title: The F-actin cortical network is a major factor influencing the organization of the secretory machinery in chromaffin cells.
abstract: We have studied how the F-actin cytoskeleton is involved in establishing the heterogeneous intracellular Ca(2+) levels ([Ca(2+)](i)) and in the organization of the exocytotic machinery in cultured bovine chromaffin cells. Simultaneous confocal visualization of [Ca(2+)](i) and transmitted light studies of the cytoskeleton showed that, following cell stimulation, the maximal signal from the Ca(2+)-sensitive fluorescent dye Fluo-3 was in the empty cytosolic spaces left by cytoskeletal cages. This was mostly due to the accumulation of the dye in spaces devoid of cytoskeletal components, as shown by the use of alternative Ca(2+)-insensitive fluorescent cytosolic markers. In addition to affecting the distribution of such compounds in the cytosol, the cytoskeleton influenced the location of L- and P-Q-type Ca(2+) channel clusters, which were associated with the borders of cytoskeletal cages in resting and stimulated cells. Indeed, syntaxin-1 and synaptotagmin-1, which are components of the secretory machinery, were present in the same location. Furthermore, granule exocytosis took place at these sites, indicating that the organization of the F-actin cytoskeletal cortex shapes the preferential sites for secretion by associating the secretory machinery with preferential sites for Ca(2+) entry. The influence of this cortical organization on the propagation of [Ca(2+)](i) can be modelled, illustrating how it serves to define rapid exocytosis.
authors.affiliation: Instituto de Neurociencias, Centro Mixto Universidad Miguel Hernández-CSIC, Sant Joan d'Alacant, Alicante 03550, Spain.
authors.forename: Cristina J
authors.initials: CJ
authors.lastname: Torregrosa-Hetland
authors.forename: José
authors.initials: J
authors.lastname: Villanueva
authors.forename: Daniel
authors.initials: D
authors.lastname: Giner
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Lopez-Font
authors.forename: Angel
authors.initials: A
authors.lastname: Nadal
authors.forename: Iván
authors.initials: I
authors.lastname: Quesada
authors.forename: Salvador
authors.initials: S
authors.lastname: Viniegra
authors.forename: Giovanna
authors.initials: G
authors.lastname: Expósito-Romero
authors.forename: Amparo
authors.initials: A
authors.lastname: Gil
authors.forename: Virginia
authors.initials: V
authors.lastname: Gonzalez-Velez
authors.forename: Javier
authors.initials: J
authors.lastname: Segura
authors.forename: Luis M
authors.initials: LM
authors.lastname: Gutiérrez
mesh_terms: D000199:Actins / Q000378:metabolism*; D000814:Aniline Compounds / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000166:cytology* / Q000378:metabolism*; D002837:Chromaffin Granules / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism* / Q000648:ultrastructure; D005089:Exocytosis / Q000502:physiology*; D005456:Fluorescent Dyes / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology; D050765:Qa-SNARE Proteins / Q000378:metabolism; D050857:Synaptotagmins / Q000378:metabolism; D014966:Xanthenes / Q000378:metabolism
chemical_list: D000199:Actins; D000814:Aniline Compounds; D015220:Calcium Channels; D005456:Fluorescent Dyes; D050765:Qa-SNARE Proteins; D014966:Xanthenes; D050857:Synaptotagmins; C059715:Fluo-3; D002118:Calcium