Differential requirements for core2 glucosaminyltransferase for endothelial L-selectin ligand function in vivo

L-selectin is a calcium-dependent lectin on leukocytes mediating leukocyte rolling in high endothelial venules and inflamed microvessels. Many selectin ligands require modification of glycoproteins by leukocyte core2 βl,6-Nacetylglucosaminyltransferase (Core2GIcNAcT-I). To test the role of Core2GIcNAcT-I for L-selectin ligand biosynthesis, we investigated leukocyte rolling in venules of untreated and TNF-α-treated cremaster muscles and in Peyer's patch high endothelial venules (HEV) of Core2GIcNAcT-I null (core2^-/-) mice. In the presence of blocking mAbs against P- and E-selectin, L-selectin-mediated leukocyte rolling was almost completely abolished in cremaster muscle venules of core2^-/- mice, but not littermate control mice. By contrast, leukocyte rolling in Peyer's patch HEV was not significantly different between core2^-/- and control mice. To probe L-selectin ligands more directly, we injected L-selectin-coated beads. These beads showed no rolling in cremaster muscle venules of core2^-/- mice, but significant rolling in controls. In Peyer's patch HEV, beads coated with a low concentration of L-selectin showed reduced rolling in core2^-/- mice. Beads coated with a 10-fold higher concentration of L-selectin rolled equivalently in core2^-/- and control mice. Our data show that endothelial L-selectin ligands relevant for rolling in inflamed microvessels of the cremaster muscle are completely Core2GIcNAcT-I dependent. In contrast, L-selectin ligands in Peyer's patch HEV are only marginally affected by the absence of Core2GIcNAcT-I, but are sufficiently functional to support L-selectin-dependent leukocyte rolling in Core2GIcNAcTI-deficient mice.