Syndecans, signaling, and cell adhesion

Proteoglycans: Systems-Level Insight into Their Expression in Healthy and Diseased Placentas

Proteoglycan macromolecules play key roles in several physiological processes (e.g., adhesion, proliferation, migration, invasion, angiogenesis, and apoptosis), all of which are important for placentation and healthy pregnancy. However, their precise roles in human reproduction have not been clarified. To fill this gap, herein, we provide an overview of the proteoglycans' expression and role in the placenta, in trophoblast development, and in pregnancy complications (pre-eclampsia, fetal growth restriction), highlighting one of the most important members of this family, syndecan-1 (SDC1). Microarray data analysis showed that of 34 placentally expressed proteoglycans, SDC1 production is markedly the highest in the placenta and that SDC1 is the most upregulated gene during trophoblast differentiation into the syncytiotrophoblast. Furthermore, placental transcriptomic data identified dysregulated proteoglycan genes in pre-eclampsia and in fetal growth restriction, including SDC1, which is supported by the lower concentration of syndecan-1 in maternal blood in these syndromes. Overall, our clinical and in vitro studies, data analyses, and literature search pointed out that proteoglycans, as important components of the placenta, may regulate various stages of placental development and participate in the maintenance of a healthy pregnancy. Moreover, syndecan-1 may serve as a useful marker of syncytialization and a prognostic marker of adverse pregnancy outcomes. Further studies are warranted to explore the role of proteoglycans in healthy and complicated pregnancies, which may help in diagnostic or therapeutic developments.

Syndecan-4 in Tumor Cell Motility

Simple Summary

Cell migration is crucial fReaor metastasis formation and a hallmark of malignancy. The primary cause of high mortality among oncology patients is the ability of cancer cells to metastasize. To form metastasis, primary tumor cells must be intrinsically able to move. The transmembrane, heparan sulfate proteoglycan syndecan-4 (SDC4) exhibits multiple functions in signal transduction by regulating Rac1 GTPase activity and consequently actin remodeling, as well as regulating focal adhesion kinase, protein kinase C-alpha and the level of intracellular calcium. By affecting several signaling pathways and biological processes, SDC4 is involved in cell migration under physiological and pathological conditions as well. In this review, we discuss the SDC4-mediated cell migration focusing on the role of SDC4 in tumor cell movement.

Abstract

Syndecan-4 (SDC4) is a ubiquitously expressed, transmembrane proteoglycan bearing heparan sulfate chains. SDC4 is involved in numerous inside-out and outside-in signaling processes, such as binding and sequestration of growth factors and extracellular matrix components, regulation of the activity of the small GTPase Rac1, protein kinase C-alpha, the level of intracellular calcium, or the phosphorylation of focal adhesion kinase. The ability of this proteoglycan to link the extracellular matrix and actin cytoskeleton enables SDC4 to contribute to biological functions like cell adhesion and migration, cell proliferation, cytokinesis, cellular polarity, or mechanotransduction. The multiple roles of SDC4 in tumor pathogenesis and progression has already been demonstrated; therefore, the expression and signaling of SDC4 was investigated in several tumor types. SDC4 influences tumor progression by regulating cell proliferation as well as cell migration by affecting cell-matrix adhesion and several signaling pathways. Here, we summarize the general role of SDC4 in cell migration and tumor cell motility.

Olmesartan alleviates bleomycin-mediated vascular smooth muscle cell senescence via the miR-665/SDC1 axis

Olmesartan (OMST) is a new angiotensin II receptor antagonist recently approved by the FDA to treat cardiovascular diseases. We investigated the molecular mechanisms by which OMST regulates vascular senescence. In the present study, bleomycin (BLM) was used to induce senescence in vascular smooth muscle cells (VSMCs); after which, the cells were treated with OMST. The effects of OMST on BLM-mediated cell senescence were evaluated using cell adhesion, NAD⁺/NADH, and Annevin V/PI double staining assays, as well as by immunofluorescence staining of γH2AX, Edu flow cytometry, and evaluations of senescence-associated β-gal activity. Differentially expressed microRNAs (DEMs) were identified by miRNA microarray assays, and subsequently validated by quantitative real time PCR. Bisulfite sequencing PCR (BSP) was used to detect the methylation status of the miR-665 promoter. The target genes of miR-665 were predicted and confirmed using luciferase reporter assays. We found that miR-665 was upregulated in VSMCs in response to BLM-induced cellular senescence. BSP studies revealed that CpG sites in the promoter region of the miR-665 gene underwent extensive demethylation during BLM-induced cellular senescence, and there was a concomitant up-regulation of miR-665 expression. SDC1 mRNA was identified as a direct target of miR-665. Either miR-665 overexpression or SDC1 knockdown significantly reversed the effects of OMST on BLM-induced VSMC senescence. Moreover, SDC1 overexpression partially reversed the changes that occurred in cells with BLM-induced senescence caused by miR-665 overexpression. Our findings suggest that the miR-665/SDC1 axis functions as a vital modulator of VSMC senescence, and may represent a novel biological target for treating atherosclerosis.

Comparison of Syndecan-1 Immunohistochemical Expression in Lobular and Ductal Breast Carcinoma with Nodal Metastases

Syndecan-1 (Sdc1) is a transmembrane heparan sulfate proteoglycan, an extracellular matrix receptor involved in intercellular communication, proliferation, angiogenesis, and metastasis. This study determined and compared Sdc1 expression in the tumor cells and stroma of 30 invasive lobular and 30 invasive ductal breast carcinomas (ILCs/IDCs), also in the axillary node metastases of ductal type, and correlated it with clinical and tumor parameters. Sdc1 was expressed in the epithelium of 90% carcinoma of both histological types. Also, it was most frequently expressed in their tumor stroma, but in ILC, stromal expression was negative in 40%. Sdc1 was expressed in 86.7% of the metastatic epithelium of IDC nodal metastases (in even 50% as high expression), while the nodal stroma was negative in 46.7%. Primary IDC showed a negative correlation between epithelial Sdc1 and progesterone receptors (PRs), whereas ILC showed a positive correlation between stromal Sdc1 and histological gradus. In the metastatic epithelium, Sdc1 was negatively correlated with a patient's age, estrogen receptors (ERs), and PRs in the primary tumors, while the stroma of metastases demonstrated a positive correlation with the focus number in primary tumors and a negative correlation with PRs in primary tumors. This research revealed identical overall epithelial Sdc1 expression in both breast carcinomas with no statistically significant difference in its stromal expression and confirmed the role of Sdc1 in the progression of both tumor types and in the development of ductal carcinoma's metastatic potential.

Functional aspects of the interaction between interleukin-8 and sulfated glycosaminoglycans

During the immune response, the cytokine interleukin 8 (IL-8, CXCL8) functions as a strong chemoattractant for polymorphonuclear leukocytes helping to direct these cells to infected/injured sites. This review focuses on the interaction of IL-8 with sulfated glycosaminoglycans expressed on cell surfaces and the extracellular matrix. This interaction contributes to the recruitment of polymorphonuclear cells from blood, penetration of these cells through the vessel wall, and their directed migration to inflammatory sites. Regulatory aspects of the interplay between IL-8 and heparan sulfate, the most abundant glycosaminoglycan, are highlighted. In this field, the large natural heterogeneity of glycosaminoglycans represents a great challenge that impedes the modeling of IL-8 functions. The interaction of IL-8 with newly developed artificial sulfated hyaluronan derivatives is also considered as these artificial substrates are an important tool for development of new materials in regenerative medicine.

A novel role for syndecan-3 in angiogenesis

Syndecan-3 is one of the four members of the syndecan family of heparan sulphate proteoglycans and has been shown to interact with numerous growth factors via its heparan sulphate chains. The extracellular core proteins of syndecan-1,-2 and -4 all possess adhesion regulatory motifs and we hypothesized that syndecan-3 may also possess such characteristics. Here we show that a bacterially expressed GST fusion protein consisting of the entire mature syndecan-3 ectodomain has anti-angiogenic properties and acts via modulating endothelial cell migration. This work identifies syndecan-3 as a possible therapeutic target for anti-angiogenic therapy.

Syndecans reside in sphingomyelin-enriched low-density fractions of the plasma membrane isolated from a parathyroid cell line

Background

Heparan sulfate proteoglycans (HSPGs) are one of the basic constituents of plasma membranes. Specific molecular interactions between HSPGs and a number of extracellular ligands have been reported. Mechanisms involved in controlling the localization and abundance of HSPG on specific domains on the cell surface, such as membrane rafts, could play important regulatory roles in signal transduction.

Methodology/Principal Findings

Using metabolic radiolabeling and sucrose-density gradient ultracentrifugation techniques, we identified [³⁵S]sulfate-labeled macromolecules associated with detergent-resistant membranes (DRMs) isolated from a rat parathyroid cell line. DRM fractions showed high specific radioactivity ([³⁵S]sulfate/mg protein), implying the specific recruitment of HSPGs to the membrane rafts. Identity of DRM-associated [³⁵S]sulfate-labeled molecules as HSPGs was confirmed by Western blotting with antibodies that recognize heparan sulfate (HS)-derived epitope. Analyses of core proteins by SDS-PAGE revealed bands with an apparent MW of syndecan-4 (30–33 kDa) and syndecan-1 (70 kDa) suggesting the presence of rafts with various HSPG species. DRM fractions enriched with HSPGs were characterized by high sphingomyelin content and found to only partially overlap with the fractions enriched in ganglioside GM1. HSPGs could be also detected in DRMs even after prior treatment of cells with heparitinase.

Conclusions/Significance

Both syndecan-1 and syndecan-4 have been found to specifically associate with membrane rafts and their association seemed independent of intact HS chains. Membrane rafts in which HSPGs reside were also enriched with sphingomyelin, suggesting their possible involvement in FGF signaling. Further studies, involving proteomic characterization of membrane domains containing HSPGs might improve our knowledge on the nature of HSPG-ligand interactions and their role in different signaling platforms.

Myofibroblast differentiation and survival in fibrotic disease

During wound healing, contractile fibroblasts called myofibroblasts regulate the formation and contraction of granulation tissue; however, pathological and persistent myofibroblast activation, which occurs in hypertrophic scars or tissue fibrosis, results in a loss of function. Many reviews outline the cellular and molecular features of myofibroblasts and their roles in a variety of diseases. This review focuses on the origins of myofibroblasts and the factors that control their differentiation and prolonged survival in fibrotic tissues. Pulmonary fibrosis is used to illustrate many key points, but examples from other tissues and models are also included. Myofibroblasts originate mostly from tissue-resident fibroblasts, and also from epithelial and endothelial cells or other mesenchymal precursors. Their differentiation is influenced by cytokines, growth factors, extracellular matrix composition and stiffness, and cell surface molecules such as proteoglycans and THY1, among other factors. Many of these effects are modulated by cell contraction. Myofibroblasts resist programmed cell death, which promotes their accumulation in fibrotic tissues. The cause of resistance to apoptosis in myofibroblasts is under ongoing investigation, but many of the same stimuli that regulate their differentiation are involved. The contributions of oxidative stress, the WNT-β-catenin pathway and PPARγ to myofibroblast differentiation and survival are increasingly appreciated.

Relevance of syndecan-1 in the trophoblastic BeWo cell syncytialization

PROBLEM

To investigate the role of syndecan-1 in the differentiation of the BeWo cells into syncytiotrophoblast.

METHOD OF STUDY

BeWo cells were stimulated with forskolin to form syncytia, and the expression of syndecan-1, desmoplakin I+II, human chorionic gonadotrophin (hCG) and angiogenesis-associated factors was analyzed. Syndecan-1 was silenced by siRNA to evaluate its involvement in the forskolin-mediated syncytia formation.

RESULTS

Treatment of the BeWo cells with forskolin led to a significant increase in the syncytia formation. It was associated with an increase in the expression of syndecan-1 with a concomitant decrease in the expression of desmoplakin I+II. Forskolin treatment of the BeWo cells also led to an increase in the secretion of soluble endoglin, whereas no change was observed in the soluble fms-like tyrosine kinase-1. Silencing of the syndecan-1 expression in BeWo cells led to a significant decrease in cell fusion both in the presence and in the absence of forskolin. It was associated with a significant decrease in hCG level in the conditioned medium.

CONCLUSION

Syndecan-1 is up-regulated in BeWo cells during differentiation and its silencing inhibits syncytialization and thus could be a useful biomarker for syncytiotrophoblast formation.

Syndecan expressions in the human amnion and chorionic plate

The syndecan family consists of four distinct membrane glycoproteins in mammals. Syndecans control cell proliferation, differentiation, adhesion and migration through participation in cell-cell interactions, anchorage of cells to the extracellular environment, and modulation of multiple growth factors. Therefore, syndecans may play a pivotal role in the regulation of cell behaviour depending on the cellular microenvironment. Here, we demonstrate that syndecan-1, syndecan-2 and syndecan-4 are expressed in fetal membrane tissue with different immunolocalizations. Syndecan-1 is expressed in the amniotic epithelium, localizing at basolateral cell surfaces. Syndecan-2 and syndecan-4, in contrast, are mostly localized in intracellular compartments, in the extravillous cytotrophoblastic cells and in some fibroblasts of the chorionic plate as well as in the amniotic epithelial cells. In the latter, syndecan-4 is mainly localized in the apical part of the cells. Our results strongly suggest a key role of syndecan-1, syndecan-2 and syndecan-4 in the determination of structural and functional characteristics of human amnion and chorionic plate. Since the solute exchanges between fetus and mother take place in fetal membranes, our data suggest that syndecans are important players in the placenta for the establishment of the fetalmaternal inter-communication.

Loss of heparan sulfate glycosaminoglycan assembly in podocytes does not lead to proteinuria

Podocytes synthesize the majority of the glomerular basement membrane components with some contribution from the glomerular capillary endothelial cells. The anionic charge of heparan sulfate proteoglycans is conferred by covalently attached heparan sulfate glycosaminoglycans and these are thought to provide critical charge selectivity to the glomerular basement membrane for ultrafiltration. One key component in herparan sulfate glycosaminoglycan assembly is the Ext1 gene product encoding a subunit of heparan sulfate co-polymerase. Here we knocked out Ext1 gene expression in podocytes halting polymerization of heparin sulfate glycosaminoglycans on the proteoglycan core proteins secreted by podocytes. Glomerular development occurred normally in these knockout animals but changes in podocyte morphology, such as foot process effacement, were seen as early as 1 month after birth. Immunohistochemical analysis showed a significant decrease in heparan sulfate glycosaminoglycans confirmed by ultrastructural studies using polyethyleneimine staining. Despite podocyte abnormalities and loss of heparan sulfate glycosaminoglycans, severe albuminuria did not develop in the knockout mice. We show that the presence of podocyte-secreted heparan sulfate glycosaminoglycans is not absolutely necessary to limit albuminuria suggesting the existence of other mechanisms that limit albuminuria. Heparan sulfate glycosaminoglycans appear to have functions that control podocyte behavior rather than be primarily an ultrafiltration barrier.

