SOD1 activity threshold and TOR signalling modulate VAP(P58S) aggregation via reactive oxygen species-induced proteasomal degradation in a Drosophila model of amyotrophic lateral sclerosis

Dis Model Mech. 2019 Feb 7;12(2):dmm033803. doi: 10.1242/dmm.033803.


Familial amyotrophic lateral sclerosis (ALS) is an incurable, late-onset motor neuron disease, linked strongly to various causative genetic loci. ALS8 codes for a missense mutation, P56S, in VAMP-associated protein B (VAPB) that causes the protein to misfold and form cellular aggregates. Uncovering genes and mechanisms that affect aggregation dynamics would greatly help increase our understanding of the disease and lead to potential therapeutics. We developed a quantitative high-throughput Drosophila S2R+ cell-based kinetic assay coupled with fluorescent microscopy to score for genes involved in the modulation of aggregates of the fly orthologue, VAP(P58S), fused with GFP. A targeted RNA interference screen against 900 genes identified 150 hits that modify aggregation, including the ALS loci Sod1 and TDP43 (also known as TBPH), as well as genes belonging to the mTOR pathway. Further, a system to measure the extent of VAP(P58S) aggregation in the Drosophila larval brain was developed in order to validate the hits from the cell-based screen. In the larval brain, we find that reduction of SOD1 levels or decreased mTOR signalling reduces aggregation, presumably by increasing the levels of cellular reactive oxygen species (ROS). The mechanism of aggregate clearance is, primarily, proteasomal degradation, which appears to be triggered by an increase in ROS. We have thus uncovered an interesting interplay between SOD1, ROS and mTOR signalling that regulates the dynamics of VAP aggregation. Mechanistic processes underlying such cellular regulatory networks will lead to better understanding of the initiation and progression of ALS.This article has an associated First Person interview with the first author of the paper.

Keywords: ALS; Aggregate; Autophagy; MG132; Rapamycin; UPS.

Publication types

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

MeSH terms

  • Amyotrophic Lateral Sclerosis / metabolism*
  • Amyotrophic Lateral Sclerosis / pathology
  • Animals
  • Autophagy
  • Brain / metabolism
  • Carrier Proteins / metabolism*
  • Cells, Cultured
  • Disease Models, Animal
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster / metabolism*
  • Larva / metabolism
  • Membrane Proteins / metabolism*
  • Models, Biological
  • Oxidative Stress
  • Proteasome Endopeptidase Complex / metabolism*
  • Protein Aggregates*
  • Proteolysis
  • RNA, Double-Stranded / metabolism
  • Reactive Oxygen Species / metabolism*
  • Receptor Protein-Tyrosine Kinases / metabolism*
  • Reverse Genetics
  • Signal Transduction
  • Superoxide Dismutase / metabolism*


  • Carrier Proteins
  • Drosophila Proteins
  • Membrane Proteins
  • Protein Aggregates
  • RNA, Double-Stranded
  • Reactive Oxygen Species
  • Vap33 protein, Drosophila
  • Sod1 protein, Drosophila
  • Superoxide Dismutase
  • Receptor Protein-Tyrosine Kinases
  • tor protein, Drosophila
  • Proteasome Endopeptidase Complex