La muqueuse des patients atteints de cancer colorectal (CCR) est anormalement colonisée par des souches d’Escherichia coli porteuses de l’îlot pathogène pks (E. coli/pks+), responsable de la synthèse de la génotoxine colibactine. Les E. coli/pks+ induisent des cassures double brin de l’ADN, l’accumulation d’aberrations chromosomiques ainsi que la sénescence, et favorisent le développement tumoral dans des modèles murins de CCR. L’autophagie est un processus des cellules eucaryotes qui permet la dégradation d’éléments cytoplasmiques par les lysosomes et est activé pour permettre l’adaptation des cellules en réponse à un stress. Un dysfonctionnement de l’autophagie est associé à plusieurs pathologies humaines, notamment les cancers. L’objectif de ce travail de thèse était d’étudier le rôle de l’autophagie dans la défense de l’hôte suite à l’infection par les E. coli/pks+. Nous avons montré une augmentation de l’expression des gènes de l’autophagie dans la muqueuse colique des patients atteints de CCR colonisée par des E. coli/pks+ comparativement à celle colonisée par des E. coli ne portant pas l’îlot pks. L’infection des cellules épithéliales intestinales humaines HCT-116 par des souches d’E. coli isolées de patients atteints de CCR entraîne l’activation de l’autophagie de façon dépendante de la présence de l’îlot pks. Les cellules déficientes pour l’autophagie présentent une augmentation des dommages à l’ADN induits par les E. coli/pks+, associée à un défaut de recrutement au niveau du noyau de la protéine de réparation des dommages à l’ADN, RAD51, ainsi qu’une augmentation de la sénescence et de la prolifération cellulaire induites par ces souches. Dans un modèle murin de CCR, le modèle de souris Apc Min/+ , déficient pour le gène de l’autophagie Atg16l1 spécifiquement dans les cellules épithéliales intestinales, nous avons montré un rôle complexe de l’autophagie dans la carcinogenèse colorectale. En effet, en condition non infectée, chez les souris Apc Min/+ , l’autophagie joue un rôle pro-tumoral. Cependant, suite à l’infection par la souche d’E. coli/pks+, 11G5, les souris déficientes pour l’autophagie présentent une augmentation de la tumorigénèse, accompagnée par une augmentation des dommages à l’ADN, de la prolifération cellulaire et de l’inflammation. Ces résultats suggèrent que l’autophagie est nécessaire pour inhiber les effets pro-tumoraux des souches d’E. coli/pks+ et ainsi limiter la carcinogenèse colorectale induite par ces dernières. De nombreuses perspectives d’études sur les mécanismes sous-jacents impliqués dans la progression tumorale induite par les souches d’E. coli/pks+ feront suite à ce projet. Notamment, l’impact du microenvironnement immunitaire et du microbiote sur la carcinogenèse colorectale seront analysés. Plus largement, cette étude permettra de mieux comprendre le rôle de l’autophagie dans la défense de l’hôte pour lutter contre les E. coli associés au CCR. À plus long terme, ce travail pourrait également contribuer au développement de nouvelles stratégies thérapeutiques basées sur la modulation de l’autophagie chez les patients présentant une colonisation par les souches d’E. coli/pks+. / Several studies have shown a role of intestinal microbiota in CRC etiology, which is the third cause of death by cancer in the world. Especially, colonic mucosa of CRC patient is abnormally colonized with E. coli strains which often carry the pathogenic pks island, leading to the synthesis of a genotoxin called by colibactin. Colibactin-producing E. coli strains induce DNA double strand breaks, chromosomic aberration and senescence in host cells enhancing the cellular proliferation and tumorigenesis in mouse models of CRC. The aim of this study is to investigate the role of autophagy, a key process in cellular homeostasis, in host defense against infection by pks-harboring E. coli (E. coli/pks+). We showed the increased expression of different autophagy-related genes in the mucosa of CRC patients colonized with E. coli/pks+ compared to that of patients colonized with E. coli without the pks island. In vitro and in vivo, we showed that autophagy is activated in intestinal epithelial cells upon infection in order to limit the pro-tumoral effects of E. coli/pks+. In a murine model of CRC, the ApcMin/+ mouse model, deficient for the Atg16l1 autophagy gene specifically in intestinal epithelial cells, we have shown a complex role of autophagy in colorectal carcinogenesis. Indeed, in uninfected conditions, autophagy plays a pro-tumoral role. However, following infection with the E. coli/pks+ 11G5 strain, mice deficient for autophagy exhibit increased tumorigenesis, accompanied by increased DNA damage, cell proliferation, and inflammation. These results suggest that autophagy is necessary to inhibit the pro-tumoral effects of E. coli/pks+ strains and thus limit the colorectal carcinogenesis induced by the latter. Future works using mouse models of CRC are required to study the role of autophagy in colonic tumorigenesis suppression following infection with E. coli/pks+. Different mechanism such as inhibition of cellular proliferation and immune response, modification of the composition of the gut microbiota will be analyzed. Together, those results will highlight the role of autophagy as a host defense mechanism against the pro-tumoral effects of pks-harboring E. coli strains. This work could also open the door to new therapeutic options in the treatment of CRC and therefore have a great impact on public health.

