scholarly journals GEF-H1 is necessary for neutrophil shear stress–induced migration during inflammation

2016 ◽  
Vol 215 (1) ◽  
pp. 107-119 ◽  
Author(s):  
Noah Fine ◽  
Ioannis D. Dimitriou ◽  
Jacob Rullo ◽  
María José Sandí ◽  
Björn Petri ◽  
...  
Keyword(s):  
Immune Response ◽  
Blood Flow ◽  
Shear Stress ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Static Conditions ◽  
Shear Stress Response

Leukocyte crawling and transendothelial migration (TEM) are potentiated by shear stress caused by blood flow. The mechanism that couples shear stress to migration has not been fully elucidated. We found that mice lacking GEF-H1 (GEF-H1−/−), a RhoA-specific guanine nucleotide exchange factor (GEF), displayed limited migration and recruitment of neutrophils into inflamed tissues. GEF-H1−/− leukocytes were deficient in in vivo crawling and TEM in the postcapillary venules. We demonstrated that although GEF-H1 deficiency had little impact on the migratory properties of neutrophils under static conditions, shear stress triggered GEF-H1–dependent spreading and crawling of neutrophils and relocalization of GEF-H1 to flotillin-2–rich uropods. Our results identify GEF-H1 as a component of the shear stress response machinery in neutrophils required for a fully competent immune response to bacterial infection.

scholarly journals Ccpg1, a Novel Scaffold Protein That Regulates the Activity of the Rho Guanine Nucleotide Exchange Factor Dbs

2006 ◽  
Vol 26 (23) ◽  
pp. 8964-8975 ◽  
Author(s):  
Elena V. Kostenko ◽  
Oyenike O. Olabisi ◽  
Sutapa Sahay ◽  
Pedro L. Rodriguez ◽  
Ian P. Whitehead
Keyword(s):  
Family Member ◽  
Guanine Nucleotide Exchange Factor ◽  
Scaffold Protein ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Novel Scaffold ◽  
Exchange Activity

ABSTRACT Dbs is a Rho-specific guanine nucleotide exchange factor (RhoGEF) with in vitro exchange activity specific for RhoA and Cdc42. Like many RhoGEF family members, the in vivo exchange activity of Dbs is restricted in a cell-specific manner. Here we report the characterization of a novel scaffold protein (designated cell cycle progression protein 1 [Ccpg1]) that interacts with Dbs and modulates its in vivo exchange specificity. When coexpressed in mammalian cells, Ccpg1 binds to the Dbl homology/pleckstrin homology domain tandem motif of Dbs and inhibits its exchange activity toward RhoA, but not Cdc42. Expression of Ccpg1 correlates with the ability of Dbs to activate endogenous RhoA in cultured cells, and suppression of endogenous Ccpg1 expression potentiates Dbs exchange activity toward RhoA. The isolated Dbs binding domain of Ccpg1 is not sufficient to suppress Dbs exchange activity on RhoA, thus suggesting a regulatory interaction. Ccpg1 mediates recruitment of endogenous Src kinase into Dbs-containing complexes and interacts with the Rho family member Cdc42. Collectively, our studies suggest that Ccpg1 represents a new class of regulatory scaffold protein that can function as both an assembly platform for Rho protein signaling complexes and a regulatory protein which can restrict the substrate utilization of a promiscuous RhoGEF family member.

scholarly journals The Rho-Guanine Nucleotide Exchange Factor Domain of Obscurin Activates RhoA Signaling in Skeletal Muscle

2009 ◽  
Vol 20 (17) ◽  
pp. 3905-3917 ◽  
Author(s):  
Diana L. Ford-Speelman ◽  
Joseph A. Roche ◽  
Amber L. Bowman ◽  
Robert J. Bloch
Keyword(s):  
Skeletal Muscle ◽  
Guanine Nucleotide Exchange Factor ◽  
Small Gtpases ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

Obscurin is a large (∼800-kDa), modular protein of striated muscle that concentrates around the M-bands and Z-disks of each sarcomere, where it is well positioned to sense contractile activity. Obscurin contains several signaling domains, including a rho-guanine nucleotide exchange factor (rhoGEF) domain and tandem pleckstrin homology domain, consistent with a role in rho signaling in muscle. We investigated the ability of obscurin's rhoGEF domain to interact with and activate small GTPases. Using a combination of in vitro and in vivo approaches, we found that the rhoGEF domain of obscurin binds selectively to rhoA, and that rhoA colocalizes with obscurin at the M-band in skeletal muscle. Other small GTPases, including rac1 and cdc42, neither associate with the rhoGEF domain of obscurin nor concentrate at the level of the M-bands. Furthermore, overexpression of the rhoGEF domain of obscurin in adult skeletal muscle selectively increases rhoA expression and activity in this tissue. Overexpression of obscurin's rhoGEF domain and its effects on rhoA alter the expression of rho kinase and citron kinase, both of which can be activated by rhoA in other tissues. Injuries to rodent hindlimb muscles caused by large-strain lengthening contractions increases rhoA activity and displaces it from the M-bands to Z-disks, similar to the effects of overexpression of obscurin's rhoGEF domain. Our results suggest that obscurin's rhoGEF domain signals at least in part by inducing rhoA expression and activation, and altering the expression of downstream kinases in vitro and in vivo.

scholarly journals Crystal and cryo-EM structures of the cytosolic G protein alpha chaperone and guanine nucleotide exchange factor Ric-8A bound to Gαi1

