I Interferon Signaling Pathway Research Articles

Epigallocatechin-3-gallate Can Prevent Type 2 Human Papillomavirus E7 from Suppressing Interferon-Stimulated Genes.

Human papillomavirus (HPV) in high-risk groups is known to suppress the type I interferon (IFN) signaling pathway leading to the transcription of interferon-stimulated genes (ISGs), which have many antiviral functions. However, the effects of HPV on the action of various ISGs in low-risk groups are not fully understood. We aimed to investigate whether antiviral ISGs are expressed in transfected keratinocytes with type 2 HPV (HPV-2) E7. The mRNA and protein expressions of ISGs and type I IFN signaling pathway components were evaluated by quantitative real-time polymerase chain reaction, western blot, immunofluorescence, and/or immunohistochemistry. Compared with normal skin, mRNA expression of all ISGs in HPV-2 positive cutaneous warts was significantly decreased (p < 0.05). In comparison with empty vector transfection, E7 transfection significantly down-regulated the mRNA and protein expressions of ISGs and type I IFN signaling pathway components, which were significantly up-regulated by E7 siRNA transfection (p < 0.05). Interestingly, epigallocatechin-3-gallate (EGCG) pretreatment up-regulated the mRNA and protein expressions of ISGs and type I IFN signaling pathway components, which were significantly down-regulated by E7 transfection (p < 0.05). Our results demonstrate that EGCG is a potential candidate for cutaneous wart prevention.

Type I interferons as key players in pancreatic β-cell dysfunction in type 1 diabetes.

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by pancreatic islet inflammation (insulitis) and specific pancreatic β-cell destruction by an immune attack. Although the precise underlying mechanisms leading to the autoimmune assault remain poorly understood, it is well accepted that insulitis takes place in the context of a conflicting dialogue between pancreatic β-cells and the immune cells. Moreover, both host genetic background (i.e., candidate genes) and environmental factors (e.g., viral infections) contribute to this inadequate dialogue. Accumulating evidence indicates that type I interferons (IFNs), cytokines that are crucial for both innate and adaptive immune responses, act as key links between environmental and genetic risk factors in the development of T1D. This chapter summarizes some relevant pathways involved in β-cell dysfunction and death, and briefly reviews how enteroviral infections and genetic susceptibility can impact insulitis. Moreover, we present the current evidence showing that, in β-cells, type I IFN signaling pathway activation leads to several outcomes, such as long-lasting major histocompatibility complex (MHC) class I hyperexpression, endoplasmic reticulum (ER) stress, epigenetic changes, and induction of posttranscriptional as well as posttranslational modifications. MHC class I overexpression, when combined with ER stress and posttranscriptional/posttranslational modifications, might lead to sustained neoantigen presentation to immune system and β-cell apoptosis. This knowledge supports the concept that type I IFNs are implicated in the early stages of T1D pathogenesis. Finally, we highlight the promising therapeutic avenues for T1D treatment directed at type I IFN signaling pathway.

Type I interferon: From innate response to treatment for COVID-19.

ABSTRACTEffective prophylactic and therapeutic interventions are urgently needed to address the coronavirus disease 2019 (COVID‐19) pandemic. Various antiviral drugs have recently been tested. Type I interferon (IFN) is a regulatory protein involved in the innate immune response, with broad‐spectrum antiviral activities and the ability to directly block viral replication and support the immune response to eliminate virus infection. Insufficient virus‐induced type I IFN production is characteristic of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection, because SARS‐CoV‐2 suppresses the IFN response by interacting with essential IFN signaling pathways. Exogenous type I IFN is recommended for treating COVID‐19. Unexpectedly however, angiotensin converting enzyme‐2 (ACE2) receptor, which acts as a SARS‐CoV‐2 receptor, was shown to be stimulated by IFN, raising doubts about the suitability of IFN use. However, further studies have excluded concerns regarding IFN administration. Type I IFNs, including IFN‐α1b, have been used clinically as antiviral drugs for many years and have shown strong antiviral activity against SARS‐CoV‐2 in vitro. Preliminary clinical studies of type I IFNs, especially when delivered via aerosol inhalation, have demonstrated efficacy for the treatment and prevention of COVID‐19. Randomized controlled trials of IFN for COVID‐19 treatment are ongoing.

