Alpha-ketoglutarate Dehydrogenase in Neurodegeneration

α-酮戊二酸脱氢酶（KGDHC）（三羧酸循环的关键酶）的活性在患有神经退行性疾病（例如阿尔茨海默病、帕金森病和Wernicke Korsakoff综合征）的个体的脑中降低。KGDHC活性的降低不仅仅是继发于神经退行性变，因为这种下降不仅发生在选择性易受退行性变影响的大脑区域，而且也发生在没有明显神经病理学的区域。KGDHC活性下降的惊人频率表明，这是对神经元损伤的重要反应，可能是导致最终死亡的级联事件中的关键步骤。对活性下降的合理解释是KGDHC对各种细胞损伤特别敏感，并且在选定区域中，活性的降低降低了细胞对导致神经变性的进一步损伤的响应能力。例如，肺细胞中的KGDHC对自由基特别敏感，并且由此产生的KGDHC缺陷干扰随后的细胞反应。了解KGDHC活性在神经元损伤中降低的机制以及受损的KGDHC活性对细胞信号转导系统的影响，可能有助于开发治疗策略来逆转由许多有害事件（包括氧化应激）引起的神经变性。实验将使用神经元样细胞系（PC 12细胞）和神经元、小胶质细胞和星形胶质细胞的原代培养物来检验具有两个相互作用的组分的假设：（1）KGDHC活性对已知导致细胞死亡的因素（例如，过量的活性氧或升高的钙）或与神经变性相关的异常蛋白质（例如，突变型早老素或淀粉样β-肽）。(2)作为推论，细胞功能对KGDHC活性的甚至轻微降低都敏感。KGDHC在细胞过程中的作用将被评估为细胞膜电位、钙稳态和活性氧水平的函数。KGDHC敏感性增强的潜在基础将通过处理细胞然后检查KGDHC中的分子变化来确定。总之，这些研究将提供KGDHC对外部因素的敏感性是否是导致包括阿尔茨海默病在内的几种神经退行性疾病中神经元死亡的级联事件中的关键步骤的机制测试。

The activity of alpha-ketoglutarate dehydrogenase (KGDHC), a key enzyme of the tricarboxylic acid cycle is reduced in brains of individuals with neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and Wernicke Korsakoff syndrome. The reduction in KGDHC activity is not just secondary to neurodegeneration, since the decline occurs not only in brain areas selective vulnerable to degeneration but also in areas without overt neuropathology. The surprising frequency of the decline in KGDHC activity suggests that this is an important response to neuronal injury and may be critical step in the cascade of events that leads to eventual death. A reasonable explanation for the decline in activity is that KGDHC is particularly sensitive to a variety of cellular insults and that in select regions the reduction in activity diminishes the cell's ability to respond to further insults resulting in neurodegeneration. For example, KGDHC in pulmonary cells is particularly sensitive to free radicals and the resulting deficit in KGDHC interferes with subsequent cellular responses. Understanding both the mechanism by which KGDHC activity is decreased in neuronal injury and the consequences of impaired KGDHC activity on cellular signal transduction systems may be helpful for the development of therapeutic strategies to reverse neurodegeneration resulting from a number of noxious events including oxidative stress. The experiments will use a neuron-like cell line (PC12 cells) and primary cultures of neurons, microglia and astrocytes to test a hypothesis with two interactive components (1) KGDHC activity is especially sensitive to factors known to lead to cell death (e.g., excess reactive oxygen species or elevated calcium) or to abnormal proteins associated with neurodegeneration (e.g., mutant presenilins or amyloid-beta-peptide). (2) As a corollary, cellular functions are sensitive to even mild reductions in KGDHC activities. The role of KGDHC in cellular processes will be assess as a function of cellular membrane potentials, calcium homeostasis and level of reactive oxygen species. The underlying basis for the enhanced sensitivity of KGDHC will be determined by treating the cells and then examining the molecular changes in KGDHC. Together, these studies will provide a mechanistic test of whether the sensitivity of KGDHC to external factors is a critical step in a cascade of events that leads to neuronal death in several neurodegenerative disorders including Alzheimer's disease.