scholarly journals An unmet actin requirement explains the mitotic inhibition of clathrin-mediated endocytosis

2014 ◽  
Author(s):  
Satdip Kaur ◽  
Andrew B Fielding ◽  
Gisela Gassner ◽  
Nicholas J Carter ◽  
Stephen J Royle
Keyword(s):  
Actin Cytoskeleton ◽  
Mammalian Cells ◽  
Membrane Tension ◽  
Mitotic Inhibition ◽  
Mitotic Phosphorylation ◽  
Early Mitosis ◽  
Mitotic Cells ◽  
Endocytic Proteins

Clathrin-mediated endocytosis (CME) is the major internalisation route for many different receptor types in mammalian cells. CME is shut down during early mitosis, but the mechanism of this inhibition is unclear. Here we show that the mitotic shutdown is due to an unmet requirement for actin in CME. In mitotic cells, membrane tension is increased and this invokes a requirement for the actin cytoskeleton to assist the CME machinery to overcome the increased load. However, the actin cytoskeleton is engaged in the formation of a rigid cortex in mitotic cells and is therefore unavailable for deployment. We demonstrate that CME can be 'restarted&' in mitotic cells despite high membrane tension, by allowing actin to engage in endocytosis. Mitotic phosphorylation of endocytic proteins is maintained in mitotic cells with restored CME, indicating that direct phosphorylation of the CME machinery does not account for shutdown. Now published as eLife DOI: http://dx.doi.org/10.7554/eLife.00829

scholarly journals An unmet actin requirement explains the mitotic inhibition of clathrin-mediated endocytosis

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Satdip Kaur ◽  
Andrew B Fielding ◽  
Gisela Gassner ◽  
Nicholas J Carter ◽  
Stephen J Royle
Keyword(s):  
Actin Cytoskeleton ◽  
Mammalian Cells ◽  
Membrane Tension ◽  
Mitotic Inhibition ◽  
Mitotic Phosphorylation ◽  
Early Mitosis ◽  
Mitotic Cells ◽  
Endocytic Proteins

Clathrin-mediated endocytosis (CME) is the major internalisation route for many different receptor types in mammalian cells. CME is shut down during early mitosis, but the mechanism of this inhibition is unclear. In this study, we show that the mitotic shutdown is due to an unmet requirement for actin in CME. In mitotic cells, membrane tension is increased and this invokes a requirement for the actin cytoskeleton to assist the CME machinery to overcome the increased load. However, the actin cytoskeleton is engaged in the formation of a rigid cortex in mitotic cells and is therefore unavailable for deployment. We demonstrate that CME can be ‘restarted’ in mitotic cells despite high membrane tension, by allowing actin to engage in endocytosis. Mitotic phosphorylation of endocytic proteins is maintained in mitotic cells with restored CME, indicating that direct phosphorylation of the CME machinery does not account for shutdown.

Cytokinesis arrest and redistribution of actin-cytoskeleton regulatory components in cells expressing the Rho GTPase CDC42Hs

1996 ◽  
Vol 109 (2) ◽  
pp. 367-377 ◽  
Author(s):  
H. Dutartre ◽  
J. Davoust ◽  
J.P. Gorvel ◽  
P. Chavrier
Keyword(s):  
Actin Cytoskeleton ◽  
Rho Gtpases ◽  
Mammalian Cells ◽  
Laser Scanning ◽  
Rho Gtpase ◽  
Laser Scanning Microscopy ◽  
Regulatory Subunit ◽  
Confocal Laser ◽  
Complex Architectures ◽  
Immunofluorescence Labelling

In mammalian cells, Rho GTPases control the reorganisation of the actin cytoskeleton in response to growth factors. In the cytoplasm, the polymerisation of actin filaments and their organisation into complex architectures is orchestrated by numerous proteins which act either directly, by interacting with actin, or by producing secondary messengers which serve as mediators between signal transduction pathways and the microfilament organisation. We sought to determine whether the intracellular distribution of some of these regulatory components may be controlled by the Rho GTPase CDC42Hs. With this aim, we have established HeLa-derived human cell lines in which expression of a constitutively activated mutant of CDC42Hs is inducible. Morphological analysis by immunofluorescence labelling and confocal laser scanning microscopy revealed a massive reorganisation of F-actin in cortical microspikes as well as podosome-like structures located at the ventral face of the cells. Concomitantly, the cells became giant and multinucleate indicating that cytokinesis was impaired. The actin bundling protein T-plastin, the vasodilatator-stimulated phosphoprotein (VASP), a profilin ligand, as well as the 85 kDa regulatory subunit of the phosphoinosite 3-kinase redistributed with F-actin into the CDC42Hs-induced structures.

