The Function Of Foot-and-mouth Disease Virus VP1 Inhibiting TPL2-mediated IRF3 Phosphorylation

Foot-and-mouth disease?FMD?is an acut and highly contagious disease caused by the foot-and-mouth disease virus?FMDV?,which mainly affects cloven-hoofed animals such as pigs,cattle,sheep etc.In order to replicate efficiently in host cells,FMDV has evoled to antagonize innate antiviral innate immune response or to evade the defense mechanism of the host.The innate immunity system of the host,the host first line of defense against viral infections,plays a crucial role in combating the early virus infection.TPL2?tumor progression locus 2?,a serine-threonine kinase of the MAPK family,also is known as Osaka Osaka thyroid?Cot?or MAPK kinase kinase 8?MAP3K8?.It plays an important role in regulating the production of host interferons and cytokines,innate immunity and adaptive immunity.TPL2 plays an important role in the infection of viruses,bacteria,and parasites.To explore whether TPL2 interacted with FMDV,coimmunoprecipitation and indirect immunofluorescence experiments showed that FMDV structural protein VP1 and VP2 and non-structural protein L interacted with TPL2.Luciferase assayes confirmed that overexpression of TPL2 could promote IRF3-mediated activation of IFN-?signaling pathways in a dose-dependent manner.Overexpression of TPL2 could promote the phosphorylation of IRF3 by transient transfection.A series of mutants that had lost some key functions were consturuted.Subsequently we transfected mutants to verify their expressions.Unlike wild-type TPL2,the TPL2?T290A?mutant failed to enhance IRF3-mediated activiting IFN-?signaling pathway when transfected into HEK 293T cells.VP1 and TPL2 plasmids were co-transfected simultaneously,revealing that VP1 had a significantly negative effect on TPL2-mediated enhancing IFN-?signaling pathways activated by IRF3.Subsequently,the cells were co-transfected with VP1 and TPL2 and then transfected with Ploy?I:C?.It was found that co-transfection of VP1 and TPL2 significantly inhibited mRNA levels of multiple downstream interferon-stimulated genes by qRCR assay.Further more,it showed that VP1 only inhibited the protein expression of TPL2 at Thr²⁹⁰ by different amounts of VP1 plasmids transfected.In this study,it was found that TPL2 could upregulate IRF3-mediated IFN-?signaling pathways activation by enhancing phosphorylation of IRF3.FMDV VP1 significantly inhibited the biological function of TPL2 by inhibiting the expression of TPL2 at Thr²⁹⁰.In addition,the underlying molecular mechanism behind the interaction between TPL2 and FMDV structural protein VP2 and non-structural protein L was unclear,which would be the direction and key point for our future research.This study accumulated data for the pathogenic mechanism of FMDV between viral proteins and host proteins,and it laid a theoretical foundation for further understanding of the molecular mechanisms between FMDV protein and host protein.