Inhibition of the glycosylation and alteration in the intracellular trafficking of mucins and other glycoproteins by GalNAcalpha-O-bn in mucosal cell lines: an effect mediated through the intracellular synthesis of complex GalNAcalpha-O-bn oligosaccharides.
To address the function of carbohydrates in mucins, GalNAcalpha-O-bn has been used in in vivo experiments on several human mucosal cultured cells as a potential competitor of the glycosylation of N-acetylgalactosamine residues. GalNAcalpha-O-bn is metabolized by glycosyltransferases expressed in the cell, and give rise to different internal derivatives starting in particular from the formation of the disaccharide Galalpha1-3GalNAcalpha-O-bn. In this line, GalNAcalpha-O-bn exposure inhibits peripheral glycosylation according a cell-type specific manner. The metabolic alterations are very important in HT-29 cell line, leading to a massive accumulation of GalNAcalpha-O-bn oligosaccharide derivatives and to a strong inhibition of the terminal elongation of O-glycans by alpha2,3 sialyltransferase ST3Gal I. GalNAcalpha-O-bn treatment also induced alterations at the cellular level, exhibiting a large scale in HT-29 cells, i.e. 1) an inhibition of mucin secretion, 2) a blockade in the targeting of some membrane glycoproteins (brush border glycoproteins such as dipeptidylpeptidase IV, carcinoembryonic antigen and the mucin-like glycoprotein MUC1, and the basolateral cell adhesion molecule CD44), 3) an inhibition in the processing of lysosomal enzymes. Morphological abnormalities have been evidenced in GalNAcalpha-O-bn treated cells, in particular the accumulation of numerous intracellular vesicles in HT-29 cells. Taken together, these data suggest that O-glycosylation might be involved in the regulation of the targeting of O-glycosylproteins through carrier vesicles.
Gouyer
V
V
Unite INSERM 377, Place de Verdun, 59045 Lille cedex, France.
Leteurtre
E
E
Zanetta
J P
JP
Lesuffleur
T
T
Delannoy
P
P
Huet
G
G
D000116:Acetylgalactosamine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology*; D001593:Benzyl Compounds / Q000378:metabolism / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D018938:Caco-2 Cells; D006031:Glycosylation / Q000187:drug effects; D019073:HT29 Cells; D006801:Humans; D008247:Lysosomes / Q000187:drug effects / Q000201:enzymology; D008562:Membrane Glycoproteins / Q000187:drug effects / Q000378:metabolism; D009077:Mucins / Q000187:drug effects* / Q000378:metabolism
D001593:Benzyl Compounds; D008562:Membrane Glycoproteins; D009077:Mucins; C080739:benzyl-alpha-N-acetylgalactosamine; D000116:Acetylgalactosamine