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 Evolutionarily diverse LIM domain-containing proteins bind stressed actin filaments through a conserved mechanism

2020 ◽  
Vol 117 (41) ◽  
pp. 25532-25542 ◽  
Author(s):  
Jonathan D. Winkelman ◽  
Caitlin A. Anderson ◽  
Cristian Suarez ◽  
David R. Kovar ◽  
Margaret L. Gardel
Keyword(s):  
Actin Cytoskeleton ◽  
Fission Yeast ◽  
Actin Filaments ◽  
Mammalian Cells ◽  
Strain Sensing ◽  
Lim Domain ◽  
Lim Domains ◽  
Mechanical Homeostasis ◽  
Functionally Diverse

The actin cytoskeleton assembles into diverse load-bearing networks, including stress fibers (SFs), muscle sarcomeres, and the cytokinetic ring to both generate and sense mechanical forces. The LIM (Lin11, Isl- 1, and Mec-3) domain family is functionally diverse, but most members can associate with the actin cytoskeleton with apparent force sensitivity. Zyxin rapidly localizes via its LIM domains to failing SFs in cells, known as strain sites, to initiate SF repair and maintain mechanical homeostasis. The mechanism by which these LIM domains associate with stress fiber strain sites (SFSS) is not known. Additionally, it is unknown how widespread strain sensing is within the LIM protein family. We identify that the LIM domain-containing region of 18 proteins from the Zyxin, Paxillin, Tes, and Enigma proteins accumulate to SFSS. Moreover, the LIM domain region from the fission yeast protein paxillin like 1 (Pxl1) also localizes to SFSS in mammalian cells, suggesting that the strain sensing mechanism is ancient and highly conserved. We then used sequence and domain analysis to demonstrate that tandem LIM domains contribute additively, for SFSS localization. Employing in vitro reconstitution, we show that the LIM domain-containing region from mammalian zyxin and fission yeast Pxl1 binds to mechanically stressed F-actin networks but does not associate with relaxed actin filaments. We propose that tandem LIM domains recognize an F-actin conformation that is rare in the relaxed state but is enriched in the presence of mechanical stress.

Interactions between Sla1p, Lsb5p and Arf3p in yeast endocytosis

2005 ◽  
Vol 33 (6) ◽  
pp. 1273-1275 ◽  
Author(s):  
R. Costa ◽  
K.R. Ayscough
Keyword(s):  
Actin Cytoskeleton ◽  
Mammalian Cells ◽  
Cell Signalling ◽  
Actin Dynamics ◽  
Cell Cortex ◽  
Pheromone Receptor ◽  
Cargo Proteins ◽  
Endocytic Machinery ◽  
Adp Ribosylation Factor ◽  
Uptake Of Nutrients

Endocytosis is critical for controlling the protein–lipid composition of the plasma membrane, uptake of nutrients as well as pathogens, and also plays an important role in regulation of cell signalling. While a number of pathways for endocytosis have been characterized in different organisms, all of these require remodelling of the cell cortex. The importance of a dynamic actin cytoskeleton for facilitating endocytosis has been recognized for many years in budding yeast, and is increasingly supported by studies in mammalian cells. Our studies have focused on proteins that we have shown to act at the interface between the actin cytoskeleton and the endocytic machinery. In particular, we have studied interactions of Sla1p, which binds to both activators of actin dynamics, i.e. Abp1p, Las17p and Pan1p, and to cargo proteins such as the pheromone receptor Ste2p. More recently we have mapped the interaction of Sla1p with Lsb5p, a protein that has a similar structure to the GGA [Golgi-localizing, γ-adaptin ear homology domain, Arf (ADP-ribosylation factor)-binding] family of proteins with an N-terminal VHS (Vps27p/Hrs/STAM)-domain and a GAT (GGAs and TOM1) domain. We show that Lsb5p can interact with yeast Arf3p (orthologous with mammalian Arf6) and we demonstrate a requirement for Arf3p expression in order to localize Lsb5p to the cell cortex.

scholarly journals Toxoplasma Invasion of Mammalian Cells Is Powered by the Actin Cytoskeleton of the Parasite

Cell ◽  
1996 ◽  
Vol 84 (6) ◽  
pp. 933-939 ◽  
Author(s):  
Janice M Dobrowolski ◽  
L.David Sibley
Keyword(s):  
Actin Cytoskeleton ◽  
Mammalian Cells

scholarly journals Newly synthesized G protein of vesicular stomatitis virus is not transported to the Golgi complex in mitotic cells.

1985 ◽  
Vol 101 (6) ◽  
pp. 2036-2046 ◽  
Author(s):  
C Featherstone ◽  
G Griffiths ◽  
G Warren
Keyword(s):  
G Protein ◽  
Vesicular Stomatitis Virus ◽  
Mammalian Cells ◽  
Intracellular Transport ◽  
Independent Method ◽  
Transport Pathway ◽  
Post Translational Modifications ◽  
Vesicular Stomatitis ◽  
G1 Cells ◽  
Mitotic Cells

Newly synthesized G protein of vesicular stomatitis virus is not transported to the surface of cultured mammalian cells during mitosis (Warren et al., 1983, J. Cell Biol. 97:1623-1628). To determine where intracellular transport is inhibited, we have examined the post-translational modifications of G protein, which are indicators of specific compartments on the transport pathway. G protein in mitotic cells had only endo H-sensitive oligosaccharides containing seven or eight mannose residues, but no terminal glucose, and was not fatty acylated. These modifications were indicative of processing only by enzymes of the endoplasmic reticulum (ER). Quantitative immunocytochemistry was used as an independent method to confirm that transport of G protein out of the ER was inhibited. The density of G protein in the ER cisternae was 2.5 times greater than in infected G1 cells treated similarly. Incubation of infected mitotic cells with cycloheximide, which inhibits protein synthesis without affecting transport, did not result in a decrease in the density of G protein in the ER cisternae, demonstrating that G protein cannot be chased out of the ER. These results suggest that intracellular transport stops at or before the first vesicle-mediated step on the pathway.

scholarly journals Macropinocytosis Is the Entry Mechanism of Amphotropic Murine Leukemia Virus

2014 ◽  
Vol 89 (3) ◽  
pp. 1851-1866 ◽  
Author(s):  
Izabela Rasmussen ◽  
Frederik Vilhardt
Keyword(s):  
Cell Surface ◽  
Actin Cytoskeleton ◽  
Murine Leukemia Virus ◽  
Mammalian Cells ◽  
Leukemia Virus ◽  
Amphotropic Murine Leukemia Virus ◽  
Conditional Expression ◽  
Nih 3T3 ◽  
Entry Mechanism ◽  
Murine Leukemia

ABSTRACTThe entry mechanism of murine amphotropic retrovirus (A-MLV) has not been unambiguously determined. We show here that A-MLV is internalized not by caveolae or other pinocytic mechanisms but by macropinocytosis. Thus, A-MLV infection of mouse embryonic fibroblasts deficient for caveolin or dynamin, and NIH 3T3 cells knocked down for caveolin expression, was unaffected. Conversely, A-MLV infection of NIH 3T3 and HeLa cells was sensitive to amiloride analogues and actin-depolymerizing drugs that interfere with macropinocytosis. Further manipulation of the actin cytoskeleton through conditional expression of dominant positive or negative mutants of Rac1, PAK1, and RhoG, to increase or decrease macropinocytosis, similarly correlated with an augmented or inhibited infection with A-MLV, respectively. The same experimental perturbations affected the infection of viruses that use clathrin-coated-pit endocytosis or other pathways for entry only mildly or not at all. These data agree with immunofluorescence studies and cryo-immunogold labeling for electron microscopy, which demonstrate the presence of A-MLV in protrusion-rich areas of the cell surface and in cortical fluid phase (dextran)-filled macropinosomes, which also account for up to a half of the cellular uptake of the cell surface-binding lectin concanavalin A. We conclude that A-MLV use macropinocytosis as the predominant entry portal into cells.IMPORTANCEBinding and entry of virus particles into mammalian cells are the first steps of infection. Understanding how pathogens and toxins exploit or divert endocytosis pathways has advanced our understanding of membrane trafficking pathways, which benefits development of new therapeutic schemes and methods of drug delivery. We show here that amphotropic murine leukemia virus (A-MLV) pseudotyped with the amphotropic envelope protein (which expands the host range to many mammalian cells) gains entry into host cells by macropinocytosis. Macropinosomes form as large, fluid-filled vacuoles (up to 10 μm) following the collapse of cell surface protrusions and membrane scission. We used drugs or the introduction of mutant proteins that affect the actin cytoskeleton and cell surface dynamics to show that macropinocytosis and A-MLV infection are correlated, and we provide both light- and electron-microscopic evidence to show the localization of A-MLV in macropinosomes. Finally, we specifically exclude some other potential entry portals, including caveolae, previously suggested to internalize A-MLV.

