title: Changes in the ratio of free NEDD8 to ubiquitin triggers NEDDylation by ubiquitin enzymes.
abstract: Ubiquitin and UBL (ubiquitin-like) modifiers are small proteins that covalently modify other proteins to alter their properties or behaviours. Ubiquitin modification (ubiquitylation) targets many substrates, often leading to their proteasomal degradation. NEDD8 (neural-precursor-cell-expressed developmentally down-regulated 8) is the UBL most closely related to ubiquitin, and its best-studied role is the activation of CRLs (cullin-RING ubiquitin ligases) by its conjugation to a conserved C-terminal lysine residue on cullin proteins. The attachment of UBLs requires three UBL-specific enzymes, termed E1, E2 and E3, which are usually well insulated from parallel UBL pathways. In the present study, we report a new mode of NEDD8 conjugation (NEDDylation) whereby the UBL NEDD8 is linked to proteins by ubiquitin enzymes in vivo. We found that this atypical NEDDylation is independent of classical NEDD8 enzymes, conserved from yeast to mammals, and triggered by an increase in the NEDD8 to ubiquitin ratio. In cells, NEDD8 overexpression leads to this type of NEDDylation by increasing the concentration of NEDD8, whereas proteasome inhibition has the same effect by depleting free ubiquitin. We show that bortezomib, a proteasome inhibitor used in cancer therapy, triggers atypical NEDDylation in tissue culture, which suggests that a similar process may occur in patients receiving this treatment.
authors: Scottish Institute for Cell Signalling, Protein Ubiquitylation Unit, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, UK.
authors: Roland
authors: R
authors: Hjerpe
authors: Yann
authors: Y
authors: Thomas
authors: Jesse
authors: J
authors: Chen
authors: Aleksandra
authors: A
authors: Zemla
authors: Siobhan
authors: S
authors: Curran
authors: Natalia
authors: N
authors: Shpiro
authors: Lawrence R
authors: LR
authors: Dick
authors: Thimo
authors: T
authors: Kurz
mesh_terms: D000818:Animals; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D004791:Enzyme Inhibitors / Q000494:pharmacology; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D000075687:NEDD8 Protein; D011719:Pyrazines / Q000494:pharmacology; D014162:Transfection; D025801:Ubiquitin / Q000032:analysis / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D014452:Ubiquitins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*
chemical_list: D001897:Boronic Acids; D004791:Enzyme Inhibitors; D000075687:NEDD8 Protein; C082860:NEDD8 protein, human; D011719:Pyrazines; D025801:Ubiquitin; D014452:Ubiquitins; D000069286:Bortezomib; D044767:Ubiquitin-Protein Ligases