title: Src kinases regulate de novo actin polymerization during exocytosis in neuroendocrine chromaffin cells.
abstract: The cortical actin network is dynamically rearranged during secretory processes. Nevertheless, it is unclear how de novo actin polymerization and the disruption of the preexisting actin network control transmitter release. Here we show that in bovine adrenal chromaffin cells, both formation of new actin filaments and disruption of the preexisting cortical actin network are induced by Ca2+ concentrations that trigger exocytosis. These two processes appear to regulate different stages of exocytosis; whereas the inhibition of actin polymerization with the N-WASP inhibitor wiskostatin restricts fusion pore expansion, thus limiting the release of transmitters, the disruption of the cortical actin network with cytochalasin D increases the amount of transmitter released per event. Further, the Src kinase inhibitor PP2, and cSrc SH2 and SH3 domains also suppress Ca2+-dependent actin polymerization, and slow down fusion pore expansion without disturbing the cortical F-actin organization. Finally, the isolated SH3 domain of c-Src prevents both the disruption of the actin network and the increase in the quantal release induced by cytochalasin D. These findings support a model where a rise in the cytosolic Ca2+ triggers actin polymerization through a mechanism that involves Src kinases. The newly formed actin filaments would speed up the expansion of the initial fusion pore, whereas the preexisting actin network might control a different step of the exocytosis process.
authors.affiliation: Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Playa Ancha, Valparaíso, Chile.
authors.forename: María José
authors.initials: MJ
authors.lastname: Olivares
authors.affiliation: Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Playa Ancha, Valparaíso, Chile.
authors.forename: Arlek M
authors.initials: AM
authors.lastname: González-Jamett
authors.affiliation: Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Playa Ancha, Valparaíso, Chile.
authors.forename: María José
authors.initials: MJ
authors.lastname: Guerra
authors.affiliation: Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Playa Ancha, Valparaíso, Chile.
authors.forename: Ximena
authors.initials: X
authors.lastname: Baez-Matus
authors.affiliation: Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Playa Ancha, Valparaíso, Chile.
authors.forename: Valentina
authors.initials: V
authors.lastname: Haro-Acuña
authors.affiliation: Departamento de Microbiología (Inmunología), Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: Narcisa
authors.initials: N
authors.lastname: Martínez-Quiles
authors.affiliation: Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Playa Ancha, Valparaíso, Chile.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Cárdenas
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015638:Cytochalasin D / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects; D007700:Kinetics; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000378:metabolism; D019061:src-Family Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C509621:4-amino-7-phenylpyrazol(3,4-d)pyrimidine; C412373:AG 1879; D000199:Actins; D011720:Pyrazoles; D011743:Pyrimidines; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D015638:Cytochalasin D; D019061:src-Family Kinases; D002118:Calcium