title: Analysis of Ca2+mediated signaling regulating Toxoplasma infectivity reveals complex relationships between key molecules.
abstract: Host cell invasion, exit and parasite dissemination is critical to the pathogenesis of apicomplexan parasites such as Toxoplasma gondii and Plasmodium spp. These processes are regulated by intracellular Ca2+signaling although the temporal dynamics of Ca2+fluxes and down-stream second messenger pathways are poorly understood. Here, we use a genetically encoded biosensor, GFP-Calmodulin-M13-6 (GCaMP6), to capture Ca2+flux in live Toxoplasma and investigate the role of Ca2+signaling in egress and motility. Our analysis determines how environmental cues and signal activation influence intracellular Ca2+flux, allowing placement of effector molecules within this pathway. Importantly, we have identified key interrelationships between cGMP and Ca2+signaling that are required for activation of egress and motility. Furthermore, we extend this analysis to show that the Ca2+Dependent Protein Kinases-TgCDPK1 and TgCDPK3-play a role in signal quenching before egress. This work highlights the interrelationships of second messenger pathways of Toxoplasma in space and time, which is likely required for pathogenesis of all apicomplexan species.
authors: The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Melbourne, Victoria, Australia.
authors: Rebecca J
authors: RJ
authors: Stewart
authors: The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Melbourne, Victoria, Australia.
authors: Lachlan
authors: L
authors: Whitehead
authors: Metabolomics Australia, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia.
authors: Brunda
authors: B
authors: Nijagal
authors: The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Melbourne, Victoria, Australia.
authors: Brad E
authors: BE
authors: Sleebs
authors: The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Melbourne, Victoria, Australia.|Department of Pharmacology and Therapeutics, The University of Melbourne, Melbourne, Victoria, Australia.
authors: Guillaume
authors: G
authors: Lessene
authors: Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Australia.
authors: Malcolm J
authors: MJ
authors: McConville
authors: The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Melbourne, Victoria, Australia.
authors: Kelly L
authors: KL
authors: Rogers
authors: The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Melbourne, Victoria, Australia.
authors: Christopher J
authors: CJ
authors: Tonkin
mesh_terms: D020013:Calcium Signaling; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D006790:Host-Parasite Interactions; D006801:Humans; D014122:Toxoplasma / Q000472:pathogenicity* / Q000502:physiology; D014123:Toxoplasmosis / Q000469:parasitology*
chemical_list: D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP