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Glaves ML, Cotter DA. Environmental Parameters Limiting Spore Germination in a Spontaneously Germinating Mutant ofDictyostelium Discoideum. Mycologia 2018. [DOI: 10.1080/00275514.1989.12025631] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Martha L. Glaves
- Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada
| | - David A. Cotter
- Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada
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Al-Anbaky Q, Al-Karakooly Z, Connor R, Williams L, Yarbrough A, Bush J, Ali N. Role of inositol polyphosphates in programed cell death in Dictyostelium discoideum and its developmental life cycle. Mol Cell Biochem 2018; 449:237-250. [PMID: 29679279 DOI: 10.1007/s11010-018-3360-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 04/16/2018] [Indexed: 11/28/2022]
Abstract
Programed cell death or apoptosis is a key developmental process that maintains tissue homeostasis in multicellular organisms. Inositol polyphosphates (InsPs) are key signaling molecules known to regulate a variety of cellular processes including apoptosis in such organisms. The signaling role of InsPs in unicellular organisms such as Dictyostelium discoideum (D. discoideum) is not well understood. We investigated whether InsPs also play any role in apoptosis in D. discoideum and whether InsPs-mediated apoptosis follows a mechanism similar to that present in higher multicellular eukaryotes. We measured known apoptotic markers in response to exogenously administered InsP6, the major InsPs in the cell. We found that InsP6 was able to cause cell death in D. discoideum cell culture in a dose- and time-dependent manner as determined by cytotoxicity assays. Fluorescence staining with acridine orange/ethidium bromide and flow cytometry results confirmed that the cell death in D. discoideum by InsP6 was due to apoptotic changes. Poly(ADP-ribose) expression, a known apoptotic marker used in D. discoideum, was also increased following InsP6 treatment suggesting a role for InsP6-mediated apoptosis in this organism. InsP6-mediated cell death was accompanied by production of reactive oxygen species and a decrease in mitochondrial membrane potential. Additionally, we studied the effects of InsP6 on the developmental life cycle of D. discoideum, the process likely affected by apoptosis. In conclusion, our studies provide evidence that InsP6-mediated cell death process is conserved in D. discoideum and plays an important signaling role in its developmental life cycle.
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Affiliation(s)
- Qudes Al-Anbaky
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA.,Department of Biology, University of Diyala, Baquba, Iraq
| | - Zeiyad Al-Karakooly
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA
| | - Richard Connor
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA
| | - Lisa Williams
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA
| | - Azure Yarbrough
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA
| | - John Bush
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA
| | - Nawab Ali
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA.
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3
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Pisani F, Livermore T, Rose G, Chubb JR, Gaspari M, Saiardi A. Analysis of Dictyostelium discoideum inositol pyrophosphate metabolism by gel electrophoresis. PLoS One 2014; 9:e85533. [PMID: 24416420 PMCID: PMC3887064 DOI: 10.1371/journal.pone.0085533] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 11/28/2013] [Indexed: 11/28/2022] Open
Abstract
The social amoeba Dictyostelium discoideum was instrumental in the discovery and early characterization of inositol pyrophosphates, a class of molecules possessing highly-energetic pyrophosphate bonds. Inositol pyrophosphates regulate diverse biological processes and are attracting attention due to their ability to control energy metabolism and insulin signalling. However, inositol pyrophosphate research has been hampered by the lack of simple experimental procedures to study them. The recent development of polyacrylamide gel electrophoresis (PAGE) and simple staining to resolve and detect inositol pyrophosphate species has opened new investigative possibilities. This technology is now commonly applied to study in vitro enzymatic reactions. Here we employ PAGE technology to characterize the D. discoideum inositol pyrophosphate metabolism. Surprisingly, only three major bands are detectable after resolving acidic extract on PAGE. We have demonstrated that these three bands correspond to inositol hexakisphosphate (IP6 or Phytic acid) and its derivative inositol pyrophosphates, IP7 and IP8. Biochemical analyses and genetic evidence were used to establish the genuine inositol phosphate nature of these bands. We also identified IP9 in D. discoideum cells, a molecule so far detected only from in vitro biochemical reactions. Furthermore, we discovered that this amoeba possesses three different inositol pentakisphosphates (IP5) isomers, which are largely metabolised to inositol pyrophosphates. Comparison of PAGE with traditional Sax-HPLC revealed an underestimation of the cellular abundance of inositol pyrophosphates by traditional methods. In fact our study revealed much higher levels of inositol pyrophosphates in D. discoideum in the vegetative state than previously detected. A three-fold increase in IP8 was observed during development of D. discoideum a value lower that previously reported. Analysis of inositol pyrophosphate metabolism using ip6k null amoeba revealed the absence of developmentally-induced synthesis of inositol pyrophosphates, suggesting that the alternative class of enzyme responsible for pyrophosphate synthesis, PP-IP5K, doesn’t’ play a major role in the IP8 developmental increase.
