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Mitogen-Activated Protein Kinases --- analysis. --- physiology.

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Insulin is a hormone involved in glucose homeostasis and in the control of lipid metabolism. In 1981, frank and his co-workers found that the glycogen metabolism, in isolated hepatocytes, was more sensitive to insulin than the insulin receptor. They explained this phenomenon by the presence of “spare receptors”. It involved that a slight activation of the insulin signalling pathway was sufficient to obtain maximal metabolic responses. Similar experiments performed in other tissues indicated that spare receptors were not present everywhere. This first aim of my work was to determine if the spare receptor phenomenon exists in the heart. Moreover, several experiments realised in our laboratory showed a difference in sensitivity between protein kinase B and the metabolic effect of insulin. This questioned the participation of this enzyme in the metabolic effect of insulin.
To answer these two questions, we incubated rat cardiomyocytes with various concentration of insulin. Dose-responses curves were established, describing the effects of insulin on its signalling pathway and on metabolism. The targets studied in the signalling pathway were the insulin receptor, phosphatidylinositol-3 kinase, protein kinase B and glycogen synthase kinase-3. The metabolic responses studied here were glucose uptake and fructose-2;6-P2 concentration. The final step was to compare the ED50 obtained for each target studied. The ED50 represents the concentration of ligand that causes 50% of the maximal effect. A similar ED50 value (± 17 nM) was obtained for all elements of the insulin signalling pathway, from IR to GSK-3. By contrast, the two metabolic responses studied here were more sensitive (± 1.2 nM). From these results, we can conclude that spare receptors for insulin indeed exist in the heart and that a role of PKB in the metabolic effects of insulin can not be excluded L’insuline joue un rôle essentiel dans l’homéostasie du glucose et dans le contrôle du métabolisme des lipides. En 1981, Frank et collaborateurs ont mis en évidence, dans des hépatocytes en suspension, la présence d’une différence de sensibilité à l’insuline entre le récepteur insulinique et le métabolisme du glycogène, ce dernier étant le plus sensible. Ils avaient, à l’époque, expliqué ce phénomène par l’existence de « récepteurs de réserve » ou « spare receptors ». La présence de ces récepteurs de réserve impliquait qu’une petit activation au départ de la voie de signalisation de l’insuline était suffisante pour obtenir des réponses métaboliques maximales. Des expériences similaires ont ensuite été effectuées dans d’autres tissus et ont montré que la présence d’une telle différence de sensibilité à l’insuline varie en fonction du tissu étudié. Le premier objectif de mon travail a été par conséquent de savoir qu’est-ce qu’il en était du tissu cardiaque. D’autre part, des expériences réalisées dans notre laboratoire avaient mis en évidence l’existence d’une différence de sensibilité à l’insuline entre la protéine kinase B et les effets métaboliques de cette hormone, dans le cœur. Cela remettait en question la participation de cette enzyme aux effets métaboliques de l’insuline. Pur pouvoir répondre à ces deux questions, la première étape a été d’incuber des cardiomyocytes de rats aves des concentrations croissantes en insuline. Des courbes doses-réponses ont ensuite été établies, celles-ci décrivant les effets de l’insuline sur sa voie de signalisation et sur le métabolisme glucidique. Les cibles qui ont été étudiées dans la voie de signalisation sont le récepteur insulinique, la phosphatidylinositol 3-kinase, la protéine kinase B et la glycogène synthase kinase-3. D’autre part, les deux réponses métaboliques qui ont été choisies sont le captage du glucose et l’augmentation de la concentration en fructose-2,6-P2. Enfin, la dernière étape a été de déterminer et de comparer les ED50 obtenues pour chacune des courbes. La ED50 désigne la concentration en ligand nécessaire pour obtenir 50% de l’effet maximal. Les ED50 sont semblables pour tous les constituants de la voie de signalisation de l’insuline (± 17 nM). Les effets métaboliques, quant à eux, sont caractérisés par une sensibilité plus élevée envers l’insuline (± 1,2 nM). Ce travail montre donc que le phénomène de récepteurs de réserve est bien présent dans le cœur. De plus, nous ne pouvons pas exclure la participation de la PKB aux effets métaboliques de l’insuline, dans le cœur

Insulin --- src Homology Domains --- Mitogen-Activated Protein Kinases --- 1-Phosphatidylinositol 3-Kinases

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Mitogen-activated protein kinases. --- Mitogens. --- Plant cellular signal transduction. --- Plant enzymes.

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To maximize the probability of survival, cells need to coordinate their intracellular activities in response to changes in the extracellular environment. MAP kinase cascades play an important role in the transduction of signals inside eukaryotic cells. In particular, stress stimuli result in the rapid activation of a highly conserved group of MAP kinases, known as SAPKs (Stress-Activated Protein Kinases). These kinases coordinate the generation of adaptive responses that are essential for cell survival, which include the modulation of several aspects of cell physiology from metabolism to gene expression. In this book, leading researchers in the field discuss the state-of-the-art of many aspects of SAPK signalling in various systems from yeast to mammals. These include various chapters on regulatory mechanisms as well as the contribution of the SAPK signalling pathways to processes such as gene expression, metabolism, cell cycle regulation, immune responses and tumorigenesis.

MAP Kinase Signaling System --- MAP Kinase Kinase Kinases --- Mitogen-Activated Protein Kinase Kinases --- Mitogen-Activated Protein Kinases --- Mitogen-activated protein kinases. --- MAP kinases --- physiology. --- metabolism. --- Protein. --- Stress. --- Mitogen-activated protein kinases --- Intracellular Signaling Peptides and Proteins --- Protein-Serine-Threonine Kinases --- Signal Transduction --- Protein-Tyrosine Kinases --- Proline-Directed Protein Kinases --- Metabolic Networks and Pathways --- Peptides --- Proteins --- Protein Kinases --- Biochemical Processes --- Metabolism --- Cell Physiological Processes --- Biochemical Phenomena --- Phosphotransferases (Alcohol Group Acceptor) --- Amino Acids, Peptides, and Proteins --- Chemical Processes --- Cell Physiological Phenomena --- Metabolic Phenomena --- Chemical Phenomena --- Chemicals and Drugs --- Phosphotransferases --- Phenomena and Processes --- Transferases --- Enzymes --- Enzymes and Coenzymes --- Animal Biochemistry --- Biochemistry --- Biology - General --- Biology --- Human Anatomy & Physiology --- Chemistry --- Health & Biological Sciences --- Physical Sciences & Mathematics --- MAPKs (Enzymes) --- Life sciences. --- Molecular biology. --- Biochemistry. --- Cell biology. --- Life Sciences. --- Biochemistry, general. --- Cell Biology. --- Molecular Medicine. --- Protein kinases --- Cytology. --- Medicine. --- Clinical sciences --- Medical profession --- Human biology --- Life sciences --- Medical sciences --- Pathology --- Physicians --- Cell biology --- Cellular biology --- Cells --- Cytologists --- Biological chemistry --- Chemical composition of organisms --- Organisms --- Physiological chemistry --- Composition --- Health Workforce --- Molecular biochemistry --- Molecular biophysics --- Biophysics --- Biomolecules --- Systems biology --- Medicine --- Biomedical Research. --- Research. --- Biological research --- Biomedical research

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In recent years, heavy metals have been widely used in agricultural, chemical, domestic, and technological applications, causing environmental and soil contaminations. Heavy metals enter the plant system through soil or via the atmosphere, and can accumulate, affecting physiological processes, plant growth, yield, and human health if heavy metals are stored in edible tissues. Understanding the regulation mechanisms of plant heavy metals accumulation and partitioning is important to improve the safety of the food chain. In this Special Issue book, a total of 19 articles were included; four reviews covering phytoremediation, manganese phytotoxicity in plants, the effect of cadmium on plant development, the genetic characteristics of Cd accumulation, and the research status of genes and QTLs in rice, respectively, as well as fifteen original research articles, mainly regarding the impact of cadmium on plants. Cadmium was therefore the predominant topic of this Special Issue, increasing the attention of the research community on the negative impacts determined by cadmium or cadmium associated with other heavy metals. The articles have highlighted a great genetic variability, suggesting different possibilities for accumulation, translocation and the reduction or control of heavy metal toxicity in plants.

Technology: general issues --- cotton (Gossypium hirsutum L.) --- transcriptome --- Cd stress --- GhHMAD5 --- overexpression --- VIGS (virus induced gene silence) --- cadmium --- glycinebetaine --- photosynthesis --- ultrastructure --- tobacco (Nicotiana tabacum L.) --- Cadmium --- hyperaccumulator --- Viola baoshanensis --- detoxification --- Cd --- PtoABCG36 --- tolerance --- poplar --- accumulation --- efflux --- phytoremediation --- heavy metals --- hyperaccumulation --- plant genotype improvement --- soil management --- cadmium accumulation --- absorption and transport --- QTL location --- mapping population --- rice (Oryza sativa L.) --- selenium --- cadmium stress --- auxin --- root architecture --- phosphate transporter --- Nicotiana tabacum --- oxidative stress --- cell cycle --- cell wall --- germination --- reproduction --- plant growth and development --- antioxidative system --- Brassicaceae family --- mitogen-activated protein kinases --- Ulva compressa --- antioxidant --- metal chelator --- in vivo chlorophyll a florescence --- physiology --- mitogen activated protein kinases --- metal accumulation --- DNA methylation --- ABCC transporters --- HMA2 --- wheat --- metal stress tolerance --- manganese toxicity --- Mn detoxification --- tolerance mechanism --- gene function --- subcellular compartment --- lead --- nicotianamine --- mugineic acid --- heavy metal --- toxic metal --- durum wheat --- Arabidopsis --- small heat shock protein --- OsMSR3 --- copper stress --- reactive oxygen species --- copper and zinc --- expression in bacteria --- metallothioneins --- marine alga --- Brassica campestris L. --- glutathione synthetase --- glutathione S-transferase --- alternative splicing --- Italian ryegrass root --- LmAUX1 --- hormesis --- growth --- chlorophyll a fluorescence --- n/a