No description available.

Apoptosis is the process by which organisms eliminate excess, damaged or hazardous cells in a controlled manner. This process is controlled by the Bcl-2 family of proteins. Bcl-2 and Bcl-XL are anti-apoptotic paralogues that can replace CED-9, the sole homologue in C. elegans. It has therefore been assumed that Bcl-2 and Bcl-XL are replaceable and functionally identical. However, evidence in some mammalian cells indicates that this may not be the case. The purpose of this project was to exhaustively compare the anti-apoptotic activities of Bcl-2 and Bcl-XL in one cell type. As Bcl-2 and Bcl-XL have been found to localize to the ER and the outer mitochondrial membrane, we also determined whether subcellular location affects the function of these proteins differently. MCF-7 breast cancer cells were stably transfected with Bcl-2 and Bcl-XL alternatively targeted to the ER or mitochondria, and exposed to various doses of doxorubicin; PARP cleavage was measured using quantitative Western blotting as an indication of apoptosis to obtain EC₅₀ values in the different cell lines. The levels of both Bcl-2 and Bcl-XL affected anti-apoptotic activity; specific degradation of both proteins was noted at higher doses of doxorubicin. Nevertheless, the results indicated clearly that there was a difference between Bcl-2 and Bcl-XL. Using EC₅₀ values Bcl-XL mutants were at least 8 times more protective than Bcl-2 mutants. Furthermore, most of the cleavage products of PARP in Bcl-XL expressing clones were due to non-caspase-7 proteases, a pattern not seen with Bcl-2. Bcl-2 and Bcl-XL localized to mitochondria were most effective, while cytosolic and ER localized Bcl-XL were less effective, and Bcl-2 at these sites did not inhibit apoptosis. / Thesis / Master of Science (MSc)

Parkinson’s disease, the second most common neurodegenerative disease, is characterized by the loss of dopaminergic neurons within the substantia nigra. Currently, the treatments available for PD are symptomatic treatments that do not stop the progression of the disease. Trophic molecules, such as glial cell-line derived neurotrophic factor (GDNF), have been evaluated as potential therapeutic molecules that could stop the loss of neurons and potentially restore some of the neurons that have already been lost. However, these trophic molecules are large making them difficult to produce and delivery. Here we characterize three peptides (DNSP-5, DNSP-11, and DNSP-17) to determine it they are stable and offer protective effects similar to GNDF allowing them to be potential therapeutic molecules. The data presented here involves the evaluation of the molecular and cellular mechanism of DNSP-5, DNSP-11, and DNSP-17, which are derived from prosequence of GDNF. Initial studies were carried out to evaluate the physical characteristics of these three peptides to determine their viability as potential therapeutic molecules. The structure and stability of these peptides were evaluated. Based on the data it was determined that the three peptides do not interact in vitro, allowing for further individual evaluations of the peptides. It was also determined that the peptides were stable when stored at both -80°C and 37°C for one month, allowing them to both potentially be stored during treatment. Cell culture assays and proteomic profiling were utilized to determine binding partners and potential mechanisms through which DNSP-11 may be able to mediate apoptosis. It was determined that DNSP-11 was able to interact with a variety of binding partners that are involved in metabolism. These studies have aided in the understanding of neurotrophic factor prosequence function, but will also serve as a starting point for the development of novel trophic factors for PD treatment. Finally, the interaction between DNSP-11 and GAPDH was evaluated as a potential anti-apoptotic mechanism. GAPDH has previously shown to play a role in mediating apoptotic pathways. It was hypothesized that the observed interaction between DNSP-11 and GAPDH could mediate that role of GAPDH in apoptosis and afford DNSP-11 its observed anti-apoptotic effects. It was observed that while DNSP-11’s interaction with GAPDH may play a role in its anti-apoptotic effects, it does not appear to be the only mechanism involved. Based on this data, it is likely that the other metabolic binding partners play a role in DNSP-11’s anti-apoptotic mechanisms and therefore, these interactions should be further evaluated.

