Nuclear translocation of heparan sulfate proteoglycans and their functional significance

Global impact of proteoglycan science on human diseases

In this comprehensive review, we will dissect the impact of research on proteoglycans focusing on recent developments involved in their synthesis, degradation, and interactions, while critically assessing their usefulness in various biological processes. The emerging roles of proteoglycans in global infections, specifically the SARS-CoV-2 pandemic, and their rising functions in regenerative medicine and biomaterial science have significantly affected our current view of proteoglycans and related compounds. The roles of proteoglycans in cancer biology and their potential use as a next-generation protein-based adjuvant therapy to combat cancer is also emerging as a constructive and potentially beneficial therapeutic strategy. We will discuss the role of proteoglycans in selected and emerging areas of proteoglycan science, such as neurodegenerative diseases, autophagy, angiogenesis, cancer, infections and their impact on mammalian diseases.

Heparan sulfate proteoglycans (HSPGs) of the ocular lens

Heparan sulfate proteoglycans (HSPGs) reside in most cells; on their surface, in the pericellular milieu and/or extracellular matrix. In the eye, HSPGs can orchestrate the activity of key signalling molecules found in the ocular environment that promote its development and homeostasis. To date, our understanding of the specific roles played by individual HSPG family members, and the heterogeneity of their associated sulfated HS chains, is in its infancy. The crystalline lens is a relatively simple and well characterised ocular tissue that provides an ideal stage to showcase and model the expression and unique roles of individual HSPGs. Individual HSPG core proteins are differentially localised to eye tissues in a temporal and spatial developmental- and cell-type specific manner, and their loss or functional disruption results in unique phenotypic outcomes for the lens, and other ocular tissues. More recent work has found that different HS sulfation enzymes are also presented in a cell- and tissue-specific manner, and that disruption of these different sulfation patterns affects specific HS-protein interactions. Not surprisingly, these sulfated HS chains have also been reported to be required for lens and eye development, with dysregulation of HS chain structure and function leading to pathogenesis and eye-related phenotypes. In the lens, HSPGs undergo significant and specific changes in expression and function that can drive pathology, or in some cases, promote tissue repair. As master signalling regulators, HSPGs may one day serve as valuable biomarkers, and even as putative targets for the development of novel therapeutics, not only for the eye but for many other systemic pathologies.

Proteolysis: a key post-translational modification regulating proteoglycans

Proteoglycans are composite molecules comprising a protein backbone, i.e., the core protein, with covalently attached glycosaminoglycan chains of distinct chemical types. Most proteoglycans are secreted or attached to the cell membrane. Their specialized structures, binding properties, and biophysical attributes underlie diverse biological roles, which include modulation of tissue mechanics, cell adhesion, and the sequestration and regulated release of morphogens, growth factors, and cytokines. As an irreversible post-translational modification, proteolysis has a profound impact on proteoglycan function, abundance, and localization. Proteolysis is required for molecular maturation of some proteoglycans, clearance of extracellular matrix proteoglycans during tissue remodeling, generation of bioactive fragments from proteoglycans, and ectodomain shedding of cell-surface proteoglycans. Genetic evidence shows that proteoglycan core protein proteolysis is essential for diverse morphogenetic events during embryonic development. In contrast, dysregulated proteoglycan proteolysis contributes to osteoarthritis, cardiovascular disorders, cancer, and inflammation. Proteolytic fragments of perlecan, versican, aggrecan, brevican, collagen XVIII, and other proteoglycans are associated with independent biological activities as so-called matrikines. Yet, proteoglycan proteolysis has been investigated to only a limited extent to date. Here, we review the actions of proteases on proteoglycans and illustrate their functional impact with several examples. We discuss the applications and limitations of strategies used to define cleavage sites in proteoglycans and explain how proteoglycanome-wide proteolytic mapping, which is desirable to fully understand the impact of proteolysis on proteoglycans, can be facilitated by integrating classical proteoglycan isolation methods with mass spectrometry-based proteomics.

Regulation of FGF-2, FGF-18 and Transcription Factor Activity by Perlecan in the Maturational Development of Transitional Rudiment and Growth Plate Cartilages and in the Maintenance of Permanent Cartilage Homeostasis

The aim of this study was to highlight the roles of perlecan in the regulation of the development of the rudiment developmental cartilages and growth plate cartilages, and also to show how perlecan maintains permanent articular cartilage homeostasis. Cartilage rudiments are transient developmental templates containing chondroprogenitor cells that undergo proliferation, matrix deposition, and hypertrophic differentiation. Growth plate cartilage also undergoes similar changes leading to endochondral bone formation, whereas permanent cartilage is maintained as an articular structure and does not undergo maturational changes. Pericellular and extracellular perlecan-HS chains interact with growth factors, morphogens, structural matrix glycoproteins, proteases, and inhibitors to promote matrix stabilization and cellular proliferation, ECM remodelling, and tissue expansion. Perlecan has mechanotransductive roles in cartilage that modulate chondrocyte responses in weight-bearing environments. Nuclear perlecan may modulate chromatin structure and transcription factor access to DNA and gene regulation. Snail-1, a mesenchymal marker and transcription factor, signals through FGFR-3 to promote chondrogenesis and maintain Acan and type II collagen levels in articular cartilage, but prevents further tissue expansion. Pre-hypertrophic growth plate chondrocytes also express high Snail-1 levels, leading to cessation of Acan and CoI2A1 synthesis and appearance of type X collagen. Perlecan differentially regulates FGF-2 and FGF-18 to maintain articular cartilage homeostasis, rudiment and growth plate cartilage growth, and maturational changes including mineralization, contributing to skeletal growth.

An Atlas of Heparan Sulfate Proteoglycans in the Postnatal Rat Lens

Purpose

The arrangement of lens cells is regulated by ocular growth factors. Although the effects of these inductive molecules on lens cell behavior (proliferation, survival, and fiber differentiation) are well-characterized, the precise mechanisms underlying the regulation of growth factor-mediated signaling in lens remains elusive. Increasing evidence highlights the importance of heparan sulfate proteoglycans (HSPGs) for the signaling regulation of growth factors; however, the identity of the different lens HSPGs and the specific roles they play in lens biology are still unknown.

Methods

Semiquantitative real-time (RT)‐PCR and immunolabeling were used to characterize the spatial distribution of all known HSPG core proteins and their associated glycosaminoglycans (heparan and chondroitin sulfate) in the postnatal rat lens. Fibroblast growth factor (FGF)-2-treated lens epithelial explants, cultured in the presence of Surfen (an inhibitor of heparan sulfate [HS]-growth factor binding interactions) were used to investigate the requirement for HS in FGF-2-induced proliferation, fiber differentiation, and ERK1/2-signaling.

Results

The lens expresses all HSPGs. These HSPGs are differentially localized to distinct functional regions of the lens. In vitro, inhibition of HS-sulfation with Surfen blocked FGF-2-mediated ERK1/2-signaling associated with lens epithelial cell proliferation and fiber differentiation, highlighting that these cellular processes are dependent on HS.

Conclusions

These findings support a requirement for HSPGs in FGF-2 driven lens cell proliferation and fiber differentiation. The identification of specific HSPG core proteins in key functional lens regions, and the divergent expression patterns of closely related HSPGs, suggests that different HSPGs may differentially regulate growth factor signaling networks leading to specific biological events involved in lens growth and maintenance.

Extracellular matrix-based cancer targeting

Tumor extracellular matrix (ECM) operates in a coordinated mode with cancer and stroma cells to evoke the multistep process of metastatic potential. The remodeled tumor-associated matrix provides a point for direct or complementary therapeutic targeting. Here, we cover and critically address the importance of ECM networks and their macromolecules in cancer. We focus on the roles of key structural and functional ECM components, and their degradation enzymes and extracellular vesicles, aiming at improving our understanding of the mechanisms contributing to tumor initiation, growth, and dissemination, and discuss potential new approaches for ECM-based therapeutic targeting and diagnosis.

What Are the Potential Roles of Nuclear Perlecan and Other Heparan Sulphate Proteoglycans in the Normal and Malignant Phenotype

The recent discovery of nuclear and perinuclear perlecan in annulus fibrosus and nucleus pulposus cells and its known matrix stabilizing properties in tissues introduces the possibility that perlecan may also have intracellular stabilizing or regulatory roles through interactions with nuclear envelope or cytoskeletal proteins or roles in nucleosomal-chromatin organization that may regulate transcriptional factors and modulate gene expression. The nucleus is a mechano-sensor organelle, and sophisticated dynamic mechanoresponsive cytoskeletal and nuclear envelope components support and protect the nucleus, allowing it to perceive and respond to mechano-stimulation. This review speculates on the potential roles of perlecan in the nucleus based on what is already known about nuclear heparan sulphate proteoglycans. Perlecan is frequently found in the nuclei of tumour cells; however, its specific role in these diseased tissues is largely unknown. The aim of this review is to highlight probable roles for this intriguing interactive regulatory proteoglycan in the nucleus of normal and malignant cell types.

