PXR (E4S1W) Rabbit mAb #44646

The pregnane X receptor (PXR) is part of the nuclear hormone receptor superfamily and is a master regulator of xenobiotic metabolism (1). PXR was initially described as being activated by pregnanes and inducing expression of the CYP3A family of steroid hydroxylases (2,3). Similar to PPAR and CAR nuclear receptors, PXR utilizes RXR as a heterodimeric partner and controls target hepatic enzyme genes to control liver metabolism in response to a wide variety of drugs (4). However, PXR is strikingly evolutionarily divergent, and the ligand-binding domain only shares around 75% identity across species. Compounds that readily activate human PXR, such as rifampicin, have little activity in rodents (5,6). In humans, in addition to naturally occurring steroids, PXR is activated by numerous xenobiotics, including anti-cancer drugs paclitaxel and tamoxifen, the HIV protease inhibitor ritonavir, and the anti-diabetic troglitazone (5,7-9). PXR has been implicated in numerous conditions, including inflammatory bowel disease, atherosclerosis, and non-alcoholic fatty liver disease (NAFLD) (10-12). PXR plays a protective role in many tumor types and its expression is generally correlated with better prognosis (13-15).