1
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Dynamics of Actin Cytoskeleton and Their Signaling Pathways during Cellular Wound Repair. Cells 2022; 11:cells11193166. [PMID: 36231128 PMCID: PMC9564287 DOI: 10.3390/cells11193166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 09/27/2022] [Accepted: 10/01/2022] [Indexed: 11/17/2022] Open
Abstract
The repair of wounded cell membranes is essential for cell survival. Upon wounding, actin transiently accumulates at the wound site. The loss of actin accumulation leads to cell death. The mechanism by which actin accumulates at the wound site, the types of actin-related proteins participating in the actin remodeling, and their signaling pathways are unclear. We firstly examined how actin accumulates at a wound site in Dictyostelium cells. Actin assembled de novo at the wound site, independent of cortical flow. Next, we searched for actin- and signal-related proteins targeting the wound site. Fourteen of the examined proteins transiently accumulated at different times. Thirdly, we performed functional analyses using gene knockout mutants or specific inhibitors. Rac, WASP, formin, the Arp2/3 complex, profilin, and coronin contribute to the actin dynamics. Finally, we found that multiple signaling pathways related to TORC2, the Elmo/Doc complex, PIP2-derived products, PLA2, and calmodulin are involved in the actin dynamics for wound repair.
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2
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Kuhn J, Lin Y, Devreotes PN. Using Live-Cell Imaging and Synthetic Biology to Probe Directed Migration in Dictyostelium. Front Cell Dev Biol 2021; 9:740205. [PMID: 34676215 PMCID: PMC8523838 DOI: 10.3389/fcell.2021.740205] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 09/08/2021] [Indexed: 12/30/2022] Open
Abstract
For decades, the social amoeba Dictyostelium discoideum has been an invaluable tool for dissecting the biology of eukaryotic cells. Its short growth cycle and genetic tractability make it ideal for a variety of biochemical, cell biological, and biophysical assays. Dictyostelium have been widely used as a model of eukaryotic cell motility because the signaling and mechanical networks which they use to steer and produce forward motion are highly conserved. Because these migration networks consist of hundreds of interconnected proteins, perturbing individual molecules can have subtle effects or alter cell morphology and signaling in major unpredictable ways. Therefore, to fully understand this network, we must be able to quantitatively assess the consequences of abrupt modifications. This ability will allow us better control cell migration, which is critical for development and disease, in vivo. Here, we review recent advances in imaging, synthetic biology, and computational analysis which enable researchers to tune the activity of individual molecules in single living cells and precisely measure the effects on cellular motility and signaling. We also provide practical advice and resources to assist in applying these approaches in Dictyostelium.
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3
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Clapis JR, Fan MJ, Kovarik ML. Supported bilayer membranes for reducing cell adhesion in microfluidic devices. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2021; 13:1535-1540. [PMID: 33690748 DOI: 10.1039/d0ay01992e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The high surface area-to-volume ratio of microfluidic channels makes them susceptible to fouling and clogging when used for biological analyses, including cell-based assays. We evaluated the role of electrostatic and van der Waals interactions in cell adhesion in PDMS microchannels coated with supported lipid bilayers and identified conditions that resulted in minimal cell adhesion. For low ionic strength buffer, optimum results were obtained for a zwitterionic coating of pure egg phosphatidylcholine; for a rich growth medium, the best results were obtained for zwitterionic bilayers or those with slight negative or moderate positive charge from the incorporation of 5-10 mol% egg phosphatidylglycerol or 30 mol% ethylphosphocholine. In both solutions, the presence of 10 g L-1 glucose in the cell suspension reduced cell adhesion. Under optimum conditions, all cells were consistently removed from the channels, demonstrating the utility of these coatings for whole-cell microfluidic assays. These results provide practical information for immediate application and suggest future research areas on cell-lipid interactions.
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Affiliation(s)
- Julia R Clapis
- Department of Chemistry, Trinity College, 300 Summit St., Hartford, CT 06106, USA.
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4
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Bodinier R, Sabra A, Leiba J, Marchetti A, Lamrabet O, Ayadi I, Filić V, Kawata T, Weber I, Cosson P. Role of LrrkA in the Control of Phagocytosis and Cell Motility in Dictyostelium discoideum. Front Cell Dev Biol 2021; 9:629200. [PMID: 33763419 PMCID: PMC7982419 DOI: 10.3389/fcell.2021.629200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 02/15/2021] [Indexed: 11/21/2022] Open
Abstract
LrrkA is a Dictyostelium discoideum kinase with leucine-rich repeats. LrrkA stimulates Kil2 and intra-phagosomal killing of ingested bacteria in response to folate. In this study, we show that genetic inactivation of lrrkA also causes a previously unnoticed phenotype: lrrkA KO cells exhibit enhanced phagocytosis and cell motility compared to parental cells. This phenotype is cell autonomous, is reversible upon re-expression of LrrkA, and is not due to an abnormal response to inhibitory quorum-sensing factors secreted by D. discoideum in its medium. In addition, folate increases motility in parental D. discoideum cells, but not in lrrkA KO cells, suggesting that LrrkA plays a pivotal role in the cellular response to folate. On the contrary, lrrkA KO cells regulate gene transcription in response to folate in a manner indistinguishable from parental cells. Overall, based on analysis of mutant phenotypes, we identify gene products that participate in the control of intracellular killing, cell motility, and gene transcription in response to folate. These observations reveal a mechanism by which D. discoideum encountering bacterially-secreted folate can migrate, engulf, and kill bacteria more efficiently.
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Affiliation(s)
- Romain Bodinier
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Ayman Sabra
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Jade Leiba
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Anna Marchetti
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Otmane Lamrabet
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Imen Ayadi
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Vedrana Filić
- Division of Molecular Biology, Ruder Boskovic Institute, Zagreb, Croatia
| | - Takefumi Kawata
- Department of Biology, Faculty of Science, Toho University, Tokyo, Japan
| | - Igor Weber
- Division of Molecular Biology, Ruder Boskovic Institute, Zagreb, Croatia
| | - Pierre Cosson
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
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5
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Abstract
Intracellular proliferation of Legionella pneumophila within a vacuole in human alveolar macrophages is essential for manifestation of Legionnaires’ pneumonia. Intravacuolar growth of the pathogen is totally dependent on remodeling the L. pneumophila-containing vacuole (LCV) by the ER and on its evasion of the endosomal-lysosomal degradation pathway. Diversion of the Legionella pneumophila-containing vacuole (LCV) from the host endosomal-lysosomal degradation pathway is one of the main virulence features essential for manifestation of Legionnaires’ pneumonia. Many of the ∼350 Dot/Icm-injected effectors identified in L. pneumophila have been shown to interfere with various host pathways and processes, but no L. pneumophila effector has ever been identified to be indispensable for lysosomal evasion. While most single effector mutants of L. pneumophila do not exhibit a defective phenotype within macrophages, we show that the MavE effector is essential for intracellular growth of L. pneumophila in human monocyte-derived macrophages (hMDMs) and amoebae and for intrapulmonary proliferation in mice. The mavE null mutant fails to remodel the LCV with endoplasmic reticulum (ER)-derived vesicles and is trafficked to the lysosomes where it is degraded, similar to formalin-killed bacteria. During infection of hMDMs, the MavE effector localizes to the poles of the LCV membrane. The crystal structure of MavE, resolved to 1.8 Å, reveals a C-terminal transmembrane helix, three copies of tyrosine-based sorting motifs, and an NPxY eukaryotic motif, which binds phosphotyrosine-binding domains present on signaling and adaptor eukaryotic proteins. Two point mutations within the NPxY motif result in attenuation of L. pneumophila in both hMDMs and amoeba. The substitution defects of P78 and D64 are associated with failure of vacuoles harboring the mutant to be remodeled by the ER and results in fusion of the vacuole to the lysosomes leading to bacterial degradation. Therefore, the MavE effector of L. pneumophila is indispensable for phagosome biogenesis and lysosomal evasion.
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van Haastert PJM. Unified control of amoeboid pseudopod extension in multiple organisms by branched F-actin in the front and parallel F-actin/myosin in the cortex. PLoS One 2020; 15:e0243442. [PMID: 33296414 PMCID: PMC7725310 DOI: 10.1371/journal.pone.0243442] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 11/23/2020] [Indexed: 02/06/2023] Open
Abstract
The trajectory of moving eukaryotic cells depends on the kinetics and direction of extending pseudopods. The direction of pseudopods has been well studied to unravel mechanisms for chemotaxis, wound healing and inflammation. However, the kinetics of pseudopod extension-when and why do pseudopods start and stop- is equally important, but is largely unknown. Here the START and STOP of about 4000 pseudopods was determined in four different species, at four conditions and in nine mutants (fast amoeboids Dictyostelium and neutrophils, slow mesenchymal stem cells, and fungus B.d. chytrid with pseudopod and a flagellum). The START of a first pseudopod is a random event with a probability that is species-specific (23%/s for neutrophils). In all species and conditions, the START of a second pseudopod is strongly inhibited by the extending first pseudopod, which depends on parallel filamentous actin/myosin in the cell cortex. Pseudopods extend at a constant rate by polymerization of branched F-actin at the pseudopod tip, which requires the Scar complex. The STOP of pseudopod extension is induced by multiple inhibitory processes that evolve during pseudopod extension and mainly depend on the increasing size of the pseudopod. Surprisingly, no differences in pseudopod kinetics are detectable between polarized, unpolarized or chemotactic cells, and also not between different species except for small differences in numerical values. This suggests that the analysis has uncovered the fundament of cell movement with distinct roles for stimulatory branched F-actin in the protrusion and inhibitory parallel F-actin in the contractile cortex.
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Cytotoxicity and Mitochondrial Dysregulation Caused by α-Synuclein in Dictyostelium discoideum. Cells 2020; 9:cells9102289. [PMID: 33066427 PMCID: PMC7602147 DOI: 10.3390/cells9102289] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 10/09/2020] [Accepted: 10/12/2020] [Indexed: 12/13/2022] Open
Abstract
Alpha synuclein has been linked to both sporadic and familial forms of Parkinson’s disease (PD) and is the most abundant protein in Lewy bodies a hallmark of Parkinson’s disease. The function of this protein and the molecular mechanisms underlying its toxicity are still unclear, but many studies have suggested that the mechanism of α-synuclein toxicity involves alterations to mitochondrial function. Here we expressed human α-synuclein and two PD-causing α-synuclein mutant proteins (with a point mutation, A53T, and a C-terminal 20 amino acid truncation) in the eukaryotic model Dictyostelium discoideum. Mitochondrial disease has been well studied in D. discoideum and, unlike in mammals, mitochondrial dysfunction results in a clear set of defective phenotypes. These defective phenotypes are caused by the chronic hyperactivation of the cellular energy sensor, AMP-activated protein kinase (AMPK). Expression of α-synuclein wild type and mutant forms was toxic to the cells and mitochondrial function was dysregulated. Some but not all of the defective phenotypes could be rescued by down regulation of AMPK revealing both AMPK-dependent and -independent mechanisms. Importantly, we also show that the C-terminus of α-synuclein is required and sufficient for the localisation of the protein to the cell cortex in D. discoideum.
