L'expansion d'une tumeur résulte d'une multiplication non contrôlée des cellules tumorales, de l'acquisition de leur capacité à migrer, ainsi que de la genèse du réseau vasculaire nécessaire à leur survie. Ces propriétés reposent en partie sur la mise en jeu de molécules impliquées dans le guidage cellulaire telles que les sémaphorines, initialement décrites pour leur implication dans le guidage axonal au cours du développement du système nerveux. Leurs fonction s'étendent actuellement au contrôle de l'angiogénèse de la migration des précurseurs nerveux ainsi que du cycle cellulaire. Les voies de signalisation intra-cellulaires des sémaphorines ne sont que partiellement connues. Les CRMP (CollapsinResponse Mediator Protein) font partie de leurs médiateurs intracytoplasmiques, décrites au cours de la rétraction du cône de croissance induit par la sémaphorine 3A (Sema3A). L'implication en pathologie tumorale de ces voies de signalisation a été découverte par l!étude de gènes tel que celui de la sémaphorine 3F (Sema3F), présents dans les régions délétées du chromosome 3 de certains types de tumeurs non neuroendocrines du poumon L'implication des CRMP a été également révélée par les syndromes neurologiques paranéoplasiques (SNP). Ces syndromes résultent d'une auto-immunisation humorale des patients contre des antigènes exprimés par la tumeur dont ils sont atteints. C'est le cas de CRMP5, protéine, identifiée dans notre laboratoire comme cible des auto-anticorps anti-CV2/ CRMP5 dans le cadre des SNP associés à des tumeurs neuroendocrines du poumon, les carcinomes à petites cellules (CPC) ainsi qu'à des thymomes. Alors que les thymomes sont des tumeurs bénignes, les CPC représentent 20% des carcinomes pulmonaires et sont, avec les carcinomes neuroendocrines à grandes cellules, les formes les plus agressives des tumeurs du poumon. Notre objectif était d'étudier l'implication physiopathologique des CRMP dans les différents types de carcinomes du poumon et dans les thymomes ainsi que dans les tumeurs du système nerveux central en relation avec la signalisation des sémaphorines. Nous avons ainsi démontré une expression exclusive de CRMP5 par les carcinomes neuroendocrines du poumon et les gliomes de haut grade par comparaison aux carcinomes non neuroendocrines et aux thymomes. CRMP5 n'est pas exprimée dans les carcinomes non neuroendocrines du poumon desquels sont dérivés les lignées H460 et H157. Ces observations ont été complétées par deux collaborations à des études portant sur les voies de signalisation des sémaphorines dans des modèles cellulaires de ces tumeurs. La première étude a montré que Sema3F, surexprimée dans la lignée H157 possède un effet anti-tumoral. La voie de signalisation de Sema3F nécessite neuropiline 2, l'inactivation de la MAPK (Mitogen Activated Protein Kinase) Erk 1/2 et entraîne l!inhibition de l'adhésion des intégrines !vß3, avec participation de CRMP1 et CRMP4 mais pas de CRMP5. La deuxième étude a établi que sous Sema3A la voie de signalisation d'Erk ½ est activée par le complexe de récepteur NRP1/VEGFR1 lors de la migration de précurseurs nerveux. Dans ces conditions Sema3A entraîne des modulations des expressions des CRMP2, CRMP4 et CRMP5 suggérant leur implication. Ainsi, ce travail montre que l!activation de certaines voies de signalisation des sémaphorines sont spécifiques des types histopathologiques et des grades des tumeurs. Ces voies de signalisations sont médiées par des complexes de récepteurs précis et mettent souvent en jeu les CRMP / Tumour growth is a consequence of uncontrolled cell proliferation, cell migration and angiogenesis. These functions are partly controlled by molecules involved in cellular guidance. Among these molecules, the semaphorins, previously described in axonal guidance during development, interestingly control cell migration, angiogenesis, apoptosis and proliferation. Signalling pathways of Semaphorins are only partially known. CRMP (Collapsin Response Mediator Protein) are involved in the signalling semaphoring pathway, precisely as mediator of Sema3A induced growth cone collapse. Implication of these signalling pathways in tumour growth was initially discovered with Sema3F localised in frequently deleted regions of the third chromosome found in non neuroendocrine lung carcinoma. CRMP involvement was also discovered in neurological paraneoplastic syndromes (NPS). These syndromes result of an auto-immunisation against tumour antigens present in some patients. CRMP5 was identified by our laboratory as a target of anti-CV2/CRMP5 auto-antibodies seen in some NPS associated with small cell lung carcinoma (SCLC) and thymoma. While thymoma are benign tumours, SCLC account for 20% of all lung tumour pathological subtypes and represent with large cell neuroendocrine carcinoma the most clinically aggressive subtypes of lung tumours. Our aim was to study the physiopathological role of CRMP among the different subtypes of lung carcinoma, thymoma and central nervous system tumours and their relationship with semaphorin signalling pathways. We showed a specific diffuse expression of CRMP5 by high grade neuroendocrine carcinoma and high grade glioma tumour cells. CRMP5 is neither expressed by non neuroendocrine lung carcinoma nor H460 or H157 derived cell lines, nor thymoma. Additionally, 2 collaborative studies were undertaken, focusing on semaphorin cell signalling in tumour derived cell lines. The first study showed an anti tumour effect of Sema3F over-expressed in H157 cell line mediated by neuropilin 2, CRMP2 and CRMP4 but not by CRMP5. It showed that Sema3F stimulation led to the inactivation of Erk1/2 MAPK (Mitogen Activated Protein Kinase) and inhibition of !vß3 integrin mediated adhesion. The second study showed that Sema3A induced DEV cells migration was mediated by neuropilin1/VEGFR1 receptor complex and activated Erk1/2 pathway. CRMP2, CRMP4 and CRMP5 expression changes suggested their involvement in that pathway. Thus, these data show that some semaphorin pathways activation were specific of tumour pathological subtype and grade. These signalling pathways were precisely mediated by specific receptor complexes and different CRMPs isoforms

Les stress abiotiques sont la cause principale des pertes de rendement agricole dans le monde. Aujourd'hui, le développement d'espèces capables de résister à ces stress est d'une importance majeure, en particulier dans le contexte de la croissance démographique actuelle et du changement climatique mondial. La phytohormone acide abscissique (ABA) contrôle divers processus cellulaires et induit un signal de protection des plantes contre les stress abiotiques. Parmi les différents évènements moléculaires impliqués dans la voie de signalisation de l'ABA, les cascades de signalisation des mitogen activated protein kinase (MAPK) jouent un rôle important dans la transmission du signal. Cependant, seulement un nombre réduit de MAPK ont été identifiées et caractérisées jusqu'à maintenant.J'ai isolé 2 proches homologues MEKK-like MAPKKKs d'Arabidopsis, MAPKKK17 et MAPKKK18, dont le niveau d'expression étaient fortement induit en réponse à l'ABA et aux stress abiotiques. Chez les mutants insensibles à l'ABA, pyr1/pyl1/pyl2/pyl4 et hab1G246D, l'expression ABA- et sel-dépendant de ces deux gènes était fortement réduite, indiquant que ces 2 kinases agissent en aval du complexe de signalisation de l'ABA. L'utilisation de plantes transgéniques exprimant, sous le contrôle de son propre promoteur, le gène MAPKKK18 fusionné à une étiquette PC2 ou YFP a permis de montrer par western blot que la protéine s'accumulait suite à un traitement à l'ABA et non pas en réponse au stress abiotiques. Ces données montrent que l'ABA est le régulateur majeur de la fonction de MAPKKK18.Suite à une approche de yeast-2-hybrid, j'ai pu identifier MKK3 comme la seule MAPKK interagissant avec MAPKKK17 and MAPKKK18. Ces résultats ont pu être confirmés via la technique de BiFC. Dans des protoplastes de mésophylle, il apparait que MAPKKK17 et MAPKKK18 activent MKK3, indiquant que ces deux gènes codent pour des kinases fonctionnelles. Afin d'apporter des preuves génétiques, j'ai isolé les T-DNA knockout mutants de ces 3 gènes. Des analyses de germination révèlent que mkk3-1 est hypersensible à l'ABA, au sel et au mannitol tandis que la lignée de surexpression Gain-de-fonction présente un phénotype opposé. Cependant, les doubles mutants mapkkk17/18 ne présentent pas de phénotype de germination. D'autres analyses ont pu montrer que mkk3-1 est sensible à la sécheresse et au stress salin tandis que les lignées surexpresseures sont plus tolérantes. Le double mutant mapkkk17/18 est quant à lui seulement sensible au NaCl. Pris dans leur ensemble, ces résultats indiquent que MAPKKK17/MAPKKK18 et MKK3 forment un complexe régulant la réponse des plantes aux stress abiotiques selon une voie dépendantes de l'ABA. / Abiotic stresses are the principal cause of crop failure worldwide. Developing crop plants better able to withstand these stresses has assumed great importance especially in the context of current population growth and global climatic change. The phytohormone abscisic acid (ABA) regulates diverse cellular processes and transduces signals to protect plants from abiotic stresses. Among the molecular elements working in ABA signaling, the mitogen activated protein kinase (MAPK) cascades play important roles in regulating the signaling network. To date, however, only a handful of MAPKs have been identified and characterized in ABA signaling. I isolated 2 closely related Arabidopsis MEKK-like MAPKKKs, MAPKKK17 and MAPKKK18, whose transcript expressions were highly induced by ABA and abiotic stresses. In 2 ABA insensitive mutants, pyr1/pyl1/pyl2/pyl4 and hab1G246D, the ABA- and NaCl-dependent expression of MAPKKK17 and MAPKKK18 was strongly reduced, indicating that these 2 kinases act downstream of the core ABA signaling complex. Western blot analysis of transgenic plants that expressed either a PC2 or YFP tagged MAPKKK18 under endogenous promoter revealed that MAPKKK18 protein strongly accumulated in response to ABA treatment but not in response to other abiotic stresses. This data indicated that ABA is the major regulator of MAPKKK18 protein function.Using yeast-2-hybrid approach, I identified MKK3 as the downstream MAPKK interactor of MAPKKK17 and MAPKKK18, and confirmed these interactions via BiFC assays. In mesophyll protoplasts, MAPKKK17 and MAPKKK18 activated MKK3, indicating that these 2 genes encode functional kinases. To provide genetic evidence of their functions, I isolated T-DNA knockout mutants of these genes. Germination assays reveal that mkk3-1 mutant was hypersensitive to ABA, NaCl and Mannitol stress whereas the over-expression line was resistant. The double homozygous mutant of mapkkk17/18 was not affected in germination. Further analysis revealed that mkk3-1 seedlings were sensitive to NaCl and terminal drought whereas the over-expression lines were resistant. The mapkkk17/18 seedlings were susceptible to NaCl but not terminal drought. Taken together, these results suggest that MAPKKK17/MAPKKK18 and MKK3 form complexes to regulate plant responses to abiotic stress in an ABA-dependent manner.

