title: The small GTPase Cdc42 modulates the number of exocytosis-competent dense-core vesicles in PC12 cells.
abstract: Although the small GTPase Rho family Cdc42 has been shown to facilitate exocytosis through increasing the amount of hormones released, the precise mechanisms regulating the quantity of hormones released on exocytosis are not well understood. Here we show by live cell imaging analysis under TIRF microscope and immunocytochemical analysis under confocal microscope that Cdc42 modulated the number of fusion events and the number of dense-core vesicles produced in the cells. Overexpression of a wild-type or constitutively-active form of Cdc42 strongly facilitated high-KCl-induced exocytosis from the newly recruited plasma membrane vesicles in PC12 cells. By contrast, a dominant-negative form of Cdc42 inhibited exocytosis from both the newly recruited and previously docked plasma membrane vesicles. The number of intracellular dense-core vesicles was increased by the overexpression of both a wild-type and constitutively-active form of Cdc42. Consistently, activation of Cdc42 by overexpression of Tuba, a Golgi-associated guanine nucleotide exchange factor for Cdc42 increased the number of intracellular dense-core vesicles, whereas inhibition of Cdc42 by overexpression of the Cdc42/Rac interactive binding domain of neuronal Wiskott-Aldrich syndrome protein decreased the number of them. These findings suggest that Cdc42 facilitates exocytosis by modulating both the number of exocytosis-competent dense-core vesicles and the production of dense-core vesicles in PC12 cells.
authors.affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan.
authors.forename: Mai
authors.initials: M
authors.lastname: Sato
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Kitaguchi
authors.forename: Rika
authors.initials: R
authors.lastname: Numano
authors.forename: Kazuya
authors.initials: K
authors.lastname: Ikematsu
authors.forename: Masaki
authors.initials: M
authors.lastname: Kakeyama
authors.forename: Masayuki
authors.initials: M
authors.lastname: Murata
authors.forename: Ken
authors.initials: K
authors.lastname: Sato
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsuboi
mesh_terms: D000818:Animals; D005089:Exocytosis; D016716:PC12 Cells; D051381:Rats; D022142:Secretory Vesicles / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000502:physiology*
chemical_list: D020764:cdc42 GTP-Binding Protein