title: CAPS and syntaxin dock dense core vesicles to the plasma membrane in neurons.
abstract: Docking to the plasma membrane prepares vesicles for rapid release. Here, we describe a mechanism for dense core vesicle docking in neurons. In Caenorhabditis elegans motor neurons, dense core vesicles dock at the plasma membrane but are excluded from active zones at synapses. We have found that the calcium-activated protein for secretion (CAPS) protein is required for dense core vesicle docking but not synaptic vesicle docking. In contrast, we see that UNC-13, a docking factor for synaptic vesicles, is not essential for dense core vesicle docking. Both the CAPS and UNC-13 docking pathways converge on syntaxin, a component of the SNARE (soluble N-ethyl-maleimide-sensitive fusion protein attachment receptor) complex. Overexpression of open syntaxin can bypass the requirement for CAPS in dense core vesicle docking. Thus, CAPS likely promotes the open state of syntaxin, which then docks dense core vesicles. CAPS function in dense core vesicle docking parallels UNC-13 in synaptic vesicle docking, which suggests that these related proteins act similarly to promote docking of independent vesicle populations.
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: Marc
authors.initials: M
authors.lastname: Hammarlund
authors.forename: Shigeki
authors.initials: S
authors.lastname: Watanabe
authors.forename: Kim
authors.initials: K
authors.lastname: Schuske
authors.forename: Erik M
authors.initials: EM
authors.lastname: Jorgensen
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism* / Q000648:ultrastructure; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002352:Carrier Proteins; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D008561:Membrane Fusion / Q000502:physiology; D009046:Motor Neurons / Q000378:metabolism* / Q000648:ultrastructure; D050765:Qa-SNARE Proteins / Q000378:metabolism*; D022142:Secretory Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D013570:Synaptic Membranes / Q000378:metabolism / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology
chemical_list: D029742:Caenorhabditis elegans Proteins; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D050765:Qa-SNARE Proteins; C107581:UNC-31 protein, C elegans; C083141:phorbol ester binding protein