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Morozov AA, Bedoshvili YD, Popova MS, Likhoshway YV. Novel subfamilies of actin-regulating proteins. Mar Genomics 2017; 37:128-134. [PMID: 29074263 DOI: 10.1016/j.margen.2017.10.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 07/28/2017] [Accepted: 10/11/2017] [Indexed: 02/07/2023]
Abstract
Ability of actin to polymerise and depolymerise makes it essential to key functions of eukaryotic cell. The functioning of actin is controlled by a host of regulatory proteins, the repertoire of which in diatoms is known to remarkably differ from other organisms. We have performed a phylogenetic analysis of 521 actin and actin-related proteins' aminoacid sequences, as well as 190 sequences of gelsolin family proteins from various genomic and transcriptomic datasets. Based on the results of this analysis, as well as on the presence of clade-specific indels in some of the actin-related proteins, we describe a novel ARP subfamily, dubbed ARP12, which is specific to heterokonts and related organisms. We also describe two novel diatom-specific subfamilies, dGRC1 and dGRC2, among short gelsolin repeat-containing proteins.
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Affiliation(s)
- A A Morozov
- Cell Ultrastructure Dept., Limnological Institute SB RAS, Irkutsk, Russia.
| | - Ye D Bedoshvili
- Cell Ultrastructure Dept., Limnological Institute SB RAS, Irkutsk, Russia
| | - M S Popova
- Cell Ultrastructure Dept., Limnological Institute SB RAS, Irkutsk, Russia
| | - Ye V Likhoshway
- Cell Ultrastructure Dept., Limnological Institute SB RAS, Irkutsk, Russia
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2
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Pizarro-Cerdá J, Chorev DS, Geiger B, Cossart P. The Diverse Family of Arp2/3 Complexes. Trends Cell Biol 2016; 27:93-100. [PMID: 27595492 DOI: 10.1016/j.tcb.2016.08.001] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 07/29/2016] [Accepted: 08/01/2016] [Indexed: 11/17/2022]
Abstract
The Arp2/3 complex has so far been considered to be a single seven-subunit protein complex required for actin nucleation and actin filament polymerization in diverse critical cellular functions including phagocytosis, vesicular trafficking and lamellipodia extension. The Arp2/3 complex is also exploited by bacterial pathogens and viruses during cellular infectious processes. Recent studies suggest that some subunits of the complex are dispensable in specific cellular contexts, pointing to the existence of alternative 'hybrid Arp2/3 complexes' containing other components such as vinculin or α-actinin, as well as different isoforms or phosphorylation variants of canonical Arp2/3 subunits. Therefore, this diversity should be now considered when assigning specific Arp2/3 assemblies to different actin-dependent cellular processes.
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Affiliation(s)
- Javier Pizarro-Cerdá
- Institut Pasteur, Unité des Interactions Bactéries Cellules, Paris F-75015, France; INSERM, U604, Paris F-75015, France; INRA, USC2020, Paris F-75015, France.
| | - Dror Shlomo Chorev
- The Weizmann Institute of Science, Department of Molecular Cell Biology, Rehovot 761001, Israel; Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, Oxford OX1 3QZ, UK
| | - Benjamin Geiger
- The Weizmann Institute of Science, Department of Molecular Cell Biology, Rehovot 761001, Israel
| | - Pascale Cossart
- Institut Pasteur, Unité des Interactions Bactéries Cellules, Paris F-75015, France; INSERM, U604, Paris F-75015, France; INRA, USC2020, Paris F-75015, France.
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3
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Koumandou VL, Wickstead B, Ginger ML, van der Giezen M, Dacks JB, Field MC. Molecular paleontology and complexity in the last eukaryotic common ancestor. Crit Rev Biochem Mol Biol 2014; 48:373-96. [PMID: 23895660 PMCID: PMC3791482 DOI: 10.3109/10409238.2013.821444] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Eukaryogenesis, the origin of the eukaryotic cell, represents one of the fundamental evolutionary transitions in the history of life on earth. This event, which is estimated to have occurred over one billion years ago, remains rather poorly understood. While some well-validated examples of fossil microbial eukaryotes for this time frame have been described, these can provide only basic morphology and the molecular machinery present in these organisms has remained unknown. Complete and partial genomic information has begun to fill this gap, and is being used to trace proteins and cellular traits to their roots and to provide unprecedented levels of resolution of structures, metabolic pathways and capabilities of organisms at these earliest points within the eukaryotic lineage. This is essentially allowing a molecular paleontology. What has emerged from these studies is spectacular cellular complexity prior to expansion of the eukaryotic lineages. Multiple reconstructed cellular systems indicate a very sophisticated biology, which by implication arose following the initial eukaryogenesis event but prior to eukaryotic radiation and provides a challenge in terms of explaining how these early eukaryotes arose and in understanding how they lived. Here, we provide brief overviews of several cellular systems and the major emerging conclusions, together with predictions for subsequent directions in evolution leading to extant taxa. We also consider what these reconstructions suggest about the life styles and capabilities of these earliest eukaryotes and the period of evolution between the radiation of eukaryotes and the eukaryogenesis event itself.
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Affiliation(s)
- V Lila Koumandou
- Biomedical Research Foundation, Academy of Athens, Soranou Efesiou 4, Athens 115 27, Greece
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4
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Liu Z, Yang X, Chen C, Liu B, Ren B, Wang L, Zhao K, Yu S, Ming H. Expression of the Arp2/3 complex in human gliomas and its role in the migration and invasion of glioma cells. Oncol Rep 2013; 30:2127-36. [PMID: 23969835 DOI: 10.3892/or.2013.2669] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 07/25/2013] [Indexed: 11/06/2022] Open
Abstract
A hallmark of directional cell migration is localized actin polymerization at the leading protrusions of the cell. The Arp2/3 complex nucleates the formation of the dendritic actin network (lamellipodia) at the leading edge of motile cells. This study was designed to investigate the role of the Arp2/3 complex in the infiltrative behavior of glioma cells. Immunofluorescence and western blotting showed a positive correlation between the expression of Arp2/3 and the malignancy of glioma specimens (r=0.686, P=0.02) and confocal microscopy demonstrated localization of the Arp2/3 complex in lamellipodia of glioma cells. Furthermore, we examined the effects of Arp2/3 complex inhibition in U251, LN229 and SNB19 glioma cells using CK666, an Arp2/3 complex inhibitor. Glioma cells lost lamellipodia and cell polarity after treatment with CK666. Inhibition of the Arp2/3 complex significantly affected the ability of glioma cells to migrate and invade. In the wound-healing assay, CK666 markedly inhibited cell migration, U251 cell migration was inhibited to 38.73±3.45% of control, LN229 cells to 57.40±2.16% of control and SNB19 cells to 34.17±3.82% of control. Also, CK666 significantly impaired Transwell chamber invasion capability of U251, LN229 and SNB19 cells compared with DMSO control by 72.70±4.86, 39.12±8.42 and 41.41±4.66%, respectively. The Arp2/3 complex is, therefore, likely to be a crucial participant in glioma cell invasion and migration, and may represent a target for therapeutic intervention.
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Affiliation(s)
- Zhifeng Liu
- Neuro-Oncology Laboratory, Tianjin Neurological Institute, Tianjin 300052, P.R. China
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5
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Abstract
Several bacterial pathogens, including Listeria monocytogenes, Shigella flexneri and Rickettsia spp., have evolved mechanisms to actively spread within human tissues. Spreading is initiated by the pathogen-induced recruitment of host filamentous (F)-actin. F-actin forms a tail behind the microbe, propelling it through the cytoplasm. The motile pathogen then encounters the host plasma membrane, forming a bacterium-containing protrusion that is engulfed by an adjacent cell. Over the past two decades, much progress has been made in elucidating mechanisms of F-actin tail formation. Listeria and Shigella produce tails of branched actin filaments by subverting the host Arp2/3 complex. By contrast, Rickettsia forms tails with linear actin filaments through a bacterial mimic of eukaryotic formins. Compared with F-actin tail formation, mechanisms controlling bacterial protrusions are less well understood. However, recent findings have highlighted the importance of pathogen manipulation of host cell–cell junctions in spread. Listeria produces a soluble protein that enhances bacterial protrusions by perturbing tight junctions. Shigella protrusions are engulfed through a clathrin-mediated pathway at ‘tricellular junctions’—specialized membrane regions at the intersection of three epithelial cells. This review summarizes key past findings in pathogen spread, and focuses on recent developments in actin-based motility and the formation and internalization of bacterial protrusions.
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Affiliation(s)
- Keith Ireton
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.
