Mutation, whether spontaneous or induced, is the premier tool for understanding gene function. One approach is to create mutations in a specific gene, and then use the resulting cell or organism to search for a phenotype. An alternative is to create mutations at random, and focus first on the identification of phenotypes. The mutation that underlies a phenotype can then be tracked down, forming the foundation of testable hypotheses. Using random chemical mutagenesis in mice, I have identified 20 heritable phenotypes affecting either the innate or adaptive branches of immunity. The genetic basis of 18 of these phenotypes was solved, caused by mutations in at least 16 unique genes. Five of these genes were not previously known to be involved in immunity, and a detailed analysis of four of them is provided in this thesis. These include genes encoding the following proteins: the inactive rhomboid protease iRhom2, which is specifically required for the secretion of tumour necrosis factor alpha; the hypothetical phospholipid flippase ATP11C, required for B cell development in the adult bone marrow; the folliculin-interacting protein FNIP1, also required for B cell development; and the zinc finger transcription factor ZBTB1, essential for the development of all lymphocyte lineages. These findings uncover new entry points for the understanding of mammalian immunity, and highlight the value of mouse forward genetics in the understanding of mammalian phenomena in general.

The type 1 insulin-like growth factor receptor (lGF-1 R) plays a significant role in tumor growth and spread, and IGF-1 R inhibitors and antibodies are now undergoing clinical testing. However, factors that regulate sensitivity to IGF-1 R inhibition remain unclear. The aim of this project is to identify proteins whose depletion regulates sensitivity to IGF-1 R inhibition, in order to design effective combination treatments to benefit patients. An IGF-1 R kinase inhibitor, AZ12253801 (provided by AstraZeneca) was able to block IGF-induced phosphorylation of IGF-1 R in DU145 prostate cancer and MCF-7 breast cancer cells, inhibited downstream signalling in DU145 cells, and also inhibited proliferation and cell survival of both cell lines. AZ12253801 was used in an unbiased siRNA screen in both cell lines, using two s'iRNA libraries (779 kinase-related Kinome and 230 DNA repair-associated siRNAs). Eight Kinome and five DNA repair-associated hits have been identified after primary and second round screens, and further validated. The strongest hit was dishevelled homolog 3 (DVL3), a member of the WNT signalling pathway, which is highly expressed in both cell lines. DVL3 silencing caused reduction in active l3-catenin and inactivated the mTOR pathway, consistent with previous studies, and did not affect IGF-1 Rand AKT activity. However, DVL3 silencing led to activation of MEK1/2-ERK1/2 in serum-starved cells and sensitized this pathway to IGF-1 stimulation, with translocation of ERK1/2 into the nucleus and increased expression of ERK1/2 target genes. A DVL PDZ domain inhibitor (DVLi) showed similar effects on active l3-catenin, mTOR signalling and ERK1/2 signalling activity. The administration of DVLi increased sensitivity to AZ12253801 in cell lines with detectable ERK1/2 activation, but not prostate cancer cells in which ERK signalling was suppressed and AKT was activated in the context of loss of functional PTEN. Furthermore, DVL3 regulated activation of ERKs by influencing signaling downstream of the IGF-1 R and upstream of RAS, and DVL3 was found in a complex with the adaptor proteins GRB2 and DAB2. GRB2 knockdown was capable of abolishing ERK1/2 activation induced by DVLi, further implicating involvement of GRB2, and DAB2 silencing sensitized to IGF-1 R inhibition, mimicking effects of DVL3 depletion. Taken together, DVL3 silencing or inhibition enhances sensitivity to IGF-1 R inhibition by negatively regulating the ERK1/2 signaling pathway. These investigations shed new light on the factors that regulate IGF signaling, and provide a rational basis for design of clinical trials of IGF-1 R inhibitors.

(no abstract available)

In Drosophila, the insulin signaling pathway is at the interface between dietary conditions and control of growth and development, reproduction, stress responses and life span. Eight insulin like peptides (Dilp1-8), an insulin tyrosine kinase receptor (dInR) and its downstream components, as well as a relaxin-like receptor type (Lgr3) form the core of this signaling. Here we showed that the dInR mediates post-mitotic cell growth specifically in about 300 peptidergic neurons expressing the basic helix loop helix (bHLH) transcription factor Dimmed (Paper I).  Overexpression of dInR in Dimm positive neurons leads to increased size of cell body, Golgi apparatus and nucleus, whereas dInR knockdown causes an opposite effect. Manipulation of downstream components of insulin signaling induces similar changes in Dimm positive neurons. This mechanism is nutrient dependent. In Paper II, we further investigate the relation between Dimmed and dInR for regulation of cell growth. Coexpressing Dimm and dInR in a range of Dimm negative neurons results in increased cell size in both larval and adult stages. We provide further evidence that dInR regulates cell growth in a Dimm dependent manner and that DILP6 from glia cells is involved in this regulation. In addition, we find that Dimm alone is capable of triggering cell growth in certain neuron types at different developmental stages. Furthermore, ectopic Dimm alone can block apoptosis.  Dimm is a known master regulator of peptidergic cell fate. In paper III we find that ectopic expression of Dimm in Dimm negative motor neurons results in transformation the neurons towards a neuroendocrine phenotype. They acquire enlarged axon terminations and boutons, lose both pre- and postsynaptic markers, and display diminished levels of wingless and its receptor dFrizzled. Furthermore they show increased expression of several Dimm targets. Finally, combined ectopic Dimm and dInR expression gives rise to stronger phenotypes. In paper IV we studied another DILP possibly involved in growth regulation, the under-investigated DILP1. We generated Dilp1-Gal4 lines and anti DILP1 antibodies and found that DILP1 is transiently expressed in brain insulin producing cells (IPCs) from pupal stages to newly hatched adult flies. Diapausing virgin female flies display a high expression level of dilp1/DILP1 over at least 9 weeks of adult life. DILP1 expression is also correlated with the persistence of larval/pupal fat body and its expression is regulated by other DILPs and short neuropeptide F (sNPF). Flies mutant in dilp1 display increased food intake, but decreased stress resistance and life span. We found no obvious role of DILP1 in growth regulation. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.</p>

Memoria para optar al título de Químico Farmacéutico / El daño ocasionado por la ocurrencia de un infarto cardiaco es complejo, generando la pérdida de viabilidad de las células cardiacas entre otros efectos deletéreos ocurridos tanto en el periodo isquémico de falta de oxígeno y nutrientes, así como también en la posterior reperfusión sanguínea. Frente a esta condición patológica los fibroblastos cardiacos (FC) son capaces de reaccionar, secretando y renovando la matriz extracelular; lo que los convierte en elementos celulares claves en la cicatrización y remodelamiento del tejido cardiaco dañado post-infarto al miocardio. Esto hace necesario el intentar regular la viabilidad de estas células para una correcta cicatrización y mantención de la función cardiaca. En relación a esto se ha reportado el efecto cardioprotector ejercido por el empleo de LPS en condiciones de daño celular causado por isquemia/reperfusión (I/R). Sin embargo, dicho efecto ha sido descrito principalmente en cardiomiocitos, por lo que su efecto en FC es aún desconocido. Nuestro trabajo estudió la capacidad cito-protectora ejercida por LPS sobre FC de ratas neonatas sometidos a un modelo de I/R in vitro e indagó las vías transduccionales implicadas en este efecto. El tratamiento de los FC con LPS (1 μg/mL) durante la isquemia y reperfusión previno la pérdida de viabilidad inducida por I/R. Sin embargo, en el pre-condicionamiento con LPS durante 24 o 16 h, y en el tratamiento con LPS durante la isquemia o reperfusión, no se observó el efecto cito-protector. En esta misma línea, demostramos que el efecto cito-protector ejercido por LPS es mediado a través del receptor TLR4 vía PI3K/Akt y ERK1/2, ya que el empleo de TAK-242, Ly29002 y PD98059, inhibidores del receptor y de las vías transduccionales respectivamente, bloquearon completamente el efecto cito-protector. La activación de TLR4 por LPS previno, además, el procesamiento de la procaspasa 8 y 3 inducido por I/R. Conjuntamente, demostramos que las vías PI3K/Akt y ERK1/2 participaban en la prevención del procesamiento de la procaspasa 8 ejercido por LPS, pero no tuvieron efecto en la activación de la caspasa 3. Nuestros resultados dan cuenta del efecto cito-protector y antiapoptótico ejercido por LPS a través de TLR4 vía PI3K/Akt y ERK1/2 frente a la muerte de FC inducida por I/R / The damage caused by a myocardial infarct is complex, causing cardiac cell viability loss, among other deleterious effects that occur during the ischemia period, such as lack of oxygen and nutrients; as well as the posterior reperfusion with blood. In this situation, cardiac fibroblasts react by secreting proteins and renewing the extracellular matrix. These properties make them a key element in the scar and remodeling process of the injured cardiac tissue. Thus, the viability of these cells are required to preserve the correct functioning of the heart. In this regard, the use of LPS as a cytoprotector agent in cardiac Ischemia/reperfusion (I/R) has been reported. However such effect has been described mostly in cardiomyocytes cells, whereas its role in cardiac fibroblasts remains unknown. Our work studied the LPS cytoprotector effect in neonate cardiac fibroblast exposed to an in vitro model of I/R, and transductional pathways involved in this process were explored. Incubation with LPS (1μg/mL) during both ischemia and reperfusion periods prevented the I/R-induced cell loss. However, LPS used only during preconditioning, ischemia or reperfusion did not induced cytoprotection. Furthermore we demonstrated that the LPS-dependent protective effects were completely abolished when TLR4 receptor (TAK-242), and PI3K/Akt and ERK1/2 (Ly29002 and PD98059, respectively) inhibitors were used. These data suggest that LPS-dependent cytoprotector effects are mediated through TLR4 receptor activation and PI3K/Akt and ERK1/2 signalling pathways. Additionally the activation of TLR4 by LPS prevented the cleave of procaspases 3 and 8 induced by I/R. Both PI3K/Akt and ERK1/2 were necessary for the prevention of the caspase 8 activation, but not of caspase 3. Our results conclude that LPS protects cardiac fibroblasts from I/R apoptosis by the activation of TLR4 and both PI3K/Akt and ERK1/2 signalling pathways / FONDECYT

<p>The design and application of effective drug carriers is a fundamental concern in the delivery of therapeutics for the treatment of cancer and other vexing health problems. Traditionally utilized chemotherapeutics are limited in efficacy due to poor bioavailability as a result of their size and solubility as well as significant deleterious effects to healthy tissue through their inability to preferentially target pathological cells and tissues, especially in treatment of cancer. Thus, a major effort in the development of nanoscopic drug delivery vehicles for cancer treatment has focused on exploiting the inherent differences in tumor physiology and limiting the exposure of drugs to non-tumorous tissue, which is commonly achieved by encapsulation of chemotherapeutics within macromolecular or supramolecular carriers that incorporate targeting ligands and that enable controlled release. The overall aim of this work is to engineer a hybrid nanomaterial system comprised of protein and silica and to characterize its potential as an encapsulating drug carrier. The synthesis of silica, an attractive nanomaterial component because it is both biocompatible as well as structurally and chemically stable, within this system is catalyzed by self-assembled elastin-like polypeptide (ELP) micelles that incorporate of a class of biologically-inspired, silica-promoting peptides, silaffins. Furthermore, this methodology produces near-monodisperse, hybrid inorganic/micellar materials under mild reaction conditions such as temperature, pH and solvent. This work studies this material system along three avenues: 1) proof-of-concept silicification (i.e. the formation and deposition of silica upon organic materials) of ELP micellar templates, 2) encapsulation and pH-triggered release of small, hydrophobic chemotherapeutics, and 3) selective silicification of templates to potentiate retention of peptide targeting ability.</p> / Dissertation

Der Mechanismus, welcher den GPCR eine Unterscheidung verschiedener Liganden ermöglicht, ist immer noch ungeklärt. Der GPCR für PTH und PTHrP (=PTH1-R) bindet PTH und das strukturell recht unterschiedliche PTHrP. Beide Liganden aktivieren mit etwa vergleichbarer Potenz eben diesen PTH1-R, indem sie sowohl an die intrazelluläre AC als auch an die PLC ankoppeln. Ein vor einigen Jahren überraschend kloniertes neues Mitglied der Sekretin/PTH/Calcitonin-Familie (= Familie B) der GPCR, der PTH2-R, antwortet jedoch nur nach Bindung von PTH bzw. TIP 39, nicht aber nach PTHrP, mit einem intrazellulären cAMP-Signal. Allerdings sind weder hPTH noch TIP39 in der Lage, eine intrazelluläre IP3-Antwort auszulösen. Welche strukturellen Gegebenheiten des PTH2-Rezeptors ermöglichen diese effiziente Ligandendiskriminierung? Analysen der Rezeptor-Liganden-Interaktion und die Aufklärung dieses Komplexes sind ein Schlüsselelement im Design spezifischer Rezeptoragonisten und –antagonisten mit bedeutendem therapeutischen Potential. Eine hochkonservierte Eigenschaft aller Rezeptoren der Familie B der GPCR ist die Lokalisation von sechs extrazellulären Cysteinen, die sowohl zur Expression intakter Rezeptoren von Nöten sind als auch durch mögliche Disulfidbrückenbildung untereinander einen entscheidenden Einfluss auf das Bindungsverhalten ausüben. Die Hypothese der vorliegenden Arbeit ist, dass zwei Cysteine, präsent in der 3. Extrazellulärschleife des PTH2-R, nicht aber in der des PTH1-R, dessen Ligandenspezifität bedingen. Tatsächlich führte das Ausschalten eines entsprechenden Cysteins im Opossum-PTH2-R zu einem exprimierten Rezeptor, der PTHrP zu einem gewissen Grad binden und daraufhin auch den AC/cAMP-Signalweg aktivieren konnte. (184) Es liegt daher die Vermutung nahe, dass diese beiden Cysteine des PTH2-R entweder durch Disulfidbrückenbildung untereinander oder zu den restlichen Cysteinen in der extrazellulären Region die sterische Konfiguration der Rezeptoren und somit auch deren Bindungs- und Signalverhalten ändern können. Auf diesen Ergebnissen und Annahmen basierend, war daher Gegenstand diesen Projekts zunächst das Einfügen verschiedener Punktmutationen in die cDNA des humanen PTH1-R. Es wurden Konstrukte konzipiert zur Einfügung beider Cysteine einzeln (Ala426Cys und Tyr443Cys) oder kombiniert (Ala426Cys/Tyr443Cys). Nach Expression der drei mutierten Rezeptoren und beider Wildtyp-Rezeptoren war Ziel, das Ligandenbindungsverhalten und somit die Expression intakter Rezeptoren an der Zelloberfläche zu untersuchen. Studien des Signalverhaltens bezüglich des AC/cAMP- und des PLC/IP3- Signalwegs, ebenso wie Internalisierungsassays strebten dann die vollständige Charakterisierung der mutierten Rezeptoren an. / Cysteine residues are structurally important for the function of the PTH-1 receptor (PTH1R), probably by forming disulfide bridges. The more recently discovered PTH-2 receptor (PTH2R) differs from the PTH1R by not recognizing PTH-related protein (PTHrP). We hypothesized, that two cystein residues present in the thrid loop of the PTH2R, but not in the PTH1R, might cause this ligand specificity. In fact, eliminating one of the corresponding cysteine residues in the opossum PTH2R resulted in recognition of PTHrP, in contrast to wildtype PTH2R (P Turner et al (1998) J Biol Chem 273: 3830-3837)

In this study, the role of histone-like proteins in gene regulation in uropathogenic Escherichia coli isolate 536 was monitored. The histone-like nucleoid structuring protein H-NS is a global regulator in Escherichia coli that has been intensively studied in non-pathogenic strains. No comprehensive study on the role of H-NS and it’s homolog StpA on gene expression in a pathogenic E. coli strain has been carried out so far. Moreover, we identified a third, so far uncharacterized member of the H-NS-like protein family in uropathogenic E. coli isolate 536, which was designated Hlp (H-NS-like protein). Hlp is a 134-amino acid protein, which shares 58 % sequence identity with H-NS. The gene coding for the Hlp protein, hlp, is found in several uropathogenic E. coli variants, but not in non-pathogenic E. coli K-12. In UPEC strains 536 and CFT073, Hlp is encoded on a possibly horizontally acquired 23-kb genomic region inserted into the serU locus. Studies on hlp transcription revealed, that the gene is transcribed monocistronically from a single promoter and that expression is repressed by H-NS. Purified Hlp protein was binding to its own and to the hns promoter, thereby mediating negative auto- and crossregulation. Furthermore, Hlp and H-NS were directly interacting, resulting in the formation of stable heteromers. Complementation studies with hns mutant strains in a K-12 background revealed that the Hlp protein had in vivo activity, being able to complement the lack of H-NS in terms of motility, growth, and repression of the proU, bgl, and clyA genes. When analyzing the role of the histone-like proteins in expression of virulence-associated genes by using DNA arrays and classical phenotypic assays, most of the observed effects were mediated by the H-NS protein alone. Expression profiling revealed that transcript level of more than 500 genes was affected by an hns mutation, resulting in increased expression of alpha-hemolysin, fimbriae and iron-uptake systems, as well as genes involved in stress adaptation. Furthermore, several other putative virulence factors were found to be part of the H-NS regulon. On the other hand, no effect of StpA alone was observed. An hns stpA double mutant, however, exhibited a distinct gene expression pattern that differed in great parts from that of the hns single mutant. This suggests a direct interaction between the two homologs and the existence of distinct regulons of H-NS and an H-NS/StpA heteromeric complex. Although the H-NS protein has – either as homomer or in complex with StpA – a marked impact on gene expression in pathogenic E. coli strains, its effect on urovirulence is ambiguous. At a high infection dose, hns mutants accelerate lethality in murine UTI and sepsis models relative to the wild type, probably due to increased production of alpha-hemolysin. At lower infectious dose, however, mutants lacking H-NS are attenuated through their impaired growth rate, which can only partially be compensated by the higher expression of numerous virulence factors. As seen with StpA, an hlp single mutant did not exhibit a notable phenotype under standard growth conditions. A severe growth defect of hns hlp double mutants at low temperatures, however, suggests a biological relevance of H-NS/Hlp heteromers under certain circumstances. Furthermore, these mutants expressed more capsular polysaccharide and curli fimbriae, thereby indicating a distinct role of H-NS and Hlp in regulation of these surface structures. The H-NS paralogs Hlp and StpA also modulated H-NS-mediated regulation of fimbrial adhesins, and are oppositely required for normal growth at low or high temperatures, respectively. Finally, expression levels of the three histone-like proteins H-NS, StpA and Hlp itself varied with different temperatures, thereby suggesting a flexible composition of the nucleoid-associated protein pool. Hence, we propose that the biological role of Hlp and StpA does not rely on a distinct function of the single protein, but rather on their interaction with the global regulator H-NS. / In dieser Studie wurde die Rolle von Histon-ähnlichen Proteinen bei der Genregulation im uropathogenen Escherichia coli (UPEC) Isolat 536 untersucht. Das Histon-ähnliche Protein H-NS (engl. histone-like nucleoid structuring protein) ist ein globaler Regulator in E. coli, der in apathogenen Stämmen eingehend untersucht worden ist. Im Gegensatz dazu liegen noch keine umfassenden Studien zur Rolle von H-NS und des homologen Proteins StpA in einem pathogenen E. coli Stamm vor. Zudem konnten wir ein drittes, bis jetzt noch nicht charakterisiertes Mitglied der Familie von H-NS-ähnlichen Protein im uropathogenen E. coli Isolat 536 identifizieren, das Hlp benannt wurde (für H-NS-like protein). Hlp ist ein aus 134 Aminosäuren bestehendes Protein, dessen Sequenz zu 58 % identisch mit der des H-NS Proteins ist. Das Gen, das für das Hlp Protein kodiert, hlp, konnte in zahlreichen uropathogenen und Fäkalisolaten nachgewiesen werden, jedoch nicht im apathogenen E. coli K-12. In den UPEC Isolaten 536 und CFT073 ist das hlp Gen auf einer 23-kb großen genomischen Insel lokalisiert, die in den serU Lokus inseriert ist und möglicherweise über horizontalen Gentransfer erworben wurde. Untersuchungen zur Transkription des hlp Gens ergaben, dass das Gen monocistronisch von einem einzigen Promotor transkribiert, und dessen Expression durch H-NS reprimiert wird. Rekombinantes Hlp Protein war befähigt, sowohl an seinen eigenen, als auch an den hns Promotor zu binden, was zu negativer Auto- und Kreuzregulation führte. Zudem konnte gezeigt werden, dass Hlp und H-NS direkt miteinander interagieren, was zu stabilen Heteromeren führte. Komplementierungsstudien in hns Mutanten einiger K-12 Stämme ergaben, dass das Hlp Protein über in vivo Aktivität verfügt, was es befähigte, die Abwesenheit von H-NS bei zahlreichen Phänotypen wie z.B. Motilität, Wachstum, und Repression der proU, bgl und clyA Gene zu komplementieren. Die Rolle der Histon-ähnlichen Proteine bei der Expression von Virulenz-assoziierten Genen wurde mittels DNA Array Technologie, sowie klassischen phänotypischen Tests analysiert. Dabei wurden die meisten der beobachteten Effekte einzig durch das H-NS Protein bedingt. Die Expressionsstudien ergaben, dass über 500 Gene von einer hns Mutation beeinflusst wurden, was eine verstärkte Expression des alpha-Hämolysins, mehrerer Fimbrien und Eisenaufnahmesysteme sowie von Genen, die in Stress-Antworten involviert sind, bedingte. Des Weiteren konnten zahlreiche putative Virulenzfaktoren dem H-NS-Regulon zugeordnet werden. Andererseits konnten keine Effekt durch StpA beobachtet werden. Eine hns stpA Doppelmutante wies jedoch ein eindeutiges Expressionsmuster auf, das in großen Teilen von dem der hns Einzelmutante abwich. Dies legt nahe, dass beide Proteine direkt miteinander interagieren, was das Auftreten von unterschiedlichen Regulons zur Folge hat, die entweder durch H-NS oder einem heteromeren H-NS/StpA Komplex beeinflusst werden. Obwohl das H-NS Protein – entweder als Homomer oder als Komplex mit StpA – einen sehr starken Einfluss auf die Genexpression pathogener E. coli Stämme nimmt, bleiben dessen Effekte auf die tatsächliche Virulenz im Urogenitaltrakt unklar. In einem experimentellen Mausmodell der aufsteigenden Harnwegsinfektion bewirken hns Mutanten, in hoher Dosis verabreicht, eine rasch eintretende Lethalität, was vermutlich der verstärkten Produktion von alpha-Hämolysin zuzuschreiben ist. In verringerter Dosis verabreicht, sind diese Mutanten durch ihre langsameren Wachstumsraten jedoch attenuiert, was nur teilweise durch die vestärkte Expression zahlreicher Virulenzfaktoren kompensiert werden kann. Wie schon bei StpA beobachtet, besitzt eine hlp Mutante keinen offensichtlichen Phänotyp, zumindest unter Standard-Wachstumsbedingungen. Jedoch macht sich in hns hlp Doppelmutanten ein starker Wachstumsdefekt bei erniedrigten Temperaturen bemerkbar, was eine biologische Relevanz von H-NS/Hlp Heteromeren unter bestimmten Bedingungen nahe legt. Des Weiteren exprimierten diese Mutanten erhöhte Mengen an Kapsel-Polysacchariden und Curli-Adhesin, was als Indiz für eine besondere Rolle für H NS und Hlp bei der Regulation dieser Oberflächenstrukturen dienen kann. Zudem hatten beide H-NS-Paraloge Hlp und StpA einen modulierenden Effekt bei der H-NS-vermittelten Regulation weiterer Fimbrien-Adhesine und waren in gegenläufigen Maßen für normales Wachstum bei erhöhten bzw. erniedrigten Temperaturen notwendig. Zuletzt variierte das Expressionsniveau der drei Histon-ähnlichen Proteine H-NS, StpA und Hlp bei unterschiedlichen Temperaturen, was auf eine flexible Zusammensetzung verfügbarer Nucleoid-assoziierter Proteine hindeutet. Dies alles impliziert, dass die biologische Relevanz von Hlp, und StpA gleichermaßen, nicht auf gesonderten Funktionen des einzelnen Proteins beruht, sondern vielmehr auf deren Interaktionen mit dem globalen Regulatorprotein H-NS.

Toll-like Rezeptoren (TLR) und Nod-like Rezeptoren (NLR) sind Muster-erkennende Rezeptoren des angeborenen Immunsystems, die bakterielle Zellwandbestandteile erkennen können. Interleukin (IL)-1beta ist ein streng reguliertes Zytokin. Durch eine erste Stimulation wird der TLR-Rezeptor ausgelöst und führt zur Expression des Vorläuferproteins proIL-1beta. Durch einen zweiten Stimulus wird ein zytoplasmatischer NLR-Rezeptor zur Caspase1-Aktivierung angeregt. Dies führt zur post-translationalen Reifung von proIL-1beta zu reifem IL-1beta und zur Aktivierung weiterer Mechanismen der Pathogen-Eliminierung während einer bakteriellen Meningitis. Im ersten Teil dieser Arbeit wurde die synergistische Beziehung zwischen TLRs und NOD2 in Bezug auf die IL-1beta-Sekretion in Astrozyten und Mikroglia untersucht. Primäre murine WT-Astrozyten und eine humane Zelllinie, die mit Lipopolysaccharid (LPS) oder Lipopeptid sowie Muramyldipeptid (MDP) stimuliert wurden, zeigten signfikant erhöhte IL-1beta-Werte. IL-1beta war in NOD2-/- Astrozyten nicht erhöht. NOD2 trägt demnach als MDP-ausgelöster Rezeptor in Astrozyten, vermutlich zusammen mit dem Inflammasom-Komplex, zur Caspase-1-Aktivierung bei. In Mikrogliazellen lässt sich der bei Astrozyten gezeigte Effekt nicht reproduzieren. Zum ersten Mal wurde gezeigt, dass die TLR-abhängige IL-1beta-Antwort durch NOD2-Beteiligung in murinen und humanen Astrozyten synergistisch erhöht wird. In einem weiteren Versuchsteil wurde in primären murinen Peritonealmakrophagen von adulten Mäusen der TLR/NLR-Synergismus untersucht. Es stellte sich überraschenderweise heraus, dass weibliche NOD2-/- Mäuse zu einer synergistisch erhöhten IL-1beta-Sekretion fähig waren. SiRNA-Versuche mit in Östrogen vorinkubierten RAW264.7-NOD2-/- Zellen zeigten eine eindeutige Synergie der TLR4- und NOD2-Rezeptoren in der IL-1beta-Ausschüttung. Östrogen scheint weiblichen Individuen einen protektiven Vorteil vor Infektionen bei NOD2-Defizienz zu verschaffen. / Toll-like receptors (TLR) and nod-like receptors (NLR) are pattern-recognition receptors that recognize lipopolysaccharide (LPS), lipopeptides and myramyldipeptide (MDP) derived from bacterial cell wall. We focus our question on the regulation of the pro-inflammatory cytokine interleukin (IL)-1beta during bacterial meningitis in primary murine astrocytes and microglia as well as cell lines and the synergism of TLR4 or TLR2 and NOD2 to amplify IL-1beta-expression. ProIL-1beta is expressed by TLR-stimulation and activation of NF-kB signal transduction. Through the activation of Caspase-1, possibly through NOD2 and the inflammasome, proIL-1beta is cleaved on post-translational level and obtains its activated status, leading to pathogen elimination during bacterial meningitis. Primary murine WT-astrocytes and a human cell line primed with LPS or lipopeptide and stimulated with MDP show significantly increased IL-1beta levels in the supernatant. NOD2-/- astrocytes do not show elevated IL-1beta levels. After screening of cytoplasmic proCaspase-1 and activated Caspase-1 by Western blot it became clear, that stimulation of NOD2 with MDP led to Caspase-1 activation and thus to IL-1beta maturation in primary murine WT-astrocytes. We demonstrate for the first time that the synergism between TLR4 and NOD2 leads to significantly elevated IL-1beta levels and that NOD2 is capable of activating caspase-1 in primary murine astrocytes. Another part of the work was to test the TLR/NLR-synergism on primary peritoneal macrophages from adult mice. Surprisingly, female NOD2-/- mice showed significantly elevated IL-1beta levels. SiRNA- and stimulation-experiments with RAW264.7-NOD2-/- cells pre-incubated in estrogen show a clear synergy in IL-1beta secretion through TLR4 and NOD2 receptors. Estrogen seems to protect females from infection when having a NOD2 deficiency.

My dissertation consists of two essays on mutual funds. The first essay examines the role of extreme positive returns on future fund flows using maximum style-adjusted daily returns (hereafter MAX) over the previous month. My results suggest that there is a positive and significant relation between MAX and future fund flows. The results are robust to controls for fund performance, fund size, age, turnover, fund fees, volatility, and skewness of fund returns. Of particular interest, this relation exits only in retail funds. Moreover, MAX is persistent from one month to the next, but MAX-based investment strategies are associated with lower risk-adjusted returns than investors could have achieved in otherwise similar funds. Overall, my analysis suggests that mutual fund investors are attracted to maximum style-adjusted daily returns, which is in line with the theoretical argument that investors exhibit a preference for lottery-like payoffs. These investors are successful in achieving a lottery-like return profile, but this strategy is costly in terms of expected returns The second essay studies the effect of recent and long-term mutual fund performance on future fund flows. I document that investors' response to recent performance depends on average long-term performance. In particular, a recent loser fund experiences outflows only if its longer-term performance is also poor. Similarly, recent good performance leads to more inflows only if the fund has also good long-run performance. In contrast, investors ignore recent performance if it provides a signal that conflicts with the longer-term signal. This implies that good fund managers with a longer-term focus will find it easier to attract future inflows than managers with a short-term horizon.