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Alzahofi N, Welz T, Robinson CL, Page EL, Briggs DA, Stainthorp AK, Reekes J, Elbe DA, Straub F, Kallemeijn WW, Tate EW, Goff PS, Sviderskaya EV, Cantero M, Montoliu L, Nedelec F, Miles AK, Bailly M, Kerkhoff E, Hume AN. Rab27a co-ordinates actin-dependent transport by controlling organelle-associated motors and track assembly proteins. Nat Commun 2020; 11:3495. [PMID: 32661310 PMCID: PMC7359353 DOI: 10.1038/s41467-020-17212-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Accepted: 06/04/2020] [Indexed: 11/09/2022] Open
Abstract
Cell biologists generally consider that microtubules and actin play complementary roles in long- and short-distance transport in animal cells. On the contrary, using melanosomes of melanocytes as a model, we recently discovered that the motor protein myosin-Va works with dynamic actin tracks to drive long-range organelle dispersion in opposition to microtubules. This suggests that in animals, as in yeast and plants, myosin/actin can drive long-range transport. Here, we show that the SPIRE-type actin nucleators (predominantly SPIRE1) are Rab27a effectors that co-operate with formin-1 to generate actin tracks required for myosin-Va-dependent transport in melanocytes. Thus, in addition to melanophilin/myosin-Va, Rab27a can recruit SPIREs to melanosomes, thereby integrating motor and track assembly activity at the organelle membrane. Based on this, we suggest a model in which organelles and force generators (motors and track assemblers) are linked, forming an organelle-based, cell-wide network that allows their collective activity to rapidly disperse the population of organelles long-distance throughout the cytoplasm.
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Affiliation(s)
- Noura Alzahofi
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Tobias Welz
- University Hospital Regensburg, Regensburg, Germany
| | | | - Emma L Page
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Deborah A Briggs
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Amy K Stainthorp
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2UH, UK
| | - James Reekes
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2UH, UK
| | - David A Elbe
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Felix Straub
- University Hospital Regensburg, Regensburg, Germany
| | - Wouter W Kallemeijn
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, London, W12 0BZ, UK
| | - Edward W Tate
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, London, W12 0BZ, UK
| | - Philip S Goff
- Cell Biology and Genetics Research Centre, St. George's, University of London, London, SW17 0RE, UK
| | - Elena V Sviderskaya
- Cell Biology and Genetics Research Centre, St. George's, University of London, London, SW17 0RE, UK
| | - Marta Cantero
- Centro Nacional de Biotecnologia (CNB-CSIC), Madrid, 28049, Spain
- CIBERER-ISCIII, Madrid, Spain
| | - Lluis Montoliu
- Centro Nacional de Biotecnologia (CNB-CSIC), Madrid, 28049, Spain
- CIBERER-ISCIII, Madrid, Spain
| | - Francois Nedelec
- Sainsbury Laboratory, Cambridge University, Cambridge, CB2 1LR, UK
| | - Amanda K Miles
- John van Geest Cancer Research Centre, Nottingham Trent University, Nottingham, NG11 8NS, UK
| | - Maryse Bailly
- UCL Institute of Ophthalmology, 11-43 Bath St, London, EC1V 9EL, UK
| | | | - Alistair N Hume
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2UH, UK.
