SYNAPTIC REGULATION OF ERK-MEDIATED AMYLOID-BETA METABOLISM

描述(申请人提供)：阿尔茨海默病(AD)是由淀粉样蛋白(A？)多肽在大脑中逐渐积累而成的有毒结构，如淀粉样斑块和可溶性寡聚体。Aü转化为这些有毒物种似乎是浓度依赖的；因此，识别调节或降低Aü水平的机制将有助于从根本上理解AD的潜在原因，并可能导致新的治疗策略。我们小组最近的工作表明，激活5-羟色胺受体(5HT-Rs)会导致阿尔茨海默病(AD)小鼠模型脑Aü水平的急剧下降(Cirrito等人，2011年)。全身应用SSRI抗抑郁药或将5-羟色胺直接注入AD小鼠模型的海马区，可导致脑间质液(ISF)的Aü水平在几小时内下降25-30%，并且在单次给药后24小时以上保持较低水平。如果用细胞外调节激酶(ERK)的抑制剂(典型的MAP激酶)对小鼠进行预处理，Aü的这种减少完全被阻断。ERK的激活似乎增加了APP的α-分泌酶的裂解，从而减少了Aü的生成，并可能降低了γ-分泌酶复合体的几个组分的基因水平。在AD小鼠模型中，长期服用SSRI 4个月可显著降低斑块负荷和脑脊液Aü水平。本研究的目的是明确ERK信号通路和相关分子调节Aü生成，特别是从5-羟色胺受体到ERK激活，再到ERK在APP处理过程中的变化的通路。虽然许多分子可以激活ERK，并且ERK可以有许多下游底物，但其活性受到显著调节，因此每个细胞外受体都可以在细胞内产生非常特异的作用。这种特异性部分是通过将受体与适当的信号复合体连接起来的支架蛋白来控制的。并不是所有激活ERK的分子都抑制Aü生成；因此，我们将确定支架和定位蛋白，如ç-arrestin和self，在为这一信号通路提供靶标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，以及我们开发的体内微透析技术，我们开发了一种随时间推移评估大脑ISF？水平的技术；我们将评估在活着的小鼠中连接5HT-Rs、ERK和A？代的细胞通路。SSRIs是FDA批准的最安全的神经活性药物之一。不仅证明了它们在降低Aü水平方面的有效性，而且还证明了它们的细胞机制，这可能为测试这类化合物在人类受试者中减弱并可能预防阿尔茨海默病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.