Permanent hexose transport upregulation in a respiration-deficient human fibroblast cell strain.
The regulation of hexose transport was studied in a human diploid fibroblast respiration-deficient cell strain (WG750). Transport of 2-deoxy-D-glucose (2-DG) was greater than sixfold higher compared with an in vivo age-matched normal cell strain (MCH55). In addition, 3-O-methylglucose transport and 14CO2 production were elevated in the mutant cell strain. Kinetic analysis revealed that the increased sugar transport in mutant cells was due to an average 5.7-fold increase in the 2-DG maximal transport rate, with no observed differences in the transport Michaelis constant for both normal and mutant cells. Also, the inhibitor constants for D-glucose inhibition of 2-DG transport were nearly identical for both cell types. Glucose deprivation led to a similar time-dependent increase in hexose transport in both cell strains. Serum refeeding of glucose-fed serum-deprived cultures led to a progressive increase in 2-DG transport in normal cells, whereas mutant cells displayed a time-delayed increase in 2-DG transport. Exposure to 67 and 670 nM insulin stimulated 2-DG transport on average 1.99 +/- 0.25- and 2.33 +/- 0.26-fold, respectively, over basal transport in the normal cells, whereas the mutant cells were significantly less sensitive to the stimulatory effects of the hormone. Insulin binding and amino acid transport (i.e., alpha-aminoisobutyric acid uptake) in the normal and mutant cells were not different. Data obtained using Western blot analysis showed that WG750 (mutant) cells expressed an increase (approximately 4-fold) in total cellular HepG2 (erythroid-brain) transporter protein compared with normal cells, thus reflecting the changes seen in hexose transport.(ABSTRACT TRUNCATED AT 250 WORDS)
Andrejchyshyn
S
S
Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, Montreal, Quebec, Canada.
Continelli
L
L
Germinario
R J
RJ
D001692:Biological Transport; D015153:Blotting, Western; D002245:Carbon Dioxide / Q000378:metabolism; D002460:Cell Line / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism; D004171:Diploidy; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D006601:Hexoses / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007700:Kinetics; D007773:Lactates / Q000378:metabolism; D009154:Mutation; D010100:Oxygen / Q000378:metabolism*; D015854:Up-Regulation
D006601:Hexoses; D007328:Insulin; D007773:Lactates; D002245:Carbon Dioxide; D003847:Deoxyglucose; D010100:Oxygen