Malignant non-teratoid medulloepithelioma of ciliary body with retinoblastic differentiation: a case report and review of literature

We present a 6-year-old child with intraocular and extraocular mass and high intraocular pressure. The tumor mass involved a disorganized anterior segment and extended through the medial cornea and sclera. A preliminary diagnosis of retinoblastoma with extraocular extension was made. An exenteration of the left globe and orbital tissue was performed. Histological examination showed that the lesion, which occupied the posterior chamber, involved the ciliary body, extending into the iris, sclera and cornea, projecting beyond the cornea anteriorly and extending to the retina posteriorly. The tumor cells were diffusely immunoreactive to vimentin, neuron specific enolase and CD 138. The medulloepithelioma cells were focally positive to cytokeratin (AE1/AE3), cytokeratin 18, CD56,CD57, S100, HMB-45 and bcl2 while areas of retinoblastic differentiation showed diffuse immunoreactivity to synaptophysin, neurofilament and CD138 with focal immunoreactivity to calretinin. All tumor cells showed no immunoreactivity to cytokeratin 7, cytokeratin 20, epithelial membrane antigen, carcinoembryonic antigen, desmin, GFAP, and chromogranin. Nuclear staining for P53 was seen in 80% of tumor cells. The ki-67 index was 90%. The tumor was described as malignant intraocular non-teratoid medulloepithelioma with retinoblastic differentiation arising from the ciliary body. Tumor satellites were seen in the adjacent periocular soft tissue. The treatment involved exenteration of the left globe and orbital tissue with secondary skin graft following chemotherapy. The patient is well and has no recurrence after 1 year of treatment. We report that medulloepithelioma can present as a case of infantile glaucoma, can show signs of intraocular calcifications and can show retinoblastic differentiation.

The Simpson-Golabi-Behmel syndrome causative glypican-3, binds to and inhibits the dipeptidyl peptidase activity of CD26

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked condition shown to be the result of deletions of the glypican-3 (GPC3) gene. GPC3 is a proteoglycan localized to the cell membrane via a glycosylphosphatidyl-inositol (GPI) anchor. To further elucidate the GPC3 function(s), we have screened various cell lines for proteins that interact with GPC3, resulting in the isolation of a 115 kDa protein, identified as CD26. The interaction occurred with both the glycosylated and unglycosylated forms of GPC3 and led to the inhibition of CD26 peptidase activity. Moreover, introduction of CD26 into Cos-1 cells was accompanied by the up-regulation of cell growth, while inclusion of recombinant GPC3 in the media reduced the growth of CD26 transfected Cos-1 cells, drastically. Furthermore, HepG2 C3A cells containing CD26 underwent apoptosis in the presence of recombinant GPC3 in both concentration and time-dependant manner. In light of the fact that inhibition of CD26 reduces the rate of cell proliferation, we propose that a number of physical findings observed in SGBS patients may be a consequence of a direct interaction of GPC3 with CD26. Furthermore, GPC3 without the GPI anchor is capable of inducing apoptosis indicating that neither the GPI anchor nor the membrane attachment is required for apoptosis induction.

Immunological localization of syndecan-1 in human endometrium throughout the menstrual cycle

OBJECTIVE

To examine the expression of syndecan-1 in the endometrium during the menstrual cycle.

DESIGN

The expression of syndecan-1 was determined by tissue microarray and immunohistochemistry.

SETTING

Academic clinical and research laboratories.

PATIENT(S)

Seventy-one regularly cycling women who underwent endometrial biopsy.

INTERVENTION(S)

Endometrial samples representing five stages of the menstrual cycle were used for the study.

MAIN OUTCOME MEASURE(S)

Semiquantitative analysis by evaluating the intensity of immunohistochemical reactivity of syndecan-1 by using a modified HSCORE.

RESULT(S)

Endometrial syndecan-1 was expressed in the luminal and glandular epithelium as well as in the stroma throughout the menstrual cycle in a nonsynchronized fashion. In the luminal epithelium, the expression of syndecan-1 was statistically significantly higher in the mid-secretory phase when compared with the proliferative phase. In the stroma, however, the expression of syndecan-1 was down-regulated after ovulation and remained at a low level through the secretory phases. Differences between the proliferative and mid secretory, as well as between the ovulatory and the early, mid, and late secretory phases, all were statistically significant.

CONCLUSION(S)

Syndecan-1 is up-regulated in luminal epithelial cells during the mid-secretory phase and is down-regulated in the stroma during the early to late secretory phases. The differential expression of syndecan-1 coincides with the endometrial remodeling throughout the menstrual cycle.

Expression of syndecans, cell-cell interaction regulating heparan sulfate proteoglycans, within the human endometrium and their regulation throughout the menstrual cycle

OBJECTIVE

To evaluate the expression of syndecan-1, -2, -3, and -4 in different phases of eutopic endometrium of normal cycling women.

DESIGN

Prospective observational study.

SETTING

University-based research center for reproductive medicine.

PATIENT(S)

Twenty-nine healthy ovulatory volunteers.

INTERVENTION(S)

mRNA and protein expression of syndecan-1 to -4 in human endometrium.

MAIN OUTCOME MEASURE(S)

Real-time polymerase chain reaction of syndecan members and further characterization of mRNA expression of syndecan-1 and -4 with multiprobe RNase protection assays of epithelial and stromal cells after purification with antibody-coated magnetic beads. For confirmation of results, protein expression and localization using immunohistochemistry for syndecan-1 and -4 was performed.

RESULT(S)

All syndecans were expressed within human endometrium. Syndecan-1 and -4 proved to be significantly upregulated in whole endometrium during the secretory phase (2.73-fold and 2.85-fold, respectively). Using multiprobe RNase protection assays, a significant upregulation of mRNA was noted in epithelial cells during the secretory phase for both syndecan-1 and -4 (7.46-fold and 2.52-fold, respectively) and confirmed by immunohistochemistry.

CONCLUSION(S)

Cycle-dependent expression of syndecan-1 and -4 suggests that these adhesion proteins are involved in the regulation of the cycling endometrium.

A practical approach to the detection of prognostically significant genomic aberrations in multiple myeloma

Multiple myeloma (MM) is a malignancy of differentiated B lymphocytes and has remained an incurable disease. Chromosomal abnormalities are among the most important prognostic parameters for MM. Cytoplasm immunoglobulin-enhanced interphase fluorescent in situ hybridization (FISH) has been a standard cell-targeting method for identifying genomic aberrations in MM. We have developed another cell-targeting approach by using CD138 magnetic microbeads to sort plasma cells for FISH analysis. The FISH panel consisted of four probes targeting RB-1, D13S319, immunoglobulin H, and p53 loci. We reviewed the FISH and conventional cytogenetic results of 60 patients with MM. The present cell-targeting approach in conjunction with the FISH probe panel was more sensitive than FISH performed on untargeted cells in detecting prognostically significant genomic aberrations (72 versus 24%, P = 0.0016). The frequencies of genomic abnormalities identified were similar to previously reported data obtained with the standard cell-targeting method. Therefore, our cell-targeting approach and FISH panel reliably detect prognostically important genomic abnormalities in MM and are potentially suitable for widespread use.

