title: Direct activation of mitochondrial apoptosis machinery by c-Jun N-terminal kinase in adult cardiac myocytes.
abstract: Although oxidative stress causes activation of c-Jun N-terminal kinase (JNK) and apoptosis in many cell types, how the JNK pathway is connected to the apoptosis pathway is unclear. The molecular mechanism of JNK-mediated apoptosis was investigated in adult rat cardiac myocytes in culture as a model system that is sensitive to oxidative stress. Oxidative stress caused JNK activation, cytochrome c release, and apoptosis without new protein synthesis. Oxidative stress-induced apoptosis was abrogated by dominant negative stress-activated protein kinase/extracellular signal-regulated kinase kinase-1 (SEK1)-mediated inhibition of the JNK pathway, whereas activation of the JNK pathway by constitutively active SEK1 was sufficient to cause apoptosis. Inhibition of caspase-9, an apical caspase in the mitochondrial apoptosis pathway, suppressed oxidative stress-induced apoptosis, whereas inhibition of caspase-8 had no effect, indicating that both the JNK pathway and the mitochondrial apoptosis machinery are central to oxidative stress-induced apoptosis. Both JNK and SEK1 localized on mitochondria where JNK was activated by oxidative stress. Furthermore, active JNK caused the release of apoptogenic factors such as cytochrome c from isolated mitochondria in a cell-free assay. These findings indicate that the JNK pathway is a direct activator of mitochondrial death machinery without other cellular components and provide a molecular linkage from oxidative stress to the mitochondrial apoptosis machinery.
authors.affiliation: Department of Molecular Cardiovascular Biology, Yamaguchi University School of Medicine, Minami Kogushi, Ube, Yamaguchi 755-8505, Japan. haoki@po.cc.yamaguchi-u.ac.jp
authors.forename: Hiroki
authors.initials: H
authors.lastname: Aoki
authors.forename: Peter M
authors.initials: PM
authors.lastname: Kang
authors.forename: James
authors.initials: J
authors.lastname: Hampe
authors.forename: Koichi
authors.initials: K
authors.lastname: Yoshimura
authors.forename: Takafumi
authors.initials: T
authors.lastname: Noma
authors.forename: Masunori
authors.initials: M
authors.lastname: Matsuzaki
authors.forename: Seigo
authors.initials: S
authors.lastname: Izumo
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D002474:Cell-Free System; D002478:Cells, Cultured; D003574:Cytochrome c Group / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation; D006861:Hydrogen Peroxide / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D048031:JNK Mitogen-Activated Protein Kinases; D020935:MAP Kinase Signaling System; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008928:Mitochondria / Q000378:metabolism*; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D018384:Oxidative Stress; D010766:Phosphorylation; D011485:Protein Binding; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors
chemical_list: D003574:Cytochrome c Group; D011994:Recombinant Proteins; D006861:Hydrogen Peroxide; D048031:JNK Mitogen-Activated Protein Kinases; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; C505528:Casp8 protein, rat; C506435:Casp9 protein, rat; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases