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Michael Simons - One of the best experts on this subject based on the ideXlab platform.
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Syndecan 4 signaling at a glance
Journal of Cell Science, 2013Co-Authors: Arye Elfenbein, Michael SimonsAbstract:Syndecan-4, a ubiquitous cell surface proteoglycan, mediates numerous cellular processes through signaling pathways that affect cellular proliferation, migration, mechanotransduction and endocytosis. These effects are achieved through Syndecan-4 functioning as both a co-receptor for the fibroblast growth factor receptors (FGFR1–FGFR4) and its ability to independently activate signaling pathways upon ligand binding. As an FGFR co-receptor, Syndecan-4 strengthens the duration and intensity of downstream signaling upon ligand binding; this is particularly evident with regard to mitogen-activated protein kinase (MAPK) signaling. In contrast, Syndecan-4 also functions as an independent receptor for heparin-binding growth factors, such as fibroblast growth factors (FGFs), vascular endothelial growth factors (VEGFs) and platelet-derived growth factors (PDGFs). These signaling cascades affect canonical signaling components, such as the mammalian target of rapamycin (mTOR), AKT1 and the Rho family of GTPases. In combination with the integrin family of proteins, Syndecan-4 is also able to form physical connections between the extracellular matrix (ECM) and cytoskeletal signaling proteins, and it has a key role in regulation of integrin turnover. This unique versatility of the interactions of Syndecan-4 is characterized in this Cell Science at a Glance article and illustrated in the accompanying poster.
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cleavage of Syndecan 4 by adamts1 provokes defects in adhesion
The International Journal of Biochemistry & Cell Biology, 2009Co-Authors: Juan Carlos Rodriguezmanzaneque, Michael Simons, Arie Horowitz, Darren R Carpizo, Maria Del Carmen Plazacalonge, Antoni X Torrescollado, Shelley N M Thai, Luisa M IruelaarispeAbstract:Syndecan-4 is a membrane-bound heparan sulfate proteoglycan that participates in cell–cell and cell–matrix interactions and modulates adhesion and migration of many cell types. Through its extracellular domain, Syndecan-4 cooperates with adhesion molecules and binds matrix components relevant for cell migration. Importantly, Syndecan-4 is a substrate of extracellular proteases, however the biological significance of this cleavage has not been elucidated. Here, we show that the secreted metalloprotease ADAMTS1, involved in angiogenesis and inflammatory processes, cleaves the ectodomain of Syndecan-4. We further showed that this cleavage results in altered distribution of cytoskeleton components, functional loss of adhesion, and gain of migratory capacities. Using Syndecan-4 null cells, we observed that ADAMTS1 proteolytic action mimics the outcome of genetic deletion of this proteoglycan with regards to focal adhesion. Our findings suggest that the shedding of Syndecan-4 by ADAMTS1 disrupts cell adhesion and promotes cell migration.
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Synectin/Syndecan-4 regulate coronary arteriolar growth during development.
Developmental Dynamics, 2007Co-Authors: Eduard I. Dedkov, Michael Simons, Mathew T. Thomas, Milan Sonka, Fuxing Yang, Thomas Chittenden, John Rhodes, Erik L. Ritman, Robert J. TomanekAbstract:Syndecan-4 and its cytoplasmic binding partner, synectin, are known to play a role in FGF-2 signaling and vascular growth. To determine their roles in coronary artery/arteriolar formation and growth, we compared Syndecan-4 and synectin null mice with their wild-type counterparts. Image analysis of arterioles visualized by smooth muscle -actin immunostaining revealed that synectin / mice had lower arteriolar length and volume densities than wild-type mice. As shown by electron microscopic analysis, arterioles from the two did not differ in morphology, including their endothelial cell junctions, and the organization and distribution of smooth muscle. Using micro-computer tomography, we found that the size and branching patterns of coronary arteries (diameters > 50 m) were similar for the two groups, a finding that indicates that the growth of arteries is not influenced by a loss of synectin. Syndecan-4 null male mice also had lower arteriolar length densities than their gender wild-type controls. However, female Syndecan-4 null mice were characterized by higher arteriolar length and volume densities than their gender-matched wild-type controls. Thus, we conclude that both synectin and Syndecan-4 play a role in arteriolar development, a finding that is consistent with previous evidence that FGF-2 plays a role in coronary arterial growth. Moreover, our data reveal that gender influences the arteriolar growth response to Syndecan-4 but not to synectin. Developmental Dynamics 236:2004 –2010, 2007. © 2007 Wiley-Liss, Inc.
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Syndecan-4 modulates basic fibroblast growth factor 2 signaling in vivo
American Journal of Physiology-heart and Circulatory Physiology, 2003Co-Authors: Yufeng Zhang, Jianyi Li, Chohreh Partovian, Frank W. Sellke, Michael SimonsAbstract:Syndecan-4 is one of the principal heparan sulfate-carrying proteins on the cell surface. Unlike other members of Syndecan family, Syndecan-4 mediates phosphatidylinositol 4,5-bisphosphate 2 (PIP2)...
