Hepatocyte growth factor/scatter factor binds with high affinity to dermatan sulfate

Binding of tenascin-X to decorin

Tenascin-X (TN-X) is an extracellular matrix protein whose absence results in an alteration of the mechanical properties of connective tissue. To understand the mechanisms of integration of TN-X in the extracellular matrix, overlay blot assays were performed on skin extracts. A 100 kDa molecule interacting with TN-X was identified by this method and this interaction was abolished when the extract was digested by chondroitinase. By solid-phase assays, we showed that dermatan sulfate chains of decorin bind to the heparin-binding site included within the fibronectin-type III domains 10 and 11 of TN-X. We thus postulate that the association of TN-X with collagen fibrils is mediated by decorin and contributes to the integrity of the extracellular network.

Epidermal transformation leads to increased perlecan synthesis with heparin-binding-growth-factor affinity

Perlecan, a proteoglycan of basement membrane and extracellular matrices, has important roles in both normal biological and pathological processes. As a result of its ability to store and protect growth factors, perlecan may have crucial roles in tumour-cell growth and invasion. Since the biological functions of different types of glycosaminoglycan vary with cellular origin and structural modifications, we analysed the expression and biological functions of perlecan produced by a normal epidermal cell line (JB6) and its transformed counterpart (RT101). Expression of perlecan in tumorigenic cells was significantly increased in both mRNA and protein levels. JB6 perlecan was exclusively substituted with heparan sulphate, whereas that of RT101 contained some additional chondroitin sulphate. Detailed structural analysis of the heparan sulphate (HS) chains from perlecan of both cell types revealed that their overall sulphation and chain length were similar (approximately 60 kDa), but the HS chains of tumour-cell-derived perlecan were less sulphated. This resulted from reduced 2-O- and 6-O-sulphation, but not N-sulphation, and an increase in the proportion of unsulphated disaccharides. Despite this, the heparan sulphate of RT101- and JB6-derived perlecan bound fibroblast growth factor-1, -2, -4 and -7 and heparin-binding epidermal growth factor with similar affinity. Therefore abundant tumour-derived perlecan may support the angiogenic responses seen in vivo and be a key player in tumorigenesis.

Anti-tumor activities of chondroitinase AC and chondroitinase B: inhibition of angiogenesis, proliferation and invasion

In the current study, two specific glycosaminoglycan lyases, chondroitinase AC and chondroitinase B, were utilized to examine the roles of chondroitin sulfates and dermatan sulfate in tumor metastasis and angiogenesis. Melanoma cells (SK-MEL) or endothelial cells were treated with either medium or chondroitinase enzyme. Chondroitinase AC inhibited melanoma invasion and proliferation as well as endothelial proliferation and angiogenesis. Apoptosis of melanoma and endothelial cells, as measured by the activity of caspase-3, was also increased by chondroitinase AC, but not by chondroitinase B. Chondroitinase B inhibited endothelial and melanoma proliferation and invasion, but to a lesser extent than chondroitinase AC. Neither chondroitinase had a detectable effect on gelatinase secretion by melanoma cells. These results indicate that both chondroitin and dermatan sulfates regulate many cellular activities related to metastasis.

Amyloid-beta interactions with chondroitin sulfate-derived monosaccharides and disaccharides. implications for drug development

In Alzheimer's disease, the major pathological features are diffuse and senile plaques that are primarily composed of the amyloid-beta (A beta) peptide. It has been proposed that proteoglycans and glycosaminoglycans (GAG) facilitate amyloid fibril formation and/or stabilize the plaque aggregates. To develop effective therapeutics based on A beta-GAG interactions, understanding the A beta binding motif on the GAG chain is imperative. Using electron microscopy, fluorescence spectroscopy, and competitive inhibition ELISAs, we have evaluated the ability of chondroitin sulfate-derived monosaccharides and disaccharides to induce the structural changes in A beta that are associated with GAG interactions. Our results demonstrate that the disaccharides GalNAc-4-sulfate(4S), Delta UA-GalNAc-6-sulfate(6S), and Delta UA-GalNAc-4,6-sulfate(4S,6S), the iduronic acid-2-sulfate analogues, and the monosaccharides d-GalNAc-4S, d-GalNAc-6S, and d-GalNAc-4S,6S, but not d-GalNAc, d-GlcNAc, or Delta UA-GalNAc, induce the fibrillar features of A beta-GAG interactions. The binding affinities of all chondroitin sulfate-derived saccharides mimic those of the intact GAG chains. The sulfated monosaccharides and disaccharides compete with the intact chondroitin sulfate and heparin GAGs for A beta binding, as illustrated by competitive inhibition ELISAs. Therefore, the development of therapeutics based on the model of A beta-chondroitin sulfate binding may lead to effective inhibitors of the GAG-induced amyloid formation that is observed in vitro.

