Figure 4 Phagosomal escape of F. tularensis. Colocalization of GFP-expressing F. tularensis strains and LAMP- 1. J774 cells were infected for 2 h with Luminespib cost F. tularensis strains expressing GFP (Green fluorescent protein) and, after washing, incubated for indicated time points. Fixed specimens were labeled for the late endosomal and lysosomal marker LAMP-1. 100 bacteria were scored per sample and time point. Results from a representative experiment are shown. Bars represent mean values and error bars are used to indicate standard deviations. Asterisks indicate that the colocalization differs significantly from that of LVS (*: P < 0.05; **: P < 0.01). Figure 5 Colocalization of GFP- expressing
F. tularensis strains and LAMP- 1. J774 cells were infected with the LVS, the ΔpdpC mutant, or the ΔiglC mutant expressing GFP (Green fluorescent protein) at an MOI of 200 and, after washing, incubated for 6 h. Colocalization of GFP-labeled F. tularensis and LAMP-1 on fixed and labeled specimens was analyzed selleck products using a confocal microscope (Nikon Eclipse 90i, Nikon, Japan). Scale bar 10 μm. Figure 6 Subcellular colocalization in J774 cells of F. tularensis bacteria. J774 cells were infected for 2 h with F. tularensis strains and, after washing, incubated for 6 h. Bacteria were examined using transmission electron microscopy (TEM) and categorized into one of four categories
depending on the preservation of the phagosomal membrane. At least 100 bacteria per sample were scored. Results from a representative experiment are shown. Figure 7 Electron micrographs of J774 macrophages infected with F. tularensis. (A) Cells infected with LVS, the ΔpdpC mutant, or the ΔiglC mutant. (B) A close-up of the
ΔpdpC micrograph from A. Black arrows indicate the borders of the remaining vacuolar membranes surrounding the intracellular bacterium. These findings appeared to be GSK2126458 concentration contradictory, since the LAMP-1 colocalization data suggested that Olopatadine the degree of phagosomal escape of ΔpdpC was similar to the ΔiglA and ΔiglC mutants, prototypes for the phagosomally located mutants, whereas the TEM data indicated distinct differences between the ΔiglC and ΔpdpC mutants. We believe that the findings can be reconciled, however, since the TEM data indicated that essentially no ΔpdpC bacteria were free in the cytoplasm, whereas ~ 80% were surrounded by slightly or highly damaged membranes. This unusual phenotype demonstrated that a majority of the ΔpdpC bacteria was closely adjacent to membrane parts, in agreement with the confocal microscopy data indicating that 60-75% of the bacteria colocalized with LAMP-1. Therefore, the mutant will show a high percentage of colocalization although not being confined to an intact phagosome. Thus, we conclude that PdpC directly or indirectly plays a very important role for the normal phagosomal escape.