Sodium is a negative allosteric regulator of the ghrelin receptor
Guillaume Ferré,
Antoniel A.S. Gomes,
Maxime Louet,
Marjorie Damian,
Paulo M. Bisch,
Olivier Saurel,
Nicolas Floquet,
Alain Milon,
Jean-Louis Banères
Affiliations
Guillaume Ferré
Institut de Pharmacologie et de Biologie Structurale IPBS, Université de Toulouse UPS, CNRS, Toulouse, France
Antoniel A.S. Gomes
Institut des Biomolécules Max Mousseron IBMM, UMR-5247, University Montpellier, CNRS, ENSCM, Montpellier, France; Laboratório de Física Biológica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-590, Brazil
Maxime Louet
Institut des Biomolécules Max Mousseron IBMM, UMR-5247, University Montpellier, CNRS, ENSCM, Montpellier, France
Marjorie Damian
Institut des Biomolécules Max Mousseron IBMM, UMR-5247, University Montpellier, CNRS, ENSCM, Montpellier, France
Paulo M. Bisch
Laboratório de Física Biológica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-590, Brazil
Olivier Saurel
Institut de Pharmacologie et de Biologie Structurale IPBS, Université de Toulouse UPS, CNRS, Toulouse, France
Nicolas Floquet
Institut des Biomolécules Max Mousseron IBMM, UMR-5247, University Montpellier, CNRS, ENSCM, Montpellier, France
Alain Milon
Institut de Pharmacologie et de Biologie Structurale IPBS, Université de Toulouse UPS, CNRS, Toulouse, France; Corresponding author
Jean-Louis Banères
Institut des Biomolécules Max Mousseron IBMM, UMR-5247, University Montpellier, CNRS, ENSCM, Montpellier, France; Corresponding author
Summary: The functional properties of G protein-coupled receptors (GPCRs) are intimately associated with the different components in their cellular environment. Among them, sodium ions have been proposed to play a substantial role as endogenous allosteric modulators of GPCR-mediated signaling. However, this sodium effect and the underlying mechanisms are still unclear for most GPCRs. Here, we identified sodium as a negative allosteric modulator of the ghrelin receptor GHSR (growth hormone secretagogue receptor). Combining 23Na-nuclear magnetic resonance (NMR), molecular dynamics, and mutagenesis, we provide evidence that, in GHSR, sodium binds to the allosteric site conserved in class A GPCRs. We further leveraged spectroscopic and functional assays to show that sodium binding shifts the conformational equilibrium toward the GHSR-inactive ensemble, thereby decreasing basal and agonist-induced receptor-catalyzed G protein activation. All together, these data point to sodium as an allosteric modulator of GHSR, making this ion an integral component of the ghrelin signaling machinery.
