Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, China.
Department of Neurology, Nanchong Central Hospital, the Second Clinical College of North Sichuan Medical College, Nanchong, China.
FASEB J. 2021 May;35(5):e21445. doi: 10.1096/fj.202002461R.
Mitochondrial Tu translation elongation factor (TUFM or EF-Tu) is part of the mitochondrial translation machinery. It is reported that TUFM expression is reduced in the brain of Alzheimer's disease (AD), suggesting that TUFM might play a role in the pathophysiology. In this study, we found that TUFM protein level was decreased in the hippocampus and cortex especially in the aged APP/PS1 mice, an animal model of AD. In HEK cells that stably express full-length human amyloid-β precursor protein (HEK-APP), TUFM knockdown or overexpression increased or reduced the protein levels of β-amyloid protein (Aβ) and β-amyloid converting enzyme 1 (BACE1), respectively. TUFM-mediated reduction of BACE1 was attenuated by translation inhibitor cycloheximide (CHX) or α-[2-[4-(3,4-Dichlorophenyl)-2-thiazolyl]hydrazinylidene]-2-nitro-benzenepropanoic acid (4EGI1), and in cells overexpressing BACE1 constructs deleting the 5' untranslated region (5'UTR). TUFM silencing increased the half-life of BACE1 mRNA, suggesting that RNA stability was affected by TUFM. In support, transcription inhibitor Actinomycin D (ActD) and silencing of nuclear factor κB (NFκB) failed to abolish TUFM-mediated regulation of BACE1 protein and mRNA. We further found that the mitochondria-targeted antioxidant TEMPO diminished the effects of TUFM on BACE1, suggesting that reactive oxygen species (ROS) played an important role. Indeed, cellular ROS levels were affected by TUFM knockdown or overexpression, and TUFM-mediated regulation of apoptosis and Tau phosphorylation at selective sites was attenuated by TEMPO. Collectively, TUFM protein levels were decreased in APP/PS1 mice. TUFM is involved in AD pathology by regulating BACE1 translation, apoptosis, and Tau phosphorylation, in which ROS plays an important role.
线粒体翻译延伸因子 TU（TUFM 或 EF-Tu）是线粒体翻译机制的一部分。有报道称，阿尔茨海默病（AD）患者大脑中的 TUFM 表达减少，这表明 TUFM 可能在病理生理学中发挥作用。在这项研究中，我们发现 TUFM 蛋白水平在 APP/PS1 小鼠（AD 的动物模型）的海马体和皮质中降低，尤其是在老年小鼠中。在稳定表达全长人淀粉样前体蛋白（HEK-APP）的 HEK 细胞中，TUFM 敲低或过表达分别增加或减少 β-淀粉样蛋白（Aβ）和 β-淀粉样前体蛋白水解酶 1（BACE1）的蛋白水平。翻译抑制剂环己酰亚胺（CHX）或 α-[2-[4-(3,4-二氯苯基)-2-噻唑基]肼基]-2-硝基苯丙酸（4EGI1）减弱了 TUFM 介导的 BACE1 减少，并且在过表达缺失 5'非翻译区（5'UTR）的 BACE1 构建体的细胞中也是如此。TUFM 沉默增加了 BACE1 mRNA 的半衰期，这表明 RNA 稳定性受到 TUFM 的影响。支持这一观点的是，转录抑制剂放线菌素 D（ActD）和核因子 κB（NFκB）的沉默都不能消除 TUFM 对 BACE1 蛋白和 mRNA 的调节作用。我们进一步发现，线粒体靶向抗氧化剂 TEMPO 减弱了 TUFM 对 BACE1 的影响，这表明活性氧（ROS）发挥了重要作用。事实上，细胞内 ROS 水平受到 TUFM 敲低或过表达的影响，而 TUFM 对凋亡和 Tau 磷酸化的调节作用在 TEMPO 存在时减弱。总的来说，APP/PS1 小鼠中的 TUFM 蛋白水平降低。TUFM 通过调节 BACE1 翻译、凋亡和 Tau 磷酸化参与 AD 病理学，其中 ROS 发挥重要作用。
