301
|
Li P, Kaiser P, Lampiris HW, Kim P, Yukl SA, Havlir DV, Greene WC, Wong JK. Stimulating the RIG-I pathway to kill cells in the latent HIV reservoir following viral reactivation. Nat Med 2016; 22:807-11. [PMID: 27294875 PMCID: PMC5004598 DOI: 10.1038/nm.4124] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 05/10/2015] [Indexed: 12/15/2022]
Abstract
The persistence of latent HIV proviruses in long-lived CD4(+) T cells despite antiretroviral therapy (ART) is a major obstacle to viral eradication. Because current candidate latency-reversing agents (LRAs) induce HIV transcription, but fail to clear these cellular reservoirs, new approaches for killing these reactivated latent HIV reservoir cells are urgently needed. HIV latency depends upon the transcriptional quiescence of the integrated provirus and the circumvention of immune defense mechanisms. These defenses include cell-intrinsic innate responses that use pattern-recognition receptors (PRRs) to detect viral pathogens, and that subsequently induce apoptosis of the infected cell. Retinoic acid (RA)-inducible gene I (RIG-I, encoded by DDX58) forms one class of PRRs that mediates apoptosis and the elimination of infected cells after recognition of viral RNA. Here we show that acitretin, an RA derivative approved by the US Food and Drug Administration (FDA), enhances RIG-I signaling ex vivo, increases HIV transcription, and induces preferential apoptosis of HIV-infected cells. These effects are abrogated by DDX58 knockdown. Acitretin also decreases proviral DNA levels in CD4(+) T cells from HIV-positive subjects on suppressive ART, an effect that is amplified when combined with suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor. Pharmacological enhancement of an innate cellular-defense network could provide a means by which to eliminate reactivated cells in the latent HIV reservoir.
Collapse
Affiliation(s)
- Peilin Li
- Infectious Diseases Section, Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA
| | - Philipp Kaiser
- Infectious Diseases Section, Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA
| | - Harry W. Lampiris
- Infectious Diseases Section, Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA
| | - Peggy Kim
- Infectious Diseases Section, Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA
| | - Steven A. Yukl
- Infectious Diseases Section, Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA
| | - Diane V. Havlir
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA
- HIV/AIDS Division, San Francisco General Hospital, San Francisco, California, USA
| | - Warner C. Greene
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA
- Department of Microbiology and Biology, University of California, San Francisco, San Francisco, California, USA
- Gladstone Institute of Virology and Immunology, San Francisco, California, USA
| | - Joseph K. Wong
- Infectious Diseases Section, Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA
| |
Collapse
|
302
|
Innate immunity against hepatitis C virus. Curr Opin Immunol 2016; 42:98-104. [PMID: 27366996 DOI: 10.1016/j.coi.2016.06.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 06/09/2016] [Accepted: 06/15/2016] [Indexed: 12/24/2022]
Abstract
Hepatitis C virus (HCV) infection tends persistent and causes chronic liver diseases, including inflammation, cirrhosis and hepatocellular carcinoma. Innate immune responses triggered by HCV infection, particularly the production of interferons and pro-inflammatory cytokines, shape the early host antiviral defense, and orchestrate subsequent HCV-specific adaptive immunity. Host has evolved multifaceted means to sense HCV infection to induce innate immune responses, whereas HCV has also developed elaborate strategies to evade immune attack. Recent studies in the field have provided many new insights into the interplay of HCV and innate immunity. In this review, we summarized these recent advances, focusing on pathogen recognition by innate sensors, newly discovered anti-HCV innate effectors and new viral strategies to evade innate immunity.
