| 1. |
- Holmström, Anna, et al.
(author)
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LcrV is a channel size-determining component of the Yop effector translocon of Yersinia
- 2001
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In: Molecular Microbiology. - : Blackwell Publishing. - 0950-382X .- 1365-2958. ; 39:3, s. 620-632
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Journal article (peer-reviewed)abstract
- Delivery of Yop effector proteins by pathogenic Yersinia across the eukaryotic cell membrane requires LcrV, YopB and YopD. These proteins were also required for channel formation in infected erythrocytes and, using different osmolytes, the contact‐dependent haemolysis assay was used to study channel size. Channels associated with LcrV were around 3 nm, whereas the homologous PcrV protein of Pseudomonas aeruginosa induced channels of around 2 nm in diameter. In lipid bilayer membranes, purified LcrV and PcrV induced a stepwise conductance increase of 3 nS and 1 nS, respectively, in 1 M KCl. The regions important for channel size were localized to amino acids 127–195 of LcrV and to amino acids 106–173 of PcrV. The size of the channel correlated with the ability to translocate Yop effectors into host cells. We suggest that LcrV is a size‐determining structural component of the Yop translocon.
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| 2. |
- Persson, Cathrine, et al.
(author)
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Cell-surface-bound Yersinia translocate the protein tyrosine phosphatase YopH by a polarized mechanism into the target cell
- 1995
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In: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 18:1, s. 135-150
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Journal article (peer-reviewed)abstract
- YopH is translocated by cell-surface-bound bacteria through the plasma membrane to the cytosol of the HeLa cell. The transfer mechanism is contact dependent and polarizes the translocation to only occur at the contact zone between the bacterium and the target cell. More than 99% of the PTPase activity is associated with the HeLa cells. In contrast to the wild-type strain, the yopBD mutant cannot deliver YopH to the cytosol. Instead YopH is deposited in localized areas in the proximity of cell-associated bacteria. A yopN mutant secretes 40% of the total amount of YopH to the culture medium, suggesting a critical role of YopN in regulation of the polarized translocation. Evidence for a region in YopH important for its translocation through the plasma membrane of the target cell but not for secretion from the pathogen is provided.
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| 3. |
- Bamyaci, Sarp, et al.
(author)
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Identification of specific sequence motif of YopN of Yersinia pseudotuberculosis required for systemic infection
- 2019
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In: Virulence. - : Taylor & Francis. - 2150-5594 .- 2150-5608. ; 10:1, s. 10-25
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Journal article (peer-reviewed)abstract
- Type III secretion systems (T3SSs) are tightly regulated key virulence mechanisms shared by many Gram-negative pathogens. YopN, one of the substrates, is also crucial in regulation of expression, secretion and activation of the T3SS of pathogenic Yersinia species. Interestingly, YopN itself is also targeted into host cells but so far no activity or direct role for YopN inside host cells has been described. Recently, we were able show that the central region of YopN is required for efficient translocation of YopH and YopE into host cells. This was also shown to impact the ability of Yersinia to block phagocytosis. One difficulty in studying YopN is to generate mutants that are not impaired in regulation of the T3SS. In this study we extended our previous work and were able to generate specific mutants within the central region of YopN. These mutants were predicted to be crucial for formation of a putative coiled-coil domain (CCD). Similar to the previously described deletion mutant of the central region, these mutants were all impaired in translocation of YopE and YopH. Interestingly, these YopN variants were not translocated into host cells. Importantly, when these mutants were introduced in cis on the virulence plasmid, they retained full regulatory function of T3SS expression and secretion. This allowed us to evaluate one of the mutants, yopNGAGA, in the systemic mouse infection model. Using in vivo imaging technology we could verify that the mutant was also attenuated in vivo and highly impaired to establish systemic infection.
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| 4. |
- Bamyaci, Sarp, et al.
