Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
Cell Death Differ. 2011 Mar;18(3):439-51. doi: 10.1038/cdd.2010.114. Epub 2010 Sep 24.
Cytosolic inhibitor of Nrf2 (INrf2) is an adaptor protein that mediates ubiquitination/degradation of NF-E2-related factor 2 (Nrf2), a master regulator of cytoprotective gene expression. In this paper, we demonstrate that INrf2 degrades endogenous antiapoptotic B-cell CLL/lymphoma 2 (Bcl-2) protein and controls cellular apoptosis. The DGR domain of INrf2 interacts with the BH2 domain of Bcl-2 and facilitates INrf2:Cul3-Rbx1-mediated ubiquitination of Bcl-2 by the conjugation of ubiquitin molecules to lysine17 of Bcl-2. Further studies showed that INrf2 enhanced etoposide-mediated accumulation of Bax, increased release of cytochrome c from mitochondria, activated caspase-3/7, and enhanced DNA fragmentation and apoptosis. Antioxidants antagonized Bcl-2:INrf2 interaction, led to the release and stabilization of Bcl-2, increased Bcl-2:Bax heterodimers and reduced apoptosis. Moreover, dysfunctional/mutant INrf2 in human lung cancer cells failed to degrade Bcl-2, resulting in decreased etoposide and UV/γ radiation-mediated DNA fragmentation. These data provide the first evidence of INrf2 control of Bcl-2 and apoptotic cell death, with implications in antioxidant protection, survival of cancer cells containing dysfunctional INrf2, and drug resistance.
细胞质 Nrf2 抑制剂（INrf2）是一种衔接蛋白，可介导 NF-E2 相关因子 2（Nrf2）的泛素化/降解，Nrf2 是细胞保护基因表达的主要调节因子。在本文中，我们证明 INrf2 降解内源性抗凋亡 B 细胞 CLL/淋巴瘤 2（Bcl-2）蛋白并控制细胞凋亡。INrf2 的 DGR 结构域与 Bcl-2 的 BH2 结构域相互作用，并通过将泛素分子连接到 Bcl-2 的赖氨酸 17 上，促进 INrf2：Cul3-Rbx1 介导的 Bcl-2 泛素化。进一步的研究表明，INrf2 增强依托泊苷诱导的 Bax 积累，增加线粒体细胞色素 c 的释放，激活 caspase-3/7，并增强 DNA 片段化和细胞凋亡。抗氧化剂拮抗 Bcl-2：INrf2 相互作用，导致 Bcl-2 的释放和稳定，增加 Bcl-2：Bax 异二聚体并减少细胞凋亡。此外，人类肺癌细胞中功能失调/突变的 INrf2 无法降解 Bcl-2，导致依托泊苷和 UV/γ 辐射介导的 DNA 片段化减少。这些数据首次提供了 INrf2 控制 Bcl-2 和细胞凋亡死亡的证据，这与抗氧化保护、含有功能失调 INrf2 的癌细胞的存活以及耐药性有关。
