Effects of proteasome inhibitor MG-132 on the parasite Schistosoma mansoni.

Proteasome is a proteolytic complex responsible for intracellular protein turnover in eukaryotes, archaea and in some actinobacteria species. Previous work has demonstrated that in Schistosoma mansoni parasites, the proteasome inhibitor MG-132 affects parasite development. However, the molecular targets affected by MG-132 in S. mansoni are not entirely known. Here, we used expression microarrays to measure the genome-wide changes in gene expression of S. mansoni adult worms exposed in vitro to MG-132, followed by in silico functional analyses of the affected genes using Ingenuity Pathway Analysis (IPA). Scanning electron microscopy was used to document changes in the parasites' tegument. We identified 1,919 genes with a statistically significant (q-value ≤ 0.025) differential expression in parasites treated for 24 h with MG-132, when compared with control. Of these, a total of 1,130 genes were up-regulated and 790 genes were down-regulated. A functional gene interaction network comprised of MG-132 and its target genes, known from the literature to be affected by the compound in humans, was identified here as affected by MG-132. While MG-132 activated the expression of the 26S proteasome genes, it also decreased the expression of 19S chaperones assembly, 20S proteasome maturation, ubiquitin-like NEDD8 and its partner cullin-3 ubiquitin ligase genes. Interestingly, genes that encode proteins related to potassium ion binding, integral membrane component, ATPase and potassium channel activities were significantly down-regulated, whereas genes encoding proteins related to actin binding and microtubule motor activity were significantly up-regulated. MG-132 caused important changes in the worm tegument; peeling, outbreaks and swelling in the tegument tubercles could be observed, which is consistent with interference on the ionic homeostasis in S. mansoni. Finally, we showed the down-regulation of Bax pro-apoptotic gene, as well as up-regulation of two apoptosis inhibitor genes, IAP1 and BRE1, and in contrast, down-regulation of Apaf-1 apoptotic activator, thus suggesting that apoptosis is deregulated in S. mansoni exposed to MG-132. A considerable insight has been gained concerning the potential of MG-132 as a gene expression modulator, and overall the data suggest that the proteasome might be an important molecular target for the design of new drugs against schistosomiasis.

Effects of curcumin on the parasite Schistosoma mansoni: a transcriptomic approach.

Schistosomiasis remains a severe problem of public health in developing countries. Several reports show that praziquantel, the drug of choice for treating schistosomiasis, can select Schistosoma mansoni strains resistant to the drug. Thus, developing new drugs against this parasitosis is a highly desirable goal. Curcumin, a phenolic compound deriving from the plant Curcuma longa, has been shown to have anticancer, anti-inflammatory and antiparasitic effects. Recently, our group has demonstrated that curcumin causes the separation of S. mansoni adult worm pairs, eggs infertility, decreased oviposition and parasite viability, leading to death. In the present work, we have investigated the effects of curcumin on S. mansoni gene expression in adult worms through microarray analyses. Our results showed 2374 genes that were significantly and differentially expressed, of which 981 were up-regulated and 1393 were down-regulated. Among the differentially expressed genes there were components of important signaling pathways involved in embryogenesis and oogenesis such as Notch and TGF-ß. Gene networks most significantly enriched with altered genes were identified, including a network related to Cellular Function and Maintenance, Molecular Transport, Organ Development, which is connected to the TGF-ß signaling pathway and might be related to the effect of curcumin on pairing of adult worm pairs, egg production and viability of worms. qPCR validation experiments with 7 genes have confirmed the expression changes detected with arrays. Here we suggest that transcriptional repression observed in Notch and TGF-ß pathways could explain the effects on oviposition and egg development described in the literature.

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

The ubiquitin-proteasome system is responsible for degradation of the majority of intracellular proteins in eukaryotic cells. The 26S proteasome proteolytic complex is composed of a 20S core particle responsible for protein degradation and the 19S lid which plays a role in the recognition of polyubiquitinated substrates. The 19S regulatory particle (Rps) is composed of ATPase (Rpt) and non-ATPase (Rpn) subunits. In this study, we analyzed the expression profile of 19S Rpt subunits in the larvae and adult stage of the Schistosoma mansoni life cycle. Conventional reverse transcriptase polymerase chain reaction (RT-PCR) revealed that the majority of the 19S Rpt subunits amplified at the expected molecular masses for various investigated stages. In addition, SmRpt1, SmRpt2, and SmRpt6 transcript levels were increased in 3 h-cultured schistosomula and reasonably maintained until 5 h in culture, as revealed by qRT-PCR. Phylogenetic analysis of 19S Rpt subunits showed high structural conservation in comparison to other Rpt orthologues. The mRNA expression profile of 19S Rpt subunits did not correlate with 26S proteasome proteolytic activity as judged by a (14)C-casein-degrading assay, in the early cultured schistosomula. Taken together, these results revealed a differential expression profile for 19S Rpt subunits whose transcript levels could not be directly associated to 26S proteasome activity.