MOLECULAR MECHANISMS OF CELL DEATH IN PD MITOCHONDRIA

特发性帕金森病（PD）折磨着大约100万美国人，在个体中引起广泛的痛苦，并因其产生的进行性运动障碍而对社会造成重大的经济损失。PD症状是由黑质多巴胺神经元过早和加速死亡引起的，通常用替代黑质纹状体通路中多巴胺突触功能的药物治疗。然而，目前还没有有效的对症药物被证明可以通过减缓人类多巴胺神经元的死亡来减少疾病的进展。研究发现，电子传递链复合体I编码的线粒体基因缺陷导致氧化应激增加、细胞内钙信号的有害变化、线粒体复制和运动改变以及线粒体功能障碍介导的细胞死亡易感性增加。该项目是帕金森研究卓越中心四个项目申请中的第三个基于实验室的研究。本项目将探索PD线粒体产生细胞死亡的分子机制，该线粒体的遗传功能在该小组开发和广泛研究的细胞质杂交（cybrid）细胞模型中被分离和扩增。PD复合物的结果将与鱼藤酮引起的慢性复合物I损伤的药理学模型进行比较。四个具体的目标将检验相互关联的假设。首先，线粒体膜电位的调节将研究线粒体周期性去极化-复极化是如何在PD中改变的，这是PI实验室首次在神经细胞中描述的。其次，确定过表达抗凋亡蛋白bcl-2和bcl-XL对PD患者线粒体周期性去极化和线粒体膜电位降低的影响。第三，将在对照和PD模型中定义连接线粒体去极化和MAPKinase级联激活的分子机制。第四，将对PD和对照脑组织中分离的线粒体过渡孔（MTP）复合物的性质进行表征。这些特性包括该小组最近的发现，即人脑MTP复合物与细胞色素c结合。将在MTP脂质体中研究去极化诱导的细胞色素c释放以及重组bcl蛋白和BH区突变体的影响。该项目与其他两个实验室项目广泛互动，并将开发模型系统，以确定PD中可能具有神经保护作用的药物的作用机制。

Idiopathic Parkinson's disease (PD) afflicts about 1 million Americans, causes widespread suffering in the individuals, and exacts a significant economic toll on society from its production on progressive motor disability. PD symptoms arise from the premature and accelerated death of substantia nigra dopamine neurons and are commonly treated with drugs that replace dopamine synaptic function in the nigrostriatal pathway. However, no available symptomatic drugs have been shown to reduce disease progression by slowing the death of dopamine neurons in humans. Studies performed mainly by the defect in mitochondrial genes coding for complex I of the electron transport chain is responsible for increased oxidative stress, detrimental changes in intracellular calcium signaling, altered mitochondrial replication and movement, and increased susceptibility to cell death mediated by mitochondrial dysfunction. This Project is the third laboratory-based study in a four Project application for a Parkinson's Research Center of Excellence. This Project will explore the molecular mechanisms of cell death produced by PD mitochondria whose genetic functions are isolated and amplified in the cytoplasmic hybrid (cybrid) cell model developed and extensively studied by this group. Results in PD cybrids will be compared to a pharmacological model of chronic complex I impairment produced by rotenone. Four Specific Aims will be examined that test interrelated hypotheses. First, the regulation of mitochondrial membrane potential will be studied with respect to the how cyclical mitochondrial depolarization-repolarization, first described in neural cells by the PI's laboratory, is altered in PD. Second, the effects of over-expressing the anti-apoptotic proteins bcl-2 and bcl-XL on cyclical mitochondrial depolarization and reduced mitochondrial membrane potential in PD will be determined. Third, the molecular mechanisms connecting mitochondrial depolarization to activation of MAPKinase cascade will be defined in control and PD models. Fourth, properties of mitochondrial transition pore (MTP) complexes isolated from PD and control brain tissues will be characterized. These properties included the very recent finding from this group that human brain MTP complexes bind cytochrome c. Depolarization-induced release of cytochrome c and the influence of recombinant bcl proteins and BH region mutants will be studied in MTP-liposomes. This project interacts extensively with the other two laboratory projects and will develop model systems to define mechanisms of action for drugs that might be neuroprotective in PD.