Tyrosine nitration of IkappaBalpha: a novel mechanism for NF-kappaB activation.
The NF-kappaB family of transcription factors is an important component of stress-activated cytoprotective signal transduction pathways. Previous studies demonstrated that some activation mechanisms require phosphorylation, ubiquitination, and degradation of the inhibitor protein, IkappaBalpha. Herein, it is demonstrated that ionizing radiation in the therapeutic dose range stimulates NF-kappaB activity by a mechanism in which IkappaBalpha tyrosine 181 is nitrated as a consequence of constitutive NO* synthase activation, leading to dissociation of intact IkappaBalpha from NF-kappaB. This mechanism does not appear to require IkappaBalpha kinase-dependent phosphorylation or proteolytic degradation of IkappaBalpha. Tyrosine 181 is involved in several noncovalent interactions with the p50 subunit of NF-kappaB stabilizing the IkappaBalpha-NF-kappaB complex. Evaluation of hydropathic interactions of the IkappaBalpha-p50 complex on the basis of the crystal structure of the complex is consistent with nitration disrupting these interactions and dissociating the IkappaBalpha-NF-kappaB complex. Tyrosine nitration is not commonly studied in the context of signal transduction. However, these results indicate that tyrosine nitration is an important post-translational regulatory modification for NF-kappaB activation and possibly for other signaling molecules modulated by mild and transient oxidative and nitrosative stresses.
Yakovlev
Vasily A
VA
Department of Radiation Oncology, Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
Barani
Igor J
IJ
Rabender
Christopher S
CS
Black
Stephen M
SM
Leach
J Kevin
JK
Graves
Paul R
PR
Kellogg
Glen E
GE
Mikkelsen
Ross B
RB
D000818:Animals; D001943:Breast Neoplasms / Q000473:pathology; D016466:CHO Cells; D045744:Cell Line, Tumor; D006224:Cricetinae; D003412:Cricetulus; D004307:Dose-Response Relationship, Radiation; D005260:Female; D017930:Genes, Reporter; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism*; D007700:Kinetics; D008156:Luciferases / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors / Q000235:genetics; D009584:Nitrogen / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D016877:Oxidants / Q000494:pharmacology; D030421:Peroxynitrous Acid / Q000494:pharmacology; D011499:Protein Processing, Post-Translational; D011789:Quantum Theory; D034741:RNA, Small Interfering / Q000378:metabolism; D011839:Radiation, Ionizing; D014162:Transfection; D014443:Tyrosine / Q000031:analogs & derivatives / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D016877:Oxidants; D034741:RNA, Small Interfering; D000072000:NF-KappaB Inhibitor alpha; D030421:Peroxynitrous Acid; C002744:3-nitrotyrosine; D014443:Tyrosine; D008156:Luciferases; C496320:NOS1 protein, human; D052248:Nitric Oxide Synthase Type I; D009584:Nitrogen