Dataset Information

Minor Antigens in Membranous Nephropathy Identified by Mass Spectrometry

ABSTRACT: Background: Multiple autoantigens have been identified in membranous nephropathy (MN) by tissue-based proteomics. However, the antigenic targets of disease are unknown for >10% of MN and >50% of membranous lupus nephritis (MLN) cases. We identified multiple new targets in PLA2R-/THSD7A-/EXT-/NELL1-quadruple negative MN biopsies through mass spectrometry (MS) of immune complexes recovered from biopsy tissue of patients with MN. Methods: MN cases negative for PLA2R, THSD7A, EXT1/2, and NELL1 were identified from a biopsy database. Protein G immunoprecipitation was used to recover immune complexes from frozen biopsy tissue, followed by interrogation by mass spectrometry (MS). Potential antigens were confirmed through paraffin immunofluorescence of protein targets, followed by co-localization with IgG within immune deposits. Consecutive series of 165 cases of PLA2R-negative MN biopsies and 95 MLN biopsies was screened to determine the frequency for each potential antigen. Results: Seven protein targets were discovered within immune complexes from MN biopsies including FCN3, CD206, EEA1, SEZ6L2, NPR3, MST1, and VASN. Peptides from these proteins on MS were not enriched in PLA2R (n=86), THSD7A (n=64), NELL1 (n=64), or EXT1/2 (n=60) controls. Between 3-30 unique peptides were detected for each target. Frequencies of each antigen, determined by staining consecutive case series, were SEZ6L2 (1/165 idiopathic; 0/95 MLN), VASN (8/165 idiopathic; 2/95 MLN), EEA1 (6/165 idiopathic; 7/95 MLN), MST1 (6/165 idiopathic; 2/95 MLN), and FCN3 (0/165 idiopathic, 6/95 MLN), NPR3 and CD206 were positive in index cases. All cases showed co-localization of IgG within immune deposits. Conclusion: Seven novel protein targets were identified in MN and MLN.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Kidney

SUBMITTER: Aaron Storey

LAB HEAD: Chris Larsen

PROVIDER: PXD035853 | Pride | 2023-04-06

REPOSITORIES: Pride

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Dataset's files

Source:

			Action	DRS
	Arkana_032521.sdia	Other
	Arkana_032521_Sample_01.dia.elib	Other
	Arkana_032521_Sample_01.raw	Raw
	Arkana_032521_Sample_02.dia.elib	Other
	Arkana_032521_Sample_02.raw	Raw

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Publications

Discovery of seven novel putative antigens in membranous nephropathy and membranous lupus nephritis identified by mass spectrometry.

Caza Tiffany N TN Storey Aaron J AJ Hassen Samar I SI Herzog Christian C Edmondson Rick D RD Arthur John M JM Kenan Daniel J DJ Larsen Christopher P CP

Kidney international 20230110 3

Multiple autoantigens have been identified in membranous nephropathy (MN) by tissue-based proteomics. However, antigenic targets of disease are unknown for over 10% of patients with MN and over half of those with membranous lupus nephritis (MLN). Here, we identified multiple new targets in PLA2R-/THSD7A-/EXT-/NELL1-quadruple negative MN biopsies through mass spectrometry of immune complexes recovered from biopsy tissue of patients with MN. Patients with MN negative for these four antigens were i ...[more]

PMID: 36638888

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Project description:Background: In recent years, an innovative strategy using laser microdissection and mass spectrometry markedly expanded the landscape of antigens associated with membranous nephropathy (MN). Specific associations with phenotypes, diseases and sometimes reversible triggers led to a novel antigen-based classification of MN, paving the way for precision medicine and stressing the need for more routine use of proteomics in MN. Methods: To explore the proteomic landscape of human glomeruli and identify podocyte antigens and disease mechanisms in MN, we expanded the original technique to an integrative approach combining laser capture microdissection, next-generation mass spectrometry and computational analysis. Next to conventional data-dependent acquisition (DDA), we used and assessed the diagnostic yield of the more comprehensive data-independent acquisition (DIA) mass spectrometry, which enables the detection and quantification of every peptide in a sample irrespective of its level of abundance or m/z value. Our proteomic pipeline was applied to residual material from kidney biopsies in 64 individuals, including 31 healthy controls; 5 disease controls; 5 PLA2R-associated MN; and 23 PLA2R-negative MN. Results: Unbiased analyses confirmed the significant enrichment in PLA2R, IgG4 and complement proteins in glomeruli from patients with PLA2R-MN compared with healthy and disease controls, while molecular characterization of complement fragments provided evidence for complement activation in PLA2R-MN. Compared to DDA, DIA mass spectrometry increased the number of glomerular proteins (~3800 vs. ~1200) identified in healthy glomeruli; allowed the detection all known antigens except NELL1 in normal glomeruli; and increased the detection rate of podocyte antigens from 50% to >80% in PLA2R-negative MN. Conclusions: This proof-of-concept study suggests that an integrative approach combining laser microdissection, DIA mass spectrometry and computational biology is a powerful tool, with translational potential, to identify podocyte antigens and unravel disease mechanisms in MN.