Involvement of tryptophan W276 and of two surrounding amino acid residues in the high constitutive activity of the ghrelin receptor GHS-R1a.
Eur J Pharmacol
; 643(2-3): 153-61, 2010 Sep 25.
Article
em En
| MEDLINE
| ID: mdl-20599926
ABSTRACT
The human ghrelin receptor (GHS-R1a) is known to display a high level of signaling in the absence of ligand. The Trp276, located in the fully conserved CWXP motif of G protein-coupled receptors, is believed to function as a rotameric switch in these receptors. A comparative modelling of GHS-R1a with the motilin receptor, the most related G protein-coupled receptor to GHS-R1a known to date, but characterized by a very low ligand-independent signaling level, revealed that only two surrounding residues of Trp276, that are Val131 and Ile134, were different from these receptors. We mutated them at once in GHS-R1a to create a "motilin receptor-like" environment of Trp276 in order to study the consequences on GHS-R1a activation. We studied the pharmacological properties of the W276A, V131L-I134M GHS-R1a mutants. Basal as well as maximal ghrelin-induced signaling was assessed both by inositol-phosphate accumulation and SRE pathways. As compared to the wild type receptor, the SRE-luciferase assay displayed a markedly impaired basal activity for W276A whereas that of V131L-I134M was, strikingly, two fold increased. Nevertheless, the efficacy of ghrelin to bind or to stimulate mutant receptors remained unchanged. It is concluded that Trp276, Val131 and Ile134 have a significant impact on constitutive signaling of GHS-R1a, V131L-I134M being the first example of a GHS-R1a mutant with a higher basal activity than the wild type receptor.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Triptofano
/
Transdução de Sinais
/
Receptores de Grelina
Limite:
Animals
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Humans
Idioma:
En
Revista:
Eur J Pharmacol
Ano de publicação:
2010
Tipo de documento:
Article
País de afiliação:
França