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2
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Akisaka T, Yoshida A. Scattered podosomes and podosomes associated with the sealing zone architecture in cultured osteoclasts revealed by cell shearing, quick freezing, and platinum-replica electron microscopy. Cytoskeleton (Hoboken) 2019; 76:303-321. [PMID: 31162808 DOI: 10.1002/cm.21543] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 05/24/2019] [Accepted: 05/30/2019] [Indexed: 01/06/2023]
Abstract
Osteoclasts (OCs) can adhere to a variety of substrate surfaces by highly dynamic actin-based cytoskeletal structures termed podosomes. This tight attachment is established by a sealing zone (SZ), which is made of interconnected individual podosomes. Compared with scattered podosomes in various cell types, the architecture of the SZ is still unclear. Especially, ultrastructural studies on the details of the cytoskeletal structure of an OC have been challenging, because the high density of filaments in their podosomes obscure visualization of individual filaments. Therefore, to study this organization in more exact detail, we employed shearing open combined with replica electron microscopy. The present study provides several new details of the podosome and SZ structure, which were previously unrecognized: (a) the SZ consists of recognizable podosomes with a dense actin network of interpodosomal regions characterized by multiple layers of crossing, branching and anastomosing actin filament networks; (b) the Arp2/3 complex is distributed throughout the actin network of podosomes and SZ, indicating that actin polymerization is concentrated at these regions; (c) a close spatial relationship between the podosome and the dorsal membrane; and (d) a network of membranous organelles in close proximity to the podosomes in the SZ. Taken together, the present study reveals that a more complicated interpodosomal actin network among neighboring individual podosomes, which is more complicated than previously thought, appears to form the SZ. Indeed, individual podosomes are not an isolated structural unit from other organelles; and, in turn, their dynamism might affect the surrounding interpodosomal cytoskeletons, membranous organelles, and plasma membrane.
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Affiliation(s)
- Toshitaka Akisaka
- Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
| | - Atsushi Yoshida
- Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
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3
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Jimenez-Lopez JC, Wang X, Kotchoni SO, Huang S, Szymanski DB, Staiger CJ. Heterodimeric capping protein from Arabidopsis is a membrane-associated, actin-binding protein. PLANT PHYSIOLOGY 2014; 166:1312-28. [PMID: 25201878 PMCID: PMC4226361 DOI: 10.1104/pp.114.242487] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 09/05/2014] [Indexed: 05/03/2023]
Abstract
The actin cytoskeleton is a major regulator of cell morphogenesis and responses to biotic and abiotic stimuli. The organization and activities of the cytoskeleton are choreographed by hundreds of accessory proteins. Many actin-binding proteins are thought to be stimulus-response regulators that bind to signaling phospholipids and change their activity upon lipid binding. Whether these proteins associate with and/or are regulated by signaling lipids in plant cells remains poorly understood. Heterodimeric capping protein (CP) is a conserved and ubiquitous regulator of actin dynamics. It binds to the barbed end of filaments with high affinity and modulates filament assembly and disassembly reactions in vitro. Direct interaction of CP with phospholipids, including phosphatidic acid, results in uncapping of filament ends in vitro. Live-cell imaging and reverse-genetic analyses of cp mutants in Arabidopsis (Arabidopsis thaliana) recently provided compelling support for a model in which CP activity is negatively regulated by phosphatidic acid in vivo. Here, we used complementary biochemical, subcellular fractionation, and immunofluorescence microscopy approaches to elucidate CP-membrane association. We found that CP is moderately abundant in Arabidopsis tissues and present in a microsomal membrane fraction. Sucrose density gradient separation and immunoblotting with known compartment markers were used to demonstrate that CP is enriched on membrane-bound organelles such as the endoplasmic reticulum and Golgi. This association could facilitate cross talk between the actin cytoskeleton and a wide spectrum of essential cellular functions such as organelle motility and signal transduction.