Antiviral Role of Serine Incorporator 5 (SERINC5) Proteins in Classical Swine Fever Virus Infection.

Serine incorporator 5 (SERINC5), a multipass transmembrane protein, protects cells from viral infections. The mechanism by which SERINC5 protects against classical swine fever virus (CSFV) infection is unknown. In this study, overexpression of SERINC5 in PK-15 and 3D4/2 cells significantly inhibited the growth of CSFV, whereas SERINC5 silencing enhanced CSFV growth. Additionally, CSFV infection reduced SERINC5 production in cells and tissues. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to identify and analyze protein and peptide molecules that potentially interact with SERINC5. A total of 33 cellular protein candidates were identified. Next, SERINC5 was shown to interact with melanoma differentiation-associated protein 5 (MDA5) by yeast two-hybrid, protein co-localization and co-immunoprecipitation assays. Furthermore, SERINC5 enhanced MDA5-mediated type I interferon (IFN) signaling in a dose-dependent manner. Our results suggest that the anti-CSFV effect of SERINC5 is dependent on the activation of the type I IFN, which may function along with MDA5. The inhibitory effect of SERINC5 on CSFV was disappeared when the endogenous expression of MDA5 was silenced using siRNA, suggesting that SERINC5 exerts an anti-CSFV effect in an MDA5-dependent manner. Our study demonstrated a novel link between SERINC5 and MDA5 in the inhibition of CSFV replication via the type I IFN signaling pathway.

Ubiquitin-Conjugating Enzyme 2S Enhances Viral Replication by Inhibiting Type I IFN Production through Recruiting USP15 to Deubiquitinate TBK1

Type I interferon (IFN) plays an essential role in the host innate immune responses. Several ubiquitin-conjugating enzyme (E2) family members were reported to regulate type I IFN production and host antiviral immune responses. However, the molecular mechanisms are still not fully understood. Here, we report that UBE2S acts as a negative regulator in the type I IFN signaling pathway. Ectopic expression of UBE2S inhibits host antiviral immune responses and enhances viral replications, whereas deficiency of UBE2S enhances host antiviral immune responses and suppresses viral replications both invitro and invivo. Inhibition of type І IFN production by UBE2S is independent on its E2 and E3 enzymic activity. Mechanistically, UBE2S interacts with TBK1 and recruits ubiquitin-specific protease 15 (USP15) to remove Lys63 (K63)-linked polyubiquitin chains of TBK1. Our findings reveal a role of the UBE2S-USP15-TBK1 axis in the regulation of host antiviral innate immune responses.

Molecular cloning and functional characterization of duck DEAD (Asp-Glu-Ala-Asp) box RNA helicase 3 (DDX3X)

DEAD (Asp-Glu-Ala-Asp) box RNA helicase 3 (DDX3X) is demonstrated to have crucial functions in the antiviral immune response. To our knowledge, little information focuses on the function of duck DDX3X. In this study, duck DDX3X (duDDX3X) was cloned and its role in the type I interferon (IFN) signaling pathway was investigated using duck embryo fibroblast (DEF) cells. Full-length duDDX3X cDNA encodes 652 amino acid residues and contains a DEADc domain and a HELICc domain. According to tissue distribution analysis, duDDX3X mRNA was widely expressed in different tissues, especially the spleen and the liver. Overexpression of duDDX3X in DEF cells induced IFN-β by activating transcription factors IRF1 and NF-κB. Knockdown of duDDX3X in DEF cells with siRNA significantly reduced IFN-β expression induced by poly(I:C), a double-stranded RNA (dsRNA) analog. Our results demonstrated that duck DDX3X was involved in the dsRNA-mediated type I IFN signaling pathway in DEF cells.

