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Bai W, Wells ML, Lai WS, Hicks SN, Burkholder AB, Perera L, Kimmel AR, Blackshear PJ. A post-transcriptional regulon controlled by TtpA, the single tristetraprolin family member expressed in Dictyostelium discoideum. Nucleic Acids Res 2021; 49:11920-11937. [PMID: 34718768 DOI: 10.1093/nar/gkab983] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 10/05/2021] [Accepted: 10/12/2021] [Indexed: 12/30/2022] Open
Abstract
Post-transcriptional processes mediated by mRNA binding proteins represent important control points in gene expression. In eukaryotes, mRNAs containing specific AU-rich motifs are regulated by binding of tristetraprolin (TTP) family tandem zinc finger proteins, which promote mRNA deadenylation and decay, partly through interaction of a conserved C-terminal CNOT1 binding (CNB) domain with CCR4-NOT protein complexes. The social ameba Dictyostelium discoideum shared a common ancestor with humans more than a billion years ago, and expresses only one TTP family protein, TtpA, in contrast to three members expressed in humans. Evaluation of ttpA null-mutants identified six transcripts that were consistently upregulated compared to WT during growth and early development. The 3'-untranslated regions (3'-UTRs) of all six 'TtpA-target' mRNAs contained multiple TTP binding motifs (UUAUUUAUU), and one 3'-UTR conferred TtpA post-transcriptional stability regulation to a heterologous mRNA that was abrogated by mutations in the core TTP-binding motifs. All six target transcripts were upregulated to similar extents in a C-terminal truncation mutant, in contrast to less severe effects of analogous mutants in mice. All six target transcripts encoded probable membrane proteins. In Dictyostelium, TtpA may control an 'RNA regulon', where a single RNA binding protein, TtpA, post-transcriptionally co-regulates expression of several functionally related proteins.
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Affiliation(s)
- Wenli Bai
- Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA
| | - Melissa L Wells
- The Signal Transduction Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Wi S Lai
- The Signal Transduction Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Stephanie N Hicks
- The Signal Transduction Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Adam B Burkholder
- Integrative Bioinformatics Support Group, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Lalith Perera
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Alan R Kimmel
- Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA
| | - Perry J Blackshear
- The Signal Transduction Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.,The Departments of Medicine and Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
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Kabra A, Kim LW. Superoxide dismutase C affects Dictyostelium contractile vacuole biogenesis and function. Dev Growth Differ 2020; 62:516-526. [PMID: 33118157 DOI: 10.1111/dgd.12698] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 08/11/2020] [Accepted: 08/12/2020] [Indexed: 01/30/2023]
Abstract
Dictyostelium cells cope with hypo-osmotic stress with a contractile vacuole (CV) system, which consists of one or two vacuoles that cyclically charge and discharge. Uniquely, a F-Actin remodeling dependent minimal mixing of the CV membrane components with the target plasmalemma during the fusion and the dischargement warrants the integrity of the CV bladder for an efficient next CV cycle. The effect of hypo-osmotic stress on F-Actin remodeling activity, however, is currently not well understood. Dictyostelium cells increase the level of intracellular superoxide level in response to hypo-osmotic stress, which in turn activates redox-sensitive Ras proteins, but not Akt, which is one of the Ras downstream targets and a major regulator of F-Actin remodeling. However, Akt is not insulated from the active Ras in cells lacking Superoxide dismutase C (SodC). We report here that sodC- cells were compromised in the CV structure and function and the attenuation of Ras/PI3K/Akt signaling in several independent means significantly improved the compromised CV structure but not the function. Interestingly, when sodC- cells were treated with 5-(N,N-Dimethyl) amiloride hydrochloride (EIPA), an inhibitor of sodium proton exchanger (NHE), both the structure and the function of the CV improved. Thus, a proper CV biogenesis in sodC- cells was insufficient to restore their CV function, which in turn indicates the presence of an additional target for SodC and EIPA that modulates CV function.
