The regulation of membrane fusion during sexual development in Dictyostelium discoideum

1989 ◽  
Vol 67 (7) ◽  
pp. 321-326 ◽  
Author(s):  
Danton H. O'Day ◽  
Michael A. Lydan
Keyword(s):  
Cyclic Amp ◽  
Membrane Fusion ◽  
Dictyostelium Discoideum ◽  
Cell Fusion ◽  
Sexual Development ◽  
Recent Literature ◽  
Developmental Regulation ◽  
Low Molecular Weight ◽  
Sexual Pheromone ◽  
Protein Cell

During the first 24 h of sexual development in Dictyostelium discoideum, three sequential events of membrane fusion occur: gamete fusion, pronuclear fusion, and phagocytosis. The early events of sexual development are regulated by a diverse group of endogenous molecules: (i) a volatile sexual pheromone, (ii) a protein cell fusion inducing factor (CFIF), (iii) a low molecular weight autoinhibitor, (iv) and cyclic AMP. CFIC enhances cell fusion while the autoinhibitor and cyclic AMP both inhibit the event. Both extracellular and intracellular calcium ions are essential for cell and pronuclear fusion. Pharmacological analyses show that the intracellular functions of the divalent cation in these processes are mediated by calmodulin. The autoinhibitor appears to function by inhibiting calmodulin activity. Glucose, mannose, and N-acetylglucosamine containing glycoproteins have been shown to function in both cell fusion and phagocytosis. The interplay between all of these diverse molecules is examined and a review of all of the recent literature is presented.Key words: biomembrane fusion, Dictyostelium, calmodulin, pheromones, cAMP, glycoproteins, developmental regulation, macrocyst, cell fusion, pronuclear fusion, calcium.

Zygote giant cell differentiation in Dictyostelium discoideum: biochemical markers of specific stages of sexual development

1992 ◽  
Vol 70 (10-11) ◽  
pp. 1200-1208 ◽  
Author(s):  
Darren D. Browning ◽  
Keith E. Lewis ◽  
Danton H. O'Day
Keyword(s):  
Alkaline Phosphatase ◽  
Cell Differentiation ◽  
Giant Cell ◽  
Dictyostelium Discoideum ◽  
Cell Fusion ◽  
Sexual Development ◽  
Giant Cells ◽  
Second Phase ◽  
Developmental Phase ◽  
Calcium Dependent

Sexual development in Dictyostelium discoideum has many unique features making it an attractive eukaryotic model system for the study of biomembrane fusion and intercellular communication. The work presented here provides primary biochemical evidence for two distinct phases during early sexual development that appear to be defined by calcium-dependent gamete cell fusion. In addition, we introduce a novel procedure for the enrichment of zygote giant cells and use this method to define certain wheat-germ agglutinin binding glycoproteins which are specifically located in zygote giant cells and others which are markers for surrounding amoebae in the second phase of development. In addition, a G protein which is present in high amounts early in development is unique to giant cells in the second phase, suggesting a role in phagocytosis. Finally, alkaline phosphatase activity was found to mark the first phase of sexual development, suggesting a role in cell fusion. This contrasts with the patterns of α-mannosidase and β-glucosidase activity that increase late in the second developmental phase, where they likely function in endocyte digestion during the cytophagic period. The developmental significance of these findings is discussed.Key words: zygote giant cell differentiation, Ca2+, glycoproteins, GTP-binding proteins, alkaline phosphatase, glycosidase, cell fusion.

The low molecular weight autoinhibitor of sexual development in Dictyostelium discoideum inhibits cell fusion and zygote differentiation

1984 ◽  
Vol 62 (8) ◽  
pp. 722-731 ◽  
Author(s):  
Stephen P. Szabo ◽  
Danton H. O'Day
Keyword(s):  
Molecular Weight ◽  
Giant Cell ◽  
Dictyostelium Discoideum ◽  
Cell Fusion ◽  
Cell Formation ◽  
Sexual Cycle ◽  
Low Molecular Weight ◽  
Heat Stable ◽  
Giant Cell Formation ◽  
Zygote Development

A previous study has shown that, during the sexual cycle of Dictyostelium discoideum, zygote giant cell formation is regulated by an autoinhibitor. Experiments reported here show that the autoinhibitor inhibits two events of zygote development: cell fusion and subsequent giant cell differentiation. The autoinhibitor is heat stable and has a molecular weight around 500. Medium containing the autoinhibitor can be diluted 500-fold without loss of activity. Preliminary experiments show that, although levels of ammonia double during the 8-h period of autoinhibitor production, added ammonia does not mimic the inhibiting effect. cAMP at 1 mM inhibits both binucleate formation and differentiation, but the concentration of cyclic AMP in 28-h cultures is only 13.4 pmol, a level which does not affect zygote development. Thus, it is established that neither of these critical regulators of other developmental processes in D. discoideum is the autoinhibitor.

