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Recent advances on the piezoelectric, electrochemical, and optical biosensors for the detection of protozoan pathogens. Trends Analyt Chem 2022. [DOI: 10.1016/j.trac.2022.116803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Hiraoka H, Wang J, Nakano T, Hirano Y, Yamazaki S, Hiraoka Y, Haraguchi T. ATP levels influence cell movement during the mound phase in Dictyostelium discoideum as revealed by ATP visualization and simulation. FEBS Open Bio 2022; 12:2042-2056. [PMID: 36054629 PMCID: PMC9623536 DOI: 10.1002/2211-5463.13480] [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: 05/06/2022] [Revised: 08/16/2022] [Accepted: 08/29/2022] [Indexed: 01/25/2023] Open
Abstract
Cell migration plays an important role in multicellular organism development. The cellular slime mold Dictyostelium discoideum is a useful model organism for the study of cell migration during development. Although cellular ATP levels are known to determine cell fate during development, the underlying mechanism remains unclear. Here, we report that ATP-rich cells efficiently move to the central tip region of the mound against rotational movement during the mound phase. A simulation analysis based on an agent-based model reproduces the movement of ATP-rich cells observed in the experiments. These findings indicate that ATP-rich cells have the ability to move against the bulk flow of cells, suggesting a mechanism by which high ATP levels determine the cell fate of differentiation.
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Affiliation(s)
- Haruka Hiraoka
- Graduate School of Frontier BiosciencesOsaka UniversityJapan,Graduate School of ScienceNagoya UniversityJapan
| | - Jiewen Wang
- Graduate School of InformaticsOsaka Metropolitan UniversityJapan
| | - Tadashi Nakano
- Graduate School of InformaticsOsaka Metropolitan UniversityJapan
| | - Yasuhiro Hirano
- Graduate School of Frontier BiosciencesOsaka UniversityJapan
| | | | - Yasushi Hiraoka
- Graduate School of Frontier BiosciencesOsaka UniversityJapan
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Sasaki H, Kubohara Y, Ishigaki H, Takahashi K, Eguchi H, Sugawara A, Oshima Y, Kikuchi H. Two New Terpenes Isolated from Dictyostelium Cellular Slime Molds. Molecules 2020; 25:molecules25122895. [PMID: 32585998 PMCID: PMC7356884 DOI: 10.3390/molecules25122895] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 06/17/2020] [Accepted: 06/18/2020] [Indexed: 12/22/2022] Open
Abstract
We report a protoilludane-type sesquiterpene, mucoroidiol, and a geranylated bicyclogermacranol, firmibasiol, isolated from Dictyostelium cellular slime molds. The methanol extracts of the fruiting bodies of cellular slime molds were separated by chromatographic methods to give these compounds. Their structures have been established by several spectral means. Mucoroidiol and firmibasiol are the first examples of more modified and oxidized terpenoids isolated from cellular slime molds. Mucoroidiol showed moderate osteoclast-differentiation inhibitory activity despite demonstrating very weak cell-proliferation inhibitory activity. Therefore, cellular slime molds produce considerably diverse secondary metabolites, and they are promising sources of new natural product chemistry.
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Affiliation(s)
- Hitomi Sasaki
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3, Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan; (H.S.); (H.E.); (A.S.); (Y.O.)
| | - Yuzuru Kubohara
- Graduate School of Health and Sports Science, Juntendo University, 1-1 Hiraga-gakuendai, Inzai, Chiba 270-1695, Japan;
| | - Hirotaka Ishigaki
- Department of Medical Technology, Faculty of Health Science, Gunma Paz University, Takasaki 370-0006, Japan; (H.I.); (K.T.)
| | - Katsunori Takahashi
- Department of Medical Technology, Faculty of Health Science, Gunma Paz University, Takasaki 370-0006, Japan; (H.I.); (K.T.)
| | - Hiromi Eguchi
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3, Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan; (H.S.); (H.E.); (A.S.); (Y.O.)
| | - Akihiro Sugawara
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3, Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan; (H.S.); (H.E.); (A.S.); (Y.O.)
| | - Yoshiteru Oshima
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3, Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan; (H.S.); (H.E.); (A.S.); (Y.O.)
| | - Haruhisa Kikuchi
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3, Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan; (H.S.); (H.E.); (A.S.); (Y.O.)
- Correspondence: ; Tel.: +81-22-795-6824
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Shaw S, DeMarco SF, Rehmann R, Wenzler T, Florini F, Roditi I, Hill KL. Flagellar cAMP signaling controls trypanosome progression through host tissues. Nat Commun 2019; 10:803. [PMID: 30778051 PMCID: PMC6379439 DOI: 10.1038/s41467-019-08696-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 01/18/2019] [Indexed: 02/07/2023] Open
Abstract
The unicellular parasite Trypanosoma brucei is transmitted between mammals by tsetse flies. Following the discovery that flagellar phosphodiesterase PDEB1 is required for trypanosomes to move in response to signals in vitro (social motility), we investigated its role in tsetse flies. Here we show that PDEB1 knockout parasites exhibit subtle changes in movement, reminiscent of bacterial chemotaxis mutants. Infecting flies with the knockout, followed by live confocal microscopy of fluorescent parasites within dual-labelled insect tissues, shows that PDEB1 is important for traversal of the peritrophic matrix, which separates the midgut lumen from the ectoperitrophic space. Without PDEB1, parasites are trapped in the lumen and cannot progress through the cycle. This demonstrates that the peritrophic matrix is a barrier that must be actively overcome and that the parasite’s flagellar cAMP signaling pathway facilitates this. Migration may depend on perception of chemotactic cues, which could stem from co-infecting parasites and/or the insect host. Trypanosoma brucei probably relies on chemotactic signals for movement through tsetse fly tissues, but the molecular basis is unknown. Here, the authors show that flagellar cAMP signaling is required for traversal of the peritrophic matrix and that, without it, parasites are trapped in the midgut lumen.
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Affiliation(s)
- Sebastian Shaw
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012, Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, CH-3012, Bern, Switzerland
| | - Stephanie F DeMarco
- Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - Ruth Rehmann
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012, Bern, Switzerland
| | - Tanja Wenzler
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012, Bern, Switzerland
| | - Francesca Florini
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012, Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, CH-3012, Bern, Switzerland
| | - Isabel Roditi
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012, Bern, Switzerland.
| | - Kent L Hill
- Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA. .,Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA, 90095, USA. .,California NanoSystems Institute, University of California, Los Angeles, CA, 90095, USA.
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Kubohara Y, Kikuchi H. Dictyostelium: An Important Source of Structural and Functional Diversity in Drug Discovery. Cells 2018; 8:E6. [PMID: 30583484 PMCID: PMC6356392 DOI: 10.3390/cells8010006] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 12/19/2018] [Accepted: 12/19/2018] [Indexed: 12/12/2022] Open
Abstract
The cellular slime mold Dictyostelium discoideum is an excellent model organism for the study of cell and developmental biology because of its simple life cycle and ease of use. Recent findings suggest that Dictyostelium and possibly other genera of cellular slime molds, are potential sources of novel lead compounds for pharmacological and medical research. In this review, we present supporting evidence that cellular slime molds are an untapped source of lead compounds by examining the discovery and functions of polyketide differentiation-inducing factor-1, a compound that was originally isolated as an inducer of stalk-cell differentiation in D. discoideum and, together with its derivatives, is now a promising lead compound for drug discovery in several areas. We also review other novel compounds, including secondary metabolites, that have been isolated from cellular slime molds.
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Affiliation(s)
- Yuzuru Kubohara
- Laboratory of Health and Life Science, Graduate School of Health and Sports Science, Juntendo University, Inzai, Chiba 270-1695, Japan.
| | - Haruhisa Kikuchi
- Laboratory of Natural Product Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
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6
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Bitsouni V, Eftimie R. Non-local Parabolic and Hyperbolic Models for Cell Polarisation in Heterogeneous Cancer Cell Populations. Bull Math Biol 2018; 80:2600-2632. [PMID: 30136211 PMCID: PMC6153854 DOI: 10.1007/s11538-018-0477-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 07/23/2018] [Indexed: 01/01/2023]
Abstract
Tumours consist of heterogeneous populations of cells. The sub-populations can have different features, including cell motility, proliferation and metastatic potential. The interactions between clonal sub-populations are complex, from stable coexistence to dominant behaviours. The cell–cell interactions, i.e. attraction, repulsion and alignment, processes critical in cancer invasion and metastasis, can be influenced by the mutation of cancer cells. In this study, we develop a mathematical model describing cancer cell invasion and movement for two polarised cancer cell populations with different levels of mutation. We consider a system of non-local hyperbolic equations that incorporate cell–cell interactions in the speed and the turning behaviour of cancer cells, and take a formal parabolic limit to transform this model into a non-local parabolic model. We then investigate the possibility of aggregations to form, and perform numerical simulations for both hyperbolic and parabolic models, comparing the patterns obtained for these models.
