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

Abstract

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 (Y535 and Y557) and the cytoplasmic free Ca2+ 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.