Department of Orthopedic Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
Department of Orthopedic Surgery, Tohoku Medical and Pharmaceutical University, Faculty of Medicine, Sendai, Japan.
J Neurotrauma. 2020 Aug 1;37(15):1687-1695. doi: 10.1089/neu.2019.6820. Epub 2020 May 4.
Autophagy is the degradation process of dysfunctional intracellular components and has a crucial function in various human diseases. There are three different types of autophagy: macroautophagy, microautophagy, and chaperone-mediated autophagy (CMA). CMA is a major route for the elimination of cellular aberrant proteins and can provide a cytoprotective effect. The present study investigated the expression of lysosome-associated membrane protein type 2A (LAMP2A), which is the hallmark of CMA activity, in damaged neural tissue after spinal cord injury (SCI) in mice. The number of LAMP2A-expressing cells was significantly increased at the lesion following SCI. The increased number of LAMP2A-positive cells was observed from 24 h and peaked at 3 days after injury. A western blot analysis confirmed that the level of LAMP2A protein was significantly increased in the injured spinal cord compared with the uninjured cord. On double staining for LAMP2A and different neural cell type markers, the increased expression of LAMP2A was observed in neurons, astrocytes, oligodendrocytes, and microglia/macrophages following injury. An electron microscopic analysis showed that secondary lysosomes were increased in damaged neurons at the lesion site. Immunoelectron microscopy revealed that the gold particles with anti-LAMP2A antibody were frequently localized at the secondary lysosomes in the injured site. These findings indicated that CMA was clearly activated in damaged neural tissue after SCI. The activation of CMA may contribute to the elimination of intracellular aberrant proteins and exert a neuroprotective effect following SCI.
自噬是细胞内功能失调成分的降解过程，在各种人类疾病中具有关键作用。自噬有三种不同的类型：巨自噬、微自噬和伴侣介导的自噬（CMA）。CMA 是细胞内异常蛋白清除的主要途径，可以提供细胞保护作用。本研究探讨了溶酶体相关膜蛋白 2A（LAMP2A）在小鼠脊髓损伤（SCI）后受损神经组织中的表达。在 SCI 后，损伤处 LAMP2A 表达细胞的数量显著增加。LAMP2A 阳性细胞的数量从损伤后 24 小时开始增加，并在 3 天达到峰值。Western blot 分析证实，与未损伤的脊髓相比，损伤的脊髓中 LAMP2A 蛋白水平显著增加。对 LAMP2A 和不同神经细胞类型标志物的双重染色显示，损伤后 LAMP2A 的表达在神经元、星形胶质细胞、少突胶质细胞和小胶质细胞/巨噬细胞中增加。电镜分析显示，损伤部位神经元中的次级溶酶体增加。免疫电镜显示，抗 LAMP2A 抗体的金颗粒在损伤部位的次级溶酶体中经常被定位。这些发现表明，CMA 在 SCI 后受损的神经组织中明显被激活。CMA 的激活可能有助于清除细胞内异常蛋白，并在 SCI 后发挥神经保护作用。
