Abstract
Sepsis is marked by dysregulated inflammation and coagulopathy, with macrophages playing a central role. However, the molecular mechanisms linking macrophage dysfunction to sepsis-associated coagulopathy remain unclear. This study investigated the role of the E3 ubiquitin ligase Peli1 in sepsis progression and its downstream mechanism. Public scRNA-seq data from sepsis patients were analyzed to identify Peli1-associated immune signatures. Peli1 expression was validated in monocytes from sepsis patients and in CLP-induced septic mice. Peli1-deficient iBMDMs and myeloid cell-specific Peli1-deficient mice were used to assess its functional role. Transcriptomic profiling (RNA-seq), RT-qPCR, Western blotting, cycloheximide (CHX) chase assays, and co-immunoprecipitation (Co-IP) assays were performed to investigate the downstream molecular mechanisms and post-translational modifications. Peli1 was highly enriched in monocytes from fatal sepsis cases and markedly upregulated in monocytes from septic patients and CLP-induced septic mice. Peli1 deficiency attenuated macrophage inflammatory activation, improved platelet aggregation abnormalities, and enhanced survival in septic mice. Mechanistically, Lipg was identified as a crucial downstream target of Peli1 from transcriptomic analysis. Western blot and RT-qPCR validation confirmed that Peli1 predominantly regulated Lipg protein abundance through a post-transcriptional or post-translational mechanism, particularly under LPS-stimulated conditions. Peli1 was detected in the Lipg-immunoprecipitated complex, suggesting an association between Peli1 and Lipg. Further biochemical mapping revealed that Peli1 facilitated polyubiquitination specifically at the critical KR2 residue of Lipg to maintain its stability and shield it from proteasomal degradation. Ectopic restoration of Lipg successfully reversed the anti-inflammatory phenotypes and blunted cytokine production caused by Peli1 deficiency. Peli1 promoted sepsis-induced hyper-inflammation and coagulopathy by post-translationally maintaining Lipg stability in macrophages via site-specific ubiquitination. Target disruption of the Peli1-Lipg axis represents a promising therapeutic avenue to attenuate detrimental inflammation and immunothrombotic responses during sepsis.