Regulation of hexose transport in respiration deficient hamster lung fibroblasts

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Abstract
The transport of [3H]2‐deoxy‐D‐glucose (2DG) and [3H]3‐O‐methyl‐D‐glucose (3‐OMG) was elevated in a respiration deficient (NADH coenzyme Q [Co Q] reductase deficient) Chinese hamster lung fibroblast cell line (G14). This sugar transport increase was related to an increased Vmax for 2DG transport, 26.9 ± 4.2 nmoles 2DG/mg protein/30 sec in the G14 cell line vs 9.5 ± 0.6 nmoles 2DG/mg protein/30 sec in the parental V79 cell line. No differences were observed in their respective Km values for 2DG transport (3.9 ±.6 vs. 3.0 ±.13 mM). Factors which increase sugar transport (e.g., glucose deprivation, serum or insulin exposure) or decrease sugar transport (e.g., serum deprivation) in the parental V79 cell line had little effect on sugar transport in the G14 respiration deficient cell lines. Amino acid transport, specific 125I‐insulin binding to cells, and insulin‐stimulated DNA synthesis, however, were similar in both cell lines. Exposure of both cell lines to varying concentrations of cycloheximide (0.1‐50 μg/ml) for 4 h resulted in differential effects on 2DG transport. In the parental cell line (V79) low cyc‐loheximide concentrations resulted in decreased 2DG transport, while higher concentrations (≥ 1 μg/ml) resulted in elevated 2DG transport. In the G14 cell line, 2DG transport decreased at all concentrations of cycloheximide (up to 50 μg/ml). The data indicate that the G14 mutant has been significantly and specifically affected in the expression of sugar transport activity and in the regulatory controls affecting sugar transport activity.