The USP18 cysteine protease promotes HBV production independent of its protease activity

BackgroundHepatitis B virus (HBV) infection remains as one of the major public health problems in the world. Type I interferon (IFN) plays an essential role in antiviral defense by induced expression of a few hundred interferon stimulated genes (ISGs), including ubiquitin-specific protease 18 (USP18). The expression level of USP18 was elevated in the pretreatment liver tissues of chronic hepatitis B(CHB) patients who did not respond to IFN treatment. Thus, this study was designed to investigate the effects of USP18 on HBV replication/production.MethodsThe levels of wild type USP18(WT-USP18) and USP18 catalytically inactive form C64S were up-regulated by plasmids transfection in HepAD38 cells, respectively. Real-time PCR and ELISA were used to quantify HBV replication. Type I IFN signaling pathway was monitored at three levels: p-STAT1 (western Blot), interferon stimulated response element (ISRE) activity (dual luciferase assay) and ISGs expression (real time PCR).ResultsOur data demonstrated that overexpression of either WT-USP18 or USP18-C64S inactive mutant increased the intracellular viral pgRNA, total DNA, cccDNA, as well as HBV DNA levels in the culture supernatant, while silencing USP18 led to opposite effect on HBV production. In addition, upregulated WT-USP18 or USP18-C64S suppressed ISRE activity and the expression levels of p-STAT1 and ISGs.ConclusionUSP18 promoted HBV replication via inhibiting type I IFN signaling pathway, which was independent of its protease activity.

RelB suppresses type I Interferon signaling in dendritic cells

Type I Interferon (IFN) signaling plays a critical role in dendritic cell (DC) development and functions. Inhibition of hyper type I IFN signaling promotes cDC2 subtype development. Relb is essential to development of cDC2 subtype and here we analyzed its effect on type I IFN signaling in DCs. We show that Relb suppresses the homeostatic type I IFN signaling in cDC2 cultures. TLR stimulation of FL-DCs led to RelB induction coinciding with fall in IFN signatures; conforming with the observation Relb expression reduced TLR stimulated IFN induction along with decrease in ISGs. Towards understanding mechanism, we show that effects of RelB are mediated by increased levels of IκBα. We demonstrate that RelB dampened antiviral responses by lowering ISG levels and the defect in cDC2 development in RelB null mice can be rescued in Ifnar1−/− background. Overall, we propose a novel role of RelB as a negative regulator of the type I IFN signaling pathway; fine tuning development of cDC2 subtype.

Exosome-Mediated Delivery of Inducible miR-423-5p Enhances Resistance of MRC-5 Cells to Rabies Virus Infection.

The human diploid cell line Medical Research Council -5 (MRC-5) is commonly utilized for vaccine development. Although a rabies vaccine developed in cultured MRC-5 cells exists, the poor susceptibility of MRC-5 cells to the rabies virus (RABV) infection limits the potential yield of this vaccine. The underlying mechanism of MRC-5 cell resistance to RABV infection remains unknown. In this study, we demonstrate that viral infection increased exosomal release from MRC-5 cells; conversely, blocking exosome release promoted RABV infection in MRC-5 cells. Additionally, RABV infection up-regulated microRNA (miR)-423-5p expression in exosomes, resulting in feedback inhibition of RABV replication by abrogating the inhibitory effect of suppressor of cytokine signaling 3 (SOCS3) on type I interferon (IFN) signaling. Furthermore, intercellular delivery of miR-423-5p by exosomes inhibited RABV replication in MRC-5 cells. We also show that RABV infection increased IFN-β production in MRC-5 cells and that blocking the type I IFN receptor promoted RABV infection. In conclusion, MRC-5 cells were protected from RABV infection by the intercellular delivery of exosomal miR-423-5p and the up-regulation of IFN-β. These findings reveal novel antiviral mechanisms in MRC-5 cells against RABV infection. miR-423-5p, exosomes, and IFN signaling pathways may therefore be potential targets for improving MRC-5 cell-based rabies vaccine production.

