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PubMed2001

Age differences in immunohistochemical localizations of large proteoglycan, PG-M/versican, and small proteoglycan, decorin, in the dermis of rats.

Proteoglycans were localized immunohistochemically in the dermis of Donryu rats, using monoclonal antibodies raised against large proteoglycan (PG-M/versican) and small proteoglycan (decorin). The localizations of these proteoglycans in the dermis were compared between young rats (22-day old) and old ones (24 or 30 months of age), and distinct age differences were observed. In the young dermis, PG-M/versican was observed to be abundant in almost all fibroblastic cells (both cytoplasm and cell processes) whose cellularity was very rich compared with the dermis of old rats. Decorin was only faintly visible in the interstitial fibrous elements of young dermis. In the old dermis, however, decorin was distinctly detected on the fibrous elements, which were diffusely distributed as a fibrous network, and likewise PG-M/versican was visible in only a few fibrous elements which seemed to be the fine processes of fibroblastic cells. In the border layer between epidermis and dermis as well as the basal layer surrounding hair follicles, both large and small proteoglycans could be observed in old dermis. Since decorin, which was abundant in old dermis, has been found to have a growth inhibitory effect, it is conceivable that decorin may be one of the Cell Growth Inhibitory Factors in aging as proposed by Tauchi et al. [17, 18].

Aging↗

PubMed1989

Proteoglycans from bovine fetal epiphyseal cartilage. Sedimentation velocity and light scattering studies of the effect of link protein on proteoglycan aggregate size and stability.

Proteoglycan monomer and link proteins were isolated from bovine fetal epiphyseal cartilage and characterized. The physical characteristics of proteoglycan monomer were: s0(20) = 21.3 S, D0t,z = 4.25 x 10(-8)cm2/sec, Mw = 3 x 10(6) and Rg,z = 980A. Link protein preparations contained link proteins 1 and 2, but little or none of the fragment, link protein 3. Link protein-stabilized and link protein-free proteoglycan aggregates were reassembled from proteoglycan monomer, link protein and hyaluronate. The effect of epiphyseal cartilage link protein on aggregate size and stability was examined in sedimentation velocity studies. Compared with link protein from mature bovine nasal and articular cartilages, which contain appreciable amounts of link protein 3, epiphyseal cartilage link protein dramatically stabilized aggregates at pH 5. In the presence of link protein, 92% of the proteoglycan monomers were bound as aggregate at pH 7, and 81% were bound at pH 5. In the absence of link protein, 51% of monomers were bound at pH 7, and only 32% were bound at pH 5. The progressive dissociation of link protein-free aggregates as a function of decreasing pH, and of increasing temperature, was also examined in dynamic light scattering studies. The results of the light scattering studies were in perfect accord with the results of the sedimentation velocity studies. However, compared with the sedimentation velocity studies, the dynamic light scattering studies provided a more detailed and informative description of the dissociation of the link-free aggregate as a function of pH, as a function of temperature, and of the capacity of link protein to stabilize aggregate against dissociation at decreased pH or elevated temperature.

Animals↗

PubMed1987

Distribution of proteoglycans antigenically related to corneal keratan sulfate proteoglycan.

Three antibodies reacting with corneal keratan sulfate proteoglycan were used to detect antigenically related molecules in 11 bovine and 13 embryonic chick tissues. Two monoclonal antibodies recognized sulfated epitopes on the keratan sulfate chain and a polyclonal antibody bound antigenic sites on the core protein of corneal keratan sulfate proteoglycan. Competitive immunoassay detected core protein and keratan sulfate antigens in guanidine HCl extracts of most tissues. Keratan sulfate antigens of most bovine tissues were only partially extracted with guanidine HCl, but the remainder could be solubilized by CNBr treatment of the guanidine-extracted residue. Keratan sulfate and core protein antigens co-eluted with purified corneal keratan sulfate proteoglycan on ion exchange high-performance liquid chromatography (HPLC). Endo-beta-galactosidase digestion of the HPLC-purified keratan sulfate antigens eliminated the binding of monoclonal anti-keratan sulfate antibodies in enzyme-linked immunosorbent assay. Extracts of all 11 bovine tissues, except those from brain and cartilage, could bind both anti-keratan sulfate monoclonal antibodies and anti-core protein polyclonal antibody simultaneously. Binding was sensitive to competition with keratan sulfate and to digestion with endo-beta-galactosidase. These results suggest widespread occurrence of a proteoglycan or sulfated glycoprotein bearing keratan sulfate-like carbohydrate and a core protein resembling that of corneal keratan sulfate proteoglycan.

