Affiliations: [a] Institute of Tumorbiology-Cancer Research, University of Vienna, Vienna, Austria | [b] 4th Dept. Intern. Med., University of Vienna, Vienna, Austria
Correspondence:
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Correspondence and reprint requests to: Dr. Józefa Węsierska-Gądek, Institute of Tumorbiology-Cancer Research, University of Vienna, Borschkegasse 8 a, A-I090 Vienna, Austria.
Abstract: Patients with primary biliary cirrhosis (PBC) frequently produce autoantibodies against gp210, an integral glycoprotein of the nuclear pores. This protein consists of three main domains: a large glycosylated lumenal domain, a single hydrophobic transmembrane segment and a short cytoplasmic tail. It has been previously shown that autoantibodies from PBC patients exclusively react with the cytoplasmic tail when recombinant rat gp210 expressed in Escherichia coli was used as antigen. Using human gp210 isolated from HeLa cells we found the lumenal domain as the major target. The aim of this study was to further characterize the dominant autoepitopes of gp210. Sera from 88 patients with autoimmune liver disease and 20 controls were used. Gp210 protein was digested with papain or endoglycosidase H and then subjected to immunoblotting. Autoantibodies against gp210 were detected in 12 of 43 (28%) PBC patients, but in none of the autoimmune hepatitis and control sera. Four of 12 (33%) anti-gp210 positive sera reacted with a fragment consisting of the cytoplasmic tail and 8 (66%) sera targeted an epitope located within the large lumenal domain. Furthermore, our data show that antigenic determinant is restricted to the 64 kD glycosylated amino-terminal fragment and that carbohydrate residues are an essential part of this novel epitope. We suggest that antigens possessing both epitopes namely: the glycosylated lumenal domain and the cytoplasmic tail should be used for screening tests in order to detect all sera with anti-gp210 specificity.
