Alfy-mediated selective macroautophagy and the pathogenesis of Huntington???s Dis

描述（由申请人提供）：亨廷顿舞蹈病（HD）是一种神经退行性疾病，由亨廷顿舞蹈病基因内遗传CAG扩增突变引起，导致含有扩增的聚谷氨酰胺（polyQ）通道的亨廷顿舞蹈病（Htt）蛋白突变。纹状体变性导致患者逐渐丧失自主运动控制、精神障碍和认知能力下降。HD的病理特征是突变Htt和泛素在整个大脑的细胞内沉积物中积累。Htt聚集与疾病症状之间的联系尚不清楚，但在抑制Htt转基因的研究中观察到细胞和行为病理学的改善。在一个可诱导的HD小鼠模型中，转基因沉默导致聚集物的消除，同时改善运动缺陷。这些发现表明，清除聚集体有可能减轻与HD相关的潜在细胞功能障碍。了解神经元处理聚集蛋白的分子机制是开发各种神经退行性疾病治疗方法的关键一步。细胞模型系统表明，Htt聚集体通过一种称为巨噬的降解过程被分解，在这种降解过程中，细胞质蛋白被隔离到一个双膜结构中，该结构与溶酶体融合以降解其货物。巨噬机制包括一组核心的自噬相关蛋白，如Atg5、Atg7和LC3。虽然这一过程最初被发现是为了应对饥饿而大量降解蛋白质，但它也可以选择性地发生在特定的底物上。我们的实验室已经确定了一种名为Alfy（自噬连接的FYVE蛋白）的蛋白质，它可以介导聚集蛋白的选择性大自噬。在表达突变Htt的细胞中，Alfy对于清除聚集体至关重要。此外，c端Alfy的过表达减少了包涵体，并在果蝇和polyQ扩增的原代神经元模型中保护神经变性。本研究旨在探讨alfy介导的选择性巨噬在脑老化和HD中的作用。从发育中的大脑中消除核心巨噬蛋白（如Atg7）会导致神经退行性和蛋白质积累，但在体内，选择性和非选择性巨噬在衰老过程中的作用仍未得到充分研究。该项目将通过使用他莫昔芬诱导的Cre来消除衰老小鼠中的Alfy或Atg7来驱动条件等位基因的切除来检查这一点（Aim 1）。这将提供对

DESCRIPTION (provided by applicant): Huntington's disease (HD) is a neurodegenerative disorder arising from an inherited CAG expansion mutation within the HD gene, resulting in mutant huntingtin (Htt) protein containing an expanded polyglutamine (polyQ) tract. Degeneration of the striatum causes patients to suffer from progressive loss of voluntary motor control, psychiatric disturbances, and debilitating cognitive decline. A pathological hallmark of HD is the accumulation of mutant Htt and ubiquitin in intracellular deposits throughout the brain. The link between Htt aggregates and disease symptoms remains unclear, but improvements in both cellular and behavioral pathology have been observed in studies that silence the Htt transgene. In an inducible HD mouse model, transgene silencing leads to the elimination of aggregates in conjunction with amelioration of motor deficits. These findings imply that aggregate removal has the potential to alleviate the underlying cellular dysfunction associated with HD. Understanding the molecular mechanisms by which neurons dispose of aggregated proteins is a critical step towards the development of therapeutics for a variety of neurodegenerative disorders. Cellular model systems have suggested that Htt aggregates are broken down by a degradation process known as macroautophagy, in which cytosolic proteins are sequestered into a double-membrane structure that fuses with a lysosome to degrade its cargo. The macroautophagic machinery comprises a core group of autophagy-related proteins, such as Atg5, Atg7, and LC3. While this process was initially found to degrade proteins in bulk in response to starvation, it can also occur selectively for particular substrates. Our lab has identified a protein called Alfy (autophagy-linked FYVE protein) that mediates selective macroautophagy of aggregated proteins. In cells expressing mutant Htt, Alfy is essential for the clearance of aggregates. Additionally, overexpression of c-terminal Alfy decreases inclusions and protects against neurodegeneration in drosophila and primary neuronal models of polyQ expansion. This proposal seeks to address the role of Alfy-mediated selective macroautophagy in aging brain and in HD. Eliminating core macroautophagic proteins such as Atg7 from developing brain results in neurodegeneration and protein accumulation, but the role of selective and nonselective macroautophagy during aging remains largely unexplored in vivo. This project will examine this by eliminating Alfy or Atg7 in aging mice using a tamoxifen-inducible Cre to drive excision of a conditional allele (Aim 1). This will provide insight into the importance of macroautophagy in aging brain. Furthermore, this project will investigate Alfy- mediated macroautophagy of Htt aggregates in vivo, by eliminating Alfy in an inducible HD mouse model (Aim 2). This will address how removal of Alfy affects clearance of mutant Htt, and whether disease reversal is dependent upon clearance of aggregates.