Structural basis for defects of Keap1 activity provoked by its point mutations in lung cancer

Nrf2 regulates the cellular oxidative stress response, whereas Keap1 represses Nrf2 through its molecular interaction. To elucidate the molecular mechanism of the Keap1 and Nrf2 interaction, we resolved the six-bladed beta propeller crystal structure of the Kelch/DGR and CTR domains of mouse Keap1 and revealed that extensive inter- and intrablade hydrogen bonds maintain the structural integrity and proper association of Keap1 with Nrf2. A peptide containing the ETGE motif of Nrf2 binds the beta propeller of Keap1 at the entrance of the central cavity on the bottom side via electrostatic interactions with conserved arginine residues. We found a somatic mutation and a gene variation in human lung cancer cells that change glycine to cysteine in the DGR domain, introducing local conformational changes that reduce Keap1's affinity for Nrf2. These results provide a structural basis for the loss of Keap1 function and gain of Nrf2 function.     

Synthesis,molecular modeling and NAD(P)H:quinone oxidoreductase 1 inducer activity of novel 2-phenylquinazolin-4-amine derivatives

Reactive oxygen species (ROS) play an integral role in the pathogenesis of most diseases. This work presents the design and synthesis of novel 2-phenylquinazolin-4-amine derivatives (2–12) and evaluation of their NAD(P)H:quinone oxidoreductase 1 (NQO1) inducer activity in murine cells. Also, molecular docking of all the new compounds was performed to assess their ability to inhibit Keap1–Nrf2 protein–protein interaction through occupying the Keap1–Nrf2-binding domain which biologically leads to a consequent Nrf2 accumulation and enhanced gene expression of NQO1. Docking results showed that all compounds have the ability to interact with Keap1; however compound 7, the most active compound in this study, showed more interactions with key amino acids.     

miR-19通过Keap-Nrf2/HO-1信号通路对卵巢癌细胞增殖的影响

摘要 目的：研究卵巢癌组织和细胞中miR-19的表达,探讨其异常表达对卵巢癌细胞Kelch样环氧氯丙烷相关蛋白-1（Kelch-like epichlorohydrin-associated protein1,Keap1）--核因子E2相关因子2（nuclearfactor-E2-relatedfactor2,Nrf2） /血红素氧合酶-1（heme oxygenase1,HO-1）信号通路及卵巢癌细胞增殖的影响。方法：回顾性收集2019年1月至2020年12月于我院就诊的患者经病理切片诊断为卵巢癌上皮细胞的手术标本30例,卵巢良性肿瘤标本30例,正常卵巢组织标本30例。免疫组化检测不同标本中Keap1、Nrf2、HO-1的表达,检测卵巢组织及细胞中miR-19、Keap1、Nrf2、HO-1的mRNA表达水平,及卵巢癌细胞中Keap1、Nrf2、HO-1的蛋白表达水平。在OVCAR-3细胞中沉默miR-19后,Western Blot检测细胞内Keap1、Nrf2、HO-1蛋白表达水平,收集沉默miR-19,对照组,沉默Nrf2、对照组的OVCAR-3细胞,继续培养0 h、24 h、48 h后,检测细胞增殖和凋亡。结果：Keap1蛋白在卵巢癌组织中的阳性表达显著低于良性卵巢肿瘤组织及正常卵巢组织;Nrf2和HO-1蛋白在卵巢癌组织中的阳性表达显著低于良性卵巢肿瘤组织及正常卵巢组织（P＜0.05）;沉默miR-19抑制其表达后,细胞内Keap1 mRNA、蛋白表达水平明显升高,Nrf2、HO-1 mRNA表达水平无明显变化,蛋白表达水平明显降低（P＜0.05）;沉默miR-19 组、沉默Nrf2组与转染阴性对照组相比,增殖能力明显降低,凋亡能力明显升高（P＜0.05）。结论：卵巢癌细胞中,miR-19表达水平升高,可通过调控Keap1-Nrf2/HO-1信号通路影响卵巢癌细胞的增值、凋亡能力。     

Involvement of Nrf2 and Keap1 in the activation of antioxidant responsive element (ARE) by chemopreventive agent peptides from soft-shelled turtle

The antioxidant response element (ARE) is a cis-acting enhancer sequence located in the region containing genes related to antioxidant and detoxification. Under oxidative stress, the induction of nuclear factor-E2-related factor 2 (Nrf2)/ARE is considered as a fundamental process involved in defending reactive oxygen species (ROS) and providing protection against toxic xenobiotics. In this study, we obtained seven antioxidant peptides from soft-shelled turtle and concluded that Glu-Asp-Tyr-Gly-Ala (EDYGA) is the most potent ARE-luciferase inducer. To gain fundamental insights into the role of EDYGA in oxidative stress, we evaluated the effects of EDYGA on the Nrf2/Keap1 system in HepG₂ cells. The results revealed that EDYGA modulated the Nrf2/ARE pathway by enhancing Nrf2 level through the stabilization of Nrf2, which was accomplished by a decrease in the level of Keap1. These actions eventually led to an increase in nuclear Nrf2 accumulation and ARE-binding activity. Moreover, silencing Nrf2 markedly reduced ARE-driven activity induced by EDYGA. Docking results proved that glutamate residues of peptide EDYGA directly bind to Arg 415 of Kelch domain receptor pocke. The results were helpful in understanding the antioxidant activity of peptides from soft-shelled turtle which have potential to be used in foods and drugs as functional ingredients.     

Drug screening assay based on the interaction of intact Keap1 and Nrf2 proteins in cancer cells

Background

The Nrf2–Keap1 interaction is the major regulatory pathway for cytoprotective responses against oxidative and electrophilic stresses. Keap1, a substrate protein of a Cul3-dependent E3 ubiquitin ligase complex, is a negative regulator of Nrf2. The use of chemicals to regulate the interaction between Keap1 and Nrf2 has been proposed as a strategy for the chemoprevention of degenerative diseases and cancers.