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Affiliation(s)
- Vasiliki Bitsouni
- Division of Mathematics, University of Dundee, Dundee, DD1 4HN, Scotland, UK.
| | - Raluca Eftimie
- Division of Mathematics, University of Dundee, Dundee, DD1 4HN, Scotland, UK
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Mamou G, Malli Mohan GB, Rouvinski A, Rosenberg A, Ben-Yehuda S. Early Developmental Program Shapes Colony Morphology in Bacteria. Cell Rep 2016; 14:1850-7. [PMID: 26904951 PMCID: PMC4785774 DOI: 10.1016/j.celrep.2016.01.071] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Revised: 11/30/2015] [Accepted: 01/22/2016] [Indexed: 12/14/2022] Open
Abstract
When grown on a solid surface, bacteria form highly organized colonies, yet little is known about the earliest stages of colony establishment. Following Bacillus subtilis colony development from a single progenitor cell, a sequence of highly ordered spatiotemporal events was revealed. Colony was initiated by the formation of leading-cell chains, deriving from the colony center and extending in multiple directions, typically in a “Y-shaped” structure. By eradicating particular cells during these early stages, we could influence the shape of the resulting colony and demonstrate that Y-arm extension defines colony size. A mutant in ymdB encoding a phosphodiesterase displayed unordered developmental patterns, indicating a role in guiding these initial events. Finally, we provide evidence that intercellular nanotubes contribute to proper colony formation. In summary, we reveal a “construction plan” for building a colony and provide the initial molecular basis for this process. Highly ordered spatiotemporal events occur during bacterial colony development Colony typically initiates by formation of leading-cell chains arranged in a Y shape Y-arm extension defines the size and the shape of the future colony A mutant in the phosphodiesterase ymdB displays aberrant developmental patterns
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Affiliation(s)
- Gideon Mamou
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, POB 12272, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | - Ganesh Babu Malli Mohan
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, POB 12272, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | - Alex Rouvinski
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, POB 12272, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | - Alex Rosenberg
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, POB 12272, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | - Sigal Ben-Yehuda
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, POB 12272, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel.
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8
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Bhowmik A, Rappel WJ, Levine H. Excitable waves and direction-sensing in Dictyostelium discoideum: steps towards a chemotaxis model. Phys Biol 2016; 13:016002. [PMID: 26824302 PMCID: PMC4887094 DOI: 10.1088/1478-3975/13/1/016002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In recent years, there have been significant advances in our understanding of the mechanisms underlying chemically directed motility by eukaryotic cells such as Dictyostelium. In particular, the local excitation and global inhibition (LEGI) model has proven capable of providing a framework for quantitatively explaining many experiments that present Dictyostelium cells with tailored chemical stimuli and monitor their subsequent polarization. In their natural setting, cells generate their own directional signals via the detection and secretion of cyclic adenosine monophosphate (cAMP). Here, we couple the LEGI approach to an excitable medium model of the cAMP wave-field that is propagated by the cells and investigate the possibility for this class of models to enable accurate chemotaxis to the cAMP waveforms expected in vivo. Our results indicate that the ultra-sensitive version of the model does an excellent job in providing natural wave rectification, thereby providing a compelling solution to the 'back-of-the-wave paradox' during cellular aggregation.
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Affiliation(s)
- Arpan Bhowmik
- Center for Theoretical Biological Physics, Rice University, Houston, TX 77096, USA
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Ho LK, Nodwell JR. David and Goliath: chemical perturbation of eukaryotes by bacteria. J Ind Microbiol Biotechnol 2015; 43:233-48. [PMID: 26433385 PMCID: PMC4752587 DOI: 10.1007/s10295-015-1686-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 09/09/2015] [Indexed: 12/20/2022]
Abstract
Environmental microbes produce biologically active small molecules that have been mined extensively as antibiotics and a smaller number of drugs that act on eukaryotic cells. It is known that there are additional bioactives to be discovered from this source. While the discovery of new antibiotics is challenged by the frequent discovery of known compounds, we contend that the eukaryote-active compounds may be less saturated. Indeed, despite there being far fewer eukaryotic-active natural products these molecules interact with a far richer diversity of molecular and cellular targets.
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Affiliation(s)
- Louis K Ho
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada
| | - Justin R Nodwell
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada.
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Tagoe DNA, Kalejaiye TD, de Koning HP. The ever unfolding story of cAMP signaling in trypanosomatids: vive la difference! Front Pharmacol 2015; 6:185. [PMID: 26441645 PMCID: PMC4561360 DOI: 10.3389/fphar.2015.00185] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 08/17/2015] [Indexed: 12/25/2022] Open
Abstract
Kinetoplastids are unicellular, eukaryotic, flagellated protozoans containing the eponymous kinetoplast. Within this order, the family of trypanosomatids are responsible for some of the most serious human diseases, including Chagas disease (Trypanosoma cruzi), sleeping sickness (Trypanosoma brucei spp.), and leishmaniasis (Leishmania spp). Although cAMP is produced during the life cycle stages of these parasites, its signaling pathways are very different from those of mammals. The absence of G-protein-coupled receptors, the presence of structurally different adenylyl cyclases, the paucity of known cAMP effector proteins and the stringent need for regulation of cAMP in the small kinetoplastid cells all suggest a significantly different biochemical pathway and likely cell biology. However, each of the main kinetoplastid parasites express four class 1-type cyclic nucleotide-specific phosphodiesterases (PDEA-D), which have highly similar catalytic domains to that of human PDEs. To date, only TbrPDEB, expressed as two slightly different isoforms TbrPDEB1 and B2, has been found to be essential when ablated. Although the genomes contain reasonably well conserved genes for catalytic and regulatory domains of protein kinase A, these have been shown to have varied structural and functional roles in the different species. Recent discovery of a role of cAMP/AMP metabolism in a quorum-sensing signaling pathway in T. brucei, and the identification of downstream cAMP Response Proteins (CARPs) whose expression levels correlate with sensitivity to PDE inhibitors, suggests a complex signaling cascade. The interplay between the roles of these novel CARPs and the quorum-sensing signaling pathway on cell division and differentiation makes for intriguing cell biology and a new paradigm in cAMP signal transduction, as well as potential targets for trypanosomatid-specific cAMP pathway-based therapeutics.
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Affiliation(s)
- Daniel N A Tagoe
- Wellcome Trust Centre for Molecular Parasitology, University of Glasgow , Glasgow, UK ; Institute of Infection, Inflammation and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow, UK ; Department of Laboratory Technology, Division of Medical Laboratory Technology, University of Cape Coast , Cape Coast, Ghana
| | - Titilola D Kalejaiye
- Institute of Infection, Inflammation and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow, UK
| | - Harry P de Koning
- Institute of Infection, Inflammation and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow, UK
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Makin L, Gluenz E. cAMP signalling in trypanosomatids: role in pathogenesis and as a drug target. Trends Parasitol 2015; 31:373-9. [PMID: 26004537 PMCID: PMC4534343 DOI: 10.1016/j.pt.2015.04.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 04/24/2015] [Accepted: 04/24/2015] [Indexed: 12/25/2022]
Abstract
Trypanosoma brucei adenylate cyclases are implicated in modulation of host immune response and social motility. First effectors downstream of cAMP signalling were identified in Trypanosoma cruzi and T. brucei. Crystal structures reveal a unique pocket in trypanosomatid phosphodiesterases. Trypanosomatid phosphodiesterase inhibitors are promising drug candidates.
Despite recent research linking cAMP signalling to virulence in trypanosomatids and detailed studies of trypanosomatid adenylyl cyclases (ACs) and phosphodiesterases (PDEs) since their discoveries 40 years ago, downstream components of the pathway and their biological functions have remained remarkably elusive. However, in recent years, significant discoveries have been made: a role for parasite ACs has been proposed in cytokinesis, evasion of the host immune response, and social motility. cAMP phosphodiesterases PDEB1 and PDEB2 were found to be essential for survival and virulence of Trypanosoma brucei and, in Trypanosoma cruzi, PDEC2 was shown to be required for normal osmoregulation. As we discuss here, these breakthroughs have led to an ongoing surge in the development of PDE inhibitors as lead compounds for trypanocidal drugs.
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Affiliation(s)
- Laura Makin
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK.
| | - Eva Gluenz
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
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Abstract
UNLABELLED The protozoan parasite Trypanosoma brucei engages in surface-induced social behavior, termed social motility, characterized by single cells assembling into multicellular groups that coordinate their movements in response to extracellular signals. Social motility requires sensing and responding to extracellular signals, but the underlying mechanisms are unknown. Here we report that T. brucei social motility depends on cyclic AMP (cAMP) signaling systems in the parasite's flagellum (synonymous with cilium). Pharmacological inhibition of cAMP-specific phosphodiesterase (PDE) completely blocks social motility without impacting the viability or motility of individual cells. Using a fluorescence resonance energy transfer (FRET)-based sensor to monitor cAMP dynamics in live cells, we demonstrate that this block in social motility correlates with an increase in intracellular cAMP levels. RNA interference (RNAi) knockdown of the flagellar PDEB1 phenocopies pharmacological PDE inhibition, demonstrating that PDEB1 is required for social motility. Using parasites expressing distinct fluorescent proteins to monitor individuals in a genetically heterogeneous community, we found that the social motility defect of PDEB1 knockdowns is complemented by wild-type parasites in trans. Therefore, PDEB1 knockdown cells are competent for social motility but appear to lack a necessary factor that can be provided by wild-type cells. The combined data demonstrate that the role of cyclic nucleotides in regulating microbial social behavior extends to African trypanosomes and provide an example of transcomplementation in parasitic protozoa. IMPORTANCE In bacteria, studies of cell-cell communication and social behavior have profoundly influenced our understanding of microbial physiology, signaling, and pathogenesis. In contrast, mechanisms underlying social behavior in protozoan parasites are mostly unknown. Here we show that social behavior in the protozoan parasite Trypanosoma brucei is governed by cyclic-AMP signaling systems in the flagellum, with intriguing parallels to signaling systems that control bacterial social behavior. We also generated a T. brucei social behavior mutant and found that the mutant phenotype is complemented by wild-type cells grown in the same culture. Our findings open new avenues for dissecting social behavior and signaling in protozoan parasites and illustrate the capacity of these organisms to influence each other's behavior in mixed communities.
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Phillips JE, Gomer RH. Partial genetic suppression of a loss-of-function mutant of the neuronal ceroid lipofuscinosis-associated protease TPP1 in Dictyostelium discoideum. Dis Model Mech 2014; 8:147-56. [PMID: 25540127 PMCID: PMC4314780 DOI: 10.1242/dmm.018820] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Neuronal ceroid lipofuscinosis (NCL) is the most common childhood-onset neurodegenerative disease. NCL is inevitably fatal, and there is currently no treatment available. Children with NCL show a progressive decline in movement, vision and mental abilities, and an accumulation of autofluorescent deposits in neurons and other cell types. Late-infantile NCL is caused by mutations in the lysosomal protease tripeptidyl peptidase 1 (TPP1). TPP1 cleaves tripeptides from the N-terminus of proteins in vitro, but little is known about the physiological function of TPP1. TPP1 shows wide conservation in vertebrates but it is not found in Drosophila, Caenorhabditis elegans or Saccharomyces cerevisiae. Here, we characterize ddTpp1, a TPP1 ortholog present in the social amoeba Dictyostelium discoideum. Lysates from cells lacking ddTpp1 show a reduced but not abolished ability to cleave a TPP1 substrate, suggesting that other Dictyostelium enzymes can perform this cleavage. ddTpp1 and human TPP1 localize to the lysosome in Dictyostelium, indicating conserved function and trafficking. Cells that lack ddTpp1 show precocious multicellular development and a reduced ability to form spores during development. When cultured in autophagy-stimulating conditions, cells lacking ddTpp1 rapidly decrease in size and are less viable than wild-type cells, suggesting that one function of ddTpp1 could be to limit autophagy. Cells that lack ddTpp1 exhibit strongly impaired development in the presence of the lysosome-perturbing drug chloroquine, and this phenotype can be suppressed through a secondary mutation in the gene that we name suppressor of tpp1− A (stpA), which encodes a protein with some similarity to mammalian oxysterol-binding proteins (OSBPs). Taken together, these results suggest that targeting specific proteins could be a viable way to suppress the effects of loss of TPP1 function.
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Affiliation(s)
- Jonathan E Phillips
- Department of Biology, Texas A&M University, College Station, TX 77843-3474, USA
| | - Richard H Gomer
- Department of Biology, Texas A&M University, College Station, TX 77843-3474, USA.
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Insect stage-specific adenylate cyclases regulate social motility in African trypanosomes. EUKARYOTIC CELL 2014; 14:104-12. [PMID: 25416239 DOI: 10.1128/ec.00217-14] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Sophisticated systems for cell-cell communication enable unicellular microbes to act as multicellular entities capable of group-level behaviors that are not evident in individuals. These group behaviors influence microbe physiology, and the underlying signaling pathways are considered potential drug targets in microbial pathogens. Trypanosoma brucei is a protozoan parasite that causes substantial human suffering and economic hardship in some of the most impoverished regions of the world. T. brucei lives on host tissue surfaces during transmission through its tsetse fly vector, and cultivation on surfaces causes the parasites to assemble into multicellular communities in which individual cells coordinate their movements in response to external signals. This behavior is termed "social motility," based on its similarities with surface-induced social motility in bacteria, and it demonstrates that trypanosomes are capable of group-level behavior. Mechanisms governing T. brucei social motility are unknown. Here we report that a subset of receptor-type adenylate cyclases (ACs) in the trypanosome flagellum regulate social motility. RNA interference-mediated knockdown of adenylate cyclase 6 (AC6), or dual knockdown of AC1 and AC2, causes a hypersocial phenotype but has no discernible effect on individual cells in suspension culture. Mutation of the AC6 catalytic domain phenocopies AC6 knockdown, demonstrating that loss of adenylate cyclase activity is responsible for the phenotype. Notably, knockdown of other ACs did not affect social motility, indicating segregation of AC functions. These studies reveal interesting parallels in systems that control social behavior in trypanosomes and bacteria and provide insight into a feature of parasite biology that may be exploited for novel intervention strategies.
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Imhof S, Knüsel S, Gunasekera K, Vu XL, Roditi I. Social motility of African trypanosomes is a property of a distinct life-cycle stage that occurs early in tsetse fly transmission. PLoS Pathog 2014; 10:e1004493. [PMID: 25357194 PMCID: PMC4214818 DOI: 10.1371/journal.ppat.1004493] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Accepted: 09/29/2014] [Indexed: 12/21/2022] Open
Abstract
The protozoan pathogen Trypanosoma brucei is transmitted between mammals by tsetse flies. The first compartment colonised by trypanosomes after a blood meal is the fly midgut lumen. Trypanosomes present in the lumen—designated as early procyclic forms—express the stage-specific surface glycoproteins EP and GPEET procyclin. When the trypanosomes establish a mature infection and colonise the ectoperitrophic space, GPEET is down-regulated, and EP becomes the major surface protein of late procyclic forms. A few years ago, it was discovered that procyclic form trypanosomes exhibit social motility (SoMo) when inoculated on a semi-solid surface. We demonstrate that SoMo is a feature of early procyclic forms, and that late procyclic forms are invariably SoMo-negative. In addition, we show that, apart from GPEET, other markers are differentially expressed in these two life-cycle stages, both in culture and in tsetse flies, indicating that they have different biological properties and should be considered distinct stages of the life cycle. Differentially expressed genes include two closely related adenylate cyclases, both hexokinases and calflagins. These findings link the phenomenon of SoMo in vitro to the parasite forms found during the first 4–7 days of a midgut infection. We postulate that ordered group movement on plates reflects the migration of parasites from the midgut lumen into the ectoperitrophic space within the tsetse fly. Moreover, the process can be uncoupled from colonisation of the salivary glands. Although they are the major surface proteins of procyclic forms, EP and GPEET are not essential for SoMo, nor, as shown previously, are they required for near normal colonisation of the fly midgut. African trypanosomes, single-celled parasites that cause human sleeping sickness and Nagana in animals, are transmitted by tsetse flies. Bloodstream form trypanosomes ingested by tsetse differentiate into procyclic forms in the midgut lumen of the insect. Successful transmission to a new mammalian host requires at least two migrations within the fly: one from the midgut lumen to the ectoperitrophic space, and a subsequent migration from the ectoperitrophic space to the salivary glands. Procyclic forms can exhibit social motility, a form of coordinated movement, on semi-solid surfaces. While social motility in bacteria is linked to virulence, the biological significance for trypanosomes is unknown. We demonstrate that social motility is a property of early procyclic forms, which are equivalent to the forms present during the first week of fly infection. In contrast, late procyclic forms characteristic for established infections are deficient for social motility. Our findings link social motility to a biological process, confirm that early and late procyclic forms are distinct life-cycle stages and imply that genes essential for social motility will be of key importance in fly transmission. We suggest that using the social motility assay as a surrogate for fly experiments should enable many more laboratories to examine this aspect of parasite transmission.
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Affiliation(s)
- Simon Imhof
- Institute of Cell Biology, University of Bern, Bern, Switzerland
- Graduate School of Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Sebastian Knüsel
- Institute of Cell Biology, University of Bern, Bern, Switzerland
- Graduate School of Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | | | - Xuan Lan Vu
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | - Isabel Roditi
- Institute of Cell Biology, University of Bern, Bern, Switzerland
- * E-mail:
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A model of filamentous cyanobacteria leading to reticulate pattern formation. Life (Basel) 2014; 4:433-56. [PMID: 25370380 PMCID: PMC4206854 DOI: 10.3390/life4030433] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 08/09/2014] [Accepted: 08/14/2014] [Indexed: 12/03/2022] Open
Abstract
The filamentous cyanobacterium, Pseudanabaena, has been shown to produce reticulate patterns that are thought to be the result of its gliding motility. Similar fossilized structures found in the geological record constitute some of the earliest signs of life on Earth. It is difficult to tie these fossils, which are billions of years old, directly to the specific microorganisms that built them. Identifying the physicochemical conditions and microorganism properties that lead microbial mats to form macroscopic structures can lead to a better understanding of the conditions on Earth at the dawn of life. In this article, a cell-based model is used to simulate the formation of reticulate patterns in cultures of Pseudanabaena. A minimal system of long and flexible trichomes capable of gliding motility is shown to be sufficient to produce stable patterns consisting of a network of streams. Varying model parameters indicate that systems with little to no cohesion, high trichome density and persistent movement are conducive to reticulate pattern formation, in conformance with experimental observations.
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Ng MR, Besser A, Danuser G, Brugge JS. Substrate stiffness regulates cadherin-dependent collective migration through myosin-II contractility. ACTA ACUST UNITED AC 2012; 199:545-63. [PMID: 23091067 PMCID: PMC3483134 DOI: 10.1083/jcb.201207148] [Citation(s) in RCA: 219] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The mechanical microenvironment is known to influence single-cell migration; however, the extent to which mechanical cues affect collective migration of adherent cells is not well understood. We measured the effects of varying substrate compliance on individual cell migratory properties in an epithelial wound-healing assay. Increasing substrate stiffness increased collective cell migration speed, persistence, and directionality as well as the coordination of cell movements. Dynamic analysis revealed that wounding initiated a wave of motion coordination from the wound edge into the sheet. This was accompanied by a front-to-back gradient of myosin-II activation and establishment of cell polarity. The propagation was faster and farther reaching on stiff substrates, indicating that substrate stiffness affects the transmission of directional cues. Manipulation of myosin-II activity and cadherin-catenin complexes revealed that this transmission is mediated by coupling of contractile forces between neighboring cells. Thus, our findings suggest that the mechanical environment integrates in a feedback with cell contractility and cell-cell adhesion to regulate collective migration.
