Structural analysis of chick-embryo cartilage proteoglycan by selective degradation with chondroitin lyases (chondroitinases) and endo-beta-D-galactosidase (keratanase)

Alteration of rat liver proteoglycans during regeneration

Sepharose CL-6B column chromatography of crude extracts from the slices of regenerating rat livers after partial hepatectomy and sham-operated controls labeled with [35S]sulfuric acid revealed an enhancement of [35S]sulfate incorporation into proteoglycan fractions during regeneration. The 35S-labeled proteoglycans contained heparan sulfate (more than 80% of the total) and chondroitin/dermatan sulfate. The 35S-incorporation into both glycosaminoglycans increased to maxima 3-5 days after partial hepatectomy and decreased thereafter toward the respective control levels. When [35S]sulfuric acid was replaced by [3H]glucosamine, similar results were obtained. These results suggest that the maximal stimulation of proteoglycan synthesis in regenerating rat liver follows the maximal mitosis of hepatic cells 1-2 days after partial hepatectomy. The 35S-labeled proteoglycans from regenerating liver 3 days after partial hepatectomy and control were analyzed further. They were similar in chromatographic behavior on a gel filtration or an anion-exchange column and in glycosaminoglycan composition. Their glycosaminoglycans were indistinguishable in electrophoretic mobility. However, these proteoglycans were slightly but significantly different in their affinity to octyl-Sepharose and in the molecular-weight distribution of their glycosaminoglycans.

Proteoglycan synthesis in human erythroleukaemia (HEL) cells

Synthesis of sulphated proteoglycans was compared in human erythroleukaemia (HEL) cells grown under control conditions and under stimulation by dimethyl sulphoxide (DMSO) and phorbol 12-myristate 13-acetate (PMA). Synthesis of [35S]sulphate-labelled proteoglycans by DMSO-treated cells was decreased by about 35% relative to controls, but synthesis of proteoglycans by PMA-treated cells increased 3-4-fold. Control and DMSO-treated cells secreted 65% of the newly synthesized proteoglycans, but PMA-treated cells secreted more than 90%. Sepharose CL-6B chromatography and SDS/PAGE suggested the presence of several proteoglycans in the cells and culture medium. The PMA-treated cells synthesized a low-Mr proteoglycan (Kav. 0.3( that was not present in controls and DMSO-treated cultures. The proteoglycans of the cells and medium from control, DMSO-treated and PMA-treated cultures could be separated into three fractions by octyl-Sepharose chromatography. The proteoglycans were resistant to trypsin but were degraded by Pronase and papain to fragments similar in size to the NaOH/NaBH4-generated glycosaminoglycans. The average chain length of the glycosaminoglycans (Kav. 0.20 on Sepharose CL-6B for controls) was decreased by DMSO (Kav. 0.25) and by PMA (Kav. 0.30-0.38). Chondroitin ABC lyase digestion of the proteoglycans from the medium of the control cultures produced two core proteins at Mr 31,000 and 36,000. The DMSO medium proteoglycans had only the 31,000-Mr core protein, and the PMA culture medium proteoglycans had core proteins of Mr 27,000, 31,000 and 36,000. Changes in synthesis of proteoglycans induced by DMSO or PMA may have relevance for the maturation of haematopoietic cells.

Changes in proteoglycan turnover in experimental canine osteoarthritic cartilage

The metabolism of newly-synthesised and total ("resident") proteoglycans was examined in control and osteoarthritic cartilage explants obtained from an experimental model (Pond and Nuki, 1973) of canine osteoarthritis. The following findings were obtained: (i) Non-labelled proteoglycans extracted from normal cartilage with 4 M guanidine HCl showed two bands visualised by staining with toluidine blue. The electrophoretic mobilities of proteoglycans from osteoarthritic cartilage were unchanged but the relative abundance of the slower migrating band increased with time after surgery. (ii) There were qualitative differences in the proteoglycan breakdown products released into the medium of explant cultures of osteoarthritic compared with control cartilage. This was apparent for both labelled and total unlabelled proteoglycans. (iii) There were similarities in the electrophoretic mobilities of the major labelled and non-labelled proteoglycan breakdown products suggesting that total ("resident") proteoglycans and newly-formed proteoglycans were degraded by similar mechanisms. There were however some differences in the labelled and non-labelled proteoglycans, suggesting that the mechanisms of breakdown were not identical. (iv) Immunoblotting techniques showed differences in the distribution of various glycosaminoglycans in proteoglycan breakdown products from control compared with osteoarthritic cartilage explant cultures. (v) Monoclonal antibodies 7-D-4 and 3-B-3 (which recognise unusual native chondroitin sulphate epitopes) showed greatly increased expression on proteoglycans from osteoarthritic cartilage compared with controls.

The phosphorylated and/or sulfated structure of the carbohydrate-protein-linkage region isolated from chondroitin sulfate in the hybrid proteoglycans of Engelbreth-Holm-Swarm mouse tumor

The structure of the linkage region of chondroitin sulfate chains attached to the hybrid proteoglycans of the Engelbreth-Holm-Swarm mouse tumor was investigated. The peptidoglycan fraction which contains oversulfated chondroitin sulfate rich in the GlcA beta 1-3GalNAc-4,6-diO-sulfate unit and undersulfated heparan sulfate rich in GlcA beta 1-4GlcNAc and GlcA beta 1-4GlcN-2N-sulfate units was isolated after exhaustive protease digestion of the acetone powder of the tumor tissue, (GlcA, glucuronic acid; GalNAc, 2-deoxy-2-N-acetylamino-D-galactose). Glycosaminoglycans were released by beta-elimination using NaB3H4 and digested with chondroitinase ABC. The linkage region fraction was separated from heparan sulfate by gel filtration and fractionated by HPLC on an amine-bound silica column. Six radiolabeled compounds (L1-L6) were obtained and structurally analyzed by cochromatography with authentic hexasaccharide alditols recently isolated by us from the linkage region, and by digestion using chondroitinase ACII, alkaline phosphatase and beta-galactosidase in conjugation with HPLC. These compounds shared the conventional hexasaccharide backbone structure: delta GlcA beta 1-3GalNAc beta 1-4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl-ol, (delta GlcA, delta 4.5-GlcA or D-gluco-4-enepyranosyluronic acid). L1 was not sulfated or phosphorylated. L2 and L4 were monosulfated at C-6 and C-4 of the GalNAc residue, respectively. Upon alkaline phosphatase digestion, L3, L5 and L6 were converted to L1, L2 and L4, respectively. Analysis of the periodate oxidation products indicated that the phosphate group in L3, L5 and L6 is located at C-2 of Xyl-ol. These results suggest that Xyl-2-O-phosphate is associated with both 4-O-sulfated and 6-O-sulfated GalNAc units and does not directly determine the sulfation pattern of chondroitin sulfate.

Biochemical and immuno- and lectin-histochemical studies of solubility and retention of bone matrix proteins during EDTA demineralization

The present study utilized biochemical and immuno- and lectin-histochemical methods to demonstrate solubility and retention of mineral-binding non-collagenous proteins in rat midshaft subperiosteal bone during EDTA demineralization. A monoclonal antibody (9-A-2) specific for chondroitin 4-sulphate and dermatan sulphate and wheat germ agglutinin (WGA) specific for N-acetyl-D-glucosamine, N-acetylneuraminic acid, and N-acetyl-D-galactosamine were used. Bone proteins were extracted from fresh unfixed or aldehyde-fixed specimens with a three step extraction procedure, 4 M guanidine HCl (GdnCl), aqueous EDTA without GdnCl, followed by GdnCl. For comparison with the second extraction step, ethanolic trimethylammonium EDTA (ethanolic EDTA) was substituted for aqueous EDTA. Based on protein staining and Western blot analysis of SDS-polyacrylamide gel electrophoresis of each extract using 9-A-2 and WGA, retention of mineral-binding proteins extractable from fresh specimens with aqueous EDTA was greatly increased in tissue when ethanolic EDTA was used. Their retention was even greater with prior aldehyde fixation. Maximum retention with no detectable solubility of 9-A-2 and WGA reactive proteins was obtained after ethanolic EDTA extraction of aldehyde-fixed specimens, which concomitantly provided the strongest immuno- and lectin staining. These results indicate that this combined method dramatically improves retention of PGs and glycoproteins during demineralization of bone tissues and provides the best method for localizing these glycoconjugates.

Proteoglycans in human burn hypertrophic scar from a patient with Ehlers-Danlos syndrome

Proteoglycans (PGs) from human burn hypertrophic scar of a patient with Ehlers-Danlos syndrome were extracted with 4M guanidinium chloride and purified by DEAE-cellulose chromatography. Differential ethanol precipitation of the PG fraction obtained after ion-exchange chromatography yielded two low mol.-wt. PGs, on rich in glucuronic acid (PGGLCA; Mr 66 kDa) and the other rich in iduronic acid (PGIDOA; Mr 48 kDa). In PGGLCA, 84% of the glycosaminoglycan chains are composed of GlcA----GalNAc(SO4) units, whereas in PGIDOA, the chains contain 95% IdoA----GalNAc(SO4) disaccharide units. Upon treatment with testicular hyaluronidase, the PGs gave different-sized oligosaccharides. Chondroitinase ABC digestion of PGGLCA or PGIDOA gave a single protein core (Mr approximately 20 kDa). The presence of glucosamine and sialic acid in PGGLCA and PGIDOA suggests that both contain N-linked oligosaccharides.

Cell surface heparan sulfate proteoglycan and chondroitin sulfate proteoglycan of arterial smooth muscle cells

Cell surface proteoglycans of aortic smooth muscle cells of atherosclerosis-susceptible White Carneau (WC) and atherosclerosis-resistant Show Racer (SR) pigeons were compared to determine differences that may be involved in the greater proliferative properties of cultured WC cells. Using [35S]-sodium sulfate and [3H]-glucosamine as labeling precursors, chondroitin sulfate-proteoglycan (CS-PG) and heparin sulfate-proteoglycan (HS-PG) were identified as distinct molecules associated with the plasma membrane. Heparan sulfate-proteoglycan was reduced up to 50% in WC compared with SR cells, and, based on interaction with ion-exchange resin, had a lower charge density. These differences were not observed for the CS-PG from the two cell types. The mode of association of the cell surface PG with the plasma membrane was examined. Dissociation with 1 mol/l (molar) sodium chloride indicated that less than 10% of total cell surface PG were ironically associated with the cells. The remainder required detergent extraction, suggesting hydrophobic interactions with the plasma membrane. Both CS-PG and HS-PG displayed affinity for octyl sepharose and both were identified in isolated plasma membranes. These data present the first description of a hydrophobic CS-PG that is a significant and distinct cell-associated PG in arterial smooth muscle cells. The observation of decreased and structurally altered HS-PG in WC compared with SR cells is consistent with a potential growth regulatory function for this molecule.

Identification of chick corneal keratan sulfate proteoglycan precursor protein in whole corneas and in cultured corneal fibroblasts

The precursor protein to the chick corneal keratan sulfate proteoglycan was identified by immunoprecipitation with antiserum to its core protein from lysates of [35S]methionine-pulsed corneas and corneal fibroblasts in cell culture. Antiserum to the keratan sulfate proteoglycan immunoprecipitated a doublet of Mr 52,000 and 50,000 and minor amounts of a Mr 40,000 protein from pulsed corneas. Pulse-chase experiments, which permitted the conversion of the precursor proteins to proteoglycans and digestion of the glycosaminoglycans on immunoprecipitated proteoglycans with keratanase or chondroitinase ABC, showed that the Mr 52,000-50,000 doublet was converted to a keratan sulfate proteoglycan and the Mr 40,000 protein was converted to a chondroitin sulfate proteoglycan. Chick corneal fibroblasts in cell culture primarily produced the smaller (Mr50,000) precursor protein, and in the presence of tunicamycin the precursor protein size was reduced to Mr35,000, which indicates that the core protein contains approximately five N-linked oligosaccharides. Pulse-chase experiments with corneal fibroblasts in culture showed that the precursor protein was processed and secreted into the medium. However, its sensitivity to endo-beta-galactosidase and resistance to keratanase indicate that the precursor protein was converted to a glycoprotein with large oligosaccharides and not to a proteoglycan. This suggests that, although the precursor protein for the proteoglycan is produced in cultured corneal fibroblasts, the sulfation enzymes for keratan sulfate may be absent.

Metabolism and turnover of cell surface-associated heparan sulfate proteoglycan and chondroitin sulfate proteoglycan in normal and cholesterol-enriched macrophages

Analysis of sulfur-35-labeled proteoglycans indicated that cholesterol-enriched pigeon peritoneal macrophages synthesized 42% more 35S-labeled proteoglycan when compared with control macrophages during a 24-hour incubation. Proteoglycan turnover was subsequently studied in radiolabeled macrophage cultures after a 1-, 3-, 6-, 12-, or 24-hour chase with fresh media. During the chase, intracellular proteoglycan disappeared rapidly, whereas there was a small accumulation of 35S-labeled proteoglycan in the media that plateaued at about 6 hours and remained relatively constant thereafter. Pericellular heparan sulfate proteoglycan and chondroitin sulfate proteoglycan disappeared throughout the chase and did not appear to accumulate in the media or in the intracellular compartment. The rapid disappearance of intracellular proteoglycans along with the relative lack in metabolism of media proteoglycans indicated that the majority of pericellular proteoglycans were metabolized via an intracellular degradative pathway. Kinetic analysis of pericellular proteoglycans revealed the presence of a single pool of heparan sulfate proteoglycan (half-life [t1/2] = 6.9 hours) and a single pool of chondroitin sulfate proteoglycan (t1/2 = 11.5 hours) in control macrophage cultures. Cholesterol-enriched macrophage cultures also contained a single pool of pericellular heparan sulfate proteoglycan (t1/2 = 7.3 hours) but contained two pools of chondroitin sulfate proteoglycan (t1/2 = 0.8 hour and 25.9 hours).

Increased aggrecan (cartilage proteoglycan) production in the sclera of myopic chicks

A previously characterized chick model of myopia was used to evaluate biochemical changes in the sclera which are associated with ocular enlargement and myopia. Chicks were monocularly occluded for 10 days and the DNA, hydroxyproline, and glycosaminoglycan contents of the sclera were compared between the normal and the myopic eyes. No significant differences could be detected in total DNA or hydroxyproline content. There was, however, a 34% increase in glycosaminoglycans and a 20.7% decrease in cell density within the posterior sclera of myopic eyes. The biosynthesis of scleral proteoglycans was determined by measuring 35SO4 incorporation in the sclera of chicks visually occluded for 5, 10, and 15 days. No differences could be detected in 35SO4 incorporation into the cornea or the anterior sclera. However, 35SO4 incorporation was significantly increased in the posterior sclera of myopic eyes by 64% at Day 5, 39% at Day 10, and 49% at Day 15. When fractionated on Sepharose CL-4B, scleral proteoglycans were resolved into two peaks which were identified by Western blot analysis as aggrecan (cartilage proteoglycan) and decorin. Furthermore, Western blot and dot blot analyses indicated that significantly more aggrecan core protein was present in the sclera of myopic eyes compared with equivalent amounts of sclera from control eyes. These results indicate that increased synthesis and accumulation of aggrecan, which increases the volume of extracellular matrix in the posterior sclera, are responsible for the ocular enlargement observed in this model of myopia.

Mammalian cartilage synthesizes both proteoglycan and non-proteoglycan forms of type IX collagen

Bovine epiphysial cartilage synthesizes both proteoglycan (PG) and non-PG forms of type IX collagen in a ratio of approx. 2:1. The PG form with its attached glycosaminoglycan on the alpha 2(IX) chain is the major form in the medium, whereas both forms are found in the tissue. The results are discussed with regard to cartilage matrix organization.

Immunohistochemical characterisation of extracellular matrix components of salivary gland tumours

Proteoglycans (PGs) were localised immunohistochemically in 52 salivary gland tumours including pleomorphic adenoma, adenoid cystic carcinoma, acinic cell carcinoma, oncocytoma, mucoepidermoid carcinoma, clear cell tumour and Warthin tumour, using antibodies raised against large PG, small PG, chondroitin 4-sulphate PG, chondroitin 6-sulphate PG, heparan sulphate PG and keratan sulphate PG. Large PGs were mainly observed in mucinous materials of extracellular matrix (ECM) and interstitial fibrous element of tumour tissues, while small PGs were located only in hyaline matrix and surrounding fibrous (capsular) connective tissues. Chondroitin 6-sulphate PG was detected in the ECM of pleomorphic adenomas and clear cell carcinomas and in pseudocystic spaces of adenoid cystic carcinomas, but only in vessel walls in non-neoplastic tissues. Keratan sulphate PG was observed to locate in mucinous material of pleomorphic adenomas, acinic cell carcinomas and clear cell carcinomas, but not in the adenoid cystic carcinomas examined, and it was also unobservable in non-neoplastic salivary gland tissues. Heparan sulphate PG was observed on the inner surfaces of true ductal spaces of adenoid cystic carcinomas and on cell surfaces of oncocytoma cells. By HPLC analysis, individual glycosaminoglycans contained in tumour tissues were compared. Chondroitin 6-sulphate PG was very rich in ECM of pleomorphic adenomas and adenoid cystic carcinomas. Pleomorphic adenomas contained relatively more low-sulphated chondroitin sulphate than adenoid cystic carcinomas and other tumours.

Effects of glutathione depletion on the synthesis of proteoglycan and collagen in cultured chondrocytes

We studied the effect of the depletion of glutathione on the synthesis of proteoglycan and collagen in cultured chick chondrocytes. When the cultured chondrocytes were incubated with 1 mM buthionine sulfoximine (BSO), a specific inhibitor of gamma-glutamyl-cysteine synthetase, the intracellular glutathione level markedly dropped within 12 h with no loss of cell viability. Incorporation of 35SO2-4 into proteoglycan was lowered in the presence of BSO. When the 35S-labeled proteoglycans were separated into two fractions by glycerol density gradient centrifugation, the inhibitory effect of BSO on the synthesis of proteoglycan was greater in the fast-sedimenting proteoglycan fraction, which consisted mainly of cartilage specific large proteoglycan (PG-H), than in the slowly sedimenting proteoglycan fraction. The inhibition by BSO of the synthesis of core protein-free glycosaminoglycan chains primed by p-nitrophenyl-beta-D-xyloside was smaller than the inhibition of the synthesis of proteoglycan. Analysis of glycosaminoglycans labeled with [3H]glucosamine indicated that the treatment of chondrocytes with BSO resulted in a small increase in the proportion of synthesis of hyaluronic acid to the synthesis of total glycosaminoglycan. The incorporation of [3H]proline into collagen was also inhibited by BSO. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the 3H-labeled collagen showed that, in the presence of BSO, processing of Type II collagen appeared to slow down and the proportion of Type X collagen synthesis was reduced.

Proteoglycans synthesized by an osteoblast-like cell line (UMR 106-01)

The proteoglycans synthesized by an osteoblast-like cell line of rat origin (UMR 106-01) were defined after biosynthetic labelling with [35S]sulphate and [3H]glucosamine. Newly synthesized labelled proteoglycans were characterized by differential enzymic digestion in combination with analytical gel filtration and SDS/PAGE. UMR 106-01 cells were found to synthesize three major species of proteoglycan: a large chondroitin sulphate proteoglycan of Mr approximately 1 x 10(6), with a core protein of Mr approximately 350,000-400,000; a small chondroitin sulphate-containing species of Mr approximately 120,000 with a core protein of Mr 43,000; and a heparan sulphate proteoglycan of Mr approximately 150,000, with a core protein of Mr approximately 80,000. Over 70% of the newly synthesized intact proteoglycan species are associated with the cell layer of near-confluent cells; however, accessibility to trypsin digestion suggests an extracellular location. Chemical characteristics of the proteoglycans and preliminary mRNA hybridization indicate that the small chondroitin sulphate proteoglycan is probably PG II (decorin). The large chondroitin sulphate proteoglycan is most likely related to a hyaluronate-aggregating species from fibroblasts (versican), and the heparan sulphate proteoglycan bears striking similarities to cell-membrane-intercalated species described for a number of cell types.

Immunohistochemical identification of proteoglycans in gelatinous membranes of cat and gerbil inner ear

Proteoglycans have been identified in gelatinous membranes of adult cat and gerbil inner ears using highly specific histochemical techniques. The tectorial and otoconial membranes and cupula of both species stained strongly with high iron diamine which is specific for sulfate esters and with monoclonal antibody against keratan sulfate proteoglycan (KSPG). The cat tectorial membrane also showed strong immunoreactivity with monoclonal antibody against chondroitin sulfate proteoglycan (CSPG) but the gerbil tectorial membrane reacted only weakly with this antibody. Otoconial membranes and the cupula of both species showed little if any immunostaining with antibodies against CSPG. Supporting cells in the vestibular neurosensory epithelium and planum semilunatum cells in the ampullae of the cat stained strongly with anti-KSPG, demonstrating the origin of KSPG in the cat. These cell types failed to stain in the gerbil, however, suggesting a different mechanism of secretion or a slower rate of turnover of membraneous KSPG in the gerbil. Interdental cells of both species failed to react with either antibody, leaving the origin of tectorial membrane proteoglycans in question. The approach used here provides a highly sensitive and reliable means of assessing the contribution of specific proteoglycans to inner ear structure and function.

Purification and N-terminal amino acid sequence of a chondroitin sulphate/dermatan sulphate proteoglycan isolated from intima/media preparations of human aorta

A proteoglycan (PG) was purified to homogeneity from intima/media preparations of human aorta specimens by the following chromatographic steps: Sepharose Q anion exchange, Sepharose CL-4B size exclusion, hydroxyapatite, MonoQ anion exchange and TSK G 4000 SW size exclusion. The purity of the preparation was established by SDS/PAGE using direct staining by silver or Dimethylmethylene Blue, as well as by Western blots of biotin-labelled samples. The electrophoretic mobility of the native PG was less than that of a 200,000-Mr standard protein. After treatment with chondroitin sulphate lyase ABC, a core protein of Mr 15,000 was revealed. The Mr of the glycosaminoglycan (GAG) peptides was less than 24,000, by comparison with a keratan sulphate peptide. The composition of the GAG chains was determined by differential digestion of the PG by chondroitin sulphate lyases AC/ABC or chondroitin sulphate lyase AC alone followed by anion-exchange chromatography of the resulting disaccharides. The GAG chains are composed of approximately one-third of dermatan sulphate and two-thirds chondroitin sulphate disaccharide units. The sequence of the 20 N-terminal amino acids is identical with the sequence previously reported for PG I isolated from human developing bone [Fisher, Termine & Young (1989) J. Biol. Chem. 264, 4571-4576]. The assignment of glycosylation sites to the serine residues in positions 5 and 10 was confirmed. The findings indicate that the chondroitin sulphate/dermatan sulphate PG is a major PG in intima/media preparations of human aorta and represents a biglycan-type PG.

Comparison of the cartilage proteoglycan core protein synthesized by chondrocytes of different ages

Chondrocytes of different ages synthesize proteoglycans which have structural differences in both the chondroitin sulfate and keratan sulfate glycosaminoglycans. In order to ascertain whether age-dependent differences also occur in the core protein, the chick limb bud mesenchymal cell culture system was utilized to analyze newly synthesized proteoglycan core protein from undifferentiated mesenchymal cells (day 1 and 2), newly differentiated cartilage (day 4), mature cartilage (day 8), and senescent cartilage (day 16). The core protein synthesized at various times was identified by radiolabeling with [3H]leucine and [35S]sulfate immediately prior to extraction and purification. The sizes of the various core protein preparations were compared by electrophoresis on a 3% polyacrylamide gel after partial deglycosylation with chondroitinase AC and keratanase. The proteoglycans from day 4, 8, and 16 cultures each give rise to a single band of approximately 475,000 daltons. The proteoglycans from day 1 and 2 cultures also give rise to the 475,000 dalton band, but each contains several other components which produce a smear of high molecular weight material on the gel. The monomer proteoglycans were incubated with cyanogen bromide and the resultant peptides separated by electrophoresis on a 5-17.5% polyacrylamide gel. The peptide displays of core proteins synthesized on days 4, 8 and 16 are virtually identical in terms of the number and electrophoretic distribution of the core protein peptides. In contrast, proteoglycan core proteins from day 1 and day 2 cultures give rise to peptide displays which resemble those from older cultures in some respects but have distinct features as well. The absence of structural variation in the newly synthesized proteoglycan core proteins from cartilage of different ages suggests that the age-related changes in the structure of the intact proteoglycans result from differences in the glycosaminoglycan biosynthetic machinery rather than alterations in the acceptor molecule (i.e., the core protein).

Proteoglycans in the mouse interphotoreceptor matrix. IV. Retinal synthesis of chondroitin sulfate proteoglycan

To determine whether the mouse retina contributes chondroitin sulfate proteoglycan (CS-PG) to the interphotoreceptor matrix (IPM), 35SO4(2-) was used as a tracer for newly synthesized proteoglycan by retinas maintained in vitro in the absence of pigment epithelium. Following incubation with the tracer for 3 hr, the 35S-labeled proteoglycans present in the incubation medium and associated with isolated photoreceptor outer segments were analyzed separately. Proteoglycan was extracted with 4 M guanidine, and then separated on a G-25 column followed by DEAE ion exchange chromatography in the presence of 8 M urea. The proteoglycan fraction was eluted with a linear NaCl gradient of 0.15-1.0 M. Eluted 35S-labeled macromolecules were susceptible to chondroitinase AC and ABC degradation, indicating that virtually all the 35S-labeled proteoglycan synthesized by the mouse retina and secreted into the incubation media is of the chondroitin sulfate type. In parallel autoradiographic analysis of retinas following 35SO4(2-) incubation, silver grains were present over all retinal compartments, with 41-48% associated with the photoreceptor layer. Quantitative autoradiography of retinas following chondroitinase AC digestion of fixed retinas revealed significant (P less than 0.025) reduction in silver grains associated with the photoreceptor outer segment layer as compared to controls. These combined biochemical and autoradiographic studies indicate that the retina, possibly the photoreceptors, synthesize at least a portion of the CS-PG present in the IPM of the mouse.

