An unfolded protein-induced conformational switch activates mammalian IRE1.

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 IRE1?'s ER-lumenal domain (hIRE1? LD) binds peptides with a characteristic amino acid bias. Peptides and unfolded proteins bind to hIRE1? 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 hIRE1? LD from its oligomerization, yet retained peptide-induced allosteric coupling within the domain. Importantly, impairing oligomerization of hIRE1? 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.

SUBMITTER: Karagoz GE 

PROVIDER: S-EPMC5699868 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature