Defects in Rho GTPase Signaling to the Spine Actin Cytoskeleton in FMR1 Knockout Mice

In mammalian cells, Rho GTPases control the reorganisation of the actin cytoskeleton in response to growth factors. In the cytoplasm, the polymerisation of actin filaments and their organisation into complex architectures is orchestrated by numerous proteins which act either directly, by interacting with actin, or by producing secondary messengers which serve as mediators between signal transduction pathways and the microfilament organisation. We sought to determine whether the intracellular distribution of some of these regulatory components may be controlled by the Rho GTPase CDC42Hs. With this aim, we have established HeLa-derived human cell lines in which expression of a constitutively activated mutant of CDC42Hs is inducible. Morphological analysis by immunofluorescence labelling and confocal laser scanning microscopy revealed a massive reorganisation of F-actin in cortical microspikes as well as podosome-like structures located at the ventral face of the cells. Concomitantly, the cells became giant and multinucleate indicating that cytokinesis was impaired. The actin bundling protein T-plastin, the vasodilatator-stimulated phosphoprotein (VASP), a profilin ligand, as well as the 85 kDa regulatory subunit of the phosphoinosite 3-kinase redistributed with F-actin into the CDC42Hs-induced structures.

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Polarized Distribution of IQGAP Proteins in Gastric Parietal Cells and Their Roles in Regulated Epithelial Cell Secretion

Molecular Biology of the Cell ◽

10.1091/mbc.e02-07-0425 ◽

2003 ◽

Vol 14 (3) ◽

pp. 1097-1108 ◽

Cited By ~ 25

Author(s):

Rihong Zhou ◽

Zhen Guo ◽

Charles Watson ◽

Emily Chen ◽

Rong Kong ◽

...

Keyword(s):

Epithelial Cell ◽

Actin Cytoskeleton ◽

Acid Secretion ◽

Rho Gtpase ◽

Apical Membrane ◽

Basolateral Membrane ◽

Parietal Cells ◽

Actin Dynamics ◽

Cell Secretion ◽

Gastric Parietal Cells

Actin cytoskeleton plays an important role in the establishment of epithelial cell polarity. Cdc42, a member of Rho GTPase family, modulates actin dynamics via its regulators, such as IQGAP proteins. Gastric parietal cells are polarized epithelial cells in which regulated acid secretion occurs in the apical membrane upon stimulation. We have previously shown that actin isoforms are polarized to different membrane domains and that the integrity of the actin cytoskeleton is essential for acid secretion. Herein, we show that Cdc42 is preferentially distributed to the apical membrane of gastric parietal cells. In addition, we revealed that two Cdc42 regulators, IQGAP1 and IQGAP2, are present in gastric parietal cells. Interestingly, IQGAP2 is polarized to the apical membrane of the parietal cells, whereas IQGAP1 is mainly distributed to the basolateral membrane. An IQGAP peptide that competes with full-length IQGAP proteins for Cdc42-binding in vitro also inhibits acid secretion in streptolysin-O-permeabilized gastric glands. Furthermore, this peptide disrupts the association of IQGAP and Cdc42 with the apical actin cytoskeleton and prevents the apical membrane remodeling upon stimulation. We propose that IQGAP2 forms a link that associates Cdc42 with the apical cytoskeleton and thus allows for activation of polarized secretion in gastric parietal cells.

