| 1. |
- Tjwa, Marc, et al.
(författare)
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Gas6 promotes inflammation by enhancing interactions between endothelial cells, platelets, and leukocytes
- 2008
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Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 111:8, s. 4096-4105
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Tidskriftsartikel (refereegranskat)abstract
- The role of Gas6 in enclothelial cell (EC) function remains incompletely characterized. Here we report that Gas6 amplifies EC activation in response to inflammatory stimuli in vitro. In vivo, Gas6 promotes and accelerates the sequestration of circulating platelets and leukocytes on activated endothelium as well as the formation and enclothelial sequestration of circulating platelet-leukocyte conjugates. In addition, Gas6 promotes leukocyte extravasation, inflammation, and thrombosis in mouse models of inflammation (endotoxinemia, vasculitis, heart transplantation). Thus, Gas6 amplifies EC activation, thereby playing a key role in enhancing the interactions between ECs, platelets, and leukocytes during inflammation.
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| 2. |
- Angelillo-Scherrer, Anne, et al.
(författare)
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Deficiency or inhibition of Gas6 causes platelet dysfunction and protects mice against thrombosis
- 2001
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Ingår i: Nature Medicine. - : Springer Science and Business Media LLC. - 1546-170X .- 1078-8956. ; 7:2, s. 215-221
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Tidskriftsartikel (refereegranskat)abstract
- The growth arrest-specific gene 6 product (Gas6) is a secreted protein related to the anticoagulant protein S but its role in hemostasis is unknown. Here we show that inactivation of the Gas6 gene prevented venous and arterial thrombosis in mice, and protected against fatal collagen/epinephrine-induced thrombo embolism. Gas6-/- mice did not, however, suffer spontaneous bleeding and had normal bleeding after tail clipping. In addition, we found that Gas6 antibodies inhibited platelet aggregation in vitro and protected mice against fatal thrombo embolism without causing bleeding in vivo. Gas6 amplified platelet aggregation and secretion in response to known agonists. Platelet dysfunction in Gas6-/- mice resembled that of patients with platelet signaling transduction defects. Thus, Gas6 is a platelet-response amplifier that plays a significant role in thrombosis. These findings warrant further evaluation of the possible therapeutic use of Gas6 inhibition for prevention of thrombosis.
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| 3. |
- d'Alessandro, Elisa, et al.
(författare)
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Thrombo-Inflammation in Cardiovascular Disease : An Expert Consensus Document from the Third Maastricht Consensus Conference on Thrombosis
- 2020
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Ingår i: Thrombosis and Haemostasis. - : Georg Thieme Verlag KG. - 0340-6245 .- 2567-689X. ; 120:4, s. 538-564
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Tidskriftsartikel (refereegranskat)abstract
- Thrombo-inflammation describes the complex interplay between blood coagulation and inflammation that plays a critical role in cardiovascular diseases. The third Maastricht Consensus Conference on Thrombosis assembled basic, translational, and clinical scientists to discuss the origin and potential consequences of thrombo-inflammation in the etiology, diagnostics, and management of patients with cardiovascular disease, including myocardial infarction, stroke, and peripheral artery disease. This article presents a state-of-the-art reflection of expert opinions and consensus recommendations regarding the following topics: (1) challenges of the endothelial cell barrier; (2) circulating cells and thrombo-inflammation, focused on platelets, neutrophils, and neutrophil extracellular traps; (3) procoagulant mechanisms; (4) arterial vascular changes in atherogenesis; attenuating atherosclerosis and ischemia/reperfusion injury; (5) management of patients with arterial vascular disease; and (6) pathogenesis of venous thrombosis and late consequences of venous thromboembolism.
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| 4. |
- 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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| 5. |
- Kozlenkov, Alexey, et al.
