Endoplasmic reticulum stress activates human IRE1α through reversible assembly of inactive dimers into small oligomers

• DOI: 10.7554/elife.74342
• Publication Date: 2022-06-22T00:00:13Z
• Authors: Vladislav Belyy; Iratxe Zuazo-Gaztelu; Andrew Alamban; Avi Ashkenazi; Peter Walter
• Keywords: Endoplasmic-reticulum-associated protein degradation

Protein folding homeostasis in the endoplasmic reticulum (ER) is regulated by a signaling network, termed unfolded protein response (UPR). Inositol-requiring enzyme 1 (IRE1) an ER membrane-resident kinase/RNase that mediates signal transmission most evolutionarily conserved branch of UPR. Dimerization and/or higher-order oligomerization IRE1 are thought to be important for its activation mechanism, yet actual oligomeric states inactive, active, and attenuated mammalian complexes remain unknown. We developed automated two-color single-molecule tracking approach dissect tagged endogenous human live cells. In contrast previous models, our data indicate exists as constitutive homodimer at baseline assembles into small oligomers upon stress. demonstrate formation inactive dimers stress-dependent fully governed IRE1’s lumenal domain. Phosphorylation kinase domain occurs more slowly than retained after disassemble back dimers. Our findings suggest assembly larger specifically enables trans- autophosphorylation, which turn drives RNase activity.