Release of chromaffin granule glycoproteins and proteoglycans from potassium-stimulated PC12 pheochromocytoma cells.
Cultured PC12 pheochromocytoma cells were labeled with [3H]glucosamine, and the glycoproteins and proteoglycans released following potassium-induced depolarization were fractionated and characterized. Exposure of PC12 cells for 20 min to a high concentration of potassium (51.5 mM in Krebs-Ringers-HEPES buffer) results in an approximately sixfold increase in the release of labeled glycoproteins and proteoglycans, compared to incubation in physiological levels of potassium (6 mM). The released complex carbohydrates include chromogranins, dopamine beta-hydroxylase, and two chondroitin sulfate/heparan sulfate proteoglycan fractions, which together account for 7.4% of the soluble cell radioactivity. The chromogranins contained galactosyl(beta 1 leads to 3)N-acetylgalactosamine, as well as several mono- and disialyl O-glycosidically-linked oligosaccharides, and the tetrasaccharide AcNeu(alpha 2 leads to 3)Gal(beta 1 leads to 3)[AcNeu(alpha 2 leads to 6)] GalNAcol, obtained by alkaline borohydride treatment of the chromogranin glycopeptides, accounted for almost half of the total chromogranin labeling. The proteoglycan fractions varied in their relative proportions of chondroitin sulfate (23-68%), heparan sulfate (16-23%), and glycoprotein oligosaccharides (16-54%), which are of the tri- and tetraantennary and O-glycosidic types. As previously found in the case of proteoglycans from bovine chromaffin granules, the more acidic species has a considerably higher proportion of carbohydrate in the form of sulfated glycosaminoglycans.
D000310:Adrenal Gland Neoplasms / Q000378:metabolism*; D000818:Animals; D002241:Carbohydrates / Q000032:analysis; D002460:Cell Line; D002837:Chromaffin Granules / Q000378:metabolism*; D002838:Chromaffin System / Q000378:metabolism*; D002864:Chromogranins / Q000302:isolation & purification; D006023:Glycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D010673:Pheochromocytoma / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology*; D011509:Proteoglycans / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats
D002241:Carbohydrates; D002864:Chromogranins; D006023:Glycoproteins; D011509:Proteoglycans; D011188:Potassium