Pervanadate-induced nuclear factor-κB activation requires tyrosine phosphorylation and degradation of IκBα -: Comparison with tumor necrosis factor-α

Tumor necrosis factor activates nuclear transcription factor kappa B (NF-kappa B) by inducing serine phosphorylation of the inhibitory subunit of NF-kappa B (I kappa B alpha), which leads to its ubiquitination and degradation. In contrast, per-vanadate (PV) activates NF-kappa B and induces tyrosine phosphorylation of I kappa B alpha (Singh, S., Darney, B. G., and Aggarwal, B. B. (1996) J. Biol. Chem. 271, 31049-31054; Imbert, V., Rupee, R. A., Antonia, L., Pahl, H. L., Traenckner, E. B.-M., Mueller-Dieckmann, C., Farahifar, D., Rossi, B., Auderger, P., Baeuerle, P. A., and Peyron, J.-F. (1996) Cell 86, 787-798). Whether PV also induces I kappa B alpha degradation and whether degradation is required for NF-kappa B activation are not understood. We investigated the effect of PV-induced tyrosine phosphorylation on I kappa B alpha degradation and NF-kappa B activation. PV activated NF-kappa B, as determined by DNA binding, NF-kappa B-dependent reporter gene expression, and phosphorylation and degradation of I kappa B alpha. Maximum degradation of I kappa B alpha occurred at 180 min, followed by NF-kappa B-dependent I kappa B alpha resynthesis. N-Acetylleucylleucylnorlucinal, a proteasome inhibitor, blocked both I kappa B alpha degradation and NF-kappa B activation, suggesting that the I kappa B alpha degradation is required for NF-kappa B activation. PV did not induce serine phosphorylation of I kappa B alpha but induced phosphorylation at tyrosine residue 42. Unlike tumor necrosis factor (TNF), PV did not induce ubiquitination of I kappa B alpha Like TNF, however, PV induced phosphorylation and degradation of I kappa B alpha, and subsequent NF-kappa B activation, which could be blocked by N-tosyl-L-phenylalanine chloromethyl ketone, calpeptin, and pyrrolidine dithiocarbomate, suggesting a close Link between PV-induced NF-kappa B activation and I kappa B alpha degradation. Overall, our studies demonstrate that PV activates NF-kappa B, which, unlike TNF, requires tyrosine phosphorylation of I kappa B alpha and its degradation.