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clustering induces redistribution of Syndecan 4 core protein into raft membrane domains
Journal of Biological Chemistry, 2002Co-Authors: Eugene Tkachenko, Michael SimonsAbstract:Abstract Syndecan-4 is a heparan sulfate-carrying core protein that has been directly implicated in fibroblast growth factor 2 (FGF2) signaling. Recent studies have suggested that many signaling proteins localize to the raft compartment of the plasma cell membrane. To establish whether Syndecan-4 is present in the raft compartment, we have studied the distribution of the core protein and an Fc receptor (FcR)-Syndecan-4 chimera prior to and following clustering with FGF2 or antibodies. Whereas unclustered Syndecan-4 was present predominantly in the non-raft membrane compartment, clustering induced extensive Syndecan-4 redistribution to the rafts as demonstrated by the sucrose gradient centrifugation and life confocal microscopy. Although Syndecan-4 and caveolin-1 moved in tandem, Syndecan-4 was not present in caveolae, a major subset of raft compartments. We conclude that Syndecan-4 clustering induces its redistribution to the non-caveolae raft compartment. This process may play an important role in Syndecan-4-mediation of FGF2 signaling.
John R Couchman - One of the best experts on this subject based on the ideXlab platform.
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Alpha-actinin interactions with Syndecan-4 are integral to fibroblast-matrix adhesion and regulate cytoskeletal architecture.
The International Journal of Biochemistry & Cell Biology, 2012Co-Authors: E. Okina, Hinke A B Multhaupt, Sandeep Gopal, A. Grossi, John R CouchmanAbstract:All cells of the musculoskeletal system possess transmembrane Syndecan proteoglycans, notably Syndecan-4. In fibroblasts it regulates integrin-mediated adhesion to the extracellular matrix. Syndecan-4 null mice have a complex wound repair phenotype while their fibroblasts have reduced focal adhesions and matrix contraction abilities. Signalling through Syndecan-4 core protein to the actin cytoskeleton involves protein kinase Cα and Rho family G proteins but also direct interactions with α-actinin. The contribution of the latter interaction to cell–matrix adhesion is not defined but investigated here since manipulation of Rho GTPase and its downstream targets could not restore a wild type microfilament organisation to Syndecan-4 null cells. Microarray and protein analysis revealed no significant alterations in mRNA or protein levels for actin- or α-actinin associated proteins when wild type and Syndecan-4 knockout fibroblasts were compared. The binding site for Syndecan-4 cytoplasmic domain was identified as spectrin repeat 4 of α-actinin while further experiments confirmed the importance of this interaction in stabilising cell–matrix junctions. However, α-actinin is also present in adherens junctions, these organelles not being disrupted in the absence of Syndecan-4. Indeed, co-culture of wild type and knockout cells led to adherens junction-associated stress fibre formation in cells lacking Syndecan-4, supporting the hypothesis that the proteoglycan regulates cell–matrix adhesion and its associated microfilament bundles at a post-translational level. These data provide an additional dimension to Syndecan function related to tension at the cell–matrix interface, wound healing and potentially fibrosis.
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Syndecan 1 and Syndecan 4 are independent indicators in breast carcinoma
Journal of Histochemistry and Cytochemistry, 2011Co-Authors: Maria Elisabeth Lendorf, Hinke A B Multhaupt, Tina Manonjensen, Pauliina Kronqvist, John R CouchmanAbstract:Syndecan proteoglycans may be key regulators of tumor invasion and metastasis because this four-member family of transmembrane receptors regulates cell adhesion, proliferation, and differentiation. Their expression can also serve as prognostic markers. In breast carcinomas, Syndecan-1 overexpression correlates with poor prognosis and aggressive phenotype. Syndecan-4 is expressed in most breast carcinoma cell lines, but its role in malignancy is unclear. A possible relationship between Syndecan-1 and Syndecan-4 expression and established prognostic factors in breast carcinomas was examined. Duplicate samples of 114 benign and malignant breast disease cases were stained for the two Syndecans. Clinicopathological information was available for all cases. Syndecan-1 was detected in 72.8% of cases, with significant association between its expression and histological tumor type (p<0.05) and high grade tumors (p<0.05). Syndecan-4 was expressed in 66.7% of cases; expression correlated significantly with positive estrogen (p<0.01) and progesterone (p<0.01) receptor status. Independent expression of the two Syndecans was noted from an analysis of single and double positive cases. There was a statistical relationship between Syndecan-1 presence in high-grade tumors and absence of Syndecan-4, whereas Syndecan-4 presence in cases positive for estrogen and progesterone receptor associated with Syndecan-1 absence. These Syndecans may, therefore, have distinct roles in regulating breast carcinoma cell behavior.
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heparan sulfate chain valency controls Syndecan 4 function in cell adhesion
Journal of Biological Chemistry, 2010Co-Authors: Sandeep Gopal, Adam Bober, James R Whiteford, Hinke A B Multhaupt, Atsuko Yoneda, John R CouchmanAbstract:Fibroblasts null for the transmembrane proteoglycan, Syndecan-4, have an altered actin cytoskeleton, compared with matching wild-type cells. They do not organize α-smooth muscle actin into bundles, but will do so when full-length Syndecan-4 is re-expressed. This requires the central V region of the core protein cytoplasmic domain, though not interactions with PDZ proteins. A second key requirement is multiple heparan sulfate chains. Mutant Syndecan-4 with no chains, or only one chain, failed to restore the wild-type phenotype, whereas those expressing two or three were competent. However, clustering of one-chain Syndecan-4 forms with antibodies overcame the block, indicating that valency of interactions with ligands is a key component of Syndecan-4 function. Measurements of focal contact/adhesion size and focal adhesion kinase phosphorylation correlated with Syndecan-4 status and α-smooth muscle actin organization, being reduced where Syndecan-4 function was compromised by a lack of multiple heparan sulfate chains.
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Regulation of the small GTPase RhoA by Syndecan‐4 and integrins in focal adhesion formation
International Journal of Experimental Pathology, 2008Co-Authors: Atsuko Yoneda, Hinke A B Multhaupt, Athanassios Dovas, John R CouchmanAbstract:Introduction The transmembrane heparan sulfate proteoglycan, Syndecan-4, and integrins are important receptors for focal adhesion (FA) formation on fibronectin (FN) substrates. The small GTPase RhoA is also known to regulate FA and stress fiber formation. It has been suggested that Syndecan-4 and integrins co-operatively regulate the assembly of FA in a Rho-dependent manner, but the mechanism is unclear. Here, we examined the function of RhoA and the Rho effector kinases ROCKs in Syndecan-4 signalling on the process of FA formation and the possible mechanism by which Syndecan-4 may regulate RhoA activity. Methods Primary rat embryonic fibroblasts (REFs) were seeded on FN or ‘RGD’-containing integrin-binding domain of FN and lysed at various time points. The amount of active form of RhoA in each lysate was analysed by pull-down experiments. Results and discussion The relative activities of RhoA showed one peak in the process of FA formation on FN, whereas no peak was obtained on the integrin-binding domain. The one peak of RhoA activity on integrin-binding domain was restored by addition of heparin-binding domain into medium. These results suggested that a signal through Syndecan-4 link to the Rho pathway. Both ROCK-I and -II isozymes were present in REF cell lysates and each could be specifically immunoprecipitated. The ROCK kinase activities in immunoprecipitates were analysed using GST-myosin light chain as a substrate. The amount of ROCK-I and -II activities changed through the adhesion process on FN and appeared to be independently regulated. Therefore, one or both ROCKs may be downstream of a Syndecan-4-mediated signalling response through RhoA. The core protein of Syndecan-4 can directly bind to and activate PKC-α. We found that PKC-α could phosphorylate Rho-Guanine Nucleotide Dissociation Inhibitor (GDI) in vitro. It has been suggested that PKC-α-mediated phosphorylation of Rho GDI stimulates GDI dissociation, thereby resulting in Rho activation. It is possible that Syndecan-4 regulates Rho/ROCK pathway through PKC-α activation on the process of FA formation.
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a conserved nxip motif is required for cell adhesion properties of the Syndecan 4 ectodomain
Journal of Biological Chemistry, 2006Co-Authors: James R Whiteford, John R CouchmanAbstract:Abstract Syndecans are cell surface proteoglycans involved in cell adhesion and motility. Syndecan-4 is an important component of focal adhesions and is involved in cytoskeletal reorganization. Previous work has shown that the Syndecan-4 ectodomain can support cell attachment. Here, three vertebrate Syndecan-4 ectodomains were compared, including that of the zebrafish, and we have demonstrated that the cell binding activity of the Syndecan-4 ectodomain is conserved. Cell adhesion to the Syndecan-4 ectodomain appears to be a characteristic of mesenchymal cells. Comparison of Syndecan-4 ectodomain sequences led to the identification of three conserved regions of sequence, of which the NXIP motif is important for cell binding activity. We have shown that cell adhesion to the Syndecan-4 ectodomain involves β1 integrins in several cell types.
Paul F. Goetinck - One of the best experts on this subject based on the ideXlab platform.
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Syndecan 4 dependent fgf stimulation of mouse vibrissae growth
Mechanisms of Development, 2006Co-Authors: Tokuro Iwabuchi, Paul F. GoetinckAbstract:Abstract The development, maintenance and regeneration of epithelial appendages such as hairs or vibrissae depend on reciprocal interactions between the epidermal and the dermal components of the integument. Growth factors are among a number of signaling molecules that have been identified during these developmental events. Growth factors such as fibroblast growth factors (FGFs) bind cell surface heparan sulfate proteoglycans (HSPGs) on their heparan sulfate side chains and as such these proteoglycans act as co-receptors for FGF receptors (FGFRs) by forming a ternary signaling complex of HSPG, FGFR and FGF. The Syndecans make up a family (Syndecan-1–4) of transmembrane HSPGs. In the present study we examined the growth response of mouse vibrissae to HSPG-binding growth factors as a function of the presence or absence of Syndecan-4 in an organ culture system. Syndecan-4 is expressed on keratinocytes that make up the inner root sheath of the vibrissa. Vibrissae from wild-type mice, but not from Syndecan-4 null mice, displayed a statistically significant and dose-dependent growth response to FGF-1, FGF-2 and FGF-7. In contrast, a statistically significant growth response is seen in vibrissae from both wild-type and Syndecan-4 null mice when the culture medium is supplemented with either hepatocyte growth factor (HGF) that binds to HSPG, insulin that does not bind to HSPG or 5% fetal bovine serum. The Syndecan-4 dependent effect of FGF-1, -2 and -7 on the transcriptional activity of IRS expressed genes and of genes involved in cell proliferation reveals a number of different response patterns. In vivo, the vibrissae of Syndecan-4 null mice are shorter and have a smaller diameter than those of wild-type mice and this phenotype may result from a suboptimal response to growth factors. Syndecan-1, which is expressed in the outer root sheath of the vibrissae shaft, does not influence the response of the vibrissae to FGF-1, -2 and -7 and the length and diameter of vibrissae of Syndecan-1 null mice do not differ from those of wild-type mice.
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Syndecan 4 regulates atf 2 transcriptional activity in a rac1 dependent manner
Journal of Biological Chemistry, 2004Co-Authors: Stefania Saoncella, Enzo Calautti, Wendy Neveu, Paul F. GoetinckAbstract:Abstract Syndecan-4 is a transmembrane heparan sulfate proteoglycan that co-operates with integrins during cell-matrix interactions for the assembly of focal adhesions and actin stress fibers and in the phosphorylation of focal adhesion kinase (FAK) on Tyr397. These cellular events are regulated by the small GTPase Rho, and in the absence of Syndecan-4 ligation, cellular levels of GTP-bound Rho are decreased implicating Syndecan-4 in the regulation of the small GTPases. In the present study we report that, compared with wild type cells, fibronectin-adherent Syndecan-4-null fibroblasts showed enhanced lamellipodia and increased Rac1 activity that could be down-regulated by re-expression of Syndecan-4 in the mutant cells. Consistent with the role for Rac1 in activating p38 and JNK signaling, Syndecan-4-null cells display higher levels of active p38 MAPK and JNK that were abolished by the expression of a dominant-negative RacN17 mutant. Since p38 and JNK regulate gene expression by phosphorylating and activating transcription factors, we compared both the phosphorylation state and the transcriptional activity of the ATF-2 transcription factor, as a direct p38 and JNK target in Syndecan-4-null and wild type cells. In the absence of Syndecan-4, both ATF-2 phosphorylation and transcriptional activity were significantly more elevated compared with wild type cells, and both activities were decreased either by the re-expression of Syndecan-4 or by the expression of RacN17. Our results reveal a novel function for Syndecan-4 in modulating nuclear transcriptional activity and indicate an underlying mechanism that acts at the level of Rac1-p38/JNK signaling.
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Syndecan 4 modulates focal adhesion kinase phosphorylation
Journal of Biological Chemistry, 2002Co-Authors: Sarah A Wilcoxadelman, Fabienne Denhez, Paul F. GoetinckAbstract:Abstract The cell-surface heparan sulfate proteoglycan Syndecan-4 acts in conjunction with the α5β1 integrin to promote the formation of actin stress fibers and focal adhesions in fibronectin (FN)-adherent cells. Fibroblasts seeded onto the cell-binding domain (CBD) fragment of FN attach but do not fully spread or form focal adhesions. Activation of Rho, with lysophosphatidic acid (LPA), or protein kinase C, using the phorbol ester phorbol 12-myristate 13-acetate, or clustering of Syndecan-4 with antibodies directed against its extracellular domain will stimulate formation of focal adhesions and stress fibers in CBD-adherent fibroblasts. The distinct morphological differences between the cells adherent to the CBD and to full-length FN suggest that Syndecan-4 may influence the organization of the focal adhesion or the activation state of the proteins that comprise it. FN-null fibroblasts (which express Syndecan-4) exhibit reduced phosphorylation of focal adhesion kinase (FAK) tyrosine 397 (Tyr397) when adherent to CBD compared with FN-adherent cells. Treating the CBD-adherent fibroblasts with LPA, to activate Rho, or the tyrosine phosphatase inhibitor sodium vanadate increased the level of phosphorylation of Tyr397 to match that of cells plated on FN. Treatment of the fibroblasts with PMA did not elicit such an effect. To confirm that this regulatory pathway includes Syndecan-4 specifically, we examined fibroblasts derived from Syndecan-4-null mice. The phosphorylation levels of FAK Tyr397 were lower in FN-adherent Syndecan-4-null fibroblasts compared with Syndecan-4-wild type and these levels were rescued by the addition of LPA or re-expression of Syndecan-4. These data indicate that Syndecan-4 ligation regulates the phosphorylation of FAK Tyr397 and that this mechanism is dependent on Rho but not protein kinase C activation. In addition, the data suggest that this pathway includes the negative regulation of a protein-tyrosine phosphatase. Our results implicate Syndecan-4 activation in a direct role in focal adhesion regulation.
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Syndecan-4: dispensable or indispensable?
Glycoconjugate Journal, 2002Co-Authors: Sarah A. Wilcox-adelman, Fabienne Denhez, Tokuro Iwabuchi, Stefania Saoncella, Enzo Calautti, Paul F. GoetinckAbstract:Studies examining the role of the cell-surface heparan sulfate proteoglycan Syndecan-4 have yielded a plethora of information regarding its role in both cell-matrix and growth-factor mediated signaling events. Many of the initial conclusions drawn from such research placed Syndecan-4 in a keystone position within various signaling pathways though the generation of Syndecan-4 null mice have surprised many in the field by indicating otherwise. These contradictory results place researchers in the frustrating and yet exhilarating position of still asking the question, “What role does Syndecan-4 play in life?” Published in 2003.
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delayed wound repair and impaired angiogenesis in mice lacking Syndecan 4
Journal of Clinical Investigation, 2001Co-Authors: Frank Echtermeyer, Fabienne Denhez, Stefania Saoncella, Sarah A Wilcoxadelman, Michael Streit, Michael Detmar, Paul F. GoetinckAbstract:The Syndecans make up a family of transmembrane heparan sulfate proteoglycans that act as coreceptors with integrins and growth factor tyrosine kinase receptors. Syndecan-4 is upregulated in skin dermis after wounding, and, in cultured fibroblasts adherent to the ECM protein fibronectin, this proteoglycan signals cooperatively with β1 integrins. In this study, we generated mice in which the Syndecan-4 gene was disrupted by homologous recombination in embryonic stem cells to test the hypothesis that Syndecan-4 contributes to wound repair. Mice heterozygous or homozygous for the disrupted Syndecan-4 gene are viable, fertile, and macroscopically indistinguishable from wild-type littermates. Compared with wild-type littermates, mice heterozygous or homozygous for the disrupted gene have statistically significant delayed healing of skin wounds and impaired angiogenesis in the granulation tissue. These results indicate that Syndecan-4 is an important cell-surface receptor in wound healing and angiogenesis and that Syndecan-4 is haplo-insufficient in these processes. J. Clin. Invest. 107:R9–R14 (2001).
Eoksoo Oh - One of the best experts on this subject based on the ideXlab platform.
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Hierarchy between the transmembrane and cytoplasmic domains in the regulation of Syndecan-4 functions.
Cellular Signalling, 2012Co-Authors: Youngsil Choi, Dongmin Kang, Eoksoo OhAbstract:Abstract Syndecan-4, a transmembrane heparan sulfate proteoglycan, plays a critical role in cell adhesion. Both the transmembrane and cytoplasmic domains of Syndecan-4 are known to contribute to its functions, but the regulatory mechanisms underlying the functional interplay between the two domains were previously unclear. Here, we examined the functional relationship between these two domains. Fluorescence resonance energy transfer (FRET)-based assays showed that Syndecan-4 expression enhanced RhoA activation. Furthermore, rat embryonic fibroblasts (REFs) plated on fibronectin fragments lacking the heparin-binding domain that interacts with Syndecan-4 showed much lower RhoA activation than that in cells plated on full-length fibronectin, indicating that RhoA is involved in Syndecan-4-mediated cell adhesion signaling. Syndecan-4 mutants defective in transmembrane domain-induced oligomerization and Syndecan-4 phosphorylation-mimicking cytoplasmic domain mutants showed decreases in RhoA activation and RhoA-related functions, such as adhesion, spreading and focal adhesion formation, and subsequent increase in cell migration, but the inhibitory effect was much higher in cells expressing the transmembrane domain mutants. The cytoplasmic domain mutants (but not the transmembrane domain mutants) retained the capacity to form SDS-resistant dimers, and the cytoplasmic mutants showed less inhibition of Syndecan-4-mediated protein kinase C activation compared to the transmembrane domain mutants. Finally, cytoplasmic domain activation failed to overcome the inhibition conferred by mutation of the transmembrane domain. Taken together, these data suggest that the transmembrane domain plays a major role in regulating Syndecan-4 functions, and further show that a domain hierarchy exists in the regulation of Syndecan-4.
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Syndecan-4 promotes the retention of phosphatidylinositol 4,5-bisphosphate in the plasma membrane
FEBS Letters, 2009Co-Authors: Soojin Kwon, Youngsil Choi, Sojoong Choi, Eoksoo OhAbstract:Although phosphatidylinositol 4,5-bisphosphate (PIP2) regulates Syndecan-4 function, the potential influence of Syndecan-4 on PIP2 remains unknown. GFP containing PIP2-binding-PH domain of phospholipase Cδ (GFP-PHδ) was used to monitor PIP2. Syndecan-4 overexpression in COS-7 cells enhanced membrane translocation of GFP-PHδ, while the opposite was observed when Syndecan-4 was knocked-down. PIP2 levels were higher in total phospholipids extracted from rat embryo fibroblasts expressing Syndecan-4. Syndecan-4-induced membrane targeting of GFP-PHδ was further enhanced by phosphoinositide-3-kinase inhibitor, but not by phospholipase C (PLC) inhibitor. Besides, both ionomycin and epidermal growth factor caused dissociation of GFP-PHδ from plasma membrane, an effect that was significantly delayed by Syndecan-4 over-expression. Collectively, these data suggest that Syndecan-4 promotes plasma membrane retention of PIP2 by negatively regulating PLC-dependent PIP2 degradation.
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the oligomeric status of Syndecan 4 regulates Syndecan 4 interaction with α actinin
European Journal of Cell Biology, 2008Co-Authors: Youngsil Choi, Sunggun Ko, Anne Woods, Eoksoo OhAbstract:Abstract Syndecan-4, a cell surface heparan sulfate proteoglycan, is known to regulate the organization of the cytoskeleton, and oligomerization is crucial for Syndecan-4 function. We therefore explored a possible regulatory effect of Syndecan-4 oligomerization on the cytoskeleton. Glutathione- S -transferase-Syndecan-4 proteins were used to show that Syndecan-4 interacted specifically with α -actinin, but not paxillin, talin, and vinculin. Interestingly, only dimeric, and not monomeric, recombinant Syndecan-4 interacted with α -actinin in the presence of phosphatidylinositol 4,5-bisphosphate (PIP2), and PIP2 potentiated the interaction of both the cytoplasmic domain Syndecan-4 peptide and recombinant Syndecan-4 proteins with α -actinin, implying that oligomerization of Syndecan-4 was important for this interaction. Consistent with this notion, α -actinin interaction was largely absent in Syndecan-4 mutants defective in transmembrane domain-induced oligomerization, and α -actinin-associated focal adhesions were decreased in rat embryo fibroblasts expressing mutant Syndecan-4. Besides, this interaction was consistently lower with the phosphorylation-mimicking Syndecan-4 mutant S183E which is known to destabilize the oligomerization of the Syndecan-4 cytoplasmic domain. Taken together, the data suggest that the oligomeric status of Syndecan-4 plays a crucial role in regulating the interaction of Syndecan-4 with α -actinin.
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structural basis of Syndecan 4 phosphorylation as a molecular switch to regulate signaling
Journal of Molecular Biology, 2006Co-Authors: Youngsang Jung, John R Couchman, James R Whiteford, Joon Shin, Eva Mortier, Pascale Zimmermann, Eoksoo OhAbstract:The Syndecan transmembrane proteoglycans are involved in the organization of the actin cytoskeleton and have important roles as cell surface receptors during cell–matrix interactions. We have shown that the Syndecan-4 cytoplasmic domain (4L) forms oligomeric complexes that bind to and stimulate PKCα activity in the presence of PtdIns(4,5)P2, emphasizing the importance of multimerization in the regulation of PKCα activation. Oligomerization of the cytoplasmic domain of Syndecan-4 is regulated either positively by PtdIns(4,5)P2 or negatively by phosphorylation of serine 183. Phosphorylation results in reduced PKCα activity by inhibiting PtdIns(4,5)P2-dependent oligomerization of the Syndecan-4 cytoplasmic domain. Data from NMR and gel-filtration chromatography show that the phosphorylated cytoplasmic domain (p-4L) exists as a dimer, similar to 4L, but not as higher-order oligomers. NMR analysis showed that the overall conformation of p-4L is a compact intertwined dimer with an unusually symmetric clamp shape, and its molecular surface is mostly positively charged. The two parallel strands form a cavity in the center of the dimeric twist. An especially marked effect of phosphorylation of the Syndecan-4 cytoplasmic domain is a dramatic conformational change near the C2 region that ablates an interaction site with the PDZ domain of syntenin. Wound healing studies further suggest that Syndecan-4 phosphorylation might influence cell migration behavior. We conclude that the phosphorylation (Ser183) of Syndecan-4 can play a critical role as a molecular switch to regulate its functions through conformational change.
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Dynamin II interacts with Syndecan-4, a regulator of focal adhesion and stress-fiber formation.
Biochemical and Biophysical Research Communications, 2005Co-Authors: Moon-jin Jeong, Eoksoo OhAbstract:Dynamin is a large mechanochemical GTPase that has been implicated in vesicle formation in multiple cellular compartments. It is believed that dynamin interacts with a variety of cellular proteins to constrict membranes. To identify potential intracellular proteins that interact with the PH domain of dynamin II, we carried out a yeast two-hybrid screen in which the PH domain of dynamin II was used as bait. The cell surface heparan sulfate proteoglycan Syndecan-4 that acts in conjunction with integrins to promote the formation of actin stress fibers and focal adhesions was isolated as a binding partner for the PH domain of dynamin II. In vitro binding assays, immunoprecipitation, and confocal microscopy analysis confirmed the association of dynamin II with Syndecan-4. Most dramatic finding of our study is that the cytoplasmic distribution of dynamin II and Syndecan-4 changes in fibroblasts that have been stimulated to form the focal adhesions and stress fibers with LPA. In quiescent cells, dynamin II is evenly distributed in the cytoplasm and colocalizes with Syndecan-4 near the nucleus. Upon treatment with LPA to induce focal adhesions and stress-fiber formation, dynamin II becomes markedly associated with Syndecan-4 at focal adhesion sites. We further established the colocalization of Syndecan-4 and dynamin with paxillin and actin as marker proteins for focal adhesions and stress fibers, respectively. All of these results suggest that the interaction between dynamin II and Syndecan-4 is important in mediating focal adhesion and stress-fiber formation.
Arie Horowitz - One of the best experts on this subject based on the ideXlab platform.
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cleavage of Syndecan 4 by adamts1 provokes defects in adhesion
The International Journal of Biochemistry & Cell Biology, 2009Co-Authors: Juan Carlos Rodriguezmanzaneque, Michael Simons, Arie Horowitz, Darren R Carpizo, Maria Del Carmen Plazacalonge, Antoni X Torrescollado, Shelley N M Thai, Luisa M IruelaarispeAbstract:Syndecan-4 is a membrane-bound heparan sulfate proteoglycan that participates in cell–cell and cell–matrix interactions and modulates adhesion and migration of many cell types. Through its extracellular domain, Syndecan-4 cooperates with adhesion molecules and binds matrix components relevant for cell migration. Importantly, Syndecan-4 is a substrate of extracellular proteases, however the biological significance of this cleavage has not been elucidated. Here, we show that the secreted metalloprotease ADAMTS1, involved in angiogenesis and inflammatory processes, cleaves the ectodomain of Syndecan-4. We further showed that this cleavage results in altered distribution of cytoskeleton components, functional loss of adhesion, and gain of migratory capacities. Using Syndecan-4 null cells, we observed that ADAMTS1 proteolytic action mimics the outcome of genetic deletion of this proteoglycan with regards to focal adhesion. Our findings suggest that the shedding of Syndecan-4 by ADAMTS1 disrupts cell adhesion and promotes cell migration.
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fibroblast growth factor specific modulation of cellular response by Syndecan 4
Journal of Cell Biology, 2002Co-Authors: Arie Horowitz, Eugene Tkachenko, Michael SimonsAbstract:Proteoglycans participate in growth factor interaction with the cell surface through their heparan sulfate chains (HS), but it is not known if they are otherwise involved in growth factor signaling. It appears now that the Syndecan-4 core protein, a transmembrane proteoglycan shown previously to bind phosphatidylinositol 4,5-bisphosphate (PIP2) and activate PKCα, participates in mediating the effects of fibroblast growth factor (FGF)2 on cell function. Mutations in the cytoplasmic tail of Syndecan-4 that either reduced its affinity to PIP2 (PIP2−) or disrupted its postsynaptic density 95, disk large, zona occludens-1 (PDZ)-dependent binding (PDZ−) produced a FGF2-specific dominant negative phenotype in endothelial cells as evidenced by the marked decline of their migration and proliferation rates and the impairment of their capacity to form tubes. In both cases, the molecular mechanism was determined to consist of a decrease in the Syndecan-4–dependent activation of PKCα. This decrease was caused either by inhibition of FGF2-induced Syndecan-4 dephosphorylation in the case of the PDZ− mutation or by disruption of basolateral targeting of Syndecan-4 and its associated PDZ-dependent complex in the case of the PIP2− mutation. These results suggest that PKCα activation and PDZ-mediated formation of a serine/threonine phosphatase-containing complex by Syndecan-4 are downstream events of FGF2 signaling.
