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Literatura académica sobre el tema "GTPasi"

Autor: Grafiati

Publicado: 11 de marzo de 2023

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Artículos de revistas sobre el tema "GTPasi"

Irving, Helen R. "Abscisic acid induction of GTP hydrolysis in maize coleoptile plasma membranes". Functional Plant Biology 25, n.º 5 (1998): 539. http://dx.doi.org/10.1071/pp98009.

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Since receptor-coupled G proteins increase GTP hydrolysis (GTPase) activity upon ligands binding to the receptor, a study was undertaken to determine if abscisic acid (ABA) induced such an effect. Plasma membranes isolated from etiolated maize (Zea mays L.) coleoptiles were enriched in GTPase activity relative to microsomal fractions. Vanadate was included in the assay to inhibit the high levels of vanadate sensitive low affinity GTPases present. Under these conditions, GTPase activity was enhanced by Mg2+, stimulated by mastoparan, and inhibited by GTPγS indicating the presence of either monomeric or heterotrimeric G proteins. The combination of NaF and AlCl3 is expected to inhibit heterotrimeric G protein activity but had little effect on GTPase activity in maize coleoptile membranes. Cholera toxin enhanced basal GTPase activity, confirming the presence of heterotrimeric G proteins in maize plasma membranes. Pertussis toxin also slightly enhanced basal GTPase activity in maize membranes. Abscisic acid enhanced GTPase activity optimally at 5 mmol/L Mg2+ in a concentration dependent manner by 1.5-fold at 10 µmol/L and up to three-fold at 100 µmol/L ABA. Abscisic acid induced GTPase activity was inhibited by GTPγS, the combination of NaF and AlCl3, and pertussis toxin. Overall, these results are typical of a receptor-coupled G protein responding to its ligand.

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Estevez, Ana Y., Tamara Bond y Kevin Strange. "Regulation of I Cl,swell in neuroblastoma cells by G protein signaling pathways". American Journal of Physiology-Cell Physiology 281, n.º 1 (1 de julio de 2001): C89—C98. http://dx.doi.org/10.1152/ajpcell.2001.281.1.c89.

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Guanosine 5′- O-(3-thiotriphosphate) (GTPγS) activated the I Cl,swell anion channel in N1E115 neuroblastoma cells in a swelling-independent manner. GTPγS-induced current was unaffected by ATP removal and broadly selective tyrosine kinase inhibitors, demonstrating that phosphorylation events do not regulate G protein-dependent channel activation. Pertussis toxin had no effect on GTPγS-induced current. However, cholera toxin inhibited the current ∼70%. Exposure of cells to 8-bromoadenosine 3′,5′-cyclic monophosphate did not mimic the effect of cholera toxin, and its inhibitory action was not prevented by treatment of cells with an inhibitor of adenylyl cyclase. These results demonstrate that GTPγS does not act through Gαi/o GTPases and that Gαs/Gβγ G proteins inhibit the channel and/or channel regulatory mechanisms through cAMP-independent mechanisms. Swelling-induced activation of I Cl,swell was stimulated two- to threefold by GTPγS and inhibited by 10 mM guanosine 5′- O-(2-thiodiphosphate). The Rho GTPase inhibitor Clostridium difficile toxin B inhibited both GTPγS- and swelling-induced activation of I Cl,swell. Taken together, these findings indicate that Rho GTPase signaling pathways regulate the I Cl,swell channel via phosphorylation-independent mechanisms.

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Uno, Tomohide, Tsubasa Moriwaki, Yuri Isoyama, Yuichi Uno, Kengo Kanamaru, Hiroshi Yamagata, Masahiko Nakamura y Michihiro Takagi. "Rab14 from Bombyx mori (Lepidoptera: Bombycidae) shows ATPase activity". Biology Letters 6, n.º 3 (13 de enero de 2010): 379–81. http://dx.doi.org/10.1098/rsbl.2009.0878.

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Rab GTPases are essential for vesicular transport, whereas adenosine triphosphate (ATP) is the most important and versatile of the activated carriers in the cell. But there are little reports to clarify the connection between ATP and Rab GTPases. A cDNA clone (Rab14) from Bombyx mori was expressed in Escherichia coli as a glutathione S-transferase fusion protein and purified. The protein bound to [ 3 H]-GDP and [ 35 S]-GTPγS. Binding of [ 35 S]-GTPγS was inhibited by guanosine diphosphate (GDP), guanosine triphosphate (GTP) and ATP. Rab14 showed GTP- and ATP-hydrolysis activity. The Km value of Rab14 for ATP was lower than that for GTP. Human Rab14 also showed an ATPase activity. Furthermore, bound [ 3 H]-GDP was exchanged efficiently with GTP and ATP. These results suggest that Rab14 is an ATPase as well as GTPase and gives Rab14 an exciting integrative function between cell metabolic status and membrane trafficking.

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Herrmann, Andrea, Britta A. M. Tillmann, Janine Schürmann, Michael Bölker y Paul Tudzynski. "Small-GTPase-Associated Signaling by the Guanine Nucleotide Exchange Factors CpDock180 and CpCdc24, the GTPase Effector CpSte20, and the Scaffold Protein CpBem1 in Claviceps purpurea". Eukaryotic Cell 13, n.º 4 (31 de enero de 2014): 470–82. http://dx.doi.org/10.1128/ec.00332-13.

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ABSTRACTMonomeric GTPases of the Rho subfamily are important mediators of polar growth and NADPH (Nox) signaling in a variety of organisms. These pathways influence the ability ofClaviceps purpureato infect host plants. GTPase regulators contribute to the nucleotide loading cycle that is essential for proper functionality of the GTPases. Scaffold proteins gather GTPase complexes to facilitate proper function. The guanine nucleotide exchange factors (GEFs) CpCdc24 and CpDock180 activate GTPase signaling by triggering nucleotide exchange of the GTPases. Here we show that CpCdc24 harbors nucleotide exchange activity for both Rac and Cdc42 homologues. The GEFs partly share the cellular distribution of the GTPases and interact with the putative upstream GTPase CpRas1. Interaction studies show the formation of higher-order protein complexes, mediated by the scaffold protein CpBem1. Besides the GTPases and GEFs, these complexes also contain the GTPase effectors CpSte20 and CpCla4, as well as the regulatory protein CpNoxR. Functional characterizations suggest a role of CpCdc24 mainly in polarity, whereas CpDock180 is involved in stress tolerance mechanisms. These findings indicate the dynamic formation of small GTPase complexes and improve the model for GTPase-associated signaling inC. purpurea.

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Shan, Shu-ou, Sowmya Chandrasekar y Peter Walter. "Conformational changes in the GTPase modules of the signal reception particle and its receptor drive initiation of protein translocation". Journal of Cell Biology 178, n.º 4 (6 de agosto de 2007): 611–20. http://dx.doi.org/10.1083/jcb.200702018.

