Global ETD Search

1	TARGET VALIDATION OF UK-101 AND FUNCTIONAL STUDIES OF β1i Wehenkel, Marie V. 01 January 2011 (has links) β1i is a major catalytic subunit of the immunoproteasome, an alternative form of the constitutive proteasome, and its upregulation has been demonstrated in a variety of disease states including cancer. Our lab has developed a small molecule inhibitor of β1i, dubbed UK-101. While UK-101 causes apoptosis in cancer cell lines, it was not clear whether this apoptotic effect was directly mediated by its irreversible inhibition of β1i. Since off-target effects are major roadblocks for the development of new and effective pharmaceuticals, target validation studies in this system would assist in the further progression of β1i inhibitors towards preclinical trials. Our hypothesis was that the expression and catalytic activity of β1i is important for the growth and proliferation of the PC-3 prostate cancer cell line, therefore the apoptotic effect seen upon treatment of PC-3 cells with UK-101 was due solely to its covalent inhibition of β1i. To test this hypothesis, a number of complementary approaches were used. The expression of β1i in PC-3 cells was increased by the treatment of these cells with interferon-gamma or tumor necrosis factor-alpha, natural inducers of the immunoproteasome. The expression of β1i in PC-3 cells was decreased using small interfering RNA or short hairpin RNA, in a transient or stable manner, respectively. All of these cells were then treated with UK-101. The efficacy of UK-101 decreased in the interferon-gamma treated cells but did not change in any other the other cell lines, suggesting that UK-101 was not specific for β1i. This was confirmed using a molecular probe of the proteasome and demonstrated that UK-101 bound to other proteasome catalytic subunits. Additional experiments were performed to determine the effect of β1i on the proliferation of PC-3 cells. Simply removing the β1i using small interfering RNA reduces the viability of these cells. Other studies demonstrated that a mutation of β1i which inhibited its catalytic activity reduced the viability of cells when compared to those containing the wild type protein. Overall, our data indicate that β1i is a potential therapeutic target in prostate cancer. Further medicinal chemistry efforts will be required develop UK-101 into a truly selective proteasome inhibitor. Immunoproteasome Target Validation β1i UK-101 proteasome inhibitor Pharmacy and Pharmaceutical Sciences
2	Target Validation For Neurofibromatosis Type 2 Therapeutics. Guinart, Alejandra 01 January 2013 (has links) Neurofibromatosis type 2 (NF2) is a benign tumor disease of the nervous system. Development of bilateral vestibular schwannomas is characteristic of NF2; however patients frequently present schwannomas on other nerves, as well as meningiomas and ependymomas. Currently, there are no drug therapies for NF2. There is an urgent need for development of NF2 therapeutics and this dissertation presents two independent potential therapeutic targets. The disease is caused by mutations in the NF2 gene that encodes a tumor suppressor called merlin. Loss of merlin function is associated with increased activity of Rac and p21-activated kinases (PAK) and deregulation of cytoskeletal organization. LIM domain kinases (LIMK1 and 2) are substrates for Cdc42/Rac-PAK, and modulate actin dynamics by phosphorylating cofilin, an actin severing and depolymerizing agent. LIMKs also translocate into the nucleus and regulate cell cycle progression. Here we report that mouse Schwann cells (MSCs) in which merlin function is lost as a result of Nf2 exon2 deletion (Nf2ΔEx2) exhibited increased levels of LIMK1, LIMK2, and active phospho-Thr508/505-LIMK1/2, as well as phospho-Ser3-cofilin, compared to wild-type normal MSCs. Similarly, levels of LIMK1 and 2 total protein and active phosphorylated forms were elevated in human vestibular schwannomas compared to normal human Schwann cells (SCs). Reintroduction of wild-type NF2 into Nf2ΔEx2 MSC reduced LIMK1 and LIMK2 levels. Pharmacological inhibition of LIMK with BMS-5, decreased the viability of Nf2ΔEx2 MSCs in a dose-dependent manner, but did not affect viability of iv control MSCs. Similarly, LIMK knockdown decreased viability of Nf2ΔEx2 MSCs. The decreased viability of Nf2ΔEx2 MSCs was due to inhibition of cell cycle progression as evidenced by accumulation of cells in G2/M phase. Inhibition of LIMKs arrest cells in early mitosis by decreasing Aurora A activation and cofilin phosphorylation. To increase the search for NF2 therapeutics, we applied an alternative approach to drug discovery with an unbiased pilot high-throughput screen of the Library of Pharmacologically Active Compounds. We assayed for compounds capable of reducing viability of Nf2ΔEx2 MSC as a cellular model for human NF2 schwannomas. AGK2, a SIRT2 (sirtuin 2) inhibitor, was identified as a candidate compound. SIRT2, a mammalian sirtuin, is a NAD+ -dependent protein deacetylase. We show that Nf2ΔEx2 MSC have higher expression levels of SIRT2 and lower levels of overall lysine acetylation than wild-type control MSC. Pharmacological inhibition of SIRT2 decreases Nf2ΔEx2 MSC viability in a dose dependent manner without substantially reducing wildtype MSC viability. Inhibition of SIRT2 activity in Nf2ΔEx2 MSC causes cell death accompanied by release of the necrotic markers lactate dehydrogenase and high mobility group box 1 protein into the medium in the absence of significant apoptosis, autophagy, or cell cycle arrest. Overall this work uncovered two novel potential therapeutic targets, LIMK and SIRT2 for NF2 and tumors associated with merlin deficiency. Neurofibromatosis type 2 limk sirt2 schwann cell target validation Molecular Biology
