Identification of residues in transmembrane regions III and VI that contribute to the ligand binding site of the serotonin 5-HT6 receptor.
J Neurochem
; 71(5): 2169-77, 1998 Nov.
Article
en En
| MEDLINE
| ID: mdl-9798944
ABSTRACT
We have examined the ligand binding site of the serotonin 5-HT6 receptor using site-directed mutagenesis. Replacing the highly conserved Asp106 in transmembrane region III by asparagine eliminated D-[3H]-lysergic acid diethylamide ([3H]LSD) binding to the mutant receptor transiently expressed in HEK293 cells. The potency of 5-HT and LSD to stimulate adenylyl cyclase was reduced by 3,600- and 500-fold, respectively, suggesting that an ionic interaction between the positively charged amino group of 5-HT and D106 is essential for high-affinity binding and important for receptor activation. In addition, basal cyclic AMP levels in cells expressing this mutant were increased. Mutation of a tryptophan residue one helix turn toward the extracellular side of transmembrane region III (Trp102) to phenylalanine produced significant changes in the binding affinity and potency of several ligands, consistent with a role of this residue in the formation of the ligand binding site. The exchange of two neighboring residues in the carboxy-terminal half of transmembrane region VI (Ala287 and Asn288) for leucine and serine resulted in a mutant receptor with increased affinities (seven- to 30-fold) for sumatriptan and several ergopeptine ligands. The identification of these interactions will help to improve models of the 5-HT6 receptor ligand binding site.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Receptores de Serotonina
Tipo de estudio:
Diagnostic_studies
Límite:
Humans
Idioma:
En
Revista:
J Neurochem
Año:
1998
Tipo del documento:
Article
País de afiliación:
Suiza