Transformed cells glycopeptides

Changes in the surface glycopeptides of tumour cells obtained from the peripheral blood of patients with active leukaemia, leukaemic transformations, or lymphosarcoma have been reported. With the exception of cells obtained from patients with chronic myelocytic leukaemia, increases in the levels of neuraminidase-labile sialic acid were found. This difference has been noted in a great many transformed cells. 

Buck, C. A., Fuhrer, J. P., Soslau, G., and Warren, L., 1974, Membrane glycopeptides from subcellular fractions of control and virus-transformed cells, J. Biol. Chem. 249 1541-1550. 

Following treatment of the fucose-labeled glycopeptides derived from the surfaces of RSV-BHK cells with neuraminidase, the radioactive products appeared similar to glycopeptides from normal cells (Warren et al., 19726). These results suggested that increased sialic acid content may account for the higher molecular weight of the glycopeptides from transformed cells. When sialyltransferase activity was as-... 

The third and final stage of synthesis of cell walls occurs outside the cytoplasmic membrane. Thus, the transpepfidation reaction results in transformation of the linear glycopeptide polymer into the CTOss-Unked form. The enzyme transpeptidase, a membrane-bound enzyme, binds pentapepfide side chains by replacing terminal o-alanines. 

Pierce, M, J Arango (1986) Rous sarcoma virus-transformed baby hamster kidney cells express higher levels of asparagine-linked tri- and tetraantennary glycopeptides containing [GlcNAc-beta (1,6)Man-alpha (1,6)Man] and poly-A-acetyllactosamine sequences than baby hamster kidney cells. J Biol Chem 261 10772-10777... 

Immunological and chemical studies on cell surfaces from normal and transformed BALB/c fibroblasts have shown alterations associated with transformation.The cells studied include normal lines which do not cause tumours when injected into BALB/c mice, viral transformants, and spontaneous transformants. Alterations in glycopeptides derived from several cellular glycoproteins are the only changes which appear to be associated with malignancy. 

Several laboratories have demonstrated that there is an enrichment of high-molecular-weight glycopeptides in virus-transformed and rapidly growing cells. Such increases are dependent on the rate of growth and are unrelated to the transformation. Thus, differences in size distribution may not be adequate criteria on which to base any evaluation of growth-dependent alterations in cell-surface glycoproteins. 

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