scholarly journals Podosomes Display Actin Turnover and Dynamic Self-Organization in Osteoclasts Expressing Actin-Green Fluorescent Protein

2003 ◽  
Vol 14 (2) ◽  
pp. 407-416 ◽  
Author(s):  
Olivier Destaing ◽  
Frédéric Saltel ◽  
Jean-Christophe Géminard ◽  
Pierre Jurdic ◽  
Frédéric Bard
Keyword(s):  
Green Fluorescent Protein ◽  
Actin Polymerization ◽  
Fluorescent Protein ◽  
Osteoclast Differentiation ◽  
Focal Adhesions ◽  
Self Organization ◽  
Cell Periphery ◽  
Continuous Formation ◽  
Actin Turnover ◽  
Green Fluorescent

Podosomes, small actin-based adhesion structures, differ from focal adhesions in two aspects: their core structure and their ability to organize into large patterns in osteoclasts. To address the mechanisms underlying these features, we imaged live preosteoclasts expressing green fluorescent protein-actin during their differentiation. We observe that podosomes always form inside or close to podosome groups, which are surrounded by an actin cloud. Fluorescence recovery after photobleaching shows that actin turns over in individual podosomes in contrast to cortactin, suggesting a continuous actin polymerization in the podosome core. The observation of podosome assemblies during osteoclast differentiation reveals that they evolve from simple clusters into rings that expand by the continuous formation of new podosomes at their outer ridge and inhibition of podosome formation inside the rings. This self-organization of podosomes into dynamic rings is the mechanism that drives podosomes at the periphery of the cell in large circular patterns. We also show that an additional step of differentiation, requiring microtubule integrity, stabilizes the podosome circles at the cell periphery to form the characteristic podosome belt pattern of mature osteoclasts. These results therefore provide a mechanism for the patterning of podosomes in osteoclasts and reveal a turnover of actin inside the podosome.

scholarly journals Live-Cell Analysis of a Green Fluorescent Protein-Tagged Herpes Simplex Virus Infection

1999 ◽  
Vol 73 (5) ◽  
pp. 4110-4119 ◽  
Author(s):  
Gillian Elliott ◽  
Peter O’Hare
Keyword(s):  
Herpes Simplex Virus ◽  
Green Fluorescent Protein ◽  
Herpes Simplex ◽  
Fluorescent Protein ◽  
Time Lapse ◽  
Live Cell ◽  
Cell Periphery ◽  
Green Fluorescent ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACT Many stages of the herpes simplex virus maturation pathway have not yet been defined. In particular, little is known about the assembly of the virion tegument compartment and its subsequent incorporation into maturing virus particles. Here we describe the construction of a herpes simplex virus type 1 (HSV-1) recombinant in which we have replaced the gene encoding a major tegument protein, VP22, with a gene expressing a green fluorescent protein (GFP)-VP22 fusion protein (GFP-22). We show that this virus has growth properties identical to those of the parental virus and that newly synthesized GFP-22 is detectable in live cells as early as 3 h postinfection. Moreover, we show that GFP-22 is incorporated into the HSV-1 virion as efficiently as VP22, resulting in particles which are visible by fluorescence microscopy. Consequently, we have used time lapse confocal microscopy to monitor GFP-22 in live-cell infection, and we present time lapse animations of GFP-22 localization throughout the virus life cycle. These animations demonstrate that GFP-22 is present in a diffuse cytoplasmic location when it is initially expressed but evolves into particulate material which travels through an exclusively cytoplasmic pathway to the cell periphery. In this way, we have for the first time visualized the trafficking of a herpesvirus structural component within live, infected cells.

scholarly journals Arfophilins Are Dual Arf/Rab 11 Binding Proteins That Regulate Recycling Endosome Distribution and Are Related to Drosophila Nuclear Fallout

2003 ◽  
Vol 14 (7) ◽  
pp. 2908-2920 ◽  
Author(s):  
Gilles R.X. Hickson ◽  
Johanne Matheson ◽  
Blake Riggs ◽  
Valerie H. Maier ◽  
Andrew B. Fielding ◽  
...  
Keyword(s):  
Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Binding Capacity ◽  
Binding Protein ◽  
Focal Adhesions ◽  
Dependent Manner ◽  
Recycling Endosome ◽  
Nuclear Fallout ◽  
Endosomal Recycling ◽  
Green Fluorescent

Arfophilin is an ADP ribosylation factor (Arf) binding protein of unknown function. It is identical to the Rab11 binding protein eferin/Rab11-FIP3, and we show it binds both Arf5 and Rab11. We describe a related protein, arfophilin-2, that interacts with Arf5 in a nucleotide-dependent manner, but not Arf1, 4, or 6 and also binds Rab11. Arfophilin-2 localized to a perinuclear compartment, the centrosomal area, and focal adhesions. The localization of arfophilin-2 to the perinuclear compartment was selectively blocked by overexpression of Arf5-T31N. In contrast, a green fluorescent protein-arfophilin-2 chimera or arfophilin-2 deletions were localized around the centrosome in a region that was also enriched for transferrin receptors and Rab11 but not early endosome markers, suggesting that the distribution of the endosomal recycling compartment was altered. The arfophilins belong to a conserved family that includes Drosophila melanogaster nuclear fallout, a centrosomal protein required for cellularization. Expression of green fluorescent protein-nuclear fallout in HeLa cells resulted in a similar phenotype, indicative of functional homology and thus implicating the arfophilins in mitosis/cytokinesis. We suggest that the novel dual GTPase-binding capacity of the arfophilins could serve as an interface of signals from Rab and Arf GTPases to regulate membrane traffic and integrate distinct signals in the late endosomal recycling compartment.

Green fluorescent protein (GFP) tagged to the cytoplasmic tail of αIIb or β3 allows the expression of a fully functional integrin αIIbβ3: effect of β3GFP on αIIbβ3 ligand binding

2001 ◽  
Vol 357 (2) ◽  
pp. 529-536 ◽  
Author(s):  
Sébastien PLANÇON ◽  
Marie-Christine MOREL-KOPP ◽  
Elisabeth SCHAFFNER-RECKINGER ◽  
Ping CHEN ◽  
Nelly KIEFFER
Keyword(s):  
Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Chinese Hamster ◽  
Focal Adhesions ◽  
Cytoplasmic Tail ◽  
Receptor Activation ◽  
Living Cells ◽  
Cell Surface Expression ◽  
Β3 Integrin ◽  
Green Fluorescent

Using green fluorescent protein (GFP) as an autofluorescent tag, we report the first successful visualization of a β3 integrin in a living cell. GFP fused in frame to the cytoplasmic tail of either αIIb or β3 allowed normal expression, heterodimerization, processing and surface exposure of αIIbGFPβ3 and αIIbβ3GFP receptors in Chinese hamster ovary (CHO) cells. Direct microscopic observation of the autofluorescent cells in suspension following antibody-induced αIIbβ3 capping revealed an intense autofluorescent cap corresponding to unlabelled immunoclustered GFP-tagged αIIbβ3. GFP-tagged αIIbβ3 receptors mediated fibrinogen-dependent cell adhesion, were readily detectable in focal adhesions of unstained living cells and triggered p125FAK tyrosine phosphorylation similar to wild-type αIIbβ3 (where FAK corresponds to focal adhesion kinase). However, GFP tagged to β3, but not to αIIb, induced spontaneous CHO cell aggregation in the presence of soluble fibrinogen, as well as binding of the fibrinogen mimetic monoclonal antibody PAC1 in the absence of αIIbβ3 receptor activation. Time-lapse imaging of living transfectants revealed a characteristic redistribution of GFP-tagged αIIbβ3 during the early stages of cell attachment and spreading, starting with αIIbβ3 clustering at the rim of the cell contact area, that gradually overlapped with the boundary of the attached cell, and, with the onset of cell spreading, to a reorganization of αIIbβ3 in focal adhesions. Taken together, our results demonstrate that (1) fusion of GFP to the cytoplasmic tail of either αIIb or β3 integrin subunits allows normal cell surface expression of a functional receptor, and (2) structural modification of the β3 integrin cytoplasmic tail, rather than the αIIb subunit, plays a major role in αIIbβ3 affinity modulation. With the successful direct visualization of functional αIIbβ3 receptors in living cells, the generation of autofluorescent integrins in transgenic animals will become possible, allowing new approaches to study the dynamics of integrin functions.

