The FOXO transcription factor DAF-16 bypasses ire-1 requirement to promote endoplasmic reticulum homeostasis

Cell Metab. 2014 Nov 4;20(5):870-881. doi: 10.1016/j.cmet.2014.09.006.

Abstract

The unfolded protein response (UPR) allows cells to adjust the capacity of the endoplasmic reticulum (ER) to the load of ER-associated tasks. We show that activation of the Caenorhabditis elegans transcription factor DAF-16 and its human homolog FOXO3 restore secretory protein metabolism when the UPR is dysfunctional.We show that DAF-16 establishes alternative ER-associated degradation systems that degrade misfolded proteins independently of the ER stress sensor ire-1 and the ER-associated E3 ubiquitin ligase complex sel-11/sel-1. This is achieved by enabling autophagy-mediated degradation and by increasing the levels of skr-5, a component of an ER associated ubiquitin ligase complex. These degradation systems can act together with the conserved UPR to improve ER homeostasis and ER stress resistance, beyond wild-type levels. Because there is no sensor in the ER that activates DAF-16 in response to intrinsic ER stress, natural or artificial interventions that activate DAF-16 may be useful therapeutic approaches to maintain ER homeostasis.

MeSH terms

  • Animals
  • Autophagy
  • Caenorhabditis elegans / cytology*
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism*
  • Endoplasmic Reticulum Stress
  • Endoplasmic Reticulum-Associated Degradation*
  • Forkhead Box Protein O3
  • Forkhead Transcription Factors / metabolism*
  • HEK293 Cells
  • Humans
  • Mutation
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Unfolded Protein Response

Substances

  • Caenorhabditis elegans Proteins
  • FOXO3 protein, human
  • Forkhead Box Protein O3
  • Forkhead Transcription Factors
  • daf-16 protein, C elegans
  • Protein Serine-Threonine Kinases
  • IRE-1 protein, C elegans