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

Abstract

In this report, we study Ca 2+ transport in permeabilized Candida parapsilosis spheroplasts prepared by a new technique using lyticase. An intracellular non-mitochondrial Ca 2+ 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 Ca 2+ accumulated was followed using the fluorescent dye acridine orange. Acidification was stimulated by the Ca 2+ chelator EGTA and inhibited by Ca 2+. These results, when added to the observation that Ca 2+ induces alkalization of a cellular compartment, provide evidence for the presence of a Ca 2+/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.