Formation of 2‐Deoxyglucose‐Containing Lipid‐Linked Oligosaccharides: Interference with Glycosylation of Glycoproteins

Abstract

Crude membrane preparations from chick embryo cells catalyse the formation of dolichyl‐di‐N‐acetylchitobiosyl diphosphate [Dol‐PP‐(GlcNAc)2] from uridine diphosphate N‐acetylglucosamine (UDP‐GlcNAc). The formation of this glycolipid was stimulated by exogenous dolichyl phosphate and inhibited by tunicamycin. Adding GDP‐mannose to the cell‐free system containing Dol‐PP‐(GlcNAc)2 by preincubation led to the formation of a lipid‐linked oligosaccharide, containing 8–9 sugar residues. The formation of lipid‐linked oligosaccharides was inhibited by GDP‐2‐deoxy‐d‐glucose (GDP‐dGlc): in this case Dol‐PP‐(GlcNAc)2‐dGlc accumulated. Subsequent additions of mannosyl residues to this trisaccharide‐lipid to form lipid‐linked oligosaccharides were not possible. Concomitantly the glycosylation of proteins was blocked. Partially inhibitory conditions were obtained by adding both GDP‐dGlc and GDP‐Man with an excess of GDP‐dGlc. Glycosylation of proteins was observed but the glycopeptides did not contain 2‐deoxyglucosyl residues. Also in these cases 2‐deoxyglucose‐containing glycolipids accumulated. The main glycolipid formed under these conditions was Dol‐PP‐(GlcNAc)2‐Man‐dGlc. Lipid‐linked oligosaccharides containing 2‐deoxyglucose were formed under these conditions, although in small amounts, but were not transferred to protein. So the molecular basis of the inhibitory action of 2‐deoxyglucose on glycosylation of protein is the incorporation of 2‐deoxyglucosyl residues during early phases of the biosynthesis of the lipid‐linked oligosaccharides. Copyright © 1978, Wiley Blackwell. All rights reserved