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Friday 29 June 2001

Ca(2+) transport into an intracellular acidic compartment of Candida parapsilosis.

By: Milani G, Schereiber AZ, Vercesi AE.

FEBS Lett 2001 Jun 29;500(1-2):80-4

In this report, we study Ca2+ transport in permeabilized Candida parapsilosis spheroplasts prepared by a new technique using lyticase. An intracellular non-mitochondrial Ca2+ uptake pathway, insensitive to orthovanadate and sensitive to the V-H(+)-ATPase inhibitor bafilomycin A(1), nigericin and carbonyl cyanide p-trifluoromethoxyphenylhydrazone was characterized. Acidification of the compartment in which Ca2+ accumulated was followed using the fluorescent dye acridine orange. Acidification was stimulated by the Ca2+ chelator EGTA and inhibited by Ca2+. These results, when added to the observation that Ca2+ induces alkalization of a cellular compartment, provide evidence for the presence of a Ca2+/nH(+) antiporter in the acid compartment membrane. Interestingly, like in acidocalcisomes of trypanosomatids, the antioxidant 3,5-dibutyl-4-hydroxytoluene inhibits the V-H(+)-ATPase. In addition, the antifungal agent ketoconazole promoted a fast alkalization of the acidic compartment. Ketoconazole effects were dose-dependent and occurred in a concentration range close to that attained in the plasma of patients treated with this drug.

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