Abstract
BackgroundThe Sperm-coating protein/Tpx-1/Ag5/PR-1/Sc7 (SCP/TAPS) domain is found across phyla and is a major structural feature of insect allergens, mammalian sperm proteins and parasitic nematode secreted molecules. Proteins containing this domain are implicated in diverse biological activities and may be important for chronic host/parasite interactions.ResultsWe report the first description of an SCP/TAPS gene family (Schistosoma mansoni venom allergen-like (SmVALs)) in the medically important Platyhelminthes (class Trematoda) and describe individual members' phylogenetic relationships, genomic organization and life cycle expression profiles. Twenty-eight SmVALs with complete SCP/TAPS domains were identified and comparison of their predicted protein features and gene structures indicated the presence of two distinct sub-families (group 1 & group 2). Phylogenetic analysis demonstrated that this group 1/group 2 split is zoologically widespread as it exists across the metazoan sub-kingdom. Chromosomal localisation and PCR analysis, coupled to inspection of the current S. mansoni genomic assembly, revealed that many of the SmVAL genes are spatially linked throughout the genome. Quantitative lifecycle expression profiling demonstrated distinct SmVAL expression patterns, including transcripts specifically associated with lifestages involved in definitive host invasion, transcripts restricted to lifestages involved in the invasion of the intermediate host and transcripts ubiquitously expressed. Analysis of SmVAL6 transcript diversity demonstrated statistically significant, developmentally regulated, alternative splicing.ConclusionOur results highlight the existence of two distinct SCP/TAPS protein types within the Platyhelminthes and across taxa. The extensive lifecycle expression analysis indicates several SmVAL transcripts are upregulated in infective stages of the parasite, suggesting that these particular protein products may be linked to the establishment of chronic host/parasite interactions.
Highlights
The Sperm-coating protein/Tpx-1/Ag5/PR-1/Sc7 (SCP/TAPS) domain is found across phyla and is a major structural feature of insect allergens, mammalian sperm proteins and parasitic nematode secreted molecules
We present the molecular characterisation of 13 SCP/TAPS family members in S. mansoni, hereafter referred to as Schistosoma mansoni Venom allergen-like 1–13 (SmVAL1-13)
Results cDNA cloning and identification of SmVAL family members To identify S. mansoni SCP/TAPS domain-containing family members, the Vespula vulgaris Wasp Venom Allergen 5 (Ves v 5, [Genbank:AAA30333]) protein sequence was used in a tBLASTn search of S. mansoni expressed sequence tag (EST) and Phat [25] predicted genes from version 1 of the publicly available S. mansoni genomic database [24]
Summary
The Sperm-coating protein/Tpx-1/Ag5/PR-1/Sc7 (SCP/TAPS) domain is found across phyla and is a major structural feature of insect allergens, mammalian sperm proteins and parasitic nematode secreted molecules Proteins containing this domain are implicated in diverse biological activities and may be important for chronic host/parasite interactions. Despite the availability of a highly effective chemotherapeutic agent (praziquantel), recent reassessment of disease-related morbidity shows schistosomiasis to be a far greater public health problem than previously estimated [2]. This reappraisal of the impact of schistosomiasis and the potential emergence of praziquantel-resistant strains argues strongly for the identification and characterisation of novel vaccine and drug targets. One interesting finding from these investigations was the identification of two adult male-associated transcripts bearing sequence similarity to the SCP/Tpx-1/Ag 5/Pr-1/Sc7 (SCP/ TAPS) family
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