Distinct synaptic localization patterns of brefeldin A-resistant guanine nucleotide exchange factors BRAG2 and BRAG3 in the mouse retina

2013 ◽  
Vol 521 (4) ◽  
pp. 860-876 ◽  
Author(s):  
Hiroyuki Sakagami ◽  
Osamu Katsumata ◽  
Yoshinobu Hara ◽  
Hideaki Tamaki ◽  
Masahiko Watanabe ◽  
...  
Keyword(s):  
Brefeldin A ◽  
Guanine Nucleotide Exchange Factors ◽  
Mouse Retina ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Synaptic Localization ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors

scholarly journals Distinct Functions for Arf Guanine Nucleotide Exchange Factors at the Golgi Complex: GBF1 and BIGs Are Required for Assembly and Maintenance of the Golgi Stack and trans-Golgi Network, Respectively

2008 ◽  
Vol 19 (2) ◽  
pp. 523-535 ◽  
Author(s):  
Florin Manolea ◽  
Alejandro Claude ◽  
Justin Chun ◽  
Javier Rosas ◽  
Paul Melançon
Keyword(s):  
Golgi Complex ◽  
Brefeldin A ◽  
Adaptor Proteins ◽  
Guanine Nucleotide Exchange Factors ◽  
Coat Proteins ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Golgi Stack ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors

We examined the relative function of the two classes of guanine nucleotide exchange factors (GEFs) for ADP-ribosylation factors that regulate recruitment of coat proteins on the Golgi complex. Complementary overexpression and RNA-based knockdown approaches established that GBF1 regulates COPI recruitment on cis-Golgi compartments, whereas BIGs appear specialized for adaptor proteins on the trans-Golgi. Knockdown of GBF1 and/or COPI did not prevent export of VSVGtsO45 from the endoplasmic reticulum (ER), but caused its accumulation into peripheral vesiculotubular clusters. In contrast, knockdown of BIG1 and BIG2 caused loss of clathrin adaptor proteins and redistribution of several TGN markers, but had no impact on COPI and several Golgi markers. Surprisingly, brefeldin A–inhibited guanine nucleotide exchange factors (BIGs) knockdown prevented neither traffic of VSVGtsO45 to the plasma membrane nor assembly of a polarized Golgi stack. Our observations indicate that COPII is the only coat required for sorting and export from the ER exit sites, whereas GBF1 but not BIGs, is required for COPI recruitment, Golgi subcompartmentalization, and cargo progression to the cell surface.

Arf, Sec7 and Brefeldin A: a model towards the therapeutic inhibition of guanine nucleotide-exchange factors

2005 ◽  
Vol 33 (6) ◽  
pp. 1265-1268 ◽  
Author(s):  
M. Zeghouf ◽  
B. Guibert ◽  
J.-C. Zeeh ◽  
J. Cherfils
Keyword(s):  
Exchange Reaction ◽  
G Proteins ◽  
Brefeldin A ◽  
Membrane Traffic ◽  
Guanine Nucleotide Exchange Factors ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Small G Proteins

GEFs (guanine nucleotide-exchange factors), which stimulate GDP dissociation from small G-proteins, are pivotal regulators of signalling pathways activated by small G-proteins. In the case of Arf proteins, which are major regulators of membrane traffic in the cell and have recently been found to be involved in an increasing number of human diseases, GDP/GTP exchange is stimulated by GEFs that carry a catalytic Sec7 domain. Recent structural results captured snapshots of the exchange reaction, revealing that Sec7 domains secure Arf-GDP to membranes before nucleotide exchange takes place, taking advantage of a built-in structural device in Arf proteins that couples their affinity for membranes to the nature of the bound nucleotide. One of the Arf–Sec7 intermediates was trapped by BFA (Brefeldin A), an uncompetitive inhibitor of Arf activation that has been instrumental in deciphering the molecular principles of membrane traffic at the Golgi. BFA targets a low-affinity Arf–Sec7 intermediate of the exchange reaction. It binds at the Arf-GDP/Sec7 interface, thus freezing the complex in an abortive conformation that cannot proceed to nucleotide dissociation. In the cell, this results in the specific inhibition of Arf1 by a subset of its GEFs, and the efficient and reversible block of membrane traffic at the Golgi. The mechanism of BFA leads to the concept of ‘interfacial inhibition’, in which a protein–protein interaction of therapeutic interest is stabilized, rather than impaired, by a drug. Up-regulated activity of small G-proteins is involved in various human diseases, making their GEFs attractive candidates to interrupt specifically the corresponding signalling pathway. Interfacial inhibitors are proposed as an alternative to competitive inhibitors that may be explored for their inhibition.

