Oversulfated dermatan sulfate exhibits neurite outgrowth-promoting activity toward embryonic mouse hippocampal neurons: implications of dermatan sulfate in neuritogenesis in the brain

Differential gene expression of multiple chondroitin sulfate modification enzymes among neural stem cells, neurons and astrocytes

Chondroitin sulfate/dermatan sulfate (CS/DS) polysaccharides have been reported to play a crucial role in the proliferation and maintenance of neural stem cells (NSCs). However, little is known about the structural changes and functional role of CS/DS chains in the differentiation of NSCs. Western blots of NSCs, neurons and astrocytes in culture, with three CS-polysaccharide antibodies of different specificities, revealed marked differences in CS structure among the three cell types. To confirm this finding, we measured gene expression levels of CS sulfotransferases and C5-epimerase in these cell types, as these are responsible for producing the high structural diversity of CS/DS. Expressions of chondroitin 4-O-sulfotransferase, chondroitin 6-O-sulfotransferase, and N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase mRNAs were low in cultures of differentiated neural cells, such as neurons and astrocytes, in comparison to NSCs. In contrast, expressions of uronyl 2-O-sulfotransferase and C5-epimerase mRNAs were higher in the differentiated neural cells than NSCs. Thus, we first provide evidence to support the hypothesis that CS/DS undergoes structural changes during NSC differentiation. The structural changes in CS/DS may be implicated in the regulation of NSC differentiation through interactions with growth/neurotrophic factors and cytokines.

Structure of pleiotrophin- and hepatocyte growth factor-binding sulfated hexasaccharide determined by biochemical and computational approaches

Endogenous pleiotrophin and hepatocyte growth factor (HGF) mediate the neurite outgrowth-promoting activity of chondroitin sulfate (CS)/dermatan sulfate (DS) hybrid chains isolated from embryonic pig brain. CS/DS hybrid chains isolated from shark skin have a different disaccharide composition, but also display these activities. In this study, pleiotrophin- and HGF-binding domains in shark skin CS/DS were investigated. A high affinity CS/DS fraction was isolated using a pleiotrophin-immobilized column. It showed marked neurite outgrowth-promoting activity and strong inhibitory activity against the binding of pleiotrophin to immobilized CS/DS chains from embryonic pig brain. The inhibitory activity was abolished by chondroitinase ABC or B, and partially reduced by chondroitinase AC-I. A pentasulfated hexasaccharide with a novel structure was isolated from the chondroitinase AC-I digest using pleiotrophin affinity and anion exchange chromatographies. It displayed a potent inhibitory effect on the binding of HGF to immobilized shark skin CS/DS chains, suggesting that the pleiotrophin- and HGF-binding domains at least partially overlap in the CS/DS chains involved in the neuritogenic activity. Computational chemistry using molecular modeling and calculations of the electrostatic potential of the hexasaccharide and two pleiotrophin-binding octasaccharides previously isolated from CS/DS hybrid chains of embryonic pig brain identified an electronegative zone potentially involved in the molecular recognition of the oligosaccharides by pleiotrophin. Homology modeling of pleiotrophin based on a related midkine protein structure predicted the binding pocket of pleiotrophin for the oligosaccharides and provided new insights into the molecular mechanism of the interactions between the oligosaccharides and pleiotrophin.

Determination of sulfation pattern in brain glycosaminoglycans by chip-based electrospray ionization ion trap mass spectrometry

Chondroitin sulfate (CS) and dermatan sulfate (DS) glycosaminoglycans display variability of sulfation in their constituent disaccharide repeats during chain elongation. Since a large proportion of the extracellular matrix of the central nervous system (CNS) is composed of proteoglycans, CS/DS disaccharide degree and profile of sulfation play important roles in the functional diversity of neurons, brain development, and some of its pathological states. To investigate the sulfation pattern of CS/DS structures expressed in CNS, we introduced here a novel method based on an advanced system encompassing fully automated chip nanoelectrospray ionization (nanoESI) in the negative ion mode and high capacity ion trap multistage mass spectrometry (MS(2)-MS(3)) by collision-induced dissociation (CID). This method, introduced here for the first time in glycomics of brain glycosaminoglycans, was particularly applied to structural investigation of disaccharides obtained by beta-elimination and digestion with chondroitin B and AC I lyase of hybrid CS/DS chains from wild-type mouse brain. Screening in the chip-MS mode of DS disaccharide fraction resulting after depolymerization with chondroitin B lyase revealed molecular ions assigned to monosulfated disaccharide species having a composition of 4,5-Delta-[IdoA-GalNAc]. By optimized CID MS(2)-MS(3), fragment ions supporting the localization of sulfate ester group at C4 within GalNAc were produced. Chip ESI MS profiling of CS disaccharide fraction obtained by depolymerization of the same CS/DS chain using chondroitin AC I lyase indicated the occurrence of mono- and bisulfated 4,5-Delta-[GlcA-GalNAc]. The site of oversulfation was determined by MS(2)-MS(3), which provided sequence patterns consistent with a rare GlcA-3-sulfate-GalNAc-6-sulfate structural motif. Figure Mouse brain GlcA-3-sulfate-GalNAc-6-sulfate structural motif.

Analysis of the structure and neuritogenic activity of chondroitin sulfate/dermatan sulfate hybrid chains from porcine fetal membranes

The amniotic membrane (AM) is the innermost layer of fetal membranes and possesses various biological activities. Although the mechanism underlying these biological activities remains unclear, unique components seem to be involved. AM contains various extracellular matrix components such as type I collagen, laminin, fibronectin, hyaluronan, and proteoglycans bearing chondroitin sulfate/dermatan sulfate (CS/DS) glycosaminoglycan side chains. Since CS/DS have been implicated in various biological processes, we hypothesized that CS/DS in AM may play a major role in the biological activities of AM. Therefore, the structure and bioactivity of the CS/DS chains from porcine fetal membranes (FM-CS/DS) were investigated. A compositional analysis using various chondroitinases revealed that the characteristic DS domain comprised of iduronic acid-containing disaccharide units is embedded in FM-CS/DS, along with predominant disaccharide units, GlcA-GalNAc, GlcA-GalNAc(4-O-sulfate), and GlcA-GalNAc(6-O-sulfate), where GlcA and GalNAc represent D-glucuronic acid and N-acetyl-D-galactosamine, respectively. The average molecular mass of FM-CS/DS chains was unusually large and estimated to be 250 - 300 kDa. The FM-CS/DS chains showed neurite outgrowth-promoting activity, which was eliminated by digestion with chondroitinase ABC of the CS/DS chains. This activity was suppressed by antibodies against growth factors including pleiotrophin, midkine, and fibroblast growth factor-2, suggesting the involvement of these growth factors in the neurite outgrowth-promoting activity. The binding of these growth factors to FM-CS/DS was also demonstrated by surface plasmon resonance spectroscopy.

Mechanisms involved in suppression of NGF-induced neuronal differentiation of PC12 cells by hyaluronic acid

In the present study, we found that hyaluronic acid (HA) suppressed the neuronal differentiation mediated by nerve growth factor (NGF). In addition, we examined the mechanism by which HA inhibits the NGF-induced neurite outgrowth of PC12 cells. We elucidated the direct interaction between NGF and HA, and found that HA did not bind to NGF directly using a quartz-crystal microbalance. Western blot analysis revealed that HA suppressed NGF-induced phosphorylation of p38 MAPK, ERKs, and transcriptional factor CREB in PC12 cells. Furthermore, HA inhibited the luciferase activity of pCRE-Luc transfected PC12 cells in the presence of NGF. We confirmed that the p38 MAPK inhibitor SB203580 and ERK inhibitor U0126 suppressed NGF-induced neurite outgrowth of PC12 cells, and found that the inhibitory effects of HA on phosphorylation of ERKs, but not of p38 MAPK, were restored by the anti-RHAMM antibody. The number of PC12 cells with neurites increased remarkably when pre-cultured with the anti-RHAMM antibody, then treated with NGF and HA. Our findings indicate that HA inhibits NGF-induced neuronal differentiation of PC12 cells partially by inhibiting ERK phosphorylation through RHAMM, and suggest that the binding of HA to RHAMM modifies the signaling pathways in PC12 cells treated with NGF.

