scholarly journals Actin dynamics as a multiscale integrator of cellular guidance cues

2021 ◽  
Author(s):  
Abby L Bull ◽  
Leonard Campanello ◽  
Matt J Hourwitz ◽  
Qixin Yang ◽  
Min Zhao ◽  
...  
Keyword(s):  
Electric Fields ◽  
Immune Cells ◽  
Actin Polymerization ◽  
Leading Edge ◽  
Actin Dynamics ◽  
Guidance Cues ◽  
Migration Direction ◽  
Actin Waves ◽  
Cell Motion ◽  
Cellular Guidance

Cells are able to integrate multiple, and potentially competing, cues to determine a migration direction. For instance, in wound healing, cells follow chemical signals or electric fields to reach the wound edge, regardless of any local guidance cues. To investigate this integration of guidance cues, we monitor the actin-polymerization dynamics of immune cells in response to cues on a subcellular scale (nanotopography) and on the cellular scale (electric fields, EFs). In the fast, amoeboid-type migration, commonly observed in immune cells, actin polymerization at the cell's leading edge is the driver of motion. The excitable systems character of actin polymerization leads to self-propagating, two-dimensional wavefronts that enable persistent cell motion. We show that EFs guide these wavefronts, leading to turning of cells when the direction of the EF changes. When nanoridges promote one-dimensional (1D) waves of actin polymerization that move along the ridges (esotaxis), EF guidance along that direction is amplified. 1D actin waves cannot turn or change direction, so cells respond to a change in EF direction by generating new 1D actin waves. At the cellular scale, the emergent response is a turning of the cell. For nanoridges perpendicular to the direction of the EF, the 1D actin waves are guided by the nanotopography, but both the average location of new actin waves and the whole cell motion are guided by the EF. Thus, actin waves respond to each cue on its intrinsic length scale, allowing cells to exhibit versatile responses to the physical microenvironment.

scholarly journals EGF stimulates an increase in actin nucleation and filament number at the leading edge of the lamellipod in mammary adenocarcinoma cells

1998 ◽  
Vol 111 (2) ◽  
pp. 199-211 ◽  
Author(s):  
A.Y. Chan ◽  
S. Raft ◽  
M. Bailly ◽  
J.B. Wyckoff ◽  
J.E. Segall ◽  
...  
Keyword(s):  
Actin Polymerization ◽  
De Novo ◽  
Leading Edge ◽  
Mammary Adenocarcinoma ◽  
Actin Dynamics ◽  
Actin Nucleation ◽  
Nucleation Sites ◽  
Nucleation Activity ◽  
Pointed End ◽  
Stimulation Of

Stimulation of metastatic MTLn3 cells with EGF causes the rapid extension of lamellipods, which contain a zone of F-actin at the leading edge. In order to establish the mechanism for accumulation of F-actin at the leading edge and its relationship to lamellipod extension in response to EGF, we have studied the kinetics and location of EGF-induced actin nucleation activity in MTLn3 cells and characterized the actin dynamics at the leading edge by measuring the changes at the pointed and barbed ends of actin filaments upon EGF stimulation of MTLn3 cells. The major result of this study is that stimulation of MTLn3 cells with EGF causes a transient increase in actin nucleation activity resulting from the appearance of free barbed ends very close to the leading edge of extending lamellipods. In addition, cytochalasin D causes a significant decrease in the total F-actin content in EGF-stimulated cells, indicating that both actin polymerization and depolymerization are stimulated by EGF. Pointed end incorporation of rhodamine-labeled actin by the EGF stimulated cells is 2.12+/−0.47 times higher than that of control cells. Since EGF stimulation causes an increase in both barbed and pointed end incorporation of rhodamine-labeled actin in the same location, the EGF-stimulated nucleation sites are more likely due either to severing of pre-existing filaments or de novo nucleation of filaments at the leading edge thereby creating new barbed and pointed ends. The timing and location of EGF-induced actin nucleation activity in MTLn3 cells can account for the observed accumulation of F-actin at the leading edge and demonstrate that this F-actin rich zone is the primary actin polymerization zone after stimulation.

