The lysosome, a multi-copy organelle, was chosen as an example to study intraorganelle dynamics. Lysosomal contents and membrane proteins were shown to intermix rapidly in fused mammalian cells, with a t_½ of ~30 min. Lysosomal content intermixing, shown by a sensitive invertase-lysosome/[¹⁴C]-sucrose-lysosome pairing assay, was inhibited greatly by ATP inhibitors and partially by cytochalasin D. Lysosomal membrane protein intermixing was shown by the transfer of LAMP-2, a mouse specific lysosomal membrane antigen, from mouse lysosomes to hamster sucrosomes, sucrose-swollen lysosomes. Lysosomal membrane protein intermixing was also shown by the co-localization of LIMP I, a rat specific lysosomal membrane antigen, and LAMP-1, a mouse specific lysosomal membrane antigen. Co-localization was assessed by both double immunofluorescent staining and double immunogold labeling of thin cryosections. Both lysosomal content and membrane protein intermixing were inhibited by nocodazole, a microtubule disruptor. In fused cells, lysosomes remained small, punctate and scattered throughout the cytoplasm. In comparison to lysosomes, the prelysosomal compartment (PLC), a single copy organelle which is related to the lysosome, congregated together to form an extended PLC complex associated with clustered nuclei. The intermixing of both resident and transient Golgi membrane proteins was studied in fused cells. Resident Golgi membrane protein intermixing was slow, with a t_½ of ~ 1.75 h; it was concomitant with the congregation of the Golgi units. In comparison, the transient Golgi membrane protein was transported much faster from Golgi units to the other Golgi units, with the t_½ ≤ 15 min. Transient Golgi membrane protein transport occurred between separate Golgi units. These results are consistent with two different pathways for resident and transient Golgi membrane protein transport: a slow, lateral diffusion along the Golgi connections transport pathway for resident Golgi membrane proteins; and a rapid, transient protein selective, vesicle-mediated transport pathway for transient Golgi membrane proteins. / Ph. D.

Seto Tai Chi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 122-138). / Abstracts in English and Chinese. / Thesis Committee --- p.ii / Statement --- p.iii / Acknowledgements --- p.iv / Abstract (in English) --- p.v / Abstract (in Chinese) --- p.vii / Table of Contents --- p.ix / List of Tables --- p.xvi / List of Figures --- p.xv / Chapter Chapter 1 --- General Introduction and Literature Review --- p.1 / Chapter 1.1 --- Introduction --- p.2 / Chapter 1.2 --- Tobacco seed as bioreactor --- p.4 / Chapter 1.2.1 --- Advantages of using tobacco seed to produce bioactive human lysosomal enzyme --- p.4 / Chapter 1.2.2 --- Disadvantages and potential problems of using tobacco seed to produce bioactive human lysosomal enzyme --- p.5 / Chapter 1.2.2.1 --- Difference of asparagine-linked N-glycosylation between plant and human protein --- p.8 / Chapter 1.2.2.2 --- Immunogenicity of recombinant protein with plant-derived N-glycan to human --- p.10 / Chapter 1.2.2.3 --- "Strategy to ""humanize"" plant-derived recombinant human lysosomal enzyme" --- p.10 / Chapter 1.2.2.4 --- Lack of specific glycan structure一mannose-6-phosphate (M6P) tag addition --- p.11 / Chapter 1.2.2.5 --- Strategy for M6P tag addition on plant-derived human lysosomal enzyme --- p.12 / Chapter 1.3 --- The plant secretory pathway --- p.13 / Chapter 1.3.1 --- Plant vacuole in tobacco seed --- p.16 / Chapter 1.3.2 --- Soluble protein trafficking in plant cell --- p.17 / Chapter 1.3.3 --- Integral membrane protein trafficking in plant cell --- p.17 / Chapter 1.3.4 --- Components involved in integral membrane protein trafficking to PSV crystalloid --- p.19 / Chapter 1.3.4.1 --- BP-80 (80-kDa binding protein) --- p.19 / Chapter 1.3.4.2 --- α-TIP (α-tonoplast intrinsic protein) --- p.20 / Chapter 1.3.5 --- Using specific integral membrane protein trafficking system to target recombinant human lysosomal enzyme to tobacco seed PSV --- p.21 / Chapter 1.4 --- Homo sapiens α-L-iduronidase (hIDUA) --- p.21 / Chapter 1.4.1 --- Global situation of lysosomal storage disease一hIDUA deficiency --- p.21 / Chapter 1.4.2 --- Physiological role --- p.22 / Chapter 1.4.3 --- Molecular property --- p.24 / Chapter 1.4.3.1 --- Mutation and polymorphism --- p.24 / Chapter 1.4.4 --- Lysosomal secretory pathway --- p.24 / Chapter 1.4.5 --- Biochemical property --- p.25 / Chapter 1.4.6 --- Clinical application --- p.27 / Chapter 1.4.6.1 --- Enzyme replacement therapy (ERT) --- p.27 / Chapter 1.4.6.2 --- Clinical trial --- p.28 / Chapter 1.4.6.3 --- Economic value --- p.29 / Chapter 1.4.7 --- Expression system --- p.29 / Chapter 1.4.7.1 --- Production (overexpression) of rhIDUA in CHO cell system --- p.30 / Chapter 1.4.7.2 --- Production of rhIDUA in tobacco plant leaf --- p.30 / Chapter 1.5 --- Project objective and long-term significance --- p.30 / Chapter 1.5.1 --- Project objective --- p.30 / Chapter 1.5.2 --- Long-term significance --- p.31 / Chapter Chapter 2 --- Generation and Characterization of Anti-IDUA Antibodies --- p.32 / Chapter 2.1 --- Introduction --- p.33 / Chapter 2.2 --- Materials --- p.33 / Chapter 2.2.1 --- Chemical --- p.33 / Chapter 2.3 --- Methods --- p.35 / Chapter 2.3.1 --- Generation of polyclonal anti-IDUA antibody --- p.35 / Chapter 2.3.1.1 --- Design of synthetic peptide --- p.35 / Chapter 2.3.1.2 --- Conjugation of synthetic peptide to carrier protein --- p.39 / Chapter 2.3.1.3 --- Immunization of rabbit --- p.39 / Chapter 2.3.2 --- Characterization of polyclonal anti-IDUA antibody in rabbit serum --- p.40 / Chapter 2.3.2.1 --- Dot-blot analysis --- p.40 / Chapter 2.3.3 --- Purification of polyclonal anti-IDUA antibody --- p.42 / Chapter 2.3.3.1 --- Construction of anti-IDUA antibody affinity column --- p.42 / Chapter 2.3.3.2 --- Affinity-purification of anti-IDUA antibody --- p.42 / Chapter 2.3.4 --- Western blot detection of denatured rhIDUA --- p.42 / Chapter 2.4 --- Results --- p.43 / Chapter 2.4.1 --- Characterization of polyclonal anti-IDUA antibody --- p.43 / Chapter 2.5 --- Discussion --- p.51 / Chapter 2.6 --- Conclusion --- p.51 / Chapter Chapter 3 --- Generation and Characterization of Transgenic Tobacco Plants Expressing rhIDUA Fusions --- p.52 / Chapter 3.1 --- Introduction --- p.53 / Chapter 3.1.1 --- Signal peptide of hIDUA (hIDUA SP) --- p.54 / Chapter 3.1.2 --- Signal peptide of proaleurain (Pro. SP) --- p.54 / Chapter 3.1.3 --- Hypothesis to be tested in this study --- p.54 / Chapter 3.2 --- Materials --- p.55 / Chapter 3.2.1 --- Chemical --- p.55 / Chapter 3.2.2 --- Primers --- p.55 / Chapter 3.2.3 --- Bacterial strain --- p.58 / Chapter 3.2.4 --- The insert-Homo sapiens α-L-iduronidase (hIDUA) cDNA used in this study --- p.58 / Chapter 3.2.5 --- The vector-pLJ526 used in this study --- p.59 / Chapter 3.3 --- Methods --- p.61 / Chapter 3.3.1 --- Construction of chimeric gene construct --- p.61 / Chapter 3.3.1.1 --- Restriction endonuclease´ؤPfIMIl --- p.61 / Chapter 3.3.1.2 --- Recombinant DNA and molecular cloning techniques used in this study --- p.61 / Chapter 3.3.1.3 --- Cloning of pSPIDUA-FLAG --- p.62 / Chapter 3.3.1.4 --- Cloning of pSPIDUA-control --- p.62 / Chapter 3.3.1.5 --- Cloning of a universal construct (pUniversal) --- p.62 / Chapter 3.3.1.6 --- Cloning of pSP-IDUA-T7 --- p.66 / Chapter 3.3.1.7 --- Cloning of pSP-IDUA-control --- p.66 / Chapter 3.3.1.8 --- Cloning