scholarly journals Hyperactivation of P21ras and the Hematopoietic-Specific Rho Gtpase, Rac2, Cooperate to Alter the Proliferation of Neurofibromin-Deficient Mast Cells in Vivo and in Vitro

2001 ◽  
Vol 194 (1) ◽  
pp. 57-70 ◽  
Author(s):  
David A. Ingram ◽  
Kelly Hiatt ◽  
Alastair J. King ◽  
Lucy Fisher ◽  
Rama Shivakumar ◽  
...  
Keyword(s):  
Mast Cells ◽  
Cross Talk ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Cell Lineage ◽  
Neurofibromatosis Type ◽  
Type I ◽  
Erk Pathway

Mutations in the NF1 tumor suppressor gene cause neurofibromatosis type I (NF1), a disease characterized by the formation of cutaneous neurofibromas infiltrated with a high density of degranulating mast cells. A hallmark of cell lines generated from NF1 patients or Nf1-deficient mice is their propensity to hyperproliferate. Neurofibromin, the protein encoded by NF1, negatively regulates p21ras activity by accelerating the conversion of Ras-GTP to Ras-GDP. However, identification of alterations in specific p21ras effector pathways that control proliferation in NF1-deficient cells is incomplete and critical for understanding disease pathogenesis. Recent studies have suggested that the proliferative effects of p21ras may depend on signaling outputs from the small Rho GTPases, Rac and Rho, but the physiologic importance of these interactions in an animal disease model has not been established. Using a genetic intercross between Nf1+/− and Rac2−/− mice, we now provide genetic evidence to support a biochemical model where hyperactivation of the extracellular signal–regulated kinase (ERK) via the hematopoietic-specific Rho GTPase, Rac2, directly contributes to the hyperproliferation of Nf1-deficient mast cells in vitro and in vivo. Further, we demonstrate that Rac2 functions as mediator of cross-talk between phosphoinositide 3-kinase (PI-3K) and the classical p21ras-Raf-Mek-ERK pathway to confer a distinct proliferative advantage to Nf1+/− mast cells. Thus, these studies identify Rac2 as a novel mediator of cross-talk between PI-3K and the p21ras-ERK pathway which functions to alter the cellular phenotype of a cell lineage involved in the pathologic complications of a common genetic disease.

p21-Activated Kinase 1 Regulates Hyperproliferation of Nf1 Haploinsufficient Mast Cells In Vitro and In Vivo Via Activation of the MAPK Pathway.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3063-3063
Author(s):  
Andrew S. McDaniel
Keyword(s):  
Mast Cells ◽  
Mammalian Cells ◽  
Rho Gtpase ◽  
Mapk Pathway ◽  
Mapk Signaling ◽  
Type I ◽  
Wild Type ◽  
Kit Ligand

Abstract p21-activated kinases (Paks) are downstream mediators of Rho GTPase proteins and have been implicated in yeast and immortalized cells as positive regulators of MAPK pathway members in modulating cell growth and cytoskeletal functions. However, their role in primary mammalian cells has not been described. NF1 encodes neurofibromin, which negatively regulates p21Ras activity by stimulating its intrinsic GTPase activity, and accelerating hydrolysis of Ras from the GTP to the GDP confirmation. Disruption of the NF1 locus results in neurofibromatosis type I (NF1), an inherited disorder characterized by the development of neurofibromas that contain large numbers of degranulating mast cells that have been implicated in tumor progression. Utilizing a genetic intercross of Pak 1−/− mice with mice haploinsufficient at the Nf1 locus, we studied the role of Pak1 in the context of normal and hyperactivated Ras-MAPK signaling in primary inflammatory mast cells. Pak1 was found to directly contribute to Ras-dependent signaling by modulating both Raf-1, Mek-1 and ERK1/2 activation. Loss of Pak1 fully corrects the hyperphosphorylation of ERK1/2 found in Nf1+/− mast cells to that of wild type controls. Deletion of Pak1 in Nf1+/− mast cells is associated with a correction of Kit ligand mediated proliferation to wild type levels in vitro. Further, after subcutaneous administration of Kit ligand via micro osmotic pumps, which is an established model that stimulates local proliferation of mast cells in vivo (Ingram, JEM 2001), we confirmed that genetic disruption of Pak1 corrects the proliferation of Nf1+/− mast cells in vivo to that of wild type controls. These data provide direct genetic evidence that Pak1 modulates the Ras-Raf-Mek-Erk pathway and identifies a specific molecular target within the inflammatory tumor microenvironment for the treatment or prevention of neurofibromas.

