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Pyong Woo Park - One of the best experts on this subject based on the ideXlab platform.
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2 o sulfated domains in syndecan 1 heparan sulfate inhibit neutrophil cathelicidin and promote staphylococcus aureus corneal infection
Journal of Biological Chemistry, 2015Co-Authors: Atsuko Hayashida, Shiro Amano, Richard L Gallo, Robert J Linhardt, Pyong Woo ParkAbstract:Abstract Ablation of syndecan-1 in mice is a gain of function mutation that enables mice to significantly resist infection by several bacterial pathogens. Syndecan-1 shedding is induced by bacterial virulence factors, and inhibition of shedding attenuates bacterial virulence, whereas administration of purified syndecan-1 Ectodomain enhances virulence, suggesting that bacteria subvert syndecan-1 Ectodomains released by shedding for their pathogenesis. However, the pro-pathogenic functions of syndecan-1 Ectodomain have yet to be clearly defined. Here, we examined how syndecan-1 Ectodomain enhances Staphylococcus aureus virulence in injured mouse corneas. We found that syndecan-1 Ectodomain promotes S. aureus corneal infection in an HS-dependent manner. Surprisingly, we found that this pro-pathogenic activity is dependent on 2-O-sulfated domains in HS, indicating that the effects of syndecan-1 Ectodomain are structure-based. Our results also showed that purified syndecan-1 Ectodomain and heparan compounds containing 2-O-sulfate motifs inhibit S. aureus killing by antimicrobial factors secreted by degranulated neutrophils, but does not affect intracellular phagocytic killing by neutrophils. Immunodepletion of antimicrobial factors with staphylocidal activities demonstrated that CRAMP, a cationic antimicrobial peptide, is primarily responsible for S. aureus killing among other factors secreted by degranulated neutrophils. Furthermore, we found that purified syndecan-1 Ectodomain and heparan compounds containing 2-O-sulfate units potently and specifically inhibit S. aureus killing by synthetic CRAMP. These results provide compelling evidence that a specific subclass of sulfate groups, and not the overall charge of HS, permits syndecan-1 Ectodomains to promote S. aureus corneal infection by inhibiting a key arm of neutrophil host defense.
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syndecan 1 promotes staphylococcus aureus corneal infection by counteracting neutrophil mediated host defense
Journal of Biological Chemistry, 2011Co-Authors: Atsuko Hayashida, Shiro Amano, Pyong Woo ParkAbstract:Many microbial pathogens subvert cell surface heparan sulfate proteoglycans (HSPGs) to infect host cells in vitro. The significance of HSPG-pathogen interactions in vivo, however, remains to be determined. In this study, we examined the role of syndecan-1, a major cell surface HSPG of epithelial cells, in Staphylococcus aureus corneal infection. We found that syndecan-1 null (Sdc1−/−) mice significantly resist S. aureus corneal infection compared with wild type (WT) mice that express abundant syndecan-1 in their corneal epithelium. However, syndecan-1 did not bind to S. aureus, and syndecan-1 was not required for the colonization of cultured corneal epithelial cells by S. aureus, suggesting that syndecan-1 does not mediate S. aureus attachment to corneal tissues in vivo. Instead, S. aureus induced the shedding of syndecan-1 Ectodomains from the surface of corneal epithelial cells. Topical administration of purified syndecan-1 Ectodomains or heparan sulfate (HS) significantly increased, whereas inhibition of syndecan-1 shedding significantly decreased the bacterial burden in corneal tissues. Furthermore, depletion of neutrophils in the resistant Sdc1−/− mice increased the corneal bacterial burden to that of the susceptible WT mice, suggesting that syndecan-1 moderates neutrophils to promote infection. We found that syndecan-1 does not affect the infiltration of neutrophils into the infected cornea but that purified syndecan-1 Ectodomain and HS significantly inhibit neutrophil-mediated killing of S. aureus. These data suggest a previously unknown bacterial subversion mechanism where S. aureus exploits the capacity of syndecan-1 Ectodomains to inhibit neutrophil-mediated bacterial killing mechanisms in an HS-dependent manner to promote its pathogenesis in the cornea.
