Inhibition of METTL3 promotes mesangial cell mitophagy and attenuates glomerular damage by alleviating FOSL1 m6A modifications via IGF2BP2-dependent mechanisms

Epigenetic changes are involved in many physiological and pathological processes. Mitophagy plays a critical role in chronic kidney disease (CKD); however, the role of N6-methyladenosine (m6A) modification in renal mitophagy remains unclear. In this research, we aim to elucidate the role of RNA methylation in modulating mitophagy and its involvement in the pathophysiology of chronic glomerulonephritis (CGN). We found that Methyltransferase-like 3 (METTL3) was significantly upregulated in biopsies from CKD patients, as well as in CGN mice and cultured mouse mesangial cells (MMCs), and was inversely correlated with glomerular filtration rate. Adeno-associated virus serotype 9 (AAV9)-mediated METTL3 silencing from mouse kidneys attenuated adenine-induced glomerular damage, and promoted renal mitophagy. METTL3 knockdown significantly reduced the oxidative stress and inflammation levels and promoted mitophagy in lipopolysaccharide (LPS)-stimulated MMCs, while its overexpression significantly aggravated these responses in vitro. Moreover, FOSL1 (Fos-like antigen 1) was identified as a target of METTL3 and the stability of FOSL1 was increased through binding of IGF2BP2 (Insulin-like Growth Factor 2 mRNA-binding Protein 2) to its m6A-modified regions. The mitophagy regulatory effects of FOSL1 were then explored both in vitro and in vivo. Mechanistically, METTL3 modulated AMPK (AMP-activated Protein Kinase)/mTOR (Mechanistic Target of Rapamycin) signaling via the m6A modification of FOSL1 in an IGF2BP2-dependent manner and exerted a mitophagy inhibitory effect. In summary, this study suggested that METTL3-mediated m6A modification is an important mechanism of mesangial cell (MCs) injury in CGN. Targeting m6A through the writer enzyme METTL3 is a potential approach for the treatment of CGN.