Keap1 is a redox-regulated substrate adaptor protein for a Cul3-dependent ubiquitin ligase complex.

The bZIP transcription factor Nrf2 controls a genetic program that protects cells from oxidative damage and maintains cellular redox homeostasis. Keap1, a BTB-Kelch protein, is the major upstream regulator of Nrf2 and controls both the subcellular localization and steady-state levels of Nrf2. In this report, we demonstrate that Keap1 functions ...
as a substrate adaptor protein for a Cul3-dependent E3 ubiquitin ligase complex. Keap1 assembles into a functional E3 ubiquitin ligase complex with Cul3 and Rbx1 that targets multiple lysine residues located in the N-terminal Neh2 domain of Nrf2 for ubiquitin conjugation both in vivo and in vitro. Keap1-dependent ubiquitination of Nrf2 is inhibited following exposure of cells to quinone-induced oxidative stress and sulforaphane, a cancer-preventive isothiocyanate. A mutant Keap1 protein containing a single cysteine-to-serine substitution at residue 151 within the BTB domain of Keap1 is markedly resistant to inhibition by either quinone-induced oxidative stress or sulforaphane. Inhibition of Keap1-dependent ubiquitination of Nrf2 correlates with decreased association of Keap1 with Cul3. Neither quinone-induced oxidative stress nor sulforaphane disrupts association between Keap1 and Nrf2. Our results suggest that the ability of Keap1 to assemble into a functional E3 ubiquitin ligase complex is the critical determinant that controls steady-state levels of Nrf2 in response to cancer-preventive compounds and oxidative stress.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Amino Acid Sequence, Amino Acid Substitution, Animals, Anticarcinogenic Agents, Antioxidants, Breast Neoplasms, COS Cells, Cell Cycle Proteins, Cell Line, Tumor, Cercopithecus aethiops, Cullin Proteins, DNA-Binding Proteins, Genes, Reporter, Humans, Hydroquinones, Immunoblotting, Intracellular Signaling Peptides and Proteins, Luciferases, Lysine, NF-E2-Related Factor 2, Oxidation-Reduction, Oxidative Stress, Precipitin Tests, Protein Structure, Tertiary, Proteins, Serine, Substrate Specificity, Thiocyanates, Trans-Activators, Ubiquitin-Protein Ligases, Ubiquitins
Mol. Cell. Biol.
Date: Dec. 01, 2004
Download Curated Data For This Publication
106171
Switch View:
  • Interactions 5
  • PTM Genes 2