Infections by coronaviruses such as severe acute respiratory syndrome （SARS） coronavirus （SCoV） and mouse hepatitis virus A59 （MHV-A59） result in very little type I interferon （IFN） production by host cells, w...Infections by coronaviruses such as severe acute respiratory syndrome （SARS） coronavirus （SCoV） and mouse hepatitis virus A59 （MHV-A59） result in very little type I interferon （IFN） production by host cells, which is potentially responsible for the rapid viral growth and severe immunopathology associated with SARS. However, the molecular mechanisms for the low IFN production in cells infected with coronaviruses remain unclear. Here, we provide evidence that Papain-like protease domain 2 （PLP2）, a catalytic domain of the nonstructural protein 3 （nsp3） of MHV-A59, can bind to IRF3, cause its deubiquitination and prevent its nuclear translocation. As a consequence, co-expression of PLP2 strongly inhibits CARDIF-, TBK1- and IRF3-mediated IFNp reporter activities. In addition, we show that wild-type PLP2 but not the mutant PLP2 lacking the deubiquitinase （DUB） activity can reduce IFN induction and promote viral growth in cells infected with VSV. Thus, our study uncovered a viral DUB which coronaviruses may use to escape from the host innate antiviral responses.展开更多
Intracellular RNA viruses are sensed by receptors retinoic acid-inducible gene 1 （RIG-I）/melanoma differentiation-associated gene 5 （MDA5） that trigger the formation of MAVS signal complex on mitochondria. Consequ...Intracellular RNA viruses are sensed by receptors retinoic acid-inducible gene 1 （RIG-I）/melanoma differentiation-associated gene 5 （MDA5） that trigger the formation of MAVS signal complex on mitochondria. Consequently, this leads to the activation of TANK-binding kinase 1 （TBK1） and phosphorylation of interferon regulatory factor 3 （IRF3）, both of which constitutively associate with cytosolic chaperone Hsp90. It remains largely unknown how MAVS activates TBK1/IRF3. In this study, we identified translocases of outer membrane 70 （Tom70）, a mitochondrial import receptor, to interact with MAVS upon RNA virus infection. Ectopic expression or knockdown of Tom70 could enhance or impair IRF3-mediated gene expression, respectively. Mechanistically, the clamp domain （R192） of Tom70 interacts with the C-terminal motif （EEVD） of Hsp90, thus recruiting TBK1/IRF3 to mitochondria. Disruption of this interaction or mislocation of Tom70 sharply impairs activation of TBK1 and IRF3. Furthermore, host antiviral responses are significantly boosted or crippled in the presence or absence of Tom70. Collectively, our study characterizes Tom70 as a critical adaptor linking MAVS to TBK1/IRF3, revealing that mitochondrion is evolutionarily integrated with innate immunity.展开更多
Viral infection causes host cells to produce type I interferons （IFNs）, which are critically involved in viral clearance. Previous studies have demonstrated that activation of the transcription factor interferon reg...Viral infection causes host cells to produce type I interferons （IFNs）, which are critically involved in viral clearance. Previous studies have demonstrated that activation of the transcription factor interferon regulatory factor （IRF）3 is essential for virus-triggered induction of type I IFNs. Here we show that the E3 ubiquitin ligase RBCC protein interacting with PKC1 （RBCK1） catalyzes the ubiquitination and degradation of IRF3. Overexpression of RBCK1 negatively regulates Sendai virus-triggered induction of type I IFNs, while knockdown of RBCK1 has the opposite effect. Plaque assays consistently demonstrate that RBCKI negatively regulates the cellular antiviral response. Furthermore, viral infection leads to induction of RBCK1 and subsequent degradation of IRF3. These findings suggest that the cellular antiviral response is controlled by a negative feedback regulatory mechanism involving RBCKl-mediated ubiquitination and degradation of IRF3.展开更多
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 membran...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 pre- mature 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 dis- tinct 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.展开更多