3	Target identification and validation studies in chemical biology & Synthesis of medium-sized ring containing compounds via oxidative fragmentation Liu, Gu January 2010 (has links) Part I of this thesis describes the development of bioactive small molecules of relevance to the study of the apicomlexan parasite Toxoplasma gondii into useful chemical tools. The research includes the target identification and validation studies, using both chemical and biological methods. Chapter 1 provides an overview of chemical genetics with a particular emphasis on methods for the identification of the protein targets of bioactive small molecules. The concept of biochemical protein target identification techniques was introduced with a detailed discussion of interesting applications from the literature. Chapter 2 focuses on the development of a tetrahydro-β-carboline based lead molecule into a chemical tool through target identification studies. The structure activity relationship (SAR) data associated with this core structure, the design of a chemical inducer of dimerisation (CID) and the synthesis of this CID are discussed in detail. Chapter 3 described work done to identify the potential protein target(s) of Conoidin A. Experiments to assess whether Conoidin A can inhibit a proposed target in vitro are also included. Further optimisation of this structural class to develop more potent inhibitors is discussed in the second part of this chapter. Part II of this thesis describes the development of methods for the synthesis of medium-sized ring containing compounds using oxidative fragmentation and rearrangement strategies. Chapter 5 provides an overview of the existing oxidative fragmentation methodology, with an emphasis on the use of oxidative fragmentation reactions for the synthesis of medium-sized ring systems (8-11 ring atoms). Chapter 6 focuses on using the established oxidative fragmentation method in the oxizino carbazolone system to investigate the diasteroselectivity of this reaction. Possible mechanisms for this transformation are investigated and discussed using both chemical and computational methods. An interesting rearrangement reaction has also been observed during this study. Chapter 7 focuses on developing an asymmetric oxidative fragmentation method, for use in the diazabenz[e]aceathrylenes system. Asymmetric oxidative fragmentation reactions using [Ru(pybox)(pydic)] catalysts are discussed. Attempts to optimise the enantiomeric excesses of the reaction by varying reaction conditions and substituents in the substrate are also included. 572
4	Micro RNA-Mediated regulation of the full-length and truncated isoforms of human neurotrophic tyrosine kinase receptor type 3 (NTRK 3) Guidi, Mònica 13 January 2009 (has links) Neurotrophins and their receptors are key molecules in the development of thenervous system. Neurotrophin-3 binds preferentially to its high-affinity receptorNTRK3, which exists in two major isoforms in humans, the full-length kinaseactiveform (150 kDa) and a truncated non-catalytic form (50 kDa). The twovariants show different 3'UTR regions, indicating that they might be differentiallyregulated at the post-transcriptional level. In this work we explore howmicroRNAs take part in the regulation of full-length and truncated NTRK3,demonstrating that the two isoforms are targeted by different sets of microRNAs.We analyze the physiological consequences of the overexpression of some of theregulating microRNAs in human neuroblastoma cells. Finally, we providepreliminary evidence for a possible involvement of miR-124 - a microRNA with noputative target site in either NTRK3 isoform - in the control of the alternativespicing of NTRK3 through the downregulation of the splicing repressor PTBP1. / Las neurotrofinas y sus receptores constituyen una familia de factores crucialespara el desarrollo del sistema nervioso. La neurotrofina 3 ejerce su funciónprincipalmente a través de una unión de gran afinidad al receptor NTRK3, del cualse conocen dos isoformas principales, una larga de 150KDa con actividad de tipotirosina kinasa y una truncada de 50KDa sin dicha actividad. Estas dos isoformasno comparten la misma región 3'UTR, lo que sugiere la existencia de unaregulación postranscripcional diferente. En el presente trabajo se ha exploradocomo los microRNAs intervienen en la regulación de NTRK3, demostrando que lasdos isoformas son reguladas por diferentes miRNAs. Se han analizado lasconsecuencias fisiológicas de la sobrexpresión de dichos microRNAs utilizandocélulas de neuroblastoma. Finalmente, se ha estudiado la posible implicación delmicroRNA miR-124 en el control del splicing alternativo de NTRK3 a través de laregulación de represor de splicing PTBP1. RISC complex retinoic acid renilla luciferase real-time quantitative PCR PTBP1 pri-miRNA pre-miRNA post-transcriptional regulation piRNA PicTar pGL4.13 PCR P-body p75NTR overexpression NTRK3 NTRK2 NTRK1 non-coding RNAs NGF neurotrophin neurotrophic signaling neuronal differentiation neurodevelopment neuroblastoma nervous system mRNA miRNA target prediction miRNA profiling miRNA mimic miRNA microarray miRNA inhibitor miRanda microRNA microarray luciferase assay Ingenuity Pathway Analysis (IPA) heLa cells gene silencing gene regulation full-length isoform (FL-NTRK3) firefly luciferase ERK disease dicer cancer development BDNF argonaute alternative splicing 3'UTR RNAhybrid RT-PCR SH-SY5Y cells siRNA standard error synaptic plasticity target validation TargetScan transfection translational repression TrkA TrkB TrkC truncated isoform (TR-NTRK3) tyrosine kinase (TK) western blot 575 61

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