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

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 ϳ5-fold better than mannose. Blotting studies reveal that the best glycoprotein ligands are those that contain N-linked glycans bearing ␣1,3-linked fucose residues. Binding is enhanced by the additional presence of ␣1,6-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.Animal lectins provide a mechanism for recognition of protein-and lipid-linked glycans. Recognition of endogenous glycoconjugates at the cell surface, in the extracellular matrix, and in serum can lead to intercellular adhesion and signaling as well as uptake and degradation. Animal lectins are diverse in structure, but they usually contain modular carbohydraterecognition domains (CRDs) 1 (1, 2). The C-type CRDs are the largest and most diverse class of CRDs. These domains share a common fold and show Ca 2ϩ -dependent sugar binding activity, although their selectivity for different carbohydrate ligands varies. Binding of sugars involves formation of a ternary complex between the protein, a bound Ca 2ϩ , and the sugar (3). Selectivity for particular sugar ligands is determined in large part by the disposition of Ca 2ϩ -ligating residues in the protein, but can also reflect additional interactions with nearby regions of the protein surface. The C-type CRDs are a subset of a larger family of protein modules, the C-type lectin-like domains (CTLDs) (4). Although the CTLDs share a common fold, many do not bind Ca 2ϩ and they often interact with ligands others than sugars.Profile analysis provides a powerful method for identifying CTLDs in proteins identified by genome sequence analysis. 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...

High glucose disrupts oligosaccharide recognition function via competitive inhibition: A potential mechanism for immune dysregulation in diabetes mellitus

“…In an insect model of obesity, disease is associated with elevated trehalose, increased lethargy and a specific parasitic infection, all implicitly in the absence of glycation (44). Insect C-type lectins with sugar-binding characteristics similar to those of mammals have been characterised and these proteins could potentially participate within processes regulating immunity, behaviour and metabolism (45). Other mammalian mannose-selective lectins exist, including the mannose receptor (CD206) and pulmonary surfactant protein A.…”

Revealing the anti-HRP epitope in Drosophila and Caenorhabditis

“…RNAi targeting the transcripts of FucTA was found to result in a decrease in anti-HRP reactivity of a Drosophila neural cell line [55]. Furthermore, an endogenous C-type receptor capable of binding to glycans with core α1-3-fucose was found in the model organism [56]. Around the same time, the first report of difucosylation on a particular protein was reported: one specific male sex peptide was found to carry such a structure [57], compatible with the non-neural staining of the Drosophila male reproductive system.…”

Drosophila C-type lectins enhance cellular encapsulation

“…This lectin, designated as DL1 (Drosophila lectin 1), bound to Gram-negative Escherichia coli and Erwinia chrysanthemi, but not to some other Gram-negative or Gram-positive bacteria (Tanji et al, 2006). CG2958 encodes a protein with a carboxyl-terminal C-type carbohydrate recognition domain (CRD) specific for fucose and mannose, and it is a potential endogenous receptor for neural-specific glycoproteins (Bouyain et al, 2002). CG1500, the furrow gene, is a member of the selectin subgroup, and it is involved in Drosophila eye and bristle development (Leshko-Lindsay and Corces, 1997).…”