Distinct autophagosomal-lysosomal fusion mechanism revealed by thapsigargin-induced autophagy arrest

Mol Cell. 2011 Jun 24;42(6):731-43. doi: 10.1016/j.molcel.2011.04.024.

Abstract

Autophagy, a catabolic pathway that delivers cellular components to lysosomes for degradation, can be activated by stressful conditions such as nutrient starvation and endoplasmic reticulum (ER) stress. We report that thapsigargin, an ER stressor widely used to induce autophagy, in fact blocks autophagy. Thapsigargin does not affect autophagosome formation but leads to accumulation of mature autophagosomes by blocking autophagosome fusion with the endocytic system. Strikingly, thapsigargin has no effect on endocytosis-mediated degradation of epidermal growth factor receptor. Molecularly, while both Rab7 and Vps16 are essential regulatory components for endocytic fusion with lysosomes, we found that Rab7 but not Vps16 is required for complete autophagy flux, and that thapsigargin blocks recruitment of Rab7 to autophagosomes. Therefore, autophagosomal-lysosomal fusion must be governed by a distinct molecular mechanism compared to general endocytic fusion.

Publication types

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

MeSH terms

  • Animals
  • Autophagy / drug effects*
  • Lysosomes / drug effects
  • Lysosomes / metabolism*
  • Mice
  • Thapsigargin / pharmacology*
  • rab GTP-Binding Proteins / antagonists & inhibitors
  • rab GTP-Binding Proteins / metabolism

Substances

  • rab7 protein
  • Thapsigargin
  • rab GTP-Binding Proteins