Elevated cAMP Protects against Diclofenac-Induced Toxicity in Primary Rat Hepatocytes: A Protective Effect Mediated by the Exchange Protein Directly Activated by cAMP/cAMP-Regulated Guanine Nucleotide Exchange Factors

ABSTRACT Angiogenesis, the process by which new blood vessels are formed from preexisting vasculature, is critical for vascular remodeling during development and contributes to the pathogenesis of diseases such as cancer. Prior studies from our laboratory demonstrate that the EphA2 receptor tyrosine kinase is a key regulator of angiogenesis in vivo. The EphA receptor-mediated angiogenic response is dependent on activation of Rho family GTPase Rac1 and is regulated by phosphatidylinositol 3-kinase. Here we report the identification of Vav2 and Vav3 as guanine nucleotide exchange factors (GEFs) that link the EphA2 receptor to Rho family GTPase activation and angiogenesis. Ephrin-A1 stimulation recruits the binding of Vav proteins to the activated EphA2 receptor. The induced association of EphA receptor and Vav proteins modulates the activity of Vav GEFs, leading to activation of Rac1 GTPase. Overexpression of either Vav2 or Vav3 in primary microvascular endothelial cells promotes Rac1 activation, cell migration, and assembly in response to ephrin-A1 stimulation. Conversely, loss of Vav2 and Vav3 GEFs inhibits Rac1 activation and ephrin-A1-induced angiogenic responses both in vitro and in vivo. In addition, embryonic fibroblasts derived from Vav2−/− Vav3−/− mice fail to spread on an ephrin-A1-coated surface and exhibit a significant decrease in the formation of ephrin-A1-induced lamellipodia and filopodia. These findings suggest that Vav GEFs serve as a molecular link between EphA2 receptors and the actin cytoskeleton and provide an important mechanism for EphA2-mediated angiogenesis.

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Family-wide Analysis of the Inhibition of Arf Guanine Nucleotide Exchange Factors with Small Molecules: Evidence of Unique Inhibitory Profiles

Biochemistry ◽

10.1021/acs.biochem.7b00706 ◽

2017 ◽

Vol 56 (38) ◽

pp. 5125-5133 ◽

Cited By ~ 8

Author(s):

Sarah Benabdi ◽

François Peurois ◽

Agata Nawrotek ◽

Jahnavi Chikireddy ◽

Tatiana Cañeque ◽

...

Keyword(s):

Small Molecules ◽

Guanine Nucleotide Exchange Factors ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors

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Activation of G proteins by guanine nucleotide exchange factors relies on GTPase activity

10.1101/032607 ◽

2015 ◽

Author(s):

Rob J Stanley ◽

Geraint MH Thomas

Keyword(s):

G Protein ◽

G Proteins ◽

Guanine Nucleotide Exchange Factors ◽

Guanine Nucleotide ◽

Gtpase Activity ◽

Nucleotide Exchange ◽

Signalling Molecules ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

Experimental Strategies

G proteins are an important family of signalling molecules controlled by guanine nucleotide exchange and GTPase activity in what is commonly called an 'activation/inactivation cycle'. The molecular mechanism by which guanine nucleotide exchange factors (GEFs) catalyse the activation of monomeric G proteins is well-established, however the complete reversibility of this mechanism is often overlooked. Here, we use a theoretical approach to prove that GEFs are unable to positively control G protein systems at steady-state in the absence of GTPase activity. Instead, positive regulation of G proteins must be seen as a product of the competition between guanine nucleotide exchange and GTPase activity -- emphasising a central role for GTPase activity beyond merely signal termination. We conclude that a more accurate description of the regulation of G proteins via these processes is as a 'balance/imbalance' mechanism. This result has implications for the understanding of many intracellular signalling processes, and for experimental strategies that rely on modulating G protein systems.

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Crucial Role of Rapgef2 and Rapgef6, a Family of Guanine Nucleotide Exchange Factors for Rap1 Small GTPase, in Formation of Apical Surface Adherens Junctions and Neural Progenitor Development in the Mouse Cerebral Cortex

eNeuro ◽

10.1523/eneuro.0142-16.2016 ◽

2016 ◽

Vol 3 (3) ◽

pp. ENEURO.0142-16.2016 ◽

Cited By ~ 16

Author(s):

Kazuhiro Maeta ◽

Hironori Edamatsu ◽

Kaori Nishihara ◽

Junji Ikutomo ◽

Shymaa E. Bilasy ◽

...

Keyword(s):

Cerebral Cortex ◽

Guanine Nucleotide Exchange Factors ◽

Small Gtpase ◽

Apical Surface ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

Mouse Cerebral Cortex

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Tankyrase regulates epithelial lumen formation via suppression of Rab11 GEFs

The Journal of Cell Biology ◽

10.1083/jcb.202008037 ◽

2021 ◽

Vol 220 (7) ◽

Author(s):

Arun A. Chandrakumar ◽

Étienne Coyaud ◽

Christopher B. Marshall ◽

Mitsuhiko Ikura ◽

Brian Raught ◽

...

Keyword(s):

Guanine Nucleotide Exchange Factors ◽

Protein Abundance ◽

Epithelial Polarity ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Lumen Formation ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

Interaction Proteomics ◽

Sequential Inhibition

Rab11 GTPase proteins are required for cytokinesis, ciliogenesis, and lumenogenesis. Rab11a is critical for apical delivery of podocalyxin (PODXL) during lumen formation in epithelial cells. SH3BP5 and SH3BP5L are guanine nucleotide exchange factors (GEFs) for Rab11. We show that SH3BP5 and SH3BP5L are required for activation of Rab11a and cyst lumen formation. Using proximity-dependent biotin identification (BioID) interaction proteomics, we have identified SH3BP5 and its paralogue SH3BP5L as new substrates of the poly-ADP-ribose polymerase Tankyrase and the E3 ligase RNF146. We provide data demonstrating that epithelial polarity via cyst lumen formation is governed by Tankyrase, which inhibits Rab11a activation through the suppression of SH3BP5 and SH3BP5L. RNF146 reduces Tankyrase protein abundance and restores Rab11a activation and lumen formation. Thus, Rab11a activation is controlled by a signaling pathway composed of the sequential inhibition of SH3BP5 paralogues by Tankyrase, which is itself suppressed by RNF146.

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Regulation of Telomerase Activity by Rab5 Guanine Nucleotide Exchange Factors

10.25148/etd.fidc007848 ◽

2019 ◽

Author(s):

Patric J Hambleton

Keyword(s):

Telomerase Activity ◽

Guanine Nucleotide Exchange Factors ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors

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RAP, a member of the Ras superfamily of small GTPases and its putative GTPase activating proteins and guanine nucleotide exchange factors in raw 264.7 macrophages

10.32920/ryerson.14652315.v1 ◽

2021 ◽

Author(s):

Monika Tucholska

Keyword(s):

Guanine Nucleotide Exchange Factors ◽

Raw 264.7 ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Fcγ Receptor ◽

Raw 264.7 Macrophages ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

Gtpase Activating Proteins ◽

Ras Superfamily

The Fcγ receptor is a cell surface protein essential in the immune response that binds IgG-opsonized particles resulting in phagocytosis. Phagocytosis is a process used to remove pathogens and confine them in a vacuole that will enable their breakdown. The members of the Ras superfamily of small G proteins have been identified in samples where the activated Fcγ receptor complex was captured and analyzed using tandem mass spectrometry. The protein Rap. beloning to the Ras superfamily, guanosine triphosphatases (GTPase) activating proteins (GAPs), which promote the dissociation of GTP, and guanine nucleotide exchange factors (GEFs), that permits the exchange of GDP for GTP, were detected by SEQUEST in RAW 264.7 macrophages and futher analyzed using various methods. In this study, Raps, RasGAPs, and RapGEFs, were observed by tandem mass spectrometry and sequence correlation analysis. The selected isoforms were confirmed by Western blots, live cell confocal microscopy with fluorescent fusion constructs and antibody staining to verify the localization of Ras proetins, specifically Rap1, p120RasGAP and C3G, a RapGEF, to activated Fc reeceptor [sic].

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