The Schistosoma mansoni Cytochrome P450 (CYP3050A1) Is Essential for Worm Survival and Egg Development

Abstract

Schistosomiasis affects millions of people in developing countries and is responsible for more than 200,000 deaths annually. Because of toxicity and limited spectrum of activity of alternatives, there is effectively only one drug, praziquantel, available for its treatment. Recent data suggest that drug resistance could soon be a problem. There is therefore the need to identify new drug targets and develop drugs for the treatment of schistosomiasis. Analysis of the Schistosoma mansoni genome sequence for proteins involved in detoxification processes found that it encodes a single cytochrome P450 (CYP450) gene. Here we report that the 1452 bp open reading frame has a characteristic heme-binding region in its catalytic domain with a conserved heme ligating cysteine, a hydrophobic leader sequence present as the membrane interacting region, and overall structural conservation. The highest sequence identity to human CYP450s is 22%. Double stranded RNA (dsRNA) silencing of S. mansoni (Sm)CYP450 in schistosomula results in worm death. Treating larval or adult worms with antifungal azole CYP450 inhibitors results in worm death at low micromolar concentrations. In addition, combinations of SmCYP450-specific dsRNA and miconazole show additive schistosomicidal effects supporting the hypothesis that SmCYP450 is the target of miconazole. Treatment of developing S. mansoni eggs with miconazole results in a dose dependent arrest in embryonic development. Our results indicate that SmCYP450 is essential for worm survival and egg development and validates it as a novel drug target. Preliminary structure-activity relationship suggests that the 1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethan-1-ol moiety of miconazole is necessary for activity and that miconazole activity and selectivity could be improved by rational drug design.

Transcriptional responses ofBiomphalaria pfeifferiandSchistosoma mansonifollowing exposure to niclosamide, with evidence for a synergistic effect on snails following exposure to both stressors

“…Particularly noteworthy is the lack of an obvious response of the single S. mansoni cytochrome p450 gene to niclosamide presence. As noted by Ziniel et al [33], the exact function of this gene product in S. mansoni is not known, but our results suggest it is not provoked by a xenobiotic like niclosamide. As noted by Ziniel et al [33] and by us previously (Buddenborg et al [24], parasitic helminths in general lack extensive cytochrome p450 repertoires, quite unlike their hosts.…”

“…As noted by Ziniel et al [33], the exact function of this gene product in S. mansoni is not known, but our results suggest it is not provoked by a xenobiotic like niclosamide. As noted by Ziniel et al [33] and by us previously (Buddenborg et al [24], parasitic helminths in general lack extensive cytochrome p450 repertoires, quite unlike their hosts. In contrast, B. pfeifferi does indeed deploy cytochrome p450 responses upon exposure to molluscicides (see below).…”

Recent Structural Insights into Cytochrome P450 Function

“…A P450 in the worm Schistosoma mansoni (CYP3050A1) has been shown to be essential for both survival and egg development [83]. Its substrate(s) is unknown but this P450 forms tight complexes with many antifungal drugs.…”

“…Its substrate(s) is unknown but this P450 forms tight complexes with many antifungal drugs. No structure is available; modeling has been done on the basis of rabbit P450 2C5 [83]. …”

TRP channels in schistosomes

“…For example, clotrimazole is a widely-used antifungal drug that inhibits cytochrome P-450 enzymes. It has recently been shown to have relatively potent anti-schistosomal activity (Ziniel et al., 2015). However, clotrimazole also acts on a variety of mammalian TRP channels, and is in fact one of the most potent inhibitors of human TRPM8, a cold and menthol receptor, with a reported IC50 of 200 nM (Meseguer et al., 2008).…”