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PubMed2001

Syndecan-3 and syndecan-4 specifically mark skeletal muscle satellite cells and are implicated in satellite cell maintenance and muscle regeneration.

Myogenesis in the embryo and the adult mammal consists of a highly organized and regulated sequence of cellular processes to form or repair muscle tissue that include cell proliferation, migration, and differentiation. Data from cell culture and in vivo experiments implicate both FGFs and HGF as critical regulators of these processes. Both factors require heparan sulfate glycosaminoglycans for signaling from their respective receptors. Since syndecans, a family of cell-surface transmembrane heparan sulfate proteoglycans (HSPGs) are implicated in FGF signaling and skeletal muscle differentiation, we examined the expression of syndecans 1-4 in embryonic, fetal, postnatal, and adult muscle tissue, as well as on primary adult muscle fiber cultures. We show that syndecan-1, -3, and -4 are expressed in developing skeletal muscle tissue and that syndecan-3 and -4 expression is highly restricted in adult skeletal muscle to cells retaining myogenic capacity. These two HSPGs appear to be expressed exclusively and universally on quiescent adult satellite cells in adult skeletal muscle tissue, suggesting a role for HSPGs in satellite cell maintenance or activation. Once activated, all satellite cells maintain expression of syndecan-3 and syndecan-4 for at least 96 h, also implicating these HSPGs in muscle regeneration. Inhibition of HSPG sulfation by treatment of intact myofibers with chlorate results in delayed proliferation and altered MyoD expression, demonstrating that heparan sulfate is required for proper progression of the early satellite cell myogenic program. These data suggest that, in addition to providing potentially useful new markers for satellite cells, syndecan-3 and syndecan-4 may play important regulatory roles in satellite cell maintenance, activation, proliferation, and differentiation during skeletal muscle regeneration.

Aging↗
PubMed2001

Transgenic expression of syndecan-1 uncovers a physiological control of feeding behavior by syndecan-3.

Transgenic expression in the hypothalamus of syndecan-1, a cell surface heparan sulfate proteoglycan (HSPG) and modulator of ligand-receptor encounters, produces mice with hyperphagia and maturity-onset obesity resembling mice with reduced action of alpha melanocyte stimulating hormone (alphaMSH). Via their HS chains, syndecans potentiate the action of agouti-related protein and agouti signaling protein, endogenous inhibitors of alphaMSH. In wild-type mice, syndecan-3, the predominantly neural syndecan, is expressed in hypothalamic regions that control energy balance. Food deprivation increases hypothalamic syndecan-3 levels several-fold. Syndecan-3 null mice, otherwise apparently normal, respond to food deprivation with markedly reduced reflex hyperphagia. We propose that oscillation of hypothalamic syndecan-3 levels physiologically modulates feeding behavior.

Aging↗
PubMed2006

The shedding of syndecan-4 and syndecan-1 from HeLa cells and human primary macrophages is accelerated by SDF-1/CXCL12 and mediated by the matrix metalloproteinase-9.

We recently demonstrated that stromal cell-derived factor-1 (SDF-1/CXCL12) forms complexes with CXCR4, but also with syndecan-4 expressed by human primary lymphocytes and macrophages, and HeLa cells. We also suggested that syndecan-4 behaves as a SDF-1-signaling molecule. Here, we demonstrate that SDF-1 strongly accelerates the shedding of syndecan-4 ectodomains and to a lesser extent that of syndecan-1 from HeLa cells. The fact that this acceleration was not inhibited by the CXCR4 antagonist AMD3100, anti-CXCR4 mAb 12G5, and CXCR4 gene silencing suggests its CXCR4-independence. Pre-treating the cells with heparitinases I, III, or with the protein kinase C (PKC) inhibitor, bisindolylmaleimide, significantly inhibited this accelerated shedding, which suggests the involvement of both cell-surface heparan sulfate and PKC transduction pathway. In contrast, Map Kinase or NF-kappaB pathway inhibitors had no effect. Moreover, SDF-1 increases the matrix metalloproteinase-9 (MMP-9) mRNA level as well as MMP-9 activity in HeLa cells, and MMP-9 silencing by RNA interference strongly decreases the syndecan-1 and -4 ectodomain shedding accelerated by SDF-1. Finally, SDF-1 also accelerates in a CXCR4-independent manner, the shedding of syndecan-1 and -4 from human primary macrophages, which is significantly inhibited by anti-MMP-9 antibodies. This strongly indicates the role of MMP-9 in these events occurring in both a tumoral cell line and in human primary macrophages. Because MMP-9 plays a crucial role in extracellular matrix degradation during cancer cell metastasis and invasion, and shed ectodomains of syndecans may likely be involved in tumor cell proliferation, these data further indicate the multiplicity of the roles played by SDF-1 on tumor cell biology.

Cell Membrane↗
PubMed2004

Inhibition by the soluble syndecan-1 ectodomains delays wound repair in mice overexpressing syndecan-1.

Wound repair is a tightly regulated process stimulated by proteases, growth factors, and chemokines, which are modulated by heparan sulfate. To characterize further the role of the heparan sulfate proteoglycan syndecan-1 in wound repair, we generated mice overexpressing syndecan-1 (Snd/Snd) and studied dermal wound repair. Wound closure, reepithelialization, granulation tissue formation, and remodeling were delayed in Snd/Snd mice. Soluble syndecan-1 was increased, and shedding was prolonged in wounds from Snd/Snd mice. Excess syndecan-1 increased the elastolytic activity of wound fluids. Additionally, cells in the granulation tissue and keratinocytes at wound edges showed markedly reduced proliferation rates in Snd/Snd mice. Skin grafting experiments between Snd/Snd and control mice indicated that the slower growth rate was mainly due to a soluble factor in the Snd/Snd mouse skin. Syndecan-1 immunodepletion and further degradation experiments identified syndecan-1 ectodomain as a dominant negative inhibitor of cell proliferation. These studies indicate that shed syndecan-1 ectodomain may enhance proteolytic activity and inhibit cell proliferation during wound repair.

Animals↗
PubMed2004

Essential and separable roles for Syndecan-3 and Syndecan-4 in skeletal muscle development and regeneration.

Syndecan-3 and syndecan-4 function as coreceptors for tyrosine kinases and in cell adhesion. Syndecan-3(-/-) mice exhibit a novel form of muscular dystrophy characterized by impaired locomotion, fibrosis, and hyperplasia of myonuclei and satellite cells. Explanted syndecan-3(-/-) satellite cells mislocalize MyoD, differentiate aberrantly, and exhibit a general increase in overall tyrosine phosphorylation. Following induced regeneration, the hyperplastic phenotype is recapitulated. While there are fewer apparent defects in syndecan-4(-/-) muscle, explanted satellite cells are deficient in activation, proliferation, MyoD expression, myotube fusion, and differentiation. Further, syndecan-4(-/-) satellite cells fail to reconstitute damaged muscle, suggesting a unique requirement for syndecan-4 in satellite cell function.

Animals↗
PubMed1995

Self-association of N-syndecan (syndecan-3) core protein is mediated by a novel structural motif in the transmembrane domain and ectodomain flanking region.

We expressed domains of the core protein of the transmembrane heparan sulfate proteoglycan N-syndecan (syndecan-3) either individually or as maltose-binding protein fusion proteins. Biochemical characterization of the purified proteins revealed that some of them were capable of self-association and formed stable, noncovalent multimeric complexes. The formation of N-syndecan core protein complexes was also demonstrated in mammalian cells by in situ cross-linking. Identification of structural motifs in the core protein of N-syndecan responsible for the formation of these complexes was accomplished by analyzing a series of constructs comprising different regions of the protein as well as site-directed mutants. Self-association was assayed by SDS-polyacrylamide gel electrophoresis, glutaraldehyde cross-linking, and size-exclusion high pressure liquid chromatography. Our results indicated that (i) the transmembrane domain of the N-syndecan core protein was required but not sufficient for the formation of stable complexes; (ii) the minimal amino acid sequence that conferred the ability of the N-syndecan core protein to form multimeric complexes included the last four amino acids (ERKE) of the extracellular domain plus the transmembrane domain; (iii) point mutations that changed the basic residues in this sequence to alanine residues either partially or completely abolished the ability of the N-syndecan core protein to form complexes; and (iv) replacement of conserved glycine residues in the transmembrane domain with leucines abolished complex formation. This property is similar to the oligomerization activity of other transmembrane receptors and suggests that regulated self-association may be important for the biological activity of transmembrane proteoglycans.

