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Rath PP, Gourinath S. The actin cytoskeleton orchestra in Entamoeba histolytica. Proteins 2020; 88:1361-1375. [PMID: 32506560 DOI: 10.1002/prot.25955] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 04/17/2020] [Accepted: 05/27/2020] [Indexed: 12/14/2022]
Abstract
Years of evolution have kept actin conserved throughout various clades of life. It is an essential protein starring in many cellular processes. In a primitive eukaryote named Entamoeba histolytica, actin directs the process of phagocytosis. A finely tuned coordination between various actin-binding proteins (ABPs) choreographs this process and forms one of the virulence factors for this protist pathogen. The ever-expanding world of ABPs always has space to accommodate new and varied types of proteins to the earlier existing repertoire. In this article, we report the identification of 390 ABPs from Entamoeba histolytica. These proteins are part of diverse families that have been known to regulate actin dynamics. Most of the proteins are primarily uncharacterized in this organism; however, this study aims to annotate the ABPs based on their domain arrangements. A unique characteristic about some of the ABPs found is the combination of domains present in them unlike any other reported till date. Calponin domain-containing proteins formed the largest group among all types with 38 proteins, followed by 29 proteins with the infamous BAR domain in them, and 23 proteins belonging to actin-related proteins. The other protein families had a lesser number of members. Presence of exclusive domain arrangements in these proteins could guide us to yet unknown actin regulatory mechanisms prevalent in nature. This article is the first step to unraveling them.
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2
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Costa WJEM, Amorim PF, Mattos JLO. Molecular phylogeny and timing of diversification in South American Cynolebiini seasonal killifishes. Mol Phylogenet Evol 2017; 116:61-68. [PMID: 28754241 DOI: 10.1016/j.ympev.2017.07.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 07/10/2017] [Accepted: 07/24/2017] [Indexed: 11/17/2022]
Abstract
The rich biological diversity of South America has motivated a series of studies associating evolution of endemic taxa with the dramatic geologic and climatic changes that occurred during the Cainozoic. The organism here studied is the killifish tribe Cynolebiini, a group of seasonal fishes uniquely inhabiting temporary pools formed during the rainy seasons. The Cynolebiini are found in open vegetation areas inserted in the main tropical and subtropical South American phytogeographical regions east of the Andes. Here, we present the first molecular phylogeny sampling all the eight genera of the Cynolebiini, using fragments of two mitochondrial and four nuclear genes for 35 species of Cynolebiini plus 19 species as outgroups. The dataset, 4448bp, was analysed under Bayesian and maximum likelihood approaches, providing a relatively well solved tree, which retrieves high support values for the Cynolebiini and most included clades. The resulting tree was used to estimate the time of divergence in included lineages using two cyprinodontiform fossils to calibrate the tree. We further investigated historical biogeography through the likelihood-based DEC model. Our estimates indicate that divergence between the clades comprising New World and Old World aplocheiloids occurred during the Eocene, about 50Mya, much more recent than the Gondwanan fragmentation scenario assumed in previous studies. This estimation is nearly synchronous to estimated splits involving other South American and African vertebrate clades, which have been explained by transoceanic dispersal through an ancient Atlantic island chain during the Palaeogene. We estimate that Cynolebiini split from its sister group Cynopoecilini in the Oligocene, about 25Mya and that Cynolebiini started to diversify giving origin to the present genera during the Miocene, about 20-14Mya. The Cynolebiini had an ancestral origin in the Atlantic Forest and probably were not present in the open vegetation formations of central and northeastern South America until the Middle Miocene, when expansion of dry open vegetation was favoured by cool temperatures and strike seasonality. Initial splitting between the genera Cynolebias and Simpsonichthys during the Miocene (about 14Mya) is attributed to the uplift of the Central Brazilian Plateau.
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Affiliation(s)
- Wilson J E M Costa
- Laboratory of Systematics and Evolution of Teleost Fishes, Institute of Biology, Federal University of Rio de Janeiro, Caixa Postal 68049, CEP 21944-970 Rio de Janeiro, RJ, Brazil.
| | - Pedro F Amorim
- Laboratory of Systematics and Evolution of Teleost Fishes, Institute of Biology, Federal University of Rio de Janeiro, Caixa Postal 68049, CEP 21944-970 Rio de Janeiro, RJ, Brazil.
| | - José Leonardo O Mattos
- Laboratory of Systematics and Evolution of Teleost Fishes, Institute of Biology, Federal University of Rio de Janeiro, Caixa Postal 68049, CEP 21944-970 Rio de Janeiro, RJ, Brazil.
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3
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Mutava RN, Prince SJK, Syed NH, Song L, Valliyodan B, Chen W, Nguyen HT. Understanding abiotic stress tolerance mechanisms in soybean: a comparative evaluation of soybean response to drought and flooding stress. Plant Physiol Biochem 2015; 86:109-120. [PMID: 25438143 DOI: 10.1016/j.plaphy.2014.11.010] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 11/14/2014] [Indexed: 05/20/2023]
Abstract
Many sources of drought and flooding tolerance have been identified in soybean, however underlying molecular and physiological mechanisms are poorly understood. Therefore, it is important to illuminate different plant responses to these abiotic stresses and understand the mechanisms that confer tolerance. Towards this goal we used four contrasting soybean (Glycine max) genotypes (PI 567690--drought tolerant, Pana--drought susceptible, PI 408105A--flooding tolerant, S99-2281--flooding susceptible) grown under greenhouse conditions and compared genotypic responses to drought and flooding at the physiological, biochemical, and cellular level. We also quantified these variations and tried to infer their role in drought and flooding tolerance in soybean. Our results revealed that different mechanisms contribute to reduction in net photosynthesis under drought and flooding stress. Under drought stress, ABA and stomatal conductance are responsible for reduced photosynthetic rate; while under flooding stress, accumulation of starch granules played a major role. Drought tolerant genotypes PI 567690 and PI 408105A had higher plastoglobule numbers than the susceptible Pana and S99-2281. Drought stress increased the number and size of plastoglobules in most of the genotypes pointing to a possible role in stress tolerance. Interestingly, there were seven fibrillin proteins localized within the plastoglobules that were up-regulated in the drought and flooding tolerant genotypes PI 567690 and PI 408105A, respectively, but down-regulated in the drought susceptible genotype Pana. These results suggest a potential role of Fibrillin proteins, FBN1a, 1b and 7a in soybean response to drought and flooding stress.
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Affiliation(s)
- Raymond N Mutava
- National Center for Soybean Biotechnology and Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Silvas Jebakumar K Prince
- National Center for Soybean Biotechnology and Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Naeem Hasan Syed
- School of Human and Life Sciences, Canterbury Christ Church University, Canterbury, CT1 1QU, United Kingdom
| | - Li Song
- National Center for Soybean Biotechnology and Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Babu Valliyodan
- National Center for Soybean Biotechnology and Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Wei Chen
- National Center for Soybean Biotechnology and Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Henry T Nguyen
- National Center for Soybean Biotechnology and Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA.
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4
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Zhao Y, Zhao S, Mao T, Qu X, Cao W, Zhang L, Zhang W, He L, Li S, Ren S, Zhao J, Zhu G, Huang S, Ye K, Yuan M, Guo Y. The plant-specific actin binding protein SCAB1 stabilizes actin filaments and regulates stomatal movement in Arabidopsis. Plant Cell 2011; 23:2314-30. [PMID: 21719691 PMCID: PMC3160031 DOI: 10.1105/tpc.111.086546] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 05/28/2011] [Accepted: 06/10/2011] [Indexed: 05/18/2023]
Abstract
Microfilament dynamics play a critical role in regulating stomatal movement; however, the molecular mechanism underlying this process is not well understood. We report here the identification and characterization of STOMATAL CLOSURE-RELATED ACTIN BINDING PROTEIN1 (SCAB1), an Arabidopsis thaliana actin binding protein. Plants lacking SCAB1 were hypersensitive to drought stress and exhibited reduced abscisic acid-, H(2)O(2)-, and CaCl(2)-regulated stomatal movement. In vitro and in vivo analyses revealed that SCAB1 binds, stabilizes, and bundles actin filaments. SCAB1 shares sequence similarity only with plant proteins and contains a previously undiscovered actin binding domain. During stomatal closure, actin filaments switched from a radial orientation in open stomata to a longitudinal orientation in closed stomata. This switch took longer in scab1 plants than in wild-type plants and was correlated with the delay in stomatal closure seen in scab1 mutants in response to drought stress. Our results suggest that SCAB1 is required for the precise regulation of actin filament reorganization during stomatal closure.
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Affiliation(s)
- Yang Zhao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
- National Institute of Biological Sciences, Beijing 102206, China
| | - Shuangshuang Zhao
- Key Laboratory of Plant Stress, Life Science College, Shandong Normal University, Jinan 250014, China
| | - Tonglin Mao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Xiaolu Qu
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Wanhong Cao
- National Institute of Biological Sciences, Beijing 102206, China
| | - Li Zhang
- National Institute of Biological Sciences, Beijing 102206, China
| | - Wei Zhang
- National Institute of Biological Sciences, Beijing 102206, China
| | - Liu He
- National Institute of Biological Sciences, Beijing 102206, China
| | - Sidi Li
- National Institute of Biological Sciences, Beijing 102206, China
| | - Sulin Ren
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Jinfeng Zhao
- National Institute of Biological Sciences, Beijing 102206, China
| | - Guoli Zhu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Shanjin Huang
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Keqiong Ye
- National Institute of Biological Sciences, Beijing 102206, China
| | - Ming Yuan
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yan Guo
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
- Address correspondence to
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Blagg SL, Battom SE, Annesley SJ, Keller T, Parkinson K, Wu JMF, Fisher PR, Thompson CRL. Cell type-specific filamin complex regulation by a novel class of HECT ubiquitin ligase is required for normal cell motility and patterning. Development 2011; 138:1583-93. [PMID: 21389049 PMCID: PMC3062426 DOI: 10.1242/dev.063800] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/25/2011] [Indexed: 11/20/2022]
Abstract
Differential cell motility, which plays a key role in many developmental processes, is perhaps most evident in examples of pattern formation in which the different cell types arise intermingled before sorting out into discrete tissues. This is thought to require heterogeneities in responsiveness to differentiation-inducing signals that result in the activation of cell type-specific genes and 'salt and pepper' patterning. How differential gene expression results in cell sorting is poorly defined. Here we describe a novel gene (hfnA) that provides the first mechanistic link between cell signalling, differential gene expression and cell type-specific sorting in Dictyostelium. HfnA defines a novel group of evolutionarily conserved HECT ubiquitin ligases with an N-terminal filamin domain (HFNs). HfnA expression is induced by the stalk differentiation-inducing factor DIF-1 and is restricted to a subset of prestalk cells (pstO). hfnA(-) pstO cells differentiate but their sorting out is delayed. Genetic interactions suggest that this is due to misregulation of filamin complex activity. Overexpression of filamin complex members phenocopies the hfnA(-) pstO cell sorting defect, whereas disruption of filamin complex function in a wild-type background results in pstO cells sorting more strongly. Filamin disruption in an hfnA(-) background rescues pstO cell localisation. hfnA(-) cells exhibit altered slug phototaxis phenotypes consistent with filamin complex hyperactivity. We propose that HfnA regulates filamin complex activity and cell type-specific motility through the breakdown of filamin complexes. These findings provide a novel mechanism for filamin regulation and demonstrate that filamin is a crucial mechanistic link between responses to differentiation signals and cell movement in patterning based on 'salt and pepper' differentiation and sorting out.
