E-selectin receptors on human leukocytes

Abstract

Selectins on activated vascular endothelium mediate inflammation by binding to complementary carbohydrates on circulating neutrophils. The human neutrophil receptor for E-selectin has not been established. We report here that sialylated glycosphingolipids with 5 N-acetyllactosamine (LacNAc, Galbeta1-4GlcNAcbeta1-3) repeats and 2 to 3 fucose residues are major functional E-selectin receptors on human neutrophils. Glycolipids were extracted from 10(10) normal peripheral blood human neutrophils. Individual glycolipid species were resolved by chromatography, adsorbed as model membrane monolayers and selectin-mediated cell tethering and rolling under fluid shear was quantified as a function of glycolipid density. E-selectin-expressing cells tethered and rolled on selected glycolipids, whereas P-selectin-expressing cells failed to interact. Quantitatively minor terminally sialylated glycosphingolipids with 5 to 6 LacNAc repeats and 2 to 3 fucose residues were highly potent E-selectin receptors, constituting more than 60% of the E-selectin-binding activity in the extract. These glycolipids are expressed on human blood neutrophils at densities exceeding those required to support E-selectin-mediated tethering and rolling. Blocking glycosphingolipid biosynthesis in cultured human neutrophils diminished E-selectin, but not P-selectin, adhesion. The data support the conclusion that on human neutrophils the glycosphingolipid NeuAcalpha2-3Galbeta1-4GlcNAcbeta1-3[Galbeta1-4(Fucalpha1-3)GlcNAcbeta1-3](2)[Galbeta1-4GlcNAcbeta1-3](2)Galbeta1-4GlcbetaCer (and closely related structures) are functional E-selectin receptors.