RT Journal Article SR Electronic T1 Me-Talnetant and Osanetant Interact within Overlapping but Not Identical Binding Pockets in the Human Tachykinin Neurokinin 3 Receptor Transmembrane Domains JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 1736 OP 1750 DO 10.1124/mol.107.042754 VO 73 IS 6 A1 Pari Malherbe A1 Caterina Bissantz A1 Anne Marcuz A1 Claudia Kratzeisen A1 Marie-Thérèse Zenner A1 Joseph G. Wettstein A1 Hasane Ratni A1 Claus Riemer A1 Will Spooren YR 2008 UL http://molpharm.aspetjournals.org/content/73/6/1736.abstract AB Recent clinical trials have indicated that neurokinin 3 receptor antagonists (S)-(+)-N-{{3-[1-benzoyl-3-(3,4-dichlorophenyl)-piperidin-3-yl]prop-1-yl}-4-phenylpiperidin-4-yl}-N-methylacetamine (SR142801; osanetant) and (S)-(-)-N-(α-ethylbenzyl)-3-hydroxy-2-phenylquinoline-4-carboxamide (SB223412; talnetant) may treat symptoms of schizophrenia. Using site-directed mutagenesis, rhodopsin-based modeling, [3H](S)-(-)-N-(α-ethylbenzyl)-3-methoxy-2-phenylquinoline-4-carboxamide (Me-talnetant) and [3H]osanetant binding, and functional Schild analyses, we have demonstrated the important molecular determinants of neurokinin B (NKB), Me-talnetant, and osanetant binding pockets. The residues Asn1382.57, Asn1422.61, Leu23245.49, Tyr3156.51, Phe3427.39, and Met3467.43 were found to be crucial for the NKB binding site. We observed that the M1342.53A, V1693.36M, F3427.39M, and S3417.38I/F3427.39M mutations resulted in the complete loss of [3H]Metalnetant and [3H]osanetant binding affinities and also abolished their functional potencies in an NKB-evoked accumulation of [3H]inositol phosphates assay, whereas the mutations V951.42A, N1422.61A, Y3156.51F, and M3467.43A behaved differently between the interacting modes of two antagonists. V951.42A and M3467.43A significantly decreased the affinity and potency of Me-talnetant. Y3156.51F, although not affecting Me-talnetant, led to a significant decrease in affinity and potency of osanetant. The mutation N1422.61A, which abolished the potency and affinity of osanetant, led to a significant increase in the affinity and potency of Me-talnetant. The proposed docking mode was further validated using (S)-2-(3,5-bis-trifluoromethyl-phenyl)-N-[4-(4-fluoro-2-methyl-phenyl)-6-((S)-4-methanesulfonyl-3-methyl-piperazin-1-yl)-pyridin-3-yl]-N-methyl-isobutyramide (RO49085940), from another chemical class. It is noteworthy that the mutation F3427.39A caused an 80-fold gain of RO4908594 binding affinity, but the same mutation resulted in the complete loss of the affinity of Me-talnetant and partial loss of the affinity of osanetant. These observations show that the binding pocket of Me-talnetant and osanetant are overlapping, but not identical. Taken together, our data are consistent with the proposed docking modes where Me-talnetant reaches deeply into the pocket formed by transmembrane (TM)1, -2, and -7, whereas osanetant fills the pocket TM3, -5, and -6 with its phenyl-piperidine moiety. The American Society for Pharmacology and Experimental Therapeutics