Sindbis Virus Glycoproteins Are Abnormally Glycosylated in Chinese Hamster Ovary Cells Deprived of Glucose

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Abstract
It was previously demonstrated that Sindbis virus infection of Chinese hamster overy (CHO) cells altered the protein glycosylation machinery of the cell, so that both normal, full-size (9 mannose-containing) oligosaccharides and abnormal, truncated (5 mannose-containing) oligosaccharides are transferred from lipid-linked precursors to newly synthesized viral membrane glycoproteins. In the present studies, the precursor oligosaccharides on viral glycoproteins that were pulse-labeled with [3H]mannose were examined in the presence or absence of glucose, since glucose starvation of uninfected CHO cells has been reported to induce synthesis of truncated precursor oligosaccharides. Pulse-labeling in the absence of glucose led to a > 10-fold increase in the relative amount of the truncated precursor oligosaccharides being transferred to the newly synthesized viral glycoproteins and to an apparent underglycosylation of some precursor viral polypeptides, with some asparaginyl sites not acquiring covalently linked oligosaccharides. The mature virion glycoproteins from CHO cells which were pulse-labeled in the absence of glucose and then chased in the presence of glucose contained proportionately more unusual Man3GlcNAc2-size oligosaccharides. These small neutral-type oligosaccharides were apparently not as good a substrate for further processing into complex acidic-type oligosaccharides as the normal Man5GlcNAc2 intermediate that results from the full-size precursors oligosaccharides.