A two-tiered system for selective receptor and transporter protein degradation

PLoS Genet. 2022 Oct 10;18(10):e1010446. doi: 10.1371/journal.pgen.1010446. eCollection 2022 Oct.

Abstract

Diverse physiology relies on receptor and transporter protein down-regulation and degradation mediated by ESCRTs. Loss-of-function mutations in human ESCRT genes linked to cancers and neurological disorders are thought to block this process. However, when homologous mutations are introduced into model organisms, cells thrive and degradation persists, suggesting other mechanisms compensate. To better understand this secondary process, we studied degradation of transporter (Mup1) or receptor (Ste3) proteins when ESCRT genes (VPS27, VPS36) are deleted in Saccharomyces cerevisiae using live-cell imaging and organelle biochemistry. We find that endocytosis remains intact, but internalized proteins aberrantly accumulate on vacuolar lysosome membranes within cells. Here they are sorted for degradation by the intralumenal fragment (ILF) pathway, constitutively or when triggered by substrates, misfolding or TOR activation in vivo and in vitro. Thus, the ILF pathway functions as fail-safe layer of defense when ESCRTs disregard their clients, representing a two-tiered system that ensures degradation of surface polytopic proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carrier Proteins / metabolism
  • Endosomal Sorting Complexes Required for Transport / genetics
  • Endosomal Sorting Complexes Required for Transport / metabolism
  • Humans
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism
  • Proteolysis
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins* / genetics
  • Saccharomyces cerevisiae Proteins* / metabolism
  • Vacuoles / genetics
  • Vacuoles / metabolism

Substances

  • Saccharomyces cerevisiae Proteins
  • Endosomal Sorting Complexes Required for Transport
  • Membrane Transport Proteins
  • Carrier Proteins
  • VPS36 protein, human
  • VPS27 protein, S cerevisiae

Grants and funding

This work was supported by Discovery Program grant #RGPIN/2017-06652 to C.L.B from the Natural Sciences and Engineering Research Council of Canada (https://www.nserc-crsng.gc.ca). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.