The Mechanism Of DDX56 Antagonizing IFN? To Promote EMCV Proliferation In Vitro

EMCV is a non-enveloped single-stranded positive-stranded RNA virus.It could cause many diseases in most of mammals,such as myocarditis,encephalitis and etc.EMCV would got huge economic losses to domestic and foreign aquaculture industries,and would be dangerous to public health.When the virus enters the body,it will quickly activate natural immunity.In order to escape innate immunity,many viruses hijack host proteins to antagonize the innate immune response mechanism to ensure the smooth progress of their own reproduction.The research team found that DDX56 promotes EMCV infection of host cells and EMCV infection of a variety of cells can effectively cause natural immune responses.In order to verify the molecular mechanism of DDX56 promoting the proliferation of EMCV in vitro,the regulation effect of DDX56 on the production of type I interferon and its upstream RLRs signaling pathway was deeply studied,and the possible mechanism of DDX56 in promoting EMCV proliferation and inhibiting RLRs signaling pathway was verified.The results of this study:1.Transiently up-regulate or down-regulate the expression of DDX56 in host cells,and it is found that DDX56 positively regulates the proliferation of EMCV in host cells.2.There is a specific interaction between EMCV 3C protein and DDX56 protein,indicating that DDX56 protein may promote the process of EMCV infection of host cells by binding to EMCV 3C protein.3.Transiently up-regulate or down-regulate the expression of DDX56 in host cells.It is found that DDX56 negatively regulates the activation of linker molecules MDA5,MAVS,TBK1 and IRF3 in the upstream RLRs signaling pathway of IFN?,inhibiting IFN? induced by EMCV;and DDX56 and MDA5,MAVS,TBK1 and IRF3 all have specific interactions,indicating that DDX56 reduces EMCV-induced type I interferon by inhibiting RLRs signaling pathway.4.DDX56 can specifically bind to the nuclear transport protein KPNA3/KPNA4,and inhibit the specific binding of IRF3 to the nuclear transport protein KPNA3/KPNA4,indicating that DDX56 inhibits the process of IRF3 entering the nucleus by binding to the protein KPNA3/KPNA4.In summary,this study initial demonstrated that DDX56 can promote the proliferation of EMCV in vitro.DDX56 specifically interacts with MDA5,MAVS,TBK1 and IRF3 and inhibits their activation,thereby negatively regulating the RLRs signaling pathway;and DDX56 can bind to the important nuclear transport protein KPNA3/KPNA4 in the process of IRF3 entering the nucleus,affecting IRF3 entering the nucleus and reducing IFN? is produced;in addition,DDX56 protein specifically interacts with EMCV virus non-structural protein 3C,which may jointly promote EMCV proliferation in vitro.These results fully indicate that EMCV can evade the host's natural immune response by hijacking the host protein DDX56 to achieve the purpose of promoting its own proliferation.This study expands the mechanism by which EMCV uses host proteins to escape the host's natural immunity,provides important information for studying the pathogenic mechanism of EMCV infection,and also provides new ideas for the prevention and control of EMCV infection.