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  • 1. Ahlstrand, Tuuli
    et al.
    Tuominen, Heidi
    Beklen, Arzu
    Torittu, Annamari
    Oscarsson, Jan
    Umeå University, Faculty of Medicine, Department of Odontology.
    Sormunen, Raija
    Pöllänen, Marja T.
    Permi, Perttu
    Ihalin, Riikka
    A novel intrinsically disordered outer membrane lipoprotein of Aggregatibacter actinomycetemcomitans binds various cytokines and plays a role in biofilm response to interleukin-1β and interleukin-82017In: Virulence, ISSN 2150-5594, E-ISSN 2150-5608, Vol. 8, no 2, p. 115-134Article in journal (Refereed)
    Abstract [en]

    Intrinsically disordered proteins (IDPs) do not have a well-defined and stable 3-dimensional fold. Some IDPs can function as either transient or permanent binders of other proteins and may interact with an array of ligands by adopting different conformations. A novel outer membrane lipoprotein, bacterial interleukin receptor I (BilRI) of the opportunistic oral pathogen Aggregatibacter actinomycetemcomitans binds a key gatekeeper proinflammatory cytokine interleukin (IL)-1β. Because the amino acid sequence of the novel lipoprotein resembles that of fibrinogen binder A of Haemophilus ducreyi, BilRI could have the potential to bind other proteins, such as host matrix proteins. However, from the tested host matrix proteins, BilRI interacted with neither collagen nor fibrinogen. Instead, the recombinant non-lipidated BilRI, which was intrinsically disordered, bound various pro/anti-inflammatory cytokines, such as IL-8, tumor necrosis factor (TNF)-α, interferon (IFN)-γ and IL-10. Moreover, BilRI played a role in the in vitro sensing of IL-1β and IL-8 because low concentrations of cytokines did not decrease the amount of extracellular DNA in the matrix of bilRI− mutant biofilm as they did in the matrix of wild-type biofilm when the biofilms were exposed to recombinant cytokines for 22 hours. BilRI played a role in the internalization of IL-1β in the gingival model system but did not affect either IL-8 or IL-6 uptake. However, bilRI deletion did not entirely prevent IL-1β internalization, and the binding of cytokines to BilRI was relatively weak. Thus, BilRI might sequester cytokines on the surface of A. actinomycetemcomitans to facilitate the internalization process in low local cytokine concentrations.

  • 2.
    Bamyaci, Sarp
    et al.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Nordfelth, Roland
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Forsberg, Åke
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Identification of specific sequence motif of YopN of Yersinia pseudotuberculosis required for systemic infection2019In: Virulence, ISSN 2150-5594, E-ISSN 2150-5608, Vol. 10, no 1, p. 10-25Article in journal (Refereed)
    Abstract [en]

    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.

  • 3.
    Bröms, Jeanette E.
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology. Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Meyer, Lena
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology. Department of Experimental Medical Science, Section for Immunology, Lund University, Lund, Sweden.
    Sjöstedt, Anders
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
    A mutagenesis-based approach identifies amino acids in the N-terminal part of Francisella tularensis IglE that critically control type VI system-mediated secretion2017In: Virulence, ISSN 2150-5594, E-ISSN 2150-5608, Vol. 8, no 6, p. 821-847Article in journal (Refereed)
    Abstract [en]

    The Gram-negative bacterium Francisella tularensis is the etiological agent of the zoonotic disease tularemia. Its life cycle is characterized by an ability to survive within phagocytic cells through phagosomal escape and replication in the cytosol, ultimately causing inflammasome activation and host cell death. Required for these processes is the Francisella Pathogenicity Island (FPI), which encodes a Type VI secretion system (T6SS) that is active during intracellular infection. In this study, we analyzed the role of the FPI-component IglE, a lipoprotein which we previously have shown to be secreted in a T6SS-dependent manner. We demonstrate that in F. tularensis LVS, IglE is an outer membrane protein. Upon infection of J774 cells, an Delta iglE mutant failed to escape from phagosomes, and subsequently, to multiply and cause cytopathogenicity. Moreover, Delta iglE was unable to activate the inflammasome, to inhibit LPS-stimulated secretion of TNF-alpha, and showed marked attenuation in the mouse model. In F. novicida, IglE was required for in vitro secretion of IglC and VgrG. A mutagenesis-based approach involving frameshift mutations and alanine substitution mutations within the first similar to 38 residues of IglE revealed that drastic changes in the sequence of the extreme N-terminus (residues 2-6) were well tolerated and, intriguingly, caused hyper-secretion of IglE during intracellular infection, while even subtle mutations further downstream lead to impaired protein function. Taken together, this study highlights the importance of IglE in F. tularensis pathogenicity, and the contribution of the N-terminus for all of the above mentioned processes.

