1
|
Khalife J, Fréville A, Gnangnon B, Pierrot C. The Multifaceted Role of Protein Phosphatase 1 in Plasmodium. Trends Parasitol 2020; 37:154-164. [PMID: 33036936 DOI: 10.1016/j.pt.2020.09.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 09/07/2020] [Accepted: 09/08/2020] [Indexed: 11/29/2022]
Abstract
Protein phosphatase type 1 (PP1) forms a wide range of Ser/Thr-specific phosphatase holoenzymes which contain one catalytic subunit (PP1c), present in all eukaryotic cells, associated with variable subunits known as regulatory proteins. It has recently been shown that regulators take a leading role in the organization and the control of PP1 functions. Many studies have addressed the role of these regulators in diverse organisms, including humans, and investigated their link to diseases. In this review we summarize recent advances on the role of PP1c in Plasmodium, its interactome and regulators. As a proof of concept, peptides interfering with the regulator binding capacity of PP1c were shown to inhibit the growth of P. falciparum, suggesting their potential as drug precursors.
Collapse
Affiliation(s)
- Jamal Khalife
- Center for Infection and Immunity of Lille, Biology of Apicomplexan Parasites, UMR 9017 CNRS, U1019 INSERM, Université de Lille, Institut Pasteur de Lille, Lille, France.
| | - Aline Fréville
- Center for Infection and Immunity of Lille, Biology of Apicomplexan Parasites, UMR 9017 CNRS, U1019 INSERM, Université de Lille, Institut Pasteur de Lille, Lille, France
| | - Bénédicte Gnangnon
- Center for Infection and Immunity of Lille, Biology of Apicomplexan Parasites, UMR 9017 CNRS, U1019 INSERM, Université de Lille, Institut Pasteur de Lille, Lille, France
| | - Christine Pierrot
- Center for Infection and Immunity of Lille, Biology of Apicomplexan Parasites, UMR 9017 CNRS, U1019 INSERM, Université de Lille, Institut Pasteur de Lille, Lille, France
| |
Collapse
|
2
|
Chemudupati M, Osmani AH, Osmani SA. A mitotic nuclear envelope tether for Gle1 also impacts nuclear and nucleolar architecture. Mol Biol Cell 2016; 27:mbc.E16-07-0544. [PMID: 27630260 PMCID: PMC5170558 DOI: 10.1091/mbc.e16-07-0544] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 09/06/2016] [Accepted: 09/08/2016] [Indexed: 01/16/2023] Open
Abstract
During Aspergillus nidulans mitosis peripheral nuclear pore complex (NPC) proteins (Nups) disperse from the core NPC structure. Unexpectedly, one predicted peripheral Nup, Gle1, remains at the mitotic NE via an unknown mechanism. Gle1 affinity purification identified MtgA ( M: itotic T: ether for G: le1), which tethers Gle1 to the NE during mitosis, but not during interphase when Gle1 is at NPCs. MtgA is the ortholog of the Schizosaccharomyces pombe telomere-anchoring inner nuclear membrane protein Bqt4. Like Bqt4, MtgA has meiotic roles but is functionally distinct from Bqt4 as MtgA is not required for tethering telomeres to the NE. Domain analyses revealed MtgA targeting to the NE requires its C-terminal transmembrane domain and a nuclear localization signal. Importantly, MtgA functions beyond Gle1 mitotic targeting and meiosis and impacts nuclear and nucleolar architecture when deleted or overexpressed. Deletion of MtgA generates small, round nuclei whereas overexpressing MtgA generates larger nuclei with altered nuclear compartmentalization resulting from NE expansion around the nucleolus. The accumulation of MtgA around the nucleolus promotes a similar accumulation of the endoplasmic reticulum (ER) protein Erg24 lowering its levels in the ER. This study extends the functions of Bqt4-like proteins to include mitotic Gle1 targeting and modulation of nuclear and nucleolar architecture.
Collapse
Affiliation(s)
- Mahesh Chemudupati
- Ohio State Biochemistry Program, Ohio State University, Columbus, Ohio 43210 Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210
| | - Aysha H Osmani
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210
| | - Stephen A Osmani
- Ohio State Biochemistry Program, Ohio State University, Columbus, Ohio 43210 Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210
| |
Collapse
|
3
|
Abstract
This review traces the historical origins and conceptual developments leading to the current state of knowledge of the three superfamilies of protein Ser/Thr phosphatases. 'PR enzyme' was identified as an enzyme that inactivates glycogen phosphorylase, although it took 10 years before this ugly duckling was recognized for its true identity as a protein Ser/Thr phosphatase. Ethanol denaturation for purification in the 1970s yielded a phosphatase that exhibited broad specificity, which was resolved into type-1 and type-2 phosphatases in the 1980s. More recent developments show that regulation and specificity are achieved through assembly of multisubunit holoenzymes, transient phosphorylation and the action of inhibitor proteins. Still not widely appreciated, there are hundreds of discrete protein Ser/Thr phosphatases available to counteract protein kinases, offering potential therapeutic targets. Signalling networks and modelling schemes need to incorporate the full gamut of protein Ser/Thr phosphatases and their interconnections.
