STUDY OF O-SIALYLATION OF GLYCOPROTEINS IN C6 GLIOMA-CELLS TREATED WITH RETINOIC ACID

When treated with retinoic acid in vivo, C6 glioma cells show an enhan cement of CMP-Neu5Ac:Gal beta 1-3 GalNAc-R alpha-2,3 sialyltransferase activity. A 300 kDa glycoprotein was detected by lectin affinoblottin g in retinoic acid-treated C6 cells which stained weakly or not at all in control cells. Comparative studies with different lectins demonstr ated that this glycoprotein contains alpha 2,3 Neu5Ac Gal-GalNAc O-gly can moieties. Cultures in the presence of an inhibitor of O-glycan syn thesis (N-acetylgalactosaminide alpha-O-benzyl) demonstrated that enha ncement of staining of the 300 kDa glycoprotein was not due to the inc rease of the alpha 2,3 sialyltransferase but to the de novo synthesis of the polypeptide chain of this glycoprotein.