Investigation on the 19S ATPase proteasome subunits (Rpt1-6) conservation and their differential gene expression in Schistosoma mansoni

Heat shock protein 70 (Hsp70) in Schistosoma mansoni and its role in decreased adult worm sensitivity to praziquantel

Schistosoma mansoni is the most common species causing schistosomiasis. It has a complex life cycle involving a vertebrate definitive host and a snail intermediate host of the genus Biomphalaria. Each stage encounters a plethora of environmental stresses specially heat stress. Another sort of stress arises from repeated exposure of the parasite to praziquantel (PZQ), the only drug used for treatment, which leads to the development of resistance in the fields and the labs. Heat shock protein 70 (Hsp70) is found in different developmental stages of S. mansoni. It is immunogenic and regulate cercarial invasion besides its chaperone function. In the Biomphalaria/S. mansoni interaction, epigenetic modulations of the Hsp70 gene underscore the susceptibility phenotype of the snail. Hsp70 is up-regulated in adult S. mansoni with decreased sensitivity to PZQ. This could be due to the induction of oxidative and endoplasmic reticulum stress, induction of apoptosis, exposure to the stressful drug pressure and increase influx of calcium ions. Up-regulation of Hsp70 might help the worm to survive the schistosomicidal effect of the drug mainly by dealing with misfolded proteins, inhibition of apoptosis, induction of autophagy, up-regulation of the P-glycoprotein transporter and attenuation of the signalling from G protein coupled receptors.

Conservation and developmental expression of ubiquitin isopeptidases in Schistosoma mansoni

Several genes related to the ubiquitin (Ub)-proteasome pathway, including those coding for proteasome subunits and conjugation enzymes, are differentially expressed during the Schistosoma mansoni life cycle. Although deubiquitinating enzymes have been reported to be negative regulators of protein ubiquitination and shown to play an important role in Ub-dependent processes, little is known about their role in S. mansoni . In this study, we analysed the Ub carboxyl-terminal hydrolase (UCHs) proteins found in the database of the parasite's genome. An in silico ana- lysis (GeneDB and MEROPS) identified three different UCH family members in the genome, Sm UCH-L3, Sm UCH-L5 and Sm BAP-1 and a phylogenetic analysis confirmed the evolutionary conservation of the proteins. We performed quantitative reverse transcription-polymerase chain reaction and observed a differential expression profile for all of the investigated transcripts between the cercariae and adult worm stages. These results were corroborated by low rates of Z-Arg-Leu-Arg-Gly-Gly-AMC hydrolysis in a crude extract obtained from cercariae in parallel with high Ub conjugate levels in the same extracts. We suggest that the accumulation of ubiquitinated proteins in the cercaria and early schistosomulum stages is related to a decrease in 26S proteasome activity. Taken together, our data suggest that UCH family members contribute to regulating the activity of the Ub-proteasome system during the life cycle of this parasite.

Characterisation of the COP9 signalosome in Schistosoma mansoni parasites

The COP9 signalosome (CSN) is an eight-subunit complex found in all eukaryotes and shares structural features with both the 26S proteasome 'lid' and translation factor eIF3. Recent data have demonstrated that the CSN is a regulator of the ubiquitin (Ub) proteasome system (UPS). CSN controls substrate ubiquitination by cullin-RING Ub ligases, a step which determines substrate specificity of the UPS. Here, we reconstructed the CSN complex in Schistosoma mansoni and identified eight homologous components. Among these homologues, five subunits were predicted with their full-length sequences. Phylogenetic analysis confirmed the evolutionary conservation and the architecture of CSN, as well as the 26S proteasome 'lid'. We performed quantitative reverse transcription-polymerase chain reaction to detect the expression of the SmCSN transcripts. The Smcsn1, Smcsn2, Smcsn3, Smcsn4, Smcsn5, Smcsn6, Smcsn7 and Smcsn8 genes were up-regulated in adult worms compared to cercariae, and the expression levels were similar to that of in vitro cultivated schistosomula. Taken together, these results suggest that the CSN complex may be important during cercariae, schistosome and adult worm development and might explain, at least in part, the differences among UPSs during the parasite life cycle.