title: Chromogranin A induces the biogenesis of granules with calcium- and actin-dependent dynamics and exocytosis in constitutively secreting cells.
abstract: Chromogranins are a family of acidic glycoproteins that play an active role in hormone and neuropeptide secretion through their crucial role in secretory granule biogenesis in neuroendocrine cells. However, the molecular mechanisms underlying their granulogenic activity are still not fully understood. Because we previously demonstrated that the expression of the major component of secretory granules, chromogranin A (CgA), is able to induce the formation of secretory granules in nonendocrine COS-7 cells, we decided to use this model to dissect the mechanisms triggered by CgA leading to the biogenesis and trafficking of such granules. Using quantitative live cell imaging, we first show that CgA-induced organelles exhibit a Ca(2+)-dependent trafficking, in contrast to native vesicle stomatitis virus G protein-containing constitutive vesicles. To identify the proteins that confer such properties to the newly formed granules, we developed CgA-stably-expressing COS-7 cells, purified their CgA-containing granules by subcellular fractionation, and analyzed the granule proteome by liquid chromatography-tandem mass spectrometry. This analysis revealed the association of several cytosolic proteins to the granule membrane, including GTPases, cytoskeleton-based molecular motors, and other proteins with actin- and/or Ca(2+)-binding properties. Furthermore, disruption of cytoskeleton affects not only the distribution and the transport but also the Ca(2+)-evoked exocytosis of the CgA-containing granules, indicating that these granules interact with microtubules and cortical actin for the regulated release of their content. These data demonstrate for the first time that the neuroendocrine factor CgA induces the recruitment of cytoskeleton-, GTP-, and Ca(2+)-binding proteins in constitutively secreting COS-7 cells to generate vesicles endowed with typical dynamics and exocytotic properties of neuroendocrine secretory granules.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (Inserm) U982, University of Rouen, Mont-Saint-Aignan 76821, France.
authors.forename: Salah
authors.initials: S
authors.lastname: Elias
authors.forename: Charlène
authors.initials: C
authors.lastname: Delestre
authors.forename: Stéphane
authors.initials: S
authors.lastname: Ory
authors.forename: Sébastien
authors.initials: S
authors.lastname: Marais
authors.forename: Maïté
authors.initials: M
authors.lastname: Courel
authors.forename: Rafael
authors.initials: R
authors.lastname: Vazquez-Martinez
authors.forename: Sophie
authors.initials: S
authors.lastname: Bernard
authors.forename: Laurent
authors.initials: L
authors.lastname: Coquet
authors.forename: Maria M
authors.initials: MM
authors.lastname: Malagon
authors.forename: Azeddine
authors.initials: A
authors.lastname: Driouich
authors.forename: Philippe
authors.initials: P
authors.lastname: Chan
authors.forename: Stéphane
authors.initials: S
authors.lastname: Gasman
authors.forename: Youssef
authors.initials: Y
authors.lastname: Anouar
authors.forename: Maité
authors.initials: M
authors.lastname: Montero-Hadjadje
mesh_terms: D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D002522:Chlorocebus aethiops; D053379:Chromogranin A / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D005089:Exocytosis / Q000187:drug effects; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D022142:Secretory Vesicles / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D053719:Tandem Mass Spectrometry
chemical_list: D000199:Actins; D053379:Chromogranin A; D002118:Calcium