Autophagy protects the retina from light-induced degeneration

J Biol Chem. 2013 Mar 15;288(11):7506-7518. doi: 10.1074/jbc.M112.439935. Epub 2013 Jan 22.

Abstract

Autophagy is a conserved feature of lysosome-mediated intracellular degradation. Dysregulated autophagy is implicated as a contributor in neurodegenerative diseases; however, the role of autophagy in retinal degeneration remains largely unknown. Here, we report that the photo-activated visual chromophore, all-trans-retinal, modulated autophagosome formation in ARPE19 retinal cells. Increased formation of autophagosomes in these cells was observed when incubated with 2.5 μM all-trans-retinal, a condition that did not cause cell death after 24 h in culture. However, autophagosome formation was decreased at concentrations, which caused cell death. Increased expression of activating transcription factor 4 (Atf4), which indicates the activation of oxidative stress, was recorded in response to light illumination in retinas of Abca4(-/-)Rdh8(-/-) mice, which showed delayed clearance of all-trans-retinal after light exposure. Expression of autophagosome marker LC3B-II and mitochondria-specific autophagy, mitophagy, regulator Park2, were significantly increased in the retinas of Abca4(-/-)Rdh8(-/-) mice after light exposure, suggesting involvement of autophagy and mitophagy in the pathogenesis of light-induced retinal degeneration. Deletion of essential genes required for autophagy, including Beclin1 systemically or Atg7 in only rod photoreceptors resulted in increased susceptibility to light-induced retinal damage. Increased photoreceptor cell death was observed when retinas lacking the rod photoreceptor-specific Atg7 gene were coincubated with 20 μM all-trans-retinal. Park2(-/-) mice also displayed light-induced retinal degeneration. Ultra-structural analyses showed mitochondrial and endoplasmic reticulum impairment in retinas of these model animals after light exposure. Taken together, these observations provide novel evidence implicating an important role of autophagy and mitophagy in protecting the retina from all-trans-retinal- and light-induced degeneration.

Publication types

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

MeSH terms

  • ATP-Binding Cassette Transporters / genetics
  • Alcohol Dehydrogenase / metabolism
  • Alcohol Oxidoreductases / genetics
  • Animals
  • Apoptosis
  • Apoptosis Regulatory Proteins / metabolism
  • Autophagy / physiology*
  • Autophagy-Related Protein 7
  • Beclin-1
  • Cell Death
  • Cell Line
  • Humans
  • Light
  • Lysosomes / metabolism*
  • Membrane Proteins / metabolism
  • Mice
  • Mice, Transgenic
  • Microtubule-Associated Proteins / metabolism
  • Photic Stimulation / adverse effects
  • Retina / metabolism*
  • Retinal Degeneration / metabolism
  • Rhodopsin / metabolism
  • Ubiquitin-Activating Enzymes / metabolism
  • Ubiquitin-Protein Ligases / metabolism
  • Vitamin A / metabolism

Substances

  • ABCA4 protein, human
  • ATP-Binding Cassette Transporters
  • Abca4 protein, mouse
  • Apoptosis Regulatory Proteins
  • Atg7 protein, mouse
  • BECN1 protein, human
  • Beclin-1
  • Becn1 protein, mouse
  • Membrane Proteins
  • Microtubule-Associated Proteins
  • Vitamin A
  • Rhodopsin
  • Alcohol Oxidoreductases
  • Alcohol Dehydrogenase
  • Rdh8 protein, mouse
  • retinol dehydrogenase
  • Ubiquitin-Protein Ligases
  • parkin protein
  • ATG7 protein, human
  • Autophagy-Related Protein 7
  • Ubiquitin-Activating Enzymes