title: Disassembly activity of actin-depolymerizing factor (ADF) is associated with distinct cellular processes in apicomplexan parasites.
abstract: Proteins of the actin-depolymerizing factor (ADF)/cofilin family have been shown to be crucial for the motility and survival of apicomplexan parasites. However, the mechanisms by which ADF proteins fulfill their function remain poorly understood. In this study, we investigate the comparative activities of ADF proteins from Toxoplasma gondii and Plasmodium falciparum, the human malaria parasite, using a conditional T. gondii ADF-knockout line complemented with ADF variants from either species. We show that P. falciparum ADF1 can fully restore native TgADF activity, demonstrating functional conservation between parasites. Strikingly, mutation of a key basic residue (Lys-72), previously implicated in disassembly in PfADF1, had no detectable phenotypic effect on parasite growth, motility, or development. In contrast, organelle segregation was severely impaired when complementing with a TgADF mutant lacking the corresponding residue (Lys-68). Biochemical analyses of each ADF protein confirmed the reduced ability of lysine mutants to mediate actin depolymerization via filament disassembly although not severing, in contrast to previous reports. These data suggest that actin filament disassembly is essential for apicomplexan parasite development but not for motility, as well as pointing to genus-specific coevolution between ADF proteins and their native actin.
authors.affiliation: Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia.
authors.forename: Silvia
authors.initials: S
authors.lastname: Haase
authors.affiliation: Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637.
authors.forename: Dennis
authors.initials: D
authors.lastname: Zimmermann
authors.affiliation: Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia.
authors.forename: Maya A
authors.initials: MA
authors.lastname: Olshina
authors.affiliation: Department of Life Sciences, Imperial College, London SW7 2AZ, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Wilkinson
authors.affiliation: Department of Life Sciences, Imperial College, London SW7 2AZ, United Kingdom.
authors.forename: Fabio
authors.initials: F
authors.lastname: Fisher
authors.affiliation: Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia.
authors.forename: Yan Hong
authors.initials: YH
authors.lastname: Tan
authors.affiliation: Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Stewart
authors.affiliation: Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Tonkin
authors.affiliation: Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia.
authors.forename: Wilson
authors.initials: W
authors.lastname: Wong
authors.affiliation: Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637.
authors.forename: David R
authors.initials: DR
authors.lastname: Kovar
authors.affiliation: Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia Department of Life Sciences, Imperial College, London SW7 2AZ, United Kingdom jake.baum@imperial.ac.uk.
authors.forename: Jake
authors.initials: J
authors.lastname: Baum
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D000818:Animals; D002465:Cell Movement / Q000502:physiology; D003599:Cytoskeleton / Q000378:metabolism; D051345:Destrin / Q000235:genetics / Q000378:metabolism*; D055786:Gene Knockout Techniques; D056726:Genetic Association Studies; D008239:Lysine / Q000378:metabolism; D010963:Plasmodium falciparum / Q000378:metabolism*; D014122:Toxoplasma / Q000378:metabolism*
chemical_list: D000199:Actins; D051345:Destrin; D008239:Lysine