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Sinha D, Ivan D, Gibbs E, Chetluru M, Goss J, Chen Q. Fission yeast polycystin Pkd2p promotes cell size expansion and antagonizes the Hippo-related SIN pathway. J Cell Sci 2022; 135:274457. [PMID: 35099006 PMCID: PMC8919332 DOI: 10.1242/jcs.259046] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 01/14/2022] [Indexed: 11/20/2022] Open
Abstract
Polycystins are conserved mechanosensitive channels whose mutations lead to the common human renal disorder autosomal dominant polycystic kidney disease (ADPKD). Previously, we discovered that the plasma membrane-localized fission yeast polycystin homolog Pkd2p is an essential protein required for cytokinesis; however, its role remains unclear. Here, we isolated a novel temperature-sensitive pkd2 mutant, pkd2-B42. Among the strong growth defects of this mutant, the most striking was that many mutant cells often lost a significant portion of their volume in just 5 min followed by a gradual recovery, a process that we termed 'deflation'. Unlike cell lysis, deflation did not result in plasma membrane rupture and occurred independently of cell cycle progression. The tip extension of pkd2-B42 cells was 80% slower than that of wild-type cells, and their turgor pressure was 50% lower. Both pkd2-B42 and the hypomorphic depletion mutant pkd2-81KD partially rescued mutants of the septation initiation network (SIN), a yeast Hippo-related signaling pathway, by preventing cell lysis, enhancing septum formation and doubling the number of Sid2p and Mob1p molecules at the spindle pole bodies. We conclude that Pkd2p promotes cell size expansion during interphase by regulating turgor pressure and antagonizes the SIN during cytokinesis. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Debatrayee Sinha
- Department of Biological Sciences, The University of Toledo, 2801 West Bancroft St, Toledo, OH 43606, USA
| | - Denisa Ivan
- Department of Biological Sciences, The University of Toledo, 2801 West Bancroft St, Toledo, OH 43606, USA
| | - Ellie Gibbs
- Department of Biological Sciences, Wellesley College, 106 Central Street, Wellesley, MA 02482, USA
| | - Madhurya Chetluru
- Department of Biological Sciences, The University of Toledo, 2801 West Bancroft St, Toledo, OH 43606, USA
| | - John Goss
- Department of Biological Sciences, Wellesley College, 106 Central Street, Wellesley, MA 02482, USA
| | - Qian Chen
- Department of Biological Sciences, The University of Toledo, 2801 West Bancroft St, Toledo, OH 43606, USA,Author for correspondence ()
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2
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Rich-Robinson J, Russell A, Mancini E, Das M. Cdc42 reactivation at growth sites is regulated by local cell-cycle-dependent loss of its GTPase-activating protein Rga4 in fission yeast. J Cell Sci 2021; 134:272049. [PMID: 34523683 DOI: 10.1242/jcs.259291] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 08/18/2021] [Indexed: 12/18/2022] Open
Abstract
In fission yeast, polarized cell growth stops during division and resumes after cytokinesis completes and cells separate. It is unclear how growth reactivation is timed to occur immediately after cell separation. We uncoupled these sequential events by delaying cytokinesis with a temporary Latrunculin A treatment. Mitotic cells recovering from treatment initiate end growth during septation, displaying a polar elongation simultaneous with septation (PrESS) phenotype. PrESS cell ends reactivate Cdc42, a major regulator of polarized growth, during septation, but at a fixed time after anaphase B. A candidate screen implicates Rga4, a negative regulator of Cdc42, in this process. We show that Rga4 appears punctate at the cell sides during G2, but is diffuse during mitosis, extending to the ends. Although the Morphogenesis Orb6 (MOR) pathway is known to promote cell separation and growth by activating protein synthesis, we find that, for polarized growth, removal of Rga4 from the ends is also necessary. Therefore, we propose that growth resumes after division once the MOR pathway is activated and the ends lose Rga4 in a cell-cycle-dependent manner.
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Affiliation(s)
- Julie Rich-Robinson
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Afton Russell
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Eleanor Mancini
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Maitreyi Das
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
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3
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Magliozzi JO, Moseley JB. Pak1 kinase controls cell shape through ribonucleoprotein granules. eLife 2021; 10:67648. [PMID: 34282727 PMCID: PMC8318594 DOI: 10.7554/elife.67648] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 07/19/2021] [Indexed: 11/29/2022] Open
Abstract
Fission yeast cells maintain a rod shape due to conserved signaling pathways that organize the cytoskeleton for polarized growth. We discovered a mechanism linking the conserved protein kinase Pak1 with cell shape through the RNA-binding protein Sts5. Pak1 (also called Shk1 and Orb2) prevents Sts5 association with P bodies by directly phosphorylating its intrinsically disordered region (IDR). Pak1 and the cell polarity kinase Orb6 both phosphorylate the Sts5 IDR but at distinct residues. Mutations preventing phosphorylation in the Sts5 IDR cause increased P body formation and defects in cell shape and polarity. Unexpectedly, when cells encounter glucose starvation, PKA signaling triggers Pak1 recruitment to stress granules with Sts5. Through retargeting experiments, we reveal that Pak1 localizes to stress granules to promote rapid dissolution of Sts5 upon glucose addition. Our work reveals a new role for Pak1 in regulating cell shape through ribonucleoprotein granules during normal and stressed growth conditions.