of chimeric gene construct into Agrobacterium binary vector --- p.66 / Chapter 3.3.2 --- Expression of chimeric gene construct in tobacco plant --- p.73 / Chapter 3.3.2.1 --- Tobacco plant --- p.73 / Chapter 3.3.2.2 --- Electroporation of Agrobacterium --- p.73 / Chapter 3.3.2.3 --- Agrobacterium-mediated transformation of tobacco plant --- p.74 / Chapter 3.3.2.4 --- Selection and regeneration of tobacco transformant --- p.75 / Chapter 3.3.3 --- Characterization of transgenic tobacco plant expressing rhIDUA fusion --- p.75 / Chapter 3.3.3.1 --- Genomic DNA polymerase chain reaction (PCR) --- p.75 / Chapter 3.3.3.2 --- Southern blot analysis --- p.76 / Chapter 3.3.3.3 --- Total RNA reverse transcription-PCR (RT-PCR) --- p.77 / Chapter 3.3.3.4 --- Northern blot analysis of tobacco leaf --- p.78 / Chapter 3.3.3.5 --- Western blot analysis --- p.79 / Chapter 3.3.4 --- Purification of plant-derived rhIDUA fusion --- p.81 / Chapter 3.3.4.1 --- Construction of affinity column with anti-IDUA antibody --- p.81 / Chapter 3.3.4.2 --- Affinity-purification of rhIDUA fusion from tobacco mature seed --- p.81 / Chapter 3.3.5 --- Confocal immunoflorescence study --- p.82 / Chapter 3.3.5.1 --- Preparation of paraffin section --- p.82 / Chapter 3.3.5.2 --- Single immunocytochemical labeling --- p.82 / Chapter 3.3.5.3 --- Double labeling with one monoclonal and one polyclonal antibodies --- p.83 / Chapter 3.3.5.4 --- Double labeling with two polyclonal antibodies --- p.83 / Chapter 3.3.5.5 --- Image collection --- p.84 / Chapter 3.4 --- Results --- p.85 / Chapter 3.4.1 --- Chimeric gene construction and confirmation --- p.85 / Chapter 3.4.2 --- Selection and regeneration of tobacco transformant with kanamycin- resistance --- p.86 / Chapter 3.4.3 --- Genomic DNA PCR screening of tobacco transformant --- p.88 / Chapter 3.4.4 --- Southern blot analysis of tobacco transformant --- p.91 / Chapter 3.4.5 --- Total RNA RT-PCR screening of tobacco transformant --- p.93 / Chapter 3.4.6 --- Northern blot analysis of tobacco transformant --- p.93 / Chapter 3.4.7 --- Western blot analysis --- p.96 / Chapter 3.4.7.1 --- Western blot analysis of pSP-IDUA-T7-121 transformant leaf --- p.96 / Chapter 3.4.7.2 --- Western blot analysis of pSP-IDUA-T7-121 transformant mature seed --- p.98 / Chapter 3.4.8 --- Affinity-purification of rhIDUA fusion --- p.98 / Chapter 3.4.9 --- Expression level of rhIDUA fusion --- p.102 / Chapter 3.4.10 --- Subcellular localization of rhIDUA fusion --- p.102 / Chapter 3.5 --- Discussion --- p.111 / Chapter Chapter 4 --- Summary and Future Perspectives --- p.117 / References --- p.122 / Appendix 1 --- p.139 / Appendix II (List of Abbreviations) --- p.141

MTOR est une sérine/thréonine kinase appartenant au complexe mTORC1 (mTOR Complexe 1), un régulateur clé de la traduction. Ce complexe joue un rôle au sein de la LTP (Potentialisation à Long Terme), une forme de plasticité synaptique qui requiert la synthèse de nouvelles protéines pour renforcer la transmission synaptique. La première partie de ma thèse porte sur les mécanismes de régulation de la voie mTORC1 dans les neurones. Dans les cellules non neuronales, cette voie de signalisation est classiquement régulée par deux voies distinctes. D’une part, les acides aminés induisent le recrutement du complexe mTORC1 à la membrane des endo-lysosomes où la protéine Rheb est enrichie et favorisent ainsi l’activation de mTORC1. D’autre part, les facteurs de croissance activent mTORC1 en stimulant la voie PI3K/Akt/TSC/Rheb. Nos résultats indiquent que les neurones sont capables d’ "utiliser" le mécanisme responsable de la translocation de mTORC1 en réponse à la supplémentation en acides aminés pour coupler l’induction de la plasticité synaptique