The Fbw7 ubiquitin ligase network: normal and neoplastic functions

Fbw7 泛素连接酶网络：正常和肿瘤功能

• 批准号: 10639893
• 负责人: Bruce E Clurman
• 金额: $ 46.3万
• 依托单位: FRED HUTCHINSON CANCER CENTER
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-06-01 至 2028-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10639893
• 关键词: Ablation; Apoptosis; Area; Binding; CCNE1 gene; Cancer Biology; Cell Proliferation; Cell physiology; Cells; Development; Dimerization; Engineering; Exhibits; Genetic Transcription; Genomic approach; Glycogen Synthase Kinase 3; Goals; Heterozygote; Human; Knock-in; Malignant Neoplasms; Metabolism; Missense Mutation; Modeling; Mus; Mutation; Normal Cell; Oncogenic; Oncoproteins; Pathway interactions; Phosphoric Monoester Hydrolases; Phosphorylation; Phosphorylation Site; Phosphotransferases; Physiological; Proliferating; Proteins; Regulation; Research; Role; Signal Pathway; Signal Transduction; Substrate Specificity; Testing; Tumor Suppressor Proteins; Ubiquitination; Work; c-myc Genes; cancer cell; cancer therapy; cell type; cellular engineering; dimer; glycosylation; neoplastic; neoplastic cell; notch protein; novel; novel therapeutic intervention; protein degradation; transcription factor; treatment strategy; tumor; tumorigenesis; ubiquitin ligase; ubiquitin-protein ligase

This application focuses on Fbw7, an E3 ubiquitin ligase and tumor suppressor, and on its substrate c-Myc (hereafter, Myc), an oncogenic transcription factor widely implicated in human cancers. E3 ligases mark protein substrates for degradation through ubiquitin conjugation. Fbw7 recognizes a network of proteins with crucial roles in proliferation, differentiation, metabolism, and apoptosis. Fbw7 substrates include important oncoproteins (e.g., cyclin E, Notch, Myc, Jun) and thus Fbw7 mutations promote tumorigenesis by deregulating its oncogenic substrates. The Fbw7 pathway therefore has broad implications for cancer biology and for the development of new therapeutic strategies. We will address important and unresolved aspects of this pathway in two general areas. The first involves how phosphorylation and Fbw7 control Myc stability and activity, in both normal cells and in cancers. The second area will address new paradigms in the ways that Fbw7 recognizes substrates and how these interactions may underlie Fbw7 mutations in cancers. This proposal may thus impact many areas of research related to Myc and the Fbw7 pathway. Fbw7 binds substrates after they are phosphorylated within motifs termed degrons, that typically contain two phosphorylated residues that interact with Fbw7. The first two Aims are focused on Myc regulation by phosphorylation of a newly discovered Myc T244 degron that acts in concert with the canonical Myc T58 degron to bind Fbw7 dimers. Aim 1 will study how T244 degron phosphorylation is regulated in normal and tumor cells and whether hierarchical Myc T244 degron phosphorylation controls Myc stability, as well as how the T58 and T244 degrons are coordinately regulated by mitogenic and oncogenic signaling pathways. Aim 2 will study the functions of the T244 degron in normal cells and tumorigenesis and how it cooperates with the T58 degron. This will be accomplished through physiologic knockin models, in human cells and mice, to create engineered Myc mutations that ablate Myc degron phosphorylations. Aim 3 will study how Fbw7 dimers interact with substrates and how these interactions underlie Fbw7 mutations and their functions in cancers. This includes determining the extent to which two separate degrons are required for degradation across the Fbw7 substrate network. Identifying these new degrons may lead to entirely new pathways that control the degradation of critical substrates and that may be abnormal in cancer cells. Tumors often have heterozygous Fbw7 missense mutations that dimerize with wt-Fbw7, and the hypothesis that these mutations specifically stabilize oncogenic substrates that require two degrons will be tested. Finally, the Myc T244 degron binds Fbw7 through a novel mode that involves Fbw7 R689, a tumor hotspot, and the role of R689 in dimer-dependent selective substrate recognition will be studied, as well as similar possible functions for other Fbw7 missense mutations.

本申请集中于Fbw 7，一种E3泛素连接酶和肿瘤抑制因子，及其底物c-Myc （下文中，Myc），一种广泛涉及人类癌症的致癌转录因子。E3连接酶标记 通过泛素缀合降解的蛋白质底物。Fbw 7识别一个蛋白质网络， 在增殖、分化、代谢和凋亡中起重要作用。FBW 7底物包括重要的 癌蛋白（例如，细胞周期蛋白E、Notch、Myc、Jun），因此Fbw 7突变通过以下方式促进肿瘤发生： 解除其致癌底物的调节。因此，Fbw 7通路对癌症具有广泛的意义 生物学和新的治疗策略的发展。我们将解决重要和悬而未决的问题， 这条道路在两个方面。第一个涉及磷酸化和Fbw 7如何控制Myc 在正常细胞和癌症中的稳定性和活性。第二个领域将探讨新的范例， Fbw 7识别底物的方式以及这些相互作用如何成为Fbw 7突变的基础， 癌的因此，这一提议可能会影响与Myc和Fbw 7通路相关的许多研究领域。 Fbw 7在底物被称为降解决定子的基序磷酸化后结合底物，降解决定子通常含有两个 与Fbw 7相互作用的磷酸化残基。前两个目标的重点是Myc调控， 新发现的Myc T244降解决定子的磷酸化，其与经典Myc T58协同作用 降解决定子结合Fbw 7二聚体。目的1：研究T244降解决定子磷酸化在正常人和正常人中的调节， 肿瘤细胞和是否分级Myc T244降解决定子磷酸化控制Myc稳定性，以及 T58和T244降解决定子如何通过促有丝分裂和致癌信号通路协调调节。 目的2研究T244降解决定子在正常细胞和肿瘤发生中的作用及其协同机制 使用T58降解决定子。这将通过在人类细胞中的生理敲入模型来实现， 小鼠，以创建消除Myc降解决定子磷酸化的工程化Myc突变。目标3将研究如何 Fbw 7二聚体与底物相互作用以及这些相互作用如何成为Fbw 7突变及其 在癌症中的作用。这包括确定在何种程度上需要两个单独的降解决定子， 在Fbw 7衬底网络上的降解。识别这些新的降解决定子可能会导致全新的 控制关键底物降解的途径，可能在癌细胞中异常。 肿瘤通常具有与wt-Fbw 7二聚化的杂合Fbw 7错义突变，并且假设 将测试这些突变特异性地稳定需要两个降解决定子的致癌底物。 最后，Myc T244降解决定子通过一种新的模式结合Fbw 7，该模式涉及Fbw 7 R689，一个肿瘤热点， 和R689在二聚体依赖性选择性底物识别中的作用将被研究，以及类似的 其他Fbw 7错义突变的可能功能。