| 1. |
- Sjöbring, Ulf, et al.
(author)
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Induction of platelet thrombi by bacteria and antibodies
- 2002
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 100:13, s. 4470-4477
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Journal article (peer-reviewed)abstract
- We have characterized 2 distinct mechanisms through which infectious agents may promote platelet adhesion and thrombus formation in flowing blood, thus contributing to the progression of disease. In one case, the process initiates when the integrin alpha(IIb)beta(3) mediates platelet arrest onto immobilized bacterial constituents that have bound plasma fibrinogen. If blood contains antibodies against the bacteria, immunoglobulin (Ig) G may cluster on the same surface and activate adherent platelets through the FcgammaRIIA receptor, leading to thrombus growth. As an alternative, bacteria that cannot bind fibrinogen may attach to substrates, such as immobilized plasma proteins or components of the extracellular matrix, which also support platelet adhesion. As a result of this colocalization, IgG bound to bacteria can activate neighboring platelets and induce thrombus growth regard-less of their ability to initiate platelet-surface contact. Our results demonstrate that intrinsic constituents of infectious agents and host proteins play distinct but complementary roles in recruiting platelets into thrombi, possibly contributing to complications of acute and chronic infections.
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| 2. |
- Ben Nasr, Abdelhakim, et al.
(author)
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Streptokinase activates plasminogen bound to human group C and group G streptococci through M-like proteins
- 1994
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In: European Journal of Biochemistry. - 0014-2956. ; 222:2, s. 76-267
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Journal article (peer-reviewed)abstract
- An ability to interact with plasminogen or plasmin could provide micro-organisms with a mechanism for invasion. Thus, group A, C and G streptococci secrete streptokinase which binds and activates plasminogen. Some streptococci also express surface structures which bind plasminogen without causing its activation. Plasminogen-binding surface proteins were extracted from one group C and one group G streptococcal isolate. Both proteins were found to bind plasmin, fibrinogen and serum albumin in addition to plasminogen. Gene fragments encoding the streptococcal proteins were amplified by PCR and were subsequently cloned and expressed in Escherichia coli. DNA sequence determination revealed for both genes open reading frames encoding proteins which contained repetitive domains and a carboxyl-terminal unrepeated region that were typical of M and M-like proteins. Though the amino-terminal regions of the group C and G streptococcal proteins demonstrated a rather high overall similarity between themselves, they were not similar to the variable regions of other M-like proteins with one exception: there was a 46% identity between the first 22 amino acids of the group G streptococcal protein and the corresponding sequence of PAM, the plasminogen-binding M-like protein of type M53 group A streptococci. Like the proteins extracted from the streptococci, the recombinant proteins bound plasminogen, fibrinogen and albumin. The three plasma proteins bound to separate sites on the streptococcal M-like proteins. Plasminogen bound by the group C and G streptococcal proteins was readily activated by streptokinase, providing evidence for a functional link between the secreted plasminogen-activator and proteins exposed on the bacterial surface.
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| 3. |
- Ringdahl, Ulrika, et al.
(author)
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Molecular co-operation between protein PAM and streptokinase for plasmin acquisition by Streptococcus pyogenes.
- 1998
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In: Journal of Biological Chemistry. - 1083-351X. ; 273:11, s. 6424-6430
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Journal article (peer-reviewed)abstract
- Bacterial surface-associated plasmin formation is believed to contribute to invasion, although the underlying molecular mechanisms are poorly understood. To define the components necessary for plasmin generation on group A streptococci we used strain AP53 which exposes an M-like protein ("PAM") that contains a plasminogen-binding sequence with two 13-amino acid residues long tandem repeats (a1 and a2). Utilizing an Escherichia coli-streptococcal shuttle vector, we replaced a 29-residue long sequence segment of Arp4, an M-like protein that does not bind plasminogen, with a single (a1) or the combined a1a2 repeats of PAM. When expressed in E. coli, the purified chimeric Arp/PAM proteins both bound plasminogen, as well as plasmin, and when used to transform group A streptococcal strains lacking the plasminogen-binding ability, transformants with the Arp/PAM constructs efficiently bound plasminogen. Moreover, when grown in the presence of plasminogen, both Arp/PAM- and PAM-expressing streptococci acquired surface-bound plasmin. In contrast, plasminogen activation failed to occur on PAM- and Arp/PAM-expressing streptococci carrying an inactivated streptokinase gene: this block was overcome by exogenous streptokinase. Together, these results provide evidence for an unusual co-operation between a surface-bound protein, PAM, and a secreted protein, streptokinase, resulting in bacterial acquisition of a host protease that is likely to spur parasite invasion of host tissues.
