京都大学 / 新制・課程博士 / 博士(薬学) / 甲第23473号 / 薬博第849号 / 新制||薬||242(附属図書館) / 京都大学大学院薬学研究科薬学専攻 / (主査)教授 髙倉 喜信, 教授 山下 富義, 教授 小野 正博 / 学位規則第4条第1項該当 / Doctor of Pharmaceutical Sciences / Kyoto University / DFAM

Introduction: Viruses, extracellular vesicles (EVs) and endogenous retroviruses (ERVs) are types of sub-micron particles which are known to be released from a vast range of cell types, across many species. There are many medically relevant sub-micron particles which can enter healthy cells and enable the intercellular delivery of functional host-derived and foreign products, through their enclosed lipid layers. While multiple particle subsets have been identified, many of the properties, behaviors and biochemical functions have not been fully described and have yet to be characterized. Materials and Methods: CD4⁺ naïve T-cells were isolated from female C57BL6/N mice and stimulated with varying concentrations of PMA/I. In addition to concentration, the length of PMA/I activation was assessed. Supernatants and cells were harvested, filtered, and stained to be subsequently analyzed by Nanoscale Flow Cytometry, Nanoparticle Tracking Analysis and Flow Cytometry. Particle populations were quantified and sorted by size, by NTA. Labelling dye CFSE was used in conjunction with fluorescently conjugated CD81 and CD9 antibodies to separate EVs, including exosomes, from background signal. Naïve T-cell purity, viability and levels of activation were assessed by flow cytometry using CD3, CD4 and CD62L antibodies and viability staining. Results: Increasing PMA concentration led to a global increase in particles by T-cells and a specific increase in smaller particle production and were demonstrated to be significant by Welch’s T-test, when compared to non-activated and DMSO controls (p<0.0001). In addition to concentration, activation length also correlated with increases in total particle counts and a specific increase in the secretion of smaller particles in comparison to non-activated and DMSO controls (p<0.0001). Labelling techniques by NFC revealed an increased presence of CFSE-CD81 positive and CFSE-CD9 positive particles secreted by T-cells, treated for 24 hours, compared to the 0- and 12-hour timepoints. Conclusion: This work demonstrates preliminary steps and outlines methods to begin assessing discrete particle populations and subsets secreted by murine naïve T-cells. Being able to identify patterns of particle secretions by naïve T-cells, especially under immune-stimulated conditions, may be the solution to uncovering the necessary information on EV physiology, that is required to understand the roles EVs play in pathology and how these conserved pathways may lead conditions to become exacerbated. This knowledge is essential to uncovering the roles EVs play in pathophysiology, and in the development of novel rapid diagnostic tests, to screen for cancers, infections, autoimmune disorders, and numerous other pathological conditions.

Pancreatic cancer (PC) is a highly aggressive disease with unmet therapeutic needs. Recent advances in the use of oncolytic viruses (OVs) as cancer therapeutic agents bring new hope to fight the notorious disease that is PC. Although OVs have shown promising results in certain cancers, some tumors remain resistant to OV therapy due to their inherent residual antiviral mechanisms. We hypothesized that the use of OV-encoded artificial microRNAs (amiRNAs) could help target the cellular antiviral components associated with the observed OV resistance and could also sensitize neighboring tumor cells to OV therapy and small molecule inhibitors through the secretion of amiRNA-containing extracellular vesicles (EVs) from infected cells. To find such amiRNAs, a viral surrogate library encoding ~16,000 unique amiRNAs was passaged in pancreatic cancer cell lines to enrich for sequences that could enhance OV replication. An amiRNA that improves PC cell killing when expressed from an OV was identified. Target identification of this amiRNA (amiR-4) revealed ARID1A as a key player in resistance to OV therapy in pancreatic cancers. This target is of particular interest, since its downregulation acts in a synthetic lethal fashion with inhibition of the EZH2 methyltransferase. Combining VSV51-amiR-4 with a small molecule inhibitor of EZH2 enhances PC cell death. Moreover, amiR-4 is packaged in cancer cell-secreted EVs which can reach neighboring naïve cells to sensitize them to EZH2 inhibition-mediated cell death and to spread the OV-mediated tumor killing effect throughout the tumor. This data translates into tumor debulking and survival in animal models of highly aggressive PC. This work not only broadens our knowledge on the resistance of select tumors to oncolytic virotherapy and the EV-mediated bystander killing effect in OV-infected tumors, but it also establishes OVs as a novel tool to produce anti-cancer therapeutic EVs in situ to improve therapeutic gain. Ultimately, our work provides new hope for a cure to the grim disease that is PC.

The exocyst is an evolutionarily conserved, hetero-octameric protein complex proposed to serve as a multi-subunit tethering complex for exocytosis, although it remains poorly understood at the molecular level. The classification of the exocyst as a multisubunit tethering complex (MTC) stems from its known interacting partners, polarized localization at the plasma membrane, and structural homology to other putative MTCs. The presence of 8 subunits begs the questions: why are so many subunits required for vesicle tethering and what are the contributions of each of these subunits to the overall structure of the complex? Additionally, are subunit or subcomplex dynamics a required feature of exocyst function? We purified endogenous exocyst complexes from Saccharomyces cerevisiae, and showed that the purified complexes are stable and consist of all eight subunits with equal stoichiometry. This conclusion contrasts starkly with current models suggesting that the yeast exocyst tethers vesicles by transient assembly of subcomplexes at sites of exocytosis. Using a combination of biochemical and auxininduced degradation experiments in yeast, we mapped the subunit connectivity, identified two stable four-subunit modules within the octamer, and demonstrated that several known exocyst binding partners are not necessary for exocyst assembly and stability. Furthermore, we visualized the structure of the yeast complex using negative stain electron microscopy; our results indicate that exocyst exists predominantly as an octameric complex in yeast with a stably assembled, elongated structure. This is the first complete structure of a CATCHR family MTC and it differs greatly from the EM structures available for the partial COG and Dsl1 complexes. Future work will be necessary to determine whether exocyst conformational changes are a required feature of vesicle tethering and how such changes are regulated. These architectural insights are now informing the design of the first in vitro functional assay for the exocyst complex. We developed methodology for attaching fluorescently-labeled exocyst complexes to glass slides and monitoring the capture of purified, endogenous secretory vesicles by single molecule TIRF microscopy. By this approach, we can monitor tethering events in real time and determine the required factors and kinetics of exocytic vesicle tethering.

Detection of cancer at the early stages greatly increases the chance for successful treatment and favourable prognosis for patients. However, a liquid-based biopsy has yet to be developed for most cancers. Extracellular vesicles (EVs) are an attractive candidate for early cancer detection since their surface proteome mirrors the cell of origin. Thus, there is a need for the development of reliable probes that can detect cancer derived EVs. In this thesis, the VBS-1 aptamer was developed to selectively bind to triple-negative breast cancer cell line derived EVs. Initially, several EV isolation methods were compared and isolated EVs were validated and characterized. Aptamer clones were developed by Systematic Evolution of Ligands by Exponential Enrichment to EVs isolated by differential ultracentrifugation and their binding was validated by flow cytometry. The binding partner of the selected VBS-1 aptamer was identified by LC-MS/MS to be the transmembrane protein ATP1A1. The presence of an ATP1A1-positive EV population was validated by flow cytometry. The selected aptamer may find further application in biosensors for the detection of EVs as cancer biomarkers in biological fluids.

