Expression of leukocyte fucosyltransferases regulates binding to E-selectin: relationship to previously implicated carbohydrate epitopes.

Abstract

E-selectin is a carbohydrate-binding endothelial cell adhesion molecule that reportedly interacts with several related sialylated and fucosylated carbohydrates. The activity of leukocyte alpha1,3-fucosyltransferases (FucT-IV or FucT-VII) is an essential step in the synthesis of E-selectin ligands. Using a panel of stably transfected hemopoietic cell lines, we have investigated the role of alpha1,3-fucosyltransferases in generating E-selectin ligands, and the relationship between adhesion to E-selectin and expression of mAb-defined carbohydrates. Expression of FucT-VII was always sufficient for binding to E- and P-selectin, while the ability of FucT-IV to construct E-selectin ligands varied among different cell types. Furthermore, FucT-IV was unable to support any binding to P-selectin in a lymphoid cell line, even when expressed at levels equivalent to those in myeloid cells. FucT-IV expression generated high levels of surface Le(x)/CD15 and CDw65, whereas expression of FucT-VII correlated with a subset of mAb-defined sialyl Lewis X (sLex)-like structures. FucT-IV-associated epitopes were present on both binding and nonbinding cells, whereas all cells that expressed FucT-VII-associated epitopes bound E-selectin. However, treatment of HL60 cells with neuraminidase destroyed FucT-VII-associated epitopes at a faster rate than E-selectin binding sites. Surface expression of a subset of mAb-defined sLex-like carbohydrates is therefore a good marker for high levels of FucT-VII activity, but these carbohydrates are not themselves required for recognition of E-selectin.