1. The structure, abundance and function of TSPO

The 18 kDa translocator protein (TSPO), previously known as a peripheral benzodiazepine receptor (PBR) [1], is a highly conserved protein with various life essential functions in eukaryotic and prokaryotic species [2]. The TSPO gene in humans is situated on the chromosome 22q13.3 [3]. The amino acid sequence of TSPO of human origin (169 amino acids): 1 mappwvpamg ftlapslgcf vgsrfvhgeg lrwyaglqkp swhpphwvlg pvwgtlysam 61 gygsylvwke

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

lggftekavv plglytgqla lnwawppiff garqmgwalv dlllvsgaaa 121 attvawyqvs plaarllypy lawlaftttl nycvwrdnhg wrggrrlpe [4].

TSPO takes part in mitochondrial ATP production and transport, and is located on cytoplasmic and nuclear membranes and on the outer membrane of mitochondria. TSPO is abundant in metabolically active cells in different organs, such as brain, kidney, and so forth. [2]. TSPO has been also found in other organs and generally is abundant in steroid-secreting tissues. Recently, it has been detected in high abundance in osteoblasts [5]. TSPO interacts with ligands to modulate various molecular cellular activities [5–9] by affecting cell death. TSPO is thought to be involved in mitochondrial cholesterol transport and related to cell death pathways (apoptosis and necrosis) as a functional part of the mitochondrial permeability transition pore (MPTP), along with additional related receptors and protein structures, for example, voltage-dependent anion channel (VDAC) and the adenine nucleotide translocase (ANT) [1, 2]. The existence of functional interconnection between TSPO and MPTP has been challenged recently in studies showing that the MPTP can induce apoptosis and cholesterol transport without the involvement of TSPO [10]. Thus, the exact mechanism of the TSPO involvement in cell death has not been determined yet, but its functional role in this process is strongly supported [1, 2, 6–8].
