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Larsen CP, Trivin-Avillach C, Coles P, Collins AB, Merchant M, Ma H, Wilkey DW, Ambruzs JM, Messias NC, Cossey LN, Rosales IA, Wooldridge T, Walker PD, Colvin RB, Klein J, Salant DJ, Beck LH. LDL Receptor-Related Protein 2 (Megalin) as a Target Antigen in Human Kidney Anti-Brush Border Antibody Disease. J Am Soc Nephrol 2017; 29:644-653. [PMID: 29074737 DOI: 10.1681/asn.2017060664] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Accepted: 09/25/2017] [Indexed: 12/24/2022] Open
Abstract
Primary renal tubulointerstitial disease resulting from proximal tubule antigen-specific antibodies and immune complex formation has not been well characterized in humans. We report a cohort of patients with a distinct, underappreciated kidney disease characterized by kidney antibrush border antibodies and renal failure (ABBA disease). We identified ten patients with ABBA disease who had a combination of proximal tubule damage, IgG-positive immune deposits in the tubular basement membrane, and circulating antibodies reactive with normal human kidney proximal tubular brush border. All but one of the patients also had segmental glomerular deposits on renal biopsy specimen. Patients with ABBA disease were elderly and presented with AKI and subnephrotic proteinuria. Serum from all patients but not controls recognized a high molecular weight protein in renal tubular protein extracts that we identified as LDL receptor-related protein 2 (LRP2), also known as megalin, by immunoprecipitation and mass spectrometry. Immunostaining revealed that LRP2 specifically colocalized with IgG in the tubular immune deposits on the ABBA biopsy specimen but not the control specimen analyzed. Finally, ABBA serum samples but not control samples showed reactivity against recombinantly expressed N-terminal LRP2 fragments on Western blots and immunoprecipitated the recombinantly expressed N-terminal region of LRP2. This case series details the clinicopathologic findings of patients with ABBA disease and shows that the antigenic target of these autoantibodies is LRP2. Future studies are needed to determine the disease prevalence, stimulus for ABBA, and optimal treatment.
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Affiliation(s)
| | - Claire Trivin-Avillach
- Renal Section, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts
| | - Paige Coles
- Renal Section, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts
| | - A Bernard Collins
- Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Michael Merchant
- Division of Nephrology & Hypertension, Department of Medicine, University of Louisville, Louisville, Kentucky; and
| | - Hong Ma
- Renal Section, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts
| | - Daniel W Wilkey
- Division of Nephrology & Hypertension, Department of Medicine, University of Louisville, Louisville, Kentucky; and
| | | | | | | | - Ivy A Rosales
- Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | | | | | - Robert B Colvin
- Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Jon Klein
- Division of Nephrology & Hypertension, Department of Medicine, University of Louisville, Louisville, Kentucky; and
| | - David J Salant
- Renal Section, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts
| | - Laurence H Beck
- Renal Section, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts;
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2
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Westphal N, Theis T, Loers G, Schachner M, Kleene R. Nuclear fragments of the neural cell adhesion molecule NCAM with or without polysialic acid differentially regulate gene expression. Sci Rep 2017; 7:13631. [PMID: 29051583 PMCID: PMC5648764 DOI: 10.1038/s41598-017-14056-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 10/04/2017] [Indexed: 02/05/2023] Open
Abstract
The neural cell adhesion molecule (NCAM) is the major carrier of polysialic acid (PSA) which modulates NCAM functions of neural cells at the cell surface. In previous studies, we have shown that stimulation of cultured neurons with surrogate NCAM ligands leads to the generation and nuclear import of PSA-lacking and -carrying NCAM fragments. Here, we show that the nuclear import of the PSA-carrying NCAM fragment is mediated by positive cofactor 4 and cofilin, which we identified as novel PSA-binding proteins. In the nucleus, the PSA-carrying NCAM fragment interacts via PSA with PC4 and cofilin, which are involved in RNA polymerase II-dependent transcription. Microarray analysis revealed that the nuclear PSA-carrying and -lacking NCAM fragments affect expression of different genes. By qPCR and immunoblot analysis we verified that the nuclear PSA-carrying NCAM fragment increases mRNA and protein expression of nuclear receptor subfamily 2 group F member 6, whereas the PSA-lacking NCAM fragment increases mRNA and protein expression of low density lipoprotein receptor-related protein 2 and α-synuclein. Differential gene expression evoked by nuclear NCAM fragments without and with PSA indicates that PSA-carrying and -lacking NCAM play different functional roles in the nervous system.
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Affiliation(s)
- Nina Westphal
- Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, Falkenried 94, 20251, Hamburg, Germany
| | - Thomas Theis
- Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, Falkenried 94, 20251, Hamburg, Germany
| | - Gabriele Loers
- Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, Falkenried 94, 20251, Hamburg, Germany
| | - Melitta Schachner
- Center for Neuroscience, Shantou University Medical College, 22 Xin Ling Road, Shantou, Guangdong, 515041, China.
- Keck Center for Collaborative Neuroscience and Department of Cell Biology and Neuroscience, Rutgers University, 604 Allison Road, Piscataway, NJ, 08854, USA.
| | - Ralf Kleene
- Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, Falkenried 94, 20251, Hamburg, Germany
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3
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Ronco P, Debiec H. A podocyte view of membranous nephropathy: from Heymann nephritis to the childhood human disease. Pflugers Arch 2017; 469:997-1005. [PMID: 28597189 DOI: 10.1007/s00424-017-2007-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 05/25/2017] [Indexed: 10/25/2022]
Abstract
Membranous nephropathy (MN) is characterized by an accumulation of immune deposits on the subepithelial side of the glomerular basement membrane, which results in complement activation and proteinuria. Since 2002, several major antigens of the podocyte have been identified in human MN, the first one being neutral endopeptidase (NEP), the alloantigen involved in neonatal cases of MN that occur in newborns from NEP-deficient mothers. This discovery opened the field to the major advances that have occurred since then in the pathophysiology and treatment of MN. It is remarkable that experimental models such as Heymann nephritis and cationic bovine serum albumin-induced MN in the rabbit predicted the pathomechanisms of the human glomerulopathy. The podocyte is at the center of the pathogenesis of MN either by providing a source of endogenous antigens or by creating an environment favorable to deposition and accumulation of immune complexes containing exogenous (non-podocyte) antigens. The podocyte is also a victim of complement activation and antibody blocking activity against enzymes or receptors. A search for innovative drugs aimed at protecting this cell against complement activation and the effects of prolonged ER stress has become a priority.
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Affiliation(s)
- Pierre Ronco
- Inserm UMR_S 1155, Hôpital Tenon, 4 rue de la Chine, 75020, Paris, France. .,Sorbonne Universités, UPMC Univ Paris 06, 75005, Paris, France. .,AP-HP, Hôpital Tenon, Service de Néphrologie et Dialyses, Paris, France.
| | - Hanna Debiec
- Inserm UMR_S 1155, Hôpital Tenon, 4 rue de la Chine, 75020, Paris, France.,Sorbonne Universités, UPMC Univ Paris 06, 75005, Paris, France
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4
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Bobkova IN, Kakhsurueva PA, Stavrovskaya EV. [Idiopathic membranous nephropathy: Evolution in understanding the problem]. TERAPEVT ARKH 2016; 88:89-94. [PMID: 27489901 DOI: 10.17116/terarkh201688689-94] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The review highlights the evolution of ideas on the. mechanisms responsible for the 'development of membranous nephropathy(MN), glomerulopathy that is the most common cause of nephrotic syndrome in adults. Primary emphasis is placed on the primary form of MN. The important step to understanding the nature of this clinical and morphological form of glomerulonephritis is to create its animal model (Heymann nephritis), then to decipher the mechanisms of immune complex damage (complement activation,a role of cellular immunity), and to identify autoantigens responsible for the development of idiopathic MN in man (podocyteneutral endopeptidase, transmembrane M-type phospholipase A2 receptor, thrombospondin type-1 domain-containing 7A. The findings constituted the basis for developing current methods for the diagnosis and treatment of MN, including the pathogenetically sound inhibition of autoantibody production, as well as a molecular orientation effect on podocyte dysfunction.
