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Sadek J, Wuo MG, Rooklin D, Hauenstein A, Hong SH, Gautam A, Wu H, Zhang Y, Cesarman E, Arora PS. Modulation of virus-induced NF-κB signaling by NEMO coiled coil mimics. Nat Commun 2020; 11:1786. [PMID: 32286300 PMCID: PMC7156456 DOI: 10.1038/s41467-020-15576-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 03/12/2020] [Indexed: 01/07/2023] Open
Abstract
Protein-protein interactions featuring intricate binding epitopes remain challenging targets for synthetic inhibitors. Interactions of NEMO, a scaffolding protein central to NF-κB signaling, exemplify this challenge. Various regulators are known to interact with different coiled coil regions of NEMO, but the topological complexity of this protein has limited inhibitor design. We undertook a comprehensive effort to block the interaction between vFLIP, a Kaposi’s sarcoma herpesviral oncoprotein, and NEMO using small molecule screening and rational design. Our efforts reveal that a tertiary protein structure mimic of NEMO is necessary for potent inhibition. The rationally designed mimic engages vFLIP directly causing complex disruption, protein degradation and suppression of NF-κB signaling in primary effusion lymphoma (PEL). NEMO mimic treatment induces cell death and delays tumor growth in a PEL xenograft model. Our studies with this inhibitor reveal the critical nexus of signaling complex stability in the regulation of NF-κB by a viral oncoprotein. NF-κB signalling involves the scaffold protein NEMO, which can be bound by the oncoprotein vFLIP to promote cell survival and oncogenic transformation. Here the authors rationally engineer a tertiary protein mimic of NEMO to disrupt the vFLIP-NEMO interaction to induce cell death.
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Affiliation(s)
- Jouliana Sadek
- Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY, 10065, USA
| | - Michael G Wuo
- Department of Chemistry, New York University, New York, NY, 10003, USA
| | - David Rooklin
- Department of Chemistry, New York University, New York, NY, 10003, USA
| | - Arthur Hauenstein
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA
| | - Seong Ho Hong
- Department of Chemistry, New York University, New York, NY, 10003, USA
| | - Archana Gautam
- Icahn School of Medicine at Mount Sinai, New York, NY, 10029-5674, USA
| | - Hao Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA
| | - Yingkai Zhang
- Department of Chemistry, New York University, New York, NY, 10003, USA.,NYU-ECNU Center for Computational Chemistry, New York University-Shanghai, 200122, Shanghai, China
| | - Ethel Cesarman
- Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY, 10065, USA.
| | - Paramjit S Arora
- Department of Chemistry, New York University, New York, NY, 10003, USA.
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2
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Fröhlich J, Grundhoff A. Epigenetic control in Kaposi sarcoma-associated herpesvirus infection and associated disease. Semin Immunopathol 2020; 42:143-157. [PMID: 32219477 PMCID: PMC7174275 DOI: 10.1007/s00281-020-00787-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 01/20/2020] [Indexed: 12/15/2022]
Abstract
Kaposi sarcoma-associated herpesvirus (KSHV) is the etiologic agent of several malignancies of endothelial and B-cell origin. The fact that latently infected tumor cells in these malignancies do not express classical viral oncogenes suggests that pathogenesis of KSHV-associated disease results from multistep processes that, in addition to constitutive viral gene expression, may require accumulation of cellular alterations. Heritable changes of the epigenome have emerged as an important co-factor that contributes to the pathogenesis of many non-viral cancers. Since KSHV encodes a number of factors that directly or indirectly manipulate host cell chromatin, it is an intriguing possibility that epigenetic reprogramming also contributes to the pathogenesis of KSHV-associated tumors. The fact that heritable histone modifications have also been shown to regulate viral gene expression programs in KSHV-infected tumor cells underlines the importance of epigenetic control during latency and tumorigenesis. We here review what is presently known about the role of epigenetic regulation of viral and host chromatin in KSHV infection and discuss how viral manipulation of these processes may contribute to the development of KSHV-associated disease.
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Affiliation(s)
- Jacqueline Fröhlich
- Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
| | - Adam Grundhoff
- Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany.
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3
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Smyth P, Sessler T, Scott CJ, Longley DB. FLIP(L): the pseudo-caspase. FEBS J 2020; 287:4246-4260. [PMID: 32096279 PMCID: PMC7586951 DOI: 10.1111/febs.15260] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 02/10/2020] [Accepted: 02/24/2020] [Indexed: 12/27/2022]
Abstract
Possessing structural homology with their active enzyme counterparts but lacking catalytic activity, pseudoenzymes have been identified for all major enzyme groups. Caspases are a family of cysteine‐dependent aspartate‐directed proteases that play essential roles in regulating cell death and inflammation. Here, we discuss the only human pseudo‐caspase, FLIP(L), a paralog of the apoptosis‐initiating caspases, caspase‐8 and caspase‐10. FLIP(L) has been shown to play a key role in regulating the processing and activity of caspase‐8, thereby modulating apoptotic signaling mediated by death receptors (such as TRAIL‐R1/R2), TNF receptor‐1 (TNFR1), and Toll‐like receptors. In this review, these canonical roles of FLIP(L) are discussed. Additionally, a range of nonclassical pseudoenzyme roles are described, in which FLIP(L) functions independently of caspase‐8. These nonclassical pseudoenzyme functions enable FLIP(L) to play key roles in the regulation of a wide range of biological processes beyond its canonical roles as a modulator of cell death.
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Affiliation(s)
- Peter Smyth
- The Patrick G Johnston Centre for Cancer Research, Queen's University, Belfast, UK
| | - Tamas Sessler
- The Patrick G Johnston Centre for Cancer Research, Queen's University, Belfast, UK
| | - Christopher J Scott
- The Patrick G Johnston Centre for Cancer Research, Queen's University, Belfast, UK
| | - Daniel B Longley
- The Patrick G Johnston Centre for Cancer Research, Queen's University, Belfast, UK
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4
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Yan L, Majerciak V, Zheng ZM, Lan K. Towards Better Understanding of KSHV Life Cycle: from Transcription and Posttranscriptional Regulations to Pathogenesis. Virol Sin 2019; 34:135-161. [PMID: 31025296 PMCID: PMC6513836 DOI: 10.1007/s12250-019-00114-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 03/14/2019] [Indexed: 02/08/2023] Open
Abstract
Kaposi’s sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus-8 (HHV-8), is etiologically linked to the development of Kaposi’s sarcoma, primary effusion lymphoma, and multicentric Castleman’s disease. These malignancies often occur in immunosuppressed individuals, making KSHV infection-associated diseases an increasing global health concern with persistence of the AIDS epidemic. KSHV exhibits biphasic life cycles between latent and lytic infection and extensive transcriptional and posttranscriptional regulation of gene expression. As a member of the herpesvirus family, KSHV has evolved many strategies to evade the host immune response, which help the virus establish a successful lifelong infection. In this review, we summarize the current research status on the biology of latent and lytic viral infection, the regulation of viral life cycles and the related pathogenesis.
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Affiliation(s)
- Lijun Yan
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Vladimir Majerciak
- National Cancer Institute, National Institutes of Health, Frederick, MD, 21702, USA
| | - Zhi-Ming Zheng
- National Cancer Institute, National Institutes of Health, Frederick, MD, 21702, USA.
| | - Ke Lan
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
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5
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Latent infection with Kaposi's sarcoma-associated herpesvirus enhances retrotransposition of long interspersed element-1. Oncogene 2019; 38:4340-4351. [PMID: 30770900 DOI: 10.1038/s41388-019-0726-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 01/18/2019] [Indexed: 12/14/2022]
Abstract
Kaposi's sarcoma (KS)-associated herpesvirus (KSHV), a gamma-2 herpesvirus, is the causative agent of KS, primary effusion lymphoma (PEL), and a plasma cell variant of multicentric Castleman's disease. Although KSHV latency is detected in KS-related tumors, oncogenic pathways activated by KSHV latent infection are not fully understood. Here, we found that retrotransposition of long interspersed element-1 (L1), a retrotransposon in the human genome, was enhanced in PEL cells. Among the KSHV latent genes, viral FLICE-inhibitory protein (vFLIP) enhanced L1 retrotransposition in an NF-κB-dependent manner. Intracellular cell adhesion molecule-1 (ICAM-1), an NF-κB target, regulated the vFLIP-mediated enhancement of L1 retrotransposition. Furthermore, ICAM-1 downregulated the expression of Moloney leukemia virus 10 (MOV10), an L1 restriction factor. Knockdown of ICAM-1 or overexpression of MOV10 relieved the vFLIP-mediated enhancement of L1 retrotransposition. Collectively, during KSHV latency, vFLIP upregulates ICAM-1 in an NF-κB-dependent manner, which, in turn, downregulates MOV10 expression and thereby enhances L1 retrotransposition. Because active L1 retrotransposition can lead to genomic instability, which is commonly found in KS and PEL, activation of L1 retrotransposition during KSHV latency may accelerate oncogenic processes through enhancing genomic instability. Our results suggest that L1 retrotransposition may be a novel target for impeding tumor development in KSHV-infected patients.
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Abstract
Kaposi sarcoma (KS) gained public attention as an AIDS-defining malignancy; its appearance on the skin was a highly stigmatizing sign of HIV infection during the height of the AIDS epidemic. The widespread introduction of effective antiretrovirals to control HIV by restoring immunocompetence reduced the prevalence of AIDS-related KS, although KS does occur in individuals with well-controlled HIV infection. KS also presents in individuals without HIV infection in older men (classic KS), in sub-Saharan Africa (endemic KS) and in transplant recipients (iatrogenic KS). The aetiologic agent of KS is KS herpesvirus (KSHV; also known as human herpesvirus-8), and viral proteins can induce KS-associated cellular changes that enable the virus to evade the host immune system and allow the infected cell to survive and proliferate despite viral infection. Currently, most cases of KS occur in sub-Saharan Africa, where KSHV infection is prevalent owing to transmission by saliva in childhood compounded by the ongoing AIDS epidemic. Treatment for early AIDS-related KS in previously untreated patients should start with the control of HIV with antiretrovirals, which frequently results in KS regression. In advanced-stage KS, chemotherapy with pegylated liposomal doxorubicin or paclitaxel is the most common treatment, although it is seldom curative. In sub-Saharan Africa, KS continues to have a poor prognosis. Newer treatments for KS based on the mechanisms of its pathogenesis are being explored.
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Affiliation(s)
- Ethel Cesarman
- Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY, USA.
| | - Blossom Damania
- Department of Microbiology and Immunology, Lineberger Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC, USA
| | | | - Jeffrey Martin
- Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA
| | - Mark Bower
- National Centre for HIV Malignancy, Chelsea & Westminster Hospital, London, UK
| | - Denise Whitby
- Leidos Biomedical Research, AIDS and Cancer Virus Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
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Ruder B, Murtadak V, Stürzl M, Wirtz S, Distler U, Tenzer S, Mahapatro M, Greten FR, Hu Y, Neurath MF, Cesarman E, Ballon G, Günther C, Becker C. Chronic intestinal inflammation in mice expressing viral Flip in epithelial cells. Mucosal Immunol 2018; 11:1621-1629. [PMID: 30104627 PMCID: PMC8063487 DOI: 10.1038/s41385-018-0068-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 07/04/2018] [Accepted: 07/10/2018] [Indexed: 02/04/2023]
Abstract
Viruses are present in the intestinal microflora and are currently discussed as a potential causative mechanism for the development of inflammatory bowel disease. A number of viruses, such as Human Herpesvirus-8, express homologs to cellular FLIPs, which are major contributors for the regulation of epithelial cell death. In this study we analyzed the consequences of constitutive expression of HHV8-viral FLIP in intestinal epithelial cells (IECs) in mice. Surprisingly, expression of vFlip disrupts tissue homeostasis and induces severe intestinal inflammation. Moreover vFlipIEC-tg mice showed reduced Paneth cell numbers, associated with excessive necrotic cell death. On a molecular level vFlip expression altered classical and alternative NFκB activation. Blocking of alternative NFκB signaling by deletion of Ikka in vivo largely protected mice from inflammation and Paneth cell loss induced by vFLIP. Collectively, our data provide functional evidence that expression of a single viral protein in IECs can be sufficient to disrupt epithelial homeostasis and to initiate chronic intestinal inflammation.
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Affiliation(s)
- Barbara Ruder
- Department of Medicine 1, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Vinay Murtadak
- Division of Molecular and Experimental Surgery, Department of Surgery, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Michael Stürzl
- Division of Molecular and Experimental Surgery, Department of Surgery, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Stefan Wirtz
- Department of Medicine 1, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Ute Distler
- Institute for Immunology, University Medical Center, Johannes Gutenberg University, Mainz, Germany
| | - Stefan Tenzer
- Institute for Immunology, University Medical Center, Johannes Gutenberg University, Mainz, Germany
| | - Mousumi Mahapatro
- Department of Medicine 1, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Florian R. Greten
- Institute for Tumor Biology and Experimental Therapy, Georg-Speyer-Haus, Frankfurt am Main, Germany
| | - Yinling Hu
- Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, USA
| | - Markus F. Neurath
- Department of Medicine 1, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Ethel Cesarman
- Department of Pathology and Laboratory Medicine, Weill Medical College of Cornell University, New York, NY, USA
| | - Gianna Ballon
- Department of Pathology and Laboratory Medicine, Northwell Health, Lake Success, NY, USA
| | - Claudia Günther
- Department of Medicine 1, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Christoph Becker
- Department of Medicine 1, University of Erlangen-Nuremberg, Erlangen, Germany
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8
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Humphreys L, Espona-Fiedler M, Longley DB. FLIP as a therapeutic target in cancer. FEBS J 2018; 285:4104-4123. [PMID: 29806737 DOI: 10.1111/febs.14523] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 05/11/2018] [Accepted: 05/24/2018] [Indexed: 12/13/2022]
Abstract
One of the classic hallmarks of cancer is disruption of cell death signalling. Inhibition of cell death promotes tumour growth and metastasis, causes resistance to chemo- and radiotherapies as well as targeted agents, and is frequently due to overexpression of antiapoptotic proteins rather than loss of pro-apoptotic effectors. FLIP is a major apoptosis-regulatory protein frequently overexpressed in solid and haematological cancers, in which its high expression is often correlated with poor prognosis. FLIP, which is expressed as long (FLIP(L)) and short (FLIP(S)) splice forms, achieves its cell death regulatory functions by binding to FADD, a critical adaptor protein which links FLIP to the apical caspase in the extrinsic apoptotic pathway, caspase-8, in a number of cell death regulating complexes, such as the death-inducing signalling complexes (DISCs) formed by death receptors. FLIP also plays a key role (together with caspase-8) in regulating another form of cell death termed programmed necrosis or 'necroptosis', as well as in other key cellular processes that impact cell survival, including autophagy. In addition, FLIP impacts activation of the intrinsic mitochondrial-mediated apoptotic pathway by regulating caspase-8-mediated activation of the pro-apoptotic Bcl-2 family member Bid. It has been demonstrated that FLIP can not only inhibit death receptor-mediated apoptosis, but also cell death induced by a range of clinically relevant chemotherapeutic and targeted agents as well as ionizing radiation. More recently, key roles for FLIP in promoting the survival of immunosuppressive tumour-promoting immune cells have been discovered. Thus, FLIP is of significant interest as an anticancer therapeutic target. In this article, we review FLIP's biology and potential ways of targeting this important tumour and immune cell death regulator.
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Affiliation(s)
- Luke Humphreys
- Drug Resistance Group, Centre for Cancer Research & Cell Biology, Queen's University Belfast, Belfast, UK
| | - Margarita Espona-Fiedler
- Drug Resistance Group, Centre for Cancer Research & Cell Biology, Queen's University Belfast, Belfast, UK
| | - Daniel B Longley
- Drug Resistance Group, Centre for Cancer Research & Cell Biology, Queen's University Belfast, Belfast, UK
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9
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Molluscum Contagiosum Virus MC159 Abrogates cIAP1-NEMO Interactions and Inhibits NEMO Polyubiquitination. J Virol 2017; 91:JVI.00276-17. [PMID: 28515292 DOI: 10.1128/jvi.00276-17] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 05/05/2017] [Indexed: 12/20/2022] Open
Abstract
Molluscum contagiosum virus (MCV) is a dermatotropic poxvirus that causes benign skin lesions. MCV lesions persist because of virally encoded immune evasion molecules that inhibit antiviral responses. The MCV MC159 protein suppresses NF-κB activation, a powerful antiviral response, via interactions with the NF-κB essential modulator (NEMO) subunit of the IκB kinase (IKK) complex. Binding of MC159 to NEMO does not disrupt the IKK complex, implying that MC159 prevents IKK activation via an as-yet-unidentified strategy. Here, we demonstrated that MC159 inhibited NEMO polyubiquitination, a posttranslational modification required for IKK and downstream NF-κB activation. Because MCV cannot be propagated in cell culture, MC159 was expressed independent of infection or during a surrogate vaccinia virus infection to identify how MC159 prevented polyubiquitination. Cellular inhibitor of apoptosis protein 1 (cIAP1) is a cellular E3 ligase that ubiquitinates NEMO. Mutational analyses revealed that MC159 and cIAP1 each bind to the same NEMO region, suggesting that MC159 may competitively inhibit cIAP1-NEMO interactions. Indeed, MC159 prevented cIAP1-NEMO interactions. MC159 also diminished cIAP1-mediated NEMO polyubiquitination and cIAP1-induced NF-κB activation. These data suggest that MC159 competitively binds to NEMO to prevent cIAP1-induced NEMO polyubiquitination. To our knowledge, this is the first report of a viral protein disrupting NEMO-cIAP1 interactions to strategically suppress IKK activation. All viruses must antagonize antiviral signaling events for survival. We hypothesize that MC159 inhibits NEMO polyubiquitination as a clever strategy to manipulate the host cell environment to the benefit of the virus.IMPORTANCE Molluscum contagiosum virus (MCV) is a human-specific poxvirus that causes persistent skin neoplasms. The persistence of MCV has been attributed to viral downregulation of host cell immune responses such as NF-κB activation. We show here that the MCV MC159 protein interacts with the NEMO subunit of the IKK complex to prevent NEMO interactions with the cIAP1 E3 ubiquitin ligase. This interaction correlates with a dampening of cIAP1 to polyubiquitinate NEMO and to activate NF-κB. This inhibition of cIAP1-NEMO interactions is a new viral strategy to minimize IKK activation and to control NEMO polyubiquitination. This research provides new insights into mechanisms that persistent viruses may use to cause long-term infection of host cells.
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Banerjee S, Uppal T, Strahan R, Dabral P, Verma SC. The Modulation of Apoptotic Pathways by Gammaherpesviruses. Front Microbiol 2016; 7:585. [PMID: 27199919 PMCID: PMC4847483 DOI: 10.3389/fmicb.2016.00585] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Accepted: 04/11/2016] [Indexed: 12/11/2022] Open
Abstract
Apoptosis or programmed cell death is a tightly regulated process fundamental for cellular development and elimination of damaged or infected cells during the maintenance of cellular homeostasis. It is also an important cellular defense mechanism against viral invasion. In many instances, abnormal regulation of apoptosis has been associated with a number of diseases, including cancer development. Following infection of host cells, persistent and oncogenic viruses such as the members of the Gammaherpesvirus family employ a number of different mechanisms to avoid the host cell’s “burglar” alarm and to alter the extrinsic and intrinsic apoptotic pathways by either deregulating the expressions of cellular signaling genes or by encoding the viral homologs of cellular genes. In this review, we summarize the recent findings on how gammaherpesviruses inhibit cellular apoptosis via virus-encoded proteins by mediating modification of numerous signal transduction pathways. We also list the key viral anti-apoptotic proteins that could be exploited as effective targets for novel antiviral therapies in order to stimulate apoptosis in different types of cancer cells.
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Affiliation(s)
- Shuvomoy Banerjee
- Amity Institute of Virology and Immunology, Amity University Noida, India
| | - Timsy Uppal
- Department of Microbiology and Immunology, Center for Molecular Medicine, School of Medicine, University of Nevada, Reno Reno, NV, USA
| | - Roxanne Strahan
- Department of Microbiology and Immunology, Center for Molecular Medicine, School of Medicine, University of Nevada, Reno Reno, NV, USA
| | - Prerna Dabral
- Department of Microbiology and Immunology, Center for Molecular Medicine, School of Medicine, University of Nevada, Reno Reno, NV, USA
| | - Subhash C Verma
- Department of Microbiology and Immunology, Center for Molecular Medicine, School of Medicine, University of Nevada, Reno Reno, NV, USA
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11
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Bagnéris C, Rogala KB, Baratchian M, Zamfir V, Kunze MBA, Dagless S, Pirker KF, Collins MK, Hall BA, Barrett TE, Kay CWM. Probing the Solution Structure of IκB Kinase (IKK) Subunit γ and Its Interaction with Kaposi Sarcoma-associated Herpes Virus Flice-interacting Protein and IKK Subunit β by EPR Spectroscopy. J Biol Chem 2015; 290:16539-49. [PMID: 25979343 PMCID: PMC4505408 DOI: 10.1074/jbc.m114.622928] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 05/13/2015] [Indexed: 01/04/2023] Open
Abstract
Viral flice-interacting protein (vFLIP), encoded by the oncogenic Kaposi sarcoma-associated herpes virus (KSHV), constitutively activates the canonical nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) pathway. This is achieved through subversion of the IκB kinase (IKK) complex (or signalosome), which involves a physical interaction between vFLIP and the modulatory subunit IKKγ. Although this interaction has been examined both in vivo and in vitro, the mechanism by which vFLIP activates the kinase remains to be determined. Because IKKγ functions as a scaffold, recruiting both vFLIP and the IKKα/β subunits, it has been proposed that binding of vFLIP could trigger a structural rearrangement in IKKγ conducive to activation. To investigate this hypothesis we engineered a series of mutants along the length of the IKKγ molecule that could be individually modified with nitroxide spin labels. Subsequent distance measurements using electron paramagnetic resonance spectroscopy combined with molecular modeling and molecular dynamics simulations revealed that IKKγ is a parallel coiled-coil whose response to binding of vFLIP or IKKβ is localized twisting/stiffening and not large-scale rearrangements. The coiled-coil comprises N- and C-terminal regions with distinct registers accommodated by a twist: this structural motif is exploited by vFLIP, allowing it to bind and subsequently activate the NF-κB pathway. In vivo assays confirm that NF-κB activation by vFLIP only requires the N-terminal region up to the transition between the registers, which is located directly C-terminal of the vFLIP binding site.
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Affiliation(s)
- Claire Bagnéris
- From the Department of Biological Sciences, Institute of Structural and Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, United Kingdom
| | - Kacper B Rogala
- From the Department of Biological Sciences, Institute of Structural and Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, United Kingdom, Institute of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Mehdi Baratchian
- MRC Centre for Medical Molecular Virology, UCL Cancer Institute and National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Potters Bar, Herts EN6 3QG, United Kingdom
| | - Vlad Zamfir
- From the Department of Biological Sciences, Institute of Structural and Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, United Kingdom, Institute of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Micha B A Kunze
- Institute of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Selina Dagless
- Institute of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Katharina F Pirker
- Institute of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Mary K Collins
- MRC Centre for Medical Molecular Virology, UCL Cancer Institute and National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Potters Bar, Herts EN6 3QG, United Kingdom
| | - Benjamin A Hall
- MRC Cancer Unit, Hutchison/MRC Research Centre, Cambridge Biomedical Campus, University of Cambridge, Cambridge CB2 0XZ, United Kingdom, and
| | - Tracey E Barrett
- From the Department of Biological Sciences, Institute of Structural and Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, United Kingdom,
| | - Christopher W M Kay
- Institute of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, United Kingdom, London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
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12
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Abstract
Molluscum contagiosum virus (MCV) is the causative agent of molluscum contagiosum (MC), the third most common viral skin infection in children, and one of the five most prevalent skin diseases worldwide. No FDA-approved treatments, vaccines, or commercially available rapid diagnostics for MCV are available. This review discusses several aspects of this medically important virus including: physical properties of MCV, MCV pathogenesis, MCV replication, and immune responses to MCV infection. Sequencing of the MCV genome revealed novel immune evasion molecules which are highlighted here. Special attention is given to the MCV MC159 and MC160 proteins. These proteins are FLIPs with homologs in gamma herpesviruses and in the cell. They are of great interest because each protein regulates apoptosis, NF-κB, and IRF3. However, the mechanism that each protein uses to impart its effects is different. It is important to elucidate how MCV inhibits immune responses; this knowledge contributes to our understanding of viral pathogenesis and also provides new insights into how the immune system neutralizes virus infections.
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13
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Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV; also known as human herpesvirus 8) is the etiologic agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. These cancers often occur in the context of immunosuppression, which has made KSHV-associated malignancies an increasing global health concern with the persistence of the AIDS epidemic. KSHV has also been linked to several acute inflammatory diseases. KSHV exists between a lytic and latent lifecycle, which allows the virus to transition between active replication and quiescent infection. KSHV encodes a number of proteins and small RNAs that are thought to inadvertently transform host cells while performing their functions of helping the virus persist in the infected host. KSHV also has an arsenal of components that aid the virus in evading the host immune response, which help the virus establish a successful lifelong infection. In this comprehensive chapter, we will discuss the diseases associated with KSHV infection, the biology of latent and lytic infection, and individual proteins and microRNAs that are known to contribute to host cell transformation and immune evasion.
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Affiliation(s)
- Louise Giffin
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Blossom Damania
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
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NEMO is essential for Kaposi's sarcoma-associated herpesvirus-encoded vFLIP K13-induced gene expression and protection against death receptor-induced cell death, and its N-terminal 251 residues are sufficient for this process. J Virol 2014; 88:6345-54. [PMID: 24672029 DOI: 10.1128/jvi.00028-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
UNLABELLED Kaposi's sarcoma-associated herpesvirus-encoded viral FLICE inhibitory protein (vFLIP) K13 was originally believed to protect virally infected cells against death receptor-induced apoptosis by interfering with caspase 8/FLICE activation. Subsequent studies revealed that K13 also activates the NF-κB pathway by binding to the NEMO/inhibitor of NF-κB (IκB) kinase gamma (IKKγ) subunit of an IKK complex and uses this pathway to modulate the expression of genes involved in cellular survival, proliferation, and the inflammatory response. However, it is not clear if K13 can also induce gene expression independently of NEMO/IKKγ. The minimum region of NEMO that is sufficient for supporting K13-induced NF-κB has not been delineated. Furthermore, the contribution of NEMO and NF-κB to the protective effect of K13 against death receptor-induced apoptosis remains to be determined. In this study, we used microarray analysis on K13-expressing wild-type and NEMO-deficient cells to demonstrate that NEMO is required for modulation of K13-induced genes. Reconstitution of NEMO-null cells revealed that the N-terminal 251 amino acid residues of NEMO are sufficient for supporting K13-induced NF-κB but fail to support tumor necrosis factor alpha (TNF-α)-induced NF-κB. K13 failed to protect NEMO-null cells against TNF-α-induced cell death but protected those reconstituted with the NEMO mutant truncated to include only the N-terminal 251 amino acid residues [the NEMO(1-251) mutant]. Taken collectively, our results demonstrate that NEMO is required for modulation of K13-induced genes and the N-terminal 251 amino acids of NEMO are sufficient for supporting K13-induced NF-κB. Finally, the ability of K13 to protect against TNF-α-induced cell death is critically dependent on its ability to interact with NEMO and activate NF-κB. IMPORTANCE Kaposi's sarcoma-associated herpesvirus-encoded vFLIP K13 is believed to protect virally infected cells against death receptor-induced apoptosis and to activate the NF-κB pathway by binding to adaptor protein NEMO/IKKγ. However, whether K13 can also induce gene expression independently of NEMO and the minimum region of NEMO that is sufficient for supporting K13-induced NF-κB remain to be delineated. Furthermore, the contribution of NEMO and NF-κB to the protective effect of K13 against death receptor-induced apoptosis is not clear. We demonstrate that NEMO is required for modulation of K13-induced genes and its N-terminal 251 amino acids are sufficient for supporting K13-induced NF-κB. The ability of K13 to protect against TNF-α-induced cell death is critically dependent on its ability to interact with NEMO and activate NF-κB. Our results suggest that K13-based gene therapy approaches may have utility for the treatment of patients with NEMO mutations and immunodeficiency.
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Inhibition of interferon gene activation by death-effector domain-containing proteins from the molluscum contagiosum virus. Proc Natl Acad Sci U S A 2013; 111:E265-72. [PMID: 24379396 DOI: 10.1073/pnas.1314569111] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Apoptosis, NF-κB activation, and IRF3 activation are a triad of intrinsic immune responses that play crucial roles in the pathogenesis of infectious diseases, cancer, and autoimmunity. FLIPs are a family of viral and cellular proteins initially found to inhibit apoptosis and more recently to either up- or down-regulate NF-κB. As such, a broad role for FLIPs in disease regulation is postulated, but exactly how a FLIP performs such multifunctional roles remains to be established. Here we examine FLIPs (MC159 and MC160) encoded by the molluscum contagiosum virus, a dermatotropic poxvirus causing skin infections common in children and immunocompromised individuals, to better understand their roles in viral pathogenesis. While studying their molecular mechanisms responsible for NF-κB inhibition, we discovered that each protein inhibited IRF3-controlled luciferase activity, identifying a unique function for FLIPs. MC159 and MC160 each inhibited TBK1 phosphorylation, confirming this unique function. Surprisingly, MC159 coimmunoprecipitated with TBK1 and IKKε but MC160 did not, suggesting that these homologs use distinct molecular mechanisms to inhibit IRF3 activation. Equally surprising was the finding that the FLIP regions necessary for TBK1 inhibition were distinct from those MC159 or MC160 regions previously defined to inhibit NF-κB or apoptosis. These data reveal previously unappreciated complexities of FLIPs, and that subtle differences within the conserved regions of FLIPs possess distinct molecular and structural fingerprints that define crucial differences in biological activities. A future comparison of mechanistic differences between viral FLIP proteins can provide new means of precisely manipulating distinct aspects of intrinsic immune responses.