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During cotranslational protein targeting, two guanosine triphosphatase (GTPase) in the signal recognition particle (SRP) and its receptor (SR) form a unique complex in which hydrolyses of both guanosine triphosphates (GTP) are activated in a shared active site. It was thought that GTP hydrolysis drives the recycling of SRP and SR, but is not crucial for protein targeting. Here, we examined the translocation efficiency of mutant GTPases that block the interaction between SRP and SR at specific stages. Surprisingly, mutants that allow SRP–SR complex assembly but block GTPase activation severely compromise protein translocation. These mutations map to the highly conserved insertion box domain loops that rearrange upon complex formation to form multiple catalytic interactions with the two GTPs. Thus, although GTP hydrolysis is not required, the molecular rearrangements that lead to GTPase activation are essential for protein targeting. Most importantly, our results show that an elaborate rearrangement within the SRP–SR GTPase complex is required to drive the unloading and initiate translocation of cargo proteins.

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Nur-E-Kamal, M. S. y H. Maruta. "The role of Gln61 and Glu63 of Ras GTPases in their activation by NF1 and Ras GAP." Molecular Biology of the Cell 3, n.º 12 (diciembre de 1992): 1437–42. http://dx.doi.org/10.1091/mbc.3.12.1437.

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Two distinct GAPs of 120 and 235 kDa called GAP1 and NF1 serve as attenuators of Ras, a member of GTP-dependent signal transducers, by stimulating its intrinsic guanosine triphosphatase (GTPase) activity. The GAP1 (also called Ras GAP) is highly specific for Ras and does not stimulate the intrinsic GTPase activity of Rap1 or Rho. Using GAP1C, the C-terminal GTPase activating domain (residues 720-1044) of bovine GAP1, we have shown previously that the GAP1 specificity is determined by the Ras domain (residues 61-65) where Gln61 plays the primary role. The corresponding domain (residues 1175-1531) of human NF1 (called NF1C), which shares only 26% sequence identity with the GAP1C, also activates Ras GTPases. In this article, we demonstrate that the NF1C, like the GAP1C, is highly specific for Ras and does not activate either Rap1 or Rho GTPases. Furthermore, using a series of chimeric Ras/Rap1 and mutated Ras GTPases, we show that Gln at position 61 of the GTPases primarily determines that NF1C as well as GAP1C activates Ras GTPases, but not Rap1 GTPases, and Glu at position 63 of the GTPases is required for maximizing the sensitivity of Ras GTPases to both NF1C and GAP1C. Interestingly, replacement of Glu63 of c-HaRas by Lys reduces its intrinsic GTPase activity and abolishes the GTPase activation by both NF1C and GAP1C. Thus, the potentiation of oncogenicity by Lys63 mutation of c-HaRas appears primarily to be due to the loss of its sensitivity to the two major Ras signal attenuators (NF1 and GAP1).

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Kötting, Carsten y Klaus Gerwert. "What vibrations tell us about GTPases". Biological Chemistry 396, n.º 2 (1 de febrero de 2015): 131–44. http://dx.doi.org/10.1515/hsz-2014-0219.

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Abstract In this review, we discuss how time-resolved Fourier transform infrared (FTIR) spectroscopy is used to understand how GTP hydrolysis is catalyzed by small GTPases and their cognate GTPase-activating proteins (GAPs). By interaction with small GTPases, GAPs regulate important signal transduction pathways and transport mechanisms in cells. The GTPase reaction terminates signaling and controls transport. Dysfunctions of GTP hydrolysis in these proteins are linked to serious diseases including cancer. Using FTIR, we resolved both the intrinsic and GAP-catalyzed GTPase reaction of the small GTPase Ras with high spatiotemporal resolution and atomic detail. This provided detailed insight into the order of events and how the active site is completed for catalysis. Comparisons of Ras with other small GTPases revealed conservation and variation in the catalytic mechanisms. The approach was extended to more nearly physiological conditions at a membrane. Interactions of membrane-anchored GTPases and their extraction from the membrane are studied using the attenuated total reflection (ATR) technique.

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Killoran, Ryan C. y Matthew J. Smith. "Conformational resolution of nucleotide cycling and effector interactions for multiple small GTPases determined in parallel". Journal of Biological Chemistry 294, n.º 25 (14 de mayo de 2019): 9937–48. http://dx.doi.org/10.1074/jbc.ra119.008653.

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Small GTPases alternatively bind GDP/GTP guanine nucleotides to gate signaling pathways that direct most cellular processes. Numerous GTPases are implicated in oncogenesis, particularly the three RAS isoforms HRAS, KRAS, and NRAS and the RHO family GTPase RAC1. Signaling networks comprising small GTPases are highly connected, and there is some evidence of direct biochemical cross-talk between their functional G-domains. The activation potential of a given GTPase is contingent on a codependent interaction with the nucleotide and a Mg2+ ion, which bind to individual variants with distinct affinities coordinated by residues in the GTPase nucleotide-binding pocket. Here, we utilized a selective-labeling strategy coupled with real-time NMR spectroscopy to monitor nucleotide exchange, GTP hydrolysis, and effector interactions of multiple small GTPases in a single complex system. We provide insight into nucleotide preference and the role of Mg2+ in activating both WT and oncogenic mutant enzymes. Multiplexing revealed guanine nucleotide exchange factor (GEF), GTPase-activating protein (GAP), and effector-binding specificities in mixtures of GTPases and resolved that the three related RAS isoforms are biochemically equivalent. This work establishes that direct quantitation of the nucleotide-bound conformation is required to accurately determine an activation potential for any given GTPase, as small GTPases such as RAS-like proto-oncogene A (RALA) or the G12C mutant of KRAS display fast exchange kinetics but have a high affinity for GDP. Furthermore, we propose that the G-domains of small GTPases behave autonomously in solution and that nucleotide cycling proceeds independently of protein concentration but is highly impacted by Mg2+ abundance.

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Kesseler, Christoph, Julian Kahr, Natalie Waldt, Nele Stroscher, Josephine Liebig, Frank Angenstein, Elmar Kirches y Christian Mawrin. "EXTH-64. SMALL GTPASES IN MENINGIOMAS: PROLIFERATION, MIGRATION, SURVIVAL, POTENTIAL TREATMENT AND INTERACTIONS". Neuro-Oncology 22, Supplement_2 (noviembre de 2020): ii101. http://dx.doi.org/10.1093/neuonc/noaa215.418.