L'épiderme est un tissu stratifié, majoritairement constitué de kératinocytes qui forme la première barrière de l'organisme contre les agressions extérieures. Après blessure cutanée, la migration des kératinocytes est une phase cruciale de la cicatrisation. Le comportement des kératinocytes est placé sous le contrôle des molécules de la matrice extracellulaire ainsi que par les facteurs solubles (facteurs de croissance et cytokines..) sécrétés dans le microenvironnement. Les cellules résidentes ou recrutées sur le site de lésion libèrent également des nucléotides extracellulaires (ATP, UTP) dans l'environnement des kératinocytes. Dans ce travail de thèse, nous avons examiné l'impact des nucléotides extracellulaires et du récepteur purinergique P2Y2 sur la migration des kératinocytes et sur l'activité motogénique de deux facteurs de croissance, l'IGF-I et de l'EGF. Dans un premier temps, nous avons pu montrer que l'activation de P2Y2 et de la protéine hétérotrimérique Gαq inhibe l'activité de l'isoforme p110α de la PI3K sur des cellules stimulées par l'IGF. Cette inhibition de la voie PI3K/Akt aboutit à une perturbation de la mobilisation de la cortactine et de la formation des lamellipodes ainsi qu'une diminution de la vitesse de migration des kératinocytes. Dans un second temps, nous avons mis en évidence que l'activation de P2Y2 inhibe l'activation de la voie ERK1/2 par l'EGF en inhibant la phosphorylation des protéines MEK1/2, ERK1/2 et p90RSK. Nous avons établi que la conséquence de cette inhibition est la stabilisation des hémidesmosomes / The epidermis is a stratified tissue, mainly composed of keratinocytes, that forms the first barrier of the organism. When skin injury occurs, the epidermis structure is altered and many signalling pathways are activated in order to re-establish its homeostasis. Among these signalling pathways, the PI3K and MAPK ERK1/2 pathways play key roles by controlling keratinocyte migration and proliferation. The aim of this thesis was to analyse the regulation of these two signalling pathways by extracellular nucleotides, acting through purinergic receptors P2Y2 and the heterotrimeric Gαq protein and to evaluate the impact of this receptor on keratinocyte migration. Firstly, we showed that P2Y2 receptor activation inhibits PI3K p110α isoform and consequently alters keratinocyte cell shape and migration. Additionally, we showed that purinergic signalling activation inhibits EGF-induced ERK1/2 pathway activation by inhibiting the phosphorylation of MEK1/2, ERK1/2 and p90RSK proteins. As a consequence, P2Y2 stabilizes α6β4 integrin localisation into hemidesmosome-like structures and inhibits keratinocyte migration. The involvement of purinergic signalling pathway in regulation of different signalling events suggests that it may play a central role in regulation of cellular events that occurred during skin wound healing process. Moreover, our present data in association with those of the literature show that extracellular nucleotides can act as a double-edged sword in the regulation of cell migration: either activate or block cell migration in a striking cell-specific manner.

