IkappaBalpha is essential for maintaining basal c-Jun N-terminal kinase (JNK) activation and regulating JNK-mediated resistance to tumor necrosis factor cytotoxicity in L929 cells.
Early activation of c-Jun N-terminal kinase (JNK) is believed to block apoptosis in response to death signals such as tumor necrosis factor (TNF). Brief exposure of murine L929 fibroblasts to anisomycin for 1 hr to activate JNK resulted in resistance to TNF killing. TNF rapidly induced cytoplasmic shrinkage in control cells, but not in the anisomycin-pretreated L929 cells. However, the induced TNF resistance was suppressed in the L929 cells which were engineered to stably inhibit IkappaBalpha protein expression by antisense mRNA ( approximately 80% reduction in protein expression). No constitutive NF-kappaB nuclear translocation and increased TNF resistance were found in these IkappaBalpha antisense cells. Notably, these cells had a significantly reduced basal level of JNK activation (50-70%), compared to vector control cells. Furthermore, brief exposure of L929 cells to wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3-kinase), resulted in resistance to TNF killing, probably due to preconsumption of caspases by wortmannin. Nonetheless, wortmannin-induced TNF resistance was suppressed in the IkappaBalpha antisense cells. Thus, these observations indicate that IkappaBalpha is essential for maintaining the basal level of JNK activation and regulating the JNK-induced TNF resistance.
Chang
N S
NS
Laboratory of Molecular Immunology, Guthrie Research Institute, 1 Guthrie Square, Sayre, Pennsylvania 18840, USA. nschang@inet.guthrie.org
D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001483:Base Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004351:Drug Resistance / Q000502:physiology; D004789:Enzyme Activation; D020672:I-kappa B Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D020928:Mitogen-Activated Protein Kinases; D000072000:NF-KappaB Inhibitor alpha; D016372:RNA, Antisense / Q000235:genetics; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D017931:DNA Primers; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; C000606205:Nfkbia protein, mouse; D016372:RNA, Antisense; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D000841:Anisomycin; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases