scholarly journals Association of Mouse Actin-binding Protein 1 (mAbp1/SH3P7), an Src Kinase Target, with Dynamic Regions of the Cortical Actin Cytoskeleton in Response to Rac1 Activation

2000 ◽  
Vol 11 (1) ◽  
pp. 393-412 ◽  
Author(s):  
Michael M. Kessels ◽  
Åsa E. Y. Engqvist-Goldstein ◽  
David G. Drubin
Keyword(s):  
Actin Cytoskeleton ◽  
Tyrosine Kinases ◽  
Actin Polymerization ◽  
De Novo ◽  
Leading Edge ◽  
Membrane Dynamics ◽  
Cellular Growth ◽  
Actin Binding ◽  
Cortical Actin ◽  
Binding Domains

Yeast Abp1p is a cortical actin cytoskeleton protein implicated in cytoskeletal regulation, endocytosis, and cAMP-signaling. We have identified a gene encoding a mouse homologue of Abp1p, and it is identical to SH3P7, a protein shown recently to be a target of Src tyrosine kinases. Yeast and mouse Abp1p display the same domain structure including an N-terminal actin-depolymerizing factor homology domain and a C-terminal Src homology 3 domain. Using two independent actin-binding domains, mAbp1 binds to actin filaments with a 1:5 saturation stoichiometry. In stationary cells, mAbp1 colocalizes with cortical F-actin in fibroblast protrusions that represent sites of cellular growth. mAbp1 appears at the actin-rich leading edge of migrating cells. Growth factors cause mAbp1 to rapidly accumulate in lamellipodia. This response can be mimicked by expression of dominant-positive Rac1. mAbp1 recruitment appears to be dependent on de novo actin polymerization and occurs specifically at sites enriched for the Arp2/3 complex. mAbp1 is a newly identified cytoskeletal protein in mice and may serve as a signal-responsive link between the dynamic cortical actin cytoskeleton and regions of membrane dynamics.

scholarly journals Capping Protein Terminates but Does Not Initiate Chemoattractant-induced Actin Assembly in Dictyostelium

1997 ◽  
Vol 139 (5) ◽  
pp. 1243-1253 ◽  
Author(s):  
R.J. Eddy ◽  
J. Han ◽  
J.S. Condeelis
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
De Novo ◽  
Leading Edge ◽  
Actin Assembly ◽  
Directed Movement ◽  
Capping Protein ◽  
End Capping

The first step in the directed movement of cells toward a chemotactic source involves the extension of pseudopods initiated by the focal nucleation and polymerization of actin at the leading edge of the cell. We have previously isolated a chemoattractant-regulated barbed-end capping activity from Dictyostelium that is uniquely associated with capping protein, also known as cap32/34. Although uncapping of barbed ends by capping protein has been proposed as a mechanism for the generation of free barbed ends after stimulation, in vitro and in situ analysis of the association of capping protein with the actin cytoskeleton after stimulation reveals that capping protein enters, but does not exit, the cytoskeleton during the initiation of actin polymerization. Increased association of capping protein with regions of the cell containing free barbed ends as visualized by exogenous rhodamine-labeled G-actin is also observed after stimulation. An approximate threefold increase in the number of filaments with free barbed ends is accompanied by increases in absolute filament number, whereas the average filament length remains constant. Therefore, a mechanism in which preexisting filaments are uncapped by capping protein, in response to stimulation leading to the generation of free barbed ends and filament elongation, is not supported. A model for actin assembly after stimulation, whereby free barbed ends are generated by either filament severing or de novo nucleation is proposed. In this model, exposure of free barbed ends results in actin assembly, followed by entry of free capping protein into the actin cytoskeleton, which acts to terminate, not initiate, the actin polymerization transient.

scholarly journals Haematopoietic lineage cell-specific protein 1 (HS1) promotes actin-related protein (Arp) 2/3 complex-mediated actin polymerization

2003 ◽  
Vol 371 (2) ◽  
pp. 485-493 ◽  
Author(s):  
Takehito URUNO ◽  
Peijun ZHANG ◽  
Jiali LIU ◽  
Jian-Jiang HAO ◽  
Xi ZHAN
Keyword(s):  
Actin Polymerization ◽  
De Novo ◽  
Primary Component ◽  
Immunofluorescent Staining ◽  
Actin Binding ◽  
Specific Gene ◽  
Actin Assembly ◽  
Related Protein ◽  
Filamentous Actin ◽  
Cortical Actin

HS1 (haematopoietic lineage cell-specific gene protein 1), a prominent substrate of intracellular protein tyrosine kinases in haematopoietic cells, is implicated in the immune response to extracellular stimuli and in cell differentiation induced by cytokines. Although HS1 contains a 37-amino acid tandem repeat motif and a C-terminal Src homology 3 domain and is closely related to the cortical-actin-associated protein cortactin, it lacks the fourth repeat that has been shown to be essential for cortactin binding to filamentous actin (F-actin). In this study, we examined the possible role of HS1 in the regulation of the actin cytoskeleton. Immunofluorescent staining demonstrated that HS1 co-localizes in the cytoplasm of cells with actin-related protein (Arp) 2/3 complex, the primary component of the cellular machinery responsible for de novo actin assembly. Furthermore, recombinant HS1 binds directly to Arp2/3 complex with an equilibrium dissociation constant (Kd) of 880nM. Although HS1 is a modest F-actin-binding protein with a Kd of 400nM, it increases the rate of the actin assembly mediated by Arp2/3 complex, and promotes the formation of branched actin filaments induced by Arp2/3 complex and a constitutively activated peptide of N-WASP (neural Wiskott–Aldrich syndrome protein). Our data suggest that HS1, like cortactin, plays an important role in the modulation of actin assembly.

scholarly journals VASP mediated actin dynamics activate and recruit a filopodia myosin

2021 ◽  
Author(s):  
Ashley L Arthur ◽  
Amy Crawford ◽  
Anne Houdusse ◽  
Margaret A Titus
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
The State ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Actin Network ◽  
Cortical Actin ◽  
Close Collaboration ◽  
Actin Binding Protein ◽  
Dynamic Regions

Filopodia are thin, actin-based structures that cells use to interact with their environments. Filopodia initiation requires a suite of conserved proteins but the mechanism remains poorly understood. The actin polymerase VASP and a MyTH-FERM (MF) myosin, DdMyo7 in amoeba, are essential for filopodia initiation. DdMyo7 is localized to dynamic regions of the actin-rich cortex. Analysis of VASP mutants and treatment of cells with anti-actin drugs shows that myosin recruitment and activation in Dictyostelium requires localized VASP-dependent actin polymerization. Targeting of DdMyo7 to the cortex alone is not sufficient for filopodia initiation; VASP activity is also required. The actin regulator locally produces a cortical actin network, that activates the MF myosin and together they shape the actin network to promote extension of parallel bundles during filopodia formation. This work reveals how filopodia initiation requires close collaboration between an actin binding protein, the state of the actin cytoskeleton and MF myosin activity.

scholarly journals VASP mediated actin dynamics activate and recruit a filopodia myosin

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Ashley L Arthur ◽  
Amy Crawford ◽  
Anne Houdusse ◽  
Margaret A Titus
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
The State ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Actin Network ◽  
Cortical Actin ◽  
Close Collaboration ◽  
Actin Binding Protein ◽  
Dynamic Regions

Filopodia are thin, actin-based structures that cells use to interact with their environments. Filopodia initiation requires a suite of conserved proteins but the mechanism remains poorly understood. The actin polymerase VASP and a MyTH-FERM (MF) myosin, DdMyo7 in amoeba, are essential for filopodia initiation. DdMyo7 is localized to dynamic regions of the actin-rich cortex. Analysis of VASP mutants and treatment of cells with anti-actin drugs shows that myosin recruitment and activation in Dictyostelium requires localized VASP-dependent actin polymerization. Targeting of DdMyo7 to the cortex alone is not sufficient for filopodia initiation; VASP activity is also required. The actin regulator locally produces a cortical actin network that activates myosin and together they shape the actin network to promote extension of parallel bundles of actin during filopodia formation. This work reveals how filopodia initiation requires close collaboration between an actin binding protein, the state of the actin cytoskeleton and MF myosin activity.

scholarly journals Dynamic cortical actin remodeling by ERM proteins controls BCR microcluster organization and integrity

2011 ◽  
Vol 208 (5) ◽  
pp. 1055-1068 ◽  
Author(s):  
Bebhinn Treanor ◽  
David Depoil ◽  
Andreas Bruckbauer ◽  
Facundo D. Batista
Keyword(s):  
Actin Cytoskeleton ◽  
B Cell ◽  
Protein Function ◽  
Actin Polymerization ◽  
Lymphocyte Activation ◽  
Dominant Negative ◽  
Temporary Increase ◽  
Cortical Actin ◽  
Erm Proteins ◽  
Diffusion Dynamics

Signaling microclusters are a common feature of lymphocyte activation. However, the mechanisms controlling the size and organization of these discrete structures are poorly understood. The Ezrin-Radixin-Moesin (ERM) proteins, which link plasma membrane proteins with the actin cytoskeleton and regulate the steady-state diffusion dynamics of the B cell receptor (BCR), are transiently dephosphorylated upon antigen receptor stimulation. In this study, we show that the ERM proteins ezrin and moesin influence the organization and integrity of BCR microclusters. BCR-driven inactivation of ERM proteins is accompanied by a temporary increase in BCR diffusion, followed by BCR immobilization. Disruption of ERM protein function using dominant-negative or constitutively active ezrin constructs or knockdown of ezrin and moesin expression quantitatively and qualitatively alters BCR microcluster formation, antigen aggregation, and downstream BCR signal transduction. Chemical inhibition of actin polymerization also altered the structure and integrity of BCR microclusters. Together, these findings highlight a crucial role for the cortical actin cytoskeleton during B cell spreading and microcluster formation and function.

scholarly journals Ultrastructure of the yeast actin cytoskeleton and its association with the plasma membrane.

1994 ◽  
Vol 125 (2) ◽  
pp. 381-391 ◽  
Author(s):  
J Mulholland ◽  
D Preuss ◽  
A Moon ◽  
A Wong ◽  
D Drubin ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Actin Cytoskeleton ◽  
Binding Proteins ◽  
Ultrastructural Level ◽  
Actin Binding ◽  
Cortical Actin ◽  
Actin Binding Proteins ◽  
Double Labeling ◽  
Wall Growth ◽  
Cortical Cytoskeleton

We characterized the yeast actin cytoskeleton at the ultrastructural level using immunoelectron microscopy. Anti-actin antibodies primarily labeled dense, patchlike cortical structures and cytoplasmic cables. This localization recapitulates results obtained with immunofluorescence light microscopy, but at much higher resolution. Immuno-EM double-labeling experiments were conducted with antibodies to actin together with antibodies to the actin binding proteins Abp1p and cofilin. As expected from immunofluorescence experiments, Abp1p, cofilin, and actin colocalized in immuno-EM to the dense patchlike structures but not to the cables. In this way, we can unambiguously identify the patches as the cortical actin cytoskeleton. The cortical actin patches were observed to be associated with the cell surface via an invagination of plasma membrane. This novel cortical cytoskeleton-plasma membrane interface appears to consist of a fingerlike invagination of plasma membrane around which actin filaments and actin binding proteins are organized. We propose a possible role for this unique cortical structure in wall growth and osmotic regulation.

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.

scholarly journals Tissue Expression and Actin Binding of a Novel N-Terminal Utrophin Isoform

2011 ◽  
Vol 2011 ◽  
pp. 1-18
Author(s):  
Richard A. Zuellig ◽  
Beat C. Bornhauser ◽  
Ralf Amstutz ◽  
Bruno Constantin ◽  
Marcus C. Schaub
Keyword(s):  
Actin Cytoskeleton ◽  
Tissue Expression ◽  
Protein Product ◽  
Binding Domain ◽  
Actin Binding ◽  
Rat Tissues ◽  
Cortical Actin ◽  
Actin Binding Domain ◽  
Spectrin Repeats

