H-Ras-specific activation of NF-κB protects NIH 3T3 cells against stimulus-dependent apoptosis

Abstract

Ras signaling involves the activation of several downstream pathways that exhibit isoform specificity. In this study, the basal and tumor necrosis factor α (TNFα)-induced activation of NF-κB has been examined in cells overexpressing H-Ras, K-Ras or N-Ras. Cells expressing H-Ras exhibited a basal κB activity that correlated with sustained IκB kinase activation and lower steady-state levels of IκBα in the cytosol. Upon activation with TNFα, the cells expressing the distinct Ras isoforms behaved similarly in terms of binding of nuclear proteins to a κB sequence and induction of a κB-dependent reporter gene. The basal activation of NF-κB in cells expressing H-Ras impaired staurosporine-induced apoptosis in these cells, through a mechanism that was NF-κB-dependent and inhibitable in the presence of z-VAD. Moreover, titration of caspase activation in response to staurosporine showed a significant resistance in cells expressing H-Ras when compared with the void vector or the N-Ras counterparts. These results indicate that the distinct Ras proteins have specific effects on the NF-κB pathway and that this action contributes to protect cells against apoptosis.