Endoplasmic reticulum stress-independent activation of unfolded protein response kinases by a small molecule ATP-mimic.

TitleEndoplasmic reticulum stress-independent activation of unfolded protein response kinases by a small molecule ATP-mimic.
Publication TypeJournal Article
Year of Publication2015
AuthorsMendez AS, Alfaro J, Morales-Soto MA, Dar AC, McCullagh E, Gotthardt K, Li H, Acosta-Alvear D, Sidrauski C, Korennykh AV, Bernales S, Shokat KM, Walter P
Date Published2015
KeywordsAdenosine Triphosphate, Animals, Biological Assay, Cell Line, Cell Survival, DNA-Binding Proteins, eIF-2 Kinase, Endoplasmic Reticulum Stress, Endoribonucleases, Enzyme Activation, Escherichia coli, Fibroblasts, Gene Expression, Genes, Reporter, HEK293 Cells, Humans, Mice, Molecular Mimicry, Protein Kinase Inhibitors, Protein-Serine-Threonine Kinases, Recombinant Fusion Proteins, Sulfur Radioisotopes, Transcription Factors, Unfolded Protein Response

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.

Alternate JournalElife
PubMed ID25986605
PubMed Central IDPMC4436593
Grant ListT32 GM064337 / GM / NIGMS NIH HHS / United States
/ / Howard Hughes Medical Institute / United States