à l’activation de mTORC1. En effet, les récepteurs NMDA et le BDNF, deux acteurs centraux de la LTP, augmentent le recrutement de mTORC1 à la membrane des endo-lysosomes même en absence d’acides aminés, et activent mTORC1. Par des stratégies induisant la translocation de mTORC1 à la membrane des endo-lysosomes, nous avons montré que ce mécanisme est important pour l’activation de mTORC1 mais n’est pas suffisant : il faut également une activation de la protéine Rheb. Le second aspect de mon projet porte sur la régulation de mTORC1 dans le cadre de la maladie d’Alzheimer, une maladie neurodégénérative caractérisée par une perte progressive de la mémoire. Les déficits cognitifs s’accompagnent d’un dysfonctionnement progressif des synapses suivi par la perte neuronale, tous deux causés par une accumulation anormale du peptide amyloïde β (Aβ). Les données de la littérature montrent que les oligomères toxiques du peptide Aβ (AβO) inhibent la plasticité synaptique dans les stades précoces de la maladie. Cependant, les mécanismes restent obscurs. Plusieurs études mettent en évidence une altération de la voie mTORC1. Nos résultats montrent que les AβO inhibent le recrutement de mTORC1 à la membrane des endo-lysosomes. Ce mécanisme est rétabli par une inhibition pharmacologique de l’AMPK. Ainsi, ces données indiquent que les AβO inhibent l’adressage de mTORC1 aux compartiments endo-lysosomaux via l’AMPK. Cela aurait pour conséquence une inhibition de la synthèse protéique décrite dans la littérature et contribuerait ainsi au dysfonctionnement synaptique. / MTOR is a serine/threonine kinase that belongs to mTORC1 (mTOR complex 1), a key regulator of translation. This complex is involved in LTP (Long Term Potentiation), a form of synaptic plasticity requiring new protein synthesis to reinforce synaptic transmission. The first part of my thesis investigates the mechanism of mTORC1’s regulation in neurons. In non-neuronal cells, mTORC1 pathway is commonly activated by two distinct pathways. On the one hand, amino acids induce mTORC1 recruitment to the membrane of endo-lysosomes where Rheb is enriched and can thus promote mTORC1 activation. On the other hand, growth factors activate mTORC1 via the PI3K/Akt/TSC/Rheb pathway. Our results indicate that neurons are capable of “using” amino acid-induced translocation of mTORC1 to connect synaptic plasticity induction to mTORC1 activation. Indeed, NMDA receptors and BDNF, two main actors of synaptic plasticity, increase mTORC1 recruitment to the membrane of endo-lysosomes even in the absence of amino acids, and activate mTORC1. Using strategies targeting mTORC1 to endo-lysosomes, we show that this mechanism promotes activation of mTORC1 but is not sufficient: Rheb activation is also required. The second part of my project is focused on the regulation of mTORC1 in Alzheimer’s disease, a neurodegenerative pathology characterized by a progressive memory loss. Cognitive deficits are widely believed to result from a progressive dysfunction of synapses, followed by a loss of neurons, both caused by an abnormal accumulation of the amyloid β peptide (Aβ). Data from others show that toxic Aβ oligomers (AβOs) inhibit synaptic plasticity at early stages of the disease. However, the mechanisms remain poorly understood. Several studies indicate an alteration of the mTORC1 pathway. Our results show that AβOs inhibit mTORC1 recruitment to the membrane of endo-lysosomes and that this effect can be rescued by a pharmacological inhibition of AMPK. Thus our data indicate that AβOs inhibit mTORC1 translocation to endo-lysosomal compartments via AMPK. This could lead to the impairment of protein synthesis reported in other studies and thus alter synaptic function.

Les cellules de mélanome humain expriment différents antigènes tumoraux qui sont reconnus par les lymphocytes T cytotoxiques CD8 + (CTL) induisant des réponses spécifiques de la tumeur in vivo. Cependant, chez les patients atteints de mélanome l'efficacité de la réponse naturelle des CTL ou stimulée par thérapie est limitée. Les mécanismes sous-jacents de l'échec de la phase effectrice des CTL contre les mélanomes sont encore largement méconnus. Notre hypothèse est que l'efficacité limitée des CTL dans leur combat contre les tumeurs est le résultat d'une balance défavorable entre la capacité des CTL à tuer les tumeurs et une résistance tumorale intrinsèque à l'activité cytolytique des CTL. Au cours de ma thèse je me suis concentrée sur la dynamique moléculaire qui se produit à la synapse lytique afin de pouvoir identifier un mécanisme précoce mis en place par les cellules de mélanome face à l'attaque des CTL. En combinant l'utilisation d'approches de microscopie de pointe et des outils moléculaires, j'ai pu montrer que, lors de l'interaction avec les CTL, les cellules de mélanome humain subissent une activation de leur trafic vésiculaire endosomal et lysosomal, lequel est intensifié à la synapse lytique et corrèle avec la dégradation par la cathepsine de la perforine et un défaut de pénétration d'entrée du granzyme B. De plus, j'ai démontré que le blocage du trafic lysosomal dépendant de SNAP23, la modification du pH (intra-vésiculaire) et l'inhibition de l'activité lysosomale protéotlytique des cellules de mélanome permet de restaurer leur sensibilité à l'attaque des CTL. Nos résultats révèlent une stratégie sans précédent d' " auto-défense " des cellules de mélanome à la synapse immunologique basée sur une sécrétion lysosomale massive et sur la dégradation de la perforine sécrétée par les CTL. Ainsi pouvoir interférer avec cette stratégie synaptique d'auto-défense des cellules de mélanome pourrait contribuer à potentialiser les réponses des CTL et les immunothérapies chez les patients atteints de mélanome. / Human melanoma cells express various tumor antigens that are recognized by CD8+ cytotoxic T lymphocytes (CTL) and elicit tumor-specific responses in vivo. However, natural and therapeutically enhanced CTL responses in melanoma patients are of limited efficacy. The mechanisms underlying the failure of CTL effector phase against melanomas are still largely elusive. Our hypothesis is that the limited efficacy of CTL in their fight against tumors is the result of an unfavorable balance between CTL ability to kill tumors and an intrinsic tumor resistance to CTL cytolytic activity. During my thesis I focused on the molecular dynamics occurring at the lytic synapse in order to identify possible "early response-mechanism" of melanoma cells to CTL attack. Using a combination of cutting edge microscopy approaches and molecular tools, I showed that upon conjugation with CTL, human melanoma cells undergo an exacerbated late endosome/lysosome trafficking, which is intensified at the lytic synapse and is paralleled by cathepsin-mediated perforin degradation and deficient granzyme B penetration. Abortion of SNAP-23-dependent lysosomal trafficking, pH perturbation or impairment of lysosomal proteolytic activity restores susceptibility to CTL attack. Our results reveal an unprecedented strategy of melanoma cell "self-defense" at the immunologic synapse based on a lysosome secretory burst and perforin degradation at the lytic synapse. Interfering with this synaptic self-defense strategy might be instrumental to potentiate CTL-mediated therapies in melanoma patients.

