p38 mitogen-activated protein (MAP) kinases represent a subgroup of MAP kinases that respond to environmental stress and inflammatory cytokines. p38 MAPK is activated by two upstream kinases, MKK3 and MKK6, by dual phosphorylation on threonine and tyrosine in conserved kinase subdomain VII. Until recently the relative roles of MKK3 and MKK6 have remained unclear. I have undertaken two strategies in an effort to understand the importance of MKK3 as a p38 MAPK activator. First, I cloned and characterized the murine mkk3 gene and determined the structure of the 5'-terminus. Comparison of the murine and human mkk3 genes revealed that the mouse gene encodes a single MKK3 isoform, MKK3b, and the human gene encodes two isoforms, MKK3a and MKK3b. Comparison of the mouse and human mkk3 genes suggests that expression of MKK3a and MKK3b is regulated from different promotors. Analysis of the mkk3 promoter demonstrates that muscle specific expression of murine MKK3b is controlled, in part, by the transcription factors MEF2 and MyoD. Second, I have utilized a gene targeting strategy to disrupt the murine mkk3 gene and to examine the effect on p38 MAPK signaling. I found that there is a p38-specific signaling defect in MKK3 deficient primary mouse embryo fibroblasts (MEF) which correlates with deficits in interleukin (IL)-1 and IL-6 production in response to tumor necrosis factor-α (TNFα) stimulation. In addition there is a defect in TNFα mediated expression of TNFα and macrophage inflammatory proteins (MIP) 1α, MIP1β and MIP2. p38 MAPK-specific signaling defects were also observed in lipopolysaccharide (LPS) stimulated mkk3 (-/-) macrophages. Additionally, mkk3 (-/-) macrophages exhibit defects in LPS and CD40-ligand (CD40L) stimulated IL-12 biosynthesis. Similar data were obtained from CD40L-stimulated mkk3 (-/-) dendritic cells. I also observe that interferon (Ifn)-γ production is diminished during T-helper-1 (TH1) differentiation of CD4+ T-cells derived from mkk3 (-/-) mice. Taken together these data demonstrate a crucial role for p38 MAPK activation by MKK3 in response to the inflammatory cytokine, TNFα and during a TH1 inflammatory response.

En cas de lymphopénie -diminution du nombre de lymphocytes T (LT) présents en périphérie-, les LT restants prolifèrent. Ce processus, dit de prolifération homéostatique, est régulé par la disponibilité de la cytokine IL-7 ainsi que par des interactions TcR/MHC et mène à la différenciation de LT effecteurs/mémoires. La prolifération homéostatique peut augmenter l’efficacité des immunothérapies anti-cancéreuses ou avoir des conséquences délétères pour l’organisme (réaction du greffon contre l’hôte, auto-immunité). Les LT naïfs, effecteurs et de mémoire produisent leur énergie via des mécanismes différents et la capacité des lymphocytes à enclencher le programme métabolique adéquat au bon moment joue un rôle essentiel dans leur différenciation. En outre, l’inhibition de la glycolyse ou de la respiration mitochondriale altère la prolifération homéostatique, suggérant que ces deux voies métaboliques sont importantes dans ce processus. Les mécanismes par lesquels les LT accroissent leur métabolisme énergétique lors de la prolifération homéostatique ne sont, à ce jour, pas encore élucidés. L’AMPK est un régulateur essentiel du métabolisme cellulaire et est la cible de différents composés déjà utilisés chez l’homme. L’objectif de notre travail a été de déterminer les conséquences de l’absence d’AMPK sur la capacité des LT à proliférer de manière homéostatique et à adapter leur métabolisme en réponse à l’IL-7. Notre hypothèse a été que l’AMPK, en permettant de réorienter le métabolisme des LT, jouerait un rôle important dans le processus de prolifération homéostatique. Au cours de ce travail, nous avons démontré que l’AMPK favorise la prolifération homéostatique des LT ainsi que l’acquisition des fonctions effectrices de type Th1. Nos résultats mettent également en évidence un rôle de l’AMPK dans le processus de graft-versus-host disease (GVHD). En effet, les LT déficients pour l’AMPK induisent une GVHD de moindre gravité. D’un point de vue métabolique, nous avons montré que les LT déficients pour l’AMPK présentent un potentiel de membrane mitochondriale réduit ainsi qu’une sensibilité accrue aux dérivés réactifs de l’oxygène (ROS). Les LT déficients pour l’AMPK ont, de plus, un défaut de switch glycolytique lors de stress mitochondriaux ainsi que lors d’une stimulation secondaire en présence d’anticorps anti-CD3/anti-CD28. Une réduction de la toxicité des ROS, associée à une plus grande flexibilité énergétique, pourrait conférer un avantage prolifératif aux LT soumis à des stimuli antigéniques de faibles affinités, tels que rencontrés lors de proliférations induites par la lymphopénie. Nos résultats suggèrent également qu’une régulation fine du métabolisme pourrait réduire la sévérité de la GVHD. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

INTRODUÇÃO: O melanoma primário da cavidade oral é uma neoplasia agressiva, rara e originada a partir da proliferação de melanócitos malignos da mucosa. Ele representa aproximadamente de 0,2 a 8% de todos os melanomas. Estudos recentes apontam algumas vias moleculares tem sido encontradas por estarem envolvidas na patogenia dos melanomas. Dentre essas vias destaca-se a via proliferativa da MAPK (mitogen activated protein kinase), esta cascata de sinalização está envolvida no controle do crescimento celular, proliferação e migração, e tem sido relacionada com um papel importante no desenvolvimento e progressão do melanoma cutâneo. OBJETIVOS: Analisar a expressão proteica e mutação pontual dos componentes da via MAPK e correlacionar com os dados clínicos-histológicos. MATERIAL E MÉTODOS: Através da imunoistoquímica avaliar a expressão proteica dos anticorpos RAS; BRAF; MEK1; MEK2; ERK1 e ERK2 em 35 casos de melanomas orais organizados em matriz (TMA: Tissue Microarray) e através de pirosequenciamento avaliar a mutação pontual dos genes BRAF; NRAS; KRAS em 14 casos de melanomas orais. RESULTADOS: Idade dos pacientes entre 9 e 91 anos, sem predileção por sexo, 75% caucasianos, 71,42% acometeram o palato, 80% com aspecto histológico grau III. A análise da expressão proteica foi: RAS (28,57%); BRAF (82,85%); MEK1 (0%); MEK2 (51,43%); ERK1 (20%)e ERK2 (74,28%). Na análise molecular observamos mutações para BRAF (9/14 casos) e NRAS (2/14 casos). CONCLUSÃO: Todos os aspectos da via MAPK necessita de outras elucidações em melanomas de áreas foto-protegidas e melanomas de mucosa e comparando diferentes populações. Entretanto, os resultados deste presente estudo apontam importante alterações na cascata RAS-RAF-MEK-ERK e estes são indicadores de prognóstico ruim em melanomas primários da mucosa oral, independente da exposição solar / BACKGROUND: Primary melanoma of the oral cavity is an aggressive and rare neoplasm and originated from the proliferation of malignant melanocytes of the mucosa. It represents approximately 0.2 to 8% of all melanomas. Recent studies indicate some molecular pathways have been found to be involved in the pathogenesis of melanomas. Among these means there is a proliferative MAPK pathway (\"mitogen activated protein kinase\"), this signaling pathway is involved in controlling cell growth, proliferation and migration, and it has been associated with a role in the development and progression of melanoma skin. OBJECTIVES: To analyze protein expression and mutation of components of the MAPK pathway and to correlate with the clinical, histological data. MATERIALS AND METHODS: Using immunohistochemistry to evaluate the protein expression of RAS, BRAF, MEK1, MEK2, ERK1 and ERK2 antibodies in 35 cases of oral melanomas organized array (TMA: Tissue Microarray) and using pyrosequencing to assess the mutation of the BRAF, NRAS, KRAS in 14 cases of oral melanomas. RESULTS: Age of patients between 9 and 91 years, regardless of gender, 75% Caucasian, 71.42% in palate, 80% with histologic grade III. Analysis of protein expression was: RAS (28.57%); BRAF (82.85%); MEK1 (0%), MEK2 (51.43%); ERK1 (20%) and ERK2 (74.28%). Molecular analysis we found BRAF mutations (9/14 cases) and NRAS (2/14 cases). CONCLUSION: All aspects of the MAPK pathway requires further elucidation in melanomas of photo-protected areas and mucosal melanomas and comparing different populations. However, the results of this study indicate important changes in the cascade RAS-RAF-MEK-ERK and these are indicators of poor prognosis in primary melanomas of the oral mucosa, regardless of sun exposure

