Figure 7

Fig. 7. Differential response of lamellipodial actin network to latrunculin A. (a) Phase contrast sequence of a locomoting Xenopus keratocyte. After addition of 0.1 µm LA at 9 min time point, the cell continued to translocate retaining the crescent-like shape. (b) Plot showing rate of front edge protrusion versus time of the cell shown in (a). LA addition (arrow) decreased rate of protrusion from about 4 µm/min before LA application to 1 µm/min at the end of the sequence. (c) Fluorescence microscopy of the boxed region of the cell shown in (a), which was lysed at 34 min time point, fixed and stained with TRITC-phalloidin. Actin staining reveals narrow bright lamellipodium at the leading edge separated by the wide actin-depleted zone from the internal actin structures. (d, e) Electron microscopy of a Xenopus keratocyte (d) or Xenopus fibroblast (e) lamellipodium treated with LA (0.1 µM, 30 min for (d) or 0.25 µM, 10 min for (e)) reveals actin depletion from the lamellipodial rear. Bars, 10 µm (a), 1 µm (d, e).