Type I interferons such as interferon-beta （IFN-β） play essential roles in the host innate immune response to herpes simplex virus type I （HSV-1） infection. The transcription of type I interferon genes is control...Type I interferons such as interferon-beta （IFN-β） play essential roles in the host innate immune response to herpes simplex virus type I （HSV-1） infection. The transcription of type I interferon genes is controlled by nuclear factor-κB （NF-κB） and interferon regulatory factor （IRF） family members including IRF3. NF-κB activation depends on the phosphorylation of inhibitor of κB （IκB）, which triggers its ubiqitination and degradation. It has been reported that neddylation inhibition by a pharmacological agent MLN4924 potently suppresses lipopolysaccharide （LPS）-induced proinflammatory cytokine production with the accumulation of phosphorylated IκBa. However, the role of neddylation in type I interferon expression remains unknown. Here, we report that neddylation inhibition with MLN4924 or upon UBA3 deficiency led to accumulation of phosphorylated IκBa, impaired IκBa degradation, and impaired NF-κB nuclear translocation in the early phase of HSV-1 infection even though phosphorylation and nuclear translocation of IRF3 were not affected. The blockade of NF-κB nuclear translocation by neddylation inhibition becomes less efficient at the later time points of HSV-1 infection. Consequently, HSV- 1-induced early phase IFN-β production significantly decreased upon MLN4924 treatment and UBA3 deficiency. NF-κB inhibitor JSH-23 mimicked the effects of neddylation inhibition in the early phase of HSV-1 infection. Moreover, the effects of neddylation inhibition on HSV-1-induced early phase IFN-c production diminished in the presence of NF-κB inhibitor JSH-23. Thus, neddylation contributes to HSV-l-induced early phase IFN-β production through, at least partially, promoting NF-κB activation.展开更多
Transcription factor IRF3-mediated type I interferon induction is essential for antiviral innate immunity.We identified the deSUMOylating enzyme Sentrin/SUMO-specific protease(SENP)2 as a negative regulator of virus-t...Transcription factor IRF3-mediated type I interferon induction is essential for antiviral innate immunity.We identified the deSUMOylating enzyme Sentrin/SUMO-specific protease(SENP)2 as a negative regulator of virus-triggered IFN-b induction.Overexpression of SENP2 caused IRF3 deSUMOylation,K48-linked ubiquitination,and degradation,whereas depletion of SENP2 had opposite effects.Both the SUMOylation and K48-linked ubiquitination of IRF3 occurred at lysines 70 and 87,and these processes are competitive.The level of virus-triggered IFN-b was markedly up-regulated and viral replication was reduced in SENP2-deficient cells comparing with wild-type controls.Our findings suggest that SENP2 regulates antiviral innate immunity by deSUMOylating IRF3 and conditioning it for ubiquitination and degradation,and provide an example of cross-talk between the ubiquitin and SUMO pathways in innate immunity.展开更多
MITA is a central adaptor in innate immune responses to DNA viruses.The mechanisms responsible for recruitment of downstream kinase TBK1 and the transcription factor IRF3 to MITA remains enigmatic.Here we identified Z...MITA is a central adaptor in innate immune responses to DNA viruses.The mechanisms responsible for recruitment of downstream kinase TBK1 and the transcription factor IRF3 to MITA remains enigmatic.Here we identified ZDHHC11,a member of DHHC palmitoyl transferase family,as a positive regulator of DNA virus-triggered signaling.Overexpression of ZDHHC11 activated the IFN-βpromoter,while ZDHHC11-deficiency specifically impaired DNA virus HSV-1-induced transcription of downstream antiviral genes.Zdhhc11^(−/−)mice exhibited lower serum cytokine levels and higher lethality after HSV-1 infection.Mechanistically,ZDHHC11 facilitated the optimal recruitment of IRF3 to MITA.Our findings support an important role for ZDHHC11 in mediating MITA-dependent innate immune responses against DNA viruses.展开更多
