Abstract
Background Schistosoma species are responsible for the disease schistosomiasis, a highly prevalent helminthic disease that requires a freshwater snail as intermediate host. The S. mansoni free-living miracidium must utilize olfaction to find a suitable snail host, and certain types of rhodopsin G protein-coupled receptors (GPCRs) and ionotropic receptors (IRs) have been identified as olfactory receptors in other animal phyla. The Schistosoma genome project, together with the recent availability of proteomic databases, allowed for studies to explore receptors within S. mansoni, some of which may contribute to host finding.ResultsWe have identified 17 rhodopsin-type GPCR sequences in S. mansoni belonging to four subclasses, including ligand-specific GPCRs (i.e. neuropeptide and opsin). RT-PCR demonstrated the expression of nine out of the 17 GPCRs in the free-living miracidia, each of which have been characterized for homology to S. haematobium. Among the nine GPCRs, two are predicted as Gq-opsins. We also describe the characterization of a Schistosoma-encoded IR based on similarity with other species IR and conservation of IR-like domains. Schistosoma mansoni IR is expressed in miracidia at 3 and 6 h post-hatch.ConclusionsThe identification of receptors in S. mansoni miracidia, presented here, contributes not only to further understanding of Schistosoma biology and signal transduction but also provides a basis for approaches that may modify parasite behaviour.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1837-2) contains supplementary material, which is available to authorized users.
Highlights
Schistosoma species are responsible for the disease schistosomiasis, a highly prevalent helminthic disease that requires a freshwater snail as intermediate host
Putative G protein-coupled receptors (GPCRs) within the S. mansoni genome Using the methodology outlined in Fig. 1a, 98 proteins with 7-TM domains were extracted from the S. mansoni genome-derived protein models, based on TMHMM prediction
All encode proteins considered as full-length, as determined by the presence of 7-TM domains, putative rhodopsin-type GPCR domains, as Comparative analysis of GPCRs present in S. mansoni miracidia with S. haematobium According to their corresponding sub-classification, phylogenetic trees were constructed for each subclass using the final set of predicted non-opsin GPCRs grouped with the S. haematobium homologs (Fig. 2), confirming the high phylogenetic similarity
Summary
Schistosoma species are responsible for the disease schistosomiasis, a highly prevalent helminthic disease that requires a freshwater snail as intermediate host. Schistosomes are responsible for the disease schistosomiasis, the most prevalent and important of the parasitic platyhelminthic diseases of humans. Schistosomiasis occurs in 76 countries, affecting approximately 207 million individuals [2], and causing 280,000 deaths per year in sub-Saharan Africa [3]. This represents a serious disease burden to socioeconomic development. During the course of its life-cycle, Schistosoma mansoni undergoes distinct stages of differentiation, whilst inhabiting three separate environments - freshwater, a molluscan intermediate host, and a vertebrate definitive host [4].
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