Collapse
Affiliation(s)
- David L Brautigan
- Department of Microbiology, Immunology and Cancer Biology, Center for Cell Signaling, University of Virginia, School of Medicine, Charlottesville, VA 22908, USA.
| |
Collapse
|
4
|
Wang W, Stukenberg PT, Brautigan DL. Phosphatase inhibitor-2 balances protein phosphatase 1 and aurora B kinase for chromosome segregation and cytokinesis in human retinal epithelial cells. Mol Biol Cell 2008; 19:4852-62. [PMID: 18716057 DOI: 10.1091/mbc.e08-05-0460] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Mitosis in Saccharomyces cerevisiae depends on IPL1 kinase, which genetically interacts with GLC8. The metazoan homologue of GLC8 is inhibitor-2 (I-2), but its function is not understood. We found endogenous and ectopic I-2 localized to the spindle, midzone, and midbody of mitotic human epithelial ARPE-19 cells. Knockdown of I-2 by RNA interference produced multinucleated cells, with supernumerary centrosomes, multipolar spindles and lagging chromosomes during anaphase. These defects did not involve changes in levels of protein phosphatase-1 (PP1), and the multinuclear phenotype was rescued by overexpression of I-2. Appearance of multiple nuclei and supernumerary centrosomes required progression through the cell cycle and I-2 knockdown cells failed cytokinesis, as observed by time-lapse microscopy. Inhibition of Aurora B by hesperadin produced multinucleated cells and reduced H3S10 phosphorylation. I-2 knockdown enhanced this latter effect. Partial knockdown of PP1Calpha prevented multiple nuclei caused by either knockdown of I-2 or treatment with hesperadin. Expression of enhanced green fluorescent protein-I-2 or hemagglutinin-I-2 made cells resistant to hesperadin. We propose that I-2 acts to enhance Aurora B by inhibiting specific PP1 holoenzymes that dephosphorylate Aurora B substrates necessary for chromosome segregation and cytokinesis. Conserved together throughout eukaryotic evolution, I-2, PP1 and Aurora B function interdependently during mitosis.
Collapse
Affiliation(s)
- Weiping Wang
- Center for Cell Signaling, Departments of Microbiology and Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | | | | |
Collapse
|
5
|
Yanagida M, Kinoshita N, Stone EM, Yamano H. Protein phosphatases and cell division cycle control. CIBA FOUNDATION SYMPOSIUM 2007; 170:130-40; discussion 140-6. [PMID: 1336448 DOI: 10.1002/9780470514320.ch9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Fission yeast has at least ten protein phosphatase genes that appear to play distinct roles in cell cycle control. Because of functional overlap, a clear lethal phenotype can be obtained only after multiple genetic alterations. Cells that have lost the protein phosphatase 1 (PP1)-like dis2/sds21 phosphatase activities prematurely enter mitosis and remain in a defective mitotic state with high H1 kinase activity and without sister chromatid disjunction. The same phenotype can be obtained in the presence of hydroxyurea. Overexpression of PP1-like phosphatase, on the other hand, delays the entry into mitosis. Cells that have lost PP2A-like ppa2 phosphatase activity also prematurely enter mitosis with a reduction in cell size. This semi-wee phenotype is enhanced in delta ppa2 mutants treated with the phosphatase inhibitor, okadaic acid. Genetic interactions between ppa2 and mitotic regulators suggest that ppa1/ppa2 phosphatase may directly or indirectly inhibit p34cdc2/cyclin kinase. Thus both PP1- and PP2A-like phosphatases in fission yeast may negatively regulate entry into mitosis. The major property of the dis2/sds21 mutant which is distinct from those of the ppa2/ppa1 mutant is its failure to inactivate the p34cdc2/cyclin complex after entry into mitosis. A novel phosphatase regulator encoded by sds22+ binds to dis2 phosphatase and controls the substrate specificity which appears to become essential in the progression from metaphase to anaphase.
Collapse
Affiliation(s)
- M Yanagida
- Department of Biophysics, Faculty of Science, Kyoto University, Japan
| | | | | | | |
Collapse
|
6
|
Luo W, Peterson A, Garcia BA, Coombs G, Kofahl B, Heinrich R, Shabanowitz J, Hunt DF, Yost HJ, Virshup DM. Protein phosphatase 1 regulates assembly and function of the beta-catenin degradation complex. EMBO J 2007; 26:1511-21. [PMID: 17318175 PMCID: PMC1829374 DOI: 10.1038/sj.emboj.7601607] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2006] [Accepted: 01/23/2007] [Indexed: 01/03/2023] Open
Abstract
The Wnt/beta-catenin signaling pathway is critical in both cellular proliferation and organismal development. However, how the beta-catenin degradation complex is inhibited upon Wnt activation remains unclear. Using a directed RNAi screen we find that protein phosphatase 1 (PP1), a ubiquitous serine/threonine phosphatase, is a novel potent positive physiologic regulator of the Wnt/beta-catenin signaling pathway. PP1 expression synergistically activates, and inhibition of PP1 inhibits, Wnt/beta-catenin signaling in Drosophila and mammalian cells as well as in Xenopus embryos. The data suggest that PP1 controls Wnt signaling through interaction with, and regulated dephosphorylation of, axin. Inhibition of PP1 leads to enhanced phosphorylation of specific sites on axin by casein kinase I. Axin phosphorylation markedly enhances the binding of glycogen synthase kinase 3, leading to a more active beta-catenin destruction complex. Wnt-regulated changes in axin phosphorylation, mediated by PP1, may therefore determine beta-catenin transcriptional activity. Specific inhibition of PP1 in this pathway may offer therapeutic approaches to disorders with increased beta-catenin signaling.