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Molecular and Cellular Mechanisms of Ectodomain Shedding
Anatomical record (Hoboken N.J. : 2007), 2010Co-Authors: Kazutaka Hayashida, Allison H. Bartlett, Ye Chen, Pyong Woo ParkAbstract:The extracellular domain of several membrane-anchored proteins is released from the cell surface as soluble proteins through a regulated proteolytic mechanism called Ectodomain shedding. Cells use Ectodomain shedding to actively regulate the expression and function of surface molecules, and modulate a wide variety of cellular and physiological processes. Ectodomain shedding rapidly converts membrane-associated proteins into soluble effectors and, at the same time, rapidly reduces the level of cell surface expression. For some proteins, Ectodomain shedding is also a prerequisite for intramembrane proteolysis, which liberates the cytoplasmic domain of the affected molecule and associated signaling factors to regulate transcription. Ectodomain shedding is a process that is highly regulated by specific agonists, antagonists, and intracellular signaling pathways. Moreover, only about 2% of cell surface proteins are released from the surface by Ectodomain shedding, indicating that cells selectively shed their protein Ectodomains. This review will describe the molecular and cellular mechanisms of Ectodomain shedding, and discuss its major functions in lung development and disease.
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syndecan 1 Ectodomain shedding is regulated by the small gtpase rab5
Journal of Biological Chemistry, 2008Co-Authors: Kazutaka Hayashida, Philip D Stahl, Pyong Woo ParkAbstract:The Ectodomain shedding of syndecan-1, a major cell surface heparan sulfate proteoglycan, modulates molecular and cellular processes central to the pathogenesis of inflammatory diseases. Syndecan-1 shedding is a highly regulated process in which outside-in signaling accelerates the proteolytic cleavage of syndecan-1 Ectodomains at the cell surface. Several extracellular agonists that induce syndecan-1 shedding and metalloproteinases that cleave syndecan-1 Ectodomains have been identified, but the intracellular mechanisms that regulate syndecan-1 shedding are largely unknown. Here we examined the role of the syndecan-1 cytoplasmic domain in the regulation of agonist-induced syndecan-1 shedding. Our results showed that the syndecan-1 cytoplasmic domain is essential because mutation of invariant cytoplasmic Tyr residues abrogates Ectodomain shedding, but not because it is Tyr phosphorylated upon shedding stimulation. Instead, our data showed that the syndecan-1 cytoplasmic domain binds to Rab5, a small GTPase that regulates intracellular trafficking and signaling events, and this interaction controls the onset of syndecan-1 shedding. Syndecan-1 cytoplasmic domain bound specifically to Rab5 and preferentially to inactive GDP-Rab5 over active GTP-Rab5, and shedding stimulation induced the dissociation of Rab5 from the syndecan-1 cytoplasmic domain. Moreover, the expression of dominant-negative Rab5, unable to exchange GDP for GTP, interfered with the agonist-induced dissociation of Rab5 from the syndecan-1 cytoplasmic domain and significantly inhibited syndecan-1 shedding induced by several distinct agonists. Based on these data, we propose that Rab5 is a critical regulator of syndecan-1 shedding that serves as an on-off molecular switch through its alternation between the GDP-bound and GTP-bound forms.
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Endogenous Attenuation of Allergic Lung Inflammation by Syndecan-1
The Journal of Immunology, 2005Co-Authors: Pyong Woo Park, Farrah Kheradmand, David B. CorryAbstract:The airway plays a vital role in allergic lung diseases by responding to inhaled allergens and initiating allergic inflammation. Various proinflammatory functions of the airway epithelium have been identified, but, equally important, anti-inflammatory mechanisms must also exist. We show in this study that syndecan-1, the major heparan sulfate proteoglycan of epithelial cells, attenuates allergic lung inflammation. Our results show that syndecan-1-null mice instilled with allergens exhibit exaggerated airway hyperresponsiveness, glycoprotein hypersecretion, eosinophilia, and lung IL-4 responses. However, administration of purified syndecan-1 Ectodomains, but not Ectodomain core proteins devoid of heparan sulfate, significantly inhibits these inflammatory responses. Furthermore, syndecan-1 Ectodomains are shed into the airway when wild-type mice are intranasally instilled with several biochemically distinct inducers of allergic lung inflammation. Our results also show that syndecan-1 Ectodomains bind to the CC chemokines (CCL7, CCL11, and CCL17) implicated in allergic diseases, inhibit CC chemokine-mediated T cell migration, and suppress allergen-induced accumulation of Th2 cells in the lung through their heparan sulfate chains. Together, these findings uncover an endogenous anti-inflammatory mechanism of the airway epithelium where syndecan-1 Ectodomains attenuate allergic lung inflammation via suppression of CC chemokine-mediated Th2 cell recruitment to the lung.
Merton Bernfield - One of the best experts on this subject based on the ideXlab platform.
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Exploitation of syndecan-1 shedding by Pseudomonas aeruginosa enhances virulence
Nature, 2001Co-Authors: Pyong Woo Park, Gerald B. Pier, Michael T. Hinkes, Merton BernfieldAbstract:Cell-surface heparan sulphate proteoglycans (HSPGs) are ubiquitous and abundant receptors/co-receptors of extracellular ligands1,2, including many microbes3,4,5,6,7,8,9,10. Their role in microbial infections is poorly defined, however, because no cell-surface HSPG has been clearly connected to the pathogenesis of a particular microbe. We have previously shown that Pseudomonas aeruginosa, through its virulence factor LasA, enhances the in vitro shedding of syndecan-1—the predominant cell-surface HSPG of epithelia11. Here we show that shedding of syndecan-1 is also activated by P. aeruginosa in vivo, and that the resulting syndecan-1 Ectodomains enhance bacterial virulence in newborn mice. Newborn mice deficient in syndecan-1 resist P. aeruginosa lung infection but become susceptible when given purified syndecan-1 Ectodomains or heparin, but not when given Ectodomain core protein, indicating that the Ectodomain's heparan sulphate chains are the effectors. In wild-type newborn mice, inhibition of syndecan-1 shedding or inactivation of the shed Ectodomain's heparan sulphate chains prevents lung infection. Our findings uncover a pathogenetic mechanism in which a host response to tissue injury—syndecan-1 shedding—is exploited to enhance microbial virulence apparently by modulating host defences.
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shedding of syndecan 1 and 4 Ectodomains is regulated by multiple signaling pathways and mediated by a timp 3 sensitive metalloproteinase
Journal of Cell Biology, 2000Co-Authors: Marilyn L Fitzgerald, Pyong Woo Park, Gillian Murphy, Zihua Wang, Merton BernfieldAbstract:The syndecan family of four transmembrane heparan sulfate proteoglycans binds a variety of soluble and insoluble extracellular effectors. Syndecan extracellular domains (Ectodomains) can be shed intact by proteolytic cleavage of their core proteins, yielding soluble proteoglycans that retain the binding properties of their cell surface precursors. Shedding is accelerated by PMA activation of protein kinase C, and by ligand activation of the thrombin (G-protein–coupled) and EGF (protein tyrosine kinase) receptors (Subramanian, S.V., M.L. Fitzgerald, and M. Bernfield. 1997. J. Biol. Chem. 272:14713–14720). Syndecan-1 and -4 Ectodomains are found in acute dermal wound fluids, where they regulate growth factor activity (Kato, M., H. Wang, V. Kainulainen, M.L. Fitzgerald, S. Ledbetter, D.M. Ornitz, and M. Bernfield. 1998. Nat. Med. 4:691–697) and proteolytic balance (Kainulainen, V., H. Wang, C. Schick, and M. Bernfield. 1998. J. Biol. Chem. 273:11563–11569). However, little is known about how syndecan Ectodomain shedding is regulated. To elucidate the mechanisms that regulate syndecan shedding, we analyzed several features of the process that sheds the syndecan-1 and -4 Ectodomains. We find that shedding accelerated by various physiologic agents involves activation of distinct intracellular signaling pathways; and the proteolytic activity responsible for cleavage of syndecan core proteins, which is associated with the cell surface, can act on unstimulated adjacent cells, and is specifically inhibited by TIMP-3, a matrix-associated metalloproteinase inhibitor. In addition, we find that the syndecan-1 core protein is cleaved on the cell surface at a juxtamembrane site; and the proteolytic activity responsible for accelerated shedding differs from that involved in constitutive shedding of the syndecan Ectodomains. These results demonstrate the existence of highly regulated mechanisms that can rapidly convert syndecans from cell surface receptors or coreceptors to soluble heparan sulfate proteoglycan effectors. Because the shed Ectodomains are found and function in vivo, regulation of syndecan Ectodomain shedding by physiological mediators indicates that shedding is a response to specific developmental and pathophysiological cues.
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Syndecans, Heparan Sulfate Proteoglycans, Maintain the Proteolytic Balance of Acute Wound Fluids
The Journal of biological chemistry, 1998Co-Authors: Varpu Kainulainen, Hui-ming Wang, Charles Schick, Merton BernfieldAbstract:Abstract An imbalance between proteases and antiproteases is thought to play a role in the inflammatory injury that regulates wound healing. The activities of some proteases and antiproteases found in inflammatory fluids can be modified in vitro by heparin, a mast cell-derived glycosaminoglycan. Because syndecans, a family of cell surface heparan sulfate proteoglycans, are the major cellular source of heparin-like glycosaminoglycan, we asked whether syndecans modify protease activities in vivo. Syndecan-1 and syndecan-4 Ectodomains are shed into acute human dermal wound fluids (Subramanian, S. V., Fitzgerald, M. L., and Bernfield, M. (1997) J. Biol. Chem. 272, 14713–14720). Moreover, purified syndecan-1 Ectodomain binds cathepsin G (K d = 56 nm) and elastase (K d = 35 nm) tightly and reduces the affinity of these proteases for their physiological inhibitors. Purified syndecan-1 Ectodomain protects cathepsin G from inhibition by α1-antichymotrypsin and squamous cell carcinoma antigen 2 and elastase from inhibition by α1-proteinase inhibitor by decreasing second order rate constants for protease-antiprotease associations (k ass) by 3700-, 32-, and 60-fold, respectively. Both enzymatic degradation of heparan sulfate and immunodepletion of the syndecan-1 and -4 in wound fluid reduce these proteolytic activities in the fluid, indicating that the proteases in the wound environment are regulated by interactions with syndecan Ectodomains. Thus, syndecans are shed into acute wound fluids, where they can modify the proteolytic balance of the fluid. This suggests a novel physiological role for these soluble heparan sulfate proteoglycans.
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regulated shedding of syndecan 1 and 4 Ectodomains by thrombin and growth factor receptor activation
Journal of Biological Chemistry, 1997Co-Authors: Sukanya V Subramanian, Marilyn L Fitzgerald, Merton BernfieldAbstract:Abstract The syndecan family of transmembrane heparan sulfate proteoglycans is abundant on the surface of all adherent mammalian cells. Syndecans bind and modify the action of various growth factors/cytokines, proteases/antiproteases, cell adhesion molecules, and extracellular matrix components. Syndecan expression is highly regulated during wound repair, a process orchestrated by many of these effectors. Each syndecan Ectodomain is shed constitutively by cultured cells, but the mechanism and significance of this shedding are not understood. Therefore, we examined (i) whether physiological agents active during wound repair influence syndecan shedding, and (ii) whether wound fluids contain shed syndecan Ectodomains. Using SVEC4–10 endothelial cells we find that certain proteases and growth factors accelerate shedding of the syndecan-1 and -4 Ectodomains. Protease-accelerated shedding is completely inhibited by serum-containing media. Thrombin activity is duplicated by the 14-amino acid thrombin receptor agonist peptide that directly activates the thrombin receptor and is not inhibited by serum. Epidermal growth factor family members accelerate shedding but FGF-2, platelet-derived growth factor-AB, transforming growth factor-β, tumor necrosis factor-α, and vascular endothelial cell growth factor 165 do not. Shed Ectodomains are soluble, stable in the conditioned medium, have the same size core proteins regardless whether shed at a basal rate, or accelerated by thrombin or epidermal growth factor-family members and are found in acute human dermal wound fluids. Thus, shedding is accelerated by activation of at least two distinct receptor classes, G protein-coupled (thrombin) and protein tyrosine kinase (epidermal growth factor). Proteases and growth factors active during wound repair can accelerate syndecan shedding from cell surfaces. Regulated shedding of syndecans suggests physiological roles for the soluble proteoglycan Ectodomains.
Ye Chen - One of the best experts on this subject based on the ideXlab platform.
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Molecular and Cellular Mechanisms of Ectodomain Shedding
Anatomical record (Hoboken N.J. : 2007), 2010Co-Authors: Kazutaka Hayashida, Allison H. Bartlett, Ye Chen, Pyong Woo ParkAbstract:The extracellular domain of several membrane-anchored proteins is released from the cell surface as soluble proteins through a regulated proteolytic mechanism called Ectodomain shedding. Cells use Ectodomain shedding to actively regulate the expression and function of surface molecules, and modulate a wide variety of cellular and physiological processes. Ectodomain shedding rapidly converts membrane-associated proteins into soluble effectors and, at the same time, rapidly reduces the level of cell surface expression. For some proteins, Ectodomain shedding is also a prerequisite for intramembrane proteolysis, which liberates the cytoplasmic domain of the affected molecule and associated signaling factors to regulate transcription. Ectodomain shedding is a process that is highly regulated by specific agonists, antagonists, and intracellular signaling pathways. Moreover, only about 2% of cell surface proteins are released from the surface by Ectodomain shedding, indicating that cells selectively shed their protein Ectodomains. This review will describe the molecular and cellular mechanisms of Ectodomain shedding, and discuss its major functions in lung development and disease.
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activation of syndecan 1 Ectodomain shedding by staphylococcus aureus alpha toxin and beta toxin
Journal of Biological Chemistry, 2004Co-Authors: Pyong Woo Park, Timothy J Foster, Eiichiro Nishi, Sheila J Duncan, Michael Klagsbrun, Ye ChenAbstract:Abstract Exploitation of host components by microbes to promote their survival in the hostile host environment has been a recurring theme in recent years. Available data indicate that bacterial pathogens activate Ectodomain shedding of host cell surface molecules to enhance their virulence. We reported previously that several major bacterial pathogens activate Ectodomain shedding of syndecan-1, the major heparan sulfate proteoglycan of epithelial cells. Here we define the molecular basis of how Staphylococcus aureus activates syndecan-1 shedding. We screened mutant S. aureus strains devoid of various toxin and protease genes and found that only strains lacking both α-toxin and β-toxin genes do not stimulate shedding. Mutations in the agr global regulatory locus, which positively regulates expression of α- and β-toxins and other exoproteins, also abrogated the capacity to stimulate syndecan-1 shedding. Furthermore, purified S. aureus α- and β-toxins, but not enterotoxin A and toxic shock syndrome toxin-1, rapidly potentiated shedding in a concentration-dependent manner. These results establish that S. aureus activates syndecan-1 Ectodomain shedding via its two virulence factors, α- and β-toxins. Toxin-activated shedding was also selectively inhibited by antagonists of the host cell shedding mechanism, indicating that α- and β-toxins shed syndecan-1 Ectodomains through stimulation of the host cell's shedding machinery. Interestingly, β-toxin, but not α-toxin, also enhanced Ectodomain shedding of syndecan-4 and heparin-binding epidermal growth factor. Because shedding of these Ectodomains has been implicated in promoting bacterial pathogenesis, activation of Ectodomain shedding by α-toxin and β-toxin may be a previously unknown virulence mechanism of S. aureus.
