Septins are evolutionarily conserved proteins with roles in chromosome congression and segregation, cytokinesis and microtubule destabilization. Septins form homo- and hetero-oligomeric complexes, which are thought to act as dynamic scaffolds. We identified SEPT2/9/11/10 as novel interacting partners of adenomatous polyposis coli (APC), a bona fide tumor suppressor. Since septins and APC have similar roles and knockdown phenotypes, I sought to determine if they work together to perform their cellular functions. I showed that APC co-immunoprecipitates with endogenous septins in colon cancer cell lines. Using siRNA, I found that SEPT2 and APC may function within the same pathway to regulate DNA congression and segregation. Co-depleting SEPT9 with APC slightly alleviates the chromosome congression and segregation defects caused by siAPC alone. siSEPT9 increased abscission times, which was rescued by co-depleting APC. Future studies should elucidate the significance of the rescue data obtained upon APC and SEPT9 co-depletion and APC’s interactions with SEPT10/11.

Ubiquitin is a highly conserved 76 amino acid protein which is a unique and versatile signalling molecule. Ubiquitin can be attached by an isopeptide bond between its C-terminal diglycine to a lysine residue of a target substrate. However, it can also bind to itself though one of its own seven lysine residues allowing the formation of different chain types. These chains act as signals for different pathways, such as DNA damage repair, and in particular lysine-48 chains signal for proteins to be degraded via the proteasome by the ubiquitin proteasome system (UPS). This allows cells to control the concentration of proteins which is important in triggering cellular events, such as cyclin levels in cell division. Whilst old and incorrect proteins need to be removed so they do not interfere with normal processes. In order to recognise and ubiquitinate substrates an enzyme cascade has evolved. Ubiquitin is transferred from an ubiquitin activation enzyme (E1) to an ubiquitin conjugating enzyme (E2). The E2 which along with a ubiquitin ligase (E3) ubiquitinates a specific substrate. Research has focused on the E3 ligases since they are responsible for identifying substrates. One important ligase is the anaphase promoting complex/cyclosome (APC/C) which is responsible for faithful segregation of chromosome during mitosis. Failure to regulate this process can lead to aneuploidy, one of the main causes of cancer. It is therefore important to understand the function and regulation of APC/C and the UPS. This work firstly shows that four S. pombe kinases, Ssp2, Ppk9, Kin1 and Chk1 all contain a kinase associated 1 (KA1) or KA2 domain which they use to interact specifically with APC/C when it contained an unphosphorylated form of a subunit called Cut9. Yeast two hybrid and native far Westerns demonstrated that the KA domains interact with the APC/C co activator Slp1. Phosphorylation assays showed that three of these kinases phosphorylated a ~30kDa band of the APC/C complex which was shown to be Mad2, an important subunit of the APC/C inhibitor complex the mitotic checkpoint complex (MCC). These finding suggest a new role for KA contain kinases as regulators of APC/C activity. Future studies to identify the residues of Mad2 which are phosphorylated by these kinases, as well as the binding site of Slp1 that the KA domains recognise, would provide a more detailed understanding of the molecular mechanisms involved in regulating APC/C activity. Secondly, this study investigated the role of the ubiquitin associated (UBA) domains in the S. pombe shuttle factor Rhp23. This protein can recognise the proteasome via an ubiquitin like (UBL) domain and ubiquitin chains via one of two UBA domains: an internal UBA1 and a C-terminal UBA2. To dissect the different functions of these two UBA domains point mutations were made that abolished the domains ability to recognise ubiquitin without altering the protein structure. The minimal domains and full length domains were tested in vitro and in vivo. These surprising results showed that the domains act differently in isolation when compared to the full length protein. They also demonstrate that the UBA1 domain is responsible for ubiquitin recognition in Rhp23, whilst the UBA2 domain appears to have little to no binding ability.

No description available.