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| 4. |
- Ringdahl, Ulrika
(author)
-
Streptococcus pyogenes and its interactions with the human host
- 2002
-
Doctoral thesis (other academic/artistic)abstract
- We have found that a set of group A streptococcal strains, primarily associated with skin infections, express surface-associated M proteins that bind plasminogen and plasmin with high affinity. The binding is mediated by a common 13 amino acid internal repeated sequence located in the NH2-terminal surface-exposed portion of these M proteins. It could be demonstrated that plasminogen, absorbed by the bacteria when grown in plasma, could be activated by exogenous and endogenous streptokinase, a potent plasminogen activating protein that is secreted by group A streptococci, thereby providing the bacteria with a surface-associated enzyme that could act on fibrin films or other tissue barriers in the infected host. While only a subset of these bacteria bind plasminogen, almost all group A streptococcal strains bind fibrinogen. It is known that this property is coupled to members of the M protein family. We first identified the fibrinogen-binding region in the type M1 and M5 proteins and then generated an isogenic strain expressing an M5 protein lacking the fibrinogen-binding region. This strain had lost the ability to resist phagocytosis in human blood, a feature that is characteristic for group A streptococci. Furthermore, streptococcal mutants expressing versions of the fibrinogen non-binding M4 protein grafted with the fibrinogen-binding regions from M1 or M5 were generated. The manipulation converted these strains from phagocytosis sensitive to phagocytosis resistant, demonstrating the importance of the fibrinogen-binding capacity for bacterial survival. The ability to bind fibrinogen also gives the bacteria the ability to interact with platelets. Fibrinogen serves as a link between the bacteria and the platelet and the subsequent binding of antibodies directed against the bacteria to the FcgRIIa receptor can induce platelet activation and aggregation, a property that may contribute to acute complications in severe group A streptococcal infection.
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| 5. |
- Sun, HM, et al.
(author)
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Plasminogen is a critical host pathogenicity factor for group A streptococcal infection
- 2004
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In: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 305:5688, s. 1283-1286
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Journal article (peer-reviewed)abstract
- Group A streptococci, a common human pathogen, secrete streptokinase, which activates the host's blood clot-dissolving protein, plasminogen. Streptokinase is highly specific for human plasminogen, exhibiting little or no activity against other mammalian species, including mouse. Here, a transgene expressing human plasminogen markedly increased mortality in mice infected with streptococci, and this susceptibility was dependent on bacterial streptokinase expression. Thus, streptokinase is a key pathogenicity factor and the primary determinant of host species specificity for group A streptococcal infection. In addition, local fibrin clot formation may be implicated in host defense against microbial pathogens.
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| 6. |
- Wistedt, AC, et al.
(author)
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Identification of a plasminogen-binding motif in PAM, a bacterial surface protein.
- 1995
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In: Molecular Microbiology. - 1365-2958. ; 18:3, s. 569-578
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Journal article (peer-reviewed)abstract
- Surface-associated plasmin(ogen) may contribute to the invasive properties of various cells. Analysis of plasmin(ogen)-binding surface proteins is therefore of interest. The N-terminal variable regions of M-like (ML) proteins from five different group A streptococcal serotypes (33, 41, 52, 53 and 56) exhibiting the plasminogen-binding phenotype were cloned and expressed in Escherichia coli. The recombinant proteins all bound plasminogen with high affinity. The binding involved the kringle domains of plasminogen and was blocked by a lysine analogue, 6-aminohexanoic acid, indicating that lysine residues in the M-like proteins participate in the interaction. Sequence analysis revealed that the proteins contain common 13-16-amino-acid tandem repeats, each with a single central lysine residue. Experiments with fusion proteins and a 30-amino-acid synthetic peptide demonstrated that these repeats harbour the major plasminogen-binding site in the ML53 protein, as well as a binding site for the tissue-type plasminogen activator. Replacement of the lysine in the first repeat with alanine reduced the plasminogen-binding capacity of the ML53 protein by 80%. The results precisely localize the binding domain in a plasminogen surface receptor, thereby providing a unique ligand for the analysis of interactions between kringles and proteins with internal kringle-binding determinants.
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| 7. |
- Sjöbring, Ulf, et al.
(author)
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Analysis of plasminogen-binding M proteins of Streptococcus pyogenes.
- 2000
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In: Methods. - 1095-9130. ; 21:2, s. 143-150
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Journal article (peer-reviewed)abstract
- Group A streptococci are common human pathogens that cause a variety of infections. They express M proteins which are important cell wall-bound type-specific virulence factors. We have found that a set of strains, associated primarily with skin infections, express M proteins that bind plasminogen and plasmin with high affinity. The binding is mediated by a 13-amino-acid internal repeated sequence located in the N-terminal surface-exposed portion of these M proteins. This sequence binds to kringle 2 in plasminogen, a domain that is not involved in the interaction with streptokinase, a potent group A streptococcal activator of plasminogen. It could be demonstrated that plasminogen, absorbed from plasma by growing group A streptococci expressing the plasminogen-binding M proteins, could be activated by exogenous and endogenous streptokinase, thereby providing the bacteria with a surface-associated enzyme that could act on the tissue barriers in the infected host.
