Interaction of myosin VI artificial dimer-coated nanospheres with extracted keratocyte lamellipodial F-actin networks. (a) Fluorescence micrograph of a fish epidermal keratocyte after extraction. (b) Platinum replica electron micrograph of an extracted fish epidermal keratocyte showing the dense, interlaced actin network in the keratocyte lamellipodium. (c) Trajectories of movement of 200-nm-diameter nanospheres coated with a single myosin VI dimer on the extracted keratocyte. (d) Sample trajectories from panel c aligned such that the cell periphery is at the top and the cell center is at the bottom. (e and f) Trajectories of movement of nanospheres coated with ∼10 myosin VI dimers, such that approximately two dimers interact with the keratocyte lamellipodium. All nanospheres, without exception, move toward the cell center. A nanosphere landing near the cell edge can traverse the entire length of the keratocyte lamellipodium. (g) Sample trajectories from panel f aligned such that the cell periphery is at the top and cell center is at the bottom. Myosin VI is a pointed end–directed motor; hence, the polarity of F-actin, inferred from the observed movement, is indicated by barbed end (+) and pointed end (−) in panels d and g. Bars, 1 µm.