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Forsberg A, Almkvist O, Engler H, Wall A, Langstrom B, Nordberg A. High PIB Retention in Alzheimers Disease is an Early Event with Complex Relationship with CSF Biomarkers and Functional Parameters. Curr Alzheimer Res 2010; 7:56-66. [DOI: 10.2174/156720510790274446] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Accepted: 08/11/2009] [Indexed: 11/22/2022]
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Johansson A, Savitcheva I, Forsberg A, Engler H, Långström B, Nordberg A, Askmark H. [11C]-PIB imaging in patients with Parkinson's disease: Preliminary results. Parkinsonism Relat Disord 2008; 14:345-7. [PMID: 17855149 DOI: 10.1016/j.parkreldis.2007.07.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Revised: 06/18/2007] [Accepted: 07/09/2007] [Indexed: 11/28/2022]
Abstract
[(11)C]-PIB positron emission tomography ([(11)C]-PIB PET) is a sensitive marker of amyloid in Alzheimer's disease (AD), but its specificity has not been fully evaluated. Vascular amyloid-beta deposition is common in Parkinson's disease (PD) and alpha-synuclein, the major component of the Lewy bodies in PD, forms amyloid fibrils. We investigated five apparently cognitively normal PD patients with [(11)C]-PIB PET. The results were compared to 16 patients with AD and six healthy controls from a previous study. [(11)C]-PIB retention was not significantly increased in our patients who all had early stage PD. Further studies of more advanced PD patients are warranted.
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Fridh I, Forsberg A, Bergbom I. Family presence and environmental factors at the time of a patient's death in an ICU. Acta Anaesthesiol Scand 2007; 51:395-401. [PMID: 17378776 DOI: 10.1111/j.1399-6576.2006.01250.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND In an intensive care unit (ICU), privacy and proximity are reported to be important needs of dying patients and their family members. It is assumed that good communication between the ICU team and families about end-of-life decisions improves the possibilities of meeting families' needs, thus guaranteeing a dignified and peaceful death in accordance with end-of-life care guidelines. The aim of this study was to explore the circumstances under which patients die in Swedish ICUs by reporting on the presence of family and whether patients die in private or shared rooms. An additional aim was to investigate the frequency of end-of-life decisions and whether nurses and family members were informed about such decisions. METHODS A questionnaire based on the research questions was completed when a patient died in the 10 ICUs included in the study. Data were collected on 192 deaths. RESULTS Forty per cent of the patients died without a next of kin at the bedside and 46% of deaths occurred in a shared room. This number decreased to 37% if a family member was present. Patients without a family member at their bedside received less analgesics and sedatives. There was a significant relationship between family presence, expected death and end-of-life decisions. CONCLUSIONS The results indicate the necessity of improving the ICU environment to promote the need for proximity and privacy for dying patients and their families. The study also highlights the risk of underestimating the needs of patients without a next of kin at their bedside at the time of death.
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Forsberg A, Wolf-Watz H. The virulence protein Yop5 ofYersinia pseudotuberculosisis regulated at transcriptional level by plasmid-plB1 -encodedtrans-acting elements controlled by temperature and calcium. Mol Microbiol 2006; 2:121-133. [DOI: 10.1111/j.1365-2958.1988.tb00013.x] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Stefanova E, Wall A, Almkvist O, Nilsson A, Forsberg A, Långström B, Nordberg A. Longitudinal PET evaluation of cerebral glucose metabolism in rivastigmine treated patients with mild Alzheimer’s disease. J Neural Transm (Vienna) 2005; 113:205-18. [PMID: 16049637 DOI: 10.1007/s00702-005-0312-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Accepted: 03/25/2005] [Indexed: 10/25/2022]
Abstract
In this study 11 patients with mild Alzheimer's disease (AD) were treated with the cholinesterase inhibitor rivastigmine (mean dose 8.6 +/- 1.3'mg) for 12 months and underwent positron emission tomography (PET) studies of cerebral glucose metabolism (CMRglc) and neuropsychological testing at baseline and after 12 months. An untreated group of 10 AD patients served as control group. While the untreated AD patients showed a significant decline of CMRglc in the temporo-parietal and frontal cortical regions after 12 months follow-up the rivastigmine-treated patients showed no decline in CMRglc in corresponding cortical brain regions. Furthermore, a significant dose-related increase in CMRglc was recorded in the right frontal association region after 12 months rivastigmine treatment. A positive correlation was observed between changes in CMRglc and several cognitive tests in patients receiving higher doses (10.5-12'mg) of rivastigmine. These results suggest a stabilization effect of rivastigmine on CMRglc in mild AD patients receiving long-term rivastigmine treatment.
