Septins arrange F-actin-containing fibers on the Chlamydia trachomatis inclusion and are required for normal release of the inclusion by extrusion.
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.
Affiliation: Institute for Medical Microbiology and Hygiene, University Medical Center Freiburg, Freiburg, Germany.Show MeSH
Related in: MedlinePlus
Mentions: Large septin structures typically are formed by heteromeric complexes that contain three or four different septins (22), suggesting that the observed structures around the inclusion contained other septins in addition to SEPT2. Our proteomic study of isolated C. trachomatis inclusions by mass spectrometry (MS) had identified SEPT2, -7, -9, and -11 on the inclusion, with substantial enrichment of SEPT2 and -9 (see the legend to Fig. 2). We therefore also stained for these septins in infected cells. We found staining very similar to that for SEPT2 with antibodies against SEPT9 and also with antibodies against SEPT11. Staining for SEPT7 was inconclusive, most likely because the antibodies available to us did not give a very clear signal in immunofluorescence (data not shown). The data, however, clearly identify fibers containing SEPT2, -9, and -11 on the C. trachomatis inclusion. Since SEPT7 appears to be a core component of most septin structures (22, 23) and it was identified by MS on the inclusion, its involvement here appears very likely.
Affiliation: Institute for Medical Microbiology and Hygiene, University Medical Center Freiburg, Freiburg, Germany.