Bruceine A protects nuclear receptor 4A1 from ubiquitin-degradation to alleviate mesangial proliferative glomerulonephritis.

The nuclear receptor 4A1(NR4A1) plays a crucial role in maintaining cellular homeostasis and is involved in various disease processes; however, its functional role and pharmacological potential in mesangial proliferative glomerulonephritis (MsPGN) remain unexplored. In this study, we found that downregulation of NR4A1 promotes the pathogenesis of MsPGN by regulating inflammatory and proliferative responses in mesangial cells (MCs), whereas overexpression of NR4A1 reverses these processes. Bruceine A (BA) binds to NR4A1 at residues D481/Q568 and exhibits NR4A1-dependent anti-inflammatory and anti-proliferative effects both in vitro and in vivo. Notably, adeno-associated virus serotype 9 (AAV9)-mediated overexpression of NR4A1 alleviates glomerular injury and inflammatory cascades, while knockout of NR4A1 impairs the renoprotective effects of BA. BA binds to the ligand-binding domain (LBD) of NR4A1 and further sterically blocks K48-linked polyubiquitination at K558, thereby stabilizing NR4A1 protein levels. This stabilization enables NR4A1 to auto-activate its own promoter, amplifying the transcriptional repression of nuclear factor kappa-B (NF-κB) signaling phosphorylation, which ultimately attenuates inflammatory cascades and mesangial proliferation to confer renal protection. This study provides a promising therapeutic avenue for the development of next-generation therapies against MsPGN.