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Affiliation(s)
- Adwait Kabra
- Department of Biological Sciences, Florida International University, Miami, Florida, USA
| | - Lou W Kim
- Department of Biological Sciences, Florida International University, Miami, Florida, USA
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3
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Mersha FB, Cortes LK, Luck AN, McClung CM, Ruse CI, Taron CH, Foster JM. Computational and experimental analysis of the glycophosphatidylinositol-anchored proteome of the human parasitic nematode Brugia malayi. PLoS One 2019; 14:e0216849. [PMID: 31513600 PMCID: PMC6742230 DOI: 10.1371/journal.pone.0216849] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 08/20/2019] [Indexed: 12/05/2022] Open
Abstract
Further characterization of essential systems in the parasitic filarial nematode Brugia malayi is needed to better understand its biology, its interaction with its hosts, and to identify critical components that can be exploited to develop novel treatments. The production of glycophosphatidylinositol-anchored proteins (GPI-APs) is essential for eukaryotic cellular and physiological function. In addition, GPI-APs perform many important roles for cells. In this study, we characterized the B. malayi GPI-anchored proteome using both computational and experimental approaches. We used bioinformatic strategies to show the presence or absence of B. malayi GPI-AP biosynthetic pathway genes and to compile a putative B. malayi GPI-AP proteome using available prediction programs. We verified these in silico analyses using proteomics to identify GPI-AP candidates prepared from the surface of intact worms and from membrane enriched extracts. Our study represents the first description of the GPI-anchored proteome in B. malayi and lays the groundwork for further exploration of this essential protein modification as a target for novel anthelmintic therapeutic strategies.
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Affiliation(s)
- Fana B. Mersha
- New England Biolabs, Ipswich MA, United States of America
| | | | - Ashley N. Luck
- New England Biolabs, Ipswich MA, United States of America
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Calcineurin Silencing in Dictyostelium discoideum Leads to Cellular Alterations Affecting Mitochondria, Gene Expression, and Oxidative Stress Response. Protist 2018; 169:584-602. [DOI: 10.1016/j.protis.2018.04.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 04/04/2018] [Accepted: 04/11/2018] [Indexed: 11/18/2022]
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5
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Dunn JD, Bosmani C, Barisch C, Raykov L, Lefrançois LH, Cardenal-Muñoz E, López-Jiménez AT, Soldati T. Eat Prey, Live: Dictyostelium discoideum As a Model for Cell-Autonomous Defenses. Front Immunol 2018; 8:1906. [PMID: 29354124 PMCID: PMC5758549 DOI: 10.3389/fimmu.2017.01906] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 12/13/2017] [Indexed: 12/11/2022] Open
Abstract
The soil-dwelling social amoeba Dictyostelium discoideum feeds on bacteria. Each meal is a potential infection because some bacteria have evolved mechanisms to resist predation. To survive such a hostile environment, D. discoideum has in turn evolved efficient antimicrobial responses that are intertwined with phagocytosis and autophagy, its nutrient acquisition pathways. The core machinery and antimicrobial functions of these pathways are conserved in the mononuclear phagocytes of mammals, which mediate the initial, innate-immune response to infection. In this review, we discuss the advantages and relevance of D. discoideum as a model phagocyte to study cell-autonomous defenses. We cover the antimicrobial functions of phagocytosis and autophagy and describe the processes that create a microbicidal phagosome: acidification and delivery of lytic enzymes, generation of reactive oxygen species, and the regulation of Zn2+, Cu2+, and Fe2+ availability. High concentrations of metals poison microbes while metal sequestration inhibits their metabolic activity. We also describe microbial interference with these defenses and highlight observations made first in D. discoideum. Finally, we discuss galectins, TNF receptor-associated factors, tripartite motif-containing proteins, and signal transducers and activators of transcription, microbial restriction factors initially characterized in mammalian phagocytes that have either homologs or functional analogs in D. discoideum.
