Mixed-disulfide folding intermediates between thyroglobulin and endoplasmic reticulum resident oxidoreductases ERp57 and protein disulfide isomerase

Mol Cell Biol. 2005 Nov;25(22):9793-805. doi: 10.1128/MCB.25.22.9793-9805.2005.

Abstract

We present the first identification of transient folding intermediates of endogenous thyroglobulin (Tg; a large homodimeric secretory glycoprotein of thyrocytes), which include mixed disulfides with endogenous oxidoreductases servicing Tg folding needs. Formation of disulfide-linked Tg adducts with endoplasmic reticulum (ER) oxidoreductases begins cotranslationally. Inhibition of ER glucosidase activity blocked formation of a subgroup of Tg adducts containing ERp57 while causing increased Tg adduct formation with protein disulfide isomerase (PDI), delayed adduct resolution, perturbed oxidative folding of Tg monomers, impaired Tg dimerization, increased Tg association with BiP/GRP78 and GRP94, activation of the unfolded protein response, increased ER-associated degradation of a subpopulation of Tg, partial Tg escape from ER quality control with increased secretion of free monomers, and decreased overall Tg secretion. These data point towards mixed disulfides with the ERp57 oxidoreductase in conjunction with calreticulin/calnexin chaperones acting as normal early Tg folding intermediates that can be "substituted" by PDI adducts only at the expense of lower folding efficiency with resultant ER stress.

Publication types

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

MeSH terms

  • Animals
  • Blotting, Western
  • Calnexin / chemistry
  • Calreticulin / chemistry
  • Cell Line
  • DNA, Complementary / metabolism
  • Dimerization
  • Disulfides* / chemistry
  • Electrophoresis, Polyacrylamide Gel
  • Endoplasmic Reticulum / metabolism*
  • HSP70 Heat-Shock Proteins / metabolism
  • Heat-Shock Proteins / metabolism
  • Heat-Shock Proteins / physiology*
  • Immunoprecipitation
  • Membrane Proteins / metabolism
  • Molecular Chaperones / chemistry
  • Molecular Chaperones / metabolism
  • Protein Binding
  • Protein Biosynthesis
  • Protein Disulfide-Isomerases / physiology*
  • Protein Folding
  • Rats
  • Thyroglobulin / chemistry*
  • Time Factors
  • Transcription, Genetic

Substances

  • Calreticulin
  • DNA, Complementary
  • Disulfides
  • GRP78 protein, rat
  • HSP70 Heat-Shock Proteins
  • Heat-Shock Proteins
  • Membrane Proteins
  • Molecular Chaperones
  • glucose-regulated proteins
  • Calnexin
  • Thyroglobulin
  • PDIA3 protein, rat
  • Protein Disulfide-Isomerases