Endoplasmic reticulum (ER) stress is involved in inflammation-induced neurotoxicity. Mitofusin 2 (Mfn2), a member of the GTPase family of proteins, resides in the ER membrane and is known to regulate ER stress. However, the potential role and underlying mechanism of Mfn2 in inflammation-induced neuronal dysfunction is unknown. In our study, we explored the potential of Mfn2 to attenuate inflammation-mediated neuronal dysfunction by inhibiting ER stress. Our data show that Mfn2 overexpression significantly ameliorated tumor necrosis factor alpha (TNFα)-induced ER stress, as indicated by the downregulation of the ER stress proteins PERK, GRP78 and CHOP. Mfn2 overexpression also prevented the TNFα-mediated activation of caspase-3, caspase-12 and cleaved poly (ADP-ribose) polymerase (PARP). Cellular antioxidant dysfunction and reactive oxygen species overproduction were also improved by Mfn2 in the setting of TNFα in mouse neuroblastoma N2a cells in vitro. Similarly, disordered calcium homeostasis, indicated by disturbed levels of calcium-related proteins and calcium overloading, was corrected by Mfn2, as evidenced by the increased expression of store-operated calcium entry (SERCA), decreased levels of inositol trisphosphate receptor (IP3R), and normalized calcium content in TNFα-treated N2a cells. Mfn2 overexpression was found to elevate Yes-associated protein (Yap) expression; knockdown of Yap abolished the regulatory effects of Mfn2 on ER stress, oxidative stress, calcium balance, neural death and inflammatory injury. These results lead us to conclude that re-activation of the Mfn2-Yap signaling pathway alleviates TNFα-induced ER stress and dysfunction of mouse neuroblastoma N2a cells. Our findings provide a better understanding of the regulatory role of Mfn2-Yap-ER stress in neuroinflammation and indicate that the Mfn2-Yap axis may be a focus of research in terms of having therapeutic value for the treatment of neurodegenerative diseases.

中文翻译：

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Mitofusin-2通过Yap-Hippo途径调节炎症介导的小鼠神经母细胞瘤N2a细胞功能障碍和内质网应激。

内质网应激（ER）参与炎症诱导的神经毒性。丝裂蛋白2（Mfn2）是蛋白质GTPase家族的成员，位于ER膜中，并且已知能调节ER应激。但是，Mfn2在炎症诱导的神经元功能障碍中的潜在作用和潜在机制尚不清楚。在我们的研究中，我们探索了Mfn2通过抑制ER应激来减轻炎症介导的神经元功能障碍的潜力。我们的数据表明，Mfn2的过表达显着改善了肿瘤坏死因子α（TNFα）诱导的内质网应激，这是由内质网应激蛋白PERK，GRP78和CHOP的下调所表明的。Mfn2的过表达还阻止了TNFα介导的caspase-3，caspase-12和裂解的聚（ADP-核糖）聚合酶（PARP）的活化。Mfn2还可以改善小鼠神经母细胞瘤N2a细胞中TNFα的设置，从而改善细胞抗氧化功能障碍和活性氧的过度产生。同样，Mfn2可以纠正钙稳态的紊乱，表现为钙相关蛋白水平紊乱和钙超载，这可以通过Mfn2纠正，这可以通过储库操作性钙进入（SERCA）表达增加，肌醇三磷酸受体（IP3R）降低， TNFα处理的N2a细胞中的钙含量正常化。发现Mfn2过表达可提高Yes相关蛋白（Yap）的表达。Yap的敲除取消了Mfn2对内质网应激，氧化应激，钙平衡，神经死亡和炎症性损伤的调节作用。这些结果使我们得出结论，Mfn2-Yap信号通路的重新激活可减轻TNFα诱导的ER应激和小鼠神经母细胞瘤N2a细胞的功能障碍。我们的发现提供了对Mfn2-Yap-ER应激在神经炎症中的调节作用的更好理解，并表明Mfn2-Yap轴可能具有神经退行性疾病治疗价值的研究重点。