title: Rac GTPase instructs nuclear factor-kappaB activation by conveying the SCF complex and IkBalpha to the ruffling membranes.
abstract: Nuclear factor-kappaB (NF-kappaB) is a ubiquitously expressed transcription factor that plays a central role in directing a vast range of cellular functions. Its activation is controlled by the Rac GTPase and relies on the coordinated cooperation of the E3-ligase complex SCF(betaTrCP), composed by Skp-1/Cullin-1, Rbx/Roc1, and the beta-TrCP proteins. Recently, Cullin-1 has been reported to form a complex with the activated Rac GTPase. Here, we show that the specific activation of the Rac GTPase, besides directing its own positioning, induces the relocalization of the SCF component Cullin-1 to the ruffling membranes. This occurred only if the ruffles were stimulated by the Rac GTPase and was accompanied by the repositioning to the same intracellular compartment of the SCF protein Skp-1 and the ubiquitin-like molecule Nedd-8. The SCF substrate IkBalpha was also directed to the ruffling membranes in a Rac-dependent way. The novelty of these findings is in respect to the demonstration that the correct positioning at the ruffling membranes is crucial for the subsequent series of events that leads to IkBalpha proteasomal degradation and the resultant activation of NF-kappaB. Consequently, this points to the role of Rac as a docking molecule in NF-kappaB activation.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale U452, IFR50, Faculté de Médecine, 06107 Nice, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Boyer
authors.forename: Sara
authors.initials: S
authors.lastname: Travaglione
authors.forename: Loredana
authors.initials: L
authors.lastname: Falzano
authors.forename: Nils C
authors.initials: NC
authors.lastname: Gauthier
authors.forename: Michel R
authors.initials: MR
authors.lastname: Popoff
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Lemichez
authors.forename: Carla
authors.initials: C
authors.lastname: Fiorentini
authors.forename: Alessia
authors.initials: A
authors.lastname: Fabbri
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D044842:Cullin Proteins / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D044786:S-Phase Kinase-Associated Proteins / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D044844:beta-Transducin Repeat-Containing Proteins / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C100318:Cullin 1; D044842:Cullin Proteins; D020672:I-kappa B Proteins; D009097:Multienzyme Complexes; D016328:NF-kappa B; C430242:NUB1 protein, human; D044786:S-Phase Kinase-Associated Proteins; D014157:Transcription Factors; D044844:beta-Transducin Repeat-Containing Proteins; D044843:SKP Cullin F-Box Protein Ligases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D020744:rac GTP-Binding Proteins