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Affiliation(s)
- I N Bobkova
- I.M. Sechenov First Moscow State Medical University, Ministry of Health of Russia, Moscow, Russia
| | - P A Kakhsurueva
- I.M. Sechenov First Moscow State Medical University, Ministry of Health of Russia, Moscow, Russia
| | - E V Stavrovskaya
- I.M. Sechenov First Moscow State Medical University, Ministry of Health of Russia, Moscow, Russia
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5
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Yasuno K, Sakashita H, Kobayashi R, Araki S, Saito R, Shirota M, Kamiie J, Shitora K. Membranous Glomerulonephropathy in a Hatano Low-avoidance Rat. J Toxicol Pathol 2013; 26:203-8. [PMID: 23914063 PMCID: PMC3695343 DOI: 10.1293/tox.26.203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 02/19/2013] [Indexed: 11/19/2022] Open
Abstract
Membranous glomerulonephropathy can be experimentally induced in rats, but spontaneous cases have been rarely reported. In this report, we present a typical case of spontaneous membranous glomerulonephropathy in a rat. A male Hatano low-avoidance (LAA) strain rat had a tumor mass on the right auricle, and was sacrificed at 41 weeks of age. Urinary screening by reagent strips revealed intense proteinuria. Histological tests revealed frequent presence of irregularly sized eosinophilic hyaline materials on the capillary wall and in the mesangium of renal glomeruli. Immunofluorescence revealed granular deposits of IgG, IgM, and C3 in the glomeruli. Subepithelial dense deposits were observed by electron microscopy accompanied by podocyte foot process effacement and occasional irregular thickening of the glomerular basement membrane. The rat also developed chronic lymphocytic pancreatitis, and the tumor mass on the right auricle was diagnosed as a fibrosarcoma. Screening tests for antibodies against major infectious agents and antinuclear antibody were negative. Western blot and indirect immunofluorescence analyses suggested the presence of an autoantibody against the pancreatic component. The glomerulopathy was considered an early stage of membranous glomerulonephropathy.
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Affiliation(s)
- Kyohei Yasuno
- Research Institute of Biosciences, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5201, Japan
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6
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Zhang J, Jia Z, Lin Z, Li J, Fu X, Huang Y, Zhao J, Nie L, Hou W, Yuan F, Wu Y. Computational prediction and experimental assessment of an HLA-A*0201-restricted cytotoxic T lymphocyte epitope from neutral endopeptidase. Immunol Res 2012; 52:231-9. [DOI: 10.1007/s12026-012-8330-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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7
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Ronco P, Debiec H. Pathogenesis of membranous nephropathy: recent advances and future challenges. Nat Rev Nephrol 2012; 8:203-13. [DOI: 10.1038/nrneph.2012.35] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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8
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Abstract
For more than 50 years researchers have debated the evidence for an autoimmune basis of human idiopathic membranous nephritis (MN). Work published in the past 2 years has substantially strengthened the belief that MN is indeed an autoimmune disease of the kidney. Autoantibodies of the IgG4 subclass to at least three podocyte membrane proteins including phospholipase A(2)-receptor, aldose reductase, and manganese superoxide dismutase have been detected by immunoblotting in sera as well as in acid eluates prepared from renal biopsy tissue of patients with this disease, using either whole tissue or microdissected glomeruli from frozen sections. In each case the podocyte antigen has been shown to co-localize with the subepithelial glomerular immune deposits in renal tissue of the same patients. It is not certain if any of these podocyte proteins is an inciting/primary autoantigen or whether they are secondary antigens recruited by intermolecular epitope-spreading, initiating from a yet-to-be-discovered autoantigen. Although it is clear that autoantibodies to podocyte membrane proteins are elicited in idiopathic MN and contribute to the formation of the subepithelial deposits, many questions remain concerning the triggers for their development and their contribution toward proteinuria and progression of the disease.
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9
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Glassock RJ. The Pathogenesis of Idiopathic Membranous Nephropathy: A 50-Year Odyssey. Am J Kidney Dis 2010; 56:157-67. [PMID: 20378220 DOI: 10.1053/j.ajkd.2010.01.008] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Accepted: 01/13/2010] [Indexed: 11/11/2022]
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10
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Fang C, Ballet C, Dugast AS, Godard A, Moreau A, Usal C, Smit H, Vanhove B, Brouard S, Harb J, Soulillou JP. Autoimmune responses against renal tissue proteins in long-term surviving allograft recipients. Transpl Int 2009; 22:1091-9. [PMID: 19624494 DOI: 10.1111/j.1432-2277.2009.00923.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Major histocompatibility complex antigens (MHC) are classical targets of recipient responses to allotransplants. However, the role of an immune response directed against autologous graft tissue determinants is poorly defined. In this study, we investigated (i) whether autologous kidney tissue extract can induce an immune response to autologous kidney proteins in normal rats, and (ii) if a similar autologous response develops in the long-term surviving LEW.1A recipients of an MHC-mismatched LEW.1W kidney (RT1(u) to RT1(a)). LEW.1A rats immunized with allo- or syngeneic soluble kidney extracts developed a T-cell response to self antigens as shown by the frequency of specific IFN-gamma-producing T cells from LEW.1A rats in the presence of extracts (ELISPOT). In contrast, they responded only marginally to dominant RT1(u) determinants. The ELISPOT against fractions of soluble autologous kidney extracts separated by an FPLC gel-filtration system indicated a preferential response to megalin, a high molecular weight protein that has been shown to be involved in experimental Heymann nephritis. In a model of long-term kidney allograft survival by anti-CD28 administration, recipients also developed humoral but not cellular responses to megalin. Our data suggest that autoimmune processes develop in long-term surviving kidney allograft recipients.
