Role of Quaking gene in regulating the niche-independent stemness of glioma stem cells

项目总结 胶质母细胞瘤是最常见的脑肿瘤类型，目前是无法治愈的。缺乏有效的 治疗突出了确定基于机制的治疗方法的迫切需要。相当可观 最近的实验证据表明，神经干细胞(NSC)样脑胶质瘤干细胞群体 (GSCs)具有取之不尽、用之不竭的自我更新能力，是胶质母细胞瘤的“根”。像NSC一样，GSC也是 已知通过与生态位相互作用来保持它们的茎，这提供了适当的线索来防止它们 差异化。但GSC如何在次优环境中维持其自我更新能力 在生态位之外，特别是在入侵和迁徙过程中，仍然不太清楚。作为我们的一部分 努力寻找参与中枢神经系统调节的潜在胶质瘤抑制因子 研究发现，RNA结合蛋白颤动(QKI)是NSC和GSC的主要调节因子 自我更新。在人脑胶质母细胞瘤中，QKI基因经常缺失或突变。使用一种新建立的动物 模型，我们从基因上证明了QKI是一种真正的胶质瘤抑制因子，它的耗竭很强。 促进神经胶质瘤的形成。在功能上，我们揭示了QKI是细胞内吞作用的关键调节因子 控制受体的运输、降解和信号脱敏。具体地说，我们展示了这种耗竭 QKI导致细胞质膜结合的Wnt和Notch受体的丰富(FrizzledNotch1) 以及随后的信号超激活。鉴于WNT和Notch1是涉及的两个主要信令级联 在保持NSC和GSC的茎的分化方面，我们认为QKI调节NSC和GSC 通过控制内溶酶体介导的FrizzledNotch1降解的自我更新和神经胶质瘤形成。至 验证这一假说，在目标1中，我们将确定QKI如何调节内溶酶体依赖的降解 NSCs和GSCs中Wnt受体Frizzed的表达。在目标2中，我们将描述分子机制 QKI调控细胞内调节子NumB和内溶酶体Notch1的RNA选择性剪接 退化。总之，这些研究将阐明QKI介导的分子机制 内溶酶体依赖的Wnt和Notch1信号激活的调节，更重要的是，它们将 有助于开发专门针对QKI耗竭的胶质母细胞瘤的治疗策略。

PROJECT SUMMARY Glioblastoma is the most common type of brain tumor and is currently incurable. The lack of effective treatments highlights the urgent need for identifying mechanism-based therapeutic approaches. Substantial experimental evidence has recently revealed a population of neural stem cell (NSC)-like glioma stem cells (GSCs) that possess an inexhaustible ability to self-renew as the “root” of glioblastoma. Like NSCs, GSCs are known to maintain their stemness by interacting with niches, which provides proper cues to prevent them from differentiating. But how GSCs manage to sustain their self-renewal capacity in the sub-optimal environment outside the niches, particularly during the process of invasion and migration, remains less clear. As part of our effort to identify potential glioma suppressors involved in the regulation of central nervous system development, we discovered that RNA binding protein Quaking (QKI) is a major regulator of NSC and GSC self-renewal. QKI is frequently deleted or mutated in human glioblastomas. Using a newly established animal model, we genetically demonstrated that QKI is a bona fide glioma suppressor whose depletion strongly promotes gliomagenesis. Functionally, we revealed that QKI is a key regulator of cellular endocytosis that controls receptor trafficking, degradation, and signaling desensitization. Specifically, we showed that depletion of QKI led to the enrichment of cytoplasmic membrane-bound Wnt and Notch receptors (Frizzled and Notch1) and subsequent signal hyperactivation. Given that Wnt and Notch1 are two major signaling cascades involved in maintaining NSC and GSC stemness against differentiation, we propose that QKI modulates NSC and GSC self-renewal and gliomagenesis by controlling endolysosome-mediated Frizzled and Notch1 degradation. To test this hypothesis, in Aim 1, we will determine how QKI regulates the endolysosome-dependent degradation of Wnt receptor Frizzled in NSCs and GSCs. In Aim 2, we will delineate the molecular mechanism by which QKI modulates RNA alternative splicing of the endocytic regulator Numb and the endolysosomal Notch1 degradation. Together, these studies will elucidate the molecular mechanisms underlying QKI-mediated endolysosome-dependent regulation of Wnt and Notch1 signal activation, and more importantly, they will contribute to the development of therapeutic strategies that specifically target QKI-depleted glioblastoma.