Neuronal FXR as a potential therapeutic target for Alzheimer's disease

项目总结/摘要 与受损、错误折叠和聚集的蛋白质积累相关的蛋白质内稳态的损失是 这是衰老和许多与年龄相关的神经退行性疾病的特征。我们假设这 可能部分是由年龄相关的自噬功能障碍驱动的，自噬建立了一个前驱过程， 导致蛋白质稳态下降和随后的神经退化越来越多的证据表明， 转录因子EB（TFEB）是自噬和溶酶体生物发生的主要调节因子， 是许多神经退行性疾病的基础基于这些发现，我们在一个 神经元细胞系中诱导TFEB的化合物。我们发现了一系列化合物 TFEB及其靶向水平远远超过经典TFEB诱导剂雷帕霉素产生的水平。我们的首席 化合物“C1”在广泛的蛋白毒性疾病模型中进行测试，包括在线虫C中。 在体外人神经元tau蛋白病模型和帕金森病的体内小鼠模型中， （PD）。结合自噬通量的升高，发现该化合物可防止 神经毒性蛋白聚集和增强的线粒体功能。随后的遗传和生物化学 分析表明，C1通过作为核激素受体β-受体的“反向激动剂”诱导TFEB。 12/FXR，通过使用已知的β-12/FXR调节剂进行验证。虽然FXR最出名的是它的能力， 在肝脏和肠道中起作用以维持脂质体内平衡，最近已显示其存在于脑神经元中 尽管它在这里的作用目前还没有被探索。我们的研究结果强调了一种新的以前未表征的作用， FXR-TFEB信号介导的自噬在年龄相关的神经退行性疾病中的作用基于这些 结果，我们假设神经元FXR机制性地调节TFEB介导的自噬水平 因此构成了治疗与年龄相关的神经变性疾病的新靶点 阿尔茨海默病（AD）。为了验证这一假设，我们建议确定是否：（1）FXR抑制结果 在下游TFEB信号传导中，触发AD中受影响的神经元内神经元自噬的增加， (2)防止随后发生已确定的AD相关病理。拟议的研究包括分析 在人iPSC衍生的神经元和来自体内AD小鼠模型的脑组织中， 与人类疾病相关，包括线粒体缺陷、Aβ和tau蛋白的进行性发展 神经病理学，突触完整性的丧失，以及小鼠中的认知功能障碍。

PROJECT SUMMARY / ABSTRACT Losses in protein homeostasis associated with accumulation of damaged, misfolded and aggregated proteins is a characteristic feature of aging and many age-related neurodegenerative diseases. We hypothesize that this may in part be driven by age-related dysfunctions in autophagy which establishes a prodromal process resulting in decreased protein homeostasis and subsequent neurodegeneration. Growing evidence suggests that reduced activity of transcription factor EB (TFEB), a master regulator of autophagy and lysosomal biogenesis, could underlie many neurodegenerative diseases. Based on these findings, we conducted a chemical screen in a neuronal cell line for chemical compounds that induce TFEB. We identified a series of compounds that induce TFEB and its targets to levels far exceeding that produced by the classic TFEB inducer rapamycin. Our lead compound `C1' was tested across a wide range of proteotoxic disease models including in the nematode C. elegans, in in vitro human neuronal tauopathy models, and in an in vivo mouse model of Parkinson's disease (PD). In conjunction with elevations in autophagic flux, the compound was found to prevent the formation of neurotoxic proteins aggregates and enhanced mitochondrial function. Subsequent genetic and biochemical analysis shows that C1 induces TFEB by acting as a “reverse agonist” of the nuclear hormone receptor DAF- 12/FXR, validated via the use of known modulators of DAF-12/FXR. Although FXR is best known for its ability to act in the liver and gut to maintain lipid homeostasis, it has recently been shown to be present in brain neurons although its role in here is currently unexplored. Our results highlight a novel previously uncharacterized role for FXR-TFEB signaling-mediated autophagy in age-associated neurodegenerative diseases. Based on these results, we hypothesize that neuronal FXR mechanistically acts to modulate levels of TFEB-mediated autophagy and as such constitutes a novel target for the treatment of age-related neurodegenerative diseases including Alzheimer's disease (AD). To test this hypothesis, we propose to determine whether: (1) FXR inhibition results in downstream TFEB signaling, triggering an increase in neuronal autophagy within neurons affected in AD and (2) prevents subsequent development of established AD-related pathologies. Proposed studies include analyses in both human iPSC-derived neurons and in brain tissues from an in vivo AD mouse model to interrogate features associated with human disease including progressive development of mitochondrial deficits, Aβ and tau neuropathology, losses in synapse integrity, and in mice, cognitive dysfunction.