Role of cofilin pathology in mouse models of cognitive impairment

丝切蛋白病理学在小鼠认知障碍模型中的作用

• 批准号: 8486049
• 负责人: JAMES R BAMBURG
• 金额: $ 22.3万
• 依托单位: COLORADO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-06-01 至 2015-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8486049
• 关键词: Actins; Alzheimer' s Disease; Alzheimer' s disease model; Amyloid; Amyloid beta-Protein; Animals; Appearance; Atrophic; Axon; Behavior; Behavioral Assay; Binding; Biological Assay; Brain; Brain region; Bundling; Cells; Characteristics; Cognitive; Cognitive deficits; Data; Dementia; Dendrites; Development; Distal; Eukaryotic Cell; Family; Functional disorder; Future; Gene Activation; Genes; Glutamates; Human; Impaired cognition; In Vitro; Knock-in Mouse; Knockout Mice; Learning; Link; Mediating; Membrane; Memory; Microfilaments; Mitochondria; Modeling; Mus; Mutant Strains Mice; Mutate; Mutation; Myosin Type II; NADPH Oxidase; Neurites; Neurons; Neuropil Threads; Nutraceutical; Organism; Oxidative Stress; Pathology; Pathway interactions; Presenile Alzheimer Dementia; Prions; Production; Protein Dephosphorylation; Protein Precursors; Proteins; Reactive Oxygen Species; Resistance; Role; Senile Plaques; Severities; Shapes; Slice; Staging; Stress; Surface; Synapses; TNF gene; Tamoxifen; Testing; Therapeutic; Transgenic Mice; Triterpenes; actin depolymerizing factor; amyloid peptide; cell behavior; cofilin; cytokine; dimer; disulfide bond; familial Alzheimer disease; high reward; high risk; human subject; in vivo; inhibitor/antagonist; member; mild cognitive impairment; mouse model; mutant; neuron loss; overexpression; oxidation; presenilin; prevent; promoter; public health relevance; recombinase; research study; retinal rods; scaffold; stressor; tau Proteins; ursolic acid

DESCRIPTION (provided by applicant): Cofilin is a well-documented promoter of actin turnover in all eukaryotic cells. It undergoes dephosphorylation (activation) and oxidation to dimers when neurons are stressed by agents associated with Alzheimer disease (AD), all of which increase reactive oxygen species (ROS). This cofilin oxidation results within neurites in the formation of rod shaped cofilin-saturated actin bundles (rods). Rods immediately after their appearance are energy conserving, but when sustained causes neurite degeneration by blocking transport. Agents can induce rods via mitochondrial inhibition that generates ROS (e.g., excitotoxic glutamate) or via a prion-dependent pathway, probably involving membrane NADPH oxidase (NOX) activation. The latter pathway is activated by the proinflammatory cytokine TNF¿ as well as by soluble SDS-stable dimers/trimers of Amyloid-¿ (A¿d/t), the A¿ form that correlates best with dementia severity. Cofilin-actin rod formation causes the synapse elimination without neuronal cell death that is characteristic of amnestic mild cognitive impairment, an early stage in progression to Alzheimer disease. Our hypothesis is that it is cofilin-actin rods that initiate and exacerbate synaptic dysfunction typical of both sporadic (SAD) and familial AD (FAD). To demonstrate definitively that rod formation per se contributes to cognitive decline associated with AD, we need to develop a mouse model resistant to rod formation. Only a rod resistant mouse will allow us to answer the critical question: Do rods, themselves, cause synaptic loss or is synaptic loss due to stress-induced changes other than rod formation? It should be possible to make such a model since we have characterized a non-rod forming mutant of cofilin (K22Q), which is able to rescue normal behavior of cofilin-silenced cells as well as wild type cofilin. Three strategies are described to make a knock-in mouse in which cofilin K22Q will replace wild type cofilin. Two of these will make a conditional mouse which expresses wild type cofilin until mice are given tamoxifen. In these mice tamoxifen activates expression of Cre recombinase, which will initiate the inactivation of the wild type gene and the activation of the K22Q cofilin gene. The project is high risk since obtaining such a mouse is not guaranteed. Ultimately these mice will be used in behavioral assays to assess their cognitive ability under normal and stress conditions mimicking SAD or FAD. Finding that rods per se are necessary for synapse loss and cognitive impairment would make this project high reward because we already have identified a nutraceutical, the pentacyclic triterpene ursolic acid (UA), that blocks and reverses A¿d/t- and TNF¿-induced rods in cultured neurons and reverses oxidative stress markers and cognitive deficits in a brain oxidative stress mouse model. Thus we will determine if UA functions by reducing cofilin pathology and if it can be a major therapy for reducing cognitive deficits in mouse models of both SAD and FAD.

描述(由申请人提供)：Cofilin是所有真核细胞中肌动蛋白周转的一个有充分证据的促进器。当神经元受到与阿尔茨海默病(AD)相关的药物的压力时，它会经历去磷酸化(激活)和氧化成二聚体，所有这些都会增加活性氧物种(ROS)。这种胶粘蛋白氧化导致神经突起中形成杆状胶粘蛋白饱和肌动蛋白束(杆)。杆状物出现后立即保存能量，但持续使用时会阻止运输而导致轴突退化。药物可以通过线粒体抑制产生ROS(如兴奋性毒性谷氨酸)或通过蛋白依赖的途径诱导杆状细胞，可能涉及膜NADPH氧化酶(NOX)的激活。后一种途径由促炎细胞因子肿瘤坏死因子和可溶性十二烷基硫酸钠稳定的淀粉样二聚体/三聚体(A？d/t)激活，A？型与痴呆症的严重程度最相关。粘连蛋白-肌动蛋白棒的形成导致突触消除，而不会导致神经细胞死亡，这是遗忘性轻度认知障碍的特征，是发展为阿尔茨海默病的早期阶段。我们的假设是，正是粘连蛋白-肌动蛋白棒启动和加剧了突触功能障碍，这两种典型的散发性(SAD) 家族性AD(FAD)。为了明确地证明视杆形成本身有助于AD相关的认知能力下降，我们需要建立一个抵抗视杆形成的小鼠模型。只有抵抗杆状突触的小鼠才能让我们回答这个关键问题：杆状突触本身是导致突触丧失的原因，还是突触丧失是由于应激诱导的变化而不是杆状形成？应该有可能建立这样的模型，因为我们已经鉴定了一个非杆状形成Cofilin的突变体(K22Q)，它能够挽救Cofilin沉默的细胞的正常行为，以及野生型Cofilin。描述了三种策略来制造敲入小鼠，其中cofilin K22Q将取代野生型cofilin。其中两个将成为一种有条件的小鼠，在给小鼠服用他莫昔芬之前表达野生型Cofilin。在这些小鼠中，他莫昔芬激活了Cre重组酶的表达，这将启动野生型基因的失活 以及K22Q核心蛋白基因的激活。该项目风险很高，因为不能保证获得这样的鼠标。最终，这些小鼠将被用于行为测试，以评估它们在模拟SAD或FAD的正常和压力条件下的认知能力。发现杆本身是突触丧失和认知障碍所必需的，这将使这个项目获得高额回报，因为我们已经确定了一种营养物质，五环三萜熊果酸(UA)，它可以阻断和逆转A？d/t-和TNF？诱导的培养神经元中的杆，并在大脑氧化应激小鼠模型中逆转氧化应激标志物和认知障碍。因此，我们将确定UA是否通过减少粘连蛋白病理发挥作用，以及它是否可以成为减少SAD和FAD小鼠模型认知缺陷的主要治疗方法。