scholarly journals RhoA is required for cortical retraction and rigidity during mitotic cell rounding

2003 ◽  
Vol 160 (2) ◽  
pp. 255-265 ◽  
Author(s):  
Amy Shaub Maddox ◽  
Keith Burridge
Keyword(s):  
Actin Cytoskeleton ◽  
Molecular Mechanisms ◽  
Shape Change ◽  
Rho Kinase ◽  
Mitotic Cell ◽  
Cortical Actin ◽  
Interphase Cell ◽  
Cell Rounding ◽  
Rhoa Activity ◽  
Cell Shape Change

Mitotic cell rounding is the process of cell shape change in which a flat interphase cell becomes spherical at the onset of mitosis. Rearrangement of the actin cytoskeleton, de-adhesion, and an increase in cortical rigidity accompany mitotic cell rounding. The molecular mechanisms that contribute to this process have not been defined. We show that RhoA is required for cortical retraction but not de-adhesion during mitotic cell rounding. The mitotic increase in cortical rigidity also requires RhoA, suggesting that increases in cortical rigidity and cortical retraction are linked processes. Rho-kinase is also required for mitotic cortical retraction and rigidity, indicating that the effects of RhoA on cell rounding are mediated through this effector. Consistent with a role for RhoA during mitotic entry, RhoA activity is elevated in rounded, preanaphase mitotic cells. The activity of the RhoA inhibitor p190RhoGAP is decreased due to its serine/threonine phosphorylation at this time. Cumulatively, these results suggest that the mitotic increase in RhoA activity leads to rearrangements of the cortical actin cytoskeleton that promote cortical rigidity, resulting in mitotic cell rounding.

scholarly journals The Drosophila afadin homologue Canoe regulates linkage of the actin cytoskeleton to adherens junctions during apical constriction

2009 ◽  
Vol 186 (1) ◽  
pp. 57-73 ◽  
Author(s):  
Jessica K. Sawyer ◽  
Nathan J. Harris ◽  
Kevin C. Slep ◽  
Ulrike Gaul ◽  
Mark Peifer
Keyword(s):  
Actin Cytoskeleton ◽  
Cell Shape ◽  
Shape Change ◽  
Adherens Junctions ◽  
Apical Constriction ◽  
Cell Shape Change ◽  
Mediate Cell Adhesion ◽  
Mediate Cell ◽  
Actomyosin Cytoskeleton ◽  
Core Part

Cadherin-based adherens junctions (AJs) mediate cell adhesion and regulate cell shape change. The nectin–afadin complex also localizes to AJs and links to the cytoskeleton. Mammalian afadin has been suggested to be essential for adhesion and polarity establishment, but its mechanism of action is unclear. In contrast, Drosophila melanogaster’s afadin homologue Canoe (Cno) has suggested roles in signal transduction during morphogenesis. We completely removed Cno from embryos, testing these hypotheses. Surprisingly, Cno is not essential for AJ assembly or for AJ maintenance in many tissues. However, morphogenesis is impaired from the start. Apical constriction of mesodermal cells initiates but is not completed. The actomyosin cytoskeleton disconnects from AJs, uncoupling actomyosin constriction and cell shape change. Cno has multiple direct interactions with AJ proteins, but is not a core part of the cadherin–catenin complex. Instead, Cno localizes to AJs by a Rap1- and actin-dependent mechanism. These data suggest that Cno regulates linkage between AJs and the actin cytoskeleton during morphogenesis.

scholarly journals RhoA GTPase inhibition organizes contraction during epithelial morphogenesis

2016 ◽  
Vol 214 (5) ◽  
pp. 603-617 ◽  
Author(s):  
Frank M. Mason ◽  
Shicong Xie ◽  
Claudia G. Vasquez ◽  
Michael Tworoger ◽  
Adam C. Martin
Keyword(s):  
Cell Shape ◽  
Shape Change ◽  
Critical Role ◽  
Central Position ◽  
Nucleotide Exchange ◽  
Apical Constriction ◽  
Cell Contractility ◽  
Rhoa Activity ◽  
Cell Shape Change ◽  
Rhoa Gtpase