Dermatan sulphate is released by proteinases of common pathogenic bacteria and inactivates antibacterial alpha-defensin

Defensins represent an evolutionarily conserved group of small peptides with potent antibacterial activities. We report here that extracellular proteinases secreted by the human pathogens Pseudomonas aeruginosa, Enterococcus faecalis and Streptococcus pyogenes release dermatan sulphate by degrading dermatan sulphate-containing proteoglycans, such as decorin. Dermatan sulphate was found to bind to neutrophil-derived alpha-defensin, and this binding completely neutralized its bactericidal activity. During infection, proteoglycan degradation and release of dermatan sulphate may therefore represent a previously unknown virulence mechanism, which could serve as a target for novel antibacterial strategies.

Preparation and structural determination of dermatan sulfate-derived oligosaccharides

Eight oligosaccharides were prepared from dermatan sulfate (DS) and their structures were elucidated. Porcine intestinal mucosal DS was subjected to controlled depolymerization using chondroitin ABC lyase (chondroitinase ABC). The oligosaccharide mixture formed was fractionated by low-pressure gel permeation chromatography (GPC). Size uniform mixtures of disaccharides, tetrasaccharides, hexasaccharides, octasaccharides, decasaccharides, and dodecasaccharides were obtained. Each size-fractionated mixture was then purified on the basis of charge by repetitive semi-preparative strong-anion-exchange (SAX) high-performance liquid chromatography (HPLC). This approach has led to the isolation of six homogeneous oligosaccharides. The size of the oligosaccharides were determined using GPC-HPLC. Treatment of tetrasaccharide and hexasaccharide fragments with Hg(OAc)2 afforded trisaccharide and pentasaccharide products, respectively. The purity of the oligosaccharides obtained was confirmed by analytical SAX-HPLC, and capillary electrophoresis (CE). The molecular mass and degree of sulfation of the eight purified oligosaccharides were elucidated using electrospray ionization (ESI) mass spectrometry and their structures were established with high field nuclear magnetic resonance (NMR) spectroscopy. These DS-oligosaccharides are currently being used to study for interaction of the DS with biologically important proteins.

Heparin and heparan sulfate bind interleukin-10 and modulate its activity

Glycosaminoglycans (GAG) are a group of negatively charged molecules that have been shown to bind and directly regulate the bioactivity of growth factors and cytokines such as basic fibroblast growth factor, transforming growth factor-β, IL-7, and interferon-γ. The ability of GAG to interact with human IL-10 (hIL-10) and the effect of these interactions on its biologic activity were analyzed. It was demonstrated by affinity chromatography that hIL-10 binds strongly to heparin–agarose at physiological pH. Biosensor-based binding kinetic analysis indicated an equilibrium dissociation constant, Kd, of 54 nmol/L for this interaction. Human IL-10 stimulated CD16 and CD64 expression on the monocyte/macrophage population within peripheral blood mononuclear cells, with optimal concentrations between 1 and 10 ng/mL. Soluble heparin, heparan sulfate, chondroitin sulfate, and dermatan sulfate were shown to inhibit the hIL-10–induced expression of CD16 and CD64 in a concentration-dependent manner. Heparin and heparan sulfate were most effective with IC50 values of 100 to 500 μg/mL. Considerably higher concentrations of dermatan sulfate and chondroitin 4-sulfate were required with an IC50 of 2000 to 5000 μg/mL, whereas chondroitin 6-sulfate was essentially inactive. The antagonistic effect of heparin on hIL-10 activity was shown to be dependent on N-sulfation, inasmuch as de-N-sulfated heparin had little or no inhibitory effect on the IL-10– induced expression of CD16, whereas the effect of de-O-sulfated heparin was comparable to that of unmodified heparin. Furthermore, the inhibition of cell-bound proteoglycan sulfation reduced the hIL-10–mediated expression of CD16 molecules on monocytes/macrophages. Taken together, these findings support the hypothesis that soluble and cell-surface GAG and, in particular, their sulfate groups are important in binding and modulation of hIL-10 activity.

Heparin and heparan sulfate bind interleukin-10 and modulate its activity

Glycosaminoglycans (GAG) are a group of negatively charged molecules that have been shown to bind and directly regulate the bioactivity of growth factors and cytokines such as basic fibroblast growth factor, transforming growth factor-β, IL-7, and interferon-γ. The ability of GAG to interact with human IL-10 (hIL-10) and the effect of these interactions on its biologic activity were analyzed. It was demonstrated by affinity chromatography that hIL-10 binds strongly to heparin–agarose at physiological pH. Biosensor-based binding kinetic analysis indicated an equilibrium dissociation constant, Kd, of 54 nmol/L for this interaction. Human IL-10 stimulated CD16 and CD64 expression on the monocyte/macrophage population within peripheral blood mononuclear cells, with optimal concentrations between 1 and 10 ng/mL. Soluble heparin, heparan sulfate, chondroitin sulfate, and dermatan sulfate were shown to inhibit the hIL-10–induced expression of CD16 and CD64 in a concentration-dependent manner. Heparin and heparan sulfate were most effective with IC50 values of 100 to 500 μg/mL. Considerably higher concentrations of dermatan sulfate and chondroitin 4-sulfate were required with an IC50 of 2000 to 5000 μg/mL, whereas chondroitin 6-sulfate was essentially inactive. The antagonistic effect of heparin on hIL-10 activity was shown to be dependent on N-sulfation, inasmuch as de-N-sulfated heparin had little or no inhibitory effect on the IL-10– induced expression of CD16, whereas the effect of de-O-sulfated heparin was comparable to that of unmodified heparin. Furthermore, the inhibition of cell-bound proteoglycan sulfation reduced the hIL-10–mediated expression of CD16 molecules on monocytes/macrophages. Taken together, these findings support the hypothesis that soluble and cell-surface GAG and, in particular, their sulfate groups are important in binding and modulation of hIL-10 activity.

Inhibition of human dermal fibroblast proliferation by removal of dermatan sulfate

In the current study, a glycosaminoglycan lyase, chondroitinase B, was used to study the role of dermatan sulfate proteoglycans on human dermal fibroblast proliferation. Pretreatment with chondroitinase B significantly decreased fibroblast proliferative responses to serum (20% to 55%). In contrast, heparinase III and chondroitinase AC were less effective in inhibiting fibroblast proliferation to serum. Analysis of glycosaminoglycans on chondroitinase B-treated fibroblasts confirmed that dermatan sulfate was removed from fibroblasts by this enzyme. Chondroitinase B treatment also decreased proliferation to basic fibroblast growth factor (bFGF) by 20% and reduced receptor binding by 25%. Heparinase III inhibited bFGF binding by 73%, but decreased proliferation to bFGF by only 21%. Chondroitinase AC had no effect on bFGF proliferation or binding. These data suggest that dermatan sulfate proteoglycans play a significant role in the control of human dermal fibroblast proliferation.

