Endoplasmic Reticulum Transport of Glutathione by Sec61 Is Regulated by Ero1 and Bip

Mol Cell. 2017 Sep 21;67(6):962-973.e5. doi: 10.1016/j.molcel.2017.08.012. Epub 2017 Sep 14.

Abstract

In the endoplasmic reticulum (ER), Ero1 catalyzes disulfide bond formation and promotes glutathione (GSH) oxidation to GSSG. Since GSSG cannot be reduced in the ER, maintenance of the ER glutathione redox state and levels likely depends on ER glutathione import and GSSG export. We used quantitative GSH and GSSG biosensors to monitor glutathione import into the ER of yeast cells. We found that glutathione enters the ER by facilitated diffusion through the Sec61 protein-conducting channel, while oxidized Bip (Kar2) inhibits transport. Increased ER glutathione import triggers H2O2-dependent Bip oxidation through Ero1 reductive activation, which inhibits glutathione import in a negative regulatory loop. During ER stress, transport is activated by UPR-dependent Ero1 induction, and cytosolic glutathione levels increase. Thus, the ER redox poise is tuned by reciprocal control of glutathione import and Ero1 activation. The ER protein-conducting channel is permeable to small molecules, provided the driving force of a concentration gradient.

Keywords: Bip; Ero1; Sec61; disulfide bond; endoplasmic reticulum; glutathione; membrane transport; oxidative protein folding; redox biosensor; redox homeostasis.

MeSH terms

  • Cytosol / enzymology
  • Endoplasmic Reticulum / enzymology*
  • Facilitated Diffusion
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Glutathione / metabolism*
  • Glutathione Disulfide / metabolism
  • Glycoproteins / genetics
  • Glycoproteins / metabolism*
  • HSP70 Heat-Shock Proteins / genetics
  • HSP70 Heat-Shock Proteins / metabolism*
  • Hydrogen Peroxide / metabolism
  • Intracellular Membranes / enzymology
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Oxidation-Reduction
  • Oxidoreductases Acting on Sulfur Group Donors / genetics
  • Oxidoreductases Acting on Sulfur Group Donors / metabolism*
  • SEC Translocation Channels / genetics
  • SEC Translocation Channels / metabolism*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Signal Transduction
  • Time Factors
  • Unfolded Protein Response

Substances

  • Fungal Proteins
  • Glycoproteins
  • HSP70 Heat-Shock Proteins
  • KAR2 protein, yeast
  • Membrane Proteins
  • SEC Translocation Channels
  • SEC61 protein, S cerevisiae
  • SSH1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Hydrogen Peroxide
  • Oxidoreductases Acting on Sulfur Group Donors
  • ERO1 protein, S cerevisiae
  • Glutathione
  • Glutathione Disulfide