TGF-β1 mimics the effect of IL-4 on the glycosylation of IgA1 by downregulating core 1 β1, 3-galactosyltransferase and Cosmc

The aberrant glycosylation of IgA1 is pivotal in the pathogenesis of IgA nephropathy (IgAN). The aim of the present study was to investigate the effect of transforming growth factor-beta 1 (TGF-beta 1) on the glycosylation of IgA1 and the associated mechanism. The mRNA levels of core1 beta 1, 3-galactosyltransferase (C1GalT1) and its molecular chaperone, Cosmc, were analyzed, as was the subsequent O-glycosylation of IgA1, in a human B-cell line stimulated with TGF-beta 1. The IgA1-positive human B-cell line was cultured with different concentrations of recombinant human TGF-beta 1 (5, 10, 15 and 30 ng/ml). The production and glycosylation of IgA1 were assayed using sandwich ELISA and enzyme-linked lectin binding assays, respectively, and the mRNA levels of C1GalT1 and Cosmc were quantified using reverse transcription-quantitative polymerase chain reaction analysis. The results showed that the production of IgA1 was stimulated by low concentrations of TGF-beta 1 (5 or 10 ng/ml) and was suppressed by high concentrations (15 or 30 ng/ml). The terminal glycosylation of secreted IgA1 was altered in response to TGF-beta 1. TGF-beta 1 stimulation significantly decreased the mRNA levels of C1GalT1 and Cosmc. TGF-beta 1 may be key in controlling the glycosylation of IgA1, in part via the downregulation of C1GalT1 and Cosmc.