SUPPRESSION OF SIALYL-LEWIS-X EXPRESSION AND E-SELECTIN-MEDIATED CELL-ADHESION IN CULTURED HUMAN LYMPHOID-CELLS BY TRANSFECTION OF ANTISENSE CDNA OF AN ALPHA-1-]3 FUCOSYL-TRANSFERASE (FUC-T-VII)

The antisense cDNA approach was used to identify the endogenous fucosy ltransferase species responsible for synthesis of the sialyl Lewis Ii (NeuAc alpha 2-->3 Gal beta 1-->4[FUC alpha 1-->31]GlcNAc beta 1-->R) determinant in human lymphoid cells, The cultured human adult T-cell l eukemia cell line, ED40515-N, expressed the message of alpha 1-->3 fuc osyltransferase (Fuc-T) IV and VII, with a low level of the Fuc-T III and VI message, and manifested the sialyl Lewis X as well as Lewis X ( Gal beta 1-->4 [Fuc alpha 1-->3]GlcNAc beta 1->-R) determinant at the cell surface, Transfection of this cell Line with the pRc/CMV vector c ontaining an antisense human Fuc-T VII construct (pRc/CMV/5'FT7AS) res ulted in a significant decrease of endogenous Fuc-T VII message and a marked reduction in the cell surface expression of sialyl Lewis Ii det erminant as well as a reduction in the enzymatic activity of alpha 1-- >3 fucosyltransferase against sialylated type 2 chain substrate, This was accompanied by diminution of cell adhesive activity toward E-selec tin on interleukin-lp-treated endothelial cells, These results indicat ed that the synthesis of the sialyl Lewis Ii determinants that were fu nctionally active as E-selectin ligands was mainly mediated by Fuc-T V II in these lymphoid cells. On the other hand, the message of Fuc-T IV showed no significant change in the transfectant clones, and the surf ace expression of the Lewis Ii antigen as well as the enzymatic activi ty of alpha 1-->3 fucosyltransferase against non-sialylated type 2 cha in substrate was well preserved, The clear contrast between the dimini shed expression of sialyl Lewis Ii and the conserved manifestation of Lewis Ii in the transfectant clones suggested that the synthesis of si alyl Lewis Ii and that of Lewis Ii are independently regulated by diff erent fucosyltransferases in human lymphoid cells. Fuc-T VII must be i nvolved in the synthesis of sialyl Lewis Ii, while the synthesis of Le wis X is mediated by an enzyme other than Fuc-T VII, most probably Fuc -T IV.