Cloning and functional analysis of SNX8 from grass carp (Ctenopharyngodon idellus).

Sorting nexin 8 (SNX8), a member of sorting nexin protein family, plays important roles in endocytosis, endosomal sorting, and innate immune response. To date, a few homologs of SNX8 have been found in fish except in mammals. In this study, a teleost SNX8 cDNA was identified from grass carp (Ctenopharyngodon idellus). CiSNX8 was up-regulated significantly after infection with poly I:C or GCRV. We found that SNX8 was mainly distributed in the endoplasmic reticulum (ER) in CIK cells. Further analysis indicated that Ci SNX8 might negatively regulate RLR signaling pathway that is quite distinct from mammalian SNX8. In addition, Ci SNX8 could interact with MAVS, STING, TBK1, IRF3 and IRF7. Either wild type Ci SNX8 or mutants of N-terminal PX domain (aa 1–245) and C-terminal BAR domain (aa 256–519) could associate with STING. These results suggested that fish SNX8 participated in innate immune response through different molecular mechanisms. • An SNX8 ortholog from grass carp (Ctenopharyngodon idella) was cloned. • CiSNX8 was significantly up-regulated after treatment with poly I:C or GCRV. • Ci SNX8 was located in the endoplasmic reticulum (ER) in CIK cells. • Ci SNX8 negatively regulate the key components of RLR pathway such as RIG-I, STING, and TBK1-mediated IFN activation. • Either wild type CiSNX8 or mutants of N-terminal PX domain and C-terminal BAR domain could associate with STING. [ABSTRACT FROM AUTHOR]