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Unfolded Protein Responses With or Without Unfolded Proteins?
Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
Received: 17 September 2012; in revised form: 15 October 2012 / Accepted: 22 October 2012 / Published: 1 November 2012
Abstract: The endoplasmic reticulum (ER) is the site of secretory protein biogenesis. The ER quality control (QC) machinery, including chaperones, ensures the correct folding of secretory proteins. Mutant proteins and environmental stresses can overwhelm the available QC machinery. To prevent and resolve accumulation of misfolded secretory proteins in the ER, cells have evolved integral membrane sensors that orchestrate the Unfolded Protein Response (UPR). The sensors, Ire1p in yeast and IRE1, ATF6, and PERK in metazoans, bind the luminal ER chaperone BiP during homeostasis. As unfolded secretory proteins accumulate in the ER lumen, BiP releases, and the sensors activate. The mechanisms of activation and attenuation of the UPR sensors have exhibited unexpected complexity. A growing body of data supports a model in which Ire1p, and potentially IRE1, directly bind unfolded proteins as part of the activation process. However, evidence for an unfolded protein-independent mechanism has recently emerged, suggesting that UPR can be activated by multiple modes. Importantly, dysregulation of the UPR has been linked to human diseases including Type II diabetes, heart disease, and cancer. The existence of alternative regulatory pathways for UPR sensors raises the exciting possibility for the development of new classes of therapeutics for these medically important proteins.
Keywords: unfolded protein response; endoplasmic reticulum; misfolded protein; BIP; stress; Ire1; inositol
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Cite This Article
MDPI and ACS Style
Snapp, E.L. Unfolded Protein Responses With or Without Unfolded Proteins? Cells 2012, 1, 926-960.
Snapp EL. Unfolded Protein Responses With or Without Unfolded Proteins? Cells. 2012; 1(4):926-960.
Snapp, Erik L. 2012. "Unfolded Protein Responses With or Without Unfolded Proteins?" Cells 1, no. 4: 926-960.