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Sakakibara S, Espigol-Frigole G, Gasperini P, Uldrick TS, Yarchoan R, Tosato G. A20/TNFAIP3 inhibits NF-κB activation induced by the Kaposi's sarcoma-associated herpesvirus vFLIP oncoprotein. Oncogene 2013; 32:1223-32. [PMID: 22525270 PMCID: PMC3594048 DOI: 10.1038/onc.2012.145] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 03/02/2012] [Accepted: 03/05/2012] [Indexed: 12/29/2022]
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) K13/vFLIP (viral Flice-inhibitory protein) induces transcription of numerous genes through NF-κB activation, including pro-inflammatory cytokines, which contribute to the pathogenesis of Kaposi's sarcoma (KS). In this study, we report that KSHV vFLIP induces the expression of the NF-κB regulatory proteins A20, ABIN-1 and ABIN-3 (A20-binding NF-κB inhibitors) in primary human endothelial cells, and that KS spindle cells express A20 in KS tissue. In reporter assays, A20 strongly impaired vFLIP-induced NF-κB activation in 293T cells, but ABIN-1 and ABIN-3 did not. Mutational analysis established that the C-terminal domain (residues 427-790) is critical for A20 modulation of NF-κB, but the ubiquitin-editing OTU (ovarian tumor) domain is not. In functional assays, A20 inhibited vFLIP-induced expression of the chemokine IP-10, reduced vFLIP-induced cell proliferation and increased IKK1 protein levels. Thus, we demonstrate that A20 negatively regulates NF-κB activation directly induced by KSHV vFLIP. By attenuating excessive and prolonged vFLIP-induced NF-κB activation that could be harmful to KSHV-infected cells, A20 likely has an important role in the pathogenesis of KSHV-associated diseases, in which vFLIP is expressed.
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Affiliation(s)
- S Sakakibara
- Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - G Espigol-Frigole
- Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - P Gasperini
- Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - TS Uldrick
- HIV and AIDS Malignancy Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - R Yarchoan
- HIV and AIDS Malignancy Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - G Tosato
- Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
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Lim KH, Choi HS, Park YK, Park ES, Shin GC, Kim DH, Ahn SH, Kim KH. HBx-induced NF-κB signaling in liver cells is potentially mediated by the ternary complex of HBx with p22-FLIP and NEMO. PLoS One 2013; 8:e57331. [PMID: 23483900 PMCID: PMC3587578 DOI: 10.1371/journal.pone.0057331] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 01/21/2013] [Indexed: 02/07/2023] Open
Abstract
Sustained activation of NF-κB is one of the causative factors for various liver diseases, including liver inflammation and hepatocellular carcinoma (HCC). It has been known that activating the NF-κB signal by hepatitis B virus X protein (HBx) is implicated in the development of HCC. However, despite numerous studies on HBx-induced NF-κB activation, the detailed mechanisms still remain unsolved. Recently, p22-FLIP, a cleavage product of c-FLIPL, has been reported to induce NF-κB activation through interaction with the IκB kinase (IKK) complex in primary immune cells. Since our previous report on the interaction of HBx with c-FLIPL, we explored whether p22-FLIP is involved in the modulation of HBx function. First, we identified the expression of endogenous p22-FLIP in liver cells. NF-κB reporter assay and electrophoretic mobility shift assay (EMSA) revealed that the expression of p22-FLIP synergistically enhances HBx-induced NF-κB activation. Moreover, we found that HBx physically interacts with p22-FLIP and NEMO and potentially forms a ternary complex. Knock-down of c-FLIP leading to the downregulation of p22-FLIP showed that endogenous p22-FLIP is involved in HBx-induced NF-κB activation, and the formation of a ternary complex is necessary to activate NF-κB signaling. In conclusion, we showed a novel mechanism of HBx-induced NF-κB activation in which ternary complex formation is involved among HBx, p22-FLIP and NEMO. Our findings will extend the understanding of HBx-induced NF-κB activation and provide a new target for intervention in HBV-associated liver diseases and in the development of HCC.
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Affiliation(s)
- Keo-Heun Lim
- Department of Pharmacology, and Center for Cancer Research and Diagnostic Medicine, IBST, Konkuk University School of Medicine, Seoul, Republic of Korea
- Institute of Functional Genomics, Konkuk University, Seoul, Republic of Korea
| | - Hyo Sun Choi
- Department of Pharmacology, and Center for Cancer Research and Diagnostic Medicine, IBST, Konkuk University School of Medicine, Seoul, Republic of Korea
| | - Yong Kwang Park
- Department of Pharmacology, and Center for Cancer Research and Diagnostic Medicine, IBST, Konkuk University School of Medicine, Seoul, Republic of Korea
| | - Eun-Sook Park
- Department of Pharmacology, and Center for Cancer Research and Diagnostic Medicine, IBST, Konkuk University School of Medicine, Seoul, Republic of Korea
| | - Gu Choul Shin
- Department of Pharmacology, and Center for Cancer Research and Diagnostic Medicine, IBST, Konkuk University School of Medicine, Seoul, Republic of Korea
| | - Doo Hyun Kim
- Department of Pharmacology, and Center for Cancer Research and Diagnostic Medicine, IBST, Konkuk University School of Medicine, Seoul, Republic of Korea
| | - Sung Hyun Ahn
- Department of Pharmacology, and Center for Cancer Research and Diagnostic Medicine, IBST, Konkuk University School of Medicine, Seoul, Republic of Korea
| | - Kyun-Hwan Kim
- Department of Pharmacology, and Center for Cancer Research and Diagnostic Medicine, IBST, Konkuk University School of Medicine, Seoul, Republic of Korea
- Institute of Functional Genomics, Konkuk University, Seoul, Republic of Korea
- * E-mail:
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Abstract
Central to NF-κB signaling pathways is IKKγ/NEMO, a regulatory subunit of the cytoplasmic IκB kinase (IKK) complex, which undergoes various posttranslational modifications, specifically phosphorylation, to regulate its function. Furthermore, Kaposi’s sarcoma-associated herpesvirus (KSHV) FADD-like interleukin-1β (IL-1β) converting enzyme (FLICE) inhibitory protein (vFLIP) activates the NF-κB signaling pathway by directly interacting with IKKγ/NEMO. However, the exact functions of IKKγ/NEMO phosphorylation and its KvFLIP interaction in NF-κB activation remain elusive. Here, we report two novel phosphorylation sites of IKKγ/NEMO and their negative effect on the IKKγ/NEMO-mediated NF-κB signaling pathway. First, the Src family protein tyrosine kinases (SF-PTKs), including Src, Fyn, Lyn, and Fgr, interact with and phosphorylate tyrosine residue 374 (Y374) of IKKγ/NEMO. Mutation of the Y374 residue to phenylalanine (Y374F) specifically abolished SF-PTK-mediated tyrosine phosphorylation, leading to increased tumor necrosis factor alpha (TNF-α)-induced NF-κB activity. Moreover, our mass spectrometry analysis found that the serine 377 residue (S377) of IKKγ/NEMO underwent robust phosphorylation upon KvFLIP expression. Replacement of the IKKγ/NEMO S377 residue by alanine (S377A) or glutamic acid (S377E) resulted in a significant increase or decrease of NF-κB activity and TNF-α-mediated IL-6 cytokine production, respectively. Our study thus demonstrates that the Y374 or S377 residue located at the C-terminal proline-rich domain of human IKKγ/NEMO undergoes phosphorylation upon TNF-α treatment or KvFLIP expression, respectively, resulting in the suppression of IKKγ/NEMO activity to induce NF-κB activation. This study suggests the potential phosphorylation-mediated feedback negative regulation of IKKγ/NEMO activity in the NF-κB signaling pathway. Since unchecked regulation of NF-κB has been linked to uncontrolled proliferation and cell death, the downregulation of the NF-κB signaling pathway is as important as its activation. Specifically, the phosphorylation-mediated modification of IKKγ/NEMO is a critical regulatory mechanism of NF-κB activity. Here, we report two novel phosphorylations of IKKγ/NEMO and their negative effects on the NF-κB signaling pathway. First, the Src family protein tyrosine kinase interacts with and phosphorylates tyrosine residue 374 of IKKγ/NEMO, suppressing tumor necrosis factor alpha (TNF-α)-induced NF-κB activity. Additionally, Kaposi’s sarcoma-associated herpesvirus (KSHV) FADD-like interleukin-1β (IL-1β) converting enzyme (FLICE) inhibitory protein (KvFLIP) expression induces a robust phosphorylation of the serine 377 residue of IKKγ/NEMO, resulting in a significant decrease of NF-κB activity. Our study thus demonstrates that the Y374 or S377 residue of IKKγ/NEMO undergoes phosphorylation upon TNF-α treatment or KvFLIP expression, respectively, resulting in the suppression of IKKγ/NEMO activity to induce NF-κB activation. This also suggests the potential phosphorylation-mediated feedback negative regulation of IKKγ/NEMO activity in the NF-κB signaling pathway.
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Punj V, Matta H, Chaudhary PM. A computational profiling of changes in gene expression and transcription factors induced by vFLIP K13 in primary effusion lymphoma. PLoS One 2012; 7:e37498. [PMID: 22624040 PMCID: PMC3356309 DOI: 10.1371/journal.pone.0037498] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 04/23/2012] [Indexed: 01/08/2023] Open
Abstract
Infection with Kaposi's sarcoma associated herpesvirus (KSHV) has been linked to the development of primary effusion lymphoma (PEL), a rare lymphoproliferative disorder that is characterized by loss of expression of most B cell markers and effusions in the body cavities. This unique clinical presentation of PEL has been attributed to their distinctive plasmablastic gene expression profile that shows overexpression of genes involved in inflammation, adhesion and invasion. KSHV-encoded latent protein vFLIP K13 has been previously shown to promote the survival and proliferation of PEL cells. In this study, we employed gene array analysis to characterize the effect of K13 on global gene expression in PEL-derived BCBL1 cells, which express negligible K13 endogenously. We demonstrate that K13 upregulates the expression of a number of NF-κB responsive genes involved in cytokine signaling, cell death, adhesion, inflammation and immune response, including two NF-κB subunits involved in the alternate NF-κB pathway, RELB and NFKB2. In contrast, CD19, a B cell marker, was one of the genes downregulated by K13. A comparison with K13-induced genes in human vascular endothelial cells revealed that although there was a considerable overlap among the genes induced by K13 in the two cell types, chemokines genes were preferentially induced in HUVEC with few exceptions, such as RANTES/CCL5, which was induced in both cell types. Functional studies confirmed that K13 activated the RANTES/CCL5 promoter through the NF-κB pathway. Taken collectively, our results suggest that K13 may contribute to the unique gene expression profile, immunophenotype and clinical presentation that are characteristics of KSHV-associated PEL.
