title: Endoplasmic reticulum-dependent redox reactions control endoplasmic reticulum-associated degradation and pathogen entry.
abstract: CONCLUSIONS
  Protein misfolding within the endoplasmic reticulum (ER) is managed by an ER quality control system that retro-translocates aberrant proteins into the cytosol for proteasomal destruction. This process, known as ER-associated degradation, utilizes the action of ER redox enzymes to accommodate the disulfide-bonded nature of misfolded proteins. Strikingly, various pathogenic viruses and toxins co-opt these redox components to reach the cytosol during entry. These redox factors thus regulate critical cellular homeostasis and host-pathogen interactions.
  
  
  BACKGROUND
  Recent studies identify specific members of the protein disulfide isomerase (PDI) family, which use their chaperone and catalytic activities, in engaging both misfolded ER proteins and pathogens.
  
  
  RESULTS
  The precise molecular mechanism by which a dedicated PDI family member disrupts the disulfide bonds in the misfolded ER proteins and pathogens, as well as how they act to unfold these substrates to promote their ER-to-cytosol membrane transport, remain poorly characterized.
  
  
  CONCLUSIONS
  How PDI family members distinguish folded versus misfolded ER substrates remains enigmatic. What physical characteristics surrounding a substrate's disulfide bond instruct PDI that it is mispaired or native? For the pathogens, as their disulfide bonds normally serve a critical role in providing physical support, what conformational changes experienced in the host enable their disulfide bonds to be disrupted? A combination of more rigorous biochemical and high-resolution structural studies should begin to address these questions.
authors.affiliation: Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Walczak
authors.forename: Kaleena M
authors.initials: KM
authors.lastname: Bernardi
authors.forename: Billy
authors.initials: B
authors.lastname: Tsai
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D006801:Humans; D018832:Molecular Chaperones / Q000378:metabolism; D010084:Oxidation-Reduction; D027382:Polyomaviridae / Q000502:physiology; D019704:Protein Disulfide-Isomerases / Q000378:metabolism / Q000502:physiology; D017510:Protein Folding; D021381:Protein Transport; D059748:Proteolysis
chemical_list: D001427:Bacterial Toxins; D004220:Disulfides; D018832:Molecular Chaperones; D019704:Protein Disulfide-Isomerases