JAK/STAT inhibition with ruxolitinib enhances oncolytic virotherapy in non-small cell lung cancer models.

The concept of using viruses to treat cancer has now shown proof of concept in several recent clinical trials, leading to the first FDA approval of virotherapy for melanoma last year. Vesicular stomatitis virus (VSV) is a promising oncolytic virus that has inhibitory effects on a number of cancer types including non-small cell lung cancer. One of the major mechanisms of resistance to VSV infection is the type I interferon (IFN) response, leading to the development of VSV expressing IFNβ which will lead to resistance of viral replication in normal cells which have intact IFN signaling but allow replication in cancer cells with defective IFNβ signaling. However, some cancer cells have intact or partially intact IFN signaling pathways leading to resistance to virotherapy. Here we utilized JAK/STAT inhibitor, ruxolitinib, in combination with VSV-IFNβ to see if inhibition of JAK/STAT signaling will enhance VSV-IFNβ therapy for lung cancer. We used five human and two murine NSCLC cell lines in vitro, and the combination treatment was assayed for cytotoxicity. We performed western blots on treated cells to see the effects of ruxolitinib on JAK/STAT signaling and PDL-1 expression in treated cells. Finally, the combination of VSV-IFNβ and ruxolitinib was tested in an immune competent murine model of NSCLC. Ruxolitinib enhanced virotherapy in resistant and sensitive NSCLC cells. The addition of ruxolitinib inhibited STAT1 phosphorylation and to a lesser extent STAT3 phosphorylation. Ruxolitinib treatment prevented NSCLC cells from enhancing PDL-1 expression in response to virotherapy. Combination ruxolitinib and VSV-IFNβ therapy resulted in a trend toward improved survival of mice without substantially effecting PDL-1 levels or levels of immune infiltration into the tumor. These results support further clinical evaluation of the combination of JAK/STAT inhibition with virotherapy.

A 113-amino-acid truncation at the NS1 C-terminus is a determinant for viral replication of H5N6 avian influenza virus in vitro and in vivo

Virulence of highly pathogenic avian influenza viruses (AIV) is determined by multiple genes and their encoded proteins. In particular, the nonstructural protein 1 (NS1) of viruses is a multifunctional protein that plays an important role in type I interferon (IFN) antagonism, pathogenicity, and determining viral host range. Naturally-occurring truncation or mutation of NS1 during virus evolution attenuates viral replication and pathogenicity, but the mechanisms underlying this phenomenon remain poorly understood. In the present study, we rescued an H5N6 AIV harboring a 113-amino-acid (aa) truncated NS1 at the C-terminus that had previously naturally occurred in an H3N8 equine influenza virus (designated as rHN109 NS1/112). The replication and pathogenicity of the rescued and parental viruses were then assessed in vitro in cells and in vivo in chickens and mice. Replication of rHN109 NS1/112 virus was significantly attenuated in various cells compared to its parental virus. The attenuation of rHN109 NS1/112 virus was subsequently clarified by investigating the effects on IFN and apoptosis signaling pathways via multiple experiments. The results indicated that the 113-aa truncation of NS1 impairs viral inhibition of IFN production and enhances cellular apoptosis in avian and mammalian cells. Animal studies further indicated that replication of the rHN109 NS1/112 virus is remarkably attenuated in chickens. The results of this study improve our understanding of C-terminal region function for NS1 proteins of influenza viruses.

Negative regulation of the RLR-mediated IFN signaling pathway by duck ubiquitin-specific protease 18 (USP18).

