Functional characterization ofSjB10, an intracellular serpin fromSchistosoma japonicum

Abstract

SUMMARYSerine protease inhibitors (serpin) play essential roles in many organisms. Mammalian serpins regulate the blood coagulation, fibrinolysis, inflammation and complement activation pathways. In parasitic helminths, serpins are less well characterized, but may also be involved in evasion of the host immune response. In this study, aSchistosoma japonicumserpin (SjB10), containing a 1212 bp open reading frame (ORF), was cloned, expressed and functionally characterized. Sequence analysis, comparative modelling and structural-based alignment revealed thatSjB10contains the essential structural motifs and consensus secondary structures of inhibitory serpins. Transcriptional profiling demonstrated thatSjB10is expressed in adult males, schistosomula and eggs but particularly in the cercariae, suggesting a possible role in cercarial penetration of mammalian host skin. RecombinantSjB10(rSjB10) inhibited pancreatic elastase (PE) in a dose-dependent manner.rSjB10was recognized strongly by experimentally infected rat sera indicating that nativeSjB10is released into host tissue and induces an immune response. By immunochemistry,SjB10localized in theS. japonicumadult foregut and extra-embryonic layer of the egg. This study provides a comprehensive demonstration of sequence and structural-based analysis of a functionalS. japonicumserpin. Furthermore, our findings suggest thatSjB10may be associated with important functional roles inS. japonicumparticularly in host-parasite interactions.