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activation of syndecan 1 Ectodomain shedding by staphylococcus aureus α toxin and β toxin
Journal of Biological Chemistry, 2004Co-Authors: Pyong Woo Park, Timothy J Foster, Eiichiro Nishi, Sheila J Duncan, Michael Klagsbrun, Ye ChenAbstract:Abstract Exploitation of host components by microbes to promote their survival in the hostile host environment has been a recurring theme in recent years. Available data indicate that bacterial pathogens activate Ectodomain shedding of host cell surface molecules to enhance their virulence. We reported previously that several major bacterial pathogens activate Ectodomain shedding of syndecan-1, the major heparan sulfate proteoglycan of epithelial cells. Here we define the molecular basis of how Staphylococcus aureus activates syndecan-1 shedding. We screened mutant S. aureus strains devoid of various toxin and protease genes and found that only strains lacking both α-toxin and β-toxin genes do not stimulate shedding. Mutations in the agr global regulatory locus, which positively regulates expression of α- and β-toxins and other exoproteins, also abrogated the capacity to stimulate syndecan-1 shedding. Furthermore, purified S. aureus α- and β-toxins, but not enterotoxin A and toxic shock syndrome toxin-1, rapidly potentiated shedding in a concentration-dependent manner. These results establish that S. aureus activates syndecan-1 Ectodomain shedding via its two virulence factors, α- and β-toxins. Toxin-activated shedding was also selectively inhibited by antagonists of the host cell shedding mechanism, indicating that α- and β-toxins shed syndecan-1 Ectodomains through stimulation of the host cell's shedding machinery. Interestingly, β-toxin, but not α-toxin, also enhanced Ectodomain shedding of syndecan-4 and heparin-binding epidermal growth factor. Because shedding of these Ectodomains has been implicated in promoting bacterial pathogenesis, activation of Ectodomain shedding by α-toxin and β-toxin may be a previously unknown virulence mechanism of S. aureus.
John R Couchman - One of the best experts on this subject based on the ideXlab platform.
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mapping of matrix metalloproteinase cleavage sites on syndecan 1 and syndecan 4 Ectodomains
FEBS Journal, 2013Co-Authors: Tina Manonjensen, Hinke A B Multhaupt, John R CouchmanAbstract:Syndecans are transmembrane heparan sulfate proteoglycans with roles in cell proliferation, differentiation, adhesion, and migration. They have been associated with multiple functions in tumour progression, through their ability to interact with a wide range of ligands as well as other receptors, which makes them key effectors in the pericellular microenvironment. Extracellular shedding of syndecans by tumour-associated matrix metalloproteinases (MMPs) may have an important role in tumour progression. Such Ectodomain shedding generates soluble Ectodomains that may function as paracrine or autocrine effectors, or as competitive inhibitors of the intact proteoglycan. Tumour-associated MMPs are shown here to cleave the Ectodomains of human syndecan-1 and syndecan-4. Two membrane proximal regions of both syndecan-1 and syndecan-4 are favoured MMP cleavage sites, six and 15 residues from the transmembrane domain. Other sites are 35–40 residues C-terminal from the heparan sulfate chain substitution sites in both syndecans. The MT1-MMP cleavage sites in syndecan-1 and syndecan-4 were confirmed by site-directed mutagenesis. These findings provide insights into the characteristics of syndecan shedding.
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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.
Atsuko Hayashida - One of the best experts on this subject based on the ideXlab platform.