Collapse
Affiliation(s)
- Wen Luo
- Department of Oncological Sciences, University of Utah, Salt Lake City, UT, USA
| | - Annita Peterson
- Department of Oncological Sciences, University of Utah, Salt Lake City, UT, USA
| | - Benjamin A Garcia
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA
| | - Gary Coombs
- Department of Oncological Sciences, University of Utah, Salt Lake City, UT, USA
| | - Bente Kofahl
- Department of Theoretical Biophysics, Institute of Biology, Humboldt University Berlin, Berlin, Germany
| | - Reinhart Heinrich
- Department of Theoretical Biophysics, Institute of Biology, Humboldt University Berlin, Berlin, Germany
| | | | - Donald F Hunt
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA
- Department of Pathology, University of Virginia, Charlottesville, VA, USA
| | - H Joseph Yost
- Department of Oncological Sciences, University of Utah, Salt Lake City, UT, USA
- Department of Pediatrics, University of Utah, Salt Lake City, UT, USA
- Center for Children at the Huntsman Cancer Institute, University of Utah, Salt Lake City, UT, USA
| | - David M Virshup
- Department of Oncological Sciences, University of Utah, Salt Lake City, UT, USA
- Department of Pediatrics, University of Utah, Salt Lake City, UT, USA
- Center for Children at the Huntsman Cancer Institute, University of Utah, Salt Lake City, UT, USA
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112-5550, USA. Tel.: +1 801 585 3408; Fax: +1 801 587 9415; E-mail:
| |
Collapse
|
7
|
Davies JR, Osmani AH, De Souza CPC, Bachewich C, Osmani SA. Potential link between the NIMA mitotic kinase and nuclear membrane fission during mitotic exit in Aspergillus nidulans. EUKARYOTIC CELL 2005; 3:1433-44. [PMID: 15590818 PMCID: PMC539031 DOI: 10.1128/ec.3.6.1433-1444.2004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have isolated TINC as a NIMA-interacting protein by using the yeast two-hybrid system and have confirmed that TINC interacts with NIMA in Aspergillus nidulans. The TINC-NIMA interaction is stabilized in the absence of phosphatase inhibitors and in the presence of kinase-inactive NIMA, suggesting that the interaction is enhanced when NIMA is not fully activated. TINC is a cytoplasmic protein. TINC homologues and a TINC-like protein (A. nidulans HETC) are conserved in other filamentous fungi. Neither deletion of tinC nor deletion of both tinC and A. nidulans hetC is lethal, but deletion of tinC does produce cold sensitivity as well as osmotic sensitivity. Expression of an amino-terminal-truncated form of TINC (DeltaN-TINC) inhibits colony growth in Aspergillus and localizes to membrane-like structures within the cell. Examination of cell cycle progression in these cells reveals that they progress through multiple defective mitoses. Many cells contain large polyploid single nuclei, while some appear to have separated masses of DNA. Examination of the nuclear envelopes of cells containing more than one DNA mass reveals that both DNA masses are contained within a single nuclear envelope, indicating that nuclear membrane fission is defective. The ability of these cells to separate DNA segregation from nuclear membrane fission suggests that this coordination is normally a regulated process in A. nidulans. Additional experiments demonstrate that expression of DeltaN-TINC results in premature NIMA disappearance in mitotic samples. We propose that TINC's interaction with NIMA and the cell cycle defects produced by DeltaN-TINC expression suggest possible roles for TINC and NIMA during nuclear membrane fission.
Collapse
Affiliation(s)
- Jonathan R Davies
- Department of Molecular Genetics, The Ohio State University, 804 Riffe Building, 496 W. 12th Ave., Columbus, OH 43210, USA
| | | | | | | | | |
Collapse
|
8
|
Osmani SA, Mirabito PM. The early impact of genetics on our understanding of cell cycle regulation in Aspergillus nidulans. Fungal Genet Biol 2004; 41:401-10. [PMID: 14998523 DOI: 10.1016/j.fgb.2003.11.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2003] [Accepted: 11/11/2003] [Indexed: 11/27/2022]
Abstract
The application of genetic analysis was crucial to the rapid progress that has been made in cell cycle research. Ron Morris, one of the first to apply genetics to cell cycle research, developed Aspergillus nidulans into an important model system for the analysis of many aspects of cell biology. Within the area of cell cycle research, Ron's laboratory is noted for development of novel cell biological and molecular genetic approaches as well as seminal insights regarding the regulation of mitosis, checkpoint regulation of the cell cycle, and the role of microtubule-based motors in chromosome segregation. In this special edition of FGB dedicated to Ron Morris, and in light of the recent progress in fungal genomics, we review the outstanding contributions his work made to our understanding of mitotic regulation. Indeed, his efforts have provided many mutants and experimental tools along with the conceptual framework for current and future studies of mitosis in A. nidulans.
