Relationship between intracellular free calcium concentrations and the intracellular development of Toxoplasma gondii.
We measured intracellular free calcium concentrations ([Ca++]i) in the subcellular compartments of Toxoplasma gondii infected living cells using microspectrofluorometry and Indo-1 staining. [Ca++]i mapping was defined in infected and uninfected cells and in the neoformed parasitophorous vacuole (PV) 24 and 48 hr after parasite inoculation. At 24 hr after infection, a [Ca++]i gradient (PV/cytoplasm) was observed in favor of the PV in 72% of infected cells (p<0.001). Inside of the PV (lumen and parasites), [Ca++]i values appeared to be homogeneously distributed. At 48 hr after infection, the parasites had replicated and formed typical rosettes of more than 16 parasites. At this step, a positive [Ca++]i gradient (PV/cytoplasm) was detected in all analyzed cells (p<0.001). This result suggests that the PV (lumen and parasites) represents an individual subcellular compartment within the host cell that includes an independent [Ca++]i. Moreover, after 48 hr the cytoplasmic [Ca++]i decreased significantly (39 nM) compared with that measured from uninfected cells (53 nM) (p <0.05). Furthermore, the exit of Toxoplasma mediated by the calcium ionophore 4BrA23187 was preceded by a rise of [Ca++]i to 1 mM in the PV. The [Ca++]i rise and the liberation of parasites from their host appear to be correlated. On the basis of these observations, we suggest that the increase of [Ca++]i in the vacuole may act as a signal that triggers the egress of T. gondii.
Pingret
L
L
INSERM U314, Laboratoire de Parasitologie, Hôpital Maison Blanche, Reims, France.
Millot
J M
JM
Sharonov
S
S
Bonhomme
A
A
Manfait
M
M
Pinon
J M
JM
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000032:analysis* / Q000502:physiology; D002451:Cell Compartmentation; D004533:Egtazic Acid / Q000494:pharmacology; D005456:Fluorescent Dyes; D006801:Humans; D007211:Indoles; D007424:Intracellular Fluid / Q000737:chemistry*; D007476:Ionophores / Q000494:pharmacology; D007624:KB Cells / Q000187:drug effects / Q000469:parasitology*; D051379:Mice; D013050:Spectrometry, Fluorescence; D014122:Toxoplasma / Q000254:growth & development*; D014617:Vacuoles / Q000737:chemistry / Q000469:parasitology
D005456:Fluorescent Dyes; D007211:Indoles; D007476:Ionophores; D000001:Calcimycin; D004533:Egtazic Acid; C048960:indo-1; D002118:Calcium