, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Hai-gang Li
- Department of Pathology, The Second Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Yun-gang Ding
- Department of Pathology, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Hong Du
- Department of Pathology, Guangzhou First Municipal People's Hospital, Guangzhou, Guangdong Province, China
| | - Chun-kui Shao
- Department of Pathology, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
- * E-mail:
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Katkere B, Rosa S, Drake JR. The Syk-binding ubiquitin ligase c-Cbl mediates signaling-dependent B cell receptor ubiquitination and B cell receptor-mediated antigen processing and presentation. J Biol Chem 2012; 287:16636-44. [PMID: 22451666 DOI: 10.1074/jbc.m112.357640] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
B cell receptor (BCR)-mediated antigen (Ag) processing and presentation lead to B cell-T cell interactions, which support affinity maturation and immunoglobulin class switching. These interactions are supported by generation of peptide-MHC class II complexes in multivesicular body-like MIIC compartments of B cells. Previous studies have shown that trafficking of Ag·BCR complexes to MVB-like MIIC occurs via an ubiquitin-dependent pathway and that ubiquitination of Ag·BCR complexes occurs by an Src family kinase signaling-dependent mechanism that is restricted to lipid raft-resident Ag·BCR complexes. This study establishes that downstream Syk-dependent BCR signaling is also required for BCR ubiquitination and BCR-mediated antigen processing and presentation. Knockdown studies reveal that of the two known Syk-binding E3 ubiquitin ligases c-Cbl and Cbl-b, only c-Cbl appears to have a central role in BCR ubiquitination, trafficking to MIIC, and ubiquitin-dependent BCR-mediated antigen processing and presentation. These results establish the novel role for Syk signaling and the Syk-binding ubiquitin ligase c-Cbl in the BCR-mediated processing and presentation of cognate antigen and define one mechanism by which antigen-induced BCR ubiquitination is modulated to impact the initiation and maturation of the humoral immune response.
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Affiliation(s)
- Bhuvana Katkere
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, New York 12208, USA
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20
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Dawson CW, Port RJ, Young LS. The role of the EBV-encoded latent membrane proteins LMP1 and LMP2 in the pathogenesis of nasopharyngeal carcinoma (NPC). Semin Cancer Biol 2012; 22:144-53. [PMID: 22249143 DOI: 10.1016/j.semcancer.2012.01.004] [Citation(s) in RCA: 221] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Revised: 01/02/2012] [Accepted: 01/03/2012] [Indexed: 02/08/2023]
Abstract
Although frequently expressed in EBV-positive malignancies, the contribution of the oncogenic latent membrane proteins, LMP1 and LMP2, to the pathogenesis of nasopharyngeal carcinoma (NPC) is not fully defined. As a key effector in EBV-driven B cell transformation and an established "transforming" gene, LMP1 displays oncogenic properties in rodent fibroblasts and induces profound morphological and phenotypic effects in epithelial cells. LMP1 functions as a viral mimic of the TNFR family member, CD40, engaging a number of signalling pathways that induce morphological and phenotypic alterations in epithelial cells. Although LMP2A plays an essential role in maintaining viral latency in EBV infected B cells, its role in epithelial cells is less clear. Unlike LMP1, LMP2A does not display "classical" transforming functions in rodent fibroblasts but its ability to engage a number of potentially oncogenic cell signalling pathways suggests that LMP2A can also participate in EBV-induced epithelial cell growth transformation. Here we review the effects of LMP1 and LMP2 on various aspects of epithelial cell behaviour highlighting key aspects that may contribute to the pathogenesis of NPC.
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Affiliation(s)
- Christopher W Dawson
- Birmingham Cancer Research UK Cancer Centre, School of Cancer Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom.