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Affiliation(s)
- Cheng Fang
- Institut National de la Santé Et de la Recherche Médicale (INSERM) - Université de Nantes, UMR 643, Nantes, France
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11
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Shah P, Tramontano A, Makker SP. Intramolecular epitope spreading in Heymann nephritis. J Am Soc Nephrol 2007; 18:3060-6. [PMID: 18003776 DOI: 10.1681/asn.2007030342] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Immunization with megalin induces active Heymann nephritis, which reproduces features of human idiopathic membranous glomerulonephritis. Megalin is a complex immunological target with four discrete ligand-binding domains (LBDs) that may contain epitopes to which pathogenic autoantibodies are directed. Recently, a 236-residue N-terminal fragment, termed "L6," that spans the first LBD was shown to induce autoantibodies and severe disease. We used this model to examine epitope-specific contributions to pathogenesis. Sera obtained from rats 4 weeks after immunization with L6 demonstrated reactivity only with the L6 fragment on Western blot, whereas sera obtained after 8 weeks demonstrated reactivity with all four recombinant fragments of interest (L6 and LBDs II, III, and IV). We demonstrated that the L6 immunogen does not contain the epitopes responsible for the reactivity to the LBD fragments. Therefore, the appearance of antibodies directed at LBD fragments several weeks after the primary immune response suggests intramolecular epitope spreading. In vivo, we observed a temporal association between increased proteinuria and the appearance of antibodies to LBD fragments. These data implicate B cell epitope spreading in antibody-mediated pathogenesis of active Heymann nephritis, a model that should prove valuable for further study of autoimmune dysregulation.
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Affiliation(s)
- Pallavi Shah
- Department of Pediatrics, University of California, Davis, School of Medicine, Davis, California 95616, USA
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12
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Zhang H, Yoshioka S, Miyazaki M, Kannagi R, Suzuki A. Core 2 GlcNAc modification and megalin ligand-binding activity. Biochim Biophys Acta Gen Subj 2007; 1780:479-85. [PMID: 18005667 DOI: 10.1016/j.bbagen.2007.10.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Revised: 10/06/2007] [Accepted: 10/17/2007] [Indexed: 11/26/2022]
Abstract
Megalin, a receptor-like transporter glycoprotein, is expressed on kidney proximal tubular cells and reabsorbs small-molecular-weight proteins from the glomerular filtrate. Here, we report that mouse megalins differently modified with core 2 beta6GlcNAc transferase had different kinetic properties to a fluorescence-labeled ligand, retinol-binding protein (RBP). BALB/c mice, a wild-type strain in terms of the expression of kidney-specific core 2 beta6GlcNAc transferase, express megalin carrying the core 2 extended Le(x) epitope, while DBA/2 mice, a mutant-strain of the core 2 beta6GlcNAc transferase, express megalin lacking the epitope. We purified these two types of megalin using lentil lectin chromatography and measured the ligand-binding activities of the megalins using Cy5-labeled RBP by applying gel permeation chromatography (GPC) and fluorescence correlation spectroscopy (FCS). The analysis by GPC indicated that the apparent V(max) of the interaction between Cy5-labeled RBP and the megalins of BALB/c and DBA/2 mice was 60 microM and 30 microM, respectively, and the apparent K(m) was 11 microM and 17 microM, respectively. Scatchard analysis demonstrated the presence of two binding sites. Linear regression analysis resulted in a two-binding-site model characterized by a high-affinity site (K(dBALB)=12.0 microM; K(dDBA)=20.9 microM) and a low-affinity site (K(dBALB)=36.2 microM; K(dDBA)=58.8 microM). FCS analysis exhibited quite different K(m) and V(max) values from those obtained by GPC, but similar K(m) values for the two types of megalin, and a lower V(max) value for DBA/2 megalin than BALB/c megalin. These results suggest that the core 2 GlcNAc extended glycan chains on megalin can change the ligand-binding affinity and capacity.
