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Benz PM, Frömel T, Laban H, Zink J, Ulrich L, Groneberg D, Boon RA, Poley P, Renne T, de Wit C, Fleming I. Cardiovascular Functions of Ena/VASP Proteins: Past, Present and Beyond. Cells 2023; 12:1740. [PMID: 37443774 PMCID: PMC10340426 DOI: 10.3390/cells12131740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 06/18/2023] [Accepted: 06/21/2023] [Indexed: 07/15/2023] Open
Abstract
Actin binding proteins are of crucial importance for the spatiotemporal regulation of actin cytoskeletal dynamics, thereby mediating a tremendous range of cellular processes. Since their initial discovery more than 30 years ago, the enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) family has evolved as one of the most fascinating and versatile family of actin regulating proteins. The proteins directly enhance actin filament assembly, but they also organize higher order actin networks and link kinase signaling pathways to actin filament assembly. Thereby, Ena/VASP proteins regulate dynamic cellular processes ranging from membrane protrusions and trafficking, and cell-cell and cell-matrix adhesions, to the generation of mechanical tension and contractile force. Important insights have been gained into the physiological functions of Ena/VASP proteins in platelets, leukocytes, endothelial cells, smooth muscle cells and cardiomyocytes. In this review, we summarize the unique and redundant functions of Ena/VASP proteins in cardiovascular cells and discuss the underlying molecular mechanisms.
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Affiliation(s)
- Peter M. Benz
- Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
- German Centre of Cardiovascular Research (DZHK), Partner Site Rhein-Main, 60596 Frankfurt am Main, Germany
| | - Timo Frömel
- Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
| | - Hebatullah Laban
- Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
| | - Joana Zink
- Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
| | - Lea Ulrich
- Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
| | - Dieter Groneberg
- Institute of Physiology I, University of Würzburg, 97070 Würzburg, Germany
| | - Reinier A. Boon
- German Centre of Cardiovascular Research (DZHK), Partner Site Rhein-Main, 60596 Frankfurt am Main, Germany
- Cardiopulmonary Institute, 60596 Frankfurt am Main, Germany
- Centre of Molecular Medicine, Institute of Cardiovascular Regeneration, Goethe-University, 60596 Frankfurt am Main, Germany
- Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Centre, 1081 HZ Amsterdam, The Netherlands
| | - Philip Poley
- Institut für Physiologie, Universität zu Lübeck, 23562 Lübeck, Germany
- German Centre of Cardiovascular Research (DZHK), Partner Site Hamburg/Kiel/Lübeck, 23562 Lübeck, Germany
| | - Thomas Renne
- Institute of Clinical Chemistry and Laboratory Medicine, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
- Center for Thrombosis and Hemostasis (CTH), Johannes Gutenberg University Medical Center, 55131 Mainz, Germany
- Irish Centre for Vascular Biology, School of Pharmacy and Biomolecular Sciences, Royal College of Surgeons in Ireland, D02 VN51 Dublin, Ireland
| | - Cor de Wit
- Institut für Physiologie, Universität zu Lübeck, 23562 Lübeck, Germany
- German Centre of Cardiovascular Research (DZHK), Partner Site Hamburg/Kiel/Lübeck, 23562 Lübeck, Germany
| | - Ingrid Fleming
- Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
- German Centre of Cardiovascular Research (DZHK), Partner Site Rhein-Main, 60596 Frankfurt am Main, Germany
- Cardiopulmonary Institute, 60596 Frankfurt am Main, Germany
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Wang F, Zhu C, Cai S, Boudreau A, Kim SJ, Bissell M, Shao J. Ser 71 Phosphorylation Inhibits Actin-Binding of Profilin-1 and Its Apoptosis-Sensitizing Activity. Front Cell Dev Biol 2021; 9:692269. [PMID: 34235154 PMCID: PMC8255618 DOI: 10.3389/fcell.2021.692269] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 05/28/2021] [Indexed: 01/25/2023] Open
Abstract
The essential actin-binding factor profilin-1 (Pfn1) is a non-classical tumor suppressor with the abilities toboth inhibit cellular proliferation and augment chemotherapy-induced apoptosis. Besides actin, Pfn1 interacts with proteins harboring the poly-L-proline (PLP) motifs. Our recent work demonstrated that both nuclear localization and PLP-binding are required for tumor growth inhibition by Pfn1, and this is at least partially due to Pfn1 association with the PLP-containing ENL protein in the Super Elongation Complex (SEC) and the transcriptional inhibition of pro-cancer genes. In this paper, by identifying a phosphorylation event of Pfn1 at Ser71 capable of inhibiting its actin-binding and nuclear export, we provide in vitro and in vivo evidence that chemotherapy-induced apoptotic sensitization by Pfn1 requires its cytoplasmic localization and actin-binding. With regard to tumor growth inhibition byPfn1, our data indicate a requirement for dynamic actin association and dissociation rendered by reversible Ser71phosphorylation and dephosphorylation. Furthermore, genetic and pharmacological experiments showed that Ser71 of Pfn1 can be phosphorylated by protein kinase A (PKA). Taken together, our data provide novel mechanistic insights into the multifaceted anticancer activities of Pfn1 and how they are spatially-defined in the cell and differentially regulated by ligand-binding.
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Affiliation(s)
- Faliang Wang
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
- Department of Surgical Oncology, The Children’s Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Cuige Zhu
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Shirong Cai
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, United States
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Aaron Boudreau
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
| | - Sun-Joong Kim
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Mina Bissell
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
| | - Jieya Shao
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
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Skruber K, Read TA, Vitriol EA. Reconsidering an active role for G-actin in cytoskeletal regulation. J Cell Sci 2018; 131:131/1/jcs203760. [PMID: 29321224 DOI: 10.1242/jcs.203760] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Globular (G)-actin, the actin monomer, assembles into polarized filaments that form networks that can provide structural support, generate force and organize the cell. Many of these structures are highly dynamic and to maintain them, the cell relies on a large reserve of monomers. Classically, the G-actin pool has been thought of as homogenous. However, recent work has shown that actin monomers can exist in distinct groups that can be targeted to specific networks, where they drive and modify filament assembly in ways that can have profound effects on cellular behavior. This Review focuses on the potential factors that could create functionally distinct pools of actin monomers in the cell, including differences between the actin isoforms and the regulation of G-actin by monomer binding proteins, such as profilin and thymosin β4. Owing to difficulties in studying and visualizing G-actin, our knowledge over the precise role that specific actin monomer pools play in regulating cellular actin dynamics remains incomplete. Here, we discuss some of these unanswered questions and also provide a summary of the methodologies currently available for the imaging of G-actin.
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Affiliation(s)
- Kristen Skruber
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL 32610, USA
| | - Tracy-Ann Read
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL 32610, USA
| | - Eric A Vitriol
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL 32610, USA
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4
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Yu-Kemp HC, Kemp JP, Brieher WM. CRMP-1 enhances EVL-mediated actin elongation to build lamellipodia and the actin cortex. J Cell Biol 2017. [PMID: 28630144 PMCID: PMC5551698 DOI: 10.1083/jcb.201606084] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
CRMP proteins regulate the cytoskeleton, but the underlying mechanisms are poorly understood. Yu-Kemp et al. show that CRMP-1 helps Ena/VASP proteins elongate actin filaments to assemble actin networks that are necessary for the integrity of epithelial sheets. Cells can control actin polymerization by nucleating new filaments or elongating existing ones. We recently identified CRMP-1 as a factor that stimulates the formation of Listeria monocytogenes actin comet tails, thereby implicating it in actin assembly. We now show that CRMP-1 is a major contributor to actin assembly in epithelial cells, where it works with the Ena/VASP family member EVL to assemble the actin cytoskeleton in the apical cortex and in protruding lamellipodia. CRMP-1 and EVL bind to one another and together accelerate actin filament barbed-end elongation. CRMP-1 also stimulates actin assembly in the presence of VASP and Mena in vitro, but CRMP-1–dependent actin assembly in MDCK cells is EVL specific. Our results identify CRMP-1 as a novel regulator of actin filament elongation and reveal a surprisingly important role for CRMP-1, EVL, and actin polymerization in maintaining the structural integrity of epithelial sheets.
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Affiliation(s)
- Hui-Chia Yu-Kemp
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
| | - James P Kemp
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
| | - William M Brieher
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
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Nejedla M, Li Z, Masser AE, Biancospino M, Spiess M, Mackowiak SD, Friedländer MR, Karlsson R. A Fluorophore Fusion Construct of Human Profilin I with Non-Compromised Poly(L-Proline) Binding Capacity Suitable for Imaging. J Mol Biol 2017; 429:964-976. [DOI: 10.1016/j.jmb.2017.01.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 12/06/2016] [Accepted: 01/03/2017] [Indexed: 10/24/2022]
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Rennella E, Sekhar A, Kay LE. Self-Assembly of Human Profilin-1 Detected by Carr-Purcell-Meiboom-Gill Nuclear Magnetic Resonance (CPMG NMR) Spectroscopy. Biochemistry 2017; 56:692-703. [PMID: 28052669 DOI: 10.1021/acs.biochem.6b01263] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein oligomerization in the cell has important implications for both health and disease, and an understanding of the mechanisms by which proteins can self-associate is, therefore, of critical interest. Initial stages of the oligomerization process can be hard to detect, as they often involve the formation of sparsely populated and transient states that are difficult to characterize by standard biophysical approaches. Using relaxation dispersion nuclear magnetic resonance spectroscopy, we study the oligomerization of human profilin-1, a protein that regulates the polymerization of actin. We show that in solution and at millimolar concentrations profilin-1 is predominantly monomeric. However, fits of concentration-dependent relaxation data are consistent with the formation of a higher-order oligomer that is generated via a multistep process. Together with crystallographic data for profilin-2, a homologue of the protein studied here, our results suggest that profilin-1 forms a sparsely populated tetrameric conformer in solution.