Collapse
|
303
|
Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus Nsp4 Cleaves VISA to Impair Antiviral Responses Mediated by RIG-I-like Receptors. Sci Rep 2016; 6:28497. [PMID: 27329948 PMCID: PMC4916416 DOI: 10.1038/srep28497] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 06/02/2016] [Indexed: 11/08/2022] Open
Abstract
Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most significant etiological agents in the swine industry worldwide. It has been reported that PRRSV infection can modulate host immune responses, and innate immune evasion is thought to play a vital role in PRRSV pathogenesis. In this study, we demonstrated that highly pathogenic PRRSV (HP-PRRSV) infection specifically down-regulated virus-induced signaling adaptor (VISA), a unique adaptor molecule that is essential for retinoic acid induced gene-I (RIG-I) and melanoma differentiation associated gene 5 (MDA5) signal transduction. Moreover, we verified that nsp4 inhibited IRF3 activation induced by signaling molecules, including RIG-I, MDA5, VISA, and TBK1, but not IRF3. Subsequently, we demonstrated that HP-PRRSV nsp4 down-regulated VISA and suppressed type I IFN induction. Importantly, VISA was cleaved by nsp4 and released from mitochondrial membrane, which interrupted the downstream signaling of VISA. However, catalytically inactive mutant of nsp4 abolished its ability to cleave VISA. Interestingly, nsp4 of typical PRRSV strain CH-1a had no effect on VISA. Taken together, these findings reveal a strategy evolved by HP-PRRSV to counteract anti-viral innate immune signaling, which complements the known PRRSV-mediated immune-evasion mechanisms.
Collapse
|
304
|
Cao Z, Zhou Y, Zhu S, Feng J, Chen X, Liu S, Peng N, Yang X, Xu G, Zhu Y. Pyruvate Carboxylase Activates the RIG-I-like Receptor-Mediated Antiviral Immune Response by Targeting the MAVS signalosome. Sci Rep 2016; 6:22002. [PMID: 26906558 PMCID: PMC4764940 DOI: 10.1038/srep22002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 02/05/2016] [Indexed: 02/07/2023] Open
Abstract
When retinoic acid-inducible gene 1 protein (RIG-I)-like receptors sense viral dsRNA in the cytosol, RIG-I and melanoma differentiation-associated gene 5 (MDA5) are recruited to the mitochondria to interact with mitochondrial antiviral signaling protein (MAVS) and initiate antiviral immune responses. In this study, we demonstrate that the biotin-containing enzyme pyruvate carboxylase (PC) plays an essential role in the virus-triggered activation of nuclear factor kappa B (NF-κB) signaling mediated by MAVS. PC contributes to the enhanced production of type I interferons (IFNs) and pro-inflammatory cytokines, and PC knockdown inhibits the virus-triggered innate immune response. In addition, PC shows extensive antiviral activity against RNA viruses, including influenza A virus (IAV), human enterovirus 71 (EV71), and vesicular stomatitis virus (VSV). Furthermore, PC mediates antiviral action by targeting the MAVS signalosome and induces IFNs and pro-inflammatory cytokines by promoting phosphorylation of NF-κB inhibitor-α (IκBα) and the IκB kinase (IKK) complex, as well as NF-κB nuclear translocation, which leads to activation of interferon-stimulated genes (ISGs), including double-stranded RNA-dependent protein kinase (PKR) and myxovirus resistance protein 1 (Mx1). Our findings suggest that PC is an important player in host antiviral signaling.
Collapse
MESH Headings
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/immunology
- Animals
- Cell Line, Tumor
- Cytokines/genetics
- Cytokines/immunology
- DEAD Box Protein 58/genetics
- DEAD Box Protein 58/immunology
- Enterovirus A, Human/genetics
- Enterovirus A, Human/immunology
- Gene Expression Regulation
- Genes, Reporter
- HEK293 Cells
- Hepatocytes/immunology
- Hepatocytes/virology
- Humans
- Immunity, Innate
- Influenza A Virus, H3N2 Subtype/genetics
- Influenza A Virus, H3N2 Subtype/immunology
- Interferon Type I/genetics
- Interferon Type I/immunology
- Interferon-Induced Helicase, IFIH1/genetics
- Interferon-Induced Helicase, IFIH1/immunology
- Luciferases/genetics
- Luciferases/immunology
- NF-KappaB Inhibitor alpha/genetics
- NF-KappaB Inhibitor alpha/immunology
- NF-kappa B/genetics
- NF-kappa B/immunology
- Pyruvate Carboxylase/antagonists & inhibitors
- Pyruvate Carboxylase/genetics
- Pyruvate Carboxylase/immunology
- RNA, Small Interfering/genetics
- RNA, Small Interfering/immunology
- RNA, Viral/genetics
- RNA, Viral/immunology
- Receptors, Immunologic
- Signal Transduction
- Vesiculovirus/genetics
- Vesiculovirus/immunology
- eIF-2 Kinase/genetics
- eIF-2 Kinase/immunology
Collapse
Affiliation(s)
- Zhongying Cao
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Yaqin Zhou
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Shengli Zhu
