RT Journal Article SR Electronic T1 Molecular Interaction of Serotonin 5-HT2A Receptor Residues Phe339(6.51) and Phe340(6.52) with Superpotent N-Benzyl Phenethylamine Agonists JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 1956 OP 1964 DO 10.1124/mol.106.028720 VO 70 IS 6 A1 Michael R. Braden A1 Jason C. Parrish A1 John C. Naylor A1 David E. Nichols YR 2006 UL http://molpharm.aspetjournals.org/content/70/6/1956.abstract AB Experiments were conducted to examine the molecular basis for the high affinity and potency of a new class of 5-HT2A receptor agonists, N-benzyl phenethylamines. Competition binding assays at several serotonin receptors confirmed that an N-arylmethyl substitution was necessary for affinity increases up to 300-fold over simple N-alkyl homologs, as well as enhanced selectivity for 5-HT2A versus 5-HT2C and 5-HT1A receptors. PI hydrolysis functional assays confirmed that these N-benzyl phenethylamines are potent and highly efficacious agonists at the rat 5-HT2A receptor. Virtual docking of these compounds into a human 5-HT2A receptor homology model indicated that the N-benzyl moiety might be interacting with Phe339(6.51), whereas the phenethylamine portion was likely to be interacting with Phe340(6.52). Experiments in h5-HT2A receptors with Phe339(6.51)L and Phe340(6.52)L mutations seem to support this hypothesis. Dramatic detrimental effects on affinity, potency, and intrinsic activity were observed with the Phe339(6.51)L mutation for all N-benzyl analogs, whereas most N-unsubstituted phenethylamines and traditional agonists were only weakly affected, if at all. Consistent with other published studies, the Phe340(6.52)L mutation detrimentally affected affinity, potency, and intrinsic activity of nearly all compounds tested, although a strong change in intrinsic activity was not seen with most N-aryl analogs. These data further validate the topology of our h5-HT2A receptor homology model. It is noteworthy that this study is the first to identify a hitherto unrecognized role for residue 6.51 in agonist activation of a serotonin G protein-coupled receptor (GPCR), whereas most previous reports have suggested a varied and sometimes contradictory role in homologous GPCRs. The American Society for Pharmacology and Experimental Therapeutics