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Affiliation(s)
- Enrico Rennella
- Departments of Molecular Genetics, Biochemistry and Chemistry, The University of Toronto , Toronto, Ontario M5S 1A8, Canada
| | - Ashok Sekhar
- Departments of Molecular Genetics, Biochemistry and Chemistry, The University of Toronto , Toronto, Ontario M5S 1A8, Canada
| | - Lewis E Kay
- Departments of Molecular Genetics, Biochemistry and Chemistry, The University of Toronto , Toronto, Ontario M5S 1A8, Canada.,Program in Molecular Structure and Function, Hospital for Sick Children , 555 University Avenue, Toronto, Ontario M5G 1X8, Canada
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7
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Arp2/3 and VASP Are Essential for Fear Memory Formation in Lateral Amygdala. eNeuro 2016; 3:eN-NWR-0302-16. [PMID: 27957528 PMCID: PMC5126706 DOI: 10.1523/eneuro.0302-16.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 10/28/2016] [Accepted: 10/30/2016] [Indexed: 11/21/2022] Open
Abstract
The actin cytoskeleton is involved in key neuronal functions such as synaptic transmission and morphogenesis. However, the roles and regulation of actin cytoskeleton in memory formation remain to be clarified. In this study, we unveil the mechanism whereby actin cytoskeleton is regulated to form memory by exploring the roles of the major actin-regulatory proteins Arp2/3, VASP, and formins in long-term memory formation. Inhibition of Arp2/3, involved in actin filament branching and neuronal morphogenesis, in lateral amygdala (LA) with the specific inhibitor CK-666 during fear conditioning impaired long-term, but not short-term, fear memory. The inactive isomer CK-689 had no effect on memory formation. We observed that Arp2/3 is colocalized with the actin-regulatory protein profilin in LA neurons of fear-conditioned rats. VASP binding to profilin is needed for profilin-mediated stabilization of actin cytoskeleton and dendritic spine morphology. Microinjection of poly-proline peptide [G(GP5)3] into LA, to interfere with VASP binding to profilin, impaired long-term but not short-term fear memory formation. Control peptide [G(GA5)3] had no effect. Inhibiting formins, which regulate linear actin elongation, in LA during fear conditioning by microinjecting the formin-specific inhibitor SMIFH2 into LA had no effect on long-term fear memory formation. We conclude that Arp2/3 and VASP, through the profilin binding site, are essential for the formation of long-term fear memory in LA and propose a model whereby these proteins subserve cellular events, leading to memory consolidation.
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Pillich H, Puri M, Chakraborty T. ActA of Listeria monocytogenes and Its Manifold Activities as an Important Listerial Virulence Factor. Curr Top Microbiol Immunol 2016; 399:113-132. [PMID: 27726006 DOI: 10.1007/82_2016_30] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Listeria monocytogenes is a ubiquitously occurring gram-positive bacterium in the environment that causes listeriosis, one of the deadliest foodborne infections known today. It is a versatile facultative intracellular pathogen capable of growth within the host's cytosolic compartment. Following entry into the host cell, L. monocytogenes escapes from vacuolar compartments to the cytosol, where the bacterium begins a remarkable journey within the host cytoplasm, culminating in bacterial spread from cell to cell, to deeper tissues and organs. This dissemination process depends on the ability of the bacterium to harness central components of the host cell actin cytoskeleton using the surface bound bacterial factor ActA (actin assembly inducing protein). Hence ActA plays a major role in listerial virulence, and its absence renders bacteria intracellularly immotile and essentially non-infectious. As the bacterium, moving by building a network of filamentous actin behind itself that is often referred to as its actin tail, encounters cell-cell contacts it forms double-vacuolar protrusions that allow it to enter the neighboring cell where the cycle then continues. Recent studies have now implicated ActA in other stages of the life cycle of L. monocytogenes. These include extracellular properties of aggregation and biofilm formation to mediate colonization of the gut lumen, promotion and enhancement of bacterial host cell entry, evasion of autophagy, vacuolar exit, as well as nuclear factor of kappa light polypeptide gene enhancer in B-cells (NF-κB) activation. These novel properties provide a new view of ActA and help explain its role as an essential virulence factor of L. monocytogenes.
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Affiliation(s)
- Helena Pillich
- Institute of Medical Microbiology, Justus-Liebig University Giessen, Schubertstrasse 81, 35392, Giessen, Germany
| | - Madhu Puri
- Institute of Medical Microbiology, Justus-Liebig University Giessen, Schubertstrasse 81, 35392, Giessen, Germany
| | - Trinad Chakraborty
- Institute of Medical Microbiology, Justus-Liebig University Giessen, Schubertstrasse 81, 35392, Giessen, Germany.
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Actoclampin (+)-end-tracking motors: How the pursuit of profilin's role(s) in actin-based motility twice led to the discovery of how cells crawl. Biophys Chem 2015; 209:41-55. [PMID: 26720287 DOI: 10.1016/j.bpc.2015.10.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 10/05/2015] [Indexed: 11/21/2022]
Abstract
The path to the discovery of the actoclampins began with efforts to define profilin's role in actin-based pathogen and endosome rocketing. That research identified a set of FPPPP-containing cargo proteins and FPPPP-binding proteins that are consistently stationed within the polymerization zone during episodes of active motility. The very same biophysical clues that forced us to abandon Brownian Ratchet models guided us to the Actoclampin Hypothesis, which asserts that every propulsive filament possesses a (+)-end-tracking motor that generates the forces cells need to crawl. Each actoclampin motor is a multi-arm oligomeric complex, employing one arm to recruit/deliver Profilin•Actin•ATP to a growth-site located at the (+)-end of the lagging subfilament, while a second arm maintains an affinity-modulated binding interaction with the extreme (+)-end of the other subfilament. The alternating actions of these arms define a true molecular motor, the processivity of which explains why propelling filaments maintain full possession of their cargo. The Actoclampin Hypothesis also suggests how the energetics of tracker interactions with the (+)-end determines whether a given actoclampin is a passive (low force-producing) or active (high force-producing) motor, the latter requiring the Gibbs free energy of ATP hydrolysis. Another aim of this review is to acknowledge an earlier notional model that emerged from efforts to comprehend profilin's pivotal role(s) in actin-based cell motility.
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Zheng K, Kitazato K, Wang Y, He Z. Pathogenic microbes manipulate cofilin activity to subvert actin cytoskeleton. Crit Rev Microbiol 2015; 42:677-95. [PMID: 25853495 DOI: 10.3109/1040841x.2015.1010139] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Actin-depolymerizing factor (ADF)/cofilin proteins are key players in controlling the temporal and spatial extent of actin dynamics, which is crucial for mediating host-pathogen interactions. Pathogenic microbes have evolved molecular mechanisms to manipulate cofilin activity to subvert the actin cytoskeletal system in host cells, promoting their internalization into the target cells, modifying the replication niche and facilitating their intracellular and intercellular dissemination. The study of how these pathogens exploit cofilin pathways is crucial for understanding infectious disease and providing potential targets for drug therapies.
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Affiliation(s)
- Kai Zheng
- a Department of Pharmacy, School of Medicine , Shenzhen University , Shenzhen , Guangdong , People's Republic of China .,c Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University , Guangzhou , China
| | - Kaio Kitazato
- b Division of Molecular Pharmacology of Infectious Agents, Department of Molecular Microbiology and Immunology , Nagasaki University , Nagasaki , Japan , and
| | - Yifei Wang
- c Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University , Guangzhou , China
| | - Zhendan He
- a Department of Pharmacy, School of Medicine , Shenzhen University , Shenzhen , Guangdong , People's Republic of China
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11
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Abstract
beta-Actin mRNA is localized near the leading edge in several cell types where actin polymerization is actively promoting forward protrusion. The localization of the beta-actin mRNA near the leading edge is facilitated by a short sequence in the 3'UTR (untranslated region), the 'zipcode'. Localization of the mRNA at this region is important physiologically. Treatment of chicken embryo fibroblasts with antisense oligonucleotides complementary to the localization sequence (zipcode) in the 3'UTR leads to delocalization of beta-actin mRNA, alteration of cell phenotype and a decrease in cell motility. The dynamic image analysis system (DIAS) used to quantify movement of cells in the presence of sense and antisense oligonucleotides to the zipcode showed that net pathlength and average speed of antisense-treated cells were significantly lower than in sense-treated cells. This suggests that a decrease in persistence of direction of movement and not in velocity results from treatment of cells with zipcode-directed antisense oligonucleotides. We postulate that delocalization of beta-actin mRNA results in delocalization of nucleation sites and beta-actin protein from the leading edge followed by loss of cell polarity and directional movement. Hence the physiological consequences of beta-actin mRNA delocalization affect the stability of the cell phenotype.
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Affiliation(s)
- John Condeelis
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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Wen KK, McKane M, Stokasimov E, Rubenstein PA. Mutant profilin suppresses mutant actin-dependent mitochondrial phenotype in Saccharomyces cerevisiae. J Biol Chem 2011; 286:41745-41757. [PMID: 21956104 DOI: 10.1074/jbc.m110.217661] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the Saccharomyces cerevisiae actin-profilin interface, Ala(167) of the actin barbed end W-loop and His(372) near the C terminus form a clamp around a profilin segment containing residue Arg(81) and Tyr(79). Modeling suggests that altering steric packing in this interface regulates actin activity. An actin A167E mutation could increase interface crowding and alter actin regulation, and A167E does cause growth defects and mitochondrial dysfunction. We assessed whether a profilin Y79S mutation with its decreased mass could compensate for actin A167E crowding and rescue the mutant phenotype. Y79S profilin alone caused no growth defect in WT actin cells under standard conditions in rich medium and rescued the mitochondrial phenotype resulting from both the A167E and H372R actin mutations in vivo consistent with our model. Rescue did not result from effects of profilin on actin nucleotide exchange or direct effects of profilin on actin polymerization. Polymerization of A167E actin was less stimulated by formin Bni1 FH1-FH2 fragment than was WT actin. Addition of WT profilin to mixtures of A167E actin and formin fragment significantly altered polymerization kinetics from hyperbolic to a decidedly more sigmoidal behavior. Substitution of Y79S profilin in this system produced A167E behavior nearly identical to that of WT actin. A167E actin caused more dynamic actin cable behavior in vivo than observed with WT actin. Introduction of Y79S restored cable movement to a more normal phenotype. Our studies implicate the importance of the actin-profilin interface for formin-dependent actin and point to the involvement of formin and profilin in the maintenance of mitochondrial integrity and function.
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Affiliation(s)
- Kuo-Kuang Wen
- Department of Biochemistry, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, Iowa 52242
| | - Melissa McKane
- Department of Biochemistry, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, Iowa 52242
| | - Ema Stokasimov
- Department of Biochemistry, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, Iowa 52242
| | - Peter A Rubenstein
- Department of Biochemistry, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, Iowa 52242.
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Regulation of the postsynaptic cytoskeleton: roles in development, plasticity, and disorders. J Neurosci 2010; 30:14937-42. [PMID: 21068295 DOI: 10.1523/jneurosci.4276-10.2010] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The small size of dendritic spines belies the elaborate role they play in excitatory synaptic transmission and ultimately complex behaviors. The cytoskeletal architecture of the spine is predominately composed of actin filaments. These filaments, which at first glance might appear simple, are also surprisingly complex. They dynamically assemble into different structures and serve as a platform for orchestrating the elaborate responses of the spine during experience-dependent plasticity. This mini-symposium review will feature ongoing research into how spines are regulated by actin-signaling pathways during development and plasticity. It will also highlight evolving studies into how disruptions to these pathways might be functionally coupled to congenital disorders such as mental retardation.
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14
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Gertler F, Condeelis J. Metastasis: tumor cells becoming MENAcing. Trends Cell Biol 2010; 21:81-90. [PMID: 21071226 DOI: 10.1016/j.tcb.2010.10.001] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 09/28/2010] [Accepted: 10/01/2010] [Indexed: 12/31/2022]
Abstract
During breast cancer metastasis cells emigrate from the primary tumor to the bloodstream, and this carries them to distant sites where they infiltrate and sometimes form metastases within target organs. These cells must penetrate the dense extracellular matrix comprising the basement membrane of the mammary duct/acinus and migrate toward blood and lymphatic vessels, processes that mammary tumor cells execute primarily using epidermal growth factor (EGF)-dependent protrusive and migratory activity. Here, we focus on how the actin regulatory protein Mena affects EGF-elicited movement, invasion and metastasis. Recent findings indicate that, in invasive migratory tumor cells, Mena isoforms that endow heightened sensitivity to EGF and increased protrusive and migratory abilities are upregulated, whereas other isoforms are selectively downregulated. This change in Mena isoform expression enables tumor cells to invade in response to otherwise benign EGF stimulus levels and could offer an opportunity to identify metastatic risk in patients.
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Affiliation(s)
- Frank Gertler
- Department of Biology and Koch Institute for Integrative Cancer Research at Massachusetts Institute of Technology (MIT), 77 Massachusetts Ave, Cambridge, MA 02138, USA.
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15
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Lin WH, Nebhan CA, Anderson BR, Webb DJ. Vasodilator-stimulated phosphoprotein (VASP) induces actin assembly in dendritic spines to promote their development and potentiate synaptic strength. J Biol Chem 2010; 285:36010-20. [PMID: 20826790 DOI: 10.1074/jbc.m110.129841] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dendritic spines are small actin-rich structures that receive the majority of excitatory synaptic input in the brain. The actin-based dynamics of spines are thought to mediate synaptic plasticity, which underlies cognitive processes, such as learning and memory. However, little is known about the molecular mechanisms that regulate actin dynamics in spines and synapses. In this study we show the multifunctional actin-binding protein vasodilator-stimulated phosphoprotein (VASP) regulates the density, size, and morphology of dendritic spines by inducing actin assembly in these structures. Knockdown of endogenous VASP by siRNA led to a significant decrease in the density of spines and synapses, whereas expression of siRNA-resistant VASP rescued this defect. The ability of VASP to modulate spine and synapse formation, maturation, and spine head enlargement is dependent on its actin binding Ena/VASP homology 2 (EVH2) domain and its EVH1 domain, which contributes to VASP localization to actin-rich structures. Moreover, VASP increases the amount of PSD-scaffolding proteins and the number of surface GluR1-containing α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs) in spines. VASP knockdown results in a reduction in surface AMPAR density, suggesting a role for this protein in regulating synaptic strength. Consistent with this, VASP significantly enhances the retention of GluR1 in spines as determined by fluorescence recovery after photobleaching and increases AMPAR-mediated synaptic transmission. Collectively, our results suggest that actin polymerization and bundling by VASP are critical for spine formation, expansion, and modulating synaptic strength.
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Affiliation(s)
- Wan-Hsin Lin
- Department of Biological Sciences and Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, Tennessee 37235, USA
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16
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Defining a core set of actin cytoskeletal proteins critical for actin-based motility of Rickettsia. Cell Host Microbe 2010; 7:388-98. [PMID: 20478540 DOI: 10.1016/j.chom.2010.04.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Revised: 03/09/2010] [Accepted: 03/25/2010] [Indexed: 01/15/2023]
Abstract
Many Rickettsia species are intracellular bacterial pathogens that use actin-based motility for spread during infection. However, while other bacteria assemble actin tails consisting of branched networks, Rickettsia assemble long parallel actin bundles, suggesting the use of a distinct mechanism for exploiting actin. To identify the underlying mechanisms and host factors involved in Rickettsia parkeri actin-based motility, we performed an RNAi screen targeting 115 actin cytoskeletal genes in Drosophila cells. The screen delineated a set of four core proteins-profilin, fimbrin/T-plastin, capping protein, and cofilin--as crucial for determining actin tail length, organizing filament architecture, and enabling motility. In mammalian cells, these proteins were localized throughout R. parkeri tails, consistent with a role in motility. Profilin and fimbrin/T-plastin were critical for the motility of R. parkeri but not Listeria monocytogenes. Our results highlight key distinctions between the evolutionary strategies and molecular mechanisms employed by bacterial pathogens to assemble and organize actin.
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Ermolina LV, Martynova NI, Zaraĭskiĭ AG. [The cytoskeletal protein zyxin--a universal regulator of cell adhesion and gene expression]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2010; 36:29-37. [PMID: 20386576 DOI: 10.1134/s1068162010010036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The attachment of a cell to an extracellular matrix or the surface of another cells affects not only the cell motility, but also gene expression. In view of this, an important problem is to establish the molecular mechanisms of signal transduction from the receptors of cell adhesion to the nucleus, in particular, to identify and investigate the protein transducers of these signals. One of these transducers, the LIM domain protein zyxin, is predominantly localized at the sites of cell adhesion, where it participates in the assembly of actin filaments. Owing to its location near the inner surface of the membrane, zyxin can interact with the transmembrane receptors of some signaling cascades and affect the signal transduction from the extracellular ligands of these receptors. Furthermore, under particular conditions, zyxin moves from the sites of cell contacts to the nucleus, where it directly participates in the regulation of gene expression. Of particular interest is the function of zyxin as a possible coordinator of gene expression and morphogenetic movements in embryogenesis. The published data discussed in the present review indicate the important role of zyxin in transmitting information from the regions of cell contacts to the genetic apparatus of the cell.
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Dominguez R. Structural insights into de novo actin polymerization. Curr Opin Struct Biol 2010; 20:217-25. [PMID: 20096561 DOI: 10.1016/j.sbi.2009.12.012] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 12/18/2009] [Accepted: 12/23/2009] [Indexed: 01/05/2023]
Abstract
Many cellular functions depend on rapid and localized actin polymerization/depolymerization. Yet, the de novo polymerization of actin in cells is kinetically unfavorable because of the instability of polymerization intermediates (small actin oligomers) and the actions of actin monomer binding proteins. Cells use filament nucleation and elongation factors to initiate and sustain polymerization. Structural biology is beginning to shed light on the diverse mechanisms by which these unrelated proteins initiate polymerization, undergo regulation, and mediate the transition of monomeric actin onto actin filaments. A prominent role is played by the W domain, which in some of these proteins occurs in tandem repeats that recruit multiple actin subunits. Pro-rich regions are also abundant and mediate the binding of profilin-actin complexes, which are the main source of polymerization competent actin in cells. Filament nucleation and elongation factors frequently interact with Rho-family GTPases, which relay signals from membrane receptors to regulate actin cytoskeleton remodeling.
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Affiliation(s)
- Roberto Dominguez
- Department of Physiology, 3700 Hamilton Walk, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6085, USA.
