The p65/RelA Subunit of NF-κB Suppresses the Sustained, Antiapoptotic Activity of Jun Kinase Induced by Tumor Necrosis Factor

Abstract

ABSTRACT Tumor necrosis factor (TNF) signaling through the TNF receptors involves the recruitment of key signaling factors, leading to the activation of both the transcription factor NF-κB and the stress-activated Jun kinase (JNK). In most cells, TNF signaling leads to a rapid and transient increase in JNK activity. However, we show that TNF treatment leads to the sustained activation of JNK in cells that are null for the p65/RelA subunit of NF-κB as well as in cells expressing the super-repressor form of IκB. In addition, the data indicate that the ability of p65/RelA to regulate gene expression is required to suppress the persistent activation of JNK. Interestingly, this suppression occurs upstream of JNK, within the signal transduction cascade leading to JNK activation, without affecting the stress-activated kinase p38. Since NF-κB has previously been shown to be involved in the suppression of TNF-induced apoptosis, we were interested in determining the role of deregulated JNK activity, induced by the loss of NF-κB, in controlling the cell death response. Through the use of different approaches for inhibition of JNK, we show that the suppression of JNK activity in cells that lack active NF-κB enhances the apoptotic response to TNF. These data suggest that the activity of JNK in cells blocked for NF-κB function provides an antiapoptotic signal and explains, at least partly, why a significant number of NF-κB null cells remain viable following TNF treatment.