Caractérisation des liens fonctionnels entre la protéine RhoGap Rgd1 et les protéines Wsc1 et Mid2, deux senseurs de l'état de la paroi chez la levure Saccharomyces cerevisiae (étude de la régulation post-traductionnelle de la protéine Rgd1)

La protéine Rgd1 est la RhoGAP de Rho3p et Rho4p chez la levure S cerevisiae. Un crible génétique a permis de mettre en évidence des interactions létales-synthétiques entre les gènes RGD1 et WSC1 ou MID2. La caractérisation de l'interaction génique entre RGD1 et WSC1 a révélé l'implication des protéines Rho3 et Rho4 dans les mécanismes conduisant à la létalité-synthétique du double mutant wsc1deltargd1delta. Les interactions géniques associant d'une part les gènes RGD1 et WSC1 et d'autre part les gènes RGD1 ET MID2 font intervenir des mécanismes différents. Nous proposons un modèle dans lequel Wsc1p et Rgd1p sont impliqués dans la régulation de la sécrétion polarisée. L'étude des mécanismes de régulation post-traductionnelle de Rgd1p a montré que cette protéine est phosphorylée de manière dynamique sur différents acides aminés. La phosphorylation de la protéine Rgd1 permet de réguler sa capacité à dimériser, à interagir avec les phospholipides et son activité RhoGAP.Rgd1p is a RhoGAP for Rho3p and Rho4p, two GTPases involved in a polarized growth in the yeast S. cerevisiae. Using a genetic screen, synthetic lethal interactions between the RGD1 gene and WSC1 or MID2 were discovered. The WSC1 and MID2 genes code for cell sensors that regulate the activity of the cell integrity pathway. Characterization of the genetic interaction between RGD1 and WSC1 revealed the implication of Rho3p and Rho4p in the synthetic lethality. Functional interactions between RGD1 and WSC1 or RGD1 and MID2 where shown to be different. We propose a model in which Wsc1p and Rgd1p act together to regulate polarized secretion. Post-translational regulation studies of Rgd1p showed that this protein is multi-phosphorylated in a dynamic way. Phosphorylation of Rgd1p regulates its ability to form a dinner, to bind phospholipids and also modify its RhoGAP activity toward Rho3p and Rho4p.BORDEAUX2-BU Santé (330632101) / SudocSudocFranceF

La polarité cellulaire chez la levure Saccharomyces cerevisiae (etude de la régulation de la protéine RhoGAP Rgd1 à domaine F-BAR)

Chez l ensemble des organismes, la capacité des cellules à se polariser est une propriété nécessaire à la croissance, à la division, à la mobilité, à la différenciation ou encore au trafic intracellulaire. Les GTPases de la famille Rho jouent des rôles prépondérants dans la régulation de ces mécanismes. Chez la levure Saccharomyces cerevisiae, nous étudions la manière dont le régulateur RhoGAP Rgd1p des protéines Rho3 et Rho4 est lui-même régulé au cours de la croissance polarisée. Nous avons montré que la protéine Rgd1 est localisée au fond du bourgeon lors de la croissance isotropique du bourgeon puis sous forme d un anneau au cou du bourgeon lors de la cytocinèse. Nous avons également montré que le trafic intracellulaire, notamment l exocytose et les phosphoinosotides tels que le PdtIns(4)P et le PdtIns(4,5)P2 ont un rôle majeur dans la régulation spatio-temporelle de la protéine Rgd1. Ces mécanismes permettraient d acheminer la protéine RhoGAP au niveau des sites de croissances afin d agir sur les protéines Rho3 et Rho4.In all organisms, the ability of cells to polarize is a property necessary for growth, cell division, mobility, cell differentiation or intracellular trafficking. GTPases of the Rho family play central roles in the regulation of these mechanisms. In the yeast Saccharomyces cerevisiae, we study how the regulator RhoGAP Rgd1p of Rho3 and Rho4 proteins may be itself regulated during polarized growth. We showed that the protein Rgd1 is located at the bud tip during isotropic growth of the bud and form a ring at the bud neck during cytokinesis. We also showed that the intracellular traffic, especially the exocytosis and phosphoinosotides as the PdtIns(4)P and PdtIns(4,5)P2 have a major role in the spatio-temporal regulation of the Rgd1 protein. These mechanisms would deliver the RhoGAP protein at growth sites to act on Rho3 and Rho4 proteins.BORDEAUX2-Bib. électronique (335229905) / SudocSudocFranceF

Interaction with In-Vehicle Electronic Systems. A Complete Description of a Neural Network Approach

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Effects of modulators of multidrug resistance on the expression of the MDR1 gene in human KB cells in culture

International audienceThe effect of four modulators of multidrug resistance (MDR) on the expression of the MDR1 gene was studied in two resistant variants of the KB cell lines, KB V1 and KB A1. This was done using a semi-quantitative assay based on mRNA reverse transcription coupled with polymerase chain reaction of the cDNA obtained. An automatic DNA sequencer was used for the measurement of the fluorescent amplification products and the MDR1 signal was compared to that of the beta-actin gene of the cells. After 24 h incubation with 15 microM of the modulators, MDR1 gene expression was slightly but significantly decreased by two of them, quinine and cyclosporine A, whereas verapamil and S-9788 had very little effect on this parameter. The effect were more pronounced in the KB A1 line than in the KB V1 line. The effect of quinine was studied over a longer time period (4-48 h) and was shown to be maximum at 24 h. These results favor the existence of a direct effect of some MDR reverters, especially quinine, on the expression of the MDR1 gene and could partially explain their modulating effect of MDR

Through its F-BAR and RhoGAP domains, Rgd1p acts in different polarized growth processes in budding yeast

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Through its F-BAR and RhoGAP domains, Rgd1p acts in different polarized growth processes in budding yeast

Protein domain architecture can be used to construct supramolecular structures, to carry out specific functions and to mediate signaling in prokaryotic and eukaryotic cells. The Rgd1p protein of budding yeast contains two domains with different functions in the cell: the F-BAR and RhoGAP domains. The F-BAR domain has been shown to interact with membrane phospholipids and is thought to induce or sense membrane curvature. The RhoGAP domain activates the GTP hydrolysis of two Rho GTPases, thereby regulating different cellular pathways. Specific molecular interactions with the F-BAR and RhoGAP domains, cell signaling and interplay between these domains may allow the Rgd1p protein to act in several different biological processes, all of which are required for polarized growth in yeast

Extended formulations for order polytopes through network flows

Mathematical psychology has a long tradition of modeling probabilistic choice via distribution-free random utility models and associated random preference models. For such models, the predicted choice probabilities often form a bounded and convex polyhedral set, or polytope. Polyhedral combinatorics have thus played a key role in studying the mathematical structure of these models. However, standard methods for characterizing the polytopes of such models are subject to a combinatorial explosion in complexity as the number of choice alternatives increases. Specifically, this is the case for random preference models based on linear, weak, semi- and interval orders. For these, a complete, linear description of the polytope is currently known only for, at most, 5–8 choice alternatives. We leverage the method of extended formulations to break through those boundaries. For each of the four types of preferences, we build an appropriate network, and show that the associated network flow polytope provides an extended formulation of the polytope of the choice model. This extended formulation has a simple linear description that is more parsimonious than descriptions obtained by standard methods for large numbers of choice alternatives. The result is a computationally less demanding way of testing the probabilistic choice model on data. We sketch how the latter interfaces with recent developments in contemporary statistics

Secretory Pathway-Dependent Localization of the Saccharomyces cerevisiae Rho GTPase-Activating Protein Rgd1p at Growth Sites

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