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Figure 1 | BMC Microbiology

Figure 1

From: Shigella flexneriutilize the spectrin cytoskeleton during invasion and comet tail generation

Figure 1

Spectrin, adducin and p4.1 are needed for efficient S. flexneri invasion. a) HeLa cells were infected with S. flexneri for 30 minutes prior to fixation and immunolocalization with antibodies targeted against spectrin, adducin or p4.1. To observe invasion events, we also probed the cells for F-actin (to visualize membrane invasion ruffles) and DNA (using DAPI, to visualize bacteria). P4.1 is recruited to S. flexneri actin-rich invasion sites, while spectrin and adducin are not recruited. Scale bars are 5 μm. b) Quantification of the presence of spectrin cytoskeletal components during S. flexneri invasion. We counted 50 invasion events, in three separate experiements, looking for distinct recruitment of the protein of interest. c) Western blots to confirm knockdown of spectrin, adducin and p4.1 in HeLa cells. d) Spectrin, adducin, or p4.1 were knocked-down in HeLa cells prior to infection with S. flexneri for 1.5 hours (including 1-hour of gentamycin to kill external bacteria), followed by immunolocalization. Quantification of invasion was performed by microscopy, enumerating each cell with 1 or more internalized bacteria as a single invasion event. Cells with spectrin, adducin, or p4.1 knocked-down had significant (*P < 0.0001) reduction in invasion as compared to the control pool treated cells. For each experiment, 25 cells were counted that had undetectable levels of the targeted proteins following knockdown. In the case of control pool treated cells, random fields of view were chosen. Each experiment was run in triplicate. e) Classical invasion assay whereby spectrin, adducin, or p4.1 were knocked-down in HeLa cells prior to infection with S. flexneri for 30 minutes, followed by 1-hour gentamycin treatment. Cells were lysed and bacteria loads were recovered by CFU enumeration. Cells with protein knock-downs exhibit a significant decrease in S. flexneri invasion. Experiments run in triplicate. * p < 0.05

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