Legionella pneumophila ist der Erreger der Legionärskrankheit. Die Pathogenität des Bakteriums basiert auf seiner Fähigkeit innerhalb menschlicher Lungenzellen zu überleben und sich zu vermehren. Demzufolge ist L. pneumophila nicht nur interessant als wichtiges Pathogen, sondern kann auch als Sonde verwendet werden, um allgemeine intrazelluläre Ereignisse zu untersuchen. Ein Beispiel hierfür ist die, durch das Pathogen gestörte, intrazelluläre Kommunikation zwischen den Organellen des endoplasmatischen Retikulums (ER) und dem Golgi Apparat (GA). In der vorliegenden Studie schlagen wir ein neues Modell vor, wie das Bakterium erfolgreich seine replikative Nische, die Legionella Vakuole (LV), innerhalb des Zytosols aufbauen könnte, um seine Ausbreitung zu garantieren. Um die Mechanismen für die erfolgreiche Ausbeutung der Wirtszelle gezielt untersuchen zu können, haben wir mit Hilfe von siRNA spezifisch verschiedene Wirtszellproteinen herunterreguliert und den Einfuß der Abwesenheit dieser Proteine auf die Vermehrung von L. pneumophila gemessen. Die Ergebnisse wiesen darauf hin, dass die LV möglicherweise den Golgi Apparat imitiert und auf diese Weise den zellulären Vesikeltransport umleitet. Diese Theorie wurde durch in silico Ergebnisse unterstützt, die in der Proteinsequenz des Legionella Effektor-Proteins LidA, das auf der Vakuole lokalisiert ist, ein SNARE-ähnliches Motiv zeigte. Dies weist auf ein auf der Vakuole lokalisiertes SNARE-Erkennungsmotiv hin, das notwendig sein könnte, um zelluläre Transportvesikel zu koppeln. Aus dem Wissen heraus, dass L. pneumophila in der Lage ist, die Aktivierung der zellulären Proteine Arf1 und Rab1 durch Phosphorylierung und Dephosphorylierung zu regulieren, machten wir uns auf die Suche nach Proteinen, die auf Infektion hin modifiziert werden. Die Kommunikation von Wirt und Pathogen über Phosphorylierung ist bekannt im Bezug auf pathogenspezifische Modifikation des Zytoskeletts und Signalkaskaden in der Anti-Apoptose. Für diese Studie wurde ein Antikörper verwendet, der spezifisch phosphorylierte Tyrosinreste erkennt. Dies resultierte in der Detektion einer Serin-Threonin-Kinase in der Amöbe Acanthamöba castellanii, die an einem Tyrosinrest phosphoryliert ist. Diese Amöben-Kinase wies in silico Homologie zu der humanen GS-Kinase 3 des Wnt-Signalwegs, bekannt aus der Forschung der embronalen Entwicklung bei Drosophila, auf. Der letzte Teil dieser Arbeit konzentrierte sich auf die, durch eine L. pneumophila-Infektion ausgelöste, anti-apoptotische Signalkaskade. Es ist bekannt, dass auf eine Infektion hin NF-kappaB aktiviert wird. Dies führt dazu, dass p65 in den Zellkern wandert und dort als Transkriptionsfaktor aktiv wird. Diese Translokation geschieht in 2 zeitversetzten Phasen. Eine Aktivierungsspitze wird nach dem Kontakt mir bakteriellem Flagellin gemessen, gefolgt, von einer dauerhaften Aktivierung, abhängig von einem funktionierenden Dot/ Icm Typ-IV-Translokationssystem. In dieser Arbeit stießen wir auf eine L. pneumophila Mutante, die den Dot/ Icm-Effektor SdbA nicht bildet, und die daraufhin NF-appaB nicht aktivieren kann. Diese Mutante war ebenfalls nicht in der Lage, sich in Epithelzellen zu vermehren. Dies ist außergewöhnlich, da das L. pneumophila Effektor Repertoire so redundant ist, dass die Abwesenheit eines einzigen Effektors selten einen so starken Einfluss auf die Replikation hat. All diese Ergebnisse zeigen zusammengenommen, auf wie vielen verschiedenen Ebenen L. pneumophila in der Lage ist, seine Wirtszelle zu manipulieren, um einerseits die nötige Nische für seine Vermehrung zu etablieren und andererseits die Zelle am Selbstmord zu hindern. Dies geschieht durch Imitation zellulärer Prozesse. / Legionella pneumophila is the causative agent of Legionnaires´ disease. The bacterium’s pathogenicity is based on its ability to survive and multiply efficiently inside human alveolar cells. Therefore, L. pneumophila is not only an important pathogen, but can also be used as a probe to investigate host cell function as for example, in the cellular trafficking pathway. In this study, we establish a new model of how this pathogen efficiently constructs its replicative niche, the