(författare)
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Function assignment to conserved residues in mammalian alkaline phosphatases
- 2002
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 277:25, s. 22992-22999
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Tidskriftsartikel (refereegranskat)abstract
- We have probed the structural/functional relationship of key residues in human placental alkaline phosphatase (PLAP) and compared their properties with those of the corresponding residues in Escherichia coli alkaline phosphatase (ECAP). Mutations were introduced in wild-type PLAP, i.e. [E429]PLAP, and in some instances also in [G429]PLAP, which displays properties characteristic of the human germ cell alkaline phosphatase isozyme. All active site metal ligands, as well as residues in their vicinity, were substituted to alanines or to the homologous residues present in ECAP. We found that mutations at Zn2 or Mg sites had similar effects in PLAP and ECAP but that the environment of the Zn1 ion in PLAP is less affected by substitutions than that in ECAP. Substitutions of the Mg and Zn1 neighboring residues His-317 and His-153 increased kcat and increased Km when compared with wild-type PLAP, contrary to what was predicted by the reciprocal substitutions in ECAP. All mammalian alkaline phosphatases (APs) have five cysteine residues (Cys-101, Cys-121, Cys-183, Cys-467, and Cys-474) per subunit, not homologous to any of the four cysteines in ECAP. By substituting each PLAP Cys by Ser, we found that disrupting the disulfide bond between Cys-121 and Cys-183 completely prevents the formation of the active enzyme, whereas the carboxylterminally located Cys-467-Cys-474 bond plays a lesser structural role. The substitution of the free Cys-101 did not significantly affect the properties of the enzyme. A distinguishing feature found in all mammalian APs, but not in ECAP, is the Tyr-367 residue involved in subunit contact and located close to the active site of the opposite subunit. We studied the A367 and F367 mutants of PLAP, as well as the corresponding double mutants containing G429. The mutations led to a 2-fold decrease in kcat, a significant decrease in heat stability, and a significant disruption of inhibition by the uncompetitive inhibitors L-Phe and L-Leu. Our mutagenesis data, computer modeling, and docking predictions indicate that this residue contributes to the formation of the hydrophobic pocket that accommodates and stabilizes the side chain of the inhibitor during uncompetitive inhibition of mammalian APs.
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| 6. |
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| 7. |
- Kozlenkov, Alexey, et al.
(författare)
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Residues determining the specific binding of uncompetitive inhibitors to mammalian alkaline phosphatases
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Recent data have suggested that the activity of human tissue-nonspecific alkaline phosphatase (TNAP) could be targeted therapeutically to ameliorate soft-tissue ossification abnormalities resulting from insufficient production of inorganic pyrophosphate (1). Thus, understanding the mechanism of action and precise binding site for inhibitors of TNAP function is paramount. We compared the modeled three-dimensional structure of TNAP with the 3D structure of human placental alkaline phosphatase (PLAP), and identified the residues that differ between these two isozymes within a 12 Å radius of the active site. We then used site-directed mutagenesis to substitute TNAP residues to their respective homologues in PLAP or in the related germ cell (GCAP) isozyme or to Ala. In addition, we mutagenized most of the corresponding residues in PLAP to their TNAP homologues, and studied the role of a conserved residue Y371 in TNAP using the A371 mutation. All mutants were characterized for their sensitivity towards the uncompetitive inhibitors Lhomoarginine (L-hArg), levamisole, theophylline and L-phenylalanine. We found that the identity of residue108 in TNAP largely determines the specificity of inhibition by LhArg. The conserved Tyr-371 is also necessary for binding of L-hArg. The selectivity of inhibition by L-Phe was determined by the identity of residues 108 and 109 in TNAP (or corresponding residues 107 and 108 in PLAP). In contrast, the binding of levamisole to TNAP is mostly dependent on His-434 and Tyr-371, but not on residues 108 or 109. Substitutions H434E (as in PLAP), H434Q (as in chicken TNAP), H434S (as in the intestinal isozyme), H434G (as in GCAP), or H434A, all lead to a significant decrease in inhibition. The reciprocal E429H mutation in PLAP improved the inhibition by levamisole by 10-fold. The main determinant of sensitivity to theophylline is His-434. The H434E substitution (as in PLAP) causes a 50-fold reduction in inhibition, making TNAP even less inhibited than wt PLAP. The reciprocal E429H mutation in PLAP improves the Ki for theophylline inhibition 30 times, close to the level of wt TNAP. Interestingly, theophylline inhibition in TNAP could be further improved by introducing an E108F mutation. Thus, we have clarified the location of the binding sites for all three TNAP inhibitors and we have also been able to exchange inhibitor specificities between TNAP and PLAP. These data will help us in drug design efforts aimed at discovering novel and better inhibitors of TNAP for clinical use.
