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Phosphatidylinositol 3-monophosphate is involved in toxoplasma apicoplast biogenesis.

Tawk L, Dubremetz JF, Montcourrier P, Chicanne G, Merezegue F, Richard V, Payrastre B, Meissner M, Vial HJ, Roy C, Wengelnik K, Lebrun M - PLoS Pathog. (2011)

Bottom Line: Imaging of PI3P in T. gondii showed that the lipid was associated with the apicoplast and apicoplast protein-shuttling vesicles.These findings point to an unexpected implication for this ubiquitous lipid and open new perspectives on how nuclear encoded proteins traffic to the apicoplast.This study also highlights the possibility of developing specific pharmacological inhibitors of the parasite PI3-kinase as novel anti-apicomplexan drugs.

View Article: PubMed Central - PubMed

Affiliation: UMR 5235 CNRS, Université Montpellier 1 & 2, Montpellier, France.

ABSTRACT
Apicomplexan parasites cause devastating diseases including malaria and toxoplasmosis. They harbour a plastid-like, non-photosynthetic organelle of algal origin, the apicoplast, which fulfils critical functions for parasite survival. Because of its essential and original metabolic pathways, the apicoplast has become a target for the development of new anti-apicomplexan drugs. Here we show that the lipid phosphatidylinositol 3-monophosphate (PI3P) is involved in apicoplast biogenesis in Toxoplasma gondii. In yeast and mammalian cells, PI3P is concentrated on early endosomes and regulates trafficking of endosomal compartments. Imaging of PI3P in T. gondii showed that the lipid was associated with the apicoplast and apicoplast protein-shuttling vesicles. Interference with regular PI3P function by over-expression of a PI3P specific binding module in the parasite led to the accumulation of vesicles containing apicoplast peripheral membrane proteins around the apicoplast and, ultimately, to the loss of the organelle. Accordingly, inhibition of the PI3P-synthesising kinase interfered with apicoplast biogenesis. These findings point to an unexpected implication for this ubiquitous lipid and open new perspectives on how nuclear encoded proteins traffic to the apicoplast. This study also highlights the possibility of developing specific pharmacological inhibitors of the parasite PI3-kinase as novel anti-apicomplexan drugs.

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Related in: MedlinePlus

Localization of PI3P in T. gondii.ImmunoEM analysis of ddFYVE expressing parasites fixed 20 min (A, B, C) or 24 h (D, E) after addition of 1 µM Shield-1. (A, B, C) The anti-GFP gold label is found on the outer membranes of the apicoplast (short arrows), on the membrane of electron-dense (C, black arrowheads) and electron-lucent (C, B, white arrowheads) vesicles, these latter accumulating in the subapical region (B, arrow). a, apicoplast; d, dense granule; IMC, inner membrane complex; m, mitochondrion; n, nucleus; PM, parasite plasma membrane. (D, E) After one day of Shield-1 treatment, the anti-GFP labels large lucent vacuoles either inside parasites (D), or accumulated in the residual body (E), while the overall structure of the tachyzoites is unaffected. The white framed boxes show enlargements of GFP-positive lucent vesicles.
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ppat-1001286-g005: Localization of PI3P in T. gondii.ImmunoEM analysis of ddFYVE expressing parasites fixed 20 min (A, B, C) or 24 h (D, E) after addition of 1 µM Shield-1. (A, B, C) The anti-GFP gold label is found on the outer membranes of the apicoplast (short arrows), on the membrane of electron-dense (C, black arrowheads) and electron-lucent (C, B, white arrowheads) vesicles, these latter accumulating in the subapical region (B, arrow). a, apicoplast; d, dense granule; IMC, inner membrane complex; m, mitochondrion; n, nucleus; PM, parasite plasma membrane. (D, E) After one day of Shield-1 treatment, the anti-GFP labels large lucent vacuoles either inside parasites (D), or accumulated in the residual body (E), while the overall structure of the tachyzoites is unaffected. The white framed boxes show enlargements of GFP-positive lucent vesicles.

Mentions: In order to further refine the localisation of PI3P, the ddFYVE signal was analyzed by immuno-electron microscopy (IEM). Due to the low level of spontaneous expression of ddFYVE, no signal could be detected in IEM in the absence of Shield-1. Experiments were therefore performed within the first hour of Shield-1 addition, at a time when the PI3P signal started diffusing around the apicoplast but before the loss of the apicoplast could occur (Figure 2A). Anti-GFP antibodies labelled the outer membranes of the apicoplast and the membrane of vesicles located in the vicinity of this organelle (Figure 5A, B, C). The vesicles were packed together and were of variable electron density: the denser ones were of uniform size, usually spherical with a diameter of 0.1±0.01 µm; the electron-lucent ones were larger, more heterogeneous in size and shape (usually ovally shaped, 0.18±0.07×0.22±0.1 µm). In parasites fixed 24 h after Shield-1 induction (Figure 5D, E), larger clusters of the electron lucent PI3P-vesicles were found, and these vesicles also massively accumulated in residual bodies (Figure 5E). In the absence of Shield-1 treatment, some electron-dense vesicles were detected around the apicoplast ([32], [33], [34] and this study), while we could not detect electron-lucent vesicles near the organelle (not shown), suggesting that their presence resulted from disturbing PI3P function.


Phosphatidylinositol 3-monophosphate is involved in toxoplasma apicoplast biogenesis.

Tawk L, Dubremetz JF, Montcourrier P, Chicanne G, Merezegue F, Richard V, Payrastre B, Meissner M, Vial HJ, Roy C, Wengelnik K, Lebrun M - PLoS Pathog. (2011)

Localization of PI3P in T. gondii.ImmunoEM analysis of ddFYVE expressing parasites fixed 20 min (A, B, C) or 24 h (D, E) after addition of 1 µM Shield-1. (A, B, C) The anti-GFP gold label is found on the outer membranes of the apicoplast (short arrows), on the membrane of electron-dense (C, black arrowheads) and electron-lucent (C, B, white arrowheads) vesicles, these latter accumulating in the subapical region (B, arrow). a, apicoplast; d, dense granule; IMC, inner membrane complex; m, mitochondrion; n, nucleus; PM, parasite plasma membrane. (D, E) After one day of Shield-1 treatment, the anti-GFP labels large lucent vacuoles either inside parasites (D), or accumulated in the residual body (E), while the overall structure of the tachyzoites is unaffected. The white framed boxes show enlargements of GFP-positive lucent vesicles.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3040667&req=5

ppat-1001286-g005: Localization of PI3P in T. gondii.ImmunoEM analysis of ddFYVE expressing parasites fixed 20 min (A, B, C) or 24 h (D, E) after addition of 1 µM Shield-1. (A, B, C) The anti-GFP gold label is found on the outer membranes of the apicoplast (short arrows), on the membrane of electron-dense (C, black arrowheads) and electron-lucent (C, B, white arrowheads) vesicles, these latter accumulating in the subapical region (B, arrow). a, apicoplast; d, dense granule; IMC, inner membrane complex; m, mitochondrion; n, nucleus; PM, parasite plasma membrane. (D, E) After one day of Shield-1 treatment, the anti-GFP labels large lucent vacuoles either inside parasites (D), or accumulated in the residual body (E), while the overall structure of the tachyzoites is unaffected. The white framed boxes show enlargements of GFP-positive lucent vesicles.
Mentions: In order to further refine the localisation of PI3P, the ddFYVE signal was analyzed by immuno-electron microscopy (IEM). Due to the low level of spontaneous expression of ddFYVE, no signal could be detected in IEM in the absence of Shield-1. Experiments were therefore performed within the first hour of Shield-1 addition, at a time when the PI3P signal started diffusing around the apicoplast but before the loss of the apicoplast could occur (Figure 2A). Anti-GFP antibodies labelled the outer membranes of the apicoplast and the membrane of vesicles located in the vicinity of this organelle (Figure 5A, B, C). The vesicles were packed together and were of variable electron density: the denser ones were of uniform size, usually spherical with a diameter of 0.1±0.01 µm; the electron-lucent ones were larger, more heterogeneous in size and shape (usually ovally shaped, 0.18±0.07×0.22±0.1 µm). In parasites fixed 24 h after Shield-1 induction (Figure 5D, E), larger clusters of the electron lucent PI3P-vesicles were found, and these vesicles also massively accumulated in residual bodies (Figure 5E). In the absence of Shield-1 treatment, some electron-dense vesicles were detected around the apicoplast ([32], [33], [34] and this study), while we could not detect electron-lucent vesicles near the organelle (not shown), suggesting that their presence resulted from disturbing PI3P function.

Bottom Line: Imaging of PI3P in T. gondii showed that the lipid was associated with the apicoplast and apicoplast protein-shuttling vesicles.These findings point to an unexpected implication for this ubiquitous lipid and open new perspectives on how nuclear encoded proteins traffic to the apicoplast.This study also highlights the possibility of developing specific pharmacological inhibitors of the parasite PI3-kinase as novel anti-apicomplexan drugs.

View Article: PubMed Central - PubMed

Affiliation: UMR 5235 CNRS, Université Montpellier 1 & 2, Montpellier, France.

ABSTRACT
Apicomplexan parasites cause devastating diseases including malaria and toxoplasmosis. They harbour a plastid-like, non-photosynthetic organelle of algal origin, the apicoplast, which fulfils critical functions for parasite survival. Because of its essential and original metabolic pathways, the apicoplast has become a target for the development of new anti-apicomplexan drugs. Here we show that the lipid phosphatidylinositol 3-monophosphate (PI3P) is involved in apicoplast biogenesis in Toxoplasma gondii. In yeast and mammalian cells, PI3P is concentrated on early endosomes and regulates trafficking of endosomal compartments. Imaging of PI3P in T. gondii showed that the lipid was associated with the apicoplast and apicoplast protein-shuttling vesicles. Interference with regular PI3P function by over-expression of a PI3P specific binding module in the parasite led to the accumulation of vesicles containing apicoplast peripheral membrane proteins around the apicoplast and, ultimately, to the loss of the organelle. Accordingly, inhibition of the PI3P-synthesising kinase interfered with apicoplast biogenesis. These findings point to an unexpected implication for this ubiquitous lipid and open new perspectives on how nuclear encoded proteins traffic to the apicoplast. This study also highlights the possibility of developing specific pharmacological inhibitors of the parasite PI3-kinase as novel anti-apicomplexan drugs.

Show MeSH
Related in: MedlinePlus