Immunological detection of the EGF-like domain of the core proteins of large proteoglycans from human and baboon cartilage

Recent data from the literature have shown that cDNA clones for the carboxyterminal domain of the core protein of large proteoglycan monomers from human cartilage contain an EGF-like domain, which appears to undergo alternative splicing. In the present study we have found that articular proteoglycans from human and baboon separated on agarose flat-bed gels and blotted onto nitrocellulose react with a rabbit antiserum to mouse EGF. In addition both forms of the proteoglycans (band I and band II) seen on these gels are reactive. Reactivity is seen with proteoglycans extracted from human articular cartilage of various ages (fetal, newborn, young and aged) and with proteoglycans extracted from cartilage of thanatophoric dysplasia and homozygous achondroplasia. Reactivity is dependent on prior digestion of the nitrocellulose blot with Chase ABC, suggesting masking of epitope by chondroitin sulfate. Reactivity of the EGF antiserum with cartilage proteoglycan core protein was also demonstrated in an ELISA system with core protein as coating antigen. The reactivity appears to reside in a tryptic peptide generated from Chase/keratanase digested core protein. The immunoreactive species migrates as a 68 KDa species on gradient gels. Immunological detection and quantitative analysis of the EGF-like domain could be useful for analysis of various proteoglycan samples.

Isolation and characterization of proteoglycans from different tissues

Two chromatographic procedures for the isolation and purification of proteoglycans (PG) and their related glycosaminoglycan (GAG) peptides are described. PG from human aorta were isolated from tissue extract by sequential ion-exchange, size-exclusion and hydroxyapatite chromatography. Final purification of samples was achieved by chromatography on Mono Q. Homogeneity of samples was demonstrated by Western blot analysis of biotin-labelled compounds prior to and after enzymatic digestion and dual-wavelength detection in size-exclusion chromatography. The purity of samples obtained by the procedure described was sufficient for protein sequence analysis. GAG preparations of bovine trachea cartilage were purified by the sequential use of strong anion-exchange supports. Molecular weight distribution and sensitivity to treatment with glycan-specific enzymes was shown by size-exclusion chromatography.

Nonspecific interaction of proteoglycans with chromatography media and surfaces: effect of this interaction on the isolation efficiencies

Nonspecific adsorption of proteoglycans to chromatography media and surfaces is demonstrated. This adsorption is highly dependent on the nature of the chromatography media and the precise buffer conditions. For a given buffer the amount of adsorption decreases as the pH of the buffer is increased. It is also highly dependent on buffer concentration and increases as the buffer concentration is increased. The effect of salts such as LiCl, NaCl, KCl, and MgCl2 was generally small and complex so that the presence of the salt both increased and decreased the amount of adsorption depending on the buffer conditions. In contrast, the effect due to the presence of guanidine hydrochloride (Gdn-HCl) was relatively large and complex. At low Gdn-HCl concentrations there generally was a large increase in the amount of adsorption, reaching a maximum at approximately 0.5 M Gdn-HCl and decreasing with further increases in Gdn-HCl concentration. Detergents such as 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (Chaps) and sodium dodecylsulfate generally reduced the amount of nonspecific adsorption, although in the presence of both the detergent and Gdn-HCl, the effect due to Gdn-HCl predominated. In commonly used buffers such as 0.5 M sodium acetate (NaOAc), pH 7.0 (buffer F), and 4 M Gdn-HCl in 0.05 M NaOAc, pH 5.8 (buffer D), adsorption to surfaces and chromatography media such as Sepharose CL-2B, cellulose, and controlled pore glass (CPG) is highly significant and it is particularly large for cellulose and CPG.(ABSTRACT TRUNCATED AT 250 WORDS)

Negative regulation of transforming growth factor-beta by the proteoglycan decorin

Decorin is a small chondroitin-dermatan sulphate proteoglycan consisting of a core protein and a single glycosaminoglycan chain. Eighty per cent of the core protein consists of 10 repeats of a leucin-rich sequence of 24 amino acids. Similar repeats have been found in two other proteoglycans, biglycan and fibromodulin, and in several other proteins including Drosophila morphogenetic proteins. Expression of high levels of decorin in Chinese hamster ovary cells has a dramatic effect on their morphology and growth properties. We now report that this effect is due at least in part to the ability of decorin to bind transforming growth factor-beta, an autocrine factor that stimulates the growth of Chinese hamster ovary cells. As transforming growth factor-beta induces synthesis of decorin in many cell types, our results suggest that decorin may be a component of a feedback system regulating cell growth.

Monoclonal antibodies specific for keratan sulfate detect epithelial-associated carbohydrates

Monoclonal antibodies that specifically recognize epitopes on keratan sulfate glycosaminoglycans were used in this study to identify carbohydrate epitopes associated with many, but not all, types of epithelial cells. Immunoreactive cells included: keratinocytes, sebaceous gland cells, eccrine sweat gland duct cells, salivary gland excretory duct cells, colon adenocarcinoma cells, embryonic chick lung epithelial cells, embryonic chick mesonephric and metanephric kidney epithelial cells, and selected embryonic chick neural tube cells. Depending upon the type of epithelium, epitopes were located either within the cytoplasm or were located on cell surfaces. These epitopes were shared by cells from both human and chick tissues, indicating the absence of species specificity. Not all anti-keratan sulfate antibodies were equally effective in identifying epithelial-associated epitopes. One of the seven antibodies employed in this study failed to detect epitopes in almost all epithelial tissues studied. Of the remaining six antibodies, three were more effective than the others in recognizing epithelial-associated epitopes. These data indicate that carbohydrates that are typically associated with extracellular matrix can also be associated with epithelial cells, but in a form that is not necessarily related to extracellular matrix. These antibodies should prove to be useful in studies of the development of epithelial cells and tissues.

Characterization of the human gene that encodes the peptide core of secretory granule proteoglycans in promyelocytic leukemia HL-60 cells and analysis of the translated product

Based upon the deduced amino acid sequence of a cDNA (cDNA-H4) that had been proposed to encode the peptide core of an eosinophil and a HL-60 cell secretory granule proteoglycan, a 16-amino acid peptide was synthesized. This peptide was then used to elicit rabbit antibodies for study of the translation and post-translational modification of this gene product in hematopoietic cells. When HL-60 cells were radiolabeled for 2 min with [35S]methionine, a protein that migrated in a sodium dodecyl sulfate-polyacrylamide electrophoresis gel with a Mr of 20,000 was immunoprecipitated with the IgG fraction of the anti-peptide serum. Kinetic experiments revealed that within 10 min this radiolabeled precursor protein was converted in HL-60 cells into an Mr approximately 150,000 chondroitin sulfate proteoglycan intermediate. After a 20-min to 1-h chase, this [35S]methionine- or [35S]sulfate-labeled proteoglycan intermediate lost its antigenicity, presumably due to proteolysis of its N terminus. A human genomic library was probed under conditions of high stringency with cDNA-H4 to isolate genomic clones that contain the gene that encodes this proteoglycan peptide core. This gene spans approximately 15 kilobases and consists of three exons. The first exon encodes the 5'-untranslated region of the mRNA transcript, as well as the entire 27-amino acid signal peptide of the translated molecule. The second exon encodes a 49-amino acid region of the peptide core, predicted to be the N terminus of the molecule after its proteolytic processing in the endoplasmic reticulum. The third exon encodes the remainder of the molecule, including its glycosaminoglycan attachment, serine-glycine repeat region. As assessed by S1 nuclease mapping and primer extension analysis, the transcription-initiation site in HL-60 cells for this gene resides 53 base pairs upstream from the translation-initiation site.

Change in synthesis of sulfated glycoconjugates during muscle development, maturation and aging in embryonic to senescent CBF-1 mouse

Previous biochemical and morphological studies have demonstrated a change in the synthetic pattern of sulfated proteoglycans during skeletal musculogenesis in the embryonic chick. These studies revealed that a transition occurs in both composition and deposition of sulfated glycoconjugates that parallels the developmental state of the tissue. The current study was undertaken to ascertain whether this transition in the embryonic chick is a conserved developmental process during musculogenesis in the mouse. Leg musculature from embryonic, newborn, juvenile, adolescent, young adult, mature adult and senescent mice, radiolabeled in vivo with [35S]sulfate, was analyzed for relative size and composition of newly synthesized sulfated macromolecules. The data reveal a transition in the synthesis of sulfated proteoglycans and glycoproteins that parallels the myogenic differentiative state of the mouse leg muscle. Embryonic mouse leg musculature synthesizes relatively large proteoglycans consisting of large chondroitin sulfate glycosaminoglycan chains. Subsequently, these major newly synthesized proteoglycans are replaced synthetically by smaller molecules composed of mixtures of dermatan sulfate, chondroitin sulfate and heparan sulfate glycosaminoglycans (newborn through 2 weeks); dermatan sulfate, heparan sulfate and chondroitin sulfate glycosaminoglycans (13 months) and heparan sulfate and dermatan sulfate glycosaminoglycans (25-26 months). The sulfated glycoproteins demonstrate a reciprocal synthetic pattern. Early in development sulfated glycoproteins form a small proportion of the newly synthesized sulfated material. With increasing developmental and maturational age, the proportion of sulfated glycoproteins increases. This continues until they become the predominant sulfated moieties synthesized by senescent mouse muscle. The results from this study thus extend observations initially made in chick to muscle development in the mouse and, therefore, suggest that the transition in synthesis of sulfated glycoconjugates is a conserved developmental process during musculogenesis.

Isolation and some structure analyses of a copolymeric chondroitin sulfate-dermatan sulfate proteoglycan from post-burn, human hypertrophic scar

A D-glucuronic acid rich, copolymeric chondroitin sulfate (CS)-dermatan sulfate (DS) proteoglycan (PG) from post-burn hypertrophic scar tissue (HSc) was obtained by DEAE-cellulose chromatography and differential ethanol fractionation, and further purified on a Sepharose CL-6B column. CS-DS-PG protein content was 14% (w/w). The amino-terminal amino acid sequence of the first ten residues was as follows: NH2-Asp-Glu-Ala-B-Gly-Ile-Gly-Pro-Glu-Val. This sequence is identical to that of human embryonic fibroblast cell (IMR-90) CS-DS-PG, as well as to human HSc-DS-PG. After chondroitinase ABC treatment, two peptides (Mr 22,000 and 16,000 daltons) were detected by sodium dodecyl sulfate-(polyacryl)amide gel electrophoresis (SDS-PAGE). ELISA analysis using rabbit antiserum raised against a synthetic peptide that contained 15 amino acids in the same sequence as the amino terminus of human fetal membrane PG showed significant reactivity with HSc CS-DS-PG. HSc CS-DS-PG had an apparent Mr of approximately 78,000 daltons, as determined by Sepharose CL-6B chromatography and SDS-PAGE. Alkaline borohydride treatment of CS-DS-PG liberated CS-DS glycosaminoglycan (GAG) chains having an Mr of 29,000 daltons. The conversion of xylose to xylitol indicated that the GAG chains are attached to the PG protein core at O-3 through a xylosyl-seryl linkage. CS-DS-PG also contained both N and O-linked oligosaccharides and did not aggregate with hyaluronic acid. These results, together with those reported previously, showed that HSc CS-DS-PG and DS-PG have the same A1-A15 amino acid sequence at the amino terminus but different protein cores. HSc CS-DS-PG was completely digested with chondroitinase AC and is, therefore, distinctly different from HSc DS-PG.

Structural analysis of purified human tracheobronchial mucins

Light scattering has been used to investigate the structure of human tracheobronchial mucin glycoproteins (HTBM) from the sputum of cystic fibrosis patients. The specimen was extracted using 6M guanidinium hydrochloride solution and fractionated by gel exclusion chromatography on Sephacryl S-1000. The fractionated HTBM was purified by density gradient ultracentrifugation. Purity of the resulting material was confirmed by SDS polyacrylamide gel electrophoresis and uv spectroscopy. Light scattering measurements on the fractionated mucins yield weight-average molecular weights Mw, and z-average radii of gyration Rg,z. The native cystic fibrosis HTBM consisted of a high molecular weight fraction with Mw = 9.3 X 10(6) daltons and a lower molecular weight fraction containing partly degraded mucins. After reduction and carboxymethylation of the high molecular weight native fraction, the resulting material was separated into three pools with Mw values of 5.1 X 10(6), 1.6 X 10(6), and 400,000. The derived molecular weights for the protein cores Mp,w, and the experimental radii of gyration are found to be consistent with the Mp,w -Rg relation established previously for submaxillary, cervical, and gastric mucins. These results imply that HTBM has the same extended-coil conformation reported for other mucins and has a molecular structure consisting of subunits, linked into linear chains via covalent (disulfide) bonds.