The study of the immune system has provided insight in the mechanism of protection induced by vaccination; primarily that most clinically protective vaccines are potent in generating neutralizing antibody responses. However, vaccination fails to protect against a wide range of acquired chronic infections caused by viruses, such as HIV, HBV and HCV. One of the major reasons for weak responses to therapeutic vaccine is the impaired function of effector T cells resulting from viral persistence. Although IL-2 can potently increase effect function of viral specific T cells, systemic administration of IL-2 induces organ pathology and expansion of Treg cells. In this study, we have now developed a novel vaccine delivery system IL-2-nanoAPC delivering antigen-MHC complexes (pMHC), co-stimulatory molecules and IL-2 to antigen specific T cells. NanoAPC are derived from the endoplasmic reticulum (ER) membranes of human B cell line 721.221 engineered with selected HLA allele and IL-2 as the ER retention proteins. The IL-2-nanoAPC interacted with antigen specific T cells, induced immune synapses and expression of high affinity IL-2 receptor and enhanced effector function of antigen specific T cells, but did not affect bystander T cells and Foxp3+ Treg cells. Together with pMHC, co-stimulatory molecules, the selective delivery of IL-2 not only increased the CD4 and CD8 T cell responses to viral antigens but also enhanced TCR proximal signalling and suppressed expression of PD1 molecules on IFNγ producing effector CD8 T cells. We also found that the co-induction of T helper responses by IL-2-nanoAPC in a mixed culture could increase CD8 T cell responses to viral antigen. The IL-2-nanoAPC effectively induced responses of CD4 and CD8 T cells from chronic HBV patients. The results demonstrate that selective delivery of IL-2, together with pMHC and co-stimulatory molecules, by nanoAPC to antigen specific T cells has potential to recover anti-viral immune responses in chronic HBV patients.

The aims of this thesis are to fabricate the single-edged Ti/APC-2 hybrid composite laminates with and without(w/wo) nanoparticles and to investigate their mechanical properties due to tensile and cyclic tests. The composite laminates were three-layered laminates with one 0.55 mm thick APC-2 lay-ups covered by two 0.5 mm thick Grand 1 titanium alloy sheets. Nanoparitcles SiO2 were dispersed uniformly on the interfaces of APC-2 with optimal amount of 1wt%. The APC-2 was stacked according to cross-ply [0/90]s sequences. The titanium sheet surface was treated by chromic acid anodic method to achieve perfectly bonding with matrix PEEK. The modified diaphragm curing process was adopted to cure Ti/APC-2 hybrid composite laminates. The cutting of single-edged cracks with Electrical Discharge Machine, such as 1.5 mm and 3.0mm and 4.5 mm and 6.0 mm. The MTS 810 material testing machine was used to conduct all the tests. The mechanical properties, such as ultimate tensile strength, longitudinal stiffness of composite laminates w/wo nanocomposite laminate were obtained from the static tensile tests. The stress-strain diagrams were plotted in laminates for the corresponding single-edged crack. The constant stress amplitude tension-tension cyclic tests were carried out by using load-control mode at a sinusoidal loading wave with frequency of 5Hz and stress ratio R=0.1. The received fatigue data were plotted in S-N curves for different single-edged crack. From the results, the conclusion were summarized. First, both ultimate strengths of Ti/APC-2 composite laminates and nanocomposite laminates are very close. Second, Ti/APC-2 cross-ply nanocomposite laminates have better fatigue resistance than that of Ti/APC-2 cross-ply composite laminates.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24196号 / 医博第4890号 / 新制||医||1060(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 伊藤 貴浩, 教授 妹尾 浩, 教授 永井 純正 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Multiple studies have implicated the POZ-ZF and methyl-DNA-binding transcription factor, Kaiso, in the regulation of genes and pathways that are important for development and tumorigenesis. In Xenopus embryos and mammalian cultured cells, Kaiso has been implicated as a negative regulator of the canonical Wnt signaling pathway. Paradoxically however, Kaiso depletion extends lifespan and delays polyp onset in the ApcMin/+ mouse model of intestinal tumorigenesis, where aberrant activation of Wnt signaling results in the development of neoplasias. These findings call into question Kaiso’s role as a negative regulator of canonical Wnt signaling and led us to hypothesize that Kaiso promotes intestinal tumorigenesis by a mechanism independent of its role in canonical Wnt signaling. To further delineate Kaiso’s role in intestinal tumorigenesis and to determine Kaiso’s role in regulating canonical Wnt signaling in the murine intestine, we generated a Kaiso transgenic mouse model expressing an intestine-specific murine Kaiso transgene. We then crossed our Kaiso transgenic mice with ApcMin/+ mice and analyzed the resultant progeny. Unexpectedly, Kaiso transgenic mice exhibited intestinal inflammation, increased expression of Wnt target genes and deregulated progenitor cell differentiation, although ectopic expression of Kaiso was not sufficient to drive tumorigenesis in the intestine. In agreement with previous studies, ectopic Kaiso expression in ApcMin/+ mice resulted in a significantly shortened lifespan and increased tumour burden. While we were unable to determine the precise mechanism by which Kaiso promotes intestinal tumour development, we found that Kaiso-induced inflammation is enhanced in the ApcMin/+ background and ectopic Kaiso expression further intensifies Wnt target gene expression in this model. Collectively, these studies have identified novel roles for Kaiso in regulating inflammation and cell-fate determination in the intestine. Furthermore, our findings suggest that Kaiso may contribute to intestinal tumorigenesis by promoting inflammation, which has been shown to be a predisposing factor for colorectal cancer development. Lastly, we have demonstrated distinct tissue and organism-specific roles for Kaiso in regulating canonical Wnt signaling. While, the aforementioned studies were the primary focus of this thesis, we also examined Kaiso’s role in DNA methylation-dependent repression of two tumour-associated genes, cyclinD1 and HIF1A. Our studies revealed that Kaiso binds and regulates the cyclinD1 locus via both sequence-specific and methylation-dependent DNA binding, suggesting that these alternate modes by which Kaiso binds to DNA may not be mutually exclusive. Furthermore, we identified a previously unexplored role for Kaiso in regulating the expression of the master regulator of hypoxia, HIF1A, which implicates Kaiso in modulating hypoxia-driven tumorigenic processes. / Thesis / Doctor of Philosophy (PhD)