Small-Molecule Screen Identifies ROS as Key Regulators of Actin Dynamics in Neutrophils

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4641-4641
Author(s):  
Hidenori Hattori ◽  
Kulandayan K Subramanian ◽  
Hongbo R. Luo
Keyword(s):  
Small Molecule ◽  
Actin Polymerization ◽  
Neutrophil Migration ◽  
Physiological Role ◽  
Leading Edge ◽  
Actin Dynamics ◽  
Functional Screening ◽  
Cellular Processes

Abstract Precise spatial and temporal control of actin polymerization and depolymerization is essential for mediating various cellular processes such as migration, phagocytosis, vesicle trafficking and adhesion. In this study, we used a small-molecule functional screening approach to identify novel regulators of actin dynamics during neutrophil migration. Here we show that NADPH-oxidase dependent Reactive Oxygen Species act as negative regulators of actin polymerization. Neutrophils with pharmacologically inhibited oxidase or isolated from Chronic Granulomatous Disease (CGD) patient and mice displayed enhanced F-actin polymerization, multiple pseudopods formation and impaired chemotaxis. ROS localized to pseudopodia and inhibited actin polymerization by driving actin glutathionylation at the leading edge of migrating cells. Consistent with these in vitro results, adoptively transferred CGD murine neutrophils also showed impaired in vivo recruitment to sites of inflammation. Together, these results present a novel physiological role for ROS in regulation of action polymerization and shed new light on the pathogenesis of CGD.

scholarly journals Tracking Retrograde Flow in Keratocytes: News from the Front

2005 ◽  
Vol 16 (3) ◽  
pp. 1223-1231 ◽  
Author(s):  
Pascal Vallotton ◽  
Gaudenz Danuser ◽  
Sophie Bohnet ◽  
Jean-Jacques Meister ◽  
Alexander B. Verkhovsky
Keyword(s):  
Actin Polymerization ◽  
Leading Edge ◽  
Membrane Resistance ◽  
Retrograde Flow ◽  
Actin Assembly ◽  
Actin Network ◽  
Freely Moving ◽  
Contractile Forces ◽  
Cell Motion ◽  
Shape Changes

Actin assembly at the leading edge of the cell is believed to drive protrusion, whereas membrane resistance and contractile forces result in retrograde flow of the assembled actin network away from the edge. Thus, cell motion and shape changes are expected to depend on the balance of actin assembly and retrograde flow. This idea, however, has been undermined by the reported absence of flow in one of the most spectacular models of cell locomotion, fish epidermal keratocytes. Here, we use enhanced phase contrast and fluorescent speckle microscopy and particle tracking to analyze the motion of the actin network in keratocyte lamellipodia. We have detected retrograde flow throughout the lamellipodium at velocities of 1–3 μm/min and analyzed its organization and relation to the cell motion during both unobstructed, persistent migration and events of cell collision. Freely moving cells exhibited a graded flow velocity increasing toward the sides of the lamellipodium. In colliding cells, the velocity decreased markedly at the site of collision, with striking alteration of flow in other lamellipodium regions. Our findings support the universality of the flow phenomenon and indicate that the maintenance of keratocyte shape during locomotion depends on the regulation of both retrograde flow and actin polymerization.

scholarly journals Regulation of leading edge microtubule and actin dynamics downstream of Rac1

2003 ◽  
Vol 161 (5) ◽  
pp. 845-851 ◽  
Author(s):  
Torsten Wittmann ◽  
Gary M. Bokoch ◽  
Clare M. Waterman-Storer
Keyword(s):  
Rho Gtpases ◽  
Actin Polymerization ◽  
Leading Edge ◽  
Time Lapse ◽  
Dominant Negative ◽  
Actin Dynamics ◽  
Retrograde Flow ◽  
Rho Proteins ◽  
Migrating Cells