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6
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Berepiki A, Lichius A, Read ND. Actin organization and dynamics in filamentous fungi. Nat Rev Microbiol 2011; 9:876-87. [PMID: 22048737 DOI: 10.1038/nrmicro2666] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Growth and morphogenesis of filamentous fungi is underpinned by dynamic reorganization and polarization of the actin cytoskeleton. Actin has crucial roles in exocytosis, endocytosis, organelle movement and cytokinesis in fungi, and these processes are coupled to the production of distinct higher-order structures (actin patches, cables and rings) that generate forces or serve as tracks for intracellular transport. New approaches for imaging actin in living cells are revealing important similarities and differences in actin architecture and organization within the fungal kingdom, and have yielded key insights into cell polarity, tip growth and long-distance intracellular transport. In this Review, we discuss the contribution that recent live-cell imaging and mutational studies have made to our understanding of the dynamics and regulation of actin in filamentous fungi.
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Affiliation(s)
- Adokiye Berepiki
- Fungal Cell Biology Group, Institute of Cell Biology, Rutherford Building, University of Edinburgh, Edinburgh, UK
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8
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Oma Y, Harata M. Actin-related proteins localized in the nucleus: from discovery to novel roles in nuclear organization. Nucleus 2011; 2:38-46. [PMID: 21647298 PMCID: PMC3104808 DOI: 10.4161/nucl.2.1.14510] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 12/15/2010] [Accepted: 12/17/2010] [Indexed: 12/18/2022] Open
Abstract
The actin family consists of conventional actin and actin-related proteins (ARPs), and the members show moderate similarity and share the same basal structure. Following the finding of various ARPs in the cytoplasm in the 1990s, multiple subfamilies that are localized predominantly in the nucleus were identified. Consistent with these cytological observations, subsequent biochemical analyses revealed the involvement of the nuclear ARPs in ATP-dependent chromatin-remodeling and histone acetyltransferase complexes. In addition to their contribution to chromatin remodeling, recent studies have shown that nuclear ARPs have roles in the organization of the nucleus that are independent of the activity of the above-mentioned complexes. Therefore, nuclear ARPs are recognized as novel key regulators of genome function, and affect not only the remodeling of chromatin but also the spatial arrangement and dynamics of chromatin within the nucleus.
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Affiliation(s)
- Yukako Oma
- Laboratory of Molecular Biology, Graduate School of Agricultural Science, Tohoku University, Sendai, Japan
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9
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Epp E, Walther A, Lépine G, Leon Z, Mullick A, Raymond M, Wendland J, Whiteway M. Forward genetics in Candida albicans that reveals the Arp2/3 complex is required for hyphal formation, but not endocytosis. Mol Microbiol 2010; 75:1182-98. [PMID: 20141603 DOI: 10.1111/j.1365-2958.2009.07038.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Candida albicans is a diploid fungal pathogen lacking a defined complete sexual cycle, and thus has been refractory to standard forward genetic analysis. Instead, transcription profiling and reverse genetic strategies based on Saccharomyces cerevisiae have typically been used to link genes to functions. To overcome restrictions inherent in such indirect approaches, we have investigated a forward genetic mutagenesis strategy based on the UAU1 technology. We screened 4700 random insertion mutants for defects in hyphal development and linked two new genes (ARP2 and VPS52) to hyphal growth. Deleting ARP2 abolished hyphal formation, generated round and swollen yeast phase cells, disrupted cortical actin patches and blocked virulence in mice. The mutants also showed a global lack of induction of hyphae-specific genes upon the yeast-to-hyphae switch. Surprisingly, both arp2 Delta/Delta and arp2 Delta/Delta arp3 Delta/Delta mutants were still able to endocytose FM4-64 and Lucifer Yellow, although as shown by time-lapse movies internalization of FM4-64 was somewhat delayed in mutant cells. Thus the non-essential role of the Arp2/3 complex discovered by forward genetic screening in C. albicans showed that uptake of membrane components from the plasma membrane to vacuolar structures is not dependent on this actin nucleating machinery.
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Affiliation(s)
- Elias Epp
- Biotechnology Research Institute, National Research Council of Canada, Montréal, QC H4P 2R2, Canada
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10
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Finka A, Saidi Y, Goloubinoff P, Neuhaus JM, Zrÿd JP, Schaefer DG. The knock-out of ARP3a gene affects F-actin cytoskeleton organization altering cellular tip growth, morphology and development in moss Physcomitrella patens. ACTA ACUST UNITED AC 2008; 65:769-84. [PMID: 18613119 DOI: 10.1002/cm.20298] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The seven subunit Arp2/3 complex is a highly conserved nucleation factor of actin microfilaments. We have isolated the genomic sequence encoding a putative Arp3a protein of the moss Physcomitrella patens. The disruption of this ARP3A gene by allele replacement has generated loss-of-function mutants displaying a complex developmental phenotype. The loss-of function of ARP3A gene results in shortened, almost cubic chloronemal cells displaying affected tip growth and lacking differentiation to caulonemal cells. In moss arp3a mutants, buds differentiate directly from chloronemata to form stunted leafy shoots having differentiated leaves similar to wild type. Yet, rhizoids never differentiate from stem epidermal cells. To characterize the F-actin organization in the arp3a-mutated cells, we disrupted ARP3A gene in the previously described HGT1 strain expressing conditionally the GFP-talin marker. In vivo observation of the F-actin cytoskeleton during P. patens development demonstrated that loss-of-function of Arp3a is associated with the disappearance of specific F-actin cortical structures associated with the establishment of localized cellular growth domains. Finally, we show that constitutive expression of the P. patens Arp3a and its Arabidopsis thaliana orthologs efficiently complement the mutated phenotype indicating a high degree of evolutionary conservation of the Arp3 function in land plants.
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Affiliation(s)
- Andrija Finka
- Department of Plant Molecular Biology, University of Lausanne, Lausanne, Switzerland.
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11
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Codlin S, Haines RL, Mole SE. btn1 affects endocytosis, polarization of sterol-rich membrane domains and polarized growth in Schizosaccharomyces pombe. Traffic 2008; 9:936-50. [PMID: 18346214 PMCID: PMC2440566 DOI: 10.1111/j.1600-0854.2008.00735.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
btn1, the Schizosaccharomyces pombe orthologue of the human Batten disease gene CLN3, exerts multiple cellular effects. As well as a role in vacuole pH homoeostasis, we now show that Btn1p is essential for growth at high temperatures. Its absence results in progressive defects at 37°C that culminate in total depolarized growth and cell lysis. These defects are preceded by a progressive failure to correctly polarize sterol-rich domains after cytokinesis and are accompanied by loss of Myo1p localization. Furthermore, we found that in Sz. pombe, sterol spreading is linked to defective formation/polarization of F-actin patches and disruption of endocytosis and that these processes are aberrant in btn1Δ cells. Consistent with a role for Btn1p in polarized growth, Btn1p has an altered location at 37°C and is retained in actin-dependent endomembrane structures near the cell poles or septum.
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Affiliation(s)
- Sandra Codlin
- MRC Laboratory for Molecular Cell Biology, University College London, WC1E 6BT London, UK
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12
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Abstract
The cellular functions of the actin cytoskeleton require precise regulation of both the initiation of actin polymerization and the organization of the resulting filaments. The actin-related protein-2/3 (ARP2/3) complex is a central player in this regulation. A decade of study has begun to shed light on the molecular mechanisms by which this powerful machine controls the polymerization, organization and recycling of actin-filament networks, both in vitro and in the living cell.
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Affiliation(s)
- Erin D Goley
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
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Muller J, Oma Y, Vallar L, Friederich E, Poch O, Winsor B. Sequence and comparative genomic analysis of actin-related proteins. Mol Biol Cell 2005; 16:5736-48. [PMID: 16195354 PMCID: PMC1289417 DOI: 10.1091/mbc.e05-06-0508] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Actin-related proteins (ARPs) are key players in cytoskeleton activities and nuclear functions. Two complexes, ARP2/3 and ARP1/11, also known as dynactin, are implicated in actin dynamics and in microtubule-based trafficking, respectively. ARP4 to ARP9 are components of many chromatin-modulating complexes. Conventional actins and ARPs codefine a large family of homologous proteins, the actin superfamily, with a tertiary structure known as the actin fold. Because ARPs and actin share high sequence conservation, clear family definition requires distinct features to easily and systematically identify each subfamily. In this study we performed an in depth sequence and comparative genomic analysis of ARP subfamilies. A high-quality multiple alignment of approximately 700 complete protein sequences homologous to actin, including 148 ARP sequences, allowed us to extend the ARP classification to new organisms. Sequence alignments revealed conserved residues, motifs, and inserted sequence signatures to define each ARP subfamily. These discriminative characteristics allowed us to develop ARPAnno (http://bips.u-strasbg.fr/ARPAnno), a new web server dedicated to the annotation of ARP sequences. Analyses of sequence conservation among actins and ARPs highlight part of the actin fold and suggest interactions between ARPs and actin-binding proteins. Finally, analysis of ARP distribution across eukaryotic phyla emphasizes the central importance of nuclear ARPs, particularly the multifunctional ARP4.