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Affiliation(s)
- Joseph O Magliozzi
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, United States
| | - James B Moseley
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, United States
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4
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Ohtsuka H, Shimasaki T, Aiba H. Genes affecting the extension of chronological lifespan in Schizosaccharomyces pombe (fission yeast). Mol Microbiol 2020; 115:623-642. [PMID: 33064911 PMCID: PMC8246873 DOI: 10.1111/mmi.14627] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 09/17/2020] [Accepted: 10/11/2020] [Indexed: 02/06/2023]
Abstract
So far, more than 70 genes involved in the chronological lifespan (CLS) of Schizosaccharomyces pombe (fission yeast) have been reported. In this mini‐review, we arrange and summarize these genes based on the reported genetic interactions between them and the physical interactions between their products. We describe the signal transduction pathways that affect CLS in S. pombe: target of rapamycin complex 1, cAMP‐dependent protein kinase, Sty1, and Pmk1 pathways have important functions in the regulation of CLS extension. Furthermore, the Php transcription complex, Ecl1 family proteins, cyclin Clg1, and the cyclin‐dependent kinase Pef1 are important for the regulation of CLS extension in S. pombe. Most of the known genes involved in CLS extension are related to these pathways and genes. In this review, we focus on the individual genes regulating CLS extension in S. pombe and discuss the interactions among them.
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Affiliation(s)
- Hokuto Ohtsuka
- Laboratory of Molecular Microbiology, Department of Basic Medicinal Sciences, Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Japan
| | - Takafumi Shimasaki
- Laboratory of Molecular Microbiology, Department of Basic Medicinal Sciences, Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Japan
| | - Hirofumi Aiba
- Laboratory of Molecular Microbiology, Department of Basic Medicinal Sciences, Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Japan
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5
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Chen C, Rodriguez Pino M, Haller PR, Verde F. Conserved NDR/LATS kinase controls RAS GTPase activity to regulate cell growth and chronological lifespan. Mol Biol Cell 2019; 30:2598-2616. [PMID: 31390298 PMCID: PMC6740195 DOI: 10.1091/mbc.e19-03-0172] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Adaptation to the nutritional environment is critical for all cells. RAS GTPase is a highly conserved GTP-binding protein with crucial functions for cell growth and differentiation in response to environmental conditions. Here, we describe a novel mechanism connecting RAS GTPase to nutrient availability in fission yeast. We report that the conserved NDR/LATS kinase Orb6 responds to nutritional cues and regulates Ras1 GTPase activity. Orb6 increases the protein levels of an Ras1 GTPase activator, the guanine nucleotide exchange factor Efc25, by phosphorylating Sts5, a protein bound to efc25 mRNA. By manipulating the extent of Orb6-mediated Sts5 assembly into RNP granules, we can modulate Efc25 protein levels, Ras1 GTPase activity, and, as a result, cell growth and cell survival. Thus, we conclude that the Orb6-Sts5-Ras1 regulatory axis plays a crucial role in promoting cell adaptation, balancing the opposing demands of promoting cell growth and extending chronological lifespan.
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Affiliation(s)
- Chuan Chen
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Marbelys Rodriguez Pino
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Patrick Roman Haller
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Fulvia Verde
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136
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6
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Nuñez I, Rodriguez Pino M, Wiley DJ, Das ME, Chen C, Goshima T, Kume K, Hirata D, Toda T, Verde F. Spatial control of translation repression and polarized growth by conserved NDR kinase Orb6 and RNA-binding protein Sts5. eLife 2016; 5. [PMID: 27474797 PMCID: PMC5011436 DOI: 10.7554/elife.14216] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 07/28/2016] [Indexed: 12/18/2022] Open
Abstract
RNA-binding proteins contribute to the formation of ribonucleoprotein (RNP) granules by phase transition, but regulatory mechanisms are not fully understood. Conserved fission yeast NDR (Nuclear Dbf2-Related) kinase Orb6 governs cell morphogenesis in part by spatially controlling Cdc42 GTPase. Here we describe a novel, independent function for Orb6 kinase in negatively regulating the recruitment of RNA-binding protein Sts5 into RNPs to promote polarized cell growth. We find that Orb6 kinase inhibits Sts5 recruitment into granules, its association with processing (P) bodies, and degradation of Sts5-bound mRNAs by promoting Sts5 interaction with 14-3-3 protein Rad24. Many Sts5-bound mRNAs encode essential factors for polarized cell growth, and Orb6 kinase spatially and temporally controls the extent of Sts5 granule formation. Disruption of this control system affects cell morphology and alters the pattern of polarized cell growth, revealing a role for Orb6 kinase in the spatial control of translational repression that enables normal cell morphogenesis.
