Molecular cloning and characterization of IL-15Rα gene in rainbow trout (Oncorhynchus mykiss)

The α-chain of IL-15 receptor complex serves as a high-affinity, specific subunit for IL-15 binding. It shares functional and structural features with IL-2 receptor α-chain. Here we report for the first time that the molecular cloning, characterization and sequence analysis of the teleostean IL-15Rα from Oncorhynchus mykiss. The full-length cDNA comprises of a 5′ untranslated region (UTR) of 167 bp, an open reading frame of 732 bp and a large 3′UTR of 630 bp, constitutively expressed in all the tissues examined. Another two variants are found derived from alternative splicing. Two copies of rainbow trout IL-15Rα (rtIL-15Rα) were detected in the genome by Southern blot hybridization. Moreover, EST evidence is also traced from other fishes. The deduced rtIL-15Rα of 243 amino acids contains a 17aa signal peptide at N-terminus and a transmembrane region at C-terminus, as well as a typical sushi domain included in the extracellular region. Phylogenetic tree analysis groups rtIL-15Rα with other IL-15Rαs but separates it from IL-2Rαs. In addition, a putative sequence was found in the sushi domain which is conserved and versatile among all species and this might relate to cytokine recognition.