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Palmer M, Leo A, Atyeo N, Tomacari C, Nguyen X, Papp B. Conserved linear motif within the immediate early protein ORF45 promotes its engagement with KSHV lytic cycle-promoting forkhead transcription factors, FOXK1 and FOXK2. J Virol 2024:e0088624. [PMID: 39287387 DOI: 10.1128/jvi.00886-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2024] [Accepted: 08/23/2024] [Indexed: 09/19/2024] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) is a gammaherpesvirus that can cause several cancers, such as Kaposi sarcoma and primary effusion lymphoma (PEL). We and others have recently demonstrated that Forkhead box (FOX) transcription factors can be dysregulated by KSHV, and they can affect KSHV infection. Herein, we focus on dissecting the role of two FOXK subfamily members, FOXK1 and FOXK2, in the KSHV life cycle. FOXK proteins are key host regulators of cellular functions, yet their role in KSHV infection remains unknown. Here, we demonstrated that both FOXK proteins are essential for efficient KSHV lytic reactivation in PEL cells. FOXK1 and FOXK2 are unique as they are the only FOX proteins that contain a Forkhead-associated (FHA) domain. The FHA domain is a specialized protein binding domain that recognizes a short linear serine/threonine-rich (S/T) motif. Through an unbiased motif survey, we found that KSHV viral protein ORF45 and its gammaherpesvirus homologs contain a putative FHA-binding motif. ORF45 is an immediate early tegument protein, vital for lytic reactivation and virus production. We demonstrated that ORF45 uses its novel conserved motif to interact with the FHA domain containing FOXK factors in the nucleus of infected cells. A single-point mutation of the conserved threonine residue in the motif within ORF45 abolished the ORF45-FOXK1/2 interaction. Our data indicates that FOXK proteins interact with ORF45 homologs encoded by murine gammaherpesvirus 68 (MHV68) and Rhesus macaque rhadinovirus (RRV), and that the FHA domains of FOXK proteins are sufficient for their interactions, highlighting a conserved mechanism.IMPORTANCEThe dysregulation of Forkhead transcription factors contributes to many different human diseases, including cancers, but their impact on herpesvirus lifecycle and pathogenesis is less understood. Our study uncovers a critical pro-lytic function of the FOXK subfamily and its requirement for KSHV lytic reactivation in PEL. We found that FOXK proteins bind to a key immediate early KSHV protein ORF45 using its novel short linear S/T motif. Notably, even though ORF45 homologs in gammaherpesviruses are highly diverse, we identified a similar S/T short linear motif in ORF45 homologs and also showed an evolutionary conserved interaction between FOXK proteins and ORF45 homologs of MHV68 and RRV. Our study provides a basis for future studies in animal models to evaluate the role of FOXK proteins and the impact of their interactions with ORF45 in gammaherpesvirus infection and pathogenesis. Targeting these interactions could allow a novel way to limit gammaherpesvirus infections.
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Affiliation(s)
- Marley Palmer
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA
| | - Alessandro Leo
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA
| | - Natalie Atyeo
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA
| | - Christiana Tomacari
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA
| | - Xuan Nguyen
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA
| | - Bernadett Papp
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA
- Genetics Institute, University of Florida, Gainesville, Florida, USA
- Health Cancer Center, University of Florida, Gainesville, Florida, USA
- Informatics Institute, University of Florida, Gainesville, Florida, USA
- Center for Orphaned Autoimmune Disorders, University of Florida, Gainesville, Florida, USA
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Cui L, Li X, Liu Z, Liu X, Zhu Y, Zhang Y, Han Z, Zhang Y, Liu S, Li H. MAPK pathway orchestrates gallid alphaherpesvirus 1 infection through the biphasic activation of MEK/ERK and p38 MAPK signaling. Virology 2024; 597:110159. [PMID: 38943781 DOI: 10.1016/j.virol.2024.110159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Revised: 06/05/2024] [Accepted: 06/20/2024] [Indexed: 07/01/2024]
Abstract
Therapies targeting virus-host interactions are seen as promising strategies for treating gallid alphaherpesvirus 1 (ILTV) infection. Our study revealed a biphasic activation of two MAPK cascade pathways, MEK/ERK and p38 MAPK, as a notably activated host molecular event in response to ILTV infection. It exhibits antiviral functions at different stages of infection. Initially, the MEK/ERK pathway is activated upon viral invasion, leading to a broad suppression of metabolic pathways crucial for ILTV replication, thereby inhibiting viral replication from the early stage of ILTV infection. As the viral replication progresses, the p38 MAPK pathway activates its downstream transcription factor, STAT1, further hindering viral replication. Interestingly, ILTV overcomes this biphasic antiviral barrier by hijacking host p38-AKT axis, which protects infected cells from the apoptosis induced by infection and establishes an intracellular equilibrium conducive to extensive ILTV replication. These insights could provide potential therapeutic targets for ILTV infection.
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Affiliation(s)
- Lu Cui
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, 150069, China
| | - Xuefeng Li
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, 150069, China; School of Basic Medical Sciences, Translational Medicine Institute, Key Laboratory of Environment and Genes Related to Diseases of the Education Ministry, Xi'an Key Laboratory of Immune Related Diseases, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University, Xi'an, 710061, China
| | - Zheyi Liu
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, 150069, China
| | - Xiaoxiao Liu
- School of Basic Medical Sciences, Translational Medicine Institute, Key Laboratory of Environment and Genes Related to Diseases of the Education Ministry, Xi'an Key Laboratory of Immune Related Diseases, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University, Xi'an, 710061, China
| | - Yongxin Zhu
- School of Basic Medical Sciences, Translational Medicine Institute, Key Laboratory of Environment and Genes Related to Diseases of the Education Ministry, Xi'an Key Laboratory of Immune Related Diseases, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University, Xi'an, 710061, China
| | - Yu Zhang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, 150069, China
| | - Zongxi Han
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, 150069, China
| | - Yilei Zhang
- School of Basic Medical Sciences, Translational Medicine Institute, Key Laboratory of Environment and Genes Related to Diseases of the Education Ministry, Xi'an Key Laboratory of Immune Related Diseases, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University, Xi'an, 710061, China.
| | - Shengwang Liu
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, 150069, China.
| | - Hai Li
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, 150069, China; School of Basic Medical Sciences, Translational Medicine Institute, Key Laboratory of Environment and Genes Related to Diseases of the Education Ministry, Xi'an Key Laboratory of Immune Related Diseases, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University, Xi'an, 710061, China.
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3
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Majerciak V, Alvarado-Hernandez B, Ma Y, Duduskar S, Lobanov A, Cam M, Zheng ZM. KSHV promotes oncogenic FOS to inhibit nuclease AEN and transactivate RGS2 for AKT phosphorylation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.27.577582. [PMID: 38410462 PMCID: PMC10896338 DOI: 10.1101/2024.01.27.577582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) ORF57 is a lytic RNA-binding protein. We applied BCBL-1 cells in lytic KSHV infection and performed UV cross-linking immunoprecipitation (CLIP) followed by RNA-seq of the CLIPed RNA fragments (CLIP-seq). We identified ORF57-bound transcripts from 544 host protein-coding genes. By comparing with the RNA-seq profiles from BCBL-1 cells with latent and lytic KSHV infection and from HEK293T cells with and without ORF57 expression, we identified FOS and CITED2 RNAs being two common ORF57-specific RNA targets. FOS dimerizes with JUN as a transcription factor AP-1 involved in cell proliferation, differentiation, and transformation. Knockout of the ORF57 gene from the KSHV genome led BAC16-iSLK cells incapable of FOS expression in KSHV lytic infection. The dysfunctional KSHV genome in FOS expression could be rescued by Lenti-ORF57 virus infection. ORF57 protein does not regulate FOS translation but binds to the 13-nt RNA motif near the FOS RNA 5' end and prolongs FOS mRNA half-life 7.7 times longer than it is in the absence of ORF57. This binding of ORF57 to FOS RNA is competitive to the binding of a host nuclease AEN (also referred to as ISG20L1). KSHV infection inhibits the expression of AEN, but not exosomal RNA helicase MTR4. FOS expression mediated by ORF57 inhibits AEN transcription, but transactivates RGS2, a regulator of G-protein coupled receptors. FOS binds a conserved AP-1 site in the RGS2 promoter and enhances RGS2 expression to phosphorylate AKT. Altogether, we have discovered that KSHV ORF57 specifically binds and stabilizes FOS RNA to increase FOS expression, thereby disturbing host gene expression and inducing pathogenesis during KSHV lytic infection.