Legionella containing vacuole (LCV), inside the host cytosol, enabling its dissemination. To investigate the mechanisms that lead to effective exploitation of the host cell, we down-regulated specific host cellular proteins via siRNA technology and measured the subsequent impact on L. pneumophila replication. The results suggest that the LCV mimicks the Golgi apparatus and via this mechanism hijacks host cellular vesicular trafficking. The L. pneumophila secreted effector protein LidA, located within the LCV, is shown to have a SNARE-like motif, suggesting a SNARE like sole connected to the LCV. Since it is known that cellular signalling proteins are controlled via phosphorylation and dephosphorylation, we went on to search for specifically modulated host cell proteins after L. pneumophila infection. The cross-talk of the pathogen with its host via phosphorylation has been connected to several sub-cellular activities leading to, for instance, cytoskeleton rearrangement and signalling events including anti-apoptosis pathways. Here we used a phosphorylated tyrosine antibody resulting in the detection of an amoeba serine-threonine-kinase, phosphorylated at its tyrosine residue. This kinase shows homologies to the human GSK3 of the wnt-signalling pathway. (“Wnt“ is merged from the names of the homologues genes Wg (Drosophila melanogaster) and Int (mouse) both employed in evolutionary developement.) The final part of this work concentrated on anti-apoptotic signalling events induced upon L. pneumophila infection. It is known that during L. pneumophila infection the activation of NF-kappaB and subsequent translocation of p65 from the cytosol into the nucleus follows a biphasic pattern. One short peak of activation is induced upon contact with bacterial flagellin, succeeded by a permanent Dot/ Icm type IV secretion system-dependent activation. In this study, we found the L. pneumophila mutant lacking the Dot/ Icm effector SdbA to be unable to activate NF-kappaB. This mutant also showed impaired growth in epithelial cells. This is remarkable due to the high redundancy of the L. pneumophila effector system, meaning deletion of a single effector rarely has such a big impact on replication. Taken together this work demonstrates, the manifold ways in which L. pneumophila on the one hand side establishes its niche to ensure replication and on the other hand side to bars its host cell from suicide. All of this is managed by mimicking cellular processes.

In organisms from insects to vertebrates, Toll-like receptors (TLRs) are primary pathogen detectors that activate downstream pathways, specifically those that direct expression of innate immune effector genes. TLRs also have roles in development in many species. The sea anemone Nematostella vectensis is a useful cnidarian model to study the origins of TLR signaling because its genome encodes a single TLR and homologs of many downstream signaling components, including the NF-κB pathway. In this dissertation, the single N. vectensis TLR (Nv-TLR) is characterized. It is demonstrated that Nv-TLR can activate canonical NF-κB signaling in human cells, the intracellular TIR domain of Nv-TLR can interact with human TLR adapter proteins MAL and MYD88, and the TIR domain of Nv-TLR is required for NF-κB activation. It is shown that the coral pathogen Vibrio coralliilyticus causes a rapidly lethal disease in N. vectensis and that heat-inactivated V. coralliilyticus and bacterial flagellin can activate a reconstituted Nv-TLR-to-NF-κB pathway in human cells. By immunostaining of anemones, Nv-TLR is shown to be expressed in a subset of cnidocytes and many of these Nv-TLR-positive cells also express Nv-NF-κB. Additionally, the nematosome, which is a Nematostella-specific multicellular structure, expresses Nv-TLR, many innate immune pathway homologs, and can engulf V. coralliilyticus. Morpholino knockdown indicates that Nv-TLR also has an essential role during early embryonic development. The characterization of this primitive TLR and identification of a bacterial pathogen for N. vectensis reveal ancient TLR functions and provide a novel model for studying the molecular basis of cnidarian disease and immunity.

