ADF/cofilin-actin rods in neurodegenerative diseases

描述（由申请人提供）：在几乎所有培养的海马神经元的神经突内，瞬态ATP消耗迅速诱导主要由肌动蛋白和ADF/cofilin （AC）组成的杆状结构。杆状细胞的形成，隔离了一部分肌动蛋白，但实际上是所有的AC，对应激神经元是暂时有益的，因为它节省了与肌动蛋白周转相关的ATP。然而，杆状体可以完全阻塞神经突，阻断运输并导致远端神经突萎缩。杆状体是阿尔茨海默病（AD）大脑的突出特征，而不是缺乏淀粉样斑块的控制性人脑。在Niemann-Pick病型动物（NPC1）和表达突变的人类淀粉样蛋白前体蛋白（APP）的转基因小鼠（Tg2576）的大脑中也发现了类似的结构。在培养的神经元和小鼠脑切片中，视杆细胞由缺血、过氧化物、一氧化氮和兴奋毒性谷氨酸诱导。在高达20%的海马神经元中，无论是来自CA1区还是CAS区，AD淀粉样蛋白β肽（Ab）也诱导杆状体：诱导是剂量依赖性的，在治疗后6小时内发生，并在12-24小时后达到平台期。与混乱肽对照相比，小至10 nM的Ab寡聚物具有显著的效果。我们将探讨只有一部分神经元对Ab敏感的本质。杆状体阻断APP的囊泡运输。含有APP的囊泡聚集在杆状体的末端和侧面。在这些停滞的囊泡中存在β -分泌酶裂解的APP，这表明这些可能是Ab产生和/或转化为更具破坏性的构象的位点。综上所述，这些结果提示了一种阿尔茨海默病的模型，在这种模型中，神经元应激（包括家族性阿尔茨海默病中形成的Ab）诱导杆状体，阻止囊泡运输并增加毒性Ab，从而在邻近细胞中诱导杆状体。这种模型可以解释淀粉样斑块的形成，它会在最初的损伤部位周围扩大。利用细胞培养和器官型脑切片，我们将确定：1)杆状体的形成需要cofilin的哪些活性；2)是否可以识别出阻止棒状细胞形成的AC突变；3)如果棒材促进Ab的产生或寡聚；4)是什么让一组神经元对Ab敏感；5)器官型脑切片如何被用作模型来研究视杆细胞在哪里形成以及它们是如何破坏突触的。与公众健康相关：老年痴呆症极大地影响了美国老年人的生活质量，85岁以上老年人中有25%受到影响。这一建议验证了AD进展的新假设，并确定了可能的靶向干预位点。

DESCRIPTION (provided by applicant): Within neurites of nearly all cultured hippocampal neurons, transient ATP depletion rapidly induces rod- shaped structures composed primarily of actin and ADF/cofilin (AC). Rod formation, which sequesters a portion of the actin but virtually all of the AC, is transiently beneficial to the stressed neuron because it spares ATP associated with actin turnover. However, rods can completely occlude the neurite, blocking transport and causing distal neurite withering. Rods are prominent features of Alzheimer's disease (AD) brain but not of control human brain lacking amyloid plaques. Similar structures are found in brains of animals with Niemann-Pick disease typed (NPC1) and of transgenic mice (Tg2576) expressing mutant human amyloid precursor protein (APP). In cultured neurons and mouse brain slices, rods are induced by ischemia, peroxide, NO, and excitotoxic glutamate. In up to 20% of hippocampal neurons, whether from region CA1 or CAS, the AD amyloid beta peptide (Ab) also induces rods: induction is dose-dependent, occurring within 6 h after treatment and reaching a plateau 12-24 h later. As little as 10 nM of Ab oligomer has a significant effect compared to the scrambled peptide control. The nature of the sensitivity of only a subset of neurons to Ab will be explored. Rods block vesicular transport of APP. APP-containing vesicles accumulate at the ends and sides of rods. Within these stalled vesicles is beta-secretase cleaved APP, suggesting that these may be sites of Ab production and/or conversion into more damaging conformers. Taken together, these results suggest a model for AD in which neuronal stress, including Ab formed in familial AD, induces rods that stall vesicle transport and increase toxic Ab, thus inducing rods in neighboring cells. Such a model could explain the formation of amyloid plaques, which would enlarge around the initial site of injury. Using cell culture and organotypic brain slices, we will determine: 1) what activities of cofilin are required for rod formation; 2) if mutations in AC can be identified that prevent rod formation; 3) if rods promote the production or oligomerization of Ab; 4) what makes a subset of neurons sensitive to Ab: and 5) how organotypic brain slices can be used as a model to study where rods form and how they disrupt synapses. Relevance to public health: AD dramatically impacts life quality of senior Americans, affecting 25% of those > 85. This proposal tests a new hypothesis for AD progression and identifies possible sites for targeted intervention.