title: Bypassing a kinase activity with an ATP-competitive drug.
abstract: Unfolded proteins in the endoplasmic reticulum cause trans-autophosphorylation of the bifunctional transmembrane kinase Ire1, which induces its endoribonuclease activity. The endoribonuclease initiates nonconventional splicing of HAC1 messenger RNA to trigger the unfolded-protein response (UPR). We explored the role of Ire1's kinase domain by sensitizing it through site-directed mutagenesis to the ATP-competitive inhibitor 1NM-PP1. Paradoxically, rather than being inhibited by 1NM-PP1, drug-sensitized Ire1 mutants required 1NM-PP1 as a cofactor for activation. In the presence of 1NM-PP1, drug-sensitized Ire1 bypassed mutations that inactivate its kinase activity and induced a full UPR. Thus, rather than through phosphorylation per se, a conformational change in the kinase domain triggered by occupancy of the active site with a ligand leads to activation of all known downstream functions.
authors.affiliation: Department of Medicine, University of California, San Francisco, CA 94143-2200, USA. frpapa@medicine.ucsf.edu
authors.forename: Feroz R
authors.initials: FR
authors.lastname: Papa
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.forename: Kevan
authors.initials: K
authors.lastname: Shokat
authors.forename: Peter
authors.initials: P
authors.lastname: Walter
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D001667:Binding, Competitive; D003600:Cytosol / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004722:Endoribonucleases / Q000378:metabolism; D004789:Enzyme Activation; D008024:Ligands; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011487:Protein Conformation; D017510:Protein Folding; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011720:Pyrazoles / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D011743:Pyrimidines / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
chemical_list: C479693:1-tert-butyl-3-naphthalen-1-ylmethyl-1H-pyrazolo(3,4-d)pyrimidin-4-ylemine; D050976:Basic-Leucine Zipper Transcription Factors; C091341:HAC1 protein, S cerevisiae; D008024:Ligands; D008562:Membrane Glycoproteins; D011720:Pyrazoles; D011743:Pyrimidines; D012333:RNA, Messenger; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; C082863:IRE1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D004722:Endoribonucleases; D004229:Dithiothreitol