ABILITY OF THE HEPARAN SULFATE PROTEOGLYCAN SYNDECAN-1 TO PARTICIPATE IN BACTERIAL TRANSLOCATION ACROSS THE INTESTINAL EPITHELIAL BARRIER

Although hundreds of microbial species reside in the human intestinal tract, comparatively few (e.g., Escherichia coli and other enterobacteria, Enterococcus faecalis, etc.) are typically associated with systemic infection in postsurgical, shock, and trauma patients. Syndecan-1 is the predominant cell surface heparan sulfate proteoglycan expressed on epithelia, and there is substantial evidence that heparan sulfate participates in interactions of a variety of frankly pathogenic microbes with mammalian cells. To investigate the role of syndecan-1 in interactions of enteric flora with intestinal epithelium, bacteria that might use the enterocyte as a portal of entry for systemic infection (including E. faecalis, E. coli, and other enterobacteria, and several species of staphylococci and streptococci) were studied for their abilities to interact with syndecan-1. Streptococcus bovis, S. agalactiae, S. pyogenes, Staphylococcus aureus, and S. epidermidis showed increased adherence to ARH-77 cells transfected to express syndecan-1. Heparin, a heparan sulfate analog, inhibited internalization of S. bovis, S. agalactiae, S. pyogenes, and S. aureus by HT-29 enterocytes (prominent syndecan-1 expression), but not Caco-2 enterocytes (relatively low syndecan-1 expression). Data from experiments with Chinese hamster ovary cells with altered glycosaminoglycan expression indicated that heparan sulfate and chondroitin sulfate (glycosaminoglycans on the syndecan-1 ectodomain) participated in bacterial interactions with mammalian cells. Thus, although E. faecalis, E. coli, and other gram-negative enterobacteria did not appear to interact with syndecan-1, this heparan sulfate proteoglycan may mediate enterocyte interactions with some staphylococci and streptococci that are known to cause systemic infections in specific populations of high-risk, immunosuppressed, postsurgical, and trauma patients.

Murine glypican-4 gene structure and expression; Sp1 and Sp3 play a major role in glypican-4 expression in 3T3-F442A cells

In this report we describe the genomic organization of the mouse glypican-4 (Gpc4), an analysis of its promoter and its transcriptional regulation in the 3T3-F442A adipocyte cell line. The Gpc4 gene consists of nine exons separated by eight introns. A series of deletion mutants and 4391 bp of the 5'-flanking region were cloned into pGL3-BASIC upstream of the luciferase reporter gene and transfected into 3T3-F442A adipocytes. Analysis of a 4.3-kb DNA fragment at the 5'-flanking region of this gene revealed that the Gpc4 promoter is a TATA-less promoter with a large cluster of GC boxes. Competitive electrophoretic mobility shift and supershift assays identified a cluster of nine functional GC boxes binding Sp1 and Sp3 in this region. Transactivation experiments in insect cells showed that both Sp1 and Sp3 are major activators of the Gpc4 promoter. Gpc4 is expressed in adipocytes where its expression is highest in confluent 3T3-F442A adipoblasts and decreases dramatically as cells differentiate. Sp protein analyses demonstrated a major decrease in Sp3 protein in differentiated adipocytes as compared to undifferentiated adipoblasts. These experiments show that Gpc4 is developmentally regulated in 3T3-F442A adipocytes and suggest that Sp transcription factors play a significant role in the regulated expression of Gpc4.

Distribution of syndecans 1-4 within the anterior segment of the human eye: expression of a variant syndecan-3 and matrix-associated syndecan-2

Control of the actomyosin network plays a role in regulating the movement of aqueous humor through the anterior segment of the eye. Receptors that could control its activity are unknown. In this study, we show that all four members of the syndecan family, which can regulate the actomyosin network, are present within the anterior segment. In both sections of human anterior segments and cultures of human trabecular meshwork (HTM), Schlemm's canal (HSC) and the ciliary muscle (HCM) cells from the anterior segment, syndecans-3 and -4 were the predominant family members. They were widely distributed throughout the anterior segment. Syndecan-3 within the anterior segment was a novel, recently described variant 55 kDa form. Low levels of syndecans-1 and -2 were also observed in situ and in all three cultures. Their expression was weaker and more localized than that observed for syndecans-3 and -4. Staining for syndecan-1 in HCM cultures was variable. In HTM and HSC cultures, syndecan-2 also co-distributed with fibronectin, laminin and type IV collagen suggesting that it was shed and associated with the extracellular matrix. Western blots supported this idea and showed syndecan-2 ectodomains in lysates from anterior segments.

IL-1-regulated responses in astrocytes: Relevance to injury and recovery

In the central nervous system (CNS), the cellular processes of astrocytes make intimate contact with essentially all areas of the brain. They have also been shown to be functionally coupled to neurons, oligodendrocytes, and other astrocytes via both contact-dependent and non-contact-dependent pathways. These observations have led to the suggestion that a major function of astrocytes in the CNS is to maintain the homeostatic environment, thus promoting the proper functioning of the neuronal network. Inflammation in the CNS disrupts this process either transiently or permanently and, as such, is thought to be tightly regulated by both astrocytes and microglia. The remarkable role that single cytokines, such as TNF and IL-1, may play in this process has now been well accepted, but the extent of the reprogramming of the transcriptional machinery initiated by these factors remains to be fully appreciated. With the advent of microarray technology, a more comprehensive analysis of this process is now available. In this report we review data obtained with this technology to provide an overview of the extent of changes induced in astrocytes by the cytokine IL-1.

Identification of a novel Ezrin-binding site in syndecan-2 cytoplasmic domain

ERM (Ezrin/Radixin/Moesin) proteins are crosslinkers between plasma membrane proteins and the actin cytoskeleton, thereby involved in the formation of cell adhesion sites. Earlier work showed that Ezrin links syndecan-2 to the actin cytoskeleton. Here we provide evidence that the Ezrin N-terminal domain binds to the syndecan-2 cytoplasmic domain with an estimated K(D) of 0.71 microM and without the requirement of other proteins. We also studied the regions in the syndecan-2 cytoplasmic domain implicated in the binding to Ezrin. By truncating the syndecan-2 cytoplasmic domain and by oligopeptide competition assays we show that the Ezrin-binding sequence is not located in the positively charged juxtamembrane region (RMRKK), but in the neighboring sequence DEGSYD. We therefore conclude that the consensus sequence for Ezrin binding is unique among membrane proteins, suggesting a distinct regulation.

Structural and functional changes in heparan sulfate proteoglycan expression associated with the myofibroblastic phenotype

The principal cells implicated as the source of the extracellular matrix in areas of progressive fibrosis are fibroblasts with the phenotypic appearance of myofibroblasts. This report describes differences in heparan sulfate proteoglycan expression between myofibroblasts and normal fibroblasts, associated with impaired responses to fibroblast growth factor-2 (FGF-2). Although both cell types responded to platelet-derived growth factor, myofibroblasts, unlike fibroblasts, did not proliferate to FGF-2. A response was acquired, however, when myofibroblasts were incubated with FGF-2 in the presence of heparan sulfate (HS) and heparin. Selective digestion with pronase, NaOH/NaBH(4), heparinase I, or low pH nitrous acid showed that each HS-glycosaminoglycan region comprised a pronase-resistant peptide separating two HS chains. The HS-glycosaminoglycan chains from myofibroblasts were larger (K(av), 0.32; molecular weight, 50 kd) than those from fibroblasts (K(av), 0.4; molecular weight, 33 kd), although their disaccharide composition was identical. The chains from myofibroblasts, however, contained three, compared to two, heparinase 1-resistant sequences separated by larger contiguous areas of low sulfation. Furthermore, although there was no difference in FGF-2-binding affinity between the two cell types, the chains secreted by myofibroblasts had twice the binding capacity of those from fibroblasts. Thus, it is likely that the difference in response to FGF-2 is because of a difference in FGF-2 sequestration and receptor interaction with FGF-2-HS complexes. A comparative investigation into HS fine structure is being undertaken to examine these findings in more detail.

The Caenorhabditis elegans sqv genes and functions of proteoglycans in development

In the nematode Caenorhabditis elegans, the vulva is a simple tubular structure linking the gonads with the external cuticle. In this review we summarize knowledge of inter- and intracellular signaling during vulval development and of the genes required for vulval invagination. Mutants of one set of these genes, the sqv genes, have a normal number of vulval precursor cells (VPCs) with an unperturbed cell lineage but the invagination space, normally a tube, is either collapsed or absent. We review evidence that the sqv genes are involved in glycosaminoglycan synthesis and speculate on ways in which defective glycosaminoglycan formation might lead to collapse of the vulval structure.