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Affiliation(s)
- Vladimir Majerciak
- Tumor Virus RNA Biology Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI/NIH, Frederick, MD, 21702, USA
| | - Beatriz Alvarado-Hernandez
- Tumor Virus RNA Biology Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI/NIH, Frederick, MD, 21702, USA
| | - Yanping Ma
- Tumor Virus RNA Biology Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI/NIH, Frederick, MD, 21702, USA
| | - Shivalee Duduskar
- Tumor Virus RNA Biology Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI/NIH, Frederick, MD, 21702, USA
| | - Alexei Lobanov
- CCR Collaborative Bioinformatics Resource, Center for Cancer Research, NCI/NIH, Bethesda, MD, 20892, USA
| | - Maggie Cam
- CCR Collaborative Bioinformatics Resource, Center for Cancer Research, NCI/NIH, Bethesda, MD, 20892, USA
| | - Zhi-Ming Zheng
- Tumor Virus RNA Biology Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI/NIH, Frederick, MD, 21702, USA
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Atyeo N, Chae MY, Toth Z, Sharma A, Papp B. Kaposi's Sarcoma-Associated Herpesvirus Immediate Early Proteins Trigger FOXQ1 Expression in Oral Epithelial Cells, Engaging in a Novel Lytic Cycle-Sustaining Positive Feedback Loop. J Virol 2023; 97:e0169622. [PMID: 36815831 PMCID: PMC10062149 DOI: 10.1128/jvi.01696-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 02/02/2023] [Indexed: 02/24/2023] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic gammaherpesvirus that can replicate in oral epithelial cells to promote viral transmission via saliva. To identify novel regulators of KSHV oral infection, we performed a transcriptome analysis of KSHV-infected primary human gingival epithelial (HGEP) cells, which identified the gene coding for the host transcription factor FOXQ1 as the top induced host gene. FOXQ1 is nearly undetectable in uninfected HGEP and telomerase-immortalized gingival keratinocytes (TIGK) cells but is highly expressed within hours of KSHV infection. We found that while the FOXQ1 promoter lacks activating histone acetylation marks in uninfected oral epithelial cells, these marks accumulate in the FOXQ1 promoter in infected cells, revealing a rapid epigenetic reprogramming event. To evaluate FOXQ1 function, we depleted FOXQ1 in KSHV-infected TIGK cells, which resulted in reduced accumulation of KSHV lytic proteins and viral DNA over the course of 4 days of infection, uncovering a novel lytic cycle-sustaining role of FOXQ1. A screen of KSHV lytic proteins demonstrated that the immediate early proteins ORF45 and replication and transcription activator (RTA) were both sufficient for FOXQ1 induction in oral epithelial cells, indicating active involvement of incoming and rapidly expressed factors in altering host gene expression. ORF45 is known to sustain extracellular signal-regulated kinase (ERK) p90 ribosomal s6 kinase (RSK) pathway activity to promote lytic infection. We found that an ORF45 mutant lacking RSK activation function failed to induce FOXQ1 in TIGK cells, revealing that ORF45 uses a shared mechanism to rapidly induce both host and viral genes to sustain lytic infection in oral epithelial cells. IMPORTANCE The oral cavity is a primary site of initial contact and entry for many viruses. Viral replication in the oral epithelium promotes viral shedding in saliva, allowing interpersonal transmission, as well as spread to other cell types, where chronic infection can be established. Understanding the regulation of KSHV infection in the oral epithelium would allow for the design of universal strategies to target the first stage of viral infection, thereby halting systemic viral pathogenesis. Overall, we uncover a novel positive feedback loop in which immediate early KSHV factors drive rapid host reprogramming of oral epithelial cells to sustain the lytic cycle in the oral cavity.
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Affiliation(s)
- Natalie Atyeo
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA
| | - Min Young Chae
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA
| | - Zsolt Toth
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA
- Genetics Institute, University of Florida, Gainesville, Florida, USA
- Health Cancer Center, University of Florida, Gainesville, Florida, USA
| | - Aria Sharma
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA
| | - Bernadett Papp
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA
- Genetics Institute, University of Florida, Gainesville, Florida, USA
- Health Cancer Center, University of Florida, Gainesville, Florida, USA
- Informatics Institute, University of Florida, Gainesville, Florida, USA
- Center for Orphaned Autoimmune Disorders, University of Florida, Gainesville, Florida, USA
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5
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Li X, Wang F, Zhang X, Sun Q, Kuang E. Suppression of KSHV lytic replication and primary effusion lymphoma by selective RNF5 inhibition. PLoS Pathog 2023; 19:e1011103. [PMID: 36656913 PMCID: PMC9888681 DOI: 10.1371/journal.ppat.1011103] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 01/31/2023] [Accepted: 01/06/2023] [Indexed: 01/20/2023] Open
Abstract
Primary effusion lymphoma (PEL), a rare aggressive B-cell lymphoma in immunosuppressed patients, is etiologically associated with oncogenic γ-herpesvirus infection. Chemotherapy is commonly used to treat PEL but usually results in poor prognosis and survival; thus, novel therapies and drug development are urgently needed for PEL treatment. Here, we demonstrated that inhibition of Ring finger protein 5 (RNF5), an ER-localized E3 ligase, suppresses multiple cellular pathways and lytic replication of Kaposi sarcoma-associated herpesvirus (KSHV) in PEL cells. RNF5 interacts with and induces Ephrin receptors A3 (EphA3) and EphA4 ubiquitination and degradation. RNF5 inhibition increases the levels of EphA3 and EphA4, thereby reducing ERK and Akt activation and KSHV lytic replication. RNF5 inhibition decreased PEL xenograft tumor growth and downregulated viral gene expression, cell cycle gene expression, and hedgehog signaling in xenograft tumors. Our study suggests that RNF5 plays the critical roles in KSHV lytic infection and tumorigenesis of primary effusion lymphoma.