<p> Bcl-2 proteins play a critical role in the regulation of apoptosis, a form of programmed cell death. Apoptosis is important during development to facilitate the elimination of supernumerary, damaged or harmful cells in multicellular organisms. Altered regulation of apoptosis is associated with many diseases such as several forms of cancer as well as autoimmune and degenerative disorders. The way in which Bcl-2 proteins regulate apoptosis is unknown and much research is focused on elucidating the molecular mechanism of their function. Bcl-2, an anti-apoptotic member of this family, is localized to the mitochondria, endoplasmic reticulum and nuclear envelope. In healthy cells, Bcl-2 adopts a typical tail-anchored topology in which the carboxyl-terminal helix (a9) is inserted into the membrane, anchoring the protein, leaving the majority of the protein in the cytosol. Previous results from our lab have shown that after the induction of apoptosis, Bcl-2 undergoes a conformational change in which the endogenous cysteine residue, C158, in the a5 helix becomes protected from a membrane impermeant cysteine specific labelling reagent, IASD (4-acetamido-4' ((iodoacetyl)amino)-stilbene-2,2'disulfonate). Modification of cysteine residues results in a change in migration ofBcl-2 in an isoelectric focusing, IEF, gel system. To investigate the nature of this conformational change, cysteine scanning mutagenesis was used to determine the topology of Bcl-2 in the late stages of apoptosis. The results from the current study showed that in rat 1 myc ERTM fibroblasts, a discontinuous sequence of residues in the a5 and a6 helices of Bcl-2 become protected from IASD labelling after the induction of apoptosis by etoposide or serum starvation. The data support a model topology in which, during apoptosis, Bcl-2 undergoes a functionally significant conformational change, going from a single spanning transmembrane protein to a polytopic membrane protein in which three helices span the membrane, a5, a6 and a9. </p> / Thesis / Master of Science (MSc)

Thesis (M.Sc.(Chemistry)) -- University of Limpopo, 2020 / Breast cancer is a malignant tumour that starts in the cells of the breast. Many studies revealed aromatase (CYP19A1) and cyclin-dependent kinase 2 (CDK2) as possible therapeutic targets regarding breast cancer treatment, because they play crucial roles in anti-apoptotic processes during cell proliferation. Quinoxaline derivatives have attracted a great deal of attention due to their biological activities against fungi, virus, bacteria and cancer. Computer modelling was employed in order to reduce time and cost by searching the library of molecules and identifying those which are likely to bind to the drug target. A library of new one hundred (100) nitro and amino quinoxaline alkyne derivatives were successfully designed and screened against target proteins (CYP19A1 and CDK2) using virtual screening technique and thirteen (13) molecules were identified to be hit compounds against both targets with the docking score ranging from -6.143 to -8.372 kcal/mol as a measure of binding affinity. The hit compounds were subjected to IFD in order to identify tight binding through intermolecular interactions with active site residues of the binding pocket of the target proteins. All identified nitro and amino quinoxaline alkyne derivatives were successfully synthesised in a multi-step reaction sequence and their spectroscopic analysis (NMR, FTIR and MS) were in good agreement with the proposed structures in a good to moderate yield. The newly synthesised novel amino and nitro-quinoxaline derivatives were evaluated for anti-proliferative activity against breast cancer (MCF-7). Compound 59 showed to possess good inhibition against MCF-7 with an IC50 of 9.102 μM, whereas compounds 34, 54, 56 and 61 showed promising activity against MCF-7 with an IC50 value of < 50 μM. However, the MTT assay results showed that 59 was found to be toxic with an IC50 value of 0.205 μM against Raw 264.7 cell line. The dose response investigations showed that 31 and 34 have the promising anti-cancer activity against CYP19A and the correlation between molecular modelling (in-silico) and CYP19A inhibition activities (in- vitro), was established as compounds 31 and 34 were identified to bind to the drug target (CYP19A) with the docking score of -8.372 and 7.630 kcal/mol respectively. All the synthesized compounds were evaluated for the antitubercular activity against Mtb H37Rv strain as a secondary study. Compounds 57-62 with nitro-quinoxaline derivatives exhibited stronger inhibitory effects on Mtb H37Rv strain. In addition, compounds 60 and 62 were found to be most active against Mtb H37Rv with the high activity at MIC90 of <0.65 and <0.64 μM respectively. All active compounds are currently investigated for their cytotoxicity which have not been investigated before / National Research Foundation (NRF) and SASOL Inzalo Foundation

No description available.