Utrophin and dystrophin present two large proteins that link the intracellular actin cytoskeleton to the extracellular matrix via the C-terminal-associated protein complex. Here we describe a novel short N-terminal isoform of utrophin and its protein product in various rat tissues (N-utro, 62 kDa, amino acids 1–539, comprising the actin-binding domain plus the first two spectrin repeats). Using different N-terminal recombinant utrophin fragments, we show that actin binding exhibits pronounced negative cooperativity (affinity constantsK1=∼5×106andK2=∼1×105 M-1) and is Ca2+-insensitive. Expression of the different fragments in COS7 cells and in myotubes indicates that the actin-binding domain alone binds exlusively to actin filaments. The recombinant N-utro analogue binds in vitro to actin and in the cells associates to the membranes. The results indicate that N-utro may be responsible for the anchoring of the cortical actin cytoskeleton to the membranes in muscle and other tissues.

scholarly journals Signaling and induction of enhanced cytoadhesiveness via the hematopoietic progenitor cell surface molecule CD34

Blood ◽  
1994 ◽  
Vol 83 (5) ◽  
pp. 1226-1234 ◽  
Author(s):  
O Majdic ◽  
J Stockl ◽  
WF Pickl ◽  
J Bohuslav ◽  
H Strobl ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Tyrosine Kinases ◽  
Actin Polymerization ◽  
De Novo ◽  
Divalent Cations ◽  
Hematopoietic Cells ◽  
Hematopoietic Progenitor Cell ◽  
Lymphocyte Function ◽  
Cell Surface Molecule ◽  
Transmembrane Glycoprotein

The transmembrane glycoprotein CD34 shows a highly restricted expression on a crucial subset of hematopoietic cells. We show here that engagement of particular determinants of CD34 can lead to signal transduction and to enhanced adhesiveness of CD34+ hematopoietic cells. Monoclonal antibodies (MoAbs) directed against O-sialoglycoprotease- sensitive epitopes of CD34 (QBEND10, ICH3, BI.3C5, MY10) but not MoAbs against O-sialoglycoprotease-resistant epitopes (9F2, 8G12) induce actin polymerization in KG-1a and KG-1 cells and strongly enhanced cytoadhesiveness. The capacity to induce adhesion requires cellular energy, divalent cations, and intact cytoskeleton but not de novo protein synthesis. The observed cytoadhesion seems at least in part to be caused by a concomitant activation of the beta 2 integrin cytoadhesion pathway. It can be significantly inhibited with lymphocyte function-associated antigen-1 and intercelluar adhesion molecule-1 antibodies. Protein kinase inhibition analyses suggest that the pathways initiated by engagement of the CD34 molecule with certain CD34 MoAbs involves protein tyrosine kinases but that protein kinase C is not critically involved.

scholarly journals A new form of actin assembly around the Shigella-containing vacuole regulates its intracellular niche

2020 ◽  
Author(s):  
Sonja Kühn ◽  
John Bergqvist ◽  
Laura Barrio ◽  
Stephanie Lebreton ◽  
Chiara Zurzolo ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
De Novo ◽  
Shigella Flexneri ◽  
Host Cells ◽  
Host Recognition ◽  
Actin Assembly ◽  
Actin Structure ◽  
New Form ◽  
Structure And Functions

SUMMARYThe enteroinvasive bacterium Shigella flexneri forces its uptake into non-phagocytic host cells through the translocation of T3SS effectors that subvert the actin cytoskeleton. Here, we report de novo actin polymerization after cellular entry around the bacterial containing vacuole (BCV) leading to the formation of a dynamic actin cocoon. This cocoon is thicker than any described cellular actin structure and functions as a gatekeeper for the cytosolic access of the pathogen. Host Cdc42, Toca-1, N-WASP, WIP, the Arp2/3 complex, cortactin, coronin, and cofilin are recruited to the actin cocoon. They are subverted by T3SS effectors, such as IpgD, IpgB1, and IcsB. IcsB immobilizes components of the actin polymerization machinery at the BCV. This represents a novel microbial subversion strategy through localized entrapment of host actin regulators causing massive actin assembly. We propose that the cocoon protects Shigella’s niche from canonical maturation or host recognition.

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