Human serotonin 5-HT_(2C) G protein-coupled receptor homology model from the β_2 adrenoceptor structure: Ligand docking and mutagenesis studies

摘要

Activation of the serotonin (5-hydroxytryptamine, 5-HT) 5HT_(2C) G protein-coupled receptor (GPCR) is proposed as novel pharmacotherapy for obesity and neuropsychiatric disorders. In contrast, activation of the 5-HT _(2A) and 5-HT_(2B) GPCRs is associated with untoward hallucinogenic and cardiopulmonary effects, respectively. There is no crystal structure available to guide design of 5-HT_(2C) receptor-specific ligands. For this reason, a homology model of the 5-HT_(2C) receptor was built based on the crystal structure of the human β_2 adrenoceptor GPCR to delineate molecular determinants of ligand-receptor interactions for drug design purposes. Computational and experimental studies were carried out to validate the model. Binding of N(CH_3) _2-PAT [(1R, 3S)-(-)-trans-1-phenyl-3-N,N-dimethylamino-1,2,3,4- tetrahydronaphthalene], a novel 5-HT_(2C) agonist/5-HT_(2A/2B) inverse agonist, and its secondary [NH(CH_3)-PAT] and primary (NH _2-PAT) amine analogs were studied at the 5-HT_(2C) wild type (WT) and D3.32A, S3.36A, and Y7.43A 5-HT_2C point-mutated receptors. Reference ligands included the tertiary amines lisuride and mesulergine and the primary amine 5-HT. Modeling results indicated that 5-HT_(2C) residues D3.32, S3.36, and Y7.43 play a role in ligand binding. Experimental ligand binding results with WT and point-mutated receptors confirmed the impact of D3.32, S3.36, and Y7.43 on ligand affinity.