Induced Dimerization of the Amyloid Precursor Protein Leads to Decreased Amyloid-β Protein Production
Induced Dimerization of the Amyloid Precursor Protein Leads to Decreased Amyloid-β Protein Production
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DOI：
10.1074/jbc.m109.038646
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发表时间：
2009-10-16
影响因子：
4.8
通讯作者：
Koo, Edward H.
中科院分区：
文献类型：
--
作者：
Eggert, Simone;Midthune, Brea;Koo, Edward H.
淀粉样前体蛋白（APP）在阿尔茨海默病（AD）发病机制中起着重要作用，因为β-和γ-分泌酶的连续裂解导致淀粉样β（A β）肽的产生，A β肽是AD个体脑中淀粉样斑块的关键成分。在几项研究中，APP最近被证明可以形成同源二聚体，并且这一事件似乎会影响A β的产生。然而，这些研究依赖于A β序列本身内的APP突变，其可能通过干扰不依赖于二聚化的分泌酶裂解来影响APP加工。因此，APP二聚化对A β产生的影响仍不清楚。为了解决这个问题，我们比较了组成型半胱氨酸诱导的APP二聚化的方法与不需要在A β序列内引入突变的可调节的二聚化系统。为此，我们通过将FK 506结合蛋白（FKBP）的结构域融合到APP的C末端来产生APP嵌合分子。添加合成的膜渗透药物AP 20187诱导APP-FKBP嵌合体的快速二聚化。使用该系统，我们能够诱导高达70%的APP二聚体。我们的结果表明，APP-FKBP的受控同源二聚化导致转染的N2 a细胞中总A β水平降低50%。用β-分泌酶裂解的直接前体C99/SPA 4CT-FKBP获得了类似的结果。此外，在该系统中APP二聚化后，不存在不同A β肽种类的调节。两者合计，我们的研究结果表明，APP二聚化可以直接影响γ-分泌酶的加工和二聚化是不需要的A β生产。
The amyloid precursor protein (APP) plays a central role in Alzheimer disease (AD) pathogenesis because sequential cleavages by beta- and gamma-secretase lead to the generation of the amyloid-beta (A beta) peptide, a key constituent in the amyloid plaques present in brains of AD individuals. In several studies APP has recently been shown to form homodimers, and this event appears to influence A beta generation. However, these studies have relied on APP mutations within the A beta sequence itself that may affect APP processing by interfering with secretase cleavages independent of dimerization. Therefore, the impact of APP dimerization on A beta production remains unclear. To address this question, we compared the approach of constitutive cysteine-induced APP dimerization with a regulatable dimerization system that does not require the introduction of mutations within the A beta sequence. To this end we generated an APP chimeric molecule by fusing a domain of the FK506-binding protein (FKBP) to the C terminus of APP. The addition of the synthetic membrane-permeant drug AP20187 induces rapid dimerization of the APP-FKBP chimera. Using this system we were able to induce up to 70% APP dimers. Our results showed that controlled homodimerization of APP-FKBP leads to a 50% reduction in total A beta levels in transfected N2a cells. Similar results were obtained with the direct precursor of beta-secretase cleavage, C99/SPA4CT-FKBP. Furthermore, there was no modulation of different A beta peptide species after APP dimerization in this system. Taken together, our results suggest that APP dimerization can directly affect gamma-secretase processing and that dimerization is not required for A beta production.