Les facteurs de transcription de la famille MAF sont impliqués d’une part au cours du développement dans des processus de différenciation terminale et d’autre part dans la carcinogenèse. Un découplage fonctionnel est observé. En effet, les gènes cibles mis en jeu au cours des processus cancéreux et de différenciation terminale semblent différents. L'activité oncogénique des protéines MAF dépend du contexte cellulaire. Ainsi, il a été proposé qu'elles exercent leur activité oncogénique dans des tissus où elles ne sont pas exprimées normalement. De plus, leur pouvoir transformant est régulé par phosphorylation. Mon travail de thèse a porté sur le rôle oncogénique de ces protéines en étudiant ces deux aspects. J'ai identifié le rôle oncogénique de NRL, un membre de la famille MAF, dans le Médulloblastome et j'ai étudié la régulation par phosphorylation des MAF dans le Myélome Multiple. L’activité oncogénique du facteur de transcription NRL, connu pour son rôle dans la différenciation terminale d’un type cellulaire de la rétine, n’avait jamais été établie. Alors que NRL n'est pas exprimé dans le cervelet sain, des études de transcriptome ont montré que NRL est surexprimé dans un sous-groupe agressif de médulloblastome, une tumeur pédiatrique du cervelet. J’ai montré pour la première fois que NRL est un oncogène. Il participe directement à la carcinogénèse de médulloblastomes, en protégeant les cellules de l’apoptose, à travers la régulation d’un membre anti-apoptotique de la famille BCL, BCL-XL. L’inhibition des protéines BCL pourrait constituer une stratégie thérapeutique potentielle dans des Médulloblastomes de mauvais pronostic et résistants aux traitements classiques.Au sein du laboratoire, un projet, auquel j’ai participé, a porté sur la régulation de l’activité oncogénique des facteurs de transcription MAF, dans des Myélomes Multiples, de mauvais pronostic. Ce travail établit que l’activité oncogénique de deux membres de la famille MAF, MAFB et c-MAF, est régulée par phosphorylation induite par la Ser/Thr kinase GSK3. La phosphorylation des facteurs de transcription MAF augmente leur activité oncogénique et paradoxalement induit leur dégradation par le protéasome. Ce travail a permis d’identifier un mécanisme de résistance potentiel de ces tumeurs et de proposer une nouvelle approche thérapeutique, basée sur l’inhibition de la phosphorylation des protéines MAF. / MAF (MusculoAponeurotic Fibrosarcoma) transcription factors are involved in terminal differentiation during normal development, and also in oncogenesis. A functional uncoupling is observed between these two functional activities. Indeed, target genes involved in cancer or terminal differentiation look different. The oncogenic activity of MAF proteins is dependent on the cellular context. Thus, it was suggested that they exert their oncogenic activity in tissues where they are not normally expressed. In addition, their transforming ability is regulated by phosphorylation. My work focused on the oncogenic role of these proteins by studying these two aspects. I identified the oncogenic role of NRL, a member of the MAF family in Medulloblastoma and I studied the regulation by phosphorylation of MAF in Multiple Myeloma.The oncogenic activity of the transcription factor NRL, known for its role in the terminal differentiation of a cell type in the retina, has never been established. While NRL is not expressed in the healthy cerebellum, transcriptome studies showed that NRL is overexpressed in an aggressive subgroup of medulloblastoma, a pediatric tumor of the cerebellum. I showed for the first time that NRL is an oncogene. NRL is directly involved in the carcinogenesis of medulloblastoma, protecting cells from apoptosis through regulation of an anti-apoptotic member of the BCL family, BCL-XL. Inhibition of the protein BCL could be a potential therapeutic strategy for medulloblastoma with a poor prognosis and resistant to conventional therapies.In the laboratory, I also participated in a project which focused on the regulation of the oncogenic activity of transcription factors, MAF, in rarely curable multiple myeloma. This work establishes that the oncogenic activity of two MAF members, MAFB and c-MAF, are regulated by phosphorylation-induced Ser/Thr kinase GSK3. Phosphorylation of transcription factors MAF increases their oncogenic activity and paradoxically induces their degradation by the proteasome. This work has identified a potential mechanism of resistance of these tumors providing a new therapeutic approach, based on the inhibition of MAF protein phosphorylation.

