Sha Chunhe, Pan Feng, Liu Xiaodong, Wang Zhiqing, Liu Guohui, Huang Kai
Department of Orthopaedics, Shanghai Jing'an District Zhabei Central Hospital, Shanghai, China.
Cell Death Discov. 2025 Jul 9;11(1):317. doi: 10.1038/s41420-025-02604-8.
Spinal cord injury (SCI) represents a profound neurological condition characterized by motor dysfunction and sensory impairment. Microglial polarization significantly influences neurorepair and regeneration post SCI. This study aims to investigate the regulatory role of the ELAV-like RNA binding protein 1 (ELAVL1)-ubiquitin-specific peptidase 29 (USP29)-transforming growth factor beta-activated kinase 1 (TAK1) axis in microglial polarization and its effects on differentiation of neural stem cells (NSCs). A rat model of SCI was established via spinal cord transection at the tenth thoracic vertebra segment, followed by short hairpin RNA (shRNA) lentivirus infection. Motor function and coordination were evaluated while histopathological analysis of spinal cord tissues was conducted. Microglial polarization and NSC differentiation were assessed via immunofluorescence and Western blot analysis. In cellular experiments, lipopolysaccharide (LPS) was utilized to induce M1 polarization in HMC3 cells, with polarization status determined by flow cytometry, immunofluorescence, and WB. Co-immunoprecipitation, GST pull-down, and ubiquitination assays elucidated USP29 effects on TAK1 ubiquitination and activation. In SCI rat spinal cord tissues and LPS-treated HMC3 cells, we observed upregulation of ELAVL1 and phosphorylated level of TAK1, while USP29 expression was downregulated. ELAVL1 was found to bind USP29 mRNA, promoting its degradation and suppressing USP29 expression. USP29 directly interacted with TAK1, inhibiting its ubiquitination and phosphorylation. Knockdown of ELAVL1 significantly enhanced USP29 mRNA stability, inhibited TAK1 activation, promoted M2 microglial polarization, and suppressed M1 polarization. In vivo downregulation of ELAVL1 promoted the differentiation of NSCs into neurons by inhibiting M1 polarization and promoting M2 polarization, thereby improving motor function, alleviating nerve injury, and facilitating spinal cord repair. ELAVL1 exacerbates SCI pathology by degrading USP29 mRNA, thereby activating TAK1 and driving M1 microglial polarization. Targeting the ELAVL1-USP29-TAK1 axis may offer therapeutic potential for enhancing neurorepair in SCI. Schematic diagram of the ELAVL1-USP29-TAK1 axis mediating M1 microglial polarization and NSC differentiation dysregulation exacerbating SCI.
脊髓损伤（SCI）是一种严重的神经系统疾病，其特征为运动功能障碍和感觉损伤。小胶质细胞极化对SCI后的神经修复和再生有显著影响。本研究旨在探讨ELAV样RNA结合蛋白1（ELAVL1）-泛素特异性肽酶29（USP29）-转化生长因子β激活激酶1（TAK1）轴在小胶质细胞极化中的调节作用及其对神经干细胞（NSC）分化的影响。通过在第十胸椎节段进行脊髓横断建立SCI大鼠模型，随后进行短发夹RNA（shRNA）慢病毒感染。评估运动功能和协调性，同时对脊髓组织进行组织病理学分析。通过免疫荧光和蛋白质印迹分析评估小胶质细胞极化和NSC分化。在细胞实验中用脂多糖（LPS）诱导HMC3细胞发生M1极化，通过流式细胞术、免疫荧光和蛋白质印迹确定极化状态。免疫共沉淀、谷胱甘肽-S-转移酶（GST）下拉和泛素化分析阐明了USP29对TAK1泛素化和激活的影响。在SCI大鼠脊髓组织和LPS处理的HMC3细胞中，我们观察到ELAVL1上调和TAK1磷酸化水平升高，而USP29表达下调。发现ELAVL1与USP29 mRNA结合，促进其降解并抑制USP29表达。USP29直接与TAK1相互作用，抑制其泛素化和磷酸化。敲低ELAVL1显著增强USP29 mRNA稳定性，抑制TAK1激活，促进M2小胶质细胞极化并抑制M1极化。体内下调ELAVL1通过抑制M1极化和促进M2极化促进NSC向神经元分化，从而改善运动功能、减轻神经损伤并促进脊髓修复。ELAVL1通过降解USP29 mRNA加剧SCI病理，从而激活TAK1并驱动M1小胶质细胞极化。靶向ELAVL1-USP29-TAK1轴可能为增强SCI中的神经修复提供治疗潜力。ELAVL1-USP29-TAK1轴介导M1小胶质细胞极化和NSC分化失调加剧SCI的示意图。
