Detection of glycosaminoglycans at the one-nanogram level by 125I-cytochrome c

Identification of a homologous heparin binding peptide sequence present in fibronectin and the 70 kDa family of heat-shock proteins

This study was undertaken to characterize the potential heparin affinity of an amino-acid sequence within the 70 kDa heat-shock family of proteins (HSPs) that shares homology with a heparin-binding sequence present in the carboxy-terminus of fibronectin (FN), defined by the synthetic peptide, FN-C/H-II (KNNQKSEPLIGRKKT). To first define the heparin binding sequence within FN-C/H-II, solid phase binding assays were performed using overlapping, short (7 amino acids) synthetic peptides corresponding to the amino-acid sequence within FN-C/H-II. Only the sequence LIGRKKT bound [3H] heparin, and the LIGRKKT peptide blocked heparin binding to intact fibronectin by 47% (+/- 0.4, p < 0.001). A computer-generated homology search revealed that two members of the 70 kDa HSP family, HSP70 and HSC70, contain the sequences LIGRK and LIGRR, respectively. Examination of heparin binding using affinity chromatography indicated that while native HSC70 binds heparin, native HSP70 does not. Treatment of the heparin-unbound fraction with heat or urea led to enhanced HSP70 binding to heparin affinity columns. Soluble LIGRKKT peptide or anti-FN-C/H-II IgG also significantly inhibited heparin binding to HSC70 that had been purified by heparin affinity chromatography. Finally, Western blot analysis of HSC70 purified by heparin affinity chromatography demonstrated that polyclonal anti-FN-C/H-II IgG could recognize HSC70. These data demonstrate that LIGRK or LIGRR represent a a common heparin binding motif in fibronectin, HSP70, and HSC70, and are consistent with a proposed role for heparin or similar polyanionic structures in the function of the 70 kDa heat-shock proteins.

Glycosaminoglycans and chondroitin/dermatan sulfate proteoglycans in the myocardium of a non-human primate

Lyophilized mid-wall left ventricular myocardial tissues of the long-tailed non-human primate, Macaca fascicularis, were examined for the presence of glycosaminoglycans and chondroitin/dermatan sulfate proteoglycans. Mean uronic acid concentration in all samples was 0.97 +/- 0.27 micrograms per mg dry weight myocardium. The distribution of the glycosaminoglycans in the myocardium, determined by cellulose acetate strip electrophoresis was 62 +/- 4% heparan sulfate, 20 +/- 6% hyaluronan, and 16 +/- 5% chondroitin/dermatan sulfate. The analysis of chondroitin/dermatan sulfate proteoglycans, done directly on the extracts of lyophilized myocardium using agarose-acrylamide gel electrophoresis and Western blotting with monoclonal antibodies to various carbohydrate epitopes and with polyclonal antibodies to the protein core, showed the presence of biglycan and decorin. That these two and no other chondroitin/dermatan sulfates were present was established by core protein analysis using SDS PAGE and Western blotting. Quantification of chondroitin/dermatan sulfate proteoglycans uncovered high individual specific variability of the chondroitin/dermatan sulfate epitopes, but only moderate variability of biglycan and decorin core proteins. The variability of the chondroitin/dermatan sulfate epitopes is most likely related to individual specific differences in chain number, iduronate content and sulfation patterns of biglycan and decorin.

Characterization of biotin-labeled proteoglycans by electrophoretic separation on minigels and blotting onto nylon membranes prior and after enzymatic digestion

Biotinylated proteoglycans were separated by sodium dodecyl sulfate electrophoresis prior and after enzymatic digestion by glycan-specific enzymes using polyacrylamide minigels. The biotin-labeled compounds were blotted onto nylon membranes either by electrophoresis or by diffusion and detected by avidin-enzyme conjugates. The method allows the nonisotopic detection of native proteoglycans and core proteins. Proteoglycans can be visualized at protein amounts as low as 0.7 ng per lane. In comparison with sensitive protein stains, compounds of enzyme preparations do not interfere with bands corresponding to core proteins. Electrophoresis, blotting, and staining of up to 12 samples per gel are accomplished in less than 3 h.

Neoplastic modulation of extracellular matrix: stimulation of chondroitin sulfate proteoglycan and hyaluronic acid synthesis in co-cultures of human colon carcinoma and smooth muscle cells

Previous studies have shown that human colon carcinomas contain elevated amounts of chondroitin sulfate proteoglycan (CS-PG) and hyaluronic acid, and that the major site of synthesis of these products is the host mesenchyme surrounding the tumor. These findings have led to the proposal that the abnormal formation of the tumor stroma is modulated by the neoplastic cells. The experiments of this paper were designed to explore further this complex phenomenon in an in vitro system using co-cultures of phenotypically stable human colon smooth muscle (SMC) and carcinoma cells (WiDr). The results showed a 3-5-fold stimulation of CS-PG and hyaluronic acid biosynthesis in the co-cultures as compared to the values predicted from the individual cell type cultured separately. The increase in CS-PG was not due to changes in specific activity of the precursor pool, but was rather due to a net increase in synthesis, inasmuch as it was associated with neither a stimulation of cell proliferation nor with an inhibition of intracellular breakdown. These biochemical changes were corroborated by ultrastructural studies which showed a marked deposition of proteoglycan granules in the co-cultures. Several lines of evidence indicated that the SMC were responsible for the overproduction of CS-PG: i) SMC synthesized primarily CS-PG when cultured alone, in contrast to the WiDr, which synthesized exclusively heparan sulfate proteoglycan; ii) only the SMC in co-culture stained with an antibody raised against the amino terminal peptide of a CS-PG (PG-40), structurally and immunologically related to that synthesized by the SMC; iii) the stimulation of CS-PG in SMC could be reproduced, though to a lesser extent, using medium conditioned by WiDr, whereas medium conditioned by SMC had no effects on WiDr. In conclusion this study has reproduced in vitro a tumor-associated matrix with a proteoglycan composition similar to that observed in vivo and provides further support to the concept that production of a proteoglycan-rich extracellular environment is regulated by specific tumor-host cell interactions.

Detection and quantitation of proteoglycans extracted from cell culture medium and cultured cartilage slices

Detection and quantitation of extracted proteoglycans, by staining with the dye Alcian blue on cellulose acetate followed by dissolution of the stained cellulose acetate strips in dimethyl sulfoxide containing 0.5% (v/v) sulfuric acid for absorbance measurement, is described. It is shown that, in the present system, the dye uptake by the proteoglycan is dependent only on the glycosaminoglycan content of the proteoglycan. The method is applied to the quantitation and characterization of proteoglycans and glycosaminoglycans, which have been extracted from radiolabeled bovine ankle cartilage and from mononuclear cell supernatant and which have been separated by DEAE-Sephacel column chromatography. The high sensitivity of the method allows detection of proteoglycans in 25-microliters samples of solutions containing as little as 1 microgram of glycosaminoglycan per milliliter of solution.

Regulation of human lung fibroblast glycosaminoglycan production by recombinant interferons, tumor necrosis factor, and lymphotoxin

Mononuclear cells may be important regulators of fibroblast glycosaminoglycan (GAG) biosynthesis. However, the soluble factors mediating these effects, the importance of intercytokine interactions in this regulation and the mechanisms of these alterations remain poorly understood. We analyzed the effect of recombinant (r) tumor necrosis factor (TNF), lymphotoxin (LT), and gamma, alpha, and beta 1 interferons (INF-gamma, -alpha and -beta 1), alone and in combination, on GAG production by normal human lung fibroblasts. rTNF, rLT, and rINF-gamma each stimulated fibroblast GAG production. In addition, rIFN-gamma synergized with rTNF and rLT to further augment GAG biosynthesis. In contrast, IFN-alpha A, -alpha D, and -beta 1 neither stimulated fibroblast GAG production nor interacted with rTNF or rLT to regulate GAG biosynthesis. The effects of the stimulatory cytokines and cytokine combinations were dose dependent and were abrogated by the respective monoclonal antibodies. In addition, these cytokines did not cause an alteration in the distribution of GAG between the fibroblast cell layer and supernatant. However, the stimulation was at least partially specific for particular GAG moieties with hyaluronic acid biosynthesis being markedly augmented without a comparable increase in the production of sulfated GAGs. Fibroblast prostaglandin production did not mediate these alterations since indomethacin did not decrease the stimulatory effects of the cytokines. In contrast, protein and mRNA synthesis appeared to play a role since the stimulatory effects of the cytokines were abrogated by cyclohexamide and actinomycin D, respectively. In addition, the cytokines and cytokine combinations increased cellular hyaluronate synthetase activity in proportion to their effects on hyaluronic acid suggesting that induction of this enzyme(s) is important in this stimulatory process. These studies demonstrate that IFN-gamma, TNF, and LT are important stimulators of fibroblast GAG biosynthesis, that interactions between these cytokines may be important in this regulatory process, that these cytokines predominantly stimulate hyaluronic acid production and that this effect may be mediated by stimulation of fibroblast hyaluronate synthetase activity.

Detection by 125I-cationized cytochrome c of proteoglycans and glycosaminoglycans immobilized on unmodified and on positively charged nylon 66

We have examined the detection by a 125I-labeled basic protein, cationized cytochrome c, of selected proteoglycans (PGs) and standard preparations of glycosaminoglycans (GAGs) immobilized on Nylon 66 and also on positively charged Nylon 66. Immobilization on Nylon 66 appears to allow a relative freedom of interaction between PGs or GAGs and 125I-cationized cytochrome c, but a more restricted reaction was observed when PGs and GAGs were immobilized to positively charged Nylon 66. On this support PGs with large numbers of GAG side chains reacted well with 125I-cationized cytochrome c, but GAGs were minimally reactive. By taking advantage of some of the properties of large-pore agarose-acrylamide gels, rapid partial characterization of some PGs can be accomplished in the 10-ng range, and therefore at a sensitivity equal to PGs with internal biosynthetic labels.

Extracellular mammalian polysaccharides: glycosaminoglycans and proteoglycans

This review of the mammalian extracellular matrix polysaccharides covered the glycosaminoglycans (GAGs) and their association into proteoglycans. As they necessarily pertain to the chromatographic and electrophoretic separations of these molecules, the structural features of the five principal GAGs were briefly reviewed. Much of the current structural work as well as the separation technology has been concerned with the sulfation state and copolymeric sequences of the individual classes of GAGs. The separation methods discussed included electrophoresis by agarose, acrylamide and cellulose acetate, high-performance liquid chromatography (HPLC), ion-exchange, gel permeation and biospecific affinity methods. Since detection systems are an integral part of chemical separation technology, current thoughts about the best methods to assay GAGs or detect column fractions were discussed. These included polysaccharide-specific detection systems such as Alcian blue dye, 1,9-dimethylmethylene blue, bovine serum albumin-Coomassie blue, as well as non-specific carbohydrate detection systems such as the carbazole or indole hydrochloride methods. Instrumentation used in the detection of chromatography fractions for these molecules was discussed, since the usual ultraviolet detector, standard with HPLC equipment, is often unsatisfactory. The most sensitive specific detection method for GAGs is the use of monoclonal antibodies, which are only now becoming commercially available. The use of these antibodies, combined with HPLC separation, appears to be the best available biochemical technology for studying the extracellular matrix polysaccharides. Finally, the association between proteoglycans, GAGs and mammalian disease processes was reviewed, emphasizing mucopolysaccharidoses and arthritis. The early detection of both of these diseases is desired for effective counselling and treatment. Many of the methods discussed here have been applied, but others are yet to be tried in efforts to further that goal.