Dermatan sulfate epimerase 1 and dermatan 4-O-sulfotransferase 1 form complexes that generate long epimerized 4-O-sulfated blocks

Enzyme-mediated green synthesis of glycosaminoglycans and catalytic process intensification

Glycosaminoglycans (GAGs) are a family of structurally complex heteropolysaccharides that play pivotal roles in biological functions, including the regulation of cell proliferation, enzyme inhibition, and activation of growth factor receptors. Therefore, the synthesis of GAGs is a hot research topic in drug development. The enzymatic synthesis of GAGs has received widespread attention due to their eco-friendly nature, high regioselectivity, and stereoselectivity. The enhancement of the enzymatic synthesis process is the key to its industrial applications. In this review, we overviewed the construction of more efficient in vitro biomimetic synthesis systems of glycosaminoglycans and presented the different strategies to improve enzyme catalysis, including the combination of chemical and enzymatic methods, solid-phase synthesis, and protein engineering to solve the problems of enzyme stability, separation and purification of the product, preparation of structurally defined sugar chains, etc., and discussed the challenges and opportunities in large-scale green synthesis of GAGs.

DSE inhibits melanoma progression by regulating tumor immune cell infiltration and VCAN

Dermatan sulfate epimerase (DSE) is a C5 epiminase that plays a key role in converting chondroitin sulfate into dermal sulfate. DSE is often upregulated during carcinogenesis of some types of cancer and can regulate growth factor signaling in cancer cells. However, the expression and function of DSE in human melanoma have not been reported. In this study, we investigated the influence of tumor-derived DSE in melanoma progression and the potential mechanism of their action. First, proteomic analysis of collected melanoma tissues revealed that DSE was significantly down-regulated in melanoma tissues. DSE silenced or overexpressed melanoma cells were constructed to detect the effect of DSE on melanoma cells, and it was found that the up-regulation of DSE significantly inhibited the proliferation, migration and invasion of melanoma cells. Data analysis and flow cytometry were used to evaluate the immune subpopulations in tumors, and it was found that the high expression of DSE was closely related to the invasion of killer immune cells. Mechanistically, DSE promoted the expression of VCAN, which inhibited the biological activity of melanoma cells. Together, these results suggest that DSE is downregulated in melanoma tissues, and that high expression of DSE can promote melanoma progression by inducing immune cell infiltration and VCAN expression.

Histories of Dermatan Sulfate Epimerase and Dermatan 4-O-Sulfotransferase from Discovery of Their Enzymes and Genes to Musculocontractural Ehlers-Danlos Syndrome

Dermatan sulfate (DS) and its proteoglycans are essential for the assembly of the extracellular matrix and cell signaling. Various transporters and biosynthetic enzymes for nucleotide sugars, glycosyltransferases, epimerase, and sulfotransferases, are involved in the biosynthesis of DS. Among these enzymes, dermatan sulfate epimerase (DSE) and dermatan 4-O-sulfotranserase (D4ST) are rate-limiting factors of DS biosynthesis. Pathogenic variants in human genes encoding DSE and D4ST cause the musculocontractural type of Ehlers-Danlos syndrome, characterized by tissue fragility, joint hypermobility, and skin hyperextensibility. DS-deficient mice exhibit perinatal lethality, myopathy-related phenotypes, thoracic kyphosis, vascular abnormalities, and skin fragility. These findings indicate that DS is essential for tissue development as well as homeostasis. This review focuses on the histories of DSE as well as D4ST, and their knockout mice as well as human congenital disorders.

The factory, the antenna and the scaffold: the three-way interplay between the Golgi, cilium and extracellular matrix underlying tissue function

The growth and development of healthy tissues is dependent on the construction of a highly specialised extracellular matrix (ECM) to provide support for cell growth and migration and to determine the biomechanical properties of the tissue. These scaffolds are composed of extensively glycosylated proteins which are secreted and assembled into well-ordered structures that can hydrate, mineralise, and store growth factors as required. The proteolytic processing and glycosylation of ECM components is vital to their function. These modifications are under the control of the Golgi apparatus, an intracellular factory hosting spatially organised, protein-modifying enzymes. Regulation also requires a cellular antenna, the cilium, which integrates extracellular growth signals and mechanical cues to inform ECM production. Consequently, mutations in either Golgi or ciliary genes frequently lead to connective tissue disorders. The individual importance of each of these organelles to ECM function is well-studied. However, emerging evidence points towards a more tightly linked system of interdependence between the Golgi, cilium and ECM. This review examines how the interplay between all three compartments underpins healthy tissue. As an example, it will look at several members of the golgin family of Golgi-resident proteins whose loss is detrimental to connective tissue function. This perspective will be important for many future studies looking to dissect the cause and effect of mutations impacting tissue integrity.