Collapse
Affiliation(s)
- Stephen A Osmani
- Department of Molecular Genetics, Ohio State University, Columbus, OH 43210, USA.
| | | |
Collapse
|
9
|
Ceulemans H, Bollen M. Functional diversity of protein phosphatase-1, a cellular economizer and reset button. Physiol Rev 2004; 84:1-39. [PMID: 14715909 DOI: 10.1152/physrev.00013.2003] [Citation(s) in RCA: 488] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The protein serine/threonine phosphatase protein phosphatase-1 (PP1) is a ubiquitous eukaryotic enzyme that regulates a variety of cellular processes through the dephosphorylation of dozens of substrates. This multifunctionality of PP1 relies on its association with a host of function-specific targetting and substrate-specifying proteins. In this review we discuss how PP1 affects the biochemistry and physiology of eukaryotic cells. The picture of PP1 that emerges from this analysis is that of a "green" enzyme that promotes the rational use of energy, the recycling of protein factors, and a reversal of the cell to a basal and/or energy-conserving state. Thus PP1 promotes a shift to the more energy-efficient fuels when nutrients are abundant and stimulates the storage of energy in the form of glycogen. PP1 also enables the relaxation of actomyosin fibers, the return to basal patterns of protein synthesis, and the recycling of transcription and splicing factors. In addition, PP1 plays a key role in the recovery from stress but promotes apoptosis when cells are damaged beyond repair. Furthermore, PP1 downregulates ion pumps and transporters in various tissues and ion channels that are involved in the excitation of neurons. Finally, PP1 promotes the exit from mitosis and maintains cells in the G1 or G2 phases of the cell cycle.
Collapse
Affiliation(s)
- Hugo Ceulemans
- Afdeling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit Leuven, Leuven, Belgium
| | | |
Collapse
|
10
|
De Souza CPC, Horn KP, Masker K, Osmani SA. The SONBNUP98 Nucleoporin Interacts With the NIMA Kinase in Aspergillus nidulans. Genetics 2003; 165:1071-81. [PMID: 14668365 PMCID: PMC1462862 DOI: 10.1093/genetics/165.3.1071] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
The Aspergillus nidulans NIMA kinase is essential for mitotic entry. At restrictive temperature, temperature-sensitive nimA alleles arrest in G2, before accumulation of NIMA in the nucleus. We performed a screen for extragenic suppressors of the nimA1 allele and isolated two cold-sensitive son (suppressor of nimA1) mutants. The sonA1 mutant encoded a nucleoporin that is a homolog of yeast Gle2/Rae1. We have now cloned SONB, a second nucleoporin genetically interacting with NIMA. sonB is essential and encodes a homolog of the human NUP98/NUP96 precursor. Similar to NUP98/NUP96, SONBNUP98/NUP96 is autoproteolytically cleaved to generate SONBNUP98 and SONBNUP96. SONBNUP98 localizes to the nuclear pore complex and contains a GLEBS domain (Gle2 binding sequence) that binds SONAGLE2. A point mutation within the GLEBS domain of SONB1NUP98 suppresses the temperature sensitivity of the nimA1 allele and compromises the physical interaction between SONAGLE2 and SONB1NUP98. The sonB1 mutation also causes sensitivity to hydroxyurea. We isolated the histone H2A-H2B gene pair as a copy-number suppressor of sonB1 cold sensitivity and hydroxyurea sensitivity. The data suggest that the nucleoporins SONAGLE2 and SONBNUP98 and the NIMA kinase interact and regulate nuclear accumulation of mitotic regulators to help promote mitosis.
Collapse
Affiliation(s)
- Colin P C De Souza
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210, USA
| | | | | | | |
Collapse
|
11
|
Osmani AH, Davies J, Oakley CE, Oakley BR, Osmani SA. TINA interacts with the NIMA kinase in Aspergillus nidulans and negatively regulates astral microtubules during metaphase arrest. Mol Biol Cell 2003; 14:3169-79. [PMID: 12925754 PMCID: PMC181558 DOI: 10.1091/mbc.e02-11-0715] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The tinA gene of Aspergillus nidulans encodes a protein that interacts with the NIMA mitotic protein kinase in a cell cycle-specific manner. Highly similar proteins are encoded in Neurospora crassa and Aspergillus fumigatus. TINA and NIMA preferentially interact in interphase and larger forms of TINA are generated during mitosis. Localization studies indicate that TINA is specifically localized to the spindle pole bodies only during mitosis in a microtubule-dependent manner. Deletion of tinA alone is not lethal but displays synthetic lethality in combination with the anaphase-promoting complex/cyclosome mutation bimE7. At the bimE7 metaphase arrest point, lack of TINA enhanced the nucleation of bundles of cytoplasmic microtubules from the spindle pole bodies. These microtubules interacted to form spindles joined in series via astral microtubules as revealed by live cell imaging. Because TINA is modified and localizes to the spindle pole bodies at mitosis, and lack of TINA causes enhanced production of cytoplasmic microtubules at metaphase arrest, we suggest TINA is involved in negative regulation of the astral microtubule organizing capacity of the spindle pole bodies during metaphase.