Cross Talk between Rho GTPases Is Critical for Hematopoietic-Derived Inflammatory Processes.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 631-631
Author(s):  
Marie-Dominique Filippi ◽  
Pierre-Yves Berclaz ◽  
Kathleen Szczur ◽  
Chad Harris ◽  
David A. Williams
Keyword(s):  
Bone Marrow ◽  
Cross Talk ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Cell Movement ◽  
Dependent Manner ◽  
Inflammatory Processes

Abstract Neutrophils are a critical cell in inflammatory processes by moving rapidly to tissue sites of inflammation to perform phagocytosis, cytokine and reactive oxygen species release. Members of the small Rho GTPase family, Rac1, Rac2, CDC42 and RhoA, are central regulators of cell movement via cytoskeleton rearrangement. We have previously demonstrated that the Rho family GTPase Rac2 is a critical regulator of neutrophil functions in vitro and in vivo (Roberts et al, Immunity 1999). We have also demonstrated that in response to formyl-methionyl-leucyl-phenylalanine (fMLP), the related GTPase Rac1 plays a distinct, but as yet ill-defined role in tail retraction during cell movement and cell spreading in vitro (Gu and Filippi et al, Science 2003). Here, we further demonstrate that Rac1 appears to be critical for β2-integrin mediated adhesion and migration likely via cross talk with another Rho GTPase, RhoA. Although, Rac1−/− PMNs show normal in vitro migration in response to fMLP using the Boyden chamber assay, Rac1−/− PMNs demonstrate a dramatic defect compared with WT cells in haptotaxis using transwell precoated with fibrinogen (1.3±0.3x103 vs 9.8±0.5x103). In addition, Rac1−/− PMNs displayed increased frequency in pseudopodia formation associated with lack of cell body contraction upon integrin ligation compared with WT (80% vs 40%). We noted that this phenotype closely mimics deregulation of the related Rho GTPase, RhoA. Remarkably, Rac1-deficiency leads to mislocalization of RhoA in neutrophils after integrin ligation and reintroduction of Rac1 into Rac1−/− cells completely restores the correct localization of RhoA. These data are consistent with the hypothesis that Rho GTPases interact in a time- and space-dependent manner. Because fMLP-induced PMN migration into the lung has previously been shown to be beta2-integrin dependent (Mackarel, Am. J. Respir. Cell. Mol. Biol 2000), we used a model of neutrophil associated lung inflammation induced by intratracheal (IT) injection of fMLP to address the physiological role of Rac1 in neutrophil-derived inflammatory processes in vivo,. To study the role of Rac1 specifically in bone marrow-derived cells, we reconstituted C57BL/6 mice with either wild type or Rac1Flox/Flox bone marrow cells. After Cre-mediated deletion of Rac1, reconstituted mice were treated with one dose of fMLP (20mg) IT. One day after fMLP exposure, bronchoalveolar lavage (BAL) from reconstituted animals showed complete loss of Rac1 expression and demonstrated significantly reduced numbers of migrated neutrophils in BAL compared with mice reconstituted with WT cells (3.1±0.65 vs 9.56±2, p<0.05). Importantly, 5 weeks after fMLP exposure IT, Rac1−/− recipients displayed a significant reduction in emphysematous lesions as compared with WT as assessed by morphometric measurement of alveolar spaces (57.6±7.8 vs 73.3±3.04, p<0.05), demonstrating the physiological relevance of Rac1 in neutrophil-related inflammatory responses in vivo. Taken together, these results suggest that Rac1 activity regulates b2 integrin-induced cell shape change and RhoA subcellular localization in PMNs and demonstrate the existence of physiological cross talk between Rac1 and RhoA where RhoA activity depends at least in part on Rac1. Thus, Rac1 and RhoA appear to coordinately regulate PMN migration into the lung during inflammation.

scholarly journals Regulation of anaphylactic responses by phosphatidylinositol phosphate kinase type I α

2005 ◽  
Vol 201 (6) ◽  
pp. 859-870 ◽  
Author(s):  
Junko Sasaki ◽  
Takehiko Sasaki ◽  
Masakazu Yamazaki ◽  
Kunie Matsuoka ◽  
Choji Taya ◽  
...  
Keyword(s):  
Mast Cells ◽  
Actin Polymerization ◽  
Negative Regulator ◽  
Type I ◽  
Filamentous Actin ◽  
Critical Signal ◽  
Cell Functions ◽  
Phosphatidylinositol Phosphate

The membrane phospholipid phosphatidylinositol 4, 5-bisphosphate [PI(4,5)P2] is a critical signal transducer in eukaryotic cells. However, the physiological roles of the type I phosphatidylinositol phosphate kinases (PIPKIs) that synthesize PI(4,5)P2 are largely unknown. Here, we show that the α isozyme of PIPKI (PIPKIα) negatively regulates mast cell functions and anaphylactic responses. In vitro, PIPKIα-deficient mast cells exhibited increased degranulation and cytokine production after Fcε receptor-I cross-linking. In vivo, PIPKIα−/− mice displayed enhanced passive cutaneous and systemic anaphylaxis. Filamentous actin was diminished in PIPKIα−/− mast cells, and enhanced degranulation observed in the absence of PIPKIα was also seen in wild-type mast cells treated with latrunculin, a pharmacological inhibitor of actin polymerization. Moreover, the association of FcεRI with lipid rafts and FcεRI-mediated activation of signaling proteins was augmented in PIPKIα−/− mast cells. Thus, PIPKIα is a negative regulator of FcεRI-mediated cellular responses and anaphylaxis, which functions by controlling the actin cytoskeleton and dynamics of FcεRI signaling. Our results indicate that the different PIPKI isoforms might be functionally specialized.

scholarly journals ARHGEF18/p114RhoGEF coordinates PKA/CREB signaling and actomyosin remodeling to drive trophoblast cell-cell fusion during placenta morphogenesis

2020 ◽  
Author(s):  
Robert Beal ◽  
Ana Alonso-Carriazo Fernandez ◽  
Dimitris K. Grammatopoulos ◽  
Karl Matter ◽  
Maria S. Balda
Keyword(s):  
Gene Expression ◽  
Cell Fusion ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Trophoblast Cell ◽  
Cell Junctions ◽  
Nucleotide Exchange ◽  
Cell Cell

SUMMARYCoordination of cell-cell adhesion, actomyosin dynamics and gene expression is crucial for morphogenetic processes underlying tissue and organ development. Rho GTPases are main regulators of the cytoskeleton and adhesion. They are activated by guanine nucleotide exchange factors in a spatially and temporally controlled manner. However, the roles of these Rho GTPase activators during complex developmental processes are still poorly understood. ARHGEF18/p114RhoGEF is a tight junction-associated RhoA activator that forms complexes with myosin II, and regulates actomyosin contractility. Here we show that p114RhoGEF/ ARHGEF18 is required for mouse syncytiotrophoblast differentiation and placenta development. In vitro and in vivo experiments identify that p114RhoGEF controls expression of AKAP12, a protein regulating PKA signalling, and is required for PKA-induced actomyosin remodelling, CREB-driven gene expression of proteins required for trophoblast differentiation, and, hence, trophoblast cell-cell fusion. Our data thus indicate that p114RhoGEF links actomyosin dynamics and cell-cell junctions to PKA/CREB signalling, gene expression and cell-cell fusion.

scholarly journals SRGAP1 Controls Small Rho GTPases To Regulate Podocyte Foot Process Maintenance

2021 ◽  
Vol 32 (3) ◽  
pp. 563-579
Author(s):  
Manuel Rogg ◽  
Jasmin I. Maier ◽  
Robert Dotzauer ◽  
Nadine Artelt ◽  
Oliver Kretz ◽  
...  
Keyword(s):  
Knockout Mice ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Conditional Knockout ◽  
Glomerular Diseases ◽  
Actin Networks ◽  
Small Rho Gtpases ◽  
Foot Process

