scholarly journals The motor activity of myosin-X promotes actin fiber convergence at the cell periphery to initiate filopodia formation

2007 ◽  
Vol 179 (2) ◽  
pp. 229-238 ◽  
Author(s):  
Hiroshi Tokuo ◽  
Katsuhide Mabuchi ◽  
Mitsuo Ikebe
Keyword(s):  
Motor Activity ◽  
Motor Function ◽  
Leading Edge ◽  
Living Cells ◽  
Cell Periphery ◽  
Actin Reorganization ◽  
Cell Biol ◽  
Actin Fiber ◽  
Myosin X ◽  
Migrating Cells

Filopodia are actin-rich fingerlike protrusions found at the leading edge of migrating cells and are believed to play a role in directional sensing. Previous studies have shown that myosin-X (myoX) promotes filopodia formation and that this is mediated through its ability to deliver specific cargoes to the cell periphery (Tokuo, H., and M. Ikebe. 2004. Biochem Biophys. Commun. 319:214–220; Zhang, H., J.S. Berg, Z. Li, Y. Wang, P. Lang, A.D. Sousa, A. Bhaskar, R.E. Cheney, and S. Stromblad. 2004. Nat. Cell Biol. 6:523–531; Bohil, A.B., B.W. Robertson, and R.E. Cheney. 2006. Proc. Natl. Acad. Sci. USA. 103:12411–12416; Zhu, X.J., C.Z. Wang, P.G. Dai, Y. Xie, N.N. Song, Y. Liu, Q.S. Du, L. Mei, Y.Q. Ding, and W.C. Xiong. 2007. Nat. Cell Biol. 9:184–192). In this study, we show that the motor function of myoX and not the cargo function is critical for initiating filopodia formation. Using a dimer-inducing technique, we find that myoX lacking its cargo-binding tail moves laterally at the leading edge of lamellipodia and induces filopodia in living cells. We conclude that the motor function of the two-headed form of myoX is critical for actin reorganization at the leading edge, leading to filopodia formation.

scholarly journals Visualization of mRNA translation in living cells

2006 ◽  
Vol 175 (1) ◽  
pp. 67-76 ◽  
Author(s):  
Alexis J. Rodriguez ◽  
Shailesh M. Shenoy ◽  
Robert H. Singer ◽  
John Condeelis
Keyword(s):  
Mrna Translation ◽  
Leading Edge ◽  
Intercellular Junctions ◽  
Mrna Localization ◽  
Living Cells ◽  
C2c12 Cells ◽  
Cell Periphery ◽  
Actin Mrna ◽  
Cell Asymmetry ◽  
Cellular Compartments

The role of mRNA localization is presumably to effect cell asymmetry by synthesizing proteins in specific cellular compartments. However, protein synthesis has never been directly demonstrated at the sites of mRNA localization. To address this, we developed a live cell method for imaging translation of β-actin mRNA. Constructs coding for β-actin, containing tetracysteine motifs, were transfected into C2C12 cells, and sites of nascent polypeptide chains were detected using the biarsenial dyes FlAsH and ReAsH, a technique we call translation site imaging. These sites colocalized with β-actin mRNA at the leading edge of motile myoblasts, confirming that they were translating. β-Actin mRNA lacking the sequence (zipcode) that localizes the mRNA to the cell periphery, eliminated the translation there. A pulse-chase experiment on living cells showed that the recently synthesized protein correlated spatially with the sites of its translation. Additionally, localization of β-actin mRNA and translation activity was enhanced at cell contacts and facilitated the formation of intercellular junctions.

scholarly journals Mechanistic of Rac and Cdc42 synchronization at the cell edge by ARHGAP39-dependent signaling nodules and the impact on protrusion dynamics

2021 ◽  
Author(s):  
Michael Howell ◽  
Violaine Delorme-Walker ◽  
Christopher Welch ◽  
Ritu Pathak ◽  
Klaus M Hahn ◽  
...  
Keyword(s):  
Cell Invasion ◽  
Src Kinase ◽  
Leading Edge ◽  
Gtpase Activating Protein ◽  
Invasion And Metastasis ◽  
Cell Edge ◽  
Motile Cells ◽  
Myosin X ◽  
The Impact ◽  
Migrating Cells

