PKR And A20 Regulate Nf-?b Pathway During Newcastle Disease Virus Infection

Newcastle disease(ND)is an acute and highly contagious disease caused by Newcastle disease virus(NDV),which results in a great economical loss in the poultry industry.The world organization for animal health(OIE)classified it as notification of infectious diseases,the Ministry of Agriculture classified it as a class of infectious disease.NDV is avian paramyxovirus type 1 of the genus Avulavirus in the family Paramyxoviridae.NDV has a broad host range being able to infect over 240 species of birds.Of them,chickens are highly susceptible to NDV.A defensive response is set up by pattern recognition receptor recognising pathogen-associated molecular patterns,then a variety of transcription factors are involved in the regulation.Double-stranded RNA activated protein kinase(PKR)is a serine/threonine protein kinase that mediates some cascade reaction,such as phosphorylation of eIF-2a,it can inhibit transcription of mRNA,thereby inhibit the synthesis of viral proteins,such as vesicular stomatitis virus.PKR is also a pattern recognition receptor that can activates NF-?B signaling pathway by self-phosphorylation.NF-?B signaling pathway can be activated by a large number of stimuli,such as bacteria,viral antigens and so on,and play an important role in anti-virus.NF-?B signaling pathway is associated with many diseases,so it is very important to understand how to regulate NF-?B signaling pathway,in order to improve the inflammatory response and maintain the balance of the body.In order to elucidate whether NDV infection induced PKR mediated activation of NF-?B signaling pathway and the negative regulation of A20 on NF-?B signaling pathway.In the present study,on the one hand,we demonstrated that NDV infection can activate PKR,and PKR mediated activation of NF-?B signaling pathway and the released of IFN-P?IL-6?IL-8 of cytokines by using Western blot?Real-time PCR?indirect immunofluresence techniques.On the other hand,in order to clarify the mechanism of A20 which regulated NF-?B signaling pathway.NF-?B signaling pathway induced expression and phosphorylation of A20 activation during NDV infection.Overexpression of A20 can inhibit the nuclear tanslocation of p65,and the deletion of the S3 81 phosphorylation site of A20 lost this function.In sum up,S3 81 phosphorylation of A20 played an important role in the negative regulation of NF-?B signaling pathway.A20 can localize to an insoluble aggresomes and lysosomes with punctate distribution in cytoplasm by indirect immunofluresence techniques.Tumor necrosis factor receptor associated factor 2(TRAF2)was a important adaptor protein of NF-?B signaling pathway,degradtion of TRAF2 after 16 hours of NDV infection,TRAF2 degradation phenomenon was more obvious after overexpression of A20,and loss of S3 81 of A20 did not have this phenomenonan.TRAF2 was also distributed in the lysosome in the cytoplasm during NDV infection by indirect immunofluorescence assay,and was colocalized with A20.These results indicated that the zinc finger protein A20 can interact with TRAF2 and drag it to lysosomes for degradation,which was another mechanism of A20 negative regulation of NF-?B signaling pathway.