Collagen Network Formation in In Vitro Models of Musculocontractural Ehlers-Danlos Syndrome

Loss-of-function mutations in carbohydrate sulfotransferase 14 (CHST14) cause musculocontractural Ehlers-Danlos syndrome-CHST14 (mcEDS-CHST14), characterized by multiple congenital malformations and progressive connective tissue fragility-related manifestations in the cutaneous, skeletal, cardiovascular, visceral and ocular system. The replacement of dermatan sulfate chains on decorin proteoglycan with chondroitin sulfate chains is proposed to lead to the disorganization of collagen networks in the skin. However, the pathogenic mechanisms of mcEDS-CHST14 are not fully understood, partly due to the lack of in vitro models of this disease. In the present study, we established in vitro models of fibroblast-mediated collagen network formation that recapacitate mcEDS-CHST14 pathology. Electron microscopy analysis of mcEDS-CHST14-mimicking collagen gels revealed an impaired fibrillar organization that resulted in weaker mechanical strength of the gels. The addition of decorin isolated from patients with mcEDS-CHST14 and Chst14^-/- mice disturbed the assembly of collagen fibrils in vitro compared to control decorin. Our study may provide useful in vitro models of mcEDS-CHST14 to elucidate the pathomechanism of this disease.

Clinical and pathophysiological delineation of musculocontractural Ehlers-Danlos syndrome caused by dermatan sulfate epimerase deficiency (mcEDS-DSE): A detailed and comprehensive glycobiological and pathological investigation in a novel patient

Musculocontractural Ehlers-Danlos syndrome caused by dermatan sulfate epimerase deficiency (mcEDS-DSE) is a rare connective tissue disorder. This is the first report describing the detailed and comprehensive clinical and pathophysiological features of mcEDS-DSE. The patient, with a novel homozygous nonsense variant (NM_013352.4:c.2601C>A:p.(Tyr867*)), exhibited mild skin hyperextensibility without fragility and small joint hypermobility, but developed recurrent large subcutaneous hematomas. Dermatan sulfate (DS) moieties on chondroitin sulfate/DS proteoglycans were significantly decreased, but remained present, in skin fibroblasts. Electron microscopy examination of skin specimens, including cupromeronic blue-staining to visualize glycosaminoglycan (GAG) chains, revealed coexistence of normally assembled collagen fibrils with attached curved GAG chains and dispersed collagen fibrils with linear GAG chains from attached collagen fibrils across interfibrillar spaces to adjacent fibrils. Residual activity of DS-epi1, encoded by DSE, and/or compensation by DS-epi2, a minor homolog of DS-epi1, may contribute to the mild skin involvement through this "mosaic" pattern of collagen fibril assembly.

An Overview of in vivo Functions of Chondroitin Sulfate and Dermatan Sulfate Revealed by Their Deficient Mice

Chondroitin sulfate (CS), dermatan sulfate (DS) and heparan sulfate (HS) are covalently attached to specific core proteins to form proteoglycans in their biosynthetic pathways. They are constructed through the stepwise addition of respective monosaccharides by various glycosyltransferases and maturated by epimerases as well as sulfotransferases. Structural diversities of CS/DS and HS are essential for their various biological activities including cell signaling, cell proliferation, tissue morphogenesis, and interactions with a variety of growth factors as well as cytokines. Studies using mice deficient in enzymes responsible for the biosynthesis of the CS/DS and HS chains of proteoglycans have demonstrated their essential functions. Chondroitin synthase 1-deficient mice are viable, but exhibit chondrodysplasia, progression of the bifurcation of digits, delayed endochondral ossification, and reduced bone density. DS-epimerase 1-deficient mice show thicker collagen fibrils in the dermis and hypodermis, and spina bifida. These observations suggest that CS/DS are essential for skeletal development as well as the assembly of collagen fibrils in the skin, and that their respective knockout mice can be utilized as models for human genetic disorders with mutations in chondroitin synthase 1 and DS-epimerase 1. This review provides a comprehensive overview of mice deficient in CS/DS biosyntheses.

Inhibition of iduronic acid biosynthesis by ebselen reduces glycosaminoglycan accumulation in mucopolysaccharidosis type I fibroblasts

Mucopolysaccharidosis type I (MPS-I) is a rare lysosomal storage disorder caused by deficiency of the enzyme alpha-L-iduronidase, which removes iduronic acid in both chondroitin/dermatan sulfate (CS/DS) and heparan sulfate (HS) and thereby contributes to the catabolism of glycosaminoglycans (GAGs). To ameliorate this genetic defect, the patients are currently treated by enzyme replacement and bone marrow transplantation, which have a number of drawbacks. This study was designed to develop an alternative treatment by inhibition of iduronic acid formation. By screening the Prestwick drug library, we identified ebselen as a potent inhibitor of enzymes that produce iduronic acid in CS/DS and HS. Ebselen efficiently inhibited iduronic acid formation during CS/DS synthesis in cultured fibroblasts. Treatment of MPS-I fibroblasts with ebselen not only reduced accumulation of CS/DS but also promoted GAG degradation. In early Xenopus embryos, this drug phenocopied the effect of downregulation of DS-epimerase 1, the main enzyme responsible for iduronic production in CS/DS, suggesting that ebselen inhibits iduronic acid production in vivo. However, ebselen failed to ameliorate the CS/DS and GAG burden in MPS-I mice. Nevertheless, the results propose a potential of iduronic acid substrate reduction therapy for MPS-I patients.

Neural Tissue Homeostasis and Repair Is Regulated via CS and DS Proteoglycan Motifs

Chondroitin sulfate (CS) is the most abundant and widely distributed glycosaminoglycan (GAG) in the human body. As a component of proteoglycans (PGs) it has numerous roles in matrix stabilization and cellular regulation. This chapter highlights the roles of CS and CS-PGs in the central and peripheral nervous systems (CNS/PNS). CS has specific cell regulatory roles that control tissue function and homeostasis. The CNS/PNS contains a diverse range of CS-PGs which direct the development of embryonic neural axonal networks, and the responses of neural cell populations in mature tissues to traumatic injury. Following brain trauma and spinal cord injury, a stabilizing CS-PG-rich scar tissue is laid down at the defect site to protect neural tissues, which are amongst the softest tissues of the human body. Unfortunately, the CS concentrated in gliotic scars also inhibits neural outgrowth and functional recovery. CS has well known inhibitory properties over neural behavior, and animal models of CNS/PNS injury have demonstrated that selective degradation of CS using chondroitinase improves neuronal functional recovery. CS-PGs are present diffusely in the CNS but also form denser regions of extracellular matrix termed perineuronal nets which surround neurons. Hyaluronan is immobilized in hyalectan CS-PG aggregates in these perineural structures, which provide neural protection, synapse, and neural plasticity, and have roles in memory and cognitive learning. Despite the generally inhibitory cues delivered by CS-A and CS-C, some CS-PGs containing highly charged CS disaccharides (CS-D, CS-E) or dermatan sulfate (DS) disaccharides that promote neural outgrowth and functional recovery. CS/DS thus has varied cell regulatory properties and structural ECM supportive roles in the CNS/PNS depending on the glycoform present and its location in tissue niches and specific cellular contexts. Studies on the fruit fly, Drosophila melanogaster and the nematode Caenorhabditis elegans have provided insightful information on neural interconnectivity and the role of the ECM and its PGs in neural development and in tissue morphogenesis in a whole organism environment.

The CNS/PNS Extracellular Matrix Provides Instructive Guidance Cues to Neural Cells and Neuroregulatory Proteins in Neural Development and Repair

Background. The extracellular matrix of the PNS/CNS is unusual in that it is dominated by glycosaminoglycans, especially hyaluronan, whose space filling and hydrating properties make essential contributions to the functional properties of this tissue. Hyaluronan has a relatively simple structure but its space-filling properties ensure micro-compartments are maintained in the brain ultrastructure, ensuring ionic niches and gradients are maintained for optimal cellular function. Hyaluronan has cell-instructive, anti-inflammatory properties and forms macro-molecular aggregates with the lectican CS-proteoglycans, forming dense protective perineuronal net structures that provide neural and synaptic plasticity and support cognitive learning. Aims. To highlight the central nervous system/peripheral nervous system (CNS/PNS) and its diverse extracellular and cell-associated proteoglycans that have cell-instructive properties regulating neural repair processes and functional recovery through interactions with cell adhesive molecules, receptors and neuroregulatory proteins. Despite a general lack of stabilising fibrillar collagenous and elastic structures in the CNS/PNS, a sophisticated dynamic extracellular matrix is nevertheless important in tissue form and function. Conclusions. This review provides examples of the sophistication of the CNS/PNS extracellular matrix, showing how it maintains homeostasis and regulates neural repair and regeneration.

The structure of human dermatan sulfate epimerase 1 emphasizes the importance of C5-epimerization of glucuronic acid in higher organisms

Dermatan sulfate epimerase 1 (DS-epi1, EC 5.1.3.19) catalyzes the conversion of d-glucuronic acid to l-iduronic acid on the polymer level, a key step in the biosynthesis of the glycosaminoglycan dermatan sulfate. Here, we present the first crystal structure of the catalytic domains of DS-epi1, solved at 2.4 Å resolution, as well as a model of the full-length luminal protein obtained by a combination of macromolecular crystallography and targeted cross-linking mass spectrometry. Based on docking studies and molecular dynamics simulations of the protein structure and a chondroitin substrate, we suggest a novel mechanism of DS-epi1, involving a His/double-Tyr motif. Our work uncovers detailed information about the domain architecture, active site, metal-coordinating center and pattern of N-glycosylation of the protein. Additionally, the structure of DS-epi1 reveals a high structural similarity to proteins from several families of bacterial polysaccharide lyases. DS-epi1 is of great importance in a range of diseases, and the structure provides a necessary starting point for design of active site inhibitors.

The glycocalyx: a central regulator of vascular function

The endothelial glycocalyx is a specialized extracellular matrix that covers the apical side of vascular endothelial cells, projecting into the lumen of blood vessels. The composition of the glycocalyx has been studied in great detail, and it is known to be composed of a mixture of proteoglycans, glycosaminoglycans, and glycoproteins. Although this structure was once believed to be a passive physical barrier, it is now recognized as a multifunctional and dynamic structure that participates in many vascular processes, including but not limited to vascular permeability, inflammation, thrombosis, mechanotransduction, and cytokine signaling. Because of its participation in many physiological and pathophysiological states, comprehensive knowledge of the glycocalyx will aid future vascular biologists in their research. With that in mind, this review discusses the biochemical structure of the glycocalyx and its function in many vascular physiological processes. We also briefly review a more recent discovery in glycocalyx biology, the placental glycocalyx.

Current state on the enzymatic synthesis of glycosaminoglycans

Glycosaminoglycans (GAGs) are linear anionic polysaccharides, and most of them show a specific sulfation pattern. GAGs have been studied for decades, and still, new biological functions are discovered. Hyaluronic acid and heparin are sold for medical or cosmetic applications. With increased market and applications, the production of GAGs stays in the focus of research groups and the industry. Common industrial GAG production relies on the extraction of animal tissue. Contamination, high dispersity, and uncontrolled sulfation pattern are still obstacles to this process. Tailored production strategies for the chemoenzymatic synthesis have been developed to address these obstacles. In recent years, enzyme cascades, including uridine-5'-diphosphate sugar syntheses, were established to obtain defined polymer size and dispersity, as well as defined sulfation patterns. Nevertheless, the complex synthesis of GAGs is still a challenging research field.

Elucidating the unusual reaction kinetics of D-glucuronyl C5-epimerase

The chemoenzymatic synthesis of heparin, through a multienzyme process, represents a critical challenge in providing a safe and effective substitute for this animal-sourced anticoagulant drug. D-glucuronyl C5-epimerase (C5-epi) is an enzyme acting on a heparin precursor, N-sulfoheparosan, catalyzing the reversible epimerization of D-glucuronic acid (GlcA) to L-iduronic acid (IdoA). The absence of reliable assays for C5-epi has limited elucidation of the enzymatic reaction and kinetic mechanisms. Real time and offline assays are described that rely on 1D 1H NMR to study the activity of C5-epi. Apparent steady-state kinetic parameters for both the forward and the pseudo-reverse reactions of C5-epi are determined for the first time using polysaccharide substrates directly relevant to the chemoenzymatic synthesis and biosynthesis of heparin. The forward reaction shows unusual sigmoidal kinetic behavior, and the pseudo-reverse reaction displays nonsaturating kinetic behavior. The atypical sigmoidal behavior of the forward reaction was probed using a range of buffer additives. Surprisingly, the addition of 25 mM each of CaCl2 and MgCl2 resulted in a forward reaction exhibiting more conventional Michaelis-Menten kinetics. The addition of 2-O-sulfotransferase, the next enzyme involved in heparin synthesis, in the absence of 3'-phosphoadenosine 5'-phosphosulfate, also resulted in C5-epi exhibiting a more conventional Michaelis-Menten kinetic behavior in the forward reaction accompanied by a significant increase in apparent Vmax. This study provides critical information for understanding the reaction kinetics of C5-epi, which may result in improved methods for the chemoenzymatic synthesis of bioengineered heparin.

Role of Chondroitin Sulfation Following Spinal Cord Injury

Traumatic spinal cord injury produces long-term neurological damage, and presents a significant public health problem with nearly 18,000 new cases per year in the U.S. The injury results in both acute and chronic changes in the spinal cord, ultimately resulting in the production of a glial scar, consisting of multiple cells including fibroblasts, macrophages, microglia, and reactive astrocytes. Within the scar, there is an accumulation of extracellular matrix (ECM) molecules—primarily tenascins and chondroitin sulfate proteoglycans (CSPGs)—which are considered to be inhibitory to axonal regeneration. In this review article, we discuss the role of CSPGs in the injury response, especially how sulfated glycosaminoglycan (GAG) chains act to inhibit plasticity and regeneration. This includes how sulfation of GAG chains influences their biological activity and interactions with potential receptors. Comprehending the role of CSPGs in the inhibitory properties of the glial scar provides critical knowledge in the much-needed production of new therapies.

Systematic investigation of the skin in Chst14-/- mice: A model for skin fragility in musculocontractural Ehlers-Danlos syndrome caused by CHST14 variants (mcEDS-CHST14)

Loss-of-function variants in CHST14 cause a dermatan 4-O-sulfotransferase deficiency named musculocontractural Ehlers-Danlos syndrome-CHST14 (mcEDS-CHST14), resulting in complete depletion of the dermatan sulfate moiety of decorin glycosaminoglycan (GAG) chains, which is replaced by chondroitin sulfate. Recently, we uncovered structural alteration of GAG chains in the skin of patients with mcEDS-CHST14. Here, we conducted the first systematic investigation of Chst14 gene-deleted homozygote (Chst14-/-) mice. We used skin samples of wild-type (Chst14+/+) and Chst14-/- mice. Mechanical fragility of the skin was measured with a tensile test. Pathology was observed using light microscopy, decorin immunohistochemistry and electron microscopy (EM) including cupromeronic blue (CB) staining. Quantification of chondroitin sulfate and dermatan sulfate was performed using enzymatic digestion followed by anion-exchange HPLC. In Chst14-/- mice, skin tensile strength was significantly decreased compared with that in Chst14+/+ mice. EM showed that collagen fibrils were oriented in various directions to form disorganized collagen fibers in the reticular layer. Through EM-based CB staining, rod-shaped linear GAG chains were found to be attached at one end to collagen fibrils and protruded outside of the fibrils, in contrast to them being round and wrapping the collagen fibrils in Chst14+/+ mice. A very low level of dermatan sulfate disaccharides was detected in the skin of Chst14-/- mice by anion-exchange chromatography. Chst14-/- mice, exhibiting similar abnormalities in the GAG structure of decorin and collagen networks in the skin, could be a reasonable model for skin fragility of patients with mcEDS-CHST14, shedding light on the role of dermatan sulfate in maintaining skin strength.

