Inhibierung von HECT-Ligasen zur Krebstherapie

泛素化酶调节无数的生理和疾病相关过程，并已成为药物发现领域的强大靶点。泛素连接酶(E3酶)是特别有趣的治疗干预点。E3家族在人类蛋白质组中估计有1000个成员，是泛素化酶类中最多样化的，它介导底物的募集进行修饰，从而在泛素信号转导中提供关键的特异性决定因素。Hect-type E3酶包含一个明确的催化中心，历史上一直被认为是“可用药的”。然而，令人惊讶的是，针对Hect E3酶的小分子发现工作几乎没有报道，尽管这些酶在人类发病机制中发挥关键作用，包括各种类型的癌症。在研究小组Martin Eilers的第一个资助期，Nikita Popov和他的同事发现，Hect E3酶HUWE1的下调为结直肠癌提供了一个治疗窗口。这项工作还导致了通过高通量筛选识别特定的小分子抑制剂。有趣的是，已鉴定的化合物被发现可以阻断结直肠癌细胞中依赖于MYC的转录激活，但在干细胞和正常结肠上皮细胞中却没有。这些选择性作用可能是由于HUWE1的一种特定底物--转录因子MIZ1的稳定，它可以与MYC形成抑制性复合体。在这些原则证明结果的基础上，我们的目标是揭示已确定的抑制剂的分子基础，利用这一知识开发优化的化合物，并对它们进行体内分析。这些研究将与系统地询问HUWE1在动态平衡和肿瘤维持中的确切作用--这是利用这种连接酶的活性进行治疗的重要前提。为了完成这项研究计划，我们将捆绑我们的结构(Sonja Lorenz)、药物化学(Stefan Laufer)和细胞生物学(Nikita Popov)的专业知识。与研究组其他成员的互动将产生额外的协同效应，特别是Martin Eilers(MYC介导的转录调控中HUWE1的生物学)、Lars Zender(马赛克小鼠模型)、Armin Wiegering(患者衍生的有机化合物)、Antti Poso(对接)和Andreas Rosenwald(组织病理学服务)。因此，我们处于一个很好的位置来定义HUWE1在癌症治疗中呈现的治疗窗口，从而为Hect E3酶在体内对特定小分子抑制的可及性提供了前所未有的证据。

Ubiquitination enzymes regulate countless physiological and disease-associated processes and have emerged as powerful targets on the drug discovery arena. Ubiquitin ligases (E3 enzymes) are particularly interesting points of therapeutic intervention. With an estimated 1000 members in the human proteome, the E3 family is the most diversified among the different classes of ubiquitination enzymes and mediates the recruitment of substrates for modification, thus providing key specificity determinants in ubiquitin signaling. HECT-type E3 enzymes contain a defined catalytic center and have historically been expected to be ‘druggable’. Surprisingly, however, few small-molecule discovery efforts targeting HECT E3 enzymes have been reported, despite crucial roles of these enzymes in human pathogeneses, including various types of cancer.During the first funding period of the Research Group Martin Eilers, Nikita Popov, and colleagues discovered that downregulation of the HECT E3 enzyme HUWE1 presents a therapeutic window in colorectal carcinoma. This work has also led to the identification of specific small-molecule inhibitors by high-throughput screening. Intriguingly, the identified compounds were found to block MYC-dependent transcriptional activation in colorectal cancer cells, but not in stem and normal colon epithelial cells. These selective effects could be pinpointed to the stabilization of a particular substrate of HUWE1, the transcription factor MIZ1, that can form repressive complexes with MYC. Building on these proof-of-principle results, we aim to uncover the molecular basis of the identified inhibitors, utilize this knowledge for the development of optimized compounds, and subject them to in vivo analyses. These studies will go hand-in-hand with a systematic interrogation of the precise roles of HUWE1 during homeostasis and tumor maintenance – a vital prerequisite for exploiting the activity of this ligase therapeutically. To accomplish this research plan we will bundle our structural (Sonja Lorenz), medicinal-chemical (Stefan Laufer), and cell biological (Nikita Popov) expertise. Additional synergies will arise from interactions with other members of the Research Group, particularly Martin Eilers (biology of HUWE1 in MYC-mediated transcriptional regulation), Lars Zender (mosaic mouse models), Armin Wiegering (patient-derived organoids), Antti Poso (docking), and Andreas Rosenwald (histopathology service). We are therefore in an excellent position to define the therapeutic window that HUWE1 presents in cancer therapy, thereby providing unprecedented evidence for the accessibility of HECT E3 enzymes to specific small-molecule inhibition in vivo.