Abstract
Schistosomiasis is a neglected tropical disease (NTD) that affects the world’s poorest people in tropical and sub-tropical regions caused by trematodes of the genus Schistosoma. Praziquantel is the only drug used in the field for treatment and there are concerns of drug resistance emerging. Fumarases are enzymes involved in cellular metabolism and DNA repair. Two biologically distinct classes exist which share no sequence homology. S. mansoni possesses two genes SmFHI (class I) and SmFHII (class II) and humans only possess a class II. Homolog searches reveal that Lophotrochozoa are the only metazoan clade to have maintained two classes of fumarase. There have also been two losses of class I in Chordata and Ecdysozoa. Class II was only lost in Cestoda and Monogenea. Phylogenetic analyses reveal the evolutionary relationships within each class of fumarase. Localisation prediction tools reveal that SmFHI possesses a mitochondrial targeting peptide while SmFH II does not, suggesting a division of labour between these two enzymes. Mining of expression data from DNA-microarray and RNA-seq meta-analysis reveals relatively high expression of bothfumarases across the human-infecting lifecycle stages. Expression in human-infective lifecycle is elucidated through qRT-PCR and reveals relatively high expression of both genes except for 24-hour schistosomula expression of SmfhII. ScRNA-seq of adult worms shows high expression across different cell types. Using RNAi it is revealed that the targeting of both fumarases elicits a phenotypic response of motility loss in male and female adult worms, however knockdown data is inconclusive for females. There isn’t a significant rise or loss of the non-targeted fumarase when compared with the control. Using computer aided drug design (CADD), a homology model of SmFI His made based on the crystal structure of Leishmania major class I fumarase LmFH-2. This model is used for in silico docking experiments against a library of 300,000 compounds. A selection of 18 compounds from those identified as hits in CADD as well as a class II fumarase inhibitor identified in the literature are screened against schistosomula. Compounds identified as a hit in these screens are then screened against adult worms for 72-hours and cytotoxicity is calculated. Neither of the compounds identified were found to be cytotoxic to human cell lines. Neither of the compounds were found to be particularly potent. Methods to improve the potency and delivery of potential mitochondrial inhibitors are discussed.
| Date of Award | 2023 |
|---|---|
| Original language | English |
| Awarding Institution |
|