scholarly journals Combating Chagas Disease Through Inhibition of Tiam1, a Rho GTPase Guanine Nucleotide Exchange Factor

2016 ◽  
Author(s):  
Chirag Krishna ◽  
Li Xie ◽  
Philip Bourne ◽  
Celine DerMarderossian
Keyword(s):  
Chagas Disease ◽  
Latin American ◽  
Rho Gtpase ◽  
Guanine Nucleotide Exchange Factor ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

Chagas disease is a major cardiovascular affliction primarily endemic to Latin American countries, affecting some ten to twelve million people worldwide. The currently available drugs, Benznidazole and Nifurtimox, are ineffective in the chronic stages and induce severe side effects. In an attempt to improve this situation we use an in silico drug repurposing strategy to correlate drug-protein interactions with positive clinical outcomes. The strategy involves a protein functional site similarity search, along with computational docking studies and, given the findings, a phosphatidylinositol (PIP) strip test to determine the activity of Posaconazole, a recently developed antifungal triazole, in conjunction with Tiam1, a Rho GTPase Guanine Nucleotide Exchange Factor. The results from both computational and in vitro studies indicate possible inhibition of phosphoinositides via Posaconazole, preventing Rho GTPase-induced proliferation of T. cruzi, the etiological agent of Chagas Disease.

scholarly journals Structure of the C-terminal guanine nucleotide exchange factor module of Trio in an autoinhibited conformation reveals its oncogenic potential

2019 ◽  
Vol 12 (569) ◽  
pp. eaav2449 ◽  
Author(s):  
Sumit J. Bandekar ◽  
Nadia Arang ◽  
Ena S. Tully ◽  
Brittany A. Tang ◽  
Brenna L. Barton ◽  
...  
Keyword(s):  
Rho Gtpase ◽  
Guanine Nucleotide Exchange Factor ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Ph Domain ◽  
Independent Manner ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Factor Module

The C-terminal guanine nucleotide exchange factor (GEF) module of Trio (TrioC) transfers signals from the Gαq/11subfamily of heterotrimeric G proteins to the small guanosine triphosphatase (GTPase) RhoA, enabling Gαq/11-coupled G protein–coupled receptors (GPCRs) to control downstream events, such as cell motility and gene transcription. This conserved signal transduction axis is crucial for tumor growth in uveal melanoma. Previous studies indicate that the GEF activity of the TrioC module is autoinhibited, with release of autoinhibition upon Gαq/11binding. Here, we determined the crystal structure of TrioC in its basal state and found that the pleckstrin homology (PH) domain interacts with the Dbl homology (DH) domain in a manner that occludes the Rho GTPase binding site, thereby suggesting the molecular basis of TrioC autoinhibition. Biochemical and biophysical assays revealed that disruption of the autoinhibited conformation destabilized and activated the TrioC module in vitro. Last, mutations in the DH-PH interface found in patients with cancer activated TrioC and, in the context of full-length Trio, led to increased abundance of guanosine triphosphate–bound RhoA (RhoA·GTP) in human cells. These mutations increase mitogenic signaling through the RhoA axis and, therefore, may represent cancer drivers operating in a Gαq/11-independent manner.

scholarly journals Gef1p, a New Guanine Nucleotide Exchange Factor for Cdc42p, Regulates Polarity inSchizosaccharomyces pombe

2003 ◽  
Vol 14 (1) ◽  
pp. 313-323 ◽  
Author(s):  
Pedro M. Coll ◽  
Yadira Trillo ◽  
Amagoia Ametzazurra ◽  
Pilar Perez
Keyword(s):  
Cell Morphology ◽  
Rho Gtpases ◽  
Genetic Interaction ◽  
Guanine Nucleotide Exchange Factor ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

Schizosaccharomyces pombe cdc42+regulates cell morphology and polarization of the actin cytoskeleton. Scd1p/Ral1p is the only described guanine nucleotide exchange factor (GEF) for Cdc42p in S. pombe. We have identified a new GEF, named Gef1p, specifically regulating Cdc42p. Gef1p binds to inactive Cdc42p but not to other Rho GTPases in two-hybrid assays. Overexpression of gef1+increases specifically the GTP-bound Cdc42p, and Gef1p is capable of stimulating guanine nucleotide exchange of Cdc42p in vitro. Overexpression ofgef1+causes changes in cell morphology similar to those caused by overexpression of the constitutively active cdc42G12V allele. Gef1p localizes to the septum. gef1+deletion is viable but causes a mild cell elongation and defects in bipolar growth and septum formation, suggesting a role for Gef1p in the control of cell polarity and cytokinesis. The double mutant gef1Δ scd1Δ is not viable, indicating that they share an essential function as Cdc42p activators. However, both deletion and overexpression of either gef1+orscd1+causes different morphological phenotypes, which suggest different functions. Genetic evidence revealed a link between Gef1p and the signaling pathway of Shk1/Orb2p and Orb6p. In contrast, no genetic interaction between Gef1p and Shk2p-Mkh1p pathway was observed.

scholarly journals Identification of a Novel Guanine Nucleotide Exchange Factor for the Rho GTPase

