MONOSPECIFIC AND COMMON GLYCOPROTEIN LIGANDS FOR E-SELECTIN AND P-SELECTIN ON MYELOID CELLS

E- and P-selectin are inducible cell adhesion molecules on endothelial cells, which function as Ca2+-dependent lectins and mediate the bindi ng of neutrophils and monocytes. We have recently identified a 150-kD glycoprotein ligand for E-selectin on mouse myeloid cells, using a rec ombinant antibody-like form of mouse E-selectin. Here, we report that this ligand does not bind to an analogous P-selectin fusion protein. I nstead, the chimeric P-selectin-IgG protein recognizes a 160-kD glycop rotein on the mouse neutrophil progenitor 32D cl 3, on mature mouse ne utrophils and on human HL60 cells. The binding is Ca2+-dependent and r equires the presence of sialic acid on the ligand. This P-selectin-lig and is not recognized by E-selectin. Removal of N-linked carbohydrate side chains from the 150-kD and the 160-kD monospecific selectin ligan ds abolishes the binding of both ligands to the respective selectin. T reatment of HL60 cells with Peptide:N-glycosidase F inhibited cell bin ding to P- and E-selectin. In addition, glycoproteins of 230 and 130 k D were found on mature mouse neutrophils, which bound both to E- and P -selectin in a Ca2+-dependent fashion. The signals detected for these ligands were 15-20-fold weaker than those for the monospecific ligands . Both proteins were heavily sialylated and selectin-binding was block ed by removal of sialic acid, but not by removal of N-linked carbohydr ates. Our data reveal that E- and P-selectin recognize two categories of glycoprotein ligands: one type requires N-linked carbohydrates for binding and is monospecific for each of the two selectins and the othe r type binds independent of N-linked carbohydrates and is common for b oth endothelial selectins.