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

 描述(申请人提供)：亨廷顿病(HD)是一种坚持不懈的进行性常染色体显性神经退行性疾病，特征是不自主运动和认知能力下降。HD是由亨廷顿蛋白(Huntingtin，HTT)基因编码区的CAG三核苷酸重复扩增引起的，其发病机制源于HTT蛋白与扩展的聚谷氨酰胺束的产生。我们发现HD患者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(PPAR)-γ共激活因子-1α(PGC-)转录失调所致。 在HD中的转录干扰中，我们对HTT相互作用蛋白进行了无偏筛选，并确定PPAR是候选的相互作用因子。当我们评估不同的PPAR时，我们在BAC-HD97转基因小鼠的大脑皮质中记录了PPAR和hTt之间的物理相互作用，并证实了PPAR在神经元中高表达。突变型hTt抑制BAC-HD97小鼠神经元中PPAR的反式激活，但可通过PPAR激动剂治疗或过度表达而恢复。这些发现为我们最初的R01项目奠定了基础，我们建议确定PPAR-PGC-1通路在HD发病机制中的作用，确定PPAR在中枢神经系统中的功能，并测试PPAR激动剂治疗HD和相关疾病是否可行。在上一个资助周期中，我们证实了PPAR-PGC-1途径在HD中的重要性，证明了HTT与PPAR物理相互作用并抑制PPAR反式激活功能导致线粒体功能障碍和神经毒性，并确定在纹状体表达显性阴性PPAR的转基因小鼠重现HD样表型。此外，我们观察了表达显性-阴性PPAR的小鼠的神经疾病表型，从而确定神经元是一种PPAR功能对动态平衡至关重要的细胞类型。最后，我们验证了选择性和有效的PPAR激动剂KD3010能够挽救HTT的神经毒性，并在HD小鼠身上进行了KD3010的临床前试验，在这些试验中，我们发现在运动功能、神经退行性变和生存方面有显著改善。在这个更新方案中，我们将通过检测PPAR对生物能量功能、自噬和线粒体质量控制的影响来确定PPAR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的周期和活性调节体来确定PPAR如何对抗HTT的神经毒性，并将通过对经过PPAR激动剂处理的HD小鼠进行转录组分析来寻找PPAR神经保护的基础，以确定PPAR神经保护所需的基因和途径。为了评估这些基因和通路对PPAR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患者的神经元中产生救援，或者能够阻止PPAR激动剂的救援。

 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.