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1.
The Rif and RhoD proteins belong to the Rho subfamily of small GTPases. Rif and RhoD have for too long remained in the shadows of the better known Rho GTPases Cdc42, Rac1 and RhoA. With this review article, our aim is to provide the currently available information regarding Rif and RhoD. Taken together, the data available to date indicate that Rif and RhoD have unique roles in the regulation of actin dynamics, and that RhoD can link actin reorganisation to endosomal vesicle transport. 相似文献
2.
The Rho family GTPases Cdc42, Rac1 and RhoA control many of the changes in the actin cytoskeleton that are triggered when growth factor receptors and integrins bind their ligands [1] [2]. Rac1 and Cdc42 stimulate the formation of protrusive structures such as membrane ruffles, lamellipodia and filopodia. RhoA regulates contractility and assembly of actin stress fibers and focal adhesions. Although prolonged integrin engagement can stimulate RhoA [3] [4] [5], regulation of this GTPase by early integrin-mediated signals is poorly understood. Here we show that integrin engagement initially inactivates RhoA, in a c-Src-dependent manner, but has no effect on Cdc42 or Rac1 activity. Additionally, early integrin signaling induces activation and tyrosine phosphorylation of p190RhoGAP via a mechanism that requires c-Src. Dynamic modulation of RhoA activity appears to have a role in motility, as both inhibition and activation of RhoA hinder migration [6] [7] [8]. Transient suppression of RhoA by integrins may alleviate contractile forces that would otherwise impede protrusion at the leading edge of migrating cells. 相似文献
3.
The TRE17 oncogene encodes a component of a novel effector pathway for Rho GTPases Cdc42 and Rac1 and stimulates actin remodeling 总被引:6,自引:0,他引:6
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The Rho family GTPases Cdc42 and Rac1 play fundamental roles in transformation and actin remodeling. Here, we demonstrate that the TRE17 oncogene encodes a component of a novel effector pathway for these GTPases. TRE17 coprecipitated specifically with the active forms of Cdc42 and Rac1 in vivo. Furthermore, the subcellular localization of TRE17 was dramatically regulated by these GTPases and mitogens. Under serum-starved conditions, TRE17 localized predominantly to filamentous structures within the cell. Epidermal growth factor (EGF) induced relocalization of TRE17 to the plasma membrane in a Cdc42-/Rac1-dependent manner. Coexpression of activated alleles of Cdc42 or Rac1 also caused complete redistribution of TRE17 to the plasma membrane, where it partially colocalized with the GTPases in filopodia and ruffles, respectively. Membrane recruitment of TRE17 by EGF or the GTPases was dependent on actin polymerization. Finally, we found that a C-terminal truncation mutant of TRE17 induced the accumulation of cortical actin, mimicking the effects of activated Cdc42. Together, these results identify TRE17 as part of a novel effector complex for Cdc42 and Rac1, potentially contributing to their effects on actin remodeling. The present study provides insights into the regulation and cellular function of this previously uncharacterized oncogene. 相似文献
4.
《Cell communication & adhesion》2013,20(2-3):237-245
The GTP-binding proteins, Rho, Rac and Cdc42 are known to regulate actin organisation. Rho induces the assembly of contractile actin-based microfilaments such as stress fibres, Rac regulates the formation of membrane ruffles and lamellipodia, and Cdc42 activation is necessary for the formation of filopodia. In addition, all three proteins can also regulate the assembly of integrin-containing focal adhesion complexes. The orchestration of these distinct cytoskeletal changes is thought to form the basis of the co-ordination of cell motility and we have investigated the roles of Rho family proteins in migration using a model system. We have found that in the macrophage cell line Bacl, the cytokine CSF-1 rapidly induces actin reorganisation: it stimulates the formation of filopodia, lamellipodia and membrane ruffles, as well as the appearance of fine actin cables within the cell. We have shown that Cdc42, Rac and Rho regulate the CSF-1 induced formation of these distinct actin filament-based structures. Using a cell tracking procedure we found that both Rho and Rac were required for CSF-1 stimulated cell translocation. In contrast, inhibition of Cdc42 does not prevent macrophages migrating in response to CSF-1, but does prevent recognition of a CSF-1 concentration gradient, so that cells now migrate randomly rather than up the gradient of this chemotactic cytokine. This implies that Cdc42, and thus probably filopodia, are required for gradient sensing and cell polarisation in macrophages. 相似文献
5.
6.
