The Omi/HtrA2 Signal Transduction Pathway

Omi/HtrA2 信号转导途径

• 批准号: 7143640
• 负责人: Emad S Alnemri
• 金额: $ 29.84万
• 依托单位: THOMAS JEFFERSON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-12 至 2010-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7143640
• 关键词: active sites; biological signal transduction; enzyme mechanism; enzyme substrate; genetic regulation; genetically modified animals; laboratory mouse; microarray technology; mitochondria; mitochondrial membrane; protein folding; protein quantitation /detection; serine proteinases; stress; transcription factor

DESCRIPTION (provided by applicant): Mitochondrial dysfunction is responsible for many human neurodegenerative diseases. The mechanism by which mitochondria senses and respond to stress is poorly understood. Recent results from our lab and others suggested that the mitochondrial serine protease Omi/HtrA2 is a sensor of mitochondrial stress. Inactivation of Omi/HtrA2 in mnd2 mice due to a point mutation in the protease domain or disruption of the Omi gene in Omi-/- knockout mice leads to neurodegeneration, muscle wasting and death by 40 days of age because of mitochondrial dysfunction. These finding suggests that Omi/HtrA2 has a vital role within the mitochondria that is required for maintenance of mitochondrial homeostasis at normal physiological conditions. Because Omi/HtrA2 shares extensive sequence and structural homology with the bacterial stress sensor DegS, we hypothesize that Omi/HtrA2, like DegS, is a stress sensor that becomes activated when its PDZ domain recognizes exposed PDZ-binding motifs in misfolded mitochondrial proteins. The activated Omi/HtrA2 then triggers a proteolytic cascade that leads to activation of specific stress response genes. The nature of the mitochondrial proteins and the types of unfolding stresses that trigger activation of Omi/HtrA2 are currently unknown. The nature of the mitochondrial Omi/HtrA2 substrates is also unknown. The mnd2 and Omi-/- mice are excellent model systems to study the role of Omi/HtrA2 in cell survival. To investigate the protective function and the signal transduction pathway of Omi/HtrA2, we propose in the first and second specific aims to carry out transgenic rescue experiments in Omi-/- and mnd2 mice to define the role of the PDZ and transmembrane domains of Omi in its protective function. We also propose to study phenotype of specific tissue expression of wildtype Omi in Omi-/- and mnd2 mice. In the remaining specific aims we propose to use biochemical, genetic, and proteomic approaches to identify and characterize the upstream mitochondrial regulators of the PDZ domain of Omi/HtrA2 and the critical mitochondrial substrates of Omi/HtrA2. We predict that Omi/HtrA2-mediated cleavage of a specific mitochondrial substrate could send a signal to the nucleus and activate transcription of Omi/HtrA2-specific stress responsive genes. We propose to identify these genes by microarray analysis. Understanding the molecular basis of stress sensing in the mitochondria and the regulation of the protease activity of Omi/HtrA2 is important for designing strategies for the treatment of mitochondrial-related neurodegenerative diseases. Mutations that reduce the activity of Omi/HtrA2 protease have recently been identified in patients with Parkinson's disease, suggesting a link between Omi/HtrA2 and neurodegeneration in some cases of Parkinson's disease and perhaps other human neurodegenerative diseases. Thus, learning about the function of Omi/HtrA2 under normal and disease conditions is a research objective of clear health interest.

描述（由申请人提供）：线粒体功能障碍负责许多人类神经退行性疾病。线粒体感知和应对压力的机制知之甚少。我们实验室和其他人的最新结果表明，线粒体丝氨酸蛋白酶OMI/HTRA2是线粒体应激的传感器。由于蛋白酶域中的点突变或OMI - / - 敲除小鼠中OMI基因的破坏导致的MND2小鼠中OMI/HTRA2在MND2小鼠中失活导致神经变性，由于线粒体功能障碍而导致神经变性，肌肉浪费和死亡40天。这些发现表明，OMI/HTRA2在线粒体中具有至关重要的作用，这是在正常生理条件下维持线粒体稳态所必需的。由于OMI/HTRA2与细菌应力传感器DEG具有广泛的序列和结构同源性，因此我们假设OMI/HTRA2像DEGS一样，是一种应力传感器，当其PDZ结构域识别出易于折叠的线粒体蛋白质中的PDZ结合基序时，其PDZ结构域被激活。然后，活化的OMI/HTRA2触发蛋白水解级联反应，从而导致特定应力反应基因的激活。目前尚不清楚线粒体蛋白的性质以及触发OMI/HTRA2激活的展开应力的类型。线粒体OMI/HTRA2底物的性质也未知。 MND2和OMI - / - 小鼠是研究OMI/HTRA2在细胞存活中的作用的出色模型系统。为了研究OMI/HTRA2的保护函数和信号转导途径，我们在OMI - / - 和MND2小鼠中进行第一个和第二个特定目的，以执行转基因救援实验，以定义PDZ和Transmmbrane域的作用在保护功能中。我们还建议研究OMI - / - 和MND2小鼠中野生型OMI特异性组织表达的表型。在其余的具体目的中，我们建议使用生化，遗传和蛋白质组学方法来识别和表征OMI/HTRA2 PDZ域的上游线粒体调节剂以及OMI/HTRA2的关键线粒体底物。我们预测，特定线粒体底物的OMI/HTRA2介导的裂解可能会向细胞核发送信号，并激活OMI/HTRA2特异性应激响应基因的转录。我们建议通过微阵列分析鉴定这些基因。了解线粒体中应力感应的分子基础以及OMI/HTRA2蛋白酶活性的调节对于设计治疗线粒体相关神经退行性疾病的策略很重要。最近在帕金森氏病患者中发现了降低OMI/HTRA2蛋白酶活性的突变，这表明在某些帕金森氏病和其他人类神经退行性疾病的情况下，OMI/HTRA2与神经变性之间存在联系。因此，在正常情况和疾病状况下学习OMI/HTRA2的功能是明确健康兴趣的研究目标。