Calcium-dependent phosphorylation alters Class XIVa myosin function in the protozoan parasite Toxoplasma gondii.

Molecular biology of the cell

PubMedID: 24989796

Tang Q, Andenmatten N, Triana MA, Deng B, Meissner M, Moreno SN, Ballif BA, Ward GE. Calcium-dependent phosphorylation alters Class XIVa myosin function in the protozoan parasite Toxoplasma gondii. Mol Biol Cell. 2014;.
Class XIVa myosins are a unique group of myosin motor proteins found in apicomplexan parasites, including those that cause malaria and toxoplasmosis. The founding member of the class XIVa family, Toxoplasma gondii myosin A (TgMyoA), is a monomeric unconventional myosin that functions at the parasite periphery to control gliding motility, host cell invasion and host cell egress. How the motor activity of TgMyoA is regulated during these critical steps in the parasite's lytic cycle is unknown. We show here that a small-molecule enhancer of T. gondii motility and invasion (compound 130038) causes an increase parasite intracellular calcium levels leading to a calcium-dependent increase in TgMyoA phosphorylation. Mutation of the major sites of phosphorylation altered parasite motile behavior upon compound 130038 treatment, and parasites expressing a non-phosphorylatable mutant myosin egressed from host cells more slowly in response to treatment with calcium ionophore. These data demonstrate that TgMyoA undergoes calcium-dependent phosphorylation, which modulates myosin-driven processes in this important human pathogen.