L-selectin interactions with novel mono- and multisulfated Lewis(x) 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-Le(x) and -Lea sequences. The binding to 3'- sialyl-Le(x) is strongly affected by the presence of 6-O-sulfate as found on oligosaccharides of the counter receptor, GlyCAM-1; 6-O-sulfate on the N- 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 Le(x) pentasaccharide sequence. We observe that, also with 3'-sulfo-Le(x), 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-Le(x) is on an extended di-N-acetyllactosamine backbone, additional 6- O-sulfates on the inner galactose and inner N-acetylglucosamine do not influence the binding. Although binding to the 6,3'-sulfo-Le(x) and 6- sulfo,3'-sialyl-Le(x) 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-Le(x) series are more potent than the corresponding 3'-sialyl-Le(x) series. Thus, for synthetic strategies to design therapeutic oligosaccharide analogs as antagonists of L-selectin binding, those based on the simpler 3'- sulfo-Le(x) (and also the 3'-sulfo-Lea) would seem most appropriate.