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19
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Dominguez R. Actin filament nucleation and elongation factors--structure-function relationships. Crit Rev Biochem Mol Biol 2009; 44:351-66. [PMID: 19874150 DOI: 10.3109/10409230903277340] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The spontaneous and unregulated polymerization of actin filaments is inhibited in cells by actin monomer-binding proteins such as profilin and Tbeta4. Eukaryotic cells and certain pathogens use filament nucleators to stabilize actin polymerization nuclei, whose formation is rate-limiting. Known filament nucleators include the Arp2/3 complex and its large family of nucleation promoting factors (NPFs), formins, Spire, Cobl, VopL/VopF, TARP and Lmod. These molecules control the time and location for polymerization, and additionally influence the structures of the actin networks that they generate. Filament nucleators are generally unrelated, but with the exception of formins they all use the WASP-Homology 2 domain (WH2 or W), a small and versatile actin-binding motif, for interaction with actin. A common architecture, found in Spire, Cobl and VopL/VopF, consists of tandem W domains that bind three to four actin subunits to form a nucleus. Structural considerations suggest that NPFs-Arp2/3 complex can also be viewed as a specialized form of tandem W-based nucleator. Formins are unique in that they use the formin-homology 2 (FH2) domain for interaction with actin and promote not only nucleation, but also processive barbed end elongation. In contrast, the elongation function among W-based nucleators has been "outsourced" to a dedicated family of proteins, Eva/VASP, which are related to WASP-family NPFs.
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Affiliation(s)
- Roberto Dominguez
- Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6085, USA.
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20
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Dickinson RB. Models for actin polymerization motors. J Math Biol 2008; 58:81-103. [PMID: 18612640 DOI: 10.1007/s00285-008-0200-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 06/06/2008] [Indexed: 01/06/2023]
Abstract
Actin polymerization drives cell membrane protrusions and the propulsion of intracellular pathogens. The molecular mechanisms driving actin polymerization are not yet fully understood. Various mathematical models have been proposed to explain how cells convert chemical energy released upon actin polymerization into a pushing force on a surface. These models have attempted to explain puzzling properties of actin-based motility, including persistent attachment of the network to the membrane during propulsion and the interesting trajectories of propelled particles. These models fall generally into two classes: those requiring filament (+)-ends to fluctuate freely from the membrane to add subunits, and those where filaments elongate with their (+)-ends persistently associated with surface through filament end-tracking proteins ("actoclampin" models). This review compares and contrasts the key predictions of these two classes of models with regard to force-velocity profiles, and evaluates them with respect to experiments with biomimetic particles, and the experimental evidence on the role of end-tracking proteins such as formins and nucleation-promoting factors in actin-based motility.
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Affiliation(s)
- Richard B Dickinson
- Departments of Chemical Engineering and Biomedical Engineering, University of Florida, Gainesville, FL, 32611, USA.
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21
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Pasic L, Kotova T, Schafer DA. Ena/VASP proteins capture actin filament barbed ends. J Biol Chem 2008; 283:9814-9. [PMID: 18283104 DOI: 10.1074/jbc.m710475200] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ena/VASP (vasodialator-stimulated protein) proteins regulate many actin-dependent events, including formation of protrusive structures, fibroblast migration, neurite extension, cell-cell adhesion, and Listeria pathogenesis. In vitro, Ena/VASP activities on actin are complex and varied. They promote actin assembly, protect filaments from cappers, bundle filaments, and inhibit filament branching. To determine the mechanisms by which Ena/VASP proteins regulate actin dynamics at barbed ends, we monitored individual actin filaments growing in the presence of VASP and profilin using total internal reflection fluorescence microscopy. Filament growth was unchanged by VASP, but filaments grew faster in profilin-actin and VASP than with profilin-actin alone. Actin filaments were captured directly by VASP-coated surfaces via interactions with growing barbed ends. End-attached filaments transiently paused but resumed growth after becoming bound to the surface via a filament side attachment. Thus, Ena/VASP proteins promote actin assembly by interacting directly with actin filament barbed ends, recruiting profilin-actin, and blocking capping.
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Affiliation(s)
- Lejla Pasic
- Departments of Biology and Cell Biology, University of Virginia, Charlottesville, VA 22903, USA
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Benz PM, Blume C, Moebius J, Oschatz C, Schuh K, Sickmann A, Walter U, Feller SM, Renné T. Cytoskeleton assembly at endothelial cell-cell contacts is regulated by alphaII-spectrin-VASP complexes. ACTA ACUST UNITED AC 2008; 180:205-19. [PMID: 18195108 PMCID: PMC2213610 DOI: 10.1083/jcb.200709181] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Directed cortical actin assembly is the driving force for intercellular adhesion. Regulated by phosphorylation, vasodilator-stimulated phosphoprotein (VASP) participates in actin fiber formation. We screened for endothelial proteins, which bind to VASP, dependent on its phosphorylation status. Differential proteomics identified αII-spectrin as such a VASP-interacting protein. αII-Spectrin binds to the VASP triple GP5-motif via its SH3 domain. cAMP-dependent protein kinase–mediated VASP phosphorylation at Ser157 inhibits αII-spectrin–VASP binding. VASP is dephosphorylated upon formation of cell–cell contacts and in confluent, but not in sparse cells, αII-spectrin colocalizes with nonphosphorylated VASP at cell–cell junctions. Ectopic expression of the αII-spectrin SH3 domain at cell–cell contacts translocates VASP, initiates cortical actin cytoskeleton formation, stabilizes cell–cell contacts, and decreases endothelial permeability. Conversely, the permeability of VASP-deficient endothelial cells (ECs) and microvessels of VASP-null mice increases. Reconstitution of VASP-deficient ECs rescues barrier function, whereas αII-spectrin binding-deficient VASP mutants fail to restore elevated permeability. We propose that αII-spectrin–VASP complexes regulate cortical actin cytoskeleton assembly with implications for vascular permeability.
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Affiliation(s)
- Peter M Benz
- Institute of Clinical Biochemistry and Pathobiochemistry, University of Würzburg, D-97080 Würzburg, Germany
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Syriani E, Gomez-Cabrero A, Bosch M, Moya A, Abad E, Gual A, Gasull X, Morales M. Profilin induces lamellipodia by growth factor-independent mechanism. FASEB J 2008; 22:1581-96. [PMID: 18184720 DOI: 10.1096/fj.06-7654com] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Profilin has been implicated in cell motility and in a variety of cellular processes, such as membrane extension, endocytosis, and formation of focal complexes. In vivo, profilin replenish the pool of ATP-actin monomers by increasing the rate of nucleotide exchange of ADP-actin for ATP-actin, promoting the incorporation of new actin monomers at the barbed end of actin filaments. For this report, we generated a membrane-permeable version of profilin I (PTD4-PfnI) for the alteration of intracellular profilin levels taking advantage of the protein transduction technique. We show that profilin I induces lamellipodia formation independently of growth factor presence in primary bovine trabecular meshwork (BTM) cells. The effects are time- and concentration-dependent and specific to the profilin I isoform. Profilin II, the neuronal isoform, failed to extend lamellipodia in the same degree as profilin I. H133S, a mutation in the polyproline binding domain, showed a reduced ability to induce lamellipodia. H199E, mutation in the actin binding domain failed to induce membrane spreading and inhibit fetal bovine serum (FBS) -induced lamellipodia extension. Incubation with a synthetic polyproline domain peptide (GP5)3, fused to a transduction domain, abolished lamellipodia induction by profilin or FBS. Time-lapse microscopy confirmed the effects of profilin on lamellipodia extension with a higher spreading velocity than FBS. PTD4-Pfn I was found in the inner lamellipodia domain, at the membrane leading edge where it colocalizes with endogenous profilin. While FBS-induced lamellipodia formation activates Rac1, PTD4-Pfn I stimulation did not induce Rac1 activation. We propose a role of profilin I favoring lamellipodia formation by a mechanism downstream of growth factor.
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Affiliation(s)
- Enrique Syriani
- IDIBAPS-Department of Physiological Sciences I, Facultad de Medicina-University of Barcelona, Barcelona, Spain
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24
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Kursula P, Kursula I, Massimi M, Song YH, Downer J, Stanley WA, Witke W, Wilmanns M. High-resolution Structural Analysis of Mammalian Profilin 2a Complex Formation with Two Physiological Ligands: The Formin Homology 1 Domain of mDia1 and the Proline-rich Domain of VASP. J Mol Biol 2008; 375:270-90. [DOI: 10.1016/j.jmb.2007.10.050] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2007] [Revised: 10/15/2007] [Accepted: 10/17/2007] [Indexed: 12/28/2022]
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Ferron F, Rebowski G, Lee SH, Dominguez R. Structural basis for the recruitment of profilin-actin complexes during filament elongation by Ena/VASP. EMBO J 2007; 26:4597-606. [PMID: 17914456 PMCID: PMC2063483 DOI: 10.1038/sj.emboj.7601874] [Citation(s) in RCA: 194] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Accepted: 09/10/2007] [Indexed: 11/09/2022] Open
Abstract
Cells sustain high rates of actin filament elongation by maintaining a large pool of actin monomers above the critical concentration for polymerization. Profilin-actin complexes constitute the largest fraction of polymerization-competent actin monomers. Filament elongation factors such as Ena/VASP and formin catalyze the transition of profilin-actin from the cellular pool onto the barbed end of growing filaments. The molecular bases of this process are poorly understood. Here we present structural and energetic evidence for two consecutive steps of the elongation mechanism: the recruitment of profilin-actin by the last poly-Pro segment of vasodilator-stimulated phosphoprotein (VASP) and the binding of profilin-actin simultaneously to this poly-Pro and to the G-actin-binding (GAB) domain of VASP. The actin monomer bound at the GAB domain is proposed to be in position to join the barbed end of the growing filament concurrently with the release of profilin.
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Affiliation(s)
- François Ferron
- Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - Grzegorz Rebowski
- Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - Sung Haeng Lee
- Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - Roberto Dominguez
- Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
- Department of Physiology, University of Pennsylvania School of Medicine, A507 Richards Building, 3700 Hamilton Walk, Philadelphia, PA 19104-6058, USA. Tel.: +1 215 573 4559; Fax: +1 215 573 5851; E-mail:
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26
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Chereau D, Dominguez R. Understanding the role of the G-actin-binding domain of Ena/VASP in actin assembly. J Struct Biol 2006; 155:195-201. [PMID: 16684607 DOI: 10.1016/j.jsb.2006.01.012] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2005] [Accepted: 01/22/2006] [Indexed: 11/26/2022]
Abstract
The Ena/VASP and WASP family of proteins play distinct roles in actin cytoskeleton remodeling. Ena/VASP is linked to actin filament elongation, whereas WASP plays a role in filament nucleation and branching mediated by Arp2/3 complex. The molecular mechanisms controlling both processes are only emerging. Both Ena/VASP and WASP are multidomain proteins. They both present poly-Pro regions, which mediate the binding of profilin-actin, followed by G-actin-binding (GAB) domains of the WASP-homology 2 (WH2) type. However, the WH2 of Ena/VASP is somewhat different from that of WASP, and has been poorly characterized. Here we demonstrate that this WH2 binds profilin-actin with higher affinity than actin alone. The results are consistent with a model whereby allosteric modulation of affinity drives the transition of profilin-actin from the poly-Pro region to the WH2 and then to the barbed end of the filament during elongation. Therefore, the function of the WH2 in Ena/VASP appears to be to "process" profilin-actin for its incorporation at the barbed end of the growing filament. Conformational changes in the newly incorporated actin subunit, resulting either from nucleotide hydrolysis or from the G- to F-actin transition, may serve as a "sensor" for the processive stepping of Ena/VASP. Conserved domain architecture suggests that WASP may work similarly.
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Affiliation(s)
- David Chereau
- Boston Biomedical Research Institute, 64 Grove Street, Watertown, MA 02472, USA
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27
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Boukhelifa M, Moza M, Johansson T, Rachlin A, Parast M, Huttelmaier S, Roy P, Jockusch BM, Carpen O, Karlsson R, Otey CA. The proline-rich protein palladin is a binding partner for profilin. FEBS J 2006; 273:26-33. [PMID: 16367745 DOI: 10.1111/j.1742-4658.2005.05036.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Palladin is an actin-associated protein that has been suggested to play critical roles in establishing cell morphology and maintaining cytoskeletal organization in a wide variety of cell types. Palladin has been shown previously to bind directly to three different actin-binding proteins vasodilator-stimulated phosphoprotein (VASP), alpha-actinin and ezrin, suggesting that it functions as an organizing unit that recruits actin-regulatory proteins to specific subcellular sites. Palladin contains sequences resembling a motif known to bind profilin. Here, we demonstrate that palladin is a binding partner for profilin, interacting with profilin via a poly proline-containing sequence in the amino-terminal half of palladin. Double-label immunofluorescence staining shows that palladin and profilin partially colocalize in actin-rich structures in cultured astrocytes. Our results suggest that palladin may play an important role in recruiting profilin to sites of actin dynamics.
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Affiliation(s)
- Malika Boukhelifa
- Department of Cell and Molecular Physiology and Neuroscience Center, University of North Carolina at Chapel Hill, 27599-7545, USA
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Chereau D, Kerff F, Graceffa P, Grabarek Z, Langsetmo K, Dominguez R. Actin-bound structures of Wiskott-Aldrich syndrome protein (WASP)-homology domain 2 and the implications for filament assembly. Proc Natl Acad Sci U S A 2005; 102:16644-9. [PMID: 16275905 PMCID: PMC1283820 DOI: 10.1073/pnas.0507021102] [Citation(s) in RCA: 203] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Wiskott-Aldrich syndrome protein (WASP)-homology domain 2 (WH2) is a small and widespread actin-binding motif. In the WASP family, WH2 plays a role in filament nucleation by Arp2/3 complex. Here we describe the crystal structures of complexes of actin with the WH2 domains of WASP, WASP-family verprolin homologous protein, and WASP-interacting protein. Despite low sequence identity, WH2 shares structural similarity with the N-terminal portion of the actin monomer-sequestering thymosin beta domain (Tbeta). We show that both domains inhibit nucleotide exchange by targeting the cleft between actin subdomains 1 and 3, a common binding site for many unrelated actin-binding proteins. Importantly, WH2 is significantly shorter than Tbeta but binds actin with approximately 10-fold higher affinity. WH2 lacks a C-terminal extension that in Tbeta4 becomes involved in monomer sequestration by interfering with intersubunit contacts in F-actin. Owing to their shorter length, WH2 domains connected in tandem by short linkers can coexist with intersubunit contacts in F-actin and are proposed to function in filament nucleation by lining up actin subunits along a filament strand. The WH2-central region of WASP-family proteins is proposed to function in an analogous way by forming a special class of tandem repeats whose function is to line up actin and Arp2 during Arp2/3 nucleation. The structures also suggest a mechanism for how profilin-binding Pro-rich sequences positioned N-terminal to WH2 could feed actin monomers directly to WH2, thereby playing a role in filament elongation.
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Affiliation(s)
- David Chereau
- Boston Biomedical Research Institute, Watertown, MA 02472, USA
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Barzik M, Kotova TI, Higgs HN, Hazelwood L, Hanein D, Gertler FB, Schafer DA. Ena/VASP proteins enhance actin polymerization in the presence of barbed end capping proteins. J Biol Chem 2005; 280:28653-62. [PMID: 15939738 PMCID: PMC1747414 DOI: 10.1074/jbc.m503957200] [Citation(s) in RCA: 243] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ena/VASP proteins influence the organization of actin filament networks within lamellipodia and filopodia of migrating cells and in actin comet tails. The molecular mechanisms by which Ena/VASP proteins control actin dynamics are unknown. We investigated how Ena/VASP proteins regulate actin polymerization at actin filament barbed ends in vitro in the presence and absence of barbed end capping proteins. Recombinant His-tagged VASP increased the rate of actin polymerization in the presence of the barbed end cappers, heterodimeric capping protein (CP), CapG, and gelsolin-actin complex. Profilin enhanced the ability of VASP to protect barbed ends from capping by CP, and this required interactions of profilin with G-actin and VASP. The VASP EVH2 domain was sufficient to protect barbed ends from capping, and the F-actin and G-actin binding motifs within EVH2 were required. Phosphorylation by protein kinase A at sites within the VASP EVH2 domain regulated anti-capping and F-actin bundling by VASP. We propose that Ena/VASP proteins associate at or near actin filament barbed ends, promote actin assembly, and restrict the access of barbed end capping proteins.
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Affiliation(s)
- Melanie Barzik
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139 the
| | - Tatyana I. Kotova
- From the Department of Biology, University of Virginia, Charlottesville, VA 22903, the
| | - Henry N. Higgs
- Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755 and the
| | | | - Dorit Hanein
- Cell Adhesion Program, The Burnham Institute, La Jolla, CA 92037
| | - Frank B. Gertler
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139 the
| | - Dorothy A. Schafer
- From the Department of Biology, University of Virginia, Charlottesville, VA 22903, the
- Address correspondence to: Dorothy A. Schafer, Department of Biology, University of Virginia, Charlottesville, VA 22903, Tel. 434-243-5297; Fax. 434-982-5626;
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Badour K, Zhang J, Siminovitch KA. Involvement of the Wiskott-Aldrich syndrome protein and other actin regulatory adaptors in T cell activation. Semin Immunol 2005; 16:395-407. [PMID: 15541654 DOI: 10.1016/j.smim.2004.08.019] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The actin cytoskeleton is a dynamic structure recognized for many years as integral to the coupling of external stimuli to cell activation and ensuing changes in morphology and movement. It is only recently, however, that a molecular understanding of actin involvement in these activities has emerged coincident with the identification of cytosolic signaling effectors that couple extracellular stimuli to induction of actin nucleation. Notable among these actin regulatory effectors are members of the Wiskott-Aldrich syndrome protein (WASp) family, a group of cytoskeletal adaptors imbued with the capacity to connect various signal transduction pathways to the Arp 2/3 complex and Arp 2/3-mediated actin polymerization. In T cells, the functional characterization of WASp and other actin-modulatory adaptors has proved instrumental in delineating the molecular interactions evoking actin cytoskeletal reorganization downstream of antigen receptor engagement and in clarifying the influence of actin-based processes on T cell activation. In this review, the structural and functional properties of the major actin regulatory cytoskeletal adaptors in T cells are described with an emphasis on the roles of these proteins in fostering the TCR actin cytoskeletal interplay required for induction of T cell activation and expression of dynamic effector responses.
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Affiliation(s)
- Karen Badour
- Department of Medicine, McLaughlin Centre of Molecular Medicine, University of Toronto, Mount Sinai Hospital, Samuel Lunenfeld and Toronto General Hospital Research Institutes, 600 University Avenue, #656A, Toronto, Ont., Canada M5G 1X5.
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Abstract
Force generation in several types of cell motility is driven by rapidly elongating cytoskeletal filaments that are persistently tethered at their polymerizing ends to propelled objects. These properties are not easily explained by force-generation models that require free (i.e., untethered) filament ends to fluctuate away from the surface for addition of new monomers. In contrast, filament end-tracking proteins that processively advance on filament ends can facilitate rapid elongation and substantial force generation by persistently tethered filaments. Such processive end-tracking proteins, termed here filament end-tracking motors, maintain possession of filament ends and, like other biomolecular motors, advance by means of 5'-nucleoside triphosphate (NTP) hydrolysis-driven affinity-modulated interactions. On-filament NTP hydrolysis/phosphate release yields substantially more energy than that required for driving steady-state assembly/disassembly of free filament ends (i.e., filament treadmilling), as revealed by an energy inventory on the treadmilling cycle. The kinetic and thermodynamic properties of two simple end-tracking mechanisms (an end-tracking stepping motor and a direct-transfer end-tracking motor) are analyzed to illustrate the advantages of an end-tracking motor over free filament-end elongation, and over passive end-trackers that operate without the benefit of NTP hydrolysis, in terms of generating force, facilitating rapid monomer addition, and maintaining tight possession of the filament ends. We describe an additional cofactor-assisted end-tracking motor to account for suggested roles of cofactors in the affinity-modulated interactions, such as profilin in actin-filament end-tracking motors and EB1 in microtubule end-tracking motors.