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Affiliation(s)
- Jean Muller
- Laboratoire de Biologie et Génomique Structurales, Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, BP 163, 67404 Illkirch Cedex, France.
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14
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D'Agostino JL, Goode BL. Dissection of Arp2/3 complex actin nucleation mechanism and distinct roles for its nucleation-promoting factors in Saccharomyces cerevisiae. Genetics 2005; 171:35-47. [PMID: 16183906 PMCID: PMC1456526 DOI: 10.1534/genetics.105.040634] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2005] [Accepted: 05/31/2005] [Indexed: 11/18/2022] Open
Abstract
Actin nucleation by the Arp2/3 complex is under tight control, remaining inactive until stimulation by nucleation-promoting factors (NPFs). Although multiple NPFs are expressed in most cell types, little is known about how they are coordinated and whether they perform similar or distinct functions. We examined genetic relationships among the four S. cerevisiae NPFs. Combining las17delta with pan1-101 or myo3delta myo5delta was lethal at all temperatures, whereas combining pan1-101 with myo3delta myo5delta showed no genetic interaction and abp1delta partially suppressed las17delta. These data suggest that NPFs have distinct and overlapping functions in vivo. We also tested genetic interactions between each NPF mutant and seven different temperature-sensitive arp2 alleles and purified mutant Arp2/3 complexes to compare their activities. Two arp2 alleles with mutations at the barbed end were severely impaired in nucleation, providing the first experimental evidence that Arp2 nucleates actin at its barbed end in vitro and in vivo. Another arp2 allele caused partially unregulated ("leaky") nucleation in the absence of NPFs. Combining this mutant with a partially unregulated allele in a different subunit of Arp2/3 complex was lethal, suggesting that cells cannot tolerate high levels of unregulated activity. Genetic interactions between arp2 alleles and NPF mutants point to Abp1 having an antagonistic role with respect to other NPFs, possibly serving to attenuate their stronger activities. In support of this model, Abp1 binds strongly to Arp2/3 complex, yet has notably weak nucleation-promoting activity and inhibits Las17 activity on Arp2/3 complex in a dose-responsive manner.
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15
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Imamura T, Kanai F, Kawakami T, Amarsanaa J, Ijichi H, Hoshida Y, Tanaka Y, Ikenoue T, Tateishi K, Kawabe T, Arakawa Y, Miyagishi M, Taira K, Yokosuka O, Omata M. Proteomic analysis of the TGF-beta signaling pathway in pancreatic carcinoma cells using stable RNA interference to silence Smad4 expression. Biochem Biophys Res Commun 2004; 318:289-96. [PMID: 15110786 DOI: 10.1016/j.bbrc.2004.04.029] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2004] [Indexed: 11/24/2022]
Abstract
Smad4 is a tumor-suppressor gene that is lost or mutated in 50% of pancreatic carcinomas. Smad4 is also an intracellular transmitter of transforming growth factor-beta (TGF-beta) signals. Although its tumor-suppressor function is presumed to reside in its capacity to mediate TGF-beta-induced growth inhibition, there seems to be a Smad4-independent TGF-beta signaling pathway. Here, we succeeded in establishing Smad4 knockdown (S4KD) pancreatic cancer cell lines using stable RNA interference. Smad4 protein expression and TGF-beta-Smad4 signaling were impaired in S4KD cells, and we compared the proteomic changes with TGF-beta stimulation using two-dimensional gel electrophoresis (2-DE) and mass spectrometry. We identified five proteins that were up-regulated and seven proteins that were down-regulated; 10 of them were novel targets for TGF-beta. These proteins function in processes such as cytoskeletal regulation, cell cycle, and oxidative stress. Introducing siRNA-mediated gene silencing into proteomics revealed a novel TGF-beta signal pathway that did not involve Smad4.
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Affiliation(s)
- Takaaki Imamura
- Department of Gastroenterology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
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16
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El-Din El-Assal S, Le J, Basu D, Mallery EL, Szymanski DB. DISTORTED2 encodes an ARPC2 subunit of the putative Arabidopsis ARP2/3 complex. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 38:526-38. [PMID: 15086808 DOI: 10.1111/j.1365-313x.2004.02065.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Arabidopsis trichomes are unicellular, branched structures that have highly constrained requirements for the cytoskeleton. The 'distorted group' genes function downstream from microtubule-based branch initiation, and are required during the actin-dependent phase of polarized stalk and branch expansion. Of the eight known 'distorted group' genes, a subset encode homologs of ARP2/3 complex subunits. In eukaryotic cells, the seven-protein ARP2/3 complex nucleates actin filament networks that push on the plasma membrane and organelles. In plants cells, the existence and function of an ARP2/3 complex is unclear. In this paper, we report that DISTORTED2 (DIS2) encodes a paralogue of the ARP2/3 complex subunit ARPC2. DIS2 has ARPC2 activity, based on its ability to rescue the growth defects of arpc2 (arc35Delta) null yeast cells. Like known ARPC2s, DIS2 physically interacts with ARPC4. Mutations in DIS2 cause a distorted trichome phenotype, defects in cell-cell adhesion, and a modest reduction in shoot FW. The actin cytoskeleton in dis2 trichomes is extensive, but developing branches fail to generate and maintain highly organized cytoplasmic actin bundles.
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Affiliation(s)
- Salah El-Din El-Assal
- Agronomy Department, Purdue University, Lilly Hall, 915 West State Street, West Lafayette, IN 47907-2054, USA
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17
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Le J, El-Assal SED, Basu D, Saad ME, Szymanski DB. Requirements for Arabidopsis ATARP2 and ATARP3 during epidermal development. Curr Biol 2003; 13:1341-7. [PMID: 12906796 DOI: 10.1016/s0960-9822(03)00493-7] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Plant cells employ the actin cytoskeleton to stably position organelles, as tracks for long distance transport, and to reorganize the cytoplasm in response to developmental and environmental cues. While diverse classes of actin binding proteins have been implicated in growth control, the mechanisms of cytoskeletal reorganization and the cellular functions of specific actin filament arrays are unclear. Arabidopsis trichome morphogenesis includes distinct requirements for the microtubule and actin filament cytoskeletons. It also is a genetically tractable process that is providing new knowledge about cytoskeleton function in plants. The "distorted group" of mutants defines a class of at least eight genes that are required during the actin-dependent phase of trichome growth. Using map-based cloning and a candidate gene approach, we identified mutations in ARP3 (ATARP3) and ARP2 (ATARP2) genes as the cause of the distorted1 (dis1) and wurm (wrm) phenotypes, respectively. ARP2 and ARP3 are components of the evolutionarily conserved ARP2/3 complex that nucleates actin filament polymerization [3]. Mutations in DIS1 and WRM caused severe trichome growth defects but had relatively mild effects on shoot development. DIS1 rescued the phenotype of Deltaarp3 when overexpressed in S. cerevisiae. Developing dis1 trichomes had defects in cytoplasmic actin bundle organization and reduced relative amounts of cytoplasmic actin filaments in developing branches.
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Affiliation(s)
- Jie Le
- Agronomy Department, Purdue University, Lily Hall, 915 West State Street, West Lafayette, IN 47907-2054, USA.
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18
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Abstract
Eukaryotic cells use actin polymerization to change shape, move, and internalize extracellular materials by phagocytosis and endocytosis, and to form contractile structures. In addition, several pathogens have evolved to use host cell actin assembly for attachment, internalization, and cell-to-cell spread. Although cells possess multiple mechanisms for initiating actin polymerization, attention in the past five years has focused on the regulation of actin nucleation-the formation of new actin filaments from actin monomers. The Arp2/3 complex and the multiple nucleation-promoting factors (NPFs) that regulate its activity comprise the only known cellular actin-nucleating factors and may represent a universal machine, conserved across eukaryotic phyla, that nucleates new actin filaments for various cellular structures with numerous functions. This review focuses on our current understanding of the mechanism of actin nucleation by the Arp2/3 complex and NPFs and how these factors work with other cytoskeletal proteins to generate structurally and functionally diverse actin arrays in cells.
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Affiliation(s)
- Matthew D Welch
- Department of Molecular and Cell Biology, 301 LSA, University of California, Berkeley 94720-3200, USA.
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Harata M, Nishimori K, Hatta S. Identification of two cDNAs for human actin-related proteins (Arps) that have remarkable similarity to conventional actin. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1522:130-3. [PMID: 11750065 DOI: 10.1016/s0167-4781(01)00315-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We identified two cDNAs coding for the novel human actin-related proteins (Arps) hArpM1 and hArpM2. Both of them show remarkable similarity to conventional actin, and the ATP-binding motif and nuclear-export signals of actin are highly conserved. Their mRNAs are expressed in all tested human tissues, but in smaller amounts than that of actin. These features suggest that hArpM1 and M2 are involved in cytoskeletal organization like other cytoplasmic Arp subfamilies.
