A novel drug-regulated gene expression system based on the nuclear receptor constitutive androstane receptor (CAR)

Purpose. To develop and characterize a new drug-regulated gene expression system based on the nuclear receptor constitutive androstane receptor (CAR). Methods. Both transient and stable transfection into HEK293 cells of luciferase plasmids under the control of either drug- and steroid-responsive nuclear receptor CAR or the tetracycline-sensitive transactivator tTA were used in development of stable cell lines. Results. A stable first-generation cell line that expresses luciferase gene under the control of nuclear receptor CAR was developed. The luciferase expression in CAR-producing cells could be suppressed by androstanes and reactivated by structurally unrelated drugs chlorpromazine, metyrapone, phenobarbital, and clotrimazole. The kinetics of luciferase expression in CAR-producing cells and the tTA system were comparable. The overall regulation of CAR system was improved by modifications to the DNA binding domain and site. Conclusions. Because of its wide ligand selectivity and transferable ligand binding domain, CAR expands the repertoire of regulated gene expression systems.