Intracellular inhibition of blood group A glycosyltransferase

We report the intracellular inhibition of blood group A N-acetylgalactosaminyltransferase in the human colorectal carcinoma cell line HT29 by 3-amino-3-deoxy-[Fuc alpha(1-2)]Gal beta-O(CH2)(7)CH3. Inhibition was demonstrated with a novel capillary electrophoresis assay that monitored decreased intracellular conversion of fluorescently labelled Fuc alpha(1-2)Gal-R acceptor to the corresponding A epitope, GalNAc alpha(1-3)[Fuc alpha(1-2)]Gal beta-R. Growth of HT29 cells with either the amino-inhibitor or a competitive substrate, Fuc alpha(1-2)Gal beta-O(CH2)(7)CH3, also resulted in decreased expression of blood group A determinants on cell-associated glycoproteins, as detected by immunoprecipitation analysis using A-specific monoclonal antibodies. Furthermore, exposure of these cells to the amino-inhibitor or competitive substrate resulted in significant reduction of cell-surface expression of blood group A determinants. As integrin alpha 3 beta 1, a cell-surface receptor mediating cell-cell and cell-extracellular matrix interactions, was shown previously to be a major carrier of blood group A determinants on HT29 cells, the studies described herein highlight the potential usefulness of these compounds for elucidating the role of blood group A determinants in biological phenomena.