Research Article

Directional Transport of a Bead Bound to Lamellipodial Surface Is Driven by Actin Polymerization

Figure 4

(a) A kymograph of 1 μm bead moving on the surface of the cell expressing RFP-actin. The width of the vertical edge of the kymograph is 2.5 μm and that of the horizontal edge is 27 s; the slope of the black line represents the velocity of the bead; for this particular example, the velocity was 87.5 nm/s. (b) Part of a lamellipodium of the cell expressing RFP-actin; kymograph of RFP-actin was generated along the white line. Horizontal bar, 5 μm. (c) The kymograph; gray arrow indicates the forward motion of the lamellipodial edge, and white arrow indicates the retrograde movement of the fluorescence pattern of RFP-actin. The width of the vertical edge is 60 sec and that of the horizontal edge is 16 μm. In this case, protrusion of lamellipodium and retrograde flow of actin occurred at the same time. The slopes of two white lines represent the velocity of the bead and the cell edge. (d) The average of the velocity of the bead bound to the lamellipodium of the cell expressing RFP-actin (62 measurements) and that of RFP-actin (87 measurements), both estimated by kymograph method. Error bar, standard deviation.
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