title: Endoplasmic reticulum stress-independent activation of unfolded protein response kinases by a small molecule ATP-mimic.
abstract: Two ER membrane-resident transmembrane kinases, IRE1 and PERK, function as stress sensors in the unfolded protein response. IRE1 also has an endoribonuclease activity, which initiates a non-conventional mRNA splicing reaction, while PERK phosphorylates eIF2α. We engineered a potent small molecule, IPA, that binds to IRE1's ATP-binding pocket and predisposes the kinase domain to oligomerization, activating its RNase. IPA also inhibits PERK but, paradoxically, activates it at low concentrations, resulting in a bell-shaped activation profile. We reconstituted IPA-activation of PERK-mediated eIF2α phosphorylation from purified components. We estimate that under conditions of maximal activation less than 15% of PERK molecules in the reaction are occupied by IPA. We propose that IPA binding biases the PERK kinase towards its active conformation, which trans-activates apo-PERK molecules. The mechanism by which partial occupancy with an inhibitor can activate kinases may be wide-spread and carries major implications for design and therapeutic application of kinase inhibitors.
authors.affiliation: Department of Cellular and Molecular Pharmacology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Aaron S
authors.initials: AS
authors.lastname: Mendez
authors.affiliation: Fundación Ciencia & Vida, Santiago, Chile.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Alfaro
authors.affiliation: Fundación Ciencia & Vida, Santiago, Chile.
authors.forename: Marisol A
authors.initials: MA
authors.lastname: Morales-Soto
authors.affiliation: Department of Cellular and Molecular Pharmacology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Arvin C
authors.initials: AC
authors.lastname: Dar
authors.affiliation: Fundación Ciencia & Vida, Santiago, Chile.
authors.forename: Emma
authors.initials: E
authors.lastname: McCullagh
authors.affiliation: Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Katja
authors.initials: K
authors.lastname: Gotthardt
authors.affiliation: Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Han
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Diego
authors.initials: D
authors.lastname: Acosta-Alvear
authors.affiliation: Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Carmela
authors.initials: C
authors.lastname: Sidrauski
authors.affiliation: Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Korennykh
authors.affiliation: Fundación Ciencia & Vida, Santiago, Chile.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Bernales
authors.affiliation: Department of Cellular and Molecular Pharmacology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Kevan M
authors.initials: KM
authors.lastname: Shokat
authors.affiliation: Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Peter
authors.initials: P
authors.lastname: Walter
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000494:pharmacology*; D000818:Animals; D001681:Biological Assay; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress; D004722:Endoribonucleases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D015870:Gene Expression; D017930:Genes, Reporter; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D018716:Molecular Mimicry; D047428:Protein Kinase Inhibitors / Q000138:chemical synthesis / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D000071701:Regulatory Factor X Transcription Factors; D013462:Sulfur Radioisotopes; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D056811:Unfolded Protein Response / Q000187:drug effects* / Q000235:genetics; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: D000255:Adenosine Triphosphate; D004268:DNA-Binding Proteins; D004722:Endoribonucleases; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011993:Recombinant Fusion Proteins; D000071701:Regulatory Factor X Transcription Factors; D013462:Sulfur Radioisotopes; D014157:Transcription Factors; D019892:eIF-2 Kinase; C460640:EIF2AK3 protein, human; C528229:ERN1 protein, human
keywords: E. coli; IPA; IRE1; PERK; biochemistry; cell biology; human; human cells; mouse; protein kinase