No description available.

Chlamydia are obligate intracellular bacterial pathogens that are responsible for infectious blindness, sexually transmitted infections, and acute respiratory disease in humans. These pathogens undergo an essential biphasic developmental cycle differentiating between two functionally distinct forms known as the infectious elementary body (EB) and the replicative reticulate body (RB). Identifying the signals and regulatory mechanisms that enable Chlamydia to establish infection, differentiate between the two developmental forms, and survive within the host cell is critical to understanding chlamydial pathogenesis and developing future therapeutic strategies. In pathogenic bacteria, serine, threonine, and tyrosine (Ser/Thr/Tyr) protein kinases and phosphatases are critical for development, metabolism, and virulence. Chlamydia encode two validated protein kinases (pkn1 and pknd), a putative protein phosphatase (ctl0511; CppA), and appear capable of global phosphorylation that differs between the developmental forms. While these findings support a role for protein phosphorylation in chlamydial pathogenesis, a validated cognate protein phosphatase for Pkn1 and PknD mediating reversible phosphorylation was lacking. We hypothesized that CppA is the partner phosphatase for the chlamydial protein kinases, and in this study we validated and characterized CppA as a broad specificity protein phosphatase type 2C. Using in vivo and in vitro approaches we demonstrated that CppA acts on P-Ser/Thr/Tyr residues and can dephosphorylate multiple chlamydial protein substrates including PknD and the FHA 2 domain of CdsD, a component of the type 3 secretion apparatus. The importance of CppA for chlamydial growth and development was determined using a chemical “knock-out” approach and study of CppA missense mutations identified in slow growing C. trachomatis L2 chemical mutants. Treatment of C. trachomatis L2, C. trachomatis D, and C. muridarum with CppA inhibitors significantly reduced progeny levels and inclusion size in a time dependent manner with more significant growth inhibition in the first 12 hours post infection. Collectively, our findings support that CppA works in conjunction with PknD, and likely Pkn1, to mediate reversible phosphorylation of multiple protein substrates leading to changes in chlamydial physiology that appear to be key for early steps in development.

No description available.

Prostate cancer is the second most often diagnosed cancer and internationally the sixth foremost cause of cancer death in males, as of 2011. Within the United States it is the most common form of cancer in men with 186,000 new cases and with an overall 28,600 deaths in 2008, and it is the second leading kind of cancer-related death in men. The widespread threat that prostate cancer poses against men across the globe cannot be understated, and its initiation and progression must be understood in order to truly comprehend its implicated risks and possible forms of treatment. As its name implies, prostate cancer is a form of cancer that develops in the prostate gland located in the male reproductive system. Its progress starts when standard semen-secreting prostate gland cells mutate into cancer cells. Although its developments may start at the prostate gland, cancer cells may metastasize to other parts of the body through circulation systems such as the lymph nodes. The main sites of metastasis for prostate cancer include the adrenal gland, the bones, the liver and the lungs. Although there are treatments available for prostate cancer, there is no definitive cure. The primary goal of this project was to find an alternative form of treatment, which is what will be necessary to combat this cancer.

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Cell division is essential for spore formation but not for viability in the filamentous streptomycetes bacteria. Failure to complete cell division instead blocks spore formation, a phenotype that can be visualized by the absence of gray (in Streptomyces coelicolor) and green (in Streptomyces venezuelae) spore-associated pigmentation. The streptomycetes divisome is however, similar to that of other prokaryotes. We hypothesized chemical inhibitors of sporulation in model streptomycetes might interfere with cell division in rod shaped bacteria. To test this, we investigated 196 compounds that inhibit sporulation in Streptomyces coelicolor. We show that 19 of these compounds cause filamentous growth in Bacillus subtilis, consistent with impaired cell division. One of the compounds is a DNA damaging agent and inhibits cell division by activating the SOS response. The remaining 18 act independently of known stress responses and may therefore act on the divisome or on divisome positioning and stability. Three of the compounds (Fil-1, 2 and 3) confer distinct cell division defects on B. subtilis. They also block B. subtilis sporulation, which is mechanistically unrelated to the sporulation pathway of streptomycetes but which is also dependent on the divisome. We discuss ways in which these differing phenotypes can be used in screens for cell division inhibitors. In addition to the molecules affecting the divisome, DNA and cell wall damage also affects the process indirectly by temporarily halting the cell division. To further explore the cell division regulation in stressful conditions, we carried the complete transcriptomic analysis of S. venezuelae after the DNA damage. The observed changes in the gene expression as a result of the DNA damage paves the way for identification of the DNAdamage induced cell division inhibitor in streptomycetes. / Thesis / Doctor of Philosophy (PhD)