O fungo filamentoso Trichoderma reesei é uma espécie de grande importância biotecnológica no que tange a degradação de biomassa lignocelulósica para a produção de bioetanol em larga escala. Seu sistema de enzimas celulolíticas é muito eficiente, apesar de ser possuir poucas celulases, sugerindo que o controle dessas enzimas vai além da regulação transcricional. Assim, neste trabalho nós obtivemos o perfil fosfoproteômico de T. reesei cultivado em glicose e bagaço de cana-de-açúcar a partir de análise fosfoproteômica LC-MS/MS por spectral counting. A comparação entre os perfis de fosfoproteínas obtidos das linhagens parental QM6a de T. reesei e dos mutantes knockout para TMK1 e TMK2 permitiu a demonstração de que essas MAPK agem de maneira interconectada com outras vias de transdução de sinal na célula, especialmente a via de TOR e de AMPc-PKA, para regulação da produção de celulases. Além disso, também demonstramos a regulação da resposta a estresse celular por TMK2, e o papel da fosforilação no controle direto de enzimas CAZy. Nossos resultados mostram que a fosforilação desempenha papel importante na regulação dessas enzimas e de outras funções celulares no fungo após a transcrição de seus respectivos genes. O agrupamento desses dados permite melhor entendimento da via de sinalização mediada pelas MAPK TMK1 e TMK2 de T. reesei, e como as modificações pós-traducionais promovidas por elas afetam no sensing de nutrientes celulares e, por consequência, na produção de enzimas celulolíticas, de forma direta ou indireta. / The filamentous fungus Trichoderma reesei has great biotechnological importance in regards to the lignocellulosic biomass degradation for large-scale production of bioethanol. Its cellulolytic system is very efficient, despite being composed by only a few cellulases, which suggests that the control of these enzymes goes beyond their transcriptional regulation. Thus, in this study, we performed a spectral counting LC-MS/MS analysis and achieved the phosphoproteomic profile of T. reesei grown either in glucose or sugarcane bagasse as sole carbon source. The comparison between the phosphoproteins profiles obtained from the parental strain QM6a and the knockout mutants for TMK1 and TMK2 allowed us to demonstrate that these MAPK act in an interconnected manner with other signaling transduction pathways, especially the TOR and cAMP-PKA pathways, in order to regulate the cellulases production. Furthermore, we were also able to determine the regulation of cellular stress response by TMK2, and the role of phosphorylation in the direct control of CAZymes. Our results show that phosphorylation plays an important role on the control of these enzymes and other cellular functions in T. reesei after the transcription of their respective genes. Taken together, this data allows better comprehension of the signaling pathways mediated by TMK1 and TMK2 in T. reesei, and how the post-translational modification promoted by these MAPK might affect the nutrient sensing and, therefore, the production of the cellulolytic enzymes, either directly or indirectly.

O FGF2 (Fibroblast Growth Factor 2) é um clássico fator peptídico de crescimento que ativa vias intracelulares de sinalização molecular promovendo a transição G0 → G1 e o comprometimento com o ciclo celular. Não surpreendentemente, seus papéis pró-tumoral e angiogênico estão bem caracterizados e estabelecidos na literatura. No entanto, um crescente corpo de evidências tem indicado que o FGF2 também pode exercer efeitos anti-tumorais in vitro e in vivo, em modelos murinos e também humanos. Neste contexto, nosso grupo publicou em 2008 que o FGF2 exerce um efeito antiproliferativo seletivo em células murinas malignas dependentes de alta atividade de K-Ras e H-Ras. Os genes ras compõem a família de oncogenes mais frequentemente mutada em tumores malignos humanos, alcançando aproximadamente 30% de todos os casos. O desenvolvimento de terapias contra tumores dependentes de Ras fracassou, apesar dos intensos esforços e investimentos desde a descoberta em 1982 de suas mutações ativadoras em múltiplos cânceres. O objetivo deste trabalho foi desvendar os mecanismos moleculares pelo quais o FGF2 inibe irreversivelmente a proliferação de células malignas dependentes da atividade de Ras, empregando como modelos experimentais a linhagem murina Y1 de células adrenocorticais, e 4 linhagens humanas derivadas de sarcomas de Ewing. Identificamos que o efeito citotóxico do FGF2 não se processa por um mecanismo novo e independente das viasproliferativas classicamente ativadas por fatores peptídicos de crescimento. Ao contrário, seu efeito tóxico é resultado de sinalização mitogênica exagerada decorrente de estimulação sustentada por FGF2. A ativação da via de MAPK, principal sinalização mitogênica intracelular, a níveis elevados e sustentados provoca estresse mitogênico, que se propaga para a fase S na forma de estresse replicativo. Nesta situação, a célula passa a depender exageradamente da sinalização protetora de ATR, de modo que a combinação de estimulação com FGF2 e inibição de ATR foi altamente letal para as células malignas dependentes de Ras empregadas neste trabalho. Também analisamos as bases moleculares de resistência a FGF2 exibida por células Y1 anteriormente selecionadas para resistir ao efeito tóxico do FGF2 (Y1FRs). Descobrimos que a pressão seletiva do FGF2 não teve efeito na expressão de seus receptores, mas provocou a eliminação de um dos dois cromossomos