CERVO Research Centre, Laval University, Quebec City, Quebec, Canada.
Division of Neuroscence, Centre Hospitalier Universitaire de Québecṣ-Université Laval Research Center, Quebec City, Québec, Canada.
Glia. 2024 Jul;72(7):1319-1339. doi: 10.1002/glia.24531. Epub 2024 Apr 5.
Neuroinflammation and chronic activation of microglial cells are the prominent features of amyotrophic lateral sclerosis (ALS) pathology. While alterations in the mRNA profile of diseased microglia have been well documented, the actual microglia proteome remains poorly characterized. Here we performed a functional characterization together with proteome analyses of microglial cells at different stages of disease in the SOD1-G93A model of ALS. Functional analyses of microglia derived from the lumbar spinal cord of symptomatic mice revealed: (i) remarkably high mitotic index (close to 100% cells are Ki67+) (ii) significant decrease in phagocytic capacity when compared to age-matched control microglia, and (iii) diminished response to innate immune challenges in vitro and in vivo. Proteome analysis revealed a development of two distinct molecular signatures at early and advanced stages of disease. While at early stages of disease, we identified several proteins implicated in microglia immune functions such as GPNMB, HMBOX1, at advanced stages of disease microglia signature at protein level was characterized with a robust upregulation of several unconventional proteins including rootletin, major vaults proteins and STK38. Upregulation of GPNMB and rootletin has been also found in the spinal cord samples of sporadic ALS. Remarkably, the top biological functions of microglia, in particular in the advanced disease, were not related to immunity/immune response, but were highly enriched in terms linked to RNA metabolism. Together, our results suggest that, over the course of disease, chronically activated microglia develop unconventional protein signatures and gradually lose their immune identity ultimately turning into functionally inefficient immune cells.
神经炎症和小胶质细胞的慢性激活是肌萎缩侧索硬化症 (ALS) 病理学的突出特征。虽然疾病小胶质细胞的 mRNA 谱的改变已经得到很好的记录，但实际的小胶质细胞蛋白质组仍然描述不足。在这里，我们在 SOD1-G93A 模型的 ALS 不同疾病阶段对小胶质细胞进行了功能特征分析和蛋白质组分析。对来自症状性小鼠的腰椎脊髓衍生的小胶质细胞进行功能分析，结果表明：（i）有丝分裂指数非常高（接近 100%的细胞为 Ki67+）；（ii）与年龄匹配的对照小胶质细胞相比，吞噬能力显著下降；（iii）体外和体内先天免疫挑战的反应能力下降。蛋白质组分析揭示了疾病早期和晚期发展出两种不同的分子特征。虽然在疾病早期，我们鉴定出几种与小胶质细胞免疫功能相关的蛋白质，如 GPNMB、HMBOX1，但在疾病晚期，小胶质细胞蛋白质组在蛋白质水平上的特征是几个非常规蛋白质的强烈上调，包括根蛋白、主要穹窿蛋白和 STK38。在散发性 ALS 的脊髓样本中也发现了 GPNMB 和根蛋白的上调。值得注意的是，小胶质细胞的顶级生物学功能，特别是在晚期疾病中，与免疫/免疫反应无关，但与 RNA 代谢相关的术语高度富集。总之，我们的研究结果表明，在疾病进展过程中，慢性激活的小胶质细胞会发展出非常规的蛋白质特征，并逐渐失去其免疫特性，最终变成功能效率低下的免疫细胞。
