Cytochalasin D inhibits actin polymerization and induces depolymerization of actin filaments formed during platelet shape change

Nature ◽  
1981 ◽  
Vol 293 (5830) ◽  
pp. 302-305 ◽  
Author(s):  
James F. Casella ◽  
Michael D. Flanagan ◽  
Shin Lin
Keyword(s):  
Actin Filaments ◽  
Actin Polymerization ◽  
Shape Change ◽  
Cytochalasin D ◽  
Platelet Shape

scholarly journals Arp2/3 complex is required for actin polymerization during platelet shape change

Blood ◽  
2002 ◽  
Vol 99 (12) ◽  
pp. 4466-4474 ◽  
Author(s):  
Zhi Li ◽  
Eric S. Kim ◽  
Elaine L. Bearer
Keyword(s):  
Actin Filaments ◽  
Actin Polymerization ◽  
Molecular Mechanisms ◽  
Early Stage ◽  
Shape Change ◽  
Thrombin Receptor ◽  
Fab Fragments ◽  
Sequential Formation ◽  
Platelet Shape

Platelets undergo a series of actin-dependent morphologic changes when activated by thrombin receptor activating peptide (TRAP) or when spreading on glass. Polymerization of actin results in the sequential formation of filopodia, lamellipodia, and stress fibers, but the molecular mechanisms regulating this polymerization are unknown. The Arp2/3 complex nucleates actin polymerization in vitro and could perform this function inside cells as well. To test whether Arp2/3 regulated platelet actin polymerization, we used recombinant Arp2 protein (rArp2) to generate Arp2-specific antibodies (αArp2). Intact and Fab fragments of αArp2 inhibited TRAP-stimulated actin-polymerizing activity in platelet extracts as measured by the pyrene assay. Inhibition was reversed by the addition of rArp2 protein. To test the effect of Arp2/3 inhibition on the formation of specific actin structures, we designed a new method to permeabilize resting platelets while preserving their ability to adhere and to form filopodia and lamellipodia on exposure to glass. Inhibition of Arp2/3 froze platelets at the rounded, early stage of activation, before the formation of filopodia and lamellipodia. By morphometric analysis, the proportion of platelets in the rounded stage rose from 2.85% in untreated to 63% after treatment with αArp2. This effect was also seen with Fab fragments and was reversed by the addition of rArp2 protein. By immunofluorescence of platelets at various stages of spreading, the Arp2/3 complex was found in filopodia and lamellipodia. These results suggest that activation of the Arp2/3 complex at the cortex by TRAP stimulation initiates an explosive polymerization of actin filaments that is required for all subsequent actin-dependent events.

scholarly journals Sound attenuation of polymerizing actin reflects supramolecular structures: viscoelastic properties of actin gels modified by cytochalasin D, profilin and α-actinin

2001 ◽  
Vol 355 (3) ◽  
pp. 771-778 ◽  
Author(s):  
Oliver WAGNER ◽  
Herwig SCHÜLER ◽  
Peter HOFMANN ◽  
David LANGER ◽  
Peter DANCKER ◽  
...  
Keyword(s):  
Sound Velocity ◽  
Actin Filaments ◽  
Actin Polymerization ◽  
Cytochalasin D ◽  
Supramolecular Structures ◽  
Lag Phase ◽  
Acoustic Attenuation ◽  
Ultrasound Attenuation ◽  
Actin Concentration

Polymerization and depolymerization of cytoskeletal elements maintaining cytoplasmic stiffness are key factors in the control of cell crawling. Rheometry is a significant tool in determining the mechanical properties of the single elements in vitro. Viscoelasticity of gels formed by these polymers strongly depends on both the length and the associations of the filaments (e.g. entanglements, annealings and side-by-side associations). Ultrasound attenuation is related to viscosity, sound velocity and supramolecular structures in the sample. In combination with a small glass fibre (2mm×50µm), serving as a viscosity sensor, an acoustic microscope was used to measure the elasticity and acoustic attenuation of actin solutions. Changes in acoustic attenuation of polymerizing actin by far exceed the values expected from calculations based on changes in viscosity and sound velocity. During the lag-phase of actin polymerization, attenuation slightly decreases, depending on actin concentration. After the half-maximum viscosity is accomplished and elasticity turns into steady state, attenuation distinctly rises. Changes in ultrasound attenuation depend on actin concentration, and they are modulated by the addition of α-actinin, cytochalasin D and profilin. Thus absorption and scattering of sound on the polymerization of actin is related to the packing density of the actin net, entanglements and the length of the actin filaments. Shortening of actin filaments by cytochalasin D was also confirmed by electron micrographs and falling-ball viscosimetry. In addition to viscosity and elasticity, the attenuation of sound proved to be a valuable parameter in characterizing actin polymerization and the supramolecular associations of F-actin.

