Objective: Tumor metastasis and resistance to chemotherapy are two critical factors that contribute to the high death rate of colorectal cancer (CRC) patients. Metastasis is facilitated by the epithelial-mesenchymal transition (EMT) of tumor cells, which has emerged not only as a fundamental process during metastasis, but is also a key process leading to chemoresistance of cancer cells. However, the underlying mechanisms of EMT in CRC cell remain unknown. Here, we aim to assess the role of dual serine/threonine and tyrosine protein kinase (DSTYK) in CRC metastasis and chemoresistance. Methods: To study the role of DSTYK in TGF-β-induced EMT, we employed techniques including Crispr/Cas9 knockout (KO) to generate DSTYK KO cell lines, RT-PCR to detect the mRNA expression, immunofluorescence analyses, and western blots to detect protein levels of DSTYK in the following 4 cell lines: control LS411N-TβRII and LS411N-TβRII/DSTYK KO, control LS513 and LS513/DSTYK KO cells, treated with/without TGF-β. The effects of DSTYK on apoptosis were investigated by MTT assays, flow cytometry assays, and TUNEL assays. The expression of DSTYK in CRC patients and its correlation with EMT markers were determined by bioinformatics analysis. For in vivo analysis, both xenograft and orthotopic tumor mouse models were employed to investigate the function of DSTYK in chemoresistance and metastasis of tumors. Results: In this study, we demonstrate that the novel kinase DSTYK promotes both TGF-β-induced EMT and the subsequent chemoresistance in CRC cells. DSTYK KO significantly attenuates TGF-β–induced EMT and chemoresistance in CRC cells. According to the Gene Expression Omnibus (GEO) database, the expression of DSTYK is not only positively correlated to the expression of TGF-β, but proportional to the death rate of CRC patients as well. Evidently, the expression of DSTYK in the metastatic colorectal cancer samples from patients was significantly higher than that of primary colorectal cancer samples. Further, we demonstrate in mouse models that chemotherapeutic drug treatment suppresses the growth of DSTYK KO tumors more effectively than control tumors. Conclusion: Our findings identify DSTYK as a novel protein kinase in regulating TGF-β–mediated EMT and chemoresistance in CRC cells, which defines DSTYK as a potential therapeutic target for CRC therapy.

Expression of cell adhesion molecule in endothelial cells upon activation by human immunodeficiency virus (HIV) infection is associated with the development of atherosclerotic vasculopathy. We postulated that induction of vascular cell adhesion molecule-1 (VCAM-1) by HIV-1 Tat protein in endothelial cells might represent an early event that could culminate in inflammatory cell recruitment and vascular injury. We determined the role of HIV-1 Tat protein in VCAM-1 expression in human pulmonary artery endothelial cells (HPAEC). HIV-1 Tat protein treatment significantly increased cell-surface expression of VCAM-1 in HPAEC. Consistently, mRNA expression of VCAM-1 was also increased by HIV-1 Tat protein as measured by RT-PCR. HIV-1 Tat protein-induced VCAM-1 expression was abolished by the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC) and the p38 MAPK inhibitor SB-203580. Furthermore, HIV-1 Tat protein enhanced DNA binding activity of NF-κB, facilitated nuclear translocation of NF-κB subunit p65, and increased production of reactive oxygen species (ROS). Similarly to VCAM-1 expression, HIV-1 Tat protein-induced NF-κB activation and ROS generation were abrogated by PDTC and SB-203580. These data indicate that HIV-1 Tat protein is able to induce VCAM-1 expression in HPAEC, which may represent a pivotal early molecular event in HIV-induced vascular/pulmonary injury. These data also suggest that the molecular mechanism underlying the HIV-1 Tat protein-induced VCAM-1 expression may involve ROS generation, p38 MAPK activation, and NF-κB translocation, which are the characteristics of pulmonary endothelial cell activation.

