Molecular characterization and functional study of galectin-related proteins from the Japanese flounder (Paralichthys olivaceus)

Galectins are a family of lectins that bind ?-galactoside sugars through their conserved carbohydrate-recognition domains (CRDs) and play integral roles in the innate immune systems of vertebrates and invertebrates. Accumulating amounts of evidence have shown that galectin-related protein (GRP) plays a crucial role in fish immunity. In this study, the GRP cDNA with a 546 bp open reading frame from Paralichthys olivaceus was identified and characterized and was designated as PoGRP. PoGRP was 92.82% similar to the GRP sequences of Seriola dumerili and Anabas testudineus. PoGRP was found to be widely expressed in all tested P. olivaceus tissues, with the highest expression levels being observed in the brain, spleen and liver. Additionally, after this fish species was challenged with Edwardsiella tarda, PoGRP expression was significantly upregulated. The recombinant PoGRP protein (rPoGRP) exhibited binding to various pathogen-associated molecular patterns (PAMPs) and to gramnegative and gram-positive bacteria. In addition, rPoGRP exhibited the ability to agglutinate different bacteria in the presence of Ca2+. In summary, our findings indicated that PoGRP plays a vital role in the immune system to protect against bacterial infection. This study lays the foundation for further functional characterization of GRP in aquatic animal immunity.

Automated summary

Galectins are a family of lectins that play crucial roles in the innate immune systems of vertebrates and invertebrates by binding to β-galactoside sugars through their conserved CRDs. This study identified and characterized a PoGRP cDNA from Paralichthys olivaceus, showing it to be widely expressed in various tissues and significantly upregulated in response to bacterial challenge. The recombinant PoGRP protein exhibited binding to various PAMPs and bacteria, suggesting a vital role in protecting against bacterial infection in fish.