Proteomic Analysis of Glomerular Proteins in Primary and Bucillamine-induced Membranous Nephropathy

Abstract

The aim of this study was to characterize glomerular proteins in primary membranous nephropathy (pMN) and drug-induced secondary MN (sMN) by laser microdissection and comparative proteomic analysis. We used renal biopsy specimens from 6 patients with anti-phospholipase A2 receptor autoantibody (PLA2R Ab) (+) pMN, 6 patients with PLA2R Ab (‒) pMN, 6 patients with bucillamine (BCL)-induced sMN, and 5 control cases (time 0 transplant biopsies). Proteins were extracted from laser-microdissected glomeruli and analyzed using mass spectrometry. The quantification values of protein abundance in each MN group were compared with those in the control group. More than 800 proteins with high confidence were identified. Principal component analysis revealed a different distribution between the pMN and sMN groups. For further analysis, 441 proteins matched with ≥3 peptides were selected. Among the pMN and sMN groups, we compared the profiles of several protein groups based on the structural and functional characteristics, such as immunoglobulins, complements, complement-regulating proteins, podocyte-associated proteins, glomerular basement membrane proteins, and several proteins that are known to be associated with kidney diseases, including MN. Between the pMN and BCL-induced sMN groups, we observed common and different alterations in protein levels such as known disease-associated proteins and potential disease marker proteins.