Lactylation Enhances the Activity of Lactate Dehydrogenase A and Promotes the Chemoresistance to Cisplatin Through Facilitating DNA Nonhomologous End Junction in Lung Adenocarcinoma

Abstract Lactylation is a novel post‐translational modification closely related to the glycolytic process, but the regulatory mechanisms between lactylation and glycolysis are far from being elucidated. Lactate dehydrogenase A (LDHA) catalyzes the formation of lactate, which provides the modifying group for protein lactylation. However, whether lactylation occurs on LDHA itself remains unknown. Here, it is found that lactylation promotes the enzymatic activity of LDHA in lung adenocarcinoma (LUAD), which in turn enhances the overall level of cellular lactylation through a positive feedback loop. Screening identified Lys81 and Lys318 as key LDHA lactylation sites, with alanyl‐tRNA synthetase 1 (AARS1) serving as the mediating lactyltransferase. Mass spectrometry reveals that numerous proteins involved in DNA nonhomologous end junction (NHEJ), including FEN1, XRCC5, and XRCC6 might be regulated by lactylation. Delactylation of these proteins significantly hinders the formation of FEN1‐RAD1‐RAD9A‐HUS1 complex, thereby leading to dysfunction of NHEJ and increasing the sensitivity of cancer cells to cisplatin. In summary, this work identifies LDHA lactylation as a critical mechanism for accelerating the progression of LUAD and reveals how this lactylation influenced cisplatin sensitivity of LUAD cells, which deepen the understanding of lactylation‐mediated tumor progression and provide a potential new anticancer strategy.