Functional characterization of a new human melanocortin-4 receptor homozygous mutation (N72K) that is associated with early-onset obesity.
Mol Biol Rep
; 41(12): 7967-72, 2014 Dec.
Article
em En
| MEDLINE
| ID: mdl-25163632
ABSTRACT
The melanocortin 4 receptor (MC4R) is expressed in the hypothalamus and is essential for regulation of appetite and energy expenditure. MC4R dysfunction in humans causes hyperphagia, impaired satiety and obesity. We have identified a novel c.216C>A (N72 K) homozygous mutation in MC4R in a girl with severe obesity. The patient presented with early-onset obesity and hyperphagia indicating an effect of the homozygous mutation on her phenotype. In silico analyses indicate a damaging effect on receptor function, and the mutation is unusual in occurring in the first intra-cellular loop of the receptor. Site-directed mutagenesis was used to generate plasmid constructs expressing wild-type and mutant MC4R. These were transfected into HEK293 cells and assessed for cAMP responsiveness to α-MSH. Cells expressing N-terminal HA and C-terminal GFP-tagged MC4R were assessed by immunofluorescence confocal microscopy and flow cytometry for correct cell-surface localization. The maximal response of the mutant MC4R to α-MSH was decreased to 20 ± 1 % of the wild type receptor response, and the EC50 was increased from 16.5 ± 5.4 nM to 37.0 ± 8.3 nM. Localization of N- and C-terminally tagged MC4R by confocal microscopy and flow cytometry showed aberrant retention of the mutant receptor in the cytoplasm. Our data describe a rare homozygous inactivating mutation in the first intra-cellular loop of MC4R that markedly impairs its function and is associated with early-onset obesity and hyperphagia.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Mutação de Sentido Incorreto
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Receptor Tipo 4 de Melanocortina
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Obesidade Infantil
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Homozigoto
Tipo de estudo:
Prognostic_studies
/
Risk_factors_studies
Limite:
Female
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Humans
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Infant
Idioma:
En
Revista:
Mol Biol Rep
Ano de publicação:
2014
Tipo de documento:
Article