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Affiliation(s)
- Francesca Pisani
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
- Department of Biology, Ecology and Earth Science, University of Calabria, Rende, Italy
| | - Thomas Livermore
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Giuseppina Rose
- Department of Biology, Ecology and Earth Science, University of Calabria, Rende, Italy
| | - Jonathan Robert Chubb
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Marco Gaspari
- Laboratory of Proteomics and Mass Spectrometry, Department of Experimental and Clinical Medicine, “Magna Græcia” University of Catanzaro, Catanzaro, Italy
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
- * E-mail:
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4
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Abstract
Much of our knowledge of molecular cellular functions is based on studies with a few number of model organisms that were established during the last 50 years. The social amoeba Dictyostelium discoideum is one such model, and has been particularly useful for the study of cell motility, chemotaxis, phagocytosis, endocytic vesicle traffic, cell adhesion, pattern formation, caspase-independent cell death, and, more recently, autophagy and social evolution. As nonmammalian model of human diseases D. discoideum is a newcomer, yet it has proven to be a powerful genetic and cellular model for investigating host-pathogen interactions and microbial infections, for mitochondrial diseases, and for pharmacogenetic studies. The D. discoideum genome harbors several homologs of human genes responsible for a variety of diseases, -including Chediak-Higashi syndrome, lissencephaly, mucolipidosis, Huntington disease, IBMPFD, and Shwachman-Diamond syndrome. A few genes have already been studied, providing new insights on the mechanism of action of the encoded proteins and in some cases on the defect underlying the disease. The opportunities offered by the organism and its place among the nonmammalian models for human diseases will be discussed.
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Affiliation(s)
- Salvatore Bozzaro
- Department of Clinical and Biological Sciences, University of Turin, Orbassano, Turin, Italy.
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5
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Jang W, Chiem B, Gomer RH. A secreted cell number counting factor represses intracellular glucose levels to regulate group size in dictyostelium. J Biol Chem 2002; 277:39202-8. [PMID: 12161440 DOI: 10.1074/jbc.m205635200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Developing Dictyostelium cells form evenly sized groups of approximately 2 x 10(4) cells. A secreted 450-kDa protein complex called counting factor (CF) regulates group size by repressing cell-cell adhesion and myosin polymerization and by increasing cAMP-stimulated cAMP production, actin polymerization, and cell motility. We find that CF regulates group size in part by repressing internal glucose levels. Transformants lacking bioactive CF and wild-type cells with extracellular CF depleted by antibodies have high glucose levels, whereas transformants oversecreting CF have low glucose levels. A component of CF, countin, affects group size in a manner similar to CF, and a 1-min exposure of cells to countin decreases glucose levels. Adding 1 mm exogenous glucose negates the effect of high levels of extracellular CF on group size and mimics the effect of depleting CF on glucose levels, cell-cell adhesion, cAMP pulse size, actin polymerization, myosin assembly, and motility. These results suggest that glucose is a downstream component in part of the CF signaling pathway and may be relevant to the observed role of the insulin pathway in tissue size regulation in higher eukaryotes.
