Fibronectin Facilitates EV71 Infection By Mediating Viral Entry And Virus-Induced GFPT2 Positively Regulates The IFN Signaling Pathway

Enterovirus 71(EV71),a positive-sense,single strand RNA virus,belongs to Picornaviridae,is one of the major agents caused hand,foot and mouth disease(HFMD).During the past decades,HFMD frequently occurred in the Asia-pacific region,posing a great threat to the security of public health.FN is a high-molecular-weight glycoprotein composed of type I,II,III repeating units,and the two forms of FN,soluble plasma FN and insoluble cellular FN,are structurally and functionally different.Soluble plasma FN dimers are secreted in an inactive form that must be activated by interaction with ?5?1 and other integrins in order to be assembled into an insoluble form via a complex mechanism.Cellular FN is a major component of extracellular matrices(ECM)and functions in morphogenesis,cell migration,inflammation,and surface receptor internalization.FN contains the RGD motif,which is required for the interaction with integrins.Synthetic peptides containing the RGD sequence have shown to be compete with FN for binding to the cell surface and thus inhibit the function of FN.We found that the RGD peptide can not only inhibit EV71 replication in the RD cells,but also attenuate EV71 infection in mice.The expression level of VP1 was markedly decreased in the RGDS pre-treated RD cells.Consistently,mice treated with RGDS and infected with EV71 had a higher survival rate and lower viral load in the brainstem and skeletal muscles than did the control group.Because RGDS peptides affect the function of FN,we questioned whether FN may play a role in EV71 infection.Our study indicates that overexpression of FN can enhance the production of EV71 virion,the expression level of VP1 and the CPE of RD cells,while knock out of FN has the opposite effect.Next,we found that FN had no effect on the stage of intracellular replication of EV71,but mainly attributed to the virus particle binding to the host cell surface,that is play a role in the stage of viral entry.Further study demonstrated that FN and EV71 particle had directly interaction and the interaction sites are in the D2 domain of FN and the N terminal of VP1.Our study found that RGDS can significantly inhibit EV71 infection,which provides clues for the treatment of HFMD.Meanwhile,it is further revealed that host factor FN plays a positive role in EV71 infection,providing a new potential antiviral target for EV71 treatment.Glutamine-fructose-6-phosphate transaminase 2(GFPT2),belongs to the family of Glucosamine-6P synthase,is a key rate-limiting enzyme in the hexosamine biosynthetic pathway,which catalyze the conversion of D-glucosamine 6-phosphate(GlcN-6-P).In this study,we found upregulated expression of GFPT2 following virous kinds of virus(Sev,VSV,IAV)infection in A549 and Hela cells.Further exploration demonstrated that GFPT2 enhance virus-triggered interferon and inflammation response by positively regulating the NF-?B signaling pathway and it can facilitate the phosphorylation of IKK and I?B-? and the nuclear translocation of p50 and p65.GFPT2 mainly participate in the glucose metabolism,while,our study found that GFPT2 play a role in the virus-triggered induction of interferon and inflammation factors,revealing the complex relationship between glucose metabolism and innate immune response.