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Affiliation(s)
- Xiaojuan Li
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
- College of Clinical Medicine, Hubei University of Chinese Medicine, Wuhan, China
| | - Fan Wang
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
| | - Xiaolin Zhang
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
| | - Qinqin Sun
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
| | - Ersheng Kuang
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou, China
- * E-mail:
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6
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Luo T, Pan Y, Liu Y, Zheng J, Zhuang Z, Ren Z, Zhu J, Gu Y, Zeng Y. LANA regulates miR-155/GATA3 signaling axis by enhancing c-Jun/c-Fos interaction to promote the proliferation and migration of KSHV-infected cells. J Med Virol 2023; 95:e28255. [PMID: 36284455 DOI: 10.1002/jmv.28255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 10/08/2022] [Accepted: 10/21/2022] [Indexed: 01/11/2023]
Abstract
Kaposi's sarcoma (KS) is the second most common tumor in people infected with human immunodeficiency virus worldwide, but its pathogenesis is still unclear. In this study, we discovered that the expression of GATA-binding protein 3 (GATA3) was lowly expressed in KS tissues and KSHV-infected cells, while microRNA-155 (miR-155) was highly expressed in KS serum and KSHV-infected cells. miR-155 promoted the proliferation, migration and invasion of KSHV infection by targeting GATA3. Further, The KSHV-encoded protein, the Latency associated nuclear antigen (LANA), promotes the proliferation, migration and invasion of KSHV-infected cells by regulating the miR-155/GATA3 axis. Regarding the molecular mechanism, c-Jun and c-Fos interact to form a complex. LANA upregulates the expression of c-Jun and c-Fos and enhances the formation of c-Jun/c-Fos complex. The complex binds to the -95∼-100 bp site of miR-155 promoter and transcriptionally activates miR-155. All in all, LANA enhances the c-Jun/c-Fos interaction, resulting in enhanced transcriptional regulation of miR-155 by the c-Jun/c-Fos complex, thereby downregulating GATA3 and promoting the proliferation, migration and invasion of KSHV-infected cells. The discovery of LANA/c-Jun/c-Fos/miR-155/GATA3 further refines the pathogenesis of KS, potentially opening a new avenue for developing effective drugs against KS.
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Affiliation(s)
- Ting Luo
- Precision Clinical Laboratory, Central People's Hospital of Zhanjiang, Zhanjiang, Guangdong, China.,Key Laboratory of Xinjiang Endemic and Ethnic Disease, School of Medicine, Shihezi University, Shihezi, Xinjiang, China
| | - Yangyang Pan
- Precision Clinical Laboratory, Central People's Hospital of Zhanjiang, Zhanjiang, Guangdong, China.,Key Laboratory of Xinjiang Endemic and Ethnic Disease, School of Medicine, Shihezi University, Shihezi, Xinjiang, China
| | - Yuhao Liu
- Beijing Key Laboratory for Radiobiology, Beijing Institute of Radiation Medicine, Beijing, China
| | - Jun Zheng
- Key Laboratory of Xinjiang Endemic and Ethnic Disease, School of Medicine, Shihezi University, Shihezi, Xinjiang, China
| | - Zhaowei Zhuang
- Key Laboratory of Xinjiang Endemic and Ethnic Disease, School of Medicine, Shihezi University, Shihezi, Xinjiang, China
| | - Zuodong Ren
- Key Laboratory of Xinjiang Endemic and Ethnic Disease, School of Medicine, Shihezi University, Shihezi, Xinjiang, China
| | - Jiaojiao Zhu
- Beijing Key Laboratory for Radiobiology, Beijing Institute of Radiation Medicine, Beijing, China
| | - Yongqing Gu
- Beijing Key Laboratory for Radiobiology, Beijing Institute of Radiation Medicine, Beijing, China
| | - Yan Zeng
- Precision Clinical Laboratory, Central People's Hospital of Zhanjiang, Zhanjiang, Guangdong, China.,Key Laboratory of Xinjiang Endemic and Ethnic Disease, School of Medicine, Shihezi University, Shihezi, Xinjiang, China
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Upregulation of ATF4-LAMP3 Axis by ORF45 Facilitates Lytic Replication of Kaposi's Sarcoma-Associated Herpesvirus. J Virol 2022; 96:e0145622. [PMID: 36377873 PMCID: PMC9749464 DOI: 10.1128/jvi.01456-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) is a γ-oncogenic herpesvirus, and both lytic and latent infections play important roles in its pathogenesis and tumorigenic properties. Multiple cellular pathways and diverse mediators are hijacked by viral proteins and are used to support KSHV lytic replication. In previous studies, we revealed that KSHV ORF45 promoted KSHV transcription and translation by inducing sustained p90 ribosomal S6 kinase (RSK) activation and the phosphorylation of its substrates c-Fos and eIF4B. However, the cellular mediators required for lytic replication remain largely unknown. Here, we reveal that ORF45 activates eIF2α phosphorylation and ATF4 translation and then upregulates the expression of lysosome-associated membrane protein 3 (LAMP3) in an ATF4-dependent manner during KSHV lytic replication. Consequently, LAMP3 promotes Akt and ERK activation and then facilitates lytic gene expression and virion production. Furthermore, ATF4 enhances lytic replication through LAMP3, and LAMP3 acts in an ATF4-independent manner. Our findings suggest that the ATF4-LAMP3 axis is upregulated by ORF45 through ER stress activation during the KSHV lytic life cycle and, in turn, facilitates optimal lytic replication. IMPORTANCE The lytic replication of Kaposi's sarcoma-associated herpesvirus (KSHV) reprograms cellular transcription and translation to generate viral proteins and virion particles. Here, we show that the mediator of ER stress ATF4 and the expression of the downstream gene LAMP3 are upregulated by ORF45 during lytic replication. Consequently, increased LAMP3 expression activates Akt and ERK and promotes lytic replication. Although several UPR transcription factors are able to promote KSHV lytic replication, the proviral effect of ATF4 on lytic replication is attenuated by LAMP3 silencing, whereas the effect of LAMP3 does not directly require ATF4 expression, indicating that LAMP3 primarily exerts effects on KSHV lytic replication downstream of ATF4 and ER stress. Taken together, our findings suggest that the ORF45-upregulated ATF4-LAMP3 axis plays an essential role in KSHV lytic replication.
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Lizcano-Perret B, Lardinois C, Wavreil F, Hauchamps P, Herinckx G, Sorgeloos F, Vertommen D, Gatto L, Michiels T. Cardiovirus leader proteins retarget RSK kinases toward alternative substrates to perturb nucleocytoplasmic traffic. PLoS Pathog 2022; 18:e1011042. [PMID: 36508477 PMCID: PMC9779665 DOI: 10.1371/journal.ppat.1011042] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 12/22/2022] [Accepted: 12/01/2022] [Indexed: 12/14/2022] Open
Abstract
Proteins from some unrelated pathogens, including small RNA viruses of the family Picornaviridae, large DNA viruses such as Kaposi sarcoma-associated herpesvirus and even bacteria of the genus Yersinia can recruit cellular p90-ribosomal protein S6 kinases (RSKs) through a common linear motif and maintain the kinases in an active state. On the one hand, pathogens' proteins might hijack RSKs to promote their own phosphorylation (direct target model). On the other hand, some data suggested that pathogens' proteins might dock the hijacked RSKs toward a third interacting partner, thus redirecting the kinase toward a specific substrate. We explored the second hypothesis using the Cardiovirus leader protein (L) as a paradigm. The L protein is known to trigger nucleocytoplasmic trafficking perturbation, which correlates with hyperphosphorylation of phenylalanine-glycine (FG)-nucleoporins (FG-NUPs) such as NUP98. Using a biotin ligase fused to either RSK or L, we identified FG-NUPs as primary partners of the L-RSK complex in infected cells. An L protein mutated in the central RSK-interaction motif was readily targeted to the nuclear envelope whereas an L protein mutated in the C-terminal domain still interacted with RSK but failed to interact with the nuclear envelope. Thus, L uses distinct motifs to recruit RSK and to dock the L-RSK complex toward the FG-NUPs. Using an analog-sensitive RSK2 mutant kinase, we show that, in infected cells, L can trigger RSK to use NUP98 and NUP214 as direct substrates. Our data therefore illustrate a novel virulence mechanism where pathogens' proteins hijack and retarget cellular protein kinases toward specific substrates, to promote their replication or to escape immunity.