Aoki J Katoh H Mori K Negishi M 《Biochemical and biophysical research communications》2000,278(3):604-608
Rho family GTPases have been shown to be involved in the regulation of neuronal cell morphology, including neurite extension and retraction. Rho activation leads to neurite retraction and cell rounding, whereas Rac and Cdc42 are implicated in the promotion of filopodia and lamellipodia formation in growth cones and, therefore, in neurite extension. In this study, we examined the morphological role of Rnd1, a new member of Rho family GTPases, in PC12 cells, and found that expression of Rnd1 by itself caused the formation of many neuritic processes from the cell body with disruption of the cortical actin filaments, the processes having microtubules but few filamentous actin and neurofilaments. Treatment with cytochalasin D, an inhibitor of actin polymerization, could mimic the effects of expression of Rnd1, in that this inhibitor disrupted the cortical actin filaments and induced the formation of many thin processes containing microtubules. The process formation induced by Rnd1 was inhibited by dominant negative Rac1. These results suggest that Rnd1 induces the Rac-dependent neuritic process formation in part by disruption of the cortical actin filaments. 相似文献
7.
Eukaryotic cells produce a variety of specialized actin-rich surface protrusions. These include filopodia-thin, highly dynamic projections that help cells to sense their external environment. Filopodia consist of parallel filaments of actin, bundled by actin crosslinking proteins. The filaments are oriented with their rapidly growing "barbed" ends at the protruding tip and their slowly growing "pointed" ends at the base. Extension occurs by polymerization at the tip and is controlled by regulation of filament capping. The Rho GTPase Cdc42 is a key mediator of filopodia formation, which it regulates through binding CRIB domain-containing effectors. Cdc42 binds and activates the WASP proteins, which in turn activate the actin-nucleating complex Arp2/3. It also binds and activates IRSp53, which recruits the Ena/WASP family protein Mena to the filopodial tip and protects elongating actin filaments from capping. Previously, we identified another Rho family GTPase, Rif, as a potent stimulator of filopodial protrusion through a mechanism that does not require Cdc42. Here we characterize the differences between filopodia induced by these two small GTPases and show that the Rif effector in this pathway is the Diaphanous-related formin mDia2. Thus, Rif and Cdc42 represent two distinct routes to the induction of filopodia-producing structures with both shared and unique properties. 相似文献
8.
Coactivation of Rac1 and Cdc42 at lamellipodia and membrane ruffles induced by epidermal growth factor
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Kurokawa K Itoh RE Yoshizaki H Nakamura YO Matsuda M 《Molecular biology of the cell》2004,15(3):1003-1010
A major function of Rho-family GTPases is to regulate the organization of the actin cytoskeleton; filopodia, lamellipodia, and stress fiber are regarded as typical phenotypes of the activated Cdc42, Rac, and Rho, respectively. Using probes based on fluorescent resonance energy transfer, we report on the spatiotemporal regulation of Rac1 and Cdc42 at lamellipodia and membrane ruffles. In epidermal growth factor (EGF)-stimulated Cos1 and A431 cells, both Rac1 and Cdc42 were activated diffusely at the plasma membrane, followed by lamellipodial protrusion and membrane ruffling. Although Rac1 activity subsided rapidly, Cdc42 activity was sustained at lamellipodia. A critical role of Cdc42 in these EGF-induced morphological changes was demonstrated as follows. First, phorbol 12-myristate 13-acetate, which activated Rac1 but not Cdc42, could not induce full-grown lamellipodia in Cos1 cells. Second, a GTPase-activating protein for Cdc42, KIAA1204/CdGAP, inhibited lamellipodial protrusion and membrane ruffling without interfering with Rac1 activation. Third, expression of the Cdc42-binding domain of N-WASP inhibited the EGF-induced morphological changes. Therefore, Rac1 and Cdc42 seem to synergistically induce lamellipodia and membrane ruffles in EGF-stimulated Cos1 cells and A431 cells. 相似文献
9.
Braga V 《Experimental cell research》2000,261(1):83-90
Cadherins are cell-cell adhesion receptors that are essential for the establishment of the epithelial cell shape and maintenance of the differentiated epithelial phenotype. In order to show efficient adhesion, cadherin receptors require an association with actin filaments and the activity of RHO proteins. The RHO family of small GTPases is primarily involved in the reorganization of the cytoskeleton. In different cell types, each member of the family can induce specific types of organization of actin filaments: stress fibers (Rho), lamellae/ruffles (Rac), or filopodia (Cdc42). This review focuses on how the function of small GTPases may impinge on the regulation of cadherin-dependent adhesion. In particular, it discusses the impact that the above cytoskeletal structures induced by RHO proteins have on the development of epithelial morphology. Finally, the participation of small GTPase-interacting proteins is considered during the remodeling of cell shape that follows cell-cell contact formation. 相似文献
10.
