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Vedrana Filić, Maja Marinović, Marko Šoštar, Igor Weber
NME proteins are reported to influence signal transduction activity of small GTPases from the Ras superfamily by diverse mechanisms in addition to their generic NDP kinase activity, which replenishes the cytoplasmic pool of GTP. Comprehensive evidence shows that NME proteins modulate the activity of Ras GTPases, in particular members of the Rho family, via binding to their major activators GEFs. Direct interaction between several NMEs and Ras GTPases were also indicated in vitro and in vivo. These modes of regulation are mainly independent of the NME's kinase activity...
February 12, 2018: Laboratory Investigation; a Journal of Technical Methods and Pathology
Wenxin Kou, Xu Xu, Shuya Ji, Mengyao Chen, Dongdong Liu, Kai Wang, Jianhui Zhuang, Qing Yu, Qian Zhao, Yawei Xu, Hongli Zhang, Wenhui Peng
T-Cell Lymphoma Invasion and Metastasis 1 (Tiam1) is a specific nucleotide exchange factor (GEF) that can activate Rho-like GTPase and Rac1 and regulate various cellular processes, including cell cycle progression and cell migration. The roles of Tiam1 in vascular intimal hyperplasia, especially in vascular smooth muscle cell proliferation and migration, are not fully understood. In this study, we investigated the effect of Tiam1 on vascular intimal hyperplasia in a carotid artery ligation model and human aortic smooth muscle cells (HASMCs)...
February 9, 2018: Biochemical and Biophysical Research Communications
Takahiro Tomino, Hirotada Tajiri, Takaaki Tatsuguchi, Takahiro Shirai, Kounosuke Oisaki, Shigeki Matsunaga, Fumiyuki Sanematsu, Daiji Sakata, Tomoharu Yoshizumi, Yoshihiko Maehara, Motomu Kanai, Jean-François Cote, Yoshinori Fukui, Takehito Uruno
Rac1 is a member of the Rho family of small GTPases that regulates cytoskeletal reorganization, membrane polarization, cell migration and proliferation. Recently, a self-activating mutation of Rac1, Rac1P29S, has been identified as a recurrent somatic mutation frequently found in sun-exposed melanomas, which possesses increased inherent GDP/GTP exchange activity and cell transforming ability. However, the role of cellular Rac1-interacting proteins in the transforming potential of Rac1P29S remains unclear. We found that the catalytic domain of DOCK1, a Rac-specific guanine nucleotide exchange factor (GEF) implicated in malignancy of a variety of cancers, can greatly accelerate the GDP/GTP exchange of Rac1P29S...
February 9, 2018: Biochemical and Biophysical Research Communications
Mirela Maier, Cindy Baldwin, Lamine Aoudjit, Tomoko Takano
Nephrotic syndrome is a kidney disease featured by heavy proteinuria. It is caused by injury to the specialized epithelial cells called "podocytes" within the filtration unit of the kidney, glomerulus. Previous studies showed that hyperactivation of the RhoGTPase, Rac1, in podocytes causes podocyte injury and glomerulosclerosis (accumulation of extracellular matrix in the glomerulus). However, the mechanism by which Rac1 is activated during podocyte injury is unknown. Trio is a guanine nucleotide exchange factor (GEF) known to activate Rac1...
February 6, 2018: International Journal of Molecular Sciences
Willem-Jan Pannekoek, Marjolein J Vliem, Johannes L Bos
Epac1 and Rap1 mediate cAMP-induced tightening of endothelial junctions. We have previously found that one of the mechanisms is the inhibition of Rho-mediated tension in radial stress fibers by recruiting the RhoGAP ArhGAP29 in a complex containing the Rap1 effectors Rasip1 and Radil. However, other mechanisms have been proposed as well, most notably the induction of tension in circumferential actin cables by Cdc42 and its GEF FGD5. Here, we have investigated how Rap1 controls FGD5/Cdc42 and how this interconnects with Radil/Rasip1/ArhGAP29...
February 1, 2018: Small GTPases
Katharina Schrade, Jessica Tröger, Adeeb Eldahshan, Kerstin Zühlke, Kamal R Abdul Azeez, Jonathan M Elkins, Martin Neuenschwander, Andreas Oder, Mohamed Elkewedi, Sarah Jaksch, Karsten Andrae, Jinliang Li, Joao Fernandes, Paul Markus Müller, Stephan Grunwald, Stephen F Marino, Tanja Vukićević, Jenny Eichhorst, Burkhard Wiesner, Marcus Weber, Michael Kapiloff, Oliver Rocks, Oliver Daumke, Thomas Wieland, Stefan Knapp, Jens Peter von Kries, Enno Klussmann
Stimulation of renal collecting duct principal cells with antidiuretic hormone (arginine-vasopressin, AVP) results in inhibition of the small GTPase RhoA and the enrichment of the water channel aquaporin-2 (AQP2) in the plasma membrane. The membrane insertion facilitates water reabsorption from primary urine and fine-tuning of body water homeostasis. Rho guanine nucleotide exchange factors (GEFs) interact with RhoA, catalyze the exchange of GDP for GTP and thereby activate the GTPase. However, GEFs involved in the control of AQP2 in renal principal cells are unknown...
