The Antiviral Function And Mechanism Of ML1-Vago-Jak/Stat Axis In Kuruma Shrimp Marsupenaeus Japonicus

Metazons have evolved multiple immunological strategies to resist to the infection of pathogens.These strategies are divided into two categories:innate immunity and adaptive immunity.The innate immunity plays a key role in defending pathogens in invertebrates because of its lack of adaptive immunity.Early studies showed that phagocytosis was the central antiviral strategy in invertebrates.However,increasing research found that invertebrate host could recognize the viral pathogens,initiate certain immune signaling pathways,and up-regulate the expression of antiviral effectors.Such induced transcription response is also an important antiviral strategy in invertebrates.1.MjML family restricted WSSV infection through as a receptor of virusThe myeloid differentiation factor 2(MD-2)related lipid recognition(ML)domain is found in multiple proteins,including MD-2,MD-1,and mite major allergen proteins.The significance of ML proteins in antibacterial signal transduction and in lipid metabolism has been well studied.However,their function in host-virus interaction remains poorly understood.In the present study,we found that the ML protein family is involved in resistance against white spot syndrome virus(WSSV)in Kuruma shrimp,Marsupenaeus japonicus.One member,which showed high similarity to mammalian MD-2/MD-1 and was designated as ML1,participated in the antiviral response by recognizing cholesta-3,5-diene(CD),a lipid component of the WSSV envelope.After recognizing CD,ML1 induced the translocation of Rel family nuclear factor kappa B(NF-?B)transcription factor Dorsal into the nucleus,resulting in the expression of Vago,an interferon-like antiviral cytokine in arthropods.Overall,this study revealed the significance of an MD-2 homolog as an immune recognition protein for virus lipids.The identification and characterization of CD-ML1-Dorsal-Vago signaling provided new insights into invertebrate antiviral immunity.2.MjVago family members activated Jak/Stat pathway then inhibited WSSV infectionVago,which is regarded as a functional homolog of interferon in arthropods,activates antiviral Janus kinase(Jak)/signal transducer and activator of transcription(Stat)signaling and limits virus replication.However,the antiviral role of Vago is independent of Domeless,the only Jak/Stat receptor in invertebrates,which is homologous to the vertebrate type-? cytokine receptor.How Vago activates the Jak/Stat pathway remains unknown.In the present study,through studying the immune response of Kuruma shrimp(Marsupenaeus japonicus)against white spot syndrome virus(WSSV),we found that Vago-induced Jak/Stat activation was dependent on integrin.MjVago plays a role in antiviral immunity by activating Jak/Stat pathway and inducing certain Stat-targeted antiviral effectors.Blocking integrin using an RGD peptide abrogated the role of MjVago.The interaction between MjVago and integrin ?3 was confirmed using both yeast two hybrid and co-immunoprecipitation assays.An aspartate residue in MjVago was found to be critical for the interaction with integrin and MjVago's antiviral role.Moreover,focal adhesion kinase(Fak),a key adaptor of integrin signaling,mediated the MjVago-induced Jak/Stat activation.Therefore,this study revealed that integrin was the receptor of arthropod Vago and mediated noncanonical Jak/Stat activation.The establishment of the MjVago/integrin/Fak/Jak/Stat axis provides new insights into antiviral cytokine signaling in invertebrates.