The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Klaus T Preissner - One of the best experts on this subject based on the ideXlab platform.
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Vitronectin in vascular context facets of a multitalented matricellular protein
Seminars in Thrombosis and Hemostasis, 2011Co-Authors: Klaus T Preissner, Ute ReuningAbstract:: Vitronectin is an abundant adhesive glycoprotein in blood plasma and is found associated with different extracellular matrix sites, the vessel wall, and tumor cells, particularly upon tissue remodeling, injury/repair, or under disease conditions. Plasma Vitronectin is a structurally labile molecule that may be converted into a multimeric/multivalent form by interaction with various (hemostatic) factors or through surface binding. Several distinct binding domains along the Vitronectin sequence for integrin-type cell adhesion receptors, for urokinase receptor or proteoglycans as well as for growth factors, endow vascular matrix- or fibrin-associated Vitronectin with differentiated cell attachment and aggregatory properties. These were found to be relevant for modulation of the cell-matrix interface in angiogenesis, hemostasis and thrombus formation, or wound repair, respectively. Other Vitronectin ligands include plasminogen activator inhibitor (PAI)-1 or high molecular weight kininogen that confer strong antiadhesive functions upon integrin- or urokinase receptor-mediated cell interactions with Vitronectin. Together, Vitronectin acts as a potent matricellular factor, coordinating cell migration with pericellular proteolysis and growth factor signaling at sites of tissue remodeling or in tumors. Structure-function studies of such Vitronectin-related ligands and receptors lead to the characterization of their mode of action, also stimulating the search for new antagonists in tumor angiogenesis, platelet aggregation, or atherosclerosis. This review focuses on new developments in Vitronectin biology, with particular emphasis on regulatory mechanisms of the protein in the context of cell adhesion/migration/proliferation and cell-dependent proteolysis, relevant for our understanding of hemostasis, thrombosis, tissue repair, and vascular diseases.
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integrin linked kinase is required for Vitronectin mediated internalization of streptococcus pneumoniae by host cells
Journal of Cell Science, 2009Co-Authors: Simone Bergmann, Klaus T Preissner, Anke Lang, Manfred Rohde, Vaibhav Agarwal, Claudia Rennemeier, Carsten Grashoff, Sven HammerschmidtAbstract:By interacting with components of the human host, including extracellular matrix (ECM) proteins, Streptococcus pneumoniae has evolved various strategies for colonization. Here, we characterized the interaction of pneumococci with the adhesive glycoprotein Vitronectin and the contribution of this protein to pneumococcal uptake by host cells in an integrin-dependent manner. Specific interaction of S. pneumoniae with the heparin-binding sites of purified multimeric Vitronectin was demonstrated by flow cytometry analysis. Host-cell-bound Vitronectin promoted pneumococcal adherence to and invasion into human epithelial and endothelial cells. Pneumococci were trapped by microspike-like structures, which were induced upon contact of pneumococci with host-cell-bound Vitronectin. αvβ3 integrin was identified as the major cellular receptor for Vitronectin-mediated adherence and uptake of pneumococci. Ingestion of pneumococci by host cells via Vitronectin required a dynamic actin cytoskeleton and was dependent on integrin-linked kinase (ILK), phosphatidylinositol 3-kinase (PI3K), and protein kinase B (Akt), as demonstrated by gene silencing or in inhibition experiments. In conclusion, pneumococci exploit the Vitronectin–αvβ3-integrin complex as a cellular receptor for invasion and this integrin-mediated internalization requires the cooperation between the host signalling molecules ILK, PI3K and Akt.
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Vitronectin is sequestered within human spermatozoa and liberated following the acrosome reaction.
Molecular Human Reproduction, 2000Co-Authors: Richard Bronson, Tatyana Peresleni, Marc Golightly, Klaus T PreissnerAbstract:Vitronectin plays a role in the regulation of complement and thrombin activities and in cell surface proteolysis. Vitronectin is also an intrinsic protein of human spermatozoa. Vitronectin message has been detected in whole testis poly-A mRNA and localized by in-situ reverse transcription-polymerase chain reaction to spermatocytes. The proportion of spermatozoa that express Vitronectin increases following their capacitation. In this study, spermatozoa from a man of proven fertility were probed with an anti-Vitronectin monoclonal antibody (VN7) before and after their permeabilization with 0.1% Triton X-100. Of fresh spermatozoa observed by confocal microscopy, 0-8% showed Vitronectin staining. However, 75% of those observed displayed Vitronectin following permeabilization. Serial confocal sections through the sperm head confirmed the internal localization of Vitronectin. The acrosomal status of capacitated spermatozoa that expressed Vitronectin was then determined. Dual colour microscopy with rhodamine-conjugated anti-Vitronectin antibody and a fluorescein-conjugated antibody directed against CD46 (a complement regulatory protein expressed on the inner acrosomal membrane) revealed that only acrosome-reacted (CD46-positive) spermatozoa displayed Vitronectin. Two populations of these spermatozoa were observed. Fifty-seven of 260 (22%) were CD46-positive/Vitronectin-positive and 72 of 260 (28%) were CD46-positive/Vitronectin-negative. No spermatozoa were CD46-negative/Vitronectin-positive. These results confirm that Vitronectin is released from a sequestered location within the spermatozoon following the acrosome reaction.
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Measurement of Vitronectin content of human spermatozoa and Vitronectin concentration within seminal fluid
Fertility and Sterility, 1997Co-Authors: Richard A. Bronson, Klaus T PreissnerAbstract:Abstract Objective : Vitronectin previously has been extracted from human spermatozoa and messenger RNA (mRNA) encoding Vitronectin localized by reverse transcriptase in situ polymerase chain reaction (PCR) to spermatocytes of human testis. In the present experiments, we have established ranges for the content of Vitronectin in living human spermatozoa and Vitronectin concentration within seminal fluid of human ejaculates. Design : Seminal fluid was obtained by centrifugation and motile sperm selected by swim-up from men with normal and abnormal ejaculates, according to World Health Organization criteria, for Vitronectin determinations. Setting : Academic research environment. Main Outcome Measure(s) : Seminal fluid Vitronectin concentrations were measured by ELISA and sperm Vitronectin content by polyacrylamide gel electrophoresis and semiquantitative Western blots. Result(s) : Vitronectin seminal fluid concentration was 1.35 ± 1.0 mg/mL (mean ± SD) for normospermic samples ( n = 26) and 0.78 ± 0.4 mg/mL for azoospermic specimens ( n = 6). Vitronectin sperm content ranged from 1 to 15 ng/10 6 motile cells ( n = 20). Both high- and low-molecular-weight material was observed. Sperm content of Vitronectin did not vary with sperm morphology. Conclusion(s) : These results suggest that spermatozoa represent a major source of seminal fluid Vitronectin, but that a secondary source exists, perhaps through transudation from serum.
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The Hemopexin-Type Repeats of Human Vitronectin Are Recognized byStreptococcus pyogenes
Biochemical and Biophysical Research Communications, 1997Co-Authors: Olin D. Liang, Klaus T Preissner, Gursharan S. ChhatwalAbstract:: The specific binding of Vitronectin to Streptococcus pyogenes is believed to play an important role in the infection process by mediating adherence of the bacteria to host cells. The domain of Vitronectin involved in the interaction with S. pyogenes is unknown. In the present study, we constructed a Vitronectin random epitope phage display library, which was used to pan against intact cells of S. pyogenes. Several phage-displayed Vitronectin peptides containing a hydrophobic pentapeptide motif within the hemopexin-type repeats were found to bind to streptococci. These data were supported by competition experiments, in which a representative 23-amino acid synthetic Vitronectin peptide comprising part of a hemopexin-type repeat inhibited binding of the bacteria to Vitronectin, while a control peptide with identical amino acid composition but a scrambled sequence had no effect. Moreover, cells of S. pyogenes were shown to bind to the synthetic peptide as well as to immobilized hemopexin, whose structural homology to the hemopexin-type repeats in the Vitronectin molecule has long been underlined. Soluble Vitronectin could inhibit streptococcal binding to immobilized hemopexin. These results provide first evidence for a biological role of hemopexin itself and respective repeats in Vitronectin in bacterial binding, suggesting that during an infection process these or other hemopexin-type repeat-containing proteins could be potential targets for bacterial attachment and subsequent colonization.
David A. Cheresh - One of the best experts on this subject based on the ideXlab platform.
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Cerebral microenvironment influences expression of the Vitronectin gene in astrocytic tumors.
Journal of Cell Science, 1995Co-Authors: Candece L. Gladson, Josiah N. Wilcox, L. Sanders, G. Y. Gillespie, David A. ChereshAbstract:Expression of the Vitronectin gene was detected in advanced human astrocytoma by in situ hybridization, whereas Vitronectin mRNA was undetectable in low grade tumors or in normal adult brain, indicating that Vitronectin is a marker of malignant astrocytoma. We established a model of human astrocytoma by transplanting U-251MG human astrocytoma cells intracerebrally into acid mice (C.B.17 severe combined immunodeficient mice). In this model, tumors progressed rapidly and Vitronectin mRNA was preferentially detected at the invading tumor margins, i.e. where tumor cells were adjacent to the normal brain tissue. Surprisingly, when U-251MG cells were injected subcutaneously into scid mice, Vitronectin mRNA was undetectable throughout the tumor. Moreover, Vitronectin mRNA or protein could not be detected among these cells in culture under a wide variety of growth conditions. These findings demonstrate that the cerebral microenvironment influences the expression of the Vitronectin gene in malignant astrocytoma. Importantly, the Vitronectin binding integrins alpha v beta 3 and alpha v beta 5 localized to distinct sites within these tumors, with beta 3 mRNA synthesized among invading cells, and alpha v and beta 5 mRNAs detected throughout the tumor. In vitro, both of these receptors were capable of promoting adhesion and invasion of astrocytoma cells on a Vitronectin substratum. These findings implicate the expression of the Vitronectin gene as a contributing factor to the biological behavior of astrocytomas within the cerebral microenvironment.
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receptor tyrosine kinase signaling required for integrin alpha v beta 5 directed cell motility but not adhesion on Vitronectin
Journal of Cell Biology, 1994Co-Authors: Richard L Klemke, Mayra Yebra, Evelyn M Bayna, David A. ChereshAbstract:FG human pancreatic carcinoma cells adhere to Vitronectin using integrin alpha v beta 5 yet are unable to migrate on this ligand whereas they readily migrate on collagen in an alpha 2 beta 1-dependent manner. We report here that epidermal growth factor receptor (EGFR) activation leads to de novo alpha v beta 5-dependent FG cell migration on Vitronectin. The EGFR specific tyrosine kinase inhibitor tyrphostin 25 selectively prevents EGFR autophosphorylation thereby preventing the EGF-induced FG cell migration response on Vitronectin without affecting constitutive migration on collagen. Protein kinase C (PKC) activation also leads to alpha v beta 5-directed motility on Vitronectin; however, this is not blocked by tyrosine kinase inhibitors. In this case, PKC activation appears to be associated with and downstream of EGFR signaling since calphostin C, an inhibitor of PKC, blocks FG cell migration on Vitronectin induced by either PKC or EGF. These findings represent the first report implicating a receptor tyrosine kinase in a specific integrin mediated cell motility event independent of adhesion.
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Vitronectin and its receptors
Current Opinion in Cell Biology, 1993Co-Authors: Brunhilde Feldinghabermann, David A. ChereshAbstract:Abstract The extracellular matrix protein Vitronectin is recognized as an adhesive substrate by cells expressing at least one of four known Vitronectin receptors: integrins αvβ1, αvβ3, αvβ5 or αIIbβ3. Cell interaction with Vitronectin may induced spreading and migration and have an effect on cell growth and differentiation in specific processes, such as tumor growth and metastasis, wound healing, bone resorption and viral infection.
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requirement of the integrin beta 3 subunit for carcinoma cell spreading or migration on Vitronectin and fibrinogen
Journal of Cell Biology, 1992Co-Authors: David I Leavesley, G D Ferguson, E A Wayner, David A. ChereshAbstract:FG human pancreatic carcinoma cells use integrin alpha v beta 5 as their primary Vitronectin receptor since they fail to express integrin alpha v beta 3. These cells are unable to form focal contacts, spread, or migrate on Vitronectin but readily do so on collagen in a beta 1 integrin-dependent manner. Transfection of FG cells with a cDNA encoding the integrin beta 3 subunit results in the surface expression of a functional integrin alpha v beta 3 heterodimer providing these cells with novel adhesive and biological properties. Specifically, FG cells expressing beta 3 acquire the capacity to attach and spread on Vitronectin as well as fibrinogen with beta 3 localization to focal contacts. Moreover, these cells gain the capacity to migrate through a porous membrane in response to either Vitronectin or fibrinogen. These results demonstrate that the beta 3 and beta 5 integrin subunits when associated with alpha v, promote distinct cellular responses to a Vitronectin extracellular environment.
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the Vitronectin receptor alpha v beta 3 binds fibronectin and acts in concert with alpha 5 beta 1 in promoting cellular attachment and spreading on fibronectin
Journal of Cell Biology, 1990Co-Authors: I F Charo, L Nannizzi, J W Smith, David A. ChereshAbstract:The Vitronectin receptor (alpha v beta 3) is a member of the integrin superfamily of adhesive protein receptors that mediate a wide spectrum of adhesive cellular interactions, including attachment to Vitronectin, von Willebrand factor, fibrinogen, and thrombospondin. We have studied the binding of fibronectin to the purified Vitronectin receptor, and the role of this receptor in the attachment of cells to fibronectin. A solid-phase microtiter assay was developed to investigate the binding properties of the Vitronectin receptor. Purified alpha v beta 3 bound fibronectin with high affinity in a saturable, divalent cation-dependent manner. Binding was inhibited by soluble Vitronectin, by RGD-containing peptides, and by LM609, a monoclonal antibody against the Vitronectin receptor known to inhibit the binding of adhesive proteins to alpha v beta 3. Immunoinhibition experiments showed that M21 human melanoma cells, which express the fibronectin receptor, alpha 5 beta 1, as well as alpha v beta 3, used both of these integrins to attach and spread on fibronectin. In support of this finding, M21-L cells, a variant cell line that specifically lacks alpha v beta 3 but expresses alpha v beta 1, attached and spread poorly on fibronectin. In addition, alpha v beta 3 from surface-labeled M21 cells was retained, and selectively eluted by RGDS from a fibronectin affinity column. These results indicate that alpha v beta 3 acts in concert with alpha 5 beta 1 in promoting fibronectin recognition by these cells. We conclude that fibronectin binds to the alpha v beta 3 Vitronectin receptor specifically and with high affinity, and that this interaction is biologically relevant in supporting cell adhesion to matrix proteins.
Peter F Zipfel - One of the best experts on this subject based on the ideXlab platform.
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conserved patterns of microbial immune escape pathogenic microbes of diverse origin target the human terminal complement inhibitor Vitronectin via a single common motif
PLOS ONE, 2016Co-Authors: Teresia Hallstrom, Peter F Zipfel, Birendra Singh, Sven Hammerschmidt, Peter Kraiczy, Christine Skerka, Kristian RiesbeckAbstract:Pathogenicity of many microbes relies on their capacity to resist innate immunity, and to survive and persist in an immunocompetent human host microbes have developed highly efficient and sophisticated complement evasion strategies. Here we show that different human pathogens including Gram-negative and Gram-positive bacteria, as well as the fungal pathogen Candida albicans, acquire the human terminal complement regulator Vitronectin to their surface. By using truncated Vitronectin fragments we found that all analyzed microbial pathogens (n = 13) bound human Vitronectin via the same C-terminal heparin-binding domain (amino acids 352–374). This specific interaction leaves the terminal complement complex (TCC) regulatory region of Vitronectin accessible, allowing inhibition of C5b-7 membrane insertion and C9 polymerization. Vitronectin complexed with the various microbes and corresponding proteins was thus functionally active and inhibited complement-mediated C5b-9 deposition. Taken together, diverse microbial pathogens expressing different structurally unrelated Vitronectin-binding molecules interact with host Vitronectin via the same conserved region to allow versatile control of the host innate immune response.
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candida albicans uses the surface protein gpm1 to attach to human endothelial cells and to keratinocytes via the adhesive protein Vitronectin
PLOS ONE, 2014Co-Authors: Crisanto M Lopez, Peter F Zipfel, Kristian Riesbeck, Christine Skerka, Reinhard WallichAbstract:Candida albicans is a major cause of invasive fungal infections worldwide. Upon infection and when in contact with human plasma as well as body fluids the fungus is challenged by the activated complement system a central part of the human innate immune response. C. albicans controls and evades host complement attack by binding several human complement regulators like Factor H, Factor H-like protein 1 and C4BP to the surface. Gpm1 (Phosphoglycerate mutase 1) is one fungal Factor H/FHL1 -binding protein. As Gpm1 is surface exposed, we asked whether Gpm1 also contributes to host cell attachment. Here, we show by flow cytometry and by laser scanning microscopy that candida Gpm1 binds to human umbilical vein endothelial cells (HUVEC) to keratinocytes (HaCaT), and also to monocytic U937 cells. Wild type candida did bind, but the candida gpm1Δ/Δ knock-out mutant did not bind to these human cells. In addition Gpm1when attached to latex beads also conferred attachment to human endothelial cells. When analyzing Gpm1-binding to a panel of extracellular matrix proteins, the human glycoprotein Vitronectin was identified as a new Gpm1 ligand. Vitronectin is a component of the extracellular matrix and also a regulator of the terminal complement pathway. Vitronectin is present on the surface of HUVEC and keratinocytes and acts as a surface ligand for fungal Gpm1. Gpm1 and Vitronectin colocalize on the surface of HUVEC and HaCaT as revealed by laser scanning microscopy. The Gpm1 Vitronectin interaction is inhibited by heparin and the interaction is also ionic strength dependent. Taken together, Gpm1 the candida surface protein binds to Vitronectin and mediates fungal adhesion to human endothelial cells. Thus fungal Gpm1 and human Vitronectin represent a new set of proteins that are relevant for fungal attachment to human cells interaction. Blockade of the Gpm1 Vitronectin interaction might provide a new target for therapy.
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the choline binding protein pspc of streptococcus pneumoniae interacts with the c terminal heparin binding domain of Vitronectin
Journal of Biological Chemistry, 2013Co-Authors: Sylvia Voss, Teresia Hallstrom, Peter F Zipfel, Kristian Riesbeck, Malek Saleh, Gerhard Burchhardt, Thomas Pribyl, Birendra Singh, Sven HammerschmidtAbstract:Adherence of Streptococcus pneumoniae is directly mediated by interactions of adhesins with eukaryotic cellular receptors or indirectly by exploiting matrix and serum proteins as molecular bridges. Pneumococci engage Vitronectin, the human adhesive glycoprotein and complement inhibitor, to facilitate attachment to epithelial cells of the mucosal cavity, thereby modulating host cell signaling. In this study, we identified PspC as a Vitronectin-binding protein interacting with the C-terminal heparin-binding domain of Vitronectin. PspC is a multifunctional surface-exposed choline-binding protein displaying various adhesive properties. Vitronectin binding required the R domains in the mature PspC protein, which are also essential for the interaction with the ectodomain of the polymeric immunoglobulin receptor and secretory IgA. Consequently, secretory IgA competitively inhibited binding of Vitronectin to purified PspC and to PspC-expressing pneumococci. In contrast, Factor H, which binds to the N-terminal part of mature PspC molecules, did not interfere with the PspC-Vitronectin interaction. Using a series of Vitronectin peptides, the C-terminal heparin-binding domain was shown to be essential for the interaction of soluble Vitronectin with PspC. Binding experiments with immobilized Vitronectin suggested a region N-terminal to the identified heparin-binding domain as an additional binding region for PspC, suggesting that soluble, immobilized, as well as cellularly bound Vitronectin possesses different conformations. Finally, Vitronectin bound to PspC was functionally active and inhibited the deposition of the terminal complement complex. In conclusion, this study identifies and characterizes (on the molecular level) the interaction between the pneumococcal adhesin PspC and the human glycoprotein Vitronectin.
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nontypeable haemophilus influenzae protein e binds Vitronectin and is important for serum resistance
Journal of Immunology, 2009Co-Authors: Teresia Hallstrom, Anna M Blom, Peter F Zipfel, Kristian RiesbeckAbstract:Nontypeable Haemophilus influenzae (NTHi) commonly causes local disease in the upper and lower respiratory tract and has recently been shown to interfere with both the classical and alternative pathways of complement activation. The terminal pathway of the complement system is regulated by Vitronectin that is a component of both plasma and the extracellular matrix. In this study, we identify protein E (PE; 16 kDa), which is a recently characterized ubiquitous outer membrane protein, as a Vitronectin-binding protein of NTHi. A PE-deficient NTHi mutant had a markedly reduced survival in serum compared with the PE-expressing isogenic NTHi wild type. Moreover, the PE-deficient mutant showed a significantly decreased binding to both soluble and immobilized Vitronectin. In parallel, PE-expressing Escherichia coli bound soluble Vitronectin and adhered to immobilized Vitronectin compared with controls. Surface plasmon resonance technology revealed a K D of 0.4 μΜ for the interaction between recombinant PE and immobilized Vitronectin. Moreover, the PE-dependent Vitronectin-binding site was located at the heparin-binding domains of Vitronectin and the major Vitronectin-binding domain was found in the central core of PE (aa 84–108). Importantly, Vitronectin bound to the surface of NTHi 3655 reduced membrane attack complex-induced hemolysis. In contrast to incubation with normal human serum, NTHi 3655 showed a reduced survival in Vitronectin-depleted human serum, thus demonstrating that Vitronectin mediates a protective role at the bacterial surface. Our findings show that PE, by binding Vitronectin, may play an important role in NTHi pathogenesis.
Sven Hammerschmidt - One of the best experts on this subject based on the ideXlab platform.
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conserved patterns of microbial immune escape pathogenic microbes of diverse origin target the human terminal complement inhibitor Vitronectin via a single common motif
PLOS ONE, 2016Co-Authors: Teresia Hallstrom, Peter F Zipfel, Birendra Singh, Sven Hammerschmidt, Peter Kraiczy, Christine Skerka, Kristian RiesbeckAbstract:Pathogenicity of many microbes relies on their capacity to resist innate immunity, and to survive and persist in an immunocompetent human host microbes have developed highly efficient and sophisticated complement evasion strategies. Here we show that different human pathogens including Gram-negative and Gram-positive bacteria, as well as the fungal pathogen Candida albicans, acquire the human terminal complement regulator Vitronectin to their surface. By using truncated Vitronectin fragments we found that all analyzed microbial pathogens (n = 13) bound human Vitronectin via the same C-terminal heparin-binding domain (amino acids 352–374). This specific interaction leaves the terminal complement complex (TCC) regulatory region of Vitronectin accessible, allowing inhibition of C5b-7 membrane insertion and C9 polymerization. Vitronectin complexed with the various microbes and corresponding proteins was thus functionally active and inhibited complement-mediated C5b-9 deposition. Taken together, diverse microbial pathogens expressing different structurally unrelated Vitronectin-binding molecules interact with host Vitronectin via the same conserved region to allow versatile control of the host innate immune response.
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the choline binding protein pspc of streptococcus pneumoniae interacts with the c terminal heparin binding domain of Vitronectin
Journal of Biological Chemistry, 2013Co-Authors: Sylvia Voss, Teresia Hallstrom, Peter F Zipfel, Kristian Riesbeck, Malek Saleh, Gerhard Burchhardt, Thomas Pribyl, Birendra Singh, Sven HammerschmidtAbstract:Adherence of Streptococcus pneumoniae is directly mediated by interactions of adhesins with eukaryotic cellular receptors or indirectly by exploiting matrix and serum proteins as molecular bridges. Pneumococci engage Vitronectin, the human adhesive glycoprotein and complement inhibitor, to facilitate attachment to epithelial cells of the mucosal cavity, thereby modulating host cell signaling. In this study, we identified PspC as a Vitronectin-binding protein interacting with the C-terminal heparin-binding domain of Vitronectin. PspC is a multifunctional surface-exposed choline-binding protein displaying various adhesive properties. Vitronectin binding required the R domains in the mature PspC protein, which are also essential for the interaction with the ectodomain of the polymeric immunoglobulin receptor and secretory IgA. Consequently, secretory IgA competitively inhibited binding of Vitronectin to purified PspC and to PspC-expressing pneumococci. In contrast, Factor H, which binds to the N-terminal part of mature PspC molecules, did not interfere with the PspC-Vitronectin interaction. Using a series of Vitronectin peptides, the C-terminal heparin-binding domain was shown to be essential for the interaction of soluble Vitronectin with PspC. Binding experiments with immobilized Vitronectin suggested a region N-terminal to the identified heparin-binding domain as an additional binding region for PspC, suggesting that soluble, immobilized, as well as cellularly bound Vitronectin possesses different conformations. Finally, Vitronectin bound to PspC was functionally active and inhibited the deposition of the terminal complement complex. In conclusion, this study identifies and characterizes (on the molecular level) the interaction between the pneumococcal adhesin PspC and the human glycoprotein Vitronectin.
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integrin linked kinase is required for Vitronectin mediated internalization of streptococcus pneumoniae by host cells
Journal of Cell Science, 2009Co-Authors: Simone Bergmann, Klaus T Preissner, Anke Lang, Manfred Rohde, Vaibhav Agarwal, Claudia Rennemeier, Carsten Grashoff, Sven HammerschmidtAbstract:By interacting with components of the human host, including extracellular matrix (ECM) proteins, Streptococcus pneumoniae has evolved various strategies for colonization. Here, we characterized the interaction of pneumococci with the adhesive glycoprotein Vitronectin and the contribution of this protein to pneumococcal uptake by host cells in an integrin-dependent manner. Specific interaction of S. pneumoniae with the heparin-binding sites of purified multimeric Vitronectin was demonstrated by flow cytometry analysis. Host-cell-bound Vitronectin promoted pneumococcal adherence to and invasion into human epithelial and endothelial cells. Pneumococci were trapped by microspike-like structures, which were induced upon contact of pneumococci with host-cell-bound Vitronectin. αvβ3 integrin was identified as the major cellular receptor for Vitronectin-mediated adherence and uptake of pneumococci. Ingestion of pneumococci by host cells via Vitronectin required a dynamic actin cytoskeleton and was dependent on integrin-linked kinase (ILK), phosphatidylinositol 3-kinase (PI3K), and protein kinase B (Akt), as demonstrated by gene silencing or in inhibition experiments. In conclusion, pneumococci exploit the Vitronectin–αvβ3-integrin complex as a cellular receptor for invasion and this integrin-mediated internalization requires the cooperation between the host signalling molecules ILK, PI3K and Akt.
Daniel A Lawrence - One of the best experts on this subject based on the ideXlab platform.
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the contributions of integrin affinity and integrin cytoskeletal engagement in endothelial and smooth muscle cell adhesion to Vitronectin
Journal of Biological Chemistry, 2007Co-Authors: Steingrimur P Stefansson, Enming J Su, Shoji Ishigami, Jacqueline M Cale, Natalia Gorlatova, Daniel A LawrenceAbstract:Abstract The serine proteinase inhibitor, plasminogen activator inhibitor type-1 (PAI-1), binds to the adhesion protein Vitronectin with high affinity at a site that is located directly adjacent to the Vitronectin RGD integrin binding sequence. The binding of PAI-1 to Vitronectin sterically blocks integrin access to this site and completely inhibits the binding of purified integrins to Vitronectin; however, its inhibition of endothelial and smooth muscle cell adhesion to Vitronectin is at most 50-75%. Because PAI-1 binds Vitronectin with ∼10-100-fold higher affinity than purified integrins, we have analyzed the mechanism whereby these cells are able to overcome this obstacle. Our studies exclude proteolytic removal of PAI-1 from Vitronectin as the mechanism, and show instead that cell adhesion in the presence of PAI-1 is dependent on integrin-cytoskeleton engagement. Disrupting endothelial or smooth muscle cell actin polymerization and/or focal adhesion assembly reduces cell adhesion to Vitronectin in the presence of PAI-1 to levels similar to that observed for the binding of purified integrins to Vitronectin. Furthermore, endothelial cell, but not smooth muscle cell adhesion to Vitronectin in the presence of PAI-1 requires both polymerized microtubules and actin, further demonstrating the importance of the cytoskeleton for integrin-mediated adhesion. Finally, we show that cell adhesion in the presence of PAI-1 leads to colocalization of PAI-1 with the integrins αvβ3 and αvβ5 at the cell-matrix interface.
