| 1. |
- Frost, Stefan, et al.
(author)
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Autoproteolysis and Intramolecular Dissociation of Yersinia YscU Precedes Secretion of Its C-Terminal Polypeptide YscU CC
- 2012
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:11
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Journal article (peer-reviewed)abstract
- Type III secretion system mediated secretion and translocation of Yop-effector proteins across the eukaryotic target cell membrane by pathogenic Yersinia is highly organized and is dependent on a switching event from secretion of early structural substrates to late effector substrates (Yops). Substrate switching can be mimicked in vitro by modulating the calcium levels in the growth medium. YscU that is essential for regulation of this switch undergoes autoproteolysis at a conserved N↑PTH motif, resulting in a 10 kDa C-terminal polypeptide fragment denoted YscUCC. Here we show that depletion of calcium induces intramolecular dissociation of YscUCC from YscU followed by secretion of the YscUCC polypeptide. Thus, YscUCC behaved in vivo as a Yop protein with respect to secretion properties. Further, destabilized yscU mutants displayed increased rates of dissociation of YscUCC in vitro resulting in enhanced Yop secretion in vivo at 30°C relative to the wild-type strain.These findings provide strong support to the relevance of YscUCC dissociation for Yop secretion. We propose that YscUCC orchestrates a block in the secretion channel that is eliminated by calcium depletion. Further, the striking homology between different members of the YscU/FlhB family suggests that this protein family possess regulatory functions also in other bacteria using comparable mechanisms.
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| 2. |
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| 3. |
- Lundgren, E, et al.
(author)
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Invasin of Yersinia pseudotuberculosis activates human peripheral B cells.
- 1996
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In: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 64:3, s. 829-35
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Journal article (peer-reviewed)abstract
- The Yersinia pseudotuberculosis cell surface-located protein invasin was found to promote binding between the pathogen and resting peripheral B cells via beta 1 integrin receptors (CD29). B cells responded by expressing several activation markers and by growing, In contrast, T cells did not react, although these cells express CD29. An isogenic invA mutant failed to activate B cells. The mutation could be complemented by providing the invA+ gene in trans. Purified invasin alone did not activate B cells, although it was able to block the binding of bacteria to the cells.
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| 4. |
- Weise, Christoph F, et al.
(author)
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Negatively charged lipid membranes promote a disorder-order transition in the Yersinia YscU protein
- 2014
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In: Biophysical Journal. - : Cell Press. - 0006-3495 .- 1542-0086. ; 107:8, s. 1950-1961
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Journal article (peer-reviewed)abstract
- The inner membrane of Gram-negative bacteria is negatively charged, rendering positively charged cytoplasmic proteins in close proximity likely candidates for protein-membrane interactions. YscU is a Yersinia pseudotuberculosis type III secretion system protein crucial for bacterial pathogenesis. The protein contains a highly conserved positively charged linker sequence that separates membrane-spanning and cytoplasmic (YscUC) domains. Although disordered in solution, inspection of the primary sequence of the linker reveals that positively charged residues are separated with a typical helical periodicity. Here, we demonstrate that the linker sequence of YscU undergoes a largely electrostatically driven coil-to-helix transition upon binding to negatively charged membrane interfaces. Using membrane-mimicking sodium dodecyl sulfate micelles, an NMR derived structural model reveals the induction of three helical segments in the linker. The overall linker placement in sodium dodecyl sulfate micelles was identified by NMR experiments including paramagnetic relaxation enhancements. Partitioning of individual residues agrees with their hydrophobicity and supports an interfacial positioning of the helices. Replacement of positively charged linker residues with alanine resulted in YscUC variants displaying attenuated membrane-binding affinities, suggesting that the membrane interaction depends on positive charges within the linker. In vivo experiments with bacteria expressing these YscU replacements resulted in phenotypes displaying significantly reduced effector protein secretion levels. Taken together, our data identify a previously unknown membrane-interacting surface of YscUC that, when perturbed by mutations, disrupts the function of the pathogenic machinery in Yersinia.
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| 5. |
- Arencibia, I, et al.
(author)
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Yersinia invasin, a bacterial beta1-integrin ligand, is a potent inducer of lymphocyte motility and migration to collagen type IV and fibronectin.