A flagelina é um agonista natural do sensor TLR5 e do inflamassoma NAIP/NLRC4 que é responsável pela secreção de IL-1β e IL-18 e pela indução de morte celular necrótica, via ativação da caspase-1. Entretanto, nós observamos que a inserção da flagelina de B. subtilis no citosol celular por meio de vesículas lipídicas, induz um processo atípico de morte nos macrófagos peritoneais (PMs) deficientes em NLRC4, ASC e caspase-1/11. A morte dos PMs manteve seu resultado antimicrobiano, sendo acompanhada da liberação de IL-1α. A morte celular e a secreção das citocinas IL-1α e IL-1β, foi mediada por catepsinas lisossomais, sugerindo uma cooperação entre a via lisossomal e os inflamassomas nas respostas induzidas pela flagelina. Além disso, a flagelina de S. typhimurium foi capaz de induzir dano lisossomal e secreção de IL-1α e IL-1β mediada pelo eixo caspase-catepsinas, na ausência de carreadores, e estas citocinas tiveram um impacto na imunidade adaptativa induzida pela flagelina, no modelo de ativação de linfócitos T específicos por células dendríticas, in vitro. / Flagellin is a natural agonist of TLR5 and NAIP/NLRC4 inflammasome that is responsible for IL-1β and IL-18 secretion and for the induction of a necrotic cell death, both mediated by caspase-1. However, we observed that flagellin from B. subtilis inserted into lipid vesicles, induced an atypical cell death in peritoneal macrophages (PMs) in the absence of NLRC4, ASC and caspase-1/11. This inflammasome-independent cell death retained its antimicrobial outcome, being accompanied with IL-1α secretion. Importantly, cell death and caspase-1-dependent IL-1α and IL-1β secretion were regulated by lysosomal cathepsins, suggesting a cooperation between the inflammasome and lysosomal pathway in response to flagellin. We also observed that flagellin from S. typhimurium is able to induce lysosomal damage and IL-1α and IL-1β secretion by PMs in the absence of a carrier, through a caspase-catepsins-dependent manner, and that cytokines were important to the ability of flagellin in to induce adaptive immune response by antigen-specific T cells.

Obesity occurs when nutrient intake exceeds energy expenditure over prolonged periods. In the modern world, obesity has reached epidemic proportions. Complications of obesity, including cardiovascular disease, non-alcoholic fatty liver disease, certain forms of cancer, and metabolic dysfunction contribute substantially to morbidity and death today. With 13% of the world’s population affected, the rising rates of obesity will grow as a public health burden. Until recently, pharmacologic attempts to treat obesity have focused on reducing food intake. However, motivated in part by recent studies in mice and by analyses of fat in humans, approaches to increasing energy expenditure, specifically thermogenic energy expenditure, may provide a new therapeutic avenue. Most simplistically, there are two classes of adipocytes: storage and thermogenic. Storage fat, typically composed of unilocular white adipocytes function as storage depots for excess calories. On the other hand, thermogenic fat containing brown or beige adipocytes, generate heat through uncoupled mitochondrial respiration, This regulated generation of heat, known as thermogenesis, is used by organisms to maintain or increase body temperature. Historically, thermogenesis has been divided into shivering and nonshivering thermogenesis. Repeated, rapid contraction of skeletal muscles generate heat and is the basis for shivering thermogenesis. Nonshivering thermogenesis (NST) describes all the other mechanisms by which an organism can generate regulated heat. Only two organelles are known to contribute to NST: the mitochondrion of brown and beige adipocytes and the sarcoplasmic reticulum of muscle. The role of other organelles has not been systematically studied. Here we show in mice that thermogenic stimuli, including a cold challenge and pyrogenic molecules, activate a lysosomal program in a known thermogenic tissue (BAT) as well as several “non-thermogenic” organs, including the spleen, liver and skeletal muscle. A similar program is activated by a cold challenge in the metazoan, Drosophila melanogaster, suggesting an evolutionarily ancient origin for this response. We show by both pharmacologic and genetic means that impairment of lysosomal function compromises the thermogenic response of individual cells ex vivo and of mice in vivo. Data from genetic manipulations find that impairment of lysosome function that leads to cold intolerance and death can modestly downregulate the classical Ucp1 thermogenic program. However, pharmacological inhibition reveals that impairment of lysosome function can compromise thermogenesis without altering the Ucp1 program. As part of our efforts to study lysosome function in thermogenesis we developed a new method of measuring thermogenesis in primary cells. Using isothermal titration calorimetry (ITC), we quantitatively measured the heat generated by cells isolated from mice. This permitted us to assess the effects of both genetic and pharmacologic manipulations on the generation of heat and allowed us, for the first time, to measure the heat (uCal/sec/cell) of BAT in the basal and stimulated state. With ITC, we demonstrated that the impairment of lysosome function had direct effects on the generation of cellular heat, independent of systemic modulators of temperature such as basal metabolic rate or circulatory dissipation. From these studies, we conclude that lysosomes are thermogenic organelles induced by cold and pyrogenic stimuli and contribute both directly and indirectly to thermogenesis. Our work also suggests that lysosome thermogenesis may provide a means of thermoregulation in non-homeotherms as well as in tissues previously not implicated in temperature regulation in mammals.

