title: Oligophrenin-1 Connects Exocytotic Fusion to Compensatory Endocytosis in Neuroendocrine Cells.
abstract: Oligophrenin-1 (OPHN1) is a protein with multiple domains including a Rho family GTPase-activating (Rho-GAP) domain, and a Bin-Amphiphysin-Rvs (BAR) domain. Involved in X-linked intellectual disability, OPHN1 has been reported to control several synaptic functions, including synaptic plasticity, synaptic vesicle trafficking, and endocytosis. In neuroendocrine cells, hormones and neuropeptides stored in large dense core vesicles (secretory granules) are released through calcium-regulated exocytosis, a process that is tightly coupled to compensatory endocytosis, allowing secretory granule recycling. We show here that OPHN1 is expressed and mainly localized at the plasma membrane and in the cytosol in chromaffin cells from adrenal medulla. Using carbon fiber amperometry, we found that exocytosis is impaired at the late stage of membrane fusion in Ophn1 knock-out mice and OPHN1-silenced bovine chromaffin cells. Experiments performed with ectopically expressed OPHN1 mutants indicate that OPHN1 requires its Rho-GAP domain to control fusion pore dynamics. On the other hand, compensatory endocytosis assessed by measuring dopamine-β-hydroxylase (secretory granule membrane) internalization is severely inhibited in Ophn1 knock-out chromaffin cells. This inhibitory effect is mimicked by the expression of a truncated OPHN1 mutant lacking the BAR domain, demonstrating that the BAR domain implicates OPHN1 in granule membrane recapture after exocytosis. These findings reveal for the first time that OPHN1 is a bifunctional protein that is able, through distinct mechanisms, to regulate and most likely link exocytosis to compensatory endocytosis in chromaffin cells.
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, UPR 3212, and Université de Strasbourg, 67084 Strasbourg, France, and.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Houy
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, UPR 3212, and Université de Strasbourg, 67084 Strasbourg, France, and.
authors.forename: Catherine
authors.initials: C
authors.lastname: Estay-Ahumada
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, UPR 3212, and Université de Strasbourg, 67084 Strasbourg, France, and.
authors.forename: Pauline
authors.identifier: http://orcid.org/0000-0002-3639-8052
authors.initials: P
authors.lastname: Croisé
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, UPR 3212, and Université de Strasbourg, 67084 Strasbourg, France, and.
authors.forename: Valérie
authors.initials: V
authors.lastname: Calco
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, UPR 3212, and Université de Strasbourg, 67084 Strasbourg, France, and.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Haeberlé
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, UPR 3212, and Université de Strasbourg, 67084 Strasbourg, France, and.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Bailly
authors.affiliation: Institut Cochin, Département Génétique et Développement, INSERM U 1016, CNRS UMR 8104, Faculté de Médecine de Paris Descartes, 75014 Paris, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Billuart
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, UPR 3212, and Université de Strasbourg, 67084 Strasbourg, France, and.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Vitale
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, UPR 3212, and Université de Strasbourg, 67084 Strasbourg, France, and.
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Bader
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, UPR 3212, and Université de Strasbourg, 67084 Strasbourg, France, and ory@inci-cnrs.unistra.fr gasman@inci-cnrs.unistra.fr.
authors.forename: Stéphane
authors.identifier: http://orcid.org/0000-0003-4359-1157
authors.initials: S
authors.lastname: Ory
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, UPR 3212, and Université de Strasbourg, 67084 Strasbourg, France, and ory@inci-cnrs.unistra.fr gasman@inci-cnrs.unistra.fr.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Gasman
mesh_terms: D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D019439:Chromaffin Cells / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology*; D005089:Exocytosis / Q000502:physiology*; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D008561:Membrane Fusion / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D009687:Nuclear Proteins / Q000378:metabolism*; D013572:Synaptic Vesicles / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; D020690:GTPase-Activating Proteins; D009687:Nuclear Proteins
keywords: amperometry; chromaffin cells; compensatory endocytosis; exocytosis; neuroendocrine cells; oligophrenin-1