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Affiliation(s)
- Jose C Jimenez-Lopez
- Departments of Biological Sciences (J.C.J.-L., X.W., S.H., C.J.S.) and Agronomy (S.O.K., D.B.S.), Bindley Bioscience Center (C.J.S.), Purdue University, West Lafayette, Indiana 47907
| | - Xia Wang
- Departments of Biological Sciences (J.C.J.-L., X.W., S.H., C.J.S.) and Agronomy (S.O.K., D.B.S.), Bindley Bioscience Center (C.J.S.), Purdue University, West Lafayette, Indiana 47907
| | - Simeon O Kotchoni
- Departments of Biological Sciences (J.C.J.-L., X.W., S.H., C.J.S.) and Agronomy (S.O.K., D.B.S.), Bindley Bioscience Center (C.J.S.), Purdue University, West Lafayette, Indiana 47907
| | - Shanjin Huang
- Departments of Biological Sciences (J.C.J.-L., X.W., S.H., C.J.S.) and Agronomy (S.O.K., D.B.S.), Bindley Bioscience Center (C.J.S.), Purdue University, West Lafayette, Indiana 47907
| | - Daniel B Szymanski
- Departments of Biological Sciences (J.C.J.-L., X.W., S.H., C.J.S.) and Agronomy (S.O.K., D.B.S.), Bindley Bioscience Center (C.J.S.), Purdue University, West Lafayette, Indiana 47907
| | - Christopher J Staiger
- Departments of Biological Sciences (J.C.J.-L., X.W., S.H., C.J.S.) and Agronomy (S.O.K., D.B.S.), Bindley Bioscience Center (C.J.S.), Purdue University, West Lafayette, Indiana 47907
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4
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Ilatovskaya DV, Chubinskiy-Nadezhdin V, Pavlov TS, Shuyskiy LS, Tomilin V, Palygin O, Staruschenko A, Negulyaev YA. Arp2/3 complex inhibitors adversely affect actin cytoskeleton remodeling in the cultured murine kidney collecting duct M-1 cells. Cell Tissue Res 2013; 354:783-92. [PMID: 24036843 DOI: 10.1007/s00441-013-1710-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Accepted: 07/19/2013] [Indexed: 12/22/2022]
Abstract
Dynamic remodeling of the actin cytoskeleton plays an essential role in cell migration and various signaling processes in living cells. One of the critical factors that controls the nucleation of new actin filaments in eukaryotic cells is the actin-related protein 2/3 (Arp2/3) complex. Recently, two novel classes of small molecules that bind to different sites on the Arp2/3 complex and inhibit its ability to nucleate F-actin have been discovered and described. The current study aims at investigating the effects of CK-0944666 (CK-666) and its analogs (CK-869 and inactive CK-689) on the reorganization of the actin microfilaments in the cortical collecting duct cell line, M-1. We show that treatment with CK-666 and CK869 results in the reorganization of F-actin and drastically affects cell motility rate. The concentrations of the compounds used in this study (100-200 μM) neither cause loss of cell viability nor influence cell shape or monolayer integrity; hence, the effects of described compounds were not due to structural side effects. Therefore, we conclude that the Arp2/3 complex plays an important role in cell motility and F-actin reorganization in M-1 cells. Furthermore, CK-666 and its analogs are useful tools for the investigation of the Arp2/3 complex.
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Affiliation(s)
- Daria V Ilatovskaya
- Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064, Russia,
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5
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Bravo-Cordero JJ, Magalhaes MAO, Eddy RJ, Hodgson L, Condeelis J. Functions of cofilin in cell locomotion and invasion. Nat Rev Mol Cell Biol 2013; 14:405-15. [PMID: 23778968 DOI: 10.1038/nrm3609] [Citation(s) in RCA: 366] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Recently, a consensus has emerged that cofilin severing activity can generate free actin filament ends that are accessible for F-actin polymerization and depolymerization without changing the rate of G-actin association and dissociation at either filament end. The structural basis of actin filament severing by cofilin is now better understood. These results have been integrated with recently discovered mechanisms for cofilin activation in migrating cells, which led to new models for cofilin function that provide insights into how cofilin regulation determines the temporal and spatial control of cell behaviour.
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Affiliation(s)
- Jose Javier Bravo-Cordero
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, New York 10461, USA.
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6
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Rácz B, Weinberg RJ. Microdomains in forebrain spines: an ultrastructural perspective. Mol Neurobiol 2013; 47:77-89. [PMID: 22983912 PMCID: PMC3538892 DOI: 10.1007/s12035-012-8345-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Accepted: 08/27/2012] [Indexed: 12/21/2022]
Abstract
Glutamatergic axons in the mammalian forebrain terminate predominantly onto dendritic spines. Long-term changes in the efficacy of these excitatory synapses are tightly coupled to changes in spine morphology. The reorganization of the actin cytoskeleton underlying this spine "morphing" involves numerous proteins that provide the machinery needed for adaptive cytoskeletal remodeling. Here, we review recent literature addressing the chemical architecture of the spine, focusing mainly on actin-binding proteins (ABPs). Accumulating evidence suggests that ABPs are organized into functionally distinct microdomains within the spine cytoplasm. This functional compartmentalization provides a structural basis for regulation of the spinoskeleton, offering a novel window into mechanisms underlying synaptic plasticity.
