title: Peroxisome proliferator-activated receptor-gamma and retinoic acid X receptor alpha represses the TGFbeta1 gene via PTEN-mediated p70 ribosomal S6 kinase-1 inhibition: role for Zf9 dephosphorylation.
abstract: Peroxisome proliferator-activated receptor (PPAR)-gamma and retinoic acid X receptor (RXR) heterodimer regulates cell growth and differentiation. Zinc finger transcription factor-9 (Zf9), whose phosphorylation promotes target genes, is a transcription factor essential for transactivation of the transforming growth factor (TGF)-beta1 gene. This study investigated whether activation of PPARgamma-RXR heterodimer inhibits TGFbeta1 gene transcription and Zf9 phosphorylation and, if so, what signaling pathway regulates it. Either 15-deoxy-delta(12,14)-prostaglandin J2 (PGJ2) or 9-cis-retinoic acid (RA) treatment decreased the TGFbeta1 mRNA level in L929 fibroblasts. PGJ2 + RA, compared with individual treatment alone, synergistically inhibited the TGFbeta1 gene expression, which was abrogated by PPARgamma antagonists. Likewise, PGJ2 + RA decreased luciferase expression from the TGFbeta1 gene promoter. Promoter deletion analysis of the TGFbeta1 gene revealed that pGL3-323 making up to -323-base pair region, but lacking PPAR-responsive elements, responded to PGJ2 + RA. PGJ2 + RA treatment inhibited the activity of p70 ribosomal S6 kinase-1 (S6K1), abolishing Zf9 phosphorylation at serine as did rapamycin [a mammalian target of rapamycin (mTOR) inhibitor]. Zf9 dephosphorylation by PGJ2 + RA was reversed by transfection of cells with the plasmid encoding constitutively active S6K1 (CA-S6K1). Transfection with dominant negative S6K1 inhibited the TGFbeta1 gene. TGFbeta1 gene repression by PGJ2 + RA was consistently antagonized by CA-S6K1. Ectopic expression of PPARgamma1 and RXRalpha repressed pGL3-323 transactivation with S6K1 inhibition, which was abrogated by CA-S6K1 transfection. PGJ2 + RA induced phosphatase and tensin homolog deleted on chromosome 10 (PTEN), whose overexpression repressed the TGFbeta1 gene through S6K1 inhibition, decreasing extracellular signal-regulated kinase 1/2-90-kDa ribosomal S6 kinase 1 and Akt-mTOR phosphorylations. Data indicate that activation of PPARgamma-RXR heterodimer represses the TGFbeta1 gene and induces Zf9 dephosphorylation via PTEN-mediated S6K1 inhibition, providing insight into pharmacological manipulation of the TGFbeta1 gene regulation.
authors.affiliation: College of Pharmacy, Seoul National University, Sillim-dong, Kwanak-gu, Seoul 151-742, Korea.
authors.forename: Seung Jin
authors.initials: SJ
authors.lastname: Lee
authors.forename: Eun Kyoung
authors.initials: EK
authors.lastname: Yang
authors.forename: Sang Geon
authors.initials: SG
authors.lastname: Kim
mesh_terms: D000077556:Alitretinoin; D000818:Animals; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D015151:Immunoblotting; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D047495:PPAR gamma / Q000819:agonists / Q000502:physiology*; D051059:PTEN Phosphohydrolase / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D015230:Prostaglandin D2 / Q000031:analogs & derivatives / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D047488:Retinoid X Receptors / Q000819:agonists / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000037:antagonists & inhibitors / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases; D014162:Transfection; D016211:Transforming Growth Factor alpha / Q000235:genetics*; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D004268:DNA-Binding Proteins; D047495:PPAR gamma; D011993:Recombinant Fusion Proteins; D047488:Retinoid X Receptors; D016211:Transforming Growth Factor alpha; C082035:Zfa protein, mouse; D000077556:Alitretinoin; D014212:Tretinoin; C037112:9-deoxy-delta-9-prostaglandin D2; D008156:Luciferases; D011494:Protein Kinases; C546843:mTOR protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D051059:PTEN Phosphohydrolase; D015230:Prostaglandin D2