RT Journal Article
SR Electronic
T1 Molecular pharmacology and ligand docking studies reveal a single amino acid difference between mouse and human serotonin 5-HT2A receptors that impacts behavioral translation of novel 4-phenyl-2-dimethylaminotetralin ligands
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP jpet.113.208637
DO 10.1124/jpet.113.208637
A1 Clinton E Canal
A1 Tania Cordova-Sintjago
A1 Yue Liu
A1 Myong S. Kim
A1 Drake Morgan
A1 Raymond G. Booth
YR 2013
UL http://jpet.aspetjournals.org/content/early/2013/09/30/jpet.113.208637.abstract
AB During translational studies to develop trans-4-phenyl-2-dimethylaminotetralin (PAT) compounds for neuropsychiatric disorders, the (+)- and (-)-enantiomers of the analog 6-OH-7-Cl-PAT demonstrated unusual pharmacology at serotonin 5-HT2 G protein-coupled-receptors (GPCRs). The enantiomers had similar affinities (Ki) at human (h) 5-HT2A receptors (~70 nM), however, in an in vivo mouse model of 5-HT2A receptor activation ((±)-(2,5)-dimethoxy-4-iodoamphetamine elicited head-twitch), (-)-6-OH-7-Cl-PAT was about 5-fold more potent than the (+)-enantiomer. It was discovered (+)-6-OH-7-Cl-PAT (only) had ~40-fold lower affinity at mouse (m) compared to h5-HT2A receptors. Molecular modeling and computational ligand docking studies indicated the 6-OH moiety of (+)- but not (-)-6-OH-7-Cl-PAT could form a hydrogen bond with serine (S) 5.46 at the h5-HT2A receptor, however, the m5-HT2A as well as m5-HT2B, h5-HT2B, m5-HT2C, and h5-HT2C receptors have alanine (A) at position 5.46, obviating this interaction; (+)-6-OH-7-Cl-PAT also showed ~50-fold lower affinity than (-)-6-OH-7-Cl-PAT at mouse and h5-HT2C receptors. Mutagenesis studies confirmed 5-HT2A S5.46 is critical for (+)- but not (-)-6-OH-7-Cl-PAT binding, as well as function. The (+)-6-OH-7-Cl-PAT enantiomer showed partial agonist effects at h5-HT2A WT and m5-HT2A A5.46S point-mutated receptors, but did not activate m5-HT2A WT and h5-HT2A S5.46A point-mutated receptors, or h5-HT2B, h5-HT2C, and m5-HT2C receptors; (-)-6-OH-7-Cl-PAT did not activate any of the 5-HT2 receptors. Experiments also included (+) and (-)-6-OMe-7-Cl-PAT to validate hydrogen bonding interactions proposed for the corresponding 6-OH analogs. Results indicate PAT ligand 3-dimensional structure impacts target receptor binding and translational outcomes, supporting the hypothesis that GPCR ligand structure governs orthosteric binding pocket molecular determinants and resulting pharmacology.