Abstract
Misfolded α-synuclein (A-syn) is widely recognized as the primal cause of neurodegenerative diseases including Parkinson's disease and dementia with Lewy bodies. The normal cellular function of A-syn has, however, been elusive. There is evidence that A-syn plays multiple roles in the exocytotic pathway in the neuron, but the underlying molecular mechanisms are unclear. A-syn has been known to interact with negatively charged phospholipids and with vesicle SNARE protein VAMP2. Using single-vesicle docking/fusion assays, we find that A-syn promotes SNARE-dependent vesicles docking significantly at 2.5 µM. When phosphatidylserine (PS) is removed from t-SNARE-bearing vesicles, the docking enhancement by A-syn disappears and A-syn instead acts as an inhibitor for docking. In contrast, subtraction of PS from the v-SNARE-carrying vesicles enhances vesicle docking even further. Moreover, when we truncate the C-terminal 45 residues of A-syn that participates in interacting with VAMP2, the promotion of vesicle docking is abrogated. Thus, the results suggest that the A-syn's interaction with v-SNARE through its C-terminal tail and its concurrent interaction with PS in trans through its amphipathic N-terminal domain facilitate SNARE complex formation, whereby A-syn aids SNARE-dependent vesicle docking.
Keywords:
SNARE proteins; exocytosis; membrane fusion; single molecule; α-synuclein.
© 2017 The Author(s); published by Portland Press Limited on behalf of the Biochemical Society.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, N.I.H., Extramural
MeSH terms
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Amino Acid Substitution
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Animals
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Humans
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Liposomes
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Membrane Fusion
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Micelles
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Models, Biological*
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Mutagenesis, Site-Directed
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Mutation
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Nerve Tissue Proteins / chemistry
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Nerve Tissue Proteins / genetics
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Nerve Tissue Proteins / metabolism
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Peptide Fragments / chemistry
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Peptide Fragments / genetics
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Peptide Fragments / metabolism
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Phosphatidylserines / metabolism*
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Protein Interaction Domains and Motifs
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Rats
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / metabolism
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SNARE Proteins / chemistry
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SNARE Proteins / genetics
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SNARE Proteins / metabolism*
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Synaptic Vesicles / metabolism*
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Synaptosomal-Associated Protein 25 / chemistry
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Synaptosomal-Associated Protein 25 / genetics
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Synaptosomal-Associated Protein 25 / metabolism*
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Synaptotagmin I / chemistry
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Synaptotagmin I / genetics
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Synaptotagmin I / metabolism
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Syntaxin 1 / chemistry
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Syntaxin 1 / genetics
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Syntaxin 1 / metabolism
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Vesicle-Associated Membrane Protein 2 / chemistry
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Vesicle-Associated Membrane Protein 2 / genetics
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Vesicle-Associated Membrane Protein 2 / metabolism*
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alpha-Synuclein / chemistry
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alpha-Synuclein / genetics
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alpha-Synuclein / metabolism*
Substances
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Liposomes
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Micelles
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Nerve Tissue Proteins
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Peptide Fragments
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Phosphatidylserines
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Recombinant Fusion Proteins
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SNAP25 protein, human
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SNARE Proteins
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SNCA protein, human
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STX1A protein, human
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Synaptosomal-Associated Protein 25
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Synaptotagmin I
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Syntaxin 1
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Syt1 protein, rat
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VAMP2 protein, human
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Vesicle-Associated Membrane Protein 2
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alpha-Synuclein