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Affiliation(s)
- Mei Rosa Ng
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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18
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Poloz Y, O'Day DH. Colchicine affects cell motility, pattern formation and stalk cell differentiation in Dictyostelium by altering calcium signaling. Differentiation 2012; 83:185-99. [PMID: 22381626 DOI: 10.1016/j.diff.2011.12.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 12/05/2011] [Accepted: 12/23/2011] [Indexed: 11/26/2022]
Abstract
Previous work, verified here, showed that colchicine affects Dictyostelium pattern formation, disrupts morphogenesis, inhibits spore differentiation and induces terminal stalk cell differentiation. Here we show that colchicine specifically induces ecmB expression and enhances accumulation of ecmB-expressing cells at the posterior end of multicellular structures. Colchicine did not induce a nuclear translocation of DimB, a DIF-1 responsive transcription factor in vitro. It also induced terminal stalk cell differentiation in a mutant strain that does not produce DIF-1 (dmtA-) and after the treatment of cells with DIF-1 synthesis inhibitor cerulenin (100 μM). This suggests that colchicine induces the differentiation of ecmB-expressing cells independent of DIF-1 production and likely through a signaling pathway that is distinct from the one that is utilized by DIF-1. Depending on concentration, colchicine enhanced random cell motility, but not chemotaxis, by 3-5 fold (10-50 mM colchicine, respectively) through a Ca(2+)-mediated signaling pathway involving phospholipase C, calmodulin and heterotrimeric G proteins. Colchicine's effects were not due to microtubule depolymerization as other microtubule-depolymerizing agents did not have these effects. Finally normal morphogenesis and stalk and spore cell differentiation of cells treated with 10 mM colchicine were rescued through chelation of Ca2+ by BAPTA-AM and EDTA and calmodulin antagonism by W-7 but not PLC inhibition by U-73122. Morphogenesis or spore cell differentiation of cells treated with 50 mM colchicine could not be rescued by the above treatments but terminal stalk cell differentiation was inhibited by BAPTA-AM, EDTA and W-7, but not U-73122. Thus colchicine disrupts morphogenesis and induces stalk cell differentiation through a Ca(2+)-mediated signaling pathway involving specific changes in gene expression and cell motility.
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Affiliation(s)
- Yekaterina Poloz
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5.
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Bestatin inhibits cell growth, cell division, and spore cell differentiation in Dictyostelium discoideum. EUKARYOTIC CELL 2012; 11:545-57. [PMID: 22345351 DOI: 10.1128/ec.05311-11] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Bestatin methyl ester (BME) is an inhibitor of Zn(2+)-binding aminopeptidases that inhibits cell proliferation and induces apoptosis in normal and cancer cells. We have used Dictyostelium as a model organism to study the effects of BME. Only two Zn(2+)-binding aminopeptidases have been identified in Dictyostelium to date, puromycin-sensitive aminopeptidase A and B (PsaA and PsaB). PSA from other organisms is known to regulate cell division and differentiation. Here we show that PsaA is differentially expressed throughout growth and development of Dictyostelium, and its expression is regulated by developmental morphogens. We present evidence that BME specifically interacts with PsaA and inhibits its aminopeptidase activity. Treatment of cells with BME inhibited the rate of cell growth and the frequency of cell division in growing cells and inhibited spore cell differentiation during late development. Overexpression of PsaA-GFP (where GFP is green fluorescent protein) also inhibited spore cell differentiation but did not affect growth. Using chimeras, we have identified that nuclear versus cytoplasmic localization of PsaA affects the choice between stalk or spore cell differentiation pathway. Cells that overexpressed PsaA-GFP (primarily nuclear) differentiated into stalk cells, while cells that overexpressed PsaAΔNLS2-GFP (cytoplasmic) differentiated into spores. In conclusion, we have identified that BME inhibits cell growth, division, and differentiation in Dictyostelium likely through inhibition of PsaA.
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20
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Sultana H, Neelakanta G, Rivero F, Blau-Wasser R, Schleicher M, Noegel AA. Ectopic expression of cyclase associated protein CAP restores the streaming and aggregation defects of adenylyl cyclase a deficient Dictyostelium discoideum cells. BMC DEVELOPMENTAL BIOLOGY 2012; 12:3. [PMID: 22239817 PMCID: PMC3316131 DOI: 10.1186/1471-213x-12-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Accepted: 01/12/2012] [Indexed: 12/02/2022]
Abstract
Background Cell adhesion, an integral part of D. discoideum development, is important for morphogenesis and regulated gene expression in the multicellular context and is required to trigger cell-differentiation. G-protein linked adenylyl cyclase pathways are crucially involved and a mutant lacking the aggregation specific adenylyl cyclase ACA does not undergo multicellular development. Results Here, we have investigated the role of cyclase-associated protein (CAP), an important regulator of cell polarity and F-actin/G-actin ratio in the aca- mutant. We show that ectopic expression of GFP-CAP improves cell polarization, streaming and aggregation in aca- cells, but it fails to completely restore development. Our studies indicate a requirement of CAP in the ACA dependent signal transduction for progression of the development of unicellular amoebae into multicellular structures. The reduced expression of the cell adhesion molecule DdCAD1 together with csA is responsible for the defects in aca- cells to initiate multicellular development. Early development was restored by the expression of GFP-CAP that enhanced the DdCAD1 transcript levels and to a lesser extent the csA mRNA levels. Conclusions Collectively, our data shows a novel role of CAP in regulating cell adhesion mechanisms during development that might be envisioned to unravel the functions of mammalian CAP during animal embryogenesis.
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Affiliation(s)
- Hameeda Sultana
- Center for Biochemistry, Medical Faculty, University of Cologne, 50931 Köln, Germany.
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21
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Zhang L, Radtke K, Zheng L, Cai AQ, Schilling TF, Nie Q. Noise drives sharpening of gene expression boundaries in the zebrafish hindbrain. Mol Syst Biol 2012; 8:613. [PMID: 23010996 PMCID: PMC3472692 DOI: 10.1038/msb.2012.45] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 08/16/2012] [Indexed: 01/24/2023] Open
Abstract
Morphogens provide positional information for spatial patterns of gene expression during development. However, stochastic effects such as local fluctuations in morphogen concentration and noise in signal transduction make it difficult for cells to respond to their positions accurately enough to generate sharp boundaries between gene expression domains. During development of rhombomeres in the zebrafish hindbrain, the morphogen retinoic acid (RA) induces expression of hoxb1a in rhombomere 4 (r4) and krox20 in r3 and r5. Fluorescent in situ hybridization reveals rough edges around these gene expression domains, in which cells co-express hoxb1a and krox20 on either side of the boundary, and these sharpen within a few hours. Computational analysis of spatial stochastic models shows, surprisingly, that noise in hoxb1a/krox20 expression actually promotes sharpening of boundaries between adjacent segments. In particular, fluctuations in RA initially induce a rough boundary that requires noise in hoxb1a/krox20 expression to sharpen. This finding suggests a novel noise attenuation mechanism that relies on intracellular noise to induce switching and coordinate cellular decisions during developmental patterning.
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Affiliation(s)
- Lei Zhang
- Department of Mathematics, University of California, Irvine, CA, USA
- Center for Complex Biological Systems, University of California, Irvine, CA, USA
- Center for Mathematical and Computational Biology, University of California, Irvine, CA, USA
- Department of Mathematics, City University of Hong Kong, Kowloon Tong, Hong Kong
| | - Kelly Radtke
- Department of Development and Cell Biology, University of California, Irvine, CA, USA
| | - Likun Zheng
- Department of Mathematics, University of California, Irvine, CA, USA
- Center for Complex Biological Systems, University of California, Irvine, CA, USA
- Center for Mathematical and Computational Biology, University of California, Irvine, CA, USA
| | - Anna Q Cai
- Department of Applied Mathematics, School of Mathematics and Statistics, University of New South Wales, Sydney, New South Wales, Australia
| | - Thomas F Schilling
- Center for Complex Biological Systems, University of California, Irvine, CA, USA
- Department of Development and Cell Biology, University of California, Irvine, CA, USA
| | - Qing Nie
- Department of Mathematics, University of California, Irvine, CA, USA
- Center for Complex Biological Systems, University of California, Irvine, CA, USA
- Center for Mathematical and Computational Biology, University of California, Irvine, CA, USA
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Lopez MA, Nguyen HT, Oberholzer M, Hill KL. Social parasites. Curr Opin Microbiol 2011; 14:642-8. [PMID: 22020108 DOI: 10.1016/j.mib.2011.09.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 09/23/2011] [Accepted: 09/27/2011] [Indexed: 11/24/2022]
Abstract
Protozoan parasites cause tremendous human suffering worldwide, but strategies for therapeutic intervention are limited. Recent studies illustrate that the paradigm of microbes as social organisms can be brought to bear on questions about parasite biology, transmission and pathogenesis. This review discusses recent work demonstrating adaptation of social behaviors by parasitic protozoa that cause African sleeping sickness and malaria. The recognition of social behavior and cell-cell communication as a ubiquitous property of bacteria has transformed our view of microbiology, but protozoan parasites have not generally been considered in this context. Works discussed illustrate the potential for concepts of sociomicrobiology to provide insight into parasite biology and should stimulate new approaches for thinking about parasites and parasite-host interactions.
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Affiliation(s)
- Miguel A Lopez
- Department of Microbiology, Immunology and Molecular Genetics, UCLA, Los Angeles, CA 90095, USA
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23
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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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Abstract
African trypanosomes are devastating human and animal pathogens that cause significant human mortality and limit economic development in sub-Saharan Africa. Studies of trypanosome biology generally consider these protozoan parasites as individual cells in suspension cultures or in animal models of infection. Here we report that the procyclic form of the African trypanosome Trypanosoma brucei engages in social behavior when cultivated on semisolid agarose surfaces. This behavior is characterized by trypanosomes assembling into multicellular communities that engage in polarized migrations across the agarose surface and cooperate to divert their movements in response to external signals. These cooperative movements are flagellum-mediated, since they do not occur in trypanin knockdown parasites that lack normal flagellum motility. We term this behavior social motility based on features shared with social motility and other types of surface-induced social behavior in bacteria. Social motility represents a novel and unexpected aspect of trypanosome biology and offers new paradigms for considering host-parasite interactions. African trypanosomes, e.g. Trypanosoma brucei, and related kinetoplastid parasites cause morbidity and mortality in several million people worldwide. Trypanosomes are protists and are thus generally considered to behave as single-celled microorganisms. In other microorganisms, social interactions among individuals lead to development of multicellular communities with specialized and advantageous capabilities versus single cells. The concept of bacteria acting as groups of cells communicating and cooperating with one another has had a major impact on our understanding of bacterial physiology and pathogenesis, but this paradigm has not been applied to parasitic protozoa. Here we report that T. brucei is capable of social behavior when exposed to semisolid surfaces. This behavior, termed social motility, is characterized by the assembly of parasites into multicellular communities with emergent properties that are not evident in single cells. Parasites within communities exhibit polarized movements and cooperate to coordinate their movements in response to an external stimulus. Social motility offers many potential advantages, such as facilitating colonization and navigation through host tissues. The identification of social behavior in T. brucei reveals a novel and unexpected aspect of parasite biology and provides new concepts for considering host-parasite interactions.
