The innate immune system initiates innate immune responses by recognizing pathogen-related molecular patterns on the surface of pathogenic microorganisms through pattern recognition receptors. Through cascade signal transduction, it activates downstream transcription factors NF-κB and interferon regulatory factors (IRFs), and then leads to the production of inflammatory cytokines and type Ⅰ interferon, which resists the infection of pathogenic microorganism. TBK1 is a central adapter protein of innate immune signaling pathway and can activate both NF-κB and IRFs. It is a key protein kinase in the process of anti-infection. The finetuning regulation of TBK1 is essential to maintain immune homeostasis and resist pathogen invasion. This paper reviews the biological functions and ubiquitin modification of TBK1 in innate immunity, to provide theoretical basis for clinical treatment of pathogenic infections and autoimmune diseases.
Immunity, Innate ; Interferon Regulatory Factor-3/metabolism* ; Protein-Serine-Threonine Kinases/genetics* ; Signal Transduction ; Ubiquitin

To acquire epidemiological data on the bovine viral diarrhea virus (BVDV) and identify cattle persistently infected (PI) with this virus, 4,327 samples from Holstein dairy cows were screened over a four-year period in Beijing, China. Eighteen BVD viruses were isolated, 12 from PI cattle. Based on genetic analysis of their 5'-untranslated region (5'-UTR), the 18 isolates were assigned to subgenotype BVDV-1m, 1a, 1d, 1q, and 1b. To investigate the innate immune responses in the peripheral-blood mononuclear cells of PI cattle, the expression of Toll-like receptors (TLRs), RIG-I-like receptors, interferon-alpha (IFN-alpha), IFN-beta, myxovirus (influenza virus) resistance 1 (MX1), and interferon stimulatory gene 15 (ISG15) was assessed by qPCR. When compared with healthy cattle, the expression of TLR-7, IFN-alpha, and IFN-beta mRNA was downregulated, but the expression of MX1 and ISG-15 mRNA was upregulated in PI cattle. Immunoblotting analysis revealed that the expression of interferon regulatory factor 3 (IRF-3) and IRF-7 was lower in PI cattle than in healthy cattle. Thus, BVDV-1m and 1a are the predominant subgenotypes in the Beijing region, and the strains are highly divergent. Our findings also suggest that the TLR-7/IRF-7 signaling pathway plays a role in evasion of host restriction by BVDV.
Animals ; Cattle* ; China* ; Diarrhea* ; Immunity, Innate* ; Immunoblotting ; Interferon Regulatory Factor-3 ; Interferon-alpha ; Interferons ; Orthomyxoviridae ; RNA, Messenger ; Toll-Like Receptors

Previously, we have reported that high mobility group box 1 (HMGB1), a proinflammatory mediator in sepsis, is released via the IFN-beta-mediated JAK/STAT pathway. However, detailed mechanisms are still unclear. In this study, we dissected upstream signaling pathways of HMGB1 release using various molecular biology methods. Here, we found that calcium/calmodulin-dependent protein kinase (CaM kinase, CaMK) is involved in HMGB1 release by regulating IFN-beta production. CaMK inhibitor, STO609, treatment inhibits LPS-induced IFN-beta production, which is correlated with the phosphorylation of interferon regulatory factor 3 (IRF3). Additionally, we show that CaMK-I plays a major role in IFN-beta production although other CaMK members also seem to contribute to this event. Furthermore, the CaMK inhibitor treatment reduced IFN-beta production in a murine endotoxemia. Our results suggest CaMKs contribute to HMGB1 release by enhancing IFN-beta production in sepsis.
Benzimidazoles ; Cytokines ; Endotoxemia ; HMGB1 Protein ; Inflammation ; Interferon Regulatory Factor-3 ; Interferon-beta ; Molecular Biology ; Naphthalimides ; Phosphorylation ; Phosphotransferases ; Protein Kinases ; Sepsis ; Signal Transduction

OBJECTIVETo detect the secretions of type I interferon and the expressions of phospho-IRF3 in murine liver dendritic cells intervened by HBV.

