Carbohydrate recognition molecules interacting with the neural specific N-glycan modification in invertebrates

In Drosophila, anti-horseradish peroxidase (anti-HRP) antibodies have been used for many years as a specific probe to stain neurons and neural pathways. A set of neuronal surface glycoproteins, belonging to the highly conserved family of cell adhesion and signalling molecules taking part in processes of neuronal guidance, have been shown immunologically (albeit not structurally at the glycan level) to bear the carbohydrate anti-HRP epitope. In Caenorhabditis and other invertebrates anti-HRP binding has also been reported. Such antibody binding is concluded to be due to the presence of core a1,3-fucosylated N-glycans. Recently, a C-type lectin (encoded by the CG2958 gene), initially identified by homology searching of the Drosophila genome, has been shown to bind core a1,3-fucosylated N-glycans; however, it is unknown where in the fly it is present and whether its expression is compatible with the neural staining pattern found for anti-HRP. It is proposed to probe its expression by in situ hybridisation and immunofluorescence microscopy, as well as to search for other endogenous fly receptors specific for core a1,3-fucosylated N-glycans by use of neoglycoconjugates. Furthermore, studies on homologous lectins from other invertebrates, specifically Caenorhabditis, will be initiated either using recombinant lectins or by searching for them by affinity purification. Since principles of neuronal guidance in vertebrates and invertebrates are similar, the obtained findings may help in general to better understand interactions between carbohydrates and ligand molecules involved in the assembly of the nervous system.