Collapse
Affiliation(s)
- Aysha H Osmani
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA.
| | | | | | | | | |
Collapse
|
12
|
Guo CY, Brautigan DL, Larner JM. Ionizing radiation activates nuclear protein phosphatase-1 by ATM-dependent dephosphorylation. J Biol Chem 2002; 277:41756-61. [PMID: 12202491 DOI: 10.1074/jbc.m207519200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Ionizing radiation (IR) is known to activate multiple signaling pathways, resulting in diverse stress responses including apoptosis, cell cycle arrest, and gene induction. IR-activated cell cycle checkpoints are regulated by Ser/Thr phosphorylation, so we tested to see if protein phosphatases were targets of an IR-activated damage-sensing pathway. Jurkat cells were subjected to IR or sham radiation followed by brief (32)P metabolic labeling. Nuclear extracts were subjected to microcystin affinity chromatography to recover phosphatases, and the proteins were analyzed by two-dimensional gel electrophoresis. Protein sequencing revealed that the microcystin-bound proteins with the greatest reduction in (32)P intensity following IR were the alpha and delta isoforms of protein phosphatase 1 (PP1). Both of these PP1 isoforms contain an Arg-Pro-Ile/Val-Thr-Pro-Pro-Arg sequence near the C terminus, a known site of phosphorylation by Cdc/Cdk kinases, and phosphorylation attenuates phosphatase activity. In wild-type Jurkat cells or ataxia telangiectasia (AT) cells that are stably transfected with full-length ATM kinase, IR resulted in net dephosphorylation of this site in PP1 and produced activation of PP1. However, in AT cells that are deficient in ATM, IR failed to induce dephosphorylation or activation of PP1. IR-induced PP1 activation in the nucleus may be a critical component in an ATM-mediated pathway controlling checkpoint activation.
Collapse
Affiliation(s)
- Chang Y Guo
- Department of Radiation Oncology, University of Virginia Health System, Charlottesville 22908, USA
| | | | | |
Collapse
|
13
|
Abstract
Activation of the retinoblastoma (RB) protein through dephosphorylation arises in cells upon exit from M phase and in response to environmental stresses, including DNA damage. We provide here for the first time evidence that these responses are co-ordinately affected in a subset of tumor derived cell lines. We find that RB dephosphorylation is not apparent in these cells during progression into G(1). Importantly these cells also do not respond with RB activation after DNA damage during S phase. Moreover and as a consequence they display phenotypes classically associated with RB(-) cells, showing accelerated apoptosis after DNA damage and DNA re-replication after spindle-checkpoint activation. A large body of literature provides evidence that controls governing inactivation of RB are lost in tumors. The results presented here indicate that the reverse reaction, namely the activation of RB from an inactive precursor, may also be compromised. Our findings indicate that this type of defect may be coupled with hypersensitivity to DNA damage and an increase in genomic instability in response to spindle-checkpoint activation thus bearing potentially important medical implications.
Collapse
Affiliation(s)
- Cristina Broceño
- Centre for Molecular and Cell Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, United Kingdom
| | | | | |
Collapse
|
14
|
Fox H, Hickey PC, Fernández-Abalos JM, Lunness P, Read ND, Doonan JH. Dynamic distribution of BIMG(PP1) in living hyphae of Aspergillus indicates a novel role in septum formation. Mol Microbiol 2002; 45:1219-30. [PMID: 12207691 DOI: 10.1046/j.1365-2958.2002.03092.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mutation of bimG, the major protein phosphatase 1 gene in Aspergillus nidulans, causes multiple cell cycle and hyphal growth defects that are associated with overphosphorylation of subcellular components. We have used functional translational fusions with the green fluorescent protein (GFP) to show that BIMG has at least four discrete locations within growing hyphae. Three of these locations, the hyphal tip, the spindle pole body and the nucleus, correlate with previously known requirements for bimG(PP1) in mitosis and hyphal growth and are highly dynamic. BIMG-GFP in the hyphal tip seemed to be associated with the plasma membrane and formed a collar of fluorescence within the apical dome. The distribution of nuclear BIMG-GFP varied depending on nutritional conditions; on poor medium, it concentrated more in the nucleolus than in the nucleoplasm, whereas on rich medium, it was more evenly distributed between the two nuclear regions. The association of BIMG-GFP with developing septa was transient, and we present evidence that BIMG phosphatase plays a direct role in septum formation, distinct from its role in mitosis. We conclude that, by being physically present at several sites, the BIMG phosphatase has roles in multiple cellular processes.
Collapse
Affiliation(s)
- H Fox
- John Innes Centre, Colney Lane, Norwich NR4 7UH, UK
| | | | | | | | | | | |
Collapse
|
15
|
Dawe AL, Willins DA, Morris NR. Increased transformation efficiency of Aspergillus nidulans protoplasts in the presence of dithiothreitol. Anal Biochem 2000; 283:111-2. [PMID: 10929816 DOI: 10.1006/abio.2000.4658] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- A L Dawe
- Department of Pharmacology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway 08854, USA.
| | | | | |
Collapse
|
16
|
Joseph JD, Heitman J, Means AR. Molecular cloning and characterization of Aspergillus nidulans cyclophilin B. Fungal Genet Biol 1999; 27:55-66. [PMID: 10413615 DOI: 10.1006/fgbi.1999.1131] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cyclophilins are an evolutionarily conserved family of proteins which serve as the intracellular receptors for the immunosuppressive drug cyclosporin A. Here we report the characterization of the first cyclophilin cloned from the filamentous fungus Aspergillus nidulans (CYPB). Sequence analysis of the cypB gene predicts an encoded protein with highest homology to the murine cyclophilin B protein. The sequence similarity includes an N-terminal sequence predicted to target the protein to the endoplasmic reticulum (ER) as well as a C-terminal sequence predicted to retain the mature protein in the ER. The bacterially expressed hexa-histidine tagged protein displays peptidyl-prolyl isomerase activity which is inhibited by cyclosporin A. In the presence of cyclosporin A, the expressed protein also inhibits purified calcineurin. When the endogenous cypB gene was disrupted and placed under the control of the regulatable alcohol dehydrogenase promoter, the strain demonstrated no detectable growth phenotype under conditions which induce or repress cypB transcription. Induction or repression of the cypB gene also did not effect sensitivity of A. nidulans to cyclosporin A. cypB mRNA levels were significantly elevated under severe heat shock conditions, indicating a possible role for the A. nidulans cyclophilin B protein during growth in high stress environments.
Collapse
Affiliation(s)
- J D Joseph
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | | | | |
Collapse
|
17
|
Abstract
This review traces the principal advances in the study of mitosis in filamentous fungi from its beginnings near the end of the 19(th) century to the present day. Meiosis and mitosis had been accurately described and illustrated by the second decade of the present century and were known to closely resemble nuclear divisions in higher eukaryotes. This information was effectively lost in the mid-1950s, and the essential features of mitosis were then rediscovered from about the mid-1960s to the mid-1970s. Interest in the forces that separate chromatids and spindle poles during fungal mitosis followed closely on the heels of detailed descriptions of the mitotic apparatus in vivo and ultrastructurally during this and the following decade. About the same time, fundamental studies of the structure of fungal chromatin and biochemical characterization of fungal tubulin were being carried out. These cytological and biochemical studies set the stage for a surge of renewed interest in fungal mitosis that was issued in by the age of molecular biology. Filamentous fungi have provided model studies of the cytology and genetics of mitosis, including important advances in the study of mitotic forces, microtubule-associated motor proteins, and mitotic regulatory mechanisms.
Collapse
Affiliation(s)
- J R Aist
- Department of Plant Pathology, College of Agriculture and Life Sciences, Ithaca, New York 14853, USA
| | | |
Collapse
|
18
|
Miller BA, Zhang MY, Gocke CD, De Souza C, Osmani AH, Lynch C, Davies J, Bell L, Osmani SA. A homolog of the fungal nuclear migration gene nudC is involved in normal and malignant human hematopoiesis. Exp Hematol 1999; 27:742-50. [PMID: 10210332 DOI: 10.1016/s0301-472x(98)00074-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The filamentous fungus Aspergillus nidulans nudC gene has an essential function in movement of nuclei following mitosis and is required for normal colony growth. Here, the molecular cloning and role in hematopoiesis of a human gene (designated HnudC) homologous to A. nidulans nudC is reported. The amino terminus of the larger human protein (HNUDC = 45 kDa) does not overlap with A. nidulans NUDC (22 kDa). However, NUDC and the C-terminal 94 amino acids of HNUDC are 67% identical. The C-terminal region of the HnudC gene fully complements the A. nidulans temperature-sensitive nudC3 mutation, suggesting that nudC has an essential function in cell growth that is conserved from filamentous fungi to humans. In initial studies, HNUDC levels were much higher in erythroid precursors compared to most other human tissues. Therefore, the potential role of HnudC in hematopoiesis was explored. In normal human bone marrow, HNUDC protein and mRNA are highly expressed in early myeloid and erythroid precursors and decline as these cells terminally differentiate. To determine whether hematopoietic growth factors induce HnudC expression, TF-1 cells were stimulated by granulocyte-macrophage colony-stimulating factor. This induced a significant increase in HNUDC protein and HnudC mRNA, suggesting that enhancement of HnudC expression in response to growth factor stimulation may be mediated at the transcription level. Furthermore, HNUDC was significantly enhanced in lysates of bone marrow aspirates from patients with acute myelogenous and acute lymphoblastic leukemia compared to aspirates from normal controls, suggesting that HnudC is involved in malignant hematopoietic cell growth as well. These data demonstrate that HNUDC is highly expressed in normal and malignant human hematopoietic precursors and suggest it is of functional importance in the proliferation of these cells.
Collapse
Affiliation(s)
- B A Miller
- Department of Pediatrics, The Pennsylvania State University College of Medicine, The Milton S. Hershey Medical Center, Hershey 17033-0850, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Dickman MB, Yarden O. Serine/threonine protein kinases and phosphatases in filamentious fungi. Fungal Genet Biol 1999; 26:99-117. [PMID: 10328981 DOI: 10.1006/fgbi.1999.1118] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein phosphorylation and dephosphorylation are one of the central currencies by which living cells perceive and respond to environmental cues. A number of fundamental processes in fungi such as the cell cycle, transcription, and mating have been shown to require protein phosphorylation. The analysis of protein kinases and phosphatases in filamentous fungi is in its infancy; however, it has already become clear that kinases and phosphatases are likely to be important mediators of fungal proliferation and development as well as signal transduction and infection-related morphogenesis. In this review, we describe, summarize, and consider the rapidly expanding field of protein phosphorylation/dephosphorylation in various aspects of filamentous fungal growth and development.
Collapse
Affiliation(s)
- M B Dickman
- Department of Plant Pathology, University of Nebraska, Lincoln, Nebraska 68583, USA
| | | |
Collapse
|
20
|
Doonan J. The Cell Division Cycle in Aspergillus nidulans. Development 1999. [DOI: 10.1007/978-3-642-59828-9_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
21
|
Fernández-Abalos JM, Fox H, Pitt C, Wells B, Doonan JH. Plant-adapted green fluorescent protein is a versatile vital reporter for gene expression, protein localization and mitosis in the filamentous fungus, Aspergillus nidulans. Mol Microbiol 1998; 27:121-30. [PMID: 9466261 DOI: 10.1046/j.1365-2958.1998.00664.x] [Citation(s) in RCA: 158] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Green fluorescent protein (GFP) is a useful reporter to follow the in vivo behaviour of proteins, but the wild-type gfp gene does not function in many organisms, including many plants and filamentous fungi. We show that codon-modified forms of gfp, produced for use in plants, function effectively in Aspergillus nidulans both as gene expression reporters and as vital reporters for protein location. To demonstrate the use of these modified gfps as reporter genes we have used fluorescence to follow ethanol-induced GFP expression from the alcA promoter. Translational fusions with the modified gfp were used to follow protein location in living cells; plant ER-retention signals targeted GFP to the endoplasmic reticulum, whereas fusion to the GAL4 DNA-binding domain targeted it to the nucleus. Nuclear-targeted GFP allowed real-time observation of nuclear movement and division. These modified gfp genes should provide useful markers to follow gene expression, organelle behaviour and protein trafficking in real time.
Collapse
|
22
|
Dayton JS, Sumi M, Nanthakumar NN, Means AR. Expression of a constitutively active Ca2+/calmodulin-dependent kinase in Aspergillus nidulans spores prevents germination and entry into the cell cycle. J Biol Chem 1997; 272:3223-30. [PMID: 9013558 DOI: 10.1074/jbc.272.6.3223] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The unique gene for Ca2+/calmodulin-dependent protein kinase (CaMK) has been shown to be essential in Aspergillus nidulans. Disruption of the gene prevents entry of spores into the nuclear division cycle. Here we show that expression of a constitutively active form of CaMK also prevents spores from entering the first S phase in response to a germinating stimulus. Expression of the constitutively active kinase induces premature activation of NIMEcyclin B/NIMXcdc2 in G0/G1. As NIMXcdc2 is present in spores, the elevation of maturation promotion factor activity may be secondary to the early production of NIMEcyclin B or post-translation modification of maturation promotion factor. The expression of the constitutively active CaMK also results in the appearance of NIMA kinase activity within 1 h of the germinating signal. These results support the contention that the activities of maturation promotion factor and NIMA are coincidentally regulated in A. nidulans and suggest that the unscheduled appearance of one or both of these activities may be sufficient to prevent A. nidulans spores from entering into DNA synthesis.