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Affiliation(s)
- Illyce Nuñez
- Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, United States
| | - Marbelys Rodriguez Pino
- Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, United States
| | - David J Wiley
- Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, United States
| | - Maitreyi E Das
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, United States
| | - Chuan Chen
- Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, United States
| | - Tetsuya Goshima
- National Research Institute of Brewing, Higashi-Hiroshima, Japan
| | - Kazunori Kume
- Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Japan
| | - Dai Hirata
- Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Japan
| | - Takashi Toda
- Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Japan.,The Francis Crick Institute, Lincoln's Inn Fields Laboratory, London, United Kingdom
| | - Fulvia Verde
- Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, United States.,Marine Biological Laboratory, Woods Hole, United States
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7
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Saitoh S, Mori A, Uehara L, Masuda F, Soejima S, Yanagida M. Mechanisms of expression and translocation of major fission yeast glucose transporters regulated by CaMKK/phosphatases, nuclear shuttling, and TOR. Mol Biol Cell 2014; 26:373-86. [PMID: 25411338 PMCID: PMC4294683 DOI: 10.1091/mbc.e14-11-1503] [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: 02/07/2023] Open
Abstract
Glucose transporters play a pivotal role in glucose homeostasis. The fission yeast high-affinity glucose transporter Ght5 is regulated with regard to transcription and localization via CaMKK and TOR pathways. These results clarify the evolutionarily conserved mechanisms underlying glucose homeostasis that prevent hyperglycemia in humans. Hexose transporters are required for cellular glucose uptake; thus they play a pivotal role in glucose homeostasis in multicellular organisms. Using fission yeast, we explored hexose transporter regulation in response to extracellular glucose concentrations. The high-affinity transporter Ght5 is regulated with regard to transcription and localization, much like the human GLUT transporters, which are implicated in diabetes. When restricted to a glucose concentration equivalent to that of human blood, the fission yeast transcriptional regulator Scr1, which represses Ght5 transcription in the presence of high glucose, is displaced from the nucleus. Its displacement is dependent on Ca2+/calmodulin-dependent kinase kinase, Ssp1, and Sds23 inhibition of PP2A/PP6-like protein phosphatases. Newly synthesized Ght5 locates preferentially at the cell tips with the aid of the target of rapamycin (TOR) complex 2 signaling. These results clarify the evolutionarily conserved molecular mechanisms underlying glucose homeostasis, which are essential for preventing hyperglycemia in humans.
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Affiliation(s)
- Shigeaki Saitoh
- Institute of Life Science, Kurume University, Hyakunen-Kohen 1-1, Kurume, Fukuoka 839-0864, Japan
| | - Ayaka Mori
- Okinawa Institute Science and Technology Graduate University, Tancha 1919-1, Onna, Okinawa 904-0495, Japan
| | - Lisa Uehara
- Okinawa Institute Science and Technology Graduate University, Tancha 1919-1, Onna, Okinawa 904-0495, Japan
| | - Fumie Masuda
- Institute of Life Science, Kurume University, Hyakunen-Kohen 1-1, Kurume, Fukuoka 839-0864, Japan
| | - Saeko Soejima
- Institute of Life Science, Kurume University, Hyakunen-Kohen 1-1, Kurume, Fukuoka 839-0864, Japan
| | - Mitsuhiro Yanagida
- Okinawa Institute Science and Technology Graduate University, Tancha 1919-1, Onna, Okinawa 904-0495, Japan
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8
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Freitag SI, Wong J, Young PG. Genetic and physical interaction of Ssp1 CaMKK and Rad24 14-3-3 during low pH and osmotic stress in fission yeast. Open Biol 2014; 4:130127. [PMID: 24451546 PMCID: PMC3909272 DOI: 10.1098/rsob.130127] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The Ssp1 calmodulin kinase kinase (CaMKK) is necessary for stress-induced re-organization of the actin cytoskeleton and initiation of growth at the new cell end following division in Schizosaccharomyces pombe. In addition, it regulates AMP-activated kinase and functions in low glucose tolerance. ssp1− cells undergo mitotic delay at elevated temperatures and G2 arrest in the presence of additional stressors. Following hyperosmotic stress, Ssp1-GFP forms transient foci which accumulate at the cell membrane and form a band around the cell circumference, but not co-localizing with actin patches. Hyperosmolarity-induced localization to the cell membrane occurs concomitantly with a reduction of its interaction with the 14-3-3 protein Rad24, but not Rad25 which remains bound to Ssp1. The loss of rad24 in ssp1− cells reduces the severity of hyperosmotic stress response and relieves mitotic delay. Conversely, overexpression of rad24 exacerbates stress response and concomitant cell elongation. rad24− does not impair stress-induced localization of Ssp1 to the cell membrane, however this response is almost completely absent in cells overexpressing rad24.
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Affiliation(s)
- Silja I Freitag
- Department of Biology, Queen's University, 116 Barrie Street, Kingston, Ontario, Canada K7L 3N6
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9
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Malecki M, Viegas SC, Carneiro T, Golik P, Dressaire C, Ferreira MG, Arraiano CM. The exoribonuclease Dis3L2 defines a novel eukaryotic RNA degradation pathway. EMBO J 2013; 32:1842-54. [PMID: 23503588 PMCID: PMC3981172 DOI: 10.1038/emboj.2013.63] [Citation(s) in RCA: 150] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 02/26/2013] [Indexed: 12/26/2022] Open
Abstract
The final step of cytoplasmic mRNA degradation proceeds in either a 5'-3' direction catalysed by Xrn1 or in a 3'-5' direction catalysed by the exosome. Dis3/Rrp44, an RNase II family protein, is the catalytic subunit of the exosome. In humans, there are three paralogues of this enzyme: DIS3, DIS3L, and DIS3L2. In this work, we identified a novel Schizosaccharomyces pombe exonuclease belonging to the conserved family of human DIS3L2 and plant SOV. Dis3L2 does not interact with the exosome components and localizes in the cytoplasm and in cytoplasmic foci, which are docked to P-bodies. Deletion of dis3l2(+) is synthetically lethal with xrn1Δ, while deletion of dis3l2(+) in an lsm1Δ background results in the accumulation of transcripts and slower mRNA degradation rates. Accumulated transcripts show enhanced uridylation and in vitro Dis3L2 displays a preference for uridylated substrates. Altogether, our results suggest that in S. pombe, and possibly in most other eukaryotes, Dis3L2 is an important factor in mRNA degradation. Therefore, this novel 3'-5' RNA decay pathway represents an alternative to degradation by Xrn1 and the exosome.
