Peripheral Degradation of Amyloid Beta-Protein

描述（由申请人提供）：淀粉样蛋白- β蛋白（ABeta）的稳态水平，在阿尔茨海默病（AD）中异常积累，反映了通过β和γ分泌酶产生的关键过程与一种或多种蛋白酶的蛋白水解降解之间的平衡。虽然基于药物阻断分泌酶的治疗方法已被广泛研究，但很少有工作研究了激活或去抑制β降解蛋白酶的补充方法。最近的证据表明，与外周β紧密结合的分子（如抗体、凝胶）可以在类似透析的反应中降低大脑中β的水平，这表明中枢和外周β池处于快速平衡状态。延伸开来，我们假设增强外周β的降解也会降低大脑的β水平，我们称之为“外周降解假说”。为了验证这一新假设，并确定新的药物靶点和作用于外周β降解的小分子药效团，我们提出以下目标。首先，为了直接验证外周降解假说，我们将利用带有肝脏特异性启动子的腺病毒，在APP转基因小鼠的外周特异性过表达abeta降解蛋白酶。其次，为了确定体内外周主要的abeta降解蛋白酶，将在野生型小鼠和缺乏特异性abeta降解蛋白酶的小鼠中比较静脉注射AB3eta的清除率。此外，人类血清中主要的β -降解蛋白酶将使用蛋白酶特异性抑制剂进行鉴定。第三，与神经退行性疾病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个小分子药效团进行高通量ABeta降解试验。总的来说，本提案中概述的研究将评估并潜在地增强外周β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.