Keap1 regulates both cytoplasmic-nuclear shuttling and degradation of Nrf2 in response to electrophiles.
BACKGROUND
Transcription factor Nrf2 regulates the expression of a set of detoxifying and anti-oxidant enzyme genes. Several lines of evidence suggest that electrophiles and reactive oxygen species liberate Nrf2 from its cytoplasmic repressor Keap1 and provoke the accumulation of Nrf2 in the nucleus. To elucidate the molecular mechanisms as to how Nrf2 is activated by inducers, we examined the cytoplasmic-nuclear shuttling and turnover of Nrf2.


RESULTS
We found that Nrf2 is rapidly degraded through the proteasome pathway, while electrophiles cause Nrf2 nuclear translocation with concomitant stabilization. Crucial to the inducible accumulation of Nrf2 is the enfeebling of the Nrf2-Keap1 interaction by electrophiles. Exploiting mice which have the LacZ reporter gene knocked into the nrf2 locus, we revealed that the inducible accumulation of Nrf2 protein by electrophiles in macrophages and intestinal epithelia could be recapitulated by the Nrf2 N-terminal region in combination with a nuclear localization signal. We also found constitutive Nrf2 nuclear accumulation in Keap1-deficient mouse macrophages.


CONCLUSIONS
Our results highlight the fact that Nrf2 protein turnover is regulated by Keap1 mediated subcellular compartmentalization.
Itoh
Ken
K
Exploratory Research for Advanced Technology, Japan Science and Technology Corporation, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8577, Japan.
Wakabayashi
Nobunao
N
Katoh
Yasutake
Y
Ishii
Tetsuro
T
O'Connor
Tania
T
Yamamoto
Masayuki
M
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D015151:Immunoblotting; D007413:Intestinal Mucosa / Q000378:metabolism; D000072019:Kelch-Like ECH-Associated Protein 1; D008099:Liver / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D009097:Multienzyme Complexes / Q000378:metabolism; D051267:NF-E2-Related Factor 2; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D015534:Trans-Activators / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; C117301:Keap1 protein, mouse; D000072019:Kelch-Like ECH-Associated Protein 1; D009097:Multienzyme Complexes; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D012333:RNA, Messenger; D015534:Trans-Activators; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex