The role of membrane homoeostasis of neural stem cell and glioma stem cells in neural development and gliomagenesis

项目总结 所有干细胞都有自我更新的能力，即在不分化的情况下产生子代干细胞的能力 转化成其他类型的细胞。干细胞从它们的缝隙中接收信号，指示它们自我更新和防止 它们不能通过一系列细胞器间的通讯过程进行分化。确凿的证据 最近揭示，胶质母细胞瘤是最常见和致命的脑肿瘤类型，其根源是 胶质瘤干细胞(GSCs)群体，具有取之不尽的自我更新能力。与神经干细胞不同 细胞(NSCs)，GSCs也能够在它们遇到的次优环境中保持它们的干性 在入侵期间在它们的壁龛外。GSC(而不是NSC)如何在 利基市场仍不明朗。为了确定影响神经干细胞和微环境相互作用的潜在胶质瘤抑制因子，我们 发现RNA结合蛋白颤动(QKI)是控制受体的内吞作用的关键调节因子 贩卖、降解和信号脱敏。从机制上讲，QKI调节血管内皮细胞前mRNA的稳定性 调节内溶酶体脂质成分的基因，特别是不饱和脂肪酸(UFAs)。作为一名 内溶酶体功能缺陷的后果，我们发现QKI的耗竭和UFA的抑制 生物合成导致细胞质膜结合受体的丰富，这些受体是维持 茎干。此外，由于多不饱和脂肪酸(PUFA)是下垂的底物， Qki缺失引起的多不饱和脂肪酸下调使GSCs对主要的肿瘤抑制因子--铁性下垂产生抵抗 机制。支持QKI和UFA调控的细胞内囊泡转运系统的重要性 在胶质母细胞瘤的生物合成中，我们发现QKI、内溶酶体和硬脂酰辅酶A去饱和酶水平较低 (SCD，不饱和脂肪酸生物合成的关键酶)均与胶质母细胞瘤较差的预后显著相关。 病人。我们的长期目标是开发针对有缺陷的内溶酶体功能的治疗方法 胶质母细胞瘤。鉴于QKI是SCD基因的主要调节者，并抑制QKI和UFA的生物合成 可以削弱内溶酶体的活性并促进胶质瘤的形成，我们假设QKI缺失/突变 通过下调不饱和脂肪酸的生物合成和修复来破坏神经干细胞和神经干细胞的内溶酶体功能 多不饱和脂肪酸水平的升高可使肿瘤细胞对铁性下垂敏感。为了检验这一假设，我们将(A)确定 SCD1/2介导的不饱和脂肪酸生物合成在QKI调节的神经干细胞和神经干细胞内溶酶体功能中的作用，(B)阐明 QKI调节NSCs和GSCs中SCD1/2前mRNA稳定性的机制，以及(C)评估 恢复多不饱和脂肪酸水平对肿瘤细胞铁性下垂的增敏作用。总而言之，这些研究将 阐明胶质瘤抑制基因QKI调控细胞内小泡转运的分子机制 在NSCs和GSCs中通过脂质代谢，更重要的是，它们将有助于 针对QKI/SCD耗竭的胶质母细胞瘤的治疗策略。

PROJECT SUMMARY All stem cells have the capacity for self-renewal, an ability to create daughter stem cells without differentiating into other cell types. Stem cells receive the signals from their niches that instruct them to self-renew and prevent them from differentiating through a cascade of inter-organelle communication processes. Substantial evidence has recently revealed that glioblastoma, the most common and lethal type of brain tumor, has “roots” in a population of glioma stem cells (GSCs) that possess an inexhaustible ability to self-renew. Unlike neural stem cells (NSCs), GSCs are also able to sustain their stemness in the suboptimal environments they encounter outside their niches during invasion. How GSCs, but not NSCs, are able to maintain their stemness outside the niches remains unclear. To identify potential glioma suppressors that affect interaction of GSCs and niches, we discovered that RNA-binding protein Quaking (QKI) is a key regulator of endocytosis that controls receptor trafficking, degradation, and signaling desensitization. Mechanistically, QKI regulates pre-mRNA stability of genes that regulate lipid components of endolysosomes, particularly the unsaturated fatty acids (UFAs). As a consequence of defective endolysosomal function, we showed that depletion of QKI and inhibition of UFA biosynthesis led to the enrichment of cytoplasmic membrane-bound receptors that are required for maintaining stemness. In addition, since polyunsaturated fatty acids (PUFAs) are the substrates of ferroptosis, downregulation of PUFA due to Qki loss renders GSCs resistant to ferroptosis, a major tumor suppression mechanism. Supporting the importance of intracellular vesicle trafficking system regulated by QKI and UFA biosynthesis in glioblastoma, we found that lower levels of QKI, endolysosome and Stearoyl-CoA desaturase (SCD, the key enzyme for UFA biosynthesis) all correlate significantly with poorer prognosis in glioblastoma patients. Our long-term goal is to develop therapies that target the defective endolysosome function in glioblastoma. Given that QKI is a major regulator of SCD genes and inhibition of both QKI and UFA biosynthesis can impair the endolysosome activity and promote gliomagenesis, we hypothesize that QKI deletions/mutations disrupt endolysosomal function in NSCs and GSCs through downregulation of UFA biosynthesis and restoration of PUFA levels can sensitize tumor cells to ferroptosis. To test this hypothesis, we will (a) determine the role of Scd1/2-mediated UFA biosynthesis in QKI-regulated endolysosome functions in both NSCs and GSCs, (b) clarify the mechanism by which QKI regulates Scd1/2 pre-mRNA stability in both NSCs and GSCs, and (c) evaluate the effects of restoration of PUFA levels in sensitizing tumor cells to ferroptosis. Together, these studies will elucidate the molecular mechanisms of how the glioma suppressor QKI regulates intracellular vesicle trafficking in NSCs and GSCs through lipid metabolism, and more importantly, they will contribute to the development of therapeutic strategies that specifically target QKI/SCD-depleted glioblastoma.