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Affiliation(s)
- Richard B Dickinson
- Department of Chemical Engineering, University of Florida Colleges of Engineering and Medicine, Gainesville, Florida 32611-6005, USA.
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Zeile WL, Zhang F, Dickinson RB, Purich DL. Listeria's right-handed helical rocket-tail trajectories: Mechanistic implications for force generation in actin-based motility. ACTA ACUST UNITED AC 2005; 60:121-8. [PMID: 15627275 DOI: 10.1002/cm.20050] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Listeria monocytogenes forms right-handed helical rocket tail trajectories during actin-based motility in cell-free extracts, and this stereochemical feature is consistent with actoclampin's affinity-modulated, clamped-filament elongation model [Dickinson and Purich, 2002: Biophys J 82:605-617]. In that mechanism, right-handed torque is generated by an end-tracking molecular motor, each comprised of a filament barbed end and clamping protein that processively traces the right-handed helix of its filament partner. By contrast, torque is not a predicted property of those models (e.g., elastic propulsion, elastic Brownian ratchet, tethered ratchet, and insertional polymerization models) requiring filament barbed ends to depart/detach from the motile object's surface during/after each monomer-addition step. Helical trajectories also explain why Listeria undergoes longitudinal-axis rotation on a length-scale matching the helical periodicity of Listeria's rocket tails.
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Affiliation(s)
- William L Zeile
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610-0245, USA
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Tapp H, Al-Naggar IM, Yarmola EG, Harrison A, Shaw G, Edison AS, Bubb MR. MARCKS is a natively unfolded protein with an inaccessible actin-binding site: evidence for long-range intramolecular interactions. J Biol Chem 2005; 280:9946-56. [PMID: 15640140 DOI: 10.1074/jbc.m414614200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Myristoylated alanine-rich C kinase substrate (MARCKS) is an unfolded protein that contains well characterized actin-binding sites within the phosphorylation site domain (PSD), yet paradoxically, we now find that intact MARCKS does not bind to actin. Intact MARCKS also does not bind as well to calmodulin as does the PSD alone. Myristoylation at the N terminus alters how calmodulin binds to MARCKS, implying that, despite its unfolded state, the distant N terminus influences binding events at the PSD. We show that the free PSD binds with site specificity to MARCKS, suggesting that long-range intramolecular interactions within MARCKS are also possible. Because of the unusual primary sequence of MARCKS with an overall isoelectric point of 4.2 yet a very basic PSD (overall charge of +13), we speculated that ionic interactions between oppositely charged domains of MARCKS were responsible for long-range interactions within MARCKS that sterically influence binding events at the PSD and that explain the observed differences between properties of the PSD and MARCKS. Consistent with this hypothesis, chemical modifications of MARCKS that neutralize negatively charged residues outside of the PSD allow the PSD to bind to actin and increase the affinity of MARCKS for calmodulin. Similarly, both myristoylation of MARCKS and cleavage of MARCKS by calpain are shown to increase the availability of the PSD so as to activate its actin-binding activity. Because abundant evidence supports the conclusion that MARCKS is an important protein in regulating actin dynamics, our data imply that post-translational modifications of MARCKS are necessary and sufficient to regulate actin-binding activity.
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Affiliation(s)
- Hazel Tapp
- Department of Medicine, University of Florida College of Medicine, Gainesville, Florida 32610, USA
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Otey CA, Rachlin A, Moza M, Arneman D, Carpen O. The palladin/myotilin/myopalladin family of actin-associated scaffolds. INTERNATIONAL REVIEW OF CYTOLOGY 2005; 246:31-58. [PMID: 16164966 DOI: 10.1016/s0074-7696(05)46002-7] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
The dynamic remodeling of the actin cytoskeleton plays a critical role in cellular morphogenesis and cell motility. Actin-associated scaffolds are key to this process, as they recruit cohorts of actin-binding proteins and associated signaling complexes to subcellular sites where remodeling is required. This review is focused on a recently discovered family of three proteins, myotilin, palladin, and myopalladin, all of which function as scaffolds that regulate actin organization. While myotilin and myopalladin are most abundant in skeletal and cardiac muscle, palladin is ubiquitously expressed in the organs of developing vertebrates. Palladin's function has been investigated primarily in the central nervous system and in tissue culture, where it appears to play a key role in cellular morphogenesis. The three family members each interact with specific molecular partners: all three bind to alpha-actinin; in addition, palladin also binds to vasodilator-stimulated phosphoprotein (VASP) and ezrin, myotilin binds to filamin and actin, and myopalladin also binds to nebulin and cardiac ankyrin repeat protein (CARP). Since mutations in myotilin result in two forms of muscle disease, an essential role for this family member in organizing the skeletal muscle sarcomere is implied.
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Affiliation(s)
- Carol A Otey
- Department of Cell and Molecular Physiology and the Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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Boukhelifa M, Parast MM, Bear JE, Gertler FB, Otey CA. Palladin is a novel binding partner for Ena/VASP family members. ACTA ACUST UNITED AC 2004; 58:17-29. [PMID: 14983521 DOI: 10.1002/cm.10173] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Palladin is an actin-associated protein that contains proline-rich motifs within its amino-terminal sequence that are similar to motifs found in zyxin, vinculin, and the Listeria protein ActA. These motifs are known to be potential binding sites for the Vasodilator-Stimulated Phosphoprotein (VASP). Here, we demonstrate that palladin is an additional direct binding partner for VASP, by using co-immunoprecipitation and blot overlay techniques with both endogenous palladin and recombinant myc-tagged palladin. These results show that VASP binds to full-length palladin and also to the amino-terminal half of palladin, where the polyproline motifs are located. Using a synthetic peptide array, two discrete binding sites for VASP were identified within palladin's proline-rich amino-terminal domain. Using double-label immunofluorescence staining of fully-spread and actively-spreading fibroblasts, the extent of co-localization of palladin and VASP was explored. These proteins were found to strongly co-localize along stress fibers, and partially co-localize in focal adhesions, lamellipodia, and focal complexes. These results suggest that the recently described actin-associated protein palladin may play an important role in recruiting VASP to sites of actin filament growth, anchorage, and crosslinking.
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Affiliation(s)
- Malika Boukhelifa
- Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, 27599-7545, USA
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36
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Limmongkon A, Giuliani C, Valenta R, Mittermann I, Heberle-Bors E, Wilson C. MAP kinase phosphorylation of plant profilin. Biochem Biophys Res Commun 2004; 324:382-6. [PMID: 15465030 DOI: 10.1016/j.bbrc.2004.09.071] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2004] [Indexed: 01/19/2023]
Abstract
Profilin is a small actin-binding protein and is expressed at high levels in mature pollen where it is thought to regulate actin filament dynamics upon pollen germination and tube growth. The majority of identified plant profilins contain a MAP kinase phosphorylation motif, P-X-T-P, and a MAP kinase interaction motif (KIM). In in vitro kinase assays, the tobacco MAP kinases p45(Ntf4) and SIPK, when activated by the tobacco MAP kinase kinase NtMEK2, can phosphorylate the tobacco profilin NtProf2. Mutagenesis of the threonine residue in this motif identified it as the site of MAP kinase phosphorylation. Fractionation of tobacco pollen extracts showed that p45(Ntf4) is found exclusively in the high-speed pellet fraction while SIPK and profilin are predominantly cytosolic. These data identify one of the first substrates to be directly phosphorylated by MAP kinases in plants.
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Affiliation(s)
- Apinun Limmongkon
- Max F. Perutz Laboratories, University Departments at the Vienna Biocenter, Institute of Microbiology and Genetics, University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna, Austria
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37
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Roy P, Jacobson K. Overexpression of profilin reduces the migration of invasive breast cancer cells. ACTA ACUST UNITED AC 2004; 57:84-95. [PMID: 14691948 DOI: 10.1002/cm.10160] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The exact role profilin plays in cell migration is not clear. In this study, we have evaluated the effect of overexpression of profilin on the migration of breast cancer cells. Overexpression was carried out by stably expressing GFP-profilin in BT474 cells. It was observed that even a moderate level of overexpression of profilin significantly impaired the ability of BT474 cells to spread on fibronectin-coated substrate and migrate in response to EGF. GFP-profilin expressing cells also showed increased resistance to detachment in response to trypsin and increased tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin compared to the parental and GFP-expressing (control) cell lines. These results suggest that perturbation of profilin levels may offer a good strategy for controlling the metastatic potential of breast cancer cells.
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Affiliation(s)
- Partha Roy
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, NC, USA.
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Abstract
Dynamin, the large guanosine triphosphatase, is generally considered to have a key role in deforming membranes to create tubules or vesicles. Dynamin, particularly dynamin2 isoforms, also are localized with actin filaments, often at locations where cellular membranes undergo remodeling. Perturbing dynamin function interferes with endocytic traffic and actin function. Thus, dynamin may regulate actin filaments coordinately with its activities that remodel membranes. This review will highlight recent observations that provide clues to mechanisms whereby dynamin might coordinate membrane remodeling and actin filament dynamics during endocytic traffic, cell morphogenesis and cell migration.
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Affiliation(s)
- Dorothy A Schafer
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA.
