Systematic Analysis of Lysine Lactylation in Nucleus Pulposus Cells

Abstract

Nucleus pulposus (NP) resides in hypoxic microenvironment due to the avascular structure of intervertebral disc (IVD) and NP cells (NPCs) primarily reply on glycolysis and produce high levels of lactate. Intracellular lactate drives lysine lactylation (Kla) as a newly epigenetic modification. However, the impact of Kla on NPCs remains unknown. Here using single-cell RNA sequencing (scRNA-seq) data of human NP, we found that glycolysis was inhibited and aerobic oxidation was enhanced in NPCs during IVD degeneration (IDD). Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), we showed a global lactylome profiling on NPCs cultured in normoxia and hypoxia environment and found that 3510 lactylation sites on 1052 proteins in NPCs on non-histone proteins. Moreover, there are 18 proteins with 129 Kla sites exclusively detected in the normoxia group, and 117 Kla sites in 27 proteins were specific in hypoxia group. KEGG and GO analysis displayed that these lactylation proteins are tightly related to a variety of biological processes, such as ribosome, spliceosome and the VEGFA-VEGFA2 signaling pathway. Together, our study reveals that Kla plays an important role in regulating cellular metabolism and may contribute to IDD progression.

Keywords: Intervertebral disc degeneration; Nucleus pulposus; Lactylation