The fruit fly Drosophila melanogaster has been a powerful model system in which to study the immune response. When microorganisms breach the mechanical barrier of the insect, phagocytosing cells and a battery of induced antimicrobial molecules rapidly attack them. These antimicrobial peptides can reach micromolar concentrations within a few hours. This immediate response is reminiscent of the mammalian innate immune response and utilizes transcription factors of the NF-κB family. We have generated loss-of-function mutants of the NF-κB-like transcription factor Relish in order to investigate Relish's role in the Drosophila immune response to microbes. Relish mutant flies have a severely impaired immune response to Gram-negative (G-) bacteria and some Gram-positive (G+) bacteria and fungi and succumb to an otherwise harmless infection. The main reason for the high susceptibility to infection is that these mutant flies fail to induce the antimicrobial peptide genes. The cellular responses appear to be normal. Relish is retained in the cytoplasm in an inactive state. We designed a set of expression plasmids to investigate the requirements for activation of Relish in a hemocyte cell line after stimulation with bacterial lipopolysaccharide. Signal-induced phosphorylation of Relish followed by endoproteolytic processing at the caspase-like target motif in the linker region released the inhibitory ankyrin-repeat (ANK) domain from the DNA binding Rel homology domain (RHD). Separation from the ANK domain allowed the RHD to move into the nucleus and initiate transcription of target genes like those that encode the inducible antimicrobial peptides, likely by binding to κB-like sites in the promoter region. By studying the immune response of the Relish mutant flies in combination with mutants for another NF-κB-like protein, Dorsal-related immunity factor (Dif), we found that the Drosophila immune system can distinguish between various microbes and generate a differential response by activating the Toll/Dif and Imd/Relish pathways. The recognition of foreign microorganisms is believed to occur through pattern recognition receptors (PRRs) that have affinity for selective pathogen-associated molecular patterns (PAMPs). We found that the Drosophila PRRs can recognize G- bacteria as a group. Interestingly, the PRRs are specific enough to distinguish between peptidoglycans from G+ bacteria such as Micrococcus luteus and Bacillus megaterium and fungal PAMPs from Beauveria bassiana and Geotrichum candidum. This thesis also investigates the expression of the antimicrobial peptide genes, Diptericin B and Attacin C, and the putative intracellular antimicrobial peptide gene Attacin D, and explores a potential evolutionary link between them.

No description available.

<p>Diacylglycerol (DAG), a lipid messenger generated upon T cell receptor (TCR) engagement, mediates signaling through the IKK/NF-&#954;B and Ras/ERK pathways. Further downstream of the Ras/ERK pathway are mammalian target of rapamycin (mTOR) and MAP kinase signal integrating kinases Mnk1 and Mnk2. While mTOR acts as a critical regulator of T cell metabolism, homeostasis and function, Mnk1 and Mnk2 phosphorylate the initiation factor eIF4E that plays an important role in cap-dependent mRNA translation. Diacylglycerol kinases (DGKs) terminate DAG-mediated signals by phosphorylating DAG into phosphatidic acid. T cells that lack both &#945; and &#950; isoforms of DGK accumulate excess DAG upon activation, resulting in hyper-activation of the IKK/NF-&#954;B, Ras/ERK and mTOR pathways, hypersensitivity to TCR stimulation, and loss of self-tolerance. Here, we have examined the mechanisms by which dysregulated DAG-mediated signaling affects T cell function. To this end, we studied the effects of hyper-activating individual DAG-mediated pathways (IKK/NF-&#954;B and TSC/mTOR) on T cell function. We also examined the role of ERK-activated kinases Mnk1 and Mnk2 in T cell function.</p><p>Using mice with T cell-specific expression of a constitutively active form of IKK&#946; (`IKK' mice), we found that uncontrolled IKK&#946;/NF-&#954;B signaling promotes T cell apoptosis and attenuates responsiveness to TCR stimulation. Defective IL-2 production and increased FasL expression contributed to enhanced IKK T cell apoptosis. Impaired IKK T cell activation and proliferation were associated with defects in TCR signaling, and upregulation of the cell surface inhibitory receptor PD1. In vivo, IKK T cells mounted a compromised antigen-specific CD8 T cell response with curtailed expansion and exaggerated contraction phases. Notably, expression of transcriptional repressor Blimp1 (a regulator of T cell exhaustion) was increased in IKK T cells, and conditionally deleting Blimp1 was able to largely restore responsiveness to TCR stimulation.