Skip to main content
NCBI home page
Biochemical Journal logoLink to Biochemical Journal
. 1996 Jan 15;313(Pt 2):655–659. doi: 10.1042/bj3130655

Acidocalcisomes in Toxoplasma gondii tachyzoites.

S N Moreno 1, L Zhong 1
PMCID: PMC1216957  PMID: 8573106

Abstract

Toxoplasma gondii tachyzoites were loaded with the fluorescent indicator fura 2 to investigate the transport mechanisms involved in maintaining their intracellular Ca2+ homoeostasis. The mitochondrial ATPase inhibitor oligomycin and the endoplasmic-reticulum Ca(2+)-ATPase inhibitor thapsigargin increased the intracellular Ca2+ concentration ([Ca2+]i), thus indicating the requirement for ATP and the involvement of the endoplasmic reticulum in maintaining intracellular Ca2+ homoeostasis. The effect of thapsigargin was more accentuated in the presence of extracellular Ca2+, clearly showing that, as occurs with other eukaryotic cells, depletion of intracellular Ca2+ pools led to an increase in the uptake of Ca2+ from the extracellular medium. In addition to these results, we found evidence that, in contrast with what occurs in mammalian cells, T. gondii tachyzoites possess a significant amount of Ca2+ stored in an acidic compartment, termed the acidocalcisome, as indicated by: (1) the increase in [Ca2+]i induced by bafilomycin A1 (a specific inhibitor of H(+)-ATPases), nigericin (a K+/H+ exchanger) or the weak base NH4Cl, in the nominal absence of extracellular Ca2+ to preclude Ca2+ entry; and (2) the effect of ionomycin, a Ca(2+)-releasing ionophore that cannot take Ca2+ out of acidic organelles and that was more effective after alkalinization of these compartments by addition of bafilomycin A1, nigericin or NH4Cl. Considering the relative importance of the ionomycin-releasable and the ionomycin + NH4Cl-releasable Ca2+ pools, it is apparent that T. gondii tachyzoites contain a significant amount of Ca2+ stored in acidocalcisomes.

Full Text

The Full Text of this article is available as a PDF (490.2 KB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Bode H. P., Eder B., Trautmann M. An investigation on the role of vacuolar-type proton pumps and luminal acidity in calcium sequestration by nonmitochondrial and inositol-1,4,5-trisphosphate-sensitive intracellular calcium stores in clonal insulin-secreting cells. Eur J Biochem. 1994 Jun 15;222(3):869–877. doi: 10.1111/j.1432-1033.1994.tb18934.x. [DOI] [PubMed] [Google Scholar]
  2. Bowman E. J., Siebers A., Altendorf K. Bafilomycins: a class of inhibitors of membrane ATPases from microorganisms, animal cells, and plant cells. Proc Natl Acad Sci U S A. 1988 Nov;85(21):7972–7976. doi: 10.1073/pnas.85.21.7972. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Busa W. B., Nuccitelli R. Metabolic regulation via intracellular pH. Am J Physiol. 1984 Apr;246(4 Pt 2):R409–R438. doi: 10.1152/ajpregu.1984.246.4.R409. [DOI] [PubMed] [Google Scholar]
  4. Carafoli E. Intracellular calcium homeostasis. Annu Rev Biochem. 1987;56:395–433. doi: 10.1146/annurev.bi.56.070187.002143. [DOI] [PubMed] [Google Scholar]
  5. Chamberland S., Kirst H. A., Current W. L. Comparative activity of macrolides against Toxoplasma gondii demonstrating utility of an in vitro microassay. Antimicrob Agents Chemother. 1991 May;35(5):903–909. doi: 10.1128/aac.35.5.903. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Coppens I., Baudhuin P., Opperdoes F. R., Courtoy P. J. Role of acidic compartments in Trypanosoma brucei, with special reference to low-density lipoprotein processing. Mol Biochem Parasitol. 1993 Apr;58(2):223–232. doi: 10.1016/0166-6851(93)90044-x. [DOI] [PubMed] [Google Scholar]
  7. Cunningham K. W., Fink G. R. Calcineurin-dependent growth control in Saccharomyces cerevisiae mutants lacking PMC1, a homolog of plasma membrane Ca2+ ATPases. J Cell Biol. 1994 Feb;124(3):351–363. doi: 10.1083/jcb.124.3.351. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Docampo R., Scott D. A., Vercesi A. E., Moreno S. N. Intracellular Ca2+ storage in acidocalcisomes of Trypanosoma cruzi. Biochem J. 1995 Sep 15;310(Pt 3):1005–1012. doi: 10.1042/bj3101005. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Endo T., Sethi K. K., Piekarski G. Toxoplasma gondii: calcium ionophore A23187-mediated exit of trophozoites from infected murine macrophages. Exp Parasitol. 1982 Apr;53(2):179–188. doi: 10.1016/0014-4894(82)90059-5. [DOI] [PubMed] [Google Scholar]
  10. Fasolato C., Zottini M., Clementi E., Zacchetti D., Meldolesi J., Pozzan T. Intracellular Ca2+ pools in PC12 cells. Three intracellular pools are distinguished by their turnover and mechanisms of Ca2+ accumulation, storage, and release. J Biol Chem. 1991 Oct 25;266(30):20159–20167. [PubMed] [Google Scholar]
  11. Grynkiewicz G., Poenie M., Tsien R. Y. A new generation of Ca2+ indicators with greatly improved fluorescence properties. J Biol Chem. 1985 Mar 25;260(6):3440–3450. [PubMed] [Google Scholar]
  12. Liu C., Hermann T. E. Characterization of ionomycin as a calcium ionophore. J Biol Chem. 1978 Sep 10;253(17):5892–5894. [PubMed] [Google Scholar]
  13. Luft B. J., Remington J. S. AIDS commentary. Toxoplasmic encephalitis. J Infect Dis. 1988 Jan;157(1):1–6. doi: 10.1093/infdis/157.1.1. [DOI] [PubMed] [Google Scholar]
  14. Moreno S. N., Docampo R., Vercesi A. E. Calcium homeostasis in procyclic and bloodstream forms of Trypanosoma brucei. Lack of inositol 1,4,5-trisphosphate-sensitive Ca2+ release. J Biol Chem. 1992 Mar 25;267(9):6020–6026. [PubMed] [Google Scholar]
  15. Negulescu P. A., Machen T. E. Intracellular ion activities and membrane transport in parietal cells measured with fluorescent dyes. Methods Enzymol. 1990;192:38–81. doi: 10.1016/0076-6879(90)92062-i. [DOI] [PubMed] [Google Scholar]
  16. Nicholls D. G. Intracellular calcium homeostasis. Br Med Bull. 1986 Oct;42(4):353–358. doi: 10.1093/oxfordjournals.bmb.a072152. [DOI] [PubMed] [Google Scholar]
  17. Norrby R., Lindholm L., Lycke E. Lysosomes of Toxoplasma gondii and their possible relation to the host-cell penetration of toxoplasma parasites. J Bacteriol. 1968 Oct;96(4):916–919. doi: 10.1128/jb.96.4.916-919.1968. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Putney J. W., Jr Inositol phosphates and calcium entry. Adv Second Messenger Phosphoprotein Res. 1992;26:143–160. [PubMed] [Google Scholar]
  19. Rooney E. K., Gross J. D. ATP-driven Ca2+/H+ antiport in acid vesicles from Dictyostelium. Proc Natl Acad Sci U S A. 1992 Sep 1;89(17):8025–8029. doi: 10.1073/pnas.89.17.8025. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Rooney E. K., Gross J. D., Satre M. Characterisation of an intracellular Ca2+ pump in Dictyostelium. Cell Calcium. 1994 Dec;16(6):509–522. doi: 10.1016/0143-4160(94)90081-7. [DOI] [PubMed] [Google Scholar]
  21. Roos A., Boron W. F. Intracellular pH. Physiol Rev. 1981 Apr;61(2):296–434. doi: 10.1152/physrev.1981.61.2.296. [DOI] [PubMed] [Google Scholar]
  22. Schwab J. C., Cao Y., Slowik M. R., Joiner K. A. Localization of azithromycin in Toxoplasma gondii-infected cells. Antimicrob Agents Chemother. 1994 Jul;38(7):1620–1627. doi: 10.1128/aac.38.7.1620. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Schwartzman J. D., Saffer L. D. How Toxoplasma gondii gets in and out of host cells. Subcell Biochem. 1992;18:333–364. doi: 10.1007/978-1-4899-1651-8_10. [DOI] [PubMed] [Google Scholar]
  24. Scott D. A., Moreno S. N., Docampo R. Ca2+ storage in Trypanosoma brucei: the influence of cytoplasmic pH and importance of vacuolar acidity. Biochem J. 1995 Sep 15;310(Pt 3):789–794. doi: 10.1042/bj3100789. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Styrt B., Klempner M. S. Lysosomotropic amines modulate neutrophil calcium homeostasis. J Cell Physiol. 1988 May;135(2):309–316. doi: 10.1002/jcp.1041350219. [DOI] [PubMed] [Google Scholar]
  26. Thastrup O., Cullen P. J., Drøbak B. K., Hanley M. R., Dawson A. P. Thapsigargin, a tumor promoter, discharges intracellular Ca2+ stores by specific inhibition of the endoplasmic reticulum Ca2(+)-ATPase. Proc Natl Acad Sci U S A. 1990 Apr;87(7):2466–2470. doi: 10.1073/pnas.87.7.2466. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Thévenod F., Dehlinger-Kremer M., Kemmer T. P., Christian A. L., Potter B. V., Schulz I. Characterization of inositol 1,4,5-trisphosphate-sensitive (IsCaP) and -insensitive (IisCaP) nonmitochondrial Ca2+ pools in rat pancreatic acinar cells. J Membr Biol. 1989 Jul;109(2):173–186. doi: 10.1007/BF01870856. [DOI] [PubMed] [Google Scholar]
  28. Vercesi A. E., Moreno S. N., Bernardes C. F., Meinicke A. R., Fernandes E. C., Docampo R. Thapsigargin causes Ca2+ release and collapse of the membrane potential of Trypanosoma brucei mitochondria in situ and of isolated rat liver mitochondria. J Biol Chem. 1993 Apr 25;268(12):8564–8568. [PubMed] [Google Scholar]
  29. Vercesi A. E., Moreno S. N., Docampo R. Ca2+/H+ exchange in acidic vacuoles of Trypanosoma brucei. Biochem J. 1994 Nov 15;304(Pt 1):227–233. doi: 10.1042/bj3040227. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Biochemical Journal are provided here courtesy of The Biochemical Society

RESOURCES