<p>The endoplasmic-reticulum (ER) transmembrane protein IRE1 mitigates ER stress through kinase-endoribonuclease and scaffolding activities. Cancer cells often co-opt IRE1 to facilitate growth. An IRE1-RNase inhibitor has entered clinical trials; however, recent work uncovered a significant nonenzymatic IRE1 dependency in cancer. To fully disrupt IRE1, we describe a proteolysis-targeting chimera (G6374) that couples an IRE1-kinase ligand to a compound that binds the ubiquitin Cullin-RING Ligase (CRL) substrate receptor, VHL. G6374 induces a stable, cooperative interaction between IRE1 and VHL, driving K48-linked ubiquitination on two principal lysine residues in the IRE1-kinase domain and inducing proteasomal IRE1 degradation. Cryogenic electron microscopy and mutagenesis studies reveal a 2:2 IRE1:VHL ternary-complex topology and critical interactional features, informing future designs. G6374 blocks growth of IRE1-dependent cancer cells irrespective of their dependency mode, while sparing IRE1-independent cells. We provide a proof-of-concept for VHL-based degradation of an ER-transmembrane protein, advancing strategies to fully disrupt IRE1.</p>

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Chemically-induced degradation of the endoplasmic-reticulum stress sensor IRE1 by a VHL-recruiting chimera

  • Jin Du,
  • Elisia Villemure,
  • Matthew Johnson,
  • Caleigh Azumaya,
  • Catarina J. Gaspar,
  • Scot Marsters,
  • David Lawrence,
  • Scott Foster,
  • Alexis Rohou,
  • Tommy K. Cheung,
  • Christopher M. Rose,
  • Thomas Garner,
  • Soo Ro,
  • Kevin Clark,
  • Maureen H. Beresini,
  • Marie-Gabrielle Braun,
  • Joachim Rudolph,
  • Peter Hsu,
  • Avi Ashkenazi

摘要

The endoplasmic-reticulum (ER) transmembrane protein IRE1 mitigates ER stress through kinase-endoribonuclease and scaffolding activities. Cancer cells often co-opt IRE1 to facilitate growth. An IRE1-RNase inhibitor has entered clinical trials; however, recent work uncovered a significant nonenzymatic IRE1 dependency in cancer. To fully disrupt IRE1, we describe a proteolysis-targeting chimera (G6374) that couples an IRE1-kinase ligand to a compound that binds the ubiquitin Cullin-RING Ligase (CRL) substrate receptor, VHL. G6374 induces a stable, cooperative interaction between IRE1 and VHL, driving K48-linked ubiquitination on two principal lysine residues in the IRE1-kinase domain and inducing proteasomal IRE1 degradation. Cryogenic electron microscopy and mutagenesis studies reveal a 2:2 IRE1:VHL ternary-complex topology and critical interactional features, informing future designs. G6374 blocks growth of IRE1-dependent cancer cells irrespective of their dependency mode, while sparing IRE1-independent cells. We provide a proof-of-concept for VHL-based degradation of an ER-transmembrane protein, advancing strategies to fully disrupt IRE1.