A small N-terminal 60-kD fragment of gp600 (Megalin), the major autoantigen of active Heymann nephritis, can induce a full-blown disease

• Published in: Journal of the American Society of Nephrology 2000, Vol.11 (1), p.57-64
• Main Authors: OLEINIKOV, A. V, FELIZ, B. J, MAKKER, S. P
• Format: Article
• Language: English
• Subjects: Animals; Autoantigens - immunology; Biological and medical sciences; Chromatography, High Pressure Liquid; Disease Models, Animal; Female; Fluorescent Antibody Technique, Indirect; Glomerulonephritis; Glomerulonephritis - immunology; Heymann Nephritis Antigenic Complex; Immunoblotting; Kidney Glomerulus - immunology; Medical sciences; Membrane Glycoproteins - chemistry; Membrane Glycoproteins - immunology; Nephrology. Urinary tract diseases; Nephropathies. Renovascular diseases. Renal failure; Peptide Fragments - chemistry; Peptide Fragments - immunology; Peptide Fragments - isolation & purification; Rats; Rats, Inbred Lew; Reference Values; Sensitivity and Specificity; Severity of Illness Index
• ISSN: 1046-6673; 1533-3450
• DOI: 10.1681/asn.v11157

Active Heymann nephritis of rat, an autoimmune glomerular disease, is an immunohistological, ultrastructural, and clinical model of human membranous glomerulonephritis. Both diseases in their full-blown form are characterized by (1) the formation of large, subepithelial glomerular immune deposits, which stain for IgG, C3, and membrane attack (C5b-9) components of complement and (2) the excretion of large amounts of protein in the urine (proteinuria). The target autoantigen of active Heymann nephritis is a large transmembrane renal glycoprotein with a molecular weight of approximately 600 kD, variously named gp600, gp330, LRP-2, or "megalin." This study was performed to identify the region in this enormously large glycoprotein that would produce full-blown active Heymann nephritis. A stable, small (60-kD) proteolytic fragment of gp600 was isolated and localized to the N-terminal end of the molecule using Western blot, sequencing, and amino acid analyses. Based on its primary structure, this fragment contains approximately 60 cysteine residues, the cross-linking of which to each other probably explains its stability. Immunization of rats with this fragment induced a full-blown disease that was comparable to the disease induced by a preparation containing the whole protein. These results indicate that this small fragment, retaining the natural disulfide bonds and probably its overall structure, contains those B and T cell epitopes that are sufficient to produce this organ-specific autoimmune disease.