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Affiliation(s)
- Michal Malecki
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
- Department of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Sandra C Viegas
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | | | - Pawel Golik
- Department of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Clémentine Dressaire
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | | | - Cecília M Arraiano
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
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10
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Chen Q, Pollard TD. Actin filament severing by cofilin is more important for assembly than constriction of the cytokinetic contractile ring. ACTA ACUST UNITED AC 2011; 195:485-98. [PMID: 22024167 PMCID: PMC3206353 DOI: 10.1083/jcb.201103067] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
When fission yeast express mutant cofilin that is inefficient at actin filament severing, cytokinetic contractile ring formation is severely impaired, but ring contraction proceeds efficiently. We created two new mutants of fission yeast cofilin to investigate why cytokinesis in many organisms depends on this small actin-binding protein. These mutant cofilins bound actin monomers normally, but bound and severed ADP-actin filaments much slower than wild-type cofilin. Cells depending on mutant cofilins condensed nodes, precursors of the contractile ring, into clumps rather than rings. Starting from clumped nodes, mutant cells slowly assembled rings from diverse intermediate structures including spiral strands containing actin filaments and other contractile ring proteins. This process in mutant cells depended on α-actinin. These slowly assembled contractile rings constricted at a normal rate but with more variability, indicating ring constriction is not very sensitive to defects in severing by cofilin. Computer simulations of the search-capture-pull and release model of contractile ring formation predicted that nodes clump when the release step is slow, so cofilin severing of actin filament connections between nodes likely contributes to the release step.
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Affiliation(s)
- Qian Chen
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA
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11
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Shiroiwa Y, Hayashi T, Fujita Y, Villar-Briones A, Ikai N, Takeda K, Ebe M, Yanagida M. Mis17 is a regulatory module of the Mis6-Mal2-Sim4 centromere complex that is required for the recruitment of CenH3/CENP-A in fission yeast. PLoS One 2011; 6:e17761. [PMID: 21445296 PMCID: PMC3061866 DOI: 10.1371/journal.pone.0017761] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 02/09/2011] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND The centromere is the chromosome domain on which the mitotic kinetochore forms for proper segregation. Deposition of the centromeric histone H3 (CenH3, CENP-A) is vital for the formation of centromere-specific chromatin. The Mis6-Mal2-Sim4 complex of the fission yeast S. pombe is required for the recruitment of CenH3 (Cnp1), but its function remains obscure. METHODOLOGY/PRINCIPAL FINDINGS Mass spectrometry was performed on the proteins precipitated with Mis6- and Mis17-FLAG. The results together with the previously identified Sim4- and Mal2-TAP precipitated proteins indicated that the complex contains 12 subunits, Mis6, Sim4, Mal2, Mis15, Mis17, Cnl2, Fta1-4, Fta6-7, nine of which have human centromeric protein (CENP) counterparts. Domain dissection indicated that the carboxy-half of Mis17 is functional, while its amino-half is regulatory. Overproduction of the amino-half caused strong negative dominance, which led to massive chromosome missegregation and hypersensitivity to the histone deacetylase inhibitor TSA. Mis17 was hyperphosphorylated and overproduction-induced negative dominance was abolished in six kinase-deletion mutants, ssp2 (AMPK), ppk9 (AMPK), ppk15 (Yak1), ppk30 (Ark1), wis4 (Ssk2), and lsk1 (P-TEFb). CONCLUSIONS Mis17 may be a regulatory module of the Mis6 complex. Negative dominance of the Mis17 fragment is exerted while the complex and CenH3 remain at the centromere, a result that differs from the mislocalization seen in the mis17-362 mutant. The known functions of the kinases suggest an unexpected link between Mis17 and control of the cortex actin, nutrition, and signal/transcription. Possible interpretations are discussed.
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Affiliation(s)
| | - Takeshi Hayashi
- Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, Japan
- Okinawa Institute of Science and Technology Promotion Corporation, Onna, Okinawa, Japan
| | - Yohta Fujita
- Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, Japan
| | | | - Nobuyasu Ikai
- Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Kojiro Takeda
- Okinawa Institute of Science and Technology Promotion Corporation, Onna, Okinawa, Japan
| | - Masahiro Ebe
- Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Mitsuhiro Yanagida
- Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, Japan
- Okinawa Institute of Science and Technology Promotion Corporation, Onna, Okinawa, Japan
- * E-mail:
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12
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Hanyu Y, Imai KK, Kawasaki Y, Nakamura T, Nakaseko Y, Nagao K, Kokubu A, Ebe M, Fujisawa A, Hayashi T, Obuse C, Yanagida M. Schizosaccharomyces pombe cell division cycle under limited glucose requires Ssp1 kinase, the putative CaMKK, and Sds23, a PP2A-related phosphatase inhibitor. Genes Cells 2009; 14:539-54. [PMID: 19371376 DOI: 10.1111/j.1365-2443.2009.01290.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Calcium/calmodulin-dependent protein kinase (CaMK) is required for diverse cellular functions, and similar kinases exist in fungi. Although mammalian CaMK kinase (CaMKK) activates CaMK and also evolutionarily-conserved AMP-activated protein kinase (AMPK), CaMKK is yet to be established in yeast. We here report that the fission yeast Schizosaccharomyces pombe Ssp1 kinase, which controls G2/M transition and response to stress, is the putative CaMKK. Ssp1 has a CaM binding domain (CBD) and associates with 14-3-3 proteins as mammalian CaMKK does. Temperature-sensitive ssp1 mutants isolated are defective in the tolerance to limited glucose, and this tolerance requires the conserved stretch present between the kinase domain and CBD. Sds23, multi-copy suppressor for mutants defective in type 1 phosphatase and APC/cyclosome, also suppresses the ssp1 phenotype, and is required for the tolerance to limited glucose. We demonstrate that Sds23 binds to type 2A protein phosphatases (PP2A) and PP2A-related phosphatase Ppe1, and that Sds23 inhibits Ppe1 phosphatase activity. Ssp1 and Ppe1 thus seem to antagonize in utilizing limited glucose. We also show that Ppk9 and Ssp2 are the catalytic subunits of AMPK and AMPK-related kinases, respectively, which bind to common beta-(Amk2) and gamma-(Cbs2) subunits.
