Glucokinase expression in rat hepatoma cells induces glucose uptake and is rate limiting in glucose utilization

Authors

  • Alfons VALERA,

    1. Department of Biochemistry and Molecular Biology, School of Veterinary Medicine, Autonomous University of Barcelona, Bellaterra, Spain
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  • Fatima BOSCH

    Corresponding author
    1. Department of Biochemistry and Molecular Biology, School of Veterinary Medicine, Autonomous University of Barcelona, Bellaterra, Spain
      Correspondence to F. Bosch, Department of Biochemistry and Molecular Biology, School of Veterinary Medicine, Autonomous University of Barcelona, E-08193-Bellaterra, Barcelona, Spain
      Fax: +34 3 5812006.
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Correspondence to F. Bosch, Department of Biochemistry and Molecular Biology, School of Veterinary Medicine, Autonomous University of Barcelona, E-08193-Bellaterra, Barcelona, Spain
Fax: +34 3 5812006.

Abstract

In contrast to hepatocytes, hepatoma cells lack glucokinase activity and show increased aerobic glycolysis. FTO-2B and H4IIE rat hepatoma cell lines were obtained in which the rat glucokinase gene was expressed (FTOGK and H4GK). These lines were generated by infection of the hepatoma cells with a retroviral vector carrying the phosphoenolpyruvate carboxykinase (PEPCK)-glucokinase chimeric gene. Both the FTOGK and H4GK cells expressed the chimeric gene in a regulated manner, like the endogenous PEPCK gene. Glucokinase activity was detected in both FTOGK and H4GK. These cell lines showed a marked increase in glucose uptake with 18.5 mM glucose in the incubation medium. FTOGK and H4GK showed an increase in the content of glucose 6-phosphate, and were able to accumulate high levels of glycogen, in contrast to FTO-2B cells, which were unable to store the polysaccharide. In addition, cells expressing glucokinase showed high concentration of fructose 2,6-bisphosphate and substantial lactate production, which was related to the glucose concentration in the medium and the time of incubation.

These results suggest that glucose phosphorylation is rate limiting for glucose uptake and utilization in FTO-2B and H4IIE cells.

Abbreviations
PEPCK

phosphoenolpyruvate carboxykinase

Fru 2.6-P2

fructose-2,6-bisphosphate

DMEM

Dulbecco's minimal essential medium

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