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Affiliation(s)
- Wonhee Jang
- Howard Hughes Medical Institute and the Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005-1892, USA
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6
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Tang L, Ammann R, Gao T, Gomer RH. A cell number-counting factor regulates group size in Dictyostelium by differentially modulating cAMP-induced cAMP and cGMP pulse sizes. J Biol Chem 2001; 276:27663-9. [PMID: 11371560 DOI: 10.1074/jbc.m102205200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A secreted counting factor (CF), regulates the size of Dictyostelium discoideum fruiting bodies in part by regulating cell-cell adhesion. Aggregation and the expression of adhesion molecules are mediated by relayed pulses of cAMP. Cells also respond to cAMP with a short cGMP pulse. We find that CF slowly down-regulates the cAMP-induced cGMP pulse by inhibiting guanylyl cyclase activity. A 1-min exposure of cells to purified CF increases the cAMP-induced cAMP pulse. CF does not affect the cAMP receptor or its interaction with its associated G proteins or the translocation of the cytosolic regulator of adenylyl cyclase to the membrane in response to cAMP. Pulsing streaming wild-type cells with a high concentration of cAMP results in the formation of small groups, whereas reducing cAMP pulse size with exogenous cAMP phosphodiesterase during stream formation causes cells to form large groups. Altering the extracellular cAMP pulse size does not phenocopy the effects of CF on the cAMP-induced cGMP pulse size or cell-cell adhesion, indicating that CF does not regulate cGMP pulses and adhesion via CF's effects on cAMP pulses. The results suggest that regulating cell-cell adhesion, the cGMP pulse size, or the cAMP pulse size can control group size and that CF regulates all three of these independently.
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Affiliation(s)
- L Tang
- Howard Hughes Medical Institute and the Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005-1892, USA
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7
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Abstract
The life cycle of Dictyostelium discoideum offers a unique opportunity to study signal transduction in eukaryotic cells at both the unicellular and multicellular levels of organization. Adding to the already extensive knowledge of the unicellular stages, classical and molecular genetics have begun to unravel transduction of signals controlling morphogenesis and behaviour (phototaxis and thermotaxis) in the multicellular 'slug' stage of the life cycle. Distributed over all seven genetic linkage groups are probably about 20, but possibly as many as 55, genes of importance for slug behaviour. The encoded proteins appear from pharmacological studies and mutant phenotypes to govern transduction pathways involving the intracellular second messengers cyclic AMP, cyclic GMP, IP3 and Ca2+. Pathways from the photo- and thermoreceptors converge first with each other and thence, at the level of the second messengers, with those from extracellular tip activation (cyclic AMP) and inhibition (Slug Turning Factor and/or ammonia and/or adenosine) signals that control slug movement and morphogenesis.
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Affiliation(s)
- P R Fisher
- School of Microbiology, La Trobe University, Bundoora, Victoria, Australia
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8
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Abstract
This review is concerned with the roles of cyclic GMP and Ca(2+) ions in signal transduction for chemotaxis of Dictyostelium. These molecules are involved in signalling between the cell surface cyclic AMP receptors and cytoskeletal myosin II involved in chemotactic cell movement. Evidence is presented for uptake and/or efflux of Ca(2+) being regulated by cyclic GMP. The link between Ca(2+), cyclic GMP and chemotactic cell movement has been explored using "streamer F" mutants whose primary defect is in the structural gene for the cyclic GMP-specific phosphodiesterase. This mutation causes the mutants to produce an abnormally prolonged peak of cyclic GMP accumulation in response to stimulation with the chemoattractant cyclic AMP. The production and relay of cyclic AMP signals is normal in these mutants, but certain events associated with movement are (like the cyclic GMP response) abnormally prolonged in the mutants. These events include Ca(2+) uptake, myosin II association with the cytoskeleton and regulation of both myosin heavy and light chain phosphorylation. These changes can be correlated with changes in the shape of the amoebae after chemotactic stimulation. Other mutants in which the accumulation of cyclic GMP in response to cyclic AMP stimulation was absent produced no myosin II responses. A model is described in which cyclic GMP (directly or indirectly via Ca(2+) regulates accumulation of myosin II on the cytoskeleton by regulating phosphorylation of the myosin heavy and light chain kinases.