- 1997
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In: Journal of Immunology. - 0022-1767 .- 1550-6606. ; 159:4, s. 1853-9
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Journal article (peer-reviewed)abstract
- The Yersinia pseudotuberculosis invasin protein was found to be a potent inducer of pseudopodia formation and chemotactic and haptotactic migration in human T lymphocytes. Checkerboard analysis confirmed that migration was directional. The Yersinia invasin triggered migration of otherwise poorly migratory normal T cells on fibronectin and in particular on collagen type IV, and augmented the migration of leukemic T cell lines on these components. Invasin-induced lymphocyte migration was inhibited by staurosporin that selectively prevented pseudopodia formation but, noteworthy, augmented adhesion. The motogenic and attractant properties of invasin (Inv) were mediated via beta1-integrins, as shown by lack of effect of Inv on the motility of a beta1-integrin-negative lymphoid cell line and inhibition of invasin-induced lymphocyte motility by anti-beta1 Abs. Inv was markedly more effective than the extracellular matrix components fibronectin, collagen type IV, and laminin, which also interact with lymphocyte beta1-integrins, with respect to induction of pseudopodia, chemotaxis, and haptotaxis. Thus, Yersinia invasin is a model ligand for induction of lymphocyte motility via beta1-integrins. The extraordinary capacity of Inv to trigger and guide T lymphocyte motility and potentiate lymphocyte migration to extracellular matrix components may be of pathogenetic significance for the movement of lymphocytes to extraintestinal sites secondary to Yersinia infection.
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| 6. |
- Andersson, K, et al.
(author)
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YopH of Yersinia pseudotuberculosis interrupts early phosphotyrosine signalling associated with phagocytosis.
- 1996
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In: Molecular Microbiology. - 0950-382X .- 1365-2958. ; 20:5, s. 1057-69
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Journal article (peer-reviewed)abstract
- The PTPase YopH of Yersinia is essential to the ability of these bacteria to block phagocytosis. Wild-type Yersinia pseudotuberculosis, but not the yopH mutant strain, resisted phagocytosis by J774 cells. Ingestion of a yopH mutant was dependent on tyrosine kinase activity. Transcomplementation with wild-type yopH restored the anti-phagocytic effect, whereas introduction of the gene encoding the catalytically inactive yopHC403A was without effect. The PTPase inhibitor orthovanadate impaired the anti-phagocytic effect of the wild-type strain, further demonstrating the importance of bacteria-derived PTPase activity for this event. The ability to resist phagocytosis indicates that the effect of the bacterium is immediately exerted when it becomes associated with the phagocyte. Within 30 s after the onset of infection, wild-type Y. pseudotuberculosis caused a YopH-dependent dephosphorylation of phosphotyrosine proteins in J774 cells. Furthermore, interaction of the cells with phagocytosable strains led to a rapid and transient increase in tyrosine phosphorylation of paxillin and some other proteins, an event dependent on the presence of the bacterial surface-located protein invasin. Co-infection with the phagocytosable strain and the wild-type strain abolished the induction of tyrosine phosphorylation. Taken together, the present findings demonstrate an immediate YopH-mediated dephosphorylation of macrophage phosphotyrosine proteins, suggesting that this PTPase acts by preventing early phagocytosis-linked signalling in the phagocyte.
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| 7. |
- Beery, T. H., et al.
(author)
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Nature to place : Rethinking the environmental connectedness perspective
- 2014
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In: Journal of Environmental Psychology. - Amsterdam : Elsevier BV. - 0272-4944 .- 1522-9610. ; 40, s. 198-205
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Journal article (peer-reviewed)abstract
- The environmental connectedness perspective posits that direct encounter with generalized, or non-specific "nature," leads to environmental connectedness and subsequent pro-environmental behavior. This article examines this perspective and proposes a place-based application of the nature encounter-environmental behavior relation. An empirical study using data from a national survey on outdoor recreation and nature-based tourism is presented. Results show a minimal relationship between measures of environmental connectedness and self-reports of environmental behavior. The following examination of the environmental connectedness perspective reveals that environmental connectedness is rooted in a material/objective perspective, neglecting the human domain of perceptions, values, and representations. The environment as "nature" is portrayed as a geographically undefined agent with the inherent power to change human attitudes and behavior. Based on this, the article concludes with a proposed replacement of the elusive concept of nature for the relational concept of place. © 2014 Elsevier Ltd.
