Intracellular Ca2+ Pool Content and Signaling and Expression of a Calcium Pump Are Linked to Virulence in Leishmania mexicana amazonesis Amastigotes

Lu, Hong-Gang; Zhong, Li; Chang, Kwang-Poo; Docampo, Roberto

doi:10.1074/jbc.272.14.9464

Cited by 100 publications

(99 citation statements)

References 64 publications

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“…1, B and C). When each ionophore was present throughout excystation, the IC 50 for ionomycin was 38 nM and for A23187 the IC 50 was 126 nM. The idea that these inhibitors were acting specifically was supported by 45 Ca uptake studies (data not shown).…”

Section: Resultsmentioning

confidence: 92%

“…The IC 50 for TG when present throughout excystation was 7 M. TG at 10 M significantly inhibited giardial excystation only during Stage II (Fig. 3).…”

Section: Resultsmentioning

confidence: 93%

“…We found that verapamil, a Ca 2ϩ channel blocker that should lower cytoplasmic Ca 2ϩ concentrations (33), strongly inhibited excystation. The IC 50 for verapamil when it was present throughout excystation was 49 M. No inhibition was observed when verapamil (100 M) was present only during pre-excystation or Stage I, but it inhibited Ͼ75% in Stage II (Fig. 1A).…”

Section: Resultsmentioning

confidence: 95%

“…Solvent was the control in each case. For initial screening and determination of 50% inhibitory concentrations (IC 50 ) of active compounds, each inhibitor was present for a 1-h preincubation at 4°C and added again during Stages I and II of excystation, because cysts were pelleted between stages. Inhibitors were not included in the emergence step to avoid possible effects on trophozoites.…”

Section: Methodsmentioning

confidence: 99%

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Calcium Signaling in Excystation of the Early Diverging Eukaryote, Giardia lamblia

Reiner

Hetsko

Meszaros

et al. 2003

Journal of Biological Chemistry

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Excystation of Giardia lamblia, which initiates infection, is a poorly understood but dramatic differentiation induced by physiological signals from the host. Our data implicate a central role for calcium homeostasis in excystation. Agents that alter cytosolic Ca 2؉ levels (1,2-bis(2-aminophenoxy)ethane-N,N,N ,N -tetraacetic acidtetra(acetyloxymethyl) ester, a Ca 2؉ channel blocker, Ca 2؉ ionophores, and thapsigargin) strongly inhibit excystation. Treatment of Giardia with thapsigargin raised intracellular Ca 2؉ levels, and peak Ca 2؉ responses increased with each stage of excystation, consistent with the kinetics of inhibition. Fluorescent thapsigargin localized to a likely Ca 2؉ storage compartment in cysts. The ability to sequester ions in membranebounded compartments is a hallmark of the eukaryotic cell. These studies support the existence of a giardial thapsigargin-sensitive Ca 2؉ storage compartment resembling the sarcoplasmic/endoplasmic reticulum calcium ATPase pump-leak system and suggest that it is important in regulation of differentiation and appeared early in the evolution of eukaryotic cells. Calmodulin antagonists also blocked excystation. The divergent giardial calmodulin localized to the eight flagellar basal bodies/centrosomes, like protein kinase A. Inhibitor kinetics suggest that protein kinase A signaling triggers excystation, whereas calcium signaling is mainly required later, for parasite activation and emergence.

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Section: Resultsmentioning

confidence: 92%

“…The IC 50 for TG when present throughout excystation was 7 M. TG at 10 M significantly inhibited giardial excystation only during Stage II (Fig. 3).…”

Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 95%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Calcium Signaling in Excystation of the Early Diverging Eukaryote, Giardia lamblia

Reiner

Hetsko

Meszaros

et al. 2003

Journal of Biological Chemistry

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“…The best preservation was obtained with high-pressure freezing followed by freeze substitution, revealing a very electron-dense aspect. Acidocalcisomes were detected in several protozoa: T. brucei (Vercesi et al 1994), T. cruzi (Docampo et al 1995), L. amazonensis (Lu et al 1997), Toxoplasma gondii (Moreno & Zhong 1996) and Plasmodium falciparum (Marchesini et al 2000). Biochemical data obtained from digitonin-permeabilized cells indicated the presence of a bafilomycin A-sensitive H + -ATPase and a vanadate-sensitive Ca 2+ pump in the acidocalcisome.…”

Section: Isolation Of the Acidocalcisomementioning

confidence: 99%

Cell fractionation of parasitic protozoa: a review

Souza

Cunha-e-Silva

2003

Mem. Inst. Oswaldo Cruz

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Cell fractionation, a methodological strategy for obtaining purified organelle preparations, has been applied successfully to parasitic protozoa by a number of investigators. Here we present and discuss the work of several groups that have obtained highly purified subcellular fractions from trypanosomatids, Apicomplexa and trichomonads, and whose work have added substantially to our knowledge of the cell biology of these parasites.

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