METHODSThe murine liver dendritic cells were isolated via anti-CD11c microbeads and were incubated in the presence of GM-CSF and IL-4 to induce the DC generation and proliferation in 24-well cell culture plates. HBV virions were isolated via ultracentrifugation and were detected by quantitative Realtime-PCR. The DCs were divided into two groups: one group was cultured with HBV virions for 24 hours, the other group was cultured without HBV as control group. The cells were harvested at Oh, 1h, 2h, 6h and 24h after being stimulated with poly I:C and the expressions of p-IRF3 and the concentration of IFN beta in supernatants were detected with western blot and ELISA respectively.

RESULTSThe IFN beta concentrations at 0 h, 6 h and 24 h in the supernatants of the HBV group and the control group were (12.38 +/- 3.71) pg/ml, (88.67 +/- 9.01) pg/ml and (69.89 +/- 5.80) pg/ml vs (10.83 +/- 4.11) pg/ml, (137.68 +/- 12.28) pg/ml and (72.25 +/- 8.61) pg/ml, respectively. No statistical differences found at 0 h (t = 0.8398, P > 0.05) and 24 h (t = 0.6820, P > 0.05) between the two groups except that at 6 h (t = 9.653, P < 0.01). The expressions of phospho-IRF3 in HBV group were lower than that in control group.

CONCLUSIONSThe type I interferon secretion and the phospho-IRF3 expression were decreased in murine liver dendritic cells when intervened by HBV.

Animals ; Cells, Cultured ; Coculture Techniques ; Dendritic Cells ; cytology ; metabolism ; Hepatitis B virus ; Hepatocytes ; cytology ; Interferon Regulatory Factor-3 ; metabolism ; Interferon Type I ; secretion ; Male ; Mice ; Mice, Inbred C57BL

The innate immune response is the first line of host defense to eliminate viral infection. Pattern recognition receptors in the cytosol, such as RIG-I-like receptors (RLR) and Nod-like receptors (NLR), and membrane bound Toll like receptors (TLR) detect viral infection and initiate transcription of a cohort of antiviral genes, including interferon (IFN) and interferon stimulated genes (ISGs), which ultimately block viral replication. Another mechanism to reduce viral spread is through RIPA, the RLR-induced IRF3-mediated pathway of apoptosis, which causes infected cells to undergo premature death. The transcription factor IRF3 can mediate cellular antiviral responses by both inducing antiviral genes and triggering apoptosis through the activation of RIPA. The mechanism of IRF3 activation in RIPA is distinct from that of transcriptional activation; it requires linear polyubiquitination of specific lysine residues of IRF3. Using RIPA-active, but transcriptionally inactive, IRF3 mutants, it was shown that RIPA can prevent viral replication and pathogenesis in mice.
Animals ; Apoptosis ; DEAD Box Protein 58 ; genetics ; immunology ; metabolism ; Humans ; Immunity, Innate ; Interferon Regulatory Factor-3 ; genetics ; immunology ; metabolism ; Mice ; Virus Diseases ; genetics ; immunology ; metabolism

BACKGROUND: Toll-like receptor 3 (TLR3) recognizes double-stranded RNA (dsRNA) and induces inflammation. In this study we attempted to ascertain if there are endogenous host molecules controlling the production of cytokines and chemokines. Two candidates, ribosomal protein L19 and L22, were analyzed to determine if they influence cytokine production followed by TLR3 activation. In this study we report that L19 acts upon production of IP-10 or IL-8 differently in glioblastoma cells. METHODS: L19 or L22 was transfected into HEK293-TLR3, A549 or A172 cells. After treatment with several inhibitors of NF-kB, PI3K, p38 or ERK, production of IL-8 or IP-10 was measured by ELISA. siRNA was introduced to suppress expression of L19. After Vesicular stomatitis virus infection, viral multiplication was measured by western blot. RESULTS: L19 increased ERK activation to produce IL-8. In A172 cells, in which TLR3 is expressed at endosomes, L19 inhibited interferon regulatory factor 3 (IRF3) activation and IP-10 production to facilitate viral multiplication, whereas L19 inhibited viral multiplication in A549 cells bearing TLR3 on their cell membrane. CONCLUSION: Our results suggest that L19 regulates TLR3 signaling, which is cell type specific and may be involved in pathogenesis of autoimmune diseases and chronic inflammatory diseases.
Autoimmune Diseases ; Chemokines ; Cytokines ; Endosomes ; Enzyme-Linked Immunosorbent Assay ; Glioblastoma ; Inflammation ; Interferon Regulatory Factor-3 ; Interleukin-8 ; NF-kappa B ; Ribosomal Proteins ; RNA, Double-Stranded ; RNA, Small Interfering ; Toll-Like Receptor 3 ; Ursidae ; Vesicular Stomatitis ; Viruses

