Characterization of the D‐allose‐mediated regulation of sugar transport in Chinese hamster fibroblasts

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Abstract
Exposure to D‐allose has been demonstrated to lead to decreased 2‐deoxyD‐glucose (2‐DG) and 3‐0‐methyl‐D‐glucose transport in the V79 Chinese hamster lung fibroblast cell line. The effect of D‐allose (1) was maximal after 4 hours exposure to the cells; (2) was optimal between 2.77 and 5.55 mM D‐allose; and (3) led to a decreased Vmax for 2‐DG transport with no change in the transport Km value. The decrease in 2‐DG transport induced by D‐allose was reversible and the reversal was differentially affected by cycloheximide, being blocked by a low concentration of cycloheximide (0.05 μg/ml) but not a high concentration of the inhibitor (5 μg/ml). D‐allose did not competitively inhibit the transport of 2‐DG while D‐glucose under similar conditions yielded a K1 for 2‐DG transport inhibition of 1.7 mM. Additionally, D‐allose did not affect the phosphorylation of 2‐DG by hexokinase in cell‐free cytosol. The data indicate that D‐allose has significant lowering effects on sugar transport activity. Additionally, while the sugar itself may be the active component in sugar transport regulation, the effect is not blocked by inhibition of protein synthesis but the synthesis of a regulatory protein(s) may be involved in the return of sugar transport following D‐allose removal.