Journal
JOURNAL OF CELL SCIENCE
Volume 135, Issue 4, Pages -Publisher
COMPANY BIOLOGISTS LTD
DOI: 10.1242/jcs.259393
Keywords
Proteasome; Protein quality control; Microautophagy; Ubiquitin; ESCRT-0; Rsp5; AMPK
Categories
Funding
- National Institutes of Health [GM136325, GM046904, SIG OD018034]
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The proteasome is involved in proteolysis and can be degraded through macroautophagy and microautophagy pathways. AMPK-dependent ESCRT-mediated microautophagy regulates proteasome trafficking and degradation in low-glucose conditions. Aberrant proteasomes are more likely to undergo microautophagy, suggesting that the ESCRT system fine-tunes proteasome quality control in response to low-glucose stress.
The proteasome is central to proteolysis by the ubiquitin-proteasome system under normal growth conditions but is itself degraded through macroautophagy under nutrient stress. A recently described AMP-activated protein kinase (AMPK)-regulated endosomal sorting complex required for transport (ESCRT)-dependent microautophagy pathway also regulates proteasome trafficking and degradation in low-glucose conditions in yeast. Aberrant proteasomes are more prone to microautophagy, suggesting the ESCRT system fine-tunes proteasome quality control under low-glucose stress. Here, we uncover additional features of the selective microautophagy of proteasomes in budding yeast. Genetic or pharmacological induction of aberrant proteasomes is associated with increased mono- or oligo-ubiquitylation of proteasome components, which appears to be recognized by ESCRT-0. AMPK controls this pathway in part by regulating the trafficking of ESCRT-0 to the vacuole surface, which also leads to degradation of the Vps27 subunit of ESCRT-0. The Rsp5 ubiquitin ligase contributes to proteasome subunit ubiquitylation, and multiple ubiquitin-binding elements in Vps27 are involved in their recognition. We propose that ESCRT-0 at the vacuole surface recognizes ubiquitylated proteasomes and initiates their microautophagic elimination during glucose depletion.
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