title: Docking of secretory vesicles is syntaxin dependent.
abstract: Secretory vesicles dock at the plasma membrane before they undergo fusion. Molecular docking mechanisms are poorly defined but believed to be independent of SNARE proteins. Here, we challenged this hypothesis by acute deletion of the target SNARE, syntaxin, in vertebrate neurons and neuroendocrine cells. Deletion resulted in fusion arrest in both systems. No docking defects were observed in synapses, in line with previous observations. However, a drastic reduction in morphologically docked secretory vesicles was observed in chromaffin cells. Syntaxin-deficient chromaffin cells showed a small reduction in total and plasma membrane staining for the docking factor Munc18-1, which appears insufficient to explain the drastic reduction in docking. The sub-membrane cortical actin network was unaffected by syntaxin deletion. These observations expose a docking role for syntaxin in the neuroendocrine system. Additional layers of regulation may have evolved to make syntaxin redundant for docking in highly specialized systems like synaptic active zones.
authors.affiliation: Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit Amsterdam and VU Medical Center, Amsterdam, Netherlands.
authors.forename: Heidi
authors.initials: H
authors.lastname: de Wit
authors.forename: L Niels
authors.initials: LN
authors.lastname: Cornelisse
authors.forename: Ruud F G
authors.initials: RF
authors.lastname: Toonen
authors.forename: Matthijs
authors.initials: M
authors.lastname: Verhage
mesh_terms: D000818:Animals; D001905:Botulinum Toxins / Q000235:genetics; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000502:physiology* / Q000648:ultrastructure; D015870:Gene Expression; D018390:Gene Targeting; D049452:Green Fluorescent Proteins / Q000235:genetics; D008561:Membrane Fusion / Q000502:physiology; D051379:Mice; D046529:Microscopy, Electron, Transmission; D051938:Munc18 Proteins / Q000502:physiology; D050765:Qa-SNARE Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D022142:Secretory Vesicles / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D051938:Munc18 Proteins; D050765:Qa-SNARE Proteins; C497938:Stxbp1 protein, mouse; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D001905:Botulinum Toxins; C096324:botulinum toxin type C