Tripartite motif-containing protein 21 (TRIM21)

Tripartite motif-containing protein 21 (TRIM21) is a multifunctional cytosolic E3 ubiquitin ligase and a high-affinity intracellular Fc receptor for IgG, IgM, and IgA [1, 2]. It serves as a critical component of the intracellular innate immune system by detecting and neutralizing antibody-coated viruses and bacteria that have escaped extracellular defenses and entered the cytoplasm [2]. Upon binding the Fc region of an antibody, TRIM21 undergoes auto-ubiquitination and recruits the 26S proteasome to rapidly degrade the entire antibody-pathogen complex, a mechanism termed antibody-dependent intracellular neutralization (ADIN) [2, 3]. Additionally, TRIM21 regulates inflammatory signaling by modulating the stability of interferon regulatory factors (IRFs) such as IRF3, IRF5, and IRF7, thereby influencing the production of type I interferons [4]. Clinically, TRIM21 is well-known as the Ro52 autoantigen, with anti-Ro52 antibodies serving as key diagnostic biomarkers for systemic lupus erythematosus and Sjögren's syndrome [1, 5]. In drug development, TRIM21 is the central effector in "Trim-Away" technology, which utilizes exogenous antibodies to trigger the targeted degradation of endogenous proteins, offering a potential therapeutic avenue for diseases driven by "undruggable" proteins [3]. [1] UniProt Consortium. (2023). P19474 (TRIM21_HUMAN). [2] Mallery, D. L., et al. (2010). Antibodies mediate intracellular immunity through tripartite motif-containing protein 21 (TRIM21). PNAS. [3] Clift, D., et al. (2017). A Method for the Acute and Rapid Degradation of Endogenous Proteins. Cell. [4] Espinosa, A., et al. (2009). The Sjögren's syndrome antigen Ro52/TRIM21 regulates T cell function and cytokine production. Journal of Immunology. [5] Schulte-Pelkum, J., et al. (2009). Clinical significance of anti-Ro52 antibodies. Clin Rev Allergy Immunol.

Other names

Ro52SSA1RNF8152 kDa Ro protein52 kDa ribonucleoprotein autoantigen Ro/SS-ASjögren syndrome antigen A1

TRIM21 is targeted primarily through the recruitment of its E3 ubiquitin ligase activity to degrade specific proteins via antibody-binding (Trim-Away) or through the modulation of its role in interferon signaling and autoantibody recognition.