51
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Pan M, Xu X, Chen Y, Jin T. Identification of a Chemoattractant G-Protein-Coupled Receptor for Folic Acid that Controls Both Chemotaxis and Phagocytosis. Dev Cell 2016; 36:428-39. [PMID: 26906738 DOI: 10.1016/j.devcel.2016.01.012] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 12/09/2015] [Accepted: 01/19/2016] [Indexed: 10/22/2022]
Abstract
Eukaryotic phagocytes search and destroy invading microorganisms via chemotaxis and phagocytosis. The social amoeba Dictyostelium discoideum is a professional phagocyte that chases bacteria through chemotaxis and engulfs them as food via phagocytosis. G-protein-coupled receptors (GPCRs) are known for detecting chemoattractants and directing cell migration, but their roles in phagocytosis are not clear. Here, we developed a quantitative phosphoproteomic technique to discover signaling components. Using this approach, we discovered the long sought after folic acid receptor, fAR1, in D. discoideum. We showed that the seven-transmembrane receptor fAR1 is required for folic acid-mediated signaling events. Significantly, we discovered that fAR1 is essential for both chemotaxis and phagocytosis of bacteria, thereby representing a chemoattractant GPCR that mediates not only chasing but also ingesting bacteria. We revealed that a phagocyte is able to internalize particles via a chemoattractant-mediated engulfment process. We propose that mammalian phagocytes may also use this mechanism to engulf and ingest bacterial pathogens.
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Affiliation(s)
- Miao Pan
- Chemotaxis Signal Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Disease, NIH, Rockville, MD 20852, USA.
| | - Xuehua Xu
- Chemotaxis Signal Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Disease, NIH, Rockville, MD 20852, USA
| | - Yong Chen
- Proteomics Core Facility, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tian Jin
- Chemotaxis Signal Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Disease, NIH, Rockville, MD 20852, USA.
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52
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Cheng Y, Othmer H. A Model for Direction Sensing in Dictyostelium discoideum: Ras Activity and Symmetry Breaking Driven by a Gβγ-Mediated, Gα2-Ric8 -- Dependent Signal Transduction Network. PLoS Comput Biol 2016; 12:e1004900. [PMID: 27152956 PMCID: PMC4859573 DOI: 10.1371/journal.pcbi.1004900] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 04/06/2016] [Indexed: 12/03/2022] Open
Abstract
Chemotaxis is a dynamic cellular process, comprised of direction sensing, polarization and locomotion, that leads to the directed movement of eukaryotic cells along extracellular gradients. As a primary step in the response of an individual cell to a spatial stimulus, direction sensing has attracted numerous theoretical treatments aimed at explaining experimental observations in a variety of cell types. Here we propose a new model of direction sensing based on experiments using Dictyostelium discoideum (Dicty). The model is built around a reaction-diffusion-translocation system that involves three main component processes: a signal detection step based on G-protein-coupled receptors (GPCR) for cyclic AMP (cAMP), a transduction step based on a heterotrimetic G protein Gα2βγ, and an activation step of a monomeric G-protein Ras. The model can predict the experimentally-observed response of cells treated with latrunculin A, which removes feedback from downstream processes, under a variety of stimulus protocols. We show that [Formula: see text] cycling modulated by Ric8, a nonreceptor guanine exchange factor for [Formula: see text] in Dicty, drives multiple phases of Ras activation and leads to direction sensing and signal amplification in cAMP gradients. The model predicts that both [Formula: see text] and Gβγ are essential for direction sensing, in that membrane-localized [Formula: see text], the activated GTP-bearing form of [Formula: see text], leads to asymmetrical recruitment of RasGEF and Ric8, while globally-diffusing Gβγ mediates their activation. We show that the predicted response at the level of Ras activation encodes sufficient 'memory' to eliminate the 'back-of-the wave' problem, and the effects of diffusion and cell shape on direction sensing are also investigated. In contrast with existing LEGI models of chemotaxis, the results do not require a disparity between the diffusion coefficients of the Ras activator GEF and the Ras inhibitor GAP. Since the signal pathways we study are highly conserved between Dicty and mammalian leukocytes, the model can serve as a generic one for direction sensing.
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Affiliation(s)
- Yougan Cheng
- School of Mathematics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Hans Othmer
- School of Mathematics, University of Minnesota, Minneapolis, Minnesota, United States of America
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Heterotrimeric G-protein shuttling via Gip1 extends the dynamic range of eukaryotic chemotaxis. Proc Natl Acad Sci U S A 2016; 113:4356-61. [PMID: 27044073 DOI: 10.1073/pnas.1516767113] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Chemotactic eukaryote cells can sense chemical gradients over a wide range of concentrations via heterotrimeric G-protein signaling; however, the underlying wide-range sensing mechanisms are only partially understood. Here we report that a novel regulator of G proteins, G protein-interacting protein 1 (Gip1), is essential for extending the chemotactic range ofDictyosteliumcells. Genetic disruption of Gip1 caused severe defects in gradient sensing and directed cell migration at high but not low concentrations of chemoattractant. Also, Gip1 was found to bind and sequester G proteins in cytosolic pools. Receptor activation induced G-protein translocation to the plasma membrane from the cytosol in a Gip1-dependent manner, causing a biased redistribution of G protein on the membrane along a chemoattractant gradient. These findings suggest that Gip1 regulates G-protein shuttling between the cytosol and the membrane to ensure the availability and biased redistribution of G protein on the membrane for receptor-mediated chemotactic signaling. This mechanism offers an explanation for the wide-range sensing seen in eukaryotic chemotaxis.
