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Septins arrange F-actin-containing fibers on the Chlamydia trachomatis inclusion and are required for normal release of the inclusion by extrusion.

Volceanov L, Herbst K, Biniossek M, Schilling O, Haller D, Nölke T, Subbarayal P, Rudel T, Zieger B, Häcker G - MBio (2014)

Bottom Line: RNAi against SEPT9 or against the combination of SEPT2/7/9 substantially reduced the number of extrusions from a culture of infected HeLa cells.Septins have previously been found to be involved in the interaction of the cell with bacteria in the cytosol.Our observation that they also organize a reaction to bacteria living in vacuoles suggests that they have a function in the recognition of foreign compartments by a parasitized human cell.

View Article: PubMed Central - PubMed

Affiliation: Institute for Medical Microbiology and Hygiene, University Medical Center Freiburg, Freiburg, Germany.

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Related in: MedlinePlus

Targeting septins by RNAi disrupts F actin structures on the inclusion, while inhibiting F actin disrupts septin cages. (A and B) HeLa cells were transfected with siRNA targeting SEPT9 (A), or SEPT2-specific shRNA was induced (B). At 24 h posttransfection/-induction, cells were infected with C. trachomatis, and they were fixed at 30 h postinfection and stained with phalloidin-Alexa 546 to detect F actin and with Hoechst dye. Inclusions are indicated by arrows. Cell nuclei are marked with asterisks. (C) HeLa cells were infected for 30 h and stained for SEPT2 or SEPT9 and F actin as indicated. To some aliquots, cytochalasin D was added 30 min prior to fixation. DNA was stained with Hoechst dye. Inclusions are indicated by arrows. Cell nuclei are marked with asterisks. Scale bar, 10 µm. All images are representative of 3 independent experiments.
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fig5: Targeting septins by RNAi disrupts F actin structures on the inclusion, while inhibiting F actin disrupts septin cages. (A and B) HeLa cells were transfected with siRNA targeting SEPT9 (A), or SEPT2-specific shRNA was induced (B). At 24 h posttransfection/-induction, cells were infected with C. trachomatis, and they were fixed at 30 h postinfection and stained with phalloidin-Alexa 546 to detect F actin and with Hoechst dye. Inclusions are indicated by arrows. Cell nuclei are marked with asterisks. (C) HeLa cells were infected for 30 h and stained for SEPT2 or SEPT9 and F actin as indicated. To some aliquots, cytochalasin D was added 30 min prior to fixation. DNA was stained with Hoechst dye. Inclusions are indicated by arrows. Cell nuclei are marked with asterisks. Scale bar, 10 µm. All images are representative of 3 independent experiments.

Mentions: The colocalization of septins with actin and the reported reciprocal interactions of septins and actin suggested the possibility of a functional interdependence of these two components. We therefore targeted septins by RNAi and stained for F actin during infection. Indeed, knockdown of either SEPT9 (Fig. 5A; see also Fig. S6A in the supplemental material) or SEPT2 (Fig. 5B) caused the reduction or loss of identifiable actin fibers on the inclusion. Conversely, when actin polymerization was inhibited by treatment with cytochalasin D, SEPT2 and -9 structures on the inclusion were also disrupted (Fig. 5C).


Septins arrange F-actin-containing fibers on the Chlamydia trachomatis inclusion and are required for normal release of the inclusion by extrusion.

Volceanov L, Herbst K, Biniossek M, Schilling O, Haller D, Nölke T, Subbarayal P, Rudel T, Zieger B, Häcker G - MBio (2014)

Targeting septins by RNAi disrupts F actin structures on the inclusion, while inhibiting F actin disrupts septin cages. (A and B) HeLa cells were transfected with siRNA targeting SEPT9 (A), or SEPT2-specific shRNA was induced (B). At 24 h posttransfection/-induction, cells were infected with C. trachomatis, and they were fixed at 30 h postinfection and stained with phalloidin-Alexa 546 to detect F actin and with Hoechst dye. Inclusions are indicated by arrows. Cell nuclei are marked with asterisks. (C) HeLa cells were infected for 30 h and stained for SEPT2 or SEPT9 and F actin as indicated. To some aliquots, cytochalasin D was added 30 min prior to fixation. DNA was stained with Hoechst dye. Inclusions are indicated by arrows. Cell nuclei are marked with asterisks. Scale bar, 10 µm. All images are representative of 3 independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4196233&req=5

fig5: Targeting septins by RNAi disrupts F actin structures on the inclusion, while inhibiting F actin disrupts septin cages. (A and B) HeLa cells were transfected with siRNA targeting SEPT9 (A), or SEPT2-specific shRNA was induced (B). At 24 h posttransfection/-induction, cells were infected with C. trachomatis, and they were fixed at 30 h postinfection and stained with phalloidin-Alexa 546 to detect F actin and with Hoechst dye. Inclusions are indicated by arrows. Cell nuclei are marked with asterisks. (C) HeLa cells were infected for 30 h and stained for SEPT2 or SEPT9 and F actin as indicated. To some aliquots, cytochalasin D was added 30 min prior to fixation. DNA was stained with Hoechst dye. Inclusions are indicated by arrows. Cell nuclei are marked with asterisks. Scale bar, 10 µm. All images are representative of 3 independent experiments.
Mentions: The colocalization of septins with actin and the reported reciprocal interactions of septins and actin suggested the possibility of a functional interdependence of these two components. We therefore targeted septins by RNAi and stained for F actin during infection. Indeed, knockdown of either SEPT9 (Fig. 5A; see also Fig. S6A in the supplemental material) or SEPT2 (Fig. 5B) caused the reduction or loss of identifiable actin fibers on the inclusion. Conversely, when actin polymerization was inhibited by treatment with cytochalasin D, SEPT2 and -9 structures on the inclusion were also disrupted (Fig. 5C).

Bottom Line: RNAi against SEPT9 or against the combination of SEPT2/7/9 substantially reduced the number of extrusions from a culture of infected HeLa cells.Septins have previously been found to be involved in the interaction of the cell with bacteria in the cytosol.Our observation that they also organize a reaction to bacteria living in vacuoles suggests that they have a function in the recognition of foreign compartments by a parasitized human cell.

View Article: PubMed Central - PubMed

Affiliation: Institute for Medical Microbiology and Hygiene, University Medical Center Freiburg, Freiburg, Germany.

Show MeSH
Related in: MedlinePlus