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 Nacetyllactosamine (LacNAc, Gal␤1-4Glc-NAc␤1-3) 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 selectinmediated 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 Pselectin, adhesion. The data support the conclusion that on human neutrophils the glycosphingolipid NeuAc␣2-3Gal IntroductionMultiple mechanisms ensure that granulocytes efficiently move into tissues when and where needed. 1 Activation of the blood vessel endothelium results in circulating granulocytes tethering and rolling, stopping, flattening, and squeezing into the surrounding tissue. A 3-step model describes leukocyte extravasation 2 : (1) Eand P-selectin on activated endothelia bind to glycans on leukocytes, initiating tethering and rolling under the shear stress of blood flow (L-selectin on some leukocytes contributes to this process).(2) Upon tethering, leukocytes are exposed to chemoattractants (eg, chemokines) generated by activated endothelium and tissueresident cells, resulting in integrin mobilization. (3) Strong cell adhesion is mediated by leukocyte integrin binding to immunoglobulin superfamily proteins on the endothelium. Each step is required for recruitment of leukocytes; blocking any one diminishes inflammation. Despite exceptions, 3 this scheme is broadly applicable.Each selectin (E-, L-, and P-) 4 has a carbohydrate recognition domain that mediates binding to specific glycans on apposing cells. They have remarkably similar protein folds and carbohydrate binding residues, 5 leading to overlap in the glycans to which they bind. Nevertheless, each selectin has distinct receptors to which it binds with high affinity.Selectins bind to the sialyl Lewis x (SLe x ) determinant "NeuAc␣2-3Gal␤1-4(Fuc␣1-3)GlcNAc." [6][7][8][9] However, SLe x , per se, does not constitute an effective selectin receptor. [10][11][12] Instead, SLe x and related sialylated, fucosylated glycans are components of more ext...

The cholesterol-dependent cytolysins pneumolysin and streptolysin O require binding to red blood cell glycans for hemolytic activity

“…Attempts were made to inhibit Ply cytotoxicity against human PMNs and PBMCs with sLeX, but no inhibition was observed. The failure of sLeX to inhibit Ply cytotoxicity against these cells may be due to the overload of sLeXcontaining glycoproteins and glycolipids on the surface of human PMNs, particularly neutrophils (39,40), or to the presence of alternative receptors for Ply on human leukocytes. However, sLeX did inhibit cytotoxicity of Ply for A549 (human alveolar) cells, suggesting that this glycan present on glycolipids and/or glycoproteins may serve as a receptor for Ply on cell types other than RBCs.…”

“…L-selectin is found on most leukocytes and binds to glycoproteins carrying an O-linked sLeX with a sulfate on the 6-hydroxyl of the GlcNAc residue, such as glycosylation-dependent cell adhesion molecule 1 (38). E-selectin is found on activated endothelium and appears to bind sLeX on sialylated glycosphingolipids on human neutrophils (39). It has also been reported that Mac1 (CD11b/ CD18) of human neutrophils, a major membrane protein decorated with sLeX, binds to E-selectin and that the sLeX moieties are critical for this interaction (40).…”

Silencing α1,3-Fucosyltransferases in Human Leukocytes Reveals a Role for FUT9 Enzyme during E-selectin-mediated Cell Adhesion

“…In particular, E-selectin ligands on mouse but not human neutrophils are pronase-sensitive (7,8). 3 In this regard, Nimrichter et al (47) suggest that a relatively minor monosialylated, polyfucosylated glycolipid with poly-lactosamine units NeuAc␣␣2,3Gal␤1,4GlcNAc␤1,3[Gal␤1,4 (Fuc␣1,3)GlcNAc␤1,3] 2 [Gal␤1,4GlcNAc␤1,3] 2 Gal␤1,4Glc␤Cer…”

G-CSF Induces Membrane Expression of a Myeloperoxidase Glycovariant that Operates as an E-selectin Ligand on Human Myeloid Cells

“…These findings suggest that G-CSF stimulates de novo expression of HECA-452-reactive moieties predominantly on N-glycans. The residual HECA-452 determinants displayed in the presence of DMJ likely reflect the native contribution(s) of sialofucosylated O-linked glycans found on both glycoproteins and glycolipids (18,19).…”