Sulfotransferases in glycosaminoglycan biosynthesis

PAPST1 regulates sulfation of heparan sulfate proteoglycans in epithelial MDCK II cells

Proteoglycan (PG) sulfation depends on activated nucleotide sulfate, 3'-phosphoadenosine-5'-phosphosulfate (PAPS). Transporters in the Golgi membrane translocate PAPS from the cytoplasm into the organelle lumen where PG sulfation occurs. Silencing of PAPS transporter (PAPST) 1 in epithelial MDCK cells reduced PAPS uptake into Golgi vesicles. Surprisingly, at the same time sulfation of heparan sulfate (HS) was stimulated. The effect was pathway specific in polarized epithelial cells. Basolaterally secreted proteoglycans (PGs) displayed an altered HS sulfation pattern and increased growth factor binding capacity. In contrast, the sulfation pattern of apically secreted PGs was unchanged while the secretion was reduced. Regulation of PAPST1 allows epithelial cells to prioritize between PG sulfation in the apical and basolateral secretory routes at the level of the Golgi apparatus. This provides sulfation patterns that ensure PG functions at the extracellular level, such as growth factor binding.

A novel eliminase from a marine bacterium that degrades hyaluronan and chondroitin sulfate

Lyases cleave glycosaminoglycans (GAGs) in an eliminative mechanism and are important tools for the structural analysis and oligosaccharide preparation of GAGs. Various GAG lyases have been identified from terrestrial but not marine organisms even though marine animals are rich in GAGs with unique structures and functions. Herein we isolated a novel GAG lyase for the first time from the marine bacterium Vibrio sp. FC509 and then recombinantly expressed and characterized it. It showed strong lyase activity toward hyaluronan (HA) and chondroitin sulfate (CS) and was designated as HA and CS lyase (HCLase). It exhibited the highest activities to both substrates at pH 8.0 and 0.5 m NaCl at 30 °C. Its activity toward HA was less sensitive to pH than its CS lyase activity. As with most other marine enzymes, HCLase is a halophilic enzyme and very stable at temperatures from 0 to 40 °C for up to 24 h, but its activity is independent of divalent metal ions. The specific activity of HCLase against HA and CS reached a markedly high level of hundreds of thousands units/mg of protein under optimum conditions. The HCLase-resistant tetrasaccharide Δ(4,5)HexUAα1-3GalNAc(6-O-sulfate)β1-4GlcUA(2-O-sulfate)β1-3GalNAc(6-O-sulfate) was isolated from CS-D, the structure of which indicated that HCLase could not cleave the galactosaminidic linkage bound to 2-O-sulfated d-glucuronic acid (GlcUA) in CS chains. Site-directed mutagenesis indicated that HCLase may work via a catalytic mechanism in which Tyr-His acts as the Brønsted base and acid. Thus, the identification of HCLase provides a useful tool for HA- and CS-related research and applications.

Endothelial and leukocyte heparan sulfates regulate the development of allergen-induced airway remodeling in a mouse model

Heparan sulfate (HS) proteoglycans (HSPGs) participate in several aspects of inflammation because of their ability to bind to growth factors, chemokines, interleukins and extracellular matrix proteins as well as promote inflammatory cell trafficking and migration. We investigated whether HSPGs play a role in the development of airway remodeling during chronic allergic asthma using mice deficient in endothelial- and leukocyte-expressed N-deacetylase/N-sulfotransferase-1 (Ndst1), an enzyme involved in modification reactions during HS biosynthesis. Ndst1-deficient and wild-type (WT) mice exposed to repetitive allergen (ovalbumin [OVA]) challenge were evaluated for the development of airway remodeling. Chronic OVA-challenged WT mice exhibited increased HS expression in the lungs along with airway eosinophilia, mucus hypersecretion, peribronchial fibrosis, increased airway epithelial thickness and smooth muscle mass. In OVA-challenged Ndst1-deficient mice, lung eosinophil and macrophage infiltration as well as airway mucus accumulation, peribronchial fibrosis and airway epithelial thickness were significantly lower than in allergen-challenged WT mice along with a trend toward decreased airway smooth muscle mass. Leukocyte and endothelial Ndst 1 deficiency also resulted in significantly decreased expression of IL-13 as well as remodeling-associated mediators such as VEGF, FGF-2 and TGF-β1 in the lung tissue. At a cellular level, exposure to eotaxin-1 failed to induce TGF-β1 expression by Ndst1-deficient eosinophils relative to WT eosinophils. These studies suggest that leukocyte and endothelial Ndst1-modified HS contribute to the development of allergen-induced airway remodeling by promoting recruitment of inflammatory cells as well as regulating expression of pro-remodeling factors such as IL-13, VEGF, TGF-β1 and FGF-2 in the lung.

Myocardial extracellular matrix: an ever-changing and diverse entity

The cardiac extracellular matrix (ECM) is a complex architectural network consisting of structural and nonstructural proteins, creating strength and plasticity. The nonstructural compartment of the ECM houses a variety of proteins, which are vital for ECM plasticity, and can be divided into 3 major groups: glycoproteins, proteoglycans, and glycosaminoglycans. The common denominator for these groups is glycosylation, which refers to the decoration of proteins or lipids with sugars. This review will discuss the fundamental role of the matrix in cardiac development, homeostasis, and remodeling, from a glycobiology point of view. Glycoproteins (eg, thrombospondins, secreted protein acidic and rich in cysteine, tenascins), proteoglycans (eg, versican, syndecans, biglycan), and glycosaminoglycans (eg, hyaluronan, heparan sulfate) are upregulated on cardiac injury and regulate key processes in the remodeling myocardium such as inflammation, fibrosis, and angiogenesis. Albeit some parallels can be made regarding the processes these proteins are involved in, their specific functions are extremely diverse. In fact, under varying conditions, individual proteins can even have opposing functions, making spatiotemporal contribution of these proteins in the rearrangement of multifaceted ECM very hard to grasp. Alterations of protein characteristics by the addition of sugars may explain the immense, yet tightly regulated, variability of the remodeling cardiac matrix. Understanding the role of glycosylation in altering the ultimate function of glycoproteins, proteoglycans, and glycosaminoglycans in the myocardium may lead to the development of new biochemical structures or compounds with great therapeutic potential for patients with heart disease.

Biphasic role of chondroitin sulfate in cardiac differentiation of embryonic stem cells through inhibition of Wnt/β-catenin signaling

The glycosaminoglycan chondroitin sulfate is a critical component of proteoglycans on the cell surface and in the extracellular matrix. As such, chondroitin sulfate side chains and the sulfation balance of chondroitin play important roles in the control of signaling pathways, and have a functional importance in human disease. In contrast, very little is known about the roles of chondroitin sulfate molecules and sulfation patterns during mammalian development and cell lineage specification. Here, we report a novel biphasic role of chondroitin sulfate in the specification of the cardiac cell lineage during embryonic stem cell differentiation through modulation of Wnt/beta-catenin signaling. Lineage marker analysis demonstrates that enzymatic elimination of endogenous chondroitin sulfates leads to defects specifically in cardiac differentiation. This is accompanied by a reduction in the number of beating cardiac foci. Mechanistically, we show that endogenous chondroitin sulfate controls cardiac differentiation in a temporal biphasic manner through inhibition of the Wnt/beta-catenin pathway, a known regulatory pathway for the cardiac lineage. Treatment with a specific exogenous chondroitin sulfate, CS-E, could mimic these biphasic effects on cardiac differentiation and Wnt/beta-catenin signaling. These results establish chondroitin sulfate and its sulfation balance as important regulators of cardiac cell lineage decisions through control of the Wnt/beta-catenin pathway. Our work suggests that targeting the chondroitin biosynthesis and sulfation machinery is a novel promising avenue in regenerative strategies after heart injury.

