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Berlin Brandenburg

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  • 1
    Language: English
    In: Science (New York, N.Y.), 17 March 2017, Vol.355(6330), pp.1211-1215
    Description: Bacteriophage transfer (lysogenic conversion) promotes bacterial virulence evolution. There is limited understanding of the factors that determine lysogenic conversion dynamics within infected hosts. A murine Typhimurium (Tm) diarrhea model was used to study the transfer of SopEΦ, a prophage from Tm SL1344, to Tm ATCC14028S. Gut inflammation and enteric disease triggered 〉55% lysogenic conversion of ATCC14028S within 3 days. Without inflammation, SopEΦ transfer was reduced by up to 10-fold. This was because inflammation (e.g., reactive oxygen species, reactive nitrogen species, hypochlorite) triggers the bacterial SOS response, boosts expression of the phage antirepressor Tum, and thereby promotes free phage production and subsequent transfer. Mucosal vaccination prevented a dense intestinal Tm population from inducing inflammation and consequently abolished SopEΦ transfer. Vaccination may be a general strategy for blocking pathogen evolution that requires disease-driven transfer of temperate bacteriophages.
    Keywords: Lysogeny ; Diarrhea -- Microbiology ; Enteritis -- Microbiology ; Salmonella Phages -- Pathogenicity ; Salmonella Typhimurium -- Pathogenicity
    ISSN: 00368075
    E-ISSN: 1095-9203
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  • 2
    Language: English
    In: Journal of Molecular Biology, 19 January 2018, Vol.430(2), pp.193-206
    Description: Inflammasome signaling impinges on the activation of inflammatory caspases (i.e., caspase-1 and caspase-4/5/11) and endows host cells with a sentinel system to sense microbial intrusion and thereby initiate appropriate immune responses. Lately, it has become evident that mammalian inflammasome-dependent responses to infection are not confined solely to cells of hematopoietic origin. Epithelial cells that line the body's mucosal surfaces use inflammasome signaling to sense and counteract pathogenic microorganisms that compromise barrier integrity. Many of the molecular mechanisms of epithelial inflammasome signaling remain unexplored. However, it now seems clear that epithelial inflammasome activation has a profound impact both on the infected cell itself and on its ability to communicate with other cell types of the mucosa. Here, we summarize current knowledge regarding the output of epithelial inflammasome activation during bacterial infection. Well-established downstream effects include epithelial cell death, release of soluble mediators, and subsequent recruitment of effector cell types, including NK cells, mast cells, and neutrophils, to sites of mucosal infection. We discuss the implications of recent findings for antibacterial defense in the mucosa and sketch out areas for future exploration.
    Keywords: Epithelium ; Inflammasomes ; Nlrc4 ; Nlrp3 ; Interleukin-18 ; Biology ; Chemistry
    ISSN: 0022-2836
    E-ISSN: 1089-8638
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  • 3
    Language: English
    In: Current Biology, 08 September 2014, Vol.24(17), pp.2000-2005
    Description: Antibiotics are powerful therapeutics but are not equally effective against all cells in bacterial populations. Bacteria that express an antibiotic-tolerant phenotype (“persisters”) can evade treatment [ ]. Persisters can cause relapses of the infection after the end of the therapy [ ]. It is still poorly understood whether persistence affects the evolution of bacterial virulence. During infections, persisters have been found preferentially at particular sites within the host [ ]. If bacterial virulence factors are required to reach such sites, treatment with antibiotics could impose selection on the expression of virulence genes, in addition to their well-established effects on bacterial resistance. Here, we report that treatment with antibiotics selects for virulence and fosters transmissibility of Typhimurium. In a mouse model for diarrhea, treatment with the broad-spectrum antibiotic ciprofloxacin reverses the outcome of competition between wild-type bacteria and avirulent mutants that can spontaneously arise during within-host evolution [ ]. While avirulent mutants take over the gut lumen and abolish disease transmission in untreated mice, ciprofloxacin tilts the balance in favor of virulent, wild-type bacteria. This is explained by the need for virulence factors to invade gut tissues and form a persistent reservoir. Avirulent mutants remain in the gut lumen and are eradicated. Upon cessation of antibiotic treatment, tissue-lodged wild-type pathogens reseed the gut lumen and thereby facilitate disease transmissibility to new hosts. Our results suggest a general principle by which antibiotic treatment can promote cooperative virulence during within-host evolution, increase duration of transmissibility, and thereby enhance the spread of an infectious disease. Diard et al. show that avirulent mutants arise during infection and reduce transmission. Antibiotics reverse this trend by eradicating avirulent mutants in the gut lumen. Virulent clones do persist in the host tissue, initiate relapses, and can be transmitted to new hosts. Thus, antibiotics can promote virulence and disease transmission.
    Keywords: Biology
    ISSN: 0960-9822
    E-ISSN: 1879-0445
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  • 4
    In: Nature, 2017, Vol.544(7651), p.498
    Description: Vaccine-induced high-avidity IgA can protect against bacterial enteropathogens by directly neutralizing virulence factors or by poorly defined mechanisms that physically impede bacterial interactions with the gut tissues ('immune exclusion')(1-3). IgA-mediated cross-linking clumps bacteria in the gut lumen and is critical for protection against infection by non-typhoidal Salmonella enterica subspecies enterica serovar Typhimurium (S. Typhimurium). However, classical agglutination, which was thought to drive this process, is efficient only at high pathogen densities (〉= 10(8) non-motile bacteria per gram). In typical infections, much lower densities(4,5) (10(0)-10(7) colony-forming units per gram) of rapidly dividing bacteria are present in the gut lumen. Here we show that a different physical process drives formation of clumps in vivo: IgA-mediated cross-linking enchains daughter cells, preventing their separation after division, and clumping is therefore dependent on growth. Enchained growth is effective at all realistic pathogen densities, and accelerates pathogen clearance from the gut lumen. Furthermore, IgA enchains plasmid-donor and -recipient clones into separate clumps, impeding conjugative plasmid transfer in vivo. Enchained growth is therefore a mechanism by which IgA can disarm and clear potentially invasive species from the intestinal lumen without requiring high pathogen densities, inflammation or bacterial killing. Furthermore, our results reveal an untapped potential for oral vaccines in combating the spread of antimicrobial resistance.
    Keywords: Medical And Health Sciences ; Basic Medicine ; Microbiology In The Medical Area ; Medicin Och Hälsovetenskap ; Medicinska Och Farmaceutiska Grundvetenskaper ; Mikrobiologi Inom Det Medicinska Området;
    ISSN: 0028-0836
    E-ISSN: 1476-4687
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  • 5
    Language: English
    In: Experimental Cell Research, 2010, Vol.316(12), pp.2017-2026
    Description: Op18/stathmin (Op18) is a microtubule-destabilizing protein that is phosphorylation-inactivated during mitosis and its normal function is to govern tubulin subunit partitioning during interphase. Human tumors frequently overexpress Op18 and a tumor-associated Q18→E mutation has been identified that confers hyperactivity, destabilizes spindle microtubules, and causes mitotic aberrancies, polyploidization, and chromosome loss in K562 leukemia cells. Here we determined whether wild-type and mutant Op18 have the potential to cause chromosomal instability by some means other than interference with spindle assembly, and thereby bypassing the spindle assembly checkpoint. Our approach was based on Op18 derivatives with distinct temporal order of activity during mitosis, conferred either by differential phosphorylation inactivation or by anaphase-specific degradation through fusion with the destruction box of cyclin B1. We present evidence that excessive Op18 activity generates chromosomal instability through interference occurring subsequent to the metaphase-to-anaphase transition, which reduces the fidelity of chromosome segregation to spindle poles during anaphase. Similar to uncorrected merotelic attachment, this mechanism evades detection by the spindle assembly checkpoint and thus provides an additional route to chromosomal instability.
