Localization of binding sites for laminin, heparan sulfate proteoglycan and fibronectin on basement membrane (type IV) collagen

Rotary shadowing electron microscopy was used to examine complexes formed by incubating combinations of the basement membrane components: type IV collagen, laminin, large heparan sulfate proteoglycan and fibronectin. Complexes were analyzed by length measurement from the globular (COOH) domain of type IV collagen, and by examination of the four arms of laminin and the two arms of fibronectin. Type IV collagen was found to contain binding sites for laminin, heparan sulfate proteoglycan and fibronectin. With laminin the most frequent site was centered approximately 81 nm from the carboxy end of type IV collagen. Less frequent sites appeared to be present at approximately 216 nm and approximately 291 nm, although this was not apparent when the sites were expressed as a fraction of the length of type IV collagen to which they were bound. For heparan sulfate proteoglycan the most frequent site occurred at approximately 206 nm with a less frequent site at approximately 82 nm. For fibronectin, a single site was present at approximately 205 nm. Laminin bound to type IV collagen through its short arms, particularly through the end of the lateral short arms and to heparan sulfate proteoglycan mainly through the end of its long arm. Fibronectin bound to type IV collagen through the free end region of its arms. Using a computer graphics program, the primary laminin binding sites of two adjacent type IV collagen molecules were found to align in the "polygonal" model of type IV collagen, whereas with the "open network" model, a wide meshed matrix is predicted. It is proposed that basement membrane may consist of a lattice of type IV collagen coated with laminin, heparan sulfate proteoglycan and fibronectin.     

Immunohistochemical evidence for the intracellular formation of basement membrane collagen (type IV) in developing tissues

Antibodies to type IV collagen obtained from the basement membrane of the mouse EHS tumor were incubated with sections of rat incisor teeth and other tissues for immunostaining by direct or indirect methods. In all locations, the immunostaining was pronounced in basement membranes in which it was restricted to the "basal lamina" layer, from which "bridges" often extended to nearby basal laminae. Usually no immunostaining was detectable in the cells associated with the basement membranes. However, examination of the capillaries at the posterior extremity of the rat incisor tooth, where tissues are at an early stage of development, showed immunostaining not only of the basement membrane, but also of the endothelial cells. The staining was localized in rough endoplasmic reticulum cisternae, some Golgi saccules and their peripheral distensions, and structures believed to be secretory granules. These findings suggest that the synthesis of type IV collagen proceeds along the classical secretory pathways through rough endoplasmic reticulum and Golgi apparatus. At the same time, immunostaining was usually lacking in the cells of the capillaries that had migrated about 2 mm away from the posterior end of the incisor tooth and also in the cells of most other tissues examined, even though the associated basal laminae were reactive. It is, therefore, presumed that the production of type IV collagen may be high in cells at an early stage of development and that any later production and turnover of basement membrane collagen can only be minimal.     

Epidermal cells adhere preferentially to type IV (basement membrane) collagen

Epidermal cells from adult guinea pig skin attach and differentiate preferentially on substrates of type IV (basement membrane) collagen, compared to those of types I--III collagen. In contrast, guinea pig dermal fibroblasts attach equally well to all four collagen substrates. Fibronectin mediates the attachment of fibroblasts but not of epidermal cells to collagen.     

Calcium-dependent binding of basement membrane protein BM-40 (osteonectin, SPARC) to basement membrane collagen type IV

Basement membrane protein BM-40, prepared from the mouse Engelbreth-Holm-Swarm tumor, was used in native, denatured and proteolytically processed form for binding to various extracellular matrix proteins. BM-40 and its derivatives were also characterized by CD spectroscopy, calcium binding and epitope analysis. Of several basement membrane proteins tested only collagen IV showed a distinct and calcium-dependent binding of BM-40 in an immobilized ligand assay. This interaction was specific as shown by a low activity of other collagen types (I, III, V, VI) in direct binding and competition assays. The binding was reduced or abolished by metal-ion-chelating or chaotropic agents, high salt and reduction of disulfide bonds in BM-40. Fragment studies indicated that domains III (alpha-helix) and/or IV (EF hand) of BM-40 possess the binding site(s) for collagen IV, while the N-terminal domains I and II provide the major antigenic determinants. A major BM-40-binding site on collagen IV was dependent on a triple-helical conformation and could be localized to a pepsin fragment from the central portion of the triple-helical domain, in agreement with electron microscopic visualization of BM-40--collagen-IV complexes.     