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| 8. |
- Björnfot, Ann-Catrin, 1981-, et al.
(author)
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Involvement of the heat shock proteins DnaK/DnaJ in Yersinia T3S
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Other publication (other academic/artistic)abstract
- Yersinia pseudotuberculosis uses a type III secretion system (T3SS) to secrete and deliver effectors called Yops into target cells. These processes are highly regulated and the pathogen senses cell contact and respond accordingly by inducing Yop-effector expression. A key component of the T3SS is the YscF needle present on the surface of the pathogen. It has been suggested that the bacterium can switch from needle export to Yop expression and secretion and that this substrate switch is important for proper regulation during infection. YscU is an essential protein regulating the substrate switch and autoproteolysis of YscU is essential for accurate T3SS regulation. To study regulation of Yop translocation in more detail, we generated mutants defective for expression of the heat shock proteins (HSPs) DnaJ and DnaK, since earlier studies had indicated a role of these proteins in regulation of effector translocation in Salmonella. The dnaJ mutant and the double dnaK/J mutant showed significant defects in Yop translocation, but surprisingly both mutants were able to secrete Yops in vitro much like the wild type. However, both mutants showed a changed export pattern of the YscF needle with a pronounced increased export of the YscF needle protein after incubation in calcium containing media. This phenotype was linked to defects in YscU autoproteolysis and in this respect the hsp-mutants were identical to earlier identified autoprocessing defective mutants in YscU (Single amino acid exchange mutants N263A and P264A). The hsp-mutants and the processing mutants accumulated full-length YscU, which surprisingly was associated with the outer membrane, while the processed form of YscU was found in the inner membrane fraction. The dnaJ and dnaK/J mutants were strongly affected in YscU autoproteolysis, which indicates a possible direct role for DnaJ in this process. Indeed a specific interaction between YscU and DnaJ could be found suggesting a direct role of the HSPs in regulation of the substrate switch in the T3SS.
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| 9. |
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| 10. |
- Engström, Patrik, et al.
(author)
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A 2-Pyridone-Amide Inhibitor Targets the Glucose Metabolism Pathway of Chlamydia trachomatis
- 2015
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In: mBio. - 2161-2129 .- 2150-7511. ; 6:1
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Journal article (peer-reviewed)abstract
- In a screen for compounds that inhibit infectivity of the obligate intracellular pathogen Chlamydia trachomatis, we identified the 2-pyridone amide KSK120. A fluorescent KSK120 analogue was synthesized and observed to be associated with the C. trachomatis surface, suggesting that its target is bacterial. We isolated KSK120-resistant strains and determined that several resistance mutations are in genes that affect the uptake and use of glucose-6-phosphate (G-6P). Consistent with an effect on G-6P metabolism, treatment with KSK120 blocked glycogen accumulation. Interestingly, KSK120 did not affect Escherichia coli or the host cell. Thus, 2-pyridone amides may represent a class of drugs that can specifically inhibit C. trachomatis infection. IMPORTANCE Chlamydia trachomatis is a bacterial pathogen of humans that causes a common sexually transmitted disease as well as eye infections. It grows only inside cells of its host organism, within a parasitophorous vacuole termed the inclusion. Little is known, however, about what bacterial components and processes are important for C. trachomatis cellular infectivity. Here, by using a visual screen for compounds that affect bacterial distribution within the chlamydial inclusion, we identified the inhibitor KSK120. As hypothesized, the altered bacterial distribution induced by KSK120 correlated with a block in C. trachomatis infectivity. Our data suggest that the compound targets the glucose-6-phosphate (G-6P) metabolism pathway of C. trachomatis, supporting previous indications that G-6P metabolism is critical for C. trachomatis infectivity. Thus, KSK120 may be a useful tool to study chlamydial glucose metabolism and has the potential to be used in the treatment of C. trachomatis infections.
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