CORE FUCOSYLATION OF HIGH-MANNOSE-TYPE OLIGOSACCHARIDES IN GLCNAC TRANSFERASE I-DEFICIENT (LEC1) CHO CELLS

During studies on the fucosylation of endogenous proteins in parental (Pro5) and N-acetyl-D-glucosamine (GlcNAc) transferase I-deficient (Led) Chinese hamster ovary (CHO) cells, we observed that Led cells incorporate similar to 10-fold less [H-3]fucose into macromolecules than Pro5 cells. Interestingly, most of the labelled oligosaccharides from both cell types could be released from the macromolecules by digestion with peptide N-glycosidase F (PNGase F). This was unexpected for Lec1 cells because they do not synthesize complex- or hybrid-type N-glycans. Structural analyses of the fucosylated oligosaccharides from Lec1 cells showed the fucose to be in an alpha 1,6 linkage to the core GlcNAc of relatively small oligomannose N-glycans (Man(4)GlcNAc(2) and Man(5)GlcNAc(2), where Man is D-mannose). Comparing the sizes of oligomannose N-glycans from Pro5 and Led cells demonstrated a much higher proportion of the small (Man(4)GlcNAc(2) and Man(5)GlcNAc(2)) oligomannase species in Led cells. These results suggest that the core alpha 1,6 fucosyltransferase will fucosylate small (Man(4)-Man(5)GlcNAc(2)), but not large (Mans(8)-Man(9)GlcNAc(2)) oligomannose N-glycans.