METTL3 Modulates Autophagy by Targeting TFEB in Myocardial Hypertrophy.

The aim of this study was to investigate the mechanism of m6A methylation in pathological myocardial hypertrophy (PMH), focusing on whether the methyltransferase METTL3 regulates the expression and nuclear translocation of the transcription factor EB (TFEB), thereby affecting autophagic activity and exacerbating the development of myocardial hypertrophy.An in vivo PMH model was established in mice via transverse aortic constriction (TAC), and an in vitro hypertrophy model was established using H9C2 cells stimulated with angiotensin II (AngII). HE staining, Western blotting, qRT-PCR, immunofluorescence, and dual-color autophagy flux analyses were employed to detect the expression of autophagy-related proteins (LC3, Beclin-1, P62, ATG5) and apoptosis levels. Changes in TFEB and key m6A-related enzymes (METTL3, ALKBH5, heterogeneous nuclear ribonucleoprotein D [HNRNPD]) were examined, and gene overexpression or knockdown experiments were performed to clarify their roles in regulating autophagy and myocardial hypertrophy. Finally, m6A MeRIP-qPCR and RIP-qPCR were conducted to explore the effect of METTL3 on m6A modification and the stability of TFEB transcripts, verifying the interplay between METTL3 and TFEB and its impact on autophagy.In both the in vivo and in vitro hypertrophy models, autophagy was significantly impaired and apoptosis was elevated, while TFEB mRNA and protein expression and its nuclear localization were clearly reduced. At the same time, global m6A methylation was markedly increased, accompanied by upregulation of METTL3 and HNRNPD, as well as downregulation of ALKBH5. Functional assays indicated that METTL3 overexpression further inhibited autophagy-related protein expression and autophagic flux, whereas METTL3 knockdown partially restored autophagy. Mechanistic studies revealed that METTL3 modulates TFEB pre-mRNA stability by influencing the binding efficiencies of ALKBH5 and HNRNPD, resulting in decreased TFEB expression. Conversely, overexpression of TFEB could partly counteract the autophagy impairment caused by METTL3 overexpression and reciprocally regulate the expression of METTL3, ALKBH5, and HNRNPD.METTL3 mediates the inhibition of TFEB via m6A modification, thereby impairing autophagy and aggravating myocardial hypertrophy. These findings suggest that the m6A-TFEB axis may serve as a novel therapeutic target for preventing and treating myocardial hypertrophy and heart failure, offering new insights into the intervention of cardiac remodeling-related diseases.