ESCRT, not intralumenal fragments, sorts ubiquitinated vacuole membrane proteins for degradation

J Cell Biol. 2021 Aug 2;220(8):e202012104. doi: 10.1083/jcb.202012104. Epub 2021 May 28.


The lysosome (or vacuole in fungi and plants) is an essential organelle for nutrient sensing and cellular homeostasis. In response to environmental stresses such as starvation, the yeast vacuole can adjust its membrane composition by selectively internalizing membrane proteins into the lumen for degradation. Regarding the selective internalization mechanism, two competing models have been proposed. One model suggests that the ESCRT machinery is responsible for the sorting. In contrast, the ESCRT-independent intralumenal fragment (ILF) pathway proposes that the fragment generated by homotypic vacuole fusion is responsible for the sorting. Here, we applied a microfluidics-based imaging method to capture the complete degradation process in vivo. Combining live-cell imaging with a synchronized ubiquitination system, we demonstrated that ILF cargoes are not degraded through intralumenal fragments. Instead, ESCRTs function on the vacuole membrane to sort them into the lumen for degradation. We further discussed challenges in reconstituting vacuole membrane protein degradation.

Publication types

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

MeSH terms

  • Ceruloplasmin / genetics
  • Ceruloplasmin / metabolism
  • Endosomal Sorting Complexes Required for Transport / genetics
  • Endosomal Sorting Complexes Required for Transport / metabolism*
  • Ferritins / genetics
  • Ferritins / metabolism
  • Glucose Transport Proteins, Facilitative / genetics
  • Glucose Transport Proteins, Facilitative / metabolism
  • Intracellular Membranes / metabolism*
  • Lysosomes / genetics
  • Lysosomes / metabolism*
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Microfluidic Analytical Techniques
  • Microscopy, Fluorescence
  • Proteolysis
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Time Factors
  • Time-Lapse Imaging
  • Ubiquitination
  • Vacuoles / genetics
  • Vacuoles / metabolism*


  • Endosomal Sorting Complexes Required for Transport
  • Glucose Transport Proteins, Facilitative
  • HXT3 protein, S cerevisiae
  • Membrane Proteins
  • Saccharomyces cerevisiae Proteins
  • Ferritins
  • Ceruloplasmin
  • FET5 protein, S cerevisiae