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Sulfation of the tumor cell surface sialomucin of the 13762 rat mammary adenocarcinoma
Author(s) -
Hull Steven R.,
Carraway Kermit L.
Publication year - 1989
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.240400108
Subject(s) - sulfation , trisaccharide , chemistry , glycosylation , biochemistry , stereochemistry
ASGP‐1, the major cell surface sialomucin of the 13762 ascites rat mammary adenocarcinoma, is at least 0.5% of the total ascites cell protein and has sulfate on 20% of its O‐linked oligosaccharide chains. We have used this system to investigate the O‐glycosylation pathway in these cells and to determine the temporal relationship between sulfation and sialylation. The two major sulfated oligosaccharides (S‐1 and S‐2) were isolated as their oligosaccharitols by alkaline boro‐hydride elimination, anion exchange HPLC, and ion‐suppression HPLC. From structural analyses S‐1 is proposed to be a branched, sulfated trisaccharide − O 4 S‐GlcNAcβ1,6‐(Galβ1,3)‐GalNAc and S‐2 its sialylated derivative − O 4 S‐GlcNAcβ1,6‐(NeuAcα2,3‐Galβ1,3)‐GalNac. Pulse labeling with sulfate indicated that sulfation occurred primarily on a form of ASGP‐1 intermediate in size between immature and mature sialomucin. Pulse‐chase analyses showed that the intermediate could be chased into mature ASGP‐1. The concomitant conversion of S‐1 into S‐2 had a half‐time of less than 5 min. Monensin treatment of the tumor cells led to a 95% inhibition of sulfation with the accumulation of unsulfated trisaccharide GlcNAcβ1,6‐(Galβ1,3)‐GalNAc and sialylated derivative GlcNAcβ1,6‐(NeuAcα2,3‐Galβ1,3)‐GalNac. These data suggest that sulfation of ASGP‐1 is an intermediate synthetic step, which competes with β‐1,4‐galactosylation for the trisaccharide intermediate and thus occurs in the same compartment as β‐1,4‐galactosylation. Moreover, sulfation precedes sialylation, but the two are rapidly successive kinetic events in the oligosaccharide assembly of ASGP‐1.