Insights into the Mechanism of Partial Agonism: Crystal Structures of the Peroxisome Proliferator-activated Receptor-gamma Ligand-Binding Domain in the Complex with Two Enantiomeric Ligands
Poster Feb 07, 2007
Giorgio Pochetti, Cristina Godio, Nico Mitro, Donatella Caruso, Samuele Scurati, Andrea Galmozzi, Fulvio Loiodice, Giuseppe Fracchiolla, Paolo Tortorella, Antonio Laghezza, Antonio Lavecchia, Ettore Novellino, Fernando Mazza, Maurizio Crestani
The peroxisome proliferator-activated receptors (PPARs) are transcriptional regulators of glucose and lipid metabolism. They are activated by natural ligands, such as fatty acids, and are also target of synthetic antidiabetic and hypolipidemic drugs. By using cell-based reporter assays, we studied the transactivation activity of two enantiomeric ureidofibrate derivatives. In particular, we show that the R-enantiomer, is a full agonist of PPAR-gamma, whereas the S-enantiomer, is a less potent partial agonist.
These two molecules affect specifically the transcriptional activity of PPAR-alpha and gamma subtypes, whereas the activity of other members of the nuclear receptor gene superfamily is not altered. Most importantly, we report the X-ray crystal structures of the PPAR-gamma ligand binding domain respectively complexed with the R- and the S-enantiomer. The analysis of the two crystal structures shows that the different degree of stabilization of the helix 12 induced by the ligand determines its behaviour as full or partial agonist.
These results support the use of hSC-CM and MEA technology for preclinical assessment of proarrhythmic risk within the proposed CiPA paradigm, and, more generally, demonstrate that automation of the CM-MEA assay can achieve high reliability and throughput for cardiac risk assessment in vitro.READ MORE
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