The PPAR-delta pathway in neural function and Huntington's disease neuropathology

 描述（由申请人提供）：亨廷顿病（HD）是一种持续进行的常染色体显性神经退行性疾病，其特征为不自主运动和认知能力下降。HD是由亨廷顿蛋白（htt）基因编码区CAG三核苷酸重复扩增引起的，其发病机制是由htt蛋白产生的多聚谷氨酰胺片段扩增引起的。我们发现HD患者的线粒体功能障碍和代谢缺陷是由于过氧化物酶体增殖物激活受体γ共激活因子1 α（PGC-γ coactivator-1 alpha，PGC-γ coactivator-1 alpha）的转录失调所致。 为了排除HD中的转录干扰，我们对ht相互作用蛋白进行了无偏筛选，并将PPARs确定为候选相互作用因子。当我们评估不同的PPARs时，我们记录了BAC-HD 97转基因小鼠皮层中PPARs和htt之间的物理相互作用，并证实PPARs在神经元中高度表达。突变体htt抑制了BAC-HD 97小鼠神经元中的PPAR β反式激活，但可以通过PPAR β激动剂治疗或过表达来挽救。这些发现形成了我们最初R 01项目的基础，在该项目中，我们提出确定PPAR β-PGC-1 β通路在HD发病机制中的作用，定义PPAR β在CNS中的功能，并测试PPAR β激动剂治疗是否可能是HD和相关疾病的可行治疗范例。在上一个资助周期中，我们通过记录htt与PPAR γ物理相互作用并抑制PPAR γ反式激活功能以产生线粒体功能障碍和神经毒性，证实了PPAR γ-PGC-1 β通路在HD中的重要性，并确定了在纹状体中表达显性负性PPAR γ的转基因小鼠重演了HD样表型。此外，我们观察到在表达显性负性PPAR β的小鼠中的神经系统疾病表型，从而将神经元鉴定为其中PPAR β功能对于稳态是必不可少的细胞类型。最后，我们验证了一种选择性和有效的PPAR β激动剂，KD 3010，能够挽救htt神经毒性，并在HD小鼠中进行了KD 3010的临床前试验，我们记录了运动功能，神经退行性变和存活率的显着改善。在这项更新提案中，我们将通过检查PPAR β对生物能量学功能，自噬和线粒体质量控制的影响来确定PPAR β如何促进神经保护。我们将通过定义正常神经元和HD神经元中PPAR β的顺式组和活性调节组来确定PPAR β如何对抗htt神经毒性，并且我们将通过用PPAR β激动剂处理的HD小鼠的转录组分析来寻找PPAR β神经保护的基础，以鉴定PPAR β神经保护所需的基因和途径。为了评估这些基因和途径对PPAR β神经保护的贡献，我们将测试靶基因的表达调节是否足以在BAC-HD和HD患者神经元中产生拯救，或者是否能够阻止PPAR β激动剂的拯救。

 DESCRIPTION (provided by applicant): Huntington's disease (HD) is a relentlessly progressive autosomal dominant neurodegenerative disorder characterized by involuntary movements and cognitive decline. HD results from a CAG trinucleotide repeat expansion in the coding region of the huntingtin (htt) gene, and pathogenesis stems from production of htt protein with an expanded polyglutamine tract. We found that the mitochondrial dysfunction and metabolic deficits in HD result from transcriptional dysregulation of peroxisome proliferator-activated receptor [PPAR] gamma coactivator-1 alpha (PGC-To determine the basis for PGC transcription interference in HD, we performed an unbiased screen for htt-interacting protins, and identified PPARs as candidate interactors. When we evaluated the different PPARs, we documented a physical interaction between PPAR and htt in the cortex of BAC-HD97 transgenic mice, and confirmed that PPAR is highly expressed in neurons. Mutant htt repressed PPAR transactivation in neurons from BAC-HD97 mice, but could be rescued by PPAR agonist treatment or over-expression. These findings formed the basis for our initial R01 project where we proposed to determine the role of the PPAR-PGC-1 pathway in HD pathogenesis, define the function of PPAR in the CNS, and test if PPAR agonist therapy might be a viable treatment paradigm for HD and related disorders. In the last funding cycle, we confirmed the importance of the PPAR-PGC-1 pathway in HD by documenting that htt physically interacts with PPAR and represses PPAR transactivation function to yield mitochondrial dysfunction and neurotoxicity, and determined that transgenic mice expressing dominant-negative PPAR in the striatum recapitulate HD-like phenotypes. Furthermore, we observed neurological disease phenotypes in mice expressing dominant-negative PPAR, thereby identifying neurons as a cell type where PPAR function is essential for homeostasis. Finally, we validated a selective and potent PPAR agonist, KD3010, as capable of rescuing htt neurotoxicity, and performed a preclinical trial of KD3010 in HD mice, where we documented significant improvements in motor function, neurodegeneration, and survival. In this renewal proposal, we will determine how PPAR promotes neuroprotection by examining the effects of PPAR on bioenergetics function, autophagy, and mitochondrial quality control. We will determine how PPAR counters htt neurotoxicity by defining the cistrome and active regulome of PPAR in normal neurons and HD neurons, and we will seek the basis for PPAR neuroprotection by transcriptome analysis of HD mice treated with PPAR agonist to identify genes and pathways required for PPAR neuroprotection. To evaluate the contribution of such genes and pathways to PPAR neuroprotection, we will test if expression modulation of target genes is sufficient to produce rescue in BAC-HD and HD patient neurons, or is capable of preventing rescue by PPAR agonists.