The Omi/HtrA2 Signal Transduction Pathway

Omi/HtrA2 信号转导途径

• 批准号: 7491010
• 负责人: Emad S Alnemri
• 金额: $ 28.97万
• 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/7491010
• 关键词: Age; Apoptotic; Binding; Biochemical Genetics; Biological Models; Catalytic Domain; Cell Nucleus; Cell Survival; Cessation of life; Condition; DNA Sequence Rearrangement; Disease; Disruption; Endopeptidases; Genes; Genetic Transcription; Health; Homeostasis; Human; Knockout Mice; Learning; Link; Maintenance; Mediating; Microarray Analysis; Mitochondria; Mitochondrial Proteins; Molecular; Mus; Muscle; Mutation; Nature; Nerve Degeneration; Neurodegenerative Disorders; Omi serine protease; Parkinson Disease; Patients; Peptide Hydrolases; Phenotype; Physiological; Point Mutation; Protease Domain; Proteomics; Regulation; Research; Role; Signal Transduction; Signal Transduction Pathway; Stress; Tissues; Transgenic Organisms; Transmembrane Domain; apoptosis inducing factor; base; biological adaptation to stress; cytochrome c; day; design; interest; mitochondrial dysfunction; research study; sensor; wasting

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）：线粒体功能障碍是许多人类神经退行性疾病的原因。人们对线粒体感知和响应压力的机制知之甚少。我们实验室和其他实验室的最新结果表明，线粒体丝氨酸蛋白酶 Omi/HtrA2 是线粒体应激的传感器。由于蛋白酶结构域的点突变或 Omi-/- 敲除小鼠中 Omi 基因的破坏，mnd2 小鼠中的 Omi/HtrA2 失活会导致神经变性、肌肉萎缩，并在 40 日龄时因线粒体功能障碍而死亡。这些发现表明 Omi/HtrA2 在线粒体内发挥着至关重要的作用，是维持正常生理条件下线粒体稳态所必需的。由于 Omi/HtrA2 与细菌应激传感器 DegS 具有广泛的序列和结构同源性，因此我们假设 Omi/HtrA2 与 DegS 一样，是一种应激传感器，当其 PDZ 结构域识别错误折叠线粒体蛋白中暴露的 PDZ 结合基序时，该传感器就会被激活。激活的 Omi/HtrA2 然后触发蛋白水解级联，导致特定应激反应基因的激活。目前尚不清楚线粒体蛋白的性质以及触发 Omi/HtrA2 激活的展开应激的类型。线粒体 Omi/HtrA2 底物的性质也是未知的。 mnd2 和 Omi-/- 小鼠是研究 Omi/HtrA2 在细胞存活中的作用的优秀模型系统。为了研究Omi/HtrA2的保护功能和信号转导通路，我们在第一个和第二个具体目标中提出在Omi-/-和mnd2小鼠中进行转基因拯救实验，以明确Omi的PDZ和跨膜结构域在其保护功能中的作用。我们还建议研究 Omi-/- 和 mnd2 小鼠中野生型 Omi 的特定组织表达的表型。在其余的具体目标中，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 结构域的上游线粒体调节因子以及 Omi/HtrA2 的关键线粒体底物。我们预测 Omi/HtrA2 介导的特定线粒体底物的裂解可以向细胞核发送信号并激活 Omi/HtrA2 特异性应激反应基因的转录。我们建议通过微阵列分析来识别这些基因。了解线粒体应激传感的分子基础以及 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非常重要。最近在帕金森病患者中发现了降低 Omi/HtrA2 蛋白酶活性的突变，这表明 Omi/HtrA2 与某些帕金森病以及其他人类神经退行性疾病病例中的神经退行性疾病之间存在联系。因此，了解 Omi/HtrA2 在正常和疾病条件下的功能是具有明确健康意义的研究目标。