scholarly journals RhoG GTPase Controls a Pathway That Independently Activates Rac1 and Cdc42Hs

1998 ◽  
Vol 9 (6) ◽  
pp. 1379-1394 ◽  
Author(s):  
Cécile Gauthier-Rouvière ◽  
Emmanuel Vignal ◽  
Mayya Mériane ◽  
Pierre Roux ◽  
Philippe Montcourier ◽  
...  
Keyword(s):  
Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Dominant Negative ◽  
Local Concentration ◽  
Cell Periphery ◽  
Growth Factor Signaling ◽  
Microtubule Depolymerization ◽  
Microtubule Network ◽  
Membrane Ruffling ◽  
Green Fluorescent

RhoG is a member of the Rho family of GTPases that shares 72% and 62% sequence identity with Rac1 and Cdc42Hs, respectively. We have expressed mutant RhoG proteins fused to the green fluorescent protein and analyzed subsequent changes in cell surface morphology and modifications of cytoskeletal structures. In rat and mouse fibroblasts, green fluorescent protein chimera and endogenous RhoG proteins colocalize according to a tubular cytoplasmic pattern, with perinuclear accumulation and local concentration at the plasma membrane. Constitutively active RhoG proteins produce morphological and cytoskeletal changes similar to those elicited by a simultaneous activation of Rac1 and Cdc42Hs, i.e., the formation of ruffles, lamellipodia, filopodia, and partial loss of stress fibers. In addition, RhoG and Cdc42Hs promote the formation of microvilli at the cell apical membrane. RhoG-dependent events are not mediated through a direct interaction with Rac1 and Cdc42Hs targets such as PAK-1, POR1, or WASP proteins but require endogenous Rac1 and Cdc42Hs activities: coexpression of a dominant negative Rac1 impairs membrane ruffling and lamellipodia but not filopodia or microvilli formation. Conversely, coexpression of a dominant negative Cdc42Hs only blocks microvilli and filopodia, but not membrane ruffling and lamellipodia. Microtubule depolymerization upon nocodazole treatment leads to a loss of RhoG protein from the cell periphery associated with a reversal of the RhoG phenotype, whereas PDGF or bradykinin stimulation of nocodazole-treated cells could still promote Rac1- and Cdc42Hs-dependent cytoskeletal reorganization. Therefore, our data demonstrate that RhoG controls a pathway that requires the microtubule network and activates Rac1 and Cdc42Hs independently of their growth factor signaling pathways.

scholarly journals New single-molecule speckle microscopy reveals modification of the retrograde actin flow by focal adhesions at nanometer scales

2014 ◽  
Vol 25 (7) ◽  
pp. 1010-1024 ◽  
Author(s):  
Sawako Yamashiro ◽  
Hiroaki Mizuno ◽  
Matthew B. Smith ◽  
Gillian L. Ryan ◽  
Tai Kiuchi ◽  
...  
Keyword(s):  
Single Molecule ◽  
Fluorescent Protein ◽  
Focal Adhesions ◽  
Actin Network ◽  
Actin Turnover ◽  
Flow Velocity Measurement ◽  
Flow Speeds ◽  
Green Fluorescent ◽  
User Friendly

