Oxidative stress sensor Keap1 functions as an adaptor for Cul3-based E3 ligase to regulate proteasomal degradation of Nrf2.
Transcription factor Nrf2 is a major regulator of genes encoding phase 2 detoxifying enzymes and antioxidant stress proteins in response to electrophilic agents and oxidative stress. In the absence of such stimuli, Nrf2 is inactive owing to its cytoplasmic retention by Keap1 and rapid degradation through the proteasome system. We examined the contribution of Keap1 to the rapid turnover of Nrf2 (half-life of less than 20 min) and found that a direct association between Keap1 and Nrf2 is required for Nrf2 degradation. In a series of domain function analyses of Keap1, we found that both the BTB and intervening-region (IVR) domains are crucial for Nrf2 degradation, implying that these two domains act to recruit ubiquitin-proteasome factors. Indeed, Cullin 3 (Cul3), a subunit of the E3 ligase complex, was found to interact specifically with Keap1 in vivo. Keap1 associates with the N-terminal region of Cul3 through the IVR domain and promotes the ubiquitination of Nrf2 in cooperation with the Cul3-Roc1 complex. These results thus provide solid evidence that Keap1 functions as an adaptor of Cul3-based E3 ligase. To our knowledge, Nrf2 and Keap1 are the first reported mammalian substrate and adaptor, respectively, of the Cul3-based E3 ligase system.
Center for Tsukuba Advanced Research Alliance, Institute of Basic Medical Sciences, and JST-ERATO Environmental Response Project, University of Tsukuba, Tsukuba 305-8575, Japan.
Akira
A
Kobayashi
Moon-Il
MI
Kang
Hiromi
H
Okawa
Makiko
M
Ohtsuji
Yukari
Y
Zenke
Tomoki
T
Chiba
Kazuhiko
K
Igarashi
Masayuki
M
Yamamoto
D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051856:Fanconi Anemia Complementation Group Proteins; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D000072019:Kelch-Like ECH-Associated Protein 1; D046911:Macromolecular Substances; D051379:Mice; D009097:Multienzyme Complexes / Q000378:metabolism*; D051267:NF-E2-Related Factor 2; D018384:Oxidative Stress; D046988:Proteasome Endopeptidase Complex; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
C102108:BACH1 protein, human; C486316:Bach1 protein, mouse; D050976:Basic-Leucine Zipper Transcription Factors; C503645:CUL3 protein, human; D018797:Cell Cycle Proteins; C503646:Cul3 protein, mouse; D044842:Cullin Proteins; D004268:DNA-Binding Proteins; D051856:Fanconi Anemia Complementation Group Proteins; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; C495636:Nfe2l2 protein, mouse; D011506:Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex