Fig. 2

Force-production by Tks5-positive invadopodia. a MDA-MB-231 cells expressing Tks5^GFP (green) were plated on top of a thin layer of type I collagen (magenta) and imaged over time. Images represent the first and last frames from a representative movie (time in hr:min, see Supplementary Movie 1). The bottom row shows the collagen layer in an inverted lookup table (pseudocolored blue). Scale bar, 10 µm. b Color-coded time projections of five images made at 10-min intervals, corresponding to the boxed region in f, showing radial expansion of Tks5 invadopodia (upper image) and associated fiber (lower image) over time. Scale bar, 5 µm. c Gallery of consecutive frames from a time-lapse sequence of Tks5^GFP-expressing cells (green) plated on a type I collagen layer (magenta). The gallery shows an invadopodia/collagen-fiber ensemble undergoing collagenolytic rupture at time 0 (red arrowhead, see Supplementary Movie 2). Rupture is followed by the elastic recoil of the invadopodia/collagen-fiber ensemble. The initial position of the invadopodia/collagen-fiber ensemble is shown by a dashed line and positions of the collagen fiber tips after rupture are indicated (lower row, white arrowheads). Open arrowheads point to regions of invadopodia disassembly (upper row). Time is indicated in min. Scale bar, 2 µm. d Invadopodia/collagen-fiber tension. The distance between the position of the collagen fiber tip (P_t) and initial position (P₀) was calculated and plotted over time. The black curve represents the mean from 85 proteolytic rupture events aligned at rupture time point (t₀). Error bars, SEM; n: number of cells analyzed from three independent experiments. The curve shows typical viscoelastic recoil after proteolytic rupture and was fitted to a “plateau followed by one-phase association” model (red)