scholarly journals Cell Wall Stress Depolarizes Cell Growth via Hyperactivation of Rho1

1999 ◽  
Vol 147 (1) ◽  
pp. 163-174 ◽  
Author(s):  
Pierre-Alain Delley ◽  
Michael N. Hall
Keyword(s):  
Cell Wall ◽  
Cell Growth ◽  
Actin Cytoskeleton ◽  
Mammalian Cells ◽  
Wall Stress ◽  
Mitogen Activated Protein Kinase ◽  
Regulatory Subunit ◽  
Cell Wall Stress ◽  
Mitogen Activated Protein ◽  
Kinase Cascade

Cells sense and physiologically respond to environmental stress via signaling pathways. Saccharomyces cerevisiae cells respond to cell wall stress by transiently depolarizing the actin cytoskeleton. We report that cell wall stress also induces a transient depolarized distribution of the cell wall biosynthetic enzyme glucan synthase FKS1 and its regulatory subunit RHO1, possibly as a mechanism to repair general cell wall damage. The redistribution of FKS1 is dependent on the actin cytoskeleton. Depolarization of the actin cytoskeleton and FKS1 is mediated by the plasma membrane protein WSC1, the RHO1 GTPase switch, PKC1, and a yet-to-be defined PKC1 effector branch. WSC1 behaves like a signal transducer or a stress-specific actin landmark that both controls and responds to the actin cytoskeleton, similar to the bidirectional signaling between integrin receptors and the actin cytoskeleton in mammalian cells. The PKC1-activated mitogen-activated protein kinase cascade is not required for depolarization, but rather for repolarization of the actin cytoskeleton and FKS1. Thus, activated RHO1 can mediate both polarized and depolarized cell growth via the same effector, PKC1, suggesting that RHO1 may function as a rheostat rather than as a simple on-off switch.

scholarly journals Rho GTPases: molecular switches that control the organization and dynamics of the actin cytoskeleton

2000 ◽  
Vol 355 (1399) ◽  
pp. 965-970 ◽  
Author(s):  
Alan Hall ◽  
Catherine D. Nobes
Keyword(s):  
Actin Cytoskeleton ◽  
Rho Gtpases ◽  
Mammalian Cells ◽  
Fundamental Property ◽  
Small Gtpases ◽  
Membrane Receptors ◽  
Embryonic Cells ◽  
Filamentous Actin ◽  
Rho Family ◽  
Plasma Membrane Receptors

The actin cytoskeleton plays a fundamental role in all eukaryotic cells—it is a major determinant of cell morphology and polarity and the assembly and disassembly of filamentous actin structures provides a driving force for dynamic processes such as cell motility, phagocytosis, growth cone guidance and cytokinesis. The ability to reorganize actin filaments is a fundamental property of embryonic cells during development; the shape changes accompanying gastrulation and dorsal closure, for example, are dependent on the plasticity of the actin cytoskeleton, while the ability of cells or cell extensions, such as axons, to migrate within the developing embryo requires rapid and spatially organized changes to the actin cytoskeleton in response to the external environment. W ork in mammalian cells over the last decade has demonstrated the central role played by the highly conserved Rho family of small GTPases in signal transduction pathways that link plasma membrane receptors to the organization of the actin cytoskeleton.

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