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Affiliation(s)
- Vasu Punj
- From Jane Anne Nohl Division of Hematology and Center for the Study of Blood Diseases, University of Southern California Keck School of Medicine, Los Angeles, California, United States of America
- Bioinformatics Core, Norris Comprehensive Cancer Center at USC Epigenome Center, University of Southern California Keck School of Medicine, Los Angeles, California, United States of America
| | - Hittu Matta
- From Jane Anne Nohl Division of Hematology and Center for the Study of Blood Diseases, University of Southern California Keck School of Medicine, Los Angeles, California, United States of America
| | - Preet M. Chaudhary
- From Jane Anne Nohl Division of Hematology and Center for the Study of Blood Diseases, University of Southern California Keck School of Medicine, Los Angeles, California, United States of America
- * E-mail:
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20
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Kaposi's sarcoma associated herpesvirus encoded viral FLICE inhibitory protein K13 activates NF-κB pathway independent of TRAF6, TAK1 and LUBAC. PLoS One 2012; 7:e36601. [PMID: 22590573 PMCID: PMC3348130 DOI: 10.1371/journal.pone.0036601] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Accepted: 04/11/2012] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Kaposi's sarcoma associated herpesvirus encoded viral FLICE inhibitory protein (vFLIP) K13 activates the NF-κB pathway by binding to the NEMO/IKKγ subunit of the IκB kinase (IKK) complex. However, it has remained enigmatic how K13-NEMO interaction results in the activation of the IKK complex. Recent studies have implicated TRAF6, TAK1 and linear ubiquitin chains assembled by a linear ubiquitin chain assembly complex (LUBAC) consisting of HOIL-1, HOIP and SHARPIN in IKK activation by proinflammatory cytokines. METHODOLOGY/PRINCIPAL FINDINGS Here we demonstrate that K13-induced NF-κB DNA binding and transcriptional activities are not impaired in cells derived from mice with targeted disruption of TRAF6, TAK1 and HOIL-1 genes and in cells derived from mice with chronic proliferative dermatitis (cpdm), which have mutation in the Sharpin gene (Sharpin(cpdm/cpdm)). Furthermore, reconstitution of NEMO-deficient murine embryonic fibroblast cells with NEMO mutants that are incapable of binding to linear ubiquitin chains supported K13-induced NF-κB activity. K13-induced NF-κB activity was not blocked by CYLD, a deubiquitylating enzyme that can cleave linear and Lys63-linked ubiquitin chains. On the other hand, NEMO was required for interaction of K13 with IKK1/IKKα and IKK2/IKKβ, which resulted in their activation by "T Loop" phosphorylation. CONCLUSIONS/SIGNIFICANCE Our results demonstrate that K13 activates the NF-κB pathway by binding to NEMO which results in the recruitment of IKK1/IKKα and IKK2/IKKβ and their subsequent activation by phosphorylation. Thus, K13 activates NF-κB via a mechanism distinct from that utilized by inflammatory cytokines. These results have important implications for the development of therapeutic agents targeting K13-induced NF-κB for the treatment of KSHV-associated malignancies.
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21
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Ohsaki E, Ueda K. Kaposi's Sarcoma-Associated Herpesvirus Genome Replication, Partitioning, and Maintenance in Latency. Front Microbiol 2012; 3:7. [PMID: 22291692 PMCID: PMC3264903 DOI: 10.3389/fmicb.2012.00007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Accepted: 01/05/2012] [Indexed: 02/03/2023] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) is thought to be an oncogenic member of the γ-herpesvirus subfamily. The virus usually establishes latency upon infection as a default infection pattern. The viral genome replicates according to the host cell cycle by recruiting the host cellular replication machinery. Among the latently expressing viral factors, LANA plays pivotal roles in viral genome replication, partitioning, and maintenance. LANA binds with two LANA-binding sites (LBS1/2) within a terminal repeat (TR) sequence and is indispensable for viral genome replication in latency. The nuclear matrix region seems to be important as a replication site, since LANA as well as cellular replication factors accumulate there and recruit the viral replication origin in latency (ori-P) by its binding activity to LBS. KSHV ori-P consists of LBS followed by a 32-bp GC-rich segment (32GC). Although it has been reported that LANA recruits cellular pre-replication complexes (pre-RC) such as origin recognition complexes (ORCs) to the ori-P through its interaction with ORCs, this mechanism does not account completely for the requirement of the 32GC. On the other hand, there are few reports about the partitioning and maintenance of the viral genome. LANA interacts with many kinds of chromosomal proteins, including Brd2/RING3, core histones, such as H2A/H2B and histone H1, and so on. The detailed molecular mechanisms by which LANA enables KSHV genome partitioning and maintenance still remain obscure. By integrating the findings reported thus far on KSHV genome replication, partitioning, and maintenance in latency, we will summarize what we know now, discuss what questions remain to be answered, and determine what needs to be done next to understand the mechanisms underlying viral replication, partitioning, and maintenance strategy.
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Affiliation(s)
- Eriko Ohsaki
- Division of Virology, Department of Microbiology and Immunology, Osaka University Graduate School of Medicine Suita, Osaka, Japan
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22
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Vitiello M, Galdiero M, Finamore E, Galdiero S, Galdiero M. NF-κB as a potential therapeutic target in microbial diseases. MOLECULAR BIOSYSTEMS 2012; 8:1108-20. [DOI: 10.1039/c2mb05335g] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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23
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Yang Y, Groshong JS, Matta H, Gopalakrishnan R, Yi H, Chaudhary PM. Constitutive NF-kappaB activation confers interleukin 6 (IL6) independence and resistance to dexamethasone and Janus kinase inhibitor INCB018424 in murine plasmacytoma cells. J Biol Chem 2011; 286:27988-97. [PMID: 21705340 DOI: 10.1074/jbc.m110.213363] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Myeloma cells are dependent on IL6 for their survival and proliferation during the early stages of disease, and independence from IL6 is associated with disease progression. The role of the NF-κB pathway in the IL6-independent growth of myeloma cells has not been studied. Because human herpesvirus 8-encoded K13 selectively activates the NF-κB pathway, we have used it as a molecular tool to examine the ability of the NF-κB pathway to confer IL6 independence on murine plasmacytomas. We demonstrated that ectopic expression of K13, but not its NF-κB-defective mutant or a structural homolog, protected plasmacytomas against IL6 withdrawal-induced apoptosis and resulted in emergence of IL6-independent clones that could proliferate long-term in vitro in the absence of IL6 and form abdominal plasmacytomas with visceral involvement when injected intraperitoneally into syngeneic mice. These IL6-independent clones were dependent on NF-κB activity for their survival and proliferation but were resistant to dexamethasone and INCB018424, a selective Janus kinase 1/2 inhibitor. Ectopic expression of human T cell leukemia virus 1-encoded Tax protein, which resembles K13 in inducing constitutive NF-κB activation, similarly protected plasmacytoma cells against IL6 withdrawal-induced apoptosis. Although K13 is known to up-regulate IL6 gene expression, its protective effect was not due to induction of endogenous IL6 production but instead was associated with sustained expression of several antiapoptotic members of the Bcl2 family upon IL6 withdrawal. Collectively, these results demonstrate that NF-κB activation cannot only promote the emergence of IL6 independence during myeloma progression but can also confer resistance to dexamethasone and INCB018424.
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Affiliation(s)
- Yanqiang Yang
- Department of Medicine, Division of Hematology-Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213, USA
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24
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Matta H, Gopalakrishnan R, Punj V, Yi H, Suo Y, Chaudhary PM. A20 is induced by Kaposi sarcoma-associated herpesvirus-encoded viral FLICE inhibitory protein (vFLIP) K13 and blocks K13-induced nuclear factor-kappaB in a negative feedback manner. J Biol Chem 2011; 286:21555-64. [PMID: 21531730 DOI: 10.1074/jbc.m111.224048] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Expression of A20, a negative regulator of the NF-κB pathway, is frequently lost in several subtypes of Hodgkin and non-Hodgkin lymphoma. We report that A20 is expressed in Kaposi sarcoma-associated herpesvirus (KSHV)-infected primary effusion lymphoma cell lines, and its expression correlates closely with the expression of KSHV-encoded viral FLICE inhibitory protein K13. Ectopic expression of K13 induced A20 expression through NF-κB-mediated activation of A20 promoter. In turn, A20 blocked K13-induced NF-κB activity and up-regulation of proinflammatory cytokines CCL20 and IL-8 in a negative feedback fashion. Both the N-terminal deubiquitinating domain and the C-terminal zinc finger domain of A20 were involved in the inhibition of K13-induced NF-κB activity. Overexpression of A20 blocked K13-induced IκBα phosphorylation, NF-κB nuclear translocation, and cellular transformation. Consistent with the above, K13-induced IκBα phosphorylation and NF-κB transcriptional activation were enhanced in A20-deficient cells. Finally, A20 was found to interact physically with K13. Taken collectively, these results demonstrate that K13 is a key determinant of A20 expression in KSHV-infected cells, and A20 is a key negative regulator of K13-induced NF-κB activity. A20 might serve to control the inflammatory response to KSHV infection and protect KSHV-infected cells from apoptosis.
