The Ro52 gene is officially termed TRIM21, as it is a member of the tripartite motif protein (TRIM) family, qualified by its RING and B-box domains. The protein is typically located in the cytoplasm, though it can move to the nucleus in the presence of pro-inflammatory signals, and it can also be expressed on the cell surface. There is evidence that Ro52 itself is a cytosolic Fc receptor. Ro52 is a regulatory protein, and negatively moderates inflammatory response, such as the secretion of pro-inflammatory cytokines in the interleukin and INF families. Ro52 can both regulate and be induced by INF cytokines. Loss of function or blockage of Ro52 results in uncontrolled inflammation at the onset of injury or disease. Patients with SLE and SS not only show elevated levels of Anti-Ro antibodies, but also elevated levels of Ro52.
Ro52 has one primary epitope to which anti-Ro/SSA binds, independent of the autoimmune disease. The most common domain anti-Ro52 targets is the coiled coil (cc) domain, as well as the RING and B-box domains.
Ro52 does not bind to small cytoplasmic non-coding RNA strands (hY-RNA). The notion that Ro52 formed a complex with Y RNA resulted from studies that suggesting that Ro52 and Ro60 formed a complex together.
Ro52 may impact the pathogenesis of autoimmune disease: patients with SLE and SS have been shown to express high levels of Ro52 transcripts. Though Ro52 and Ro60 are often seen in elevated levels together in patients with autoimmune disease, Ro52 manifests without Ro60 in SS. Additionally, Anti-Ro52 antibody has been identified at elevated levels in patients with interstitial lung disease, as well as in autoimmune hepatitis type 1.