Biosynthesis of sialylated and fucosylated selectin ligands of HL-60 cells in vitro. Midchain alpha3-fucose units inhibit terminal alpha6-sialylation but not alpha3-sialylation of polylactosamines.
Polylactosamines Neu5Ac alpha2-3'Lex beta1-3'Lex beta1-3'Lex and Neu5Ac alpha2-3'LNbeta1-3'Lex beta1-3'Lex [Lex, Gal beta1-4(Fuc alpha1-3)GlcNAc; LN, Gal beta1-4GlcNAc] decorate selectin counterreceptors in human HL-60 cells. Here, we show that HL-60 cell lysates catalyze distal alpha3-sialylation of LNbeta1-3'LNbeta1-3'LN and LNbeta1-3'Lex beta1-3'Lex efficiently, outlining two potential sets of biosynthetic pathways leading to the selectin ligands. In one set, alpha3-sialylation precedes internal fucosylation of the polylactosamine backbone, whereas in the other one, internal fucosylation is initiated before alpha3-sialylation. In contrast to alpha3-sialylation, LNbeta1-3'Lex beta1-3'Lex was alpha6-sialylated much less efficiently than LNbeta1-3'LNbeta1-3'LN by HL-60 cell lysates. Hence, internal fucosylation may regulate the extent of alpha6-sialylation of polylactosamines in these cells.
Natunen
J
J
Institute of Biotechnology and Department of Biosciences (Division of Biochemistry), University of Helsinki, Finland.
Parmanne
P
P
Helin
J
J
Aitio
O
O
Majuri
M L
ML
Niemelä
R
R
Renkonen
R
R
Renkonen
O
O
D000606:Amino Sugars / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D005643:Fucose / Q000378:metabolism*; D006031:Glycosylation; D018922:HL-60 Cells; D006801:Humans; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid / Q000378:metabolism*; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism; D011134:Polysaccharides / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification; D019087:Selectins / Q000378:metabolism*; D012799:Sialyltransferases / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity
D000606:Amino Sugars; D009844:Oligosaccharides; D011134:Polysaccharides; D019087:Selectins; C066929:polylactosamine; D005643:Fucose; D012799:Sialyltransferases; D019158:N-Acetylneuraminic Acid