Year: 2013
Type: dissertation
Abstract: It has long been known that the social amoeba Dictyostelium discoideum initiates and controls its developmental processes by the creation and transmission of the purinergic molecule; cyclic AMP. It is also known that it possesses P2X receptors which are localised on the inside of the cell. Despite the lack of cell surface ATP receptors, previous studies have indicated the existence of Dictyostelium ecto-ATPases and calcium responses to the addition of exogenous ATP. \nIn these experiments it was found, using the luciferase assay, that the cells condition their media with ATP during axenic growth and development. Treatment of cells with apyrase, a potato enzyme known to degrade ATP, did not affect the rate of growth, but led to a delay in the appearance of streams during development. This delay corresponded with the formation of “clumps” of cells, but no evidence could be found that the cells had increased expression of adhesion molecules. \nApyrase also caused developing cells to form fewer fruiting bodies, despite the fact that there was no difference in the number of aggregates formed, implying that the apyrase was interfering in the transition between these stages. The apyrase fruiting bodies also contained fewer viable cells, though whether it was fewer cells in general or less healthy ones could not be confirmed. \nThe malachite green assay was used to measure the rate of activity of the cell surface ecto-ATPases and the results suggested that the common ecto-ATPase inhibitor suramin would affect them. Cells allowed to develop in the presence of suramin showed no abnormal timing in the stages of development or in number of fruiting bodies, but did contain significantly more viable cells. \nAltogether these results are consistent with the hypothesis that ATP, ATP receptors and ATPases play a role in the regulation and co-ordination of development in Dictyostelium discoideum, despite the fact that it possesses no known cell surface P2X receptors.
Author: Peter Woolman
Language: English
Subfield: Physiology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2180292024