title: Oncogene PKCε controls INrf2-Nrf2 interaction in normal and cancer cells through phosphorylation of INrf2.
abstract: The INrf2 (Keap1)-Nrf2 cell sensor complex has a crucial role in protection against chemical- and radiation-induced oxidative stress and cellular transformation. INrf2, in association with Cul3-Rbx1, ubiquitylates and degrades Nrf2. Exposure to stressors leads to stabilization of Nrf2 and the coordinated activation of cytoprotective proteins and cellular protection. However, the molecular signal(s) that regulate control of Nrf2 by INrf2 remain elusive. In this report, we demonstrate that phosphorylation of INrf2 at Ser599 and Ser602 by the oncoprotein PKCε is essential for INrf2-Nrf2 interaction, and the subsequent ubiquitylation and degradation of Nrf2. Inhibition of PKCε, knockdown of PKCε and the INrf2S602A mutant all failed to phosphorylate INrf2, leading to loss of the INrf2-Nrf2 interaction, Nrf2 degradation and enhanced cytoprotection and drug resistance. Molecular modeling analyses revealed that phosphorylation of S599 exposes the deeply buried S602 for phosphorylation and enhanced INrf2-Nrf2 interaction. Analysis of human lung and liver tumor protein arrays showed lower PKCε and higher Nrf2 levels, which presumably promoted cancer cell survival and drug resistance. In conclusion, phosphorylation of INrf2 by PKCε leads to regulation of Nrf2, with significant implications for the survival of cancer cells, which often express lower levels of PKCε.
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, 655 West Baltimore Street, Baltimore, MD 21201, USA.
authors.forename: Suryakant K
authors.initials: SK
authors.lastname: Niture
authors.forename: Averell
authors.initials: A
authors.lastname: Gnatt
authors.forename: Anil K
authors.initials: AK
authors.lastname: Jaiswal
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D061745:Antioxidant Response Elements; D000975:Antioxidants / Q000494:pharmacology; D002470:Cell Survival; D019008:Drug Resistance, Neoplasm; D005786:Gene Expression Regulation; D056945:Hep G2 Cells; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism*; D000072019:Kelch-Like ECH-Associated Protein 1; D051379:Mice; D008958:Models, Molecular; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D009857:Oncogenes; D010766:Phosphorylation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D051744:Protein Kinase C-epsilon / Q000502:physiology*; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D059748:Proteolysis; D015398:Signal Transduction
chemical_list: D000975:Antioxidants; D006873:Hydroquinones; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; C018855:2-tert-butylhydroquinone; C497255:PRKCE protein, human; D051744:Protein Kinase C-epsilon
keywords: Cell survival; INrf2 (Keap1); Lung cancer; Nrf2; PKCε