11.
DEF6, a novel PH-DH-like domain protein, is an upstream activator of the Rho GTPases Rac1, Cdc42, and RhoA 总被引:1,自引:0,他引:1
In this paper, we describe the characterization of DEF6, a novel PH-DH-like protein related to SWAP-70 that functions as an upstream activator of Rho GTPases. In NIH 3T3 cells, stimulation of the PI 3-kinase signaling pathway with either H2O2 or platelet-derived growth factor (PDGF) resulted in the translocation of an overexpressed DEF6-GFP fusion protein to the cell membrane and induced the formation of filopodia and lamellipodia. In contrast to full-length DEF6, expression of the DH-like (DHL) domain as a GFP fusion protein potently induced actin polymerization, including stress fiber formation in COS-7 cells, in the absence of PI 3-kinase signaling, indicating that it was constitutively active. The GTP-loading of Cdc42 was strongly enhanced in NIH 3T3 cells expressing the DH domain while filopodia formation, membrane ruffling, and stress fiber formation could be inhibited by the co-expression of the DH domain with dominant negative mutants of either N17Rac1, N17Cdc42, or N19RhoA, respectively. This indicated that DEF6 acts upstream of the Rho GTPases resulting in the activation of the Cdc42, Rac1, and RhoA signaling pathways. In vitro, DEF6 specifically interacted with Rac1, Rac2, Cdc42, and RhoA, suggesting a direct role for DEF6 in the activation of Rho GTPases. The ability of DEF6 to both stimulate actin polymerization and bind to filamentous actin suggests a role for DEF6 in regulating cell shape, polarity, and movement. 相似文献
12.
Rho GTPases regulate the assembly of cellular actin structures and are activated by GEFs (guanine-nucleotide-exchange factors) and rendered inactive by GAPs (GTPase-activating proteins). Using the Rho GTPases Cdc42, Rac1 and RhoA, and the GTPase-binding portions of the effector proteins p21-activated kinase and Rhophilin1, we have developed split luciferase assays for detecting both GEF and GAP regulation of these GTPases. The system relies on purifying split luciferase fusion proteins of the GTPases and effectors from bacteria, and our results show that the assays replicate GEF and GAP specificities at nanomolar concentrations for several previously characterized Rho family GEFs (Dbl, Vav2, Trio and Asef) and GAPs [p190, Cdc42 GAP and PTPL1-associated RhoGAP]. The assay detected activities associated with purified recombinant GEFs and GAPs, cell lysates expressing exogenous proteins, and immunoprecipitates of endogenous Vav1 and p190. The results demonstrate that the split luciferase system provides an effective sensitive alternative to radioactivity-based assays for detecting GTPase regulatory protein activities and is adaptable to a variety of assay conditions. 相似文献
13.
Shamsideen A. Ojelade Summer F. Acevedo Geetha Kalahasti Aylin R. Rodan Adrian Rothenfluh 《PloS one》2015,10(9)
Responses to the effects of ethanol are highly conserved across organisms, with reduced responses to the sedating effects of ethanol being predictive of increased risk for human alcohol dependence. Previously, we described that regulators of actin dynamics, such as the Rho-family GTPases Rac1, Rho1, and Cdc42, alter Drosophila’s sensitivity to ethanol-induced sedation. The GTPase activating protein RhoGAP18B also affects sensitivity to ethanol. To better understand how different RhoGAP18B isoforms affect ethanol sedation, we examined them for their effects on cell shape, GTP-loading of Rho-family GTPase, activation of the actin-severing cofilin, and actin filamentation. Our results suggest that the RhoGAP18B-PA isoform acts on Cdc42, while PC and PD act via Rac1 and Rho1 to activate cofilin. In vivo, a loss-of-function mutation in the cofilin-encoding gene twinstar leads to reduced ethanol-sensitivity and acts in concert with RhoGAP18B. Different RhoGAP18B isoforms, therefore, act on distinct subsets of Rho-family GTPases to modulate cofilin activity, actin dynamics, and ethanol-induced behaviors. 相似文献
14.