Amino Acid Sequence↗
PubMed2001

Characterization of syndecan-4 expression in 3T3-F442A mouse adipocytes: link between syndecan-4 induction and cell proliferation.

Heparan sulfate proteoglycans are found on the surface of most cells. Syndecan-4 is a widely expressed transmembrane heparan sulfate proteoglycan. Using quantitative RNase protection assays and immunoblotting, syndecan-4 expression was characterized in 3T3-F442A mouse adipoblasts. These cells exhibit dramatic changes in their biological and morphological characteristics during differentiation to adipocytes. During this process, the levels of syndecan-4 protein and mRNA expression changed dramatically. They peaked at the time when quiescent cells reentered the cell cycle before differentiation. Serum depletion-repletion also replicated the syndecan-4 mRNA induction when the cells were released back into proliferation, and a cycloheximide treatment abolished the peak of induction. In addition, inhibiting syndecan-4 induction with antisense oligonucleotides inhibited the proliferation of 3T3-F442A cells. In the terminally differentiated adipocytes characterized by the loss of proliferation capability, the serum inducibility of syndecan-4 is repressed, emphasizing the link between syndecan-4 induction in 3T3-F442A cells and cell proliferation.

3T3 Cells↗
PubMed2003

Interaction of RANTES with syndecan-1 and syndecan-4 expressed by human primary macrophages.

Interaction of RANTES with its membrane ligands or receptors transduces multiple intracellular signals. Whether RANTES uses proteoglycans (PGs) belonging to the syndecan family to attach to primary cells expressing RANTES G-protein-coupled receptors (GPCRs) was investigated. We demonstrate that RANTES specifically binds to high and low affinity binding sites on human monocyte-derived macrophages (MDM). We show by co-immunoprecipitation experiments that RANTES is associated on these cells with syndecan-1 and syndecan-4, but neither with syndecan-2 nor with betaglycan, in addition to CD44 and its GPCRs, CCR5 and CCR1. Glycosaminidases pre-treatment of the monocyte derived-macrophages strongly decreases the binding of RANTES to syndecan-1 and syndecan-4 and also to CCR5, and abolishes RANTES binding to CD44. This suggests that glycosaminoglycans (GAGs) are involved in RANTES binding to the PGs and that such bindings facilitate the subsequent interaction of RANTES with CCR5, on the MDM, characterized by low membrane expression of CCR5. The role of these interactions in the pathophysiology of RANTES deserves further study.

Cell Membrane↗
PubMed1994

Isolation of a neuronal cell surface receptor of heparin binding growth-associated molecule (HB-GAM). Identification as N-syndecan (syndecan-3).

HB-GAM (heparin binding growth-associated molecule; pleiotrophin) is a secretory, extracellular matrix-associated protein that is strongly expressed in developing nervous tissues and belongs to a novel family of differentiation/growth factors. It promotes axonal growth from perinatal rat brain neurons and is suggested to be mitogenic for some cell types and to display cell-transforming activity. Since the receptors of HB-GAM in cells are unknown, we have started isolation of putative cell surface receptors from brain neurons and from perinatal rat brain. For this purpose, recombinant HB-GAM was produced with the aid of a baculovirus vector and used as an affinity matrix in receptor isolation. A detergent-solubilized component from cultured brain neurons and from brain was identified that binds specifically to HB-GAM and migrates on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a broad smear with an apparent molecular mass of about 200 kDa. This cell surface component was found to contain heparan sulfate chains, which are bound to a core protein with an apparent molecular mass of 120 kDa. Gel electrophoretic characteristics, immunochemical analysis, and partial peptide sequencing revealed that the cell surface component isolated as an HB-GAM receptor is N-syndecan (syndecan-3). In a solid phase binding assay, N-syndecan was found to bind to HB-GAM in a similar manner as to basic fibroblast growth factor (KD = 0.6 nM). Immunofluorescence microscopy indicated that in brain neurons, N-syndecan occurs at the surface of the cell soma and of the neurites that grow along HB-GAM-coated substrates. Anti-N-syndecan antibodies added to culture media had an inhibitory effect on HB-GAM-induced neurite outgrowth. We suggest that N-syndecan mediates the neurite outgrowth-promoting signal from HB-GAM to the cytoskeleton of growing neurites.

Amino Acid Sequence↗
PubMed2002

Protein kinase C regulation of glypican-1, syndecan-1 and syndecan-4 mRNAs expression during rat Sertoli cell development.

Our previous studies indicated that cell surface proteoglycans were mostly heparan sulfate ones (HSPG) in 20 day-old Sertoli cells [Biochim. Biophys. Acta 1510 (2001) 474]. Among these HSPG, glypican-1, syndecans-1 and -4 mRNAs were expressed and differentially regulated. Glypican-1 and syndecan-1 mRNA expression was up-regulated under PKC activation in contrast to syndecan-4 mRNA expression which was not affected [Biochim. Biophys. Acta 1474 (2000) 31]. Rat Sertoli cells undergo extensive changes during the postnatal period both in structure and function, as the hematotesticular barrier establishment occurs at around 20 day-old. The testicular PKCalpha expression in developing Sertoli cells results in (i) a soluble (inactive) form which is maximal at the age of 1 day and declines gradually thereafter and (ii) a particulate (active) form which is low at birth, increases six-fold on days 8-11 of age and declines thereafter. The present study focused on the glypican-1, syndecan-1 and syndecan-4 mRNA expression and regulation under PKC activation by the phorbol myristate acetate (PMA) in 10-30 day-old Sertoli cells. Our data indicated that the regulation of their expression specifically depends on the nature of HSPG and Sertoli cell developmental stage and evidenced a specific PKC regulation of HSPG mRNA expression.

Animals↗
PubMed1997

Phosphorylation of recombinant N-syndecan (syndecan 3) core protein.

The cytoplasmic domain of the syndecan family of heparan sulfate proteoglycans is punctuated by the presence of four regularly spaced tyrosine residues. In this report, we explore the possibility of whether the four tyrosine residues in the cytoplasmic domain of N-syndecan (Syndecan 3) are potential substrates for phosphorylation by a tyrosine kinase. Bacterially expressed elk kinase was used to phosphorylate a series of bacterially expressed N-syndecan fusion proteins. Our results clearly demonstrate that the tyrosine residues in the cytoplasmic domain of N-syndecan can be phosphorylated by a tyrosine-specific kinase, and that all four tyrosine residues are capable of being phosphorylated.

Amino Acid Sequence↗
PubMed1995

Co-expression of heparin-binding growth-associated molecule (HB-GAM) and N-syndecan (syndecan-3) in developing rat brain.

Biochemical and cell biological studies have previously identified N-syndecan as a neuronal cell surface receptor in neurite outgrowth induced by heparin-binding growth-associated molecule (HB-GAM). In the present study we have compared temporal and spatial expression patterns of N-syndecan and HB-GAM using Northern and Western blotting and immunohistochemistry. Expression of N-syndecan mRNA and protein peaks during the perinatal developmental stage of the brain in the same manner as the expression of HB-GAM mRNA and protein. In addition, both proteins are preferentially localized to fiber tracts of developing brain. We suggest that HB-GAM and N-syndecan form ligand-receptor complexes in developing axon tracts of brain.

Amino Acid Sequence↗
PubMed1999

Molecular polymorphism of the syndecans. Identification of a hypo-glycanated murine syndecan-1 splice variant.

We have identified a cDNA that encodes a variant form of murine syndecan-1. The variant cDNA lacks the sequence corresponding to the first 132 nucleotides of the third exon of the syndecan-1 gene. The corresponding message is rare. The alternative splice respects the reading frame and deletes 44 amino acids from the protein, joining the S45GS47GT sequence to a variant immediate downstream context. This sequence context initiates with alanine instead of glycine as residue 50, reducing the number of SGXG sequence motifs in the protein from two to one. Expression of this variant syndecan-1 in Madin-Darby canine kidney or MOLT-4 cells yielded a recombinant proteoglycan with a reduced number and clustering of the heparan sulfate chains. Both the conversions of Ala50 and of Lys53 into glycine enhanced the heparan sulfate substitution of the variant protein. These findings support the concept that serine-glycine dipeptide signals for glycosaminoglycan/heparan sulfate synthesis depend on sequence context (Zhang, L., David, G., and Esko, J. D. (1995) J. Biol. Chem. 270, 27127-27135) and imply that alternative splicing mechanisms may in part control the molecular polymorphism of syndecan-1 and, therefore, the efficiency and versatility of this protein in its co-receptor functions.

