Supplementary Material for: Loss of the Golgi Matrix Protein 130 Cause Aberrant IgA1 Glycosylation in IgA Nephropathy

Background: Aberrant O-glycosylation IgA1 production is a major factor in the pathogenesis of IgA nephropathy, but the underlying mechanism is still unclear. IgA1 glycosylation modification is in Golgi, and downregulation of the Golgi peripheral membrane protein Golgi matrix protein 130 (GM130) could lead to glycosylation deficiency. In this study, we aimed to explore the role of GM130 in glycosylate deficiency IgA1 (Gd-IgA1) production. Methods: We enrolled 27 IgA nephropathy patients, 12 patients with chronic tonsillitis, 15 non-IgAN chronic kidney disease patients, and 15 healthy volunteers as healthy control. We explored GM130 expression in Tonsillar tissue by immunofluorescence staining and Western blotting and expression in peripheral blood mononuclear cells (PBMCs) by flow cytometry. The concentration of IgA1 and level of O-glycosylation were determined by ELISA and Vicia Villosa lectin-binding assay. Real-time PCR and Western blot were used to analyze the levels of β1,3-Gal transferase (C1GALT1) and ST6GalNAC2, respectively. To explore the contribution of GM130 in IgA1 O-glycosylation modification, cells were subjected to experiments for evaluation of GM130 silencing by GM130-siRNA transfection. Results: GM130 expression was significantly decreased in tonsil tissues and PBMC of IgAN patients; the expression of C1GALT1 decreased and Gd-IgA1 level increased significantly in patients with IgAN patients. The expression of GM130 was negatively related to Gd-IgA1 production. By siRNA transfection, our results clearly indicated that the downregulation of GM130 can increase IgA1 O-glycosylation deficiency, which is thought to reduce C1GALT1 expression but not affect the expression of ST6GalNAC2. Conclusion: We identified and demonstrated that GM130 plays an important role in IgA1 O-glycans deficiency in IgAN patients, by negatively regulating C1GALT1 expression. We believe that this finding will provide theoretical foundations for a new mechanism of Gd-IgA1 production in IgAN patients.