Ovarian carcinoma afflicts over 22,000 women each year with a 5 year survival rate of only 18% for stage IV patients [23]. Current treatment options are limited due to high rates of drug resistance and recurrence. Further, the identity of "precursor lesions" which give rise to various subclasses of epithelial ovarian cancer has been evasive. This is due to discovery of the cancer at already an advanced stage. Interestingly, endometriosis a benign but invasive gynecological disease has been described as a "precursor lesion" in the development of specific subtypes of ovarian cancer. Endometriotic cyst development involves the accumulation of "old blood" components including iron-rich heme. Published evidence implicates excess iron that is involved in the transformation of normal surface epithelial cells inducing morphological characteristics of clear cell ovarian cancer cells [13, 34]. Due to excess iron in endometriotic cysts, this essential element may play a transformative role in the development of clear cell ovarian cancer and possibly other subtypes [13, 35-38]. Further, studies show increased risk of developing ovarian cancer, particularly clear cell and endometrioid ovarian subtypes, in patients diagnosed with endometriosis [36, 37, 39, 40] . This thesis aims to initiate an investigation regarding the contribution of iron and endometriotic lesions in the development and progression of specific subtypes of epithelial ovarian cancers. Since there is a lack of well-validated and characterized endometriotic cell lines that could be used for endometriosis studies, we sought to develop an immortalized cell line for future endometriotic in vitro and in vivo studies. Thus, in Chapter 3 we present our efforts in developing a novel life-span extended epithelial endometriotic cell line. The cells were derived from the endometriotic tissue of a patient with endometriosis. We describe our attempts at immortalization and the characterization of this endometriotic cell line in relation to previously reported/available endometrial/endometriotic cell lines. In Chapter 4 we investigated the role of iron in modulating functional aspects of various gynecological cell lines. Although our expectation was that iron could transform normal ovarian surface epithelial cells (OSE) to a carcinoma-like phenotype, we instead discovered that ovarian cell lines containing Ras mutations (or with H-Ras overexpression) responded to iron (presented as ferric ammonium citrate (FAC)) with a reduced growth response. Further treatment with iron induced an apoptotic/necrotic death response in the Ras mutated HEY ovarian carcinoma cell line. Interestingly, we identified that iron induced autophagic activation in all ovarian cell lines investigate, although autophagy contributed only modestly to the cell death event. Furthermore, we noted that iron activated the MAPK pathway and its inhibition (via U0126, a MAPK inhibitor) allowed survival of cells. In Chapter 5, we briefly explore the role of iron in ovarian cell types growing under anchorage-independent conditions. We found that the cell lines displayed increased cleaved PARP and apoptosis when placed under these conditions. Treatment with iron led to a reduction in cleaved PARP suggesting that iron promotes cell survival in anchorage-independent conditions. Further, inhibition of autophagy via chloroquine led to increased cleaved PARP suggesting that autophagy may mediate a protective role against anchorage-independent apoptotic response In Chapter 6, we attempted to elucidate the downstream mechanism following Ras/MAPK activation in response to iron. This study identified several signaling pathways including that involved in translational control, iron metabolism, as well as mitochondrial function. The inhibition of the iron regulatory and translation control pathway did not significantly lead to rescue of iron-induced cell death of Ras mutated/overexpressed cells. However, we noted mitochondrial stress and damage including altered expression of mitochondrial markers (TOM20/TOM70, outer membrane transporters) which occurred concurrently with iron-induced cell death. The inhibition of iron import into mitochondria using a calcium uniporter channel inhibitor (Ru360) led to a marked reversal