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Protist Dec 2016Amoeba often use cell movement as a mechanism to find food, such as bacteria, in their environment. The chemotactic movement of the soil amoeba Dictyostelium to folate...
Amoeba often use cell movement as a mechanism to find food, such as bacteria, in their environment. The chemotactic movement of the soil amoeba Dictyostelium to folate or other pterin compounds released by bacteria is a well-documented foraging mechanism. Acanthamoeba can also feed on bacteria but relatively little is known about the mechanism(s) by which this amoeba locates bacteria. Acanthamoeba movement in the presence of folate or bacteria was analyzed in above agar assays and compared to that observed for Dictyostelium. The overall mobility of Acanthamoeba was robust like that of Dictyostelium but Acanthamoeba did not display a chemotactic response to folate. In the presence of bacteria, Acanthamoeba only showed a marginal bias in directed movement whereas Dictyostelium displayed a strong chemotactic response. A comparison of genomes revealed that Acanthamoeba and Dictyostelium share some similarities in G protein signaling components but that specific G proteins used in Dictyostelium chemotactic responses were not present in current Acanthamoeba genome sequence data. The results of this study suggest that Acanthamoeba does not use chemotaxis as the primary mechanism to find bacterial food sources and that the chemotactic responses of Dictyostelium to bacteria may have co-evolved with chemotactic responses that facilitate multicellular development.
Topics: Acanthamoeba; Chemotaxis; Dictyostelium; Phylogeny; Protozoan Proteins; Signal Transduction
PubMed: 27693864
DOI: 10.1016/j.protis.2016.08.006 -
Current Topics in Developmental Biology 1993
Review
Topics: Animals; Base Sequence; Dictyostelium; Fungal Proteins; Genes, Fungal; Models, Biological; Molecular Sequence Data; Spores, Fungal
PubMed: 8348838
DOI: 10.1016/s0070-2153(08)60208-2 -
Eukaryotic Cell May 2009
Review
Topics: Animals; Biological Transport; Calcium; Cyclic AMP; Dictyostelium; Gene Expression; Signal Transduction
PubMed: 19252125
DOI: 10.1128/EC.00360-08 -
Journal of Cell Science Mar 2018Macropinocytosis is a conserved endocytic process used by amoebae for feeding on liquid medium. To further as a model for macropinocytosis, we developed a...
Macropinocytosis is a conserved endocytic process used by amoebae for feeding on liquid medium. To further as a model for macropinocytosis, we developed a high-throughput flow cytometry assay to measure macropinocytosis, and used it to identify inhibitors and investigate the physiological regulation of macropinocytosis. has two feeding states: phagocytic and macropinocytic. When cells are switched from phagocytic growth on bacteria to liquid media, the rate of macropinocytosis slowly increases, due to increased size and frequency of macropinosomes. Upregulation is triggered by a minimal medium containing three amino acids plus glucose and likely depends on macropinocytosis itself. The presence of bacteria suppresses macropinocytosis while their product, folate, partially suppresses upregulation of macropinocytosis. Starvation, which initiates development, does not of itself suppress macropinocytosis: this can continue in isolated cells, but is shut down by a conditioned-medium factor or activation of PKA signalling. Thus macropinocytosis is a facultative ability of cells, regulated by environmental conditions that are identified here.This article has an associated First Person interview with the first author of the paper.