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Affiliation(s)
- Belén Lizcano-Perret
- Molecular Virology unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Cécile Lardinois
- Molecular Virology unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Fanny Wavreil
- Molecular Virology unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Philippe Hauchamps
- Computational Biology and Bioinformatics unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Gaëtan Herinckx
- MASSPROT platform, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Frédéric Sorgeloos
- Molecular Virology unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Didier Vertommen
- MASSPROT platform, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Laurent Gatto
- Computational Biology and Bioinformatics unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Thomas Michiels
- Molecular Virology unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
- * E-mail:
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9
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The ORF45 Protein of Kaposi's Sarcoma-Associated Herpesvirus and Its Critical Role in the Viral Life Cycle. Viruses 2022; 14:v14092010. [PMID: 36146816 PMCID: PMC9506158 DOI: 10.3390/v14092010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 09/07/2022] [Accepted: 09/07/2022] [Indexed: 11/17/2022] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) protein ORF45 is a virion-associated tegument protein that is unique to the gammaherpesvirus family. Generation of KSHV ORF45-knockout mutants and their subsequent functional analyses have permitted a better understanding of ORF45 and its context-specific and vital role in the KSHV lytic cycle. ORF45 is a multifaceted protein that promotes infection at both the early and late phases of the viral life cycle. As an immediate-early protein, ORF45 is expressed within hours of KSHV lytic reactivation and plays an essential role in promoting the lytic cycle, using multiple mechanisms, including inhibition of the host interferon response. As a tegument protein, ORF45 is necessary for the proper targeting of the viral capsid for envelopment and release, affecting the late stage of the viral life cycle. A growing list of ORF45 interaction partners have been identified, with one of the most well-characterized being the association of ORF45 with the host extracellular-regulated kinase (ERK) p90 ribosomal s6 kinase (RSK) signaling cascade. In this review, we describe ORF45 expression kinetics, as well as the host and viral interaction partners of ORF45 and the significance of these interactions in KSHV biology. Finally, we discuss the role of ORF45 homologs in gammaherpesvirus infections.
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10
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Alexa A, Sok P, Gross F, Albert K, Kobori E, Póti ÁL, Gógl G, Bento I, Kuang E, Taylor SS, Zhu F, Ciliberto A, Reményi A. A non-catalytic herpesviral protein reconfigures ERK-RSK signaling by targeting kinase docking systems in the host. Nat Commun 2022; 13:472. [PMID: 35078976 PMCID: PMC8789800 DOI: 10.1038/s41467-022-28109-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 01/07/2022] [Indexed: 12/16/2022] Open
Abstract
The Kaposi's sarcoma associated herpesvirus protein ORF45 binds the extracellular signal-regulated kinase (ERK) and the p90 Ribosomal S6 kinase (RSK). ORF45 was shown to be a kinase activator in cells but a kinase inhibitor in vitro, and its effects on the ERK-RSK complex are unknown. Here, we demonstrate that ORF45 binds ERK and RSK using optimized linear binding motifs. The crystal structure of the ORF45-ERK2 complex shows how kinase docking motifs recognize the activated form of ERK. The crystal structure of the ORF45-RSK2 complex reveals an AGC kinase docking system, for which we provide evidence that it is functional in the host. We find that ORF45 manipulates ERK-RSK signaling by favoring the formation of a complex, in which activated kinases are better protected from phosphatases and docking motif-independent RSK substrate phosphorylation is selectively up-regulated. As such, our data suggest that ORF45 interferes with the natural design of kinase docking systems in the host.
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Affiliation(s)
- Anita Alexa
- Biomolecular Interactions Research Group, Institute of Organic Chemistry, Research Center for Natural Sciences, H-1117, Budapest, Hungary
| | - Péter Sok
- Biomolecular Interactions Research Group, Institute of Organic Chemistry, Research Center for Natural Sciences, H-1117, Budapest, Hungary
| | - Fridolin Gross
- IFOM, Istituto FIRC di Oncologia Molecolare, 20139, Milan, Italy
| | - Krisztián Albert
- Biomolecular Interactions Research Group, Institute of Organic Chemistry, Research Center for Natural Sciences, H-1117, Budapest, Hungary
| | - Evan Kobori
- Department of Chemistry and Biochemistry, University of California San Diego, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0654, USA
| | - Ádám L Póti
- Biomolecular Interactions Research Group, Institute of Organic Chemistry, Research Center for Natural Sciences, H-1117, Budapest, Hungary
| | - Gergő Gógl
- Biomolecular Interactions Research Group, Institute of Organic Chemistry, Research Center for Natural Sciences, H-1117, Budapest, Hungary
| | - Isabel Bento
- European Molecular Biology Laboratory, Hamburg, Germany
| | - Ersheng Kuang
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306-4370, USA
| | - Susan S Taylor
- Department of Pharmacology, University of California San Diego, 9500 Gilman Drive, La Jolla, San Diego, CA, 92093-0654, USA
| | - Fanxiu Zhu
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306-4370, USA
| | - Andrea Ciliberto
- IFOM, Istituto FIRC di Oncologia Molecolare, 20139, Milan, Italy
| | - Attila Reményi
- Biomolecular Interactions Research Group, Institute of Organic Chemistry, Research Center for Natural Sciences, H-1117, Budapest, Hungary.
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11
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Liu Z, Liu C, Wang X, Li W, Zhou J, Dong P, Xiao MZX, Wang C, Zhang Y, Fu J, Zhu F, Liang Q. RSK1 SUMOylation is required for KSHV lytic replication. PLoS Pathog 2021; 17:e1010123. [PMID: 34871326 PMCID: PMC8675914 DOI: 10.1371/journal.ppat.1010123] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 12/16/2021] [Accepted: 11/16/2021] [Indexed: 01/01/2023] Open
Abstract
RSK1, a downstream kinase of the MAPK pathway, has been shown to regulate multiple cellular processes and is essential for lytic replication of a variety of viruses, including Kaposi's sarcoma-associated herpesvirus (KSHV). Besides phosphorylation, it is not known whether other post-translational modifications play an important role in regulating RSK1 function. We demonstrate that RSK1 undergoes robust SUMOylation during KSHV lytic replication at lysine residues K110, K335, and K421. SUMO modification does not alter RSK1 activation and kinase activity upon KSHV ORF45 co-expression, but affects RSK1 downstream substrate phosphorylation. Compared to wild-type RSK1, the overall phosphorylation level of RxRxxS*/T* motif is significantly declined in RSK1K110/335/421R expressing cells. Specifically, SUMOylation deficient RSK1 cannot efficiently phosphorylate eIF4B. Sequence analysis showed that eIF4B has one SUMO-interacting motif (SIM) between the amino acid position 166 and 170 (166IRVDV170), which mediates the association between eIF4B and RSK1 through SUMO-SIM interaction. These results indicate that SUMOylation regulates the phosphorylation of RSK1 downstream substrates, which is required for efficient KSHV lytic replication.