Scorbutic and fasted guinea pig sera contain an insulin-like growth factor I-reversible inhibitor of proteoglycan and collagen synthesis in chick embryo chondrocytes and adult human skin fibroblasts

Chick embryo chondrocytes cultured in sera from scorbutic and fasted guinea pigs exhibited decreases in collagen and proteoglycan production to about 30-50% of control values (I. Oyamada et al., 1988, Biochem. Biophys. Res. Commun. 152, 1490-1496). Here we show by pulse-chase labeling experiments that in the chondrocyte system, as in the cartilage of scorbutic and fasted guinea pigs, decreased incorporation of precursor into collagen was due to decreased synthesis rather than to increased degradation. There was a concomitant decrease in type II procollagen mRNA to about 32% of the control level. As in scorbutic cartilage, proteoglycan synthesis by chondrocytes in scorbutic serum was blocked at the stage of glycosaminoglycan chain initiation. Scorbutic and fasted guinea pig sera also caused a 50-60% decrease in the rates of collagen and proteoglycan synthesis in adult human skin fibroblasts, which synthesize mainly type I collagen. Decreased matrix synthesis in both cell types resulted from the presence of an inhibitor in scorbutic and fasted sera. Elevated cortisol levels in these sera were not responsible for inhibition, as determined by the addition of dexamethasone to chondrocytes cultured in normal serum. Insulin-like growth factor I (IGF-I, 300-350 ng/ml) reversed the inhibition of extracellular matrix synthesis by scorbutic and fasted guinea pig sera in both cell types and prevented the decrease in type II procollagen mRNA in chondrocytes. Therefore, in addition to its established role in proteoglycan metabolism, IGF-I also regulates the synthesis of several collagen types. An increase in the circulating inhibitor of IGF-I action thus could lead to the negative regulation of collagen and cartilage proteoglycan synthesis that occurs in ascorbate-deficient and fasted guinea pigs.

The effect of maturation and aging on the structure and content of link proteins in rabbit articular cartilage

We have examined extracts of articular cartilage from rabbits aged 3-100 weeks for evidence of age-related changes in the structure and content of link protein (LP) in this tissue, with the following findings: (a) Two major molecular weight forms of LP were seen on SDS-PAGE (41 and 48 kDa) and the proportion of these changed markedly with age. The 48 kDa species was predominant in young animals (representing about 78% of the total LP at 5 weeks) whereas the 41 kDa species increased in amount with age (representing 35% of the total LP at 100 weeks). A minor form of about 43 kDa, representing less than 20% of the total, was present only during the growth phase. A small amount of fragmented link protein (less than 5% of the total) of about 25-30 kDa was present in samples from mature and aged rabbits only. (b) The quantitation of LP in guanidinium: HCl extracts of cartilage, by radioimmunoassay with monoclonal antibody 8-A-4, was markedly influenced by the conditions of preparation and pretreatment of samples. Assays of dialyzed guanidine extracts following treatment at 80 degrees C for 15 min in 0.025% (w/v) SDS indicated that immature and mature cartilage contains about 50 and 180 micrograms of LP/g of tissue, respectively. On the other hand, assays following treatment at 100 degrees C for 20 min in 0.1% (w/v) SDS suggested that rabbit cartilage contains about 300 micrograms of LP/g of tissue at all ages; finally, assay of CsCl purified proteoglycan samples under these conditions indicated a content of about 500 micrograms of LP/g at all ages. (c) Calculations based on the analysis of proteoglycan preparations for aggregating monomer and link protein suggest that a LP:aggregating monomer molar ratio of about 0.9 is maintained in the articular cartilage throughout maturation and aging in the rabbit.

Aortic endothelial cells synthesize a large chondroitin sulphate proteoglycan capable of binding to hyaluronate

Confluent cultures of mouse aortic endothelial (END-D) were incubated with either [35S]methionine or 35SO4 2-, and the radiolabelled proteoglycans in media and cell layers were analysed for their hyaluronate-binding activity. The proteoglycan subfraction which bound to hyaluronate accounted for about 18% (media) and 10% (cell layers) of the total 35S radioactivity of each proteoglycan fraction. The bound proteoglycan molecules could be dissociated from the aggregates either by digestion with hyaluronate lyase or by treatment with hyaluronate decasaccharides. Digestion of [methionine-35S]proteoglycans with chondroitinase and/or heparitinase, followed by SDS/polyacrylamide-gel electrophoresis, indicated that the medium and cell layer contain at least three chondroitin sulphate proteoglycans, one dermatan sulphate proteoglycan, and two heparan sulphate proteoglycans which differ from one another in the size of core molecules. Among these, only the hydrodynamically large chondroitin sulphate species with an Mr 550,000 core molecule was shown to bind to hyaluronate. A very similar chondroitin sulphate proteoglycan capable of binding to hyaluronate was also found in cultures of calf pulmonary arterial endothelial cells (A.T.C.C. CCL 209). These observations, together with the known effects of hyaluronate on various cellular activities, suggest the existence of possible specialized functions of this proteoglycan subspecies in cellular processes characteristic of vascular development and diseases.

Heterogeneity in glycosylation of dermatan sulfate proteoglycan core proteins isolated from human aorta

Small proteoglycans were dissociatively extracted from normal human thoracic aorta with 4 M guanidine hydrochloride containing protease inhibitors, and purified by Sepharose CL-4B chromatography, dissociative cesium chloride density gradient centrifugation, and diethylaminoethyl cellulose chromatography. The intact proteoglycans migrated in the 270,000-340,000 range on 4-20% sodium dodecyl sulfate polyacrylamide gradient gels. Core proteins prepared following digestion of the intact proteoglycan monomer with chondroitinase ABC consisted of a major Coomassie blue-staining protein band of 50,000 along with a minor band of 44,000. Subsequent studies using endoglycosidases H, F, and N-glycanase demonstrated that mainly complex type N-linked glycans were present on the 50,000 cores while the 44,000 cores appeared to be devoid of N-linked glycans. Western blotting demonstrated that both of these cores were recognized by the monoclonal antibody 2-B-6, indicating the presence of the terminal 4-sulfated unsaturated disaccharide (delta Di-4S) remaining on the linkage region following chondroitinase ABC digestion. In contrast, a diffuse pattern of delta Di-4S epitopes ranging from 50,000 to approximately 60,000 was observed following chondroitinase AC II digestion of the dermatan sulfate proteoglycan, suggesting the presence of iduronate residues in close proximity to the glycosaminoglycan-linkage region. Conversely, the large chondroitin sulfate-proteoglycan core proteins from aorta (Mr 200,000-400,000) did not react with either monoclonal antibody 3-B-3 (recognizing the terminal delta DI-6S) or 2-B-6 following chondroitinase AC II digestion, although both delta DI-4S and delta DI-6S were present on these cores following chondroitinase ABC digestion. Additional studies using antisera against synthetic peptides derived from sequences of the core proteins of human bone small PG I and PG II indicated the presence of both gene products in PG isolated from human thoracic aorta. The Mr approximately 44,000 and 50,000 core proteins represent small PG I type cores while a closely spaced doublet (Mr 49,000 and 51,000) represented small PG II type cores. The results demonstrate that the core proteins of dermatan sulfate proteoglycan from human aorta are heterogeneous in primary structure and in the content of N-linked glycans.

Immunohistochemical localization of proteoglycans in interstitial elements of human pancreas and biliary system

The immunohistochemical localization of large proteoglycan and small proteoglycan was observed, using antibodies 2B1 and 6B6 (Sobue et al., 1988, 1989a), in fetal and adult pancreas and biliary system as well as in tumour tissues, obtained from 11 autopsies and 74 biopsies. The distribution of chondroitin 4- and 6-sulphate side chains, type I and IV collagen and elastin were also studied. In adult pancreas and all the biliary tracts examined, periductal fibrous tissues consisted mainly of dermatan sulphate small proteoglycan with networks of fibrous elements, which were composed of large proteoglycan, elastin, type I collagen and type IV collagen. In the interstitial components of cystadenoma of pancreas and biliary duct carcinoma, similar small proteoglycan-rich components were relatively abundant, although large proteoglycan was present in much larger amounts than that in non-neoplastic adult tissues. In some cholangiomas, the extra- and intracellular hyaline globules formed by the carcinoma cells were found to contain chondroitin sulphate large proteoglycan, laminin and fibronectin. The distribution of proteoglycans was observed to be different in the arterial walls of the interlobular tissues of the adult and the fetal pancreas. The biological significance of large and small proteoglycans in the interstitial connective tissues was discussed.

Characterization of glycoconjugates found in granular cell tumors, with special reference to keratan sulfate

Nine granular cell tumors (GCTs) were studied using the immunoperoxidase technique with a mouse monoclonal antibody to keratan sulfate and a polyclonal antibody to S-100 protein. Various lectins and basic dye stains were also employed. Schwannomas benign and a malignant, a neurofibroma, a leiomyoma, two examples of nevus pigmentosus and a congenital epulis were similarly examined to compare the histochemical reactivities. Tumor cells of all the GCTs reacted intensely with the antibodies to keratan sulfate and S-100 protein. Peripheral nerve bundles and other neurogenic tumors showed stained for S-100 protein but not for keratan sulfate. Basic dye stain indicated the presence of sulfated glycoconjugates in GCTs. Lectin stains demonstrated that GCTs were rich in glycoconjugates but the reactivity patterns for 14 lectins differed between GCTs and normal tissue components. None of the lectins used in this study was specific for GCTs. These results indicate that GCTs contain abundant glycoconjugates and that the monoclonal antibody to keratan sulfate may be an immunohistochemical marker for GCT.

Secondary structure of a core protein from pig skin proteodermatan sulfate: CD and Fourier transform IR spectroscopic studies in solution

The secondary structure of a 38 kDa core protein from pig skin proteodermatan sulfate (PDS), was investigated in solution using CD and Fourier transform (FT) ir spectroscopy. Both techniques generally have provided complementary data on the secondary structures of proteins. CD spectral analysis has shown that the core protein contains 60% beta-turn and alpha-helical structures, the rest being "unordered" structure. FT ir data do not permit calculation of quantitative contributions of substructures, at the present time, to the overall secondary structure of the core protein. CD spectrum of the intact PDS is similar to the core protein CD spectrum.

Bovine cartilage types VI and IX collagens. Characterization of their forms in vivo

1. Collagens were extracted from bovine cartilage by 4 M-guanidinium chloride in the presence of proteinase inhibitors and identified by immunoblotting with specific anti-collagen sera. 2. The collagens retained their native conformations (shown by the resistance of their triple-helical domains to pepsin digestion), and the molecular masses of their component alpha-chains indicated that the chains were intact. 3. Type VI collagen was extracted as a large-molecular-mass disulphide-bonded aggregate composed of components of molecular mass 140 kDa and 200-240 kDa, and was therefore similar to type VI collagen identified in noncartilaginous tissues. Immunoblotting established the 200-240 kDa components as intact forms of the alpha 3(VI) chain. 4. Type IX collagen consisted of three clearly separable components of molecular mass 84 kDa, 72 kDa and 66 kDa, which were assigned to the alpha 1(IX)-, alpha 3(IX)- and alpha 2(IX)-chains respectively, and a large proportion of this collagen had no covalently bound glycosaminoglycan attached to the alpha 2(IX)-chain. 5. Differences between the type IX collagen extracted from bovine cartilage and that identified in biosynthetic studies on chick cartilage are discussed.

Sulfated proteoglycans synthesized by Neuro 2a neuroblastoma cells: comparison between cells with and without ganglioside-induced neurites

Mouse neuroblastoma Neuro 2a cells are known to extend neurite-like processes in response to gangliosides added to the culture medium. We compared the structural features of proteoglycans (PG) synthesized by conventional Neuro 2a cells with those of neurite-bearing cells. Two different proteoglycans labeled with [35S]sulfate, namely, chondroitin sulfate proteoglycan (CS-PG) and heparan sulfate proteoglycan (HS-PG), were found both in the cell layer and in the culture medium of the conventional cells. CS-PG isolated from the cell layer had a Kav value of 0.38 on Sepharose CL-6B, and had CS side chains with Mr of 27,000. HS-PG in the cell layer was slightly larger (Kav of 0.33) in terms of hydrodynamic size than CS-PG, and the apparent Mr of the heparan sulfate side chains was 10,000. The structural parameters of CS-PG and HS-PG isolated from the medium were almost identical to those of the PGs in the cell layer. In addition to these PGs, single-chain HS, with an average Mr of 2,500, was observed only in the cell layer and this component was the major sulfated component in the cell layers of both control and ganglioside treated cells. The neurite-bearing cells also synthesized both CS-PG and HS-PG which were very similar in hydrodynamic size to those synthesized by the conventional cells, but the size of HS side chains was greater. Radioactivity, as 35S, of each sulfated component from the ganglioside-treated culture seemed to be slightly less than that of the corresponding component from the control culture. These findings indicate that the marked morphological change in Neuro 2a cells, induced by gangliosides is not accompanied by major changes in the synthesis of PGs.