The Endosome-associated Deubiquitinating Enzyme USP8 Regulates BACE1 Enzyme Ubiquitination and Degradation
The Endosome-associated Deubiquitinating Enzyme USP8 Regulates BACE1 Enzyme Ubiquitination and Degradation
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DOI：
10.1074/jbc.m116.718023
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发表时间：
2016-07-22
影响因子：
4.8
通讯作者：
Tesco, Giuseppina
中科院分区：
文献类型：
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作者：
Funmilayo, Eniola;Yeates, Aduke;Tesco, Giuseppina
β位点淀粉样前体蛋白裂解酶（BACE 1）是淀粉样β蛋白产生的限速酶，淀粉样β蛋白是一种在受阿尔茨海默病影响的受试者大脑中积累的毒性肽。我们以前的研究表明，BACE 1通过溶酶体途径降解，并且由于溶酶体降解受损，运输分子高尔基体定位的含γ-耳的ARF结合蛋白3（GGA 3）的消耗导致BACE 1水平和活性增加。我们还确定GGA 3调节BACE 1水平需要其结合泛素的能力。因此，我们报道了BACE 1在赖氨酸501处被泛素化，并且在赖氨酸501处缺乏泛素化产生BACE 1稳定化。泛素结合是由去泛素化酶介导的可逆过程。泛素特异性肽酶8（USP 8）是一种内体相关的去泛素化酶，调节多种质膜蛋白的泛素化、运输和溶酶体降解。在这里，我们报告说，RNA干扰介导的USP 8的耗竭降低了H4人神经胶质瘤细胞中异位表达和内源性BACE 1的水平。此外，USP 8耗竭增加BACE 1泛素化，促进BACE 1在早期内体和晚期内体/溶酶体中的积累，并降低再循环内体中BACE 1的水平。我们还发现BACE 1蛋白水平的降低伴随着BACE 1介导的淀粉样前体蛋白裂解和淀粉样β蛋白水平的降低。我们的研究结果表明，USP 8通过去泛素化赖氨酸501在BACE 1的运输和降解中起着关键作用。这些研究表明，能够加速BACE 1降解（例如通过增加BACE 1泛素化）的疗法可能代表阿尔茨海默病的潜在治疗方法。
The beta-site amyloid precursor protein-cleaving enzyme (BACE1) is the rate-limiting enzyme in the production of amyloid-beta, the toxic peptide that accumulates in the brain of subjects affected by Alzheimer disease. Our previous studies have shown that BACE1 is degraded via the lysosomal pathway and that that depletion of the trafficking molecule Golgi-localized gamma-ear-containing ARF-binding protein 3 (GGA3) results in increased BACE1 levels and activity because of impaired lysosomal degradation. We also determined that GGA3 regulation of BACE1 levels requires its ability to bind ubiquitin. Accordingly, we reported that BACE1 is ubiquitinated at lysine 501 and that lack of ubiquitination at lysine 501 produces BACE1 stabilization. Ubiquitin conjugation is a reversible process mediated by deubiquitinating enzymes. The ubiquitin-specific peptidase 8 (USP8), an endosome-associated deubiquitinating enzyme, regulates the ubiquitination, trafficking, and lysosomal degradation of several plasma membrane proteins. Here, we report that RNAi-mediated depletion of USP8 reduced levels of both ectopically expressed and endogenous BACE1 in H4 human neuroglioma cells. Moreover, USP8 depletion increased BACE1 ubiquitination, promoted BACE1 accumulation in the early endosomes and late endosomes/lysosomes, and decreased levels of BACE1 in the recycling endosomes. We also found that decreased BACE1 protein levels were accompanied by a decrease in BACE1-mediated amyloid precursor protein cleavage and amyloid-beta levels. Our findings demonstrate that USP8 plays a key role in the trafficking and degradation of BACE1 by deubiquitinating lysine 501. These studies suggest that therapies able to accelerate BACE1 degradation (e.g. by increasing BACE1 ubiquitination) may represent a potential treatment for Alzheimer disease.