Activation of lysosomal function in the course of autophagy via mTORC1 suppression and autophagosome-lysosome fusion

Cell Res. 2013 Apr;23(4):508-23. doi: 10.1038/cr.2013.11. Epub 2013 Jan 22.

Abstract

Lysosome is a key subcellular organelle in the execution of the autophagic process and at present little is known whether lysosomal function is controlled in the process of autophagy. In this study, we first found that suppression of mammalian target of rapamycin (mTOR) activity by starvation or two mTOR catalytic inhibitors (PP242 and Torin1), but not by an allosteric inhibitor (rapamycin), leads to activation of lysosomal function. Second, we provided evidence that activation of lysosomal function is associated with the suppression of mTOR complex 1 (mTORC1), but not mTORC2, and the mTORC1 localization to lysosomes is not directly correlated to its regulatory role in lysosomal function. Third, we examined the involvement of transcription factor EB (TFEB) and demonstrated that TFEB activation following mTORC1 suppression is necessary but not sufficient for lysosomal activation. Finally, Atg5 or Atg7 deletion or blockage of the autophagosome-lysosome fusion process effectively diminished lysosomal activation, suggesting that lysosomal activation occurring in the course of autophagy is dependent on autophagosome-lysosome fusion. Taken together, this study demonstrates that in the course of autophagy, lysosomal function is upregulated via a dual mechanism involving mTORC1 suppression and autophagosome-lysosome fusion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autophagy / drug effects*
  • Autophagy-Related Protein 5
  • Autophagy-Related Protein 7
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / agonists
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / genetics
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / metabolism
  • Fibroblasts / cytology
  • Fibroblasts / drug effects
  • Fibroblasts / metabolism
  • Gene Expression Regulation / drug effects
  • HeLa Cells
  • Humans
  • Indoles / pharmacology
  • Lysosomes / drug effects*
  • Lysosomes / genetics
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2
  • Membrane Fusion / drug effects
  • Membrane Fusion / genetics
  • Mice
  • Microtubule-Associated Proteins / antagonists & inhibitors
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism
  • Naphthyridines / pharmacology
  • Phagosomes / drug effects*
  • Phagosomes / genetics
  • Purines / pharmacology
  • Signal Transduction / drug effects
  • Sirolimus / pharmacology
  • TOR Serine-Threonine Kinases / antagonists & inhibitors
  • TOR Serine-Threonine Kinases / genetics*
  • TOR Serine-Threonine Kinases / metabolism
  • Ubiquitin-Activating Enzymes / antagonists & inhibitors
  • Ubiquitin-Activating Enzymes / genetics
  • Ubiquitin-Activating Enzymes / metabolism

Substances

  • 1-(4-(4-propionylpiperazin-1-yl)-3-(trifluoromethyl)phenyl)-9-(quinolin-3-yl)benzo(h)(1,6)naphthyridin-2(1H)-one
  • ATG5 protein, human
  • Autophagy-Related Protein 5
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
  • Indoles
  • Microtubule-Associated Proteins
  • Multiprotein Complexes
  • Naphthyridines
  • Purines
  • TFEB protein, human
  • MTOR protein, human
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2
  • TOR Serine-Threonine Kinases
  • ATG7 protein, human
  • Autophagy-Related Protein 7
  • Ubiquitin-Activating Enzymes
  • PP242
  • Sirolimus