The Actin Regulator Coronin-1A Modulates Platelet Shape Change and Consolidates Arterial Thrombosis

2018 ◽  
Vol 118 (12) ◽  
pp. 2098-2111 ◽  
Author(s):  
Thomas Stocker ◽  
Joachim Pircher ◽  
Artid Skenderi ◽  
Andreas Ehrlich ◽  
Clemens Eberle ◽  
...  
Keyword(s):  
Arterial Thrombosis ◽  
Actin Polymerization ◽  
Thrombus Formation ◽  
Shape Change ◽  
Actin Binding ◽  
Cellular Processes ◽  
Reduced Density ◽  
Induced Aggregation ◽  
Platelet Shape

AbstractCoronin-1A (Coro1A) belongs to a family of highly conserved actin-binding proteins that regulate cytoskeletal re-arrangement. In mammalians, Coro1A expression is most abundant in the haematopoietic lineage, where it regulates various cellular processes. The role of Coro1A in platelets has been previously unknown. Here, we identified Coro1A in human and mouse platelets. Genetic absence of Coro1A in mouse platelets inhibited agonist-induced actin polymerization and altered cofilin phosphoregulation, leading to a reduction in spreading and low-dose collagen induced aggregation. Furthermore, Coro1A-deficient mice displayed a defect in ferric chloride-induced arterial thrombosis with prolonged thrombus formation and reduced thrombus size. Immunofluorescence analysis revealed a less compact thrombus structure with reduced density of platelets and fibrinogen. In summary, Coro1A has a role in platelet biology with impact on spreading, aggregation and thrombosis.

scholarly journals Mechanism of shape change in chilled human platelets

Blood ◽  
1995 ◽  
Vol 85 (7) ◽  
pp. 1796-1804 ◽  
Author(s):  
R Winokur ◽  
JH Hartwig
Keyword(s):  
Intracellular Calcium ◽  
Actin Filament ◽  
Actin Filaments ◽  
Cytochalasin B ◽  
Shape Change ◽  
Receptor Activation ◽  
Actin Assembly ◽  
Nucleation Sites ◽  
Shape Changes ◽  
Platelet Shape

The so-called cold activation of platelets that precludes refrigeration of platelets for storage has long been recognized, but its mechanism has remained a mystery. Cooling of discoid resting platelets to temperatures below 15 degrees C causes shape distortions, and the chilled cells rewarmed to above 25 degrees C are spheres rather than discs. As platelet shape change responsive to receptor activation at normal temperatures requires the remodeling of an actin scaffolding (Hartwig JH, 1992, J Cell Biol 118:1421–1442), we examined the role of actin in the morphologic changes induced by cooling. The addition of actin monomers onto the fast-exchanging (barbed) ends of actin filaments accompanies the initial physiologic platelet shape changes, and a key control point in this growth is the removal of proteins (caps) from the filament ends. This uncapping of actin filament ends is mediated by polyphosphoinositide aggregates in vitro, suggesting that cold-induced phase changes in membrane lipids might uncap actin filaments and thereby account for actin assembly-mediated shape alterations during cooling. Consistent with this hypothesis, reversible inhibition of actin assembly with cytochalasin B prevented the distortions in shape, although cooled platelets had increased actin nucleation sites and became spherical. Another step in normal platelet shape changes requires the severing of actin filaments that maintain the resting platelet. The proteins that sever initially bind to the broken filament ends, and uncapping of these fragmented filaments provides numerous nucleation sites for growth of actin filaments to fill in spreading filopodia and lamellae. Actin filament fragmentation requires a rise in intracellular calcium, and we showed that chilling platelets from 37 degrees C to 4 degrees C increases free cytosolic calcium levels from 80 nmol/L to approximately 200 nmol/L in minutes, thus providing an explanation for the spherical shape of cooled, rewarmed platelets. Blocking the calcium transient with nanomolar concentrations of the permeant calcium chelators Quin-2 and Fura-2 prevented the increase in nucleation sites and the sphering, but not the other shape changes of chilled and rewarmed platelets. However, a combination of micromolar cytochalasin B and millimolar intracellular calcium chelators preserved the discoid shapes of chilled and rewarmed platelets. After removal of cytochalasin B and addition of sufficient extracellular calcium, these platelets responded with normal morphologic alterations to glass and thrombin activation.

scholarly journals Elongation of the fertilization tubule in Chlamydomonas: new observations on the core microfilaments and the effect of transient intracellular signals on their structural integrity.

