O agente etiológico da Febre Maculosa das Montanhas Rochosas (RMSF), conhecida no Brasil como Febre Maculosa Brasileira, é a bactéria Rickettsia rickettsii. Essa bactéria é transmitida ao homem pela picada de diferentes espécies de carrapatos ixodídeos. No Brasil, os vetores são Amblyomma cajennense e A. aureolatum. As taxas de prevalência de R. rickettsii nas populações de carrapatos de áreas endêmicas para RMSF são baixas, em geral abaixo de 1%. Essa baixa prevalência parece estar associada a menores taxas reprodutivas e de sobrevivência de linhagens infectadas, sugerindo que R. rickettsii seja patogênica também para os seus vetores. Infecções experimentais demonstraram que 80-100% dos indivíduos de uma colônia de A. aureolatum mantida em laboratório são infectados por R. rickettsii, enquanto apenas 10-60% de A. cajennense adquirem a bactéria. Esses dados indicam que as respostas dessas duas espécies de carrapatos à infecção sejam diferentes, resultando em diferentes taxas de prevalência da bactéria. Dessa maneira, a caracterização molecular das interações entre carrapatos do gênero Amblyomma e a bactéria R. rickettsii é importante, podendo gerar informações não somente para o esclarecimento acerca dos mecanismos de patogenicidade de R. rickettsii para os carrapatos, mas também para um melhor entendimento dos mecanismos responsáveis pela aparente restringência de A. cajennense à infecção. Assim, os objetivos do presente estudo foram: (i) analisar os efeitos da infecção por R. rickettsii sobre o perfil de expressão gênica de carrapatos A. cajennense por hibridação subtrativa por supressão (SSH), (ii) validar os dados de SSH por reação em cadeia de polimerase quantitativa precedida por transcrição reversa (RT-qPCR) e (iii) caracterizar funcionalmente dois genes com expressão induzida pela infecção por RNA de interferência (RNAi). Após a análise bioinformática dos dados de SSH, 44 sequências únicas foram obtidas, das quais 36 representam genes com expressão induzida e 8 genes com expressão reprimida pela infecção. A indução dos genes codificadores da subunidade I da citocromo c oxidase (COX1), da subunidade IV da NADH desidrogenase, de uma proteína com domínio de inibidor de serina-proteases Kunitz-type (papilina-like), identificados por SSH, e de um peptídeo antimicrobiano (hebraeína), foi confirmada por RT-qPCR. O silenciamento gênico da hebraeína e da papilina-like não teve nenhum efeito na aquisição de R. rickettsii pelo vetor, indicando que, isoladamente, não são responsáveis pela proteção de A. cajennense contra a infecção. Os dados gerados pelo presente estudo abrem perspectivas para que outros genes sejam avaliados quanto ao seu papel na aquisição de R. rickettsii, os quais, no futuro, podem ser considerados como alvos para o desenvolvimento de vacinas. / The etiologic agent of the Rocky Mountain Spotted Fever (RMSF), also known as Brazilian Spotted Fever in Brazil, is the bacterium Rickettsia rickettsii. This rickettsia is transmitted to humans by the bite of various tick species. In Brazil, Amblyomma cajennense and A. aureolatum are known as vectors. The prevalence rates of R. rickettsii infected ticks in RMSF endemic areas are low, oscillating around 1%. These low prevalence rates seems to be associated with lower reproductive and survival rates of infected ticks, suggesting that R. rickettsii is also pathogenic to its vectors. Experimental infections with R. rickettsii have demonstrated that 80 to 100% of A. aureolatum ticks from a laboratory colony acquire this bacterium, whereas only 10 to 60% of A. cajennense ticks become infected. These results indicate that the responses of these two tick species against infection are different, resulting in different prevalence rates of the bacterium. Therefore, the elucidation of the interactions between ticks of the genera Amblyomma and the bacterium R. rickettsii at a molecular level is important to provide information to better understand the mechanisms of pathogenicity of R. rickettsii against ticks as well as for the elucidation of the mechanisms responsible for the apparent refractoriness of A. cajennense against infection. Therefore, the objectives of the current study were: (i) analyze the effets of the infection with R. rickettsii on the gene expression of ticks A. cajennense by suppression subtractive hybridization (SSH), (ii) validate SSH data by reverse transcription quantitative polymerase chain reaction (RT-qPCR), and (iii) functionally characterize two genes induced by infection using RNA interference (RNAi). After bioinformatics analysis of SSH data, 44 unique sequences were obtained, among which 36 represent genes with expression induced and 8 repressed genes by infection. The induction of genes encoding subunit I of cytochrome c oxidase (COX1), the NADH dehydrogenase subunit IV, a protein containing Kunitz-type inhibitor domain (papilin-like), identified by SSH, and an antimicrobial peptide (hebraein), was confirmed by RT-qPCR. The effects of knockdown of hebraein and papilin-like encoding genes had no effect on the acquisition of R. rickettsii by the vector. Data of the current study may be used to evaluate the role of other genes in acquisition of R. rickettsii, which, in the future, may be considered as target for vaccine development.