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Affiliation(s)
- Zhenshan Liu
- Research Center of Translational Medicine, Shanghai Children’s Hospital, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Chengrong Liu
- Research Center of Translational Medicine, Shanghai Children’s Hospital, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xin Wang
- Research Center of Translational Medicine, Shanghai Children’s Hospital, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Wenwei Li
- Department of Biological Science, Florida State University, Tallahassee, Flordia, United States of America
| | - Jingfan Zhou
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Peixian Dong
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Maggie Z. X. Xiao
- Faculty of Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Chunxia Wang
- Department of Critical Care Medicine, Shanghai Children’s Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Yucai Zhang
- Department of Critical Care Medicine, Shanghai Children’s Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Joyce Fu
- Department of Statistics, University of California, Riverside, Riverside, California, United States of America
| | - Fanxiu Zhu
- Department of Biological Science, Florida State University, Tallahassee, Flordia, United States of America
- * E-mail: (FZ); (QL)
| | - Qiming Liang
- Research Center of Translational Medicine, Shanghai Children’s Hospital, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- State Key Laboratory of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai, China
- * E-mail: (FZ); (QL)
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12
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Wang Z, Qiao Y, Chen Z, Liang Y, Cui L, Zhang Y, Li X, Xu L, Wei P, Liu S, Li H. Fos Facilitates Gallid Alpha-Herpesvirus 1 Infection by Transcriptional Control of Host Metabolic Genes and Viral Immediate Early Gene. Viruses 2021; 13:v13061110. [PMID: 34207926 PMCID: PMC8229045 DOI: 10.3390/v13061110] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 06/04/2021] [Accepted: 06/08/2021] [Indexed: 12/24/2022] Open
Abstract
Gallid alpha-herpesvirus 1, also known as avian infectious laryngotracheitis virus (ILTV), continues to cause huge economic losses to the poultry industry worldwide. Similar to that of other herpesvirus-encoded proteins, the expression of viral genes encoded by ILTV is regulated by a cascade, and the underlying regulatory mechanism remains largely unclear. The viral immediate-early (IE) gene ICP4 plays a prominent role in the initiation of the transcription of early and late genes during ILTV replication. In this study, we identified AP-1 as the key regulator of the transcription of ILTV genes by bioinformatics analysis of genome-wide transcriptome data. Subsequent functional studies of the key members of the AP-1 family revealed that Fos, but not Jun, regulates ILTV infection through AP-1 since knockdown of Fos, but not Jun, by gene silencing significantly reduced ICP4 transcription and subsequent viral genome replication and virion production. Using several approaches, we identified ICP4 as a bona fide target gene of Fos that regulated Fos and has Fos response elements within its promoter. Neither the physical binding of Jun to the promoter of ICP4 nor the transcriptional activity of Jun was observed. In addition, knockdown of Fos reduced the transcription of MDH1 and ATP5A1, genes encoding two host rate-limiting enzymes essential for the production of the TCA intermediates OAA and ATP. The biological significance of the transcriptional regulation of MDH1 and ATP5A1 by Fos in ILTV infection was supported by the fact that anaplerosis of OAA and ATP rescued both ICP4 transcription and virion production in infected cells under when Fos was silenced. Our study identified the transcription factor Fos as a key regulator of ILTV infection through its transcription factor function on both the virus and host sides, improving the current understanding of both avian herpesvirus–host interactions and the roles of AP-1 in viral infection.
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Affiliation(s)
- Zhitao Wang
- State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150069, China; (Z.W.); (Y.Q.); (Z.C.); (Y.L.); (L.C.); (Y.Z.); (X.L.); (L.X.)
- College of Veterinary Medicine, Northeast Agricultural University, Harbin 150030, China
| | - Yangyang Qiao
- State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150069, China; (Z.W.); (Y.Q.); (Z.C.); (Y.L.); (L.C.); (Y.Z.); (X.L.); (L.X.)
| | - Zhijie Chen
- State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150069, China; (Z.W.); (Y.Q.); (Z.C.); (Y.L.); (L.C.); (Y.Z.); (X.L.); (L.X.)
- College of Veterinary Medicine, Northeast Agricultural University, Harbin 150030, China
| | - Yumeng Liang
- State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150069, China; (Z.W.); (Y.Q.); (Z.C.); (Y.L.); (L.C.); (Y.Z.); (X.L.); (L.X.)
| | - Lu Cui
- State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150069, China; (Z.W.); (Y.Q.); (Z.C.); (Y.L.); (L.C.); (Y.Z.); (X.L.); (L.X.)
| | - Yanhui Zhang
- State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150069, China; (Z.W.); (Y.Q.); (Z.C.); (Y.L.); (L.C.); (Y.Z.); (X.L.); (L.X.)
| | - Xuefeng Li
- State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150069, China; (Z.W.); (Y.Q.); (Z.C.); (Y.L.); (L.C.); (Y.Z.); (X.L.); (L.X.)
| | - Li Xu
- State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150069, China; (Z.W.); (Y.Q.); (Z.C.); (Y.L.); (L.C.); (Y.Z.); (X.L.); (L.X.)
| | - Ping Wei
- College of Veterinary Medicine, Northeast Agricultural University, Harbin 150030, China
- Correspondence: (P.W.); (S.L.); (H.L.); Tel.: +86-451-51051700 (H.L.)
| | - Shengwang Liu
- State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150069, China; (Z.W.); (Y.Q.); (Z.C.); (Y.L.); (L.C.); (Y.Z.); (X.L.); (L.X.)
- Correspondence: (P.W.); (S.L.); (H.L.); Tel.: +86-451-51051700 (H.L.)
| | - Hai Li
- State Key Laboratory of Veterinary Biotechnology, National Poultry Laboratory Animal Resource Center, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150069, China; (Z.W.); (Y.Q.); (Z.C.); (Y.L.); (L.C.); (Y.Z.); (X.L.); (L.X.)
- Correspondence: (P.W.); (S.L.); (H.L.); Tel.: +86-451-51051700 (H.L.)
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13
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KDM2B Overexpression Facilitates Lytic De Novo KSHV Infection by Inducing AP-1 Activity Through Interaction with the SCF E3 Ubiquitin Ligase Complex. J Virol 2021; 95:JVI.00331-21. [PMID: 33692209 PMCID: PMC8139688 DOI: 10.1128/jvi.00331-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
It is still largely unknown what host factors are involved in controlling the expression of the lytic viral gene RTA during primary infection, which determines if Kaposi's sarcoma-associated herpesvirus (KSHV) establishes latent or lytic infection. We have recently identified the histone demethylase KDM2B as a repressor of RTA expression during both de novo KSHV infection and latency based on an epigenetic factor siRNA screen. Here, we report that surprisingly, KDM2B overexpression can promote lytic de novo infection by using a mechanism that differs from what is needed for its repressor function. Our study revealed that while the DNA-binding and demethylase activities of KDM2B linked to its transcription repressive function are dispensable, its C-terminal F-box and LRR domains are required for the lytic infection-inducing function of KDM2B. We found that overexpressed KDM2B increases the half-life of the AP-1 subunit c-Jun protein and induces the AP-1 signaling pathway. This effect is dependent upon the binding of KDM2B to the SKP1-CUL1-F-box (SCF) E3 ubiquitin ligase complex via its F-box domain. Importantly, the inhibition of AP-1 reduces KDM2B-mediated lytic de novo KSHV infection. Overall, our findings indicate that KDM2B may induce the degradation of some host factors by using the SCF complex resulting in the enrichment of c-Jun. This leads to increased AP-1 transcriptional activity, which facilitates lytic gene expression following de novo infection interfering with the establishment of viral latency.SignificanceThe expression of epigenetic factors is often dysregulated in cancers or upon specific stress signals, which often results in a display of non-canonical functions of the epigenetic factors that are independent from their chromatin-modifying roles. We have previously demonstrated that KDM2B normally inhibits KSHV lytic cycle using its histone demethylase activity. Surprisingly, we found that KDM2B overexpression can promote lytic de novo infection, which does not require its histone demethylase or DNA-binding functions. Instead, KDM2B uses the SKP1-CUL1-F-box (SCF) E3 ubiquitin ligase complex to induce AP-1 transcriptional activity, which promotes lytic gene expression. This is the first report that demonstrates a functional link between SFCKDM2B and AP-1 in the regulation of KSHV lytic cycle.