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21
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Di Marcotullio L, Greco A, Mazzà D, Canettieri G, Pietrosanti L, Infante P, Coni S, Moretti M, De Smaele E, Ferretti E, Screpanti I, Gulino A. Numb activates the E3 ligase Itch to control Gli1 function through a novel degradation signal. Oncogene 2011; 30:65-76. [PMID: 20818436 DOI: 10.1038/onc.2010.394] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Revised: 07/21/2010] [Accepted: 07/28/2010] [Indexed: 02/07/2023]
Abstract
Hedgehog pathway regulates tissue patterning and cell proliferation. Gli1 transcription factor is the major effector of Hedgehog signaling and its deregulation is often associated to medulloblastoma formation. Proteolytic processes represent a critical mechanism by which this pathway is turned off. Here, we characterize the regulation of an ubiquitin-mediated mechanism of Gli1 degradation, promoted by the coordinated action of the E3 ligase Itch and the adaptor protein Numb. We show that Numb activates the catalytic activity of Itch, releasing it from an inhibitory intramolecular interaction between its homologous to E6-AP C-terminus and WW domains. The consequent activation of Itch, together with the recruitment of Gli1 through direct binding with Numb, allows Gli1 to enter into the complex, resulting in Gli1 ubiquitination and degradation. This process is mediated by a novel Itch-dependent degron, composed of a combination of two PPXYs and a phospho-serine/proline motifs, localized in Gli1 C-terminal region, indicating the role of two different WW docking sites in Gli1 ubiquitination. Remarkably, Gli1 protein mutated in these modules is no longer regulated by Itch and Numb, and determines enhanced Gli1-dependent medulloblastoma growth, migration and invasion abilities, as well as in vitro transforming activity. Our data reveal a novel mechanism of regulation of Gli1 stability and function, which influences Hedgehog/Gli1 oncogenic potential.
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Affiliation(s)
- L Di Marcotullio
- Department of Molecular Medicine, Sapienza University, Rome, Italy
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22
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Fotheringham JA, Mazzucca S, Raab-Traub N. Epstein-Barr virus latent membrane protein-2A-induced DeltaNp63alpha expression is associated with impaired epithelial-cell differentiation. Oncogene 2010; 29:4287-96. [PMID: 20498633 PMCID: PMC2912443 DOI: 10.1038/onc.2010.175] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Epstein-Barr virus (EBV) is an oncogenic γ-herpes virus associated with malignancies that develop in both lymphoid and epithelial cells including nasopharyngeal carcinoma (NPC). The EBV protein latent membrane protein 2A (LMP2A) is expressed in NPC and can modulate epithelial proliferation, transformation, and differentiation, and as such, may promote malignancy. A key regulator of epithelial cell differentiation is the transcription factor p63, a member of the p53 family. This study examines the potential contribution of p63 to LMP2A-mediated inhibition of epithelial differentiation. Stable expression of LMP2A increased the protein level and stability of the ΔNp63α isoform, and in two epithelial cell lines, LMP2A interacted with ΔNp63α under stable and transient expression systems. LMP2A and ΔNp63α were localized to the cytoplasm and nuclear membrane and co-immunoprecipitated in the same fractions. Following induction of epithelial cell differentiation by calcium, expression of differentiation markers was impaired in both ΔNp63α and LMP2 expressing cells. Induction of p63α, association of p63α with LMP2A, and impairment of differentiation required the PY and ITAM signaling motif of LMP2A. By associating with and being regulated by LMP2A,ΔNp63α may function as a unique regulator of LMP2A effects on epithelial differentiation and contribute to EBV-associated epithelial cancers.
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Affiliation(s)
- J A Fotheringham
- Department of Microbiology and Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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23
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Azakir BA, Desrochers G, Angers A. The ubiquitin ligase Itch mediates the antiapoptotic activity of epidermal growth factor by promoting the ubiquitylation and degradation of the truncated C-terminal portion of Bid. FEBS J 2010; 277:1319-30. [DOI: 10.1111/j.1742-4658.2010.07562.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Abstract
The highly controlled degradation of proteins via the ubiquitin-proteasome pathway represents a key mechanism for cell regulation and homeostasis. Ubiquitin-dependent proteolysis, carried out in large part by the E3 ubiquitin ligases, is a critical mode of post-translational modification that is important in regulation of cell cycle progression, signal transduction, gene transcription, antigen receptor signaling, immune response and cell differentiation. Recent studies demonstrate that increasing numbers of proteins with ubiquitin ligase activity are being characterized. Identification and characterization of their substrates indicate that they regulate the turnover of key cell cycle proteins (p27Kip1, p21Cip1, p57Kip2, cyclin E), tumor suppressor proteins (p53, RB), signaling kinases (Src, Zap70, PI-3 kinase), apoptosis regulators (Bcl-2, Bax, Bik) and transcription factors (Myc, NF-kappaB, E1F1), all of which have been implicated in the pathogenesis of malignant lymphoma. Studies to determine the functional role of ubiquitin ligases in the pathogenesis of malignant lymphoma represent potential areas of investigation.
