| 1. |
- Vaca, Diana J, et al.
(författare)
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Interaction of Bartonella henselae with Fibronectin Represents the Molecular Basis for Adhesion to Host Cells
- 2022
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Ingår i: Microbiology spectrum. - : American Society for Microbiology. - 2165-0497. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial adhesion to the host is the most decisive step in infections. Trimeric autotransporter adhesins (TAA) are important pathogenicity factors of Gram-negative bacteria. The prototypic TAA Bartonella adhesin A (BadA) from human-pathogenic Bartonella henselae mediates bacterial adherence to endothelial cells (ECs) and extracellular matrix proteins. Here, we determined the interaction between BadA and fibronectin (Fn) to be essential for bacterial host cell adhesion. BadA interactions occur within the heparin-binding domains of Fn. The exact binding sites were revealed by mass spectrometry analysis of chemically cross-linked whole-cell bacteria and Fn. Specific BadA interactions with defined Fn regions represent the molecular basis for bacterial adhesion to ECs and these data were confirmed by BadA-deficient bacteria and CRISPR-Cas knockout Fn host cells. Interactions between TAAs and the extracellular matrix might represent the key step for adherence of human-pathogenic Gram-negative bacteria to the host. IMPORTANCE Deciphering the mechanisms of bacterial host cell adhesion is a clue for preventing infections. We describe the underestimated role that the extracellular matrix protein fibronectin plays in the adhesion of human-pathogenic Bartonella henselae to host cells. Fibronectin-binding is mediated by a trimeric autotransporter adhesin (TAA) also present in many other human-pathogenic Gram-negative bacteria. We demonstrate that both TAA and host-fibronectin contribute significantly to bacterial adhesion, and we present the exact sequence of interacting amino acids from both proteins. Our work shows the domain-specific pattern of interaction between the TAA and fibronectin to adhere to host cells and opens the perspective to fight bacterial infections by inhibiting bacterial adhesion which represents generally the first step in infections.
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| 2. |
- Eble, Johannes A., et al.
(författare)
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Collagen XVI harbors an integrin alpha 1 beta 1 recognition site in its C-terminal domains
- 2006
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 281:35, s. 25745-25756
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Tidskriftsartikel (refereegranskat)abstract
- Collagen XVI is integrated tissue-dependently into distinct fibrillar aggregates, such as D-banded cartilage fibrils and fibrillin-1-containing microfibrils. In skin, the distribution of collagen XVI overlaps that of the collagen-binding integrins alpha 1 beta 1 and alpha 2 beta 1. Basal layer keratinocytes express integrin alpha 2 beta 1, whereas integrin alpha 1 beta 1 occurs in smooth muscle cells surrounding blood vessels, in hair follicles, and on adipocytes. Cells bearing the integrins alpha 1 beta 1 and alpha 2 beta 1 attach and spread on recombinant collagen XVI. Furthermore, collagen XVI induces the recruitment of these integrins into focal adhesion plaques, a principal step in integrin signaling. Of potential physiological relevance, these integrin-collagen XVI interactions may connect cells with specialized fibrils, thus contributing to the organization of fibrillar and cellular components within connective tissues. In cell-free binding assays, collagen XVI is more avidly bound by alpha 1 beta 1 integrin than by alpha 2 beta 1 integrin. Both integrins interact with collagen XVI via the A domain of their alpha subunits. A tryptic collagen XVI fragment comprising the collagenous domains 1 - 3 is recognized by alpha 1 beta 1 integrin. Electron microscopy of complexes of alpha 1 beta 1 integrin with this tryptic collagen XVI fragment or with full-length collagen XVI revealed a unique alpha 1 beta 1 integrin-binding site within collagen XVI located close to its C-terminal end.
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| 3. |
- Kardeby, Caroline, 1989-, et al.
(författare)
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Synthetic glycopolymers and natural fucoidans cause human platelet aggregation via PEAR1 and GPIbα
- 2019
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Ingår i: Blood Advances. - : American Society of Hematology. - 2473-9529 .- 2473-9537. ; 3:3, s. 275-287
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Tidskriftsartikel (refereegranskat)abstract
- Fucoidans are sulfated fucose-based polysaccharides that activate platelets and have pro- and anticoagulant effects; thus, they may have therapeutic value. In the present study, we show that 2 synthetic sulfated α-l-fucoside-pendant glycopolymers (with average monomeric units of 13 and 329) and natural fucoidans activate human platelets through a Src- and phosphatidylinositol 3-kinase (PI3K)-dependent and Syk-independent signaling cascade downstream of the platelet endothelial aggregation receptor 1 (PEAR1). Synthetic glycopolymers and natural fucoidan stimulate marked phosphorylation of PEAR1 and Akt, but not Syk. Platelet aggregation and Akt phosphorylation induced by natural fucoidan and synthetic glycopolymers are blocked by a monoclonal antibody to PEAR1. Direct binding of sulfated glycopolymers to epidermal like growth factor (EGF)-like repeat 13 of PEAR1 was shown by avidity-based extracellular protein interaction screen technology. In contrast, synthetic glycopolymers and natural fucoidans activate mouse platelets through a Src- and Syk-dependent pathway regulated by C-type lectin-like receptor 2 (CLEC-2) with only a minor role for PEAR1. Mouse platelets lacking the extracellular domain of GPIbα and human platelets treated with GPIbα-blocking antibodies display a reduced aggregation response to synthetic glycopolymers. We found that synthetic sulfated glycopolymers bind directly to GPIbα, substantiating that GPIbα facilitates the interaction of synthetic glycopolymers with CLEC-2 or PEAR1. Our results establish PEAR1 as the major signaling receptor for natural fucose-based polysaccharides and synthetic glycopolymers in human, but not in mouse, platelets. Sulfated α-l-fucoside-pendant glycopolymers are unique tools for further investigation of the physiological role of PEAR1 in platelets and beyond.
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| 4. |
- Martínez-Botía, Patricia, et al.
(författare)
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Dissecting platelet proteomics to understand the pathophysiology of immune thrombocytopenia : studies in mouse models
- 2022
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Ingår i: Blood Advances. - : American Society of Hematology. - 2473-9529 .- 2473-9537. ; 6:11, s. 3529-3534
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Tidskriftsartikel (refereegranskat)abstract
- Immune thrombocytopenia (ITP) is an autoimmune disease characterized by enhanced platelet clearance and defective platelet production. Diagnosis by exclusion and trial-and-error treatment strategies is common practice, and despite the advancement in treatment options, many patients remain refractory. Although the existence of different pathophysiological entities is acknowledged, we are still far from stratifying and understanding ITP. To investigate, we sought to dissect the platelet proteome dynamics in so-called passive and active preclinical ITP mouse models, with which we propose to phenocopy respectively acute/newly diagnosed and persistent/chronic stages of ITP in humans. We obtained the platelet proteome at the thrombocytopenic stage and after platelet count recovery (reached naturally or by IVIg-treatment, depending on the model). Although most of the proteomic alterations were common to both ITP models, there were model-specific protein dynamics that accompanied and explained alterations in platelet aggregation responses, as measured in the passive ITP model. The expression dynamics observed in Syk may explain, extrapolated to humans and pending validation, the increased bleeding tendency of patients with ITP when treated with fostamatinib as third or later- as opposed to second line of treatment. We propose that the platelet proteome may give diagnostic and prognostic insights into ITP and that such studies should be pursued in humans.
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| 5. |
- Navdaev, Alexei, et al.
(författare)
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The C-terminus of the gamma2 chain but not of the beta3 chain of laminin-332 is indirectly but indispensably necessary for integrin-mediated cell reactions
- 2008
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Ingår i: Experimental Cell Research. - : Elsevier BV. - 1090-2422 .- 0014-4827. ; 314:3, s. 489-497
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Tidskriftsartikel (refereegranskat)abstract
- Using a recombinant mini-laminin-332, we showed that truncation of the three C-terminal amino acids of the gamma2 chain, but not of the C-terminal amino acid of the beta3 chain, completely abolished alpha3beta1 integrin binding and its cellular functions, such as attachment and spreading. However, a synthetic peptide mimicking the gamma2 chain C-terminus did not interfere with alpha3beta1 integrin binding or cell adhesion and spreading on laminin-332 as measured by protein interaction assays and electric cell-substrate impedance sensing. Nor was the soluble peptide able to restore the loss of integrin-mediated cell adhesiveness to mini-laminin-332 after deletion of the gamma2 chain C-terminus. These findings spoke against the hypothesis that the gamma2 chain C-terminus of laminin-332 is a part of the alpha3beta1 integrin interaction site. In addition, structural studies with electron microscopy showed that truncation of the gamma2 chain C-terminus opened up the compact supradomain structure of LG1-3 domains. Thus, by inducing or stabilizing an integrin binding-competent conformation or array of the LG1-3 domains, the gamma2 chain C-terminus plays an indirect but essential role in laminin-332 recognition by alpha3beta1 integrin and, hence, its cellular functions.
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