    Keywords: Aneuploidy ; Micronucleus ; Merotely ; Merotelic ; Phosphorylation ; APC/C ; Biology
    ISSN: 0014-4827
    E-ISSN: 1090-2422
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  • 6
    Language: English
    In: Cellular and Molecular Life Sciences, 2009, Vol.66(20), pp.3263-3276
    Description: The microtubule-system organizes the cytoplasm during interphase and segregates condensed chromosomes during mitosis. Four unrelated conserved proteins, XMAP215/Dis1/TOGp, MCAK, MAP4 and Op18/stathmin, have all been implicated as predominant regulators of tubulin monomer–polymer partitioning in animal cells. However, while studies employing the Xenopus egg extract model system indicate that the partitioning is largely governed by the counteractive activities of XMAP215 and MCAK, studies of human cell lines indicate that MAP4 and Op18 are the predominant regulators of the interphase microtubule-array. Here, we review functional interplay of these proteins during interphase and mitosis in various cell model systems. We also review the evidence that MAP4 and Op18 have interphase-specific, counteractive and phosphorylation-inactivated activities that govern tubulin subunit partitioning in many mammalian cell types. Finally, we discuss evidence indicating that partitioning regulation by MAP4 and Op18 may be of significance to establish cell polarity.
    Keywords: Microtubules ; Oncoprotein 18 ; Microtubule-associated proteins ; PAR1 ; MARK ; XKCM1 ; Calmodulin ; CaM-dependent kinase
    ISSN: 1420-682X
    E-ISSN: 1420-9071
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  • 7
    Language: English
    In: Molecular Biology of the Cell, 2011, Vol.22(23), pp.4588-4601
    Description: Septin family proteins oligomerize through GTP-binding domains into core heteromers, which in turn polymerize at the cleavage furrow of dividing fungal and animal cells. Septin assemblies during the interphase of animal cells remain poorly defined and are the topic of this report. Here we developed protocols for visualization of authentic higher-order assemblies using tagged septins to effectively replace the endogenous gene-product within septin core heteromers in human cells. Our analysis revealed that septins assemble into microtubule-supported disc-like structures at the plasma membrane. In the absence of cell substrate-adhesion, this is the predominant higher-order arrangement in interphase cells and each one of the 7 to 8 septin family members expressed by the two analyzed cell types appears equally represented. However, studies of myeloid and lymphoid cell model systems revealed cell type specific alterations of higher-order septin arrangements in response to substrate-adhesion. Live-cell observations suggested that all higher-order septin assemblies are mutually exclusive with plasma membrane regions undergoing remodeling. The combined data point to a mechanism by which densely arranged cortical microtubules, which are typical for non-adhered spherical cells, support plasma membrane-bound disc-like septin assemblies.
    Keywords: Medical And Health Sciences ; Basic Medicine ; Cell And Molecular Biology ; Medicin Och Hälsovetenskap ; Medicinska Och Farmaceutiska Grundvetenskaper ; Cell- Och Molekylärbiologi ; Cellforskning ; Cellforskning ; Filament Formation ; Budding Yeast ; Saccharomyces-Cerevisiae ; Organization ; Tubulin ; Actin ; Localization ; Cytoskeleton ; Interphase ; Dynamics ; Filament Formation; Budding Yeast; Saccharomyces-Cerevisiae; Organization; Tubulin; Actin; Localization; Cytoskeleton; Interphase; Dynamics
    ISSN: 1059-1524
    E-ISSN: 19394586
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  • 8
    Language: English
    In: Molecular Biology of the Cell, 2012, Vol.23(21), pp.4242-4255
    Description: Septin-family proteins assemble into rod-shaped heteromeric complexes that form higher-order arrangements at the cell cortex, where they serve apparently conserved functions as diffusion barriers and molecular scaffolds. There are 13 confirmed septin paralogues in mammals, which may be ubiquitous or tissue specific. Septin hetero-oligomerization appears homology subgroup directed, which in turn determines the subunit arrangement of six- to eight-subunit core heteromers. Here we address functional properties of human SEPT9, which, due to variable mRNA splicing, exists as multiple isoforms that differ between tissues. Myeloid K562 cells express three SEPT9 isoforms, all of which have an equal propensity to hetero-oligomerize with SEPT7-containing hexamers to generate octameric heteromers. However, due to limiting amounts of SEPT9, K562 cells contain both hexameric and octameric heteromers. To generate cell lines with controllable hexamer-to-octamer ratios and that express single SEPT9 isoforms, we developed a gene product replacement strategy. By this means we identified SEPT9 isoform-specific properties that either facilitate septin heteromer polymerization along microtubules or modulate the size range of submembranous septin disks-a prevalent septin structure in nonadhered cells. Our findings show that the SEPT9 expression level directs the hexamer-to-octamer ratio, and that the isoform composition and expression level together determine higher-order arrangements of septins.
