Degradation of engulfed mitochondria is rate-limiting in Optineurin-mediated mitophagy in neurons

Elife. 2020 Jan 14:9:e50260. doi: 10.7554/eLife.50260.

Abstract

Mitophagy, the selective removal of damaged mitochondria, is thought to be critical to maintain neuronal homeostasis. Mutations of proteins in the pathway cause neurodegenerative diseases, suggesting defective mitochondrial turnover contributes to neurodegeneration. In primary rat hippocampal neurons, we developed a mitophagy induction paradigm where mild oxidative stress induced low levels of mitochondrial damage. Mitophagy-associated proteins were sequentially recruited to depolarized mitochondria followed by sequestration into autophagosomes. The localization of these mitophagy events had a robust somal bias. In basal and induced conditions, engulfed mitochondria remained in non-acidified organelles for hours to days, illustrating efficient autophagosome sequestration but delayed lysosomal fusion or acidification. Furthermore, expression of an ALS-linked mutation in the pathway disrupted mitochondrial network integrity and this effect was exacerbated by oxidative stress. Thus, age-related decline in neuronal health or expression of disease-associated mutations in the pathway may exacerbate the slow kinetics of neuronal mitophagy, leading to neurodegeneration.

Keywords: autophagy; cell biology; lysosome acidification; mitochondrial quality control; mitophagy; mouse; neurodegeneration; neuroscience; parkin; rat.

Publication types

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

MeSH terms

  • Animals
  • Autophagosomes / metabolism
  • Autophagy
  • Axons / metabolism
  • HeLa Cells
  • Hippocampus / metabolism
  • Humans
  • Kinetics
  • Lysosomes / metabolism
  • Membrane Potential, Mitochondrial
  • Mitochondria / metabolism*
  • Mitophagy*
  • Mutation
  • Neurodegenerative Diseases / metabolism
  • Neurons / metabolism*
  • Oxidative Stress
  • Phagosomes
  • Protein Kinases / metabolism
  • RNA, Small Interfering / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Reactive Oxygen Species / metabolism
  • Transcription Factor TFIIIA / metabolism*

Substances

  • OPTN protein, rat
  • RNA, Small Interfering
  • Reactive Oxygen Species
  • Tpk1 protein, rat
  • Transcription Factor TFIIIA
  • Protein Kinases