title: Molecular mechanisms of human IRE1 activation through dimerization and ligand binding.
abstract: IRE1 transduces the unfolded protein response by splicing XBP1 through its C-terminal cytoplasmic kinase-RNase region. IRE1 autophosphorylation is coupled to RNase activity through formation of a back-to-back dimer, although the conservation of the underlying molecular mechanism is not clear from existing structures. We have crystallized human IRE1 in a back-to-back conformation only previously seen for the yeast homologue. In our structure the kinase domain appears primed for catalysis but the RNase domains are disengaged. Structure-function analysis reveals that IRE1 is autoinhibited through a Tyr-down mechanism related to that found in the unrelated Ser/Thr protein kinase Nek7. We have developed a compound that potently inhibits human IRE1 kinase activity while stimulating XBP1 splicing. A crystal structure of the inhibitor bound to IRE1 shows an increased ordering of the kinase activation loop. The structures of hIRE in apo and ligand-bound forms are consistent with a previously proposed model of IRE1 regulation in which formation of a back-to-back dimer coupled to adoption of a kinase-active conformation drive RNase activation. The structures provide opportunities for structure-guided design of IRE1 inhibitors.
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester, United Kingdom.|Cancer Research UK Leicester Centre, University of Leicester, Leicester, United Kingdom.
authors.forename: Amar
authors.initials: A
authors.lastname: Joshi
authors.affiliation: Cancer Research UK Cancer Therapeutics Unit, Division of Cancer Therapeutics, The Institute of Cancer Research, London, United Kingdom.
authors.forename: Yvette
authors.initials: Y
authors.lastname: Newbatt
authors.affiliation: Cancer Research UK Cancer Therapeutics Unit, Division of Cancer Therapeutics, The Institute of Cancer Research, London, United Kingdom.
authors.forename: P Craig
authors.initials: PC
authors.lastname: McAndrew
authors.affiliation: Cancer Research UK Cancer Therapeutics Unit, Division of Cancer Therapeutics, The Institute of Cancer Research, London, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Stubbs
authors.affiliation: Cancer Research UK Cancer Therapeutics Unit, Division of Cancer Therapeutics, The Institute of Cancer Research, London, United Kingdom.
authors.forename: Rosemary
authors.initials: R
authors.lastname: Burke
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester, United Kingdom.|Cancer Research UK Leicester Centre, University of Leicester, Leicester, United Kingdom.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Richards
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester, United Kingdom.|Cancer Research UK Leicester Centre, University of Leicester, Leicester, United Kingdom.
authors.forename: Chitra
authors.initials: C
authors.lastname: Bhatia
authors.affiliation: Cancer Research UK Cancer Therapeutics Unit, Division of Cancer Therapeutics, The Institute of Cancer Research, London, United Kingdom.
authors.forename: John J
authors.initials: JJ
authors.lastname: Caldwell
authors.affiliation: Cancer Research UK Cancer Therapeutics Unit, Division of Cancer Therapeutics, The Institute of Cancer Research, London, United Kingdom.
authors.forename: Tatiana
authors.initials: T
authors.lastname: McHardy
authors.affiliation: Cancer Research UK Cancer Therapeutics Unit, Division of Cancer Therapeutics, The Institute of Cancer Research, London, United Kingdom.
authors.forename: Ian
authors.initials: I
authors.lastname: Collins
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester, United Kingdom.|Cancer Research UK Leicester Centre, University of Leicester, Leicester, United Kingdom.
authors.forename: Richard
authors.initials: R
authors.lastname: Bayliss
mesh_terms: D055808:Drug Discovery; D004722:Endoribonucleases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D010766:Phosphorylation; D011487:Protein Conformation; D047428:Protein Kinase Inhibitors / Q000737:chemistry / Q000494:pharmacology; D055503:Protein Multimerization; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012260:Ribonucleases / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014162:Transfection
chemical_list: D008024:Ligands; D047428:Protein Kinase Inhibitors; C528229:ERN1 protein, human; D017346:Protein Serine-Threonine Kinases; D004722:Endoribonucleases; D012260:Ribonucleases
keywords: RNase; UPR; drug discovery; kinase