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Bosmani C, Leuba F, Hanna N, Bach F, Burdet F, Pagni M, Hagedorn M, Soldati T. Vacuolins and myosin VII are required for phagocytic uptake and phagosomal membrane recycling in Dictyostelium discoideum. J Cell Sci 2020; 133:jcs242974. [PMID: 32482795 DOI: 10.1242/jcs.242974] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 05/18/2020] [Indexed: 12/17/2022] Open
Abstract
Flotillins are lipid raft residents involved in membrane trafficking and recycling of plasma membrane proteins. Dictyostelium discoideum uses phagocytosis to kill, digest and feed on bacteria. It possesses three flotillin-like vacuolins that are strongly associated with membranes and that gradually accumulate on maturing phagosomes. Absence of vacuolins reduced adhesion and particle recognition resulting in a drastic reduction in the uptake of various types of particles. This was caused by a block in the recycling of plasma membrane components and the absence of their specific cortex-associated proteins. In addition, absence of vacuolins also impaired phagolysosome biogenesis, without significantly impacting killing and digestion of a range of bacteria. Strikingly, both absence and overexpression of vacuolins induced a strong downregulation of myosin VII (also known as MyoI) expression, as well as its binding partner talin A. Episomal expression of myosin VII fully rescued defects in uptake and adhesion but not in phagosome maturation. These results suggest a dual role for vacuolins: a novel mechanism involving membrane microdomains and myosin VII-talin A in clustering phagosomal receptors and adhesion molecules at the plasma membrane, and a role in phagolysosomal biogenesis.
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Affiliation(s)
- Cristina Bosmani
- Départment de Biochimie, Faculté des Sciences, Université de Genève, CH-1205 Geneva, Switzerland
| | - Florence Leuba
- Départment de Biochimie, Faculté des Sciences, Université de Genève, CH-1205 Geneva, Switzerland
| | - Nabil Hanna
- Départment de Biochimie, Faculté des Sciences, Université de Genève, CH-1205 Geneva, Switzerland
| | - Frauke Bach
- Section Parasitology, Bernhard Nocht Institute for Tropical Medicine, D-20359 Hamburg, Germany
| | - Frédéric Burdet
- Vital-IT, Swiss Institute of Bioinformatics, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Marco Pagni
- Vital-IT, Swiss Institute of Bioinformatics, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Monica Hagedorn
- Section Parasitology, Bernhard Nocht Institute for Tropical Medicine, D-20359 Hamburg, Germany
| | - Thierry Soldati
- Départment de Biochimie, Faculté des Sciences, Université de Genève, CH-1205 Geneva, Switzerland
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9
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Paschke P, Knecht DA, Williams TD, Thomason PA, Insall RH, Chubb JR, Kay RR, Veltman DM. Genetic Engineering of Dictyostelium discoideum Cells Based on Selection and Growth on Bacteria. J Vis Exp 2019:58981. [PMID: 30735174 PMCID: PMC7039707 DOI: 10.3791/58981] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Dictyostelium discoideum is an intriguing model organism for the study of cell differentiation processes during development, cell signaling, and other important cellular biology questions. The technologies available to genetically manipulate Dictyostelium cells are well-developed. Transfections can be performed using different selectable markers and marker re-cycling, including homologous recombination and insertional mutagenesis. This is supported by a well-annotated genome. However, these approaches are optimized for axenic cell lines growing in liquid cultures and are difficult to apply to non-axenic wild-type cells, which feed only on bacteria. The mutations that are present in axenic strains disturb Ras signaling, causing excessive macropinocytosis required for feeding, and impair cell migration, which confounds the interpretation of signal transduction and chemotaxis experiments in those strains. Earlier attempts to genetically manipulate non-axenic cells have lacked efficiency and required complex experimental procedures. We have developed a simple transfection protocol that, for the first time, overcomes these limitations. Those series of large improvements to Dictyostelium molecular genetics allow wild-type cells to be manipulated as easily as standard laboratory strains. In addition to the advantages for studying uncorrupted signaling and motility processes, mutants that disrupt macropinocytosis-based growth can now be readily isolated. Furthermore, the entire transfection workflow is greatly accelerated, with recombinant cells that can be generated in days rather than weeks. Another advantage is that molecular genetics can further be performed with freshly isolated wild-type Dictyostelium samples from the environment. This can help to extend the scope of approaches used in these research areas.
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Affiliation(s)
| | - David A Knecht
- Department of Molecular and Cell Biology, University of Connecticut
| | | | | | | | - Jonathan R Chubb
- MRC Laboratory for Molecular Cell Biology, University College London; Department of Cell and Developmental Biology, University College London
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10
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Batsios P, Ishikawa-Ankerhold HC, Roth H, Schleicher M, Wong CCL, Müller-Taubenberger A. Ate1-mediated posttranslational arginylation affects substrate adhesion and cell migration in Dictyostelium discoideum. Mol Biol Cell 2018; 30:453-466. [PMID: 30586322 PMCID: PMC6594445 DOI: 10.1091/mbc.e18-02-0132] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The highly conserved enzyme arginyl-tRNA-protein transferase (Ate1) mediates arginylation, a posttranslational modification that is only incompletely understood at its molecular level. To investigate whether arginylation affects actin-dependent processes in a simple model organism, Dictyostelium discoideum, we knocked out the gene encoding Ate1 and characterized the phenotype of ate1-null cells. Visualization of actin cytoskeleton dynamics by live-cell microscopy indicated significant changes in comparison to wild-type cells. Ate1-null cells were almost completely lacking focal actin adhesion sites at the substrate-attached surface and were only weakly adhesive. In two-dimensional chemotaxis assays toward folate or cAMP, the motility of ate1-null cells was increased. However, in three-dimensional chemotaxis involving more confined conditions, the motility of ate1-null cells was significantly reduced. Live-cell imaging showed that GFP-tagged Ate1 rapidly relocates to sites of newly formed actin-rich protrusions. By mass spectrometric analysis, we identified four arginylation sites in the most abundant actin isoform of Dictyostelium, in addition to arginylation sites in other actin isoforms and several actin-binding proteins. In vitro polymerization assays with actin purified from ate1-null cells revealed a diminished polymerization capacity in comparison to wild-type actin. Our data indicate that arginylation plays a crucial role in the regulation of cytoskeletal activities.
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Affiliation(s)
- Petros Batsios
- Department of Cell Biology (Anatomy III), Ludwig Maximilian University of Munich, 82152 Planegg-Martinsried, Germany
| | - Hellen C Ishikawa-Ankerhold
- Department of Cell Biology (Anatomy III), Ludwig Maximilian University of Munich, 82152 Planegg-Martinsried, Germany
| | - Heike Roth
- Department of Cell Biology (Anatomy III), Ludwig Maximilian University of Munich, 82152 Planegg-Martinsried, Germany
| | - Michael Schleicher
- Department of Cell Biology (Anatomy III), Ludwig Maximilian University of Munich, 82152 Planegg-Martinsried, Germany
| | - Catherine C L Wong
- National Center for Protein Science Shanghai, Institute of Biochemistry and Cell Biology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Annette Müller-Taubenberger
- Department of Cell Biology (Anatomy III), Ludwig Maximilian University of Munich, 82152 Planegg-Martinsried, Germany
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11
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Sattler N, Bosmani C, Barisch C, Guého A, Gopaldass N, Dias M, Leuba F, Bruckert F, Cosson P, Soldati T. Functions of the Dictyostelium LIMP-2 and CD36 homologues in bacteria uptake, phagolysosome biogenesis and host cell defence. J Cell Sci 2018; 131:jcs218040. [PMID: 30054386 DOI: 10.1242/jcs.218040] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 07/17/2018] [Indexed: 12/17/2023] Open
Abstract
Phagocytic cells take up, kill and digest microbes by a process called phagocytosis. To this end, these cells bind the particle, rearrange their actin cytoskeleton, and orchestrate transport of digestive factors to the particle-containing phagosome. The mammalian lysosomal membrane protein LIMP-2 (also known as SCARB2) and CD36, members of the class B of scavenger receptors, play a crucial role in lysosomal enzyme trafficking and uptake of mycobacteria, respectively, and generally in host cell defences against intracellular pathogens. Here, we show that the Dictyostelium discoideum LIMP-2 homologue LmpA regulates phagocytosis and phagolysosome biogenesis. The lmpA knockdown mutant is highly affected in actin-dependent processes, such as particle uptake, cellular spreading and motility. Additionally, the cells are severely impaired in phagosomal acidification and proteolysis, likely explaining the higher susceptibility to infection with the pathogenic bacterium Mycobacterium marinum, a close cousin of the human pathogen Mycobacterium tuberculosis Furthermore, we bring evidence that LmpB is a functional homologue of CD36 and specifically mediates uptake of mycobacteria. Altogether, these data indicate a role for LmpA and LmpB, ancestors of the family of which LIMP-2 and CD36 are members, in lysosome biogenesis and host cell defence.
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Affiliation(s)
- Natascha Sattler
- Départment de Biochimie, Faculté des Sciences, Université de Genève, Sciences II, 30 quai Ernest Ansermet, CH-1211 Genève-4, Switzerland
| | - Cristina Bosmani
- Départment de Biochimie, Faculté des Sciences, Université de Genève, Sciences II, 30 quai Ernest Ansermet, CH-1211 Genève-4, Switzerland
| | - Caroline Barisch
- Départment de Biochimie, Faculté des Sciences, Université de Genève, Sciences II, 30 quai Ernest Ansermet, CH-1211 Genève-4, Switzerland
| | - Aurélie Guého
- Départment de Biochimie, Faculté des Sciences, Université de Genève, Sciences II, 30 quai Ernest Ansermet, CH-1211 Genève-4, Switzerland
| | - Navin Gopaldass
- Départment de Biochimie, Faculté des Sciences, Université de Genève, Sciences II, 30 quai Ernest Ansermet, CH-1211 Genève-4, Switzerland
| | - Marco Dias
- Department of Cell Physiology and Metabolism, Centre Médical Universitaire, University of Geneva, 1 rue Michel Servet, CH-1211 Geneva 4, Switzerland
| | - Florence Leuba
- Départment de Biochimie, Faculté des Sciences, Université de Genève, Sciences II, 30 quai Ernest Ansermet, CH-1211 Genève-4, Switzerland
| | - Franz Bruckert
- Laboratoire des Matériaux et du Génie Physique (LMGP), Grenoble Institute of Technology, 3 parvis Louis Néel, BP 257, 38016 Grenoble cedex 1, France
| | - Pierre Cosson
- Department of Cell Physiology and Metabolism, Centre Médical Universitaire, University of Geneva, 1 rue Michel Servet, CH-1211 Geneva 4, Switzerland
| | - Thierry Soldati
- Départment de Biochimie, Faculté des Sciences, Université de Genève, Sciences II, 30 quai Ernest Ansermet, CH-1211 Genève-4, Switzerland
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12
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Paschke P, Knecht DA, Silale A, Traynor D, Williams TD, Thomason PA, Insall RH, Chubb JR, Kay RR, Veltman DM. Rapid and efficient genetic engineering of both wild type and axenic strains of Dictyostelium discoideum. PLoS One 2018; 13:e0196809. [PMID: 29847546 PMCID: PMC5976153 DOI: 10.1371/journal.pone.0196809] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 03/15/2018] [Indexed: 02/03/2023] Open
Abstract
Dictyostelium has a mature technology for molecular-genetic manipulation based around transfection using several different selectable markers, marker re-cycling, homologous recombination and insertional mutagenesis, all supported by a well-annotated genome. However this technology is optimized for mutant, axenic cells that, unlike non-axenic wild type, can grow in liquid medium. There is a pressing need for methods to manipulate wild type cells and ones with defects in macropinocytosis, neither of which can grow in liquid media. Here we present a panel of molecular genetic techniques based on the selection of Dictyostelium transfectants by growth on bacteria rather than liquid media. As well as extending the range of strains that can be manipulated, these techniques are faster than conventional methods, often giving usable numbers of transfected cells within a few days. The methods and plasmids described here allow efficient transfection with extrachromosomal vectors, as well as chromosomal integration at a 'safe haven' for relatively uniform cell-to-cell expression, efficient gene knock-in and knock-out and an inducible expression system. We have thus created a complete new system for the genetic manipulation of Dictyostelium cells that no longer requires cell feeding on liquid media.
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Affiliation(s)
- Peggy Paschke
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - David A. Knecht
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, United States of America
| | | | - David Traynor
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | | | - Peter A. Thomason
- Cancer Research UK Beatson Institute Glasgow, Glasgow, United Kingdom
| | - Robert H. Insall
- Cancer Research UK Beatson Institute Glasgow, Glasgow, United Kingdom
| | - Jonathan R. Chubb
- MRC Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Robert R. Kay
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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Jahan MGS, Yumura S. Traction force and its regulation during cytokinesis in Dictyostelium cells. Eur J Cell Biol 2017. [PMID: 28633918 DOI: 10.1016/j.ejcb.2017.06.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Cytokinesis is the final stage of cell division. Dictyostelium cells have multiple modes of cytokinesis, including cytokinesis A, B and C. Cytokinesis A is a conventional mode, which depends on myosin II in the contractile ring. Myosin II null cells divide depending on substratum-attachment (cytokinesis B) or in a multi-polar fashion independent of the cell cycle (cytokinesis C). We investigated the traction stress exerted by dividing cells in the three different modes using traction force microscopy. In all cases, the traction forces were directed inward from both poles. Interestingly, the traction stress of cytokinesis A was the smallest of the three modes. Latrunculin B, an inhibitor of actin polymerization, completely diminished the traction stress of dividing cells, but blebbistatin, an inhibitor of myosin II ATPase, increased the traction stress. Myosin II is proposed to contribute to the detachment of cell body from the substratum. When the cell-substratum attachment was artificially strengthened by a poly-lysine coating, wild type cells increased their traction stress in contrast to myosin II null and other cytokinesis-deficient mutant cells, which suggests that wild type cells may increase their own power to conduct their cytokinesis. The cytokinesis-deficient mutants frequently divided unequally, whereas wild type cells divided equally. A traction stress imbalance between two daughter halves was correlated with cytokinesis failure. We discuss the regulation of cell shape changes during cell division through mechanosensing.
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Affiliation(s)
- Md Golam Sarowar Jahan
- Department of Functional Molecular Biology, Graduate School of Medicine, Yamaguchi University, Yamaguchi, Japan; Department of Biochemistry and Molecular Biology, University of Rajshahi, Rajshahi, Bangladesh
| | - Shigehiko Yumura
- Department of Functional Molecular Biology, Graduate School of Medicine, Yamaguchi University, Yamaguchi, Japan.
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Dias M, Brochetta C, Marchetti A, Bodinier R, Brückert F, Cosson P. Role of SpdA in Cell Spreading and Phagocytosis in Dictyostelium. PLoS One 2016; 11:e0160376. [PMID: 27512991 PMCID: PMC4981364 DOI: 10.1371/journal.pone.0160376] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 07/18/2016] [Indexed: 11/18/2022] Open
Abstract
Dictyostelium discoideum is a widely used model to study molecular mechanisms controlling cell adhesion, cell spreading on a surface, and phagocytosis. In this study we isolated and characterize a new mutant created by insertion of a mutagenic vector in the heretofore uncharacterized spdA gene. SpdA-ins mutant cells produce an altered, slightly shortened version of the SpdA protein. They spread more efficiently than WT cells when allowed to adhere to a glass substrate, and phagocytose particles more efficiently. On the contrary, a functional spdA knockout mutant where a large segment of the gene was deleted phagocytosed less efficiently and spread less efficiently on a substrate. These phenotypes were highly dependent on the cellular density, and were most visible at high cell densities, where secreted quorum-sensing factors inhibiting cell motility, spreading and phagocytosis are most active. These results identify the involvement of SpdA in the control of cell spreading and phagocytosis. The underlying molecular mechanisms, as well as the exact link between SpdA and cell spreading, remain to be established.
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Affiliation(s)
- Marco Dias
- Department for Cell Physiology and Metabolism, Faculty of Medicine, Geneva University, Geneva, Switzerland
| | - Cristiana Brochetta
- Department for Cell Physiology and Metabolism, Faculty of Medicine, Geneva University, Geneva, Switzerland
| | - Anna Marchetti
- Department for Cell Physiology and Metabolism, Faculty of Medicine, Geneva University, Geneva, Switzerland
| | - Romain Bodinier
- Department for Cell Physiology and Metabolism, Faculty of Medicine, Geneva University, Geneva, Switzerland
| | - Franz Brückert
- Laboratoire des Matériaux et du Génie Physique (LMGP), UMR CNRS-Grenoble INP5628 Université Grenoble Alpes, 3 parvis Louis Néel, BP 257, Grenoble cedex 1, France
| | - Pierre Cosson
- Department for Cell Physiology and Metabolism, Faculty of Medicine, Geneva University, Geneva, Switzerland
- * E-mail:
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Plak K, Pots H, Van Haastert PJM, Kortholt A. Direct Interaction between TalinB and Rap1 is necessary for adhesion of Dictyostelium cells. BMC Cell Biol 2016; 17:1. [PMID: 26744136 PMCID: PMC4861126 DOI: 10.1186/s12860-015-0078-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Accepted: 12/22/2015] [Indexed: 11/10/2022] Open
Abstract
Background The small G-protein Rap1 is an important regulator of cellular adhesion in Dictyostelium, however so far the downstream signalling pathways for cell adhesion are not completely characterized. In mammalian cells talin is crucial for adhesion and Rap1 was shown to be a key regulator of talin signalling. Results In a proteomic screen we identified TalinB as a potential Rap1 effector in Dictyostelium. In subsequent pull-down experiments we demonstrate that the Ras association (RA) domain of TalinB interacts specifically with active Rap1. Studies with a mutated RA domain revealed that the RA domain is essential for TalinB-Rap1 interaction, and that this interaction contributes to cell-substrate adhesion during single-celled growth and is crucial for cell-cell adhesion during multicellular development. Conclusions Dictyostelium Rap1 directly binds to TalinB via the conserved RA domain. This interaction is critical for adhesion, which becomes essential for high adhesive force demanding processes, like morphogenesis during multicellular development of Dictyostelium. In mammalian cells the established Rap1-talin interaction is indirect and acts through the scaffold protein - RIAM. Interestingly, direct binding of mouse Rap1 to the RA domain of Talin1 has recently been demonstrated. Electronic supplementary material The online version of this article (doi:10.1186/s12860-015-0078-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Katarzyna Plak
- Department of Cell Biochemistry, University of Groningen, Nijenborgh 7, Groningen, AG 9747, The Netherlands. .,Current address: BIOTEC center, Technical University Dresden, Tatzberg 47/49, 01307, Dresden, Germany.
| | - Henderikus Pots
- Department of Cell Biochemistry, University of Groningen, Nijenborgh 7, Groningen, AG 9747, The Netherlands.
| | - Peter J M Van Haastert
- Department of Cell Biochemistry, University of Groningen, Nijenborgh 7, Groningen, AG 9747, The Netherlands.
| | - Arjan Kortholt
- Department of Cell Biochemistry, University of Groningen, Nijenborgh 7, Groningen, AG 9747, The Netherlands.
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Cell substratum adhesion during early development of Dictyostelium discoideum. PLoS One 2014; 9:e106574. [PMID: 25247557 PMCID: PMC4172474 DOI: 10.1371/journal.pone.0106574] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 07/31/2014] [Indexed: 11/30/2022] Open
Abstract
Vegetative and developed amoebae of Dictyostelium discoideum gain traction and move rapidly on a wide range of substrata without forming focal adhesions. We used two independent assays to quantify cell-substrate adhesion in mutants and in wild-type cells as a function of development. Using a microfluidic device that generates a range of hydrodynamic shear stress, we found that substratum adhesion decreases at least 10 fold during the first 6 hr of development of wild type cells. This result was confirmed using a single-cell assay in which cells were attached to the cantilever of an atomic force probe and allowed to adhere to untreated glass surfaces before being retracted. Both of these assays showed that the decrease in substratum adhesion was dependent on the cAMP receptor CAR1 which triggers development. Vegetative cells missing talin as the result of a mutation in talA exhibited slightly reduced adhesive properties compared to vegetative wild-type cells. In sharp contrast to wild-type cells, however, these talA mutant cells did not show further reduction of adhesion during development such that after 5 hr of development they were significantly more adhesive than developed wild type cells. In addition, both assays showed that substrate adhesion was reduced in 0 hr cells when the actin cytoskeleton was disrupted by latrunculin. Consistent with previous observations, substrate adhesion was also reduced in 0 hr cells lacking the membrane proteins SadA or SibA as the result of mutations in sadA or sibA. However, there was no difference in the adhesion properties between wild type AX3 cells and these mutant cells after 6 hr of development, suggesting that neither SibA nor SadA play an essential role in substratum adhesion during aggregation. Our results provide a quantitative framework for further studies of cell substratum adhesion in Dictyostelium.
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17
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Dubravcic D, van Baalen M, Nizak C. An evolutionarily significant unicellular strategy in response to starvation in Dictyostelium social amoebae. F1000Res 2014; 3:133. [PMID: 25309731 PMCID: PMC4184345 DOI: 10.12688/f1000research.4218.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/01/2014] [Indexed: 02/04/2024] Open
Abstract
The social amoeba Dictyostelium discoideum is widely studied for its multicellular development program as a response to starvation. Aggregates of up to 10 (6) cells form fruiting bodies containing (i) dormant spores (~80%) that can persist for months in the absence of nutrients, and (ii) dead stalk cells (~20%) that promote the dispersion of the spores towards nutrient-rich areas. It is often overlooked that not all cells aggregate upon starvation. Using a new quantitative approach based on time-lapse fluorescence microscopy and a low ratio of reporting cells, we have quantified this fraction of non-aggregating cells. In realistic starvation conditions, up to 15% of cells do not aggregate, which makes this third cell fate a significant component of the population-level response of social amoebae to starvation. Non-aggregating cells have an advantage over cells in aggregates since they resume growth earlier upon arrival of new nutrients, but have a shorter lifespan under prolonged starvation. We find that phenotypic heterogeneities linked to cell nutritional state bias the representation of cells in the aggregating vs. non-aggregating fractions, and thus affect population partitioning. Next, we report that the fraction of non-aggregating cells depends on genetic factors that regulate the timing of starvation, signal sensing efficiency and aggregation efficiency. In addition, interactions between clones in mixtures of non-isogenic cells affect the partitioning of each clone into both fractions. We further build a numerical model to test the evolutionary significance of the non-aggregating cell fraction. The partitioning of cells into aggregating and non-aggregating fractions is optimal in fluctuating environments with an unpredictable duration of starvation periods. Our study highlights the unicellular component of the response of social amoebae to starvation, and thus extends its evolutionary and ecological framework.
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Affiliation(s)
- Darja Dubravcic
- CNRS, LIPHY, F-38000 Grenoble, France
- Laboratory of Ecology and Evolution, CNRS UMR7625, Ecole Normale Supérieure, Université Pierre et Marie Curie, Paris Universitas, CNRS, Paris, France
| | - Minus van Baalen
- Laboratory of Ecology and Evolution, CNRS UMR7625, Ecole Normale Supérieure, Université Pierre et Marie Curie, Paris Universitas, CNRS, Paris, France
| | - Clément Nizak
- CNRS, LIPHY, F-38000 Grenoble, France
- Laboratory of Biochemistry, UMR 8231 ESPCI ParisTech/CNRS, PSL Research University, Paris, France
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18
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Dubravcic D, van Baalen M, Nizak C. An evolutionarily significant unicellular strategy in response to starvation in Dictyostelium social amoebae. F1000Res 2014; 3:133. [PMID: 25309731 PMCID: PMC4184345 DOI: 10.12688/f1000research.4218.2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/01/2014] [Indexed: 11/20/2022] Open
Abstract
The social amoeba Dictyostelium discoideum is widely studied for its multicellular development program as a response to starvation. Aggregates of up to 10 (6) cells form fruiting bodies containing (i) dormant spores (~80%) that can persist for months in the absence of nutrients, and (ii) dead stalk cells (~20%) that promote the dispersion of the spores towards nutrient-rich areas. It is often overlooked that not all cells aggregate upon starvation. Using a new quantitative approach based on time-lapse fluorescence microscopy and a low ratio of reporting cells, we have quantified this fraction of non-aggregating cells. In realistic starvation conditions, up to 15% of cells do not aggregate, which makes this third cell fate a significant component of the population-level response of social amoebae to starvation. Non-aggregating cells have an advantage over cells in aggregates since they resume growth earlier upon arrival of new nutrients, but have a shorter lifespan under prolonged starvation. We find that phenotypic heterogeneities linked to cell nutritional state bias the representation of cells in the aggregating vs. non-aggregating fractions, and thus affect population partitioning. Next, we report that the fraction of non-aggregating cells depends on genetic factors that regulate the timing of starvation, signal sensing efficiency and aggregation efficiency. In addition, interactions between clones in mixtures of non-isogenic cells affect the partitioning of each clone into both fractions. We further build a numerical model to test the evolutionary significance of the non-aggregating cell fraction. The partitioning of cells into aggregating and non-aggregating fractions is optimal in fluctuating environments with an unpredictable duration of starvation periods. Our study highlights the unicellular component of the response of social amoebae to starvation, and thus extends its evolutionary and ecological framework.
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Affiliation(s)
- Darja Dubravcic
- CNRS, LIPHY, F-38000 Grenoble, France ; Laboratory of Ecology and Evolution, CNRS UMR7625, Ecole Normale Supérieure, Université Pierre et Marie Curie, Paris Universitas, CNRS, Paris, France
| | - Minus van Baalen
- Laboratory of Ecology and Evolution, CNRS UMR7625, Ecole Normale Supérieure, Université Pierre et Marie Curie, Paris Universitas, CNRS, Paris, France
| | - Clément Nizak
- CNRS, LIPHY, F-38000 Grenoble, France ; Laboratory of Biochemistry, UMR 8231 ESPCI ParisTech/CNRS, PSL Research University, Paris, France
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Moving towards a paradigm: common mechanisms of chemotactic signaling in Dictyostelium and mammalian leukocytes. Cell Mol Life Sci 2014; 71:3711-47. [PMID: 24846395 DOI: 10.1007/s00018-014-1638-8] [Citation(s) in RCA: 153] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 04/24/2014] [Accepted: 04/29/2014] [Indexed: 12/31/2022]
Abstract
Chemotaxis, or directed migration of cells along a chemical gradient, is a highly coordinated process that involves gradient sensing, motility, and polarity. Most of our understanding of chemotaxis comes from studies of cells undergoing amoeboid-type migration, in particular the social amoeba Dictyostelium discoideum and leukocytes. In these amoeboid cells the molecular events leading to directed migration can be conceptually divided into four interacting networks: receptor/G protein, signal transduction, cytoskeleton, and polarity. The signal transduction network occupies a central position in this scheme as it receives direct input from the receptor/G protein network, as well as feedback from the cytoskeletal and polarity networks. Multiple overlapping modules within the signal transduction network transmit the signals to the actin cytoskeleton network leading to biased pseudopod protrusion in the direction of the gradient. The overall architecture of the networks, as well as the individual signaling modules, is remarkably conserved between Dictyostelium and mammalian leukocytes, and the similarities and differences between the two systems are the subject of this review.
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20
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Identification of the protein kinases Pyk3 and Phg2 as regulators of the STATc-mediated response to hyperosmolarity. PLoS One 2014; 9:e90025. [PMID: 24587195 PMCID: PMC3934975 DOI: 10.1371/journal.pone.0090025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 01/24/2014] [Indexed: 11/19/2022] Open
Abstract
Cellular adaptation to changes in environmental osmolarity is crucial for cell survival. In Dictyostelium, STATc is a key regulator of the transcriptional response to hyperosmotic stress. Its phosphorylation and consequent activation is controlled by two signaling branches, one cGMP- and the other Ca(2+)-dependent, of which many signaling components have yet to be identified. The STATc stress signalling pathway feeds back on itself by upregulating the expression of STATc and STATc-regulated genes. Based on microarray studies we chose two tyrosine-kinase like proteins, Pyk3 and Phg2, as possible modulators of STATc phosphorylation and generated single and double knock-out mutants to them. Transcriptional regulation of STATc and STATc dependent genes was disturbed in pyk3(-), phg2(-), and pyk3(-)/phg2(-) cells. The absence of Pyk3 and/or Phg2 resulted in diminished or completely abolished increased transcription of STATc dependent genes in response to sorbitol, 8-Br-cGMP and the Ca(2+) liberator BHQ. Also, phospho-STATc levels were significantly reduced in pyk3(-) and phg2(-) cells and even further decreased in pyk3(-)/phg2(-) cells. The reduced phosphorylation was mirrored by a significant delay in nuclear translocation of GFP-STATc. The protein tyrosine phosphatase 3 (PTP3), which dephosphorylates and inhibits STATc, is inhibited by stress-induced phosphorylation on S448 and S747. Use of phosphoserine specific antibodies showed that Phg2 but not Pyk3 is involved in the phosphorylation of PTP3 on S747. In pull-down assays Phg2 and PTP3 interact directly, suggesting that Phg2 phosphorylates PTP3 on S747 in vivo. Phosphorylation of S448 was unchanged in phg2(-) cells. We show that Phg2 and an, as yet unknown, S448 protein kinase are responsible for PTP3 phosphorylation and hence its inhibition, and that Pyk3 is involved in the regulation of STATc by either directly or indirectly activating it. Our results add further complexities to the regulation of STATc, which presumably ensure its optimal activation in response to different environmental cues.
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21
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Cell Migration: Regulation of cytoskeleton by Rap1 in Dictyostelium discoideum. J Microbiol 2012; 50:555-61. [PMID: 22923101 DOI: 10.1007/s12275-012-2246-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Accepted: 06/29/2012] [Indexed: 10/28/2022]
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22
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Tumor suppressor Hippo/MST1 kinase mediates chemotaxis by regulating spreading and adhesion. Proc Natl Acad Sci U S A 2012; 109:13632-7. [PMID: 22847424 DOI: 10.1073/pnas.1211304109] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Chemotaxis depends on a network of parallel pathways that coordinate cytoskeletal events to bias cell movement along a chemoattractant gradient. Using a forward genetic screen in Dictyostelium discoideum, we identified the Ste20 kinase KrsB, a homolog of tumor suppressors Hippo and MST1/2, as a negative regulator of cell spreading and substrate attachment. The excessive adhesion of krsB(-) cells reduced directional movement and prolonged the streaming phase of multicellular aggregation. These phenotypes depended on an intact kinase domain and phosphorylation of a conserved threonine (T176) within the activation loop. Chemoattractants triggered a rapid, transient autophosphorylation of T176 in a heterotrimeric G protein-dependent and PI3K- and TorC2-independent manner. The active phosphorylated form of KrsB acts to decrease adhesion to the substrate. Taken together these studies suggest that cycling between active and inactive forms of KrsB may provide the dynamic regulation of cell adhesion needed for proper cell migration and chemotaxis. KrsB interacts genetically with another D. discoideum Hippo/MST homolog, KrsA, but the two genes are not functionally redundant. These studies show that Hippo/MST proteins, like the tumor suppressor PTEN and oncogenes Ras and PI3K, play a key role in cell morphological events in addition to their role in regulating cell growth.
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23
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Froquet R, le Coadic M, Perrin J, Cherix N, Cornillon S, Cosson P. TM9/Phg1 and SadA proteins control surface expression and stability of SibA adhesion molecules in Dictyostelium. Mol Biol Cell 2012; 23:679-86. [PMID: 22219373 PMCID: PMC3279395 DOI: 10.1091/mbc.e11-04-0338] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
ETOC: TM9/Phg1 proteins are essential for cellular adhesion in many systems, from Dictyostelium to human cells, yet their exact role remains unknown. We demonstrate that TM9 proteins participate in adhesion in Dictyostelium cells by controlling the surface levels of SibA adhesion molecules, notably by influencing their sorting in the endocytic pathway. TM9 proteins form a family of conserved proteins with nine transmembrane domains essential for cellular adhesion in many biological systems, but their exact role in this process remains unknown. In this study, we found that genetic inactivation of the TM9 protein Phg1A dramatically decreases the surface levels of the SibA adhesion molecule in Dictyostelium amoebae. This is due to a decrease in sibA mRNA levels, in SibA protein stability, and in SibA targeting to the cell surface. A similar phenotype was observed in cells devoid of SadA, a protein that does not belong to the TM9 family but also exhibits nine transmembrane domains and is essential for cellular adhesion. A contact site A (csA)-SibA chimeric protein comprising only the transmembrane and cytosolic domains of SibA and the extracellular domain of the Dictyostelium surface protein csA also showed reduced stability and relocalization to endocytic compartments in phg1A knockout cells. These results indicate that TM9 proteins participate in cell adhesion by controlling the levels of adhesion proteins present at the cell surface.
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Affiliation(s)
- Romain Froquet
- Département de Physiologie Cellulaire et Métabolisme, Centre Médical Universitaire, 1211 Geneva 4, Switzerland
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24
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Dias M, Blanc C, Thazar-Poulot N, Ben Larbi S, Cosson P, Letourneur F. Dictyostelium ACAP-A is an ArfGAP involved in cytokinesis, cell migration and actin cytoskeleton dynamics. J Cell Sci 2012; 126:756-66. [DOI: 10.1242/jcs.113951] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
ACAPs and ASAPs are Arf-GTPase-activating proteins with BAR, PH, GAP and ankyrin repeat domains and are known to regulate vesicular traffic and actin cytoskeleton dynamics in mammalian cells. The amoeba Dictyostelium has only two proteins with this domain organization instead of six in human, enabling a more precise functional analysis. Genetic invalidation of acapA, resulted in multinucleated cells with cytokinesis defects. Mutant acapA− cells were hardly motile and their multicellular development was significantly delayed. In addition, formation of filopodial protrusions was deficient in these cells. Conversely, re-expression of ACAP-A-GFP resulted in numerous and long filopodia-like protrusions. Mutagenesis studies showed that ACAP-A actin remodeling function was dependent on its ability to activate its substrate, the small GTPase ArfA. Likewise, the expression of a constitutively active ArfA•GTP mutant in wild-type cells led to a significant reduction of filopodia length. Together our data support a role for ACAP-A in the control of the actin cytoskeleton organization and dynamics through an ArfA-dependent mechanism.
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25
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Paxillin and phospholipase D interact to regulate actin-based processes in Dictyostelium discoideum. EUKARYOTIC CELL 2011; 10:977-84. [PMID: 21531871 DOI: 10.1128/ec.00282-10] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The actin cytoskeleton forms a membrane-associated network whose proper regulation is essential for numerous processes, including cell differentiation, proliferation, adhesion, chemotaxis, endocytosis, exocytosis, and multicellular development. In this report, we show that in Dictyostelium discoideum, paxillin (PaxB) and phospholipase D (PldB) colocalize and coimmunoprecipitate, suggesting that they interact physically. Additionally, the phenotypes observed during development, cell sorting, and several actin-required processes, including cyclic AMP (cAMP) chemotaxis, cell-substrate adhesion, actin polymerization, phagocytosis, and exocytosis, reveal a genetic interaction between paxB and pldB, suggesting a functional interaction between their gene products. Taken together, our data point to PldB being a required binding partner of PaxB during processes involving actin reorganization.
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26
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Synchronization of Dictyostelium discoideum adhesion and spreading using electrostatic forces. Bioelectrochemistry 2010; 79:198-210. [PMID: 20472511 DOI: 10.1016/j.bioelechem.2010.04.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Revised: 04/13/2010] [Accepted: 04/14/2010] [Indexed: 11/21/2022]
Abstract
Synchronization of cell spreading is valuable for the study of molecular events involved in the formation of adhesive contacts with the substrate. At a low ionic concentration (0.17 mM) Dictyostelium discoideum cells levitate over negatively charged surfaces due to electrostatic repulsion. First, a two-chamber device, divided by a porous membrane, allows to quickly increase the ionic concentration around the levitating cells. In this way, a good synchronization was obtained, the onsets of cell spreading being separated by less than 5 s. Secondly applying a high potential pulse (2.5 V/Ref, 0.1s) to an Indium Tin Oxide surface attracts the cells toward the surface where they synchronously spread as monitored by LimE(Deltacoil)-GFP. During spreading, actin polymerizes in series of active spots. On average, the first spot appears 8-11s after the electric pulse and the next ones appear regularly, separated by about 10s. Synchronized actin-polymerization activity continues for 40s. Using an electric pulse to control the exact time point at which cells contact the surface has allowed for the first time to quantify the cellular response time for actin polymerization. Electrochemical synchronization is therefore a valuable tool to study intracellular responses to contact.
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27
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Lee S, Shen Z, Robinson DN, Briggs S, Firtel RA. Involvement of the cytoskeleton in controlling leading-edge function during chemotaxis. Mol Biol Cell 2010; 21:1810-24. [PMID: 20375144 PMCID: PMC2877640 DOI: 10.1091/mbc.e10-01-0009] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Cells activate signaling pathways at the site closest to the chemoattractant source that lead to pseudopod formation and directional movement up the gradient. We demonstrate that cytoskeletal components required for cortical tension, including MyoII and IQGAP/cortexillins help regulate the level and timing of leading-edge pathways. In response to directional stimulation by a chemoattractant, cells rapidly activate a series of signaling pathways at the site closest to the chemoattractant source that leads to F-actin polymerization, pseudopod formation, and directional movement up the gradient. Ras proteins are major regulators of chemotaxis in Dictyostelium; they are activated at the leading edge, are required for chemoattractant-mediated activation of PI3K and TORC2, and are one of the most rapid responders, with activity peaking at ∼3 s after stimulation. We demonstrate that in myosin II (MyoII) null cells, Ras activation is highly extended and is not restricted to the site closest to the chemoattractant source. This causes elevated, extended, and spatially misregulated activation of PI3K and TORC2 and their effectors Akt/PKB and PKBR1, as well as elevated F-actin polymerization. We further demonstrate that disruption of specific IQGAP/cortexillin complexes, which also regulate cortical mechanics, causes extended activation of PI3K and Akt/PKB but not Ras activation. Our findings suggest that MyoII and IQGAP/cortexillin play key roles in spatially and temporally regulating leading-edge activity and, through this, the ability of cells to restrict the site of pseudopod formation.
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Affiliation(s)
- Susan Lee
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0380, USA
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28
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Dictyostelium discoideum paxillin regulates actin-based processes. Protist 2009; 160:221-32. [PMID: 19213599 DOI: 10.1016/j.protis.2008.09.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Accepted: 09/13/2008] [Indexed: 10/21/2022]
Abstract
Paxillin is a key player in integrating the actin cytoskeleton with adhesion, and thus is essential to numerous cellular processes, including proliferation, differentiation, and migration in animal cells. PaxB, the Dictyostelium discoideum orthologue of paxillin, has been shown to be important for adhesion and development, much like its mammalian counterpart. Here, we use the overproduction of PaxB to gain better insight into its role in regulating the actin cytoskeleton and adhesion. We find that PaxB-overexpressing (PaxBOE) cells can aggregate and form mounds normally, but are blocked in subsequent development. This arrest can be rescued by addition of wild-type cells, indicating a non-cell autonomous role for PaxB. PaxBOE cells also have alterations in several actin-based processes, including adhesion, endocytosis, motility, and chemotaxis. PaxBOE cells exhibit an EDTA-sensitive increase in cell-cell cohesion, suggesting that PaxB-mediated adhesion is Ca(2+) or Mg(2+) dependent. Interestingly, cells overexpressing paxB are less adhesive to the substratum. In addition, PaxBOE cells display decreased motility under starved conditions, decreased endocytosis, and are unable to efficiently chemotax up a folate gradient. Taken together, the data suggest that proper expression of PaxB is vital for the regulation of development and actin-dependent processes.
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29
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Parkinson K, Bolourani P, Traynor D, Aldren NL, Kay RR, Weeks G, Thompson CRL. Regulation of Rap1 activity is required for differential adhesion, cell-type patterning and morphogenesis in Dictyostelium. J Cell Sci 2009; 122:335-44. [PMID: 19126673 PMCID: PMC2724730 DOI: 10.1242/jcs.036822] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/13/2008] [Indexed: 12/19/2022] Open
Abstract
Regulated cell adhesion and motility have important roles during growth, development and tissue homeostasis. Consequently, great efforts have been made to identify genes that control these processes. One candidate is Rap1, as it has been implicated in the regulation of adhesion and motility in cell culture. To further study the role of Rap1 during multicellular development, we generated a mutant in a potential Rap1 GTPase activating protein (RapGAPB) in Dictyostelium. rapGAPB(-) cells have increased levels of active Rap1 compared with wild-type cells, indicating that RapGAPB regulates Rap1 activity. Furthermore, rapGAPB(-) cells exhibit hallmark phenotypes of other known mutants with hyperactivated Rap1, including increased substrate adhesion and abnormal F-actin distribution. However, unlike these other mutants, rapGAPB(-) cells do not exhibit impaired motility or chemotaxis, indicating that RapGAPB might only regulate specific roles of Rap1. Importantly, we also found that RapGAPB regulates Rap1 activity during multicellular development and is required for normal morphogenesis. First, streams of aggregating rapGAPB(-) cells break up as a result of decreased cell-cell adhesion. Second, rapGAPB(-) cells exhibit cell-autonomous defects in prestalk cell patterning. Using cell-type-specific markers, we demonstrate that RapGAPB is required for the correct sorting behaviour of different cell types. Finally, we show that inactivation of RapGAPB affects prestalk and prespore cell adhesion. We therefore propose that a possible mechanism for RapGAPB-regulated cell sorting is through differential adhesion.
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Affiliation(s)
- Katie Parkinson
- Faculty of Life Sciences, University of Manchester, Michael Smith Building, Manchester, UK
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Involvement of Sib proteins in the regulation of cellular adhesion in Dictyostelium discoideum. EUKARYOTIC CELL 2008; 7:1600-5. [PMID: 18676957 DOI: 10.1128/ec.00155-08] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Molecular mechanisms ensuring cellular adhesion have been studied in detail in Dictyostelium amoebae, but little is known about the regulation of cellular adhesion in these cells. Here, we show that cellular adhesion is regulated in Dictyostelium, notably by the concentration of a cellular secreted factor accumulating in the medium. This constitutes a quorum-sensing mechanism allowing coordinated regulation of cellular adhesion in a Dictyostelium population. In order to understand the mechanism underlying this regulation, we analyzed the expression of recently identified Dictyostelium adhesion molecules (Sib proteins) that present features also found in mammalian integrins. sibA and sibC are both expressed in vegetative Dictyostelium cells, but the expression of sibC is repressed strongly in conditions where cellular adhesion decreases. Analysis of sibA and sibC mutant cells further suggests that variations in the expression levels of sibC account largely for changes in cellular adhesion in response to environmental cues.
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31
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Kortholt A, van Haastert PJM. Highlighting the role of Ras and Rap during Dictyostelium chemotaxis. Cell Signal 2008; 20:1415-22. [PMID: 18385017 DOI: 10.1016/j.cellsig.2008.02.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Accepted: 02/06/2008] [Indexed: 10/22/2022]
Abstract
Chemotaxis, the directional movement towards a chemical compound, is an essential property of many cells and has been linked to the development and progression of many diseases. Eukaryotic chemotaxis is a complex process involving gradient sensing, cell polarity, remodelling of the cytoskeleton and signal relay. Recent studies in the model organism Dictyostelium discoideum have shown that chemotaxis does not depend on a single molecular mechanism, but rather depends on several interconnecting pathways. Surprisingly, small G-proteins appear to play essential roles in all these pathways. This review will summarize the role of small G-proteins in Dictyostelium, particularly highlighting the function of the Ras subfamily in chemotaxis.
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Affiliation(s)
- Arjan Kortholt
- Department of Molecular Cell Biology, University of Groningen, Kerklaan 30, 9751NN Haren, The Netherlands
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Froquet R, Cherix N, Birke R, Benghezal M, Cameroni E, Letourneur F, Mösch HU, De Virgilio C, Cosson P. Control of cellular physiology by TM9 proteins in yeast and Dictyostelium. J Biol Chem 2008; 283:6764-72. [PMID: 18178563 DOI: 10.1074/jbc.m704484200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TM9 proteins constitute a well defined family, characterized by the presence of a large variable extracellular domain and nine putative transmembrane domains. This family is highly conserved throughout evolution and comprises three members in Dictyostelium discoideum and Saccharomyces cerevisiae and four in humans and mice. In Dictyostelium, previous analysis demonstrated that TM9 proteins are implicated in cellular adhesion. In this study, we generated TM9 mutants in S. cerevisiae and analyzed their phenotype with particular attention to cellular adhesion. S. cerevisiae strains lacking any one of the three TM9 proteins were severely suppressed for adhesive growth and filamentous growth under conditions of nitrogen starvation. In these mutants, expression of the FLO11-lacZ reporter gene was strongly reduced, whereas expression of FRE(Ty1)-lacZ was not, suggesting that TM9 proteins are implicated at a late stage of nutrient-controlled signaling pathways. We also reexamined the phenotype of Dictyostelium TM9 mutant cells, focusing on nutrient-controlled cellular functions. Although the initiation of multicellular development and autophagy was unaltered in Dictyostelium TM9 mutants, nutrient-controlled secretion of lysosomal enzymes was dysregulated in these cells. These results suggest that in both yeast and amoebae, TM9 proteins participate in the control of specific cellular functions in response to changing nutrient conditions.
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Affiliation(s)
- Romain Froquet
- Département de Physiologie et Métabolisme Cellulaire, Centre Médical Universitaire, Université de Genève, rue Michel Servet 1, CH-1211 Genève 4, Switzerland
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33
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Endocytosis and the Actin Cytoskeleton in Dictyostelium discoideum. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 267:343-97. [DOI: 10.1016/s1937-6448(08)00633-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Phagocytosis and host-pathogen interactions in Dictyostelium with a look at macrophages. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 271:253-300. [PMID: 19081545 DOI: 10.1016/s1937-6448(08)01206-9] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Research into phagocytosis and host-pathogen interactions in the lower eukaryote Dictyostelium discoideum has flourished in recent years. This chapter presents a glimpse of where this research stands, with emphasis on the cell biology of the phagocytic process and on the wealth of molecular genetic data that have been gathered. The basic mechanistic machinery and most of the underlying genes appear to be evolutionarily conserved, reflecting the fact that phagocytosis arose as an efficient way to ingest food in single protozoan cells devoid of a rigid cell wall. In spite of some differences, the signal transduction pathways regulating phagosome biogenesis are also emerging as ultimately similar between Dictyostelium and macrophages. Both cell types are hosts for many pathogenic invasive bacteria, which exploit phagocytosis to grow intracellularly. We present an overwiew, based on the analysis of mutants, on how Dictyostelium contributes as a genetic model system to decipher the complexity of host-pathogen interactions.
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Jeon TJ, Lee DJ, Lee S, Weeks G, Firtel RA. Regulation of Rap1 activity by RapGAP1 controls cell adhesion at the front of chemotaxing cells. ACTA ACUST UNITED AC 2007; 179:833-43. [PMID: 18039932 PMCID: PMC2099181 DOI: 10.1083/jcb.200705068] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Spatial and temporal regulation of Rap1 is required for proper myosin assembly and cell adhesion during cell migration in Dictyostelium discoideum. Here, we identify a Rap1 guanosine triphosphatase–activating protein (GAP; RapGAP1) that helps mediate cell adhesion by negatively regulating Rap1 at the leading edge. Defects in spatial regulation of the cell attachment at the leading edge in rapGAP1− (null) cells or cells overexpressing RapGAP1 (RapGAP1OE) lead to defective chemotaxis. rapGAP1− cells have extended chemoattractant-mediated Rap1 activation kinetics and decreased MyoII assembly, whereas RapGAP1OE cells show reciprocal phenotypes. We see that RapGAP1 translocates to the cell cortex in response to chemoattractant stimulation and localizes to the leading edge of chemotaxing cells via an F-actin–dependent pathway. RapGAP1 localization is negatively regulated by Ctx, an F-actin bundling protein that functions during cytokinesis. Loss of Ctx leads to constitutive and uniform RapGAP1 cortical localization. We suggest that RapGAP1 functions in the spatial and temporal regulation of attachment sites through MyoII assembly via regulation of Rap1–guanosine triphosphate.
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Affiliation(s)
- Taeck J Jeon
- Section of Cell and Developmental Biology, Division of Biological Sciences, Center for Molecular Genetics, University of California, San Diego, La Jolla, CA 92093, USA
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Galdeen SA, Stephens S, Thomas DD, Titus MA. Talin influences the dynamics of the myosin VII-membrane interaction. Mol Biol Cell 2007; 18:4074-84. [PMID: 17671169 PMCID: PMC1995725 DOI: 10.1091/mbc.e06-07-0586] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Myosin VII (M7) and talin are ancient and ubiquitous actin-binding proteins with conserved roles in adhesion. Talin serves to link membrane receptors to the underlying actin cytoskeleton and forms a complex with M7 in Dictyostelium. The levels of talinA are tightly linked to M7 levels in Dictyostelium. Cells lacking M7 exhibit an 80% decrease in steady-state levels of talinA, whereas increased levels of M7 result in concomitant increases in total talinA. In contrast, changes in talinA levels do not affect M7 levels. Immunoprecipitation reveals that talinA and M7 are associated with each other in membrane fractions. Fluorescence recovery after photobleaching experiments on green fluorescent protein (GFP)-M7 cells expressing different levels of the M7 and talinA show that changes in the overall amounts of these two proteins influences the dynamics of membrane-associated M7. The recovery of GFP-M7 on the membrane is faster in cells lacking talinA and limited in the presence of excess amounts of talinA and M7. These results establish that M7 stabilizes talinA in the cytosol and, in return, talinA regulates the residence time of M7 at the plasma membrane, suggesting that these two proteins are both part of the same dynamic adhesion complex on the plasma membrane.
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Affiliation(s)
| | | | - David D. Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
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Jeon TJ, Lee DJ, Merlot S, Weeks G, Firtel RA. Rap1 controls cell adhesion and cell motility through the regulation of myosin II. ACTA ACUST UNITED AC 2007; 176:1021-33. [PMID: 17371831 PMCID: PMC2064086 DOI: 10.1083/jcb.200607072] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We have investigated the role of Rap1 in controlling chemotaxis and cell adhesion in Dictyostelium discoideum. Rap1 is activated rapidly in response to chemoattractant stimulation, and activated Rap1 is preferentially found at the leading edge of chemotaxing cells. Cells expressing constitutively active Rap1 are highly adhesive and exhibit strong chemotaxis defects, which are partially caused by an inability to spatially and temporally regulate myosin assembly and disassembly. We demonstrate that the kinase Phg2, a putative Rap1 effector, colocalizes with Rap1–guanosine triphosphate at the leading edge and is required in an in vitro assay for myosin II phosphorylation, which disassembles myosin II and facilitates filamentous actin–mediated leading edge protrusion. We suggest that Rap1/Phg2 plays a role in controlling leading edge myosin II disassembly while passively allowing myosin II assembly along the lateral sides and posterior of the cell.
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Affiliation(s)
- Taeck J Jeon
- Section of Cell and Developmental Biology, Division of Biological Sciences, Center for Molecular Genetics, University of California, San Diego, La Jolla, CA 92093, USA
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38
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Caracino D, Jones C, Compton M, Saxe CL. The N-terminus of Dictyostelium Scar interacts with Abi and HSPC300 and is essential for proper regulation and function. Mol Biol Cell 2007; 18:1609-20. [PMID: 17314411 PMCID: PMC1855017 DOI: 10.1091/mbc.e06-06-0518] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Scar/WAVE proteins, members of the conserved Wiskott-Aldrich syndrome (WAS) family, promote actin polymerization by activating the Arp2/3 complex. A number of proteins, including a complex containing Nap1, PIR121, Abi1/2, and HSPC300, interact with Scar/WAVE, though the role of this complex in regulating Scar function remains unclear. Here we identify a short N-terminal region of Dictyostelium Scar that is necessary and sufficient for interaction with HSPC300 and Abi in vitro. Cells expressing Scar lacking this N-terminal region show abnormalities in F-actin distribution, cell morphology, movement, and cytokinesis. This is true even in the presence of wild-type Scar. The data suggest that the first 96 amino acids of Scar are necessary for participation in a large-molecular-weight protein complex, and that this Scar-containing complex is responsible for the proper localization and regulation of Scar. The presence of mis-regulated or unregulated Scar has significant deleterious effects on cells and may explain the need to keep Scar activity tightly controlled in vivo either by assembly in a complex or by rapid degradation.
