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

项目摘要 胶质母细胞瘤是最常见的脑肿瘤类型，目前无法治愈。缺乏有效 治疗方法突出了确定基于机制的治疗方法的迫切需要。实质性 实验证据最近揭示了一群神经干细胞（NSC）样胶质瘤干细胞 作为胶质母细胞瘤的“根”，具有取之不尽的自我更新能力的GSC。与NSC一样，GSC 已知通过与小生境相互作用来保持它们的干性，这提供了适当的线索来防止它们 差异化但是，在次优环境下，GSC如何维持自我更新能力 在生态位之外，特别是在入侵和迁移过程中，仍然不太清楚。作为我们 努力鉴定参与中枢神经系统调节的潜在胶质瘤抑制剂 我们发现RNA结合蛋白Quaking（QKI）是NSC和GSC的主要调节因子 自我更新QKI在人胶质母细胞瘤中经常缺失或突变。使用一种新建立的动物 模型，我们从遗传学上证明了QKI是一个真正的胶质瘤抑制因子， 促进神经胶质瘤的发生在功能上，我们发现QKI是细胞内吞作用的关键调节因子， 控制受体运输、降解和信号脱敏。具体来说，我们发现， QKI导致细胞质膜结合的Wnt和Notch受体（Frizzled和Notch1）富集 以及随后的信号过度激活鉴于Wnt和Notch1是两个主要的信号级联， 在维持NSC和GSC的干性对抗分化方面，我们认为QKI调节NSC和GSC 通过控制内溶酶体介导的Frizzled和Notch1降解来自我更新和胶质瘤发生。到 为了验证这一假设，在目标1中，我们将确定QKI如何调节内溶酶体依赖性降解， Wnt受体Frizzled在神经干细胞和GSC中的表达。在目标2中，我们将描述分子机制， QKI调节内吞调节因子Numb和内溶酶体Notch1的RNA选择性剪接 降解总之，这些研究将阐明QKI介导的细胞凋亡的分子机制。 Wnt和Notch1信号激活的内溶酶体依赖性调节，更重要的是，它们将 有助于开发特异性靶向QKI缺失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.