Structure of the O-glycans in GlyCAM-1, an endothelial-derived ligand for L-selectin.
L-selectin, the leukocyte selectin, mediates the carbohydrate-dependent attachment of circulating leukocytes to endothelium, preceding emigration into tissues. It functions in inflammatory leukocyte trafficking and in lymphocyte homing to lymph nodes. From previous work, the binding of L-selectin to endothelial-associated glycoprotein ligands, GlyCAM-1 and CD34, requires oligosaccharide sialylation, sulfation, and probably fucosylation. We have recently identified a major capping group in GlyCAM-1 as 6' sulfated sialyl Lewis x, a novel structure which potentially satisfies all of these requirements. In the present study, we define the complete structure of beta-eliminated chains of GlyCAM-1 using metabolic radiolabeling, plant lectin binding, and glycosidase digestions in conjunction with high pH anion-exchange chromatography. The majority of the O-glycans in GlyCAM-1 contain the T-antigen, i.e. Gal beta 1-->3GalNAc, which is incorporated into the core-2 structure, i.e. Gal beta 1-->3[GlcNAc beta 1-->6]GalNAc or larger core structures with additional GlcNAc residues. The structures of two O-glycans, based on core-2, were determined to be: [sequence: see text] The implications of these structures and more complex O-glycans for binding by L-selectin are discussed.
Hemmerich
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S
Department of Anatomy, University of California, San Francisco 94143-0452, USA.
Leffler
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Rosen
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SD
D000595:Amino Acid Sequence; D000818:Animals; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002850:Chromatography, Gel; D004730:Endothelium, Vascular / Q000378:metabolism*; D005643:Fucose / Q000737:chemistry; D006031:Glycosylation; D019041:L-Selectin; D037102:Lectins / Q000378:metabolism; D007962:Leukocytes / Q000166:cytology; D008024:Ligands; D008198:Lymph Nodes / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009077:Mucins / Q000737:chemistry* / Q000378:metabolism; D019158:N-Acetylneuraminic Acid; D009924:Organ Culture Techniques; D019887:Peanut Agglutinin; D010446:Peptide Fragments / Q000276:immunology; D011134:Polysaccharides / Q000737:chemistry*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D012794:Sialic Acids / Q000737:chemistry; D013431:Sulfates / Q000737:chemistry
D015815:Cell Adhesion Molecules; D037102:Lectins; D008024:Ligands; D009077:Mucins; D019887:Peanut Agglutinin; D010446:Peptide Fragments; D011134:Polysaccharides; D012794:Sialic Acids; D013431:Sulfates; D019041:L-Selectin; C075185:sulfated glycoprotein p50; D005643:Fucose; D019158:N-Acetylneuraminic Acid