Different affinities of glycosaminoglycan oligosaccharides for monomeric and dimeric interleukin-8: a model for chemokine regulation at inflammatory sites

The binding of interleukin-8 (IL-8) to heparan sulfate (HS) proteoglycans on the surface of endothelial cells is crucial for the recruitment of neutrophils to an inflammatory site. Fluorescence anisotropy measurements yielded an IL-8 dimerization constant of 120 nM. The binding affinities, obtained by isothermal fluorescence titration, of size-defined heparin and HS oligosaccharides to the chemokine were found to depend on the oligomerization state of IL-8: high affinity was detected for monomeric and low affinity was detected for dimeric IL-8, referring to a self-regulatory mechanism for its chemoattractant effect. The highest affinity for monomeric IL-8 was detected for the HS octamer with a K(d) < 5 nM whereas the dissociation constants of dimeric IL-8 were found in the medium micromolar range. No indication for increasing affinities for monomeric IL-8 with increasing oligosaccharide chain length was found. Instead, a periodic pattern was obtained for the dissociation constants of the GAG oligosaccharides with respect to chain length, referring to optimum and least optimum chain lengths for IL-8 binding. GAG disaccharides were identified to be the minimum length for chemokine binding. Conformational changes of the dimeric chemokine, determined using CD spectroscopy, were detected only for the IL-8/HS complexes and not for heparin, pointing to an HS-induced activation of the chemokine with respect to receptor binding. Thermal unfolding of IL-8 yielded a single transition at 56 degrees C which was completely prevented by the presence of undigested HS or heparin, indicating structural stabilization, thereby prolonging the biological effect of the chemokine.

Role of syndecan in the elongation of postoral arms in sea urchin larvae

Ac-SYN is the core protein of a cell surface proteoglycan of the sea urchin Anthocidaris crassispina. To examine the functions of Ac-SYN, embryos were cultured in the presence of affinity-purified antibody against Ac-SYN. At the late pluteus stage, severe inhibition of elongation of the postoral arms was seen in treated embryos compared with control embryos. Blastocoeleic microinjection of the antibody did not affect morphogenesis. The relationship between the number of cells in the postoral arms and the length of the postoral rods was investigated in normal embryos. This showed that postoral arm elongation has two phases: the first phase accompanies the increase in cell numbers while the second does not. The syndecan antibody inhibited the increase in cell numbers in the postoral arms. Furthermore, in the treated embryos, cell numbers continued to increase normally until 31 h post fertilization (hpf), while cell division stopped after 31 hpf. These results suggest that Ac-SYN participates in postoral arm formation via cell division in sea urchin embryos.

Foxl1 controls the Wnt/beta-catenin pathway by modulating the expression of proteoglycans in the gut

Foxl1 is a winged helix transcription factor expressed in the mesenchyme of the gastrointestinal tract. Foxl1 null mice display severe structural defects in the epithelia of the stomach, duodenum, and jejunum. Here we addressed the molecular mechanisms by which Foxl1 controls gastrointestinal differentiation. First we showed that the abnormalities found in the epithelia of the null mice are the result of an increase in the number of proliferating cells and not a change in the rate of cell migration. Next we investigated the regulatory circuits affected by Foxl1. We focused on the Wnt/beta-catenin signaling pathway as a possible target of Foxl1 as it has been shown to play a central role in gastrointestinal proliferation. We demonstrated that Foxl1 activates the Wnt/beta-catenin pathway by increasing extracellular proteoglycans, which act as co-receptors for Wnt. Thus we establish that Foxl1 is involved in the regulation of the Wnt/beta-catenin pathway, providing a novel link in mesenchymal/epithelial cross-talk in the gut. Moreover, we provide the first example implicating proteoglycans in the regulation of cellular proliferation in the gastrointestinal tract.

Syndecan-2 expression in colorectal cancer-derived HT-29 M6 epithelial cells induces a migratory phenotype

Members of the heparan sulfate proteoglycan family, the syndecans have emerged as integrators of extracellular signals, such as ECM components or growth factors, that activate cytoplasmic signaling cascades and regulate cytoskeletal functions. Specifically, syndecan-2 has been implicated in various cellular processes, from differentiation to migration, including its participation in cell-cell and cell-matrix adhesion. Here, we focused on the involvement of syndecan-2 in epithelial versus mesenchymal differentiation. Colorectal cancer-derived HT-29 M6 epithelial cells were stably transfected with full-length syndecan-2 cDNA, and the effect on cell morphology, adhesion, and mobility was evaluated. Characteristic features of migratory cells such as loss of intercellular contacts, flatter shape and multiple membrane projections were observed in syndecan-2 transfectants. Western blot analysis of the major component of epithelial adherens junctions, E-cadherin, revealed decreased expression levels. Furthermore, syndecan-2 induced stronger adhesion to collagen type I, specifically inhibited by heparin. This was correlated with an increased ability for migration, as demonstrated by wound healing experiments and transwell assays, without affecting their growth rate. These results indicate that syndecan-2 expression in mucus-secreting HT-29 M6 cells induces differentiation toward a migratory mesenchymal-like phenotype.

Heparan sulfate and control of cell division: adhesion and proliferation of mutant CHO-745 cells lacking xylosyl transferase

We have examined the role of cell surface glycosaminoglycans in cell division: adhesion and proliferation of Chinese hamster ovary (CHO) cells. We used both wild-type (CHO-K1) cells and a mutant (CHO-745) which is deficient in the synthesis of proteoglycans due to lack of activity of xylosyl transferase. Using different amounts of wild-type and mutant cells, little adhesion was observed in the presence of laminin and type I collagen. However, when fibronectin or vitronectin was used as substrate, there was an enhancement in the adhesion of wild-type and mutant cells. Only CHO-K1 cells showed a time-dependent adhesion on type IV collagen. These results suggest that the two cell lines present different adhesive profiles. Several lines of experimental evidence suggest that heparan sulfate proteoglycans play a role in cell adhesion as positive modulators of cell proliferation and as key participants in the process of cell division. Proliferation and cell cycle assays clearly demonstrate that a decrease in the amount of glycosaminoglycans does not inhibit the proliferation of mutant CHO-745 cells when compared to the wild type CHO-K1, in agreement with the findings that both CHO-K1 and CHO-745 cells take 8 h to enter the S phase.

Engineering of vascular ingrowth matrices: are protein domains an alternative to peptides?

Anastomotic intimal hyperplasia and surface thrombogenicity are the main reasons for the high failure rate of prosthetic small-diameter vascular grafts. While anastomotic intimal hyperplasia is a multifactorial event, ongoing surface thrombogenicity is primarily caused by the lack of an endothelium, even after years of clinical implantation. After decades of poorly performing synthetic artery-grafts, tissue engineering has emerged as a promising approach to generate biologically functional bio-synthetic hybrid grafts mimicking native arteries regarding the presence of an endothelial lining on the blood surface. "In vitro endothelialization" represented the first generation of such tissue-engineered vascular grafts, utilising cell culture techniques for the creation of a confluent autologous endothelium on ePTFE grafts. The clinical long-term results with this method in almost 200 patients are highly encouraging, showing patencies equal to vein grafts. Since "in vitro endothelialization" requires cell culture facilities, it will always be confined to large centres. Therefore, research of the 1990s turned to the development of spontaneously endothelializing implants, to make tissue-engineered grafts amenable to the entire vascular-surgical community. Apart from scaffold designs allowing transmural ingrowth, biological signalling through a facilitating ingrowth matrix holds a key to spontaneous endothelialization. In biological signalling, the increasingly deeper understanding of bio-active molecules and the discovery of domains and peptide sequences during the 1980s created the expectation in the 1990s that peptide signalling may be all that is needed. This present review highlights the possible problems associated with such a reductionist approach. Using the fibronectin molecule, we demonstrated that domains may be more suitable modules in tissue engineering than peptide sequences.