Actin in migrating cells is regulated by Rho GTPases. However, Rho proteins might also affect microtubules (MTs). Here, we used time-lapse microscopy of PtK1 cells to examine MT regulation downstream of Rac1. In these cells, “pioneer” MTs growing into leading-edge protrusions exhibited a decreased catastrophe frequency and an increased time in growth as compared with MTs further from the leading edge. Constitutively active Rac1(Q61L) promoted pioneer behavior in most MTs, whereas dominant-negative Rac1(T17N) eliminated pioneer MTs, indicating that Rac1 is a regulator of MT dynamics in vivo. Rac1(Q61L) also enhanced MT turnover through stimulation of MT retrograde flow and breakage. Inhibition of p21-activated kinases (Paks), downstream effectors of Rac1, inhibited Rac1(Q61L)-induced MT growth and retrograde flow. In addition, Rac1(Q61L) promoted lamellipodial actin polymerization and Pak-dependent retrograde flow. Together, these results indicate coordinated regulation of the two cytoskeletal systems in the leading edge of migrating cells.

scholarly journals Filopodia formation and Disabled degradation downstream of Reelin

2004 ◽  
Vol 384 (1) ◽  
Author(s):  
Steven J. WINDER
Keyword(s):  
Actin Polymerization ◽  
Leading Edge ◽  
Negative Control ◽  
Actin Dynamics ◽  
Abelson Tyrosine Kinase ◽  
Motile Cells ◽  
Biochemical Journal ◽  
Subtle Effect ◽  
Important Regulator ◽  
Syndrome Protein

During Drosophila embryogenesis, Abl (Abelson tyrosine kinase) is localized in the axons of the CNS (central nervous system). Mutations in Abl have a subtle effect on the morphology of the embryonic CNS, and the mutant animals survive to the pupal and adult stages. However, genetic screens have identified several genes that, when mutated along with the Abl gene, modified the phenotypes. Two prominent genes that arose from these screens were enabled (Ena) and disabled (Dab). It has been known for some time that Enabled and its mammalian homologues are involved in the regulation of actin dynamics, and promote actin polymerization at the leading edge of motile cells. It was a defect in actin polymerization in migrating neurons in particular that resulted in the identification of Enabled as an important regulator of neuronal migration. Defects in Disabled, in both Drosophila and mammals, also gave rise to neuronal defects which, in mice, were indistinguishable from phenotypes observed in the reeler mouse. These observations suggested that mDab1 (mammalian Disabled homologue 1) acted in a pathway downstream of Reelin, the product of the reelin gene found to be defective in reeler mice. Now, in this issue of the Biochemical Journal, Takenawa and colleagues have demonstrated that Disabled also acts in a pathway to regulate actin dynamics through the direct activation of N-WASP (neuronal Wiskott–Aldrich syndrome protein). Furthermore, they were also able to link several lines of investigation from other groups to show that the ability of mDab1 to regulate actin dynamics during cell motility was under the negative control of tyrosine phosphorylation, leading to ubiquitin-mediated degradation of mDab1.

scholarly journals Amphiphysin 1 Is Important for Actin Polymerization during Phagocytosis

2007 ◽  
Vol 18 (11) ◽  
pp. 4669-4680 ◽  
Author(s):  
Hiroshi Yamada ◽  
Emiko Ohashi ◽  
Tadashi Abe ◽  
Norihiro Kusumi ◽  
Shun-AI Li ◽  
...  
Keyword(s):  
Rna Interference ◽  
Sertoli Cells ◽  
Small Interfering Rna ◽  
Actin Polymerization ◽  
Actin Dynamics ◽  
Polymerization Process ◽  
Amphiphysin 1 ◽  
Phagocytic Cups ◽  
Interfering Rna ◽  
Constitutively Active

