Characterization of the subpellicular network, a filamentous membrane skeletal component in the parasite Toxoplasma gondii

Mann, Tara; Beckers, Con J.

doi:10.1016/s0166-6851(01)00289-4

Cited by 220 publications

(279 citation statements)

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“…Toxoplasma gondii tachyzoites (strain RH) were cultivated in human foreskin fibroblast (HFF) cells as previously described (Roos et al, 1994) Plasmid ptubIMC1-YFP/sagCAT was engineered by amplifying the IMC1 gene from a cDNA plasmid (Mann and Beckers, 2001) using primers 5Ј-GTTagatctATGTTTAAGGACTGCGCCGATCCT-TGCA-3Ј, and 5Ј-TGGcctaggGCACTGGCATCGGCACACACCAT-CACC-3Ј, digestion with BglII and Avr II, and ligation in place of ␤TUB in ptub-␤TUB-YFP/sagCAT . The resulting plasmid is based on Bluescript pKSϩ (Stratagene, La Jolla, CA), and contains an ␣-tubulin promoter (Nagel and Boothroyd, 1988) separated from the IMC1 coding sequence by a BglII site, an inframe Avr II site separating IMC1 coding sequence from YFP, a 3Ј untranslated region derived from the T. gondii DHFR-TS gene (Roos, 1993), and a NotI site separating these sequences from a chloramphenicol acetyl transferase selectable marker under the control of 5Ј and 3Ј sequences derived from the T. gondii P30 gene (Kim et al, 1993).…”

Section: Methodsmentioning

confidence: 99%

“…What checkpoints regulate the parasite cell cycle? To investigate questions such as these, we have combined IMC1 (Mann and Beckers, 2001), a subunit of the membrane skeleton of the inner membrane complex or subpellicular network, with various fluorescent reporter proteins (Chalfie et al, 1994;Pepperkok et al, 1999). IMC1-YFP has been exploited to directly observe daughter assembly in real time using time-lapse video microscopy, yielding insights into the biology of mitotic replication in Apicomplexan parasites.…”

Section: Introductionmentioning

confidence: 99%

“…IMC1 is a subunit of the subpellicular network, the apparent membrane skeleton associated with the cytoplasmic face of the inner membrane complex. It associates with the inner membrane complexes of both mother and daughters (Mann and Beckers, 2001).During mitotic cell division in T. gondii (endodyogeny), daughter inner membrane complexes develop within the mother while the mother's inner membrane complex is still present, as diagrammed in Figure 1B (Ogino and Yoneda, 1966;Sheffield and Melton, 1968). Antibody staining of proteins associated with the inner membrane complex permits visualization of both the mother and the two developing daughters (Figure 2A).…”

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confidence: 99%

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Daughter Cell Assembly in the Protozoan ParasiteToxoplasma gondii

Hu¹,

Mann

Striepen

et al. 2002

MBoC

169

230

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The phylum Apicomplexa includes thousands of species of obligate intracellular parasites, many of which are significant human and/or animal pathogens. Parasites in this phylum replicate by assembling daughters within the mother, using a cytoskeletal and membranous scaffolding termed the inner membrane complex. Most apicomplexan parasites, including Plasmodium sp. (which cause malaria), package many daughters within a single mother during mitosis, whereas Toxoplasma gondii typically packages only two. The comparatively simple pattern of T. gondii cell division, combined with its molecular genetic and cell biological accessibility, makes this an ideal system to study parasite cell division. A recombinant fusion between the fluorescent protein reporter YFP and the inner membrane complex protein IMC1 has been exploited to examine daughter scaffold formation in T. gondii. Time-lapse video microscopy permits the entire cell cycle of these parasites to be visualized in vivo. In addition to replication via endodyogeny (packaging two parasites at a time), T. gondii is also capable of forming multiple daughters, suggesting fundamental similarities between cell division in T. gondii and other apicomplexan parasites. INTRODUCTIONToxoplasma gondii is a ubiquitous protozoan parasite, chronically infecting 10 -90% of human populations worldwide. Sexual differentiation occurs only in the cat, but asexual T. gondii parasites can invade, proliferate, and encyst in virtually any nucleated cell (Frenkel, 1973;Bonhomme et al., 1992;Smith, 1995;Dubey, 1998;Dubey et al., 1998). Primary infection during pregnancy poses a risk of abortion or severe birth defects. Reactivation of dormant parasite tissue cysts (bradyzoites) gives rise to rapidly replicating tachyzoites, which may be fatal in immunocompromised individuals. Pathogenesis in both congenital infection and immunosuppressed patients is directly attributable to parasite proliferation (Frenkel, 1973;Dubey, 1998). Understanding the replication process of this parasite is therefore essential for the development of improved treatment but little is known about cell cycle control in these parasites.Like other members of the phylum Apicomplexa, T. gondii is an obligate intracellular parasite. Haploid tachyzoites invade into host cells, establishing a parasitophorous vacuole whose membrane is derived from the host plasma membrane (Joiner et al., 1994;Suss-Toby et al., 1996;Mordue et al., 1999; Figure 1A). Two parasites are typically produced in each mitotic cell cycle (ϳ7-10 h), and replication proceeds synchronously, resulting in geometric expansion of clonal progeny until the host cell is lysed, ϳ48 h postinfection.In contrast to replication by binary fission (as observed in most animal, plant, and bacterial cells), parasite replication proceeds via assembly of daughters within the mother (Figure 1B). Because asexual replication of T. gondii tachyzoites typically produces two parasites per mitotic cell cycle, this process is often termed "endodyogeny" (Sheffield and Melton, 1968). In c...

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Daughter Cell Assembly in the Protozoan ParasiteToxoplasma gondii

Hu¹,

Mann

Striepen

et al. 2002

MBoC

169

230

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“…The cytoplasmic face of the IMC is intimately associated with the basket of subpellicular microtubules that run along the apical two-thirds of the parasite length (Morrissette et al, 1997) through a network of intermediate-like filaments formed by alveolin-containing proteins (named ALVs or IMCs) that are conserved in apicomplexans (Mann and Beckers, 2001;Gould et al, 2008;Anderson-White et al, 2011). The IMC family is composed of 14 members in T. gondii and none of them has a predicted TMD, but 10 have putative palmitoylation sites that probably anchor the proteins to the cytoplasmic face of the IMC (Anderson-White et al, 2011).…”

Section: Imc-localised Palmitoylated Proteins Are Important For Divisionmentioning

confidence: 99%

Emerging roles for protein S-palmitoylation in Toxoplasma biology

Frénal

Kemp

Soldati‐Favre

2014

International Journal for Parasitology

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a b s t r a c tPost-translational modifications are refined, rapidly responsive and powerful ways to modulate protein function. Among post-translational modifications, acylation is now emerging as a widespread modification exploited by eukaryotes, bacteria and viruses to control biological processes. Protein palmitoylation involves the attachment of palmitic acid, also known as hexadecanoic acid, to cysteine residues of integral and peripheral membrane proteins and increases their affinity for membranes. Importantly, similar to phosphorylation, palmitoylation is reversible and is becoming recognised as instrumental for the regulation of protein function by modulating protein interactions, stability, folding, trafficking and signalling. Palmitoylation appears to play a central role in the biology of the Apicomplexa, regulating critical processes such as host cell invasion which is vital for parasite survival and dissemination. The recent identification of over 400 palmitoylated proteins in Plasmodium falciparum erythrocytic stages illustrates the broad spread and impact of this modification on parasite biology. The main enzymes responsible for protein palmitoylation are multi-membrane protein S-acyl transferases harbouring a catalytic Asp-HisHis-Cys (DHHC) motif. A global functional analysis of the repertoire of protein S-acyl transferases in Toxoplasma gondii and Plasmodium berghei has recently been performed. The essential nature of some of these enzymes illustrates the key roles played by this post-translational modification in the corresponding substrates implicated in fundamental processes such as parasite motility and organelle biogenesis. Toward a better understanding of the depalmitoylation event, a protein with palmitoyl protein thioesterase activity has been identified in T. gondii. TgPPT1/TgASH1 is the main target of specific acyl protein thioesterase inhibitors but is dispensable for parasite survival, suggesting the implication of other genes in depalmitoylation. Palmitoylation/depalmitoylation cycles are now emerging as potential novel regulatory networks and T. gondii represents a superb model organism in which to explore their significance.

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“…These microtubules radiate from the apical POLAR RING, which functions as a microtubule-organizing centre. A recent study has described the existence of a filamentous network that associates with the cytoplasmic face of the IMC along the length of the parasite [12]. The filaments, which are 8-10 nm in length, comprise the complexes TgIMC1 and TgIMC2 and seem to act as a membrane skeleton that possibly contributes to maintenance of the lattice organization, mechanical strength and the determination of cell shape.…”

Section: Glossarymentioning

confidence: 99%