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Affiliation(s)
- P C Newell
- Department of Biochemistry, University of Oxford, UK
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9
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Calcium, cyclic GMP and the control of myosin II during chemotactic signal transduction ofDictyostelium. J Biosci 1995. [DOI: 10.1007/bf02703835] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Lydan MA, Cotter DA. The role of Ca2+ during spore germination in Dictyostelium: autoactivation is mediated by the mobilization of Ca2+ while amoebal emergence requires entry of external Ca2+. J Cell Sci 1995; 108 ( Pt 5):1921-30. [PMID: 7657715 DOI: 10.1242/jcs.108.5.1921] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
One of the developmental pathways used by the social amoeba Dictyostelium discoideum produces dormant spores. As with any temporary resistant stage, these spores must be able to germinate rapidly in response to positive environmental stimuli. One such stimulus is the autoactivator, an endogenous, diffusible molecule that is secreted by spores. Previous work has shown that three phases of germination, autoactivation, spore swelling and amoebal emergence, require the activity of the Ca(2+)-dependent, regulatory protein calmodulin, implicating Ca2+ as an essential cation during germination. In this study we used a pharmacological approach coupled with the direct measurement of Ca2+ levels in germinating spore populations by atomic adsorption to examine Ca(2+)-dependent signal transduction during spore activation and germination in D. discoideum. Inhibitors of both phospholipase C and internal Ca2+ release inhibited autoactivation while exogenously added Ins(1,4,5)P3, acted synergistically with the autoactivator. The antagonists specifically affected spore activation as mediated by the autoactivator, since neither had any effect on heat-activated spores. In contrast, La3+, an inhibitor of Ca2+ uptake, had little or no effect on either autoactivation or the swelling of autoactivated spores. However, an inhibition of Ca2+ influx by La3+ inhibited both the swelling of heat-activated spores and amoebal emergence following each period of autoactivation or heat activation. Ca2+ levels change in the spore population during germination. During activation and swelling, Ca2+ efflux occurs from the spores. Both of the activating stimuli used here, the autoactivator and heat, caused this Ca2+ efflux. The efflux is reversed during emergence when there is a net Ca2+ uptake by the spores and cells from the medium. Together these data provide the first evidence that autoactivation is mediated by Ca(2+)-dependent signal transduction, leading to Ca2+ efflux, and that the late event of germination, amoebal emergence, requires Ca2+ uptake to proceed. The data also suggest that the responses of the spore to the each of autoactivator and heat, i.e. Ca2+ movements and germination, are mediated by different mechanisms.
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Affiliation(s)
- M A Lydan
- Department of Biological Sciences, University of Windsor, Ontario, Canada
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11
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Abe F, Maeda Y. Specific expression of a gene encoding a novel calcium-binding protein, CAF-1, during transition of Dictyostelium cells from growth to differentiation. Dev Growth Differ 1995. [DOI: 10.1046/j.1440-169x.1995.00005.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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12
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Protein kinase C in hydrozoans: involvement in metamorphosis of Hydractinia and in pattern formation of Hydra. ACTA ACUST UNITED AC 1994; 203:422-428. [PMID: 28305948 DOI: 10.1007/bf00188691] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/1993] [Accepted: 02/10/1994] [Indexed: 10/26/2022]
Abstract
A wealth of information has suggested the involvement of protein kinase C (PKC) in metamorphosis of Hydractinia echinata and in pattern formation of Hydra magnipapillata. We have identified a Ca2+- and phospholipid-dependent kinase activity in extracts of both species. The enzyme was characterized as being similar to mammalian PKC by ion exchange chromatography. Gel filtration experiments revealed a molecular weight of about 70 kD. In phosphorylation assays of endogenous Hydractinia proteins, a protein with a molecular weight of 22.5 kD was found to be phoshorylated upon addition of phosphatidylserine. Bacterial induction of metamorphosis of Hydractinia echinata caused an increase in endogenous diacylglycerol, the physiological activator of PKC, suggesting that the bacterial inducer acts by activating receptor-regulated phospholipid metabolism. Exogenous diacylglycerol leads to membrane translocation of PKC, indicative of an activation. On the basis of our results and those of Freeman and Ridgway (1990) a model for the biochemical events during metamorphosis is presented.
