Abstract
Apicomplexan actin is important during the parasite's life cycle. Its polymerization kinetics are unusual, permitting only short, unstable F-actin filaments. It has not been possible to study actin in vivo and so its physiological roles have remained obscure, leading to models distinct from conventional actin behaviour. Here a modified version of the commercially available actin-chromobody was tested as a novel tool for visualising F-actin dynamics in Toxoplasma gondii. Cb labels filamentous actin structures within the parasite cytosol and labels an extensive F-actin network that connects parasites within the parasitophorous vacuole and allows vesicles to be exchanged between parasites. In the absence of actin, parasites lack a residual body and inter-parasite connections and grow in an asynchronous and disorganized manner. Collectively, these data identify new roles for actin in the intracellular phase of the parasites lytic cycle and provide a robust new tool for imaging parasitic F-actin dynamics.
Highlights
Toxoplasma gondii is a wide-spread obligate intracellular parasite that is thought to infect over two billion people worldwide
Remnants of the mother cell remain at the posterior end of the daughter parasites in a structure known as the residual body (RB), which has a role in organizing the parasites into their characteristic rosette pattern within the parasitophorous vacuole (PV) (Muniz-Hernandez et al, 2011; Hu et al, 2002)
A recent study demonstrated a role for actin in parasite replication (Haase et al, 2015) and we used the act1 cKO to further examine the role of actin in parasite growth
Summary
Toxoplasma gondii is a wide-spread obligate intracellular parasite that is thought to infect over two billion people worldwide. The pathological manifestation is caused in a large part by repeated rounds of the parasite’s lytic cycle, beginning with active invasion of the host cell by the parasite, replication within a specialized vacuole termed the parasitophorous vacuole (PV), followed by egress and lysis of the host cell. Replication occurs via a unique process of endodyogeny, where two daughter parasites are constructed within the mother, before elongating and budding, leading to the breakdown of the maternal parasite (Francia and Striepen, 2014). Remnants of the mother cell remain at the posterior end of the daughter parasites in a structure known as the residual body (RB), which has a role in organizing the parasites into their characteristic rosette pattern within the PV (Muniz-Hernandez et al, 2011; Hu et al, 2002). To date little is known about the molecular mechanisms underlying these
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