Comparison of non-collagenous type IV collagen components in the human glomerulus and EHS tumor

27 kDa extracellular matrix protein revealed by a monoclonal antibody raised against rat testis

In search of unique components of the seminiferous tubule extracellular matrix, monoclonal antibodies were raised against an isolated seminiferous tubule extracellular matrix, and the monoclonal antibody 12G11 was cloned. By immunofluorescence microscopy in eight kinds of rat tissues (testis, lung, liver, small intestine, cardiac muscle, skeletal muscle, kidney, and brain), 12G11 antigen existed only in the testis. Immunoelectron microscopy revealed that the antigen is localized in the basement membrane of the seminiferous tubule and in the basement membranes of myoid cells. For a biochemical analysis, eight kinds of rat extracellular matrices were isolated and solubilized with 8 M urea and 2% beta-mercaptoethanol. Immunoblot analysis of these samples in 0.8% agarose gel also showed that the antigen was specific for the testis, and in a two high-molecular weight aggregates. These aggregates seemed to contain type IV collagen and laminin chains. The antigen of 12G11 antibody was shown to be 27 kDa by 10% SDS-PAGE followed by immunoblotting. From these data, the existence of a testis specific 27 kDa basement membrane protein, which associate with type IV collagen and laminin, was suggested.

Alterations of glomerular basement membrane charge and structure in diabetic nephropathy

We examined glomerular basement membrane anionic site distribution identified by cationic gold in seven patients with insulin-dependent and four patients with non-insulin-dependent diabetes mellitus, presenting a spectrum of clinical and glomerular changes. Anionic sites were investigated by pretreatment of tissue with glycosaminoglycan-degrading enzymes prior to cationic gold staining. The distribution of chondroitin sulphate proteoglycans--a previously unrecognized glomerular basement membrane component--and type IV collagen was examined by immunoelectron microscopy to identify structural changes in the basement membrane. Findings were compared with those of non-diabetic patients showing minor proteinuria and morphologically normal glomerular basement membranes. Two patients, originally diagnosed as having diabetic nephropathy were also examined at 19 weeks and 5 years after renal transplantation. Characteristic redistribution of type IV collagen and chondroitin sulphate proteoglycans was noted in thickened glomerular basement membrane segments (> 400 nm) of diabetic patients and those with renal transplants. Extension of anionic sites deep into the glomerular basement membrane at pH 2.5, together with loss of interna sites at pH 5.8 is unique to diabetic nephropathy. Reduced charge density was apparent in some patients due to thickening of the glomerular basement membrane, although the number of anionic sites per unit length of membrane was actually increased. Thus, charge aberration in diabetic nephropathy is due to displacement rather than loss of anionic sites. Removal of more than 90% of these sites by heparitinase, confirms their association with heparan sulphate proteoglycans. Similar derangement of anionic sites in all patients with diabetic nephropathy irrespective of the degree of proteinuria, suggests that a heparan sulphate proteoglycan-related charge barrier plays a minor role in controlling permeability of the diabetic glomerular basement membrane.

Study of EHS type IV collagen lacking Goodpasture's epitope in glomerulonephritis in rats

The Goodpasture's epitope has been mapped to the alpha 3 non-collagenous chain (NC1) of type (IV) collagen [alpha 3col(IV)]. We have developed a model of experimental autoimmune glomerulonephritis (EAG) in rats immunized once with collagenase solubilized GBM (csGBM). Engelbreth-Holm-Swarm (EHS) tumor contains abundant col(IV) with little or no alpha 3col(IV). To test the hypothesis that antigens related to Goodpasture epitope are required to produce EAG in our model, we immunized rats once with 40 micrograms csEHS. Positive controls immunized with csGBM developed typical EAG with GBM bound antibody, proteinuria, and glomerulonephritis. EHS rats developed circulating and bound antibody to mesangium and tubular basement membrane with minimal GBM deposits, but did not develop proteinuria or glomerulonephritis. Although circulating antibody in EHS rats bound to csGBM by ELISA, there was no binding in ELISA to M2 antigen containing the Goodpasture epitope while EAG rat's serum did bind. By Western blot with antisera to Goodpasture epitope, EHS antigen was less complex than GBM in the monomer/dimer regions and appeared to lack NC1 corresponding to alpha 3col(IV). Blotting with sera from EHS rats demonstrated reactivity to various components of GBM but not to alpha 3col(IV). EAG sera and renal eluates bound to alpha 3col(IV). EAG rats evidenced cell mediated immunity while EHS rats did not (stimulation index EHS 1.1, EAG rats 8.0).(ABSTRACT TRUNCATED AT 250 WORDS)

Proliferative autoimmune glomerulonephritis in rats: a model for autoimmune glomerulonephritis in humans

Some forms of glomerulonephritis (GN) in humans appear consequent to autoimmunity. Experimental autoimmune GN (EAG) has been described in sheep, but attempts to develop EAG in other mammals have resulted only in antibody and proteinuria but no GN. We have developed a model of EAG in an inbred mammalian species to further study pathogenetic mechanisms. We immunized Brown Norway (BN) and Wistar-Kyoto (WKY) rats with glomerular basement membrane (GBM) or collagenase solubilized GBM (csGBM). Circulating and bound anti-GBM antibody developed in all rats. Only interstitial nephritis occurred in BN rats despite amounts of glomerular and serum anti GBM antibodies similar to WKY animals. One hundred percent of WKY rats immunized with csGBM/acid developed reproducible severe GN at two to three weeks with proteinuria and decreased kidney function which progressed to glomerulosclerosis and interstitial fibrosis. Antigen in acid was a requisite for induction of EAG. EAG rats had positive tests for delayed type hypersensitivity, their T cells underwent antigen specific transformation, and T cells and macrophages were present histologically. Passive transfer of EAG serum to naive rats resulted in fixation to recipient GBM but no proteinuria or GN. This new model of EAG in rats appears dependent on genetic factors, may involve cellular immunity in pathogenesis, requires exposure of the nephritogenic antigen, and is highly similar to rapidly progressive GN in humans.

The hepatic extracellular matrix. I. Components and distribution in normal liver

The unique nature of the hepatic extracellular matrix (ECM) is predicated by the special configuration of the space of Disse. Whereas other epithelial organs have two basement membranes (BM) and a substantial ECM interposed between endothelial and epithelial cells, the liver lobule has no BM and only an attenuated ECM, consisting mostly of fibronectin, some collagen type I, and minor quantities of types III, IV, V, and VI. This configuration, together with the abundant fenestrations and gaps of the sinusoidal endothelial cells, seems ideally suited to facilitate the rapid bidirectional exchange of macromolecules normally taking place between plasma and hepatocytes. During organogenesis, the liver anlage is vascularized by continuous capillaries with BM, but by day 13.5 of development (in the rat) the vessels in the immediate proximity of hepatocytes become fenestrated, lacking specialized junctions and BM, suggesting that the hepatocytes produce signals capable of modulating the endothelial phenotype. In regeneration, hepatocyte proliferation precedes vascular proliferation resulting in the formation of hepatocyte clusters that, temporarily, lack sinusoids. Eventually, vascular proliferation follows and the normal hepatocyte-vascular relationships are restored. During this period laminin synthesis by Ito cells is prominent. As soon as hepatocytes become stable, secretion of the sinusoid phenotype-maintaining factors resumes and laminin synthesis and secretion terminates. The interplay between extracellular matrix and liver cells is essential for normal homeostasis and its modification results in deranged hepatic function.

