Redox-Regulated Pathway of Tyrosine Phosphorylation Underlies NF-κB Induction by an Atypical Pathway Independent of the 26S Proteasome

• Published in: Biomolecules (Basel, Switzerland) Vol. 5; no. 1; pp. 95 - 112
• Main Authors: Cullen, Sarah, Ponnappan, Subramaniam, Ponnappan, Usha
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI 09.02.2015; MDPI AG
• Subjects: Aclarubicin - analogs & derivatives; Aclarubicin - pharmacology; Animals; Cell Line; Enzyme Activation - drug effects; Humans; hypoxia/reoxygenation; I-kappa B Kinase - chemistry; I-kappa B Kinase - metabolism; IκBα; Mice; Mitogen-Activated Protein Kinase Kinases - antagonists & inhibitors; NF-kappa B - metabolism; NF-κB; Oxidation-Reduction - drug effects; oxidative stress; Oxidative Stress - drug effects; pervanadate; Phosphorylation - drug effects; phosphotyrosine; proteasome; Proteasome Endopeptidase Complex - metabolism; Proteasome Inhibitors - pharmacology; Protein Kinase Inhibitors - pharmacology; Protein Tyrosine Phosphatases - metabolism; Signal Transduction - drug effects; src-Family Kinases - antagonists & inhibitors; Tyrosine - metabolism; Vanadates - pharmacology
• ISSN: 2218-273X; 2218-273X
• DOI: 10.3390/biom5010095

Alternative redox stimuli such as pervanadate or hypoxia/reoxygenation, induce transcription factor NF-κB by phospho-tyrosine-dependent and proteasome-independent mechanisms. While considerable attention has been paid to the absence of proteasomal regulation of tyrosine phosphorylated IκBα, there is a paucity of information regarding proteasomal regulation of signaling events distinct from tyrosine phosphorylation of IκBα. To delineate roles for the ubiquitin-proteasome pathway in the phospho-tyrosine dependent mechanism of NF-κB induction, we employed the proteasome inhibitor, Aclacinomycin, and the phosphotyrosine phosphatase inhibitor, pervanadate (PV). Results from these studies demonstrate that phospho-IκBα (Tyr-42) is not subject to proteasomal degradation in a murine stromal epithelial cell line, confirming results previously reported. Correspondingly, proteasome inhibition had no discernable effect on the key signaling intermediaries, Src and ERK1/2, involved in the phospho-tyrosine mechanisms regulating PV-mediated activation of NF-κB. Consistent with previous reports, a significant redox imbalance leading to the activation of tyrosine kinases, as occurs with pervanadate, is required for the induction of NF-κB. Strikingly, our studies demonstrate that proteasome inhibition can potentiate oxidative stress associated with PV-stimulation without impacting kinase activation, however, other cellular implications for this increase in intracellular oxidation remain to be fully delineated.