Sulfated glycolipids are ligands for a lymphocyte homing receptor, L-selectin (LECAM-1), Binding epitope in sulfated sugar chain

Abstract

Specific sugar ligands which bind to rat L-selectin (LECAM-1, lymphocyte homing receptor)-IgG chimera were investigated by thin-layer chromatography-binding assay and ELISA. Rat L-selectin-IgG bound to native sulfated glycolipids such as sulfatide (I3SO3-GalCer), seminolipid, SM3(II3SO3-LacCer), SB2(III3SO3,II3SO3-Gg3Cer), SB1a (IV3SO3,II3SO3-Gg4Cer). The binding activity of the SM2 (II3SO3-Gg3Cer) carrying the internal sulfated Gal was very low, indicating that non-reducing terminal SO3H-3Gal beta 1- structure is essential for the binding. The reactivity of sulfatide was higher than that of sialyl Le(x) [Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3Gal beta 1-4Glc beta 1-Ceramide] either in the presence of 1 mM Ca2+ or 1 mM Ca2+ and 5 mM EGTA. All the non-fucosylated gangliosides including ganglio-series and lacto-series type I and II chains tested gave a negative reaction. Neutral glycosphingolipids tested were all negative. Binding assay using synthetic sulfatide analogs indicated that the L-selectin-binding to its sulfated sugar ligands is position specific and depends on the number of the sulfate group, i.e., (SO3)3-3,4,6Gal- > (SO3)2-3,6Gal- > SO3-3Gal- > SO3-3Glc- > SO3-6Gal- > SO3-2Gal-. Lower reactivity of the chimera to SO3-3Glc-rather than SO3-3Gal- indicates that the chimera recognizes the configuration of hydroxyl group linked to the 4 carbon atom of the pyranose ring in galactose.