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From the * Division of Tumor Immunology, the Dana Farber Cancer Institute; and the Proteins cleaved by interleukin-1
Department of
Medicine, Division of Rheumatology and Immunology, Brigham & Women's Hospital, Boston,
Massachusetts 02115
converting enzyme family proteases during apoptosis are
common targets for autoantibody production in patients with systemic lupus erythematosus
(SLE). We have tested the possibility that proteins phosphorylated in cells undergoing apoptosis
are also targets for autoantibody production in patients with autoimmune disease. Sera from 9/12
patients containing antinuclear antibodies (10/12 meeting diagnostic criteria for SLE or a lupus
overlap syndrome), precipitated new phosphoproteins from lysates derived from Jurkat T cells
treated with apoptotic stimuli (i.e., Fas-ligation, gamma irradiation, ultraviolet irradiation), but
not with an activation (i.e., CD3-ligation) stimulus. Sera derived from individual patients precipitated different combinations of seven distinct serine-phosphorylated proteins. None of
these phosphoproteins were included in precipitates prepared using sera from patients with diseases that are not associated with autoantibody production or using serum from rheumatoid arthritis patients. Protein phosphorylation precedes, or is coincident with, the induction of DNA
fragmentation, and is not observed when apoptosis is inhibited by overexpression of bcl-2. Serum from four patients precipitated a serine/threonine kinase from apoptotic cell lysates that
phosphorylates proteins of 23-, 34-, and 46-kD in in vitro kinase assays. Our results suggest
that proteins phosphorylated during apoptosis may be preferred targets for autoantibody production in patients with SLE.
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