401
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Affiliation(s)
- Antonello Covacci
- Immunobiological Research Institute of Siena (IRIS), Chiron S.p.A., 53100 Siena, Italy
| | - Rino Rappuoli
- Immunobiological Research Institute of Siena (IRIS), Chiron S.p.A., 53100 Siena, Italy
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402
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Chan AY, Bailly M, Zebda N, Segall JE, Condeelis JS. Role of cofilin in epidermal growth factor-stimulated actin polymerization and lamellipod protrusion. J Cell Biol 2000; 148:531-42. [PMID: 10662778 PMCID: PMC2174812 DOI: 10.1083/jcb.148.3.531] [Citation(s) in RCA: 201] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/1999] [Accepted: 01/04/2000] [Indexed: 11/29/2022] Open
Abstract
Stimulation of metastatic MTLn3 cells with epidermal growth factor (EGF) causes a rapid and transient increase in actin nucleation activity resulting from the appearance of free barbed ends at the extreme leading edge of extending lamellipods. To investigate the role of cofilin in EGF-stimulated actin polymerization and lamellipod extension in MTLn3 cells, we examined in detail the temporal and spatial distribution of cofilin relative to free barbed ends and characterized the actin dynamics by measuring the changes in the number of actin filaments. EGF stimulation triggers a transient increase in cofilin in the leading edge near the membrane, which is precisely cotemporal with the appearance of free barbed ends there. A deoxyribonuclease I binding assay shows that the number of filaments per cell increases by 1.5-fold after EGF stimulation. Detection of pointed ends in situ using deoxyribonuclease I binding demonstrates that this increase in the number of pointed ends is confined to the leading edge compartment, and does not occur within stress fibers or in the general cytoplasm. Using a light microscope severing assay, cofilin's severing activity was observed directly in cell extracts and shown to be activated after stimulation of the cells with EGF. Microinjection of function-blocking antibodies against cofilin inhibits the appearance of free barbed ends at the leading edge and lamellipod protrusion after EGF stimulation. These results support a model in which EGF stimulation recruits cofilin to the leading edge where its severing activity is activated, leading to the generation of short actin filaments with free barbed ends that participate in the nucleation of actin polymerization.
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Affiliation(s)
- Amanda Y. Chan
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Maryse Bailly
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Noureddine Zebda
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Jeffrey E. Segall
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461
| | - John S. Condeelis
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461
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403
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Taunton J, Rowning BA, Coughlin ML, Wu M, Moon RT, Mitchison TJ, Larabell CA. Actin-dependent propulsion of endosomes and lysosomes by recruitment of N-WASP. J Cell Biol 2000; 148:519-30. [PMID: 10662777 PMCID: PMC2174808 DOI: 10.1083/jcb.148.3.519] [Citation(s) in RCA: 331] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/1999] [Accepted: 12/20/1999] [Indexed: 01/24/2023] Open
Abstract
We examined the spatial and temporal control of actin assembly in living Xenopus eggs. Within minutes of egg activation, dynamic actin-rich comet tails appeared on a subset of cytoplasmic vesicles that were enriched in protein kinase C (PKC), causing the vesicles to move through the cytoplasm. Actin comet tail formation in vivo was stimulated by the PKC activator phorbol myristate acetate (PMA), and this process could be reconstituted in a cell-free system. We used this system to define the characteristics that distinguish vesicles associated with actin comet tails from other vesicles in the extract. We found that the protein, N-WASP, was recruited to the surface of every vesicle associated with an actin comet tail, suggesting that vesicle movement results from actin assembly nucleated by the Arp2/3 complex, the immediate downstream target of N-WASP. The motile vesicles accumulated the dye acridine orange, a marker for endosomes and lysosomes. Furthermore, vesicles associated with actin comet tails had the morphological features of multivesicular endosomes as revealed by electron microscopy. Endosomes and lysosomes from mammalian cells preferentially nucleated actin assembly and moved in the Xenopus egg extract system. These results define endosomes and lysosomes as recruitment sites for the actin nucleation machinery and demonstrate that actin assembly contributes to organelle movement. Conversely, by nucleating actin assembly, intracellular membranes may contribute to the dynamic organization of the actin cytoskeleton.
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Affiliation(s)
- J Taunton
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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404
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Mullins RD. How WASP-family proteins and the Arp2/3 complex convert intracellular signals into cytoskeletal structures. Curr Opin Cell Biol 2000; 12:91-6. [PMID: 10679362 DOI: 10.1016/s0955-0674(99)00061-7] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
In most cells, the structure of the actin cytoskeleton is regulated by Rho-family G proteins. Recent work has outlined a highly conserved signaling pathway from G protein activation to actin assembly. The key downstream components are WASP family proteins - adaptor molecules that bind multiple signaling and cytoskeletal proteins - and the Arp2/3 complex - a multi-functional protein complex that nucleates and crosslinks actin filaments.