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Jian Feng
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Xueyuan Chen
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Shi Liu
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Nanfang Peng
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Xiaodan Yang
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Gang Xu
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Ying Zhu
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan 430072, China
| |
Collapse
|
305
|
Targeting Innate Immunity for Antiviral Therapy through Small Molecule Agonists of the RLR Pathway. J Virol 2015; 90:2372-87. [PMID: 26676770 DOI: 10.1128/jvi.02202-15] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 12/06/2015] [Indexed: 12/28/2022] Open
Abstract
UNLABELLED The cellular response to virus infection is initiated when pathogen recognition receptors (PRR) engage viral pathogen-associated molecular patterns (PAMPs). This process results in induction of downstream signaling pathways that activate the transcription factor interferon regulatory factor 3 (IRF3). IRF3 plays a critical role in antiviral immunity to drive the expression of innate immune response genes, including those encoding antiviral factors, type 1 interferon, and immune modulatory cytokines, that act in concert to restrict virus replication. Thus, small molecule agonists that can promote IRF3 activation and induce innate immune gene expression could serve as antivirals to induce tissue-wide innate immunity for effective control of virus infection. We identified small molecule compounds that activate IRF3 to differentially induce discrete subsets of antiviral genes. We tested a lead compound and derivatives for the ability to suppress infections caused by a broad range of RNA viruses. Compound administration significantly decreased the viral RNA load in cultured cells that were infected with viruses of the family Flaviviridae, including West Nile virus, dengue virus, and hepatitis C virus, as well as viruses of the families Filoviridae (Ebola virus), Orthomyxoviridae (influenza A virus), Arenaviridae (Lassa virus), and Paramyxoviridae (respiratory syncytial virus, Nipah virus) to suppress infectious virus production. Knockdown studies mapped this response to the RIG-I-like receptor pathway. This work identifies a novel class of host-directed immune modulatory molecules that activate IRF3 to promote host antiviral responses to broadly suppress infections caused by RNA viruses of distinct genera. IMPORTANCE Incidences of emerging and reemerging RNA viruses highlight a desperate need for broad-spectrum antiviral agents that can effectively control infections caused by viruses of distinct genera. We identified small molecule compounds that can selectively activate IRF3 for the purpose of identifying drug-like molecules that can be developed for the treatment of viral infections. Here, we report the discovery of a hydroxyquinoline family of small molecules that can activate IRF3 to promote cellular antiviral responses. These molecules can prophylactically or therapeutically control infection in cell culture by pathogenic RNA viruses, including West Nile virus, dengue virus, hepatitis C virus, influenza A virus, respiratory syncytial virus, Nipah virus, Lassa virus, and Ebola virus. Our study thus identifies a class of small molecules with a novel mechanism to enhance host immune responses for antiviral activity against a variety of RNA viruses that pose a significant health care burden and/or that are known to cause infections with high case fatality rates.
Collapse
|
306
|
Kato H, Fujita T. RIG-I-like receptors and autoimmune diseases. Curr Opin Immunol 2015; 37:40-5. [PMID: 26530735 DOI: 10.1016/j.coi.2015.10.002] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 09/26/2015] [Accepted: 10/08/2015] [Indexed: 12/24/2022]
Abstract
Type I interferon (IFN) plays an essential role in antiviral innate immune responses and also in adaptive immune responses. Defects in the production of IFN markedly increase susceptibility to viral invasion and attenuate the acquired immunity. Recently an increased expression of type I IFN, also termed IFN signature, has been reported in patients with autoimmune diseases such as systemic lupus erythematosus (SLE) and Aicardi-Goutières syndrome (AGS). The evidence clearly shows that the initiation and termination of IFN production should be tightly controlled. RIG-I-like receptors (RLRs) are viral RNA sensors and are essential for type I IFN induction. We herein summarize recent reports on RLR mutations in patients and MDA5 mutant mice, and discuss possible mechanisms by which aberrant activation of RLRs can cause autoimmunity.
