Molecular cloning, expression, and chromosomal mapping of human chondroitin 4-sulfotransferase, whose expression pattern in human tissues is different from that of chondroitin 6-sulfotransferase

Enhancing the expression of chondroitin 4-O-sulfotransferase for one-pot enzymatic synthesis of chondroitin sulfate A

Chondroitin sulfate (CS) stands as a pivotal compound in dietary supplements for osteoarthritis treatment, propelling significant interest in the biotechnological pursuit of environmentally friendly and safe CS production. Enzymatic synthesis of CS for instance CSA has been considered as one of the most promising methods. However, the bottleneck consistently encountered is the active expression of chondroitin 4-O-sulfotransferase (C4ST) during CSA biosynthesis. This study meticulously delved into optimizing C4ST expression through systematic enhancements in transcription, translation, and secretion mechanisms via modifications in the 5' untranslated region, the N-terminal encoding sequence, and the Komagataella phaffii chassis. Ultimately, the active C4ST expression escalated to 2713.1 U/L, representing a striking 43.7-fold increase. By applying the culture broth supernatant of C4ST and integrating the 3'-phosphoadenosine-5'-phosphosulfate (PAPS) biosynthesis module, we constructed a one-pot enzymatic system for CSA biosynthesis, achieving a remarkable sulfonation degree of up to 97.0 %. The substantial enhancement in C4ST expression and the development of an engineered one-pot enzymatic synthesis system promises to expedite large-scale CSA biosynthesis with customizable sulfonation degrees.

Installation of O-glycan sulfation capacities in human HEK293 cells for display of sulfated mucins

The human genome contains at least 35 genes that encode Golgi sulfotransferases that function in the secretory pathway, where they are involved in decorating glycosaminoglycans, glycolipids, and glycoproteins with sulfate groups. Although a number of important interactions by proteins such as selectins, galectins, and sialic acid–binding immunoglobulin-like lectins are thought to mainly rely on sulfated O-glycans, our insight into the sulfotransferases that modify these glycoproteins, and in particular GalNAc-type O-glycoproteins, is limited. Moreover, sulfated mucins appear to accumulate in respiratory diseases, arthritis, and cancer. To explore further the genetic and biosynthetic regulation of sulfated O-glycans, here we expanded a cell-based glycan array in the human embryonic kidney 293 (HEK293) cell line with sulfation capacities. We stably engineered O-glycan sulfation capacities in HEK293 cells by site-directed knockin of sulfotransferase genes in combination with knockout of genes to eliminate endogenous O-glycan branching (core2 synthase gene GCNT1) and/or sialylation capacities in order to provide simplified substrates (core1 Galβ1–3GalNAcα1–O-Ser/Thr) for the introduced sulfotransferases. Expression of the galactose 3-O-sulfotransferase 2 in HEK293 cells resulted in sulfation of core1 and core2 O-glycans, whereas expression of galactose 3-O-sulfotransferase 4 resulted in sulfation of core1 only. We used the engineered cell library to dissect the binding specificity of galectin-4 and confirmed binding to the 3-O-sulfo-core1 O-glycan. This is a first step toward expanding the emerging cell-based glycan arrays with the important sulfation modification for display and production of glycoconjugates with sulfated O-glycans.

Chondroitin sulfate in tissue remodeling: Therapeutic implications for pulmonary fibrosis

Fibrosis is characterized by the deposition of extracellular matrix (ECM) proteins, while idiopathic pulmonary fibrosis (IPF) is a chronic respiratory disease characterized by dysregulated tissue repair and remodeling. Anti-inflammatory drugs, such as corticosteroids and immunosuppressants, and antifibrotic drugs, like pirfenidone and nintedanib, are used in IPF therapy. However, their limited effects suggest that single mediators are inadequate to control IPF. Therefore, therapies targeting the multifactorial cascades that regulate tissue remodeling in fibrosis could provide alternate solutions. ECM molecules have been shown to modulate various biological functions beyond tissue structure support and thus, could be developed into novel therapeutic targets for modulating tissue remodeling. Among ECM molecules, glycosaminoglycans (GAG) are linear polysaccharides consisting of repeated disaccharides, which regulate cell-matrix interactions. Chondroitin sulfate (CS), one of the major GAGs, binds to multifactorial mediators in the ECM and reportedly participates in tissue remodeling in various diseases; however, to date, its biological functions have drawn considerably less attention than other GAGs, like heparan sulfate. In the present review, we discuss the involvement and regulation of CS in tissue remodeling and pulmonary fibrotic diseases, its role in pulmonary fibrosis, and the therapeutic approaches targeting CS.

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.

Sulfation pattern of chondroitin sulfate in human osteoarthritis cartilages reveals a lower level of chondroitin-4-sulfate

Chondroitin sulfates (CS) account for more than 80% of the glycosaminoglycans of articular cartilage, which impart its physiological functions. We quantified the absolute concentration of the CS components of the full thickness cartilages from the knees of patients with terminal-phase osteoarthritis. Osteochondrol biopsies were removed from the medial femoral condyle and lateral femoral condyle of sixty female patients received total knee arthroplasty, aged from 58 to 83 years old. We found the total CS concentrations and chondroitin-4-sulfate disaccharide were significantly lowered in osteoarthritic samples. Microstructure analysis indicated while chondroitin-0-sulfate was equally distributed across different zones of the osteoarthritic cartilages, chondroitin-4-sulfate is significantly less in the deep zones. Down-regulation of sulfotransferases, the enzymes responsible for CS sulfation, in the lesion site of cartilage were observed. Our study suggested chondroitin-4-sulfate down-regulation can be a diagnostic marker for degraded osteoarthritis cartilage, with potential implications in cartilage regeneration.

Interaction of receptor type of protein tyrosine phosphatase sigma (RPTPσ) with a glycosaminoglycan library

Receptor type of protein tyrosine phosphatase sigma (RPTPσ) functions as a glycosaminoglycan (GAG) receptor of neuronal cells in both the central and peripheral nervous systems. Both chondroitin sulphate (CS) and heparan sulphate (HS) are important constituents of GAG ligands for RPTPσ, although they have opposite effects on neuronal cells. CS inhibits neurite outgrowth and neural regeneration through RPTPσ, whereas HS enhances them. We prepared recombinant RPTPσ N-terminal fragment containing the GAG binding site and various types of biotin-conjugated GAG (CS and HS) with chemical modification and chemo-enzymatic synthesis. Then interaction of the RPTPσ N-terminal fragment was analysed using GAG-biotin immobilized on streptavidin sensor chips by surface plasmon resonance. Interaction of RPTPσ with the CS library was highly correlated to the degree of disulphated disaccharide E unit, which had two sulphate groups at C-4 and C-6 positions of the N-acetylgalactosamine residue (CSE). The optimum molecular mass of CSE was suggested to be approximately 10 kDa. Heparin showed higher affinity to RPTPσ than the CS library. Our GAG library will not only contribute to the fields of carbohydrate science and cell biology, but also provide medical application to regulate neural regeneration.

CHST11/13 Regulate the Metastasis and Chemosensitivity of Human Hepatocellular Carcinoma Cells Via Mitogen-Activated Protein Kinase Pathway

BACKGROUND

Carbohydrate sulfotransferases 11-13 (CHST11-13), that catalyze the transfer of sulfate to position 4 of the GalNAc residue of chondroitin, have been implicated in various diseases.

AIM

This study aimed to clarify the association of CHST11-13 expression with metastasis and drug sensitivity in hepatocellular carcinoma (HCC) cells.

METHODS

We measured the levels of CHST11 and CHST13 in a series of HCC cells using real-time PCR and Western blotting. After RNAi and forced expression treatment of CHST11 and CHST13 in MHCC97L and MHCC97H cells, metastatic potential and drug sensitivity of the two cells were investigated with ECM invasion assay, drug sensitivity assay, and in vivo antitumor activity assay. By real-time PCR and Western blotting, we explored the possible impacts of these two genes on mitogen-activated protein kinase (MAPK) signal pathway. MAPK pathway was blocked by PD98059 or SP600125 to elucidate the effects of MAPK pathway on metastasis and chemosensitivity.

RESULTS

Significantly reduced levels of CHST11 and CHST13 were observed in highly invasive MHCC97H cells compared with those of MHCC97L cell line with low metastatic potential. Decreased or forced expression of CHST11 and CHST13 altered metastatic potential and drug sensitivity of MHCC97L and MHCC97H cells. Remarkable alteration of MAPK activity was shown in two HCC cells with genetic manipulation. Conversely, pharmacologic inhibition of the MAPK pathway suppressed invasive potential and rescued drug sensitivity of MHCC97H cells.

CONCLUSIONS

Our results have demonstrated that CHST11 and CHST13 negatively modulate metastasis and drug resistance of HCC cells probably via oncogenic MAPK signal pathway.

Construction of a chondroitin sulfate library with defined structures and analysis of molecular interactions

Chondroitin sulfate (CS) is a linear acidic polysaccharide, composed of repeating disaccharide units of glucuronic acid and N-acetyl-D-galactosamine and modified with sulfate residues at different positions, which plays various roles in development and disease. Here, we chemo-enzymatically synthesized various CS species with defined lengths and defined sulfate compositions, from chondroitin hexasaccharide conjugated with hexamethylenediamine at the reducing ends, using bacterial chondroitin polymerase and recombinant CS sulfotransferases, including chondroitin-4-sulfotransferase 1 (C4ST-1), chondroitin-6-sulfotransferase 1 (C6ST-1), N-acetylgalactosamine 4-sulfate 6-sulfotransferase (GalNAc4S-6ST), and uronosyl 2-sulfotransferase (UA2ST). Sequential modifications of CS with a series of CS sulfotransferases revealed their distinct features, including their substrate specificities. Reactions with chondroitin polymerase generated non-sulfated chondroitin, and those with C4ST-1 and C6ST-1 generated uniformly sulfated CS containing >95% 4S and 6S units, respectively. GalNAc4S-6ST and UA2ST generated highly sulfated CS possessing ∼90% corresponding disulfated disaccharide units. Sequential reactions with UA2ST and GalNAc4S-6ST generated further highly sulfated CS containing a mixed structure of disulfated units. Surprisingly, sequential reactions with GalNAc4S-6ST and UA2ST generated a novel CS molecule containing ∼29% trisulfated disaccharide units. Enzyme-linked immunosorbent assay and surface plasmon resonance analysis using the CS library and natural CS products modified with biotin at the reducing ends, revealed details of the interactions of CS species with anti-CS antibodies, and with CS-binding molecules such as midkine and pleiotrophin. Chemo-enzymatic synthesis enables the generation of CS chains of the desired lengths, compositions, and distinct structures, and the resulting library will be a useful tool for studies of CS functions.

Abnormal developmental control of replication-timing domains in pediatric acute lymphoblastic leukemia

Abnormal replication timing has been observed in cancer but no study has comprehensively evaluated this misregulation. We generated genome-wide replication-timing profiles for pediatric leukemias from 17 patients and three cell lines, as well as normal B and T cells. Nonleukemic EBV-transformed lymphoblastoid cell lines displayed highly stable replication-timing profiles that were more similar to normal T cells than to leukemias. Leukemias were more similar to each other than to B and T cells but were considerably more heterogeneous than nonleukemic controls. Some differences were patient specific, while others were found in all leukemic samples, potentially representing early epigenetic events. Differences encompassed large segments of chromosomes and included genes implicated in other types of cancer. Remarkably, differences that distinguished leukemias aligned in register to the boundaries of developmentally regulated replication-timing domains that distinguish normal cell types. Most changes did not coincide with copy-number variation or translocations. However, many of the changes that were associated with translocations in some leukemias were also shared between all leukemic samples independent of the genetic lesion, suggesting that they precede and possibly predispose chromosomes to the translocation. Altogether, our results identify sites of abnormal developmental control of DNA replication in cancer that reveal the significance of replication-timing boundaries to chromosome structure and function and support the replication domain model of replication-timing regulation. They also open new avenues of investigation into the chromosomal basis of cancer and provide a potential novel source of epigenetic cancer biomarkers.

Dermatan sulfotransferase Chst14/D4st1, but not chondroitin sulfotransferase Chst11/C4st1, regulates proliferation and neurogenesis of neural progenitor cells

Chondroitin sulfates (CSs) and dermatan sulfates (DSs) are enriched in the microenvironment of neural stem cells (NSCs) during development and in the adult neurogenic niche, and have been implicated in mechanisms governing neural precursor migration, proliferation and differentiation. In contrast to previous studies, in which a chondroitinaseABC-dependent unselective deglycosylation of both CSs and DSs was performed, we used chondroitin 4-O-sulfotransferase-1 (Chst11/C4st1)- and dermatan 4-O-sulfotransferase-1 (Chst14/D4st1)-deficient NSCs specific for CSs and DSs, respectively, to investigate the involvement of specific sulfation profiles of CS and DS chains, and thus the potentially distinct roles of CSs and DSs in NSC biology. In comparison to wild-type controls, deficiency for Chst14 resulted in decreased neurogenesis and diminished proliferation of NSCs accompanied by increased expression of GLAST and decreased expression of Mash-1, and an upregulation of the expression of the receptors for fibroblast growth factor-2 (FGF-2) and epidermal growth factor (EGF). By contrast, deficiency in Chst11 did not influence NSC proliferation, migration or differentiation. These observations indicate for the first time that CSs and DSs play distinct roles in the self-renewal and differentiation of NSCs.

The chondroitin/dermatan sulfate synthesizing and modifying enzymes in laryngeal cancer: expressional and epigenetic studies

Background

Significant biochemical changes are observed in glycosaminoglycans in squamous cell laryngeal carcinoma. The most characteristics are in chondroitin/dermatan sulfate fine structure and proportion, which might be due to differential expression of the enzymes involved in their biosynthesis. The aim of the present work was the investigation in expressional and epigenetic level of the enzymes involved in chondroitin/dermatan sulfate biosynthesis in laryngeal cancer.

Methods

Tissues subjected to total RNA and DNA isolation, and protein extraction. The techniques used in this study were RT-PCR analysis, western blotting and methylation specific PCR.

Results

We identified that many enzymes were expressed in the cancerous specimens intensively. Dermatan sulfate epimerase was expressed exclusively in the cancerous parts and in minor amounts in healthy tissues; in the macroscopically normal samples it was not detected. Furthermore, chondroitin synthase I and chondroitin polymerizing factor were strongly expressed in the cancerous parts compared to the corresponding normal tissues. Sulfotransferases, like chondroitin 6 sulfotransferase 3, were highly expressed mainly in healthy specimens.

Conclusions

The study of the various chondroitin/dermatan synthesizing enzymes revealed that they were differentially expressed in cancer, in human laryngeal cartilage, leading to specific chondroitin/dermatan structures which contributed to proteoglycan formation with specific features. The expression of the examined enzymes correlated with the glycosaminoglycan profile observed in previous studies.

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.

N-linked oligosaccharides are required to produce and stabilize the active form of chondroitin 4-sulphotransferase-1

C4ST-1 (chondroitin 4-sulphotransferase-1) transfers sulphate to position 4 of N-acetylgalactosamine in chondroitin. We showed previously that purified C4ST-1 from the culture medium of rat chondrosarcoma cells was a glycoprotein containing approx. 35% N-linked oligosaccharides. In the present paper, we investigated the functional role of the N-linked oligosaccharides attached to C4ST-1. We found that (i) treatment of recombinant C4ST-1 with peptide N-glycosidase F caused a marked decrease in activity, (ii) production of the active form of C4ST-1 by COS-7 cells transfected with cDNA of C4ST-1 was inhibited by tunicamycin, (iii) deletion of the N-glycosylation site located at the C-terminal region of C4ST-1 abolished activity, (iv) attachment of a single N-glycan at the C-terminal region supported production of the active form of C4ST-1, but the resulting recombinant enzyme was much more unstable at 37 degrees C than the control recombinant protein, and (v) truncation of C-terminal region up to the N-glycosylation site at the C-terminal region resulted in total loss of activity. These observations strongly suggest that N-linked oligosaccharides attached to C4ST-1 contribute to the production and stability of the active form of C4ST-1. In addition, the N-linked oligosaccharide at the C-terminal region appears to affect the glycosylation pattern of recombinant C4ST; a broad protein band of the wildtype protein resulting from microheterogeneity of N-linked oligosaccharides disappeared and four discrete protein bands with different numbers of N-linked oligosaccharides appeared when the N-linked oligosaccharide at the C-terminal region was deleted.

Functions of Chondroitin Sulfate/Dermatan Sulfate Chains in Brain Development

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

Maintenance of chondroitin sulfation balance by chondroitin-4-sulfotransferase 1 is required for chondrocyte development and growth factor signaling during cartilage morphogenesis

Glycosaminoglycans (GAGs) such as heparan sulfate and chondroitin sulfate are polysaccharide chains that are attached to core proteins to form proteoglycans. The biosynthesis of GAGs is a multistep process that includes the attachment of sulfate groups to specific positions of the polysaccharide chains by sulfotransferases. Heparan-sulfate and heparan sulfate-sulfotransferases play important roles in growth factor signaling and animal development. However, the biological importance of chondroitin sulfation during mammalian development and growth factor signaling is poorly understood. We show that a gene trap mutation in the BMP-induced chondroitin-4-sulfotransferase 1 (C4st1) gene (also called carbohydrate sulfotransferase 11 - Chst11), which encodes an enzyme specific for the transfer of sulfate groups to the 4-O-position in chondroitin, causes severe chondrodysplasia characterized by a disorganized cartilage growth plate as well as specific alterations in the orientation of chondrocyte columns. This phenotype is associated with a chondroitin sulfation imbalance, mislocalization of chondroitin sulfate in the growth plate and an imbalance of apoptotic signals. Analysis of several growth factor signaling pathways that are important in cartilage growth plate development showed that the C4st1(gt/gt) mutation led to strong upregulation of TGFbeta signaling with concomitant downregulation of BMP signaling, while Indian hedgehog (Ihh) signaling was unaffected. These results show that chondroitin 4-O-sulfation by C4st1 is required for proper chondroitin sulfate localization, modulation of distinct signaling pathways and cartilage growth plate morphogenesis. Our study demonstrates an important biological role of differential chondroitin sulfation in mammalian development.

Differential expression and enzymatic properties of GalNAc-4-sulfotransferase-1 and GalNAc-4-sulfotransferase-2

We have cloned two GalNAc-4-sulfotransferases, GalNAc-4-ST1 and GalNAc-4-ST2, that transfer sulfate to terminal beta1,4-linked GalNAc. In conjunction with the action of protein-specific beta1,4GalNAc-transferases, GalNAc-4-ST1 and GalNAc-4-ST2 account for the presence of terminal beta1,4-linked GalNAc-4-SO(4) on glycoproteins such as lutropin, thyrotropin (TSH), proopiomelanocortin (POMC), carbonic anhydratase-VI (CA-VI), and tenascin-R. GalNAc-4-ST1 and GalNAc-4-ST2 can be distinguished by their differing specificity for oligosaccharide acceptors and temperature lability. The differences in properties have been used to show that the levels of GalNAc-4-ST1 and GalNAc-4-ST2 activity are proportionate to the levels of their respective transcripts. Furthermore, we have found that both transcript and activity levels of GalNAc-4-ST1 and GalNAc-4-ST2 vary widely among different tissues indicating that the regulation of their expression differs. Differences in specificity and the regulation of expression may account for existence of two GalNAc-4-sulfotransferases in vivo. The highest levels of both GalNAc-4-ST1 and GalNAc-4-ST2 transcripts are present in the pituitary of the mouse with multiple cell types that produce glycoproteins terminating with GalNAc-4-SO(4). Genetic ablation of both GalNAc-4-ST1 and GalNAc-4-ST2 may be necessary to alter the pattern and/or extent of sulfate addition to terminal beta1,4GalNAc in tissues such as pituitary.

Chondroitin 4-sulphotransferase-1 and chondroitin 6-sulphotransferase-1 are affected differently by uronic acid residues neighbouring the acceptor GalNAc residues

C4ST-1 (chondroitin 4-sulphotransferase-1) and C6ST-1 (chondroitin 6-sulphotransferase-1) transfer sulphate from PAPS (adenosine 3'-phosphate 5'-phosphosulphate) to positions 4 and 6 respectively of the GalNAc residues of chondroitin. We showed previously that C4ST-1 purified from rat chondrosarcoma and recombinant C4ST-1 both transfer sulphate efficiently to position 4 of the GalNAc residues of DSDS (desulphated dermatan sulphate). We report here the specificity of C4ST-1 and C6ST-1 in terms of uronic acid residue recognition around the GalNAc residue to which sulphate is transferred. When [35S]glycosaminoglycans formed from DSDS after incubation with [35S]PAPS and C4ST-1 were digested with chondroitinase ACII, a major part of the radioactivity was recovered in disaccharide fractions and the remainder distributed to tetrasaccharides and larger fractions, indicating that C4ST-1 mainly transferred sulphate to position 4 of the GalNAc residue located at the GlcA-GalNAc-GlcA sequence. Structural analysis of tetrasaccharide and larger oligosaccharide fractions indicated that C4ST-1 mainly transferred sulphate to the GalNAc residue adjacent to the reducing side of the GlcA residue. On the other hand, when [35S]glycosaminoglycans formed from DSDS after incubation with [35S]PAPS and C6ST-1 were digested with chondroitinase ACII, a major part of the radioactivity was recovered in fractions larger than hexasaccharides, indicating that C6ST-1 transferred sulphate to the GalNAc residues located in the L-iduronic acid-rich region. Structural analysis of the tetrasaccharide and larger oligosaccharide fractions indicated that C6ST-1 showed very little preference for the GalNAc residue neighbouring the GlcA residue. These results indicate that C4ST-1 and C6ST-1 differ from each other in the recognition of uronic acid residues adjacent to the targeted GalNAc residue.

Deregulation of the carbohydrate (chondroitin 4) sulfotransferase 11 (CHST11) gene in a B-cell chronic lymphocytic leukemia with a t(12;14)(q23;q32)

The t(12;14)(q23;q32) breakpoints in a case of B-cell chronic lymphocytic leukemia (B-CLL) were mapped by fluorescence in situ hybridization (FISH) and Southern blot analysis and cloned using an IGH switch-gamma probe. The translocation affected a productively rearranged IGH allele and the carbohydrate (chondroitin 4) sulfotransferase 11 (CHST11) locus at 12q23, with a reciprocal break in intron 2 of the CHST11 gene. CHST11 belongs to the HNK1 family of Golgi-associated sulfotransferases, a group of glycosaminoglycan-modifying enzymes, and is expressed mainly in the hematopoietic lineage. Northern Blot analysis of tumor RNA using CHST11-specific probes showed expression of two CHST11 forms of abnormal size. 5'- and 3'-Rapid Amplification of cDNA Ends (RACE) revealed IGH/CHST11 as well as CHST11/IGH fusion RNAs expressed from the der(14) and der(12) chromosomes. Both fusion species contained open reading frames making possible the translation of two truncated forms of CHST11 protein. The biological consequence of t(12;14)(q23;q32) in this case presumably is a disturbance of the cellular distribution of CHST11 leading to deregulation of a chondroitin-sulfate-dependent pathway specific to the hematopoietic lineage.

Confirmation and refinement of a genetic locus for disseminated superficial actinic porokeratosis (DSAP1) at 12q23.2-24.1

BACKGROUND

Our previous study has identified two loci for disseminated superficial actinic porokeratosis (DSAP), but the genes responsible are still unknown.

OBJECTIVES

To narrow down the candidate regions and to assess candidate genes.

METHODS

A genome-wide scan and linkage analysis were carried out in a newly collected five-generation Chinese family with DSAP. In addition, six candidate genes were screened for possible DSAP-associated mutations.

RESULTS

DSAP in this family was associated with chromosome 12q. Fine mapping and haplotype construction refined the DSAP1 locus to a 4.4-cM interval. No disease-associated mutation was detected in CRY1, C4ST1, TXNRD1, HCF2, CMKLR1 or KIAA0789 genes.

CONCLUSIONS

The DSAP1 locus was localized to a 4.4-cM interval at chromosome 12q23.2-24.1. CRY1, C4ST1, TXNRD1, HCF2, CMKLR1 and KIAA0789 genes were not associated with DSAP1.

Specificities of three distinct human chondroitin/dermatan N-acetylgalactosamine 4-O-sulfotransferases demonstrated using partially desulfated dermatan sulfate as an acceptor: implication of differential roles in dermatan sulfate biosynthesis

4-O-Sulfation of GalNAc is a high frequency modification of chondroitin sulfate and dermatan sulfate (DS), and three major GalNAc 4-O-sulfotransferases including dermatan 4-O-sulfotransferase-1 (D4ST-1) and chondroitin 4-O-sulfotransferases-1 and -2 (C4ST-1 and -2) have been identified. 4-O-Sulfation of GalNAc during DS biosynthesis had long been postulated to be a prerequisite for iduronic acid (IdoUA) formation by C5-epimerization of GlcUA. This hypothesis has recently been argued based on enzymological studies using microsomes that C5-epimerization precedes 4-O-sulfation, which was further supported by the specificity of the cloned D4ST-1 with predominant preference for IdoUA-GalNAc flanked by GlcUA-GalNAc over IdoUA-GalNAc flanked by IdoUA-GalNAc in exhaustively desulfated dermatan. Whereas the counterproposal explains the initial reactions, apparently it cannot rationalize the synthetic mechanism of IdoUA-GalNAc(4-O-sulfate)-rich clusters typical of mature DS chains. In this study, we examined detailed specificities of the three recombinant human 4-O-sulfotransferases using partially desulfated DS as an acceptor. Enzymatic analysis of the transferase reaction products showed that D4ST-1 far more efficiently transferred sulfate to GalNAc residues in -IdoUA-Gal-NAc-IdoUA-than in -GlcUA-GalNAc-GlcUA-sequences. In contrast, C4ST-1 showed the opposite preference, and C4ST-2 used GalNAc residues in both sequences to comparable degrees, being consistent with its phylogenetic relations to D4ST-1 and C4ST-1. Structural analysis of the oligosaccharides, which were isolated after chondroitinase AC-I digestion of the 35S-labeled transferase reaction products, revealed for the first time that D4ST-1, as compared with C4ST-1 and C4ST-2, most efficiently utilized GalNAc residues located not only in the sequence -IdoUA-GalNAc-IdoUA- but also in -GlcUA-Gal-NAc-IdoUA- and -IdoUA-GalNAc-GlcUA-. The isolated oligosaccharide structures also suggest that 4-O-sulfation promotes subsequent 4-O-sulfation of GalNAc in the neighboring disaccharide unit.