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Affiliation(s)
- Megan S Lim
- Division of Anatomic Pathology, Department of Pathology, University of Utah, Salt Lake City, Utah 84132, USA.
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25
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Azakir BA, Angers A. Reciprocal regulation of the ubiquitin ligase Itch and the epidermal growth factor receptor signaling. Cell Signal 2009; 21:1326-36. [DOI: 10.1016/j.cellsig.2009.03.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 03/18/2009] [Accepted: 03/24/2009] [Indexed: 01/22/2023]
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26
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Ikeda M, Longnecker R. The c-Cbl proto-oncoprotein downregulates EBV LMP2A signaling. Virology 2008; 385:183-91. [PMID: 19081591 DOI: 10.1016/j.virol.2008.11.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Revised: 09/28/2008] [Accepted: 11/11/2008] [Indexed: 11/16/2022]
Abstract
Latent membrane protein 2A (LMP2A) of Epstein-Barr virus (EBV) plays a key role in regulating viral latency and EBV pathogenesis by functionally mimicking signals induced by the B-cell receptor (BCR) altering normal B cell development. As c-Cbl ubiquitin ligase (E3) is a critical negative regulator in the BCR signal pathway, the role of c-Cbl in the function and formation of the LMP2A signalosome was examined. c-Cbl promoted LMP2A degradation through ubiquitination, specifically degraded the Syk protein tyrosine kinase in the presence of LMP2A, and inhibited LMP2A induction of the EBV lytic cycle. Our earlier studies indicated that LMP2A-dependent Lyn degradation was mediated by Nedd4-family E3s in LMP2A expressing cells. Combine with these new findings, we propose a model in which c-Cbl and Nedd4-family E3s cooperate to degrade target proteins at discrete steps in the function of the LMP2A signalosome.
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Affiliation(s)
- Masato Ikeda
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
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27
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Role of latent membrane protein 2 isoforms in Epstein-Barr virus latency. Trends Microbiol 2008; 16:520-7. [PMID: 18835714 DOI: 10.1016/j.tim.2008.08.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2008] [Revised: 08/27/2008] [Accepted: 08/28/2008] [Indexed: 12/12/2022]
Abstract
The oncogenic Epstein-Barr virus (EBV) infects the majority of the human population without doing harm and establishes a latent infection in the memory B-cell compartment. To accomplish this, EBV hijacks B-cell differentiation pathways and uses its own viral genes to interfere with B-cell signalling to achieve life-long persistence. EBV latent membrane protein 2A (LMP2A) provides a surrogate B-cell receptor signal essential for cell survival and is believed to have a crucial role in the maintenance of latency by blocking B-cell activation which would otherwise lead to lytic EBV infection. These two functions demand tight control of LMP2A activity and expression levels. Based on recent insights in the function of LMP2B, an isoform of LMP2A, we propose a model for how LMP2B modulates the activity of LMP2A contributing to maintenance of EBV latency.
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28
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Siler CA, Raab-Traub N. Rhesus lymphocryptovirus latent membrane protein 2A activates beta-catenin signaling and inhibits differentiation in epithelial cells. Virology 2008; 377:273-9. [PMID: 18570966 DOI: 10.1016/j.virol.2008.03.033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Revised: 02/06/2008] [Accepted: 03/27/2008] [Indexed: 12/25/2022]
Abstract
Rhesus lymphocryptovirus (LCV) is a gamma-herpesvirus closely related to Epstein-Barr virus (EBV). The rhesus latent membrane protein 2A (LMP2A) is highly homologous to EBV LMP2A. EBV LMP2A activates the phosphatidylinositol 3-kinase (PI3K) and beta-catenin signaling pathways in epithelial cells and affects differentiation. In the present study, the biochemical and biological properties of rhesus LMP2A in epithelial cells were investigated. The expression of rhesus LMP2A in epithelial cells induced Akt activation, GSK3beta inactivation and accumulation of beta-catenin in the cytoplasm and nucleus. The nuclear translocation, but not accumulation of beta-catenin was dependent on Akt activation. Rhesus LMP2A also impaired epithelial cell differentiation; however, this process was not dependent upon Akt activation. A mutant rhesus LMP2A lacking six transmembrane domains functioned similarly to wild-type rhesus LMP2A indicating that the full number of transmembrane domains is not required for effects on beta-catenin or cell differentiation. These results underscore the similarity of LCV to EBV and the suitability of the macaque as an animal model for studying EBV pathogenesis.
