scholarly journals Pitx2a Expression Alters Actin-Myosin Cytoskeleton and Migration of HeLa Cells through Rho GTPase Signaling

2002 ◽  
Vol 13 (2) ◽  
pp. 683-697 ◽  
Author(s):  
Qize Wei ◽  
Robert S. Adelstein
Keyword(s):  
Cell Morphology ◽  
Hela Cells ◽  
Rho Gtpase ◽  
Expression System ◽  
Ectopic Expression ◽  
Cell Spreading ◽  
Dominant Negative ◽  
Nucleotide Exchange ◽  
Cell Contacts ◽  
Cell Cell

We ectopically expressed the transcription factor Pitx2a, one of the Pitx2 isoforms, in HeLa cells by using a tetracycline-inducible expression system and examined whether Pitx2a was capable of modulating Rho GTPase signaling and altering the cell's cytoskeleton. Ectopic expression of Pitx2a induced actin-myosin reorganization, leading to increased cell spreading, suppression of cell migration, and the strengthening of cell-cell adhesion, marked by the accumulation and localization of β-catenin and N-cadherin to the sites of cell-cell contacts. Moreover, Pitx2a expression resulted in activation of the Rho GTPases Rac1 and RhoA, and the dominant negative Rac1 mutant N17Rac1 inhibited cell spreading and disrupted localization of β-catenin to the sites of cell-cell contacts. Both reorganization of actin-myosin and cell spreading require phosphatidylinositol 3-kinase activity, which is also necessary for activation of the Rho GTPase proteins. Pitx2a induced the expression of Trio, a guanine nucleotide exchange factor for Rac1 and RhoA, which preceded cell spreading, and the expression of Trio protein was down-regulated after the changes in cell spreading and cell morphology were initiated. In addition, Pitx2a also induces cell cycle arrest at G0/G1, most likely due to the accumulation of the tumor suppressor proteins p53 and p21. Our data indicate that the transcriptional activities initiated in the nucleus by Pitx2a result in profound changes in HeLa cell morphology, migration, and proliferation.

scholarly journals An Elmo–Dock complex locally controls Rho GTPases and actin remodeling during cadherin-mediated adhesion

2014 ◽  
Vol 207 (5) ◽  
pp. 577-587 ◽  
Author(s):  
Christopher P. Toret ◽  
Caitlin Collins ◽  
W. James Nelson
Keyword(s):  
Cell Adhesion ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Cell Contact ◽  
Nucleotide Exchange ◽  
Cell Contacts ◽  
Guanine Nucleotide Exchange ◽  
A Genome ◽  
Dependent Cell ◽  
Cell Cell

Cell–cell contact formation is a dynamic process requiring the coordination of cadherin-based cell–cell adhesion and integrin-based cell migration. A genome-wide RNA interference screen for proteins required specifically for cadherin-dependent cell–cell adhesion identified an Elmo–Dock complex. This was unexpected as Elmo–Dock complexes act downstream of integrin signaling as Rac guanine-nucleotide exchange factors. In this paper, we show that Elmo2 recruits Dock1 to initial cell–cell contacts in Madin–Darby canine kidney cells. At cell–cell contacts, both Elmo2 and Dock1 are essential for the rapid recruitment and spreading of E-cadherin, actin reorganization, localized Rac and Rho GTPase activities, and the development of strong cell–cell adhesion. Upon completion of cell–cell adhesion, Elmo2 and Dock1 no longer localize to cell–cell contacts and are not required subsequently for the maintenance of cell–cell adhesion. These studies show that Elmo–Dock complexes are involved in both integrin- and cadherin-based adhesions, which may help to coordinate the transition of cells from migration to strong cell–cell adhesion.

N-cadherin in adult rat cardiomyocytes in culture. I. Functional role of N-cadherin and impairment of cell-cell contact by a truncated N-cadherin mutant

1996 ◽  
Vol 109 (1) ◽  
pp. 1-10 ◽  
Author(s):  
C.M. Hertig ◽  
M. Eppenberger-Eberhardt ◽  
S. Koch ◽  
H.M. Eppenberger
Keyword(s):  
Ectopic Expression ◽  
Extracellular Domain ◽  
Large Deletion ◽  
Binding Domain ◽  
Dominant Negative ◽  
Cell Contact ◽  
Rat Cardiomyocytes ◽  
Cell Contacts ◽  
Adult Rat ◽  
Cell Cell

