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Host cell egress and invasion induce marked relocations of glycolytic enzymes in Toxoplasma gondii tachyzoites.

Pomel S, Luk FC, Beckers CJ - PLoS Pathog. (2008)

Bottom Line: Translocation of glycolytic enzymes to and from the Toxoplasma pellicle appears to occur in response to changes in extracellular [K(+)] experienced during egress and invasion, a signal that requires changes of [Ca(2+)](c) in the parasite during egress.Enzyme translocation is, however, not dependent on either F-actin or intact microtubules.We propose that this ability allows Toxoplasma to optimize ATP delivery to those cellular processes that are most critical for survival outside host cells and those required for growth and replication of intracellular parasites.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell & Developmental Biology, University of North Carolina, Chapel Hill, North Carolina, USA.

ABSTRACT
Apicomplexan parasites are dependent on an F-actin and myosin-based motility system for their invasion into and escape from animal host cells, as well as for their general motility. In Toxoplasma gondii and Plasmodium species, the actin filaments and myosin motor required for this process are located in a narrow space between the parasite plasma membrane and the underlying inner membrane complex, a set of flattened cisternae that covers most the cytoplasmic face of the plasma membrane. Here we show that the energy required for Toxoplasma motility is derived mostly, if not entirely, from glycolysis and lactic acid production. We also demonstrate that the glycolytic enzymes of Toxoplasma tachyzoites undergo a striking relocation from the parasites' cytoplasm to their pellicles upon Toxoplasma egress from host cells. Specifically, it appears that the glycolytic enzymes are translocated to the cytoplasmic face of the inner membrane complex as well as to the space between the plasma membrane and inner membrane complex. The glycolytic enzymes remain pellicle-associated during extended incubations of parasites in the extracellular milieu and do not revert to a cytoplasmic location until well after parasites have completed invasion of new host cells. Translocation of glycolytic enzymes to and from the Toxoplasma pellicle appears to occur in response to changes in extracellular [K(+)] experienced during egress and invasion, a signal that requires changes of [Ca(2+)](c) in the parasite during egress. Enzyme translocation is, however, not dependent on either F-actin or intact microtubules. Our observations indicate that Toxoplasma gondii is capable of relocating its main source of energy between its cytoplasm and pellicle in response to exit from or entry into host cells. We propose that this ability allows Toxoplasma to optimize ATP delivery to those cellular processes that are most critical for survival outside host cells and those required for growth and replication of intracellular parasites.

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Related in: MedlinePlus

Redistribution of other glycolytic enzymes to the pellicle of extracellular parasites.The subcellular location of myc-tagged hexokinase (mHK), glyceraldehyde-3-phosphate dehydrogenase-1 (mGAPDH1), pyruvate kinase-1 (mPK1), or lactate dehydrogenase-1 (mLDH1) was determined in (A) intracellular and (B) extracellular Toxoplasma tachyzoites by immunofluorescence microscopy after fixation in −20°C methanol. The IMC of the parasites was visualized using antibodies to IMC1 (red) and their nuclei using DAPI (blue). The separate images are shown in Figure S5. Bars = 2 µm.
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ppat-1000188-g008: Redistribution of other glycolytic enzymes to the pellicle of extracellular parasites.The subcellular location of myc-tagged hexokinase (mHK), glyceraldehyde-3-phosphate dehydrogenase-1 (mGAPDH1), pyruvate kinase-1 (mPK1), or lactate dehydrogenase-1 (mLDH1) was determined in (A) intracellular and (B) extracellular Toxoplasma tachyzoites by immunofluorescence microscopy after fixation in −20°C methanol. The IMC of the parasites was visualized using antibodies to IMC1 (red) and their nuclei using DAPI (blue). The separate images are shown in Figure S5. Bars = 2 µm.

Mentions: Although we did not detect any redistribution of aldolase-1 in motile Toxoplasma tachyzoites and the translocation of aldolase-1 to the parasite periphery was not affected by cytochalasin-D (Figure 7D), these findings do not necessarily conflict with a role of peripheral aldolase-1 in providing a link between the adhesin MIC2 and F-actin as was suggested by Jewett and Sibley [1]. We did, however, want to consider an alternative possibility in which translocation of aldolase-1 from the Toxoplasma cytoplasm to its periphery was only one element in the relocation of the entire glycolytic apparatus and hence a major source of ATP. To test this model, we expressed epitope-tagged versions of other enzymes along the glycolytic pathway of Toxoplasma tachyzoites and monitored their distribution in intracellular and extracellular parasites. As can be seen in Figure 8 and Figure S5, enzymes at the beginning (hexokinase), in the middle (glyceraldehyde-3-phosphate dehydrogenase-1), and at the end of the glycolytic pathway (pyruvate kinase-1) demonstrated subcellular distribution patterns that are very similar to those of aldolase-1. All three enzymes are found throughout the cytoplasm of intracellular Toxoplasma and associated with the pellicles of extracellular parasites.


