Hsc70-4 Deforms Membranes to Promote Synaptic Protein Turnover by Endosomal Microautophagy

Neuron. 2015 Nov 18;88(4):735-48. doi: 10.1016/j.neuron.2015.10.012.


Synapses are often far from their cell bodies and must largely independently cope with dysfunctional proteins resulting from synaptic activity and stress. To identify membrane-associated machines that can engulf synaptic targets destined for degradation, we performed a large-scale in vitro liposome-based screen followed by functional studies. We identified a presynaptically enriched chaperone Hsc70-4 that bends membranes based on its ability to oligomerize. This activity promotes endosomal microautophagy and the turnover of specific synaptic proteins. Loss of microautophagy slows down neurotransmission while gain of microautophagy increases neurotransmission. Interestingly, Sgt, a cochaperone of Hsc70-4, is able to switch the activity of Hsc70-4 from synaptic endosomal microautophagy toward chaperone activity. Hence, Hsc70-4 controls rejuvenation of the synaptic protein pool in a dual way: either by refolding proteins together with Sgt, or by targeting them for degradation by facilitating endosomal microautophagy based on its membrane deforming activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autophagy / genetics*
  • Drosophila
  • Drosophila Proteins / genetics
  • Electron Microscope Tomography
  • Endosomes / metabolism
  • Endosomes / ultrastructure
  • Escherichia coli
  • Escherichia coli Proteins
  • HSC70 Heat-Shock Proteins / genetics*
  • Microscopy, Fluorescence
  • Molecular Chaperones
  • Polymerization
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins / genetics
  • Synapses / metabolism
  • Synapses / ultrastructure
  • Synaptic Membranes / metabolism*
  • Synaptic Membranes / ultrastructure
  • Synaptic Transmission
  • Synaptic Vesicles / metabolism*
  • Synaptic Vesicles / ultrastructure


  • Drosophila Proteins
  • Escherichia coli Proteins
  • HSC70 Heat-Shock Proteins
  • Hsc70-4 protein, Drosophila
  • Molecular Chaperones
  • Saccharomyces cerevisiae Proteins