Laboratory for Alzheimer's Disease, Department of Life Science, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan.
Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Structure. 2024 Oct 3;32(10):1793-1807.e6. doi: 10.1016/j.str.2024.06.018. Epub 2024 Jul 19.
Intracellular tau aggregation requires a local protein concentration increase, referred to as "droplets". However, the cellular mechanism for droplet formation is poorly understood. Here, we expressed OptoTau, a P301L mutant tau fused with CRY2olig, a light-sensitive protein that can form homo-oligomers. Under blue light exposure, OptoTau increased tau phosphorylation and was sequestered in aggresomes. Suppressing aggresome formation by nocodazole formed tau granular clusters in the cytoplasm. The granular clusters disappeared by discontinuing blue light exposure or 1,6-hexanediol treatment suggesting that intracellular tau droplet formation requires microtubule collapse. Expressing OptoTau-ΔN, a species of N-terminal cleaved tau observed in the Alzheimer's disease brain, formed 1,6-hexanediol and detergent-resistant tau clusters in the cytoplasm with blue light stimulation. These intracellular stable tau clusters acted as a seed for tau fibrils in vitro. These results suggest that tau droplet formation and N-terminal cleavage are necessary for neurofibrillary tangles formation in neurodegenerative diseases.
细胞内 tau 聚集需要局部蛋白质浓度增加，称为“液滴”。然而，液滴形成的细胞机制还了解甚少。在这里，我们表达了 OptoTau，一种 P301L 突变 tau 与 CRY2olig 融合，CRY2olig 是一种光敏感蛋白，可以形成同源寡聚体。在蓝光照射下，OptoTau 增加了 tau 的磷酸化，并被隔离在聚集物中。用 nocodazole 抑制聚集物形成会在细胞质中形成 tau 颗粒簇。中断蓝光照射或 1,6-己二醇处理会使颗粒簇消失，表明细胞内 tau 液滴的形成需要微管崩溃。表达 OptoTau-ΔN，一种在阿尔茨海默病脑中观察到的 N 端切割 tau 形式，在蓝光刺激下会在细胞质中形成 1,6-己二醇和去污剂抗性 tau 簇。这些细胞内稳定的 tau 簇在体外作为 tau 原纤维的种子。这些结果表明，tau 液滴形成和 N 端切割是神经退行性疾病中神经纤维缠结形成所必需的。