Type IV collagen of Engelbreth-Holm-Swarm tumor matrix: identification of constituent chains

The noncollagenous hexamer (NC1) domain of type IV collagen from Engelbreth-Holm-Swarm (EHS) sarcoma matrix was subjected to electrophoretic, amino-terminal amino acid sequence, and immunochemical analysis to determine which of the five known kinds of alpha(IV) chains are present. Electrophoretic analysis, whether by one-dimensional or two-dimensional electrophoresis, showed that nonlathyritic and lathyritic hexamer gave nearly identical patterns. Amino-terminal amino acid sequence analysis of hexamer subunits, transblotted from two-dimensional gels, revealed that the hexamer subunits were derived exclusively from the alpha 1 and alpha 2 chains. Western blots of hexamer subunits confirmed the sequence results, as the subunits. identified as alpha 1(IV) and alpha 2(IV) NC1 domains reacted with antibodies directed specifically against those subunits. Conversely, no reactivity of NC1 hexamer subunits was seen with Goodpasture serum, or with antibodies directed specifically against the alpha 3, alpha 4, and alpha 5 NC1 domains, confirming the lack of alpha 3, alpha 4, and alpha 5 chains. These results revealed that the type IV collagen component of the EHS sarcoma matrix is comprised exclusively of alpha 1 and alpha 2 chains. Its relative homogeneity simplifies, but restricts, interpretation of studies that employ it as a model type IV collagen because the studies would be based only on alpha 1 and alpha 2 chains.

Ontogenesis of glomerular basement membrane: structural and functional properties

Protein A-gold immunocytochemistry was applied in combination with morphometrical approaches to reveal the alpha 1(IV), alpha 2(IV), and alpha 3(IV) chains of type IV collagen as well as entactin on renal basement membranes, particularly on the glomerular one, during maturation. The results have indicated that a heterogeneity between renal basement membranes appears during the maturation process. In the glomerulus at the capillary loop stage, both the epithelial and endothelial cell basement membranes were labeled for the alpha 1(IV) and alpha 2(IV) chains of type IV collagen and entactin. After fusion, both proteins were present on the entire thickness of the typical glomerular basement membrane. At later stages, the labeling for alpha 1(IV) and alpha 2(IV) chains of type IV collagen decreased and drifted towards the endothelial side, whereas the labeling for the alpha 3(IV) chain increased and remained centrally located. Entactin remained on the entire thickness of the basement membrane during maturation and in adult stage. The distribution of endogenous serum albumin in the glomerular wall was studied during maturation, as a reference for the functional properties of the glomerular basement membrane. This distribution, dispersed through the entire thickness of the basement membrane at early stages, shifted towards the endothelial side of the lamina densa with maturation, demonstrating a progressive acquisition of the permselectivity. These results demonstrate that modifications in the content and organization of the different constituents of basement membranes occur with maturation and are required for the establishment of the filtration properties of the glomerular basement membrane.

Characterization of monoclonal antibodies to the globular domain of collagen IV

Monoclonal antibodies were produced against NC1, the globular noncollagenous domain of collagen IV, isolated from bovine glomerular basement membrane. Cells from eight positive wells were cloned and the resulting monoclonal antibodies were studied in detail by immunofluorescence on human kidney sections, by Western blot and by ELISA against denatured subunits from NC1 hexamers and against native NC1 hexamers from different tissues. The monoclonal antibodies could be divided into two groups. Firstly, those monoclonal antibodies that, in ELISA and Western blot, reacted with peptides related to the alpha 1 chain of collagen IV and stained all basement membranes in the kidney. Secondly, a monoclonal antibody that, in ELISA and Western blot, reacted with peptides related to the Goodpasture antigen, the alpha 3 chain of collagen IV. When this antibody was applied to human kidney sections it stained the glomerular basement membrane very intensively. Bowman's capsule and some tubular basement membrane were also stained, although to a lesser extent. This staining pattern is the same as that observed with sera from patients with Goodpasture's syndrome. An attempt was made to separate different subtypes of the NC1 hexamer. A monoclonal antibody from the first group was used to make an affinity chromatography column. Glomerular basement membrane digested with collagenase was separated on this column and the collected fractions were analyzed by ELISA and SDS-PAGE. The result from this study support the idea that glomerular basement membrane is composed of at least two different subtypes of type IV collagen.

Expression of novel basement membrane components in the developing human kidney and eye

The distribution of two novel human, basement-membrane (BM) collagens has been characterized by immunohistochemical analysis of developing and mature tissue using monoclonal antibodies specific for the non-collagenous (NC1) domain of each molecule. A distribution more restricted than that of type IV collagen was observed. In the kidney, the 28K parent molecules appear relatively late, at the early capillary-loop stage of glomerular development, whereas type IV collagen is present in all BM, including those of the ureteric bud, S-form, primitive glomerulus, and vessels. Antibody to the Alport familial nephritis antigen (a 26K peptide), which is missing from epidermal BM and glomerular BM in Alport syndrome, reacted with the ureteral bud BM and all stages of glomerular BM development from the early capillary-loop stage onward, but not with BM of more primitive glomeruli (vesicles and S forms). In the human fetal eye, the collagen molecules from which the 28K NC1 peptides are derived appear later in development than type IV collagen. They are present in trace amounts in Bruch's membrane but are not detected until after birth in the retinal internal limiting membrane and cuticular and non-pigmented epithelial BM of the ciliary process. In contrast, the BM of the lens capsule and Descemet's membrane were reactive with anti-28K antibodies early in development. In all instances, the 28K peptides are detected in BM that also contain the Alport antigen, although the later is present in some BM not containing the 28K peptides. The distribution of Alport antigen and type IV collagen in developing eye is similar to that observed in the mature eye. The 28K parent molecules appear to be expressed in concert with the maturation of the BM, coincident with fusion of glomerular endothelial and epithelial BM, whereas the lens capsule BM and Descemet's membrane contain these restricted components much earlier in gestation.

Comparison of non-collagenous type IV collagen subunits in human glomerular basement membrane, alveolar basement membrane, and placenta

This study examines the similarities and differences in the noncollagenous domain (NC1) of type IV collagen from human glomerular basement membrane (hGBM), alveolar basement membrane (hABM), and placenta (hPBM). Following collagenase digestion, NC1 domain was isolated on Bio-Gel A-0.5m or by cation exchange chromatography on S-Sepharose. NC1 from each source was characterized by SDS PAGE, and two dimension NEPHGE/SDS PAGE. Immunoblotting and ELISA inhibition was performed using antibody probes specific for M28 , M28+, M26 and M24 monomer subunits of human NC1. It was observed that all NC1 subunits were present in hGBM and hABM derived material, however M28 and M28+ monomers were absent in hPBM NC1. These findings indicate that while alpha 1(IV) and alpha 2(IV) collagen chains are present in hGBM, hABM and hPBM, alpha 3(IV) and alpha 4(IV) collagen chains are only found in hGBM and hABM but are absent in hPBM. It can now be appreciated that heterogeneity of alpha (IV) chain composition exists in basement membranes from various organs.

Abnormalities in the NC1 domain of collagen type IV in GBM in canine hereditary nephritis

Samoyed hereditary glomerulopathy (SHG) in dogs serves as a model for human X-linked hereditary nephritis (HN). We previously showed that glomerular capillaries of affected males did not stain by immunofluorescence (IF) using serum from a patient with Goodpasture's syndrome. Our goal in the present study was to determine whether the NC1 domain of the collagen type IV molecule, which contains Goodpasture antigen (GPA), could be demonstrated in these dogs, and to assess its immunological reactivity. By SDS-PAGE, NC1 in collagenase digests of glomerular basement membranes (GBM) of unaffected and carrier female dogs in the family with SHG showed 24 kilodalton (kD), 26 kD and 28 kD monomer, and 46 kD and 47 kD dimer components, but the 24 kD monomer was diminished in the affected males. By IF, a rabbit antibody to NCl stained glomerular capillaries of unaffected, affected male, and carrier female dogs. In contrast, a human anti-GBM plasmapheresis fluid (PPF) stained glomerular capillaries of only the unaffected and carrier female dogs. By RIA, both antibodies reacted strongly with NCl in collagenase digests of GBM of the unaffected and carrier female dogs, but showed reduced reactivity with NCl of affected males. By Western blotting, both antibodies bound to dimers and 24 kD and 26 kD monomers of the NCl domain in collagenase digests of GBM of unaffected and carrier female dogs. However, in affected males, the rabbit anti-NCl antibody did not bind to the 24 kD monomer, while the human anti-GBM PPF showed weak binding to the 24 kD and 26 kD monomers.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal antibodies to native basement membranes reveal heterogeneous immunoreactivity patterns

