1
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Wang F, Zhu C, Cai S, Boudreau A, Kim SJ, Bissell M, Shao J. Ser 71 Phosphorylation Inhibits Actin-Binding of Profilin-1 and Its Apoptosis-Sensitizing Activity. Front Cell Dev Biol 2021; 9:692269. [PMID: 34235154 PMCID: PMC8255618 DOI: 10.3389/fcell.2021.692269] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 05/28/2021] [Indexed: 01/25/2023] Open
Abstract
The essential actin-binding factor profilin-1 (Pfn1) is a non-classical tumor suppressor with the abilities toboth inhibit cellular proliferation and augment chemotherapy-induced apoptosis. Besides actin, Pfn1 interacts with proteins harboring the poly-L-proline (PLP) motifs. Our recent work demonstrated that both nuclear localization and PLP-binding are required for tumor growth inhibition by Pfn1, and this is at least partially due to Pfn1 association with the PLP-containing ENL protein in the Super Elongation Complex (SEC) and the transcriptional inhibition of pro-cancer genes. In this paper, by identifying a phosphorylation event of Pfn1 at Ser71 capable of inhibiting its actin-binding and nuclear export, we provide in vitro and in vivo evidence that chemotherapy-induced apoptotic sensitization by Pfn1 requires its cytoplasmic localization and actin-binding. With regard to tumor growth inhibition byPfn1, our data indicate a requirement for dynamic actin association and dissociation rendered by reversible Ser71phosphorylation and dephosphorylation. Furthermore, genetic and pharmacological experiments showed that Ser71 of Pfn1 can be phosphorylated by protein kinase A (PKA). Taken together, our data provide novel mechanistic insights into the multifaceted anticancer activities of Pfn1 and how they are spatially-defined in the cell and differentially regulated by ligand-binding.
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Affiliation(s)
- Faliang Wang
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
- Department of Surgical Oncology, The Children’s Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Cuige Zhu
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Shirong Cai
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, United States
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Aaron Boudreau
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
| | - Sun-Joong Kim
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Mina Bissell
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
| | - Jieya Shao
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
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2
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Zhu C, Kim SJ, Mooradian A, Wang F, Li Z, Holohan S, Collins PL, Wang K, Guo Z, Hoog J, Ma CX, Oltz EM, Held JM, Shao J. Cancer-associated exportin-6 upregulation inhibits the transcriptionally repressive and anticancer effects of nuclear profilin-1. Cell Rep 2021; 34:108749. [PMID: 33596420 PMCID: PMC8006859 DOI: 10.1016/j.celrep.2021.108749] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Revised: 12/29/2020] [Accepted: 01/21/2021] [Indexed: 01/22/2023] Open
Abstract
Aberrant expression of nuclear transporters and deregulated subcellular localization of their cargo proteins are emerging as drivers and therapeutic targets of cancer. Here, we present evidence that the nuclear exporter exportin-6 and its cargo profilin-1 constitute a functionally important and frequently deregulated axis in cancer. Exportin-6 upregulation occurs in numerous cancer types and is associated with poor patient survival. Reducing exportin-6 level in breast cancer cells triggers antitumor effects by accumulating nuclear profilin-1. Mechanistically, nuclear profilin-1 interacts with eleven-nineteen-leukemia protein (ENL) within the super elongation complex (SEC) and inhibits the ability of the SEC to drive transcription of numerous pro-cancer genes including MYC. XPO6 and MYC are positively correlated across diverse cancer types including breast cancer. Therapeutically, exportin-6 loss sensitizes breast cancer cells to the bromodomain and extra-terminal (BET) inhibitor JQ1. Thus, exportin-6 upregulation is a previously unrecognized cancer driver event by spatially inhibiting nuclear profilin-1 as a tumor suppressor.
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Affiliation(s)
- Cuige Zhu
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Sun-Joong Kim
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Arshag Mooradian
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Faliang Wang
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Surgical Oncology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou 310052, China
| | - Ziqian Li
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Microbial and Biochemical Pharmacy, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Sean Holohan
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Patrick L Collins
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH 43210, USA
| | - Keren Wang
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Zhanfang Guo
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Jeremy Hoog
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Cynthia X Ma
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Eugene M Oltz
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH 43210, USA
| | - Jason M Held
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Jieya Shao
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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3
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Gómez-Gil E, Martín-García R, Vicente-Soler J, Franco A, Vázquez-Marín B, Prieto-Ruiz F, Soto T, Pérez P, Madrid M, Cansado J. Stress-activated MAPK signaling controls fission yeast actomyosin ring integrity by modulating formin For3 levels. eLife 2020; 9:57951. [PMID: 32915139 PMCID: PMC7511234 DOI: 10.7554/elife.57951] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 09/10/2020] [Indexed: 11/13/2022] Open
Abstract
Cytokinesis, which enables the physical separation of daughter cells once mitosis has been completed, is executed in fungal and animal cells by a contractile actin- and myosin-based ring (CAR). In the fission yeast Schizosaccharomyces pombe, the formin For3 nucleates actin cables and also co-operates for CAR assembly during cytokinesis. Mitogen-activated protein kinases (MAPKs) regulate essential adaptive responses in eukaryotic organisms to environmental changes. We show that the stress-activated protein kinase pathway (SAPK) and its effector, MAPK Sty1, downregulates CAR assembly in S. pombe when its integrity becomes compromised during cytoskeletal damage and stress by reducing For3 levels. Accurate control of For3 levels by the SAPK pathway may thus represent a novel regulatory mechanism of cytokinesis outcome in response to environmental cues. Conversely, SAPK signaling favors CAR assembly and integrity in its close relative Schizosaccharomyces japonicus, revealing a remarkable evolutionary divergence of this response within the fission yeast clade.
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Affiliation(s)
- Elisa Gómez-Gil
- Yeast Physiology Group, Departamento de Genética y Microbiología, Facultad de Biología. Universidad de Murcia, Murcia, Spain
| | - Rebeca Martín-García
- Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas, Universidad de Salamanca, Salamanca, Spain
| | - Jero Vicente-Soler
- Yeast Physiology Group, Departamento de Genética y Microbiología, Facultad de Biología. Universidad de Murcia, Murcia, Spain
| | - Alejandro Franco
- Yeast Physiology Group, Departamento de Genética y Microbiología, Facultad de Biología. Universidad de Murcia, Murcia, Spain
| | - Beatriz Vázquez-Marín
- Yeast Physiology Group, Departamento de Genética y Microbiología, Facultad de Biología. Universidad de Murcia, Murcia, Spain
| | - Francisco Prieto-Ruiz
- Yeast Physiology Group, Departamento de Genética y Microbiología, Facultad de Biología. Universidad de Murcia, Murcia, Spain
| | - Teresa Soto
- Yeast Physiology Group, Departamento de Genética y Microbiología, Facultad de Biología. Universidad de Murcia, Murcia, Spain
| | - Pilar Pérez
- Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas, Universidad de Salamanca, Salamanca, Spain
| | - Marisa Madrid
- Yeast Physiology Group, Departamento de Genética y Microbiología, Facultad de Biología. Universidad de Murcia, Murcia, Spain
| | - Jose Cansado
- Yeast Physiology Group, Departamento de Genética y Microbiología, Facultad de Biología. Universidad de Murcia, Murcia, Spain
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4
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Zambon P, Palani S, Jadhav SS, Gayathri P, Balasubramanian MK. Genetic suppression of defective profilin by attenuated Myosin II reveals a potential role for Myosin II in actin dynamics in vivo in fission yeast. Mol Biol Cell 2020; 31:2107-2114. [PMID: 32614646 PMCID: PMC7530902 DOI: 10.1091/mbc.e20-04-0224] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The actin cytoskeleton plays a variety of roles in eukaryotic cell physiology, ranging from cell polarity and migration to cytokinesis. Key to the function of the actin cytoskeleton is the mechanisms that control its assembly, stability, and turnover. Through genetic analyses in Schizosaccharomyces pombe, we found that myo2-S1 (myo2-G515D), a Myosin II mutant allele, was capable of rescuing lethality caused by partial defects in actin nucleation/stability caused, for example, through compromised function of the actin-binding protein Cdc3-profilin. The mutation in myo2-S1 affects the activation loop of Myosin II, which is involved in physical interaction with subdomain 1 of actin and in stimulating the ATPase activity of Myosin. Consistently, actomyosin rings in myo2-S1 cell ghosts were unstable and severely compromised in contraction on ATP addition. These studies strongly suggest a role for Myo2 in actin cytoskeletal disassembly and turnover in vivo, and that compromise of this activity leads to genetic suppression of mutants defective in actin filament assembly/stability at the division site.
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Affiliation(s)
- Paola Zambon
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Saravanan Palani
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Shekhar Sanjay Jadhav
- Biology Division, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India
| | - Pananghat Gayathri
- Biology Division, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India
| | - Mohan K Balasubramanian
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, United Kingdom
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5
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Antoine M, Patrick KL, Soret J, Duc P, Rage F, Cacciottolo R, Nissen KE, Cauchi RJ, Krogan NJ, Guthrie C, Gachet Y, Bordonné R. Splicing Defects of the Profilin Gene Alter Actin Dynamics in an S. pombe SMN Mutant. iScience 2019; 23:100809. [PMID: 31927482 PMCID: PMC6957872 DOI: 10.1016/j.isci.2019.100809] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 09/13/2019] [Accepted: 12/23/2019] [Indexed: 12/18/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a devastating motor neuron disorder caused by mutations in the survival motor neuron (SMN) gene. It remains unclear how SMN deficiency leads to the loss of motor neurons. By screening Schizosaccharomyces pombe, we found that the growth defect of an SMN mutant can be alleviated by deletion of the actin-capping protein subunit gene acp1+. We show that SMN mutated cells have splicing defects in the profilin gene, which thus directly hinder actin cytoskeleton homeostasis including endocytosis and cytokinesis. We conclude that deletion of acp1+ in an SMN mutant background compensates for actin cytoskeleton alterations by restoring redistribution of actin monomers between different types of cellular actin networks. Our data reveal a direct correlation between an impaired function of SMN in snRNP assembly and defects in actin dynamics. They also point to important common features in the pathogenic mechanism of SMA and ALS. Splicing defects in the profilin gene in an S. pombe SMN mutant SMN mutant contains excessively polymerized actin Altered actin dynamics in the SMN mutant hinders endocytosis and cytokinesis Deletion of the acp1 subunit restores actin dynamics in the SMN mutant
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Affiliation(s)
- Marie Antoine
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | | | - Johann Soret
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | - Pauline Duc
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | - Florence Rage
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | - Rebecca Cacciottolo
- Department of Physiology and Biochemistry, University of Malta, Msida, Malta
| | | | - Ruben J Cauchi
- Department of Physiology and Biochemistry, University of Malta, Msida, Malta
| | | | | | - Yannick Gachet
- Centre de Biologie Integrative, University of Toulouse, CNRS, Toulouse, France
| | - Rémy Bordonné
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France.
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6
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Arbizzani F, Rincon SA, Paoletti A. Increasing ergosterol levels delays formin-dependent assembly of F-actin cables and disrupts division plane positioning in fission yeast. J Cell Sci 2019; 132:jcs.227447. [PMID: 31217286 DOI: 10.1242/jcs.227447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 05/31/2019] [Indexed: 11/20/2022] Open
Abstract
In most eukaryotes, cytokinesis is mediated by the constriction of a contractile acto-myosin ring (CR), which promotes the ingression of the cleavage furrow. Many components of the CR interact with plasma membrane lipids suggesting that lipids may regulate CR assembly and function. Although there is clear evidence that phosphoinositides play an important role in cytokinesis, much less is known about the role of sterols in this process. Here, we studied how sterols influence division plane positioning and CR assembly in fission yeast. We show that increasing ergosterol levels in the plasma membrane blocks the assembly of F-actin cables from cytokinetic precursor nodes, preventing their compaction into a ring. Abnormal F-actin cables form after a delay, leading to randomly placed septa. Since the formin Cdc12 was detected on cytokinetic precursors and the phenotype can be partially rescued by inhibiting the Arp2/3 complex, which competes with formins for F-actin nucleation, we propose that ergosterol may inhibit formin dependent assembly of F-actin cables from cytokinetic precursors.
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Affiliation(s)
| | - Sergio A Rincon
- Institut Curie, PSL University, CNRS UMR 144, 75005 Paris, France .,Instituto de Biología Funcional y Genómica and Departamento de Microbiología y Genética, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca, Salamanca 37007, Spain
| | - Anne Paoletti
- Institut Curie, PSL University, CNRS UMR 144, 75005 Paris, France
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7
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Internetwork competition for monomers governs actin cytoskeleton organization. Nat Rev Mol Cell Biol 2016; 17:799-810. [PMID: 27625321 DOI: 10.1038/nrm.2016.106] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Cells precisely control the formation of dynamic actin cytoskeleton networks to coordinate fundamental processes, including motility, division, endocytosis and polarization. To support these functions, actin filament networks must be assembled, maintained and disassembled at the correct time and place, and with proper filament organization and dynamics. Regulation of the extent of filament network assembly and of filament network organization has been largely attributed to the coordinated activation of actin assembly factors through signalling cascades. Here, we discuss an intriguing model in which actin monomer availability is limiting and competition between homeostatic actin cytoskeletal networks for actin monomers is an additional crucial regulatory mechanism that influences the density and size of different actin networks, thereby contributing to the organization of the cellular actin cytoskeleton.
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8
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Liu X, Qu X, Jiang Y, Chang M, Zhang R, Wu Y, Fu Y, Huang S. Profilin Regulates Apical Actin Polymerization to Control Polarized Pollen Tube Growth. MOLECULAR PLANT 2015; 8:1694-709. [PMID: 26433093 DOI: 10.1016/j.molp.2015.09.013] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Revised: 09/14/2015] [Accepted: 09/25/2015] [Indexed: 05/23/2023]
Abstract
Pollen tube growth is an essential step during flowering plant reproduction, whose growth depends on a population of dynamic apical actin filaments. Apical actin filaments were thought to be involved in the regulation of vesicle fusion and targeting in the pollen tube. However, the molecular mechanisms that regulate the construction of apical actin structures in the pollen tube remain largely unclear. Here, we identify profilin as an important player in the regulation of actin polymerization at the apical membrane in the pollen tube. Downregulation of profilin decreased the amount of filamentous actin and induced disorganization of apical actin filaments, and reduced tip-directed vesicle transport and accumulation in the pollen tube. Direct visualization of actin dynamics revealed that the elongation of actin filaments originating at the apical membrane decreased in profilin mutant pollen tubes. Mutant profilin that is defective in binding poly-L-proline only partially rescues the actin polymerization defect in profilin mutant pollen tubes, although it fully rescues the actin turnover phenotype. We propose that profilin controls the construction of actin structures at the pollen tube tip, presumably by favoring formin-mediated actin polymerization at the apical membrane.
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Affiliation(s)
- Xiaonan Liu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China; Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Xiaolu Qu
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Joint Center for Life Sciences, Beijing 100084, China
| | - Yuxiang Jiang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Ming Chang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Ruihui Zhang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Youjun Wu
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Ying Fu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Shanjin Huang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China; National Center for Plant Gene Research, Beijing 100101, China.
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9
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Jack of all trades: functional modularity in the adherens junction. Curr Opin Cell Biol 2015; 36:32-40. [DOI: 10.1016/j.ceb.2015.06.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Revised: 05/20/2015] [Accepted: 06/30/2015] [Indexed: 11/22/2022]
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10
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Hoffman CS, Wood V, Fantes PA. An Ancient Yeast for Young Geneticists: A Primer on the Schizosaccharomyces pombe Model System. Genetics 2015; 201:403-23. [PMID: 26447128 PMCID: PMC4596657 DOI: 10.1534/genetics.115.181503] [Citation(s) in RCA: 146] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The fission yeast Schizosaccharomyces pombe is an important model organism for the study of eukaryotic molecular and cellular biology. Studies of S. pombe, together with studies of its distant cousin, Saccharomyces cerevisiae, have led to the discovery of genes involved in fundamental mechanisms of transcription, translation, DNA replication, cell cycle control, and signal transduction, to name but a few processes. However, since the divergence of the two species approximately 350 million years ago, S. pombe appears to have evolved less rapidly than S. cerevisiae so that it retains more characteristics of the common ancient yeast ancestor, causing it to share more features with metazoan cells. This Primer introduces S. pombe by describing the yeast itself, providing a brief description of the origins of fission yeast research, and illustrating some genetic and bioinformatics tools used to study protein function in fission yeast. In addition, a section on some key differences between S. pombe and S. cerevisiae is included for readers with some familiarity with budding yeast research but who may have an interest in developing research projects using S. pombe.
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Affiliation(s)
- Charles S Hoffman
- Biology Department, Boston College, Chestnut Hill, Massachusetts 02467
| | - Valerie Wood
- Cambridge Systems Biology Centre and Department of Biochemistry, University of Cambridge, CB2 1GA Cambridge, United Kingdom
| | - Peter A Fantes
- School of Biological Sciences, College of Science and Engineering, University of Edinburgh EH9 3JR Edinburgh, United Kingdom
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11
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Diamond MI, Cai S, Boudreau A, Carey CJ, Lyle N, Pappu RV, Swamidass SJ, Bissell M, Piwnica-Worms H, Shao J. Subcellular localization and Ser-137 phosphorylation regulate tumor-suppressive activity of profilin-1. J Biol Chem 2015; 290:9075-86. [PMID: 25681442 DOI: 10.1074/jbc.m114.619874] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Indexed: 12/18/2022] Open
Abstract
The actin-binding protein profilin-1 (Pfn1) inhibits tumor growth and yet is also required for cell proliferation and survival, an apparent paradox. We previously identified Ser-137 of Pfn1 as a phosphorylation site within the poly-l-proline (PLP) binding pocket. Here we confirm that Ser-137 phosphorylation disrupts Pfn1 binding to its PLP-containing ligands with little effect on actin binding. We find in mouse xenografts of breast cancer cells that mimicking Ser-137 phosphorylation abolishes cell cycle arrest and apoptotic sensitization by Pfn1 and confers a growth advantage to tumors. This indicates a previously unrecognized role of PLP binding in Pfn1 antitumor effects. Spatial restriction of Pfn1 to the nucleus or cytoplasm indicates that inhibition of tumor cell growth by Pfn1 requires its nuclear localization, and this activity is abolished by a phosphomimetic mutation on Ser-137. In contrast, cytoplasmic Pfn1 lacks inhibitory effects on tumor cell growth but rescues morphological and proliferative defects of PFN1 null mouse chondrocytes. These results help reconcile seemingly opposed cellular effects of Pfn1, provide new insights into the antitumor mechanism of Pfn1, and implicate Ser-137 phosphorylation as a potential therapeutic target for breast cancer.
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Affiliation(s)
- Marc I Diamond
- From the Center for Alzheimer's and Neurodegenerative Diseases, University of Texas, Southwestern Medical Center, Dallas, Texas 75390
| | - Shirong Cai
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77230
| | - Aaron Boudreau
- Department of Laboratory Medicine, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, California 94143
| | - Clifton J Carey
- Division of Laboratory and Genomic Medicine, Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Nicholas Lyle
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130
| | - Rohit V Pappu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130
| | - S Joshua Swamidass
- Division of Laboratory and Genomic Medicine, Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Mina Bissell
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and
| | - Helen Piwnica-Worms
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77230
| | - Jieya Shao
- Breast Oncology Program, Division of Oncology, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
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12
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Suarez C, Carroll RT, Burke TA, Christensen JR, Bestul AJ, Sees JA, James ML, Sirotkin V, Kovar DR. Profilin regulates F-actin network homeostasis by favoring formin over Arp2/3 complex. Dev Cell 2014; 32:43-53. [PMID: 25543282 DOI: 10.1016/j.devcel.2014.10.027] [Citation(s) in RCA: 188] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 09/12/2014] [Accepted: 10/30/2014] [Indexed: 10/24/2022]
Abstract
Fission yeast cells use Arp2/3 complex and formin to assemble diverse filamentous actin (F-actin) networks within a common cytoplasm for endocytosis, division, and polarization. Although these homeostatic F-actin networks are usually investigated separately, competition for a limited pool of actin monomers (G-actin) helps to regulate their size and density. However, the mechanism by which G-actin is correctly distributed between rival F-actin networks is not clear. Using a combination of cell biological approaches and in vitro reconstitution of competition between actin assembly factors, we found that the small G-actin binding protein profilin directly inhibits Arp2/3 complex-mediated actin assembly. Profilin is therefore required for formin to compete effectively with excess Arp2/3 complex for limited G-actin and to assemble F-actin for contractile ring formation in dividing cells.
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Affiliation(s)
- Cristian Suarez
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Robert T Carroll
- Department of Cell and Developmental Biology, State University of New York (SUNY) Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
| | - Thomas A Burke
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Jenna R Christensen
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Andrew J Bestul
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Jennifer A Sees
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Michael L James
- Department of Cell and Developmental Biology, State University of New York (SUNY) Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
| | - Vladimir Sirotkin
- Department of Cell and Developmental Biology, State University of New York (SUNY) Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA.
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA; Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA.
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13
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Bestul AJ, Christensen JR, Grzegorzewska AP, Burke TA, Sees JA, Carroll RT, Sirotkin V, Keenan RJ, Kovar DR. Fission yeast profilin is tailored to facilitate actin assembly by the cytokinesis formin Cdc12. Mol Biol Cell 2014; 26:283-93. [PMID: 25392301 PMCID: PMC4294675 DOI: 10.1091/mbc.e13-05-0281] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The evolutionarily conserved small actin-monomer binding protein profilin is believed to be a housekeeping factor that maintains a general pool of unassembled actin. However, despite similar primary sequences, structural folds, and affinities for G-actin and poly-L-proline, budding yeast profilin ScPFY fails to complement fission yeast profilin SpPRF temperature-sensitive mutant cdc3-124 cells. To identify profilin's essential properties, we built a combinatorial library of ScPFY variants containing either WT or SpPRF residues at multiple positions and carried out a genetic selection to isolate variants that support life in fission yeast. We subsequently engineered ScPFY(9-Mut), a variant containing nine substitutions in the actin-binding region, which complements cdc3-124 cells. ScPFY(9-Mut), but not WT ScPFY, suppresses severe cytokinesis defects in cdc3-124 cells. Furthermore, the major activity rescued by ScPFY(9-Mut) is the ability to enhance cytokinesis formin Cdc12-mediated actin assembly in vitro, which allows cells to assemble functional contractile rings. Therefore an essential role of profilin is to specifically facilitate formin-mediated actin assembly for cytokinesis in fission yeast.
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Affiliation(s)
- Andrew J Bestul
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Jenna R Christensen
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | | | - Thomas A Burke
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Jennifer A Sees
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Robert T Carroll
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
| | - Vladimir Sirotkin
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
| | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637 Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637
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14
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Huang J, Huang Y, Yu H, Subramanian D, Padmanabhan A, Thadani R, Tao Y, Tang X, Wedlich-Soldner R, Balasubramanian MK. Nonmedially assembled F-actin cables incorporate into the actomyosin ring in fission yeast. ACTA ACUST UNITED AC 2013. [PMID: 23185032 PMCID: PMC3514790 DOI: 10.1083/jcb.201209044] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In many eukaryotes, cytokinesis requires the assembly and constriction of an actomyosin-based contractile ring. Despite the central role of this ring in cytokinesis, the mechanism of F-actin assembly and accumulation in the ring is not fully understood. In this paper, we investigate the mechanism of F-actin assembly during cytokinesis in Schizosaccharomyces pombe using lifeact as a probe to monitor actin dynamics. Previous work has shown that F-actin in the actomyosin ring is assembled de novo at the division site. Surprisingly, we find that a significant fraction of F-actin in the ring was recruited from formin-Cdc12p nucleated long actin cables that were generated at multiple nonmedial locations and incorporated into the ring by a combination of myosin II and myosin V activities. Our results, together with findings in animal cells, suggest that de novo F-actin assembly at the division site and directed transport of F-actin cables assembled elsewhere can contribute to ring assembly.
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Affiliation(s)
- Junqi Huang
- Cell Division Laboratory, Temasek Life Sciences Laboratory, Singapore 117604
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15
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Identification of SIN pathway targets reveals mechanisms of crosstalk between NDR kinase pathways. Curr Biol 2013; 23:333-8. [PMID: 23394829 DOI: 10.1016/j.cub.2013.01.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 12/04/2012] [Accepted: 01/03/2013] [Indexed: 12/15/2022]
Abstract
The septum initiation network (SIN) regulates multiple functions during late mitosis to ensure successful completion of cytokinesis in Schizosaccharomyces pombe. One mechanism by which the SIN promotes cytokinesis is by inhibiting a competing polarity pathway called the MOR, which is required for initiation of polarized growth following completion of cytokinesis. Mutual antagonism between the two NDR kinase pathways, SIN and MOR, is required to coordinate cytoskeletal rearrangements during the mitosis-interphase transition. To determine how the SIN regulates the MOR pathway, we developed a proteomics approach that allowed us to identify multiple substrates of the SIN effector kinase Sid2, including the MOR pathway components Nak1 kinase and an associated protein, Sog2. We show that Sid2 phosphorylation of Nak1 causes removal of Nak1 from the spindle pole bodies, which may both relieve Nak1 inhibition of the SIN and block MOR signaling by preventing interaction of Nak1 with the scaffold protein Mor2. Because the SIN and MOR are conserved in mammalian cells (Hippo and Ndr1/2 pathways, respectively), this work may provide important insight into how the activities of these essential pathways are coordinated.
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16
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Fan T, Zhai H, Shi W, Wang J, Jia H, Xiang Y, An L. Overexpression of profilin 3 affects cell elongation and F-actin organization in Arabidopsis thaliana. PLANT CELL REPORTS 2013; 32:149-60. [PMID: 23052593 DOI: 10.1007/s00299-012-1349-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/06/2012] [Accepted: 09/18/2012] [Indexed: 05/13/2023]
Abstract
KEY MESSAGE : Reduced levels of profilin 3 do not have a noticeable phenotypic effect; however, elevated profilin 3 levels result in decreased hypocotyl length due to a reduction in cell elongation and F-actin reorganization. The actin cytoskeleton is critical for a variety of cellular processes. The small actin monomer proteins, profilins (PRFs), are encoded by five highly conserved isoforms in Arabidopsis thaliana. PRF3, one of the vegetative isoforms, has 36 more N-terminal amino acid residues than the other four PRFs; however, the functions of PRF3 are mostly unknown. In this study, we demonstrated that PRF3 was strongly expressed in young seedlings, rosette leaves, and cauline leaves, but was weakly expressed in 14-day-old seedlings and flowers. Our data also showed that PRF3 could increase the critical concentration (Cc) of actin assembly in vitro. Overexpression of the full-length PRF3 cDNA resulted in a decrease in the lengths of roots and hypocotyls and delayed seed germination, but PRF3-ΔN36 transgenic plants and prf3 mutant plants showed normal growth when compared with wild-type plants. Microscopy observation revealed that cell elongation was inhibited in the hypocotyl and that F-actin was reorganized by destabilizing microfilaments. These results suggest that the dwarf phenotype of the PRF3 overexpression seedlings may be related to a reduction in cell length and F-actin rearrangement.
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Affiliation(s)
- Tingting Fan
- School of Life Sciences, Lanzhou University, Lanzhou 730000, PR China.
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17
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Ding Z, Bae YH, Roy P. Molecular insights on context-specific role of profilin-1 in cell migration. Cell Adh Migr 2012; 6:442-9. [PMID: 23076048 DOI: 10.4161/cam.21832] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Profilin-1 (Pfn1) is a ubiquitously expressed actin-monomer binding protein that has been linked to many cellular activities ranging from control of actin polymerization to gene transcription. Traditionally, Pfn1 has been considered to be an essential control element for actin polymerization and cell migration. Seemingly contrasting this view, a few recent studies have shown evidence of an inhibitory action of Pfn1 on motility of certain types of carcinoma cells. In this review, we summarize biochemistry and functional aspects of Pfn1 in normal cells and bring in newly emerged action of Pfn1 in cancer cells that may explain its context-specific role in cell migration.
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Affiliation(s)
- Zhijie Ding
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
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18
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Lee IJ, Coffman VC, Wu JQ. Contractile-ring assembly in fission yeast cytokinesis: Recent advances and new perspectives. Cytoskeleton (Hoboken) 2012; 69:751-63. [PMID: 22887981 DOI: 10.1002/cm.21052] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 07/16/2012] [Indexed: 11/07/2022]
Abstract
The fission yeast Schizosaccharomyces pombe is an excellent model organism to study cytokinesis. Here, we review recent advances on contractile-ring assembly in fission yeast. First, we summarize the assembly of cytokinesis nodes, the precursors of a normal contractile ring. IQGAP Rng2 and myosin essential light chain Cdc4 are recruited by the anillin-like protein Mid1, followed by the addition of other cytokinesis node proteins. Mid1 localization on the plasma membrane is stabilized by interphase node proteins. Second, we discuss proteins and processes that contribute to the search, capture, pull, and release mechanism of contractile-ring assembly. Actin filaments nucleated by formin Cdc12, the motor activity of myosin-II, the stiffness of the actin network, and severing of actin filaments by cofilin all play essential roles in contractile-ring assembly. Finally, we discuss the Mid1-independent pathway for ring assembly, and the possible mechanisms underlying the ring maturation and constriction. Collectively, we provide an overview of the current understanding of contractile-ring assembly and uncover future directions in studying cytokinesis in fission yeast.
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Affiliation(s)
- I-Ju Lee
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, USA
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19
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Cortés JCG, Sato M, Muñoz J, Moreno MB, Clemente-Ramos JA, Ramos M, Okada H, Osumi M, Durán A, Ribas JC. Fission yeast Ags1 confers the essential septum strength needed for safe gradual cell abscission. ACTA ACUST UNITED AC 2012; 198:637-56. [PMID: 22891259 PMCID: PMC3514033 DOI: 10.1083/jcb.201202015] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
The α(1-3)glucan synthase Ags1 is essential for both secondary septum
formation and the primary septum structural strength needed to counter cell
turgor pressure during cell separation. Fungal cytokinesis requires the assembly of a dividing septum wall. In yeast, the
septum has to be selectively digested during the critical cell separation
process. Fission yeast cell wall α(1-3)glucan is essential, but nothing
is known about its localization and function in the cell wall or about
cooperation between the α- and β(1-3)glucan synthases Ags1 and Bgs
for cell wall and septum assembly. Here, we generate a physiological Ags1-GFP
variant and demonstrate a tight colocalization with Bgs1, suggesting a
cooperation in the important early steps of septum construction. Moreover, we
define the essential functions of α(1-3)glucan in septation and cell
separation. We show that α(1-3)glucan is essential for both secondary
septum formation and the primary septum structural strength needed to support
the physical forces of the cell turgor pressure during cell separation.
Consequently, the absence of Ags1 and therefore α(1-3)glucan generates a
special and unique side-explosive cell separation due to an instantaneous
primary septum tearing caused by the turgor pressure.
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Affiliation(s)
- Juan Carlos G Cortés
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca, 37007 Salamanca, Spain
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20
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Pittman KJ, Skop AR. Anterior PAR proteins function during cytokinesis and maintain DYN-1 at the cleavage furrow in Caenorhabditis elegans. Cytoskeleton (Hoboken) 2012; 69:826-39. [PMID: 22887994 DOI: 10.1002/cm.21053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Revised: 07/16/2012] [Accepted: 07/17/2012] [Indexed: 12/25/2022]
Abstract
PAR proteins are key regulators of cellular polarity and have links to the endocytic machinery and the actin cytoskeleton. Our data suggest a unique role for PAR proteins in cytokinesis. We have found that at the onset of cytokinesis, anterior PAR-6 and posterior PAR-2 proteins are redistributed to the furrow membrane in a temporal and spatial manner. PAR-6 and PAR-2 localize to the furrow membrane during ingression but PAR-2-GFP is distinct in that it is excluded from the extreme tip of the furrow. Once the midbody has formed, PAR-2-GFP becomes restricted to the midbody region (the midbody plus the membrane flanking it). Depletion of both anterior PAR proteins, PAR-3 and PAR-6, led to an increase in multinucleate embryos, suggesting that the anterior PAR proteins are necessary during cytokinesis and that PAR-3 and PAR-6 function in cytokinesis may be partially redundant. Lastly, anterior PAR proteins play a role in the maintenance of DYN-1 in the cleavage furrow. Our data indicate that the PAR proteins are involved in the events that occur during cytokinesis and may play a role in promoting the membrane trafficking and remodeling events that occur during this time.
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Affiliation(s)
- Kelly J Pittman
- Laboratory of Genetics and Medical Genetics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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21
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Yap KL, Fraley SI, Thiaville MM, Jinawath N, Nakayama K, Wang J, Wang TL, Wirtz D, Shih IM. NAC1 is an actin-binding protein that is essential for effective cytokinesis in cancer cells. Cancer Res 2012; 72:4085-96. [PMID: 22761335 DOI: 10.1158/0008-5472.can-12-0302] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
NAC1 is a transcriptional corepressor protein that is essential to sustain cancer cell proliferation and migration. However, the underlying molecular mechanisms of NAC1 function in cancer cells remain unknown. In this study, we show that NAC1 functions as an actin monomer-binding protein. The conserved BTB protein interaction domain in NAC1 is the minimal region for actin binding. Disrupting NAC1 complex function by dominant-negative or siRNA strategies reduced cell retraction and abscission during late-stage cytokinesis, causing multinucleation in cancer cells. In Nac1-deficient murine fibroblasts, restoring NAC1 expression was sufficient to partially avert multinucleation. We found that siRNA-mediated silencing of the actin-binding protein profilin-1 in cancer cells caused a similar multinucleation phenotype and that NAC1 modulated the binding of actin to profillin-1. Taken together, our results indicate that the NAC1/actin/profilin-1 complex is crucial for cancer cell cytokinesis, with a variety of important biologic and clinical implications.
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Affiliation(s)
- Kai Lee Yap
- Department of Pathology, Pathobiology Graduate Program, Oncology Center, Johns Hopkins University, Baltimore, Maryland 21231, USA
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22
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Jayadev R, Kuk CY, Low SH, Murata-Hori M. Calcium sensitivity of α-actinin is required for equatorial actin assembly during cytokinesis. Cell Cycle 2012; 11:1929-37. [PMID: 22544326 DOI: 10.4161/cc.20277] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The actin cross-linking protein, α-actinin, plays a crucial role in mediating furrow ingression during cytokinesis. However, the mechanism by which its dynamics are regulated during this process is poorly understood. Here we have investigated the role of calcium sensitivity of α-actinin in the regulation of its dynamics by generating a functional calcium-insensitive mutant (EFM). GFP-tagged EFM (EFM-GFP) localized to the equatorial regions during cell division. However, the maximal equatorial accumulation of EFM-GFP was significantly smaller in comparison to α-actinin-GFP when it was expressed in normal cells and cells depleted of endogenous α-actinin. No apparent defects in cytokinesis were observed in these cells. However, F-actin levels at the equator were significantly reduced in cells expressing EFM-GFP as compared with α-actinin-GFP at furrow initiation but were recovered during furrow ingression. These results suggest that calcium sensitivity of α-actinin is required for its equatorial accumulation that is crucial for the initial equatorial actin assembly but is dispensable for cytokinesis. Equatorial RhoA localization was not affected by EFM-GFP overexpression, suggesting that equatorial actin assembly is predominantly driven by the RhoA-dependent mechanism. Our observations shed new light on the role and regulation of the accumulation of pre-existing actin filaments in equatorial actin assembly during cytokinesis.
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Affiliation(s)
- Ranjay Jayadev
- Cell Biology Program, Temasek Life Sciences Laboratory; Singapore
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23
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Calvert MEK, Wright GD, Leong FY, Chiam KH, Chen Y, Jedd G, Balasubramanian MK. Myosin concentration underlies cell size-dependent scalability of actomyosin ring constriction. ACTA ACUST UNITED AC 2012; 195:799-813. [PMID: 22123864 PMCID: PMC3257563 DOI: 10.1083/jcb.201101055] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The rate of actomyosin ring constriction in cells of different sizes correlates with myosin motor concentration in Neurospora crassa cells, leading to increased division rates in larger cells during cytokinesis. In eukaryotes, cytokinesis is accomplished by an actomyosin-based contractile ring. Although in Caenorhabditis elegans embryos larger cells divide at a faster rate than smaller cells, it remains unknown whether a similar mode of scalability operates in other cells. We investigated cytokinesis in the filamentous fungus Neurospora crassa, which exhibits a wide range of hyphal circumferences. We found that N. crassa cells divide using an actomyosin ring and larger rings constricted faster than smaller rings. However, unlike in C. elegans, the total amount of myosin remained constant throughout constriction, and there was a size-dependent increase in the starting concentration of myosin in the ring. We predict that the increased number of ring-associated myosin motors in larger rings leads to the increased constriction rate. Accordingly, reduction or inhibition of ring-associated myosin slows down the rate of constriction. Because the mechanical characteristics of contractile rings are conserved, we predict that these findings will be relevant to actomyosin ring constriction in other cell types.
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Affiliation(s)
- Meredith E K Calvert
- Temasek Life Sciences Laboratory, The National University of Singapore, Singapore 117604.
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24
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Yan H, Balasubramanian MK. A Meiotic Actin Ring (MeiAR) Essential for Proper Sporulation in Fission Yeast. J Cell Sci 2012. [DOI: 10.1242/jcs.jcs091561] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Sporulation is a unique form of cytokinesis that occurs following meiosis II in many yeasts, during which four daughter cells (spores) are generated within a single mother cell. Here we characterize the role of F-actin in the process of sporulation in the fission yeast Schizosaccharomyces pombe. As shown previously, we find that F-actin assembles into 4 ring structures per ascus, referred to as the MeiAR (meiotic actin ring). The actin nucleators Arp2/3 and formin-For3 assemble into ring structures that overlap with Meu14, a protein known to assemble into the so-called leading edge, a ring structure that is known to guide forespore membrane assembly. Interestingly, F-actin makes rings that occupy a larger region behind the leading edge ring. Time-lapse microscopy showed that the MeiAR assembles near the spindle pole bodies and undergoes an expansion in diameter during the early stages of meiosis II, followed by closure in later stages of meiosis II. MeiAR closure completes the process of forespore membrane assembly. Loss of MeiAR leads to excessive assembly of forespore membranes with a deformed appearance. The rate of closure of the MeiAR is dictated by the function of the Septation Initiation Network (SIN). We conclude that the MeiAR ensures proper targeting of the membrane biogenesis machinery to the leading edge, thereby ensuring the formation of spherically shaped spores.
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25
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Abstract
Filamentous (F)-actin is a known regulator of the synaptic vesicle (SV) cycle, with roles in SV mobilization, fusion, and endocytosis. However, the molecular pathways that regulate its dynamic assembly within presynaptic boutons remain unclear. In this study, we have used shRNA-mediated knockdown to demonstrate that Piccolo, a multidomain protein of the active zone cytomatrix, is a key regulator of presynaptic F-actin assembly. Boutons lacking Piccolo exhibit enhanced activity-dependent Synapsin1a dispersion and SV exocytosis, and reduced F-actin polymerization and CaMKII recruitment. These phenotypes are rescued by stabilizing F-actin filaments and mimicked by knocking down Profilin2, another regulator of presynaptic F-actin assembly. Importantly, we find that mice with a targeted deletion of exon 14 from the Pclo gene, reported to lack >95% of Piccolo, continue to express multiple Piccolo isoforms. Furthermore, neurons cultured from these mice exhibit no defects in presynaptic F-actin assembly due to the expression of these isoforms at presynaptic boutons. These data reveal that Piccolo regulates neurotransmitter release by facilitating activity-dependent F-actin assembly and the dynamic recruitment of key signaling molecules into presynaptic boutons, and highlight the need for new genetic models with which to study Piccolo loss of function.
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26
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Gupta S, McCollum D. Crosstalk between NDR kinase pathways coordinates cell cycle dependent actin rearrangements. Cell Div 2011; 6:19. [PMID: 22079013 PMCID: PMC3224761 DOI: 10.1186/1747-1028-6-19] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 11/11/2011] [Indexed: 12/13/2022] Open
Abstract
Regulation of cytoskeletal remodeling is essential for cell cycle transitions. In fission yeast two NDR kinase signaling cascades, MOR and SIN, regulate the actin cytoskeleton to promote polarized growth during interphase and cytokinesis respectively. Our understanding of how these signaling pathways are coordinated to assist transition between the two cell-cycle stages is limited. Here, we review work from our laboratory, which reveals that cross talk between the SIN and MOR pathways is required for inhibition of interphase polarity programs during cytokinesis. Given the conservation of NDR kinase signaling pathways, our results may define general mechanisms by which these pathways are coordinated in higher organisms.
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Affiliation(s)
- Sneha Gupta
- Department of Microbiology and Physiological Systems, and Program in Cell Dynamics, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
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27
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Goyal A, Takaine M, Simanis V, Nakano K. Dividing the spoils of growth and the cell cycle: The fission yeast as a model for the study of cytokinesis. Cytoskeleton (Hoboken) 2011; 68:69-88. [PMID: 21246752 PMCID: PMC3044818 DOI: 10.1002/cm.20500] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Revised: 12/15/2010] [Accepted: 12/20/2010] [Indexed: 12/12/2022]
Abstract
Cytokinesis is the final stage of the cell cycle, and ensures completion of both genome segregation and organelle distribution to the daughter cells. Cytokinesis requires the cell to solve a spatial problem (to divide in the correct place, orthogonally to the plane of chromosome segregation) and a temporal problem (to coordinate cytokinesis with mitosis). Defects in the spatiotemporal control of cytokinesis may cause cell death, or increase the risk of tumor formation [Fujiwara et al., 2005 (Fujiwara T, Bandi M, Nitta M, Ivanova EV, Bronson RT, Pellman D. 2005. Cytokinesis failure generating tetraploids promotes tumorigenesis in p53-null cells. Nature 437:1043–1047); reviewed by Ganem et al., 2007 (Ganem NJ, Storchova Z, Pellman D. 2007. Tetraploidy, aneuploidy and cancer. Curr Opin Genet Dev 17:157–162.)]. Asymmetric cytokinesis, which permits the generation of two daughter cells that differ in their shape, size and properties, is important both during development, and for cellular homeostasis in multicellular organisms [reviewed by Li, 2007 (Li R. 2007. Cytokinesis in development and disease: variations on a common theme. Cell Mol Life Sci 64:3044–3058)]. The principal focus of this review will be the mechanisms of cytokinesis in the mitotic cycle of the yeast Schizosaccharomyces pombe. This simple model has contributed significantly to our understanding of how the cell cycle is regulated, and serves as an excellent model for studying aspects of cytokinesis. Here we will discuss the state of our knowledge of how the contractile ring is assembled and disassembled, how it contracts, and what we know of the regulatory mechanisms that control these events and assure their coordination with chromosome segregation.
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Affiliation(s)
- Anupama Goyal
- EPFL SV ISREC UPSIMSV2.1830, Station 19, CH 1015 Lausanne, Switzerland
| | - Masak Takaine
- Structural Biosciences, Graduate School of Environmental and Life Sciences, University of Tsukuba1-1-1 Tennohdai, Tsukuba, Ibaraki 305-8577, Japan
| | - Viesturs Simanis
- EPFL SV ISREC UPSIMSV2.1830, Station 19, CH 1015 Lausanne, Switzerland
| | - Kentaro Nakano
- Structural Biosciences, Graduate School of Environmental and Life Sciences, University of Tsukuba1-1-1 Tennohdai, Tsukuba, Ibaraki 305-8577, Japan
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28
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Bendezú FO, Martin SG. Actin cables and the exocyst form two independent morphogenesis pathways in the fission yeast. Mol Biol Cell 2010; 22:44-53. [PMID: 21148300 PMCID: PMC3016976 DOI: 10.1091/mbc.e10-08-0720] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
In fission yeast, long-range transport and vesicle tethering by the exocyst are individually dispensable but together essential for cell morphogenesis. Both pathways function downstream of Cdc42. The exocyst localizes to growing cell tips independently of the cytoskeleton and instead depends on PIP2. Cell morphogenesis depends on polarized exocytosis. One widely held model posits that long-range transport and exocyst-dependent tethering of exocytic vesicles at the plasma membrane sequentially drive this process. Here, we describe that disruption of either actin-based long-range transport and microtubules or the exocyst did not abolish polarized growth in rod-shaped fission yeast cells. However, disruption of both actin cables and exocyst led to isotropic growth. Exocytic vesicles localized to cell tips in single mutants but were dispersed in double mutants. In contrast, a marker for active Cdc42, a major polarity landmark, localized to discreet cortical sites even in double mutants. Localization and photobleaching studies show that the exocyst subunits Sec6 and Sec8 localize to cell tips largely independently of the actin cytoskeleton, but in a cdc42 and phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2)–dependent manner. Thus in fission yeast long-range cytoskeletal transport and PIP2-dependent exocyst represent parallel morphogenetic modules downstream of Cdc42, raising the possibility of similar mechanisms in other cell types.
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Affiliation(s)
- Felipe O Bendezú
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, CH-1015 Lausanne, Switzerland
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29
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Ray S, Kume K, Gupta S, Ge W, Balasubramanian M, Hirata D, McCollum D. The mitosis-to-interphase transition is coordinated by cross talk between the SIN and MOR pathways in Schizosaccharomyces pombe. ACTA ACUST UNITED AC 2010; 190:793-805. [PMID: 20805322 PMCID: PMC2935563 DOI: 10.1083/jcb.201002055] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The SIN pathway blocks inappropriate actin rearrangements during cytokinesis by preventing activation of the MOR pathway component Orb6. The mechanisms that regulate cytoskeletal remodeling during the transition between mitosis and interphase are poorly understood. In fission yeast the MOR pathway promotes actin polarization to cell tips in interphase, whereas the SIN signaling pathway drives actomyosin ring assembly and cytokinesis. We show that the SIN inhibits MOR signaling in mitosis by interfering with Nak1 kinase-mediated activation of the most downstream MOR component, the NDR family kinase Orb6. Inactivation of the MOR may be a key function of the SIN because attenuation of MOR signaling rescued the cytokinetic defects of SIN mutants and allowed weak SIN signaling to trigger ectopic cytokinesis. Furthermore, failure to inhibit the MOR is toxic when the cell division apparatus is compromised. Together, our results reveal a mutually antagonistic relationship between the SIN and MOR pathways, which is important for completion of cytokinesis and coordination of cytoskeletal remodeling at the mitosis-to-interphase transition.
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Affiliation(s)
- Samriddha Ray
- Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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30
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Zou L, Ding Z, Roy P. Profilin-1 overexpression inhibits proliferation of MDA-MB-231 breast cancer cells partly through p27kip1 upregulation. J Cell Physiol 2010; 223:623-9. [PMID: 20143334 DOI: 10.1002/jcp.22058] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Profilin-1 (Pfn1), a ubiquitously expressed actin-binding protein, has gained interest in epithelial-derived cancer because of its downregulation in expression in various adenocarcinoma. Pfn1 overexpression impairs tumorigenic ability of human breast cancer xenografts thus suggesting that Pfn1 could be a tumor-suppressor protein. The objective of the present study was to determine how Pfn1 overexpression affects cell-cycle progression of breast cancer cells. We show that Pfn1 overexpression in MDA-MB-231 breast cancer cells causes cell-cycle arrest in G1 phase and dramatically reduced proliferation in culture. Pfn1 overexpression results in increased protein stability of p27(kip1) (p27-a major cyclin-dependent kinase inhibitor) and marked elevation in the overall cellular level of p27. Proliferation defect of Pfn1 overexpressers can be partly rescued by silencing p27 expression thus suggesting a critical role of p27 in Pfn1-induced growth inhibition of MDA-MB-231 cells. Finally, Pfn1 overexpression was found to sensitize MDA-MB-231 cells to apoptosis in response to cytotoxic stimulus thus suggesting for the first time that survival of breast cancer cells can also be negatively influenced by Pfn1 upregulation. These findings may provide novel insights underlying Pfn1's tumor-suppressive action.
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Affiliation(s)
- Li Zou
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15219, USA
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31
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Impact of marine drugs on cytoskeleton-mediated reproductive events. Mar Drugs 2010; 8:881-915. [PMID: 20479959 PMCID: PMC2866467 DOI: 10.3390/md8040881] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 03/02/2010] [Accepted: 03/23/2010] [Indexed: 12/30/2022] Open
Abstract
Marine organisms represent an important source of novel bioactive compounds, often showing unique modes of action. Such drugs may be useful tools to study complex processes such as reproduction; which is characterized by many crucial steps that start at gamete maturation and activation and virtually end at the first developmental stages. During these processes cytoskeletal elements such as microfilaments and microtubules play a key-role. In this review we describe: (i) the involvement of such structures in both cellular and in vitro processes; (ii) the toxins that target the cytoskeletal elements and dynamics; (iii) the main steps of reproduction and the marine drugs that interfere with these cytoskeleton-mediated processes. We show that marine drugs, acting on microfilaments and microtubules, exert a wide range of impacts on reproductive events including sperm maturation and motility, oocyte maturation, fertilization, and early embryo development.
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Vidali L, Augustine RC, Fay SN, Franco P, Pattavina KA, Bezanilla M. Rapid screening for temperature-sensitive alleles in plants. PLANT PHYSIOLOGY 2009; 151:506-14. [PMID: 19666707 PMCID: PMC2754644 DOI: 10.1104/pp.109.143727] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Accepted: 08/06/2009] [Indexed: 05/21/2023]
Abstract
We developed a simple and fast method to identify temperature-sensitive alleles of essential plant genes. We used primary and tertiary structure information to identify residues in the core of the protein of interest. These residues were mutated and tested for temperature sensitivity, taking advantage of the exceptionally rapid 1-week complementation assay in the moss Physcomitrella patens. As test molecules, we selected the actin-binding proteins profilin and actin-depolymerizing factor, because they are essential and their loss-of-function phenotype can be fully rescued. Screening a small number of candidate mutants, we successfully identified temperature-sensitive alleles of both profilin and actin-depolymerizing factor. Plants harboring these alleles grew well at the permissive temperature of 20 degrees C to 25 degrees C but showed a complete loss of function at the restrictive temperature of 32 degrees C. Notably, the profilin mutation identified in the moss gene can be transferred to profilins from other plant species, also rendering them temperature sensitive. The ability to routinely generate temperature-sensitive alleles of essential plant proteins provides a powerful tool for the study of gene function in plants.
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Affiliation(s)
- Luis Vidali
- Biology Department, University of Massachusetts, Amherst, Massachusetts 01003, USA
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Takaine M, Numata O, Nakano K. Fission yeast IQGAP arranges actin filaments into the cytokinetic contractile ring. EMBO J 2009; 28:3117-31. [PMID: 19713940 DOI: 10.1038/emboj.2009.252] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2009] [Accepted: 07/27/2009] [Indexed: 11/09/2022] Open
Abstract
The contractile ring (CR) consists of bundled actin filaments and myosin II; however, the actin-bundling factor remains elusive. We show that the fission yeast Schizosaccharomyces pombe IQGAP Rng2 is involved in the generation of CR F-actin and required for its arrangement into a ring. An N-terminal fragment of Rng2 is necessary for the function of Rng2 and is localized to CR F-actin. In vitro the fragment promotes actin polymerization and forms linear arrays of F-actin, which are resistant to the depolymerization induced by the actin-depolymerizing factor Adf1. Our findings indicate that Rng2 is involved in the generation of CR F-actin and simultaneously bundles the filaments and regulates its dynamics by counteracting the effects of Adf1, thus enabling the reconstruction of CR F-actin bundles, which provides an insight into the physical properties of the building blocks that comprise the CR.
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Affiliation(s)
- Masak Takaine
- Department of Structural Biosciences, Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
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Du Y, Zhou J, Fan J, Shen Z, Chen X. Streamline proteomic approach for characterizing protein-protein interaction network in a RAD52 protein complex. J Proteome Res 2009; 8:2211-7. [PMID: 19338310 DOI: 10.1021/pr800662x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Large-scale identification of protein-protein interactions (PPIs) in functional complexes represents an efficient route to elucidate the regulatory rules of cellular functions. Whereas many methods have been developed to identify the PPIs associated with particular target/bait protein in complexes, little information is available about the interaction relationships among all components in a complex. Here, we have established a strategy of integrating proteomic identification of complex components with mammalian two-hybrid screening of their binary relationships to achieve information content of both breadth (i.e., identifying all potential interacting partners of the protein of interest) and depth (i.e., detailed mapping of the physical interactions of a subset of the identified and functionally related proteins) in characterizing protein complexes. In the initial phase of quantitative proteomic analysis of this streamline, the proteins that specifically complex with the target/bait protein were pulled down by immunoprecipitation and identified by mass spectrometry (MS)-based "dual-tagging" quantitative proteomic approach. In the second phase of in-depth characterizations of binary relationships, the physical interactions of a subset of functionally closely related complex components are mapped by mammalian two-hybrid assay. The screening for binary relationships of complex components not only serves as a validation of the first phase of proteomic identification, but also further deepens the understanding of the protein complex of interest. With this streamlined approach, we studied the protein complexes that are associated with a DNA recombination protein RAD52. In the initial phase, multiple proteins both known and unknown to interact with RAD52 were identified by the "dual-tagging" proteomic method. In the second phase, a complex protein-protein interaction network, which may play important roles in coordinating the activity of DNA repair with that of cell division, was defined by the mammalian two-hybrid assay.
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Affiliation(s)
- Yuchun Du
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7260, USA
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35
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Profilin 1 is required for abscission during late cytokinesis of chondrocytes. EMBO J 2009; 28:1157-69. [PMID: 19262563 DOI: 10.1038/emboj.2009.58] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Accepted: 02/11/2009] [Indexed: 01/20/2023] Open
Abstract
Profilins are key factors for dynamic rearrangements of the actin cytoskeleton. However, the functions of profilins in differentiated mammalian cells are uncertain because profilin deficiency is early embryonic lethal for higher eukaryotes. To examine profilin function in chondrocytes, we disrupted the profilin 1 gene in cartilage (Col2pfn1). Homozygous Col2pfn1 mice develop progressive chondrodysplasia caused by disorganization of the growth plate and defective chondrocyte cytokinesis, indicated by the appearance of binucleated cells. Surprisingly, Col2pfn1 chondrocytes assemble and contract actomyosin rings normally during cell division; however, they display defects during late cytokinesis as they frequently fail to complete abscission due to their inability to develop strong traction forces. This reduced force generation results from an impaired formation of lamellipodia, focal adhesions and stress fibres, which in part could be linked to an impaired mDia1-mediated actin filament elongation. Neither an actin nor a poly-proline binding-deficient profilin 1 is able to rescue the defects. Taken together, our results demonstrate that profilin 1 is not required for actomyosin ring formation in dividing chondrocytes but necessary to generate sufficient force for abscission during late cytokinesis.
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Skau CT, Neidt EM, Kovar DR. Role of tropomyosin in formin-mediated contractile ring assembly in fission yeast. Mol Biol Cell 2009; 20:2160-73. [PMID: 19244341 DOI: 10.1091/mbc.e08-12-1201] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Like animal cells, fission yeast divides by assembling actin filaments into a contractile ring. In addition to formin Cdc12p and profilin, the single tropomyosin isoform SpTm is required for contractile ring assembly. Cdc12p nucleates actin filaments and remains processively associated with the elongating barbed end while driving the addition of profilin-actin. SpTm is thought to stabilize mature filaments, but it is not known how SpTm localizes to the contractile ring and whether SpTm plays a direct role in Cdc12p-mediated actin polymerization. Using "bulk" and single actin filament assays, we discovered that Cdc12p can recruit SpTm to actin filaments and that SpTm has diverse effects on Cdc12p-mediated actin assembly. On its own, SpTm inhibits actin filament elongation and depolymerization. However, Cdc12p completely overcomes the combined inhibition of actin nucleation and barbed end elongation by profilin and SpTm. Furthermore, SpTm increases the length of Cdc12p-nucleated actin filaments by enhancing the elongation rate twofold and by allowing them to anneal end to end. In contrast, SpTm ultimately turns off Cdc12p-mediated elongation by "trapping" Cdc12p within annealed filaments or by dissociating Cdc12p from the barbed end. Therefore, SpTm makes multiple contributions to contractile ring assembly during and after actin polymerization.
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Affiliation(s)
- Colleen T Skau
- Department of Molecular Genetics, The University of Chicago, IL 60637, USA
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Ezezika OC, Younger NS, Lu J, Kaiser DA, Corbin ZA, Nolen BJ, Kovar DR, Pollard TD. Incompatibility with formin Cdc12p prevents human profilin from substituting for fission yeast profilin: insights from crystal structures of fission yeast profilin. J Biol Chem 2008; 284:2088-97. [PMID: 19028693 DOI: 10.1074/jbc.m807073200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Expression of human profilin-I does not complement the temperature-sensitive cdc3-124 mutation of the single profilin gene in fission yeast Schizosaccharomyces pombe, resulting in death from cytokinesis defects. Human profilin-I and S. pombe profilin have similar affinities for actin monomers, the FH1 domain of fission yeast formin Cdc12p and poly-L-proline (Lu, J., and Pollard, T. D. (2001) Mol. Biol. Cell 12, 1161-1175), but human profilin-I does not stimulate actin filament elongation by formin Cdc12p like S. pombe profilin. Two crystal structures of S. pombe profilin and homology models of S. pombe profilin bound to actin show how the two profilins bind to identical surfaces on animal and yeast actins even though 75% of the residues on the profilin side of the interaction differ in the two profilins. Overexpression of human profilin-I in fission yeast expressing native profilin also causes cytokinesis defects incompatible with viability. Human profilin-I with the R88E mutation has no detectable affinity for actin and does not have this dominant overexpression phenotype. The Y6D mutation reduces the affinity of human profilin-I for poly-l-proline by 1000-fold, but overexpression of Y6D profilin in fission yeast is lethal. The most likely hypotheses to explain the incompatibility of human profilin-I with Cdc12p are differences in interactions with the proline-rich sequences in the FH1 domain of Cdc12p and wider "wings" that interact with actin.
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Affiliation(s)
- Obidimma C Ezezika
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA
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38
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Neidt EM, Skau CT, Kovar DR. The cytokinesis formins from the nematode worm and fission yeast differentially mediate actin filament assembly. J Biol Chem 2008; 283:23872-83. [PMID: 18577519 DOI: 10.1074/jbc.m803734200] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Formins drive actin filament assembly for diverse cellular processes including motility, establishing polarity, and cell division. To investigate the mechanism of contractile ring assembly in animal cells, we directly compared the actin assembly properties of formins required for cytokinesis in the nematode worm early embryo (CYK-1) and fission yeast (Cdc12p). Like Cdc12p and most other formins, CYK-1 nucleates actin filament assembly and remains processively associated with the elongating barbed end while facilitating the addition of profilin-actin above the theoretical diffusion-limited rate. However, specific properties differ significantly between Cdc12p and CYK-1. Cdc12p efficiently nucleates filaments that in the presence of profilin elongate at approximately the same rate as control filaments without formin (approximately 10.0 subunits/s). CYK-1 is an inefficient nucleator but allows filaments to elongate profilin-actin 6-fold faster than Cdc12p (approximately 60 subunits/s). Both Cdc12p and CYK-1 bind to pre-assembled actin filaments with low nanomolar affinity, but CYK-1 dissociates 2 orders of magnitude more quickly. However, CYK-1 rapidly re-associates with free barbed ends. Cdc12p allows barbed ends to elongate in the presence of excess capping protein, whereas capping protein inhibits CYK-1-mediated actin assembly. Therefore, these evolutionarily diverse formins can drive contractile ring assembly by a generally similar mechanism, but cells with unique dimensions and physical parameters might require proteins with carefully tuned actin assembly properties.
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Affiliation(s)
- Erin M Neidt
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
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39
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Yan H, Ge W, Chew TG, Chow JY, McCollum D, Neiman AM, Balasubramanian MK. The meiosis-specific Sid2p-related protein Slk1p regulates forespore membrane assembly in fission yeast. Mol Biol Cell 2008; 19:3676-90. [PMID: 18562696 DOI: 10.1091/mbc.e07-10-1060] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Cytokinesis in all organisms involves the creation of membranous barriers that demarcate individual daughter cells. In fission yeast, a signaling module termed the septation initiation network (SIN) plays an essential role in the assembly of new membranes and cell wall during cytokinesis. In this study, we have characterized Slk1p, a protein-kinase related to the SIN component Sid2p. Slk1p is expressed specifically during meiosis and localizes to the spindle pole bodies (SPBs) during meiosis I and II in a SIN-dependent manner. Slk1p also localizes to the forespore membrane during sporulation. Cells lacking Slk1p display defects associated with sporulation, leading frequently to the formation of asci with smaller and/or fewer spores. The ability of slk1 Delta cells to sporulate, albeit inefficiently, is fully abolished upon compromise of function of Sid2p, suggesting that Slk1p and Sid2p play overlapping roles in sporulation. Interestingly, increased expression of the syntaxin Psy1p rescues the sporulation defect of sid2-250 slk1 Delta. Thus, it is likely that Slk1p and Sid2p play a role in forespore membrane assembly by facilitating recruitment of components of the secretory apparatus, such as Psy1p, to allow membrane expansion. These studies thereby provide a novel link between the SIN and vesicle trafficking during cytokinesis.
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Affiliation(s)
- Hongyan Yan
- Cell Division Laboratory, Department of Biological Sciences, National University of Singapore, Singapore
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Clifford DM, Wolfe BA, Roberts-Galbraith RH, McDonald WH, Yates JR, Gould KL. The Clp1/Cdc14 phosphatase contributes to the robustness of cytokinesis by association with anillin-related Mid1. ACTA ACUST UNITED AC 2008; 181:79-88. [PMID: 18378776 PMCID: PMC2287289 DOI: 10.1083/jcb.200709060] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Cdc14 phosphatases antagonize cyclin-dependent kinase–directed phosphorylation events and are involved in several facets of cell cycle control. We investigate the role of the fission yeast Cdc14 homologue Clp1/Flp1 in cytokinesis. We find that Clp1/Flp1 is tethered at the contractile ring (CR) through its association with anillin-related Mid1. Fluorescent recovery after photobleaching analyses indicate that Mid1, unlike other tested CR components, is anchored at the cell midzone, and this physical property is likely to account for its scaffolding role. By generating a mutation in mid1 that selectively disrupts Clp1/Flp1 tethering, we reveal the specific functional consequences of Clp1/Flp1 activity at the CR, including dephosphorylation of the essential CR component Cdc15, reductions in CR protein mobility, and CR resistance to mild perturbation. Our evidence indicates that Clp1/Flp1 must interact with the Mid1 scaffold to ensure the fidelity of Schizosaccharomyces pombe cytokinesis.
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Affiliation(s)
- Dawn M Clifford
- Howard Hughes Medical Institute, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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41
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Chew TG, Balasubramanian MK. Nuc2p, a subunit of the anaphase-promoting complex, inhibits septation initiation network following cytokinesis in fission yeast. PLoS Genet 2008; 4:e17. [PMID: 18225957 PMCID: PMC2213707 DOI: 10.1371/journal.pgen.0040017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Accepted: 12/06/2007] [Indexed: 02/07/2023] Open
Abstract
In most cell types, mitosis and cytokinesis are tightly coupled such that cytokinesis occurs only once per cell cycle. The fission yeast Schizosaccharomyces pombe divides using an actomyosin-based contractile ring and is an attractive model for the study of the links between mitosis and cytokinesis. In fission yeast, the anaphase-promoting complex/cyclosome (APC/C) and the septation initiation network (SIN), a spindle pole body (SPB)–associated GTPase-driven signaling cascade, function sequentially to ensure proper coordination of mitosis and cytokinesis. Here, we find a novel interplay between the tetratricopeptide repeat (TPR) domain–containing subunit of the APC/C, Nuc2p, and the SIN, that appears to not involve other subunits of the APC/C. Overproduction of Nuc2p led to an increase in the presence of multinucleated cells, which correlated with a defect in actomyosin ring maintenance and localization of the SIN component protein kinases Cdc7p and Sid1p to the SPBs, indicative of defective SIN signaling. Conversely, loss of Nuc2p function led to increased SIN signaling, characterized by the persistent localization of Cdc7p and Sid1p on SPBs and assembly of multiple actomyosin rings and division septa. Nuc2p appears to function independently of the checkpoint with FHA and ring finger (CHFR)–related protein Dma1p, a known inhibitor of the SIN in fission yeast. Genetic and biochemical analyses established that Nuc2p might influence the nucleotide state of Spg1p GTPase, a key regulator of the SIN. We propose that Nuc2p, by inhibiting the SIN after cell division, prevents further deleterious cytokinetic events, thereby contributing to genome stability. Cytokinesis is the process by which a mother cell is physically partitioned into two daughter cells. Cytokinesis is well coordinated with segregation of the genetic material to ensure that the genome is not damaged by the cell division apparatus. How untimely cytokinesis is prevented is not fully understood, and is a topic of current interest. Studies of the mechanisms of segregation of the genetic material and cytokinesis have benefited extensively from the use of the fission yeast Schizosaccharomyces pombe. In this study, we make the discovery that fission yeast Nuc2p, a protein previously known to form part of a multi-protein machine that regulates genome segregation, has a second function in regulating cytokinesis. Nuc2p appears to dampen the septation initiation network, which is an important signaling pathway that is essential for cytokinesis. Thus, Nuc2p prevents the occurrence of cytokinetic events prior to segregation of the genetic material and thereby contributes to genome stability. Since the multi-component machinery that Nuc2p forms part of, as well as Nuc2p itself, has relatives in essentially all eukaryotic cells, a similar mechanism might operate in other cells as well.
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Affiliation(s)
- Ting Gang Chew
- Cell Division Laboratory, Temasek Life Sciences Laboratory and the Department of Biological Sciences, National University of Singapore, Singapore
| | - Mohan K Balasubramanian
- Cell Division Laboratory, Temasek Life Sciences Laboratory and the Department of Biological Sciences, National University of Singapore, Singapore
- * To whom correspondence should be addressed. E-mail:
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Yonetani A, Lustig RJ, Moseley JB, Takeda T, Goode BL, Chang F. Regulation and targeting of the fission yeast formin cdc12p in cytokinesis. Mol Biol Cell 2008; 19:2208-19. [PMID: 18305104 DOI: 10.1091/mbc.e07-07-0731] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Formins are conserved actin nucleators which promote the assembly of actin filaments for the formation of diverse actin structures. In fission yeast Schizosaccharomyces pombe, the formin cdc12p is required specifically in assembly of the actin-based contractile ring during cytokinesis. Here, using a mutational analysis of cdc12p, we identify regions of cdc12p responsible for ring assembly and localization. Profilin-binding residues of the FH1 domain regulate actin assembly and processive barbed-end capping by the FH2 domain. Studies using photobleaching (FRAP) and sensitivity to latrunculin A treatment show that profilin binding modulates the rapid dynamics of actin and cdc12p within the ring in vivo. Visualized by functional GFP-fusion constructs expressed from the endogenous promoter, cdc12p appears in a small number of cytoplasmic motile spot structures that deliver the formin to the ring assembly site, without detectable formation of an intermediate band of "nodes." The FH3/DID region directs interphase spot localization, while an N-terminal region and the FH1-FH2 domains of cdc12p can target its localization to the ring. Mutations in putative DID and DAD regions do not alter regulation, suggesting that cdc12p is not regulated by a canonical autoinhibition mechanism. Our findings provide insights into the regulation of formin activity and the mechanisms of contractile ring dynamics and assembly.
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Affiliation(s)
- Ann Yonetani
- Department of Microbiology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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43
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Kuhn TB, Bamburg JR. Tropomyosin and ADF/cofilin as collaborators and competitors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 644:232-49. [PMID: 19209826 DOI: 10.1007/978-0-387-85766-4_18] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Dynamics of actin filaments is pivotal to many fundamental cellular processes such as Dcytokinesis, motility, morphology, vesicle and organelle transport, gene transcription and senescence. In vivo kinetics of actin filament dynamics is far from the equilibrium in vitro and these profound differences are attributed to large number of regulatory proteins. In particular, proteins of the ADF/cofilin family greatly increase actin filament dynamics by severing filaments and enhancing depolymerization of ADP-actin monomers from their pointed ends. Cofilin binds cooperatively to a minor conformer of F-actin in which the subunits are slightly under rotated along the filament helical axis. At high stoichiometry of cofilin to actin subunits, cofilin actually stabilizes actin filaments. Many isoforms oftropomyosin appear to compete with ADF/cofilin proteins for binding to actin filaments. Tropomyosin isoforms studied to date prefer binding to the "untwisted" conformer of F-actin and through their protection and stabilization of F-actin, recruit myosin II and assemble different actin superstructures from the cofilin-actin filaments. However, some tropomyosin isoforms may synergize with ADF/cofilin to enhance filament dynamics, suggesting that the different isoforms of tropomyosins, many of which show developmental or tissue specific expression profiles, play major roles in the assembly and turnover of actin superstructures. Different actin superstructures can overlap both spatially and temporally within a cell, but can be differentiated from each other based upon their kinetic and kinematic properties. Furthermore, local regulation of ADF/cofilin activity through signal transduction pathways could be one mechanism to alter the dynamic balance in F-actin-binding of certain tropomyosin isoforms in subcellular domains.
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Affiliation(s)
- Thomas B Kuhn
- Department of Chemistry, University of Alaska Fairbanks, Fairbanks, Alaska, USA
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Grallert A, Martín-García R, Bagley S, Mulvihill DP. In vivo movement of the type V myosin Myo52 requires dimerisation but is independent of the neck domain. J Cell Sci 2007; 120:4093-8. [PMID: 18003699 DOI: 10.1242/jcs.012468] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Intracellular movement is a fundamental property of all cell types. Many organelles and molecules are actively transported throughout the cytoplasm by molecular motors, such as the dimeric type V myosins. These possess a long neck, which contains an IQ motif, that allow it to make 36-nm steps along the actin polymer. Live cell imaging of the fission yeast type V myosin Myo52 reveals that the protein moves rapidly throughout the cytoplasm. Here, we describe analysis of this movement and have established that Myo52 moves long distances on actin filaments in an ATP-dependent manner at approximately 0.5 mum/second. Myo51 and the microtubule cytoskeleton have no discernable role in modulating Myo52 movements, whereas rigour mutations in Myo52 abrogated its movement. We go on to show that, although dimerisation is required for Myo52 movement, deleting its neck has no discernable affect on Myo52 function or velocity in vivo.
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Affiliation(s)
- Agnes Grallert
- Cancer Research UK Cell Division Group, CR-UK Paterson Institute for Cancer Research, Manchester, M20 4BX, UK
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Vidali L, Augustine RC, Kleinman KP, Bezanilla M. Profilin is essential for tip growth in the moss Physcomitrella patens. THE PLANT CELL 2007; 19:3705-22. [PMID: 17981997 PMCID: PMC2174871 DOI: 10.1105/tpc.107.053413] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Revised: 10/05/2007] [Accepted: 10/10/2007] [Indexed: 05/19/2023]
Abstract
The actin cytoskeleton is critical for tip growth in plants. Profilin is the main monomer actin binding protein in plant cells. The moss Physcomitrella patens has three profilin genes, which are monophyletic, suggesting a single ancestor for plant profilins. Here, we used RNA interference (RNAi) to determine the loss-of-function phenotype of profilin. Reduction of profilin leads to a complete loss of tip growth and a partial inhibition of cell division, resulting in plants with small rounded cells and fewer cells. We silenced all profilins by targeting their 3' untranslated region sequences, enabling complementation analyses by expression of profilin coding sequences. We show that any moss or a lily (Lilium longiflorum) profilin support tip growth. Profilin with a mutation in its actin binding site is unable to rescue profilin RNAi, while a mutation in the poly-l-proline binding site weakly rescues. We show that moss tip growing cells contain a prominent subapical cortical F-actin structure composed of parallel actin cables. Cells lacking profilin lose this structure; instead, their F-actin is disorganized and forms polarized cortical patches. Plants expressing the actin and poly-l-proline binding mutants exhibited similar F-actin disorganization. These results demonstrate that profilin and its binding to actin are essential for tip growth. Additionally, profilin is not needed for formation of F-actin, but profilin and its interactions with actin and poly-l-proline ligands are required to properly organize F-actin.
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Affiliation(s)
- Luis Vidali
- Biology Department, University of Massachusetts, Amherst, Massachusetts 01003, USA
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Abstract
Expression of profilin-1 (Pfn1) is downregulated in breast cancer cells, the functional significance of which is yet to be understood. To address this question, in this study we evaluated how perturbing Pfn1 affects motility and invasion of breast cancer cells. We show that loss of Pfn1 expression leads to enhanced motility and matrigel invasiveness of MDA-MB-231 breast cancer cells. Interestingly, silencing Pfn1 expression is associated with downregulation of both cell–cell and cell–matrix adhesions with concomitant increase in motility and dramatic scattering of normal human mammary epithelial cells. Thus, these data for the first time suggest that loss of Pfn1 expression may have significance in breast cancer progression. Consistent with these findings, even a moderate overexpression of Pfn1 induces actin stress-fibres, upregulates focal adhesion, and dramatically inhibits motility and matrigel invasiveness of MDA-MB-231 cells. Using mutants of Pfn1 that are defective in binding to either actin or proline-rich ligands, we further show that overexpressed Pfn1 must have a functional actin-binding site to suppress cell motility. Finally, animal experiments reveal that overexpression of Pfn1 suppresses orthotopic tumorigenicity and micro-metastasis of MDA-MB-231 cells in nude mice. These data imply that perturbing Pfn1 could be a good molecular strategy to limit the aggressiveness of breast cancer cells.
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Skoumpla K, Coulton AT, Lehman W, Geeves MA, Mulvihill DP. Acetylation regulates tropomyosin function in the fission yeast Schizosaccharomyces pombe. J Cell Sci 2007; 120:1635-45. [PMID: 17452625 DOI: 10.1242/jcs.001115] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Tropomyosin is an evolutionarily conserved alpha-helical coiled-coil protein that promotes and maintains actin filaments. In yeast, Tropomyosin-stabilised filaments are used by molecular motors to transport cargoes or to generate motile forces by altering the dynamics of filament growth and shrinkage. The Schizosaccharomyces pombe tropomyosin Cdc8 localises to the cytokinetic actomyosin ring during mitosis and is absolutely required for its formation and function. We show that Cdc8 associates with actin filaments throughout the cell cycle and is subjected to post-translational modification that does not vary with cell cycle progression. At any given point in the cell cycle 80% of Cdc8 molecules are acetylated, which significantly enhances their affinity for actin. Reconstructions of electron microscopic images of actin-Cdc8 filaments establish that the majority of Cdc8 strands sit in the 'closed' position on actin filaments, suggesting a role in the regulation of myosin binding. We show that Cdc8 regulates the equilibrium binding of myosin to actin without affecting the rate of myosin binding. Unacetylated Cdc8 isoforms bind actin, but have a reduced ability to regulate myosin binding to actin. We conclude that although acetylation of Cdc8 is not essential, it provides a regulatory mechanism for modulating actin filament integrity and myosin function.
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Affiliation(s)
- Kalomoira Skoumpla
- Cell and Developmental Biology Group, Department of Biosciences, University of Kent at Canterbury, Canterbury, CT2 7NJ, UK
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Pilo Boyl P, Di Nardo A, Mulle C, Sassoè-Pognetto M, Panzanelli P, Mele A, Kneussel M, Costantini V, Perlas E, Massimi M, Vara H, Giustetto M, Witke W. Profilin2 contributes to synaptic vesicle exocytosis, neuronal excitability, and novelty-seeking behavior. EMBO J 2007; 26:2991-3002. [PMID: 17541406 PMCID: PMC1894775 DOI: 10.1038/sj.emboj.7601737] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2006] [Accepted: 05/03/2007] [Indexed: 11/08/2022] Open
Abstract
Profilins are actin binding proteins essential for regulating cytoskeletal dynamics, however, their function in the mammalian nervous system is unknown. Here, we provide evidence that in mouse brain profilin1 and profilin2 have distinct roles in regulating synaptic actin polymerization with profilin2 preferring a WAVE-complex-mediated pathway. Mice lacking profilin2 show a block in synaptic actin polymerization in response to depolarization, which is accompanied by increased synaptic excitability of glutamatergic neurons due to higher vesicle exocytosis. These alterations in neurotransmitter release correlate with a hyperactivation of the striatum and enhanced novelty-seeking behavior in profilin2 mutant mice. Our results highlight a novel, profilin2-dependent pathway, regulating synaptic physiology, neuronal excitability, and complex behavior.
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Affiliation(s)
| | | | - Christophe Mulle
- UMR CNRS 5091, Institut François Magendie, Physiologie Cellulaire de la Synapse, Bordeaux, France
| | - Marco Sassoè-Pognetto
- Department of Anatomy, Pharmacology and Forensic Medicine and Istituto Nazionale di Neuroscienze, University of Turin, Torino, Italy
| | - Patrizia Panzanelli
- Department of Anatomy, Pharmacology and Forensic Medicine and Istituto Nazionale di Neuroscienze, University of Turin, Torino, Italy
| | - Andrea Mele
- Università di Roma ‘La Sapienza', Laboratorio di Psicobiologia, Dipart. di Genetica e Biologia Molecolare, Roma, Italy
| | - Matthias Kneussel
- Centre for Molecular Neurobiology, ZMNH, University of Hamburg, Hamburg, Germany
| | - Vivian Costantini
- Università di Roma ‘La Sapienza', Laboratorio di Psicobiologia, Dipart. di Genetica e Biologia Molecolare, Roma, Italy
| | | | | | - Hugo Vara
- Department of Anatomy, Pharmacology and Forensic Medicine and Istituto Nazionale di Neuroscienze, University of Turin, Torino, Italy
| | - Maurizio Giustetto
- Department of Anatomy, Pharmacology and Forensic Medicine and Istituto Nazionale di Neuroscienze, University of Turin, Torino, Italy
| | - Walter Witke
- EMBL, Mouse Biology Unit, Monterotondo, Italy
- EMBL, Mouse Biology Unit, Adriano Buzzati-Traverso Campus, Via Ramarini 32, 00015 Monterotondo, Italy. Tel.: +0039 06 90091 268; Fax: +0039 06 90091 272; E-mail:
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Takaine M, Mabuchi I. Properties of actin from the fission yeast Schizosaccharomyces pombe and interaction with fission yeast profilin. J Biol Chem 2007; 282:21683-94. [PMID: 17533155 DOI: 10.1074/jbc.m611371200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The fission yeast Schizosaccharomyces pombe serves as a model system for studying role of actin cytoskeleton, since it has simple actin cytoskeletons and is genetically tractable. In contrast, biochemical approaches using this organism are still developing; fission yeast actin has so far not been isolated in its native form and characterized, and therefore, biochemical assays of fission yeast actin-binding proteins (ABPs) or myosin have been performed using rabbit skeletal muscle actin that may interact with the fission yeast ABPs in a manner different from fission yeast actin. Here, we report a novel method for isolating functionally active actin from fission yeast cells. The highly purified fission yeast actin polymerized with kinetics somewhat different from those of muscle actin and forms filaments that are structurally indistinguishable from skeletal muscle actin filaments. The fission yeast actin was a significantly weaker activator of Mg(2+)-ATPase of HMM of skeletal muscle myosin than muscle actin. The fission yeast profilin Cdc3 suppressed polymerization of fission yeast actin more effectively than that of muscle actin and showed an affinity for fission yeast actin higher than for muscle actin. The establishment of purification of fission yeast actin will enable reconstruction of physiologically relevant interactions between the actin and fission yeast ABPs or myosins and contribute to clarification of function of actin cytoskeleton in various cellular activities.
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Affiliation(s)
- Masak Takaine
- Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Hongo, Tokyo, Japan
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La Carbona S, Le Goff C, Le Goff X. Fission yeast cytoskeletons and cell polarity factors: connecting at the cortex. Biol Cell 2007; 98:619-31. [PMID: 17042740 DOI: 10.1042/bc20060048] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Cell polarity is a fundamental property of cells from unicellular to multicellular organisms. Most of the time, it is essential so that the cells can achieve their function. The fission yeast Schizosaccharomyces pombe is a powerful genetic model organism for studying the molecular mechanisms of the cell polarity process. Indeed, S. pombe cells are rod-shaped and cell growth is restricted at the poles. The accurate localization of the cell growth machinery at the cell cortex, which involves the actin cytoskeleton, depends on cell polarity pathways that are temporally and spatially regulated. The importance of interphase microtubules and cell polarity factors acting at the cortex of cell ends in this process has been shown. Here, we review recent advances in knowledge of molecular pathways leading to the establishment of a cellular axis in fission yeast. We also describe the role of cortical proteins and mitotic cytoskeletal rearrangements that control the symmetry of cell division.
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Affiliation(s)
- Stéphanie La Carbona
- CNRS UMR6061 Génétique et Développement, Université de Rennes 1, IFR140 Génétique Fonctionnelle, Agronomie et Santé, Faculté de Médecine, 2 Av. du Prof. Léon Bernard, 35043 Rennes Cedex, France
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