MEK kinase is involved in tumor necrosis factor alpha- induced NF-kappaB activation and degradation of IkappaB-alpha.
Signal-dependent activation of the transcription factor NF-kappaB is dominantly regulated by degradation of IkappaB-alpha protein. However, the signaling pathways that lead to the degradation are not clear. Here we report that mitogen-activated protein kinase/ extracellular signal-regulated kinase kinase ( MEK) kinase, an activator of stress-activated protein kinases/jun kinase-1 (SAPKs/ JNK1), is involved in such signaling pathways. The transient overexpression of MEK kinase in NIH3T3 fibroblasts activates kappaB-CAT reporter expression in a synergistic manner with TNFalpha stimulation. In contrast, overexpression of kinase-negative MEK kinase suppresses TNFalpha-induced reporter expression. The overexpression of MEK kinase suppresses the inhibitory activity of co-transfected IkappaB-alpha on the kappaB-CAT or human immunodeficiency virus-long terminal repeat-luciferase reporter expression and causes the simultaneous disappearance of the overexpressed IkappaB-alpha. The disappearance of exogenous IkappaB-alpha by the overexpression of MEK kinase is prevented by calpain inhibitor-I, an inhibitor of IkappaB-alpha degradation. These results suggest that MEK kinase is a signal mediator involved in TNFalpha- induced NF-kappaB activation and that the activation of NF-kappaB by MEK kinase is regulated through the degradation of IkappaB-alpha.[1]References
- MEK kinase is involved in tumor necrosis factor alpha-induced NF-kappaB activation and degradation of IkappaB-alpha. Hirano, M., Osada, S., Aoki, T., Hirai, S., Hosaka, M., Inoue, J., Ohno, S. J. Biol. Chem. (1996) [Pubmed]
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