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Affiliation(s)
- M Harata
- Laboratory of Molecular Biology, Department of Molecular and Cell Biology, Division of Life Science, Graduate School of Agricultural Science, Tohoku University, Tsutsumidori-Amamiyamachi 1-1, Aoba-ku, 981-8555, Sendai, Japan.
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20
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Goldberg MB. Actin-based motility of intracellular microbial pathogens. Microbiol Mol Biol Rev 2001; 65:595-626, table of contents. [PMID: 11729265 PMCID: PMC99042 DOI: 10.1128/mmbr.65.4.595-626.2001] [Citation(s) in RCA: 175] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
A diverse group of intracellular microorganisms, including Listeria monocytogenes, Shigella spp., Rickettsia spp., and vaccinia virus, utilize actin-based motility to move within and spread between mammalian host cells. These organisms have in common a pathogenic life cycle that involves a stage within the cytoplasm of mammalian host cells. Within the cytoplasm of host cells, these organisms activate components of the cellular actin assembly machinery to induce the formation of actin tails on the microbial surface. The assembly of these actin tails provides force that propels the organisms through the cell cytoplasm to the cell periphery or into adjacent cells. Each of these organisms utilizes preexisting mammalian pathways of actin rearrangement to induce its own actin-based motility. Particularly remarkable is that while all of these microbes use the same or overlapping pathways, each intercepts the pathway at a different step. In addition, the microbial molecules involved are each distinctly different from the others. Taken together, these observations suggest that each of these microbes separately and convergently evolved a mechanism to utilize the cellular actin assembly machinery. The current understanding of the molecular mechanisms of microbial actin-based motility is the subject of this review.
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Affiliation(s)
- M B Goldberg
- Infectious Disease Division, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
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21
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Nakano K, Satoh K, Morimatsu A, Ohnuma M, Mabuchi I. Interactions among a fimbrin, a capping protein, and an actin-depolymerizing factor in organization of the fission yeast actin cytoskeleton. Mol Biol Cell 2001; 12:3515-26. [PMID: 11694585 PMCID: PMC60272 DOI: 10.1091/mbc.12.11.3515] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We report studies of the fission yeast fimbrin-like protein Fim1, which contains two EF-hand domains and two actin-binding domains (ABD1 and ABD2). Fim1 is a component of both F-actin patches and the F-actin ring, but not of F-actin cables. Fim1 cross-links F-actin in vitro, but a Fim1 protein lacking either EF-hand domains (Fim1A12) or both the EF-hand domains and ABD1 (Fim1A2) has no actin cross-linking activity. Overexpression of Fim1 induced the formation of F-actin patches throughout the cell cortex, whereas the F-actin patches disappear in cells overexpressing Fim1A12 or Fim1A2. Thus, the actin cross-linking activity of Fim1 is probably important for the formation of F-actin patches. The overexpression of Fim1 also excluded the actin-depolymerizing factor Adf1 from the F-actin patches and inhibited the turnover of actin in these structures. Thus, Fim1 may function in stabilizing the F-actin patches. We also isolated the gene encoding Acp1, a subunit of the heterodimeric F-actin capping protein. fim1 acp1 double null cells showed more severe defects in the organization of the actin cytoskeleton than those seen in each single mutant. Thus, Fim1 and Acp1 may function in a similar manner in the organization of the actin cytoskeleton. Finally, genetic studies suggested that Fim1 may function in cytokinesis in cooperation with Cdc15 (PSTPIP) and Rng2 (IQGAP), respectively.
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Affiliation(s)
- K Nakano
- Division of Biology, Department of Life Sciences, Graduate Program in Interdisciplinary Sciences, School of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan.
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22
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Affiliation(s)
- L M Machesky
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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23
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Khamessan A, Naghibalhossaini F, Vedadi M, Johnstone RM. Mutated-gamma-actin restores growth to a yeast amino acid transport defective mutant. J Cell Physiol 2001; 186:124-35. [PMID: 11147807 DOI: 10.1002/1097-4652(200101)186:1<124::aid-jcp1007>3.0.co;2-q] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
A mutated yeast cell 22574d lacking all three proline transporters, PUT4, UGA4, and GAP1, and incapable of growth on proline recovers its lost ability to grow on proline as sole nitrogen source when transformed with a mutagenized mouse gamma-actin cDNA (M-gamma-A). Native mouse gamma-actin cDNA is ineffective. The 3'-region of gamma-actin cDNA was mutagenized to resemble E51 cDNA previously isolated from Ehrlich tumor cells. The E51 cDNA has an extended reading frame in the 3'-region compared to that in native gamma-actin. The extension of the open reading frame in E51 cDNA, was found to be due to an additional pair of bases (TG) at position 1104 of E51 cDNA. After site-directed mutagenesis of the 3'-region of native gamma-actin cDNA to resemble that of E51 cDNA, the construct, M-gamma-A cDNA, was expressed in the 22574d yeast. While the transformation with M-gamma-A increased the uptake of both proline and gamma-amino butyric acid, the transport of five other solutes was not changed by this transformation. Northern blotting of the nontransformed and the M-gamma-A-transformed 22574d cells with gene-specific probes for the three proline transporters showed the expression of an mRNA for UGA4 in both transformed and nontransformed cells but no evidence for the expression of GAP1 or PUT4. The mRNA for UGA4 was expressed at a lower level in strain 22574d than in the parent yeast sigma1278b. Furthermore, the message in the mutated cells is smaller in size by about 15%. These results are consistent with the synthesis of a mutated transporter which requires the coexpression of M-gamma-A, but not native gamma-actin, to restore physiological function, i.e., proline or gamma-amino acid transport.
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Affiliation(s)
- A Khamessan
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
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24
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Jay P, Bergé-Lefranc JL, Massacrier A, Roessler E, Wallis D, Muenke M, Gastaldi M, Taviaux S, Cau P, Berta P. ARP3beta, the gene encoding a new human actin-related protein, is alternatively spliced and predominantly expressed in brain neuronal cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:2921-8. [PMID: 10806390 DOI: 10.1046/j.1432-1327.2000.01306.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A cDNA encoding a new human actin-related protein (ARP) was cloned. The corresponding protein is highly conserved with the previously described ARP3 protein, suggesting that it represents a second isoform of the human ARP3 subfamily. This new actin-related protein was subsequently named ARP3beta and represents the second example of multiple isoforms of an actin-related protein in a single organism. The ARP3beta gene was mapped to chromosome band 7q34, centromeric to Sonic Hedgehog. Gene structure analysis revealed that at least part of the observed ARP3beta mRNA heterogeneity is caused by alternative splicing resulting in exon skipping. Transcripts produced after exon 2 skipping are predicted to encode truncated products, whose functionality is still unclear. An ARP3beta pseudogene was detected on chromosome 2p11 by database searching. Several ARP3beta mRNA species were detected by Northern blotting and their abundance varied importantly among tissues: the highest expression levels were detected in fetal and adult brain, whereas lower levels were observed in liver, muscle and pancreas. In contrast, ARP3 mRNAs were detected in all tissues tested. Using in situ hybridization, the expression of ARP3beta in brain was shown to be restricted to neurons and epithelial cells from choroid plexus. This suggests a specific function for ARP3beta in the physiology of the development and/or maintenance of distinct subsets of nerve cells.
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Affiliation(s)
- P Jay
- Institut de Génétique Humaine, CNRS UPR 1142, Montpellier, France.
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25
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Szelei J, Soto AM, Geck P, Desronvil M, Prechtl NV, Weill BC, Sonnenschein C. Identification of human estrogen-inducible transcripts that potentially mediate the apoptotic response in breast cancer. J Steroid Biochem Mol Biol 2000; 72:89-102. [PMID: 10775800 DOI: 10.1016/s0960-0760(00)00025-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Hormone manipulation has been used for several decades with the purpose of inducing breast cancer regression. On the one hand, hormone ablation and antiestrogen administration were used on the rationale that estrogens induce proliferation of their target cells. Before the advent of the antiestrogen tamoxifen, on the other hand, the estrogen agonist DES was used to obtain clinical remissions. The rationale for the use of diethylstilbestrol (DES) was totally empirical. In fact, the efficacy of both treatments was comparable. A mechanistic explanation for estrogen-induced regression is urgently needed in order to provide a rationale for its use in therapeutic fields, and to develop markers to identify this phenotype in order to recognize responsive tumors. In this report, we use E8CASS cells (a MCF7 variant) as a model to study estrogen-mediated regression. The proliferation rate of E8CASS cells is decreased by estrogens. In order to isolate mRNA sequences induced by estradiol, a subtracted library was prepared from E8CASS cells grown in the presence and absence of estrogens. Twenty nine differentially expressed unique sequences were found. Seven of them were homologous to known genes, 12 of them were homologous to expressed sequence tags (EST), and 10 sequences had no homologues in the databases. The two sequences showing the highest induction by estradiol (E9 and E43) were chosen for further analysis. The sequence of the E43 coding region has 96% homology to the bovine actin2 gene and 100% identity to bovine actin2 protein, and it is homologous to the human actin-related protein 3 (Arp3). It has been suggested that Arp3 is involved in actin nucleation. The phenotype of E8CASS cells is clearly affected by estrogen treatment. It is likely that E43 may be involved in these morphological changes. The E9 cDNA is a putative zinc-finger protein of the PHD family of transcriptional transactivators. A member of this family, Requiem, is involved in apoptosis. The E9 mRNA is highly expressed in E8CASS cells treated with estrogens, a treatment which results in decreased proliferation rate and increased DNA degradation. This correlation suggests that E9 may be a mediator of estrogen-induced regression of breast cancer.
