Translocator Protein

The translocator protein (TSPO), previously known as the peripheral benzodiazepine receptor or PBR, is an 18 KDa protein that is ubiquitously expressed and localized to the outer mitochondrial membrane in eukaryotes. It was first identified in 1977 as a secondary binding site for benzodiazepines, but its function remains obscure. Crystal and NMR structures have revealed that the protein has some characteristics of both a transporter and a G-protein coupled receptor. Cholesterol, porphyrins and the naturally occurring polypeptide diazepam binding inhibitor (DBI) have been proposed as endogenous ligands for the protein.

TSPO likely has a role in the stress response, being induced by a diverse range of environmental stress conditions across many species, including inflammation and cancer in animals. Expression of TSPO is upregulated in the mitochondria of microglial cells when activated in response to inflammatory stimuli, so TSPO ligands have been proposed as imaging agents for neuroinflammatory conditions, such as Parkinson's and Alzheimer's diseases, as well as brain tumors. The protein also appears to be involved in steroidogenesis, as TSPO ligands promote steroid formation in adrenal, gonad, brain, placenta and liver tissues. Studies have additionally suggested a role for TSPO in the formation and function of adipocytes, so it is a potential target for therapy in type 2 diabetes and obesity.

External sources of pharmacological information for Translocator Protein :

• IUPHAR Receptor Code

Translocator Protein Gene Data