Glycosaminoglycan Domain Mapping of Cellular Chondroitin/Dermatan Sulfates

Glycosaminoglycans (GAGs) are polysaccharides produced by most mammalian cells and involved in a variety of biological processes. However, due to the size and complexity of GAGs, detailed knowledge about the structure and expression of GAGs by cells, the glycosaminoglycome, is lacking. Here we report a straightforward and versatile approach for structural domain mapping of complex mixtures of GAGs, GAGDoMa. The approach is based on orthogonal enzymatic depolymerization of the GAGs to generate internal, terminating, and initiating domains, and nanoflow reversed-phase ion-pairing chromatography with negative mode higher-energy collision dissociation (HCD) tandem mass spectrometry (MS/MS) for structural characterization of the individual domains. GAGDoMa provides a detailed structural insight into the glycosaminoglycome, and offers an important tool for deciphering the complexity of GAGs in cellular physiology and pathology.

Recombinant dermatan sulfate is a potent activator of heparin cofactor II-dependent inhibition of thrombin

The glycosaminoglycan dermatan sulfate (DS) is a well-known activator of heparin cofactor II-dependent inactivation of thrombin. In contrast to heparin, dermatan sulfate has never been prepared recombinantly from material of non-animal origin. Here we report on the enzymatic synthesis of structurally well-defined DS with high anticoagulant activity. Using a microbial K4 polysaccharide and the recombinant enzymes DS-epimerase 1, dermatan 4-O-sulfotransferase 1, uronyl 2-O-sulfotransferase and N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase, several new glycostructures have been prepared, such as a homogenously sulfated IdoA-GalNAc-4S polymer and its 2-O-, 6-O- and 2,6-O-sulfated derivatives. Importantly, the recombinant highly 2,4-O-sulfated DS inhibits thrombin via heparin cofactor II, approximately 20 times better than heparin, enabling manipulation of vascular and extravascular coagulation. The potential of this method can be extended to preparation of specific structures that are of importance for binding and activation of cytokines, and control of inflammation and metastasis, involving extravasation and migration.

Analysis of homologous and heterologous interactions between UDP-galactose transporter and beta-1,4-galactosyltransferase 1 using NanoBiT

Split luciferase complementation assay is one of the approaches enabling identification and analysis of protein-protein interactions in vivo. The NanoBiT technology is the most recent improvement of this strategy. Nucleotide sugar transporters and glycosyltransferases of the Golgi apparatus are the key players in glycosylation. Here we demonstrate the applicability of the NanoBiT system for studying homooligomerization of these proteins. We also report and discuss a novel heterologous interaction between UDP-galactose transporter and beta-1,4-galactosyltransferase 1.

Recent Advances in the Pathophysiology of Musculocontractural Ehlers-Danlos Syndrome

Musculocontractural Ehlers–Danlos Syndome (mcEDS) is a type of EDS caused by biallelic pathogenic variants in the gene for carbohydrate sulfotransferase 14/dermatan 4-O-sulfotransferase 1 (CHST14/D4ST1, mcEDS-CHST14), or in the gene for dermatan sulfate epimerase (DSE, mcEDS-DSE). Thus far, 41 patients from 28 families with mcEDS-CHST14 and five patients from four families with mcEDS-DSE have been described in the literature. Clinical features comprise multisystem congenital malformations and progressive connective tissue fragility-related manifestations. This review outlines recent advances in understanding the pathophysiology of mcEDS. Pathogenic variants in CHST14 or DSE lead to reduced activities of relevant enzymes, resulting in a negligible amount of dermatan sulfate (DS) and an excessive amount of chondroitin sulfate. Connective tissue fragility is presumably attributable to a compositional change in the glycosaminoglycan chains of decorin, a major DS-proteoglycan in the skin that contributes to collagen fibril assembly. Collagen fibrils in affected skin are dispersed in the papillary to reticular dermis, whereas those in normal skin are regularly and tightly assembled. Glycosaminoglycan chains are linear in affected skin, stretching from the outer surface of collagen fibrils to adjacent fibrils; glycosaminoglycan chains are curved in normal skin, maintaining close contact with attached collagen fibrils. Homozygous (Chst14^−/−) mice have been shown perinatal lethality, shorter fetal length and vessel-related placental abnormalities. Milder phenotypes in mcEDS-DSE might be related to a smaller fraction of decorin DS, potentially through residual DSE activity or compensation by DSE2 activity. These findings suggest critical roles of DS and DS-proteoglycans in the multisystem development and maintenance of connective tissues, and provide fundamental evidence to support future etiology-based therapies.

