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Figure 2.
Figure 2: Localized activation or inactivation of PA-Rac1
induces myosin-dependent migration. a, Protrusion/retraction
map after a single pulse of activating illumination. MEFs
expressing PA-Rac1 (left) generated protrusions at the site of
irradiation (red) and retraction at the opposite side of the
cell (blue) (in all 50 cells studied). Irradiation of the
dominant-negative T17N mutant of PA-Rac1 (right) produced
retraction near the point of irradiation, with protrusion in
area(s) other than the site of irradiation (in all 25 cells
studied). b, Repeated activation of PA-Rac1 at the cell edge
induces directional migration. (MEF, 2-min intervals, average
0.8  m
movement per pulse, n = 6.) c, Localized activation of PA-Rac1
in the presence of ML-7 (MLCK inhibitor, 1 M),
blebbistatin (myosin II ATPase inhibitor, 1 M)
or Y-27632 (ROCK inhibitor, 10 M).
Protrusions analysed as in panel a. d, Effect of myosin or ROCK
inhibition on the ability of Rac1 to specify the direction of
movement. The cosine of the angle between two lines (from the
irradiation spot to the cell centroid at time 0, from the
centroid at time 0 to the centroid at the end of the experiment)
indicated how much the cell deviates from the direction
specified by local irradiation. For c, d, n > 25; means  95%
confidence intervals; throughout Fig. 3 irradiation at 458 nm,
spot diameter = 10 m;
time shown is in minutes and seconds.
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