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13
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Valkema R, Van Haastert PJ. Inhibition of receptor-stimulated guanylyl cyclase by intracellular calcium ions in Dictyostelium cells. Biochem Biophys Res Commun 1992; 186:263-8. [PMID: 1352966 DOI: 10.1016/s0006-291x(05)80802-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
In Dictyostelium discoideum extracellular cAMP stimulates guanylyl cyclase and phospholipase C; the latter enzyme produces Ins(1,4,5)P3 which releases Ca2+ from internal stores. The following data indicate that intracellular Ca2+ ions inhibit guanylyl cyclase activity. 1) In vitro, Ca2+ inhibits guanylyl cyclase with IC50 = 41 nM Ca2+ and Hill-coefficient of 2.1. 2) Extracellular Ca2+ does not affect basal cGMP levels of intact cells. In electro-permeabilized cells, however, cGMP levels are reduced by 85% within 45 s after addition of 10(-6) M Ca2+ to the medium; halfmaximal reduction occurs at 200 nM extracellular Ca2+. 3) Receptor-stimulated activation of guanylyl cyclase in electro-permeabilized cells is also inhibited by extracellular Ca2+ with half-maximal effect at 200 nM Ca2+. 4) In several mutants an inverse correlation exists between receptor-stimulated Ins(1,4,5)P3 production and cGMP formation. We conclude that receptor-stimulated cytosolic Ca2+ elevation is a negative regulator of receptor-stimulated guanylyl cyclase.
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Affiliation(s)
- R Valkema
- Department of Biochemistry, University of Groningen, The Netherlands
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14
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Simon MN, Pelegrini O, Veron M, Kay RR. Mutation of protein kinase A causes heterochronic development of Dictyostelium. Nature 1992; 356:171-2. [PMID: 1312226 DOI: 10.1038/356171a0] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In heterochronic mutants the relative timing of developmental events is altered compared with the wild type. This generally results in a disordered embryo, though heterochronic mutations may also be an important source of evolutionary variation. In the rapidly developing (rde) mutants of Dictyostelium, stalk and spore cells differentiate before morphogenesis is complete. We have traced the lesion in one class of these mutants to the regulatory subunit of cyclic AMP-dependent protein kinase (pk-A). Inactivation of this protein results in the unrestrained activity of the catalytic subunit, so prematurely triggering terminal cell differentiation.
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Affiliation(s)
- M N Simon
- Unité de Biochimie Cellulaire, CNRS URA1129, Institut Pasteur, France
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15
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Stracke ML, Krutzsch HC, Unsworth EJ, Arestad A, Cioce V, Schiffmann E, Liotta LA. Identification, purification, and partial sequence analysis of autotaxin, a novel motility-stimulating protein. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)45911-x] [Citation(s) in RCA: 151] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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16
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Tirlapur UK, Gross J, Nanjundiah V. Spatial variation of sequestered calcium in the multicellular stage of Dictyostelium discoideum as assayed by chlortetracycline fluorescence. Differentiation 1991; 48:137-46. [PMID: 1804739 DOI: 10.1111/j.1432-0436.1991.tb00252.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We have used chlortetracycline (CTC) as a fluorescent probe to detect the distribution of sequestered calcium in multicellular stages of Dictyostelium discoideum. Tips of late aggregates, slugs and early culminating masses fluoresce very strongly. Most of the fluorescence is intracellular in origin and emanates from a small number of intense punctate sources. The sources correspond in part to autophagic vacuoles vis. neutral-red staining, acidic digestive vesicles, and may also include intracellular organelles; cytoplasmic fluorescence is much weaker in comparison. The level of fluorescence drops in the middle portion of slugs and rises again in the posteriormost region, though not to as high a level as in the tip. This holds good irrespective of whether CTC is applied only in the neighbourhood of the aggregate centre, only in the aggregate periphery, or to the whole aggregate. We infer that there must be a good deal of mixing in the stages leading from aggregation to slug formation; thus the serial order in which cells enter an aggregate does not bear any relation to their ultimate fates. The other implication of our study is that calcium sequestration is much more extensive in prestalk and anterior-like cells than in prespore cells. These findings are discussed with regard to possible implications for pattern formation.