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The atypical Rho GTPase RhoD is a regulator of actin cytoskeleton dynamics and directed cell migration

Experimental Cell Research ◽

10.1016/j.yexcr.2017.02.013 ◽

2017 ◽

Vol 352 (2) ◽

pp. 255-264 ◽

Cited By ~ 15

Author(s):

Magdalena Blom ◽

Katarina Reis ◽

Johan Heldin ◽

Johan Kreuger ◽

Pontus Aspenström

Keyword(s):

Cell Migration ◽

Actin Cytoskeleton ◽

Rho Gtpase ◽

Directed Cell Migration ◽

Cytoskeleton Dynamics

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WAVE signalling: from biochemistry to biology

Biochemical Society Transactions ◽

10.1042/bst0340073 ◽

2006 ◽

Vol 34 (1) ◽

pp. 73-76 ◽

Cited By ~ 28

Author(s):

S.H. Soderling ◽

J.D. Scott

Keyword(s):

Cell Division ◽

Actin Cytoskeleton ◽

Rho Gtpase ◽

Current Knowledge ◽

Biological Significance ◽

Molecular Switches ◽

Small Gtpases ◽

Present Review ◽

Cellular Targets ◽

Syndrome Protein

The small GTPases Rho, Rac and Cdc42 (cell-division cycle 42) function as molecular switches to modulate the actin cytoskeleton. They achieve this by modulating the activity of downstream cellular targets. One group of Rho GTPase effectors, WAVE (Wiskott–Aldrich syndrome protein verprolin homologous)-1, WAVE-2 and WAVE-3, function as scaffolds for actin-based signalling complexes. The present review highlights current knowledge regarding the biochemistry of the WAVE signalling complexes and their biological significance.

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Rho GTPase signaling modulates cell shape and contractile phenotype in an isoactin-specific manner

AJP Cell Physiology ◽

10.1152/ajpcell.00177.2003 ◽

2003 ◽

Vol 285 (5) ◽

pp. C1116-C1121 ◽

Cited By ~ 28

Author(s):

Alexey Y. Kolyada ◽

Kathleen N. Riley ◽

Ira M. Herman

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Actin Cytoskeleton ◽

Cell Size ◽

Rho Gtpase ◽

Small Gtpases ◽

Protein Isoforms ◽

Stress Fibers ◽

Contractile Phenotype ◽

Specific Manner

Rho family small GTPases (Rho, Rac, and Cdc42) play an important role in cell motility, adhesion, and cell division by signaling reorganization of the actin cytoskeleton. Here, we report an isoactin-specific, Rho GTPase-dependent signaling cascade in cells simultaneously expressing smooth muscle and nonmuscle actin isoforms. We transfected primary cultures of microvascular pericytes, cells related to vascular smooth muscle cells, with various Rho-related and Rho-specific expression plasmids. Overexpression of dominant positive Rho resulted in the formation of nonmuscle actin-containing stress fibers. At the same time, α-vascular smooth muscle actin (αVSMactin) containing stress fibers were disassembled, resulting in a dramatic reduction in cell size. Rho activation also yielded a disassembly of smooth muscle myosin and nonmuscle myosin from stress fibers. Overexpression of wild-type Rho had similar but less dramatic effects. In contrast, dominant negative Rho and C3 exotransferase or dominant positive Rac and Cdc42 expression failed to alter the actin cytoskeleton in an isoform-specific manner. The loss of smooth muscle contractile protein isoforms in pericyte stress fibers, together with a concomitant decrease in cell size, suggests that Rho activation influences “contractile” phenotype in an isoactin-specific manner. This, in turn, should yield significant alteration in microvascular remodeling during developmental and pathologic angiogenesis.

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The small Rho GTPase Rif and actin cytoskeletal remodelling

Biochemical Society Transactions ◽

10.1042/bst20110625 ◽

2012 ◽

Vol 40 (1) ◽

pp. 268-272 ◽

Cited By ~ 14

Author(s):

Lifei Fan ◽

Harry Mellor

Keyword(s):

Actin Cytoskeleton ◽

Rho Gtpase ◽

Active Form ◽

Present Review ◽

Gtpase Domain ◽

Domain Structures ◽

Downstream Effectors ◽

Inactive Form ◽

The Family ◽

Recent Addition

The Rif GTPase is a recent addition to small Rho GTPase family; it shares low homology with other members in the family and evolutionarily parallels with the development of vertebrates. Rif has the conserved Rho GTPase domain structures and cycles between a GDP-bound inactive form and a GTP-bound active form. In its active form, Rif signals through multiple downstream effectors. In the present review, our aim is to summarize the current information about the Rif effectors and how Rif remodels actin cytoskeleton in many aspects.