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Abstract PURPOSE To evaluate the role of the small GTPases RhoA, Rac1 and Cdc42 in meningiomas as therapeutic targets and their interactions in meningiomas. EXPERIMENTAL DESIGN We analyzed expression of GTPases in human meningioma samples and meningioma cell lines of various WHO grades. Malignant IOMM-Lee meningioma cells were used to generate shRNA mediated knockdowns of GTPases RhoA, Rac1 or Cdc42 and to study knockdown effects on proliferation and migration, as well as analysis of cell morphology by confocal microscopy. The same tests were used to investigate effects of the two inhibitors Fasudil and EHT-1864 of malignant IOMM-Lee, KT21 and benign Ben-Men cells and the effects of these drugs on IOMM-Lee knockdown cells. The effects of GTPase knockdowns and Fasudil treatment were studied in terms of overall survival by intracranial xenografts of mice. Potential interactions of GTPases regarding NF2, mTOR and FAK-Paxillin were examined. RESULTS Small GTPases were upregulated in meningiomas of higher tumor grades. Reduced proliferation and migration could be achieved by GTPase knockdown in IOMM-Lee cells. Additionally, the ROCK-inhibitor Fasudil and Rac1-inhibitor EHT-1864 reduced proliferation in different meningioma cell lines and reduced proliferation and migration independent of GTPase knockdowns/status. Moreover, overall survival in vivo could also be increased by knockdowns of RhoA and Rac1 as well as Fasudil treatment. GTPase expression was affected dependent on the NF2 status but effects were not very distinct, indicating that NF2 is not strongly involved in GTPase regulation in meningiomas. In terms of mTOR and FAK-Paxillin signaling, each GTPase changes those pathways in a different manner. CONCLUSION Small GTPases are important effectors in meningioma proliferation and migration in vitro as well as survival in vivo and their inhibition should be considered as potential treatment option.

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Humphries, Brock A., Zhishan Wang y Chengfeng Yang. "MicroRNA Regulation of the Small Rho GTPase Regulators—Complexities and Opportunities in Targeting Cancer Metastasis". Cancers 12, n.º 5 (28 de abril de 2020): 1092. http://dx.doi.org/10.3390/cancers12051092.

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The small Rho GTPases regulate important cellular processes that affect cancer metastasis, such as cell survival and proliferation, actin dynamics, adhesion, migration, invasion and transcriptional activation. The Rho GTPases function as molecular switches cycling between an active GTP-bound and inactive guanosine diphosphate (GDP)-bound conformation. It is known that Rho GTPase activities are mainly regulated by guanine nucleotide exchange factors (RhoGEFs), GTPase-activating proteins (RhoGAPs), GDP dissociation inhibitors (RhoGDIs) and guanine nucleotide exchange modifiers (GEMs). These Rho GTPase regulators are often dysregulated in cancer; however, the underlying mechanisms are not well understood. MicroRNAs (miRNAs), a large family of small non-coding RNAs that negatively regulate protein-coding gene expression, have been shown to play important roles in cancer metastasis. Recent studies showed that miRNAs are capable of directly targeting RhoGAPs, RhoGEFs, and RhoGDIs, and regulate the activities of Rho GTPases. This not only provides new evidence for the critical role of miRNA dysregulation in cancer metastasis, it also reveals novel mechanisms for Rho GTPase regulation. This review summarizes recent exciting findings showing that miRNAs play important roles in regulating Rho GTPase regulators (RhoGEFs, RhoGAPs, RhoGDIs), thus affecting Rho GTPase activities and cancer metastasis. The potential opportunities and challenges for targeting miRNAs and Rho GTPase regulators in treating cancer metastasis are also discussed. A comprehensive list of the currently validated miRNA-targeting of small Rho GTPase regulators is presented as a reference resource.

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Tesis sobre el tema "GTPasi"

ZAMBERLAN, MARGHERITA. "La piccola GTPasi Rap1 interposta tra la proteina mitocondriale Opa1 e l'inibizione dell'angiogenesi". Doctoral thesis, Università degli studi di Padova, 2022. https://hdl.handle.net/11577/3460979.

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OPA1 is a protein with pleiotropic functions ranging from the orchestration of mitochondrial fusion and cristae remodeling to transcriptional reprogramming 1, 2. Here we present two different mechanisms by which OPA1 exerts a transcriptional regulation activity in endothelial and breast cancer cells. Mitochondria are dynamic organelles that are now recognized as regulators of signal transduction able to impact on cellular genetic programs 3, 4. Increasing evidence support a fundamental role for mitochondrial shape in the orchestration of cellular transcriptional programs, but how cells sense and respond to changes in mitochondrial shape is unclear 5. We recently discovered that angiogenesis is transcriptionally modulated by the key mitochondrial fusion gene OPA1 through NFκB activation1. In particular, ablation of OPA1 in vivo and in vitro leads to developmental and tumor angiogenesis inhibition 1. A deep RNA sequencing analysis identified a signature for the Ras-proximate-1 RAP1, and its cyclic AMP (cAMP)-activated nucleotide exchange factor EPAC1 upon OPA1 deletion in Human Umbilical Vein Endothelial Cells (HUVECs). Previously, several studies had reported the essential role of Rap1 in developmental angiogenesis and vessel stabilization 6, 7. After birth, Rap1 is not essential, but it participates in the maintenance of vasculature and nitric oxide (NO) homeostasis 6, 8. Albeit EPAC1 is highly abundant and cover numerous functions in endothelial cells, its role in angiogenesis remained to be clarified 9. Likewise, EPAC1 was shown to be important for endothelial cells biology 10, 11. A handful of studies retrieved EPAC1 in mitochondria, and RAP1 in mitochondria associated membranes (MAMs) by proteomics, suggesting that they might be linked to mitochondria 12, 13. Whether the EPAC1/RAP1 axis could sense changes in mitochondria driven by OPA1 deletion was unknown. Our results show that EPAC1 and RAP1 localize in proximity to mitochondria and in MAMs, that are emerging as hubs for mitochondria-derived signals. Moreover, EPAC1 accumulates on mitochondria upon pharmacological activation and following OPA1 silencing. OPA1 silencing results in an increase in Ca2+ and in localized cAMP increase in proximity of mitochondria that in turn activated EPAC1 and therefore RAP1. Notably, Ca2+ chelation by BAPTA-AM treatment suppress the EPAC1/RAP1 activation elicited by OPA1 downregulation. Furthermore, the analysis of angiogenic parameters like migration and tubulogenesis revealed that the blockage of EPAC1 and RAP1 signaling could correct the defects caused by OPA1 downregulation. Thus, our work places EPAC1/RAP1 in the retrograde signaling pathway connecting mitochondria to angiogenesis and highlights the intricate network of signals and second messengers that can execute transcriptional changes when mitochondria are perturbed.
OPA1 is a protein with pleiotropic functions ranging from the orchestration of mitochondrial fusion and cristae remodeling to transcriptional reprogramming 1, 2. Here we present two different mechanisms by which OPA1 exerts a transcriptional regulation activity in endothelial and breast cancer cells. Mitochondria are dynamic organelles that are now recognized as regulators of signal transduction able to impact on cellular genetic programs 3, 4. Increasing evidence support a fundamental role for mitochondrial shape in the orchestration of cellular transcriptional programs, but how cells sense and respond to changes in mitochondrial shape is unclear 5. We recently discovered that angiogenesis is transcriptionally modulated by the key mitochondrial fusion gene OPA1 through NFκB activation1. In particular, ablation of OPA1 in vivo and in vitro leads to developmental and tumor angiogenesis inhibition 1. A deep RNA sequencing analysis identified a signature for the Ras-proximate-1 RAP1, and its cyclic AMP (cAMP)-activated nucleotide exchange factor EPAC1 upon OPA1 deletion in Human Umbilical Vein Endothelial Cells (HUVECs). Previously, several studies had reported the essential role of Rap1 in developmental angiogenesis and vessel stabilization 6, 7. After birth, Rap1 is not essential, but it participates in the maintenance of vasculature and nitric oxide (NO) homeostasis 6, 8. Albeit EPAC1 is highly abundant and cover numerous functions in endothelial cells, its role in angiogenesis remained to be clarified 9. Likewise, EPAC1 was shown to be important for endothelial cells biology 10, 11. A handful of studies retrieved EPAC1 in mitochondria, and RAP1 in mitochondria associated membranes (MAMs) by proteomics, suggesting that they might be linked to mitochondria 12, 13. Whether the EPAC1/RAP1 axis could sense changes in mitochondria driven by OPA1 deletion was unknown. Our results show that EPAC1 and RAP1 localize in proximity to mitochondria and in MAMs, that are emerging as hubs for mitochondria-derived signals. Moreover, EPAC1 accumulates on mitochondria upon pharmacological activation and following OPA1 silencing. OPA1 silencing results in an increase in Ca2+ and in localized cAMP increase in proximity of mitochondria that in turn activated EPAC1 and therefore RAP1. Notably, Ca2+ chelation by BAPTA-AM treatment suppress the EPAC1/RAP1 activation elicited by OPA1 downregulation. Furthermore, the analysis of angiogenic parameters like migration and tubulogenesis revealed that the blockage of EPAC1 and RAP1 signaling could correct the defects caused by OPA1 downregulation. Thus, our work places EPAC1/RAP1 in the retrograde signaling pathway connecting mitochondria to angiogenesis and highlights the intricate network of signals and second messengers that can execute transcriptional changes when mitochondria are perturbed.

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Normandin, Caroline. "Identification et caractérisation de GTPases Activating Proteins spécifiques à la petite GTPase RAB21". Mémoire, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11544.

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L’autophagie est un processus de dégradation et de recyclage des composés cellulaires. Ce mécanisme est nécessaire que ce soit à l’état basal pour éliminer des agrégats protéiques ou des organites endommagés ou en condition de stress, tels que la carence nutritionnelle, l’hypoxie ou encore des traitements anticancéreux. De ce fait, l’autophagie est un processus essentiel à la survie ainsi qu’au maintien de l’homéostasie cellulaire. Connaître les joueurs et comprendre les mécanismes de régulation de l’autophagie sont donc importants. Les GTPases RABs sont des régulateurs importants de ce processus. Celles-ci agissent comme des interrupteurs moléculaires permettant d’exécuter rapidement des fonctions dans la cellule. Les RABs sont activées par des Guanine Nucleotide Exchange Factors (GEF) alors que les GTPase Activating Proteins (GAP) accélèrent la désactivation de la RAB. RAB21 est essentielle dans les étapes tardives de l’autophagie. En effet, RAB21 est activée par la carence nutritionnelle, via sa GEF MTMTR13, et permet le trafic d’une SNARE requise pour le flux autophagique. Lors d’une carence prolongée, l’activité de RAB21 diminue rapidement, suggérant ainsi le rôle d’une GAP dans cette régulation négative. Toutefois, aucune GAP pour RAB21 n’a été identifiée jusqu’à maintenant. Un criblage génétique chez la drosophile a permis d’identifier quelques candidats. Suite à des essais d’interactions protéiques, il s’est avéré que seule la GAP TBC1D25 interagissait avec RAB21. De plus, cette interaction est augmentée en fonction de la carence nutritionnelle. Des immunofluorescences par microscopie confocale ont révélé que l’interaction RAB21-TBC1D25 était située en partie au niveau des endosomes précoces. Par ailleurs, une activation prolongée de RAB5, située sur les endosomes précoces, inhibe l’interaction RAB21-TBC1D25. De plus amples expériences devront être réalisées afin d’expliquer ces résultats. Dans un autre ordre d’idée, RAB21 est surexprimée dans les cellules ayant un flux autophagique élevé ainsi que dans certaines tumeurs de cancer du côlon (données non publiées du laboratoire). L’expression de Tbc1d25 dans ces mêmes tumeurs ne semble pas augmentée, indiquant que TBC1D25 pourrait être un inhibiteur autophagique spécifique aux cellules ayant un flux autophagique élevé. À la lumière des résultats obtenus, TBC1D25 semble être une GAP pour RAB21 qui permet sa régulation négative suivant l’activation de l’autophagie induite par la carence nutritionnelle.
Abstract : Autophagy is defined as the lysosomal degradation and recycling of cellular constituents. At basal levels, autophagy eliminates protein aggregates or damaged organelles. In condition of stress, such as in condition of nutritional deficiency, hypoxia or cancer treatments, autophagy allow cells to adapt and survive. Therefore, autophagy is an essential system required for survival and maintenance of cellular homeostasis. It is thus essential to identify the cellular entities and mechanisms regulating this process. RAB GTPases were identified as master regulators of autophagy. These particular proteins act as molecular switches for the rapid execution of cellular responses. RABs are activated by Guanine Nucleotide Exchange Factors (GEF) whereas GTPase Activating Proteins (GAP) accelerates RAB deactivation. RAB21 is essential in the late stages of autophagy. Indeed, RAB21 is activated by nutritional deficiency, via its GEF MTMTR13, to allow trafficking of a SNARE required for autophagic flux. During starvation, RAB21 is deactivated which suggest that a GAP could negatively regulate RAB21 activity. However, to date no GAP for RAB21 has been identified. An eye modifier genetic screen in Drosophila was performed to identify potential RAB21 GAPs and some candidates were identified. As a result of this screen, the GAP TBC1D25 was identified as interacting with RAB21. Moreover, this interaction was increased by starvation. Proximity ligation assays revealed that the RAB21-TBC1D25 interaction partially localized at early endosomes. Moreover, prolonged activation of RAB5, located at early endosomes, inhibited RAB21-TBC1D25 interaction. Further experiments will be carried out to explain these results. With respect to the roles of autophagy in cancer, RAB21 was shown to be overexpressed in cells with high autophagic flux as well as in some colon cancer tumors. Importantly, the expression of Tbc1d25 in these same tumors does not appear to be increased, indicating that TBC1D25 could be an autophagic inhibitor specific to cells with a high autophagic flow. My work suggests that TBC1D25 could function as a GAP to negatively regulate RAB21 activity in condition of prolonged starvation.

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Chan, King-chung Fred y 陳敬忠. "Functional characterization of StAR-related lipid transfer domain containing 13 (DLC 2) RhoGAP in the nervous system". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43278449.

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Chan, King-chung Fred. "Functional characterization of StAR-related lipid transfer domain containing 13 (DLC 2) RhoGAP in the nervous system". Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43278449.

