Wang Mingguang, Jing Tian, Wang Xuan, Yao Dan
Department of Neurology, Xuzhou Children's Hospital, 18 Suti North Road, Xuzhou, 221006, China.
Department of Neurology, Xuzhou Children's Hospital, 18 Suti North Road, Xuzhou, 221006, China.
Neurosci Lett. 2018 Oct 15;685:63-67. doi: 10.1016/j.neulet.2018.08.016. Epub 2018 Aug 16.
Amyloid-β proteins deposition and aggregation occur in extracellular space and form neuritic plaques in Alzheimer's disease (AD) brain. Beta-site amyloid precursor protein cleaving enzyme 1 (BACE1)/ β-secretase and γ-secretase Presenilin 1 (PSEN1) conduct sequential cleavage of amyloid- β precursor protein (APP) and yield amyloid- β proteins. However the details of the interactions of APP with the enzymes and transportation of catalytic products are unclear. Here we reveal distinctive targeting patterns of the proteins in subcellular organelles in N2A cells. We find all three proteins co-localize in endosomes with APP and PSEN1 co-localize and associate on cell membrane and nucleus. By selectively knocking down BACE1 or PSEN 1 with siRNA, we discover that BACE1 functions as the enzyme initiating the first cleavage step and serves a scaffold for APP and PSEN1 endocytosis. PSEN1 knocking-down only leads to the reduction of BACE1 in cell membrane and nucleus. We conclude that BACE1 facilitates the transportation of APP and formation of the complex with γ-secretase, resulting in the stepwise cleavages of APP. After BACE1 cleavage APP binds to PSEN1 and transfers to cell membrane or nucleus for final processing and amyloid genesis.
淀粉样β蛋白的沉积和聚集发生在细胞外空间，并在阿尔茨海默病（AD）大脑中形成神经炎性斑块。β位点淀粉样前体蛋白裂解酶1（BACE1）/β分泌酶和γ分泌酶早老素1（PSEN1）对淀粉样β前体蛋白（APP）进行顺序切割，产生淀粉样β蛋白。然而，APP与这些酶的相互作用细节以及催化产物的运输情况尚不清楚。在此，我们揭示了N2A细胞中亚细胞器中这些蛋白质独特的靶向模式。我们发现这三种蛋白质均在内体中共定位，且APP和PSEN1在细胞膜和细胞核上共定位并相互关联。通过用小干扰RNA（siRNA）选择性敲低BACE1或PSEN1，我们发现BACE1作为启动第一步切割的酶，并为APP和PSEN1的内吞作用提供支架。敲低PSEN1仅导致细胞膜和细胞核中BACE1减少。我们得出结论，BACE1促进APP的运输并与γ分泌酶形成复合物，从而导致APP的逐步切割。BACE1切割后，APP与PSEN1结合并转移到细胞膜或细胞核进行最终加工和淀粉样蛋白生成。
