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Protein disulfide isomerases contribute differentially to the endoplasmic reticulum-associated degradation of apolipoprotein B and other substrates.

ER-associated degradation (ERAD) rids the early secretory pathway of misfolded or misprocessed proteins. Some members of the protein disulfide isomerase (PDI) family appear to facilitate ERAD substrate selection and retrotranslocation, but a thorough characterization of PDIs during the degradation of diverse substrates has not been undertaken, in part because there are 20 PDI family members in mammals. PDIs can also exhibit disulfide redox, isomerization, and/or chaperone activity, but which of these activities is required for the ERAD of different substrate classes is unknown. We therefore examined the fates of unique substrates in yeast, which expresses five PDIs. Through the use of a yeast expression system for apolipoprotein B (ApoB), which is disulfide rich, we discovered that Pdi1 interacts with ApoB and facilitates degradation through its chaperone activity. In contrast, Pdi1's redox activity was required for the ERAD of CPY* (a misfolded version of carboxypeptidase Y that has five disulfide bonds). The ERAD of another substrate, the alpha subunit of the epithelial sodium channel, was Pdi1 independent. Distinct effects of mammalian PDI homologues on ApoB degradation were then observed in hepatic cells. These data indicate that PDIs contribute to the ERAD of proteins through different mechanisms and that PDI diversity is critical to recognize the spectrum of potential ERAD substrates.

Pubmed ID: 22190736

Authors

  • Grubb S
  • Guo L
  • Fisher EA
  • Brodsky JL

Journal

Molecular biology of the cell

Publication Data

February 16, 2012

Associated Grants

  • Agency: NIDDK NIH HHS, Id: DK65161
  • Agency: NIDDK NIH HHS, Id: DK79307
  • Agency: NIGMS NIH HHS, Id: GM75061
  • Agency: NHLBI NIH HHS, Id: HL58541
  • Agency: NIDDK NIH HHS, Id: P30 DK072506

Mesh Terms

  • Apolipoproteins B
  • Carboxypeptidases
  • Endoplasmic Reticulum
  • Humans
  • Oxidation-Reduction
  • Protein Disulfide-Isomerases
  • Proteolysis
  • Saccharomyces cerevisiae Proteins