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Affiliation(s)
- Bence Rácz
- Department of Anatomy and Histology, Faculty of Veterinary Science, Szent István University, 1078, Budapest, Hungary.
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7
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Nuclear transport of the serum response factor coactivator MRTF-A is downregulated at tensional homeostasis. EMBO Rep 2011; 12:963-70. [PMID: 21799516 PMCID: PMC3166461 DOI: 10.1038/embor.2011.141] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/13/2011] [Accepted: 06/16/2011] [Indexed: 11/09/2022] Open
Abstract
The serum response factor (SRF) coactivator myocardin-related transcription factor A (MAL/MKL1/MRTF-A), the nuclear transport and activity of which is regulated by monomeric actin, has been implicated in tension-based regulation of SRF-mediated transcriptional activity. However, the mechanisms involved remain unclear. We used fibroblasts grown within collagen matrices to explore whether MRTF-A transport is regulated by tissue tension. We show that MRTF-A nuclear accumulation following stimulation with serum, actin drugs or acute mechanical stress is prevented within mechanically loaded, anchored matrices at tensional homeostasis. This is accompanied by a higher G/F actin ratio, defective nuclear import and increased cofilin expression. We propose that tension regulates MRTF-A/SRF activity through cofilin-mediated modulation of actin dynamics.
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8
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Keren K. Cell motility: the integrating role of the plasma membrane. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2011; 40:1013-27. [PMID: 21833780 PMCID: PMC3158336 DOI: 10.1007/s00249-011-0741-0] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/23/2011] [Accepted: 07/24/2011] [Indexed: 11/30/2022]
Abstract
The plasma membrane is of central importance in the motility process. It defines the boundary separating the intracellular and extracellular environments, and mediates the interactions between a motile cell and its environment. Furthermore, the membrane serves as a dynamic platform for localization of various components which actively participate in all aspects of the motility process, including force generation, adhesion, signaling, and regulation. Membrane transport between internal membranes and the plasma membrane, and in particular polarized membrane transport, facilitates continuous reorganization of the plasma membrane and is thought to be involved in maintaining polarity and recycling of essential components in some motile cell types. Beyond its biochemical composition, the mechanical characteristics of the plasma membrane and, in particular, membrane tension are of central importance in cell motility; membrane tension affects the rates of all the processes which involve membrane deformation including edge extension, endocytosis, and exocytosis. Most importantly, the mechanical characteristics of the membrane and its biochemical composition are tightly intertwined; membrane tension and local curvature are largely determined by the biochemical composition of the membrane and the biochemical reactions taking place; at the same time, curvature and tension affect the localization of components and reaction rates. This review focuses on this dynamic interplay and the feedbacks between the biochemical and biophysical characteristics of the membrane and their effects on cell movement. New insight on these will be crucial for understanding the motility process.
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Affiliation(s)
- Kinneret Keren
- Department of Physics, The Network Biology Research Laboratories and The Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
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9
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The effect of MMP inhibitor GM6001 on early fibroblast-mediated collagen matrix contraction is correlated to a decrease in cell protrusive activity. Eur J Cell Biol 2011; 90:26-36. [DOI: 10.1016/j.ejcb.2010.09.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 09/14/2010] [Accepted: 09/20/2010] [Indexed: 12/20/2022] Open
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10
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Brooks SP, Coccia M, Tang HR, Kanuga N, Machesky LM, Bailly M, Cheetham ME, Hardcastle AJ. The Nance-Horan syndrome protein encodes a functional WAVE homology domain (WHD) and is important for co-ordinating actin remodelling and maintaining cell morphology. Hum Mol Genet 2010; 19:2421-32. [PMID: 20332100 PMCID: PMC2876887 DOI: 10.1093/hmg/ddq125] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Nance–Horan syndrome (NHS) is an X-linked developmental disorder, characterized by bilateral congenital cataracts, dental anomalies, facial dysmorphism and mental retardation. Null mutations in a novel gene, NHS, cause the syndrome. The NHS gene appears to have multiple isoforms as a result of alternative transcription, but a cellular function for the NHS protein has yet to be defined. We describe NHS as a founder member of a new protein family (NHS, NHSL1 and NHSL2). Here, we demonstrate that NHS is a novel regulator of actin remodelling and cell morphology. NHS localizes to sites of cell–cell contact, the leading edge of lamellipodia and focal adhesions. The N-terminus of isoforms NHS-A and NHS-1A, implicated in the pathogenesis of NHS, have a functional WAVE homology domain that interacts with the Abi protein family, haematopoietic stem/progenitor cell protein 300 (HSPC300), Nap1 and Sra1. NHS knockdown resulted in the disruption of the actin cytoskeleton. We show that NHS controls cell morphology by maintaining the integrity of the circumferential actin ring and controlling lamellipod formation. NHS knockdown led to a striking increase in cell spreading. Conversely, ectopic overexpression of NHS inhibited lamellipod formation. Remodelling of the actin cytoskeleton and localized actin polymerization into branched actin filaments at the plasma membrane are essential for mediating changes in cell shape, migration and cell contact. Our data identify NHS as a new regulator of actin remodelling. We suggest that NHS orchestrates actin regulatory protein function in response to signalling events during development.