BackgroundPrevious research demonstrated that small Rho GTPases, modulators of the actin cytoskeleton, are drivers of podocyte foot-process effacement in glomerular diseases, such as FSGS. However, a comprehensive understanding of the regulatory networks of small Rho GTPases in podocytes is lacking.MethodsWe conducted an analysis of podocyte transcriptome and proteome datasets for Rho GTPases; mapped in vivo, podocyte-specific Rho GTPase affinity networks; and examined conditional knockout mice and murine disease models targeting Srgap1. To evaluate podocyte foot-process morphology, we used super-resolution microscopy and electron microscopy; in situ proximity ligation assays were used to determine the subcellular localization of the small GTPase-activating protein SRGAP1. We performed functional analysis of CRISPR/Cas9-generated SRGAP1 knockout podocytes in two-dimensional and three-dimensional cultures and quantitative interaction proteomics.ResultsWe demonstrated SRGAP1 localization to podocyte foot processes in vivo and to cellular protrusions in vitro. Srgap1fl/fl*Six2Cre but not Srgap1fl/fl*hNPHS2Cre knockout mice developed an FSGS-like phenotype at adulthood. Podocyte-specific deletion of Srgap1 by hNPHS2Cre resulted in increased susceptibility to doxorubicin-induced nephropathy. Detailed analysis demonstrated significant effacement of podocyte foot processes. Furthermore, SRGAP1-knockout podocytes showed excessive protrusion formation and disinhibition of the small Rho GTPase machinery in vitro. Evaluation of a SRGAP1-dependent interactome revealed the involvement of SRGAP1 with protrusive and contractile actin networks. Analysis of glomerular biopsy specimens translated these findings toward human disease by displaying a pronounced redistribution of SRGAP1 in FSGS.ConclusionsSRGAP1, a podocyte-specific RhoGAP, controls podocyte foot-process architecture by limiting the activity of protrusive, branched actin networks. Therefore, elucidating the complex regulatory small Rho GTPase affinity network points to novel targets for potentially precise intervention in glomerular diseases.

scholarly journals Characterization of a Rac1- and RhoGDI-Associated Lipid Kinase Signaling Complex

1998 ◽  
Vol 18 (2) ◽  
pp. 762-770 ◽  
Author(s):  
Kimberley F. Tolias ◽  
Anthony D. Couvillon ◽  
Lewis C. Cantley ◽  
Christopher L. Carpenter
Keyword(s):  
Nadph Oxidase ◽  
Rho Gtpases ◽  
Actin Polymerization ◽  
Cellular Proliferation ◽  
Type I ◽  
Lipid Kinase ◽  
C Terminus ◽  
Lipid Kinases

ABSTRACT Rho family GTPases regulate a number of cellular processes, including actin cytoskeletal organization, cellular proliferation, and NADPH oxidase activation. The mechanisms by which these G proteins mediate their effects are unclear, although a number of downstream targets have been identified. The interaction of most of these target proteins with Rho GTPases is GTP dependent and requires the effector domain. The activation of the NADPH oxidase also depends on the C terminus of Rac, but no effector molecules that bind to this region have yet been identified. We previously showed that Rac interacts with a type I phosphatidylinositol-4-phosphate (PtdInsP) 5-kinase, independent of GTP. Here we report the identification of a diacylglycerol kinase (DGK) which also associates with both GTP- and GDP-bound Rac1. In vitro binding analysis using chimeric proteins, peptides, and a truncation mutant demonstrated that the C terminus of Rac is necessary and sufficient for binding to both lipid kinases. The Rac-associated PtdInsP 5-kinase and DGK copurify by liquid chromatography, suggesting that they bind as a complex to Rac. RhoGDI also associates with this lipid kinase complex both in vivo and in vitro, primarily via its interaction with Rac. The interaction between Rac and the lipid kinases was enhanced by specific phospholipids, indicating a possible mechanism of regulation in vivo. Given that the products of the PtdInsP 5-kinase and the DGK have been implicated in several Rac-regulated processes, and they bind to the Rac C terminus, these lipid kinases may play important roles in Rac activation of the NADPH oxidase, actin polymerization, and other signaling pathways.

Regulation of Rho GTPases by the Hematopoietic-Specific Guanine Nucleotide Exchange Factor Vav1 Is Critical for Hematopoietic Stem Cell Retention in the Endosteal Niche and Engraftment.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 80-80
Author(s):  
Abel Sanchez-Aguilera ◽  
Yun-Jung Lee ◽  
Cristina Lo Celso ◽  
Kristina Brumme ◽  
Charles P Lin ◽  
...  
Keyword(s):  
Rho Gtpases ◽  
Rho Gtpase ◽  
Nucleotide Exchange ◽  
Hematopoietic Progenitor ◽  
Hematopoietic Stem ◽  
Guanine Nucleotide Exchange ◽  
Endosteal Niche ◽  
Gtpase Activation