Ovarian cancer (OVCA) is the most lethal gynecological cancer with a 5-year survival rate less than 50%. Despite new therapeutic strategies, such as targeted therapies and immune checkpoint blockers (ICBs), tumor recurrence and drug resistance remain key obstacles in achieving long term therapeutic success. Therefore, there is an urgent need to understand the cellular and molecular mechanisms of immune dysregulation in chemoresistant ovarian cancer in order to harness the host’s immune system to improve cancer survival. Early diagnosis and residual disease are key determinants of favorable survival in OVCA; however, CA125 which is the conventional marker is not reliable and has modest diagnostic accuracy. There is therefore an urgent need to discover reliable biomarkers to optimize individualized treatment and diagnostic recommendations. Plasma gelsolin (pGSN; an actin binding protein) is the secreted isoform of the gelsolin (GSN) gene implicated in inflammatory disorders, colon cancer and prostate cancer. Increased expression of total GSN is associated with poor survival of patients with gynecological cancers. As to whether this is due to pGSN is yet to be investigated. Increased expression of pGSN is significantly associated with the down-regulation of immune cell markers; however, the exact mechanism has not been explored. If and how pGSN is involved in the cellular and molecular mechanisms of OVCA remains to be determined. In our current research, we have demonstrated that pGSN is involved in the regulation of immune cells, early diagnosis, tumor recurrence and chemoresistance in OVCA, using standard in vitro techniques and human clinical samples (North America, Asia and public datasets). We have shown that pGSN is highly expressed and secreted in chemoresistant OVCA cells than their chemosensitive counterparts. pGSN, secreted and transported via exosomes, upregulated HIF1α–mediated pGSN expression in chemoresistant OVCA cells in an autocrine manner as well as conferred cisplatin resistance in otherwise chemosensitive OVCA cells. pGSN also induced the OVCA expression of the antioxidant and tumor growth promoter, glutathione (GSH), by activating Nuclear factor erythroid 2-related factor 2 (NRF2), a response that attenuated cisplatin (CDDP)-induced apoptosis. In human tumor tissues, increased pGSN mRNA and protein expressions were significantly associated with advanced tumor stage, suboptimal residual disease, tumor recurrence, chemoresistance and poor survival regardless of patients’ ethnic background and histologic subtypes. Increased Infiltration of CD8+ T cells was significantly associated with favorable patient survival; however, increased pGSN hindered the survival impact of these infiltrated CD8+ T cells. Further investigation revealed that pGSN induced CD8+ T cell death via caspase-3 activation, an action that resulted in decreased IFNγ levels. Increased epithelial pGSN expression was significantly associated with reduced survival benefits of infiltrated M1 macrophages, through caspase-3-dependent apoptosis as well as reduced production of TNFα and iNOS. The clinical application of circulatory pGSN as a biomarker for early detection and patients’ survival was investigated. Pre-operative circulating pGSN presented as a favorable and independent biomarker for early disease detection and residual disease prediction compared with CA125. The test accuracy of pGSN was significantly enhanced when combined with CA125 in multianalyte index assay. The findings suggest that pGSN is a potential target for chemoresistant OVCA and presents as a diagnostic marker for early stage disease and surgical outcomes, interventions that could maximize the therapeutic success of immunotherapies.

Le développement larvaire de Leptopilina boulardi (guêpe endoparasitoïde) a lieu dans la larve de Drosophile hôte, principalement D. melanogaster. La réponse immunitaire de l’hôte est l’encapsulement, formation d’une capsule mélanisée formée de couches d’hémocytes spécialisés, les lamellocytes, autour de l’œuf du parasitoïde. Le succès de L. boulardi repose sur l’injection de venin qui bloque l’action des lamellocytes. Ce venin, contient des composants protéiques et des vésicules originales baptisées vénosomes. J’ai montré que deux facteurs de virulence (VFs), LbGAP et LbGAP2, s’intègrent aux vénosomes lors de leur assemblage qui semble se faire de façon extracellulaire dans le canal reliant la glande à venin au réservoir. La microinjection de vénosomes purifiés comme celle du venin inhibe l’encapsulement. Les vénosomes marqués par fluorescence et les VFs co-immunolocalisent dans les lamellocytes de l’hôte après injection, leur internalisation passe par une endocytose flotilline/raft-domaine dépendante. Le taux d’internalisation diffère fortement entre les espèces hôtes de Drosophile testées (D. melanogaster>D. simulans>D. yakuba>D. suzukii) et il est corrélé au taux de réussite parasitaire, suggérant l’existence d’un récepteur spécifique sur les lamellocytes de D. melanogaster. Grâce à la souche mutante HopTum-l qui produit des lamellocytes constitutivement, j’ai séparé ces cellules et entrepris l’analyse protéomique de leur membrane pour identifier des récepteurs candidats. Mes résultats démontrent que les vénosomes sont des véhicules de transport interespèces impliqués dans la virulence parasitaire et qu’ils représentent un nouveau niveau de spécificité d’hôte. / Endoparasitoid wasps, such as Leptopilina boulardi (Figitidae), develop inside Drosophila host larvae, mainly D. melanogaster. Egg oviposition normally results in a capsule formation by specialized haemocytes, the lamellocytes, associated with a melanization reaction. The parasitic success of L. boulardi relies on injection with the egg of venom that blocks the action of lamellocytes. This venom, synthesized at the level of a specialized gland and stored in a reservoir, contains protein components and original vesicles (venosomes). I have shown that two described virulence factors, LbGAP and LbGAP2 (VFs), are embedded in venosomes during their assembly which seems to occur extracellularly in the duct connecting the venom gland to the reservoir. Microinjection of purified venosomes protects the egg from encapsulation like venom injection. Fluorescently labelled venosomes and VFs co-immunolocalize in lamellocytes after injection and their internalization involves a flotillin/raft-domain-dependent endocytosis. The venosomes internalization rate differs significantly between the Drosophila host species tested (D. melanogaster>D. simulans>D. yakuba>D. suzukii) and is correlated with the parasite success rate, suggesting the existence of specific receptor on lamellocytes of D. melanogaster. Using the HopTum-1 mutant that constitutively produces lamellocytes, I have purified these cells and performed proteomic analysis of their membrane to identify candidate receptors. My results demonstrate that venosomes are interspecies transport vehicles involved in parasite virulence that represent a new level of host specificity.