Requirement for Rho GTPases and PI 3-kinases during apoptotic cell phagocytosis by macrophages 总被引:6,自引:0,他引:6
In vivo, apoptotic cells are removed by surrounding phagocytes, a process thought to be essential for tissue remodeling and the resolution of inflammation [1]. Although apoptotic cells are known to be efficiently phagocytosed by macrophages, the mechanisms whereby their interaction with the phagocytes triggers their engulfment have not been described in mammals. Here, we report that primary murine bone marrow-derived macrophages (using alpha(v)beta(3) integrin for apoptotic cell uptake) extend lamellipodia to engulf apoptotic cells and form an actin cup where phosphotyrosine accumulates. Rho GTPases and PI 3-kinases have been widely implicated in the regulation of the actin cytoskeleton [2, 3]. We show that inhibition of Rho GTPases by Clostridium difficile toxin B prevents apoptotic cell phagocytosis and inhibits the accumulation of both F-actin and phosphotyrosine. Importantly, the Rho GTPases Rac1 and Cdc42 are required for apoptotic cell uptake whereas Rho inhibition enhances uptake. The PI 3-kinase inhibitor LY294002 also prevents apoptotic cell phagocytosis but has no effect on the accumulation of F actin and phosphotyrosine. These results indicate that both Rho GTPases and PI 3-kinases are involved in apoptotic cell phagocytosis but that they play distinct roles in this process. 相似文献
15.
Polarized trafficking of E-cadherin is regulated by Rac1 and Cdc42 in Madin-Darby canine kidney cells 总被引:1,自引:0,他引:1
Wang B Wylie FG Teasdale RD Stow JL 《American journal of physiology. Cell physiology》2005,288(6):C1411-C1419
E-cadherin is a major cell-cell adhesion protein of epithelia that is trafficked to the basolateral cell surface in a polarized fashion. The exact post-Golgi route and regulation of E-cadherin transport have not been fully described. The Rho GTPases Cdc42 and Rac1 have been implicated in many cell functions, including the exocytic trafficking of other proteins in polarized epithelial cells. These Rho family proteins are also associated with the cadherin-catenin complexes at the cell surface. We have used functional mutants of Rac1 and Cdc42 and inactivating toxins to demonstrate specific roles for both Cdc42 and Rac1 in the post-Golgi transport of E-cadherin. Dominant-negative mutants of Cdc42 and Rac1 accumulate E-cadherin at a distinct post-Golgi step. This accumulation occurs before p120ctn interacts with E-cadherin, because p120ctn localization was not affected by the Cdc42 or Rac1 mutants. Moreover, the GTPase mutants had no effect on the trafficking of a targeting mutant of E-cadherin, consistent with the selective involvement of Cdc42 and Rac1 in basolateral trafficking. These results provide a new example of Rho GTPase regulation of basolateral trafficking and demonstrate novel roles for Cdc42 and Rac1 in the post-Golgi transport of E-cadherin. Rho family GTPases; catenin; polarity; sorting; actin 相似文献
16.
The mechanisms by which Rho family GTPases (Rho, Rac and Cdc42) regulate coordinated changes to the actin cytoskeleton are being elucidated. This review will focus on the current evidence that the p21-activated kinases (PAKs) are involved in regulating some of the diverse cytoskeletal changes induced by Rac and Cdc42. PAKs have been shown to be required for processes including neurite formation and axonal guidance, development of cell polarity and motile responses. Signaling molecules interacting with PAKs that might contribute to the regulation of such processes have recently been identified. 相似文献
17.
RhoA/ROCK-mediated switching between Cdc42- and Rac1-dependent protrusion in MTLn3 carcinoma cells 总被引:1,自引:0,他引:1
El-Sibai M Pertz O Pang H Yip SC Lorenz M Symons M Condeelis JS Hahn KM Backer JM 《Experimental cell research》2008,314(7):1540-1552
Rho GTPases are versatile regulators of cell shape that act on the actin cytoskeleton. Studies using Rho GTPase mutants have shown that, in some cells, Rac1 and Cdc42 regulate the formation of lamellipodia and filopodia, respectively at the leading edge, whereas RhoA mediates contraction at the rear of moving cells. However, recent reports have described a zone of RhoA/ROCK activation at the front of cells undergoing motility. In this study, we use a FRET-based RhoA biosensor to show that RhoA activation localizes to the leading edge of EGF-stimulated cells. Inhibition of Rho or ROCK enhanced protrusion, yet markedly inhibited cell motility; these changes correlated with a marked activation of Rac-1 at the cell edge. Surprisingly, whereas EGF-stimulated protrusion in control MTLn3 cells is Rac-independent and Cdc42-dependent, the opposite pattern is observed in MTLn3 cells after inhibition of ROCK. Thus, Rho and ROCK suppress Rac-1 activation at the leading edge, and inhibition of ROCK causes a switch between Cdc42 and Rac-1 as the dominant Rho GTPase driving protrusion in carcinoma cells. These data describe a novel role for Rho in coordinating signaling by Rac and Cdc42. 相似文献
18.