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Affiliation(s)
- Catherine A Siler
- Department of Microbiology and Immunology, CB#7290, University of North Carolina-Chapel Hill, 804 Mary Ellen Jones, Chapel Hill, NC 27599-7295, USA
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29
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Epstein-Barr virus latent membrane protein 2A preferentially signals through the Src family kinase Lyn. J Virol 2008; 82:8520-8. [PMID: 18579586 DOI: 10.1128/jvi.00843-08] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Latent membrane protein 2A (LMP2A) is a viral protein expressed during Epstein-Barr virus (EBV) latency in EBV-infected B cells both in cell culture and in vivo. LMP2A has important roles in modulating B-cell receptor signal transduction and provides survival and developmental signals to B cells in vivo. Although Lyn has been shown to be important in mediating LMP2A signaling, it is still unclear if Lyn is used preferentially or if LMP2A associates promiscuously with other Src family kinase (SFK) members. To investigate the role of various SFKs in LMP2A signaling, we crossed LMP2A transgenic mice (TgE) with Lyn(-/-), Fyn(-/-), or Blk(-/-) mice. TgE Lyn(-/-) mice had a larger immunoglobulin M (IgM)-positive B-cell population than TgE mice, suggesting that the absence of Lyn prevents LMP2A from delivering survival and developmental signals to the B cells. Both TgE Fyn(-/-) and TgE Blk(-/-) mice have an IgM-negative population of splenic B cells, similar to the TgE mice. LMP2A was also transiently transfected into the human EBV-negative B-cell line BJAB to determine which SFK members associate with LMP2A. Lyn was detected in LMP2A immunoprecipitates, whereas Fyn was not. Both Lyn and Fyn were able to bind to an LMP2A mutant which contained a sequence shown previously to bind tightly to the SH2 domain of multiple SFK members. From these results, we conclude that LMP2A preferentially associates with and signals through Lyn compared to its association with other SFKs. This preferential association is due in part to the SH2 domain of Lyn associating with LMP2A.
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30
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Herpes simplex virus type 2 UL56 interacts with the ubiquitin ligase Nedd4 and increases its ubiquitination. J Virol 2008; 82:5220-33. [PMID: 18353951 DOI: 10.1128/jvi.02515-07] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The herpes simplex virus UL56 gene is conserved among most members of the Alphaherpesvirinae family and plays a critical role in viral pathogenicity in vivo. The HSV-2 UL56 protein (UL56) is a C-terminally anchored type II membrane protein that is predicted to be inserted into the virion envelope, leaving its N-terminal domain in the tegument. UL56 interacts with KIF1A and UL11. Here we report that UL56 also interacts with the ubiquitin ligase Nedd4 and increases its ubiquitination. Nedd4 was identified as a UL56-interacting protein by a yeast two-hybrid screen. UL56 bound to Nedd4 via its PY motifs. Nedd4 was phosphorylated and degraded in wild-type HSV-2-infected cells but not in cells infected with a UL56-deficient mutant. Ubiquitination assays revealed that UL56 increased ubiquitinated Nedd4, which was actively degraded in infected cells. UL56 also caused a decrease in Nedd4 protein levels and the increased ubiquitination in cotransfected cells. However, UL56 itself was not ubiquitinated, despite its interaction with Nedd4. Based on these findings, we propose that UL56 regulates Nedd4 in HSV-2-infected cells, although deletion of UL56 had no apparent effect on viral growth in vitro.
