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274 results on '"Stournaras C"'

24. Control of transforming growth factor beta signal transduction by small GTPases

Author

Kardassis, D., Murphy, C., Fotsis, T., Moustakas, A., and Stournaras, C.

Subjects
Protein Transport, Transforming Growth Factor beta/*metabolism, Animals, Humans, Monomeric GTP-Binding Proteins/*metabolism, Nuclear Pore/metabolism, Smad Proteins/metabolism, Models, Biological, Endocytosis, Signal Transduction
Abstract

The integrated roles of small GTPases in executing the transforming growth factor beta (TGFbeta) signaling pathway have attracted increasing attention in recent years. In this review, we summarize recent findings on TGFbeta signaling during receptor endocytosis, Smad trafficking and actin cytoskeleton remodeling, and emphasize the role of small GTPases in these processes. First, we give an overview of the different endocytic routes taken by TGFbeta receptors, their impact on active TGFbeta signaling versus degradation and their regulation by the small GTPases Rab, RalA/Ral-binding protein 1 and Rap2. Second, we focus on the mechanisms and regulation of Smad trafficking in the cytoplasm, through the nuclear pores and into the nucleus, and the contribution of Ran GTPase to these events. Third, we summarize the role of Rho small GTPases in early and late cytoskeleton remodeling in various cell models and diseases, and the positive and negative cross-talk between Rho GTPases and the TGFbeta/Smad pathway. The biological significance of this exciting research field, the perspectives and critical open questions are discussed. FEBS J

Published
2009

27. PLC-gamma1 signaling pathway and villin activation are involved in actin cytoskeleton reorganization induced by Na+/Pi cotransport up-regulation

Author

Evangelia Papakonstanti, Ds, Emmanouel, Gravanis A, and Stournaras C

Subjects
macromolecular substances, digestive system, Cell Line, Phosphates, Phosphatidylinositol 3-Kinases, Animals, Phosphorylation, Phosphotyrosine, Cytoskeleton, Microscopy, Confocal, Symporters, Phospholipase C gamma, Microfilament Proteins, Sodium, Biological Transport, Sodium-Phosphate Cotransporter Proteins, Opossums, Genistein, Actins, Up-Regulation, Enzyme Activation, Isoenzymes, Actin Cytoskeleton, Solubility, Type C Phospholipases, Carrier Proteins, Protein Binding, Signal Transduction, Research Article
Abstract

BACKGROUND: The brief incubation of opossum kidney (OK) cells with low P(i) results in Na+/P(i) cotransport up-regulation and in substantial, but transient, cytoskeletal reorganization. In this study, we examined signaling events involved in the depolymerization of microfilaments. RESULTS: Confocal laser scanning microscopy, immunoblot and immunoprecipitation experiments revealed villin co-localization with mainly actin short filaments and monomers, indicating that under the conditions used, villin acted as an actin-severing protein. Further analysis revealed that low concentrations of extracellular phosphate resulted in phospholipase Cgammal (PLC-gammal) translocation to the actin cytoskeleton, without increases in its tyrosine phosphorylation. Additionally, tyrosine phosphorylation of a portion of insoluble villin was increased; whereas, only tyrosine phosphorylated villin associated with PLC-gammal. Although, tyrosine phosphorylation of PLC-gammal was not observed during Na+/P(i) cotransport up-regulation, genistein treatment abolished the enzyme's translocation to the actin cytoskeleton, as well as its association with villin. In addition, villin was found to associate with the 85-KDa subunit (p85) of phosphatidylinositol (PI)-3 kinase, concomitant with PLC-gammal, in the cytoskeletal fraction of Na+/P(i) cotransport up-regulated cells. CONCLUSIONS: Our observations suggest a signaling mechanism linking low ambient P(i) levels to the acute up-regulation of its cotransport with sodium and the depolymerization of the subcortical actin cytoskeleton.

Published
2000

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