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Affiliation(s)
- Simon P Brooks
- 1UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
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11
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Abstract
Motile cells - fan-like keratocytes, hand-shaped nerve growth cones, polygonal fibroblasts, to name but a few - come in different shapes and sizes. We discuss the origins of this diversity as well as what shape tells us about the physics and biochemistry underlying cell movement. We start with geometric rules describing cell-edge kinetics that govern cell shape, followed by a discussion of the underlying biophysics; we consider actin treadmilling, actin-myosin contraction, cell-membrane deformations, adhesion, and the complex interactions between these modules, as well as their regulation by microtubules and Rho GTPases. Focusing on several different cell types, including keratocytes and fibroblasts, we discuss how dynamic cell morphology emerges from the interplay between the different motility modules and the environment.
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Kotchoni SO, Zakharova T, Mallery EL, Le J, El-Assal SED, Szymanski DB. The association of the Arabidopsis actin-related protein2/3 complex with cell membranes is linked to its assembly status but not its activation. PLANT PHYSIOLOGY 2009; 151:2095-109. [PMID: 19801398 PMCID: PMC2785977 DOI: 10.1104/pp.109.143859] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Accepted: 09/28/2009] [Indexed: 05/18/2023]
Abstract
In growing plant cells, the combined activities of the cytoskeleton, endomembrane, and cell wall biosynthetic systems organize the cytoplasm and define the architecture and growth properties of the cell. These biosynthetic machineries efficiently synthesize, deliver, and recycle the raw materials that support cell expansion. The precise roles of the actin cytoskeleton in these processes are unclear. Certainly, bundles of actin filaments position organelles and are a substrate for long-distance intracellular transport, but the functional linkages between dynamic actin filament arrays and the cell growth machinery are poorly understood. The Arabidopsis (Arabidopsis thaliana) "distorted group" mutants have defined protein complexes that appear to generate and convert small GTPase signals into an Actin-Related Protein2/3 (ARP2/3)-dependent actin filament nucleation response. However, direct biochemical knowledge about Arabidopsis ARP2/3 and its cellular distribution is lacking. In this paper, we provide biochemical evidence for a plant ARP2/3. The plant complex utilizes a conserved assembly mechanism. ARPC4 is the most critical core subunit that controls the assembly and steady-state levels of the complex. ARP2/3 in other systems is believed to be mostly a soluble complex that is locally recruited and activated. Unexpectedly, we find that Arabidopsis ARP2/3 interacts strongly with cell membranes. Membrane binding is linked to complex assembly status and not to the extent to which it is activated. Mutant analyses implicate ARP2 as an important subunit for membrane association.