Host cell egress and invasion induce marked relocations of glycolytic enzymes in Toxoplasma gondii tachyzoites.

Pomel S, Luk FC, Beckers CJ - PLoS Pathog. (2008)

Redistribution of other glycolytic enzymes to the pellicle of extracellular parasites.The subcellular location of myc-tagged hexokinase (mHK), glyceraldehyde-3-phosphate dehydrogenase-1 (mGAPDH1), pyruvate kinase-1 (mPK1), or lactate dehydrogenase-1 (mLDH1) was determined in (A) intracellular and (B) extracellular Toxoplasma tachyzoites by immunofluorescence microscopy after fixation in −20°C methanol. The IMC of the parasites was visualized using antibodies to IMC1 (red) and their nuclei using DAPI (blue). The separate images are shown in Figure S5. Bars = 2 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2563030&req=5

ppat-1000188-g008: Redistribution of other glycolytic enzymes to the pellicle of extracellular parasites.The subcellular location of myc-tagged hexokinase (mHK), glyceraldehyde-3-phosphate dehydrogenase-1 (mGAPDH1), pyruvate kinase-1 (mPK1), or lactate dehydrogenase-1 (mLDH1) was determined in (A) intracellular and (B) extracellular Toxoplasma tachyzoites by immunofluorescence microscopy after fixation in −20°C methanol. The IMC of the parasites was visualized using antibodies to IMC1 (red) and their nuclei using DAPI (blue). The separate images are shown in Figure S5. Bars = 2 µm.
Mentions: Although we did not detect any redistribution of aldolase-1 in motile Toxoplasma tachyzoites and the translocation of aldolase-1 to the parasite periphery was not affected by cytochalasin-D (Figure 7D), these findings do not necessarily conflict with a role of peripheral aldolase-1 in providing a link between the adhesin MIC2 and F-actin as was suggested by Jewett and Sibley [1]. We did, however, want to consider an alternative possibility in which translocation of aldolase-1 from the Toxoplasma cytoplasm to its periphery was only one element in the relocation of the entire glycolytic apparatus and hence a major source of ATP. To test this model, we expressed epitope-tagged versions of other enzymes along the glycolytic pathway of Toxoplasma tachyzoites and monitored their distribution in intracellular and extracellular parasites. As can be seen in Figure 8 and Figure S5, enzymes at the beginning (hexokinase), in the middle (glyceraldehyde-3-phosphate dehydrogenase-1), and at the end of the glycolytic pathway (pyruvate kinase-1) demonstrated subcellular distribution patterns that are very similar to those of aldolase-1. All three enzymes are found throughout the cytoplasm of intracellular Toxoplasma and associated with the pellicles of extracellular parasites.

Bottom Line: Translocation of glycolytic enzymes to and from the Toxoplasma pellicle appears to occur in response to changes in extracellular [K(+)] experienced during egress and invasion, a signal that requires changes of [Ca(2+)](c) in the parasite during egress.Enzyme translocation is, however, not dependent on either F-actin or intact microtubules.We propose that this ability allows Toxoplasma to optimize ATP delivery to those cellular processes that are most critical for survival outside host cells and those required for growth and replication of intracellular parasites.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell & Developmental Biology, University of North Carolina, Chapel Hill, North Carolina, USA.

ABSTRACT
Apicomplexan parasites are dependent on an F-actin and myosin-based motility system for their invasion into and escape from animal host cells, as well as for their general motility. In Toxoplasma gondii and Plasmodium species, the actin filaments and myosin motor required for this process are located in a narrow space between the parasite plasma membrane and the underlying inner membrane complex, a set of flattened cisternae that covers most the cytoplasmic face of the plasma membrane. Here we show that the energy required for Toxoplasma motility is derived mostly, if not entirely, from glycolysis and lactic acid production. We also demonstrate that the glycolytic enzymes of Toxoplasma tachyzoites undergo a striking relocation from the parasites' cytoplasm to their pellicles upon Toxoplasma egress from host cells. Specifically, it appears that the glycolytic enzymes are translocated to the cytoplasmic face of the inner membrane complex as well as to the space between the plasma membrane and inner membrane complex. The glycolytic enzymes remain pellicle-associated during extended incubations of parasites in the extracellular milieu and do not revert to a cytoplasmic location until well after parasites have completed invasion of new host cells. Translocation of glycolytic enzymes to and from the Toxoplasma pellicle appears to occur in response to changes in extracellular [K(+)] experienced during egress and invasion, a signal that requires changes of [Ca(2+)](c) in the parasite during egress. Enzyme translocation is, however, not dependent on either F-actin or intact microtubules. Our observations indicate that Toxoplasma gondii is capable of relocating its main source of energy between its cytoplasm and pellicle in response to exit from or entry into host cells. We propose that this ability allows Toxoplasma to optimize ATP delivery to those cellular processes that are most critical for survival outside host cells and those required for growth and replication of intracellular parasites.

Show MeSH
Related in: MedlinePlus