101
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Charest PG, Firtel RA. Feedback signaling controls leading-edge formation during chemotaxis. Curr Opin Genet Dev 2006; 16:339-47. [PMID: 16806895 DOI: 10.1016/j.gde.2006.06.016] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2006] [Accepted: 06/09/2006] [Indexed: 01/17/2023]
Abstract
Chemotactic cells translate shallow chemoattractant gradients into a highly polarized intracellular response that includes the localized production of PI(3,4,5)P(3) on the side of the cell facing the highest chemoattractant concentration. Research over the past decade began to uncover the molecular mechanisms involved in this localized signal amplification controlling the leading edge of chemotaxing cells. These mechanisms have been shown to involve multiple positive feedback loops, in which the PI(3,4,5)P(3) signal amplifies itself independently of the original stimulus, as well as inhibitory signals that restrict PI(3,4,5)P(3) to the leading edge, thereby creating a steep intracellular PI(3,4,5)P(3) gradient. Molecules involved in positive feedback signaling at the leading edge include the small G-proteins Rac and Ras, phosphatidylinositol-3 kinase and F-actin, as part of interlinked feedback loops that lead to a robust production of PI(3,4,5)P(3).
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Affiliation(s)
- Pascale G Charest
- Division of Biological Sciences, and Center for Molecular Genetics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0380, USA
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102
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Bakthavatsalam D, Meijer HJG, Noegel AA, Govers F. Novel phosphatidylinositol phosphate kinases with a G-protein coupled receptor signature are shared by Dictyostelium and Phytophthora. Trends Microbiol 2006; 14:378-82. [PMID: 16876997 DOI: 10.1016/j.tim.2006.07.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Revised: 06/30/2006] [Accepted: 07/18/2006] [Indexed: 11/19/2022]
Abstract
G-protein coupled receptors (GPCR) and phosphatidylinositol phosphate kinases (PIPK) are important key switches in signal transduction pathways. A novel class of proteins was identified in the genomes of two unrelated organisms that harbor both a GPCR and a PIPK domain. Dictyostelium discoideum contains one GPCR-PIPK, which is crucial in cell-density sensing, and the genomes of Phytophthora sojae and Phytophthora ramorum each encode twelve GPCR-PIPKs. Intriguingly, these are currently the only species that have these two domains combined in one protein. Here, the structural and regulatory characteristics of GPCR-PIPKs are presented and discussed. It is hypothesized that, upon activation, GPCR-PIPKs are able to trigger heterotrimeric G-protein signaling and phosphoinositide second-messenger synthesis.
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Affiliation(s)
- Deenadayalan Bakthavatsalam
- Centre for Biochemistry, Institute of Biochemistry I, Medical Faculty and Centre for Molecular Medicine Cologne, University of Cologne, D-50931 Cologne, Germany.
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103
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Franca-Koh J, Kamimura Y, Devreotes P. Navigating signaling networks: chemotaxis in Dictyostelium discoideum. Curr Opin Genet Dev 2006; 16:333-8. [PMID: 16782326 DOI: 10.1016/j.gde.2006.06.001] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Accepted: 06/08/2006] [Indexed: 01/21/2023]
Abstract
Studies of chemotaxis in the social amoeba Dictyostelium discoideum have revealed numerous conserved signaling networks that are activated by chemoattractants. In the presence of a uniformly distributed stimulus, these pathways are transiently activated, but in a gradient they are activated persistently and can be localized to either the front or the back of the cell. Recent studies have begun to elucidate how chemoattractant signaling regulates the three main components of chemotaxis: directional sensing, pseudopod extension, and polarization.