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Affiliation(s)
- Simone L. Blagg
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Suzanne E. Battom
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Sarah J. Annesley
- Department of Microbiology, La Trobe University, VIC 3086, Australia
| | - Thomas Keller
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Katie Parkinson
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Jasmine M. F. Wu
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Paul R. Fisher
- Department of Microbiology, La Trobe University, VIC 3086, Australia
| | - Christopher R. L. Thompson
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
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6
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Abstract
The vertebrate filamin family (A, B, and C) is part of the spectrin family of actin cross-linking proteins. Family members share high sequence similarity (>64%) and have both common and isoform-distinct functionalities. To identify the basis for isoform-specific functionality, we perform an evolutionary trace of chordate filamin at the granularity of single residues. Our trace methodology is constrained to focus on neofunctionality by requiring that one isoform remain the ancestral type, whereas at least one isoform has an accepted mutation. We call divergence meeting these characteristics "class-distinctive." To obtain a temporal and spatial context for class-distinctive residues, we derive an all-atom model of full-length filamin A by homology modeling and joining individual domains. We map onto our model both conserved and class-distinctive residues along with the period (Teleostei, Amphibian, and Mammalian) in which they diverged. Our phylogenetic analysis suggests that filamins diverged from a common ancestral gene between urochordate and vertebrate lineages. Filamins also diverged the most just after gene duplication, in the Teleostei period, with filamin C remaining closest to ancestral filamin. At the residue level, domains with well-characterized interfaces, IgFLN 17 and IgFLN 21 (immunoglobulin, Ig), have diverged in potentially critical residues in their adhesion protein-binding interfaces, signifying that isoforms may bind or regulate ligand binding differentially. Similarly, isoform divergence in a region associated with F actin-binding regulation suggests that isoforms differentially regulate F-actin binding. In addition, we observe some class-distinctive residues in the vicinity of missense mutations that cause filamin A and B-associated skeletal disorders. Our analysis, utilizing both spatial and temporal granularity, has identified potentially important residues responsible for vertebrate filamin isoform-specific divergence-significantly in regions where few binding partners have been discovered to date- and suggests yet to be discovered filamin-binding partners and isoform-specific differential regulation with these binding partners.
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Affiliation(s)
- Barry A. Kesner
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill
- Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill
| | - Sharon L. Milgram
- Office of Intramural Training and Education, National Institute of Health, Bethesda, MD
| | - Brenda R.S. Temple
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill
- R. L. Juliano Structural Bioinformatics Core Facility, University of North Carolina at Chapel Hill
| | - Nikolay V. Dokholyan
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill
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7
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Ithychanda SS, Hsu D, Li H, Yan L, Liu D, Das M, Plow EF, Qin J. Identification and characterization of multiple similar ligand-binding repeats in filamin: implication on filamin-mediated receptor clustering and cross-talk. J Biol Chem 2009; 284:35113-21. [PMID: 19828450 PMCID: PMC2787372 DOI: 10.1074/jbc.m109.060954] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 10/09/2009] [Indexed: 11/06/2022] Open
Abstract
The actin-binding protein filamin links membrane receptors to the underlying cytoskeleton. The cytoplasmic domains of these membrane receptors have been shown to bind to various filamin immunoglobulin repeats. Notably, among 24 human filamin repeats, repeat 17 was reported to specifically bind to platelet receptor glycoprotein Ibalpha and repeat 21 to integrins. However, a complete sequence alignment of all 24 human filamin repeats reveals that repeats 17 and 21 actually belong to a distinct filamin repeat subgroup (containing repeats 4, 9, 12, 17, 19, 21, and 23) that shares a conserved ligand-binding site. Using isothermal calorimetry and NMR analyses, we show that all repeats in this subgroup can actually bind glycoprotein Ibalpha, integrins, and a cytoskeleton regulator migfilin in similar manners. These data provide a new view on the ligand specificity of the filamin repeats. They also suggest a multiple ligand binding mechanism where similar repeats within a filamin monomer may promote receptor clustering or receptor cross-talking for regulation of the cytoskeleton organization and diverse filamin-mediated cellular activities.
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Affiliation(s)
| | - Dennis Hsu
- the Cleveland Clinic Lerner College of Medicine, Cleveland Clinic, Cleveland, Ohio 44195
| | - Hanhan Li
- the Cleveland Clinic Lerner College of Medicine, Cleveland Clinic, Cleveland, Ohio 44195
| | - Linda Yan
- From the Department of Molecular Cardiology, Lerner Research Institute, and
| | - Darwen Liu
- From the Department of Molecular Cardiology, Lerner Research Institute, and
| | - Mitali Das
- From the Department of Molecular Cardiology, Lerner Research Institute, and
| | - Edward F. Plow
- From the Department of Molecular Cardiology, Lerner Research Institute, and
| | - Jun Qin
- From the Department of Molecular Cardiology, Lerner Research Institute, and
- the Cleveland Clinic Lerner College of Medicine, Cleveland Clinic, Cleveland, Ohio 44195
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Abstract
Calponin is an actin filament-associated regulatory protein expressed in smooth muscle and non-muscle cells. Calponin is an inhibitor of the actin-activated myosin ATPase. Three isoforms of calponin have been found in the vertebrates. Whereas the role of calponin in regulating smooth muscle contractility has been extensively investigated, the function and regulation of calponin in non-muscle cells is much less understood. Based on recent progresses in the field, this review focuses on the studies of calponin in non-muscle cells, especially its regulation by cytoskeleton tension and function in cell motility. The ongoing research has demonstrated that calponin plays a regulatory role in non-muscle cell motility. Therefore, non-muscle calponin is an attractive target for the control of cell proliferation, migration and phagocytosis, and the treatment of cancer metastasis.
