Impaired Mitochondrial Energy Production Causes Light-Induced Photoreceptor Degeneration Independent of Oxidative Stress

Manish Jaiswal, Nele A Haelterman, Hector Sandoval, Bo Xiong, Taraka Donti, Auinash Kalsotra, Shinya Yamamoto, Thomas A Cooper, Brett H Graham, Hugo J Bellen

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

Two insults often underlie a variety of eye diseases including glaucoma, optic atrophy, and retinal degeneration--defects in mitochondrial function and aberrant Rhodopsin trafficking. Although mitochondrial defects are often associated with oxidative stress, they have not been linked to Rhodopsin trafficking. In an unbiased forward genetic screen designed to isolate mutations that cause photoreceptor degeneration, we identified mutations in a nuclear-encoded mitochondrial gene, ppr, a homolog of human LRPPRC. We found that ppr is required for protection against light-induced degeneration. Its function is essential to maintain membrane depolarization of the photoreceptors upon repetitive light exposure, and an impaired phototransduction cascade in ppr mutants results in excessive Rhodopsin1 endocytosis. Moreover, loss of ppr results in a reduction in mitochondrial RNAs, reduced electron transport chain activity, and reduced ATP levels. Oxidative stress, however, is not induced. We propose that the reduced ATP level in ppr mutants underlies the phototransduction defect, leading to increased Rhodopsin1 endocytosis during light exposure, causing photoreceptor degeneration independent of oxidative stress. This hypothesis is bolstered by characterization of two other genes isolated in the screen, pyruvate dehydrogenase and citrate synthase. Their loss also causes a light-induced degeneration, excessive Rhodopsin1 endocytosis and reduced ATP without concurrent oxidative stress, unlike many other mutations in mitochondrial genes that are associated with elevated oxidative stress and light-independent photoreceptor demise.

Original languageEnglish (US)
Pages (from-to)e1002197
JournalPLoS biology
Volume13
Issue number7
DOIs
StatePublished - Jul 2015

Keywords

  • Adenosine Triphosphate
  • Animals
  • Citrate (si)-Synthase
  • Drosophila
  • Drosophila Proteins
  • Electroretinography
  • Endocytosis
  • Mitochondria
  • Mitochondrial Proteins
  • Oxidative Stress
  • Photoreceptor Cells, Invertebrate
  • Pyruvate Dehydrogenase Complex
  • RNA-Binding Proteins
  • Reactive Oxygen Species
  • Retinal Diseases
  • Rhodopsin
  • Vision, Ocular
  • Journal Article
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

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