The main hallmark of many forms of familiar and sporadic amyotrophic lateral sclerosis (ALS) is a reduction in nuclear TDP-43 protein and its inclusion in cytoplasmic aggregates in motor neurons. In order to understand which cellular and molecular mechanisms underlie the mislocalization of TDP-43, we examined human skin fibroblasts from two individuals with familial ALS, both with mutations in TDP-43, and two individuals with sporadic ALS, both without TDP-43 mutations or mutations in other ALS related genes. We found that all ALS fibroblasts had a partially cytoplasmic localization of TDP-43 and had reduced cell metabolism as compared to fibroblasts from apparently healthy individuals. ALS fibroblasts showed an increase in global protein synthesis and an increase in 4E-BP1 and rpS6 phosphorylation, which is indicative of mTORC1 activity. We also observed a decrease in glutathione (GSH), which suggests that oxidative stress is elevated in ALS. ERK1/2 activity regulated the extent of oxidative stress and the localization of TDP-43 in the cytoplasm in all ALS fibroblasts. Lastly, ALS fibroblasts showed reduced stress granule formation in response to H2O2 stress. In conclusion, these findings identify specific cellular and molecular defects in ALS fibroblasts, thus providing insight into potential mechanisms that may also occur in degenerating motor neurons.

中文翻译：

---

ALS 皮肤成纤维细胞显示氧化应激和 ERK1/2 介导的 TDP-43 细胞质定位。

许多形式的常见和散发性肌萎缩侧索硬化 (ALS) 的主要标志是核 TDP-43 蛋白减少及其包含在运动神经元的细胞质聚集体中。为了了解 TDP-43 错误定位的细胞和分子机制，我们检查了来自两个家族性 ALS 个体（均具有 TDP-43 突变）和两个散发性 ALS 个体（均无 TDP-43 突变）的人类皮肤成纤维细胞或其他 ALS 相关基因的突变。我们发现所有 ALS 成纤维细胞都具有 TDP-43 的部分细胞质定位，并且与来自明显健康个体的成纤维细胞相比，细胞代谢降低。ALS 成纤维细胞显示整体蛋白质合成增加以及 4E-BP1 和 rpS6 磷酸化增加，这表明 mTORC1 活性。我们还观察到谷胱甘肽 (GSH) 的减少，这表明 ALS 中的氧化应激升高。ERK1/2 活性调节氧化应激的程度和 TDP-43 在所有 ALS 成纤维细胞的细胞质中的定位。最后，ALS 成纤维细胞显示出响应 H2O2 应力的应力颗粒形成减少。总之，这些发现确定了 ALS 成纤维细胞中的特定细胞和分子缺陷，从而提供了对退化运动神经元也可能发生的潜在机制的见解。