1983 ◽  
Vol 97 (2) ◽  
pp. 522-532 ◽  
Author(s):  
P A Detmers ◽  
U W Goodenough ◽  
J Condeelis
Keyword(s):  
Mating Type ◽  
Actin Filaments ◽  
Actin Polymerization ◽  
Time Course ◽  
Structural Integrity ◽  
Cytochalasin D ◽  
Ultrastructural Observation ◽  
Intracellular Signals ◽  
Myosin Subfragment ◽  
Myosin Subfragment 1

Experimental manipulations of gametes of Chlamydomonas reinhardi and ultrastructural observation were used to examine the composition of the microfilaments in the fertilization tubule, their probable mode of formation, and their interaction with intracellular signals. Decoration with myosin subfragment-1 was used to demonstrate that the microfilaments in the fertilization tubule were actin filaments having uniform polarity: Myosin subfragment-1 arrowheads pointed away from the membrane at the tip of the process. Filaments were attached to the cone-shaped "doublet zone" at the base of the process by their pointed ends. Discrete attachment sites for filaments on the surface of the doublet zone were seen in stereo view. To test whether actin polymerization might accompany elongation of the fertilization tubule, mating gametes were exposed to cytochalasin D in an attempt to block actin polymerization. Treatment of mating type "plus" gametes with cytochalasin D prior to and during mating inhibited the appearance of actin filaments in fertilization tubules, suppressed fertilization tubule outgrowth, and lowered mating efficiency from 90 to 15%. The role of signals generated by flagellar adhesion in maintaining the structural integrity of the microfilament-doublet zone complex was examined by correlating flagellar disadhesion with the kinetics of breakdown of the complex. In zygotes, where flagellar disadhesion occurred after cell fusion, the complex disassembled within 3 h after mating. In gametes that had been agglutinated by isolated mating type "minus" flagella, microfilaments and fertilization tubules progressively disassembled over a 3-h time course following flagellar disadhesion. Disassembly of microfilaments was inhibited by maintaining flagellar agglutination, suggesting that signals generated by flagellar adhesion were necessary to maintain microfilaments intact.

Lithium preserves F-actin from the disarrangement induced by either DNase I or cytochalasin D

1993 ◽  
Vol 71 (9-10) ◽  
pp. 440-446
Author(s):  
Isabella DalleDonne ◽  
Aldo Milzani ◽  
Umberto Fascio ◽  
Antonia Ratti ◽  
Roberto Colombo
Keyword(s):  
Light Scattering ◽  
Actin Filaments ◽  
Actin Polymerization ◽  
Dnase I ◽  
Cytochalasin D ◽  
Cross Linking ◽  
Lithium Ions ◽  
Scattering Intensity ◽  
Light Scattering Intensity ◽  
Rodlike Particles

Light scattering at 546 nm, which is mainly related to the presence of rodlike particles longer than 50 nm, showed that Li+ accelerates the formation of actin filaments. Intermolecular cross-linking with N,N′-1,4-phenylene-bismaleimide proved that the observed enhancement in the light-scattering intensity is caused by the increase in the concentration of actin oligomers, which gradually elongate to form longer filaments. DNase-I-related F-actin disassembly was reduced in the presence of lithium ions, as demonstrated by fluorimetric and viscometric experiments. Li+–F-actin showed an apparently similar behaviour when exposed to cytochalasin D. We confirm that Li+ acts on actin polymerization by stabilizing actin nuclei and polymers. The stabilization of cytoskeletal polymers really appears as one of the mechanisms by which lithium ions influence some of the cell activities.Key words: lithium, F-actin stability, cytochalasin D, DNase I.

scholarly journals Effects of cytochalasin D and latrunculin B on mechanical properties of cells

2001 ◽  
Vol 114 (5) ◽  
pp. 1025-1036 ◽  
Author(s):  
T. Wakatsuki ◽  
B. Schwab ◽  
N.C. Thompson ◽  
E.L. Elson
Keyword(s):  
Mechanical Properties ◽  
Actin Filaments ◽  
Actin Polymerization ◽  
Dynamic Stiffness ◽  
Strong Dependence ◽  
Degree Of Polymerization ◽  
Cytochalasin D ◽  
The State ◽  
Latrunculin B ◽  
Wide Range

