Influenza virus contains three integral membrane proteins:haemagglutinin,neuraminidase,and matrix protein(M1 and M2).Among them,M2 protein functions as an ion channel,important for virus uncoating in endosomes of virus-infected cells and essential for virus replication.In an effort to explore potential new functions of M2 in the virus life cycle,we used yeast two-hybrid system to search for M2-associated cellular proteins.One of the positive clones was identified as human Hsp40/Hdj1,a DnaJ/Hsp40 family protein.Here,we report that both BM2(M2 of influenza B virus)and A/M2(M2 of influenza A virus)interacted with Hsp40 in vitro and in vivo.The region of M2-Hsp40 interaction has been mapped to the CTD1 domain of Hsp40.Hsp40 has been reported to be a regulator of PKR signaling pathway by interacting with p58^(IPK) that is a cellular inhibitor of PKR.PKR is a crucial component of the host defense response against virus infection.We therefore attempted to understand the relationship among M2,Hsp40 and p58^(IPK) by further experimentation.The results demonstrated that both A/M2 and BM2 are able to bind to p58^(IPK)in vitro and in vivo and enhance PKR autophosphorylation probably via forming a stable complex with Hsp40 and P58^(IPK),and consequently induce cell death.These results suggest that influenza virus M2 protein is involved in p58^(IPK)mediated PKR regulation during influenza virus infection,therefore affecting infected-cell life cycle and virus replication.
Zhenhong GuanDi LiuShuofu MiJie ZhangQinong YeMing WangGeorge F.GaoJinghua Yan
In March and early April 2009,a new swine-origin influenza A (H1N1) virus (S-OIV) emerged in Mexico and the United States. The virus spreads worldwide by human-to-human transmission.
Although worldwide concern has been raised since the large-scale outbreak of highly pathogenic avian influenza in wild birds at Qinghai Lake,China in 2005,the factors responsible for the ability to kill waterfowl remain unclear. The why and how questions of the H5N1 virus species-jump into its reservoir host need to be answered. In this report we test the pathogenicity and adaptation of Qinghai Lake (Clade 2.2) isolate to Muscovy ducks for further understanding of this virus. The isolate was highly pathogenic in ducks and retained its high pathogenicity even after 20 generations of passage in ducks. During the process of serial passages,only the NS gene developed non-synonymous substitutions,which caused two mutations in NS1 protein (Val23Ala and Leu207Pro) and one in NS2 (Phe55Leu). These mutations persisted immutably through all subsequent passages and the pathogenicity remained high,implying that highly pathogenic H5N1 virus remains stable in aquatic birds through oral transmission. Although the exact functions of these mutations are not known,our results provide an important foundation for further understanding the characteristics of the Qinghai Lake isolates.
