title: Chemical genetics reveals a kinase-independent role for protein kinase R in pyroptosis.
abstract: Formation of the inflammasome, a scaffolding complex that activates caspase-1, is important in numerous diseases. Pyroptotic cell death induced by anthrax lethal toxin (LT) is a model for inflammasome-mediated caspase-1 activation. We discovered 7-desacetoxy-6,7-dehydrogedunin (7DG) in a phenotypic screen as a small molecule that protects macrophages from LT-induced death. Using chemical proteomics, we identified protein kinase R (PKR) as the target of 7DG and show that RNAi knockdown of PKR phenocopies treatment with 7DG. Further, we show that PKR's role in ASC assembly and caspase-1 activation induced by several different inflammasome stimuli is independent of PKR's kinase activity, demonstrating that PKR has a previously uncharacterized role in caspase-1 activation and pyroptosis that is distinct from its reported kinase-dependent roles in apoptosis and inflammasome formation in lipopolysaccharide-primed cells. Remarkably, PKR has different roles in two distinct cell death pathways and has a broad role in inflammasome function relevant in other diseases.
authors.affiliation: Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, USA. hett@molbio.mgh.harvard.edu
authors.forename: Erik C
authors.initials: EC
authors.lastname: Hett
authors.forename: Louise H
authors.initials: LH
authors.lastname: Slater
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Mark
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Kawate
authors.forename: Brian G
authors.initials: BG
authors.lastname: Monks
authors.forename: Andrea
authors.initials: A
authors.lastname: Stutz
authors.forename: Eicke
authors.initials: E
authors.lastname: Latz
authors.forename: Deborah T
authors.initials: DT
authors.lastname: Hung
mesh_terms: D000818:Animals; D001408:Bacillus anthracis / Q000201:enzymology; D020170:Caspase 1 / Q000378:metabolism; D020134:Catalytic Domain; D016923:Cell Death; D002460:Cell Line; D004797:Enzyme-Linked Immunosorbent Assay; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007249:Inflammation; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008954:Models, Biological; D010447:Peptide Hydrolases / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011487:Protein Conformation; D019892:eIF-2 Kinase / Q000737:chemistry*
chemical_list: D018841:HSP90 Heat-Shock Proteins; D019892:eIF-2 Kinase; D010447:Peptide Hydrolases; D020170:Caspase 1; D046988:Proteasome Endopeptidase Complex