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Binamé F, Pawlak G, Roux P, Hibner U. What makes cells move: requirements and obstacles for spontaneous cell motility. MOLECULAR BIOSYSTEMS 2010; 6:648-61. [PMID: 20237642 DOI: 10.1039/b915591k] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Movement of individual cells and of cellular cohorts, chains or sheets requires physical forces that are established through interactions of cells with their environment. In vivo, migration occurs extensively during embryonic development and in adults during wound healing and tumorigenesis. In order to identify the molecular events involved in cell movement, in vitro systems have been developed. These have contributed to the definition of a number of molecular pathways put into play in the course of migratory behaviours, such as mesenchymal and amoeboid movement. More recently, our knowledge of migratory modes has been enriched by analyses of cells exploring and moving through three-dimensional (3D) matrices. While the cells' morphologies differ in 2D and 3D environments, the basic mechanisms that put a cellular body into motion are remarkably similar. Thus, in both 2D and 3D, the polarity of the migrating cell is initially defined by a specific subcellular localization of signalling molecules and components of molecular machines required for motion. While the polarization can be initiated either in response to extracellular signalling or be a chance occurrence, it is reinforced and sustained by positive feedback loops of signalling molecules. Second, adhesion to a substratum is necessary to generate forces that will propel the cell engaged in either mesenchymal or ameboid migration. For collective cell movement, intercellular coordination constitutes an additional requirement: a cell cohort remains stationary if individual cells pull in opposite directions. Finally, the availability of space to move into is a general requirement to set cells into motion. Lack of free space is probably the main obstacle for migration of most healthy cells in an adult multicellular organism. Thus, the requirements for cell movement are both intrinsic to the cell, involving coordinated signalling and interactions with molecular machines, and extrinsic, imposed by the physicochemical nature of the environment. In particular, the geometry and stiffness of the support act on a range of signalling pathways that induce specific cell migratory responses. These issues are discussed in the present review in the context of published work and our own data on collective migration of hepatocyte cohorts.
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Affiliation(s)
- Fabien Binamé
- CNRS, UMR 5535, IGMM, 1919 route de Mende, 34293 Montpellier, France
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Jeon TJ, Lee S, Weeks G, Firtel RA. Regulation of Dictyostelium morphogenesis by RapGAP3. Dev Biol 2009; 328:210-20. [PMID: 19284976 DOI: 10.1016/j.ydbio.2009.01.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2008] [Revised: 12/16/2008] [Accepted: 01/08/2009] [Indexed: 12/01/2022]
Abstract
Rap1 is a key regulator of cell adhesion and cell motility in Dictyostelium. Here, we identify a Rap1-specific GAP protein (RapGAP3) and provide evidence that Rap1 signaling regulates cell-cell adhesion and cell migration within the multicellular organism. RapGAP3 mediates the deactivation of Rap1 at the late mound stage of development and plays an important role in regulating cell sorting during apical tip formation, when the anterior-posterior axis of the organism is formed, by controlling cell-cell adhesion and cell migration. The loss of RapGAP3 results in a severely altered morphogenesis of the multicellular organism at the late mound stage. Direct measurement of cell motility within the mound shows that rapGAP3(-) cells have a reduced speed of movement and, compared to wild-type cells, have a reduced motility towards the apex. rapGAP3(-) cells exhibit some increased EDTA/EGTA sensitive cell-cell adhesion at the late mound stage. RapGAP3 transiently and rapidly translocates to the cell cortex in response to chemoattractant stimulation, which is dependent on F-actin polymerization. We suggest that the altered morphogenesis and the cell-sorting defect of rapGAP3(-) cells may result in reduced directional movement of the mutant cells to the apex of the mound.
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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, 9500 Gilman Drive, La Jolla, CA 92093-0380, USA
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Abstract
Chemotactic eukaryotic cells are able to detect chemoattractant gradients that are both shallow and have a low background concentration. Under these conditions, the noise in the number of bound receptors can be significant and needs to be taken into account in determining the directional sensing process. Here, we quantify numerically the number of bound receptors on the membrane of a disk-shaped cell by using a numerical Monte Carlo tool. The obtained time traces of the receptor occupancy can be used as inputs for any directional sensing model. We investigate the response of the local excitation global inhibition model and a recently developed balanced inactivation model. We determine a measure for the motility of the cell for each model, based on the relevant output variable, as a function of experimental parameters, resulting in several experimentally testable predictions. Furthermore, we show that these two models behave in a qualitatively different fashion when the background concentration is varied. Thus, to properly characterize the sensitivity of cells to receptor occupancy, it is not sufficient to examine the input signal. Rather, one needs to take into account the response of the second messenger pathway.
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A protein with similarity to PTEN regulates aggregation territory size by decreasing cyclic AMP pulse size during Dictyostelium discoideum development. EUKARYOTIC CELL 2008; 7:1758-70. [PMID: 18676953 DOI: 10.1128/ec.00210-08] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
An interesting but largely unanswered biological question is how eukaryotic organisms regulate the size of multicellular tissues. During development, a lawn of Dictyostelium cells breaks up into territories, and within the territories the cells aggregate in dendritic streams to form groups of approximately 20,000 cells. Using random insertional mutagenesis to search for genes involved in group size regulation, we found that an insertion in the cnrN gene affects group size. Cells lacking CnrN (cnrN(-)) form abnormally small groups, which can be rescued by the expression of exogenous CnrN. Relayed pulses of extracellular cyclic AMP (cAMP) direct cells to aggregate by chemotaxis to form aggregation territories and streams. cnrN(-) cells overaccumulate cAMP during development and form small territories. Decreasing the cAMP pulse size by treating cnrN(-) cells with cAMP phosphodiesterase or starving cnrN(-) cells at a low density rescues the small-territory phenotype. The predicted CnrN sequence has similarity to phosphatase and tensin homolog (PTEN), which in Dictyostelium inhibits cAMP-stimulated phosphatidylinositol 3-kinase signaling pathways. CnrN inhibits cAMP-stimulated phosphatidylinositol 3,4,5-trisphosphate accumulation, Akt activation, actin polymerization, and cAMP production. Our results suggest that CnrN is a protein with some similarities to PTEN and that it regulates cAMP signal transduction to regulate territory size.
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Aragão KS, Satre M, Imberty A, Varrot A. Structure determination of discoidin II from Dictyostelium discoideum and carbohydrate binding properties of the lectin domain. Proteins 2008; 73:43-52. [DOI: 10.1002/prot.22038] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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30
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Gao T, Roisin-Bouffay C, Hatton RD, Tang L, Brock DA, DeShazo T, Olson L, Hong WP, Jang W, Canseco E, Bakthavatsalam D, Gomer RH. A cell number-counting factor regulates levels of a novel protein, SslA, as part of a group size regulation mechanism in Dictyostelium. EUKARYOTIC CELL 2007; 6:1538-51. [PMID: 17660362 PMCID: PMC2043358 DOI: 10.1128/ec.00169-07] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Developing Dictyostelium cells form aggregation streams that break into groups of approximately 2 x 10(4) cells. The breakup and subsequent group size are regulated by a secreted multisubunit counting factor (CF). To elucidate how CF regulates group size, we isolated second-site suppressors of smlA(-), a transformant that forms small groups due to oversecretion of CF. smlA(-) sslA1(CR11) cells form roughly wild-type-size groups due to an insertion in the beginning of the coding region of sslA1, one of two highly similar genes encoding a novel protein. The insertion increases levels of SslA. In wild-type cells, the sslA1(CR11) mutation forms abnormally large groups. Reducing SslA levels by antisense causes the formation of smaller groups. The sslA(CR11) mutation does not affect the extracellular accumulation of CF activity or the CF components countin and CF50, suggesting that SslA does not regulate CF secretion. However, CF represses levels of SslA. Wild-type cells starved in the presence of smlA(-) cells, recombinant countin, or recombinant CF50 form smaller groups, whereas sslA1(CR11) cells appear to be insensitive to the presence of smlA(-) cells, countin, or CF50, suggesting that the sslA1(CR11) insertion affects CF signal transduction. We previously found that CF reduces intracellular glucose levels. sslA(CR11) does not significantly affect glucose levels, while glucose increases SslA levels. Together, the data suggest that SslA is a novel protein involved in part of a signal transduction pathway regulating group size.
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Affiliation(s)
- Tong Gao
- Howard Hughes Medical Institute, MS-140, Rice University, 6100 S. Main Street, Houston, TX 77005-1892, USA
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Tsai JW, Bremner KH, Vallee RB. Dual subcellular roles for LIS1 and dynein in radial neuronal migration in live brain tissue. Nat Neurosci 2007; 10:970-9. [PMID: 17618279 DOI: 10.1038/nn1934] [Citation(s) in RCA: 330] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Accepted: 06/05/2007] [Indexed: 12/23/2022]
Abstract
During brain development, neural precursor cells migrate along radial glial fibers to populate the neocortex. RNA interference (RNAi) of the lissencephaly gene LIS1 (also known as PAFAH1b1) inhibits somal movement but not process extension of neural precursors in live brain slices. Here we report imaging of the subcellular events accompanying neural precursor migration and the effects of LIS1, cytoplasmic dynein and myosin II inhibition. Centrosomes move continuously and often far in advance of nuclei, which show extreme saltatory behavior. LIS1 and dynein RNAi inhibit centrosomal and nuclear movement independently, whereas myosin II inhibition blocks only nuclear translocation. Imaging of the microtubule end-binding protein 3 (EB3) reveals a centrosome-centered array of microtubules in live neural precursors under all conditions examined. Dynein is concentrated both at a swelling in the leading process reported to initiate each migratory cycle and in the soma. Thus, dynein pulls on the microtubule network from the swelling. The nucleus is transported along the trailing microtubules by dynein assisted by myosin II.