(author)
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YopN Is Required for Efficient Effector Translocation and Virulence in Yersinia pseudotuberculosis
- 2018
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In: Infection and Immunity. - : AMER SOC MICROBIOLOGY. - 0019-9567 .- 1098-5522. ; 86:8
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Journal article (peer-reviewed)abstract
- Type III secretion systems (T3SSs) are used by various Gram-negative pathogens to subvert the host defense by a host cell contact-dependent mechanism to secrete and translocate virulence effectors. While the effectors differ between pathogens and determine the pathogenic life style, the overall mechanism of secretion and translocation is conserved. T3SSs are regulated at multiple levels, and some secreted substrates have also been shown to function in regulation. In Yersinia, one of the substrates, YopN, has long been known to function in the host cell contact-dependent regulation of the T3SS. Prior to contact, through its interaction with TyeA, YopN blocks secretion. Upon cell contact, TyeA dissociates from YopN, which is secreted by the T3SS, resulting in the induction of the system. YopN has also been shown to be translocated into target cells by a T3SS-dependent mechanism. However, no intracellular function has yet been assigned to YopN. The regulatory role of YopN involves the N-terminal and C-terminal parts, while less is known about the role of the central region of YopN. Here, we constructed different in-frame deletion mutants within the central region. The deletion of amino acids 76 to 181 resulted in an unaltered regulation of Yop expression and secretion but triggered reduced YopE and YopH translocation within the first 30 min after infection. As a consequence, this deletion mutant lost its ability to block phagocytosis by macrophages. In conclusion, we were able to differentiate the function of YopN in translocation and virulence from its function in regulation.
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| 5. |
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| 6. |
- 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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| 7. |
- Fahlgren, Anna, et al.
(author)
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Colonization of cecum is important for development of persistent infection by Yersinia pseudotuberculosis
- 2014
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In: Infection and Immunity. - : American Society for Microbiology. - 0019-9567 .- 1098-5522. ; 82:8, s. 3471-3482
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Journal article (peer-reviewed)abstract
- Yersiniosis is a human disease caused by the bacterium Yersinia pseudotuberculosis or Yersinia enterocolitica. The infection is usually resolved but can lead to postinfectious sequelae, including reactive arthritis and erythema nodosum. The commonly used Yersinia mouse infection model mimics acute infection in humans to some extent but leads to systemic infection and eventual death. Here, we analyzed sublethal infection doses of Y. pseudotuberculosis in mice in real time using bioluminescent imaging and found that infections using these lower doses result in extended periods of asymptomatic infections in a fraction of mice. In a search for the site for bacterial persistence, we found that the cecum was the primary colonization site and was the site where the organism resided during a 115-day infection period. Persistent infection was accompanied by sustained fecal shedding of cultivable bacteria. Cecal patches were identified as the primary site for cecal colonization during persistence. Y. pseudotuberculosis bacteria were present in inflammatory lesions, in localized foci, or as single cells and also in neutrophil exudates in the cecal lumen. The chronically colonized cecum may serve as a reservoir for dissemination of infection to extraintestinal sites, and a chronic inflammatory state may trigger the onset of postinfectious sequelae. This novel mouse model for bacterial persistence in cecum has potential as an investigative tool to unveil a deeper understanding of bacterial adaptation and host immune defense mechanisms during persistent infection.
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| 8. |
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| 9. |
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| 10. |
- Kauppi, Anna, 1971-, et al.
(author)
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Targeting bacterial Virulence : Inhibitors of type III secretion in Yersinia
- 2003
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In: Chemistry and Biology. - 1074-5521 .- 1879-1301. ; 10:3, s. 241-249
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Journal article (peer-reviewed)abstract
- Agents that target bacterial virulence without detrimental effect on bacterial growth are useful chemical probes for studies of virulence and potential candidates for drug development. Several gram-negative pathogens employ type III secretion to evade the innate immune response of the host. Screening of a chemical library with a luciferase reporter gene assay in viable Yersinia pseudotuberculosis furnished several compounds that inhibit the reporter gene signal expressed from the yopE promoter and effector protein secretion at concentrations with no or modest effect on bacterial growth. The selectivity patterns observed for inhibition of various reporter gene strains indicate that the compounds target the type III secretion machinery at different levels. Identification of this set of inhibitors illustrates the approach of utilizing cell-based assays to identify compounds that affect complex bacterial virulence systems.
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