The involvement of suppressors of cytokine signaling 2 (SOCS2) in immune defense responses of Chinese mitten crab Eriocheir sinensis.

The suppressors of cytokine signaling 2 (SOCS2) has been identified as negative feedback inhibitors for various cytokines signaling via the JAK/STAT pathway. In the present studies, the cDNA of Eriocheir sinensis SOCS2 (designated as EsSOCS2) was cloned by expressed sequence tag (EST) and rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of EsSOCS2 was of 2535bp, consisting of an open reading frame (a ORF) of 1071bp encoding a polypeptide of 357 amino acids. The deduced amino acid sequence of EsSOCS2 shared 55-62% similarity with other SOCS2 family members. There were three typical conserved SOCS family domains in EsSOCS2, including an N-terminal ESS formed from a single amphipathic helix, a central SH2 domain with a classic phosphotyrosine (pY) site and a C-terminal SOCS box. The sequence and structural similarity of EsSOCS2 with SOCS2 proteins from other organisms indicated that EsSOCS2 should be a new member of the SOCS2 family. Phylogenetic analysis revealed that EsSOCS2 was clustered with SOCS2 from the other invertebrates, and fell into the group of type II SOCS subfamily as a sister branch to CIS and SOCS2 from vertebrate, suggesting the great divergence of SOCS2 of vertebrate from invertebrate and complex evolution of SOCS2 family members. The mRNA transcript of EsSOCS2 could be detected by semi-quantitative RT-PCR in all examined tissues of healthy crabs, including haemocytes, hepatopancreas, gill, muscle, heart and gonad. The mRNA expression of EsSOCS2 in haemocytes was up-regulated to 3.5-fold at 8h after Listonella anguillarum challenge, 3-fold and 3.5-fold at 4 and 6h, respectively, after Micrococcus luteus challenge. These results collectively suggested that EsSOCS2 could be induced by bacteria challenge, and it was involved in the immune defense responses in E. sinensis.