Dermatan sulfate domains defined by the novel antibody GD3A12, in normal tissues and ovarian adenocarcinomas

Dermatan sulfate (DS) expression in normal tissue and ovarian cancer was investigated using the novel, phage display-derived antibody GD3A12 that was selected against embryonic glycosaminoglycans (GAGs). Antibody GD3A12 was especially reactive with DS rich in IdoA-GalNAc4S disaccharide units. IdoA residues are important for antibody recognition as DS polymers with low numbers of IdoA residues were less reactive, and expression of the DS epimerase in ovarian carcinoma cells was associated with expression of the GD3A12 epitope. Moreover, staining of antibody GD3A12 was abolished by chondroitinase-B lyase digestion. Expression of DS domains defined by antibody GD3A12 was confined to connective tissue of most organs examined and presented as a typical fibrillar-type of staining. Differential expression of the DS epitopes recognized by antibodies GD3A12 and LKN1 (4/2,4 di-O-sulfated DS) was best seen in thymus and spleen, indicating differential expression of various DS domains in these organs. In ovarian carcinomas strong DS expression was found in the stromal parts, and occasionally on tumor cells. Partial co-localization in ovarian carcinomas was observed with decorin, versican and type I collagen suggesting a uniform distribution of this specific DS epitope. This unique anti-DS antibody may be instrumental to investigate the function, expression, and localization of specific DS domains in health and disease.

The bright side of the glial scar in CNS repair

Following CNS injury, in an apparently counterintuitive response, scar tissue formation inhibits axonal growth, imposing a major barrier to regeneration. Accordingly, scar-modulating treatments have become a leading therapeutic goal in the field of spinal cord injury. However, increasing evidence suggests a beneficial role for this scar tissue as part of the endogenous local immune regulation and repair process. How can these opposing effects be reconciled? Perhaps it is all a matter of timing.

Isolation and characterization of a novel chondroitin sulfate from squid liver integument rich in N-acetylgalactosamine(4,6-disulfate) and glucuronate(3-sulfate) residues

Novel chondroitin sulfate (CS) chains with an average molecular mass of 79.6 kDa were purified from squid liver integument. A compositional analysis of the CS chains using chondroitinases (CSases) ABC and AC-I revealed a range of variably sulfated disaccharides with GlcAbeta1-->3GalNAc(6-sulfate), GlcAbeta1-->3GalNAc(4-sulfate), and GlcAbeta1-->3GalNAc(4,6-disulfate) as the major ones, significant amounts of rare 3-sulfated GlcA-containing disaccharides, and a small amount of nonsulfated GlcAbeta1-->3GalNAc. The CS chains exhibited neurite outgrowth-promoting activity toward embryonic mouse hippocampal neurons, which was abolished completely by digestion with CSase ABC or AC-I. Consequently, whether these CS chains interact with heparin-binding growth factors was tested in a BIAcore system. All of the growth factors exhibited concentration-dependent and specific binding. CS chains from squid liver integument, with their unique composition and strong biological activities, may be a good candidate for therapeutic application.

Decorin and its galactosaminoglycan chain: extracellular regulator of cellular function?

A molecular network of extracellular matrix molecules determines the tissue architecture and accounts for mechanical properties like compressibility or stretch resistance. It is widely accepted that the elements of the cellular microenvironment are important regulators of the cellular behavior in vitro and in vivo. One large group comprising these molecules is the family of proteoglycans. Both, the core proteins and, in particular, the attached galactosaminoglycans, contribute to the regulation network as they bind a variety of signaling molecules, e.g. cytokines, chemokines, growth, and differentiation factors. We would like to emphasize specific patterns of epimerization and sulfation within the galactosaminoglycans chains, because these result in "motifs" that are responsible for the modulation of signal factor binding, release and activity. This property is crucial in physiological and pathological conditions, for example development and wound healing.

Effect of bitter gourd and spent turmeric on glycoconjugate metabolism in streptozotocin-induced diabetic rats

AIM

Changes in glycoconjugate metabolism during the development of diabetic complications and their modulation by feeding bitter gourd and spent turmeric as fiber-rich source.

METHOD

This was studied by measuring the contents of total sugar, uronic acid, amino sugar, and sulfate in the streptozotocin-induced diabetic rats.

RESULTS

Total sugar content decreased in liver, spleen, and brain, while an increase was observed in heart and lungs. Uronic acid content in liver, spleen, and brain decreased, and marginal increase was observed in testis. Amino sugar content decreased in liver, spleen, lungs and heart during diabetes, and augmentation was observed to different extents. Decrease in sulfation of glycoconjugates was observed in liver, spleen, lungs and heart during diabetes and was significantly ameliorated by bitter gourd and spent turmeric, except brain. Protein content decreased in liver, while an increase was observed in brain. The studies clearly showed alteration in glycoconjugate metabolism during diabetes and amelioration to different extents by feeding bitter gourd and spent turmeric.

CONCLUSION

Improvement is due to slow release of glucose by fiber in the gastrointestinal track and short-chain fatty acid production from fiber by colon microbes.

Contactin-1 is a functional receptor for neuroregulatory chondroitin sulfate-E

Chondroitin sulfate (CS) plays critical roles in central nervous system development and regeneration, and individual modifications of CS form a "sulfation code" that regulates growth factor signaling or neuronal growth. Although we have shown that CS-E polysaccharide, but not CS-A or -C polysaccharide, has an inherent ability to promote neurite outgrowth toward primary neurons, its molecular mechanism remains elusive. Here, we show the involvement of a plasma membrane-tethered cell adhesion molecule, contactin-1 (CNTN-1), in CS-E-mediated neurite extension in a mouse neuroblastoma cell line and primary hippocampal neurons. CS-E, but not CS-A, -C, or heparan sulfate, engaged CNTN-1 with significant affinity and induced intracellular signaling downstream of CNTN-1, indicating that CS-E is a selective ligand for a potential CS receptor, CNTN-1, leading to neurite outgrowth. Our data provide the first evidence that biological functions of CS are exerted through the CS receptor-mediated signaling pathway(s).

Oversulfated chondroitin sulfate plays critical roles in the neuronal migration in the cerebral cortex

Chondroitin sulfate (CS) proteoglycans bind with various proteins through CS chains in a CS structure-dependent manner, in which oversulfated structures, such as iB (IdoA(2-O-sulfate)alpha1-3GalNAc(4-O-sulfate)), D (GlcA(2-O-sulfate)beta1-3GalNAc(6-O-sulfate)), and E (GlcAbeta1-3GalNAc(4,6-O-disulfate)) units constitute the critical functional module. In this study, we examined the expression and function of three CS sulfotransferases in the developing neocortex: uronyl 2-O-sulfotransferase (UST), N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase (4,6-ST) and dermatan 4-O-sulfotransferase-1 (D4-ST), which are responsible for the synthesis of oversulfated structures. The CS chains of the neocortex of mouse embryos contained significant amounts of D and E units that are generated by UST and 4,6-ST, respectively. UST and 4,6-ST mRNAs were expressed in the ventricular and subventricular zones, and their expression increased during late embryonic development. In utero electroporation experiments indicated that knockdown of UST and 4,6-ST resulted in the disturbed migration of cortical neurons. The neurons electroporated with the short hairpin RNA constructs of UST and 4,6-ST accumulated in the lower intermediate zone and in the subventricular zone, showing a multipolar morphology. The cDNA constructs of UST and 4,6-ST rescued the defects caused by the RNA interference, and the neurons were able to migrate radially. On the other hand, knockdown of D4-ST, which is involved in the biosynthesis of the iB unit, caused no migratory defects. These results revealed that specific oversulfated structures in CS chains play critical roles in the migration of neuronal precursors during cortical development.