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Affiliation(s)
- R D Mullins
- Department of Cellular and Molecular Pharmacology, University of California Medical School, San Francisco, CA 94129, USA. dyche@itsa. ucsf.edu
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405
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Stein M, Rappuoli R, Covacci A. Tyrosine phosphorylation of the Helicobacter pylori CagA antigen after cag-driven host cell translocation. Proc Natl Acad Sci U S A 2000; 97:1263-8. [PMID: 10655519 PMCID: PMC15590 DOI: 10.1073/pnas.97.3.1263] [Citation(s) in RCA: 441] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Helicobacter pylori strains associated with severe tissue damage and inflammation possess a unique genetic locus, cag, containing 31 genes originating from a distant event of horizontal transfer and retained as a pathogenicity island. The cag system is an Helicobacter-specific type IV secretion engine involved in cellular responses like induction of pedestals, secretion of IL-8, and phosphorylation of proteic targets. It has previously been reported that cocultivation of epithelial cells with Helicobacter pylori triggers signal transduction and tyrosine phosphorylation of a 145-kDa putative host cell protein. Herein, we demonstrate that this protein is not derived from the host but rather is the bacterial immunodominant antigen CagA, a virulence factor commonly expressed in peptic ulcer disease and thought to be an orphan of a specific biological function. Thus, CagA is delivered into the epithelial cells by the cag type IV secretion system where it is phosphorylated on tyrosine residues by an as yet unidentified host cell kinase and wired to eukaryotic signal transduction pathways and cytoskeletal plasticity.
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Affiliation(s)
- M Stein
- Immunobiological Research Institute of Siena, Chiron SpA, Via Fiorentina 1, 53100 Siena, Italy
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406
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Schaerer-Brodbeck C, Riezman H. Saccharomyces cerevisiae Arc35p works through two genetically separable calmodulin functions to regulate the actin and tubulin cytoskeletons. J Cell Sci 2000; 113 ( Pt 3):521-32. [PMID: 10639338 DOI: 10.1242/jcs.113.3.521] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Analysis of the arc35-1 mutant has revealed previously that this component of the Arp2/3 complex is involved in organization of the actin cytoskeleton. Further characterization uncovered a cell division cycle phenotype with arrest as large-budded cells. Cells with correctly positioned metaphase spindles accumulated at the restrictive temperature. The observed metaphase arrest most likely occurs by activation of the spindle assembly checkpoint, because arc35-1 was synthetically lethal with a deletion of BUB2. Arc35p activity is required late in G(1) for its cell cycle function. Both the actin and microtubule defects of arc35-1 can be suppressed by overexpression of calmodulin. Analysis of a collection of ts cmd1 mutants for their ability to suppress the actin and/or microtubule defect revealed that the two defects observed in arc35-1 are genetically separable. These data suggest that the actin defect is probably not the cause of the microtubule defect.
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Affiliation(s)
- C Schaerer-Brodbeck
- Biozentrum of the University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
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407
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Abstract
The reconstitution of microbial rocketing motility in vitro with purified proteins has recently established definitively that no myosin motor is required for protrusion. Instead, actin polymerization, in conjunction with a small number of proteins, is sufficient. A dendritic pattern of nucleation controlled by the Arp2/3 complex provides an efficient pushing force for lamellipodial motility.
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Affiliation(s)
- G G Borisy
- Laboratory of Molecular Biology, University of Wisconsin, Madison, WI 53706, USA.
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408
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Lechler T, Shevchenko A, Shevchenko A, Li R. Direct involvement of yeast type I myosins in Cdc42-dependent actin polymerization. J Cell Biol 2000; 148:363-73. [PMID: 10648569 PMCID: PMC2174278 DOI: 10.1083/jcb.148.2.363] [Citation(s) in RCA: 170] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/1999] [Accepted: 12/06/1999] [Indexed: 11/22/2022] Open
Abstract
The generation of cortical actin filaments is necessary for processes such as cell motility and cell polarization. Several recent studies have demonstrated that Wiskott-Aldrich syndrome protein (WASP) family proteins and the actin-related protein (Arp) 2/3 complex are key factors in the nucleation of actin filaments in diverse eukaryotic organisms. To identify other factors involved in this process, we have isolated proteins that bind to Bee1p/Las17p, the yeast WASP-like protein, by affinity chromatography and mass spectroscopic analysis. The yeast type I myosins, Myo3p and Myo5p, have both been identified as Bee1p-interacting proteins. Like Bee1p, these myosins are essential for cortical actin assembly as assayed by in vitro reconstitution of actin nucleation sites in permeabilized yeast cells. Analysis using this assay further demonstrated that the motor activity of these myosins is required for the polymerization step, and that actin polymerization depends on phosphorylation of myosin motor domain by p21-activated kinases (PAKs), downstream effectors of the small guanosine triphosphatase, Cdc42p. The type I myosins also interact with the Arp2/3 complex through a sequence at the end of the tail domain homologous to the Arp2/3-activating region of WASP-like proteins. Combined deletions of the Arp2/3-interacting domains of Bee1p and the type I myosins abolish actin nucleation sites at the cortex, suggesting that these proteins function redundantly in the activation of the Arp2/3 complex.
