Prokaryotic expression, cell and tissue distribution of the class B scavenger receptor in Portunus trituberculatus

Class B scavenger receptors are a subclass of scavenger receptors family that can recognize a large repertoire of ligands, and they have been shown to have a wide range of functions in lipids metabolism and immune defence. To better understand the functions of class B scavenger receptors in Portunus trituberculatus (Pt-SRB), the extracellular loop of Pt-SRB was sequenced and subcloned into the expression vector, and the expressed recombinant rPt-SRB protein was obtained in present study. Then the rPt-SRB was purified by nickel-nitrilotriacetic acid chromatography, and the polyclonal antibody against rPt-SRB was obtained from an immunized rat using a conventional method. Results of SDS-PAGE showed that the recombinant protein had a molecular mass of 49.18 ku and was predominantly expressed in the insoluble fraction. Moreover, Western-blot analysis revealed that antiserum could specifically react with the rPt-SRB. Furthermore, immunofluorescent staining technique was used to determine the tissue distribution and the cellular localization of Pt-SRB in this study. The results showed that the Pt-SRB were expressed in the tissues including intestine, hepatopancreas, gills, heart and muscle, but the Pt-SRB were located in different tissue structures. The results displayed that the green fluorescent signals were mainly located in the connective tissue of digestive tract and gland, epithelial cells of the gill and hepatopancreatic tubules. In the crab hemocytes, the green fluorescent signals were located in the membrane and cytoplasm, but not in the nucleus, which suggested that Pt-SRB was localized both in membrane and cytoplasm in the crab hemocytes. Our findings will help us to better understand potential functions of Pt-SRB.