Alternative Splicing↗
PubMed2000

Expression of glypican-1, syndecan-1 and syndecan-4 mRNAs protein kinase C-regulated in rat immature Sertoli cells by semi-quantitative RT-PCR analysis.

In seminiferous tubules, Sertoli cells provide structural and nutritional support for the developing germinal cells. Cell to cell signalization and cell adhesion require proteoglycans expressed at the cell membrane. A preliminary biochemical and structural approach indicated that cell surface proteoglycans are mostly heparan sulfate (HSPG) in immature rat Sertoli cells. The present study focused on the qualitative and quantitative expression of three membrane HSPG, syndecan-1, syndecan-4 and glypican-1 in Sertoli cells of 20-day-old rat. A semi-quantitative multiplex RT-PCR strategy was developed to appreciate the effect of PKC activation on the mRNA expression of the three HSPG. Our data show that the syndecan-1 and glypican-1 mRNA expression is increased by the phorbol myristate acetate (PMA) suggesting a regulation of their expression by the phosphatidyl inositol pathway, as previously hypothesized (Fagen et al., Biochim. Biophys. Acta, 1472 (1999) 250-261). In addition, a physiological effector of the PKC as ATP gave similar effects. Thus, this over-expression could be related with paracrine factors secreted by germ cells.

Adenosine Triphosphate↗
PubMed2002

Regulation of glypican-1, syndecan-1 and syndecan-4 mRNAs expression by follicle-stimulating hormone, cAMP increase and calcium influx during rat Sertoli cell development.

In seminiferous tubules, Sertoli cells provide structural and nutritional support for the developing germinal cells. Cell- to-cell signaling and cell adhesion require proteoglycans expressed at the cell membrane. A preliminary biochemical and structural approach indicated that cell surface proteoglycans are mostly heparan sulfate proteoglycans (HSPG). Glypican-1, syndecans-1 and -4 were identified using a molecular approach. Their differential regulation was demonstrated in immature rat Sertoli cells. Follicle-stimulating hormone (FSH) is the main regulator of Sertoli cell function. Signal transduction triggered by FSH involves both an increased intracellular cAMP synthesis and a calcium influx. This study demonstrates that FSH, through its second messengers (increase in intracellular cAMP and intracellular calcium), downregulated the glypican-1 mRNA expression in Sertoli cells from 20-day-old rats. On the other hand, syndecan-1 mRNA expression is not modulated by FSH as it would result from the antagonistic effects of increased intracellular cAMP and intracellular calcium levels. Finally, syndecan-4 mRNA expression is not regulated by this pathway. The present study was extended during Sertoli cell development. Indeed, Sertoli cells undergo extensive changes during the postnatal period both in structure and function. These important transformations are critical for the establishment of spermatogenesis and development of the adult pattern of testicular function. Our data indicated that the regulation of HSPG mRNA expression is HSPG-specific and depends on the Sertoli cell developmental stage.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2003

Syndecan-3 and syndecan-4 are enriched in Schwann cell perinodal processes.

BACKGROUND: Nodes of Ranvier correspond to specialized axonal domains where voltage-gated sodium channels are highly concentrated. In the peripheral nervous system, they are covered by Schwann cells microvilli, where three homologous cytoskeletal-associated proteins, ezrin, radixin and moesin (ERM proteins) have been found, to be enriched. These glial processes are thought to play a crucial role in organizing axonal nodal domains during development. However, little is known about the molecules present in Schwann cell processes that could mediate axoglial interactions. The aim of this study is to identify by immunocytochemistry transmembrane proteins enriched in Schwann cells processes that could interact, directly or indirectly, with axonal proteins. RESULTS: We show that syndecan-3 (S3) and syndecan-4 (S4), two proteoglycans expressed in Schwann cells, are enriched in perinodal processes in rat sciatic nerves. S3 labeling was localized in close vicinity of sodium channels as early as post-natal day 2, and highly concentrated at nodes of Ranvier in the adult. S4 immunoreactivity accumulated at nodes later, and was also prominent in internodal regions of myelinated fibers. Both S3 and S4 were co-localized with ezrin in perinodal processes. CONCLUSIONS: Our data identify S3 and S4 as transmembrane proteins specifically enriched in Schwann cell perinodal processes, and suggest that S3 may be involved in early axoglial interactions during development.

