Stress-induced clustering of the UPR sensor IRE1α is driven by disordered regions within its ER lumenal domain

Kettel, Paulina; Marosits, Laura; Spinetti, Elena; Rechberger, Michael; Radler, Philipp; Niedermoser, Isabell; Fischer, Ilse; Versteeg, Gijs A.; Loose, Martin; Covino, Roberto; Karagöz, G. Elif

doi:10.1101/2023.03.30.534746

Cited by 3 publications

(3 citation statements)

References 75 publications

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“…Despite the functional importance of the C-terminal part of Ire1-LD for oligomerisation and BiP binding (as demonstrated in this and previous studies 8,13,18,30 ), to date, only very limited information is available about the last 150 residues of Ire1-LD (residues 301 to 449). Given that the majority of this region lacks electron density (PDB IDs 2HZ6 12 and 6SHC 18 ) and is reported to be highly dynamic 18 , a deeper understanding of how this region orchestrates BiP binding and oligomerization is needed.…”

Section: Resultsmentioning

confidence: 70%

“…The flexible C-terminal region of Ire1-LD (residues H301-S449) has been previously suggested to bind BiP 18 and be important for Ire1-LD oligomerisation and clustering 13,8,30 ; however, the exact BiP binding site(s) has not been identified. We employed the state-of-the-art BiPPred algorithm 31 to predict potential BiP binding motifs in this flexible C-terminal region.…”

Section: Resultsmentioning

confidence: 99%

“…As expected for canonical Hsp70 substrates 33 , the addition of either of 310 GSTLPLLE 317 and 356 RNYWLLI 362 peptides results in enhanced ATPase activity of WT BiP, comparable with the effect observed in the presence of the model substrate HTFPAVL 31,32 (Figure 3b). Interestingly, while perturbations in the 310 GSTLPLLE 317 and 356 RNYWLLI 362 region in the full-length Ire1-LD considerably affect Ire1-LD oligomerisation and clustering of Ire1-LD 13,8,30 , perturbations in either motif were insufficient to eliminate Ire1-LD oligomerization and BiP-induced de-oligomerisation completely (Supplementary Figure 12), indicative of the multivalent nature of these interactions between Ire1-LD oligomers and BiP.…”

Section: Resultsmentioning

confidence: 99%

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Molecular chaperone BiP controls activity of the ER stress sensor Ire1 through interactions with its oligomers

Dawes,

Hurst,

Grey

et al. 2024

Preprint

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The complex multistep activation cascade of Ire1, the most evolutionary conserved stress-sensor in the endoplasmic reticulum (ER), involves changes in the Ire1 conformation and oligomeric state. Ire1 activation enhances ER folding capacity, in part by overexpressing the ER Hsp70 molecular chaperone BiP; in turn, BiP provides tight negative control of Ire1 activation. This study demonstrates that one of the mechanisms by which BiP regulates Ire1 activation is through a direct BiP interaction with Ire1 oligomers. Particularly, we demonstrated that the binding of Ire1 luminal domain (LD) to unfolded protein substrates does not only trigger conformational changes in Ire1-LD that favour the formation of Ire1-LD oligomers but also exposes BiP binding motifs, enabling the molecular chaperone BiP to directly bind to Ire1-LD in a chaperone-like, ATP-dependent manner. These transient interactions between BiP and two short motifs in the disordered region of Ire1-LD that destabilize Ire1-LD oligomers and trigger their de-oligomerisation are reminiscent of interactions between clathrin and another Hsp70, cytoplasmic Hsc70. BiP binding to substrate-bound Ire1-LD oligomers enables unfolded protein substrates and BiP to synergistically and dynamically control Ire1-LD oligomerisation. These findings reveal a new mechanism by which BiP acts to return Ire1 to its deactivated state when an ER stress response is no longer required.

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Section: Resultsmentioning

confidence: 70%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Molecular chaperone BiP controls activity of the ER stress sensor Ire1 through interactions with its oligomers

Dawes,

Hurst,

Grey

et al. 2024

Preprint

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“IGF2BP1 phosphorylation regulates ribonucleoprotein condensate formation by impairing low-affinity protein and RNA interactions”

Hornegger,

Muratovic,

Anisimova

et al. 2023

Preprint

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The insulin-like growth factor 2 mRNA binding protein (IGF2BP1) is a conserved RNA-binding protein that regulates RNA stability, localization, and translation. IGF2BP1 is part of various ribonucleoprotein (RNP) condensates regulating RNA outputs. However, the mechanism that regulates its assembly into condensates remains unknown. Here we found, using proteomics, that IGF2BP1 phosphorylation at S181 in a disordered linker is regulated in a stress-dependent manner. Phosphomimetic mutations in two disordered linkers, S181E and Y396E, modulated RNP condensate formation by IGF2BP1 without impacting its binding affinity for RNA. Intriguingly, the S181E mutant, which lies in linker 1, impaired IGF2BP1 condensate formationin vitroand in cells, whereas a Y396E mutant in the second linker increased condensate size and dynamics. Structural approaches showed that the first linker binds RNAs nonspecifically through its RGG/RG motif, an interaction weakened in the S181E mutant. Notably, linker 2 interacts with IGF2BP1’s folded domains and these interactions were partially impaired in the Y396E mutant. Our data reveal how phosphorylation modulates low affinity interaction networks in disordered linkers to regulate RNP condensate formation.

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Chaperone BiP controls ER stress sensor Ire1 through interactions with its oligomers

Dawes,

Hurst,

Grey

et al. 2024

Life Sci. Alliance

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The complex multistep activation cascade of Ire1 involves changes in the Ire1 conformation and oligomeric state. Ire1 activation enhances ER folding capacity, in part by overexpressing the ER Hsp70 molecular chaperone BiP; in turn, BiP provides tight negative control of Ire1 activation. This study demonstrates that BiP regulates Ire1 activation through a direct interaction with Ire1 oligomers. Particularly, we demonstrated that the binding of Ire1 luminal domain (LD) to unfolded protein substrates not only trigger conformational changes in Ire1-LD that favour the formation of Ire1-LD oligomers but also exposes BiP binding motifs, enabling the molecular chaperone BiP to directly bind to Ire1-LD in an ATP-dependent manner. These transient interactions between BiP and two short motifs in the disordered region of Ire1-LD are reminiscent of interactions between clathrin and another Hsp70, cytoplasmic Hsc70. BiP binding to substrate-bound Ire1-LD oligomers enables unfolded protein substrates and BiP to synergistically and dynamically control Ire1-LD oligomerisation, helping to return Ire1 to its deactivated state when an ER stress response is no longer required.

show abstract

Stress-induced clustering of the UPR sensor IRE1α is driven by disordered regions within its ER lumenal domain

Cited by 3 publications

References 75 publications

Molecular chaperone BiP controls activity of the ER stress sensor Ire1 through interactions with its oligomers

Molecular chaperone BiP controls activity of the ER stress sensor Ire1 through interactions with its oligomers

“IGF2BP1 phosphorylation regulates ribonucleoprotein condensate formation by impairing low-affinity protein and RNA interactions”

Chaperone BiP controls ER stress sensor Ire1 through interactions with its oligomers

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