Sulfation of the tumor cell surface sialomucin of the 13762 rat mammary adenocarcinoma

✍ Scribed by Steven R. Hull; Kermit L. Carraway

• Publisher: John Wiley and Sons
• Year: 1989
• Tongue: English
• Weight: 747 KB
• Volume: 40
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.240400108

✦ Synopsis

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 0-linked oligosaccharide chains. We have used this system to investigate the 0-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 borohydride elimination, anion exchange HPLC, and ion-suppression HPLC. From structural analyses S-1 is proposed to be a branched, sulfated trisaccharide -04S-GlcNAc/31 ,6-(Gal/?1,3)-GalNAc and S-2 its sialylated derivative -0,s-GlcNAc/31,6-(NeuAccu2,3-Gal/31,3)-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 GlcNAc/31,6-(Gal/31,3)-GalNAc and sialylated derivative GlcNAc/31,6-(NeuAca2,3-Gal/?l,3)-GalNAc. These data suggest that sulfation of ASGP-1 is an intermediate synthetic step, which competes with /3-1,4-galactosylation for the trisaccharide intermediate and thus occurs in the same compartment as /3-1 ,4-galactosylation. Moreover, sulfation precedes sialylation, but the two are rapidly successive kinetic events in the oligosaccharide assembly of ASGP-1.