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Affiliation(s)
- Kai-Chun Wu
- Section of Molecular Cardiology, Evanston Northwestern Healthcare, Northwestern University Feinberg School of Medicine, Evanston, IL 60201, USA
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9
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Abstract
Formins are a widely expressed family of proteins that govern cell shape, adhesion, cytokinesis, and morphogenesis by remodeling the actin and microtubule cytoskeletons. These large multidomain proteins associate with a variety of other cellular factors and directly nucleate actin polymerization through a novel mechanism. The signature formin homology 2 (FH2) domain initiates filament assembly and remains persistently associated with the fast-growing barbed end, enabling rapid insertion of actin subunits while protecting the end from capping proteins. On the basis of structural and mechanistic work, an integrated model is presented for FH2 processive motion. The adjacent FH1 domain recruits profilin-actin complexes and accelerates filament elongation. The most predominantly expressed formins in animals and fungi are autoinhibited through intramolecular interactions and appear to be activated by Rho GTPases and additional factors. Other classes of formins lack the autoinhibitory and/or Rho-binding domains and thus are likely to be controlled by alternative mechanisms.
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Affiliation(s)
- Bruce L Goode
- Department of Biology and Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts 02454, USA.
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Michelot A, Derivery E, Paterski-Boujemaa R, Guérin C, Huang S, Parcy F, Staiger CJ, Blanchoin L. A Novel Mechanism for the Formation of Actin-Filament Bundles by a Nonprocessive Formin. Curr Biol 2006; 16:1924-30. [PMID: 17027489 DOI: 10.1016/j.cub.2006.07.054] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2006] [Revised: 06/28/2006] [Accepted: 07/21/2006] [Indexed: 11/16/2022]
Abstract
Actin-filament bundles (or cables) have a structural role during cell division and morphogenesis, but also serve as important "tracks" for the transport of materials during cytokinesis and polarized cell growth. However, the dynamic formation of these longitudinal actin-filament higher-order structures is not understood. Recently, several lines of evidence suggest that formins provide one avenue for the initiation of actin cables in vivo. A popular model for the mechanism of polymerization of actin filaments by formin involves the processive movement of formin attached at the barbed end of an elongating filament. In the present study, we use an in vitro system to reconstitute the dynamic formation of actin-filament bundles generated by Arabidopsis FORMIN1 (AFH1). To be able to visualize individual events in such a complex system, we used real-time evanescent-wave microscopy. Surprisingly, we find that AFH1 is a nonprocessive formin that moves from the barbed end to the side of an actin filament after the nucleation event. We show why this new mechanism of nucleation by a member of the formin family is important for bundle formation. Finally, we analyze the different parameters controlling the dynamic formation of such longitudinal actin-filament bundles.
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Affiliation(s)
- Alphée Michelot
- Departement Réponse et Dynamique Cellulaire, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Joseph Fourier, F38054 Grenoble, France
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Strehle A, Schleicher M, Faix J. Trix, a novel Rac guanine-nucleotide exchange factor from Dictyostelium discoideum is an actin-binding protein and accumulates at endosomes. Eur J Cell Biol 2006; 85:1035-45. [PMID: 16781009 DOI: 10.1016/j.ejcb.2006.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Small Rho family GTPases are involved in regulation of actin cytoskeleton dynamics. These molecular switches are themselves mainly controlled by specific GTPase-activating proteins (GAPs) and guanine-nucleotide exchange factors (GEFs). We have cloned and initially characterized a novel putative RhoGEF from Dictyostelium discoideum. The predicted 135-kDa protein displays a unique domain organization in its N-terminus by harboring two type3 calponin homology (CH) domains followed by a single type1 CH domain. The C-terminal region encompasses a diffuse B-cell lymphoma homology/pleckstrin homology tandem domain that is typically found in RhoGEFs. We therefore refer to this protein as Trix (triple CH-domain array exchange factor). A recombinant N-terminal region of Trix carrying all three CH domains binds to F-actin and bundles actin filaments. Trix-null mutants are viable and display only subtle defects when compared to wild-type cells with the exception of a substantial decrease in exocytosis of a fluid-phase marker. GFP fusions with the full-length protein or the N-terminal part containing all three CH domains revealed that Trix localizes to the cortical region and strongly accumulates on late endosomes. Our results suggest that Trix is specifically involved in a Rho GTPase-signaling pathway that is required for regulation of the actin cytoskeleton during exocytosis.
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Affiliation(s)
- Axel Strehle
- A. Butenandt-Institut/Zellbiologie, Ludwig-Maximilians-Universität, Schillerstr. 42, D-80336 München, Germany
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12
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Hagens O, Ballabio A, Kalscheuer V, Kraehenbuhl JP, Schiaffino MV, Smith P, Staub O, Hildebrand J, Wallingford JB. A new standard nomenclature for proteins related to Apx and Shroom. BMC Cell Biol 2006; 7:18. [PMID: 16615870 PMCID: PMC1481537 DOI: 10.1186/1471-2121-7-18] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2006] [Accepted: 04/14/2006] [Indexed: 11/10/2022] Open
Abstract
Shroom is a recently-described regulator of cell shape changes in the developing nervous system. This protein is a member of a small family of related proteins that are defined by sequence similarity and in most cases by some link to the actin cytoskeleton. At present these proteins are named Shroom, APX, APXL, and KIAA1202. In light of the growing interest in this family of proteins, we propose here a new standard nomenclature.
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Affiliation(s)
- Olivier Hagens
- Dept. of Human Molecular Genetics, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | | | - Vera Kalscheuer
- Dept. of Human Molecular Genetics, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Jean-Pierre Kraehenbuhl
- Swiss Institute for Experimental Cancer Research and the Institute of Biochemistry, University of Lausanne, Lausanne, Switzerland
| | | | - Peter Smith
- Dept. of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Olivier Staub
- Dept. of Pharmacology & Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Jeff Hildebrand
- Dept. of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - John B Wallingford
- Dept. of Molecular Cell and Developmental Biology & Institute for Cellular and Molecular Biology, University of Texas, Austin, TX, USA
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13
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Krupp M, Weinmann A, Galle PR, Teufel A. Actin binding LIM protein 3 (abLIM3). Int J Mol Med 2006; 17:129-33. [PMID: 16328021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023] Open
Abstract
LIM domain proteins were demonstrated to play key roles in various biological processes such as embryonic development, cell lineage determination, and cancer differentiation. Actin binding LIM protein 1 (abLIM1) was reported to be localized in a genomic region often deleted in human cancers and suggested to be involved in axon guidance. Recently, existence of a second family member was reported, actin binding LIM protein 2. By means of computational biology and comparative genomics, we now characterized an additional, third member of the actin binding LIM protein subgroup, actin binding LIM protein 3 (abLIM3). The human mRNA sequence was previously annotated as differentially regulated in hepatoblastoma compared to normal livers. Conservation of key structural features of abLIM1 and abLIM2, four LIM domains and a VHD domain, suggested comparable biological function of abLIM3 as a linker between actin cytoskeleton and cell signaling pathways. AbLIM3 was found to be conserved in vertebrates, as orthologous sequences were characterized for mouse, fish, and frog. In addition, we report the existence of abLIM2 orthologs in fish and frog, suggesting a similar degree of evolutionary conservation. The intracellular localization of the abLIM3 protein was predicted to be nuclear by means of Reinhardt's neural network and the k-nearest neighbor algorithm. The corresponding abLIM3 gene was localized to chromosome 5q32 and spanned 119 kb, organized in 24 exons. An RT-PCR based expression profile available from the human unidentified gene-encoded (HUGE) database demonstrated highest expression for abLIM3 in heart, lung, liver, and brain/cerebellum accompanied by lower expression in multiple other tissues. Furthermore, abLIM3 was expressed in fetal liver, CNS, and spinal cord.
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Affiliation(s)
- Markus Krupp
- Department of Internal Medicine I, Johannes Gutenberg University, 55101 Mainz, Germany
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Ohkouchi S, Saito H, Aruga F, Maeda T, Shibata H, Maki M. Dictyostelium discoideumrequires an Alix/AIP1 homolog, DdAlix, for morphogenesis in alkaline environments. FEBS Lett 2005; 579:1745-50. [PMID: 15757670 DOI: 10.1016/j.febslet.2005.02.036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2005] [Revised: 01/31/2005] [Accepted: 02/08/2005] [Indexed: 11/30/2022]
Abstract
Alix and its homologs are involved in various phenomena such as endosomal protein-sorting and adaptation to stress conditions. In this study, we found that development of Dictyostelium discoideum Alix (DdAlix) deletion mutant (alx-) cells was impaired in alkaline pH environments. The fruiting body formation efficiency of alx- cells at pH 9.0 was significantly lower than that of wild-type cells (6.8+/-4.2% vs 93+/-6.3%). The alkaline-sensitive phenotype of alx- cells was rescued by addition of salt. The phenotype was rescued by exogenous expression of human Alix as well as DdAlix but not by that of either Saccharomyces cerevisiae Alix homolog Rim20 or Bro1. DdAlix may be, structurally and functionally, more related to human Alix than to yeast Rim20 and Bro1.
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Affiliation(s)
- Susumu Ohkouchi
- Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
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15
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Abstract
The gelsolin gene family encodes a number of higher eukaryotic actin-binding proteins that are thought to function in the cytoplasm by severing, capping, nucleating or bundling actin filaments. Recent evidence, however, suggests that several members of the gelsolin family may have adopted unexpected nuclear functions including a role in regulating transcription. In particular, flightless I, supervillin and gelsolin itself have roles as coactivators for nuclear receptors, despite the fact that their divergence appears to predate the evolutionary appearance of nuclear receptors. Flightless I has been shown to bind both actin and the actin-related BAF53a protein, which are subunits of SWI/SNF-like chromatin remodelling complexes. The primary sequences of some actin-related proteins such as BAF53a exhibit conservation of residues that, in actin itself, are known to interact with gelsolin-related proteins. In summary, there is a growing body of evidence supporting a biological role in the nucleus for actin, Arps and actin-binding proteins and, in particular, the gelsolin family of actin-binding proteins.
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Affiliation(s)
- Stuart K Archer
- Molecular Genetics and Evolution Group and Centre for the Molecular Genetics of Development, Research School of Biological Sciences, Australian National University, Canberra, ACT 2601, Australia
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16
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Abstract
The actin cytoskeleton is essential for cellular remodeling and many developmental and morphological processes. Twinfilin is a ubiquitous actin monomer-binding protein whose biological function has remained unclear. We discovered and cloned the Drosophila twinfilin homologue, and show that this protein is ubiquitously expressed in different tissues and developmental stages. A mutation in the twf gene leads to a number of developmental defects, including aberrant bristle morphology. This results from uncontrolled polymerization of actin filaments and misorientation of actin bundles in developing bristles. In wild-type bristles, twinfilin localizes diffusively to cytoplasm and to the ends of actin bundles, and may therefore be involved in localization of actin monomers in cells. We also show that twinfilin and the ADF/cofilin encoding gene twinstar interact genetically in bristle morphogenesis. These results demonstrate that the accurate regulation of size and dynamics of the actin monomer pool by twinfilin is essential for a number of actin-dependent developmental processes in multicellular eukaryotes.
