Synaptotagmin 7 is targeted to the axonal plasma membrane through γ-secretase processing to promote synaptic vesicle docking in mouse hippocampal neurons

Elife. 2021 Sep 20;10:e67261. doi: 10.7554/eLife.67261.

Abstract

Synaptotagmin 7 (SYT7) has emerged as a key regulator of presynaptic function, but its localization and precise role in the synaptic vesicle cycle remain the subject of debate. Here, we used iGluSnFR to optically interrogate glutamate release, at the single-bouton level, in SYT7KO-dissociated mouse hippocampal neurons. We analyzed asynchronous release, paired-pulse facilitation, and synaptic vesicle replenishment and found that SYT7 contributes to each of these processes to different degrees. 'Zap-and-freeze' electron microscopy revealed that a loss of SYT7 diminishes docking of synaptic vesicles after a stimulus and inhibits the recovery of depleted synaptic vesicles after a stimulus train. SYT7 supports these functions from the axonal plasma membrane, where its localization and stability require both γ-secretase-mediated cleavage and palmitoylation. In summary, SYT7 is a peripheral membrane protein that controls multiple modes of synaptic vesicle (SV) exocytosis and plasticity, in part, through enhancing activity-dependent docking of SVs.

Keywords: Synaptotagmin 7; gamma secretase; hippocampus; iGluSnFR; mouse; neuroscience; rat; short-term synaptic plasticity; zap-and-freeze.

Publication types

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

MeSH terms

  • Amyloid Precursor Protein Secretases / metabolism*
  • Animals
  • Axons / enzymology*
  • Axons / ultrastructure
  • Cell Membrane / enzymology*
  • Cell Membrane / ultrastructure
  • Cells, Cultured
  • Exocytosis
  • Hippocampus / enzymology*
  • Hippocampus / ultrastructure
  • Lipoylation
  • Mice, Knockout
  • Molecular Docking Simulation
  • Neuronal Plasticity
  • Protein Processing, Post-Translational
  • Protein Transport
  • Proteolysis
  • Rats, Sprague-Dawley
  • Synaptic Transmission
  • Synaptic Vesicles / enzymology*
  • Synaptic Vesicles / ultrastructure
  • Synaptotagmins / genetics
  • Synaptotagmins / metabolism*
  • Time Factors

Substances

  • Syt7 protein, mouse
  • Syt7 protein, rat
  • Synaptotagmins
  • Amyloid Precursor Protein Secretases