Defining a novel 75-kDa phosphoprotein associated with SS-A/Ro and identification of distinct human autoantibodies

Citation
Dr. Wang et al., Defining a novel 75-kDa phosphoprotein associated with SS-A/Ro and identification of distinct human autoantibodies, J CLIN INV, 104(9), 1999, pp. 1265-1275
Citations number
41
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Medical Research General Topics
Journal title
JOURNAL OF CLINICAL INVESTIGATION
ISSN journal
0021-9738 → ACNP
Volume
104
Issue
9
Year of publication
1999
Pages
1265 - 1275
Database
ISI
SICI code
0021-9738(199911)104:9<1265:DAN7PA>2.0.ZU;2-L
Abstract
Mothers of children with neonatal lupus erythematosus (NLE) and heart block , as well as patients with Sjogren's syndrome (SS) and systemic lupus eryth ematosus, have serum autoantibodies that recognize SS-A/Ro autoantigens inc luding the 60-kDa ribonucleoprotein. By yeast 2-hybrid screening, we identi fied a novel 75-kDa protein (pp75) that interacts with the carboxyl 70% of 60-kDa SS-A/Ro. The specificity of interaction was confirmed using mammalia n 2-hybrid and chemical crosslinking studies. Immunoprecipitation with radi olabeled HeLa cell extracts showed that pp75 was phosphorylated and associa ted with 2 other phosphoproteins of 64 kDa. In Northern blot analysis, pp75 was expressed in all tissues analyzed; the highest expression was in the h uman heart. Based on immunofluorescence of transfected HeLa cells, pp75 is localized predominantly in the cytoplasm, an observation confirmed by immun ohistochemistry in untransfected cells. Based on Western blot and ELISA ass ays, sera from 14 of 84 mothers of children with NLE recognized pp75, inclu ding 1 mother in whom anti-SS-A/Ro antibodies were not detected. In additio n, sera from 5 of 80 patients with SS were-positive for anti-pp75 antibody. Identification of molecular partners is a first step toward elucidating th e functions and possible involvement in pathogenesis of long-recognized aut oantigens such as 60-kDa SS-A/Ro, which are at present poorly understood.