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Affiliation(s)
- Jin-Wu Tsai
- Integrated Program in Cellular, Molecular and Biophysical Studies, Columbia University, 630 W 168th Street, New York, New York 10032, USA
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32
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Tomlin CJ, Axelrod JD. Biology by numbers: mathematical modelling in developmental biology. Nat Rev Genet 2007; 8:331-40. [PMID: 17440530 DOI: 10.1038/nrg2098] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In recent years, mathematical modelling of developmental processes has earned new respect. Not only have mathematical models been used to validate hypotheses made from experimental data, but designing and testing these models has led to testable experimental predictions. There are now impressive cases in which mathematical models have provided fresh insight into biological systems, by suggesting, for example, how connections between local interactions among system components relate to their wider biological effects. By examining three developmental processes and corresponding mathematical models, this Review addresses the potential of mathematical modelling to help understand development.
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Affiliation(s)
- Claire J Tomlin
- Department of Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, California 94720, USA.
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Otsuji M, Ishihara S, Co C, Kaibuchi K, Mochizuki A, Kuroda S. A mass conserved reaction-diffusion system captures properties of cell polarity. PLoS Comput Biol 2007; 3:e108. [PMID: 17559299 PMCID: PMC1892603 DOI: 10.1371/journal.pcbi.0030108] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2006] [Accepted: 04/29/2007] [Indexed: 12/23/2022] Open
Abstract
Cell polarity is a general cellular process that can be seen in various cell types such as migrating neutrophils and Dictyostelium cells. The Rho small GTP(guanosine 5′-tri phosphate)ases have been shown to regulate cell polarity; however, its mechanism of emergence has yet to be clarified. We first developed a reaction–diffusion model of the Rho GTPases, which exhibits switch-like reversible response to a gradient of extracellular signals, exclusive accumulation of Cdc42 and Rac, or RhoA at the maximal or minimal intensity of the signal, respectively, and tracking of changes of a signal gradient by the polarized peak. The previous cell polarity models proposed by Subramanian and Narang show similar behaviors to our Rho GTPase model, despite the difference in molecular networks. This led us to compare these models, and we found that these models commonly share instability and a mass conservation of components. Based on these common properties, we developed conceptual models of a mass conserved reaction–diffusion system with diffusion–driven instability. These conceptual models retained similar behaviors of cell polarity in the Rho GTPase model. Using these models, we numerically and analytically found that multiple polarized peaks are unstable, resulting in a single stable peak (uniqueness of axis), and that sensitivity toward changes of a signal gradient is specifically restricted at the polarized peak (localized sensitivity). Although molecular networks may differ from one cell type to another, the behaviors of cell polarity in migrating cells seem similar, suggesting that there should be a fundamental principle. Thus, we propose that a mass conserved reaction–diffusion system with diffusion-driven instability is one of such principles of cell polarity. Eukaryotic cells such as neutrophils and Dictyostelium cells respond to temporal and spatial gradients of extracellular signals with directional movements. In a migrating cell, specific molecular events take place at the front and back edges. The spatially distinctive molecular accumulation inside cells is known as cell polarity. Despite numerous experimental and theoretical studies, its mechanism of emergence has yet to be clarified. We first developed a mathematical model of the Rho small GTP(guanosine 5′-tri phosphate)ases that cooperatively regulate cell polarity, and showed that the model generates specific spatial accumulation of the molecules. Based on our Rho GTPases model and other models, we further established a conceptual model, a mass conserved reaction–diffusion system, and showed that diffusion-driven instability and a mass conservation of molecules that have active and inactive states are sufficient for polarity formation. We numerically and analytically found that molecular accumulations at multiple sites are unstable, resulting in a single stable front–back axis, and that sensitivity toward changes of a signal gradient is specifically restricted at the front of a polarized cell. We propose that a mass conserved reaction–diffusion system is one of the fundamental principles of cell polarity.
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Affiliation(s)
- Mikiya Otsuji
- Department of Anesthesiology, Faculty of Medicine, University of Tokyo, Tokyo, Japan.
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Skupsky R, McCann C, Nossal R, Losert W. Bias in the gradient-sensing response of chemotactic cells. J Theor Biol 2007; 247:242-58. [PMID: 17462672 PMCID: PMC2763186 DOI: 10.1016/j.jtbi.2007.02.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Revised: 01/15/2007] [Accepted: 02/27/2007] [Indexed: 12/22/2022]
Abstract
We apply linear stability theory and perform perturbation studies to better characterize, and to generate new experimental predictions from, a model of chemotactic gradient sensing in eukaryotic cells. The model uses reaction-diffusion equations to describe 3(') phosphoinositide signaling and its regulation at the plasma membrane. It demonstrates a range of possible gradient-sensing mechanisms and captures such characteristic behaviors as strong polarization in response to static gradients, adaptation to differing mean levels of stimulus, and plasticity in response to changing gradients. An analysis of the stability of polarized steady-state solutions indicates that the model is most sensitive to off-axis perturbations. This biased sensitivity is also reflected in responses to localized external stimuli, and leads to a clear experimental prediction, namely, that a cell which is polarized in a background gradient will be most sensitive to transient point-source stimuli lying within a range of angles that are oblique with respect to the polarization axis. Stimuli at angles below this range will elicit responses whose directions overshoot the stimulus angle, while responses to stimuli applied at larger angles will undershoot the stimulus angle. We argue that such a bias is likely to be a general feature of gradient sensing in highly motile cells, particularly if they are optimized to respond to small gradients. Finally, an angular bias in gradient sensing might lead to preferred turn angles and zigzag movements of cells moving up chemotactic gradients, as has been noted under certain experimental conditions.
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Affiliation(s)
- Ron Skupsky
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892 USA
- Physics Department, University of Maryland, College Park, MD 20742 USA
| | - Colin McCann
- Physics Department, University of Maryland, College Park, MD 20742 USA
| | - Ralph Nossal
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892 USA
| | - Wolfgang Losert
- Physics Department, University of Maryland, College Park, MD 20742 USA
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35
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Song L, Nadkarni SM, Bödeker HU, Beta C, Bae A, Franck C, Rappel WJ, Loomis WF, Bodenschatz E. Dictyostelium discoideum chemotaxis: threshold for directed motion. Eur J Cell Biol 2006; 85:981-9. [PMID: 16529846 DOI: 10.1016/j.ejcb.2006.01.012] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The chemotactic response of Dictyostelium discoideum cells to stationary, linear gradients of cyclic adenosine 3',5'-monophosphate (cAMP) was studied using microfluidic devices. In shallow gradients of less than 10(-3) nM/microm, the cells showed no directional response and exhibited a constant basal motility. In steeper gradients, cells moved up the gradient on average. The chemotactic speed and the motility increased with increasing steepness up to a plateau at around 10(-1) nM/microm. In very steep gradients, above 10 nM/microm, the cells lost directionality and the motility returned to the sub-threshold level. In the regime of optimal response the difference in receptor occupancy at the front and back of the cell is estimated to be only about 100 molecules.
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Affiliation(s)
- Loling Song
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA
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36
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Liu CI, Cheng TL, Chen SZ, Huang YC, Chang WT. LrrA, a novel leucine-rich repeat protein involved in cytoskeleton remodeling, is required for multicellular morphogenesis in Dictyostelium discoideum. Dev Biol 2005; 285:238-51. [PMID: 16051212 DOI: 10.1016/j.ydbio.2005.05.045] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2004] [Revised: 05/07/2005] [Accepted: 05/25/2005] [Indexed: 12/17/2022]
Abstract
Cell sorting by differential cell adhesion and movement is a fundamental process in multicellular morphogenesis. We have identified a Dictyostelium discoideum gene encoding a novel protein, LrrA, which composes almost entirely leucine-rich repeats (LRRs) including a putative leucine zipper motif. Transcription of lrrA appeared to be developmentally regulated with robust expression during vegetative growth and early development. lrrA null cells generated by homologous recombination aggregated to form loose mounds, but subsequent morphogenesis was blocked without formation of the apical tip. The cells adhered poorly to a substratum and did not form tight cell-cell agglomerates in suspension; in addition, they were unable to polarize and exhibit chemotactic movement in the submerged aggregation and Dunn chamber chemotaxis assays. Fluorescence-conjugated phalloidin staining revealed that both vegetative and aggregation competent lrrA(-) cells contained numerous F-actin-enriched microspikes around the periphery of cells. Quantitative analysis of the fluorescence-stained F-actin showed that lrrA(-) cells exhibited a dramatically increase in F-actin as compared to the wild-type cells. When developed together with wild-type cells, lrrA(-) cells were unable to move to the apical tip and sorted preferentially to the rear and lower cup regions. These results indicate that LrrA involves in cytoskeleton remodeling, which is needed for normal chemotactic aggregation and efficient cell sorting during multicellular morphogenesis, particularly in the formation of apical tip.
