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. 2014 Oct 9;9(10):e108948. doi: 10.1371/journal.pone.0108948

Figure 4. Membrane breakages of vMVBs and ILVs revealed by electron tomography.

Figure 4

In the EV1-infected SAOS-α2β1 cells, areas of vMVB and ILV membranes were observed “broken” (C, D and E, white arrows) at 3.5 hours p.i. Projections (A, tilt angles from left to right, top to bottom: −33°, −11°, 11°, 33°) were collected at one-degree tilt interval between −65° and +58° (B) for 3D volume reconstruction and subsequent rendering shown in C. The stereogram of vMVBs were captured from the representative vMVBs with eight-degree seperation between the paired views. The inserts represent higher magnification of the rupture sites in the membrane of ILV (D) and vMVB (E) at 3.5 hour p.i. and correspond to the marked areas in C. Arrowheads indicate the distance of the rupture sites in the ILV and vMVB membrane structures measuring 76 nm (D) and 60 and 33 nm (E). Density of α2β1-integrin clusters were measured by manually drawing a region including vMVB membrane and a subregion including membrane near rupture sites. The measured density was 15.8% higher (22.0×10−6/nm3 and 19.0×10−6/nm3 gold particles near ruptures sites and in whole membrane, respectively) in the region including membrane near rupture sites. The measurements were consistent with reconstruction using a statistical method (Fig. S1). Scale bars: 50 nm (D and E).