The Essential Role And Mechanism Study Of Host Factor Musashi-2 In Avian Influenza A(H7N9) Infection

Since the outbreak in 2013,avian influenza A virus H7N9 had been reported 5 waves epidemically,causing about more than 1500 infections and 500 deaths included,posing direct threats to human beings.The poultry trade and live poultry market represents one of the most reasons for avian influenza A virus H7N9 outbreak.Related researches showed that H7N9 virus had been a kind of recombinant virus which the Hemagglutinin comes from domestic ducks carrying H7N3 influenza virus,the Neuraminidase comes from wild birds carrying H7N9 virus and the remaining genes come from domestic poultry carrying H9N2 virus.Infected with H7N9 virus,the human can dispose overall pro-inflammatory response,ARDS,shock or multi-organ functional dysregulation syndromes.So,it would be helpful to develop vaccines clinically for prevent the influenza virus epidemics with deeper study of mechanisms on H7N9 virus.The host innate immune system has been established to prevent microbes during the long-termed evolution and represents the first defense to sensor the outer microbe infections and to eliminate the microbes.When the viruses infect host cells,host cells could sense the PAMPs(Pathogen-associated Molecular Patterns)through different RLRs(RIG-1-like Receptors)to induce a serial of downstream anti-viral responses.Vrial RNA could be recognized by RIG-1-like Receptors and activates a serial of down-stream signaling pathway to induce the production of type I interferons.Recently,mounting evidences show that some host proteins are involved in mediating the antiviral innate immune responses,therefore,it represents important meaning to understand and study the host proteins in antiviral processes.Musashi family proteins is kind of RNA-binding ones and widely distributed in tissues,mainly participate in regulating the mRNAs posttranscriptionally,playing crucial roles in maintaining lots of life activities.The muasahsi family has two proteins,Musashi-1 and Musashi-2.Recent report showed that Musashi-1 showed import part in Zika virus infection.As the Musashi-1 and Musashi-2 shared 75%amino acid similiarities and highly homolous structurally,and we speculated Musashi-2 also palyed an important role in Influenz A H7N9 infection.Therefore,our study firsty explored that the expression change in Influenz A H7N9 infection,and then,we investigated the possible connection between Musashi-2 and Influenza A H7N9 virus infection.Lastly,we studied the relations between Musashi-2 and host innate immune responses and relative mechanisms as the host innate immune response is crucial in viral infection.In our study,we discovered that the H7N9 avian influenza could degrade the Musashi-2 expression in a time-dependent and virus titer-dependent manners.Subsequently,knockdown of endogenous Musashi-2 by Musashi-2 siRNAs/Musashi-2 shRNAs increased the H7N9 avian influenza virus infection,in contrast,exogenous Musashi-2 expression could inhibit the H7N9 avian influenza virus replication.H7N9 avian influenza virus stimulates the host innate immune response to produce such I type IFNs and proinflammatorys such as IL-6,TNF-a,RANTES and IP-10 which protect the host from virus infection.In this study,we demonstrated that knockdown of Musashi-2 could decrease the produciton of IL-6,TNF-a,RANTES and IP-10 after H7N9 avian influenza infection which further proves that Musashi-2 was involved in H7N9 avina influenza virus-induced innate immune response.The nuclear translocation of IRF-3 and NF-κB in H7N9 avian influenza virus infection could activate the transcription of proinflammatorys.Thus,this study was to explore the relationship between Musashi-2 and nuclear translocation factors IRF-3 and NF-κB,and it proved that Musashi-2 could induce the nuclear translocation of IRF-3 and NF-κB and then inhibits the H7N9 avian influenza virus infection.This study further explored the functions of Musashi-2 in JAK-STAT signaling pathway and the downstream ISGs expression.Besides the role in the innate immune response,the Musashi-2 was also found to be interacted with H7N9 avian influenza sturctural NP protein to inhibit the interaction between H7N9 NP protein and importin-a prohibiting the transcription and H7N9 genome replication.The above results indicates that Musashi-2 inhibits H7N9 avian influenza virus through the induction of innate immune response and interaction with NP protein.The results firstly demonstrate the biological functions and mechanisms in Avian Influenza H7N9 virus.Firstly,in Avian Influenza H7N9 virus infection,Musashi-2 promotes the nuclear translocation of IRF-3 and NF-κB to induce the production of cytokines such as IFN-P,IL-6,TNF-a,RANTES and IP-10.Secondly,Musashi-2 is involved in the activation of JAK-STAT signaling pathway which subsequently induces the release of ISGs such as ISG15 and MxA.Thirldly,Musashi-2 inhibits the replication of Avian Influenza H7N9 virus through disrupting the interaction of NP-Importin-αcomplexes.This study helps to elucidate the biological functions and mechanisms of Musashi-2 in Avian Influenza H7N9 virus and to provides theoretical guide for Avian Influenza H7N9 virus prevention and anti-virus drugs development.