Interferon-induced transmembrane protein 3 (IFITM3) is a restriction factor that can be induced by viral infectionand interferons (IFNs). It inhibits the entry and replication of many viruses, which are independent of...Interferon-induced transmembrane protein 3 (IFITM3) is a restriction factor that can be induced by viral infectionand interferons (IFNs). It inhibits the entry and replication of many viruses, which are independent of receptorusage but dependent on processes that occur in endosomes. In this study, we demonstrate that IFITM3 playsimportant roles in regulating the RNA-virus-triggered production of IFN-β in a negative-feedback manner.Overexpression of IFITM3 inhibited Sendai virus-triggered induction of IFN-β, whereas knockdown of IFITM3 hadthe opposite effect. We also showed that IFITM3 was constitutively associated with IRF3 and regulated thehomeostasis of IRF3 by mediating the autophagic degradation of IRF3. These findings suggest a novel inhibitoryfunction of IFITM3 on the RNA-virus-triggered production of type I IFNs and cellular antiviral responses.展开更多
Interferon regulatory factor （IRF）3 is critical for the transcriptional induction of chemokines and cytokines during viral or bacterial invasion. The kinases Tank binding kinase （TBK）1 and Ikappa B kinase （IKK）...Interferon regulatory factor （IRF）3 is critical for the transcriptional induction of chemokines and cytokines during viral or bacterial invasion. The kinases Tank binding kinase （TBK）1 and Ikappa B kinase （IKK）ε can phosphorylate the C-terminal part of IRF3 and play important roles in IRF3 activation. In this study, we show that another kinase, c-Jun-NH2-terminal kinase （JNK）, phosphorylates IRF3 on its N-terminal serine 173 residue, and TAK1 can stimu- late IRF3 phosphorylation via JNK. JNK specific inhibitor SP600125 inhibits the N-terminal phosphorylation with- out affecting the C-terminal phosphorylation. In addition, IRF3-mediated gene expressions on lipopolysaccharide （LPS） or polyinosinic-cytidylic acid （polyI：C） treatment are severely impaired by SP600125, as well as for reporter gene assay of IRF3 activation. Knockdown of TAK1 further confirmed these observations. Interestingly, constitu- tive active IRF3（5D） can be inhibited by SP600125; JNK1 can synergize the action of IRF3（5D）, but not the S173A- IRF3（5D） mutant. More importantly, polyI：C failed to induce the phosphorylation of mutant S173A and SP600125 dramatically abrogated IRF3 phosphorylation and dimerization that was stimulated by polyhC. Thus, this study demonstrates that the TAK1-JNK cascade is required for IRF3 function, in addition to TBK1/IKKε, uncovering a new mechanism for mitogen-activated protein （MAP） kinase to regulate the innate immunity.展开更多
Bile acids(BAs)are natural metabolites in mammals and have the potential to function as drugs against viral infection.However,the limited understanding of chenodeoxycholic acid(CDCA)receptors and downstream signaling,...Bile acids(BAs)are natural metabolites in mammals and have the potential to function as drugs against viral infection.However,the limited understanding of chenodeoxycholic acid(CDCA)receptors and downstream signaling,along with its lower suppression efficiency in inhibiting virus infection limits its clinical application.In this study,we demonstrate that farnesoid X receptor(FXR),the receptor of CDCA,negatively regulates interferon signaling,thereby contributing to the reduced effectiveness of CDCA against virus replication.FXR deficiency or pharmacological inhibition enhances interferon signaling activation to suppress virus infection.Mechanistically,FXR impairs the DNA binding and transcriptional abilities of activated interferon regulatory factor 3(IRF3)through interaction.Reduced IRF3 transcriptional activity by FXReIRF3 interaction significantly undermines the expression of Interferon Beta 1(IFNB1)and the antiviral response of cells,especially upon the CDCA treatment.In FXR-deficient cells,or when combined with Z-guggulsterone(GUGG)treatment,CDCA exhibits a more potent ability to restrict virus infection.Thus,these findings suggest that FXR serves as a limiting factor for CDCA in inhibiting virus replication,which can be attributed to the“signaling-brake”roles of FXR in interferon signaling.Targeting FXR inhibition represents a promising pharmaceutical strategy for the clinical application of BAs metabolites as antiviral drugs.展开更多
