Abstract

The endoplasmic reticulum (ER) extends throughout a cell and plays a critical role in maintaining cellular homeostasis. Changes in ER shape could provide a clue to explore the mechanisms that underlie the fate determination of neurons after axon injury because the ER drastically changes its morphology under neuronal stress to maintain cellular homeostasis and recover from damage. Because of their tiny structures and richness in the soma, the detailed morphology of the ER and its dynamics have not been well analysed. In this study, the focused ion beam/scanning electron microscopy (FIB/SEM) analysis was performed to explore the ultra-structures of the ER in the somata of motor neuron with axon regenerative injury models. In normal motor neurons, ER in the somata is abundantly localised near the perinucleus and represents lamella-like structures. After injury, analysis of the ER volume and ER branching points indicated a collapse of the normal distribution and a transformation from lamella-like structures to mesh-like structures. Furthermore, accompanied by ER accumulation near the plasma membrane (PM), the contact between the ER and PM (ER-PM contacts) significantly increased after injury. The accumulation of extended-synaptotagmin 1 (E-Syt1), a tethering protein of the ER and PM that regulates Ca²⁺-dependent lipid transfer, was also identified by immunohistochemistry and quantitative Real-time PCR after injury. These morphological alterations of ER and the increase in ER-PM contacts may be crucial events that occur in motor neurons as a resilient response for the survival after axonal injury.

中文翻译：

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神经损伤后运动神经元内质网形态及其与质膜接触的动态变化

摘要

内质网（ER）延伸到整个细胞，在维持细胞稳态中发挥着关键作用。内质网形状的变化可以为探索轴突损伤后神经元命运决定的机制提供线索，因为内质网在神经元应激下会急剧改变其形态，以维持细胞稳态并从损伤中恢复。由于它们的微小结构和体细胞的丰富性，内质网的详细形态及其动力学尚未得到很好的分析。在本研究中，采用聚焦离子束/扫描电子显微镜（FIB/SEM）分析来探索轴突再生损伤模型运动神经元体细胞内质网的超微结构。在正常运动神经元中，体细胞中的 ER 大量位于核周附近，并呈现片状结构。受伤后，对内质网体积和内质网分支点的分析表明，正态分布崩溃，从片状结构转变为网状结构。此外，伴随着质膜（PM）附近的ER积累，损伤后ER和PM之间的接触（ER-PM接触）显着增加。损伤后通过免疫组织化学和定量实时 PCR 也鉴定了延伸突触结合蛋白 1 (E-Syt1) 的积累，该蛋白是 ER 和 PM 的束缚蛋白，调节 Ca ²⁺依赖性脂质转移。 ER 的这些形态学改变和 ER-PM 接触的增加可能是运动神经元中发生的关键事件，作为轴突损伤后生存的弹性反应。