SYNAPTIC REGULATION OF ERK-MEDIATED AMYLOID-BETA METABOLISM

描述（由申请人提供）：阿尔茨海默病（AD）是由淀粉样蛋白（A β）肽作为毒性结构如淀粉样蛋白斑和可溶性寡聚物在脑中进行性积累而引发的。Ablation转化为这些有毒物质似乎是浓度依赖性的;因此，确定调节或降低Ablation水平的机制将提供对AD根本原因的基本理解，并可能导致新的治疗策略。我们小组最近的工作表明，5-羟色胺受体（5 HT-Rs）的活化导致AD小鼠模型中脑Ablation水平的急性降低（Cirrito等人，2011年）。全身性给予SSRI抗抑郁药或将5-羟色胺直接输注到AD小鼠模型的海马体中导致脑间质液（ISF）Ablast水平在几小时内下降25-30%，并且Ablast水平在单次给药后保持低水平超过24小时。如果用细胞外调节激酶（ERK）（原型MAP激酶）的抑制剂预处理小鼠，则Ablg 2的这种减少被完全阻断。ERK激活似乎增加APP的α-分泌酶切割，从而减少APP生成，并可能降低γ-分泌酶复合物几种组分的mRNA水平。长期给予SSRI 4个月显著降低了AD小鼠模型中的斑块负荷和CSF中的腺苷水平。本提案的目的是定义ERK信号通路和调节APP生成的相关分子，特别是从5-羟色胺受体到ERK激活，然后ERK到APP加工变化的通路。虽然许多分子可以激活ERK，并且ERK可以具有许多下游底物，但其活性受到显着调节，使得每个细胞外受体可以在细胞内产生非常特异性的作用。这种特异性部分通过将受体与适当的信号复合物连接的支架蛋白来控制。并不是所有激活ERK的分子都抑制Akt的产生;因此，我们将确定支架和定位蛋白（如Akt-抑制蛋白和Self）在为该信号传导途径提供靶特异性方面所起的作用。使用遗传学，生物化学和药理学的组合，以及体内微透析技术，我们开发了评估大脑ISF Ablation水平随着时间的推移，我们将评估细胞通路连接5 HT-Rs，ERK，和Ablation生成活小鼠。SSRIs是FDA批准的最安全的神经活性药物之一。不仅证明它们在降低AD水平方面的有效性，而且证明它们起作用的细胞机制，可以为测试这类化合物在人类受试者中减弱和可能预防AD的能力提供强大的动力。

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) is initiated by the progressive accumulation of amyloid-ß (Aß) peptide in the brain as toxic structures such as amyloid plaques and soluble oligomers. Conversion of Aß into these toxic species appears to be concentration-dependent; therefore identifying mechanisms that regulate or lower Aß levels will provide a fundamental understanding of the underlying causes of AD and may lead to new therapeutic strategies. Recent work by our group demonstrates that activation of serotonin receptors (5HT-Rs) cause an acute reduction in brain Aß levels in mouse models of AD (Cirrito et al., 2011). Systemic administration of SSRI antidepressants or direct infusion of serotonin into the hippocampus of a mouse model of AD causes brain interstitial fluid (ISF) Aß levels to decline by 25-30% within a few hours and with Aß levels remaining low for over 24 hours after a single administration. This reduction in Aß is completely blocked if mice are pretreated with inhibitors of the extracellular regulated kinase (ERK), the prototypical MAP kinase. ERK activation appears to increase α-secretase cleavage of APP, thus reducing Aß generation as well as may reduce mRNA levels of several components of the γ-secretase complex. Chronic administration of a SSRI for 4 months dramatically reduces plaque load and CSF Aß levels in a mouse model of AD. The objective of this proposal is to define the ERK signaling pathways and related molecules that regulate Aß generation, in particular the pathways that lead from serotonin receptor to activation of ERK and then ERK to changes in APP processing. While many molecules can activate ERK and ERK can have many downstream substrates, its activity is remarkably regulated so that each extracellular receptor can very specific effects within a cell This specificity is partially controlled via scaffold proteins that link receptors with appropriate signaling complexes. Not all molecules that activate ERK suppress Aß generation; therefore we will determine the role that scaffold and localization proteins, such as ß-arrestin and Self, play n providing target specificity for this signaling pathway. Using a combination of genetics, biochemistry, and pharmacology, as well as an in vivo microdialysis technique we developed to assess brain ISF Aß levels over time; we will assess the cellular pathways linking 5HT-Rs, ERK, and Aß generation in living mice. SSRIs are one of the safest neuroactive drugs approved by the FDA. A demonstration not only of their effectiveness in lowering Aß levels, but also the cellular mechanisms by which they act, may provide a strong impetus for testing this class of compounds for their ability to attenuate, and possibly prevent, AD in human subjects.