IKKε is an IκB kinase participating in the control of NF-κB and type Ⅰ IFN signal pathways in mammals.However,the function of IKKε in regulating immune response is largely unknown in teleost.Herein,an IKKε homol...IKKε is an IκB kinase participating in the control of NF-κB and type Ⅰ IFN signal pathways in mammals.However,the function of IKKε in regulating immune response is largely unknown in teleost.Herein,an IKKε homologue named AjIKKε was characterized in Japanese eel(Anguilla japonica).AjIKKε has an N-terminal kinase domain,a ubiquitin-like domain,and a coiled coil-containing domain(CC),which is conserved and similar to its counterpart in mammals.Expression analysis showed that AjIKKεcould be up-regulated in kidney,spleen,and particularly in liver under the stimulation of poly Ⅰ:C,LPS,and Aeromonas hydrophila infection.In vitro,the mRNA levels of AjIKKεwere significantly provoked in eel liver cells stimulated by LPS and poly I:C,or the different concentrations of A.hydrophila.The overexpression of AjIKKε could not only induce a significantly higher level of promoter activity of human NF-κB,AP-1,and IFN-β in a dose-dependent manner but also up-regulate the activation of promoters of Japanese eel cRel,AP1,IL6,IFN4,IRF3,and IRF7 in HEK293 cells.RNAi studies showed that after AjIKKε was knocked down,the expression levels of IL1,IL6,TNFα,c-Jun,IFN2,IFN3,MX1,MX2,and IRF3 genes were significantly down-regulated in liver,spleen,and kidney of Japanese eels.In addition,the mutants of AjIKKε-K39A,AjIKKε-S174A,and AjIKKε-ΔCC failed to activate Japanese eel IFN4,IRF3 and human IFN-β promoters in HEK293 cells.Collectively,these results suggest that AjIKKεmay function as a positive regulator of NF-κB,MAPK,and IRF3-mediated type Ⅰ IFN signaling pathways related to immune response evoked by bacterial and viral infection.展开更多
基金These authors contributed equally to this work. We thank Drs S Vaidya and E Chow （University of California Los Angeles, USA） for their help in setting up critical experimental systems. We greatly thank Dr K Holmes （University of Colorado Health Sciences Center, USA） for sharing with us 17C1-1 cell line and helping to optimize the protocol to produce high titered MHV-A59 virus stock. We also thank Drs R Baric and L Su （University of North Carolina, USA） for the gift of MHV-A59 and guidance of virus infection. We thank Dr K Lim （National Neuroscience Institute, Singapore） for the gift of Ubi plasmids. We thank Dr M Wathelet （University of Cincinnati College of Medicine, USA） for sharing the nsp3 construct. Also we thank Dr G Gao （Institute of Biophysics, CAS） for providing us with VSV. This research was partly supported by grants from the National Natural Science Foundation of China （30728006） to Genhong Cheng and the National Basic Research Program of MOST （2004BA519A61, 2006CB504300, 2007DFC30190） to Hong Tang.
文摘Infections by coronaviruses such as severe acute respiratory syndrome （SARS） coronavirus （SCoV） and mouse hepatitis virus A59 （MHV-A59） result in very little type I interferon （IFN） production by host cells, which is potentially responsible for the rapid viral growth and severe immunopathology associated with SARS. However, the molecular mechanisms for the low IFN production in cells infected with coronaviruses remain unclear. Here, we provide evidence that Papain-like protease domain 2 （PLP2）, a catalytic domain of the nonstructural protein 3 （nsp3） of MHV-A59, can bind to IRF3, cause its deubiquitination and prevent its nuclear translocation. As a consequence, co-expression of PLP2 strongly inhibits CARDIF-, TBK1- and IRF3-mediated IFNp reporter activities. In addition, we show that wild-type PLP2 but not the mutant PLP2 lacking the deubiquitinase （DUB） activity can reduce IFN induction and promote viral growth in cells infected with VSV. Thus, our study uncovered a viral DUB which coronaviruses may use to escape from the host innate antiviral responses.