Chloroquine inhibits cell fusion during sexual development in Dictyostelium discoideum

1987 ◽  
Vol 33 (12) ◽  
pp. 1125-1129 ◽  
Author(s):  
Jiji Rivera ◽  
Danton H. O'Day
Keyword(s):  
Dictyostelium Discoideum ◽  
Cell Fusion ◽  
Cell Morphology ◽  
Sexual Development ◽  
Protease Activity ◽  
Current Knowledge ◽  
Dependent Manner ◽  
Receptor Recycling ◽  
Sexual Cell ◽  
Dose Dependent

Chloroquine inhibits sexual cell fusion and macrocyst formation in heterothallic Dictyostelium discoideum in a dose-dependent manner. As judged by cell morphology, the effect of chloroquine is not due to nonspecific toxicity, and normal macrocyst development ensues upon the removal of the drug. The mode of action of chloroquine on both receptor recycling and protease activity is discussed in terms of current knowledge of sexual cell fusion in D. discoideum.

Concanavalin A and wheat germ agglutinin binding glycoproteins associated with cell fusion and zygote differentiation in Dictyostelium discoideum: effects of calcium ions and tunicamycin on glycoprotein profiles

1991 ◽  
Vol 69 (4) ◽  
pp. 282-290 ◽  
Author(s):  
Darren D. Browning ◽  
Danton H. O'Day
Keyword(s):  
Dictyostelium Discoideum ◽  
Cell Fusion ◽  
Concanavalin A ◽  
Calcium Ions ◽  
Sexual Development ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Dictyostelium Cell

To determine which glycoproteins may be critical to sexual development in Dictyostelium discoideum, cell samples from different developmental stages were separated by sodium dodecyl sulfate – polyacrylamide gel electrophoresis and blotted to nitrocellulose. Concanavalin A (ConA) and wheat germ agglutinin (WGA) binding proteins were visualized on the blots using an immunochemical procedure employing peroxidase–antiperoxidase. ConA labelled at least 28 proteins, but only one band showed calcium-dependent changes in its expression. WGA bound at least 30 proteins and changes in several bands were observed that did not occur in calcium-deficient controls. Two WGA-binding glycoproteins which migrated at 200 and 166 kilodaltons (kDa), respectively, showed developmental changes associated with the time of cell fusion. One WGA-binding and one ConA-binding glycoprotein migrating at 130 and 126 kDa, respectively, appeared later during sexual development, in association with the phase of zygote differentiation. Several WGA- and ConA-binding glycoproteins decreased during sexual development, but were not affected by the absence of calcium ions. Tunicamycin (1 μg/mL) inhibited cell fusion when added to sexual cultures prior to the appearance of the 166-kDa glycoprotein gp166. The effects of this inhibitor on development support the importance of glycoproteins to cell fusion during sexual development in D. discoideum.Key words: Dictyostelium, cell fusion, glycoprotein, tunicamycin, concanavalin A, wheat germ agglutinin, calcium.

scholarly journals Regulation of development in Dictyostelium discoideum. IV. Effects of ions on the rate of differentiation and cellular response to cyclic AMP.

1980 ◽  
Vol 87 (3) ◽  
pp. 823-827 ◽  
Author(s):  
F T Marin ◽  
F G Rothman
Keyword(s):  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Early Development ◽  
Maximum Rate ◽  
Cellular Response ◽  
Developmental Regulation ◽  
Intrinsic Rate ◽  
Rate Of Development ◽  
High Concentrations ◽  
Early Developmental

The effects of ionic environment on both the intrinsic rate of differentiation and the response to exogenous cyclic AMP in Dictyostelium discoideum have been examined. K+ specifically inhibits the rate of early development when present at concentrations > 15 mM. Na+ does not inhibit at concentrations up to 25 mM, and can partially overcome K+ inhibition. The maximum rate of development also depends upon the presence of adequate levels of extracellular Ca++. The effect of exogenous cyclic AMP on the rate of development is inhibited by the absence of Ca++, and/or the presence of high concentrations of K+. Under optimal ionic conditions, the only effect of exogenous cyclic AMP on early developments of K+. Under optimal ionic conditions, the only effect of exogenous cyclic AMP on early development is a specific inhibition. The implications of these results for current models of early developmental regulation are discussed.

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