During morphogenesis, contraction of the actomyosin cytoskeleton within individual cells drives cell shape changes that fold tissues. Coordination of cytoskeletal contractility is mediated by regulating RhoA GTPase activity. Guanine nucleotide exchange factors (GEFs) activate and GTPase-activating proteins (GAPs) inhibit RhoA activity. Most studies of tissue folding, including apical constriction, have focused on how RhoA is activated by GEFs to promote cell contractility, with little investigation as to how GAPs may be important. Here, we identify a critical role for a RhoA GAP, Cumberland GAP (C-GAP), which coordinates with a RhoA GEF, RhoGEF2, to organize spatiotemporal contractility during Drosophila melanogaster apical constriction. C-GAP spatially restricts RhoA pathway activity to a central position in the apical cortex. RhoGEF2 pulses precede myosin, and C-GAP is required for pulsation, suggesting that contractile pulses result from RhoA activity cycling. Finally, C-GAP expression level influences the transition from reversible to irreversible cell shape change, which defines the onset of tissue shape change. Our data demonstrate that RhoA activity cycling and modulating the ratio of RhoGEF2 to C-GAP are required for tissue folding.

FilGAP and its close relatives: a mediator of Rho–Rac antagonism that regulates cell morphology and migration

2013 ◽  
Vol 453 (1) ◽  
pp. 17-25 ◽  
Author(s):  
Fumihiko Nakamura
Keyword(s):  
Actin Cytoskeleton ◽  
Gene Product ◽  
Rho Kinase ◽  
Leading Edge ◽  
Filamin A ◽  
Filamentous Actin ◽  
Rhoa Activity ◽  
Cell Protrusion ◽  
And Migration ◽  
Close Relatives

Cell migration, phagocytosis and cytokinesis are mechanically intensive cellular processes that are mediated by the dynamic assembly and contractility of the actin cytoskeleton. GAPs (GTPase-activating proteins) control activities of the Rho family proteins including Cdc42, Rac1 and RhoA, which are prominent upstream regulators of the actin cytoskeleton. The present review concerns a class of Rho GAPs, FilGAP (ARHGAP24 gene product) and its close relatives (ARHGAP22 and AHRGAP25 gene products). FilGAP is a GAP for Rac1 and a binding partner of FLNa (filamin A), a widely expressed F-actin (filamentous actin)-cross-linking protein that binds many different proteins that are important in cell regulation. Phosphorylation of FilGAP serine/threonine residues and binding to FLNa modulate FilGAP's GAP activity and, as a result, its ability to regulate cell protrusion and spreading. FLNa binds to FilGAP at F-actin-enriched sites, such as at the leading edge of the cell where Rac1 activity is controlled to inhibit actin assembly. FilGAP then dissociates from FLNa in actin networks by myosin-dependent mechanical deformation of FLNa's FilGAP-binding site to relocate at the plasma membrane by binding to polyphosphoinositides. Since actomyosin contraction is activated downstream of RhoA–ROCK (Rho-kinase), RhoA activity regulates Rac1 through FilGAP by signalling to the force-generating system. FilGAP and the ARHGAP22 gene product also act as mediators between RhoA and Rac1 pathways, which lead to amoeboid and mesenchymal modes of cell movements respectively. Therefore FilGAP and its close relatives are key regulators that promote the reciprocal inhibitory relationship between RhoA and Rac1 in cell shape changes and the mesenchymal–amoeboid transition in tumour cells.

scholarly journals Localized recruitment and activation of RhoA underlies dendritic spine morphology in a glutamate receptor–dependent manner

2006 ◽  
Vol 172 (3) ◽  
pp. 453-467 ◽  
Author(s):  
Vanessa Schubert ◽  
Jorge Santos Da Silva ◽  
Carlos G. Dotti
Keyword(s):  
Actin Cytoskeleton ◽  
Dendritic Spine ◽  
Hippocampal Neurons ◽  
Molecular Mechanisms ◽  
Excitatory Synapses ◽  
Dependent Manner ◽  
Rhoa Activity ◽  
Spine Shape ◽  
Local Reduction ◽  
Dendritic Spine Morphology