N-cadherin is a transmembrane Ca(2+)-dependent glycoprotein that is part of adherens junctions. It functions with the cell adhesion N-terminal extracellular domain as a site of homophilic cell-cell contacts. The intracellular C-terminal domain provides via a catenin complex the interaction with the cytoskeleton. Ectopic expression of chicken N-cadherin in adult rat cardiomyocytes (ARC) in culture was obtained after microinjection into non-dividing cardiomyocytes; it was demonstrated that the exogenous protein colocalized with the endogenous N-cadherin at the plasma membrane of the cell and formed contact sites. A dominant negative chicken N-cadherin mutant was constructed by a large deletion of the extracellular domain. This mutant was expressed and inhibited the function of the endogenous rat N-cadherin probably by competing for the catenin complex binding domain, which is essential for the formation of a stable cell-cell contact of ARC. The injected cells lost contact with neighbouring cells and retracted; the connexons of the gap junctions were pulled out as well. This could be avoided by another N-cadherin mutation, which, in addition to the N-terminal truncation, contained a deletion of the catenin binding domain. In the case of the truncated N-cadherin at the N terminus, the sarcomeric structure of the myofibrils of ARC was also affected. Myofibrils were the most vulnerable cytoskeletal structures affected by the overexpressed dominant negative N-cadherin mutation. Similar behaviour was shown when cardiomyocytes separated following Ca2+ depletion and when new cell-cell contacts were formed after Ca2+ replenishment. N-cadherin is thought to be the essential component for establishing new cell-cell contacts which eventually led to a new formation of intercalated disc-like structures in the cardiac cell culture.

The Leukemia-Associated Rho Guanine Nucleotide Exchange Factor (LARG) /ARHGEF12 Is Important For Erythroid Differentiation

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3682-3682
Author(s):  
Li Gao ◽  
Yong Zhou ◽  
JingYan Tang ◽  
Shuhong Shen
Keyword(s):  
Rho Gtpase ◽  
Conflicts Of Interest ◽  
Regulatory Protein ◽  
Erythroid Differentiation ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Antibody Array ◽  
Fusion Partner ◽  
Nucleotide Exchange ◽  
Rho A

Abstract ARHGEF12,which was initially identified as a fusion partner of MLL in acute myeloid leukemia, is a regulatory protein involved in the GDP/GTP exchange reaction of the Rho A and activates a Rho-GTPase-dependent signaling pathway. However, the role of ARHGEF12 in hematopoiesis remains unknown. Here, we first report that ARHGEF12 takes part in erythroid differentiation not only in erythroleukemia cell line K562 but also in zebra fish based on knockdown technology. Although primitive hematopoiesis including erythroid differentiation progressed normally, double silencing of both orthologues arhgef12a and arhgef12b in Danio rerio with morpholino caused erythropenia during definitive hematopoiesis. Meanwhile, cytology assay reveal less mature red blood cells with large and loose nuclear in morpholino injected embryos. The phenotype of blocked erythroid differentiation can be rescured by mRNA overexpression of RhoA active mutant. On the other hand, injection of mRNA transcripted from the dominant negative mutant of RhoA could replicate the phenotype of arhgef12 silencing. Antibody array screen of kinase phosphorylation suggested STAT1 and MAPK pathways downstream of Rho A may be important for erythroid differentiation in our modles. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Dual roles of myocardin-related transcription factors in epithelial–mesenchymal transition via slug induction and actin remodeling

2007 ◽  
Vol 179 (5) ◽  
pp. 1027-1042 ◽  
Author(s):  
Tsuyoshi Morita ◽  
Taira Mayanagi ◽  
Kenji Sobue
Keyword(s):  
Transcription Factors ◽  
Actin Cytoskeleton ◽  
Nuclear Translocation ◽  
Epithelial Mesenchymal Transition ◽  
Ectopic Expression ◽  
Cytoskeletal Proteins ◽  
Mesenchymal Transition ◽  
Cell Contacts ◽  
Tgf Β1 ◽  
Cell Cell

Epithelial–mesenchymal transition (EMT) is a critical process occurring during embryonic development and in fibrosis and tumor progression. Dissociation of cell–cell contacts and remodeling of the actin cytoskeleton are major events of the EMT. Here, we show that myocardin-related transcription factors (MRTFs; also known as MAL and MKL) are critical mediators of transforming growth factor β (TGF-β) 1–induced EMT. In all epithelial cell lines examined here, TGF-β1 triggers the nuclear translocation of MRTFs. Ectopic expression of constitutive-active MRTF-A induces EMT, whereas dominant-negative MRTF-A or knockdown of MRTF-A and -B prevents the TGF-β1–induced EMT. MRTFs form complexes with Smad3. Via Smad3, the MRTF–Smad3 complexes bind to a newly identified cis-element GCCG-like motif in the promoter region of Canis familiaris and the human slug gene, which activates slug transcription and thereby dissociation of cell–cell contacts. MRTFs also increase the expression levels of actin cytoskeletal proteins via serum response factor, thereby triggering reorganization of the actin cytoskeleton. Thus, MRTFs are important mediators of TGF-β1–induced EMT.

scholarly journals A Spatiotemporally Coordinated Cascade of Protein Kinase C Activation Controls Isoform-Selective Translocation

