Mechanisms Of SOCS1 Deubiquitination Regulation On IFN Antiviral Activity

Background and purpose:In 1997,SOCS1 was found as a negative regulator of the JAK-STAT pathway.Thereare three means by which SOCS1 negatively regulates IFNs signaling pathway.Firstly,SOCS1 can interact with JAKs and inhibits JAK kinase activity,thereby restricting JAK-STAT signaling pathway.Secondly,SH2 domain of SOCS1 binds to activated JAKs and STATs,and then results in their degradation by the protesome pathway.Thirdly,SOCS1 directly combines with IFNs receptor,thus competitively inhibits the phosphorylation of tyrosine and phosphorylation of STATs.The current studies clearly demonstrate that SOCS1 protein is a negative regulator in IFN signaling pathway.The regulation of SOCS1 ubiquitination and its antiviral response have not yet been reported.Ubiquitination is thr precise regulation by the ubiquitin proteasome system.Deubiquitases play crucial roles in the UPS,which become more and more popular.Identifying the important proteins involved in the diseases may provide a scientific basis for clinical targeted therapies.SOCS1 is a negative regulator of IFNs signaling,and the regulation and function of its ubiquitination are still unknown.This study aims to investigate the role of JOSD1 in regulating SOCS1 ubiquitination in IFN signaling,in order to provide a potential target for IFN-mediated antiviral therapy.Methods:Myc-SOCS1 was transfected into HEK293T cells.Ubiquitination and degradation were analyzed by Western blot.Deubiquitinase of SOCS1 protein were identified by using deubiquitinase library.Analyses of the DUB of SOCS1 with Western blot and Real-time qPCR in several respects,including protein level,interaction,deubiquitination,stability and correlation.The effect of JOSD1 via on stabilizing SOCS1 in IFN I signaling pathway and its antiviral function were explored by Western blot and immunofluorescence technique.Results:1.SOCS1 can form polyubiquitination modification and the lysine 48(K48)-linked polyUbiquitination is the major form of SOCS1 ubiquitination.2.Deubiquitinase JOSD1 up-regulates the level of SOCS1 protein.3.JOSD1 physically interacts with SOCS1.4.JOSD1 deubiquitinates SOCS1.5.JOSD1 stabilizes SOCS1.6.The levels of JOSD1 and SOCS1 undergo down-regulation during the early stage of viral infections.7.JOSD1 negatively regulates IFN-I-mediated signaling pathway and restricted its antiviral defense.Conclusions:As the deubiquitase of SOCS1,JOSD1 upregulates SOCS1 protein levels and deubiqutinates SOCS1,thereby enhancing SOCS1 protein stability.Importantly,JOSD1 inhibits IFN-I-induced signaling pathway and restricts IFN-I-mediated antviral response during viral infections.