文摘Intracellular RNA viruses are sensed by receptors retinoic acid-inducible gene 1 （RIG-I）/melanoma differentiation-associated gene 5 （MDA5） that trigger the formation of MAVS signal complex on mitochondria. Consequently, this leads to the activation of TANK-binding kinase 1 （TBK1） and phosphorylation of interferon regulatory factor 3 （IRF3）, both of which constitutively associate with cytosolic chaperone Hsp90. It remains largely unknown how MAVS activates TBK1/IRF3. In this study, we identified translocases of outer membrane 70 （Tom70）, a mitochondrial import receptor, to interact with MAVS upon RNA virus infection. Ectopic expression or knockdown of Tom70 could enhance or impair IRF3-mediated gene expression, respectively. Mechanistically, the clamp domain （R192） of Tom70 interacts with the C-terminal motif （EEVD） of Hsp90, thus recruiting TBK1/IRF3 to mitochondria. Disruption of this interaction or mislocation of Tom70 sharply impairs activation of TBK1 and IRF3. Furthermore, host antiviral responses are significantly boosted or crippled in the presence or absence of Tom70. Collectively, our study characterizes Tom70 as a critical adaptor linking MAVS to TBK1/IRF3, revealing that mitochondrion is evolutionarily integrated with innate immunity.
基金We thank members of our laboratory for technical help and stimulating discussion. This work was supported by the National Basic Research Program of China （No. 2006CB504301） and the National Natural Science Foundation of China （No. 30630019 and No. 30570959）.
文摘Viral infection causes host cells to produce type I interferons （IFNs）, which are critically involved in viral clearance. Previous studies have demonstrated that activation of the transcription factor interferon regulatory factor （IRF）3 is essential for virus-triggered induction of type I IFNs. Here we show that the E3 ubiquitin ligase RBCC protein interacting with PKC1 （RBCK1） catalyzes the ubiquitination and degradation of IRF3. Overexpression of RBCK1 negatively regulates Sendai virus-triggered induction of type I IFNs, while knockdown of RBCK1 has the opposite effect. Plaque assays consistently demonstrate that RBCKI negatively regulates the cellular antiviral response. Furthermore, viral infection leads to induction of RBCK1 and subsequent degradation of IRF3. These findings suggest that the cellular antiviral response is controlled by a negative feedback regulatory mechanism involving RBCKl-mediated ubiquitination and degradation of IRF3.
文摘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 pre- mature 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 dis- tinct 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.
文摘Type I interferons such as interferon-beta （IFN-β） play essential roles in the host innate immune response to herpes simplex virus type I （HSV-1） infection. The transcription of type I interferon genes is controlled by nuclear factor-κB （NF-κB） and interferon regulatory factor （IRF） family members including IRF3. NF-κB activation depends on the phosphorylation of inhibitor of κB （IκB）, which triggers its ubiqitination and degradation. It has been reported that neddylation inhibition by a pharmacological agent MLN4924 potently suppresses lipopolysaccharide （LPS）-induced proinflammatory cytokine production with the accumulation of phosphorylated IκBa. However, the role of neddylation in type I interferon expression remains unknown. Here, we report that neddylation inhibition with MLN4924 or upon UBA3 deficiency led to accumulation of phosphorylated IκBa, impaired IκBa degradation, and impaired NF-κB nuclear translocation in the early phase of HSV-1 infection even though phosphorylation and nuclear translocation of IRF3 were not affected. The blockade of NF-κB nuclear translocation by neddylation inhibition becomes less efficient at the later time points of HSV-1 infection. Consequently, HSV- 1-induced early phase IFN-β production significantly decreased upon MLN4924 treatment and UBA3 deficiency. NF-κB inhibitor JSH-23 mimicked the effects of neddylation inhibition in the early phase of HSV-1 infection. Moreover, the effects of neddylation inhibition on HSV-1-induced early phase IFN-c production diminished in the presence of NF-κB inhibitor JSH-23. Thus, neddylation contributes to HSV-l-induced early phase IFN-β production through, at least partially, promoting NF-κB activation.
