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Molecular Characterization of Toxoplasma gondii Formin 3, an Actin Nucleator Dispensable for Tachyzoite Growth and Motility

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2012
Author Daher W, Klages N, Carlier MF, Soldati-Favre D,
Project Study of factors governing the invasive and replicative modes in Apicomplexa
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Original article (peer-reviewed)

Journal EUKARYOTIC CELL
Volume (Issue) 11(3)
Page(s) 343 - 352
Title of proceedings EUKARYOTIC CELL

Open Access

URL http://archive-ouverte.unige.ch/unige:18953
Type of Open Access Repository (Green Open Access)

Abstract

to enter host cells. Drugs interfering with the actin cytoskeleton block parasite motility, host cell invasion, and egress from infected cells. Myosin A, profilin, formin 1, formin 2, and actin-depolymerizing factor have all been implicated in parasite motility, yet little is known regarding the importance of actin polymerization and other myosins for the remaining steps of the parasite lytic cycle. Here we establish that T. gondii formin 3 (TgFRM3), a newly described formin homology 2 domain (FH2)-containing protein, binds to Toxoplasma actin and nucleates rabbit actin assembly in vitro. TgFRM3 expressed as a transgene exhibits a patchy localization at several distinct structures within the parasite. Disruption of the TgFRM3 gene by double homologous recombination in a ku80-ko strain reveals no vital function for tachyzoite propagation in vitro, which is consistent with its weak level of expression in this life stage. Conditional stabilization of truncated forms of TgFRM3 suggests that different regions of the molecule contribute to distinct localizations. Moreover, expression of TgFRM3 lacking the C-terminal domain severely affects parasite growth and replication. This work provides a first insight into how this specialized formin, restricted to the group of coccidia, completes its actin-nucleating activity.
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