The effect of cycloheximide on the glycosylation of lactating-rabbit mammary glycoproteins

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Abstract
Cycloheximide inhibited immediately the incorporation of L-[4,5-3H]leucine and D-[2-3H]mannose into mammary proteins, suggesting that the mannosylation of mammary glycoproteins requires the continued supply of newly synthesized polypeptides. The incorporation of radioactivity from N-acetyl-D-[1-14C]glucosamine into protein was not inhibited until .apprx. 30 min after cycloheximide addition. Much (> 90%) of this radioactivity was present as N-acetylgalactosamine. N-Glycosylation appears to be inhibited immediately by cycloheximide due to a lack of newly synthesized acceptor polypeptides; O-glycosylation continues for 30 min, the time taken for acceptor peptides to move from their synthesis site to the Golgi region and for glycosylation completion. There was a transient increase in the incorporation of mannose into lipid-linked oligosaccharide in the presence of cycloheximide, followed by a decrease in the radioactivity in this fraction. The major lipid-linked oligosaccharide extracted from explants incubated for 2 h in the presence of cycloheximide (6-7 monosaccharide units) was smaller than that extracted from control explants (10-12 monosaccharide units).