title: c-Jun N-terminal protein kinase 1 (JNK1), but not JNK2, is essential for tumor necrosis factor alpha-induced c-Jun kinase activation and apoptosis.
abstract: Two ubiquitously expressed isoforms of c-Jun N-terminal protein kinase (JNK), JNK1 and JNK2, have shared functions and different functions. However, the molecular mechanism is unknown. Here we report that JNK1, but not JNK2, is essential for tumor necrosis factor alpha (TNF-alpha)-induced c-Jun kinase activation, c-Jun expression, and apoptosis. Using mouse fibroblasts deficient in either Jnk1 or Jnk2, we found that JNK1 was activated by TNF-alpha, whereas JNK2 activation was negligible. In addition, JNK2 interfered with JNK1 activation via its "futile" phosphorylation by upstream kinases. Consequently, expression and activation of c-Jun, which depends on JNK activity, were impaired in Jnk1 null cells but enhanced in Jnk2 null cells. TNF-alpha-induced apoptosis was also suppressed in Jnk1 null fibroblasts but increased in Jnk2 null cells. Thus, our results provide a molecular mechanism underlying the different biological functions of JNK isoforms.
authors.affiliation: Ben May Institute for Cancer Research, The University of Chicago, 5841 S. Maryland Ave., MC 60627, Chicago, IL 60637, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Minemoto
authors.forename: Anning
authors.initials: A
authors.lastname: Lin
mesh_terms: D000818:Animals; D017209:Apoptosis; D020169:Caspases / Q000032:analysis / Q000378:metabolism; D002457:Cell Extracts; D002461:Cell Line, Transformed; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D015151:Immunoblotting; D051379:Mice; D018345:Mice, Knockout; D048055:Mitogen-Activated Protein Kinase 8 / Q000235:genetics / Q000378:metabolism*; D048056:Mitogen-Activated Protein Kinase 9 / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D010766:Phosphorylation; D011233:Precipitin Tests; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D002457:Cell Extracts; D016755:Proto-Oncogene Proteins c-jun; D014409:Tumor Necrosis Factor-alpha; D005982:Glutathione Transferase; D048056:Mitogen-Activated Protein Kinase 9; D048055:Mitogen-Activated Protein Kinase 8; D020169:Caspases