An unfolded protein-induced conformational switch activates mammalian IRE1.

TitleAn unfolded protein-induced conformational switch activates mammalian IRE1.
Publication TypeJournal Article
Year of Publication2017
AuthorsKaragöz GElif, Acosta-Alvear D, Nguyen HT, Lee CP, Chu F, Walter P
JournalElife
Volume6
Date Published2017 Oct 03
ISSN2050-084X
Abstract

The unfolded protein response (UPR) adjusts the cell's protein folding capacity in the endoplasmic reticulum (ER) according to need. IRE1 is the most conserved UPR sensor in eukaryotic cells. It has remained controversial, however, whether mammalian and yeast IRE1 use a common mechanism for ER stress sensing. Here, we show that similar to yeast, human IRE1α's ER-lumenal domain (hIRE1α LD) binds peptides with a characteristic amino acid bias. Peptides and unfolded proteins bind to hIRE1α LD's MHC-like groove and induce allosteric changes that lead to its oligomerization. Mutation of a hydrophobic patch at the oligomerization interface decoupled peptide binding to hIRE1α LD from its oligomerization, yet retained peptide-induced allosteric coupling within the domain. Importantly, impairing oligomerization of hIRE1α LD abolished IRE1's activity in living cells. Our results provide evidence for a unifying mechanism of IRE1 activation that relies on unfolded protein binding-induced oligomerization.

DOI10.7554/eLife.30700
Alternate JournalElife
PubMed ID28971800