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Affiliation(s)
- Heng Zhang
- Sphingolipid Expression Laboratory, RIKEN Frontier Research System, Wako, Saitama, Japan
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13
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Ronco P, Debiec H. Target antigens and nephritogenic antibodies in membranous nephropathy: of rats and men. Semin Immunopathol 2007; 29:445-58. [PMID: 17899086 DOI: 10.1007/s00281-007-0091-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Accepted: 08/17/2007] [Indexed: 01/31/2023]
Abstract
Membranous nephropathy, a disease characterized by an accumulation of immune deposits on the outer aspect of the glomerular basement membrane, is the most common cause of idiopathic nephrotic syndrome in white adults. In the rat model of Heymann nephritis, the target antigen of antibodies is megalin, a multiligand receptor expressed at the podocyte cell surface. This review summarizes key findings provided by this experimental model and by our discovery of neutral endopeptidase being the alloantigen involved in neonatal cases of membranous nephropathy. We discuss the role of alloimmunization as a new mechanism of renal disease and the approach that we use to identify new podocyte antigens. We also summarize current knowledge on the mechanism of proteinuria, with special emphasis on the role of complement. In conclusion, substantial progresses have been made in understanding molecular mechanisms of membranous nephropathy, which should lead to novel therapeutic approaches.
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Affiliation(s)
- P Ronco
- INSERM Unit 702, Hôpital Tenon, 4 rue de la Chine, 75020, Paris, France.
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14
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Ronco P, Debiec H. Molecular dissection of target antigens and nephritogenic antibodies in membranous nephropathy: towards epitope-driven therapies. J Am Soc Nephrol 2006; 17:1772-4. [PMID: 16775025 DOI: 10.1681/asn.2006050497] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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15
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Tramontano A, Knight T, Vizzuso D, Makker SP. Nested N-terminal megalin fragments induce high-titer autoantibody and attenuated Heymann nephritis. J Am Soc Nephrol 2006; 17:1979-85. [PMID: 16762989 DOI: 10.1681/asn.2005101144] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
It was shown previously that an N-terminal fragment (nM60) that encompasses amino acid residues 1 to 563 of megalin could induce active Heymann nephritis (AHN) as efficiently as the native protein. For delineation of a minimal structure within this fragment that is sufficient to induce AHN, smaller protein fragments that encompass residues 1 to 236 (L6), 1 to 195 (L5), 1 to 156 (L4), and 1 to 120 (L3), representing successive C-terminal truncations within ligand-binding repeats of nM60, were cloned and produced in a baculovirus insect cell expression system. Protein fragments L4, L5, and L6 clearly were glycosylated. All four fragments stimulated proliferation of megalin-sensitized lymph node cells and induced high-titer anti-megalin autoantibodies in Lewis rats. A full-blown disease, as assessed by severity of proteinuria, was observed in rats that were immunized with L6 and L5, whereas animals that were immunized with L4 and L3 developed only mild disease. The proteinuria levels correlated with staining for complement (C3, C5b-9) and IgG1 isotype in glomerular immune deposits. The results suggest that one or more molecular determinants on the region that comprises amino acid residues 157 to 236 contribute to the induction of a full-blown form of AHN. Study of the structure, conformation, and posttranslational modifications of these determinants could provide greater insight into the molecular correlates of immunopathogenesis in this disease model.
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Affiliation(s)
- Alfonso Tramontano
- Department of Pediatrics, University of California, Davis, School of Medicine, 1 Shields Avenue, Davis, CA 95616, USA
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16
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Moncayo R. Cubilin and megalin in radiation-induced renal injury with labelled somatostatin analogues: are we just dealing with the kidney? Eur J Nucl Med Mol Imaging 2006; 32:1131-5. [PMID: 16133381 DOI: 10.1007/s00259-005-1885-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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17
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Nangaku M, Shankland SJ, Couser WG. Cellular Response to Injury in Membranous Nephropathy. J Am Soc Nephrol 2005; 16:1195-204. [PMID: 15800119 DOI: 10.1681/asn.2004121098] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The pathogenesis of membranous nephropathy (MN) involves in situ formation of subepithelial immune deposits that produce glomerular injury by damaging and/or activating podocytes through complement-dependent processes. C5b-9 formation and insertion into podocyte cell membranes causes glomerular injury in MN. C5b-9 in sublytic quantities stimulates podocytes to produce proteases, oxidants, prostanoids, extracellular matrix components, and cytokines including TGF-beta. C5b-9 also causes alterations of the cytoskeleton that lead to abnormal distribution of slit diaphragm protein and detachment of viable podocytes that are shed into Bowman's space. These events result in disruption of the functional integrity of the glomerular basement membrane and the protein filtration barrier of podocytes with subsequent development of massive proteinuria. Complement components in proteinuric urine also induce tubular epithelial cell injury and mediate progressive interstitial disease in MN. Measurements of urinary C5b-9 or podocyte excretion in the urine may be useful in the diagnosis of MN and as measures of disease activity and response to therapy. Recent studies of cell-cycle proteins and DNA damage in podocytes have clarified why podocytes fail to proliferate in response to C5b-9-mediated injury and podocyte loss in MN, resulting in the development of glomerular sclerosis and renal failure. Improved understanding of the role of complement in the pathogenesis of MN and of the cellular response to C5b-9 attack creates several new opportunities for therapeutic intervention that may benefit patients with MN in the future.
