Syndecans
Syndecan-2
Syndecan-1
Syndecan-4
Syndecan-3
Syntenins
Heparan Sulfate Proteoglycans
Heparitin Sulfate
Syndecan-1 expression has prognostic significance in head and neck carcinoma. (1/356)
The syndecans are a family of cell-surface heparan sulphate proteoglycans that regulate cell behaviour by binding extracellular matrix molecules such as growth factors. The syndecan family has four members, of which syndecan-1 is the most studied and best characterized. We have studied the prognostic significance of syndecan-1 expression in squamous cell carcinoma (SCC) of the head and neck treated with surgery and post-operative radiotherapy. Paraffin-embedded tissue samples taken from 175 patients with primary SCC, followed up from 2 to 15 years after surgery, were studied for expression of syndecan-1 by immunohistochemistry. A low number (< or =50%, the median value) of syndecan-1-positive tumour cells was associated with low histological grade of differentiation (P<0.0001), a large primary tumour size (T1-2 vs. T3-4, P = 0.02), positive nodal status (NO vs. N1-3, P = 0.0006), and high clinical stage (stage I or II vs. III or IV, P<0.0001). Low syndecan-1 expression was also associated with unfavourable overall survival in a univariate analysis (P = 0.001). In a multivariate survival analysis, the clinical stage and syndecan-1 expression were the only independent prognostic factors. We conclude that syndecan-1 is a novel prognostic factor in SCC of the head and neck treated with surgery and post-operative radiotherapy. (+info)Fatty acids modulate the composition of extracellular matrix in cultured human arterial smooth muscle cells by altering the expression of genes for proteoglycan core proteins. (2/356)
In diabetes-associated microangiopathies and atherosclerosis, there are alterations of the extracellular matrix (ECM) in the intima of small and large arteries. High levels of circulating nonesterified fatty acids (NEFAs) are present in insulin resistance and type 2 diabetes. High concentrations of NEFAs might alter the basement membrane composition of endothelial cells. In arteries, smooth muscle cells (SMCs) are the major producers of proteoglycans and glycoproteins in the intima, and this is the site of lipoprotein deposition and modification, key events in atherogenesis. We found that exposure of human arterial SMCs to 100-300 micromol/albumin-bound linoleic acid lowered their proliferation rate and altered cell morphology. SMCs expressed 2-10 times more mRNA for the core proteins of the proteoglycans versican, decorin, and syndecan 4 compared with control cells. There was no change in expression of fibronectin and perlecan. The decorin glycosaminoglycan chains increased in size after exposure to linoleic acid. The ECM produced by cells grown in the presence of linoleic acid bound 125I-labeled LDL more tightly than that of control cells. Darglitazone, a peroxisome proliferator-activated receptor (PPAR)-gamma ligand, neutralized the NEFA-mediated induction of the decorin gene. This suggests that some of the NEFA effects are mediated by PPAR-gamma. These actions of NEFAs, if present in vivo, could contribute to changes of the matrix of the arterial intima associated with micro- and macroangiopathies. (+info)Human immunodeficiency virus-associated Hodgkin's disease derives from post-germinal center B cells. (3/356)
Human immunodeficiency virus-associated Hodgkin's disease (HIV-HD) displays several peculiarities when compared with HD of the general population. These include overrepresentation of clinically aggressive histologic types and frequent infection of Reed-Sternberg (RS) cells by Epstein-Barr virus (EBV). Recently, we have reported that the histogenesis of HD of the general population may be assessed by monitoring the expression pattern of BCL-6, a transcription factor expressed in germinal center (GC) B cells, and of CD138/syndecan-1 (syn-1), a proteoglycan associated with post-GC, terminal B-cell differentiation. In this study, we have applied these two markers to the study of HIV-HD histogenesis and correlated their expression status to the virologic features of this disease. We have found that RS cells of all histologic categories of HIV-HD consistently display the BCL-6(-)/syn-1(+) phenotype and thus reflect post-GC B cells. Although BCL-6(-)/syn-1(+) RS cells of HIV-HD express CD40, they are not surrounded by CD40 ligand-positive (CD40L+) reactive T lymphocytes, which, in HD of the general population, are thought to regulate the disease phenotype through CD40/CD40L interactions. Conversely, RS cells of virtually all HIV-HD express the EBV-encoded latent membrane protein 1 (LMP1), which, being functionally homologous to CD40, may contribute, at least in part, to the modulation of the HIV-HD phenotype. (+info)Extracellular matrix-dependent activation of syndecan-1 expression in keratinocyte growth factor-treated keratinocytes. (4/356)
Syndecan-1 is a major heparan sulfate proteoglycan of the epidermis. Its expression is strongly induced in migrating and proliferating keratinocytes during wound healing and, on the other hand, diminished or lost in invasive squamous cell carcinoma. We have recently found in the syndecan-1 gene an enhancer (fibroblast growth factor-inducible response element (FiRE)) that activates gene expression in wound edge keratinocytes (Jaakkola, P., Kontusaari, S., Kauppi, T., Maatta, A., and Jalkanen, M. (1998) FASEB J. 12, 959-969). Now, we demonstrate that the activation of this enhancer by keratinocyte growth factor (KGF) is modulated by the components of the extracellular matrix (ECM). MCA-3D mouse immortal keratinocytes growing on fibrillar collagen failed to activate FiRE and subsequently to induce syndecan-1 in response to KGF. The same cells growing on fibronectin or laminin, however, increased FiRE-dependent reporter gene expression upon KGF treatment. The inhibition of the KGF induction by collagen appears to be specific for signaling to FiRE, as the increase in cell proliferation by KGF was not affected. The effect was selective to KGF, as EGF-induction was independent on ECM composition. Changes in the transcription factor binding were not involved in the differential activation of FiRE, as the levels and composition of the AP-1 complexes were unchanged. However, application of anisomycin, an activator of Jun amino-terminal kinase, resulted in a lower response in cells growing on collagen compared with fibronectin. These results indicate that the composition of ECM and availability of growth factors can play a role in the epidermal regulation of syndecan-1 expression and that FiRE is a novel target for gene regulation by the extracellular matrix. (+info)The syndecans, tuners of transmembrane signaling. (5/356)
Syndecans, a family of transmembrane proteoglycans, are putative integrators of extracellular signals. The interaction of syndecans with extracellular ligands via particular motifs in their heparan sulfate chains, their clustering, association with particular cytoskeletal structures, binding to cytoplasmic effectors, and intracellular phosphorylation represent as many means to bring this role to a successful conclusion. In this review, we will briefly address the characteristics of syndecans as heparan sulfate proteoglycans (HSPGs) and focus mainly on the properties, binding interactions, and potential signaling functions of the cytoplasmic domains of these molecules. (+info)Molecular polymorphism of the syndecans. Identification of a hypo-glycanated murine syndecan-1 splice variant. (6/356)
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. (+info)Differential involvement of the transcription factor Blimp-1 in T cell-independent and -dependent B cell differentiation to plasma cells. (7/356)
Along humoral immune responses, different stimuli drive the differentiation of B lymphocytes to Ig-secreting plasma cells in discrete microenvironments. The Blimp-1 transcription factor is up-regulated early during the transition of mature B cells to IgM-secreting plasma cells. In the present study, we have examined the requirement of Blimp-1 in plasma cell formation after both T cell-independent (LPS) and -dependent (CD40 + IL-4, Th cell lines) stimulation of spleen B cells. B lymphocyte-induced maturation protein (Blimp-1) was expressed early after in vitro LPS stimulation, mainly in a population of IgM+Syndecan+CD43+ preplasma cells. In contrast, the BSAP transcription factor expressed in mature B cells was down-regulated during the differentiation to plasma cells. Treatment of these cultures with Blimp-1-specific antisense phosphorothioate oligonucleotides suppressed both Blimp-1 protein levels and the emergence of IgM+Syndecan+ cells and plasma cells. However, T-B cell cocultures of spleen B cells from C3H/HeJ (H-2k) mice and syngeneic autoreactive SR.10 Th2 cells submitted to the anti-Blimp-1 therapy did not show any significant reduction in IgM- and IgG1-secreting plasma cell formation. Spleen B cells treated with anti-CD40 mAb + IL-4 differentiated to IgG1-secreting cells without significant transcription of the Blimp-1 gene; anti-Blimp-1 treatment subsequently did not have any effect in the later cultures. Altogether, these results suggest that Blimp-1 transcription factor specifically promotes T cell-independent B cell differentiation to plasma cells, probably at preplasma cell stages. In contrast, T cell-dependent plasma cell formation likely evolves through Blimp-1-independent pathways. (+info)Expression cloning of an ascidian syndecan suggests its role in embryonic cell adhesion and morphogenesis. (8/356)
Expression cloning of maternally expressed genes of the ascidian Ciona savignyi demonstrated that the overexpression of syndecan, a member of a multigene family of integral membrane heparan sulfate proteoglycans, resulted in a disturbance of cell adhesion and morphogenesis. The Ciona syndecan gene was expressed both maternally and zygotically. The maternal transcript was distributed evenly in fertilized eggs and early embryos up to the 32-cell stage without any special localization and then became barely detectable in the 64-cell and gastrula stages. The zygotic transcription became evident during neurulation, mainly in cells of epidermis, the central nervous system, and mesenchyme. Embryos with syndecan overexpression via RNA injection cleaved as did normal embryos, but showed loose blastomere adhesion after the 32-cell stage. Gastrulation occurred, but the closure of the blastopore was markedly delayed, resulting in larvae without normal morphology. About half of the syndecan-overexpressing embryos hatched, and differentiation of epidermis, endoderm, muscle, and notochord was evident. However, the formation of pigment cells of the sensory organs was markedly disturbed. These results indicate that an appropriate level of syndecan expression is required for normal cell adhesion and morphogenesis of the ascidian embryo. (+info)Syndecans are a group of transmembrane proteoglycans that play important roles in various cellular functions, such as cell adhesion, migration, and growth regulation. They consist of a core protein with one or more covalently attached glycosaminoglycan (GAG) chains. These GAG chains can interact with extracellular matrix components, growth factors, and cytokines, thereby mediating various cell-matrix and cell-cell interactions. Syndecans have been implicated in several biological processes, including embryonic development, angiogenesis, wound healing, and tumor progression.
Syndecan-2 is a type of transmembrane heparan sulfate proteoglycan that is widely expressed in various cell types, including endothelial cells and fibroblasts. It plays a crucial role in the regulation of cellular signaling, adhesion, and migration by interacting with extracellular matrix components, growth factors, and cytokines. Syndecan-2 has been implicated in several biological processes, including angiogenesis, wound healing, and tumor progression.
In medical terms, Syndecan-2 is defined as a cell surface proteoglycan that belongs to the syndecan family of four members (Syndecan-1, -2, -3, and -4). It has a molecular weight of approximately 25-30 kDa and consists of a core protein with attached heparan sulfate chains. The cytoplasmic domain of Syndecan-2 interacts with various intracellular signaling molecules, such as kinases, adaptor proteins, and cytoskeletal components, thereby mediating cellular responses to extracellular stimuli.
Syndecan-2 has been shown to be involved in the regulation of several signaling pathways, including the Wnt/β-catenin, fibroblast growth factor (FGF), and vascular endothelial growth factor (VEGF) pathways. Dysregulation of Syndecan-2 expression or function has been associated with various pathological conditions, such as cancer, fibrosis, and inflammation.
In summary, Syndecan-2 is a crucial regulator of cellular signaling, adhesion, and migration, and its dysregulation has been implicated in several diseases.
Syndecan-1 is a type of transmembrane heparan sulfate proteoglycan that is widely expressed in various tissues, including epithelial cells and platelets. It plays a crucial role in cell proliferation, differentiation, migration, and angiogenesis by interacting with extracellular matrix components, growth factors, and cytokines. Syndecan-1 is also known as CD138 or Leu-19 and can be used as a marker for plasma cells in the diagnosis of certain diseases such as multiple myeloma.
Syndecan-4 is a type of cell surface proteoglycan, which is a type of protein that contains covalently attached glycosaminoglycans (GAGs). It is a member of the syndecan family, which includes four members (syndecan-1, -2, -3, and -4) that are involved in various cellular functions such as cell adhesion, migration, and growth regulation.
Syndecan-4 is widely expressed in many tissues, including the vascular endothelium, fibroblasts, and epithelial cells. It has a single transmembrane domain and a short cytoplasmic tail that interacts with intracellular signaling molecules, making it a key player in signal transduction pathways.
Syndecan-4 is involved in various biological processes such as wound healing, inflammation, and angiogenesis. It has been implicated in the regulation of cell proliferation, differentiation, and survival, as well as in the modulation of extracellular matrix (ECM) organization and turnover. Dysregulation of syndecan-4 expression or function has been associated with various pathological conditions such as cancer, fibrosis, and cardiovascular diseases.
Syndecan-3 is a type of transmembrane heparan sulfate proteoglycan that is widely expressed in various tissues, including the nervous system. It plays important roles in cell adhesion, migration, and differentiation by interacting with extracellular matrix components, growth factors, and cytokines. Syndecan-3 has been implicated in several physiological and pathological processes, such as neuronal development, neuroinflammation, and neurodegenerative diseases. It is also known to be involved in the regulation of synaptic plasticity and pain perception.
Proteoglycans are complex, highly negatively charged macromolecules that are composed of a core protein covalently linked to one or more glycosaminoglycan (GAG) chains. They are a major component of the extracellular matrix (ECM) and play crucial roles in various biological processes, including cell signaling, regulation of growth factor activity, and maintenance of tissue structure and function.
The GAG chains, which can vary in length and composition, are long, unbranched polysaccharides that are composed of repeating disaccharide units containing a hexuronic acid (either glucuronic or iduronic acid) and a hexosamine (either N-acetylglucosamine or N-acetylgalactosamine). These GAG chains can be sulfated to varying degrees, which contributes to the negative charge of proteoglycans.
Proteoglycans are classified into four major groups based on their core protein structure and GAG composition: heparan sulfate/heparin proteoglycans, chondroitin/dermatan sulfate proteoglycans, keratan sulfate proteoglycans, and hyaluronan-binding proteoglycans. Each group has distinct functions and is found in specific tissues and cell types.
In summary, proteoglycans are complex macromolecules composed of a core protein and one or more GAG chains that play important roles in the ECM and various biological processes, including cell signaling, growth factor regulation, and tissue structure maintenance.
Syntenins are a group of proteins that play a role in the organization and maintenance of the cell membrane. They are characterized by the presence of a conserved N-terminal domain called the SAP (SAF-A/B, Acinus, and PIAS) domain, which mediates protein-protein interactions, and a C-terminal domain that contains binding sites for various proteins involved in the organization of the cytoskeleton and cell adhesion.
Syntenins are thought to function as scaffolding proteins, helping to link together different components of the cell membrane and the cytoskeleton. They have been implicated in a variety of cellular processes, including the formation and maintenance of cell-cell junctions, the regulation of cell shape and motility, and the organization of signaling complexes at the cell membrane.
There are three known syntenin isoforms, syntenin-1, syntenin-2, and syntenin-3, which are encoded by different genes but share a similar overall structure. Syntenin-1 is the most well-studied isoform and is widely expressed in various tissues. Mutations in the syntenin-1 gene have been associated with certain neurological disorders, highlighting its importance in normal brain function.
Heparan sulfate proteoglycans (HSPGs) are complex molecules composed of a core protein to which one or more heparan sulfate (HS) glycosaminoglycan chains are covalently attached. They are widely distributed in animal tissues and play crucial roles in various biological processes, including cell-cell communication, growth factor signaling, viral infection, and cancer metastasis.
