The role of Myosin L in the survival of Toxoplasma gondii and the importance of MLC1 for in vitro and in vivo Myosin F motility

My thesis discusses the work that I have conducted on two myosins in Toxoplasma gondii, which is an obligate intracellular parasite that has chronically infected around 10% of the American population. It causes toxoplasmosis and severe health consequences for individuals with compromised immune systems or when infections occur in utero. However, immunocompetent individuals are asymptomatic or present with subclinical symptoms. In the Heaslip lab, I investigated two myosins in the parasite: Myosin L and Myosin F. MyoL is an uncharacterized motor that localizes at the apical end of the parasite. It was shown to be important for parasite survival. However, it is not involved with the localizations of apical secretory organelles or the organization of structural proteins. Based on its predicted structure, the protein could be involved in capturing actin at the conoid to translocate to MyoH. For actin organization, MyoF is theorized to be an actin linker protein that is associated with the light chains called CaM and MLC1. CaM was shown to be essential for MyoF motility, while it is unknown how essential or important MLC1 is for MyoF motility in vitro and in vivo. Using motility assays, MLC1 is shown to be nonessential for MyoF motility, and it cannot rescue MyoF motility when CaM is removed. Further, MLC1 is not essential in vivo with the directed velocities of dense granules and the localizations of apicoplasts unaffected after MLC1 is knocked out.