In this paper we describe the development of basement membrane (BM) reactive monoclonal antibodies (MA), by immunization of mice with intact denuded BM. The MA raised against denuded amniotic BM (clones 1052, 1053 and 1065) showed heterogeneous staining patterns. MA 1052 and 1053 reacted with epithelial BM of the epidermis and epidermal adnexa and furthermore with the epithelial alveolar BM in the lung and the superficial part of the epithelial BM in the gastrointestinal tract. MA 1065 showed immunoreactivity with the epithelial BM of epidermis and epidermal adnexa and the epithelial BM of trachea and oesophagus, and furthermore pericellular staining of the basal keratinocytes and basal corneal epithelial cells. MA 1087, raised against human glomerular BM, showed immunoreactivity with all BM, except the central epithelial BM in the cornea. The precise localization of the target epitopes in the BM was investigated on chemically cleaved human skin. Reactivity for the MA occurred predominantly in the BM lamina adherent to the dermis, suggesting that the target epitopes reside in the lamina densa and/or lamina fibroreticularis. We furthermore examined the nature of the epitopes by preincubation of tissue sections with various enzymes prior to immunohistochemistry. The reactivity of the target epitopes was not affected by bacterial collagenase, but after various protease treatments the reactivity disappeared, suggesting that the epitopes are not localized on the triple helical part of collagenous proteins.

Reductive cleavage and reformation of the interchain and intrachain disulfide bonds in the globular hexameric domain NC1 involved in network assembly of basement membrane collagen (type IV)

The formation of collagen IV dimers in the extracellular space requires the association of two C-terminal globular domains giving rise to a large hexameric structure NC1 (Mr = 170,000). NC1 hexamer was purified from collagenase digests of a mouse tumor and several human tissues. It was shown by electrophoresis to consist of two kinds of cross-linked, dimeric segments, Da and Db (Mr about 50,000), and monomeric segments in a molar ratio of about 3:1. In the native hexamers free SH groups were detectable by N-[14C]ethylmaleimide and other sulfhydryl reagents. They account for 4-11% of the total number of cysteine residues with some variations between preparations from different sources and in the distribution between monomers and dimers. Reduction with 10 mM dithioerythritol under non-denaturing condition completely converted dimers into monomers and allowed the alkylation of all twelve cysteine residues present in each monomeric NC1 segment. A monomeric intermediate with four to six free SH groups and a higher electrophoretic mobility than the final product was observed. Generation of this intermediate from dimers Da and Db follows apparently different routes proceeding either directly or through a dimeric intermediate respectively. The time course of conversion is best described by a mechanism consisting of two (Db) or three (Da) consecutive steps with pseudo-first-order rate constants ranging from 0.14 ms-1 to 0.5 ms-1. Glutathione-catalyzed reoxidation of completely reduced NC1 in the presence of 2 M urea results in a product indistinguishable from native material by ultracentrifugation and electrophoresis pattern. The data suggest that in situ formation of NC1 structures is catalyzed by a small fraction (5-10%) of intrinsic SH groups leading to the formation and stabilization of dimers by rearrangement of disulfide bonds.

Alport familial nephritis. Absence of 28 kilodalton non-collagenous monomers of type IV collagen in glomerular basement membrane

Alport-type familial nephritis (FN), a genetic disorder, results in progressive renal insufficiency and sensorineural hearing loss. Immunochemical and biochemical analyses of the non-collagenous (NC1) domain of type IV collagen isolated from the glomerular basement membranes (GBM) of three males with this disease demonstrate absence of the normally occurring 28-kilodalton (kD) NC1 monomers, but persistence of the 26- and 24-kD monomeric subunits derived from alpha 1 and 2 (both type IV) collagen chains, respectively.