Drug discovery targeting human 5-HT_2C receptors: Residues S3.36 and Y7.43 impact ligand¡ªBinding pocket structure via hydrogen bond formation

详细信息    查看全文

• 作者：Clinton E. Canal ; Tania C. Cordova-Sintjago ; Nancy Y. Villa ; Li-Juan Fang ; Raymond G. Booth ; ^{booth@cop.ufl.edu}
• 关键词：G protein-coupled receptor ; Molecular modeling ; Mutagenesis ; Serotonin 2C receptor
• 刊名：European Journal of Pharmacology
• 出版年：2011
• 出版时间：30 December, 2011
• 年：2011
• 卷：673
• 期：1-3
• 页码：1-12
• 全文大小：1K

文摘

Specific activation of serotonin (5-HT) 5-HT_2C G protein-coupled receptors may be therapeutic for obesity and neuropsychiatric disorders. Mutagenesis coupled with computational and molecular modeling experiments based on the human ¦Â₂ adrenergic receptor structure was employed to delineate the interactions of different ligands at human 5-HT_2C residues D3.32, S3.36 and Y7.43. No binding of the tertiary amine radioligand ([³H]-mesulergine) could be detected when the 5-HT_2C D3.32 residue was mutated to alanine (D3.32A). The S3.36A point-mutation greatly reduced affinity of primary amine ligands, modestly reduced affinity of a secondary amine, and except for the 5-HT_2C-specific agonist N(CH₃)₂-PAT, affinity of tertiary amines was unaffected. Molecular modeling results indicated that the primary amines form hydrogen bonds with the S3.36 residue, whereas, with the exception of N(CH₃)₂-PAT, tertiary amines do not interact considerably with this residue. The Y7.43A point-mutation greatly reduced affinity of 5-HT, yet reduced to a lesser extent the affinity of tryptamine that lacks the 5-hydroxy moiety present in 5-HT; modeling results indicated that the 5-HT 5-hydroxy moiety hydrogen bonds with Y7.43 at the 5-HT_2C receptor. Additional modeling results showed that 5-HT induced a hydrogen bond between Y7.43 and D3.32. Finally, modeling results revealed two low-energy binding modes for 5-HT in the 5-HT_2C binding pocket, supporting the concept that multiple agonist binding modes may stabilize different receptor active conformations to influence signaling. Ligand potencies for modulating WT and point-mutated 5-HT_2C receptor-mediated phospholipase C activity were in accordance with the affinity data. Ligand efficacies, however, were altered considerably by the S3.36A mutation only.