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MESH Headings
- Actins/genetics
- Amino Acid Sequence
- Animals
- Apoptosis/drug effects
- Apoptosis/genetics
- Base Sequence
- Breast Neoplasms/genetics
- Breast Neoplasms/metabolism
- Breast Neoplasms/pathology
- Cattle
- Cell Division/drug effects
- DNA Primers/genetics
- DNA, Complementary/genetics
- DNA, Neoplasm/genetics
- Estradiol/pharmacology
- Female
- Gene Expression
- Gene Library
- Humans
- Molecular Sequence Data
- Neoplasms, Hormone-Dependent/genetics
- Neoplasms, Hormone-Dependent/metabolism
- Neoplasms, Hormone-Dependent/pathology
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Neoplasm/genetics
- RNA, Neoplasm/metabolism
- Sequence Homology, Amino Acid
- Tumor Cells, Cultured
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Affiliation(s)
- J Szelei
- Department of Anatomy and Cell Biology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
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26
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Abstract
Actin-related proteins (Arps) participate in a diverse array of cellular processes. They modulate assembly of conventional actin, contribute to microtubule-based motility catalyzed by dynein, and serve as integral components of large protein complexes required for gene expression. We highlight here recent work aimed at understanding the roles played by Arps in each of these processes.
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Affiliation(s)
- D A Schafer
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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27
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Higgs HN, Pollard TD. Regulation of actin polymerization by Arp2/3 complex and WASp/Scar proteins. J Biol Chem 1999; 274:32531-4. [PMID: 10551802 DOI: 10.1074/jbc.274.46.32531] [Citation(s) in RCA: 213] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- H N Higgs
- Structural Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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28
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Arellano M, Coll PM, Pérez P. RHO GTPases in the control of cell morphology, cell polarity, and actin localization in fission yeast. Microsc Res Tech 1999; 47:51-60. [PMID: 10506761 DOI: 10.1002/(sici)1097-0029(19991001)47:1<51::aid-jemt5>3.0.co;2-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The fission yeast Schizosaccharomyces pombe undergoes morphogenetic changes during both vegetative and sexual cell cycles that require asymmetric cell growth and actin cytoskeleton reorganisations. Different complex signal transduction pathways participate in S. pombe morphogenesis. The Rho family of GTPases are present in all eukaryotic cells, from yeast to mammals, and their role as key regulators in the signalling pathways that control actin organisation and morphogenetic processes is well known. In this review, we will briefly summarize the role of the Rho GTPases in the establishment and maintenance of cell polarity and growth of S. pombe. As in other fungi, S. pombe morphogenesis is closely related to cell wall biosynthesis, and Rho GTPases are critical modulators of this process. They provide the coordinated regulation of cell wall biosynthetic enzymes and actin organisation required to maintain cell integrity and polarised growth.
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Affiliation(s)
- M Arellano
- Instituto de Microbiología Bioquímica, CSIC / Universidad de Salamanca. Edificio Departamental, 37007 Salamanca, Spain
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29
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Abstract
The actin-related proteins (Arps) constitute a recently characterized family of proteins, many of which function as members of multiprotein complexes. The discovery that two family members, Arp2 and Arp3, act as multifunctional organizers of actin filaments in all eukaryotes has generated much excitement. Over the past two years, newly discovered properties of the Arp2/3 complex have suggested a central role in the control of actin polymerization. First, it promotes actin assembly on the surface of the motile intracellular pathogen Listeria monocytogenes. Second, it can nucleate and cross-link actin filaments in vitro. Third, it localizes with dynamic actin-rich spots of mammalian cells suggesting a role in protrusion; it is found in cortical actin patches in the budding and fission yeasts where it may control patch movement and cortical actin function. Clearly, the complex has a central role in actin cytoskeletal function and will be the subject of much research in the coming years.
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Affiliation(s)
- L M Machesky
- Department of Biochemistry University of Birmingham Edgbaston Birmingham B15 2TT UK.
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30
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Machesky LM, Insall RH. Scar1 and the related Wiskott-Aldrich syndrome protein, WASP, regulate the actin cytoskeleton through the Arp2/3 complex. Curr Biol 1998; 8:1347-56. [PMID: 9889097 DOI: 10.1016/s0960-9822(98)00015-3] [Citation(s) in RCA: 717] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND The actin-related proteins Arp2 and Arp3 are part of a seven-protein complex which is localized in the lamellipodia of a variety of cell types, and in actin-rich spots of unknown function. The Arp2/3 complex enhances actin nucleation and causes branching and crosslinking of actin filaments in vitro; in vivo it is thought to drive the formation of lamellipodia and to be a control center for actin-based motility. The Wiskott-Aldrich syndrome protein, WASP, is an adaptor protein implicated in the transmission of signals from tyrosine kinase receptors and small GTPases to the actin cytoskeleton. Scar1 is a member of a new family of proteins related to WASP, and it may also have a role in regulating the actin cytoskeleton. Scar1 is the human homologue of Dictyostelium Scar1, which is thought to connect G-protein-coupled receptors to the actin cytoskeleton. The mammalian Scar family contains at least four members. We have examined the relationships between WASP, Scar1, and the Arp2/3 complex. RESULTS We have identified WASP and its relative Scar1 as proteins that interact with the Arp2/3 complex. We have used deletion analysis to show that both WASP and Scar1 interact with the p21 subunit of the Arp2/3 complex through their carboxyl termini. Overexpression of carboxy-terminal fragments of Scar1 or WASP in cells caused a disruption in the localization of the Arp2/3 complex and, concomitantly, induced a complete loss of lamellipodia and actin spots. The induction of lamellipodia by platelet-derived growth factor was also suppressed by overexpression of the fragment of Scar1 that binds to the Arp2/3 complex. CONCLUSIONS We have identified a conserved sequence domain in proteins of the WASP family that binds to the Arp2/3 complex. Overexpression of this domain in cells disrupts the localization of the Arp2/3 complex and inhibits lamellipodia formation. Our data suggest that WASP-related proteins may regulate the actin cytoskeleton through the Arp2/3 complex.
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Affiliation(s)
- L M Machesky
- MRC-LMCB, Department of Molecular Medicine, University College London, Gower Street, London WC1E 6BT, UK.
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31
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Huang ME, Souciet JL, Chuat JC, Galibert F. Identification of ACT4, a novel essential actin-related gene in the yeast Saccharomyces cerevisiae. Yeast 1998. [DOI: 10.1002/(sici)1097-0061(199607)12:9<839::aid-yea982>3.0.co;2-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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32
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Huang ME, Manus V, Chuat JC, Galibert F. Analysis of a 62 kb DNA sequence of chromosome X reveals 36 open reading frames and a gene cluster with a counterpart on chromosome XI. Yeast 1998. [DOI: 10.1002/(sici)1097-0061(199607)12:9<869::aid-yea964>3.0.co;2-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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33
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Arai R, Nakano K, Mabuchi I. Subcellular localization and possible function of actin, tropomyosin and actin-related protein 3 (Arp3) in the fission yeast Schizosaccharomyces pombe. Eur J Cell Biol 1998; 76:288-95. [PMID: 9765059 DOI: 10.1016/s0171-9335(98)80007-1] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
We investigated subcellular localizations and interactions of actin and two actin cytoskeleton-related proteins, Cdc8 tropomyosin and actin-related protein 3, Arp3, in the fission yeast Schizosaccharomyces pombe, using specific antibodies and by gene disruption. Actin was localized to the medial microfilamentous ring in the region of the septum during cytokinesis and to cortical patches by immunoelectron microscopy. F-actin cables were detected throughout the cell cycle by fluorescent staining with Bodipy-phallacidin. Cables were often linked to the patches and to the medial ring during its formation. Tropomyosin was localized to the medial ring and the cables. It was also distributed in the cell as patches, although co-localization with F-actin was not frequent. In cdc8ts mutant cells, F-actin cables were not observed although the F-actin patches were detected and cell polarity was maintained. These observations suggest that the F-actin cables may be involved in the formation of the medial ring, and that tropomyosin plays an important role in organizing both the ring and the cable, but is not involved in the F-actin patch formation or maintenance of cell polarity. Binding of Arp3 to actin was revealed by immunoprecipitation as well as by DNase I column chromatography. Arp3 seemed to form a complex with several proteins in the cell extracts, as previously reported for other organisms. Contrary to a previous report (McCollum et al., EMBO J. 15, 6438-6446, 1996), Arp3 was found to be concentrated in the medial region from early anaphase to late cytokinesis. Following arp3 gene disruption, F-actin patches were delocalized throughout the cell and cells did not undergo polarized growth, suggesting that Arp3 influences the proper localization of the actin patches in the cell and thereby controls the polarized growth of the cell.
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Affiliation(s)
- R Arai
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Japan.
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34
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Welch MD, Rosenblatt J, Skoble J, Portnoy DA, Mitchison TJ. Interaction of human Arp2/3 complex and the Listeria monocytogenes ActA protein in actin filament nucleation. Science 1998; 281:105-8. [PMID: 9651243 DOI: 10.1126/science.281.5373.105] [Citation(s) in RCA: 386] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Actin filament assembly at the cell surface of the pathogenic bacterium Listeria monocytogenes requires the bacterial ActA surface protein and the host cell Arp2/3 complex. Purified Arp2/3 complex accelerated the nucleation of actin polymerization in vitro, but pure ActA had no effect. However, when combined, the Arp2/3 complex and ActA synergistically stimulated the nucleation of actin filaments. This mechanism of activating the host Arp2/3 complex at the L. monocytogenes surface may be similar to the strategy used by cells to control Arp2/3 complex activity and hence the spatial and temporal distribution of actin polymerization.
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Affiliation(s)
- M D Welch
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143, USA
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35
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Venkatesh B, Brenner S. Genomic structure and sequence of the pufferfish (Fugu rubripes) gene encoding an actin-related protein. Gene X 1998; 211:169-75. [PMID: 9573354 DOI: 10.1016/s0378-1119(98)00096-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Using a polymerase chain reaction (PCR)-generated gene fragment as a probe, we isolated and sequenced a gene encoding an actin-related protein belonging to the Arp3 family from the pufferfish, Fugu rubripes. The Fugu Arp3 gene spans 3.7kb from the transcription start site to the polyadenylation signal. This is the first report of the genomic sequence of a vertebrate Arp3 gene. The Fugu Arp3 gene consists of 12 exons and 11 introns compared to Drosophila homologue, which has six exons and five introns. The protein sequence encoded by the Fugu gene is 97% and 80% identical to bovine and Drosophila homologues, respectively. The Fugu Arp3 gene is expressed in a wide range of tissues, with higher levels detected in the gills, kidney, ovary, skin and testis. Three different size transcripts of the Arp3 gene (1.4kb, 1.8kb and 2.2kb) were identified in various tissues.
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Affiliation(s)
- B Venkatesh
- Institute of Molecular, Cell Biology, 30 Medical Drive, ????, Singapore.
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36
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Poch O, Winsor B. Who's who among the Saccharomyces cerevisiae actin-related proteins? A classification and nomenclature proposal for a large family. Yeast 1997; 13:1053-8. [PMID: 9290209 DOI: 10.1002/(sici)1097-0061(19970915)13:11<1053::aid-yea164>3.0.co;2-4] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Inspection of the complete Saccharomyces cerevisiae genome sequence and analysis of the actin-related proteins (ARPs) found therein revealed seven proteins, in addition to the previously designated actin-related proteins Arp1, Arp2 and Arp3, which contained substantial blocks of conservation relative to a chosen sub-set of actins. We have ordered the new ARPs relative to this group of actins and propose to name the more distantly related ARP members, according to their amino acid identity and similarity, Arp4-Arp10. Most of these proteins appear to represent the first example of new classes of ARPs, each of which may have specific localization(s) and cellular function(s). Recently reported ARPs from other species have also been included in the phylogenetic tree derived from the overall alignment of 29 actins and 28 ARPs.
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Affiliation(s)
- O Poch
- UPR 9005 du CNRS, Institut de Biologie Moléculaire et Cellulaire, Strasbourg, France
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37
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Welch MD, DePace AH, Verma S, Iwamatsu A, Mitchison TJ. The human Arp2/3 complex is composed of evolutionarily conserved subunits and is localized to cellular regions of dynamic actin filament assembly. J Cell Biol 1997; 138:375-84. [PMID: 9230079 PMCID: PMC2138188 DOI: 10.1083/jcb.138.2.375] [Citation(s) in RCA: 402] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/1997] [Revised: 06/03/1997] [Indexed: 02/04/2023] Open
Abstract
The Arp2/3 protein complex has been implicated in the control of actin polymerization in cells. The human complex consists of seven subunits which include the actin related proteins Arp2 and Arp3, and five others referred to as p41-Arc, p34-Arc, p21-Arc, p20-Arc, and p16-Arc (p omplex). We have determined the predicted amino acid sequence of all seven subunits. Each has homologues in diverse eukaryotes, implying that the structure and function of the complex has been conserved through evolution. Human Arp2 and Arp3 are very similar to family members from other species. p41-Arc is a new member of the Sop2 family of WD (tryptophan and aspartate) repeat-containing proteins and may be posttranslationally modified, suggesting that it may be involved in regulating the activity and/or localization of the complex. p34-Arc, p21-Arc, p20-Arc, and p16-Arc define novel protein families. We sought to evaluate the function of the Arp2/3 complex in cells by determining its intracellular distribution. Arp3, p34-Arc, and p21-Arc were localized to the lamellipodia of stationary and locomoting fibroblasts, as well to Listeria monocytogenes assembled actin tails. They were not detected in cellular bundles of actin filaments. Taken together with the ability of the Arp2/3 complex to induce actin polymerization, these observations suggest that the complex promotes actin assembly in lamellipodia and may participate in lamellipodial protrusion.
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Affiliation(s)
- M D Welch
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California 94143-0450, USA.
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38
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Mullins RD, Stafford WF, Pollard TD. Structure, subunit topology, and actin-binding activity of the Arp2/3 complex from Acanthamoeba. J Cell Biol 1997; 136:331-43. [PMID: 9015304 PMCID: PMC2134809 DOI: 10.1083/jcb.136.2.331] [Citation(s) in RCA: 186] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/1996] [Revised: 10/02/1996] [Indexed: 02/03/2023] Open
Abstract
The Arp2/3 complex, first isolated from Acanthamoeba castellani by affinity chromatography on profilin, consists of seven polypeptides; two actin-related proteins, Arp2 and Arp3; and five apparently novel proteins, p40, p35, p19, p18, and p14 (Machesky et al., 1994). The complex is homogeneous by hydrodynamic criteria with a Stokes' radius of 5.3 nm by gel filtration, sedimentation coefficient of 8.7 S, and molecular mass of 197 kD by analytical ultracentrifugation. The stoichiometry of the subunits is 1:1:1:1:1:1:1, indicating the purified complex contains one copy each of seven polypeptides. In electron micrographs, the complex has a bilobed or horseshoe shape with outer dimensions of approximately 13 x 10 nm, and mathematical models of such a shape and size are consistent with the measured hydrodynamic properties. Chemical cross-linking with a battery of cross-linkers of different spacer arm lengths and chemical reactivities identify the following nearest neighbors within the complex: Arp2 and p40; Arp2 and p35; Arp3 and p35; Arp3 and either p18 or p19; and p19 and p14. By fluorescent antibody staining with anti-p40 and -p35, the complex is concentrated in the cortex of the ameba, especially in linear structures, possibly actin filament bundles, that lie perpendicular to the leading edge. Purified Arp2/3 complex binds actin filaments with a Kd of 2.3 microM and a stoichiometry of approximately one complex molecule per actin monomer. In electron micrographs of negatively stained samples, Arp2/3 complex decorates the sides of actin filaments. EDC/NHS cross-links actin to Arp3, p35, and a low molecular weight subunit, p19, p18, or p14. We propose structural and topological models for the Arp2/3 complex and suggest that affinity for actin filaments accounts for the localization of complex subunits to actin-rich regions of Acanthamoeba.
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Affiliation(s)
- R D Mullins
- Department of Cell Biology and Anatomy, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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39
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McCollum D, Feoktistova A, Morphew M, Balasubramanian M, Gould KL. The Schizosaccharomyces pombe actin-related protein, Arp3, is a component of the cortical actin cytoskeleton and interacts with profilin. EMBO J 1996; 15:6438-46. [PMID: 8978671 PMCID: PMC452469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The gene encoding the actin-related protein Arp3 was first identified in the fission yeast Schizosaccharomyces pombe and is a member of an evolutionarily conserved family of actin-related proteins. Here we present several key findings that define an essential role for Arp3p in the functioning of the cortical actin cytoskeleton. First, mutants in arp3 interact specifically with profilin and actin mutants. Second, Arp3 localizes to cortical actin patches which are required for polarized cell growth. Third, the arp3 gene is required for the reorganization of the actin cytoskeleton during the cell cycle. Finally, the Arp3 protein is present in a large protein complex. We believe that this complex may mediate the cortical functions of profilin at actin patches in S. pombe.
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Affiliation(s)
- D McCollum
- Howard Hughes Medical Institute and the Department of Cell Biology, Vanderbilt University, School of Medicine, Nashville, TN 37232, USA
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40
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Holleran EA, Tokito MK, Karki S, Holzbaur EL. Centractin (ARP1) associates with spectrin revealing a potential mechanism to link dynactin to intracellular organelles. J Cell Biol 1996; 135:1815-29. [PMID: 8991093 PMCID: PMC2133946 DOI: 10.1083/jcb.135.6.1815] [Citation(s) in RCA: 201] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Centractin (Arp1), an actin-related protein, is a component of the dynactin complex. To investigate potential functions of the protein, we used transient transfections to overexpress centractin in mammalian cells. We observed that the overexpressed polypeptide formed filamentous structures that were significantly longer and more variable in length than those observed in the native dynactin complex. The centractin filaments were distinct from conventional actin in subunit composition and pharmacology as demonstrated by the absence of immunoreactivity of these filaments with an actin-specific antibody, by resistance to treatment with the drug cytochalasin D, and by the inability to bind phalloidin. We examined the transfected cells for evidence of specific associations of the novel centractin filaments with cellular organelles or cytoskeletal proteins. Using immunocytochemistry we observed the colocalization of Golgi marker proteins with the centractin polymers. Additional immunocytochemical analysis using antibodies to non-erythroid spectrin (fodrin) and Golgi-spectrin (beta I sigma *) revealed that spectrin colocalized with the centractin filaments in transfected cells. Biochemical assays demonstrated that spectrin was present in dynactin-enriched cellular fractions, was coimmunoprecipitated from rat brain cytosol using antibodies to dynactin subunits, and was coeluted with dynactin using affinity chromatography. Immunoprecipitations and affinity chromatography also revealed that actin is not a bona fide component of dynactin. Our results indicate that spectrin is associated with the dynactin complex. We suggest a model in which dynactin associates with the Golgi through an interaction between the centractin filament of the dynactin complex and a spectrin-linked cytoskeletal network.
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Affiliation(s)
- E A Holleran
- Cell and Molecular Biology Graduate Group, University of Pennsylvania, Philadelphia 19104, USA
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41
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Moreau V, Madania A, Martin RP, Winson B. The Saccharomyces cerevisiae actin-related protein Arp2 is involved in the actin cytoskeleton. J Cell Biol 1996; 134:117-32. [PMID: 8698808 PMCID: PMC2120930 DOI: 10.1083/jcb.134.1.117] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Arp2p is an essential yeast actin-related protein. Disruption of the corresponding ARP2 gene leads to a terminal phenotype characterized by the presence of a single large bud. Thus, Arp2p may be important for a late stage of the cell cycle (Schwob, E., and R.P. Martin, 1992. Nature (Lond.). 355:179-182). We have localized Arp2p by indirect immunofluorescence. Specific peptide antibodies revealed punctate staining under the plasma membrane, which partially colocalizes with actin. Temperature-sensitive arp2 mutations were created by PCR mutagenesis and selected by an ade2/SUP11 sectoring screen. One temperature-sensitive mutant that was characterized, arp2-H330L, was osmosensitive and had an altered actin cytoskeleton at a nonpermissive temperature, suggesting a role of Arp2p in the actin cytoskeleton. Random budding patterns were observed in both haploid and diploid arp2-H330L mutant cells. Endocytosis, as judged by Lucifer yellow uptake, was severely reduced in the mutant, at all temperatures. In addition, genetic interaction was observed between temperature-sensitive alleles arp2-H330L and cdc10-1. CDC10 is a gene encoding a neck filament-associated protein that is necessary for polarized growth and cytokinesis. Overall, the immunolocalization, mutant phenotypes, and genetic interaction suggest that the Arp2 protein is an essential component of the actin cytoskeleton that is involved in membrane growth and polarity, as well as in endocytosis.
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Affiliation(s)
- V Moreau
- Institut de Biologie Moléculaire et Cellulaire du C.N.R.S. U.P.R. 9005, Strasbourg, France
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42
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Huang ME, Manus V, Chuat JC, Galibert F. Analysis of a 62 kb DNA sequence of chromosome X reveals 36 open reading frames and a gene cluster with a counterpart on chromosome XI. Yeast 1996; 12:869-75. [PMID: 8840504 DOI: 10.1002/(sici)1097-0061(199607)12:9%3c869::aid-yea964%3e3.0.co;2-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We have sequenced a 61.989 bp stretch located between genes RAD7 and FIP1 of Saccharomyces cerevisiae chromosome X. This stretch contains 36 open reading frames (ORFs) of at least 100 codons. Fourteen of these correspond to sequences previously published as HIT1, CDC8, YAP17, CBF1, NAT1, RPA12, CCT5, TOR1, RFC2, PEM2, CDC11, MIR1, STE18 and GRR1. The proteins deduced from four ORFs (YJR059w, YJR065c, YJR075w, YJR078w) have significant similarity to proteins of known function from yeast or other organisms, including S. cerevisiae serine/threonine-specific protein kinase. Schizosaccharomyces pombe Act2 protein, S. cerevisiae mannosyltransferase OCH1 protein and mouse indoleamine 2,3-dioxygenase, respectively. Four of the remaining 18 ORFs have similarity to proteins with unknown function, six are weakly similar to other known sequences, while another eight exhibit no similarity to any known sequence. In addition, three tRNA genes have been recognized. Three genes clustered within 22 kb (YJR059w, YJR061w and TOR1) have counterparts arranged within 15 kb on the left arm of chromosome XI.
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Affiliation(s)
- M E Huang
- UPR41-CNRS Recombinaisons Génétiques, Faculté de Médecine, Rennes, France
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43
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Huang ME, Souciet JL, Chuat JC, Galibert F. Identification of ACT4, a novel essential actin-related gene in the yeast Saccharomyces cerevisiae. Yeast 1996; 12:839-48. [PMID: 8840501 DOI: 10.1002/(sici)1097-0061(199607)12:9%3c839::aid-yea982%3e3.0.co;2-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Actin molecules are major cytoskeleton components of all eukaryotic cells. All conventional actins that have been identified so far are 374-376 amino acids in size and exhibit at least 70% amino acid sequence identity when compared with one another. In the yeast Saccharomyces cerevisiae, one conventional actin gene ACT1 and three so-called actin-related genes, ACT2, ACT3 and ACT5, have been identified. We report here the discovery of a new actin-related gene in this organism, which we have named ACT4. The deduced protein, Act4, of 449 amino acids, exhibits only 33.4%, 26.7%, 23.4% and 29.2% identity to Act1, Act2, Act3 and Act5, respectively. In contrast, it is 68.4% identical to the product of the Schizosaccharomyces pombe Act2 gene and has a similar level of identity to other Sch. pombe Act2 homologues. This places Act4 in the Arp3 family of actin-related proteins. ACT4 gene disruption and tetrad analysis demonstrate that this gene is essential for the vegetative growth of yeast cells. The act4 mutants exhibit heterogenous morphological phenotypes. We hypothesize that Act4 may have multiple roles in the cell cycle.
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Affiliation(s)
- M E Huang
- Laboratoire de Biochimie et Biologie Moléculaire, UPR 41 CNRS, Recombinaisons Génétiques, Faculté de Médecine, Rennes, France
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44
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Song K, Mach KE, Chen CY, Reynolds T, Albright CF. A novel suppressor of ras1 in fission yeast, byr4, is a dosage-dependent inhibitor of cytokinesis. J Cell Biol 1996; 133:1307-19. [PMID: 8682866 PMCID: PMC2120903 DOI: 10.1083/jcb.133.6.1307] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
A novel gene, designated byr4, was identified in Schizosaccharomyces pombe that affects the mitotic cell cycle and shows genetic interactions with the ras1 signaling pathways. Null alleles of byr4 cause cell cycle arrest in late mitosis and permit multiple rounds of septation. The multiple septa typically divide two nuclei, but the nuclei frequently do not stain equally with 4',6-diamidino-2-phenylindole (DAPI), suggesting that byr4 is required for proper karyokinesis. Overexpression of byr4 inhibits cytokinesis, but cell cycle progression continues leading to multinucleate cells. When byr4 is overexpressed, the early steps in the cytokinesis pathway, including formation of the medial F-actin ring, occur normally; however, the later steps in the pathway, including contraction of the F-actin ring, septation, and rearrangement of the medial F-actin following mitosis, rarely occur, byr4 shows two genetic interactions with ras1. The inhibition of cytokinesis by byr4 overexpression was exacerbated by null alleles of ras1 and scd1, suggesting a link between pathways needed for cell polarity and cytokinesis. Overexpression of byr4 also partially bypasses the need for ras1 for sporulation. The electrophoretic mobility of the byr4 protein varied in response to mutants that perturb cytokinesis and karyokinesis, suggesting interactions between byr4 and these gene products. A more rapidly migrating byr4 protein was found in cells with mutations in cdc16, which undergo repeated septation, and in cdc15, which fail to form a medial F-actin ring in mitosis. A slower migrating byr4 protein was found in cells with a mutation in the beta-tubulin gene, which arrests cells at the metaphase-anaphase transition.