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Affiliation(s)
- Yuichiro Hanyu
- CREST Research Project, Japan Science Technology Corporation, Kyoto, Japan
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13
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Seiler S, Vogt N, Ziv C, Gorovits R, Yarden O. The STE20/germinal center kinase POD6 interacts with the NDR kinase COT1 and is involved in polar tip extension in Neurospora crassa. Mol Biol Cell 2006; 17:4080-92. [PMID: 16822837 PMCID: PMC1593175 DOI: 10.1091/mbc.e06-01-0072] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Members of the Ste20 and NDR protein kinase families are important for normal cell differentiation and morphogenesis in various organisms. We characterized POD6 (NCU02537.2), a novel member of the GCK family of Ste20 kinases that is essential for hyphal tip extension and coordinated branch formation in the filamentous fungus Neurospora crassa. pod-6 and the NDR kinase mutant cot-1 exhibit indistinguishable growth defects, characterized by cessation of cell elongation, hyperbranching, and altered cell-wall composition. We suggest that POD6 and COT1 act in the same genetic pathway, based on the fact that both pod-6 and cot-1 can be suppressed by 1) environmental stresses, 2) altering protein kinase A activity, and 3) common extragenic suppressors (ropy, as well as gul-1, which is characterized here as the ortholog of the budding and fission yeasts SSD1 and Sts5, respectively). Unlinked noncomplementation of cot-1/pod-6 alleles indicates a potential physical interaction between the two kinases, which is further supported by coimmunoprecipitation analyses, partial colocalization of both proteins in wild-type cells, and their common mislocalization in dynein/kinesin mutants. We conclude that POD6 acts together with COT1 and is essential for polar cell extension in a kinesin/dynein-dependent manner in N. crassa.
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Affiliation(s)
- Stephan Seiler
- Deutsche Forschungsgemeinschaft Research Center of Molecular Physiology of the Brain (CMPB), Abteilung Molekulare Mikrobiologie, Universität Göttingen, D-37077 Göttingen, Germany.
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14
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Ogiso Y, Sugiura R, Kamo T, Yanagiya S, Lu Y, Okazaki K, Shuntoh H, Kuno T. Lub1 participates in ubiquitin homeostasis and stress response via maintenance of cellular ubiquitin contents in fission yeast. Mol Cell Biol 2004; 24:2324-31. [PMID: 14993272 PMCID: PMC355854 DOI: 10.1128/mcb.24.6.2324-2331.2004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ubiquitin-dependent proteolysis plays a pivotal role in stress responses. To investigate the mechanisms of these cellular processes, we have been studying Schizosaccharomyces pombe mutants that have altered sensitivities to various stress conditions. Here, we showed that Lub1, a homologue of Ufd3p/Zzz4p/Doa1p in budding yeast, is involved in the regulation of ubiquitin contents. Disruption of the lub1+ gene resulted in monoubiquitin as well as multiubiquitin depletion without change in mRNA level and in hypersensitivity to various stress conditions. Consistently, overexpression of genes encoding ubiquitin suppressed the defects associated with lub1 mutation, indicating that the phenotypes of the lub1 mutants under stress conditions were due to cellular ubiquitin shortage at the posttranscriptional level. In addition, the lub1-deleted cells showed aberrant functions in ubiquitin/proteasome-dependent proteolysis, with accelerated degradation of ubiquitin. Also Cdc48, a stress-induced chaperon-like essential ATPase, was found to interact with Lub1, and this association might contribute to the stabilization of Lub1. Our results indicated that Lub1 is responsible for ubiquitin homeostasis at the protein level through a negative regulation of ubiquitin degradation.
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Affiliation(s)
- Yasunari Ogiso
- Division of Molecular Pharmacology and Pharmacogenomics, Department of Genome Sciences, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
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15
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Sugiura R, Sio SO, Shuntoh H, Kuno T. Calcineurin phosphatase in signal transduction: lessons from fission yeast. Genes Cells 2002; 7:619-27. [PMID: 12081640 DOI: 10.1046/j.1365-2443.2002.00557.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Calcineurin (protein phosphatase 2B), the only serine/threonine phosphatase under the control of Ca2+/calmodulin, is an important mediator in signal transmission, connecting the Ca2+-dependent signalling to a wide variety of cellular responses. Furthermore, calcineurin is specifically inhibited by the immunosuppressant drugs cyclosporin A and tacrolimus (FK506), and these drugs have been a powerful tool for identifying many of the roles of calcineurin. Calcineurin is enriched in the neural tissues, and also distributes broadly in other tissues. The structure of the protein is highly conserved from yeast to man. The combined use of powerful genetics and of specific calcineurin inhibitors in fission yeast Schizosaccharomyces pombe (S. pombe) identified new components of the calcineurin pathway, and defined new roles of calcineurin in the regulation of the many cellular processes. Recent data has revealed functional interactions in which calcineurin phosphatase is involved, such as the cross-talk between the Pmk1 MAP kinase signalling, or the PI signalling. Calcineurin also participates in membrane traffic and cytokinesis of fission yeast through its functional connection with members of the small GTPase Rab/Ypt family, and Type II myosin, respectively. These findings highlight the potential of fission yeast genetic studies to elucidate conserved elements of signal transduction cascades.
