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.

An auto-inhibitor of zygote giant cell formation in Dictyostelium discoideum

1981 ◽  
Vol 131 (2) ◽  
pp. 456-458 ◽  
Author(s):  
Danton H. O'Day ◽  
Stephen P. Szabo ◽  
Abdul H. Chagla
Keyword(s):  
Giant Cell ◽  
Dictyostelium Discoideum ◽  
Cell Formation ◽  
Giant Cell Formation

scholarly journals Giant cell formation in sarcoidosis: cell fusion or proliferation with non-division?

2009 ◽  
Vol 155 (3) ◽  
pp. 476-486 ◽  
Author(s):  
T. C. M. Th. van Maarsseveen ◽  
W. Vos ◽  
P. J. van Diest
Keyword(s):  
Giant Cell ◽  
Cell Fusion ◽  
Cell Formation ◽  
Giant Cell Formation

Macrocyst development in Dictyostelium discoideum. II. Mating-type-specific cell fusion and acquisition of fusion-competence

1983 ◽  
Vol 60 (1) ◽  
pp. 157-168
Author(s):  
Y. Saga ◽  
H. Okada ◽  
K. Yanagisawa
Keyword(s):  
Dictyostelium Discoideum ◽  
Cell Fusion ◽  
Mating Type ◽  
Cell Formation ◽  
Giant Cells ◽  
Specific Cell ◽  
Restrictive Temperature ◽  
Opposite Mating Type ◽  
Multinucleated Cells ◽  
Giant Cell Formation

The early events of macrocyst development in Dictyostelium discoideum have been investigated using a new culturing system. When cells of opposite mating-types, HM1 and NC4, are cultured together at the appropriate temperature in the dark, giant cells appear, ingest the surrounding amoebae, and develop into macrocysts. Although these giant cells have been assumed to be the products of the fusion of opposite mating-type cells, no experimental evidence to prove this assumption has been obtained using such mixed-culture systems. In order to avoid the complexities involved in mixed-culturing, we have developed a new system involving the separate culture, and later mixing, of opposite mating-type cells. This has enabled us to obtain direct evidence that giant cells are produced by fusion between opposite mating-type cells. Cell fusion occurs immediately after mixing and is completed within 30 min. As a number of cells fuse simultaneously, giant cells produced by this method are very large multinucleated cells, and not binucleated zygotes. Using this system we also discovered the following facts related to giant cell formation: (1) cells can acquire their fusion competence without the presence of cells of the opposite mating-type; (2) only HM1 cells require darkness to acquire their fusion competence; (3) the restrictive temperature, 25 degrees C, inhibits the induction of fusion competence in HM1 cells, but not in NC4 cells.

scholarly journals Components involved in virally mediated membrane fusion and permeability changes

1980 ◽  
Vol 190 (3) ◽  
pp. 625-638 ◽  
Author(s):  
A M Wyke ◽  
C C Impraim ◽  
S Knutton ◽  
C A Pasternak
Keyword(s):  
Giant Cell ◽  
Cell Fusion ◽  
Fluorescence Enhancement ◽  
Cell Formation ◽  
Permeability Changes ◽  
Giant Cell Formation ◽  
Assay Methods ◽  
Osmotic Treatment ◽  
Physical Treatments ◽  
Determining Factor

1. Intact F glycoprotein is required to induce permeability changes in Lettrée cells or in erythrocytes. Some HN glycoproteins may also be required. Permeability changes thus offer a simple, accurate and rapid means of assaying the integrity of F glycoprotein in certain viral preparations. 2. The ‘1-day’ virus (which contains intact F glycoprotein but which differs morphologically from ‘3 day’ virus) does not cause permeability changes; it can be rendered active by various physical treatments. It is concluded that the environment in which F glycoprotein is embedded is a determining factor for permeability changes. 3. The entry of fluorescently labelled peptides into cells made permeable by virus has been measured. Peptides having a molecular weight in excess of 1000 enter poorly, suggesting a ‘pore’ size of approx. 1 nm in diameter. 4. Two novel assay methods concerned with virus—cell fusion are described. The first measures the fluorescence enhancement that occurs when anthroylstearate is transferred from anthroylstearate-labelled virus to cells. The second measures the giant-cell formation that occurs when partially fused erythrocytes are exposed to hypo-osmotic treatment. The ‘1-day’ virus is active in these assays. In contrast with permeability changes, virus—cell fusion is insensitive to changes in external Ca2+-concentration. 5. The results are compatible with a model [Knutton & Pasternak (1979) Trends Biochem. Sci. 4, 220—223; Impraim, Foster, Micklem & Pasternak (1980) Biochem. J. 186, 847—860] in which virus—cell fusion is a prerequisite for permeability changes, and in which permeability changes are the cause of haemolysis and giant-cell (polykaryon) formation.

Sensory Behaviour in Dictyostelium Discoideum Slugs: Phototaxis and Thermotaxis are not Mediated by a Change in Slug Speed

1982 ◽  
Vol 54 (1) ◽  
pp. 329-339
Author(s):  
ELIZABETH SMITH ◽  
PAUL R. FISHER ◽  
WARWICK N. GRANT ◽  
KEITH L. WILLIAMS
Keyword(s):  
Molecular Weight ◽  
Temperature Gradient ◽  
Light Intensity ◽  
Dictyostelium Discoideum ◽  
Low Molecular Weight ◽  
Light Intensities ◽  
Slug Movement

The speed of sustained migration of Dictyostelium discoideum slugs was similar in a temperature gradient and at different light intensities, including a light intensity sufficient to cause significant disorientation of slugs. No change was observed in slug speed in the presence of high levels of Slug Turning Factor (STF), a low molecular weight compound through which phototaxis and thermotaxis are mediated. Thus orientation of D. discoideum slugs is not mediated by a sustained changed in slug speed and we propose that slug movement is not directly coupled to tactic responses. Slug speed depended on the size, age and genotype of slugs as well as the nature of the substratum (charcoal-containing water agar versus water agar).

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