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Affiliation(s)
- G Wahlström
- Developmental Biology Program, Institute of Biotechnology, Viikki Biocenter, FIN-00014 University of Helsinki, Finland
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17
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Weins A, Schwarz K, Faul C, Barisoni L, Linke WA, Mundel P. Differentiation- and stress-dependent nuclear cytoplasmic redistribution of myopodin, a novel actin-bundling protein. J Cell Biol 2001; 155:393-404. [PMID: 11673475 PMCID: PMC2150840 DOI: 10.1083/jcb.200012039] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
We report the cloning and functional characterization of myopodin, the second member of the synaptopodin gene family. Myopodin shows no significant homology to any known protein except synaptopodin. Northern blot analysis resulted in a 3.6-kb transcript for mouse skeletal and heart muscle. Western blots showed an 80-kD signal for skeletal and a 95-kD signal for heart muscle. Myopodin contains one PPXY motif and multiple PXXP motifs. Myopodin colocalizes with alpha-actinin and is found at the Z-disc as shown by immunogold electron microscopy. In myoblasts, myopodin shows preferential nuclear localization. During myotube differentiation, myopodin binds to stress fibers in a punctuated pattern before incorporation into the Z-disc. Myopodin can directly bind to actin and contains a novel actin binding site in the center of the protein. Myopodin has actin-bundling activity as shown by formation of latrunculin-A-sensitive cytosolic actin bundles and nuclear actin loops in transfected cells expressing green fluorescent protein-myopodin. Under stress conditions, myopodin accumulates in the nucleus and is depleted from the cytoplasm. Nuclear export of myopodin is sensitive to leptomycin B, despite the absence of a classical nuclear export sequence. We propose a dual role for myopodin as a structural protein also participating in signaling pathways between the Z-disc and the nucleus.
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Affiliation(s)
- A Weins
- Department of Medicine and Department of Anatomy and Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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18
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Affiliation(s)
- E M De La Cruz
- University of Pennsylvania School of Medicine, Department of Physiology, Pennsylvania Muscle Institute, Philadelphia, Pennsylvania 19104, USA
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19
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Sun D, Leung CL, Liem RK. Characterization of the microtubule binding domain of microtubule actin crosslinking factor (MACF): identification of a novel group of microtubule associated proteins. J Cell Sci 2001; 114:161-172. [PMID: 11112700 DOI: 10.1242/jcs.114.1.161] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
MACF (microtubule actin cross-linking factor) is a large, 608-kDa protein that can associate with both actin microfilaments and microtubules (MTs). Structurally, MACF can be divided into 3 domains: an N-terminal domain that contains both a calponin type actin-binding domain and a plakin domain; a rod domain that is composed of 23 dystrophin-like spectrin repeats; and a C-terminal domain that includes two EF-hand calcium-binding motifs, as well as a region that is homologous to two related proteins, GAR22 and Gas2. We have previously demonstrated that the C-terminal domain of MACF binds to MTs, although no homology was observed between this domain and other known microtubule-binding proteins. In this report, we describe the characterization of this microtubule-binding domain of MACF by transient transfection studies and in vitro binding assays. We found that the C-terminus of MACF contains at least two microtubule-binding regions, a GAR domain and a domain containing glycine-serine-arginine (GSR) repeats. In transfected cells, the GAR domain bound to and partially stabilized MTs to depolymerization by nocodazole. The GSR-containing domain caused MTs to form bundles that are still sensitive to nocodazole-induced depolymerization. When present together, these two domains acted in concert to bundle MTs and render them stable to nocodazole treatment. Recently, a study has shown that the N-terminal half of the plakin domain (called the M1 domain) of MACF also binds MTs. We therefore examined the microtubule binding ability of the M1 domain in the context of the entire plakin domain with and without the remaining N-terminal regions of two different MACF isoforms. Interestingly, in the presence of the surrounding sequences, the M1 domain did not bind MTs. In addition to MACF, cDNA sequences encoding the GAR and GSR-containing domains are also found in the partial human EST clone KIAA0728, which has high sequence homology to the 3′ end of the MACF cDNA; hence, we refer to it as MACF2. The C-terminal domain of mouse MACF2 was cloned and characterized. The microtubule-binding properties of MACF2 C-terminal domain are similar to that of MACF. The GAR domain was originally found in Gas 2 protein and here we show that it can associate with MTs in transfected cells. Plectin and desmoplakin have GSR-containing domains at their C-termini and we further demonstrate that the GSR-containing domain of plectin, but not desmoplakin, can bind to MTs in vivo.
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Affiliation(s)
- D Sun
- Departments of Pathology and Anatomy and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA
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20
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Abstract
Ubiquitous among eukaryotes, the ADF/cofilins are essential proteins responsible for the high turnover rates of actin filaments in vivo. In vertebrates, ADF and cofilin are products of different genes. Both bind to F-actin cooperatively and induce a twist in the actin filament that results in the loss of the phalloidin-binding site. This conformational change may be responsible for the enhancement of the off rate of subunits at the minus end of ADF/cofilin-decorated filaments and for the weak filament-severing activity. Binding of ADF/cofilin is competitive with tropomyosin. Other regulatory mechanisms in animal cells include binding of phosphoinositides, phosphorylation by LIM kinases on a single serine, and changes in pH. Although vertebrate ADF/cofilins contain a nuclear localization sequence, they are usually concentrated in regions containing dynamic actin pools, such as the leading edge of migrating cells and neuronal growth cones. ADF/cofilins are essential for cytokinesis, phagocytosis, fluid phase endocytosis, and other cellular processes dependent upon actin dynamics.