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Affiliation(s)
- Joe Dan Dunn
- Faculty of Sciences, Department of Biochemistry, University of Geneva, Geneva, Switzerland
| | - Cristina Bosmani
- Faculty of Sciences, Department of Biochemistry, University of Geneva, Geneva, Switzerland
| | - Caroline Barisch
- Faculty of Sciences, Department of Biochemistry, University of Geneva, Geneva, Switzerland
| | - Lyudmil Raykov
- Faculty of Sciences, Department of Biochemistry, University of Geneva, Geneva, Switzerland
| | - Louise H Lefrançois
- Faculty of Sciences, Department of Biochemistry, University of Geneva, Geneva, Switzerland
| | - Elena Cardenal-Muñoz
- Faculty of Sciences, Department of Biochemistry, University of Geneva, Geneva, Switzerland
| | | | - Thierry Soldati
- Faculty of Sciences, Department of Biochemistry, University of Geneva, Geneva, Switzerland
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Devreotes PN, Bhattacharya S, Edwards M, Iglesias PA, Lampert T, Miao Y. Excitable Signal Transduction Networks in Directed Cell Migration. Annu Rev Cell Dev Biol 2017; 33:103-125. [PMID: 28793794 DOI: 10.1146/annurev-cellbio-100616-060739] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Although directed migration of eukaryotic cells may have evolved to escape nutrient depletion, it has been adopted for an extensive range of physiological events during development and in the adult organism. The subversion of these movements results in disease, such as cancer. Mechanisms of propulsion and sensing are extremely diverse, but most eukaryotic cells move by extending actin-filled protrusions termed macropinosomes, pseudopodia, or lamellipodia or by extension of blebs. In addition to motility, directed migration involves polarity and directional sensing. The hundreds of gene products involved in these processes are organized into networks of parallel and interconnected pathways. Many of these components are activated or inhibited coordinately with stimulation and on each spontaneously extended protrusion. Moreover, these networks display hallmarks of excitability, including all-or-nothing responsiveness and wave propagation. Cellular protrusions result from signal transduction waves that propagate outwardly from an origin and drive cytoskeletal activity. The range of the propagating waves and hence the size of the protrusions can be altered by lowering or raising the threshold for network activation, with larger and wider protrusions favoring gliding or oscillatory behavior over amoeboid migration. Here, we evaluate the variety of models of excitable networks controlling directed migration and outline critical tests. We also discuss the utility of this emerging view in producing cell migration and in integrating the various extrinsic cues that direct migration.
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Affiliation(s)
- Peter N Devreotes
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205;
| | - Sayak Bhattacharya
- Department of Electrical and Computer Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, Maryland 21218
| | - Marc Edwards
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205;
| | - Pablo A Iglesias
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205; .,Department of Electrical and Computer Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, Maryland 21218
| | - Thomas Lampert
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205;
| | - Yuchuan Miao
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205;
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7
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Castillo B, Kim SH, Sharief M, Sun T, Kim LW. SodC modulates ras and PKB signaling in Dictyostelium. Eur J Cell Biol 2016; 96:1-12. [PMID: 27919433 DOI: 10.1016/j.ejcb.2016.11.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 11/16/2016] [Indexed: 01/12/2023] Open
Abstract
We have previously reported that the basal RasG activity is aberrantly high in cells lacking Superoxide dismutase C (SodC). Here we report that other Ras proteins such as RasC and RasD activities are not affected in sodC- cells and mutagenesis studies showed that the presence of the Cys118 in the Ras proteins is essential for the superoxide-mediated activation of Ras proteins in Dictyostelium. In addition to the loss of SodC, lack of extracellular magnesium ions increased the level of intracellular superoxide and active RasG proteins. Aberrantly active Ras proteins in sodC- cells persistently localized at the plasma membrane, but those in wild type cells under magnesium deficient medium exhibited intracellular vesicular localization. Interestingly, the aberrantly activated Ras proteins in wild type cells were largely insulated from their normal downstream events such as Phosphatidylinositol-3,4,5-P3 (PIP3) accumulation, Protein Kinase B (PKB) activation, and PKBs substrates phosphorylation. Intriguingly, however, aberrantly activated Ras proteins in sodC- cells were still engaged in signaling to their downstream targets, and thus excessive PKBs substrates phosphorylation persisted. In summary, we suggest that SodC and RasG proteins are essential part of a novel inhibitory mechanism that discourages oxidatively stressed cells from chemotaxis and thus inhibits the delivery of potentially damaged genome to the next generation.