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Affiliation(s)
- Masaomi Nangaku
- Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, Tokyo, Japan
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18
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Barabas AZ, Cole CD, Barabas AD, Cowan JM, Yoon CS, Waisman DM, Lafreniere R. Presence of immunoglobulin M antibodies around the glomerular capillaries and in the mesangium of normal and passive Heymann nephritis rats. Int J Exp Pathol 2005; 85:201-12. [PMID: 15312125 PMCID: PMC2517517 DOI: 10.1111/j.0959-9673.2004.00395.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Summary Diffuse distribution of small, faintly staining, beaded deposits of rat immunoglobulin M (IgM) around the glomerular capillary blood vessels, and a more intensely staining larger deposition in the mesangium, were observed on the kidney sections of normal rats. As glomerular-fixed nephritogenic antigens are known to be present on the epithelial aspect of the glomerular basement membrane (GBM), especially at the soles of foot processes and at the slit pores, it was assumed that the IgM antibodies were directed against these antigens. Investigation by immunofluorescent antibody double-staining techniques of rat kidney sections obtained from normal and rabbit anti-FX1A-injected rats stained for the nephritogenic antigen showed that a number of antigenic sites in the glomeruli and in the mesangium shared antibody hits by heterologous rabbit IgG and autologous rat IgM antibodies. Most sites in the glomeruli stained specifically for rat IgM or rabbit IgG, but preferentially for the latter. The intensely fluorescent mesangial deposits stained mainly for rat IgM, indicating that at these sites the antigenic material was virtually saturated, while areas at the entry to the mesangial space also stained for rabbit IgG, indicating that at these locations free nephritogenic epitopes were still available for reaction with the anti-FX1A antibody. Western blot analysis have shown that the rabbit anti-rat FX1A IgG and the rat anti-rat KF3 IgM antibodies are directed against the same renal tubular-derived antigen with a molecular weight of 70,000. These experimental findings collectively demonstrate that the heterologous IgG and autologous IgM antibodies are directed against the same nephritogenic antigen, which is found in the glomeruli, the mesangium and the proximal convoluted tubules. Thus, the IgM autoantibody has a possible physiological role but, in addition, there is evidence of active immunophagocytic events, manifested in a rapid and continuous entrapment and expulsion of macromolecules after their processing by the mesangial cells of normal and passive Heymann nephritis rats.
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Affiliation(s)
- Arpad Z Barabas
- Department of Surgery, University of Calgary, Health Sciences Centre, Calgary, Alberta, Canada.
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Barabas AZ, Cole CD, Barabas AD, Lafreniere R. Down-regulation of pathogenic autoantibody response in a slowly progressive Heymann nephritis kidney disease model. Int J Exp Pathol 2005; 85:321-34. [PMID: 15566429 PMCID: PMC2517532 DOI: 10.1111/j.0959-9673.2004.00388.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
In the present article, we describe an antigen-specific down-regulation of a pathogenic autoantibody (aab)-mediated disease process in an experimental autoimmune kidney disease in rats called slowly progressive Heymann nephritis (SPHN). This autoimmune disease is initiated and maintained by pathogenic immunoglobulin G (IgG) autoantibodies (aabs), which cause an immune-complex (IC) glomerulonephritis associated with proteinuria. We achieved down-regulated pathogenic aab response in SPHN rats by injections of an IC containing the native nephritogenic antigen and specific high-titred nonpathogenic IgM aabs, in antigen excess. The injected IC increased the level of circulating nonpathogenic IgM aabs; the increased levels of specific IgM aabs in turn facilitated the removal of the injected altered nephritogenic and liberated autoantigens from the renal tubules and greatly diminished the production of pathogenic aabs and the build up of immune deposits in the glomeruli. While animals treated early had advantages over rats whose kidney disease was well established before treatment; animals treated late into the disease still manifested noticeable improvements in similar areas, i.e. with lessened proteinuria, kidney lesion reduction and a decreased pathogenic aab response. At the end of the experiment at 29 weeks, 80% of all the treated rats had insignificantly low levels of circulating IgG aabs, indicating cessation of pathogenic aab production and corresponding termination of the disease process. In contrast, most untreated rats with the kidney disease still had high levels of circulating pathogenic aabs at the end of the experiment, which maintained disease progression.
