Structural Features of the Nerve Growth Factor Inducible Large External Glycoprotein of PC12 Pheochromocytoma Cells and Brain

Abstract: We have examined the oligosaccharide structure of a major M_r= 230,000 cell surface glycoprotein from rat PC12 pheochromocytoma cells, and of the immunochemically cross‐reactive species present in brain. In response to nerve growth factor (NGF) the PC12 cells extend long processes and acquire other properties similar to those of differentiated sympathetic neurons. These morphological changes are accompanied by a 3‐ to 5‐fold increase in the concentration and labeling of this cell surface glycoprotein, which has previously been named the NGF‐inducible large external, or NILE, glycoprotein. Tri‐ and tetraantennary complex oligosaccharides are the predominant carbohydrate units present in the NILE glycoprotein from both brain and PC12 cells, where they represent 77–90% of the biosynthetically labeled oligosaccharides. Most of these are not substituted by fucose on the core N‐acetylglucosamine which is linked to asparagine, and are accompanied by smaller proportions of biantennary and high‐mannose oligosaccharides. Sequential lectin‐agarose affinity chromatography employing concanavalin A, lentil lectin, and the leukoagglutinating lectin of Phaseolus vulgaris, together with neuraminidase treatment of the fractionated glycopeptides, demonstrated a moderate degree of microheterogeneity among the predominant tri‐ and tetraantennary oligosaccharide units with respect to the presence of core fucose, outer galactose and sialic acid residues, and the substitution positions on the α‐linked mannose residues. NGF treatment of the PC12 cells had no significant effect on the oligosaccharide structure of the NILE glycoprotein. The greater molecular size of the PC12 cell NILE glycoprotein as compared to the immunochemically cross‐reactive species present in brain (M_r= 205,000) is apparently due to the greater size of the PC12 cell tri‐ and tetraantennary complex oligosaccharides.