Mitochondrial benzodiazepine receptor (PBR)

The so-called "mitochondrial diazepam binding inhibitor receptor" usually refers to the **mitochondrial benzodiazepine receptor (PBR)**, now widely known as the **translocator protein (TSPO)**. This outer mitochondrial membrane protein binds various benzodiazepine drugs with high affinity, but is functionally distinct from the central, synaptic GABA_A receptor-associated benzodiazepine binding sites. The endogenous ligand is the **diazepam binding inhibitor (DBI)**, which modulates cholesterol trafficking into mitochondria and is critical for **steroid hormone biosynthesis** in steroidogenic tissues. TSPO/PBR also plays roles in apoptosis, cell proliferation, and mitochondrial homeostasis, and is implicated in various diseases, including cancer, neurodegeneration, and inflammation. It is a well-characterized target for drug development, with PK 11195 and related ligands extensively used in research and clinical imaging.

Other names

Peripheral-type benzodiazepine receptorMitochondrial benzodiazepine receptorPeripheral benzodiazepine receptor (PBR)Translocator protein (TSPO)MBR18 kDa translocator proteinOuter mitochondrial membrane benzodiazepine receptor

Modulation of cholesterol import into mitochondria, affecting steroidogenesis. Modulation by drugs (e.g., PK 11195, Ro5-4864, diazepam) alters receptor's role in cholesterol transport, and downstream steroid synthesis or apoptosis. Inhibitors can block hormone-stimulated steroidogenesis; agonists can stimulate it.