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Gonzalez V, Combe A, David V, Malmquist NA, Delorme V, Leroy C, Blazquez S, Ménard R, Tardieux I. Host cell entry by apicomplexa parasites requires actin polymerization in the host cell. Cell Host Microbe 2009; 5:259-72. [PMID: 19286135 DOI: 10.1016/j.chom.2009.01.011] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Revised: 12/09/2008] [Accepted: 01/27/2009] [Indexed: 12/30/2022]
Abstract
Apicomplexa are obligate intracellular parasites that actively invade host cells using their membrane-associated, actin-myosin motor. The current view is that host cell invasion by Apicomplexa requires the formation of a parasite-host cell junction, which has been termed the moving junction, but does not require the active participation of host actin. Using Toxoplasma gondii tachyzoites and Plasmodium berghei sporozoites, we show that host actin participates in parasite entry. Parasites induce the formation of a ring-shaped F-actin structure in the host cell at the parasite-cell junction, which remains stable during parasite entry. The Arp2/3 complex, an actin-nucleating factor, is recruited at the ring structure and is important for parasite entry. We propose that Apicomplexa invasion of host cells requires not only the parasite motor but also de novo polymerization of host actin at the entry site for anchoring the junction on which the parasite pulls to penetrate the host cell.
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Affiliation(s)
- Virginie Gonzalez
- Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France
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14
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Zuchero JB, Coutts AS, Quinlan ME, Thangue NBL, Mullins RD. p53-cofactor JMY is a multifunctional actin nucleation factor. Nat Cell Biol 2009; 11:451-9. [PMID: 19287377 PMCID: PMC2763628 DOI: 10.1038/ncb1852] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Accepted: 01/29/2009] [Indexed: 12/25/2022]
Abstract
Many cellular structures are assembled from networks of actin filaments, and the architecture of these networks depends on the mechanism by which the filaments are formed. Several classes of proteins are known to assemble new filaments, including the Arp2/3 complex, which creates branched filament networks, and Spire, which creates unbranched filaments. We find that JMY, a vertebrate protein first identified as a transcriptional co-activator of p53, combines these two nucleating activities by both activating Arp2/3 and assembling filaments directly using a Spire-like mechanism. Increased levels of JMY expression enhance motility, whereas loss of JMY slows cell migration. When slowly migrating HL-60 cells are differentiated into highly motile neutrophil-like cells, JMY moves from the nucleus to the cytoplasm and is concentrated at the leading edge. Thus, JMY represents a new class of multifunctional actin assembly factor whose activity is regulated, at least in part, by sequestration in the nucleus.
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15
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Nicholson-Dykstra SM, Higgs HN. Arp2 depletion inhibits sheet-like protrusions but not linear protrusions of fibroblasts and lymphocytes. ACTA ACUST UNITED AC 2008; 65:904-22. [PMID: 18720401 DOI: 10.1002/cm.20312] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The Arp2/3 complex-mediated assembly and protrusion of a branched actin network at the leading edge occurs during cell migration, although some studies suggest it is not essential. In order to test the role of Arp2/3 complex in leading edge protrusion, Swiss 3T3 fibroblasts and Jurkat T cells were depleted of Arp2 and evaluated for defects in cell morphology and spreading efficiency. Arp2-depleted fibroblasts exhibit severe defects in formation of sheet-like protrusions at early time points of cell spreading, with sheet-like protrusions limited to regions along the length of linear protrusions. However, Arp2-depleted cells are able to spread fully after extended times. Similarly, Arp2-depleted Jurkat T lymphocytes exhibit defects in spreading on anti-CD3. Interphase Jurkats in suspension are covered with large ruffle structures, whereas mitotic Jurkats are covered by finger-like linear protrusions. Arp2-depleted Jurkats exhibit defects in ruffle assembly but not in assembly of mitotic linear protrusions. Similarly, Arp2-depletion has no effect on the highly dynamic linear protrusion of another suspended lymphocyte line. We conclude that Arp2/3 complex plays a significant role in assembly of sheet-like protrusions, especially during early stages of cell spreading, but is not required for assembly of a variety of linear actin-based protrusions.
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16
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Abstract
Changes in the morphology of a dendritic spine require remodeling of its actin-based cytoskeleton. Biochemical mechanisms underlying actin remodeling have been studied extensively, but little is known about the physical organization of the actin-binding proteins that mediate remodeling in spines. Long-term potentiation-inducing stimuli trigger expansion of the spine head, suggesting local extension and branching of actin filaments. Because filament branching requires the Arp2/3 complex, we used quantitative immunoelectron microscopy to elucidate the organization of ARPC-2 (Arp2/3 complex subunit 2), an essential component of the complex. Our data from CA1 hippocampus indicate that Arp2/3 concentrates within spines in a previously unrecognized torroidal domain, apparently specialized to mediate actin filament branching.
