Abstract
Sec1-related proteins function in most, if not all, membrane trafficking pathways in eukaryotic cells. The Sec1-related protein required in neurons for synaptic vesicle exocytosis is UNC-18. Several models for UNC-18 function during vesicle exocytosis are under consideration. We have tested these models by characterizing unc-18 mutants of the nematode Caenorhabditis elegans. In the absence of UNC-18, the size of the readily releasable pool is severely reduced. Our results show that the near absence of fusion-competent vesicles is not caused by a reduction in syntaxin levels, by a mislocalization of syntaxin, by a defect in fusion or by a failure to open syntaxin during priming. Rather, we found a reduction of docked vesicles at the active zone in unc-18 mutants, suggesting that UNC-18 functions, directly or indirectly, as a facilitator of vesicle docking.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Caenorhabditis elegans
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Caenorhabditis elegans Proteins / genetics
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Caenorhabditis elegans Proteins / metabolism*
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Cell Differentiation / genetics
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Electric Stimulation
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Exocytosis / physiology*
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Green Fluorescent Proteins
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Luminescent Proteins
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Membrane Fusion / physiology
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Membrane Proteins / genetics
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Membrane Proteins / metabolism
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Microscopy, Electron
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Models, Animal
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Motor Neurons / cytology
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Motor Neurons / physiology
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Mutation / physiology
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Neuromuscular Junction / cytology
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Neuromuscular Junction / growth & development
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Neuromuscular Junction / physiology
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Phosphoproteins*
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Presynaptic Terminals / metabolism*
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Presynaptic Terminals / ultrastructure
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Protein Transport / genetics
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Qa-SNARE Proteins
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R-SNARE Proteins
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Receptors, GABA / genetics
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Receptors, GABA / metabolism
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Recombinant Fusion Proteins
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Synaptic Transmission / genetics*
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Synaptic Vesicles / metabolism*
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Synaptic Vesicles / ultrastructure
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Vesicular Transport Proteins*
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gamma-Aminobutyric Acid / metabolism
Substances
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Caenorhabditis elegans Proteins
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Carrier Proteins
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Luminescent Proteins
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Membrane Proteins
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Phosphoproteins
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Qa-SNARE Proteins
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R-SNARE Proteins
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Receptors, GABA
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Recombinant Fusion Proteins
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Unc-18 protein, C elegans
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Vesicular Transport Proteins
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Green Fluorescent Proteins
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gamma-Aminobutyric Acid