Role of the GLUT 2 glucose transporter in the response of the L-type pyruvate kinase gene to glucose in liver-derived cells.
Twenty-six different hepatoma cell lines established from cancer-prone transgenic mice exhibited a close correlation between expression of the GLUT 2 glucose transporter and activation of the L-type pyruvate kinase (L-PK) gene by glucose, as judged by Northern blot analyses and transient transfection assays. The L-PK gene and a transfected L-PK construct were silent in GLUT 2(+) cells and active in GLUT 2(-) cells cultured in glucose-free medium. Transfection of GLUT 2(-) cells with a GLUT 2 expression vector restored the inducibility of the L-PK promoter by glucose, mainly by suppressing the glucose-independent activity of this promoter. Culture of GLUT 2(-) cells, in which the L-PK gene is constitutively expressed, in a culture medium using fructose as fuel selected GLUT 2(+) clones in which the L-PK gene responded to glucose. The expression of the L-PK gene in GLUT 2(-) cells cultured in the absence of glucose was correlated with a high intracellular glucose 6-phosphate (Glu-6-P) concentration while under similar culture conditions Glu-6-P concentration was very low in GLUT 2(+) cells. Consequently, a role of GLUT 2 in the glucose responsiveness of glucose-sensitive genes in cultured hepatoma cells could be to allow for Glu-6-P depletion under gluconeogenic culture conditions. In the absence of GLUT 2, glucose endogeneously produced might be unable to be exported from the cells and would be phosphorylated again to Glu-6-P by constitutively expressed hexokinase isoforms, continuously generating the glycolytic intermediates active on the L-PK gene transcription.
Antoine
B
B
Institut National de la Santé et de la Recherche Médicale U.129, Institut Cochin de Génétique Moléculaire, Université René Descartes, 75014 Paris, France.
Lefrançois-Martinez
A M
AM
Le Guillou
G
G
Leturque
A
A
Vandewalle
A
A
Kahn
A
A
D000818:Animals; D000957:Antigens, Viral, Tumor / Q000096:biosynthesis / Q000235:genetics; D002478:Cells, Cultured; D004790:Enzyme Induction / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology*; D051272:Glucose Transporter Type 1; D051273:Glucose Transporter Type 2; D006801:Humans; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D011770:Pyruvate Kinase / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D013539:Simian virus 40 / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured
D000957:Antigens, Viral, Tumor; D051272:Glucose Transporter Type 1; D051273:Glucose Transporter Type 2; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; C495677:SLC2A1 protein, human; D011770:Pyruvate Kinase; D005947:Glucose