SHP1 tyrosine phosphatase gets involved in host defense against Streptococcus agalactiae infection and BCR signaling pathway in Nile tilapia (Oreochromis niloticus)

Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP1), a kind of protein tyrosine phosphatases (PTPs), is a critical regulator of antigen receptor signal transduction . Signal transduction of BCR is regulated by phosphatases in teleost as in mammals. In this study, SHP1 from Nile tilapia ( Oreochromis niloticus ) (OnSHP1) was identified and characterized, including the expression pattern against bacterial infection and regulation function in BCR signaling pathway. The open reading frame of OnSHP1 contains 1749 bp of nucleotide sequence , encoding a protein of 582 amino acids. The OnSHP1 protein was highly conversed compared to that of other species, including two amino-terminal SH2 domains at the N terminus and a PTP catalytic domain . Transcriptional expression analysis revealed that OnSHP1 was detected in all examined tissues and highly expressed in spleen . The up-regulated OnSHP1 expression was observed in peripheral blood, spleen and anterior kidney following challenge with Streptococcus agalactiae or lipopolysaccharide (LPS) in vivo , as well as that displayed in leukocytes stimulated with S. agalactiae or LPS in vitro . Further, after induction with mouse anti-tilapia IgM monoclonal antibody in vitro , OnSHP1 was significantly up-regulated in leukocytes. When spleen leukocytes treated with PTP Inhibitor II in vitro , the phosphorylation level of OnSHP1 at the phosphorylation sites (Y 535 and Y 557 ) and the cytoplasmic free Ca 2+ concentration were up-regulated significantly. Overall, the findings of this study indicate that SHP1 gets involved in host defense against bacterial infection and BCR signaling pathway in Nile tilapia .