title: Structural requirements to obtain highly potent and selective 18 kDa Translocator Protein (TSPO) Ligands.
abstract: The (18 kDa) Translocator Protein (TSPO), was initially identified in 1977 as peripheral binding site for the benzodiazepine diazepam and named "Peripheral-type benzodiazepine receptor (PBR)". It is an evolutionarily well-conserved protein particularly located at the outer/inner mitochondrial membrane contact sites, in closely association with the 32 kDa voltage-dependent anion channel (VDAC) and the 30 kDa adenine nucleotide translocase (ANT), thus forming the mitochondrial permeability transition pore (MPTP). TSPO is ubiquitary expressed in peripheral tissues (steroid producing tissues, liver, heart, kidney, lung, immune system) and in lower levels in the central nervous system, where it is mainly located in glial cells, and in neurons. TSPO is involved in a variety of biological processes such as cholesterol transport, steroidogenesis, calcium homeostasis, lipid metabolism, mitochondrial oxidation, cell growth and differentiation, apoptosis induction, and regulation of immune functions. In the last decade, many studies have reported that TSPO basal expression is altered in a number of human pathologies, such as cancer and neurodegenerative disorders (Huntington's and Alzheimer's diseases), as well as in various forms of brain injury and inflammation and anxiety. Consequently, TSPO has not only been suggested as a promising drug target for a number of therapeutic applications (anticonvulsant, anxiolytic, immunomodulating, etc.), but also as valid diagnostic marker for related-disease state and progression, prompting the development of specific labelled ligands as powerful tools for imaging techniques. A number of structurally different classes of ligands have been reported, showing high affinity and selectivity towards TSPO. Indeed, most of these ligands have been designed starting from selective CBR ligands which were structurally modified in order to shift their affinity towards TSPO. Extensive structure-activity relationship studies were performed allowing to hypothesize various TSPO pharmacophore models. The purpose of this paper is to highlight the structural requirements needed to obtain TSPO ligands with high affinity and selectivity.
authors.affiliation: Dipartimento di Scienze Farmaceutiche, Università di Pisa, Via Bonanno 6, 56126 Pisa, Italy. taliani@farm.unipi.it
authors.forename: Sabrina
authors.initials: S
authors.lastname: Taliani
authors.forename: Isabella
authors.initials: I
authors.lastname: Pugliesi
authors.forename: Federico
authors.initials: F
authors.lastname: Da Settimo
mesh_terms: D000813:Anilides / Q000138:chemical synthesis / Q000494:pharmacology; D000818:Animals; D014151:Anti-Anxiety Agents / Q000138:chemical synthesis* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000494:pharmacology; D001569:Benzodiazepines / Q000138:chemical synthesis / Q000494:pharmacology; D006801:Humans; D007154:Immune System Diseases / Q000188:drug therapy; D007155:Immunologic Factors / Q000138:chemical synthesis* / Q000494:pharmacology; D007210:Indoleacetic Acids / Q000138:chemical synthesis / Q000494:pharmacology; D007546:Isoquinolines / Q000138:chemical synthesis / Q000494:pharmacology; D008024:Ligands; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D009369:Neoplasms / Q000188:drug therapy; D019636:Neurodegenerative Diseases / Q000188:drug therapy; D011725:Pyridines / Q000138:chemical synthesis / Q000494:pharmacology; D051381:Rats; D018079:Receptors, GABA / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D000813:Anilides; D014151:Anti-Anxiety Agents; D000970:Antineoplastic Agents; C463819:Bzrp protein, mouse; D007155:Immunologic Factors; D007210:Indoleacetic Acids; D007546:Isoquinolines; D008024:Ligands; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D011725:Pyridines; D018079:Receptors, GABA; C499229:TSPO protein, human; D001569:Benzodiazepines; C015950:indoleacetamide