Figure 3. Integrin waves are distinct from podosomes and focal adhesions in U2OS cells.

(A) LEFT: Spinning disk confocal and phase-contrast images of a U2OS cell expressing α_V integrin-EGFP. Scale bar = 10 µm. RIGHT: Images from a time-lapse series of the region highlighted by a yellow box, time in min shown. The phase contrast image does not exhibit podosome structures as the integrin wave propagates across the ventral surface of the cell. Scale bar = 5 µm. (B) Distance from the cell edge of integrin waves (wave) and focal adhesions (FA) measured in U2OS cells expressing α_V integrin-EGFP. Values are represented as mean ± SD; P-values determined with Student's t-test. (C) Area of waves and FAs measured in U2OS cells expressing α_V integrin-EGFP. Values are represented as mean ± SD; P-values determined with Student's t-test. (D) Fluorescence density of waves and FAs measured in U2OS cells expressing α_V integrin-EGFP. Values are represented as mean ± SD; P-values determined with Student's t-test. (E) Lifetimes of waves and FAs measured in U2OS cells expressing α_V integrin-EGFP. FA lifetimes longer than 45 min were recorded as 45 min. Values are represented as mean ± SD; P-values determined with Student's t-test. (F) LEFT: TIRFM image of a cell expressing α_V integrin-EGFP. Scale bar = 10 µm. RIGHT: Fluorescent speckle microscopy kymographs of the regions (highlighted with arrows at left) of i) a sliding focal adhesion (FA) and ii) a propagating integrin wave (wave). Magenta lines highlight the path of integrin spekcles within kymographs. Velocity was measured from the slope of the line. (G) Average velocity of integrin speckles within FA or wave structures. Velocity of integrin speckles in FA or waves were measured from the slope of kymographs, as in (F). Integrin speckles in waves remain stationary relative to the substrate. Values are represented as mean ± SD.