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Affiliation(s)
- U K Tirlapur
- Centre for Theoretical Studies, Indian Institute of Science, Bangalore
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17
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Stoker M, Gherardi E. Regulation of cell movement: the motogenic cytokines. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1072:81-102. [PMID: 2018780 DOI: 10.1016/0304-419x(91)90008-9] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- M Stoker
- Department of Medicine, University of Cambridge, U.K
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18
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Abstract
cAR1, a G-protein-linked surface cAMP receptor, plays a central role in the development of Dictyostelium. To investigate its role, we sought to target the cAR1 gene by homogolous recombination. Transformation of these amoebas with appropriately designed vectors results in integration into the cAR1 locus with high frequency. cAR1 "null" mutants, resulting from double crossover events, fail to bind or sense cAMP and arrest in early development. The null mutants can be rescued by constitutive expression of a wild-type cAR1 cDNA. Carboxy-terminal deletion mutants, derived from single crossover events, express a truncated form of cAR1 that binds and senses cAMP. These cells proceed through the developmental program, albeit with a delay. Constitutive expression of a similar truncated form of cAR1 also rescues the null mutant. These observations prove that cAR1-mediated signal transduction controls the development of Dictyostelium and allow structural/functional studies of a G-protein-linked receptor in its natural context.
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Affiliation(s)
- T J Sun
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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19
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Saxe CL, Johnson R, Devreotes PN, Kimmel AR. Multiple genes for cell surface cAMP receptors in Dictyostelium discoideum. DEVELOPMENTAL GENETICS 1991; 12:6-13. [PMID: 2049880 DOI: 10.1002/dvg.1020120104] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We have cloned and characterized three genes (CAR1, CAR2, CAR3) encoding potential cell surface, cyclic adenosine 3':5' monophosphate (AMP) receptors from Dictyostelium discoideum. The three proteins are predicted to be substantially similar in amino acid sequence throughout most of their transmembrane (TM) and loop domains but are distinctly different in their carboxyl terminal segments. In addition, all three genes possess an intron which interrupts an equivalent codon of TM3. CAR1 is expressed early in development when the cAMP relay system is being established. As development proceeds multiple size forms of CAR1 RNA are detected which apparently result from differences in their 5'-untranslated regions. Late in development levels of CAR1 RNA decrease. In contrast, CAR2 encodes a single sized RNA which is expressed only during postaggregative development. CAR3 expression is approximately 10% of CAR1 during early development, is maximal during tight aggregate formation but declines thereafter. Only one size class of CAR3 mRNA is detected throughout development. Because RNA for each of the three genes is present in postaggregative cells, it was of interest to determine the cell type distribution of each RNA. Gene-specific probes were hybridized to RNAs isolated from cells of Percoll gradient-enriched prespore and prestalk fractions and relative levels of hybridization compared. CAR1 and CAR3 show approximately the same pattern of accumulation; a 3-4 fold enrichment in prestalk cells. CAR2, however, is highly enriched in prestalk cells, more than 10 fold relative to prespore cells.
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Affiliation(s)
- C L Saxe
- Laboratory of Cellular and Developmental Biology, National Institutes of Health, Bethesda, Maryland 20892
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21
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Abstract
Membrane-associated phosphoinositidase C activity has been identified in Dictyostelium discoideum using phosphatidylinositol 4,5-bisphosphate as exogenous substrate. Maximal activity was observed with 0.4 mM phosphatidylinositol 4,5-bisphosphate at pH 7.0. The enzyme was stimulated by micromolar concentrations of free calcium with maximal activity at 100 microM.
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Affiliation(s)
- G A Lundberg
- Biochemistry Department, University of Oxford, UK
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23
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Abstract
A number of Ca2(+)-activated actin filament severing proteins have been identified in eukaryotic cells of diverse lineages. Gelsolin and villin, with molecular mass of about 80-90 kDa, and severin and fragmin, with molecular mass of about 40 kDa, have been isolated from vertebrates and invertebrates, respectively. We report here a direct comparison of the functional properties of gelsolin and severin, and the finding that the actin filament severing activity of severin, like that of gelsolin, is inhibited by polyphosphoinositides. However, severin does not nucleate actin filament assembly as well as gelsolin. These characteristics are very similar to those ascribed to the NH2-terminal half of gelsolin, supporting the idea that they are evolutionarily related. Regulation of severin by polyphospholipids raises the possibility that it may participate in agonist-stimulated regulation of the actin cytoskeleton in Dictyostelium discoideum.