Chondrocyte culture in three dimensional alginate sulfate hydrogels promotes proliferation while maintaining expression of chondrogenic markers

The loss of expression of chondrogenic markers during monolayer expansion remains a stumbling block for cell-based treatment of cartilage lesions. Here, we introduce sulfated alginate hydrogels as a cartilage biomimetic biomaterial that induces cell proliferation while maintaining the chondrogenic phenotype of encapsulated chondrocytes. Hydroxyl groups of alginate were converted to sulfates by incubation with sulfur trioxide-pyridine complex (SO3/pyridine), yielding a sulfated material cross-linkable with calcium chloride. Passage 3 bovine chondrocytes were encapsulated in alginate and alginate sulfate hydrogels for up to 35 days. Cell proliferation was five-fold higher in alginate sulfate compared with alginate (p=0.038). Blocking beta1 integrins in chondrocytes within alginate sulfate hydrogels significantly inhibited proliferation (p=0.002). Sulfated alginate increased the RhoA activity of chondrocytes compared with unmodified alginate, an increase that was blocked by β1 blocking antibodies (p=0.017). Expression and synthesis of type II collagen, type I collagen, and proteoglycan was not significantly affected by the encapsulation material evidenced by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemistry. Alginate sulfate constructs showed an opaque appearance in culture, whereas the unmodified alginate samples remained translucent. In conclusion, alginate sulfate provides a three dimensional microenvironment that promotes both chondrocyte proliferation and maintenance of the chondrogenic phenotype and represents an important advance for chondrocyte-based cartilage repair therapies providing a material in which cell expansion can be done in situ.

Legionella oakridgensis ATCC 33761 genome sequence and phenotypic characterization reveals its replication capacity in amoebae

Legionella oakridgensis is able to cause Legionnaires' disease, but is less virulent compared to L. pneumophila strains and very rarely associated with human disease. L. oakridgensis is the only species of the family legionellae which is able to grow on media without additional cysteine. In contrast to earlier publications, we found that L. oakridgensis is able to multiply in amoebae. We sequenced the genome of L. oakridgensis type strain OR-10 (ATCC 33761). The genome is smaller than the other yet sequenced Legionella genomes and has a higher G+C-content of 40.9%. L. oakridgensis lacks a flagellum and it also lacks all genes of the flagellar regulon except of the alternative sigma-28 factor FliA and the anti-sigma-28 factor FlgM. Genes encoding structural components of type I, type II, type IV Lvh and type IV Dot/Icm, Sec- and Tat-secretion systems could be identified. Only a limited set of Dot/Icm effector proteins have been recognized within the genome sequence of L. oakridgensis. Like in L. pneumophila strains, various proteins with eukaryotic motifs and eukaryote-like proteins were detected. We could demonstrate that the Dot/Icm system is essential for intracellular replication of L. oakridgensis. Furthermore, we identified new putative virulence factors of Legionella.

Iduronic acid in chondroitin/dermatan sulfate affects directional migration of aortic smooth muscle cells

Aortic smooth muscle cells produce chondroitin/dermatan sulfate (CS/DS) proteoglycans that regulate extracellular matrix organization and cell behavior in normal and pathological conditions. A unique feature of CS/DS proteoglycans is the presence of iduronic acid (IdoA), catalyzed by two DS epimerases. Functional ablation of DS-epi1, the main epimerase in these cells, resulted in a major reduction of IdoA both on cell surface and in secreted CS/DS proteoglycans. Downregulation of IdoA led to delayed ability to re-populate wounded areas due to loss of directional persistence of migration. DS-epi1-/- aortic smooth muscle cells, however, had not lost the general property of migration showing even increased speed of movement compared to wild type cells. Where the cell membrane adheres to the substratum, stress fibers were denser whereas focal adhesion sites were fewer. Total cellular expression of focal adhesion kinase (FAK) and phospho-FAK (pFAK) was decreased in mutant cells compared to control cells. As many pathological conditions are dependent on migration, modulation of IdoA content may point to therapeutic strategies for diseases such as cancer and atherosclerosis.

Expression of chondroitin/dermatan sulfate glycosyltransferases during early zebrafish development

BACKGROUND

Chondroitin/dermatan sulfate (CS/DS) proteoglycans present in the extracellular matrix have important structural and regulatory functions.

RESULTS

Six human genes have previously been shown to catalyze CS/DS polymerization. Here we show that one of these genes, chpf, is represented by two copies in the zebrafish genome, chpfa and chpfb, while the other five human CS/DS glycosyltransferases csgalnact1, csgalnact2, chpf2, chsy1, and chsy3 all have single zebrafish orthologues. The putative zebrafish CS/DS glycosyltransferases are spatially and temporally expressed. Interestingly, overlapping expression of multiple glycosyltransferases coincides with high CS/DS deposition. Finally, whereas the relative levels of the related polysaccharide HS reach steady-state at around 2 days post fertilization, there is a continued relative increase of the CS amounts per larvae during the first 6 days of development, matching the increased cartilage formation.

CONCLUSIONS

There are 7 CS/DS glycosyltransferases in zebrafish, which, based on homology, can be divided into the CSGALNACT, CHSY, and CHPF families. The overlap between intense CS/DS production and the expression of multiple CS/DS glycosyltransferases suggests that efficient CS/DS biosynthesis requires a combination of several glycosyltransferases.

Defective initiation of glycosaminoglycan synthesis due to B3GALT6 mutations causes a pleiotropic Ehlers-Danlos-syndrome-like connective tissue disorder

Proteoglycans are important components of cell plasma membranes and extracellular matrices of connective tissues. They consist of glycosaminoglycan chains attached to a core protein via a tetrasaccharide linkage, whereby the addition of the third residue is catalyzed by galactosyltransferase II (β3GalT6), encoded by B3GALT6. Homozygosity mapping and candidate gene sequence analysis in three independent families, presenting a severe autosomal-recessive connective tissue disorder characterized by skin fragility, delayed wound healing, joint hyperlaxity and contractures, muscle hypotonia, intellectual disability, and a spondyloepimetaphyseal dysplasia with bone fragility and severe kyphoscoliosis, identified biallelic B3GALT6 mutations, including homozygous missense mutations in family 1 (c.619G>C [p.Asp207His]) and family 3 (c.649G>A [p.Gly217Ser]) and compound heterozygous mutations in family 2 (c.323_344del [p.Ala108Glyfs(∗)163], c.619G>C [p.Asp207His]). The phenotype overlaps with several recessive Ehlers-Danlos variants and spondyloepimetaphyseal dysplasia with joint hyperlaxity. Affected individuals' fibroblasts exhibited a large decrease in ability to prime glycosaminoglycan synthesis together with impaired glycanation of the small chondroitin/dermatan sulfate proteoglycan decorin, confirming β3GalT6 loss of function. Dermal electron microcopy disclosed abnormalities in collagen fibril organization, in line with the important regulatory role of decorin in this process. A strong reduction in heparan sulfate level was also observed, indicating that β3GalT6 deficiency alters synthesis of both main types of glycosaminoglycans. In vitro wound healing assay revealed a significant delay in fibroblasts from two index individuals, pointing to a role for glycosaminoglycan defect in impaired wound repair in vivo. Our study emphasizes a crucial role for β3GalT6 in multiple major developmental and pathophysiological processes.

