Comparative genome analysis reveals a conserved family of actin-like proteins in apicomplexan parasites

Gordon, Jennifer L.; Sibley, L. David

doi:10.1186/1471-2164-6-179

Cited by 82 publications

(78 citation statements)

References 60 publications

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“…Using a conditional knockout for act1 it was demonstrated that no ACT1 filament formation can occur as early as 48 h after removal of act1 [28]. Finally, although apicomplexans possess actin-like proteins, it is unlikely that they can compensate for ACT1 and form filaments [27, 51]. Here, we performed a careful quantification of actin levels at different time points in the act1 conditional knockout and find that actin is still detectable at 48 h, but fully depleted by 96 h after induction with rapamycin.…”

Section: Discussionmentioning

confidence: 99%

Surface attachment, promoted by the actomyosin system of Toxoplasma gondii is important for efficient gliding motility and invasion

et al. 2017

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BackgroundApicomplexan parasites employ a unique form of movement, termed gliding motility, in order to invade the host cell. This movement depends on the parasite’s actomyosin system, which is thought to generate the force during gliding. However, recent evidence questions the exact molecular role of this system, since mutants for core components of the gliding machinery, such as parasite actin or subunits of the MyoA-motor complex (the glideosome), remain motile and invasive, albeit at significantly reduced efficiencies. While compensatory mechanisms and unusual polymerisation kinetics of parasite actin have been evoked to explain these findings, the actomyosin system could also play a role distinct from force production during parasite movement.ResultsIn this study, we compared the phenotypes of different mutants for core components of the actomyosin system in Toxoplasma gondii to decipher their exact role during gliding motility and invasion. We found that, while some phenotypes (apicoplast segregation, host cell egress, dense granule motility) appeared early after induction of the act1 knockout and went to completion, a small percentage of the parasites remained capable of motility and invasion well past the point at which actin levels were undetectable. Those act1 conditional knockout (cKO) and mlc1 cKO that continue to move in 3D do so at speeds similar to wildtype parasites. However, these mutants are virtually unable to attach to a collagen-coated substrate under flow conditions, indicating an important role for the actomyosin system of T. gondii in the formation of attachment sites.ConclusionWe demonstrate that parasite actin is essential during the lytic cycle and cannot be compensated by other molecules. Our data suggest a conventional polymerisation mechanism in vivo that depends on a critical concentration of G-actin. Importantly, we demonstrate that the actomyosin system of the parasite functions in attachment to the surface substrate, and not necessarily as force generator.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-016-0343-5) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 99%

Surface attachment, promoted by the actomyosin system of Toxoplasma gondii is important for efficient gliding motility and invasion

et al. 2017

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“…This protein complex facilitates endosomal protein sorting by stimulating Arp2/3 to nucleate F-actin on endosomal membranes. Since the Arp2/3 nucleator complex is absent in apicomplexan parasites [61], the classical endosome-to-PM recycling pathway might have been lost in these organisms and an alternative form of PM recycling, possibly dependent on microtubules, has evolved in apicomplexan parasites. Nonetheless, it would be interesting to investigate the role of actin in endosomal trafficking in apicomplexan parasites.…”

Section: Endosomal Factors Involved In the Biogenesis Of Secretory Ormentioning

confidence: 99%

Vacuolar protein sorting mechanisms in apicomplexan parasites

Jiménez-Ruiz

Morlon-Guyot

Daher

et al. 2016

Molecular and Biochemical Parasitology

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The phylum Apicomplexa comprises more than 5000 species including pathogens of clinical and economical importance. These obligate intracellular parasites possess a highly complex endomembrane system to build amongst others three morphologically distinct secretory organelles: rhoptries, micronemes and dense granules. Proteins released by these organelles are essential for invasion and hijacking of the host cell. Due to the complexity of the internal organization of these parasites, a wide panoply of trafficking factors was expected to be required for the correct sorting of proteins towards the various organelles. However, Toxoplasma gondii and other apicomplexan parasites contain only a core set of these factors and several of the vacuolar protein sorting (VPS) homologues found in most eukaryotes have been lost in this phylum.In this review, we will summarise our current knowledge about the role of trafficking complexes in T. gondii, highlighting recent studies focused on complexes formed by VPS proteins. We also present a novel, hypothetical model, suggesting the recycling of parasite membrane and micronemal proteins.

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“…The myosin family has several additional members whose roles in cytoskeletal development and cell division have yet to be evaluated (Foth et al, 2006; Heintzelman, Schwartzman, 2001; Polonais et al , 2011a; Santos et al , 2009). In addition, a role for IMC assembly was suggested for ALP1 (Gordon et al, 2008), which is also a member of an extensive family (Gordon, Sibley, 2005). Although the function of these myosins and actin-like proteins has not been determined, it is likely that some of these function in cell division.…”

Section: Mechanistic Insights From Disruption Of Cytoskeletal Compmentioning

confidence: 99%

Cytoskeleton Assembly in Toxoplasma gondii Cell Division

Anderson-White

Beck

Chen

et al. 2012

International Review of Cell and Molecular Biology

103

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Cell division across members of the protozoan parasite phylum Apicomplexa displays a surprising diversity between different species as well as between different life stages of the same parasite. In most cases, infection of a host cell by a single parasite results in the formation of a polyploid cell from which individual daughters bud in a process dependent on a final round of mitosis. Unlike other apicomplexans, Toxoplasma gondii divides by a binary process consisting of internal budding that results in only two daughter cells per round of division. Since T. gondii is experimentally accessible and displays the simplest division mode, it has manifested itself as a model for apicomplexan daughter formation. Here we review newly emerging insights in the prominent role that assembly of the cortical cytoskeletal scaffold plays in the process of daughter parasite formation.

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Comparative genome analysis reveals a conserved family of actin-like proteins in apicomplexan parasites

Cited by 82 publications

References 60 publications

Surface attachment, promoted by the actomyosin system of Toxoplasma gondii is important for efficient gliding motility and invasion

Surface attachment, promoted by the actomyosin system of Toxoplasma gondii is important for efficient gliding motility and invasion

Vacuolar protein sorting mechanisms in apicomplexan parasites

Cytoskeleton Assembly in Toxoplasma gondii Cell Division

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