Pregnane X receptor

Pregnane X receptor (PXR), also known as the steroid and xenobiotic sensing nuclear receptor (SXR), is a protein that in humans is encoded by the NR1I2 (nuclear receptor subfamily 1, group I, member 2) gene. PXR is a member of the nuclear receptor family of transcription factors and is activated by a variety of compounds and drugs.

Function

Pregnane X receptor plays a central role in the body's defense against potentially harmful, foreign chemicals. It is primarily expressed in the liver and intestine, two major sites of xenobiotic detoxification. PXR regulates the expression of Phase I and Phase II enzymes, as well as drug transporters, which are involved in the metabolism and elimination of various potentially harmful compounds.

Ligands

Pregnane X receptor is activated by a wide range of chemicals. These include not only prescription drugs, such as rifampicin and paclitaxel, but also dietary supplements, herbal remedies, and even compounds found in the environment. This broad ligand specificity is thought to be a result of the large and flexible ligand-binding pocket of PXR.

Clinical significance

Given its role in drug metabolism, PXR is of significant clinical interest. Variations in the PXR gene can affect an individual's response to drugs, potentially leading to adverse drug reactions or therapeutic failure. Furthermore, PXR activation has been implicated in drug-drug interactions, as well as in the development of certain diseases, such as cancer and metabolic syndrome.

See also

• Nuclear receptor
• Xenobiotic
• Drug metabolism