Novel Keap1-Nrf2 Inhibitors as Chemopreventive Agents

描述(由申请人提供)： 过去十年的研究表明，Keap1-Nrf2-抗氧化反应元件(ARE)系统在许多化学物质(如萝卜硫素、姜黄素和从水果、蔬菜和茶制品等天然来源中提取的表儿茶酚没食子酸酯)的癌症化学预防中发挥着关键作用。这些天然的亲电体，如异硫氰酸酯和Michael受体，对氧化还原“传感器”蛋白Keap1中发现的敏感半胱氨酸残基进行修饰，被认为是导致Keap1-Nrf2复合体解离和随后氧化应激反应酶上调的原因。为了解决人们对纯化的天然硫醇活性化合物作为化学预防药物的普遍使用的担忧，设计并筛选了专门用于抑制Keap1-Nrf2相互作用的新型短肽和有机小分子。这些抑制剂将模仿活性氧类和亲电体(如异硫氰酸酯和Michael受体)在诱导细胞保护酶中的作用，但可能会更具选择性和特异性。本文提出了两种基于结构的方法，从最近可用的Keap1Kelch结构域与Nrf2肽的三维X射线共晶体结构入手，发现新的选择性Keap1-Nrf2抑制剂：a)设计构象受限的环肽来模拟Nrf2与Keap1相互作用的发夹环；b)用于电子筛选能够与Keap1高亲和力结合的小分子的虚拟文库，从而阻止NRF2的结合。这些研究将提供关于Keap1和Nrf2之间蛋白质-蛋白质相互作用的重要信息和新的小分子抑制剂，并有助于开发更有效和更具选择性的Keap1-Nrf2抑制剂作为氧化应激反应酶的诱导剂。

DESCRIPTION (provided by applicant): Research over the last decade has demonstrated that Keap1-Nrf2-antioxidant response element (ARE) system plays a key role in cancer chemoprevention by many chemicals like sulforaphane, curcumin, and epigallo- catechol gallate derived from natural sources such as fruits, vegetables, and tea products. Modification, by these natural electrophiles such as isothiocyanates and Michael acceptors, of sensitive cysteine residues found in the redox "sensor" protein Keap1 is believed to be responsible for causing the dissociation of Keap1- Nrf2 complex and subsequent upregulation of oxidative stress response enzymes. To address concerns over the general use of purified natural thiol-reactive compounds as chemopreventive agents, novel short peptides and small organic molecules are designed and screened specifically for the inhibition of Keap1-Nrf2 interaction. These inhibitors will mimic the actions of reactive oxygen species and electrophiles like isothiocyanates and Michael acceptors in the induction of cytoprotective enzymes but will potentially be more selective and specific. Two structure-based approaches are proposed here to start from the recently available 3-D X-ray cocrystal structure of Keap1 Kelch domain with Nrf2 peptide to discover novel selective Keap1-Nrf2 inhibitors: a) to design conformationally restricted cyclic peptides to mimic the ¿-hairpin loop of Nrf2 that interacts with Keap1 and b) to use in silico screening of virtual libraries for small molecules that could bind to Keap1 with high affinity and thus prevent the binding of Nrf2. These studies will provide important information about, and novel small molecule inhibitors of, the protein-protein interaction between Keap1 and Nrf2, and facilitate the development of more potent and selective Keap1-Nrf2 inhibitors as inducers of oxidative stress response enzymes.