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| 8. |
- Wistedt, AC, et al.
(author)
-
Kringle 2 mediates high affinity binding of plasminogen to an internal sequence in streptococcal surface protein PAM.
- 1998
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In: Journal of Biological Chemistry. - 1083-351X. ; 273:38, s. 24420-24424
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Journal article (peer-reviewed)abstract
- Many cells express receptors for plasminogen (Pg), although the responsible molecules in most cases are poorly defined. In contrast, the group A streptococcal surface protein PAM contains a domain with two 13-amino acid residue long repeated sequences (a1 and a2) responsible for Pg binding. Here we identify the region in Pg that interacts with PAM. A radiolabeled proteolytic plasminogen fragment containing the first three kringles (K1-K3) interacted with streptococci expressing PAM or a chimeric surface protein harboring the a1a2 sequence. In contrast, plasminogen fragments containing kringle 4 or kringle 5 and the activable serine proteinase domain failed to bind to PAM-expressing group A streptococci. A synthetic and a recombinant polypeptide containing the a1a2 sequence both bound to immobilized recombinant K2 (rK2) but not to rK1 or rK3. The interaction between the a repeat region and rK2 was reversible, and rK2 completely blocked the binding of Pg to the a1a2 region. The binding of the a repeat containing polypeptide to K2 occurred with an equilibrium association constant of 4.5 x 10(7) M-1, as determined by surface plasmon resonance, a value close to that (1.6 x 10(7) M-1) calculated for the a1a2-Pg interaction. Inhibition experiments suggested involvement of the lysine-binding site of K2 in the interaction. These data demonstrate that K2 contains the major Pg-binding site for PAM, providing the first well defined example of an interaction between an internal Pg-binding region in a protein and a single kringle domain.
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| 9. |
- Gerdtsson, Anna Sandström, et al.
(author)
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Plasma protein profiling in a stage defined pancreatic cancer cohort – Implications for early diagnosis
- 2016
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In: Molecular Oncology. - : Wiley. - 1574-7891. ; 10:8, s. 1305-1316
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Journal article (peer-reviewed)abstract
- Pancreatic ductal adenocarcinoma (PDAC) is a disease where detection preceding clinical symptoms significantly increases the life expectancy of patients. In this study, a recombinant antibody microarray platform was used to analyze 213 Chinese plasma samples from PDAC patients and normal control (NC) individuals. The cohort was stratified according to disease stage, i.e. resectable disease (stage I/II), locally advanced (stage III) and metastatic disease (stage IV). Support vector machine analysis showed that all PDAC stages could be discriminated from controls and that the accuracy increased with disease progression, from stage I to IV. Patients with stage I/II PDAC could be discriminated from NC with high accuracy based on a plasma protein signature, indicating a possibility for early diagnosis and increased detection rate of surgically resectable tumors.
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| 10. |
- Ghatnekar, Ola, et al.
(author)
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Modelling the benefits of early diagnosis of pancreatic cancer using a biomarker signature.
- 2013
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In: International Journal of Cancer. - : Wiley. - 0020-7136. ; 133:10, s. 2392-2397
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Journal article (peer-reviewed)abstract
- Pancreatic cancer (PC) has a poor prognosis, with a 5-year survival of 3-4%. This is mainly due to late diagnosis because of diffuse symptoms, where 80-85% of the patients are inoperable. Consequently, early diagnosis would be of significant benefit, resulting in a potential 5-year survival of 30-40%. However, new technologies must be carefully evaluated concerning effectiveness and healthcare costs. We have developed a framework for modelling cost and health effects from early detection of PC, which for the first time allowed us to analyse its cost-effectiveness. A probabilistic cohort model for estimating costs and quality adjusted life-years (QALY) arising from screening for PC, compared to a "wait-and-see"-approach, was designed. The test accuracy, Swedish survival and costs by tumour stage, expected life gain from early detection and pre-test probabilities in risk-groups, were retrieved from previous investigations. In a cohort of newly diagnosed diabetic patient (incidence 0.71%) the incremental cost per QALY gained (ICER) was €13,500, which is considered cost-effective in Europe. Results were mainly sensitive to the incidence with the ICER ranging from €315 to €204,000 (familial PC 35% and general population 0.046%, respectively). This is the first study focusing on clinical implementation of advanced testing and what is required for novel technologies in cancer care to be cost-effective. The model clearly demonstrated the potential of multiplexed proteomic-testing of PC and also identified the requirements for test accuracy. Consequently, it can serve as a model for assessing the possibilities to introduce advanced test platforms also for other cancer indications. © 2013 Wiley Periodicals, Inc.
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