Loss of dermatan sulfate epimerase (DSE) function results in musculocontractural Ehlers-Danlos syndrome

The sulfated polysaccharide dermatan sulfate (DS) forms proteoglycans with a number of distinct core proteins. Iduronic acid-containing domains in DS have a key role in mediating the functions of DS proteoglycans. Two tissue-specific DS epimerases, encoded by DSE and DSEL, and a GalNAc-4-O-sulfotransferase encoded by CHST14 are necessary for the formation of these domains. CHST14 mutations were previously identified for patients with the musculocontractural type of Ehlers-Danlos syndrome (MCEDS). We now identified a homozygous DSE missense mutation (c.803C>T, p.S268L) by the positional candidate approach in a male child with MCEDS, who was born to consanguineous parents. Heterologous expression of mutant full-length and soluble recombinant DSE proteins showed a loss of activity towards partially desulfated DS. Patient-derived fibroblasts also showed a significant reduction in epimerase activity. The amount of DS disaccharides was markedly decreased in the conditioned medium and the cell fraction from cultured fibroblasts of the patient when compared with a healthy control subject, whereas no apparent difference was observed in the chondroitin sulfate (CS) chains from the conditioned media. However, the total amount of CS disaccharides in the cell fraction from the patient was increased ∼1.5-fold, indicating an increased synthesis or a reduced conversion of CS chains in the cell fraction. Stable transfection of patient fibroblasts with a DSE expression vector increased the amount of secreted DS disaccharides. DSE deficiency represents a specific defect of DS biosynthesis. We demonstrate locus heterogeneity in MCEDS and provide evidence for the importance of DS in human development and extracellular matrix maintenance.

Neural stem cell survival factors

Neural stem and progenitor cells (NSCs and NPs) give rise to the central nervous system (CNS) during embryonic development. NSCs and NPs differentiate into three main cell-types of the CNS; astrocytes, oligodendrocytes, and neurons. NSCs are present in the adult CNS and are important in maintenance and repair. Adult NSCs hold great promise for endogenous or self-repair of the CNS. Intriguingly, NSCs have been implicated as the cells that give rise to brain tumors. Thus, the balance between survival, growth and differentiation is a critical aspect of NSC biology, during development, in the adult, and in disease processes. In this review, we survey what is known about survival factors that control both embryonic and adult NSCs. We discuss the neurosphere culture system as this is widely used to measure NSC activity and behavior in vitro and emphasize the importance of clonality. We define here NSC survival factors in their broadest sense to include any factor that influences survival and proliferation of NSCs and NPs. NSC survival factors identified to date include growth factors, morphogens, proteoglycans, cytokines, hormones, and neurotransmitters. Understanding NSC and NP interaction in response to these survival factors will provide insight to CNS development, disease and repair.

Expression of N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase involved in chondroitin sulfate synthesis is responsible for pulmonary metastasis

Chondroitin sulfate (CS) containing E-disaccharide units, glucuronic acid-N-acetylgalactosamine(4, 6-O-disulfate), at surfaces of tumor cells plays a key role in tumor metastasis. However, the molecular mechanism of the metastasis involving the CS chain-containing E-units is not fully understood. In this study, to clarify the role of E-units in the metastasis and to search for potential molecular targets for anticancer drugs, the isolation and characterization of Lewis lung carcinoma (LLC) cells stably downregulated by the knockdown for the gene encoding N-acetylgalactosamine 4-O-sulfate 6-O-sulfotransferase (GalNAc4S-6ST), which is responsible for the formation of E-units in CS chains, were performed. Knockdown of GalNAc4S-6ST in LLC cells resulted in a reduction in the proportion of E-units, in adhesiveness to extracellular matrix adhesion molecules and in proliferation in vitro. Furthermore, the stable downregulation of GalNAc4S-6ST expression in LLC cells markedly inhibited the colonization of the lungs by inoculated LLC cells and invasive capacity of LLC cells. These results provide clear evidence that CS chain-containing E-units and/or GalNAc4S-6ST play a crucial role in pulmonary metastasis at least through the increased adhesion and the invasive capacity of LLC cells and also provides insights into future drug targets for anticancer treatment.

A New C-Xyloside induces modifications of GAG expression, structure and functional properties

Proteoglycans (PGs) are critically involved in major cellular processes. Most PG activities are due to the large interactive properties of their glycosaminoglycan (GAG) polysaccharide chains, whose expression and fine structural features are tightly controlled by a complex and highly regulated biosynthesis machinery. Xylosides are known to bypass PG-associated GAG biosynthesis and prime the assembly of free polysaccharide chains. These are, therefore, attractive molecules to interfere with GAG expression and function. Recently, we have developed a new xyloside derivative, C-Xyloside, that shares classical GAG-inducing xyloside activities while exhibiting improved metabolic stability. We have previously shown that C-Xyloside had beneficial effects on skin homoeostasis/regeneration using a number of models, but its precise effects on GAG expression and fine structure remained to be addressed. In this study, we have therefore investigated this in details, using a reconstructed dermal tissue as model. Our results first confirmed that C-Xyloside strongly enhanced synthesis of GAG chains, but also induced significant changes in their structure. C-Xyloside primed GAGs were exclusively chondroitin/dermatan sulfate (CS/DS) that featured reduced chain size, increased O-sulfation, and changes in iduronate content and distribution. Surprisingly, C-Xyloside also affected PG-borne GAGs, the main difference being observed in CS/DS 4-O/6-O-sulfation ratio. Such changes were found to affect the biological properties of CS/DS, as revealed by the significant reduction in binding to Hepatocyte Growth Factor observed upon C-Xyloside treatment. Overall, this study provides new insights into the effect of C-Xyloside on GAG structure and activities, which opens up perspectives and applications of such compound in skin repair/regeneration. It also provides a new illustration about the use of xylosides as tools for modifying GAG fine structure/function relationships.