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The Cell Wall Integrity MAPK pathway controls actin cytoskeleton assembly during fungal somatic cell fusion

10.1101/2020.08.12.246843 ◽

2020 ◽

Author(s):

Antonio Serrano ◽

Hamzeh H. Hammadeh ◽

Natalie Schwarz ◽

Ulrike Brandt ◽

André Fleißner

Keyword(s):

Cell Wall ◽

Actin Cytoskeleton ◽

Somatic Cell ◽

Cell Fusion ◽

Rho Gtpase ◽

Cell Wall Integrity ◽

Physical Contact ◽

Functional Link ◽

Somatic Cell Fusion ◽

Gtpase Rac

AbstractSomatic cell fusion is widely studied in the filamentous fungus Neurospora crassa. The interaction of genetically identical germlings is mediated by a signaling mechanism in which the cells take turns in signal-sending and receiving. The switch between these physiological states is represented by the alternating membrane recruitment of the SO protein and the MAPK MAK-2. This dialog-like behavior is observed until the cells establish physical contact, when the cell-wall-integrity MAK-1 is recruited to the contact area to control the final steps of the cell fusion process. This work revealed, for the first-time, an additional MAK-1-function during the tropic growth phase. Specific inhibition of MAK-1 during tropic-growth resulted in disassembly of the actin-aster, and mislocalization of SO and MAK-2. Similar defects were observed after the inhibition of the Rho-GTPase RAC-1, suggesting a functional link between them, being MAK-1 upstream of RAC-1. In contrast, after inhibition of MAK-2, the actin-aster stayed intact, however, its subcellular localization became instable within the cell-membrane. Together these observations led to a new working model, in which MAK-1 promotes the formation and stability of the actin-aster, while MAK-2 controls its positionning and cell growth directionality.Summary statementThe CWI MAPK MAK-1 pathway controls actin cytoskeleton assembly at the cell tips through activation of the Rho-GTPase RAC-1 exclusively on somatic cell fusion.

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Cell motility: can Rho GTPases and microtubules point the way?

Journal of Cell Science ◽

10.1242/jcs.114.21.3795 ◽

2001 ◽

Vol 114 (21) ◽

pp. 3795-3803 ◽

Cited By ~ 2

Author(s):

Torsten Wittmann ◽

Clare M. Waterman-Storer

Keyword(s):

Actin Cytoskeleton ◽

Cell Motility ◽

Rho Gtpases ◽

Molecular Mechanisms ◽

Rho Gtpase ◽

Cell Types ◽

Small Gtpases ◽

Cell Polarization ◽

Microtubule Cytoskeleton ◽

Filament Bundles

Migrating cells display a characteristic polarization of the actin cytoskeleton. Actin filaments polymerise in the protruding front of the cell whereas actin filament bundles contract in the cell body, which results in retraction of the cell’s rear. The dynamic organization of the actin cytoskeleton provides the force for cell motility and is regulated by small GTPases of the Rho family, in particular Rac1, RhoA and Cdc42. Although the microtubule cytoskeleton is also polarized in a migrating cell, and microtubules are essential for the directed migration of many cell types, their role in cell motility is not well understood at a molecular level. Here, we discuss the potential molecular mechanisms for interplay of microtubules, actin and Rho GTPase signalling in cell polarization and motility. Recent evidence suggests that microtubules locally modulate the activity of Rho GTPases and, conversely, Rho GTPases might be responsible for the initial polarization of the microtubule cytoskeleton. Thus, microtubules might be part of a positive feedback mechanism that maintains the stable polarization of a directionally migrating cell.

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