unfolded protein response
Saturday 14 January 2006
UPR, unfolded-protein response
The endoplasmic reticulum (ER) responds to the accumulation of unfolded proteins in its lumen (ER stress) by activating intracellular signal transduction pathways, cumulatively called the unfolded protein response (UPR).
Together, at least three mechanistically distinct arms of the UPR regulate the expression of numerous genes that function within the secretory pathway but also affect broad aspects of cell fate and the metabolism of proteins, amino acids and lipids.
The arms of the UPR are integrated to provide a response that remodels the secretory apparatus and aligns cellular physiology to the demands imposed by ER stress.
Folding in the endoplasmic reticulum (ER) must couple protein-synthesis pathways operating outside of the compartment with ER-assisted folding (ERAF) pathways in the lumen.
Chaperone-mediated folding imbalances that are associated with numerous misfolding diseases, including diabetes, trigger the unfolded-protein response (UPR), using both transcriptional and translational pathways to correct the problem.
Small-molecule inhibitors could be useful to help rebalance protein synthesis with ERAF pathways through the ribosomal initiating factor eIF2alpha. Reprogramming stress pathways with drugs provides a potential new approach for balancing ER-protein load with cellular-folding capacity, thus correcting disease.
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