Schistosoma mansoni: SmE78, a nuclear receptor orthologue of Drosophila ecdysone-induced protein 78.

Drosophila ecdysone-induced protein 78 (E78) belongs to the nuclear receptor (NR) superfamily, it plays a role directly related to ecdysone signaling. We isolated a cDNA of Drosophila E78 orthologue from the Platyhelminth Schistosoma mansoni (SmE78). It is the first E78 orthologue known outside of the molting animals--the Ecdysozoa. The SmE78 cDNA is 3471 base pairs long and contains an entire open reading frame (ORF) encoding a 1087 amino acid protein. Phylogenetic analysis of the ligand-binding domain (LBD) demonstrates that the LBD of SmE78 is phylogenetically related to the Drosophila E78. Gene structure of SmE78 was determined showing it to consist of six exons spanning more than 32 kbp. Quantitative real-time reverse-transcriptase polymerase chain reaction (RT-PCR) demonstrated that SmE78 was expressed throughout schistosome development but with the highest levels of expression in miracidia and egg stage. The result is consistent with the previous studies that Ecdysterone was effective in stimulating host location activities in miracidia. The data suggest that SmE78 may be involved in transduction of an ecdysone signal in S. mansoni.