Apolipoprotein E receptor binding versus heparan sulfate proteoglycan binding in its regulation of smooth muscle cell migration and proliferation

This study showed that synthetic peptides containing either a single copy or tandem repeat of the receptor binding domain sequence of apolipoprotein (apo) E, or a peptide containing its C-terminal heparin binding domain, apoE-(211-243), were all effective inhibitors of platelet-derived growth factor (PDGF)-stimulated smooth muscle cell proliferation. In contrast, only the peptide containing a tandem repeating unit of the receptor binding domain sequence of apoE, apoE-(141-155)(2), was capable of inhibiting PDGF-directed smooth muscle cell migration. Peptide containing only a single unit of this sequence, apoE-(141-155), or the apoE-(211-243) peptide were ineffective in inhibiting PDGF-directed smooth muscle cell migration. Additional experiments showed that reductively methylated apoE, which is incapable of receptor binding yet retains its heparin binding capability, was equally effective as apoE in inhibiting PDGF-stimulated smooth muscle cell proliferation. However, reductively methylated apoE was unable to inhibit smooth muscle cell migration toward PDGF. Additionally, the receptor binding domain-specific apoE antibody 1D7 also mitigated the anti-migratory properties of apoE on smooth muscle cells. Finally, pretreatment of cells with heparinase failed to abolish apoE inhibition of smooth muscle cell migration. Taken together, these data documented that apoE inhibition of PDGF-stimulated smooth muscle cell proliferation is mediated by its binding to heparan sulfate proteoglycans, while its inhibition of cell migration is mediated through apoE binding to cell surface receptors.

Thrombospondin-1 inhibits TCR-mediated T lymphocyte early activation

Biological activities of the matrix glycoprotein thrombospondin-1 (TSP1) are cell type specific and depend on the relative expression or activation of several TSP1 receptors. Although engaging individual TSP1 receptors in T lymphocytes can elicit costimulating signals, in this study we show that intact TSP1 inhibits TCR-mediated T cell activation, assessed globally using cDNA microarrays. TSP1 signaling suppressed expression of several genes induced in Jurkat T cells, including the T cell activation markers CD69, early growth response gene-1 (Egr-1), and phosphatase of activated cells (PAC-1). TCR-stimulated and CD47-costimulated IL-2 secretion and cell surface CD69 expression were also inhibited by TSP1. The specific inhibitory effect of TSP1 was verified in freshly isolated human PBMCs. TSP1 inhibited TCR-mediated but not protein kinase C-mediated T cell activation. Using CD69 expression as a marker, we demonstrated that the inhibitory activity of TSP1 depended on two TSP1 receptors, CD47 and integrin-associated protein heparan sulfate proteoglycans. Signals from these receptors inhibited TCR signaling downstream of ZAP70, but upstream of NF-AT. Therefore, the expression of TSP1 induced during wound repair and in tumor stroma may limit T cell activation at these sites.

In vivo regulation of syndecan-3 expression in the rat uterus by 17 beta-estradiol

The immature rat uterus has been extensively used as an in vivo model system to study the molecular mechanisms of steroid hormone actions. In this study, we demonstrated the regulated expression of syndecan-3 in the rat uterus by the steroid hormone 17 beta-estradiol. Administration of a single physiological dose of 17 beta-estradiol (40 microg/kg) to ovariectomized immature animals induced a rapid and transient increase in uterine syndecan-3 mRNA. Transcript levels reached a peak elevation of 3-fold above saline control tissues 4 h after hormone administration. Inhibition of message up-regulation by actinomycin D but not cycloheximide indicated a hormone response dependent on RNA transcription but not new protein synthesis. The estrogenic ligands estriol and tamoxifen were also effective at raising syndecan-3 mRNA levels; however, nonestrogenic ligands, including progesterone, 5 alpha-dihydrotestosterone, and dexamethasone, failed to stimulate a change in mRNA levels. Hormone-induced changes in mRNA led to transient changes in syndecan-3 protein content and significant alteration in the temporal and spatial expression in endometrial epithelial cells. Collectively, these data show that the steroid hormone 17 beta-estradiol, regulates transcription of the syndecan-3 gene in the uterus via an estrogen receptor-dependent mechanism. This estrogen-regulated expression of syndecan-3 may play an important role in changes in tissue ultrastructure crucial for proper uterine growth.

Syndecans and cell adhesion

Now that transmembrane signaling through primary cell-matrix receptors, integrins, is being elucidated, attention is turning to how integrin-ligand interactions can be modulated. Syndecans are transmembrane proteoglycans implicated as coreceptors in a variety of physiological processes, including cell adhesion, migration, response to growth factors, development, and tumorigenesis. This review will describe this family of proteoglycans in terms of their structures and functions and their signaling in conjunction with integrins, and indicate areas for future research.

Proliferative effect of lipoprotein lipase on human vascular smooth muscle cells

Vascular smooth muscle cell (VSMC) proliferation is a key event in the development and progression of atherosclerotic lesions. Accumulating evidence suggests that lipoprotein lipase (LPL) produced in the vascular wall may exert proatherogenic effects. The aim of the present study was to examine the effect of LPL on VSMC proliferation. Incubation of growth-arrested human VSMCs with purified endotoxin-free bovine LPL for 48 and 72 hours, in the absence of any added exogenous lipoproteins, resulted in a dose-dependent increase in VSMC growth. Addition of VLDLs to the culture media did not further enhance the LPL effect. Treatment of growth-arrested VSMCs with purified human or murine LPL (1 microg/mL) led to a similar increase in cell proliferation. Neutralization of bovine LPL by the monoclonal 5D2 antibody, irreversible inhibition, or heat inactivation of the lipase suppressed the LPL stimulatory effect on VSMC growth. Moreover, preincubation of VSMCs with the specific protein kinase C inhibitors calphostin C and chelerythrine totally abolished LPL-induced VSMC proliferation. In LPL-treated VSMCs, a significant increase in protein kinase C activity was observed. Treatment of VSMCs with heparinase III (1 U/mL) totally inhibited LPL-induced human VSMC proliferation. Taken together, these data indicate that LPL stimulates VSMC proliferation. LPL enzymatic activity, protein kinase C activation, and LPL binding to heparan sulfate proteoglycans expressed on VSMC surfaces are required for this effect. The stimulatory effect of LPL on VSMC proliferation may represent an additional mechanism through which the enzyme contributes to the progression of atherosclerosis.

Restructuring of focal adhesion plaques by PI 3-kinase. Regulation by PtdIns (3,4,5)-p(3) binding to alpha-actinin

Focal adhesions are an elaborate network of interconnecting proteins linking actin stress fibers to the extracellular matrix substrate. Modulation of the focal adhesion plaque provides a mechanism for the regulation of cellular adhesive strength. Using interference reflection microscopy, we found that activation of phosphoinositide 3-kinase (PI 3-kinase) by PDGF induces the dissipation of focal adhesions. Loss of this close apposition between the cell membrane and the extracellular matrix coincided with a redistribution of alpha-actinin and vinculin from the focal adhesion complex to the Triton X-100-soluble fraction. In contrast, talin and paxillin remained localized to focal adhesions, suggesting that activation of PI 3-kinase induced a restructuring of the plaque rather than complete dispersion. Furthermore, phosphatidylinositol (3,4, 5)-trisphosphate (PtdIns (3,4,5)-P(3)), a lipid product of PI 3-kinase, was sufficient to induce restructuring of the focal adhesion plaque. We also found that PtdIns (3,4,5)-P(3) binds to alpha-actinin in PDGF-treated cells. Further evidence demonstrated that activation of PI 3-kinase by PDGF induced a decrease in the association of alpha-actinin with the integrin beta subunit, and that PtdIns (3,4,5)-P(3) could disrupt this interaction in vitro. Modification of focal adhesion structure by PI 3-kinase and its lipid product, PtdIns (3,4,5)-P(3), has important implications for the regulation of cellular adhesive strength and motility.