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Affiliation(s)
- Arpad Z Barabas
- Department of Surgery, University of Calgary, Health Sciences Centre 2802, 3330 Hospital Dr N.W., Calgary, Alberta, Canada T2N 4N1.
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Barabas AZ, Cole CD, Barabas AD, Lafreniere R. Production of Heymann nephritis by a chemically modified renal antigen. Int J Exp Pathol 2004; 85:277-85. [PMID: 15379960 PMCID: PMC2517528 DOI: 10.1111/j.0959-9673.2004.00389.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
An autoimmune kidney disease morphologically and functionally similar to Heymann nephritis (HN) was induced in mature male Sprague Dawley rats by repeated weekly IP injections of a chemically modified azo sonicated ultracentrifuged (u/c) rat kidney fraction 3 (rKF3) antigen in an aqueous medium. The experiment was terminated 15 weeks after the first injection of the chemically altered antigen. Serum samples collected and analysed by an indirect fluorescent antibody test on normal rat kidney sections during the course of the experiment showed a gradual rise in circulating pathogenic autoantibodies directed against the proximal tubular brush border regions. Proteinuria was present and significantly increased in the urine of two of eight rats. The arising immune-complex glomerulonephritis (ICGN) revealed typical HN kidney disease lesions in 70% of the rats in histological, direct fluorescent antibody and electron-microscopical examinations. Control rats injected similarly with the an unmodified version of the same antigen did not develop the HN-characteristic morphological and functional changes. To our knowledge, this is the first time that the autoimmune kidney disease designated as an active HN has been produced by the administration of a chemically altered renal antigen in an aqueous solution and not by the usual presentation of the nephritogenic renal antigen in an adjuvant.
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Affiliation(s)
- Arpad Z Barabas
- Department of Surgery, University of Calgary, Health Sciences Centre, Calgary, Alberta, Canada.
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Tramontano A, Makker SP. Conformation and glycosylation of a megalin fragment correlate with nephritogenicity in Heymann nephritis. THE JOURNAL OF IMMUNOLOGY 2004; 172:2367-73. [PMID: 14764706 DOI: 10.4049/jimmunol.172.4.2367] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Active Heymann nephritis (AHN), a rat model of autoimmune glomerulonephritis, is induced by immunization with autologous megalin, a 600-kDa cell surface glycoprotein isolated from crude renal extracts. Recombinant proteins containing a 563-residue N-terminal sequence of megalin were obtained from Escherichia coli and baculovirus-insect cell expression systems. Rats immunized with the soluble, secreted protein encoded by a baculovirus construct elicited high titer anti-megalin autoantibodies and developed glomerular immune deposits and elevated proteinuria consistent with AHN. Rats treated with the bacterial or nonsecreted insect cell proteins produced a milder anti-megalin response and did not develop the disease. Nephritogenicity appeared to correlate with conformational or other structural features of native megalin. All three recombinant proteins were reactive in Western blots with rabbit anti-megalin antiserum, whereas the insect cell-derived proteins reacted preferentially in Western blot and ELISA with anti-megalin autoantibodies from rats with AHN induced by native megalin. Only the secreted insect cell product was stained in a lectin blot, suggesting its specific glycosylation. These observations provide evidence that a megalin N-terminal domain includes B and T cell epitopes sufficient for a pathogenic autoimmune response and that a native-like conformation and glycosylation are essential for the induction of disease. The importance of conformational B cell epitopes for pathogenic autoantibodies recapitulates observations made in other models of organ-specific autoimmune disease. Glycosidic modifications could influence the presentation of either B or T cell epitopes in AHN, consistent with emerging evidence of the role of post-translational modifications in pathogenic autoimmune responses.
