An Endogenous Drosophila Receptor for Glycans Bearing α1,3-Linked Core Fucose Residues

Samuel Bouyain,Nicholas J Silk,Gustáv Fabini,Kurt Drickamer

doi:10.1074/jbc.m202825200

Abstract

The genome of Drosophila melanogaster encodes several proteins that are predicted to contain Ca(2+)-dependent, C-type carbohydrate-recognition domains. The CG2958 gene encodes a protein containing 359 amino acid residues. Analysis of the CG2958 sequence suggests that it consists of an N-terminal domain found in other Drosophila proteins, a middle segment that is unique, and a C-terminal C-type carbohydrate-recognition domain. Expression studies show that the full-length protein is a tetramer formed by noncovalent association of disulfide-linked dimers that are linked through cysteine residues in the N-terminal domain. The expressed protein binds to immobilized yeast invertase through the C-terminal carbohydrate-recognition domain. Competition binding studies using monosaccharides demonstrate that CG2958 interacts specifically with fucose and mannose. Fucose binds approximately 5-fold better than mannose. Blotting studies reveal that the best glycoprotein ligands are those that contain N-linked glycans bearing alpha1,3-linked fucose residues. Binding is enhanced by the additional presence of alpha1,6-linked fucose. It has previously been proposed that labeling of the Drosophila neural system by anti-horseradish peroxidase antibodies is a result of the presence of difucosylated N-linked glycans. CG2958 is a potential endogenous receptor for such neural-specific carbohydrate epitopes.

Highlights

Animal lectins provide a mechanism for recognition of protein- and lipid-linked glycans
The results presented here demonstrate that Drosophila protein CG2958 is a fucose-binding lectin that interacts with ␣1,3-linked fucose attached to the core of N-linked glycans
This binding can occur with oligosaccharides that are attached to proteins, so CG2958 is a potential endogenous receptor for Drosophila glycoproteins that bear core ␣1,3-fucosylated glycans

Summary

Introduction

Animal lectins provide a mechanism for recognition of protein- and lipid-linked glycans. Using information about the structures and sugar binding activities of known C-type CRDs, it is possible to identify CTLDs that are likely to display carbohydrate binding activity. This approach has been applied to the complete genomic sequences of model organisms such as Caenorhabditis elegans [5] and Drosophila melanogaster [2] as well as to the human genome (see ctld.glycob.ox.ac.uk for a current update). The Ca2ϩligating residues are in the same configuration as those in serum mannose-binding protein and other C-type lectins that bind sugars with hydroxyl groups in the orientation corresponding to the 3- and 4-hydroxyl groups of mannose [6]. CG2958 appears to be an endogenous receptor for ␣1,3-linked fucose residues linked to the core GlcNAc residue of N-linked oligosaccharides in Drosophila

Methods

Results

Conclusion