2006 ◽  
Vol 26 (6) ◽  
pp. 2247-2261 ◽  
Author(s):  
Alejandra Collazos ◽  
Barthélémy Diouf ◽  
Nathalie C. Guérineau ◽  
Corinne Quittau-Prévostel ◽  
Marion Peter ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Fluorescent Protein ◽  
Functional Dependence ◽  
Receptor Activation ◽  
Dominant Negative ◽  
Cell Contacts ◽  
Kinase C ◽  
Trh Receptor ◽  
Cell Cell

ABSTRACT In pituitary GH3B6 cells, signaling involving the protein kinase C (PKC) multigene family can self-organize into a spatiotemporally coordinated cascade of isoform activation. Indeed, thyrotropin-releasing hormone (TRH) receptor activation sequentially activated green fluorescent protein (GFP)-tagged or endogenous PKCβ1, PKCα, PKCε, and PKCδ, resulting in their accumulation at the entire plasma membrane (PKCβ and -δ) or selectively at the cell-cell contacts (PKCα and -ε). The duration of activation ranged from 20 s for PKCα to 20 min for PKCε. PKCα and -ε selective localization was lost in the presence of Gö6976, suggesting that accumulation at cell-cell contacts is dependent on the activity of a conventional PKC. Constitutively active, dominant-negative PKCs and small interfering RNAs showed that PKCα localization is controlled by PKCβ1 activity and is calcium independent, while PKCε localization is dependent on PKCα activity. PKCδ was independent of the cascade linking PKCβ1, -α, and -ε. Furthermore, PKCα, but not PKCε, is involved in the TRH-induced β-catenin relocation at cell-cell contacts, suggesting that PKCε is not the unique functional effector of the cascade. Thus, TRH receptor activation results in PKCβ1 activation, which in turn initiates a calcium-independent but PKCβ1 activity-dependent sequential translocation of PKCα and -ε. These results challenge the current understanding of PKC signaling and raise the question of a functional dependence between isoforms.

scholarly journals Distinct Rho GTPase Activities Regulate Epithelial Cell Localization of the Adhesion Molecule CEACAM1: Involvement of the CEACAM1 Transmembrane Domain

2003 ◽  
Vol 23 (20) ◽  
pp. 7291-7304 ◽  
Author(s):  
Bénédicte Fournès ◽  
Jennifer Farrah ◽  
Melanie Olson ◽  
Nathalie Lamarche-Vane ◽  
Nicole Beauchemin
Keyword(s):  
Epithelial Cell ◽  
Epithelial Cells ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Transmembrane Domain ◽  
Rho Kinase ◽  
Cell Contacts ◽  
Cell Localization ◽  
Downstream Effector ◽  
Cell Cell

ABSTRACT CEACAM1 is an intercellular adhesion glycoprotein. As CEACAM1 plays an important role in epithelial cell signaling and functions, we have examined its localization in epithelial cells. We have observed that distribution at cell contacts is not always seen in these cells, suggesting that CEACAM1 localization might be regulated. In Swiss 3T3 cells, the targeting of CEACAM1 at cell-cell boundaries is regulated by the Rho GTPases. In the present study, we have used the MDCK epithelial cells to characterize the effects of the Rho GTPases and their effectors on CEACAM1 intercellular targeting. Activated Cdc42 and Rac1 or their downstream effector PAK1 targeted CEACAM1 to sites of cell-cell contacts. On the other hand, neither activated RhoA nor activated Rho kinase directed CEACAM1 to cell boundaries, resulting in a condensed distribution of CEACAM1 at the cell surface. Interestingly, inhibition of this pathway resulted in CEACAM1 intercellular localization suggesting that a tightly regulated balance of Rho GTPase activities is necessary to target CEACAM1 at cell-cell boundaries. In addition, using CEACAM1 mutants and chimeric fusion constructs containing domains of the colony-stimulating factor receptor, we have shown that the transmembrane domain of CEACAM1 is responsible for the Cdc42-induced targeting at cell-cell contacts.

scholarly journals Nucleotide Exchange Factor ECT2 Interacts with the Polarity Protein Complex Par6/Par3/Protein Kinase Cζ (PKCζ) and Regulates PKCζ Activity

2004 ◽  
Vol 24 (15) ◽  
pp. 6665-6675 ◽  
Author(s):  
Xiu-Fen Liu ◽  
Hiroshi Ishida ◽  
Razi Raziuddin ◽  
Toru Miki
Keyword(s):  
Protein Kinase ◽  
Cell Polarity ◽  
Mdck Cells ◽  
Dominant Negative ◽  
Cell Contact ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Cell Functions ◽  
Nucleotide Exchange Factor ◽  
Cell Cell