基金supported by the grants from the National Natural Science Foundation of China (30921001 and 91029302).
文摘Transcription factor IRF3-mediated type I interferon induction is essential for antiviral innate immunity.We identified the deSUMOylating enzyme Sentrin/SUMO-specific protease(SENP)2 as a negative regulator of virus-triggered IFN-b induction.Overexpression of SENP2 caused IRF3 deSUMOylation,K48-linked ubiquitination,and degradation,whereas depletion of SENP2 had opposite effects.Both the SUMOylation and K48-linked ubiquitination of IRF3 occurred at lysines 70 and 87,and these processes are competitive.The level of virus-triggered IFN-b was markedly up-regulated and viral replication was reduced in SENP2-deficient cells comparing with wild-type controls.Our findings suggest that SENP2 regulates antiviral innate immunity by deSUMOylating IRF3 and conditioning it for ubiquitination and degradation,and provide an example of cross-talk between the ubiquitin and SUMO pathways in innate immunity.
基金supported by grants from the National Key R&D Program of China(2017YFA0505800,2016YFA0502102)the National Natural Science Foundation of China(31630045,31521091,91429304 and 31671465)+1 种基金the Fundamental Research Funds for the Central Universities(2042017kf0205,2042017kf0242)Wuhan University Experiment Technology Project Funding.
文摘MITA is a central adaptor in innate immune responses to DNA viruses.The mechanisms responsible for recruitment of downstream kinase TBK1 and the transcription factor IRF3 to MITA remains enigmatic.Here we identified ZDHHC11,a member of DHHC palmitoyl transferase family,as a positive regulator of DNA virus-triggered signaling.Overexpression of ZDHHC11 activated the IFN-βpromoter,while ZDHHC11-deficiency specifically impaired DNA virus HSV-1-induced transcription of downstream antiviral genes.Zdhhc11^(−/−)mice exhibited lower serum cytokine levels and higher lethality after HSV-1 infection.Mechanistically,ZDHHC11 facilitated the optimal recruitment of IRF3 to MITA.Our findings support an important role for ZDHHC11 in mediating MITA-dependent innate immune responses against DNA viruses.
基金This work was supported by grants from the Ministry of Science and Technology of China(2014CB910103)the National Natural Science Foundation of China(31370867,31521091)the Fundamental Research Funds for the Central University(2042015kf0182)。
文摘Interferon-induced transmembrane protein 3 (IFITM3) is a restriction factor that can be induced by viral infectionand interferons (IFNs). It inhibits the entry and replication of many viruses, which are independent of receptorusage but dependent on processes that occur in endosomes. In this study, we demonstrate that IFITM3 playsimportant roles in regulating the RNA-virus-triggered production of IFN-β in a negative-feedback manner.Overexpression of IFITM3 inhibited Sendai virus-triggered induction of IFN-β, whereas knockdown of IFITM3 hadthe opposite effect. We also showed that IFITM3 was constitutively associated with IRF3 and regulated thehomeostasis of IRF3 by mediating the autophagic degradation of IRF3. These findings suggest a novel inhibitoryfunction of IFITM3 on the RNA-virus-triggered production of type I IFNs and cellular antiviral responses.
文摘Interferon regulatory factor （IRF）3 is critical for the transcriptional induction of chemokines and cytokines during viral or bacterial invasion. The kinases Tank binding kinase （TBK）1 and Ikappa B kinase （IKK）ε can phosphorylate the C-terminal part of IRF3 and play important roles in IRF3 activation. In this study, we show that another kinase, c-Jun-NH2-terminal kinase （JNK）, phosphorylates IRF3 on its N-terminal serine 173 residue, and TAK1 can stimu- late IRF3 phosphorylation via JNK. JNK specific inhibitor SP600125 inhibits the N-terminal phosphorylation with- out affecting the C-terminal phosphorylation. In addition, IRF3-mediated gene expressions on lipopolysaccharide （LPS） or polyinosinic-cytidylic acid （polyI：C） treatment are severely impaired by SP600125, as well as for reporter gene assay of IRF3 activation. Knockdown of TAK1 further confirmed these observations. Interestingly, constitu- tive active IRF3（5D） can be inhibited by SP600125; JNK1 can synergize the action of IRF3（5D）, but not the S173A- IRF3（5D） mutant. More importantly, polyI：C failed to induce the phosphorylation of mutant S173A and SP600125 dramatically abrogated IRF3 phosphorylation and dimerization that was stimulated by polyhC. Thus, this study demonstrates that the TAK1-JNK cascade is required for IRF3 function, in addition to TBK1/IKKε, uncovering a new mechanism for mitogen-activated protein （MAP） kinase to regulate the innate immunity.
