Poly-N-acetyllactosaminyl O-glycans attached to leukosialin. The presence of sialyl Le(x) structures in O-glycans.
Poly-N-acetyllactosamine extension has been found in O-glycans in addition to N-glycans and glycosphingolipids. Attempts were made in HL-60 and K562 cells to determine the amount of poly-N-acetyllactosaminyl O-glycans in the major sialoglycoprotein, leukosialin. Leukosialin was immunoprecipitated from [3H]glucosamine-labeled HL-60 and K562 cells. Glycopeptides were prepared by Pronase digestion, and O-glycan-containing glycopeptides were isolated by affinity chromatography using Jacalin-agarose. The glycopeptides bound to Jacalin-agarose and those unbound were treated with alkaline borohydride, and the released O-glycans were fractionated by Bio-Gel P-4 filtration. Sequential glycosidase digestion of the O-glycans, with or without pretreatment by fucosidase or neuraminidase, revealed the following conclusions. 1) Leukosialin from HL-60 cells contains about 1-2 poly-N-acetyllactosaminyl O-glycan chains/molecule. 2) About 50% of these poly-N-acetyllactosaminyl O-glycans contain sialyl Le(x) termini, NeuNAc alpha 2-->3Gal beta 1-->4 (Fuc alpha 1-->3)GlcNAc beta 1-->R. The amount of sialyl Le(x) structure in leukosialin is roughly equivalent to that on cell surfaces of HL-60 cells. 3) Leukosialin from K562 cells, on the other hand, contains no detectable amount of poly-N-acetyllactosaminyl O-glycans. 4) The presence of poly-N-acetyllactosamine in O-glycans is dependent on the core 2 beta 1,6-N-acetylglucosaminyl transferase. 5) Jacalin-agarose binds to sialylated small oligosaccharides such as NeuNAc alpha 2-->3Gal beta 1-->3(NeuNAc alpha 2-->6) GalNAc but not the hexasaccharide NeuNAc alpha 2-->3Gal beta 1-->3(NeuNAc alpha 2-->3Gal beta 1-->4GlcNAc beta 1-->6) GalNAc. These results indicate that the formation of polylactosaminyl O-glycans and sialyl Le(x) structure in O-glycans is dependent on the core 2 formation.
Maemura
K
K
La Jolla Cancer Research Foundation, Cancer Research Center, California 92037.
Fukuda
M
M
D015703:Antigens, CD / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D006020:Glycopeptides / Q000737:chemistry / Q000302:isolation & purification; D006026:Glycoside Hydrolases; D016695:Glycosyltransferases / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive; D015473:Leukemia, Promyelocytic, Acute; D051917:Leukosialin; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry* / Q000302:isolation & purification; D011134:Polysaccharides / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D012795:Sialoglycoproteins / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D014407:Tumor Cells, Cultured
D015703:Antigens, CD; D006020:Glycopeptides; D051917:Leukosialin; D009844:Oligosaccharides; D011134:Polysaccharides; C465014:SPN protein, human; D012795:Sialoglycoproteins; C037199:poly-N-acetyllactosamine; D016695:Glycosyltransferases; D006026:Glycoside Hydrolases