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Anti-nephrin autoantibodies in minimal change disease and focal segmental glomerulosclerosis (phospho-proteomics)

ABSTRACT: Background: Minimal change disease (MCD) and focal-segmental glomerulosclerosis (FSGS) are immune-mediated glomerular diseases manifesting as nephrotic syndrome. Autoantibodies against the podocyte slit diaphragm protein nephrin were recently identified in a subset of patients with minimal change disease, but their clinical and pathophysiological significance is largely unknown. Methods: Using immunoprecipitation assays, we performed a blinded screening for anti-nephrin antibodies in diagnostic and follow-up serum samples from adult patients with biopsy-proven MCD, FSGS, IgA nephropathy, and membranous nephropathy in comparison to healthy controls in two independent patient cohorts from Hamburg, Germany, and Bari, Italy. We further established a mouse model of anti-nephrin antibody-induced disease by active immunization using the recombinant murine nephrin ectodomain. Results: Anti-nephrin autoantibodies were detected in 50 of 110 (45%) patients with MCD, 8 of 107 (7%) patients with FSGS, 1 of 50 (2%) patients with membranous nephropathy, 0 of 48 (0%) patients with IgA nephropathy, and 0 of 67 (0%) healthy individuals. During follow-up, presence, and absence of anti-nephrin autoantibodies in patients with MCD and FSGS strongly correlated with active disease and remission, respectively. Immunization of mice induced anti-nephrin autoantibody formation and a highly dynamic phenotype with severe nephrotic syndrome and the histological features of MCD. Mechanistically, anti-nephrin autoantibodies induced nephrin phosphorylation at Tyr1191, cytoskeletal rearrangement, and downregulation of key podocyte proteins. Conclusion: Anti-nephrin antibodies are a valuable biomarker of disease activity in patients with MCD and FSGS, and binding of anti-nephrin antibodies at the podocyte slit diaphragm induces MCD with nephrotic syndrome.

INSTRUMENT(S): Orbitrap Exploris 480

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Glomerular Cell, Kidney, Renal Glomerulus

DISEASE(S): Focal Segmental Glomerulosclerosis

SUBMITTER: Moritz Lassé

LAB HEAD: Prof. Dr. Markus M. Rinschen

PROVIDER: PXD047421 | Pride | 2024-05-27

REPOSITORIES: Pride

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			Action	DRS
	20231110_111349_Nephrin-Phosphoproteome.sne	Other
	231109_HH-P0049_Nephrin-Wk3-P-Proteome-10.raw	Raw
	231109_HH-P0049_Nephrin-Wk3-P-Proteome-6.raw	Raw
	231109_HH-P0049_Nephrin-Wk3-P-Proteome-7.raw	Raw
	231109_HH-P0049_Nephrin-Wk3-P-Proteome-8.raw	Raw

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Project description:Introduction: Minimal change disease (MCD) is a major cause of nephrotic syndrome. With a substantial number of patients requiring long-term immunosuppression leading to significant morbidity, the study aim was to determine MCD glomerular transcriptome to serve as a basis for biomarker discovery and novel drug target identification. Animal work showed podocyte injury induced by IL-7/IL-7R signaling (Zhai S, BBRC, 2018). Methods: Renal biopsies from adult patients representing the following groups were selected from the Norwegian Kidney Biopsy Registry: MCD (n=14), as well as normal tissue (n=8) and primary membranous nephropathy (MN; n=12) as the two reference groups. RNA for 75 base-pair paired-end RNASeq was obtained by dissecting glomeruli via laser capture microdissection (LCM) from FFPE cross-sections. Systematic delineation of condition-specific alteration in transcriptional landscapes was achieved by combining pathway-centered analyses with methodologies derived from network science and integrating multiple bioinformatics resources. Results: Compared to normal glomeruli, glomeuli from MCD displayed an inflammatory signature that appeared to be predominantly governed by the IL1 and IL7 systems. While enrichment of IL1 production and secretion was a shared feature of MCD and MN compared to normal tissue, responses involving IL7 pathway activation were unique to MCD. Indeed, IL7R expressed by glomeruli was the most up-regulated gene of to the interleukin-family in MCD vs normal controls. IL7 pathway activation was paralleled by significant enrichment in adaptive immune system processes and transcriptional regulation and depletion in pathways related to energy metabolism and transcription. Downregulation of these organ function-related themes again occurred predominately in MDC and were significantly less pronounced in MN. Conclusion: Our results demonstrate that archival FFPE-biopsies can be used to generate glomeruli-specific gene expression profiles suitable for systematic delineation of kidney-associated diseases. Here the latter provides a data-driven rationale to experimentally address these MCD-specific features as biomarkers and as novel drug targets. In this context inhibiting activation of the IL7 pathway may be particularly promising.

Project description:Recurrence of focal segmental glomerulosclerosis (rFSGS) after kidney transplantation is a cause of early and accelerated graft loss. Immuneadsorption can alleviate renal dysfunction and suggests that circulating antibodies (Ab) are likely implicated in disease pathogenesis. To evaluate pathogenic Ab in rFSGS, we processed 141 unique serum samples from patients with and without primary rFSGS (n=64) and 34 non-FSGS control, transplanted at five (US and EU) hospitals. 9000 antigens were screened in pre-transplant sera by protein arrays and 10 Ab targeting glomerular antigens were selected for ELISA validation. A panel of 7 Ab (CD40, PTPRO, CGB-5, FAS, P2RY11, SNRPB2 and APOL2) could predict post-transplant FSGS recurrence with 92% accuracy. Pre-transplant elevation of anti-CD40 Ab levels alone had a substantial impact (78% accuracy) on the identification of rFSGS risk after transplantation. Epitope mapping of CD40 with customized peptide arrays and rFSGS sera demonstrated altered immunogenicity of the extracellular CD40 domain in rFSGS. Immunohistochemistry of CD40 demonstrated a differential expression of these antigens in FSGS compared to non-FSGS. Anti-CD40 Ab purified from rFSGS patients were uniquely pathogenic in human podocyte cultures; injection of these Ab resulted in heightened proteinuria, independently and in combination with suPAR in a rodent model, abrogated by injection of monoclonal Ab to CD40. In conclusion, a panel of 7 Ab can identify primary FSGS patients at high risk of recurrence prior to transplantation, allowing for customized therapies and improved patient selection for transplant. Intra-renal CD40 is an important axis of disease pathogenesis, and human trials of anti-CD40 therapies are warranted to evaluate their efficacy in preventing rFSGS and improving graft survival. The purpose of the study was to identify potential auto-Abs associated with rFSGS. We used a discovery set of pre-transplant sera from 20 unique patients with biopsy confirmed diagnosis of primary FSGS as their cause of ESRD, of which 10 had progressed to rFSGS within the first post-transplant year and 10 did not have recurrence of proteinuria or histological disease after transplantation (nrFSGS).

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Anti-nephrin autoantibodies in minimal change disease and focal segmental glomerulosclerosis (phospho-proteomics)

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