Abstract Abstract 80 Background: Rho GTPases are molecular switches that regulate actin cytoskeleton dynamics, cell proliferation and survival. In hematopoietic stem cells and progenitors (HSC/P), several Rho GTPases (including Rac1, Rac2 and Cdc42) function as critical regulators of engraftment through the integration of diverse extracellular signals, such as those transmitted by growth factor, chemokine and adhesion receptors. In addition, Rac-deficient mice show significantly increased numbers of mobilized HSC/P. GTPase activation downstream of these and other receptors is mediated by a large family of guanine nucleotide exchange factors (GEF). Functional interactions between receptors, GEF and Rho GTPases are potentially complex and the crucial biochemical pathways regulating HSC activity have not been defined. Among the Rho/Rac GEFs, Vav1 shows hematopoietic-specific expression and has been previously implicated in immune cell processes, such as immunoreceptor signaling in lymphocytes and neutrophil migration. To further explore the mechanism of Rho GTPase regulation of HSC engraftment, we investigated the role of Vav1 GEF in Rho GTPase activation after ligation of multiple HSC receptors and the effect of genetic deletion of Vav1 on HSC homing, retention and engraftment in the hematopoietic microenvironment. Methods: GTPase activation (Rac, Cdc42, RhoA) was analyzed by in vitro pulldown assays. The HSC/P compartment of Vav1−/− mice was studied by flow cytometry, colony forming cell (CFC) assays, progenitor (CFC) homing, competitive and non-competitive repopulation assays. HSC localization in the endosteal niche was determined by intravital microscopy 1 h and 48 h after transplant. Results: At the biochemical level, Vav1−/− hematopoietic progenitors showed a dysfunctional Rho GTPase activation pattern, with increased baseline levels of GTP-bound Rac, Cdc42 and RhoA; however, in the absence of Vav1, these GTPases were unresponsive to stimulation by stem cell factor and SDF1α, critical proteins in HSC engraftment. In spite of this biochemical abnormality, Vav1−/− mice at baseline had nearly normal numbers of immunophenotypically defined HSC, myeloid and lymphoid progenitors in the bone marrow (BM), and normal hematopoietic progenitor content as defined by CFC, although reduced rather than increased circulating HSC/P. Vav1−/− HSC/P transplanted into irradiated recipients exhibited normal BM CFC homing efficiency (∼5%) and normal early endosteal localization of HSC in vivo (1 h after injection) as determined by intravital microscopy. Surprisingly-but in concordance with the normal BM homing of HSC/P in vivo- the loss of Vav1 did not affect hematopoietic progenitor chemotaxis or short-term adhesion to fibronectin in vitro. However, there was a significant decrease in the retention of HSC in the endosteal space at 48 h after transplant (Vav1−/− HSC numbers were reduced to 46%, relative to WT HSC) and this defect was associated with a profound loss of short- and long-term engraftment. In competitive repopulation assays, Vav1−/− cells virtually did not contribute to the graft (Table 1), whereas in a non-competitive setting, they either failed to rescue the recipient (60% survival vs 100% at 1 month, Vav1−/− vs WT) or showed significantly delayed hematopoietic reconstitution (Table 2). Conclusions: The hematopoietic-specific GEF Vav1 is essential for the appropriate microenvironment-induced Rho GTPase activation in HSC/P after transplant and is required for the retention of HSC/P in the BM endosteal niche and subsequent engraftment. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Phosphorylation of RhoGDI by Src Regulates Rho GTPase Binding and Cytosol-Membrane Cycling

2006 ◽  
Vol 17 (11) ◽  
pp. 4760-4768 ◽  
Author(s):  
Céline DerMardirossian ◽  
Gabriel Rocklin ◽  
Ji-Yeon Seo ◽  
Gary M. Bokoch
Keyword(s):  
Rho Gtpases ◽  
Cell Function ◽  
Rho Gtpase ◽  
Physiological Mechanism ◽  
In Vitro Assays ◽  
Cortical Actin ◽  
Membrane Ruffling ◽  
Reactive Oxidant