No description available.

This work will first introduce the problems related to the colorectal cancer - its epidemiology and screening possibilities. Next the main topic is addressed - i.e. to ascertain the influence of national screening programmes for colorectal cancer on really observed data of lethality and incidence of this disease. Group of so-called APC models was selected as a useful tool for this purpose. Applying these methods on data of The National Oncological Registry of the Czech Republic for the period between 1980 till 2009 this work aims to prove expected reducing effect of area-wide screening programme on incidence and lethality related to colorectal cancer. Using the AP model and data of previous period before the screening introduction (i.e. 1980-1999) the values of incidence and lethality were predicted for the period in question (i.e. 2000-2009). Mere comparison of this predicted values with really observed data showed that real lethality and incidence was significantly lower in both sexes as compared to the model without the screening intervention. Difference between predicted and real data corroborates positive influence of colorectal cancer screening.

Plus de 80% des cancers colorectaux sont initiés par la perte de fonction du gène Apc. Afin d’identifier de nouvelles cibles thérapeutiques, nous avons utilisé des modèles murins présentant des mutations du gène Apc et recherché par des analyses de puces à ADN de nouveaux événements moléculaires impliqués au cours de la carcinogenèse intestinale.Cette approche nous a permis d’identifier une activation de la signalisation Notch tout au long du processus tumoral. Toutefois, cette activation n’est pas un élément clé de la progression tumorale puisque son inhibition n’empêche pas le phénotype tumoral induit par la perte du gène Apc. En parallèle, nos travaux ont permis d’identifier une induction de l’autophagie tout au long de la carcinogenèse intestinale. L’activation de ce processus biologique ouvre, quant à lui, de nouvelles perspectives thérapeutiques dans le traitement du CCR. / Over 80% of colorectal cancers are linked to an Apc mutation. To identify new therapeutic targets, we used mouse models with Apc mutations and performed microarray experiments to identify key molecular events involved in intestinal carcinogenesis. This approach allowed usto identify an activation of the Notch signaling all along tumor progression. However, this induction is dispensable for tumor development since its inhibition did not prevent the Apc phenotype. In addition, we have identified an induction of autophagy throughout intestinal carcinogenesis which appears to be an attractive therapeutic target in the treatment of CRC patients.