Isei Michael O, Girardi Peter A, Rodwell-Bullock Joel, Nehrke Keith, Johnson Gail Vw
University of Rochester, Department of Anesthesiology & Perioperative Medicine, Rochester, New York, USA.
University of Rochester, Department of Medicine, Nephrology Division, Rochester, New York, USA.
bioRxiv. 2023 Feb 19:2023.02.19.529131. doi: 10.1101/2023.02.19.529131.
Phosphorylation of tau at sites associated with Alzheimer's disease (AD) likely plays a role in the disease progression. Mitochondrial impairment, correlating with increased presence of phosphorylated tau, has been identified as a contributing factor to neurodegenerative processes in AD. However, how tau phosphorylated at specific sites impacts mitochondrial function has not been fully defined. We examined how AD-relevant phosphomimetics of tau impact selected aspects of mitochondrial biology. To mimic phosphorylation at AD-associated sites, the Ser/Thr sites in wild-type GFP tagged-tau (T4) were converted to glutamic acid (E) to make pseudophosphorylated GFP tagged-Ser-396/404 (2EC) and GFP tagged-Thr-231/Ser-235 (2EM) constructs. These constructs were expressed in neuronal HT22 cells and their impact on specific mitochondrial functions and responses to stressors were measured. Phosphomimetic tau altered mitochondrial distribution. Specifically, mitochondria accumulated in the soma of cells expressing either 2EC or 2EM, and neurite-like extensions in 2EC cells were shorter. Additionally, ATP levels were reduced in both 2EC and 2EM expressing cells, and ROS production increased in 2EC cells during oxidation of succinate when compared to T4 expressing cells. Thapsigargin reduced mitochondrial membrane potential (Ψ ) and increased ROS production in both 2EC and 2EM cells relative to T4 cells, with no significant difference in the effects of rotenone. These results show that tau phosphorylation at specific AD-relevant epitopes negatively affects mitochondria, with the extent of dysfunction and stress response varying according to the sites of phosphorylation. Altogether, these findings extend our understanding of potential mechanisms whereby phosphorylated tau promotes mitochondria dysfunction in tauopathies, including AD.
R01 AG067617.
与阿尔茨海默病（AD）相关位点的tau蛋白磷酸化可能在疾病进展中起作用。线粒体损伤与磷酸化tau蛋白的增加相关，已被确定为AD神经退行性过程的一个促成因素。然而，特定位点磷酸化的tau蛋白如何影响线粒体功能尚未完全明确。我们研究了与AD相关的tau蛋白磷酸模拟物如何影响线粒体生物学的选定方面。为了模拟AD相关位点的磷酸化，将野生型绿色荧光蛋白标记的tau（T4）中的丝氨酸/苏氨酸位点转换为谷氨酸（E），以构建假磷酸化的绿色荧光蛋白标记的Ser-396/404（2EC）和绿色荧光蛋白标记的Thr-231/Ser-235（2EM）构建体。这些构建体在神经元HT22细胞中表达，并测量它们对特定线粒体功能和应激反应的影响。磷酸模拟tau蛋白改变了线粒体分布。具体而言，线粒体在表达2EC或2EM的细胞体中积累，并且2EC细胞中的神经突样延伸较短。此外，与表达T4的细胞相比，表达2EC和2EM的细胞中的ATP水平均降低，并且在琥珀酸氧化期间2EC细胞中的活性氧生成增加。毒胡萝卜素相对于T4细胞降低了2EC和2EM细胞中的线粒体膜电位（Ψ ）并增加了活性氧生成，鱼藤酮的作用没有显著差异。这些结果表明特定AD相关表位的tau蛋白磷酸化对线粒体产生负面影响，功能障碍和应激反应的程度根据磷酸化位点而有所不同。总之，这些发现扩展了我们对磷酸化tau蛋白在包括AD在内的tau蛋白病中促进线粒体功能障碍的潜在机制的理解。
R01 AG067617。