The HS chains are long, linear polysaccharides composed of repeating disaccharide units of glucosamine and uronic acid (either glucuronic or iduronic acid). These chains contain sulfate groups at various positions, which give them a negative charge and allow them to interact with numerous proteins, growth factors, and enzymes.
HSPGs can be found on the cell surface (syndecans and glypicans) or in the extracellular matrix (perlecans and agrin). They act as co-receptors for many signaling molecules, such as fibroblast growth factors (FGFs), wingless-type MMTV integration site family members (WNTs), and hedgehog proteins. By modulating the activity of these signaling pathways, HSPGs help regulate various cellular functions, including proliferation, differentiation, migration, and adhesion.
Dysregulation of HSPGs has been implicated in several diseases, such as cancer, fibrosis, and viral infections (e.g., HIV and herpes simplex virus). Therefore, understanding the structure and function of HSPGs is essential for developing new therapeutic strategies to target these diseases.
Membrane glycoproteins are proteins that contain oligosaccharide chains (glycans) covalently attached to their polypeptide backbone. They are integral components of biological membranes, spanning the lipid bilayer and playing crucial roles in various cellular processes.
The glycosylation of these proteins occurs in the endoplasmic reticulum (ER) and Golgi apparatus during protein folding and trafficking. The attached glycans can vary in structure, length, and composition, which contributes to the diversity of membrane glycoproteins.
Membrane glycoproteins can be classified into two main types based on their orientation within the lipid bilayer:
1. Type I (N-linked): These glycoproteins have a single transmembrane domain and an extracellular N-terminus, where the oligosaccharides are predominantly attached via asparagine residues (Asn-X-Ser/Thr sequon).
2. Type II (C-linked): These glycoproteins possess two transmembrane domains and an intracellular C-terminus, with the oligosaccharides linked to tryptophan residues via a mannose moiety.
Membrane glycoproteins are involved in various cellular functions, such as:
* Cell adhesion and recognition
* Receptor-mediated signal transduction
* Enzymatic catalysis
* Transport of molecules across membranes
* Cell-cell communication
* Immunological responses
Some examples of membrane glycoproteins include cell surface receptors (e.g., growth factor receptors, cytokine receptors), adhesion molecules (e.g., integrins, cadherins), and transporters (e.g., ion channels, ABC transporters).
Heparin sulfate is not exactly referred to as "heparitin sulfate" in medical terminology. The correct term is heparan sulfate, which is a type of glycosaminoglycan (GAG), a long unbranched chain of repeating disaccharide units composed of a hexuronic acid and a hexosamine.
Heparan sulfate is found on the cell surface and in the extracellular matrix, where it plays crucial roles in various biological processes, including cell signaling, regulation of growth factor activity, and control of blood coagulation. It is also an important component of the proteoglycans, which are complex molecules that help to maintain the structural integrity and function of tissues and organs.
Like heparin, heparan sulfate has a high negative charge due to the presence of sulfate groups, which allows it to bind to and interact with various proteins and growth factors. However, heparan sulfate has a more diverse structure than heparin, with variations in the pattern of sulfation along the chain, which leads to specificity in its interactions with different proteins.
Defects in heparan sulfate biosynthesis or function have been implicated in various human diseases, including certain forms of cancer, developmental disorders, and infectious diseases.
Cell adhesion refers to the binding of cells to extracellular matrices or to other cells, a process that is fundamental to the development, function, and maintenance of multicellular organisms. Cell adhesion is mediated by various cell surface receptors, such as integrins, cadherins, and immunoglobulin-like cell adhesion molecules (Ig-CAMs), which interact with specific ligands in the extracellular environment. These interactions lead to the formation of specialized junctions, such as tight junctions, adherens junctions, and desmosomes, that help to maintain tissue architecture and regulate various cellular processes, including proliferation, differentiation, migration, and survival. Disruptions in cell adhesion can contribute to a variety of diseases, including cancer, inflammation, and degenerative disorders.