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Krause M, Dent EW, Bear JE, Loureiro JJ, Gertler FB. Ena/VASP proteins: regulators of the actin cytoskeleton and cell migration. Annu Rev Cell Dev Biol 2004; 19:541-64. [PMID: 14570581 DOI: 10.1146/annurev.cellbio.19.050103.103356] [Citation(s) in RCA: 508] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ena/VASP proteins are a conserved family of actin regulatory proteins made up of EVH1, EVH2 domains, and a proline-rich central region. They have been implicated in actin-based processes such as fibroblast migration, axon guidance, and T cell polarization and are important for the actin-based motility of the intracellular pathogen Listeria monocytogenes. Mechanistically, these proteins associate with barbed ends of actin filaments and antagonize filament capping by capping protein (CapZ). In addition, they reduce the density of Arp2/3-dependent actin filament branches and bind Profilin at sites of actin polymerization. Vertebrate Ena/VASP proteins are substrates for PKA/PKG serine/threonine kinases. Phosphorylation by these kinases appears to modulate Ena/VASP function within cells, although the mechanism underlying this regulation remains to be determined.
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Affiliation(s)
- Matthias Krause
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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40
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Quinlan MP. Vinculin, VASP, and profilin are coordinately regulated during actin remodeling in epithelial cells, which requires de novo protein synthesis and protein kinase signal transduction pathways. J Cell Physiol 2004; 200:277-90. [PMID: 15174098 DOI: 10.1002/jcp.20009] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Transformation progression of epithelial cells involves alterations in their morphology, polarity, and adhesive characteristics, all of which are associated with the loss and/or reorganization of actin structures. To identify the underlying mechanism of formation of the adhesion-dependent, circumferential actin network, the expression and localization of the actin binding and regulating proteins (ABPs), vinculin, VASP, and profilin were evaluated. Experimental depolarization of epithelial cells results in the loss of normal F-actin structures and the transient upregulation of vinculin, VASP, and profilin. This response is due to the loss of cell-cell, and not cell-substrate interactions, since cells that no longer express focal adhesions or stress fibers are still sensitive to changes in adhesion and manifest this in the altered profile of expression of these ABPs. Transient upregulation is dependent upon de novo protein synthesis, and protein kinase-, but not phosphatase-sensitive signal transduction pathway(s). Inhibition of the synthesis of these proteins is accompanied by dephosphorylation of the ribosomal S6 protein, but does not involve inhibition of the PI3-kinase-Akt-mTOR pathway. Constitutive expression of VASP results in altered cell morphology and adhesion and F-actin and vinculin structures. V12rac1 expressing epithelial cells are constitutively nonadhesive, malignantly transformed, and constitutively express high levels of these ABPs, with altered subcellular localizations. Transformation suppression is accompanied by the restoration of normal levels of the three ABPs, actin structures, adhesion, and epithelial morphology. Thus, vinculin, VASP, and profilin are coordinately regulated by signal transduction pathways that effect a translational response. Additionally, their expression profile maybe indicative of the adhesion and transformation status of epithelial cells.
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Affiliation(s)
- Margaret P Quinlan
- Laboratory of Molecular Cell Biology, Guthrie Research Institute, 1 Guthrie Square, Sayre, Pennsylvania 18840, USA.
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41
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Chen SH, Bubb MR, Yarmola EG, Zuo J, Jiang J, Lee BS, Lu M, Gluck SL, Hurst IR, Holliday LS. Vacuolar H+-ATPase binding to microfilaments: regulation in response to phosphatidylinositol 3-kinase activity and detailed characterization of the actin-binding site in subunit B. J Biol Chem 2003; 279:7988-98. [PMID: 14662773 DOI: 10.1074/jbc.m305351200] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Vacuolar H(+)-ATPase (V-ATPase) binds microfilaments, and that interaction may be mediated by an actin binding domain in subunit B of the enzyme. To test for possible physiologic functions of the actin binding activity of V-ATPase, early responses of resorbing osteoclasts to inhibition of phosphatidylinositol 3-kinase activity by wortmannin and LY294002 were examined. Rapid co-localization between V-ATPase and F-actin was demonstrated by immunocytochemistry, and corresponding association between V-ATPase and F-actin in immunoprecipitations and pelleting assays was detected. This response was reversed as osteoclasts recovered resorptive activity after inhibitors were removed. By expressing and characterizing fusion proteins containing segments of the actin-binding amino-terminal regions of the B subunits of V-ATPase, we mapped the actin-binding site to a 44-amino acid domain. An 11-amino acid segment with a sequence similar to the actin-binding site of human profilin I was detected within this region. 13-Mers containing these profilin-like segments bound actin in fluorescent anisotropy studies and competed with profilin for binding to actin. Using site-directed mutagenesis, the 11-amino acid profilin-like actin-binding motifs (amino acids 49-59 of B1 and 55-65 of B2) were replaced with an 11-amino acid spacer with a sequence based on the homologous sequence from subunit B of Pyrococcus horikoshii, an organism that lacks an actin cytoskeleton. These substitutions eliminated the actin-binding activity of the B subunit fusion proteins. In summary, binding between V-ATPase and F-actin in osteoclasts occurs in response to blocking phosphatidylinositol 3-kinase activity. This response was fully reversible. The actin binding activities of the B subunits of V-ATPase required 11-amino acid actin-binding motifs that are similar in sequence to the actin-binding site of mammalian profilin I.
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Affiliation(s)
- Shih-Hua Chen
- Department of Orthodontics, University of Florida College of Dentistry, Gainesville, Florida 32610, USA
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42
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Ackermann M, Matus A. Activity-induced targeting of profilin and stabilization of dendritic spine morphology. Nat Neurosci 2003; 6:1194-200. [PMID: 14555951 DOI: 10.1038/nn1135] [Citation(s) in RCA: 212] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2003] [Accepted: 09/15/2003] [Indexed: 11/09/2022]
Abstract
Morphological changes in dendritic spines have been implicated in connective plasticity in brain circuitry, but the underlying pathway leading from synaptic transmission to structural change is unknown. Using primary neurons expressing GFP-tagged proteins, we found that profilin, a regulator of actin polymerization, is targeted to spine heads when postsynaptic NMDA receptors are activated and that actin-based changes in spine shape are concomitantly blocked. Profilin targeting was triggered by electrical stimulation patterns known to induce the long-term changes in synaptic responsiveness associated with memory formation. These results suggest that, in addition to electrophysiological changes, NMDA receptor activation initiates changes in the actin cytoskeleton of dendritic spines that stabilize synaptic structure.
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43
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Zimmermann J, Kühne R, Volkmer-Engert R, Jarchau T, Walter U, Oschkinat H, Ball LJ. Design of N-substituted peptomer ligands for EVH1 domains. J Biol Chem 2003; 278:36810-8. [PMID: 12857736 DOI: 10.1074/jbc.m305934200] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ena/VASP proteins are implicated in cytoskeletal reorganization during actin-dependent motility processes. Recruitment to subcellular sites of actin polymerization is mediated by the highly conserved N-terminal EVH1 domain, which interacts with target proteins containing proline-rich motifs. The VASP EVH1 domain specifically binds peptides with the consensus motif FPPPP present in all its binding partners, including the Listerial ActA protein. Previous studies have shown that the Phe and first and final Pro residues are highly conserved and cannot be substituted with any other natural amino acid without significant loss of binding affinity. We have incorporated peptoid building blocks (sarcosine derived, non-natural amino acids) into the peptide SFEFPPPPTEDEL from the Listerial ActA protein and were able to substitute the most highly conserved residues of this motif while maintaining binding to the VASP EVH1 domain with affinities in the range of 45-180 microm. We then used NMR chemical shift perturbations to locate specific domain residues involved in particular interactions. These studies may open up the way for designing selective modulators of VASP function for biological studies and for the development of novel therapeutics for diseases involving pathologically altered cell adhesion or cell motility.
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Affiliation(s)
- Jürgen Zimmermann
- Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
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44
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Bubb MR, Yarmola EG, Gibson BG, Southwick FS. Depolymerization of actin filaments by profilin. Effects of profilin on capping protein function. J Biol Chem 2003; 278:24629-35. [PMID: 12730212 DOI: 10.1074/jbc.m302796200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Profilin interacts with the barbed ends of actin filaments and is thought to facilitate in vivo actin polymerization. This conclusion is based primarily on in vitro kinetic experiments using relatively low concentrations of profilin (1-5 microm). However, the cell contains actin regulatory proteins with multiple profilin binding sites that potentially can attract millimolar concentrations of profilin to areas requiring rapid actin filament turnover. We have studied the effects of higher concentrations of profilin (10-100 microm) on actin monomer kinetics at the barbed end. Prior work indicated that profilin might augment actin filament depolymerization in this range of profilin concentration. At barbed-end saturating concentrations (final concentration, approximately 40 microm), profilin accelerated the off-rate of actin monomers by a factor of four to six. Comparable concentrations of latrunculin had no detectable effect on the depolymerization rate, indicating that profilin-mediated acceleration was independent of monomer sequestration. Furthermore, we have found that high concentrations of profilin can successfully compete with CapG for the barbed end and uncap actin filaments, and a simple equilibrium model of competitive binding could explain these effects. In contrast, neither gelsolin nor CapZ could be dissociated from actin filaments under the same conditions. These differences in the ability of profilin to dissociate capping proteins may explain earlier in vivo data showing selective depolymerization of actin filaments after microinjection of profilin. The finding that profilin can uncap actin filaments was not previously appreciated, and this newly discovered function may have important implications for filament elongation as well as depolymerization.
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Affiliation(s)
- Michael R Bubb
- The Research Service, Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida 32608, USA.