Changing patterns of fibronectin, laminin, type IV collagen, and a basement membrane proteoglycan during rat Mullerian duct regression

Antibodies to type IV collagen, laminin, heparan sulfate proteoglycan, and fibronectin were used to study the regression of the rat Mullerian duct. All four of these matrix constituents are located at the perimeter of the Mullerian duct within the ductal basement membrane. As the Mullerian duct regresses, the staining of all of these basement membrane constituents becomes irregular and discontinuous. Fibronectin, which is also present in the interstitium, becomes undetectable in the mesenchyme which condenses around the regressing Mullerian duct. These data indicate that degradation of the extracellular matrix around the male Mullerian duct is a central event in the regression of this structure.     

Immunofluorescent localization of collagen types I,III and IV,fibronectin, laminin,and basement membrane proteoglycan in developing mouse skin

Summary The distribution of various extracellular matrix components was studied in frozen sections of embryonic (14–18 days) and early postnatal (birth and 4 days post parturn) dorsal mouse skin using monospecific antibodies and indirect immunofluorescence. Basement membrane zone components — type IV collagen, laminin and heparan sulphate proteoglycan — were found to be uniformly and unchangingly distributed along the dermal-epidermal junction. In contrast, the distribution of interstitial matrix components — types I and III collagen, and fibronectin — was heterogeneous and varied with the stages of hair development. Collagens became sparse and were eventually completely removed from the prospective dermal papilla and from a one-cell-thick sheath of dermal cells around hair buds. They remained absent from the dermal papilla throughout hair organogenesis. Fibronectin was always present around dermal papilla cells and was particularly abundant along the dermal-epidermal junction of hair rudiments, as well as underneath hair buds. In contrast, in interfollicular skin, collagens accumulated in increasing density, while fibronectin became progressively sparser. It thus appears that interstitial collagens and fibronectin are distributed in a manner which is related to hair morphogenesis. In morphogenetically active regions, collagen density is low, while that of fibronectin is high. Conversely, in histologically stabilized zones, collagen is abundant and fibronectin is sparse. This microheterogeneous distribution of interstitial collagens and of fibronectin might thus constitute part of the morphogenetic message that the dermis is known to transmit to the epidermis during the development of skin and of cutaneous appendages.     

Isolation and characterization of pepsin-solubilized human basement membrane (type IV) collagen peptides

Native type IV collagen was isolated from human placental tissue by pepsin digestion, fractional salt precipitation, reduction and alkylation, a second pepsin digestion, and chromatography on diethylaminoethyl- and carboxymethyl-cellulose. After denaturation, 10 distinct peptides were isolated from this material by molecular sieve, ion-exchange, and high-performance liquid chromatography. All of the peptides were found to have amino acid compositions characteristic of type IV collagen. Analysis of the eight major peptides by amino-terminal amino acid sequencing and by cyanogen bromide and tryptic peptide mapping has revealed the manner in which they are derived from type IV collagen. Pepsin liberates two large peptides by attacking non-triple-helical regions, one derived from the alpha 1 (IV) chain (F2, Mr 90 000) and one derived from the alpha 2 (IV) chain (F3, Mr 75 000). The alpha 1 (IV)-derived F2 peptide is also represented in the pepsin digest by amino-terminal and carboxy-terminal subfragments [F4c (Mr 41 000) and F4a (Mr 60 000)], as is the alpha 2 (IV)-derived F3 peptide [F5 (Mr 28 000) and F4b (Mr 50 000), respectively]. These findings indicate that the molecular regions from which the larger peptides are derived in themselves contain pepsin-sensitive (non-triple-helical) domains. In addition, several of the peptides examined were found to be present in two slightly different forms, suggesting that closely adjacent pepsin-sensitive sites often exist within the type IV collagen molecules. The methods outlined here provide a reliable means by which identifiable type IV collagen peptides can be isolated.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunogold quantitation of laminin, type IV collagen, and heparan sulfate proteoglycan in a variety of basement membranes

A series of basement membranes was immunolabeled for laminin, type IV collagen, and heparan sulfate proteoglycan in the hope of comparing the content of these substances. The basement membranes, including thin ones (less than 0.3 micron) from kidney, colon, enamel organ, and vas deferens, and thick ones (greater than 2 micron), i.e., Reichert's membrane, Descemet's membrane, and EHS tumor matrix, were fixed in formaldehyde, embedded in Lowicryl, and treated with specific antisera or antibodies followed by anti-rabbit immunoglobulin bound to gold. The density of gold particles, expressed per micron2, was negligible in controls (less than or equal to 1.1), but averaged 307, 146, and 23, respectively, for laminin, collagen IV, and proteoglycan over the thick basement membranes (except for Descemet's membranes, over which the density was 16, 5, and 34, respectively) and 117, 72, and 64, respectively, over the lamina densa of the thin basement membranes. Lower but significant reactions were observed over the lamina lucida. Interpretation of the gold particle densities was based on (a) the similarity between the ultrastructure of most thick basement membranes and of the lamina densa of most thin basement membranes, and (b) the biochemical content of the three substances under study in the EHS tumor matrix (Eur J Biochem 143:145, 1984). It was proposed that thick basement membranes (except Descemet's) contained more laminin and collagen IV but less heparan sulfate proteoglycan than the lamina densa of thin basement membranes. In the latter, there was a fair variation from tissue to tissue, but a tendency towards a similar molar content of the three substances.     