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Affiliation(s)
- H L Yin
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas
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Patton WF, Dhanak MR, Jacobson BS. Analysis of plasma membrane protein changes in Dictyostelium discoideum during concanavalin A induced receptor redistribution using two-dimensional gel electrophoresis. Electrophoresis 1990; 11:79-85. [PMID: 2156691 DOI: 10.1002/elps.1150110116] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The 127 major polypeptides obtained from the purified plasma membrane of Dictyostelium discoideum were examined using two-dimensional gel electrophoresis and a microcomputer-based videodensitometer. Plasma membrane proteins were analyzed at four discrete stages of concanavalin A induced cell surface capping; (i) the cell surface in the absence of ligand (unbound), (ii) the surface immediately after ligand binding (bound), (iii) the cell surface after receptors had patched (patched) and (iv) the cell surface after receptors had capped (capped). Plasma membranes were obtained at various stages of capping by using a colloidal silica density perturbation technique which immediately immobilized the proteins, preserving their lateral distribution in the bilayer during the isolation. Proteins were characterized with respect to post-translational modification changes resulting from the capping process as well as changes in their association with the plasma membrane fraction. Posttranslational changes of plasma membrane proteins, such as phosphorylation, methylation and proteolytic cleavage, were not observed during the four stages of capping. Myosin heavy chain phosphorylation, however, decreased almost twofold during patching and capping. Actin, which is known to colocalize directly underneath capped receptors did not appear to be recruited to the cap from the cytoplasm.
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Affiliation(s)
- W F Patton
- Department of Biochemistry, University of Massachusetts, Amherst
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Firtel RA, van Haastert PJ, Kimmel AR, Devreotes PN. G protein linked signal transduction pathways in development: dictyostelium as an experimental system. Cell 1989; 58:235-9. [PMID: 2546676 DOI: 10.1016/0092-8674(89)90837-4] [Citation(s) in RCA: 121] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- R A Firtel
- Department of Biology, University of California, San Diego, La Jolla 92093
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Temporal control of autoactivator synthesis and secretion during spontaneous spore germination in Dictyostelium discoideum. Arch Microbiol 1989. [DOI: 10.1007/bf00447010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Kumagai A, Pupillo M, Gundersen R, Miake-Lye R, Devreotes PN, Firtel RA. Regulation and function of G alpha protein subunits in Dictyostelium. Cell 1989; 57:265-75. [PMID: 2539262 DOI: 10.1016/0092-8674(89)90964-1] [Citation(s) in RCA: 200] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have examined the developmental regulation and function of two G alpha protein subunits, G alpha 1 and G alpha 2, from Dictyostelium. G alpha 1 is expressed in vegetative cells through aggregate stages while G alpha 2 is inducible by cAMP pulses and preferentially expressed in aggregation. Our results suggest that G alpha 2 encodes the G alpha protein subunit associated with the cAMP receptor and mediates all known receptor-activated intracellular signal transduction processes, including chemotaxis and gene regulation. G alpha 1 appears to function in both the cell cycle and development. Overexpression of G alpha 1 results in large, multinucleated cells that develop abnormally. The central role that these G alpha proteins play in signal transduction processes and in controlling Dictyostelium development is discussed.
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Affiliation(s)
- A Kumagai
- Department of Biology, University of California, San Diego, La Jolla 92093
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Affiliation(s)
- S H Zigmond
- Biology Department, University of Pennsylvania, Philadelphia
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Segall JE, Gerisch G. Genetic approaches to cytoskeleton function and the control of cell motility. Curr Opin Cell Biol 1989; 1:44-50. [PMID: 2560931 DOI: 10.1016/s0955-0674(89)80035-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- J E Segall
- Max Planck Institute of Biochemistry, Martinsried, Federal Republic of Germany
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30
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Hegemann P, Bruck B. Light-induced stop response inChlamydomonas reinhardtii: Occurrence and adaptation phenomena. ACTA ACUST UNITED AC 1989. [DOI: 10.1002/cm.970140408] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Durkin JP, Chakravarthy B, Franks D, Mealing G, Schwartz JL, Tremblay R, Whitfield JF. Early cellular responses to the activation of a mitogenic/oncogenic viral K-RAS protein. Ann N Y Acad Sci 1988; 551:186-200. [PMID: 3266723 DOI: 10.1111/j.1749-6632.1988.tb22337.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- J P Durkin
- Division of Biological Sciences, National Research Council of Canada, Ottawa
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