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Affiliation(s)
- K Song
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
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45
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McDowell JM, Huang S, McKinney EC, An YQ, Meagher RB. Structure and evolution of the actin gene family in Arabidopsis thaliana. Genetics 1996; 142:587-602. [PMID: 8852856 PMCID: PMC1206991 DOI: 10.1093/genetics/142.2.587] [Citation(s) in RCA: 152] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Higher plants contain families of actin-encoding genes that are divergent and differentially expressed. Progress in understanding the functions and evolution of plant actins has been hindered by the large size of the actin gene families. In this study, we characterized the structure and evolution of the actin gene family in Arabidopsis thaliana. DNA blot analyses with gene-specific probes suggested that all 10 of the Arabidopsis actin gene family members have been isolated and established that Arabidopsis has a much simpler actin gene family than other plants that have been examined. Phylogenetic analyses suggested that the Arabidopsis gene family contains at least two ancient classes of genes that diverged early in land plant evolution and may have separated vegetative from reproductive actins. Subsequent divergence produced a total of six distinct subclasses of actin, and five showed a distinct pattern of tissue specific expression. The concordance of expression patterns with the phylogenetic structure is discussed. These subclasses appear to be evolving independently, as no evidence of gene conversion was found. The Arabidopsis actin proteins have an unusually large number of nonconservative amino acid substitutions, which mapped to the surface of the actin molecule, and should effect protein-protein interactions.
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Affiliation(s)
- J M McDowell
- Department of Biology, University of North Carolina, Chapel Hill 27599, USA
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46
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Abstract
A family of proteins has been discovered over the past three years whose members have clear sequence homology to actin but are distinguished from actin by their structural and functional diversity. The ranks of this family, whose members are known as the actin-related proteins (arps), are expanding rapidly. Arps are but one branch of a larger superfamily which includes the actins, hsp/hsc70s, sugar kinases and several cell cycle proteins from bacteria. The existence of the superfamily has been inferred from tertiary structural data. In the case of the arps, their identification and classification has been based upon primary structural data. Placing the arps in a functional context is proving a slower process, although genetic and biochemical analyses are converging in several cases. In the past year, different arps have been linked to functions mediated by actin filaments (arp2 and arp3), microtubules (arp1) and the structural elements of chromatin (arp4 and arp6).
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Affiliation(s)
- S Frankel
- Department of Biology, Yale University, New Haven, CT 06520-8103, USA.
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47
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Kelleher JF, Atkinson SJ, Pollard TD. Sequences, structural models, and cellular localization of the actin-related proteins Arp2 and Arp3 from Acanthamoeba. J Cell Biol 1995; 131:385-97. [PMID: 7593166 PMCID: PMC2199984 DOI: 10.1083/jcb.131.2.385] [Citation(s) in RCA: 154] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We cloned and sequenced the two actin-related proteins (Arps) present in the profilin-binding complex of Acanthamoeba (Machesky, L. M., S. J. Atkinson, C. Ampe, J. Vandekerckhove, and T. D. Pollard. 1994, J. Cell Biol. 127:107-115). The sequence of Arp2 is more similar to other Arp2s than to actin, while the sequence of Arp3 is more similar to other Arp3s than to actin. Phylogenetic analysis of all known Arps demonstrates that most group into three major families, which are likely to be shared across all eukaryotic phyla. Together with conventional actins, the Arps form a larger family distinct from structurally related ATPases such as Hsp70's and sugar kinases. Atomic models of the Arps based on their sequences and the structure of actin provide some clues about function. Both Arps have atoms appropriately placed to bind ATP and divalent cation. Arp2, but not Arp3, has a conserved profilin-binding site. Neither Arp has the residues required to copolymerize with actin, but an Arp heterodimer present in the profilin-binding complex might serve as a pointed end nucleus for actin polymerization. Both Acanthamoeba Arps are soluble in cell homogenates, and both are concentrated in the cortex of Acanthamoeba. The cellular concentrations are 1.9 microM Arp2 and 5.1 microM Arp3, substoichiometric to actin (200 microM) but comparable to many actin-binding proteins.
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Affiliation(s)
- J F Kelleher
- Department of Cell Biology and Anatomy, Johns Hopkins Medical School, Baltimore, Maryland 21205, USA
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48
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Weber V, Harata M, Hauser H, Wintersberger U. The actin-related protein Act3p of Saccharomyces cerevisiae is located in the nucleus. Mol Biol Cell 1995; 6:1263-70. [PMID: 8573785 PMCID: PMC301286 DOI: 10.1091/mbc.6.10.1263] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Actin-related proteins, a group of protein families that exhibit about 50% sequence identity among each other and to conventional actin, have been found in a variety of eukaryotic organisms. In the budding yeast Saccharomyces cerevisiae, genes for one conventional actin (ACT1) and for three actin-related proteins (ACT2, ACT3, and ACT5) are known. ACT3, which we recently discovered, is an essential gene coding for a polypeptide of 489 amino acids (Act3p), with a calculated molecular mass of 54.8 kDa. Besides its homology to conventional actin, Act3p possesses a domain exhibiting weak similarity to the chromosomal protein HMG-14 as well as a potential nuclear localization signal. An antiserum prepared against a specific segment of the ACT3 gene product recognizes a polypeptide band of approximately 55 kDa in yeast extract. Indirect immunofluorescence experiments with this antiserum revealed that Act3p is located in the nucleus. Nuclear staining was observed in all cells regardless of the stage of the cell cycle. Independently, immunoblotting experiments with subcellular fractions showed that Act3p is indeed highly enriched in the nuclear fraction. We suggest that Act3p is an essential constituent of yeast chromatin.
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Affiliation(s)
- V Weber
- Department of Molecular Genetics, University of Vienna, Wien, Austria
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49
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Robb MJ, Wilson MA, Vierula PJ. A fungal actin-related protein involved in nuclear migration. MOLECULAR & GENERAL GENETICS : MGG 1995; 247:583-90. [PMID: 7603438 DOI: 10.1007/bf00290350] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The ro-4 mutant of the filamentous fungus Neurospora crassa forms distinctive colonies in which hyphae grow into rope-like aggregates. This unusual morphology coincides with a defect in hyphal nuclear migration. The ro-4 gene was cloned from a cosmid library by complementation of the closely linked pab-2 gene. The deduced 380 amino acid protein is most similar to the vertebrate actin-related protein/centractin. The RO4 protein is not essential for cell viability, and new strains created by inducing point mutations at the ro-4 locus have a phenotype which is very similar to that of the original mutant. This study provides genetic evidence that an actin-related protein plays a role in nuclear motility. Since nuclear motility is believed to be a microtubule-dependent process, the ro-4 gene product may function as a component of the dynactin complex which activates force generation by cytoplasmic dynein.
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Affiliation(s)
- M J Robb
- Department of Biology, Carleton University, Ottawa, Canada
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50
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Chen X, Rubenstein PA. A mutation in an ATP-binding loop of Saccharomyces cerevisiae actin (S14A) causes a temperature-sensitive phenotype in vivo and in vitro. J Biol Chem 1995; 270:11406-14. [PMID: 7744777 DOI: 10.1074/jbc.270.19.11406] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The Ser14 hydroxyl group of actin is one of six groups that potentially form hydrogen bonds with the gamma-phosphate of the ATP bound in the cleft separating the two domains of the protein. To understand the importance of this group in actin function, we mutated Ser14 of Saccharomyces cerevisiae actin and studied the effects of these mutations in vivo and in vitro. Substitution of Cys of Gly resulted in cell death. Substitution of Thr for Ser resulted in an actin with wild-type properties in vivo and in vitro. Cells carrying the Ser14-->Ala (S14A) mutation were viable but displayed a temperature sensitive lethality at 37 degrees C preceded by delocalization of actin patches, the appearance of bar-like structures, and finally the disappearance of identifiable actin structures. The mutation caused no effect on the critical concentration of polymerization but resulted in an actin with an increased rate of polymerization, an altered protease susceptibility, and a decreased filament ATPase activity. At 37 degrees C, Mg-, but not Ca-S14A-actin irreversibly lost the ability to polymerize. These results demonstrate the importance of the ATP-Ser14 hydroxyl hydrogen bond in regulating actin function in vivo and in vitro and the magnification of the effects of the mutation when Mg2+ is substituted for Ca2+ in the protein.
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Affiliation(s)
- X Chen
- Department of Biochemistry, University of Iowa College of Medicine, Iowa City 52242-1104, USA
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