| 1. |
- Engman, Jakob, et al.
(författare)
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Neisseria meningitidis Polynucleotide Phosphorylase Affects Aggregation, Adhesion, and Virulence
- 2016
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Ingår i: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 84:5, s. 1501-1513
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Tidskriftsartikel (refereegranskat)abstract
- Neisseria meningitidis autoaggregation is an important step during attachment to human cells. Aggregation is mediated by type IV pili and can be modulated by accessory pilus proteins, such as PilX, and posttranslational modifications of the major pilus subunit PilE. The mechanisms underlying the regulation of aggregation remain poorly characterized. Polynucleotide phosphorylase ( PNPase) is a 3'-5' exonuclease that is involved in RNA turnover and the regulation of small RNAs. In this study, we biochemically confirm that NMC0710 is the N. meningitidis PNPase, and we characterize its role in N. meningitidis pathogenesis. We show that deletion of the gene encoding PNPase leads to hyperaggregation and increased adhesion to epithelial cells. The aggregation induced was found to be dependent on pili and to be mediated by excessive pilus bundling. PNPase expression was induced following bacterial attachment to human cells. Deletion of PNPase led to global transcriptional changes and the differential regulation of 469 genes. We also demonstrate that PNPase is required for full virulence in an in vivo model of N. meningitidis infection. The present study shows that PNPase negatively affects aggregation, adhesion, and virulence in N. meningitidis.
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| 2. |
- Sigurlásdóttir, Sara, et al.
(författare)
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Host cell-derived lactate functions as an effector molecule in Neisseria meningitidis microcolony dispersal
- 2017
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Ingår i: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- The development of meningococcal disease, caused by the human pathogen Neisseria meningitidis, is preceded by the colonization of the epithelial layer in the nasopharynx. After initial adhesion to host cells meningococci form aggregates, through pilus-pilus interactions, termed microcolonies from which the bacteria later detach. Dispersal from microcolonies enables access to new colonization sites and facilitates the crossing of the cell barrier; however, this process is poorly understood. In this study, we used live-cell imaging to investigate the process of N. meningitidis microcolony dispersal. We show that direct contact with host cells is not required for microcolony dispersal, instead accumulation of a host-derived effector molecule induces microcolony dispersal. By using a host-cell free approach, we demonstrated that lactate, secreted from host cells, initiate rapid dispersal of microcolonies. Interestingly, metabolic utilization of lactate by the bacteria was not required for induction of dispersal, suggesting that lactate plays a role as a signaling molecule. Furthermore, Neisseria gonorrhoeae microcolony dispersal could also be induced by lactate. These findings reveal a role of host-secreted lactate in microcolony dispersal and virulence of pathogenic Neisseria.
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| 3. |
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| 4. |
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Dialogues : Dialogues, Valand Academy Yearbook 2015
- 2015
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Publikationen 'Dialogues' består av texter, visuella gestaltningar, dokumentationer, fragment och utsnitt ur pågående forskningsprojekt under 2015. Bidragen är redaktionellt utvalda och kommer från studenter, lärare och forskare vid institutionen.
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| 5. |
- Eriksson, Jens, et al.
(författare)
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Characterization of motility and piliation in pathogenic Neisseria
- 2015
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Ingår i: BMC Microbiology. - : Springer Science and Business Media LLC. - 1471-2180. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Background: The type IV pili (Tfp) of pathogenic Neisseria (i. e., N. gonorrhoeae and N. meningitidis) are essential for twitching motility. Tfp retraction, which is dependent on the ATPase PilT, generates the forces that move bacteria over surfaces. Neisseria motility has mainly been studied in N. gonorrhoeae whereas the motility of N. meningitidis has not yet been characterized. Results: In this work, we analyzed bacterial motility and monitored Tfp retraction using live- cell imaging of freely moving bacteria. We observed that N. meningitidis moved over surfaces at an approximate speed of 1.6 mu m/s, whereas N. gonorrhoeae moved with a lower speed (1.0 mu/s). An alignment of the meningococcal and gonococcal pilT promoters revealed a conserved single base pair variation in the -10 promoter element that influence PilT expression. By tracking mutants with altered pilT expression or pilE sequence, we concluded that the difference in motility speed was independent of both. Live-cell imaging using total internal reflection fluorescence microscopy demonstrated that N. gonorrhoeae more often moved with fewer visible retracting filaments when compared to N. meningitidis. Correspondingly, meningococci also displayed a higher level of piliation in transmission electron microscopy. Nevertheless, motile gonococci that had the same number of filaments as N. meningitidis still moved with a lower speed. Conclusions: These data reveal differences in both speed and piliation between the pathogenic Neisseria species during twitching motility, suggesting a difference in Tfp-dynamics.
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| 6. |
- Faria, Vanda, et al.
(författare)
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Do You Believe It? Verbal Suggestions Influence the Clinical and Neural Effects of Escitalopram in Social Anxiety Disorder : A Randomized Trial
- 2017
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Ingår i: EBioMedicine. - : Elsevier BV. - 2352-3964. ; 24, s. 179-188
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Tidskriftsartikel (refereegranskat)abstract
- Background: Selective serotonin reuptake inhibitors (SSRIs) are commonly prescribed for depression and anxiety, but their efficacy relative to placebo has been questioned. We aimed to test how manipulation of verbally induced expectancies, central for placebo, influences SSRI treatment outcome and brain activity in patients with social anxiety disorder (SAD).Methods: We did a randomized clinical trial, within an academic medical center (Uppsala, Sweden), of individuals fulfilling the DSM-IV criteria for SAD, recruited through media advertising. Participants were 18 years or older and randomized in blocks, through a computer-generated sequence by an independent party, to nine weeks of overt or covert treatment with escitalopram(20 mg daily). The overt group received correct treatment information whereas the covert group was treated deceptively with the SSRI described, by the psychiatrist, as active placebo. The treating psychiatrist was necessarily unmasked while the research staff was masked from intervention assignment. Treatment efficacy was assessed primarily with the self-rated Liebowitz Social Anxiety Scale (LSAS-SR), administered at week 0, 1, 3, 6 and 9, also yielding a dichotomous estimate of responder status (clinically significant improvement). Before and at the last week of treatment, brain activity during an emotional face-matching task was assessed with functional magnetic resonance imaging (fMRI) and during fMRI sessions, anticipatory speech anxiety was also assessed with the Spielberger State-Trait Anxiety Inventory - State version (STAI-S). Analyses included all randomized patients with outcome data at posttreatment. This study is registered at ISRCTN, number 98890605.Findings: Between March 17th 2014 and May 22nd 2015, 47 patients were recruited. One patient in the covert group dropped out after a few days of treatment and did not provide fMRI data, leaving 46 patients with complete outcome data. After nine weeks of treatment, overt (n = 24) as compared to covert (n = 22) SSRI administration yielded significantly better outcome on the LSAS-SR (adjusted difference 21.17, 95% CI 10.69–31.65, p < 0.0001) with more than three times higher response rate (50% vs. 14%; χ2(1) = 6.91, p = 0.009) and twice the effect size (d = 2.24 vs. d = 1.13) from pre-to posttreatment. There was no significant between-group difference on anticipatory speech anxiety (STAI-S), both groups improving with treatment. No serious adverse reactions were recorded. On fMRI outcomes, there was suggestive evidence for a differential neural response to treatment between groups in the posterior cingulate, superior temporal and inferior frontal gyri (all z thresholds exceeding 3.68, p ≤ 0.001). Reduced social anxiety with treatment correlated significantly with enhanced posterior cingulate (z threshold 3.24, p = 0.0006) and attenuated amygdala (z threshold 2.70, p = 0.003) activity.Interpretation: The clinical and neural effects of escitalopram were markedly influenced by verbal suggestions. This points to a pronounced placebo component in SSRI-treatment of SAD and favors a biopsychosocial over a biomedical explanatory model for SSRI efficacy.
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| 8. |
- Holm, Cecilia Koskinen, et al.
(författare)
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Lack of SIRP alpha phosphorylation and concomitantly reduced SHP-2-PI3K-Akt2 signaling decrease osteoblast differentiation
- 2016
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 478:1, s. 268-273
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Tidskriftsartikel (refereegranskat)abstract
- Normal differentiation of bone forming osteoblasts is a prerequisite for maintenance of skeletal health and is dependent on intricate cellular signaling pathways, including the essential transcription factor Runx2. The cell surface glycoprotein CD47 and its receptor signal regulatory protein alpha (SIRP alpha) have both been suggested to regulate bone cell differentiation. Here we investigated osteoblastic differentiation of bone marrow stromal cells from SIRP alpha mutant mice lacking the cytoplasmic signaling domain of SIRPa. An impaired osteoblastogenesis in SIRP alpha-mutant cell cultures was demonstrated by lower alkaline phosphatase activity and less mineral formation compared to wild-type cultures. This reduced osteoblastic differentiation potential in SIRPa-mutant stromal cells was associated with a significantly reduced expression of Runx2, osterix, osteocalcin, and alkaline phosphatase mRNA, as well as a reduced phosphorylation of SHP-2 and Akt2, as compared with that in wild-type stromal cells. Addition of a PI3K-inhibitor to wild-type stromal cells could mimic the impaired osteoblastogenesis seen in SIRP alpha-mutant cells. In conclusion, our data suggest that SIRPa signaling through SHP-2-PI3K-Akt2 strongly influences osteoblast differentiation from bone marrow stromal cells.
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