CUL4A promotes glycolytic activation of fibroblast-like synoviocytes by targeting FGF2 in rheumatoid arthritis

The central role in the pathogenesis of rheumatoid arthritis (RA) is played by fibroblast-like synoviocytes (FLS), which drive disease progression through aberrant proliferation, inflammatory cell recruitment, and subsequent cartilage and bone degradation. CUL4A is an important member of the Cullin family, which is a scaffolding protein for the E3 ubiquitin ligase complex. In this study, we investigated the functional significance and molecular mechanisms of CUL4A in the pathogenesis of RA. We identified elevated CUL4A expression in synovial tissues, TNFα-stimulated FLS, and peripheral blood mononuclear cells from RA patients. Knockdown of CUL4A led to a marked suppression of both cytokine production and glycolytic activity in FLS in vitro. RNA-seq analysis and validation revealed the PI3K/AKT pathway as a key mediator in this process, with a significant functional interaction between CUL4A and fibroblast growth factor 2 (FGF2). Furthermore, knocking down FGF2 significantly suppresses synovial inflammation in RA FLS. In vivo experiments, knocking down CUL4A significantly reduced synovial inflammation in K/BxN serum transfer arthritis mice and inhibited glycolytic activity. Additionally, the expression level of CUL4A mRNA shows a positive correlation with both clinical disease activity and inflammatory markers in RA. In conclusion, our findings reveal that CUL4A, via FGF2 binding, initiates PI3K/AKT pathway signaling, fostering the glycolysis process and synovial inflammation. Consequently, CUL4A holds significant promise as a target for early intervention against this pathogenic cascade.