A Pro-Tumorigenic Effect of Heparanase 2 (Hpa2) in Thyroid Carcinoma Involves Its Localization to the Nuclear Membrane

Activity of the endo-beta-glucuronidase heparanase, capable of cleaving heparan sulfate (HS), is most often elevated in many types of tumors, associating with increased tumor metastasis and decreased patients' survival. Heparanase is therefore considered to be a valid drug target, and heparanase inhibitors are being evaluated clinically in cancer patients. Heparanase 2 (Hpa2) is a close homolog of heparanase that gained very little attention, likely because it lacks HS-degrading activity typical of heparanase. The role of Hpa2 in cancer was not examined in detail. In head and neck cancer, high levels of Hpa2 are associated with decreased tumor cell dissemination to regional lymph nodes and prolonged patients' survival, suggesting that Hpa2 functions to attenuate tumor growth. Here, we examined the role of Hpa2 in normal thyroid tissue and in benign thyroid tumor, non-metastatic, and metastatic papillary thyroid carcinoma (PTC) utilizing immunostaining in correlation with clinicopathological parameters. Interestingly, we found that Hpa2 staining intensity does not significantly change in the transition from normal thyroid gland to benign, non-metastatic, or metastatic thyroid carcinoma. Remarkably, we observed that in some biopsies, Hpa2 is accumulating on the membrane (envelop) of the nucleus and termed this cellular localization NM (nuclear membrane). Notably, NM localization of Hpa2 occurred primarily in metastatic PTC and was associated with an increased number of positive (metastatic) lymph nodes collected at surgery. These results describe for the first time unrecognized localization of Hpa2 to the nuclear membrane, implying that in PTC, Hpa2 functions to promote tumor metastasis.

Biology of the Heparanase-Heparan Sulfate Axis and Its Role in Disease Pathogenesis

Cell surface proteoglycans are important constituents of the glycocalyx and participate in cell-cell and cell-extracellular matrix (ECM) interactions, enzyme activation and inhibition, and multiple signaling routes, thereby regulating cell proliferation, survival, adhesion, migration, and differentiation. Heparanase, the sole mammalian heparan sulfate degrading endoglycosidase, acts as an "activator" of HS proteoglycans, thus regulating tissue hemostasis. Heparanase is a multifaceted enzyme that together with heparan sulfate, primarily syndecan-1, drives signal transduction, immune cell activation, exosome formation, autophagy, and gene transcription via enzymatic and nonenzymatic activities. An important feature is the ability of heparanase to stimulate syndecan-1 shedding, thereby impacting cell behavior both locally and distally from its cell of origin. Heparanase releases a myriad of HS-bound growth factors, cytokines, and chemokines that are sequestered by heparan sulfate in the glycocalyx and ECM. Collectively, the heparan sulfate-heparanase axis plays pivotal roles in creating a permissive environment for cell proliferation, differentiation, and function, often resulting in the pathogenesis of diseases such as cancer, inflammation, endotheliitis, kidney dysfunction, tissue fibrosis, and viral infection.

Heparan Sulfate Glycosaminoglycans: (Un)Expected Allies in Cancer Clinical Management

In an era when cancer glycobiology research is exponentially growing, we are witnessing a progressive translation of the major scientific findings to the clinical practice with the overarching aim of improving cancer patients' management. Many mechanistic cell biology studies have demonstrated that heparan sulfate (HS) glycosaminoglycans are key molecules responsible for several molecular and biochemical processes, impacting extracellular matrix properties and cellular functions. HS can interact with a myriad of different ligands, and therefore, hold a pleiotropic role in regulating the activity of important cellular receptors and downstream signalling pathways. The aberrant expression of HS glycan chains in tumours determines main malignant features, such as cancer cell proliferation, angiogenesis, invasion and metastasis. In this review, we devote particular attention to HS biological activities, its expression profile and modulation in cancer. Moreover, we highlight HS clinical potential to improve both diagnosis and prognosis of cancer, either as HS-based biomarkers or as therapeutic targets.

Mechano growth factor interacts with nucleolin to protect against cisplatin-induced neurotoxicity

Mechano growth factor (MGF) is an alternatively spliced form of insulin-like growth factor-1 (IGF-1) that has shown to be neuroprotective against 6-hydroxydopamine toxicity and ischemic injury in the brain. MGF also induces neural stem cell proliferation in the hippocampus and preserves olfactory function in aging mice. Cisplatin is a chemotherapy drug that induces peripheral neuropathy in 30-40% of treated patients. Our studies were designed to see if MGF would protect dorsal root ganglion (DRG) neurons from cisplatin-induced neurotoxicity and to identify potential mechanisms that may be involved. Expression of endogenous MGF in adult DRG neurons in vivo ameliorated cisplatin-induced thermal hyperalgesia. Exogenous MGF and MGF with a cysteine added to the N-terminus (CMGF) also protected embryonic DRG neurons from cisplatin-induced cell death in vitro. Mass spectroscopy analysis of proteins bound to MGF showed that nucleolin is a key-binding partner. Antibodies against nucleolin prevented the neuroprotective effect of MGF and CMGF in culture. Both nucleolin and MGF are located in the nucleolus of DRG neurons. RNAseq of RNA associated with MGF indicated that MGF may be involved in RNA processing, protein targeting and transcription/translation. Nucleolin is an RNA binding protein that is readily shuttled between the nucleus, cytoplasm and plasma membrane. Nucleolin and MGF may work together to prevent cisplatin-induced neurotoxicity. Exploring the known mechanisms of nucleolin may help us better understand the mechanisms of cisplatin toxicity and how MGF protects DRG neurons.

