title: Optogenetic monitoring identifies phosphatidylthreonine-regulated calcium homeostasis inToxoplasma gondii.
abstract: Toxoplasma gondiiis an obligate intracellular parasite, which inflicts acute as well as chronic infections in a wide range of warm-blooded vertebrates. Our recent work has demonstrated the natural occurrence and autonomous synthesis of an exclusive lipid phosphatidylthreonine inT. gondii. Targeted gene disruption of phosphatidylthreonine synthase impairs the parasite virulence due to unforeseen attenuation of the consecutive events of motility, egress and invasion. However, the underlying basis of such an intriguing phenotype in the parasite mutant remains unknown. Using an optogenetic sensor (gene-encoded calcium indicator, GCaMP6s), we show that loss of phosphatidylthreonine depletes calcium stores in intracellular tachyzoites, which leads to dysregulation of calcium release into the cytosol during the egress phase of the mutant. Consistently, the parasite motility and egress phenotypes in the mutant can be entirely restored by ionophore-induced mobilization of calcium. Collectively, our results suggest a novel regulatory function of phosphatidylthreonine in calcium signaling of a prevalent parasitic protist. Moreover, our application of an optogenetic sensor to monitor subcellular calcium in a model intracellular pathogen exemplifies its wider utility to other entwined systems.
authors.affiliation: Humboldt University, Berlin, Germany.
authors.forename: Arunakar
authors.initials: A
authors.lastname: Kuchipudi
authors.affiliation: Humboldt University, Berlin, Germany.
authors.forename: Ruben D
authors.initials: RD
authors.lastname: Arroyo-Olarte
authors.affiliation: Humboldt University, Berlin, Germany.
authors.forename: Friederike
authors.initials: F
authors.lastname: Hoffmann
authors.affiliation: Max-Planck Institute for Infection Biology, Berlin, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Brinkmann
authors.affiliation: Humboldt University, Berlin, Germany.|Max-Planck Institute for Infection Biology, Berlin, Germany.
authors.forename: Nishith
authors.initials: N
authors.lastname: Gupta
keywords: Toxoplasma gondii; calcium homeostasis; gene-encoded calcium indicator; intracellular parasite; lytic cycle; optogenetics; phosphatidylthreonine