Differentiation-dependent glycosylation of gp190, an oncofetal crypt cell antigen expressed by Caco-2 cells

gp190 is a glycoprotein expressed on the cell surface of several human colo n carcinoma cells in culture, on epithelial cells of fetal colon, but not o n the normal mucosa of adult colon; thus it is referred to as an oncofetal crypt cell antigen. We report the characterisation of O-linked glycans carr ied by gp190 synthesised by [H-3]glucosamine-labelled Caco-2 cells at the c onfluence (undifferentiated cells) and at three weeks of postconfluence (di fferentiated cells). By using a specific monoclonal antibody, gp190 was iso lated and analysed by sodium dodecyl sulphate-polyacrylamide gel electropho resis. The mobility of gp190 from differentiated cells was found to be lowe r than that from undifferentiated cells, suggesting a more extensive glycos ylation process in the former glycoprotein. The major results of the glycan characterisation have been as follows: (i) gp190 carries mainly, if not ex clusively, O-linked glycans with the core-2 structure; (ii) the elongation with N-acetyllactosamine units of the Gal beta1,4GlcNAc beta1,6(Gal beta1,3 )GalNAc tetrasaccharide predominates in gp190 synthesised by differentiated cells, whereas the direct alpha2,3sialylation of the tetrasaccharide is pr evalent in gp190 synthesised by undifferentiated cells. The increment in th e core-2 beta1,6GlcNAc-transferase activity under the Caco-2 differentiatio n process may be relevant in producing the larger occurrence of polylactosa minoglycans in gp190 from differentiated cells. Since no change in the acti vity of the alpha2,3sialyltransferases upon cell differentiation was observ ed, we suggest that the lower alpha2,3sialylation in gp190 synthesised by p olarised cells might be due to a changed transit-rate through the distal Go lgi apparatus.