Membrane glycopeptides from virus-transformed hamster fibroblasts and the normal counterpart

Abstract

Comparisons of membrane glycopeptides from baby hamster kidney fibroblasts (BHK21/C13) and a clone transformed by Rous sarcoma virus (C13/B4) were made by using cells metabolically labeled with radioactive D-glucose and L-fucose. Most of the glycopeptides were metabolically labeled with both the general and the specific glycoprotein precursors. The glycopeptides obtained from the cell surface by controlled trypsinization were representative of the surface membrane as shown by comparing them with those of purified membrane preparations. The trypsin-removable glycopeptides from both cell types were further processed and examined by successive chromatography on Sephadex G-50 and DEAE-cellulose. The chromatographic distribution patterns showed that each cell type had glycopeptides of similar characteristics, although the proportions of the glycopeptides differed dramatically between the two cell types. After transformation there was an increase in the larger, more highly charged glycopeptides. This was verified by the increased sialic acid content in these glycopeptides. Some of the glycopeptides were homogeneous after the size and charge separations, since a variety of procedures did not separate them further. The apparent homogeneity and reasonably few species obtained may be due to the methods of isolation, with the procedures selecting particular glycopeptides from the external portion of the membrane. These results corroborate the concept and show for the first time that virus transformation is accompanied by an increase in certain species of glycopeptides rather than de novo synthesis.

Changes in surface glycopeptides after malignant transformation of rat liver cells and during the regression of hepatoma cells

“…These differences reflect actual changes in carbohydrate moieties exposed at the cell surface since whole cells as well as plasma membranes digested by pronase give identical glycopeptide patterns. This has been observed in other cell systems [32,33]. The most prominent characteristic is the presence in hepatoma cells of a macroglycopeptide of high molecular weight (M, = 70,000), made up of 0-linked glycan chains, probably combined in clusters.…”

Partial characterization of sialoglycopeptides produced by cultured human melanoma cells and melanocytes

“…The purified Q H-higher molecular weight glycopeptides (referred to as group A by Warren et al, 1978) has been correlated with the active growth state and tumorigenicity of cancer cells (Buck et al, 1971;Glick et al, 1973;Muramatsu et al, 1973;Van Beek et al, 1977). The purification and partial structure of one of these larger glycopeptides isolated from Rous sarcoma virus transformed baby hamster kidney cells were recently reported (Glick, 1979;Santer & Glick, 1979).…”

“…Differences in the glycoproteins produced by malignant cells compared to normal cells have been reported (Bramwell & Harris, 1978;Buck et al, 1979;Ceccarini & Atkinson, 1977;Codington et al, 1979;Glick, 1979;Muramatsu et al, 1979;Takasaki et al, 1980;van Beek et al, 1977). A molecular description of these alterations is of importance because it will help to understand the biological properties of malignant cells.…”

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

“…The larger RSV glycopeptides were presumably enriched in triantennary or quartantennary structures, or both [(NeuNAc-Gal-GlcNAc)3-4(Man)3GlcNAc2-Asn, with either one or two ,B-1,4-linked N-acetylglucosamine plus two ,8-1,2-linked N-acetylglucosamines in the three or four branch chains] versus the diantennary structures [(NeuNAc-Gal-GlcNAc)2(Man)3GlcNAc2-Asn, with two (8-1,2,-linked N-acetylglucosamines in the two branch chains] reported for the smaller acidictype glycopeptides from Sindbis virus grown in untransformed BHK and CEF cells (5). An analogous increase in triantennary acidic-type structures was observed in the cellular membrane glycopeptides from RSV-transformed versus untransformed BHK cells, and a similar enrichment for more highly sialylated and branched acidic-type oligosaccharides was suggested as the major transformation-dependent alteration in the glycosylation of these cellular membrane proteins (8,25).…”