The regulation mechanism of interferon (IFN) and IFN-stimulated genes is a very complex procedure and is dependent on cell types and virus species. We observed molecular changes related to anti-viral responses in endothelial cells during Hantaan virus (HTNV) infection. We found that there are two patterns of gene expression, the first pattern of gene expression being characterized by early induction and short action, as in that of type I IFNs,' and the other being characterized by delayed induction and long duration, as those of IRF-7, MxA, and TAP-1/2. Even though there are significant differences in their induction folds, we found that all of IFN-alpha/beta , IRF- 3/7, MxA, and TAP-1/2 mRNA expressions reached the peak when the viral replication was most active, which took place 3 days of post infection (d.p.i.). In addition, an interesting phenomenon was observed; only one gene was highly expressed in paired genes such as IFN-alpha/beta??(3/277-folds), IRF-3/7 (2.2/29.4-folds), and TAP- 1/2 (26.2/6.1-folds). Therefore, IFN-beta, IRF-7, and TAP-1 seem to be more important for the anti-viral response in HTNV infection. MxA was increased to 296-folds at 3 d.p.i. and kept continuing 207-folds until 7 d.p.i.. The above results indicate that IFN-beta works for an early anti-viral response, while IRF7, MxA, and TAP-1 work for prolonged anti-viral response in HTNV infection.
ATP-Binding Cassette Transporters/*genetics ; Blotting, Western ; Cells, Cultured ; Endothelial Cells/metabolism/*virology ; GTP-Binding Proteins/*genetics ; *Gene Expression Regulation ; Hantaan virus/*immunology ; Histocompatibility Antigens Class I/analysis ; Humans ; Interferon Regulatory Factor-3/genetics ; Interferon Regulatory Factor-7/*genetics ; Interferons/*genetics ; RNA, Messenger/analysis

SARS coronavirus (SARS-CoV) develops an antagonistic mechanism by which to evade the antiviral activities of interferon (IFN). Previous studies suggested that SARS-CoV papain-like protease (PLpro) inhibits activation of the IRF3 pathway, which would normally elicit a robust IFN response, but the mechanism(s) used by SARS PLpro to inhibit activation of the IRF3 pathway is not fully known. In this study, we uncovered a novel mechanism that may explain how SARS PLpro efficiently inhibits activation of the IRF3 pathway. We found that expression of the membrane-anchored PLpro domain (PLpro-TM) from SARS-CoV inhibits STING/TBK1/IKKε-mediated activation of type I IFNs and disrupts the phosphorylation and dimerization of IRF3, which are activated by STING and TBK1. Meanwhile, we showed that PLpro-TM physically interacts with TRAF3, TBK1, IKKε, STING, and IRF3, the key components that assemble the STING-TRAF3-TBK1 complex for activation of IFN expression. However, the interaction between the components in STING-TRAF3-TBK1 complex is disrupted by PLpro-TM. Furthermore, SARS PLpro-TM reduces the levels of ubiquitinated forms of RIG-I, STING, TRAF3, TBK1, and IRF3 in the STING-TRAF3-TBK1 complex. These results collectively point to a new mechanism used by SARS-CoV through which PLpro negatively regulates IRF3 activation by interaction with STING-TRAF3-TBK1 complex, yielding a SARS-CoV countermeasure against host innate immunity.
Dimerization ; HEK293 Cells ; Humans ; I-kappa B Kinase ; metabolism ; Interferon Regulatory Factor-3 ; metabolism ; Interferon Type I ; antagonists & inhibitors ; metabolism ; Membrane Proteins ; chemistry ; genetics ; metabolism ; Papain ; metabolism ; Peptide Hydrolases ; chemistry ; metabolism ; Phosphorylation ; Protein Binding ; Protein Structure, Tertiary ; Protein-Serine-Threonine Kinases ; metabolism ; SARS Virus ; enzymology ; Signal Transduction ; TNF Receptor-Associated Factor 3 ; metabolism ; Ubiquitination