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54
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Frequency and amplitude control of cortical oscillations by phosphoinositide waves. Nat Chem Biol 2016; 12:159-66. [PMID: 26751515 DOI: 10.1038/nchembio.2000] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 11/17/2015] [Indexed: 01/08/2023]
Abstract
Rhythmicity is prevalent in the cortical dynamics of diverse single and multicellular systems. Current models of cortical oscillations focus primarily on cytoskeleton-based feedbacks, but information on signals upstream of the actin cytoskeleton is limited. In addition, inhibitory mechanisms--especially local inhibitory mechanisms, which ensure proper spatial and kinetic controls of activation--are not well understood. Here, we identified two phosphoinositide phosphatases, synaptojanin 2 and SHIP1, that function in periodic traveling waves of rat basophilic leukemia (RBL) mast cells. The local, phase-shifted activation of lipid phosphatases generates sequential waves of phosphoinositides. By acutely perturbing phosphoinositide composition using optogenetic methods, we showed that pulses of PtdIns(4,5)P2 regulate the amplitude of cyclic membrane waves while PtdIns(3,4)P2 sets the frequency. Collectively, these data suggest that the spatiotemporal dynamics of lipid metabolism have a key role in governing cortical oscillations and reveal how phosphatidylinositol 3-kinases (PI3K) activity could be frequency-encoded by a phosphatase-dependent inhibitory reaction.
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55
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Matsuoka S, Miyanaga Y, Ueda M. Multi-State Transition Kinetics of Intracellular Signaling Molecules by Single-Molecule Imaging Analysis. Methods Mol Biol 2016; 1407:361-379. [PMID: 27271914 DOI: 10.1007/978-1-4939-3480-5_25] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The chemotactic signaling of eukaryotic cells is based on a chain of interactions between signaling molecules diffusing on the cell membrane and those shuttling between the membrane and cytoplasm. In this chapter, we describe methods to quantify lateral diffusion and reaction kinetics on the cell membrane. By the direct visualization and statistic analyses of molecular Brownian movement achieved by single-molecule imaging techniques, multiple states of membrane-bound molecules are successfully revealed with state transition kinetics. Using PTEN, a phosphatidylinositol-3,4,5-trisphosphate (PI(3,4,5)P3) 3'-phosphatase, in Dictyostelium discoideum undergoing chemotaxis as a model, each process of the analysis is described in detail. The identified multiple state kinetics provides an essential clue to elucidating the molecular mechanism of chemoattractant-induced dynamic redistribution of the signaling molecule asymmetrically on the cell membrane. Quantitative parameters for molecular reactions and diffusion complement a conventional view of the chemotactic signaling system, where changing a static network of molecules connected by causal relationships into a spatiotemporally dynamic one permits a mathematical description of stochastic migration of the cell along a shallow chemoattractant gradient.
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Affiliation(s)
- Satomi Matsuoka
- Laboratory for Cell Signaling Dynamics, RIKEN Quantitative Biology Center, 6-2-3 Furuedai, Suita, Osaka, 565-0874, Japan.
| | - Yukihiro Miyanaga
- Laboratory of Single Molecule Biology, Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka, Japan
| | - Masahiro Ueda
- Laboratory of Single Molecule Biology, Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka, Japan
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56
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Abstract
The study of chemotaxis has benefited greatly from computational models that describe the response of cells to chemoattractant stimuli. These models must keep track of spatially and temporally varying distributions of numerous intracellular species. Moreover, recent evidence suggests that these are not deterministic interactions, but also include the effect of stochastic variations that trigger an excitable network. In this chapter we illustrate how to create simulations of excitable networks using the Virtual Cell modeling environment.
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Affiliation(s)
- Sayak Bhattacharya
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Pablo A Iglesias
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, 21205, MD, USA.
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57
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Yang HW, Collins SR, Meyer T. Locally excitable Cdc42 signals steer cells during chemotaxis. Nat Cell Biol 2015; 18:191-201. [PMID: 26689677 PMCID: PMC5015690 DOI: 10.1038/ncb3292] [Citation(s) in RCA: 124] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 11/23/2015] [Indexed: 12/14/2022]
Abstract
Neutrophils and other amoeboid cells chemotax by steering their front towards chemoattractant. While Ras, Rac, Cdc42, and RhoA small GTPases all regulate chemotaxis, it has been unclear how they spatiotemporally control polarization and steering. Using fluorescence biosensors in neutrophil-like PLB-985 cells and photorelease of chemoattractant, we show that local Cdc42 signals, but not those of Rac, RhoA or Ras, precede cell turning during chemotaxis. Furthermore, preexisting local Cdc42 signals in morphologically unpolarized cells predict the future direction of movement upon uniform stimulation. Moreover, inhibition of actin polymerization uncovers recurring local Cdc42 activity pulses, suggesting that Cdc42 has the excitable characteristic of the compass activity proposed in models of chemotaxis. Globally, Cdc42 antagonizes RhoA, and maintains a steep spatial activity gradient during migration, while Ras and Rac form shallow gradients. Thus, chemotactic steering and de novo polarization are both directed by locally excitable Cdc42 signals.
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Affiliation(s)
- Hee Won Yang
- Department of Chemical & Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Sean R Collins
- Department of Chemical & Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Tobias Meyer
- Department of Chemical & Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
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58
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Nichols JME, Veltman D, Kay RR. Chemotaxis of a model organism: progress with Dictyostelium. Curr Opin Cell Biol 2015; 36:7-12. [DOI: 10.1016/j.ceb.2015.06.005] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 05/22/2015] [Accepted: 06/27/2015] [Indexed: 11/25/2022]
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59
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Sarris M, Sixt M. Navigating in tissue mazes: chemoattractant interpretation in complex environments. Curr Opin Cell Biol 2015; 36:93-102. [DOI: 10.1016/j.ceb.2015.08.001] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 07/30/2015] [Accepted: 08/13/2015] [Indexed: 12/13/2022]
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