scholarly journals EPLIN regulates actin dynamics by cross-linking and stabilizing filaments

2003 ◽  
Vol 160 (3) ◽  
pp. 399-407 ◽  
Author(s):  
Raymond S. Maul ◽  
Yuhong Song ◽  
Kurt J. Amann ◽  
Sachi C. Gerbin ◽  
Thomas D. Pollard ◽  
...  
Keyword(s):  
Actin Filament ◽  
Actin Polymerization ◽  
Binding Activity ◽  
Stress Fibers ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Membrane Ruffling ◽  
Cross Links ◽  
As Stress ◽  
Kinetics Of

Epithelial protein lost in neoplasm (EPLIN) is a cytoskeleton-associated protein encoded by a gene that is down-regulated in transformed cells. EPLIN increases the number and size of actin stress fibers and inhibits membrane ruffling induced by Rac. EPLIN has at least two actin binding sites. Purified recombinant EPLIN inhibits actin filament depolymerization and cross-links filaments in bundles. EPLIN does not affect the kinetics of spontaneous actin polymerization or elongation at the barbed end, but inhibits branching nucleation of actin filaments by Arp2/3 complex. Side binding activity may stabilize filaments and account for the inhibition of nucleation mediated by Arp2/3 complex. We propose that EPLIN promotes the formation of stable actin filament structures such as stress fibers at the expense of more dynamic actin filament structures such as membrane ruffles. Reduced expression of EPLIN may contribute to the motility of invasive tumor cells.

scholarly journals Burkholderia pseudomalleitype III secreted protein BipC: role in actin modulation and translocation activities required for the bacterial intracellular lifecycle

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2532 ◽  
Author(s):  
Wen Tyng Kang ◽  
Kumutha Malar Vellasamy ◽  
Lakshminarayanan Rajamani ◽  
Roger W. Beuerman ◽  
Jamuna Vadivelu
Keyword(s):  
Actin Polymerization ◽  
Cell Interaction ◽  
Binding Activity ◽  
Host Cells ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Virulence Determinants ◽  
Secretion Systems ◽  
Number Of Patients

Melioidosis, an infection caused by the facultative intracellular pathogenBurkholderia pseudomallei, has been classified as an emerging disease with the number of patients steadily increasing at an alarming rate.B. pseudomalleipossess various virulence determinants that allow them to invade the host and evade the host immune response, such as the type III secretion systems (TTSS). The products of this specialized secretion system are particularly important for theB. pseudomalleiinfection. Lacking in one or more components of the TTSS demonstrated different degrees of defects in the intracellular lifecycle ofB. pseudomallei. Further understanding the functional roles of proteins involved inB. pseudomalleiTTSS will enable us to dissect the enigma ofB. pseudomallei-host cell interaction. In this study, BipC (a translocator), which was previously reported to be involved in the pathogenesis ofB. pseudomallei, was further characterized using the bioinformatics and molecular approaches. ThebipCgene, coding for a putative invasive protein, was first PCR amplified fromB. pseudomalleiK96243genomic DNA and cloned into an expression vector for overexpression inEscherichia coli. The soluble protein was subsequently purified and assayed for actin polymerization and depolymerization. BipC was verified to subvert the host actin dynamics as demonstrated by the capability to polymerize actinin vitro. Homology modeling was also attempted to predict the structure of BipC. Overall, our findings identified that the protein encoded by thebipCgene plays a role as an effector involved in the actin binding activity to facilitate internalization ofB. pseudomalleiinto the host cells.

scholarly journals TetraThymosinβ Is Required for Actin Dynamics in Caenorhabditis elegans and Acts via Functionally Different Actin-binding Repeats

2004 ◽  
Vol 15 (10) ◽  
pp. 4735-4748 ◽  
Author(s):  
Marleen Van Troys ◽  
Kanako Ono ◽  
Daisy Dewitte ◽  
Veronique Jonckheere ◽  
Natalie De Ruyck ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Actin Filament ◽  
Actin Polymerization ◽  
Actin Dynamics ◽  
Actin Binding ◽  
In Vitro Assays ◽  
Filamentous Actin ◽  
Lethal Mutant ◽  
Interaction Sites

Generating specific actin structures via controlled actin polymerization is a prerequisite for eukaryote development and reproduction. We here report on an essential Caenorhabditis elegans protein tetraThymosinβ expressed in developing neurons and crucial during oocyte maturation in adults. TetraThymosinβ has four repeats, each related to the actin monomer-sequestering protein thymosinβ 4 and assists in actin filament elongation. For homologues with similar multirepeat structures, a profilin-like mechanism of ushering actin onto filament barbed ends, based on the formation of a 1:1 complex, is proposed to underlie this activity. We, however, demonstrate that tetraThymosinβ binds multiple actin monomers via different repeats and in addition also interacts with filamentous actin. All repeats need to be functional for attaining full activity in various in vitro assays. The activities on actin are thus a direct consequence of the repeated structure. In containing both G- and F-actin interaction sites, tetraThymosinβ may be reminiscent of nonhomologous multimodular actin regulatory proteins implicated in actin filament dynamics. A mutation that suppresses expression of tetraThymosinβ is homozygous lethal. Mutant organisms develop into adults but display a dumpy phenotype and fail to reproduce as their oocytes lack essential actin structures. This strongly suggests that the activity of tetraThymosinβ is of crucial importance at specific developmental stages requiring actin polymerization.

