Oxidative and electophilic stresses activate Nrf2 through inhibition of ubiquitination activity if Keap1
Oxidative and electophilic stresses activate Nrf2 through inhibition of ubiquitination activity if Keap1
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DOI：
10.1128/mcb.26.1.221-229.2006
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发表时间：
2006-01-01
影响因子：
5.3
通讯作者：
Yamamoto, M
中科院分区：
文献类型：
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作者：
Kobayashi, A;Kang, MI;Yamamoto, M
Keap1-Nrf2系统是细胞保护基因表达的主要调控途径，可抵抗氧化和/或亲电应激。Keap1在该系统中作为压力感受器蛋白。当Keap1在非应激条件下结构性地抑制Nrf2活性时，氧化剂或亲电剂会引起Keap1活性的抑制，从而诱导Nrf2的激活。然而，在压力存在的情况下，Nrf2从Keap1抑制中解放出来的确切分子机制仍有待阐明。我们假设氧化和亲电应激通过影响Keap1介导的Nrf2的快速周转而诱导Nrf2的核积累，因为这种积累被蛋白质合成抑制剂放线菌亚胺抑制。虽然Keap1的Cys273和Cys288残基都是抑制Nrf2核聚集所必需的，但用亲电体处理细胞或将这些半胱氨酸残基突变为丙氨酸并不影响Keap1与Nrf2在体内或体外的结合。相反，这些治疗削弱了Keap1介导的Nrf2蛋白酶体降解。这些结果支持这样一种观点，即应激后合成的从头合成的Nrf2蛋白通过绕过Keap1门积累在细胞核中，氧化和亲电应激的感觉机制与Nrf2的降解机制密切相关。
The Keap1-Nrf2 system is the major regulatory pathway of cytoprotective gene expression against oxidative and/or electrophilic stresses. Keap1 acts as a stress sensor protein in this system. While Keap1 constitutively suppresses Nrf2 activity under unstressed conditions, oxidants or electrophiles provoke the repression of Keap1 activity, inducing the Nrf2 activation. However, the precise molecular mechanisms behind the liberation of Nrf2 from Keap1 repression in the presence of stress remain to be elucidated. We hypothesized that oxidative and electrophilic stresses induce the nuclear accumulation of Nrf2 by affecting the Keap1-mediated rapid turnover of Nrf2, since such accumulation was diminished by the protein synthesis inhibitor cycloheximide. While both the Cys273 and Cys288 residues of Keap1 are required for suppressing Nrf2 nuclear accumulation, treatment of cells with electrophiles or mutation of these cysteine residues to alanine did not affect the association of Keap1 with Nrf2 either in vivo or in vitro. Rather, these treatments impaired the Keap1-mediated proteasomal degradation of Nrf2. These results support the contention that Nrf2 protein synthesized de novo after exposure to stress accumulates in the nucleus by bypassing the Keap1 gate and that the sensory mechanism of oxidative and electrophilic stresses is closely linked to the degradation mechanism of Nrf2.