Ubiquitin-specific protease 18 (USP18) plays an important role in regulating type I interferon (IFN) signaling in innate immunity, and has a crucial impact on the IFN therapeutic effect. Although significant progress has been made in elucidating USP18 function in mammals, the role of USP18 in ducks (duUSP18) remains poorly understood. In this study, we cloned the USP18 gene from white crested ducks by reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of complementary DNA (cDNA) ends. We determined that duUSP18 cDNA contains a 52-bp 5'UTR, a 1,131-bp open reading frame and a 356-bp 3'UTR, and encodes a 376-amino acid protein. Multiple sequence alignments showed that duUSP18 shares high similarity with USP18 from other vertebrates. Overexpression of duUSP18 inhibited nuclear factor-κB (NF-κB) and interferon regulatory factor 1 (IRF1) activity, and reduced IFN-β production following 5' triphosphate double-stranded RNA (5'ppp dsRNA) or lipopolysaccharide (LPS) stimulation. duUSP18 knockdown significantly activated 5'ppp dsRNA-induced and LPS-induced NF-κB and IRF1 activation, and induced IFN-β expression in duck embryo fibroblasts. Furthermore, Quantitative real-time PCR (qRT-PCR) revealed that overexpression or knockdown of duUSP18 could alter the expression of genes related to the RLR-mediated IFN signaling pathway following the treatment with 5'ppp dsRNA. In addition, site-directed mutation analysis revealed that cysteine 66 (C66), histidine 313 (H313), and histidine 321 (H321) of duUSP18 were critical for inhibiting IFN-β activity. Taken together, these results suggest that duck USP18 plays an important role in innate immune responses against double-stranded RNA viruses in the RLR-mediated IFN signaling pathway, and that further studies are warranted to elucidate its underlying mechanisms, which could provide molecular insights into the effect of the treatment of duck diseases.

Influenza A Virus Infection Triggers Pyroptosis and Apoptosis of Respiratory Epithelial Cells through the Type I Interferon Signaling Pathway in a Mutually Exclusive Manner.

Respiratory epithelial cell death by influenza virus infection is responsible for the induction of inflammatory responses, but the exact cell death mechanism is not understood. Here we showed that influenza virus infection induces apoptosis and pyroptosis in normal or precancerous human bronchial epithelial cells. Apoptosis was induced only in malignant tumor cells infected with influenza virus. In human precancerous respiratory epithelial cells (PL16T), the number of apoptotic cells increased at early phases of infection, but pyroptotic cells were observed at late phases of infection. These findings suggest that apoptosis is induced at early phases of infection but the cell death pathway is shifted to pyroptosis at late phases of infection. We also found that the type I interferon (IFN)-mediated JAK-STAT signaling pathway promotes the switch from apoptosis to pyroptosis by inhibiting apoptosis possibly through the induced expression of the Bcl-xL anti-apoptotic gene. Further, the inhibition of JAK-STAT signaling repressed pyroptosis but enhanced apoptosis in infected PL16T cells. Collectively, we propose that type I IFN signaling pathway triggers pyroptosis but not apoptosis in the respiratory epithelial cells in a mutually exclusive manner to initiate proinflammatory responses against influenza virus infection.IMPORTANCE Respiratory epithelium functions as a sensor of infectious agents to initiate inflammatory responses along with cell death. However, the exact cell death mechanism responsible for inflammatory responses by influenza virus infection is still unclear. We showed that influenza virus infection induced apoptosis and pyroptosis in normal or precancerous human bronchial epithelial cells. Apoptosis was induced at early phases of infection, but the cell death pathway was shifted to pyroptosis at late phases of infection under the regulation of type I IFN signaling to promote proinflammatory cytokine production. Taken together, our results indicate that the type I IFN signaling pathway plays an important role to induce pyroptosis but represses apoptosis in the respiratory epithelial cells to initiate proinflammatory responses against influenza virus infection.

Synthetic RNA derived from the foot-and-mouth disease virus genome elicits antiviral responses in bovine and porcine cells through IRF3 activation

Foot-and-mouth disease virus (FMDV) is the causative agent of a highly transmissible disease affecting wild and domestic animals including pigs, cattle and sheep. The ability of synthetic RNA transcripts mimicking distinct domains in the non-coding regions of the FMDV genome (ncRNAs) to induce a potent innate immune response in swine cultured cells and mice has been previously described, as well as their enhancing effect on conventional inactivated FMD vaccines. Here, we provide evidence of the activation of interferon regulatory factor 3 (IRF3), a key transcriptional regulator of type I interferon (IFN)-dependent immune responses after transfection of swine and bovine cells with transcripts corresponding to the FMDV 3´ non-coding region (3´NCR). Induction of IFN-β and Mx1expression, concomitantly with antiviral activity and IRF3 activation was observed in bovine MDBK cells transfected with the 3´NCR. Our results link the stimulation of the innate immune response observed in 3´NCR-transfected cells to the intracellular type I IFN signaling pathway and suggest the potential use of these molecules for antiviral strategies in cattle.

Interplay between type I interferon signaling and AIM2 inflammasome in Francisella novicida infection

Abstract Inflammasomes are crucial for mediating protection against microbial infection. Type I interferon (IFN) signaling is required for driving activation of the AIM2 inflammasome in macrophages in response to infection by Francisella tularensis subspecies novicida (F. novicida). Here, we showed that mice lacking type I IFN signaling had intact inflammasome responses after F. novicida infection. Mice lacking the type I IFN receptor subunit, IFNAR1 or IFNAR2, and core components of the type I IFN signaling pathway were resistant to infection by F. novicida compared with wild-type mice, whereas mice lacking AIM2 were more susceptible. Importantly, we found that mice lacking both AIM2 and IFNAR2 were more resistant to the infection with an impaired ability to induce activation of apoptotic caspases than infected wild-type mice. These results suggested that while type I IFN signaling and AIM2 were essential for activation of the Francisella-induced inflammasome in macrophages, they have strikingly opposing effects in vivo. Furthermore, type I IFN signaling is a dominant regulator of anti-microbial activity during F. novicida infection in vivo even in the absence of AIM2 responses.

Analysis of Mouse Brain Transcriptome After Experimental Duvenhage Virus Infection Shows Activation of Innate Immune Response and Pyroptotic Cell Death Pathway

Rabies is an important neglected disease, characterized by invariably fatal encephalitis. Several studies focus on understanding the pathogenic mechanisms of the prototype lyssavirus rabies virus (RABV) infection, and little is known about the pathogenesis of rabies caused by other lyssaviruses. We sought to characterize the host response to Duvenhage virus infection and compare it with responses observed during RABV infection by gene expression profiling of brains of mice with the respective infections. We found in both infections differentially expressed genes leading to increased expression of type I interferons (IFNs), chemokines, and proinflammatory cytokines. In addition several genes of the IFN signaling pathway are up-regulated, indicating a strong antiviral response and activation of the negative feedback mechanism to limit type I IFN responses. Furthermore we provide evidence that in the absence of significant neuronal apoptotic death, cell death of neurons is mediated via the pyroptotic pathway in both infections. Taken together, we have identified several genes and/or pathways for both infections that could be used to explore novel approaches for intervention strategies against rabies.

Interferon α subtypes in HIV infection

Type I interferons (IFN), which are immediately induced after most virus infections, are central for direct antiviral immunity and link innate and adaptive immune responses. However, several viruses have evolved strategies to evade the IFN response by preventing IFN induction or blocking IFN signaling pathways. Thus, therapeutic application of exogenous type I IFN or agonists inducing type I IFN responses are a considerable option for future immunotherapies against chronic viral infections. An important part of the type I IFN family are 12 IFNα subtypes, which all bind the same receptor, but significantly differ in their biological activities. Up to date only one IFNα subtype (IFNα2) is being used in clinical treatment against chronic virus infections, however its therapeutic success rate is rather limited, especially during Human Immunodeficiency Virus (HIV) infection. Recent studies addressed the important question if other IFNα subtypes would be more potent against retroviral infections in in vitro and in vivo experiments. Indeed, very potent IFNα subtypes were defined and their antiviral and immunomodulatory properties were characterized. In this review we summarize the recent findings on the role of individual IFNα subtypes during HIV and Simian Immunodeficiency Virus infection. This includes their induction during HIV/SIV infection, their antiretroviral activity and the regulation of immune response against HIV by different IFNα subtypes. The findings might facilitate novel strategies for HIV cure or functional cure studies.

Molecular cloning and characterization of FADD from the orange-spotted grouper (Epinephelus coioides)

Fas-associated protein with death domain (FADD) is the key adaptor protein that transmits apoptotic signals mediated by the main death receptors. Besides being an essential instrument in cell death, FADD is also implicated in proliferation, cell cycle progression, tumor development, inflammation, innate immunity, and autophagy. In the present study, a FADD homologue (EcFADD) from the orange-spotted grouper (Epinephelus coioides) was cloned and its possible role in fish immunity was analyzed. The full length cDNA of EcFADD contains 808 base pairs (bp), including a 573 bp open reading frame that encodes a 190 amino acid protein with a predicted molecular mass of 21.81 kDa. Quantitative real-time polymerase chain reaction analysis indicated that EcFADD was distributed in all examined tissues. The expression of EcFADD in the spleen of E. coioides was differentially up-regulated when challenged with Singapore grouper iridovirus (SGIV) or polyinosine-polycytidylic acid(poly[I:C]). EcFADD was abundantly distributed in both the cytoplasm and nucleus in grouper spleen (GS) and fathead minnow (FHM) epithelial cells. Over-expression of EcFADD inhibited SGIV infection and replication and SGIV-induced apoptosis. To achieve antiviral and anti-apoptosis activities, FADD promoted the activation of interferon-stimulated response element (ISRE) and type I interferon (IFN) genes in the antiviral IFN signaling pathway and inhibited activation of apoptosis-related transcription factors p53. Our results not only characterize FADD but also reveal new immune functions and the molecular mechanisms by which FADD responds to virus infection and virus-induced apoptosis.

Functional characterization of tumor necrosis factor receptor-associated factor 3 of sea perch (Lateolabrax japonicas) in innate immune

Tumor necrosis factor receptor-associated factor 3 (TRAF3) is a multifunctional regulator implicated in both bacterial defense and antiviral immunity. Here, a TRAF3 gene from the seawater fish sea perch, designated as LjTRAF3, was characterized. The full-length cDNA of LjTRAF3 was 2972 bp including a 5′ untranslated region (UTR) of 243 bp, a 3′UTR of 941 bp and a putative open reading frame of 1608 bp encoding a putative protein of 536 amino acid. The deduced LjTRAF3 protein contained a RING finger, two zinc fingers, a coiled-coil, and a meprin and TRAF-C homology domain. Phylogenetic analysis showed that LjTRAF3 shared the closest genetic relationship with Larimichthys crocea TRAF3. Gene expression analyses suggested that LjTRAF3 mRNA was ubiquitously expressed in all the tissues tested, and was up-regulated post red spotted grouper nervous necrosis virus (RGNNV) infection in vivo and in vitro. Reporter gene assay showed that LjTRAF3 significantly activated zebrafish type I interferon (IFN) promoter in vitro. During RGNNV infection, ectopic expression of LjTRAF3 significantly reduced the RNA dependent RNA polymerase transcription of RGNNV, and enhanced the expression of RIG-I-like receptors (RLR), janus kinase-signal transducers and activators of transcription (JAK-STAT) signaling pathway related genes and IFN stimulated genes (ISGs), including ISG15, PKR, VIG and TRIM39. Taken together, our results suggested that LjTRAF3 might trigger the expression of various ISGs to counter RGNNV infection by regulating the RLR-induced IFN and JAK-STAT signaling pathways.

Fine-tuning type I IFN signaling: A new chapter in the IFN saga.

Type I interferon (IFN) signaling is critical for intracellular antimicrobial programmes, affecting both innate and adaptive immune responses. The paper recently published in Cell demonstrates a new regulatory mechanism of the type I IFN signaling pathway by histone-lysine N-methyltransferase SETD2.