Peripheral Degradation of Amyloid Beta-Protein

描述(由申请人提供)：在阿尔茨海默病(AD)中异常积累的淀粉样β蛋白(ABETA)的稳态水平反映了通过β和伽马分泌酶产生的关键过程与由一种或多种蛋白酶降解的关键过程之间的平衡。虽然基于药物阻断分泌酶的治疗已经被广泛研究，但很少有工作研究激活或抑制ABETA降解酶的互补方法。最近的证据表明，在外周与ABeta紧密结合的分子(如抗体、明胶)可以降低大脑中ABeta的水平，这一反应类似于透析，表明中枢和外周ABeta池存在快速平衡。推而广之，我们假设增强外周ABeta的降解也会降低大脑ABeta的水平，我们将这一想法称为“外周退化假说”。为了验证这一新假说，并确定作用于外周ABeta降解的新药物靶点和小分子药效团，我们提出了以下目标。首先，为了直接验证外周降解假说，通过使用带有肝脏特异性启动子的腺病毒，ABeta降解蛋白水解酶将在APP转基因小鼠的外周过度表达。其次，为了确定体内外周的主要ABeta降解酶，将比较野生型小鼠和缺乏特定ABeta降解酶的小鼠静脉注射AB3eta的清除率。此外，人体血清中主要的ABeta降解酶将使用特定于蛋白水解酶的抑制剂进行鉴定。第三，与神经变性药物发现实验室合作，将使用人血清或重组蛋白酶作为ABeta降解活性的来源，对大约60,000个小分子药效载体进行高通量ABeta降解试验。总的来说，这项提案中概述的研究将评估--并有可能增强--外周ABeta降解蛋白酶作为AD新治疗靶点的潜力。

DESCRIPTION (provided by applicant): Steady-state levels of the amyloid beta-protein (ABeta), which accumulates abnormally in Alzheimer's disease (AD), reflect the balance between the key processes of production, via the beta- and gamma- secretases, and proteolytic degradation, by one or more proteases. While therapies based on pharmacological blockade of the secretases have been extensively studied, very little work has examined the complimentary approach of activating or disinhibiting ABeta degrading proteases. Recent evidence shows that molecules that bind tightly to ABeta in the periphery (e.g., antibodies, gelsolin) can decrease levels of ABeta in the brain in a reaction akin to dialysis, indicating that central and peripheral pools of ABeta exist in rapid equilibrium. By extension, we hypothesize that enhancing degradation of ABeta in the periphery will also lower brain ABeta levels, an idea we call the "peripheral degradation hypothesis." To test this new hypothesis, and to identify novel drug targets and small molecule pharmacophores acting on peripheral ABeta degradation, we propose the following Aims. First, to directly test the peripheral degradation hypothesis, ABeta-degrading proteases will be overexpressed exclusively in the periphery of APP transgenic mice by using adenovirus with liver-specific promoters. Second, to identify the principal ABeta-degrading proteases in the periphery in vivo, the rate of clearance of intravenously administered AB3eta will be compared in wildtype mice and in mice lacking specific ABeta-degrading proteases. In addition, the major ABeta-degrading proteases in human serum will be identified using protease-specific inhibitors. Third, in collaboration with the Laboratory for Drug Discovery in Neurodegeneration, a high throughput ABeta-degradation assay will be performed on approximately 60,000 small molecule pharmacophores using human serum or recombinant proteases as the source of ABeta degrading activity. Collectively, the studies outlined in this proposal will evaluate--and potentially enhance--the potential of peripheral ABeta-degrading proteases as novel therapeutic targets in AD.