scholarly journals Ect2 and MgcRacGAP regulate the activation and function of Cdc42 in mitosis

2005 ◽  
Vol 168 (2) ◽  
pp. 221-232 ◽  
Author(s):  
Fabian Oceguera-Yanez ◽  
Kazuhiro Kimura ◽  
Shingo Yasuda ◽  
Chiharu Higashida ◽  
Toshio Kitamura ◽  
...  
Keyword(s):  
Rna Interference ◽  
Rho Gtpase ◽  
Dominant Negative ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Microtubule Attachment ◽  
Nucleotide Exchange Factor ◽  
Spindle Microtubules ◽  
And Function

Although Rho regulates cytokinesis, little was known about the functions in mitosis of Cdc42 and Rac. We recently suggested that Cdc42 works in metaphase by regulating bi-orient attachment of spindle microtubules to kinetochores. We now confirm the role of Cdc42 by RNA interference and identify the mechanisms for activation and down-regulation of Cdc42. Using a pull-down assay, we found that the level of GTP-Cdc42 elevates in metaphase, whereas the level of GTP-Rac does not change significantly in mitosis. Overexpression of dominant-negative mutants of Ect2 and MgcRacGAP, a Rho GTPase guanine nucleotide exchange factor and GTPase activating protein, respectively, or depletion of Ect2 by RNA interference suppresses this change of GTP-Cdc42 in mitosis. Depletion of Ect2 also impairs microtubule attachment to kinetochores and causes prometaphase delay and abnormal chromosomal segregation, as does depletion of Cdc42 or expression of the Ect2 and MgcRacGAP mutants. These results suggest that Ect2 and MgcRacGAP regulate the activation and function of Cdc42 in mitosis.

scholarly journals GM130-dependent Control of Cdc42 Activity at the Golgi Regulates Centrosome Organization

2009 ◽  
Vol 20 (4) ◽  
pp. 1192-1200 ◽  
Author(s):  
Andrew Kodani ◽  
Irene Kristensen ◽  
Lan Huang ◽  
Christine Sütterlin
Keyword(s):  
Golgi Apparatus ◽  
Mammalian Cells ◽  
Rho Gtpase ◽  
Nucleotide Exchange ◽  
Interacting Protein ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Golgi Protein ◽  
And Function

The physical proximity of the Golgi apparatus and the centrosome is a unique feature of mammalian cells whose functional significance is only poorly understood. Here, we demonstrate that the previously described regulation of centrosome organization and function by the Golgi protein, GM130, involves a Golgi-associated complex consisting of GM130, the Rho GTPase, Cdc42, and its guanine nucleotide exchange factor, Tuba. We identified Tuba as a novel GM130-interacting protein and showed that this association controls Tuba-mediated activation of Cdc42 at the Golgi apparatus. Blocking either Tuba or Cdc42 activity reproduced the GM130 depletion phenotype of aberrant, nonfunctional centrosomes. Expression of constitutively active Cdc42 bypassed the requirement for GM130 in centrosome regulation, indicating that Cdc42 functions downstream of GM130. Our studies demonstrate that Cdc42 has a novel role in controlling centrosome organization in unstimulated cells in addition to its known function as a regulator of centrosome reorientation in stimulated cells. This first description of a regulatory pathway between the Golgi apparatus and the interphase centrosome that complements the known role of Golgi proteins in controlling spindle formation during mitosis and may provide an explanation for the pericentriolar position of the mammalian Golgi apparatus during interphase.

scholarly journals ErbB2 directly activates the exchange factor Dock7 to promote Schwann cell migration

2008 ◽  
Vol 181 (2) ◽  
pp. 351-365 ◽  
Author(s):  
Junji Yamauchi ◽  
Yuki Miyamoto ◽  
Jonah R. Chan ◽  
Akito Tanoue
Keyword(s):  
Cell Migration ◽  
Schwann Cell ◽  
Rho Gtpase ◽  
Morphological Changes ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Schwann Cell Migration ◽  
Subsequent Activation

The cellular events that precede myelination in the peripheral nervous system require rapid and dynamic morphological changes in the Schwann cell. These events are thought to be mainly controlled by axonal signals. But how signals on the axons are coordinately organized and transduced to promote proliferation, migration, radial sorting, and myelination is unknown. We describe that the axonal signal neuregulin-1 (NRG1) controls Schwann cell migration via activation of the atypical Dock180-related guanine nucleotide exchange factor (GEF) Dock7 and subsequent activation of the Rho guanine triphosphatases (GTPases) Rac1 and Cdc42 and the downstream c-Jun N-terminal kinase. We show that the NRG1 receptor ErbB2 directly binds and activates Dock7 by phosphorylating Tyr-1118. Dock7 knockdown, or expression of Dock7 harboring the Tyr-1118–to–Phe mutation in Schwann cells, attenuates the effects of NRG1. Thus, Dock7 functions as an intracellular substrate for ErbB2 to promote Schwann cell migration. This provides an unanticipated mechanism through which ligand-dependent tyrosine phosphorylation can trigger the activation of Rho GTPase-GEFs of the Dock180 family.

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 PDZRhoGEF and myosin II localize RhoA activity to the back of polarizing neutrophil-like cells

2007 ◽  
Vol 179 (6) ◽  
pp. 1141-1148 ◽  
Author(s):  
Kit Wong ◽  
Alexandra Van Keymeulen ◽  
Henry R. Bourne
Keyword(s):  
Rho Gtpase ◽  
Myosin Ii ◽  
Nucleotide Exchange ◽  
Dependent Protein Kinase ◽  
Rhoa Activity ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Long Tails ◽  
Dependent Protein ◽  
Atpase Inhibition

Chemoattractants such as formyl-Met-Leu-Phe (fMLP) induce neutrophils to polarize by triggering divergent pathways that promote formation of a protrusive front and contracting back and sides. RhoA, a Rho GTPase, stimulates assembly of actomyosin contractile complexes at the sides and back. We show here, in differentiated HL60 cells, that PDZRhoGEF (PRG), a guanine nucleotide exchange factor (GEF) for RhoA, mediates RhoA-dependent responses and determines their spatial distribution. As with RNAi knock-down of PRG, a GEF-deleted PRG mutant blocks fMLP-dependent RhoA activation and causes neutrophils to exhibit multiple fronts and long tails. Similarly, inhibition of RhoA, a Rho-dependent protein kinase (ROCK), or myosin II produces the same morphologies. PRG inhibition reduces or mislocalizes monophosphorylated myosin light chains in fMLP-stimulated cells, and myosin II ATPase inhibition reciprocally disrupts normal localization of PRG. We propose a cooperative reinforcing mechanism at the back of cells, in which PRG, RhoA, ROCK, myosin II, and actomyosin spatially cooperate to consolidate attractant-induced contractility and ensure robust cell polarity.

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