Collapse
Affiliation(s)
- Hiroki Kato
- Laboratory of Molecular Genetics, Institute for Virus Research, and Laboratory of Molecular and Cellular Immunology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan; PRESTO, Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
| | - Takashi Fujita
- Laboratory of Molecular Genetics, Institute for Virus Research, and Laboratory of Molecular and Cellular Immunology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan.
| |
Collapse
|
307
|
Kell A, Stoddard M, Li H, Marcotrigiano J, Shaw GM, Gale M. Pathogen-Associated Molecular Pattern Recognition of Hepatitis C Virus Transmitted/Founder Variants by RIG-I Is Dependent on U-Core Length. J Virol 2015; 89:11056-68. [PMID: 26311867 PMCID: PMC4621103 DOI: 10.1128/jvi.01964-15] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 08/19/2015] [Indexed: 12/25/2022] Open
Abstract
UNLABELLED Despite the introduction of direct-acting antiviral (DAA) drugs against hepatitis C virus (HCV), infection remains a major public health concern because DAA therapeutics do not prevent reinfection and patients can still progress to chronic liver disease. Chronic HCV infection is supported by a variety of viral immune evasion strategies, but, remarkably, 20% to 30% of acute infections spontaneously clear prior to development of adaptive immune responses, thus implicating innate immunity in resolving acute HCV infection. However, the virus-host interactions regulating acute infection are unknown. Transmission of HCV involves one or a few transmitted/founder (T/F) variants. In infected hepatocytes, the retinoic acid-inducible gene I (RIG-I) protein recognizes 5' triphosphate (5'ppp) of the HCV RNA and a pathogen-associated molecular pattern (PAMP) motif located within the 3' untranslated region consisting of poly-U/UC. PAMP binding activates RIG-I to induce innate immune signaling and type 1 interferon antiviral defenses. HCV poly-U/UC sequences can differ in length and complexity, suggesting that PAMP diversity in T/F genomes could regulate innate immune control of acute HCV infection. Using 14 unique poly-U/UC sequences from HCV T/F genomes recovered from acute-infection patients, we tested whether RIG-I recognition and innate immune activation correlate with PAMP sequence characteristics. We show that T/F variants are recognized by RIG-I in a manner dependent on length of the U-core motif of the poly-U/UC PAMP and are recognized by RIG-I to induce innate immune responses that restrict acute infection. PAMP recognition of T/F HCV variants by RIG-I may therefore impart innate immune signaling and HCV restriction to impact acute-phase-to-chronic-phase transition. IMPORTANCE Recognition of nonself molecular patterns such as those seen with viral nucleic acids is an essential step in triggering the immune response to virus infection. Innate immunity is induced by hepatitis C virus infection through the recognition of viral RNA by the cellular RIG-I protein, where RIG-I recognizes a poly-uridine/cytosine motif in the viral genome. Variation within this motif may provide an immune evasion strategy for transmitted/founder viruses during acute infection. Using 14 unique poly-U/UC sequences from HCV T/F genomes recovered from acutely infected HCV patients, we demonstrate that RIG-I binding and activation of innate immunity depend primarily on the length of the uridine core within this motif. T/F variants found in acute infection contained longer U cores within the motif and could activate RIG-I and induce innate immune signaling sufficient to restrict viral infection. Thus, recognition of T/F variants by RIG-I could significantly impact the transition from acute to chronic infection.
Collapse
Affiliation(s)
- Alison Kell
- Center for Innate Immunity and Immune Disease, Department of Immunology, School of Medicine, University of Washington, Seattle, Washington, USA
| | - Mark Stoddard
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Hui Li
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Joe Marcotrigiano
- Center for Advanced Biotechnology and Medicine, Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey, USA
| | - George M Shaw
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Michael Gale
- Center for Innate Immunity and Immune Disease, Department of Immunology, School of Medicine, University of Washington, Seattle, Washington, USA
| |
Collapse
|
308
|
Wang C, Huang Y, Sheng J, Huang H, Zhou J. Estrogen receptor alpha inhibits RLR-mediated immune response via ubiquitinating TRAF3. Cell Signal 2015; 27:1977-83. [PMID: 26186972 DOI: 10.1016/j.cellsig.2015.07.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 07/13/2015] [Accepted: 07/13/2015] [Indexed: 12/20/2022]
Abstract
RIG-I-like receptors (RLRs) function as key sentinel receptor for invading viruses. Moderate activation of RLR signaling is critical for efficient viral clearance without harmful immunopathology. Estrogen receptor alpha (ERα) is a member of the nuclear receptor superfamily of ligand-activated transcription factors and is involved in the regulation of innate immune responses. However, the effects of ERα on RLR signaling and the molecular mechanisms are poorly understood. In this study, we identify ERα as a negative regulator of RLR-triggered antiviral immune responses. The expression level of ERα is upregulated following RLR activation in macrophages. In the absence of ligand, VSV infection phosphorylates ERα at serine 167. ERα inhibits VSV-induced IRF3 activation. We further demonstrate that ERα directly interacts with TRAF3 and promotes K48-linked proteasomal degradation of TRAF3. Consistently, ERα inhibits VSV-triggered IFN-β production in macrophages in a ligand independent mechanism. Thus, ERα functions as a negative feedback regulator of RLR-triggered antiviral immune responses. These findings also provide the insights that separate the immune effects of ERα from its ligand-induced hormonal effects.