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Tomaszewski-Flick MJ, Rowe DT. Minimal protein domain requirements for the intracellular localization and self-aggregation of Epstein-Barr Virus Latent Membrane Protein 2. Virus Genes 2007; 35:225-34. [PMID: 17564822 DOI: 10.1007/s11262-007-0118-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2007] [Accepted: 05/14/2007] [Indexed: 12/11/2022]
Abstract
The EBV Latent Membrane Protein 2 (LMP2) may have a role in the establishment and maintenance of in vivo latency. The gene is transcribed into two mRNAs that produce two LMP2 protein isoforms. The LMP2a protein isoform has 12 transmembrane segments (TMs) and an amino terminal cytoplasmic signaling domain (CSD) while the LMP2b isoform is identical but lacks the CSD. There has not been a consensus on the cellular membrane localization being sometimes ascribed to either a plasma membrane or an intracellular location [M. Rovedo, R. Longnecker, J. Virol. 81:89-94, 2007; D. Lynch, J. Zimmerman, D.T. Rowe, J. Gen. Virol. 83:1025-1035, 2002; C. Dawson, J. George, S. Blake, R. Longnecker, L.S. Young, Virology 289:192-207, 2001]. Fluorescent marker and epitope tagged LMP2b truncation mutants progressively removing TMs from the N and C termini were used to assess the localization and aggregation properties of LMP2b. wtLMP2b had an exclusively intracellular perinuclear localization, while all truncations of the protein resulted in localization to the cell surface. By epitope loop-tagging, all the truncated LMP2b proteins were verified to be in the predicted membrane orientation. In co-transfection experiments, the C-terminal region was implicated in the self-aggregation properties of LMP2b. Thus, an intact 12 TM domain was required for intracellular localization and protein-protein interaction while a C-terminal region was responsible for auto-aggregative properties.
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Affiliation(s)
- Monica Jo Tomaszewski-Flick
- Department of Infectious Diseases and Microbiology, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto St, Pittsburgh, PA 15213, USA
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32
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Zhang M, Veselits M, O'Neill S, Hou P, Reddi AL, Berlin I, Ikeda M, Nash PD, Longnecker R, Band H, Clark MR. Ubiquitinylation of Igβ Dictates the Endocytic Fate of the B Cell Antigen Receptor. THE JOURNAL OF IMMUNOLOGY 2007; 179:4435-43. [PMID: 17878339 DOI: 10.4049/jimmunol.179.7.4435] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In both infection and autoimmunity, the development of high-affinity Abs and memory requires B cells to efficiently capture and process Ags for presentation to cognate T cells. Although a great deal is known about how Ags are processed, the molecular mechanisms by which the BCR captures Ag for processing are still obscure. In this study, we demonstrate that the Ig beta component of the BCR is diubiquitinylated and that this is dependent on the E3 ligase Itch. Itch-/- B lymphocytes manifest both a defect in ligand-induced BCR internalization and endocytic trafficking to late endosomal Ag-processing compartments. In contrast, analysis of ubiquitinylation-defective receptors demonstrated that the attachment of ubiquitins to Ig beta is required for endosomal sorting and for the presentation of Ag to T cells, yet, ubiquitinylation is dispensable for receptor internalization. Membrane-bound Ig mu was not detectably ubiquitinylated nor were the conserved lysines in the mu cytosolic tail required for trafficking to late endosomes. These results demonstrate that ubiquitinylation of a singular substrate, Ig beta, is required for a specific receptor trafficking event. However, they also reveal that E3 ligases play a broader role in multiple processes that determine the fate of Ag-engaged BCR complexes.
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Affiliation(s)
- Miao Zhang
- Section of Rheumatology, Department of Medicine, University of Chicago, IL 60637, USA
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Mancao C, Hammerschmidt W. Epstein-Barr virus latent membrane protein 2A is a B-cell receptor mimic and essential for B-cell survival. Blood 2007; 110:3715-21. [PMID: 17682125 PMCID: PMC2077319 DOI: 10.1182/blood-2007-05-090142] [Citation(s) in RCA: 165] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Many cells latently infected with Epstein-Barr virus (EBV), including certain virus-associated tumors, express latent membrane protein 2A (LMP2A), suggesting an important role for this protein in viral latency and oncogenesis. LMP2A mimics B-cell receptor signaling but can also act as a decoy receptor blocking B-cell receptor (BCR) activation. Studies of peripheral B cells have not resolved this apparent contradiction because LMP2A seems to be dispensable for EBV-induced transformation of these B cells in vitro. We show here that LMP2A is essential for growth transformation of germinal center B cells, which do not express the genuine BCR because of deleterious somatic hypermutations in their immunoglobulin genes. BCR-positive (BCR(+)) and BCR-negative (BCR(-)) B cells are readily transformed with a recombinant EBV encoding a conditional, floxed LMP2A allele, but the survival and continued proliferation of both BCR(+) and BCR(-) B cells is strictly dependent on LMP2A. These findings indicate that LMP2A has potent, distinct antiapoptotic and/or transforming characteristics and point to its role as an indispensable BCR mimic in certain B cells from which human B-cell tumors such as Hodgkin lymphoma originate.