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Affiliation(s)
- Chia-I Liu
- Department of Biochemistry, National Cheng Kung University Medical College, Tainan 701, Taiwan, ROC
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37
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Abstract
We develop a mathematical model of phosphoinositide-mediated gradient sensing that can be applied to chemotactic behavior in highly motile eukaryotic cells such as Dictyostelium and neutrophils. We generate four variants of our model by adjusting parameters that control the strengths of coupled positive feedbacks and the importance of molecules that translocate from the cytosol to the membrane. Each variant exhibits a qualitatively different mode of gradient sensing. Simulations of characteristic behaviors suggest that differences between the variants are most evident at transitions between efficient gradient detection and failure. Based on these results, we propose criteria to distinguish between possible modes of gradient sensing in real cells, where many biochemical parameters may be unknown. We also identify constraints on parameters required for efficient gradient detection. Finally, our analysis suggests how a cell might transition between responsiveness and nonresponsiveness, and between different modes of gradient sensing, by adjusting its biochemical parameters.
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Affiliation(s)
- R Skupsky
- Laboratory of Integrative and Medical Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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38
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Lusche DF, Kaneko H, Malchow D. cGMP-phosphodiesterase antagonists inhibit Ca2+-influx in Dictyostelium discoideum and bovine cyclic-nucleotide-gated-channel. Eur J Pharmacol 2005; 513:9-20. [PMID: 15878705 DOI: 10.1016/j.ejphar.2005.01.047] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Revised: 12/24/2004] [Accepted: 01/27/2005] [Indexed: 11/27/2022]
Abstract
We used antagonists of cGMP-phosphodiesterases to examine the role of cGMP for light-scattering oscillations and cAMP-induced Ca(2+)-influx in Dictyostelium discoideum, however, SCH 51866 (cis-5,6a,7,8,9,9a-hexahydro-2-[4-(trifluoromethyl)phenylmethyl]-5-methyl-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one) and sildenafil citrate (1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1-H-pyrazolo[4,3-d]pyrimidin-5-yl)-4-ethoxyphenyl]sulfonyl]-4-methylpiperazine citrate) were poor inhibitors of cGMP-hydrolysis. Instead, SCH 51866 (IC(50) = 16 microM) and sildenafil, blocked chemoattractant (cAMP)-induced Ca(2+)-influx as determined with a Ca(2+)-specific electrode. SCH 51866 (150 microM) affected neither spontaneous cGMP transients during light-scattering-oscillations nor cAMP-mediated K(+)-efflux. SCH 51866 and sildenafil are competitive inhibitors of cGMP phosphodiesterases. However, the activity of cGMP-dependent protein kinase Ialpha (PKGIalpha) was not altered by SCH 51866 (150 microM). By contrast, patch-clamp measurements of bovine cone cGMP-gated-channels (cyclic-nucleotide-gated-channel, CNGA3), stably expressed in human embryonic kidney cells, HEK 293 cells, revealed reversible, competitive and dose-dependent inhibition of sodium currents by SCH 51866 (IC(50) = 25 microM) and sildenafil, but not by another inhibitor of cGMP-phosphodiesterases, UK 114,542. The possibility that D. discoideum cells also express a cGMP-regulated channel is supported by our finding that LY 83583 (6-(phenylamino)-5,8-quinolinedione) (35 microM), known to inhibit cyclic-nucleotide-gated-channels as well as guanylyl-cyclases, reduced cAMP-induced Ca(2+)-influx in D. discoideum, but did not affect cAMP-induced cGMP accumulation. Utilizing a PDED null strain that exhibits a prolonged and elevated cGMP transient following receptor activation, we found that the inhibition of Ca(2+)-influx by SCH 51866 in the wildtype was absent in the mutant. Our results show that SCH 51866 and sildenafil are antagonists of a Ca(2+)-permeable channel (CNGA3) and that both compete with cGMP for a regulatory site of Ca(2+)-influx in D. discoideum.
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Abstract
For pollination to succeed, pollen must carry sperm through a variety of different floral tissues to access the ovules within the pistil. The pistil provides everything the pollen requires for success in this endeavor including distinct guidance cues and essential nutrients that allow the pollen tube to traverse enormous distances along a complex path to the unfertilized ovule. Although the pistil is a great facilitator of pollen function, it can also be viewed as an elaborate barrier that shields ovules from access from inappropriate pollen, such as pollen from other species. Each discrete step taken by pollen tubes en route to the ovules is a potential barrier point to ovule access and waste by inappropriate mates. In this review, we survey the current molecular understanding of how pollination proceeds, and ask to what extent is each step important for mate discrimination. As this field progresses, this synthesis of functional biology and evolutionary studies will provide insight into the molecular basis of the species barriers that maintain the enormous diversity seen in flowering plants.
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Affiliation(s)
- Robert Swanson
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Illinois 60637, USA.
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40
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Myers SA, Han JW, Lee Y, Firtel RA, Chung CY. A Dictyostelium homologue of WASP is required for polarized F-actin assembly during chemotaxis. Mol Biol Cell 2005; 16:2191-206. [PMID: 15728724 PMCID: PMC1087228 DOI: 10.1091/mbc.e04-09-0844] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The actin cytoskeleton controls the overall structure of cells and is highly polarized in chemotaxing cells, with F-actin assembled predominantly in the anterior leading edge and to a lesser degree in the cell's posterior. Wiskott-Aldrich syndrome protein (WASP) has emerged as a central player in controlling actin polymerization. We have investigated WASP function and its regulation in chemotaxing Dictyostelium cells and demonstrated the specific and essential role of WASP in organizing polarized F-actin assembly in chemotaxing cells. Cells expressing very low levels of WASP show reduced F-actin levels and significant defects in polarized F-actin assembly, resulting in an inability to establish axial polarity during chemotaxis. GFP-WASP preferentially localizes at the leading edge and uropod of chemotaxing cells and the B domain of WASP is required for the localization of WASP. We demonstrated that the B domain binds to PI(4,5)P2 and PI(3,4,5)P3 with similar affinities. The interaction between the B domain and PI(3,4,5)P3 plays an important role for the localization of WASP to the leading edge in chemotaxing cells. Our results suggest that the spatial and temporal control of WASP localization and activation is essential for the regulation of directional motility.
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Affiliation(s)
- Scott A Myers
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville TN 37232-6600, USA
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41
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Kawata T, Nakagawa M, Shimada N, Fujii S, Oohata AA. A gene encoding, prespore-cell-inducing factor in Dictyostelium discoideum. Dev Growth Differ 2004; 46:383-92. [PMID: 15367206 DOI: 10.1111/j.1440-169x.2004.00749.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two factors that exist in conditioned medium (CM) of Dictyostelium discoideum induce amoebae to differentiate into prespore cells when they are incubated at a very low cell density in submerged monolayer culture. Previously, we purified one of them, a glycoprotein factor with an apparent molecular mass of 106 kDa, and we named it psi factor (psi, prespore-inducing factor). Based on the partial amino acid sequence of the purified psi factor, we have isolated the corresponding cDNA clone, which is expressed maximally at the loose mound stage. The cDNA encodes a novel protein and the predicted molecular mass of the mature secreted protein is 60 kDa. Knockout mutant strains of the psi factor gene, psiA(-), were created by targeted integration. Although these mutant strains appear to develop normally, CM from these mutants showed reduced prespore-cell-inducing activity. Rescuing the mutant strains by expression of psi factor under control of a constitutive promoter causes overproduction of psi factor protein and CM from such cells showed a 20-fold higher level of prespore-cell-inducing activity than that from wild-type cells. Further, CM from parental cells induced prespore cell division, while that from psiA null strains showed no cell division inducing activity. Our results indicate that psi factor protein is a novel type of growth factor that does not belong to any of the families of growth factor so far identified in animals.
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Affiliation(s)
- Takefumi Kawata
- Department of Biology, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan
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42
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Noegel AA, Blau-Wasser R, Sultana H, Müller R, Israel L, Schleicher M, Patel H, Weijer CJ. The cyclase-associated protein CAP as regulator of cell polarity and cAMP signaling in Dictyostelium. Mol Biol Cell 2003; 15:934-45. [PMID: 14595119 PMCID: PMC329405 DOI: 10.1091/mbc.e03-05-0269] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cyclase-associated protein (CAP) is an evolutionarily conserved regulator of the G-actin/F-actin ratio and, in yeast, is involved in regulating the adenylyl cyclase activity. We show that cell polarization, F-actin organization, and phototaxis are altered in a Dictyostelium CAP knockout mutant. Furthermore, in complementation assays we determined the roles of the individual domains in signaling and regulation of the actin cytoskeleton. We studied in detail the adenylyl cyclase activity and found that the mutant cells have normal levels of the aggregation phase-specific adenylyl cyclase and that receptor-mediated activation is intact. However, cAMP relay that is responsible for the generation of propagating cAMP waves that control the chemotactic aggregation of starving Dictyostelium cells was altered, and the cAMP-induced cGMP production was significantly reduced. The data suggest an interaction of CAP with adenylyl cyclase in Dictyostelium and an influence on signaling pathways directly as well as through its function as a regulatory component of the cytoskeleton.
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Affiliation(s)
- Angelika A Noegel
- Center for Biochemistry, Medical Faculty, University of Cologne, 50931 Cologne, Germany
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43
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Klausen M, Aaes-Jørgensen A, Molin S, Tolker-Nielsen T. Involvement of bacterial migration in the development of complex multicellular structures in Pseudomonas aeruginosa biofilms. Mol Microbiol 2003; 50:61-8. [PMID: 14507363 DOI: 10.1046/j.1365-2958.2003.03677.x] [Citation(s) in RCA: 350] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Detailed knowledge of the developmental process from single cells scattered on a surface to complex multicellular biofilm structures is essential in order to create strategies to control biofilm development. In order to study bacterial migration patterns during Pseudomonas aeruginosa biofilm development, we have performed an investigation with time-lapse confocal laser scanning microscopy of biofilms formed by various combinations of colour-coded P. aeruginosa wild type and motility mutants. We show that mushroom-shaped multicellular structures in P. aeruginosa biofilms can form in a sequential process involving a non-motile bacterial subpopulation and a migrating bacterial subpopulation. The non-motile bacteria form the mushroom stalks by growth in certain foci of the biofilm. The migrating bacteria form the mushroom caps by climbing the stalks and aggregating on the tops in a process which is driven by type-IV pili. These results lead to a new model for biofilm formation by P. aeruginosa.
