Some pathogens can use host suppressor of cytokine signaling I （SOCS-1）, an important negative-feedback molecule, as the main mode of immune evasion. Here we found that group A Streptococcus （GAS） is capable of in...Some pathogens can use host suppressor of cytokine signaling I （SOCS-1）, an important negative-feedback molecule, as the main mode of immune evasion. Here we found that group A Streptococcus （GAS） is capable of inducing SOCS-1 expression in RAW264.7 and BMDM macrophages. IFN-p plays a role in GAS-induced SOCS-1 expression in macrophages following the induction of cytokine expression by GAS, representing the classical pathway of SOCS-1 expression. However, GAS also induced STAT1 activation and SOCS-1 expression when GAS-infected cells were incubated with anti-IFN-p monoclonal antibody in this study. Moreover, upon comparing TLR4-/- BMDM macrophages with wild-type （WT） cells, we found that TLR4 also plays an essential role in the induction of SOCS-1. MyD88, which is an adaptor protein for TLR4, contributes to STAT1 activation and phosphorylation by forming a complex with Janus kinase 1 （JAK1） and signal transducer and activator of transcription 1 （STAT1） in macrophages. GAS-stimulated expression of STAT1 was severely impaired in MyD88-/- macrophages, whereas expression of JAK1 was unaffected, suggesting that MyD88 was involved in STAT1 expression and phosphorylation. Together, these data demonstrated that in addition to IFN-p signaling and MyD88 complex formation, JAK1 and STAT1 act in a novel pathway to directly induce SOCS-1 expression in GAS-infected macrophages, which may be more conducive to rapid bacterial infection.展开更多
文摘Some pathogens can use host suppressor of cytokine signaling I （SOCS-1）, an important negative-feedback molecule, as the main mode of immune evasion. Here we found that group A Streptococcus （GAS） is capable of inducing SOCS-1 expression in RAW264.7 and BMDM macrophages. IFN-p plays a role in GAS-induced SOCS-1 expression in macrophages following the induction of cytokine expression by GAS, representing the classical pathway of SOCS-1 expression. However, GAS also induced STAT1 activation and SOCS-1 expression when GAS-infected cells were incubated with anti-IFN-p monoclonal antibody in this study. Moreover, upon comparing TLR4-/- BMDM macrophages with wild-type （WT） cells, we found that TLR4 also plays an essential role in the induction of SOCS-1. MyD88, which is an adaptor protein for TLR4, contributes to STAT1 activation and phosphorylation by forming a complex with Janus kinase 1 （JAK1） and signal transducer and activator of transcription 1 （STAT1） in macrophages. GAS-stimulated expression of STAT1 was severely impaired in MyD88-/- macrophages, whereas expression of JAK1 was unaffected, suggesting that MyD88 was involved in STAT1 expression and phosphorylation. Together, these data demonstrated that in addition to IFN-p signaling and MyD88 complex formation, JAK1 and STAT1 act in a novel pathway to directly induce SOCS-1 expression in GAS-infected macrophages, which may be more conducive to rapid bacterial infection.
