METTL14-Mediated m6A Modification of TUG1 Represses Ferroptosis in Alzheimer's Disease via Inhibiting GDF15 Ubiquitination

Background: Alzheimer’s disease (AD) is a neurodegenerative disease that remains a serious global health issue. Ferroptosis has been recognized as a vital driver of pathological progression of AD. However, the detailed regulatory mechanisms of ferroptosis during AD progression remain unclear. This study aimed to explore the regulatory role and mechanism of methyltransferase like 14 (METTL14) in ferroptosis in AD models. Methods: Serum samples were collected from 18 AD patients and 18 healthy volunteers to evaluate clinical correlation. Scopolamine-treated mice and Aβ1–42-stimulated SH-SY5Y cells were served as the in vivo and in vitro models of AD. Ferroptosis was detected by reactive oxygen species (ROS), Fe2+, total iron levels, and ferroptosis-related proteins glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11). Cell viability was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) assay. The N6-methyladenosine (m6A) modification was detected by RNA methylation quantification kit and methylated RNA immunoprecipitation sequencing-quantitative real-time polymerase chain reaction (MeRIP-qPCR). Molecular mechanisms were investigated by RNA pull-down, RNA immunoprecipitation (RIP), and co-immunoprecipitation (Co-IP) assays. Cognitive disorder of AD mice was measured by Morris water maze test. Results: METTL14 was down-regulated, while lncRNA taurine upregulated gene 1 (TUG1) was up-regulated in clinical patients and experimental models of AD. Functional experiments demonstrated that METTL14 overexpression or TUG1 silencing effectively attenuated Aβ1–42-induced ferroptosis and neurotoxicity in SH-SY5Y cells. Mechanistically, METTL14-mediated m6A modification reduced the stability of TUG1. Moreover, TUG1 promoted the ubiquitination and degradation of growth differentiation factor 15 (GDF15) by directly interacted with Smad ubiquitin regulatory factor 1 (SMURF1), which consequently inactivated nuclear factor erythroid 2-related factor 2 (NRF2). Rescue experiments indicated that GDF15 depletion reversed sh-TUG1-mediated protection against ferroptosis and neurotoxicity. Finally, Mettl14 overexpression repressed ferroptosis to ameliorate the cognitive disorder via modulating Tug1/Gdf15/Nrf2 pathway in vivo. Conclusion: METTL14 inhibited ferroptosis to ameliorate AD pathological development by m6A modification of TUG1 to activate GDF15/NRF2 axis, providing a novel therapeutic target for AD.