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Affiliation(s)
- Mikkel Klausen
- Molecular Microbial Ecology Group, BioCentrum-DTU, Technical University of Denmark, DK-2800 Lyngby, Denmark.
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44
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Xu J, Wang F, Van Keymeulen A, Herzmark P, Straight A, Kelly K, Takuwa Y, Sugimoto N, Mitchison T, Bourne HR. Divergent signals and cytoskeletal assemblies regulate self-organizing polarity in neutrophils. Cell 2003; 114:201-14. [PMID: 12887922 DOI: 10.1016/s0092-8674(03)00555-5] [Citation(s) in RCA: 531] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Like neutrophilic leukocytes, differentiated HL-60 cells respond to chemoattractant by adopting a polarized morphology, with F-actin in a protruding pseudopod at the leading edge and contractile actin-myosin complexes at the back and sides. Experiments with pharmacological inhibitors, toxins, and mutant proteins show that this polarity depends on divergent, opposing "frontness" and "backness" signals generated by different receptor-activated trimeric G proteins. Frontness depends upon Gi-mediated production of 3'-phosphoinositol lipids (PI3Ps), the activated form of Rac, a small GTPase, and F-actin. G12 and G13 trigger backness signals, including activation of a second GTPase (Rho), a Rho-dependent kinase, and myosin II. Functional incompatibility causes the two resulting actin assemblies to aggregate into separate domains, making the leading edge more sensitive to attractant than the back. The latter effect explains both the neutrophil's ability to polarize in uniform concentrations of chemoattractant and its response to reversal of an attractant gradient by performing a U-turn.
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Affiliation(s)
- Jingsong Xu
- Department of Cellular and Molecular Pharmacology and The Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA 94143, USA
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45
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Palanivelu R, Brass L, Edlund AF, Preuss D. Pollen tube growth and guidance is regulated by POP2, an Arabidopsis gene that controls GABA levels. Cell 2003; 114:47-59. [PMID: 12859897 DOI: 10.1016/s0092-8674(03)00479-3] [Citation(s) in RCA: 338] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
During angiosperm reproduction, pollen grains form a tube that navigates through female tissues to the micropyle, delivering sperm to the egg; the signals that mediate this process are poorly understood. Here, we describe a role for gamma-amino butyric acid (GABA) in pollen tube growth and guidance. In vitro, GABA stimulates pollen tube growth, although vast excesses are inhibitory. The Arabidopsis POP2 gene encodes a transaminase that degrades GABA and contributes to the formation of a gradient leading up to the micropyle. pop2 flowers accumulate GABA, and the growth of many pop2 pollen tubes is arrested, consistent with their in vitro GABA hypersensitivity. Some pop2 tubes continue to grow toward ovules, yet they are misguided, presumably because they target ectopic GABA on the ovule surface. Interestingly, wild-type tubes exhibit normal growth and guidance in pop2 pistils, perhaps by degrading excess GABA and sharpening the gradient leading to the micropyle.
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Affiliation(s)
- Ravishankar Palanivelu
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
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46
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Abstract
Cancer cells possess a broad spectrum of migration and invasion mechanisms. These include both individual and collective cell-migration strategies. Cancer therapeutics that are designed to target adhesion receptors or proteases have not proven to be effective in slowing tumour progression in clinical trials--this might be due to the fact that cancer cells can modify their migration mechanisms in response to different conditions. Learning more about the cellular and molecular basis of these different migration/invasion programmes will help us to understand how cancer cells disseminate and lead to new treatment strategies.
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Affiliation(s)
- Peter Friedl
- Department of Dermatology, University of Würzburg, Josef-Schneider-Str. 2, 97080 Würzburg, Germany
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47
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Gao T, Ehrenman K, Tang L, Leippe M, Brock DA, Gomer RH. Cells respond to and bind countin, a component of a multisubunit cell number counting factor. J Biol Chem 2002; 277:32596-605. [PMID: 12070154 DOI: 10.1074/jbc.m203075200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In Dictyostelium discoideum counting factor (CF), a secreted approximately 450-kDa complex of polypeptides, inhibits group and fruiting body size. When the gene encoding countin (a component of CF) was disrupted, cells formed large groups. We find that recombinant countin causes developing cells to form small groups, with an EC(50) of approximately 3 ng/ml, and affects cAMP signal transduction in the same manner as semipurified CF. Recombinant countin increases cell motility, decreases cell-cell adhesion, and regulates gene expression in a manner similar to the effect of CF. However, countin does not decrease adhesion or group size to the extent that semipurified CF does. A 1-min exposure of developing cells to countin causes an increase in F-actin polymerization and myosin phosphorylation and a decrease in myosin polymerization, suggesting that countin activates a rapid signal transduction pathway. (125)I-Labeled countin has countin bioactivity, and binding experiments suggest that vegetative and developing cells have approximately 53 cell-surface sites that bind countin with a K(D) of approximately 1.5 ng/ml or 60 pm. We hypothesize that countin regulates cell development through the same pathway as CF and that other proteins within the complex may modify the activity of countin and/or have independent size-regulating activities.
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Affiliation(s)
- Tong Gao
- Howard Hughes Medical Institute, Rice University, Houston, Texas 77005-1892, USA
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Rappel WJ, Thomas PJ, Levine H, Loomis WF. Establishing direction during chemotaxis in eukaryotic cells. Biophys J 2002; 83:1361-7. [PMID: 12202361 PMCID: PMC1302234 DOI: 10.1016/s0006-3495(02)73906-4] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Several recent studies have demonstrated that eukaryotic cells, including amoeboid cells of Dictyostelium discoideum and neutrophils, respond to chemoattractants by translocation of PH-domain proteins to the cell membrane, where these proteins participate in the modulation of the cytoskeleton and relay of the signal. When the chemoattractant is released from a pipette, the localization is found predominantly on the proximal side of the cell. The recruitment of PH-domain proteins, particularly for Dictyostelium cells, occurs very rapidly (<2 s). Thus, the mechanism responsible for the first step in the directional sensing process of a cell must be able to establish an asymmetry on the same time scale. Here, we propose a simple mechanism in which a second messenger, generated by local activation of the membrane, diffuses through the interior of the cell, suppresses the activation of the back of the cell, and converts the temporal gradient into an initial cellular asymmetry. Numerical simulations show that such a mechanism is plausible. Available evidence suggests that the internal inhibitor may be cGMP, which accumulates within less than a second following treatment of cells with external cAMP.
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Affiliation(s)
- Wouter-Jan Rappel
- Department of Physics, University of California, San Diego, La Jolla, California 92093-0319, USA.
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Deery WJ, Gao T, Ammann R, Gomer RH. A single cell density-sensing factor stimulates distinct signal transduction pathways through two different receptors. J Biol Chem 2002; 277:31972-9. [PMID: 12070170 DOI: 10.1074/jbc.m204539200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In Dictyostelium discoideum, cell density is monitored by levels of a secreted protein, conditioned medium factor (CMF). CMFR1 is a putative CMF receptor necessary for CMF-induced G protein-independent accumulation of the SP70 prespore protein but not for CMF-induced G protein-dependent inositol 1,4,5-trisphosphate production. Using recombinant fragments of CMF, we find that stimulation of the inositol 1,4,5-trisphosphate pathway requires amino acids 170-180, whereas SP70 accumulation does not, corroborating a two-receptor model. Cells lacking CMFR1 do not aggregate, due to the lack of expression of several important early developmentally regulated genes, including gp80. Although many aspects of early developmental cAMP-stimulated signal transduction are mediated by CMF, CMFR1 is not essential for cAMP-stimulated cAMP and cGMP production or Ca(2+) uptake, suggesting the involvement of a second CMF receptor. Exogenous application of antibodies against either the region between a first and second or a second and third possible transmembrane domain of CMFR1 induces SP70 accumulation. Antibody- and CMF-induced gene expression can be inhibited by recombinant CMFR1 corresponding to the region between the first and third potential transmembrane domains, indicating that this region is extracellular and probably contains the CMF binding site. These observations support a model where a one- or two-transmembrane CMFR1 regulates gene expression and a G protein-coupled CMF receptor mediates cAR1 signal transduction.
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Affiliation(s)
- William J Deery
- Howard Hughes Medical Institute, Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005-1892, USA
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Glöckner G, Eichinger L, Szafranski K, Pachebat JA, Bankier AT, Dear PH, Lehmann R, Baumgart C, Parra G, Abril JF, Guigó R, Kumpf K, Tunggal B, Cox E, Quail MA, Platzer M, Rosenthal A, Noegel AA. Sequence and analysis of chromosome 2 of Dictyostelium discoideum. Nature 2002; 418:79-85. [PMID: 12097910 DOI: 10.1038/nature00847] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The genome of the lower eukaryote Dictyostelium discoideum comprises six chromosomes. Here we report the sequence of the largest, chromosome 2, which at 8 megabases (Mb) represents about 25% of the genome. Despite an A + T content of nearly 80%, the chromosome codes for 2,799 predicted protein coding genes and 73 transfer RNA genes. This gene density, about 1 gene per 2.6 kilobases (kb), is surpassed only by Saccharomyces cerevisiae (one per 2 kb) and is similar to that of Schizosaccharomyces pombe (one per 2.5 kb). If we assume that the other chromosomes have a similar gene density, we can expect around 11,000 genes in the D. discoideum genome. A significant number of the genes show higher similarities to genes of vertebrates than to those of other fully sequenced eukaryotes. This analysis strengthens the view that the evolutionary position of D. discoideum is located before the branching of metazoa and fungi but after the divergence of the plant kingdom, placing it close to the base of metazoan evolution.
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Affiliation(s)
- Gernot Glöckner
- IMB Jena, Department of Genome Analysis, Beutenbergstr. 11, 07745 Jena, Germany.
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