Figure 7.

Maintenance of β1 integrins in focal adhesions and their calcium-dependent redistribution are not affected by gelsolin-induced stress fiber disassembly under cell-free conditions. VPMs from adherent fibroblasts were fixed immediately after preparation on ice (A and B) or were incubated 3 min at 0°C with 4 μM gelsolin to disrupt F-actin (C–H). After the treatment with gelsolin, VPMs were either fixed (C and D) or incubated 15 min at 37°C in HCB (E–H). VPMs were then fixed (E and F) or incubated for a further 15 min at 37°C in LCB (G and H). After fixation, all samples were processed for immunofluorescence with the β1-cyto antibody and TRITC-conjugated anti-rabbit IgG (A, C, E, and G). FITC-phalloidin (B, D, F, and H) was used to stain F-actin. The same fields are shown in A and B, C and D, E and F, and G and H. Arrowheads in A and B show colocalization of integrins in focal adhesions (A) with the tip of actin stress fibers (B). Asterisks in E and F show areas at the periphery of the VPM where a portion of the dorsal plasma membrane is present and some F-actin is still visible. Bar, 10 μm.