A vassoura-de-bruxa é a doença mais importante da cultura do cacaueiro, nos países onde ela ocorre. Em 1989 foi constatada pela primeira vez a presença do patógeno causador dessa doença na principal região produtora do Brasil. A falta de medidas de controle eficientes resultou, nos últimos anos, em menor produção, mudanças no uso da terra, venda de propriedades, diminuição do nível de emprego e danos ao meio ambiente. Em vista do pouco conhecimento sobre aspectos epidemiológicos da doença nas condições do sudeste da Bahia, elaborou-se o presente trabalho com os seguintes objetivos: estudar o gradiente de infecção da vassoura-de-bruxa em ramos e frutos em cacaueiros enxertados; comparar o efeito de genótipos e três tratamentos (poda fitossanitária semestral, poda fitossanitária mensal e poda fitossanitária aliada a aplicação de fungicida mensais) no controle da doença; estudar o progresso da vassoura-de-bruxa no tempo, quantificado em ramos e frutos doentes. O experimento foi conduzido em Uruçuca, BA, em área contendo 16 genótipos diferentes, adjacente a uma área com cacaueiros abandonados com alta incidência da doença. A área experimental foi dividida em três partes, as quais receberam os seguintes tratamentos: poda fitossanitária semestral, poda fitossanitária mensal e poda fitossanitária aliada a aplicação de fungicida mensal. Pelo menos uma vez por mês foram contados os ramos e frutos com vassoura. Os resultados mostraram a ausência de evidência clara da existência de gradiente de doença. Os níveis de resistência genética à vassoura-de-bruxa de ramos e frutos não foram correlacionados entre si. Houve bom ajuste do progresso da doença ao modelo monomolecular. As menores taxas de crescimento foram obtidas no tratamento com poda e aplicação de fungicida mensal. O tratamento que combinou poda e pulverização com fungicida apresentou diferença significativa na redução do percentual de frutos com vassoura. Os genótipos NO-34, NO-17 e NO-02 foram os que apresentaram menores percentagens de frutos com vassoura, sendo significativamente diferentes dos genótipos NO-24 e NO-13. / Witches' broom is the most important disease of cocoa, in the countries where it occurs. In 1989, it was verified for the first time the presence of the pathogen in the main producing area of Brazil. The lack of efficient control measures resulted, in the last years, in losses in the production, changes in the use of the soil, sale of properties, decrease of the employment level and damages to the environment. In view of the little knowledge on epidemic aspects of the disease in the conditions of the southeast of Bahia, the present work was elaborated with the following objectives: to study the gradient of the witches' broom infection in flushes and pods in grafted cocoa; to compare the effect of genotypes and three treatments (half-yearly phytosanitation, monthly phytosanitation and monthly phytosanitation allied to fungicide application) in the control of the disease; to study the witches' broom temporal progress, quantified in flushes and pods. Trials were carried out in Uruçuca, BA, in area contends 16 different genotypes, adjacent an area with abandoned cocoa with high incidence of the disease. The experimental area was divided in three parts, which received the following treatments: half-yearly phytosanitation, monthly phytosanitation and monthly phytosanitation allied to fungicide application. At least once a month, flushes and pods with broom were counted. Results showed the absence of clear evidence of the existence of disease gradient. The levels of genetic resistance to the witches' broom of flushes and pods were not correlated to each other. There was good adjustment of progress of the disease to the monomolecular model. The smallest growth rates were obtained in the treatment with monthly phytosanitation and fungicide application. The treatment that allied phytosanitation and fungicide application presented significant difference in the reduction of the percentage of witches' broom infected pods. The genotypes NO-34, NO-17 and NO-02 presented smaller percentages of diseased pods, being significantly different from the genotypes NO-24 and NO-13.