Altered content composition and structure of glycosaminoglycans and proteoglycans in gastric carcinoma

Glycosaminoglycans (GAGs) in proteoglycan (PG) forms or as free GAGs are implicated in the growth and progression of malignant tumors. These macromolecules were investigated in human gastric carcinoma (HGC) and compared with those in human normal gastric mucosa (HNG). We report that HGC contained about 2-fold increased amounts of GAGs in comparison to HNG. Specifically, HGC showed 3- and 2.5-fold net increase in chondroitin sulphate (CS) and hyaluronan (HA) contents, respectively. Dermatan sulphate (DS) was slightly increased, but the amount of heparan sulphate (HS) was decreased. Of particular, interest were the quite different sulphation profiles of CS and DS chains in HGC in which, non-sulphated and 6-sulphated disaccharide units were increased 10 and 4 times, respectively, in comparison to HNG. On PG level, three different populations were identified in both HNG and HGC, being HSPGs, versican (CS/DS chains) and decorin (CS/DS chains). In HGC, the amounts of versican and decorin were significantly increased about 3- and 8-fold, respectively. These PGs were also characterized by marked decrease in hydrodynamic size and GAG content per PG molecule. Analysis of Delta-disaccharide of versican and decorin from HGC showed an increase of 6-sulphated Delta-disaccharides (Delta di-6S) and non-sulphated Delta-disaccharides (Delta di-0S) with a parallel decrease of 4-sulphated Delta-disaccharides (Delta di-4S) as compared to HNG, which closely correlated with the increase of CS content. In addition, the accumulation of core proteins of versican and decorin in HGC was also associated with many post-translational modifications, referring to the number, size, degree and patterns of sulphation and epimerization of CS/DS chains. Studies on the modified metabolism of PGs/GAGs are under progress and will help in deeper understanding of the environment in which tumor cells proliferate and invade.

Arterial wall chondroitin sulfate proteoglycans: diverse molecules with distinct roles in lipoprotein retention and atherogenesis

Chondroitin sulfate proteoglycans (CSPGs) of the arterial wall are generally considered to be atherogenic because of their ability to trap cholesterol-rich lipoproteins in vitro. Nevertheless, CSPGs are a diverse group of molecules with a long evolutionary history and distinct biologic functions. The three principal CSPGs in the arterial wall are versican, which is part of the hyalectan gene family; and decorin and biglycan, which are members of a separate gene family, the small leucine-rich proteoglycans. Importantly, there is now substantial evidence that the different molecular species of CSPGs participate unequally in lipoprotein retention, and that they exert unequal regulatory effects that are related to atherogenesis. Recently available murine models with genetic manipulations that affect CSPGs now allow causal studies of the roles of these molecules to be conducted in vivo, with occasionally surprising results. Moreover, tools are being developed to examine human genetic variations that are relevant to CSPGs, which may provide additional important insights into the human disease. The era in which proteoglycans are regarded as a nondescript backdrop, playing purely nonspecific structural roles, is over. Studies in manipulated animals and in human populations will continue to reveal precise, dynamic roles for these fascinating and ancient molecules.

Molecular cloning and characterization of GalNAc 4-sulfotransferase expressed in human pituitary gland

We have previously cloned chondroitin-4-sulfotransferase (C4ST) cDNA from mouse brain. In this paper, we report cloning and characterization of GalNAc 4-sulfotransferase (GalNAc4ST), which transfers sulfate to position 4 of the nonreducing terminal GalNAc residue. The obtained cDNA contains a single open reading frame that predicts a type II transmembrane protein composed of 424 amino acid residues. Identity of the amino acid sequence between GalNAc4ST and human C4ST was 30%. When the cDNA was transfected in COS-7 cells, sulfotransferase activity toward carbonic anhydrase VI was overexpressed but no sulfotransferase activity toward chondroitin or desulfated dermatan sulfate was increased over the control. Sulfation of carbonic anhydrase VI by the recombinant GalNAc4ST occurred at position 4 of the GalNAc residue of N-linked oligosaccharides. The recombinant GalNAc4ST transferred sulfate to position 4 of GalNAc residue of p-nitrophenyl GalNAc, indicating that this sulfotransferase transfers sulfate to position 4 at the nonreducing terminal GalNAc residue. Dot blot analysis showed that the message of GalNAc4ST was expressed strongly in the human pituitary, suggesting that the cloned GalNAc4ST may be involved in the synthesis of the nonreducing terminal GalNAc 4-sulfate residues found in the N-linked oligosaccharides of pituitary glycoprotein hormones.