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

• Published in: Cell calcium (Edinburgh) Vol. 29; no. 3; pp. 171 - 182
• Main Authors: Schlatterer, C., Walther, P., Müller, M., Mendgen, K., Zierold, Karl, Knoll, G.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01-03-2001
• Subjects: Animals; Calcium - physiology; Cell Differentiation - physiology; Dictyostelium - cytology; Dictyostelium - physiology; Signal Transduction - physiology
• ISSN: 0143-4160; 1532-1991
• DOI: 10.1054/ceca.2000.0181

Dictyostelium discoideum pseudoplasmodia exhibit a gradient of the cytosolic free Ca2+-concentration ([Ca2+]i) along their anterior–posterior axis involved in cell-type specific differentiation. [Ca2+]iis high in prestalk and low in prespore cells. We determined the content and localization of calcium and other elements in cryosectioned cells of pseudoplasmodia and fruiting bodies by X-ray microanalysis. Granular stores rich in Ca, Mg and P were ident ified. Average Ca was higher in prespore than prestalk granules (225vs 111mmol/kg dry weight). Total Ca stored in granules was also higher in prespore than prestalk cells. The amount of P and S in granules differed between the two cell types indicating different store composition. In spores mean granular Ca was 120mmol/kg dry weight. Stalk cells had smaller granules with 360mmol Ca/kg dry weight. Complementary to microanalysis, vesicular Ca2+-fluxes were studied in fractionated cell homogenates. The rate of Ca2+-uptake was higher in pellet fractions of prespore than prestalk amoebae (4.7 vs 3.4nmol/minemg). Ca2+-release was greater in supernatant fractions from prestalk than prespore cells (16.5vs 7.7nmol/108cells). 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 [Ca2+]i-gradient.