Το πολλαπλούν μυέλωμα είναι μια νεοπλασία η οποία, έως και σήμερα, παραμένει ανίατη. Στο ΠΜ, το ανοσοποιητικό σύστημα δε κατορθώνει να καταστρέψει τα κακοήθη πλασμοκύτταρα, ενώ υπάρχουν ενδείξεις ότι τα κύτταρα του όγκου παίζουν ενεργό ρόλο σε αυτό. Στην παρούσα διατριβή, ελέγξαμε ποικίλλες μυελωματικές σειρές σχετικά με την έκφραση των προ- και αντι-αποπτωτικών γονιδίων. Βρήκαμε ότι τα μυελωματικά κύτταρα εκφράζουν έναν μη φυσιολογικό φαινότυπο (fas high/bcl low). Μελετώντας τα κύτταρα του μυελού των οστών ενός ασθενούς με ΠΜ τύπου IgG/k σταδίου ΙΙΙΑ, διαπιστώσαμε ότι αυτά τα κύτταρα εξέφραζαν τα γονίδια granzyme B και perforin, τα οποία υπό κανονικές συνθήκες εκφράζονται μόνο από τα κυτταροτοξικά Τ λεμφοκύτταρα (CTLs) και τα φυσικά φονικά κύτταρα (ΝΚ). Προτείνουμε ότι πιθανόν το παραπάνω γεγονός αποτελεί έναν επιπλέον αμυντικό μηχανισμό των κυττάρων του όγκου εναντίον των CTLs και ΝΚ κυττάρων. Συγκεκριμένα υποθέτουμε ότι τα κύτταρα του όγκου προσελκύουν τα CTLs και τα ΝΚ κύτταρα και τα καταστρέφουν με τη διαδικασία της κυτταρόλυσης. Τα διφωσφονικά οξέα χρησιμοποιούνται ευρέως για τη θεραπεία του ΠΜ, ενώ η θαλιδομίδη χρησιμοποιείται σήμερα για τη θεραπεία πολλών τύπων ΠΜ. Μελετήσαμε την επίδραση της θαλιδομίδης, του ζολεδρονικού οξέος και το συνδυασμό τους στην επιβίωση των μυελωματικών κυττάρων. Βρήκαμε ένα συνεργιστικό αποτέλεσμα των δύο αυτών ουσιών. Όταν η θαλιδομίδη συγχοηγηθεί με το ζολεδρονικό οξύ σε ελάχιστους μη δραστικούς μηχανισμούς, μειώνει την τοξική επίδραση 50% του τελευταίου 3-4 φορές. / Multiple Myeloma (MM) is a plasma cell neoplasia which, to this day, remains incurable. In MM, the immune system fails to destroy the malignant plasmocytes, and evidence exists that the tumor plays an active part in this. In the present study, we tested various MM cell lines for the expression of pro- and anti-apoptotic genes. We found that MM cells express an abnormal phenotype, namely fas high/bcl low. By studying bone marrow cells from a patient suffering of MM IgG/k type stage IIIA, we found that those cells expressed granzyme B nad perforin, normally expressed by cytotoxic T cells (CTLs) and natural killer (NK) cells. We propose that this may constitute an additional acquired mechanism by the tumor cells to protect themselves against the host.