2018: PloS One
Javier Robles-Valero, L Francisco Lorenzo-Martín, Isabel Fernández-Pisonero, Xosé R Bustelo
Rho GDP/GTP exchange factors (GEFs), the enzymes that trigger the stimulation of Rho GTPases during cell signaling, are widely deemed as potential therapeutic targets owing to their protumorigenic functions. However, the sparse use of animal models has precluded a full understanding of their pathophysiological roles at the organismal level. In a recent article in Cancer Cell, we have reported that the Vav1 GEF unexpectedly acts as a tumor suppressor by mediating the noncatalytic nucleation of cytoplasmic complexes between the E3 ubiquitin ligase Cbl-b and the active Notch1 intracellular domain (ICN1)...
January 9, 2018: Small GTPases
Campbell D Lawson, Anne J Ridley
Cell migration is dependent on the dynamic formation and disassembly of actin filament-based structures, including lamellipodia, filopodia, invadopodia, and membrane blebs, as well as on cell-cell and cell-extracellular matrix adhesions. These processes all involve Rho family small guanosine triphosphatases (GTPases), which are regulated by the opposing actions of guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Rho GTPase activity needs to be precisely tuned at distinct cellular locations to enable cells to move in response to different environments and stimuli...
December 12, 2017: Journal of Cell Biology
Eun-Kyoung Choi, Jae-Gyu Kim, Hee-Jun Kim, Jung-Yoon Cho, Hwalrim Jeong, Yohan Park, Rokibul Islam, Cuong Kim Cap, Jae-Bong Park
Rho GTPases play significant roles in cellular function and their activity is regulated by guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs), providing activation and inactivation of these GTPases, respectively. Active GTP-bound form of RhoA activates its effector proteins while the inactive GDP-bound form of RhoA exists in a RhoA-RhoGDI (guanine nucleotide dissociation inhibitor) complex in the cytosol. In particular, IκB kinase γ IKKγ/NF-κB essential modulator (NEMO) plays a role as a GDI displacement factor (GDF) for RhoA activation through binding to RhoA-RhoGDI complex...
December 3, 2017: Small GTPases
Richard G Hodge, Anne J Ridley
Rho GTPases play central roles in a wide variety of cellular processes, including cytoskeletal dynamics, cell adhesion and cell polarity. RhoU and RhoV are Rho GTPases that have some atypical properties compared with classical Rho family members, such as the presence of N- and C-terminal extension regions, unusual GDP/GTP cycling and post-translational modification by palmitoylation but not prenylation. Their activity and localization is regulated by the N-terminal and C-terminal regions, and so far no GEFs or GAPs have been identified for them...
November 30, 2017: Small GTPases
Noah Fine, Ioannis D Dimitriou, Robert Rottapel
Neutrophils in circulation experience significant shear forces due to blood flow when they tether to the vascular endothelium. Biochemical and biophysical responses of neutrophils to the physical force of flowing blood modulate their behavior and promote tissue recruitment under pro-inflammatory conditions. Neutrophil mechanotransduction responses occur through mechanisms that are not yet fully understood. In our recent work, we showed that GEF-H1, a RhoA specific guanine nucleotide exchange factor (GEF), is required to maintain neutrophil motility and migration in response to shear stress...
November 30, 2017: Small GTPases
Yan Zuo, John d'Aigle, Anjali Chauhan, Jeffrey A Frost
Macrophages are innate immune cells that constantly patrol an organism to fulfill protective and homeostatic roles. Previous studies have shown that Rho GTPase activity is required for macrophage mobility, yet the roles of upstream regulatory proteins controlling Rho GTPase function in these cells are not well defined. Previously we have shown that the RhoA GEF Net1 is required for human breast cancer cell motility and extracellular matrix invasion. To assess the role of Net1 in macrophage motility, we isolated bone marrow macrophage (BMM) precursors from wild type and Net1 knockout mice...
December 31, 2017: Small GTPases
Anita Kovacs-Kasa, Kyung Mi Kim, Mary Cherian-Shaw, Stephen M Black, David J Fulton, Alexander D Verin
We have previously shown that Gs-coupled adenosine receptors (A2a) are primarily involved in adenosine-induced human pulmonary artery endothelial cell (HPAEC) barrier enhancement. However, the downstream events that mediate the strengthening of the endothelial cell (EC) barrier via adenosine signaling are largely unknown. In the current study we tested the overall hypothesis that adenosine-induced Rac1 activation and EC barrier enhancement is mediated by Gs-dependent stimulation of cAMP-dependent Epac1-mediated signaling cascades...
November 23, 2017: Journal of Cellular Physiology
Javier Robles-Valero, L Francisco Lorenzo-Martín, Mauricio Menacho-Márquez, Isabel Fernández-Pisonero, Antonio Abad, Mireia Camós, María L Toribio, Lluis Espinosa, Anna Bigas, Xosé R Bustelo
Rho guanine exchange factors (GEFs), the enzymes that stimulate Rho GTPases, are deemed as potential therapeutic targets owing to their protumorigenic functions. However, the understanding of the spectrum of their pathobiological roles in tumors is still very limited. We report here that the GEF Vav1 unexpectedly possesses tumor-suppressor functions in immature T cells. This function entails the noncatalytic nucleation of complexes between the ubiquitin ligase Cbl-b and the intracellular domain of Notch1 (ICN1) that favors ICN1 ubiquitinylation and degradation...