Topics: Amino Acids; Dictyostelium; Glucose; Phagocytosis; Pinocytosis; Protozoan Proteins
PubMed: 29440238
DOI: 10.1242/jcs.213736 -
Journal of Muscle Research and Cell... 2002Little is known about how organisms regulate the size of multicellular structures. This review condenses some of the observations about how Dictyostelium regulates the... (Review)
Review
Little is known about how organisms regulate the size of multicellular structures. This review condenses some of the observations about how Dictyostelium regulates the size of fruiting bodies. Very large fruiting bodies tend to fall over, and one of the ways Dictyostelium cells prevent this is by breaking up the aggregation streams when there is an excessive number of cells in the stream. Developing cells simultaneously secrete and sense counting factor (CF), a 450 kDa complex of proteins. Diffusion calculations showed that as the number of cells in a stream or group increases, the local concentration of CF will increase, allowing the cells to sense the number of cells in the stream or group. Computer simulations predicted that a high level of CF could trigger stream breakup by decreasing cell-cell adhesion and/or increasing cell motility, effectively causing the stream to dissipate and begin to fall apart. The prediction that adhesion and motility affect group size is supported by observations that decreasing adhesion by adding antibodies that bind to adhesion protein causes the formation of smaller groups, while increasing adhesion by overexpressing adhesion proteins, or decreasing motility with drugs that disrupt actin function both cause the formation of larger groups. CF both decreases adhesion and increases motility. CF increases motility in part by increasing actin polymerization and myosin phosphorylation, and decreasing myosin polymerization. New observations using a fusion of a green fluorescent protein to a protein fragment that binds polymerized actin show that in live cells CF does not affect the distribution of polymerized actin. CF increases the levels of ABP-120, an actin-bundling protein, and new observations indicate that very low levels of CF cause an increase in levels of myoB, an unconventional myosin. Our current understanding of group size regulation in Dictyostelium is thus that motility plays a key role, and that to regulate group size cells regulate the expression of at least two proteins, as well as regulating the polymerization of both actin and myosin.
Topics: Animals; Cell Aggregation; Cell Size; Dictyostelium; Movement; Mutagenesis; Signal Transduction
PubMed: 12952079
DOI: 10.1023/a:1024487930787 -
Development, Growth & Differentiation May 2011The social amoeba Dictyostelium discoideum is a simple but powerful model organism for the study of cell-cell adhesion molecules and their role in morphogenesis during... (Review)
Review
The social amoeba Dictyostelium discoideum is a simple but powerful model organism for the study of cell-cell adhesion molecules and their role in morphogenesis during development. Three adhesive systems have been characterized and studied in detail. The spatiotemporal expression of these adhesion proteins is stringently regulated, often coinciding with major shifts in the morphological complexity of development. At the onset of development, amoeboid cells express the Ca(2+) -dependent cell-cell adhesion molecule DdCAD-1, which initiates weak homophilic interactions between cells and assists in the recruitment of individuals into cell streams. DdCAD-1 is unique because it is synthesized as a soluble protein in the cytoplasm. It is targeted for presentation on the cell surface by an unconventional protein transport mechanism via the contractile vacuole. Concomitant with the aggregation stage is the expression of the contact sites A glycoprotein csA/gp80 and TgrC1, both of which mediate Ca(2+) /Mg(2+) -independent cell-cell adhesion. Whereas csA/gp80 is a homophilic binding protein, TgrC1 binds to a heterophilic receptor on the cell. During cell aggregation, csA/gp80 associates preferentially with lipid rafts, which facilitate the rapid assembly of adhesion complexes. TgrC1 is synthesized at low levels during aggregation and rapid accumulation occurs initially in the peripheral cells of loose mounds. The extracellular portion of TgrC1 is shed and becomes part of the extracellular matrix. Additionally, analyses of knockout mutants have revealed important biological roles played by these adhesion proteins, including size regulation, cell sorting and cell-type proportioning.
Topics: Cell Adhesion; Dictyostelium; Nuclear Magnetic Resonance, Biomolecular; Protozoan Proteins
PubMed: 21585356
DOI: 10.1111/j.1440-169X.2011.01267.x -
Trends in Genetics : TIG May 1991A central unresolved issue in modern cell biology concerns how eukaryotic cell migration is achieved. Although the underlying mechanics of cell locomotion appear similar... (Review)
Review
A central unresolved issue in modern cell biology concerns how eukaryotic cell migration is achieved. Although the underlying mechanics of cell locomotion appear similar in cells ranging from amoebae to leukocytes, the organisms that have been historically studied have not been amenable to the techniques of modern molecular genetics. The recent development of high-efficiency gene targeting technology for Dictyostelium discoideum, coupled with the classic cell migration behavior of this organism, offers an opportunity to resolve many of the controversial issues concerning cell locomotion.
