Early Golgi Abnormalities and Neurodegeneration upon Loss of Presynaptic Proteins Munc18-1, Syntaxin-1, or SNAP-25

J Neurosci. 2017 Apr 26;37(17):4525-4539. doi: 10.1523/JNEUROSCI.3352-16.2017. Epub 2017 Mar 27.


The loss of presynaptic proteins Munc18-1, syntaxin-1, or SNAP-25 is known to produce cell death, but the underlying features have not been compared experimentally. Here, we investigated these features in cultured mouse CNS and DRG neurons. Side-by-side comparisons confirmed massive cell death, before synaptogenesis, within 1-4 DIV upon loss of t-SNAREs (syntaxin-1, SNAP-25) or Munc18-1, but not v-SNAREs (synaptobrevins/VAMP1/2/3 using tetanus neurotoxin (TeNT), also in TI-VAMP/VAMP7 knock-out (KO) neurons). A condensed cis-Golgi was the first abnormality observed upon Munc18-1 or SNAP-25 loss within 3 DIV. This phenotype was distinct from the Golgi fragmentation observed in apoptosis. Cell death was too rapid after syntaxin-1 loss to study Golgi abnormalities. Syntaxin-1 and Munc18-1 depend on each other for normal cellular levels. We observed that endogenous syntaxin-1 accumulates at the Golgi of Munc18-1 KO neurons. However, expression of a non-neuronal Munc18 isoform that does not bind syntaxin-1, Munc18-3, in Munc18-1 KO neurons prevented cell death and restored normal cis-Golgi morphology, but not synaptic transmission or syntaxin-1 targeting. Finally, we observed that DRG neurons are the only Munc18-1 KO neurons that do not degenerate in vivo or in vitro In these neurons, cis-Golgi abnormalities were less severe, with no changes in Golgi shape. Together, these data demonstrate that cell death upon Munc18-1, syntaxin-1, or SNAP-25 loss occurs via a degenerative pathway unrelated to the known synapse function of these proteins and involving early cis-Golgi abnormalities, distinct from apoptosis.SIGNIFICANCE STATEMENT This study provides new insights in a neurodegeneration pathway triggered by the absence of specific proteins involved in synaptic transmission (syntaxin-1, Munc18-1, SNAP-25), whereas other proteins involved in the same molecular process (synaptobrevins, Munc13-1/2) do not cause degeneration. Massive cell death occurs in cultured neurons upon depleting syntaxin-1, Munc18-1, and/or SNAP-25, well before synapse formation. This study characterizes several relevant cellular phenotypes, especially early cis-Golgi abnormalities, distinct from abnormalities observed during apoptosis, and rules out several other phenotypes as causal (defects in syntaxin-1 targeting and synaptic transmission). As proteins, such as syntaxin-1, Munc18-1, or SNAP-25, modulate α-synuclein neuropathy and/or are dysregulated in Alzheimer's disease, understanding this type of neurodegeneration may provide new links between synaptic defects and neurodegeneration in humans.

Keywords: exocytosis; neurodegeneration; presynaptic proteins; synaptic transmission.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Cell Death / genetics
  • Cells, Cultured
  • Exocytosis / genetics
  • Golgi Apparatus / genetics*
  • Golgi Apparatus / metabolism*
  • Golgi Apparatus / pathology
  • Mice
  • Mice, Knockout
  • Munc18 Proteins / genetics*
  • Neurodegenerative Diseases / genetics*
  • Neurodegenerative Diseases / metabolism*
  • Neurodegenerative Diseases / pathology
  • Synapses / pathology
  • Synaptosomal-Associated Protein 25 / genetics*
  • Syntaxin 1 / genetics*


  • Munc18 Proteins
  • Snap25 protein, mouse
  • Synaptosomal-Associated Protein 25
  • Syntaxin 1