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Kuoppa K, Forsberg A, Norqvist A. Construction of a reporter plasmid for screening in vivo promoter activity in Francisella tularensis. FEMS Microbiol Lett 2001; 205:77-81. [PMID: 11728719 DOI: 10.1111/j.1574-6968.2001.tb10928.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Francisella tularensis is a facultative intracellular bacterium that survives and multiplies inside macrophages. Here we constructed a new promoter probe plasmid denoted pKK214 by introduction of a promoter-less chloramphenicol acetyltransferase (cat) gene into the shuttle vector pKK202. A promoter library was created in F. tularensis strain LVS by cloning random chromosomal DNA fragments into pKK214. Approximately 15% of the recombinant bacteria showed chloramphenicol resistance in vitro. The promoter library was also used to infect macrophages in the presence of chloramphenicol and after two cycles of infection the library contained essentially only chloramphenicol resistance clones which shows that pKK214 can be used to monitor F. tularensis genes that are expressed during infection.
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Hinnebusch J, Cherepanov P, Du Y, Rudolph A, Dixon JD, Schwan T, Forsberg A. Murine toxin of Yersinia pestis shows phospholipase D activity but is not required for virulence in mice. Int J Med Microbiol 2000; 290:483-7. [PMID: 11111930 DOI: 10.1016/s1438-4221(00)80070-3] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022] Open
Abstract
Purified murine toxin (Ymt) of Yersinia pestis is highly toxic for mice and rats but less active in other animals such as guinea pigs, rabbits, dogs and monkeys. This suggested that Ymt contributes to the very low infectious dose of Y. pestis in mice. The gene encoding Ymt (ymt) is localised on the 100-kb plasmid pFra, which is unique for Y. pestis. Sequence analysis revealed that Ymt showed homology to proteins of the phospholipase D (PLD) superfamily of proteins. Y. pestis strains expressing Ymt possessed PLD activity whereas strains carrying deletions in the ymt gene showed no detectable PLD activity. Western blot analysis showed that Ymt was associated with bacteria under normal growth conditions, and immunogold EM revealed that Ymt was mainly localised in the bacterial cytoplasm. Ymt was purified to homogeneity, and the purified toxin showed a dose-dependent PLD activity. Substitution of amino acids in the PLD consensus motif of Ymt essentially abolished the enzymatic activity and these variants of the toxin were no longer toxic to mice. Interestingly, an in-frame deletion mutant of ymt in the Y pestis strain KIM was not significantly attenuated for mouse virulence. Together with the observation that expression of Ymt was higher at room temperature compared to 37 degrees C this prompted us to investigate the role of Ymt in the flea vector. Fleas were infected with isogenic ymt+ or ymt- mutant strains of Y. pestis. Preliminary results suggest that Ymt is important for survival of Y. pestis in the flea and thereby also for the flea-borne route of infection.