  • 4.
    Thanikkal, Edvin J.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Kumar Gahlot, Dharmender
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Liu, Junfa
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Fredriksson Sundbom, Marcus
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Gurung, Jyoti M.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Ruuth, Kristina
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Francis, Monika K.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Obi, Ikenna R.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Thompson, Karl M.
    Chen, Shiyun
    Dersch, Petra
    Francis, Matthew S.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    The Yersinia pseudotuberculosis Cpx envelope stress system contributes to transcriptional activation of rovM2019In: Virulence, ISSN 2150-5594, E-ISSN 2150-5608, Vol. 10, no 1, p. 37-57Article in journal (Refereed)
    Abstract [en]

    The Gram-negative enteropathogen Yersinia pseudotuberculosis possesses a number of regulatory systems that detect cell envelope damage caused by noxious extracytoplasmic stresses. The CpxA sensor kinase and CpxR response regulator two-component regulatory system is one such pathway. Active Cpx signalling upregulates various factors designed to repair and restore cell envelope integrity. Concomitantly, this pathway also down-regulates key determinants of virulence. In Yersinia, cpxA deletion accumulates high levels of phosphorylated CpxR (CpxR~P). Accumulated CpxR~P directly repressed rovA expression and this limited expression of virulence-associated processes. A second transcriptional regulator, RovM, also negatively regulates rovA expression in response to nutrient stress. Hence, this study aimed to determine if CpxR~P can influence rovA expression through control of RovM levels. We determined that the active CpxR~P isoform bound to the promoter of rovM and directly induced its expression, which naturally associated with a concurrent reduction in rovA expression. Site-directed mutagenesis of the CpxR~P binding sequence in the rovM promoter region desensitised rovM expression to CpxR~P. These data suggest that accumulated CpxR~P inversely manipulates the levels of two global transcriptional regulators, RovA and RovM, and this would be expected to have considerable influence on Yersinia pathophysiology and metabolism.

  • 5.
    Wu, Yao-Wen
    et al.
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Science and Technology, Department of Chemistry. Chemical Genomics Centre of the Max Planck Society, Dortmund, Germany; Max Planck Institute of Molecular Physiology, Dortmund, Germany.
    Li, Fu
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Science and Technology, Department of Chemistry. Chemical Genomics Centre of the Max Planck Society, Dortmund, Germany; Max Planck Institute of Molecular Physiology, Dortmund, Germany.
    Bacterial interaction with host autophagy2019In: Virulence, ISSN 2150-5594, E-ISSN 2150-5608, Vol. 10, no 1, p. 352-362Article, review/survey (Refereed)
    Abstract [en]

    Autophagy is a conserved and fundamental cellular process mainly to recycle or eliminate dysfunctional cellular organelles or proteins. As a response to cellular stress, autophagy is used as a defense mechanism to combat the infection with pathogenic bacteria. However, many intracellular bacteria have developed diverse mechanisms to evade recognition, to manipulate the autophagic pathway, and to hijack the autophagosomal compartment for replication. In this review, we discuss recent understandings on how bacteria interact with host autophagy.

  • 6.
    Överby Wernstedt, Anna
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Weber, Friedemann
    Hiding from intracellular pattern recognition receptors, a passive strategy of flavivirus immune evasion2011In: Virulence, ISSN 2150-5594, E-ISSN 2150-5608, Vol. 2, no 3, p. 238-240Article in journal (Refereed)
    Abstract [en]

    Tick-borne encephalitis virus (TBEV) is a medically important flavivirus in Europe and Asia, causing meningitis and encephalitis in thousands of people annually. Despite its relevance for public health, the interaction of TBEV with the type I interferon (IFN) system is poorly characterized. Induction of these antiviral cytokines is normally triggered by cytoplasmic recognition of viral signature molecules such as double-stranded (ds) RNA. In a recent paper, we showed that TBEV infection leads to formation of intracellular membrane vesicles which protect the viral dsRNA from cellular recognition. This delays the onset of antiviral IFN production sufficiently enough for an unhindered release of progeny viruses over 24 h. Thus, TBEV has evolved a stealth strategy to outrun the antiviral IFN response.

1 - 6 of 6
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