Lin Zhidi, Lu Xiao, Xu Guangyu, Song Jian, Wang Hongli, Xia Xinlei, Lu Feizhou, Jiang Jianyuan, Zhu Wei, Yu Zuochong, Ma Xiaosheng, Zou Fei
Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, China.
Department of Orthopedics, Jinshan Hospital, Fudan University, Shanghai, China.
Bone Res. 2025 Aug 12;13(1):72. doi: 10.1038/s41413-025-00449-6.
Intervertebral disc degeneration (IVDD) is the primary contributor to a range of spinal diseases. Dynamin-related protein 1 (Drp1)-mediated mitochondrial fission has recently been identified as a new cause of nucleus pulposus cell (NPC) death and IVDD, but the underlying mechanisms remain unclear. Although the effects of Drp1 phosphorylation in IVDD have been studied, it is currently unknown if small ubiquitin-like modifications (SUMOylation) of Drp1 regulate IVDD. This study aimed to investigate the functions and mechanisms of mitochondria-anchored protein ligase (MAPL), a mitochondrial SUMO E3 ligase, during IVDD progression. The expression of genes related to SUMOylation and mitochondrial dynamics in TNF-α-stimulated NPCs was analysed via RNA sequencing. The levels of total and mitochondrial SUMO1 conjugates were elevated with MAPL upregulation in TNF-α-treated NPCs. Additionally, mitochondrial fragmentation and dysfunction were induced by TNF-α stimulation. MAPL overexpression promoted mitochondrial SUMOylation and SUMO1 modification of Drp1, thereby facilitating the mitochondrial translocation of Drp1 and mitochondrial fission. MAPL-induced ROS accumulation and ΔΨm loss led to increased NPC apoptosis. Mutation of the SUMO-acceptor lysine residues of Drp1 hindered its SUMOylation and rescued the mitochondrial phenotypes caused by MAPL. SENP5 overexpression phenocopied MAPL silencing, negatively modulating the SUMO1 modification of Drp1 and mitochondrial fission in NPCs. In a rat IVDD model, forced expression of MAPL by using an adeno-associated virus (AAV) vector aggravated IVD tissue damage, whereas the knockdown of MAPL delayed IVDD progression. Our findings highlight the importance of SUMOylation in IVDD. The inhibition of MAPL-mediated Drp1 SUMOylation alleviates mitochondrial fission and limits IVDD development, providing a potential strategy for IVDD treatment.
椎间盘退变（IVDD）是一系列脊柱疾病的主要原因。动力相关蛋白1（Drp1）介导的线粒体分裂最近被确定为髓核细胞（NPC）死亡和IVDD的新原因，但其潜在机制仍不清楚。尽管已经研究了Drp1磷酸化在IVDD中的作用，但目前尚不清楚Drp1的小泛素样修饰（SUMO化）是否调节IVDD。本研究旨在探讨线粒体锚定蛋白连接酶（MAPL），一种线粒体SUMO E3连接酶，在IVDD进展过程中的功能和机制。通过RNA测序分析了TNF-α刺激的NPC中与SUMO化和线粒体动力学相关的基因表达。在TNF-α处理的NPC中，随着MAPL上调，总SUMO1共轭物和线粒体SUMO1共轭物的水平升高。此外，TNF-α刺激诱导了线粒体碎片化和功能障碍。MAPL过表达促进了Drp1的线粒体SUMO化和SUMO1修饰，从而促进了Drp1的线粒体易位和线粒体分裂。MAPL诱导的ROS积累和ΔΨm丧失导致NPC凋亡增加。Drp1的SUMO受体赖氨酸残基突变阻碍了其SUMO化，并挽救了由MAPL引起的线粒体表型。SENP5过表达模拟了MAPL沉默，负向调节NPC中Drp1的SUMO1修饰和线粒体分裂。在大鼠IVDD模型中，使用腺相关病毒（AAV）载体强制表达MAPL加重了IVD组织损伤，而敲低MAPL则延迟了IVDD进展。我们的研究结果突出了SUMO化在IVDD中的重要性。抑制MAPL介导的Drp1 SUMO化可减轻线粒体分裂并限制IVDD发展，为IVDD治疗提供了一种潜在策略。