Compartmentalization of GTPase regulators into signaling nodules dictates the GTPase pathways selected. Rac and Cdc42 are synchronized at the cell edge for effective protrusion in motile cells but how their activity is coordinated remains elusive. Here, we discovered that ARHGAP39, a Rac and Cdc42 GTPase-activating protein, sequentially interacts with WAVE and mDia2 to control Rac/lamellipodia and Cdc42/filopodia protrusions, respectively. Mechanistically, ARHGAP39 binds to WAVE and, upon phosphorylation by Src kinase, inactivates Rac to promote Cdc42-induced filopodia formation. With our optimized FRET biosensor, we detected active Cdc42 at the filopodia tips that controls filopodia extension. ARHGAP39 is transported to filopodia tips by Myosin-X where it binds mDia2 and inactivates Cdc42 leading to filopodia retraction. Failure in lamellipodia to filopodia switch by defective ARHGAP39 impairs cell invasion and metastasis. Our study reveals that compartmentalization of ARHGAP39 within Rac/Cdc42 signaling nodules orchestrates the synchronization of lamellipodia/filopodia crosstalk and highlights the intricate regulation of leading edge dynamics in migrating cells.

scholarly journals DENND2B activates Rab13 at the leading edge of migrating cells and promotes metastatic behavior

2015 ◽  
Vol 208 (5) ◽  
pp. 629-648 ◽  
Author(s):  
Maria S. Ioannou ◽  
Emily S. Bell ◽  
Martine Girard ◽  
Mathilde Chaineau ◽  
Jason N.R. Hamlin ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Cancer Progression ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Leading Edge ◽  
Cell Periphery ◽  
Nucleotide Exchange ◽  
Migrating Cells

The small guanosine triphosphatase Rab13 functions in exocytic vesicle trafficking in epithelial cells. Alterations in Rab13 activity have been observed in human cancers, yet the mechanism of Rab13 activation and its role in cancer progression remain unclear. In this paper, we identify the DENN domain protein DENND2B as the guanine nucleotide exchange factor for Rab13 and develop a novel Förster resonance energy transfer–based Rab biosensor to reveal activation of Rab13 by DENND2B at the leading edge of migrating cells. DENND2B interacts with the Rab13 effector MICAL-L2 at the cell periphery, and this interaction is required for the dynamic remodeling of the cell’s leading edge. Disruption of Rab13-mediated trafficking dramatically limits the invasive behavior of epithelial cells in vitro and the growth and migration of highly invasive cancer cells in vivo. Thus, blocking Rab13 activation by DENND2B may provide a novel target to limit the spread of epithelial cancers.

HVEM Analysis of Microfilament Patterns in The Margins of Tissue Cells

1980 ◽  
Vol 38 ◽  
pp. 808-811
Author(s):  
Carol Allen
Keyword(s):  
Cell Movement ◽  
Cell Spreading ◽  
Living Cells ◽  
Tissue Cell ◽  
Large Sample Size ◽  
Cell Periphery ◽  
Whole Cell ◽  
Critical Point Drying ◽  
Lamellar Region ◽  
Tissue Cells

When provided with a suitable solid substrate, tissue cells undergo a rapid conversion from the spherical form expressed in suspension culture to a characteristic flattened morphology. As a result of this conversion, called cell spreading, the cell nucleus and organelles come to occupy a central region of “deep cytoplasm” which slopes steeply into a peripheral “lamellar” region less than 1 pm thick at its outer edge and generally free of cell organelles. Cell spreading is accomplished by a continuous outward repositioning of the lamellar margins. Cell translocation on the substrate results when the activity of the lamellae on one side of the cell become dominant. When this occurs, the cell is “polarized” and moves in the direction of the “leading lamellae”. Careful analysis of tissue cell locomotion by time-lapse microphotography (1) has shown that the deformational movements of the leading lamellae occur in a repeating cycle of advance and retreat in the direction of cell movement and that the rate of such deformations are positively correlated with the speed of cell movement. In the present study, the physical basis for these movements of the cell margin has been examined by comparative light microscopy of living cells with whole-mount electron microscopy of fixed cells. Ultrastructural observations were made on tissue cells grown on Formvar-coated grids, fixed with glutaraldehyde, further processed by critical-point drying, and then photographed in the High Voltage Electron Microscope. This processing and imaging system maintains the 3-dimensional organization of the whole cell, the relationship of the cell to the substrate, and affords a large sample size which facilitates quantitative analysis. Comparative analysis of film records of living cells with the whole-cell micrographs revealed that specific patterns of microfilament organization consistently accompany recognizable stages of lamellar formation and movement. The margins of spreading cells and the leading lamellae of locomoting cells showed a similar pattern of MF repositionings (Figs. 1-4). These results will be discussed in terms of a working model for the mechanics of lamellar motility which includes the following major features: (a) lamellar protrusion results when an intracellular force is exerted at a locally weak area of the cell periphery; (b) the association of cortical MFs with one another determines the local resistance to this force; (c) where MF-to-MF association is weak, the cell periphery expands and some cortical MFs are dragged passively forward; (d) contact of the expanded area with the substrate then triggers the lateral association and reorientation of these cortical MFs into MF bundles parallel to the direction of the expansion; and (e) an active interaction between these MF bundles associated with the cortex of the expanded lamellae and the cortical MFs which remained in the sub-lamellar region then pulls the latter MFs forward toward the expanded area. Thus, the advance of the cell periphery on the substrate occurs in two stages: a passive phase in which some cortical MFs are dragged outward by the force acting to expand the cell periphery, and an active phase in which additional cortical MFs are pulled forward by interaction with the first set. Subsequent interactions between peripheral microfilament bundles and filaments in the deeper cytoplasm could then transmit the advance gained by lamellar expansion to the bulk of the cytoplasm.

Efeitos da terapia por contensão induzida nas lesões encefálicas adquiridas

2016 ◽  
Vol 17 (1) ◽  
pp. 30
Author(s):  
Gabriela Da Silva Matuti ◽  
Rafaela Do Nascimento Borges Marques ◽  
Amanda Conte Magesto ◽  
Rafael Eras Garcia ◽  
Clarissa Barros De Oliveira
Keyword(s):  
Motor Activity ◽  
Motor Function ◽  
Function Test ◽  
Wolf Motor Function Test

Introdução: A Terapia por Contensão Induzida (TCI) é uma técnica de reabilitação que tem como objetivo melhora da função do membro superior.acometido. Objetivos: Determinar se o protocolo da TCI é adequado para a reabilitação do membro superior em adultos com Lesões Encefálicas Adquiridas (LEA), analisar a manutenção dos resultados e identificar possíveis preditores de eficácia da técnica. Método: Estudo retrospectivo, 40 pacientes. As escalas utilizadas foram Motor Activity Log (MAL), Quantidade (QT) e Qualidade (QL) de movimento do membro superior acometido e Wolf Motor Function Test (WMFT). Resultados e discussão: As médias de QT e QL do membro superior acometido no pré e pós-tratamento tiveram um aumento significativo (p < 0,001), enquanto as do WMFT apresentaram uma redução significativa do tempo (p < 0,001), o que representa uma melhora na habilidade motora e maior uso fora do ambiente terapêutico. Os ganhos foram mantidos após 12 meses do término do protocolo, e não foi evidenciado nenhum preditor de evolução. Conclusão: A TCI demonstrou eficácia na melhora da habilidade motora e reversão do não uso aprendido do membro superior acometido, estes resultados foram mantidos após um ano da intervenção. Não foi evidenciado no estudo nenhum fator preditor de eficácia da técnica.Palavras-chave: lesões encefálicas adquiridas, hemiplegia, terapia por contensão induzida, reabilitação.

scholarly journals Molecular Regulation of Actin Turnover at the Leading Edge of Migrating Cells

2015 ◽  
Vol 108 (2) ◽  
pp. 179a-180a
Author(s):  
Brannon R. McCullough ◽  
David J. Odde
Keyword(s):  
Leading Edge ◽  
Molecular Regulation ◽  
Actin Turnover ◽  
Migrating Cells

scholarly journals Smurf1 regulates tumor cell plasticity and motility through degradation of RhoA leading to localized inhibition of contractility

2006 ◽  
Vol 176 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Erik Sahai ◽  
Raquel Garcia-Medina ◽  
Jacques Pouysségur ◽  
Emmanuel Vial
Keyword(s):  
Cell Migration ◽  
Tumor Cell ◽  
Rho Gtpases ◽  
Rho Kinase ◽  
Cell Movement ◽  
Leading Edge ◽  
Cell Periphery ◽  
Tumor Cell Migration ◽  
Tumor Cell Motility

Rho GTPases participate in various cellular processes, including normal and tumor cell migration. It has been reported that RhoA is targeted for degradation at the leading edge of migrating cells by the E3 ubiquitin ligase Smurf1, and that this is required for the formation of protrusions. We report that Smurf1-dependent RhoA degradation in tumor cells results in the down-regulation of Rho kinase (ROCK) activity and myosin light chain 2 (MLC2) phosphorylation at the cell periphery. The localized inhibition of contractile forces is necessary for the formation of lamellipodia and for tumor cell motility in 2D tissue culture assays. In 3D invasion assays, and in in vivo tumor cell migration, the inhibition of Smurf1 induces a mesenchymal–amoeboid–like transition that is associated with a more invasive phenotype. Our results suggest that Smurf1 is a pivotal regulator of tumor cell movement through its regulation of RhoA signaling.

scholarly journals R-Ras Controls Membrane Protrusion and Cell Migration through the Spatial Regulation of Rac and Rho

2005 ◽  
Vol 16 (1) ◽  
pp. 84-96 ◽  
Author(s):  
Michele A. Wozniak ◽  
Lina Kwong ◽  
David Chodniewicz ◽  
Richard L. Klemke ◽  
Patricia J. Keely
Keyword(s):  
Cell Migration ◽  
Molecular Mechanisms ◽  
Leading Edge ◽  
Pi3 Kinase ◽  
Dominant Negative ◽  
Cell Periphery ◽  
Membrane Protrusion ◽  
Spatial Regulation ◽  
Entire Cell ◽  
Migratory Cells

Although it is known that the spatial coordination of Rac and Rho activity is essential for cell migration, the molecular mechanisms regulating these GTPases during migration are unknown. We found that the expression of constitutively activated R-Ras (38V) blocked membrane protrusion and random migration. In contrast, expression of dominant negative R-Ras (41A) enhanced migrational persistence and membrane protrusion. Endogenous R-Ras is necessary for cell migration, as cells that were transfected with siRNA for R-Ras did not migrate. Expression of R-Ras (38V) decreased Rac activity and increased Rho activity around the entire cell periphery, whereas expression of dominant negative R-Ras (41A) showed the converse, suggesting that R-Ras can spatially activate Rho and inactivate Rac. Consistent with this role, endogenous R-Ras localized and was preferentially activated at the leading edge of migratory cells in response to adhesion. The effects of R-Ras on cell migration are mediated by PI3-Kinase, as an effector mutant that uncouples PI3-Kinase binding from R-Ras (38V) rescued migration. From these data, we hypothesize that R-Ras plays a key role in cell migration by locally regulating the switch from Rac to Rho activity after membrane protrusion and adhesion.

GIT1 functions in a motile, multi-molecular signaling complex that regulates protrusive activity and cell migration

2002 ◽  
Vol 115 (7) ◽  
pp. 1497-1510 ◽  
Author(s):  
Ri-ichiroh Manabe ◽  
Mykola Kovalenko ◽  
Donna J. Webb ◽  
Alan Rick Horwitz
Keyword(s):  
Leading Edge ◽  
Binding Domain ◽  
Cell Periphery ◽  
Molecular Signaling ◽  
Cytoskeletal Organization ◽  
Signaling Complex ◽  
Binding Domains ◽  
Arf Gtpases ◽  
Cytoplasmic Structures ◽  
Signaling Components

GIT1 is a multidomain protein that is thought to function as an integrator of signaling pathways controlling vesicle trafficking, adhesion and cytoskeletal organization. It regulates ARF GTPases and has binding domains for paxillin and PIX, which is a PAK-binding protein and an exchange factor for Rac. We show that GIT1 cycles between at least three distinct subcellular compartments, including adhesion-like structures, the leading edge and cytoplasmic complexes. The cytoplasmic structures, which also contain paxillin, PAK and PIX, do not detectably co-localize with endosomal Golgi or membrane markers, suggesting that they represent a novel supramolecular complex. The GIT1 cytoplasmic complexes are motile and tended to move toward the cell periphery where they joined existing adhesions. In retracting regions of the cells, the GIT1 complexes moved away from the disassembling adhesions toward the cell body. Using deletion mutants, we have identified domains that target GIT1 to each of the compartments. Localization to adhesions and the leading edge requires the paxillin-binding domain, which comprises the C-terminal 140 residues (cGIT1), whereas targeting to the cytoplasmic complexes requires the central region that contains ankyrin repeats and the PIX-binding domain. Expression of GIT1 or cGIT, but not nGIT1 in which the paxillin-binding domain is deleted, increases the rate of migration and the size and number of protrusions. The latter are inhibited when GIT1 is co-expressed with a kinase-dead PAK, suggesting that the GIT1 interaction with PAK is required for enhanced migration and protrusive activity. Furthermore,GIT1 targets constitutively activated PAK to adhesions and the leading edge via its interaction with paxillin. Since expression of cGIT targets endogenous GIT1 to the leading edge, it appears that the leading edge is the location of GIT1 responsible for these activities. Thus, GIT1 is a component of a motile,multimolecular complex that traffics a set of signaling components to specific locations in the cell where they regulate localized activities.

Sign in / Sign up

Export Citation Format

Share Document