基金supported by the National Natural Science Foundation(NNSF)of China(Nos.82371774 and 81901613)Beijing Nova Program(20230484342,China)Natural Science Foundation of Guangdong Province(2020A1515011299,China).
文摘Bile acids(BAs)are natural metabolites in mammals and have the potential to function as drugs against viral infection.However,the limited understanding of chenodeoxycholic acid(CDCA)receptors and downstream signaling,along with its lower suppression efficiency in inhibiting virus infection limits its clinical application.In this study,we demonstrate that farnesoid X receptor(FXR),the receptor of CDCA,negatively regulates interferon signaling,thereby contributing to the reduced effectiveness of CDCA against virus replication.FXR deficiency or pharmacological inhibition enhances interferon signaling activation to suppress virus infection.Mechanistically,FXR impairs the DNA binding and transcriptional abilities of activated interferon regulatory factor 3(IRF3)through interaction.Reduced IRF3 transcriptional activity by FXReIRF3 interaction significantly undermines the expression of Interferon Beta 1(IFNB1)and the antiviral response of cells,especially upon the CDCA treatment.In FXR-deficient cells,or when combined with Z-guggulsterone(GUGG)treatment,CDCA exhibits a more potent ability to restrict virus infection.Thus,these findings suggest that FXR serves as a limiting factor for CDCA in inhibiting virus replication,which can be attributed to the“signaling-brake”roles of FXR in interferon signaling.Targeting FXR inhibition represents a promising pharmaceutical strategy for the clinical application of BAs metabolites as antiviral drugs.
基金financially supported by“Nature Science Foundation of Fujian Province”(No.2020J01671,2021J01830).
文摘IKKε is an IκB kinase participating in the control of NF-κB and type Ⅰ IFN signal pathways in mammals.However,the function of IKKε in regulating immune response is largely unknown in teleost.Herein,an IKKε homologue named AjIKKε was characterized in Japanese eel(Anguilla japonica).AjIKKε has an N-terminal kinase domain,a ubiquitin-like domain,and a coiled coil-containing domain(CC),which is conserved and similar to its counterpart in mammals.Expression analysis showed that AjIKKεcould be up-regulated in kidney,spleen,and particularly in liver under the stimulation of poly Ⅰ:C,LPS,and Aeromonas hydrophila infection.In vitro,the mRNA levels of AjIKKεwere significantly provoked in eel liver cells stimulated by LPS and poly I:C,or the different concentrations of A.hydrophila.The overexpression of AjIKKε could not only induce a significantly higher level of promoter activity of human NF-κB,AP-1,and IFN-β in a dose-dependent manner but also up-regulate the activation of promoters of Japanese eel cRel,AP1,IL6,IFN4,IRF3,and IRF7 in HEK293 cells.RNAi studies showed that after AjIKKε was knocked down,the expression levels of IL1,IL6,TNFα,c-Jun,IFN2,IFN3,MX1,MX2,and IRF3 genes were significantly down-regulated in liver,spleen,and kidney of Japanese eels.In addition,the mutants of AjIKKε-K39A,AjIKKε-S174A,and AjIKKε-ΔCC failed to activate Japanese eel IFN4,IRF3 and human IFN-β promoters in HEK293 cells.Collectively,these results suggest that AjIKKεmay function as a positive regulator of NF-κB,MAPK,and IRF3-mediated type Ⅰ IFN signaling pathways related to immune response evoked by bacterial and viral infection.
