title: Biochemical and cellular effects of inhibiting Nedd8 conjugation.
abstract: The conjugation of proteins with the ubiquitin-like protein Nedd8 is an essential cellular process and an important anti-cancer therapeutic target. The major known role of Nedd8 is the attachment to and activation of Cullin RING E3 ubiquitin ligases (CRL). The attachment of Nedd8 to its substrates occurs via a process analogous to ubiquitin transfer, involving a Nedd8 E1 activating enzyme and a Nedd8 E2 conjugating enzyme, Ubc12, which transfers Nedd8 onto lysine residues of target proteins. In this study, we utilize dominant-negative Ubc12 (dnUbc12) and the Nedd8 E1 inhibitor MLN4924 to inhibit cellular neddylation. We demonstrate that dnUbc12 functions by depleting cellular Nedd8 concentrations. Inhibition of cellular neddylation leads to rapid accumulation of CRL substrates and an enlarged and flattened morphology in HEK293 cells. Inhibiting Nedd8 conjugation also causes abnormalities in the actin cytoskeleton. This is likely at least partially mediated via accumulation of the small GTPase RhoA, a recently identified CRL substrate. We indeed found that siRNA mediated knockdown of RhoA can reverse the morphological changes observed upon inhibition of cellular neddylation. In conclusion, the Nedd8 pathway plays an important role in regulating the actin cytoskeleton and cellular morphology. Dysfunction of the actin cytoskeleton may contribute to the anti-cancer effect of Nedd8 inhibition.
authors.affiliation: Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Yee Chin
authors.initials: YC
authors.lastname: Leck
authors.forename: Yin Yin
authors.initials: YY
authors.lastname: Choo
authors.forename: Chia Yee
authors.initials: CY
authors.lastname: Tan
authors.forename: Peter G
authors.initials: PG
authors.lastname: Smith
authors.forename: Thilo
authors.initials: T
authors.lastname: Hagen
mesh_terms: D000199:Actins / Q000378:metabolism*; D002460:Cell Line; D044842:Cullin Proteins / Q000378:metabolism; D003517:Cyclopentanes / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D000075687:NEDD8 Protein; D011743:Pyrimidines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism*; D014452:Ubiquitins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D044842:Cullin Proteins; D003517:Cyclopentanes; D000075687:NEDD8 Protein; C082860:NEDD8 protein, human; D011743:Pyrimidines; D034741:RNA, Small Interfering; D014452:Ubiquitins; D044763:Ubiquitin-Conjugating Enzymes; D020742:rhoA GTP-Binding Protein; C539933:pevonedistat