Prmt1-mediated methylation regulates Ncoa4 stability to transactivate Adamts genes and promote bone extracellular matrix degradation in chronic hematogenous osteomyelitis
Background:
Protein arginine methyltransferases (Prmts) are critical enzymes involved in regulating a variety of biological processes and have been associated with the development and progression of numerous diseases. Despite their known functions in other pathological conditions, the specific role of Prmts in osteomyelitis remains largely unexplored.
Methods:
To investigate this, a mouse model of chronic hematogenous osteomyelitis (CHOM) was developed through intravenous injection of *Staphylococcus aureus* (*S. aureus*). Gene and protein expression levels were measured using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and immunoblotting techniques. Protein-protein interactions were assessed using immunoprecipitation and co-immunoprecipitation assays. Both in vitro and in vivo experiments were conducted to analyze protein methylation and ubiquitination. Bone tissue damage and extracellular matrix (ECM) degradation were evaluated using histological analysis.
Results:
Out of nine identified Prmt family members, Prmt1 was uniquely and significantly upregulated in mice with osteomyelitis. The study showed that the inflammatory microenvironment induced by infection specifically increased Prmt1 expression in osteoblasts and osteocytes. This elevation of Prmt1 enhanced its interaction with nuclear receptor coactivator 4 (Ncoa4), a transcriptional activator. Prmt1 mediated the arginine methylation of Ncoa4, which in turn stabilized the Ncoa4 protein by preventing its degradation. Stabilized Ncoa4 subsequently formed a transcriptional complex with CREB-binding protein (Cbp), a histone acetyltransferase, and Activator Protein 1 (Ap1), a transcription factor. This complex promoted the transcription of four ECM-degrading genes—*Adamts3*, *Adamts8*, *Adamts12*, and *Adamts14*—in osteoblasts and osteocytes, thereby accelerating ECM degradation.
Conversely, when Prmt1 was depleted or pharmacologically inhibited, Ncoa4 was no longer methylated following inflammatory stimulation. This led to its ubiquitination by the E3 ubiquitin ligase Rnf8, resulting in proteasomal degradation of Ncoa4 and subsequent suppression of *Adamts* gene expression. Pharmacological inhibitors of Prmt1, iCARM1, specifically TCE-5003 and MS023, were shown to significantly reduce ECM degradation and effectively hinder the progression of osteomyelitis in *S. aureus*-infected mice.
Conclusion:
This study identifies Prmt1 as a central regulator of bone ECM degradation in osteomyelitis through its role in stabilizing Ncoa4. These findings suggest that Prmt1 plays a key pathogenic role in osteomyelitis and could serve as a novel therapeutic target for treating this severe bone infection.