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Paul, Florian [Verfasser]. "Developing quantitative GTPase affinity purification (qGAP) to identify interaction partners of Rho GTPases / Florian Paul". Berlin : Freie Universität Berlin, 2015. http://d-nb.info/1069532711/34.

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Paul, Florian Ernst Rudolf Benjamin [Verfasser]. "Developing quantitative GTPase affinity purification (qGAP) to identify interaction partners of Rho GTPases / Florian Paul". Berlin : Freie Universität Berlin, 2015. http://d-nb.info/1069532711/34.

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Bery, Nicolas. "Nouvelle stratégie de ciblage de la GTPase RhoB : développement d'intracorps conformationnels sélectifs et leur fonctionnalisation en tant qu'inhibiteurs intracellulaires de l'activité de RhoB". Toulouse 3, 2014. http://thesesups.ups-tlse.fr/2734/.

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La GTPase RhoB partage 85% d'homologie avec RhoA et RhoC. Ces protéines alternent entre deux conformations : une active liée au GTP et une inactive liée au GDP. Des dérégulations de leur expression et de leur activation sont retrouvées dans de nombreux cancers. A ce jour, aucun inhibiteur sélectif de ces GTPases n'a pu être développé afin de bloquer l'activité de l'une ou l'autre de ces Rho. Ce travail doctoral a permis de mettre au point une approche innovante ciblant sélectivement l'état activé de la protéine RhoB. Suite à la caractérisation d'une nouvelle banque d'anticorps à simple domaine, sa validation par phage display contre divers antigènes a fourni de nombreux anticorps de haute fonctionnalité dans plusieurs applications. L'établissement d'une stratégie de sélection directe d'anticorps intracellulaire (intracorps) dirigés contre RhoB a permis d'identifier plusieurs intracorps conformationnels de la forme active de RhoB, dont un discriminant RhoB de ses homologues RhoA et RhoC. La fonctionnalisation d'intracorps par un domaine Fbox conduisant une dégradation de la cible a ensuite fourni la première stratégie efficace d'inhibition sélective de l'activité de RhoB. Ces travaux ont notamment démontré que l'extinction de l'activité de RhoB par intracorps fonctionnalisé augmente la migration et l'invasion de cellules pulmonaires. Ainsi cette avancée permettra de déterminer si l'activité de RhoB peut être une nouvelle cible thérapeutique et ouvre de nouvelles perspectives d'étude fine de l'activité des GTPases
RhoB GTPase shares more than 85% of homology with RhoA and RhoC. These proteins switch between an active conformation bound to GTP and an inactive one bound to GDP. Deregulations of their expression and/or their activity are often found in many cancers. To date, no selective inhibitor of these GTPases has been developed in order to block selectively Rho's activity. This project showed an original approach targeting RhoB's activity. After a new single domain antibody library characterization, its validation using the phage display technology against various antigens gave many highly functional antibodies in many applications. Set up of a new direct screening strategy of intracellular antibody (intrabody) raised against RhoB allowed us to identify several conformational intrabodies of RhoB active form, one of them discriminating RhoB from its homologs RhoA and RhoC. Intrabody functionalization with an Fbox domain driving target to degradation led to the identification of the first efficient selective RhoB activity inhibitory strategy. These work demonstrated that RhoB activity knockdown with functionalized intrabodies increased migration and invasion of pulmonary cells. In conclusion this tool will allow to determine if RhoB activity could be a new therapeutic target and open new perspectives to study GTPases activity

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Ghiaur, Gabriel. "The role of Rho GTPases in hematopoietic stem cell biology RhoA GTPase regulates adult HSC engraftment and Rac1 GTPases is important for embryonic HSC /". Cincinnati, Ohio : University of Cincinnati, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204374567.

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Peurois, François. "Activation des petites GTPases à la périphérie des membranes". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLN037.

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Les petites GTPases sont des régulateurs majeurs de nombreux processus cellulaires. La dérégulation de l’activation des petites GTPases est à l’origine de nombreuses maladies comme, entre autres, certains diabètes et cancers. In vivo, l’activation des petites GTPases se fait par des facteurs d’échange nucléotidiques (GEF), qui interagissent avec les GTPases à la périphérie des membranes cellulaires. Au delà d’un simple lieu de co-localisation, les membranes biologiques possèdent des propriétés physico-chimiques impactant directement l’activation des petites GTPases par les GEFs. Ce projet de thèse s’articule autour de trois axes, 1) proposer une stratégie expérimentale pour mesurer quantitativement les effets des membranes dans cette activation, 2) établir un modèle d’activation à la périphérie des membranes du GEF EPAC1, cible thérapeutique de maladies cardiaques 3) caractériser des petites molécules inhibitrices connues d’ArfGEF dans un contexte membranaire. Les résultats ont montré que les membranes modifiaient l’efficacité catalytique des GEFs, et questionnait leur spécificité vis à vis des petites GTPases. Les membranes apparaissent également comme de véritables actrices de l’activation d’EPAC1 en coopération avec l’AMPc. Ces effets pourraient être expliqués par une colocalisation entre GEFs et GTPases à la surface des membranes, l’induction d’un réarrangement conformationnel du GEF par les membranes, une modification de la diffusion latérale des GEF, ou encore une géométrie catalytiquement avantageuse du complexe GEF-GTPase-membrane. Enfin comprendre et expliciter l’implication des membranes dans cette activation amène à imaginer de nouvelles stratégies d’inhibition thérapeutique
Small GTPases are major regulators of many cellular processes. Nucleotide exchange factors (GEF) activate small GTPases. Deregulation of the activation of small GTPases is at the origin of several diseases, such as certain diabetes and cancers. GTPases and GEFs interact together at the periphery of cell membranes. Beyond a simple place of co-localization, biological membranes have physicochemical properties directly impacting the activation of small GTPases by GEFs. This thesis project is based on three axes, 1) to propose an experimental strategy to quantitatively measure the effects of membranes in this activation 2) to establish a model of the activation at the periphery of membranes of the GEF EPAC1, a therapeutic target in heart diseases, 3) to characterize known ArfGEF inhibitory small molecules in a membrane context. The results showed that membranes modified GEF catalytic efficiency, and questioned their specificity towards small GTPases. The membranes also appear as partners for the activation of EPAC1 in cooperation with cAMP. These effects could be explained by a co-localization between GEF and GTPases on the membranes surfaces, a conformational rearrangement of the GEF induced by membranes, a modification of lateral diffusion of the GEF, or a catalytically advantageous geometry of the GEF-GTPase-membrane complex. Finally, understanding the involvement of membranes in this activation leads us to imagine new therapeutic inhibition strategies

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Keller, Laura. "Conception de nano-anticorps conformationnels comme nouveaux outils d'étude de l'activité des GTPases de la sous-famille RHOA". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30005/document.

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Les GTPases de la sous famille RHOA participent à la régulation de nombreuses voies de signalisation qui contrôlent la dynamique du cytosquelette cellulaire et une grande diversité de fonctions telles que la prolifération, la division, la migration et la polarité cellulaires. Ce sont de véritables interrupteurs moléculaires qui, en réponse à un stimulus, changent de conformation tridimensionnelle pour activer leurs protéines effectrices cibles. Elles existent donc sous deux formes, une forme inactive liant le GDP et une forme active, liant le GTP. La proportion de forme active est extrêmement régulée au niveau spatial et temporel dans une cellule et représente moins de 10% de sa totalité. Depuis près de 20 ans, le seul outil disponible pour étudier leur activation est constitué par le domaine de liaison d'un effecteur, le RBD. Peu stable, faiblement soluble et peu adaptable, de nouveaux outils sont nécessaires afin de mieux comprendre la fine régulation de ces protéines. Les anticorps à simple domaine, VHH ou nanobodies, sont caractérisés par leur stabilité, solubilité, haut rendement de production et versatilité de fonctionnalisation. A partir d'une nouvelle banque d'anticorps à simple domaine optimisée pour la production d'intracorps, nous avons isolés différents clones capables de reconnaître in vitro et de bloquer in cellulo la forme active de ces protéines. L'un de ces clones permettra le développement d'un nouvel outil de mesure de l'activité de ces protéines in vitro tandis qu'un autre, in cellulo, permettra de mieux comprendre la régulation spatiale et temporelle des protéines endogènes
RHOA small GTPase belongs to a subfamily acting as a molecular switch activating major signaling pathways that regulate cytoskeletal dynamics and a variety of cellular responses such as cell cycle progression, cytokinesis, migration and polarity. RHOA activity resides in a few percent of GTP loaded protein, which is finely tuned by a crosstalk between regulators of the GTPase cycle. Manipulating a single RHO at the expression level often induces imbalance in the activity of other RHO GTPases, suggesting that more specific tools targeting these active pools are needed to decipher RHOA functions in time and space. We decided to use single domain antibodies, also known as VHH or nanobodies, as a new tool for studying RHOA activation. We produced and screened a novel fully synthetic phage display library of humanized nanobodies (NaLi-H1) to develop conformational sensors of the GTP loaded active conformation of RHO subfamily. We obtained several high affinity nanobodies against RHOA's active form which we characterized as RHO active antibodies in vitro and RHO signaling blocking intrabodies in cellulo. These new tools will facilitate and improve our current knowledge of this peculiar protein subfamily and will be a paradigm for the study of other RHO related small GTPases

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Más fuentes

Libros sobre el tema "GTPasi"

Manser, Ed y Thomas Leung. GTPase Protocols. New Jersey: Humana Press, 2002. http://dx.doi.org/10.1385/1592592813.

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Joan, Marsh y Goode Jamie, eds. The GTPase superfamily. Chichester: Wiley, 1993.

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Rush, Mark y Peter D’Eustachio, eds. The Small GTPase Ran. Boston, MA: Springer US, 2001. http://dx.doi.org/10.1007/978-1-4615-1501-2.

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Corda, D., H. Hamm y A. Luini. GTPase-controlled molecular machines. Rome: Ares-Serono Symposia Publications, 1994.

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Pandey, Girdhar K., Manisha Sharma, Amita Pandey y Thiruvenkadam Shanmugam. GTPases. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-11611-2.

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Ed, Manser y Leung Thomas, eds. GTPase protocols: The Ras superfamily. Totowa, N.J: Humana Press, 2002.

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Holmes, L. P. Gtpase protocols: The ras superfamily. [Place of publication not identified]: Humana, 2010.

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Li, Guangpu y Nava Segev, eds. Rab GTPases. New York, NY: Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-1346-7.

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Li, Guangpu, ed. Rab GTPases. New York, NY: Springer New York, 2015. http://dx.doi.org/10.1007/978-1-4939-2569-8.

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Rivero, Francisco, ed. Rho GTPases. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-61779-442-1.

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Capítulos de libros sobre el tema "GTPasi"

Edelstein-Keshet, Leah. "Pattern Formation Inside Living Cells". En SEMA SIMAI Springer Series, 79–95. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-86236-7_5.

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AbstractWhile most of our tissues appear static, in fact, cell motion comprises an important facet of all life forms, whether in single or multicellular organisms. Amoeboid cells navigate their environment seeking nutrients, whereas collectively, streams of cells move past and through evolving tissue in the development of complex organisms. Cell motion is powered by dynamic changes in the structural proteins (actin) that make up the cytoskeleton, and regulated by a circuit of signaling proteins (GTPases) that control the cytoskeleton growth, disassembly, and active contraction. Interesting mathematical questions we have explored include (1) How do GTPases spontaneously redistribute inside a cell? How does this determine the emergent polarization and directed motion of a cell? (2) How does feedback between actin and these regulatory proteins create dynamic spatial patterns (such as waves) in the cell? (3) How do properties of single cells scale up to cell populations and multicellular tissues given interactions (adhesive, mechanical) between cells? Here I survey mathematical models studied in my group to address such questions. We use reaction-diffusion systems to model GTPase spatiotemporal phenomena in both detailed and toy models (for analytic clarity). We simulate single and multiple cells to visualize model predictions and study emergent patterns of behavior. Finally, we work with experimental biologists to address data-driven questions about specific cell types and conditions.

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Del Pulgar, Teresa Gómez y Juan Carlos Lacal. "GTPase". En Encyclopedia of Cancer, 1–6. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-642-27841-9_2533-2.

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Del Pulgar, Teresa Gómez y Juan Carlos Lacal. "GTPase". En Encyclopedia of Cancer, 1968–73. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-46875-3_2533.

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Pulgar, Teresa Gómez Del y Juan Carlos Lacal. "GTPase". En Encyclopedia of Cancer, 1609–13. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-16483-5_2533.

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Konstantinidis, Diamantis G. y Theodosia A. Kalfa. "Rac GTPase". En Encyclopedia of Signaling Molecules, 4408–14. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-67199-4_597.

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Konstantinidis, Diamantis G. y Theodosia A. Kalfa. "Rac GTPase". En Encyclopedia of Signaling Molecules, 1–7. New York, NY: Springer New York, 2017. http://dx.doi.org/10.1007/978-1-4614-6438-9_597-1.

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Dempsey, Brian R., Anne C. Rintala-Dempsey, Gary S. Shaw, Yuan Xiao Zhu, A. Keith Stewart, Jaime O. Claudio, Constance E. Runyan et al. "Small GTPase". En Encyclopedia of Signaling Molecules, 1752. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4419-0461-4_101254.

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McCormick, F. "GTPase Activating Proteins". En GTPases in Biology I, 345–59. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-78267-1_23.

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Stefanini, Lucia, Robert H. Lee y Wolfgang Bergmeier. "GTPases". En Platelets in Thrombotic and Non-Thrombotic Disorders, 263–84. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-47462-5_20.

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Pandey, Girdhar K., Manisha Sharma, Amita Pandey y Thiruvenkadam Shanmugam. "Overview of G Proteins (GTP-Binding Proteins) in Eukaryotes". En GTPases, 1–7. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-11611-2_1.