Involvement of Syndecan-1 and Heparanase in Cancer and Inflammation

The cell surface heparan sulfate proteoglycan Syndecan-1 acts as an important co-receptor for receptor tyrosine kinases and chemokine receptors, and as an adhesion receptor for structural glycoproteins of the extracellular matrix. It serves as a substrate for heparanase, an endo-β-glucuronidase that degrades specific domains of heparan sulfate carbohydrate chains and thereby alters the functional status of the proteoglycan and of Syndecan-1-bound ligands. Syndecan-1 and heparanase show multiple levels of functional interactions, resulting in mutual regulation of their expression, processing, and activity. These interactions are of particular relevance in the context of inflammation and malignant disease. Studies in animal models have revealed a mechanistic role of Syndecan-1 and heparanase in the regulation of contact allergies, kidney inflammation, multiple sclerosis, inflammatory bowel disease, and inflammation-associated tumorigenesis. Moreover, functional interactions between Syndecan-1 and heparanase modulate virtually all steps of tumor progression as defined in the Hallmarks of Cancer. Due to their prognostic value in cancer, and their mechanistic involvement in tumor progression, Syndecan-1 and heparanase have emerged as important drug targets. Data in preclinical models and preclinical phase I/II studies have already yielded promising results that provide a translational perspective.

SNAIL expression correlates with the translocation of syndecan‑1 intracellular domain into the nucleus in prostate cancer cell lines

Zinc finger protein SNAI1 (SNAIL) and zinc finger protein SNAI2 (SLUG) transcription factors promote epithelial-mesenchymal transition, a process through which epithelial cells acquire a mesenchymal phenotype, increasing their migratory and invasive properties. In prostate cancer (PCa) progression, increased expression levels of SNAIL and SLUG have been described. In advanced PCa, a decrease in the cell surface proteoglycan syndecan-1 (SDC-1), which has a role in cell-to-extracellular matrix adhesion, has been observed. Notably, SDC-1 nuclear location has been observed in mesenchymal cancers. The present study aimed to determine if SNAIL and SLUG may be associated with the nuclear location of SDC-1 in PCa. To determine the location of SDC-1, antibodies against its intracellular domain (ID) or extracellular domain (ED) were used in benign prostatic hyperplasia (BPH) and PCa samples with high Gleason scores. Only ID-SDC-1 was located in the cell nuclei in advanced PCa samples, but not in the BPH samples. ED-SDC-1 was located in the cell membrane and cytoplasm, exhibiting decreased levels in PCa in comparison with those in BPH. Furthermore, LNCaP and PC3 PCa cell lines with ectopic SNAIL expression exhibited nuclear ID-SDC-1. No change was observed in the ED-SDC-1 levels, and maintained its location in the cell membrane and cytoplasm. SLUG induced no change in ID-SDC-1 location. At the protein level, an association between SNAIL and nuclear ID-SDC-1 was observed. In conclusion, the results of the present study demonstrated that nuclear ID-SDC-1 localization was associated with SNAIL expression in PCa cell lines.

Discovery of HSPG2 (Perlecan) as a Therapeutic Target in Triple Negative Breast Cancer

In recent years, there have been significant advances in the treatment of breast cancer resulting in remarkably high survival rates. However, treatment options for metastatic triple negative breast cancer (TNBC) are quite limited due to a lack of identifiable, unique markers. Using a phage display-based whole cell biopanning procedure, we developed two human antibodies that bind to tumor cells with a metastatic TNBC phenotype. Our studies further identified domain 1 of HSPG2 (perlecan) protein as the cognate cell surface antigen bound by the antibody. Immunohistochemistry studies utilizing patient tissue samples revealed significant cell surface expression of HSPG2 in both primary tumors and metastatic lesions. Further, higher HSPG2 expression correlated with poor survival in TNBC. The affinity-matured antibody inhibited the growth of triple negative MDA-MB-231 tumors to a greater extent in nude mice than in NSG mice, pointing to the potential role of natural killer cell-mediated antibody-dependent cell cytotoxicity. This mechanism of action was confirmed through in vitro assays using mouse splenocytes and human peripheral blood mononuclear cells (PBMCs). These results suggest that HSPG2 is a promising target in metastatic TNBC and HSPG2-targeted antibodies could represent a potentially novel class of targeted therapeutics for TNBC.

