USP5 promotes glycolysis of fibroblast-like synoviocytes by stabilizing the METTL14/m6A/GLUT1 axis in rheumatoid arthritis

Fibroblast-like synoviocytes (FLSs) contribute to the advancement of rheumatoid arthritis (RA) through enhanced metabolic reprogramming. This research focused on exploring the role and underlying mechanism of ubiquitin-specific protease 5 (USP5) in modulating the glycolysis and activation of RA-FLSs. Here, we identified that knockdown of USP5 in RA rats reduced synovial inflammation and glycolytic activity, as evidenced by decreased serum lactate levels and GLUT1 expression. In RA-FLSs, USP5 knockdown or treatment with 2-DG reduced cell proliferation, migration, invasion, cytokine production, and glycolysis, while increased apoptosis. Mechanistically, USP5 stabilized METTL14 by inhibiting its ubiquitination, while METTL14 enhanced the m⁶A modification of GLUT1 mRNA, thereby increasing its expression. Furthermore, overexpression of METTL14 partially reversed the effects of USP5 knockdown on glycolysis and inflammatory activation in RA-FLSs. Additionally, knockdown of METTL14 inhibited RA-FLS glycolysis and inflammatory activation by downregulating GLUT1. Collectively, USP5 stabilized METTL14-mediated m⁶A modification of GLUT1 by inhibiting the ubiquitination of METTL14, thereby enhancing glycolysis and inflammatory activation in RA-FLSs. These results suggest that the USP5/METTL14/GLUT1 axis could be a potential therapeutic target for RA.