Cloning and expression analysis of an Atlantic salmon (Salmo salar L.) tapasin gene

Loading of the major histocompatibility complex (MHC) class I molecule with peptide is mediated by the multimeric peptide-loading complex in the ER where the glycoprotein tapasin (TAPBP) is required for stabilization of the complex and for control of peptide loading onto MHC class I. To expand our knowledge on antigen presentation genes in Atlantic salmon, we isolated a full-length salmon tapasin cDNA sequence (Sasa-TAPBP). It encoded a 443 bp amino acid sequence with two N-glycosylation sites, two conserved mammalian tapasin signature motifs, two Ig superfamily (IgSf) domains, a transmembrane (TM) domain and an ER-retention KK motif at the C-terminal end, indicative of a similar function as mammalian tapasins. We analysed the regulation of Sasa-TAPBP under immunostimulatory conditions and found an mRNA-upregulation during early infectious salmon anemia virus (ISAV) infection and poly I:C stimulation in vivo and in vitro, in line with our previous findings for other MHC class I pathway genes.