Spatiotemporal expression of chondroitin sulfate sulfotransferases in the postnatal developing mouse cerebellum

Chondroitin sulfate (CS) proteoglycans are major components of the cell surface and the extracellular matrix in the developing brain and bind to various proteins via CS chains in a CS structure-dependent manner. This study demonstrated the expression pattern of three CS sulfotransferase genes, dermatan 4-O-sulfotransferase (D4ST), uronyl 2-O-sulfotransferase (UST), and N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase (GalNAc4S-6ST), in the mouse postnatal cerebellum. These sulfotransferases are responsible for the biosynthesis of oversulfated structures in CS chains such as B, D, and E units, which constitute the binding sites for various heparin-binding proteins. Real-time reverse transcription-polymerase chain reaction analysis indicated that the expression of UST increased remarkably during cerebellar development. The amounts of B and D units, which are generated by UST activity, in the cerebellar CS chains also increased during development. In contrast, the expression of GalNAc4S-6ST and its biosynthetic product, E unit, decreased during postnatal development. In situ hybridization experiments revealed the levels of UST and GalNAc4S-6ST mRNAs to correlate inversely in many cells including Purkinje cells, granule cells in the external granular layer, and inhibitory interneurons. In these neurons, the expression of UST increased and that of GalNAc4S-6ST decreased during development and/or maturation. D4ST was also expressed by many neurons, but its expression was not simply correlated with development, which might contribute to the diversification of CS structures expressed by distinct neurons. These results suggest that the CS structures of various cerebellar neurons change during development and such changes of CS are involved in the regulation of various signaling pathways.

Is human placenta proteoglycan remodeling involved in pre-eclampsia?

Impaired placento-fetal communication is a coherent symptom of exaggerated pre-eclampsia. The impact of the cellular expression of different glycosaminoglycans (GAGs) in this event on the placenta in pre-eclampsia is still obscure. This is the first study aimed at discovering the relationship between structural alterations of different sulfated GAGs at the molecular level and the development of pre-eclampsia in inflicted placenta. Sulfated GAGs were isolated and purified from control and pre-eclampsia placentas. The amount and the molecular weight of GAG in each tissue sample were measured. The polydispersity of the recovered GAG samples were determined by polyacrylamide gel electrophoresis. The disaccharide composition of chondroitin sulfate, dermatan sulfate and heparan sulfate were deduced by chondroitinase and heparinase depolymerization followed by liquid chromatography-mass spectrometry. The in vivo sulfo-modulation of GAGs in pre-eclampsia and control placenta were examined using RT-PCR to determine the transcription levels of different sulfotransferases involved in GAG biosynthesis. Marked differences in GAG sulfation patterns and mRNA level of encoding selected GAG O-sulfotransferases were observed in pre-eclampsia. These data suggest a linkage between pre-eclampsia and the observed alterations in placental GAGs and could provide new insights about the modulating role of GAGs in the development and the severity of placental pre-eclampsia.

Chondroitinase-mediated degradation of rare 3-O-sulfated glucuronic acid in functional oversulfated chondroitin sulfate K and E

Chondroitin sulfate K (CS-K) from king crab cartilage rich in rare 3-O-sulfated glucuronic acid (GlcUA(3S)) displayed neuritogenic activity and affinity toward various growth factors like CS-E from squid cartilage. CS-K-mediated neuritogenesis of mouse hippocampal neurons in culture was abolished by digestion with chondroitinase (CSase) ABC, indicating the possible involvement of GlcUA(3S). However, identification of GlcUA(3S) in CS chains by conventional high performance liquid chromatography has been hampered by its CSase ABC-mediated degradation. To investigate the degradation process, an authentic CS-E tetrasaccharide, Delta4,5HexUA-GalNAc(4S)-GlcUA(3S)-GalNAc(4S), was digested with CSase ABC, and the end product was identified as GalNAc(4S) by electrospray ionization mass spectrometry (ESI-MS). Putative GalNAc(6S) and GalNAc(4S,6S), derived presumably from GlcUA(3S)-GalNAc(6S) and GlcUA(3S)-GalNAc(4S,6S), respectively, were also detected by ESI-MS in the CSase ABC digest of a CS-E oligosaccharide fraction resistant to CSases AC-I and AC-II. Intermediates during the CSase ABC-mediated degradation of Delta4,5HexUA(3S)-GalNAc(4S) to GalNAc(4S) were identified through ESI-MS of a partial CSase ABC digest of a CS-K tetrasaccharide, GlcUA(3S)-GalNAc(4S)-GlcUA(3S)-GalNAc(4S), and the conceivable mechanism behind the degradation of the GlcUA(3S) moiety was elucidated. Although a fucose branch was also identified in CS-K, defucosylated CS-K exhibited greater neuritogenic activity than the native CS-K, excluding the possibility of the involvement of fucose in the activity. Rather, (3S)-containing disaccharides are likely involved. These findings will enable us to detect GlcUA(3S)-containing disaccharides in CS chains to better understand CS-mediated biological processes.

Antibody GD3G7 selected against embryonic glycosaminoglycans defines chondroitin sulfate-E domains highly up-regulated in ovarian cancer and involved in vascular endothelial growth factor binding

Chondroitin sulfate (CS) is abundantly present in the tumor stroma, and tumor-specific CS modifications might be potential targets to influence tumor development. We applied the phage display technology to select antibodies that identify these tumor-specific CS modifications. Antibody GD3G7 was selected against embryonic glycosaminoglycans, and it reacted strongly with CS-E (rich in GlcA-GalNAc4S6S units). In ovarian adenocarcinomas, strong expression of this CS-E epitope was found in the extracellular matrix, and occasionally on tumor cells. No expression was found in normal ovary and cystadenomas. Differential expression was found in ovarian carcinoma cell lines, which correlated with the gene expression of the GalNAc4S-6st enzyme, involved in biosynthesis of CS-E. Vascular endothelial growth factor (VEGF)-sensitive fenestrated (in normal tissues) and tumor blood vessels were both identified by antibody GD3G7, which might implicate a role for CS-E in VEGF biology. VEGF bound to CS-E and antibody GD3G7 could compete for binding of VEGF to CS-E. In conclusion, antibody GD3G7 identified rare CS-E-like structures that were strongly expressed in ovarian adenocarcinomas. This antibody might therefore be instrumental for identifying tumor-related CS alterations.

Functions of Chondroitin Sulfate/Dermatan Sulfate Chains in Brain Development

Chondroitin sulfate (CS) and dermatan sulfate (DS) have been implicated in the processes of neural development in the brain. In this study, we characterized developmentally regulated brain CS/DS chains using a single chain antibody, GD3G7, produced by the phage display technique. Evaluation of the specificity of GD3G7 toward various glycosaminoglycan preparations showed that this antibody specifically reacted with squid CS-E (rich in the GlcUAbeta1-3GalNAc(4,6-O-sulfate) disaccharide unit E), hagfish CS-H (rich in the IdoUAalpha1-3GalNAc(4,6-O-sulfate) unit iE), and shark skin DS (rich in both E and iE units). In situ hybridization for the expression of N-acetylgalac-tosamine-4-sulfate 6-O-sulfotransferase in the postnatal mouse brain, which is involved in the biosynthesis of CS/DS-E, showed a widespread expression of the transcript in the developing brain except at postnatal day 7, where strong expression was observed in the external granule cell layer in the cerebellum. The expression switched from the external to internal granule cell layer with development. Immunohistochemical localization of GD3G7 in the mouse brain showed that the epitope was relatively abundant in the cerebellum, hippocampus, and olfactory bulb. GD3G7 suppressed the growth of neurites in embryonic hippocampal neurons mediated by CS-E, suggesting that the epitope is embedded in the neurite outgrowth-promoting motif of CS-E. In addition, a CS-E decasaccharide fraction was found to be the critical minimal structure needed for recognition by GD3G7. Four discrete decasaccharide epitopic sequences were identified. The antibody GD3G7 has broad applications in investigations of CS/DS chains during the central nervous system's development and under various pathological conditions.

[Regulation of neuronal cell function by glyco-signals]

Gangliosides and proteoglycans with various sugar chains exist abundantly in the brain. They participate in intercellular recognition by revealing the sugar chains on the cell surface, and some of them show neurite-extension activity. Several recognition features that are mediated by the sugar chains are known such as saccharide-saccharide interaction and cell-surface sugar-chain receptor-mediated recognition. Experiments on animals lacking the sugar-chain synthetic system with the technique of gene targeting suggest that phylogenetically "old" sugar chains such as chondroitin sulfate appear necessary for early development of the organism while relatively "new" sugar chains such as gangliosides, which appear with further development of the brain, are necessary for differentiation maturity processes. On the other hand, research using primary cultured neurons showed similar effects of the gangliosides and chondroitin sulfate on cell differentiation. It is possible that these sugar chains share the glyco-receptor-mediated signal transduction system.

Chondroitin sulfate and keratan sulfate are the major glycosaminoglycans present in the adult zebrafish Danio rerio (Chordata-Cyprinidae)

The zebrafish Danio rerio (Chordata-Cyprinidae) is a model organism frequently used to study the functions of proteoglycans and their glycosaminoglycan (GAG) chains. Although several studies clearly demonstrate the participation of these polymers in different biological and cellular events that take place during embryonic development, little is known about the GAGs in adult zebrafish. In the present study, the total GAGs were extracted from the whole fish by proteolytic digestion, purified by anion-exchange chromatography and characterized by electrophoresis after degradation with specific enzymes and/or by high-performance liquid chromatography (HPLC) analysis of the disaccharides. Two GAGs were identified: a low-molecular-weight chondroitin sulfate (CS) and keratan sulfate (KS), corresponding to approximately 80% and 20% of the total GAGs, respectively. In the fish eye, KS represents approximately 80% of total GAGs. Surprisingly, no heparinoid was detected, but may be present in the fish at concentrations lower than the limit of the method used. HPLC of the disaccharides formed after chondroitin AC or ABC lyase degradation revealed that the zebrafish CS is composed by DeltaUA-1-->3-GalNAc(4SO4) (59.4%), DeltaUA-1-->3-GalNAc(6SO4) (23.1%), and DeltaUA-1-->3-GalNAc (17.5%) disaccharide units. No disulfated disaccharides were detected. Immunolocalization on sections from zebrafish retina using monoclonal antibodies against CS4- or 6-sulfate showed that in the retina these GAGs are restricted to the outer and inner plexiform layers. This is the first report showing the presence of KS in zebrafish eye, and the structural characterization of CS and its localization in the zebrafish retina. Detailed information about the structure and tissue localization of GAGs is important to understand the functions of these polymers in this model organism.

Structural determination of novel sulfated octasaccharides isolated from chondroitin sulfate of shark cartilage and their application for characterizing monoclonal antibody epitopes

Twelve octasaccharide fractions were obtained from chondroitin sulfate C derived from shark cartilage after hyaluronidase digestion. Their sugar and sulfate composition was assigned by matrix-assisted laser desorption ionization time of flight mass spectrometry. The sequences were determined at low picomole amounts by a combination of enzymatic digestions with high-performance liquid chromatography, and were composed of disaccharide building units including O [GlcUAbeta1-3GalNAc], C [GlcUAbeta1-3GalNAc(6S)], A [GlcUAbeta1-3GalNAc(4S)], and/or D [GlcUA(2S)beta1-3GalNAc(6S)], where 2S, 4S, and 6S represent 2-O-, 4-O-, and 6-O-sulfate, respectively. As many as 24 different sequences including minor ones were revealed, exhibiting a high degree of structural diversity reflecting the enormous heterogeneity of the parent polysaccharides. Nineteen of them were novel, with the other four reported previously as unsaturated counterparts obtained after digestion with chondroitinase. Microarrays of these structurally defined octasaccharide fractions were prepared using low picomole amounts of their lipid-derivatives to investigate the binding specificity of four commercial anti-chondroitin sulfate antibodies CS-56, MO-225, 2H6, and LY111. The results revealed that multiple unique sequences were recognized by each antibody, which implies that the common conformation shared by the multiple primary sequences in the intact chondroitin sulfate chains is important as an epitope for each monoclonal antibody. Comparison of the specificity of the tested antibodies indicates that CS-56 and MO-225 specifically recognize octasaccharides containing an A-D tetrasaccharide sequence, whereas 2H6 and LY111 require a hexasaccharide as a minimum size for their binding, and prefer sequences with A- and C-units such as C-C-A-C (2H6) or C-C-A-O, C-C-A-A, and C-C-A-C (LY111) for strong binding but require no D-unit.

Mutational study of heparan sulfate 2-O-sulfotransferase and chondroitin sulfate 2-O-sulfotransferase

Heparan sulfate (HS) and chondroitin sulfate (CS) are highly sulfated polysaccharides with a wide range of biological functions. Heparan sulfate 2-O-sulfotransferase (HS-2OST) transfers the sulfo group from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to the 2-OH position of the hexauronic acid that is adjacent to N-sulfated glucosamine, whereas chondroitin sulfate 2-O-sulfotransferase (CS-2OST) transfers the sulfo group to the hexauronic acid that is adjacent to N-acetylated galactosamine. Here we report a systematic mutagenesis study of HS-2OST and CS-2OST based on their structural homology to estrogen sulfotransferase and HS 3-O-sulfotransferase isoform 3 (3-OST3), for which crystal structures exist. We have identified six residues possibly involved in binding to PAPS. HS-2OST carrying mutations of these residues lacks sulfotransferase activity and the ability to bind 3'-phosphoadenosine 5'-phosphate, a PAPS analogue, as determined by isothermal titration calorimetry. Similar residues involved in binding to PAPS were also identified in CS-2OST. Additional residues that participate in carbohydrate substrate binding were also identified in both enzymes. Mutations at these residues led to the loss of sulfotransferase activity but maintained the ability to bind to phosphoadenosine 5'-phosphate. The catalytic function of HS-2OST appears to involve two histidine residues (His140 and His142), whereas only one histidine (His168) of CS 2-OST is likely to be critical. This unique feature of HS 2-OST catalytic residues directed us to characterize the Drosophila heparan sulfate 2-O-sulfotransferase. The results from this study provide insight into the differences and similarities various residues play in the biological roles of the HS-2OST and CS-2OST enzymes.