Arenaviruses are enveloped negative-strand RNA viruses that cause significant human disease. Despite decades of research, it is still unclear how these viruses establish a lifelong, asymptomatic infection in their rodent hosts while infection of humans often results in severe disease. Unable to enter a state of bona fide latency, the transcription and replication of the viral genomic RNA is likely highly regulated in time and subcellular space. Moreover, we hypothesize that the viral nucleoprotein (NP), responsible for the encapsidation of the viral RNA and the most highly expressed viral gene product, plays a key role in the regulation of the viral gene expression program. Further, exploring host-virus interactions may elucidate the basic aspects of arenavirus biology and how they cause such severe disease in humans. To explore these questions in greater detail, this dissertation has pursued three main avenues. First, to better understand lymphocytic choriomeningitis mammarenavirus (LCMV) genome replication and transcription at the single-cell level, we established a high-throughput, single-molecule (sm)FISH image acquisition and analysis pipeline and followed viral RNA species from viral entry through the late stages of persistent infection in vitro. This work provided support for a cyclical model of persistence where individual cells are initially transiently infected, clear active infection, and become re-infected from neighboring reservoir cells within the population. Second, we used FISH to visualize viral genomic RNA to describe the subcellular sites where LCMV RNAs localize during infection. We observed that, viral RNA concentrates in large subcellular structures located near the cellular microtubule organizing center and colocalizes with the early endosomal marker Rab5c and the viral glycoprotein in a proportion of infected cells. We propose that the virus is using the surface of a cellular membrane bound organelle as a site for the pre-assembly of viral components including genomic RNA and viral glycoprotein prior to their transport to the plasma membrane where new particles will bud. Last, we used mass spectrometry to identify human proteins that interact with the NPs of LCMV and Junín mammareanavirus (JUNV) strain Candid #1. We provided a detailed map of the host machinery engaged by arenavirus NPs, and in particular, showed that NP associates with the double-stranded RNA (dsRNA)-activated protein kinase (PKR), a well-characterized antiviral protein that inhibits cap-dependent protein translation initiation via phosphorylation of eIF2α. We demonstrated that JUNV antagonizes the antiviral activity of PKR completely, effectively abrogating the antiviral activity of this surveillance pathway. In sum, the work composing this dissertation has given us fresh insight into how arenaviruses establish and maintain persistence; the nature of the subcellular site where viral genomic RNA is transcribed, replicated, and assembled with other viral components; and a global view of the cellular machinery hijacked by the viral nucleoprotein. This work improves our basic understanding of the arenavirus life cycle and may suggest novel antiviral therapeutic targets that could be exploited in the future.

Le viroïde de la mosaïque latente du pêcher (PLMVd) est un pathogène mondialement répandu et responsable de pertes (directes et indirectes) relativement importantes au niveau de la culture des pêchers. Cependant, peu de données sont actuellement disponibles en ce qui concerne dune part le(s) déterminant(s) de pathogénicité de ce viroïde et dautre part les éventuels mécanismes de résistance des plantes vis-à-vis des viroïdes. Lapproche originale de ce travail a été de jeter les bases de cette double caractérisation. Dans un premier temps, le rôle du pseudo-nud P8, commun à tous les variants du PLMVd actuellement séquencés, a été étudié par mutagenèse dirigée. Dans un second temps, la réponse moléculaire de plants de pêchers infectés par des variants de pathogénicités différentes a été caractérisée par le biais de la cDNA-AFLP. Lobjectif principal de cette thèse était didentifier une voie métabolique éventuellement impliquée dans la résistance des plants de pêcher contre ce viroïde. Au terme de ce travail, il est apparu que le pseudo-nud P8 était impliqué soit dans la stabilité du viroïde au sein des cellules infectées soit dans la réplication du viroïde. En effet, le variant inoculé présentant un pseudo-nud déstabilisé a montré une réplication réduite au cours des douze mois de létude. De plus, bien que le viroïde muté soit présent dans les plantes inoculées, aucun symptôme na été observé. Il est cependant trop tôt pour déterminer si cette latence apparente est due à une quantité trop faible du viroïde ou bien à une implication du pseudo-nud dans la pathogénicité du viroïde. La caractérisation de lexpression des gènes de plants de pêchers infectés par des variants de pathogénicité différente a permis de montrer que le PLMVd réprimait des gènes impliqués dans la photosynthèse et en particulier dans la