Loss of constitutive activity of the growth hormone secretagogue receptor in familial short stature
Jacques Pantel, Marie Legendre, Sylvie Cabrol, Latifa Hilal, Yassir Hajaji, Séverine Morisset, Sylvie Nivot, Marie-Pierre Vie-Luton, Dominique Grouselle, Marc de Kerdanet, Abdelkrim Kadiri, Jacques Epelbaum, Yves Le Bouc, Serge Amselem
Jacques Pantel, Marie Legendre, Sylvie Cabrol, Latifa Hilal, Yassir Hajaji, Séverine Morisset, Sylvie Nivot, Marie-Pierre Vie-Luton, Dominique Grouselle, Marc de Kerdanet, Abdelkrim Kadiri, Jacques Epelbaum, Yves Le Bouc, Serge Amselem
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Research Article Endocrinology

Loss of constitutive activity of the growth hormone secretagogue receptor in familial short stature

Abstract

The growth hormone (GH) secretagogue receptor (GHSR) was cloned as the target of a family of synthetic molecules endowed with GH release properties. As shown recently through in vitro means, this receptor displays a constitutive activity whose clinical relevance is unknown. Although pharmacological studies have demonstrated that its endogenous ligand — ghrelin — stimulates, through the GHSR, GH secretion and appetite, the physiological importance of the GHSR-dependent pathways remains an open question that gives rise to much controversy. We report the identification of a GHSR missense mutation that segregates with short stature within 2 unrelated families. This mutation, which results in decreased cell-surface expression of the receptor, selectively impairs the constitutive activity of the GHSR, while preserving its ability to respond to ghrelin. This first description, to our knowledge, of a functionally significant GHSR mutation, which unveils the critical importance of the GHSR-associated constitutive activity, discloses an unusual pathogenic mechanism of growth failure in humans.

Authors

Jacques Pantel, Marie Legendre, Sylvie Cabrol, Latifa Hilal, Yassir Hajaji, Séverine Morisset, Sylvie Nivot, Marie-Pierre Vie-Luton, Dominique Grouselle, Marc de Kerdanet, Abdelkrim Kadiri, Jacques Epelbaum, Yves Le Bouc, Serge Amselem

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Expression of the A204E mutant GHSR1a at the cellular level. (A) Specifi...
Expression of the A204E mutant GHSR1a at the cellular level. (A) Specific binding of 125I-ghrelin to HEK293 cells transiently transfected with empty vector (mock), or HA-GHSR-WT (WT) or HA-GHSR-A204E (A204E), as determined on whole cells. Transfected cells were incubated over 4 hours at 4°C with 125I-ghrelin (30 pM). The specific binding, which represents the difference between total binding and nonspecific binding, is expressed as a percentage of the binding associated with the WT GHSR1a receptor. A representative experiment of 3 independent experiments (each performed in triplicate) is shown. (B) Displacement curves for 125I-ghrelin binding to whole HEK293 cells stably expressing the A204E mutant or the WT GHSR1a. The binding of 30 pM of 125I-ghrelin was displaced by increasing concentrations of cold ghrelin. A representative experiment of 3 independent experiments (each performed in triplicate) is shown. (C) Immunolocalization of HA-tagged WT and A204E mutant receptors transiently expressed in COS-7 cells (×40). The immunostaining of HA-tagged GHSR1a receptors was performed by means of an anti-HA monoclonal primary antibody incubated in the absence or in the presence of a permeabilizing reagent in order to visualize the receptors located at the cell surface or at both the cell surface and the intracellular level, respectively. Anti-HA mAb labeling was revealed by an Alexa Fluor 568 goat anti-mouse secondary antibody. Merge pictures show the anti-HA Alexa Fluor 568 staining (red) together with the staining of nuclei with DAPI (blue).