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Affiliation(s)
- Hittu Matta
- Jane Ann Nohl Division of Hematology and Center for the Study of Blood Diseases, University of Southern California Keck School of Medicine, Los Angeles, California 90033, USA
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Kavuri SM, Geserick P, Berg D, Dimitrova DP, Feoktistova M, Siegmund D, Gollnick H, Neumann M, Wajant H, Leverkus M. Cellular FLICE-inhibitory protein (cFLIP) isoforms block CD95- and TRAIL death receptor-induced gene induction irrespective of processing of caspase-8 or cFLIP in the death-inducing signaling complex. J Biol Chem 2011; 286:16631-46. [PMID: 21454681 DOI: 10.1074/jbc.m110.148585] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Death receptors (DRs) induce apoptosis but also stimulate proinflammatory "non-apoptotic" signaling (e.g. NF-κB and mitogen-activated protein kinase (MAPK) activation) and inhibit distinct steps of DR-activated maturation of procaspase-8. To examine whether isoforms of cellular FLIP (cFLIP) or its cleavage products differentially regulate DR signaling, we established HaCaT cells expressing cFLIP(S), cFLIP(L), or mutants of cFLIP(L) (cFLIP(D376N) and cFLIP(p43)). cFLIP variants blocked TRAIL- and CD95L-induced apoptosis, but the cleavage pattern of caspase-8 in the death inducing signaling complex was different: cFLIP(L) induced processing of caspase-8 to the p43/41 fragments irrespective of cFLIP cleavage. cFLIP(S) or cFLIP(p43) blocked procaspase-8 cleavage. Analyzing non-apoptotic signaling pathways, we found that TRAIL and CD95L activate JNK and p38 within 15 min. cFLIP variants and different caspase inhibitors blocked late death ligand-induced JNK or p38 MAPK activation suggesting that these responses are secondary to cell death. cFLIP isoforms/mutants also blocked death ligand-mediated gene induction of CXCL-8 (IL-8). Knockdown of caspase-8 fully suppressed apoptotic and non-apoptotic signaling. Knockdown of cFLIP isoforms in primary human keratinocytes enhanced CD95L- and TRAIL-induced NF-κB activation, and JNK and p38 activation, underscoring the regulatory role of cFLIP for these DR-mediated signals. Whereas the presence of caspase-8 is critical for apoptotic and non-apoptotic signaling, cFLIP isoforms are potent inhibitors of TRAIL- and CD95L-induced apoptosis, NF-κB activation, and the late JNK and p38 MAPK activation. cFLIP-mediated inhibition of CD95 and TRAIL DR could be of crucial importance during keratinocyte skin carcinogenesis and for the activation of innate and/or adaptive immune responses triggered by DR activation in the skin.
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Affiliation(s)
- Shyam M Kavuri
- Department of Dermatology and Venereology, Laboratory for Experimental Dermatology, Otto-von-Guericke-University Magdeburg, Magdeburg 39120, Germany
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26
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Cai Q, Verma SC, Lu J, Robertson ES. Molecular biology of Kaposi's sarcoma-associated herpesvirus and related oncogenesis. Adv Virus Res 2010; 78:87-142. [PMID: 21040832 PMCID: PMC3142360 DOI: 10.1016/b978-0-12-385032-4.00003-3] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Kaposi's Sarcoma-associated Herpesvirus (KSHV), also known as human herpesvirus 8 (HHV-8), is the most recently identified human tumor virus,and is associated with the pathogenesis of Kaposi's sarcoma and two lymphoproliferative disorders known to occur frequently in AIDS patients-primary effusion lymphoma and multicentric Castleman disease. In the 15 years since its discovery, intense studies have demonstrated an etiologic role for KSHV in the development of these malignancies. Here, we review the recent advances linked to understanding KSHV latent and lytic life cycle and the molecular mechanisms of KSHV-mediated oncogenesis in terms of transformation, cell signaling, cell growth and survival, angiogenesis, immune invasion and response to microenvironmental stress, and highlight the potential therapeutic targets for blocking KSHV tumorigenesis.
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Affiliation(s)
- Qiliang Cai
- Department of Microbiology, Abramson, Comprehensive Cancer Center, University of Pennsylvania Medical School, Philadelphia, Pennsylvania, USA
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Punj V, Matta H, Schamus S, Tamewitz A, Anyang B, Chaudhary PM. Kaposi's sarcoma-associated herpesvirus-encoded viral FLICE inhibitory protein (vFLIP) K13 suppresses CXCR4 expression by upregulating miR-146a. Oncogene 2009; 29:1835-44. [PMID: 20023696 PMCID: PMC2845732 DOI: 10.1038/onc.2009.460] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Kaposi's sarcoma (KS)-associated herpesvirus (KSHV)-encoded viral FLICE inhibitory protein (vFLIP) K13 is a potent activator of the nuclear factor-kappaB (NF-kappaB) pathway. In this study, we show that infection with KHSV and ectopic expression of K13, but not its NF-kappaB-defective mutant, suppressed the expression of CXCR4. Suppression of CXCR4 by KSHV and K13 was associated with upregulated expression of miR-146a, a microRNA that is known to bind to the 3'-untranslated region of CXCR4 mRNA. Reporter studies identified two NF-kappaB sites in the promoter of miR-146a that were essential for its activation by K13. Accordingly, ectopic expression of K13, but not its NF-kappaB-defective mutant or other vFLIPs, strongly stimulated the miR-146a promoter activity, which could be blocked by specific genetic and pharmacological inhibitors of the NF-kappaB pathway. Finally, expression of CXCR4 was downregulated in clinical samples of KS and this was accompanied by an increased expression of miR-146a. Our results show that K13-induced NF-kappaB activity suppresses CXCR4 through upregulation of miR-146a. Downregulation of CXCR4 expression by K13 may contribute to KS development by promoting premature release of KSHV-infected endothelial progenitors into the circulation.
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Affiliation(s)
- V Punj
- Division of Hematology-Oncology, Department of Medicine, Hillman Cancer Center, University of Pittsburgh Cancer Institute, University of Pittsburgh, Pittsburgh, PA 15213-1863, USA
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Punj V, Matta H, Schamus S, Chaudhary PM. Integrated microarray and multiplex cytokine analyses of Kaposi's Sarcoma Associated Herpesvirus viral FLICE Inhibitory Protein K13 affected genes and cytokines in human blood vascular endothelial cells. BMC Med Genomics 2009; 2:50. [PMID: 19660139 PMCID: PMC2732924 DOI: 10.1186/1755-8794-2-50] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2008] [Accepted: 08/06/2009] [Indexed: 11/10/2022] Open
Abstract
Background Kaposi's sarcoma (KS) associated herpesvirus (KSHV) is the etiological agent of KS, a neoplasm characterized by proliferating spindle cells, extensive neoangiogenesis and a prominent inflammatory infiltrate. Infection of blood vascular endothelial cells with KSHV in vitro results in their spindle cell transformation, which is accompanied by increased expression of inflammatory chemokines and cytokines, and acquisition of lymphatic endothelial markers. Mimicking the effect of viral infection, ectopic expression of KSHV-encoded latent protein vFLIP K13 is sufficient to induce spindle transformation of vascular endothelial cells. However, the effect of K13 expression on global gene expression and induction of lymphatic endothelial markers in vascular endothelial cells has not been studied. Methods We used gene array analysis to determine change in global gene expression induced by K13 in human vascular endothelial cells (HUVECs). Results of microarray analysis were validated by quantitative RT-PCR, immunoblotting and a multiplex cytokine array. Results K13 affected the expression of several genes whose expression is known to be modulated by KSHV infection, including genes involved in immune and inflammatory responses, anti-apoptosis, stress response, and angiogenesis. The NF-κB pathway was the major signaling pathway affected by K13 expression, and genetic and pharmacological inhibitors of this pathway effectively blocked K13-induced transcriptional activation of the promoter of CXCL10, one of the chemokines whose expression was highly upregulated by K13. However, K13, failed to induce expression of lymphatic markers in blood vascular endothelial cells. Conclusion While K13 may account for change in the expression of a majority of genes observed following KSHV infection, it is not sufficient for inducing lymphatic reprogramming of blood vascular endothelial cells.
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Affiliation(s)
- Vasu Punj
- Department of Medicine, Division of Hematology-Oncology, Hillman Cancer Center, University of Pittsburgh Cancer Institute, University of Pittsburgh, Pittsburgh, PA, USA.
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Induction of CCL20 production by Kaposi sarcoma-associated herpesvirus: role of viral FLICE inhibitory protein K13-induced NF-kappaB activation. Blood 2009; 113:5660-8. [PMID: 19324905 DOI: 10.1182/blood-2008-10-186403] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8, is the etiologic agent of Kaposi sarcoma (KS), an angioproliferative lesion characterized by dramatic angiogenesis and inflammatory infiltration. In this study, we report that expression of chemokine CCL20, a potent chemoattractant of dendritic cells and lymphocytes, is strongly induced in cultured cells either by KSHV infection or on ectopic expression of viral FLICE inhibitory protein K13. This induction is caused by transcriptional activation of CCL20 gene, which is mediated by binding of the p65, p50, and c-Rel subunits of the transcription factor nuclear factor-kappaB (NF-kappaB) to an atypical NF-kappaB-binding site present in the CCL20 gene promoter. The CCL20 gene induction is defective in K13 mutants that lack NF-kappaB activity, and can be blocked by specific genetic and pharmacologic inhibitors of the NF-kappaB pathway. CCR6, the specific receptor for CCL20, is also induced in cultured cells either by KSHV infection or on K13 expression. Finally, expression of CCL20 and CCR6 is increased in clinical samples of KS. These results suggest that KSHV and K13-mediated induction of CCL20 and CCR6 may contribute to the recruitment of dendritic cells and lymphocytes into the KS lesions, and to tumor growth and metastases.
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Poxvirus MC160 protein utilizes multiple mechanisms to inhibit NF-kappaB activation mediated via components of the tumor necrosis factor receptor 1 signal transduction pathway. J Virol 2009; 83:3162-74. [PMID: 19158250 DOI: 10.1128/jvi.02009-08] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Poxviruses express proteins that limit host immune responses to infection. For example, the molluscum contagiosum virus MC160 protein inhibits tumor necrosis factor alpha (TNF-alpha)-induced NF-kappaB activation. This event correlates with MC160-induced IKK1 protein degradation, suggesting a mechanism for the above-mentioned phenotype. IKK1 is stabilized when it associates with the cellular heat shock protein 90 (Hsp90). Here, Hsp90 overexpression restored IKK1 levels in MC160-expressing cells, suggesting that MC160 competitively interacted with Hsp90. In support of this, further investigation showed that a mutant MC160 protein comprising only the C-terminal region (C protein) immunoprecipitated with Hsp90. In contrast, Hsp90 IP with a mutant MC160 protein consisting of only the N-terminal tandem death effector domains (DEDs) (N protein) was dramatically decreased. Since cells expressing either the N or C mutant MC160 protein remained similarly resistant to TNF-alpha-induced NF-kappaB activation, the N mutant protein probably utilized a different mechanism for inhibiting NF-kappaB. One likely mechanism for the N protein lies in its association with the DED-containing procaspase-8 protein, a cellular apoptosis precursor protein that regulates NF-kappaB activation. Here, IPs revealed that this association relied on the presence of the DED-containing N terminus of the MC160 protein but not the C-terminal portion. These interactions appear to have relevance with NF-kappaB activation, since the expression of the viral DEDs strongly inhibited procaspase-8-mediated NF-kappaB activation, an event not substantially altered by the C protein. Thus, the MC160 protein utilizes at least two distinct mechanisms for impeding NF-kappaB activation, association with Hsp90 to result in IKK1 protein degradation or interaction with procaspase-8.
