Complex carbohydrates of cultured PC12 pheochromocytoma cells. Effects of nerve growth factor and comparison with neonatal and mature rat brain.

The composition and biosynthesis of glycoproteins, proteoglycans, and gangliosides have been studied in a clonal line of rat pheochromocytoma (PC12) cells. Glycoproteins account for approximately 78% of the glucosamine-labeled complex carbohydrates found in the culture medium, together with 17% chondroitin sulfate and 5% heparan sulfate. 10% of the glycoproteins but less than 1% of the proteoglycans are released by trypsin treatment of the cells, whose complex carbohydrates are composed of 93% glycoproteins, 1.3% chondroitin sulfate, 3.4% heparan sulfate, and 2.6% of mono- and disialogangliosides. Sequential lectin affinity chromatography and alkali treatment of glycopeptides prepared from the medium, trypsin-releasable, membrane, and cell-soluble glycoproteins demonstrated that in all of the subfractions large tri- and tetraantennary complex oligosaccharides account for 82 to 97% of those present in PC12 cell glycoproteins. Biantennary oligosaccharides account for approximately 2-6% of those in medium and trypsinate, as compared to 10-13% in the membrane and cell soluble glycoproteins, and there were large differences (ranging from 7 to 60%) in the proportions of biantennary oligosaccharides which are substituted by fucose on the core N-acetylglucosamine which is linked to asparagine. High mannose oligosaccharides are present predominantly in the cell membrane and soluble glycoproteins, where they account for 4 to 5% of the total glycoprotein labeling. In response to nerve growth factor (NGF), the PC12 cells extend long processes and acquire other properties similar to those of differentiated sympathetic neurons. Significant alterations were also observed in the complex carbohydrates of NGF-treated cells, the most striking of which were an almost 3-fold increase in labeled gangliosides and a 75% increase in trypsin-releasable glycoproteins. Cellular heparan sulfate decreased by 70% in response to NGF and increased by an equivalent amount in the culture medium, whereas an NGF-induced increase in chondroitin sulfate labeling occurred specifically in the cell membranes.