OBJECTIVETo explore the possible mechanism of the inhibitory effect of liver X receptor alpha (LXRalpha) on lipopolysaccharide (LPS)-induced inflammation in mouse Kupffer cells (KCs).

METHODSThe KCs isolated from the liver of male KM mice and cultured in RPMI 1640 containing 20% FBS for 24 h were divided into control, LPS, T0901317, and LPS+T0901317 groups with corresponding treatments. The expressions of LXRalpha, interferon regulatory factor 3 (IRF3) and glucocorticoid receptor interacting protein 1 (GRIP1) in the KCs were detected by Western blotting. The levels of interferon beta (IFNbeta), tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) in the supernatant were detected by enzyme-linked immunosorbent assay (ELISA).

RESULTSThe level of LXRalpha protein was highest in T0901317 group and lowest in LPS group, and was significantly higher in LPS+T0901317 group than in LPS group but lower than in T0901317 group (P<0.05). The levels of IRF3 and GRIP1 protein were the highest in LPS group, and significantly lowered by T0901317 treatment (P<0.05). The expression of IRF3 and GRIP1 proteins in LPS group and LPS+ T0901317 group were significantly higher than those in the control and T0901317 groups (P<0.05). The concentration of IFN-beta was significantly higher in LPS group than in the control and T0901317 group (P<0.05), and decreased in LPS+T0901317 group in comparison with that in LPS group (P<0.05). IFN-beta was the lowest in T0901317 group. The levels of TNF-alpha and IL-1beta were the highest in LPS group (P<0.05), and comparable between the other 3 groups (P>0.05).

CONCLUSIONPre-treatment with T0901317 before LPS stimulation can suppress the expressions of IRF3 and GRIP1 to inhibit the inflammation and hence Kupffer cell activation.

Animals ; Cells, Cultured ; Hydrocarbons, Fluorinated ; pharmacology ; Inflammation ; chemically induced ; Interferon Regulatory Factor-3 ; metabolism ; Kupffer Cells ; cytology ; metabolism ; Lipopolysaccharides ; pharmacology ; Liver X Receptors ; Male ; Mice ; Nuclear Receptor Coactivator 2 ; metabolism ; Orphan Nuclear Receptors ; physiology ; Sulfonamides ; pharmacology

Retinoic acid inducible gene-I (RIG-I) is a caspase recruitment domain (CARD) containing protein that acts as an intracellular RNA receptor and senses virus infection. After binding to double stranded RNA (dsRNA) or 5'-triphosphate single stranded RNA (ssRNA), RIG-I transforms into an open conformation, translocates onto mitochondria, and interacts with the downstream adaptor mitochondrial antiviral signaling (MAVS) to induce the production of type I interferon and inflammatory factors via IRF3/7 and NF-κB pathways, respectively. Recently, accumulating evidence suggests that RIG-I could function in non-viral systems and participate in a series of biological events, such as inflammation and inflammation related diseases, cell proliferation, apoptosis and even senescence. Here we review recent advances in antiviral study of RIG-I as well as the functions of RIG-I in other fields.
Antiviral Agents ; chemistry ; DEAD Box Protein 58 ; DEAD-box RNA Helicases ; chemistry ; metabolism ; physiology ; Humans ; Inflammation ; metabolism ; Interferon Regulatory Factor-3 ; metabolism ; NF-kappa B ; metabolism ; RNA Viruses ; metabolism ; RNA, Double-Stranded ; metabolism ; Signal Transduction