Figure 6.

Schematic model summarizing the major results obtained in this study. (A) The lamellipodium is built by components, which fall into different categories. Here, we distinguish four of those categories, based on their localization pattern within the lamellipodial structure, their dynamics and/or function: tip components driving actin assembly from the barbed end (WAVE complex components or VASP); capping protein, also largely associating with the tip; components incorporating into and building the network (actin and Arp2/3 complex), clearly displaying treadmilling behaviour; and factors associating with the entire lamellipodium (cofilin and cortactin) without treadmilling. (B) Summary of the turnover rates measured for these lamellipodial regulators as indicated. Colour code is displayed on the right. Note that for components with biased recovery from the lamellipodium tip (actin and Arp2/3 complex), recovery times differ dependent on the distance from the distal tip. For cortactin, the gradual decrease in colour intensity indicates the decrease in fluorescence intensity from front to rear of the lamellipodium observed for this component, but not for cofilin. Cream-coloured boxes summarize turnover rates (expressed as half-times of recovery of fluorescence intensity) as measured for different components in different intra-lamellipodial regions. ^*Value measured for the cortactin–EGFP construct used in Figure 3.