</p><p>Investigating Mnk1/2 double knockout (DKO) mice, we found that Mnk1 and Mnk2 are dispensable for T cell development and function, but important for the pathogenesis of experimental autoimmune encephalomyelitis (EAE). TCR engagement activated Mnk1/2 in a Ras/ERK-dependent manner in primary T cells, and was inhibited by DGK &#945; and &#950;. Mnk1/2 deficiency did not affect the development of conventional &#945;&#946; T cells, regulatory T cells, or invariant NKT cells. Mature T cells from DKO mice showed normal activation and CD4 TH differentiation ex vivo, but DKO mice developed lower clinical scores than WT counterparts in an EAE model, correlating with a smaller pool of MOG-reactive IL-17-producing and IFN&#947;-producing CD4 cells. These results suggest that Mnk1/2 may play a minimal role in T cell development and function but may control non-T cell lineages to regulate TH1 and TH17 differentiation in vivo. </p><p>To determine the effect of constitutive mTOR complex 1 activity on anti-bacterial CD8 responses, we investigated mice with T cell-specific deletion of TSC1, a suppressor of mTOR complex 1 activity. Using an established model system of transgenic (OT1) CD8 cell adoptive transfer and challenge with Listeria monocytogenes expressing a cognate antigen, we found that TSC1 deficiency impairs antigen-specific CD8 responses. Fewer TSC1-deficient OT1 cells were present in the peripheral blood and spleen at the peak of the response and fewer memory cells were found at later time points, in individual and competitive adoptive transfer experiments with WT counterparts. Weak expansion of TSC1-deficient cells was correlated with defects in survival and proliferation in vivo, while exaggerated contraction was associated with an increased ratio of SLECs to MPECs in the effector cell population. This perturbation in effector-memory differentiation was concomitant with enhanced T-bet expression and decreased Eomes expression among activated TSC1 KO cells. Upon competitive adoptive transfer with WT counterparts and antigen re-challenge, TSC1-deficient memory cells showed moderate defects in expansion but not cytokine production. Taken together, these findings provide direct evidence of a CD8 cell-intrinsic role for TSC1 in regulating antigen-specific primary and memory responses.</p><p>In sum, findings from these studies provide deeper insight into the regulation of T cell function by DAG-mediated pathways, and may have implications for the design of immune-modulation strategies during vaccination, autoimmunity and cancer immunotherapy.</p> / Dissertation

Elevation of VEGFR-3, the primary mediator of lymphangiogenesis (i.e., new lymphatic vessel formation), is frequently associated with inflammation related to chronic disease and cancer. In the latter case, VEGFR-3 dependent lymphangiogenesis induced by inflamed tumors increases the incidence of distant metastasis, leading to decreased patient survival. However, the molecular mechanisms underlying inflammation-induced VEGFR-3 elevation and lymphangiogenesis are currently unknown. Two potential candidate genes that may regulate expression of VEGFR-3 are Prox1, the primary mediator of embryonic lymphangiogenesis, and NF-κB, the key intracellular regulator of inflammation-induced transcription. We hypothesized that the key inflammatory mediator, NF-κB, regulates transcription of key mediators of lymphangiogenesis, VEGFR-3 and Prox1. We further hypothesized that inflammation-induced elevation of VEGFR-3 and Prox1 are essential steps required for robust lymphangiogenesis in response to inflammation. The three primary goals of this study were to (1) delineate the time-course of events leading to inflammation-induced lymphangiogenesis in vivo; (2) clone and characterize the VEGFR-3 promoter and identify factors regulating VEGFR-3 expression in vitro; and (3) characterize the lymphatic phenotype of NF-κB p50 knockout mice. To begin testing these hypotheses, we used a mouse model of peritonitis to characterize induction of lymphangiogenesis and expression kinetics of NF-κB, Prox1 and VEGFR-3. In vivo time-course analysis of inflammation-induced lymphangiogenesis showed activation of NF-κB followed by sequential upregulation of Prox1 and VEGFR-3 that preceded lymphangiogenesis by 4 and 2 days, respectively. Characterization of the VEGFR-3 promoter by luciferase-reporter and ChIP assays showed direct activation by Prox1, NF-κB p50 and p65 transcription factors. This also revealed that Prox1 and NF-κB p50 bind in close proximity and synergistically activate the VEGFR-3 promoter. Characterization of p50 knockout mice revealed significantly decreased lymphatic vessel density in several organs that corresponded to reduced VEGFR-3 and Prox1 expression. Activation of NF-κB by inflammatory stimuli also elevated expression of NF-κB, Prox1 and VEGFR-3 in cultured lymphatic endothelial cells, which enhanced proliferation and migration in response to the VEGFR-3-specific ligand, VEGF-C152S. Collectively, our findings suggest that induction of the NF-κB pathway by inflammatory stimuli activates Prox1, and both NF-κB and Prox1 activate the VEGFR-3 promoter leading to increased receptor expression in lymphatic endothelial cells. This, in turn, enhances the responsiveness of pre-existing lymphatic endothelium to VEGFR-3 binding factors, VEGF-C and VEGF-D, ultimately resulting in robust lymphangiogenesis.