2020 ◽  
Author(s):  
Levi J. McClelland ◽  
Kaiming Zhang ◽  
Tung-Chung Mou ◽  
Jake Johnston ◽  
Cindee Yates-Hansen ◽  
...  
Keyword(s):  
G Protein ◽  
Domain Architecture ◽  
Guanine Nucleotide Exchange Factor ◽  
Chaperone Activity ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

Ric-8A is a cytosolic Guanine Nucleotide exchange Factor (GEF) that activates heterotrimeric G protein alpha subunits (Gα)1. Ric-8A is essential to life in multicellular eukaryotes by virtue of its chaperone activity that is required for Gα biogenesis and membrane localization2, 3. Ric-8A adopts an armadillo (ARM)/HEAT repeat domain architecture and is structurally unrelated to G Protein-Coupled Receptors (GPCR)4. Both GEF and chaperone activities are stimulated by Casein Kinase II phosphorylation5. The mechanisms by which Ric-8A catalyzes GDP release and GTP binding to Gα, or exerts chaperone activity are unknown. Here, we report the structure of the nanobody-stabilized complex of nucleotide-free Gαi1 (isoform 1 of Gα family i) and phosphorylated Ric-8A at near atomic resolution by cryo-electron microscopy and X-ray crystallography. We find that Ric-8A envelops the GTPase domain of Gα, disrupting all three switch regions that convey Gα nucleotide-binding and signaling activity, and displaces the C-terminal helix and helical domain of Gα. These cooperative interactions dismantle the GDP binding site and promote GDP release, while protecting structural elements of Gα that are dynamic in the nucleotide-free state. The structures also show how in vivo phosphorylation stabilizes Gα-binding elements of Ric-8A, thereby enhancing its GEF and chaperone activities.

scholarly journals Inositol phospholipids regulate the guanine-nucleotide-exchange factor Tiam1 by facilitating its binding to the plasma membrane and regulating GDP/GTP exchange on Rac1

2004 ◽  
Vol 382 (3) ◽  
pp. 857-865 ◽  
Author(s):  
Ian N. FLEMING ◽  
Ian H. BATTY ◽  
Alan R. PRESCOTT ◽  
Alex GRAY ◽  
Gursant S. KULAR ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Inositol Phosphates ◽  
Pleckstrin Homology Domain ◽  
Membrane Association ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Pleckstrin Homology ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

Binding of the Rac1-specific guanine-nucleotide-exchange factor, Tiam1, to the plasma membrane requires the N-terminal pleckstrin homology domain. In the present study, we show that membrane-association is mediated by binding of PtdIns(4,5)P2 to the pleckstrin homology domain. Moreover, in 1321N1 astrocytoma cells, translocation of Tiam1 to the cytosol, following receptor-mediated stimulation of PtdIns(4,5)P2 breakdown, correlates with decreased Rac1-GTP levels, indicating that membrane-association is required for GDP/GTP exchange on Rac1. In addition, we show that platelet-derived growth factor activates Rac1 in vivo by increasing PtdIns(3,4,5)P3 concentrations, rather than the closely related lipid, PtdIns(3,4)P2. Finally, the data demonstrate that PtdIns(4,5)P2 and PtdIns(3,4,5)P3 bind to the same pleckstrin homology domain in Tiam1 and that soluble inositol phosphates appear to compete with lipids for this binding. Together, these novel observations provide strong evidence that distinct phosphoinositides regulate different functions of this enzyme, indicating that local concentrations of signalling lipids and the levels of cytosolic inositol phosphates will play crucial roles in determining its activity in vivo.

scholarly journals The two guanine nucleotide exchange factor domains of Trio link the Rac1 and the RhoA pathways in vivo

Oncogene ◽  
1998 ◽  
Vol 16 (2) ◽  
pp. 147-152 ◽  
Author(s):  
Jean-Michel Bellanger ◽  
Jean-Bernard Lazaro ◽  
Sylvie Diriong ◽  
Anne Fernandez ◽  
Ned Lamb ◽  
...  
Keyword(s):  
Guanine Nucleotide Exchange Factor ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

scholarly journals Ras guanine nucleotide exchange factor RasGRP1 promotes acute inflammatory response and restricts inflammation-contributed cancer cell growth

2021 ◽  
Author(s):  
Cong Wang ◽  
Xue Li ◽  
Changping Yu ◽  
Luoling Wang ◽  
Rilin Deng ◽  
...  
Keyword(s):  
Inflammatory Response ◽  
Acute Inflammation ◽  
Mrna Level ◽  
Acute Inflammatory Response ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Cancer Cell Growth ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

AbstractAcute inflammatory response needs to be tightly regulated for promoting the elimination of pathogens and preveting the risk of tumorigenesis, but the mechanism has not been fully elucidated. Here, we report that Ras guanine nucleotide releasing protein 1 (RasGRP1) plays a bifunctional regulator that promotes acute inflammation and inhibits inflammation-associated cancer. At the mRNA level, RasGRP1 strengthens the inflammatory response by functioning as a competing endogenous RNA to specifically promote IL-6 expression by sponging let-7a. In vivo overexpression of the RasGRP1 3’ untranslated region significantly aggravated lipopolysaccharide-induced systemic inflammation and dextran sulphate sodium-induced colitis in IL-6+/+ mice but not in IL-6-/- mice. At the protein level, RasGRP1 restricts the growth of inflammation-contributed cancer cells by impairing EGFR-SOS1-Ras-AKT signalling. Tumour patients with high RasGRP1 expression showed a better clinical outcome than those with low expression. Considering acute inflammation rarely leads to tumorigenesis, this work reveals that RasGRP1 is an essential bifunctional regulator for acute inflammatory response.

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