Encounters of APC clusters with the cell edge correlate with transient actin-driven protrusions. (A) Tip of the APC-induced process in a REF52 cell expressing EGFP-APC (cyan) together with dsRed-cortactin (red). Bar, 5 µm. (B) Kymograph taken along the yellow arrow in A shows APC tracks hitting the cell edge (cyan arrows) and cortactin-rich accumulations formed shortly after (red arrows). Time scale (t), 1 min; distance scale (d), 2 µm. (C and D) Frames from time-lapse sequences of the corresponding boxed regions in A. (E) Frames from time-lapse sequences of REF52 cell expressing EGFP-APC and mCherry-cortactin. Cyan arrows in C–E mark moving EGFP-APC clusters until they encounter the cell edge; red arrows mark subsequent enrichment of cortactin at the site of the encounter. Time is shown in min:s. Scale bars, 2 µm. (F) Frames from a time-lapse sequence of a COS7 cell expressing YFP-APC and mCherry-F-tractin. An entry of the APC-decorated microtubule tip into a small protrusion between 0 and 15 s is followed by accumulation of F-tractin starting from t = 30 s and expansion of the protrusion. Scale bar, 5 µm.