Detection and localization of a Ca2+-ATPase activity in Toxoplasma gondii |
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Authors: | Bouchot A Jaillet J D Bonhomme A Alessandro N P Laquerriere P Kilian L Burlet H Gomez-Marin J E Pluot M Bonhomme P Pinon J M |
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Institution: | UPRES EA 2070 et Laboratoire de Parasitologie-Mycologie, CHU Maison Blanche, Reims, France. annie.bonhomme@univ-reims.fr |
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Abstract: | Toxoplasma gondii, the agent causing toxoplasmosis, is an obligate intracellular protozoan parasite. A calcium signal appears to be essential for intracellular transduction during the active process of host cell invasion. We have looked for a Ca2+-transport ATPase in tachyzoites and found Ca2+-ATPase activity (11-22 nmol Pi liberated/mg protein/min) in the tachyzoite membrane fraction. This ATP-dependent activity was stimulated by Ca2+ and Mg2+ ions and by calmodulin, and was inhibited by pump inhibitors (sodium orthovanadate or thapsigargin). We used cytochemistry and X-ray microanalysis of cerium phosphate precipitates and immunolabelling to find the Ca2+, Mg2+-ATPase. It was located mainly in the membrane complex, the conoid, nucleus, secretory organelles (rhoptries, dense granules) and in vesicles with a high calcium concentration. Thus, Toxoplasma gondii possesses Ca2+-pump ATPase (Ca2+, Mg2+-ATPase) as do eukaryotic cells. |
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