Differential regulation of endogenous glucose-6-phosphatase and phosphoenolpyruvate carboxykinase gene expression by the forkhead transcription factor FKHR in H4IIE-hepatoma cells.
The insulin responsive H4IIEC3 rat hepatoma cell line (H4 cells) was used in order to determine the role of the transcription factor FKHR in the regulation of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase). Both PEPCK and G6Pase contain putative FKHR binding sites in their promoter sequence. Using a retroviral expression system, we stably overexpressed FKHR in H4-cells. FKHR was phosphorylated in a PI 3-kinase- and Akt-dependent manner, and was translocated from the nucleus to the cytoplasm in response to insulin. Furthermore, overexpression of FKHR markedly increased the expression of the catalytic subunit of G6Pase (basal about 2.5-fold, dexamethasone/cAMP stimulated about fivefold, respectively). In contrast, both basal and dexamethasone/cAMP-induced levels of PEPCK mRNA were unaffected by FKHR-overexpression. These data suggest a specific function for FKHR in the regulation of hepatic gluconeogenesis at the level of G6Pase, but not PEPCK gene expression.
Barthel
A
A
Institut für Pharmakologie und Toxikologie, RWTH Aachen, Aachen, D-52057, Germany. Andreas.Barthel@post.rwth-aachen.de
Schmoll
D
D
Krüger
K D
KD
Bahrenberg
G
G
Walther
R
R
Roth
R A
RA
Joost
H G
HG
D021581:Active Transport, Cell Nucleus; D000818:Animals; D002262:Carboxy-Lyases / Q000235:genetics*; D006528:Carcinoma, Hepatocellular; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051858:Forkhead Transcription Factors; D015971:Gene Expression Regulation, Enzymologic; D005943:Gluconeogenesis / Q000235:genetics; D005952:Glucose-6-Phosphatase / Q000235:genetics*; D007328:Insulin / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008113:Liver Neoplasms; D009419:Nerve Tissue Proteins; D010728:Phosphoenolpyruvate; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D020218:Response Elements; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D000071161:Forkhead Box Protein O1
D002262:Carboxy-Lyases; D004268:DNA-Binding Proteins; D051858:Forkhead Transcription Factors; D005952:Glucose-6-Phosphatase; D007328:Insulin; D009419:Nerve Tissue Proteins; D010728:Phosphoenolpyruvate; D011994:Recombinant Proteins; D014157:Transcription Factors; C074639:Foxo1 protein, rat; D000071161:Forkhead Box Protein O1