Faculty of Science and Engineering, Waseda University, TWIns, 2-2 Wakamatsu, Shinjuku, Tokyo, 162-8480, Japan.
Faculty of Science and Engineering, Waseda University, TWIns, 2-2 Wakamatsu, Shinjuku, Tokyo, 162-8480, Japan; Research Organization for Nano-life Innovation, Waseda University, Japan.
Biochem Biophys Res Commun. 2020 Mar 26;524(1):236-241. doi: 10.1016/j.bbrc.2020.01.078. Epub 2020 Jan 23.
Cereblon (CRBN) was identified as a gene that causes intellectual disabilities. The encoded CRBN protein, containing 442 amino acids, is located in several organs. Cytosolic CRBN was reported to mainly act as a component of the E3 ubiquitin ligase complex. CRBN is one of the substrate receptors of the E3 ubiquitin ligase complex and promotes the degradation of targeted proteins. Studies have reported that CRBN recognizes the C-terminal region of the amyloid precursor protein (APP), a protein known for its involvement in the development of Alzheimer's disease. Although CRBN may interact with the C-terminal region of APP in mice, the CRBN-mediated degradation mechanism of human APP remains unclear. Here, we analyzed the CRBN-mediated degradation mechanism of human APP via the ubiquitin-proteasome system. Immunoprecipitation experiments showed that CRBN interacts with human full-length APP via its C-terminal region. Next, we examined CRBN-mediated degradation of APP in the ubiquitin-proteasome system. CRBN recognizes Lys in human APP and ubiquitinates it in SH-SY5Y cells. Overexpression of CRBN decreased wild-type APP expression levels. In contrast, the expression level of K751R APP remained unchanged by CRBN overexpression, while knockdown of endogenous CRBN increased APP levels. As such, our results suggest that CRBN ubiquitinates Lys of human APP thereby degrading it via the ubiquitin-proteasome system.
Cereblon (CRBN) 被鉴定为导致智力障碍的基因。编码的 CRBN 蛋白含有 442 个氨基酸，位于多个器官中。细胞质 CRBN 主要作为 E3 泛素连接酶复合物的组成部分发挥作用。CRBN 是 E3 泛素连接酶复合物的底物受体之一，可促进靶蛋白的降解。研究报告称，CRBN 识别淀粉样前体蛋白 (APP) 的 C 末端区域，APP 是一种已知与阿尔茨海默病发展有关的蛋白质。虽然 CRBN 可能在小鼠中与 APP 的 C 末端区域相互作用，但 CRBN 介导的人 APP 降解机制尚不清楚。在这里，我们通过泛素蛋白酶体系统分析了 CRBN 介导的人 APP 降解机制。免疫沉淀实验表明，CRBN 通过其 C 末端区域与人全长 APP 相互作用。接下来，我们检查了泛素蛋白酶体系统中 CRBN 介导的 APP 降解。CRBN 识别人 APP 中的 Lys 并使其在 SH-SY5Y 细胞中泛素化。CRBN 的过表达降低了野生型 APP 的表达水平。相比之下，CRBN 过表达对 K751R APP 的表达水平没有影响，而内源性 CRBN 的敲低增加了 APP 水平。因此，我们的结果表明，CRBN 泛素化人 APP 的 Lys，从而通过泛素蛋白酶体系统降解它。
