Calcium regulation in the intraerythrocytic malaria parasite Plasmodium falciparum.
The regulation of intracellular Ca(2+) in the intraerythrocytic form of the human malaria parasite, Plasmodium falciparum, was investigated using parasites 'isolated' from their host cells by saponin-permeabilisation of the erythrocyte membrane. The isolated parasites maintained tight control over their resting cytosolic Ca(2+) concentration which ranged from approximately 100 nM in the absence of extracellular Ca(2+) to approximately 700 nM in the presence of 1 mM extracellular Ca(2+). The parasite has two functionally discrete intracellular Ca(2+) stores. One is an 'endoplasmic reticulum (ER)-like' store, the other an 'acidic store'. The ER-like store was discharged by cyclopiazonic acid (CPA), an inhibitor of sarco/endoplasmic reticulum Ca(2+)-ATPases (SERCAs) of animal and plant cells, but not by thapsigargin (TG), a more specific inhibitor of SERCAs of animal cells. The acidic store was discharged by nigericin and by NH(4)(+). The amount of Ca(2+) in the ER-like store increased with increasing extracellular Ca(2+) concentration, whereas the amount of Ca(2+) in the acidic store did not. Ca(2+) released from the ER-like store by CPA was cleared from the parasite cytosol by uptake into the acidic store (over a range of extracellular Ca(2+) concentrations), consistent with the acidic store serving as a Ca(2+) reservoir within the intracellular parasite.
Alleva
L M
LM
School of Biochemistry and Molecular Biology, Faculty of Science, The Australian National University, Canberra, ACT 0200, Australia.
Kirk
K
K
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003470:Culture Media; D004912:Erythrocytes / Q000469:parasitology*; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D007211:Indoles / Q000494:pharmacology; D016778:Malaria, Falciparum / Q000469:parasitology; D009550:Nigericin / Q000494:pharmacology; D010963:Plasmodium falciparum / Q000502:physiology*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology
D003470:Culture Media; D007211:Indoles; D000644:Quaternary Ammonium Compounds; D019284:Thapsigargin; D009550:Nigericin; D002118:Calcium; C000543:cyclopiazonic acid