    Keywords: Medical And Health Sciences ; Medicin Och Hälsovetenskap ; Medical And Health Sciences ; Basic Medicine ; Cell And Molecular Biology ; Medicin Och Hälsovetenskap ; Medicinska Och Farmaceutiska Grundvetenskaper ; Cell- Och Molekylärbiologi
    ISSN: 1059-1524
    E-ISSN: 19394586
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  • 9
    Language: English
    In: Molecular Biology of the Cell, 2014, Vol. 25(10), pp. 1594-1607
    Description: Septins are filament-forming proteins important for organizing the cortex of animal and fungal cells. In mammals, 13 septin paralogues were recently shown to assemble into core heterohexamer and heterooctamer complexes, which serve as building blocks for apolar filamentous structures that differ among cell types. To determine how tissue-specific septin paralogue expression may shape core heteromer repertoires and thereby modulate properties of septin filaments, we devised protocols to analyze native septin heteromers with distinct numbers of subunits. Our evidence based on genetically manipulated human cells supports and extends recent concepts of homology subgroup-restricted assembly into distinct categories of apolar heterohexamers and heterooctamers. We also identify a category of tetramers that have a subunit composition equivalent to an octameric building block. These atypical tetramers are prevalent in lymphocytes and neural tissues, in which octamers are abundant but hexamers are rare. Our results can be explained by tissue-specific expression of SEPT3 subgroup members: SEPT3, SEPT9, and SEPT12. These serve as cognate subunits in either heterooctamers or atypical tetramers but exhibit different preferences in various tissues. The identified tissue-specific repertoires of septin heteromers provide insights into how higher-order septin structures with differential properties and stabilities may form in diverse animal cell types.
    Keywords: Medical And Health Sciences ; Medical Biotechnology ; Medical Biotechnology (With A Focus On Cell Biology (Including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry Or Biopharmacy) ; Medicin Och Hälsovetenskap ; Medicinsk Bioteknologi ; Medicinsk Bioteknologi (Med Inriktning Mot Cellbiologi (Inklusive Stamcellsbiologi), Molekylärbiologi, Mikrobiologi, Biokemi Eller Biofarmaci)
    ISSN: 1059-1524
    E-ISSN: 19394586
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  • 10
    Language: English
    In: Molecular Biology of the Cell, 2011, Vol. 22(17), pp. 3152-3164
    Description: Septins are conserved GTP-binding proteins that assemble into lateral diffusion barriers and molecular scaffolds. Vertebrate genomes contain 9-17 septin genes that encode both ubiquitous and tissue-specific septins. Expressed septins may assemble in various combinations through both heterotypic and homotypic G-domain interactions. However, little is known regarding assembly states of mammalian septins and mechanisms directing ordered assembly of individual septins into heteromeric units, which is the focus of this study. Our analysis of the septin system in cells lacking or overexpressing selected septins reveals inter-dependencies coinciding with previously described homology subgroups. Hydrodynamic and single-particle data show that individual septins exist solely in the context of stable six-to eight-subunit core heteromers, all of which contain SEPT2 and SEPT6 subgroup members and SEPT7, while heteromers comprising more than six subunits also contain SEPT9. The combined data suggest a generic model for how the temporal order of septin assembly is homology subgroup-directed, which in turn determines the subunit arrangement of native heteromers. Because mammalian cells normally express multiple members and/or isoforms of some septin subgroups, our data also suggest that only a minor fraction of native heteromers are arranged as perfect palindromes.
    Keywords: Medical And Health Sciences ; Basic Medicine ; Cell And Molecular Biology ; Medicin Och Hälsovetenskap ; Medicinska Och Farmaceutiska Grundvetenskaper ; Cell- Och Molekylärbiologi
    ISSN: 1059-1524
    E-ISSN: 19394586
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