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Affiliation(s)
- Christoph Mancao
- GSF-National Research Center for Environment and Health Department of Gene Vectors, Munich, Germany
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Ikeda M, Longnecker R. Cholesterol is critical for Epstein-Barr virus latent membrane protein 2A trafficking and protein stability. Virology 2006; 360:461-8. [PMID: 17150237 PMCID: PMC1868700 DOI: 10.1016/j.virol.2006.10.046] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Revised: 10/17/2006] [Accepted: 10/27/2006] [Indexed: 12/12/2022]
Abstract
Latent membrane protein 2A (LMP2A) of Epstein-Barr virus (EBV) plays a key role in regulating viral latency and EBV pathogenesis by functionally mimicking signals induced by the B cell receptor (BCR) altering normal B cell development. LMP2A specifically associates with Nedd4 family ubiquitin-protein ligases which downmodulate LMP2A activity by ubiquitinating LMP2A and LMP2A-associated protein tyrosine kinases (PTKs). Since specific ubiquitin tags provide an endocytic sorting signal for plasma membrane proteins which traffic to membrane vesicles, we examined LMP2A localization and trafficking. We found that LMP2A is secreted through exosomes, small endocytic membrane vesicles, as previously demonstrated for LMP1. Interestingly, the treatment of cells with methyl-beta-cyclodextrin (MCD), which depletes cholesterol from plasma membrane, dramatically increased LMP2A abundance and LMP2A exosome secretion. Cholesterol depletion also blocked LMP2A endocytosis resulting in the accumulation of LMP2A on plasma membrane. LMP2A phosphorylation and ubiquitination were blocked by cholesterol depletion. LMP2A in the exosomal fraction was ubiquitinated but not phosphorylated. These results indicate that cholesterol-dependent LMP2A trafficking determines the fate of LMP2A degradation.
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Affiliation(s)
| | - Richard Longnecker
- *Corresponding author, Phone: +1-312-503-0467, Fax: +1-312-503-1339, E-mail:
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Mouchantaf R, Azakir BA, McPherson PS, Millard SM, Wood SA, Angers A. The ubiquitin ligase itch is auto-ubiquitylated in vivo and in vitro but is protected from degradation by interacting with the deubiquitylating enzyme FAM/USP9X. J Biol Chem 2006; 281:38738-47. [PMID: 17038327 DOI: 10.1074/jbc.m605959200] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Itch is a ubiquitin ligase that has been implicated in the regulation of a number of cellular processes. We previously have identified Itch as a binding partner for the endocytic protein Endophilin and found it to be localized to endosomes. Using affinity purification coupled to mass spectrometry, we have now identified the ubiquitin-protease FAM/USP9X as a binding partner of Itch. The association between Itch and FAM/USP9X was confirmed in vitro by glutathione S-transferase pulldown and in vivo through coimmunoprecipation. Itch and FAM partially colocalize in COS-7 cells at the trans-Golgi network and in peripheral vesicles. We mapped the FAM-binding domain on Itch to the WW domains, a region known to be involved in substrate recognition. However, transient overexpression of FAM/USP9X resulted in the deubiquitylation of Itch. Moreover, we show that Itch auto-ubiquitylation leads to its degradation in the proteasome. By examining the amounts of Itch and FAM in various cell lines and rat tissues, a positive correlation was found in the expression of both proteins. This observation suggests that the levels of FAM expression could have an influence on Itch in cells. Experimental decrease in FAM levels by RNA interference leads to a significant reduction in intracellular levels of endogenous Itch, which can be prevented by treatment with the proteasome inhibitor lactacystin. Accordingly, overexpression of FAM/USP9X resulted in a marked increase in endogenous Itch levels. These results demonstrate an intriguing interplay between a ubiquitin ligase and a ubiquitin protease, based on direct interaction between the two proteins.