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Affiliation(s)
- Jonathan Franca-Koh
- Johns Hopkins University, School of Medicine, Department of Cell Biology, 725 North Wolfe Street, 114 WBSB, Baltimore, MD 21205, USA
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104
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Dormann D, Weijer CJ. Chemotactic cell movement during Dictyostelium development and gastrulation. Curr Opin Genet Dev 2006; 16:367-73. [PMID: 16782325 DOI: 10.1016/j.gde.2006.06.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2006] [Accepted: 06/08/2006] [Indexed: 11/26/2022]
Abstract
Many developmental processes involve chemotactic cell movement up or down dynamic chemical gradients. Studies of the molecular mechanisms of chemotactic movement of Dictyostelium amoebae up cAMP gradients highlight the importance of PIP3 signaling in the control of cAMP-dependent actin polymerization, which drives the protrusion of lamellipodia and filopodia at the leading edge of the cell, but also emphasize the need for myosin thick filament assembly and motor activation for the contraction of the back of the cell. These process become even more important during the multicellular stages of development, when propagating waves of cAMP coordinate the chemotactic movement of tens of thousands of cells, resulting in multicellular morphogenesis. Recent experiments show that chemotaxis, especially in response to members of the FGF, PDGF and VEGF families of growth factors, plays a key role in the guidance of mesoderm cells during gastrulation in chick, mouse and frog embryos. The molecular mechanisms of signal detection and signaling to the actin-myosin cytoskeleton remain to be elucidated.
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Affiliation(s)
- Dirk Dormann
- Division of Cell and Developmental Biology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
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105
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Clarke M, Maddera L. Phagocyte meets prey: uptake, internalization, and killing of bacteria by Dictyostelium amoebae. Eur J Cell Biol 2006; 85:1001-10. [PMID: 16782228 DOI: 10.1016/j.ejcb.2006.05.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Dictyostelium cells are professional phagocytes that avidly consume bacteria, their natural prey. Fluorescent probes have allowed us to monitor the initial steps in this process in living cells. Using probes that bind to F-actin, we have visualized the assembly and disassembly of actin filaments responsible for extending the phagocytic cup to engulf a bacterium, and, after the phagosome has sealed, the assembly of new actin filaments to propel the phagosome away from the site of uptake. Using bacteria expressing fluorescent proteins that are susceptible to proteolysis, we have monitored the loss of that fluorescent signal and the staining of the bacterial contents with neutral red, indicating permeabilization of the bacterial cell wall and acidification of the cytoplasm. We find that acidification occurs during a period of microtubule-based transport that promotes fusion of the phagosome with microtubule-associated acidic endosomes. Actin-powered phagosome internalization, transport of the phagosome along microtubules, proteolysis and acidification of bacterial contents, all typically occur within the first six or seven minutes after formation of the phagosome. Thus, tracking individual phagosomes has revealed that early steps in phagosome maturation occur much more rapidly than had been inferred from previous population studies.
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Affiliation(s)
- Margaret Clarke
- Program in Molecular, Cell, and Developmental Biology, Oklahoma Medical Research Foundation, 825 N.E. 13th Street, Oklahoma City, OK 73104, USA.
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106
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Matsuoka S, Iijima M, Watanabe TM, Kuwayama H, Yanagida T, Devreotes PN, Ueda M. Single-molecule analysis of chemoattractant-stimulated membrane recruitment of a PH-domain-containing protein. J Cell Sci 2006; 119:1071-9. [PMID: 16507590 DOI: 10.1242/jcs.02824] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Molecular mechanisms of chemotactic response are highly conserved among many eukaryotic cells including human leukocytes and Dictyostelium discoideum cells. The cells can sense the differences in chemoattractant concentration across the cell body and respond by extending pseudopods from the cell side facing to a higher concentration. Pseudopod formation is regulated by binding of pleckstrin homology (PH)-domain-containing proteins to phosphatidylinositol 3,4,5-trisphosphates [PtdIns(3,4,5)P3] localized at the leading edge of chemotaxing cells. However, molecular mechanisms underlying dynamic features of a pseudopod have not been fully explained by the known properties of PH-domain-containing proteins. To investigate the mechanisms, we visualized single molecules of green fluorescent protein tagged to Crac (Crac-GFP), a PH-domain-containing protein in D. discoideum cells. Whereas populations of Crac molecules exhibited a stable steady-state localization at pseudopods, individual molecules bound transiently to PtdIns(3,4,5)P3 for approximately 120 milliseconds, indicating dynamic properties of the PH-domain-containing protein. Receptor stimulation did not alter the binding stability but regulated the number of bound PH-domain molecules by metabolism of PtdIns(3,4,5)P3. These results demonstrate that the steady-state localization of PH-domain-containing proteins at the leading edge of chemotaxing cells is dynamically maintained by rapid recycling of individual PH-domain-containing proteins. The short interaction between PH domains and PtdIns(3,4,5)P3 contributes to accurate and sensitive chemotactic movements through the dynamic redistributions. These dynamic properties might be a common feature of signaling components involved in chemotaxis.
