Characterization of cellular oligosaccharides from normal and cystic fibrotic fibroblasts using sequential...

A method was developed for obtaining detailed oligosaccharide profiles from [2-3H]mannose- or [6-3H]fucose-labeled cellular glycoproteins. The oligosaccharides were segregated first according to class, using endo-beta-N-acetylglucosaminidase H (Endo H) to release the high mannose species, and then with peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase (PNGase F), which provided a complete array of complex oligosaccharide chains. The high mannose and complex oligosaccharides were fractionated subsequently according to net negative charge on QAE-Sephadex. High resolution gel filtration on TSK HW-40(S) resolved the neutral high mannose population into species of the type Man9-5 N-acetylglucosamine. Desialylation of the complex chains with neuraminidase allowed resolution of these oligosaccharides into their corresponding asialo bi-, tri-, and tetraantennary species. Fibroblasts from normal and cystic fibrosis cells were analyzed for differences in their glycosylation patterns using these techniques. Over 95% of the [2-3H]mannose-labeled glycoproteins were susceptible to the combined glycosidase digestions, but no difference in either the high mannose or complex oligosaccharides were observed. Nonetheless, the methodology developed in this study provides an important new approach for investigating oligosaccharides of different cell types and variants of the same type. Metabolic changes induced in cellular glycoproteins, as illustrated by use of the processing inhibitor swainsonine, demonstrated the versatility of this procedure for investigating questions relating to glycoprotein structure and enzyme specificity. Thus, by employing a variation of this method, it was possible to confirm the location of fucose in the core of PNGase F-released hybrid oligosaccharides by the subsequent release with Endo H of the disaccharide, fucosyl-N-acetylglucosamine.