Activated Protein C Modulates YBX1 Expression and Glycolysis in Diabetic Nephropathy

Background: Diabetic kidney disease (DKD), the leading cause of end-stage renal disease worldwide and a major driver of cardiovascular disease, is characterized by pathophysiological and metabolic changes in the kidney. The cytoprotective coagulation protease activated protein C (aPC) is known to reduce mitochondrial ROS production in tubular cells and attenuate the associated sterile inflammation, yet the mechanisms by which aPC regulates tubular cell metabolism remain unexplored. Methods: Persistent hyperglycaemia was induced by streptozotocin (STZ) administration to 8-week-old wild-type (WT) and transgenic mice with high aPC–expression (hPC), and maintained under hyperglycaemic conditions for 24 weeks. Metabolic profiling (Seahorse) was performed in control and YBX1-deficient tubular cells pretreated with aPC with or without high glucose. Glycolytic gene expression in these cells was analysed by qRT-PCR. Results: Here we show that aPC reduces the extracellular acidification rate (ECAR) in tubular cells under hyperglycemic conditions, indicating altered metabolic activity. Since aPC regulates the cold shock protein Y-box-binding protein 1 (YBX1), an important mediator of cell fate and metabolism, in tubular cells, we investigated a possible interaction of aPC and YBX1 in DKD. In a DKD mouse model, YBX1 expression was significantly reduced in tubular cells of WT mice, but not in diabetic hPC mice. In vitro, aPC prevented YBX1 degradation and phosphorylation, promoting its cytoplasmic retention and inhibiting nuclear translocation under high-glucose conditions. Additionally, high glucose reduced YBX1 expression, and silencing YBX1 enhanced glycolysis, suggesting its role in glucose metabolism. The metabolic effects of aPC were lost in YBX1-deficient cells. Mechanistically, phosphorylation of YBX1, which regulates its nuclear translocation, was attenuated by aPC via PI3K/AKT signaling. Conclusion: Our results identify YBX1 as a key mediator of aPC’s effect on glucose metabolism in tubular cells in DKD. These data suggest that aPC induces protective metabolic reprogramming and reduces reactive metabolites by preventing the degradation of YBX1 and attenuating its phosphorylation via the PI3K/AKT pathway, thus modulating its subcellular localization. These findings identify the aPC–YBX1 interaction as a potential therapeutic target for reducing metabolic dysfunction in tubular cells in DKD. Funding: Government Support – Non-U.S.