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Affiliation(s)
- J R Bamburg
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins 80523, USA.
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21
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Abstract
The number of actin binding proteins for which (part of) the three-dimensional structure is known, is steadily increasing. This has led to a picture in which defined structural modules with actin binding capacity are shared between different actin binding proteins. A classification of these based on their common three-dimensional modules appears a logical future step and in this review we provide an initial list starting from the currently known structures. The discussed cases illustrate that a comparison of the similarities and variations within the common structural actin binding unit of different members of a particular class may ultimately provide shortcuts for defining their actin target site and for understanding their effect on actin dynamics. Within this concept, the multitude of possible interactions by an extensive, and still increasing, list of actin binding proteins becomes manageable because they can be presented as variations upon a limited number of structural themes. We discuss the possible evolutionary routes that may have produced the present array of actin binding modules.
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Affiliation(s)
- M Van Troys
- Flanders Interuniversity Institute for Biotechnology, Department of Biochemistry, Faculty of Medicine, University of Gent, Belgium
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22
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Abstract
BACKGROUND Profilins are small eukaryotic proteins involved in modulating the assembly of actin microfilaments in the cytoplasm. They are able to bind both phosphatidylinositol-4,5-bisphosphate and poly-L-proline (PLP) and thus play a critical role in signaling pathways. Plant profilins are of interest because immunological cross-reactivity between pollen and human profilin may be the cause of hay fever and broad allergies to pollens. RESULTS The determination of the Arabidopsis thaliana profilin isoform I structure, using multiwavelength anomalous diffraction (MAD) to obtain structure-factor phases, is reported here. The structure of Arabidopsis profilin is similar to that of previously determined profilin structures. Conserved amino acid residues in profilins from plants, mammals, and lower eukaryotes are critically important in dictating the geometry of the PLP-binding site and the overall polypeptide fold. The main feature distinguishing plant profilins from other profilins is a solvent-filled pocket located in the most variable region of the fold. CONCLUSIONS Comparison of the structures of SH3 domains with those of profilins from three distinct sources suggests that the mode of PLP binding may be similar. A comparison of three profilin structures from different families reveals only partial conservation of the actin-binding surface. The proximity of the semi-conserved actin-binding site and the binding pocket characteristic of plant profilins suggests that epitopes encompassing both features are responsible for the cross-reactivity of antibodies between human and plant profilins thought to be responsible for type I allergies.
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Affiliation(s)
- K S Thorn
- Henry H Hoyt Laboratory, Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
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23
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Abstract
Platelets circulate in the blood as discoid cells which, when activated, change shape by polymerizing actin into various structures, such as filopodia and stress fibers. In order to understand this process, it is necessary to determine how many other proteins are involved. As a first step in defining the full complement of actin-binding proteins in platelets, filamentous (F)-actin affinity chromatography was used. This approach identified > 30 different proteins from ADP-activated human blood platelets which represented 4% of soluble protein. Although a number of these proteins are previously identified platelet actin-binding proteins, many others appeared to be novel. Fourteen different polyclonal antibodies were raised against these apparently novel proteins and used to sort them into nine categories based on their molecular weights and on their location in the sarcomere of striated muscle, in fibroblasts and in spreading platelets. Ninety-three percent of these proteins (13 of 14 proteins tested) were found to be associated with actin-rich structures in vivo. Four distinct actin filament structures were found to form during the initial 15 min of activation on glass: filopodia, lamellipodia, a contractile ring encircling degranulating granules, and thick bundles of filaments resembling stress fibers. Actin-binding proteins not localized in the discoid cell became highly concentrated in one or another of these actin-based structures during spreading, such that each structure contains a different complement of proteins. These results present crucial information about the complexity of the platelet cytoskeleton, demonstrating that four different actin-based structures form during the first 15 min of surface activation, and that there remain many as yet uncharacterized proteins awaiting further investigation that are differentially involved in this process.
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Affiliation(s)
- E L Bearer
- Division of Biology and Medicine, Brown University, Providence, RI 02912, USA
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24
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Collod G, Babron MC, Jondeau G, Coulon M, Weissenbach J, Dubourg O, Bourdarias JP, Bonaïti-Pellié C, Junien C, Boileau C. A second locus for Marfan syndrome maps to chromosome 3p24.2-p25. Nat Genet 1994; 8:264-8. [PMID: 7632217 PMCID: PMC2045693 DOI: 10.1038/ng1194-264] [Citation(s) in RCA: 135] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Marfan syndrome (MFS) is an autosomal dominant connective-tissue disorder characterized by skeletal, ocular and cardiovascular defects of highly variable expressivity. The diagnosis relies solely on clinical criteria requiring anomalies in at least two systems. By excluding the chromosome 15 disease locus, fibrillin 1 (FBN1), in a large French family with typical cardiovascular and skeletal anomalies, we raised the issue of genetic heterogeneity in MFS and the implication of a second locus (MFS2). Linkage analyses, performed in this family, have localized MFS2 to a region of 9 centiMorgans between D3S1293 and D3S1283, at 3p24.2-p25. In this region, the highest lod score was found with D3S2336, of 4.89 (theta = 0.05). By LINKMAP analyses, the most probable position for the second locus in MFS was at D3S2335.