Heparan Sulfate Mimetics in Cancer Therapy: The Challenge to Define Structural Determinants and the Relevance of Targets for Optimal Activity

Beyond anticoagulation, the therapeutic potential of heparin derivatives and heparan sulfate (HS) mimetics (functionally defined HS mimetics) in oncology is related to their ability to bind and modulate the function of a vast array of HS-binding proteins with pivotal roles in cancer growth and progression. The definition of structural/functional determinants and the introduction of chemical modifications enabled heparin derivatives to be identified with greatly reduced or absent anticoagulant activity, but conserved/enhanced anticancer activity. These studies paved the way for the disclosure of structural requirements for the inhibitory effects of HS mimetics on heparanase, selectins, and growth factor receptor signaling, as well as for the limitation of side effects. Actually, HS mimetics affect the tumor biological behavior via a multi-target mechanism of action based on their effects on tumor cells and various components of the tumor microenvironment. Emerging evidence indicates that immunomodulation can participate in the antitumor activity of these agents. Significant ability to enhance the antitumor effects of combination treatments with standard therapies was shown in several tumor models. While the first HS mimetics are undergoing early clinical evaluation, an improved understanding of the molecular contexts favoring the antitumor action in certain malignancies or subgroups is needed to fully exploit their potential.

The nature of the conserved basic amino acid sequences found among 437 heparin binding proteins determined by network analysis

In multicellular organisms, a large number of proteins interact with the polyanionic polysaccharides heparan sulphate (HS) and heparin. These interactions are usually assumed to be dominated by charge-charge interactions between the anionic carboxylate and/or sulfate groups of the polysaccharide and cationic amino acids of the protein. A major question is whether there exist conserved amino acid sequences for HS/heparin binding among these diverse proteins. Potentially conserved HS/heparin binding sequences were sought amongst 437 HS/heparin binding proteins. Amino acid sequences were extracted and compared using a Levenshtein distance metric. The resultant similarity matrices were visualised as graphs, enabling extraction of strongly conserved sequences from highly variable primary sequences while excluding short, core regions. This approach did not reveal extensive, conserved HS/heparin binding sequences, rather a number of shorter, more widely spaced sequences that may work in unison to form heparin-binding sites on protein surfaces, arguing for convergent evolution. Thus, it is the three-dimensional arrangement of these conserved motifs on the protein surface, rather than the primary sequence per se, which are the evolutionary elements.

Molecular targets and signaling pathways regulated by nuclear translocation of syndecan-1

Background

The cell-surface heparan sulfate proteoglycan syndecan-1 is important for tumor cell proliferation, migration, and cell cycle regulation in a broad spectrum of malignancies. Syndecan-1, however, also translocates to the cell nucleus, where it might regulate various molecular functions.

Results

We used a fibrosarcoma model to dissect the functions of syndecan-1 related to the nucleus and separate them from functions related to the cell-surface. Nuclear translocation of syndecan-1 hampered the proliferation of fibrosarcoma cells compared to the mutant lacking nuclear localization signal. The growth inhibitory effect of nuclear syndecan-1 was accompanied by significant accumulation of cells in the G0/G1 phase, which indicated a possible G1/S phase arrest.

We implemented multiple, unsupervised global transcriptome and proteome profiling approaches and combined them with functional assays to disclose the molecular mechanisms that governed nuclear translocation and its related functions. We identified genes and pathways related to the nuclear compartment with network enrichment analysis of the transcriptome and proteome. The TGF-β pathway was activated by nuclear syndecan-1, and three genes were significantly altered with the deletion of nuclear localization signal: EGR-1 (early growth response 1), NEK11 (never-in-mitosis gene a-related kinase 11), and DOCK8 (dedicator of cytokinesis 8). These candidate genes were coupled to growth and cell-cycle regulation. Nuclear translocation of syndecan-1 influenced the activity of several other transcription factors, including E2F, NFκβ, and OCT-1. The transcripts and proteins affected by syndecan-1 showed a striking overlap in their corresponding biological processes. These processes were dominated by protein phosphorylation and post-translation modifications, indicative of alterations in intracellular signaling. In addition, we identified molecules involved in the known functions of syndecan-1, including extracellular matrix organization and transmembrane transport.

Conclusion

Collectively, abrogation of nuclear translocation of syndecan-1 resulted in a set of changes clustering in distinct patterns, which highlighted the functional importance of nuclear syndecan-1 in hampering cell proliferation and the cell cycle. This study emphasizes the importance of the localization of syndecan-1 when considering its effects on tumor cell fate.

Electronic supplementary material

The online version of this article (10.1186/s12860-017-0150-z) contains supplementary material, which is available to authorized users.