Glycosaminoglycans: A Link Between Development and Regeneration in the Lung

What can we learn from embryogenesis to increase our understanding of how regeneration of damaged adult lung tissue could be induced in serious lung diseases such as chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and asthma? The local tissue niche determines events in both embryogenesis and repair of the adult lung. Important constituents of the niche are extracellular matrix (ECM) molecules, including proteoglycans and glycosaminoglycans (GAGs). GAGs, strategically located in the pericellular and extracellular space, bind developmentally active growth factors (GFs) and morphogens such as fibroblast growth factors (FGFs), transforming growth factor-β (TGF-β), and bone morphogenetic proteins (BMPs) aside from cytokines. These interactions affect activities in many cells, including stem cells, important in development and tissue regeneration. Moreover, it is becoming clear that the "inherent code," such as sulfation of disaccharides of GAGs, is a strong determinant of cellular outcome. Sulfation patterns, deacetylations, and epimerizations of GAG chains function as tuning forks in gradient formation of morphogens, growth factors, and cytokines. Learning to tune these fine instruments, that is, interactions between GFs, chemokines, and cytokines with the specific disaccharide code of GAGs in the adult lung, could become the key to unlock inherent regenerative forces to override pathological remodeling. This review aims to provide an overview of the role GAGs play during development and similar events in regenerative efforts in the adult lung.

The dual role of the glycosaminoglycan chondroitin-6-sulfate in the development, progression and metastasis of cancer

The remarkable structural heterogeneity of chondroitin sulfate (CS) and dermatan sulfate (DS) generates biological information that can be unique to each of these glycosaminoglycans (GAGs), and changes in their composition are translated into alterations in the binding profiles of these molecules. CS/DS can bind to various cytokines and growth factors, cell surface receptors, adhesion molecules, enzymes and fibrillar glycoproteins of the extracellular matrix, thereby influencing both cell behavior and the biomechanical and biochemical properties of the matrix. In this review, we summarize the current knowledge concerning CS/DS metabolism in the human cancer stroma. The remodeling of the GAG profile in the tumor niche is manifested as a substantial increase in the CS content and a gradual decrease in the proportion between DS and CS. Furthermore, the composition of CS and DS is also affected, which results in a substantial increase in the 6‐O‐sulfated and/or unsulfated disaccharide content, which is concomitant with a decrease in the 4‐O‐sulfation level. Here, we discuss the possible impact of alterations in the CS/DS sulfation pattern on the binding capacity and specificity of these GAGs. Moreover, we propose potential consequences of the stromal accumulation of chondroitin‐6‐sulfate for the progression and metastasis of cancer.

DSE regulates the malignant characters of hepatocellular carcinoma cells by modulating CCL5/CCR1 axis

Abnormal expression of dermatan sulfate epimerase (DSE) has been found in many types of cancer, while its expression and biological functions in hepatocellular carcinoma (HCC) progression remains obscure. Here we report that DSE, the enzyme that catalyzes the conversion of chondroitin sulfate (CS) to dermatan sulfate (DS), is a critical mediator of malignant character in HCC, through regulation of CCL5 signaling. DSE mRNA and protein were downregulated frequently in HCC tumors, where these events were associated with advanced tumor stages, metastases, and poor survival. DSE-mediated tumor growth was evaluated in immune-deficient and immune-complement mice models. Restoring DSE expression in HCC cells suppressed tumor growth, as well as decreased IL-1β and CCL5 levels in transplanted tumor tissue. Mechanistic investigations revealed that the expression of DSE altered CCL5 signaling and cell surface binding in HCC cells. Accordingly, DSE suppressed CCL5-induced cell growth, migration, and invasion, whereas silencing of DSE enhanced CCL5-triggered malignant phenotypes. Inhibiting CCR1 activity with BX471 decreased CCL5-induced malignant characters caused by siRNA-mediated knockdown of DSE in HCC cells, establishing the critical role of the CCL5/CCR1 axis in mediating the effects of DSE expression. Taken together, our results suggest that DSE dysregulation contributes to the malignant behavior of HCC cells. This provides novel insight into the significance of DSE in CCL5 signaling and HCC pathogenesis.