Abstract：
The aim of this study was to investigate the underlying molecular mechanism behind the promotion of cell survival under conditions of glucose deprivation by l-lactate. To accomplish this, we performed tissue microarray and immunohistochemistry staining to analyze the correlation between the abundance of pan-Lysine lactylation and prognosis. In vivo evaluations of tumor growth were conducted using the KPC and nude mice xenograft tumor model. For mechanistic studies, multi-omics analysis, RNA interference, and site-directed mutagenesis techniques were utilized. Our findings robustly confirmed that l-lactate promotes cell survival under glucose deprivation conditions, primarily by relying on GLS1-mediated glutaminolysis to support mitochondrial respiration. Mechanistically, we discovered that l-lactate enhances the NMNAT1-mediated NAD+ salvage pathway while concurrently inactivating p-38 MAPK signaling and suppressing DDIT3 transcription. Notably, Pan-Kla abundance was significantly upregulated in patients with Pancreatic adenocarcinoma (PAAD) and associated with poor prognosis. We identified the 128th Lysine residue of NMNAT1 as a critical site for lactylation and revealed EP300 as a key lactyltransferase responsible for catalyzing lactylation. Importantly, we elucidated that lactylation of NMNAT1 enhances its nuclear localization and maintains enzymatic activity, thereby supporting the nuclear NAD+ salvage pathway and facilitating cancer growth. Finally, we demonstrated that the NMNAT1-dependent NAD+ salvage pathway promotes cell survival under glucose deprivation conditions and is reliant on the activity of Sirt1. Collectively, our study has unraveled a novel molecular mechanism by which l-lactate promotes cell survival under glucose deprivation conditions, presenting a promising strategy for targeting lactate and NAD+ metabolism in the treatment of PAAD.
摘要：
这项研究的目的是研究在乳酸葡萄糖剥夺条件下促进细胞存活的潜在分子机制。要做到这一点，我们进行了组织微阵列和免疫组织化学染色，以分析泛赖氨酸乳酸化的丰度与预后之间的相关性。使用KPC和裸小鼠异种移植肿瘤模型进行肿瘤生长的体内评估。对于机械学研究，多组学分析，RNA干扰,并利用了定点诱变技术。我们的发现有力地证实了L-乳酸在葡萄糖剥夺条件下促进细胞存活，主要依靠GLS1介导的谷氨酰胺分解来支持线粒体呼吸。机械上,我们发现L-乳酸增强NMNAT1介导的NAD+救助途径,同时失活p-38MAPK信号并抑制DDIT3转录.值得注意的是,Pan-Kla丰度在胰腺腺癌（PAAD）患者中显著上调，并与不良预后相关。我们将NMNAT1的第128个赖氨酸残基鉴定为乳酸化的关键位点，并揭示了EP300是负责催化乳酸化的关键乳酸转移酶。重要的是,我们阐明NMNAT1的乳酸化增强其核定位并保持酶活性，从而支持核NAD+挽救途径并促进癌症生长。最后,我们证明了NMNAT1依赖性NAD+救助途径在葡萄糖剥夺条件下促进细胞存活，并且依赖于Sirt1的活性。总的来说，我们的研究揭示了一种新的分子机制，L-乳酸在葡萄糖剥夺条件下促进细胞存活，为PAAD的治疗提供了靶向乳酸和NAD+代谢的有希望的策略。
