An Actin-Based Wave Generator Organizes Cell Motility
Figure 2
Rac Activity and the Arp2/3 Complex Spatially Correlate with but Are more Homogeneous than Hem-1 Waves
(A) Pak-GBD-YFP (Rac activity probe) dynamics during acute cell stimulation (chemoattractant added to pre-polarized cell at t = 0 s)—see Video S8. Rac activation is initially uniform and then polarizes (arrow), similar to the spatial dynamics of Hem-1 waves (compare to Figure 4B). Rac exhibits relatively homogeneous zones of activation in contrast to discrete points and waves of Hem-1.
(B) Rac activity dynamics during cell migration (see Video S9). Rac-GTP (assayed by Pak-GBD-YFP) concentrates at the leading edge (and dominant pseudopod when multiple pseudopodia are present) in cells migrating in uniform chemoattractant. Green dots are included in first and last frame as fiduciary marks to clarify relative cell positions.
(C) The Arp3-GFP component of the Arp2/3 complex fills the leading edge (arrow) and exhibits a more homogeneous distribution than Hem-1 waves (Video S10). The cell is representative of more than five similar cells.
(D) Actin-YFP is more homogeneously distributed than Hem-1 waves throughout the leading edge of polarized cells. Latrunculin treatment of actin-YFP–expressing cell abolishes leading edge accumulation of actin-YFP. Cells are representative of more than five similar cells.