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Tafazoli F, Holmström A, Forsberg A, Magnusson KE. Apically exposed, tight junction-associated beta1-integrins allow binding and YopE-mediated perturbation of epithelial barriers by wild-type Yersinia bacteria. Infect Immun 2000; 68:5335-43. [PMID: 10948163 PMCID: PMC101797 DOI: 10.1128/iai.68.9.5335-5343.2000] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2000] [Accepted: 05/30/2000] [Indexed: 01/12/2023] Open
Abstract
Using polarized epithelial cells, primarily MDCK-1, we assessed the mode of binding and effects on epithelial cell structure and permeability of Yersinia pseudotuberculosis yadA-deficient mutants. Initially, all bacteria except the invasin-deficient (inv) mutant adhered apically to the tight junction areas. These contact points of adjacent cells displayed beta1-integrins together with tight junction-associated ZO-1 and occludin proteins. Indeed, beta1-integrin expression was maximal in the tight junction area and then gradually decreased along the basolateral membranes. Wild-type bacteria also opened gradually the tight junction to paracellular permeation of different-sized markers, viz., 20-, 40-, and 70-kDa dextrans and 45-kDa ovalbumin, as well as to their own translocation between adjacent cells in intimate contact with beta1-integrins. The effects on the epithelial cells and their barrier properties could primarily be attributed to expression of the Yersinia outer membrane protein YopE, as the yopE mutant bound but caused no cytotoxicity. Moreover, the apical structure of filamentous actin (F-actin) was disturbed and tight junction-associated proteins (ZO-1 and occludin) were dispersed along the basolateral membranes. It is concluded that the Yersinia bacteria attach to beta1-integrins at tight junctions. Via this localized injection of YopE, they perturb the F-actin structure and distribution of proteins forming and regulating tight junctions. Thereby they promote paracellular translocation of bacteria and soluble compounds.
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Abstract
In order to promote health, nurses and other health care professionals need to discover and articulate the meaning that is implicit in experiencing life after liver transplantation. From such an understanding, appropriate nursing interventions can be based. The aim of this study was to investigate the subjective experiences of the meaning of having a liver transplant, 1 year after the transplantation. After approval from the ethics committee at Goteborg University, 12 patients, nine women and three men, were interviewed. The study sample was chosen strategically to represent common diagnoses preceding liver transplantation. A phenomenological approach was chosen for the study. Analyses of the interviews were based on a modified version of a phenomenological method by Karlsson. Seven categories emerged: facing the inevitable; recapturing the body; emotional chaos; leaving the experts; family and friends; the threat of graft rejection; and honouring the donor. Having undergone a liver transplant meant living in a paradoxical situation. Knowing that you survived, it was a struggle to regain physical strength under great emotional stress. The recipients had to self-administer life-long medication, recognize symptoms indicating a potential problem and monitor for the possibility of graft rejection. Social support was essential for recovery. Meeting others with the same experience helped liver-transplanted patients to deal with their identity crises as well as undergo a transformation from being utterly unique to a survivor among others. The clinical implications from this study are that interventions, such as patient education, and social and mental support, are important tools to optimize both self-care capacity and the ability to maintain a healthy perception of identity after having a liver transplant at least up to 12 months post-transplant.
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Forsberg A, Lorenzon U, Nilsson F, Bäckmana L. Pain and health related quality of life after heart, kidney, and liver transplantation. Clin Transplant 1999; 13:453-60. [PMID: 10617233 DOI: 10.1034/j.1399-0012.1999.130603.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
No study has focused particularly on the sensory and affective experience of bodily pain among transplanted patients. The aim of this study was to explore pain and other factors that influence health related quality of life (HRQOL) in heart, kidney, and liver transplant recipients during the first 2 yr after transplantation, and to define similarities and/or differences in the three groups. A total of 76 patients, 18-60 yr old, undergoing heart, kidney, or liver transplantation between 1995 and 1997 with a follow-up of 6-24 months were included. HRQOL and pain were investigated by using the Short-Form-36 items (SF-36), the Hospital Anxiety and Depression Scale (HAD), and the Pain-O-Meter (POM). Overall, the patients show satisfactory HRQOL. There were no differences in experienced HRQOL 6 24 months after transplantation between kidney, liver, and heart transplant recipients except in the area of Role-Physical (RP). Fifty-three percent of all patients reported bodily pain. The most common locations were the hands, feet, and back, and sensory experiences were burning, stabbing, or dull pain. There was a correlation between number of rejections and total score for POM-VAS (p < 0.05) (rho = 0.47). There was also a correlation between the number of rejection episodes and the total pain intensity score for POM-WDS (p < 0.05) (rho = 0.48). Patients with pain scored higher in the area of depression (p < 0.05). Bodily pain is an important problem after organ transplantation, affecting daily living even in patients with good allograft function and it limits physical function. vitality, and general health.
