Cell Biology

Directing Quality Control

Science Signaling  04 Oct 2011:
Vol. 4, Issue 193, pp. ec278
DOI: 10.1126/scisignal.4193ec278

The unfolded protein response (UPR) is triggered when misfolded secretory and membrane proteins accumulate within the endoplasmic reticulum (ER). It remains unclear how the misfolded state of proteins in the ER is sensed by the transmembrane signal transducing kinase, Ire1. Gardner and Walter (see the Perspective by Kawaguchi and Ng) now provide evidence that supports the notion that Ire1 directly interacts with misfolded proteins, thereby leading to dimerization and activation of Ire1. Yeast in vitro experiments showed that the luminal domain of Ire1 can bind to peptides enriched in hydrophobic and basic residues typical of misfolded proteins. Furthermore, a misfolded model protein directly interacted with Ire1 in intact yeast cells.

B. M. Gardner, P. Walter, Unfolded proteins are Ire1-activating ligands that directly induce the unfolded protein response. Science 333, 1891–1894 (2011). [Abstract] [Full Text]

S. Kawaguchi, D. T. W. Ng, Sensing ER stress. Science 333, 1830–1831 (2011). [Abstract] [Full Text]