title: Physical interaction between neurofibromin and serotonin 5-HT6 receptor promotes receptor constitutive activity.
abstract: Active G protein-coupled receptor (GPCR) conformations not only are promoted by agonists but also occur in their absence, leading to constitutive activity. Association of GPCRs with intracellular protein partners might be one of the mechanisms underlying GPCR constitutive activity. Here, we show that serotonin 5 hydroxytryptamine 6 (5-HT6) receptor constitutively activates the Gs/adenylyl cyclase pathway in various cell types, including neurons. Constitutive activity is strongly reduced by silencing expression of the Ras-GTPase activating protein (Ras-GAP) neurofibromin, a 5-HT6receptor partner. Neurofibromin is a multidomain protein encoded by the NF1 gene, the mutation of which causes Neurofibromatosis type 1 (NF1), a genetic disorder characterized by multiple benign and malignant nervous system tumors and cognitive deficits. Disrupting association of 5-HT6receptor with neurofibromin Pleckstrin Homology (PH) domain also inhibits receptor constitutive activity, and PH domain expression rescues 5-HT6receptor-operated cAMP signaling in neurofibromin-deficient cells. Furthermore, PH domains carrying mutations identified in NF1 patients that prevent interaction with the 5-HT6receptor fail to rescue receptor constitutive activity in neurofibromin-depleted cells. Further supporting a role of neurofibromin in agonist-independent Gs signaling elicited by native receptors, the phosphorylation of cAMP-responsive element-binding protein (CREB) is strongly decreased in prefrontal cortex of Nf1+/-mice compared with WT mice. Moreover, systemic administration of a 5-HT6receptor inverse agonist reduces CREB phosphorylation in prefrontal cortex of WT mice but not Nf1+/-mice. Collectively, these findings suggest that disrupting 5-HT6receptor-neurofibromin interaction prevents agonist-independent 5-HT6receptor-operated cAMP signaling in prefrontal cortex, an effect that might underlie neuronal abnormalities in NF1 patients.
authors: Centre de Biophysique Moléculaire, CNRS, Unité Propre de Recherche 4301, Université d'Orléans, 45071 Orleans, France.
authors: Wissem
authors: W
authors: Deraredj Nadim
authors: Institut de Génomique Fonctionnelle, CNRS UMR 5203, INSERM U1191, Université de Montpellier, F-34094 Montpellier Cedex 5, France.
authors: Séverine
authors: S
authors: Chaumont-Dubel
authors: Centre de Biophysique Moléculaire, CNRS, Unité Propre de Recherche 4301, Université d'Orléans, 45071 Orleans, France.
authors: Fahima
authors: F
authors: Madouri
authors: Centre de Biophysique Moléculaire, CNRS, Unité Propre de Recherche 4301, Université d'Orléans, 45071 Orleans, France.
authors: Laetitia
authors: L
authors: Cobret
authors: Centre de Biophysique Moléculaire, CNRS, Unité Propre de Recherche 4301, Université d'Orléans, 45071 Orleans, France.
authors: Marie-Ludivine
authors: ML
authors: De Tauzia
authors: Department of Medicinal Chemistry, Jagiellonian University Medical College, 30-688 Kraków, Poland.
authors: Pawel
authors: P
authors: Zajdel
authors: Centre de Biophysique Moléculaire, CNRS, Unité Propre de Recherche 4301, Université d'Orléans, 45071 Orleans, France.
authors: Hélène
authors: H
authors: Bénédetti
authors: Institut de Génomique Fonctionnelle, CNRS UMR 5203, INSERM U1191, Université de Montpellier, F-34094 Montpellier Cedex 5, France.
authors: Philippe
authors: P
authors: Marin
authors: Centre de Biophysique Moléculaire, CNRS, Unité Propre de Recherche 4301, Université d'Orléans, 45071 Orleans, France; severine.morisset-lopez@cnrs-orleans.fr.
authors: Séverine
authors: S
authors: Morisset-Lopez
mesh_terms: D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D004195:Disease Models, Animal; D005786:Gene Expression Regulation / Q000235:genetics; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D009456:Neurofibromatosis 1 / Q000235:genetics* / Q000473:pathology; D025542:Neurofibromin 1 / Q000235:genetics* / Q000378:metabolism; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D000070539:Pleckstrin Homology Domains / Q000235:genetics; D017397:Prefrontal Cortex / Q000187:drug effects / Q000473:pathology; D011985:Receptors, Serotonin / Q000235:genetics*; D012701:Serotonin / Q000235:genetics / Q000378:metabolism*
chemical_list: D025542:Neurofibromin 1; D011985:Receptors, Serotonin; C097216:serotonin 6 receptor; D012701:Serotonin; D000242:Cyclic AMP; D000262:Adenylyl Cyclases
keywords: 5-HT6 receptor; G protein-coupled receptor; constitutive activity; neurofibromatosis type 1; neurofibromin