Orientador: Antonio Carlos Boschero / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-17T15:59:13Z (GMT). No. of bitstreams: 1 Santos_GustavoJorge_M.pdf: 2550633 bytes, checksum: 914361a57f5efd5794bcee99ff8ce2a4 (MD5) Previous issue date: 2011 / Resumo: Diabetes Mellitus (DM) é uma síndrome metabólica, de etiologia múltipla, caracterizada por hiperglicemia crônica, decorrente da falta de insulina, às vezes, associado à resistência dos tecidos periféricos a esse hormônio. O DM1 é caracterizado pela infiltração de macrófagos e linfócitos do tipo T-CD4+ e T-CD8+ no pâncreas, devido a uma falha do reconhecimento no sistema autoimune, que desencadeiam processos inflamatórios com liberação de óxido nítrico (NO), de radicais livres e de citocinas tais como: interleucina-1? (IL-1 ?) e Interferon- ? (IFN- ?). Essas citocinas pró-inflamatórias ativam mecanismos que levam a morte celular por apoptose, com perda da massa funcional das células beta. Esses mecanismos podem ser reproduzidos in-vitro pela exposição de células beta a essas citocinas ou à Aloxana. O CNTF é uma citocina de sobrevivência neuronal, e em células beta age sobre o controle glicêmico inibindo secreção de insulina e promovendo sobrevivência de ilhotas. A AMPK é uma proteína quinase que em células beta atua como um sensor do estado energético celular e, quando as concentrações intracelulares de ATP diminuem, a AMPK é ativada estimulando geração de ATP e inibindo o consumo desse nucleotídeo. Em ilhotas, a AMPK desempenha função importante na regulação da secreção de insulina sendo que a inibição de AMPK protege as células beta da apoptose mediada por citosinas (IL-1? e IFN-?) ou induzidas por células T do tipo CD8+ e CD4+. Diante do exposto, conclui-se que CNTF e AMPK desempenham funções importantes e correlatas nas células beta pancreáticas e, podem ser considerados alvos terapêuticos para o tratamento do DM tipo I. Contudo, a interação entre esses dois fatores (CNTF e AMPK) em células secretoras de insulina permanece desconhecida. Assim, o objetivo deste trabalho foi investigar a possível papel da interação entre CNTF e AMPK na morte celular induzida pelos agentes diabetogênicos IL-1? e Aloxana. Nossos resultados indicaram que: A Aloxana e a IL-1? dependem da via da AMPK para induzir apoptose em células MIN6; O CNTF modula a via da AMPK em células MIN6 e ilhotas de camundongos Swiss neonato. O CNTF foi capaz de impedir a morte celular induzida por Aloxana e por IL-1? através da downregulation da via da AMPK em células MIN6. / Abstract: Diabetes Mellitus (DM) is a metabolic syndrome of multiple etiologies, resulting from the lack of insulin sometime associated with an increase in the resistance to the hormone by insulin-target tissues. DM1 is characterized by the infiltration of macrophages and T-type CD4 + and T-CD8 + cells in the pancreas, due to a failure of the autoimmune system, causing inflammation and leading to the release of nitric oxide (NO), free radicals, and cytokines such as interleukin-1? (IL-1?) and interferon-? (IFN-?). These pro-inflammatory cytokines activate pro-apoptotic mechanisms, triggering beta cell death apoptosis, leading to a loss in functional beta cell mass. These mechanisms may be reproduced in vitro with exposure of beta cells to pro-inflammatory cytokines such as IL-1? or to Alloxan. The cytokine CNTF is a neuronal survival factor. Besides, CNTF modulates glycemia, inhibiting insulin secretion and promoting islet cells survival. AMPK is a protein kinase that acts on pancreatic beta cells as a sensor of the cellular energy state, and is activated when the cellular ATP concentrations decrease, stimulating ATP generation and inhibiting ATP consumption. In islets, AMPK plays an important role in regulating insulin secretion and inhibition of AMPK protects beta cells from apoptosis mediated by either cytokines (IL-1? and IFN-?) and/or induced T cell CD8 + and CD4 +. AIMS: Given that, both CNTF and AMPK play important role in beta cells and may be used as therapeutic targets for the treatment of DM1. However, the interaction between these two factors (CNTF and AMPK) in pancreatic beta cells remains unknown. Thus, the objective of this work was to investigate the relationship between interaction of AMPK and CNTF on pancreatic beta cell death, induced by Alloxan or IL-1?. Our results indicated that both Alloxan and IL-1? are dependent of AMPK pathway to induce apoptosis in MIN6 cells; CNTF inhibits AMPK pathway in MIN6 cells as well as in islets of newborn Swiss mice; CNTF prevents beta cell death, induced by Alloxan and IL-1?, through downregulation of AMPK pathway in MIN6 cells. / Mestrado / Fisiologia / Mestre em Biologia Funcional e Molecular