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Persson C, Nordfelth R, Andersson K, Forsberg A, Wolf-Watz H, Fällman M. Localization of the Yersinia PTPase to focal complexes is an important virulence mechanism. Mol Microbiol 1999; 33:828-38. [PMID: 10447891 DOI: 10.1046/j.1365-2958.1999.01529.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The protein tyrosine phosphatase YopH, produced by the pathogen Yersinia pseudotuberculosis, is an essential virulence determinant involved in antiphagocytosis. Upon infection, YopH is translocated into the target cell, where it recognizes focal complexes. Genetic analysis revealed that YopH harbours a region that is responsible for specific localization of this PTPase to focal complexes in HeLa cells and professional phagocytes. This region is a prerequisite for blocking an immediate-early Yersinia-induced signal within target cells. The region is also essential for antiphagocytosis and virulence, illustrating the biological significance of localization of YopH to focal complexes during Yersinia infection. These results also indicate that focal complexes play a role in the general phagocytic process.
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Pettersson J, Holmström A, Hill J, Leary S, Frithz-Lindsten E, von Euler-Matell A, Carlsson E, Titball R, Forsberg A, Wolf-Watz H. The V-antigen of Yersinia is surface exposed before target cell contact and involved in virulence protein translocation. Mol Microbiol 1999; 32:961-76. [PMID: 10361299 DOI: 10.1046/j.1365-2958.1999.01408.x] [Citation(s) in RCA: 183] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Type III-mediated translocation of Yop effectors is an essential virulence mechanism of pathogenic Yersinia. LcrV is the only protein secreted by the type III secretion system that induces protective immunity. LcrV also plays a significant role in the regulation of Yop expression and secretion. The role of LcrV in the virulence process has, however, remained elusive on account of its pleiotropic effects. Here, we show that anti-LcrV antibodies can block the delivery of Yop effectors into the target cell cytosol. This argues strongly for a critical role of LcrV in the Yop translocation process. Additional evidence supporting this role was obtained by genetic analysis. LcrV was found to be present on the bacterial surface before the establishment of bacteria target cell contact. These findings suggest that LcrV serves an important role in the initiation of the translocation process and provides one possible explanation for the mechanism of LcrV-induced protective immunity.
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Leary SE, Griffin KF, Galyov EE, Hewer J, Williamson ED, Holmström A, Forsberg A, Titball RW. Yersinia outer proteins (YOPS) E, K and N are antigenic but non-protective compared to V antigen, in a murine model of bubonic plague. Microb Pathog 1999; 26:159-69. [PMID: 10089156 DOI: 10.1006/mpat.1998.0261] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The pathogenic Yersiniae produce a range of virulence proteins, encoded by a 70 kb plasmid, which are essential for infection, and also form part of a contact-dependent virulence mechanism. One of these proteins, V antigen, has been shown to confer a high level of protection against parenteral infection with Y. pestis in murine models, and is considered to be a protective antigen. In this study, the protective efficacy of V antigen has been compared in the same model with that of other proteins (YopE, YopK and YopN), which are part of the contact-dependent virulence mechanism. Mice immunised with two intraperitoneal doses of V antigen or each of the Yops, administered with either Alhydrogel or interleukin-12, produced high antigen-specific serum IgG titres. As shown in previous studies, V+Alhydrogel was fully protective, and 5/5 mice survived a subcutaneous challenge with 90 or 9x10(3) LD50's of Y. pestis GB. In addition, these preliminary studies also showed that V+IL-12 was partially protective: 4/5 or 3/5 mice survived a challenge with 90 or 9x10(3) LD50's, respectively. In contrast, none of the mice immunised with the Yops survived the challenges, and there was no significant delay in the mean time to death compared to mice receiving a control protein. These results show that using two different vaccine regimens, Yops E, K and N, failed to elicit protective immune responses in a murine model of plague, whereas under the same conditions, V antigen was fully or partially protective.