Estrogen receptor beta as epigenetic mediator of miR-10b and miR-145 in mammary cancer

Even though the role of estrogen receptor alpha (ERα) in the modulation of breast cancer cells' behavior is thoroughly studied, the biological functions of its isoform, ERβ, are less elucidated. The suppression of ERβ in the aggressive ERα-negative MDA-MB-231 breast cancer cells resulted in the inhibition of epithelial to mesenchymal transition (EMT) and major changes in the basic functional properties and expression levels of certain matrix components of breast cancer cells. This arrest in metastatic potential of breast cancer cells suggests the contribution of ERβ in the induction of a more aggressive phenotype in MDA-MB-231 breast cancer cells. The epigenetic alterations are responsible for the ability of the tumor cells to metastasize. Here, we report for the first time that the suppression of ERβ in MDA-MB-231 breast cancer cells leads to significant changes in the expression profiles of specific microRNAs, including miR-10b, miR-200b and miR-145. Growth of MCF-7 and MDA-MB-231 cells in estrogen-free medium has a diverse impact on miRNA expression and the behavior of these cells, suggesting the specific effect of estradiol on the miRNA expression profile depending on the ER status of breast cancer cells. Enhanced miR-10b expression or silencing of miR-145 clearly revealed that these microRNAs can regulate the functional properties, EMT program and the expression of major matrix components known to be implicated in breast cancer aggressiveness. Our data revealed that miR-10b is strongly implicated in the regulation of functional properties, EMT program and Erk1/2 signaling in shERβ MDA-MB-231 cells, thus affecting the extracellular matrix (ECM) composition, including syndecan-1, proteolytic behavior, especially MMP2, MMP7 and MMP9 expression and subsequently the aggressiveness of these cells. Accordingly, the inhibition of miR-145 expression significantly increased the aggressiveness of shERβ MDA-MB-231 cells and induced EMT. Moreover, miR-145 inhibition resulted in important changes in the gene and protein levels of ECM mediators, such as HER2 and several MMPs, whereas it significantly increased the phosphorylated levels of Erk1/2 kinases in these cells, suggesting the crucial role of miR-145 in this signaling pathway. These novel results suggest that the alterations in cell behavior and in ECM composition caused by the suppression of ERβ in MDA-MB-231 cells are closely related to certain epigenetic miRNA-induced alterations. Targeting the ERβ-regulated miR-10b and miR-145 is a promising tool for diagnosis and pharmaceutical targeting in breast cancer.

2-O, 3-O Desulfated Heparin Blocks High Mobility Group Box 1 Release by Inhibition of p300 Acetyltransferase Activity

High mobility group box 1 (HMGB1) is an alarmin released from macrophages after infection or inflammation and is a biomarker of lung disease progression in patients with cystic fibrosis. We reported that 2-O, 3-O desulfated heparin (ODSH) inhibits the release of HMGB1 from murine macrophages triggered by neutrophil elastase both in vivo and in vitro. HMGB1 shuttles between the nucleus and the cytoplasm. When acetylated at lysine residues in the nuclear localization signal domains, HMGB1 is sequestered in the cytoplasm and is fated for secretion. In this study, we investigated the mechanism by which ODSH blocks HMGB1 secretion. We tested whether ODSH inhibits the activity of p300, a histone acetyltransferase that has been linked to HMGB1 acetylation and release. ODSH inhibited both neutrophil elastase and LPS-triggered HMGB1 release from the murine macrophage cell line RAW264.7 in a concentration-dependent manner. Fluorescein-labeled ODSH was taken up by RAW264.7 cells into the cytoplasm as well as the nucleus, suggesting an intracellular site of action of ODSH for blocking HMGB1 release. ODSH inhibited RAW264.7 cell nuclear extract, human macrophage nuclear extract, and recombinant p300 HAT activity in vitro, resulting in the failure to acetylate HMGB1. In silico molecular modeling predicted that of the numerous possible ODSH sequences, a small number preferentially recognizes a specific binding site on p300. Fluorescence binding studies showed that ODSH bound p300 tightly (dissociation constant ∼1 nM) in a highly cooperative manner. These results suggest that ODSH inhibited HMGB1 release, at least in part, by direct molecular inhibition of p300 HAT activity.

Syndecan 1 represses cell growth and FSH responsiveness in human granulosa cells

Albeit devoid of intrinsic catalytic activity, the transmembrane heparan sulphate proteoglycan syndecan 1 plays critical roles in cellular processes such as extracellular matrix crosstalk, cytoskeletal organization, cell spreading, proliferation and differentiation. During the ovarian cycle, the expression of syndecan 1 in granulosa cells shows cyclic variation suggesting that it might fulfil specific roles in follicle development. To investigate its physiological roles on granulosa cells, syndecan 1 was overexpressed in human granulosa cell line KGN which retains features of granulosa cells from small antral follicle such as estradiol (E2) synthesis and low expression of functional FSH receptor (FSHR). We demonstrated that overexpression of syndecan 1 in immature granulosa cells (KGN-SDC1) induces a profound alteration in their intrinsic characteristics including enhanced spreading and attachment, both associated with a reduced growth rate. Flow cytometry analysis revealed that syndecan 1 overexpression increases the percentage of KGN cells in quiescent phase. This partial cell cycle exit is concordant with downregulated levels of CCND1 and CDK4 and upregulated expression of CDK inhibitor CDKN1A. In parallel both unstimulated and FSH-induced E2 synthesis are reduced in KGN-SDC1 through both repression of CYP19A1 and FSHR mRNA associated with decreased levels of potential regulators NR5A1 and ESR2. Additionally, we provide evidence that transient cAMP accumulation reduction in cells overexpressing syndecan 1 is accompanied by an increase in cAMP-hydrolysing PDE activity. Our results demonstrated that syndecan 1 might regulate differentiation of granulosa cells and follicular development by means of various mechanisms involving morphological changes, control of signalling pathways and alterations in gene expressions.

