L-selectin Interactions with Novel Mono- and Multisulfated Lewisx Sequences in Comparison with the Potent Ligand 3′-Sulfated Lewisa

Abstract The cell adhesion molecule L-selectin binds to 3′-sialyl-Lewis (Le)x and -Lea and to 3′-sulfo-Lex and -Lea sequences. The binding to 3′-sialyl-Lex is strongly affected by the presence of 6-O-sulfate as found on oligosaccharides of the counter receptor, GlyCAM-1; 6-O-sulfate on theN-acetylglucosamine (6-sulfation) enhances, whereas 6-O-sulfate on the galactose (6′-sulfation) virtually abolishes binding. To extend knowledge on the specificity of L-selectin, we have investigated interactions with novel sulfo-oligosaccharides based on the Lex pentasaccharide sequence. We observe that, also with 3′-sulfo-Lex, the 6-sulfation enhances and 6′-sulfation suppresses L-selectin binding. The 6′-sulfation without 3′-sialyl or 3′-sulfate gives no binding signal with L-selectin. Where the 6-sulfo,3′-sialyl-Lex is on an extended di-N-acetyllactosamine backbone, additional 6-O-sulfates on the inner galactose and innerN-acetylglucosamine do not influence the binding. Although binding to the 6,3′-sulfo-Lex and 6-sulfo,3′-sialyl-Lex sequences is comparable, the former is a more effective inhibitor of L-selectin binding. This difference is most apparent when L-selectin is in paucivalent form (predominantly di- and tetramer) rather than multivalent. Indeed, as inhibitors of the paucivalent L-selectin, the 3′-sulfo-Lex series are more potent than the corresponding 3′-sialyl-Lex series. Thus, for synthetic strategies to design therapeutic oligosaccharide analogs as antagonists of L-selectin binding, those based on the simpler 3′-sulfo-Lex (and also the 3′-sulfo-Lea) would seem most appropriate.