title: PKCdelta-dependent deubiquitination and stabilization of Gadd45 in A431 cells overexposed to EGF.
abstract: Epidermal growth factor (EGF) receptor-overexpressing p53-deficient A431 cells response to toxic dose of EGF by G1 arrest and apoptosis was studied. We previously reported an increased expression of growth arrest and DNA-damage-inducible gene, Gadd45, in EGF-overexposed A431 cells. The mechanism for this induction was increased half-lives of mRNA and protein. In this study, using phorbol ester (a PKC activator) and specific inhibitors of PKC isoforms, we showed that protein kinase C-delta (PKCdelta) was involved in the increase of Gadd45 protein stability. We further demonstrated that Gadd45 is ubiquitinated and is regulated by proteolysis. While EGF induced ubiquitination of total cellular proteins, there was a decrease in Gadd45 ubiquitination, which could be inhibited by Rottlerin, a PKCdelta-specific inhibitor. These results suggest that an increase in Gadd45 stability may involve PKCdelta-dependent ubiquitin-proteasome pathway.
authors.affiliation: Bioactive Products Research Group, City University of Hong Kong, Kowloon, Hong Kong SAR, China.
authors.forename: C H
authors.initials: CH
authors.lastname: Leung
authors.forename: W
authors.initials: W
authors.lastname: Lam
authors.forename: W J
authors.initials: WJ
authors.lastname: Zhuang
authors.forename: N S
authors.initials: NS
authors.lastname: Wong
authors.forename: M S
authors.initials: MS
authors.lastname: Yang
authors.forename: W F
authors.initials: WF
authors.lastname: Fong
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D001578:Benzopyrans / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D004249:DNA Damage; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000502:physiology*; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007700:Kinetics; D007976:Leupeptins / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051745:Protein Kinase C-delta; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014452:Ubiquitins / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases; D000097642:GADD45 Proteins
chemical_list: D000098:Acetophenones; D001578:Benzopyrans; D003513:Cycloheximide; D004791:Enzyme Inhibitors; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D005419:Flavonoids; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D007976:Leupeptins; D020928:Mitogen-Activated Protein Kinases; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D011506:Proteins; D011725:Pyridines; D011994:Recombinant Proteins; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate; D014452:Ubiquitins; D048051:p38 Mitogen-Activated Protein Kinases; D000097642:GADD45 Proteins; C085746:rottlerin; C497258:PRKCD protein, human; C093642:SB 203580; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one