Newly produced synaptic vesicle proteins are preferentially used in synaptic transmission

EMBO J. 2018 Aug 1;37(15):e98044. doi: 10.15252/embj.201798044. Epub 2018 Jun 27.

Abstract

Aged proteins can become hazardous to cellular function, by accumulating molecular damage. This implies that cells should preferentially rely on newly produced ones. We tested this hypothesis in cultured hippocampal neurons, focusing on synaptic transmission. We found that newly synthesized vesicle proteins were incorporated in the actively recycling pool of vesicles responsible for all neurotransmitter release during physiological activity. We observed this for the calcium sensor Synaptotagmin 1, for the neurotransmitter transporter VGAT, and for the fusion protein VAMP2 (Synaptobrevin 2). Metabolic labeling of proteins and visualization by secondary ion mass spectrometry enabled us to query the entire protein makeup of the actively recycling vesicles, which we found to be younger than that of non-recycling vesicles. The young vesicle proteins remained in use for up to ~ 24 h, during which they participated in recycling a few hundred times. They were afterward reluctant to release and were degraded after an additional ~ 24-48 h. We suggest that the recycling pool of synaptic vesicles relies on newly synthesized proteins, while the inactive reserve pool contains older proteins.

Keywords: organelle aging; protein aging; synaptic vesicle; turnover; vesicle pools.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cells, Cultured
  • Exocytosis / physiology
  • Hippocampus / cytology*
  • Mass Spectrometry
  • Neurons / metabolism*
  • Protein Biosynthesis / physiology
  • Rats
  • Synaptic Transmission / physiology*
  • Synaptic Vesicles / physiology*
  • Synaptosomal-Associated Protein 25 / metabolism*
  • Synaptotagmin I / metabolism*
  • Vesicle-Associated Membrane Protein 2 / metabolism*
  • Vesicular Inhibitory Amino Acid Transport Proteins / metabolism*

Substances

  • Snap25 protein, rat
  • Synaptosomal-Associated Protein 25
  • Synaptotagmin I
  • Vamp2 protein, rat
  • Vesicle-Associated Membrane Protein 2
  • Vesicular Inhibitory Amino Acid Transport Proteins
  • Viaat protein, rat