Animals↗
PubMed2003

Binding of the CC-chemokine RANTES to syndecan-1 and syndecan-4 expressed on HeLa cells.

It is believed that proteoglycans influence biological properties of chemokines. We show that the CC chemokine RANTES binds not only to high-affinity binding sites on CCR5-positive HeLa cells but also to low-affinity binding sites on HeLa cells expressing or lacking RANTES G protein-coupled receptors. Coimmunoprecipitation studies demonstrate that RANTES forms complexes with glycanated syndecan (SD)-1 and -4, in addition to CCR5 on the CCR5-positive HeLa cells. Moreover, confocal microscopy analysis shows the colocalization of RANTES with SD-1 and -4. Glycosaminoglycans removal from the cells by glycosaminidases treatment prevented RANTES binding to SD-1 and -4 and decreased RANTES binding to CCR5 on the CCR5-positive HeLa cells. Removal of glycosaminoglycans by glycosaminidases treatment of the complexes, RANTES/SD-1/SD-4/+/-CCR5, immobilized on beads, reversed SD-1 and -4 bindings. Therefore, RANTES bindings to SD-1 and -4 depend on glycosaminoglycans and facilitate RANTES interaction with CCR5. Extracting plasma membrane cholesterol abolished the coimmunoprecipitation of SD-1 with RANTES, suggesting that rafts are involved in RANTES association to SD-1. Confocal microscopy analysis as well as coimmunoprecipitation experiments show a RANTES-independent heteromeric complex on the CCR5-positive HeLa cells, SD-1, SD-4, and CCR5. This complex is likely a functional unit in which proteoglycans may modulate RANTES binding to CCR5.

Cell Membrane↗
PubMed2004

RANTES (CCL5) induces a CCR5-dependent accelerated shedding of syndecan-1 (CD138) and syndecan-4 from HeLa cells and forms complexes with the shed ectodomains of these proteoglycans as well as with those of CD44.

We recently demonstrated that RANTES forms complexes with CCR5, syndecan-1 (SD-1), SD-4, and CD44 expressed by human primary macrophages and that SD-1 and SD-4 but neither CD44 nor SD-2 coimmunoprecipitate with CCR5. Here we show that RANTES directly binds in a glycosaminoglycan-dependent manner to SD-1, SD-4, and CD44. Moreover, RANTES accelerates the shedding of SD-1 and SD-4 ectodomains from HeLa cells expressing CCR5 and, by contrast, has no effect on the constitutive shedding of CD44 from these cells. These accelerated sheddings are prevented by the MEK1/2 inhibitor, U0126, and by the protein kinase C inhibitor bisindolylmaleimide I. This indicates that both MAP kinase--and protein kinase C-dependent signaling pathways are involved in these RANTES-induced accelerated sheddings. RANTES also induces a decreased expression of SD-1 and SD-4 by HeLa cells expressing CCR5 and on the contrary an increased expression of CD44 by these cells. By contrast, RANTES neither accelerates the shedding of SD-1 and SD-4 ectodomains from HeLa cells lacking CCR5, nor changes the SD-1-, SD-4-, and CD44-plasma membrane expressions of these cells. CCR5 is therefore involved in the RANTES-induced accelerated shedding of SD-1 and SD-4 ectodomains. Nevertheless, the fact that RANTES stimulates in Hela cells (expressing or lacking CCR5) the mRNA synthesis of SD-1 and SD-4 indicates that the molecular events that follow the synthesis of these proteoglycans differ, according to the presence or not of CCR5. Finally, RANTES forms GAG-dependent complexes with the shed ectodomains of SD-1 and SD-4 as well as with those of CD44. The role of these events in the pathophysiology of RANTES deserves further study.

Chemokine CCL5↗