Inhibition of TOR in Chlamydomonas reinhardtii Leads to Rapid Cysteine Oxidation Reflecting Sustained Physiological Changes

Cells. 2019 Sep 28;8(10):1171. doi: 10.3390/cells8101171.


The target of rapamycin (TOR) kinase is a master metabolic regulator with roles in nutritional sensing, protein translation, and autophagy. In Chlamydomonas reinhardtii, a unicellular green alga, TOR has been linked to the regulation of increased triacylglycerol (TAG) accumulation, suggesting that TOR or a downstream target(s) is responsible for the elusive "lipid switch" in control of increasing TAG accumulation under nutrient limitation. However, while TOR has been well characterized in mammalian systems, it is still poorly understood in photosynthetic systems, and little work has been done to show the role of oxidative signaling in TOR regulation. In this study, the TOR inhibitor AZD8055 was used to relate reversible thiol oxidation to the physiological changes seen under TOR inhibition, including increased TAG content. Using oxidized cysteine resin-assisted capture enrichment coupled with label-free quantitative proteomics, 401 proteins were determined to have significant changes in oxidation following TOR inhibition. These oxidative changes mirrored characterized physiological modifications, supporting the role of reversible thiol oxidation in TOR regulation of TAG production, protein translation, carbohydrate catabolism, and photosynthesis through the use of reversible thiol oxidation. The delineation of redox-controlled proteins under TOR inhibition provides a framework for further characterization of the TOR pathway in photosynthetic eukaryotes.

Keywords: Chlamydomonas reinhardtii; photosynthesis; proteomics; redox signaling; target of rapamycin.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Chlamydomonas reinhardtii / physiology*
  • Chromatography, Liquid
  • Cysteine / chemistry*
  • Morpholines / pharmacology*
  • Oxidation-Reduction / drug effects
  • Photosynthesis / drug effects
  • Plant Proteins / metabolism
  • Proteomics / methods
  • Signal Transduction / drug effects
  • TOR Serine-Threonine Kinases / antagonists & inhibitors
  • TOR Serine-Threonine Kinases / metabolism*
  • Tandem Mass Spectrometry
  • Triglycerides / metabolism


  • Morpholines
  • Plant Proteins
  • Triglycerides
  • (5-(2,4-bis((3S)-3-methylmorpholin-4-yl)pyrido(2,3-d)pyrimidin-7-yl)-2-methoxyphenyl)methanol
  • TOR Serine-Threonine Kinases
  • Cysteine