Amphiphysin 1 is involved in clathrin-mediated endocytosis. In this study, we demonstrate that amphiphysin 1 is essential for cellular phagocytosis and that it is critical for actin polymerization. Phagocytosis in Sertoli cells was induced by stimulating phosphatidylserine receptors. This stimulation led to the formation of actin-rich structures, including ruffles, phagocytic cups, and phagosomes, all of which showed an accumulation of amphiphysin 1. Knocking out amphiphysin 1 by RNA interference in the cells resulted in the reduction of ruffle formation, actin polymerization, and phagocytosis. Phagocytosis was also drastically decreased in amph 1 (−/−) Sertoli cells. In addition, phosphatidylinositol-4,5-bisphosphate–induced actin polymerization was decreased in the knockout testis cytosol. The addition of recombinant amphiphysin 1 to the cytosol restored the polymerization process. Ruffle formation in small interfering RNA-treated cells was recovered by the expression of constitutively active Rac1, suggesting that amphiphysin 1 functions upstream of the protein. These findings support that amphiphysin 1 is important in the regulation of actin dynamics and that it is required for phagocytosis.

scholarly journals Tropomyosin inhibits ADF/cofilin-dependent actin filament dynamics

2002 ◽  
Vol 156 (6) ◽  
pp. 1065-1076 ◽  
Author(s):  
Shoichiro Ono ◽  
Kanako Ono
Keyword(s):  
Actin Filament ◽  
Actin Filaments ◽  
Actin Polymerization ◽  
Biological Properties ◽  
Actin Dynamics ◽  
Background Suppression ◽  
Thin Filaments ◽  
Actin Organization ◽  
C Elegans ◽  
Filament Dynamics

Tropomyosin binds to actin filaments and is implicated in stabilization of actin cytoskeleton. We examined biochemical and cell biological properties of Caenorhabditis elegans tropomyosin (CeTM) and obtained evidence that CeTM is antagonistic to ADF/cofilin-dependent actin filament dynamics. We purified CeTM, actin, and UNC-60B (a muscle-specific ADF/cofilin isoform), all of which are derived from C. elegans, and showed that CeTM and UNC-60B bound to F-actin in a mutually exclusive manner. CeTM inhibited UNC-60B–induced actin depolymerization and enhancement of actin polymerization. Within isolated native thin filaments, actin and CeTM were detected as major components, whereas UNC-60B was present at a trace amount. Purified UNC-60B was unable to interact with the native thin filaments unless CeTM and other associated proteins were removed by high-salt extraction. Purified CeTM was sufficient to restore the resistance of the salt-extracted filaments from UNC-60B. In muscle cells, CeTM and UNC-60B were localized in different patterns. Suppression of CeTM by RNA interference resulted in disorganized actin filaments and paralyzed worms in wild-type background. However, in an ADF/cofilin mutant background, suppression of CeTM did not worsen actin organization and worm motility. These results suggest that tropomyosin is a physiological inhibitor of ADF/cofilin-dependent actin dynamics.

scholarly journals Contribution of Filopodia to Cell Migration: A Mechanical Link between Protrusion and Contraction

2010 ◽  
Vol 2010 ◽  
pp. 1-13 ◽  
Author(s):  
Fei Xue ◽  
Deanna M. Janzen ◽  
David A. Knecht
Keyword(s):  
Cell Migration ◽  
Actin Polymerization ◽  
Myosin Ii ◽  
Temporal Distribution ◽  
Leading Edge ◽  
Distal Portion ◽  
Actin Binding ◽  
Actin Networks ◽  
Motile Cells ◽  
A Cell

Numerous F-actin containing structures are involved in regulating protrusion of membrane at the leading edge of motile cells. We have investigated the structure and dynamics of filopodia as they relate to events at the leading edge and the function of the trailing actin networks. We have found that although filopodia contain parallel bundles of actin, they contain a surprisingly nonuniform spatial and temporal distribution of actin binding proteins. Along the length of the actin filaments in a single filopodium, the most distal portion contains primarily T-plastin, while the proximal portion is primarily bound byα-actinin and coronin. Some filopodia are stationary, but lateral filopodia move with respect to the leading edge. They appear to form a mechanical link between the actin polymerization network at the front of the cell and the myosin motor activity in the cell body. The direction of lateral filopodial movement is associated with the direction of cell migration. When lateral filopodia initiate from and move toward only one side of a cell, the cell will turn opposite to the direction of filopodial flow. Therefore, this filopodia-myosin II system allows actin polymerization driven protrusion forces and myosin II mediated contractile force to be mechanically coordinated.

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