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Frithz-Lindsten E, Holmström A, Jacobsson L, Soltani M, Olsson J, Rosqvist R, Forsberg A. Functional conservation of the effector protein translocators PopB/YopB and PopD/YopD of Pseudomonas aeruginosa and Yersinia pseudotuberculosis. Mol Microbiol 1998; 29:1155-65. [PMID: 9767584 DOI: 10.1046/j.1365-2958.1998.00994.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Virulent Yersinia species cause systemic infections in rodents, and Y. pestis is highly pathogenic for humans. Pseudomonas aeruginosa, on the other hand, is an opportunistic pathogen, which normally infects only compromised individuals. Surprisingly, these pathogens both encode highly related contact-dependent secretion systems for the targeting of toxins into eukaryotic cells. In Yersinia, YopB and YopD direct the translocation of the secreted Yop effectors across the target cell membrane. In this study, we have analysed the function of the YopB and YopD homologues, PopB and PopD, encoded by P. aeruginosa. Expression of the pcrGVHpopBD operon in defined translocation-deficient mutants (yopB/yopD) of Yersinia resulted in complete complementation of the cell contact-dependent, YopE-induced cytotoxicity of Y. pseudotuberculosis on HeLa cells. We demonstrated that the complementation fully restored the ability of Y. pseudotuberculosis to translocate the effector molecules YopE and YopH into the HeLa cells. Similar to YopB, PopB induced a lytic effect on infected erythrocytes. The lytic activity induced by PopB could be prevented if the erythrocytes were infected in the presence of sugars larger than 3 nm in diameter, indicating that PopB induced a pore of similar size compared with that induced by YopB. Our findings show that the contact-dependent toxin-targeting mechanisms of Y. pseudotuberculosis and P. aeruginosa are conserved at the molecular level and that the translocator proteins are functionally interchangeable. Based on these similarities, we suggest that the translocation of toxins such as ExoS, ExoT and ExoU by P. aeruginosa across the eukaryotic cell membrane occurs via a pore induced by PopB.
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Frithz-Lindsten E, Du Y, Rosqvist R, Forsberg A. Intracellular targeting of exoenzyme S of Pseudomonas aeruginosa via type III-dependent translocation induces phagocytosis resistance, cytotoxicity and disruption of actin microfilaments. Mol Microbiol 1997; 25:1125-39. [PMID: 9350868 DOI: 10.1046/j.1365-2958.1997.5411905.x] [Citation(s) in RCA: 172] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Exoenzyme S (ExoS) is an ADP-ribosyltransferase secreted by the opportunistic pathogen Pseudomonas aeruginosa. The amino-terminal half of ExoS exhibits homology to the YopE cytotoxin of pathogenic Yersinia. Recently, YopE was found to be translocated into the host cell by a bacteria-cell contact-dependent mechanism involving the ysc-encoded type III secretion system. By using an approach in which exoS was expressed in different strains of Yersinia, including secretion and translocation mutants, we could demonstrate that ExoS was secreted and translocated into HeLa cells by a similar mechanism to that described previously for YopE. Similarly to YopE, the presence of ExoS in the host cell elicited a cytotoxic response, correlating with disruption of the actin microfilament structure. A similar cytotoxic response was also induced by a mutated form of ExoS with a more than 2000-fold reduced ADP-ribosyltransferase activity. However, the enzymatically active ExoS elicited a more definite rounding up of the HeLa cells, which also correlated with decreased viability of the cells after prolonged infection compared with cells infected with strains expressing mutated ExoS or YopE. This suggests that ExoS can act through two different mechanisms on the host cell. The expression of ExoS by Yersinia also mediated an anti-phagocytic effect on macrophages. In addition, we present evidence that extracellularly located P. aeruginosa is able to target ExoS into eukaryotic cells. Taken together, our data suggest that P. aeruginosa, by analogy with Yersinia, targets virulence proteins into the eukaryotic cytosol via a type III secretion-dependent mechanism as part of an anti-phagocytic strategy.
