3 '-azidothymidine potently inhibits the biosynthesis of highly branched N-linked oligosaccharides and poly-N-acetyllactosamine chains in cells

Previous studies in our laboratory have characterized 3'-azido-3'-deoxythym idine (AZT) as a potent inhibitor of glycosphingolipid biosynthesis in cult ured cells (Steet, R,, Alizadeh, M,, Melancon, P,, and Kuchta, R, D, (1999) Glycoconj. J. 16, 237-245; Yan, J.-P,, Ilsley, D, D,, Frohlick, C,, Steet, R,, Hall, E, T,, Kuchta, R, D,, and Melancon, P, (1995) J, Biol, Chem, 270 , 22836-22841), Here, we report that AZT treatment of K562 cells results in significant alterations in the profile of N-linked oligosaccharides, Fract ionation of [H-3]mannose-labeled oligosaccharides from AZT-treated K562 cel ls using lectin affinity chromatography revealed striking changes in the br anching and processing of N-linked glycoconjugates, AZT treatment resulted in the production of fewer highly branched complex glycans (60% of control at 20 mu M AZT) and a significant accumulation of core-fucosylated biantenn ary oligosaccharides, In addition, extension of branched oligosaccharides w ith multiple poly-N-acetyllactosamine repeats is nearly abolished by AZT co ncentrations as low as 2 mu M, A Shift from multiantennary to moderately br anched oligosaccharides was also apparent in the melanoma cell line SK-MEL- 30 upon AZT treatment. N-Linked glycans from both cell lines exhibited incr eased affinity for the beta-galactoside-binding lectin RCA-I in the presenc e of AZT, suggesting that the addition of terminal sialic acid is sensitive to the drug. These results demonstrate the ability of AZT to modulate stro ngly the processing of asparagine-linked glycoconjugates in whole cells and reveal a novel mechanism by which AZT treatment may cause anemia.