of the cell death response. Collectively, these studies suggest that increased mitochondrial permeabilization may be responsible for the observed iron-induced cell death response. Overall, the studies presented in this thesis have revealed novel responses to iron in the gynecological cell types investigated. We initially sought to understand the role of iron in precursor lesions which included the development of a novel life-span extended epithelial endometriotic cell type. Remarkably, our findings revealed a Ras driven sensitivity to excess iron. Treatment with iron caused decreased cell growth and increased cell death in cell types containing Ras mutation/overexpression. Further, we found that the mechanism leading to the iron-induced cell death events was mediated via the MAPK pathway. We then determined that the cell death response was associated with mitochondrial permeabilization. Loss of mitochondrial integrity occurred in Ras sensitive cell lines and inhibition of iron import into the mitochondria (via the calcium uniporter channel inhibitor, Ru360) led to reversal of this response. We show herein the cellular response of excess iron and its potential implication in ovarian cancer research.

Addendum inserted at back Includes bibliographical references (leaves 266-287). 1. Introduction -- 2. Materials and general methods -- 3. Characterisation and partial purification of the lysosomal sulphate transporter -- 4. Identification of proteins involved in lysosomal sulphate transport -- 5. The relationship between a sulphate anion transporter family and the lysosomal sulphate transporter -- 6. Investigation of sulphate transport in human skin fibroblasts -- 7. Concluding remarks

Addendum inserted at back / Includes bibliographical references (leaves 266-287). / xxiv, 289 leaves, [2] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Paediatrics, 2001

Chronic exposure to some oxysterols might contribute to deterioration of human or environmental health. Oxysterols are both biomarkers of oxidative stress as well as mediators of its damage, and play a central role in many independent, but converging, disease processes, such as atherosclerosis, Alzheimer's disease, and age-related macular degeneration. Therefore, the aim of this thesis was to identify enzymes capable of transforming oxysterols to either reduce their toxicity or facilitate their metabolism or excretion. 7-ketocholesterol (7KC), being amongst the most cytotoxic and recalcitrant of these compounds, was the main focus of this work. We isolated various bacteria capable of utilizing 7KC as a sole carbon and energy source. One of these, Rhodococcus jostii RHAl , was subjected to rigorous transcriptomic and mutational analysis to elucidate its 7KC degradation pathway, which was similar, but not identical, to that of cholesterol. Metabolite screening revealed the reduction and subsequent removal of the 7-keto moiety prior to the step catalyzed by HsaC, the enzyme responsible for cleavage of sterol ring A. Furthermore, cloning and expression of a number of reductases from two gene clusters that were highly up-regulated during growth on 7KC identified three reductases that are active against several closely related structural analogs, though not 7KC itself. 7KC and a number of analogs were assayed for toxicity against human fibroblasts Several enzymes were overexpressed in these fibroblasts by transient transfection with mammalian expression vectors to screen for their ability to mitigate 7KC-induced cytotoxicity. A LAMP1/cholesterol oxidase chimera was found to be significantly cytoprotective to exposure to up to 50 μM 7KC compared to mock transfection as well as 7KC-transforming enzymes targeted to either the mitochondria or cytosol. Additionally, transfection with LAMP1 alone and treatment with 0.9% hydroxypropyl β-cyclodextrin also reduced toxicity. Therefore, it seems likely that addressing 7KC toxicity within the lysosome is critical for cytoprotection. This work provides preliminary evidence to support this approach, and may have implications for the treatment of oxysterol-associated diseases. However, further research is needed to evaluate the effects and safety of heterologous gene expression within the lysosome, both in vitro and in vivo.