Tumoren entwickeln während einer Chemotherapie häufig Resistenzen gegen strukturell und funktionell unabhängige Zytostatika - ein Phänomen, das als Multidrug-Resistenz (MDR) bezeichnet wird und die Hauptursache für das Scheitern einer Chemotherapie ist. Die klassische MDR ist mit einer Überexpression des ABC-Transporters MDR1/P-gp assoziiert. Der vorliegende gentherapeutische Ansatz beinhaltet eine selektiv gegen MDR1/P-gp gerichtete und vor allem effiziente Strategie zur Überwindung des MDR-Phänotyps humaner Tumorzellen. Basierend auf der Integration verschiedener anti-MDR1 shRNA Expressionskassetten in adenovirale Gentherapievektoren, konnte mit Hilfe der RNA-Interferenz Technologie (RNAi) die MDR1/P-gp Expression selektiv inhibiert werden. Mittels des hoch effizienten Adenovirus Ad5U6/MDR-C wurde die MDR1 mRNA- sowie Protein-Expression soweit reprimiert, dass eine vollständige Aufhebung der biologischen Aktivität der Effluxpumpe MDR1/P-gp und eine Reversion des Resistenz Phänotyps gegenüber den typischen MDR1/P-g-Substraten Daunorubicin (87 % in EPP85-181RDB bzw. 66 % in EPG85-257RDB) sowie Vincristin (96 % bzw. 82 %) resultierte. Zudem wurde gezeigt, dass E1-deletierte und damit replikationsinkompetente Adenoviren in multidrug-resistenten Tumorzellen replizieren können. Damit wirkt Ad5U6/MDR-C in MDR-Tumorzellen onkolytisch. Zwar konnte die Adenovirusreplikation mit dem DNA-Synthese-Hemmer Hydroxyurea (HU) zu 94 % inhibiert werden, die anti-MDR1 Effizienz von Ad5U6/MDR-C wurde dennoch erhöht (+5 % in HeLaRDB, +12 % in EPG85-257RDB), was für eine erfolgreiche und niedrig dosierte Ad-Gentherapie multidrug-resistenter Tumoren in Kombination mit HU ausgenutzt werden kann. Außerdem wurde der entscheidende Einfluss des regulatorischen Proteins YB-1 auf die selektive Replikation von Ad5U6/MDR-C in MDR1/P-gp überexprimierenden Tumorzellen gezeigt. Eine 90 %ige Inhibition von YB-1 bedingt eine Hemmung der Adenovirusreplikation um 70 % und damit eine verringerte Effizienz der RNAi-vermittelten Inhibition von MDR1/P-gp um 40 %. Mit diesem gentherapeutischen Ansatz können die Effekte der YB-1-abhängigen und der die Zelllyse bedingenden Adenovirusreplikation sowie der anti-MDR1 shRNA vermittelten Chemosensitivierung kombiniert und zu einer verbesserten Eliminierung von MDR-Tumorzellen führen. / Simultaneous resistance of cancer cells to multiple cytotoxic drugs, multidrug resistance (MDR), is the major limitation to the successful chemotherapeutic treatment of disseminated neoplasms. The ‘classical’ MDR phenotype is conferred by MDR1/P-glycoprotein (MDR1/P-gp) that is expressed in almost 50% of human cancers. Recent developments in the use of small interfering RNAs for specific inhibition of gene expression have highlighted their potential use as therapeutic agents. DNA cassettes encoding RNA polymerase III promoter-driven siRNA-like short hairpin RNAs (shRNAs) allow long-term expression of therapeutic RNAs in targeted cells. A variety of viral vectors have been used to deliver such cassettes to mammalian cells. In this study, the construction of different adenoviruses for anti- MDR1/P-gp shRNA delivery in different human multidrug-resistant cancer cells was investigated. It could be demonstrated that MDR1/P-gp mRNA and protein expression could be completely inhibited by adenoviral delivery of anti-MDR1/P-gp shRNAs. This down regulation in mRNA and protein expression was accompanied by a complete inhibition of the pump activity of MDR1/P-gp and a reversal of the multidrug-resistant phenotype. Moreover, it could be demonstrated that MDR-tumour cells facilitate adenoviral replication of originally E1- and E3-deleted and thus replication deficient adenoviral vectors through stable relocation of the fundamental regulatory factor YB-1 to the nucleus. To analyse the impact of YB-1 on adenoviral replication, two specific in vitro MDR models were used which stably trigger YB-1 posttranscriptional gene-silencing via the RNA interference (RNAi) pathway, i.e. the MDR cell line EPG85-257RDB well as its drug-sensitive counterpart EPG85-257P. The YB-1 gene-silencing effects of 90 % were accompanied by a reduction of adenoviral gene expression of 70 %. In conclusion, the data demonstrate that an highly efficient adenoviral delivery of shRNAs can chemosensitise human cancer cells and that YB-1 is involved in the regulation of adenoviral gene expression of originally replication deficient Ad-vectors in MDR cancer cells.

Die Infektion mit Filarien (Nematoden) ruft massive Schädigungen beim Menschen hervor. Strategien zur Bekämpfung dieser Parasitose basieren auf einer Massenbehandlung mit Ivermectin und Derivaten. Allerdings ist die Behandlung der Patienten zeitaufwändig und teuer. In diesem Zusammenhang stellt Aufklärung molekularer Mechanismen, die die parasitische Lebensform dieser Würmer ermöglichen, einen neuen Ansatzpunkt für die Entwicklung von Therapeutika und Präventivmaßnahmen dar. Die Moleküle Cystatin und Chitinase wurden, auf Grund ihrer immunodulatorischen und katalytischen Eigenschaften, bei der Nager-Filarie Acanthocheilonema viteae als essentielle Proteine identifiziert. Ziel der vorliegenden Arbeit war daher die detaillierte, funktionale Charakterisierung dieser beiden Proteine. Um das räumliche Expressionsmuster und damit potentielle Funktionen des Sekretionsprotein Cystatins zu ermitteln, wurde der frei lebende Nematode Caenorhabditis elegans als heterologes Expressionssystem genutzt. Unter dem Einfluss des Cystatin-Promoters konnte GFP in pharyngealen und rektalen Zellen von C. elegans exprimiert werden. Möglicherweise ist das Cystatin damit bei A. viteae in den Häutungsprozess involviert, da bei C. elegans derartige Enzyme in den pharyngealen Zellen gespeichert werden. Des Weiteren wurde der Häutungsprozess der infektiösen L3 zum Stadium der L4 durch Ausschalten des Gens mittels RNAi um drei Tage verzögert. Allerdings war der Effekt transient und die Verzögerung des Häutungsprozesses beeinflusste weder die Viabilität noch die Infektiösität der Larven. Die Analyse der Regulation von Cystatin während der Entwicklung des Parasiten mittels der Real-Time PCR zeigte, dass das Gen im Stadium der Mikrofilarien, die der Immunantwort des Wirtes voll exponiert sind, maximal exprimiert wird. Für die Chitinase von A. viteae konnte eine essentielle Rolle im Häutungsprozess nachgewiesen werden. Das Ausschalten des Gens führte zu einer Hemmung der Häutung bei 90 % der L3 und damit zu ihrem Tod. Die maximale Expression im L3 Stadium des Parasiten ist ein weiterer Hinweis darauf, dass dieses Protein in den Häutungsprozess involviert ist. Mittels RNAi bei adulten Parasiten konnte die katalytische Rolle der Chitinase beim Abbau des Chitins im Ei bestätigt werden, da hier nur ungeschlüpfte Mikrofilarien ausgeschieden wurden. Die Ergebnisse dieser Arbeit liefern weitere Hinweise darauf, dass sowohl das Cystatin als auch die Chitinase von A. viteae auf Grund ihrer essentiellen endogenen Funtionen attraktive Zielmoleküle in der Bekämpfung von Filariosen darstellen. / Nematodes which cause filariasis have detrimental effect on humans. Strategies to eliminate this disease are based on mass treatment with drugs like ivermectin. However, they have several drawbacks such as long duration required for treatment and tenuous financial supports. Understanding the molecular mechanisms of genes required for parasitism will help to develop novel therapeutic and preventive strategies. The aim of this study was a detailed functional characterization of cystatin and chitinase of Acanthocheilonema viteae, a rodent filarial nematode. To this end, C. elegans was used as a heterologous system to determine the spatial expression pattern of A. viteae cystatin and chitinase and thereby their possible functions. The promoter of cystatin drove the expression of reporter, GFP, to the pharyngeal and rectal gland cells of transgenic C. elegans lines, this being compatible with the fact that cystatin is secreted in the parasites. This also suggests that cystatin in A. viteae is probably required for moulting since generally in C. elegans the enzymes required for moulting are stored in the pharyngeal gland cells. Moreover, knockdown of cystatin by RNAi delayed moulting of the infective L3 to the L4. However, the RNAi effect was transient and the delay in moulting did not affect the viability and infectivity of the larvae. Analyses of the developmental regulation of cystatin by real-time PCR showed that it is maximally expressed in the blood microfilarial stage, which are exposed to the full force of host immune responses. This is compatible to the fact that A. viteae cystatin immunomodulates the host immune responses. This study also determined that chitinase of A. viteae plays an essential role in the moulting of the L3 larvae since knockdown of chitinase inhibited moulting in 90% of the L3 larvae thereby killing them. Moreover, maximum expression of chitinase was observed by real-time PCR in the L3 stage supplementing that it is involved in moulting. RNAi of chitinase in adults led to the release of unhatched microfilariae confirming the essential catalytic role of chitinase in the degradation of the chitin egg shells. This study substantiates that cystatin and chitinase of A. viteae are attractive intervention targets due to their essential endogenous functions in the parasite.

Chlamydia trachomatis ist ein obligat intrazellulär lebendes Bakterium. Es wird mit einer Vielzahl von Krankheiten in Verbindung gebracht. Das Überleben von Chlamydia trachomatis hängt in nahezu allen Aspekten von der Wirtszelle ab, angefangen bei der Anheftung an die Wirtszelle, über die Invasion, bis zur intrazellulären Replikation. Für ein vollständiges Bild der Pathogenese sind sowohl das Verstehen der dazu beitragenden bakteriellen wie auch Wirtszellfaktoren essenziell. Die vorliegende Arbeit konzentriert sich dabei auf die an der Infektion beteiligten Wirtsfaktoren. Mit Hilfe eines RNA-Interferenz-vermittelten Funktionsverlustscreens wurden 59 Wirtszellgene identifiziert, die einen Einfluss auf die Infektion und Vermehrung von Chlamydia trachomatis hatten. Unter Zuhilfenahme von bioinformatischen Signaltransduktionsweganalyse-Programmen konnten einige der Hits bekannten zellulären Signalnetzwerken, unter anderem dem Ras/Raf/Mek/Erk-Signalweg, zugeordnet werden. Insbesondere der Funktionsverlust zweier validierter Targets, Ras und Raf1, erhöhte das Chlamydien-Wachstum und deren Vermehrung. Bisher wurde angenommen, dass die bei der Chlamydien-Infektion beobachtete Aktivierung der Kinase Erk, die mit der Aktivierung der Phospholipase cPLA2, der Induktion des Interleukins 8 sowie der Stabilisierung des antiapoptotischen Faktors Mcl-1 in Verbindung steht, über den Ras/Raf/Mek-Signalweg vermittelt wird. Ich konnte jedoch zeigen, dass die Chlamydien-induzierte Erk-Aktivierung unabhängig von Ras und Raf1 stattfindet. Vielmehr wird während der Chlamydien-Infektion, Raf1, abhängig von der Kinase Akt, durch Phosphorylierung an Serin259 inaktiviert. Zudem wird das inaktivierte Raf1 zur bakteriellen Inklusion rekrutiert. Dies lässt vermuten, dass das Überleben derChlamydien und deren Wachstum nicht nur von der Erk-Aktivierung und dessen Substrate, sondern auch von der Inaktivierung von Raf1 und dessen Rekrutierung zur Inklusion abhängt. / Chlamydia trachomatis is a Gram-negative obligate intracellular bacterial pathogen with a major impact on human health. As an obligate intracellular pathogen, Chlamydia rely on host cell for all aspects of their survival. Here we present RNAi screen that identified 59 host cell genes influencing C. trachomatis infection and infectivity. Network analysis of hits revealed several prominent signaling networks, including Ras-Raf-MEK-ERK pathway. Knockdown of Ras and Raf1 components of the aforesaid pathway led to increased Chlamydial growth and survival. In Chlamydia infections, ERK activation is believed to be activated through upstream kinases Ras-Raf-MEK and involved in activation of cPLA2, induction of IL8 and stabilization of the anti-apoptotic Mcl-1. However, I could show that ERK activation after Chlamydia infection is independent of Ras and Raf1. Moreover, I also showed that Raf1 is inactivated by phosphorylation at Ser259 in an Akt dependent manner. Consequently, the Ser259 phosphorylated Raf1 was recruited to the Chlamydia inclusion in an Akt and 14-3-3β dependent manner. This strongly suggests that Chlamydia survival and replication in the host cell depends not only on the activation of ERK and its downstream targets such as cPLA2, but also on the inactivation of Raf1 by phosphorylation and recruitment to the inclusion.

Caenorhabditis elegans possui quatro genes de kpcs (kex2/subtilisin-like proprotein convertases): kpc-1, kpc-2/egl-3, kpc-3/aex-5, kpc-4/bli-4. Em C. elegans, dois dos quatro polipeptídeos de vitelogenina encontrados dentro dos ovócitos, YP115 e YP88, se originam a partir de um precursor polipeptídico (VIT-6) clivado pós-traducionalmente após o motivo RGKR. Nematóides transgênicos foram produzidos com construções repórteres transcricionais de GFP. Foi verificada expressão de kpc-1 tanto em neurônios quanto em células musculares e intestinais. Esses dados, aliados aos dados da literatura para os outros genes kpc de C. elegans, sugerem o envolvimento de KPC-1 no processamento de VIT-6, que é secretada por células intestinais. Ensaios de Western-blot compararam o processamento de VIT-6 em nematóides selvagens, mutantes e knock-down por RNAi para os diferentes genes kpc. A análise de nematóides mutantes e knock-down por RNAi combinado para os outros três genes de convertase de C. elegans confirmou a redundância da atividade dessas enzimas no processamento de VIT-6. / Four kpc genes are found in the Caenorhabditis elegans genome: (kex2/subtilisin-like proprotein convertases): kpc-1, kpc-2/egl-3, kpc-3/aex-5, kpc-4/bli-4. Two of the four vitellogenin polypeptides, YP115 and YP88, originate from a precursor, VIT-6. VIT-6 is cleaved post-translationally after the RGKR motif. Transgenic worms carrying GFP transcription reporter constructs were produced. Expression of kpc-1 has been localized to neurons as well as muscular and intestinal cells. These data, together with the ones available from the literature for the other kpc genes, suggest the involvement of KPC-1 in the processing of VIT-6, which is secreted from intestinal cells. Western-blot analysis compared the pattern of VIT-6 processing in wild-type, mutants and RNAi-treated worms for the other kpcs. Analysis of worms treated by combined RNAi confirmed the redundancy of KPCs in VIT-6 processing.

A região N-terminal de OTI-VIT-1 foi expressa e os polipeptídeos recombinantes foram purificados. OTI-VIT-1 pode ser homólogo da vitelina YP170B de C. elegans. Foram identificados um intron na região 5´ e dois na região 3´ do gene Oti-vit-1. Antissoro monoespecífico para PVIT1HisC confirmou que o gene Oti-vit-1 codifica VT1. O polipeptídeo recombinante P40-H, correspondente à região N-terminal da proteína OTI-VIT-6 interage com um polipeptídeo de aproximadamente 100 kDa (P100) presente em extratos proteicos totais de O. tipulae. Estudamos também o papel da Proteína Microssômica Transportadora de Triglicerídeos (MTP) na biossíntese de Vitelogenina do nematoide C. elegans. Ensaios de RNAi em C. elegans, utilizando parte da sequência do gene da MTP (Cel-dsc-4) foram realizados nas linhagens N2 e DH1033. Microscopia de fluorescência de vermes adultos da linhagem DH1033, submetidos a RNAi, mostrou acúmulo de YP170B::GFP no interior dos enterócitos. Este acúmulo sugere a participação da MTP na secreção de VTG. Análise imunológica da vitelogenina nestes mesmos vermes não detectaram alterações no processamento de CEL-VIT-6, sugerindo que o mesmo ocorra não só no pseudoceloma, mas também no interior dos enterócitos. / The N-terminal region of OTI-VIT-1 was expressed and the recombinant polypeptides were purified. OTI-VIT-1 may be homologous to the vitellin YP170B from C. elegans. We identified an intron in the 5 \'region and two in 3\' region from Oti-vit-1. Monospecific antisera to PVIT1HisC confirmed that the gene Oti-vit-1 encodes VT1. The recombinant polypeptide P40-H, corresponding to the N-terminal region of the protein OTI-VIT-6, interacts with a polypeptide of approximately 100 kDa (P100) present in total protein extracts of O. tipulae. The role of microsomal triglyceride transfer protein (MTP) in the biosynthesis of vitellogenin was studied in the nematode C. elegans. Trials of RNAi in C. elegans, using the sequence of the MTP gene (Cel-dsc-4) were performed in the strains N2 and DH1033. Fluorescence microscopy of adult worms of strain DH1033, subjected to RNAi, showed accumulation of YP170B:: GFP within the enterocytes. This accumulation suggests the involvement of MTP in the secretion of VTG. Analysis using anti-vitellogenin immune serum did not detect changes in the processing of CEL-VIT-6, suggesting that it occurs not only in pseudocoelom but also within the enterocytes.

Le réseau de signalisation qui répond à l’insuline et aux nutriments est conservé chez les métazoaires, où il joue un rôle central dans le contrôle du métabolisme et de la croissance. Les nutriments assimilés sont soit directement utilisés pour la croissance tissulaire, soit stockés principalement sous forme de triglycérides. Chez la drosophile, l’activation de ce réseau de signalisation dans le corps gras, un organe qui remplit à la fois les fonctions hépatiques et destockage, induit une augmentation du stockage de lipides sous forme de nombreuses gouttelettes lipidiques (LDs). A l’inverse, la carence alimentaire se traduit par une augmentation de la taille des LDs et une diminution de lipides stockés. La kinase TOR (TargetOf Rapamycine) et son substrat S6 Kinase (S6K) jouent un rôle central dans cette régulation.Chez la drosophile, ces 2 kinases (dTOR et dS6K) contrôlent les aspects autonome-cellulaireset hormonaux de la croissance. En dépit de nombreuses études sur divers organismes modèles,destinées à comprendre les mécanismes régulateurs de S6K, rien n’est connu à ce jour sur lecontrôle de sa dégradation.Nous avons utilisé une banque de lignées exprimant des ARN interférant (RNAi) contre unegrande quantité de gènes de la drosophile, pour réaliser 3 des cribles génétiques destinés à identifier de nouveaux régulateurs du métabolisme et de la croissance. Dans le premier crible,les RNAi ont été induits dans la glande prothoracique, siège de la production de l’hormonestéroïde ecdysone connue pour réguler la croissance et les étapes du développement, souscontrôle de la nutrition et de la signalisation dTOR. Sur 7000 gènes criblés, 620 ont étéidentifiés comme nécessaire à la production d’ecdysone. Dans le second crible, nous avonsexprimé les RNAi de 4000 gènes dans le corps gras pour rechercher ceux qui induisaient uneaugmentation de la taille des LDs. L’objectif était d’identifier des gènes impliqués dans la réponse à la carence alimentaire, et nous avons ainsi retenu 24 candidats intéressants. Le troisième crible représente la majeure partie du travail de thèse, où nous avons criblé les RNAi susceptibles de modifier un phénotype de croissance induit par dS6K. Sur 7000 gènes testés,nous en avons retenu 45 qui ont ensuite été utilisés pour générer un diagramme d’interaction en utilisant les informations disponibles dans les banques de données. Les candidats les plus intéressants ont ensuite été analysés en culture de cellules pour identifier ceux qui régulent l’activité de dS6K et ceux qui régulent sont niveau d’expression. Parmi ces derniers, nousavons identifié le gène codant pour Archipelago (Ago), connue pour contrôler la dégradationrégulée des protéines-cibles au niveau du protéasome. Nous avons réalisé de nombreusesexpériences qui montrent que ago et dS6K interagissent génétiquement. En outre, il est indiquédans les banques de données que ces protéines interagissent entre elles par la technique des 2-hybrides en levure. Tous ces résultats révèlent que Ago régule la dégradation de dS6K, etposent les premières pierres de ce niveau de régulation. / The evolutionary conserved insulin and nutrient signaling network regulates growth andmetabolism. Nutrients are directly utilized for growth or stored, mostly as triglycerides. InDrosophila, activation of insulin/nutrient signaling in the fat body (the fly equivalent of liverand adipose tissue), causes an increase in fat stores composed of several small-size lipiddroplets (LDs). Conversely, fasting produces an increase in LD size and a decrease in fatcontents. The TOR kinase and its substrate S6 kinase (S6K) play a central role in this response,and particularly in Drosophila, they have been shown to orchestrate cell-autonomous andhormone-controlled growth. However, despite extensive research studies on different modelorganisms (mouse, fly, worm) to decipher the molecular and physiological functions of S6K,nothing is known about how its degradation is regulated.Taking advantage of the inducible RNA interfering (RNAi) library from NIG (Japan), we haveperformed three genetic screens to identify novel regulators of steroidogenesis, lipidmetabolism and dS6K-dependent growth. First, RNAi lines were screened in the ring gland; anorgan that controls the progression of the developmental steps by producing the steroidhormone ecdysone. Out of 7,000 genes screened, 620 positive candidates were identified toproduce developmental arrest and/or overgrowth phenotypes. Then, we challenged 4,000 genesby RNAi screening able to recapitulate the larger sized LD phenotype as obtained uponstarvation, leading to the identification of 24 potential candidates. Finally, the RNAi lines werescreened for their ability to enhance a growth phenotype dependent of the Drosophila S6K(dS6K). Out of 7,000 genes screened, 45 genes were identified as potential negative regulatorsof dS6K. These genes were further used to design a novel protein-protein interaction networkcentered on dS6K through the available data from yeast-2-hybrid (Y2H) assay. The most potentinteractors were then analyzed by treatment of cultured S2 cells with the corresponding doublestrand RNA (dRNA). Western blotting thus, allowed us to discriminate between the geneproducts that regulate dS6K levels versus those that regulate its phosphorylation, as a hallmarkfor its kinase activity. Interestingly, archipelago (ago), which encodes a component of an SCFubiquitinligase known to regulate the degradation of dMyc, Cyclin E and Notch, was identifiedas a negative regulator of dS6K-dependent growth. Based on the Y2H available data showingthat Ago and dS6K interact each other and the presence of a putative Ago-interaction motif indS6K, we hypothesized that Ago causes an ubiquitin-mediated degradation of dS6K. Ourmolecular data showed that loss of ago caused an elevated level of dS6K, which confirms arole of Ago in controlling dS6K degradation. Altogether our findings emphasize the importanceof the saturating screening strategies in Drosophila to identify novel regulators of metabolicand signaling pathways.

Bakterielle Infektionen aktivieren den Transkriptionsfaktor NF-κB. Dies trägt sowohl zur Immunantwort, als auch zum Überleben der Wirtszellen bei. In Infektionen mit dem Bakterium Helicobacter pylori stellt diese doppelte Funktion einen mechanistischen Link zwischen der chronischen Entzündung und der Krebsentstehung dar. Für das intrazelluläre Bakterium Legionella pneumophila ist das Überleben der Wirtszelle notwendig für die Vermehrung. Bisher sind jedoch bei beiden Infektionen die Signalwege, die zur NF-κB-Aktivierung führen, nicht ausreichend untersucht. Um NF-κB analysieren zu können, wurden hier monoklonale Zelllinien hergestellt, die ein Fusionsprotein der NF-κB-Untereinheit p65 mit GFP stabil exprimieren. Die Kerntranslokation von p65-GFP kann mit Fluoreszenz-Mikroskopie visualisiert und mit automatischer Bildanalyse quantifiziert werden. Mit dieser Methode konnte zum ersten Mal eine durch ein Bakterium induzierte Oszillation von p65-GFP gezeigt werden. In einem RNAi-basierten Hochdurchsatzscreen wurde diese Methode eingesetzt um neue Faktoren im NF-κB-Signalweg zu identifizieren. Dabei wurde die Infektion mit H. pylori mit den Induktoren TNFα und IL-1β verglichen. Insgesamt wurden 24 Regulatoren identifiziert. Die Identifikation dieser Faktoren vertieft nicht nur unser Verständnis des NF-κB-Signalweges, sondern bietet auch neue molekulare Ziele für mögliche zukünftige Therapien. Bei der detaillierten Analyse der L. pneumophila-induzierten NF-κB-Aktivierung konnte ein einzigartiger, zwei-phasiger Ablauf gezeigt werden. Zunächst verursachte bakterielles Flagellin eine starke, aber kurze Aktivierung. Später war p65 dauerhaft über Stunden im Kern lokalisiert, was eng an die Replikation der Bakterien gekoppelt war. Da die kontinuierliche Kernlokalisation für Transkriptionsfaktoren der NF-κB Familie sehr ungewöhnlich ist, könnte dies ein Hinweis für eine Manipulation durch das Bakterium sein, um das Überleben der Wirtszelle zu sichern. / Infection with pathogens leads to activation of the transcription factor NF-κB. This contributes both to the immune response as well as survival of host cells. In infection with the bacterium Helicobacter pylori, this dual function provides a mechanistic link between the chronic inflammation and cancer development. In infection with the intracellular pathogen Legionella pneumophila, the survival oft he host cell is necessary for replication. However, in both infections, the signaling pathways leading to NF-κB activation are not well understood. Here, in order to investigate NF-κB activation, monoclonal cell lines were generated that stably express the NF-κB subunit p65 fused to GFP. Nuclear translocation of p65-GFP can be visualized by fluorescence microscopy and quantified by software-based picture analysis. Using this technology, oscillations of p65-GFP nuclear translocation could be shown after H. pylori infection. To identify new factors important for NF-κB activation, the new assay was used to conduct an RNAi-based screen. In the screen, infection with H. pylori was compared to induction with the cytokines TNFα and IL-1β. In total, 24 key regulators for NF-κB were identified. The identification of these factors broadens our understanding of NF-κB signaling and could provide targets for future therapies. Finally, detailed observation of NF-κB activation induced by L. pneumophila in single cells revealed a unique, biphasic NF-κB activation. During the first hours, bacterial flagellin induced strong but transient activation. Then, p65 translocated continuously to the nucleus over hours without oscillation. Testing an array of bacterial mutants, a tight link between bacterial replication and continuous NF-κB activation could be shown. Because this continuous nuclear localization is very unusual for a transcription factor of the NF-κB family, this indicates that L. pneumophila could manipulate NF-κB to ensure host cell survival.

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No description available.