Cell turnover is a common feature of many organs in all animals and is required to maintain organ structure and function. It is achieved by a tightly regulated balance between cell death and cell division, which can be re-adjusted in response to injury and nutrient availability. How the balance between dying and dividing cells is coordinated has however remained unclear. Planarians represent an important model for studying cell turnover in adult animals, because all tissues undergo continuous cell turnover and a single stem cell type – the neoblast – is the exclusive source of all new cells. Moreover, planarians change their body size proportionally and reversibly depending on the nutritional status: feeding induces rapid and transient neoblast proliferation that results in animal growth, while starvation increases the rate of cell death, leading to de-growth. Importantly, also during starvation neoblasts keep proliferating at a basal-level. The hypothesis I addressed with my thesis research is that planarian energy metabolism might be a central mediator of cell turnover, particularly proliferation control and growth. I approached this hypothesis at several levels, including the characterization of the planarian energy metabolism and energy stores, the dependency of proliferation on the diet, and genetic requirements of proliferation control during starvation and feeding. I found that planarians have orthologs of key enzymes of most animal metabolic pathways, but, surprisingly, seem to lack fatty acid synthase. This suggests that planarians are likely not only auxotrophic for cholesterol, but also for fatty acids. I described that planarians store energy as triacylglycerols (TAGs, stored in lipid droplets) and glycogen, with the intestine as the main storage organ. Interestingly, the amount of TAGs and glycogen changes with size and is higher for larger animals, suggesting a regulatory interplay with the known size-dependency of growth/degrowth rates. Further, we demonstrated that the energy stores are the physiological basis of Kleiber’s law that describes the near-universal scaling between metabolic rate and body mass. I further showed that proliferation occurs in three different modes, one during starvation when proliferation is maintained at basal levels and two after feeding, an initial proliferation mode (at three hours after feeding), which is diet independent and a later proliferation (at 24 hours after feeding), which is diet dependent. The two feeding-induced proliferation modes differ not only in their diet-dependencies, but also in their gene expression profiles, as assessed by RNA-sequencing. To identify genes involved in proliferation regulation, I assessed the requirements of different candidate genes in all three proliferation modes in a small-scale RNA interference screen. This screen revealed that insulin signaling, TORC1 and FGFR are involved in regulating basal proliferation during starvation and – most interestingly –that AMP-activated protein kinase (AMPK)-depleted animals showed increased proliferation during starvation at levels characteristic of recently fed animals. This result uncovered AMPK as a modulator that adjusts the neoblast proliferative activity to the nutritional state, potentially independently of TOR. In sum, my work shows how energy metabolism and storage are coordinated with proliferation and growth in planarians and identified AMPK as a central modulator that adjust proliferation to cellular energy states. I discuss potential mechanisms by which AMPK modulates proliferation and putative links between AMPK and cell death, the second process of cell turnover. The energy state as the central mediator of cell turnover and the key players and mechanisms that my work revealed in planarians might also apply across different species:Chapter 1 1. Introduction 1 1.1 Cell turnover is a crucial process for tissue homeostasis 1 1.2 Cell division 2 1.2.1 Control mechanisms of cell division 2 1.2.1.1 Cell cycle machinery 2 1.2.1.2 Organization of the cell cycle control system – cell-cycle intrinsic regulation by Cdk-cyclin complexes 3 1.2.1.3 External control of cell cycle progression 4 1.2.1.4 Metabolic control of cell cycle progression 6 1.2.2 Metabolic requirements of proliferating cells 10 1.2.2.1 The energy stores 11 1.3 Cell death 13 1.4 Suggested mechanisms that coordinate cell death and division and their caveats 14 1.5 Planarians as a model to study cell turnover 16 1.6 Planarian body anatomy 18 1.7 Planarian stem cell system 19 1.7.1 Neoblasts form a heterogeneous population 19 1.7.2 Neoblast proliferative activity 21 1.7.3 Neoblast cell cycle machinery 22 1.7.4 Regulation of neoblast proliferative activity 22 1.8 Cell death in planarians 23 1.9 Mechanisms that coordinate the rate of dividing and dying cells in planarians still remain elusive 24 1.10 Scope of the thesis 24 Chapter 2 2. Planarian energy metabolism and the regulation of planarian growth dynamics 26 2.1 Introduction 26 2.2 Part 1: Planarian energy metabolism 27 2.2.1 The metabolic machinery of S. mediterranea 27 2.2.2 Planarian energy stores 30 2.2.2.1 Visualization of lipid and glycogen storage compartments in planarians 30 2.2.2.2 Investigation of feeding-dependent changes in lipid and glycogen stores 31 2.3 Part 2: Role of planarian organismal energy stores in regulating their growth and degrowth dynamics 36 2.3.1 Background information about known aspects of growth and degrowth dynamics in planarians 36 2.3.1.1 Growth and degrowth arise mainly from changes in cell number 36 2.3.1.2 Growth and degrowth rates are size dependent 37 2.3.2 Energy stores increase disproportionately with size and strongly contribute to the size-dependent dry mass increase 38 2.3.3 Metabolic rate and energy intake are unlikely causes of the size-dependency of the energy stores 41 2.4 Summary and Discussion 43 2.4.1 Part 1: First insights into planarian energy metabolism 43 2.4.1.1 Core planarian metabolic pathways 43 2.4.1.2 Characterization of planarian energy stores 44 2.4.2 Part 2: Implications of size-dependent behavior of planarian energy stores 44 2.4.2.1 Role of energy stores as the physiological origin of Kleiber’s law in planarians 44 2.5 Outlook 46 Chapter 3 3. Towards understanding a systems-level regulation of neoblast proliferative activity 48 3.1 Introduction 48 3.2 Assay development for quantitative determination of proliferating cells 50 3.3 Food quantity and quality affect the later proliferation phase, but not the initial response to feeding 53 3.4 Deep sequencing time course provides insights into gene-expression changes in response to feeding 56 3.5 Discussion 59 3.5.1 Evidence for feeding-induced neoblast regulation at the G0/G1-to-S transition 59 3.5.2 Three distinct modes of neoblast proliferation 59 3.5.3 Early and late proliferation modes show distinct transcriptional profiles 59 3.5.4 Implications from feeding and gene expression profiling experiments 60 3.5.4.1 Potential explanations for diet dependence of the late proliferation mode 60 3.5.4.2 Potential mechanisms of diet-independent early proliferation response 61 3.5.5 Summary and Outlook 61 Chapter 4 4. Towards identifying the mechanisms underlying the regulation of neoblast proliferation 63 4.1 Introduction 63 4.1.1 Chosen gene candidates and their known role in proliferation 64 4.2 RNAi-mediated depletion of candidate genes to test their regulatory role in proliferation 67 4.2.1 Assay design and optimization for the functional RNAi screen 67 4.2.2 Results of small-scale RNAi screen 69 4.3 AMPK - a potential integrator of neoblast proliferation to the nutritional state of the animal 73 4.3.1 AMPK and LKB1 knockdown increases proliferation during starvation 73 4.3.2 AMPK depletion-phenotype of increased proliferation during starvation seems to be TOR independent 73 4.4 Discussion 76 4.4.1 Evidence for a mechanism that regulates basal proliferation during starvation 76 4.4.2 AMPK integrates neoblast activity in response to feeding 77 4.4.2.1 Implications of my observations 77 4.4.2.2 Possible experiments to test the role of AMPK during the regulation of proliferation 78 4.4.3 AMPK potentially regulates proliferation independently of TOR 79 4.4.4 An evolutionarily conserved stem cell switch? 80 4.4.5 Summary and Outlook 80 Chapter 5 5. Discussion and Outlook 81 5.1 Cell-autonomous roles of AMPK in proliferation regulation 83 5.1.1 Independent regulation of ribosomal translation elongation as a potential modulator of neoblast proliferation 83 5.1.2 AMPK might regulate cell cycle progression directly 85 5.1.3 AMPK might regulate symmetric versus asymmetric cell division 85 5.2 Cell non-autonomous roles of AMPK in proliferation regulation 86 5.2.1 AMPK might modulate the release of lipid stores 86 5.3 Possible role of AMPK in regulation of autophagic cell death 87 5.4 AMPK as a potential modulator of cell turnover that couples cell proliferation and cell death to the animal’s energy state 88 5.5 Summary and Outlook 89 Materials and Methods 91 List of Figures 106 List of Tables 107 Acknowledgments 108 References 110