Collapse
Affiliation(s)
- J S Dayton
- Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | | | | | | |
Collapse
|
23
|
Pu RT, Xu G, Wu L, Vierula J, O'Donnell K, Ye XS, Osmani SA. Isolation of a functional homolog of the cell cycle-specific NIMA protein kinase of Aspergillus nidulans and functional analysis of conserved residues. J Biol Chem 1995; 270:18110-6. [PMID: 7629122 DOI: 10.1074/jbc.270.30.18110] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
To investigate the degree of conservation of the cell cycle-specific NIMA protein kinase of Aspergillus nidulans, and to help direct its functional analysis, we cloned a homolog (designated nim-1) from Neurospora crassa. Over the catalytic domain NIM-1 is 75% identical to NIMA, but overall the identity drops to 52%. nim-1 was able to functionally complement nimA5 in A. nidulans. Mutational analysis of potential activating phosphorylation sites found in NIMA, NIM-1, and related protein kinases was performed on NIMA. Mutation of threonine 199 (conserved in all NIMA-related kinases) inhibited NIMA beta-casein kinase activity and abolished its in vivo function. This site conforms to a minimal consensus phosphorylation site for NIMA (FXXT) and is analogous to the autophosphorylation site of cyclic-AMP-dependent protein kinases. However, mutation of a unique cysteine residue found only in the catalytic site of NIMA and NIM-1 had no effect on NIMA kinase activity or function. Three temperature-sensitive alleles of nimA that cause arrest in G2 were sequenced and shown to generate three different amino acid substitutions. None of the mutations prevented accumulation of NIMA protein during G2 arrest, but all prevented the p34cdc2/cyclin B-dependent phosphorylation of NIMA normally seen during mitotic initiation even though p34cdc2/cyclin B H1 kinase activity was fully activated.
Collapse
Affiliation(s)
- R T Pu
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822-2617, USA
| | | | | | | | | | | | | |
Collapse
|
24
|
Paulson JR, Ciesielski WA, Schram BR, Mesner PW. Okadaic acid induces dephosphorylation of histone H1 in metaphase-arrested HeLa cells. J Cell Sci 1994; 107 ( Pt 1):267-73. [PMID: 8175913 DOI: 10.1242/jcs.107.1.267] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It is shown here that treatment of metaphase-arrested HeLa cells with okadaic acid (0.15-2.5 microM) leads to dephosphorylation of histone H1. This effect is presumably due to the specific ability of okadaic acid to inhibit protein phosphatases 1 and/or 2A, because okadaic acid tetraacetate, which is not a phosphatase inhibitor, has no effect. Dephosphorylation of H1 does not occur if okadaic acid-treated cells are simultaneously treated with 20 nM calyculin A, or if the okadaic acid concentration is 5.0 microM or greater. The mechanism behind this phenomenon is not known. However, the results suggest that the chain of events leading to histone dephosphorylation may be negatively controlled by a protein phosphatase 2A, while the phosphatase which actually dephosphorylates H1 could be a protein phosphatase 1. It remains to be determined whether the phosphatase involved here is the same enzyme as that which dephosphorylates H1 at the end of normal mitosis.
Collapse
Affiliation(s)
- J R Paulson
- Department of Chemistry, University of Wisconsin-Oshkosh 54901
| | | | | | | |
Collapse
|
25
|
Durfee T, Becherer K, Chen PL, Yeh SH, Yang Y, Kilburn AE, Lee WH, Elledge SJ. The retinoblastoma protein associates with the protein phosphatase type 1 catalytic subunit. Genes Dev 1993; 7:555-69. [PMID: 8384581 DOI: 10.1101/gad.7.4.555] [Citation(s) in RCA: 1228] [Impact Index Per Article: 39.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The retinoblastoma protein (p110RB) interacts with many cellular proteins in complexes potentially important for its growth-suppressing function. We have developed and used an improved version of the yeast two-hybrid system to isolate human cDNAs encoding proteins able to bind p110RB. One clone encodes a novel type 1 protein phosphatase catalytic subunit (PP-1 alpha 2), which differs from the originally defined PP-1 alpha by an amino-terminal 11-amino-acid insert. In vitro-binding assays demonstrated that PP-1 alpha isoforms preferentially bind the hypophosphorylated form of p110RB. Moreover, similar p110RB sequences are required for binding PP-1 alpha 2 and SV40 large T antigen. Cell cycle synchrony experiments revealed that this association occurs from mitosis to early G1. The implications of these findings on the regulation of both proteins are discussed.
Collapse
Affiliation(s)
- T Durfee
- Center for Molecular Medicine/Institute of Biotechnology, University of Texas Health Science Center, San Antonio 78245
| | | | | | | | | | | | | | | |
Collapse
|
26
|
Holmes CF, Boland MP. Inhibitors of protein phosphatase-1 and -2A; two of the major serine/threonine protein phosphatases involved in cellular regulation. Curr Opin Struct Biol 1993. [DOI: 10.1016/0959-440x(93)90159-i] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
27
|
Abstract
Amenable to sophisticated genetic and molecular analysis, the simple filamentous fungus Aspergillus nidulans has provided some novel insights into the mechanisms and regulation of cell division. Mutational analysis has identified over fifty genes necessary for nuclear division, nuclear movement and cytokinesis. Molecular and cellular analysis of these mutants has led to the discovery of novel components of the cytoskeleton as well as to clarifying the role of established cytoskeletal proteins. Mutations leading to defects in the kinases (i.e. p34cdc2) and phosphatases (i.e. cdc25 and PP1), which are known to regulate mitosis in other eukaryotes, have been identified in Aspergillus. Additional, as yet novel, mitotic regulatory molecules, encoded by the nimA and bimE genes, have also been discovered in Aspergillus.
Collapse
Affiliation(s)
- J H Doonan
- Department of Cell Biology, John Innes Institute, Norwich, UK
| |
Collapse
|