title: p38alpha- and DYRK1A-dependent phosphorylation of caspase-9 at an inhibitory site in response to hyperosmotic stress.
abstract: The cysteine aspartyl protease caspase-9 is a critical component of the intrinsic apoptotic pathway. Activation of caspase-9 is inhibited by phosphorylation at Thr125, which is catalysed by the mitogen-activated protein kinases (MAPKs) ERK1/2 in response to growth factors, by the cyclin-dependent protein kinase CDK1-cyclin B1 during mitosis, and at a basal level by the dual-specificity tyrosine-phosphorylation regulated protein kinase DYRK1A. Here we show that inhibitory phosphorylation of caspase-9 at Thr125 is induced in mammalian cells by hyperosmotic stress. This response does not require ERK1/2 or ERK5, but it is diminished by ablation of DYRK1A expression by siRNA or chemical inhibition of DYRK1A by harmine. Phosphorylation of Thr125 in response to hyperosmotic stress is also reduced by chemical inhibition of p38 MAPK and is abolished in p38 alpha(-/-) mouse embryonic fibroblasts. These results show that both DYRK1A and p38 alpha play roles in the inhibitory phosphorylation of caspase-9 following hyperosmotic stress and suggest a functional interaction between these protein kinases. Phosphorylation of caspase-9 at Thr125 may restrain apoptosis during the acute response to hyperosmotic stress.
authors: Biomedical Research Institute, School of Medicine, College of Medicine, Dentistry and Nursing, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, UK.
authors: Anne
authors: A
authors: Seifert
authors: Paul R
authors: PR
authors: Clarke
mesh_terms: D000818:Animals; D017209:Apoptosis; D053453:Caspase 9 / Q000378:metabolism*; D061945:Caspase Inhibitors; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D006247:Harmine / Q000494:pharmacology; D051379:Mice; D048308:Mitogen-Activated Protein Kinase 14 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D009997:Osmotic Pressure; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D000097603:Dyrk Kinases
chemical_list: D053453:Caspase 9; D061945:Caspase Inhibitors; D048049:Extracellular Signal-Regulated MAP Kinases; D006247:Harmine; D048308:Mitogen-Activated Protein Kinase 14; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D034741:RNA, Small Interfering; D000097603:Dyrk Kinases