Orientador: Helena Coutinho Franco de Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-19T14:08:09Z (GMT). No. of bitstreams: 1 Kato_LarissaSayuri_M.pdf: 3085711 bytes, checksum: 2c9b592f72e52ceb332be3af215a87fe (MD5) Previous issue date: 2011 / Resumo: O estudo das vias de sinalização envolvidas no metabolismo energético é de grande relevância fisiológica, uma vez que um desequilíbrio da homeostase energética pode resultar em obesidade e/ou síndrome metabólica e aumento da mortalidade por doença cardiovascular. Estudos recentes de nosso grupo em três modelos experimentais que exibem distintos tipos de dislipidemias revelaram alterações significativas da composição corporal, gasto energético e padrão de ingestão alimentar. Neste trabalho estudamos a homeostase energética desses modelos dislipidêmicos avaliando: (1) a expressão e fosforilação da proteína quinase dependente de AMP (AMPK), um importante regulador do metabolismo energético, bem como de seu alvo, a enzima acetil-CoA carboxilase (ACC), em fígado e músculo esquelético de camundongos hipoalfalipoproteinêmicos e hipercolesterolêmicos e (2) o efeito da alimentação pareada em animais hipertrigliceridêmicos que apresentam alterações de comportamento alimentar, metabolismo corporal e maior atividade do canal mitocondrial de potássio sensível ao ATP (mitoKATP). Considerando os animais hipoalfalipoproteinêmicos (transgênicos para CETP), os quais apresentam aumento de gasto energético global, verificamos que estes apresentam redução da massa relativa dos depósitos adiposos quando comparados os controles wild type (WT). O estudo da ativação da AMPK e da ACC mostra que o estado energético dos tecidos muscular e hepático parece não diferir nos animais CETP e WT. Tanto no fígado como no músculo dos animais CETP não houve alteração da massa e do estado de ativação da AMPK e da ACC. Estes resultados sugerem que não ocorrem variações significativas na síntese, armazenamento e "exportação" de lípides no fígado destes animais. Em relação ao músculo sóleo, pode-se concluir que não há alteração de síntese e catabolismo lipídico nos animais CETP. De modo geral, podemos dizer que a sinalização da AMPK não está ativada nestes tecidos e, portanto, que o maior metabolismo corporal observado nestes animais deve estar sendo causado por outros tecidos do organismo, por exemplo, o próprio tecido adiposo. Em animais machos e fêmeas hipercolesterolêmicas (LDLR0) observamos redução da massa corporal, porém sem alteração significativa da massa relativa dos depósitos adiposos quando comparados aos animais controles wild type. Os resultados sobre ativação da AMPK e da ACC mostram que o estado energético em tecidos periféricos é diferente nos animais LDLR0 e controles (WT). No fígado das fêmeas hipercolesterolêmicas observamos aumento da ativação da AMPK sem alteração significativa da fosforilação da ACC. Isso significa que não houve inibição da lipogênese ou ativação da beta-oxidação no fígado dos animais hipercolesterolêmicos, embora possa ter havido aumento de catabolismo de outros nutrientes. No músculo sóleo das fêmeas e dos machos não houve alteração de fosforilação de ambas AMPK e ACC. Pode-se então concluir que não há deprivação energética no músculo destes animais. Considerando o estudo em animais hipertrigliceridêmicos (HTG), quando submetidos ao regime de paired feeding (PF) observamos uma redução de 17% no consumo alimentar nas fêmeas e nos machos HTG quando comparados aos HTG alimentados ad libitum (ad lib). Isso levou a uma redução significativa do ganho de peso dos HTG-PF comparados aos WT-ad lib, em ambos os sexos. Os animais HTG-PF mantiveram a massa dos depósitos adiposos da carcaça semelhantes aos WT-ad lib e HTG-ad lib. No entanto, o depósito adiposo visceral das fêmeas HTG-ad lib é menor que dos WT-ad lib, enquanto