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Fibroblast growth factor–specific modulation of cellular response by Syndecan-4
Journal of Cell Biology, 2002Co-Authors: Arie Horowitz, Eugene Tkachenko, Michael SimonsAbstract:Proteoglycans participate in growth factor interaction with the cell surface through their heparan sulfate chains (HS), but it is not known if they are otherwise involved in growth factor signaling. It appears now that the Syndecan-4 core protein, a transmembrane proteoglycan shown previously to bind phosphatidylinositol 4,5-bisphosphate (PIP2) and activate PKCα, participates in mediating the effects of fibroblast growth factor (FGF)2 on cell function. Mutations in the cytoplasmic tail of Syndecan-4 that either reduced its affinity to PIP2 (PIP2−) or disrupted its postsynaptic density 95, disk large, zona occludens-1 (PDZ)-dependent binding (PDZ−) produced a FGF2-specific dominant negative phenotype in endothelial cells as evidenced by the marked decline of their migration and proliferation rates and the impairment of their capacity to form tubes. In both cases, the molecular mechanism was determined to consist of a decrease in the Syndecan-4–dependent activation of PKCα. This decrease was caused either by inhibition of FGF2-induced Syndecan-4 dephosphorylation in the case of the PDZ− mutation or by disruption of basolateral targeting of Syndecan-4 and its associated PDZ-dependent complex in the case of the PIP2− mutation. These results suggest that PKCα activation and PDZ-mediated formation of a serine/threonine phosphatase-containing complex by Syndecan-4 are downstream events of FGF2 signaling.
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Syndecan 4 mediated signalling
Cellular Signalling, 2001Co-Authors: Michael Simons, Arie HorowitzAbstract:Abstract The paradigm of cell surface proteoglycan function has been centered on the role of the ectoplasmic heparan sulfate (HS) chains as acceptors of a wide array of ligands, including extracellular matrix (ECM) proteins and soluble growth factors. Within this picture, the core proteins were assigned only a passive role of carrying the glycosaminoglycan (GAG) chains without direct participation in mediating outside-in signals generated by the binding of the above ligands. It appears now, however, that, side by side with the integrins and the tyrosine kinase receptors, the core proteins of the Syndecan family of transmembrane proteoglycans are involved in signaling. The highly conserved tails of all the four members of the Syndecan family contain a carboxy-terminal PDZ (Postsynaptic density 95, Disk large, Zona occludens-1)-binding motif, capable of forming multimolecular complexes through the binding of PDZ adaptor proteins. The cytoplasmic tail of the ubiquitously expressed Syndecan-4 is distinct from the other Syndecans in its capacity to bind phosphatidylinositol 4, 5-bisphosphate (PIP 2 ) and to activate protein kinase C (PKC) α. These properties may confer on Syndecan-4 specific and unique signaling functions.
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phosphorylation of the cytoplasmic tail of Syndecan 4 regulates activation of protein kinase cα
Journal of Biological Chemistry, 1998Co-Authors: Arie Horowitz, Michael SimonsAbstract:Abstract Syndecans are transmembrane proteoglycans capable of carrying both heparan and chondroitin sulfate chains. The cytoplasmic tail of Syndecan-4 was recently reported to undergoin vivo phosphorylation on Ser183 in the membrane-proximal part of the tail (Horowitz, A., and Simons, M. (1998)J. Biol. Chem. 273, 10914–10918). However, the functional consequences of this event remain unknown. The cytoplasmic tail of Syndecan-4 is known to undergo multimerization and to activate protein kinase Cα (PKCα), with both events depending on the presence of the commonly occurring phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2). In the present investigation we found that phosphorylation of Ser183 produced a 10-fold reduction in the ability of Syndecan-4 to activate PKCα, without affecting its ability to bind the PKC. Because Ser183 is adjacent to positively charged lysine groups that resemble PIP2-binding regions in several other proteins, phosphorylation of this serine may affect the binding affinity of the Syndecan-4 cytoplasmic tail to PIP2. We found that the Ser183-phosphorylated cytoplasmic tail of Syndecan-4 has indeed a significantly lower affinity to PIP2 compared with the nonphosphorylated tail. Furthermore, Ser183phosphorylation abolished PIP2-dependent oligomerization of Syndecan-4 cytoplasmic tails. We conclude that Ser183 phosphorylation regulates Syndecan-4-dependent activation of PKCα by reducing the affinity to PIP2 and inhibiting the oligomerization of Syndecan-4 cytoplasmic tails. These results further support the role of Syndecan-4 in signal transduction in endothelial cells.