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Affiliation(s)
- Boris Castillo
- Department of Biological Sciences, Florida International University, Miami, FL 33199, USA
| | - Seon-Hee Kim
- Department of Biological Sciences, Florida International University, Miami, FL 33199, USA
| | - Mujataba Sharief
- Biochemistry PhD Program, Florida International University, Miami, FL 33199, USA
| | - Tong Sun
- Department of Biological Sciences, Florida International University, Miami, FL 33199, USA
| | - Lou W Kim
- Biochemistry PhD Program, Florida International University, Miami, FL 33199, USA.
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8
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Rodriguez Pino M, Castillo B, Kim B, Kim LW. PP2A/B56 and GSK3/Ras suppress PKB activity during Dictyostelium chemotaxis. Mol Biol Cell 2015; 26:4347-57. [PMID: 26424797 PMCID: PMC4666131 DOI: 10.1091/mbc.e14-06-1130] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 09/21/2015] [Indexed: 01/22/2023] Open
Abstract
We have previously shown that the Dictyostelium protein phosphatase 2A regulatory subunit B56, encoded by psrA, modulates Dictyostelium cell differentiation through negatively affecting glycogen synthase kinase 3 (GSK3) function. Our follow-up research uncovered that B56 preferentially associated with GDP forms of RasC and RasD, but not with RasG in vitro, and psrA(-) cells displayed inefficient activation of multiple Ras species, decreased random motility, and inefficient chemotaxis toward cAMP and folic acid gradient. Surprisingly, psrA(-) cells displayed aberrantly high basal and poststimulus phosphorylation of Dictyostelium protein kinase B (PKB) kinase family member PKBR1 and PKB substrates. Expression of constitutively active Ras mutants or inhibition of GSK3 in psrA(-) cells increased activities of both PKBR1 and PKBA, but only the PKBR1 activity was increased in wild-type cells under the equivalent conditions, indicating that either B56- or GSK3-mediated suppressive mechanism is sufficient to maintain low PKBA activity, but both mechanisms are necessary for suppressing PKBR1. Finally, cells lacking RasD or RasC displayed normal PKBR1 regulation under GSK3-inhibiting conditions, indicating that RasC or RasD proteins are essential for GSK3-mediated PKBR1 inhibition. In summary, B56 constitutes inhibitory circuits for PKBA and PKBR1 and thus heavily affects Dictyostelium chemotaxis.
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Affiliation(s)
| | - Boris Castillo
- Department of Biological Sciences, Florida International University, Miami, FL 33199
| | - Bohye Kim
- Department of Biological Sciences, Florida International University, Miami, FL 33199
| | - Lou W Kim
- Department of Biological Sciences, Florida International University, Miami, FL 33199 Biochemistry PhD Program, Florida International University, Miami, FL 33199 Biomolecular Sciences Institutes, Florida International University, Miami, FL 33199
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9
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Rosengarten RD, Santhanam B, Fuller D, Katoh-Kurasawa M, Loomis WF, Zupan B, Shaulsky G. Leaps and lulls in the developmental transcriptome of Dictyostelium discoideum. BMC Genomics 2015; 16:294. [PMID: 25887420 PMCID: PMC4403905 DOI: 10.1186/s12864-015-1491-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 03/26/2015] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Development of the soil amoeba Dictyostelium discoideum is triggered by starvation. When placed on a solid substrate, the starving solitary amoebae cease growth, communicate via extracellular cAMP, aggregate by tens of thousands and develop into multicellular organisms. Early phases of the developmental program are often studied in cells starved in suspension while cAMP is provided exogenously. Previous studies revealed massive shifts in the transcriptome under both developmental conditions and a close relationship between gene expression and morphogenesis, but were limited by the sampling frequency and the resolution of the methods. RESULTS Here, we combine the superior depth and specificity of RNA-seq-based analysis of mRNA abundance with high frequency sampling during filter development and cAMP pulsing in suspension. We found that the developmental transcriptome exhibits mostly gradual changes interspersed by a few instances of large shifts. For each time point we treated the entire transcriptome as single phenotype, and were able to characterize development as groups of similar time points separated by gaps. The grouped time points represented gradual changes in mRNA abundance, or molecular phenotype, and the gaps represented times during which many genes are differentially expressed rapidly, and thus the phenotype changes dramatically. Comparing developmental experiments revealed that gene expression in filter developed cells lagged behind those treated with exogenous cAMP in suspension. The high sampling frequency revealed many genes whose regulation is reproducibly more complex than indicated by previous studies. Gene Ontology enrichment analysis suggested that the transition to multicellularity coincided with rapid accumulation of transcripts associated with DNA processes and mitosis. Later development included the up-regulation of organic signaling molecules and co-factor biosynthesis. Our analysis also demonstrated a high level of synchrony among the developing structures throughout development. CONCLUSIONS Our data describe D. discoideum development as a series of coordinated cellular and multicellular activities. Coordination occurred within fields of aggregating cells and among multicellular bodies, such as mounds or migratory slugs that experience both cell-cell contact and various soluble signaling regimes. These time courses, sampled at the highest temporal resolution to date in this system, provide a comprehensive resource for studies of developmental gene expression.
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Affiliation(s)
- Rafael David Rosengarten
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA.
| | - Balaji Santhanam
- Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA.
| | - Danny Fuller
- Section of Cell and Developmental Biology, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.
| | - Mariko Katoh-Kurasawa
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA.
| | - William F Loomis
- Section of Cell and Developmental Biology, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.
| | - Blaz Zupan
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA.
- Faculty of Computer and Information Science, University of Ljubljana, Trzaska cesta 25, Ljubljana, SI-1001, Slovenia.
| | - Gad Shaulsky
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA.
- Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA.
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10
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Sun T, Kim B, Kim LW. Glycogen Synthase Kinase 3 influences cell motility and chemotaxis by regulating PI3K membrane localization in Dictyostelium. Dev Growth Differ 2013; 55:723-34. [PMID: 24102085 DOI: 10.1111/dgd.12078] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 06/07/2013] [Accepted: 08/13/2013] [Indexed: 11/27/2022]
Abstract
Glycogen Synthase Kinase 3 (GSK3) is a multifunctional kinase involved in diverse cellular activities such as metabolism, differentiation, and morphogenesis. Recent studies showed that GSK3 in Dictyostelium affects chemotaxis via TorC2 pathway and Daydreamer. Now we report that GSK3 affects PI3K membrane localization, of which the mechanism has remained to be fully understood in Dictyostelium. The membrane localization domain (LD) of Phosphatidylinositol-3-kinase 1 (PI3K1) is phosphorylated on serine residues in a GSK3 dependent mechanism and PI3K1-LD exhibited biased membrane localization in gsk3(-) cells compared to the wild type cells. Furthermore, multiple GSK3-phosphorylation consensus sites exist in PI3K1-LD, of which phosphomimetic substitutions restored cAMP induced transient membrane localization of PI3K1-LD in gsk3(-) cells. Serine to alanine substitution mutants of PI3K1-LD, in contrast, displayed constitutive membrane localization in wild type cells. Biochemical analysis revealed that GSK3 dependent serine phosphorylation of PI3K1-LD is constitutive during the course of cAMP stimulation. Together, these data suggest that GSK3 dependent serine phosphorylation is a prerequisite for chemoattractant cAMP induced PI3K membrane localization.
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Affiliation(s)
- Tong Sun
- Department of Biological Sciences, Florida International University, Miami, FL, 33199, USA
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Swaney KF, Huang CH, Devreotes PN. Eukaryotic chemotaxis: a network of signaling pathways controls motility, directional sensing, and polarity. Annu Rev Biophys 2010; 39:265-89. [PMID: 20192768 DOI: 10.1146/annurev.biophys.093008.131228] [Citation(s) in RCA: 359] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Chemotaxis, the directed migration of cells in chemical gradients, is a vital process in normal physiology and in the pathogenesis of many diseases. Chemotactic cells display motility, directional sensing, and polarity. Motility refers to the random extension of pseudopodia, which may be driven by spontaneous actin waves that propagate through the cytoskeleton. Directional sensing is mediated by a system that detects temporal and spatial stimuli and biases motility toward the gradient. Polarity gives cells morphologically and functionally distinct leading and lagging edges by relocating proteins or their activities selectively to the poles. By exploiting the genetic advantages of Dictyostelium, investigators are working out the complex network of interactions between the proteins that have been implicated in the chemotactic processes of motility, directional sensing, and polarity.
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Affiliation(s)
- Kristen F Swaney
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205, USA
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12
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Teo R, Lewis KJ, Forde JE, Ryves WJ, Reddy JV, Rogers BJ, Harwood AJ. Glycogen synthase kinase-3 is required for efficient Dictyostelium chemotaxis. Mol Biol Cell 2010; 21:2788-96. [PMID: 20534815 PMCID: PMC2912363 DOI: 10.1091/mbc.e09-10-0891] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
We present a new role for glycogen synthase kinase (GSK) in the regulation of aggregation and chemotaxis in Dictyostelium. GSK regulates two chemotactic pathways, PIP3 and TORC2; hence, a loss of function of GSK leads to poor chemotaxis, an observation not previously seen when only one chemotactic pathway was targeted. Glycogen synthase kinase-3 (GSK3) is a highly conserved protein kinase that is involved in several important cell signaling pathways and is associated with a range of medical conditions. Previous studies indicated a major role of the Dictyostelium homologue of GSK3 (gskA) in cell fate determination during morphogenesis of the fruiting body; however, transcriptomic and proteomic studies have suggested that GSK3 regulates gene expression much earlier during Dictyostelium development. To investigate a potential earlier role of GskA, we examined the effects of loss of gskA on cell aggregation. We find that cells lacking gskA exhibit poor chemotaxis toward cAMP and folate. Mutants fail to activate two important regulatory signaling pathways, mediated by phosphatidylinositol 3,4,5-trisphosphate (PIP3) and target of rapamycin complex 2 (TORC2), which in combination are required for chemotaxis and cAMP signaling. These results indicate that GskA is required during early stages of Dictyostelium development, in which it is necessary for both chemotaxis and cell signaling.
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Affiliation(s)
- Regina Teo
- Cardiff School of Biosciences, Cardiff University, CF10 3AX Cardiff, United Kingdom.
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13
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Abstract
Both Ras and Nox represent ancient gene families which control a broad range of cellular responses. Both families mediate signals governing motility, differentiation, and proliferation, and both inhabit overlapping subcellular microdomains. Yet little is known of the precise functional relationship between these two ubiquitous families. In this review, we examine the interface where these two large fields meet.
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Affiliation(s)
| | - Lance S. Terada
- Correspondence to: Lance S. Terada; Pulmonary and Critical Care Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390. Fax: 214-648-9104. E-mail:
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