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14
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Chander Y, Kumar R, Khandelwal N, Singh N, Shringi BN, Barua S, Kumar N. Role of p38 mitogen-activated protein kinase signalling in virus replication and potential for developing broad spectrum antiviral drugs. Rev Med Virol 2021; 31:1-16. [PMID: 33450133 DOI: 10.1002/rmv.2217] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 12/21/2020] [Accepted: 12/23/2020] [Indexed: 12/11/2022]
Abstract
Mitogen-activated protein kinases (MAPKs) play a key role in complex cellular processes such as proliferation, development, differentiation, transformation and apoptosis. Mammals express at least four distinctly regulated groups of MAPKs which include extracellular signal-related kinases (ERK)-1/2, p38 proteins, Jun amino-terminal kinases (JNK1/2/3) and ERK5. p38 MAPK is activated by a wide range of cellular stresses and modulates activity of several downstream kinases and transcription factors which are involved in regulating cytoskeleton remodeling, cell cycle modulation, inflammation, antiviral response and apoptosis. In viral infections, activation of cell signalling pathways is part of the cellular defense mechanism with the basic aim of inducing an antiviral state. However, viruses can exploit enhanced cell signalling activities to support various stages of their replication cycles. Kinase activity can be inhibited by small molecule chemical inhibitors, so one strategy to develop antiviral drugs is to target these cellular signalling pathways. In this review, we provide an overview on the current understanding of various cellular and viral events regulated by the p38 signalling pathway, with a special emphasis on targeting these events for antiviral drug development which might identify candidates with broad spectrum activity.
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Affiliation(s)
- Yogesh Chander
- National Centre for Veterinary Type Cultures, ICAR-National Research Centre on Equines, Hisar, Haryana, India.,Department of Bio and Nano Technology, Guru Jambeshwar University of Science and Technology, Hisar, Haryana, India
| | - Ram Kumar
- National Centre for Veterinary Type Cultures, ICAR-National Research Centre on Equines, Hisar, Haryana, India.,Department of Veterinary Microbiology and Biotechnology, Rajasthan University of Veterinary and Animal Sciences, Bikaner, India
| | - Nitin Khandelwal
- National Centre for Veterinary Type Cultures, ICAR-National Research Centre on Equines, Hisar, Haryana, India.,Department of Biotechnology, GLA University, Mathura, India
| | - Namita Singh
- Department of Bio and Nano Technology, Guru Jambeshwar University of Science and Technology, Hisar, Haryana, India
| | - Brij Nandan Shringi
- Department of Veterinary Microbiology and Biotechnology, Rajasthan University of Veterinary and Animal Sciences, Bikaner, India
| | - Sanjay Barua
- National Centre for Veterinary Type Cultures, ICAR-National Research Centre on Equines, Hisar, Haryana, India
| | - Naveen Kumar
- National Centre for Veterinary Type Cultures, ICAR-National Research Centre on Equines, Hisar, Haryana, India
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15
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Koganti R, Suryawanshi R, Shukla D. Heparanase, cell signaling, and viral infections. Cell Mol Life Sci 2020; 77:5059-5077. [PMID: 32462405 PMCID: PMC7252873 DOI: 10.1007/s00018-020-03559-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 05/17/2020] [Accepted: 05/22/2020] [Indexed: 12/13/2022]
Abstract
Heparanase (HPSE) is a multifunctional protein endowed with many non-enzymatic functions and a unique enzymatic activity as an endo-β-D-glucuronidase. The latter allows it to serve as a key modulator of extracellular matrix (ECM) via a well-regulated cleavage of heparan sulfate side chains of proteoglycans at cell surfaces. The cleavage and associated changes at the ECM cause release of multiple signaling molecules with important cellular and pathological functions. New and emerging data suggest that both enzymatic as well as non-enzymatic functions of HPSE are important for health and illnesses including viral infections and virally induced cancers. This review summarizes recent findings on the roles of HPSE in activation, inhibition, or bioavailability of key signaling molecules such as AKT, VEGF, MAPK-ERK, and EGFR, which are known regulators of common viral infections in immune and non-immune cell types. Altogether, our review provides a unique overview of HPSE in cell-survival signaling pathways and how they relate to viral infections.
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Affiliation(s)
- Raghuram Koganti
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 W. Taylor St, Chicago, IL, 60612, USA
| | - Rahul Suryawanshi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 W. Taylor St, Chicago, IL, 60612, USA
| | - Deepak Shukla
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 W. Taylor St, Chicago, IL, 60612, USA.
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, 60612, USA.
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16
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Activator protein-1 transactivation of the major immediate early locus is a determinant of cytomegalovirus reactivation from latency. Proc Natl Acad Sci U S A 2020; 117:20860-20867. [PMID: 32788362 DOI: 10.1073/pnas.2009420117] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Human cytomegalovirus (HCMV) is a ubiquitous pathogen that latently infects hematopoietic cells and has the ability to reactivate when triggered by immunological stress. This reactivation causes significant morbidity and mortality in immune-deficient patients, who are unable to control viral dissemination. While a competent immune system helps prevent clinically detectable viremia, a portrait of the factors that induce reactivation following the proper cues remains incomplete. Our understanding of the complex molecular mechanisms underlying latency and reactivation continues to evolve. We previously showed the HCMV-encoded G protein-coupled receptor US28 is expressed during latency and facilitates latent infection by attenuating the activator protein-1 (AP-1) transcription factor subunit, c-fos, expression and activity. We now show AP-1 is a critical component for HCMV reactivation. Pharmacological inhibition of c-fos significantly attenuates viral reactivation. In agreement, infection with a virus in which we disrupted the proximal AP-1 binding site in the major immediate early (MIE) enhancer results in inefficient reactivation compared to WT. Concomitantly, AP-1 recruitment to the MIE enhancer is significantly decreased following reactivation of the mutant virus. Furthermore, AP-1 is critical for derepression of MIE-driven transcripts and downstream early and late genes, while immediate early genes from other loci remain unaffected. Our data also reveal MIE transcripts driven from the MIE promoter, the distal promoter, and the internal promoter, iP2, are dependent upon AP-1 recruitment, while iP1-driven transcripts are AP-1-independent. Collectively, our data demonstrate AP-1 binding to and activation of the MIE enhancer is a key molecular process controlling reactivation from latency.
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17
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Mirzaei H, Khodadad N, Karami C, Pirmoradi R, Khanizadeh S. The AP-1 pathway; A key regulator of cellular transformation modulated by oncogenic viruses. Rev Med Virol 2019; 30:e2088. [PMID: 31788897 DOI: 10.1002/rmv.2088] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 09/16/2019] [Accepted: 09/16/2019] [Indexed: 12/13/2022]
Abstract
Cancer progression is critically associated with modulation of host cell signaling pathways. Activator protein-1 (AP-1) signaling is one such pathway whose deregulation renders the host more susceptible to cancer development. Oncogenic viruses, including hepatitis B virus, hepatitis C virus, human papilloma virus, Epstein-Barr virus, human T-cell lymphotropic virus type 1, and Kaposi's sarcoma-associated herpes virus, are common causes of cancer. This review discusses how these oncoviruses by acting through various aspects of the host cell signaling machinery such as the AP-1 pathway might affect oncoviral tumorigenesis, replication, and pathogenesis. The review also briefly considers how the pathway might be targeted during infections with these oncogenic viruses.
