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Abstract
Toxoplasma gondii is an Apicomplexan parasite that infects one third of the world’s population. The disease caused by this obligate intracellular parasite, toxoplasmosis, is clinically relevant for immunocompromised patients and for the unborn fetus. The pathogenicity of the parasite derived from its lytic cycle where it invades, replicates and egresses out of a host cell. Calcium signaling is part of the signaling pathways that regulates the expression and activation of proteins that are essential for the pathogenicity of T. gondii. Calcium increase in the cytosol resulting from influx or release from intracellular stores, will trigger a signaling cascade that can activate a variety of effectors that will activate vital cellular functions like the ones that are part of the parasite pathogenic cycle. The majority of the molecules that form part of this signaling pathway remain uncharacterized. In this work we identified and characterized the first Ca2+ channel in T. gondii. Additionally, we characterize a organellar Ca2+-binding protein which senses changes of luminal organellar Ca2+. Lastly, we provide evidence of additional roles of previously characterized Ca2+-binding proteins in regulating Ca2+ channels. Apicomplexa belong to an early branch in the eukaryotic evolutionary tree and the discovery of new signaling molecules will generate important information about the origins of complex signaling networks in eukaryotes. In addition, new molecules may provide for potential targets for future chemotherapy.