Autoantibodies to the functionally active RING-domain of Ro52/SSA are associated with disease activity in patients with lupus

Abstract

The Ro52 protein of the Ro/SSA antigen was recently defined as an E3 ligase controlling cytokine production. Autoantibodies from systemic lupus erythematosus (SLE) patients targeting the Ro52-RING domain, containing the E3 ligase activity, have been shown to inhibit the E3 ligase activity of Ro52. The objective of the present study was to investigate correlations between clinical parameters in patients with SLE and levels of Ro/SSA (Ro52 and Ro60) and La/SSB autoantibodies, including autoantibodies directed towards the functional RING and B-box domains of the Ro52 protein. SLE patients ( n = 232) were clinically examined and disease activity indices collected concurrently to blood sampling. The samples were analyzed for immunological parameters including autoantibodies. Ro52 autoantibody levels were associated with more variables than the other analyzed antibodies and were significantly associated with several individual items related to sSS and the diagnosis of sSS itself ( p = 0.004). Other associated variables were high sedimentation rate ( p = 0.0003), levels of immunoglobulins ( p = 0.0003), and an inverse correlation with levels of lymphocytes ( p = 0.003) and leukocytes ( p = 0.01). Antibodies to the RING domain of Ro52, which is the functionally active domain with E3 ligase activity, were significantly correlated with disease activity as measured by the SLAM score. We conclude that autoantibodies against Ro52 and in particular its functional RING domain are important in lupus patients and associated with several clinical and laboratory features of the disease. The impact on disease activity of Ro52-RING specific antibodies was especially noted, and could imply a functional role for these autoantibodies in inhibiting Ro52 activity, which is important for the control of proinflammatory cytokine production, including type 1 interferons.