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Affiliation(s)
- Habibollah Mirzaei
- Hepatitis Research Center, Lorestan University of Medical Sciences, Khorramabad, Iran.,Department of Virology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Nastaran Khodadad
- Department of Virology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.,Infectious and Tropical Disease Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Chiman Karami
- Department of Virology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.,Infectious and Tropical Disease Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Roya Pirmoradi
- Department of Virology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Sayyad Khanizadeh
- Hepatitis Research Center, Lorestan University of Medical Sciences, Khorramabad, Iran.,Department of Virology, School of Medicine, Lorestan University of Medical Sciences, Khorramabad, Iran
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18
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DuShane JK, Maginnis MS. Human DNA Virus Exploitation of the MAPK-ERK Cascade. Int J Mol Sci 2019; 20:ijms20143427. [PMID: 31336840 PMCID: PMC6679023 DOI: 10.3390/ijms20143427] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 07/09/2019] [Accepted: 07/11/2019] [Indexed: 12/19/2022] Open
Abstract
The extracellular signal-regulated kinases (ERKs) comprise a particular branch of the mitogen-activated protein kinase cascades (MAPK) that transmits extracellular signals into the intracellular environment to trigger cellular growth responses. Similar to other MAPK cascades, the MAPK-ERK pathway signals through three core kinases—Raf, MAPK/ERK kinase (MEK), and ERK—which drive the signaling mechanisms responsible for the induction of cellular responses from extracellular stimuli including differentiation, proliferation, and cellular survival. However, pathogens like DNA viruses alter MAPK-ERK signaling in order to access DNA replication machineries, induce a proliferative state in the cell, or even prevent cell death mechanisms in response to pathogen recognition. Differential utilization of this pathway by multiple DNA viruses highlights the dynamic nature of the MAPK-ERK pathway within the cell and the importance of its function in regulating a wide variety of cellular fates that ultimately influence viral infection and, in some cases, result in tumorigenesis.
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Affiliation(s)
- Jeanne K DuShane
- Department of Molecular and Biomedical Sciences, The University of Maine, Orono, ME 04401, USA
| | - Melissa S Maginnis
- Department of Molecular and Biomedical Sciences, The University of Maine, Orono, ME 04401, USA.
- Graduate School in Biomedical Sciences and Engineering, The University of Maine, Orono, ME 04401, USA.
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19
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Development of an ORF45-Derived Peptide To Inhibit the Sustained RSK Activation and Lytic Replication of Kaposi's Sarcoma-Associated Herpesvirus. J Virol 2019; 93:JVI.02154-18. [PMID: 30842327 DOI: 10.1128/jvi.02154-18] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 02/27/2019] [Indexed: 01/03/2023] Open
Abstract
The lytic replication of Kaposi's sarcoma-associated herpesvirus (KSHV) requires sustained extracellular signal-regulated kinase (ERK)-p90 ribosomal S6 kinase (RSK) activation, which is induced by an immediate early (IE) gene-encoded tegument protein called ORF45, to promote the late transcription and translation of viral lytic genes. An ORF45-null or single-point F66A mutation in ORF45 abolishes ORF45-RSK interaction and sustained ERK-RSK activation during lytic reactivation and subsequently results in a significant decrease in late lytic gene expression and virion production, indicating that ORF45-mediated RSK activation plays a critical role in KSHV lytic replication. Here, we demonstrate that a short ORF45-derived peptide in the RSK-binding region is sufficient for disrupting ORF45-RSK interaction, consequently suppressing lytic gene expression and virion production. We designed a nontoxic cell-permeable peptide derived from ORF45, TAT-10F10, which is composed of the ORF45 56 to 76 amino acid (aa) region and the HIV Tat protein transduction domain, and this peptide markedly inhibits KSHV lytic replication in iSLK.219 and BCBL1 cells. Importantly, this peptide enhances the inhibitory effect of rapamycin on KSHV-infected cells and decreases spontaneous and hypoxia-induced lytic replication in KSHV-positive lymphoma cells. These findings suggest that a small peptide that disrupts ORF45-RSK interaction might be a promising agent for controlling KSHV lytic infection and pathogenesis.IMPORTANCE ORF45-induced RSK activation plays an essential role in KSHV lytic replication, and ORF45-null or ORF45 F66A mutagenesis that abolishes sustained RSK activation and RSK inhibitors significantly decreases lytic replication, indicating that the ORF45-RSK association is a unique target for KSHV-related diseases. However, the side effects, low affinity, and poor efficacy of RSK modulators limit their clinical application. In this study, we developed a nontoxic cell-permeable ORF45-derived peptide from the RSK-binding region to disrupt ORF45-RSK associations and block ORF45-induced RSK activation without interfering with S6K1 activation. This peptide effectively suppresses spontaneous, hypoxia-induced, or chemically induced KSHV lytic replication and enhances the inhibitory effect of rapamycin on lytic replication and sensitivity to rapamycin in lytic KSHV-infected cells. Our results reveal that the ORF45-RSK signaling axis and KSHV lytic replication can be effectively targeted by a short peptide and provide a specific approach for treating KSHV lytic and persistent infection.
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Epstein-Barr Virus BKRF4 Gene Product Is Required for Efficient Progeny Production. J Virol 2017; 91:JVI.00975-17. [PMID: 28904200 DOI: 10.1128/jvi.00975-17] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 09/08/2017] [Indexed: 12/14/2022] Open
Abstract
Epstein-Barr virus (EBV), a member of human gammaherpesvirus, infects mainly B cells. EBV has two alternative life cycles, latent and lytic, and is reactivated occasionally from the latent stage to the lytic cycle. To combat EBV-associated disorders, understanding the molecular mechanisms of the EBV lytic replication cycle is also important. Here, we focused on an EBV lytic gene, BKRF4. Using our anti-BKRF4 antibody, we revealed that the BKRF4 gene product is expressed during the lytic cycle with late kinetics. To characterize the role of BKRF4, we constructed BKRF4-knockout mutants using the bacterial artificial chromosome (BAC) and CRISPR/Cas9 systems. Although disruption of the BKRF4 gene had almost no effect on viral protein expression and DNA synthesis, it significantly decreased progeny virion levels in HEK293 and Akata cells. Furthermore, we show that BKRF4 is involved not only in production of progeny virions but also in increasing the infectivity of the virus particles. Immunoprecipitation assays revealed that BKRF4 interacted with a virion protein, BGLF2. We showed that the C-terminal region of BKRF4 was critical for this interaction and for efficient progeny production. Immunofluorescence analysis revealed that BKRF4 partially colocalized with BGLF2 in the nucleus and perinuclear region. Finally, we showed that BKRF4 is a phosphorylated, possible tegument protein and that the EBV protein kinase BGLF4 may be important for this phosphorylation. Taken together, our data suggest that BKRF4 is involved in the production of infectious virions.IMPORTANCE Although the latent genes of EBV have been studied extensively, the lytic genes are less well characterized. This study focused on one such lytic gene, BKRF4, which is conserved only among gammaherpesviruses (ORF45 of Kaposi's sarcoma-associated herpesvirus or murine herpesvirus 68). After preparing the BKRF4 knockout virus using B95-8 EBV-BAC, we demonstrated that the BKRF4 gene was involved in infectious progeny particle production. Importantly, we successfully generated a BKRF4 knockout virus of Akata using CRISPR/Cas9 technology, confirming the phenotype in this separate strain. We further showed that BKRF4 interacted with another virion protein, BGLF2, and demonstrated the importance of this interaction in infectious virion production. These results shed light on the elusive process of EBV progeny maturation in the lytic cycle. Notably, this study describes a successful example of the generation and characterization of an EBV construct with a disrupted lytic gene using CRISPR/Cas9 technology.
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Bonjardim CA. Viral exploitation of the MEK/ERK pathway - A tale of vaccinia virus and other viruses. Virology 2017; 507:267-275. [PMID: 28526201 DOI: 10.1016/j.virol.2016.12.011] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 12/07/2016] [Accepted: 12/09/2016] [Indexed: 12/14/2022]
Abstract
The VACV replication cycle is remarkable in the sense that it is performed entirely in the cytoplasmic compartment of vertebrate cells, due to its capability to encode enzymes required either for regulating the macromolecular precursor pool or the biosynthetic processes. Although remarkable, this gene repertoire is not sufficient to confer the status of a free-living microorganism to the virus, and, consequently, the virus relies heavily on the host to successfully generate its progeny. During the complex virus-host interaction, viruses must deal not only with the host pathways to accomplish their temporal demands but also with pathways that counteract viral infection, including the inflammatory, innate and acquired immune responses. This review focuses on VACV and other DNA or RNA viruses that stimulate the MEK (MAPK - Mitogen Activated Protein Kinase)/ERK- Extracellular signal-Regulated Kinase) pathway as part of their replication cycle.
