The suppressor of cytokine signaling (SOCS) family plays a pivotal role in regulating diverse biological processes, including cytokines expression, nitric oxide (NO), and reactive oxygen species (ROS) production, primarily through modulation of the JAK-STAT pathway. This study identified and characterized a homolog of SOCS3 from Scomber japonicus (designated SjSOCS3a). The coding sequence of SjSOCS3a is composed of 618 bp, encoding 205 amino acids containing SH2 domain (39-137 residues) and SOCS3 box domain (165-205 residues). Pairwise sequence alignment discovered that SjSOCS3a had the highest homology with the ortholog from Thunnus maccoyii and the lowest homology with Bos taurus SOCS3. Multiple alignments of SOCS3 homolog revealed that both SH2 and SOCS box domains were conserved across all selected species. Phylogenetic analysis showed diverged distinct taxonomic clusters of SOCS3, including fish, amphibia, leaves, reptiles, and mammals.
SjSOCS3a mRNA was ubiquitously expressed in almost all of the collected tissues with the highest level in the heart and the lowest level in the liver. The mRNA expression of SjSOCS3a in blood was significantly increased at 12 hours upon poly I:C, LPS, Vibrio harveyi, and Streptococcus iniae challenges. In vitro assays revealed that SjSOCS3a transfection into RAW 264.7 cells significantly reduced NO and ROS production under LPS treatment (Fig 1). In conclusion, these findings indicate that SjSOCS3a may regulate the innate immune response of Scomber japonicus.