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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The chemistry of mono and multiple anions of methylheteroaromatics

Portlock, David Edward 11 May 2010 (has links)
Heterocyclic compounds are prevalent in all biological systems and are essential to the maintenance of life. The synthesis of natural products is continuously pursued to make available large enough quantities to be used in medicinal research. The functionalization of available starting materials provides an approach to a synthetic plan in which methylheteroaromatics offer a simple keystone. At present the use of sodium hydride for the introduction of appropriate building blocks onto a side-chain in heteroaromatics does not appear to have been studied. In this connection the acylation of a series of methylheteroaromatics was studied using sodium hydride in dimethoxyethane (DME). The use of multiple anions of methylheteroaromatics was also investigated in several model systems. These methods offer a convenient means of drug design in a variety of different heterocycles of medicinal importance. / Ph. D.
2

The Ubiquitin Sensor and Adaptor Protein p62 Mediates Signal Transduction of a Viral Oncogenic Pathway

Wang, Ling, Howell, Mary E., Sparks-Wallace, Ayrianna, Zhao, Juan, Hensley, Culton R., Nicksic, Camri A., Horne, Shanna R., Mohr, Kaylea B., Moorman, Jonathan P., Yao, Zhi Q., Ning, Shunbin 01 October 2021 (has links)
The Epstein-Barr virus (EBV) protein LMP1 serves as a paradigm that engages complicated ubiquitination-mediated mechanisms to activate multiple transcription factors. p62 is a ubiquitin sensor and a signal-transducing adaptor that has multiple functions in diverse contexts. However, the interaction between p62 and oncogenic viruses is poorly understood. We recently reported a crucial role for p62 in oncovirus-mediated oxidative stress by acting as a selective autophagy receptor. In this following pursuit, we further discovered that p62 is upregulated in EBV type 3 compared to type 1 latency, with a significant contribution from NF-kB and AP1 activities downstream of LMP1 signaling. In turn, p62 participates in LMP1 signal transduction through its interaction with TRAF6, promoting TRAF6 ubiquitination and activation. As expected, short hairpin RNA (shRNA)-mediated knockdown (KD) of p62 transcripts reduces LMP1-TRAF6 interaction and TRAF6 ubiquitination, as well as p65 nuclear translocation, which was assessed by Amnis imaging flow cytometry. Strikingly, LMP1-stimulated NF-kB, AP1, and Akt activities are all markedly reduced in p622/2 mouse embryo fibroblasts (MEFs) and in EBV-negative Burkitt’s lymphoma (BL) cell lines with CRISPR-mediated knockout (KO) of the p62-encoding gene. However, EBV-positive BL cell lines (type 3 latency) with CRISPR-mediated KO of the p62-encoding gene failed to survive. In consequence, shRNA-mediated p62 KD impairs the ability of LMP1 to regulate its target gene expression, promotes etoposide-induced apoptosis, and reduces the proliferation of lymphoblastic cell lines (LCLs). These important findings have revealed a previously unrecognized novel role for p62 in EBV latency and oncogenesis, which advances our understanding of the mechanism underlying virus-mediated oncogenesis. IMPORTANCE As a ubiquitin sensor and a signal-transducing adaptor, p62 is crucial for NF-kB activation, which involves the ubiquitin machinery, in diverse contexts. However, whether p62 is required for EBV LMP1 activation of NF-kB is an open question. In this study, we provide evidence that p62 is upregulated in EBV type 3 latency and, in turn, p62 mediates LMP1 signal transduction to NF-kB, AP1, and Akt by promoting TRAF6 ubiquitination and activation. In consequence, p62 deficiency negatively regulates LMP1-mediated gene expression, promotes etoposide-induced apoptosis, and reduces the proliferation of LCLs. These important findings identified p62 as a novel signaling component of the key viral oncogenic signaling pathway.
3

Development of techniques for studying the platelet glycoprotein receptors GPVI and GPIb localisation and signalling / Entwicklung von Methoden zur Untersuchung zur der Lokalisation und Signaltransduktion der Thrombozytenrezeptoren GPVI und GPIb

Neagoe, Raluca Alexandra Iulia January 2024 (has links) (PDF)
Platelets play an important role in haemostasis by mediating blood clotting at sites of blood vessel damage. Platelets, also participate in pathological conditions including thrombosis and inflammation. Upon vessel damage, two glycoprotein receptors, the GPIb-IX-V complex and GPVI, play important roles in platelet capture and activation. GPIb-IX-V binds to von Willebrand factor and GPVI to collagen. This initiates a signalling cascade resulting in platelet shape change and spreading, which is dependent on the actin cytoskeleton. This thesis aimed to develop and implement different super-resolution microscopy techniques to gain a deeper understanding of the conformation and location of these receptors in the platelet plasma membrane, and to provide insights into their signalling pathways. We suggest direct stochastic optical reconstruction microscopy (dSTORM) and structured illumination microscopy (SIM) as the best candidates for imaging single platelets, whereas expansion microscopy (ExM) is ideal for imaging platelets aggregates. Furthermore, we highlighted the role of the actin cytoskeleton, through Rac in GPVI signalling pathway. Inhibition of Rac, with EHT1864 in human platelets induced GPVI and GPV, but not GPIbα shedding. Furthermore, EHT1864 treatment did not change GPVI dimerisation or clustering, however, it decreased phospholipase Cγ2 phosphorylation levels, in human, but not murine platelets, highlighting interspecies differences. In summary, this PhD thesis demonstrates that; 1) Rac alters GPVI signalling pathway in human but not mouse platelets; 2) our newly developed ExM protocol can be used to image platelet aggregates labelled with F(ab’) fragments / Thrombozyten, spielen in der Hämostase eine entscheidende Rolle, indem sie die Blutstillung bei Gefäßverletzung vermitteln. Sie sind jedoch auch an pathologischen Prozessen wie zum Beispiel der Thrombose und Entzündungen beteiligt. Bei einer Gefäßverletzung spielen zwei Glykoproteinrezeptoren eine wichtige Rolle bei der Adhäsion und Aktivierung von Thrombozyten: der GPIb-IX-V-Komplex und GPVI. GPIb-IX-V bindet an den von-Willebrand-Faktor und GPVI an Kollagen. Dies initiiert eine Signalkaskade, die zu einer Änderung der Morphologie der Thrombozyten führt, welche vom Aktin-Zytoskelett abhängig ist. Ziel dieser Doktorarbeit war die Entwicklung und Anwendung verschiedener hochauflösender Mikroskopietechniken, um ein tieferes Verständnis der Konformation und Lokalisation dieser Rezeptoren in der Plasmamembran der Thrombozyten zu erlangen und Einblicke in ihre Signalwege zu gewinnen. Hierbei etablierten wir dSTORM und die structured illumination microscopy (SIM) als die geeignetsten Methoden für die mikroskopische Untersuchung einzelner Thrombozyten, während die Expansionsmikroskopie (ExM) ideal für die Darstellung von Thrombozytenaggregaten ist. Darüber heben unsere Ergebnisse zur Funktion von Rac im GPVI Signalweg die wichtige Rolle des Aktin-Zytoskeletts hervor. Die Hemmung von Rac mit EHT1864 in menschlichen Thrombozyten induzierte das Abscheiden (shedding) von GPVI und GPV, nicht jedoch von GPIbα. Darüber hinaus blieb die GPVI Dimerisierung und GPVI-Clusterbildung durch EHT1864-Behandlung unverändert, jedoch verringerte sich die Phosphorylierung der Phospholipase Cγ2 in humanen, aber nicht in murinen Thrombozyten, was Unterschiede zwischen den Spezies aufzeigt. Zusammenfassend zeigen die Ergebnisse dieser Doktorarbeit, dass; 1) Rac den GPVI Signalweg in humanen aber nicht in murinen Thrombozyten beeinflusst; 2) unser neu entwickeltes ExM-Protokoll zur Darstellung von F(ab’)-Fragment markierten Thrombozytenaggregaten verwendet werden kann.
4

Genetic and environmental determinants of Paget's disease of bone

Rios Visconti, Micaela January 2015 (has links)
Genetic factors play an important role in the pathogenesis of Paget’s Disease of Bone (PDB). The most important predisposing gene is SQSTM1 which is mutated in about 10% of patients, additionally common variants at seven other loci have also been shown to predispose to PDB as well as environmental factors which are also important in the pathogenesis of PDB. Little research has been conducted on the relationship between the genetic variants that predispose to PDB and disease severity. Similarly, only limited information exists on the role that gene-environment interactions play in the pathogenesis of PDB or its severity. The aim of the present thesis was to explore these issues in participants of the Paget’s Disease Randomised Trial of Intensive versus Symptomatic Management study (PRISM) and other study cohorts. In chapter 3, I investigate the relationship between SQSTM1 mutation status, disease severity and clinical outcome in 737 patients from the PRISM study. Mutations of SQSTM1 were detected in 80/737 (10.9%) patients. Mutation carriers had an earlier age at diagnosis; a greater number of affected bones and more commonly had required orthopaedic surgery and bisphosphonate therapy than those without mutations. Quality of life was significantly reduced in carriers and during the study; fractures were more common although most of these occurred in unaffected bone. This study demonstrates that SQSTM1 mutations are strongly associated with disease severity and complications of PDB. In chapter 4, I study associations between common genetic variants identified by genome wide association (GWAS), clinical severity and extent of PDB, alone and in combination with SQSTM1 mutations. This showed that these common variants were also associated with severity and extent of PDB in PRISM, but with weaker effects than SQSTM1 mutations. The findings were replicated in a multinational study involving 1940 subjects from centres in Italy, Spain and Australia. In all cohorts the GWAS risk alleles acted in an additive manner with SQSTM1 mutations to regulate disease severity and extent. By combining information from SQSTM1 status and the new risk alleles, however, we are able to develop a genetic risk score which delineated three distinct groups with markedly differing effects on disease extent and severity. In chapter 5, I study associations between PDB, severity and extent in relation to circulating levels of IgG antibodies against various viruses including Rubella, respiratory syncytial virus, distemper, varicella zoster virus, measles and mumps. We found little evidence of an interaction between viral antibody titres and SQSTM1 in predicting disease severity with the notable exception of mumps virus where subjects with the highest levels of antibodies that were SQSTM1 positive had in increased age at diagnosis than the other genotype / viral antibody groups. Overall the studies do provide no support for the notion that patients with PDB have an abnormal antibody response to paramyxovirus or have had previous infections with these viruses more frequently than controls. This of course does not exclude the possibility that PDB patients might have a clinically occult slow virus infection which is not accompanied by an abnormality in the immune response. . This raises the possibility that genetic testing may be of value in identifying individuals at risk of developing severe disease and those at risk of complications. I also demonstrate that PBD patients have abnormalities in circulating antibodies to various viruses suggesting that the disease may be associated with disturbance in the response of the immune system to infectious agents but further investigation is required. This, perhaps, could explain the changes in the severity and prevalence of PDB that have been observed over recent years in several countries.
5

The Adaptor Protein p62 Mediates EBV LMP1 Signal Transduction

Sparks-Wallace, Ayrianna, Ning, Shunbin 04 May 2020 (has links)
Epstein-Barr Virus (EBV) is well known to manipulate the host ubiquitin machinery to facilitate its latent persistence and oncogenesis, exemplified by LMP1 signal transduction that activates multiple transcription factors, including NFκB, AP1, and IRF7/IRF4, which promote cell survival and outgrowth, and control immune response and inflammation. It is therefore vital to delineate the detailed mechanisms underlying LMP1 signal transduction for understanding EBV-mediated oncogenesis. p62 (also called SQSTM1, Sequestosome 1) is a ubiquitin sensor and a signal transducing adaptor that interacts with TRAF6 and facilitates the recruitment of ubiquitinated signal intermediators for the activation of NFκB and AP1 in diverse contexts. In turn, p62 is induced by NFκB. However, the interaction between p62 and EBV latency has never been studied. We have recently published interesting and important results, which imply a crucial role for p62 in EBV-mediated oxidative stress. In this study, we further show that p62 is upregulated in EBV latency, with the contribution of LMP1-mediated NFκB and AP1 activities. In turn, p62 participates in LMP1 signal transduction through its interaction with TRAF6, promoting TRAF6 ubiquitination. shRNA-mediated p62 depletion downregulates LMP1-TRAF6 interaction and TRAF6 ubiquitination, and significantly impairs AP1 activity; however, with no detectable effects on NFκB activity. These observations imply that TRAF6-p62 interaction differentiates LMP1 signaling to NFκB and AP1 activation. As a consequence, p62 depletion promotes etoposide-induced apoptosis. These findings identify p62 as a novel player in EBV LMP1 signaling to AP1 activation that is crucial for LMP1-mediated ROS production.
6