Rho GTPases (Rac, Rho, and Cdc42) play important roles in regulating cell function through their ability to coordinate the actin cytoskeleton, modulate the formation of signaling reactive oxidant species, and control gene transcription. Activation of Rho GTPase signaling pathways requires the regulated release of Rho GTPases from RhoGDI complexes, followed by their reuptake after membrane cycling. We show here that Src kinase binds and phosphorylates RhoGDI both in vitro and in vivo at Tyr156. Analysis of Rho GTPase–RhoGDI complexes using in vitro assays of complexation and in vivo by coimmunoprecipitation analysis indicates that Src-mediated phosphorylation of Tyr156 causes a dramatic decrease in the ability of RhoGDI to form a complex with RhoA, Rac1, or Cdc42. Phosphomimetic mutation of Tyr156→Glu results in the constitutive association of RhoGDIY156E with the plasma membrane and/or associated cortical actin. Substantial cortical localization of tyrosine-phosphorylated RhoGDI is also observed in fibroblasts expressing active Src, where it is most evident in podosomes and regions of membrane ruffling. Expression of membrane-localized RhoGDIY156E mutant is associated with enhanced cell spreading and membrane ruffling. These results suggest that Src-mediated RhoGDI phosphorylation is a novel physiological mechanism for regulating Rho GTPase cytosol membrane–cycling and activity.

The role of RhoJ in endothelial cell biology and angiogenesis

2011 ◽  
Vol 39 (6) ◽  
pp. 1606-1611 ◽  
Author(s):  
Katarzyna Leszczynska ◽  
Sukhbir Kaur ◽  
Eleanor Wilson ◽  
Roy Bicknell ◽  
Victoria L. Heath
Keyword(s):  
Focal Adhesion ◽  
Rho Gtpases ◽  
Cell Biology ◽  
Rho Gtpase ◽  
Vascular Endothelial ◽  
Small Rho Gtpases ◽  
Endothelial Growth Factor

RhoJ is an endothelially expressed member of the Cdc42 (cell division cycle 42) subfamily of small Rho GTPases. It is expressed in both the developing mammalian vasculature and the vascular beds of a number of adult tissues, with its expression regulated by the endothelial transcription factor ERG (ETS-related gene). RhoJ has been shown to regulate endothelial motility, tubulogenesis and lumen formation in vitro, and modulates the vascularization of Matrigel plugs in vivo. Both vascular endothelial growth factor and semaphorin 3E have been found to affect its activation. RhoJ has been shown to be a focal-adhesion-localized Rho GTPase which can modulate focal adhesion number, actomyosin contractility and activity of Cdc42 and Rac1. The present review discusses the biology of RhoJ with a focus on recent reports of its role in endothelial cells and angiogenesis.

scholarly journals ARHGEF18/p114RhoGEF Coordinates PKA/CREB Signaling and Actomyosin Remodeling to Promote Trophoblast Cell-Cell Fusion During Placenta Morphogenesis

2021 ◽  
Vol 9 ◽  
Author(s):  
Robert Beal ◽  
Ana Alonso-Carriazo Fernandez ◽  
Dimitris K. Grammatopoulos ◽  
Karl Matter ◽  
Maria S. Balda
Keyword(s):  
Gene Expression ◽  
Cell Fusion ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Trophoblast Cell ◽  
Cell Junctions ◽  
Nucleotide Exchange ◽  
Cell Cell

Coordination of cell-cell adhesion, actomyosin dynamics and gene expression is crucial for morphogenetic processes underlying tissue and organ development. Rho GTPases are main regulators of the cytoskeleton and adhesion. They are activated by guanine nucleotide exchange factors in a spatially and temporally controlled manner. However, the roles of these Rho GTPase activators during complex developmental processes are still poorly understood. ARHGEF18/p114RhoGEF is a tight junction-associated RhoA activator that forms complexes with myosin II, and regulates actomyosin contractility. Here we show that p114RhoGEF/ARHGEF18 is required for mouse syncytiotrophoblast differentiation and placenta development. In vitro and in vivo experiments identify that p114RhoGEF controls expression of AKAP12, a protein regulating protein kinase A (PKA) signaling, and is required for PKA-induced actomyosin remodeling, cAMP-responsive element binding protein (CREB)-driven gene expression of proteins required for trophoblast differentiation, and, hence, trophoblast cell-cell fusion. Our data thus indicate that p114RhoGEF links actomyosin dynamics and cell-cell junctions to PKA/CREB signaling, gene expression and cell-cell fusion.

Sign in / Sign up

Export Citation Format

Share Document