Several cell cycle events require specific forms of the cyclin-CDK complexes. It has been known for some time that cyclins not only contribute by activating the CDK but also by choosing substrates and/or specifying the location of the CDK holoenzyme. There are several examples of B-type cyclins identifying certain peptide motifs in their specific substrates through a conserved region in their structure. Such interactions were not known for the G1 class of cyclins, which are instrumental in helping the cell decide whether or not to commit to a new cell cycle, a function that is non-redundant with B-type cylins in budding yeast. In this dissertation, I have presented evidence that some G1 cyclins in budding yeast, Cln1/2, specifically identify substrates by interacting with a leucine-proline rich sequence different from the ones used by B-type cyclins. These “LP” type docking motifs determine cyclin specificity, promote phosphorylation of suboptimal CDK sites and multi-site phosphorylation of substrates both in vivo and in vitro. Subsequently, we have discovered the substrate-binding region in Cln2 and further showed that this region is highly conserved amongst a variety of fungal G1 cyclins from budding yeasts to molds and mushrooms, thus suggesting a conserved function across fungal evolution. Interestingly, this region is close to but not same as the one implicated in B-type cyclins to binding substrates. We discovered that the main effect of obliterating this interaction is to delay cell cycle entry in budding yeast, such that cells begin DNA replication and budding only at a larger than normal cell size, possibly resulting from incomplete multi-site phosphorylation of several key substrates. The docking-deficient Cln2 was also defective in promoting polarized bud morphogenesis. Quite interestingly, we found that a CDK inhibitor, Far1, could regulate the Cln2-CDK1 activity partly by inhibiting the Cln2-substrate interaction, thus demonstrating that docking interactions can be targets of regulation. Finally, by studying many fungal cyclins exogenously expressed in budding yeast, we discovered that some have the ability to make the CDK hyper-potent, which suggests that these cyclins confer special properties to the CDK. My work provides mechanistic clues for cyclinspecific events during the cell cycle, demonstrates the usefulness of synthetic strategies in problem solving and also possibly resolves long-standing uncertainties regarding functions of some cell cycle proteins.

The proper transmission of genetic materials into progeny cells is crucial for maintenance of genetic integrity in eukaryotes and fundamental for reproduction of organisms. To achieve this goal, chromosomes must be attached to microtubules emanating from opposite poles in a bi-oriented manner at metaphase, and then should be separated equally through proper spindle elongation in anaphase. Failure to do so leads to aneuploidy, which is often associated with cancer. Despite the presence of a safety device called the spindle assembly checkpoint (SAC) to monitor chromosome bi-orientation, mammalian cells frequently possess merotelic kinetochore orientation, in which a single kinetochore binds microtubules emanating from both poles. Merotelically attached kinetochores escape from the surveillance mechanism of the SAC and when cells proceed to anaphase cause lagging chromosomes, which are a leading cause of aneuploidy in mammalian tissue cultured cells. The fission yeast monopolin complex functions in prevention of mal-orientation of kinetochores including merotelic attachments during mitosis. Despite the known importance of Cdk1 activity during mitosis, it has been unclear how oscillations in Cdk1 activity drive the dramatic changes in chromosome behavior and spindle dynamics that occur at the metaphase/anaphase transition. In two separate studies, we show how dynamic Cdk1 phosphorylation regulates chromosome segregation. First, we demonstrate that sequential phosphorylation and dephosphorylation of monopolin by Cdk1 and Cdc14 phosphatase respectively helps ensure the orderly execution of two discrete steps in mitosis, namely sister kinetochore bi-orientation at metaphase and spindle elongation in anaphase. Second, we show that elevated Cdk1 activity is crucial for correction of merotelic kinetochores produced in monopolin and heterochromatin mutants.

