Role of calcium during Toxoplasma gondii invasion and egress.

Calcium is a ubiquitous signalling molecule involved in a large number of cellular processes in eukaryotic cells. In the obligate intracellular parasite, Toxoplasma gondii, for example, a rise in calcium concentration is associated with significant morphological changes, secretion of proteins involved in host cell invasion and rapid egress from the host cell. Recent findings indicate that calcium released from the parasite's intracellular pools is necessary and sufficient to induce some of the events critical for invasion and egress. In addition, ethanol, a powerful inducer of invasion-related events, is shown here to also induce rapid egress from the host cell, indicating that a common mechanism for calcium release might be involved during both invasion and egress.