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Affiliation(s)
- Diana Caracino
- *Department of Cell Biology and
- Graduate Program in Microbiology and Molecular Genetics, Emory University School of Medicine, Atlanta, GA 30322; and
| | | | - Mark Compton
- Department of Poultry Science, School of Agriculture, University of Georgia, Athens, GA 30602
| | - Charles L. Saxe
- *Department of Cell Biology and
- Graduate Program in Microbiology and Molecular Genetics, Emory University School of Medicine, Atlanta, GA 30322; and
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Lim J, Wiedemann A, Tzircotis G, Monkley SJ, Critchley DR, Caron E. An essential role for talin during alpha(M)beta(2)-mediated phagocytosis. Mol Biol Cell 2007; 18:976-85. [PMID: 17202407 PMCID: PMC1805113 DOI: 10.1091/mbc.e06-09-0813] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The cytoskeletal, actin-binding protein talin has been previously implicated in phagocytosis in Dictyostelium discoideum and mammalian phagocytes. However, its mechanism of action during internalization is not understood. Our data confirm that endogenous talin can occasionally be found at phagosomes forming around IgG- and C3bi-opsonized red blood cells in macrophages. Remarkably, talin knockdown specifically abrogates uptake through complement receptor 3 (CR3, CD11b/CD18, alpha(M)beta(2) integrin) and not through the Fc gamma receptor. We show that talin physically interacts with CR3/alpha(M)beta(2) and that this interaction involves the talin head domain and residues W747 and F754 in the beta(2) integrin cytoplasmic domain. The CR3/alpha(M)beta(2)-talin head interaction controls not only talin recruitment to forming phagosomes but also CR3/alpha(M)beta(2) binding activity, both in macrophages and transfected fibroblasts. However, the talin head domain alone cannot support phagocytosis. Our results establish for the first time at least two distinct roles for talin during CR3/alpha(M)beta(2)-mediated phagocytosis, most noticeably activation of the CR3/alpha(M)beta(2) receptor and phagocytic uptake.
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Affiliation(s)
- Jenson Lim
- *Centre for Molecular Microbiology and Infection and Division of Cell and Molecular Biology, Imperial College London, London SW7 2AZ, United Kingdom; and
| | - Agnès Wiedemann
- *Centre for Molecular Microbiology and Infection and Division of Cell and Molecular Biology, Imperial College London, London SW7 2AZ, United Kingdom; and
| | - George Tzircotis
- *Centre for Molecular Microbiology and Infection and Division of Cell and Molecular Biology, Imperial College London, London SW7 2AZ, United Kingdom; and
| | - Susan J. Monkley
- Department of Biochemistry, University of Leicester, Leicester LE1 9HN, United Kingdom
| | - David R. Critchley
- Department of Biochemistry, University of Leicester, Leicester LE1 9HN, United Kingdom
| | - Emmanuelle Caron
- *Centre for Molecular Microbiology and Infection and Division of Cell and Molecular Biology, Imperial College London, London SW7 2AZ, United Kingdom; and
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Mercanti V, Charette SJ, Bennett N, Ryckewaert JJ, Letourneur F, Cosson P. Selective membrane exclusion in phagocytic and macropinocytic cups. J Cell Sci 2006; 119:4079-87. [PMID: 16968738 DOI: 10.1242/jcs.03190] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Specialized eukaryotic cells can ingest large particles and sequester them within membrane-delimited phagosomes. Many studies have described the delivery of lysosomal proteins to the phagosome, but little is known about membrane sorting during the early stages of phagosome formation. Here we used Dictyostelium discoideum amoebae to analyze the membrane composition of newly formed phagosomes. The membrane delimiting the closing phagocytic cup was essentially derived from the plasma membrane, but a subgroup of proteins was specifically excluded. Interestingly the same phenomenon was observed during the formation of macropinosomes, suggesting that the same sorting mechanisms are at play during phagocytosis and macropinocytosis. Analysis of mutant strains revealed that clathrin-associated adaptor complexes AP-1, -2 and -3 were not necessary for this selective exclusion and, accordingly, ultrastructural analysis revealed no evidence for vesicular transport around phagocytic cups. Our results suggest the existence of a new, as yet uncharacterized, sorting mechanism in phagocytic and macropinocytic cups.
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Affiliation(s)
- Valentina Mercanti
- Université de Genève, Centre Médical Universitaire, Département de Physiologie Cellulaire et Métabolisme, 1 rue Michel Servet, CH-1211 Genève 4, Switzerland
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Cherix N, Froquet R, Charette SJ, Blanc C, Letourneur F, Cosson P. A Phg2-Adrm1 pathway participates in the nutrient-controlled developmental response in Dictyostelium. Mol Biol Cell 2006; 17:4982-7. [PMID: 16987957 PMCID: PMC1679667 DOI: 10.1091/mbc.e06-07-0619] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Dictyostelium amoebae grow as single cells but upon starvation they initiate multicellular development. Phg2 was characterized previously as a kinase controlling cellular adhesion and the organization of the actin cytoskeleton. Here we report that Phg2 also plays a role during the transition between growth and multicellular development, as evidenced by the fact that phg2 mutant cells can initiate development even in the presence of nutrients. Even at low cell density and in rich medium, phg2 mutant cells express discoidin, one of the earliest predevelopmental markers. Complementation studies indicate that, in addition to the kinase domain, the core region of Phg2 is involved in the initiation of development. In this region, a small domain contiguous with a previously described ras-binding domain was found to interact with the Dictyostelium ortholog of the mammalian adhesion-regulating molecule (ADRM1). In addition, adrm1 knockout cells also exhibit abnormal initiation of development. These results suggest that a Phg2-Adrm1 signaling pathway is involved in the control of the transition from growth to differentiation in Dictyostelium. Phg2 thus plays a dual role in the control of cellular adhesion and initiation of development.
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Affiliation(s)
- Nathalie Cherix
- *Département de Physiologie et Métabolisme Cellulaire, Centre Médical Universitaire, Université de Genève, CH-1211 Genève 4, Switzerland; and
| | - Romain Froquet
- *Département de Physiologie et Métabolisme Cellulaire, Centre Médical Universitaire, Université de Genève, CH-1211 Genève 4, Switzerland; and
| | - Steve J. Charette
- *Département de Physiologie et Métabolisme Cellulaire, Centre Médical Universitaire, Université de Genève, CH-1211 Genève 4, Switzerland; and
| | - Cédric Blanc
- Institut de Biologie et Chimie des Protéines, UMR 5086, CNRS/Université Lyon I, IFR 128 BioSciences Lyon-Gerland, F-69367 Lyon Cedex 07, France
| | - François Letourneur
- Institut de Biologie et Chimie des Protéines, UMR 5086, CNRS/Université Lyon I, IFR 128 BioSciences Lyon-Gerland, F-69367 Lyon Cedex 07, France
| | - Pierre Cosson
- *Département de Physiologie et Métabolisme Cellulaire, Centre Médical Universitaire, Université de Genève, CH-1211 Genève 4, Switzerland; and
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42
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Kortholt A, Rehmann H, Kae H, Bosgraaf L, Keizer-Gunnink I, Weeks G, Wittinghofer A, Van Haastert PJM. Characterization of the GbpD-activated Rap1 pathway regulating adhesion and cell polarity in Dictyostelium discoideum. J Biol Chem 2006; 281:23367-76. [PMID: 16769729 DOI: 10.1074/jbc.m600804200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The regulation of cell polarity plays an important role in chemotaxis. GbpD, a putative nucleotide exchange factor for small G-proteins of the Ras family, has been implicated in adhesion, cell polarity, and chemotaxis in Dictyostelium. Cells overexpressing GbpD are flat, exhibit strongly increased cell-substrate attachment, and extend many bifurcated and lateral pseudopodia. These cells overexpressing GbpD are severely impaired in chemotaxis, most likely due to the induction of many protrusions rather than an enhanced adhesion. The GbpD-overexpression phenotype is similar to that of cells overexpressing Rap1. Here we demonstrate that GbpD activates Rap1 both in vivo and in vitro but not any of the five other characterized Ras proteins. In a screen for Rap1 effectors, we overexpressed GbpD in several mutants defective in adhesion or cell polarity and identified Phg2 as Rap1 effector necessary for adhesion, but not cell polarity. Phg2, a serine/threonine-specific kinase, directly interacts with Rap1 via its Ras association domain.
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Affiliation(s)
- Arjan Kortholt
- Department of Molecular Cell Biology, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands
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Cornillon S, Gebbie L, Benghezal M, Nair P, Keller S, Wehrle-Haller B, Charette SJ, Brückert F, Letourneur F, Cosson P. An adhesion molecule in free-living Dictyostelium amoebae with integrin beta features. EMBO Rep 2006; 7:617-21. [PMID: 16699495 PMCID: PMC1479592 DOI: 10.1038/sj.embor.7400701] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2005] [Revised: 02/16/2006] [Accepted: 03/15/2006] [Indexed: 11/09/2022] Open
Abstract
The study of free-living amoebae has proven valuable to explain the molecular mechanisms controlling phagocytosis, cell adhesion and motility. In this study, we identified a new adhesion molecule in Dictyostelium amoebae. The SibA (Similar to Integrin Beta) protein is a type I transmembrane protein, and its cytosolic, transmembrane and extracellular domains contain features also found in integrin beta chains. In addition, the conserved cytosolic domain of SibA interacts with talin, a well-characterized partner of mammalian integrins. Finally, genetic inactivation of SIBA affects adhesion to phagocytic particles, as well as cell adhesion and spreading on its substrate. It does not visibly alter the organization of the actin cytoskeleton, cellular migration or multicellular development. Our results indicate that the SibA protein is a Dictyostelium cell adhesion molecule presenting structural and functional similarities to metazoan integrin beta chains. This study sheds light on the molecular mechanisms controlling cell adhesion and their establishment during evolution.
