Effects of a membrane sugar analogue, 6-deoxy-6-fluoro-d-galactose,on the L1210 leukemic cell ectosialyltransferase system

In L1210 leukemia cells, 6-deoxy-6-fluoro-d-galactose specifically inhibited the incorporation of ³H]-d-galactose, while that of other precursors of glycoconjugate biosynthesis, including mannose and glucosamine, was unaffected. The activation of 6-³H]-6-deoxy-6-fluoro-d-galactose to a nucleotide sugar was similar to that found for ³H]-d-galactose. The incorporation of either sugar after 1 hr was visualized by electron microscopic autoradiography to be in the Golgi region. Treatment of L1210 cells with 6-deoxy-6-fluoro-d-galactose in vitro or in vivo resulted in a specific, dose- and time-dependent decrease in the activity of cell surface sialyltransferase (ectosialyltransferase) but not of 5′-nucleotidase, a plasma membrane marker enzyme. The decrease in ectosialyltransferase activity appeared to be selective and is suggested to be due to structural modification of the cell surface galactoprotein acceptors for this enzyme. The data indicate that 6-deoxy-6-fluoro-d-galactose is an effective modifier of cellular glycoconjugate in that its incorporation into certain cell surface components results in a modification of plasma membrane structure and function.