Free French abstract: A French translation of this abstract is freely available at http://www.reproduction-online.org/content/153/6/797/suppl/DC2

Glycosaminoglycanomics: where we are

Glycosaminoglycans regulate numerous physiopathological processes such as development, angiogenesis, innate immunity, cancer and neurodegenerative diseases. Cell surface GAGs are involved in cell-cell and cell-matrix interactions, cell adhesion and signaling, and host-pathogen interactions. GAGs contribute to the assembly of the extracellular matrix and heparan sulfate chains are able to sequester growth factors in the ECM. Their biological activities are regulated by their interactions with proteins. The structural heterogeneity of GAGs, mostly due to chemical modifications occurring during and after their synthesis, makes the development of analytical techniques for their profiling in cells, tissues, and biological fluids, and of computational tools for mining GAG-protein interaction data very challenging. We give here an overview of the experimental approaches used in glycosaminoglycomics, of the major GAG-protein interactomes characterized so far, and of the computational tools and databases available to analyze and store GAG structures and interactions.

Immunohistochemical expression of heparanase isoforms and syndecan-1 proteins in colorectal adenomas

The proteoglycan syndecan-1 and the endoglucuronidases heparanase-1 and heparanase-2 are involved in molecular pathways that deregulate cell adhesion during carcinogenesis. Few studies have examined the expression of syndecan-1, heparanase-1 and mainly heparanase-2 proteins in non-neoplastic and neoplastic human colorectal adenoma tissues. The aim of this study was to analyze the correlation among the heparanase isoforms and the syndecan-1 proteins through immunohistochemical expression in the tissue of colorectal adenomas. Primary anti-human polyclonal anti-HPSE and anti-HPSE2 antibodies and primary anti-human monoclonal anti-SDC1 antibody were used in the immunohistochemical study. The expressions of heparanase-1 and heparanase-2 proteins were determined in tissue samples from 65 colorectal adenomas; the expression of syndecan-1 protein was obtained from 39 (60%) patients. The histological type of adenoma was tubular in 44 (67.7%) patients and tubular-villous in 21 (32.3%); there were no villous adenomas. The polyps were <1.0 cm in size in 54 (83.1%) patients and ≥1.0 cm in 11 (16.9%). The images were quantified by digital counter with a computer program for this purpose. The expression index represented the relationship between the intensity expression and the percentage of positively stained cells. The results showed that the average of heparanase-1, heparanase-2 and syndecan-1 expression index was 73.29 o.u./µm², 93.34 o.u./µm², and 55.29 o.u./µm², respectively. The correlation between the heparanase-1 and syndecan-1 expression index was positive (R=0.034) and significant (P=0.035). There was a negative (R= -0.384) and significant (P=0.016) correlation between the expression index of heparanase-1 and heparanase-2. A negative (R= -0.421) and significant (P=0.008) correlation between the expression index of heparanase-2 and syndecan-1 was found. We concluded that in colorectal adenomas, the heparanase-1 does not participate in syndecan-1 degradation; the heparanase-2 does not stimulate syndecan-1 degradation by the action of heparanase-1, and the heparanase-2 may be involved in the modulation of the heparanase-1 activity.

Serum Syndecan-1 Levels and Its Relationship to Disease Activity in Patients with Crohn's Disease

Background. Syndecan-1 (SDC-1), a member of the family of heparan sulfate proteoglycans, plays an important role in the resolution of inflammation. This study aimed to investigate the relationship between SDC-1 and disease activity in Crohn's disease (CD). Methods. Serum samples of 54 patients with CD and 30 healthy controls were obtained. First, SDC-1 levels of the CD patients were compared to the control group. Subsequently, SDC-1 levels were analyzed in patients with CD in active and remission periods. Finally, SDC-1 efficacy in predicting disease activity was evaluated by performing correlation analysis between SDC-1 and C-reactive protein (CRP) and Crohn's disease activity index (CDAI). Results. SDC-1 level was higher in the CD group (61.9 ± 42.6 ng/mL) compared with the control group (34.1 ± 8.0 ng/mL) (p = 0.03). SDC-1 levels were higher in active CD patients (97.1 ± 40.3 ng/mL) compared with those in remission (33.7 ± 13.5 ng/mL) (p < 0.001). A significant positive correlation was found between SDC-1 and CRP (r = 0.687, p < 0.001) and between SDC-1 and CDAI (r = 0.747, p < 0.001). Conclusion. Serum levels of SDC-1 are higher in CD compared to the normal population and can be an effective marker of disease severity.

