Mechanism By Which Host Transmembrane Protein IFITM Activates IFN-β To Inhibit EMCV Replication

Interferon(IFN)-α and β exerts antiviral effects by inducing the expression of downstream interferon-stimulated genes(ISGs).These include interferon-induced transmembrane(IFITM),a class of membrane proteins that primarily inhibit the process of viral invasion into host cells.In the present study,IFITMs were used to verify their role in the replication and proliferation of EMCVs and to explore the related mechanisms.The mechanism of IFITMs as activators of the IFN-β signaling pathway was investigated,as it was demonstrated that IFITMs had a significant inhibitory effect on EMCV replication and proliferation,while IFITMs were able to promote the expression of IFN-β.The results obtained in this study were as follows:1.transient up-or down-regulation of IFITMs expression in host cells revealed that IFITMs inhibited or promoted the proliferation of EMCV in host cells;IFITMs protein had no significant effect on virus adsorption,but significantly inhibited the virus entry process;cell culture supernatants with up-regulated IFITMs protein not only inhibited the proliferation of EMCV,but more importantly,significantly promoted The cell culture supernatant with upregulated IFITMs protein not only inhibited the proliferation of EMCV,but more importantly,significantly promoted the expression of IFN-β,in which the role of IFITM2 was particularly prominent.2.Overexpression of IFITM2 promoted the expression of MDA5 of type Ⅰ IFN signaling pathway;the specific interaction between IFITM2 protein and MDA5 was detected by immunoprecipitation;the ability of IFITM2 protein to activate IFN-β was significantly inhibited after interfering with the expression of MDA5,indicating that MDA5 may be a target molecule for IFITM2 action,and in the process of IFITM2 The antiviral activity and the ability to promote IFN-β expression of IFITM2 Nterminal structural domain were significantly stronger than that of C-terminal.3.IFITM1/3 had a significant promotion effect on MDA5 expression,but only the interactions between IFITM1 and MDA5 existed,and there was no interaction between IFITM3 and MDA5.In conclusion,it was shown that IFITM2 could significantly inhibit the proliferation of EMCV,while IFITM2 could promote the expression of IFN-β by targeting MDA5.In addition,a positive feedback loop was established between IFITMs and type Ⅰ IFN signaling pathway,which played a crucial role in its antiviral effect.