This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.The obligate intracellular infectious agent Toxoplasma gondii is a member of the phylum Apicomplexa, which includes the organisms responsible for malaria and coccidiosis. Although most Toxoplasma infections are asymptomatic, they can lead to severe disease and even death in utero and in individuals immunocompromised by AIDS or cancer. Some of the devastating effects of a Toxoplasma infection are a direct consequence of its lytic cycle, which consists of attachment to the host cell, invasion, intracellular replication and egress. Both invasion and egress involve fluctuation in intracellular calcium concentration, morphological rearrangements and modifications to the host cell. The specific genes and cues involved in these rapid and active events are not known. It has been observed, however, that a decrease in potassium concentration within the host cell can serve as a signal for Toxoplasma egress. It is the goal of this proposal to elucidate the unknown genetic and molecular mechanisms utilized by this pathogen to sense changes in the environment as it specifically regards to potassium fluxes. This will be accomplished by isolating and characterizing mutants with an altered sensitivity to potassium concentration changes. The phenotypic and molecular analysis of these mutants will identify the genes involved in perceiving the pivotal changes in potassium concentration important during egress as well shed light to events critical to host-pathogen communication.
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