Structural variations of O-linked oligosaccharides present in leukosialin isolated from erythroid, myeloid, and T-lymphoid cell lines.

Abstract

Structuresof 0-linked oligosaccharides of leukosialin isolated from K562 erythroid, HL-60 promyelocytic, and HSB-2 T-lymphoid cell lines were examined.Leukosialin was isolated by specific immunoprecipitation from cells which were metabolically labeled with [3H]glucosamine, and glycopeptides were isolated after Pronase digestion.0-Linked oligosaccharides were released by alkaline borohydride treatment, and the structures of purified oligosaccharides were elucidated by specific exoglycosidase digestion, Smith degradation, and methylation anaylsis.Oligosaccharides from K562 cells were found to be GalNAcOH, Gal@1+ 3GalNAcOH, NeuNAca2+6GalNAcOH, NeuNAcaZ+ 3Galb1+3GalNAcOH, Gal/31+3(NeuNAcaZ+G)Gal- NAcOH, and NeuNAca2+3Gav1+3(NeuNAcaZ+ 6)GalNAcOH.On the other hand, oligosaccharides from HL-60 and HSB-2 cells were found to be Neu-NAca2+3Galj31+3GalNAcOH, NeuNAca2+3Gavl+ 4GlcNAc~1+6(Ga~1+3)GalNAcOH, Gal@1+4Glc-NAc@1+6(NeuNAca2+3Gal@1+3)GalNAcOH, and NeuNAca2+3Gal~1+4GlcNAc@1+6(NeuNAc~2+3-Galj31+3)GalNAcOH.These results clearly indicate that leukosialin can be differently glycosylated with 0-linked chains, and each erythroid or myeloid (and T-lymphoid) cell line expresses a characteristic set of 0-linked oligosaccharides which differ in core structures as well as in sialylation. ~ ~~~ ~In the preceding paper (I), we showed that various leukemic cell lines express a family of sialoglycoproteins which are closely related to each other.Although these glycoproteins isolated from different cell lines show significant differences in molecular weight, as estimated by SDS-polyacrylamide gel electrophoresis, their polypeptide portions appear to be very similar or the same, based on their size and reactivity with antibodies.These glycoproteins, termed leukosialin, were shown to contain a large number of 0-linked oligosaccharides and one asparagine-linked oligosaccharide/molecule (1).In this study, we present the evidence that the apparent differences in molecular weight of leukosialin in different cell lines are due to variations in 0-linked oligosaccharides; the