Dynamic alterations of membrane tethers stabilize leukocyte rolling on P-selectin.

Leukocytes rolling on selectins extrude thin membrane tethers that might stabilize rolling velocities despite marked alterations in wall shear stress. To test this hypothesis, we used differential interference contrast videomicroscopy to visualize formation and breakage of membrane tethers as neutrophils rolled on P-selectin under flow. Neutrophils rapidly increased tether number as wall shear stress rose and decreased tether number as wall shear stress declined.

N-terminal residues in murine P-selectin glycoprotein ligand-1 required for binding to murine P-selectin.

P-selectin binds to the N-terminal region of human P-selectin glycoprotein ligand-1 (PSGL-1). For optimal binding, this region requires sulfation on 3 tyrosines and specific core-2 O-glycosylation on a threonine. P-selectin is also thought to bind to the N terminus of murine PSGL-1, although it has a very different amino acid sequence than human PSGL-1.

Discordant expression of selectin ligands and sialyl Lewis x-related epitopes on murine myeloid cells.

Murine leukocytes are thought to express alpha2-3-sialylated and alpha1-3-fucosylated selectin ligands such as sialyl Lewis x (sLe(x)), although monoclonal antibodies (mAbs) to sLe(x) or Le(x) reportedly do not bind to murine leukocytes. We observed that P- and E-selectin bound to pronase-sensitive ligands on murine monocytic WEHI-3 cells and murine neutrophils, indicating that the ligands for both selectins are glycoproteins. CSLEX-1, HECA-452, and other widely used mAbs to sLe(x) and Le(x) did not bind to WEHI-3 cells and bound at very low levels to murine neutrophils.