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Rossi AM, Bohnert KA, Gould KL. The fission yeast cytokinetic ring component Fic1 promotes septum formation. Biol Open 2023; 12:308901. [PMID: 37158439 PMCID: PMC10184318 DOI: 10.1242/bio.059957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 04/19/2023] [Indexed: 05/10/2023] Open
Abstract
In Schizosaccharomyces pombe, septum formation is coordinated with cytokinetic ring constriction but the mechanisms linking these events are unclear. In this study, we explored the role of the cytokinetic ring component Fic1, first identified by its interaction with the F-BAR protein Cdc15, in septum formation. We found that the fic1 phospho-ablating mutant, fic1-2A, is a gain-of-function allele that suppresses myo2-E1, the temperature-sensitive allele of the essential type-II myosin, myo2. This suppression is achieved by the promotion of septum formation and required Fic1's interaction with the F-BAR proteins Cdc15 and Imp2. Additionally, we found that Fic1 interacts with Cyk3 and that this interaction was likewise required for Fic1's role in septum formation. Fic1, Cdc15, Imp2, and Cyk3 are the orthologs of the Saccharomyces cerevisiae ingression progression complex, which stimulates the chitin synthase Chs2 to promote primary septum formation. However, our findings indicate that Fic1 promotes septum formation and cell abscission independently of the S. pombe Chs2 ortholog. Thus, while similar complexes exist in the two yeasts that each promote septation, they appear to have different downstream effectors.
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Affiliation(s)
- Anthony M Rossi
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - K Adam Bohnert
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Kathleen L Gould
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
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2
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Rossi AM, Bohnert KA, Gould KL. The fission yeast cytokinetic ring component Fic1 promotes septum formation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.13.532462. [PMID: 36993237 PMCID: PMC10054984 DOI: 10.1101/2023.03.13.532462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
In Schizosaccharomyces pombe septum formation is coordinated with cytokinetic ring constriction but the mechanisms linking these events are unclear. In this study, we explored the role of the cytokinetic ring component Fic1, first identified by its interaction with the F-BAR protein Cdc15, in septum formation. We found that the fic1 phospho-ablating mutant, fic1-2A , is a gain-of-function allele that suppresses myo2-E1 , the temperature-sensitive allele of the essential type-II myosin, myo2 . This suppression is achieved by the promotion of septum formation and required Fic1's interaction with the F-BAR proteins Cdc15 and Imp2. Additionally, we found that Fic1 interacts with Cyk3 and that this interaction was likewise required for Fic1's role in septum formation. Fic1, Cdc15, Imp2, and Cyk3 are the orthologs of the Saccharomyces cerevisiae ingression progression complex, which stimulates the chitin synthase Chs2 to promote primary septum formation. However, our findings indicate that Fic1 promotes septum formation and cell abscission independently of the S. pombe Chs2 ortholog. Thus, while similar complexes exist in the two yeasts that each promote septation, they appear to have different downstream effectors. Summary Statement The S. pombe cytokinetic ring protein Fic1 promotes septum formation in a manner dependent on interactions with the cytokinetic ring components Cdc15, Imp2, and Cyk3.
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Bellingham-Johnstun K, Commer B, Levesque B, Tyree ZL, Laplante C. Imp2p forms actin-dependent clusters and imparts stiffness to the contractile ring. Mol Biol Cell 2022; 33:ar145. [PMID: 36287824 PMCID: PMC9727792 DOI: 10.1091/mbc.e22-06-0221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The contractile ring must anchor to the plasma membrane and cell wall to transmit its tension. F-BAR domain containing proteins including Imp2p and Cdc15p in fission yeast are likely candidate anchoring proteins based on their mutant phenotypes. Cdc15p is a node component, links the actin bundle to the plasma membrane, recruits Bgs1p to the division plane, prevents contractile ring sliding, and contributes to the stiffness of the contractile ring. Less is known about Imp2p. We found that similarly to Cdc15p, Imp2p contributes to the stiffness of the contractile ring and assembles into protein clusters. Imp2p clusters contain approximately eight Imp2p dimers and depend on the actin network for their stability at the division plane. Importantly, Imp2p and Cdc15p reciprocally affect the amount of each other in the contractile ring, indicating that the two proteins influence each other during cytokinesis, which may partially explain their similar phenotypes.
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Affiliation(s)
| | - Blake Commer
- Department of Molecular Biomedical Sciences, North Carolina State University, Raleigh, NC 27607
| | - Brié Levesque
- Department of Molecular Biomedical Sciences, North Carolina State University, Raleigh, NC 27607
| | - Zoe L Tyree
- Department of Molecular Biomedical Sciences, North Carolina State University, Raleigh, NC 27607
| | - Caroline Laplante
- Department of Molecular Biomedical Sciences, North Carolina State University, Raleigh, NC 27607
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Willet AH, Igarashi MG, Chen JS, Bhattacharjee R, Ren L, Cullati SN, Elmore ZC, Roberts-Galbraith RH, Johnson AE, Beckley JR, Gould KL. Phosphorylation in the intrinsically disordered region of F-BAR protein Imp2 regulates its contractile ring recruitment. J Cell Sci 2021; 134:271847. [PMID: 34279633 DOI: 10.1242/jcs.258645] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 07/12/2021] [Indexed: 11/20/2022] Open
Abstract
The F-BAR protein Imp2 is an important contributor to cytokinesis in the fission yeast, Schizosaccharomyces pombe. Because cell cycle regulated phosphorylation of the central intrinsically disordered region (IDR) of the Imp2 paralog, Cdc15, controls Cdc15 oligomerization state, localization, and ability to bind protein partners, we investigated whether Imp2 is similarly phosphoregulated. We found that Imp2 is endogenously phosphorylated on 28 sites within its IDR with the bulk of phosphorylation being constitutive. In vitro, casein kinase 1 (CK1) Hhp1 and Hhp2 can phosphorylate 17 sites and Cdk1 the remaining 11 sites. Mutations that prevent Cdk1 phosphorylation result in precocious Imp2 recruitment to the cell division site, and mutations designed to mimic these phosphorylation events delay Imp2 CR accumulation. Mutations that eliminated CK1 phosphorylation sites allowed CR sliding, and phosphomimetic substitutions at these sites reduced Imp2 protein levels and slowed CR constriction. Thus, like Cdc15, the Imp2 IDR is phosphorylated at many sites by multiple kinases. In contrast to Cdc15, for which phosphorylation plays a major cell cycle regulatory role, Imp2 phosphorylation is primarily constitutive with milder effects on localization and function.
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Affiliation(s)
- Alaina H Willet
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Maya G Igarashi
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Jun-Song Chen
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Rahul Bhattacharjee
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Liping Ren
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Sierra N Cullati
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Zachary C Elmore
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Rachel H Roberts-Galbraith
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Alyssa E Johnson
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Janel R Beckley
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Kathleen L Gould
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
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5
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Schutt KL, Moseley JB. The phosphatase inhibitor Sds23 regulates cell division symmetry in fission yeast. Mol Biol Cell 2019; 30:2880-2889. [PMID: 31553675 PMCID: PMC6822584 DOI: 10.1091/mbc.e19-05-0254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Animal and fungal cells divide through the assembly, anchoring, and constriction of a contractile actomyosin ring (CAR) during cytokinesis. The timing and position of the CAR must be tightly controlled to prevent defects in cell division, but many of the underlying signaling events remain unknown. The conserved heterotrimeric protein phosphatase PP2A controls the timing of events in mitosis, and upstream pathways including Greatwall-Ensa regulate PP2A activity. A role for PP2A in CAR regulation has been less clear, although loss of PP2A in yeast causes defects in cytokinesis. Here, we report that Sds23, an inhibitor of PP2A family protein phosphatases, promotes the symmetric division of fission yeast cells through spatial control of cytokinesis. We found that sds23∆ cells divide asymmetrically due to misplaced CAR assembly, followed by sliding of the CAR away from its assembly site. These mutant cells exhibit delayed recruitment of putative CAR anchoring proteins including the glucan synthase Bgs1. Our observations likely reflect a broader role for regulation of PP2A in cell polarity and cytokinesis because sds23∆ phenotypes were exacerbated when combined with mutations in the fission yeast Ensa homologue, Igo1. These results identify the PP2A regulatory network as a critical component in the signaling pathways coordinating cytokinesis.
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Affiliation(s)
- Katherine L Schutt
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - James B Moseley
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH 03755
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Mangione MC, Snider CE, Gould KL. The intrinsically disordered region of the cytokinetic F-BAR protein Cdc15 performs a unique essential function in maintenance of cytokinetic ring integrity. Mol Biol Cell 2019; 30:2790-2801. [PMID: 31509478 PMCID: PMC6789166 DOI: 10.1091/mbc.e19-06-0314] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 08/21/2019] [Accepted: 09/05/2019] [Indexed: 11/17/2022] Open
Abstract
Successful separation of two daughter cells (i.e., cytokinesis) is essential for life. Many eukaryotic cells divide using a contractile apparatus called the cytokinetic ring (CR) that associates dynamically with the plasma membrane (PM) and generates force that contributes to PM ingression between daughter cells. In Schizosaccharomyces pombe, important membrane-CR scaffolds include the paralogous F-BAR proteins Cdc15 and Imp2. Their conserved protein structure consists of the archetypal F-BAR domain linked to an SH3 domain by an intrinsically disordered region (IDR). Functions have been assigned to the F-BAR and SH3 domains. In this study we probed the function of the central IDR. We found that the IDR of Cdc15 is essential for viability and cannot be replaced by that of Imp2, whereas the F-BAR domain of Cdc15 can be swapped with several different F-BAR domains, including that of Imp2. Deleting part of the IDR results in CR defects and abolishes calcineurin phosphatase localization to the CR. Together these results indicate that Cdc15's IDR has a nonredundant essential function that coordinates regulation of CR architecture.
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Affiliation(s)
- MariaSanta C. Mangione
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240
| | - Chloe E. Snider
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240
| | - Kathleen L. Gould
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240
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Sethi K, Palani S, Cortés JCG, Sato M, Sevugan M, Ramos M, Vijaykumar S, Osumi M, Naqvi NI, Ribas JC, Balasubramanian M. A New Membrane Protein Sbg1 Links the Contractile Ring Apparatus and Septum Synthesis Machinery in Fission Yeast. PLoS Genet 2016; 12:e1006383. [PMID: 27749909 PMCID: PMC5066963 DOI: 10.1371/journal.pgen.1006383] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 09/23/2016] [Indexed: 01/14/2023] Open
Abstract
Cytokinesis in many organisms requires a plasma membrane anchored actomyosin ring, whose contraction facilitates cell division. In yeast and fungi, actomyosin ring constriction is also coordinated with division septum assembly. How the actomyosin ring interacts with the plasma membrane and the plasma membrane-localized septum synthesizing machinery remains poorly understood. In Schizosaccharomyces pombe, an attractive model organism to study cytokinesis, the β-1,3-glucan synthase Cps1p / Bgs1p, an integral membrane protein, localizes to the plasma membrane overlying the actomyosin ring and is required for primary septum synthesis. Through a high-dosage suppressor screen we identified an essential gene, sbg1+ (suppressor of beta glucan synthase 1), which suppressed the colony formation defect of Bgs1-defective cps1-191 mutant at higher temperatures. Sbg1p, an integral membrane protein, localizes to the cell ends and to the division site. Sbg1p and Bgs1p physically interact and are dependent on each other to localize to the division site. Loss of Sbg1p results in an unstable actomyosin ring that unravels and slides, leading to an inability to deposit a single contiguous division septum and an important reduction of the β-1,3-glucan proportion in the cell wall, coincident with that observed in the cps1-191 mutant. Sbg1p shows genetic and / or physical interaction with Rga7p, Imp2p, Cdc15p, and Pxl1p, proteins known to be required for actomyosin ring integrity and efficient septum synthesis. This study establishes Sbg1p as a key member of a group of proteins that link the plasma membrane, the actomyosin ring, and the division septum assembly machinery in fission yeast. Cell division in many organisms requires the function of an actomyosin ring, an apparatus that resembles the force generating machinery in the muscle. This ring apparatus is attached to the cell periphery (cell membranes) such that when it contracts, it brings the cell periphery together with it, leading to cell division. How the actomyosin ring is attached to the cell membrane at the division site is unknown. In this manuscript, we identify and describe Sbg1, a protein that links the actomyosin ring and the cell membranes since Sbg1 has a sequence that allows it to be inserted into the cell membrane. Sbg1 specifically localizes to the cell division site and also cooperates with a cell wall biosynthetic enzyme Bgs1 to achieve cell division. Consistently, in the absence of Sbg1, cells fail to divide leading to lethality. Sbg1 interacts with a number of cell division proteins, such as Cdc15, Rga7, Imp2, and Pxl1, to achieve its function as a bridge between the cell membrane and the actomyosin ring. Our work identifies a direct molecular link between the actomyosin ring and the cell membranes, explaining how ring contraction leads to inward movement of the cell periphery.
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Affiliation(s)
- Kriti Sethi
- Temasek Life Sciences Laboratory, National University of Singapore, 1 Research Link, Singapore
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Saravanan Palani
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Juan C. G. Cortés
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Cinetificas/Universidad de Salamanca, Salamanca, Spain
| | - Mamiko Sato
- Laboratory of Electron Microscopy/Bio-imaging Centre, and Department of Chemical and Biological Sciences, Faculty of Sciences, Japan Women’s University, Mejirodai, Bunkyo-ku, Tokyo, Japan
| | - Mayalagu Sevugan
- Temasek Life Sciences Laboratory, National University of Singapore, 1 Research Link, Singapore
| | - Mariona Ramos
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Cinetificas/Universidad de Salamanca, Salamanca, Spain
| | - Shruthi Vijaykumar
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Masako Osumi
- Laboratory of Electron Microscopy/Bio-imaging Centre, and Department of Chemical and Biological Sciences, Faculty of Sciences, Japan Women’s University, Mejirodai, Bunkyo-ku, Tokyo, Japan
- NPO Integrated Imaging Research Support, Hirakawa-cho, Chiyoda-ku, Tokyo, Japan
| | - Naweed I. Naqvi
- Temasek Life Sciences Laboratory, National University of Singapore, 1 Research Link, Singapore
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Juan Carlos Ribas
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Cinetificas/Universidad de Salamanca, Salamanca, Spain
| | - Mohan Balasubramanian
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
- * E-mail:
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8
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Pérez P, Cortés JCG, Martín-García R, Ribas JC. Overview of fission yeast septation. Cell Microbiol 2016; 18:1201-7. [PMID: 27155541 DOI: 10.1111/cmi.12611] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 05/02/2016] [Accepted: 05/05/2016] [Indexed: 02/04/2023]
Abstract
Cytokinesis is the final process of the vegetative cycle, which divides a cell into two independent daughter cells once mitosis is completed. In fungi, as in animal cells, cytokinesis requires the formation of a cleavage furrow originated by constriction of an actomyosin ring which is connected to the plasma membrane and causes its invagination. Additionally, because fungal cells have a polysaccharide cell wall outside the plasma membrane, cytokinesis requires the formation of a septum coincident with the membrane ingression. Fission yeast Schizosaccharomyces pombe is a unicellular, rod-shaped fungus that has become a popular model organism for the study of actomyosin ring formation and constriction during cell division. Here we review the current knowledge of the septation and separation processes in this fungus, as well as recent advances in understanding the functional interaction between the transmembrane enzymes that build the septum and the actomyosin ring proteins.
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Affiliation(s)
- Pilar Pérez
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Salamanca, Salamanca, 37007, Spain
| | - Juan C G Cortés
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Salamanca, Salamanca, 37007, Spain
| | - Rebeca Martín-García
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Salamanca, Salamanca, 37007, Spain
| | - Juan C Ribas
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Salamanca, Salamanca, 37007, Spain
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9
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Abstract
As cells grow, move, and divide, they must reorganize and rearrange their membranes and cytoskeleton. The F-BAR protein family links cellular membranes with actin cytoskeletal rearrangements in processes including endocytosis, cytokinesis, and cell motility. Here we review emerging information on mechanisms of F-BAR domain oligomerization and membrane binding, and how these activities are coordinated with additional domains to accomplish scaffolding and signaling functions.
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Affiliation(s)
- Nathan A McDonald
- a Department of Cell and Developmental Biology , Vanderbilt University , Nashville , TN , USA
| | - Kathleen L Gould
- a Department of Cell and Developmental Biology , Vanderbilt University , Nashville , TN , USA
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10
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Cortés JCG, Ramos M, Osumi M, Pérez P, Ribas JC. Fission yeast septation. Commun Integr Biol 2016; 9:e1189045. [PMID: 27574536 PMCID: PMC4988442 DOI: 10.1080/19420889.2016.1189045] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 05/03/2016] [Accepted: 05/06/2016] [Indexed: 11/09/2022] Open
Abstract
In animal cells cytokinesis relies on the contraction of an actomyosin ring that pulls the plasma membrane to create a cleavage furrow, whose ingression finally divides the mother cell into two daughter cells. Fungal cells are surrounded by a tough and flexible structure called cell wall, which is considered to be the functional equivalent of the extracellular matrix in animal cells. Therefore, in addition to cleavage furrow ingression, fungal cytokinesis also requires the centripetal formation of a septum wall structure that develops between the dividing cells, whose genesis must be strictly coordinated with both the actomyosin ring closure and plasma membrane ingression. Here we briefly review what is known about the septum structure and composition in the fission yeast Schizosaccharomyces pombe, the recent progress about the relationship between septum biosynthesis and actomyosin ring constriction, and the importance of the septum and ring in the steady progression of the cleavage furrow.
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Affiliation(s)
- Juan C G Cortés
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca , Salamanca, Spain
| | - Mariona Ramos
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca , Salamanca, Spain
| | - Masako Osumi
- Faculty of Science, Laboratory of Electron Microscopy, Japan Women's University, Tokyo, Japan; Integrated Imaging Research Support, Tokyo, Japan
| | - Pilar Pérez
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca , Salamanca, Spain
| | - Juan Carlos Ribas
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca , Salamanca, Spain
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11
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Zobel T, Brinkmann K, Koch N, Schneider K, Seemann E, Fleige A, Qualmann B, Kessels MM, Bogdan S. Cooperative functions of the two F-BAR proteins Cip4 and Nostrin in the regulation of E-cadherin in epithelial morphogenesis. J Cell Sci 2016; 128:499-515. [PMID: 25413347 DOI: 10.1242/jcs.155929] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
F-BAR proteins are prime candidates to regulate membrane curvature and dynamics during different developmental processes. Here, we analyzed nostrin, a so-far-unknown Drosophila melanogaster F-BAR protein related to Cip4. Genetic analyses revealed a strong synergism between nostrin and cip4 functions.Whereas single mutant flies are viable and fertile, combined loss of nostrin and cip4 results in reduced viability and fertility. Double mutant escaper flies show enhanced wing polarization defects and females exhibit strong egg chamber encapsulation defects. Live imaging analysis suggests that the observed phenotypes are caused by an impaired turnover of E-cadherin at the membrane. Simultaneous knockdown of Cip4 and Nostrin strongly increases the formation of tubular E-cadherin vesicles at adherens junctions. Cip4 and Nostrin localize at distinct membrane subdomains. Both proteins prefer similar membrane curvatures but seem to form distinct membrane coats and do not heterooligomerize. Our data suggest an important synergistic function of both F-BAR proteins in membrane dynamics. We propose a cooperative recruitment model, in which Cip4 initially promotes membrane invagination and early-actin-based endosomal motility, and Nostrin makes contacts with microtubules through the kinesin Khc-73 for trafficking of recycling endosomes.
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12
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McDonald NA, Takizawa Y, Feoktistova A, Xu P, Ohi MD, Vander Kooi CW, Gould KL. The Tubulation Activity of a Fission Yeast F-BAR Protein Is Dispensable for Its Function in Cytokinesis. Cell Rep 2016; 14:534-546. [PMID: 26776521 PMCID: PMC4731314 DOI: 10.1016/j.celrep.2015.12.062] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 11/23/2015] [Accepted: 12/10/2015] [Indexed: 11/28/2022] Open
Abstract
F-BAR proteins link cellular membranes to the actin cytoskeleton in many biological processes. Here we investigated the function of the Schizosaccharomyces pombe Imp2 F-BAR domain in cytokinesis and find that it is critical for Imp2's role in contractile ring constriction and disassembly. To understand mechanistically how the F-BAR domain functions, we determined its structure, elucidated how it interacts with membranes, and identified an interaction between dimers that allows helical oligomerization and membrane tubulation. Using mutations that block either membrane binding or tubulation, we find that membrane binding is required for Imp2's cytokinetic function but that oligomerization and tubulation, activities often deemed central to F-BAR protein function, are dispensable. Accordingly, F-BARs that do not have the capacity to tubulate membranes functionally substitute for the Imp2 F-BAR, establishing that its major role is as a cell-cycle-regulated bridge between the membrane and Imp2 protein partners, rather than as a driver of membrane curvature.
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Affiliation(s)
- Nathan A McDonald
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Yoshimasa Takizawa
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Anna Feoktistova
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Ping Xu
- Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Lexington, KY 40536, USA
| | - Melanie D Ohi
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Craig W Vander Kooi
- Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Lexington, KY 40536, USA
| | - Kathleen L Gould
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA.
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13
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G. Cortés JC, Pujol N, Sato M, Pinar M, Ramos M, Moreno B, Osumi M, Ribas JC, Pérez P. Cooperation between Paxillin-like Protein Pxl1 and Glucan Synthase Bgs1 Is Essential for Actomyosin Ring Stability and Septum Formation in Fission Yeast. PLoS Genet 2015; 11:e1005358. [PMID: 26132084 PMCID: PMC4489101 DOI: 10.1371/journal.pgen.1005358] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 06/13/2015] [Indexed: 01/19/2023] Open
Abstract
In fungal cells cytokinesis requires coordinated closure of a contractile actomyosin ring (CAR) and synthesis of a special cell wall structure known as the division septum. Many CAR proteins have been identified and characterized, but how these molecules interact with the septum synthesis enzymes to form the septum remains unclear. Our genetic study using fission yeast shows that cooperation between the paxillin homolog Pxl1, required for ring integrity, and Bgs1, the enzyme responsible for linear β(1,3)glucan synthesis and primary septum formation, is required for stable anchorage of the CAR to the plasma membrane before septation onset, and for cleavage furrow formation. Thus, lack of Pxl1 in combination with Bgs1 depletion, causes failure of ring contraction and lateral cell wall overgrowth towards the cell lumen without septum formation. We also describe here that Pxl1 concentration at the CAR increases during cytokinesis and that this increase depends on the SH3 domain of the F-BAR protein Cdc15. In consequence, Bgs1 depletion in cells carrying a cdc15ΔSH3 allele causes ring disassembly and septation blockage, as it does in cells lacking Pxl1. On the other hand, the absence of Pxl1 is lethal when Cdc15 function is affected, generating a large sliding of the CAR with deposition of septum wall material along the cell cortex, and suggesting additional functions for both Pxl1 and Cdc15 proteins. In conclusion, our findings indicate that CAR anchorage to the plasma membrane through Cdc15 and Pxl1, and concomitant Bgs1 activity, are necessary for CAR maintenance and septum formation in fission yeast. Cytokinesis requires assembly of an actomyosin ring adjacent to the plasma membrane, which upon contraction pulls the membrane to form a cleavage furrow. In fungi ring closure is coordinated with the synthesis of a cell wall septum. Knowledge about the molecules anchoring the ring to the membrane is very limited. We have found that fission yeast paxillin, located at the ring, and Bgs1, the enzyme responsible for primary septum formation, located at the membrane, cooperate during cytokinesis. Both are required to anchor the ring to the membrane and to maintain it during cytokinesis. Moreover, both proteins cooperate to form the septum. Accordingly, paxillin is essential when Bgs1 is depleted. When both proteins are missing, the contractile ring forms but the lateral cell wall overgrows inwards without a defined cleavage furrow and septum formation. During cytokinesis there is an increase of paxillin which depends on the SH3 domain of the F-BAR protein Cdc15. Consequently the absence of this domain mimics the phenotype of paxillin absence in Bgs1-depleted cells. Interestingly, a decreased function of both Cdc15 and paxillin uncouples the septum synthesis from the ring contraction, indicating an essential cooperation between these proteins and Bgs1 for proper cytokinesis.
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Affiliation(s)
- Juan C. G. Cortés
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC) / Universidad de Salamanca, Salamanca, Spain
- * E-mail:
| | - Nuria Pujol
- Department of Ciències Mèdiques, Bàsiques,Institut de Recerca Biomèdica (IRB) de Lleida, Faculty of Medicine, University of Lleida, Lleida, Spain
| | - Mamiko Sato
- Laboratory of Electron Microscopy/Open Research Centre, and Department of Chemical and Biological Sciences, Japan Women’s University, Mejirodai, Bunkyo-ku, Tokyo, Japan
| | - Mario Pinar
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Mariona Ramos
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC) / Universidad de Salamanca, Salamanca, Spain
| | - Belén Moreno
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC) / Universidad de Salamanca, Salamanca, Spain
| | - Masako Osumi
- Laboratory of Electron Microscopy/Open Research Centre, and Department of Chemical and Biological Sciences, Japan Women’s University, Mejirodai, Bunkyo-ku, Tokyo, Japan
| | - Juan Carlos Ribas
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC) / Universidad de Salamanca, Salamanca, Spain
| | - Pilar Pérez
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC) / Universidad de Salamanca, Salamanca, Spain
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14
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Arasada R, Pollard TD. A role for F-BAR protein Rga7p during cytokinesis in S. pombe. J Cell Sci 2015; 128:2259-68. [PMID: 25977474 DOI: 10.1242/jcs.162974] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2014] [Accepted: 05/07/2015] [Indexed: 12/22/2022] Open
Abstract
F-BAR proteins are known to participate in cytokinesis, but their mechanisms are not well understood. Here we investigated Rga7p, an Schizosaccharomyces pombe F-BAR protein with a RhoGAP domain. Localization of Rga7p to the cytokinetic cleavage furrow depends on its F-BAR domain, actin filaments, the formins Cdc12p and For3p, and the presence of a contractile ring. Rga7p is not required for the constriction of the contractile ring but does participate in the transport of a β-glucan synthetase (Bgs4p) from the late Golgi compartments to plasma membrane that is adjacent to the contractile ring. Cells without Rga7p moved Bgs4p normally from the poles to the Golgi complex near to the cell center, but Bgs4p then moved slowly from the late Golgi compartments to the cleavage site. The late arrival and lower than normal numbers of Bgs4p result in septal defects late in cytokinesis, and in the lysis of separating cells, similar to that in cells with mutations in the cwg1(+) gene (which encodes Bgs4p).
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Affiliation(s)
- Rajesh Arasada
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA
| | - Thomas D Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA Department of Cell Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA
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15
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Kettenbach AN, Deng L, Wu Y, Baldissard S, Adamo ME, Gerber SA, Moseley JB. Quantitative phosphoproteomics reveals pathways for coordination of cell growth and division by the conserved fission yeast kinase pom1. Mol Cell Proteomics 2015; 14:1275-87. [PMID: 25720772 DOI: 10.1074/mcp.m114.045245] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Indexed: 11/06/2022] Open
Abstract
Complex phosphorylation-dependent signaling networks underlie the coordination of cellular growth and division. In the fission yeast Schizosaccharomyces pombe, the Dual specificity tyrosine-(Y)-phosphorylation regulated kinase (DYRK) family protein kinase Pom1 regulates cell cycle progression through the mitotic inducer Cdr2 and controls cell polarity through unknown targets. Here, we sought to determine the phosphorylation targets of Pom1 kinase activity by SILAC-based phosphoproteomics. We defined a set of high-confidence Pom1 targets that were enriched for cytoskeletal and cell growth functions. Cdr2 was the only cell cycle target of Pom1 kinase activity that we identified in cells. Mutation of Pom1-dependent phosphorylation sites in the C terminus of Cdr2 inhibited mitotic entry but did not impair Cdr2 localization. In addition, we found that Pom1 phosphorylated multiple substrates that function in polarized cell growth, including Tea4, Mod5, Pal1, the Rho GAP Rga7, and the Arf GEF Syt22. Purified Pom1 phosphorylated these cell polarity targets in vitro, confirming that they are direct substrates of Pom1 kinase activity and likely contribute to regulation of polarized growth by Pom1. Our study demonstrates that Pom1 acts in a linear pathway to control cell cycle progression while regulating a complex network of cell growth targets.
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Affiliation(s)
- Arminja N Kettenbach
- ‡Department of Biochemistry, ¶Norris Cotton Cancer Center, The Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA
| | | | | | | | - Mark E Adamo
- ¶Norris Cotton Cancer Center, The Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA
| | - Scott A Gerber
- ‡Department of Biochemistry, §Department of Genetics, The Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA; ¶Norris Cotton Cancer Center, The Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA
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16
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Kita A, Higa M, Doi A, Satoh R, Sugiura R. Imp2, the PSTPIP homolog in fission yeast, affects sensitivity to the immunosuppressant FK506 and membrane trafficking in fission yeast. Biochem Biophys Res Commun 2015; 457:273-9. [PMID: 25580011 DOI: 10.1016/j.bbrc.2014.12.100] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Accepted: 12/22/2014] [Indexed: 11/18/2022]
Abstract
Cytokinesis is a highly ordered process that divides one cell into two cells, which is functionally linked to the dynamic remodeling of the plasma membrane coordinately with various events such as membrane trafficking. Calcineurin is a highly conserved serine/threonine protein phosphatase, which regulates multiple biological functions, such as membrane trafficking and cytokinesis. Here, we isolated imp2-c3, a mutant allele of the imp2(+) gene, encoding a homolog of the mouse PSTPIP1 (proline-serine-threonine phosphatase interacting protein 1), using a genetic screen for mutations that are synthetically lethal with calcineurin deletion in fission yeast. The imp2-c3 mutants showed a defect in cytokinesis with multi-septated phenotypes, which was further enhanced upon treatment with the calcineurin inhibitor FK506. Notably, electron micrographs revealed that the imp2-c3 mutant cells accumulated aberrant multi-lamella Golgi structures and putative post-Golgi secretory vesicles, and exhibited fragmented vacuoles in addition to thickened septa. Consistently, imp2-c3 mutants showed a reduced secretion of acid phosphatase and defects in vacuole fusion. The imp2-c3 mutant cells exhibited a weakened cell wall, similar to the membrane trafficking mutants identified in the same genetic screen such as ypt3-i5. These findings implicate the PSTPIP1 homolog Imp2 in Golgi/vacuole function, thereby affecting various cellular processes, including cytokinesis and cell integrity.
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Affiliation(s)
- Ayako Kita
- Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Higashi-Osaka 577-8502, Japan
| | - Mari Higa
- Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Higashi-Osaka 577-8502, Japan
| | - Akira Doi
- Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Higashi-Osaka 577-8502, Japan; Japan Society for the Promotion of Science, 1-8 Chiyoda-ku, Tokyo 102-8472, Japan
| | - Ryosuke Satoh
- Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Higashi-Osaka 577-8502, Japan
| | - Reiko Sugiura
- Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Higashi-Osaka 577-8502, Japan.
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17
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Ren L, Willet AH, Roberts-Galbraith RH, McDonald NA, Feoktistova A, Chen JS, Huang H, Guillen R, Boone C, Sidhu SS, Beckley JR, Gould KL. The Cdc15 and Imp2 SH3 domains cooperatively scaffold a network of proteins that redundantly ensure efficient cell division in fission yeast. Mol Biol Cell 2014; 26:256-69. [PMID: 25428987 PMCID: PMC4294673 DOI: 10.1091/mbc.e14-10-1451] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The fission yeast F-BAR proteins Cdc15 and Imp2 and their combined SH3-domain partners appear to act as “molecular glue” to stabilize the interaction between the plasma membrane and a complex network of proteins at the division site that mediates cell division. Schizosaccharomyces pombe cdc15 homology (PCH) family members participate in numerous biological processes, including cytokinesis, typically by bridging the plasma membrane via their F-BAR domains to the actin cytoskeleton. Two SH3 domain–containing PCH family members, Cdc15 and Imp2, play critical roles in S. pombe cytokinesis. Although both proteins localize to the contractile ring, with Cdc15 preceding Imp2, only cdc15 is an essential gene. Despite these distinct roles, the SH3 domains of Cdc15 and Imp2 cooperate in the essential process of recruiting other proteins to stabilize the contractile ring. To better understand the connectivity of this SH3 domain–based protein network at the CR and its function, we used a biochemical approach coupled to proteomics to identify additional proteins (Rgf3, Art1, Spa2, and Pos1) that are integrated into this network. Cell biological and genetic analyses of these SH3 partners implicate them in a range of activities that ensure the fidelity of cell division, including promoting cell wall metabolism and influencing cell morphogenesis.
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Affiliation(s)
- Liping Ren
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Alaina H Willet
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Rachel H Roberts-Galbraith
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Nathan A McDonald
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Anna Feoktistova
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Jun-Song Chen
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Haiming Huang
- Terrence Donnelly Center for Cellular and Biomolecular Research, Banting and Best Department of Medical Research, University of Toronto, Toronto, ON M5G 1L6, Canada
| | - Rodrigo Guillen
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Charles Boone
- Terrence Donnelly Center for Cellular and Biomolecular Research, Banting and Best Department of Medical Research, University of Toronto, Toronto, ON M5G 1L6, Canada
| | - Sachdev S Sidhu
- Terrence Donnelly Center for Cellular and Biomolecular Research, Banting and Best Department of Medical Research, University of Toronto, Toronto, ON M5G 1L6, Canada
| | - Janel R Beckley
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Kathleen L Gould
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
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18
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Martín-García R, Coll PM, Pérez P. F-BAR domain protein Rga7 collaborates with Cdc15 and Imp2 to ensure proper cytokinesis in fission yeast. J Cell Sci 2014; 127:4146-58. [PMID: 25052092 DOI: 10.1242/jcs.146233] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
F-BAR domain proteins act as linkers between the cell cortex and cytoskeleton, and are involved in membrane binding and bending. Rga7 is one of the seven F-BAR proteins present in the fission yeast Schizosaccharomyces pombe. In addition to the F-BAR domain in the N-terminal region, Rga7 possesses a Rho GTPase-activating protein (GAP) domain at its C-terminus. We show here that Rga7 is necessary to prevent fragmentation of the contracting ring and incorrect septum synthesis. Accordingly, cultures of cells lacking Rga7 contain a higher percentage of dividing cells and more frequent asymmetric or aberrant septa, which ultimately might cause cell death. The Rga7 F-BAR domain is necessary for the protein localization to the division site and to the cell tips, and also for the Rga7 roles in cytokinesis. In contrast, Rga7 GAP catalytic activity seems to be dispensable. Moreover, we demonstrate that Rga7 cooperates with the two F-BAR proteins Cdc15 and Imp2 to ensure proper cytokinesis. We have also detected association of Rga7 with Imp2, and its binding partners Fic1 and Pxl1. Taken together, our findings suggest that Rga7 forms part of a protein complex that coordinates the late stages of cytokinesis.
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Affiliation(s)
- Rebeca Martín-García
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas/Universidad de Salamanca, 37007 Salamanca, Spain
| | - Pedro M Coll
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas/Universidad de Salamanca, 37007 Salamanca, Spain
| | - Pilar Pérez
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas/Universidad de Salamanca, 37007 Salamanca, Spain
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19
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Hof1 and Rvs167 have redundant roles in actomyosin ring function during cytokinesis in budding yeast. PLoS One 2013; 8:e57846. [PMID: 23469085 PMCID: PMC3585203 DOI: 10.1371/journal.pone.0057846] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 01/28/2013] [Indexed: 11/19/2022] Open
Abstract
The Hof1 protein (Homologue of Fifteen) regulates formation of the primary septum during cytokinesis in the budding yeast Saccharomyces cerevisiae, whereas the orthologous Cdc15 protein in fission yeast regulates the actomyosin ring by using its F-BAR domain to recruit actin nucleators to the cleavage site. Here we show that budding yeast Hof1 also contributes to actin ring assembly in parallel with the Rvs167 protein. Simultaneous deletion of the HOF1 and RVS167 genes is lethal, and cells fail to assemble the actomyosin ring as they progress through mitosis. Although Hof1 and Rvs167 are not orthologues, they both share an analogous structure, with an F-BAR or BAR domain at the amino terminus, capable of inducing membrane curvature, and SH3 domains at the carboxyl terminus that bind to specific proline-rich targets. The SH3 domain of Rvs167 becomes essential for assembly of the actomyosin ring in cells lacking Hof1, suggesting that it helps to recruit a regulator of the actin cytoskeleton. This new function of Rvs167 appears to be independent of its known role as a regulator of the Arp2/3 actin nucleator, as actin ring assembly is not abolished by the simultaneous inactivation of Hof1 and Arp2/3. Instead we find that recruitment to the bud-neck of the Iqg1 actin regulator is defective in cells lacking Hof1 and Rvs167, though future studies will be needed to determine if this reflects a direct interaction between these factors. The redundant role of Hof1 in actin ring assembly suggests that the mechanism of actin ring assembly has been conserved to a greater extent across evolution than anticipated previously.
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20
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Meitinger F, Palani S, Hub B, Pereira G. Dual function of the NDR-kinase Dbf2 in the regulation of the F-BAR protein Hof1 during cytokinesis. Mol Biol Cell 2013; 24:1290-304. [PMID: 23447700 PMCID: PMC3639042 DOI: 10.1091/mbc.e12-08-0608] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The conserved NDR-kinase Dbf2 plays a critical role in cytokinesis in budding yeast. Among its cytokinesis-related substrates is the F-BAR protein Hof1. Hof1 colocalizes at the cell division site with the septin complex and, as mitotic exit progresses, moves to the actomyosin ring (AMR). Neither the function of Hof1 at the septin complex nor the mechanism by which Hof1 supports AMR constriction is understood. Here we establish that Dbf2 has a dual function in Hof1 regulation. First, we show that the coiled-coil region, which is adjacent to the conserved F-BAR domain, is required for the binding of Hof1 to septins. The Dbf2-dependent phosphorylation of Hof1 at a single serine residue (serine 313) in this region diminishes the recruitment of Hof1 to septins both in vitro and in vivo. Genetic and functional analysis indicates that the binding of Hof1 to septins is important for septin rearrangement and integrity during cytokinesis. Furthermore, Dbf2 phosphorylation of Hof1 at serines 533 and 563 promotes AMR constriction most likely by inhibiting the SH3-domain-dependent interactions of Hof1. Thus our data show that Dbf2 coordinates septin and AMR functions during cytokinesis through the regulation/control of Hof1.
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Affiliation(s)
- Franz Meitinger
- Molecular Biology of Centrosomes and Cilia Unit, DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany
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21
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Bohnert KA, Gould KL. Cytokinesis-based constraints on polarized cell growth in fission yeast. PLoS Genet 2012; 8:e1003004. [PMID: 23093943 PMCID: PMC3475658 DOI: 10.1371/journal.pgen.1003004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Accepted: 08/15/2012] [Indexed: 11/18/2022] Open
Abstract
The rod-shaped fission yeast Schizosaccharomyces pombe, which undergoes cycles of monopolar-to-bipolar tip growth, is an attractive organism for studying cell-cycle regulation of polarity establishment. While previous research has described factors mediating this process from interphase cell tips, we found that division site signaling also impacts the re-establishment of bipolar cell growth in the ensuing cell cycle. Complete loss or targeted disruption of the non-essential cytokinesis protein Fic1 at the division site, but not at interphase cell tips, resulted in many cells failing to grow at new ends created by cell division. This appeared due to faulty disassembly and abnormal persistence of the cell division machinery at new ends of fic1Δ cells. Moreover, additional mutants defective in the final stages of cytokinesis exhibited analogous growth polarity defects, supporting that robust completion of cell division contributes to new end-growth competency. To test this model, we genetically manipulated S. pombe cells to undergo new end take-off immediately after cell division. Intriguingly, such cells elongated constitutively at new ends unless cytokinesis was perturbed. Thus, cell division imposes constraints that partially override positive controls on growth. We posit that such constraints facilitate invasive fungal growth, as cytokinesis mutants displaying bipolar growth defects formed numerous pseudohyphae. Collectively, these data highlight a role for previous cell cycles in defining a cell's capacity to polarize at specific sites, and they additionally provide insight into how a unicellular yeast can transition into a quasi-multicellular state.
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Affiliation(s)
- K. Adam Bohnert
- Howard Hughes Medical Institute and Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Kathleen L. Gould
- Howard Hughes Medical Institute and Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- * E-mail:
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22
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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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23
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Arasada R, Pollard TD. Distinct roles for F-BAR proteins Cdc15p and Bzz1p in actin polymerization at sites of endocytosis in fission yeast. Curr Biol 2011; 21:1450-9. [PMID: 21885283 DOI: 10.1016/j.cub.2011.07.046] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 06/30/2011] [Accepted: 07/27/2011] [Indexed: 11/17/2022]
Abstract
BACKGROUND Genetic analyses of budding and fission yeast identified >50 proteins that assemble at sites of clathrin-mediated endocytosis in structures called actin patches. These proteins include clathrin, clathrin-interacting proteins, actin binding proteins, and peripheral membrane proteins such as F-BAR proteins. Many questions remain regarding the interactions of these proteins, particularly the participation of F-BAR proteins in the assembly of actin filaments. RESULTS Our microscopic and genetic interaction experiments on fission yeast show that F-BAR proteins Cdc15p and Bzz1p accumulate in two distinct zones on invaginating membrane tubules and interact with Myo1p and Wsp1p, nucleation-promoting factors for Arp2/3 complex. The two F-BAR proteins peak prior to movement of the actin patch and their accumulation in actin patches depends on the nucleation-promoting factors. At their peak local concentrations, we estimated the stoichiometries of the proteins in actin patches to be one Bzz1p per two Wsp1p and one Cdc15p per Myo1p. Purified Bzz1p has two SH3 domains that interact with Wsp1p and stimulate actin polymerization by Arp2/3 complex. Cells lacking either Cdc15p or Bzz1p assemble 3- to 5-fold less actin in patches (in spite of normal levels of Wsp1p, Myo1p, and Arp2/3 complex), and patches move shorter distances from the plasma membrane. CONCLUSION We propose that during clathrin-mediated endocytosis, F-BAR proteins interact with nucleation-promoting factors to stimulate Arp2/3 complex in two different zones along the invaginating tubule. We further propose that polymerization of actin filaments in these two zones contributes to membrane scission.
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Affiliation(s)
- Rajesh Arasada
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA
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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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Böhmer C, Ripp C, Bölker M. The germinal centre kinase Don3 triggers the dynamic rearrangement of higher-order septin structures during cytokinesis in Ustilago maydis. Mol Microbiol 2009; 74:1484-96. [PMID: 19906182 DOI: 10.1111/j.1365-2958.2009.06948.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The dimorphic phytopathogenic fungus Ustilago maydis grows in its haploid phase by budding. Cytokinesis and separation of daughter cells are accomplished by the consecutive formation of two distinct septa. Here, we show that both septation events involve the dynamic rearrangement of septin assemblies from hourglass-shaped collars into ring-like structures. Using a chemical genetic approach we demonstrate that the germinal centre kinase Don3 triggers this septin reorganization during secondary septum formation. Although chemical inhibition of an analogue-sensitive version of Don3 prevented septation, a stable septin collar was assembled at the presumptive septation site. Interestingly, the essential light chain of type II myosin, Cdc4, was already associated with this septin collar. Release of Don3 kinase inhibition triggered immediate dispersal of septin filaments and concomitant incorporation of Cdc4 into a contractile actomyosin ring, which also contained the F-BAR domain protein Cdc15. Inhibition of actin polymerization or deletion of the cdc15 gene, did not affect assembly of the initial collar consisting of septin and myosin light chain. However, reassembly of septin filaments into a ring-like structure was prevented in the absence of either F-actin or Cdc15, indicating that septin ring formation in U. maydis depends on a functional contractile actomyosin ring.
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Affiliation(s)
- Christian Böhmer
- Department of Biology, Philipps-University Marburg, Karl-von-Frisch-Str. 8, D-35032 Marburg, Germany
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Gonzalez Y, Meerbrey K, Chong J, Torii Y, Padte NN, Sazer S. Nuclear shape, growth and integrity in the closed mitosis of fission yeast depend on the Ran-GTPase system, the spindle pole body and the endoplasmic reticulum. J Cell Sci 2009; 122:2464-72. [PMID: 19571115 DOI: 10.1242/jcs.049999] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The double lipid bilayer of the nuclear envelope (NE) remains intact during closed mitosis. In the fission yeast Schizosaccharomyces pombe, the intranuclear mitotic spindle has envelope-embedded spindle pole bodies (SPB) at its ends. As the spindle elongates and the nucleus divides symmetrically, nuclear volume remains constant but nuclear area rapidly increases by 26%. When Ran-GTPase function is compromised in S. pombe, nuclear division is strikingly asymmetrical and the newly synthesized SPB is preferentially associated with the smaller nucleus, indicative of a Ran-dependent SPB defect that interferes with symmetrical nuclear division. A second defect, which specifically influences the NE, results in breakage of the NE upon spindle elongation. This defect, but not asymmetric nuclear division, is partially rescued by slowing spindle elongation, stimulating endoplasmic reticulum (ER) proliferation or changing conformation of the ER membrane. We propose that redistribution of lipid within the ER-NE network is crucial for mitosis-specific NE changes in both open and closed mitosis.
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Affiliation(s)
- Yanira Gonzalez
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
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27
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Abstract
Among an increasing number of lipid-binding domains, a group that not only binds to membrane lipids but also changes the shape of the membrane has been found. These domains are characterized by their strong ability to transform globular liposomes as well as flat plasma membranes into elongated membrane tubules both in vitro and in vivo. Biochemical studies on the structures of these proteins have revealed the importance of the amphipathic helix, which potentially intercalates into the lipid bilayer to induce and/or sense membrane curvature. Among such membrane-deforming domains, BAR and F-BAR/EFC domains form crescent-shaped dimers, suggesting a preference for a curved membrane, which is important for curvature sensing. Bioinformatics in combination with structural analyses has been identifying an increasing number of novel families of lipid-binding domains. This review attempts to summarize the evidence obtained by recent studies in order to gain general insights into the roles of membrane-deforming domains in a variety of biological events.
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Affiliation(s)
- Toshiki Itoh
- Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kusunoki-cho, Chuo-ku, Japan.
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28
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Roberts-Galbraith RH, Chen JS, Wang J, Gould KL. The SH3 domains of two PCH family members cooperate in assembly of the Schizosaccharomyces pombe contractile ring. ACTA ACUST UNITED AC 2009; 184:113-27. [PMID: 19139265 PMCID: PMC2615086 DOI: 10.1083/jcb.200806044] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Schizosaccharomyces pombe cdc15 homology (PCH) family members participate in many cellular processes by bridging the plasma membrane and cytoskeleton. Their F-BAR domains bind and curve membranes, whereas other domains, typically SH3 domains, are expected to provide cytoskeletal links. We tested this prevailing model of functional division in the founding member of the family, Cdc15, which is essential for cytokinesis in S. pombe, and in the related PCH protein, Imp2. We find that the distinct functions of Imp2 and Cdc15 are SH3 domain independent. However, the Cdc15 and Imp2 SH3 domains share an essential role in recruiting proteins to the contractile ring, including Pxl1 and Fic1. Together, Pxl1 and Fic1, a previously uncharacterized C2 domain protein, add structural integrity to the contractile ring and prevent it from fragmenting during division. Our data indicate that the F-BAR proteins Cdc15 and Imp2 contribute to a single biological process with both distinct and overlapping functions.
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Aspenström P. Roles of F-BAR/PCH proteins in the regulation of membrane dynamics and actin reorganization. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 272:1-31. [PMID: 19121815 DOI: 10.1016/s1937-6448(08)01601-8] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The Pombe Cdc15 Homology (PCH) proteins have emerged in many species as important coordinators of signaling pathways that regulate actomyosin assembly and membrane dynamics. The hallmark of the PCH proteins is the presence of a Fes/CIP4 homology-Bin/Amphiphysin/Rvsp (F-BAR) domain; therefore they are commonly referred to as F-BAR proteins. The prototype F-BAR protein, Cdc15p of Schizosaccharomyces pombe, has a role in the formation of the contractile actomyosin ring during cytokinesis. Vertebrate F-BAR proteins have an established role in binding phospholipids and they participate in membrane deformations, for instance, during the internalization of transmembrane receptors. This way the F-BAR proteins will function as linkers between the actin polymerization apparatus and the machinery regulating membrane dynamics. Interestingly, some members of the F-BAR proteins are implicated in inflammatory or neurodegenerative disorders and the observations can be expected to have clinical implications for the treatment of the diseases.
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Affiliation(s)
- Pontus Aspenström
- Ludwig Institute for Cancer Research, Uppsala University, SE-751 24 Uppsala, Sweden
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30
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Martín-García R, Valdivieso MH. The fission yeast Chs2 protein interacts with the type-II myosin Myo3p and is required for the integrity of the actomyosin ring. J Cell Sci 2006; 119:2768-79. [PMID: 16772338 DOI: 10.1242/jcs.02998] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Schizosaccharomyces pombe cytokinesis requires the function of a contractile actomyosin ring. Fission yeast Chs2p is a transmembrane protein structurally similar to chitin synthases that lacks such enzymatic activity. Chs2p localisation and assembly into a ring that contracts during division requires the general system for polarised secretion, some components of the actomyosin ring, and an active septation initiation network. Chs2p interacts physically with the type-II myosin Myo3p revealing a physical link between the plasma membrane and the ring. In chs2Delta mutants, actomyosin ring integrity is compromised during the last stages of contraction and it remains longer in the midzone. In synchronous cultures, chs2Delta cells exhibit a delay in septation with respect to the control strain. All these results show that Chs2p participates in the correct functioning of the medial ring.
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Affiliation(s)
- Rebeca Martín-García
- Departamento de Microbiología y Genética/Instituto de Microbiología Bioquímica, Universidad de Salamanca/CSIC, Edificio Departamental, Laboratorio 231, Campus Miguel de Unamuno, 37007 Salamanca, Spain
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31
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Abstract
Actin ring formation is a prerequisite for osteoclast bone resorption. Although gelsolin null osteoclasts failed to exhibit podosomes, actin ring was observed in these osteoclasts. Wiscott-Aldrich syndrome protein (WASP) was observed in the actin ring of gelsolin null osteoclast. Osteoclasts stimulated with osteopontin simulated the effects of Rho and Cdc42 in phosphatidylinositol 4,5-bisphosphate (PIP2) association with WASP as well as formation of podosomes, peripheral microfilopodia-like structures, and actin ring. To explore the potential functions of Rho and Cdc42, TAT-mediated delivery of Rho proteins into osteoclasts was performed. Although Rho and Cdc42 are required for actin ring formation, transduction of either one of the proteins alone is insufficient for this process. Addition of osteopontin to osteoclasts transduced with Cdc42Val12 or transduction of osteoclasts with both RhoVal14 and Cdc42Val12 augments the formation of WASP-Arp2/3 complex and actin ring. Neomycin, an antibiotic, blocked the effects of osteopontin or TAT-RhoVal14 on PIP2 interaction with WASP. WASP distribution was found to be cytosolic in these osteoclasts. Depletion of WASP by short interfering RNA-mediated gene silencing blocked actin polymerization as well as actin ring formation in osteoclasts. These results suggest that Rho-mediated PIP2 interaction with WASP may contribute to the activation and membrane targeting of WASP. Subsequent interaction of Cdc42 and Arp2/3 with WASP may enhance cortical actin polymerization in the process of actin ring formation in osteoclasts.
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Affiliation(s)
- Meenakshi A Chellaiah
- Department of Biomedical Sciences, Dental School, University of Maryland, Baltimore, Maryland 21201, USA.
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Blondel M, Bach S, Bamps S, Dobbelaere J, Wiget P, Longaretti C, Barral Y, Meijer L, Peter M. Degradation of Hof1 by SCF(Grr1) is important for actomyosin contraction during cytokinesis in yeast. EMBO J 2005; 24:1440-52. [PMID: 15775961 PMCID: PMC1142548 DOI: 10.1038/sj.emboj.7600627] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2004] [Accepted: 02/23/2005] [Indexed: 11/08/2022] Open
Abstract
SCF-type (SCF: Skp1-Cullin-F-box protein complex) E3 ligases regulate ubiquitin-dependent degradation of many cell cycle regulators, mainly at the G1/S transition. Here, we show that SCF(Grr1) functions during cytokinesis by degrading the PCH protein Hof1. While Hof1 is required early in mitosis to assemble a functional actomyosin ring, it is specifically degraded late in mitosis and remains unstable during the entire G1 phase of the cell cycle. Degradation of Hof1 depends on its PEST motif and a functional 26S proteasome. Interestingly, degradation of Hof1 is independent of APC(Cdh1), but instead requires the SCF(Grr1) E3 ligase. Grr1 is recruited to the mother-bud neck region after activation of the mitotic-exit network, and interacts with Hof1 in a PEST motif-dependent manner. Our results also show that downregulation of Hof1 at the end of mitosis is necessary to allow efficient contraction of the actomyosin ring and cell separation during cytokinesis. SCF(Grr1)-mediated degradation of Hof1 may thus represent a novel mechanism to couple exit from mitosis with initiation of cytokinesis.
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Affiliation(s)
- Marc Blondel
- CNRS, Station Biologique, UMR7150, Amyloids and Cell Division Cycle Laboratory, Place G Teissier, Roscoff, Bretagne, France.
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33
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Wu JQ, Kuhn JR, Kovar DR, Pollard TD. Spatial and temporal pathway for assembly and constriction of the contractile ring in fission yeast cytokinesis. Dev Cell 2003; 5:723-34. [PMID: 14602073 DOI: 10.1016/s1534-5807(03)00324-1] [Citation(s) in RCA: 321] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Microscopy of fluorescent fusion proteins and genetic dependencies show that fission yeast assemble and constrict a cytokinetic contractile ring in a precisely timed, sequential order. More than 90 min prior to separation of the spindle pole bodies (SPB), the anillin-like protein (Mid1p) migrates from the nucleus and specifies a broad band of cortex around the equator as the division site. Between 10 min before and 2 min after SPB separation, conventional myosin-II (Myo2p), IQGAP (Rng2p), PCH protein (Cdc15p), and formin (Cdc12p) join the broad band independent of actin filaments. Over the subsequent 10 min prior to anaphase B, this broad band of proteins condenses into a contractile ring including actin, tropomyosin (Cdc8p), and alpha-actinin (Ain1p). During anaphase B, unconventional myosin-II (Myp2p) joins the ring followed by the septin (Spn1p). Ring contraction and disassembly begin 37 min after SPB separation. This spatial and temporal hierarchy provides the framework for analysis of molecular mechanisms.
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Affiliation(s)
- Jian-Qiu Wu
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
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34
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Carnahan RH, Gould KL. The PCH family protein, Cdc15p, recruits two F-actin nucleation pathways to coordinate cytokinetic actin ring formation in Schizosaccharomyces pombe. J Cell Biol 2003; 162:851-62. [PMID: 12939254 PMCID: PMC2172828 DOI: 10.1083/jcb.200305012] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cytokinetic actin ring (CAR) formation in Schizosaccharomyces pombe requires two independent actin nucleation pathways, one dependent on the Arp2/3 complex and another involving the formin Cdc12p. Here we investigate the role of the S. pombe Cdc15 homology family protein, Cdc15p, in CAR assembly and find that it interacts with proteins from both of these nucleation pathways. Cdc15p binds directly to the Arp2/3 complex activator Myo1p, which likely explains why actin patches and the Arp2/3 complex fail to be medially recruited during mitosis in cdc15 mutants. Cdc15p also binds directly to Cdc12p. Cdc15p and Cdc12p not only display mutual dependence for CAR localization, but also exist together in a ring-nucleating structure before CAR formation. The disruption of these interactions in cdc15 null cells is likely to be the reason for their complete lack of CARs. We propose a model in which Cdc15p plays a critical role in recruiting and coordinating the pathways essential for the assembly of medially located F-actin filaments and construction of the CAR.
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Affiliation(s)
- Robert H Carnahan
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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35
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Rajagopalan S, Wachtler V, Balasubramanian M. Cytokinesis in fission yeast: a story of rings, rafts and walls. Trends Genet 2003; 19:403-8. [PMID: 12850446 DOI: 10.1016/s0168-9525(03)00149-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Srividya Rajagopalan
- Laboratory of Cell Division, Temasek Life Sciences Laboratory, 1 Research Link, The National University of Singapore, 117604 Singapore
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Salus SS, Demeter J, Sazer S. The Ran GTPase system in fission yeast affects microtubules and cytokinesis in cells that are competent for nucleocytoplasmic protein transport. Mol Cell Biol 2002; 22:8491-505. [PMID: 12446769 PMCID: PMC139886 DOI: 10.1128/mcb.22.24.8491-8505.2002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Misregulation of the evolutionarily conserved GTPase Ran in fission yeast results in defects in several cellular processes in cells that are competent for nucleocytoplasmic protein transport. These results suggest that transport is neither the only nor the primary Ran-dependent process in living cells. The ability of Ran to independently regulate multiple cellular processes in vivo is demonstrated by showing that (i) eight different transport-competent RanGEF (guanine nucleotide exchange factor) mutants have defects in mitotic spindle formation; (ii) the RanGEF temperature-sensitive mutant pim1-d1 has abnormal actin ring structures at the septum. Overexpression of Imp2p, which specifically destabilizes these structures, restores viability. (iii) Ran-dependent processes differ in their requirements for active Ran in vivo. Microtubule function, cytokinesis, and nuclear envelope structure are the Ran-dependent processes most sensitive to the amount of Ran protein in the cell, whereas nucleocytoplasmic protein transport is the most robust. Therefore, the ability of Ran from Schizosaccharomyces pombe to independently regulate multiple cellular processes may reflect differences in its interactions with the binding proteins that mediate these functions and explain the complex phenotypic consequences of its misregulation in vivo.
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Affiliation(s)
- Sandra S Salus
- Interdepartmental Program in Cell and Molecular Biology, Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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Anderson M, Ng SS, Marchesi V, MacIver FH, Stevens FE, Riddell T, Glover DM, Hagan IM, McInerny CJ. Plo1(+) regulates gene transcription at the M-G(1) interval during the fission yeast mitotic cell cycle. EMBO J 2002; 21:5745-55. [PMID: 12411492 PMCID: PMC131061 DOI: 10.1093/emboj/cdf564] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The regulation of gene expression plays an important part in cell cycle controls. We describe the molecular machinery that co-ordinates gene transcription at the M-G(1) interval during the fission yeast mitotic cell cycle. A sequence is identified in the cdc15(+) promoter that we call a PCB (pombe cell cycle box), which confers M-G(1)-specific transcription. Sequences similar to the PCB are present in the promoters of seven other genes, spo12(+), cdc19(+), fin1(+), sid2(+), ppb1(+), mid1(+)/dmf1(+) and plo1(+), which we find to be transcribed at M-G(1). A transcription factor complex is identified that binds to the PCB sequence, which we name PBF, for PCB-binding factor. Finally, we show that PBF binding activity and consequent gene transcription are regulated by the Plo1p protein kinase, thus invoking a potential auto-feedback loop mechanism that regulates mitotic gene transcription and passage through septation and cytokinesis.
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Affiliation(s)
| | | | | | - Fiona H. MacIver
- Division of Biochemistry and Molecular Biology, Institute of Biological and Life Sciences, University of Glasgow, Glasgow G12 8QQ,
Paterson Institute for Cancer Research, Christie Hospital, Wilmslow Road, Withington, Manchester M20 4BX and Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK Corresponding author e-mail:
| | - Frances E. Stevens
- Division of Biochemistry and Molecular Biology, Institute of Biological and Life Sciences, University of Glasgow, Glasgow G12 8QQ,
Paterson Institute for Cancer Research, Christie Hospital, Wilmslow Road, Withington, Manchester M20 4BX and Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK Corresponding author e-mail:
| | | | - David M. Glover
- Division of Biochemistry and Molecular Biology, Institute of Biological and Life Sciences, University of Glasgow, Glasgow G12 8QQ,
Paterson Institute for Cancer Research, Christie Hospital, Wilmslow Road, Withington, Manchester M20 4BX and Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK Corresponding author e-mail:
| | - Iain M. Hagan
- Division of Biochemistry and Molecular Biology, Institute of Biological and Life Sciences, University of Glasgow, Glasgow G12 8QQ,
Paterson Institute for Cancer Research, Christie Hospital, Wilmslow Road, Withington, Manchester M20 4BX and Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK Corresponding author e-mail:
| | - Christopher J. McInerny
- Division of Biochemistry and Molecular Biology, Institute of Biological and Life Sciences, University of Glasgow, Glasgow G12 8QQ,
Paterson Institute for Cancer Research, Christie Hospital, Wilmslow Road, Withington, Manchester M20 4BX and Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK Corresponding author e-mail:
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Abstract
Cytokinesis is the final event of the cell division cycle, and its completion results in irreversible partition of a mother cell into two daughter cells. Cytokinesis was one of the first cell cycle events observed by simple cell biological techniques; however, molecular characterization of cytokinesis has been slowed by its particular resistance to in vitro biochemical approaches. In recent years, the use of genetic model organisms has greatly advanced our molecular understanding of cytokinesis. While the outcome of cytokinesis is conserved in all dividing organisms, the mechanism of division varies across the major eukaryotic kingdoms. Yeasts and animals, for instance, use a contractile ring that ingresses to the cell middle in order to divide, while plant cells build new cell wall outward to the cortex. As would be expected, there is considerable conservation of molecules involved in cytokinesis between yeast and animal cells, while at first glance, plant cells seem quite different. However, in recent years, it has become clear that some aspects of division are conserved between plant, yeast, and animal cells. In this review we discuss the major recent advances in defining cytokinesis, focusing on deciding where to divide, building the division apparatus, and dividing. In addition, we discuss the complex problem of coordinating the division cycle with the nuclear cycle, which has recently become an area of intense research. In conclusion, we discuss how certain cells have utilized cytokinesis to direct development.
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Affiliation(s)
- David A Guertin
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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39
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Nikki M, Meriläinen J, Lehto VP. Focal adhesion protein FAP52 self-associates through a sequence conserved among the members of the PCH family proteins. Biochemistry 2002; 41:6320-9. [PMID: 12009893 DOI: 10.1021/bi015991n] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
FAP52 is a recently described focal adhesion-associated protein. It is a member of an emerging PCH (pombe Cdc15 homology) family of proteins characterized by a common domain organization and involvement in actin cytoskeleton organization, cytokinesis, and vesicular trafficking. Using gel filtration, surface plasmon resonance, and native polyacrylamide gel electrophoresis analysis, combined with chemical cross-linking of both native and recombinant protein, we show that FAP52 self-associates in vitro and suggest that it occurs predominantly as a trimer also in vivo. Analysis of the various domains of FAP52 by surface plasmon resonance showed that the highly alpha-helical region in the N-terminal half of the protein provides the self-association interface. Overexpression of the oligomerization domain in cultured cells was accompanied by major alterations in cellular morphology, actin organization, and the structure of focal adhesions, suggesting that an orderly coming together of FAP52 molecules is crucial for a proper actin filament organization and cytoskeletal structure. Comparison of the primary structures shows that all of the members of the PCH family have, in their N-terminal halves, a similar, highly alpha-helical region, suggesting that they all have a capacity to self-associate.
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Affiliation(s)
- Marko Nikki
- Department of Pathology, University of Oulu, FIN-90014 Oulu, Finland
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40
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Arai R, Mabuchi I. F-actin ring formation and the role of F-actin cables in the fission yeastSchizosaccharomyces pombe. J Cell Sci 2002; 115:887-98. [PMID: 11870208 DOI: 10.1242/jcs.115.5.887] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cells of the fission yeast Schizosaccharomyces pombe divide by the contraction of the F-actin ring formed at the medial region of the cell. We investigated the process of F-actin ring formation in detail using optical sectioning and three-dimensional reconstruction fluorescence microscopy. In wild-type cells, formation of an aster-like structure composed of F-actin cables and accumulation of F-actin cables were recognized at the medial cortex of the cell during prophase to metaphase. The formation of the aster-like structure seemed to initiate from branching of the longitudinal F-actin cables at a site near the spindle pole bodies, which had been duplicated but not yet separated. A single cable extended from the aster and encircled the cell at the equator to form a primary F-actin ring during metaphase. During anaphase,the accumulated F-actin cables were linked to the primary F-actin ring, and then all of these structures seemed to be packed to form the F-actin ring. These observations suggest that formation of the aster-like structure and the accumulation of the F-actin cables at the medial region of the cell during metaphase may be required to initiate the F-actin ring formation. In the nda3 mutant, which has a mutation in ß-tubulin and has been thought to be arrested at prophase, an F-actin ring with accumulated F-actin cables similar to that of anaphase wild-type cells was formed at a restrictive temperature. Immediately after shifting to a permissive temperature, this structure changed into a tightly packed ring. This suggests that the F-actin ring formation progresses beyond prophase in the nda3 cells once the cells enter prophase. We further examined F-actin structures in both cdc12 and cdc15 early cytokinesis mutants. As a result,Cdc12 seemed to be required for the primary F-actin ring formation during prophase, whereas Cdc15 may be involved in both packing the F-actin cables to form the F-actin ring and rearrangement of the F-actin after anaphase. In spg1, cdc7 and sid2 septum initiation mutants, the F-actin ring seemed to be formed in order.
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Affiliation(s)
- Ritsuko Arai
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, 153-8902, Japan
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41
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Affiliation(s)
- I M Hagan
- School of Biological Sciences, University of Manchester, United Kingdom
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42
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McCollum D, Gould KL. Timing is everything: regulation of mitotic exit and cytokinesis by the MEN and SIN. Trends Cell Biol 2001; 11:89-95. [PMID: 11166217 DOI: 10.1016/s0962-8924(00)01901-2] [Citation(s) in RCA: 208] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Proper completion of mitosis requires careful coordination of numerous cellular events. It is crucial, for example, that cells do not initiate spindle disassembly and cytokinesis until chromosomes have been properly segregated. Cells have developed numerous safeguards or checkpoints to delay exit from mitosis and initiation of the next cell cycle in response to defects in late mitosis. In this review, we discuss recent work on two homologous signaling pathways in budding and fission yeast, termed the mitotic exit network (MEN) and septation initiation network (SIN), respectively, that are essential for coordinating completion of mitosis and cytokinesis with other mitotic events.
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Affiliation(s)
- D McCollum
- Dept of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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43
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Abstract
The microtubule cytoskeleton plays a pivotal role in cytoplasmic organization, cell division, and the correct transmission of genetic information. In a screen designed to identify fission yeast genes required for chromosome segregation, we identified a strain that carries a point mutation in the SpRan GTPase. Ran is an evolutionarily conserved eukaryotic GTPase that directly participates in nucleocytoplasmic transport and whose loss affects many biological processes. Recently a transport-independent effect of Ran on spindle formation in vitro was demonstrated, but the in vivo relevance of these findings was unclear. Here, we report the characterization of a Schizosaccharomyces pombe Ran GTPase partial loss of function mutant in which nucleocytoplasmic protein transport is normal, but the microtubule cytoskeleton is defective, resulting in chromosome missegregation and abnormal cell shape. These abnormalities are exacerbated by microtubule destabilizing drugs, by loss of the spindle checkpoint protein Mph1p, and by mutations in the spindle pole body component Cut11p, indicating that SpRan influences microtubule integrity. As the SpRan mutant phenotype can be partially suppressed by the presence of extra Mal3p, we suggest that SpRan plays a role in microtubule stability.