Cette thèse montre que le GHB et les neurostéroïdes protègent efficacement contre la mort neuronale induite par les facteurs étiologiques de la maladie d'Alzheimer, notamment la sur-expression de l'amyloid precursor protein et le stress oxydant. Nous avons identifié un effet additif du GHB et de l'alloprégnanolone qui pourrait résulter de la combinaison des stimulations partielles évoquées par ces molécules sur l'expression des protéines anti-apoptotiques. L'effet du GHB est bloqué par un inhibiteur de l'aromatase, suggérant que le GHB induirait la neuroprotection via la stimulation de la neurostéroïdogenèse. Pour étudier les effets du GHB et des neurostéroïdes sur l’activité des MMP-2 et MMP-9, qui dégradent les peptides amyloïdes, nous avons optimisé un test enzymatique basé sur l’expression de ces protéases dans la levure. Nos résultats préliminaires ne permettent pas encore de conclure mais leur amélioration et combinaison avec des données de RT-qPCR contribueront à déterminer l'action du GHB et des neurostéroïdes sur l'activité et/ou l'expression des MMP. Notre travail suggère que le GHB et les neurostéroïdes pourraient être associés pour élaborer des stratégies neuroprotectrices contre les pertes neuronales provoquées par la maladie d'Alzheimer. / This PhD work showed that GHB and neurosteroids efficiently protect against nerve cell death caused by Alzheimer's disease etiological factors including amyloid precursor protein overexpression and oxidative stress. Interestingly, we identified an additive action of GHB and allopregnanolone that may result from the combination of partial stimulations of anti-apoptotic protein expression induced by both compounds. GHB protective effect was blocked by aromatase inhibitor, suggesting that GHB may also induce neuroprotection via the activation of neurosteroidogenesis. Finally, we have used a yeast-based MMP activity assay to check whether GHB and neurosteroids regulate MMP-2 and MMP-9 activities which control Aβ peptide degradation. We cannot yet conclude from our preliminary results but their improvement and combination with RT-qPCR analyzes will help to determine the modulatory action of GHB and neurosteroids on MMP activity and/or expression. Together, our data suggest that GHB and neurosteroids may be used to develop combined neuroprotective strategies against neuronal loss in AD.

La régulation de l’apoptose fait partie des nouvelles cibles thérapeutiques dans la lutte contre le cancer. L’apoptose est l’autodestruction programmée des cellules qui, suite à un besoin physiologique, permet de réguler le développement des cellules. Dans de nombreux cancers, ce mécanisme est inhibé par une surexpression des protéines anti-apoptotiques de la famille Bcl-2 comme Bcl-xL et Mcl-1. Ce phénomène entraîne le développement des cellules tumorales et des résistances aux chimiothérapies. Dans cette optique, notre équipe à l’Institut de Chimie des Substances Naturelles a développé un criblage de plantes tropicales sur ces cibles. Des écorces d’une annonacée de Malaisie, Meiogyne Cylindrocarpa, a été isolé un sesquiterpène dimère, la meiogynine A, présentant une bonne affinité vis-à-vis de Bcl-xL (Ki = 10.7 M). Sa synthèse totale a été réalisée au laboratoire afin de déterminer sa configuration absolue et d’étudier les premières relations structure activité. Un de ses diastéréoisomères a également présenté une bonne affinité vis-à-vis de la protéine Bcl-xL.Afin d’étudier et d’approfondir les premières relations structure activité, la modulation de la meiogynine A a été réalisée. La synthèse des diénophiles acides a été optimisée afin de conduire majoritairement aux diénophiles précurseurs des composés actifs. Différents triènes ont également été synthétisés au laboratoire en vue de modifier la partie Sud de la meiogynine A. Plusieurs analogues ont ainsi pu être obtenus et ont été évalués biologiquement sur des tests in vitro et ex vivo. Des études de modélisation moléculaire et de RMN structurale ont également été réalisées. / The control of the apoptosis is one of the new modern key to fight against the cancer. The apoptosis is the self destruction of cells, part of the homeostasis, which regulates the cell developement. In several cancers, the over-expression of anti-apoptotic proteins, as Bcl-xL and Mcl-1 parts of the Bcl-2 proteins family, inhibate this naturel process. This phenomenum induce the tumoral cells developement and the chemotherapy’s resistance. In order to find new compounds which can regulate the apoptosis, our group in the Institut de Chimie des Substances Naturelles has screened different tropical plants on these targets. A Malaysian plant, Meiogynine Cylindrocarpa, was selected and the phyotchemist work on this plant gave us a new sesquiterpen , the meiogynin A (Ki = 10.7 M on Bcl-xL). Its total synthesis was realised in our laboratory in order to determine its absolute configuration and find the first structure activity relation. One of the synthetised diastereoisomers has presented a better affinity toward the protein. In order to precise these first structure activity relations, the modulation of the meiogynin A was initiated. The synthesis of the acid dienophiles was optimised, the main compounds are the precursors of the active decalins. New triene was also obtained in order to modulate the South Part of the meiogynin A. Thanks to a Diels-Alder reaction, these precursors were combined in order to form new analogues of the meiogynin A. All these compounds were biologically tested (in vitro et ex vivo). Experiments of molecular docking and 2D NMR were also realised.