Structural remodeling of proteoglycans upon retinoic acid-induced differentiation of NCCIT cells

Pluripotent and multipotent cells become increasingly lineage restricted through differentiation. Alterations to the cellular proteoglycan composition and structure should accompany these changes to influence cell proliferation, delineation of tissues and acquisition of cell migration capabilities. Retinoic acid plays an important role in pre-patterning of the early embryo. Retinoic acid can be used in vitro to induce differentiation, causing pluripotent and multipotent cells to become increasingly lineage restricted. We examined retinoic acid-induced changes in the cellular proteoglycan composition of the well-characterized teratocarcinoma line NCCIT. Our analysis revealed changes in the abundance of transcripts for genes encoding core proteins, enzymes that are responsible for early and late linkage region biosynthesis, as well as enzymes for GAG chain extension and modification. Transcript levels for genes encoding core proteins used as backbones for polysaccharide synthesis revealed highly significant increases in expression of lumican and decorin, 1,500-fold and 2,800-fold, respectively. Similarly, glypican 3, glypican 5, versican and glypican 6 showed increases between 5 and 70-fold. Significant decreases in biglycan, serglycin, glypican 4, aggrecan, neurocan, CD74 and glypican 1 were observed. Disaccharide analysis of the glycans in heparin/heparan sulfate and chondroitin/dermatan sulfate revealed retinoic acid-induced changes restricted to chondroitin/dermatan sulfate glycans. Our study provides the first detailed analysis of changes in the glycosaminoglycan profile of human pluripotent cells upon treatment with the retinoic acid morphogen.

Proteoglycan synthesis and Golgi organization in polarized epithelial cells

A large number of complex glycosylation mechanisms take place in the Golgi apparatus. In epithelial cells, glycosylated protein molecules are transported to both the apical and the basolateral surface domains. Although the prevailing view is that the Golgi apparatus provides the same lumenal environment for glycosylation of apical and basolateral cargo proteins, there are indications that proteoglycans destined for the two opposite epithelial surfaces are exposed to different conditions in transit through the Golgi apparatus. We will here review data relating proteoglycan and glycoprotein synthesis to characteristics of the apical and basolateral secretory pathways in epithelial cells.

Estrogen affects the glycosaminoglycan layer of the murine bladder

OBJECTIVES

Urinary tract infections (UTIs), commonly caused by uropathogenic Escherichia coli (UPEC), confer significant morbidity among postmenopausal women. Glycosaminoglycans (GAGs) comprise the first line of defense at the bladder's luminal surface. Our objective was to use a murine model of menopause to determine whether estrogen status affects the GAG layer in response to UPEC infection.

METHODS

Adult female mice underwent sham surgery (SHAM, n = 18) or oophorectomy (OVX, n = 66) to establish a murine model of menopause. A subset of oophorectomized mice underwent hormone therapy (HT, n = 33) with 17β-estradiol. Mice were inoculated with UPEC and killed at various time points; bladders were collected and GAG layer thickness was assessed in multiple bladder sections. Sixteen measurements were made per bladder. A repeated-measures 2-way analysis of variance was performed to determine the effect of time after infection and hormonal condition on GAG thickness. We also investigated the molecular underpinnings of GAG biosynthesis in response to alterations in estrogen status and infection.

RESULTS

We did not observe significant difference of GAG thickness among the 3 hormonal conditions; however, the time course of GAG thickness was significantly different (P < 0.05). The OVX mice demonstrated significantly greater thickness at 72 hours after infection (P = 0.0001), and this effect was shifted earlier (24 hours after infection) on the addition of HT (P = 0.001). At 2 to 4 weeks after infection, GAG thickness among all cohorts was not significantly different from baseline. In addition, quantitative reverse transcription-polymerase chain reaction analysis revealed that GAG biosynthesis is altered by estrogen status at basal level and on infection.

CONCLUSIONS

The GAG layer is dynamically altered during the course of UTI. Our data show that HT positively regulates GAG layer thickness over time, as well as the composition of the GAGs. In addition, the GAG sulfation status can be influenced by estrogen levels in response to UPEC infection. The protective effects of the GAG layer in UTI may represent pharmacologic targets for the treatment and prevention of postmenopausal UTI.

Understanding the substrate specificity of the heparan sulfate sulfotransferases by an integrated biosynthetic and crystallographic approach

Heparan sulfates (HSs) have potential therapeutic value as anti-inflammatory and antimetastasis drugs, in addition to their current use as anticoagulants. Recent advances in chemoenzymatic synthesis of HS provide a way to conveniently produce homogenous HS with different biological properties. Crystal structures of sulfotransferases involved in this process are providing atomic detail of their substrate binding clefts and interactions with their HS substrates. In theory, the flexibility of this method can be increased by modifying the specificities of the sulfotransferases based on the structures, thereby producing a new array of products.

Normal sulfation levels regulate spinal cord neural precursor cell proliferation and differentiation

Background

Sulfated glycosaminoglycan chains are known for their regulatory functions during neural development and regeneration. However, it is still unknown whether the sulfate residues alone influence, for example, neural precursor cell behavior or whether they act in concert with the sugar backbone. Here, we provide evidence that the unique 473HD-epitope, a representative chondroitin sulfate, is expressed by spinal cord neural precursor cells in vivo and in vitro, suggesting a potential function of sulfated glycosaminoglycans for spinal cord development.

Results

Thus, we applied the widely used sulfation inhibitor sodium chlorate to analyze the importance of normal sulfation levels for spinal cord neural precursor cell biology in vitro. Addition of sodium chlorate to spinal cord neural precursor cell cultures affected cell cycle progression accompanied by changed extracellular signal-regulated kinase 1 or 2 activation levels. This resulted in a higher percentage of neurons already under proliferative conditions. In contrast, the relative number of glial cells was largely unaffected. Strikingly, both morphological and electrophysiological characterization of neural precursor cell-derived neurons demonstrated an attenuated neuronal maturation in the presence of sodium chlorate, including a disturbed neuronal polarization.

Conclusions

In summary, our data suggest that sulfation is an important regulator of both neural precursor cell proliferation and maturation of the neural precursor cell progeny in the developing mouse spinal cord.

Expression of heparan sulfate proteoglycans in murine models of experimental colitis

BACKGROUND

Heparan sulfate proteoglycans (HSPGs) are considered important in maintaining physiological homeostasis in many systems. Their expression is altered greatly in several pathophysiological conditions. Herein, we assess the expression and cellular localization of HSPGs in two murine models of human inflammatory bowel disease (IBD).

METHODS

Expression and localization of HSPGs, syndecans, and HS epitopes were examined in the colon of 129SvEv interleukin 10 knockout (IL10(-/-)), C3Bir IL10(-/-), and their genetic control (IL10(+/+)) counterparts (129SvEv; C3H/HeJ). mRNA expression of syndecans and heparan sulfate biosynthesis enzymes were evaluated by real-time polymerase chain reaction (PCR). Localization of HSPGs was determined by immunofluorescence.

RESULTS

mRNA for all syndecans was detected and expression in colonic tissues altered in IL10(-/-) mice. Syndecan-1 protein was expressed in the intestinal epithelium and on lamina propria cells of IL10(-/-) and control mice but was significantly reduced on the intestinal epithelial cells of IL10(-/-), mice particularly with severe colitis. Syndecan-2 was not detected, whereas syndecan-3 immunoreactivity was localized in the lamina propria but did not differ between control and IL10(-/-) mice. Syndecan-4 was present on epithelial cells of all mice but was significantly reduced in IL10(-/-) mice. Differences in the expression of HS epitopes between control and IL10(-/-) mice were also confirmed.

CONCLUSIONS

The study has revealed altered expression of syndecan-1 and -4 and HS epitopes in the gut of mice with an IBD-like gut disorder. The IL10(-/-) mouse is a useful model for further study of the functional role of HSPGs in chronic inflammation and in maintaining healthy gut barrier.

Mechanistic overview of reactive species-induced degradation of the endothelial glycocalyx during hepatic ischemia/reperfusion injury

Endothelial cells are covered by a delicate meshwork of glycoproteins known as the glycocalyx. Under normophysiological conditions the glycocalyx plays an active role in maintaining vascular homeostasis by deterring primary and secondary hemostasis and leukocyte adhesion and by regulating vascular permeability and tone. During (micro)vascular oxidative and nitrosative stress, which prevails in numerous metabolic (diabetes), vascular (atherosclerosis, hypertension), and surgical (ischemia/reperfusion injury, trauma) disease states, the glycocalyx is oxidatively and nitrosatively modified and degraded, which culminates in an exacerbation of the underlying pathology. Consequently, glycocalyx degradation due to oxidative/nitrosative stress has far-reaching clinical implications. In this review the molecular mechanisms of reactive oxygen and nitrogen species-induced destruction of the endothelial glycocalyx are addressed in the context of hepatic ischemia/reperfusion injury as a model disease state. Specifically, the review focuses on (i) the mechanisms of glycocalyx degradation during hepatic ischemia/reperfusion, (ii) the molecular and cellular players involved in the degradation process, and (iii) its implications for hepatic pathophysiology. These topics are projected against a background of liver anatomy, glycocalyx function and structure, and the biology/biochemistry and the sources/targets of reactive oxygen and nitrogen species. The majority of the glycocalyx-related mechanisms elucidated for hepatic ischemia/reperfusion are extrapolatable to the other aforementioned disease states.

C4ST-1/CHST11-controlled chondroitin sulfation interferes with oncogenic HRAS signaling in Costello syndrome

Costello syndrome is a pediatric genetic disorder linked to oncogenic germline mutations in the HRAS gene. The disease is characterized by multiple developmental abnormalities, as well as predisposition to malignancies. Our recent observation that heart tissue from patients with Costello syndrome showed a loss of the glycosaminoglycan chondroitin-4-sulfate (C4S) inspired our present study aimed to explore a functional involvement of the chondroitin sulfate (CS) biosynthesis gene Carbohydrate sulfotransferase 11/Chondroitin-4-sulfotransferase-1 (CHST11/C4ST-1), as well as an impaired chondroitin sulfation balance, as a downstream mediator of oncogenic HRAS in Costello syndrome. Here we demonstrate a loss of C4S, as well as a reduction in C4ST-1 mRNA and protein expression, in primary fibroblasts from Costello syndrome patients. We go on to show that expression of oncogenic HRAS in normal fibroblasts can repress C4ST-1 expression, whereas interference with oncogenic HRAS signaling in Costello syndrome fibroblasts elevated C4ST-1 expression, thus identifying C4ST-1 as a negatively regulated target gene of HRAS signaling. Importantly, we show that forced expression of C4ST-1 in Costello fibroblasts could rescue the proliferation and elastogenesis defects associated with oncogenic HRAS signaling in these cells. Our results indicate reduced C4ST-1 expression and chondroitin sulfation imbalance mediating the effects of oncogenic HRAS signaling in the pathogenesis of Costello syndrome. Thus, our work identifies C4ST-1-dependent chondroitin sulfation as a downstream vulnerability in oncogenic RAS signaling, which might be pharmacologically exploited in future treatments of not only Costello syndrome and other RASopathies, but also human cancers associated with activating RAS mutations.

Chondroitin sulfate synthase 1 (Chsy1) is required for bone development and digit patterning

Joint and skeletal development is highly regulated by extracellular matrix (ECM) proteoglycans, of which chondroitin sulfate proteoglycans (CSPGs) are a major class. Despite the requirement of joint CSPGs for skeletal flexibility and structure, relatively little is understood regarding their role in establishing joint positioning or in modulating signaling and cell behavior during joint formation. Chondroitin sulfate synthase 1 (Chsy1) is one of a family of enzymes that catalyze the extension of chondroitin and dermatan sulfate glycosaminoglycans. Recently, human syndromic brachydactylies have been described to have loss-of-function mutations at the CHSY1 locus. In concordance with these observations, we demonstrate that mice lacking Chsy1, though viable, display chondrodysplasia and decreased bone density. Notably, Chsy1(-/-) mice show a profound limb patterning defect in which orthogonally shifted ectopic joints form in the distal digits. Associated with the digit-patterning defect is a shift in cell orientation and an imbalance in chondroitin sulfation. Our results place Chsy1 as an essential regulator of joint patterning and provide a mouse model of human brachydactylies caused by mutations in CHSY1.

Chondroitin 4-O-sulfotransferase-2 regulates the number of chondroitin sulfate chains initiated by chondroitin N-acetylgalactosaminyltransferase-1

Recently, it has been shown that a deficiency in ChGn-1 (chondroitin N-acetylgalactosaminyltransferase-1) reduced the numbers of CS (chondroitin sulfate) chains, leading to skeletal dysplasias in mice. Although these results indicate that ChGn-1 regulates the number of CS chains, the mechanism mediating this regulation is not clear. ChGn-1 is thought to initiate CS biosynthesis by transferring the first GalNAc (N-acetylgalactosamine) to the tetrasaccharide in the protein linkage region of CS. However, in vitro chondroitin polymerization does not occur on the non-reducing terminal GalNAc-linkage pentasaccharide structure. In the present study we show that several different heteromeric enzyme complexes composed of different combinations of four chondroitin synthase family members synthesized more CS chains when a GalNAc-linkage pentasaccharide structure with a non-reducing terminal 4-O-sulfation was the CS acceptor. In addition, C4ST-2 (chondroitin 4-O-sulfotransferase-2) efficiently transferred sulfate from 3′-phosphoadenosine 5′-phosphosulfate to position 4 of non-reducing terminal GalNAc-linkage residues, and the number of CS chains was regulated by the expression levels of C4ST-2 and of ChGn-1. Taken together, the results of the present study indicate that C4ST-2 plays a key role in regulating levels of CS synthesized via ChGn-1.

Smad proteins differentially regulate transforming growth factor-β-mediated induction of chondroitin sulfate proteoglycans

Traumatic injury to the CNS results in increased expression and deposition of chondroitin sulfate proteoglycans (CSPGs) that are inhibitory to axonal regeneration. Transforming growth factor-β (TGF-β) has been implicated as a major mediator of these changes, but the mechanisms through which TGF-β regulates CSPG expression are not known. Using lentiviral expressed Smad-specific ShRNA we show that TGF-β induction of CSPG expression in astrocytes is Smad-dependent. However, we find a differential dependence of the synthetic machinery on Smad2 and/or Smad3. TGF-β induction of neurocan and xylosyl transferase 1 required both Smad2 and Smad3, whereas induction of phosphacan and chondroitin synthase 1 required Smad2 but not Smad3. Smad3 knockdown selectively reduced induction of chondroitin-4-sulfotransferase 1 and the amount of 4-sulfated CSPGs secreted by astrocytes. Additionally, Smad3 knockdown in astrocytes was more efficacious in promoting neurite outgrowth of neurons cultured on the TGF-β-treated astrocytes. Our data implicate TGF-β Smad3-mediated induction of 4-sulfation as a critical determinant of the permissiveness of astrocyte secreted CSPGs for axonal growth.