que portam a amplificação gênica de ras nesta linhagem, enquanto o segundo cromossomo foi mantido por ser a única fonte de genes ribossomais ativos. Suas cópias de ras, no entanto, mostraram-se transcricionalmente silenciadas. Além disso, as sublinhagens Y1FRs não expressam o principal RasGEF, GRP4, encontrado nas células parentais Y1, o que pode ter influenciado o surgimento do fenótipo resistente ao FGF2. As linhagens resistentes mostraram grande redução no número de cromossomos e aumento da frequência de fusões entre cromossomos não homólogos em relação às células parentais. / FGF2 (Fibroblast Growth Factor 2) is a classic peptide growth factor that activates intracellular molecular signaling pathways promoting the G0 → G1 transition and cell cycle commitment. Not surprisingly, its pro-tumor and angiogenic roles are well characterized and established in the literature. However, a growing body of evidence has indicated that FGF2 may also exert anti-tumor effects in vitro and in vivo in murine and human models. In this context, our group reported in 2008 that FGF2 exerts a selective antiproliferative effect in murine cells dependent on high activity of K-Ras and H-Ras. Ras genes make up the most frequently mutated oncogene family in human malignant tumors, reaching approximately 30% of all cases. The development of therapies against Ras-dependent tumors has failed despite intense efforts and investments since the discovery in 1982 of its activating mutations in multiple cancers. The objective of this work was to uncover the molecular mechanisms by which FGF2 irreversibly inhibits the proliferation of malignant cells dependent on Ras activity, using as experimental models the Y1 murine lineage of adrenocortical malignant cells and 4 human lineages derived from Ewing sarcomas. We showed that the cytotoxic effect of FGF2 did not involve novel cell cycle regulatory pathways; instead, this cytotoxic effect is a result of sustainedhyper mitogenic stimulation by FGF2. Activation of the KRas/MAPK pathway, the major intracellular mitogenic signaling, at high and sustained levels provokes mitogenic stress, which is propagated to S phase as replicative stress. In this situation, the cell dependence on the ATR protective signaling is enhanced, so that the combination of stimulation with FGF2 and inhibition of ATR was highly lethal for the Ras dependent malignant cells employed in this work. We also analyzed the molecular basis of FGF2 resistance exhibited by Y1 cells previously selected for resistance to FGF2. We found that the selective pressure of FGF2 had no effect on the expression of its receptors but promoted the elimination of one of the two marker chromosomes that carry the K-ras amplified copies, while the second chromosome was maintained because it is the only source of active ribosomal genes; however, its K-ras amplified copies were transcriptionally silenced. In addition, the Y1FRs sublines did not express the main RasGEF, GRP4, found in the parental Y1 cells, which might have played a role in the emergence of the FGF2-resistant phenotype. The resistant Y1FRs sublines showed a large reduction in chromosome numbers and increased frequency of fusions between non-homologous chromosomes in relation to parental cells.

O FGF2 (Fibroblast Growth Factor 2) é um clássico fator peptídico de crescimento que ativa vias intracelulares de sinalização molecular promovendo a transição G0 → G1 e o comprometimento com o ciclo celular. Não surpreendentemente, seus papéis pró-tumoral e angiogênico estão bem caracterizados e estabelecidos na literatura. No entanto, um crescente corpo de evidências tem indicado que o FGF2 também pode exercer efeitos anti-tumorais in vitro e in vivo, em modelos murinos e também humanos. Neste contexto, nosso grupo publicou em 2008 que o FGF2 exerce um efeito antiproliferativo seletivo em células murinas malignas dependentes de alta atividade de K-Ras e H-Ras. Os genes ras compõem a família de oncogenes mais frequentemente mutada em tumores malignos humanos, alcançando aproximadamente 30% de todos os casos. O desenvolvimento de terapias contra tumores dependentes de Ras fracassou, apesar dos intensos esforços e investimentos desde a descoberta em 1982 de suas mutações ativadoras em múltiplos cânceres. O objetivo deste trabalho foi desvendar os mecanismos moleculares pelo quais o FGF2 inibe irreversivelmente a proliferação de células malignas dependentes da atividade de Ras, empregando como modelos experimentais a linhagem murina Y1 de células adrenocorticais, e 4 linhagens humanas derivadas de sarcomas de Ewing. Identificamos que o efeito citotóxico do FGF2 não se processa por um mecanismo novo e independente das viasproliferativas classicamente ativadas por fatores peptídicos de crescimento. Ao contrário, seu efeito tóxico é resultado de sinalização mitogênica exagerada decorrente de estimulação sustentada por FGF2. A ativação da via de MAPK, principal sinalização mitogênica intracelular, a níveis elevados e sustentados provoca estresse mitogênico, que se propaga para a fase S na forma de estresse replicativo. Nesta situação, a célula passa a depender exageradamente da sinalização protetora de ATR, de modo que a combinação de estimulação com FGF2 e inibição de ATR foi altamente letal para as células malignas dependentes de Ras empregadas neste trabalho. Também analisamos as bases moleculares de resistência a FGF2 exibida por células Y1 anteriormente selecionadas para resistir ao efeito