La réponse et l’adaptation des plantes à un stress métallique mettent en jeu de nombreux mécanismes afin de limiter les effets néfastes des éléments toxiques. Bien que certains de ces mécanismes soient bien caractérisés, de nombreux acteurs cellulaires et moléculaires restent à identifier pour mieux comprendre la diversité des stratégies mises en œuvre dans ces processus complexes et vitaux pour les plantes.Dans un premier temps, nous nous sommes intéressés au rôle de deux modifications post-traductionnelles, la phosphorylation et la méthylation des protéines non-histone dans la réponse à un stress induit par deux éléments non essentiels et toxiques, le cadmium (Cd) et l’uranium (U). Nous avons analysé la dynamique de ces modifications chez trois espèces du genre Arabidopsis : A. thaliana et A. lyrata, deux espèces sensibles au Cd, et A. halleri, espèce naturellement capable de tolérer et d’hyper-accumuler ce métal toxique dans ses feuilles. En utilisant une combinaison d’analyses par Western blot et par spectrométrie de masse nous avons montré que les patterns de méthylation des protéines changent au cours de stress métalliques. Puis, nous avons analysé l’expression des gènes codant les enzymes impliquées dans les réactions de phosphorylation et méthylation des protéines dans différentes conditions de stress. Ces analyses ont montré qu’un grand nombre de protéines kinases sont régulés au niveau transcriptionnel par un stress métallique tandis que seules quelques une en ce qui concerne la méthylation. Pour finir, nous avons mis en place un criblage génétique de mutants d’A. thaliana et identifié deux gènes codant des protéines lysine méthyltransférases impliqués dans la tolérance au Cd.Dans un deuxième temps, nous avons étudié les mécanismes cellulaires de la réponse du système racinaire d’A. thaliana lors d’une exposition à l’U. L’utilisation de différents systèmes rapporteurs et la mesure de différents paramètres physiologiques nous ont permis de mettre en évidence que l’architecture racinaire est fortement modulée en réponse à l’U et ceci de façon dose dépendante. Cet effet est lié à l’inhibition du cycle cellulaire et à la synthèse d’espèces réactives de l’oxygène et d’oxyde nitrique dont l’accumulation provoque la mort cellulaire. Ces changements sont associés à une perturbation du transport et de la distribution de l’auxine dans les racines. Ces événements sont temporellement corrélés avec l’accumulation de polymères de défense (callose et lignine) impliqués dans l’imperméabilisation des cellules et des parois. Cette étude confirme enfin que le stress induit par l’U est intimement lié à une perturbation de l’homéostasie de certains macronutriments (phosphate et fer) et partage les cascades de signalisation d’une carence en phosphate.Ce travail met en évidence des mécanismes de réponse et d’adaptation aux métaux toxiques à travers la régulation fine des phénomènes de méthylation des protéines non-histone et l’identification de processus cellulaires impliqués dans la réponse à la toxicité de l’U dans le système racinaire. / Plant response and adaptation to metallic stress are involving numerous mechanisms limiting the toxic effect of metals. Although a large number of these mechanisms are well characterized, many processes are in need to be identified in order to have a better understanding of strategies involved in plant response to toxic elements.In first instance, we investigated the role of two post-translational modifications, phosphorylation and methylation of non-histone proteins in response to stress induced by two toxic metals, cadmium and uranium. We analyzed the dynamic of these modifications in three species of Arabidopsis: A. thaliana, A. lyrata two species sensitive to cadmium and A. halleri, a species which naturally tolerate and hyperaccumulate toxic metals in her leaves. By using Western blots and mass spectrometry in parallel, we showed that lysine methylation pattern were changing during metallic stresses. Next, we analyzed the gene expression of enzymes involved in phosphorylation and lysine methylation processes in plants exposed to different adverse conditions. These analyses showed that numerous kinases expressions were differentially regulated in response to metallic stress. Concerning protein lysine methyltransferases, only a few enzymes were differentially regulated. Finally, through a mutant genetic screening we identified two genes coding for protein lysine methyltransferases involved in tolerance to a stress induced by cadmium.Secondly, we studied the physiological and cellular processes involved in the response of A. thaliana root system to uranium. Through the utilization of several reporters and the measure of physiological parameters, we demonstrated that the root architecture was strongly modulated in response to a stress induced by uranium and that in a dose dependent manner. These effects are linked to a cell cycle inhibition and the synthesis and accumulation of reactive oxygen species and nitric oxyde wich participated in the root apex cell death. These changes were associated with perturbation in auxin transport and distribution at the root apex and were temporally correlated to the deposition of defense polymers (callose and lignin) involved in cell proofing and cell wall stiffness. This study is confirming the fact that uranium induced stress is intimately linked to a disruption of phosphate and iron homeostasis. Furthermore, uranium-signaling cascade are sharing a part of the phosphate starvation-signaling cascade.Together, these two studies are revealing mechanisms involved in plant response and adaptation to metallic trace elements through the thin tuning of non-histone methylation and the identification of cellular process involved in the toxicity of uranium in roots.