November 13, 2017: Cancer Cell
Aiko Iwata-Otsubo, Alyssa L Ritter, Brooke Weckselbatt, Nicole R Ryan, David Burgess, Laura K Conlin, Kosuke Izumi
Dedicator of cytokinesis (DOCK) family are evolutionary conserved guanine nucleotide exchange factors (GEFs) for the Rho GTPases, Rac, and Cdc42. DOCK3 functions as a GEF for Rac1, and plays an important role in promoting neurite and axonal growth by stimulating actin dynamics and microtubule assembly pathways in the central nervous system. Here we report a boy with developmental delay, hypotonia, and ataxia due to biallelic DOCK3 deletion. Chromosomal single nucleotide polymorphism (SNP) microarray analysis detected a 170 kb homozygous deletion including exons 6-12 of the DOCK3 gene at 3p21...
November 12, 2017: American Journal of Medical Genetics. Part A
Aniko Keller-Pinter, Bettina Ughy, Monika Domoki, Aladar Pettko-Szandtner, Tamas Letoha, Jozsef Tovari, Jozsef Timar, Laszlo Szilak
The small GTPases of the Rho family comprising RhoA, Rac1 and Cdc42 function as molecular switches controlling several essential biochemical pathways in eukaryotic cells. Their activity is cycling between an active GTP-bound and an inactive GDP-bound conformation. The exchange of GDP to GTP is catalyzed by guanine nucleotide exchange factors (GEFs). Here we report a novel regulatory mechanism of Rac1 activity, which is controlled by a phosphomimetic (Ser179Glu) mutant of syndecan-4 (SDC4). SDC4 is a ubiquitously expressed transmembrane, heparan sulfate proteoglycan...
2017: PloS One
Wei Chen, Yue Zhao, Xian C Li, Jacek Z Kubiak, Rafik M Ghobrial, Malgorzata Kloc
Macrophages play crucial role in tissue homeostasis and the innate and adaptive immune response. Depending on the state of activation macrophages acquire distinct phenotypes that depend on actin, which is regulated by small GTPase RhoA. The naive M0 macrophages are slightly elongated, pro-inflammatory M1 are round and M2 anti-inflammatory macrophages are elongated. We showed previously that interference with RhoA pathway (RhoA deletion or RhoA/ROCK kinase inhibition) disrupted actin, produced extremely elongated (hummingbird) macrophage phenotype and inhibited macrophage movement toward transplanted hearts...
October 20, 2017: International Journal of Biochemistry & Cell Biology
Melanie Graessl, Johannes Koch, Abram Calderon, Dominic Kamps, Soumya Banerjee, Tomáš Mazel, Nina Schulze, Jana Kathrin Jungkurth, Rutuja Patwardhan, Djamschid Solouk, Nico Hampe, Bernd Hoffmann, Leif Dehmelt, Perihan Nalbant
Rho GTPase-based signaling networks control cellular dynamics by coordinating protrusions and retractions in space and time. Here, we reveal a signaling network that generates pulses and propagating waves of cell contractions. These dynamic patterns emerge via self-organization from an activator-inhibitor network, in which the small GTPase Rho amplifies its activity by recruiting its activator, the guanine nucleotide exchange factor GEF-H1. Rho also inhibits itself by local recruitment of actomyosin and the associated RhoGAP Myo9b...
December 4, 2017: Journal of Cell Biology
Katharine R Smith, Dipen Rajgor, Jonathan G Hanley
Brain ischemia causes oxygen and glucose deprivation (OGD) in neurons, triggering a cascade of events leading to synaptic accumulation of glutamate. Excessive activation of glutamate receptors causes excitotoxicity and delayed cell death in vulnerable neurons. Following global cerebral ischemia, hippocampal CA1 pyramidal neurons are more vulnerable to injury than their cortical counterparts, but the mechanisms that underlie this difference are unclear. Signaling via Rho-family small GTPases, their upstream guanine nucleotide exchange factors, and GTPase-activating proteins (GAPs) is differentially dysregulated in response to OGD/ischemia in hippocampal and cortical neurons...
December 8, 2017: Journal of Biological Chemistry
Laura S Schmidt, W Marston Linehan
Germline mutations in the novel tumor suppressor gene FLCN are responsible for the autosomal dominant inherited disorder Birt-Hogg-Dubé (BHD) syndrome that predisposes to fibrofolliculomas, lung cysts and spontaneous pneumothorax, and an increased risk for developing kidney tumors. Although the encoded protein, folliculin (FLCN), has no sequence homology to known functional domains, x-ray crystallographic studies have shown that the C-terminus of FLCN has structural similarity to DENN (differentially expressed in normal cells and neoplasia) domain proteins that act as guanine nucleotide exchange factors (GEFs) for small Rab GTPases...
January 15, 2018: Gene
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