Neuritogenic activity of chondroitin/dermatan sulfate hybrid chains of embryonic pig brain and their mimicry from shark liver. Involvement of the pleiotrophin and hepatocyte growth factor signaling pathways

Accumulating evidence suggests the involvement of chondroitin sulfate (CS) and dermatan sulfate (DS) hybrid chains in the brain's development and critical roles for oversulfated disaccharides and IdoUA residues in the growth factor-binding and neuritogenic activities of these chains. In the pursuit of sources of CS/DS with unique structures, neuritogenic activity, and therapeutic potential, two novel CS/DS preparations were isolated from shark liver by anion exchange chromatography. The major (80%) low sulfated and minor (20%) highly sulfated fractions had an average molecular mass of 3.8-38.9 and 75.7 kDa, respectively. Digestion with various chondroitinases (CSases) revealed a large panel of disaccharides with either GlcUA or IdoUA scattered along the polysaccharide chains in both of the fractions. The higher M(r) fraction, richer in IdoUA(2-O-sulfate)alpha1-3GalNAc(4-O-sulfate) and GlcUAbeta/IdoUAalpha1-3GalNAc(4,6-O-disulfate) units, exerted greater neurite outgrowth-promoting (NOP) activity and better promoted the binding of various heparin-binding growth factors, including pleiotrophin (PTN), midkine, recombinant human heparin-binding epidermal growth factor-like growth factor, VEGF(165), fibroblast growth factor-2, fibroblast growth factor-7, and hepatocyte growth factor (HGF). These activities were largely abolished by digestion with CSase ABC or B but only moderately affected by a mixture of CSases AC-I and AC-II. In addition, the NOP activity of the larger fraction was markedly reduced by desulfation with alkali, suggesting a role for the 2-O-sulfate of IdoUA(2-O-sulfate)alpha1-3GalNAc(4-O-sulfate). The NOP activity of the higher molecular weight fraction and that of the embryonic pig brain-derived CS/DS fraction were also sup pressed to a large extent by antibodies against HGF, PTN, and their individual receptors cMet and anaplastic lymphoma kinase, revealing the involvement of the HGF and PTN signaling pathways in the activity.

Specific Cell Behavior of Human Fibroblast onto Carbohydrate Surface Detected by Glycoblotting Films

We synthesized an aminooxyl polymer that is reactive with the reduced end of carbohydrates using our sugar-displaying approach. The carbohydrates were easily immobilized on the polymer film (glycoblotting film) by simple immersion in a in sugar solution through stable oxime bond. The in vitro behaviors of human fibroblasts on the carbohydrate-coated surface were investigated. The adhesion of human fibroblasts on the cellobiose- and cellotriose-coated surfaces was much greater than on the other coated surfaces and the noncoated surface. This result indicated that simple structural differences in carbohydrates induced biological changes in human cells, especially cell adhesion. Our approach provides a high-throughput assay system for carbohydrate-related cell adhesion and proliferation.

Chondroitin sulfate perlecan enhances collagen fibril formation. Implications for perlecan chondrodysplasias

Inactivation of the perlecan gene leads to perinatal lethal chondrodysplasia. The similarity to the phenotypes of the Col2A1 knock-out and the disproportionate micromelia mutation suggests perlecan involvement in cartilage collagen matrix assembly. We now present a mechanism for the defect in collagen type II fibril assembly by perlecan-null chondrocytes. Cartilage perlecan is a heparin sulfate or a mixed heparan sulfate/chondroitin sulfate proteoglycan. The latter form binds collagen and accelerates fibril formation in vitro, with more defined fibril morphology and increased fibril diameters produced in the presence of perlecan. Interestingly, the enhancement of collagen fibril formation is independent on the core protein and is mimicked by chondroitin sulfate E but neither by chondroitin sulfate D nor dextran sulfate. Furthermore, perlecan chondroitin sulfate contains the 4,6-disulfated disaccharides typical for chondroitin sulfate E. Indeed, purified glycosaminoglycans from perlecan-enriched fractions of cartilage extracts contain elevated levels of 4,6-disulfated chondroitin sulfate disaccharides and enhance collagen fibril formation. The effect on collagen assembly is proportional to the content of the 4,6-disulfated disaccharide in the different cartilage extracts, with growth plate cartilage glycosaminoglycan being the most efficient enhancer. These findings demonstrate a role for perlecan chondroitin sulfate side chains in cartilage extracellular matrix assembly and provide an explanation for the perlecan-null chondrodysplasia.

Selection and characterization of a unique phage display-derived antibody against dermatan sulfate

Dermatan sulfate (DS) is a member of the glycosaminoglycan (GAG) family and is primarily located in the extracellular matrix. Using a modified phage display procedure, we selected 2 different antibodies against DS of which one antibody, LKN1, was specific for DS. LKN1 was especially reactive with 4/2,4-di-O-sulfated DS, and did not react with other classes of GAGs including chondroitin sulfate and heparan sulfate. Immunohistochemical analysis of kidney, skin and tendon showed a typical fibrillar staining pattern, co-localizing with type I collagen. Staining was abolished by specific enzymatic digestion of DS. Immunoelectron microscopy confirmed the association of the DS epitope with collagen fibrils. The location of DS did not follow the main banding period of collagen, which is in line with the current concept that the core protein rather than the DS moiety of DS-proteoglycans specifically binds to collagen fibrils. This unique anti-DS antibody and the availability of its coding DNA may be instrumental in studies of the structure and function of DS.

Chondroitin sulfate/dermatan sulfate hybrid chains in the development of cerebellum. Spatiotemporal regulation of the expression of critical disulfated disaccharides by specific sulfotransferases

Chondroitin sulfate/dermatan sulfate (CS/DS) chains regulate the development of the central nervous system in vertebrates. Previously, we demonstrated that CS/DS hybrid chains from embryonic pig brain exhibit neuritogenic and growth factor binding activities, which depended on their IdoUA content defining the DS-like structure. To elucidate the distribution of such functional sugar chains during the development of the brain, in situ hybridization was performed to examine expression of three CS/DS GalNAc 4-O-sulfotransferases, D4ST-1, C4ST-1, and C4ST-2, and a single uronyl 2-O-sulfotransferase (UST) involved in the biosynthesis of DS in addition to CS intermediates. C4ST-1 and C4ST-2 were ubiquitously expressed in the postnatal mouse brain, whereas the expression of D4ST-1 and UST was restricted in the developing cerebellum and culminated at postnatal day 14 as shown by reverse transcriptase-PCR analysis. In situ analysis of the disaccharides of CS/DS in brain sections revealed that the concentration of CS/DS increases 2-fold during development (postnatal day 7 to 7 weeks). The proportions of DS-specific, principal disaccharides, IdoUA-Gal-NAc(4-O-sulfate) (iA) and IdoUA(2-O-sulfate)-GalNAc(4-O-sulfate) (iB), produced by the sequential actions of D4ST-1 and UST, were higher in the CS/DS chains from cerebellum than those from whole brain sections. A dramatic increase (10-fold) in the proportion of iB during development was noteworthy. In contrast, GlcUA/IdoUA(2-O-sulfate)-GalNAc(6-O-sulfate) (D/iD) and GlcUA/IdoUA-GalNAc(4, 6-O-disulfate) (E/iE) decreased to 50 and 30%, respectively, in the developing cerebellum. These results suggest that the IdoUA-containing iA and iB units along with D/iD and E/iE units in the CS/DS hybrid play important roles in the formation of the cerebellar neural network during postnatal brain development.

A tandem mass spectrometric approach to determination of chondroitin/dermatan sulfate oligosaccharide glycoforms

Dermatan sulfate (DS) chains are variants of chondroitin sulfate (CS) that are expressed in mammalian extracellular matrices and are particularly prevalent in skin. DS has been implicated in varied biological processes including wound repair, infection, cardiovascular disease, tumorigenesis, and fibrosis. The biological activities of DS have been attributed to its high content of IdoA(alpha1-3)GalNAc4S(beta1-4) disaccharide units. Mature CS/DS chains consist of blocks with high and low GlcA/IdoA ratios, and sulfation may occur at the 4- and/or 6-position of GalNAc and 2-position of IdoA. Traditional methods for the analysis of CS/DS chains involve differential digestion with specific chondroitinases followed by steps of chromatographic isolation of the products and di-saccharide analysis on the individual fraction. This work reports the use of tandem mass spectrometry to determine the patterns of sulfation and epimerization of CS/DS oligosaccharides in a single step. The approach is first validated and then applied to a series of skin DS samples and to decorins from three different tissues. DS samples ranged from 74 to 99% of CSB-like repeats, using this approach. Decorin samples ranged from 30% CSB-like repeats for those samples from articular cartilage to 75% for those from sclera. These values agree with known levels of glucuronyl C5-epimerase in these tissues.

The Binding of Chondroitin Sulfate to Pleiotrophin/Heparin-binding Growth-associated Molecule Is Regulated by Chain Length and Oversulfated Structures

Pleiotrophin is an 18-kDa heparin-binding growth factor, which uses chondroitin sulfate (CS) proteoglycan, PTPzeta as a receptor. It has been suggested that the D-type structure (GlcA(2S)beta1-3GalNAc(6S)) in CS contributes to the high affinity binding between PTPzeta and pleiotrophin. Here, we analyzed the interaction of shark cartilage CS-D with pleiotrophin using a surface plasmon resonance biosensor to reveal the importance of D-type structure. CS-D was partially digested with chondroitinase ABC, and fractionated using a Superdex 75pg column. The > or =18-mer CS fractions showed significant binding to pleiotrophin, and the longer fractions had stronger affinity for pleiotrophin than the shorter ones. The approximately 46-mer CS fraction bound to densely immobilized pleiotrophin with high affinity (K(D) = approximately 30 nM), and the binding reactions fitted the bivalent analyte model. However, when the density of the immobilized pleiotrophin was lowered, the strength of affinity remarkably decreased (K(D) = approximately 2.5 microM), and the reactions no longer fitted the model and were considered to be monovalent binding. The 20 approximately 24-mer fractions showed low affinity binding to densely immobilized pleiotrophin (K(D) = 3 approximately 20 microM), which seemed to be monovalent. When approximately 22-mer CS oligosaccharides were fractionated by strong anion exchange HPLC, each fraction differed in affinity for pleiotrophin (K(D) = 0.36 approximately >10 microM), and the affinity correlated with the amounts of D- and E- (GlcAbeta1-3GalNAc(4S,6S)) type oversulfated structures. These results suggest that the binding of pleiotrophin to CS is regulated by multivalency with CS approximately 20 mer as a unit and by the amounts of oversulfated structures.

Demonstration of the Pleiotrophin-binding Oligosaccharide Sequences Isolated from Chondroitin Sulfate/Dermatan Sulfate Hybrid Chains of Embryonic Pig Brains

Mammalian brains contain significant amounts of chondroitin sulfate (CS), dermatan sulfate (DS), and CS/DS hybrid chains. CS/DS chains isolated from embryonic pig brains (E-CS/DS) promote the outgrowth of neurites in embryonic mouse hippocampal neurons in culture by interacting with pleiotrophin (PTN), a heparin-binding growth factor. Here, we analyzed oligosaccharides isolated from E-CS/DS, which showed that octasaccharides were the minimal size capable of interacting with PTN at a physiological salt concentration. Five and eight sequences were purified from fluorescently labeled PTN-bound and -unbound octasaccharide fractions, respectively, by enzymatic digestion followed by PTN-affinity chromatography. Their sequences were determined by enzymatic digestion in conjunction with high performance liquid chromatography, revealing a critical role for oversulfated D and/or iD disaccharides in the low yet significant affinity for PTN, which is required for neuritogenesis. The critical D and iD units are GlcUA(2-O-sulfate)beta1-3GalNAc(6-O-sulfate) and IdoUA(2-O-sulfate)alpha1-3GalNAc(6-O-sulfate), respectively, where IdoUA represents L-iduronic acid. In contrast, high affinity interactions with PTN required decasaccharides with E units (GlcUAbeta1-3GalNAc(4, 6-O-disulfate)), B units (GlcUA(2-O-sulfate)beta1-3GalNAc(4-O-sulfate)), and/or their IdoUA-containing counterparts (iE and iB) in addition to D/iD units, although the biological significance of such strong interactions remains to be investigated. Thus, chain size and composition are crucial to the interaction with PTN, and PTN binds to multiple sequences in E-CS/DS chains with distinct affinity. Notably, not only heparan sulfate but also CS/DS hybrid chain structures of mammalian brains contain a high degree of microheterogeneity with a cluster of oversulfated disaccharides and appear to play roles in regulating the functions of PTN.

Regulation of the chondroitin/dermatan fine structure by transforming growth factor-beta1 through effects on polymer-modifying enzymes

The chondroitin/dermatan sulfate proteoglycans (CS/DSPGs), biglycan, decorin, and versican play several important roles in extracellular matrix influencing matrix organization, cell proliferation, and recruitment. Moreover, they bind and regulate growth factors in the extracellular matrix. We have previously shown that cultured human lung fibroblasts treated with transforming growth factor-beta (TGF-beta) alone or in combination with epidermal growth factor and platelet-derived growth factor, increase the production of these PGs. In this report, we describe that the structure of their galactosaminoglycan side chains is altered, albeit there is no alteration of polysaccharide length. The findings showed that iduronic acid content is reduced by 50% in decorin and biglycan, whereas 4-O-sulfation is increased 2-fold in versican. To unravel the mechanism behind these changes, the activities of chondroitin C-5 epimerase and of O-sulfotransferases in cellular fractions prepared from fibroblasts were quantitated, and transcript levels of the relevant sulfotransferases were measured by real time polymerase chain reaction (RT-PCR). The C-5 epimerase activity was reduced by 25% in TGF-beta1 treated cells and 50% in fibroblasts treated with the growth factor combination. No change in activity in dermatan 4-O sulfotransferase was observed, and only a minor decrease in dermatan 4-O-sulfotransferase-1 (D4ST-1) mRNA was observed. On the other hand, chondroitin 4-O sulfotransferase activity increased 2-fold upon TGF-beta1 treatment and 3-fold upon treatment with the growth factor combination. This is in agreement with a 2-fold up-regulation of chondroitin-4-O-sulfotransferase 1 (C4ST-1) mRNA, and no changes in chondroitin-4-O-sulfotransferase 2 (C4ST-2) mRNA. Thus, cellular activity and transcript level correlated well with the changes in the structure of the dermatan/chondroitin sulfate chains.

A Functional Dermatan Sulfate Epitope Containing Iduronate(2-O-sulfate)α1–3GalNAc(6-O-sulfate) Disaccharide in the Mouse Brain

Oversulfated chondroitin sulfate (CS), dermatan sulfate (DS), and CS/DS hybrid structures bind growth factors, promote the neurite outgrowth of hippocampal neurons in vitro, and have been implicated in the development of the brain. To investigate the expression of functional oversulfated DS structures in the brain, a novel monoclonal antibody (mAb), 2A12, was generated against DS (An-DS) from ascidian Ascidia nigra, which contains a unique iD disaccharide unit, iduronic acid (2-O-sulfate)alpha1-->3GalNAc(6-O-sulfate), as a predominant disaccharide. mAb 2A12 specifically reacted with the immunogen, and recognized iD-enriched decasaccharides as minimal structures. The 2A12 epitope was specifically observed in the hippocampus and cerebellum of the mouse brain on postnatal day 7, and the expression in the cerebellum disappeared in the adult brain, suggesting a spatiotemporally regulated expression of this epitope. Embryonic hippocampal neurons were immunopositive for 2A12, and the addition of the antibody to the culture medium significantly reduced the neurite growth of hippocampal neurons. In addition, two minimum 2A12-reactive decasaccharide sequences with multiple consecutive iD units were isolated from the An-DS chains, which exhibited stronger inhibitory activity against the binding of various growth factors and neurotrophic factors to immobilized embryonic pig brain CS/DS chains (E-CS/DS) than the intact E-CS/DS, suggesting that the 2A12 epitope at the neuronal surface acts as a receptor or co-receptor for these molecules. Thus, we have selected a unique antibody that recognizes iD-enriched oversulfated DS structures, which are implicated in the development of the hippocampus and cerebellum in the central nervous system. The antibody will also be applicable for investigating structural alterations in CS/DS in aging and pathological conditions.

Evaluation of chondroitin sulfate bioactivity in hippocampal neurones and the astrocyte cell line U373: influence of position of sulfate groups and charge density

Chondroitin sulfates are linear polysaccharides of alternating glucuronic acid and N-acetylgalactosamine, sulfated in varying positions. They form the extracellular framework providing the information for the structural establishment of tissues in multicellular organisms. Growth cones of neurones modulate their outgrowth according to signals received from proteoglycans. The exact molecular structures behind these functions are not fully understood, but structural details of the carbohydrate backbone are crucial. In this report we have employed quantitative cytometry on hippocampal neurite outgrowth in the presence of chondroitin sulfate added in solution to determine the influence of the position and density of the sulfate groups of the N-acetyl-D-galactosamine-residues of chondroitin sulfates. It is of profound interest whether externally added chondroitin sulfates can compete with core protein bound chondroitin sulfate to modulate the effects of tissue-synthesized matrix. In series of microscopic images 3 parameters of neuritic outgrowth activity, neurite length, number of neurites and fasciculation (thickness of neurites) are analyzed at concentrations occurring in intact tissues. Fasciculation increased and number of neurites decreased with high di-sulfation. No significant differences on process length reduction were found between the isotypes. Specificity of effects found is emphasized, as no influence on cell proliferation with U373 human astrocyte cell line is detectable, while neurones clearly are inhibited. The IC30 and IC50 values of chondroitin sulfates isoforms are presented for neurones. The data indicate that the soluble fragments from chondroitin sulfate are actively modulating cell development. Besides dosage, sulfation density and position are relevant for effects of chondroitin sulfate in neuronal regenerative activity.

Chondroitin 6-sulphate synthesis is up-regulated in injured CNS, induced by injury-related cytokines and enhanced in axon-growth inhibitory glia

Chondroitin sulphate proteoglycans (CSPGs) are up-regulated in the CNS after injury and inhibit axon regeneration mainly through their glycosaminoglycan (CS-GAG) chains. We have analysed the mRNA levels of the CS-GAG synthesizing enzymes and measured the CS-GAG disaccharide composition by chromatography and immunocytochemistry. Chondroitin 6-sulfotransferase 1 (C6ST1) is up-regulated in most glial types around cortical injuries, and its sulphated product CS-C is also selectively up-regulated. Treatment with TGFalpha and TGFbeta, which are released after brain injury, promotes the expression of C6ST1 and the synthesis of 6-sulphated CS-GAGs in primary astrocytes. Oligodendrocytes, oligodendrocyte precursors and meningeal cells are all inhibitory to axon regeneration, and all express high levels of CS-GAG, including high levels of 6-sulphated GAG. In axon growth-inhibitory Neu7 astrocytes C6ST1 and 6-sulphated GAGs are expressed at high levels, whereas in permissive A7 astrocytes they are not detectable. These results suggest that the up-regulation of CSPG after CNS injury is associated with a specific sulphation pattern on CS-GAGs, mediating the inhibitory properties of proteoglycans on axonal regeneration.

Structural and Sequence Motifs in Dermatan Sulfate for Promoting Fibroblast Growth Factor-2 (FGF-2) and FGF-7 Activity

Glycosaminoglycans have been implicated in the binding and activation of a variety of growth factors, cytokines, and chemokines. In this way, glycosaminoglycans are thought to participate in events such as development and wound repair. In particular, heparin and heparan sulfate have been well studied, and specific aspects of their structure dictate their participation in a variety of activities. In contrast, although dermatan sulfate participates in many of the same biological processes as heparin and heparan sulfate, the interactions of dermatan sulfate have been less well studied. Dermatan sulfate is abundant in the wound environment and binds and activates growth factors such as fibroblast growth factor-2 (FGF-2) and FGF-7, which are present during the wound repair process. To determine the minimum size and sulfation content of active dermatan sulfate oligosaccharides, dermatan sulfate was first digested and then separated by size exclusion high pressure liquid chromatography, and the activity to facilitate FGF-2 and FGF-7 was assayed by the cellular proliferation of cell lines expressing FGFR1 or FGFR2 IIIb. The minimum size required for the activation of FGF-2 was an octasaccharide and for FGF-7 a decasaccharide. Active fractions were rich in monosulfated, primarily 4-O-sulfated, disaccharides and iduronic acid. Increasing the sulfation to primarily 2/4-O-sulfated and 2/6-O-sulfated disaccharides did not increase activity. Cell proliferation decreased or was abolished with higher sulfated dermatan sulfate preparations. This indicated a preference for specific dermatan sulfate oligosaccharides capable of promoting FGF-2- and FGF-7-dependent cell proliferation. These data identify critical oligosaccharides that promote specific members of the FGF family that are important for wound repair and angiogenesis.

Heparin-binding growth factor, pleiotrophin, mediates neuritogenic activity of embryonic pig brain-derived chondroitin sulfate/dermatan sulfate hybrid chains

Chondroitin sulfate (CS) and dermatan sulfate (DS) chains play roles in the central nervous system. Most notably, CS/DS hybrid chains (E-CS/DS) purified from embryonic pig brains bind growth factors and promote neurite outgrowth toward embryonic mouse hippocampal neurons in culture. However, the neuritogenic mechanism is not well understood. Here we showed that pleiotrophin (PTN), a heparin-binding growth factor, produced mainly by glia cells, was the predominant binding partner for E-CS/DS in the membrane-associated protein fraction of neonatal rat brain. The CS/DS chains were separated on a PTN column into unbound, low affinity, and high affinity fractions. The latter two fractions promoted outgrowth of dendrite- and axon-like neurites, respectively, whereas the unbound fraction showed no such activity. The activity of the low affinity fraction was abolished by an anti-PTN antibody or when glia cells were removed from the culture. In contrast, the high affinity fraction displayed activity under both these conditions. Hence, PTN mainly from glia cells mediated the activity of the low affinity but not the high affinity fraction. The anti-CS antibody 473HD neutralized the neuritogenic activities of both fractions. Interaction analysis indicated that the 473HD epitope and PTN-binding domains in the E-CS/DS chains largely overlap. The three affinity subfractions differed in disaccharide composition and the distribution of l-iduronic acid-containing disaccharides along the chains. Oversulfated disaccharides and nonconsecutive iduronic acid-containing units were the requirements for the E-CS/DS chains to bind PTN and to exhibit the neuritogenic activities. Thus, CS subpopulations with distinct structures in the mammalian brain play different roles in neuritogenesis through distinct molecular mechanisms, at least in part by regulating the functions of growth factors.