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 Side-binding proteins modulate actin filament dynamics

2014 ◽  
Author(s):  
Alvaro H. Crevenna ◽  
Marcelino Arciniega ◽  
Aurelie Dupont ◽  
Kaja Kowalska ◽  
Oliver Lange ◽  
...  
Keyword(s):  
Actin Filament ◽  
Brownian Dynamics ◽  
Actin Polymerization ◽  
Actin Dynamics ◽  
Central Feature ◽  
Filament Dynamics ◽  
Filament Structure ◽  
The Rich ◽  
Dynamics Simulations ◽  
Pointed End

Actin filament dynamics govern many key physiological processes from cell motility to tissue morphogenesis. A central feature of actin dynamics is the capacity of the filament to polymerize and depolymerize at its ends in response to cellular conditions. It is currently thought that filament kinetics can be described by a single rate constant for each end. Here, using direct visualization of single actin filament elongation, we show that actin polymerization kinetics at both filament ends are strongly influenced by proteins that bind to the lateral filament surface. We also show that the less dynamic end, called the pointed-end, has a non-elongating state that dominates the observed filament kinetic asymmetry. Estimates of filament flexibility and Brownian dynamics simulations suggest that the observed kinetic diversity arises from structural alteration. Tuning filament kinetics by exploiting the natural malleability of the actin filament structure may be a ubiquitous mechanism to generate the rich variety of observed cellular actin dynamics.

scholarly journals Dynamics of Tpm1.8 domains on actin filaments with single molecule resolution

2020 ◽  
Author(s):  
Ilina Bareja ◽  
Hugo Wioland ◽  
Miro Janco ◽  
Philip R. Nicovich ◽  
Antoine Jégou ◽  
...  
Keyword(s):  
Actin Filament ◽  
Single Molecule ◽  
Actin Filaments ◽  
High Probability ◽  
Actin Binding ◽  
Single Molecule Level ◽  
Filament Dynamics ◽  
Kinetics Of ◽  
Insight Into

ABSTRACTTropomyosins regulate dynamics and functions of the actin cytoskeleton by forming long chains along the two strands of actin filaments that act as gatekeepers for the binding of other actin-binding proteins. The fundamental molecular interactions underlying the binding of tropomyosin to actin are still poorly understood. Using microfluidics and fluorescence microscopy, we observed the binding of fluorescently labelled tropomyosin isoform Tpm1.8 to unlabelled actin filaments in real time. This approach in conjunction with mathematical modeling enabled us to quantify the nucleation, assembly and disassembly kinetics of Tpm1.8 on single filaments and at the single molecule level. Our analysis suggests that Tpm1.8 decorates the two strands of the actin filament independently. Nucleation of a growing tropomyosin domain proceeds with high probability as soon as the first Tpm1.8 molecule is stabilised by the addition of a second molecule, ultimately leading to full decoration of the actin filament. In addition, Tpm1.8 domains are asymmetrical, with enhanced dynamics at the edge oriented towards the barbed end of the actin filament. The complete description of Tpm1.8 kinetics on actin filaments presented here provides molecular insight into actin-tropomyosin filament formation and the role of tropomyosins in regulating actin filament dynamics.

scholarly journals The Two ADF-H Domains of Twinfilin Play Functionally Distinct Roles in Interactions with Actin Monomers

2002 ◽  
Vol 13 (11) ◽  
pp. 3811-3821 ◽  
Author(s):  
Pauli J. Ojala ◽  
Ville O. Paavilainen ◽  
Maria K. Vartiainen ◽  
Roman Tuma ◽  
Alan G. Weeds ◽  
...  
Keyword(s):  
Binding Site ◽  
Binding Activity ◽  
Size Exclusion ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Actin Monomer ◽  
Wild Type ◽  
Native Page ◽  
Exclusion Chromatography