Stimulation of DNA synthesis and cell proliferation of human mammary myoepithelial-like cells by hepatocyte growth factor/scatter factor depends on heparan sulfate proteoglycans and sustained phosphorylation of mitogen-activated protein kinases p42/44

Hepatocyte growth factor/scatter factor (HGF/SF) is a heparan/dermatan sulfate-binding growth factor produced by stromal cells that acts as a paracrine effector on neighboring epithelia. HGF/SF stimulated DNA synthesis in human mammary (Huma) 109 myoepithelial-like cells grown on collagen I and fibronectin substrata but not when grown on plastic. Dual phosphorylation of mitogen-activated protein kinases (p42/44(MAPK)) was required for this stimulation of DNA synthesis. In Huma 109 cells cultured on plastic, HGF/SF stimulated a transient phosphorylation of p42/44(MAPK), which reached a maximum at 10 min after addition of the growth factor and returned to near basal levels after 20 min. In contrast, the phosphorylation of p42/44(MAPK) stimulated by HGF/SF in cells cultured on collagen I or fibronectin was sustained over 45 min. In Huma 109 cells deficient in sulfated glycosaminoglycans, HGF/SF failed to stimulate p42/44(MAPK) phosphorylation or DNA synthesis on any substratum, even when soluble heparan sulfate proteoglycans purified from the cells or from the culture medium were added. However, HGF/SF stimulated DNA synthesis and a sustained phosphorylation of p42/44(MAPK) in sulfated glycosaminoglycan-deficient Huma 109 cells plated on a substratum of medium HSPGs but not cell HSPGs. The HGF/SF-induced proliferation is thus highly dependent on heparan sulfate proteoglycans in myoepithelial-like cells.

Diversity and functions of glycosaminoglycan sulfotransferases

Sulfate residues attached to the specific position of the component sugar residues of glycosaminoglycans play important roles in the formation of functional domain structures. The introduction of a sulfate group is catalyzed by various sulfotransferases with strict substrate specificities. A rapid development achieved in the cloning of various glycosaminoglycan sulfotransferases has allowed us to study the biological functions of glycosaminoglycan sulfotransferases and their products, sulfated glycosaminoglycans.

Impaired elastogenesis in Hurler disease: dermatan sulfate accumulation linked to deficiency in elastin-binding protein and elastic fiber assembly

Hurler disease resulting from a deficiency in alpha-L-iduronidase, which causes an accumulation of dermatan sulfate and heparan sulfate glycosaminoglycans, is characterized by connective tissue and skeletal deformations, cardiomyopathy, cardiac valve defects, and progressive coronary artery stenosis. In this report, we present evidence that accumulation of dermatan sulfate but not heparan sulfate moieties is linked to impaired elastic fiber assembly that, in turn, contributes substantially to the development of the clinical phenotype in Hurler disease. Our data suggest that dermatan sulfate-bearing moieties bind to and cause functional inactivation of the 67-kd elastin-binding protein, a molecular chaperone for tropoelastin, which normally facilitates its secretion and assembly into elastic fibers. We demonstrate that, in contrast to normal skin fibroblasts and cells from Sanfilippo disease, which accumulate heparan sulfate, Hurler fibroblasts show reduced expression of elastin-binding protein and do not assemble elastic fibers, despite an adequate synthesis of tropoelastin and sufficient production of a microfibrillar scaffold of elastic fibers. Because cultured Hurler fibroblasts proliferate more quickly than their normal counterparts and the addition of exogenous insoluble elastin reduces their proliferation, we suggest that cell contacts with insoluble elastin play an important role in controlling their proliferation.

Elucidation of the structural features of heparan sulfate important for interaction with the Hep-2 domain of fibronectin

The interaction of fibronectin with cell surface heparan sulfate proteoglycans is important biologically in inducing reorganization of the cytoskeleton and the assembly of focal adhesions. The major heparan sulfate-binding site in fibronectin, which is also implicated in these morphological events, is the COOH-terminal Hep-2 domain. We describe the first extensive study of the structural determinants required for the interaction between heparan sulfate/heparin and Hep-2. It is clear that, in heparan sulfate, there is a very prominent role for N-sulfate groups, as opposed to a relatively small apparent contribution from carboxyl groups. Furthermore, a minimal octasaccharide binding sequence appeared to contain at least two 2-O-sulfated iduronate residues, but no 6-O-sulfate groups. However, affinity was enhanced by the presence of 6-O-sulfates, and the interaction with Hep-2 also increased progressively with oligosaccharide size up to a maximum length of a tetradecasaccharide. This overall specificity is compatible with recent information on the structure of Hep-2 (Sharma, A., Askari, J. A., Humphries, M. J., Jones, E. Y., and Stuart, D. I. (1999) EMBO J. 18, 1468-1479) in which two separate, positively charged clusters, involving up to 11 basic amino acid residues (mostly arginines with their preferential ability to co-ordinate sulfate groups), could form a single extended binding site.

