Lactylation of PTBP1 drives a pro-apoptotic positive feedback loop in microglia following oxygen-glucose deprivation/reoxygenation-induced injury.

Cerebral hypoxia-ischemia disrupts cellular energy metabolism and exacerbates microglial apoptosis through mechanisms that remain elusive. In this study, given the substantial lactate accumulation under hypoxic-ischemic conditions, we explored how lactylation, a lactate-derived post-translational modification, drives apoptotic signaling to identify potential therapeutic targets. Global lactylome profiling of microglia subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) revealed widespread protein hyperlactylation, involving 2 555 lactylated sites across 1 071 proteins. Notably, we identified the RNA-binding splicing regulator PTBP1 as a novel non-histone target lactylated at lysine residues K258 and K452 in a manner dynamically regulated by the delactylase Sirt1 and functionally correlated with the induction of microglial apoptotic signaling. Mechanistically, hyperlactylated PTBP1 directly suppressed the expression of USP18, triggering FTO protein degradation and subsequent downregulation of delactylase SIRT1. This loss of SIRT1-mediated lactylate removal further amplified PTBP1 lactylation, ultimately exacerbating apoptotic activation and establishing a self-reinforcing pro-apoptotic positive feedback loop. Consistently, lactylation-deficient mutations (K258R and K452R) on PTBP1 significantly attenuated apoptotic signaling. Our findings delineate a lactylation-driven signaling cascade centered on PTBP1 that critically mediates OGD/R-induced microglial apoptosis, and propose therapeutic targeting of the lactylation-governed PTBP1-USP18-FTO-SIRT1 signaling axis as a promising strategy to ameliorate apoptosis-related neurological pathogenesis.