Immunochemical and autoantigenic properties of the globular domain of basement membrane collagen (type IV)

Polyclonal rabbit antibodies raised against the globular domain NC1 of collagen IV from human placenta and a mouse tumor react with conformational antigenic determinants present on the NC1 hexamers and also with the three major subunits obtained after dissociation. The antibodies recognized unique structures within basement membranes and showed a broad tissue reactivity but only limited species cross-reactivity. Using these antibodies, it was possible to detect small amounts of collagen IV antigens from cell cultures and in serum. Monoclonal rat antibodies against mouse NC1 revealed a similar reaction potential. Autoantibodies could be produced in mice against mouse NC1 which react with kidney and lung basement membranes in a pathological manner, mimicking Goodpasture syndrome.     

Localization of laminin, type IV collagen, fibronectin, and heparan sulfate proteoglycan in chick retinal pigment epithelium basement membrane during embryonic development

Type IV collagen, laminin, heparan sulfate proteoglycan, and fibronectin were localized in the basement membrane (BM) of chick retinal pigment epithelium (RPE) during various stages of eye development. At different times over a 4-17 day period after fertilization, chick embryo eyes were dissected, fixed in periodate-lysine-paraformaldehyde, and 6 micron frozen sections through the central regions of the eye were prepared. Sections were postfixed in -20 degrees C methanol and stained immediately by indirect immunofluorescence using sheep anti-mouse laminin, sheep antimouse type IV collagen, rabbit anti-mouse heparan sulfate proteoglycan, and mouse monoclonal anti-porcine plasma fibronectin. Fluorescein-labeled F(ab')2 fragments of the appropriate immunoglobulins (IgGs) were used as secondary antibodies. Laminin could be readily demonstrated in the BM of the RPE during all stages of development. The staining for type IV collagen, fibronectin, and heparan sulfate proteoglycan HSPG) was less intense than that for laminin, but was also localized in the BM along the basal side of the RPE. In addition to staining the BM, antiserum to HSPG, gave a diffuse labeling from day 9 onward, above the RPE extending into the region of the photoreceptors. Whereas the intensity of staining generally increased between day 4 and day 17 of development, the distribution of the different BM components did not change. Hence the presence of type IV collagen, laminin, fibronectin, and HSPG in the BM of RPE in vivo during all the stages of development investigated supports the concept that these macromolecules are important basic components of this, and other, BMs. Furthermore, these results indicate that the composition of the BM of RPE cells in vivo is similar to the BM material deposited by RPE cells in vitro (Turksen K, Aubin JE, Sodek JE, Kalnins VI: Collagen Rel Res, 4:413-426, 1984) and that the in vitro cultures can therefore serve as a useful model for studying BM formation.     

Basement membrane (type IV) collagen is a heteropolymer

Type IV collagen was isolated in high yield from bovine kidney cortex. The protein revealed Mr = 380,000 and contained, in a 2:1 ratio, two different disulfide-linked polypeptide chains, C-1 and D-1 (Mr = 125,000). Carboxymethyl-cellulose chromatography before and after reduction proved that the two polypeptide chains are arranged in a single triple helical molecule with the chain composition (C-1)2(D-1). The disulfide bridges appear to be located 180 amino acid residues from the NH2 terminus of the chains.     

Differential expression of type IV collagen isoforms, α5(IV) and α6(IV) chains, in basement membranes surrounding smooth muscle cells

 Smooth muscle is composed of cigar-shaped, non-striated cells, each of which is encapsulated by a basement membrane and forms the contractile portion of tubular organs such as the gastrointestinal tract, pulmonary tract, genitourinary tract, and vasculature, in which slow and sustained contractions are needed. We examined basement membranes produced by smooth muscle cells and, using α(IV) chain-specific monoclonal antibodies, analyzed type IV collagens in these organs. Detailed distribution analysis of the α chains in normal and Alport cases by use of specific antibodies indicated that there are at least three molecular forms of type IV collagen, [α1(IV)]₂α2(IV), α3(IV)α4(IV)α5(IV), and α5(IV)/α6(IV). Smooth muscle cells in the urinary bladder and uterus were enclosed by basement membranes composed of α1, α2, α5, and α6 chains. The same α chains were present around smooth muscle cells in the muscular layer of the fundus of the stomach, whereas those in the antrum and further distal side of the gastrointestinal tract expressed mostly α1 and α2 chains. In addition, immunostaining analysis of the vasculature also showed that most of the smooth muscle cells were positive for α1 and α2 chains; however, α5 and α6 chains were also expressed by smooth muscle cells in the aorta and some arteries where blood pressure changes significantly. These results suggest that the smooth muscle cells enclosed by α5/α6-containing basement membranes might have some particular function related to mechanical stress or tensile strength during the characteristic contractile activity of tubular organs. Accepted: 23 March 1998     

Domain and basement membrane specificity of a monoclonal antibody against chicken type IV collagen

A monoclonal antibody, IV-IA8, generated against chicken type IV collagen has been characterized and shown to bind specifically to a conformational-dependent site within a major, triple helical domain of the type IV molecule. Immunohistochemical localization of the antigenic determinant with IV-IA8 revealed that the basement membranes of a variety of chick tissues were stained but that the basement membrane of the corneal epithelium showed little, if any, staining. Thus, basement membranes may differ in their content of type IV collagen, or in the way in which it is assembled. The specificity of the antibody was determined by inhibition ELISA using purified collagen types I-V and three purified molecular domains of chick type IV collagen ([F1]2F2, F3, and 7S) as inhibitors. Only unfractionated type IV collagen and the (F1)2F2 domain bound the antibody. Antibody binding was destroyed by thermal denaturation of the collagen, the loss occurring at a temperature similar to that at which previous optical rotatory dispersion studies had shown melting of the triple helical structure of (F1)2F2. Such domain-specific monoclonal antibodies should prove to be useful probes in studies involving immunological dissection of the type IV collagen molecule, its assembly within basement membranes, and changes in its distribution during normal development and in disease.     

Glomerular basement membrane. Identification of a fourth chain, alpha 4, of type IV collagen

The noncollagenous domain hexamer of collagen IV from bovine glomerular basement membrane was further investigated to determine the types of collagen chain from which subunits M2*b and M3 are derived. M2*b was shown to be a shorter form, containing 9 fewer residues, of M2*a which was previously established as the noncollagenous domain of a third chain, alpha 3, of collagen IV (Saus, J., Wieslander, J., Langeveld, J.P.M., Quinones, S., and Hudson, B.G. (1988) J. Biol. Chem. 263, 13374-13380). M3 was identified as the noncollagenous domain of a fourth chain, alpha 4, of type IV collagen, on the basis of additional sequence data together with previous findings. A comparison of the collagenous-noncollagenous junction regions of alpha 3(IV) and alpha 4(IV) chains with those of classical alpha 1(IV) and alpha 2(IV) chains reveals structural information which provides a potential strategy for molecular cloning of these novel chains. The results further reveal the complexity of electrophoresis patterns of the hexamer and potential ambiguities in using one-dimensional patterns to determine whether molecular defects of collagen IV occur in pathological processes affecting basement membranes.     

Complete primary structure of the alpha 1-chain of human basement membrane (type IV) collagen

We have determined the primary structure of the alpha 1(IV)-chain of human type IV collagen by nucleotide sequencing of overlapping cDNA clones that were isolated from a human placental cDNA library. The present data provide the sequence of 295 amino acids not previously determined. Altogether, the alpha 1(IV)-chain contains 1642 amino acids and has a molecular mass of 157625 Da. There are 1413 residues in the collagenous domain and 229 amino acids in the carboxy-terminal globular domain. The human alpha 1(IV)-chain contains a total of 21 interruptions in the collagenous Gly-X-Y repeat sequence. These interruptions vary in length between two and eleven residues. The alpha 1(IV)-chain contains four cysteine residues in the triple-helical domain, four cysteines in the 15-residue long noncollagenous sequence at the amino-terminus and 12 cysteines in the carboxy-terminal NC-domain.     

Proposed alignment of helical interruptions in the two subunits of the basement membrane (type IV) collagen

We have isolated a cDNA clone for part of the alpha 2 type IV collagen (pCIV-2-176). Deoxynucleotide sequence analysis shows that this clone codes for 439 amino acids from the helical domain adjacent to the C-terminal globular domain of the alpha 2 (IV) chain. By aligning the deduced amino acid sequence of the alpha 2 (IV) chain with the published sequence for the alpha 1 (IV) chain, we find that all interruptions in the alpha 1 (IV) chain coincide with an interruption in the alpha 2 (IV) chain. Additional interruptions in the alpha 2 (IV) chain exist, however, three out of the four analysed only slightly disturb the collagen triple helix.