Actin is the major cytoskeletal source of dendritic spines, which are highly specialized protuberances on the neuronal surface where excitatory synaptic transmission occurs (Harris, K.M., and S.B. Kater. 1994. Annu. Rev. Neurosci. 17:341–371; Yuste, R., and D.W. Tank. 1996. Neuron. 16:701–716). Stimulation of excitatory synapses induces changes in spine shape via localized rearrangements of the actin cytoskeleton (Matus, A. 2000. Science. 290:754–758; Nagerl, U.V., N. Eberhorn, S.B. Cambridge, and T. Bonhoeffer. 2004. Neuron. 44:759–767). However, what remains elusive are the precise molecular mechanisms by which different neurotransmitter receptors forward information to the underlying actin cytoskeleton. We show that in cultured hippocampal neurons as well as in whole brain synaptosomal fractions, RhoA associates with glutamate receptors (GluRs) at the spine plasma membrane. Activation of ionotropic GluRs leads to the detachment of RhoA from these receptors and its recruitment to metabotropic GluRs. Concomitantly, this triggers a local reduction of RhoA activity, which, in turn, inactivates downstream kinase RhoA-specific kinase, resulting in restricted actin instability and dendritic spine collapse. These data provide a direct mechanistic link between neurotransmitter receptor activity and the changes in spine shape that are thought to play a crucial role in synaptic strength.

scholarly journals Actin, RhoA, and Rab11 Participation during Encystment inEntamoeba invadens

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
M. Herrera-Martínez ◽  
V. I. Hernández-Ramírez ◽  
A. E. Lagunes-Guillén ◽  
B. Chávez-Munguía ◽  
P. Talamás-Rohana
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
Decisive Role ◽  
Small Gtpase ◽  
Cell Rounding ◽  
Rhoa Activity ◽  
High Level ◽  
Entamoeba Invadens ◽  
Related Proteins ◽  
Wall Components

In the genusEntamoeba, actin reorganization is necessary for cyst differentiation; however, its role is still unknown. The aim of this work was to investigate the role of actin and encystation-related proteins duringEntamoeba invadensencystation. Studied proteins were actin, RhoA, a small GTPase involved through its effectors in the rearrangement of the actin cytoskeleton; Rab11, a protein involved in the transport of encystation vesicles; and enolase, as an encystment vesicles marker. Results showed a high level of polymerized actin accompanied by increased levels of RhoA-GTP during cell rounding and loss of vacuoles. Cytochalasin D, an actin polymerization inhibitor, and Y27632, an inhibitor of RhoA activity, reduced encystment in 80%. These inhibitors also blocked cell rounding, disposal of vacuoles, and the proper formation of the cysts wall. At later times, F-actin and Rab11 colocalized with enolase, suggesting that Rab11 could participate in the transport of the cyst wall components through the F-actin cytoskeleton. These results suggest that actin cytoskeleton rearrangement is playing a decisive role in determining cell morphology changes and helping with the transport of cell wall components to the cell surface during encystment ofE. invadens.

Cdc42 and RhoA have opposing roles in regulating membrane type 1-matrix metalloproteinase localization and matrix metalloproteinase-2 activation

2008 ◽  
Vol 295 (3) ◽  
pp. C600-C610 ◽  
Author(s):  
Eric Ispanovic ◽  
Damiano Serio ◽  
Tara L. Haas
Keyword(s):  
Endothelial Cells ◽  
Cell Surface ◽  
Matrix Metalloproteinase ◽  
Actin Cytoskeleton ◽  
Cortical Actin ◽  
Rhoa Activity ◽  
Surface Localization ◽  
Cell Surface Localization ◽  
Membrane Type

Proteolysis of the basement membrane and interstitial matrix occurs early in the angiogenic process and requires matrix metalloproteinase (MMP) activity. Skeletal muscle microvascular endothelial cells exhibit robust actin stress fibers, low levels of membrane type 1 (MT1)-MMP expression, and minimal MMP-2 activation. Depolymerization of the actin cytoskeleton increases MT1-MMP expression and MMP-2 activation. Rho family GTPases are regulators of actin cytoskeleton dynamics, and their activity can be modulated in response to angiogenic stimuli such as vascular endothelial growth factor (VEGF). Therefore, we investigated their roles in MMP-2 and MT1-MMP production. Endothelial cells treated with H1152 [an inhibitor of Rho kinase (ROCK)] induced stress fiber depolymerization and an increase in cortical actin. Both MMP-2 and MT1-MMP mRNA increased, which translated into greater MMP-2 protein production and activation. ROCK inhibition rapidly increased cell surface localization of MT1-MMP and increased PI3K activity, which was required for MMP-2 activation. Constitutively active Cdc42 increased cortical actin polymerization, phosphatidylinositol 3-kinase activity, MT1-MMP cell surface localization, and MMP-2 activation similarly to inhibition of ROCK. Activation of Cdc42 was sufficient to decrease RhoA activity. Capillary sprout formation in a three-dimensional collagen matrix was increased in cultures treated with RhoAN19 or Cdc42QL and, conversely, decreased in cultures treated with dominant negative Cdc42N17. VEGF stimulation also induced activation of Cdc42 while inhibiting RhoA activity. Furthermore, VEGF-dependent activation of MMP-2 was reduced by inhibition of Cdc42. These results suggest that Cdc42 and RhoA have opposing roles in regulating cell surface localization of MT1-MMP and MMP-2 activation.

scholarly journals Runx3 Induces a Cell Shape Change and Suppresses Migration and Metastasis of Melanoma Cells by Altering a Transcriptional Profile

2021 ◽  
Vol 22 (4) ◽  
pp. 2219
Author(s):  
Ning Wang ◽  
Haiying Zhang ◽  
Xiulin Cui ◽  
Chao Ma ◽  
Linghui Wang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Actin Cytoskeleton ◽  
Cell Shape ◽  
Shape Change ◽  
Hdac Inhibitors ◽  
Metastatic Potential ◽  
Melanoma Cells ◽  
Transcriptional Profile ◽  
Cell Shape Change ◽  
Related Transcription Factor

Runt-related transcription factor-3 (Runx3) is a tumor suppressor, and its contribution to melanoma progression remains unclear. We previously demonstrated that Runx3 re-expression in B16-F10 melanoma cells changed their shape and attenuated their migration. In this study, we found that Runx3 re-expression in B16-F10 cells also suppressed their pulmonary metastasis. We performed microarray analysis and uncovered an altered transcriptional profile underlying the cell shape change and the suppression of migration and metastasis. This altered transcriptional profile was rich in Gene Ontology/Kyoto Encyclopedia of Genes and Genomes (GO/KEGG) annotations relevant to adhesion and the actin cytoskeleton and included differentially expressed genes for some major extracellular matrix (ECM) proteins as well as genes that were inversely associated with the increase in the metastatic potential of B16-F10 cells compared to B16-F0 melanoma cells. Further, we found that this altered transcriptional profile could have prognostic value, as evidenced by myelin and lymphocyte protein (MAL) and vilin-like (VILL). Finally, Mal gene expression was correlated with metastatic potential among the cells and was targeted by histone deacetylase (HDAC) inhibitors in B16-F10 cells, and the knockdown of Mal gene expression in B16-F0 cells changed their shape and enhanced the migratory and invasive traits of their metastasis. Our study suggests that self-entrapping of metastatic Runx3-negative melanoma cells via adhesion and the actin cytoskeleton could be a powerful therapeutic strategy.

Biomechanical analysis of actin cytoskeleton function based on a spring network cell model

2016 ◽  
Vol 231 (7) ◽  
pp. 1308-1323 ◽  
Author(s):  
Hamed Ghaffari ◽  
Mohammad Said Saidi ◽  
Bahar Firoozabadi
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Filaments ◽  
Cell Shape ◽  
Binding Proteins ◽  
Cell Model ◽  
Shape Change ◽  
Cell Deformation ◽  
Actin Binding ◽  
Actin Binding Proteins ◽  
Cell Shape Change

In this study, a new method for the simulation of the time-dependent behavior of actin cytoskeleton during cell shape change is proposed. For this purpose, a three-dimensional model of endothelial cell consisting of cell membrane, nucleus membrane, and main components of cytoskeleton, namely actin filaments, microtubules, and intermediate filaments is utilized. Actin binding proteins, which play a key role in regulating actin cytoskeleton behavior, are also simulated by using a novel technique. The actin cytoskeleton in this model is more dynamic and adoptable during cell deformation in comparison to previous models. The proposed model is subjected to compressive force between parallel micro plates in order to investigate actin cytoskeleton role in cell stiffening behavior, nucleus deformation, and cell shape change. The validity of the model is examined through the comparison of the obtained results with the data presented in previous literature. Not only does the model force deformation curve lie within a range of the experimental data, but also the elastic modulus of the cell model is in accordance with former studies. Our findings demonstrate that augmentation of actin filaments concentration within the cell reduces force transmission from cell membrane to the nucleus. Furthermore, actin binding proteins concentration increases by the enhancement of cell deformation and it is also indicated that cell stiffening with an increase in applied force is significantly affected by actin filaments reorientation, actin binding proteins reorganization and actin binding proteins augmentation.

scholarly journals Inversin modulates the cortical actin network during mitosis

2013 ◽  
Vol 305 (1) ◽  
pp. C36-C47 ◽  
Author(s):  
Michael E. Werner ◽  
Heather H. Ward ◽  
Carrie L. Phillips ◽  
Caroline Miller ◽  
Vincent H. Gattone ◽  
...  
Keyword(s):  
Cell Division ◽  
Mammalian Cells ◽  
Cyst Formation ◽  
Mitotic Cell ◽  
Mouse Embryos ◽  
Cortical Actin ◽  
Division Plane ◽  
Spindle Positioning ◽  
Actin Organization ◽  
Cell Rounding

Mutations in inversin cause nephronophthisis type II, an autosomal recessive form of polycystic kidney disease associated with situs inversus, dilatation, and kidney cyst formation. Since cyst formation may represent a planar polarity defect, we investigated whether inversin plays a role in cell division. In developing nephrons from inv−/− mouse embryos we observed heterogeneity of nuclear size, increased cell membrane perimeters, cells with double cilia, and increased frequency of binuclear cells. Depletion of inversin by siRNA in cultured mammalian cells leads to an increase in bi- or multinucleated cells. While spindle assembly, contractile ring formation, or furrow ingression appears normal in the absence of inversin, mitotic cell rounding and the underlying rearrangement of the cortical actin cytoskeleton are perturbed. We find that inversin loss causes extensive filopodia formation in both interphase and mitotic cells. These cells also fail to round up in metaphase. The resultant spindle positioning defects lead to asymmetric division plane formation and cell division. In a cell motility assay, fibroblasts isolated from inv−/− mouse embryos migrate at half the speed of wild-type fibroblasts. Together these data suggest that inversin is a regulator of cortical actin required for cell rounding and spindle positioning during mitosis. Furthermore, cell division defects resulting from improper spindle position and perturbed actin organization contribute to altered nephron morphogenesis in the absence of inversin.

scholarly journals Unidirectional Eph/ephrin signaling creates a cortical actomyosin differential to drive cell segregation

2016 ◽  
Vol 215 (2) ◽  
pp. 217-229 ◽  
Author(s):  
Audrey K. O’Neill ◽  
Abigail A. Kindberg ◽  
Terren K. Niethamer ◽  
Andrew R. Larson ◽  
Hsin-Yi Henry Ho ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Rho Kinase ◽  
Mouse Genetics ◽  
Tissue Formation ◽  
Cortical Actin ◽  
Mammalian Embryo ◽  
Actomyosin Contractility ◽  
Bidirectional Signaling ◽  
Fundamental Process ◽  
Cell Segregation

Cell segregation is the process by which cells self-organize to establish developmental boundaries, an essential step in tissue formation. Cell segregation is a common outcome of Eph/ephrin signaling, but the mechanisms remain unclear. In craniofrontonasal syndrome, X-linked mosaicism for ephrin-B1 expression has been hypothesized to lead to aberrant Eph/ephrin-mediated cell segregation. Here, we use mouse genetics to exploit mosaicism to study cell segregation in the mammalian embryo and integrate live-cell imaging to examine the underlying cellular and molecular mechanisms. Our data demonstrate that dramatic ephrin-B1–mediated cell segregation occurs in the early neuroepithelium. In contrast to the paradigm that repulsive bidirectional signaling drives cell segregation, unidirectional EphB kinase signaling leads to cell sorting by the Rho kinase–dependent generation of a cortical actin differential between ephrin-B1– and EphB-expressing cells. These results define mechanisms of Eph/ephrin-mediated cell segregation, implicating unidirectional regulation of cortical actomyosin contractility as a key effector of this fundamental process.

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