Harnessing E3 Ligases for Cancer Therapy

靶向蛋白质降解已经作为一种强大的药物发现范式出现，用于靶向不可用药 蛋白酶体降解的蛋白质。这项技术利用了被称为蛋白质降解靶向的双功能降解剂 嵌合体(PROTAC)，由连接到E3连接酶征募者的蛋白质靶向配体组成，泛素化和 蛋白酶体降解感兴趣的蛋白质。而靶向蛋白质降解可以潜在地用于靶向 对于任何细胞内蛋白质的降解，这种方法的一个主要挑战是缺乏E3连接酶 招聘人员。使用一种称为基于活性的蛋白质图谱(ABPP)的化学蛋白质组平台，该平台使用 基于反应性的化学探针用于描述蛋白质组范围的反应性、功能性和可配基的热点 最近发现抗癌天然产物尼姆博莱德，一种从印扎中分离出来的三萜类化合物 ...‘>与E3泛素连接酶RNF114的N端半胱氨酸(C8)以三价结合的形式发生反应. 阴性的乳腺癌细胞。我们的初步数据显示，宁波利特对RNF114的共价修饰 导致肿瘤抑制基因p21泛素化受损，其机制依赖于尼莫利特。 RNF114与底物的结合作用，从而为其抗癌作用提供了潜在的机制 这种天然产物。Nimbolide靶向RNF114内底物识别结构域的这一认识 提示宁波利特有可能作为RNF114用于PROTAC应用的一种新的招募剂。 与这一前提一致，我们已经证明了连接nimbolide和BRD4抑制剂JQ1的PROTAC，XH2 导致乳腺癌细胞中蛋白酶体依赖的BRD4降解。这种降解是RNF114- 依赖，如BRD4在RNF114野生型细胞中的降解，但在RNF114基因敲除细胞中不是。在这 建议，我们将结合化学蛋白质组学和靶向蛋白质降解平台来研究 RNF114调节剂在肿瘤中的治疗潜力及利用尼波利特等共价化合物 以RNF114的C8为目标的配体，作为PROTAC应用的招募人员。

Targeted protein degradation has arisen as a powerful drug discovery paradigm for targeting undruggable proteins for proteasomal degradation. This technology utilizes bifunctional degraders called proteolysis targeting chimeras (PROTACs) that consist of a protein-targeting ligand linked to an E3 ligase recruiter to ubiquitinate and proteasomally degrade proteins of interest. While targeted protein degradation can potentially be used to target any intracellular protein for degradation, a major challenge of this approach has been the dearth of E3 ligase recruiters. Using a chemoproteomic platform termed activity-based protein profiling (ABPP), which uses reactivity-based chemical probes to profile proteome-wide reactive, functional, and ligandable hotspots, we recently discovered that the anti-cancer natural product nimbolide, a triterpenoid isolated from Azadirachta indica or neem, covalently reacts with an N-terminal cysteine (C8) of the E3 ubiquitin ligase RNF114 in triple- negative breast cancer cells. Our preliminary data revealed that covalent modification of RNF114 by nimbolide leads to impaired ubiquitination of the tumor suppressor p21 through a nimbolide-dependent destabilization of the RNF114-substrate binding interaction, thus providing a potential mechanism for the anti-cancer effects of this natural product. This realization that nimbolide targeted a substrate recognition domain within RNF114 suggested that nimbolide could potentially be used as a novel recruiter for RNF114 for PROTAC applications. Consistent with this premise, we have shown that a PROTAC, XH2, linking nimbolide to a BRD4 inhibitor JQ1 led to proteasome-dependent degradation of BRD4 in breast cancer cells. This degradation was RNF114- dependent, as shown by BRD4 degradation in RNF114 wild-type cells, but not in RNF114 knockout cells. In this proposal, we will combine chemoproteomic and targeted protein degradation platforms to investigate the therapeutic potential of RNF114 modulators in cancer and exploit nimbolide and other covalent ligands targeting C8 of RNF114 as recruiters for PROTAC applications.