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Affiliation(s)
- Reiko Sugiura
- Division of Molecular Pharmacology and Pharmacogenomics, Department of Genome Sciences, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
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16
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Won M, Park SK, Hoe KL, Jang YJ, Chung KS, Kim DU, Kim HB, Yoo HS. Rkp1/Cpc2, a fission yeast RACK1 homolog, is involved in actin cytoskeleton organization through protein kinase C, Pck2, signaling. Biochem Biophys Res Commun 2001; 282:10-5. [PMID: 11263963 DOI: 10.1006/bbrc.2001.4535] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Rkp1/Cpc2, a fission yeast RACK1 homolog, interacted with Pck2, one of the known PKC homologs, in vivo and in vitro. The rkp1-deletion mutants (Deltarkp1) are elongated and the pck2-deletion mutant (Deltapck2) showed abnormal morphology. The double-deletion mutant (Deltarkp1Deltapck2) showed more aberrant cell shapes and was sensitive to high salt concentration. Both Deltarkp1 and Deltapck2 cells were sensitive to latrunculin B (Lat B) which inhibits actin polymerization. The cells expressing the human RACK1 homolog complemented the latrunculin B sensitivity of Deltarkp1 indicating that human RACK1 is a functional homolog of Rkp1/Cpc2. We propose that Rkp1/Cpc2 may function as a receptor for Pck2 in the regulation of actin cytoskeleton organization during cell wall synthesis and morphogenesis of Schizosaccharomyces pombe.
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Affiliation(s)
- M Won
- Genome Research Center, Korea Research Institute of Bioscience and Biotechnology, Yusong, Taejon, 305-333, Korea
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17
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Ibeas JI, Yun DJ, Damsz B, Narasimhan ML, Uesono Y, Ribas JC, Lee H, Hasegawa PM, Bressan RA, Pardo JM. Resistance to the plant PR-5 protein osmotin in the model fungus Saccharomyces cerevisiae is mediated by the regulatory effects of SSD1 on cell wall composition. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2001; 25:271-80. [PMID: 11208019 DOI: 10.1046/j.1365-313x.2001.00967.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The capacity of plants to counter the challenge of pathogenic fungal attack depends in part on the ability of plant defense proteins to overcome fungal resistance by being able to recognize and eradicate the invading fungi. Fungal genes that control resistance to plant defense proteins are therefore important determinants that define the range of fungi from which an induced defense protein can protect the plant. Resistance of the model fungus Saccharomyces cerevisiae to osmotin, a plant defense PR-5 protein, is strongly dependent on the natural polymorphism of the SSD1 gene. Expression of the SSD1-v allele afforded resistance to the antifungal protein. Conversely, yeast strains carrying the SSD1-d allele or a null ssd1Delta mutation displayed high sensitivity to osmotin. The SSD1-v protein mediates osmotin resistance in a cell wall-dependent manner. Deletion of SSD1-v or SSD1-d impeded sorting of the PIR proteins (osmotin-resistance factors) to the cell wall without affecting mRNA levels, indicating that SSD1 functions in post-transcriptional regulation of gene expression. The sensitivity of ssd1Delta cells to osmotin was only partially suppressed by over-accumulation of PIR proteins in the cell wall, suggesting an additional function for SSD1 in cell wall-mediated resistance. Accordingly, cells carrying a null ssd1 mutation also displayed aberrant cell-wall morphology and lower levels of alkali-insoluble cell-wall glucans. Therefore SSD1 is an important regulator of fungal cell-wall biogenesis and composition, including the deposition of PIR proteins which block the action of plant antifungal PR-5 proteins.
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Affiliation(s)
- J I Ibeas
- Departamento de Ciencias Ambientales, Universidad Pablo Olavide, Sevilla, E-41013, Spain
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18
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Murray JM, Johnson DI. Isolation and characterization of Nrf1p, a novel negative regulator of the Cdc42p GTPase in Schizosaccharomyces pombe. Genetics 2000; 154:155-65. [PMID: 10628977 PMCID: PMC1460887 DOI: 10.1093/genetics/154.1.155] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Cdc42p GTPase and its regulators, such as the Saccharomyces cerevisiae Cdc24p guanine-nucleotide exchange factor, control signal-transduction pathways in eukaryotic cells leading to actin rearrangements. A cross-species genetic screen was initiated based on the ability of negative regulators of Cdc42p to reverse the Schizosaccharomyces pombe Cdc42p suppression of a S. cerevisiae cdc24(ts) mutant. A total of 32 S. pombe nrf (negative regulator of Cdc forty two) cDNAs were isolated that reversed the suppression. One cDNA, nrf1(+), encoded an approximately 15 kD protein with three potential transmembrane domains and 78% amino-acid identity to a S. cerevisiae gene, designated NRF1. A S. pombe Deltanrf1 mutant was viable but overexpression of nrf1(+) in S. pombe resulted in dose-dependent lethality, with cells exhibiting an ellipsoidal morphology indicative of loss of polarized cell growth along with partially delocalized cortical actin and large vacuoles. nrf1(+) also displayed synthetic overdose phenotypes with cdc42 and pak1 alleles. Green fluorescent protein (GFP)-Cdc42p and GFP-Nrf1p colocalized to intracellular membranes, including vacuolar membranes, and to sites of septum formation during cytokinesis. GFP-Nrf1p vacuolar localization depended on the S. pombe Cdc24p homolog Scd1p. Taken together, these data are consistent with Nrf1p functioning as a negative regulator of Cdc42p within the cell polarity pathway.
