Distribution and Function of Filamentous and Globular Actin in Mitochondrial Translocation During Ascidian Sperm Activation

2001 ◽  
Vol 7 (S2) ◽  
pp. 448-449
Author(s):  
E. Zebadua ◽  
L. Blackwell ◽  
R.A. Koch
Keyword(s):  
Actin Polymerization ◽  
Relative Distribution ◽  
Filamentous Actin ◽  
Penetration Process ◽  
Sperm Activation ◽  
Mitochondrial Translocation ◽  
Sea Squirt ◽  
And Function ◽  
Ascidia Ceratodes ◽  
Vitelline Coat

During fertilization in the sea squirt, Ascidia ceratodes,the penetration process of requires mitochondrial translocation, a process that defines sperm activation in this species, to generate the driving force for passage through the vitelline coat. When a sperm cell come into contact with an egg, the mitochondrion translocates off the head and migrates along the tail via an actimmyosin-dependent process. The presence of actin and myosin on the head and tail has been demonstrated. However, the nature of the relative distribution of filamentous actin (F-actin) and monomeric actin (G-actin) has not been thoroughly studied. And, whereas the signaling cascade that leads to myosin activation has been studied, the events leading to actin polymerization and whether it is required for mitochondrial translocation has not.This project addresses two research questions: What is the distribution of F-actin and G-actin in unactivated and activated sperm cells? And, can preexisting F-actin support mitochondrial translocation or must actin polymerization occur simultaneously with the mitochondrial translocation process?

scholarly journals CXCL9 inhibits eosinophil responses by a CCR3- and Rac2-dependent mechanism

Blood ◽  
2005 ◽  
Vol 106 (2) ◽  
pp. 436-443 ◽  
Author(s):  
Patricia C. Fulkerson ◽  
Hongyan Zhu ◽  
David A. Williams ◽  
Nives Zimmermann ◽  
Marc E. Rothenberg
Keyword(s):  
Actin Polymerization ◽  
Platelet Activating Factor ◽  
Interferon Γ ◽  
Leukotriene B4 ◽  
Induced Responses ◽  
Filamentous Actin ◽  
Receptor Antagonism ◽  
Guanosine Triphosphatase ◽  
And Function ◽  
Dependent Mechanism

Abstract Recently, inhibitory cytokine pathways for leukocyte chemoattraction and activation have been identified, but there is little insight into the operational mechanisms except for models that rely on simple receptor antagonism. We have previously identified the existence of a murine eosinophil inhibitory pathway mediated by the CXC chemokine ligand 9 (CXCL9, Mig [monokine induced by interferon-γ]) that impressively blocks eosinophil chemoattraction and function, but the mechanism has remained elusive. We now demonstrate that Mig's inhibitory action extends beyond receptor antagonism alone. Notably, in addition to inhibiting eotaxin-induced filamentous actin (F-actin) formation and chemoattraction, Mig potently blocks platelet activating factor (PAF)– and leukotriene B4 (LTB4)–induced responses. Remarkably, Mig-treated eosinophils display an abnormal F-actin assembly in the absence of agonist stimulation. Additionally, Mig pretreatment inhibits eotaxin-induced activation of the Rho–guanosine triphosphatase (GTPase) Rac, and Rac2-deficient eosinophils demonstrate an impaired transmigration and actin polymerization response to eotaxin stimulation. Furthermore, Mig was unable to inhibit eotaxin-induced responses in Rac2-deficient eosinophils. Finally, using CCR3 gene–targeted cells, Mig's inhibitory activity is demonstrated to be mediated by CC chemokine receptor 3 (CCR3). Thus, by altering agonist-induced signaling and abrogating cytoskeletal reorganization by a Rac2-dependent mechanism, Mig markedly inhibits eosinophil responses to diverse stimuli. These results establish evidence that distinct chemokines can use CCR3 to induce opposing signals in eosinophils.

scholarly journals Small GTP-binding Protein TC10 Differentially Regulates Two Distinct Populations of Filamentous Actin in 3T3L1 Adipocytes

2002 ◽  
Vol 13 (7) ◽  
pp. 2334-2346 ◽  
Author(s):  
Makoto Kanzaki ◽  
Robert T. Watson ◽  
June Chunqiu Hou ◽  
Mark Stamnes ◽  
Alan R. Saltiel ◽  
...  
Keyword(s):  
Protein Trafficking ◽  
Actin Polymerization ◽  
Coat Proteins ◽  
Filamentous Actin ◽  
Cortical Actin ◽  
Amino Terminal ◽  
Gtp Binding ◽  
Subcellular Compartmentalization ◽  
Constitutively Active

