| The peroxisome proliferator-activated receptor γ (PPARγ) belongs to nuclearreceptor families. It plays important roles in regulation of lipid and glucosehomeostasis. PPARγ has been developed as an important target in the treatment ofdiabetes, inflammation, dyslipidemia, hypertension and cancer. The recent researchhas indicated that the antagonist or partial agonist of PPARγ has been received moreand more attention in the discovery of novel antidiabetic agents that may retainefficacious insulin-sensitizing properties and minimize potential side effects. In thiswork, the dipeptide H-Trp-Glu-OH (G3335) was discovered to be a novel PPARγantagonist. Surface plasmon resonance (SPR) technique based Biacore resultsshowed that G3335 exhibited a highly specific binding affinity against PPARγ andwas able to block rosiglitazone in the stimulation of PPARγ/RXR interaction. Inaddition, G3335 was further confirmed as an antagonist of PPARγ by the yeasttwo-hybrid and transactivation assays. Furthermore, homology modeling andmolecular docking analyses found that the Cys285 residue of PPARγ was importantfor G3335/PPARγ interaction, and the result was also identified with point mutationassay. It is hoped that our current work will provide a powerful approach for thediscovery of PPARγ antagonists, and that G3335 might be developed as a possiblelead compound in diabetes research. (These data have been published onChemBioChem 2006, 7, 74-82).15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2) is a natural agonist ofPPARγ, which is able to activate adipogenesis and plays an important role in theregulation of the inflammatory process. It is reported that 15d-PGJ2 could regulatethe activity of Smad2. However, no quantification data have been yet reported, andwhether 15d-PGJ2 could regulate Smad2 activity depending on PPARγ still keepssuspenseful. In this work, by analyzing the location of EGFP-Smad2 in CHO cellsaccording to the Nucleus Trafficking Analysis Module based on IN Cell Analyzer1000 platform, TGFβ stimulated EGFP-Smad2 translocation regulated by 15d-PGJ2was quantitatively investigated. The results showed: (1) TGFβ could induceEGFP-Smad2 translocation from cytoplasm to nucleus with EC50 of 8.83 pM;(2)15d-PGJ2 could impede TGFβ stimulated Smad2 translocation through PPARγ;(3)different from the case for 15d-PGJ2, rosiglitazone, another PPARγ agonist, couldenhance Smad2 translocation to nucleus, suggesting that rosiglitazone and 15d-PGJ2might take different modes in the activation of PPARγ within PPARγ/TGFβ/Smad2pathway. Our work has provided some new ideas in the investigation of the PPARγagonist functions within the complex pharmacological pathways. (This work hasbeen accepted on Cellular Physiology and Biochemistry, 2006 In press). |