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Actas de conferencias sobre el tema "GTPasi"

Na, Sungsoo. "Engineering Tools for Studying Coordination Between Biochemical and Biomechanical Activities in Cell Migration". En ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53709.

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Cell migration is achieved by the dynamic feedback interactions between traction forces generated by the cell and exerted onto the underlying extracellular matrix (ECM), and intracellular mechano-chemical signaling pathways, e.g., Rho GTPase (RhoA, Rac1, and Cdc42) activities [1,2,3]. These components are differentially distributed within a cell, and thus the coordination between tractions and mechanotransduction (i.e, RhoA and Rac1 activities) must be implemented at a precise spatial and temporal order to achieve optimized, directed cell migration [4,5]. Recent studies have shown that focal adhesions at the leading edge exert strong tractions [6], and these traction sites are co-localized with focal adhesion sites [7]. Further, by using the fluorescence resonance energy transfer (FRET) technology coupled with genetically encoded biosensors, researchers reported that Rho GTPases, such as RhoA [8], Rac1 [9], and Cdc42 [10] are maximally activated at the leading edge, suggesting the leading edge of the cell as its common functional site for Rho GTPase activities. All these works, however, were done separately, and the relationship between tractions and mechanotransduction during cell migration has not been demonstrated directly because of the difficulty in simultaneously recording tractions and mechanotransduction in migrating cells, precluding direct comparison between these results. Furthermore, these studies have been conducted by monitoring cells on glass coverslips, the stiffness of which is ∼ 65 giga pascal (GPa), at least three to six order higher than the physiological range of ECM stiffness. Although it is increasingly accepted that ECM stiffness influences cell migration, it is not known exactly how physiologically relevant ECM stiffness (order of kPa range) affects the dynamics of RhoA and Rac1 activities. For a complete understanding of the mechanism of mechano-chemical signaling in the context of cell migration, the dynamics and interplay between biomechanical (e.g., tractions) and biochemical (e.g., Rho GTPase) activities should be visualized within the physiologically relevant range of ECM stiffness.

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Mondal, Subhanjan, Said Goueli y Kevin Hsiao. "Abstract C204: GTPase/GAP/GEF-Glo™: A bioluminescent system to measure GTPase, GAP, and GEF activities." En Abstracts: AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics--Oct 19-23, 2013; Boston, MA. American Association for Cancer Research, 2013. http://dx.doi.org/10.1158/1535-7163.targ-13-c204.

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Mondal, Subhanjan y Said A. Goueli. "Abstract B44: GTPase/GAP/GEF-Glo™: A bioluminescent system to measure GTPase, GAP, and GEF activities". En Abstracts: AACR Special Conference on RAS Oncogenes: From Biology to Therapy; February 24-27, 2014; Lake Buena Vista, FL. American Association for Cancer Research, 2014. http://dx.doi.org/10.1158/1557-3125.rasonc14-b44.

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Schulze, J., L. Heinkele, M. Steffens, A. Warnecke, T. Lenarz, I. Just y A. Rohrbeck. "Rho-GTPase und p38 vermittelte Neuroprotektion in Spiralganglienzellen". En Abstract- und Posterband – 89. Jahresversammlung der Deutschen Gesellschaft für HNO-Heilkunde, Kopf- und Hals-Chirurgie e.V., Bonn – Forschung heute – Zukunft morgen. Georg Thieme Verlag KG, 2018. http://dx.doi.org/10.1055/s-0038-1641056.

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Authi, K. S., B. J. Evenden y N. Crawford. "ACTION OF GTPγS [GUANOSINE 5∲-0-(3-THIOPHOSPHATE)] ON SAPONIN-PERMEABILISED PLATELETS: INVOLVEMENT OF 'G' PROTEINS IN PLATELET ACTIVATION". En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644514.

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Certain ligand-receptor interactions at cell surfaces lead to the phospholipase-C (PLC) hydrolysis of phosphatidyl inositol (4.5) bisphosphate (PIP2). The products serve as intracellular second messengers, e.g. inositol (1.4.5) trisphosphate (IP3) releases Ca2+ from intracellular stores and diacylglycerol activates protein kinase-C. From studies using GTP and analogues (e.g. GTPγS) there is evidence of a key role for a guanine nucleotide binding protein(s) as a link between receptors and PIP2 hydrolysis. We report the actions of GTPγS on washed human platelets permeabilised with saponin (12-14 μg/ml) to allow penetration of low MWt polar substances. The responses to GTPγS are dose dependent (range 9-60 μM) and at 60 μM the agent induces shape change, aggregation and the secretion of 50% of previously incorporated [14C]-5HT. No effect of GTPγS is seen with intact cells. Shape change occurs 25-30 sec after GTPγS; aggregation and secretion is complete after 3 min. When GTP was used (up to 135 μM) with similarly permeabilised platelets no responses were initiated. Phosphatidylinositol turnover was monitored using 32P-labelling before permeabilisation. The addition of 90 μM GTPγS resulted in a 143 ± 23% (n=4) increase in 32P-phosphatidic acid (PA) with respect to the basal levels of “saponised control” cells. These findings suggest that GTPγS stimulates PLC activity through a ‘G’ protein interaction. The GDP analogue (GDPβS) produced no activation responses in saponised platelets but inhibited responses induced by GTPγS in a dose dependent manner (0-480 μM, max inhibition 480 μM). At 960 μM, GDPβS totally inhibited aggregation and secretion initiated by low doses of thrombin (0.1 U/ml) and collagen (1 μg/ml). Identical inhibition by GDPβS of thrombin and collagen-induced activation of intact platelets was observed indicating membrane penetration of this analogue. Shape change effects were not inhibited by GDPSS. The inhibitory effects of GDPSS towards thrombin and collagen induced secretion could be progressively overcome at higher doses of thrombin (0.2 U/ml - 2 U/ml) and collagen (5 μg/ml - 60 μg/ml) suggesting that at higher concentrations these agonists may exert effects through 'G' protein-independent mechanisms.

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Weber, Igor. "Oscillatory dynamics of small GTPase Rac1 in motile cells". En European Microscopy Congress 2020. Royal Microscopical Society, 2021. http://dx.doi.org/10.22443/rms.emc2020.1187.

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Jakobs, K. H., P. Gierschik y R. Grandt. "THE ROLE OF GTP-BINDING PROTEINS EXHIBITING GTPase ACTIVITY IN PLATELET ACTIVATION". En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644773.

