PK 11195 is a ligand of the peripheral translocator protein (TSPO) which was previously known as the peripheral benzodiazepine receptor. PK 11195 binds to TSPO with selectivity and high affinity (Ki = 3.1 nM in cerebellum, 4.1 nM in spinal cord), capable of blocking binding of typical benzodiazepines to TSPO. TSPO, a protein primarily localized in the outer mitochondrial membrane, is present in many peripheral tissues but highly enriched in steroid-synthesizing tissues including the brain, based on which the binding of labeled PK 11195 to tissues is used to detect the presence of TSPO and discriminate the central benzodiazepine receptor from TSPO.?
References:
1.?Watanabe Y, Shibuya T, Khatami S, et al. Comparison of typical and atypical benzodiazepines on the central and peripheral benzodiazepine receptors. The Japanese Journal of Pharmacology, 1986, 42(2): 189-197.
2.?Olson JM, Junck L, Young AB, et al. Isoquinoline and peripheral-type benzodiazepine binding in gliomas: implications for diagnostic imaging. Cancer Research, 1988, 48(20): 5837-5841.
3.?Pike VW, Halldin C, Crouzel C, et al. Radioligands for PET studies of central benzodiazepine receptors and PK (peripheral benzodiazepine) binding sites--current status. Nuclear Medicine and Biology, 1993, 20(4): 503-525.
4. Rupprecht R, Papadopoulos V, Rammes G, et al. Translocator protein (18 kDa) (TSPO) as a therapeutic target for neurological and psychiatric disorders. Nature Reviews Drug Discovery, 2010, 9: 971-988.
