METTL3 and ALKBH5 oppositely regulate m⁶A modification of TFEB mRNA, which dictates the fate of hypoxia/reoxygenation-treated cardiomyocytes

Abstract

N 6-methyladenosine (m 6 A) mRNA modifications play critical roles in various biological processes. However, no study addresses the role of m 6 A in macroautophagy/autophagy. Here, we show that m 6 A modifications are increased in H/R-treated cardiomyocytes and ischemia/reperfusion (I/R)-treated mice heart. We found that METTL3 (methyltransferase like 3) is the primary factor involved in aberrant m 6 A modification. Silencing METTL3 enhances autophagic flux and inhibits apoptosis in H/R-treated cardiomyocytes. However, overexpression of METTL3 or inhibition of the RNA demethylase ALKBH5 has an opposite effect, suggesting that METTL3 is a negative regulator of autophagy. Mechanistically, METTL3 methylates TFEB, a master regulator of lysosomal biogenesis and autophagy genes, at two m 6 A residues in the 3ʹ-UTR, which promotes the association of the RNA-binding protein HNRNPD with TFEB pre-mRNA and subsequently decreases the expression levels of TFEB. Further experiments show that autophagic flux enhanced by METTL3 deficiency is TFEB dependent. In turn, TFEB regulates the expression levels of METTL3 and ALKBH5 in opposite directions: it induces ALKBH5 and inhibits METTL3. TFEB binds to the ALKBH5 promoter and activates its transcription. In contrast, inhibition of METTL3 by TFEB does not involve transcriptional repression but rather downregulation of mRNA stability, thereby establishing a negative feedback loop. Together, our work uncovers a critical link between METTL3-ALKBH5 and autophagy, providing insight into the functional importance of the reversible mRNA m 6 A methylation and its modulators in ischemic heart disease.

Targeting CLK3 inhibits the progression of cholangiocarcinoma by reprogramming nucleotide metabolism

“…As described previously (Song et al, 2019), we cultured HEK293T cells to perform the dual-luciferase reporter assays.…”

RNA N6-methyladenosine: a promising molecular target in metabolic diseases

“…Suppressing adipogenesis by promoting cell cycle transition in mitotic clonal expansion [89] YTHDF2 Inhibiting autophagy and adipogenesis by decreasing protein expression of ATG5 and ATG7 and shortening the lifespan of their m 6 A-modified mRNAs [87] Suppressing adipogenesis by increasing m 6 A methylation of CCNA2 and CDK2 and reversing the methylation effect of FTO on CCNA2 and CDK2 [90,91] Inhibiting adipogenesis via the downregulation of CCND1 [92] NAFLD FTO Down-regulating mitochondrial content and up-regulating TG deposition [101] Promoting hepatic fat accumulation by increasing the expression of lipogenic genes, including FASN, SCD and MOGAT1, and intracellular TG level in HepG2 cells [101] Increasing oxidative stress and lipid deposition [99] YTHDF2 Increasing lipid accumulation by decreasing both PPARα mRNA lifetime and expression [105] METTL3 Increasing lipid accumulation by decreasing both PPARα mRNA lifetime and expression [105] Hypertension m 6 A-SNPs EncodIing β1-adrenoreceptor, a hypertension-susceptibility candidate gene [108,109] Altering BP-related gene expression, mRNA stability and homeostasis [110] Cardiovascular diseases FTO Decreasing fibrosis and enhancing angiogenesis in mouse models of myocardial infarction [111] METTL3 Driving cardiomyocyte hypertrophy by catalyzing methylation of m 6 A on certain subsets of mRNAs [112] Decreasing eccentric cardiomyocyte remodeling and dysfunction [112] Inhibiting cellular autophagic flux and promoting apoptosis in hypoxia/reoxygenation-treated cardiomyocytes [113] Osteoporosis METTL3 Inhibiting adipogenesis and adipogenic differentiation via JAK1/STAT5/C/EBPβ pathway in bone marrow stem cells [119] Inhibiting osteoporosis pathological phenotypes, consisting of decreased bone mass and increased marrow adiposity via PTH/PTH1R signaling axis [118] FTO Promoting the differentiation of adipocyte and osteoblast by upregulating GDF11-FTO-PPARγ signalling way [116] Enhancing the stability of mRNA of proteins which function to protect osteoblasts from genotoxic damage through Hspa1a-NF-κB signaling way [120] Immune-related MDs ALKBH5 Expressing highly in organs enriched in immune cells with frequent immune reactions [10,123] METTL3 Stimulating T cell activation and the development of T lymphocytes in the thymus by regulating the translation of CD40, CD80 and TLR4 signaling adaptor TIRAP transcripts in den...…”

“…Whereas, diminished METTL3 promotes eccentric cardiomyocyte remodeling and dysfunction [112]. Moreover, METTL3 upregulation inhibits cellular autophagic flux and promotes apoptosis in hypoxia/reoxygenation-treated cardiomyocytes [113].…”

Transcriptome-wide map of m6A circRNAs identified in hypoxic pulmonary hypertension rat model

“…Up to now, no consistent conclusion was reached about the link between m 6 A and hypoxia. Previous reports found that the m 6 A abundance in mRNA was increased under hypoxia stress in HEK293T cells and cardiomyocytes (37, 38). The increased m 6 A level stabilized the mRNAs of Glucose Transporter 1 (Glut1), Myc proto-oncogene bHLH transcription factor (Myc), Dual Specificity Protein Phosphatase 1 (Dusp1), Hairy and Enhancer of Split 1 (Hes1), and Jun Proto-Oncogene AP-1 Transcription Factor Subunit (Jun) without influencing their protein level (37).…”

“…Hypoxia increased demethylation by stimulating hypoxia-inducible factor (HIF)-1α- and HIF-2α–dependent over-expression of ALKBH5 (26). In addition, transcription factor EB activates the transcription of ALKBH5 and downregulates the stability of METTL3 mRNA in hypoxia/reoxygenation (H/R)-induced autophagy in ischemic diseases (38). Our study found that m 6 A abundance in total circRNAs was decreased by hypoxia exposure.…”