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Sequestration of host metabolism by an intracellular pathogen.

Gehre L, Gorgette O, Perrinet S, Prevost MC, Ducatez M, Giebel AM, Nelson DE, Ball SG, Subtil A - Elife (2016)

Bottom Line: We provide evidence that bacterial glycogen metabolism enzymes are secreted into the vacuole lumen through type 3 secretion.Our data bring strong support to the following scenario: bacteria co-opt the host transporter SLC35D2 to import UDP-glucose into the vacuole, where it serves as substrate for de novo glycogen synthesis, through a remarkable adaptation of the bacterial glycogen synthase.Based on these findings we propose that parasitophorous vacuoles not only offer protection but also provide a microorganism-controlled metabolically active compartment essential for redirecting host resources to the pathogens.

View Article: PubMed Central - PubMed

Affiliation: Unité de Biologie cellulaire de l'infection microbienne, Institut Pasteur, Paris, France.

ABSTRACT
For intracellular pathogens, residence in a vacuole provides a shelter against cytosolic host defense to the cost of limited access to nutrients. The human pathogen Chlamydia trachomatis grows in a glycogen-rich vacuole. How this large polymer accumulates there is unknown. We reveal that host glycogen stores shift to the vacuole through two pathways: bulk uptake from the cytoplasmic pool, and de novo synthesis. We provide evidence that bacterial glycogen metabolism enzymes are secreted into the vacuole lumen through type 3 secretion. Our data bring strong support to the following scenario: bacteria co-opt the host transporter SLC35D2 to import UDP-glucose into the vacuole, where it serves as substrate for de novo glycogen synthesis, through a remarkable adaptation of the bacterial glycogen synthase. Based on these findings we propose that parasitophorous vacuoles not only offer protection but also provide a microorganism-controlled metabolically active compartment essential for redirecting host resources to the pathogens.

No MeSH data available.


Related in: MedlinePlus

Luminal and cytoplasmic glycogen differs in size.Cells were infected for 30 hr with C. trachomatis. The picture on the right shows an enlargement of the boxed region. Glycogen is visualized by TEM after PATAg stain. Glycogen deposits in the inclusion lumen (arrowheads) are on average of bigger size than in the host cell cytoplasm (arrows). Scale bar: 1 µm.DOI:http://dx.doi.org/10.7554/eLife.12552.005
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fig1s2: Luminal and cytoplasmic glycogen differs in size.Cells were infected for 30 hr with C. trachomatis. The picture on the right shows an enlargement of the boxed region. Glycogen is visualized by TEM after PATAg stain. Glycogen deposits in the inclusion lumen (arrowheads) are on average of bigger size than in the host cell cytoplasm (arrows). Scale bar: 1 µm.DOI:http://dx.doi.org/10.7554/eLife.12552.005

Mentions: To determine whether glycogen accumulated in the host cytosol, in the inclusion, or both, we labeled polysaccharides using periodic-acid-Schiff (PAS) staining at different times of infection. Large glycogen particles were detected in most non-infected cells (Figure 1—figure supplement 1). Twenty-four hours post infection (hpi), glycogen was still detected in the cytoplasm of some of the infected cells, and the inclusions only showed weak PAS staining. However, 48 hpi no glycogen particle was detected in the cytoplasm of infected cells, while inclusions heavily stained with PAS, indicating that the global increase in glycogen content is accompanied by a shift in its original cytosolic localization, in favor of the bacterial inclusion. We used transmission electron microscopy (TEM) to determine more precisely its subcellular localization and detected the polysaccharide in two locations: in the inclusion lumen, and within EBs (Figure 1B). Intraluminal glycogen deposits are physically larger than in the cytoplasm (Figure 1—figure supplement 2). We did not observe glycogen in RBs, in contrast to an earlier report (Chiappino et al., 1995). In that publication, the presence of glycogen in the inclusion lumen was interpreted as the result of glycogen release from lysed bacteria. Considering the abundance of glycogen in the inclusion lumen relative to its amount in bacteria we considered this hypothesis unlikely. We tested it by depriving the cells of Glc for 48 hr before infecting them. Under these conditions, the inclusions contained no glycogen 24 hpi (Figure 1C). Restoring Glc availability for 4 hr was sufficient to trigger the accumulation of glycogen in the inclusion lumen, but not in the bacteria (Figure 1D). This experiment demonstrates that glycogen in the inclusion lumen does not result from the release of bacterial stores. The kinetics of glycogen appearance in the inclusion was carefully examined next by TEM. Luminal glycogen first appeared between 16 and 20 hpi (Figure 1—figure supplement 3), and was abundant 24 hpi. Thus, luminal glycogen deposit took place at a time when RBs largely predominate over EBs. This observation suggests that, while glycogen accumulation in the inclusion is most obvious at later stages of infection, when EBs accumulate, the process is initiated by RBs.


Sequestration of host metabolism by an intracellular pathogen.

Gehre L, Gorgette O, Perrinet S, Prevost MC, Ducatez M, Giebel AM, Nelson DE, Ball SG, Subtil A - Elife (2016)

Luminal and cytoplasmic glycogen differs in size.Cells were infected for 30 hr with C. trachomatis. The picture on the right shows an enlargement of the boxed region. Glycogen is visualized by TEM after PATAg stain. Glycogen deposits in the inclusion lumen (arrowheads) are on average of bigger size than in the host cell cytoplasm (arrows). Scale bar: 1 µm.DOI:http://dx.doi.org/10.7554/eLife.12552.005
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4829429&req=5

fig1s2: Luminal and cytoplasmic glycogen differs in size.Cells were infected for 30 hr with C. trachomatis. The picture on the right shows an enlargement of the boxed region. Glycogen is visualized by TEM after PATAg stain. Glycogen deposits in the inclusion lumen (arrowheads) are on average of bigger size than in the host cell cytoplasm (arrows). Scale bar: 1 µm.DOI:http://dx.doi.org/10.7554/eLife.12552.005
Mentions: To determine whether glycogen accumulated in the host cytosol, in the inclusion, or both, we labeled polysaccharides using periodic-acid-Schiff (PAS) staining at different times of infection. Large glycogen particles were detected in most non-infected cells (Figure 1—figure supplement 1). Twenty-four hours post infection (hpi), glycogen was still detected in the cytoplasm of some of the infected cells, and the inclusions only showed weak PAS staining. However, 48 hpi no glycogen particle was detected in the cytoplasm of infected cells, while inclusions heavily stained with PAS, indicating that the global increase in glycogen content is accompanied by a shift in its original cytosolic localization, in favor of the bacterial inclusion. We used transmission electron microscopy (TEM) to determine more precisely its subcellular localization and detected the polysaccharide in two locations: in the inclusion lumen, and within EBs (Figure 1B). Intraluminal glycogen deposits are physically larger than in the cytoplasm (Figure 1—figure supplement 2). We did not observe glycogen in RBs, in contrast to an earlier report (Chiappino et al., 1995). In that publication, the presence of glycogen in the inclusion lumen was interpreted as the result of glycogen release from lysed bacteria. Considering the abundance of glycogen in the inclusion lumen relative to its amount in bacteria we considered this hypothesis unlikely. We tested it by depriving the cells of Glc for 48 hr before infecting them. Under these conditions, the inclusions contained no glycogen 24 hpi (Figure 1C). Restoring Glc availability for 4 hr was sufficient to trigger the accumulation of glycogen in the inclusion lumen, but not in the bacteria (Figure 1D). This experiment demonstrates that glycogen in the inclusion lumen does not result from the release of bacterial stores. The kinetics of glycogen appearance in the inclusion was carefully examined next by TEM. Luminal glycogen first appeared between 16 and 20 hpi (Figure 1—figure supplement 3), and was abundant 24 hpi. Thus, luminal glycogen deposit took place at a time when RBs largely predominate over EBs. This observation suggests that, while glycogen accumulation in the inclusion is most obvious at later stages of infection, when EBs accumulate, the process is initiated by RBs.

Bottom Line: We provide evidence that bacterial glycogen metabolism enzymes are secreted into the vacuole lumen through type 3 secretion.Our data bring strong support to the following scenario: bacteria co-opt the host transporter SLC35D2 to import UDP-glucose into the vacuole, where it serves as substrate for de novo glycogen synthesis, through a remarkable adaptation of the bacterial glycogen synthase.Based on these findings we propose that parasitophorous vacuoles not only offer protection but also provide a microorganism-controlled metabolically active compartment essential for redirecting host resources to the pathogens.

View Article: PubMed Central - PubMed

Affiliation: Unité de Biologie cellulaire de l'infection microbienne, Institut Pasteur, Paris, France.

ABSTRACT
For intracellular pathogens, residence in a vacuole provides a shelter against cytosolic host defense to the cost of limited access to nutrients. The human pathogen Chlamydia trachomatis grows in a glycogen-rich vacuole. How this large polymer accumulates there is unknown. We reveal that host glycogen stores shift to the vacuole through two pathways: bulk uptake from the cytoplasmic pool, and de novo synthesis. We provide evidence that bacterial glycogen metabolism enzymes are secreted into the vacuole lumen through type 3 secretion. Our data bring strong support to the following scenario: bacteria co-opt the host transporter SLC35D2 to import UDP-glucose into the vacuole, where it serves as substrate for de novo glycogen synthesis, through a remarkable adaptation of the bacterial glycogen synthase. Based on these findings we propose that parasitophorous vacuoles not only offer protection but also provide a microorganism-controlled metabolically active compartment essential for redirecting host resources to the pathogens.

No MeSH data available.


Related in: MedlinePlus