Optimization of an enzyme-linked immunosorbent assay to screen ligand of Peroxisome proliferator-activated receptor alpha.

Peroxisome proliferator-activated receptors (PPARs) are transcription factor which directly modulate gene expression by binding to specific agonists. It has been reported that PPARalpha controls lipid metabolism, inflammation, and atherosclerosis. PPARalpha activation by PPARalpha agonist can ultimately reduce the progression of atherosclerosis and decrease the incidence of coronary heart disease. In this study, we optimized enzyme-linked immunosorbent assay (ELISA) systems in order to screen putative PPARalpha agonists. These methods are based on the activation mechanism of PPARalpha where the ligand binding to PPARalpha induces the interaction of the receptor with transcriptional co-activators. Among co-activators such as SRC-1, TIF-2, and p300, although ligand-unbound PPARalpha had more strong binding with p300 at a lower concentrations of PPARalpha, ligand-bound PPARalpha had more specific and strong binding with SRC-1. We optimized and developed a novel and useful ELISA system to screen PPARalpha agonists. Wy14,643 and linoleic acid, the well-known PPARalpha ligands, increased the binding between PPARalpha and co-activators in a ligand dose-dependent manner. In this ELISA method to screen PPARalpha ligands, the use of specific anti-PPARalpha N-terminus antibody, full-length recombinant protein of human PPARalpha but not ligand-binding domain (LBD) of human PPARalpha, and his-tagged PPARalpha recombinant proteins but not GST-fused PPARalpha recombinant proteins is the critical factors. Development of this screening system may be useful in the discovery of PPARalpha ligands from various candidates such as chemical library and phytochemicals.