Regulation of PPAR gamma transcriptional activity in 3T3-L1 adipocytes.
PPAR gamma is a member of the nuclear hormone receptor superfamily and functions as a transcriptional regulator of genes linked to adipogenesis and lipid metabolism. The regulation of PPAR gamma activity by insulin signaling molecules in adipocytes has yet to be clarified. Therefore, it is important to measure endogenous PPAR gamma transcriptional activities in response to various stimuli in adipocytes. Herein, with a transcription reporter assay using recombinant adenovirus vectors expressing PPRE (PPAR responsive elements)-reporter genes, we established a novel system for measuring endogenous PPAR gamma transcriptional activity in 3T3-L1 adipocytes. By means of this system, a marked increase (8.5-fold) in PPAR gamma transcriptional activity was detected after treatment with 10(-6)M pioglitazone, a thiazolidinedione (TZD), indicating that this system can measure PPAR gamma activity accurately. Furthermore, MAPK activation, achieved by overexpressing constitutively activated MEK1, inhibited PPAR gamma transcriptional activity. In contrast, treatment with PKA stimulators markedly increased PPAR gamma activity. Interestingly, PI 3-kinase overexpression resulted in a marked decrease in PPAR gamma activity. These observations have important implications for understanding the regulation of PPAR gamma transcriptional activity.
Watanabe
Masaki
M
Saitama Medical School Research Center for Genomic Medicine, 38 Morohongo, Moroyama, Iruma-gun, Saitama 350-0495, Japan.
Inukai
Kouichi
K
Katagiri
Hideki
H
Awata
Takuya
T
Oka
Yoshitomo
Y
Katayama
Shigehiro
S
D016475:3T3 Cells; D000256:Adenoviridae / Q000235:genetics; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000077205:Pioglitazone; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D020218:Response Elements; D013844:Thiazoles / Q000494:pharmacology; D045162:Thiazolidinediones; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
D018160:Receptors, Cytoplasmic and Nuclear; D013844:Thiazoles; D045162:Thiazolidinediones; D014157:Transcription Factors; D019869:Phosphatidylinositol 3-Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D000077205:Pioglitazone