Les troubles neurodégénératifs, tels que la sclérose latérale amyotrophique (SLA) et la démence frontotemporale (DFT), ont été associés aux protéines de liaison à l'ARN (RBP). Les principales caractéristiques de la SLA sont l'agrégation d'une protéine de liaison à l'ARN appelée protéine de liaison TAR (TDP-43). Il a été démontré que TDP-43 se lie à G3BP1, un facteur de nucléation pour l'assemblage des granules de stress, pour le stabiliser. Les granules de stress sont des structures séparées par phases qui se forment dans des conditions stressantes et favorisent la survie cellulaire. Une altération de l’assemblage des granules de stress et une réduction du G3BP1 sont signalées dans la SLA. Cette réduction est due à un défaut dans les transcriptions codantes pour G3BP1 stabilisant TDP-43. Par conséquent, une réponse défaillante des granules de stress pourrait jouer un rôle majeur dans la maladie. Ainsi, ce projet de recherche se concentre sur la restauration de G3BP1, dont la déplétion est liée à la perte de fonction de TDP-43. En utilisant des composés de petites molécules identifiés lors d'une campagne de dépistage de médicaments, nous cherchons à augmenter l'expression de G3BP1, rétablissant ainsi le mécanisme SG endogène et favorisant la survie neuronale. La découverte de candidats principaux (NPX-047, NPX-000-115 et NPX-001-280) qui sauvent efficacement l'expression et la fonction de G3BP1 est prometteuse pour des thérapies potentielles contre la SLA. Ces composés ont été testés sur des cellules SHSY5Y traitées avec du si-TDP, mais aucune récupération de l'ARNm de G3BP1 n'a été observée malgré des niveaux plus élevés de signaux de luciférase. Ainsi, une enquête approfondie sur les divergences dans nos résultats constitue notre prochaine étape, ce qui n’a pas été possible pendant la durée limitée de cette mémoire. De plus, les cibles non ciblées de ces composés seront étudiées à l’aide du séquençage Bru Chase. Dans l’ensemble, cette étude explore de nouvelles stratégies pour restaurer l’expression de G3BP1, offrant ainsi une voie potentielle d’intervention thérapeutique dans la SLA. / Neurodegenerative disorders, such as Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD), have been associated with RNA-binding proteins (RBPs). Major hallmark of ALS is aggregation of an RNA-binding protein called TAR binding protein (TDP-43). TDP-43 has shown to bind to G3BP1, a nucleating factor for stress granule assembly, to stabilize it. Stress granules (SGs) are phase separated structures that form under stressful conditions and promote cell survival. Impaired stress granules assembly and reduced G3BP1 is reported in ALS. This reduction is due to a defect in TDP-43 stabilizing G3BP1 encoding transcripts; thus, a failed stress granule response could have a major role in the disease. Thus, this research focuses on restoring G3BP1, whose depletion is linked to TDP-43 loss of function. By utilizing small-molecule compounds identified through a drug screening campaign, we seek to increase G3BP1 expression, consequently reinstating the endogenous SG mechanism and promoting neuronal survival. The discovery of lead candidates (NPX-047, NPX-000-115, and NPX-001-280) that effectively rescue G3BP1 expression and function offers promise for potential ALS therapies. These compounds were tested on SH-SY5Y cells treated with si-TDP however no rescue of G3BP1 mRNA was observed despite higher levels of luciferase signals. Thus, in-depth investigation of discrepancies in our results is our next step which was not possible during the limited timeline of this thesis. In addition, off-targets of these compounds will be investigated using BruChase-sequencing. Overall, this study explores novel strategies to restore G3BP1 expression, providing a potential avenue for therapeutic intervention in ALS.

Light chain (AL) amyloidosis is a disease that occurs due to the presence of a small plasma-cell clone, which produces amyloidogenic light chains. These chains can misfold and aggregate, leading to the deposition of amyloid fibrils in tissues. If left untreated or if treatment is ineffective, this can result in irreversible organ dysfunction and eventual death. Current therapeutic treatments generally target and remove the clonal plasma cell population responsible for secreting full-length light chains which is not always effective or safe, however, a different approach to halt pathological LC misfolding would be to inhibit the amyloidogenesis cascade at its starting point. Small molecules have been identified that have the ability to bind to highly conserved residues in the interface between heavy and light chains which can be used to potentially impede the process of amyloid fibril deposition before the native FL LC can misfold or undergo proteolysis to form amyloid fibrils. To test whether small-molecule kinetic stabilizers are effective in stabilizing light chains, we measured the ability of the small molecule to bind to LCs, and the ability of light chains to aggregate and unfold in the absence and presence of small-molecule. Our findings suggest that the binding of stabilizers to the interface between variable domains of the LC dimer can increase equilibrium stability and decrease the rate of aggregation, thereby delaying the onset of amyloid formation.

No description available.

No description available.