| 1. |
- McArthur, Jason D, et al.
(författare)
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Allelic variants of streptokinase from Streptococcus pyogenes display functional differences in plasminogen activation.
- 2008
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Ingår i: The FASEB journal : official publication of the Federation of American Societies for Experimental Biology. - : Wiley. - 1530-6860. ; 22:9, s. 3146-3153
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Tidskriftsartikel (refereegranskat)abstract
- A common mammalian defense mechanism employed to prevent systemic dissemination of invasive bacteria involves occlusion of local microvasculature and encapsulation of bacteria within fibrin networks. Acquisition of plasmin activity at the bacterial cell surface circumvents this defense mechanism, allowing invasive disease initiation. To facilitate this process, S. pyogenes secretes streptokinase, a plasminogen-activating protein. Streptokinase polymorphism exhibited by S. pyogenes isolates is well characterized. However, the functional differences displayed by these variants and the biological significance of this variation has not been elucidated. Phylogenetic analysis of ska sequences from 28 S. pyogenes isolates revealed 2 main sequence clusters (clusters 1 and 2). All strains secreted streptokinase, as determined by Western blotting, and were capable of acquiring cell surface plasmin activity after incubation in human plasma. Whereas culture supernatants from strains containing cluster 1 ska alleles also displayed soluble plasminogen activation activity, supernatants from strains containing cluster 2 ska alleles did not. Furthermore, plasminogen activation activity in culture supernatants from strains containing cluster 2 ska alleles could only be detected when plasminogen was prebound with fibrinogen. This study indicates that variant streptokinase proteins secreted by S. pyogenes isolates display differing plasminogen activation characteristics and may therefore play distinct roles in disease pathogenesis.-McArthur, J. D., McKay, F. C., Ramachandran, V., Shyam, P., Cork, A. J., Sanderson-Smith, M. L., Cole, J. N., Ringdahl, U., Sjöbring, U., Ranson, M., Walker, M. J. Allelic variants of streptokinase from Streptococcus pyogenes display functional differences in plasminogen activation.
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| 4. |
- Shannon, Oonagh, et al.
(författare)
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Severe streptococcal infection is associated with M protein-induced platelet activation and thrombus formation.
- 2007
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Ingår i: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 65:5, s. 1147-1157
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Tidskriftsartikel (refereegranskat)abstract
- Disturbed haemostasis is a central finding in severe Streptococcus pyogenes infection. In particular, microthrombi are found both at the local site of infection and at distant sites. Platelets are responsible for maintaining vascular function and haemostasis. We report here that M1 protein of S. pyogenes triggers immune-mediated platelet activation and thrombus formation. M1 protein is released from the bacterial surface and forms complexes with plasma fibrinogen. These complexes bind to the fibrinogen receptor on resting platelets. When these complexes also contain immunoglobulin G (IgG) against M1 protein, this will engage the Fc receptor on the platelets and activation will occur. Activation of the platelets leads to platelet aggregation and the generation of platelet-rich thrombi. Neutrophils and monocytes are in turn activated by the platelets. Platelet thrombi are deposited in the microvasculature, and aggregated platelets, IgG and M1 protein colocalize in biopsies from patients diagnosed with S. pyogenes toxic shock syndrome. This chain of events results in a procoagulant and pro-inflammatory state typical of severe S. pyogenes infection.
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