Department of Human Biology and Human Genetics, Technical University of Kaiserslautern, Erwin-Schrödinger-Str. 13, 67663, Kaiserslautern, Germany.
MPI of Molecular Cell Biology and Genetics, Dresden, Germany.
Cell Mol Life Sci. 2020 Dec;77(24):5223-5242. doi: 10.1007/s00018-020-03467-1. Epub 2020 Feb 17.
Endocytosis of the amyloid precursor protein (APP) is critical for generation of β-amyloid, aggregating in Alzheimer's disease. APP endocytosis depending on the intracellular NPTY motif is well investigated, whereas involvement of the YTSI (also termed BaSS) motif remains controversial. Here, we show that APP lacking the YTSI motif (ΔYTSI) displays reduced localization to early endosomes and decreased internalization rates, similar to APP ΔNPTY. Additionally, we show that the YTSI-binding protein, PAT1a interacts with the Rab5 activator RME-6, as shown by several independent assays. Interestingly, knockdown of RME-6 decreased APP endocytosis, whereas overexpression increased the same. Similarly, APP ΔNPTY endocytosis was affected by PAT1a and RME-6 overexpression, whereas APP ΔYTSI internalization remained unchanged. Moreover, we could show that RME-6 mediated increase of APP endocytosis can be diminished upon knocking down PAT1a. Together, our data identify RME-6 as a novel player in APP endocytosis, involving the YTSI-binding protein PAT1a.
淀粉样前体蛋白（APP）的内吞作用对于β-淀粉样蛋白的产生至关重要，而β-淀粉样蛋白在阿尔茨海默病中会聚集。APP 内吞作用依赖于细胞内的 NPTY 基序，这一点已经得到了很好的研究，而 YTSI（也称为 BaSS）基序的参与仍存在争议。在这里，我们表明，缺乏 YTSI 基序的 APP（ΔYTSI）显示出向早期内体的定位减少和内化率降低，这与 APP ΔNPTY 相似。此外，我们还表明，YTSI 结合蛋白 PAT1a 与 Rab5 激活蛋白 RME-6 相互作用，这一点通过几个独立的实验得到了证明。有趣的是，RME-6 的敲低降低了 APP 的内吞作用，而过表达则增加了该作用。同样，PAT1a 和 RME-6 的过表达影响了 APP ΔNPTY 的内吞作用，而 APP ΔYTSI 的内化则保持不变。此外，我们还可以表明，RME-6 介导的 APP 内吞作用的增加可以通过敲低 PAT1a 而减少。总之，我们的数据确定了 RME-6 作为 APP 内吞作用中的一个新的参与者，涉及到 YTSI 结合蛋白 PAT1a。