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Affiliation(s)
- J M Murray
- Department of Microbiology and Molecular Genetics and the Markey Center for Molecular Genetics, University of Vermont, Burlington, Vermont 05405, USA
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19
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Arellano M, Valdivieso MH, Calonge TM, Coll PM, Duran A, Perez P. Schizosaccharomyces pombe protein kinase C homologues, pck1p and pck2p, are targets of rho1p and rho2p and differentially regulate cell integrity. J Cell Sci 1999; 112 ( Pt 20):3569-78. [PMID: 10504305 DOI: 10.1242/jcs.112.20.3569] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Schizosaccharomyces pombe rho1(+) is required for maintenance of cell integrity and polarization of the actin cytoskeleton. However, no other effector besides the (1,3)beta-D-glucan synthase enzyme has been identified in S. pombe. We have further investigated if rho1(+)signalling could be also mediated by the two protein kinase C homologues, pck1p and pck2p. We show in this study that both kinases interact with rho1p and rho2p only when bound to GTP, as most GTPase effectors do. Interestingly, the interaction was mapped in a different part of the proteins than in Saccharomyces cerevisiae Pkc1p. Thus, active rho1p binds to the amino-terminal region of the pcks where two HR1 motifs are located, and binding to the GTPase dramatically stabilizes the kinases. Detailed biochemical analysis suggests that pck2p is more important in the regulation of the enzyme (1–3)beta-D-glucan synthase. Thus, overexpression of pck2(+), but not pck1(+), caused a general increase in cell wall biosynthesis, mainly in beta-glucan, and (1–3)beta-D-glucan synthase activity was considerably augmented. When this activity was separated into soluble and membrane fractions and reconstituted, the increase caused by pck2(+) overexpression was exclusively detected in the membrane component. We also show that both protein kinase C homologues are required for the maintenance of cell integrity. pck1delta and pck2delta strains present a number of defects related to the cell wall, indicating that this structure might be co-ordinately regulated by both kinases. In addition, pck2p, but not pck1p, seems to be involved in keeping cell polarity. Genetic evidence indicates that both pck1(+) and pck2(+) interact with cps1(+) and gls2(+), two genes similar to S. cerevisiae FKS1 and FKS2 that encode membrane subunits of the (1–3)beta-D-glucan synthase. pck1(+)also showed a genetic interaction with ras1(+) and ral1(+) suggesting the existence of a functional link between both signalling pathways.
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Affiliation(s)
- M Arellano
- Instituto de Microbiología Bioquímica, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca, Edificio Departamental, Spain.
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20
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Rupes I, Jia Z, Young PG. Ssp1 promotes actin depolymerization and is involved in stress response and new end take-off control in fission yeast. Mol Biol Cell 1999; 10:1495-510. [PMID: 10233158 PMCID: PMC25317 DOI: 10.1091/mbc.10.5.1495] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The ssp1 gene encodes a protein kinase involved in alteration of cell polarity in Schizosaccharomyces pombe. ssp1 deletion causes stress sensitivity, reminiscent of defects in the stress-activated MAP kinase, Spc1; however, the two protein kinases do not act through the same pathway. Ssp1 is localized mainly in the cytoplasm, but after a rise in external osmolarity it is rapidly recruited to the plasma membrane, preferentially to active growth zones and septa. Loss of Ssp1 function inhibits actin relocalization during osmotic stress, in cdc3 and cdc8 mutant backgrounds, and in the presence of latrunculin A, implicating Ssp1 in promotion of actin depolymerization. We propose a model in which Ssp1 can be activated independently of Spc1 and can partially compensate for its loss. The ssp1 deletion mutant exhibited monopolar actin distribution, but new end take-off (NETO) could be induced in these cells by exposure to KCl or to latrunculin A pulse treatment. This treatment induced NETO in cdc10 cells arrested in G1 but not in tea1 cells. This suggests that cells that contain intact cell end markers are competent to undergo NETO throughout interphase, and Ssp1 is involved in generating the NETO stimulus by enlarging the actin monomer pool.
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Affiliation(s)
- I Rupes
- Department of Biology, Queen's University, Kingston, Ontario K7L 3N6, Canada
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21
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Katayama S, Hirata D, Arellano M, Pérez P, Toda T. Fission yeast alpha-glucan synthase Mok1 requires the actin cytoskeleton to localize the sites of growth and plays an essential role in cell morphogenesis downstream of protein kinase C function. J Cell Biol 1999; 144:1173-86. [PMID: 10087262 PMCID: PMC2150588 DOI: 10.1083/jcb.144.6.1173] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/1998] [Revised: 02/04/1999] [Indexed: 11/22/2022] Open
Abstract
In fission yeast protein kinase C homologues (Pck1 and Pck2) are essential for cell morphogenesis. We have isolated mok1(+) in a genetic screen to identify downstream effectors for Pck1/2. mok1(+) is essential for viability and encodes a protein that has several membrane-spanning domains and regions homologous to glucan metabolic enzymes. mok1 mutant shows abnormal cell shape, randomization of F-actin and weak cell wall. Biochemical analysis shows that Mok1 appears to have alpha-glucan synthase activity. Mok1 localization undergoes dramatic alteration during the cell cycle. It localizes to the growing tips in interphase, the medial ring upon mitosis, a double ring before and dense dot during cytokinesis. Double immunofluorescence staining shows that Mok1 exists in close proximity to actin. The subcellular localization of Mok1 is dependent upon the integrity of the F-actin cytoskeleton. Conversely, overexpression of mok1(+) blocks the translocation of cortical actin from one end of the cell to the other. pck2 mutant is synthetically lethal with mok1 mutant, delocalizes Mok1 and shows a lower level of alpha-glucan. These results indicate that Mok1 plays a crucial role in cell morphogenesis interdependently of the actin cytoskeleton and works as one of downstream effectors for Pck1/2.
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Affiliation(s)
- S Katayama
- Laboratory of Cell Regulation, Imperial Cancer Research Fund, London WC2A 3PX, United Kingdom
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22
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Affiliation(s)
- K E Sawin
- Imperial Cancer Research Fund, London, United Kingdom
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23
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Ishiguro J. Genetic control of fission yeast cell wall synthesis: the genes involved in wall biogenesis and their interactions in Schizosaccharomyces pombe. Genes Genet Syst 1998; 73:181-91. [PMID: 9880916 DOI: 10.1266/ggs.73.181] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The fungal cell wall is an essential structure which protects cells from various environmental stresses such as hyper- or hypo-osmosis, and endows them with specific morphology in response to their life or cell division cycle. In addition, the cell wall has a variety of enzymatic activities per se, which are required for nutritional uptake, secretion, and cell adhesion including mating processes. In addition to these cytological interests, clinical demands to clarify the regulatory mechanisms of cell wall synthesis have been increasing, since the cell wall is a unique and effective target of antifungal agents. However, the molecular mechanisms are poorly understood at present, although the role of several signal transduction pathways have recently been implicated in regulation. In this review, the author focuses on genes and their interactions which are involved in fission yeast cell wall biogenesis.
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Affiliation(s)
- J Ishiguro
- Department of Biology, Faculty of Science, Konan University, Kobe, Japan
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24
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May KM, Hyams JS. The yeast cytoskeleton: the closer We look, the more We See. Fungal Genet Biol 1998; 24:110-22. [PMID: 9742197 DOI: 10.1006/fgbi.1998.1073] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
May, K. M., and Hyams, J. S. 1998. The yeast cytoskeleton: The closer we look, the more we see. Copyright 1998 Academic Press.
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Affiliation(s)
- KM May
- Department of Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom
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25
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Rupes I, Jochová J, Young PG. Markers of cell polarity during and after nitrogen starvation in Schizosaccharomyces pombe. Biochem Cell Biol 1998; 75:697-708. [PMID: 9599658 DOI: 10.1139/o97-084] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In Schizosaccharomyces pombe, nitrogen starvation induces transient acceleration of cell division and reduction in cell size with a final arrest in G1. The division size control appears to be impaired by mutations in cdr1/nim1 and cdr2, genes that encode protein kinases mediating nutritional control over the mitotic cycle. cdr- cells arrest after fewer rounds of division and are larger than the wild type. Recent work suggests that long-term nitrogen starvation causes S. pombe wild-type cells to become spherical, which suggests loss of cell polarity. cdr mutants retain the elongated shape, indicating a potential difference in cell polarity control relative to the wild type. We examined several markers related to maintenance of cell polarity in S. pombe following nitrogen starvation including cell division scar pattern and actin and microtubule cytoskeleton. Wild-type cells as well as cdr mutants maintained a normal cell division scar pattern throughout nitrogen starvation but cells dividing under these conditions developed a wall malformation in the center of the septum. In cells arrested by nitrogen starvation, actin patches, normally associated with sites of cell wall deposition, were larger and distributed randomly along the cell surface. Cytoplasmic arrays of microtubules, which are thought to be involved in control of the polarity signal, were not visibly affected. The effects were similar in wild-type cells and in cdr- mutants. Upon refeeding, the new growth always reoccurred at the tip zones and there were only small deviations of its direction from the original axis. The results indicate that cell polarity is preserved both in wild-type cells, which arrest in G1 and appear spherical, and in cdr1/nim1 and cdr2 mutants, which arrest in G2 and appear polarized throughout the starvation period.
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Affiliation(s)
- I Rupes
- Department of Biology, Queen's University, Kingston, ON, Canada
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26
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Hirata D, Nakano K, Fukui M, Takenaka H, Miyakawa T, Mabuchi I. Genes that cause aberrant cell morphology by overexpression in fission yeast: a role of a small GTP-binding protein Rho2 in cell morphogenesis. J Cell Sci 1998; 111 ( Pt 2):149-59. [PMID: 9405296 DOI: 10.1242/jcs.111.2.149] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To identify the genes involved in cell morphogenesis in Schizosaccharomyces pombe, we screened for the genes that cause aberrant cell morphology by overexpression. The isolated genes were classified on the basis of morphology conferred. One of the genes causing a rounded morphology was identified as the rho2+ gene encoding a small GTP-binding protein. The overexpression of rho2+ resulted in a randomized distribution of cortical F-actin and formation of a thick cell wall. Analyses using cdc mutants suggested that the overexpression of rho2+ prevents the establishment of growth polarity in G1. The rho2+ gene was not essential, but among cells deleted for rho2+, those with an irregular shape were observed. The disruptant also showed a defect in cell wall integrity. An HA-Rho2 expressed in the cell was suggested to be present as a membrane-bound form by a cell fractionation experiment. A GFP-Rho2 was localized at the growing end(s) of the cell and the septation site. The localization of GFP-Rho2 during interphase was partially dependent on sts5+. These results indicate that Rho2 is involved in cell morphogenesis, control of cell wall integrity, control of growth polarity, and maintenance of growth direction. Analysis of functional overlapping between Rho2 and Rho1 revealed that their functions are distinct from each other, with partial overlapping.
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Affiliation(s)
- D Hirata
- Department of Molecular Biotechnology, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739, Japan.
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