Unstructured regions in IRE1α specify BiP-mediated destabilisation of the luminal domain dimer and repression of the UPR
Abstract
Coupling of endoplasmic reticulum stress to dimerisation‑dependent activation of the UPR transducer IRE1 is incompletely understood. Whilst the luminal co-chaperone ERdj4 promotes a complex between the Hsp70 BiP and IRE1's stress-sensing luminal domain (IRE1LD) that favours the latter's monomeric inactive state and loss of ERdj4 de-represses IRE1, evidence linking these cellular and in vitro observations is presently lacking. We report that enforced loading of endogenous BiP onto endogenous IRE1α repressed UPR signalling in CHO cells and deletions in the IRE1α locus that de-repressed the UPR in cells, encode flexible regions of IRE1LD that mediated BiP‑induced monomerisation in vitro. Changes in the hydrogen exchange mass spectrometry profile of IRE1LD induced by ERdj4 and BiP confirmed monomerisation and were consistent with active destabilisation of the IRE1LD dimer. Together, these observations support a competition model whereby waning ER stress passively partitions ERdj4 and BiP to IRE1LD to initiate active repression of UPR signalling.
Data availability
Diffraction data have been deposited in PDB under the accession code 6SHCAll data generated or analysed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 1 - 7.
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Crystal structure of human IRE1 luminal domain Q105CProtein Data Bank, 6HSC.
Article and author information
Author details
Funding
Medical Research Council
- Niko Amin-Wetzel
European Molecular Biology Organization
- Lisa Neidhardt
Deutsche Forschungsgemeinschaft (SFB1036 TP9)
- Matthias P Mayer
Wellcome (Wellcome 996 100140)
- David Ron
Wellcome (Wellcome 200848/Z/16/Z)
- David Ron
Deutsche Forschungsgemeinschaft (MA 1278/4-3)
- Matthias P Mayer
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, Amin-Wetzel et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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