Interferon-α induces up-regulation and nuclear translocation of the Ro52 autoantigen as detected by a panel of novel Ro52-specific monoclonal antibodies

Interferon-alpha (IFN-alpha) has been implicated in the pathogenesis of Sjogren's syndrome and systemic lupus erythematosus. Ro52, which was recently identified as an E3 ligase with anti-proliferative and pro-apoptotic properties, is a major autoantigen targeted in both these conditions. Microarray analyses have indicated up-regulation of Ro52 by INF-alpha, and the objective of the present study was to address the potential link between IFN-alpha and Ro52. To investigate the influence of IFN-alpha on Ro52 protein levels and cellular localization, we generated a panel of monoclonal antibodies to different domains of Ro52. These novel monoclonal antibodies were characterized by immunoprecipitation, Western blot, and enzyme-linked immunosorbent assay using cell lysates, recombinant Ro52 protein, and synthetic peptides. Ro52 was up-regulated in HeLa cells and human B cells at the messenger RNA and protein levels in response to IFN-alpha stimulation as detected by reverse transcriptase polymerase chain reaction and Western blot. After up-regulation, Ro52 translocated from the cytoplasm to the nucleus. The nuclear translocation of Ro52 was observed after staining with generated monoclonal antibodies specific for both the RING, coiled-coil, and B30.2 domains of Ro52 and the nuclear translocation of Ro52 preceded IFN-alpha-induced apoptotic cell death detected by caspase-3 and TUNEL staining in the treated cultures. In conclusion, our data show that IFN-alpha first induces up-regulation of Ro52 protein and then prompts translocation of the up-regulated Ro52 protein in to the nucleus. The translocation precedes apoptosis of the IFN-alpha exposed cells, suggesting a role for Ro52 in mediating the anti-proliferative or pro-apoptotic effects of the autoimmune-related cytokine IFN-alpha.