Collapse
Affiliation(s)
- Changxing Wang
- The Key Laboratory of Reproductive Genetics, Ministry of Education (Zhejiang University), Hangzhou, Zhejiang, China; Department of Cell Biology, School of Medicine, Zhejiang University, Hangzhou 310058, China
| | - Yue Huang
- The Key Laboratory of Reproductive Genetics, Ministry of Education (Zhejiang University), Hangzhou, Zhejiang, China
| | - Jianzhong Sheng
- The Key Laboratory of Reproductive Genetics, Ministry of Education (Zhejiang University), Hangzhou, Zhejiang, China
| | - Hefeng Huang
- The Key Laboratory of Reproductive Genetics, Ministry of Education (Zhejiang University), Hangzhou, Zhejiang, China
| | - Jun Zhou
- The Key Laboratory of Reproductive Genetics, Ministry of Education (Zhejiang University), Hangzhou, Zhejiang, China; Department of Cell Biology, School of Medicine, Zhejiang University, Hangzhou 310058, China.
| |
Collapse
|
309
|
Minassian A, Zhang J, He S, Zhao J, Zandi E, Saito T, Liang C, Feng P. An Internally Translated MAVS Variant Exposes Its Amino-terminal TRAF-Binding Motifs to Deregulate Interferon Induction. PLoS Pathog 2015. [PMID: 26221961 PMCID: PMC4519330 DOI: 10.1371/journal.ppat.1005060] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Activation of pattern recognition receptors and proper regulation of downstream signaling are crucial for host innate immune response. Upon infection, the NF-κB and interferon regulatory factors (IRF) are often simultaneously activated to defeat invading pathogens. Mechanisms concerning differential activation of NF-κB and IRF are not well understood. Here we report that a MAVS variant inhibits interferon (IFN) induction, while enabling NF-κB activation. Employing herpesviral proteins that selectively activate NF-κB signaling, we discovered that a MAVS variant of ~50 kDa, thus designated MAVS50, was produced from internal translation initiation. MAVS50 preferentially interacts with TRAF2 and TRAF6, and activates NF-κB. By contrast, MAVS50 inhibits the IRF activation and suppresses IFN induction. Biochemical analysis showed that MAVS50, exposing a degenerate TRAF-binding motif within its N-terminus, effectively competed with full-length MAVS for recruiting TRAF2 and TRAF6. Ablation of the TRAF-binding motif of MAVS50 impaired its inhibitory effect on IRF activation and IFN induction. These results collectively identify a new means by which signaling events is differentially regulated via exposing key internally embedded interaction motifs, implying a more ubiquitous regulatory role of truncated proteins arose from internal translation and other related mechanisms. Host innate immune signaling plays critical roles in defeating pathogen infection. In response to viral infection, cellular signaling events cumulate in the activation of NF-κB and interferon regulatory factors. How these two signaling ramifications are differentially regulated remains an open question. Here we report an internally translated MAVS variant deregulates IRF activation via exposing N-terminal TRAF-binding motifs. As such, the short form of MAVS efficiently competes for binding to TRAF2 and TRAF6 against full-length MAVS, thereby sequestering key adaptors from the signaling cascades mediated by full-length MAVS. Our study uncovers a delicate regulatory mechanism of truncated proteins bearing key protein-interacting motifs that is enabled by internal translation initiation and potentially other relevant means.
Collapse
Affiliation(s)
- Arlet Minassian
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Junjie Zhang
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Shanping He
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Jun Zhao
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Ebrahim Zandi
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Takeshi Saito
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Chengyu Liang
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Pinghui Feng
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
- * E-mail:
| |
Collapse
|