Pharmacological analysis of wild-type alpha, gamma and delta subtypes of the human peroxisome proliferator-activated receptor.

Three distinct peroxisome proliferator-activated receptor (PPAR) cDNAs were isolated from human brain RNA. Whereas the PPARdelta subtype perfectly matched the amino acid sequences reported in the Genbank database, several differences were found for the PPARalpha (Lys(123)Met, Ala(268)Val, Gly(296)Ala and Val(444)Ala) and PPARgamma2 (Met(8)Ile, Pro(9)Ala, Met(186)Ile, Pro(187)Ala and the deletion of a Gln(213) residue) subtypes. A pharmacological analysis was undertaken by co-expressing each PPAR subtype with a reporter plasmid containing a luciferase gene under the transcriptional control of a synthetic, triplicated PPAR response element in either HepG2 or Cos-7 cells. Whereas fenofibrate unselectively activated the PPARalpha and PPARdelta subtypes, the related BM-17.0744 compound was more potent and selective for PPARalpha. The thiazolidine dione derivatives rosiglitazone and pioglitazone were potent and selective PPARgamma2 agonists. L-165041, reported as a selective and potent PPARdelta ligand, displayed in this specified transactivation system, apart from its highly efficacious PPARdelta agonist activity, partial and full agonism at, respectively, PPARalpha and PPARgamma2 subtypes. In conclusion, transcriptional control of a luciferase gene by wild-type PPAR subtypes provides powerful recombinant assays to evaluate ligand's efficacy at these nuclear receptors.