Aging-Impaired Filamentous Actin Polymerization Signaling Reduces Alveolar Macrophage Phagocytosis of Bacteria

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.

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Coxiella burnetii Induces Reorganization of the Actin Cytoskeleton in Human Monocytes

Infection and Immunity ◽

10.1128/iai.66.11.5527-5533.1998 ◽

1998 ◽

Vol 66 (11) ◽

pp. 5527-5533 ◽

Cited By ~ 40

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.

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

eLife ◽

10.7554/elife.42669 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 27

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.

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

Journal of Experimental Biology ◽

10.1242/jeb.199.4.741 ◽

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.

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

Journal of Experimental Medicine ◽

10.1084/jem.20062324 ◽

2007 ◽

Vol 204 (9) ◽

pp. 2213-2224 ◽

Cited By ~ 123

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.

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