The Cell Biology of Neurodegeneration Caused by the Prion Protein

朊病毒蛋白引起的神经变性的细胞生物学

• 批准号: 7968761
• 负责人: Ramanujan S Hegde
• 金额: $ 30.73万
• 依托单位: EUNICE KENNEDY SHRIVER NATIONAL INSTITUTE OF CHILD HEALTH & HUMAN DEVELOPMENT
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7968761
• 关键词: Anabolism; Animals; Biogenesis; Biological Models; Bovine Spongiform Encephalopathy; Cell Culture Techniques; Cell Death; Cells; Cellular biology; Cessation of life; Classification; Cytosol; Defect; Disease; Endoplasmic Reticulum; Event; Functional disorder; Future; Genes; Goals; Golgi Apparatus; Inherited; Lead; Light; Locales; Location; Lysosomes; Mediating; Membrane Glycoproteins; Membrane Proteins; Metabolism; Molecular; Mus; Mutation; Nerve Degeneration; Neurodegenerative Disorders; Neuronal Dysfunction; Pathway interactions; Prion Diseases; Prions; Process; Property; Protein Biosynthesis; Proteins; Quality Control; Recruitment Activity; Route; Site; Therapeutic Intervention; Transgenic Mice; base; cytotoxic; disease-causing mutation; in vivo; interest; mutant; neurodegenerative phenotype; neuron loss; protein aggregate; protein metabolism; protein misfolding; trafficking

The prion protein (PrP) is a widely expressed and highly conserved cell surface glycoprotein of uncertain function. Aberrant metabolism of PrP is responsible for a variety of neurodegenerative diseases in both people and animals. These diseases include the transmissible 'prion diseases' such as bovine spongiform encephalopathy, as well as inheritable neurodegenerative diseases caused by mutations in the PrP gene. In neither case is the pathway(s) leading to cell death and neuronal damage understood. The overall goal of this project is to define the pathways of PrP-mediated neurodegeneration. To achieve this goal, we are studying the molecular pathways of PrP biosynthesis, intracellular trafficking, metabolism, and degradation. A quantitative analyses of these events are expected to shed light on how the various inherited mutations in PrP influence its biosynthesis or metabolism in a manner that leads the cellular dysfunction. Our analysis suggests that at least two cytotoxic forms of PrP (termed CtmPrP and cyPrP) are during the initial translocation of PrP into the endoplasmic reticulum (ER). Transgenic mice have now been created to determine whether CtmPrP-mediated neurodegeneration and cyPrP-mediated neurodegeneration can be averted in vivo by modulating this newly discovered step during PrP biogenesis. We are also investigating the pathways by which the various forms of PrP are normally metabolized by the cell to determine whether modulation of these events are involved in the progression of neurodegeneration. It is anticipated that a combination of defects in biosynthesis and/or clearance of certain forms of PrP collaborate to eventually cause neuronal dysfunction and death. Conversely, manipulation of these events may be able to slow or reverse the neurodegenerative process in these diseases. In parallel, we are also performing a systematic analysis of the biosynthesis, trafficking, and metabolism of disease-associated PrP mutants. The aim of these studies is to identify precisely the cellular locale and mechanism of PrP misfolding that initiates the disease process. Our current analyses have found that for a large number of mutants, misfolded PrP is found in a post-ER location, from where it is routed to lysosomes for degradation. This observation is notable because it suggests that the misfolded PrP species have somehow escaped the normal cellular quality control mechanisms in the ER, and instead use yet unidentified quality control pathways in the Golgi. These new pathways of quality control are now being investigated. In parallel studies, the downstream consequences of PrP misfolding and aggregation are being studied to identify the mechanism by which these events lead to cellular dysfunction. We have now found that these aggregates recruit various cellular factors, therby depleting their functional availability. One such factor is of particular importance because its disruption in mice leads directly to a neurodegenerative phenotype reminiscent of diseases caused by PrP. And finally, we are investigating the general properties of protein aggregates, which are associated with a wide range of diseases. We have discovered the the presence of cytosolic aggregates can significantly influence the pathways of normal cellular quality control. In one specific example, we have found that aggregates influence the fate of mislocalized secretory and membrane proteins. Rather than being rapidly degraded, the presence of aggregates causes these proteins to remain undegraded in the cytosol. This leads to their co-aggregation, facilitating the propogation of the existing aggregates and causing cell death. The molecular basis of this phenomenon is now being investigated.

朊病毒蛋白（PrP）是一种广泛表达且高度保守的细胞表面糖蛋白，其功能不确定。 PrP 代谢异常是导致人和动物多种神经退行性疾病的原因。这些疾病包括传染性“朊病毒病”，例如牛海绵状脑病，以及由 PrP 基因突变引起的遗传性神经退行性疾病。在这两种情况下，导致细胞死亡和神经元损伤的途径都未被了解。该项目的总体目标是确定 PrP 介导的神经变性的途径。为了实现这一目标，我们正在研究 PrP 生物合成、细胞内运输、代谢和降解的分子途径。对这些事件的定量分析有望揭示 PrP 的各种遗传突变如何影响其生物合成或代谢，从而导致细胞功能障碍。 我们的分析表明，在 PrP 最初易位到内质网 (ER) 的过程中，至少存在两种​​细胞毒性形式的 PrP（称为 CtmPrP 和 cyPrP）。现在已经创建了转基因小鼠，以确定是否可以通过调节 PrP 生物发生过程中这一新发现的步骤来在体内避免 CtmPrP 介导的神经变性和 cyPrP 介导的神经变性。我们还在研究细胞正常代谢各种形式的 PrP 的途径，以确定这些事件的调节是否参与神经退行性变的进展。预计某些形式的 PrP 的生物合成和/或清除缺陷的组合最终会导致神经元功能障碍和死亡。相反，操纵这些事件可能能够减缓或逆转这些疾病的神经退行性过程。 与此同时，我们还对疾病相关 PrP 突变体的生物合成、运输和代谢进行系统分析。这些研究的目的是准确识别引发疾病过程的 PrP 错误折叠的细胞部位和机制。我们目前的分析发现，对于大量突变体，错误折叠的 PrP 存在于 ER 后位置，从那里它被路由到溶酶体进行降解。这一观察结果值得注意，因为它表明错误折叠的 PrP 物种以某种方式逃脱了 ER 中的正常细胞质量控制机制，而是使用高尔基体中尚未识别的质量控制途径。目前正在研究这些新的质量控制途径。 在平行研究中，正在研究 PrP 错误折叠和聚集的下游后果，以确定这些事件导致细胞功能障碍的机制。我们现在发现这些聚集体招募各种细胞因子，从而耗尽它们的功能可用性。其中一个因素尤为重要，因为它在小鼠体内的破坏直接导致神经退行性表型，让人想起由 PrP 引起的疾病。 最后，我们正在研究与多种疾病相关的蛋白质聚集体的一般特性。我们发现胞质聚集体的存在可以显着影响正常细胞质量控制的途径。在一个具体的例子中，我们发现聚集体影响错误定位的分泌蛋白和膜蛋白的命运。聚集体的存在导致这些蛋白质在细胞质中保持不降解，而不是被快速降解。这导致它们共同聚集，促进现有聚集体的传播并导致细胞死亡。目前正在研究这种现象的分子基础。