Tau Conformation in Tauopathies and Neuronal Function

描述(由申请人提供)：牛磺酸病理学是多种神经系统疾病的显著特征，统称为牛顿病。这些疾病包括阿尔茨海默病(AD)、进行性核上性麻痹(PSP)、皮质基底膜变性(CBD)、皮克氏病和与17号染色体相关的帕金森氏症的额颞部痴呆。其中一些疾病是遗传性的，与tau基因突变有关，但正常的tau也可能是病理性的。虽然每一种肌萎缩侧索硬化症都有特定的疾病表型、组织学表现、形态和神经表现，但它们都与tau的错误折叠和tau的磷酸化改变有关。这种临床多样性阻碍了对共同致病机制的探索。最近的两个发现为tau病理提供了新的见解。第一个是鉴定构象特异性tau抗体，它识别一些但不是所有的tau病理形式，提示tau病中的构象多样性。第二，我们最近展示了tau氨基末端的一个生物活性基序，它激活了涉及蛋白磷酸酶1(PP1)和糖原合成酶激酶3b(GSK3b)的信号通路：17个氨基酸组成一个磷酸酶激活结构域(PAD)，为tau病中改变的激酶活性提供了分子基础。这一应用的中心假设是，tau的致病形式代表了正常生物学功能的错误调节，因为tau是定位和调节基于微管的激酶和磷酸酶的支架。到目前为止，这种PAD区域在所有病理形式的tau中都有异常的表现，是至少两种tau毒性的必要组成部分：抑制快速轴突运输和培养中的细胞毒性。我们认为在不同的疾病中，tau的病理形式在结构上是不同的，其毒性程度是不同的。本应用中的实验将表征不同来源的tau的构象。 使用真实的和人工合成的聚集体，评估它们在影响PP1/GSK3b途径和轴突运输方面的相对毒性。我们进一步假设，不同tau构象的毒性可能受到疾病特异性tau磷酸化和构象模式的调节。这些改变的疾病特定模式将被确定为AD、PSP和CBD。我们将对tau的正常和病理功能进行分析，以检验tau作为支架将特定的激酶和磷酸酶定位和调节到微管的假设。我们将重点研究tau在轴突微管富集区PP1和GSK3b的正常调节中的作用，并确定这些磷酸转移酶与tau的相互作用区域。Tau对PP1/GSK3b通路的定位允许对这些活动进行空间和时间控制，我们认为PAD的呈递仅限于正常神经元中特定的亚细胞间隔，并在病理状态下解除调控。与这个模型一致的是，tau、PP1和GSK3b都与神经元发育有关。Tau异构体、构象和磷酸化的发育调控可能在神经元发育中起关键作用。我们认为，在正常的神经元发育和功能过程中，PAD的调节呈现对于轴突的生长和轴突蛋白的靶向是重要的，这使我们能够理解错误折叠的tau的毒性和正常tau功能之间的关系。

DESCRIPTION (provided by applicant): Taupathology is a prominent feature of multiple neurological diseases known collectively as tauopathies. These include Alzheimer's disease (AD), Progressive Supranuclear Palsy (PSP), Cortical Basal Degeneration (CBD), Pick's disease, and Frontotemporal Dementia with Parkinsonism linked to chromosome 17. Some of these diseases are hereditary, associated with mutations in the tau gene, but normal tau may also be pathological. Although each tauopathy has a disease specific phenotype, histological presentation, morphology, and neurological presentation, all of them are associated with misfolded tau and altered phosphorylation of tau. The search for a common pathogenic mechanism has been hindered by this clinical diversity. Two recent findings provide new insight into tau pathology. The first is identification of conformation specific tau antibodies that recognize some, but not all, pathological forms of tau, suggesting conformational diversity within the tauopathies. Second, our recent demonstration of a biologically active motif in the tau amino terminus that activates a signaling pathway involving protein phosphatase 1 (PP1) and glycogen synthase kinase 3b (GSK3b): 17 amino acids comprising a Phosphatase Activation Domain (PAD) provides a molecular basis for altered kinase activities in tauopathies. The central hypothesis of this application is that pathogenic forms of tau represent a misregulation of a normal biological function for tau as a scaffold for localization and regulation of microtubule based kinases and phosphatases. This PAD region is aberrantly displayed in all pathological forms of tau examined to date and is a necessary component of at least two forms of tau toxicity: inhibition of fast axonal transport and cell toxicity in culture. We propose that pathological forms of tau in different tauopathies are structurally distinct with variable degrees f toxicity. Experiments in this application will characterize the conformations of tau from different tauopathies and evaluate their relative toxicity in affecting the PP1/GSK3b pathway and axonal transport using authentic and synthetic aggregates. We further hypothesize that toxicity of different tau conformers may be modulated by disease specific patterns of tau phosphorylation and conformation. Disease specific patterns of these alterations will be determined for AD, PSP and CBD. Normal and pathological functions of tau will be analyzed to test the hypothesis that tau serves as a scaffold for localizing and regulating specific kinases and phosphatases to microtubules. We will focus on the role of tau in the normal regulation of PP1 and GSK3b in microtubule rich domains of the axon and identify interaction domains with tau for these phosphotransferases. The localization of the PP1/GSK3b pathway by tau allows for spatial and temporal control of these activities and we propose that presentation of PAD is restricted to specific subcellular compartments in normal neurons and deregulated in pathological states. Consistent with this model, tau, PP1 and GSK3b have all been implicated in neuronal development. Developmental regulation of tau isoforms, conformation, and phosphorylation may play critical roles in neuronal development. We suggest that the regulated presentation of PAD is important for neurite outgrowth and targeting of axonal proteins during normal neuronal development and function, allowing us to understand the relationship between the toxicity of misfolded tau and normal tau function.