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Affiliation(s)
- Cláudio A Bonjardim
- Signal Transduction Group/Viruses Laboratory, Department of Microbiology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, CEP: 31.270-901, Belo Horizonte, Minas Gerais, Brazil.
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Huang L, Yang M, Yuan Y, Li X, Kuang E. Niclosamide inhibits lytic replication of Epstein-Barr virus by disrupting mTOR activation. Antiviral Res 2016; 138:68-78. [PMID: 27939840 DOI: 10.1016/j.antiviral.2016.12.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 11/30/2016] [Accepted: 12/05/2016] [Indexed: 12/31/2022]
Abstract
Infection with the oncogenic γ-herpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) cause several severe malignancies in humans. Inhibition of the lytic replication of EBV and KSHV eliminates the reservoir of persistent infection and transmission, consequently preventing the occurrence of diseases from the sources of infection. Antiviral drugs are limited in controlling these viral infectious diseases. Here, we demonstrate that niclosamide, an old anthelmintic drug, inhibits mTOR activation during EBV lytic replication. Consequently, niclosamide effectively suppresses EBV lytic gene expression, viral DNA lytic replication and virion production in EBV-infected lymphoma cells and epithelial cells. Niclosamide exhibits cytotoxicity toward lymphoma cells and induces irreversible cell cycle arrest in lytically EBV-infected cells. The ectopic overexpression of mTOR reverses the inhibition of niclosamide in EBV lytic replication. Similarly, niclosamide inhibits KSHV lytic replication. Thus, we conclude that niclosamide is a promising candidate for chemotherapy against the acute occurrence and transmission of infectious diseases of oncogenic γ-herpesviruses.
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Affiliation(s)
- Lu Huang
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
| | - Mengtian Yang
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
| | - Yan Yuan
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
| | - Xiaojuan Li
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
| | - Ersheng Kuang
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China; Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou, China.
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Chloroquine inhibits lytic replication of Kaposi's sarcoma-associated herpesvirus by disrupting mTOR and p38-MAPK activation. Antiviral Res 2016; 133:223-33. [PMID: 27521848 DOI: 10.1016/j.antiviral.2016.08.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 08/08/2016] [Indexed: 12/19/2022]
Abstract
Lytic infection is essential for the persistent infection and pathogenesis of Kaposi's sarcoma-associated herpesvirus (KSHV), and inhibiting KSHV lytic replication may effectively prevent the occurrence of KSHV-related diseases. Chloroquine (CQ), a well-known antimalarial drug and autophagy inhibitor, exerts broad-spectrum antiviral effects and shows anti-cancer therapeutic potential. However, the ability of CQ and its derivatives to control infection of oncogenic γ-herpesvirus remains undefined. Here we reveal that CQ suppresses KSHV lytic gene expression and virion production, and shows cytotoxicity toward KSHV lytically infected B cells at clinically acceptable doses. CQ suppresses mTOR and p38-MAPK pathway activation during KSHV lytic replication but not latent infection. Furthermore, CQ blocks Epstein-Barr virus (EBV) lytic replication via a distinct mechanism that is invoked to block virion production but does not affect viral gene expression. These results suggest that CQ is an effective antiviral drug against KSHV lytic infection. Our findings indicate that CQ treatment should be considered for controlling KSHV-related diseases, particularly for primary use in co-infection of KSHV with malaria.
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Abstract
Kaposi’s sarcoma (KS)-associated herpesvirus (KSHV) is an oncogenic human herpesvirus. KSHV is associated with three cancers in the human population: KS, primary effusion lymphoma (PEL), and multicentric Castleman’s disease (MCD). KS is the leading cause of cancer in HIV-infected individuals. In this review, we discuss the most recent discoveries behind the mechanisms of KSHV latency maintenance and lytic replication. We also review current therapies for KSHV-associated cancers.
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Affiliation(s)
- Nathan J Dissinger
- Lineberger Comprehensive Cancer Center and Department of Microbiology & Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Blossom Damania
- Lineberger Comprehensive Cancer Center and Department of Microbiology & Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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Phosphoproteomic Analysis of KSHV-Infected Cells Reveals Roles of ORF45-Activated RSK during Lytic Replication. PLoS Pathog 2015; 11:e1004993. [PMID: 26133373 PMCID: PMC4489790 DOI: 10.1371/journal.ppat.1004993] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 06/02/2015] [Indexed: 12/13/2022] Open
Abstract
Kaposi’s Sarcoma-Associated Herpesvirus (KSHV) is an oncogenic virus which has adapted unique mechanisms to modulate the cellular microenvironment of its human host. The pathogenesis of KSHV is intimately linked to its manipulation of cellular signaling pathways, including the extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) pathway. We have previously shown that KSHV ORF45 contributes to the sustained activation of both ERK and p90 ribosomal S6 kinase (RSK, a major functional mediator of ERK/MAPK signaling) during KSHV lytic replication. ORF45-activated RSK is required for optimal KSHV lytic gene expression and progeny virion production, though the underlying mechanisms downstream of this activation are still unclear. We hypothesized that the activation of RSK by ORF45 causes differential phosphorylation of cellular and viral substrates, affecting biological processes essential for efficient KSHV lytic replication. Accordingly, we observed widespread and significant differences in protein phosphorylation upon induction of lytic replication. Mass-spectrometry-based phosphoproteomic screening identified putative substrates of ORF45-activated RSK in KSHV-infected cells. Bioinformatic analyses revealed that nuclear proteins, including several transcriptional regulators, were overrepresented among these candidates. We validated the ORF45/RSK-dependent phosphorylation of several putative substrates by employing KSHV BAC mutagenesis, kinase inhibitor treatments, and/or CRISPR-mediated knockout of RSK in KSHV-infected cells. Furthermore, we assessed the consequences of knocking out these substrates on ORF45/RSK-dependent regulation of gene expression and KSHV progeny virion production. Finally, we show data to support that ORF45 regulates the translational efficiency of a subset of viral/cellular genes with complex secondary structure in their 5’ UTR. Altogether, these data shed light on the mechanisms by which KSHV ORF45 manipulates components of the host cell machinery via modulation of RSK activity. Thus, this study has important implications for the pathobiology of KSHV and other diseases in which RSK activity is dysregulated. Kaposi’s sarcoma-associated herpesvirus (KSHV) is a human tumor virus which hijacks the host signaling pathways in order to maintain persistent infection. We previously discovered that the KSHV protein ORF45 binds to and activates the cellular kinase RSK (p90 ribosomal S6 kinase), and that this activation is vital for optimal KSHV gene expression and virion production. Here, we performed a phosphoproteomic analysis of KSHV-infected cells to further characterize the specific substrates of ORF45-activated RSK. Bioinformatic analyses provided insights into the functional roles of these substrates. We verified the ORF45/RSK-dependent phosphorylation of a subset of these substrates by various means. Finally, we used genome editing to knock out RSK, as well as several cellular substrates identified by our screening, and characterized the consequent effect(s) on regulation of gene expression and virion production. Thus, this work further elucidates one of the key signaling nodes modulated by KSHV, and implicates ORF45-mediated activation of RSK in the regulation of viral and host gene expression during KSHV lytic replication.
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