scholarly journals The Phosphatidylinositol (3,4,5)-Trisphosphate-dependent Rac Exchanger 1·Ras-related C3 Botulinum Toxin Substrate 1 (P-Rex1·Rac1) Complex Reveals the Basis of Rac1 Activation in Breast Cancer Cells

2015 ◽  
Vol 290 (34) ◽  
pp. 20827-20840 ◽  
Author(s):  
Christina M. Lucato ◽  
Michelle L. Halls ◽  
Lisa M. Ooms ◽  
Heng-Jia Liu ◽  
Christina A. Mitchell ◽  
...  
Keyword(s):  
Botulinum Toxin ◽  
Tyrosine Kinases ◽  
Critical Role ◽  
Structural Data ◽  
Guanine Nucleotide Exchange Factors ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Rac Gtpases ◽  
G Protein Coupled

The P-Rex (phosphatidylinositol (3,4,5)-trisphosphate (PIP3)-dependent Rac exchanger) family (P-Rex1 and P-Rex2) of the Rho guanine nucleotide exchange factors (Rho GEFs) activate Rac GTPases to regulate cell migration, invasion, and metastasis in several human cancers. The family is unique among Rho GEFs, as their activity is regulated by the synergistic binding of PIP3 and Gβγ at the plasma membrane. However, the molecular mechanism of this family of multi-domain proteins remains unclear. We report the 1.95 Å crystal structure of the catalytic P-Rex1 DH-PH tandem domain in complex with its cognate GTPase, Rac1 (Ras-related C3 botulinum toxin substrate-1). Mutations in the P-Rex1·Rac1 interface revealed a critical role for this complex in signaling downstream of receptor tyrosine kinases and G protein-coupled receptors. The structural data indicated that the PIP3/Gβγ binding sites are on the opposite surface and markedly removed from the Rac1 interface, supporting a model whereby P-Rex1 binding to PIP3 and/or Gβγ releases inhibitory C-terminal domains to expose the Rac1 binding site.

scholarly journals Rac GTPases play critical roles in early T-cell development

Blood ◽  
2009 ◽  
Vol 113 (17) ◽  
pp. 3990-3998 ◽  
Author(s):  
Celine Dumont ◽  
Agnieszka Corsoni-Tadrzak ◽  
Sandra Ruf ◽  
Jasper de Boer ◽  
Adam Williams ◽  
...  
Keyword(s):  
T Cell ◽  
Notch Signaling ◽  
T Cell Development ◽  
Cell Development ◽  
Guanine Nucleotide Exchange Factors ◽  
Nucleotide Exchange ◽  
Thymic Development ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Rac Gtpases

Abstract The Rac1 and Rac2 GTPases play important roles in many processes including cytoskeletal reorganization, proliferation, and survival, and are required for B-cell development. Previous studies had shown that deficiency in Rac2 did not affect T-cell development, whereas the function of Rac1 in this process has not been investigated. We now show that simultaneous absence of both GTPases resulted in a very strong developmental block at the pre-TCR checkpoint and in defective positive selection. Unexpectedly, deficiency of Rac1 and Rac2 also resulted in the aberrant survival of thymocytes lacking expression of TCRβ, showing hallmarks of hyperactive Notch signaling. Furthermore, we found a similar novel phenotype in the absence of Vav1, Vav2, and Vav3, which function as guanine nucleotide exchange factors for Rac1 and Rac2. These results show that a pathway containing Vav and Rac proteins may negatively regulate Notch signaling during early thymic development.

scholarly journals GEFs and Rac GTPases control directional specificity of neurite extension along the anterior–posterior axis

2016 ◽  
Vol 113 (25) ◽  
pp. 6973-6978 ◽  
Author(s):  
Chaogu Zheng ◽  
Margarete Diaz-Cuadros ◽  
Martin Chalfie
Keyword(s):  
Intracellular Signaling ◽  
Neurite Growth ◽  
Guanine Nucleotide Exchange Factors ◽  
Signaling Proteins ◽  
Nucleotide Exchange ◽  
Directional Bias ◽  
Neurite Extension ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Rac Gtpases

Although previous studies have identified many extracellular guidance molecules and intracellular signaling proteins that regulate axonal outgrowth and extension, most were conducted in the context of unidirectional neurite growth, in which the guidance cues either attract or repel growth cones. Very few studies addressed how intracellular signaling molecules differentially specify bidirectional outgrowth. Here, using the bipolar PLM neurons in Caenorhabditis elegans, we show that the guanine nucleotide exchange factors (GEFs) UNC-73/Trio and TIAM-1 promote anterior and posterior neurite extension, respectively. The Rac subfamily GTPases act downstream of the GEFs; CED-10/Rac1 is activated by TIAM-1, whereas CED-10 and MIG-2/RhoG act redundantly downstream of UNC-73. Moreover, these two pathways antagonize each other and thus regulate the directional bias of neuritogenesis. Our study suggests that directional specificity of neurite extension is conferred through the intracellular activation of distinct GEFs and Rac GTPases.

Epac proteins: specific ligands and role in cardiac remodelling

2014 ◽  
Vol 42 (2) ◽  
pp. 257-264 ◽  
Author(s):  
Malik Bisserier ◽  
Jean-Paul Blondeau ◽  
Frank Lezoualc’h
Keyword(s):  
High Throughput Screening ◽  
Therapeutic Potential ◽  
Critical Role ◽  
Guanine Nucleotide Exchange Factors ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Cardiac Pathophysiology ◽  
Cardiac Disorders

Epacs (exchange proteins directly activated by cAMP) act as guanine-nucleotide-exchange factors for the Ras-like small G-proteins Rap1 and Rap2, and are now recognized as incontrovertible factors leading to complex and diversified cAMP signalling pathways. Given the critical role of cAMP in the regulation of cardiac function, several studies have investigated the functional role of Epacs in the heart, providing evidence that Epacs modulate intracellular Ca2+ and are involved in several cardiac pathologies such as cardiac hypertrophy and arrhythmia. The present review summarizes recent data on the Epac signalling pathway and its role in cardiac pathophysiology. We also discuss recent advances in the discovery of novel pharmacological modulators of Epacs that were identified by high-throughput screening and their therapeutic potential for the treatment of cardiac disorders.

scholarly journals Involvement of the Switch 2 Domain of Ras in Its Interaction with Guanine Nucleotide Exchange Factors

1996 ◽  
Vol 271 (19) ◽  
pp. 11076-11082 ◽  
Author(s):  
Lawrence A. Quilliam ◽  
Mark M. Hisaka ◽  
Sheng Zhong ◽  
Amy Lowry ◽  
Raymond D. Mosteller ◽  
...  
Keyword(s):  
Guanine Nucleotide Exchange Factors ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors

scholarly journals Essential Role of Vav Family Guanine Nucleotide Exchange Factors in EphA Receptor-Mediated Angiogenesis

2006 ◽  
Vol 26 (13) ◽  
pp. 4830-4842 ◽  
Author(s):  
Sonja G. Hunter ◽  
Guanglei Zhuang ◽  
Dana Brantley-Sieders ◽  
Wojciech Swat ◽  
Christopher W. Cowan ◽  
...  
Keyword(s):  
Guanine Nucleotide Exchange Factors ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Rac1 Gtpase ◽  
Rho Family ◽  
Epha Receptor

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.

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

Biochemistry ◽  
2017 ◽  
Vol 56 (38) ◽  
pp. 5125-5133 ◽  
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

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

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.

scholarly journals Tankyrase regulates epithelial lumen formation via suppression of Rab11 GEFs

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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