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| 8. |
- Peetermans, Marijke, et al.
(författare)
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Plasminogen activation by staphylokinase enhances local spreading of S. aureus in skin infections.
- 2014
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Ingår i: BMC microbiology. - : Springer Science and Business Media LLC. - 1471-2180. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Background Staphylococcus aureus (S. aureus) is a frequent cause of skin and soft tissue infections. A unique feature of S. aureus is the combined presence of coagulases that trigger fibrin formation and of the plasminogen activator staphylokinase (SAK). Whereas the importance of fibrin generation for S. aureus virulence has been established, the role of SAK remains unclear.We studied the role of plasminogen activation by SAK in a skin infection model in mice and evaluated the impact of alpha-2-antiplasmin (¿2AP) deficiency on the spreading and proteolytic activity of S. aureus skin infections. The species-selectivity of SAK was overcome by adenoviral expression of human plasminogen. Bacterial spread and density was assessed non-invasively by imaging the bioluminescence of S. aureus Xen36.ResultsSAK-mediated plasmin activity increased the local invasiveness of S. aureus, leading to larger lesions with skin disruption as well as decreased bacterial clearance by the host. Even though fibrin and bacterial surfaces protected SAK-mediated plasmin activity from inhibition by ¿2AP, the deficiency of ¿2AP resulted in increased bacterial spreading. SAK-mediated plasmin also induced secondary activation of gelatinases, shown both in vitro and in lesions from the in vivo model.ConclusionSAK contributes to the phenotype of S. aureus skin infections by enhancing bacterial spreading as a result of fibrinolytic and proteolytic activation.
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| 9. |
- Wennberg, Charlotte, et al.
(författare)
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Structure, genomic DNA typing and kinetic characterization of the D allozyme of placental alkaline phosphatase
- 2002
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Ingår i: Human Mutation. - : Hindawi Limited. - 1059-7794 .- 1098-1004. ; 19:3, s. 258-267
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Tidskriftsartikel (refereegranskat)abstract
- The D allozyme of placental alkaline phosphatase (PLAP) displays enzymatic properties at variance with those of the common PLAP allozymes. We have deduced the amino acid sequence of the PLAP D allele by PCR cloning of its gene, ALPP. Two coding substitutions were found in comparison with the cDNA of the common PLAP F allele, i.e., 692C>G and 1352A>G, which translate into a P209R and E429G substitution. A single nucleotide primer extension (SNuPE) assay was developed using PCR primers that enable the amplification of a 1.9 kb PLAP fragment. Extension primers were then used on this PCR fragment to detect the 692C>G and 1352A>G substitution. The SNuPE assay on these two nucleotide substitutions enabled us to distinguish the PLAP F and D alleles from the PLAP S/I alleles. Functional studies on the D allozyme were made possible by constructing and expressing a PLAP D cDNA, i.e., [Arg209, Gly429]PLAP, into wild-type Chinese hamster ovary cells. We determined the kcat and Km, of the PLAP S, F, and D allozymes using the non-physiological substrate p-nitrophenylphosphate at an optimal pH (9.8) as well as two physiological substrates, i.e., pyridoxal-5-phosphate and inorganic pyrophosphate at physiological pH (7.5). We found that the biochemical properties of the D allozyme of PLAP are significantly different from those of the common PLAP allozymes. These biochemical findings suggest that a suboptimal enzymatic function by the PLAP D allozyme may be the basis for the apparent negative selective pressure of the PLAP D allele. The development of the SNuPE assay will enable us to test the hypothesis that the PLAP D allele is subjected to intrauterine selection by examining genomic DNA from statistically informative population samples.
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