Mitochondrial calcium overload and necrosis in tauopathies caused by inhibition of Mfn2 and NCLX

摘要 Tau聚集体（也称为神经元缠结或NFT）是神经退行性疾病的标志。 统称为tau蛋白病的疾病。这些疾病是一个广泛的类别，有十几种或更多的痴呆症 包括额颞叶痴呆、皮克病和慢性创伤性脑病。阿尔茨海默 也是一种tau蛋白病，尽管这种疾病以淀粉样斑块的形成而闻名。在这种情况下， 细胞外淀粉样蛋白斑诱导细胞内tau聚集。tau聚集体的形成是 在此之前是tau寡聚化，其被认为是毒性的主要原因，最终诱导细胞凋亡。 死亡最近的几篇论文表明，tau寡聚体或聚集体抑制钙释放， 线粒体，然后通过线粒体通透性的开放通过坏死触发细胞死亡 过渡孔（MPTP）。这种抑制作用的靶点是Na+/Ca 2+交换器NCLX，它定位于细胞膜上， 线粒体内膜目前尚不清楚胞质tau寡聚体和聚集体如何干扰NCLX 因为它们的细胞位置不同。这项补助的父母补助金数据提供了一个 潜在的抑制机制。这些数据表明，线粒体内膜上的NCLX是 由外膜上的Mfn 2控制。mfn 2是两种线粒体外膜融合蛋白之一， 但它也在线粒体与内质网的连接中起作用， 对调节线粒体功能很重要。父母补助金的重点是连接的影响， Mfn 2和NCLX之间的患者具有周围神经病变（Charcot玛丽牙病CMT 2A），和 研究了CMT 2A是由过量的Ca 2+释放到胞质溶胶中引起的可能性， NCLX。在这里，我们假设胞质tau寡聚体或tau聚集体具有相反的作用， NCLX功能丧失导致细胞死亡，并且这种毒性是通过干扰Mfn 2功能介导的。的 导致线粒体中的Ca 2+过载然后可通过打开MPTP而引起坏死。在这种情况下，Mfn 2 将在tau聚集体定位的胞质溶胶和NCLX之间提供桥梁。 内膜因此，本补充的目的是确定tau寡聚体或 聚集是由于线粒体中的钙超载，如果这种超载是由干扰Mfn 2引起的， 及其下游效应子NCLX。tau蛋白寡聚体和聚集体对Mfn 2/NCLX介导的Ca ~（2+）的影响 将首先使用现有的用于tau蛋白病的培养细胞模型（HEK 293）研究释放和细胞死亡 传感器细胞），然后与越来越复杂的系统（分化的神经元和斑马鱼）， 准备提交R 01与小鼠模型。发现这种新的tau诱导的 毒性也为药物治疗（Mfn 2和NCLX）提供了新的靶点。用几种不同的 候选分子将作为该补充的一部分进行，为大规模筛选做准备， 其他的分子。

Abstract Tau aggregates (also known as neurofibrillary tangles or NFTs) are hallmarks of the neurodegenerative diseases collectively known as tauopathies. These diseases are a broad class of a dozen or more dementias that include the frontotemporal dementias, Pick’s disease, and chronic traumatic encephalopathy. Alzheimer’s is also a tauopathy, even though this disease is best known for the formation of amyloid plaques. In this case, the extracellular amyloid plaques induce intracellular tau aggregation. The formation of tau aggregates is preceded by tau oligomerization, which is considered the primary cause of toxicity, ultimately inducing cell death. Several recent papers suggest that tau oligomers or aggregates inhibit calcium release from mitochondria, which then triggers cell death through necrosis by opening of the mitochondrial permeability transition pore (MPTP). The target of this inhibition is the Na+/Ca2+ exchanger NCLX, which is localized to the mitochondrial inner membrane. It is unclear how cytosolic tau oligomers and aggregates interfere with NCLX function because of their different cellular locations. Data from the parent grant of this supplement provides a potential mechanism for inhibition. These data show that NCLX on the mitochondrial inner membrane is controlled by Mfn2 on the outer membrane. Mfn2 is one of two mitochondrial outer membrane fusion proteins, but it also plays a role in tethering of mitochondria to the endoplasmic reticulum where calcium exchange is important for regulating mitochondrial functions. The parent grant focuses on the effects that the connection between Mfn2 and NCLX have on a peripheral neuropathy (the Charcot Marie Tooth disease CMT2A), and investigates the possibility that CMT2A is caused by excessive Ca2+ release into the cytosol through overactive NCLX. Here, we hypothesize that cytosolic tau oligomers or tau aggregates have the opposite effect, causing cell death by loss of NCLX function, and that this toxicity is mediated by interference with Mfn2 function. The resulting Ca2+ overload in mitochondria can then cause necrosis by opening MPTP. In this scenario, Mfn2 would provide a bridge between the cytosol, which is where tau aggregates are localized, and NCLX on the inner membrane. The aim of this supplement is therefore to determine whether the toxicity of tau oligomers or aggregates is due to calcium overload in mitochondria and if this overload is caused by interference with Mfn2 and its downstream effector NCLX. The effects of tau oligomers and aggregates on Mfn2/NCLX-mediated Ca2+ release and cell death will first be investigated using an existing cultured cell model for tauopathies (HEK293 sensor cells) and then with increasingly more complex systems (differentiated neurons and Zebrafish) in preparation for submitting an R01 with mouse models. The discovery of this novel pathway for tau-induced toxicity also provides new targets for drug treatment (Mfn2 and NCLX). Pilot experiments with several candidate molecules will be conducted as part of this supplement in preparation for large scale screens for other molecules as this project progresses.