An important role for the alpha 1,3 fucosyltransferase, FucT-VII, in leukocyte adhesion to E-selectin

E-selectin is an adhesion molecule expressed on the surface of activated endothelial cells, which has been shown to be important in the initial steps of leukocyte extravasation into inflamed tissues. E- selectin binds neutrophils, monocytes, eosinophils, basophils, natural killer (NK) cells, and subsets of lymphocytes, although the precise ligand(s) on these cells have not been identified. Several studies have proposed certain carbohydrate structures, including sLex and related structures, as E-selectin ligands. In contrast to these studies, we report here the identification of several human B cell lines that exhibit binding to E-selectin without expression of any of the previously identified E-selectin binding carbohydrate epitopes. The unique carbohydrate phenotype of these B cell lines suggests that they may express a novel, sialylated carbohydrate structure(s) that binds to E-selectin. To investigate the enzymatic basis of this novel form of E- selectin binding, we examined the expression of the two principal leukocyte alpha 1,3 fucosyltransferases, FucT-IV and FucT-VII, in a panel of human hematopoietic cell lines. FucT-VII was expressed in all E-selectin binding cell lines except one, whereas FucT-IV was expressed by nearly all cell lines, regardless of their ability to bind E- selectin. In addition, transfection of cells with cDNA encoding FucT- VII conferred E-selectin binding ability. Taken together, these data suggest that, regardless of surface carbohydrate phenotype, E-selectin binding ability is determined largely by expression of FucT-VII.