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A nuclear role for Kaposi's sarcoma-associated herpesvirus-encoded K13 protein in gene regulation. Oncogene 2008; 27:5243-53. [PMID: 18469854 DOI: 10.1038/onc.2008.150] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV)-encoded viral FLICE inhibitory protein K13 interacts with a cytosolic IkappaB kinase (IKK) complex to activate nuclear factor-kappaB (NF-kappaB). We recently reported that K13 antagonizes KSHV lytic regulator RTA (replication and transcription activator) and blocks lytic replication, but spares RTA-induced viral interleukin-6 (vIL6). Here we report that K13 is also present in the nuclear compartment, a property not shared by its structural homologs. K13 interacts with and activates the nuclear IKK complex, and binds to the IkappaBalpha promoter. K13 mutants that are retained in the cytosol lack NF-kappaB activity. However, neither the IKKs nor NF-kappaB activation is required for nuclear localization of K13. Instead, this ability is dependent on a nuclear localization signal located in its N-terminal 40 amino acids. Finally, K13, along with p65/RelA, binds to the promoters of a number of KSHV lytic genes, including RTA, ORF57 and vGPCR, but not to the promoter of the vIL6 gene. Thus, K13 has an unexpected nuclear role in viral and cellular gene regulation and its differential binding to the promoters of lytic genes may not only contribute to the inhibition of KSHV lytic replication, but may also account for the escape of vIL6 from K13-induced transcriptional suppression.
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Lacoste V, Nicot C, Gessain A, Valensi F, Gabarre J, Matta H, Chaudhary PM, Mahieux R. In primary effusion lymphoma cells, MYB transcriptional repression is associated with v-FLIP expression during latent KSHV infection while both v-FLIP and v-GPCR become involved during the lytic cycle. Br J Haematol 2007; 138:487-501. [PMID: 17659053 DOI: 10.1111/j.1365-2141.2007.06697.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Primary effusion lymphoma (PEL) is a rare, distinct subtype of non-Hodgkin lymphoma, which is associated with Kaposi sarcoma-associated herpesvirus (KSHV) infection. Although MYB levels are high in most neoplastic B cells, we found that, unexpectedly, both PEL cells and uncultured PEL patients' samples contained very low levels of MYB mRNA when compared to B-cell leukaemia samples obtained from KSHV(-) patients. These results were further confirmed at the protein level. Both latent viral FLICE inhibitory protein (v-FLIP) and early lytic viral G protein coupled receptor (v-GPCR) KSHV proteins were found to activate nuclear factor (NF)-kappaB and transrepress a MYB promoter reporter construct. In contrast, a dominant negative inhibitor of NF-kappaB (IkappaB-alpha) mutant prevented v-FLIP and v-GPCR from inhibiting MYB functions while a v-GPCR mutant that was impaired for NF-kappaB activation could not repress the MYB construct. Transduction of a v-FLIP expressing vector or stable transfection of v-GPCR both resulted in a marked downregulation of the endogenous MYB protein expression. However, MYB expression transactivated the lytic switch Replication and Transcription Activator (RTA) promoter in transient transfection assays. Taken together, our results demonstrate that, contrary to a number of other haematological malignancies, MYB expression is not required for PEL cell proliferation. Repressing MYB expression also helps in maintaining the virus in latency.
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MESH Headings
- CASP8 and FADD-Like Apoptosis Regulating Protein/metabolism
- Cell Line, Tumor
- Cell Transformation, Viral
- Gene Expression
- Gene Expression Regulation, Viral
- Genes, myb
- Herpesvirus 8, Human/physiology
- Humans
- Immediate-Early Proteins/metabolism
- Lymphoma, AIDS-Related/metabolism
- Lymphoma, AIDS-Related/virology
- Lymphoma, Non-Hodgkin/metabolism
- Lymphoma, Non-Hodgkin/virology
- NF-kappa B/metabolism
- Proto-Oncogene Proteins c-myb/analysis
- Receptors, G-Protein-Coupled/metabolism
- Sarcoma, Kaposi/metabolism
- Sarcoma, Kaposi/virology
- Trans-Activators/metabolism
- Transcription, Genetic
- Transduction, Genetic
- Transfection
- Viral Proteins/metabolism
- Virus Activation
- Virus Latency
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Affiliation(s)
- Vincent Lacoste
- Unité d'Epidémiologie et Physiopathologie des Virus Oncogènes, Institut Pasteur, Paris, France
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Matta H, Mazzacurati L, Schamus S, Yang T, Sun Q, Chaudhary PM. Kaposi's sarcoma-associated herpesvirus (KSHV) oncoprotein K13 bypasses TRAFs and directly interacts with the IkappaB kinase complex to selectively activate NF-kappaB without JNK activation. J Biol Chem 2007; 282:24858-65. [PMID: 17597077 DOI: 10.1074/jbc.m700118200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Kaposi's sarcoma herpesvirus oncoprotein vFLIP K13 is a potent activator of NF-kappaB and plays a key role in viral pathogenesis. K13 contains a putative TRAF-interacting motif, which is reportedly required for its interaction with TRAF2. The K13-TRAF2 interaction is believed to be essential for the recruitment of K13 to the I-kappaB kinase (IKK) complex and for K13-induced NF-kappaB and JNK activation. In addition, TRAF3 has been reported to be required for K13-induced NF-kappaB and JNK activation. We have re-examined the role of the TRAFs in K13 signaling and report that mutations in the putative TRAF-interacting motif of K13 have no deleterious effect on its ability to interact with the IKK complex or activation of the NF-kappaB pathway. Furthermore, endogenously expressed TRAF2 and TRAF3 do not interact with K13 and play no role in K13-induced NF-kappaB activation or its interaction with the IKK complex. Finally, K13 does not activate the JNK pathway. Our results support a model in which K13 bypasses the upstream components of the tumor necrosis factor receptor signaling pathway and directly interacts with the IKK complex to selectively activate the NF-kappaB pathway without affecting the JNK pathway. Selective NF-kappaB activation by K13 might represent a novel strategy employed by the virus to promote latency.
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Affiliation(s)
- Hittu Matta
- Department of Medicine, Division of Hematology-Oncology, The University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA
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Elgui de Oliveira D. DNA viruses in human cancer: An integrated overview on fundamental mechanisms of viral carcinogenesis. Cancer Lett 2007; 247:182-96. [PMID: 16814460 DOI: 10.1016/j.canlet.2006.05.010] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2006] [Revised: 05/17/2006] [Accepted: 05/18/2006] [Indexed: 11/18/2022]
Abstract
The first experimental data suggesting that neoplasm development in animals might be influenced by infectious agents were published in the early 1900s. However, conclusive evidence that DNA viruses play a role in the pathogenesis of some human cancers only emerged in the 1950s, when Epstein-Barr virus (EBV) was discovered within Burkitt lymphoma cells. Besides EBV, other DNA viruses consistently associated with human cancers are the hepatitis B virus (HBV), human papillomavirus (HPV), and Kaposi sarcoma herpesvirus (KSHV). Although each virus has unique features, it is becoming clearer that all these oncogenic agents target multiple cellular pathways to support malignant transformation and tumor development.
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Affiliation(s)
- Deilson Elgui de Oliveira
- Department of Pathology, Botucatu School of Medicine, State University of Sao Paulo (UNESP), Brazil.
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35
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Abstract
The Kaposi sarcoma herpesvirus (KSHV) encodes multiple proteins that disrupt host antiviral responses, including four viral proteins that have homology to the interferon regulatory factor (IRF) family of transcription factors. At least three of the KSHV vIRFs (vIRFs 1-3) alter responses to cellular IRFs and to interferons (IFNs), whereas functional changes resulting from the fourth vIRF (vIRF-4) have not been reported. The vIRFs also affect other important regulatory proteins in the cell, including responses to transforming growth factor beta (TGF-beta) and the tumor suppressor protein p53. This review examines the expression of the vIRFs during the life cycle of KSHV and the functional consequences of their expression.
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Affiliation(s)
- M K Offermann
- Winship Cancer Institute, 1365-B Clifton Rd NE, Atlanta, GA 30322, USA.
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36
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Matta H, Surabhi RM, Zhao J, Punj V, Sun Q, Schamus S, Mazzacurati L, Chaudhary PM. Induction of spindle cell morphology in human vascular endothelial cells by human herpesvirus 8-encoded viral FLICE inhibitory protein K13. Oncogene 2006; 26:1656-60. [PMID: 16936773 DOI: 10.1038/sj.onc.1209931] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Human herpesvirus 8 (HHV8), also known as Kaposi's sarcoma-associated herpesvirus, is linked to the development of Kaposi's sarcoma, a disease characterized by the presence of distinctive proliferating spindle-like cells. Although HHV8 can induce spindle cell transformation of vascular endothelial cells in vitro, the viral gene(s) responsible for this phenotype remain to be identified. We demonstrate that expression of HHV8-encoded viral Fas-associated death domain protein-like IL-1beta-converting enzyme inhibitory protein K13 is sufficient to induce spindle cell phenotype in human umbilical vein endothelial cells (HUVEC), which is associated with the activation of the nuclear factor-kappaB (NF-kappaB) pathway and can be blocked by Bay-11-7082, a specific inhibitor of this pathway. K13 induces the expression of several genes known to be upregulated in HHV8-transformed vascular endothelial cells, such as interleukin (IL)-6, IL-8, CXC ligand 3 (CXCL3), orphan G protein coupled receptor (RDC1), cyclooxygenase-2 (COX-2) and dual-specificity phosphatase 5 (DUSP5). Furthermore, similar to K13, HHV8-induced spindle cell transformation of HUVEC is associated with NF-kappaB activation and can be blocked by Bay-11-7082. Thus, ectopic expression of a single latent gene of HHV8 is sufficient for the acquisition of spindle cell phenotype by vascular endothelial cells and NF-kappaB activation plays an essential role in this process.
