A Janus Kinase in the JAK/STAT signaling pathway from Litopenaeus vannamei is involved in antiviral immune response

• A novel Janus Kinase gene (LvJAK) is identified from pacific white shrimp Litopenaeus vannamei.
• There is a potential positive feedback loop mediated by LvJAK protein present in shrimp JAK/STAT pathway.
• LvJAK is ubiquitously distributed and its expression is up regulated by Poly (I:C) and WSSV challenges.
• LvJAK is involved in antiviral immune defense against WSSV.

The JAK/STAT signaling pathways are conserved in evolution and mediate diversity immune responses to virus infection. In the present study, a Janus kinase (designated as LvJAK) gene was cloned and characterized from Litopenaeus vannamei. LvJAK contained the characteristic JAK homology domain (JH domain) from JH1 to JH7 and showed 19% identity (34% similarity) and 21% identity (35% similarity) to Drosophila Hopscotch protein and Human JAK2 protein, respectively. The mRNA of LvJAK was highly expressed in hepatopancreas of L. vannamei and its expression level was prominently upregulated after the stimulation of Poly (I:C) and white spot syndrome virus (WSSV) challenges. There were 10 putative STAT binding motifs in the promoter region of LvJAK, and it could be regulated by LvJAK self or (and) LvSTAT, suggesting that LvJAK is the JAK/STAT pathway target gene and could function as a positive regulator to form a positive feedback loop. In addition, the silencing of LvJAK caused higher mortality rate and virus load, suggesting that LvJAK could play an important role in defense against WSSV. This is the first report about the complete set of JAK/STAT proteins in shrimp and the results provide the evidence of the positive feedback loop mediated by JAK protein present in the JAK/STAT pathway in invertebrates.