Peroxisome proliferator-activated receptor gamma inhibits expression of minichromosome maintenance proteins in vascular smooth muscle cells.
Using a cDNA array consisting only of cell cycle genes, we found that a novel nonthiazolidinedione partial peroxisome proliferator-activated receptor gamma (PPARgamma) agonist (nTZDpa) inhibited expression of minichromosome maintenance (MCM) proteins 6 and 7 in vascular smooth muscle cells. MCM proteins are required for the initiation and elongation stages of DNA replication and are regulated by the transcription factor E2F. Mitogen-induced MCM6 and MCM7 mRNA expression was potently inhibited by nTZDpa and to a lesser degree by the full PPARgamma agonist, rosiglitazone. Inhibition of MCM6 and MCM7 expression by nTZDpa and rosiglitazone paralleled their effect to inhibit phosphorylation of the retinoblastoma protein and cell proliferation. Transient transfection experiments revealed that the nTZDpa inhibited mitogen-induced MCM6 and MCM7 promoter activity, implicating a transcriptional mechanism. Adenoviral-mediated E2F overexpression reversed the suppressive effect of nTZDpa on MCM6 and MCM7 expression. Furthermore, activity of a luciferase reporter plasmid driven by multiple E2F elements was inhibited by nTZDpa, indicating that their down-regulation by nTZDpa involves an E2F-dependent mechanism. Overexpression of dominant-negative PPARgamma or addition of a PPARgamma antagonist, GW 9662, blocked nTZDpa inhibition of MCM7 transcription. Adenovirus-mediated overexpression of constitutively active PPARgamma inhibited MCM7 expression in a similar manner as the nTZDpa. These findings provide strong evidence that activation of PPARgamma attenuates MCM7 transcription and support the important role of this nuclear receptor in regulating vascular smooth muscle cell proliferation.
Bruemmer
Dennis
D
Division of Endocrinology, Diabetes and Hypertension and The Gonda (Goldschmied) Diabetes Center, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA.
Yin
Fen
F
Liu
Joey
J
Berger
Joel P
JP
Kiyono
Tohru
T
Chen
Jasmine
J
Fleck
Eckart
E
Van Herle
Andre J
AJ
Forman
Barry M
BM
Law
Ronald E
RE
D000818:Animals; D001011:Aorta / Q000166:cytology; D018797:Cell Cycle Proteins / Q000187:drug effects / Q000235:genetics*; D002455:Cell Division / Q000187:drug effects; D004261:DNA Replication / Q000187:drug effects*; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000235:genetics*; D015870:Gene Expression / Q000187:drug effects; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D009687:Nuclear Proteins / Q000187:drug effects / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists*; D000077154:Rosiglitazone; D016196:S Phase / Q000187:drug effects; D013440:Sulfides / Q000494:pharmacology*; D045162:Thiazolidinediones / Q000494:pharmacology*; D014157:Transcription Factors / Q000819:agonists*; D015533:Transcriptional Activation / Q000187:drug effects*
C479635:5-chloro-1-(4-chlorobenzyl)-3-(phenylthio)indole-2-carboxylic acid; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D007211:Indoles; D009687:Nuclear Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D013440:Sulfides; D045162:Thiazolidinediones; D014157:Transcription Factors; D000077154:Rosiglitazone