Fig. 3. Inhibition of myosin II affects cortex thickness and fluctuations more drastically than inhibition of nucleators.

(A) Confocal imaging of actin in live LifeAct dendritic cells treated with DMSO, 50 μM CK666, 12.5 μM SMIFH2, and 50 μM blebbistatin (left to right). After treatment by CK666, protrusions appear to be sharper; SMIFH2 treatment strongly reduces the number of protrusions; blebbistatin treatment slightly affects protrusion morphology. (B) Typical temporal evolution of the cortex thickness in control cells (blue), blebbistatin-treated cells (yellow), and LatA-treated cells (purple). (C) Median cortex thickness for control cells (blue, n = 67, N = 10) and cells treated with CK666 (light purple, n = 36, N = 4), SMIFH2 (green, n = 40, N = 5), blebbistatin (yellow, n = 31, N = 5), and LatA (dark purple, n = 26, N = 5). Control and LatA data are the same as in Fig. 1. (D) Amplitude of the cortex thickness fluctuations for control and treated cells [the same conditions as in (C)]. Myosin II inhibition has the strongest effect on fluctuations after LatA treatment but does not affect the morphology of the cell protrusions (A), leading to the conclusion that the measured fluctuations are not the signature of protrusion but rather fluctuations of the thickness of the underlying cortex. Control and LatA data are the same as in Fig. 2. (E) Frequency of peaks above 100 nm for control and treated cells. The reduced number of peak events in blebbistatin-treated cortices as well as with Arp2/3 and SMIFH2 inhibition is in agreement with the trend on fluctuation amplitude shown in (D). (F) Frequency of peaks larger than 600 nm for control and treated cells.