Hippo signaling pathway represents organ size control mechanism constrained between all metazoans. Individual components of the Hippo signaling pathway were identified as key tumor-suppressors which phosphorylate and inhibit activity of several oncogenic factors and signaling pathways (such as YAP/TAZ, PI3K and mTOR). MST1 kinase is a part of central protein complex of the Hippo signaling pathway and its activation is involved in anti-cancer activity of several drugs. We have demonstrated activation of the MST1 kinase by natural compounds in leukemic cells followed by inhibition of proliferation and induction of apoptosis. Shikonin represents natural naphthoquinonic compound isolated from Lithospermum erythrorhizon which acts as inhibitor of glycolysis and mitochondrial respiratory chain in human cells. Shikonin induces fast activation of the MST1 protein in leukemic cells however mechanism of this activation remains unknown. Therefore, we tried to characterize posttranslational modifications of the MST1 kinase during shikonin treatment of leukemic cells. Firstly, we isolated MST1 kinase from control and shikonin-treated cells using immunoprecipitation. Then we characterized posttranslational modifications of the MST1 protein employing mass spectrometry. Using this approach we found out...

Skeletal muscle atrophy is a debilitating condition caused by pathological conditions including cancer cachexia, disuse and denervation. Disuse atrophy is characterized by reduction in fiber size, fiber-type change and induction of markers of atrophy such as MuRF1 and Fn14. Recent studies have focused on understanding the fundamental role of signalling pathways and the proteolytic system in response to muscle atrophy. Unfortunately the exact mechanisms behind atrophy remain poorly understood. I recently demonstrated that cIAP1 and/or cIAP2 proteins are critical regulators of NF-kB activation, which has been shown to be involved in skeletal muscle atrophy. Here, I used genetic and pharmacological means to investigate the role of cIAP1 in a denervation-induced skeletal muscle atrophy model. Interestingly, I found that upon denervation loss of cIAP1 rescues muscle fiber size, prevents fiber-type changing and inhibits the expression of MuRF1 and Fn14. Moreover, treatment of mice with Smac mimetic compounds (SMC), a novel class of small molecule IAP antagonists, showed successful knockdown of cIAP1 in muscle and protects against denervation-induced muscle atrophy. Taken together, these data reveal that cIAP1 is both a novel mediator of skeletal muscle atrophy and an important therapeutic target.

La perception et l’adaptation à l’environnement sont des processus indispensables pour la survie des organismes vivants. Le champignon phytopathogène Botrytis cinerea peut ainsi percevoir différents types de signaux qu’ils soient chimiques ou physiques. La voie de signalisation de la MAPK Sak1 est impliquée dans l’adaptation au stress osmotique, oxydatif et pariétal, mais aussi dans la sporulation et le pouvoir pathogène en régulant la pénétration de la plante et le développement des nécroses. Afin d’approfondir les connaissances existantes sur la voie de Sak1, nous avons réalisé des études globales basées sur des techniques de protéomique et phosphoprotéomique. L’analyse de protéomique comparative entre la souche sauvage et les mutants de signalisation ∆bos1 et ∆sak1 a notamment mis en évidence que la MAPK Sak1 régule l’abondance de protéines impliquées dans la voie des protéines G et la voie calcique. Cette connexion avec les protéines G a été confirmée par une baisse de la concentration en AMPc chez le mutant ∆sak1. L’utilisation du fludioxonil comme signal de l’activation de la MAPK Sak1 pour l’analyse par phosphoprotéomique a mis en évidence des modifications de l’état de phosphorylation de protéines. Parmi ces protéines différentiellement phosphorylées, la présence de PKAR (sous-unité régulatrice de la protéine kinase A) et du facteur de transcription CRZ1, indiquent respectivement une action sur la voie via protéines G et la voie calcique, validant les résultats obtenus par protéomique. Le phosphoprotéome a révélé une « phosducin-like protein », PhnA. Sa caractérisation fonctionnelle montre son rôle dans l’adaptation aux stress, la sporulation et la germination, ainsi que dans le pouvoir pathogène mettant ainsi en évidence un nouveau facteur de pathogénicité chez B. cinerea. Notre étude a permis de révéler des interactions entre Sak1 et d’autres voies de signalisation non suspectées, agissant aussi bien sur la production de certains composants (régulations transcriptionnelles et traductionnelles) que sur la phosphorylation (modifications post-traductionnelles). Nos résultats constitueront la base de nouvelles recherches pour compléter nos connaissances sur ces interactions impliquant l’adaptation au stress et la pathogénie de B. cinerea. / Perception and adaptation to the environment are essential processes for the survival of living organisms. The phytopathogenic fungus Botrytis cinerea can thus perceive different types of signals, whether they are chemical or physical. The signalling pathway of the Sak1 MAPK is involved in the adaptation to osmotic, oxidative and cell wall stress, but also in sporulation and pathogenicity by regulating plant penetration and necrosis development. In order to deepen existing knowledge of the Sak1 pathway, we have carried out global studies based on proteomics and phosphoproteomics techniques. A comparative proteomics analysis between the wild type and the signalling mutants ∆bos1 and ∆sak1 showed, among others, that Sak1 regulates the abundance of proteins involved in the G-protein pathway and calcium pathway. This connection with G-proteins was confirmed by a decrease in cAMP concentration in the ∆sak1 mutant. Using fludioxonil as signal for the activation of Sak1 for a phosphoproteomic analysis revealed changes in the state of protein phosphorylation. Among these differentially phosphorylated proteins, the presence of PKAR (regulatory subunit of protein kinase A) and the transcription factor CRZ1, indicates an action on the G-protein and calcium pathway respectively, validating the results obtained by proteomics. Phosphoproteomics revealed a phosducin-like protein, PhnA. Its functional characterization reveals its role in stress adaptation, sporulation and germination, as well as in pathogenicity, thus demonstrating a new pathogenicity factor in B. cinerea. Our study revealed interactions between Sak1 and other unsuspected signalling pathways, affecting both the production of certain components (transcriptional and translational regulations) and phosphorylation (post-translational modifications). Our results will create the basis for new research questions to complement our understanding of these interactions involving adaptation to stress and pathogenesis of B. cinerea.

<p>Functioning as a “powerhouse”, the liver adapts to the metabolic needs of the body by maintaining a homeostatic balance. Prolactin receptor (PRLR) has been found to have a copious existence in the liver. Having established a well-defined role in both reproductive and endocrine systems, the role of this transmembrane protein in hepatocytes is yet to be elucidated. Due to its abundant nature, we hypothesized that PRLR is required for maintaining hepatic homeostasis and plays a role in liver diseases. To test this hypothesis, we defined two specific aims. The first was to explore whether PRLR loss-of-function affects liver structure and function in physiological conditions. The second was to determine whether PRLR is associated with liver pathology. We deleted the <i>Prlr</i> gene specifically in hepatocytes using a virus-based approach and evaluated liver function, transcriptome, and activities of downstream signaling molecules. Due to the absence of PRLR, we found that the urea cycle was disrupted, concomitant with excessive accumulation of urea in the blood; 133 genes exhibited differential expression, largely associated with hepatocyte structure, metabolism, and inflammation; and the activities of STAT3 and 5 were reduced. The results signify that PRLR indeed plays a homeostatic role in the liver. We also used <i>Prlr</i>^+/- mice to assess whether the loss of one allele of the <i>Prlr</i> gene alters maternal hepatic adaptations to pregnancy. As a result, in the pre-pregnancy state and during the first half of gestation, the expression of maternal hepatic PRLR protein was reduced approximately by half owing to <i>Prlr</i> insufficiency. However, during the second half of pregnancy, we observed compensatory upregulation of this molecule, leading to minimal interference in STAT 3 and 5 signaling and liver size. Contrary to a previous study in the breast and ovary, our results suggest that one allele of <i>Prlr</i> may be sufficient for the maternal liver to respond to this physiological stimulus (pregnancy). Furthermore, we examined the expression and activity of PRLR in fatty as well as cholestatic livers. Using a high fat diet, we induced non-alcoholic fatty liver disease (NAFLD). Strikingly and for the first time, we discovered that the short isoform of PRLR (PRLR-S) was completely inactivated in response to NAFLD, whereas the long isoform remained unchanged. This finding strongly suggests the involvement of PRLR-S in lipid metabolism. We also postulate that PRLR-L may be the major regulator of STAT signaling in the liver, consistent with other reports. Lastly, we induced extrahepatic cholestasis via bile duct ligation (BDL) in mice. As this liver disease progressed, the expression of both isoforms of PRLR generally declined and was surprisingly accompanied by increased STAT 3 and 5 activity. The data suggests that PRLR participates in this disease progression, with a disconnection between PRLR signaling and STAT proteins. Collectively, our preliminary studies suggest that PRLR signaling is required to maintain liver homeostasis and more prominently, is involved in liver diseases, especially NAFLD. These findings lay a foundation for our future studies.</p>

Indiana University-Purdue University Indianapolis (IUPUI) / Functioning as a “powerhouse”, the liver adapts to the metabolic needs of the body by maintaining a homeostatic balance. Prolactin receptor (PRLR) has been found to have a copious existence in the liver. Having established a well-defined role in both reproductive and endocrine systems, the role of this transmembrane protein in hepatocytes is yet to be elucidated. Due to its abundant nature, we hypothesized that PRLR is required for maintaining hepatic homeostasis and plays a role in liver diseases. To test this hypothesis, we defined two specific aims. The first was to explore whether PRLR loss-of-function affects liver structure and function in physiological conditions. The second was to determine whether PRLR is associated with liver pathology. We deleted the Prlr gene specifically in hepatocytes using a virus-based approach and evaluated liver function, transcriptome, and activities of downstream signaling molecules. Due to the absence of PRLR, we found that the urea cycle was disrupted, concomitant with excessive accumulation of urea in the blood; 133 genes exhibited differential expression, largely associated with hepatocyte structure, metabolism, and inflammation; and the activities of STAT3 and 5 were reduced. The results signify that PRLR indeed plays a homeostatic role in the liver. We also used Prlr+/- mice to assess whether the loss of one allele of the Prlr gene alters maternal hepatic adaptations to pregnancy. As a result, in the pre-pregnancy state and during the first half of gestation, the expression of maternal hepatic PRLR protein was reduced approximately by half owing to Prlr insufficiency. However, during the second half of pregnancy, we observed compensatory upregulation of this molecule, leading to minimal interference in STAT 3 and 5 signaling and liver size. Contrary to a previous study in the breast and ovary, our results suggest that one allele of Prlr may be sufficient for the maternal liver to respond to this physiological stimulus (pregnancy). Furthermore, we examined the expression and activity of PRLR in fatty as well as cholestatic livers. Using a high fat diet, we induced non-alcoholic fatty liver disease (NAFLD). Strikingly and for the first time, we discovered that the short isoform of PRLR (PRLR-S) was completely inactivated in response to NAFLD, whereas the long isoform remained unchanged. This finding strongly suggests the involvement of PRLR-S in lipid metabolism. We also postulate that PRLR-L may be the major regulator of STAT signaling in the liver, consistent with other reports. Lastly, we induced extrahepatic cholestasis via bile duct ligation (BDL) in mice. As this liver disease progressed, the expression of both isoforms of PRLR generally declined and was surprisingly accompanied by increased STAT 3 and 5 activity. The data suggests that PRLR participates in this disease progression, with a disconnection between PRLR signaling and STAT proteins. Collectively, our preliminary studies suggest that PRLR signaling is required to maintain liver homeostasis and more prominently, is involved in liver diseases, especially NAFLD. These findings lay a foundation for our future studies.

La paroi, qui est une structure dynamique entourant chaque cellule végétale, joue un rôle primordial dans le développement des plantes et la transduction de signaux en réponse à des changements environnementaux et à des attaques par des pathogènes. Un des composants majeurs de la paroi primaire est la cellulose qui y est enchevêtrée avec d’autres polysaccharides tels que les hémicelluloses et les pectines. L’objectif de la thèse était de comprendre comment la synthèse de cellulose est coordonnée avec l’assemblage et le remodelage de la paroi au cours de la croissance. Au cours de ces vingt dernières années, de nombreuses molécules inhibant la synthèse de la cellulose (CBI) ont été identifiées et représentent de très bons outils pour disséquer la biologie cellulaire du remodelage pariétale. Ces CBI présentent différentes structures ce qui suggère qu’il existe plusieurs cibles pour perturber la biosynthèse de la cellulose. En étudiant 5 d’entre eux et nous avons pu confirmer qu’ils provoquaient une disparition ou une immobilisation des complexes de cellulose synthase (CSC) à la membrane plasmique. Par contre la caractérisation d’un nouveau CBI, l’Hypostuntine, a permis de montrer qu’il agissait différemment des CBI déjà décrits. L’Hypostuntine inhibe la croissance sans changement détectable des CSC au niveau de la membrane plasmique suggérant que l’Hypostuntine ne cible pas directement le CSC. Des études en microscopie électronique à transmission des parois de plantules traitées à l’HS ont permis de montrer que l’Hypostuntine interfère au niveau du mécanisme cellulaire qui coordonne la biosynthèse de la cellulose et l’assemblage d’une paroi extensible. Pour distinguer le rôle de ces six CBI étudiés, des tests de résistance croisés, des analyses de la composition pariétale et de voies de signalisation ont également été étudiées. Les résultats montrent que toutes ces réponses dépendent entre autres de THESEUS1, un récepteur like kinase de la famille des Catharanthus roseus récepteur kinases CrRLK1L mais suggèrent aussi la présence d’autres acteurs spécifiques induits par chaque CBI. / The cell wall, which is a dynamic structure surrounding each plant cell, plays a fundamental role in the plant development and in the signalling pathways in response to environmental changes and pathogen attacks. One of the major component of the primary cell wall is the cellulose polymer which is embedded between hemicelluloses and pectins. The question of the PhD was how the synthesis of cellulose is coordinated with the assembly and remodelling of the cell wall during cell expansion? During these last twenty years, a multitude of molecules that inhibit cellulose synthesis (CBI) have been identified and they represent powerful tools to dissect the cell biology of cell wall assembly. The large variation in chemical composition of the CBI suggests the existence of multiple targets for these molecules for perturbing the cellulose biosynthesis. I studied five of these molecules and confirmed that they promote a clearance or an immobilisation of the cellulose synthase complex (CSC) from the plasma membrane. The characterisation of the new molecule, named Hypostuntin, showed that it mode of action on CSC is different from the ones described for the other CBI. Hypostuntin inhibits cell growth without detectable changes in CSC activity. This suggests that the CSC is not the primary target of Hypostuntin. Transmission electron microscopy on developing cell walls suggests that Hypostuntin interferes with a process that coordinates cellulose synthesis with the assembly of an extensible wall. To ascertain the role of the six studied CBI, we performed tests of cross resistance, analysis of cell wall composition and signalling pathways. Our results show that the responses are THESEUS 1 dependent, a receptor belonging to the Catharanthus roseus receptor like kinase CrRLK1L but also suggest the presence of other actors specific of the molecules.

Les néoplasmes myéloprolifératifs classiques sont des maladies clonales dues à des mutations acquises de JAK2V617F ou de la Calréticuline (CALRm) au niveau des cellules souches hématopoïétiques (CSH) et conduisant à une surproduction de cellules myéloïdes. L’interféron alpha (IFNa) est le seul traitement curatif qui induit une réponse hématologique et moléculaire. Le but de notre projet est de comprendre son mécanisme d’action en utilisant une cohorte de 47 patients, des lignées cellulaires et des modèles de souris JAK2V617F. Ainsi, nous avons constaté que l’IFNa cible plus rapidement les CSH que les cellules matures chez les patients JAK2V617F, ce qui semble différent des patients CALRm. Grâce aux lignées cellulaires et aux souris, nous avons montré que JAK2V617F induit une pré-activation des voies de l’IFNa et une inhibition du cycle cellulaire des CSH. La découverte complète de ce mécanisme d’action conduira à l’amélioration du traitement. / Classical BCR-ABL-negative myeloproliferative neoplasms (MPN) include Polycythemia Vera (PV), Essential Thrombocytemia (ET) and Primary Myelofibrosis (PMF). They are acquired clonal disorders of hematopoietic stem cells (HSC) leading to the hyperplasia of one or several myeloid lineages. They are due to three main recurrent mutations affecting the JAK/STAT signaling pathway: JAK2V617F and mutations in calreticulin (CALR) and thrombopoietin receptor (MPL). Interferon alpha (IFNα) is the only curative treatment that induces not only a hematological response of ET, PV and early MF but also a molecular response both on JAK2V617F or CALR mutated cells. In this study, we wanted to know how and with what kinetics IFN impacts the different mutated hematopoietic compartments. Thus, we have performed a prospective study with a cohort of 50 patients treated by IFNα for 3-5 years. The MPN diseases distribution was 44% ET, 45% PV and 11% MF. This cohort included 33 JAK2V617F-mutated patients, 11 CALR-mutated patients (7 type 1/type 1-like and 4 type 2/type 2-like), 2 both JAK2V617F- and CALR-mutated patients and 1 MPLW515K-mutated patient. At 4-month intervals, the JAK2V617F or/and CALR mutation variant allele frequency was measured in mature cells (granulocytes, platelets). Simultaneously, we have also determined the clonal architecture by studying the presence of the JAK2V617F or CALR mutations in colonies derived from the different hematopoietic stem and progenitor cell (HSPC) populations (CD90+CD34+CD38- HSC-enriched progenitors, CD90-CD34+CD38- immature progenitors and CD90- CD34+CD38+ committed progenitors). After a median follow-up of 30 months, we observed that IFNα targets more efficiently and rapidly the HSPC particularly in HSC-enriched progenitors, than the mature blood cells in JAK2V617F patients (p<.05). Moreover, homozygous JAK2V617F clones responded more rapidly than heterozygous clones in all hematopoietic cell compartments showing that the intensity of JAK2V617F signaling is correlated with the efficacy of IFNα. These observations were slightly increased after a median follow-up of 51 months. In contrast, with a median follow-up of 30 months for CALR mutated patients, IFNα targeted similarly the HSPC and the mature cells. Moreover, IFNα induced a less rapid response to target CALR-mutated HSPC than the JAK2V617F HSPC (p<.05). The role of associated mutations at diagnosis was also investigated in the IFNα-mediated HSPC molecular responses using a NGS targeted myeloid panel. While in JAK2V617F-mutated patients, we found that the number of associated mutations did not impact the HSPC molecular response of the JAK2V617F clone, in CALR-mutated patients, even if the number of cases was low, the only molecular responders were those not associated with other mutations. Using Ba/F3-MPL cellular models and primary cells, we observed that JAK2V617F was more prone to sensitize to IFNα signaling (increased Phospho-STAT1 and IFN-stimulating genes (ISGs)) compared to controls or CALRdel52 mutated cells.Altogether, our results show that IFNα differentially targets the human JAK2V617F- and CALR-mutated HSPC and mature cells. Moreover, the molecular response was dependent not only on the JAK2V617F or CALR mutated status but also on the presence of other associated mutations.

Ovarian cancer is the most common cause of death from gynecological malignancy. Taxanes and platinum derivatives are most used therapeutics for its treatment. Development of multi drug resistance to chemotherapy represents a serious complication of the treatment. Therefore, new chemotherapeutic and therapeutic targets are investigated, which could help to overcome tumor cell resistance. The main objectives of the thesis were to study: i) the efficiency of new derivatives of conventional taxanes in vitro with the aim to determine the potentially most effective taxane derivatives in resistant tumor ovarian cells and, ii) the gene expression profile of the Notch signaling pathway, as a possible therapeutic target for the treatment of ovarian cancer. Specifically, the thesis focused on the relationship between levels of Notch signaling gene expression in patients with ovarian carcinoma and their prognosis, progression and survival. This thesis revealed that Stony Brook Taxanes - "SB-T"; SB-T-121402, SB-T-121605, and SB-T-121606 derivatives are very effective in NCI/ADR-RES tumor carcinoma cells resistant to conventional taxane - paclitaxel, and should be further studied in more advanced models, e.g. in vivo patient derived xenografts. In a study of the importance of the Notch signaling pathway in...

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Background: Neurite outgrowth is an important aspect of neuronal plasticity and regeneration after neuronal injury. Alpha-lipoic acid (LA) has been used as a therapeutic approach for a variety of neural disorders. We recently reported that LA prevents local anesthetics-induced neurite loss. In this study, we hypothesized that LA administration promotes neurite outgrowth. Methods: To test our hypothesis, we treated mouse neuroblastoma N2a cells and primary neurons with LA. Neurite outgrowth was evaluated by examination of morphological changes and by immunocytochemistry for α-tubulin-3. ROS production was examined, as were the phosphorylation levels of ERK and Akt. In separate experiments, we determined the effects of the inhibition of ERK or PI3K/Akt as well as ROS production on LA-induced neurite outgrowth. Results: LA promoted significantly neurite outgrowth in a time- and concentration-dependent manner. LA stimulation significantly increased the phosphorylation levels of both Akt and ERK and transiently induced ROS production. PI3K/Akt inhibition did not affect LA-induced neurite outgrowth. However, the inhibition of ERK activation completely abolished LA-induced neurite outgrowth. Importantly, the prevention of ROS production by antioxidants attenuated LA-stimulated ERK activation and completely abolished LA-promoted neurite outgrowth. Conclusion: Our data suggest that LA stimulates neurite outgrowth through the activation of ERK signaling, an effect mediated through a ROS-dependent mechanism. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.