AUTOPHAGY, DNA DAMAGE AND ONSET OF HUNTINGTON'S DISEASE.

自噬、DNA 损伤和亨廷顿病的发作。

• 批准号: 7085095
• 负责人: JUNYING YUAN
• 金额: $ 33.83万
• 依托单位: HARVARD MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-04-01 至 2011-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7085095
• 关键词: DNA damage; Huntington' s disease; aging; amidohydrolases; autophagy; cell line; cyclin dependent kinase; disease /disorder onset; free radical oxygen; gene expression; gene induction /repression; gene mutation; genetic promoter element; genetically modified animals; laboratory mouse; mitochondria; nerve /myelin protein; neural degeneration; neurogenetics; neuropathology; oxidative stress; transcription factor

The goal of this proposal is to test the hypothesis that the reduction of key autophagy gene expression and autophagy function as a result of DNA damage during the aging process plays a key role in mediating the onset of Huntington's disease (HD). Mouse, Drosophila and C. elegans models of HD suggest that the cytotoxicity of expanded polyglutamine is highly dependent upon protein context and protein expression levels of mutant Htt. Autophagy plays an important role in regulating the intracellular accumulation of mutant Htt with expanded polyQ. The expression of beclin 1, a key gene involved in autophagy, decreased in an age-dependent fashion in human brains. Since beclin 1 gene is haploid insufficient in regulating autophagosome function, age-dependent decrease of beclin 1 expression may lead to a reduction of autophagic activity during aging. The hypothesis is that reduction of autophagy function in aging results in both increased oxidative stress induced DNA damage and reduced long-lived protein turnover which promotes the accumulation of mutant Htt. Increased accumulation of mutant Htt and oxidative stress may play an important role in promoting the onset of HD. This hypothesis will be tested in the following specific aims. Specific Aim 1 is to test,the hypothesis that the reduction of beclin 1 expression in aging human brains contributes to the onset of HD by generating beclin 1+/-; HdhQ111 mice and examining if 50% reduction of beclin 1 expression led to an increased accumulation of mutant Htt as well as to determine the consequence of autophagy deficiency on neuronal survival and functions. Specific Aim 2 is to examine the mechanism which led to the age-dependent reduction of beclin 1 expression by testing if the promoter of beclin 1 is preferentially damaged in aging human brains and particularly susceptible to oxidative damage in cellular models. The contribution of reduced expression of transcriptional factors regulating beclin 1 expression will also be considered. Specific Aim 3 is to test the hypothesis that the reduction of autophagy function exacerbates the DNA damage during aging by increasing the accumulation of damaged mitochondria which further promotes the levels of intracellular ROS by examining aging beclin 1+/- mice and autophagy deficient cells for evidence of increased damaged mitochondria. Specific Aim 4 is to investigate the functional role of autophagy to oxidative DNA damage using CK-p25 mice as a model and to examine the roles of of DNA damage and autophagy deficiency to the accumulation of mutant Htt in HdhQ111; CKp25 mice. The ability of SIRT1 activating molecules (STACs) to restore the autophagy function in CK-p25 mice and to delay the onset of motor dysfunction in HD models will be determined. Understanding the mechanism by which DNA damage negatively regulates autophagy during aging would allow us to develop strategies to maintain normal autophagy function during aging process which may delay or prevent the onset of HD and other aging related neurodegenerative diseases.

这项提议的目的是检验一个假设，即关键自噬基因表达的减少和 在衰老过程中DNA损伤导致的自噬功能在介导衰老过程中起着关键作用。 亨廷顿病（HD）的发病。小鼠、果蝇和C. HD的elegans模型表明， 扩增的聚谷氨酰胺的细胞毒性高度依赖于蛋白质环境和蛋白质表达 突变Htt的水平。自噬在调节突变体的细胞内积累中起重要作用 使用扩展polyQ的Htt。自噬关键基因Beclin 1的表达降低， 人类大脑中与年龄相关的方式。由于beclin 1基因是单倍体， 自噬体功能，beclin 1表达的年龄依赖性降低可能导致自噬体功能的降低。 衰老过程中的自噬活性。该假说认为，衰老过程中自噬功能的降低导致 增加氧化应激诱导的DNA损伤和减少长寿命蛋白质周转， 促进突变体Htt的积累。突变型Htt和氧化应激的积累增加可能 在促进HD发病中起重要作用。这一假设将在以下具体情况下进行检验： 目标。具体目的1是检验衰老人脑中beclin 1表达减少的假设， 通过产生beclin 1+/-; HdhQ 111小鼠并检查是否有50%的减少导致HD的发作。 beclin 1的表达导致突变体Htt的积累增加， 自噬缺陷对神经元存活和功能的影响。具体目标2是检查 通过检测Beclin 1的启动子是否能抑制Beclin 1的表达， Beclin 1在老化的人脑中优先受损， 细胞模型调节beclin 1的转录因子表达减少的作用 表达也将被考虑。具体目标3是检验自噬减少 在衰老过程中，通过增加受损DNA的积累， 线粒体，其通过检查老化的beclin 1+/-小鼠进一步促进细胞内ROS水平， 自噬缺陷细胞的证据增加受损的线粒体。具体目标4是调查 以CK-p25小鼠为模型，研究自噬在氧化性DNA损伤中的作用， DNA损伤和自噬缺陷对HdhQ 111; CKp 25中突变型Htt积累的作用 小鼠SIRT 1激活分子（STACs）恢复CK-p25自噬功能的能力 将确定小鼠的运动功能障碍和延迟HD模型中运动功能障碍的发作。了解 DNA损伤在衰老过程中负调节自噬的机制将使我们能够开发 在衰老过程中维持正常自噬功能的策略，可能会延迟或预防发病 HD和其他与衰老相关的神经退行性疾病。