No description available.

The aim of this thesis was to verify the hypothesis implying that n-3 polyunsaturated fatty acids inhibit the development of mild chronic inflammation. The experiment was conducted on rats with different diets (control, with the addition of safflower oils, fish oils and oils from algae Schizochytrium). For processing the results of the collected tissues was used determination of expression of selected genes by qRT-PCR, detection of proteins and in the cytosol and nuclear fractions by Western blot and the quantification of cytokines by ELISA. Feeding oil from algae Schizochytrium has led to lowering the final weight and blood glucose, further to enhance expression of PPAR-gama and increasing the production of anti-inflammatory cytokines IL-10 and TGF-beta1. In kontrast, no difference was observed in the expression of GPR120 and adiponectin receptors or proteins in an amount of NF-kappaB and PPAR-gama between diets. Elevated plasma levels of adiponectin were found. The results of the experiment shows that it is possible to recommend oil from algae Schizochytrium as a useful supplement of human diet as prevention of chronic degenerative diseases.

Doctor of Philosophy / Department of Diagnostic Medicine/Pathobiology / Philip R. Hardwidge / Diarrheagenic Escherichia coli (E. coli) strains are common etiological agents of diarrhea. Diarrheagenic E. coli are classified into enterotoxigenic E. coli (ETEC), Shiga toxin-producing E. coli (STEC or enterohemorrhagic E. coli [EHEC]), enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC), enteroaggregative E. coli (EAEC), diffuse-adherent E. coli (DAEC), and adherent invasive E. coli (AIEC). In addition to encoding toxins that cause diarrhea, diarrheagenic E. coli have evolved numerous strategies to interfere with host defenses. In the first project, we identified an ETEC-secreted factor (ESF) that blocked TNF-induced NF-[kappa]B activation. One of the consequences of TNF-induced NF-[kappa]B activation is the production of pro-inflammatory cytokines that help to eliminate pathogens. Modulation of NF-[kappa]B signaling may promote ETEC colonization of the host small intestine. In this study, we fractionated ETEC supernatants and identified flagellin as necessary and sufficient for blocking the degradation of the NF-[kappa]B inhibitor I[kappa]B[alpha] in response to TNF[alpha]. In the second project, we attempted to identify an ETEC cAMP importer. ETEC diarrhea leads to cAMP release into the lumen of the small intestine. cAMP is a key secondary messenger that regulates ETEC adhesin expression. We hypothesized that a cAMP importer is present in ETEC, accounting for its hypersensitivity to extracellular cAMP. We used Tn5 transposome-mediated mutagenesis to construct a mutant library and screen for cAMP-hyporesponsive mutants. However, none of the 17,956 mutants we screened were cAMP-hyporesponsive. In the third project, we focused on gut microbiota and the T3SS effector NleH. We used the mouse-specific pathogen C. rodentium and transplanted performed microbiota between different mouse strains. We evaluated microbiota populations as a function of infection with WT and [Delta]nleH C. rodentium strains before and after microbiota transplantation. Microbiota transfer altered the resistance to WT C. rodentium infection in C57BL/10ScNJ mice and the NleH effector promoted host resistance to C. rodentium.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22742号 / 医博第4660号 / 新制||医||1046(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 武田 俊一, 教授 武藤 学, 教授 滝田 順子 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM