Lactylation increases the stability of <scp>RBM15</scp> to drives <scp>m6A</scp> modification in non‐small‐cell lung cancer cells
Zhenyu Zhao, Zhe Zhang, Qidong Cai, Rui Yang, Hengxing Liang, Banglun Qian, Bing Xiao, Yupeng Jiang, Li Wang, Xiang Wang, Juan Cai
Abstract
Emerging evidence supports the involvement of N6-Methyladenosine (m6A) modification in the etiology and progression of lung adenocarcinoma (LUAD), highlighting its potential as a therapeutic target. RNA-binding protein 15 (RBM15) is a well-known m6A writer protein that enhances global m6A methylation levels by associating with the METTL3-WTAP complex. Previous studies have demonstrated that RBM15 is upregulated and exerts an oncogenic role in LUAD by promoting the N6-methyladenosine-mediated mRNA stability. However, the regulatory mechanisms of RBM15 remain elusive. In this study, we observed that L-lactate upregulates RBM15 protein levels in non-small-cell lung cancer cell lines A549 and H23 in a time- and dosage-dependent manner. Furthermore, we discovered that lactate uptake mediated by Monocarboxylate transporter 1 (MCT1) is essential for RBM15 induction. Subsequent investigations revealed that L-lactate promotes lactylation of RBM15 majorly at Lys850 (K850), while histone deacetylase 3 (HDAC3) acts as the delactylase for RBM15. Importantly, lactylation of RBM15 stabilizes itself by inhibiting proteasome-mediated ubiquitin degradation. Mutation of the lactylation site K850R disrupts the association between RBM15 and METTL3, leading to a reduction in global m6A levels. Moreover, K850R significantly abrogated RBM15-mediated cell proliferation and migration in LUAD cells. Collectively, these findings unveil lactylation as a novel regulatory mechanism affecting both stability and m6A methylation activity of RBM15 in LUAD cells.