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Title: In vitro farnesoid X receptor ligand sensor assay using surface plasmon resonance and based on ligand-induced coactivator association. Author: Fujino T, Sato Y, Une M, Kanayasu-Toyoda T, Yamaguchi T, Shudo K, Inoue K, Nishimaki-Mogami T. Journal: J Steroid Biochem Mol Biol; 2003 Dec; 87(4-5):247-52. PubMed ID: 14698205. Abstract: Ligand binding to nuclear receptors leads to a conformational change that increases the affinity of the receptors to coactivator proteins. We have developed a ligand sensor assay for farnesoid X receptor (FXR) in which the receptor-coactivator interaction can be directly monitored using surface plasmon resonance biosensor technology. A 25-mer peptide from coactivator SRC1 containing the LXXLL nuclear receptor interaction motif was immobilized on the surface of a BIAcore sensor chip. Injection of the FXR ligand binding domain (FXRLBD) with or without the most potent natural ligand, chenodeoxycholic acid (CDCA), over the surface of the chip resulted in a ligand- and LXXLL motif-dependent interaction. Kinetic analysis revealed that CDCA and its conjugates decreased the equilibrium dissociation constant (K(d)) by 8-11-fold, indicating an increased affinity. Using this technique, we found that a synthetic bile acid sulfonate, 3alpha,7alpha-dihydroxy-5beta-cholane-24-sulfonate, which was inactive in a FXR response element-driven luciferase assay using CV-1 cells, caused the most potent interaction, comparable to the reaction produced by CDCA. This method provides a rapid and reliable in vitro ligand assay for FXR. This kinetic analysis-featured technique may be applicable to mechanistic studies.[Abstract] [Full Text] [Related] [New Search]