New Look of EBV LMP1 Signaling Landscape

Wang, Ling, Ning, Shunbin 01 November 2021 (has links)
The Epstein–Barr Virus (EBV) principal oncoprotein Latent Membrane Protein 1 (LMP1) is a member of the Tumor Necrosis Factor Receptor (TNFR) superfamily with constitutive activity. LMP1 shares many features with Pathogen Recognition Receptors (PRRs), including the use of TRAFs, adaptors, and kinase cascades, for signal transduction leading to the activation of NFκB, AP1, and Akt, as well as a subset of IRFs and likely the master antioxidative transcription factor NRF2, which we have gradually added to the list. In recent years, we have discovered the Linear UBiquitin Assembly Complex (LUBAC), the adaptor protein LIMD1, and the ubiquitin sensor and signaling hub p62, as novel components of LMP1 signalosome. Functionally, LMP1 is a pleiotropic factor that reprograms, balances, and perturbs a large spectrum of cellular mechanisms, including the ubiquitin machinery, metabolism, epigenetics, DNA damage response, extracellular vehicles, immune defenses, and telomere elongation, to promote oncogenic transformation, cell proliferation and survival, anchorage‐independent cell growth, angiogenesis, and metastasis and invasion, as well as the development of the tumor microenvironment. We have recently shown that LMP1 induces p62‐mediated selective autophagy in EBV latency, at least by contributing to the induction of p62 expression, and Reactive Oxygen Species (ROS) production. We have also been collecting evidence supporting the hypothesis that LMP1 activates the Keap1‐NRF2 pathway, which serves as the key antioxidative defense mechanism. Last but not least, our preliminary data shows that LMP1 is associated with the deregulation of cGAS‐STING DNA sensing pathway in EBV latency. A comprehensive understanding of the LMP1 signaling landscape is essential for identifying potential targets for the development of novel strategies towards targeted therapeutic applications.
7

Etude de la régulation de l’autophagie au cours de la différenciation des cellules de leucémie aiguë promyélocytaire : rôles dans la survie et la différenciation cellulaire / Regulation and functions of autophagy during differentiation of Acute Promylocytic Leukemia cells

