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     The image is immunohistochemistry of paraffin-embedded Human ovarian cancer tissue using P01838(TRIM21 Antibody) at dilution 1/20. (Original magnification: ×200)    

  
  

TRIM21 (Tripartite motif-containing protein 21), also known as Ro52. is a member of the TRIM protein family characterized by its conserved RING, B-box, and coiled-coil domains. Primarily localized in the cytoplasm, TRIM21 functions as an E3 ubiquitin ligase and plays a critical role in innate immunity. It recognizes antibody-opsonized pathogens (e.g., viruses) that enter cells via Fc receptor-independent mechanisms, bridging adaptive and innate immune responses. Upon binding to the constant region (Fc) of antibodies attached to intracellular pathogens, TRIM21 catalyzes the ubiquitination of viral particles, targeting them for proteasomal degradation via the ubiquitin-proteasome system. Concurrently, it activates inflammatory signaling pathways, including NF-κB and AP-1. to amplify antiviral defenses.

TRIM21 is also implicated in autoimmune diseases, particularly systemic lupus erythematosus (SLE) and Sj?gren’s syndrome, where autoantibodies against TRIM21 are common. Its dual role—as both an antiviral effector and an autoantigen—highlights its complex involvement in immune regulation. Recent studies explore its therapeutic potential, leveraging its ability to degrade pathogenic proteins or its utility in engineered proteolysis-targeting chimeras (PROTACs). Despite advances, its precise regulatory mechanisms and disease-related pathways remain under investigation, making TRIM21 a focal point in immunology and autoimmunity research.