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Affiliation(s)
- Satomi Matsuoka
- Laboratories for Nanobiology, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
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107
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Loovers HM, Postma M, Keizer-Gunnink I, Huang YE, Devreotes PN, van Haastert PJM. Distinct roles of PI(3,4,5)P3 during chemoattractant signaling in Dictyostelium: a quantitative in vivo analysis by inhibition of PI3-kinase. Mol Biol Cell 2006; 17:1503-13. [PMID: 16421252 PMCID: PMC1415331 DOI: 10.1091/mbc.e05-09-0825] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The role of PI(3,4,5)P(3) in Dictyostelium signal transduction and chemotaxis was investigated using the PI3-kinase inhibitor LY294002 and pi3k-null cells. The increase of PI(3,4,5)P(3) levels after stimulation with the chemoattractant cAMP was blocked >95% by 60 microM LY294002 with half-maximal effect at 5 microM. This correlated well with the inhibition of the membrane translocation of the PH-domain protein, PHcracGFP. LY294002 did not reduce cAMP-mediated cGMP production, but significantly reduced the cAMP response up to 75% in wild type and completely in pi3k-null cells. LY294002-treated cells were round, not elongated as control cells. Interestingly, cAMP induced a time and dose-dependent recovery of cell elongation. These elongated LY294002-treated wild-type and pi3k-null cells exhibited chemotactic orientation toward cAMP that is statistically identical to chemotactic orientation of control cells. In control cells, PHcrac-GFP and F-actin colocalize upon cAMP stimulation. However, inhibition of PI3-kinases does not affect the first phase of the actin polymerization at a wide range of chemoattractant concentrations. Our data show that severe inhibition of cAMP-mediated PI(3,4,5)P(3) accumulation leads to inhibition of cAMP relay, cell elongation and cell aggregation, but has no detectable effect on chemotactic orientation, provided that cAMP had sufficient time to induce cell elongation.
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Affiliation(s)
- Harriët M Loovers
- Department of Molecular Cell Biology, University of Groningen, 9751 NN Haren, The Netherlands
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108
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Lecaudey V, Gilmour D. Organizing moving groups during morphogenesis. Curr Opin Cell Biol 2005; 18:102-7. [PMID: 16352429 DOI: 10.1016/j.ceb.2005.12.001] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Accepted: 12/01/2005] [Indexed: 10/25/2022]
Abstract
The directed migration of cells drives the formation of many complex organ systems. Although in this morphogenetic context cells display a strong preference for migrating in organized, cohesive groups, little is known about the mechanisms that coordinate their movements. Recent studies on several model systems have begun to dissect the organization of these migrating tissues in vivo and have shown that cell guidance is mediated by a combination of chemical and mechanical cues.
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Affiliation(s)
- Virginie Lecaudey
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
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109
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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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110
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Abstract
We review insights in signaling pathways controlling cell polarization and cytoskeletal organization during chemotactic movement in Dictyostelium amoebae and neutrophils. We compare and contrast these insights with our current understanding of pathways controlling chemotactic movements in more-complex multicellular developmental contexts.
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Affiliation(s)
- Markus Affolter
- Department of Cell Biology, Biozentrum University of Basel, Klingelbergstr. 70, CH-4056 Basel, Switzerland
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