| 1. |
- Bengtson, Sara, et al.
(författare)
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Activation of TAFI on the Surface of Streptococcus pyogenes Evokes Inflammatory Reactions by Modulating the Kallikrein/Kinin System
- 2009
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Ingår i: Journal of Innate Immunity. - : S. Karger AG. - 1662-811X .- 1662-8128. ; 1:1, s. 18-28
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Tidskriftsartikel (refereegranskat)abstract
- Bacteria-controlled regulation of host responses to infection is an important virulence mechanism that has been demonstrated to contribute to disease progression. Here we report that the human pathogen Streptococcus pyogenes employs the procarboxypeptidase TAR (thrombin-activatablefibrinolysis inhibitor) to modulate the kallikrein/kinin system. To this end, bacteria initiate a chain of events starting with the recruitment and activation of TAFI. This is followed by the assembly and induction of the contact system at the streptococcal surface, eventually triggering the release of bradykinin (BK). BK is then carboxyterminally truncated by activated TAFI, which converts the peptide from a kinin B-2 receptor ligand to a kinin B-1 receptor (B1R) agonist. Finally, we show that streptococcal supernatants indirectly amplify the B1R response as they act on peripheral blood mononuclear cells to secrete inflammatory cytokines that in turn stimulate upregulation of the B1R on human fibroblasts. Taken together our findings implicate a critical and novel role for streptococci-bound TAR, as it processes BK to a B1R agonist at the bacterial surface and thereby may redirect inflammation from a transient to a chronic state. Copyright (C) 2008 S. Karger AG, Basel
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| 2. |
- Sandén, Caroline
(författare)
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G protein-coupled receptor regulation: The role of protein interactions and receptor trafficking
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The superfamily of G protein-coupled receptors (GPCR) is the largest gene family in the human genome. GPCR-mediated signaling operates in every human cell, and about 50% of existing clinically useful drugs act through GPCR. Kinins are proinflammatory peptides that are rapidly produced extracellularly following pathological insults and tissue damage. These peptides act through two GPCR subtypes, B1 (B1R) and B2 (B2R), to elicit numerous inflammatory responses including vasodilatiation, increased vascular permeability, and pain. GPER1 (G protein-coupled estrogen receptor 1) has recently been suggested as a novel estrogen receptor. Much controversy surrounds this receptor regarding its subcellular localization and activation. The aim of the present thesis was to explore the role of receptor trafficking and protein-interactions in kinin receptor regulation, as well as studying the receptor trafficking and signaling of GPER1. B1R forms homo-oligomers, which is required for proper B1R maturation and cell-surface expression. Furthermore, the endopeptidase EP24.15 is able to degrade BK intracellularly and attenuate maximal B2R responsiveness without influencing the potency of BK. Finally, GPER1 is localized both intracellularly and on the cell surface, where it is subject to rapid, constitutive endocytosis. Estrogen was found to elevate the level of cAMP in mouse myotube C2C12 cells, in a GPER1-dependent manner, but it is still not clear whether estrogen is the true agonist for GPER1. Taken together, the present thesis demonstrates the importance of protein-protein interactions and trafficking for B1R, B2R, and GPER1 regulation and activity. Understanding these mechanisms will be of great benefit in drug development by presenting novel drug targets.
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| 3. |
- Sandén, Caroline, et al.
(författare)
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Kinin B2 Receptor-Mediated Bradykinin Internalization and Metalloendopeptidase EP24.15-Dependent Intracellular Bradykinin Degradation.
- 2008
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Ingår i: Journal of Pharmacology and Experimental Therapeutics. - : American Society for Pharmacology & Experimental Therapeutics (ASPET). - 1521-0103 .- 0022-3565. ; 326:1, s. 24-32
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Tidskriftsartikel (refereegranskat)abstract
- Kinins are potent proinflammatory peptides that are produced extracellularly and rapidly degraded by extracellular peptidases and by intracellular peptidases accessed by kinins via receptor-mediated endocytosis. Here, we developed model cell systems expressing the kinin B2 receptor (B2R) and the metalloendopeptidase thimet oligopeptidase (EC 3.4.24.15; EP24.15) either individually or together to address 1) the cellular and functional relationship between these proteins and 2) the participation of EP24.15 in the metabolism of bradykinin (BK) following BK internalization via B2R. B2R was localized almost exclusively in the plasma membrane, whereas EP24.15 was localized both intracellularly and on the cell surface, and secreted in the media. Intracellular EP24.15 was present throughout the cell, both cytosolic and particulate, with less nuclear localization and no co-localization with either the endoplasmatic reticulum marker calnexin or Golgi marker GM130. No direct co-localization of B2R and EP24.15 was observed using immunofluorescence microscopy. However, the two proteins co-immunoprecipitated specifically, and EP24.15 attenuated maximal B2R responsiveness without influencing the potency of BK to stimulate phosphoinositide hydrolysis and intracellular Ca(2+) mobilization. Cell surface-bound BK remained intact in cells overexpressing EP24.15 but was degraded intracellularly in an EP24.15-dependent manner upon B2R-mediated endocytosis. These results show that EP24.15 acts to negatively regulate B2R responsiveness and by serving as an intracellular peptidase in the degradation of BK specifically internalized via this receptor.
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