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Affiliation(s)
- Rania Mouchantaf
- Départment de sciences biologiques, Université de Montréal, Station Centre-Ville, Montreal, Quebec H3C 3J7, Canada
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Brinkmann MM, Schulz TF. Regulation of intracellular signalling by the terminal membrane proteins of members of the Gammaherpesvirinae. J Gen Virol 2006; 87:1047-1074. [PMID: 16603506 DOI: 10.1099/vir.0.81598-0] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The human gamma(1)-herpesvirus Epstein-Barr virus (EBV) and the gamma(2)-herpesviruses Kaposi's sarcoma-associated herpesvirus (KSHV), rhesus rhadinovirus (RRV), herpesvirus saimiri (HVS) and herpesvirus ateles (HVA) all contain genes located adjacent to the terminal-repeat region of their genomes, encoding membrane proteins involved in signal transduction. Designated 'terminal membrane proteins' (TMPs) because of their localization in the viral genome, they interact with a variety of cellular signalling molecules, such as non-receptor protein tyrosine kinases, tumour-necrosis factor receptor-associated factors, Ras and Janus kinase (JAK), thereby initiating further downstream signalling cascades, such as the MAPK, PI3K/Akt, NF-kappaB and JAK/STAT pathways. In the case of TMPs expressed during latent persistence of EBV and HVS (LMP1, LMP2A, Stp and Tip), their modulation of intracellular signalling pathways has been linked to the provision of survival signals to latently infected cells and, hence, a contribution to occasional cellular transformation. In contrast, activation of similar pathways by TMPs of KSHV (K1 and K15) and RRV (R1), expressed during lytic replication, may extend the lifespan of virus-producing cells, alter their migration and/or modulate antiviral immune responses. Whether R1 and K1 contribute to the oncogenic properties of KSHV and RRV has not been established satisfactorily, despite their transforming qualities in experimental settings.
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Affiliation(s)
- Melanie M Brinkmann
- Institut für Virologie, Medizinische Hochschule Hannover, Carl-Neuberg Str. 1, D-30625 Hannover, Germany
| | - Thomas F Schulz
- Institut für Virologie, Medizinische Hochschule Hannover, Carl-Neuberg Str. 1, D-30625 Hannover, Germany
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Abstract
Ubiquitylation of membrane proteins has gained considerable interest in recent years. It has been recognized as a signal that negatively regulates the cell surface expression of many plasma membrane proteins both in yeast and in mammalian cells. Moreover, it is also involved in endoplasmic reticulum-associated degradation of membrane proteins, and it acts as a sorting signal both in the secretory pathway and in endosomes, where it targets proteins into multivesicular bodies in the lumen of vacuoles/lysosomes. In this review we discuss the progress in understanding these processes, achieved during the past several years.
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Affiliation(s)
- Olivier Staub
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.
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Novobrantseva TI, Majeau GR, Amatucci A, Kogan S, Brenner I, Casola S, Shlomchik MJ, Koteliansky V, Hochman PS, Ibraghimov A. Attenuated liver fibrosis in the absence of B cells. J Clin Invest 2006; 115:3072-82. [PMID: 16276416 PMCID: PMC1265860 DOI: 10.1172/jci24798] [Citation(s) in RCA: 194] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2005] [Accepted: 08/23/2005] [Indexed: 12/15/2022] Open
Abstract
Analysis of mononuclear cells in the adult mouse liver revealed that B cells represent as much as half of the intrahepatic lymphocyte population. Intrahepatic B cells (IHB cells) are phenotypically similar to splenic B2 cells but express lower levels of CD23 and CD21 and higher levels of CD5. IHB cells proliferate as well as splenic B cells in response to anti-IgM and LPS stimulation in vitro. VDJ gene rearrangements in IHB cells contain insertions of N,P region nucleotides characteristic of B cells maturing in the adult bone marrow rather than in the fetal liver. To evaluate whether B cells can have an impact on liver pathology, we compared CCl4-induced fibrosis development in B cell-deficient and wild-type mice. CCl4 caused similar acute liver injury in mutant and wild-type mice. However, following 6 weeks of CCl4 treatment, histochemical analyses showed markedly reduced collagen deposition in B cell-deficient as compared with wild-type mice. By analyzing mice that have normal numbers of B cells but lack either T cells or immunoglobulin in the serum, we established that B cells have an impact on fibrosis in an antibody- and T cell-independent manner.