Presentation of IFN-gamma to nitric oxide-producing cells: a novel function for mast cells

We report that mast cells can bind and present IFN-gamma in a functionally active form to macrophages. Flow-cytometric analysis revealed that biotinylated IFN-gamma bound equally well to purified peritoneal mast cells from both IFN-gammaR knockout and wild-type mice, indicating a non-IFN-gammaR binding site. Purified peritoneal mast cells, loaded with IFN-gamma for 30 min and washed, were able to induce NO synthesis by peritoneal macrophages. This response required cell contact and expression of IFN-gammaR on the responding macrophages, but not the mast cells. Human HMC-1 mast cells were also able to present IFN-gamma to mouse macrophages. Enzyme treatment of mouse mast cells revealed that binding of IFN-gamma was predominantly to chondroitin sulfate B (dermatan sulfate). Binding of IFN-gamma to dermatan sulfate was confirmed by inhibition ELISA. This study demonstrates for the first time that mast cells can present IFN-gamma to other cells via glycosaminoglycans. Mast cells may act as a reservoir of surface-stored functionally active cytokines.

Survey of the 1998 optical biosensor literature

The utilization of optical biosensors to study molecular interactions continues to expand. In 1998, 384 articles relating to the use of commercial biosensors were published in 130 different journals. While significant strides in new applications and methodology were made, a majority of the biosensor literature is of rather poor quality. Basic information about experimental conditions is often not presented and many publications fail to display the experimental data, bringing into question the credibility of the results. This review provides suggestions on how to collect, analyze and report biosensor data.

A monoclonal antibody which recognizes a glycosaminoglycan epitope in both dermatan sulfate and chondroitin sulfate proteoglycans of human skin

Studies have been initiated to identify various cell surface and matrix components of normal human skin through the production and characterization of murine monoclonal antibodies. One such antibody, termed PG-4, identifies both cell surface and matrix antigens in extracts of human foetal and adult skin as the dermatan sulfate proteoglycans, decorin and biglycan, and the chondroitin sulfate proteoglycan versican. Treatment of proteoglycans with chondroitinases completely abolishes immunoreactivity for all of these antigens which suggests that the epitope resides within their glycosaminoglycan chains. Further evidence for the carbohydrate nature of the epitope derives from competition studies where protein-free chondroitin sulfate chains from shark cartilage react strongly; however, chondroitin sulfate chains from bovine tracheal cartilage fail to exhibit a significant reactivity, an indication that the epitope, although present in some chondroitin sulfate chains, does not consist of random chondroitin 4- or 6-sulfate disaccharides. The presence of the epitope on dermatan sulfate chains and on decorin was also demonstrated using competition assays. Thus, PG-4 belongs to a class of antibodies that recognize native epitopes located within glycosaminoglycan chains. It differs from previously described antibodies in this class in that it identifies both chondroitin sulfate and dermatan sulfate proteoglycans. These characteristics make PG-4 a useful monoclonal antibody probe to identify the total population of proteoglycans in human skin.

Differential regulation of hepatocyte growth factor/scatter factor by cell surface proteoglycans and free glycosaminoglycan chains

Hepatocyte growth factor interacts with both heparan and dermatan sulphates, in addition to its specific signalling receptor, Met. However, the extent of glycosaminoglycan involvement in its biological activity remains uncertain. We have investigated the effects of exogenous glycosaminoglycan addition upon hepatocyte growth factor-stimulated motility of Madin-Darby canine kidney cells. Exogenous heparan/dermatan sulphate chains behave similarly as either potentiators or inhibitors of cell motility (depending upon the assay). Specific heparan sulphate oligosaccharides, of octasaccharide or larger, elicit similar effects, though with reduced potency. Additionally we have investigated the motility of cells made completely deficient in functional proteoglycans by metabolic inhibition of glycosaminoglycan sulphation, using chlorate. Such cells are completely unresponsive to hepatocyte growth factor, both in terms of downstream phosphorylation of mitogen-activated protein kinase and actual cell motility, though they do remain responsive to phorbol ester. Interestingly, although cell responsiveness to hepatocyte growth factor is not restored by exogenous heparan/dermatan sulphate chains, it is by an immobilised heparan sulphate proteoglycan substratum. These findings suggest that hepatocyte growth factor activity is not only critically dependent upon the presence of glycosaminoglycan, but specifically requires an intact proteoglycan structure located in close apposition to cell surface Met.

Demonstration of a novel sulfotransferase in fetal bovine serum, which transfers sulfate to the C6 position of the GalNAc residue in the sequence iduronic acid alpha1-3GalNAc beta1-4iduronic acid in dermatan sulfate

A novel sulfotransferase activity was discovered in fetal bovine serum using pig skin dermatan sulfate as an acceptor and [35S]3'-phosphoadenosine 5'-phosphosulfate as a sulfate donor. The enzyme was separated from chondroitin:GalNAc 6-O-sulfotransferase by chromatographic techniques. Enzymatic analysis of the reaction products demonstrated that the enzyme transferred sulfate to the C6 position of the GalNAc residue in the sequence -iduronic acid alpha1-3GalNAc beta1-4iduronic acid-. Thus, the enzyme has been identified as a hitherto unreported dermatan sulfate:GalNAc 6-O-sulfotransferase. The finding is in sharp contrast to the current concept that in dermatan sulfate biosynthesis GalNAc 4-O-sulfation is a prerequisite for iduronic acid formation by C5 epimerase.

Structural determination of novel tetra- and hexasaccharide sequences isolated from chondroitin sulfate H (oversulfated dermatan sulfate) of hagfish notochord

Oversulfated chondroitin sulfate H (CS-H) isolated from hagfish notochord is a unique dermatan sulfate consisting mainly of IdoAalpha1-3GalNAc(4S,6S), where IdoA, GalNAc, 4S and 6S represent L-iduronic acid, Nacetyl-D-galactosamine, 4-O-sulfate and 6-O-sulfate, respectively. Several tetra- and hexasccharide fractions were isolated from CS-H after partial digestion with bacterial chondroitinase B to investigate the sequential arrangement of the IdoAalpha1-3GalNAc(4S,6S) unit in the CS-H polysaccharide. A structural analysis of the isolated oligosaccharides by enzymatic digestions, mass spectrometry and 1H NMR spectroscopy demonstrated that the major tetrasaccharides shared the common disulfated core structure delta4,5HexAalpha1-3GalNAc(4S)beta1-4IdoAalpha1-3 GalNAc (4S) with 0 approximately 3 additional O-sulfate groups, where delta4,5HexA represents 4-deoxy-alpha-L-threo-hex-4-enepyranosyluronic acid. The major hexasaccharides shared the common trisulfated core structure delta4,5HexAalpha1-3 GalNAc(4S)beta1-4 IdoAalpha1-3 GalNAc(4S)beta1-4IdoAalpha1-3 GalNAc(4S) with 1 approximately 4 additional O-sulfate groups. Some extra sulfate groups in both tetra- and hexasaccharides were located at the C-2 position of a delta4,5HexA or an internal IdoA residue, or C-6 position of 4-O-sulfated GalNAc residues, forming the unique disulfated or trisulfated disaccharide units, IdoA (2S)-GalNAc(4S), IdoA-GalNAc(4S,6S) and IdoA (2S)-GalNAc(4S,6S), where 2S represents 2-O-sulfate. Of the demonstrated sequences, five tetra- and four hexasaccharide sequences containing these units were novel.

Dermatan sulfate activates nuclear factor-kappab and induces endothelial and circulating intercellular adhesion molecule-1

Proteoglycans (PGs) can influence cell behaviors through binding events mediated by their glycosaminoglycan (GAG) chains. This report demonstrates that chondroitin sulfate B, also known as dermatan sulfate (DS), a major GAG released during the inflammatory phase of wound repair, directly activates cells at the physiologic concentrations of DS found in wounds. Cultured human dermal microvascular endothelial cells exposed to DS responded with rapid nuclear translocation of nuclear factor-kappaB (NF-kappaB), increased expression of intercellular adhesion molecule-1 (ICAM-1) mRNA, and increased ICAM-1 cell surface protein. Heparan sulfate and chondroitin sulfates A and C had no effect on activation of NF-kappaB or induction of ICAM-1. Inhibition of NF-kappaB activation blocked the effect of DS. The increase in cell surface ICAM-1 did not involve TNF-alpha or IL-1 release by endothelial cells, but it was facilitated by autocrine factors whose release was initiated by DS. The ICAM-1-inductive activity of DS was confirmed in vivo. Injection of DS, but not heparin or other chondroitin sulfates, into mice greatly increased circulating levels of soluble ICAM. These data provide evidence that DS, but not other GAGs, initiates a previously unrecognized cell signaling event that can act during the response to injury.

Dynamic expression of proteoglycans during chicken skeletal muscle development and maturation

Skeletal muscle development is a complex process in which cell migration and adhesion play important roles. Because these cellular activities involve cell surface and extracellular matrix molecules, proteoglycan analysis was performed for developing chick skeletal muscle. Proteoglycans are macromolecular conjugates of protein and carbohydrate found in the extracellular matrix and at the cell surface. In developing muscle, both in vivo and in vitro, there is a development-related progression from synthesis of primarily large proteoglycans at earlier stages to mainly small proteoglycans at later stages. This progression was demonstrated by radiolabeling developing muscle and extracting and characterizing the proteoglycans. The large proteoglycans synthesized earlier in myogenesis have been identified as the large chondroitin sulfate proteoglycan, versican. Among the small proteoglycans synthesized at later stages is the small dermatan sulfate proteoglycan, decorin. Immunolocalization of these proteoglycans shows that versican is initially present in pericellular locations around developing myotubes, whereas decorin is observed in the epimysium early in development, and then its distribution gradually spreads to also include the perimysium and endomysium. Studies of regenerating muscle show that there is a recapitulation of the embryonic pattern of proteoglycan synthesis, which, coupled with the results from embryonic muscle development, suggests a role for versican in some early aspect of myogenesis.

Molecular cloning and characterization of a human uronyl 2-sulfotransferase that sulfates iduronyl and glucuronyl residues in dermatan/chondroitin sulfate

A partial-length human cDNA with a predicted amino acid sequence homologous to a previously described heparan sulfate iduronyl 2-sulfotransferase (Kobayashi, M., Habuchi, H., Yoneda, M., Habuchi, O., and Kimata, K. (1997) J. Biol. Chem. 272, 13980-13985) was obtained by searching the expressed sequence-tagged data bank. Northern blot analysis was performed using this homologous cDNA as a probe, which demonstrated ubiquitous expression of messages of 5.1 and 2.0 kilobases in a number of human tissues and in several human cancer cell lines. Since the human lymphoma Raji cell line had the highest level of expression, it was used to isolate a full-length cDNA clone. The full-length cDNA was found to contain an open reading frame that predicted a type II transmembrane protein composed of 406 amino acid residues. The cDNA in a baculovirus expression vector was expressed in Sf9 insect cells, and cell extracts were then incubated together with 3'-phosphoadenosine 5'-phospho[35S]sulfate and potential glycosaminoglycan acceptors. This demonstrated substantial sulfotransferase activity with dermatan sulfate, a small degree of activity with chondroitin sulfate, but no sulfotransferase activity with desulfated N-resulfated heparin. Analysis of [35S]sulfate-labeled disaccharide products of chondroitin ABC, chondroitin AC, and chondroitin B lyase treatment demonstrated that the enzyme only transferred sulfate to the 2-position of uronyl residues, which were preponderantly iduronyl residues in dermatan sulfate, but some lesser transfer to glucuronyl residues of chondroitin sulfate.

Glycosaminoglycans differentially bind HARP and modulate its biological activity

Heparin affin regulatory peptide (HARP) is a polypeptide belonging to a family of heparin binding growth/differentiation factors. The high affinity of HARP for heparin suggests that this secreted polypeptide should also bind to heparan sulfate proteoglycans derived from cell surface and extracellular matrix defined as extracellular compartments. Using Western blot analysis, we detected HARP bound to heparan sulfate proteoglycans in the extracellular compartments of MDA-MB 231 and MC 3T3-E1 as well as NIH3T3 cells overexpressing HARP protein. Heparitinase treatment of BEL cells inhibited HARP-induced cell proliferation, and the biological activity of HARP in this system was restored by the addition of heparin. We report that heparan sulfate, dermatan sulfate, and to a lesser extent, chondroitin sulfate A, displaced HARP bound to the extracellular compartment. Binding analyses with a biosensor showed that HARP bound heparin with fast association and dissociation kinetics (kass = 1.6 x 10(6) M-1 s-1; kdiss = 0.02 s-1), yielding a Kd value of 13 nM; the interaction between HARP and dermatan sulfate was characterized by slower association kinetics (kass = 0.68 x 10(6) M-1 s-1) and a lower affinity (Kd = 51 nM). Exogenous heparin, heparan sulfate, and dermatan sulfate potentiated the growth-stimulatory activity of HARP, suggesting that corresponding proteoglycans could be involved in the regulation of the mitogenic activity of HARP.

Temporal changes in disaccharide composition of dermatan sulfate in the skin after epicutaneous application of hapten

Glycosaminoglycans change their amount, structure and distribution with age, differentiation and pathologic conditions. In order to investigate temporal changes in dermatan sulfate in the skin during inflammation and subsequent healing, 2,4-dinitrofluorobenzene (DNFB) was applied once to the dorsal skin of female BALB/cA mice, and the disaccharide composition of dermatan sulfate was examined. Application of DNFB induced a transient increase in the thickness of the dermis, which reached a maximum on day 15 and decreased to the control level on day 35. The total amount of unsaturated disaccharides from dermatan sulfate per cm2 in the DNFB-treated skin showed a temporal pattern similar to that of the thickness of the dermis. Mol% of 4,5-unsaturated 2-sulfo-hexuronic acid-4-sulfated N-acetylgalactosamine (deltaDi-diSB), the second most abundant unsaturated disaccharide from dermatan sulfate, decreased rapidly on day 3 in the DNFB-treated skin, remained less than the control on days 7 and 15, and returned to the control level on day 35. These results suggest that a single application of DNFB induces temporal changes not only in the amount but also in the structure of dermatan sulfate.

Dermatan sulfate released after injury is a potent promoter of fibroblast growth factor-2 function

Proteoglycans have been shown in vitro to bind multiple components of the cellular microenvironment that function during wound healing. To study the composition and function of these molecules when derived from an in vivo source, soluble proteoglycans released into human wound fluid were characterized and evaluated for influence on fibroblast growth factor-2 activity. Immunoblot analysis of wound fluid revealed the presence of syndecan-1, syndecan-4, glypican, decorin, perlecan, and versican. Sulfated glycosaminoglycan concentrations ranged from 15 to 65 microgram/ml, and treatment with chondroitinase B showed that a large proportion of the glycosaminoglycan was dermatan sulfate. The total glycosaminoglycan mixture present in wound fluid supported the ability of fibroblast growth factor-2 to signal cell proliferation. Dermatan sulfate, and not heparan sulfate, was the major contributor to this activity, and dermatan sulfate bound FGF-2 with Kd = 2.48 microM. These data demonstrate that proteoglycans released during wound repair are functionally active and provide the first evidence that dermatan sulfate is a potent mediator of fibroblast growth factor-2 responsiveness.