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Affiliation(s)
- Sophie Cornillon
- Département de Physiologie Cellulaire et Métabolisme, Centre Médical Universitaire, 1 rue Michel Servet, 1211 Geneva 4, Switzerland
| | - Leigh Gebbie
- Département de Physiologie Cellulaire et Métabolisme, Centre Médical Universitaire, 1 rue Michel Servet, 1211 Geneva 4, Switzerland
| | - Mohammed Benghezal
- Département de Physiologie Cellulaire et Métabolisme, Centre Médical Universitaire, 1 rue Michel Servet, 1211 Geneva 4, Switzerland
| | - Prashant Nair
- Département de Physiologie Cellulaire et Métabolisme, Centre Médical Universitaire, 1 rue Michel Servet, 1211 Geneva 4, Switzerland
| | - Sebastien Keller
- Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR314 CNRS, CEA, 38054 Grenoble, France
| | - Bernhard Wehrle-Haller
- Département de Physiologie Cellulaire et Métabolisme, Centre Médical Universitaire, 1 rue Michel Servet, 1211 Geneva 4, Switzerland
| | - Steve J Charette
- Département de Physiologie Cellulaire et Métabolisme, Centre Médical Universitaire, 1 rue Michel Servet, 1211 Geneva 4, Switzerland
| | - Franz Brückert
- Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR314 CNRS, CEA, 38054 Grenoble, France
| | - François Letourneur
- IFR 128 BioSciences Lyon-Gerland, Institut de Biologie et de Chimie des Protéines, UMR 5086, CNRS/Université Lyon I, 7 passage du Vercors, 69367 Lyon Cedex 07, France
| | - Pierre Cosson
- Département de Physiologie Cellulaire et Métabolisme, Centre Médical Universitaire, 1 rue Michel Servet, 1211 Geneva 4, Switzerland
- Tel: +41 22 702 5293; Fax: +41 22 702 5260; E-mail:
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Benghezal M, Fauvarque MO, Tournebize R, Froquet R, Marchetti A, Bergeret E, Lardy B, Klein G, Sansonetti P, Charette SJ, Cosson P. Specific host genes required for the killing of Klebsiella bacteria by phagocytes. Cell Microbiol 2006; 8:139-48. [PMID: 16367873 DOI: 10.1111/j.1462-5822.2005.00607.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The amoeba Dictyostelium discoideum shares many traits with mammalian macrophages, in particular the ability to phagocytose and kill bacteria. In response, pathogenic bacteria use conserved mechanisms to fight amoebae and mammalian phagocytes. Here we developed an assay using Dictyostelium to monitor phagocyte-bacteria interactions. Genetic analysis revealed that the virulence of Klebsiella pneumoniae measured by this test is very similar to that observed in a mouse pneumonia model. Using this assay, two new host resistance genes (PHG1 and KIL1) were identified and shown to be involved in intracellular killing of K. pneumoniae by phagocytes. Phg1 is a member of the 9TM family of proteins, and Kil1 is a sulphotransferase. The loss of PHG1 resulted in Dictyostelium susceptibility to a small subset of bacterial species including K. pneumoniae. Remarkably, Drosophila mutants deficient for PHG1 also exhibited a specific susceptibility to K. pneumoniae infections. Systematic analysis of several additional Dictyostelium mutants created a two-dimensional virulence array, where the complex interactions between host and bacteria are visualized.
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Affiliation(s)
- Mohammed Benghezal
- Athelas SA, Chemin des Aulx 18, 1228 Plan-les-Ouates, Geneva, Switzerland
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Blanc C, Charette S, Cherix N, Lefkir Y, Cosson P, Letourneur F. A novel phosphatidylinositol 4,5-bisphosphate-binding domain targeting the Phg2 kinase to the membrane in Dictyostelium cells. Eur J Cell Biol 2005; 84:951-60. [PMID: 16325504 DOI: 10.1016/j.ejcb.2005.09.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2005] [Revised: 09/13/2005] [Accepted: 09/14/2005] [Indexed: 11/17/2022] Open
Abstract
Phg2 is a ser/thr kinase involved in adhesion, motility, actin cytoskeleton dynamics, and phagocytosis in Dictyostelium cells. In a search for Phg2 domains required for its localization to the plasma membrane, we identified a new domain interacting with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) and phosphatidylinositol 4-phosphate (PI(4)P) membrane phosphoinositides. Deletion of this domain prevented membrane recruitment of Phg2 and proper function of the protein in the phagocytic process. Moreover, the overexpression of this PI(4,5)P(2)-binding domain specifically had a dominant-negative effect by inhibiting phagocytosis. Therefore, plasma membrane recruitment of Phg2 is essential for its function. The PI(4,5)P(2)-binding domain fused to GFP (green fluorescent protein) (GFP-Nt-Phg2) was also used to monitor the dynamics of PI(4,5)P(2) during macropinocytosis and phagocytosis. GFP-Nt-Phg2 disappeared from macropinosomes immediately after their closure. During phagocytosis, PI(4,5)P(2) disappeared even before the sealing of phagosomes as it was already observed in mammalian cells. Together these results demonstrate that PI(4,5)P(2) metabolism regulates the dynamics and the function of Phg2.
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Affiliation(s)
- Cédric Blanc
- IFR 128 BioSciences Lyon-Gerland, Institut de Biologie et Chimie des Protéines, UMR5086, CNRS/Université Lyon I, France
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Charette SJ, Cornillon S, Cosson P. Identification of low frequency knockout mutants in Dictyostelium discoideum created by single or double homologous recombination. J Biotechnol 2005; 122:1-4. [PMID: 16198440 DOI: 10.1016/j.jbiotec.2005.08.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2005] [Revised: 08/19/2005] [Accepted: 08/24/2005] [Indexed: 11/16/2022]
Abstract
Generation and characterization of knockout clones is a widely used approach to evaluate the specific function of a gene product in Dictyostelium discoideum. The mutant clones are generally obtained by double homologous recombination in the target gene. A frequent limitation to obtaining mutants is the low frequency of homologous recombination. Here we present an easy method to identify rare mutants, based on PCR analysis of pools of clones. This method also allows the isolation of functional knockout mutants created by a single homologous recombination event, which can be more frequent than a double recombination event.
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Affiliation(s)
- Steve J Charette
- Université de Genève, Centre Médical Universitaire, Département de Physiologie Cellulaire et Métabolisme, Switzerland.
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Fache S, Dalous J, Engelund M, Hansen C, Chamaraux F, Fourcade B, Satre M, Devreotes P, Bruckert F. Calcium mobilization stimulatesDictyostelium discoideumshear-flow-induced cell motility. J Cell Sci 2005; 118:3445-57. [PMID: 16079287 DOI: 10.1242/jcs.02461] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Application of hydrodynamic mild shear stress to adherent Dictyostelium discoideum vegetative cells triggers active actin cytoskeleton remodeling resulting in net cell movement along the flow. The average cell speed is strongly stimulated by external calcium (Ca2+, K50%=22 μM), but the directionality of the movement is almost unaffected. This calcium concentration is ten times higher than the one promoting cell adhesion to glass surfaces (K50%=2 μM). Addition of the calcium chelator EGTA or the Ca2+-channel blocker gadolinium (Gd3+) transiently stops cell movement. Monitoring the evolution of cell-surface contact area with time reveals that calcium stimulates cell speed by increasing the amplitude of both protrusion and retraction events at the cell edge, but not the frequency. As a consequence, with saturating external calcium concentrations, cells are sensitive to very low shear forces (20 pN; σ=0.1 Pa). Moreover, a null-mutant lacking the unique Gβ subunit does not respond to external Ca2+ changes (K50%>1000 μM), although the directionality of the movement is comparable with that of wild-type cells. Furthermore, cells lacking the inositol 1,4,5-trisphosphate receptor (IP3-receptor) exhibit a markedly reduced Ca2+ sensitivity. Thus, calcium release from internal stores and calcium entry through the plasma membrane modulate cell speed in response to shear stress.
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Affiliation(s)
- Sébastien Fache
- Structures et Propriétés des Architectures Moléculaires (UMR 5919 CNRS), Département de Recherche Fondamentale sur la Matière Condensée, CEA-Grenoble, DRFMC/SI3M, 17 rue des Martyrs, 38054 Grenoble Cedex 09, France
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Khurana T, Brzostowski JA, Kimmel AR. A Rab21/LIM-only/CH-LIM complex regulates phagocytosis via both activating and inhibitory mechanisms. EMBO J 2005; 24:2254-64. [PMID: 15962002 PMCID: PMC1173156 DOI: 10.1038/sj.emboj.7600716] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2005] [Accepted: 05/24/2005] [Indexed: 11/08/2022] Open
Abstract
We have identified two LIM domain proteins, LimF and ChLim, from Dictyostelium that interact with each other and with the small, Rab5-related, Rab21 GTPase to collectively regulate phagocytosis. To investigate in vivo functions, we generated cell lines that lack or overexpress LimF and ChLim and strains that express activating or inhibiting variants of Rab21. Overexpression of LimF, loss of ChLim, or expression of constitutively active Rab21 increases the rate of phagocytosis above that of wild type. Conversely, loss of LimF, overexpression of ChLim, or expression of a dominant-negative Rab21 inhibits phagocytosis. Our studies using cells carrying multiple mutations in these genes further indicate that ChLim antagonizes the activating function of Rab21-GTP during phagocytosis; in turn, LimF is required for Rab21-GTP function. Finally, we demonstrate that ChLim and LimF localize to the phagocytic cup and phago-lysosomal vesicles. We suggest that LimF, ChLim, and activated Rab21-GTP participate as a novel signaling complex that regulates phagocytic activity.
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Affiliation(s)
- Taruna Khurana
- Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, MD, USA
| | - Joseph A Brzostowski
- Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, MD, USA
| | - Alan R Kimmel
- Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, MD, USA
- Laboratory of Cellular and Developmental Biology, National Institutes of Health, NIDDK, MMDS, Building 6/B1-22, NIH, Bethesda, MD 20892-2715, USA. Tel.: +1 301 496 3016; Fax: +1 301 496 5239; E-mail:
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Abstract
Myosin VII (M7) plays a role in adhesion in both Dictyostelium and mammalian cells where it is a component of a complex of proteins that serve to link membrane receptors to the underlying actin cytoskeleton. The nature of this complex is not fully known, prompting a search for M7-binding proteins. Co-immunoprecipitation experiments reveal that Dictyostelium M7 (DdM7) interacts with talinA, an actin-binding protein with a known role in cell-substrate adhesion. No additional proteins are observed in the immunoprecipitate, indicating that the interaction is direct. The N-terminal region of the DdM7 tail that lies between the region of predicted coil and the first MyTH4 domain is found to harbor the talinA binding site. Localization experiments reveal that talinA does not serve as a membrane receptor for DdM7 and vice versa. These findings reveal that talinA is a major DdM7 binding partner and suggest that their interaction induces a conformational change in each that, in combination with membrane receptor binding, promotes the assembly of a high avidity receptor complex essential for adhesion of the cell to substrata.
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Affiliation(s)
- Richard I Tuxworth
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota 55455, USA
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