Structural characterization of the epitopes of the monoclonal antibodies 473HD, CS-56, and MO-225 specific for chondroitin sulfate D-type using the oligosaccharide library

The variation in the sulfation profile of chondroitin sulfate (CS)/dermatan sulfate (DS) chains regulates central nervous system development in vertebrates. Notably, the disulfated disaccharide D-unit, GlcUA(2-O-sulfate)-GalNAc(6-O-sulfate), correlates with the promotion of neurite outgrowth through the DSD-1 epitope that is embedded in the CS moiety of the proteoglycan DSD-1-PG/phosphacan. Monoclonal antibody (mAb) 473HD inhibits the DSD-1-dependent neuritogenesis and also recognizes shark cartilage CS-D, which is characterized by the prominent D-unit and is also recognized by two other mAbs, CS-56 and MO-225. We investigate the oligosaccharide epitope structures of these CS-D-reactive mAbs by ELISA and oligosaccharide microarrays using lipid-derivatized CS oligosaccharides. CS-56 and MO-225 recognized the octa- and larger oligosaccharides, though the latter also bound one unique hexasaccharide D-A-D, where A denotes the disaccharide A-unit GlcUA-GalNAc(4-O-sulfate). The octasaccharides reactive with CS-56 and MO-225 shared a core A-D tetrasaccharide, whereas the neighboring structural elements located on the reducing and/or nonreducing sides of the A-D gave a differential preference additionally to the recognition sequence for each antibody. In contrast, 473HD reacted with multiple hexa- and larger oligosaccharides, which also contained A-D or D-A tetrasaccharide sequences. Consistent with the distinct specificity of 473HD as compared with CS-56 and MO-225, the 473HD epitope displayed a different expression pattern in peripheral mouse organs as revealed by immunohistology, extending the previously reported CNS-restricted expression. The epitope of 473HD, but not of CS-56 or MO-225, was eliminated from DSD-1-PG by digestion with chondroitinase B, suggesting the close association of L-iduronic acid with the 473HD epitope. Despite such supplemental information, the integral epitope remains to be isolated for identification and comprehensive analytical characterisation. Thus novel information on the sugar sequences containing the A-D tetrasaccharide core was obtained for the epitopes of these three useful mAbs.

A disaccharide derived from chondroitin sulphate proteoglycan promotes central nervous system repair in rats and mice

Chondroitin sulphate proteoglycan (CSPG) inhibits axonal regeneration in the central nervous system (CNS) and its local degradation promotes repair. We postulated that the enzymatic degradation of CSPG generates reparative products. Here we show that an enzymatic degradation product of CSPG, a specific disaccharide (CSPG-DS), promoted CNS recovery by modulating both neuronal and microglial behaviour. In neurons, acting via a mechanism that involves the PKCalpha and PYK2 intracellular signalling pathways, CSPG-DS induced neurite outgrowth and protected against neuronal toxicity and axonal collapse in vitro. In microglia, via a mechanism that involves ERK1/2 and PYK2, CSPG-DS evoked a response that allowed these cells to manifest a neuroprotective phenotype ex vivo. In vivo, systemically or locally injected CSPG-DS protected neurons in mice subjected to glutamate or aggregated beta-amyloid intoxication. Our results suggest that treatment with CSPG-DS might provide a way to promote post-traumatic recovery, via multiple cellular targets.

Structural and Functional Characterization of Oversulfated Chondroitin Sulfate/Dermatan Sulfate Hybrid Chains from the Notochord of Hagfish

Oversulfated chondroitin sulfate (CS)/dermatan sulfate (DS) hybrid chains were purified from the notochord of hagfish. The chains (previously named CS-H for hagfish) have an average molecular mass of 18 kDa. Composition analysis using various chondroitinases demonstrated a variety of D-glucuronic acid (GlcUA)- and L-iduronic acid (IdoUA)-containing disaccharides variably sulfated with a higher proportion of GlcUA/IdoUA-GalNAc 4,6-O-disulfate, revealing complex CS/DS hybrid features. The hybrid chains showed neurite outgrowth-promoting activity of an axonic nature, which resembled the activity of squid cartilage CS-E and which was abolished fully by chondroitinase ABC digestion and partially by chondroitinase AC-I or B digestion, suggesting the involvement of both GlcUA and IdoUA in neuritogenic activity. Purified CS-H exhibited interactions in a BIAcore system with various heparin-binding proteins and neurotrophic factors (viz. fibroblast growth factor-2, -10, -16, and -18; midkine; pleiotrophin; heparin-binding epidermal growth factor-like growth factor; vascular endothelial growth factor; brain-derived neurotrophic factor; and glial cell line-derived neurotrophic factor), most of which are expressed in the brain, although fibroblast growth factor-1 and ciliary neurotrophic factor showed no binding. Kinetic analysis revealed high affinity binding of these growth factors and, for the first time, of the neurotrophic factors. Competitive inhibition revealed the involvement of both IdoUA and GlcUA in the binding of these growth factors, suggesting the importance of the hybrid nature of CS-H for the efficient binding of these growth factors. These findings, together with those from the recent analysis of brain CS/DS chains from neonatal mouse and embryonic pig (Bao, X., Nishimura, S., Mikami, T., Yamada, S., Itoh, N., and Sugahara, K. (2004) J. Biol. Chem. 279, 9765-9776), suggest physiological roles of the hybrid chains in the development of the brain.

Novel 70-kDa chondroitin sulfate/dermatan sulfate hybrid chains with a unique heterogeneous sulfation pattern from shark skin, which exhibit neuritogenic activity and binding activities for growth factors and neurotrophic factors

Chondroitin sulfate (CS) and dermatan sulfate (DS) hybrid chains of proteoglycans are critical in growth factor binding, neuritogenesis, and brain development. Here we isolated CS/DS hybrid chains from shark skin aiming to develop therapeutic agents. Digestion with various chondroitinases showed that both GlcUA- and IdoUA-containing disaccharides are scattered along the polysaccharide chains with an unusually large average molecular mass of 70 kDa. The CS/DS chains were separated into major (80%) and minor (20%) fractions by anion-exchange chromatography. Both fractions had relatively low degrees of sulfation (sulfate/disaccharide molar ratio=1.17 versus 0.87), showing a unique feature compared with the marine CS and DS isolated to date, most of which are oversulfated. They were highly heterogeneous and characterized by multiple disaccharides including GlcUA-GalNAc, GlcUA-GalNAc(6S), GlcUA-GalNAc(4S), IdoUA-GalNAc(4S), GlcUA-GalNAc(4S,6S), IdoUA-GalNAc(4S,6S), GlcUA(2S)-GalNAc(6S), and/or IdoUA(2S)-GalNAc(6S), IdoUA(2S)-GalNAc(4S) and novel GlcUA(2S)-GalNAc(4S), where 2S, 4S, and 6S represent 2-O-, 4-O- and 6-O-sulfate, respectively. The CS/DS chains bound two neurotrophic factors and various growth factors expressed in the brain with high affinity as evaluated for the major fraction by kinetic analysis using a surface plasmon resonance detector, and also promoted the outgrowth of neurites of both an axonic and a dendritic nature. The neuritogenic activity was abolished completely by digestion with chondroitinase ABC, AC-I, or B, suggesting the importance of both GlcUA- and IdoUA-containing moieties. It also showed anti-heparin cofactor II activity comparable to that exhibited by DS from porcine skin. Thus, by virtue of its unique structure and biological activities, DS will find a potential use in therapeutics.