FIGURE 8.

Caveolin is necessary for the localization of membrane protrusion in a fibrillar matrix. Fibroblasts were allowed to embed into cell-derived matrix for 4 h before preparing lysates for Rac1 activity, fixing, or tracking migration for 10 h. A, measurement of Rac1 activity in a fibrous environment by effector pulldown. B, distribution of cortactin and caveolin in CDM. False color images represent the intensity of cortactin staining. C and E, values of speed (distance/time), Euclidean distance per hour (displacement/time), persistence (displacement/distance), and curvature (see “Experimental Procedures” and Ref. 6) were calculated for each cell. Gray columns indicate the experimentally determined threshold for random migration. C and F, Western blots indicating the efficiency of caveolin knockdown or re-expression in migration experiments as appropriate. The results represent an analysis of >100 cells/condition. Error bars indicate mean ± S.E. Significance was tested by Kruskal-Wallis test. **, p < 0.005. D, example migration tracks from C. G, time projection of the outlines of β₁-integrin-GFP fibroblasts at 2.5-h intervals. Images were derived from supplemental Movie S4. Scale bars = 10 μm.