title: Heterologous SUMO-2/3-ubiquitin chains optimize IκBα degradation and NF-κB activity.
abstract: The NF-κB pathway is regulated by SUMOylation at least at three levels: the inhibitory molecule IκBα, the IKK subunit γ/NEMO and the p52 precursor p100. Here we investigate the role of SUMO-2/3 in the degradation of IκBα and activation of NF-κB mediated by TNFα. We found that under conditions of deficient SUMOylation, an important delay in both TNFα-mediated proteolysis of IκBα and NF-κB dependent transcription occurs. In vitro and ex vivo approaches, including the use of ubiquitin-traps (TUBEs), revealed the formation of chains on IκBα containing SUMO-2/3 and ubiquitin after TNFα stimulation. The integration of SUMO-2/3 appears to promote the formation of ubiquitin chains on IκBα after activation of the TNFα signalling pathway. Furthermore, heterologous chains of SUMO-2/3 and ubiquitin promote a more efficient degradation of IκBα by the 26S proteasome in vitro compared to chains of either SUMO-2/3 or ubiquitin alone. Consistently, Ubc9 silencing reduced the capture of IκBα modified with SUMO-ubiquitin hybrid chains that display a defective proteasome-mediated degradation. Thus, hybrid SUMO-2/3-ubiquitin chains increase the susceptibility of modified IκBα to the action of 26S proteasome, contributing to the optimal control of NF-κB activity after TNFα-stimulation.
authors.affiliation: Proteomics Unit, CIC bioGUNE, CIBERehd, Derio, Bizkaia, Spain.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Aillet
authors.forename: Fernando
authors.initials: F
authors.lastname: Lopitz-Otsoa
authors.forename: Isabel
authors.initials: I
authors.lastname: Egaña
authors.forename: Roland
authors.initials: R
authors.lastname: Hjerpe
authors.forename: Paul
authors.initials: P
authors.lastname: Fraser
authors.forename: Ron T
authors.initials: RT
authors.lastname: Hay
authors.forename: Manuel S
authors.initials: MS
authors.lastname: Rodriguez
authors.forename: Valérie
authors.initials: V
authors.lastname: Lang
mesh_terms: D003593:Cytoplasm / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D059748:Proteolysis; D015398:Signal Transduction / Q000187:drug effects; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism*; D058207:Sumoylation; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D025801:Ubiquitin / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism*; D014452:Ubiquitins / Q000378:metabolism*; D000098843:Ubiquitin-Conjugating Enzyme UBC9
chemical_list: D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C117909:SUMO2 protein, human; C492189:SUMO3 protein, human; D025841:Small Ubiquitin-Related Modifier Proteins; D014409:Tumor Necrosis Factor-alpha; D025801:Ubiquitin; D014452:Ubiquitins; D000072000:NF-KappaB Inhibitor alpha; D044763:Ubiquitin-Conjugating Enzymes; D046988:Proteasome Endopeptidase Complex; D000098843:Ubiquitin-Conjugating Enzyme UBC9