Background:The eastern oyster, an important estuarine species, is parasitized by a protozoan in a galectin-dependent manner. Results: A variety of paucimannosidic, hybrid, and complex neutral and acidic N-linked oligosaccharides was found.
Conclusion:The oyster possesses a complex repertoire of glycans with some features reminiscent of vertebrates. Significance: The N-glycome of the eastern oyster correlates well with the specificity of its own galectin CvGal1.
Trichomonad species are widespread unicellular flagellated parasites of vertebrates which interact with their hosts through carbohydrate-lectin interactions. In the past, some data have been accumulated regarding their lipo(phospho)glycans, a major glycoconjugate on their cell surfaces; on the other hand, other than biosynthetic aspects, few details about their N-linked oligosaccharides are known. In this study, we present both mass spectrometric and high-performance liquid chromatography data about the N-glycans of different strains of Trichomonas vaginalis, a parasite of the human reproductive tract. The major structure in all strains examined is a truncated oligomannose form (Man(5)GlcNAc(2)) with α1,2-mannose residues, compatible with a previous bioinformatic examination of the glycogenomic potential of T. vaginalis. In addition, dependent on the strain, N-glycans modified by pentose residues, phosphate or phosphoethanolamine and terminal N-acetyllactosamine (Galβ1,4GlcNAc) units were found. The modification of N-glycans by N-acetyllactosamine in at least some strains is shared with the lipo(phospho)glycan and may represent a further interaction partner for host galectins, thereby playing a role in binding of the parasite to host epithelia. On the other hand, the variation in glycosylation between strains may be the result of genetic diversity within this species.
The HL241 mutant strain of the cellular slime mold Dictyostelium
discoideum is a potential model for human congenital disorder
of glycosylation type IL (ALG9-CDG) and has been previously predicted
to possess a lower degree of modification of its N-glycans with anionic
moieties than the parental wild-type. In this study, we first showed
that this strain has a premature stop codon in its alg9 mannosyltransferase gene compatible with the occurrence of truncated
N-glycans. These were subject to an optimized analytical workflow,
considering that the mass spectrometry of acidic glycans often presents
challenges due to neutral loss and suppression effects. Therefore,
the protein-bound N-glycans were first fractionated, after serial
enzymatic release, by solid phase extraction. Then primarily single
glycan species were isolated by mixed hydrophilic-interaction/anion-exchange
or reversed-phase HPLC and analyzed using chemical and enzymatic treatments
and MS/MS. We show that protein-linked N-glycans of the mutant are
of reduced size as compared to those of wild-type AX3, but still contain
core α1,3-fucose, intersecting N-acetylglucosamine,
bisecting N-acetylglucosamine, methylphosphate, phosphate,
and sulfate residues. We observe that a single N-glycan can carry
up to four of these six possible modifications. Due to the improved
analytical procedures, we reveal fuller details regarding the N-glycomic
potential of this fascinating model organism.
The canine heartworm (Dirofilaria immitis) is a mosquito-borne parasitic nematode whose range is extending due to climate change. In a four-dimensional analysis involving HPLC, MALDI-TOF–MS and MS/MS in combination with chemical and enzymatic digestions, we here reveal an N-glycome of unprecedented complexity. We detect N-glycans of up to 7000 Da, which contain long fucosylated HexNAc-based repeats, as well as glucuronylated structures. While some modifications including LacdiNAc, chitobiose, α1,3-fucose and phosphorylcholine are familiar, anionic N-glycans have previously not been reported in nematodes. Glycan array data show that the neutral glycans are preferentially recognised by IgM in dog sera or by mannose binding lectin when antennal fucose and phosphorylcholine residues are removed; this pattern of reactivity is reversed for mammalian C-reactive protein, which can in turn be bound by the complement component C1q. Thereby, the N-glycans of D. immitis contain features which may either mediate immunomodulation of the host or confer the ability to avoid immune surveillance.
The occurrence of anionic and zwitterionic glycans in the Lepidoptera data is not only of glycoanalytical and evolutionary interest, but is of biotechnological relevance as lepidopteran cell lines are potential factories for recombinant glycoprotein production.
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