Extracellular matrix as target for antitumor therapy

The aim of the present review is to survey the accumulated knowledge on the extracellular matrix (ECM) of tumors referring to its putative utility as therapeutic target. Following the traditional observation on the extensive morphological alteration in the tumor-affected tissue, the well-documented aberrant cellular regulation indicated that ECM components have an active role in tumor progression. However, due to the diverse functions and variable expression of proteoglycans, matrix proteins, and integrins, it is rather difficult to identify a comprehensive therapeutic target among ECM components. At present, the elevated level of heparanase and the prominent expression of αvβ5 integrin are considered as promising therapeutic targets. The inhibition of glycosaminoglycan offers another promising approach in the treatment of those tumors which are stimulated by proteoglycans. It can be ascertained that a selective ECM inhibitor would be a great asset to control metastasis driven by ECM-mediated signaling.

Distribution of syndecan-1 protein in developing mouse teeth

Syndecan-1 is a cell surface proteoglycan involved in the regulation of various biological processes such as proliferation, migration, condensation and differentiation of cells, intercellular communication, and morphogenesis. The extracellular domain of syndecan-1 can bind to extracellular matrix components and signaling molecules, while its intracellular domain interacts with cytoskeletal proteins, thus allowing the transfer of information about extracellular environment changes into the cell that consequently affect cellular behavior. Although previous studies have shown syndecan-1 expression during precise stages of tooth development, there is no equivalent study regrouping the expression patterns of syndecan-1 during all stages of odontogenesis. Here we examined the distribution of syndecan-1 protein in embryonic and post-natal developing mouse molars and incisors. Syndecan-1 distribution in mesenchymal tissues such as dental papilla and dental follicle was correlated with proliferating events and its expression was often linked to stem cell niche territories. Syndecan-1 was also expressed in mesenchymal cells that will differentiate into the dentin producing odontoblasts, but not in differentiated functional odontoblasts. In the epithelium, syndecan-1 was detected in all cell layers, by the exception of differentiated ameloblasts that form the enamel. Furthermore, syndecan-1 was expressed in osteoblast precursors and osteoclasts of the alveolar bone that surrounds the developing tooth germs. Taken together these results show the dynamic nature of syndecan-1 expression during odontogenesis and suggest its implication in various processes of tooth development and homeostasis.

Fell-Muir Lecture: Syndecans: from peripheral coreceptors to mainstream regulators of cell behaviour

In the 25 years, as the first of the syndecan family was cloned, interest in these transmembrane proteoglycans has steadily increased. While four distinct members are present in mammals, one is present in invertebrates, including C. elegans that is such a powerful genetic model. The syndecans, therefore, have a long evolutionary history, indicative of important roles. However, these roles have been elusive. The knockout in the worm has a developmental neuronal phenotype, while knockouts of the syndecans in the mouse are mild and mostly limited to post-natal rather than developmental effects. Moreover, their association with high-affinity receptors, such as integrins, growth factor receptors, frizzled and slit/robo, have led to the notion that syndecans are coreceptors, with minor roles. Given that their heparan sulphate chains can gather many different protein ligands, this gave credence to views that the importance of syndecans lay with their ability to concentrate ligands and that only the extracellular polysaccharide was of significance. Syndecans are increasingly identified with roles in the pathogenesis of many diseases, including tumour progression, vascular disease, arthritis and inflammation. This has provided impetus to understanding syndecan roles in more detail. It emerges that while the cytoplasmic domains of syndecans are small, they have clear interactive capabilities, most notably with the actin cytoskeleton. Moreover, through the binding and activation of signalling molecules, it is likely that syndecans are important receptors in their own right. Here, an overview of syndecan structure and function is provided, with some prospects for the future.

Heparin and liver heparan sulfate can rescue hepatoma cells from topotecan action

Topotecan (TpT) is a major inhibitory compound of topoisomerase (topo) I that plays important roles in gene transcription and cell division. We have previously reported that heparin and heparan sulfate (HS) might be transported to the cell nucleus and they can interact with topoisomerase I. We hypothesized that heparin and HS might interfere with the action of TpT. To test this hypothesis we isolated topoisomerase I containing cell nuclear protein fractions from normal liver, liver cancer tissues, and hepatoma cell lines. The enzymatic activity of these extracts was measured in the presence of heparin, liver HS, and liver cancer HS. In addition, topo I activity, cell viability, and apoptosis of HepG2 and Hep3B cells were investigated after heparin and TpT treatments. Liver cancer HS inhibited topo I activity in vitro. Heparin treatment abrogated topo I enzyme activity in Hep3B cells, but not in HepG2 cells, where the basal activity was higher. Heparin protected the two hepatoma cell lines from TpT actions and decreased the rate of TpT induced S phase block and cell death. These results suggest that heparin and HS might interfere with the function of TpT in liver and liver cancer.