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Holmström A, Petterson J, Rosqvist R, Håkansson S, Tafazoli F, Fällman M, Magnusson KE, Wolf-Watz H, Forsberg A. YopK of Yersinia pseudotuberculosis controls translocation of Yop effectors across the eukaryotic cell membrane. Mol Microbiol 1997; 24:73-91. [PMID: 9140967 DOI: 10.1046/j.1365-2958.1997.3211681.x] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Introduction of anti-host factors into eukaryotic cells by extracellular bacteria is a strategy evolved by several Gram-negative pathogens. In these pathogens, the transport of virulence proteins across the bacterial membranes is governed by closely related type III secretion systems. For pathogenic Yersinia, the protein transport across the eukaryotic cell membrane occurs by a polarized mechanism requiring two secreted proteins, YopB and YopD. YopB was recently shown to induce the formation of a pore in the eukaryotic cell membrane, and through this pore, translocation of Yop effectors is believed to occur (Håkansson et al., 1996b). We have previously shown that YopK of Yersinia pseudotuberculosis is required for the development of a systemic infection in mice. Here, we have analysed the role of YopK in the virulence process in more detail. A yopK-mutant strain was found to induce a more rapid YopE-mediated cytotoxic response in HeLa cells as well as in MDCK-1 cells compared to the wild-type strain. We found that this was the result of a cell-contact-dependent increase in translocation of YopE into HeLa cells. In contrast, overexpression of YopK resulted in impaired translocation. In addition, we found that YopK also influenced the YopB-dependent lytic effect on sheep erythrocytes as well as on HeLa cells. A yopK-mutant strain showed a higher lytic activity and the induced pore was larger compared to the corresponding wild-type strain, whereas a strain overexpressing YopK reduced the lytic activity and the apparent pore size was smaller. The secreted YopK protein was found not to be translocated but, similar to YopB, localized to cell-associated bacteria during infection of HeLa cells. Based on these results, we propose a model where YopK controls the translocation of Yop effectors into eukaryotic cells.
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Rosqvist R, Håkansson S, Forsberg A, Wolf-Watz H. Functional conservation of the secretion and translocation machinery for virulence proteins of yersiniae, salmonellae and shigellae. EMBO J 1995; 14:4187-95. [PMID: 7556059 PMCID: PMC394501 DOI: 10.1002/j.1460-2075.1995.tb00092.x] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Virulent bacteria of the genera Yersinia, Shigella and Salmonella secrete a number of virulence determinants, Yops, Ipas and Sips respectively, by a type III secretion pathway. The IpaB protein of Shigella flexneri was expressed in Yersinia pseudotuberculosis and found to be secreted under the same conditions required for Yop secretion. Likewise, YopE was secreted by the wild-type strain LT2 of Salmonella typhimurium, but YopE was not secreted by the isogenic invA mutant. Secretion of both IpaB and YopE required their respective chaperones, IpgC and YerA. In addition, yopE-containing S. typhimurium expressed a YopE-mediated cytotoxicity on cultured HeLa cells. YopE was detected in the cytosol of the infected HeLa cells and the amount of translocated YopE correlated with the degree of cytotoxicity. Both translocation and cytotoxicity were prevented by the addition of gentamicin. Treatment of HeLa cells with cytochalasin D prior to infection prevented internalization of bacteria, but translocation of YopE was still observed. These results favour the hypothesis that YopE is translocated through the plasma membrane by surface-located bacteria. We propose that virulent Salmonella and Shigella deliver virulence effector molecules into the target cell through the utilization of a functionally conserved secretion/translocation machinery similar to that shown for Yersinia.