Trocoli, Aurore 09 December 2013 (has links)
L’autophagie, processus catabolique lysosomal de recyclage de constituants cellulaires, est essentielle à la survie, à la différenciation et au maintien de l’homéostasie cellulaire. Ce processus est fréquemment impliqué dans la survie et la chimiorésistance des tumeurs. La leucémie aiguë promyélocytaire (LAP) est caractérisée par un blocage de la différenciation de la lignée hématopoïétique au stade promyélocytaire. Le traitement des LAP a considérablement progressé depuis l’administration aux patients de doses pharmacologiques d’acide rétinoïque tout-trans (ATRA), un puissant agent de différenciation. L’objectif de ma thèse a consisté à étudier la régulation de l’autophagie au cours de l’induction de différenciation des cellules de LAP par l’ATRA et de rechercher son implication éventuelle dans les mécanismes d’action de ce traitement et les modes d’échappement observés. Lors de mon travail de thèse, j’ai mis en évidence une activation de l’autophagie lors de l’induction de la différenciation granulocytaire des cellules de LAP par l’ATRA. J’ai montré que cette réponse était associée à une inhibition de la voie mTOR et une induction de l’expression des protéines BECLIN 1 et p62/SQSTM1. De façon intéressante, les cellules de LAP résistantes à la maturation par l’ATRA ne sont pas capables d’induire l’expression de p62/SQSTM1 en réponse à l’ATRA. De même, l’expression de p62/SQSTM1 dans les blastes des patients atteints de leucémie aiguë myéloïde est plus faible que celle des granulocytes de sujets sains. L’ensemble de ces données indique que l’expression de p62/SQSTM1 est réprimée dans les phénotypes immatures des cellules myéloïdes mais au contraire induite dans les cellules leucémiques qui s’engagent vers une différenciation terminale (granulocytes/neutrophiles). Enfin, j’ai démontré que les protéines BECLIN 1 et p62/SQSTM1 sont essentielles à la survie de cellules de LAP matures mais non pas à l’engagement de ces cellules vers la différenciation granulocytaire. Ainsi, ces résultats suggèrent qu’en permettant la survie des cellules de LAP différenciées, p62/SQSTM1 et BECLIN 1 pourraient contribuer au développement des résistances à l’ATRA et/ou à l’induction des complications associées à ce traitement tel que le syndrome de différenciation. / Autophagy, a lysosomal process used by the cell to degrade and recycle cytoplasmic constituents, is essential for cell survival, differentiation and the maintenance of cellular homeostasis. Autophagy is often involved in cell survival and resistance to anti-tumor therapy. Acute promyelocytic leukemia (APL) results from a blockade of granulocyte differentiation at the promyelocytic stage. All-trans retinoic acid (ATRA), a potent differentiation agent, has been shown to induce clinical remission in APL patients. The aim of our study was to investigate the regulation and roles of autophagy during ATRA-induced APL cells maturation into neutrophils/granulocytes with the ultimate objective to identify critical mechanisms involved in chemoresistance of APL patients. During my thesis, I demonstrated that autophagy is upregulated during the course of ATRA-induced neutrophil/granulocyte differentiation of APL cells. This response is associated with inhibition of mTOR activity and upregulation of both BECLIN 1 and p62/SQSTM1 proteins. Interestingly, induction of p62/SQSTM1 by ATRA was impaired in maturation-resistant NB4 cells but is re-activated when differentiation was restored in these cells. Accordingly, primary blast cells of AML patients exhibited significantly lower p62/SQSTM1 mRNA levels than did granulocytes from healthy donors. Together, these results highlight that p62/SQSTM1 expression level is repressed in immature myeloid cells compared to mature ones. Moreover, I demonstrated that BECLIN 1 and p62/SQSTM1 proteins are essential for the survival of myeloid cells that undergo differentiation but have no crucial effect on the granulocytic differentiation. This finding may help to elucidate the mechanisms involved in ATRA resistance of APL patients, and in the ATRA syndrome caused by an accumulation of mature APL cells.
8

The Role of the Nrf2-Keap1 Pathway in Autophagy and How it Contributes to Arsenic Carcinogenicity

