Galactosylated Fucose Epitopes in Nematodes: INCREASED EXPRESSION IN A CAENORHABDITIS MUTANT ASSOCIATED WITH ALTERED LECTIN SENSITIVITY AND OCCURRENCE IN PARASITIC SPECIES

Shi Yan,Silvia Bleuler-Martinez,David Fernando Plaza,Markus Künzler,Markus Aebi,Anja Joachim,Ebrahim Razzazi-Fazeli,Verena Jantsch,Rudolf Geyer,Iain B.H Wilson,Katharina Paschinger

doi:10.1074/jbc.m112.353128

Abstract

The modification of α1,6-linked fucose residues attached to the proximal (reducing-terminal) core N-acetylglucosamine residue of N-glycans by β1,4-linked galactose ("GalFuc" epitope) is a feature of a number of invertebrate species including the model nematode Caenorhabditis elegans. A pre-requisite for both core α1,6-fucosylation and β1,4-galactosylation is the presence of a nonreducing terminal N-acetylglucosamine; however, this residue is normally absent from the final glycan structure in invertebrates due to the action of specific hexosaminidases. Previously, we have identified two hexosaminidases (HEX-2 and HEX-3) in C. elegans, which process N-glycans. In the present study, we have prepared a hex-2;hex-3 double mutant, which possesses a radically altered N-glycomic profile. Whereas in the double mutant core α1,3-fucosylation of the proximal N-acetylglucosamine was abolished, the degree of galactosylation of core α1,6-fucose increased, and a novel Galα1,2Fucα1,3 moiety attached to the distal core N-acetylglucosamine residue was detected. Both galactosylated fucose moieties were also found in two parasitic nematodes, Ascaris suum and Oesophagostomum dentatum. As core modifications of N-glycans are known targets for fungal nematotoxic lectins, the sensitivity of the C. elegans double hexosaminidase mutant was assessed. Although this mutant displayed hypersensitivity to the GalFuc-binding lectin CGL2 and the N-acetylglucosamine-binding lectin XCL, the mutant was resistant to CCL2, which binds core α1,3-fucose. Thus, the use of C. elegans mutants aids the identification of novel N-glycan modifications and the definition of in vivo specificities of nematotoxic lectins with potential as anthelmintic agents.

Highlights

Galactosylation of core fucose residues is a peculiar feature of invertebrate N-glycans
Preparation of a Nematode Double Hexosaminidase Mutant— In our previous studies on C. elegans hexosaminidases we identified two enzymes (HEX-2 and HEX-3) that remove the GlcNAc residue transferred by GlcNAc-TI and so are putatively involved in the formation of paucimannosidic N-glycans in vivo [16]
We hypothesized that multiple hexosaminidases are involved in N-glycan processing in the nematode in vivo and so a double hexosaminidase mutant was prepared by crossing the relevant single mutants

Summary

Introduction

Galactosylation of core fucose residues is a peculiar feature of invertebrate N-glycans. The modification of ␣1,6-linked fucose residues attached to the proximal (reducing-terminal) core N-acetylglucosamine residue of N-glycans by ␤1,4-linked galactose (“GalFuc” epitope) is a feature of a number of invertebrate species including the model nematode Caenorhabditis elegans. Whereas in the double mutant core ␣1,3-fucosylation of the proximal N-acetylglucosamine was abolished, the degree of galactosylation of core ␣1,6-fucose increased, and a novel Gal␣1,2Fuc␣1,3 moiety attached to the distal core N-acetylglucosamine residue was detected. Both galactosylated fucose moieties were found in two parasitic nematodes, Ascaris suum and Oesophagostomum dentatum. The use of C. elegans mutants aids the identification of novel N-glycan modifications and the defi-

Results

Discussion

Conclusion