Selective modulation of Gamma-secretase processing through substrate binding

许多证据支持这一假设，即靶向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）的化学物质正在被开发为AD治疗剂，因为它们 能够选择性地降低Ap 42。第一个被发现的GSM是非甾体类药物 非甾体类抗炎药（NSAID），降低Ap 42而不抑制APP加工。作为一个整体的GSM 最小程度地改变总Abeta产生，而不是转移γ-分泌酶切割Abeta的位置。的 GSM的机制仍然是未知的，尽管人们对它们的活动提出了不同的解释 包括：1）与γ-分泌酶的变构结合2）Rho-ROCK信号通路的抑制3） 早老素的构象变化或4）APP的二聚化减少。我们最近发现 使用新的GSM光亲和探针，这些药物不标记γ-分泌酶， 通过与底物APP结合来调节切割。我们假设GSM与APP的结合 转移APP-CTF在膜中的位置，导致γ-分泌酶切割改变。这 假设将通过以下具体目标进行检验：1）研究底物靶向如何 通过GSMs产生的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GSMs通过γ-分泌酶影响APP蛋白水解的特异性， 与其他底物比较和3）掺入非天然氨基酸以研究APPCTF的蛋白水解 y分泌酶。这些研究将为NSAID和其他GSM如何转变提供更多的见解 A（3）切割以及它们如何在体内发挥其保护作用。这项工作还将指导今后的努力， 设计更有效的GSMs，作为化学探针用于了解分泌酶的生物学 并作为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.