Involvement of human natural killer-1 (HNK-1) sulfotransferase in the biosynthesis of the GlcUA(3-O-sulfate)-Gal-Gal-Xyl tetrasaccharide found in α-thrombomodulin from human urine

Thrombomodulin (TM) is an integral membrane glycoprotein, which occurs as both a chondroitin sulfate (CS) proteoglycan (PG) form (β-TM) and a non-PG form without a CS chain (α-TM) and hence is a part-time PG. An α-TM preparation isolated from human urine contained the glycosaminoglycan linkage region tetrasaccharide GlcUAβ1-3Galβ1-3Galβ1-4xylose, and the nonreducing terminal GlcUA residue is 3-O-sulfated. Because the human natural killer-1 sulfotransferase (HNK-1ST) transfers a sulfate group from 3'-phosphoadenosine 5'-phosphosulfate to the C-3 position of the nonreducing terminal GlcUA residue in the HNK-1 antigen precursor trisaccharide, GlcUAβ1-3Galβ1-4GlcNAc, the sulfotransferase activity toward the linkage region was investigated. In fact, the activity of HNK-1ST toward the linkage region was much higher than that toward the glucuronylneolactotetraosylceramide, the precursor of the HNK-1 epitope. HNK-1ST may be responsible for regulating the sorting of α- and β-TM. Furthermore, HNK-1ST also transferred a sulfate group from 3'-phosphoadenosine 5'-phosphosulfate to the C-3 position of the nonreducing terminal GlcUA residue of a chondroitin chain. Intriguingly, the HNK-1 antibody recognized CS chains and the linkage region if they contained GlcUA(3-O-sulfate), suggesting that HNK-1ST not only synthesizes the HNK-1 epitope but may also be involved in the generation of part-time PGs.

Chondroitin sulfates play a major role in breast cancer metastasis: a role for CSPG4 and CHST11 gene expression in forming surface P-selectin ligands in aggressive breast cancer cells

Introduction

We have previously demonstrated that chondroitin sulfate glycosaminoglycans (CS-GAGs) on breast cancer cells function as P-selectin ligands. This study was performed to identify the carrier proteoglycan (PG) and the sulfotransferase gene involved in synthesis of the surface P-selectin-reactive CS-GAGs in human breast cancer cells with high metastatic capacity, as well as to determine a direct role for CS-GAGs in metastatic spread.

Methods

Quantitative real-time PCR (qRT-PCR) and flow cytometry assays were used to detect the expression of genes involved in the sulfation and presentation of chondroitin in several human breast cancer cell lines. Transient transfection of the human breast cancer cell line MDA-MB-231 with the siRNAs for carbohydrate (chondroitin 4) sulfotransferase-11 (CHST11) and chondroitin sulfate proteoglycan 4 (CSPG4 ) was used to investigate the involvement of these genes in expression of surface P-selectin ligands. The expression of CSPG4 and CHST11 in 15 primary invasive breast cancer clinical specimens was assessed by qRT-PCR. The role of CS-GAGs in metastasis was tested using the 4T1 murine mammary cell line (10 mice per group).

Results

The CHST11 gene was highly expressed in aggressive breast cancer cells but significantly less so in less aggressive breast cancer cell lines. A positive correlation was observed between the expression levels of CHST11 and P-selectin binding to cells (P < 0.0001). Blocking the expression of CHST11 with siRNA inhibited CS-A expression and P-selectin binding to MDA-MB-231 cells. The carrier proteoglycan CSPG4 was highly expressed on the aggressive breast cancer cell lines and contributed to the P-selectin binding and CS-A expression. In addition, CSPG4 and CHST11 were over-expressed in tumor-containing clinical tissue specimens compared with normal tissues. Enzymatic removal of tumor-cell surface CS-GAGs significantly inhibited lung colonization of the 4T1 murine mammary cell line (P = 0.0002).

Conclusions

Cell surface P-selectin binding depends on CHST11 gene expression. CSPG4 serves as a P-selectin ligand through its CS chain and participates in P-selectin binding to the highly metastatic breast cancer cells. Removal of CS-GAGs greatly reduces metastatic lung colonization by 4T1 cells. The data strongly indicate that CS-GAGs and their biosynthetic pathways are promising targets for the development of anti-metastatic therapies.

Differential use of chondroitin sulfate to regulate hyaluronan binding by receptor CD44 in Inflammatory and Interleukin 4-activated Macrophages

CD44 is a cell surface receptor for the extracellular matrix glycosaminoglycan hyaluronan and is involved in processes ranging from leukocyte recruitment to wound healing. In the immune system, the binding of hyaluronan to CD44 is tightly regulated, and exposure of human peripheral blood monocytes to inflammatory stimuli increases CD44 expression and induces hyaluronan binding. Here we sought to understand how mouse macrophages regulate hyaluronan binding upon inflammatory and anti-inflammatory stimuli. Mouse bone marrow-derived macrophages stimulated with tumor necrosis factor α or lipopolysaccharide and interferon-γ (LPS/IFNγ) induced hyaluronan binding by up-regulating CD44 and down-regulating chondroitin sulfation on CD44. Hyaluronan binding was induced to a lesser extent in interleukin-4 (IL-4)-activated macrophages despite increased CD44 expression, and this was attributable to increased chondroitin sulfation on CD44, as treatment with β-d-xyloside to prevent chondroitin sulfate addition significantly enhanced hyaluronan binding. These changes in the chondroitin sulfation of CD44 were associated with changes in mRNA expression of two chondroitin sulfotransferases, CHST3 and CHST7, which were decreased in LPS/IFNγ-stimulated macrophages and increased in IL-4-stimulated macrophages. Thus, inflammatory and anti-inflammatory stimuli differentially regulate the chondroitin sulfation of CD44, which is a dynamic physiological regulator of hyaluronan binding by CD44 in mouse macrophages.

Chondroitin 4-O-sulfotransferase-1 regulates the chain length of chondroitin sulfate in co-operation with chondroitin N-acetylgalactosaminyltransferase-2

Previously, we demonstrated that sog9 cells, a murine L cell mutant, are deficient in the expression of C4ST (chondroitin 4-O-sulfotransferase)-1 and that they synthesize fewer and shorter CS (chondroitin sulfate) chains. These results suggested that C4ST-1 regulates not only 4-O-sulfation of CS, but also the length and amount of CS chains; however, the mechanism remains unclear. In the present study, we have demonstrated that C4ST-1 regulates the chain length and amount of CS in co-operation with ChGn-2 (chondroitin N-acetylgalactosaminyltransferase 2). Overexpression of ChGn-2 increased the length and amount of CS chains in L cells, but not in sog9 mutant cells. Knockdown of ChGn-2 resulted in a decrease in the amount of CS in L cells in a manner proportional to ChGn-2 expression levels, whereas the introduction of mutated C4ST-1 or ChGn-2 lacking enzyme activity failed to increase the amount of CS. Furthermore, the non-reducing terminal 4-O-sulfation of N-acetylgalactosamine residues facilitated the elongation of CS chains by chondroitin polymerase consisting of chondroitin synthase-1 and chondroitin-polymerizing factor. Overall, these results suggest that the chain length of CS is regulated by C4ST-1 and ChGn-2 and that the enzymatic activities of these proteins play a critical role in CS elongation.

