Dynamics of polymorphism of acidocalcisomes in Leishmania parasites

Abstract

Growth of Leishmania mexicana amazonensis promastigotes in different culture media resulted in structurally and chemically different acidocalcisomes. When grown in SDM-79 medium, the promastigotes showed large spherical acidocalcisomes of up to 1.2 mm diameter distributed throughout the cell. X-ray microanalysis and elemental mapping of the organelles showed large amounts of oxygen, phosphorus, sodium, potassium, magnesium, calcium, and zinc. Immunofluorescence microscopy using antisera raised against a peptide sequence of the vacuolar-type proton pyrophosphatase of Arabidopsis thaliana that is conserved in the Leishmania enzyme, indicated localization in acidocalcisomes. When cells were transferred to Warren's medium, the acidocalcisomes transformed from spherical into branched tubular organelles. The labeling pattern of the vacuolar proton-pyrophosphatase, considered as a marker for the organelle, changed accompanying the structural changes of the acidocalcisomes, and the enzyme showed an apparently lower proton-transporting activity when measured in digitonin-permeabilized promastigotes. X-ray microanalysis and elemental mapping of these structures revealed the additional presence of iron. Together, the results reveal that the morphology and composition of acidocalcisomes are greatly influenced by the culture con-ditions.

A proton pumping pyrophosphatase in acidocalcisomes of Herpetomonas sp.

“…(Fig. 1), determined by electron probe X-ray microanalysis, showed the presence of acidocalcisome-like organelles which have been reported to be rich in these elements [31][32][33][34][35][36][37][38]. This assumption was supported by the finding that the parasites displayed a vacuolar H + -PPase localized in organelles of same size and distribution (Fig.…”

“…Variations of H + were followed by measuring the changes in the absorbance spectrum of acridine orange [31][32][33], using a CINTRA 20 spectrophotometer at the wavelength pair 530-493, at room temperature (25 • C). Cells (1 mg/ml) were added to a reaction medium containing 125 mM sucrose, 65 mM KCl, 2 mM MgCl 2 , 2 mM Pi-Tris, 10 mM Hepes buffer pH 7.2, 1 mg/ml antimycin A, 2 mg/ml oligomycin, 125 mM EGTA, 1 g/ml acridine orange (AO) and 80 mM digitonina.…”

“…Acidocalcisomes have been readily analyzed in whole intact cells by transmission electron microscopy [11,31,32]. With whole unfixed Herpetomonas sp.…”

“…V-H + -PPases have been shown to localize in vacuoles of higher plants cells [34,41], and in acidocalcisomes [11,25,31] and plasma membrane of trypanosomatids [23]. We therefore investigated whether it is also present in Herpetomonas sp.…”

Kinetics of pyrophosphate-driven proton uptake by acidocalcisomes of Leptomonas wallacei

“…Acidocalcisomes are calcium-rich acidic organelles first described in Trypanosoma brucei [6] and Trypanosoma cruzi [12], and then in several other trypanosomatids such as Leishmania [10,13,14], Phytomonas [11,15], Herpetomonas [16], Crithidia, Blastocrithidia, and Leptomonas [17], in apicomplexan parasites such as Plasmodium [18,19] and Toxoplasma [20][21][22], in other unicellular organisms such as Chlamydomonas reinhardtii [23], Dictyostelium discoideum [24], and in the bacteria Agrobacterium tumefaciens [25] and Rhodospirillum rubrum [26]. Acidification of acidocalcisomes is promoted by a V-type proton ATPase (V-H + -ATPase) [27,28] and a V-type pyrophosphatase (V-H + -PPase) [8,10].…”