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Activation of platelets by agonists acting via cell surface-located receptors apparently involves as an early event in transmembrane signalling an interaction of the agonist-occupied receptor with a guanine nucleotide-binding regulatory protein (G-protein). The activated G-protein, then, transduces the information to the effector molecule, being responsible for the changes in intracellular second messengers. At least two changes in intracellular signal molecules are often found to be associated with platelet activation by agonists, i.e., increases in inositol trisphosphate and diacylglycerol levels caused by activation of a polyphosphoinositide-specific phospholipase C and decrease in cyclic AMP concentration caused by inhibition of adenylate cyclase.Both actions of platelet-activating agents apparently involve G-proteins as transducing elements. Generally, the function of a G-protein in signal transduction can be measured either by its ability to regulate the activity of the effector molecule (phospholipase C or adenylate cyclase) or the binding affinity of an agonist to its specific receptor or by the abitlity of the G-protein to bind and hydrolyze GTP or one of its analogs in response to agonist-activated receptors. Some platelet-activating agonists (e.g. thrombin) can cause both adenylate cyclase inhibition and phospholipase C activation, whereas others induce either inhibition of adenylate cyclase (e.g. α2-adrenoceptor agonists) or activation of phospholipase C (e.g. stable endoperoxide analogs) . It is not yet known whether the simultaneous activation of two signal transduction systems is due to activation of two separate G-proteins by one receptor, to two distinct receptors activating each a distinct G-protein or to activation of two effector molecules by one G-protein.For some of the G-proteins, rather specific compounds are available causing inactivation of their function. In comparison to Gs, the stimulatory G-protein of the adenylate cyclase system, the adenylate cyclase inhibitory Gi-protein is rather specifically inactivated by ADP-ribosylation of its a-subunit by pertussis toxin, “unfortunately” not acting in intact platelets, and by SH-group reactive agents such as N-ethylmaleimide and diamide, apparently also affecting the Giα-subunit. Both of these treatments completely block α2-adrenoceptor-induced GTPase stimulation and adenylate cyclase inhibition and also thrombin-induced inhibition of adenylate cyclase. In order to know whether the G-protein coupling receptors to phospholipase C is similar to or different from the Gi-protein, high affinity GTPase stimulation by agents known to activate phospholipase C was evaluated in platelet membranes. The data obtained indicated that GTPase stimulation by agents causing both adenylate cyclase inhibition and phospholipase C activation is reduced, but only partially, by the above mentioned Gi-inactivating agents, while stimulation of GTPase by agents stimulating only phospholipase C is not affected by these treatments. These data suggested that the G-protein regulating phospholipase C activity in platelet membranes is different from the Gi-protein and may also not be a substrate for pertussis toxin. Measuring thrombin stimulation of inositol phosphate and diacylglycerol formation in saponin-permeabilized platelets, apparently contradictory data were reported after pertussis toxin treatment, being without effect or causing even an increase in thrombin stimulation of inositol phosphate formation (Lapetina: BBA 884, 219, 1986) or being inhibitory to thrombin stimulation of diacylglycerol formation (Brass et al.: JBC 261, 16838, 1986). These data indicate that the nature of the phospholipase C-related G-protein(s) is not yet defined and that their elucidation requires more specific tools as well as purification and reconstitution experiments. Preliminary data suggest that some antibiotics may serve as useful tools to characterize the phospho-lipase-related G-proteins. The possible role of G-protein phosphorylation by intracellular signal molecule-activated protein kinases in attenuation of signal transduction in platelets will be discussed.

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Acosta, Lehi, Aaron Rogers, Jingfu Peng, Alan Mueller, Zongzhong Tong, Donghan Shin, Jae Hyuk Yoo et al. "Abstract 4367: The small GTPase ARF6 is necessary for melanomagenesis". En Proceedings: AACR Annual Meeting 2018; April 14-18, 2018; Chicago, IL. American Association for Cancer Research, 2018. http://dx.doi.org/10.1158/1538-7445.am2018-4367.

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Schulze, J., L. Heinkele, M. Steffens, A. Warnecke, T. Lenarz, I. Just y A. Rohrbeck. "Rho-GTPase and p38 mediated neuroprotection in spiral ganglion cells". En Abstract- und Posterband – 89. Jahresversammlung der Deutschen Gesellschaft für HNO-Heilkunde, Kopf- und Hals-Chirurgie e.V., Bonn – Forschung heute – Zukunft morgen. Georg Thieme Verlag KG, 2018. http://dx.doi.org/10.1055/s-0038-1641057.

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Pusapati, Ganesh Varma, An Rykx, Sandy Vandoninck, Johan van Lint, Guido Adler y Thomas Seufferlein. "Abstract 296: Protein kinase D regulates Rho GTPase activity through rhotekin". En Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC. American Association for Cancer Research, 2010. http://dx.doi.org/10.1158/1538-7445.am10-296.

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Informes sobre el tema "GTPasi"

Simpson, Kaylene J. Rho GTPase Involvement in Breast Cancer Migration and Invasion. Fort Belvoir, VA: Defense Technical Information Center, marzo de 2005. http://dx.doi.org/10.21236/ada435395.

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Simpson, Kaylene J. Rho GTPase Involvement in Breast Cancer Migration and Invasion. Fort Belvoir, VA: Defense Technical Information Center, marzo de 2007. http://dx.doi.org/10.21236/ada469757.

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Yang, Zhenbiao. ROP GTPase Signaling in The Hormonal Regulation of Plant Growth. Office of Scientific and Technical Information (OSTI), mayo de 2013. http://dx.doi.org/10.2172/1080178.

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Kandpal, Rajendra P. y G. M. Nagaraja. Involvement of a Novel Rho GTPase Activating Protein in Breast Tumorigenesis. Fort Belvoir, VA: Defense Technical Information Center, julio de 2001. http://dx.doi.org/10.21236/ada404607.

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Band, Vimia. Human Mammary Epithelial Cell Transformation by Rho GTPase through a Novel Mechanism. Fort Belvoir, VA: Defense Technical Information Center, agosto de 2008. http://dx.doi.org/10.21236/ada500910.

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Kleer, Celina G. Detection of Metastatic Potential in Breast Cancer by RhoC-GTPase and WISP3 Proteins. Fort Belvoir, VA: Defense Technical Information Center, mayo de 2005. http://dx.doi.org/10.21236/ada442688.

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Kleer, Celina G. Detection of Metastatic Potential in Breast Cancer by RhoC-GTPase and WISP3 Proteins. Fort Belvoir, VA: Defense Technical Information Center, mayo de 2006. http://dx.doi.org/10.21236/ada456604.

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Kleer, Celina G. Detection of Metastatic Potential in Breast Cancer by RhoC-GTPase and WISP3 Proteins. Fort Belvoir, VA: Defense Technical Information Center, mayo de 2004. http://dx.doi.org/10.21236/ada426448.

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Kleer, Celina G. Detection of Metastatic Potential in Breast Cancer by RhoC-GTPase and WISP3 Proteins. Fort Belvoir, VA: Defense Technical Information Center, mayo de 2003. http://dx.doi.org/10.21236/ada422281.

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Kleer, Celina G. Detection of Metastatic Potential in Breast Cancer by RhoC-GTPase and WISP3 Proteins. Fort Belvoir, VA: Defense Technical Information Center, mayo de 2007. http://dx.doi.org/10.21236/ada473395.

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