title: Distinct signalling pathways control Toxoplasma egress and host-cell invasion.
abstract: Calcium signalling coordinates motility, cell invasion, and egress by apicomplexan parasites, yet the key mediators that transduce these signals remain largely unknown. One underlying assumption is that invasion into and egress from the host cell depend on highly similar systems to initiate motility. Using a chemical-genetic approach to specifically inhibit select calcium-dependent kinases (CDPKs), we instead demonstrate that these pathways are controlled by different kinases: both TgCDPK1 and TgCDPK3 were required during ionophore-induced egress, but only TgCDPK1 was required during invasion. Similarly, microneme secretion, which is necessary for motility during both invasion and egress, universally depended on TgCDPK1, but only exhibited TgCDPK3 dependence when triggered by certain stimuli. We also demonstrate that egress likely comes under a further level of control by cyclic GMP-dependent protein kinase and that its activation can induce egress and partially compensate for the inhibition of TgCDPK3. These results demonstrate that separate signalling pathways are integrated to regulate motility in response to the different signals that promote invasion or egress during infection by Toxoplasma gondii.
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO 63110, USA.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Lourido
authors.forename: Keliang
authors.initials: K
authors.lastname: Tang
authors.forename: L David
authors.initials: LD
authors.lastname: Sibley
mesh_terms: D015153:Blotting, Western; D000001:Calcimycin; D020013:Calcium Signaling / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D005434:Flow Cytometry; D051418:Focal Adhesion Kinase 2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D055786:Gene Knockout Techniques; D015723:Gene Library; D005822:Genetic Vectors / Q000235:genetics; D006790:Host-Parasite Interactions / Q000502:physiology*; D036341:Intercellular Signaling Peptides and Proteins; D008856:Microscopy, Fluorescence; D009068:Movement / Q000502:physiology*; D010455:Peptides; D015800:Protozoan Proteins / Q000378:metabolism*; D012044:Regression Analysis; D014122:Toxoplasma / Q000502:physiology*
chemical_list: D017931:DNA Primers; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D015800:Protozoan Proteins; C063391:syntide-2; D000001:Calcimycin; D051418:Focal Adhesion Kinase 2; D017869:Cyclic GMP-Dependent Protein Kinases