Animals↗

PubMed1986

Changes in proteoglycan composition during development of rat skin. The occurrence in fetal skin of a chondroitin sulfate proteoglycan with high turnover rate.

Extraction of the skin of newborn rat yielded two populations of galactosaminoglycan-containing proteoglycan: a Mr = 111,000-200,000 dermatan sulfate proteoglycan (DS-PG) with a Mr congruent to 55,000 core glycoprotein and a Mr congruent to 10(6) chondroitin sulfate proteoglycan (CS-PGs) composed of two subpopulations with different size core-glycoproteins (Mr congruent to 480,000 and 520,000). Tryptic peptide mapping of chondroitinase-treated DS-PG and CS-PGs indicated that the peptide patterns observed with the two core molecules from CS-PGs were identical with each other but distinct from the peptide pattern of the DS-PG core molecule. It is likely therefore that the two forms of CS-PGs are derived from the same gene product by post-translational modification or partial degradation, but DS-PG is derived from a distinct gene product. Comparison of the concentration (hexuronate/DNA) of the proteoglycans in newborn and fetal rat skin showed an age-related change in proteoglycan composition; at 4 days before birth, the uronic acid proportions, DS-PG:CS-PGs, were about 14:1 and during the next 4 days, DS-PG increased 2.2-fold whereas CS-PGs decreased 4-fold. On a per DNA basis, the rate of [3H]serine incorporation into CS-PGs was 2.5 times the rate for DS-PG at 4 days before birth but decreased by 95% during the next 4 days. The rate for DS-PG also decreased but to a much lesser extent, so that by 2 days before birth, it began to exceed the rate for CS-PGs. The striking change in the concentration and labeling rate of CS-PGs can be interpreted either as a decrease of CS-PGs synthesis, or as an increase of CS-PGs breakdown, or both, a process which might be involved in the transition of extracellular matrix from a fetal type to a newborn or adult type.

Animals↗

PubMed1988

Proteoglycans of bovine articular cartilage. Studies of the direct interaction of link protein with hyaluronate in the absence of proteoglycan monomer.

When link protein binds to hyaluronate in the absence of proteoglycan monomer a high molecular weight complex is formed. Two assay procedures have been developed to examine the formation of the complex and the rate and stoichiometry of binding of link protein to hyaluronate in the complex. In the first, the complex is isolated by differential centrifugation, and the stoichiometry of binding of link protein to hyaluronate in the sedimented complex is determined. In the second assay, which involves turbidimetry, the rate of complex formation (delta A420/min) is determined, and the amount of complex formed is determined in terms of the maximum turbidity (A420,max) attained. The effects of temperature, pH, initial total solute concentration, and the ratio by weight of link protein to hyaluronate on the amount of complex formed and on the rate of complex formation were examined. There is a linear correlation between the amount of complex formed as determined by turbidity and by differential centrifugation. Using these assays, we examined the specificity of the binding of link protein to hyaluronate and the capacity of hyaluronate oligosaccharides to competitively inhibit the binding of link protein to hyaluronate. Hyaluronate decasaccharide is the oligosaccharide of minimum size that strongly inhibits the binding of link protein to hyaluronate. Proteoglycan monomers dissociate from hyaluronate as the pH is decreased from pH 7 to pH 5. Turbidimetric studies show that the rate of binding of link protein to hyaluronate increases with decreasing pH. The binding affinity of proteoglycan monomers for hyaluronate is decreased at pH 5, whereas the binding affinity of link protein for hyaluronate is not. This difference in the effect of pH on the stability of binding of link protein to hyaluronate, compared with proteoglycan monomer, explains in part the capacity of link protein to stabilize the binding of proteoglycan monomer to hyaluronate at pH 5.

Animals↗

PubMed1996

The NG2 chondroitin sulfate proteoglycan: a multifunctional proteoglycan associated with immature cells.

In this review, we discuss the properties of the NG2 chondroitin sulfate proteoglycan, a structurally unique, integral membrane proteoglycan that is found on the surfaces of several different types of immature cells. NG2 is associated with multipotential glial precursor cells (O2A progenitor cells), chondroblasts of the developing cartilage, brain capillary endothelial cells, aortic smooth muscle cells, skeletal myoblasts and human melanoma cells. One common feature of these diverse cell types is that they retain the ability to divide throughout the life of the organism. The NG2 proteoglycan is a multifunctional protein; in vitro studies have shown that NG2 binds type VI collagen, interacts with and modulates the activity of the platelet-derived growth factor-alpha receptor, and inhibits neurite outgrowth. These functional properties are analogous to those of other proteoglycans such as syndecan, betaglycan, and neurocan, suggesting that structurally divergent proteoglycans can carry out similar functions within the organism.

Animals↗

PubMed1987

Immunity to cartilage proteoglycans in BALB/c mice with progressive polyarthritis and ankylosing spondylitis induced by injection of human cartilage proteoglycan.

Intraperitoneal injection of human fetal cartilage proteoglycan (depleted of chondroitin sulfate) in Freund's complete or incomplete adjuvant induces a chronic erosive polyarthritis and spondylitis in all female BALB/c mice. This occurrence is strain-specific but not haplotype-specific, and it is sex-related. The development of the arthritis is associated with the natural presence of cellular immunity to the immunizing antigen and to chondroitinase ABC-treated mouse cartilage proteoglycan. In addition, relatively more antibody to the immunizing proteoglycan is elicited in arthritic mice, and antibodies are produced that cross-react with native mouse proteoglycan. This combination of immune responses is not observed in mice that do not develop arthritis. Associated with the arthritis is the development of cytotoxicity to mouse chondrocytes and, in some animals, of rheumatoid factor, immune deposits in joint tissues and kidneys, and the production of autoantibodies to mouse type II collagen. These observations might be related to our earlier demonstration that immunity to human cartilage proteoglycan is observed in some patients with ankylosing spondylitis.

Adult↗

PubMed2002

Tenascin and proteoglycans: the role of tenascin and proteoglycans in canine tumours.

Tenascin is a high molecular weight, extracellular matrix glycoprotein, subject to complex spatial and temporal patterns of expression during embryogenesis, wound healing and neoplastic processes. Proteoglycans are complex macromolecules, containing one or more glycosaminoglycans attached to a core protein, which are involved in cell-cell and cell-matrix interaction. Altered expression of both tenascin and proteoglycans has been found in tumours and expression of these two extracellular matrix proteins seems to be modulated in the same way in human and canine tumours. The quantitative and qualitative changes in tenascin and proteoglycan composition may significantly affect behaviour of tumour cells. While tenascin and proteoglycans have many biological functions likely to influence tumour development and progression, their exact role in regulation of tumour cell-cell interaction, proliferation, invasion and metastasis remains to be established. This review focuses on the role of tenascin and proteoglycans in neoplasia and recent developments in canine tumours.

Animals↗

PubMed1976

Interaction between proteoglycan subunit and type II collagen from bovine nasal cartilage, and the preferential binding of proteoglycan subunit to type I collagen.

We studied the interaction of proteoglycan subunit with both types I and II collagen. All three molecular species were isolated from the ox. Type II collagen, prepared from papain-digested bovine nasal cartilage, was characterized by gel electrophoresis, amino acid analysis and CM-cellulose chromatography. By comparison of type I collagen, prepared from papain-digested calf skin, with native calf skin acid-soluble tropocollagen, we concluded that the papain treatment left the collagen molecules intact. Interactions were carried out at 4 degrees C in 0.06 M-sodium acetate, pH 4.8, and the results were studied by two slightly different methods involving CM-cellulose chromatography and polyacrylamide-gel electrophoresis. It was demonstrated that proteoglycan subunit, from bovine nasal cartilage, bound to cartilage collagen. Competitive-interaction experiments showed that, in the presence of equal amounts of calf skin acid-soluble tropocollagen (type I) and bovine nasal cartilage collagen (type II), proteoglycan subunit bound preferentially to the type I collagen. We suggest from these results that, although not measured under physiological conditions, it is unlikely that the binding in vivo between type II collagen and proteoglycan is appreciably stronger than that between type I collagen and proteoglycan.

Amino Acids↗

PubMed1977

The degradation of cartilage proteoglycans by tissue proteinases. Proteoglycan structure and its susceptibility to proteolysis.

1. Proteoglycan was obtained from bovine nasal cartilage by a procedure involving sequential extraction with a low-ionic-strength KCl solution, then a high-ionic-strength CaCl2 solution. Purification was by CsCl-density-gradient centrifugation. 2. The CaCl2- extracted proteoglycan was subjected to proteolytic degradation by papain, trypsin, cathepsin D, cathepsin B, lysosomal elastase or cathepsin G. Degradation was allowed to proceed until no further decrease in viscosity was detectable. 3. The size and chemical composition of the final degradation products varied with the different proteinases. Cathepsin D and cathepsin G produced glycosaminoglycan-peptides of largest average size, and papain produced the smallest product. 4. The KCl-extracted proteoglycan was intermediate in molecular size and composition between the CaCl2-extracted proteoglycan and the largest final degradation products, and may have been formed by limited proteolysis during the extraction procedure. 5. It is postulated that the glycosaminoglycan chains are arranged in groups along the proteoglycan core protein. Proteolytic cleavage between the groups may be common to the majority of proteinases, whereas clevage within the groups is dependent on the specificity of each individual proteinase.

Amino Acids↗

PubMed1977

The degradation of cartilage proteoglycans by tissue proteinases. Proteoglycan heterogeneity and the pathway of proteolytic degradation.

1. CaCl2-extracted proteoglycan from bovine nasal cartilage was degraded by four tissue proteinases till no further decrease in hydroynamic size was obtained. The proteoglycan and its final degradation products were then fractionated by Sepharose 2B chromatography. 2. The average size of the degradation products was least for cathepsin B and lysosomal elastase, and greatest for cathepsin D and cathepsin G. The latter two proteinases also produced degradation products that showed the widest range of sizes. 3. The structure of the degradation products ranged from peptides containing a single glycosaminoglycan chain to those containing twelve or more chains. Of the four proteinases, only cathepsin B produced peptides that contained a single chondroitin sulphate chain. 4. The proteoglycan was very heterogeneous with respect to size and chemical composition. Its behaviour on electrophoresis suggested that at least two genetically distinct core proteins might exist. 5. Irrespective of their structural variations, all proteoglycan molecules were able to interact with hyaluronic acid. In contrast, none of the degradation products were capable of this type of interaction. 6. A pathway for the proteolytic degradation of proteoglycans is postulated in which the sites of initial cleavage may be common to the majority of proteinases, whereas the production of the final clusters is dependent on the specificity of the proteinase. Only those proteinases of broadest specificity can produce single-chain chondroitin sulphate-peptides.

Animals↗

PubMed1978

Characterization of proteoglycan and the proteoglycan--hyaluronic acid complex by electric birefringence.

An electric field causes partial alignment of macromolecules in a dilute solution. The accompanying changes in the solution birefringence offer a sensitive and quick means of monitoring the rates of particle orientation and hence the size of the solute molecules. Such measurements are reported for dilute solutions of proteoglycans in the absence and presence of added hyaluronic acid. The proteoglycan molecules are shown to be some 580 nm long. In the presence of hyaluronic acid they form aggregates that appear to be consistent with the model previously proposed in which the proteoglycans attach radially to the extended hyaluronic acid chain. The electric-birefringence relaxation rates indicate aggregates of similar length to that of the extended hyaluronic acid chain, with the proteoglycans spaced on average at 29nm intervals. A proteoglycan sample the cystine residues of which had been reduced and alkylated showed no evidence of aggregation with hyaluronic acid up to the concentrations of the acid corresponding to 1% of the total uronic acid content. The electric-birefringence method is shown to have a large potential in the study of associating polysaccharide solutions.

Alkylation↗

PubMed1980

Collagen--proteoglycan interactions. Localization of proteoglycans in tendon by electron microscopy.

Proteoglycan in foetal- and adult-rat tail tendon and adult-rabbit achilles tendon was stained for electron microscopy with a cationic phthalocyanin-like dye, based on cinchomeronic acid, in a 'critical electrolyte concentration' method [Scott (1973) Biochem. Soc. Trans. 1, 787-806). Provided that the tissue was fixed with glutaraldehyde or formaldehyde, regular orthogonal perifibrillar arrays of filamentous material (proteoglycan) were observed, but no intra-fibrillar proteoglycan was seen. Specific proteoglycan-collagen interactions are inferred, and a model is proposed. Without fixation, the filamentous arrays disaggregated in the MgCl2 solutions (0.3 M) used during staining. End-to-end proteoglycan aggregation is implied. Tendon and cartilage are compared. Problems of electron-histochemical localization of extended space-filling polyanions by the use of cationic electron-dense precipitants are discussed, particularly polyanion-domain collapse, specificity of staining and fixation. A two-stage staining procedure that markedly enhances contrast is described, based on the multivalent nature of the dye, and the consequent anion-exchange properties of the dye-polyanion complex.

Achilles Tendon↗

PubMed1991

Proteoglycans of human articular cartilage. Identification of several populations of large and small proteoglycans and of hyaluronic acid-binding proteins in successive cartilage extracts.

Two specimens of human articulage were successively extracted with solutions of phosphate-buffered saline (PBS), 7 M-urea and 4 M-guanidine hydrochloride (Gdn-HCl). Proteoglycans from individual extracts were fractionated by DEAE-Sephacel chromatography and gel chromatography on Sephacryl S-400. The presence of three populations of large proteoglycans was demonstrated in all three extracts by composite agarose/polyacrylamide-gel electrophoresis (CAPAGE). The population corresponding to the fastest CAPAGE band of aggregating proteoglycans was shown to be extremely polydisperse, having Mr (as estimated by SDS/PAGE) decreasing continuously from more than 300,000 to the size corresponding to 'free' hyaluronic acid-binding region (HABR) (about 70,000). A rather polydisperse set of HABR-containing fragments which spanned a broad range of sizes, and also differed in their keratan sulphate contents, was isolated from both 7 M-urea and 4 M-Gdn-HCl extracts. PBS and 7 M-urea extracts, but not the Gdn-HCl extract, further contained small proteoglycans, identified as fast-migrating bands on CAPAGE electrophoretograms. One of those small species was recognized with an antibody against the small proteoglycan PG II; the other two remain to be positively identified. However, the glycosaminoglycan of the small species which was present exclusively in the PBS extract was identified as keratan sulphate; this species may thus belong to the family of small keratan sulphate-containing proteolygans.

Adult↗

PubMed1988

The cell surface proteoglycan of mouse mammary epithelial cells. The extracellular domain contains N terminus and a peptide sequence present in a conditioned medium proteoglycan.

The cell surface proteoglycan of mouse mammary epithelial (NMuMG) cells behaves as a receptor for interstitial matrix materials and consists of a membrane-associated domain and an extracellular domain (ectodomain). The ectodomain can be released intact from the cell surface by mild trypsin treatment and appears to be shed from the cells into the culture medium by cleavage from the membrane-associated domain. We have examined the chemical relationship between the trypsin-released proteoglycan and shed proteoglycan to assess their relationship to each other and to the cell surface. Purification and amino acid sequencing of the ectodomain released by mild trypsin treatment resulted in no clear signal until the protein was cleaved by CNBr treatment, suggesting that its N terminus is blocked and oriented extracellularly. The amino acid sequence identified in the trypsin-released ectodomain is present near the N terminus of the shed proteoglycan purified from conditioned medium, indicating that both forms possess closely related (if not identical) core proteins. The sequence reveals a pentapeptide identical to one near the C terminus of the rat hepatic lectin (RHL-1, rat asialoglycoprotein receptor). The medium proteoglycan, which migrates as a smear on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (between 93 and 200 kDa), is heterogeneous due to varying amounts of glycosaminoglycan and substituted O-linked oligosaccharide present on an approximately 46-kDa polypeptide.