protection des deux photosystèmes. Cette expression particulière des gènes des plantes infectées peut être mise en relation avec les symptômes de chlorose et de mosaïque sexprimant au cours dune infection par le PLMVd. Cependant, nous ne pouvons encore affirmer avec certitude si elle est une cause ou une conséquence de ces symptômes. De même, la cDNA-AFLP a permis de mettre en évidence la répression de protéines de choc thermique (HSPs) dans les feuilles symptomatiques. Ces protéines jouent généralement un rôle dans le repliement des protéines ainsi que dans leur assemblage, leur déplacement, leur stabilisation et leur dégradation. La régulation de leur expression peut donc avoir une grande influence dans les plantes infectées et, peut-être, jouer un rôle dans lexpression des symptômes. De même, le gène codant pour une novel cap-binding protein (nCBP) est apparu sous-exprimé dans les feuilles symptomatiques. Le rôle de ces protéines est encore mal connu mais elles pourraient intervenir dans la régulation de la traduction des ARNm. Leur répression peut donc également avoir un impact important et déstabiliser diverses voies métaboliques. Enfin deux gènes codant clairement pour des protéines de défense des plantes ont été identifiés. Il sagit dun gène codant pour un intermédiaire de la thiamine (impliquée dans le déclenchement de la SAR, surexprimé dans les feuilles asymptomatiques) et dun autre gène codant pour une protéine inhibitrice des polygalacturonases (sur-exprimé dans les feuilles symptomatiques). Le rôle exact de ces protéines dans la protection des plantes vis-à-vis du viroïde nest cependant pas encore clair. Ce travail constitue une première étude des relations hôte-pathogène établies durant une infection de plants de pêcher par le PLMVd. Cest également le premier, à notre connaissance à avoir analysé lexpression des gènes de plantes infectées en fonction des symptômes observés./ The Peach latent mosaic viroid (PLMVd) infects peach trees in all production areas. This pathogen is responsible of direct and indirect crop losses. However only a few data are available as regards on one hand the determinant of pathogenicity of this viroid and on the other hand the resistance mechanisms of plants against this pathogen. The original approach of this work was to give the foundation of this double characterization. Firstly, the role of the P8 pseudoknot, present in every sequenced PLMVd, was studied by directed mutagenesis. Secondly, the molecular response of different peach trees infected by different variants was evaluated by the use of the cDNA-AFLP. The main objective of this thesis was to identify a metabolic pathway implicated in the plant defence against the PLMVd. In the term of this work, it seemed that the P8 pseudoknot was implicated either in the stability or in the replication of the viroid into the infected cells. Indeed, the inoculated variant (with a destabilized pseudoknot) has shown a reduced replication during the cultural season. In spite of the presence of the mutated variant in the plants, no symptom was observed on the peach tree leaves. However, we cannot conclude if this absence of symptom is due to the low viroid quantity either to an implication of the pseudo-knot in the pathogenicity of the PLMVd. The characterization of the gene expression in the infected peach trees has allowed to highlight that the PLMVd represses genes implicated in the photosynthesis and more specifically genes involved in the protection of the two photosystems. This particular gene expression in the infected leaves was linked to the chlorosis and mosaic induced by the PLMVd. However, we cannot conclude with certitude if these symptoms are a cause or a consequence of this particular genes expression. The cDNA-AFLP has also allowed to identify the repression of genes coding for heat shock proteins (HSPs) in symptomatic leaves. These proteins generally have a role in the protein folding, assembly, translocation, stabilization and degradation. The regulation of their expression may have a great influence in the infected plants and, maybe, play a role in the symptoms expression. The gene coding for the novel cap-binding protein (nCBP) was also identified has repressed in the symptomatic leaves. The biological role of these proteins is unclear but it seems that these proteins act in the regulation of the mRNA translation. The repression of nCBP may thus have an important impact and to destabilize various biological pathways. Finally, two genes implicated in the plant defence were identified. One coding for a polygalacturonase inhibitor (over-expressed in symptomatic leaves) and the other one coding for a thiamine intermediate (involved in the SAR and over-expressed in the non-symptomatic leaves). The role of these proteins in the plant defence against the PLMVd is however unclear. To our knowledge, this is the first work where the host-pathogen relationship established during a PLMVd infection are studied. This is also the first time were the gene expression is linked to the viroid-induced symptoms.