Actin microfilaments transmit traction and contraction forces generated within a cell to the extracellular matrix during embryonic development, wound healing and cell motility, and to maintain tissue structure and tone. Therefore, the state of the actin cytoskeleton strongly influences the mechanical properties of cells and tissues. Cytochalasin D and Latrunculin are commonly used reagents that, by different mechanisms, alter the state of actin polymerization or the organization of actin filaments. We have investigated the effect of a wide range of Cytochalasin D and Latrunculin B concentrations (from 40 pM to 10 microM) on the mechanical properties of the cells within fibroblast populated collagen matrices. Contractile force and dynamic stiffness were measured by uniaxial stress-strain testing. The range of effective concentrations of Cytochalasin D (200 pM-2 microM) was broader than that of Latrunculin B (20 nM-200 nM). Activating the cells by serum did not change the effective range of Cytochalasin D concentrations but shifted that of Latrunculin B upward by tenfold. Simple mathematical binding models based on the presumed mechanisms of action of Cytochalasin D and Latrunculin B simulated the concentration-dependent mechanical changes reasonably well. This study shows a strong dependence of the mechanical properties of cells and tissues on the organization and degree of polymerization of actin filaments.

Platelet Aggregation Caused by Dithiothreitol

1984 ◽  
Vol 51 (01) ◽  
pp. 119-124 ◽  
Author(s):  
M B Zucker ◽  
N C Masiello
Keyword(s):  
Shape Change ◽  
Blood Platelets ◽  
Dense Granule ◽  
Metabolic Inhibitors ◽  
Electrophoretic Patterns ◽  
Discernible Effect ◽  
Variable Extent ◽  
Triton X ◽  
Induced Aggregation ◽  
Platelet Shape

SummaryMacIntyre et al. showed that over 1 mM dithiothreitol (DTT) aggregates blood platelets in the presence of fibrinogen; aggregation is not inhibited by prostaglandin E1. We confirmed their data and found that 70 mM 2-mercaptoethanol was also active. DTT- induced aggregation was not associated with platelet shape change or secretion of dense granule contents, was not inhibited by tetracaine or metabolic inhibitors, was prevented at pH 6.5, and prevented, reversed, or arrested by EDTA, depending on when the EDTA was added. DTT did not cause aggregation of thrombasthenic, EDTA-treated, or cold (0° C) platelets, which also failed to aggregate with ADP. Platelets stimulated with DTT bound 125I-labeled fibrinogen. Thus DTT appears to “expose” the fibrinogen receptors. SDS gel electrophoresis of platelet fractions prepared by use of Triton X-114 showed that aggregating concentrations of DTT reduced proteins of apparent Mr 69,000 and 52,000 (probably platelet albumin) and, to a variable extent, glycoproteins Ib, IIb and III. Exposure of unlabeled or 125I- labeled platelets to ADP had no discernible effect on the electrophoretic patterns.

Adenosine Diphosphate (ADP)-Induced ⍺-Granules Release from Platelets of Native Whole Blood Is Reduced by Ticlopidine but Not by Aspirin or Dipyridamole

1986 ◽  
Vol 56 (02) ◽  
pp. 147-150 ◽  
Author(s):  
V Pengo ◽  
M Boschello ◽  
A Marzari ◽  
M Baca ◽  
L Schivazappa ◽  
...  
Keyword(s):  
Whole Blood ◽  
Light Transmission ◽  
Ex Vivo ◽  
Early Stage ◽  
Shape Change ◽  
Adenosine Diphosphate ◽  
Dose Dependent ◽  
Plateletderived Growth Factor ◽  
Platelet Shape

SummaryA brief contact between native whole blood and ADP promotes a dose-dependent release of platelet a-granules without a fall in the platelet number. We assessed the “ex vivo” effect of three widely used antiplatelet drugs, aspirin dipyridamole and ticlopidine, on this system. Aspirin (a single 800 mg dose) and dipyridamole (300 mg/die for four days) had no effect, while ticlopidine (500 mg/die for four days) significantly reduced the a-granules release for an ADP stimulation of 0.4 (p <0.02), 1.2 (p <0.01) and 2 pM (p <0.01). No drug, however, completeley inhibits this early stage of platelet activation. The platelet release of α-granules may be related to platelet shape change of the light transmission aggregometer and may be important “in vivo” by enhancing platelet adhesiveness and by liberating the plateletderived growth factor.

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