A novel chemerin receptor 1 (Chemerin1) takes part in the immune response of cobia (Rachycentron canadum)

Chemerin receptor 1 (Chemerin₁) plays a critical role in innate and adaptive immune systems. In this study, a cobia (Rachycentron canadum) Chemerin₁ was identified, and its molecular characterization and expression patterns were analyzed. Multiple sequence alignment revealed that the RcChemerin₁ possessed a typical dynein regulatory complex (DRC) motif. There was also a potential N-glycosylation site in the extracellular regions of the N-terminus and intracellular loops (ICL) 1 region. Phylogenetic analysis demonstrated that the RcChemerin₁ was clustered together with homologous proteins from other fish species. RcChemerin₁ was constitutively expressed in a wide range of tissues (especially in immune-related tissues) with different expression levels, which suggests that the RcChemerin₁ plays different roles in un-stimulated tissues. RcChemerin₁ expression showed up-regulation in the head kidney after Vibrio harveyi challenge. Up-regulation in the head kidney and spleen was also observed after polyinosinic-polycytidylic acid (poly I: C) challenge, which suggests that RcChemerin₁ may play vital roles during bacterial and viral infection. The differential responses of immune organs to bacteria and poly I: C imply the differences in defense mechanisms against viruses and bacteria.