Unstructured regions in IRE1α specify BiP-mediated destabilisation of the luminal domain dimer and repression of the UPR

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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 (IRE1^LD) 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 IRE1^LD that mediated BiP‑induced monomerisation in vitro. Changes in the hydrogen exchange mass spectrometry profile of IRE1^LD induced by ERdj4 and BiP confirmed monomerisation and were consistent with active destabilisation of the IRE1^LD dimer. Together, these observations support a competition model whereby waning ER stress passively partitions ERdj4 and BiP to IRE1^LD 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.

The following data sets were generated

(2019) Crystal structure of human IRE1 luminal domain Q105C
Protein Data Bank, 6HSC.

http://www.rcsb.org/structure/6HSC

Article and author information

Author details

Niko Amin-Wetzel

Cambridge Institute for Medical Research (CIMR), University of Cambridge, Cambridge, United Kingdom

Competing interests
No competing interests declared.
Lisa Neidhardt

Cambridge Institute for Medical Research (CIMR), University of Cambridge, Cambridge, United Kingdom

Competing interests
No competing interests declared.

"This ORCID iD identifies the author of this article:" 0000-0003-0256-5040
Yahui Yan

Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom

Competing interests
No competing interests declared.

"This ORCID iD identifies the author of this article:" 0000-0001-6934-9874
Matthias P Mayer

Zentrum für Molekulare Biologie der Universität Heidelberg, University of Heidelberg, Heidelberg, Germany

Competing interests
No competing interests declared.

"This ORCID iD identifies the author of this article:" 0000-0002-7859-3112
David Ron

Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom

For correspondence
dr360@medschl.cam.ac.uk

Competing interests
David Ron, Senior editor, eLife.

"This ORCID iD identifies the author of this article:" 0000-0002-3014-5636

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.

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