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Ingham RJ, Raaijmakers J, Lim CSH, Mbamalu G, Gish G, Chen F, Matskova L, Ernberg I, Winberg G, Pawson T. The Epstein-Barr virus protein, latent membrane protein 2A, co-opts tyrosine kinases used by the T cell receptor. J Biol Chem 2005; 280:34133-42. [PMID: 16087662 DOI: 10.1074/jbc.m507831200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Epstein-Barr virus (EBV) is the causative agent of infectious mononucleosis and is associated with several human malignancies. The EBV protein latent membrane protein 2A (LMP2A) promotes viral latency in memory B cells by interfering with B cell receptor signaling and provides a survival signal for mature B cells that have lost expression of surface immunoglobulin. The latter function has suggested that LMP2A may enhance the survival of EBV-positive tumors. EBV is associated with several T cell malignancies and, since LMP2A has been detected in several of these disorders, we examined the ability of LMP2A to transmit signals and interfere with T cell receptor signaling in T cells. We show that LMP2A is tyrosine-phosphorylated in Jurkat TAg T cells, which requires expression of the Src family tyrosine kinases, Lck and Fyn. Lck and Fyn are recruited to the tyrosine-phosphorylated Tyr112 site in LMP2A, whereas phosphorylation of an ITAM motif in LMP2A creates a binding site for the ZAP-70/Syk tyrosine kinases. LMP2A also associates through its two PPPPY motifs with AIP4, a NEDD4 family E3 ubiquitin ligase; this interaction results in ubiquitylation of LMP2A and serves to regulate the stability of LMP2A and LMP2A-kinase complexes. Furthermore, stable expression of LMP2A in Jurkat T cells down-regulated T cell receptor levels and attenuated T cell receptor signaling. Thus, through recruiting tyrosine kinases involved in T cell receptor activation, LMP2A may provide a survival signal for EBV-positive T cell tumors, whereas LMP2A-associated NEDD4 E3 ligases probably titer the strength of this signal.
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Affiliation(s)
- Robert J Ingham
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada
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Portis T, Ikeda M, Longnecker R. Epstein–Barr virus LMP2A: regulating cellular ubiquitination processes for maintenance of viral latency? Trends Immunol 2004; 25:422-6. [PMID: 15275641 DOI: 10.1016/j.it.2004.05.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Toni Portis
- Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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Abstract
Epstein-Barr virus (EBV), a human herpesvirus associated with lymphoid and epithelial cell tumors, encodes several proteins that exploit the ubiquitin-proteasome system to regulate latency and allow the persistence of infected cells in immunocompetent hosts. Further modifications of ubiquitin-dependent proteolysis by activated cellular oncogenes contribute to malignant transformation. A detailed understanding of these processes may lead to the development of new therapeutic strategies for EBV-associated cancers.
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Affiliation(s)
- Maria G Masucci
- Microbiology and Tumor Biology Center, Karolinska Institutet, Box 280, S-171 77 Stockholm, Sweden.
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Casola S, Otipoby KL, Alimzhanov M, Humme S, Uyttersprot N, Kutok JL, Carroll MC, Rajewsky K. B cell receptor signal strength determines B cell fate. Nat Immunol 2004; 5:317-27. [PMID: 14758357 DOI: 10.1038/ni1036] [Citation(s) in RCA: 432] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2003] [Accepted: 12/02/2003] [Indexed: 11/09/2022]
Abstract
B cell receptor (BCR)-mediated antigen recognition is thought to regulate B cell differentiation. BCR signal strength may also influence B cell fate decisions. Here, we used the Epstein-Barr virus protein LMP2A as a constitutively active BCR surrogate to study the contribution of BCR signal strength in B cell differentiation. Mice carrying a targeted replacement of Igh by LMP2A leading to high or low expression of the LMP2A protein developed B-1 or follicular and marginal zone B cells, respectively. These data indicate that BCR signal strength, rather than antigen specificity, determines mature B cell fate. Furthermore, spontaneous germinal centers developed in gut-associated lymphoid tissue of LMP2A mice, indicating that microbial antigens can promote germinal centers independently of BCR-mediated antigen recognition.
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Affiliation(s)
- Stefano Casola
- CBR Institute for Biomedical Research, Harvard Medical School, Boston, MA 02115, USA.
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