DNMT1 and Sp1 competitively regulate the expression of BACE1 in A2E-mediated photo-oxidative damage in RPE cells
DNMT1 and Sp1 competitively regulate the expression of BACE1 in A2E-mediated photo-oxidative damage in RPE cells
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DNMT1和Sp1在A2E介导的RPE细胞光氧化损伤中竞争性调节BACE1的表达
DOI：
10.1016/j.neuint.2018.09.001
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发表时间：
2018-12-01
影响因子：
4.2
通讯作者：
Sun, Xiaodong
中科院分区：
文献类型：
--
作者：
Huang, Peirong;Sun, Junran;Sun, Xiaodong
淀粉样蛋白β（amyloid-beta，A β）对视网膜的损伤作用已成为众多研究的焦点，提示A β可能是年龄相关性黄斑变性（age-related macular degeneration，AMD）的潜在致病机制。然而，AMD患者中A β沉积的潜在机制仍然未知。β位点淀粉样前体蛋白裂解酶1（BACE 1）是A β生成的限速酶，在A β在大脑中的沉积中起重要作用。在本研究中，我们的目的是阐明BACE 1的调控机制，并探索潜在的药物靶点，使用脂褐质荧光团A2 E介导的光氧化模型。在该模型中，A β（1.40）和A β（1.42）水平随着BACE 1表达的增强而同时增加。这些变化与BACE 1基因启动子内特定位点的低甲基化和DNA甲基转移酶1（DNMT 1）水平的降低有关。此外，我们注意到在BACE 1启动子内的差异甲基化CpG岛和特异性蛋白（Sp1）结合位点的重叠区域。我们采用染色质免疫沉淀（ChIP）试验来验证DNMT 1降低BACE 1启动子甲基化能够增加Sp1和BACE 1启动子之间的结合，从而进一步增强BACE 1转录。光神霉素A（MTM）抑制Sp1可下调BACE 1的表达，减轻RPE屏障形态和功能损害。我们的研究结果首次显示了光氧化后转录因子Sp1和DNMT 1对BACE 1的竞争性调节，并证实了MTM对RPE细胞的潜在新保护作用。
Numerous studies have focused on the deteriorate role of amyloid-beta (A beta) on retina, implying the potential pathogenic mechanism underlying age-related macular degeneration (AMD). However, the mechanism underlying the A beta deposition in AMD patients remains unknown. Beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1), rate-limiting enzyme for A beta production, plays an important role in A beta deposition in the brain. In the current study, we aimed to clarify the regulation mechanism of BACE1 and explore potential drug targets using a lipofuscinfluorophore A2E-mediated photo-oxidation model. In this model, A beta(1.40) and A beta(1.42) levels increased simultaneously with the enhanced BACE1 expression. These changes were associated with the hypomethylation of specific loci within the BACE1 gene promoter and the decreased levels of DNA methyltransferase 1 (DNMT1). Furthermore, we noticed overlapping regions of differentially methylated CpG islands and specificity protein (Sp1) binding sites within the BACE1 promoter. We employed chromatin immunoprecipitation (ChIP) assay to verify that the decreased BACE1 promoter methylation by DNMT1 enabled increased binding between Sp1 and the BACE1 promoter, which further enhanced BACE1 transcription. The inhibition of Sp1 with mithramycin A (MTM) could down-regulate the expression of BACE1 as well as alleviate the RPE barrier morphology and function impairment. Our results for the first time show the competitive regulation of BACE1 by transcription factor Sp1 and DNMT1 after photo-oxidation and confirm the potential novel protective role of MTM on RPE cells.