Topics: Cell Movement; Dictyostelium; Models, Genetic
PubMed: 2068788
DOI: 10.1016/0168-9525(91)90380-9 -
BioEssays : News and Reviews in... May 1997The life cycle of Dictyostelium discoideum offers a unique opportunity to study signal transduction in eukaryotic cells at both the unicellular and multicellular levels... (Review)
Review
The life cycle of Dictyostelium discoideum offers a unique opportunity to study signal transduction in eukaryotic cells at both the unicellular and multicellular levels of organization. Adding to the already extensive knowledge of the unicellular stages, classical and molecular genetics have begun to unravel transduction of signals controlling morphogenesis and behaviour (phototaxis and thermotaxis) in the multicellular 'slug' stage of the life cycle. Distributed over all seven genetic linkage groups are probably about 20, but possibly as many as 55, genes of importance for slug behaviour. The encoded proteins appear from pharmacological studies and mutant phenotypes to govern transduction pathways involving the intracellular second messengers cyclic AMP, cyclic GMP, IP3 and Ca2+. Pathways from the photo- and thermoreceptors converge first with each other and thence, at the level of the second messengers, with those from extracellular tip activation (cyclic AMP) and inhibition (Slug Turning Factor and/or ammonia and/or adenosine) signals that control slug movement and morphogenesis.
Topics: Animals; Cell Movement; Cyclic AMP; Dictyostelium; Light; Mutation; Photobiology; Signal Transduction; Temperature
PubMed: 9174405
DOI: 10.1002/bies.950190507 -
Current Opinion in Microbiology Dec 2000GSK-3, Dd-STATa, PKA, rZIP and Ras all play important roles in cell type determination of Dictyostelium discoideum. The fact that homologs of these proteins also... (Review)
Review
GSK-3, Dd-STATa, PKA, rZIP and Ras all play important roles in cell type determination of Dictyostelium discoideum. The fact that homologs of these proteins also function in metazoan development emphasizes the importance of Dictyostelium as a model microbial organism for studying the molecular mechanisms that regulate development. The recent elaboration of the central role for GSK-3 in cell type determination has been of particular importance. The stimulatory effect of extracellular cAMP on GSK-3 activity has been shown to act through the cell surface receptor cAR3 and a tyrosine protein kinase ZAK1, which directly activates and phosphorylates GSK-3. Several proteins, including Dd-STATa, have been identified as substrates for GSK-3, and are therefore potential transducers of the signals involved in cell type determination.
Topics: Animals; Calcium-Calmodulin-Dependent Protein Kinases; Cell Differentiation; Dictyostelium; Glycogen Synthase Kinase 3; Signal Transduction
PubMed: 11121784
DOI: 10.1016/s1369-5274(00)00151-x -
Seminars in Cell & Developmental Biology Dec 1999The spatial patterning of prestalk and prespore cells in the slug arises from the differential sorting of newly differentiated cell types as the mound forms. This... (Review)
Review
The spatial patterning of prestalk and prespore cells in the slug arises from the differential sorting of newly differentiated cell types as the mound forms. This pattern is highly organized along an anterior-posterior axis and is constant irrespective of the size of the organism. Cell-type differentiation is plastic until late in development. A change in the ratio of cell types resulting from removal of part of the slug leads to a rapid restoration of the original ratio of the cell types through a pathway involving dedifferentiation, redifferentiation, and sorting of the existing cells. This review provides insight into various molecules, morphogens, and pathways regulating spatial patterning and cell-type proportioning.
Topics: Animals; Cell Communication; Cell Differentiation; Dictyostelium; Signal Transduction
PubMed: 10706824
DOI: 10.1006/scdb.1999.0343