No description available.

Lipids are increasingly recognized as bioactive mediators of extracellular vesicle (EV) functions. However, while EV proteins and nucleic acids are well described, EV lipids are insufficiently understood due to lack of adequate quantitative methods. We adapted an established targeted and quantitative mass spectrometry (LC-MS/MS) method originally developed for analysis of 94 eicosanoids and seven polyunsaturated fatty acids (PUFA) in human plasma. Additionally, the influence of freeze–thaw (FT) cycles, injection volume, and extraction solvent were investigated. The modified protocol was applied to lipidomic analysis of differently polarized macrophage-derived EVs. We successfully quantified three PUFAs and eight eicosanoids within EVs. Lipid extraction showed reproducible PUFA and eicosanoid patterns. We found a particularly high impact of FT cycles on EV lipid profiles, with significant reductions of up to 70%. Thus, repeated FT will markedly influence analytical results and may alter EV functions, emphasizing the importance of a standardized sample pretreatment protocol for the analysis of bioactive lipids in EVs. EV lipid profiles differed largely depending on the polarization of the originating macrophages. Particularly, we observed major changes in the arachidonic acid pathway. We emphasize the importance of a standardized sample pretreatment protocol for the analysis of bioactive lipids in EVs.

<p>Obesity is associated with an increase in low grade systemic inflammation. Skeletal muscle of individuals with obesity undergo numerous biochemical and morphological alterations including an increase in ectopic lipid accumulation in skeletal muscle and increased macrophage infiltration. Increased intermuscular adipose tissue and macrophages contribute to skeletal muscle inflammation and insulin resistance by secreting elevated proinflammatory cytokines and lipids. This also contributes to reduction in skeletal muscle quality, increasing the susceptibility of muscle to damage and impairing the regenerative response to muscle. Exercise training can reduce inflammation and improve skeletal muscle quality. Importantly reductions in inflammation occur without change in adiposity. Peroxisome proliferator activated receptor g coactivator 1-a (PGC-1a) exerts protective effects on skeletal muscle against damaging insults and may improve muscle regeneration.</p><p> The primary aim of my dissertation was to determine the mechanisms that lead to deficits in skeletal muscle integrity and regeneration in persons with obesity. In Chapter 1, an introduction to the various physiological, pathological, and clinical topics is provided. In Chapter 2, we investigated how exercise training and obesity independently alter skeletal muscle extracellular vesicle (EV) miRNA (miR) content. We found that obesity alters EV miR content indicative of altered anabolic signaling, while exercise training altered EV miR content in a manner indicative of reduced inflammation. In Chapter 3, we report that overexpression of PGC-1a reduces cardiotoxin induced damage of primary human myotubes but limits the ability of undifferentiated cells to reenter the cell cycle and produce progeny that could aid in the restoration of myotubes. In Chapter 4, we demonstrate that exposure to an obesogenic environment increases cardiotoxin induced damage of primary human myotubes from obese donors. In this study we also found that the restoration of myotube fusion index was reduced in lean and obese subjects when incubated with obesogenic media. In Chapter 5 is a review and summary of the outcomes described in Chapters 2-4, a discussion of the limitations of these experiments, and a discussion of future directions.</p>