nos machos, os HGT-PF apresentaram maior adiposo visceral que os HTG-ad lib. Quando comparados aos WT-ad lib, verificamos que as fêmeas HTG-PF mantiveram aumento significativo da atividade (abertura) do canal de potássio mitocondrial sensível ao ATP (mitoKATP) e da produção corporal de CO2. No entanto, nos machos HTG-PF houve fechamento dos mitoKATP, redução da produção de CO2 e manutenção da massa corporal. Assim, pode-se inferir que o metabolismo corporal (produção de CO2) reflete o aumento do metabolismo celular causado por aumento da atividade do mitoKATP que desacopla levemente as mitocôndrias e que estas adaptações são revertidas pela restrição alimentar nos machos, mas não nas fêmeas HTG / Abstract: An imbalance of energy homeostasis can result in obesity and/or metabolic syndrome and increased mortality from cardiovascular disease. Recent studies by our group in three experimental models that exhibit different types of dyslipidemia have shown significant changes in body composition, energy expenditure and food intake. In this work we studied the energy homeostasis in these models through: (1) quantifying the expression and phosphorylation of AMP-dependent protein kinase (AMPK), a key regulator of energy metabolism, as well as its target, the enzyme acetyl-CoA carboxylase (ACC) in liver and skeletal muscle in hypoalphalipoproteinemic and hypercholesterolemic mice and (2) the effect of paired feeding regimen on hypertriglyceridemic mice that present increased food intake, body CO2 production and increased activity of the mitochondrial potassium channel sensitive to ATP (mitoKATP). Considering the hypoalphalipoproteinemic mice (transgenic for CETP), which show an increased overall energy expenditure, we found that these mice have reduced relative fat depot mass when compared to wild type controls (WT). Western blot analyses showed that, in both tissues, liver and muscle, there were no changes in mass and state of activation of AMPK and ACC in CETP compared to WT mice. These results suggest that no significant variations in the synthesis, storage and secretion of lipids in the liver of these mice. Regarding the soleus muscle, these results suggest that there is no change in lipid synthesis and catabolism in CETP mice. Overall we may say that AMPK signaling is not activated in liver and muscle tissues and, therefore, that the increased body metabolism observed in these CETP mice must be caused by other body tissues, for example, the adipose tissue itself. In hypercholesterolemic male and female mice (LDLR0) we observed a reduction in body mass, but no significant change in the relative mass of fat depots when compared to WT. The results on activation of AMPK and ACC show that the liver of LDLR0 females had increased activation of AMPK without significant change in the phosphorylation of ACC. This means that there was no inhibition of lipogenesis and activation of ?-oxidation in the liver of hypercholesterolemic mice, although there may have been increased catabolism of other nutrients. In the soleus muscle of females and males there were no changes in the phosphorylation state of both AMPK and ACC. Then, we can conclude that there is no energy deprivation in the muscle of these LDLR0 mice. Considering the study with hypertriglyceridemic (HTG) mice, when subjected to the paired feeding (PF) we observed a 17% reduction in food intake of females and males when compared to HTG mice fed ad libitum (ad lib). This led to a significant reduction in HTG-PF weight gain compared to WT-ad lib in both sexes. HTG-PF mice retained the mass of carcass fat deposits similar to WT and HTG ad lib. Compared to WT-ad lib, HTG-PF mice maintained significant increased activity (opening) of the mitoKATP and body CO2 production. These data showed that the regimen of paired feeding in which HTG mice were submitted did not change the high rate body metabolism and mitochondrial resting respiration observed in HTG-ad lib mice. These results suggest that the metabolic adaptation of HTG (higher activity of mitoKATP) is not sensitive to changes in food restriction and compromises the rate of body growth / Mestrado / Fisiologia / Mestre em Biologia Funcional e Molecular

With an increased popularity for systems-based approaches in biology, a wide spectrum of techniques has been applied to the simulation and analysis of biochemical systems which involves uncertainty and stochasticity. It is particularly concerned with modelling and analysis of metabolic pathways, regulatory and signal transduction networks for understanding intra-cellular pathway behaviour. Typically, parameter estimation in ordinary differential equations(ODEs) models is used for this purpose when there is large number of molecules involved in the reaction system. However this approach is correct when the system is large enough to be deterministic in nature. But there are uncertainty involved in the system and the processes are stochastic in nature due to smaller population molecules participating in the pathway reactions. In this thesis the common theme is the study of uncertainties in the chemical kinetics of biochemical reaction systems associated with various intra-cellular pathways and channels. The study is at the mesoscale of the system, i.e., we study systems that do not have too few molecules disallowing any higher scale system level approximation nor too many where a non-stochastic (mesoscale) system approximation will be valid. In our first study we estimate the parameters in the mitogen activated protein kinase (MAPK) signal transduction pathway involved in the departure from the normal Epithelial Growth Factor(EGF) dose-dependency in prostate cancer cells. A model-based pathway analysis is performed. The pathway is mathematically modelled with 28 rate equations yielding those many ordinary differential equations(ODE) with kinetic rate constants that have been reported to take random values in the existing literature. This has led to us treating the ODE model of the pathways kinetics as a random differential equations(RDE) system in which the parameters are random variables. The most likely set of values of the kinetic rate constants obtained from fitting the RDE model into the experimental data is then used in a direct transcription based dynamic optimization method for computing the changes needed in these kinetic rate constant values for the restoration of the normal EGF dose response. It identifies the parameters, i.e., the kinetic rate constants in the RDE model, that are the most sensitive to the change in the EGF dose response behaviour in the PC3 prostate cancer cells. Biochemical pathways involving chemical kinetics equations in terms of low concen-trations of the model variables can be represented as chemical Langevin equations(CLE) as there is stochasticity involved in the processes. Most CLE systems come with the implicit constraint that the concentration state cannot be negative at any time over the sample path. Due to the inherent stiffness(especially in diffusion coefficient) of the CLE system, it has been difficult for numerical schemes to meet this positivity constraint during numerical simulations. Most available methods resort to heuristics by dropping selective noise terms from the original CLE inconsistent with the mesoscale physics involved in forming the CLE. Other methods take very small time steps thus making the simulation inefficient. In our second study we preserve positivity by using a physically consistent numerical scheme which is a modified form of fully stochastic α method for stiff stochastic differential equation. Ion channels are fundamental molecules in the nervous system that catalyse the flux of ions across the cell membrane. Single ion channel flux activity is comparable to the catalytic activity of single enzyme molecules. Saturating concentrations of substrate induce dynamic disorder in the kinetic rate processes of single enzyme molecules and consequently, develop correlative memory of the previous history of activities. Conversely, binding of substrate ion is known to alter the catalytic turnover of single ion channels. Here, we investigated the possible existence of dynamic disorder and molecular memory in single human TREK1 channel due to binding of substrate/agonist using the excised inside-out patch-clamp technique. Our results suggest that single hTREK1 channel behaves as a typical Michaelis-Menten enzyme molecule with a single high-affinity binding site for substrate K+ ion but with uncertainty in reaction rates.

