Regulation of PGC-1 promoter activity by protein kinase B and the forkhead transcription factor FKHR.
Peroxisome proliferator-activated receptor-gamma coactivator-1 (PGC-1) plays a major role in mediating hepatic gluconeogenesis in response to starvation, during which PGC-1 is induced by the cyclic AMP response element binding protein. Although it is observed that insulin counteracts PGC-1 transcription, the mechanism by which insulin suppresses the transcription of PGC-1 is still unclear. Here, we show that forkhead transcription factor FKHR contributes to mediating the effects of insulin on PGC-1 promoter activity. Reporter assays demonstrate that insulin suppresses the basal PGC-1 promoter activity and that coexpression of protein kinase (PK)-B mimics the effect of insulin in HepG2 cells. Insulin response sequences (IRSs) are addressed in the PGC-1 promoter as the direct target for FKHR in vivo. Coexpression of FKHR stimulates the PGC-1 promoter activity via interaction with the IRSs, while coexpression of FKHR (3A), in which the three putative PKB sites in FKHR are mutated, mainly abolishes the suppressive effect of PKB. Whereas deletion of the IRSs prevents the promoter stimulation by FKHR, that activity is still partially inhibited by insulin. These results indicate that signaling via PKB to FKHR can partly account for the effect of insulin to regulate the PGC-1 promoter activity via the IRSs.
Daitoku
Hiroaki
H
Center for Tsukuba Advanced Research Alliance, Institute of Applied Biochemistry, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8577, Japan.
Yamagata
Kazuyuki
K
Matsuzaki
Hitomi
H
Hatta
Mitsutoki
M
Fukamizu
Akiyoshi
A
D000730:Androstadienes / Q000494:pharmacology; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D017353:Gene Deletion; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007163:Immunosorbent Techniques; D007328:Insulin / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008156:Luciferases / Q000235:genetics; D016296:Mutagenesis; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D011993:Recombinant Fusion Proteins; D020218:Response Elements; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics* / Q000494:pharmacology*; D014162:Transfection; D000077191:Wortmannin
D000730:Androstadienes; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C085126:FOXO1 protein, human; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; C526292:IRS1 protein, human; C526297:IRS2 protein, human; C491585:IRS3P protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1; D008156:Luciferases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000077191:Wortmannin