Amino Acid Sequence↗

PubMed1987

Cartilage proteoglycan aggregates. The link protein and proteoglycan amino-terminal globular domains have similar structures.

Cartilage proteoglycan aggregates contain two components (proteoglycan monomer and link protein) which interact with each other and with hyaluronic acid. Data from amino acid sequence analysis are presented that shows that a domain of the proteoglycan, the hyaluronic acid binding region, which interacts with link protein and hyaluronic acid is very similar to link protein in terms of its primary structure. However, the pattern of glycosylation in the hyaluronic acid binding region is different from that found in link protein. After removal of N-linked oligosaccharides, the tryptically prepared hyaluronic acid binding region from rat chondrosarcoma has a mass by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of 43 +/- 2 kDa. The COOH-terminal two-thirds of rat chondrosarcoma link protein, starting at residue 105, has 41.3% identity with a similar region in the hyaluronic acid binding region. We show that, in addition to the hyaluronic acid binding region, proteoglycan contains another region with similarity to the two repeating loop structures in the COOH-terminal two-thirds of link protein. This presumably corresponds to the second globular domain reported in rotary shadowing studies of cartilage proteoglycans. We have deduced the positions of all of the disulfide bonds in the hyaluronic acid binding region and find them to be in the same positions as would be expected from comparison of these sequences with link protein.

Amino Acid Sequence↗

PubMed1985

Binding and degradation of proteoglycans by cultured arterial smooth muscle cells. II. Binding sites of proteoglycans on the cell surface.

Exogenous proteoglycans stained for electron microscopy with colloidal gold and/or cuprolinic blue bind to the surface of cultured arterial smooth muscle cells at two different sites. (I) About 20% of the proteoglycans adsorbed to the cells from the culture medium interact as monomeric and multimeric proteoglycans with smooth or coated membrane areas. (II) The bulk of exogenous proteoglycans exhibits high affinity binding to cell membrane-associated 10 nm fibrils containing or being closely associated with fibronectin and to collagen. It is suggested that the self association of proteoglycans and their binding to the cell membrane and to cell surface-associated fibronectin and collagen are important for maintaining an appropriate micro-environment for the cultured cells.

Arteries↗

PubMed1995

Proteoglycan form of colony-stimulating factor-1 (proteoglycan-100). Stimulation of activity by glycosaminoglycan removal and proteolytic processing.

A proteoglycan had been isolated from the conditioned media of a human osteosarcoma cell line and had tentatively been named proteoglycan-100 (PG-100) because of the size of its core glycoprotein. Amino acid sequencing of the purified proteoglycan and cDNA analysis were consistent with the assumption that PG-100 is identical with the proteoglycan form of CSF-1 (or macrophage colony-stimulating factor). PG-100 induced mouse macrophage differentiation. Proliferation of macrophages was stimulated in a dose-dependent manner. On a molar basis, however, about 100- to 300-fold higher doses of PG-100 than of recombinant human (rh)CSF-1 were required for the half-maximal growth-stimulating effect. Upon enzymatic removal of the glycosaminoglycan chain, the purified core protein exhibited higher activity, but was still about 20-fold less active than rhCSF-1. Incubation of the purified proteoglycan for 48 h at 37 degrees C led to the formation of a glycosaminoglycan-free 50-kDa fragment either by autoproteolysis or by the action of a protease not yet identified. The purified fragment exhibited almost the same biologic activity as rhCSF-1. The glycosaminoglycan chain of the growth factor was not only shown to inhibit CSF-1 activity but also to increase the stability of the core protein when the CSF-1-producing osteosarcoma cells were maintained in a collagen lattice. These findings provide a link between a soluble, highly active cytokine and its extracellular matrix storage form of comparatively low activity.

Amino Acid Sequence↗