tóxico do FGF2 (Y1FRs). Descobrimos que a pressão seletiva do FGF2 não teve efeito na expressão de seus receptores, mas provocou a eliminação de um dos dois cromossomos que portam a amplificação gênica de ras nesta linhagem, enquanto o segundo cromossomo foi mantido por ser a única fonte de genes ribossomais ativos. Suas cópias de ras, no entanto, mostraram-se transcricionalmente silenciadas. Além disso, as sublinhagens Y1FRs não expressam o principal RasGEF, GRP4, encontrado nas células parentais Y1, o que pode ter influenciado o surgimento do fenótipo resistente ao FGF2. As linhagens resistentes mostraram grande redução no número de cromossomos e aumento da frequência de fusões entre cromossomos não homólogos em relação às células parentais. / FGF2 (Fibroblast Growth Factor 2) is a classic peptide growth factor that activates intracellular molecular signaling pathways promoting the G0 → G1 transition and cell cycle commitment. Not surprisingly, its pro-tumor and angiogenic roles are well characterized and established in the literature. However, a growing body of evidence has indicated that FGF2 may also exert anti-tumor effects in vitro and in vivo in murine and human models. In this context, our group reported in 2008 that FGF2 exerts a selective antiproliferative effect in murine cells dependent on high activity of K-Ras and H-Ras. Ras genes make up the most frequently mutated oncogene family in human malignant tumors, reaching approximately 30% of all cases. The development of therapies against Ras-dependent tumors has failed despite intense efforts and investments since the discovery in 1982 of its activating mutations in multiple cancers. The objective of this work was to uncover the molecular mechanisms by which FGF2 irreversibly inhibits the proliferation of malignant cells dependent on Ras activity, using as experimental models the Y1 murine lineage of adrenocortical malignant cells and 4 human lineages derived from Ewing sarcomas. We showed that the cytotoxic effect of FGF2 did not involve novel cell cycle regulatory pathways; instead, this cytotoxic effect is a result of sustainedhyper mitogenic stimulation by FGF2. Activation of the KRas/MAPK pathway, the major intracellular mitogenic signaling, at high and sustained levels provokes mitogenic stress, which is propagated to S phase as replicative stress. In this situation, the cell dependence on the ATR protective signaling is enhanced, so that the combination of stimulation with FGF2 and inhibition of ATR was highly lethal for the Ras dependent malignant cells employed in this work. We also analyzed the molecular basis of FGF2 resistance exhibited by Y1 cells previously selected for resistance to FGF2. We found that the selective pressure of FGF2 had no effect on the expression of its receptors but promoted the elimination of one of the two marker chromosomes that carry the K-ras amplified copies, while the second chromosome was maintained because it is the only source of active ribosomal genes; however, its K-ras amplified copies were transcriptionally silenced. In addition, the Y1FRs sublines did not express the main RasGEF, GRP4, found in the parental Y1 cells, which might have played a role in the emergence of the FGF2-resistant phenotype. The resistant Y1FRs sublines showed a large reduction in chromosome numbers and increased frequency of fusions between non-homologous chromosomes in relation to parental cells.

Células dendríticas são as principais células apresentadoras de antígeno e apresentam alterações em pacientes com câncer. As vias de sinalização ERK 1/2 e p38 MAPK participam da diferenciação de DCs derivadas de monócitos (Mo-DCs). A exposição ao sobrenadante tumoral (ST) da linhagem MCF-7 levou à diminuição de CD1a e aumento de CD14 (frequência), além do aumento de IL-6 e IL-10. A inibição da via ERK1/2 MAPK corrigiu a expressão de CD14 e corrigiu parcialmente a produção das citocinas. A inibição da via p38 MAPK corrigiu a expressão de CD1a e CD14 e diminuiu parcialmente a produção das citocinas. Identificamos a proteína de choque térmico HSP27. A exposição à HSP27 não levou às alterações observados quando as células foram expostas ao ST. Por fim, em Mo-DCs de pacientes com câncer de mama o tratamento com o inibidor da p38 MAPK diminuiu a expressão de CD86 e HLA-DR. Portanto, os resultados deste trabalho sugerem que a inibição da via p38 MAPK não parece ser uma abordagem interessante na manipulação de Mo-DCs de pacientes com carcinoma ductal invasivo de mama. / Dendritic cells are the main presenting cells and present alterations in cancer patients. The signaling pathways p38 and ERK1/2 MAPK participate of monocyte-derived dendritic cells (Mo-DCs) differentiation. Exposition to MCF-7s supernatant (TS) decreased CD14 and CD1a expression (frequency) while enhanced IL-6 and IL-10 production. Inhibition of ERK1/2 MAPK reverted CD14 expression and partially reverted cytokines production. Inhibition of p38 MAPK reverted CD1a and CD14 expression and partially reverted cytokines production too. We identified the heat shock protein HSP27. Exposition to HSP27 did not cause the observed alterations seen when the cells were exposed to TS. Lastly, treatment of Mo-DCs from breast cancer patients with the p38 inhibitor decreased CD86 and HLA-DR expression. Therefore, the data presented in this study suggest that p38 MAPK inhibition does not appear to be an interesting approach in the manipulation of Mo-DCs from breast cancer patients.