TC10 is a member of the Rho family of small GTP-binding proteins that has previously been implicated in the regulation of insulin-stimulated GLUT4 translocation in adipocytes. In a manner similar to Cdc42-stimulated actin-based motility, we have observed that constitutively active TC10 (TC10/Q75L) can induce actin comet tails in Xenopus oocyte extracts in vitro and extensive actin polymerization in the perinuclear region when expressed in 3T3L1 adipocytes. In contrast, expression of TC10/Q75L completely disrupted adipocyte cortical actin, which was specific for TC10, because expression of constitutively active Cdc42 was without effect. The effect of TC10/Q75L to disrupt cortical actin was abrogated after deletion of the amino terminal extension (ΔN-TC10/Q75L), whereas this deletion retained the ability to induce perinuclear actin polymerization. In addition, alteration of perinuclear actin by expression of TC10/Q75L, a dominant-interfering TC10/T31N mutant or a mutant N-WASP protein (N-WASP/ΔVCA) reduced the rate of VSV G protein trafficking to the plasma membrane. Furthermore, TC10 directly bound to Golgi COPI coat proteins through a dilysine motif in the carboxyl terminal domain consistent with a role for TC10 regulating actin polymerization on membrane transport vesicles. Together, these data demonstrate that TC10 can differentially regulate two types of filamentous actin in adipocytes dependent on distinct functional domains and its subcellular compartmentalization.

scholarly journals TORC2-Gad8-dependent myosin phosphorylation modulates regulation by calcium

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Karen Baker ◽  
Irene A Gyamfi ◽  
Gregory I Mashanov ◽  
Justin E Molloy ◽  
Michael A Geeves ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Cell Cycle Progression ◽  
Actin Polymerization ◽  
Neck Region ◽  
Signaling Networks ◽  
Tor Signaling ◽  
Multicellular Development ◽  
Membrane Reorganization ◽  
And Function

Cells respond to changes in their environment through signaling networks that modulate cytoskeleton and membrane organization to coordinate cell-cycle progression, polarized cell growth and multicellular development. Here, we define a novel regulatory mechanism by which the motor activity and function of the fission yeast type one myosin, Myo1, is modulated by TORC2-signalling-dependent phosphorylation. Phosphorylation of the conserved serine at position 742 (S742) within the neck region changes both the conformation of the neck region and the interactions between Myo1 and its associating calmodulin light chains. S742 phosphorylation thereby couples the calcium and TOR signaling networks that are involved in the modulation of myosin-1 dynamics to co-ordinate actin polymerization and membrane reorganization at sites of endocytosis and polarised cell growth in response to environmental and cell-cycle cues.

scholarly journals Coxiella burnetii Induces Reorganization of the Actin Cytoskeleton in Human Monocytes

1998 ◽  
Vol 66 (11) ◽  
pp. 5527-5533 ◽  
Author(s):  
Sonia Meconi ◽  
Véronique Jacomo ◽  
Patrice Boquet ◽  
Didier Raoult ◽  
Jean-Louis Mege ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Coxiella Burnetii ◽  
Actin Polymerization ◽  
Q Fever ◽  
Morphological Changes ◽  
Critical Role ◽  
Filamentous Actin ◽  
Cytoskeleton Reorganization ◽  
Membrane Protrusions ◽  
Actin Protrusions

ABSTRACT Coxiella burnetii, an obligate intracellular bacterium which survives in myeloid cells, causes Q fever in humans. We previously demonstrated that virulent C. burnetiiorganisms are poorly internalized by monocytes compared to avirulent variants. We hypothesized that a differential mobilization of the actin cytoskeleton may account for this distinct phagocytic behavior. Scanning electron microscopy demonstrated that virulent C. burnetii stimulated profound and polymorphic changes in the morphology of THP-1 monocytes, consisting of membrane protrusions and polarized projections. These changes were transient, requiring 5 min to reach their maximum extent and vanishing after 60 min of incubation. In contrast, avirulent variants of C. burnetii did not induce any significant changes in cell morphology. The distribution of filamentous actin (F-actin) was then studied with a specific probe, bodipy phallacidin. Virulent C. burnetii induced a profound and transient reorganization of F-actin, accompanied by an increase in the F-actin content of THP-1 cells. F-actin was colocalized with myosin in cell protrusions, suggesting that actin polymerization and the tension of actin-myosin filaments play a role in C. burnetii-induced morphological changes. In addition, contact between the cell and the bacterium seems to be necessary to induce cytoskeleton reorganization. Bacterial supernatants did not stimulate actin remodeling, and virulent C. burnetii organisms were found in close apposition with F-actin protrusions. The manipulation of the actin cytoskeleton by C. burnetiimay therefore play a critical role in the internalization strategy of this bacterium.

scholarly journals Three F-actin assembly centers regulate organelle inheritance, cell-cell communication and motility in Toxoplasma gondii

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Nicolò Tosetti ◽  
Nicolas Dos Santos Pacheco ◽  
Dominique Soldati-Favre ◽  
Damien Jacot
Keyword(s):  
Protein Kinase ◽  
Toxoplasma Gondii ◽  
Actin Polymerization ◽  
Cell Communication ◽  
Residual Body ◽  
Filamentous Actin ◽  
Calcium Dependent ◽  
Actin Regulatory Proteins ◽  
Parasite Motility ◽  
Cell Cell

Toxoplasma gondii possesses a limited set of actin-regulatory proteins and relies on only three formins (FRMs) to nucleate and polymerize actin. We combined filamentous actin (F-actin) chromobodies with gene disruption to assign specific populations of actin filaments to individual formins. FRM2 localizes to the apical juxtanuclear region and participates in apicoplast inheritance. Restricted to the residual body, FRM3 maintains the intravacuolar cell-cell communication. Conoidal FRM1 initiates a flux of F-actin crucial for motility, invasion and egress. This flux depends on myosins A and H and is controlled by phosphorylation via PKG (protein kinase G) and CDPK1 (calcium-dependent protein kinase 1) and by methylation via AKMT (apical lysine methyltransferase). This flux is independent of microneme secretion and persists in the absence of the glideosome-associated connector (GAC). This study offers a coherent model of the key players controlling actin polymerization, stressing the importance of well-timed post-translational modifications to power parasite motility.

scholarly journals Shape oscillations of human neutrophil leukocytes: characterization and relationship to cell motility.

1996 ◽  
Vol 199 (4) ◽  
pp. 741-747
Author(s):  
M U Ehrengruber ◽  
D A Deranleau ◽  
T D Coates
Keyword(s):  
Light Scattering ◽  
Actin Polymerization ◽  
Cellular Migration ◽  
Human Neutrophils ◽  
Filamentous Actin ◽  
Cytoskeletal Component ◽  
Morphological Polarity ◽  
Shape Oscillations ◽  
Shape Changes ◽  
Neutrophil Leukocytes

When neutrophil leukocytes are stimulated by chemotactic factors or by substratum contact, they change their shape. Shape changes are a prerequisite for cellular migration and typically involve the extrusion of thin, veil-like lamellipods and the development of morphological polarity. Stimulation also leads to changes in the neutrophil content of filamentous actin (F-actin), which is the major cytoskeletal component. Suspensions of human neutrophils stimulated with chemoattractants exhibit sinusoidal light-scattering oscillations with a period of approximately 8 s at 37 degrees C. These oscillations arise from periodic fluctuations in the cell body size caused by lamellipod extension and retraction cycles. The light-scattering oscillations are paralleled by corresponding oscillations in F-actin content. This raises the interesting possibility that cyclic actin polymerization constitutes the driving force for shape oscillations of suspended neutrophils. Similar periodic shape changes are present in neutrophils crawling on a surface, suggesting that shape oscillations are important for neutrophil motion. This review summarizes our present knowledge about shape oscillations in suspended and crawling neutrophils and discusses a possible role for these oscillations in neutrophil motility.

scholarly journals Tropomyosin Tpm3.1 is required to maintain the structure and function of the axon initial segment

2019 ◽  
Author(s):  
Amr Abouelezz ◽  
Holly Stefen ◽  
Mikael Segerstråle ◽  
David Micinski ◽  
Rimante Minkeviciene ◽  
...  
Keyword(s):  
Actin Filaments ◽  
Hippocampal Neurons ◽  
Initial Segment ◽  
Actin Polymerization ◽  
Firing Frequency ◽  
Axon Initial Segment ◽  
Action Potential Initiation ◽  
Sodium Ion Channels ◽  
And Function ◽  
Filament Network

ABSTRACTThe axon initial segment (AIS) is the site of action potential initiation and serves as a vesicular filter and diffusion barrier that help maintain neuronal polarity. Recent studies have revealed details about a specialized structural complex in the AIS. While an intact actin cytoskeleton is required for AIS formation, pharmacological disruption of actin polymerization compromises the AIS vesicle filter but does not affect overall AIS structure. In this study, we found that the tropomyosin isoform Tpm3.1 decorates a population of relatively stable actin filaments in the AIS. Inhibiting Tpm3.1 in cultured hippocampal neurons led to the loss of AIS structure, the AIS vesicle filter, the clustering of sodium ion channels, and reduced firing frequency. We propose that Tpm3.1-decorated actin filaments form a stable actin filament network under the AIS membrane which provides a scaffold for membrane organization and AIS proteins.

scholarly journals Unregulated actin polymerization by WASp causes defects of mitosis and cytokinesis in X-linked neutropenia