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Holmström A, Rosqvist R, Wolf-Watz H, Forsberg A. Virulence plasmid-encoded YopK is essential for Yersinia pseudotuberculosis to cause systemic infection in mice. Infect Immun 1995; 63:2269-76. [PMID: 7768608 PMCID: PMC173296 DOI: 10.1128/iai.63.6.2269-2276.1995] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The virulence plasmid common to pathogenic Yersinia species encodes a number of secreted proteins denoted Yops (Yersinia outer proteins). Here, we identify and characterize a novel plasmid-encoded virulence determinant of Yersinia pseudotuberculosis, YopK. The yopK gene was found to be conserved among the three pathogenic Yersinia species and to be homologous to the previously described yopQ and yopK genes of Y. enterocolitica and Y. pestis, respectively. Similar to the other Yops, YopK expression and secretion were shown to be regulated by temperature and by the extracellular Ca2+ concentration; thus, yopK is part of the yop regulon. In addition, YopK secretion was mediated by the specific Yop secretion system. In Y. pseudotuberculosis, YopK was shown neither to have a role in this bacterium's ability to resist phagocytosis by macrophages nor to cause cytotoxicity in HeLa cells. YopK was, however, shown to be required for the bacterium to cause a systemic infection in both intraperitoneally and orally infected mice. Characterization of the infection kinetics showed that, similarly to the wild-type strain, the yopK mutant strain colonized and persisted in the Peyer's patches of orally infected mice. A yopE mutant which is impaired in cytotoxicity and in antiphagocytosis was, however, found to be rapidly cleared from these lymphoid organs. Neither the yopK nor the yopE mutant strain could overcome the primary host defense and reach the spleen. This finding implies that YopK acts at a different level during the infections process than the antiphagocytic YopE cytotoxin does.
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Frithz-Lindsten E, Rosqvist R, Johansson L, Forsberg A. The chaperone-like protein YerA of Yersinia pseudotuberculosis stabilizes YopE in the cytoplasm but is dispensible for targeting to the secretion loci. Mol Microbiol 1995; 16:635-47. [PMID: 7476159 DOI: 10.1111/j.1365-2958.1995.tb02426.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The virulence plasmid-encoded YopE cytotoxin of Yersinia pseudotuberculosis is secreted across the bacterial membranes and subsequently translocated into the eukaryotic cell. Translocation of YopE into target cells was recently shown to be polarized and only occurred at the zone of contact between the pathogen and the eukaryotic cell. Immunogold electron microscopy on cryosectioned Y. pseudotuberculosis revealed that YopE is secreted and deposited on the bacterial cell surface when the bacteria are grown in Ca(2+)-depleted media at 37 degrees C. No YopE was detected in the cytoplasm or in the membranes. In yerA mutants which are downregulated for YopE at a post-transcriptional level, the cytotoxin could only be detected in the cytoplasm. The overall recovery of YopE from the yerA mutant strain was, however, considerably lower than from the wild-type strain. yerA had no major effect on the translation of YopE, but was found to stabilize YopE in the cytoplasm. YerA was shown to specifically interact with YopE in the cytoplasm in vivo and this binding also correlated with YopE secretion. Targeting of YopE to the secretion loci as well as translocation of YopE into HeLa cells occurred also in the absence of YerA. Based on our findings, we suggest that YerA by binding to YopE stabilizes and maintains the cytotoxin in a secretion-competent conformation.
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Beuscher HU, Rödel F, Forsberg A, Röllinghoff M. Bacterial evasion of host immune defense: Yersinia enterocolitica encodes a suppressor for tumor necrosis factor alpha expression. Infect Immun 1995; 63:1270-7. [PMID: 7890384 PMCID: PMC173146 DOI: 10.1128/iai.63.4.1270-1277.1995] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The ability of the enteropathogenic Yersinia enterocolitica to survive and proliferate in host tissue depends on a 70-kb plasmid known to encode a number of released Yersinia outer proteins that act as virulence factors by inducing cytotoxicity and inhibiting phagocytosis. This study demonstrates that one of the Yersinia outer proteins, the 41-kDa YopB, suppresses the production of tumor necrosis factor alpha (TNF-alpha), a macrophage-derived cytokine with central roles in the regulation of immune and inflammatory responses to infection. This conclusion is based on several lines of evidence. First, in macrophage cultures, suppression of TNF-alpha mRNA expression was induced by culture supernatant (CS+) of plasmid-bearing yersiniae, the effect which was blocked by anti-YopB antiserum. Second, suppression of TNF-alpha production, but not of interleukin-1 (IL-1) and IL-6, was induced by purified YopB. Third, in Yersinia-infected mice, no increase in TNF-alpha mRNA expression was observed in Peyer's patches, the primary site of bacterial invasion, compared with IL-1 (alpha and beta) mRNA. Finally, administration of anti-YopB antiserum to mice prior to infection with Y. enterocolitica increased TNF activity levels in Peyer's patches and coincided with a reduction in bacterial growth. The results thus provide direct evidence for a secreted eubacterial virulence factor that mediates selective suppression of TNF-alpha production. Although suppression of this single cytokine response is probably not sufficient to facilitate survival of the infecting organisms, the results suggest that suppression of TNF-alpha production by YopB significantly contributes to the evasion of Y. enterocolitica from antibacterial host defense.
