title: Involvement of calcium and calmodulin in Toxoplasma gondii tachyzoite invasion.
abstract: The tachyzoite of Toxoplasma gondii must successfully invade a host cell before it can replicate. Depletion of the Ca2+ in the external medium (EGTA) reduced tachyzoite invasion, suggesting that the initial tachyzoite-host cell interaction is Ca2+ dependent. The interaction of tachyzoites with host cells was also inhibited by Ca2+ channel blockers (verapamil) and calmodulin antagonists (trifluoperazine, calmidazolium). The calmodulin concentrated at the apical end of the tachyzoite could be involved in cytoskeleton movement and conoid extrusion. Invasion also depends on changes in tachyzoite cytosolic calcium. Depletion of Ca2+ with A23187+EGTA and release of Ca2+ from intratachyzoite pools (nuclear and perinuclear areas) inhibited invasion. In contrast, Ca-ionophore and thapsigargin which increase host cell cytosolic Ca2+, significantly decreased tachyzoite invasion. We therefore suggest that the effect of the drug is significantly different from the localized Ca2+ signal that is produced after parasite attachment to its host cell receptors and leads to its internalization into the host cell.
authors.affiliation: INSERM U314 et Laboratoire de Parasitologie-CHU, Université de Reims Champagne-Ardenne, France.
authors.forename: N
authors.initials: N
authors.lastname: Pezzella
authors.forename: A
authors.initials: A
authors.lastname: Bouchot
authors.forename: A
authors.initials: A
authors.lastname: Bonhomme
authors.forename: L
authors.initials: L
authors.lastname: Pingret
authors.forename: C
authors.initials: C
authors.lastname: Klein
authors.forename: H
authors.initials: H
authors.lastname: Burlet
authors.forename: G
authors.initials: G
authors.lastname: Balossier
authors.forename: P
authors.initials: P
authors.lastname: Bonhomme
authors.forename: J M
authors.initials: JM
authors.lastname: Pinon
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002147:Calmodulin / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology*; D002294:Carcinoma, Squamous Cell; D003600:Cytosol / Q000378:metabolism; D004847:Epithelial Cells / Q000469:parasitology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D014122:Toxoplasma / Q000472:pathogenicity*; D014268:Trifluoperazine / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D002147:Calmodulin; D007093:Imidazoles; D007476:Ionophores; D014268:Trifluoperazine; D000001:Calcimycin; C031938:calmidazolium; D014700:Verapamil; D002118:Calcium