Calcium stores in differentiated Dictyostelium discoideum: prespore cells sequester calcium more efficiently than prestalk cells

Abstract

2;-uptake was higher in pellet fractions of prespore than prestalk amoebae (4.7 vs 3.4 nmol/min mg). Ca 2; -release was greater in supernatant fractions from prestalk than prespore cells (16.5 vs 7.7 nmol/10 8 cells). In summary, prestalk and prespore cells possess qualitatively different, high-capacity stores containing distinct amounts of Ca and probably being involved in regulation of the anterior-posterior [Ca 2; ] igradient.

Acidocalcisomes Are Functionally Linked to the Contractile Vacuole of Dictyostelium discoideum

“…In addition to these biochemical studies, mass-dense granules containing large amounts of calcium together with phosphorus were found in freeze-dried cryosections of rapid-frozen D. discoideum amebas using energy-dispersive x-ray microanalysis (13,14). These granules are similar in their chemical composition to the polyphosphate bodies described in many microorganisms (15,16), including D. discoideum (17), and to the more recently described acidocalcisomes of trypanosomatids and apicomplexan parasites (18,19).…”

“…Vacuoles of D. discoideum-Mass-dense granules are recognized by their high electron density when they are observed in transmission electron micrographs of cryosectioned cells (13,14). Abundant vacuoles with high electron density of varying diameter (average of 200 nm) were seen when whole D. discoideum amebas were observed by transmission electron microscopy without fixation and staining (Fig.…”

The contractile vacuole in Ca2+-regulation in Dictyostelium: its essential function for cAMP-induced Ca2+-influx

“…Acidic means that the stores are equipped with a V-type H + -ATPase. Acidic vesicular Ca 2+ -stores in Dictyostelium comprise the CV-system, endosomes and acidocalcisomes [ 12 , 13 ]. In the present study we focus on the contribution of the CV-system to intracellular Ca 2+ regulation.…”

cAMP controls cytosolic Ca2+ levels in Dictyostelium discoideum

“…When compared to wild type, lower doses of EGTA were sufficient to reduce chemotactic speed. The effect of EGTA treatment is most probably due to emptying of the storage compartments [34]; the presence or absence of extracellular Ca 2+ affects the Ca 2+ -content of stores [35,36]. RegA - cells are more sensitive than wild type amoebae because of the lower threshold for Ca 2+ release and thus a more rapid depletion of Ca 2+ in the cells.…”