《Cell cycle (Georgetown, Tex.)》2013,12(7):853-855
Rho GTPases including Rho, Rac and Cdc42 are involved in cell morphogenesis by inducing specific types of actin cytoskeleton and alignment and stabilization of microtubules. Previous studies suggest that they also regulate cell cycle progression; Rho, Rac and Cdc42 regulate the G1-S progression and Rho controls cytokinesis. However, a role of Rho GTPases in nuclear division has not been definitely shown. We have recently found that Cdc42 and its downstream effector mDia3 are involved in bi-orientation and stabilization of spindle microtubules attachment to kinetochores and regulate chromosome alignment and segregation. Here, we discuss how this is coordinated with other events in mitosis, particularly, with the action of Rho in cytokinesis and how attachment of microtubules to kinetochores is achieved and stabilized. We also discuss redundancy of Cdc42 and Cdc42-related GTPase(s) and potential mechanisms of chromosome instability in cancer 相似文献
19.
BACKGROUND: The ability of a cell to polarize and move is governed by remodeling of the cellular adhesion/cytoskeletal network that is in turn controlled by the Rho family of small GTPases. However, it is not known what signals lie downstream of Rac1 and Cdc42 during peripheral actin and adhesion remodeling that is required for directional migration. RESULTS: We show here that individual members of the Rho family, RhoA, Rac1, and Cdc42, direct the specific intracellular targeting of c-Src tyrosine kinase to focal adhesions, lamellipodia, or filopodia, respectively, and that the adaptor function of c-Src (the combined SH3/SH2 domains coupled to green fluorescent protein) is sufficient for targeting. Furthermore, Src's catalytic activity is absolutely required at these peripheral cell-matrix attachment sites for remodeling that converts RhoA-dependent focal adhesions into smaller focal complexes along Rac1-induced lamellipodia (or Cdc42-induced filopodia). Consequently, cells in which kinase-deficient c-Src occupies peripheral adhesion sites exhibit impaired polarization toward migratory stimuli and reduced motility. Furthermore, phosphorylation of FAK, an Src adhesion substrate, is suppressed under these conditions. CONCLUSIONS: Our findings demonstrate that individual Rho GTPases specify Src's exact peripheral localization and that Rac1- and Cdc42-induced adhesion remodeling and directed cell migration require Src activity at peripheral adhesion sites. 相似文献
20.
Integrin-mediated Signals Regulated by Members of the Rho Family of GTPases 总被引:28,自引:1,他引:27
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Edwin A. Clark Warren G. King Joan S. Brugge Marc Symons Richard O. Hynes 《The Journal of cell biology》1998,142(2):573-586
The organization of the actin cytoskeleton can be regulated by soluble factors that trigger signal transduction events involving the Rho family of GTPases. Since adhesive interactions are also capable of organizing the actin-based cytoskeleton, we examined the role of Cdc42-, Rac-, and Rho-dependent signaling pathways in regulating the cytoskeleton during integrin-mediated adhesion and cell spreading using dominant-inhibitory mutants of these GTPases. When Rat1 cells initially adhere to the extracellular matrix protein fibronectin, punctate focal complexes form at the cell periphery. Concomitant with focal complex formation, we observed some phosphorylation of the focal adhesion kinase (FAK) and Src, which occurred independently of Rho family GTPases. However, subsequent phosphorylation of FAK and paxillin occurs in a Rho-dependent manner. Moreover, we found Rho dependence of the assembly of large focal adhesions from which actin stress fibers radiate. Initial adhesion to fibronectin also stimulates membrane ruffling; we show that this ruffling is independent of Rho but is dependent on both Cdc42 and Rac. Furthermore, we observed that Cdc42 controls the integrin-dependent activation of extracellular signal–regulated kinase 2 and of Akt, a kinase whose activity has been demonstrated to be dependent on phosphatidylinositol (PI) 3-kinase. Since Rac-dependent membrane ruffling can be stimulated by PI 3-kinase, it appears that Cdc42, PI 3-kinase, and Rac lie on a distinct pathway that regulates adhesion-induced membrane ruffling. In contrast to the differential regulation of integrin-mediated signaling by Cdc42, Rac, and Rho, we observed that all three GTPases regulate cell spreading, an event that may indirectly control cellular architecture. Therefore, several separable signaling pathways regulated by different members of the Rho family of GTPases converge to control adhesion-dependent changes in the organization of the cytoskeleton, changes that regulate cell morphology and behavior. 相似文献