TY - JOUR T1 - Identification of Determinants Required for Agonistic and Inverse Agonistic Ligand Properties at the ADP Receptor P2Y<sub>12</sub> JF - Molecular Pharmacology JO - Mol Pharmacol SP - 256 LP - 266 DO - 10.1124/mol.112.082198 VL - 83 IS - 1 AU - Philipp Schmidt AU - Lars Ritscher AU - Elizabeth N. Dong AU - Thomas Hermsdorf AU - Maxi Cöster AU - Doreen Wittkopf AU - Jens Meiler AU - Torsten Schöneberg Y1 - 2013/01/01 UR - http://molpharm.aspetjournals.org/content/83/1/256.abstract N2 - The ADP receptor P2Y12 belongs to the superfamily of G protein–coupled receptors (GPCRs), and its activation triggers platelet aggregation. Therefore, potent antagonists, such as clopidogrel, are of high clinical relevance in prophylaxis and treatment of thromboembolic events. P2Y12 displays an elevated basal activity in vitro, and as such, inverse agonists may be therapeutically beneficial compared with antagonists. Only a few inverse agonists of P2Y12 have been described. To expand this limited chemical space and improve understanding of structural determinants of inverse agonist-receptor interaction, this study screened a purine compound library for lead structures using wild-type (WT) human P2Y12 and 28 constitutively active mutants. Results showed that ATP and ATP derivatives are agonists at P2Y12. The potency at P2Y12 was 2-(methylthio)-ADP &gt; 2-(methylthio)-ATP &gt; ADP &gt; ATP. Determinants required for agonistic ligand activity were identified. Molecular docking studies revealed a binding pocket for the ATP derivatives that is bordered by transmembrane helices 3, 5, 6, and 7 in human P2Y12, with Y105, E188, R256, Y259, and K280 playing a particularly important role in ligand interaction. N-Methyl-anthraniloyl modification at the 3′-OH of the 2′-deoxyribose leads to ligands (mant-deoxy-ATP [dATP], mant-deoxy-ADP) with inverse agonist activity. Inverse agonist activity of mant-dATP was found at the WT human P2Y12 and half of the constitutive active P2Y12 mutants. This study showed that, in addition to ADP and ATP, other ATP derivatives are not only ligands of P2Y12 but also agonists. Modification of the ribose within ATP can result in inverse activity of ATP-derived ligands. ER -