2007 ◽  
Vol 204 (9) ◽  
pp. 2213-2224 ◽  
Author(s):  
Dale A. Moulding ◽  
Michael P. Blundell ◽  
David G. Spiller ◽  
Michael R.H. White ◽  
Giles O. Cory ◽  
...  
Keyword(s):  
Live Cell Imaging ◽  
Actin Polymerization ◽  
Cell Imaging ◽  
Human Gene ◽  
Filamentous Actin ◽  
Gene Encoding ◽  
Activating Mutations ◽  
Spindle Midzone ◽  
Underlying Mechanisms ◽  
Syndrome Protein

Specific mutations in the human gene encoding the Wiskott-Aldrich syndrome protein (WASp) that compromise normal auto-inhibition of WASp result in unregulated activation of the actin-related protein 2/3 complex and increased actin polymerizing activity. These activating mutations are associated with an X-linked form of neutropenia with an intrinsic failure of myelopoiesis and an increase in the incidence of cytogenetic abnormalities. To study the underlying mechanisms, active mutant WASpI294T was expressed by gene transfer. This caused enhanced and delocalized actin polymerization throughout the cell, decreased proliferation, and increased apoptosis. Cells became binucleated, suggesting a failure of cytokinesis, and micronuclei were formed, indicative of genomic instability. Live cell imaging demonstrated a delay in mitosis from prometaphase to anaphase and confirmed that multinucleation was a result of aborted cytokinesis. During mitosis, filamentous actin was abnormally localized around the spindle and chromosomes throughout their alignment and separation, and it accumulated within the cleavage furrow around the spindle midzone. These findings reveal a novel mechanism for inhibition of myelopoiesis through defective mitosis and cytokinesis due to hyperactivation and mislocalization of actin polymerization.

scholarly journals The N-Terminus ofDictyosteliumScar Interacts with Abi and HSPC300 and Is Essential for Proper Regulation and Function

2007 ◽  
Vol 18 (5) ◽  
pp. 1609-1620 ◽  
Author(s):  
Diana Caracino ◽  
Cheryl Jones ◽  
Mark Compton ◽  
Charles L. Saxe
Keyword(s):  
Actin Polymerization ◽  
Terminal Region ◽  
Wild Type ◽  
Large Molecular Weight ◽  
Weight Protein ◽  
And Function ◽  
Necessary And Sufficient

Scar/WAVE proteins, members of the conserved Wiskott-Aldrich syndrome (WAS) family, promote actin polymerization by activating the Arp2/3 complex. A number of proteins, including a complex containing Nap1, PIR121, Abi1/2, and HSPC300, interact with Scar/WAVE, though the role of this complex in regulating Scar function remains unclear. Here we identify a short N-terminal region of Dictyostelium Scar that is necessary and sufficient for interaction with HSPC300 and Abi in vitro. Cells expressing Scar lacking this N-terminal region show abnormalities in F-actin distribution, cell morphology, movement, and cytokinesis. This is true even in the presence of wild-type Scar. The data suggest that the first 96 amino acids of Scar are necessary for participation in a large-molecular-weight protein complex, and that this Scar-containing complex is responsible for the proper localization and regulation of Scar. The presence of mis-regulated or unregulated Scar has significant deleterious effects on cells and may explain the need to keep Scar activity tightly controlled in vivo either by assembly in a complex or by rapid degradation.

scholarly journals Overexpression of cofilin stimulates bundling of actin filaments, membrane ruffling, and cell movement in Dictyostelium.

1996 ◽  
Vol 132 (3) ◽  
pp. 335-344 ◽  
Author(s):  
H Aizawa ◽  
K Sutoh ◽  
I Yahara
Keyword(s):  
Actin Filaments ◽  
Cell Movement ◽  
Structure And Function ◽  
Cross Linking ◽  
Low Molecular Weight ◽  
Filamentous Actin ◽  
Membrane Ruffling ◽  
And Function

Cofilin is a low molecular weight actin-modulating protein whose structure and function are conserved among eucaryotes. Cofilin exhibits in vitro both a monomeric actin-sequestering activity and a filamentous actin-severing activity. To investigate in vivo functions of cofilin, cofilin was overexpressed in Dictyostelium discoideum cells. An increase in the content of D. discoideum cofilin (d-cofilin) by sevenfold induced a co-overproduction of actin by threefold. In cells over-expressing d-cofilin, the amount of filamentous actin but not that of monomeric actin was increased. Overexpressed d-cofilin co-sedimented with actin filaments, suggesting that the sequestering activity of d-cofilin is weak in vivo. The overexpression of d-cofilin increased actin bundles just beneath ruffling membranes where d-cofilin was co-localized. The overexpression of d-cofilin also stimulated cell movement as well as membrane ruffling. We have demonstrated in vitro that d-cofilin transformed latticework of actin filaments cross-linked by alpha-actinin into bundles probably by severing the filaments. D. discoideum cofilin may sever actin filaments in vivo and induce bundling of the filaments in the presence of cross-linking proteins so as to generate contractile systems involved in membrane ruffling and cell movement.

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