京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第12969号 / 論医博第2102号 / 新制||医||1012(附属図書館) / 32407 / 新制||医||1012 / 京都大学大学院医学研究科医学専攻 / (主査)教授 山田 泰広, 教授 福田 和彦, 教授 伊達 洋至 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

Calcium tolerant pig and rabbit cardiomyocytes were isolated using retrograde aortic perfusion of nominally calcium-free collagenase. Preconditioning protocols used 1 or 3 x l0-min episodes of ischemic pelleting or pre-incubation with 100 μM adenosine, followed by a 15-min post-incubation and 180-240-min ischemic pelleting. Control cells were incubated and washed in parallel with the experimental groups. Injury was assessed by determination of cell morphology, trypan blue permeability following osmotic swelling, lactate and HPLC analysis of adenine nucleotides. Preconditioned pig cardiomyocytes had a reduced rate of ischemic contracture, but protection occurred without conservation of ATP. Preconditioned rabbit cardiomyocytes were protected without significant changes in rates of ischemic contracture or ATP depletion. Incubation of ischemic cells with the protein phosphatase inhibitor, fostriecin, at PP2A-selective concentrations (0.1-10 μM), mimicked preconditioning in both rabbit and pig cardiomyocytes. In rabbits, the K(ATP) channel blocker, 5-hydroxydecanoate (5-HD), did not block preconditioning or fostriecin protection. In the pig, 5-HD blocked both preconditioning and fostriecin protection, with return of the rates of ischemic contracture to control. However, 5-HD was an effective blocker of protection only in early ischemia. Fostriecin mimicked preconditioning in the rabbit and the early responses of the preconditioned pig. Preconditioning appears associated with protein phosphorylation in both the rabbit and the pig, but major pathways leading to protection may differ in the two species.

Indiana University-Purdue University Indianapolis (IUPUI) / Modulation of sphingolipid-induced apoptosis is a potential mechanism to enhance the effectiveness of chemotherapeutic drugs. Ceramide is a pleiotropic, sphingolipid produced by cells in response to inflammatory cytokines, chemotherapeutic drugs and ionizing radiation. Ceramide is a potent activator of protein phosphatases, including protein phosphatase 2A (PP2A) leading to dephosphorylation of substrates important in regulating mitochondrial dysfunction and apoptosis. Previous studies demonstrated that death associated protein kinase (DAPK) plays a role in ceramide-induced apoptosis via an unknown mechanism. The tumor suppressor DAPK is a calcium/calmodulin regulated serine/threonine kinase with an important role in regulating cytoskeletal dynamics. Auto-phosphorylation within the calmodulin-binding domain at serine308 inhibits DAPK catalytic activity. Dephosphorylation of serine308 by a hitherto unknown phosphatase enhances kinase activity and proteasomal mediated degradation of DAPK. In these studies, using a tandem affinity purification procedure coupled to LC-MS/MS, we have identified two holoenzyme forms of PP2A as DAPK interacting proteins. These phosphatase holoenzymes dephosphorylate DAPK at Serine308 in vitro and in vivo resulting in enhanced kinase activity of DAPK. The enzymatic activity of PP2A also negatively regulates DAPK protein levels by enhancing proteasomal-mediated degradation of the kinase, as a means to attenuate prolonged kinase activation. These studies also demonstrate that ceramide causes a caspase-independent cell detachment in HeLa cells, a human cervical carcinoma cell line. Subsequent to detachment, these cells underwent caspase-dependent apoptosis due to lack of adhesion, termed anoikis. Overexpression of wild type DAPK induced cell rounding and detachment similar to cells treated with ceramide; however, this effect was not observed following expression of a phosphorylation mutant, S308E DAPK. Finally, the endogenous interaction of DAPK and PP2A was determined to be required for ceramide-induced cell detachment and anoikis. Together these studies have provided exciting and essential new data regarding the mechanisms of cell adhesion and anoikis. These results define a novel cellular pathway initiated by ceramide-mediated activation of PP2A and DAPK to regulate inside-out signaling and promote anoikis.