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: 8664331
• 负责人: JAMES R BAMBURG
• 金额: $ 18.59万
• 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 2016-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8664331
• 关键词: Actins; Alzheimer' s Disease; Alzheimer' s disease model; Amyloid; Amyloid beta-Protein; Amyloid beta-Protein Precursor; 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; 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更新的充分记录的启动子。当神经元受到与阿尔茨海默病（AD）相关的试剂的应激时，它经历去磷酸化（活化）和氧化成二聚体，所有这些都会增加活性氧（ROS）。这种cofilin氧化导致神经突内形成棒状cofilin饱和的肌动蛋白束（棒）。在它们出现后立即出现的杆是能量保存的，但是当持续时，通过阻断运输而导致神经突变性。药剂可以通过产生ROS的线粒体抑制来诱导视杆细胞（例如，兴奋性毒性谷氨酸）或通过朊病毒依赖性途径，可能涉及膜NADPH氧化酶（NOX）活化。后一种途径由促炎细胞因子TNF ²以及淀粉样蛋白（A ² d/t）的可溶性SDS稳定二聚体/三聚体（A ² d/t）激活，淀粉样蛋白是与痴呆严重程度最相关的A ²形式。Cofilin-actin杆的形成导致突触消除而没有神经元细胞死亡，这是遗忘性轻度认知障碍的特征，这是阿尔茨海默病进展的早期阶段。我们的假设是，它是cofilin-actin杆启动和加剧突触功能障碍典型的散发性（SAD） 家族性AD（FAD）为了明确地证明杆形成本身有助于与AD相关的认知下降，我们需要开发一种抵抗杆形成的小鼠模型。只有一个杆抵抗小鼠将允许我们回答关键的问题：杆，本身，导致突触损失或突触损失是由于压力引起的变化以外的杆的形成？由于我们已经表征了cofilin的非杆状形成突变体（K22 Q），其能够拯救cofilin沉默细胞以及野生型cofilin的正常行为，因此应该可以制作这样的模型。描述了三种策略来制备敲入小鼠，其中切丝蛋白K22 Q将取代野生型切丝蛋白。其中两个将产生表达野生型cofilin的条件小鼠，直到小鼠被给予他莫昔芬。在这些小鼠中，他莫昔芬激活Cre重组酶的表达，这将启动野生型基因的失活 以及K22 Q cofilin基因的激活。该项目是高风险的，因为无法保证获得这样的鼠标。最终，这些小鼠将用于行为测定，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。发现杆本身是突触丢失和认知障碍所必需的，这将使该项目获得高回报，因为我们已经确定了一种营养药物，五环三萜熊果酸（UA），它可以阻断和逆转培养神经元中A <$d/t和TNF <$d诱导的杆，并逆转脑氧化应激小鼠模型中的氧化应激标记和认知缺陷。因此，我们将确定UA是否通过减少cofilin病理而起作用，以及它是否可以成为减少SAD和FAD小鼠模型中认知缺陷的主要疗法。