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Frithz-Lindsten E, Rosqvist R, Forsberg A. YerA mediates the secretion of the YopE cytotoxin of Yersinia pseudotuberculosis. CONTRIBUTIONS TO MICROBIOLOGY AND IMMUNOLOGY 1995; 13:225-229. [PMID: 8833840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Forsberg A, Rosqvist R, Wolf-Watz H. Regulation and polarized transfer of the Yersinia outer proteins (Yops) involved in antiphagocytosis. Trends Microbiol 1994; 2:14-9. [PMID: 8162430 DOI: 10.1016/0966-842x(94)90339-5] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Pathogenic Yersinia express a number of strictly regulated, plasmid-encoded virulence determinants (Yops), some of which are important in enabling the pathogen to block phagocytosis. The events mediating antiphagocytosis and the regulation of this process are becoming increasingly well understood.
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Forsberg A, Rosqvist R. In vivo expression of virulence genes of Yersinia pseudotuberculosis. INFECTIOUS AGENTS AND DISEASE 1993; 2:275-8. [PMID: 8173809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The common virulence plasmid of pathogenic Yersinia species encodes a number of secreted proteins denoted Yops. YopE and YopH are indispensable for virulence and act in concert to mediate resistance to phagocytosis. In vitro all yop genes are coordinately regulated, with maximal expression and secretion at 37 degrees C in medium lacking Ca2+. In order to facilitate studies of in vivo expression of yopE and yopH we constructed operon fusions between these two genes and a promoterless luxAB operon from Vibrio harveyi in Y. pseudotuberculosis. Groups of 10 mice were infected with each fusion strain, and colonization and luciferase expression in Peyer's patches and spleen were followed by sacrificing two mice from each group daily. Peyer's patches were found to be colonized from the first day of infection, whereas the spleen was not colonized until the third day of infection. Luciferase expression could easily be monitored if the sample contained > or = 10(4) bacteria. Expression levels tended to be highest at the early stages of colonization for the respective organ (day 1 for Peyer's patches and day 3 or 4 for spleen). When in vivo expression was compared with in vitro expression, it was found that during infection the expression levels were as high or even higher than the in vitro expression observed for strains grown at 37 degrees C in Ca(2+)-depleted media.
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Galyov EE, Håkansson S, Forsberg A, Wolf-Watz H. A secreted protein kinase of Yersinia pseudotuberculosis is an indispensable virulence determinant. Nature 1993; 361:730-2. [PMID: 8441468 DOI: 10.1038/361730a0] [Citation(s) in RCA: 269] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Phosphorylation of proteins catalysed by protein kinases is associated with central functions in growth and proliferation of the eukaryotic cell, and kinases are particularly important in the signal transduction pathways. Enterobacterial protein kinases are structurally and functionally different from eukaryotic protein kinases, and no prokaryotic kinase has so far been described implicating a direct role for this activity in virulence. Virulent Yersinia possess a common virulence plasmid that encodes a number of secreted proteins (Yops), of which YopH has protein-tyrosine phosphatase activity with a key function in the block of phagocytosis by the pathogen. Here we report that the virulence plasmid of Yersinia pseudotuberculosis encodes a secreted protein kinase (YpkA) with extensive homology to eukaryotic Ser/Thr protein kinases. Specific mutants of ypkA resulted in avirulent strains. Thus, YpkA is, to our knowledge, the first reported prokaryotic secreted protein kinase involved in pathogenicity, presumably by interfering with the signal transduction pathways of the target cell.
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Kiessling AA, Crowell RC, Brettler D, Forsberg A, Wolf B. Human immunodeficiency virus detection and differential leukocyte counts are accurate and safer with formaldehyde-fixed blood. Blood 1993; 81:864-5. [PMID: 8427979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
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