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2 o sulfated domains in syndecan 1 heparan sulfate inhibit neutrophil cathelicidin and promote staphylococcus aureus corneal infection
Journal of Biological Chemistry, 2015Co-Authors: Atsuko Hayashida, Shiro Amano, Richard L Gallo, Robert J Linhardt, Pyong Woo ParkAbstract:Abstract Ablation of syndecan-1 in mice is a gain of function mutation that enables mice to significantly resist infection by several bacterial pathogens. Syndecan-1 shedding is induced by bacterial virulence factors, and inhibition of shedding attenuates bacterial virulence, whereas administration of purified syndecan-1 Ectodomain enhances virulence, suggesting that bacteria subvert syndecan-1 Ectodomains released by shedding for their pathogenesis. However, the pro-pathogenic functions of syndecan-1 Ectodomain have yet to be clearly defined. Here, we examined how syndecan-1 Ectodomain enhances Staphylococcus aureus virulence in injured mouse corneas. We found that syndecan-1 Ectodomain promotes S. aureus corneal infection in an HS-dependent manner. Surprisingly, we found that this pro-pathogenic activity is dependent on 2-O-sulfated domains in HS, indicating that the effects of syndecan-1 Ectodomain are structure-based. Our results also showed that purified syndecan-1 Ectodomain and heparan compounds containing 2-O-sulfate motifs inhibit S. aureus killing by antimicrobial factors secreted by degranulated neutrophils, but does not affect intracellular phagocytic killing by neutrophils. Immunodepletion of antimicrobial factors with staphylocidal activities demonstrated that CRAMP, a cationic antimicrobial peptide, is primarily responsible for S. aureus killing among other factors secreted by degranulated neutrophils. Furthermore, we found that purified syndecan-1 Ectodomain and heparan compounds containing 2-O-sulfate units potently and specifically inhibit S. aureus killing by synthetic CRAMP. These results provide compelling evidence that a specific subclass of sulfate groups, and not the overall charge of HS, permits syndecan-1 Ectodomains to promote S. aureus corneal infection by inhibiting a key arm of neutrophil host defense.
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syndecan 1 promotes staphylococcus aureus corneal infection by counteracting neutrophil mediated host defense
Journal of Biological Chemistry, 2011Co-Authors: Atsuko Hayashida, Shiro Amano, Pyong Woo ParkAbstract:Many microbial pathogens subvert cell surface heparan sulfate proteoglycans (HSPGs) to infect host cells in vitro. The significance of HSPG-pathogen interactions in vivo, however, remains to be determined. In this study, we examined the role of syndecan-1, a major cell surface HSPG of epithelial cells, in Staphylococcus aureus corneal infection. We found that syndecan-1 null (Sdc1−/−) mice significantly resist S. aureus corneal infection compared with wild type (WT) mice that express abundant syndecan-1 in their corneal epithelium. However, syndecan-1 did not bind to S. aureus, and syndecan-1 was not required for the colonization of cultured corneal epithelial cells by S. aureus, suggesting that syndecan-1 does not mediate S. aureus attachment to corneal tissues in vivo. Instead, S. aureus induced the shedding of syndecan-1 Ectodomains from the surface of corneal epithelial cells. Topical administration of purified syndecan-1 Ectodomains or heparan sulfate (HS) significantly increased, whereas inhibition of syndecan-1 shedding significantly decreased the bacterial burden in corneal tissues. Furthermore, depletion of neutrophils in the resistant Sdc1−/− mice increased the corneal bacterial burden to that of the susceptible WT mice, suggesting that syndecan-1 moderates neutrophils to promote infection. We found that syndecan-1 does not affect the infiltration of neutrophils into the infected cornea but that purified syndecan-1 Ectodomain and HS significantly inhibit neutrophil-mediated killing of S. aureus. These data suggest a previously unknown bacterial subversion mechanism where S. aureus exploits the capacity of syndecan-1 Ectodomains to inhibit neutrophil-mediated bacterial killing mechanisms in an HS-dependent manner to promote its pathogenesis in the cornea.