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Affiliation(s)
- H Matta
- Department of Medicine, Division of Hematology-Oncology and the Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA 15213-1863, USA
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37
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Sun Q, Matta H, Lu G, Chaudhary PM. Induction of IL-8 expression by human herpesvirus 8 encoded vFLIP K13 via NF-kappaB activation. Oncogene 2006; 25:2717-26. [PMID: 16418726 DOI: 10.1038/sj.onc.1209298] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Human herpesvirus 8 (HHV-8) encodes a viral FLICE inhibitory protein (vFLIP), called K13, with homology to the prodomain of caspase 8. K13 has been postulated to protect virally infected cells against death receptor-induced apoptosis. We report that K13 leads to constitutive upregulation of IL-8 secretion by transcriptional upregulation of its promoter. K13-induced IL-8 promoter activation is dependent on an intact NF-kappaB-binding site and is associated with increased binding of classical NF-kappaB pathway subunits p65, c-Rel and p50, respectively. IL-8 production is defective in K13 mutants defective in classical NF-kappaB activation and is blocked by genetic and pharmacological inhibitors of this pathway. In contrast, K13 failed to activate the JNK/AP-1 pathway and deletion of AP-1-binding site in the IL-8 promoter or use of a specific JNK inhibitor had only a partial effect on K13-induced IL-8 promoter activation. Collectively, above results demonstrate that K13 is a major mediator of IL-8 production and therapeutic agents targeting K13-induced NF-kappaB pathway may have a role in the treatment of conditions in which HHV-8-induced IL-8 production plays a pathogenic role.
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Affiliation(s)
- Q Sun
- Hamon Center for Therapeutic Oncology Research, UT Southwestern Medical Center, Dallas, TX, USA
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Sun Q, Matta H, Chaudhary PM. Kaposi's sarcoma associated herpes virus-encoded viral FLICE inhibitory protein activates transcription from HIV-1 Long Terminal Repeat via the classical NF-kappaB pathway and functionally cooperates with Tat. Retrovirology 2005; 2:9. [PMID: 15713234 PMCID: PMC554086 DOI: 10.1186/1742-4690-2-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2004] [Accepted: 02/15/2005] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND The nuclear transcription factor NF-kappaB binds to the HIV-1 long terminal repeat (LTR) and is a key regulator of HIV-1 gene expression in cells latently infected with this virus. In this report, we have analyzed the ability of Kaposi's sarcoma associate herpes virus (KSHV, also known as Human Herpes virus 8)-encoded viral FLIP (Fas-associated death domain-like IL-1 beta-converting enzyme inhibitory protein) K13 to activate the HIV-1 LTR. RESULTS We present evidence that vFLIP K13 activates HIV-1 LTR via the activation of the classical NF-kappaB pathway involving c-Rel, p65 and p50 subunits. K13-induced HIV-1 LTR transcriptional activation requires the cooperative interaction of all three components of the IKK complex and can be effectively blocked by inhibitors of the classical NF-kappaB pathway. K13 mutants that lacked the ability to activate the NF-kappaB pathway also failed to activate the HIV-1 LTR. K13 could effectively activate a HIV-1 LTR reporter construct lacking the Tat binding site but failed to activate a construct lacking the NF-kappaB binding sites. However, coexpression of HIV-1 Tat with K13 led to synergistic activation of HIV-1 LTR. Finally, K13 differentially activated HIV-1 LTRs derived from different strains of HIV-1, which correlated with their responsiveness to NF-kappaB pathway. CONCLUSIONS Our results suggest that concomitant infection with KSHV/HHV8 may stimulate HIV-1 LTR via vFLIP K13-induced classical NF-kappaB pathway which cooperates with HIV-1 Tat protein.
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Affiliation(s)
- Qinmiao Sun
- Hamon Center for Therapeutic Oncology Research, UT Southwestern Medical Center, Dallas TX 75390-8593, USA
| | - Hittu Matta
- Hamon Center for Therapeutic Oncology Research, UT Southwestern Medical Center, Dallas TX 75390-8593, USA
- Department of Medicine, Division of Hematology-Oncology and the Hillman Cancer Center, University of Pittsburgh, PA 15213, USA
| | - Preet M Chaudhary
- Hamon Center for Therapeutic Oncology Research, UT Southwestern Medical Center, Dallas TX 75390-8593, USA
- Department of Medicine, Division of Hematology-Oncology and the Hillman Cancer Center, University of Pittsburgh, PA 15213, USA
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Direkze S, Laman H. Regulation of growth signalling and cell cycle by Kaposi's sarcoma-associated herpesvirus genes. Int J Exp Pathol 2005; 85:305-19. [PMID: 15566428 PMCID: PMC2517533 DOI: 10.1111/j.0959-9673.2004.00407.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) is the primary aetiological agent of at least three malignancies associated with HIV infection and immunosuppression: Kaposi's sarcoma, primary effusion lymphoma and multicentric Castleman's disease. KSHV encodes proteins that deregulate key checkpoints in the signalling pathways governing cell proliferation, which may ultimately contribute to the virus' oncogenic potential. To alter cellular signalling associated with proliferation, these viral proteins function like growth factor ligands/receptors, signal transduction proteins, transcription factors and cell cycle regulators. This review focuses on the mechanisms by which some KSHV-encoded proteins activate signalling pathways and cell proliferation and their role in the pathogenesis of KSHV-driven mechanisms.
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Affiliation(s)
- Shamindra Direkze
- Cancer Research UK, Viral Oncology Laboratory, Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK
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Kreuz S, Siegmund D, Rumpf JJ, Samel D, Leverkus M, Janssen O, Häcker G, Dittrich-Breiholz O, Kracht M, Scheurich P, Wajant H. NFkappaB activation by Fas is mediated through FADD, caspase-8, and RIP and is inhibited by FLIP. ACTA ACUST UNITED AC 2004; 166:369-80. [PMID: 15289496 PMCID: PMC2172264 DOI: 10.1083/jcb.200401036] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Fas (APO-1/CD95) is the prototypic death receptor, and the molecular mechanisms of Fas-induced apoptosis are comparably well understood. Here, we show that Fas activates NFκB via a pathway involving RIP, FADD, and caspase-8. Remarkably, the enzymatic activity of the latter was dispensable for Fas-induced NFκB signaling pointing to a scaffolding-related function of caspase-8 in nonapoptotic Fas signaling. NFκB was activated by overexpressed FLIPL and FLIPS in a cell type–specific manner. However, in the context of Fas signaling both isoforms blocked FasL-induced NFκB activation. Moreover, down-regulation of both endogenous FLIP isoforms or of endogenous FLIPL alone was sufficient to enhance FasL-induced expression of the NFκB target gene IL8. As NFκB signaling is inhibited during apoptosis, FasL-induced NFκB activation was most prominent in cells that were protected by Bcl2 expression or caspase inhibitors and expressed no or minute amounts of FLIP. Thus, protection against Fas-induced apoptosis in a FLIP-independent manner converted a proapoptotic Fas signal into an inflammatory NFκB-related response.
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Affiliation(s)
- Sebastian Kreuz
- Institute of Cell Biology and Immunology, University of Stuttgart, Germany
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Rathore N, Matta H, Chaudhary PM. An evolutionary conserved pathway of nuclear factor-kappaB activation involving caspase-mediated cleavage and N-end rule pathway-mediated degradation of IkappaBalpha. J Biol Chem 2004; 279:39358-65. [PMID: 15252032 DOI: 10.1074/jbc.m406712200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The Drosophila nuclear factor-kappaB (NF-kappaB)-like transcription factor Relish is activated by an endoproteolytic cleavage step mediated by the Drosophila caspase Dredd. We have examined the contribution of the caspase cascade to NF-kappaB activation via TRAIL, a mammalian tumor necrosis factor family ligand that is a potent activator of caspases. Our results demonstrate that TRAIL activates NF-kappaB in two phases as follows: an early caspase independent phase and a late caspase dependent phase. The late phase of the TRAIL-induced NF-kappaB is critically dependent on caspase 8 and can be blocked by pharmacological and genetic inhibitors of caspase 8 activation, such as benzyloxycarbonyl-VAD-fluoromethyl ketone, benzyloxycarbonyl-IETD-fluoromethyl ketone, and small interfering RNA targeting caspase 8 and FADD. Whereas caspase 3 is required for TRAIL-induced apoptosis, it is not involved in TRAIL-induced NF-kappaB activation. The late phase of TRAIL-induced NF-kappaB activation involves caspase mediated cleavage of IkappaBalpha between Asp(31) and Ser(32) residues to generate an N-terminal truncated fragment that is degraded by the proteasome via the N-end rule pathway. Our results demonstrate that caspases play an evolutionarily conserved role as regulated entry points to the N-end rule pathway and in NF-kappaB activation in mammalian cells.
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Affiliation(s)
- Nisha Rathore
- Hamon Center for Therapeutic Oncology Research, Texas 75390-8593, USA
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Matta H, Chaudhary PM. Activation of alternative NF-kappa B pathway by human herpes virus 8-encoded Fas-associated death domain-like IL-1 beta-converting enzyme inhibitory protein (vFLIP). Proc Natl Acad Sci U S A 2004; 101:9399-404. [PMID: 15190178 PMCID: PMC438988 DOI: 10.1073/pnas.0308016101] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Kaposi's sarcoma-associated herpesvirus (KSHV, also called human herpesvirus 8) has been linked to KS and primary effusion lymphoma (PEL) in immunocompromised individuals. We report that PEL cell lines have constitutive active alternative NF-kappa B pathway and demonstrate high-level expression of NF-kappa B2/p100 precursor and its processed subunit p52. To elucidate the mechanism of activation of the alternative NF-kappa B pathway in PEL cells, we have investigated the role of KSHV-encoded viral Fas-associated death domain-like IL- beta 1-converting enzyme inhibitory protein (vFLIP) K13. We demonstrate that stable expression of K13, but not other FLIPs, in a variety of cell lines constitutively up-regulates p100/NF-kappa B2 expression and leads to its processing into the p52 subunit. K13-induced up-regulation and processing of p100 critically depends on the I kappa B kinase (IKK)alpha/IKK1 subunit of the IKK complex, whereas IKK beta/IKK2, receptor-interacting protein, and NF-kappa B-inducing kinase are dispensable for this process. Silencing of endogenous K13 expression by siRNA inhibits p100 processing and cellular proliferation. Our results demonstrate for the first time, to our knowledge, that KSHV vFLIP K13 is required for the growth and proliferation of PEL cells and alternative NF-kappa B pathway plays a key role in this process. Therapeutic agents targeting the alternative NF-kappa B pathway may have a role in the treatment of KSHV-associated lymphomas.
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Affiliation(s)
- Hittu Matta
- Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, 75390-8593, USA
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