α-Synuclein may cross-bridge v-SNARE and acidic phospholipids to facilitate SNARE-dependent vesicle docking

Biochem J. 2017 Jun 6;474(12):2039-2049. doi: 10.1042/BCJ20170200.

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Substitution
  • Animals
  • Humans
  • Liposomes
  • Membrane Fusion
  • Micelles
  • Models, Biological*
  • Mutagenesis, Site-Directed
  • Mutation
  • Nerve Tissue Proteins / chemistry
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Peptide Fragments / chemistry
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism
  • Phosphatidylserines / metabolism*
  • Protein Interaction Domains and Motifs
  • Rats
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / metabolism
  • SNARE Proteins / chemistry
  • SNARE Proteins / genetics
  • SNARE Proteins / metabolism*
  • Synaptic Vesicles / metabolism*
  • Synaptosomal-Associated Protein 25 / chemistry
  • Synaptosomal-Associated Protein 25 / genetics
  • Synaptosomal-Associated Protein 25 / metabolism*
  • Synaptotagmin I / chemistry
  • Synaptotagmin I / genetics
  • Synaptotagmin I / metabolism
  • Syntaxin 1 / chemistry
  • Syntaxin 1 / genetics
  • Syntaxin 1 / metabolism
  • Vesicle-Associated Membrane Protein 2 / chemistry
  • Vesicle-Associated Membrane Protein 2 / genetics
  • Vesicle-Associated Membrane Protein 2 / metabolism*
  • alpha-Synuclein / chemistry
  • alpha-Synuclein / genetics
  • alpha-Synuclein / metabolism*

Substances

  • Liposomes
  • Micelles
  • Nerve Tissue Proteins
  • Peptide Fragments
  • Phosphatidylserines
  • Recombinant Fusion Proteins
  • SNAP25 protein, human
  • SNARE Proteins
  • SNCA protein, human
  • STX1A protein, human
  • Synaptosomal-Associated Protein 25
  • Synaptotagmin I
  • Syntaxin 1
  • Syt1 protein, rat
  • VAMP2 protein, human
  • Vesicle-Associated Membrane Protein 2
  • alpha-Synuclein