Twinfilin is a ubiquitous and abundant actin monomer–binding protein that is composed of two ADF-H domains. To elucidate the role of twinfilin in actin dynamics, we examined the interactions of mouse twinfilin and its isolated ADF-H domains with G-actin. Wild-type twinfilin binds ADP-G-actin with higher affinity (K D = 0.05 μM) than ATP-G-actin (K D = 0.47 μM) under physiological ionic conditions and forms a relatively stable (k off = 1.8 s−1) complex with ADP-G-actin. Data from native PAGE and size exclusion chromatography coupled with light scattering suggest that twinfilin competes with ADF/cofilin for the high-affinity binding site on actin monomers, although at higher concentrations, twinfilin, cofilin, and actin may also form a ternary complex. By systematic deletion analysis, we show that the actin-binding activity is located entirely in the two ADF-H domains of twinfilin. Individually, these domains compete for the same binding site on actin, but the C-terminal ADF-H domain, which has >10-fold higher affinity for ADP-G-actin, is almost entirely responsible for the ability of twinfilin to increase the amount of monomeric actin in cosedimentation assays. Isolated ADF-H domains associate with ADP-G-actin with rapid second-order kinetics, whereas the association of wild-type twinfilin with G-actin exhibits kinetics consistent with a two-step binding process. These data suggest that the association with an actin monomer induces a first-order conformational change within the twinfilin molecule. On the basis of these results, we propose a kinetic model for the role of twinfilin in actin dynamics and its possible function in cells.

scholarly journals Insights into the evolution of regulated actin dynamics via characterization of primitive gelsolin/cofilin proteins from Asgard archaea

2020 ◽  
Vol 117 (33) ◽  
pp. 19904-19913 ◽  
Author(s):  
Caner Akıl ◽  
Linh T. Tran ◽  
Magali Orhant-Prioux ◽  
Yohendran Baskaran ◽  
Edward Manser ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Filament ◽  
Calcium Binding ◽  
Mammalian Cells ◽  
Actin Polymerization ◽  
Calcium Release ◽  
Duplication Event ◽  
Cellular Level ◽  
Actin Dynamics

Asgard archaea genomes contain potential eukaryotic-like genes that provide intriguing insight for the evolution of eukaryotes. The eukaryotic actin polymerization/depolymerization cycle is critical for providing force and structure in many processes, including membrane remodeling. In general, Asgard genomes encode two classes of actin-regulating proteins from sequence analysis, profilins and gelsolins. Asgard profilins were demonstrated to regulate actin filament nucleation. Here, we identify actin filament severing, capping, annealing and bundling, and monomer sequestration activities by gelsolin proteins from Thorarchaeota (Thor), which complete a eukaryotic-like actin depolymerization cycle, and indicate complex actin cytoskeleton regulation in Asgard organisms. Thor gelsolins have homologs in other Asgard archaea and comprise one or two copies of the prototypical gelsolin domain. This appears to be a record of an initial preeukaryotic gene duplication event, since eukaryotic gelsolins are generally comprise three to six domains. X-ray structures of these proteins in complex with mammalian actin revealed similar interactions to the first domain of human gelsolin or cofilin with actin. Asgard two-domain, but not one-domain, gelsolins contain calcium-binding sites, which is manifested in calcium-controlled activities. Expression of two-domain gelsolins in mammalian cells enhanced actin filament disassembly on ionomycin-triggered calcium release. This functional demonstration, at the cellular level, provides evidence for a calcium-controlled Asgard actin cytoskeleton, indicating that the calcium-regulated actin cytoskeleton predates eukaryotes. In eukaryotes, dynamic bundled actin filaments are responsible for shaping filopodia and microvilli. By correlation, we hypothesize that the formation of the protrusions observed from Lokiarchaeota cell bodies may involve the gelsolin-regulated actin structures.

scholarly journals Changes in Vasodilator-Stimulated Phosphoprotein Phosphorylation, Profilin-1, and Cofilin-1 in Accreta and Protection by DHA

2018 ◽  
Vol 26 (6) ◽  
pp. 757-765 ◽  
Author(s):  
Mehboob Ali ◽  
Lynette K. Rogers ◽  
Kathryn M. Heyob ◽  
Catalin S. Buhimschi ◽  
Irina A. Buhimschi
Keyword(s):  
Actin Polymerization ◽  
Cellular Proliferation ◽  
Placenta Accreta ◽  
Gestational Trophoblastic Disease ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Migration And Invasion ◽  
Aberrant Expression ◽  
Vasp Phosphorylation ◽  
And Migration

Accreta and gestational trophoblastic disease (ie, choriocarcinoma) are placental pathologies characterized by hyperproliferative and invasive trophoblasts. Cellular proliferation, migration, and invasion are heavily controlled by actin-binding protein (ABP)-mediated actin dynamics. The ABP vasodilator-stimulated phosphoprotein (VASP) carries key regulatory role. Profilin-1, cofilin-1, and VASP phosphorylated at Ser157 (pVASP-S157) and Ser239 (pVASP-S239) are ABPs that regulate actin polymerization and stabilization and facilitate cell metastases. Docosahexaenoic acid (DHA) inhibits cancer cell migration and proliferation. We hypothesized that analogous to malignant cells, ABPs regulate these processes in extravillous trophoblasts (EVTs), which exhibit aberrant expression in placenta accreta. Placental–myometrial junction biopsies of histologically confirmed placenta accreta had significantly increased immunostaining levels of cofilin-1, VASP, pVASP-S239, and F-actin. Treatment of choriocarcinoma-derived trophoblast (BeWo) cells with DHA (30 µM) for 24 hours significantly suppressed proliferation, migration, and pVASP-S239 levels and altered protein profiles consistent with increased apoptosis. We concluded that in accreta changes in the ABP expression profile were a response to restore homeostasis by counteracting the hyperproliferative and invasive phenotype of the EVT. The observed association between VASP phosphorylation, apoptosis, and trophoblast proliferation and migration suggest that DHA may offer a therapeutic solution for conditions where EVT is hyperinvasive.

scholarly journals Actin-depolymerizing Factor and Cofilin-1 Play Overlapping Roles in Promoting Rapid F-Actin Depolymerization in Mammalian Nonmuscle Cells

2005 ◽  
Vol 16 (2) ◽  
pp. 649-664 ◽  
Author(s):  
Pirta Hotulainen ◽  
Eija Paunola ◽  
Maria K. Vartiainen ◽  
Pekka Lappalainen
Keyword(s):  
Cell Motility ◽  
Actin Filament ◽  
Actin Filaments ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Actin Depolymerizing Factor ◽  
Cytoskeletal Dynamics ◽  
Nonmuscle Cells ◽  
In Cells

Actin-depolymerizing factor (ADF)/cofilins are small actin-binding proteins found in all eukaryotes. In vitro, ADF/cofilins promote actin dynamics by depolymerizing and severing actin filaments. However, whether ADF/cofilins contribute to actin dynamics in cells by disassembling “old” actin filaments or by promoting actin filament assembly through their severing activity is a matter of controversy. Analysis of mammalian ADF/cofilins is further complicated by the presence of multiple isoforms, which may contribute to actin dynamics by different mechanisms. We show that two isoforms, ADF and cofilin-1, are expressed in mouse NIH 3T3, B16F1, and Neuro 2A cells. Depleting cofilin-1 and/or ADF by siRNA leads to an accumulation of F-actin and to an increase in cell size. Cofilin-1 and ADF seem to play overlapping roles in cells, because the knockdown phenotype of either protein could be rescued by overexpression of the other one. Cofilin-1 and ADF knockdown cells also had defects in cell motility and cytokinesis, and these defects were most pronounced when both ADF and cofilin-1 were depleted. Fluorescence recovery after photobleaching analysis and studies with an actin monomer-sequestering drug, latrunculin-A, demonstrated that these phenotypes arose from diminished actin filament depolymerization rates. These data suggest that mammalian ADF and cofilin-1 promote cytoskeletal dynamics by depolymerizing actin filaments and that this activity is critical for several processes such as cytokinesis and cell motility.

scholarly journals Cobl-like promotes actin filament formation and dendritic branching using only a single WH2 domain

2017 ◽  
Vol 217 (1) ◽  
pp. 211-230 ◽  
Author(s):  
Maryam Izadi ◽  
Dirk Schlobinski ◽  
Maria Lahr ◽  
Lukas Schwintzer ◽  
Britta Qualmann ◽  
...  
Keyword(s):  
Actin Filament ◽  
Cell Biology ◽  
Network Formation ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Filament Formation ◽  
Uncharacterized Protein ◽  
Dendritic Branching ◽  
Wh2 Domain ◽  
Actin Nucleator

Local actin filament formation powers the development of the signal-receiving arbor of neurons that underlies neuronal network formation. Yet, little is known about the molecules that drive these processes and may functionally connect them to the transient calcium pulses observed in restricted areas in the forming dendritic arbor. Here we demonstrate that Cordon-Bleu (Cobl)–like, an uncharacterized protein suggested to represent a very distantly related, evolutionary ancestor of the actin nucleator Cobl, despite having only a single G-actin–binding Wiskott–Aldrich syndrome protein Homology 2 (WH2) domain, massively promoted the formation of F-actin–rich membrane ruffles of COS-7 cells and of dendritic branches of neurons. Cobl-like hereby integrates WH2 domain functions with those of the F-actin–binding protein Abp1. Cobl-like–mediated dendritic branching is dependent on Abp1 as well as on Ca2+/calmodulin (CaM) signaling and CaM association. Calcium signaling leads to a promotion of complex formation with Cobl-like’s cofactor Abp1. Thus, Ca2+/CaM control of actin dynamics seems to be a much more broadly used principle in cell biology than previously thought.

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