A systems biology approach for the investigation of the heparin/heparan sulfate interactome

A large body of evidence supports the involvement of heparan sulfate (HS) proteoglycans in physiological processes such as development and diseases including cancer and neurodegenerative disorders. The role of HS emerges from its ability to interact and regulate the activity of a vast number of extracellular proteins including growth factors and extracellular matrix components. A global view on how protein-HS interactions influence the extracellular proteome and, consequently, cell function is currently lacking. Here, we systematically investigate the functional and structural properties that characterize HS-interacting proteins and the network they form. We collected 435 human proteins interacting with HS or the structurally related heparin by integrating literature-derived and affinity proteomics data. We used this data set to identify the topological features that distinguish the heparin/HS-interacting network from the rest of the extracellular proteome and to analyze the enrichment of gene ontology terms, pathways, and domain families in heparin/HS-binding proteins. Our analysis revealed that heparin/HS-binding proteins form a highly interconnected network, which is functionally linked to physiological and pathological processes that are characteristic of higher organisms. Therefore, we then investigated the existence of a correlation between the expansion of domain families characteristic of the heparin/HS interactome and the increase in biological complexity in the metazoan lineage. A strong positive correlation between the expansion of the heparin/HS interactome and biosynthetic machinery and organism complexity emerged. The evolutionary role of HS was reinforced by the presence of a rudimentary HS biosynthetic machinery in a unicellular organism at the root of the metazoan lineage.

Down-regulation of chondroitin 4-O-sulfotransferase-1 by Wnt signaling triggers diffusion of Wnt-3a

During metazoan development, Wnt molecules are secreted from Wnt-producing cells, diffuse to target cells, and determine cell fates; therefore, Wnt secretion is tightly regulated. However, the molecular mechanisms controlling Wnt diffusion are not fully elucidated. The specific chondroitin sulfate (CS) structure synthesized by chondroitin-4-O-sulfotransferase-1 (C4ST-1) binds to Wnt-3a with high affinity (Nadanaka, S., Ishida, M., Ikegami, M., and Kitagawa, H. (2008) J. Biol. Chem. 283, 27333-27343). In this study we tested whether Wnt signaling regulates sulfation patterns of cell-associated CS chains by suppressing expression of C4ST-1 to trigger release of Wnt molecules from Wnt-producing cells. C4ST-1 expression was dramatically reduced in L cells that stably expressed Wnt-3a (L-Wnt-3a cells) and had CS with low affinity for Wnt-3a. Forced expression of C4ST-1 in L-Wnt-3a cells inhibited diffusion of Wnt-3a due to structural alterations in CS chains mediated by C4ST-1. Furthermore, sustained Wnt signaling negatively regulated C4ST-1 expression in a cell-autonomous and non-cell autonomous fashion. These results demonstrated that C4ST-1 is a key downstream target of Wnt signaling that regulates Wnt diffusion from Wnt-producing cells.

Congenital disorders of glycosylation with emphasis on loss of dermatan-4-sulfotransferase

The autosomal, recessively inherited, adducted thumb-clubfoot syndrome (ATCS) represents a generalized connective tissue disorder with congenital malformations, contractures of thumbs and feet, and a typical facial appearance. Cognitive development is normal in ATCS patients during childhood. ATCS is caused by homozygous nonsense and missense mutations in CHST14 which encodes an N-acetylgalactosamine 4-O-sulfotransferase 1 (D4ST1) that catalyzes the 4-O-sulfation of N-acetylgalactosamine in the repeating iduronic acid-alpha-1,3-N-acetylgalactosamine disaccharide sequence to form dermatan sulfate (DS). ATCS mutations lead to either a decrease or a loss of D4ST1 activity, as revealed by absence of DS and an excess of chondroitin sulfate (CS) in patient's fibroblasts. Either of these effects or their combination might cause the observed clinical symptoms by altering the physiological pattern of dermatan and CS chains on their corresponding proteoglycans (PGs). ATCS is the only recognized disorder resulting from a defect that is specific to DS biosynthesis, and thus represents another class of the congenital glycosylation disorders. Congenital disorders of glycosylation (CDG) include all genetic diseases that result from defects in the synthesis of glycans. These disorders cause a wide range of human diseases, with examples emanating from all medical subspecialties. ATCS is the first human disorder that emphasizes a role for DS in human development and extracellular matrix maintenance.

Identification of chondroitin/dermatan sulfotransferases in the protochordate, Ciona intestinalis

Sulfated glycosaminoglycans are important components of connective tissues. The pattern of sulfation is important for their biological functions. Ascidians, the closest relatives of vertebrates, have a simple chordate body plan. In the present study, we identified an almost complete set of genes encoding proteins homologous to chondroitin/dermatan sulfotransferases in the genome of the ascidian Ciona intestinalis. We found eight genes encoding 4-O-sulfotransferases, eight genes encoding 6-O-sulfotransferases, and three genes encoding uronyl 2-O-sulfotransferases. The number of sulfotransferase genes was unexpectedly large, considering that ascidians do not have a well-developed endoskeleton. In addition, most of the genes within each sub-family seemed to have arisen by gene duplication events that occurred in the ascidian lineage after divergence from the main chordate lineage. This suggests that a unique pattern of sulfation independently developed during ascidian evolution. Some of the genes identified in the present study showed tissue-specific expression in the epidermis, notochord, muscle, and central nervous system. Region-specific expression in the epidermis was also observed. The present study provides useful information for further comparative and functional analyses of sulfotransferases and proteoglycans in chordate embryos.

Identification of key functional residues in the active site of human {beta}1,4-galactosyltransferase 7: a major enzyme in the glycosaminoglycan synthesis pathway

Glycosaminoglycans (GAGs) play a central role in many pathophysiological events, and exogenous xyloside substrates of β1,4-galactosyltransferase 7 (β4GalT7), a major enzyme of GAG biosynthesis, have interesting biomedical applications. To predict functional peptide regions important for substrate binding and activity of human β4GalT7, we conducted a phylogenetic analysis of the β1,4-galactosyltransferase family and generated a molecular model using the x-ray structure of Drosophila β4GalT7-UDP as template. Two evolutionary conserved motifs, (163)DVD(165) and (221)FWGWGREDDE(230), are central in the organization of the enzyme active site. This model was challenged by systematic engineering of point mutations, combined with in vitro and ex vivo functional assays. Investigation of the kinetic properties of purified recombinant wild-type β4GalT7 and selected mutants identified Trp(224) as a key residue governing both donor and acceptor substrate binding. Our results also suggested the involvement of the canonical carboxylate residue Asp(228) acting as general base in the reaction catalyzed by human β4GalT7. Importantly, ex vivo functional tests demonstrated that regulation of GAG synthesis is highly responsive to modification of these key active site amino acids. Interestingly, engineering mutants at position 224 allowed us to modify the affinity and to modulate the specificity of human β4GalT7 toward UDP-sugars and xyloside acceptors. Furthermore, the W224H mutant was able to sustain decorin GAG chain substitution but not GAG synthesis from exogenously added xyloside. Altogether, this study provides novel insight into human β4GalT7 active site functional domains, allowing manipulation of this enzyme critical for the regulation of GAG synthesis. A better understanding of the mechanism underlying GAG assembly paves the way toward GAG-based therapeutics.