Syndecan-2 is involved in the mitogenic activity and signaling of granulocyte-macrophage colony-stimulating factor in osteoblasts

We previously showed that granulocyte-macrophage colony-stimulating factor (GM-CSF) binds to heparan sulfate proteoglycans expressed at the surface of osteoblastic cells and that the mitogenic activity of this cytokine is dependent on the presence of fully sulfated proteoglycans. In this study, we determined if GM-CSF interacts with syndecans, a family of cell surface heparan sulfate proteoglycans. Human primary osteoblasts were found to express syndecan-2 and -4 but few syndecan-1 transcripts and proteins. Recombinant human GM-CSF coupled to biotin was found to bind to syndecan-2. Immunocytochemical transmission electron microscope analysis showed co-localization of syndecan-2 and GM-CSF at the cell membrane surface. Syndecan-2 also co-localized at the cell surface and co-immunoprecipitated with the GM-CSF receptor alpha chain, suggesting a strong interaction between the cytokine, its receptor, and syndecan-2. Phosphorylation of tyrosine residues in syndecan-2 associated with the alpha chain of the GM-CSF receptor was increased after cell stimulation by GM-CSF. Antisense oligonucleotides that reduced specifically the expression of syndecan-2 inhibited the mitogenic activity of GM-CSF and the activation of extracellular signal-regulated kinase-1 induced by the cytokine. Our results indicate functional interactions between syndecan-2 and GM-CSF in osteoblasts, and we propose that syndecan-2 plays a role as a co-receptor for this cytokine.

Heparan sulfate chains from glypican and syndecans bind the Hep II domain of fibronectin similarly despite minor structural differences

Numerous functions of heparan sulfate proteoglycans are mediated through interactions between their heparan sulfate glycosaminoglycan chains and extracellular ligands. Ligand binding specificity for some molecules, including many growth factors, is determined by complex heparan sulfate fine structure, where highly sulfated, iduronate-rich domains alternate with N-acetylated domains. Syndecan-4, a cell surface heparan sulfate proteoglycan, has a distinct role in cell adhesion, suggesting its chains may differ from those of other cell surface proteoglycans. To determine whether the specific role of syndecan-4 correlates with a distinct heparan sulfate structure, we have analyzed heparan sulfate chains from the different surface proteoglycans of a single fibroblast strain and compared their ability to bind the Hep II domain of fibronectin, a ligand known to promote focal adhesion formation through syndecan-4. Despite distinct molecular masses of glypican and syndecan glycosaminoglycans and minor differences in disaccharide composition and sulfation pattern, the overall proportion and distribution of sulfated regions and the affinity for the Hep II domain were similar. Therefore, adhesion regulation requires core protein determinants of syndecan-4.

Heparan sulfate proteoglycans on the cell surface: versatile coordinators of cellular functions

Heparan sulfate proteoglycans are complex molecules composed of a core protein with covalently attached glycosaminoglycan chains. While the protein part determines localization of the proteoglycan on the cell surfaces or in the extracellular matrix, the glycosaminoglycan component, heparan sulfate, mediates interactions with a variety of extracellular ligands such as growth factors and adhesion molecules. Through these interactions, heparan sulfate proteoglycans participate in many events during cell adhesion, migration, proliferation and differentiation. We are determining the multitude of proteoglycan functions, as their intricate roles in many pathways are revealed. They act as coreceptors for growth factors, participate in signalling during cell adhesion, modulate the activity of a broad range of molecules, and partake in many developmental and pathological processes, including tumorigenesis and wound repair. This review concentrates on biological roles of cell surface heparan sulfate proteoglycans, namely syndecans and glypicans, and outlines the progress achieved during the last decade in unraveling the molecular interactions behind proteoglycan functions.

Immunohistochemical study of chondroitin-6-sulphate and tenascin in the larynx: a loss of chondroitin-6-sulphate expression accompanies squamous cell carcinoma invasion

Chondroitin 6-sulphate is a glycosaminoglycan component of both cell membrane and basement membrane proteoglycans. In vitro it can inhibit tenascin, a molecule critical for epithelial cell migration during development and in wound healing. The immunohistochemical expression of chondroitin-6-sulphate and tenascin has been examined in 143 laryngeal biopsies from 38 patients, with particular attention to changes occurring with squamous cell carcinoma invasion. All tissues were formalin-fixed and paraffin-embedded. An avidin-biotin complex immunoperoxidase technique was used. Immunostaining for chondroitin-6-sulphate was seen in the basement membrane and/or cell membranes of basal and suprabasal cells of the laryngeal epithelium. Immunostaining of cell or basement membrane was seen at least focally in 67 of 71 (94 per cent) biopsies with no atypia, in 39 of 45 (87 per cent) biopsies with mild/moderate atypia, and in 16 of 16 (100 per cent) biopsies with severe dysplasia or carcinoma in situ (CIS); but in only 2 of 18 biopsies with invasion, although in neither of these was chondroitin-6-sulphate immunostaining seen at the actual site of invasion. Tenascin immunostaining was seen along the basement membrane in all biopsies. Those with CIS or invasion showed, in addition, strong tenascin staining of the adjacent stroma. The loss of chondroitin-6-sulphate immunostaining concurrent with squamous cell carcinoma invasion in the larynx suggests that loss of a chondroitin-6-sulphate-containing proteoglycan, or a change in proteoglycan side-chain composition, is a critical step in laryngeal epithelial tumour invasion.

Expression pattern alterations of syndecans and glypican-1 in normal and pathological trophoblast

Syndecans (syn-1, -2, -3, -4) and glypican-1 are proteoglycans expressed during development in association with changes in tissue organization and differentiation. They participate in the modulation of growth factor actions and in cell-cell and cell-matrix adhesion. The expression of syn-1, -2, -3, -4, and glypican-1 has been studied in normal human placenta and in gestational trophoblastic disease such as hydatidiform mole, invasive mole, and choriocarcinoma, using immunohistochemistry and western blots. Syndecan-3 was not expressed in normal or pathological tissues. During normal gestation, the other proteoglycans showed a specific staining pattern, which for some was modified during pregnancy. For instance, syn-1 was only expressed in syncytiotrophoblast; syn-4 was mainly localized in the villous and extravillous cytotrophoblast in the first trimester, whereas at term it was expressed in the syncytiotrophoblast. The most striking results are the altered expression patterns of syndecans and glypican-1 in pathological tissues. These proteoglycans showed a progressive decrease of immunostaining related to the increase of severity of trophoblastic disease, in particular in invasive mole and choriocarcinoma. In addition, dysregulation in the localization of the expression patterns was observed for syn-2 and -4. Because changes in syndecan expression enable cells to become more or less responsive to their micro-environment, the down-regulation and/or dysregulation of syndecans in relation to the degree of severity of trophoblastic diseases provides new insights into the progression of these pathologies.