O fungo filamentoso Trichoderma reesei é uma espécie de grande importância biotecnológica no que tange a degradação de biomassa lignocelulósica para a produção de bioetanol em larga escala. Seu sistema de enzimas celulolíticas é muito eficiente, apesar de ser possuir poucas celulases, sugerindo que o controle dessas enzimas vai além da regulação transcricional. Assim, neste trabalho nós obtivemos o perfil fosfoproteômico de T. reesei cultivado em glicose e bagaço de cana-de-açúcar a partir de análise fosfoproteômica LC-MS/MS por spectral counting. A comparação entre os perfis de fosfoproteínas obtidos das linhagens parental QM6a de T. reesei e dos mutantes knockout para TMK1 e TMK2 permitiu a demonstração de que essas MAPK agem de maneira interconectada com outras vias de transdução de sinal na célula, especialmente a via de TOR e de AMPc-PKA, para regulação da produção de celulases. Além disso, também demonstramos a regulação da resposta a estresse celular por TMK2, e o papel da fosforilação no controle direto de enzimas CAZy. Nossos resultados mostram que a fosforilação desempenha papel importante na regulação dessas enzimas e de outras funções celulares no fungo após a transcrição de seus respectivos genes. O agrupamento desses dados permite melhor entendimento da via de sinalização mediada pelas MAPK TMK1 e TMK2 de T. reesei, e como as modificações pós-traducionais promovidas por elas afetam no sensing de nutrientes celulares e, por consequência, na produção de enzimas celulolíticas, de forma direta ou indireta. / The filamentous fungus Trichoderma reesei has great biotechnological importance in regards to the lignocellulosic biomass degradation for large-scale production of bioethanol. Its cellulolytic system is very efficient, despite being composed by only a few cellulases, which suggests that the control of these enzymes goes beyond their transcriptional regulation. Thus, in this study, we performed a spectral counting LC-MS/MS analysis and achieved the phosphoproteomic profile of T. reesei grown either in glucose or sugarcane bagasse as sole carbon source. The comparison between the phosphoproteins profiles obtained from the parental strain QM6a and the knockout mutants for TMK1 and TMK2 allowed us to demonstrate that these MAPK act in an interconnected manner with other signaling transduction pathways, especially the TOR and cAMP-PKA pathways, in order to regulate the cellulases production. Furthermore, we were also able to determine the regulation of cellular stress response by TMK2, and the role of phosphorylation in the direct control of CAZymes. Our results show that phosphorylation plays an important role on the control of these enzymes and other cellular functions in T. reesei after the transcription of their respective genes. Taken together, this data allows better comprehension of the signaling pathways mediated by TMK1 and TMK2 in T. reesei, and how the post-translational modification promoted by these MAPK might affect the nutrient sensing and, therefore, the production of the cellulolytic enzymes, either directly or indirectly.

Le génome est sans cesse menacé dans sa structure par des stress génotoxiques d’origine endogène (stress oxydant, blocage de la réplication…) ou exogène (irradiations, produits chimiques, métaux lourds…). La voie de réponse aux dommages de l’ADN coordonne un réseau d’événements en cascades qui incluent les points de surveillance du cycle cellulaire, la réplication/réparation/recombinaison de l’ADN et la mort cellulaire programmée. Ces voies collaborent pour assurer la transmission fidèle du génome et empêcher la prolifération des cellules qui aurait accumulé des altérations génétiques. En général, des défauts dans une de ces voies entraînent un changement de sensibilité aux agents génotoxiques, une instabilité génétique et une prédisposition au cancer. La recombinaison homologue (RH) est une voie essentielle pour la réparation de l’ADN ; elle joue un rôle fondamental dans le maintien de la stabilité du génome. Le stress oxydant, résultant d’une augmentation de la concentration intracellulaire de ERO, est une des causes majeures de dommages aux lipides, aux protéines et à l’ADN et pour cela, il représente un défi pour la survie cellulaire et pour la stabilité du génome. Les ERO apparaissent physiologiquement lors de la respiration cellulaire ou résultent d’un stress environnemental, comme l’exposition aux radiations UV ou agents chimiques oxydants. Elles contribuent à certains processus comme la croissance cellulaire, l’activité et au repliement des protéines, la sénescence et la mort cellulaire programmée. Il est important de souligner qu’un état redox altéré est souvent associé à un fonctionnement anormal des cellules, comme il est observé pour les cellules cancéreuses et les cellules sénescentes. L’objectif de ce projet a été d’analyser l’interface entre les voies DDR et SAPK (Stress activated protein kinase) évolutivement conservées et d’en étudier les conséquences sur la stabilité du génome en utilisant comme organisme modèle la levure à fission. Nos résultats montrent que la voie SAPK joue un rôle sur la RH en promouvant la phosphorylation de Rad52, une protéine impliquée dans différentes sous-voies de la RH. Nous avons aussi montré que Rad52 est phosphorylée sur différents acides aminés, parmi lesquels certains sont les cibles de kinases inconnues qui n’ont aucun lien avec la voie SAPK. Nous avons observé que Rad52 est phosphorylée soit après un stress oxydant, soit dans des cellules génétiquement sujettes à des perturbations de la RH. Nous avons identifié deux sites de phosphorylation de la protéine Rad52, dont un seul est dépendant de la voie SAPK. En étudiant la phosphorylation de Rad52 dans les cellules invalidées pour la voie SAPK ou mutées pour un des sites de phosphorylation de Rad52, nous avons pu montrer que la RH est modulée par la voie SAPK même en