Project description:The emerging threat to global health associated with the Zika virus (ZIKV) epidemics and its link to severe complications highlights a growing need to better understand the pathogenic mechanisms of ZIKV. Accumulating evidence for a critical role of type I interferon (IFN-I) in protecting hosts from ZIKV infection lies in the findings that ZIKV has evolved various strategies to subvert the host defense line by counteracting the early IFN induction or subsequent IFN signaling. Yet, mechanisms underlying the counter-IFN capability of ZIKV and its proteins, which might contribute to the well-recognized broad cellular tropisms and persistence of ZIKV, remain to be fully understood. In our current study, using RNA sequencing-based transcriptional profiling from the whole blood cells isolated from patients acutely infected by ZIKV, we found that transcriptional signatures of antiviral interferon-stimulated genes and innate immune sensors was absent in ZIKV-infected patients presents inactive as compared to healthy donors, suggesting that ZIKV might suppress the induction of IFN-I during the natural infection process in human. Furthermore, utilizing cellular or extracellular analysis of molecular interaction in a ZIKV NS4A-overexpression system, or in the context of actual ZIKV infection, we have identified that ZIKV NS4A directly binds MAVS and thereby interrupts RIG-I/MAVS interaction through its CARD-TM domains, leading to attenuated production of IFN-I. Taken together, these findings originated from patient studies have added new knowledge and molecular details to our understanding regarding how ZIKV mediates suppression of the IFN-I system and may provide new basis for future development of anti-ZIKV strategies.
Project description:The RIG-I-like receptors (RLRs: RIG-I, MDA5 and LGP2) trigger inflammatory and antiviral responses by sensing non-self RNA molecules produced during viral replication. LGP2 regulation of RIG-I and MDA5-dependant type-I interferon signaling is a matter of controversy. Here we show that LGP2 interacts with different components of the RNA silencing machinery. Particularly, we identified a direct protein-protein interaction between LGP2 and interferon-inducible double-stranded RNA-dependent protein kinase activator A (PACT). The LGP2-PACT interaction is mediated by the regulatory C-terminal domain of LGP2 and is necessary for inhibiting the RIG-I- and amplifying the MDA5-responses. We describe a point mutation within LGP2 that disrupts LGP2-PACT interaction and leads to the loss of LGP2 regulatory activity over RIG-I and MDA5. These results provide a model in which PACT-LGP2 interaction regulates RIG-I and MDA5 inflammatory response and allows cellular RNA silencing machinery to coordinate the innate immune response.
Project description:MAVS-mediated cytosolic RNA sensing plays a central role in tumor immunogenicity. However, the effects of host MAVS signaling on antitumor immunity remains uncertain. Here, we demonstrate that host MAVS pathway drives accelerated tumor growth and impairs antitumor immunity, while MAVS knockout in dendritic cells (DCs) promotes tumor-reactive CD8+ T cell responses. Specifically, the CD8+ T cell priming capacity is enhanced by lack of functional MAVS in a type I interferon-independent, but IL-12-dependent, manner. Mechanistically, loss of RIG-I/MAVS cascade activates non-canonical NF-κB pathway and in turn induces IL-12 production by DCs, resulting in CD8+ T cell: DC crosstalk licensed by IFN-γ and IL-12. Moreover, ablation of host MAVS sensitizes tumors to immunotherapy and attenuates radiation resistance, thereby facilitating the maintenance of effector CD8+ T cells. These findings identify that host MAVS pathway acts as an immune checkpoint of DC-driven antitumor immunity, indicating the development of DC-based immunotherapies through MAVS signaling antagonism.
Project description:The project aims to evaluate the contribution of ADAR1 RNA editing to B cell lymphomagenesis, specifically in diffuse large B cell lymphoma (DLBCL). Within our DLBCL cohort, RNA editing targets transcripts within known lymphoma-driving pathways such as apoptosis, p53 and NF-kB signaling, as well as the previously unrecognized RIG-I-like pathway. In the latter context, we show that ADAR1-mediated editing in the MAVS transcript correlates with increased MAVS protein expression levels, associating with increased interferon/NF-kB signaling and increased T cell exhaustion. To confirm this mechanism, we have performed LC-MSMS analysis on a DLBCL cell line (RCK8) in the presence or absence of ADAR1 (Figure S11D ). Additionally, using targeted RNA base editing tools to restore editing within MAVS 3'UTR in ADAR1-deficient cells, we demonstrate that editing is likely to be causal to an increase in downstream signaling in the absence of activation by canonical nucleic acid receptor sensing. To confirm that this signaling increase depends on an increase of MAVS protein upon specific editing, we have performed LC-MSMS analysis on the same samples (Figure 4G).
Project description:Epstein-Barr virus (EBV) causes infectious mononucleosis, triggers multiple sclerosis and is associated with 200,000 cancers/year. EBV colonizes the B-cell compartment and periodically reactivates, inducing expression of 80 viral proteins. Yet much remains unknown about how EBV remodels host cells and dismantles key antiviral responses. We therefore created a proteomic map of EBV-host and EBV-EBV interactions in B-cells undergoing EBV replication, uncovering conserved herpesvirus versus EBV-specific host cell targets. The EBV-encoded G-protein coupled receptor BILF1 associated with MAVS and the UFM1 E3 ligase UFL1. Whereas UFMylation of 14-3-3 proteins drives RIG-I/MAVS signaling, BILF1-directed MAVS UFMylation instead triggered MAVS packaging into mitochondrial-derived vesicles and lysosomal proteolysis. In the absence of BILF1, EBV replication activated the NLRP3 inflammasome, which impaired viral replication and triggered pyroptosis. Our results provide a viral protein interaction network resource, reveal a UFM1-dependent pathway for selective degradation of mitochondrial cargo and highlight BILF1 as a novel therapeutic target.
Project description:Internal N6-methyladenosine (m6A) modification of RNA is one of the most common and abundant modifications in eukaryotic cells as well as in viruses. However, the biological role(s) of RNA m6A in virus-host interaction remains elusive. Using human metapneumovirus (hMPV), a medically important non-segmented negative-sense RNA virus as a model, we demonstrate that m6A serves as a molecular marker for innate immune discrimination self and nonself RNAs. We show that hMPV RNAs are m6A methylated and that viral m6A methylation promotes hMPV replication and gene expression. HMPV infection leads to differential expression of interferon-related genes involved in innate immune signaling pathways. Inactivating these m6A sites with synonymous mutations resulted in m6A deficient recombinant hMPVs that induced significantly higher expression of type I interferon that restricted viral replication. Notably, the induction of type I interferons by m6A-deficient rhMPVs and virion RNA was dependent on the cytoplasmic RNA sensor RIG-I, not MDA5. Mechanistically, m6A-deficient virion RNA induces higher expression of RIG-I, enhances its binding affinity to RIG-I, and facilitates the conformational change of RIG-I, leading to enhanced induction of type I IFN expression. The replication of m6A-deficient rhMPVs was attenuated in wild type A459 cells but was restored in cells knocked out for RIG-I and MAVS. Furthermore, m6A-deficient rhMPVs triggered higher type I interferon in vivo and were significantly attenuated in the lower respiratory tract yet retained high immunogenicity in cotton rats. Collectively, our results highlight that (i) virus acquires m6A in their RNAs as a means of mimicking cellular RNA to avoid the detection by innate immunity; and (ii) viral m6A RNA can serve as a novel target to attenuate hMPV for vaccine purposes.
Project description:Detection of viral RNA in the cytosol of infected cells depends on RIG-I-lilke recptors that use MAVS as an adapter protein to activate antiviral gene expression. MAVS is tail-anchored on mitochondria, mitochondria-associated membranes and peroxisomes. As peroxisomal membrane proteins can be mistargeted to mitochondria in the absence of peroxisomes, we hypothesized that MAVS-dependent antiviral gene expression is activated more efficiently in this instance. Pex19 deficient skin firoblasts derived from a Zellweger syndrome patient lack peroxisomes. We introduced wild type Pex19 into these cells to restore peroxisome formation and assessed alterations in the gene expression profile of these cells after reovirus infection. 6 samples: 9 and 16 hrs after reovirus infection at an MOI of 100 total RNA was extracted from Pex19 reconstituted and deficient cell lines. Gene expression data was compared to uninfected cells.
Project description:Targeting FBXO44 or SUV39H1 transcriptionally reactivates repetitive elements, triggering RIG-I-MDA5-MAVS and cGAS-STING antiviral defense responses and IFN signaling, specifically in cancer cells
Project description:The RIG-I-like receptors (RLRs) form filaments to activate type-I interferon (IFN-I) and NF-KB signaling through their adaptor protein MAVS and downstream cascades. These filaments are recognized and regulated by cell-encoded machinery for correct activation. Here, we identified the stress-sensitive heat shock protein, HSPA6, was induced to express upon RLR-MAVS activation to act as a negative regulator of IFN-I signaling. Interestingly, by using MAVS-KO cells, we showed that HSPA6 was upregulated dependent on the presence of IFN-competent RLRs but not MAVS. Gene knockout (KO) tests indicated that the E3 ligases, stress granules (SGs), and transcription factors IRF1 and AP1 were all shared to induce HSPA6 and the canonical IFNb. Kinetic analysis showed that HSPA6 upregulated slower than IFNb, implicating these two genes competed machinery for transcription activation. Further tests suggested the induced HSPA6 bound to IFN-competent MDA5 to dissolve the filaments and downregulated IFN induction. Thus, our study uncovered a new gene activation mechanism by the IFN-competent RLRs to serve as negative feedback, arguing for a gene regulatory role of functional filaments of innate immunity.