Proteasome stress responses in Schistosoma mansoni.

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The proteasome proteolytic system is the major ATP-dependent protease in eukaryotic cells responsible for intracellular protein turnover. Schistosoma mansoni has been reported to contain an ubiquitin-proteasome proteolytic pathway, and many studies have suggested a biological role of proteasomes in the development of this parasite. Additionally, evidence has suggested diversity in proteasome composition under several cellular conditions, and this might contribute to the regulation of its function in this parasite. The proteasomal system has been considered important to support the protein homeostasis during cellular stress. In this study, we described in vitro effects of oxidative stress, heat shock, and chemical stress on S. mansoni adults. Our findings showed that chemical stress induced with curcumin, IBMX, and MG132 modified the gene expression of the proteasomal enzymes SmHul5 and SmUbp6. Likewise, the expression of these genes was upregulated during oxidative stress and heat shock. Analyses of the S. mansoni life cycle showed differential gene expression in sporocysts, schistosomulae, and miracidia. These results suggested that proteasome accessory proteins participate in stress response during the parasite development. The expression level of SmHul5 and SmUbp6 was decreased by 16-fold and 9-fold, respectively, by the chemical stress induced with IBMX, which suggests proteasome disassembly. On the other hand, curcumin, MG132, oxidative stress, and heat shock increased the expression of these genes. Furthermore, the gene expression of maturation proteasome protein (SmPOMP) was increased in stress conditions induced by curcumin, MG132, and H₂O₂, which could be related to the synthesis of new proteasomes. S. mansoni adult worms were found to utilize similar mechanisms to respond to different conditions of stress. Our results demonstrated that oxidative stress, heat shock, and chemical stress modified the expression profile of genes related to the ubiquitin-proteasome system and suggested that the proteasome might be important in the cellular stress response in this parasite.