1996 ◽  
Vol 271 (41) ◽  
pp. 25452-25458 ◽  
Author(s):  
Matthew J. Hart ◽  
Sanju Sharma ◽  
Nadia elMasry ◽  
Rong-Guo Qiu ◽  
Peter McCabe ◽  
...  
Keyword(s):  
Rho Gtpase ◽  
Guanine Nucleotide Exchange Factor ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

The guanine-nucleotide-exchange factor P-Rex1 is activated by protein phosphatase 1α

2012 ◽  
Vol 443 (1) ◽  
pp. 173-183 ◽  
Author(s):  
Mark A. Barber ◽  
Annick Hendrickx ◽  
Monique Beullens ◽  
Hugo Ceulemans ◽  
David Oxley ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Guanine Nucleotide Exchange Factor ◽  
Site Directed Mutagenesis ◽  
Similar Degree ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

P-Rex1 is a GEF (guanine-nucleotide-exchange factor) for the small G-protein Rac that is activated by PIP3 (phosphatidylinositol 3,4,5-trisphosphate) and Gβγ subunits and inhibited by PKA (protein kinase A). In the present study we show that PP1α (protein phosphatase 1α) binds P-Rex1 through an RVxF-type docking motif. PP1α activates P-Rex1 directly in vitro, both independently of and additively to PIP3 and Gβγ. PP1α also substantially activates P-Rex1 in vivo, both in basal and PDGF (platelet-derived growth factor)- or LPA (lysophosphatidic acid)-stimulated cells. The phosphatase activity of PP1α is required for P-Rex1 activation. PP1β, a close homologue of PP1α, is also able to activate P-Rex1, but less effectively. PP1α stimulates P-Rex1-mediated Rac-dependent changes in endothelial cell morphology. MS analysis of wild-type P-Rex1 and a PP1α-binding-deficient mutant revealed that endogenous PP1α dephosphorylates P-Rex1 on at least three residues, Ser834, Ser1001 and Ser1165. Site-directed mutagenesis of Ser1165 to alanine caused activation of P-Rex1 to a similar degree as did PP1α, confirming Ser1165 as a dephosphorylation site important in regulating P-Rex1 Rac-GEF activity. In summary, we have identified a novel mechanism for direct activation of P-Rex1 through PP1α-dependent dephosphorylation.

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 structure of a guanine nucleotide exchange factor encoded by the scrub typhus pathogenOrientia tsutsugamushi

2020 ◽  
Vol 117 (48) ◽  
pp. 30380-30390
Author(s):  
Christopher Lim ◽  
Jason M. Berk ◽  
Alyssa Blaise ◽  
Josie Bircher ◽  
Anthony J. Koleske ◽  
...  
Keyword(s):  
Rho Gtpases ◽  
Sequence Similarity ◽  
Ectopic Expression ◽  
Guanine Nucleotide Exchange Factor ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

Rho family GTPases regulate an array of cellular processes and are often modulated by pathogens to promote infection. Here, we identify a cryptic guanine nucleotide exchange factor (GEF) domain in the OtDUB protein encoded by the pathogenic bacteriumOrientia tsutsugamushi. A proteomics-based OtDUB interaction screen identified numerous potential host interactors, including the Rho GTPases Rac1 and Cdc42. We discovered a domain in OtDUB with Rac1/Cdc42 GEF activity (OtDUBGEF), with higher activity toward Rac1 in vitro. While this GEF bears no obvious sequence similarity to known GEFs, crystal structures of OtDUBGEFalone (3.0 Å) and complexed with Rac1 (1.7 Å) reveal striking convergent evolution, with a unique topology, on a V-shaped bacterial GEF fold shared with other bacterial GEF domains. Structure-guided mutational analyses identified residues critical for activity and a mechanism for nucleotide displacement. Ectopic expression of OtDUB activates Rac1 preferentially in cells, and expression of the OtDUBGEFalone alters cell morphology. Cumulatively, this work reveals a bacterial GEF within the multifunctional OtDUB that co-opts host Rac1 signaling to induce changes in cytoskeletal structure.

scholarly journals Lck regulates Vav activation of members of the Rho family of GTPases.

1997 ◽  
Vol 17 (3) ◽  
pp. 1346-1353 ◽  
Author(s):  
J Han ◽  
B Das ◽  
W Wei ◽  
L Van Aelst ◽  
R D Mosteller ◽  
...  
Keyword(s):  
Animal Cell ◽  
Guanine Nucleotide Exchange Factor ◽  
Biological Data ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Rho Family

Vav is a member of a family of oncogene proteins that share an approximately 250-amino-acid motif called a Dbl homology domain. Paradoxically, Dbl itself and other proteins containing a Dbl domain catalyze GTP-GDP exchange for Rho family proteins, whereas Vav has been reported to catalyze GTP-GDP exchange for Ras proteins. We present Saccharomyces cerevisiae genetic data, in vitro biochemical data, and animal cell biological data indicating that Vav is a guanine nucleotide exchange factor for Rho-related proteins, but in similar genetic and biochemical experiments we fail to find evidence that Vav is a guanine nucleotide exchange factor for Ras. Further, we present data indicating that the Lck kinase activates the guanine nucleotide exchange factor and transforming activity of Vav.

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