scholarly journals Localization of Large ADP-Ribosylation Factor-Guanine Nucleotide Exchange Factors to Different Golgi Compartments: Evidence for Distinct Functions in Protein Traffic

2002 ◽  
Vol 13 (1) ◽  
pp. 119-133 ◽  
Author(s):  
Xinhua Zhao ◽  
Troy K.R. Lasell ◽  
Paul Melancİon
Keyword(s):  
Golgi Complex ◽  
Brefeldin A ◽  
Guanine Nucleotide Exchange Factors ◽  
Dependent Manner ◽  
Coat Proteins ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Adp Ribosylation ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors

Activation of several ADP-ribosylation factors (ARFs) by guanine nucleotide exchange factors (GEFs) regulates recruitment of coat proteins (COPs) on the Golgi complex and is generally assumed to be the target of brefeldin A (BFA). The large ARF-GEFs Golgi-specific BFA resistance factor 1 (GBF1) and BFA-inhibited GEFs (BIGs) localize to this organelle but catalyze exchange preferentially on class II and class I ARFs, respectively. We now demonstrate using quantitative confocal microscopy that these GEFs show a very limited overlap with each other (15 and 23%). In contrast, GBF1 colocalizes with the cis-marker p115 (86%), whereas BIGs overlap extensively with TGN38 (83%). Consistent with these distributions, GBF1, but not BIG1, partially relocalized to peripheral sites after incubation at 15°C. The new GBF1 structures represent peripheral vesicular tubular clusters (VTCs) because 88% of structures analyzed stained for both GBF1 and p115. Furthermore, as expected of VTCs, they rapidly reclustered to the Golgi complex in a microtubule-dependent manner upon warm-up. These observations suggest that GBF1 and BIGs activate distinct subclasses of ARFs in specific locations to regulate different types of reactions. In agreement with this possibility, COPI overlapped to a greater extent with GBF1 (64%) than BIG1 (31%), whereas clathrin showed limited overlap with BIG1, and virtually none with GBF1.

scholarly journals Enhancement of β-catenin activity by BIG1 plus BIG2 via Arf activation and cAMP signals

2016 ◽  
Vol 113 (21) ◽  
pp. 5946-5951 ◽  
Author(s):  
Chun-Chun Li ◽  
Kang Le ◽  
Jiro Kato ◽  
Joel Moss ◽  
Martha Vaughan
Keyword(s):  
Brefeldin A ◽  
Direct Interaction ◽  
Guanine Nucleotide Exchange Factors ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Nucleotide Exchange Factor ◽  
Anchoring Protein

Multifunctional β-catenin, with critical roles in both cell–cell adhesion and Wnt-signaling pathways, was among HeLa cell proteins coimmunoprecipitated by antibodies against brefeldin A-inhibited guanine nucleotide-exchange factors 1 and 2 (BIG1 or BIG2) that activate ADP-ribosylation factors (Arfs) by accelerating the replacement of bound GDP with GTP. BIG proteins also contain A-kinase anchoring protein (AKAP) sequences that can act as scaffolds for multimolecular assemblies that facilitate and limit cAMP signaling temporally and spatially. Direct interaction of BIG1 N-terminal sequence with β-catenin was confirmed using yeast two-hybrid assays and in vitro synthesized proteins. Depletion of BIG1 and/or BIG2 or overexpression of guanine nucleotide-exchange factor inactive mutant, but not wild-type, proteins interfered with β-catenin trafficking, leading to accumulation at perinuclear Golgi structures. Both phospholipase D activity and vesicular trafficking were required for effects of BIG1 and BIG2 on β-catenin activation. Levels of PKA-phosphorylated β-catenin S675 and β-catenin association with PKA, BIG1, and BIG2 were also diminished after BIG1/BIG2 depletion. Inferring a requirement for BIG1 and/or BIG2 AKAP sequence in PKA modification of β-catenin and its effect on transcription activation, we confirmed dependence of S675 phosphorylation and transcription coactivator function on BIG2 AKAP-C sequence.

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
Sign in / Sign up

Export Citation Format

Share Document