Pregnane X Receptor (PXR) Redistribution Assay

• Designed to assay compounds for their ability to induce nuclear accumulation of PXR
• Coupled to EGFP for easy monitoring of the cellular translocation event
• Robust cell-based assay for use in high content analysis and fluorescence microscope applications

• Biologically relevant data: Compounds tested in a cellular environment
• Validated: Functionally tested cells provided with an optimized assay protocol
• Easy to use: Just plate cells, add compounds, and image

The pregnane X receptor (PXR), also known as the steroid and xenobiotic receptor (SXR) or pregnenolone-activated receptor (PAR), is a member of the nuclear receptor family of ligand-activated transcription factors, and a key transcriptional regulator of the expression of metabolizing and detoxifying enzymes involved in endobiotic and xenobiotic metabolism. PXR is expressed predominantly in liver and intestine and is activated by a variety of structurally distinct ligands, triggering up-regulation of genes central to drug metabolism and drug efflux transporter genes, thereby increasing metabolism and excretion of therapeutic agents as well as in drug-drug interactions. In addition, PXR is also activated by a variety of endogenous ligands including pregnanes, bile acids, hormones, and dietary vitamins. Genes regulated by PXR include phase 1 (e.g. cytochrome P450 (CYP450)) and phase II drug-metabolizing enzymes as well as drug transporters such as ABC transporters and multi drug resistance proteins MDR1 and MDR2. Induction of drug efflux transporters and drug-metabolizing proteins is a major underlying mechanism in the development of drug resistance in cancer. The PXR Redistribution assay makes it possible to evaluate PXR-mediated drug metabolism of test compounds at an early stage during drug discovery as well as being an early indicator of drug toxicity.

Figure 2. Concentration response of reference compounds in the PXR Redistribution Assay. A) Concentration response was measured in 9 point half log dilution series. Cells were incubated with anisomycin for 24 h. Cells were then fixed and the translocation was measured using the Cellomics ArrayScan V^TI Reader and the RedistributionV3 BioApplication. % activity was calculated relative to the positive (300 nM anisomycin) and negative control (0.25% DMSO). The EC₅₀ of anisomycin is approximately 200 nM, n=12. B) A panel of compounds with known toxic profile was profiled in the PXR Redistribution assay. Data points in bold indicate concentrations of compound with tox effects on cell morphology.