DEFAR - Departamento de Farmácia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/530
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Item Possible involvement of a phosphatidylinositol-type signaling pathway in glucose-induced activation of plasma membrane ATPase and cellular proton in the yeast Sacchamyces cerevisiae.(1994) Brandão, Rogélio Lopes; Rocha, Neuza Maria de Magalhaes; Alijo, Rafael; Ramos, José; Thevelein, Johan MariaAddition of glucose to cells of the yeast Saccharomyces cerevisiae causes rapid activation of plasma membrane H+-ATPase and a stimulation of cellular H ÷ extrusion. We show that addition of diacylglycerol and other activators of protein kinase C to intact cells also activates the H+-ATPase and causes at the same time a stimulation of H ÷ extrusion from the cells. Both effects are reversed by addition of staurosporine, a protein kinase C inhibitor. Addition of staurosporine or calmidazolium, an inhibitor of Ca2+/calmodulin-dependent protein kinases, separately, causes a partial inhibition of glucose-induced H+-ATPase activation and stimulation of cellular H + extrusion; together they cause a more potent inhibition. Addition of neomycin, which complexes with phosphatidylinositol 4,5-bisphosphate, or addition of compound 48/80, a phospholipase C inhibitor, also causes near complete inhibition. Diacylglycerol and other protein kinase C activators had no effect on the activity of the K+-uptake system and the activity of trehalase and glucose-induced activation of the K+-uptake system and trehalase was not inhibited by neomycin, supporting the specificity of the effects observed on the H+-ATPase. The results support a model in which glucose-induced activation of H+-ATPase is mediated by a phosphatidylinositol-type signaling pathway triggering phosphorylation of the enzyme both by protein kinase C and one or more Ca2+/calmodulin-dependent protein kinases.Item New aspects of the glucose activation of the H-ATPase in the yeast Saccharomyces cerevisae.(2001) Souza, Marco Antônio Andrade de; Trópia, Maria José Magalhães; Brandão, Rogélio LopesThe glucose-induced activation of plasma membrane ATPase from Saccharomyces cerevisiae was first described by Serrano in 1983. Many aspects of this signal transduction pathway are still obscure. In this paper, evidence is presented for the involvement of Snf3p as the glucose sensor related to this activation process. It is shown that, in addition to glucose detection by Snf3p, sugar transport is also necessary for activation of the ATPase. The participation of the G protein, Gpa2p, in transducing the internal signal (phosphorylated sugars) is also demonstrated. Moreover, the involvement of protein kinase C in the regulation of ATPase activity is confirmed. Finally, a model pathway is presented for sensing and transmission of the glucose activation signal of the yeast HM-ATPase.Item Relationship between Protein kinase C and derepression of different enzymes.(2002) Salgado, Ana Paula Carneiro; Schuller, Dorit; Casal, Margarida; Leão, Cecília; Leiper, F. C.; Carling, D.; Gomes, Luciano; Trópia, Maria José Magalhães; Castro, Ieso de Miranda; Brandão, Rogélio LopesThe PKC1 gene in the yeast Saccharomyces cerevisiae encodes for protein kinase C which is known to control a MAP kinase cascade consisting of di¡erent kinases: Bck1, Mkk1 and Mkk2, and Mpk1. This cascade a¡ects the cell wall integrity but the phenotype of pkc1v mutants suggests additional targets that have not yet been identi¢ed [Heinisch et al., Mol. Microbiol. 32 (1999) 671^680]. The pkc1v mutant, as opposed to other mutants in the MAP kinase cascade, displays defects in the control of carbon metabolism. One of them occurs in the derepression of SUC2 gene after exhaustion of glucose from the medium, suggesting an involvement of Pkc1p in the derepression process that is not shared by the downstream MAP kinase cascade. In this work, we demonstrate that Pkc1p is required for the increase of the activity of enzymatic systems during the derepression process. We observed that Pkc1p is involved in the derepression of invertase and alcohol dehydrogenase activities. On the other hand, it seems not to be necessary for the derepression of the enzymes of the GAL system. Our results suggest that Pkc1p is acting through the main glucose repression pathway, since introduction of an additional mutation in the PKC1 gene in yeast strains already presenting mutations in the HXKII or MIG1 genes does not interfere with the typical derepressed phenotype observed in these single mutants. Moreover, our data indicate that Pkc1p participates in this process through the control of the cellular localization of the Mig1 transcriptional factor.Item The PLC1 encoded phospholipase C in the yeast Saccharomyces cerevisiae is essential for glucose-induced phosphatidylinositol turnover and activation of plasma membrane H -ATPase.(1998) Coccetti, Paola; Tisi, Renata; Martegani, Enzo; Teixeira, Leonardo Souza; Brandão, Rogélio Lopes; Castro, Ieso de Miranda; Thevelein, Johan MariaAddition of glucose to glucose-deprived cells of the yeast Saccharomyces cerevisiae triggers rapid turnover of phosphatidylinositol, phosphatidylinositol-phosphate and phosphatidylinositol 4,5-bisphosphate. Glucose stimulation of PI turnover was measured both as an increase in the specific ratio of 32P-labeling and as an increase in the level of diacylglycerol after addition of glucose. Glucose also causes rapid activation of plasma membrane H.-ATPase. We show that in a mutant lacking the PLC1 encoded phospholipase C, both processes were strongly reduced. Compound 48/80, a known inhibitor of mammalian phospholipase C, inhibits both processes. However, activation of the plasma membrane H.- ATPase is only inhibited by concentrations of compound 48/80 that strongly inhibit phospholipid turnover. Growth was inhibited by even lower concentrations. Our data suggest that in yeast cells, glucose triggers through activation of the PLC1 gene product a signaling pathway initiated by phosphatidylinositol turnover and involved in activation of the plasma membrane H.-ATPase.