The sun is the primary source of all chemical energy on the planet. Starch granules have evolved as storage deposits for captured light energy. Many complex biological functions take place at the starch granule surface, including starch granule metabolism and defense. The starch granule-associated protein puroindoline is a known antimicrobial with unique functional and biological properties, attributed to the presence of a unique tryptophan-rich domain. To test puroindoline's tight association, puroindoline removed from the starch granule surface during water-washing was assessed. Washing more than eight times failed to further reduce puroindoline content of starch granules, suggesting a strong association of puroindoline with the starch granule surface. To identify the tryptophan-rich domain tightly associated with the starch granule surface, we used a combination of in situ tryptic digestion and mass spectrometry. We identified the tryptophan-rich domain of puroindoline directly bound to the starch granule surface of wheat. This is the first instance of the tryptophan-rich domain directly observed at the starch granule surface. In addition, using mass spectrometry, we determined that during development and maturation, wheat seeds appear to have resisted infection and lysed the pathogens where, upon desiccation, the molecular evidence remained fixed at the starch granule surface. Proteins with known antimicrobial activity were identified, as well as several proteins from the plant pathogens Agrobacterium tumefaciens, Pectobacterium carotovorum, Fusarium graminearum, Magnaporthe grisea, Xanthomonas axonopodis, and X. oryzae. Future characterization may reveal previously unknown host-pathogen interactions. Finally, we have demonstrated that puroindoline, when expressed in the seeds of transgenic corn, will localize and associate with the starch granule surface in a pattern similar to the puroindoline expression pattern observed in wheat. Surprisingly, puroindoline expression in transgenic corn is correlated with an increase in total seed oil content.

The sun is the primary source of all chemical energy on the planet. Starch granules have evolved as storage deposits for captured light energy. Many complex biological functions take place at the starch granule surface, including starch granule metabolism and defense. The starch granule-associated protein puroindoline is a known antimicrobial with unique functional and biological properties, attributed to the presence of a unique tryptophan-rich domain. To test puroindoline's tight association, puroindoline removed from the starch granule surface during water-washing was assessed. Washing more than eight times failed to further reduce puroindoline content of starch granules, suggesting a strong association of puroindoline with the starch granule surface. To identify the tryptophan-rich domain tightly associated with the starch granule surface, we used a combination of in situ tryptic digestion and mass spectrometry. We identified the tryptophan-rich domain of puroindoline directly bound to the starch granule surface of wheat. This is the first instance of the tryptophan-rich domain directly observed at the starch granule surface. In addition, using mass spectrometry, we determined that during development and maturation, wheat seeds appear to have resisted infection and lysed the pathogens where, upon desiccation, the molecular evidence remained fixed at the starch granule surface. Proteins with known antimicrobial activity were identified, as well as several proteins from the plant pathogens Agrobacterium tumefaciens, Pectobacterium carotovorum, Fusarium graminearum, Magnaporthe grisea, Xanthomonas axonopodis, and X. oryzae. Future characterization may reveal previously unknown host-pathogen interactions. Finally, we have demonstrated that puroindoline, when expressed in the seeds of transgenic corn, will localize and associate with the starch granule surface in a pattern similar to the puroindoline expression pattern observed in wheat. Surprisingly, puroindoline expression in transgenic corn is correlated with an increase in total seed oil content.

