The nematode Caenorhabditis elegans synthesizes unusual O-linked glycans: identification of glucose-substituted mucin-type O-glycans and short chondroitin-like oligosaccharides

Abstract

The free-living nematode Caenorhabditis elegans is a relevant model for studies on the role of glycoconjugates during development of multicellular organisms. Several genes coding for glycosyltransferases involved in the synthesis of N- and O-linked glycans have already been isolated, but, apart from repetitive dimers of glycosaminoglycans, no detailed structure of either type of component has been published so far. This study aimed to establish the structures of the major O-glycans synthesized by C. elegans to give an insight into the endogenous glycosyltransferase activities expressed in this organism. By the use of NMR and MS, we have resolved the sequence of seven of these components that present very unusual features. Most of them were characterized by the type-1 core substituted on Gal and/or GalNAc by (beta1-4)Glc and (beta1-6)Glc residues. Another compound exhibited the GalNAc(beta1-4)N-acetylglucosaminitol sequence in the terminal position, to which was attached a tetramer of beta-Gal substituted by both Fuc and 2-O-methyl-fucose residues. Our experimental procedure led also to the isolation of glycosaminoglycan-like components and oligomannosyl-type N-glycans. In particular, the data confirmed that C. elegans synthesizes the ubiquitous linker sequence GlcA(beta1-3)Gal(beta1-3)Gal(beta1-4)Xyl.

A glycomics platform for the analysis of permethylated oligosaccharide alditols

“…Peak B contains a Hex1,6-arm and Peak C contains a Hex1,4-arm. These tetrasaccharide assignments are consistent with the general structural paradigm seen in O-glycans that have been documented in C. elegans [34,49]. The structural assignments are shown to the right of the spectra in Figure 6.…”

“…Here the voltage offset C. elegans produces neutral O-glycans that contain a mammalian-like Gal␤1,3GalNAc type I core and are highly branched and short [34,49]. Both core residues can be highly substituted.…”

“…Both core residues can be highly substituted. The core Gal of the neutral O-glycans has been reported to be 4,6-disubstituted, while only GlcA has been reported to substitute the C-3 position [34,49]. The core GalNAc can be up to 3,4,6-trisubstituted, whereas the C-3 position has been reported to contain Gal exclusively [49].…”

“…The core GalNAc can be up to 3,4,6-trisubstituted, whereas the C-3 position has been reported to contain Gal exclusively [49]. The GalNAc C-6 position has been reported to be Gal-or Glc-substituted [49]. Mutant strains that are affected in O-glycan biosynthesis have altered susceptibilities to bacterial and fungal pathogens and are currently used to study host-pathogen interactions and innate immunity [34, 50 -52].…”

Synthesis of Fluorescence-Labeled Gal.BETA.1-3Fuc and Gal.BETA.1-4Fuc as Probes for the Endogenous Glyco-Epitope Recognized by Galectins in Caenorhabditis elegans

“…[5][6][7][8] Among galectins from invertebrate species including Caenorhabditis elegans, specificity for N-acetyllactosamine was reported, although the existence of the glycan containing N-acetyllactosamine units has not been confirmed in C. elegans. [9][10][11][12][13][14] This discrepancy raised a question concerning the endogenous glyco-epitope that is recognized by galectins in C. elegans. To search for it, Takeuchi et al isolated N-type glycoproteins bound by C. elegans galectin LEC-6.…”