Activation of protein kinase C increases proteoglycan synthesis in immature rat Sertoli cells

In order to determine the signal transduction pathways involved in the regulation of proteoglycan (PG) synthesis in immature rat Sertoli cells (SC), we have examined the effect of the tumor promoter phorbol ester PMA (phorbol myristate acetate) on [35S]sulfate and [3H]glucosamine incorporation into PG molecules neosynthesized by cultured rat SC. PMA induced a dose- and time-dependent stimulation of labeled cell-associated PG as determined by quantitative solid phase assay. The overall effect of PMA resulted from enhancement of both glycosylation and catabolism of cell PG, this latter effect leading to a drastic decrease of their residence time in the membrane. Besides these quantitative effects, activation of protein kinase C by PMA induced qualitative changes as reflected by increase in relative proportion of heparan sulfate PG (HSPG) in cell membrane PG. In light of our previous results suggesting an inverse relationship between PG synthesis and FSH responsiveness in immature rat Sertoli cells, the PMA-induced upregulation of cell membrane PG, and particularly HSPG, could constitute one mechanism involved in the repression of FSH-stimulated steroidogenesis induced by PKC activation.

β1 Integrin- and Proteoglycan-Mediated Stimulation of T Lymphoma Cell Adhesion and Mitogen-Activated Protein Kinase Signaling by Thrombospondin-1 and Thrombospondin-1 Peptides

Cell-cell and cell-matrix interactions play important regulatory roles in lymphocyte homeostasis. Thrombospondin-1 (TSP1) is a matricellular protein that differentially promotes the adhesion of resting and activated T cells. In this work, we show that adhesion of Jurkat T cells on substrates coated with TSP1 or TSP1-derived peptides is mediated by β1 integrins, CD47, and heparan sulfate proteoglycans. Interactions with TSP1 or TSP1 peptides stimulated CD3-induced Ras activation and tyrosine phosphorylation of several T cell proteins. The signals from TSP1 and its derived peptides differentially synergized with activation of the TCR to induce phosphorylation of linker for activation of T cells (LAT) and extracellular signal-regulated kinase (ERK) 1/2, c-Jun N-terminal kinase, and p38 kinases. The phosphorylation of ERK in the presence of full-length TSP1 was transient and dependent on a β1 integrin receptor. Interestingly, peptides derived from the type 1 repeats of TSP1 and a CD47-binding peptide from the carboxyl-terminal domain of TSP1 also stimulated mitogen-activated protein (MAP) kinase phosphorylation. Moreover, the TSP1 heparin-binding peptide synergized with Ab-ligated TCR to transduce signals to the nucleus, detected by activation of AP-1- and Elk-dependent transcription. This TSP1 peptide-dependent activation of AP-1 was inhibited by both heparin and the MAP/ERK kinase inhibitor PD98059, providing a functional link between adhesion molecule interaction and nuclear transactivation events via the MAP kinase pathways. These findings have implications for the role of extracellular TSP1 and TSP1 fragments in the regulation of T cell function during hemostasis, wound repair, and other inflammatory responses.

Regulated expression and subcellular localization of syndecan heparan sulfate proteoglycans and the syndecan-binding protein CASK/LIN-2 during rat brain development

The syndecan family of cell surface heparan sulfate proteoglycans interacts via their cytoplasmic C-terminal tail with the PDZ domain of CASK/LIN-2, a membrane-associated guanylate kinase homolog. The syndecan-CASK interaction may be involved in intercellular signaling and/or cell adhesion. Here we show that syndecan-1 to syndecan-4 have distinctive mRNA distributions in adult rat brain by in situ hybridization, with syndecan-2 and -3 being the major syndecans expressed in neurons of the forebrain. At the protein level, syndecan-2 and -3 are differentially localized within neurons; syndecan-3 is concentrated in axons, whereas syndecan-2 is localized in synapses. The synaptic accumulation of syndecan-2 occurs late in synapse development. CASK is a cytoplasmic-binding partner for syndecans, and its subcellular distribution changes strikingly during development, shifting from a primarily axonal distribution in the first 2 postnatal weeks to a somatodendritic distribution in adult brain. This change in CASK distribution correlates temporally and spatially with the expression patterns of syndecan-3 and -2, consistent with the association of both of these syndecans with CASK in vivo. In support of this, we were able to coimmunoprecipitate a complex of CASK and syndecan-3 from brain extracts. Our results indicate that specific syndecans are differentially expressed in various cell types of the brain and are targeted to distinct subcellular compartments in neurons, where they may serve specialized functions. Moreover, CASK is appropriately expressed and localized to interact with both syndecan-2 and -3 in different compartments of the neuron throughout postnatal development.

Heparin in inflammation: potential therapeutic applications beyond anticoagulation

In this chapter we have described anti-inflammatory functions of heparin distinct from its traditional anticoagulant activity. We have presented in vivo data showing heparin's beneficial effects in various preclinical models of inflammatory disease as well as discussed some clinical studies showing that the anti-inflammatory activities of heparin may translate into therapeutic uses. In vivo models that use low-anticoagulant heparins indicate that the anticoagulant activity can be distinguished from heparin's anti-inflammatory properties. In certain cases such as hypovolemic shock, the efficacy of a low-anticoagulant heparin derivative (GM1892) exceeds heparin. Data also suggest that nonconventional delivery of heparin, specifically via inhalation, has therapeutic potential in improving drug pharmacokinetics (as determined by measuring blood coagulation parameters) and in reducing the persistent concerns of systemic hemorrhagic complications. Results from larger clinical trials with heparin and LMW heparins are eagerly anticipated and will allow us to assess our predictions on the effectiveness of this drug class to treat a variety of human inflammatory diseases.

Cysteine-rich domain of human ADAM 12 (meltrin alpha) supports tumor cell adhesion

The ADAMs (A disintegrin and metalloprotease) comprise a family of membrane-anchored cell surface proteins with a putative role in cell-cell and/or cell-matrix interactions. By immunostaining, ADAM 12 (meltrin alpha) was up-regulated in several human carcinomas and could be detected along the tumor cell membranes. Because of this intriguing staining pattern, we investigated whether human ADAM 12 supports tumor cell adhesion. Using an in vitro assay using recombinant polypeptides expressed in Escherichia coli, we examined the ability of individual domains of human ADAM 12 and ADAM 15 to support tumor cell adhesion. We found that the disintegrin-like domain of human ADAM 15 supported adhesion of alphavbeta3-expressing A375 melanoma cells. In the case of human ADAM 12, however, recombinant polypeptides of the cysteine-rich domain but not the disintegrin-like domain supported cell adhesion of a panel of carcinoma cell lines. On attachment to recombinant polypeptides from the cysteine-rich domain of human ADAM 12, most tumor cell lines, such as MDA-MB-231 breast carcinoma cells, were rounded and associated with numerous actin-containing filopodia and used a cell surface heparan sulfate proteoglycan to attach. Finally, we demonstrated that authentic full-length human ADAM 12 could bind to heparin Sepharose. Together these results suggest a novel role of the cysteine-rich domain of ADAM 12 -- that of supporting tumor cell adhesion.

Chondroitin sulphate and heparan sulfate proteoglycan are sequentially expressed in the uterine extracellular matrix during early pregnancy in the rat

Chondroitin sulfate proteoglycan (CSPG) and heparan sulfate proteoglycan (HSPG) are extracellular matrix proteins that regulate cell adhesion, growth, migration, differentiation and gene expression in many systems. In this study, stromal CSPG label was intense within 10 microm of the uterine lumen. From that distance to the myometrium, CSPG was de-expressed. From the time of implantation on Day 6, this pattern was reversed. CSPG was de-expressed from the uterine epithelium to a distance of approximately 10 microm from the uterine lumen. From that region to the myometrium, labeling was homogeneously intense. This finding suggests that CSPG may inhibit attachment and implantation. Heparan sulfate core proteoglycan (perlecan) was increasingly expressed in the uterine epithelium from the time of implantation, commencing in the basement membrane on Day 6 and extending to the apical epithelium and lateral plasma membranes by Day 7. Perlecan thus appears to facilitate trophoblast attachment and implantation. We propose that attachment and implantation is regulated, at least in part, by the selective and sequential expression of CSPG and perlecan.