Kuzuya Akira, Uemura Kengo, Kitagawa Naoyuki, Aoyagi Nobuhisa, Kihara Takeshi, Ninomiya Haruaki, Ishiura Shoichi, Takahashi Ryosuke, Shimohama Shun
Department of Neurology, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
J Neurosci Res. 2007 Jan;85(1):153-65. doi: 10.1002/jnr.21104.
One of the pathologic hallmarks of Alzheimer's disease is the excessive deposition of beta-amyloid peptides (Abeta) in senile plaques. Abeta is generated when beta-amyloid precursor protein (APP) is cleaved sequentially by beta-secretase, identified as beta-site APP-cleaving enzyme 1 (BACE1), and gamma-secretase, a putative enzymatic complex containing presenilin 1 (PS1). However, functional interaction between PS1 and BACE1 has never been known. In addition to this classical role in the generation of Abeta peptides, it has also been proposed that PS1 affects the intracellular trafficking and maturation of selected membrane proteins. We show that the levels of exogenous and endogenous mature BACE1 expressed in presenilin-deficient mouse embryonic fibroblasts (PS-/-MEFs) were reduced significantly compared to those in wild-type MEFs. Moreover, the levels of mature BACE1 were increased in human neuroblastoma cell line, SH-SY5Y, stably expressing wild-type PS1, compared to native cells. Conversely, the maturation of BACE1 was compromised under the stable expression of dominant-negative mutant PS1 overexpression. Immunoprecipitation assay showed that PS1 preferably interacts with proBACE1 rather than mature BACE1, indicating that PS1 can be directly involved in the maturation process of BACE1. Further, endogenous PS1 was immunoprecipitated with endogenous BACE1 in SH-SY5Y cells and mouse brain tissue. We conclude that PS1 is directly involved in the maturation of BACE1, thus possibly functioning as a regulator of both beta- and gamma-secretase in Abeta generation.
阿尔茨海默病的病理特征之一是β-淀粉样肽（Aβ）在老年斑中过度沉积。当β-淀粉样前体蛋白（APP）先后被β-分泌酶（即β位点APP切割酶1，BACE1）和γ-分泌酶（一种含有早老素1，PS1的假定酶复合物）切割时，会产生Aβ。然而，PS1和BACE1之间的功能相互作用此前尚不为人所知。除了在Aβ肽生成中的这一经典作用外，也有人提出PS1会影响特定膜蛋白的细胞内运输和成熟。我们发现，与野生型小鼠胚胎成纤维细胞（PS-/-MEFs）相比，早老素缺陷型小鼠胚胎成纤维细胞中外源和内源性成熟BACE1的水平显著降低。此外，与天然细胞相比，稳定表达野生型PS1的人神经母细胞瘤细胞系SH-SY5Y中成熟BACE1的水平有所增加。相反，在显性负性突变体PS1过表达的稳定状态下，BACE1的成熟受到损害。免疫沉淀试验表明，PS1更倾向于与前体BACE1相互作用，而不是成熟的BACE1，这表明PS1可能直接参与BACE1的成熟过程。此外，在SH-SY5Y细胞和小鼠脑组织中，内源性PS1与内源性BACE1一起被免疫沉淀。我们得出结论，PS1直接参与BACE1的成熟，因此可能在Aβ生成过程中作为β-和γ-分泌酶的调节剂发挥作用。