Rapidly growing tumor cells outgrow their blood supply resulting in a microenvironment with reduced oxygen and nutrients. Using an in vitro transformation model we found that cancer cells expressing the SV40 ST antigen (+ST cells) are more resistant to glucose deprivation-induced cell death than cells lacking the SV40 ST antigen (−ST cells). Mechanistically, we found that the ST antigen mediates this effect by activating a nutrient-sensing kinase, AMP-activated protein kinase (AMPK). We further show that AMPK mediates its effects, at least in part, by inhibiting mTOR (mammalian target of rapamycin), thereby shutting down protein translation, and by inducing autophagy as an alternate energy source. Resistance to anoikis upon anchorage-deprivation is yet another form of stress tolerated by both normal stem/progenitor cells of various tissues in our body and by cancer cells. Using mammospheres as a model to enrich for stem/progenitor cells we found that mammosphere formation is accompanied with increased activation of AMPK. Concomitant with AMPK activation, we detected increased phosphorylation of the anti-apoptotic protein PED/PEA15. We further demonstrate that AMPK directly interacts with and phosphorylates PEA15 at Ser116, thus establishing PEA15 as a new AMPK target. Thus, our study has identified AMPK-PEA15 signaling as a key component of sphere formation by both normal and cancerous breast tissues. During metastasis, epithelial cells lose attachments to their neighbors, acquire a mesenchymal-like morphology, a process termed as epithelial-mesenchymal transition (EMT) and become motile. Our results indicate that AMPK regulates EMT by both transcriptional and post-translational modification of EMT-inducing transcription factor, Twist. Thus, our study has identified a role for AMPK in nutrient deprivation, anchorage-independent growth, and epithelial-mesenchymal transition involved in metastasis. In addition, we have identified two novel substrates of AMPK, PEA15 and Twist, that may play key roles in cancer progression. Thus, our study suggests that targeting AMPK, or its newly identified substrates, can be explored as possible anti-cancer mechanisms.

AMP-activated protein kinase (AMPK) is an important metabolic sensor in eukaryotic organisms and it plays an important role in regulating energy homeostasis, at both the cells and the whole organism. AMPK controls glucose and lipid metabolism by direct stimulation of enzymes or by long term stimulation of the gene expression of energy metabolism. Skeletal muscles significantly contribute to the total body weight and metabolic rate and to the maintenance of glucose homeostasis. Due to the ability of the muscle to increase energy expenditure to 95% of whole-body energy expenditure, could be the proper development and programming of metabolism in the early postnatal period crucial for the further development of the organism in adulthood. Early postnatal development leads to substantial changes in energy requirements of the body and this suggests the significant involvement of AMPK in this period. The aim of this thesis was to study the activity and expression of isoforms of the catalytic subunit of AMPK in skeletal muscle during early postnatal development of both mouse strains A/J and C57BL/6 that differ in the development of diet-induced obesity. The next task was to analyze the expression of selected genes involved in energy metabolism - GLUT4, PGC-1α and UCP3 that AMPK regulates. It was found that the...

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