Cellular Signaling and Production of Galactose-Deficient IgA1 in IgA Nephropathy, an Autoimmune Disease

Figure 1

IgA1 and hinge-region O-glycosylation in IgAN patients. Figure of monomeric IgA1, with the hinge-region amino-acid sequence below to show the S/T residues that are O-glycosylated (numbered in red). Three to six core 1 O-glycans are attached per hinge region, with N-acetylgalactosamine (white square) being the first sugar added; galactose (blue circle) may be then attached. Both glycans may be sialylated by N-acetylneuraminic acid (pink diamond), attached to N-acetylgalactosamine in an α2,6 linkage and to galactose in an α2,3 linkage. Patients with IgAN have elevated levels of circulatory IgA1 with some galactose-deficient O-glycans, consisting of terminal or sialylated N-acetylgalactosamine.