<p><italic>Cryptococcus neoformans</italic> is an opportunistic fungal pathogen that initiates infection following inhalation. As a result, the pulmonary immune response provides a first line of defense against <italic>C. neoformans</italic>. Surfactant protein D (SP-D) is an important regulator of pulmonary immune responses and is typically host protective against bacterial and viral respiratory infections. However, SP-D is not protective against <italic>C. neoformans</italic>. This is evidenced by previous work from our laboratory demonstrating that SP-D-deficient mice infected with a highly virulent <italic>C. neoformans</italic> strain (H99 Stud) have a lower fungal burden and live longer compared to wild-type (WT) control animals. We hypothesized that SP-D alters susceptibility to <italic>C. neoformans</italic> by dysregulating the innate pulmonary immune response following infection. For this reason, inflammatory cells and cytokines were compared in the bronchoalveolar lavage fluid from WT and SP-D<super>-/-</super> mice after <italic>C. neoformans</italic> infection. Post-infection, mice lacking SP-D had reduced eosinophil infiltration and IL-5 in lung lavage fluid. To further explore the interplay of SP-D, eosinophils, and IL-5, mice expressing altered levels of eosinophils and/or IL-5 were used to assess the role these innate immune mediators play during the host response to <italic>C. neoformans</italic>. IL-5 overexpressing mice had increased pulmonary eosinophilia and were more susceptible to <italic>C. neoformans</italic> infection as compared to WT mice. Furthermore, the response to <italic>C. neoformans</italic> infection in SP-D<super>-/-</super> mice could be restored to that of WT mice by increasing IL-5 and eosinophils, via crossing the IL-5 transgene onto the SP-D<super>-/-</super> background. Together, these studies support the conclusion that SP-D increases susceptibility to <italic>C. neoformans</italic> infection by promoting <italic>C. neoformans</italic>-driven pulmonary IL-5 and eosinophil infiltration.</p> / Dissertation

The sun is the primary source of all chemical energy on the planet. Starch granules have evolved as storage deposits for captured light energy. Many complex biological functions take place at the starch granule surface, including starch granule metabolism and defense. The starch granule-associated protein puroindoline is a known antimicrobial with unique functional and biological properties, attributed to the presence of a unique tryptophan-rich domain. To test puroindoline's tight association, puroindoline removed from the starch granule surface during water-washing was assessed. Washing more than eight times failed to further reduce puroindoline content of starch granules, suggesting a strong association of puroindoline with the starch granule surface. To identify the tryptophan-rich domain tightly associated with the starch granule surface, we used a combination of in situ tryptic digestion and mass spectrometry. We identified the tryptophan-rich domain of puroindoline directly bound to the starch granule surface of wheat. This is the first instance of the tryptophan-rich domain directly observed at the starch granule surface. In addition, using mass spectrometry, we determined that during development and maturation, wheat seeds appear to have resisted infection and lysed the pathogens where, upon desiccation, the molecular evidence remained fixed at the starch granule surface. Proteins with known antimicrobial activity were identified, as well as several proteins from the plant pathogens Agrobacterium tumefaciens, Pectobacterium carotovorum, Fusarium graminearum, Magnaporthe grisea, Xanthomonas axonopodis, and X. oryzae. Future characterization may reveal previously unknown host-pathogen interactions. Finally, we have demonstrated that puroindoline, when expressed in the seeds of transgenic corn, will localize and associate with the starch granule surface in a pattern similar to the puroindoline expression pattern observed in wheat. Surprisingly, puroindoline expression in transgenic corn is correlated with an increase in total seed oil content.

Salmonella enterica serovar Typhimurium is a facultative intracellular pathogen that has evolved to take advantage of the eukaryotic host cells it inhabits during infection. It uses bacterial effectors translocated into the host cell cytosol to manipulate host cell machinery and establish a replicative niche. In this thesis I study the function of two of these effectors, SopD and SopB, which have been shown to act cooperatively to induce phenotypes associated with gastroenteritis (fluid secretion and neutrophil influx into the intestinal lumen). In addition to promoting gastroenteritis, SopD has also been implicated in systemic and persistent infection of mice. Although recently implicated in invasion, the precise function of SopD has remained elusive. Here I show that SopD affects membrane dynamics during S. Typhimurium invasion of epithelial cells. SopD promotes membrane sealing and macropinosome formation, events that may have important consequences for efficiency of bacterial cell entry in vivo. Furthermore, we demonstrate that SopD is recruited to the invasion site membranes through the phosphatase activity of SopB, suggesting a mechanism for their cooperative action during induction of gastroenteritis. Unlike SopD, SopB has been a focus of intense research efforts and its role in invasion as a phosphoinositide phosphatase is well documented. However, we have observed that SopB also inhibits fusion of lysosomes with Salmonella-containing vacuoles (SCVs) following invasion. This ability depends on SopB-mediated reduction of negative membrane charge of the SCV during invasion by hydrolysis of the phosphoinositide PI(4,5)P2. Membrane charge alterations driven by SopB result in removal of Rab GTPases from the SCV that depend on electrostatic interactions for their targeting. Two of these Rabs, Rab23 and Rab35 were previously shown to promote phagosome-lysosome fusion. Therefore their removal from the SCV may promote SCV trafficking away from the degradative endocytic pathway of host cells. This represents a new mechanism by which an invasion associated effector controls SCV maturation. Together, this work advances our knowledge of the interaction between S. Typhimurium and its host. This research also suggests a new mechanism by which pathogens other than S. Typhimurium could promote their intracellular survival.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 3 uppsatser.