Selective modulation of Gamma-secretase processing through substrate binding

大量证据支持以下假设：靶向A[342]是一种理想的治疗策略 预防和/或治疗阿尔茨海默病(AD)，这是导致老年人痴呆的主要原因。 被称为γ-分泌酶调节剂(GSM)的化学物质正被开发为治疗AD的药物，因为它们 能够选择性地降低Ap42。第一批被发现的GSM是非类固醇抗炎药物 药物(非甾体抗炎药)，在不抑制APP处理的情况下降低Ap42。作为一个整体，GSM 最小限度地改变Abeta的总产量，而不是改变伽马分泌酶分解Abeta的位置。这个 尽管对GSM的活性提出了不同的解释，但GSM的作用机制仍不清楚 包括：1)变构与γ-分泌酶的结合2)抑制Rho-Rock信号通路3) 早老素的构象变化或4)APP的二聚化减少。我们最近发现 使用新型GSM光亲和探针，这些药物不标记γ-分泌酶，而是相反 通过与底物APP结合来调节切割。我们假设GSM对APP的绑定 改变APP-CTF在膜中的位置，导致伽马分泌酶裂解的改变。这 假设将通过以下具体目标进行检验：1)调查底物靶向 通过GSM产生AP切割模式的转变，使用分子生物学和 蛋白质生物化学2)确定GSM通过γ-分泌酶影响APP蛋白分解的特异性 与其他底物的比较和3)掺入非天然氨基酸研究APPCTF的蛋白降解 由y-分泌酶。这些研究将为非甾体抗炎药和其他GSM如何转变提供更多的洞察力 A(3)卵裂以及它们如何在体内发挥保护作用。这项工作还将指导今后的努力 设计更有效的GSM，作为了解分泌酶生物学的化学探针 作为治疗阿尔茨海默病的潜在疗法。

Numerous lines of evidence support the hypothesis that targeting A[342 is an ideal therapeutic strategy to prevent and/or treat Alzheimer's disease (AD), the major cause of dementia among the elderly. Chemicals called y-secretase modulators (GSMs), are being developed as AD therapeutics because they are able to selectively decrease Ap42. The first GSMs to be discovered were non-steroidal antiinflammatory drugs (NSAIDs), which lower Ap42 without inhibition of APP processing. As a whole GSMs minimally alter total Abeta production and instead shift where gamma-secretase cleaves Abeta. The mechanism of GSMs is still unknown although different explanations for their activity have been proposed including: 1) allosteric binding to y-secretase 2) inhibition of the Rho-ROCK signaling pathway 3) conformational changes in presenilin or 4) decreased dimerization of APP. We have recently discovered using novel GSM photoaffinity probes that these drugs do not label the y-secretase enzyme but instead modulate cleavage by binding to the substrate, APP. We hypothesize that binding of APP by GSMs shifts the position of APP-CTF in the membrane resulting in altered gamma-secretase cleavage. This hypothesis will be tested through the following specific aims: 1) investigate how substrate targeting by GSMs produces a shift in the cleavage pattern of Ap using a combination of molecular biology and protein biochemistry 2) determine the specificity of GSMs for affecting APP proteolysis by y-secretase in comparison to other substrates and 3) incorporate unnatural amino acids to study proteolysis of APPCTF by y-secretase. These studies will provide additional insight into how NSAIDs and other GSMs shift A(3 cleavage and how they exert their protective effects in vivo. This work will also guide future efforts to design more potent GSMs which will be useful as chemical probes for understanding the biology of ysecretase and as potential therapeutics for Alzheimer's disease.