Molecular Mechanism Of Foot-and-mouth Disease Virus VP3 Protein Promoting Pathogenicity By Regulating Apoptosis And Autophagy

Picornavirus is a kind of unencapsulated single stranded RNA virus,including a variety of important pathogens in humans and animals,such as foot-and-mouth disease virus,enterovirus,hepatitis virus,heart disease virus.Programmed cell death(PCD)is a kind of cell death triggered by internal or external stimulation and regulated by a series of genes,which plays a key role in animal development,tissue homeostasis and disease.Viral pathogenicity is frequently associated with the ability of virus to kill host cells.Picornavirus have evolved a variety of strategies to regulate and control cell death in host to ensure their continuous replication and release.In this study,we found that the members of picornaviruses family,containing foot-and-mouth disease virus(FMDV),poliovirus(PV)and Seneca virus(SVA)structural protein VP3 can induce apoptosis and autophagy.However,the underlying mechanism of the association between apoptosis/autophage and viral pathogenicity remains unclear.In order to clarify the mechanism and biological meaning,the following studies have been carried out:FMDV,an important model virus of picornavirus,can induce both apoptosis and autophagy in vivo,but the main type of cell death is apoptosis.We firstly analyzed the apoptotic function site of FMDV-VP3.The results showed that Gly129 mutated to Ala significantly reduced the degree of FMDV-VP3-induced apoptosis and autophagy.By structural prediction,the Gly129 locates at a bend region of random coil structure,the mutation of Gly to Ala remarkably shrunk the volume of viral cavity.Coincidentally,the Gly is conserved in the similarly location of other picornaviruses,including poliovirus(PV),enterovirus 71(EV71),coxsackievirus(CV)and seneca valley virus(SVA).FMDV-VP3 contributes to p53 translocation from the nucleus into the cytoplasm,and then VP3 interacts directly with p53 in cytoplasm and promotes its phosphorylation.Activated p53 interacts with Bad on mitochondria and activates Bcl-2 family-mediated apoptosis and LC3-dependent autophagy.Gly129 plays an important role in apoptosis,autophagy induction and interaction with p53.Reverse genetic techniques were used to rescue recombinant viruses that Gly129 mutated or not,named rVP3-129/FMDV and rVP3/FMDV.Virus infection experiments in vivo and in vitro showed that Gly129 mutation significantly reduced the ability of FMDV promotes p53 nucleoplasmic transport and colocalization of VP3 and p53.Meanwhile,we also studied the effects of VP3-induced apoptosis and autophagy on viral pathogenicity.The results showed that Gly129 mutation did not affect virus invasion,but the degree of apoptosis and autophagy induced by FMDV in vitro and in vivo decreased significantly.At the same time,the titer of the virus and the degree of tissue damage decreased significantly.The results showed that the cell death induced by VP3 is a critical factor to enhance FMDV pathogenicity.We also found that the cell death induced by VP3 mainly occurred in the middle and late stage of virus infection,the viral replication level decreased significantly while the Gly129 mutated.It is suggested that apoptosis and autophagy induced by VP3 is a way for FMDV release and replication in the later stage of infection.As a summary,FMDV-VP3-induced apoptosis and autophagy by directly interacting with p53 are the main mechanism of viral replication and pathogenicity.And because the position of Gly129 in picornaviruses is relatively conservative,its function of inducing cell death may also be conservative.This study provides a theoretical basis and a new idea for the study of foot-and-mouth disease and picornavirus.