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MESH Headings
- Animals
- Autoantibodies/biosynthesis
- Autoantigens/genetics
- Autoantigens/immunology
- Autoantigens/metabolism
- Binding Sites, Antibody
- Blotting, Western
- Cloning, Molecular
- Epitopes, B-Lymphocyte/genetics
- Epitopes, B-Lymphocyte/immunology
- Epitopes, B-Lymphocyte/metabolism
- Epitopes, T-Lymphocyte/genetics
- Epitopes, T-Lymphocyte/immunology
- Epitopes, T-Lymphocyte/metabolism
- Female
- Glomerulonephritis/immunology
- Glomerulonephritis/metabolism
- Glomerulonephritis/pathology
- Glycosylation
- Immunohistochemistry
- Injections, Intradermal
- Low Density Lipoprotein Receptor-Related Protein-2/chemistry
- Low Density Lipoprotein Receptor-Related Protein-2/genetics
- Low Density Lipoprotein Receptor-Related Protein-2/immunology
- Low Density Lipoprotein Receptor-Related Protein-2/metabolism
- Peptide Fragments/chemistry
- Peptide Fragments/genetics
- Peptide Fragments/immunology
- Peptide Fragments/metabolism
- Protein Conformation
- Rats
- Rats, Inbred Lew
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/immunology
- Recombinant Fusion Proteins/metabolism
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Affiliation(s)
- Alfonso Tramontano
- Department of Pediatrics, University of California School of Medicine, Davis, CA 95616, USA
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Yammani RR, Seetharam S, Dahms NM, Seetharam B. Transcobalamin II receptor interacts with megalin in the renal apical brush border membrane. J Membr Biol 2003; 193:57-66. [PMID: 12879166 DOI: 10.1007/s00232-002-2007-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2002] [Indexed: 10/26/2022]
Abstract
Purified human transcobalamin II receptor (TC II-R) binds to megalin, a 600 kDa endocytic receptor with an association constant, K(a), of 66 n M and bound(max) of 1.1 mole of TC II-R/mole of megalin both in the presence and absence of its ligand, transcobalamin II (TC II). Immunoprecipitation followed by immunoblotting of Triton X-100 extracts of the apical brush border membrane (BBM) from rabbit renal cortex revealed association of these two proteins. (35)[S]-TC II complexed with cobalamin (Cbl; Vitamin B(12)) bound to Sepharose-megalin affinity matrix and the binding was enhanced 5-fold when TC II-R was prebound to megalin. Megalin antiserum inhibited both the TC II-R-dependent and -independent binding of (35)[S]-TC II-Cbl to megalin, while TC II-R antiserum inhibited only the TC II-R-dependent binding. In rabbits with circulating antiserum to megalin, renal apical BBM megalin was present as an immune complex, but its levels were not altered. However, the protein levels of both TC II-R and the cation-independent mannose 6-phosphate receptor (CIMPR) were drastically reduced and the urinary excretion of TC II, albumin, and other low-molecular weight proteins was significantly increased. These results suggest that megalin contains a distinct single high-affinity binding site for TC II-R and their association in the native renal BBM is important for tubular reabsorption of many proteins, including TC II.
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Affiliation(s)
- R R Yammani
- Division of Gastroenterology and Hepatology, Department of Medicine, Zablocki Veteran's Administration Medical Center and Medical College of Wisconsin, 5000 West National Avenue, Milwaukee, Wisconsin, 53295, USA
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Abstract
Glomerular podocytes are highly specialized cells with a complex cytoarchitecture. Their most prominent features are interdigitated foot processes with filtration slits in between. These are bridged by the slit diaphragm, which plays a major role in establishing the selective permeability of the glomerular filtration barrier. Injury to podocytes leads to proteinuria, a hallmark of most glomerular diseases. New technical approaches have led to a considerable increase in our understanding of podocyte biology including protein inventory, composition and arrangement of the cytoskeleton, receptor equipment, and signaling pathways involved in the control of ultrafiltration. Moreover, disturbances of podocyte architecture resulting in the retraction of foot processes and proteinuria appear to be a common theme in the progression of acquired glomerular disease. In hereditary nephrotic syndromes identified over the last 2 years, all mutated gene products were localized in podocytes. This review integrates our recent physiological and molecular understanding of the role of podocytes during the maintenance and failure of the glomerular filtration barrier.
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Affiliation(s)
- Hermann Pavenstädt
- Division of Nephrology, Department of Medicine, University Hospital Freiburg, Freiburg, Germany.
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