Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, CA, USA.
Biomedical Sciences Graduate Program, University of California, San Francisco, San Francisco, CA, USA.
J Neuroinflammation. 2024 Aug 8;21(1):198. doi: 10.1186/s12974-024-03165-w.
Astrocytes respond and contribute to neuroinflammation by adopting inflammatory reactive states. Although recent efforts have characterized the gene expression signatures associated with these reactive states, the cell biology underlying inflammatory reactive astrocyte phenotypes remains under-explored. Here, we used CRISPR-based screening in human iPSC-derived astrocytes to identify mTOR activation a driver of cytokine-induced endolysosomal system remodeling, manifesting as alkalinization of endolysosomal compartments, decreased autophagic flux, and increased exocytosis of certain endolysosomal cargos. Through endolysosomal proteomics, we identified and focused on one such cargo-IL-32, a disease-associated pro-inflammatory cytokine not present in rodents, whose secretion mechanism is not well understood. We found that IL-32 was partially secreted in extracellular vesicles likely to be exosomes. Furthermore, we found that IL-32 was involved in the polarization of inflammatory reactive astrocyte states and was upregulated in astrocytes in multiple sclerosis lesions. We believe that our results advance our understanding of cell biological pathways underlying inflammatory reactive astrocyte phenotypes and identify potential therapeutic targets.
星形胶质细胞通过采用炎症反应状态来响应并促进神经炎症。尽管最近的研究已经描述了与这些反应状态相关的基因表达特征，但炎症反应性星形胶质细胞表型的细胞生物学仍未得到充分探索。在这里，我们使用基于 CRISPR 的筛选技术在人诱导多能干细胞衍生的星形胶质细胞中鉴定了 mTOR 激活是细胞因子诱导的内溶酶体系统重塑的驱动因素，表现为内溶酶体区室的碱化、自噬流的减少以及某些内溶酶体货物的胞吐作用增加。通过内溶酶体蛋白质组学，我们鉴定并关注了一种这样的货物——IL-32，这是一种在啮齿动物中不存在的与疾病相关的促炎细胞因子，其分泌机制尚未得到很好的理解。我们发现，IL-32 部分分泌到细胞外囊泡中，可能是外泌体。此外，我们发现 IL-32 参与了炎症反应性星形胶质细胞状态的极化，并在多发性硬化症病变中的星形胶质细胞中上调。我们相信，我们的研究结果推进了我们对炎症反应性星形胶质细胞表型的细胞生物学途径的理解，并确定了潜在的治疗靶点。
