Structures of the O-linked oligosaccharides of the major cell surface sialoglycoprotein of MAT-B1 and MAT-C1 ascites sublines of the 13762 rat mammary adenocarcinoma
Structures of the principal O-glycosides from the major cell surface sialoglycoprotein (ASGP-1) of the MAT-B1 and MAT-C1 ascites sublines of the 13762 rat mammary adenocarcinoma have been determined. Oligosaccharitols were released by alkaline borohydride treatments of ASGP-1 and purified by gel filtration, DEAE-Sephadex ion exchange chromatography, and high performance liquid chromatography. On the basis of carbohydrate composition, methylation analysis, periodate oxidation, and exoglycosidase digestion, the five major oligosaccharides released by mild alkaline borohydride were assigned the following structures: Component II-3: (NeuAcα2→3Galβ1→4GlcNAcβ1→6)Ga1NAcOH(3←1βGa13←2αNeuAc); III-2a: (Ga1β1→4GlcNAcβ1→Ga1NAcOH(3←1βGa13←2αNeuAc); III-2c: (Ga1α1→3Ga1β1→4G1cNAcβ1→6)Ga1NAcOH(3←1βGa13←2αNeuAc); IV-1a: (Ga1β1→4G1cNAcβ1→6)Ga1NAcOH(3←1βGa1); IV-1c: (Ga1α1→3Ga1β1→4G1cNAcβ1→6)Ga1NAcOH(3←1βGa1). Fucosylated derivatives of III-2a, IV-1a, and IV-Ic were found in smaller amounts with the fucose tentatively assigned to the 2-position of the lactosamine galactose. Components II-3, III-2a and the fucosylated derivative of III-2A were found in both MAT-B1 and MAT-C1 sublines. The α-galactosides were found in detectable quantities only in subline MAT-B1. Oligosaccharides from MAT-C1 cells were enriched in sialic acid when compared to those from MAT-B1 cells. These results suggest that the 13762 ascites sublines, which bear different oligosaccharides, will provide models useful for the investigation of mechanisms regulating the expression of structures of the larger O-linked oligosaccharides.