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Affiliation(s)
- Terry Lechler
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115
| | - Anna Shevchenko
- Peptide and Protein Group, European Molecular Biology Laboratory (EMBL), 69012 Heidelberg, Germany
| | - Andrej Shevchenko
- Peptide and Protein Group, European Molecular Biology Laboratory (EMBL), 69012 Heidelberg, Germany
| | - Rong Li
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115
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409
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Evangelista M, Klebl BM, Tong AH, Webb BA, Leeuw T, Leberer E, Whiteway M, Thomas DY, Boone C. A role for myosin-I in actin assembly through interactions with Vrp1p, Bee1p, and the Arp2/3 complex. J Cell Biol 2000; 148:353-62. [PMID: 10648568 PMCID: PMC2174279 DOI: 10.1083/jcb.148.2.353] [Citation(s) in RCA: 190] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Type I myosins are highly conserved actin-based molecular motors that localize to the actin-rich cortex and participate in motility functions such as endocytosis, polarized morphogenesis, and cell migration. The COOH-terminal tail of yeast myosin-I proteins, Myo3p and Myo5p, contains an Src homology domain 3 (SH3) followed by an acidic domain. The myosin-I SH3 domain interacted with both Bee1p and Vrp1p, yeast homologues of human WASP and WIP, adapter proteins that link actin assembly and signaling molecules. The myosin-I acidic domain interacted with Arp2/3 complex subunits, Arc40p and Arc19p, and showed both sequence similarity and genetic redundancy with the COOH-terminal acidic domain of Bee1p (Las17p), which controls Arp2/3-mediated actin nucleation. These findings suggest that myosin-I proteins may participate in a diverse set of motility functions through a role in actin assembly.
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Affiliation(s)
- Marie Evangelista
- Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada
| | - Bert M. Klebl
- Genetics Division, Institut de Recherche en Biotechnologie, 6100, Avenue Royalmount, Montreal, Quebec, H4P 2R2, Canada
| | - Amy H.Y. Tong
- Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada
| | - Bradley A. Webb
- Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada
| | - Thomas Leeuw
- Genetics Division, Institut de Recherche en Biotechnologie, 6100, Avenue Royalmount, Montreal, Quebec, H4P 2R2, Canada
| | - Ekkehard Leberer
- Genetics Division, Institut de Recherche en Biotechnologie, 6100, Avenue Royalmount, Montreal, Quebec, H4P 2R2, Canada
| | - Malcolm Whiteway
- Genetics Division, Institut de Recherche en Biotechnologie, 6100, Avenue Royalmount, Montreal, Quebec, H4P 2R2, Canada
| | - David Y. Thomas
- Genetics Division, Institut de Recherche en Biotechnologie, 6100, Avenue Royalmount, Montreal, Quebec, H4P 2R2, Canada
| | - Charles Boone
- Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada
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410
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Loisel TP, Boujemaa R, Pantaloni D, Carlier MF. Reconstitution of actin-based motility of Listeria and Shigella using pure proteins. Nature 1999; 401:613-6. [PMID: 10524632 DOI: 10.1038/44183] [Citation(s) in RCA: 748] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Actin polymerization is essential for cell locomotion and is thought to generate the force responsible for cellular protrusions. The Arp2/3 complex is required to stimulate actin assembly at the leading edge in response to signalling. The bacteria Listeria and Shigella bypass the signalling pathway and harness the Arp2/3 complex to induce actin assembly and to propel themselves in living cells. However, the Arp2/3 complex alone is insufficient to promote movement. Here we have used pure components of the actin cytoskeleton to reconstitute sustained movement in Listeria and Shigella in vitro. Actin-based propulsion is driven by the free energy released by ATP hydrolysis linked to actin polymerization, and does not require myosin. In addition to actin and activated Arp2/3 complex, actin depolymerizing factor (ADF, or cofilin) and capping protein are also required for motility as they maintain a high steady-state level of G-actin, which controls the rate of unidirectional growth of actin filaments at the surface of the bacterium. The movement is more effective when profilin, alpha-actinin and VASP (for Listeria) are also included. These results have implications for our understanding of the mechanism of actin-based motility in cells.
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Affiliation(s)
- T P Loisel
- Dynamique du Cytosquelette, LEBS, CNRS, Gif-sur-Yvette, France
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411
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