absence de insulte externe. Notre travail ouvre le chemin vers une nouvelle compréhension des mécanismes fondamentaux du maintien de l’intégrité du génome. / Genomes are routinely submitted to injuries from either endogenous stress (oxidative stress, DNA replication block…) or from exogenous sources (radiations, chemicals, heavy metals…). The DNA damage response (DDR) coordinates a network of pathways including cell cycle checkpoints, DNA replication/repair/recombination, and programmed cell death, ensuring faithful genome transmission and preventing from the proliferation of cells bearing genetic alterations. Defect in one of these pathways generally results in altered sensitivity to genotoxins, genetic instability and cancer predisposition. Homologous recombination (HR) is an essential DNA repair pathway playing pivotal role to maintain genome stability.Oxidative stress, resulting from increased intracellular concentration of ROS, is one of the major causes of lipid, protein and DNA damage, and therefore a challenge for cell survival and genome stability. ROS are generated physiologically as by-products of cellular respiration, or as result of environmental stresses, such as exposure to solar UV radiations or to oxidant chemicals, and they actively participate in processes such as cellular growth, protein activity and folding, senescence and programmed cell death. It is noteworthy that an altered redox homeostasis is often associated to abnormally functioning cells, such as cancer and senescent cells. The aim of this project was to study the interface between two major evolutionarily conserved pathways, DDR and SAPK (Stress activated protein kinase) and the consequences on genome stability using fission yeast as a model organism. We report data showing that SAPK pathway impinges on HR by promoting phosphorylation of Rad52, a key protein involved in all sub-pathways of HR. We also revealed that Rad52 is phosphorylated at multiple different sites some of which are substrate for unidentified kinases unrelated to the SAPK pathway. Rad52 phosphorylation occurs either after oxidative stress or in cells genetically prone to HR perturbation. We identified two sites of phosphorylation, one of which is dependent on functional SAPK pathway. By studying Rad52 phosphorylation in cells mutated in the SAPK pathway or mutated at the Rad52 site of phosphorylation, we showed that HR is modulated by SAPK even in the absence of external insults. Our work pave the way to a novel understanding of fundamental mechanisms required for genome integrity maintenance.

Diante do quadro atual de previsões de mudanças climáticas, estudos a respeito das possíveis respostas dos organismos a estas alterações são importantes. Com a finalidade de prever e verificar se estas serão de fato deletérias ou se os organismos são capazes de lidar com elas sem alterações na sua fisiologia, e consequentemente na estrutura do ambiente, E. brasiliensis foi utilizada como modelo para estudar possíveis impactos do aumento da temperatura e acidificação dos oceanos na sua fisiologia. Para isso, espécimes foram expostos a 9 possíveis combinações de temperatura (24ºC, 28ºC e 30ºC) e pH (8.0, 7.7 e 7.3) em diferentes intervalos de tempo (1, 3, 12, 24 e 48 h). Amostras de gônadas e fluido celomático foram coletadas para avaliar a expressão das proteínas de estresse HSP70, AIF-1 e p38-MAPK, e a variação no número e viabilidade dos celomócitos. Nossos resultados mostram que o modelo é sensibilizado pelas mudanças no ambiente, através da hiper-regulação das proteínas de estresse. O cenário considerado mais extremo (30°C + pH7.3) ocasionou a morte de 100% dos organismos após 24horas. E o segundo cenário mais severo (30°C + pH7.7) desencadeou o desenvolvimento de ulceração de pele. Os efeitos são mais pronunciados nos celomócitos e a acidificação da água parece ter efeitos antagônicos com a temperatura nos celomócitos e sinérgicos nas gônadas. Embora a resposta tenha sido sistêmica, o grau e a dinâmica foram distintos em relação às diferentes amostras e estresses. Podendo causar modificações na resposta imune dos organismos e consequentemente na sobrevivência da espécie a longo prazo. / Under the current Climate Change context, studies about the potential responses of the organisms to their changing environment are of extreme importance. Recent studies point out the synergy of temperature and ocean acidification altogether. In this study, we used the sea star E. brasiliensis to assess the physiological effects of rising temperature, seawater acidification and the interaction of both factors. Independent individuals (N=225) were exposed to 9 possible combinations of temperature (24ºC, 28ºC and 30ºC) and pH (8.0, 7.7 and 7.3), for 1, 3, 12, 24 and 48 h. We compared the stress produced by these treatments measuring the expression of heat shock proteins (HSP70), the production of the allograft inflammatory factor (AIF−1) and the activation of mitogen kinases (MAPKs) at both gonad and celomic fluid. Furthermore, we assessed the quantity and quality of coelomocytes. Our results demonstrated that E. brasiliensis is vulnerable to the interaction of temperature and acidification. All the stress proteins evaluated were upregulated. The extreme scenario (30°C + pH7.3) caused the death of 100% of organisms after 24 hours, while the second most severe scenario (30°C + pH7.7) triggered skin ulceration. Nevertheless, we found that water acidification produces antagonistic effects to the temperature in coelomocytes and synergistic effects in gonad cells. Furthermore, these effects were more pronounced in the coelomocytes than in the gonads. The systemic response found in this study suggest that the interactive effects of elevated temperatures in conjunction with ocean acidification may endanger the survival of this species, and it could compromise the ecosystem functioning at long term.