Targeting CD44 in mast cell regulation

IMPORTANCE OF THE FIELD

Accumulating evidence suggests that mast cells are involved in a wide variety of immune responses including chronic inflammation, immune tolerance and tumor immunity. Mast cells originate from hematopoietic stem cells and undergo terminal differentiation in the tissues, in which they are ultimately resident. Heterogeneity of tissue mast cells is, therefore, one of the key concepts for a better understanding of various immune responses.

AREAS COVERED IN THIS REVIEW

This review describes the candidate genes involved in regulation of cutaneous mast cell differentiation, with a particular attention to CD44, which is the primary receptor for hyaluronan.

WHAT THE READER WILL GAIN

CD44 is involved in various aspects of cutaneous inflammation. Regarding mast cells, CD44 is upregulated upon differentiation and maturation of mast cells, and plays a critical role in regulation of cutaneous mast cell number. Since both degradation and decrease of hyaluronan are often observed upon chronic inflammation, CD44 might be involved in modulation of local immune responses through regulation of cutaneous mast cell functions.

TAKE HOME MESSAGE

Understanding of cutaneous immune responses should require clarification of local mast cell functions, a part of which is regulated by extracellular matrix components and their membrane receptors.

Chondroitin sulfate and growth factor signaling in the skeleton: Possible links to MPS VI

Mucopolysaccharidosis type VI (MPS VI), also called Maroteaux-Lamy syndrome, is an autosomal recessive lysosomal storage disorder caused by deficiency of a specific enzyme required for glycosaminoglycan catabolism. Deficiency in the N-acetylgalactosamine-4-sulfatase (4S) enzyme, also called arylsulfatase B (ARSB), may have profound skeletal consequences. In MPS VI, partially degraded glycosaminoglycans (GAGs) such as dermatan sulfate and chondroitin sulfate accumulate within lysosomes. Through mechanisms that remain unclear, the abnormal GAG metabolism impacts several aspects of cellular function, particularly in the growth plate. This article explores the hypothesis that accrued partially degraded GAGs may contribute to deregulation of signaling pathways that normally orchestrate skeletal development, with a focus on members of the transforming growth factor-β (TGF-β) family. Understanding the molecular mechanisms disrupted by MPS VI may yield insight to improve the efficacy of MPS VI therapies, including bone marrow transplantation and enzyme replacement therapies.

The roles of chondroitin-4-sulfotransferase-1 in development and disease

The glycosaminoglycan chondroitin sulfate (CS) consists of long linear chains of repeating disaccharide units, which are covalently attached to core proteins to form CS-proteoglycans. These molecules have been shown to fulfill important biological functions in development, disease, and signaling. Biosynthesis of CS takes place in the Golgi apparatus. Concomitant to chondroitin chain elongation, sulfation of specific carbon residues by chondroitin sulfotransferase enzymes takes place. The sulfation balance and pattern of CS on specific carbon residues are tightly regulated during development, injury, and disease, with the temporal and spatial expression of chondroitin sulfotransferase genes believed to be a crucial determinant of this fine balance of chondroitin sulfation. Chondroitin-4-sulfotransferase-1 (C4ST-1)/carbohydrate sulfotransferase 11 (CHST11) is one of the enzymes involved in the sulfation of chondroitin by catalyzing the transfer of sulfate groups from a sulfate donor to the carbon-4 position of the N-acetylgalactosamine sugar of the repeating disaccharide units. Here, I summarize the significant recent advances in our understanding of the roles of C4ST-1 in vertebrate development, disease, and signaling pathways, and the transcriptional regulation of the C4ST-1 gene. Proper 4-sulfation of chondroitin by C4ST-1 plays a crucial role in the skeletal development and signaling events, and new evidence is suggestive of a potential role for C4ST-1 in human disease, including cancer.

Hyaluronan reversed proteoglycan synthesis inhibited by mechanical stress: possible involvement of antioxidant effect

INTRODUCTION

Abnormal mechanical stress loaded on the cartilage leads to the osteoarthritis (OA). Although intraarticular hyaluronan (HA) injection is an effective treatment for OA, the underlying mechanism has not been made clear.

METHODS

Mechanical compression was loaded on the bovine cartilage using the Biopress system. Proteoglycan (PG) and reactive oxygen species (ROS) synthesis were measured with [(35)S] incorporation and fluorescent dye, respectively. Accumulation of peroxynitrite was determined with western blotting using nitrotyrosine antibody.

RESULTS

Mechanical compression inhibited PG synthesis and enhanced ROS. Externally added HA reversed stress-inhibited PG synthesis and attenuated ROS synthesis. HA also significantly decreased the generation of nitrotyrosine.

CONCLUSIONS

HA neutralized stress-enhanced ROS synthesis and resulted in the reversing of PG synthesis. These data suggest that HA plays an anabolic effect as an antioxidant.

Glycan gene expression signatures in normal and malignant breast tissue; possible role in diagnosis and progression

Glycosylation is the stepwise procedure of covalent attachment of oligosaccharide chains to proteins or lipids, and alterations in this process have been associated with malignant transformation. Simultaneous analysis of the expression of all glycan-related genes clearly gives the advantage of enabling a comprehensive view of the genetic background of the glycobiological changes in cancer cells. Studies focusing on the expression of the whole glycome have now become possible, which prompted us to review the present knowledge on glycosylation in relation to breast cancer diagnosis and progression, in the light of available expression data from tumors and breast tissue of healthy individuals. We used various data resources to select a set of 419 functionally relevant genes involved in synthesis, degradation and binding of N-linked and O-linked glycans, Lewis antigens, glycosaminoglycans (chondroitin, heparin and keratan sulfate in addition to hyaluronan) and glycosphingolipids. Such glycans are involved in a number of processes relevant to carcinogenesis, including regulation of growth factors/growth factor receptors, cell-cell adhesion and motility as well as immune system modulation. Expression analysis of these glycan-related genes revealed that mRNA levels for many of them differ significantly between normal and malignant breast tissue. An associative analysis of these genes in the context of current knowledge of their function in protein glycosylation and connection(s) to cancer indicated that synthesis, degradation and adhesion mediated by glycans may be altered drastically in mammary carcinomas. Although further analysis is needed to assess how changes in mRNA levels of glycan genes influence a cell's glycome and the precise role that such altered glycan structures play in the pathogenesis of the disease, lessons drawn from this study may help in determining directions for future research in the rapidly-developing field of glycobiology.