Heterogeneity of the glucose transporter in malignant and suppressed hybrid cells

Previous work has demonstrated unequivocally that the kinetics of glucose transport of tumorigenic and suppressed hybrid cells show a consistent difference. This lies in an increased affinity for glucose in the tumorigenic cell lines (i.e., a reduced Km). Evidence has also been presented that the degree of glycosylation of the transporter may affect the Km. When a suitable antiserum to the transporter present in these cells became available, it was of interest to examine the patterns of binding to immunoblots of extracts of the hybrid cell pairs. It became apparent that there was a clear difference between the two parental cell lines and that this difference was reflected in the hybrid cells. Both the tumorigenic parent and the tumorigenic hybrid cell presented a much more heterogeneous distribution of apparent molecular weights than the nontumorigenic parent or suppressed cell line. That this was probably due to differences in glycosylation was indicated by the effect of tunicamycin on the cells; this gave rise to a more homogeneous band of lower molecular weight. The significance of these differences is discussed in relation to results obtained with other tumorigenic cell lines and to the published structure of the human erythrocyte glucose transporter.