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Affiliation(s)
- U Fleig
- Institut für Mikrobiologie, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany.
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Paoletti A, Chang F. Analysis of mid1p, a protein required for placement of the cell division site, reveals a link between the nucleus and the cell surface in fission yeast. Mol Biol Cell 2000; 11:2757-73. [PMID: 10930468 PMCID: PMC14954 DOI: 10.1091/mbc.11.8.2757] [Citation(s) in RCA: 161] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
mid1 is required for the proper placement of the contractile actin ring for cytokinesis at a medial site overlying the nucleus. Here we find that mid1 protein (mid1p) shuttles between the nucleus and a cortical medial broad band during interphase and early mitosis. The position of this broad band, which overlies the nucleus, is linked to nuclear position even in cells with displaced or multiple nuclei. We identified and created mutations in an NLS and in two crm1-dependent NES sequences in mid1p. NES mutations caused mid1p accumulation in the nucleus and loss of function. An NLS mutations greatly reduced nuclear localization but did not perturb cytoplasmic localization or function. mid1p localization to the medial broad band was also not dependent on mid1p PH domain or microtubule and actin cytoskeletons. Overexpression of mid1p produced ectopic cell growth at this band during interphase and abnormal karmellae-like nuclear membrane structures. In plo1-1, mid1p formed a medial broad band but did not incorporate into a tight ring, suggesting that polo kinase plo1p is required for activation of mid1p function. Thus, the mid1p broad band defines a compartment at the medial cell surface, whose localization is linked to the position of the nucleus, and whose function may be to position the plane of cell division.
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Affiliation(s)
- A Paoletti
- Columbia University, Department of Microbiology, New York, NY 10032, USA.
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45
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Merla A, Johnson DI. The Cdc42p GTPase is targeted to the site of cell division in the fission yeast Schizosaccharomyces pombe. Eur J Cell Biol 2000; 79:469-77. [PMID: 10961446 DOI: 10.1078/0171-9335-00073] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Rho-family GTPase Cdc42p regulates many aspects of cell polarity and growth in eukaryotic cells, including the organization of the actin cytoskeleton. To further examine Cdc42p function in the fission yeast Schizosaccharomyces pombe, a functional green fluorescent protein (GFP)-Cdc42p fusion protein was generated. GFP-Cdc42p was observed at the medial region of the cell at the cell-division site early in cytokinesis and remained there through cell separation, and was also localized to the periphery of the cell and to internal membranes. Unexpectedly, treatment with the actin-depolymerizing drug latrunculin-A disrupted the medial region targeting pattern, and cells deficient in the actin-binding proteins tropomyosin and profilin also did not exhibit medial GFP-Cdc42p staining. In addition, medial GFP-Cdc42p localization was eliminated in a number of cytokinesis mutants, including strains defective in assembling the medial actinomyosin ring, medial ring contraction, and septum assembly. GFP-Cdc42p targeting was less affected in mutants that formed misplaced or multiple septa. These results suggest that the localization of Cdc42p at the cell-division site was dependent upon the actin cytoskeleton and that Cdc42p may function in the interdependent processes of cytokinesis and septation.
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Affiliation(s)
- A Merla
- Department of Microbiology and Molecular Genetics and the Markey Center for Molecular Genetics, University of Vermont, Burlington 05405, USA
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46
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Balasubramanian MK, McCollum D, Surana U. Tying the knot: linking cytokinesis to the nuclear cycle. J Cell Sci 2000; 113 ( Pt 9):1503-13. [PMID: 10751142 DOI: 10.1242/jcs.113.9.1503] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
For the survival of both the parent and the progeny, it is imperative that the process of their physical division (cytokinesis) be precisely coordinated with progression through the mitotic cell cycle. Recent studies in the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe are beginning to unravel the nature of the links between cytokinesis and the nuclear division cycle. The cyclin-dependent kinases and a novel surveillance mechanism that monitors cytokinesis and/or morphogenesis appear to play important regulatory roles in forging these links. It is becoming increasingly clear that the inactivation of the mitosis-promoting cyclin-dependent kinase, which marks the completion of the nuclear division cycle, is essential for actomyosin ring constriction and division septum assembly in both yeasts. Additionally, the spindle pole bodies are emerging as important transient locale for proteins that might play a key role in coupling the completion of mitosis to the onset of cytokinesis.
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Affiliation(s)
- M K Balasubramanian
- Cell Division Laboratory, Institute of Molecular Agrobiology, The National University of Singapore, Singapore 117604.
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47
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Abstract
Pombe Cdc15 homology (PCH) proteins constitute an extensive protein family whose members have been found in diverse eukaryotic organisms. These proteins are characterized by the presence of several conserved sequence and structural motifs. Recent studies in yeast and mammalian cultured cells have implicated these proteins in actin-based processes, in particular, cytokinesis. Here we review the recent findings on the in vivo localization, function, and binding partners of PCH family members. We also provide new microscopy data regarding the in vivo dynamics of a budding yeast PCH protein involved in cytokinesis.
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Affiliation(s)
- J Lippincott
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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48
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Vallen EA, Caviston J, Bi E. Roles of Hof1p, Bni1p, Bnr1p, and myo1p in cytokinesis in Saccharomyces cerevisiae. Mol Biol Cell 2000; 11:593-611. [PMID: 10679017 PMCID: PMC14796 DOI: 10.1091/mbc.11.2.593] [Citation(s) in RCA: 186] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cytokinesis in Saccharomyces cerevisiae occurs by the concerted action of the actomyosin system and septum formation. Here we report on the roles of HOF1, BNI1, and BNR1 in cytokinesis, focusing on Hof1p. Deletion of HOF1 causes a temperature-sensitive defect in septum formation. A Hof1p ring forms on the mother side of the bud neck in G2/M, followed by the formation of a daughter-side ring. Around telophase, Hof1p is phosphorylated and the double rings merge into a single ring that contracts slightly and may colocalize with the actomyosin structure. Upon septum formation, Hof1p splits into two rings, disappearing upon cell separation. Hof1p localization is dependent on septins but not Myo1p. Synthetic lethality suggests that Bni1p and Myo1p belong to one functional pathway, whereas Hof1p and Bnr1p belong to another. These results suggest that Hof1p may function as an adapter linking the primary septum synthesis machinery to the actomyosin system. The formation of the actomyosin ring is not affected by bni1Delta, hof1Delta, or bnr1Delta. However, Myo1p contraction is affected by bni1Delta but not by hof1Delta or bnr1Delta. In bni1Delta cells that lack the actomyosin contraction, septum formation is often slow and asymmetric, suggesting that actomyosin contraction may provide directionality for efficient septum formation.
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Affiliation(s)
- E A Vallen
- Department of Biology, Swarthmore College, Swarthmore, Pennsylvania 19081, USA
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49
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Hales KG, Bi E, Wu JQ, Adam JC, Yu IC, Pringle JR. Cytokinesis: an emerging unified theory for eukaryotes? Curr Opin Cell Biol 1999; 11:717-25. [PMID: 10600712 DOI: 10.1016/s0955-0674(99)00042-3] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In animal and fungal cells, cytokinesis involves an actomyosin ring that forms and contracts at the division plane. Important new details have emerged concerning the composition, assembly, and dynamics of these contractile rings. In addition, recent advances suggest that targeted membrane addition is a central feature of cytokinesis in animal cells - as it is in fungi and plants - and the coordination of actomyosin ring function with targeted exocytosis at the cleavage plane is being explored. Important new information has also emerged about the spatial and temporal regulation of cytokinesis, especially in relation to the function of the spindle midzone in animal cells and the control of cytokinesis by GTPase systems.
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Affiliation(s)
- K G Hales
- Department of Biology and Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599-3280, USA.
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50
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Liu J, Wang H, McCollum D, Balasubramanian MK. Drc1p/Cps1p, a 1,3-beta-glucan synthase subunit, is essential for division septum assembly in Schizosaccharomyces pombe. Genetics 1999; 153:1193-203. [PMID: 10545452 PMCID: PMC1460829 DOI: 10.1093/genetics/153.3.1193] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Schizosaccharomyces pombe divides by medial fission through the use of an actomyosin-based contractile ring. A division septum is formed centripetally, concomitant with ring constriction. Although several genes essential for cytokinesis have been described previously, enzymes that participate in the assembly of the division septum have not been identified. Here we describe a temperature-sensitive mutation, drc1-191, that prevents division septum assembly and causes mutant cells to arrest with a stable actomyosin ring. Unlike the previously characterized cytokinesis mutants, which undergo multiple mitotic cycles, drc1-191 is the first cytokinesis mutant that arrests with two interphase nuclei. Interestingly, unlike drc1-191, drc1-null mutants proceed through multiple mitotic cycles, leading to the formation of large cells with many nuclei. drc1 is allelic to cps1, which encodes a 1,3-beta-glucan synthase subunit. We conclude that Drc1p/Cps1p is not required for cell elongation and cell growth, but plays an essential role in assembly of the division septum. Furthermore, it appears that constriction of the actomyosin ring might depend on assembly of the division septum. We discuss possible mechanisms that account for the differences in the phenotypes of the drc1-191 and the drc1-null mutants and also reflect the potential links between Drc1p and other cytokinesis regulators.
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Affiliation(s)
- J Liu
- Cell Division Laboratory, Institute of Molecular Agrobiology, The National University of Singapore, Singapore 117604
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