title: Toxoplasma gondii attachment to host cells is regulated by a calmodulin-like domain protein kinase.
abstract: The role of calcium-dependent protein kinases in the invasion of Toxoplasma gondii into its animal host cells was analyzed. KT5926, an inhibitor of calcium-dependent protein kinases in other systems, is known to block the motility of Toxoplasma tachyzoites and their attachment to host cells. In vivo, KT5926 blocks the phosphorylation of only three parasite proteins, and in parasite extracts only a single KT5926-sensitive protein kinase activity was detected. This activity was calcium-dependent but did not require calmodulin. In a search for calcium-dependent protein kinases in Toxoplasma, two members of the class of calmodulin-like domain protein kinases (CDPKs) were detected. TgCDPK2 was only expressed at the mRNA level in tachyzoites, but no protein was detected. TgCDPK1 protein was expressed in Toxoplasma tachyzoites and cofractionated precisely with the peak of KT5926-sensitive protein kinase activity. TgCDPK1 kinase activity was calcium-dependent but did not require calmodulin or phospholipids. TgCDPK1 was found to be inhibited effectively by KT5926 at concentrations that block parasite attachment to host cells. In vitro, TgCDPK1 phosphorylated three parasite proteins that migrated identical to the three KT5926-sensitive phosphoproteins detected in vivo. Based on these observations, a central role is suggested for TgCDPK1 in regulating Toxoplasma motility and host cell invasion.
authors.affiliation: Division of Geographic Medicine, Department of Cell Biology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
authors.forename: H
authors.initials: H
authors.lastname: Kieschnick
authors.forename: T
authors.initials: T
authors.lastname: Wakefield
authors.forename: C A
authors.initials: CA
authors.lastname: Narducci
authors.forename: C
authors.initials: C
authors.lastname: Beckers
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002227:Carbazoles; D002459:Cell Fusion; D017931:DNA Primers; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007211:Indoles; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010802:Phylogeny; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins; D017386:Sequence Homology, Amino Acid; D014122:Toxoplasma / Q000502:physiology*
chemical_list: D000470:Alkaloids; C490308:CDPK2 protein, Toxoplasma gondii; D002135:Calcium-Binding Proteins; D002227:Carbazoles; D017931:DNA Primers; D004791:Enzyme Inhibitors; D007211:Indoles; D015800:Protozoan Proteins; C063769:KT 5926; D011494:Protein Kinases