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45
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Grenklo S, Geese M, Lindberg U, Wehland J, Karlsson R, Sechi AS. A crucial role for profilin-actin in the intracellular motility of Listeria monocytogenes. EMBO Rep 2003; 4:523-9. [PMID: 12776739 PMCID: PMC1319178 DOI: 10.1038/sj.embor.embor823] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
We have examined the effect of covalently crosslinked profilin-actin (PxA), which closely matches the biochemical properties of ordinary profilin-actin and interferes with actin polymerization in vitro and in vivo, on Listeria monocytogenes motility. PxA caused a marked reduction in bacterial motility, which was accompanied by the detachment of bacterial tails. The effect of PxA was dependent on its binding to proline-rich sequences, as shown by the inability of PH133SxA, which cannot interact with such sequences, to impair Listeria motility. PxA did not alter the motility of a Listeria mutant that is unable to recruit Ena (Enabled)/VASP (vasodilator-stimulated phosphoprotein) proteins and profilin to its surface. Finally, PxA did not block the initiation of actin-tail formation, indicating that profilin-actin is only required for the elongation of actin filaments at the bacterial surface. Our findings provide further evidence that profilin-actin is important for actin-based processes, and show that it has a key function in Listeria motility.
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Affiliation(s)
- Staffan Grenklo
- Department of Cell Biology, The Wenner–Gren Institute, Stockholm University, S-10691 Stockholm, Sweden
| | - Marcus Geese
- Department of Cell Biology, Gesellschaft für Biotechnologische Forschung (GBF), Mascheroder Weg 1, D-38124 Braunschweig, Germany
| | - Uno Lindberg
- Department of Cell Biology, The Wenner–Gren Institute, Stockholm University, S-10691 Stockholm, Sweden
| | - Jürgen Wehland
- Department of Cell Biology, Gesellschaft für Biotechnologische Forschung (GBF), Mascheroder Weg 1, D-38124 Braunschweig, Germany
| | - Roger Karlsson
- Department of Cell Biology, The Wenner–Gren Institute, Stockholm University, S-10691 Stockholm, Sweden
| | - Antonio S. Sechi
- Department of Cell Biology, Gesellschaft für Biotechnologische Forschung (GBF), Mascheroder Weg 1, D-38124 Braunschweig, Germany
- Tel: +49 531 6181241; Fax: +49 531 6181444;
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Abstract
Nervous system development is reliant on neuronal pathfinding, the process in which axons are guided to their target cells by specific extracellular cues. The ability of neurons to extend over long distances in response to environmental guidance signals is made possible by the growth cone, a highly motile structure found at the end of neuronal processes. Growth cones detect directional cues and respond with either attractive or repulsive movements. The motility of growth cones is dependent on rapid reorganization of the actin cytoskeleton, presumably mediated by actin-associated proteins under the control of incoming guidance signals. This article reviews how one such family of proteins, the ADF/cofilins, are emerging as key regulators of growth cone actin dynamics. These proteins are essential for rapid actin turnover in a variety of different cell types. ADF/cofilins are heavily co-localized with actin in growth cones and are necessary for neurite outgrowth. ADF/cofilin activities are regulated through reversible phosphorylation by LIM kinases and slingshot phosphatases. LIM kinases are downstream effectors of the Rho GTPases Rho, Rac, and Cdc42. Growing evidence suggests that extracellular guidance cues may locally alter actin dynamics by regulating the activity of LIM kinase and ADF/cofilin phosphatases via the Rho GTPases. In this way, ADF/cofilins and their upstream effectors may be pivotal to our understanding of how guidance information is translated into physical alterations of the growth cone actin cytoskeleton.
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Affiliation(s)
- Ravine A Gungabissoon
- Department of Biochemistry and Molecular Biology and Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado 80523-1870, USA
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Han YH, Chung CY, Wessels D, Stephens S, Titus MA, Soll DR, Firtel RA. Requirement of a vasodilator-stimulated phosphoprotein family member for cell adhesion, the formation of filopodia, and chemotaxis in dictyostelium. J Biol Chem 2002; 277:49877-87. [PMID: 12388544 DOI: 10.1074/jbc.m209107200] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have examined the function of a member of the vasodilator-stimulated phosphoprotein family of proteins (DdVASP) in Dictyostelium. Ddvasp null cells lack filopodia, whereas targeting DdVASP to the plasma membrane with a myristoyl tag results in a significant increase in filopodia. The proline-rich domain-Ena/VASP homology 2 structure is required for both actin polymerization activity and filopodia formation. Ddvasp null cells exhibit a chemotaxis defect, which appears to be due to a defect in the ability of the cells to properly adhere to the substratum and to suppress lateral pseudopod extension. We demonstrate that during chemotaxis, the anterior approximately 50% of the cell lifts from the substratum and remains elevated for up to 1 min. These defects lead to a significant decrease in chemotaxis efficiency. DdVASP localizes to the leading edge in migrating cells and to the tips of filopodia. In addition, Ddvasp null cells have a defect in particle adhesion but internalize particles normally. Our results provide new insights into the function of DdVASP in controlling the actin cytoskeleton during chemotaxis and filopodia formation.
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Affiliation(s)
- Young-Hoon Han
- Section of Cell and Developmental Biology, Division of Biological Sciences, Center for Molecular Genetics, University of California-San Diego, 9500 Gilman Drive, La Jolla, California 92093-0634, USA
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48
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Idrissi FZ, Wolf BL, Geli MI. Cofilin, but not profilin, is required for myosin-I-induced actin polymerization and the endocytic uptake in yeast. Mol Biol Cell 2002; 13:4074-87. [PMID: 12429847 PMCID: PMC133615 DOI: 10.1091/mbc.02-04-0052] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mutations in the budding yeast myosins-I (MYO3 and MYO5) cause defects in the actin cytoskeleton and in the endocytic uptake. Robust evidence also indicates that these proteins induce Arp2/3-dependent actin polymerization. Consistently, we have recently demonstrated, using fluorescence microscopy, that Myo5p is able to induce cytosol-dependent actin polymerization on the surface of Sepharose beads. Strikingly, we now observed that, at short incubation times, Myo5p induced the formation of actin foci that resembled the yeast cortical actin patches, a plasma membrane-associated structure that might be involved in the endocytic uptake. Analysis of the machinery required for the formation of the Myo5p-induced actin patches in vitro demonstrated that the Arp2/3 complex was necessary but not sufficient in the assay. In addition, we found that cofilin was directly involved in the process. Strikingly though, the cofilin requirement seemed to be independent of its ability to disassemble actin filaments and profilin, a protein that closely cooperates with cofilin to maintain a rapid actin filament turnover, was not needed in the assay. In agreement with these observations, we found that like the Arp2/3 complex and the myosins-I, cofilin was essential for the endocytic uptake in vivo, whereas profilin was dispensable.
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Affiliation(s)
- Fatima-Zahra Idrissi
- Biochemiezentrum of the University of Heidelberg (BZH), D-69120 Heidelberg, Germany
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49
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Dickinson RB, Southwick FS, Purich DL. A direct-transfer polymerization model explains how the multiple profilin-binding sites in the actoclampin motor promote rapid actin-based motility. Arch Biochem Biophys 2002; 406:296-301. [PMID: 12361718 DOI: 10.1016/s0003-9861(02)00212-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The high actin-based motility rates observed in nonmuscle cells require the per-second addition of 400-500 monomers to the barbed ends of growing actin filaments. The chief polymerization-competent species is profilin.actin.ATP (present at 5-40 microM intracellular concentrations), whereas G-actin.ATP is much less abundant ( approximately 0.1-1 microM). While earlier studies unambiguously demonstrated that profilin.actin is highly concentrated within the polymerization zone, profilin-actin localization on the motile surface cannot increase the local solution-phase concentration of polymerizable actin. To explain these high rates of actin polymerization, we present and analyze a novel polymerization model in which monomers are directly transferred to growing filament ends in the actoclampin motor. This direct-transfer polymerization mechanism endows the polymerization zone with properties unavailable to bulk-phase actin monomers, and our model also indicates why profilin is the ideal mobile carrier for actin monomers.
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Affiliation(s)
- Richard B Dickinson
- Department of Chemical Engineering, University of Florida Colleges of Engineering and Medicine, Gainesville, FL 32610-0245, USA
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50
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Zhang F, Southwick FS, Purich DL. Actin-based phagosome motility. CELL MOTILITY AND THE CYTOSKELETON 2002; 53:81-8. [PMID: 12211106 DOI: 10.1002/cm.10058] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Despite abundant evidence of actin's involvement at the particle internalization stage of phagocytosis, little is known about whether phagosomes undergo the same type of actin-based motility as observed with endocytic vesicles or such intracellular pathogens as Listeria and Shigella. By employing video microscopy to follow the fate of latex bead-containing phagosomes within the cytoplasm of bone marrow macrophages, we have made the novel observation of actin-based phagosome motility. Immunofluorescence microscopy confirmed that phagosomes containing IgG-opsonized, bovine serum albumin (or BSA) -coated or uncoated latex beads all formed actin-rich rocket tails that persisted only during a brief, 1-2 min period of actin-based motility. Average speeds of actin-based phagosome motility were 0.13 +/- 0.06 microm/s for IgG-coated beads, 0.14 +/- 0.04 microm/s for BSA-coated beads, and 0.11+/- 0.03 microm/s for uncoated beads. Moreover, the speeds and motile-phase duration of each type of phagosome were comparable to the behavior of pinosomes [Merrifield et al., 1999: Nat. Cell Biol. 1:72-74.]. Determination of optimal conditions for observing and analyzing actin-based phagosome motility should facilitate future investigations of phagocytosis and phagosome maturation.
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Affiliation(s)
- Fangliang Zhang
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Health Science Center, Gainesville, FL 32610-0245, USA
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