In silico analysis of the fucosylation-associated genome of the human blood fluke Schistosoma mansoni: cloning and characterization of the enzymes involved in GDP-L-fucose synthesis and Golgi import

Abstract

BackgroundCarbohydrate structures of surface-expressed and secreted/excreted glycoconjugates of the human blood fluke Schistosoma mansoni are key determinants that mediate host-parasite interactions in both snail and mammalian hosts. Fucose is a major constituent of these immunologically important glycans, and recent studies have sought to characterize fucosylation-associated enzymes, including the Golgi-localized fucosyltransferases that catalyze the transfer of L-fucose from a GDP-L-fucose donor to an oligosaccharide acceptor. Importantly, GDP-L-fucose is the only nucleotide-sugar donor used by fucosyltransferases and its availability represents a bottleneck in fucosyl-glycotope expression.MethodsA homology-based genome-wide bioinformatics approach was used to identify and molecularly characterize the enzymes that contribute to GDP-L-fucose synthesis and Golgi import in S. mansoni. Putative functions were further investigated through molecular phylogenetic and immunocytochemical analyses.ResultsWe identified homologs of GDP-D-mannose-4,6-dehydratase (GMD) and GDP-4-keto-6-deoxy-D-mannose-3,5-epimerase-4-reductase (GMER), which constitute a de novo pathway for GDP-L-fucose synthesis, in addition to a GDP-L-fucose transporter (GFT) that putatively imports cytosolic GDP-L-fucose into the Golgi. In silico primary sequence analyses identified characteristic Rossman loop and short-chain dehydrogenase/reductase motifs in GMD and GMER as well as 10 transmembrane domains in GFT. All genes are alternatively spliced, generating variants of unknown function. Observed quantitative differences in steady-state transcript levels between miracidia and primary sporocysts may contribute to differential glycotope expression in early larval development. Additionally, analyses of protein expression suggest the occurrence of cytosolic GMD and GMER in the ciliated epidermal plates and tegument of miracidia and primary sporocysts, respectively, which is consistent with previous localization of highly fucosylated glycotopes.ConclusionsThis study is the first to identify and characterize three key genes that are putatively involved in the synthesis and Golgi import of GDP-L-fucose in S. mansoni and provides fundamental information regarding their genomic organization, genetic variation, molecular phylogenetics, and developmental expression in intramolluscan larval stages.

In silico analyses of protein glycosylating genes in the helminth Fasciola hepatica (liver fluke) predict protein-linked glycan simplicity and reveal temporally-dynamic expression profiles

“…No data are available on these biosynthetic genes in flatworms aside from the fucosylation-associated genes reported in S . mansoni 16 . This study therefore represents the first comprehensive description of nucleotide sugar biosynthesis genes in any flatworm parasite.…”

“…Prior to this study, there was no information concerning NSTs in flatworms beyond a single study describing one GDP-Fucose transporter in S . mansoni (SmGFT 16 ). We have identified nine NSTs in the F .…”

“…employed phylogenetic comparisons with a broad range of other NSTs to classify SmGFT, in line with previous work showing that NSTs can be accurately separated into functional groups by phylogenetic analyses 48 , 49 . Many of the clades revealed by these studies included closely-related NSTs with aberrant substrate specificities 16 . We have adapted Peterson’s analysis to incorporate the nine NSTs identified from the F .…”

“…hepatica 15 . No data are available on the glycosylating pathways of liver fluke, nor for any flatworm apart from a single study focusing on the fucosylation subset of transferases in Schistosoma mansoni 16 . Therefore, this work represents the most in depth study of glycosylation pathways in phylum Platyhelminthes, and the first such study in F .…”

Advances in gastropod immunity from the study of the interaction between the snail Biomphalaria glabrata and its parasites: A review of research progress over the last decade

“…C1q-like proteins may interact with fucosylated determinants that are absent in snail [105] but that predominate on parasite tegument [106][107][108]. In addition, Castillo and coworkers have demonstrated that the binding activity of some fucose-binding proteins promotes adhesion of snail hemocytes to sporocysts [109].…”