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17
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Lladó A, Timpson P, Vilà de Muga S, Moretó J, Pol A, Grewal T, Daly RJ, Enrich C, Tebar F. Protein kinase Cdelta and calmodulin regulate epidermal growth factor receptor recycling from early endosomes through Arp2/3 complex and cortactin. Mol Biol Cell 2007; 19:17-29. [PMID: 17959830 DOI: 10.1091/mbc.e07-05-0411] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The intracellular trafficking of the epidermal growth factor receptor (EGFR) is regulated by a cross-talk between calmodulin (CaM) and protein kinase Cdelta (PKCdelta). On inhibition of CaM, PKCdelta promotes the formation of enlarged early endosomes and blocks EGFR recycling and degradation. Here, we show that PKCdelta impairs EGFR trafficking due to the formation of an F-actin coat surrounding early endosomes. The PKCdelta-induced polymerization of actin is orchestrated by the Arp2/3 complex and requires the interaction of cortactin with PKCdelta. Accordingly, inhibition of actin polymerization by using cytochalasin D or by overexpression of active cofilin, restored the normal morphology of the organelle and the recycling of EGFR. Similar results were obtained after down-regulation of cortactin and the sequestration of the Arp2/3 complex. Furthermore we demonstrate an interaction of cortactin with CaM and PKCdelta, the latter being dependent on CaM inhibition. In summary, this study provides the first evidence that CaM and PKCdelta organize actin dynamics in the early endosomal compartment, thereby regulating the intracellular trafficking of EGFR.
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Affiliation(s)
- Anna Lladó
- Departament de Biologia Cellular, Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036-Barcelona, Spain
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Cai L, Marshall TW, Uetrecht AC, Schafer DA, Bear JE. Coronin 1B coordinates Arp2/3 complex and cofilin activities at the leading edge. Cell 2007; 128:915-29. [PMID: 17350576 PMCID: PMC2630706 DOI: 10.1016/j.cell.2007.01.031] [Citation(s) in RCA: 191] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Revised: 11/13/2006] [Accepted: 01/24/2007] [Indexed: 12/24/2022]
Abstract
Actin filament formation and turnover within the treadmilling actin filament array at the leading edge of migrating cells are interdependent and coupled, but the mechanisms coordinating these two activities are not understood. We report that Coronin 1B interacts simultaneously with Arp2/3 complex and Slingshot (SSH1L) phosphatase, two regulators of actin filament formation and turnover, respectively. Coronin 1B inhibits filament nucleation by Arp2/3 complex and this inhibition is attenuated by phosphorylation of Coronin 1B at Serine 2, a site targeted by SSH1L. Coronin 1B also directs SSH1L to lamellipodia where SSH1L likely regulates Cofilin activity via dephosphorylation. Accordingly, depleting Coronin 1B increases phospho-Cofilin levels, and alters lamellipodial dynamics and actin filament architecture at the leading edge. We conclude that Coronin 1B's coordination of filament formation by Arp2/3 complex and filament turnover by Cofilin is required for effective lamellipodial protrusion and cell migration.
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Affiliation(s)
- Liang Cai
- University of North Carolina at Chapel Hill, Lineberger Comprehensive Cancer Center & Dept. of Cell and Developmental Biology
| | - Thomas W. Marshall
- University of North Carolina at Chapel Hill, Lineberger Comprehensive Cancer Center & Dept. of Cell and Developmental Biology
| | - Andrea C. Uetrecht
- University of North Carolina at Chapel Hill, Lineberger Comprehensive Cancer Center & Dept. of Cell and Developmental Biology
| | - Dorothy A. Schafer
- University of Virginia, Charlottesville, VA, Depts. of Biology and Cell Biology
| | - James E. Bear
- University of North Carolina at Chapel Hill, Lineberger Comprehensive Cancer Center & Dept. of Cell and Developmental Biology
- Corresponding Author: Phone: 919-966-5471, Fax: 919-966-3015, E-mail:
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