ABSTRACT Regulation of cell polarity is an important biological event that governs diverse cell functions such as localization of embryonic determinants and establishment of tissue and organ architecture. The Rho family GTPases and the polarity complex Par6/Par3/atypical protein kinase C (PKC) play a key role in the signaling pathway, but the molecules that regulate upstream signaling are still not known. Here we identified the guanine nucleotide exchange factor ECT2 as an activator of the polarity complex. ECT2 interacted with Par6 as well as Par3 and PKCζ. Coexpression of Par6 and ECT2 efficiently activated Cdc42 in vivo. Overexpression of ECT2 also stimulated the PKCζ activity, whereas dominant-negative ECT2 inhibited the increase in PKCζ activity stimulated by Par6. ECT2 localization was detected at sites of cell-cell contact as well as in the nucleus of MDCK cells. The expression and localization of ECT2 were regulated by calcium, which is a critical regulator of cell-cell adhesion. Together, these results suggest that ECT2 regulates the polarity complex Par6/Par3/PKCζ and possibly plays a role in epithelial cell polarity.

scholarly journals Novel Roles of Hakai in Cell Proliferation and Oncogenesis

2009 ◽  
Vol 20 (15) ◽  
pp. 3533-3542 ◽  
Author(s):  
Angélica Figueroa ◽  
Hirokazu Kotani ◽  
Yoshinobu Toda ◽  
Krystyna Mazan-Mamczarz ◽  
Eva-Christina Mueller ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Rna Binding ◽  
Tumor Development ◽  
Human Colon ◽  
Dominant Negative ◽  
Interacting Protein ◽  
Cell Contacts ◽  
Cellular Processes ◽  
Important Regulator ◽  
Cell Cell

During tumor development, cells acquire multiple phenotypic changes upon misregulation of oncoproteins and tumor suppressor proteins. Hakai was originally identified as an E3 ubiquitin-ligase for the E-cadherin complex that regulates cell–cell contacts. Here, we present evidence that Hakai plays a crucial role in various cellular processes and tumorigenesis. Overexpression of Hakai affects not only cell–cell contacts but also proliferation in both epithelial and fibroblast cells. Furthermore, the knockdown of Hakai significantly suppresses proliferation of transformed epithelial cells. Expression of Hakai is correlated to the proliferation rate in human tissues and is highly up-regulated in human colon and gastric adenocarcinomas. Moreover, we identify PTB-associated splicing factor (PSF), an RNA-binding protein, as a novel Hakai-interacting protein. By using cDNA arrays, we have determined various specific PSF-associated mRNAs encoding proteins that are involved in several cancer-related processes. Hakai affects the ability of PSF to bind these mRNAs, and expression of PSF short hairpin RNA or a dominant-negative PSF mutant significantly suppresses proliferation of Hakai-overexpressing cells. Collectively, these results suggest that Hakai is an important regulator of cell proliferation and that Hakai may be an oncoprotein and a potential molecular target for cancer treatment.

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 Rab35 regulates cadherin-mediated adherens junction formation and myoblast fusion

2013 ◽  
Vol 24 (3) ◽  
pp. 234-245 ◽  
Author(s):  
Sophie Charrasse ◽  
Franck Comunale ◽  
Sylvain De Rossi ◽  
Arnaud Echard ◽  
Cécile Gauthier-Rouvière
Keyword(s):  
Adherens Junction ◽  
Phosphatidyl Inositol ◽  
Myoblast Fusion ◽  
Small Gtpase ◽  
Dominant Negative ◽  
Cell Contact ◽  
Dependent Manner ◽  
Cell Contacts ◽  
Contact Sites ◽  
Cell Cell

Cadherins are homophilic cell–cell adhesion molecules implicated in many fundamental processes, such as morphogenesis, cell growth, and differentiation. They accumulate at cell–cell contact sites and assemble into large macromolecular complexes named adherens junctions (AJs). Cadherin targeting and function are regulated by various cellular processes, many players of which remain to be uncovered. Here we identify the small GTPase Rab35 as a new regulator of cadherin trafficking and stabilization at cell–cell contacts in C2C12 myoblasts and HeLa cells. We find that Rab35 accumulates at cell–cell contacts in a cadherin-dependent manner. Knockdown of Rab35 or expression of a dominant-negative form of Rab35 impaired N- and M-cadherin recruitment to cell–cell contacts, their stabilization at the plasma membrane, and association with p120 catenin and led to their accumulation in transferrin-, clathrin-, and AP-2–positive intracellular vesicles. We also find that Rab35 function is required for PIP5KIγ accumulation at cell–cell contacts and phosphatidyl inositol 4,5-bisphosphate production, which is involved in cadherin stabilization at contact sites. Finally, we show that Rab35 regulates myoblast fusion, a major cellular process under the control of cadherin-dependent signaling. Taken together, these results reveal that Rab35 regulates cadherin-dependent AJ formation and myoblast fusion.

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