Effect of energy depletion on the glycosylation of a viral glycoprotein.

In energy-depleted cells the formation of mannosylphosphoryldolichol is inhibited. Glucosyl-phosphoryldolichol, di-N-acetylchitobiosyl-pyrophosphoryl-dolichol and also GDP-mannose are still present, indicating that the formation of mannosyl-phosphoryl-dolichol and hence glycosylation of proteins via the lipid-linked oligosaccharide (Glc)3(Man)9(GlcNAc)2-pyrophosphoryl-dolichol, are under metabolic control. In the energy-depleted cells the endo-beta-N-acetylglucosaminidase H-resistant, lipid-linked oligosaccharides (Man)x(GlcNAc)2-pyrophosphoryl-dolichol (X = 1 to 5) are still formed. Despite the absence of mannosyl-phosphoryl-dolichol protein glycosylation is not blocked. The influenza virus hemagglutinin is glycosylated with endo-beta-N-acetylglucosaminidase H-resistant, but not complex, oligosaccharides. These oligosaccharides can be processed to protein-linked (Man)5(GlcNAc)2 and (Man)4(GlcNAc)2, and may represent glucosylated species. However, the rate at which the hemagglutinin leaves the rough endoplasmic reticulum and, probably therefore, the rate of oligosaccharide-processing are decreased in the energy-depleted cells. Both inhibition of formation of mannosyl-phosphoryl-dolichol and of intracellular migration are reserved when the energy status is brought back to normal levels.