Lau, Alexandria G. January 2012 (has links)
NF-E2-related factor 2 (Nrf2) is a transcription factor that is responsible for maintaining cellular homeostasis by controlling the fate of cells through transcriptional upregulation of antioxidant response element-bearing genes critical for eliminating toxicants and carcinogens. Under quiescent conditions, basal levels of Nrf2 are relatively low due to tight regulation by Keap1, a substrate adaptor protein for a Cullin 3 (Cul3)-E3 ubiquitin ligase complex that facilitates the ubiquitination and degradation of Nrf2. It is thought that when cells are exposed to oxidative stress, naturally-occurring compounds, or synthetic chemicals, cysteine residues in Keap1, particularly cysteine 151 (C151), are modified causing a conformational change that compromises the ability of the Keap1-Cul3-E3 ubiquitin ligase complex to properly ubiquitinate Nrf2. It is then stabilized and allowed to translocate into the nucleus to transcriptionally activate downstream genes. Interestingly, recent emerging data has revealed the "dark side" of Nrf2. Epigentic alterations and somatic mutations in either Nrf2 or Keap1 disrupting the Nrf2-Keap1 axis and causing constitutive activation of Nrf2 have been found in many human cancer cell lines and tumors. Thus, Nrf2 provides mutated cells a protective advantage against cytotoxic chemotherapeutics, allowing for further cell survival and growth. It is well known that arsenic is a human carcinogen and can activate the Nrf2 pathway through a Keap1-C151 independent mechanism. It has also been shown that arsenic can activate autophagy, a bulk-lysosomal degradation pathway. In this dissertation, we establish the cross-talk between the Nrf2-Keap1 pathway and autophagy by elucidating a novel non-canonical mechanism of Nrf2 activation. We found that deregulation of autophagy causes accumulation of p62, a substrate adaptor protein, which sequesters Keap1 into autophagosomes and activates the Nrf2 pathway. Moreover, we also demonstrate how arsenic blocks autophagic flux and prolongs Nrf2 activation through this novel mechanism. Additionally, activation of the Nrf2 pathway has been shown to confer protection against arsenic-induced toxicity and carcinogenicity. We demonstrate that co-treatment with sulforaphane alleviates arsenic-mediated autophagy. These studies suggest that the Keap1-C151 dependent mechanism triggers the chemopreventive role of Nrf2 while activation through p62 elicits the dark side. Therefore, the use of Keap1-C151-dependent compounds to counteract environmental insults continuous to be a promising strategy for cancer prevention.
9

Vliv změněné funkce autofagosomů na patofyziologii Huntingtonovy choroby . / Role of modified autophagosomal function in patophysiology of Huntington's disease.

Kotrčová, Eva January 2013 (has links)
Huntington's disease, an autosomal dominant neurodegenerative disease, affects the cell in several toxical ways. One of them is accumulation of protein aggregates in cytoplasma, which could become a serious problem especially for long-lived cells such as neurons. Autophagy (macroautophagy) is an important catabolic pathway, crucial for cell survival. If fully functional, it should eliminate protein aggregates and reduce the toxic effect on the cell. However, recent works show that this pathway might be defective, most probably in the cytoplasmic cargo recognition. In my work I used a transgenic miniature pig model of Huntington's disease to verify the hypothesis of autophagical dysfunction in individuals suffering from Huntington's disease. I studied levels of autophagosomal markers - LC3 and p62 in mesenchymal stem cells after different autophagy stimulation treatments, and ammonium chloride was found the most effective. In addition I evaluated the effect of age of the animals on autophagic function, but no significant changes were identified, even if animal genotype was considered. Moreover I had an opportunity to study proteins levels in three porcine brain tissues - cortex, cerebellum and striatum. Even though there is no significant diference, we can observe a trend of LC3 II and p62 increase in...
10

The study of two transmembrane autophagy proteins and the autophagy receptor, p62

Runwal, Gautam January 2019 (has links)
Autophagy is an evolutionarily conserved process across eukaryotes that is responsible for degradation of cargo such as aggregate-prone proteins, pathogens, damaged organelles, macromolecules etc. via its delivery to lysosomes. The process is known to involve the formation of a double-membraned structure, called autophagosome, that engulfs the cargo destined for degradation and delivers its contents by fusing with lysosomes. This process involves several proteins at its core which include two transmembrane proteins, ATG9 and VMP1. While ATG9 and VMP1 has been discovered for about a decade and half, the trafficking and function of these proteins remain relatively unclear. My work in this thesis identifies and characterises a novel trafficking route for ATG9 and VMP1 and shows that both these proteins traffic via the dynamin-independent ARF6-associated pathway. Moreover, I also show that these proteins physically interact with each other. In addition, the tools developed during these studies helped me identify a new role for the most common autophagy receptor protein, p62. I show that p62 can specifically associate with and sequester LC3-I in autophagy-impaired cells (ATG9 and ATG16 null cells) leading to formation of LC3-positive structures that can be misinterpreted as mature autophagosomes. Perturbations in the levels of p62 were seen to affect the formation of these LC3-positive structures in cells. This observation, therefore, questions the reliability of LC3-immunofluorescence assays in autophagy-impaired cells as method of assessing autophagy and points towards the homeostatic function played by p62 in autophagy-impaired cells.

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