Ro60 and La ribonucleoproteins become self-aggregated by cell stress

Ro and La antigens are of clinical interest in subacute cutaneous lupus erythematosus because skin lesions appear after UV irradiation, which induces the translocation of intracellular Ro and La ribonucleoproteins and trigger autoantibody production. Present studies address the question whether cellular stressors modify molecular characteristics and distribution of Ro60 and La proteins. To accomplish our goal HEp-2 cells were stressed by heat and UV irradiation and Ro and La expression was studied by indirect immunofluorescence and Western blot and crossed-immunoprecipitation using monoclonal anti-Ro/La or anti-HSP70 linked to CNBr-Sepharose 4B. Results of present studies confirm that Ro60 and La were located in the nuclei of non stressed cells; however under stress, both ribonucleoproteins were redistributed within cytoplasm and nucleoplasm, interestingly the stress induces self aggregation of both ribonucleoproteins, as demonstrated the Western blot assays. Ro and La proteins interact with the cytoskeleton protein via HSP70. In conclusion, the cell stress redistributes Ro and La proteins whiting nucleo-cytoplasmic compartments. This redistribution is accompanied by self aggregation of Ro and La which became associated with HSP70. Finally, the cell stress is an important factor for antigenic redistribution.