Speckle microscopy directly visualizes the retrograde actin flow, which is believed to promote cell-edge protrusion when linked to focal adhesions (FAs). However, it has been argued that, due to rapid actin turnover, the use of green fluorescent protein–actin, the lack of appropriate analysis algorithms, and technical difficulties, speckle microscopy does not necessarily report the flow velocities of entire actin populations. In this study, we developed a new, user-friendly single-molecule speckle (SiMS) microscopy using DyLight dye-labeled actin. Our new SiMS method enables in vivo nanometer-scale displacement analysis with a low localization error of ±8–8.5 nm, allowing accurate flow-velocity measurement for actin speckles with lifetime <5 s. In lamellipodia, both short- and long-lived F-actin molecules flow with the same speed, indicating they are part of a single actin network. These results do not support coexistence of F-actin populations with different flow speeds, which is referred to as the lamella hypothesis. Mature FAs, but not nascent adhesions, locally obstruct the retrograde flow. Interestingly, the actin flow in front of mature FAs is fast and biased toward FAs, suggesting that mature FAs attract the flow in front and actively remodel the local actin network.

scholarly journals Toxofilin, a Novel Actin-binding Protein from Toxoplasma gondii, Sequesters Actin Monomers and Caps Actin Filaments

2000 ◽  
Vol 11 (1) ◽  
pp. 355-368 ◽  
Author(s):  
Olivier Poupel ◽  
Haralabia Boleti ◽  
Sophie Axisa ◽  
Evelyne Couture-Tosi ◽  
Isabelle Tardieux
Keyword(s):  
Green Fluorescent Protein ◽  
Toxoplasma Gondii ◽  
Host Cell ◽  
Actin Filaments ◽  
Actin Polymerization ◽  
Fluorescent Protein ◽  
Binding Protein ◽  
Actin Binding ◽  
Actin Binding Protein ◽  
Green Fluorescent

Toxoplasma gondii relies on its actin cytoskeleton to glide and enter its host cell. However, T. gondii tachyzoites are known to display a strikingly low amount of actin filaments, which suggests that sequestration of actin monomers could play a key role in parasite actin dynamics. We isolated a 27-kDa tachyzoite protein on the basis of its ability to bind muscle G-actin and demonstrated that it interacts with parasite G-actin. Cloning and sequence analysis of the gene coding for this protein, which we named Toxofilin, showed that it is a novel actin-binding protein. In in vitro assays, Toxofilin not only bound to G-actin and inhibited actin polymerization as an actin-sequestering protein but also slowed down F-actin disassembly through a filament end capping activity. In addition, when green fluorescent protein-tagged Toxofilin was overexpressed in mammalian nonmuscle cells, the dynamics of actin stress fibers was drastically impaired, whereas green fluorescent protein-Toxofilin copurified with G-actin. Finally, in motile parasites, during gliding or host cell entry, Toxofilin was localized in the entire cytoplasm, including the rear end of the parasite, whereas in intracellular tachyzoites, especially before they exit from the parasitophorous vacuole of their host cell, Toxofilin was found to be restricted to the apical end.

Zyxin Is not Colocalized with Vasodilator-stimulated Phosphoprotein (VASP) at Lamellipodial Tips and Exhibits Different Dynamics to Vinculin, Paxillin, and VASP in Focal Adhesions

2001 ◽  
Vol 12 (10) ◽  
pp. 3103-3113 ◽  
Author(s):  
Klemens Rottner ◽  
Matthias Krause ◽  
Mario Gimona ◽  
J. Victor Small ◽  
Jürgen Wehland
Keyword(s):  
Focal Adhesion ◽  
Actin Polymerization ◽  
Fluorescent Protein ◽  
Protein Complexes ◽  
Focal Adhesions ◽  
Stress Fibers ◽  
Live Cells ◽  
Fusion Construct ◽  
Focal Adhesion Protein ◽  
Green Fluorescent

Actin polymerization is accompanied by the formation of protein complexes that link extracellular signals to sites of actin assembly such as membrane ruffles and focal adhesions. One candidate recently implicated in these processes is the LIM domain protein zyxin, which can bind both Ena/vasodilator-stimulated phosphoprotein (VASP) proteins and the actin filament cross-linking protein α-actinin. To characterize the localization and dynamics of zyxin in detail, we generated both monoclonal antibodies and a green fluorescent protein (GFP)-fusion construct. The antibodies colocalized with ectopically expressed GFP-VASP at focal adhesions and along stress fibers, but failed to label lamellipodial and filopodial tips, which also recruit Ena/VASP proteins. Likewise, neither microinjected, fluorescently labeled zyxin antibodies nor ectopically expressed GFP-zyxin were recruited to these latter sites in live cells, whereas both probes incorporated into focal adhesions and stress fibers. Comparing the dynamics of zyxin with that of the focal adhesion protein vinculin revealed that both proteins incorporated simultaneously into newly formed adhesions. However, during spontaneous or induced focal adhesion disassembly, zyxin delocalization preceded that of either vinculin or paxillin. Together, these data identify zyxin as an early target for signals leading to adhesion disassembly, but exclude its role in recruiting Ena/VASP proteins to the tips of lamellipodia and filopodia.

scholarly journals α4β1 Integrin Regulates Lamellipodia Protrusion via a Focal Complex/Focal Adhesion-independent Mechanism

2002 ◽  
Vol 13 (9) ◽  
pp. 3203-3217 ◽  
Author(s):  
Karen A. Pinco ◽  
Wei He ◽  
Joy T. Yang
Keyword(s):  
Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Focal Adhesions ◽  
Leading Edge ◽  
Time Lapse ◽  
Random Motility ◽  
Protein Fusion ◽  
Green Fluorescent

α4β1 integrin plays an important role in cell migration. We show that when ectopically expressed in Chinese hamster ovary cells, α4β1 is sufficient and required for promoting protrusion of broad lamellipodia in response to scratch-wounding, whereas α5β1 does not have this effect. By time-lapse microscopy of cells expressing an α4/green fluorescent protein fusion protein, we show that α4β1 forms transient puncta at the leading edge of cells that begin to protrude lamellipodia in response to scratch-wounding. The cells expressing a mutant α4/green fluorescent protein that binds paxillin at a reduced level had a faster response to scratch-wounding, forming α4-positive puncta and protruding lamellipodia much earlier. While enhancing lamellipodia protrusion, this mutation reduces random motility of the cells in Transwell assays, indicating that lamellipodia protrusion and random motility are distinct types of motile activities that are differentially regulated by interactions between α4β1 and paxillin. Finally, we show that, at the leading edge, α4-positive puncta and paxillin-positive focal complexes/adhesions do not colocalize, but α4β1 and paxillin colocalize partially in ruffles. These findings provide evidence for a specific role of α4β1 in lamellipodia protrusion that is distinct from the motility-promoting functions of α5β1 and other integrins that mediate cell adhesion and signaling events through focal complexes and focal adhesions.

scholarly journals Astrocyte-to-neuron transportation of enhanced green fluorescent protein in cerebral cortex requires F-actin dependent tunneling nanotubes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jing Chen ◽  
Junyan Cao
Keyword(s):  
Cerebral Cortex ◽  
Green Fluorescent Protein ◽  
Actin Polymerization ◽  
Enhanced Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Cell Contact ◽  
Neural Cells ◽  
Tunneling Nanotubes ◽  
Layer V ◽  
Green Fluorescent

AbstractTunneling nanotube (TNT), a dynamic cell–cell contact, is dependent on actin polymerization. TNTs are efficient in transporting ions, proteins and organelles intercellularly, which are important mechanisms in physiological and pathological processes. Reported studies on the existence and function of TNTs among neural cells focus on cultured cell for the convenience in detecting TNTs’ ultrastructure. In this study, the adeno-associated virus (AAV-GFAP-EGFP-p2A-cre) was injected into the cerebral cortex of knock-in mice ROSA26 GNZ. GFAP promoter initiated the expression of enhanced green fluorescent protein (EGFP) in infected astrocytes. At 10 days post injection (10 DPI), EGFP transferred from astrocytes in layer I–III to neurons in layer V. The dissemination of EGFP was not through endocytosis or exosome. Applying microscopes, we found that the intercellular transportation of EGFP through contact connection was F-actin dependent. Therefore, we concluded that EGFP transported from astrocytes to neurons in cortex via F-actin dependent TNTs. This study first proved that proteins transported intercellularly via TNTs in brain.

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