title: Intersectin-1L nucleotide exchange factor regulates secretory granule exocytosis by activating Cdc42.
abstract: Rho GTPases are key regulators of the actin cytoskeleton in membrane trafficking events. We previously reported that Cdc42 facilitates exocytosis in neuroendocrine cells by stimulating actin assembly at docking sites for secretory granules. These findings raise the question of the mechanism activating Cdc42 in exocytosis. The neuronal guanine nucleotide exchange factor, intersectin-1L, which specifically activates Cdc42 and is at an interface between membrane trafficking and actin dynamics, appears as an ideal candidate to fulfill this function. Using PC12 and chromaffin cells, we now show the presence of intersectin-1 at exocytotic sites. Moreover, through an RNA interference strategy coupled with expression of various constructs encoding the guanine nucleotide exchange domain, we demonstrate that intersectin-1L is an essential component of the exocytotic machinery. Silencing of intersectin-1 prevents secretagogue-induced activation of Cdc42 revealing intersectin-1L as the factor integrating Cdc42 activation to the exocytotic pathway. Our results extend the current role of intersectin-1L in endocytosis to a function in exocytosis and support the idea that intersectin-1L is an adaptor that coordinates exo-endocytotic membrane trafficking in secretory cells.
authors.affiliation: Département Neurotransmission & Sécrétion Neuroendocrine, Institut des Neurosciences Cellulaires et Intégratives (UMR 7168/LC2), Centre National de la Recherche Scientifique & Université Louis Pasteur, Strasbourg, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Malacombe
authors.forename: Mara
authors.initials: M
authors.lastname: Ceridono
authors.forename: Valérie
authors.initials: V
authors.lastname: Calco
authors.forename: Sylvette
authors.initials: S
authors.lastname: Chasserot-Golaz
authors.forename: Peter S
authors.initials: PS
authors.lastname: McPherson
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Bader
authors.forename: Stéphane
authors.initials: S
authors.lastname: Gasman
mesh_terms: D000199:Actins / Q000378:metabolism; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D019439:Chromaffin Cells / Q000166:cytology / Q000378:metabolism; D005089:Exocytosis / Q000502:physiology; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D018613:Microscopy, Confocal; D016716:PC12 Cells; D051381:Rats; D022142:Secretory Vesicles / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000199:Actins; D033942:Adaptor Proteins, Vesicular Transport; D020662:Guanine Nucleotide Exchange Factors; C485568:ITSN1 protein, human; D020764:cdc42 GTP-Binding Protein; D002118:Calcium