Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.
Cell Death Dis. 2020 Feb 6;11(2):103. doi: 10.1038/s41419-020-2284-8.
N6 methyladenosine (mA) is one of the most prevalent epitranscriptomic modifications of mRNAs, and plays a critical role in various bioprocesses. Bone-derived mesenchymal stem cells (BMSCs) can attenuate apoptosis of nucleus pulposus cells (NPCs) under compression; however, the underlying mechanisms are poorly understood. This study showed that the level of mA mRNA modifications was decreased, and the autophagic flux was increased in NPCs under compression when they were cocultured with BMSCs. We report that under coculture conditions, RNA demethylase ALKBH5-mediated FIP200 mRNA demethylation enhanced autophagic flux and attenuated the apoptosis of NPCs under compression. Specific silencing of ALKBH5 results in impaired autophagic flux and a higher proportion of apoptotic NPCs under compression, even when cocultured with BMSCs. Mechanistically, we further identify that the mA "reader" YTHDF2 is likely to be involved in the regulation of autophagy, and lower mA levels in the coding region of FIP200 lead to a reduction in YTHDF2-mediated mRNA degradation of FIP200, a core molecular component of the ULK1 complex that participates in the initiating process of autophagy. Taken together, our study reveals the roles of ALKBH5-mediated FIP200 mRNA demethylation in enhancing autophagy and reducing apoptosis in NPCs when cocultured with BMSCs.
N6 甲基腺苷（mA）是最普遍的 mRNA 转录后修饰之一，在各种生物过程中发挥着关键作用。骨源性间充质干细胞（BMSCs）在受压时可以减轻髓核细胞（NPCs）的凋亡；然而，其潜在机制尚不清楚。本研究表明，当 NPCs 与 BMSCs 共培养时，受压下 mA mRNA 修饰水平降低，自噬流增加。我们报告说，在共培养条件下，RNA 去甲基酶 ALKBH5 介导的 FIP200 mRNA 去甲基化增强了自噬流，并减轻了 NPCs 的凋亡。当与 BMSCs 共培养时，特异性沉默 ALKBH5 会导致自噬流受损和更多受压 NPC 凋亡。从机制上讲，我们进一步确定 mA“阅读器”YTHDF2 可能参与了自噬的调控，FIP200 编码区的 mA 水平降低导致 YTHDF2 介导的 FIP200 mRNA 降解减少，而 FIP200 是参与自噬起始过程的 ULK1 复合物的核心分子成分。综上所述，我们的研究揭示了 ALKBH5 介导的 FIP200 mRNA 去甲基化在增强共培养的 BMSCs 中 NPC 自噬和减少凋亡中的作用。