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Affiliation(s)
- Gwenaëlle Collod
- Génétique, chromosome et cancer
INSERM : U383Université René Descartes - Paris VGh Necker - Enfants Malades
149-161, Rue de Sevres
75743 PARIS CEDEX 15,FR
- * Correspondence should be adressed to: Gwenaëlle Collod
| | - Marie-Claude Babron
- Epidémiologie génétique
INSERM : U155Chateau de Longchamp
, Carrefour de Longchamp, Bois de boulogne
75016 PARIS Cedex,FR
| | - Guillaume Jondeau
- Service de Cardiologie
AP-HP Hôpital Ambroise Paré9, avenue Charles-de-Gaulle
92104 Boulogne cedex,FR
| | - Monique Coulon
- Génétique, chromosome et cancer
INSERM : U383Université René Descartes - Paris VGh Necker - Enfants Malades
149-161, Rue de Sevres
75743 PARIS CEDEX 15,FR
| | | | - Olivier Dubourg
- Service de Cardiologie
AP-HP Hôpital Ambroise Paré9, avenue Charles-de-Gaulle
92104 Boulogne cedex,FR
| | - Jean-Pierre Bourdarias
- Service de Cardiologie
AP-HP Hôpital Ambroise Paré9, avenue Charles-de-Gaulle
92104 Boulogne cedex,FR
| | - Catherine Bonaïti-Pellié
- Epidémiologie génétique
INSERM : U155Chateau de Longchamp
, Carrefour de Longchamp, Bois de boulogne
75016 PARIS Cedex,FR
| | - Claudine Junien
- Génétique, chromosome et cancer
INSERM : U383Université René Descartes - Paris VGh Necker - Enfants Malades
149-161, Rue de Sevres
75743 PARIS CEDEX 15,FR
- Laboratoire Central de Biochimie et de Génétique Moléculaire
AP-HP Hôpital Ambroise Paré9 avenue Charles de Gaulle
92104 Boulogne Cedex,FR
| | - Catherine Boileau
- Génétique, chromosome et cancer
INSERM : U383Université René Descartes - Paris VGh Necker - Enfants Malades
149-161, Rue de Sevres
75743 PARIS CEDEX 15,FR
- Laboratoire Central de Biochimie et de Génétique Moléculaire
AP-HP Hôpital Ambroise Paré9 avenue Charles de Gaulle
92104 Boulogne Cedex,FR
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25
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Goldstein C, Liaw P, Jimenez SA, Buchberg AM, Siracusa LD. Of mice and Marfan: genetic linkage analyses of the fibrillin genes, Fbn1 and Fbn2, in the mouse genome. Mamm Genome 1994; 5:696-700. [PMID: 7873879 DOI: 10.1007/bf00426075] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The fibrillin genes, FBN1 and FBN2, encode large extracellular matrix glycoproteins involved in the structure and function of microfibrils. Mutations in FBN1 are found in patients with Marfan syndrome, a heritable connective tissue disease that primarily affects the cardiovascular, ocular, and skeletal systems. We extended the studies of these genes by determining their chromosomal position in the mouse genome. Restriction fragment length polymorphisms (RFLPs) between the progenitors of an interspecific backcross involving AEJ/Gn and Mus spretus mice were used to establish the segregation patterns of the murine homologs, Fbn1 and Fbn2, in the backcross progeny. The results position Fbn1 between the B2m and Illa genes on mouse Chromosome (Chr) 2 and establish its candidacy for the Tight skin (Tsk) mutation. The results position Fbn2 between the D18Mit35 and Pdgfrb loci in the central region of mouse Chr 18. Fbn2 maps near three mutations [bouncy (bc), plucked (pk), and shaker with syndactyly (sy)] and may be a candidate for the pk mutation.
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Affiliation(s)
- C Goldstein
- Department of Microbiology and Immunology, Jefferson Cancer Institute, Philadelphia, Pennsylvania 19107
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26
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Pope B, Way M, Matsudaira PT, Weeds A. Characterisation of the F-actin binding domains of villin: classification of F-actin binding proteins into two groups according to their binding sites on actin. FEBS Lett 1994; 338:58-62. [PMID: 8307157 DOI: 10.1016/0014-5793(94)80116-9] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The F-actin binding properties of chicken villin, its headpiece and domains 2-3 (V2-3) have been analysed to identify sites involved in bundle formation. Headpiece and V2-3 bind actin with Kd values of approximately 7 microM and approximately 0.3 microM, respectively, at low ionic strength. V2-3 binding, like that of villin, is weakened with increasing salt concentration; headpiece binding is not. Competition experiments show that headpiece and V2-3 bind to different sites on actin, forming the two cross-linking sites of villin. Headpiece does not compete with the F-actin binding domains of gelsolin or alpha-actinin, but it dissociates actin depolymerizing factor. We suggest that the F-actin binding domains of actin severing, crosslinking and capping proteins can be organized into two classes.
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Affiliation(s)
- B Pope
- MRC Laboratory of Molecular Biology, Cambridge, UK
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27
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Abstract
Recent research on F-actin capping proteins has concentrated on three main areas. The discovery that controlled actin polymerization is the driving force for intracellular movement suggests an important role for capping proteins in regulating filament number and length. A capping protein from Dictyostelium (related to heat-shock protein HSP70) has been characterized that is activated by external stimuli. This provides a pivotal connection between extracellular signalling, cytoskeletal reorganization and locomotory behaviour. The roles of individual actin-binding sites in the gelsolin family of severing/capping proteins and binding sites for phosphatidylinositol 4,5-bisphosphate have been identified.
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Affiliation(s)
- A Weeds
- MRC Laboratory of Molecular Biology, Cambridge, UK
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28
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Affiliation(s)
- A G Weeds
- M.R.C. Laboratory of Molecular Biology, Cambridge, U.K
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