Transformation-dependent alterations in the oligosaccharides of Prague C Rous sarcoma virus glycoproteins

Abstract

The influence of cell transformation on the glycosylation of viral envelope glycoproteins was examined by high-resolution gel filtration and specific glycosidase digestions of 3H-sugar-labeled glycopeptides from nondefective and transformation-defective Prague C strains of Rous sarcoma virus replicated in fibroblasts from the same chicken embryo. The major difference in glycosylation attributable to the viral transformation of the host cells was an increase in the relative amount of larger acidic-type oligosaccharides containing additional "branch" sugars (NeuNAc-Gal-GlcNAc-) compared with the smaller acidic-type and neutral-type oligosaccharides. There was also a shift in size distribution of neutral-type oligosaccharides toward smaller oligomannosyl cores in the transforming versus nontransforming virus glycopeptides. These alterations were consistent with a transformation-dependent increase in the extent of intracellular processing of a common precursor structure for the asparagine-linked oligosaccharides of Rous sarcoma virus.

Rous sarcoma virus glycoproteins contain hybrid-type oligosaccharides

“…Previous gel filtration and glycosidase digestion studies with [3H]mannose-and [3H]glucosamine-labeled glycopeptides from Rous sarcoma virus, Prague C strain (PrC RSV), indicated that the viral glycoprotein contained asparagine-linked oligosaccharides of both the complex, acidic type [(NeuNAc-Gal-GlcNAc)2-4Man3GlcNAc2-ASN] and the mannose-rich, neutral type (Mans9GlcNAc2-ASN) (6) and that these oligosaccharides were more extensively processed in virus glycoprotein from transformed than from untransformed chicken embryo fibroblasts (5). An unusual oligosaccharide product of endo-/8-N-acetylglucosaminidase H (endo-H)-digested glycopeptides was observed, but not characterized, in these earlier gel filtration analyses.…”

Comparison of the oligosaccharide moieties of the major envelope glycoproteins of the subgroup A and subgroup B avian myeloblastosis-associated viruses

“…The host cell may be especially important in the analysis of the carbohydrate moieties of AMV or MAV-2 glycoproteins: the oligosaccharides were antigenically reactive when derived from virus isolated from sera of infected chickens or AMV-infected myeloblasts in culture, but not when derived from virus grown in CEF (27,28). In addition, the host cell-dependent glycosylation of avian retrovirus glycoproteins is altered in transformed versus nontransformed CEF (10,17).…”

“…MATERIALS AND METHODS Preparation of radiolabeled virus. CEF of C/E phenotype were prepared from embryonated eggs (Life Sciences Inc., St. Petersburg, Fla.) and grown in tissue culture as described previously (10,13). Cultures derived from the same embryos were infected at the third passage with either MAV-1, MAV-2, or RAV-1.…”

“…Radiolabeled gp85 was extensively digested with pronase (Calbiochem) (5), and the glycopeptides were desalted on a column of Sephadex G15/ G50 (Pharmacia Fine Chemicals) (11). Glycopeptides and oligosaccharides were analyzed by gel filtration through columns (120 by 1.5 cm) of Bio-Gel P-4 (minus 400 mesh; Bio-Rad Laboratories) along with unlabeled and "C-labeled gel filtration markers (10,11,13). The elution positions of a series of neutral oligomannosyl cores of known composition [(Man)"GlcNAcj; n = 3…”

“…to 9] were used to calibrate the Bio-Gel P-4 columns before the gel filtration of endo-o-N-acetylglucosaminidase digestion products (8,10).…”