Control of APP processing and Aβ generation level by BACE1 enzymatic activity and transcription
Control of APP processing and Aβ generation level by BACE1 enzymatic activity and transcription
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DOI：
10.1096/fj.05-4986com
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发表时间：
2006-02-01
期刊：
影响因子：
4.8
通讯作者：
Song, Weihong
中科院分区：
文献类型：
--
作者：
Li, Yu;Zhou, Weihui;Song, Weihong
淀粉样蛋白（A β）沉积是阿尔茨海默病（AD）神经病理学的特征之一。β -分泌酶是一种β位点APP切割酶1 (BACE1)，是a- β生物合成的必需酶。尽管BACE1的抑制被认为是AD的有效治疗靶点，但BACE1在调节APP加工和a β生成中的酶动力学尚未完全确定。为了研究这一问题，我们利用外皮激素诱导系统在神经细胞系N2ABP1和非神经细胞系E2BP1中建立了严格控制的诱导BACE1基因表达。诱导剂ponasterone a处理BACE1稳定诱导细胞后，BACE1蛋白水平呈时间和剂量依赖性增加，β分泌酶产物APP CTF β的生成随BACE1蛋白表达水平成比例增加。然而，A β 40/42的表达急剧增加至平台水平，BACE1的表达增加相对较小。虽然进一步增加BACE1的表达增加了β分泌酶的活性，但对A β的产生没有额外的影响。此外，我们发现BACE1 mRNA水平和BACE1启动子活性显著低于APP mRNA水平和APP启动子活性。我们的数据表明，在正常情况下，较低的BACE转录是导致少数APP经历淀粉样变途径和相对较低的A β生成的原因，并且BACE1的轻微增加可以诱导A β生成的急剧升高，这表明BACE1的增加可能会增加病理状态下的神经斑块形成。
Deposition of amyloid beta protein (A beta) is one of the characteristic features of Alzheimer's disease (AD) neuropathology. Beta-secretase, a beta-site APP cleaving enzyme 1 (BACE1), is essential for A beta biosynthesis. Although inhibition of BACE1 is considered a valid therapeutic target for AD, the enzymatic dynamics of BACE1 in regulating APP processing and A beta generation has not yet been fully defined. To examine this issue, tightly controlled inducible BACE1 gene expression was established in the neuronal cell line N2ABP1 and the non-neuronal cell line E2BP1 using an ecdysone-inducible system. The BACE1 protein level was increased in a time- and dosage-dependent manner in the inducible BACE1 stable cells by treatment with inducer ponasterone A. The generation of APP CTF beta, the beta-secretase product, increased proportionally with the level of BACE1 protein expression. However, A beta 40/42 production sharply increased to the plateau level with a relatively small increase in BACE1 expression. Although further increasing BACE1 expression increased beta-secretase activity, it had no additional effect on A beta production. Furthermore, we found that BACE1 mRNA levels and BACE1 promoter activity were significantly lower than APP mRNA levels and APP promoter activity. Our data demonstrate that lower BACE transcription is responsible for the minority of APP undergoing the amyloidogenic pathway and relatively lower A beta production in the normal conditions, and that a slight increase in BACE1 can induce a dramatic elevation in A beta production, indicating that the increase in BACE1 can potentially increase neuritic plaque formation in the pathological condition.