Small nuclear ribonucleoprotein particles contain glycoproteins recognized by rheumatic disease-associated...

Proteins from U1 and U2 small nuclear ribonucleoprotein (snRNP) particles, which are common targets of autoantibodies found in some rheumatic diseases, were analysed for the presence of glycans. A glycan detection assay revealed that the U1-specific proteins 68K and A and the U2-specific protein B" are glycosylated. However, none of the Sm proteins, which are common to all the major snRNP particles, showed a detectable level of glycosylation. With the use of specific lectins, an analysis of the particular carbohydrate(s) attached to the U1 snRNP 68K protein demonstrated the presence of at least one N-linked oligosaccharide chain. Lectin detection of galactose, glucose, mannose and N-acetylglucosamine on 68K was confirmed by chemical analysis of the carbohydrates. The glycopeptide nature of these antigens may be important for understanding the role of autoantigens in the pathogenesis of autoimmune disorder.